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Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II.
Am J Clin Nutr 2005; 81(1):110-4AJ

Abstract

BACKGROUND

Cobalamin attached to transcobalamin II (TC II), known as holo-TC II, is the active cobalamin fraction taken up by tissues. Holo-TC II is also the form in which absorbed cobalamin enters the circulation from the ileum. Therefore, holo-TC II has been proposed variously as a marker of cobalamin adequacy, cobalamin absorption, or both, including even its advocacy as a surrogate Schilling test. Such claims carry conflicting diagnostic implications because metabolic adequacy and absorption are not identical.

OBJECTIVE

The objective was to examine metabolic and absorptive influences on holo-TC II.

DESIGN

Treated patients with pernicious anemia (PA), who have abnormal absorption but a normal metabolic status, were chosen as the model to differentiate between the effects of the 2 cobalamin-related characteristics. Serum holo-TC II and indexes of cobalamin metabolism in 23 treated patients were compared with those of 6 untreated PA patients (abnormal absorption and metabolic status) and 33 control subjects (normal absorption and metabolic status).

RESULTS

Holo-TC II, which correlated directly with cobalamin and inversely with homocysteine, was significantly higher in treated PA patients in metabolic remission than in untreated PA patients (74 +/- 59 compared with 9 +/- 6 pmol/L) and was significantly lower than in control subjects (105 +/- 58 pmol/L), although the latter difference was small and the values overlapped greatly.

CONCLUSIONS

Metabolic cobalamin status is a major determinant of serum holo-TC II. Absorption status may have mild influence as well, although other explanations remain possible. Serum holo-TC II cannot be used clinically to diagnose cobalamin malabsorption because of overlap with normal values. The influences on holo-TC II are complex and require careful analysis.

Authors+Show Affiliations

Department of Medicine, New York Methodist Hospital, Brooklyn, NY 11215, USA.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15640468

Citation

Chen, Xinke, et al. "Influence of Cobalamin Deficiency Compared With That of Cobalamin Absorption On Serum Holo-transcobalamin II." The American Journal of Clinical Nutrition, vol. 81, no. 1, 2005, pp. 110-4.
Chen X, Remacha AF, Sardà MP, et al. Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II. Am J Clin Nutr. 2005;81(1):110-4.
Chen, X., Remacha, A. F., Sardà, M. P., & Carmel, R. (2005). Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II. The American Journal of Clinical Nutrition, 81(1), pp. 110-4.
Chen X, et al. Influence of Cobalamin Deficiency Compared With That of Cobalamin Absorption On Serum Holo-transcobalamin II. Am J Clin Nutr. 2005;81(1):110-4. PubMed PMID: 15640468.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Influence of cobalamin deficiency compared with that of cobalamin absorption on serum holo-transcobalamin II. AU - Chen,Xinke, AU - Remacha,Angel F, AU - Sardà,M Pilar, AU - Carmel,Ralph, PY - 2005/1/11/pubmed PY - 2005/2/16/medline PY - 2005/1/11/entrez SP - 110 EP - 4 JF - The American journal of clinical nutrition JO - Am. J. Clin. Nutr. VL - 81 IS - 1 N2 - BACKGROUND: Cobalamin attached to transcobalamin II (TC II), known as holo-TC II, is the active cobalamin fraction taken up by tissues. Holo-TC II is also the form in which absorbed cobalamin enters the circulation from the ileum. Therefore, holo-TC II has been proposed variously as a marker of cobalamin adequacy, cobalamin absorption, or both, including even its advocacy as a surrogate Schilling test. Such claims carry conflicting diagnostic implications because metabolic adequacy and absorption are not identical. OBJECTIVE: The objective was to examine metabolic and absorptive influences on holo-TC II. DESIGN: Treated patients with pernicious anemia (PA), who have abnormal absorption but a normal metabolic status, were chosen as the model to differentiate between the effects of the 2 cobalamin-related characteristics. Serum holo-TC II and indexes of cobalamin metabolism in 23 treated patients were compared with those of 6 untreated PA patients (abnormal absorption and metabolic status) and 33 control subjects (normal absorption and metabolic status). RESULTS: Holo-TC II, which correlated directly with cobalamin and inversely with homocysteine, was significantly higher in treated PA patients in metabolic remission than in untreated PA patients (74 +/- 59 compared with 9 +/- 6 pmol/L) and was significantly lower than in control subjects (105 +/- 58 pmol/L), although the latter difference was small and the values overlapped greatly. CONCLUSIONS: Metabolic cobalamin status is a major determinant of serum holo-TC II. Absorption status may have mild influence as well, although other explanations remain possible. Serum holo-TC II cannot be used clinically to diagnose cobalamin malabsorption because of overlap with normal values. The influences on holo-TC II are complex and require careful analysis. SN - 0002-9165 UR - https://www.unboundmedicine.com/medline/citation/15640468/Influence_of_cobalamin_deficiency_compared_with_that_of_cobalamin_absorption_on_serum_holo_transcobalamin_II_ L2 - https://academic.oup.com/ajcn/article-lookup/doi/10.1093/ajcn/81.1.110 DB - PRIME DP - Unbound Medicine ER -