The role of holotranscobalamin in examination of vitamin B12 status

Abstract

Holotranscobalamin contains biologically available cobalamin because only holotranscobalamin promotes the uptake of the cobalamin therein by all cells, via specific receptors. Therefore holotranscobalamin has been proposed as a potentially useful alternative indicator of vitamin B12 status. The aim of the present study was to assess usefulness of holotranscobalamin in the evaluation of vitamin B12 status. We examined serum level of holotranscobalamin in 135 subjects divided in four groups according to the serum concentration of vitamin B12: 30 subjects with vitamin B12 <154 pmol/l, 50 subjects with vitamin B12 154-250, 30 subjects with vitamin B12 2251-350 pmol/l, 25 subjects with vitamin B12 >350 pmol/l. The results show that in subjects with low vitamin B12 serum level there are those with normal holotranscobalamin concentration (60%) and that in subjects with normal vitamin B12 there are those with low holotranscobalamin concentration (22%). The obtained results also show positive significant correlation between levels of holotranscobalamin and vitamin B12 (r = 0.62, p < -0.001). We can conclude that biologically active cobalamin, holotranscobalamin, is a useful tool when examining vitamin B12 status especially in subjects with borderline and low vitamin B12 concentrations. Measurements of the serum holotranscobalamin may be superior to total serum cobalamin.