Marker Of Vitamin B12 Deficiency Research Articles

Vitamin B12 status and hyperhomocysteinemia in patients with Rheumatoid arthritis treated with methotrexate and folic acid

BackgroundRheumatoid arthritis (RA) is an inflammatory arthritis in which the immune system targets synovial joints. Methotrexate serves as the mainstay of treatment for RA due to its efficacy. However, patients treated with methotrexate are uniquely at risk for vitamin B12 deficiency and hyperhomocysteinemia due to coincident disease risk factors and the fact that methotrexate use is associated with malabsorption. The objective of this study was to assess for vitamin B12 deficiency among patients with RA treated with methotrexate and folic acid. MethodsThis cross-sectional study included 50 patients with RA treated with methotrexate and folic acid and 49 patients with RA treated with other therapies. Patients were matched by age, sex, race, renal function, and disease activity. We compared plasma vitamin B12, methylmalonic acid, and homocysteine levels between these two groups utilizing quantitative and categorical analyses. ResultsThirty-seven (74%) RA patients on methotrexate and folic acid had elevated plasma homocysteine levels compared with only 27 (55%) RA patients receiving other therapies (P < 0.05). The proportion of patients with low vitamin B12 and high methylmalonic acid levels did not differ between the two groups. ConclusionsOur data show high plasma homocysteine levels among RA patients treated with methotrexate and folic acid. While plasma vitamin B12 levels were similar between the two groups, high plasma homocysteine is also a sensitive marker of vitamin B12 deficiency. Additional studies should evaluate for the presence of clinical features of vitamin B12 deficiency and hyperhomocysteinemia among RA patients treated with methotrexate and folic acid.

Plasma methylmalonic acid predicts risk of acute myocardial infarction and mortality in patients with coronary heart disease: A prospective 2-cohort study.

Elevated plasma methylmalonic acid (MMA) is reported in patients with established coronary heart disease (CHD) and is considered a marker of vitamin B12 deficiency. Moreover, MMA-dependent reactions have been linked to alterations in mitochondrial energy metabolism and oxidative stress, key features in the pathophysiology of cardiovascular diseases (CVDs). We examined whether plasma MMA prospectively predicted the long-term risk of acute myocardial infarction (AMI) and mortality. Using Cox modeling, we estimated hazard ratios (HRs) for endpoints according to per 1-SD increment of log-transformed plasma MMA in two independent populations: the Western Norway Coronary Angiography Cohort (WECAC) (patients evaluated for CHD; n=4137) and the Norwegian Vitamin Trial (NORVIT) (patients hospitalized with AMI; n=3525). In WECAC and NORVIT, 12.8% and 18.0% experienced an AMI, whereas 21.8% and 19.9% died, of whom 45.5% and 60.3% from CVD-related causes during follow-up (range 3-11 years), respectively. In WECAC, age- and gender-adjusted HRs (95% confidence interval) were 1.18 (1.09-1.28), 1.25 (1.18-1.33), and 1.28 (1.17-1.40) for future AMI, total mortality, and CVD mortality, respectively. Corresponding risk estimates were 1.19 (1.10-1.28), 1.22 (1.14-1.31), and 1.30 (1.19-1.42) in NORVIT. These estimates were only slightly attenuated after multivariable adjustments. Across both cohorts, the MMA-risk association was stronger in older adults, women, and non-smokers. Elevated MMA was associated with an increased risk of AMI and mortality in patients with suspected or verified CHD.

Proton pump inhibitor use and its effect on vitamin B12 and homocysteine levels among men and women: A large cross-sectional study.

