Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II

Chen, Xinke; Remacha, Ángel F.; Sardà, M. Pilar; Carmel, Ralph

doi:10.1093/ajcn/81.1.110

Cited by 20 publications

(20 citation statements)

References 19 publications

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“…However, according to Chen et al, HoloTC concentrations most probably reflect vitamin B 12 status independently of its recent absorption (22). Questions are still raised concerning the specificity of the HoloTC assay.…”

Section: Discussionmentioning

confidence: 99%

Determination of serum holotranscobalamin concentrations with the AxSYM active B₁₂ assay: cut-off point evaluation in the clinical laboratory

Bamonti

Moscato

Novembrino

et al. 2009

Clinical Chemistry and Laboratory Medicine

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Background: A reliable early marker is required for diagnosis of cobalamin deficiency. We calculated an appropriate holotranscobalamin (HoloTC) cut-off point for identifying cobalamin deficiency using an immunoenzymatic assay. Methods: Determination of the cut-off threshold and correlation between HoloTC and the other diagnostic parameters routinely used for vitamin B 12 deficiency wtotal vitamin B 12 (tB 12 ), folate, homocysteinex were measured in 250 routine blood specimens from 107 men (mean age 59.0"18.8 years) and 143 women (mean age 54.2"23.1 years). The inclusion criterion was serum tB 12 concentration F221 pmol/L. Results: Analytical performance results agreed with those reported by others. A weak correlation (Rs0.42) was found between HoloTC and tB 12 . A 40 pmol/L cut-off threshold was chosen for HoloTC and the associated sensitivity and

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Section: Discussionmentioning

confidence: 99%

Determination of serum holotranscobalamin concentrations with the AxSYM active B₁₂ assay: cut-off point evaluation in the clinical laboratory

Bamonti

Moscato

Novembrino

et al. 2009

Clinical Chemistry and Laboratory Medicine

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“…Measuring holo-TC-II is believed to reflect the bioavailable vitamin B12 as the protein is responsible for the immediate transfer of the newly absorbed vitamin from the ileal enterocytes to the target cells. Chen et al found that the metabolic status of vitamin B12 was a major determinant of holo-TC-II serum levels (64). Furthermore, they concluded that the absorption status of vitamin B12 also influenced serum holo-TC-II levels.…”

Section: Holo-tc-ii Testmentioning

confidence: 99%

Metformin and Vitamin B12 Deficiency: Where Do We Stand?

Ahmed

2016

J Pharm Pharm Sci

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-The association between metformin use and low vitamin B12 levels in type 2 diabetes mellitus patients is well-established. However, many aspects of the topic remain to be elucidated. There is still controversy on the current diagnostic approaches to vitamin B12 deficiency. It is now believed that measuring the serum levels of the vitamin may not reflect its metabolic status. Moreover, there were conflicting results from studies attempting to quantify and explore metformin-associated vitamin B12 deficiency and its clinical impacts. This article reviews the cellular functions of vitamin B12, the biomarkers utilized to define the vitamin deficiency and metformin-induced vitamin B12 deficiency with an emphasis on its prevalence and clinical impacts.

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“…The laboratory evaluation of B 12 status follows different strategies whose advantages and disadvantages are intensely debated [8,9,[11][12][13][14][15][16][17]. Measurement of the total B 12 in blood plasma (Cbl-saturated HC [holoHC] + holoTC) has been used for decades because of the simplicity of the method.…”

Section: Introductionmentioning

confidence: 99%

Metabolic signs of vitamin B12 deficiency in humans: computational model and its implications for diagnostics

Fedosov

2010

Metabolism

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Early diagnostics of cobalamin (Cbl, vitamin B 12 ) deficiency is primarily based on measurements of the relevant metabolic markers in blood plasma-total B 12 , specific Cbl-saturated transporter holo-transcobalamin (holoTC), and substrates of Cbl-dependent enzymatic reactions methylmalonic acid (MMA) and homocysteine (Hcy). Concentrations of B 12 and holoTC decrease whereas MMA and Hcy increase under deficiency. Yet, the results of individual tests are often contradictory and do not guarantee unambiguous diagnosis. The current work describes the metabolic manifestation of vitamin B 12 deficiency in terms of flux equations fitted to data sets from literature. The model mathematically connects all the markers and presents 4 independent measurements as a single point (x, y) in the combined coordinates x = (holoTC·B 12 ) ½ and y = ½log 10 (MMA·Hcy). Pairwise averaging compensates for the individual fluctuations of the markers caused by (1) irregular spikes of holoTC, (2) delayed change of the total plasma B 12 buffered by an internal Cbl depot, and (3) variations in the production/ excretion velocities of MMA and Hcy. Bivariate distribution of the marker combinations (x, y) reveals several peaks of frequency in the analyzed mixed population. The peaks seem to represent the reference subgroups with different B 12 physiology and characteristic values of "wellness parameter": w = log 10 (holoTC n ) + log 10 (B 12n ) − log 10 (MMA n ) − log 10 (Hcy n ), where concentrations are normalized (eg, MMA n = MMA/MMA normal ). Dynamic response of the organism to B 12 intake is quantified and described as an additional analytical tool when classifying uncertain cases. The discussed mathematical approaches are of general applicability in diagnostics.

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Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II

Cited by 20 publications

References 19 publications

Determination of serum holotranscobalamin concentrations with the AxSYM active B₁₂ assay: cut-off point evaluation in the clinical laboratory

Determination of serum holotranscobalamin concentrations with the AxSYM active B₁₂ assay: cut-off point evaluation in the clinical laboratory

Metformin and Vitamin B12 Deficiency: Where Do We Stand?

Metabolic signs of vitamin B12 deficiency in humans: computational model and its implications for diagnostics

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Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II

Cited by 20 publications

References 19 publications

Determination of serum holotranscobalamin concentrations with the AxSYM active B12 assay: cut-off point evaluation in the clinical laboratory

Determination of serum holotranscobalamin concentrations with the AxSYM active B12 assay: cut-off point evaluation in the clinical laboratory

Metformin and Vitamin B12 Deficiency: Where Do We Stand?

Metabolic signs of vitamin B12 deficiency in humans: computational model and its implications for diagnostics

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Product

Resources

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Determination of serum holotranscobalamin concentrations with the AxSYM active B₁₂ assay: cut-off point evaluation in the clinical laboratory

Determination of serum holotranscobalamin concentrations with the AxSYM active B₁₂ assay: cut-off point evaluation in the clinical laboratory