The body of research on B12 and pernicious anemia continues to grow. Below, you can find a large list of academic publications along with a summary of their key points.
Pernicious anemia (also known as Biermer’s disease) is an autoimmune atrophic gastritis, predominantly of the fundus, and is responsible for a deficiency in vitamin B12 (cobalamin) due to its malabsorption. Its prevalence is 0.1% in the general population and 1.9% in subjects over the age of 60 years. Pernicious anemia represents 20%–50% of the causes of vitamin B12 deficiency in adults.
Optimal management of pernicious anemia
Recent estimates suggest high rates of vitamin B12 defciency among the vegetarian and vegan populations, particularly in pregnant women or women of child-bearing age who, for ethical and health reasons, are shifting towards higher consumption of plant-based foods in ever-increasing numbers. Vitamin B12 plays crucial metabolic roles across the life-course and in particular during pregnancy and in early development (first 1000 days of life). Evidence now implicates vitamin B12 defciency with increased risk to a range of neuro, vascular, immune, and infammatory disorders. However, the current UK recommended nutrient intake for vitamin B12 does not adequately consider the vitamin B12 deficit for those choosing a plant-based diet, including vegetarianism and in particular veganism, representing a hidden hunger. We provide a cautionary note on the importance of preventing vitamin B12 deficits for those individuals choosing a plant-based diet and the health professionals advising them.
The importance of vitamin B12 for individuals choosing plant‑based diets
A growing body of data indicates the importance of ethnic and racial factors to many clinical and scientific considerations of cobalamin metabolism and its disorders. Blacks have significantly higher cobalamin and transcobalamin (especially transcobalamin II) levels than whites. Because serum cobalamin levels are often influenced by factors unrelated to cobalamin intake, stores, or deficiency, it is unclear whether the differences in levels reflect cobalamin status or not. The ethnic differences, which are present in cord blood, childhood, and pregnancy as well, probably arise from combinations of hereditary and acquired causes.
Ethnic and racial factors in cobalamin metabolism and its disorders
Anti-intrinsic factor or anti-parietal gastric cells antibodies were found in 87.5% and 62% of the patients (at least one antibody, in 96%).
Update of pernicious anemia. A retrospective study of 49 cases
Vitamin B12 deficiency is a common complication in patients after gastrectomy. Elevated methylmalonic acid (MMA) and homocysteine are better indications of vitamin B12 deficiency than vitamin B12 serum level. We compared MMA and homocysteine levels of patients with gastric cancer after gastrectomy (n = 151) with controls (n = 142) and evaluated the prevalence of vitamin B12 deficiency using MMA and homocysteine in patients. MMA and homocysteine levels were significantly higher (p < 0.05) in patients with gastric cancer after gastrectomy. Of the 151 patients assessed after gastrectomy, 32 patients (21.2%) were vitamin B12 deficient as defined by serum MMA levels > 350 nmol/L, and 8 patients (5.3%) were vitamin B12 deficient as defined by serum homocysteine levels > 15 μmol/L. Both MMA and homocysteine levels were elevated in 7 patients. Among 33 patients with elevated MMA or homocysteine levels, 8 patients (24.2%) were vitamin B12 deficient based on a serum vitamin B12 level < 200 pg/mL. Additionally, levels of MMA and homocysteine were compared pre- and post-gastrectomy in 27 patients. The median MMA level was higher in patients with post-gastrectomy compared to pre-gastrectomy, while the median serum homocysteine level was not significantly different. These results indicate that using serum vitamin B12 levels alone may fail to detect vitamin B12 deficiency. Additional assessments of MMA and homocysteine levels are useful to evaluate possible vitamin B12 deficiency in patients who underwent a gastrectomy, and MMA is a better indicator than homocysteine to detect early changes in vitamin B12 levels.
Methylmalonic Acid and Homocysteine as Indicators of Vitamin B12 Deficiency in Patients with Gastric Cancer after Gastrectomy
It is important to be aware that failure of CBLA assays to detect cobalamin deficiency can occur, especially in cases of pernicious anemia where IF‐blocking antibodies have been implicated in causing assay interference. In addition, early or subclinical cases of cobalamin deficiency may not be detected with current testing platforms and standard reference ranges.
Laboratory testing for cobalamin deficiency in megaloblastic anemia
The clinical picture is the most important factor in assessing the significance of test results assessing cobalamin status because there is no ‘gold standard’ test to define deficiency. Serum cobalamin currently remains the first-line test, with additional second-line plasma methylmalonic acid to help clarify uncertainties of underlying biochemical/functional deficiencies. Serum holotranscobalamin has the potential as a first-line test, but an indeterminate ‘grey area’ may still exist. Plasma homocysteine may be helpful as a second-line test, but is less specific than methylmalonic acid. The availability of these second-line tests is currently limited. Definitive cut-off points to define clinical and subclinical deficiency states are not possible, given the variety of methodologies used and technical issues, and local reference ranges should be established. In the presence of discordance between the test result and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment.
Guidelines for the diagnosis and treatment of cobalamin and folate disorders
Instigating a patient support group for patients with pernicious anaemia (PA) revealed dissatisfaction with its current diagnosis and treatment.
Patient journeys: diagnosis and treatment of pernicious anaemia
One-third of patients experienced symptoms for up to 1 year before diagnosis; 14% waited more than 10 years for a diagnosis. Neurological features were highly prevalent, the most common being memory loss and poor concentration. Nearly two-thirds of respondents were dissatisfied with current treatment; 10% used a non-licensed form of B12 to supplement their prescribed injections.
We describe a case of functional vitamin B12 deficiency where the repeated measurement of a serum B12 level within the normal range led to delay in the diagnosis of subacute combined degeneration of the spinal cord, and possibly permanent neurological damage as a result. Failure of intracellular transport of B12 by transcobalamin-2 can lead to functional B12 deficiency but with apparently normal serum levels, and is suggested by raised levels of either serum methylmalonic acid or homocysteine, associated with low levels of transcobalamin-2. Such patients may respond to repeated high-dose injections of B12.
Functional vitamin B12 deficiency
Two types of autoantibodies to intrinsic factor have been described in the serum of certain patients with pernicious anemia. One type, termed the blocking antibody, inhibits the combination of intrinsic factor and vitamin B12; it can be detected by various technics in approximately 60 percent of patients with pernicious anemia. The second type, binding or precipitating antibody, also interacts with intrinsic factor but does not prevent the subsequent combination of intrinsic factor and vitamin B12, and is present in approximately 30 percent of these patients. The binding autoantibody almost always coexists with the blocking antibody, but not vice versa.
The Autoimmune Aspects of Pernicious Anemia
For practical purposes, the presence of autoantibodies to intrinsic factor represents strong evidence in favor of the diagnosis of pernicious anemia.
Although autoantibody to gastric parietal cell is found in up to 90 per cent of patients with pernicious anemia, this autoantibody is not considered diagnostic of the disease. It is known to occur in 5 to 8 per cent of the random population between the ages of thirty and sixty years and in 14 per cent of women over the age of sixty. Moreover the antibody is present in 60 per cent of patients simple atrophic gastritis and in a variable but significant percentage of patients with thyroid disease. Nonetheless, this antibody is found so frequently in pernicious anemia that its absence should make the clinical suspect another diagnosis.
Steroids are immunosuppressants capable of reversing or retarding certain immune-mediated phenomena. Investigators both in the United States and abroad have clearly demonstrated that administration of steroids to patients with pernicious anemia results in regeneration of the atrophic gastric mucosa with subsequent production of intrinsic factor, that is, steroids appear to reverse the histologic and laboratory evidence of this disease. Furthermore, this therapy can also decrease the titer of serum autoantibodies to intrinsic factor, although the appearance of gastric intrinsic factor appears to precede rather than to coincide with or follow the diminution of serum antibodies. The beneficial effect of steroids, however, has also been observed in patients with pernicious anemia who have no detectable antibodies to intrinsic factor. With discontinuation of steroid therapy the disease state (atrophic gastric mucosa with absent intrinsic factor) recurs. These observations have suggested that immune phenomena may play important roles in the pathogenesis of pernicious anemia; however, other therapeutic properties of steroids, such as their anti-inflammatory activity, might also be responsible for their remarkable effect in this disorder. The effect of steroids is both fascinating and provocative and may well offer a fruitful avenue for further delineation and understanding of the autoimmune mechanisms in pernicious anemia.
Cobalamin (vitamin B12) assays have been central to the diagnosis of clinical cobalamin deficiency such as pernicious anemia because the diagnostic sensitivities of older assays have been approximately 95%. However, the competitive-binding luminescence assay (CBLA) replaced older microbiologic and radioisotope-dilution assays during the past decade. Few studies have compared these methods, and cobalamin CBLA has received less-focused scrutiny than older methods have received in the past.
The diagnostic failures with all three CBLAs suggest widespread CBLA malfunction; The advice becomes untenable when assay failure rates are 22 to 35%. Manufacturers, who have access to proprietary information, must instead transparently identify and permanently correct the defect or defects.
Failures of Cobalamin Assays in Pernicious Anemia
The clinical picture is the most important factor in assessing the significance of test results assessing cobalamin status because there is no ‘gold standard’ test to define deficiency.
Guidelines for the diagnosis and treatment of cobalamin and folate disorder
There is no ideal test to define deficiency and therefore the clinical condition of patients is of the utmost importance.
There is evidence that new techniques such as the measurement of holotranscobalamin and methylmalonic acid levels seem useful in more accurately defining deficiency.
If the clinical features suggest deficiency then it is important to treat patients to avoid neurological impairment even if there may be discordance between the results and clinical features.
Vitamin B12 Deficiency
The preferred route of administration of vitamin B12 has also been debated for a long time. Majority of cobalamin in the circulation is bound to haptocorrin and is unavailable for cellular uptake. Only cobalamin bound to transcobalamin is taken up by endocytosis mediated by the cell surface transcobalamin receptor. Only 6-20% of total plasma vitamin B12 is in the active form, bound to transcobalamin II (9) . Most of the studies of oral vitamin B12 therapy used serum levels of vitamin and its metabolites as the markers of response to therapy. However, correction of an abnormal laboratory value does not mean successful outcome. An objective improvement in health outcome is only meaningful if accompanied by a clinical response. For example, in a study of 80 patients over a 3-month period, although 80-90% of patients achieved normal serum cobalamin levels on an oral dose of 650 to 1000mcg daily, clinical improvement was observed only in 20 – 30% of patients (10) . Similarly, in an open study of vitamin B12 deficiency related to food-cobalamin malabsorption in 10 patients, oral crystalline cobalamin was prescribed at a dose of 650mcg per day for at least 3 months. Normalization of vitamin levels was seen in 80% of patients, along with significant increase in hemoglobin levels and decrease in mean corpuscular volume but clinical improvement occurred only in 20% of patients (11) . We can only speculate the reasons behind lack of response to oral vitamin B12 and it may be that cobalamin somehow undergoes a transformation in the portal circulation so is made less able to be internalized by the cells and only when cobalamin is able to bypass portal circulation, the cells internalize it. This seems to be a saturable process since a minority of patients responds clinically to oral therapy.
Re: Vitamin B12 Deficiency
Among 141 consecutive patients with neuro-psychiatric abnormalities due to cobalamin deficiency, we found that 40 (28 percent) had no anemia or macrocytosis.
We conclude that neuropsychiatric disorders due to cobalamin deficiency occur commonly in the absence of anemia or an elevated mean cell volume and that measurements of serum methylmalonic acid and total homocysteine both before and after treatment are useful in the diagnosis of these patients.
Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis
We therefore consider that a massive dose methyl vitamin B12 therapy may be useful as an adjunct to immunosuppressive treatment for chronic progressive MS.
Vitamin B12 metabolism and massive-dose methyl vitamin B12 therapy in Japanese patients with multiple sclerosis
Pernicious Anemia primarily affects people of northern European ancestry. It’s rare in children and infants. Onset typically occurs after age 35, and incidence increases with age. It affects about 2% of people older than age 60.
Professional Guide to Diseases
Intellectual satisfaction derived from making a correct diagnosis is heightened by the knowledge that treatment, free of side effects, can prevent further progression of disease and may even reverse some or all of the disease manifestations. The paradigm for this situation in neurology has been the disease pernicious anemia (PA), with its associated deficiency of cobalamin (Cbl) leading, if untreated, to progressive spinal cord degeneration, neuropathy, and cerebral complications. There was a time when an astute clinician might have considered that the diagnosis of PA or other causes of Cbl deficiency was relatively simple and treatment straightfor-ward. A patient experiencing neurologic complaints, often affecting sensory and motor function in the lower extremities, would have been found to have macrocytic anemia. To confirm the suspicion, the patient might have had a smooth tongue, prematurely graying hair, lemon-yellow skin, and a family history of anemia requiring monthly “vitamin shots.” The diagnosis would have been confirmed by a serum Cbl determination followed by treatment with vitamin cyanocobalamin (vitamin B12; B12).
Despite, or perhaps because of, a number of advances in our understanding of Cbl metabolism, we more frequently encounter patients with unusual or atypical clinical and laboratory features who have underlying Cbl deficiency. Subacute combined degeneration of the spinal cord, neuropathy, and other classic manifestations of Cbl deficiency in the nervous system are often easy to recognize, but we now know that there are many atypical presentations. Some patients have neurologic syndromes without anemia or macrocytosis, whereas others have a normal serum Cbl level, yet are found to have other biochemical evidence of Cbl deficiency such as raised levels of the metabolites methylmalonic acid and homocysteine. Appropriate investigation is critical, because early treatment affords the possibility of excellent recovery.
Current concepts in the diagnosis of cobalamin deficiency
Thus, in patients who display only neurological manifestations of disease, underlying Cbl deficiency may be revealed by the finding of raised serum or urine levels of MMA. Similarly, unsuspected folate deficiency may be disclosed by the finding of a raised serum HCYS. This may have important implications with respect to disease risk, since there is mounting evidence that sub-optimal folate nutritional status may be associated with increased risks of vascular disease, neoplasia and birth defects. Finally, the measurement of serum levels of MMA, HCYS and other metabolites that accumulate in Cbl and folate deficiencies may provide important new insights into the mechanism whereby these vitamin deficiencies lead to different patterns and manifestations of disease.
Metabolite assays in cobalamin and folate deficiency
There are too many cases recorded from this hospital and from outside sources who have been treated solely with Vitamin B12 with great success for it to be denied that this substance has a significant influence on the growth rate of neuroblastoma.
Neuroblastoma: An Evaluation of Its Natural History and the Effects of Therapy, with Particular Reference to Treatment by Massive Doses of Vitamin B12
While low serum cobalamin levels do not necessarily imply deficiency, an abnormally high serum cobalamin level forms a warning sign requiring exclusion of a number of serious underlying pathologies. Functional cobalamin deficiency can thus occur at any serum level.
The pathophysiology of elevated vitamin B12 in clinical practice
Vitamin B12 (cobalamin) is a cobalt-containing compound synthesized by bacteria and an essential nutrient in mammals, which take it up from diet. The absorption and distribution of dietary vitamin B12 to the organism is a complex process involving several gene products including carrier proteins, plasma membrane receptors and transporters. Disturbed cellular entry, transit or egress of vitamin B12 may lead to low vitamin B12 status or deficiency and eventually hematological and neurological disorders.
Vitamin B12 absorption: mammalian physiology and acquired and inherited disorders
Pernicious anaemia is an autoimmune atrophic gastritis inducing vitamin B12 deficiency by malabsorption. This disease may be diagnosed in the absence of any anaemia, on a neuropathy or when one or several autoimmune disorders co-exist. Typically, pernicious anaemia is revealed by macrocytic megaloblastic anaemia. Diagnosis is done on low serum vitamin B12, raised serum homocysteine, parietal cell and, intrinsic factor antibodies.
Biermer’s disease
Pernicious anemia is the end stage of type A chronic atrophic (autoimmune) gastritis. The gastritis results in the loss of parietal cells in the fundus and body of the stomach. The loss of these cells is associated with the failure of intrinsic-factor production and results in vitamin B12 deficiency and megaloblastic anemia.
Pernicious anemia
The identification of gastric H+/K+–ATPase as the target of parietal-cell autoantibodies was a major breakthrough in our understanding of the molecular and immunologic basis of autoimmune gastritis. The immunologic mechanisms that allow the initiation and progression of the T-cell response to this enzyme, leading to autoimmune gastritis, remain to be established. Pernicious anaemia is an autoimmune atrophic gastritis inducing vitamin B12 deficiency by malabsorption. This disease may be diagnosed in the absence of any anaemia, on a neuropathy or when one or several autoimmune disorders co-exist. Typically, pernicious anaemia is revealed by macrocytic megaloblastic anaemia. Diagnosis is done on low serum vitamin B12, raised serum homocysteine, parietal cell and, intrinsic factor antibodies.
Combining IFA and PCA testing significantly increases their diagnostic performance for ABG and PA, yielding a 73% sensitivity for PA. The non-invasive combined PCA and IFA assessment may be useful in selecting patients at risk for autoimmune gastritis to be confirmed by gastroscopic-histologic examination.
Reassessment of intrinsic factor and parietal cell autoantibodies in atrophic gastritis with respect to cobalamin deficiency
Serum concentrations of vitamin B12 were ultra-high during treatment due to the lack of urinary excretion. After 6 months of treatment, the patients’ pain or paresthesia had lessened, and the ulnar motor and median sensory nerve conduction velocities showed significant improvement. There were no side effects.
Intravenous methylcobalamin treatment for uremic and diabetic neuropathy in chronic hemodialysis patients
The genes and proteins corresponding to all eight complementation groups defined in patients have provided most of the elements required to describe the intracellular processing of vitamin B12 (Fig. 2)
Genetic disorders of vitamin B12 metabolism: eight complementation groups – eight genes
Although all eight genes predicted through complementation analysis have been identified, additional genes are anticipated. Most notably, the mechanism of the mitochondrial transport of B12 remains unknown. The involvement of cblD defects in both the cytosolic and mitochondrial pathways suggests that the MMADHC protein is an accessory to the mitochondrial uptake of vitamin B12.
The discovery that high-dose vitamin B12 can overcome pathway deficits in some patients has given new life to individuals with an otherwise potentially severe or fatal disease. The early discovery that OHCbl is effective in the treatment of cblC disorder while CNCbl is not is a powerful illustration of the complexity of vitamin B12 biochemistry. The more recent finding that AdoCbl or MeCbl may have a significant stabilising effect on MMACHC protein, despite ultimately being hydrolysed to cob(II)alamin, reminds us that there is still much to be learned on behalf of the patient. Strikingly, the most recent success with gene therapy to treat mice with knockout of the Mut gene (Ref. 151) has opened up a new avenue for treatment that might ultimately benefit patients with metabolically ‘unresponsive’ disorders. The application of widespread newborn screening for homocysteine and methylmalonate underscores the opportunity to identify and treat these patients before the onset of potentially irreversible disease.
APCA can be found in 85-90% of patients with PA. Their presence is not sufficient for diagnosis, because they are not specific for PA as they are also found in the circulation of individuals with other diseases. APCA are more prevalent in the serum of patients with T1D, autoimmune thyroid diseases, vitiligo, celiac disease. People with autoimmune diseases should be closely screened for AAG/PA. The anemia develops longitudinally over many years in APCA-positive patients, symptomless, slowly promotes atrophy of the gastric mucosa and parietal cells. APCA are present in 7.8-19.5% of the general healthy adult population. A fraction of these sero-positive people, will never develop AAG or PA. An interesting and not fully explained question is whether APCA presence is related to Helicobacter pylori infection. APCA are found in up to 20.7% of these patients. H. pylori is implicated as one of the candidates causing AAG.
Anti-parietal Cell Antibodies – Diagnostic Significance
Intrinsic factor and parietal cell antibodies are useful surrogate markers of PA, with 73% sensitivity and 100% specificity. PA is mainly considered a disease of the elderly, but younger patients represent about 15% of patients.
PA is frequently associated with autoimmune thyroid disease (40%) and other autoimmune disorders, such as diabetes mellitus (10%), as part of the autoimmune polyendocrine syndrome. PA is the end-stage of ABG. Long-standing Helicobacter pylori infection probably plays a role in many patients with PA, in whom the active infectious process has been gradually replaced by an autoimmune disease that terminates in a burned-out infection and the irreversible destruction of the gastric body mucosa. Human leucocyte antigen-DR genotypes suggest a role for genetic susceptibility in PA. PA patients should be managed by cobalamin replacement treatment and monitoring for onset of iron deficiency.
PA is an often silent and under-diagnosed autoimmune disease, because its onset and progression are very slow and patients may become used to their complaints. Nevertheless, the clinical consequences of undiagnosed PA may be serious, including gastric neoplastic lesions. Thus, gastroenterologists should increase their awareness of this disorder, whose definite histological diagnosis may be preceded by reliable noninvasive serological screening.
Pernicious anemia: New insights from a gastroenterological point of view
In both groups, mean serum vitamin B12 increased after 30 days of treatment and was maintained up to 90 days. No adverse effects related to oral or intramuscular vitamin B12 replacements were noted. Both groups showed decreased homocysteine levels. Before treatment, 29 patients in the oral vitamin B12 group had neurologic symptoms related to vitamin B12 deficiency. After oral vitamin B12 treatment, 28 patients experienced symptom relief, and 16 patients were symptom free. Conclusions: Oral vitamin B12 replacement is an effective and safe treatment for vitamin B12 deficiency in gastric cancer patients after total gastrectomy.
Oral vitamin B12 replacement: an effective treatment for vitamin B12 deficiency after total gastrectomy in gastric cancer patients
Since 1975 cells lines from patients with suspected inborn errors of vitamin B12 metabolism have been referred to our laboratory because of elevations of homocysteine, methylmalonic acid, or both.
The study of highly selected patients with suspected inborn errors of metabolism has consistently resulted in the discovery of previously unknown metabolic steps and has provided new lessons in biology.
Lessons in biology from patients with inborn errors of vitamin B12 metabolism
Cobalamin and holo-transcobalamin II levels are uninformative because they rise with cobalamin influx regardless of therapeutic effectiveness, the extent varying only with the timing in relation to injection.
How I treat cobalamin (vitamin B12) deficiency
Vitamin B12 is of singular interest in any discussion of vegetarian diets because this vitamin is not found in plant foods as are other vitamins. Many of the papers in the literature give values of vitamin B-12 in food that are false because as much as 80% of the activity by this method is due to inactive analogues of vitamin B12.
Vitamin B-12: plant sources, requirements, and assay
No adverse effects have been associated with excess B12 intake from food or supplements in healthy individuals.
Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline
Our results show that ABCD4 colocalizes with the lysosomal proteins LAMP1 and LMBD1, the latter of which is deficient in the cblF defect. Furthermore, we show that mutations altering the putative ATPase domain of ABCD4 affect its function, suggesting that the ATPase activity of ABCD4 may be involved in intracellular processing of vitamin B12.
Mutations in ABCD4 cause a new inborn error of vitamin B12 metabolism
We have shown the ultra-high-dose methylcobalamin (25 mg/day i.m.) slows down the progressive reduction of the CMAP (compound muscle action potential) amplitudes in ALS in the short term (4 weeks). The latencies of SSR (sympathetic skin response) were shorter after treatment (50 mg/day i.v., 2 weeks). In the long-term effect of methylcobalamin (50 mg/day i.m., twice a week), the survival time (or the period to become respirator-bound) was significantly longer in the treated group than in the untreated.
Clinical trials of ultra-high-dose methylcobalamin in ALS
In conclusion, genetic determinants affecting the cellular availability or MTRR-dependent reduction of B12 may increase the risk of spina bifida.
Transcobalamin and methionine synthase reductase mutated polymorphisms aggravate the risk of neural tube defects in humans
Two infants presented at three and five weeks of age with megaloblastic anemia and systemic manifestations of vitamin B12 deficiency in spite of normal levels of serum vitamin B12. A deficiency of vitamin B12 transport protein transcobalamin II (TC II) was demonstrated in both infants by DEAE-cellulose ion-exchange chromatography and polyacrylamide gel electrophoresis. Complete hematologic remission was achieved by parenteral administration of large amounts of vitamin B12 at a dose of 2000 μg per week. Withdrawal of therapy in one sibling led to relapse of megaloblastic anemia in six weeks. Absorption studies in the older sibling showed decreased absorption of vitamin B12, which was not corrected by intrinsic factor, suggesting that TC II has a role in absorption of the vitamin. Hematologically normal parents and several other members of the family had low levels of vitamin B12 binding capacity of TC II, suggesting an autosomal recessive mode of inheritance for TC II deficiency.
Neonatal Megaloblastic Anemia Due to Inherited Transcobalamin II Deficiency in Two Siblings
Persistent deficiency of serum B 12 -binding alpha-1 globulin was demonstrated in two brothers, manifesting primarily as low serum B 12 levels. Despite the inability of one subject to maintain normal levels of B 12 in the blood, as shown by persistently low serum values despite monthly injections of B 12 , no evidence of metabolic B 12 deficiency could be found. Tissue B 12 -storing ability appeared to be intact. His brother exhibited only minimal hypersegmentation of neutrophil nuclei; otherwise, he too presented a completely normal picture. The normally present alpha globulin B 12 -binder was virtually absent from saliva and peripheral leukocyte extracts of both subjects. Current indirect evidence favors neutrophils as at least a partial source of the serum globulin. The cause of the possibly hereditary defect in the 2 subjects is unknown. Neither excessive B 12 -binding protein excretion nor a destructive factor in their serum or leukocytes was found.
Deficiency of vitamin B12-binding alpha globulin in two brothers
Derivatives of vitamin B12 (cobalamin) are essential cofactors for enzymes required in intermediary metabolism. Defects in cobalamin metabolism lead to disorders characterized by the accumulation of methylmalonic acid and/or homocysteine in blood and urine. The most common inborn error of cobalamin metabolism, combined methylmalonic acidemia and hyperhomocysteinemia, cblC type, is caused by mutations in MMACHC. However, several individuals with presumed cblC based on cellular and biochemical analysis do not have mutations in MMACHC. We used exome sequencing to identify the genetic basis of an X-linked form of combined methylmalonic acidemia and hyperhomocysteinemia, designated cblX. A missense mutation in a global transcriptional coregulator, HCFC1, was identified in the index case.
An X-linked cobalamin disorder caused by mutations in transcriptional coregulator HCFC1
Hydroxocobalamin is safe when administered in a 5 gram intravenous dose, and effectively decreases the low whole blood cyanide levels found in heavy smokers.
Hydroxocobalamin as a cyanide antidote: safety, efficacy and pharmacokinetics in heavily smoking normal volunteers
Based on these results we suggest that TC II deficiency due to lack of TC II protein/mRNA in these patients is due to heterogeneous types of nonsense mutations.
Nonsense Mutations in Human Transcobalamin II Deficiency
Juvenile “congenital” pernicious anemia is characterized by vitamin B12 deficiency appearing in early life as the result of a congenital lack of gastric intrinsic factor with no other apparent abnormality of the stomach or its secretions. This is in contrast to the far more frequent adult form of pernicious anemia, in which achlorhydria and gastric atrophy are uniformly present. Furthermore, serum antibodies to intrinsic factor and gastric parietal cells, commonly detected in the adult syndrome, are conspicuously absent in the patients with juvenile “congenital” pernicious anemia.
Juvenile Congenital Pernicious Anemia — Clinical and Immunologic Studies
It was found that in patients with decreased serum folate concentration, urinary excretion of vitamin B12 was increased in a statistically highly significant way.
The influence of serum folate on urinary excretion of vitamin B12
The fetus, the neonate, and the pregnant woman have a greater requirement for folic acid and vitamin B12 and are more likely to suffer from a deficiency of these vitamins. This article reviews the source, requirement, absorption, and metabolism of these vitamins and discusses the problems attributed to their deficiency in pregnancy and in the neonatal period.