Previous studies have demonstrated an association between proton pump inhibitors (PPI) use and vitamin B12 deficiency. However, data regarding PPI use and elevated serum homocysteine level, an important marker of vitamin B12 deficiency, are scant. Data were collected from medical records of subjects examined at a screening center in Israel. Cross sectional analysis was conducted on 25,953 subjects. Levels of vitamin B12 and homocysteine were compared between subjects who consumed PPI medications and those who did not. The mean age of the study population was 45 years and 33% were females. Subjects who received PPI medications had a minor higher vitamin B12 levels (320 pmol/L vs 300 pmol/L, p=0.024). Levels of vitamin B12 remained higher in females receiving PPI medications after performing a stratified analysis according to subjects' gender. Homocysteine levels were higher in subjects receiving PPI medications as compared to those who did not (12.0 μmol/L vs 11.6 0 μmol/L, p<0.001). Levels remained higher in female subjects after performing a stratified analysis according to subjects' sex. There was no statistically significant difference in the prevalence of vitamin B12 deficiency (according to two cutoffs: vitamin B12≤200 or ≤140 pmol/L) as well as the prevalence of hyperhomocysteinemia (defined as homocysteine >15.0 μmol/L) between the two groups. According to our study, no association was found between PPI medication use and vitamin B12 deficiency or hyperhomocysteinemia. Patients receiving PPI medications had slightly higher levels of vitamin B12 and homocysteine, however these differences were too small to have any clinical relevance.

Status of maternal serum B vitamins and pregnancy outcomes: New insights from in vitro fertilization and embryo transfer (IVF-ET) treatment.

The influence of B vitamins on human fertility and infertility treatments remains elusive. Therefore, this study investigated the association of most B vitamins with IVF-ET outcomes. A total of 216 subjects aged <35 year in their first oocyte retrieval cycle were recruited. Blood samples from the participants were collected before the oocyte pick-up procedure, and serum levels of riboflavin, niacin, pantothenic acid, vitamin B6 (including PA and PLP), folate, and methylmalonic acid (MMA) were detected using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Endpoints were classified into three groups according to tertiles (lower, middle, and upper) of each vitamin index, and the association of the serum vitamin status with intermediate and clinical outcomes was analyzed using a generalized estimating equation model. Higher riboflavin levels were associated with elevated probabilities of high-quality embryos, as well as clinical pregnancy after embryo transfer. A greater likelihood of transferable embryos was found in the middle tertile of serum folate. Similarly, a negative correlation of serum MMA, a marker of vitamin B12 deficiency, with high-quality embryos was identified. No significance was observed for other vitamins in terms of all endpoints. Therefore, sufficient levels of pre-conception riboflavin, folate, and vitamin B12 are recommended for successful infertility treatment and pregnancy planning; further evidence is needed to confirm our conclusion.

Increased serum methylmalonic acid levels were associated with the presence of cardiovascular diseases.

BackgroundFunctional vitamin B12 deficiency is common in cardiovascular diseases (CVDs), such as heart failure and myocardial infarction. Methylmalonic acid (MMA) is a specific and sensitive marker of vitamin B12 deficiency. However, there are scarce data in regard to the relationship between MMA and CVDs.Materials and methodsIn this cross-sectional study, we analyzed data of 5,313 adult participants of the National Health and Nutrition Examination Survey (NHANES) 2013–2014. Associations between MMA and other variables were assessed with linear regression models. Univariable and multivariable logistic regression models were employed to explore the association between MMA and CVDs.ResultsThe weighted prevalence of CVDs was 8.8% in the general population of the USA. Higher MMA levels were found in participants with CVDs (p < 0.001). Linear regression models revealed positive associations between serum MMA level and age (p < 0.001), glycohemoglobin (p = 0.023), fasting glucose (p = 0.044), mean cell volume (p = 0.038), and hypertension (p = 0.003). In the multivariable logistic model adjusting for age, gender, ethnicity, smoking, hypertension, glycohemoglobin, body mass index (BMI), low-density lipoprotein-cholesterol (LDL-C), renal dysfunction and vitamin B12, serum MMA (adjusted odds ratio, 3.08; 95% confidence interval: 1.63–5.81, p = 0.002, per ln nmol/L increment) was associated with CVDs.ConclusionOur study demonstrated that elevated serum MMA levels were independently associated with the presence of CVDs and may be used to predict the occurrence of CVDs.

