Rotein is saturated with vitamin B-12 (2). Transcobalamin transports vitamin B-
These days a number of suitable techniques are available to measure holoTC, and information on its analytic and clinical aspects are accumulating EXO AND HOFFMANN-LUCKEB-12 deficient or nondeficient. {Major|Significant|Main|Key|Big quickly. Haptocorrin is an pretty much fully saturated vitamin B-12 binding glycoprotein of unknown function that carries the main element of circulating vitamin B-12 and, additionally, the inactive types of the vitamin, the so-called analogs. The metabolism of the protein is slow, with a turnover of '0.1 nmol vitamin B-12 each day (four). We and other folks have established solutions for analysis purposes which might be appropriate for measurement of transcobalamin and haptocorrin, whether saturated or not (7). However, clinicians have been interested mainly in measurements of total vitamin B-12 (ten) and holoTC. The truth that only vitamin B-12 that binds to transcobalamin is offered for cells has fostered the idea that measurement of holoTC would be more clinically meaningful than measurement of total vitamin B-12 (all of the vitamin B-12 that binds to transcobalamin and haptocorrin). Quite a few years ago, Victor Herbert suggested staging vitamin B-12 status with holoTC as the firstFrom the Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark. two Presented at the conference "NHANES Monitoring of Biomarkers of Folate and Vitamin B-12 Status: a Roundtable Overview," held in Rockville, MD, 156 July 2010. three The present evaluation is, to a sizable extent, primarily based on results from a European Union demonstration project (HoloTC: Early B12 Marker, QLK3-CT-200201775, 2002006) with participants from Denmark: Ebba Nexo (coordinator), Tore F Hardlei, Anne-Mette Hvas, Anne Louise Morkbak], England (Robert Clarke), Ireland (Anne Molloy, John M Scott), Norway (Jorn Schneede, Per Magne Ueland), and Scotland (Edward Valente). four Supported by the Danish Medical Analysis Council plus the Lundbeck Foundation. The National Center for Well being Statistics of your Centers for Disease Control and Prevention as well as the Office of Dietary Supplements on the National Institutes of Health cosponsored and supported the roundtable. 5 Address correspondence and reprint requests to E Nexo, Division of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Norrebrogade 44, DK 8000 Aarhus C, Denmark. E-mail: e.nexo@dadlnet.dk. doi: 10.3945/ajcn.111.013458.Why does a single measure cobalamin (vitamin B-12) rather than the fraction from the vitamin that will enter the cells, holotranscobalamin (holoTC) Within the 1980s the late Victor Herbert often asked this question (1). At the time, holoTC could only be measured by calculation on the distinction in between vitamin B-12 (eg, 500 pmol/L) and also the fraction of vitamin B-12 that was not attached to transcobalamin (eg, 420 pmol/L). Because of this, the uncertainty of your holoTC values was also big to allow correct evaluation of holoTC's clinical usefulness compared with other markers of vitamin B-12 status [plasma cobalamin (vitamin B12), homocysteine (tHcy), and methylmalonic acid (MMA)]. These days a number of appropriate methods are accessible to measure holoTC, and information on its analytic and clinical aspects are accumulating rapidly. The present evaluation summarizes current understanding about the analytic elements and concerning determinants of plasma holoTC. This overview also addresses the clinical efficiency of holoTC compared with that of total vitamin B-12. We conclude that mea-Am J Clin Nutr doi: 10.3945/ajcn.111.013458.
