The TCN2 776CNG polymorphism correlates with vitamin B(12) cellular delivery in healthy adult populations

OBJECTIVES: Vitamin B(12), or B(12), is an essential nutrient for humans, and its deficiency is a public health problem, especially in elderly population. Around 30% of circulating total B(12) levels are attached to transcobalamin II (TCN2), being referred as holotranscobalamin (holo-TC), and representing the biologically active fraction. After cellular uptake, B(12) participates in the homocysteine (Hcy) metabolism. The potential influence of the described TCN2 776CNG polymorphism upon B(12) intracellular delivery is a current target of research and we aimed to investigate its biochemical significance upon a healthy adult population.

DESIGN AND METHODS: The TCN2 776CNG polymorphism was screened by PCR-RFLP in 122 individuals. Concentrations of plasma total B(12), holo-TC, total Hcy and folate, as well as red blood cell folate, were determined.

RESULTS AND CONCLUSIONS: The studied polymorphism is common in the Portuguese population and significantly affects holo-TC but neither total B(12) nor total Hcy plasma concentrations, confirming that the TCN2 776CNG genotype exerts a significant influence upon B(12) cellular delivery.