Cutaneous hyperpigmentation as a diagnostic marker of vitamin B12 deficiency: a case report

&lt;p&gt;Cutaneous hyperpigmentation and glossitis are recognized but often overlooked early signs of vitamin B12 deficiency (VB12D). Pernicious anaemia is the most common cause of VB12D. Many clinicians miss the diagnosis of this potentially fatal but treatable condition in the absence of the more often reported life-threatening neuropsychiatric and haematologic features, notwithstanding the concomitant presence of characteristic cutaneous signs. These apperceptions of conspicuous and early dermatologic signs lead to diagnostic delay, which can result in dire consequences for the patient. We report the case of a 24-year-old young woman who for two years had repeated blood transfusions, iron supplementation and haematinics on account of anaemia of undetermined aetiology of a yet to be determined aetiology, despite the simultaneous presence of a constellation of glaring dermatologic clues to vitamin B12 deficiency. Following diagnosis and the institution of the appropriate therapy, the patient made remarkable improvement with a reversal of pigmentation and correction of the anaemia within a month. She continues to see the haematologists for follow-up.&lt;/p&gt;

Comparison of Serum Holotranscobalamin with Serum Vitamin B12 in Population Prone to Megaloblastic Anemia and their Correlation with Nerve Conduction Study.

Early detection of megaloblastic anemia and associated neurological complications is crucial for management. This study was conducted to compare serum holotranscobalamin level with serum vitamin B12 level as early biomarker in people prone to megaloblastic anemia and to evaluate co-relation between these biomarkers and nerve conduction study in study patients. 83 adult patients (Hb > 12 gm/dl) prone to megaloblastic anemia were studied for basic haematological investigations, random blood sugar, thyroid function test, liver function test, kidney function test, serum vitamin B12, serum holotranscobalamin and serum folic acid levels. 45 patients among them underwent nerve conduction studies. All study patients were classified in 6 groups on the basis of risk factors for megaloblastic anemia. 29 patients (34.9%) were on antiepileptic drugs, 26 (31.3%) were chronic alcoholic, 10 patients (12%) each, had malabsorption and ileal tuberculosis, 6 (7.22%) had chronic pancreatitis and 2 (2.4%) had ileal resection. 30 patients (36.14%) had low serum holotranscobalamin, including 7 patients (8.43%) with low serum vitamin B12 level also, unmasking vitamin B12 deficiency in 23 patients (27.7%). 7 patients (8.43%) had mean corpuscular volume (MCV) > 100fL and 8 patients (9.63%) had vitamin B12 deficiency related changes on peripheral smear. Serum vitamin B12 and holotranscobalamin levels were significantly low in patients with peripheral smear changes, with p value 0.039 and 0.041 respectively, while no such association seen with MCV. Subclinical peripheral neuropathy was detected in 18 (40%) out of 45 patients on nerve conduction study. Serum holotranscobalamin levels were significantly lower (p = 0.031) than serum vitamin B12 levels (p = 0.2) in patients with neuropathic changes. Rest investigations and serum folic acid levels were normal in all patients. Holotranscobalamin levels can be considered early and reliable marker for vitamin B12 deficiency and deficiency associated peripheral neuropathy, even in patients who are prone to megaloblastic anemia, and not yet anemic or symptomatic for neuropathy.

Maternal Vitamin B12 Status During Pregnancy and Its Association With Outcomes of Pregnancy and Health of the Offspring: A Systematic Review and Implications for Policy in India.