Folic acid and vitamin B12 deficiency in pregnancy and in the neonatal period
Background: Conventional tests for vitamin B12 deficiency measure total serum vitamin B12, whereas only that portion of vitamin B12 carried by transcobalamin (holotranscobalamin) is metabolically active. Measurement of holotranscobalamin (holoTC) may be more diagnostically accurate for detecting B12 deficiency that requires therapy. We developed an automated assay for holoTC that can be used on the Abbott AxSYM immunoassay analyzer. Methods: AxSYM Active B12 is a 2-step sandwich microparticle enzyme immunoassay. In step 1, a holoTC-specific antibody immobilized onto latex microparticles captures holoTC in samples of serum or plasma. In step 2, the captured holoTC is detected with a conjugate of alkaline phosphatase and antiTC antibody. Results: Neither apoTC nor haptocorrin exhibited detectable cross-reactivity. The detection limit was 0.1 pmol/L. Within-run and total imprecision (CV ranges) were 3.4%–5.1% and 6.3%–8.5%, respectively. Assay CVs were <20% from at least 3 pmol/L to 107 pmol/L. With diluted serum samples, measured concentrations were 104%–114% of the expected values in the working range of the assay. No interference from bilirubin, hemoglobin, triglycerides, erythrocytes, rheumatoid factor, or total protein was detected at expected (abnormal) concentrations. A comparison of the AxSYM Active B12 assay with a commercial RIA for holoTC yielded the regression equation: AxSYM = 0.98RIA + 4.7 pmol/L (Syx, 11.4 pmol/L; n = 204). Assay throughput was 45 tests/h. A 95% reference interval of 19–134 pmol/L holoTC was established with samples from 292 healthy individuals. Conclusions: The AxSYM Active B12 assay allows rapid, precise, sensitive, specific, and automated measurement of human holoTC in serum and plasma.
Active B12: A Rapid, Automated Assay for Holotranscobalamin on the Abbott AxSYM Analyzer
Congenital P.A.’s inheritance is thought to be autosomal recessive. Growth retardation and acceleration appeared to be related to B12 deficiency and treatment. I.Q.’s of around 70 in each child may represent the effects of B12 deficiency on cerebral growth. An initial malabsorption of B12 was shown to improve markedly with B12 treatment. In diagnosis of megaloblastic anemia, only that due to B12 deficiency will respond to dosage of 2 to 5 µg B12 (intramuscular) daily. Early diagnosis and treatment may prevent brain damage.
CONGENITAL PERNICIOUS ANEMIA: EFFECTS ON GROWTH, BRAIN, AND ABSORPTION OF B12
There are a large number of causes of megaloblastic anaemia. The most frequent are disorders resulting in vitamin B(12) or folate deficiency. The diagnostic process often consists first of establishing the presence of B(12) or folate deficiency and then of determining the cause of deficiency. The blood count, blood film, serum B(12) assay, and red cell and serum folate assays are the primary investigations. Other useful investigations include serum/plasma methylmalonic acid (MMA), plasma total homocysteine (tHCYS) and serum holo-transcobalamin II assays. All currently used tests have limitations regarding specificity or sensitivity or both and the metabolite assays are not widely available. An understanding of these limitations is essential in formulating any diagnostic strategy. The wide use of serum B(12) and metabolite assays has resulted in the increasingly early diagnosis of B(12) deficiency, often in patients without B(12)-related symptoms (subclinical deficiency). Food cobalamin malabsorption is the most frequent cause of a low serum B(12). At least 25% of low serum B(12) levels are not associated with elevated metabolite levels and may not indicate B(12) deficiency. Some of these are caused by partial deficiency of transcobalamine I.
Diagnosis of megaloblastic anaemias
Vitamin B-12 deficiency is a common problem encountered in developing countries of the world. In Europe and North America it is frequently encountered in the elderly and in people whose diets are compromised such as alcoholics. Recent data has shown that cobalamin deficiency may occur in 5% to 40% of the general population. The prevalence as stated earlier is higher in the elderly and in nursing home residents. Vitamin B-12 deficiency may take decades to develop and patients may be asymptomatic or may present with a wide spectrum of hematological and neuropsychiatric manifestations. The history of research in Vitamin B-12 deficiency is fascinating and the noble prize has been awarded twice to investigators involved in it.
Neurological Manifestations Of Vitamin B-12 Deficiency
We propose the designation cblG for the mutation in those patients with methylcobalamin deficiency and decreased synthase activity. The results of these studies suggest that the products of at least two loci are required for cobalamin-dependent methionine biosynthesis in mammalian cells.
Genetic heterogeneity among patients with methylcobalamin deficiency. Definition of two complementation groups, cblE and cblG
An increasing variety of hereditary disorders of intracellular cobalamin metabolism, usually first detected because of the presence of methylmalonic aciduria (cblA, cblB, and cblF mutations), homocystinuria (cblE and cblG mutations), or both (cbIC and cblDmutations), have been defined on the basis of complementation studies.
Hereditary defect of cobalamin metabolism (cblG mutation) presenting as a neurologic disorder in adulthood
We prospectively studied 478 patients with megaloblastic anemia living in Tunisia. Overall, 98% of patients had vitamin B12 deficiency. Pernicious anemia accounted for most of these cases, and median age at presentation was 45 years. Megaloblastic anemia occurred in 19 subjects under 15 years of age, and of these, nine had the Immerslund-Graesbeck syndrome.
Megaloblastic anemia in North Africa
Preferential depletion of corrinoids on transcobalamin II (i.e., sharply reduced holo transcobalamin II (TC II)) occurs early in vitamin B12 deficiency. We measured corrinoids (Cor) and cobalamins (Cbl) on transcobalamins I and III (TC I + III) and on TC II. We also measured the unsaturated B12 binding capacities of transcobalamin I and III and TC II in serum from patients with B12 deficiency (N = 5) (with or without concurrent folate deficiency), with pernicious anemia in remission (N = 7) (1 month after therapy), and in several control groups including healthy volunteers (N = 6), hematologically normal elderly hospitalized patients (N = 5), and non-B12 nonfolate deficient anemic elderly hospitalized volunteers (N = 5). In B12 deficient patients, Cor = 177 +/- 92 pg/ml, Cbl = 56 +/- 20 pg/ml, TC II Cor = 1.0 +/- 2.2 pg/ml, and TC II Cbl = 4.4 +/- 4.9 pg/ml in contrast to pooled controls with Cor = 730 +/- 229, Cbl = 523 +/- 198, TC II Cor = 100 +/- 84, and TC II Cbl = 88 +/- 70 (all values expressed in picograms/milliliters). In pernicious anemia in remission, Cor = 505 +/- 138, Cbl = 294 +/- 77, TC II Cor = 80 +/- 31 and TC II Cbl = 37 +/- 36. TC II unsaturated B12 binding capacity was significantly higher in B12 deficient patients than in pooled controls. These data support that: (a) holo TC II is sharply depleted in untreated B12 deficiency; (b) normally, the only Cor on TC II are cobalamins; (c) in treated pernicious anemia, TC II appears to also bind non-cobalamin corrinoids; (d) continued malabsorption of vitamin B12 may result in reduced B12 on TC II within a month after the last parenteral therapy with 1000 micrograms of cyanocobalamin, and (e) TC II UBBC rises as B12 deficiency is developing. Further investigation is required for definitive delineation of whether sharply reduced Cor on TC II in untreated B12 deficiency can diagnose “true” B12 deficiency, in view of false positive or false negative results which occur in all serum B12 assays.
Depletion of serum holotranscobalamin II. An early sign of negative vitamin B12 balance
When one stops eating vitamin B−12 (cobalamins), one passes through four stages of negative cobalamin balance: serum depletion [low holotranscobalamin II, ie, low vitamin B−12 on transcobalamin II (TCII)], cell depletion (decreasing holohaptocorrin and low red cell vitamin B−12 concentrations), biochemical deficiency (slowed DNA synthesis, elevated serum homocysteine and methylmalonate concentrations), and, finally, clinical deficiency (anemia). Serum vitamin B−12 is on two proteins: the circulating vitamin B−12 delivery protein, TCII, and the circulating vitamin B−12 storage protein, haptocorrin. Because TCII is depleted of vitamin B−12 within days after absorption stops, the best screening test for early negative vitamin B−12 balance is a measurement of vitamin B−12 on TCII (holoTCII). HoloTCII falls below the bottom of its normal range long before total serum vitamin B−12 (which is mainly vitamin B−12 on haptocorrin) falls below the bottom of its normal range.
Staging vitamin B−12 (cobalamin) status in vegetarians
The incidence of an antibody against gastric parietal cells was determined with an immunofluorescence method in relatives of 21 patients who suffered from pernicious anemia and had the antibody. It was found in 42 out of 220 of these relatives (20 per cent). In a group of 120 patients with pernicious anemia a positive result was obtained in 87 per cent. Three out of 78 allied relatives who were studied as a control group had the parietal cell antibody.
A family study of pernicious anemia by an immunologic method
This case study demonstrated that 5 different Total B12 assays from 4 manufacturers all gave falsely elevated results in a patient with confirmed pernicious anaemia. The same failing described by Carmel and Agrawal and Yang and Cook (see below) is again apparent in this case study and demonstrates why Total B12 results can be unreliable.
Falsely elevated cobalamin concentration in multiple assays in a patient with pernicious anemia: a case study
Methylcobalamin is a highly photolabile and unstable molecule and hence, studies regarding photodegradation of methylcobalamin were carried out. In order to investigate the stability studies, the drug was subjected to photodegradation by exposing it to different light conditions in the validated photostability chamber as per ICH Q1B guideline. The drug was found to be less degraded in the blue light and was more prone to degradation under fluorescent light. Validated stability indicating liquid chromatography method was used for separating the methylcobalamin and its degradation products. The methylcobalamin peak with a retention time of 2.978 min was observed to decrease with a commensurate increase in a degradant peak at 4 min. The observed degradant peak was suspected to be hydroxocobalamin and was further confirmed by molecular weight determination.
PHOTODEGRADATION OF METHYLCOBALAMIN AND ITS DETERMINATION IN A COMMERCIAL FORMULATION
Methylcobalamin is one of four members of the vitamin B12 family. We recently discovered the ability of methylcobalamin to spontaneously convert to hydroxocobalamin in aqueous solutions (Yefimov S, 2022). This discovery made it clear why the chromatograms of methylcobalamin solution show the presence of hydroxocobalamin. The light sensitivity of methylcobalamin has been known for a long time (Mehmood Y et al., 2015; Chamle A et al., 2019), so all manipulations with methylcobalamin and its solutions are carried out in a dark room. Since the process of converting methylcobalamin to hydroxocobalamin in solution is continuous, it is natural to carry out a quantitative analysis of methylcobalamin together with hydroxocobalamin. The work is devoted to the validation of this method
Analysis of Methylcobalamin and Hydroxocobalamin by HPLC/MS. Method Validation
We have been performing vitamin B12 assays on the Siemens Dimension Vista system at our institution. A review of the package insert shows that the manufacturers are aware of this issue and recommend testing for intrinsic factor–blocking antibodies if test results are in conflict with the clinical diagnosis. We are in the midst of evaluating other platforms for this assay and have notified our clinicians of the issues described. However, we are concerned that there is insufficient awareness in the medical community of the possibility of spuriously high vitamin B12 levels; we urge pathologists to review their methods and clinicians to incorporate the information presented here into their diagnostic evaluations.
Spurious Elevations of Vitamin B12 with Pernicious Anemia
Testing for vitamin B12 deficiency should start with holotranscobalamin measurement. Holotranscobalamin between 23 and 75 pM should be followed by MMA testing that can filter substantial number of deficient cases in the grey range in individuals with normal renal function. This diagnostic strategy may significantly improve assessing vitamin B12 deficiency.
Utility and limitations of biochemical markers of vitamin B12 deficiency
No association between serum vitamin B₁₂ concentrations and cognitive decline or dementia was found. However, four studies that used newer biomarkers of vitamin B₁₂ status (methylmalonic acid and holotranscobalamin (holoTC)) showed associations between poor vitamin B₁₂ status and the increased risk of cognitive decline or dementia diagnosis.
Vitamin B12 status, cognitive decline and dementia: a systematic review of prospective cohort studies
HoloTC has a better diagnostic accuracy than vitamin B(12) and can replace the existing vitamin B(12) assay as a primary screening test in patients suspected of vitamin B(12) deficiency. Critical evaluation of cut-off values of holoTC indicated that a cut-off value of 32 pmol/L can be considered in screening for metabolic vitamin B(12) deficiency (defined by MMA > 0.45μmol/L) in a mixed patient population.
Screening for metabolic vitamin B12 deficiency by holotranscobalamin in patients suspected of vitamin B12 deficiency : a multi-centre study
After excluding 20 cases of incident dementia, increased tHcy remained associated with poorer performance in episodic memory, execution functions and verbal expression. Higher holoTC levels tended to be related to better performance in executive functions and psychomotor speed, while elevated serum folate concentrations were significantly related to higher scores in global cognition and verbal expression tests.
Serum homocysteine, holotranscobalamin, folate and cognition in the elderly : a longitudinal study
Cobalamin (Cbl, vitamin B12) consists of a corrinoid structure with cobalt in the centre of the molecule. Neither humans nor animals are able to synthesize this vitamin. Foods of animal source are the only natural source of cobalamin in human diet. There are only two enzymatic reactions in mammalian cells that require cobalamin as cofactor. Methylcobolamin is a cofactor for methionine synthase. The enzyme methylmalonyl-CoA-mutase requires adenosylcobalamin as a cofactor. Therefore, serum concentrations of homocysteine (tHcy) and methylmalonic acid (MMA) will increase in cobalamin deficiency. The cobalamin absorption from diet is a complex process that involves different proteins: haptocorrin, intrinsic factor and transcobalamin (TC). Cobalamin that is bound to TC is called holotranscobalamin (holoTC) which is the metabolically active vitamin B12 fraction. HoloTC consists 6 and 20% of total cobalamin whereas 80% of total serum cobalamin is bound to another binding protein, haptocorrin. Cobalamin deficiency is common worldwide. Cobalamin malabsorption is common in elderly subjects which might explain low vitamin status. Subjects who ingest low amount of cobalamin like vegetarians develop vitamin deficiency. No single parameter can be used to diagnose cobalamin deficiency. Total serum cobalamin is neither sensitive nor it is specific for cobalamin deficiency. This might explain why many deficient subjects would be overlooked by utilizing total cobalamin as status marker. Concentration of holotranscobalamin (holoTC) in serum is an earlier marker that becomes decreased before total serum cobalamin. Concentrations of MMA and tHcy increase in blood of cobalamin deficient subjects. Despite limitations of these markers in patients with renal dysfunction, concentrations of MMA and tHcy are useful functional markers of cobalamin status. The combined use of holoTC and MMA assays may better indicate cobalamin status than either of them. Because Cbl deficiency is a risk factor for neurodegenerative diseases an early diagnosis of a low B12 status is required which should be followed by an effective treatment in order to prevent irreversible damages.
Cobalamin deficiency
Laboratory indicators of vitamin B-12 or folate status involve the measurement of either the total or a physiologically relevant fraction of the vitamin in a compartment such as blood. Thus, assays to measure vitamin B-12 or folate in plasma or serum as well as folate in red blood cells are in widespread use, and more recently, methods to measure vitamin B-12 associated with the plasma binding protein transcobalamin (holotranscobalamin) have been developed. Alternatively, concentrations of surrogate biochemical markers that reflect the metabolic function of the vitamin can be used. Surrogates most commonly used are plasma homocysteine, for detection of either vitamin B-12 or folate deficiency, and methylmalonic acid for detection of vitamin B-12 deficiency.
Indicators for assessing folate and vitamin B-12 status and for monitoring the efficacy of intervention strategies
Approximately one-quarter of circulating cobalamin (vitamin B-12) binds to transcobalamin (holoTC) and is thereby available for the cells of the body. For this reason, holoTC is also referred to as active vitamin B-12. HoloTC was suggested as an optimal marker of early vitamin B-12 deficiency >20 y ago. This suggestion led to the development of suitable assays for measurement of the compound and clinical studies that aimed to show the benefit of measurement of holoTC rather than of vitamin B-12. Today holoTC can be analyzed by 3 methods: direct measurement of the complex between transcobalamin and vitamin B-12, measurement of vitamin B-12 attached to transcobalamin, or measurement of the amount of transcobalamin saturated with vitamin B-12. These 3 methods give similar results, but direct measurement of holoTC complex is preferable in the clinical setting from a practical point of view. HoloTC measurement has proven useful for the identification of the few patients who suffer from transcobalamin deficiency. In addition, holoTC is part of the CobaSorb test and therefore useful for assessment of vitamin B-12 absorption. Clinical studies that compare the ability of holoTC and vitamin B-12 to identify individuals with vitamin B-12 deficiency (elevated concentration of methylmalonic acid) suggest that holoTC performs better than total vitamin B-12. To date, holoTC has not been used for population-based assessments of vitamin B-12 status, but we suggest that holoTC is a better marker than total vitamin B-12 for such studies.
Holotranscobalamin, a marker of vitamin B-12 status: analytical aspects and clinical utility
Vitamin B₁₂ deficiency is common among the elderly, and early detection is clinically important. However, clinical signs and symptoms have limited diagnostic accuracy and there is no accepted reference test method. Results: Serum holoTC was the best predictor, with area under the ROC curve (95% CI) 0.90 (0.86-0.93), and this was significantly better (P ≤ 0.0002) than the next best predictors; serum cobalamin, 0.80 (0.75-0.85), and MMA, 0.78 (0.72-0.83). For these 3 analytes, we constructed a 3-zone partition of positive and negative zones and a deliberate indeterminate zone between. The boundaries were values of each test that resulted in a posttest probability of deficiency of 60% and a posttest probability of no deficiency of 98%. The proportion of indeterminate observations for holoTC, cobalamin, and MMA was 14%, 45%, and 50%, respectively. Within the holoTC indeterminate zone (defined as 20-30 pmol/L), discriminant analysis selected only erythrocyte folate, which correctly allocated 65% (58/89) of the observations. Renal dysfunction compromised the diagnostic accuracy of MMA but not holoTC or serum cobalamin. Conclusions: This study supports the use of holoTC as the first-line diagnostic procedure for vitamin B₁₂ status.
Diagnostic Accuracy of Holotranscobalamin, Methylmalonic Acid, Serum Cobalamin, and Other Indicators of Tissue Vitamin B12 Status in the Elderly
The holoTC and serum Cbl concentrations were highest in individuals within the lowest MMA quartile. In such a case, normal Cbl together with normal folate status may prevent HCY accumulation (median HCY, 10.8 μmol/L). However, in the highest MMA quartile, increased HCY (median, 15.4 μmol/L) may indicate impaired folate utilization despite normal serum folate. A role of Cbl in regulating folate metabolism has been suggested. Interestingly, given that HCY is an established CVD risk factor in the Syrian population, the median HCY concentrations in the first two MMA quartiles seem in accordance with the widely accepted cutoff value (12 μmol/L) above which HCY may become a risk factor. Also of note is that the median holoTC concentrations in the two highest MMA quartiles (34 and 24 pmol/L) were both below the cutoff (35 pmol/L) used in other population groups.
Cobalamin Status (Holo-Transcobalamin, Methylmalonic Acid) and Folate as Determinants of Homocysteine Concentration
Our data support the concept that the measurement of holoTC and MMA provides a better index of cobalamin status than the measurement of total vitamin B12. HoloTC is the most sensitive marker, followed by MMA. The use of holoTC and MMA enables us to differentiate between storage depletion and functional vitamin B12 deficiency. Renal patients have a higher requirement of circulating holoTC. In renal dysfunction, holoTC cannot be used as a marker of vitamin B12 status.
Functional vitamin B12 deficiency and determination of holotranscobalamin in populations at risk
We report that serum holotranscobalamin (holoTC) compares favorably with serum vitamin B12 for identifying vegans likely to have vitamin B12 deficiency as judged by measurements of the metabolites methylmalonic acid (MMA) and homocysteine (tHcy). We also report that measurement of holoTC may possibly replace combined testing with serum vitamin B12 (B12), MMA, and tHcy in this population.
Holotranscobalamin as an Indicator of Dietary Vitamin B12 Deficiency
Individuals with low concentrations of both total vitamin B12 and holoTC had significantly higher concentrations of methylmalonic acid and homocysteine than did individuals with total vitamin B12 and/or holoTC within the reference intervals (P < 0.001).
HoloTC and total vitamin B12 have equal diagnostic accuracy in screening for metabolic vitamin B12 deficiency. Measurement of both holoTC and total vitamin B12 provides a better screen for vitamin B12 deficiency than either assay alone.
Measurement of total vitamin B12 and holotranscobalamin, singly and in combination, in screening for metabolic vitamin B12 deficiency
Objective: To examine the relation between serum levels of homocysteine (tHcy) and holotranscobalamin (holoTC), the active fraction of vitamin B12, and risk of incident Alzheimer disease (AD) in a sample of Finnish community-dwelling elderly. Methods: A dementia-free sample of 271 subjects aged 65-79 years derived from the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study was followed up for 7 years to detect incident AD. The association between serum tHcy and holoTC with AD was analyzed with multiple logistic regression after adjusting for several potential confounders, including common vascular risk factors. Results: The odds ratios (ORs) (95% confidence interval [CI]) for AD were 1.16 (1.04-1.31) per increase of 1 μmol/L of tHcy at baseline and 0.980 (0.965-0.995) for each increase of 1 pmol/L baseline holoTC. Adjustment for several potential confounders including age, sex, education, APOE ε4 allele, body mass index, Mini-Mental State Examination, smoking, stroke, and blood pressure did not alter the associations: ORs (95% CI) for AD became 1.19 (1.01-1.39) for tHcy and 0.977 (0.958-0.997) for holoTC. Adjusting for holoTC attenuated the tHcy-AD link (OR changed from 1.16 to 1.10, 95% CI 0.96-1.25). The holoTC-AD relationship was less influenced by controlling for tHcy (OR changed from 0.980 to 0.984, 95% CI 0.968-1.000). Addition of folate did not change any of the results. Conclusions: This study suggests that both tHcy and holoTC may be involved in the development of AD. The tHcy-AD link may be partly explained by serum holoTC. The role of holoTC in AD should be further investigated.
Homocysteine and holotranscobalamin and the risk of Alzheimer disease: a longitudinal study
To date, the determination of serum vitamin B12 levels has been the most common laboratory test for the assessment of vitamin B12 status; however, the diagnostic accuracy of this test is low. To obtain a more sensitive marker, a new test to measure holotranscobalamin (holoTC) levels has been introduced. In this study, we assessed 45 patients for whom a vitamin B12 test had been requested and 139 anemic patients. We investigated the associations between the levels of homocysteine (Hcy) and those of holoTC, serum vitamin B12, and folate and assessed the diagnostic value of holoTC levels as a marker for vitamin B12 deficiency. We also determined the precision of the AxSYM holoTC assay by calculating the coefficient of variance (CV). The within-run and betweenrun precision values were excellent, as all CV values were less than 3.5%. The holoTC levels were low (<35 pmol/L) in 7 samples, and 6 of these samples had normal total serum vitamin B12 levels. In 2 of these samples, high Hcy levels (>12 mmol/L) indicated vitamin B12 deficiency. Thus, the holoTC levels were more sensitive than the serum vitamin B12 levels for indicating vitamin B12 status. If the serum vitamin B12 level is 151-300 pmol/L, the levels of holoTC alone or in combination with serum vitamin B12 levels are likely to be more useful markers than serum vitamin B12 levels alone.
Relationship between the Levels of Holotranscobalamin and Vitamin B12
Low plasma concentrations of vitamin B-12 are common in Indians, possibly due to low dietary intakes of animal-source foods. Whether malabsorption of the vitamin contributes to this has not been investigated. A rise in the plasma holotranscobalamin (holo-TC) concentration after a standard dose of oral vitamin B-12 has been proposed as a measure of gastrointestinal absorption in people with normal plasma vitamin B-12 concentrations. We studied 313 individuals (children and parents, 109 families) in the Pune Maternal Nutrition Study. They received 3 doses of 10 mg (n = 191) or 2 mg (n = 122) of cyanocobalamin at 6-h intervals. A rise in plasma holo-TC of $15% and .15 pmol/L above baseline was considered normal vitamin B-12 absorption. The baseline plasma vitamin B-12 concentration was ,150 pmol/L in 48% of participants; holo-TC was ,35 pmol/L in 98% and total homocysteine was high in 50% of participants (.10 mmol/L in children and .15 mmol/L in adults). In the 10 mg group, the plasma holo-TC concentration increased by 4.8-fold from (mean 6 SD) 9.3 6 7.0 pmol/L to 53.8 6 25.9 pmol/L and in the 2 mg group by 2.2-fold from 11.1 6 8.5 pmol/L to 35.7 6 19.3 pmol/L. Only 10% of the participants, mostly fathers, had an increase less than the suggested cut-points. Our results suggest that an increase in plasma holo-TC may be used to assess vitamin B-12 absorption in individuals with low vitamin B-12 status. Because malabsorption is unlikely to be a major reason for the low plasma vitamin B-12 concentrations in this population, increasing dietary vitamin B-12 should improve their status.
Increases in Plasma Holotranscobalamin Can Be Used to Assess Vitamin B-12 Absorption in Individuals with Low Plasma Vitamin B-12
Serum concentrations of homocysteine (Hcy) and methylmalonic acid (MMA) become increased in B12-deficient subjects and are therefore, considered specific markers of B12 deficiency. Serum level of holotranscobalamin (holoTC) becomes decreased before the development of the metabolic dysfunction. We investigated the usefulness of holoTC in diagnosing B12 deficiency in some clinical settings. We measured serum concentrations of holoTC, MMA, Hcy and total B12 in omnivores, vegetarians, elderly people and haemodialysis patients. Our results indicated that the incidence of holoTC <35 pmol/L was highest in the vegans (76%). Low holoTC and elevated MMA were detected in 64% of the vegans and 43% of the lacto- and lacto-ovovegetarians. An elevated MMA and a low holoTC were found in subjects with total serum B12 as high as 300 pmol/L. The distribution of holoTC in elderly people was similar to that in younger adults (median holoTC 55 pmol/L in both groups). A low holoTC and an elevated MMA were found in 16% of the elderly group. An elevated MMA and a normal holoTC were found in 20% of the elderly group who had a relatively high median serum concentration of creatinine (106.1 micromol/L). Serum concentrations of holoTC in dialysis patients were considerably higher than all other groups (median 100 pmol/L). This was also associated with severely increased serum levels of MMA (median 987 nmol/L). From these results it can be concluded that serum concentration of holoTC is a much better predictor of B12 status than total B12. This was particularly evident in case of dietary B12 deficiency. Serum concentrations of holoTC as well as MMA can be affected by renal dysfunction. Elevated MMA and normal holoTC in patients with renal insufficiency may not exclude vitamin B12 deficiency. HoloTC seems not to be a promising marker in predicting B12 status in renal patients.
The usefulness of holotranscobalamin in predicting vitamin B12 status in different clinical settings
We represent an update on diagnosing and treatment of vitamin B12 deficiency. Vitamin B12 deficiency should be suspected in all patients with unexplained anaemia and/or neurological symptoms,as well as in patients at risk of developing vitamin B12 deficiency such as the elderly and patients with intestinal diseases. Measurement of plasma cobalamins is suggested as the primary analysis followed by measurement of plasma methylmalonic acid in unsettled cases. Accumulating evidence indicates that the biologically active cobalamin, plasma holotranscobalamin (holoTC), may be superior to plasma cobalamins, and measurement of holoTC is currently introduced in the clinical setting. No consensus exists concerning evaluation of the cause for vitamin B12 deficiency,and pros and cons on the different tests mainly aiming at evaluation of the function of the gastric mucosa are presented. Once the diagnosis of vitamin B12 deficiency has been confirmed efficient treatment can be ensured either by injections every 2-3 month or by a daily dose of 1 mg vitamin B12.
Diagnosis and treatment of vitamin B12 deficiency – an update
We confirm a decrease in cobalamins during pregnancy, and report that the active part of cobalamins (holotranscobalamin, holoTC) remains unchanged. The decrease in cobalamins is explained by a decreased holohaptocorrin (holoHC), suggesting that holoTC rather than cobalamins should be used as a marker of vitamin B12 deficiency during pregnancy.
