Role of Vitamin D in Cardiovascular Health

The active form of vitamin (Vit) D (1,25[OH]₂ vitamin D) is bound to vitamin D–binding protein (DBP) in circulation, crosses the cell membrane, and binds to vitamin D receptor (VDR). The conjugated vitamin D with its receptor forms a heterodimer complex with retinoid X receptor (RXR) and with other factors, attaches to vitamin D–responsive elements on deoxyribonucleic acid, and alters gene expression. RNA = ribonucleic acid.

Metabolism and biologic actions of vitamin D. The major biologic form of vitamin D, vitamin D₃, is synthesized in the skin from the precursor (pre-D) under direct sunlight. Vitamin D from cutaneous synthesis and nutritional sources enters the circulation and is bound to vitamin D–binding protein (DBP). A series of enzymatic hydroxylations in the liver and kidneys transform vitamin D to biologically active 1,25(OH)₂ vitamin D. Parathyroid hormone regulates the hydroxylation in kidney. Activated vitamin D exerts multiple cardiovascular and noncardiovascular actions. BP = blood pressure; GI = gastrointestinal; TG = triglyceride; VLDL = very low density lipoprotein.