BackgroundVitamins B12 and folate participate in the one-carbon metabolism cycle and hence regulate fetal growth. Though vitamin B12 deficiency is widely prevalent, the current public health policy in India is to supplement only iron and folic acid for the prevention of anaemia. Prompted by our research findings of the importance of maternal vitamin B12 status for a healthy pregnancy, birth and offspring health outcomes, we evaluated available literature evidence using a systematic review approach, to inform policy.MethodsA systematic search was performed for relevant Indian studies in the MEDLINE/PubMed and IndMed databases. We selected studies reporting maternal vitamin B12 status (dietary intake or blood concentrations), and/or metabolic markers of vitamin B12 deficiency (homocysteine, methylmalonic acid) or haematological indices during pregnancy and their associations with outcomes of pregnancy, infancy or in later life. Intervention trials of vitamin B12 during pregnancy were also included. Quality of evidence was assessed on the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.ResultsOf the 635 articles identified, 46 studies met the inclusion criteria (cohort studies-26, case-control studies-13, RCT’s -7). There is a high prevalence of vitamin B12 deficiency in Indian women during pregnancy (40-70%) (3 studies). Observational studies support associations (adjusted for potential sociodemographic confounders, maternal body size, postnatal factors) of lower maternal B12, higher homocysteine or an imbalance between vitamin B12-folate status with a higher risk of NTDs (6 studies), pregnancy complications (recurrent pregnancy losses, gestational diabetes, pre-eclampsia) (9 studies), lower birth weight (10 studies) and adverse longer-term health outcomes in the offspring (cognitive functions, adiposity, insulin resistance) (11 studies). Vitamin B12 supplementation (7 RCT’s) in pregnancy showed a beneficial effect on offspring neurocognitive development and an effect on birth weight was inconclusive. There is a high quality evidence to support the role of low maternal vitamin B12 in higher risk for NTD and low birth weight and moderate-quality evidence for higher risk of gestational diabetes and later life adverse health outcomes (cognitive functions, risk for diabetes) in offspring.ConclusionIn the Indian population low maternal vitaminB12 status, is associated with adverse maternal and child health outcomes. The level of evidence supports adding vitamin B12 to existing nutritional programs in India for extended benefits on outcomes in pregnancy and offspring health besides control of anaemia.Systematic Review Registration[website], identifier [registration number]

Methylmalonic acid, vitamin B12, renal function, and risk of all-cause mortality in the general population: results from the prospective Lifelines-MINUTHE study

BackgroundMethylmalonic acid (MMA) is best known for its use as a functional marker of vitamin B12 deficiency. However, MMA concentrations not only depend on adequate vitamin B12 status, but also relate to renal function and endogenous production of propionic acid. Hence, we aimed to investigate to what extent variation in MMA levels is explained by vitamin B12 and eGFR and whether MMA levels are associated with mortality if vitamin B12 and eGFR are taken into account.MethodsA total of 1533 individuals (aged 60–75 years, 50% male) were included from the Lifelines Cohort and Biobank Study. Individuals were included between 2006 and 2013, and the total follow-up time was 8.5 years.ResultsMedian [IQR] age of the study population was 65 [62–69] years, 50% was male. At baseline, median MMA concentration was 170 [138–216] nmol/L, vitamin B12 290 [224–362] pmol/L, and eGFR 84 [74–91] mL/min/1.73 m2. Log2 vitamin B12, log2 eGFR, age, and sex were significantly associated with log2 MMA in multivariable linear regression analyses (model R2 = 0.22). After a total follow-up time of 8.5 years, 72 individuals had died. Log2 MMA levels were significantly associated with mortality (hazard ratio [HR] 1.67 [95% CI 1.25–2.22], P < 0.001). Moreover, we found a significant interaction between MMA and eGFR with respect to mortality (Pinteraction < 0.001).ConclusionsOnly 22% of variation in MMA levels was explained by vitamin B12, eGFR, age, and sex, indicating that a large part of variation in MMA levels is attributable to other factors (e.g., catabolism, dietary components, or gut microbial production). Higher MMA levels are associated with an increased risk for mortality, independent of vitamin B12, eGFR, and sex. This association was more pronounced in individuals with impaired renal function.

Low Vitamin B12 Levels: An Underestimated Cause Of Minimal Cognitive Impairment And Dementia.