Holotranscobalamin remains unchanged during pregnancy. Longitudinal changes of cobalamins and their binding proteins during pregancy and postpartum
Maternal Cbl status and diagnostic delay are the major factors influencing severity and progression of Cbl deficiency in breastfed infants. In our cohort, propionylcarnitine was not sufficiently sensitive marker of Cbl deficiency. Although symptoms are reversible on Cbl substitution, permanent neurological damage can result. Selective screening for Cbl deficiency is indicated in all breastfed infants with failure to thrive, hypotonia, developmental delay, microcephaly or megaloblastic anaemia. The best prevention in future could be the screening of all pregnant women.
Clinical presentation and metabolic consequences in 40 breastfed infants with nutritional vitamin B12 deficiency–what have we learned?
Although early epidemiologic studies showed a protective effect of adequate maternal folic acid (FA) status against neural tube defects (NTDs), the role of adequate vitamin B-12 nutrition in the putative reduction of NTD frequency has remained uncertain. Evaluating vitamin B-12 status was complicated by the need to control for altered FA status after fortification in Canada. More recent studies have made use of better biomarkers of vitamin B-12 status, including methylmalonic acid and holotranscobalamin (holoTC). HoloTC provides a useful measure of vitamin B-12 status because it represents the bioavailable fraction of circulating vitamin B-12. By assessing bioavailable vitamin B-12 status in a large Canadian cohort accrued before and after FA fortification, we found a 3-fold increase in the risk of NTDs in mothers who had vitamin B-12 status in the lower quartile, regardless of FA fortification. Our work suggests that vitamin B-12 fortification, analogous to the FA fortification program, may reduce NTDs more than FA fortification alone. A multicenter randomized controlled trial comparing periconceptional vitamin B-12 in combination with FA against FA alone is warranted.
Vitamin B-12 and neural tube defects: the Canadian experience
Background: Cobalamin-saturated transcobalamin, also called holotranscobalamin (holoTC), constitutes only between 6% and 20% of total plasma B(12). Serum concentration of holoTC is a new marker in laboratory diagnosis of cobalamin deficiency. We tested the utility of holoTC in assessing vitamin B(12) status. Methods: We measured concentrations of holoTC and methylmalonic acid (MMA) in 1018 serum samples that were referred to our laboratory for total cobalamin testing. Results: Concentrations of MMA were lower in females compared to males and this difference was no more significant after adjusting for serum creatinine. Moreover, age was associated with higher concentrations of serum MMA, higher holoTC and slightly higher concentrations of total cobalamin. Higher concentrations of serum creatinine were associated with higher concentrations of MMA and holoTC. However, no association between serum creatinine and total cobalamin was observed. Only subjects with normal serum creatinine showed a negative correlation between serum holoTC and MMA (r= -0.36, p<0.001). In subjects with MMA > or =300 nmol/L and holoTC < or =35 pmol/L, concentrations of total cobalamin were well within the normal range (median; 25th/75th percentiles=212; 171/272 pmol/L). Receiver operating characteristic (ROC) curve analysis displayed a higher sensitivity and specificity for holoTC compared with vitamin B(12) for detecting concentrations of MMA > or =300 nmol/L in individuals with normal renal function. Conclusions: Compared to total cobalamin, we observed a better performance of holoTC assay in detecting elevated concentrations of MMA in subjects with normal renal function. The majority of subjects with combined low holoTC and elevated MMA had normal concentrations of total cobalamin. HoloTC can be used as a first line parameter in detecting cobalamin deficiency.
Holotranscobalamin in laboratory diagnosis of cobalamin deficiency compared to total cobalamin and methylmalonic acid
Eight patients with Addisonian pernicious anaemia were given 20 mg of prednisolone daily for up to 20 weeks. Improvement in absorption of vitamin B12 as judged by the Schilling test occurred in six cases and was pronounced in four, and there was increased secretion of gastric intrinsic factor in four cases. Gastric biopsies showed regeneration of specialized gastric glands in four cases; chief cells were demonstrated histochemically and parietal cells by an immunofluorescent procedure using serum containing parietal cell antibody. There was no correlative change in titre of serum antibody to gastric parietal cells or gastric intrinsic factor. The improved absorption of vitamin B12 was not maintained after prednisolone was stopped, indicating that the regenerated gastric mucosa reverted to the atrophic state. These effects of corticosteroids on gastric function in pernicious anaemia are in keeping with their known capacity to modify damage resulting from antigen–antibody interaction.
Prednisolone and gastric atrophy
The effect of corticosteroids on the gastric mucusa in patients with pernicious anemia is of particular interest in view of the possibility that atrophic gastritis, the primary pathologic lesion in pernicious anemia, may result from destruction of gastric glands by an autoimmune process.
The effect of prednisolone on gastric mucosal histology, gastric secretion, and vitamin B 12 absorption in patients with pernicious anemia
This study indicates that the atrophic gastric mucosa in patients with pernicious anemia may retain its potential to regenerate parietal cells – that atrophy is not due to a loss of regenerative potential. Regeneration was seen in patients with the higher titers of parietal cell antibody and did not occur in patients with low titers who also exhibited extensive intestinal metaplasia. It is suggested that persisting high titers of gastric parietal cell antibody in patients with pernicious anemia may be stimulated by the release of antigen from degenerating cells in atrophic gastric glands.
Eleven out of twenty-three patients with thyroid disease and intrinsic-factor (I.F.) antibodies in serum had an atrophic gastritis which did not progress to pernicious anæmia over a period of 3-7 years. In these patients the absorption of vitamin B12 remained normal, and the amount of acid and I.F. in the gastric secretion remained unchanged.
Intrinsic-factor Antibodies in Absence of Pernicious Anæmia. 3-7 Year FollowUp
It is concluded that the patients with I.F. antibody and a non-progressive atrophic gastritis differ from patients with pernicious anæmia in that the I.F. antibody appears in serum at a relatively early phase in the evolution of gastritis when adequate amounts of I.F. are still being produced.
Disorders of intracellular cobalamin metabolism have a variable phenotype and age of onset that are influenced by the severity and location within the pathway of the defect. The prototype and best understood phenotype is cblC; it is also the most common of these disorders.
Disorders of Intracellular Cobalamin Metabolism
Megaloblastic anemias are a subgroup of macrocytic anemias, in which distinctive morphologic abnormalities occur in red cell precursors in bone marrow, namely megaloblastic erythropoiesis. Of the many causes of megaloblastic anemia, the most common are disorders resulting from cobalamin or folate deficiency. The clinical symptoms are weakness, fatigue, shortness of breath and neurologic abnormalities. The presence of oral signs and symptoms, including glossitis, angular cheilitis, recurrent oral ulcer, oral candidiasis, diffuse erythematous mucositis and pale oral mucosa offer the dentist an opportunity to participate in the diagnosis of this condition. Early diagnosis is important to prevent neurologic signs, which could be irreversible. The aim of this paper is to describe the oral changes in a patient with megaloblastic anemia caused by a dietary deficiency of cobalamin.
Oral Manifestations of Vitamin B12 Deficiency: A Case Report
Significant changes in vitamin B12 status occurred in the course of pregnancy. Serum vitamin B12 concentrations and percentage of saturation of vitamin B12-binding proteins decreased steadily throughout pregnancy. In the third trimester, 35% of the participants had serum vitamin B12 concentrations <150 pmol/L and 68.6% had <15% saturation of total vitamin B12-binding capacities, but no women had RBC vitamin B12 concentrations <148 pmol/L. However, the decrease in these indices was not associated with reduced hemoglobin concentrations or RBC count or with increased tHcy concentrations.
Longitudinal Concentrations of Vitamin B12 and Vitamin B12-binding Proteins during Uncomplicated Pregnancy
Metabolic B12 deficiency is common, being present in 10%-40% of the population; is frequently missed; is easily treated; and contributes importantly to cognitive decline and stroke in older people. Measuring serum B12 alone is not sufficient for diagnosis; it is necessary to measure holotranscobalamin or functional markers of B12 adequacy such as methylmalonic acid or plasma total homocysteine. B-vitamin therapy with cyanocobalamin reduces the risk of stroke in patients with normal renal function but is harmful (perhaps because of thiocyanate accumulation from cyanide in cyanocobalamin) in patients with renal impairment. Methylcobalamin may be preferable in renal impairment. B12 therapy slowed gray matter atrophy and cognitive decline in the Homocysteine and B Vitamins in Cognitive Impairment Trial. Undiagnosed metabolic B12 deficiency may be an important missed opportunity for prevention of dementia and stroke; in patients with metabolic B12 deficiency, it would be prudent to offer inexpensive and nontoxic supplements of oral B12, preferably methylcobalamin or hydroxycobalamin.
Metabolic vitamin B12 deficiency: a missed opportunity to prevent dementia and stroke
The primarily function of cobalt in humans is based on its role in cobalamin (Cbl, vitamin B12). Therefore, this chapter will focus on the physiological roles of Cbl and the importance of cobalt in human health. Cbl acts as the cofactor for two enzymes, i.e., methylmalonyl-CoA mutase and methionine synthase, in humans. Both enzymes are important for health. In addition, unlike other water-soluble vitamins, there is a unique absorption, delivery, and activation system for Cbl in mammals.
Cobalt: its role in health and disease
In the coming years, we will continue to understand more of the merits and caveats associated with the holotranscobalamin assay for the assessment of B12 status. With its increased application in large patient populations will come acceleration in this learning – a process that it is hoped will be aided by early holotranscobalamin assay harmonisation.
Holotranscobalamin: in the middle of difficultly lies opportunity
Studies had shown that about 70% of patients with pernicious anemia will produce detectable levels of such autoantibodies. The clinical symptoms of pernicious anemia developed slowly as B12 stores are sufficient for about 5 years before deficiency lead to the onset of clinical symptoms. Therefore, the full clinical picture of severe intramedullary hemolysis culminating in progressively severe chronic anemia, along with severe neurological symptoms with demyelinisation leading to weakness and paraplegia occurs only rarely. Treatment with parenteral vitamin B12 will lead to a rapid increase of reticulocytes (within 48–72 h) and subsequent correction of anemia.
Megaloblastic Anemia
It is more common in males than in females and has an age peak around 60 year. In pernicious anemia, the gastric mucosa is atrophic and the secretion of intrinsic factor is defective. Inflammatory infiltrate of the gastric submucosa is the earliest gastric lesion in patients with PA. A type A gastritis involving the fundus and sparing the antrum is the typical finding in a patient with autoimmune pernicious anemia. The autoantibodies both to parietal cells and intrinsic factor are detectable both in the serum and gastric secretions. These autoanti- bodies particularly target the H+/K+-ATPase in the parietal cell resulting to gastric atrophy and achlorhydria. Studies had shown that parietal cell autoantibody is detectable in 90% of patients with pernicious anemia and also in 30% of first degree relatives who do not have pernicious anemia, and only about 2–8% of the normal population have low titer of these autoantibodies.
Disorders of malabsorption (food cobalamin malabsorption, intrinsic factor deficiency and abnormal enterocyte cobalamin processing) and transport proteins (transcobalamin II deficiency, R-binder deficiency) mostly lead to disturbed function of the two cobalamin requiring enzymes, methylmalonyl CoA mutase and methionine synthase. Defects of early steps of intracellular cobalamin (cblF, cbl C/D) result in marked deficiencies of both cobalamin co-enzymes and homocystinuria combined with methylmalonic aciduria. Defective synthesis of adenosyl cobalamin in the cbl A/B defects leads to methylmalonyl CoA mutase. Isolated methionine synthase deficiency is also classified as a cobalamin disorder due to its associated deficient formation of methylcobalamin.
Genetic defects of folate and cobalamin metabolism
It seems that there may be a time-limited window of opportunity for effective intervention in patients with cognitive dysfunction and low serum cobalamin.
Prevalence of vitamin B12 deficiency among demented patients and cognitive recovery with cobalamin replacement
Breastfed infants of women who have had gastric or intestinal bypass procedures may develop nutritional deficiencies. We describe a 10-month-old exclusively breastfed white male infant who presented with vomiting, failure to thrive, and megaloblastic anemia. He was found to have vitamin B12 deficiency. His mother had undergone a gastric bypass procedure for morbid obesity 2 years prior to her pregnancy with this child. She had subclinical vitamin B12 deficiency, with an abnormal Schilling test that corrected with the addition of intrinsic factor. Therefore, we believe that the mother’s gastric bypass had caused a decrease in available intrinsic factor, resulting in subclinical vitamin B12 deficiency and decreased breast milk B12. Although she was asymptomatic, her breastfed infant developed symptomatic B12 deficiency. This is the first reported case of a maternal gastric bypass resulting in vitamin B12 deficiency in an infant. These mothers should receive vitamin supplements, including vitamin B12, during and after pregnancy, and may require parenterally administered vitamin B12.
Nutritional vitamin B12 deficiency in a breastfed infant following maternal gastric bypass
This entity is probably not as rare as originally thought. It must be considered in the differential diagnosis of low serum cobalamin levels, even among elderly patients, whose conditions often tend to be automatically diagnosed as pernicious anemia.
R-Binder Deficiency: A Clinically Benign Cause of Cobalamin Pseudodeficiency
We conclude that Cbl malabsorption in these children is due to an abnormal IF that is markedly susceptible to acid and proteolytic enzymes which cause a decrease in its molecular weight and Cbl-binding ability and a loss of antigenic determinants that are recognized by the anti-human IF serum.
Cobalamin malabsorption in three siblings due to an abnormal intrinsic factor that is markedly susceptible to acid and proteolysis
Autoimmune diseases are characterized by tissue damage and loss of function due to an immune response that is directed against specific organs. This review is focused on the role of impaired intestinal barrier function on autoimmune pathogenesis.
Leaky gut and autoimmune diseases
This study reports reactions with gastric parietal cells of human and rat origin, of sera from the adult ‘normal’ population of Busselton, Western Australia (3492 sera) and from patients known to have autoimmune gastritis (43 sera). In the normal sera the prevalence of the ‘true’ autoantibody reactive with human gastric parietal cells was 4.8% and there was an age-related increase; the prevalence of heteroantibody reactive with only rat parietal cells was 3.1 %, with no age-related increase. The sera of 43 patients with known pernicious anaemia or atrophic gastritis all reacted with human parietal cells. Two further patients in whom only heteroantibody was demonstrable were shown to have intact gastric function and structure.
The parietal cell heteroantibody in human sera: Prevalence in a normal population and relationship to parietal cell autoantibody
The autoantibodies against gastric parietal cell H+/K+ ATPase had a sensitivity of 68.2% with a specificity of 91.7% for the diagnosis of pernicious anaemia. The respective rates for the autoantibodies against intrinsic factor were 40.9% and 98.6%. The combined sensitivity and specificity rates for both autoantibodies were 86.36% and 90.28%, respectively, the combined positive predictive value was 73.08% and the combined negative predictive value was 95.59%.
Pernicious Anaemia–Diagnostic Benefit of the Detection of Autoantibodies Against Intrinsic Factor and Gastric Parietal Cells Antigen H+/K+ ATPase
The detection of both autoantibodies is helpful in diagnosing pernicious anaemia and the combination of the two assays increases diagnostic sensitivity.
This study provides evidence that testing for gastric parietal cell antibodies is an appropriate screening test for pernicious anaemia, with intrinsic factor antibodies reserved for confirmatory testing or in patients with other autoantibodies that mask the GPC pattern; B12 levels are not related to autoantibody status.
Limited Value of Testing for Intrinsic Factor Antibodies With Negative Gastric Parietal Cell Antibodies in Pernicious Anaemia
Early disease recognition and treatment are therefore crucial for prevention of cobalamin deficiency-related central nervous system damage. However, the initial non-specific clinical features of cobalamin deficiency and the insidious progression of the condition make diagnosis difficult, particularly in elderly patients with multiple age-related disorders. Although abnormal laboratory results may provide important evidence for confirmation of the disease, the commonly used cutoff for diagnosis of B12 deficiency (serum cobalamin level of <200 pg/mL) has poor sensitivity. In Carmel and Agrawal’s report, for example, 22%–35% of patients with B12 deficiency (mostly due to pernicious anemia) had normal serum cobalamin levels. In such cases, measurements of serum homocysteine (Hcy) and methylmalonic acid (MMA) – by-products of the cobalamin metabolic pathway – are currently recommended for confirming B12 deficiency. However, serum Hcy and MMA have low or questionable specificity; moreover, serum Hcy level is influenced by lifestyle factors (smoking and alcohol or coffee consumption). These tests are also expensive, and therefore it would be useful to have reliable clinical markers that could be used to identify patients who need further verification with Hcy or MMA determination.
Diagnostic value of oral “beefy red” patch in vitamin B12 deficiency
The demonstration by Minot and Murphy that the feeding of liver brings about complete remission in pernicious anemia led to the development of liver extracts of various types, of which that of Cohn and his associates is most generally used. A search for the effective substance in liver led to partial purification of the material, but these more or less purified substances developed by Cohn and his associates and by West and his associates have proved too expensive to be practical in the treatment of pernicious anemia. To Gänsslen belongs the credit of having first prepared at moderate expense an extract of liver suitable for injection intramuscularly. He injected daily into the gluteal muscles 2 cc., equal in effect to from 200 to 400 Gm. of liver. Castle and Taylor obtained a maximal response in reticulocytes from a single intravenous injection of the extract.
INJECTION OF LIVER EXTRACT IN THE TREATMENT OF PERNICIOUS ANEMIA
Nitrous oxide produces irreversible oxidation to the Co++ and Co forms that renders vitamin B12 inactive. Five cases (four from the literature and one new case) are presented in which patients unsuspected of having vitamin B12 deficiency developed subacute combined degeneration of the spinal cord following nitrous oxide anesthesia. Patients with vitamin B12 deficiency are exceedingly sensitive to neurologic deterioration following nitrous oxide anesthesia. If unrecognized, the neurologic deterioration becomes irreversible and may result in death.
Neurologic degeneration associated with nitrous oxide anesthesia in patients with vitamin B12 deficiency
Given the scale of use which would result from routine use of nitrous oxide in children undergoing painful procedures, there should be real concern about the potential for an accident in a child with occult cobalamin deficiency. The message must be: never forget vitamin B12 when thinking of using nitrous oxide.
Nitrous oxide and vitamin B12
Phillip Lee and colleagues (March 13, p 554) highlight the danger of giving nitrous oxide to patients who may have unrecognised vitamin B12 deficiency. The number of patients reported to develop neurological problems is now into double figures. However, the worrying aspect of this report, from an anaesthetist’s point of view, is that nitrous oxide was given for only 65 min. Since many operations last considerably longer than 1 h the implication is that are are putting a substantial number of patients at risk. How can we best manage patients with potential vitamin B12 deficiency who are about to undergo a general anaesthetic? Haemoglobin and mean corpuscular volume do not accurately reflect vitamin B12 concentrations. The investigators comment that serum vitamin B12 concentrations would have been helpful in the case described, but even this test is not entirely sensitive. Measurements of serum methylmalonic acid and total homocysteine are required to confidently rule out a deficiency in total body stores. Furthermore, screening every patient would be impractical, whereas limiting testing to vegetarians and those already known to have a disorder associated with vitamin B12 deficiency would inevitably mean missing some casesNitrous oxide is certainly not essential for general anaesthesia; therefore, the safest answer is not to use it. However, if anaesthetists wish to use nitrous oxide, an alternative approach is perhaps to give vitamin B12 to all patients perioperatively for everything but the shortest of procedures.
Vitamin B12 deficiency and nitrous oxide
A significant association between cobalamin [b12] status and performance on tests measuring fluid intelligence, spatial ability and short-term memory with formerly vegan kids scoring lower than omnivorous kids in each case … reasoning, the capacity to solve complex problems, abstract thinking ability and the ability to learn. Any defect in this area may have far-reaching consequences for individual functioning.
Signs of impaired cognitive function in adolescents with marginal cobalamin status
Long-term metformin therapy is significantly associated with lower serum vitamin B12 concentration, yet those at risk are often not monitored for B12 deficiency. Because metformin is first line therapy for type 2 diabetes, clinical decision support should be considered to promote serum B12 monitoring among long-term metformin users for timely identification of the potential need for B12 replacement.
Long-term Metformin Therapy and Monitoring for Vitamin B12 Deficiency Among Older Veterans
A case of the exclusively breast-fed infant of a vegetarian mother is reported. Neurological deterioration commenced between three and six months of age, and progressed to a comatose premoribund state by the age of nine months. Investigations revealed a mild nutritional vitamin B12 deficiency in the mother, and a very severe nutritional B12 deficiency in the infant, with severe megaloblastic anaemia. Treatment of the infant with vitamin B12 resulted in a rapid clinical and haematological improvement, but neurological recovery was incomplete.
Brain damage in infancy and dietary vitamin B12 deficiency
Anti-parietal cell antibody has been reported in nearly all patients with pernicious anaemia in past studies, in contrast with anti-intrinsic factor (IF) antibody which occurs in only 50-70% of such patients. However, observations in the more diverse patient population at our hospital suggest that these prevalences, originally described in predominantly elderly, white patients of European origin, no longer apply. Anti-IF antibody was found in 70% of the 324 patients, with blacks (84%) and Latin Americans (69%) having a significantly higher prevalence than whites (55%). In contrast, only 55% of the 266 patients tested had anti-parietal cell antibody. It was noteworthy that this low rate was similar in all racial groups. However, patients lacking anti-parietal cell antibody were significantly younger than those who had the antibody. Overall, a striking 30% of all patients had anti-IF antibody but not anti-parietal cell antibody, while only 13% had the latter antibody without having anti-IF antibody.
Reassessment of the relative prevalences of antibodies to gastric parietal cell and to intrinsic factor in patients with pernicious anaemia: influence of patient age and race
Summary of key recommendations: 1. The clinical picture is the most important factor in assessing the significance of test results assessing cobalamin status because there is no ‘gold standard’ test to define deficiency. 2. Serum cobalamin currently remains the first-line test, with additional second-line plasma methylmalonic acid to help clarify uncertainties of underlying biochemical/functional deficiencies. Serum holotranscobalamin has the potential as a first-line test, but an indeterminate ‘grey area’ may still exist. Plasma homocysteine may be helpful as a second-line test, but is less specific than methylmalonic acid. The availability of these second-line tests is currently limited. 3. Definitive cut-off points to define clinical and subclinical deficiency states are not possible, given the variety of methodologies used and technical issues, and local reference ranges should be established. 4. In the presence of discordance between the test result and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment. 5. Treatment of cobalamin deficiency is recommended in line with the British National Formulary. Oral therapy may be suitable and acceptable provided appropriate doses are taken and compliance is not an issue. 6. Serum folate offers equivalent diagnostic capability to red cell folate and is the first-line test of choice to assess folate status.
Guidelines for the diagnosis and treatment of cobalamin and folate disorders
Taken together, the data indicates an enhanced detection rate by ELISA over immunofluorescence and validates it as a robust diagnostic assay for parietal cell antibody. As parietal cell antibody marks asymptomatic autoimmune gastritis that may progress to end stage gastric atrophy and haematological complications, and as autoimmune gastritis is associated with autoimmune thyroiditic and type 1 diabetes mellitus, early detection of parietal cell antibody by a sensitive ELISA will enable early follow-up of at risk subjects.
Parietal Cell Antibody Identified by ELISA Is Superior to Immunofluorescence, Rises With Age and Is Associated With Intrinsic Factor Antibody
Antibodies of type I, so-called blocking antibodies, were detected in 66% of cases where the diagnosis of pernicious anemia was made. Type II, so-called precipitating antibodies, were found in 47% of patients with antibodies of type I and only in the latter. Certain etiological factors, already noted in the world literature, were found, in particular the link with the female sex and with blood group A. The specificity of these antibodies is very great and false positives are exceptional. We did not find them in any of the 104 controls. They were observed, however, in 5 of the 56 patients where the diagnosis of pernicious anemia was not definite, but it is likely that, in these 5 cases, pernicious anemia existed with some other disease. Our study also showed the limits of other methods of investigation of this disease; hypovitaminimia B12 is often corrected by treatment without proper inductions and B12 malabsorption on the Schilling test may not be corrected by the addition of intrinsic factor.
Search for Anti-Intrinsic Factor Antibodies in the Diagnosis of Biermer’s Anemia
Thirty-nine percent of subjects had plasma vitamin B-12 concentrations <258 pmol/L, 17% had concentrations <185 pmol/L, and 9% had concentrations <148 pmol/L, with little difference between age groups. Supplement users were significantly less likely than non-supplement-users to have concentrations <185 pmol/L (8% compared with 20%, respectively). Among non-supplement-users, there were significant differences between those who consumed fortified cereal >4 times/wk (12%) and those who consumed no fortified cereal (23%) and between those in the highest and those in the lowest tertile of dairy intake (13% compared with 24%, respectively), but no significant differences by meat tertile. Regression of plasma vitamin B-12 on log of intake, by source, yielded significant slopes for each contributor adjusted for the others. For the total group, b = 40.6 for vitamin B-12 from vitamin supplements. Among non-supplement-users, b = 56.4 for dairy products, 35.2 for cereal, and 16.7 for meat. Only the meat slope differed significantly from the others.
Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study
The prevalence of hyperhomocysteinemia was higher in vegetarians than in controls (53.3 vs. 10.3%, p < 0.001). Serum vitamin B(12) levels were lower in vegetarians than in control subjects (171.2 +/- 73.6 vs. 265.0 +/- 52.2 pmol/l, p < 0.01; normal range 220-740 pmol/l). In vegetarian subjects, significant inverse correlations were found between tHcy and serum vitamin B(12) levels (r = -0.776, p < 0.001) and between tHcy and serum folate levels (r = -0.340, p < 0.05). Positive correlations were found between tHcy and mean red cell volume (r = 0.44, p < 0.01) and between tHcy and fat-free mass (r = 0.36, p < 0.05). Conclusion: Vegetarian subjects presented significantly higher tHcy levels, higher prevalence of hyperhomocysteinemia, and lower serum vitamin B(12) levels than controls.
Effect of vegetarian diet on homocysteine levels
Thus, with few exceptions, the reviewed studies documented relatively high deficiency prevalence among vegetarians. Vegans who do not ingest vitamin B12 supplements were found to be at especially high risk. Vegetarians, especially vegans, should give strong consideration to the use of vitamin B12 supplements to ensure adequate vitamin B12 intake. Vegetarians, regardless of the type of vegetarian diet they adhere to, should be screened for vitamin B12 deficiency.
The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature
Nevertheless, the data are compelling, and they indicate that vegetarians should routinely take cobalamin or vitamin B-12 supplements, which in their generic form are relatively inexpensive. In developing countries, other formidable problems were incurred in attempts to implement a program of supplementation of other vitamins. Yet the lack of a comprehensive initiative to protect vegetarians from vitamin B-12 deficiency can lead to a whole generation of cobalamin-deficient children (and adults) who are incapable of making good decisions because of the additional burden of neurologic deficits induced by cobalamin deficiency. The international nutrition community must take up the challenge posed by this body of evidence and enact practical steps to ensure parity in the vitamin B-12 status of vegetarians and omnivores.
Vegetarianism and vitamin B-12 (cobalamin) deficiency
The vitamin B(12) concentration of an algal health food, spirulina (Spirulina sp.) tablets, was determined by both Lactobacillus leichmannii ATCC 7830 microbiological and intrinsic factor chemiluminescence methods. The values determined with the microbiological method were approximately 6-9-fold greater in the spirulina tablets than the values determined with the chemiluminescence method. Although most of the vitamin B(12) determined with the microbiological method was derived from various vitamin B(12) substitutive compounds and/or inactive vitamin B(12) analogues, the spirulina contained a small amount of vitamin B(12) active in the binding of the intrinsic factor. Two intrinsic factor active vitamin B(12) analogues (major and minor) were purified from the spirulina tablets and partially characterized. The major (83%) and minor (17%) analogues were identified as pseudovitamin B(12) and vitamin B(12), respectively, as judged from data of TLC, reversed-phase HPLC, (1)H NMR spectroscopy, ultraviolet-visible spectroscopy, and biological activity using L. leichmannii as a test organism and the binding of vitamin B(12) to the intrinsic factor.
