Vitamin D: Sources, metabolism and mechanisms of action

Confined for a long time to its role in calcium and phosphate metabolism, vitamin D appears today as a vitamin with a large potential, through its involvement in many physiological processes. Due to its double origin (from food and endogenous synthesis), vitamin D is a vitamin apart, with sources and requirements difficult to define that are currently in discussion. However, the metabolism of the vitamin D begins to be known more precisely. This metabolism involves a first hepatic hydroxylation leading to the formation of 25(OH) D and second hydroxylation in kidney resulting in the formation of 1,25(OH) 2D, the active metabolite of vitamin D. This metabolite is responsible for the various genomic and non-genomic effects of vitamin D, whose mechanism of action involves a specific nuclear receptor, the vitamin D receptor VDR), and various signaling pathways controlled by a membrane receptor, the protein disulfide isomerase family A member (C) 2014 Societe franc, aise de nutrition. Published by Elsevier Masson SAS. All rights reserved.