BackgroundVitamin B12 deficiency is linked to impaired cognition and memory along with a sensation of tingling and numbness, an outcome of poor myelination. Elevated methylmalonic acid and serum homocysteine levels are markers of Vitamin B12 deficiency. Elevated homocysteine levels are also often associated with Alzheimer’s disease and stroke. We conducted this study to determine the effect of vitamin B12 replacement therapy on vitamin B12-deficient patients with noted cognitive impairment.MethodsWe conducted a cross-sectional, multicenter study of patients with minimal cognitive impairment (MCI) to assess for Vitamin B12 and homocysteine levels. All patients found to be deficient in vitamin B12 underwent replacement therapy and were assessed again after three months via the Mini-Mental State Examination (MMSE) and a review of symptoms.ResultsA total of 202 patients were included in the study. Of those, 171 (84%) patients reported marked symptomatic improvement after vitamin B12 replacement while MMSE scores improved in 158 (78%) patients. Of the remaining 44 patients who reported no symptomatic improvement, MMSE scores improved in 26 while 18 patients showed no MMSE score improvements.ConclusionsVitamin B12 deficiency is linked to cognition, and replacement therapy may be an option to improve patient cognition outcomes. Further studies are needed to confirm and refine the observed associations over a larger scale and to determine whether these findings will translate to a reduction in cognitive decline.

Acrofacial Hyperpigmentation as A Sole Manifestation in A Case of Pancytopenia Due to Vitamin B12 Deficiency-A Diagnostic Alert

Vitamin B12 deficiency presents with a spectrum of manifestations ranging from anemia to gastrointestinal disturbances and potentially lethal cardiovascular and neuropsychiatric illnesses. Diffuse acral hyperpigmentation with knuckle pad accentuation is a reliable marker of Vitamin B12 deficiency. We, hereby report a case of 49 years old male who presented with hyperpigmentation on face, hands and feet with knuckle pad accentuation. On investigations, he was found to have pancytopenia & Vitamin B12 deficiency. He showed marked improvement on administration of Vitamin B12.

Is folate deficiency a common cause of distal symmetric polyneuropathy in Zambian clinics?

ObjectivesTo evaluate the odds of vitamin B12 and folate deficiencies among Zambian clinic attendees with distal symmetric polyneuropathy (DSP) and age, sex, and HIV matched controls. MethodsCases were adults from clinics in urban/peri-urban Zambia. Controls were enrolled among persons not seeking personal medical care, such as a caregiver or person collecting antiretrovirals without a medical complaint. Participants underwent structured interviews, physician examination, and assessments of complete blood count, renal and liver profiles, serum vitamin B12 and folate, erythrocyte folate, plasma total homocysteine and methylmalonic acid. HIV testing and CD4 counts were performed when appropriate. ResultsAmong 107 consenting matched case-control pairs, 65% were female, 52% HIV positive, with mean age of 47.6 (SD 13.5) years. Among HIV positive participants, mean CD4 count was 484 (SD 221) and 482 (SD 236) for cases and controls, respectively (p = .93). DSP symptoms and severity did not differ by HIV status (p's > 0.05). Height, history of tuberculosis treatment, alcohol use, education, asset index, dietary diversity, and nutritional supplement use did not differ between cases and controls (p's > 0.05). DSP cases had at least 3:1 odds of having low serum folate (p = .0001), severely low erythrocyte folate (p = .014), and elevated total homocysteine (p = .001) levels compared to controls. Markers of vitamin B12 deficiency were not associated with case status (p's > 0.05). ConclusionMarkers of folate deficiency are highly associated with DSP among Zambian clinic attendees. Future studies should consider a broader range of comorbid nutritional deficiencies, and strategies for interventions.