Pseudovitamin B(12) is the predominant cobamide of an algal health food, spirulina tablets
The vitamin B12 (VB12) parameter was studied in the serum and cerebrospinal fluid (CSF) of 14 demented patients. Eleven of these patients were in a state of dementia of the degenerative type such as Alzheimer’s disease, senile dementia and Pick’s disease. The serum VB12 concentration in all the patients was within normal limits, i.e. 500-1,300 pg/ml. There was no significant difference between the CSF-VB12 levels and the severity of dementia. The serum and CSF-VB12 levels of the demented patients did not show any significant elevation after the oral administration of CH3-B12, 2 mg per day. On the other hand, there was a marked elevation of both the serum and CSF-VB12 after an oral medication (2 mg per day) plus intramuscular administrations (500 micrograms per day). These results confirm that the intramuscular administration of CH3-B12 is an effective way to get a higher value of the serum and CSF-VB12 levels.
Serum and cerebrospinal fluid vitamin B12 levels in demented patients with CH3-B12 treatment–preliminary study
Through an active transport mechanism B12 is released to the cerebrospinal fluid (CSF). The protein-B12 complex in the CSF then delivers the B12 to the brain cells. Ordonez states that additional direct uptake by the blood-brain-barrier may be involved. Circumstantial evidence is available indicating that CSF B12 levels can be regarded as indicative for brain tissue B12 status.
Vitamin B 12 Levels of Cerebrospinal Fluid in Patients with Organic Mental Disorder
The study by Drs. Norman and Morrison made very interesting and informative reading. The high prevalence and availability of therapy for cobalamin deficiency in the elderly make any noninvasive diagnostic index valuable. In this context, I would like to draw your attention to some additional data on this subject. Yamauchi and coworkers studied the relation of urinary methylmalonic acid (MMA) excretion and vitamin B12 deficiency. They found that patients with neurologic disturbances excreted larger amounts of MMA than those without neurologic disorders. They also concluded that MMA could be a useful adjunct to distinguish megaloblastic anemia from myelodysplasia with niegaloblastosis. As 2% of the general population are carriers of inherited methylmalonic acidemia, Rasmussen and Nathan examined the urinary excretion of MMA in patients with methylmalonic acidemia. They found urinary MMA levels to range from 1.18 to 2.48 mmol per mol of creatinine (reference range 0.58 to 3.56). This reveals that heterozygotes for inherited methylmalonic acidemia would not give false-positive results for cobalamin deficiency, and hence testing for urinary MMA remains useful in this subgroup. Finally, Rasmussen has described the use of another method for the measurement of urinary MMA, anion exchange extraction using formate and formic acid. This technique was found to be both reliable and convenient for the evaluation of cobalamin deficiency, particularly in patients with normal or moderately reduced serum cobalamin levels. The above data, in conjunction with the authors’ study, promise to attenuate an important treatable cause of permanent neurologic disability in the elderly.
Urinary methylmalonic acid and cobalamin deficiency in the elderly
Vitamin B12 deficiency is a frequently considered diagnosis for which there is no single, commonly available and accurate test. A urinary methylmalonic acid assay using gas chromatography-mass spectrometry has been proposed as the preferred test. We reviewed vitamin B12 assays on 1599 consecutive patients and prospectively studied all patients with low serum B12 levels (n = 75) and a random sample of patients with normal levels (n = 68). Of 96 evaluable patients, 7 had clinical deficiency. All 7 deficient patients had urinary methylmalonic acid levels greater than 5 micrograms/mg creatine (sensitivity, 100%; confidence interval, 65% to 100%). Of the 89 patients who were not clinically deficient, 88 had urinary methylmalonic acid levels less than or equal to 5 micrograms/mg creatinine (specificity, 99%). The overall test accuracy in this population was 99%. If the high sensitivity and specificity of the gas chromatography-mass spectrometry assay for urinary methylmalonic acid is supported by other clinical studies, the methylmalonic acid assay may become the reference standard for the diagnosis of vitamin B12 deficiency.
Isotope-dilution assay for urinary methylmalonic acid in the diagnosis of vitamin B12 deficiency. A prospective clinical evaluation
Urinary methylmalonic acid (MMA) excretion in megaloblastic anemia due to vitamin B12 (B12) deficiency was studied using a colorimetric method. Average MMA excretion in 20 patients with untreated B12 deficiency was 164 mg/day, whereas it increased to 518 mg/day following oral administration of 10 g L-valine. Urinary MMA correlated significantly with platelet number, erythroblast percentage and deoxyuridine suppression test, while no correlation was found with hemoglobin, leukocyte number, reticulocyte, serum LDH, serum B12 and folate concentration. Patients with neurological disturbances excreted significantly larger amounts of MMA than those without neurological disorders. The results also indicated that MMA could be a useful adjunct for differentiation of megaloblastic anemia from myelodysplastic syndromes showing marked megaloblastic changes.
Urinary methylmalonic acid excretion and clinical features in megaloblastic anemia due to vitamin B12 deficiency
The sensitivity and specificity of the IF Ab test was compared to the Schilling test with regard to making a diagnosis of PA in patients presenting with megaloblastic anaemia and low serum vitamin B12 levels.
The Value of the Intrinsic Factor Antibody Test in Diagnosing Pernicious Anaemia
Relevant statistical analysis showed that in the correct clinical setting, a confident diagnosis of PA could be made without Schilling tests in patients with megaloblastic anaemia, vitamin B12 deficiency and positive IF Ab tests. In a small proportion of patients in whom the IF Ab is negative, Schilling tests still need to be performed.
With the increased concern over rising medical costs and where limited facilities are available, the IF Ab, in the correct clinical setting, is a cost effective and reliable test for diagnosis of PA.
A variety of autoantibodies can be detected in serum samples from patients with pernicious anemia, including antibodies to gastric parietal cells and to intrinsic factor (IF). Antiparietal cell antibodies may have a causative role in the autoimmune gastritis of pernicious anemia and are present in about 85% of affected patients. Antiparietal cell antibodies are nonspecific; they are often present in patients with autoimmune endocrinopathies and are present in 3% to 10% of healthy persons, depending on age.
Laboratory Diagnosis of Vitamin B12 and Folate Deficiency
Compared with the antiparietal cell assay, the anti–IF antibody test is relatively insensitive; only about half of the patients with pernicious anemia have detectable anti-IF antibody. However, anti-IF antibody is highly specific; it is rarely present in healthy patients or in patients with other autoimmune disorders, although it may be detected in some patients with Graves disease. In such cases, a nonprogressive atrophic gastritis (with normal production of IF) has been described.
Vitamin B12 or cobalamin deficiency occurs frequently (> 20%) among elderly people, but it is often unrecognized because the clinical manifestations are subtle; they are also potentially serious, particularly from a neuropsychiatric and hematological perspective. Causes of the deficiency include, most frequently, food-cobalamin malabsorption syndrome (> 60% of all cases), pernicious anemia (15%-20% of all cases), insufficient dietary intake and malabsorption.
Vitamin B12 (cobalamin) deficiency in elderly patients
Intravenous ultra-high dose MeCbl treatment is a safe and potentially efficacious therapy for patients with peripheral neuropathy and chronic axonal degeneration.
Safety and Efficacy of Intravenous Ultra-high Dose Methylcobalamin Treatment for Peripheral Neuropathy: A Phase I/II Open Label Clinical Trial
Functional methionine synthase deficiency due to the cblE and cblG mutations is characterized by homocystinuria and defective biosynthesis of methionine. Most patients have presented in the first few months of life with megaloblastic anemia and developmental delay. At least one patient presented in early adulthood with a misdiagnosis of multiple sclerosis. The distribution of cobalamin derivatives was altered in cultured cells, with decreased levels of methylcobalamin (MeCbl) as compared with normal fibroblasts. The cblE disorder is associated with low methionine synthase activity when the enzyme assay is performed with low levels of reducing agent, whereas the cblG disorder is associated with low activity under all assay conditions. Both diseases respond to treatment with hydroxocobalamin (OHCbl).
Inherited Disorders of Folate and Cobalamin Transport and Metabolism
Elevated levels of serum cobalamin may be a sign of a serious, even life-threatening, disease. Hematologic disorders like chronic myelogeneous leukemia, promyelocytic leukemia, polycythemia vera and also the hypereosinophilic syndrome can result in elevated levels of cobalamin. Not surprisingly, a rise of the cobalamin concentration in serum is one of the diagnostic criteria for the latter two diseases. The increase in circulating cobalamin levels is predominantly caused by enhanced production of haptocorrin. Several liver diseases like acute hepatitis, cirrhosis, hepatocellular carcinoma and metastatic liver disease can also be accompanied by an increase in circulating cobalamin. This phenomenon is predominantly caused by cobalamin release during hepatic cytolysis and/or decreased cobalamin clearance by the affected liver. Altogether it can be concluded that an observed elevation of cobalamin in blood merits the a full diagnostic work up to assess the presence of disease.
Significance of elevated cobalamin
Transcobalamin (TC) deficiency is a rare autosomal recessive inborn error of cobalamin transport which clinically manifests in early infancy. We describe a child with TC deficiency who presented with classical clinical and lab stigmata of inborn error of vitamin B12 metabolism except normal serum B12 levels. He was started on empirical parenteral cobalamin supplements at 2 months of age; however, the definitive diagnosis could only be established at 6 years of age when a genetic evaluation revealed homozygous nonsense variation in exon 8 of the TCN2 gene (chr22:g.31019043C>T).
Transcobalamin deficiency: vitamin B12 deficiency with normal serum B12 levels
Transcobalamin II (TC) is an essential plasma protein for the absorption, transportation, and cellular uptake of cobalamin. TC deficiency presents in the first year of life with failure to thrive, hypotonia, lethargy, diarrhea, pallor, mucosal ulceration, anemia, pancytopenia, and agammaglobulinemia. Herein, we present TC deficiency diagnosed in two cases (twin siblings) with a novel variant in the TCN2 gene.
Transcobalamin II deficiency in twins with a novel variant in the TCN2 gene: case report and review of literature
4-month-old twins were admitted with fever, respiratory distress, vomiting, diarrhea, and failure to thrive. Physical examination findings revealed developmental delay and hypotonia with no head control, and laboratory findings were severe anemia, neutropenia, and hypogammaglobulinemia. Despite normal vitamin B12 and folate levels, homocysteine and urine methylmalonic acid levels were elevated in both patients. Bone marrow examinations revealed hypocellular bone marrow in both cases. The patients had novel pathogenic homozygous c.241C>T (p.Gln81Ter) variant in the TCN2 gene. In both cases, with intramuscular hydroxycobalamin therapy, laboratory parameters improved, and a successful clinical response was achieved.
In infants with pancytopenia, growth retardation, gastrointestinal manifestations, and immunodeficiency, the inborn error of cobalamin metabolism should be kept in mind. Early diagnosis and treatment are crucial for better clinical outcomes. What is new? In literature, to date, less than 50 cases with TC deficiency were identified. In this report, we presented twins with TCN2 gene mutation. Both patients emphasized that early and aggressive treatment is crucial for achieving optimal outcomes. In this report, we identified a novel variation in TCN2 gene.
A male Caucasian infant presented at 6 weeks of age with failure to thrive, diarrhoea, macrocytic anaemia, and decreased IgG. He had normal serum B12 and folate levels. Serum cobalamin binding capacity showed no detectable transcobalamin II. Both parents showed levels consistent with a heterozygous state. The literature is extensively reviewed, and the importance of early diagnosis to prevent neurological dysfunction is stressed.
Transcobalamin II deficiency: case report and review of the literature
A second family with transcobalamin II (TC II) deficiency was detected. Megaloblastic anemia developed in early life in association with normal serum levels of vitamin B12, but all vitamin B12 was bound to alpha-1-globulin (TCI), and the normal beta-binder (TCII) was lacking. Family studies are compatible with autosomal recessive inheritance.
Hereditary transcobalamin II deficiency: Clinical findings in a new family
Homocysteine levels were significantly higher among individuals with low holo-tc II, low total vitamin B12 concentrations and low holo-tc II percentages. These low holo-tc II percentages are probably caused by reduced affinity of TC II for vitamin B12, which may be explained by genetic variation in the TC II gene. Vitamin B12 supplementation might therefore be warranted, in addition to folate, in the prevention of NTD.
Reduced vitamin B12 binding by transcobalamin II increases the risk of neural tube defects
In the United States and the United Kingdom, the prevalence of vitamin B12 deficiency is approximately 6% in persons younger than 60 years, and nearly 20% in those older than 60 years. Latin American countries have a clinical or subclinical deficiency rate of approximately 40%. The prevalence is 70% in Kenyan school children, 80% in East Indian preschool-aged children, and 70% in East Indian adults.
Vitamin B12 Deficiency: Recognition and Management
We report the case of a 56-year-old man who, 17 years after a subtotal gastrectomy, presented with a diffuse sensory-motor demyelinating peripheral neuropathy with multifocal alteration of conduction confirmed by electromyography. Its causal relationship with vitamin B12 deficiency was biologically demonstrated. This neuropathy improved within a few days after intramuscular hydroxocobalamin treatment. Both clinical and electrophysiological signs had totally disappeared 3 months later on.
Reversible peripheral neuropathy induced by vitamin B12 deficiency
The application of sensitive metabolic tests, such as the deoxyuridine suppression test and measurement of homocysteine and methylmalonic acid, to cobalamin status has identified the entity of mild, preclinical cobalamin deficiency. This state, common in the elderly, responds to cobalamin therapy. Preclinical deficiency may exist within the nervous system as well, although this requires further study. Nevertheless, it is well to remember that not all low cobalamin levels and not all abnormal metabolite results reflect cobalamin deficiency. Interpretation of metabolic results still requires caution, as do proposals to raise the cut-off point for low cobalamin levels to capture some normal levels that are associated with metabolic abnormality. The recognition of mild, preclinical deficiency has opened up many important issues. These include identifying its causes, what should be done about it, and what the clinical impact of the hyperhomocysteinemia itself is. Although malabsorptive disorders, especially food-cobalamin malabsorption, underlie about half of all cases of preclinical deficiency, no cause can be found in the remainder of these cases; poor dietary intake appears to be uncommon. In addition, unusual states of neurologically symptomatic cobalamin deficiency are being recognized, such as nitrous oxide exposure in patients with unrecognized deficiency and severe deficiency in children of mildly deficient mothers. All of these have broadened and complicated the picture of cobalamin deficiency while providing greater opportunities for prevention.
Current concepts in cobalamin deficiency
MeCbl is primarily involved along with folate in hematopiesis and development of the brain during childhood. Whereas deficiency of AdCbl disturbs the carbohydrate, fat and amino-acid metabolism, and hence interferes with the formation of myelin.
Treatment of vitamin B12 deficiency-methylcobalamine? Cyancobalamine? Hydroxocobalamin?-clearing the confusion
A patient developed numbness and tingling in distal extremities with subsequent weakness. Evaluation revealed B12 deficiency. She had evidence of myelopathy on imaging studies and polyneuropathy on electrodiagnostic testing. Treatment with B12 caused remittance of symptoms and resolution/improvement of abnormalities found on the imaging and electrodiagnostic studies. This case demonstrates that early intervention with B12 supplementation can cause reversal of both central and peripheral nervous system dysfunction.
Recovery of neurologic dysfunction with early intervention of vitamin B12
Inherited disorders of vitamin B12 include those which involve the inability of the vitamin to be absorbed from the gut and transported to the appropriate tissues, and those in which the vitamin is not utilised by target cells. The former include intrinsic factor abnormalities, selective malabsorption of vitamin B12 with proteinuria, and deficiencies of transcobalamin I and transcobalamin II. The latter include a defect in the release of free vitamin B12 from lysosomes (cblF), and defects in the formation of both vitamin B12 cofactors (cblC, cblD) or of adenosyl-B12 (cblA, cblB) or methyl-B12 alone (cblE, CblE variant). This article reviews the major clinical manifestations of these diseases, and provides an approach to the diagnosis of transcobalamin II deficiency and the cbl mutations using cultured cells.
Inherited disorders of vitamin B12 metabolism
Sixty female rats aged 22 to 25 days received an adequate synthetic basal diet, the diet supplemented in mg. per kg. by vitamin B1, riboflavin and vitamin B6 20, Ca pantothenate and nicotinic acid 60, biotin 5, folic acid 10, p-aminobeneoic acid 400 and inositol 80, and by 150 µg. vitamin B12, or the diet supplemented with 10 per cent. whole liver powder. After 12 weeks, the average weight of the rats on the basal diet was 215 g., on basal diet with extra B vitamins 229 g., and on basal diet with whole liver 248 g. The length of time was measured in which rats from each dietary group would swim in water at 36° and 20° C. before remaining submerged for at least 15 sec. There was no significant difference in performance at 36° C. among rats from the 3 groups, all surviving a test period of 120 min. At 20° C., rats receiving the basal diet swam for an average of 13.3 min., the diet with vitamins 13.4 min., while 9 of 12 rats receiving liver swam for over 120 min., the others for 63 to 87, indicating the presence of a protective factor in liver against the stress due to swimming in cold water.
Beneficial effect of liver feeding on swimming capacity of rats in cold water
Transcobalamin (TC) transports cobalamin from blood into cells. TC deficiency is a rare autosomal recessive disorder usually presenting in early infancy with failure to thrive, weakness, diarrhoea, pallor, anemia, and pancytopenia or agammaglobulinemia. It can sometimes resemble neonatal leukemia or severe combined immunodeficiency disease. Diagnosis of TC deficiency is suspected based on megaloblastic anemia, elevation of total plasma homocysteine, and blood or urine methylmalonic acid. It is confirmed by studying the synthesis of TC in cultured fibroblasts, or by molecular analysis of the TCN2 gene. TC deficiency is treatable with supplemental cobalamin, but the optimal type, route and frequency of cobalamin administration and long term patient outcomes are unknown. Here we present a series of 30 patients with TC deficiency, including an update on multiple previously published patients, in order to evaluate the different treatment strategies and provide information about long term outcome. Based on the data presented, current practice appears to favour treatment of individuals with TC deficiency by intramuscular injections of hydroxy- or cyanocobalamin. In most cases presented, at least weekly injections (1 mg IM) were necessary to ensure optimal treatment. Most centres adjusted the treatment regimen based on monitoring CBC, total plasma homocysteine, plasma and urine methylmalonic acid, as well as, clinical status. Finally, continuing IM treatment into adulthood appears to be beneficial.
Update on transcobalamin deficiency: clinical presentation, treatment and outcome
Transcobalamin II deficiency is one of the rare causes of inherited vitamin B12 disorders in which the patients have characteristically normal or high vitamin B12 levels related to the transport defect of vitamin B12 into the cell, ending up with intracellular cobalamin depletion and high homocysteine and methylmalonic acid levels. Herein, we describe the findings at presentation of four patients who were diagnosed to have transcobalamin II deficiency with novel mutations. These patients with transcobalamin II deficiency were found to have novel mutations, of whom 2 had the same large deletion (homozygous c.1106+1516-1222+1231del). Transcobalamin II deficiency should be considered in differential diagnosis of any infant with pancytopenia, failure to thrive, diarrhea, and vomiting.
Transcobalamin II Deficiency in Four Cases with Novel Mutations
We describe the case of a 31 years old woman who at the age of 30 days presented with the classical clinical and laboratory signs of an inborn error of vitamin B12 metabolism. Family history revealed a sister who died at the age of 3 months with a similar clinical syndrome and with pancytopenia. She was started on empirical intramuscular (IM) cobalamin supplements (injections of hydroxocobalamin 1 mg/day for 1 week and then 1 mg twice a week) and several transfusions of washed and concentrated red blood cells. With these treatments a clear improvement in symptoms was observed, with the disappearance of vomiting, diarrhea and normalization of the full blood count. At 8 years of age injections were stopped for about two and a half months causing the appearance of pancytopenia. IM hydroxocobalamin was then restarted sine die. The definitive diagnosis could only be established at 29 years of age when a genetic evaluation revealed the homozygous c.1115_1116delCA mutation of TCN2 gene (p.Q373GfsX38).
Long-term outcome of a patient with Transcobalamin deficiency caused by the homozygous c.1115_1116delCA mutation in TCN2 gene: a case report
Transcobalamin II is a serum transport protein for vitamin B12. Small variations in TC-II affinity were recently linked to a high homocysteine level and increased frequency of neural tube defects. Complete absence of TC-II or total functional abnormality causes tissue vitamin B12 deficiency resulting in a severe disease with megaloblastic anemia and immunologic and intestinal abnormalities in the first months of life. This condition was described in hereditary autosomal-recessive form. Low serum TC-II without any symptoms or clinical significance was noted in relatives of affected homozygotes. To study 23 members of a four-generation family with hereditary vitamin B12 deficiency and neurologic disorders. Thorough neurologic, hematologic and family studies were supplemented by transcobalamin studies in 20 family members. Partial TC-II deficiency was found in 19 subjects. Apo TC-II (free TC-II unbound to vitamin B12) and total unsaturated B12 binding capacity were low in all tested individuals but one, and holo TC-II (TC-II bound by vitamin B12) was low in all family members. The presentation of the disease was chronic rather than acute. Early signs in children and young adults were dyslexia, decreased IQ, vertigo, plantar clonus and personality disorders. Interestingly, affected children and young adults had normal or slightly decreased serum vitamin B12 levels but were not anemic. Low serum B12 levels were measured in early adulthood. In mid-late adulthood megaloblastic anemia and subacute combined degeneration of the spinal cord were diagnosed. Treatment with B12 injections resulted in a significant improvement. The pedigree is compatible with an autosomal-dominant transmission. This family study suggests a genetic heterogeneity of TC-II deficiency. We report the first family with a hereditary transmitted condition of low serum TC-II (partial TC-II deficiency) associated with neurologic and mental manifestations in childhood. Partial TC-II deficiency may decrease the amount of stored cobalamin, resulting in increased susceptibility to impaired intestinal delivery of cobalamin and predisposing to clinically expressed megaloblastic anemia at a later age. Partial TC-II deficiency should be suspected in families with megaloblastic anemia and in individuals with neurologic and mental disturbances–despite normal serum vitamin B12 levels. Low serum UBBC and apo TC-II should confirm the diagnosis. Early vitamin B12 therapy may prevent irreversible neurologic damage.
Hereditary partial transcobalamin II deficiency with neurologic, mental and hematologic abnormalities in children and adults
Pernicious anemia is still a neglected disorder in many medical contexts and is underdiagnosed in many patients. Pernicious anemia is linked to but different from autoimmune gastritis. Pernicious anemia occurs in a later stage of autoimmune atrophic gastritis when gastric intrinsic factor deficiency and consequent vitamin B12 deficiency may occur. The multifaceted nature of pernicious anemia is related to the important role of cobalamin, which, when deficient, may lead to several dysfunctions, and thus, the proteiform clinical presentations of pernicious anemia. Indeed, pernicious anemia may lead to potentially serious long-term complications related to micronutrient deficiencies and their consequences and the development of gastric cancer and type 1 gastric neuroendocrine tumors. When not recognized in a timely manner or when pernicious anemia is diagnosed with delay, these complications may be potentially life-threatening and sometimes irreversible. The current review aimed to focus on epidemiology, pathogenesis, and clinical presentations of pernicious anemia in an attempt to look beyond borders of medical specialties. It aimed to focus on micronutrient deficiencies besides the well-known vitamin B12 deficiency, the diagnostic approach for pernicious anemia, its long-term complications and optimal clinical management, and endoscopic surveillance of patients with pernicious anemia.
Pernicious Anemia: The Hematological Presentation of a Multifaceted Disorder Caused by Cobalamin Deficiency
Vitamin B12 is synthesized only by certain bacteria and archaeon, but not by plants. The synthesized vitamin B12 is transferred and accumulates in animal tissues, which can occur in certain plant and mushroom species through microbial interaction. In particular, the meat and milk of herbivorous ruminant animals (e.g. cattle and sheep) are good sources of vitamin B12 for humans. Ruminants acquire vitamin B12, which is considered an essential nutrient, through a symbiotic relationship with the bacteria present in their stomachs. In aquatic environments, most phytoplankton acquire vitamin B12 through a symbiotic relationship with bacteria, and they become food for larval fish and bivalves. Edible plants and mushrooms rarely contain a considerable amount of vitamin B12, mainly due to concomitant bacteria in soil and/or their aerial surfaces. Thus, humans acquire vitamin B12 formed by microbial interaction via mainly ruminants and fish (or shellfish) as food sources. In this review, up-to-date information on vitamin B12 sources and bioavailability are also discussed. Impact statement To prevent vitamin B12 (B12) deficiency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify foods that contain high levels of B12. B12 is synthesized by only certain bacteria and archaeon, but not by plants or animals. The synthesized B12 is transferred and accumulated in animal tissues, even in certain plant tissues via microbial interaction. Meats and milks of herbivorous ruminant animals are good sources of B12 for humans. Ruminants acquire the essential B12 through a symbiotic relationship with bacteria inside the body. Thus, we also depend on B12-producing bacteria located in ruminant stomachs. While edible plants and mushrooms rarely contain a considerable amount of B12, mainly due to concomitant bacteria in soil and/or their aerial surfaces. In this mini-review, we described up-to-date information on B12 sources and bioavailability with reference to the interaction of microbes as B12-producers.
Vitamin B 12 sources and microbial interaction
Context: The clinical consequences of excess vitamin B12 induced by multiple oral doses of cyanocobalamin are not well-known. Case details: A young woman was treated with multiple daily doses of 1 mg of cyanocobalamin for severe pernicious anemia. After a total dose of 12 mg, she developed acne, palpitations, anxiety, akathisia, facial ruddiness, headache, and insomnia. She improved two weeks after stopping the drug. There were no sequelae nor complications.
Toxicity induced by multiple high doses of vitamin B 12 during pernicious anemia treatment: a case report
In the UK vitamin B12 deficiency occurs in approximately 20% of adults aged >65 years. This incidence is significantly higher than that among the general population. The reported incidence invariably depends on the criteria of deficiency used, and in fact estimates rise to 24% and 46% among free-living and institutionalised elderly respectively when methylmalonic acid is used as a marker of vitamin B12 status. The incidence of, and the criteria for diagnosis of, deficiency have drawn much attention recently in the wake of the implementation of folic acid fortification of flour in the USA. This fortification strategy has proved to be extremely successful in increasing folic acid intakes pre-conceptually and thereby reducing the incidence of neural-tube defects among babies born in the USA since 1998. However, in successfully delivering additional folic acid to pregnant women fortification also increases the consumption of folic acid of everyone who consumes products containing flour, including the elderly. It is argued that consuming additional folic acid (as ‘synthetic’ pteroylglutamic acid) from fortified foods increases the risk of ‘masking’ megaloblastic anaemia caused by vitamin B12 deficiency. Thus, a number of issues arise for discussion. Are clinicians forced to rely on megaloblastic anaemia as the only sign of possible vitamin B12 deficiency? Is serum vitamin B12 alone adequate to confirm vitamin B12 deficiency or should other diagnostic markers be used routinely in clinical practice? Is the level of intake of folic acid among the elderly (post-fortification) likely to be so high as to cure or ‘mask’ the anaemia associated with vitamin B12 deficiency?
Folate and vitamin B12: friendly or enemy nutrients for the elderly
Schwann cells (SCs) are constituents of the peripheral nervous system. The differentiation of SCs in injured peripheral nerves is critical for regeneration after injury. Methylcobalamin (MeCbl) is a vitamin B12 analog that is necessary for the maintenance of the peripheral nervous system. In this study, we estimated the effect of MeCbl on SCs. We showed that MeCbl downregulated the activity of Erk1/2 and promoted the expression of the myelin basic protein in SCs. In a dorsal root ganglion neuron-SC coculture system, myelination was promoted by MeCbl. In a focal demyelination rat model, MeCbl promoted remyelination and motor and sensory functional regeneration. MeCbl promoted the in vitro differentiation of SCs and in vivo myelination in a rat demyelination model and may be a novel therapy for several types of nervous disorders.
