Inactivation of 1,25(OH)2D occurs via C23/C24 oxidation catalysed by cytochrome CYP24A1 enzyme (Christakos et al. 2017) and it has been estimated that upwards of 2000 genes are directly or indirectly regulated which are involved in calcium homeostasis, immune responses, cellular growth, differentiation and apoptosis (Hossein-nezhad et al. 1,25(OH)2D acts by binding to nuclear vitamin D receptors (Neme et al. At the physiological level, this conversion is mediated by the 25-hydroxylase enzyme in its liver site. The first hydroxylation takes place in the liver followed by subsequent transport to the kidney where the second hydroxylation takes place. On the other hand, the other alternative for exogenous supplementation, calcifediol, is the result of the hydroxylation of cholecalciferol in its carbon 25 position, forming 25-hydroxy-vitamin D3, a molecule known as calcifediol or calcidiol. Vitamin D undergoes two subsequent hydroxylations to form the active form of the vitamin, 1-alpha, 25-dihydroxyvitamin D (1,25(OH)2D). The metabolites of vitamin D are carried in the circulation bound to a plasma protein called vitamin D binding protein (GC) (for review see Delanghe et al. A small number of countries in the world artificially fortify a few foods with vitamin D. oily fish, mushrooms exposed to sunlight and cod liver oil) are natural sources of vitamin D.
It is obtained from the diet and produced in the skin by photolysis of 7-dehydrocholesterol and released into the bloodstream. The amount of vitamin D your skin makes depends on many factors, including the time of day, season, latitude and your skin pigmentation. Vitamin D3 (VD3, cholecalciferol) is a steroid hormone that principally plays roles in regulating intestinal calcium absorption and in bone metabolism. Your body also makes vitamin D when direct sunlight converts a chemical in your skin into an active form of the vitamin (calciferol).
0 kommentar(er)