Newborn Screening for Vitamin B12 Deficiency in Germany—Strategies, Results, and Public Health Implications

To evaluate a systematic newborn screening (NBS) strategy for vitamin B12 deficiency. In a prospective single-center NBS study, a systematic screening strategy for vitamin B12 deficiency was developed and evaluated. Tandem-mass spectrometry screening was complemented by 2 second-tier strategies, measuring methylmalonic/3-OH-propionic/methylcitric acid, and homocysteine from dried blood spots. In a cohort of 176 702 children screened over 27months, 33 children were detected by NBS in whom (maternal) vitamin B12 deficiency was confirmed. Homocysteine was the most sensitive marker for vitamin B12 deficiency, but only combination with a second-tier strategy evaluating methylmalonic acid allowed for detection of all 33 children. Mothers were of various ethnic origins, and 89% adhered to a balanced diet. Treatment in children was performed predominantly by oral vitamin B12 supplementation (84%), and all children remained without clinical symptoms at short-term follow-up. Vitamin B12 deficiency is a treatable condition but can cause severe neurologic sequelae in infants if untreated. The proposed screening strategy is feasible and effective to identify moderate and severe cases of vitamin B12 deficiency. With an incidence of 1:5355 newborns, vitamin B12 deficiency is more frequent than inborn errors of metabolism included in NBS panels. Treatment of vitamin B12 deficiency is easy, and additional benefits can be achieved for previously undiagnosed affected mothers. This supports inclusion of vitamin B12 deficiency into NBS but also stresses the need for increased awareness of vitamin B12 deficiency in caregivers of pregnant women.

Assessing Diagnostic Accuracy of Serum Holotranscobalamin (Active-B12) in Comparison with Other Markers of Vitamin B12 Deficiency.

About 15-40% India is Vitamin B12 deficient (commonly diagnosed by total Vitamin B12) but, as only holoTC (active form) is taken up by body cells, thus measuring holoTC is more reflective of Vitamin B12 status than the former. We aimed to assess diagnostic accuracy of serum holoTC in comparison with total Vitamin B12 and total Homocysteine (HCY) as indicator of serum Vitamin B12 status. 217 human subjects (99 males and 118 females) ranging from 17 to 83years were divided into Vitamin B12 deficient (n = 70), borderline (n = 100) and sufficient groups (n = 47) who were further assessed for markers of Vitamin B12 deficiency-holoTC, HCY, Mean Corpuscular Volume (MCV), Folate, heamoglobin and creatinine. Samples were analysed using Siemens Advia Centaur Xpi. Total Vitamin B12 deficient group had - 84.3% holoTC deficient; 15.7% holoTC sufficient; 72.9% with elevated HCY; 27.1% with normal HCY; 11.4% with megaloblastic anaemia. Borderline group had - 34% holoTC deficient; 28% elevated HCY. A strong positive correlation was found between Total Vitamin B12 and holoTC (r = 0.754, p = <0.001) but strong negative correlation existed between holoTC and HCY (r = - 0.471, p = <0.001). Concordance between Total Vit B12 and HCY (Kappa index = 0.51, p < 0.001); between holoTC and HCY (Kappa index = 0.52, p = <0.001) were statically significant but the latter had a better sensitivity and specificity. Also, statically significant association exists between Total Vitamin B12 and holoTC with HCY (p = <0.001). Therefore, it is ascertained that Active Vitamin B12 assay is a better test and can be considered as an early marker of vitamin B12 deficiency.