METHYLCOBALAMIN PROMOTES THE DIFFERENTIATION OF SCHWANN CELLS AND REMYELINATION IN LYSOPHOSPHATIDYLCHOLINE-INDUCED DEMYELINATION OF THE RAT SCIATIC NERVE
Gastric parietal-cell antibody has been detected in the sera of 76 per cent of patients with Addisonian pernicious anemia, in 31 per cent of patients with Hashimoto thyroiditis or spontaneous hypothyroidism, in 24 per cent of patients with thyrotoxicosis, in eight out of 47 patients with chronic iron deficiency anemia in the absence of gross blood loss, in eight out of 21 patients with idiopathic adrenal insufficiency and in five per cent of control subjects.
THE CLINICAL AND PATHOLOGICAL SIGNIFICANCE OF GASTRIC PARIETAL CELL ANTIBODY
The view is taken that in Addisonian pernicious anemia, in certain forms of thyroid disease and in idiopathic adrenal insufficiency there is a genetically determined disorder of immunological tolerance characterized by the production of a multiplicity of antibodies t h a t are precise in their specificity for distinct components of individual tissues.
The pathogenesis of human spontaneous abortion involves a complex interaction of several genetic and environmental factors. The firm association between increased homocysteine concentration and neural tube defects (NTD) has led to the hypothesis that high concentrations of homocysteine might be embryotoxic and lead to decreased fetal viability. There are several genetic polymorphisms that are associated with defects in folate- and vitamin B12-dependent homocysteine metabolism. The methylenetetrahydrofolate reductase (MTHFR) 677C>T and 1298A>C polymorphisms cause elevated homocysteine concentration and are associated with an increased risk of NTD. Additionally, low concentration of vitamin B12 (cobalamin) or transcobalamin that delivers vitamin B12 to the cells of the body leads to hyperhomocysteinemia and is associated with NTD. This effect involves the transcobalamin (TC) 776C>G polymorphism. Importantly, the biochemical consequences of these polymorphisms can be modified by folate and vitamin B12 supplementation. In this review, I focus on recent studies on the role of hyperhomocysteinemia-associated polymorphisms in the pathogenesis of human spontaneous abortion and discuss the possibility that periconceptional supplementation with folate and vitamin B12 might lower the incidence of miscarriage in women planning a pregnancy.
Methylenetetrahydrofolate reductase and transcobalamin genetic polymorphisms in human spontaneous abortion: biological and clinical implications
When treated with a vitamin B12-B6-folate combination, patients with mild cognitive impairment and hyperhomocysteinaemia appear to improve their blood-brain barrier function. They may also stabilise their cognitive status. Further investigations are warranted on the role of blood-brain barrier dysfunction in the pathogenesis of dementia.
VITAMIN B12-B6-FOLATE TREATMENT IMPROVES BLOOD-BRAIN BARRIER FUNCTION IN PATIENTS WITH HYPERHOMOCYSTEINAEMIA AND MILD COGNITIVE IMPAIRMENT
Vitamin B12 concentrations were determined in serum and cerebrospinal fluid (CSF) of 32 controls and 102 patients with dementia. The dementias were classified as Alzheimer’s disease (AD), senile dementia of Alzheimer type (SDAT) and multi-infarct dementia (MID). A substantial number of patients (n = 42) could not be assigned to any of these diagnostic groups, as their dementias were of non-AD/SDAT and non-MID types. They were instead assigned to a group called non ultra descriptum (NUD). CSF B12 correlated significantly with serum B12. There were no statistically significant differences in serum B12 levels between the groups. Although with considerable overlap, CSF B12 concentrations and CSF/serum B12 ratios were significantly lower in the NUD group than in the control group. The NUD group had significantly lower CSF/serum B12 ratios than the group of patients with AD/SDAT. There was significant male predominance in the group of demented patients that had low CSF/serum B12 ratios outside the bivariate reference region. CSF and serum B12 levels appear insufficient as measures of the true brain vitamin B12 status. It may be a more dynamic approach to use the CSF/serum B12 ratio as an indication of transport function across the blood brain barrier, and possibly also across the CSF brain cell barrier.
Vitamin B12 in CSF: reduced CSF/serum B12 ratio in demented men
The present study demonstrated for the first time that ultra-high dose methylcobalamin can significantly prolong survival and retard progression in ALS if administered early.
Ultra-high dose methylcobalamin (E0302) prolongs survival of ALS: Report of 7 years’ randomised double-blind, phase 3 clinical trial
Cobalamin deficiency may cause cognitive deficits and even dementia. In Alzheimer’s disease, the most frequent cause of dementia in elderly persons, low serum levels of vitamin B12, may be misleading. The aim of this work was to characterize the cognitive pattern of B12 deficiency and to compare it with that of Alzheimer’s disease. Nineteen patients with low levels of vitamin B12 were neuropsychologically evaluated before treatment and a year later. Results were compared with those of 10 healthy control subjects. Final results suggest that there is a different pattern in both diseases. Twelve elderly patients with dementia improved with treatment. Seven elderly demented patients did not improve; they deteriorated after 1 year although their levels of cobalamin were normal. Analysis of the initial evaluation showed that the 2 groups of patients had a different neuropsychological profile. The group that improved had initially more psychotic problems and more deficits in concentration, visuospatial performance, and executive functions. They did not show language problems and ideomotor apraxia, which were present in the second group. Their memory pattern was also different. These findings suggest that cobalamin deficiency may cause a reversible dementia in elderly patients. This dementia may be differentiated from that of Alzheimer’s disease by a thorough neuropsychological evaluation.
Neuropsychology of vitamin B12 deficiency in elderly dementia patients and control subjects
A previously healthy 7-year-old Caucasian boy was hospitalised for evaluation of acute ataxia and failure to thrive, initially suspicious for an intracranial mass. Weight and body mass index were below the third percentile and he demonstrated loss of joint position and vibratory sense on examination. Laboratory studies revealed megaloblastic anaemia while an initial MRI of the brain showed no evidence of mass lesions or other abnormalities. A dietary history revealed the child subscribed to a restrictive vegan diet with little to no intake of animal products or other fortified foods. The child was diagnosed with presumed vitamin B12 deficiency and was treated with intramuscular B12 injections. Neurological symptoms resolved promptly within several days after starting therapy. This case underlines the importance of assessing nutritional status in the evaluation of neurological dysfunction in the pediatric patient.
Vitamin B12 deficiency presenting as acute ataxia
Allergic reactions to proprietary preparations of vitamin B12 might be due to substances added to the solutions as preservatives or for other reasons, to impurities from the production, or to the vitamin B12 itself.
ANAPHYLACTIC REACTION AFTER INJECTION OF VITAMIN B12
Methylmalonate, a specific marker of B12 deficiency, may affect cognition by reducing total brain volume whereas the effect of homocysteine (nonspecific to vitamin B12 deficiency) on cognitive performance may be mediated through increased white matter hyperintensity and cerebral infarcts. Vitamin B12 status may affect the brain through multiple mechanisms.
VITAMIN B12, COGNITION, AND BRAIN MRI MEASURES
Low cobalamin concentrations are common in the elderly. Although only a minority of such persons display clinically obvious symptoms or signs, metabolic data clearly show cellular deficiency of cobalamin in most cases. The evidence suggests that this is not a normal physiologic expression of the aging process. Rather, the elderly seem at increased risk for mild, preclinical cobalamin deficiency. Classical disorders such as pernicious anemia are the cause of this deficiency in only a small proportion of the elderly. A more frequent problem is food-cobalamin malabsorption, which usually arises from atrophic gastritis and hypochlorhydria but other mechanisms seem to be involved in some patients. The diminished absorption should not be viewed as a natural consequence of aging. The partial nature of this form of malabsorption produces a more slowly progressive depletion of cobalamin than does the more complete malabsorption engendered by disruption of intrinsic factor-mediated absorption. The slower progression of depletion probably explains why mild, preclinical deficiency is associated with food-cobalamin malabsorption more often than with pernicious anemia. Decisions about the optimal management of the very common problem of mild, preclinical cobalamin deficiency in the elderly await further clarification of the processes and the complex issues involved, including the possibility that routine nitrous oxide use during surgery, proposed dietary changes, and other practices may further stress the marginal cobalamin status of many elderly people.
Cobalamin, the stomach, and aging
Patients undergoing bariatric surgery must be continuously educated on proper nutrition, the risk of developing significant vitamin B12 deficiency, and the role of supplements in avoiding catastrophic consequences.
Vitamin B12 deficiency in patients undergoing bariatric surgery: preventive strategies and key recommendations
Vitamin B12 deficiency is common in untreated celiac disease, and concentrations should be measured routinely before hematinic replacement. Vitamin B12 concentrations normalize on a gluten-free diet alone, but symptomatic patients may require supplementation.
Vitamin B12 deficiency in untreated celiac disease
Vitamin B(12) abnormalities are common in patients with CD and patients with a prior ileal or ileocolonic resection are at particular risk. Routine screening for B(12) deficiency in patients with CD is warranted.
Prevalence of and risk factors for vitamin B(12) deficiency in patients with Crohn’s disease
Vitamin B-12 deficiency is often associated with cognitive deficits. Here we review evidence that cognition in the elderly may also be adversely affected at concentrations of vitamin B-12 above the traditional cutoffs for deficiency. By using markers such as holotranscobalamin and methylmalonic acid, it has been found that cognition is associated with vitamin B-12 status across the normal range. Possible mediators of this relation include brain atrophy and white matter damage, both of which are associated with low vitamin B-12 status. Intervention trials have not been adequately designed to test whether these associations are causal. Pending the outcome of better trials, it is suggested that the elderly in particular should be encouraged to maintain a good, rather than just an adequate, vitamin B-12 status by dietary means.
Vitamin B-12 and cognition in the elderly
Higher rates of deficiency were reported among vegans compared with vegetarians and among individuals who had adhered to a vegetarian diet since birth compared with those who had adopted such a diet later in life. The main finding of this review is that vegetarians develop B12 depletion or deficiency regardless of demographic characteristics, place of residency, age, or type of vegetarian diet. Vegetarians should thus take preventive measures to ensure adequate intake of this vitamin, including regular consumption of supplements containing B12.
How prevalent is vitamin B(12) deficiency among vegetarians?
In large surveys in the United States and the United Kingdom, approximately 6% of those aged > or =60 y are vitamin B-12 deficient (plasma vitamin B-12 < 148 pmol/L), with the prevalence of deficiency increasing with age. Closer to 20% have marginal status (plasma vitamin B-12: 148-221 pmol/L) in later life. In developing countries, deficiency is much more common, starting in early life and persisting across the life span. Inadequate intake, due to low consumption of animal-source foods, is the main cause of low serum vitamin B-12 in younger adults and likely the main cause in poor populations worldwide; in most studies, serum vitamin B-12 concentration is correlated with intake of this vitamin. In older persons, food-bound cobalamin malabsorption becomes the predominant cause of deficiency, at least in part due to gastric atrophy, but it is likely that most elderly can absorb the vitamin from fortified food.
How common is vitamin B-12 deficiency?
The proposed algorithm, which combines erythrocyte folate, serum folate, holotranscobalamin and methylmalonic acid, but eliminate B12 and tHcy measurements, is a useful alternative for vitamin B12 deficiency screening in an elderly institutionalized cohort.
Algorithm for the early diagnosis of vitamin B12 deficiency in elderly people
Serum holoTC in healthy elderly men shows the same distribution as earlier described for a younger reference population. In this group of elderly subjects, holoTC did not correlate to reduced renal function. Thus, holoTC appears to be a promising tool for evaluating cobalamin status also in elderly populations.
Holotranscobalamin is not influenced by decreased renal function in elderly men: the MrOS Sweden study
In the general population, the main causes of cobalamin deficiency are pernicious anemia and food-cobalamin malabsorption. Food-cobalamin malabsorption syndrome, which has only recently been identified, is a disorder characterized by the inability to release cobalamin from food or its binding proteins. This syndrome is usually caused by atrophic gastritis, related or unrelated to Helicobacter pylori infection, and long-term ingestion of antacids and biguanides. Besides these syndromes, mutations in genes encoding endocytic receptors involved in the ileal absorption and cellular uptake of cobalamin have been recently uncovered and explain, at least in part, the hereditary component of megaloblastic anemia. Management of cobalamin deficiency with cobalamin injections is currently well codified, but new routes of cobalamin administration (oral and nasal) are being studied, especially oral cobalamin therapy for food-cobalamin malabsorption.
An update on cobalamin deficiency in adults
Studies performed on the nutritional status of the Spanish population have been very heterogeneous with respect to methodology, sample size, geographical location, socio-economic level and health status of the subjects involved. In order to gain an overall view of the state of knowledge in this area, a meta-analysis was performed on the results of all such studies undertaken in Spain between 1990 and 1999.
Vitamin status in different groups of the Spanish population: a meta-analysis of national studies performed between 1990 and 1999
Sixty-three articles reporting on studies from 15 European countries were selected. Low folate intakes were observed in Norway, Sweden, Denmark and the Netherlands. Low intakes of vitamin B12 were not common and only seen in one small Greek study. In the countries with a low intake of folate, the recommended levels were generally not achieved, which was also reflected in the folate status. Vitamin B12 intake was not strongly associated with the vitamin B12 status, which can explain why in the Netherlands and Germany the vitamin B12 status was inadequate, despite sufficient intake levels. In countries with a low folate intake in particular, the Hcy concentration was higher than ideal.
Dietary intake and status of folate and vitamin B12 and their association with homocysteine and cardiovascular disease in European populations
Food-cobalamin malabsorption is marked by the inability to release cobalamin from food, which therefore cannot be taken up by intrinsic factor for absorption. The defect is not detectable by classical clinical tests like the Schilling test which are all based on the absorption of free, crystalline cobalamin. Tests of food-cobalamin absorption have been devised, the most popular ones using cobalamin bound to eggs or to chicken serum. The disparity between the abnormal results of these tests and the normal results with the Schilling test defines the disorder of food-cobalamin malabsorption. Release of cobalamin from food requires acid and pepsin, and most food-cobalamin malabsorptive states can be traced to gastric defects. However, other mechanisms may also play a role. The malabsorption is limited to food cobalamin and any free cobalamin, presumably including recycled biliary cobalamin, will be absorbed normally, which may explain its frequently insidious nature. The effect on cobalamin status covers a broad spectrum. At one extreme, some individuals, perhaps in the earliest stages, have normal cobalamin status, while at the other extreme may be found deficiency every bit as severe as in the most florid case of pernicious anaemia. Most often, however, the deficiency is mild, frequently marked by only a low serum cobalamin level, mild evidence of metabolic insufficiency and, sometimes, minimal clinical sequelae. Moreover, in some cases the gastric defect progresses and intrinsic factor secretion is affected, thus transforming into classical pernicious anaemia; this is not inevitable, however, and probably occurs in only a minority of patients. The course of food-cobalamin malabsorption is therefore a varied one. Nevertheless, it may be the most common cause of subtle or mild cobalamin deficiency and it is also sometimes associated with severe deficiency. Its identification and treatment need to be considered more widely in the clinical setting.
Malabsorption of food cobalamin
Vitamin B12 level was negatively associated with the severity of negative symptoms (r = -0.406, p = 0.002), while folate level negatively correlated with general psychopathology score (r = -0.365, p = 0.006) in PANSS. These results indicate that the severity of one-carbon metabolism alterations and HDL deficiency might be associated with family history of schizophrenia and cannabis abuse. Lower vitamin B12 and folate along with elevated Hcy may influence the severity of FES psychopathology.
Elevated homocysteine level in first-episode schizophrenia patients–the relevance of family history of schizophrenia and lifetime diagnosis of cannabis abuse
Coronary artery disease (CAD) has been increasing alarmingly in India. We had earlier shown that vitamin B12 deficiency is associated with CAD in Indian population. However, only about a quarter of the total vitamin B12 is internalised in the cells by the proteins transcobalamin II. Vitamin B12-bound transcobalamin II (holotranscobalamin, holoTC) is thus referred to as biologically active B12. In this study, we ascertained the levels of holoTC in 501 CAD cases and 1253 healthy controls and for the first time show that holoTC levels are significantly lower (p = 2.57E-4) in CAD (26.81 pmol/l) cases as compared to controls (29.97 pmol/l).
Low holo-transcobalamin levels are prevalent in vegetarians and is associated with coronary artery disease in Indian population
A 90-year-old woman with orthostatic hypotension and near-syncope was found to have a low-normal level of vitamin B(12) and no other medical findings that could explain her orthostasis. Her symptoms responded to vitamin B(12) replacement therapy. This case shows that vitamin B(12) deficiency can induce orthostatic hypotension and syncope that are correctable by vitamin B(12) replacement.
Orthostatic hypotension as a manifestation of vitamin B12 deficiency
Sixty-five patients with thalamic pain were randomly divided into two group: 33 patients received the combined treatment with duloxetine capsule 40 mg·d-1 and mecobalamin tablets 1 500 μg·d-1 (combined-treatment group), and 32 patients of controls received duloxetine capsule 40 mg·d-1(control group). There was significant difference in visual analogue scale (VAS) of the combined-treatment group before and after the treatment with no difference in the control group. There was significant difference in VAS and clinical cure rate (67% vs 34%) between the two group after the treatment. The adverse reactions rate of the combined-treatment group and the control group was 12% and 12%, respectively. The curative effect of combined treatment with duloxetine and mecobalamin is better than that of duloxetine single used.
Clinical study on combined treatment of thalamic pain using duloxetine and mecobalamin
A high prevalence of low levels of cobalamin had been found in a survey of multi-ethnic normal individuals in Israel. The purpose of this study was to investigate the incidence of cobalamin deficiency among Israeli couples suffering from infertility. All couples seen at the in vitro fertilization clinic at an urban hospital (Shaare Zedek Medical Center) in Jerusalem for a 6-month period were invited. Mean cobalamin levels were 259.2 pg ml(-1) in males and 275.1 pg ml(-1) in females (normal >200 pg ml(-1)), 35.5% of 172 men and 23.3% of 223 females had cobalamin deficiency (P = 0.01). There were 171 couples with complete demographic questionnaires and cobalamin values for each partner. In 74 couples (43.3%), one partner was cobalamin deficient, with no significant difference between those with unexplained infertility versus those with explained infertility; and in 13 couples, both partners were cobalamin deficient. Thirty-nine per cent of all men with an abnormal semen analysis had cobalamin deficiency, a finding that requires further investigation. This study questions whether higher rates of male infertility in Israel are partially ascribable to cobalamin deficiency. Recommendation for supplementation in both males and females to achieve high-normal levels of cobalamin would be prudent.
Prevalence of low serum cobalamin in infertile couples
Methylcobalamin (CH3-B12) was administrated in a dose of 6 mg per day (group A, 16 cases) or 12 mg per day (group B, 23 cases) for 16 weeks to patients with oligozoospermia. There was no difference between group A and group B regarding vitamin B12 concentrations in the serum or seminal fluid. CH3-B12 appeared to be transported to seminal fluid very efficiently. However, results from group A and group B did not differ with respect to this parameter. The efficacy rate for group A was 37.5% and that for group B was 39.1%. From these results, it was concluded that a long-term, high dose treatment of CH3-B12 was useful for the treatment of patients with oligozoospermia.
Studies on the usefulness of a long-term, high-dose treatment of methylcobalamin in patients with oligozoospermia
The results of this study suggest that lower vitamin B12 levels are associated with abnormal cervical cytology. It is recommended that women should consume not only folate-rich foods such as fruits and vegetables but also vitamin B12-rich foods such as meat, fish, milk products and eggs in a balanced way.
Folate and vitamin B12 levels in abnormal pap smears: a case control study
An oligomenorrheic infertile patient with evidence of vitamin B12 (cobalamin) deficiency is described. Treatment consisted of clomiphene citrate, human chorionic gonadotropin (hCG), conjugated estrogens, dexamethasone, and ferrous sulfate. Pregnancy occurred after 1,000 micrograms of vitamin B12 was added to the treatment regimen. We believe the patient’s infertility was in part related to the megaloblastic anemia. A possible correlation between vitamin B12 deficiency and failure to ovulate is presented.
Vitamin B12 deficiency and infertility: report of a case
The classic oral manifestations of vitamin B(12) deficiency are considered nonspecific. We describe 4 patients with oral linear lesions associated with vitamin B(12) deficiency. Patients were free of neurologic symptoms and anemia at diagnosis. We believe that glossitis with linear lesions is an early clinical sign of vitamin B(12) deficiency. We recommend the determination of vitamin B(12) in such patients, even in the absence of anemia.
Glossitis with linear lesions: an early sign of vitamin B12 deficiency
This report describes the clinical and histologic features of a case of megaloblastic anemia, resulting from a gastric bypass operation, in which oral symptoms were the first significant finding. Although this case appears to be the first of its type reported in the literature, the potential for future cases is increasing with the increased use of the gastric bypass operation in the treatment of morbid obesity.
Megaloblastic anemia with oral lesions: A consequence of gastric bypass surgery
Recurrent nonspecific stomatitis may be an oral sign of pernicious anemia. Repeated examinations and blood studies are important when the cause of stomatitis is not clear on initial evaluation of a complaint of sore mouth. Three cases of pernicious anemia are presented to illustrate the similarities and differences in oral signs of pernicious anemia.
Nonspecific stomatitis—A presenting sign in pernicious anemia
Glossitis and glossodynia are commonly seen by the dental practitioner. The awareness that these symptoms in conjunction with other oral signs indicate pernicious anemia is important for the clinician. Correct diagnosis can be made, and neurological complications avoided. Two case reports are presented and typical oral and systemic features of pernicious anemia are discussed.
Pernicious anemia with associated glossodynia
A case of pernicious anemia is reported in a 24-year-old black woman whose presenting complaint was burning erythematous macules of the buccal and labial mucosa. Glossitis was not a prominent sign. Diagnosis was delayed 1 year while the patient was treated for allergic stomatitis. An erythematous lesion was biopsied and the histologic characteristics of the mucosal epithelium are described and related to previous studies.
Clinical and histologic changes of the oral mucosa in pernicious anemia
The spectrum of etiologies associated with macrocytic anemia includes nutritional deficiencies (e.g., vitamin B12 and folate), drugs, primary bone marrow disorders (e.g., myelodysplasia and leukemia) and other chronic illnesses. Macrocytosis due to vitamin B12 or folate deficiency is a direct result of ineffective or dysplastic erythropoiesis. These important vitamins and cofactors are required for normal maturation of all cells. Marrow erythroblasts are no exception. When either of these two factors is deficient, RBC proliferation and maturation result in large erythroblasts with nuclear/cytoplasmic asynchrony. These abnormalities are caused by a defect in DNA synthesis that interferes with cellular proliferation and maturation. RNA synthesis and cytoplasmic components remain relatively unaffected. The marrow is hypercellular with all forms of the myeloid cell line being increased and erythroid elements being dominant on the marrow aspirate smear preparations. The erythroblasts become large, oval shaped and contain a characteristic immature, lacy nucleus. These bone marrow features are called “megaloblastic” and are highly suspicious of a vitamin B12 or folate deficiency. Megaloblastoid (megaloblastic-like) abnormalities of the marrow are frequently seen in other hematologic disorders not associated with vitamin B12 or folate deficiency, (e.g., myelodysplasia and leukemia) and a careful examination of the bone marrow is necessary to make this distinction.
Megaloblastic Anemia and Other Causes of Macrocytosis
The oral manifestations of glossitis, stomatitis and mucosal ulceration in vitamin B12 deficiency have long been recognised. These oral changes may occur in the absence of symptomatic anaemia or of macrocytosis. The aim of this paper is to describe a retrospective study of the wide range of oral signs and symptoms reported by 14 patients found to have a previously undiagnosed vitamin B12 deficiency. None of the patients described in this study had generalised symptoms sufficiently advanced to arouse suspicions of vitamin B12 deficiency. The essential criteria for the diagnosis of pernicious anaemia are also discussed.
Oral signs and symptoms in patients with undiagnosed vitamin B12 deficiency
Atrophic glossitis is often linked to an underlying nutritional deficiency of iron, folic acid, vitamin B12, riboflavin, or niacin and resolves with correction of the underlying condition.
Common tongue conditions in primary care
The use of H(2)-receptor antagonists and/or PPIs may impair the absorption of protein-bound dietary vitamin B(12) and could contribute to the development of vitamin B(12) deficiency with prolonged use. Patients taking these medications for extended periods of time, particularly >4 years, should be monitored for vitamin B(12) status.
Vitamin B(12) deficiency associated with histamine(2)-receptor antagonists and a proton-pump inhibitor
The first case of cobalamin deficiency with megaloblastic anaemia in a patient under long-term omeprazole therapy is presented. This patient received omeprazole at a daily dose of 40-60 mg for 4 years as treatment for a gastro-oesophagal reflux complicated by peptic oesophagitis. Seric vitamin B12 was dramatically decreased at 80 pmol L-1. The Schilling test was normal (13%) with crystalline [57Co] cobalamin and it was at 0% with [57Co] cobalamin-labelled trout meat. All other assimilation tests were normal except an expiratory hydrogen breath test performed with lactulose. The haematological status was restored after intramuscular treatment with cobalamin. In conclusion, prolonged omeprazole therapy can be responsible for a cobalamin deficiency due to protein-bound cobalamin malabsorption.
Cobalamin deficiency with megaloblastic anaemia in one patient under long-term omeprazole therapy
Thirty patients with a wide range of sore mouth that led to the diagnosis of iron deficiency in 12 patients, pernicious anemia in 8 patients, combined deficiency of iron and vitamin B12 in 2 patients, and anemia of chronic disease in 8 patients were investigated. The oral signs and symptoms included glossitis, glossodynia, angular cheilitis, recurrent oral ulcer, oral candidosis, diffuse erythematous mucositis, and pale oral mucosa. The values of hemoglobin in 30 patients varied from normal to severe life-threatening levels, but none had developed generalized symptoms sufficiently advanced to arouse suspicions of anemia before they visited the Oral Medicine Clinic. The aim of this paper is to describe a retrospective study of 30 patients with oral changes as the initial manifestation of nutritional deficiency or anemia of chronic diseases. Improved diagnosis and classification of anemia based on the mean and heterogeneity of red cell size will be discussed.
Initial diagnosis of anemia from sore mouth and improved classification of anemias by MCV and RDW in 30 patients
A 69-year-old Japanese woman presented with a 4-week history of painful tongue and reduced sense of taste. On physical examination, she had a smooth, red tongue without dorsal papillae, suggestive of glossitis. Results from laboratory tests were consistent with macrocytosis without anemia: mean corpuscular volume 104.9 (normal range 80–97) fL, hemoglobin 121 (normal range 110–165) mmol/L, iron 10.92 (normal range 8.95–26.85) μmol/L, ferritin 72 (normal range 5–157) μg/L and serum vitamin B12 77.49 (normal range 147.6–442.8) pmol/L. In addition, an endoscopic biopsy of her gastric mucosa showed atrophic gastritis, and the result from a test for the presence of serum anti-intrinsic antibodies was positive. We diagnosed pernicious anemia.
Pernicious anemia presenting as glossitis
Hypercoagulability due to raised homocysteine levels may lead to fetal loss when vitamin B12 deficiency first develops. A more prolonged deficiency results in infertility by causing changes in ovulation or development of the ovum or changes leading to defective implantation.
Vitamin B12 deficiency, infertility and recurrent fetal loss
The mainstay for cobalamin deficiency is correction of the underlying disorder and replacement therapy. Because the defect is often one of absorption, parenteral or intranasal routes are recommended. In most cases, replacement therapy is all that is needed. The vitamin preparation most commonly used is cyanocobalamin (also called vitamin B12), which has no known physiologic role but instead is converted to a biologically active form before it can be used by tissues. The studies reviewed in this article clearly show that omeprazole therapy will decrease the absorption of vitamin B12 by preventing its cleavage from dietary proteins. However, these data are insufficient to infer that clinically significant deficiency will occur over time. In fact, some of the studies suggest that the simple addition of juices or other acidic drinks into the diet may dramatically increase cobalamin absorption. Clearly, well-designed clinical trials are needed to evaluate this theory over an extended follow-up period to determine the clinical significance of omeprazole-associated vitamin B12 deficiency and possibly identify patients at risk for deficiency. In conclusion, the possibility of dietary vitamin B12 malabsorption should be considered in patients receiving chronic omeprazole treatment and presenting with signs and symptoms of deficiency. All healthcare workers should be made aware of the potential clinical complications of omeprazole-associated vitamin B12 deficiency since it may go unrecognized and is easily corrected. This is particularly relevant for elderly patients with poor dietary intake of vitamin B12, impaired vitamin B12 stores, and certain gastrointestinal disorders.
