Low holo-transcobalamin levels are prevalent in vegetarians and is associated with coronary artery disease in Indian population.

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).

Vitamin B12 and its binding proteins in hepatocellular carcinoma and chronic liver diseases.

BACKGROUND: The vitamin B12 (B12)-binding protein haptocorrin (HC) has proven to be a potentially useful biomarker in patients with fibrolamellar hepatocellular carcinoma (HCC). Little is known concerning the level of HC and other B12-related proteins in patients with HCC as compared to patients with other chronic liver diseases (CLDs) and healthy controls. We hypothesized that HC could be a biomarker of HCC. AIMS: To investigate levels of HC and B12-related proteins in HCC compared to CLDs and healthy controls. METHODS: We investigated two patient populations: A cross-sectional cohort of HCC patients (n = 130), CLD patients (n = 102) and healthy controls (n = 46) and a cohort of 38 HCC patients studied at baseline and 1, 4, and 12 weeks following ablative treatment. Patients were evaluated by standard biochemistry, Child-Pugh-score and Barcelona Clinic Liver Cancer (BCLC) classification. We analyzed total B12 by routine methods and HC, transcobalamin (TC), B12 saturated TC (holoTC), and the soluble cell surface receptor for holoTC (sCD320) by in-house enzyme-linked immunosorbent assay. RESULTS: HC showed higher median (range) levels for both HCC (590 [290-5860]) and CLD patients (620 [310-4010]) compared to controls (460 [250-2020]) (p < 0.01). Total B12, TC, holoTC, and sCD320 showed elevated levels in both HCC and CLD compared to controls. Only holoTC changed following treatment, without a concurrent change in TC. CONCLUSION: B12 and B12-related proteins (total B12, HC, TC, holoTC, and sCD320) show elevations in both HCC and CLD patients compared to controls, suggesting a relation to CLD in general rather than to primary liver cancer. Thus, HC is not useful as a biomarker for HCC.

Holo-transcobalamin is not associated with the risk of all-cause mortality in the general population.

BACKGROUND & AIMS: Holo-Transcobalamin (holo-TC) is the biologically active form of vitamin B12, a vitamin essential in human metabolism. The association between vitamin B12 (total cobalamin) and mortality risk has been controversially reported, whereas the relation between holo-TC and survival is unknown. In a population-based sample (n = 862, female share 42.8%, median age 62.3 years), we related serum holo-TC to the risk of all-cause mortality. METHODS: We measured serum holo-TC by electro-chemiluminescence. Multivariable-adjusted Cox proportional hazards regression models were used to quantify the association between serum holo-TC and all-cause mortality. RESULTS: Over a median follow-up time of 10.9 years, n = 99 individuals died. We did not find significant associations between serum holo-TC and the risk of all-cause mortality (HR: 1.00 [95% CI 0.97-1.03] per 5-point increment in holo-TC), neither in the overall sample, nor in subgroups stratified by sex, diabetes, or hypertension. CONCLUSION: The biologically active form of vitamin B12, holo-TC, is not related to the risk of all-cause mortality in a moderate-sized sample from the general population.

Diagnostic reliability of serum active B12 (holo-transcobalamin) in true evaluation of vitamin B12 deficiency: Relevance in current perspective.

OBJECTIVE: Measurement of total vitamin B12 (vit B12) concentration raised concerns over early detection of vit B12 deficiency due to its clinical unreliability. In this present article we aimed to assess the efficacy of holo-transcobolamin (active vit B12) for true evaluation of vit B12 deficiency. METHODS: This retrospective study included 100 participants referred for vit B12 assay. Serum total vit B12, active vit B12 and homocysteine were estimated. RESULTS: Our study showed 59% of the total participants with vit B12 deficiency (185 ± 64.62 pg/ml) and 18% with hyper-cobalaminemia (1666.9 ± 367.13 pg/ml) based on their total vit B12 concentrations. A comparative study on total vit B12 and active vit B12 was done which reflected a striking disparity in results. Active vit B12 reported 28.8% patients with vit B12 deficiency (19.8 ± 17.48 pg/ml) and only 16.6% patients with hyper-cobalaminemia (224.14 ± 10 pg/ml). Active vit B12 appeared to be more sensitive (82.35% vs 65%) and specific (46.6% vs. 43.8%) diagnostic marker compared to total vit B12. Pearson Correlation study indicated a strong positive correlation (r = 0.695 at p < 0.01) hence justified use of the two methods. CONCLUSION: We claim that active vit B12 is a much more reliable biomarker than total vit B12 for early diagnosis of vit B12 deficiency.

The Revised D-A-CH-Reference Values for the Intake of Vitamin B12 : Prevention of Deficiency and Beyond.

SCOPE: The nutrition societies of Germany, Austria, and Switzerland are the joint editors of the "D-A-CH reference values for nutrient intake", which are revised regularly. METHODS AND RESULTS: By reviewing vitamin-B12 -related biomarker studies, the reference values for vitamin B12 were revised in 2018. For adults, the estimated intake is based on the adequate serum concentrations of holotranscobalamin and methylmalonic acid. The estimated values for children and adolescents are extrapolated from the adult reference value by considering differences in body mass, an allometric exponent, and growth factors. For infants below 4 months of age, an estimated value is set based on the vitamin B12 intake via breast milk. The reference values for pregnant and lactating women consider the requirements for the fetus and for loss via breast milk. The estimated values for vitamin B12 intake for infants, children, and adolescents range from 0.5 to 4.0 µg d-1 . For adults, the estimated values are set at 4.0 µg d-1 , and for pregnant and lactating women, they are set at 4.5 and 5.5 µg d-1 , respectively. CONCLUSION: Based on the data of several vitamin B12 status biomarkers studies, the reference value for vitamin B12 intake for adults is raised from 3.0 to 4.0 µg d-1 .