Failure of the holotranscobalamin assay in vitamin B12-deficient patients

AbstractBackgroundIt has been demonstrated that vitamin B12 determinations fail, especially in patients with pernicious anemia with high titers of intrinsic factor antibody. Consistent with this finding, we observed a case of falsely normal holotranscobalamin (HoloTC) results in a patient with pernicious anemia and severe vitamin B12 deficiency. We aimed to investigate whether such a situation can also be seen in other individuals.MethodsWithin the frameworks of the SENIORLAB study and routine samples from a mixed patient population referred to a laboratory for investigation of B12 status, we searched for study participants displaying a normal HoloTC level (≥50 pmol/L) together with a decreased total vitamin B12 level (&lt;125 pmol/L). Thereafter, we determined whether samples with discrepant biochemical markers (i.e. low vitamin B12, normal HoloTC) also had increased functional markers of vitamin B12 deficiency (methyl malonic acid [MMA], homocysteine [Hcy]) and/or a low value of Fedosov’s combined indicator of vitamin B12 status (&lt;−0.5).ResultsThe prevalence of a normal HoloTC level and low total vitamin B12 level among the group of healthy seniors (n=1451) was 0.21% (95% confidence interval [CI], CI, 0.08–0.6%). Among the 106,635 routine samples with concurrent HoloTC and total vitamin B12 determination, 176 (i.e. 0.17%, 95% CI, 0.14–0.19%) had discrepant biochemical markers. Among them, 24 who were identified as having discrepant biochemical markers and a diagnosis of vitamin B12 deficiency could be confirmed with functional markers.ConclusionsInitial and isolated screening for vitamin B12 deficiency using a HoloTC cut-off of ≥50 pmol/L in a small subset of patients may reveal false-negative (normal) results, meaning that patients with vitamin B12 deficiency may remain undetected.

Vitamin B12 deficiency and impaired expression of amnionless during aging.

BackgroundPhysical frailty and loss of mobility in elderly individuals lead to reduced independence, quality of life, and increased mortality. Vitamin B12 deficiency has been linked to several age‐related chronic diseases, including in the musculo‐skeletal system, where vitamin B12 deficiency is generally believed to be linked to poor nutritional intake. In the present study, we asked whether aging and frailty associate with altered vitamin B12 homeostasis in humans and investigated the underlying molecular mechanisms using preclinical models.MethodsWe analysed a subset of the Singapore Longitudinal Aging Study and stratified 238 participants based on age and Fried frailty criteria. Levels of methyl‐malonic acid (MMA), a marker for vitamin B12 deficiency, and amnionless, the vitamin B12 co‐receptor that anchors the vitamin B12 transport complex to the membrane of epithelial cells, were measured in plasma. In addition, vitamin B12 levels and the molecular mechanisms of vitamin B12 uptake and excretion were analysed in ileum, kidney, liver, and blood using a rat model of natural aging where nutritional intake is fully controlled.ResultsWe demonstrate that aging and frailty are associated with a higher prevalence of functional vitamin B12 deficiency that can be detected by increased levels of MMA in blood (ρ = 0.25; P = 0.00013). The decline in circulating vitamin B12 levels is recapitulated in a rat model of natural aging where food composition and intake are stable. At the molecular level, these perturbations involve altered expression of amnionless in the ileum and kidney. Interestingly, we demonstrate that amnionless can be detected in serum where its levels increase during aging in both rodents and human (P = 3.3e‐07 and 9.2e‐07, respectively). Blood amnionless levels negatively correlate with vitamin B12 in rats (r2 = 0.305; P = 0.0042) and positively correlate with the vitamin B12 deficiency marker MMA in humans (ρ = 0.22; P = 0.00068).ConclusionsOur results demonstrate that aging and frailty cause intrinsic vitamin B12 deficiencies, which can occur independently of nutritional intake. Mechanistically, vitamin B12 deficiency involves the physio‐pathological decline of both the intestinal uptake and the renal reabsorption system for vitamin B12. Finally, amnionless is a novel biomarker which can detect perturbed vitamin B12 bioavailability during aging and physical frailty.