Omeprazole and vitamin B12 deficiency
Glossodynia, or painful sensation of the tongue, can have a spectrum of etiologies, such as local infection, trauma, nerve damage, glossitis, or the enigmatic neuropathic pain syndrome, burning mouth disorder (BMD; also known as burning mouth syndrome). Careful history-taking, physical examination, and appropriate laboratory screening can differentiate these causes of glossodynia and direct further therapy.
Atrophic Glossitis From Vitamin B12 Deficiency: A Case Misdiagnosed as Burning Mouth Disorder
A 73-year-old woman presented with several months of glossodynia having previously been diagnosed by her primary care physician with primary BMD. Subsequently, she consulted an otolaryngologist, who pursued further diagnostic evaluation.
Examination revealed the presence of a beefy, red, smooth tongue, and further laboratory evaluation yielded a low serum vitamin B12 level and macrocytosis. Three months of oral vitamin B12 supplementation led to partial restoration of serum vitamin B12 levels and a modest improvement in symptoms. Her final diagnoses were atrophic glossitis and glossodynia secondary to vitamin B12 deficiency, most likely due to pernicious anemia.
The results of this case have important clinical implications for the diagnostic evaluation and management of patients with glossodynia and apparent BMD. Pathogenic mechanisms of nutrient deficiency in atrophic glossitis are discussed.
A review of the clinical findings in six infants with nutritional vitamin B12 deficiency seen during the last 10 years was undertaken and an attempt made to obtain long-term neurologic follow-up. There was a consistent clinical pattern in vitamin B12-deficient infants; irritability, anorexia, and failure to thrive were associated with marked developmental regression and poor brain growth. Two of the four patients who qualified for long-term review had a poor intellectual outcome. Although early response to treatment is satisfying, the long-term consequences of nutritional vitamin B12 deficiency in infants emphasize the need for prevention or early recognition of this syndrome.
Long-term neurologic consequences of nutritional vitamin B12 deficiency in infants
Despite limitations, this case may underline the observation that mood disorders with psychotic features especially with accompanying extrapyramidal symptoms lacking a clear etiology may be rare manifestation of vitamin B12 and/or folate deficiency in children and adolescents and be potentially amenable to treatment.
Mood disorder with mixed, psychotic features due to vitamin b12 deficiency in an adolescent: case report
The photodecomposition of methylcobalamin has been studied in aqueous solution at different oxygen concentrations. In the presence of excess oxygen methylcobalamin is photolyzed at a rapid rate to yield aquocobalamin and formaldehyde as the major products. On the other hand, photolysis in the presence of only a trace of oxygen is slow and yields vitamin B12, formaldehyde, methane, and ethane. The yield of methanol is small and is not affected to an appreciable extent by the oxygen concentration. At limiting oxygen concentrations many side reactions take place which probably lead to modification of the corrin nucleus.
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It is clear that photolysis of methylcobalamin in the presence of only a trace of oxygen is very complex. At moderate light intensities the rate of photolysis is very low, probably due to the recombination of vitamin B12 and the methyl radical. The aqueous solvent may affect the photolysis by providing a “solvent cage” around the photolyzed molecule and thus favor recombination of the radicals (Hammond and Turro, 1963). At high light intensity many side reactions occur, and more than 30% of the radioactivity cannot be accounted for. The results presented above indicate that anaerobic photolysis of the alkylcobalamins does not only yield vitamin B12 but several alkylated vitamin B12 derivatives.
THE PHOTOLYSIS OF METHYLCOBALAMIN
This Perspective Article highlights recent theoretical developments, and summarizes the current understanding of the photolytic properties of cobalamins from a computational point of view. The primary focus is on two alkyl cobalamins, methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), as well as two non-alkyl cobalamins, cyanocobalamin (CNCbl) and hydroxocobalamin (HOCbl). Photolysis of alkyl-cobalamins involves low-lying singlet excited states where photodissociation of the Co-C bond leads to formation of singlet-born alkyl/cob(II)alamin radical pairs (RPs). Potential energy surfaces (PESs) associated with the low-lying excited states as a function of both axial bonds, provides the most reliable tool for initial analysis of the photochemical and photophysical properties of cobalamins. Due to the complexity, and size limitations associated with the cobalamins, the primary method for calculating ground state properties is density functional theory (DFT), while time-dependent DFT (TD-DFT) is used for electronically excited states. For alkyl cobalamins, energy pathways on the lowest singlet surface, connecting metal-to-ligand charge transfer (MLCT) and ligand field (LF) minima, can be associated with photo-homolysis of the Co-C bond observed experimentally. Additionally, energy pathways between minima and seams associated with crossing of S1 /S0 surfaces, are the most efficient for internal conversion (IC) to the ground state. Depending on the specific cobalamin, such IC may involve simultaneous elongation of both axial bonds (CNCbl), or detachment of axial base followed by corrin ring distortion (MeCbl). The possibility of intersystem crossing, and the formation of triplet RPs is also discussed based on Landau-Zener theory.
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The photo-homolysis of the Co-C bond in alkyl cobalamins, such as MeCbl or AdoCbl, was first noted fifty years ago. Since then, the ability to generate radicals via light has become the subject of vast experimental research. It is now generally accepted that the photolysis of alkyl cobalamins results in formation of cob(II)alamin and alkyl radical pairs, similar to the intermediates from (AdoCbl)-dependent enzymatic catalysis. On the other hand non-alkyl cobalamins are generally photostable, with HOCbl being the exception, when using short wavelength excitations, which generate hydroxyl radicals. The photolysis of cobalamins depends upon a number of factors, such as the nature of both axial ligands, the local environment, and the excitation wavelengths applied. The mechanisms of photolysis at the molecular level represent a complex problem, and only recently has it become possible to use computational methods to understand the photolytic properties of cobalamins, and provide a detailed comparison with experiment. Preliminary results for the four cobalamins in this Perspective are very promising, and provide a more in-depth understanding of recent experimental results.
PHOTOLYTIC PROPERTIES OF COBALAMINS: A THEORETICAL PERSPECTIVE
Because of the interdependence of folate and cobalamin (vitamin B12) metabolism, megaloblastic anemia is also a frequent clinical expression of cobalamin deficiency (present in 70–80% of cases of deficiency). Indeed, DNA synthesis is impaired by low vitamin B12, which hampers the activation of folate and, as a result, decreases normal red blood cell production, impairing oxygen delivery.
Vitamins and Minerals for Energy, Fatigue and Cognition: A Narrative Review of the Biochemical and Clinical Evidence
Deficiencies in cobalamin (vitamin B12) can result in diminished energy and exercise tolerance, together with fatigue and shortness of breath. These hematologic symptoms regress and disappear with supplementation with vitamin B12, for which doses and routes will depend on the cause and severity of deficiency.
Cobalamin (vitamin B12) deficiency induces neurological dysfunction, including myelopathy, neuropathy and neuropsychiatric abnormalities. Such neurological damage has been reported in 20–30% of cases of vitamin B12 deficiency, and can even occur before serum vitamin B12 concentrations reach a level that would be considered deficient by standard criteria. It is likely due to progressive neuronal degeneration, due to the inhibition of methionine synthase. In addition, deficiencies in vitamin B12 are associated with mental and cognitive impairment, such as irritability, memory loss, depression, and cognitive disturbances up to dementia.
Our preliminary results suggest a relationship between vitamin B12 deficiency and increased levels of fatigue and depression in lacunar stroke patients. If these findings could be replicated in a larger and general stroke sample, this would open treatment options and may improve quality of life after stroke.
Association of vitamin B12 deficiency with fatigue and depression after lacunar stroke
H2RAs have the potential to cause vitamin B12 deficiency. This may be important in patients with inadequate stores of vitamin B12 (e.g., poor diet), particularly those receiving H2RA therapy continuously for more than two years. Healthcare providers should be aware of this potential adverse effect.
Effect of histamine H2-receptor antagonists on vitamin B12 absorption
A mechanism of Co−C bond photolysis in the base-off form of the methylcobalamin cofactor (MeCbl) and the influence of its axial base on Co−C bond photo-dissociation has been investigated by time-dependent density functional theory (TD-DFT). At low pH, the MeCbl cofactor adopts the base-off form in which the axial nitrogenous ligand is replaced by a water molecule. Ultrafast excited-state dynamics and photolysis studies have revealed that a new channel for rapid nonradiative decay in base-off MeCbl is opened, which competes with bond dissociation. To explain these experimental findings, the corresponding potential energy surface of the S 1 state was constructed as a function of Co−C and Co−O bond distances, and the manifold of low-lying triplets was plotted as a function of Co−C bond length. In contrast to the base-on form of MeCbl in which two possible photodissociation pathways were identified on the basis of whether the Co−C bond (path A) or axial Co−N bond (path B) elongates first, only path B is active in base-off MeCbl. Specifically, path A is inactive because the energy barrier associated with direct dissociation of the methyl ligand is higher than the barrier of intersection between two different electronic states: a metal-to-ligand charge transfer state (MLCT), and a ligand field state (LF) along the Co−O coordinate of the S 1 PES. Path B initially involves displacement of the water molecule, followed by the formation of an LF-type intermediate, which possesses a very shallow energy minimum with respect to the Co−C coordinate. This LF-type intermediate on path B may result in either S 1 /S 0 internal conversion or singlet radical pair generation. In addition, intersystem crossing (ISC) resulting in generation of a triplet radical pair is also feasible.
Mechanism of Co−C Bond Photolysis in Methylcobalamin: Influence of Axial Base
As 2% of the general population are carriers of inherited methylmalonic acidemia, Rasmussen and Nathan examined the urinary excretion of MMA in patients with methylmalonic acidemia. They found urinary MMA levels to range from 1.18 to 2.48 mm01 per mol of creatinine (reference range 0.58 to 3.56). This reveals that heterozygotes for inherited methylmalonic acidemia would not give false-positive results for cobalamin deficiency, and hence testing for urinary MMA remains useful in this subgroup.
URINARY METHYLMALONlC ACID AND COBALAMIN DEFICIENCY IN THE ELDERLY
Antivitamins B 12 represent an important class of vitamin B 12 analogues that have gained recent interest in several research areas. In particular, 4-ethylphenylcobalamin (EtPhCbl) and phenylethynylcobalamin (PhEtyCbl) exemplify two such antivitamins B 12 which have been characterized structurally and chemically. From a spectroscopic point of view, EtPhCbl is photolabile with a very low quantum yield of photoproducts, while PhEtyCbl is incredibly photostable. Herein, DFT and TD-DFT computations are provided to explore the photolytic properties of these compounds to shed light on the electronic properties that are indicative of these differences. Potential energy surfaces (PESs) were constructed to investigate the mechanisms of photo- dissociation leading to radical pair (RP) formation and the mechanisms of deactivation to the ground state. The S 1 PESs for each antimetabolite contain two energy minima, one being the metal-to-ligand charge transfer (MLCT) and another the ligand- field (LF) state. There are two possible pathways for photodissociation that can be identified for EtPhCbl but only one (path B) is energetically feasible and involves the lengthening of the Co−N Im bond through the MLCT region followed by the lengthening of the Co−C bond through the LF region. For PhEtyCbl, there is not an energetically favorable path for photolysis; rather, internal conversion (IC) is the significantly preferred photophysical event.
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In conclusion, we have provided a theoretical analysis of the photolytic properties of two newly characterized non-natural cobalamins. These theoretical results provide insights into the electronic structure of the lowest excited state, which directly determines photolability and conversely photostability of the investigated antivitamins. There are two pathways for photolysis, and based on energetics, an optimum path can be determined. EtPhCbl (Im-[Co III (corrin)]-EtPh + ) can photo- dissociate via path B through the LF state with a substantially elongated axial base, although the quantum yield of photo- products is low. Similarly for PhEtyCbl (Im-[Co III (corrin)]- PhEty + ), two pathways can be identified; however, neither are energetically feasible for Co−C bond photolysis, thus explain- ing the incredible photostability of this antimetabolite. These results for the model complexes have important implications for understanding experimental results. As a result of the overwhelming energetic favorability for IC, PhEtyCbl is photostable. In contrast, for EtPhCbl, there is a competition of sorts between IC and photodissociation as the energetic barriers are comparable. It is not surprising that EtPhCbl and PhEtyCbl both exhibit difficulty in dissociating the upper axial ligand as these cobalamins have been shown to be metabolically inert. Photohomolysis of the Co−C bond will result in a photoactive metabolite with potential medicinal applications. In addition, the results gathered in this study are of particular importance especially as more applications for synthetic vitamin-B 12 derivatives continue to be realized.
PHOTOLYTIC PROPERTIES OF ANTIVITAMINS B12
Vitamin B12 deficiency is widely prevalent in women of childbearing age, especially in developing countries. In the present study, through dietary restriction, we have established mouse models of severe and moderate vitamin B12 deficiencies to elucidate the impact on body composition, biochemical parameters, and reproductive performance. Female weanling C57BL/6 mice were fed for 4 weeks: (a) control AIN-76A diet, (b) vitamin B12-restricted AIN-76A diet with pectin as dietary fiber (severe deficiency group, as pectin inhibits vitamin B12 absorption), or (c) vitamin B12-restricted AIN-76A diet with cellulose as dietary fiber (moderate deficiency group as cellulose does not interfere with vitamin B12 absorption). After confirming deficiency, the mice were mated with male colony mice and maintained on their respective diets throughout pregnancy, lactation, and thereafter till 12 weeks. Severe vitamin B12 deficiency increased body fat% significantly, induced adiposity and altered lipid profile. Pregnant dams of both the deficient groups developed anemia. Severe vitamin B12 deficiency decreased the percentage of conception and litter size, pups were small-for-gestational-age and had significantly lower body weight at birth as well as weaning. Most of the offspring born to severely deficient dams died within 24 h of birth. Stress markers and adipocytokines were elevated in severe deficiency with concomitant decrease in antioxidant defense. The results show that severe but not moderate vitamin B12 restriction had profound impact on the physiology of C57BL/6 mice. Oxidative and corticosteroid stress, inflammation and poor antioxidant defense seem to be the probable underlying mechanisms mediating the deleterious effects.
Severe but Not Moderate Vitamin B12 Deficiency Impairs Lipid Profile, Induces Adiposity, and Leads to Adverse Gestational Outcome in Female C57BL/6 Mice
B vitamins are enzyme cofactors that play an important role in energy metabolism. The aim of this study was to elucidate whether B vitamin administration can reduce body weight (BW) gain by improving energy metabolism-related enzyme activities in rats fed on a highfat diet. Fifty rats were randomly assigned to one of the following five groups: control group (C), including rats fed on standard rat chow; four treatment groups (HO, HI, H2, and H3), in which rats were fed on a high-fat diet. Rats in the HI group were treated daily with 100 mg/kg BW thiamine (VB1), 100 mg/kg BW riboflavin (VB2), and 250 mg/kg BW niacin (VPP); rats in the H2 group were treated daily with 100 mg/kg BW pyridoxine (VB6), 100 mg/kg BW cobalamin (VB12), and 5 mg/kg BW folate (FA); and rats in the H3 group were treated daily with all of the B vitamins administered to the HI and H2 groups. After 12 weeks, the BW gains from the initial value were 154.5±58.4 g and 159.1±53.0 g in the HI and C groups, respectively, which were significantly less than the changes in the HO group (285.2±14.8 g, P<0.05). In the HO group, the plasma total cholesterol (CHO) and triglyceride (TG) levels were 1.59±0.30 mmol/L and 1,55±0.40 mmol/L, respectively, which were significantly greater than those in the HI group (1.19±0.18 mmol/L and 0.76±0.34 mmol/L, respectively, P<0.05). The activities of transketolase (TK), glutathione reductase, and Na+/K+ adenosine triphosphatase were significantly increased in the B vitamin-treated groups and were significantly greater than those in the HO group (P<0.05). Furthermore, the glucose-6-phosphate dehydrogenase, pyruvic acid kinase, and succinate dehydrogenase activities also were increased after treatment with B vitamins. Supplementation with B vitamins could effectively reduce BW gain and plasma levels of lipids by improving energy metabolism-related enzyme activities in rats, thus possibly providing potential benefits to humans.
B Vitamins Can Reduce Body Weight Gain by Increasing Metabolism-related Enzyme Activities in Rats Fed on a High-Fat Diet
Serum vitamin B12 concentrations were lower among obese adults compared with non-obese adults. After adjustment for age, gender, race/ethnicity, socioeconomic status, dietary and lifestyle factors, use of medications that could affect the serum vitamin B12 levels, dietary supplement use and fasting time, the multivariable-adjusted ORs (95% CIs) of obesity were 1.00 (reference), 0.95 (0.79, 1.14), 0.86 (0.74, 0.99), and 0.71 (0.60, 0.84) (p for trend <0.001) for increasing quartiles of serum vitamin B12 concentrations.
Inverse Association Between Serum Vitamin B12 Concentration and Obesity Among Adults in the United States
Obesity is a worldwide epidemic responsible for 5% of global mortality. The risks of developing other key metabolic disorders like diabetes, hypertension and cardiovascular diseases (CVDs) are increased by obesity, causing a great public health concern. A series of epidemiological studies and animal models have demonstrated a relationship between the importance of vitamin B12 (B12) and various components of metabolic syndrome. High prevalence of low B12 levels has been shown in European (27%) and South Indian (32%) patients with type 2 diabetes (T2D). A longitudinal prospective study in pregnant women has shown that low B12 status could independently predict the development of T2D five years after delivery. Likewise, children born to mothers with low B12 levels may have excess fat accumulation which in turn can result in higher insulin resistance and risk of T2D and/or CVD in adulthood. However, the independent role of B12 on lipid metabolism, a key risk factor for cardiometabolic disorders, has not been explored to a larger extent. In this review, we provide evidence from pre-clinical and clinical studies on the role of low B12 status on lipid metabolism and insights on the possible epigenetic mechanisms including DNA methylation, micro-RNA and histone modifications.
Low Vitamin B12 and Lipid Metabolism: Evidence from Pre-Clinical and Clinical Studies
Increase in body mass index-standard deviation score was associated with a decrease in vitamin B12 levels.
Negative correlation among vitamin B12 levels, obesity severity and metabolic syndrome in obese children: A case control study
Vitamin B12 deficiency is the most common cause of megaloblastic anemia. Vitamin B12 deficiency is caused by insufficient dietary intake, as in the cases of vegetarians or malnutrition, malabsorption due to the absence of intrinsic factor caused by pernicious anemia or following gastric surgery, congenital disorders, such as transcobalamin II deficiency, or exposure to nitrous oxide.
The result of one study, conducted in Japan, indicated that the most common cause of megaloblastic anemia is pernicious anemia (61%), followed by vitamin B12 deficiency due to gastrectomy (34%), vitamin B12 deficiency due to other causes (2%), and folate deficiency (2%). Vitamin B12 is contained in animal foods, and the daily intake is approximately 3‐30 μg. The daily required amount is approximately 1‐3 μg, and except for stomach or intestinal obstruction, or being a strict vegetarian, vitamin B12 deficiency is rare.
Vitamin B12 binds to intrinsic factor secreted by the gastric parietal cells, and it is absorbed in the terminal ileum. Once absorbed, vitamin B12 acts as a coenzyme in the enzymatic reaction that produces methionine from homocysteine. As a result, folic acid is converted into its active form. When vitamin B12 is deficient, active folic acid is also deficient. As a result, the intracellular reaction involving the coenzyme form of folic acid is affected. Thus, not only vitamin B12 but also folate deficiencies impair DNA synthesis. Because a large amount of vitamin B12 is stored in the liver, it takes 5‐10 years for clinical problems to manifest following decreased intake or absorption of vitamin B12.
The signs and symptoms induced by megaloblastic anemia due to vitamin B12 deficiency are fatigue, headache, palpitations, and dyspnea, and neurological symptoms such as dysesthesia and hypoesthesia may also be present. In severe cases, ataxia, decreased proprioception, and vibratory sensation, collectively known as subacute combined degeneration, may be present. Neurologic symptoms are not generally seen in folate deficiency. Vitamin B12 deficiency does not necessarily lead to anemia and macrocytosis. Other symptoms include Hunter’s glossitis and gray hair.
Peripheral blood smear reveals macrocytic anemias and pancytopenia, and hypersegmented neutrophils may be present in severe cases. Megaloblastic changes in erythroblasts and giant metamyelocytes are seen in bone marrow, resulting from impaired nuclear differentiation. Biochemical analysis of blood shows increased levels of indirect bilirubin and lactate dehydrogenase (LDH), and a decreased level of haptoglobin. Vitamin B12 deficiency is treated with parenteral administration of vitamin B12, and hematological levels generally return to normal within one month. For patients with a permanent decrease in the ability to absorb dietary vitamin B12, such as associated with pernicious anemia or total gastrectomy, lifelong treatment is necessary. During hematopoietic recovery, an iron deficiency may develop. Although it is not an established treatment, recently it has been reported that oral treatment is effective, because 1%‐5% of vitamin B12 absorption in the terminal ileum is by passive diffusion, which does not involve intrinsic factor.
Diagnosis and treatment of macrocytic anemias in adults
In humans, vitamin B12 is needed as a cofactor for two reactions: methylcobalamin is the cofactor for the cytoplasmic enzyme, methionine synthase, while adenosylcobalamin is the cofactor for the mitochondrial enzyme, methylmalonyl coenzyme A mutase. Hence, vitamin B12 deficiency results in the accumulation of homocysteine and methylmalonic acid. Cobalamin is essential for DNA synthesis, haematopoiesis and myelination.
Severe vitamin B12 deficiency in a 15-year-old boy: presentation with haemolysis and pancytopenia
In a context of mechanical hemolysis with thrombocytopenia in a patient admitted to the emergency department, very high LDH levels and a low reticulocyte count are strongly suggestive of pseudo-TMA and should prompt the physician to screen for cobalamin deficiency.
Hemolysis and schistocytosis in the emergency department: consider pseudothrombotic microangiopathy related to vitamin B12 deficiency
This paper presents a transient absorption study of the primary photolysis of ethyl- and n-propylcobalamin in water and a comparison of the photolysis of methyl-, ethyl-,n-propyl-, and adenosylcobalamin at two different excitation wavelengths. Excitation of methyl-, ethyl-, and n-propyl cobalamin at 520 nm in the low-lying αβ absorption band results in bond homolysis proceeding via a bound cob(III)alamin MLCT state. Theprincipal distinction between methyl-, ethyl-, andn-propyl-cobalamin lies in the relative stability of this MLCT state, with the terminal alkyl groups in ethyl and n-propyl acting as electron donors to destabilize the partial carbon anion in the MLCT state. The lifetime of the MLCT state is inversely related to the size of the alkyl ligand: 1 ns (methyl), 48 ps (ethyl), 32 ps (n-propyl), and ≤ 14 ps (adenosyl, if the MLCT state is present).Excitation at 400 nm opens a pathway for direct photohomolysis of the carbon-cobalt bond in methyl-, ethyl-, and n-propylcobalamin. This direct dissociation pathway is significant for methylcobalamin, and dominant for ethyl- and n-propylcobalamins. In contrast the photolysis of adenosylcobalamin in aqueous solution is independent of wavelength for excitation at 400 and 520 nm. The photolysis of adenosylcobalamin is also distinguished by the presence of an additional intermediate with a 110 ps lifetime that has no analogue in the other cobalamins studied.
Time-Resolved Spectroscopic Studies of B12Coenzymes: A Comparison of the Primary Photolysis Mechanism in Methyl-,Ethyl-,n-Propyl-, and 5′-Deoxyadenosylcobalamin
Patients with low serum vitamin B12 levels may have no symptoms (yet). Nevertheless, they are at high risk for development of symptoms. There is a tendency among physicians to consider a serum vitamin B12 level higher than 140 pmol/L as normal, but many symptomatic patients may present with such levels, for instance because of taking oral vitamin supplementation. This does not mean that their tissue vitamin B12 levels are normal as well. Methylmalonic acid and homocysteine are not very sensitive biomarkers, but there is currently no good alternative, although systematic evaluation of more advanced metabolic factors may lead to the application of better biomarkers. When serum total vitamin B12 levels are low or questionable, the combination of total vitamin B12, active vitamin B12, MMA, and homocysteine may be the best strategy, but the validity of this combined biomarker approach needs to be validated in larger prospective studies and especially validated against objective markers of treatment response. In case of doubt, when results of biomarker measurements are equivocal, a trial with parenteral hydroxocobalamin injections may be considered, as was done in patients B and D. Because symptom improvement in long-standing (subclinical) vitamin B12 deficiency may take some time, we usually advise a treatment regimen of twice weekly hydroxocobalamin injections for 3 months, after which a thorough reevaluation is performed with systematic evaluation of symptom score as demonstrated in patient B. There is no proof in large prospective, double-blind studies that oral supplementation is as effective in reducing symptoms associated with vitamin B12 deficiency as parenteral treatment.
The Many Faces of Cobalamin (Vitamin B12) Deficiency
In the general population, vitamin B12 insufficiency is a relatively common finding, with an increased incidence with age. The majority of cases result in mild symptoms and are due to FBCM, while pernicious anaemia is much rarer nowadays but is associated with severe deficiency. One of the greatest issues in this area is knowing what ‘normal’ vitamin B12 levels should be and the consequential paucity of diagnostic criteria. Taking into consideration a thorough history and clinical manifestations is therefore paramount. A trial of cobalamin therapy can be very helpful in these cases. In the future, assays for markers such as holotranscobalamin should become available to determine more specifically the cause of the deficit, enabling treatment that is tailored to the patient. In addition, there will hopefully be a shift from injections to daily tablets, a move which should improve patient comfort.
Vitamin B12 deficiency – A 21st century perspective
Evidence has been presented that oral treatment with vitamin B12 cannot replace body stores in patients with Addisonian pernicious anaemia where there is a lack of gastric intrinsic factor due to an autoimmune gastritis causing malabsorption of vitamin B12 or in those who have undergone total gastrectomy or ileal resection. Such patients will require life-long parenteral vitamin B12 therapy.
Cyanocobalamin- a case for withdrawal: discussion paper
If the indiscriminate dumping of industrial cyanide waste continues unchecked with the inherent risk of pollution of food and water supplies there may well come a time when more widespread chronic cyanide neurotoxicity occurs in the Western hemisphere from a dietary source in persons with a genetic or acquired error of cyanide or vitamin B12 metabolism.
Objective: To assess the efficacy and safety of mecobalamin acupoint injection with acupuncture for treating intractable facial paralysis. Methods: Seventy patients with intractable facial paralysis were randomly divided into treatment group and control group, 35 patients in each group.The treatment group was treated with mecobalamin acupoint injection with acupuncture treatment, and the control group with single acupuncture treatment. 40d later,their therapeutic effects were observed. Results: All the results were analyzed on the basis of intention-to-treat (ITT) and per-protocol population (PP), the total effective rate was 77.14% or 81.26% in the treatment group and 51.43% or 56.67% in the control group. There was a statistical difference between the two groups (P0.05). ITT and PP analysis revealed similar results. No adverse effect was found in the observation. Conclusion: The efficacy and safety of mecobalamin acupoint injection with acupuncture for treatment of intractable facial paralysis are definite. It is worthy of spreading in clinic.
Clinical observation of mecobalamin acupoint injection with acupuncture for treating intractable facial paralysis
The forms of vitamin B12 were determined in foods, most of which had been prepared for consumption. 2. Five forms were detected: adenosylcobalamin, hydroxocobalamin, methylcobalamin, cyanocobalamin and sulphitocobalamin. Adenoxylcobalamin and hydroxocobalamin were the predominant forms. 3. The intestinal absorption of sulphitocobalamin was estimated and found to be lower than that of cyanocobalamin.