Measurement of total Transcobalamin employing a commercially available assay for Active B12.

INTRODUCTION: Vitamin B12 deficiency is mostly caused by insufficient gastro-intestinal absorption and in rare conditions by Transcobalamin (TC) deficiency. Unsaturated Transcobalamin (apoTC) can be measured by a binding assay using radiolabeled cobalamin. The Active B12 test analyzes saturated Transcobalamin (holoTC) and we hypothesize that this test can be used to measure total TC by additional in vitro saturation with cobalamin. METHODS: Serum was saturated in vitro (16 times dilution) with a cyanocobalamin solution and total TC was selectively measured with the Abbott Active B12 test. ApoTC was calculated by subtracting endogenous holoTC from total TC after correction for dilution. Linearity was determined with a pool serum dilution series. Precision was investigated according to the CLSI EP15 protocol. Method comparison was performed against a binding assay using radiolabeled cobalamin. Reference values were determined in 100 healthy controls. RESULTS: The method was linear in the range of 240 to 1933pmol/L (R2=0.997, lack of fit F=1.61). Precision of low- and high-pool total TC in serum were; 5.2% and 4.3% respectively. Method comparison against a radiolabeled cobalamin binding assay showed a proportional bias of 30% (y=0.70x+126). Total TC reference values were determined at 500-1276pmol/L. CONCLUSION: We describe a rapid method to quantify total TC, which can be implemented on routine platforms using commercial Active B12 tests. In addition, apoTC can be assessed by subtracting endogenous holoTC concentration which can be measured in the same run, securing the same calibration level for all three parameters (holoTC, apoTC and total TC). This method is applicable in clinical diagnostics and in larger epidemiological studies.

Corrigendum: Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency.

[This corrects the article on p. 27 in vol. 3, PMID: 27446930.].

Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency.

Vitamin B12 (cobalamin, Cbl, B12) is an indispensable water-soluble micronutrient that serves as a coenzyme for cytosolic methionine synthase (MS) and mitochondrial methylmalonyl-CoA mutase (MCM). Deficiency of Cbl, whether nutritional or due to inborn errors of Cbl metabolism, inactivate MS and MCM leading to the accumulation of homocysteine (Hcy) and methylmalonic acid (MMA), respectively. In conjunction with total B12 and its bioactive protein-bound form, holo-transcobalamin (holo-TC), Hcy, and MMA are the preferred serum biomarkers utilized to determine B12 status. Clinically, vitamin B12 deficiency leads to neurological deterioration and megaloblastic anemia, and, if left untreated, to death. Subclinical vitamin B12 deficiency (usually defined as a total serum B12 of <200 pmol/L) presents asymptomatically or with rather subtle generic symptoms that oftentimes are mistakenly ascribed to unrelated disorders. Numerous studies have now established that serum vitamin B12 has limited diagnostic value as a stand-alone marker. Low serum levels of vitamin B12 not always represent deficiency, and likewise, severe functional deficiency of the micronutrient has been documented in the presence of normal and even high levels of serum vitamin B12. This review discusses the usefulness and limitations of current biomarkers of B12 status in newborn screening, infant and adult diagnostics, the algorithms utilized to diagnose B12 deficiency and unusual findings of vitamin B12 status in various human disorders.

Low levels of cobalamin, epidermal growth factor, and normal prions in multiple sclerosis spinal cord.

We have previously demonstrated that multiple sclerosis (MS) patients have abnormal cerebrospinal fluid (CSF) levels of the key myelin-related molecules cobalamin (Cbl), epidermal growth factor (EGF), and normal cellular prions (PrP(C)s), thus confirming that some CSF abnormalities may be co-responsible for remyelination failure. We determined the levels of these three molecules in post-mortem spinal cord (SC) samples taken from MS patients and control patients. The control SC samples, almost all of which came from non-neurological patients, did not show any microscopic lesions of any type. All of the samples were supplied by the U.K. MS Tissue Bank. The Cbl, EGF, and PrP(C) levels were determined using enzyme-linked immunosorbent assays. The SC total homocysteine level was determined using a competitive immunoenzymatic assay. CSF samples, taken from a further group of MS patients, were used for the assay of holo-transcobalamin (holo-TC) levels. The Cbl, EGF, and PrP(C) levels were significantly decreased in MS SCs in comparison with controls and, paradoxically, the decreased Cbl levels were associated with decreased SC levels of homocysteine, a biochemical marker of Cbl deficiency. The trends of EGF and PrP(C) levels paralleled those previously found in CSF, whereas that of Cbl was the opposite. There was no significant difference in CSF holo-TC levels between the MS patients and the controls. Given that we have previously demonstrated that Cbl positively regulates central nervous system EGF levels, it is conceivable that the low EGF levels in the MS SC may be causally related to a local decrease in Cbl levels. Only PrP(C) levels were invariably decreased in both the SC and CSF regardless of the clinical course of the disease. These findings suggest that the simultaneous lack of Cbl, EGF, and PrP(C)s may greatly hamper the remyelination process in MS patients, because they are key molecules of the machinery for remyelination.