Folate and vitamin B12 status is associated with insulin resistance and metabolic syndrome in morbid obesity

Low vitamin B12 and high folate during pregnancy are associated with visceral obesity and insulin resistance in offspring. In the general population, high folate exacerbates the increase of methylmalonic acid, a marker of vitamin B12 deficiency. However, the influence of vitamin B12 and folate and their related markers on insulin resistance and metabolic syndrome remains unknown in severe obesity. To evaluate the influence of vitamin B12 and folate on HOMA-IR and components of metabolic syndrome in severe obesity. 278 consecutive obese patients were assessed prospectively for HOMA-IR, red blood cell (RBC) folates, homocysteine and methylmalonic acid. We compared the associations with the components of metabolic syndrome during the preoperative multidisciplinary evaluation (period-1) and before bariatric surgery (period-2). The HOMA-IR was higher in patients with highest tertile of RBC and either lowest tertile of plasma B12 or highest tertile of MMA (p<0.034 and 0.011, respectively). Lg HOMA-IR was negatively correlated with Lg homocysteine (p<0.0001) and positively correlated with Lg serum folate (p<0.001). The independent predictors for HOMA-IR at period 2 were either BMI and homocysteine (model 1 without serum folate, p=0.010 and p=0.002, respectively)or BMI and MMA (model 2 without homocysteine, p=0.030 and p=0.004, respectively). Age and RBC folate remained independently associated with the number of metabolic syndrome components (p=0.006 and 0.020, respectively). RBC folate, homocysteine, and MMA predict HOMA-IR in severe obesity. Our findings challenge the benefit of folate fortified food in severe obesity, in particular in patients with a deficit of vitamin B12. The cohort study was registered at clinicaltrials.gov as NCT02663388.

Holotranscobalamin (HoloTC, Active-B12) and Herbert's model for the development of vitamin B12 deficiency: a review and alternative hypothesis.

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.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-2252-z) contains supplementary material, which is available to authorized users.

Homocysteine and methylmalonate: when should I measure them and what do they mean?

Plasma total homocysteine has traditionally been considered a risk factor for atherosclerosis. More recently, it is being adopted as a marker of vitamin B12 deficiency. The association between mild hyperhomocysteinaemia...

Experimental vitamin B12 deficiency in a human subject: a longitudinal investigation of the performance of the holotranscobalamin (HoloTC, Active-B12) immunoassay.

Based on Victor Herbert’s model for sequential stages in the development of vitamin B12 deficiency, the holotranscobalamin (HoloTC) immunoassay has controversially been promoted as a more specific and sensitive replacement for the total vitamin B12 test, for the diagnosis of deficiency. There have been no longitudinal studies, by means of experimental cobalamin deficiency, because ethical considerations prevent such risky studies on patients or healthy human volunteers. The objective was to provide a detailed record of the response of HoloTC, compared to total vitamin B12 and metabolites, to the development of experimental vitamin B12 deficiency in an initially replete human subject. This 54 year old male, with a vitamin B12 deficiency possibly caused by a defect in the intracellular cobalamin metabolism, ensured an initially replete condition by means of oral doses of cyanocobalamin supplements at 1000 μg/day for 12 weeks. The subject then depleted himself of vitamin B12, by withholding treatment and using a low-cobalamin diet, until significant metabolic disturbances were observed. The responses of serum total vitamin B12 and HoloTC and the two metabolites, plasma methylmalonic acid and homocysteine, were monitored by weekly blood tests. HoloTC was not significantly more sensitive than either total serum vitamin B12 or total homocysteine, and was much less sensitive than methylmalonic acid. HoloTC decreased from an initial concentration of >128 pmol/L to a minimum of 33 pmol/L on day 742, the only day on which it fell below the lower limit of the reference interval. Total vitamin B12 decreased from an initial concentration of 606 pmol/L to a minimum of 171 pmol/L on day 728. Total homocysteine increased from an initial concentration of 8.4 μmol/L to a maximum of 14.2 μmol/L on day 609. Methylmalonic acid unexpectedly contained four distinct peaks; initially at 0.17 μmol/L, it first exceeded the upper limit of the reference interval on day 386, finally reaching a maximum peak of 0.90 μmol/L on day 658. The results of this experiment are inconsistent with Herbert’s hypothesis that HoloTC is the earliest marker of vitamin B12 deficiency, and therefore do not support his model for the staged development of vitamin B12 deficiency.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-1740-5) contains supplementary material, which is available to authorized users.