The forms of vitamin B12 in foods
Methionine is a precursor for S-adenosyl methionine, which is a methyl donor and is required to maintain the integrity of the neuron sheath. A deficiency of vitamin B12 disrupts this reaction, which leads to reduced formation of S- adenosyl methionine. This impairs methylation of myelin basic protein and lipids and leads to damage to the myelin sheath. Homocysteine methyltransferase also catalyzes the conversion of 5-methyl-tetrahydrofolate to tetrahydrofolate, which acts as a one-carbon donor for DNA synthesis. A deficiency of vitamin B12 causes folate to be trapped in its methylated form of 5-methyl-tetrahydrofolate.
Subacute Combined Degeneration of the Spinal Cord
Although cyanocobalamin and hydroxycobalamin are the most commonly encountered supplemental forms of vitamin B12, adenosyl- and methylcobalamin are the primary forms of vitamin B12 in the human body, and are the metabolically active forms required for B12-dependent enzyme function. Evidence indicates these coenzyme forms of vitamin B12, in addition to having a theoretical advantage over other forms of B12, actually do have metabolic and therapeutic applications not shared by the other forms of vitamin B12.
The Coenzyme Forms of Vitamin B12: Toward an Understanding of their Therapeutic Potential
To evaluate the possible role of glutathionylcobalamin (GS-Cbl) in the intracellular metabolism of cobalamin, the following reactions were analyzed using extracts of rabbit spleen: (i) decyanation of cyanocobalamin; (ii) utilization of GS-Cbl by cobalamin reductase; (iii) participation of GS-Cbl in methionine biosynthesis; and (iv) conversion of GS-Cbl to adenosylcobalamin. Decyanation of cyanocobalamin required reduced glutathione which appeared to form a complex with the cobalamin. This complex decomposed during the extraction steps to sulfitocobalamin which was identified by high-performance liquid chromatography. Cobalamin reductase in spleen extract was more active with GS-Cbl than with aquocobalamin or cyanocobalamin as substrates (specific activities: 10.4, 2.8 and 0.93 nmol/mg/min, respectively). Methionine synthase utilized GS-Cbl as cofactor more efficiently than aquocobalamin or cyanocobalamin based on initial rates of enzyme activity. This suggests that GS-Cbl is a more direct precursor of the coenzyme required for methionine synthase. Formation of adenosylcobalaminm from GS-Cb1 was four times greater than from aquocobalamin alone. Based on these results, we propose that GS-Cbl or a closely related thiol-cobalamin adduct is a proximal precursor in cobalamin coenzyme biosynthesis.
Glutathionylcobalamin as an intermediate in the formation of cobalamin coenzymes
Patients who had myeloproliferative disorders had a high prevalence of vitamin B12 deficiency, despite high serum vitamin B12 levels. Therefore, vitamin B12 status should be evaluated in patients with myeloproliferative disorders. Holotranscobalamin level may be the best initial test and may replace vitamin B12 assay to accompany MMA and homocysteine levels.
Diagnosis of Vitamin B12 Deficiency in Patients With Myeloproliferative Disorders
Research reports indicate that vitamin B12 levels show racial differences, which suggests that using the reference ranges of varied populations may lead to inaccurate results. This study aimed to determine normal serum levels of vitamin beta12 among children and young people in the Konya region of Turkey. It evaluated 1,109 samples; 54 were from cord-blood and 1,055 were from healthy subjects aged 0-24 year(s), who were admitted to primary healthcare centres. The normal reference levels obtained for vitamin B12 at 2.5-97.5 percentile (P2.5-P97.5) range were 127-606 pg/mL for girls, 127-576 pg/mL for boys, and 127-590 pg/mL for the entire study group. The reported reference values for vitamin B12 in other studies were higher than the current results. Vitamin B12 levels vary from country to country; comparisons between countries may not be valid, and normal levels for each population should be obtained.
Vitamin B12 Levels of Subjects Aged 0-24 Year(s) in Konya, Turkey
Deficiency of folate or vitamin B(12) (cobalamin) causes megaloblastic anemia, a disease characterized by pancytopenia due to the excessive apoptosis of hematopoietic progenitor cells. Clinical and experimental studies of megaloblastic anemia have demonstrated an impairment of DNA synthesis and repair in hematopoietic cells that is manifested by an increased percentage of cells in the DNA synthesis phase (S phase) of the cell cycle, compared with normal hematopoietic cells. Both folate and cobalamin are required for normal de novo synthesis of thymidylate and purines. However, previous studies of impaired DNA synthesis and repair in megaloblastic anemia have concerned mainly the decreased intracellular levels of thymidylate and its effects on nucleotide pools and misincorporation of uracil into DNA. An in vitro model of folate-deficient erythropoiesis was used to study the relationship between the S-phase accumulation and apoptosis in megaloblastic anemia. The results indicate that folate-deficient erythroblasts accumulate in and undergo apoptosis in the S phase when compared with control erythroblasts. Both the S-phase accumulation and the apoptosis were induced by folate deficiency in erythroblasts from p53 null mice. The complete reversal of the S-phase accumulation and apoptosis in folate-deficient erythroblasts required the exogenous provision of specific purines or purine nucleosides as well as thymidine. These results indicate that decreased de novo synthesis of purines plays as important a role as decreased de novo synthesis of thymidylate in the pathogenesis of megaloblastic anemia.
Apoptosis in megaloblastic anemia occurs during DNA synthesis by a p53-independent, nucleoside-reversible mechanism
Metabolic B12 deficiency is present in 20% of people over 65 years of age, and in 30% of vascular patients above 70 years, so higher doses of B12 are needed in elderly patients. However, high-dose cyanocobalamin leads to accumulation of cyanide in patients with renal failure. B vitamin therapy is beneficial in patients with good renal function, but harmful in patients with significantly impaired renal function (a glomerular filtration rate <50). It seems likely that in patients with renal impairment, methylcobalamin should be used instead cyanocobalamin.
B vitamin therapy for homocysteine: renal function and vitamin B12 determine cardiovascular outcomes
Seven patients with MP and four controls were injected with 0.04 to 0.05 microgram of [57Co] cyanocobalamin i.m. or i.v. in order to study the shift of binding with time and the conversion of one Cbl to another. The initial pattern of binding reflected the proportion of the apo forms of TC II and R binders. In MP there was more initial binding of the injected Cbl to R-type binders and less to TC II. During the first 48 hr after intake, the injected Cbl remained mostly as cyanocobalamin. Some adenosylcobalamin appeared transiently in both control and MP subjects. Radioactive methylcobalamin did not appear in the circulation until after 48 hr, and the conversion of cyanocobalamin to methylcobalamin within the circulation was greater in MP subjects.
The forms and transport of plasma cobalamins in normal man and in myeloproliferative states
The authors relate the results of studying intellectual work fitness in patients with anorexia nervosa (in the stage of cachexia) receiving the vitamin-like drugs carnitine and cobamamide. It has been shown that the long-term food deprivation leads to a reduction of intellectual work fitness, lability of productivity, fluctuations in the work quality, appearance of latent fatigue. In spite of the fact that standard nonspecific treatment ameliorates intellectual work fitness, it does not lead to its normalization. The use of carnitine and cobamamide in the course of nonspecific treatment results in the reduction of the time spent on task implementation, a rise of the work rate as compared to the control group. However, this does not fully remove latent fatigue and does not bring about complete recovery to normal of intellectual work fitness. The combined use of carnitine and cobamamide eliminates fluctuations in the work rate and normalizes the scope and productivity of intellectual work.
Effects of carnitine and cobamamide on the dynamics of mental work capacity in patients with anorexia nervosa
In 124 cases with lumbar disc herniation, 62 received short term intravenous drip of mecobalamin, and the other 62 cases received intravenous methylprednisolone .VAS pain scale and Lasegue score was used to record the degree of the patients′ radicular pain before the treatment, 2 hours, 6 hours, 1 day, 3 days, 6 days and 8 days after the treatment to evaluate the recovery. Investigate on the improvement rate about the symptom of radicular pain and numbness. The patients in the mecobalamin group got significant pain relief in the end of treatment. After drug withdrawal for 2 days,the difference of Lasegue score between the mecobalamin and methylprednisolone group was significant. The improvement rate about the subjective symptoms were both satisfactory. Conclusion: Mecobalamin can relieve radicular pain and numbness of the lower limbs effectively, and make up for the deficiency of glucocorticoid treatment. Therefore, mecobalamin might have brighter future, but needs further discussion and research.
Conservative Treatment of Lumbar Disc Herniation:Mecobalamin Intravenous Drip Compared with Corticosteroid
Two adolescent patients suffering from persistent sleep-wake schedule disorders appear to have responded to treatment with vitamin B12 (methylcobalamin). A 15-year-old girl with delayed sleep phase syndrome (DSPS) and a 17-year-old boy with hypernychthemeral syndrome complained of not being able to attend school despite many trials of medication. The improvement of the sleep-wake rhythm disorders appeared immediately after the administration of high doses (3,000 micrograms/day) of methylcobalamin. Neither patient showed any laboratory or clinical evidence of vitamin B12 deficiency or hypothyroidism (which can cause B12 deficiency). Serum concentrations of vitamin B12 during treatment were in the high range of normal or above normal. The duration of the sleep period of the DSPS patient decreased gradually from 10 hours to 7 hours, and the time of sleep onset advanced from 2 a.m. to midnight. The period of the sleep-wake cycle of the hypernychthemeral patient was 24.6 hours before treatment and 24.0 hours after treatment. The relationship between the circadian basis of these disorders and vitamin B12 and its metabolites is discussed.
Treatment of persistent sleep-wake schedule disorders in adolescents with methylcobalamin (vitamin B12)
The effect of methylcobalamin on the accommodative function of subjects with deteriorated accommodation by induced experimental visual work was studied by measuring small fluctuations of accommodation. The deterioration of small fluctuations of accommodations were difficult to find after visual work in the group receiving methylcobalamin. However, a significant difference of small fluctuations of accommodation was recognized in the non-administered group and in the placebo group (P less than 0.05), and that change was higher in the non-administered group than in the placebo group. Although, the placebo effect of methylcobalamin was undeniable, it was objectively confirmed that methylcobalamin produced a good effect on deteriorated accommodation induced by the visual work.
Effect of methylcobalamin in accommodative dysfunction of eye by visual load
Various cobalamins act as important enzyme cofactors and modulate cellular function. We investigated cobalamins for their abilities to modify productive human immunodeficiency virus-1 (HIV-1) infection of hematopoietic cells in vitro. We show that hydroxocobalamin (OH-Cbl), methylcobalamin (Me-Cbl), and adenosylcobalamin Ado-Cbl (Ado-Cbl) inhibit HIV-1 infection of normal human blood monocytes and lymphocytes. The inhibitory effects were noted when analyzing the monocytotropic strains HIV-1-BaL and HIV-1-ADA as well as the lymphocytotropic strain HIV-1-LAI. Cobalamins did not modify binding of gp120 to CD4 or block early steps in viral life cycle, inhibit reverse transcriptase, inhibit induction of HIV-1 expression from cells with established or latent infection, or modify monocyte interferon-alpha production. Because of the ability to achieve high blood and tissue levels of cobalamins in vivo and the general lack of toxicity, cobalamins should be considered as potentially useful agents for the treatment of HIV-1 infection.
Inhibition of productive human immunodeficiency virus-1 infection by cobalamins
The patient was a 48-year-old woman with gait disturbance as her initial symptom. Two years after the onset of the gait disturbance, she developed motor weakness and a sensory disturbance in her limbs, and dementia. On admission to our hospital, the patient’s serum vitamin B12 and folic acid levels were low, and she was found to have normochromic anemia. She also had widespread coarse hair and canities was diagnosed. The patient’s paresthesia resolved in response to injection of 500 micrograms mecobalamin every other day, and the Hasegawa dementia scale score and the patient’s hand grip strength improved. Her gait also improved, and she became able to walk on tiptoe. Her hair returned to normal. Supplementation with high-dose methyl B12 appeared to be effective to some extent in treating a broad range of neurologic disorders besides subacute combined degeneration of the spinal cord. In addition, the hair abnormality may be a marker of vitamin B12 deficiency.
A case of vitamin B12 deficiency with broad neurologic disorders and canities
Poisoning of rabbits with phenylhydrazine resulted in development of haemolytic hyperchromic anemia accompanied by impairment of hemopoiesis in bone marrow as well as by an increase of total vitamin B12 content in blood. The ration of individual forms of cobalamins was firstly estimated in blood serum of healthy rabbits and of the animals treated with phenylhydrazine. Distinct decrease in the methyl cobalamin content was observed in blood serum during spontaneous recovery. Administration of methyl cobalamin led to complete normalization of some blood and hematopoiesis patterns, as well as to restoration of total cobalamins content and the spectrum of their individual forms. Adenosyl cobalamin exhibited distinctly lower effect on the patterns studied. The data obtained suggest that methyl cobalamin possessed a lot of advantages in treatment of hemolytic anemias.
Effect of methylcobalamin and adenosylcobalamin on the process of hematopoiesis and vitamin B12 exchange in experimental phenylhydrazine-induced anemia in rabbits
The purpose of this study was to evaluate the effects of the orally administered mecobalamin, an analogue of vitamin B12, for carpal tunnel syndrome (CTS) in the nonparetic side in patients following stroke. In a randomized open label and prospective study of stroke patients, 67 received of 1500 μg mecobalamin daily for 2 years, and the remaining 68 (untreated group) did not. At baseline, sensory nerve conduction velocity, motor nerve conduction velocity, sensory nerve action potentials (SNAP) at the wrist, palm-to-wrist distal sensory latency, palm-to-wrist SNAP, motor nerve conduction velocity compound motor action potentials, and distal motor latency of median nerve were significantly more abnormal on the nonparetic side than on the hemiparetic side or in controls. Before the treatment 21 patients (31%) of untreated and 20 patients (30%) of treated group met electrophysiologic criteria for CTS. Sensory impairment of the nonparetic side had lessened in the treated group. After 2 years, all electrophysiologic indices of nonparetic side were significantly improved in the treated group compared with those in the untreated group. The improvement from baseline of electrophysiologic parameters in sensory nerve in the treated group was greater than the improvement measured in motor nerve. There were no side effects. Oral mecobalamin treatment is a safe and potentially beneficial therapy for CTS in stroke patients.
Amelioration by mecobalamin of subclinical carpal tunnel syndrome involving unaffected limbs in stroke patients
We examined the antitumor effect of vitamin B12 (methyl-B12) using C3H/He, C57BL/6 and BALB/C mice for animals and MH134 hepatoma ascites cells, Lewis lung cancer cells and Ehrlich ascites tumor cells for tumor cells. At 1.0-10 micrograms/ml, methyl-B12 enhanced PHA- and Con-A-induced lymphocyte blastoformation of C3H/He mice. The growth of MH134 tumors on the backs of C3H/He mice were suppressed by the 7-day administration of 50 or 100 micrograms/day i.p. and their survival was longer than that of untreated mice. However, methyl-B12 administration did not positively affect the survival of C3H/He mice that had been irradiated with 60Co 300 R on the day before tumor cell inoculation. The growth of Ehrlich ascites tumor cells inoculated into BALB/C mice was also reduced at 17 and 19 days after tumor inoculation by administration of methyl-B12 50 micrograms/day i.p. and the mice survived longer than the untreated mice.
Experimental study of antitumor effect of methyl-B12
The effect of cobalamin (vitamin B12) on the survival time of mice bearing P388 leukemia has been examined. Among the three cobalamins studied, the enzymatically active derivatives, methylcobalamin and 5′-deoxyadenosylcobalamin, were able to significantly increase the survival time of mice implanted intraperitoneally with the tumor cells. The pharmaceutical form, cyanocobalamin, was not active. The antitumor activity of these cobalamins may be associated with their functions in metabolism.
Influence of cobalamin on the survival of mice bearing ascites tumor
Three topics affecting cobalamin, folate, and homocysteine that have generated interest, activity, and advances in recent years are discussed. These are: (I). the application of an expanded variety of tools to the diagnosis of cobalamin deficiency, and how these affect and are affected by our current understanding of deficiency; (II). the nature of the interaction between homocysteine and vascular disease, and how the relationship is affected by vitamins; and (III). the improved understanding of relevant genetic disorders and common genetic polymorphisms, and how these interact with environmental influences. The diagnostic approach to cobalamin deficiency now allows better diagnosis of difficult and atypical cases and more confident rejection of the diagnosis when deficiency does not exist. However, the process has also become a complex and sometimes vexing undertaking. Part of the difficulty derives from the lack of a diagnostic gold standard among the many available tests, part from the overwhelming numerical preponderance of patients with subclinical deficiency (in which isolated biochemical findings exist without clinical signs or symptoms) among the cobalamin deficiency states, and part from the decreased availability of reliable tests to identify the causes of a patient’s cobalamin deficiency and thus a growing deemphasis of that important part of the diagnostic process. In Section I, Dr. Carmel discusses the tests, the diagnostic issues, and possible approaches to the clinical evaluation. It is suggested no single algorithm fits all cases, some of which require more biochemical proof than others, and that differentiating between subclinical and clinical deficiency, despite their overlap, may be a helpful and practical point of departure in the evaluation of patients encountered in clinical practice. The arguments for and against a suggested expansion of the cobalamin reference range are also weighed. The epidemiologic data suggest that homocysteine elevation is a risk factor for vascular and thrombotic disease. In Section II, Dr. Green notes that the interactions of metabolism and clinical risk are not well understood and a causative relationship remains unproven despite new reports that lowering homocysteine levels may reduce vascular complications. Genetic and acquired influences may interact in important ways that are still being sorted out. The use of vitamins, especially folate, often reduces homocysteine levels but also carries potential disadvantages and even risks. Folate fortification of the diet and supplement use have also markedly reduced the frequency of folate deficiency, and cobalamin deficiency is now the more common deficiency state, especially among the elderly. Although genetic disorders are rare, they illuminate important metabolic mechanisms and pose diagnostic challenges, especially when clinical presentation occurs later in life. In Section III, Drs. Rosenblatt and Watkins use selected disorders to illustrate the subject. Imerslund-Gräsbeck syndrome, a hereditary disorder of cobalamin absorption at the ileal level, demonstrates genetic heterogeneity. Finnish patients show mutation of the gene for cubilin, the multiligand receptor for intrinsic factor. Surprisingly, Norwegian and other patients have been found recently to have mutations of the AMN (amnionless) gene, mutations that are lethal in mice at the embryonic stage. Two disorders of cobalamin metabolism, cblG and cblE, are now known to arise from mutations of the methionine synthase and methionine synthase reductase genes, respectively. These disorders feature megaloblastic anemia and neurologic manifestations. The folate disorder selected for illustration, methylenetetrahydrofolate reductase (MTHFR) deficiency, paradoxically causes neurological problems but no megaloblastic anemia. This rare deficiency is the most common inborn error of folate metabolism. It is distinct from the very common MTHFR gene polymorphisms, mutations that cause mild to moderate reductions in MTHFR activity but no direct clinical manifestations. The MTHFR polymTHFR polymorphisms, especially the 677C–>T mutation, may contribute to vascular and birth defect risks, while reducing the risk of certain malignancies, such as colon cancer. These polymorphisms and those of genes for other enzymes and proteins related to cobalamin, folate, and homocysteine metabolism may be important role players in frequent interactions between genes and the environment.
Update on cobalamin, folate, and homocysteine
Investigation of possible B12 and folate deficiencies requires measurement of these vitamins in serum. There is evidence that holotranscobalamin (holoTC), the active portion of B12 available to cells, is a more specific marker of early B12 deficiency than total B12. The availability of immunoassays for holoTC prompted an international collaborative study to assign a holoTC value to the World Health Organization (WHO) 1st International Standard (IS) for vitamin B12 and serum folate, 03/178.
An International Standard for holotranscobalamin (holoTC): international collaborative study to assign a holoTC value to the International Standard for vitamin B12 and serum folate
The detection and correction of vitamin B12 (B12) deficiency prevents megaloblastic anaemia and potentially irreversible neuropathy and neuropsychiatric changes. B12 status is commonly estimated using the abundance of the vitamin in serum, with ∼148 pmol/L (200 ng/L) typically set as the threshold for diagnosing deficiency. Serum B12 assays measure the sum of haptocorrin-bound and transcobalamin-bound (known as holotranscobalamin) B12 It is only holotranscobalamin that is taken up by cells to meet metabolic demand. Although receiver operator characteristic curves show holotranscobalamin measurement to be a moderately more reliable marker of B12 status than serum B12, both assays have an indeterminate range. Biochemical evidence of metabolic abnormalities consistent with B12 insufficiency is frequently detected despite an apparently sufficient abundance of the vitamin. Laboratory B12 status markers that reflect cellular utilisation rather than abundance are available. Two forms of B12 act as coenzymes for two different reactions. Methionine synthase requires methylcobalamin for the remethylation of methionine from homocysteine. A homocysteine concentration >20 µmol/L may suggest B12 deficiency in folate-replete patients. In the second B12-dependent reaction, methylmalonyl-CoA mutase uses adenosylcobalamin to convert methylmalonyl-CoA to succinyl-CoA. In B12 deficiency excess methylmalonyl-CoA is hydrolysed to methylmalonic acid. A serum concentration >280 nmol/L may suggest suboptimal status in young patients with normal renal function. No single laboratory marker is suitable for the assessment of B12 status in all patients. Sequential assay selection algorithms or the combination of multiple markers into a single diagnostic indicator are both approaches that can be used to mitigate inherent limitations of each marker when used independently.
Laboratory assessment of vitamin B12 status
Aim: To investigate the effect of clonidine, moxonidine, folic acid, and mecobalamin on arterial baroreflex (ABR) function in stroke-prone spontaneously hypertensive rats (SHR-SP) and the possible mechanisms involved. Methods: Eighty-one SHR-SP were divided into 7 groups. Four groups were designated for the intragastric (ig) administration of clonidine (1.0 and 10.0 μg/kg), moxonidine (0.1 and 1.0 mg/kg), folic acid (1.0 mg/kg), and mecobalamin (1.0 mg/kg). Three groups were for the intracerebroventricular (icv) injection of clonidine (4 μg/4 μL), moxonidine (5 μg/4 μL), and mecobalamin (20 μg/4 μL). Blood pressure (BP) was recorded in the conscious state for 30 min and baroreflex sensitivity (BRS) was determined respectively before and after drug administration. Results: Clonidine and moxonidine significantly decreased BP, prolonged the heart period (HP), and increased BRS when administered as either ig or icv injections. Both BP and HP were unchanged by ig folic acid or mecobalamin injection. However, BRS was significantly increased by both. Conclusion: Clonidine, moxonidine, folic acid, and mecobalamin improved impaired ABR function in SHR-SP. The central mechanism was involved in this effect of either clonidine or moxonidine. Mecobalamin improved ABR function through the peripheral mechanism.
Clonidine, moxonidine, folic acid, and mecobalamin improve baroreflex function in stroke-prone, spontaneously hypertensive rats
Sixty patients with Bell’s palsy were included in an open randomized trial. Patients were assigned into three treatment groups: steroid (group 1), methylcobalamin (group 2) and methylcobalamin + steroid (group 3). Comparison between the three groups was based on the number of days needed to attain full recovery, facial nerve scores, and improvement of concomitant symptoms. The time required for complete recovery of facial nerve function was significantly shorter ( p < 0.001) in the methylcobalamin (mean of 1.95 +/- 0.51 weeks) and methylcobalamin plus steroid groups (mean of 2.05 +/- 1.23 weeks) than in the steroid group (mean of 9.60 +/- 7.79 weeks). The facial nerve score after 1-3 weeks of treatment was significantly more severe (p < 0.001) in the steroid group compared to the methylcobalamin and methylcobalamin plus steroid groups. The improvement of concomitant symptoms was better in the methylcobalamin treated groups than the group treated with steroid alone.
Methylcobalamin treatment of Bell’s palsy
In this Japanese population with a high baseline fracture risk, combined treatment with folate and vitamin B12 is safe and effective in reducing the risk of a hip fracture in elderly patients following stroke.
Effect of Folate and Mecobalamin on Hip Fractures in Patients With Stroke A Randomized Controlled Trial
Objective: To investigate the convenient and effective treatment for cervical spondylosis in the upper cervical spine. Methods: Forty patients with cervical spondylosis were divided into two groups. The patients in control and observation groups were treated with the routine rehabilitation treatments,and those in observation group were subjected to the neck muscle exercise and paravertebral injection of mecobalamin additionally. Results: There was no significant difference in the curative effectiveness,safety and recurrence between two groups. However,the satisfaction of treatment modality in observation group was superior to that in control group (P0.05). Conclusion: The paravertebral injection with mecobalamin combined with routine rehabilitation training can be a convenient and effective treatment for cervical spondylosis.
Treatment of Cervical Spondylosis in the Upper Cervical Spine
To clarify the effect of vitamin B12 on the human circadian clock, five healthy male adults participated in two constant routine procedures, 2 or 3 weeks apart. In one, subjects received intravenous saline injections (placebo trial) and in the other, intravenous injections of methylcobalamin (MB12) (drug trial). Intravenous administration of MB12 increased rectal temperature in the later hours of the daytime during the constant routine. The activity did not change between treatments in any period during the constant routine. During the later hours of the constant routine, alertness assessed with visual analog scale was higher in the drug trial than in the placebo trial. The period in which drug treatment produced greater alertness almost coincided with that in which MB12 elevated rectal temperature. These results may provide evidence of an effect of vitamin B12 on the circadian clock.
Effects of vitamin B12 on human circadian body temperature rhythm
We studied the clinical and neurophysiological effects of methylcobalamin on patients with diabetic neuropathy. In a double-blind study, the active group showed statistical improvement in the somatic and autonomic symptoms with regression of signs of diabetic neuropathy. Motor and sensory nerve conduction studies showed no statistical improvement after 4 months. The drug was easily tolerated by the patients and no side effects were encountered.
Effects of methylcobalamin on diabetic neuropathy
The main finding of the present study is the determination of the range of vitamin B12 concentration which may favor better hemoglobin synthesis in athletes. They should regularly monitor vitamin B12 concentration and maintain the range of 400-700 pg/mL as it may improve red blood cell parameters. We might suggest application of a supplementation if necessary. Special attention is required in athletes with a vitamin B12 concentration below 400 pg/mL.
Vitamin B12 Status and Optimal Range for Hemoglobin Formation in Elite Athletes
The concentration of total vitamin B12 in serum is not a sufficiently sensitive or specific indicator for the reliable diagnosis of vitamin B12 deficiency. Victor Herbert proposed a model for the staged development of vitamin B12 deficiency, in which holotranscobalamin (HoloTC) is the first indicator of deficiency. Based on this model, a commercial immunoassay has been controversially promoted as a replacement for the total vitamin B12 test. HoloTC is cobalamin (vitamin B12) attached to the transport protein transcobalamin, in the serum, for delivery to cells for metabolism. Although there have been many published reports supporting the claims for HoloTC, the results of some studies were inconsistent with the claim of HoloTC as the most sensitive marker of vitamin B12 deficiency. This review examines the evidence for and against the use of HoloTC, and concludes that the HoloTC immunoassay cannot be used to measure vitamin B12 status any more reliably than total vitamin B12, or to predict the onset of a metabolic deficiency, because it is based on an erroneous hypothesis and a flawed model for the staged development of vitamin B12 deficiency. The author proposes an alternative model for the development of vitamin B12 deficiency.
Holotranscobalamin (HoloTC, Active-B12) and Herbert’s model for the development of vitamin B12 deficiency: a review and alternative hypothesis
Methylmalonic acid (MMA) in plasma or serum is widely used for assessment of vitamin B12 status. However, data are sparse regarding factors, besides renal function, that may influence MMA concentrations. We searched for important determinants of plasma MMA in the general population.
Determinants of Plasma Methylmalonic Acid in a Large Population: Implications for Assessment of Vitamin B12 Status
Identified determinants accounted for <17% of the overall variation in plasma MMA. The difference in MMA between middle-aged and elderly individuals is only partly explained by creatinine and vitamin B12 concentrations.
Mild TC I/HC deficiency is frequently associated with low cobalamin, is often familial, and its biochemical phenotype appears identical to the heterozygous state of severe TC I/HC deficiency. Severe TC I/HC deficiency also appears to be more common than suspected. Both diagnoses should be considered in all patients with unexplained low serum cobalamin.
Mild Transcobalamin I (Haptocorrin) Deficiency and Low Serum Cobalamin Concentrations
Vitamin B12 is an essential vitamin that is widely used in medical and food industries. Vitamin B12 biosynthesis is confined to few bacteria and archaea, and as such its production relies on microbial fermentation. Rational strain engineering is dependent on efficient genetic tools and a detailed knowledge of metabolic pathways, regulation of which can be applied to improve product yield. Recent advances in synthetic biology and metabolic engineering have been used to efficiently construct many microbial chemical factories. Many published reviews have probed the vitamin B12 biosynthetic pathway. To maximize the potential of microbes for vitamin B12 production, new strategies and tools are required. In this review, we provide a comprehensive understanding of advances in the microbial production of vitamin B12, with a particular focus on establishing a heterologous host for the vitamin B12 production, as well as on strategies and tools that have been applied to increase microbial cobalamin production. Several worthy strategies employed for other products are also included.
Microbial production of vitamin B12: a review and future perspectives
Once upon a time we thought that we knew how to diagnose cobalamin (Cbl) deficiency. It started with a patient. He, or more often she, lacked energy. If you were lucky she might have a sore mouth and a smooth tongue and even some pins-and-needles sensation in fingers and/or toes. But the main pointer came with the blood count which, in the absence of thalassaemia trait, showed macrocytosis in almost all patients, usually with other abnormalities in the blood.
DIAGNOSIS OF COBALAMIN DEFICIENCY: THE OLD AND THE NEW
Vitamin B12 and folate are two vitamins that have interdependent roles in nucleic acid synthesis. Deficiencies of either vitamin can cause megaloblastic anemia; however, inappropriate treatment of B12 deficiency with folate can cause irreversible nerve degeneration. Inadequate folate nutrition during early pregnancy can cause neural tube defects in the developing fetus. In addition, folate and vitamin B12 deficiency and the compensatory increase in homocysteine are a significant risk factor for cardiovascular disease. Laboratory support for the diagnosis and management of these multiple clinical entities is controversial and somewhat problematic. Automated ligand binding measurements of vitamin B12 and folate are easiest to perform and widely used. Unfortunately, these tests are not the most sensitive indicators of disease. Measurement of red cell folate is less dependent on dietary fluctuations, but these measurements may not be reliable. Homocysteine and methylmalonic acid are better metabolic indicators of deficiencies at the tissue level. There are no “gold standards” for the diagnosis of these disorders, and controversy exists regarding the best diagnostic approach. Healthcare strategies that consider the impact of laboratory tests on the overall costs and quality of care should consider the advantages of including methylmalonic acid and homocysteine in the early evaluation of patients with suspected deficiencies of vitamin B12 and folate.
Cobalamin and Folate Evaluation: Measurement of Methylmalonic Acid and Homocysteine vs Vitamin B12 and Folate
A combined analysis of MMA and tHcy provides complementary diagnostic information. When interpreting MMA and tHcy values, age, gender and renal function in particular must be taken into account. Typical combinations of MMA and tHcy concentration intervals could be proposed, which could either exclude deficiency or indicate likely diagnoses and/or influence of confounders.
Routine determination of serum methylmalonic acid and plasma total homocysteine in Norway
Since plasma methylmalonic acid (MMA) was introduced in Denmark in 1992 both MMA and P-cobalamins have been increasingly employed to diagnose vitamin B-12 deficiency, and the consumption of vitamin B-12 has been almost doubled during the same period. The controversy about diagnosing vitamin B-12 deficiency is reflected in a huge geographical variation both in requisition of MMA and P-cobalamins and in the vitamin B-12 consumption. On the basis of studies performed so far we conclude that MMA is a reliable method with a good nosographic sensitivity. However, the nosographic specificity is sparsely examined, and the evidence to use MMA as a primary test for diagnosing vitamin B-12 deficiency is still insufficient. We recommend P-cobalamins as the first line test, and if P-cobalamins are in the grey area 125-250 pmol/l we recommend supplementation with MMA. For patients who also have an MMA in the grey area (0.29-0.75 mumol/l) we recommend that the patient is re-examined after about a year.
Diagnosis of vitamin B12 deficiency–time for reflection
We report on the performance of a new test, holotranscobalamin, as compared to well established markers of vitamin B12 deficiency (plasma cobalamins, methylmalonic acid, and homocysteine). Holotranscobalamin was analyzed in 143 samples by a competitive radiobinding assay (Axis-Shield). Employing a cut-off value of 50 pmol/l, holotranscobalamin showed a sensitivity of 1.00 and a specificity of 0.89 as regards discriminating between individuals with test results indicating vitamin B12 deficiency (methylmalonic acid > 0.70 micromol/l and plasma cobalamins < 200 pmol/l, n = 35) and individuals with test results inside the reference intervals (methylmalonic acid < 0.29 micromol/l and plasma cobalamins > or = 200 pmol/l, n = 35). In a group (n = 37) with low plasma cobalamins (< 200 pmol/l) and normal methylmalonic acid (< 0.29 micromol/l), 27 individuals had low holotranscobalamin, and in nine of these individuals plasma homocysteine supported the deficiency state (homocysteine > 15 micromol/l). Holotranscobalamin was low in 12 individuals with increased methylmalonic acid (> 0.40 micromol/l) and normal plasma cobalamins (> or = 200 pmol/l) (n = 36), and plasma homocysteine supported the deficiency state in four of these individuals. We conclude that holotranscobalamin is likely to be a sensitive marker of vitamin B12 deficiency that also has a reasonable specificity. Large-scale clinical studies are warranted in order to clarify the usefulness of holotranscobalamin in the clinical setting.
Holotranscobalamin as a predictor of vitamin B12 status
In 1992 plasma methylmalonic acid (MMA) was introduced in Denmark for diagnosing vitamin B‐12 deficiency. Now, 10 years later, we report on a health technology assessment (HTA) suggesting that the clinical usefulness of MMA is uncertain. MMA is an obvious component for measurement in the diagnosis of vitamin B‐12 deficiency because MMA accumulates when there is a lack of vitamin B‐12, and technologically the analysis is of high quality. The diagnostic sensitivity of MMA is high, whereas the diagnostic specificity is debatable, and our results suggest it to be relatively low. The organizational aspect implies that both MMA and P‐cobalamins have been increasingly employed, though no consensus on the use of the analyses has emerged. The benefit to the patient is not obvious. An increased level of MMA does not predict further increases over time, and vitamin B‐12 treatment shows limited clinical benefit in individuals with a moderately increased MMA. The economic consequences of introducing MMA were an increase in the costs of MMA and P‐cobalamins of 12% per year during 1992–2000 and an increase in the turnover of vitamin B‐12 preparations of 9% per year. In conclusion, MMA was introduced on sound grounds for both pathophysiological considerations and analytical quality. Our HTA shows that the resources employed to diagnose and to treat vitamin B‐12 deficiency have increased considerably, but yet we have no evidence to suggest the clinical benefit.
Health technology assessment in clinical biochemistry. Methylmalonic acid: a Danish showcase
Eight young males were subjected to a single blind cross-over test to see the effects of vitamin B12 (methylcobalamin; VB12) on the phase-response of the circadian melatonin rhythm to a single bright light exposure. VB12 (0.5 mg/day) or vehicle was injected intravenously at 1230 h for 11 days, which was followed by oral administration (2 mg x 3/day) for 7 days. A serial blood sampling was performed under dim light condition (less than 200 lx) and plasma melatonin rhythm was determined before and after a single bright light exposure (2500 lx for 3 h) at 0700 h. The melatonin rhythm before the light exposure showed a smaller amplitude in the VB12 trial than in the placebo. The light exposure phase-advanced the melatonin rhythm significantly in the VB12 trail, but not in the placebo. These findings indicate that VB12 enhances the light-induced phase-shift in the human circadian rhythm.
Vitamin B12 enhances the phase-response of circadian melatonin rhythm to a single bright light exposure in humans
Vitamin B12 deficiency may be underestimated in the general population. High-risk groups for the deficiency syndrome include the elderly, patients taking ulcer medications over long periods, patients with acquired immunodeficiency syndrome, vegetarians, patients who have undergone stomach resection or small bowel resection, or both, and patients with dementia. The vitamin B12 deficiency syndrome is characterized by five stages, the fifth of which results in irreversible neuropsychiatric manifestations. Although the deficiency is easily treated, diagnosis is somewhat complicated by the shortcomings of the various tests. Current state-of-the-art testing uses serum cobalamin levels as a screening test and serum or urine homocysteine and methylmalonic acid determinations as confirmatory tests. Vitamin B12 deficiency is treatable with monthly injections, large doses of daily oral supplement tablets, or an intranasal gel, which is far better absorbed than comparable oral supplements.
An update of vitamin B12 metabolism and deficiency states
At one time, the diagnosis of a deficiency of vitamin B12 or folate was considered to be relatively straightforward. As knowledge has accumulated, the limitations of such tests as serum vitamin level measurements and the Schilling test have become apparent. With the development of newer tests, atypical and subclinical deficiency states have been recognized. In this review, available tests used in the diagnosis of vitamin B12 and folate deficiency are discussed, and a rational approach to the diagnosis of these deficiency states is presented.
Laboratory diagnosis of vitamin B12 and folate deficiency: a guide for the primary care physician
Intestinal absorption of 14CH3- and/or 57Co-methylcobalamin (CH3-B12) was studied with regard to chemical changes. It was found that absorption of a physiologic dose of CH3-B12-57Co in the rat was the same as that of cyanocobalamin (CN-B12) in quantity and speed, but more radioactivity accumulated in liver after 8 hours, indicating a gradual conversion of CH3-B12 to hydroxocobalamin and cobamide coenzyme. Schilling test with CH3-B12-57Co yielded urinary excretion about 1 3 that with CN-B12-57Co, and similar changes of CH3-B12 in human body were suggested. In the rat, expiration of 14CO2 following oral administration of 14CH3-B12 was small, as contrasted by quick and massive evolution of 14CO2 when photolyzed 14CH3-B12 was given. With supraphysiologic doses, more than 60 per cent of 14C disappeared from the gastrointestinal tract in 2 to 3 hours, suggesting instability of free CH3-B12, and there was a distinct difference in tissue distribution between 14C and 57Co following administration of 14CH3-B12-57Co. It seems, therefore, that cleavage of -CH3 in vivo is different in mechanism from that in vitro or after photolysis. Paper chromatography of digested ileal mucosa obtained after oral administration of a small dose of CH3-B12-57Co, demonstrated unchanged CH3-B12 and some other cobamides. It is concluded that in the alimentary tract, free CH3-B12 is labile and loses CH3 progressively. However, in a physiologic situation where intrinsic factor is operative, CH3-B12 may be partially protected by it from such chemical changes.
Intestinal absorption and concurrent chemical changes of methylcobalamin
A 13-year-old male with adrenoleukodystrophy (ALD) developed a sleep-wake disorder after complete vision loss. He had a 25-h sleep-wake cycle. After methyl B12 therapy, circadian rhythms in his plasma melatonin and beta-endorphin levels approximated those of healthy volunteers, and his peak cortisol time shifted backward. Daily deep body temperature (DBT) amplitude was smaller than in healthy males before and after the treatment, and his acrophase did not change. However, his sleep-wake rhythm became normal. Methyl B12 is considered useful for treating circadian rhythm disturbances in patients having central nervous system disorders and blindness.
Circadian rhythm abnormalities in adrenoleukodystrophy and methyl B12 treatment
CH3-B12 was administered daily (1,500 micrograms/day, for 4 to 24 weeks) to 26 infertile male patients who visited our clinic from January to December, 1982. It was not administered, however, to patients with azoospermia. Semen analysis was conducted from 8 weeks after the administration of CH3-B12. Sperm concentration increased in 10 cases (38.4%), total sperm counts increased in 14 cases (53.8%), sperm motility increased in 13 cases (50.0%) and total motile sperm count increased in 13 cases (50.0%). Semen volume, however, could not be evaluated due to wide variation. Serum LH, FSH and testosterone were unchanged. Judging by our criteria, 11 cases (42.3%) improved, 11 cases (42.3%) were unchanged and the remaining 4 cases (15.4%) had aggravated.
Clinical experience with methylcobalamin (CH3-B12) for male infertility
This preliminary study investigates effects of methyl- and cyanocobalamin on circadian rhythms, well-being, alertness, and concentration in healthy subjects. Six women (mean age 35 years) and 14 men (mean age 37 years) were randomly assigned to treatment for 14 days with 3 mg cyano-(CB12) or methylcobalamin (MB12) after 9 days of pre-treatment observation. Levels in the CB12 group increased rapidly in the first, then slowly in the second treatment week, whereas increase in the MB12 group was linear. Urinary aMT6s excretion was reduced by both forms of vitamin B12 over 24 hours with a significant decrease between 0700-1100 hours, whereas urinary excretion of potassium was significantly increased between 0700-1100 hours. Activity from 2300-0700 hours increased significantly under both forms of vitamin B12. Sleep time was significantly reduced under MB12 intake. In this group the change in the visual analogue scales items “sleep quality,” “concentration,” and “feeling refreshed” between pretreatment and the first week of treatment showed significant correlations with vitamin B12 plasma levels. Cortisol excretion and temperature were not affected by either medication. We conclude that vitamin B12 exerts a direct influence on melatonin. Only MB12 has a positive psychotropic alerting effect with a distribution of the sleep-wake cycle toward sleep reduction.
Effects of vitamin B12 on performance and circadian rhythm in normal subjects
It has been postulated that the accumulation of homocysteine in plasma may induce arteriosclerosis. In order to explore the possible contribution of homocysteine to the occurrence of macroangiopathy in patients with non-insulin-dependent diabetes mellitus, the concentrations of total homocysteine in plasma were determined in 52 diabetic patients with clinical macroangiopathy, 84 diabetic patients without macroangiopathy, and 57 non-diabetic control subjects. The levels of total homocysteine in plasma were significantly higher in diabetic patients with macroangiopathy (10.8 +/- 3.8 nmol/ml) than in those without macroangiopathy (8.3 +/- 3.1 mmol/ml, P < 0.001) or non-diabetic subjects (7.5 +/- 2.1 nmol/ml, P < 0.001). Among all diabetic patients, multiple logistic regression analysis after adjustment for age, sex, and systolic blood pressure revealed that high levels of plasma homocysteine were significantly associated with the presence of diabetic macroangiopathy (P = 0.01). By an intramuscular injection of 1000 micrograms methylcobalamin daily for 3 weeks, the plasma levels of homocysteine in 10 diabetic patients were significantly decreased (14.7 +/- 7.5 vs. 10.2 +/- 6.0 nmol/ml, P < 0.01). Our results suggest that plasma homocysteine levels could be one of a number of independent risk factors for macroangiopathy in patients with diabetes mellitus and that they can be reduced by parenteral treatment with methylcobalamin.
Plasma homocysteine concentrations in Japanese patients with non-insulin-dependent diabetes mellitus: effect of parenteral methylcobalamin treatment
Despite intensive searches for therapeutic agents, few substances have been convincingly shown to enhance nerve regeneration in patients with peripheral neuropathies. Recent biochemical evidence suggests that an ultra-high dose of methylcobalamin (methyl-B12) may up-regulate gene transcription and thereby protein synthesis. We examined the effects of ultra-high dose of methyl-B12 on the rate of nerve regeneration in rats with acrylamide neuropathy, using the amplitudes of compound muscle action potentials (CMAPs) after tibial nerve stimulation as an index of the number of regenerating motor fibers. After intoxication with acrylamide, all the rats showed equally decreased CMAP amplitudes. The animals were then divided into 3 groups; rats treated with ultra-high (500 micrograms/kg body weight, intraperitoneally) and low (50 micrograms/kg) doses of methyl-B12, and saline-treated control rats. Those treated with ultra-high dose showed significantly faster CMAP recovery than saline-treated control rats, whereas the low-dose group showed no difference from the control. Morphometric analysis revealed a similar difference in fiber density between these groups. Ultra-high doses of methyl-B12 may be of clinical use for patients with peripheral neuropathies.
Ultra-high dose methylcobalamin promotes nerve regeneration in experimental acrylamide neuropathy
Active vitamin B12 absorption is followed by an increase in holotranscobalamin (holoTC) upon loading with a high physiological dose of the vitamin (the CobaSorb test). This study evaluates the use of a newly launched EIA kit for measurement of holoTC (active B12) in relation to the CobaSorb test.
Vitamin B12 absorption judged by measurement of holotranscobalamin, active vitamin B12: evaluation of a commercially available EIA kit
The association between PA and spinal cord lesions was described by Lichtheim (1887) and a full account was published by Russell et al (1900), who coined the term ‘subacute combined degeneration of the spinal cord’ (SCDC) although they were not convinced of its relation to PA. Arthur Hurst at Guy’s Hospital, London, confirmed the association of the neuropathy with PA and added, too, the association of loss of hydrochloric acid in the gastric juice (Hurst & Bell, 1922). Cabot (1908) found that numbness and tingling of the extremities were present in almost all of his 1200 patients and 10% had ataxia. William Hunter (1901) noted the prevalence of a sore tongue in PA, which was present in 40% of Cabot’s series.
A history of pernicious anaemia
By the time Cbl had been isolated from liver it was already known that it was also present in fermentation flasks growing bacteria such as streptomyces species. Other organisms gave higher yields so that kilogram quantities of pure Cbl were obtained; these sources have replaced liver in the production of Cbl. By adding a radioactive form of cobalt to the fermentation flasks instead of ordinary cobalt, labelled Cbl became available (Chaiet et al, 1950). The importance of labelled Cbl is that it made it possible to carry out Cbl absorption tests in patients, to design isotope-dilution assays for serum Cbl, to design ways of assaying intrinsic factor (IF), to detect antibodies to IF and even to measure glomerular filtratration rate, as free Cbl is excreted by the glomerulus without any reabsorption by the renal tubules. It also forms the basis for many research studies related to Cbl. The most useful isotope is Cbl labelled with 57Co which provides the least amount of radiation exposure, but has a scintillation spectrum with a single energy peak that provides a high degree of counting efficiency.
The urinary excretion of injected cyanocobalamin was studied in 30 previously untreated vitamin B(12)-deficient patients by measuring the urinary radioactivity after repeated injections of (58)Co vitamin B(12). The dose range used was 54 to 30,000 mug., each patient receiving the same dose at each injection. The results show that there is no constant trend to the excretion of greater or smaller proportions of the amount injected. It is also shown that there is a wide variation in the amounts excreted by each individual and between individual patients and that the capacity of the tissues to retain injected cyanocobalamin is very great, the amounts retained often being greatly in excess of the normal body stores. The excretion of radioactivity after parenteral infections of (58)Co vitamin B(12) was usually complete within 24 hours but exceptions to this were seen.
THE URINARY EXCRETION AND TISSUE RETENTION OF CYANOCOBALAMIN BY SUBJECTS GIVEN REPEATED PARENTERAL DOSES
The effect of methylcobalamin on 3H-methotrexate uptake by tumor and normal tissues of mice with mammary adenocarcinoma (Ca-755) was studied. Methylcobalamin stimulated the rate of 3H-methotrexate influx into the tumor and small intestine but did not change its influx into the spleen. The effect was dependent on the dose of methylcobalamin. Comparative analysis of the kinetic differences in 3H-methotrexate influx and efflux in tumor and susceptible host tissues revealed the optimal dose of methylcobalamin 0.01 mg/kg to improve the antitumor drug action.
Effect of methylcobalamin on methotrexate transport in normal and tumorous tissues
Objective: To investigate the effects of trabeculectomy combined with mecobalamin in treating late glaucoma. Methods: 46 patients with late glaucoma were treated by trabeculectomy. Adjustable suture was applied. All patients received mecobalamin therapy after operation for 3 to 6 months. Results: Mean intraocular pressure (IOP) before and after operation was 38.97±2.91mmHg,and 14.41±2.17mmHg.In terms of vision change 2 weeks after operation: 10 eyes (21.74%) improved by more than two lines,20 eyes(43.48%) improved by less than two lines, 14 eyes (30.43%) showed no improvement,and 2 eyes(4.34%) decreased. All 46 patients were followed-up for 6 to 24 months, no loss of vision ever found. In terms of visual field after operation: 8 eyes (17.39%) improved, 34 eyes (73.91%) had no change, and 4 eyes (8.70%) worsened. Conclusion: For late glaucoma, trabeculectormy combined with neuroprotective agents can effectively control IOP and slow down the loss of visual function.
CLINICAL EFFECTS OF TRABECULECTOMY COMBINED WITH MECOBALAMIN IN TREATING LATE GLAUCOMA
Chronic administration of methylcobalamin protects cultured retinal neurons against N-methyl-D-aspartate-receptor-mediated glutamate neurotoxicity, probably by altering the membrane properties through SAM-mediated methylation.
Protective effects of methylcobalamin, a vitamin B12 analog, against glutamate-induced neurotoxicity in retinal cell culture
The effects of methylcobalamin, a vitamin B12 analog, on glutamate-induced neurotoxicity were examined using cultured rat cortical neurons. Cell viability was markedly reduced by a brief exposure to glutamate followed by incubation with glutamate-free medium for 1 h. Glutamate cytotoxicity was prevented when the cultures were maintained in methylcobalamin-containing medium. Glutamate cytotoxicity was also prevented by chronic exposure to S-adenosylmethionine, which is formed in the metabolic pathway of methylcobalamin. Chronic exposure to methylcobalamin and S-adenosylmethionine also inhibited the cytotoxicity induced by N-methyl-D-aspartate or sodium nitroprusside that releases nitric oxide. In cultures maintained in a standard medium, glutamate cytotoxicity was not affected by adding methylcobalamin to the glutamate-containing medium. In contrast, acute exposure to MK-801, a NMDA receptor antagonist, prevented glutamate cytotoxicity. These results indicate that chronic exposure to methylcobalamin protects cortical neurons against NMDA receptor-mediated glutamate cytotoxicity.
Protective effects of a vitamin B12 analog, methylcobalamin, against glutamate cytotoxicity in cultured cortical neurons
AIM: To observe the effect of in mecobalamin in treating cubital tunnel syndrome. METHODS: Sixty four patients with cubital tunnel syndrome were divided into 2 groups. Thirty one patients received mecobalamin 500 μg, im, qd for 1 mo, then 500 μg, po, tid for 5 mo. Another thirty three patients received vitamin B 1 50 mg, po, tid for 6 mo. Both groups had been performed routine neurolysis of the ulnar nerve and its subcutaneous anterior transposition. All patients were followed up 6 mo using EMG and clinical examination. RESULTS: The treatment outcome of mecobalamin group was better than the vitamin B 1 group (P 0.05). CONCLUSION: Mecobalamin can promote the postoperative recovery of cubital tunnel syndrome.
Mecobalamin in treating cubital tunnel syndrome
Methylcobalamin is a vitamin B12 analog and is necessary for the maintenance of the nervous system. Although some previous studies have referred to the effects of methylcobalamin on neurons, the precise mechanism of this effect remains obscure. Here we show that methylcobalamin at concentrations above 100 nM promotes neurite outgrowth and neuronal survival and that these effects are mediated by the methylation cycle, a metabolic pathway involving methylation reactions. We also demonstrate that methylcobalamin increases Erk1/2 and Akt activities through the methylation cycle. In a rat sciatic nerve injury model, continuous administration of high doses of methylcobalamin improves nerve regeneration and functional recovery. Therefore, methylcobalamin may provide the basis for better treatments of nervous disorders through effective systemic or local delivery of high doses of methylcobalamin to target organs.
Methylcobalamin increases Erk1/2 and Akt activities through the methylation cycle and promotes nerve regeneration in a rat sciatic nerve injury model
Methylcobalamin is one of the coenzymatically active cobalamin derivates and required for the activity of the cytoplasmic enzyme methionine synthetase catalyzing the methylation of homocysteine into methionine. The effect of methylcobalamin on the proliferation of malignant cells has been examined. Methylcobalamin inhibited the proliferation of androgen-sensitive SC-3 cells (a cloned cell line from Shionogi mouse mammary tumor, SC115) in culture at the concentration of 100-300 micrograms/ml. An inhibitory activity of methylcobalamin on the proliferation was also observed in other cell lines (estrogen-sensitive B-1F cells from mouse Leydig cell tumor and MCF-7 cells from human mammary tumor) at the concentration of 500 micrograms/ml. Moreover, large doses of methylcobalamin injected intraperitoneally (100 mg/kg body weight/day) were non-toxic and suppressed the tumor growth of SC115 and B-1F cells in mice fed a vitamin B12 deficient diet. These results show that methylcobalamin inhibits the proliferation of malignant cells in culture and in vivo and propose the possibility of methylcobalamin as a candidate of potentially useful agents for the treatment for some malignant tumors.
Effects of methylcobalamin on the proliferation of androgen-sensitive or estrogen-sensitive malignant cells in culture and in vivo
The effects of carnitine and cobamamide were studied at the unspecific stage of anorexia nervosa treatment. Carnitine and cobamamide accelerated the amelioration of the patients’ somatic state (body weight gain, gastrointestinal functions normalization). Experimental psychological technique of involved deciphering discovered that latent fatigue disappeared and mental performance sharply increased under carnitine and cobamamide treatment. Experimental model of anorexia nervosa was used for electron microscopy and morphometry of neocortical tissue structure after starvation period and in feeding rehabilitation with carnitine and cobamamide. These drugs were shown to promote cerebral mass growth, increase in neocortical layers thickness, pyramidal neurons volume, that led to full restoration of normal structure of neocortex. The data provide a basis suitable to recommend carnitine and cobamamide to treat patients with relevant anorexia.
Clinico-experimental substantiation of the use of carnitine and cobalamin in the treatment of anorexia nervosa
The rate of destruction of crystalline vitamin B12 in neutral aqueous solutions, when exposed to direct sunlight, indirect sunlight, dim daylight, artificial light, ultraviolet light, and various monochromatic light sources has been determined. Sunlight, at a brightness of 8,000 foot-candles, causes a ten per cent loss for each half hour of exposure. Below 300 foot-candles, no destruction is noticeable. Artificial light of about 14,000 foot-candles causes a loss of about twelve per cent per half hour. A brightness of 3,600 foot-candles causes no alteration after two hours. With ultraviolet light the pattern of destruction is similar to that obtained with sunlight. For monochromatic light sources, photolysis is higher in the short wave length region. No destruction was observed in the red.
Photolysis of vitamin B12
We showed that patients with B12 deficiency have higher than expected frequency of MTHFR mutation and patients with both abnormalities have an abnormal endothelial function.
Examining B12 Deficiency Associated With C677T Mutation on MTHFR Gene in Terms of Commonness and Endothelial Function
The aim of this study was to examine the association of homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation and vitamin B12 deficiency in 360 asymptomatic individuals and to investigate forearm endothelial function in C677T homozygotes. MTHFR C677T mutation and levels of vitamin B12, folic acid, and homocysteine were measured in study participants. Frequency of homozygosity for the C677T mutation was 67/360 (18.6%). Homocysteine levels were elevated in homozygous compared with heterozygous subjects or those without the mutation (20.6 +/- 18.8 vs. 9.4 +/- 3.2 mumol/l; P < 0.0001). The number of subjects with vitamin B12 deficiency (<150 pmol/l) was significantly higher among the homozygote than the heterozygote subjects or subjects without mutation [20/67 (29.8%) vs. 27/293 (9.2%); P < 0.0001]. Homozygote subjects had 4.2 times higher probability of having B12 deficiency (95% confidence interval = 2.1-8.3). Forearm endothelial function was assessed in 33 homozygote and 12 control subjects. Abnormal endothelial function was observed in homozygous subjects and was worse in homozygote subjects with vitamin B12 deficiency. Endothelial function was normalized after B12 and folic acid treatment. We found that homozygosity for the C677T mutation is strongly associated with B12 deficiency. Coexistence of homozygosity for the C677T mutation and B12 deficiency is associated with endothelial dysfunction and can be corrected with vitamin B12 and folic acid treatment.
High frequency of vitamin B12 deficiency in asymptomatic individuals homozygous to MTHFR C677T mutation is associated with endothelial dysfunction and homocysteinemia
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