Inositol nicotinate

Inositol nicotinate and other niacins directly and noncompetitively inhibit microsomal enzyme diacylglycerol acyltransferase 2 (DGAT2) responsible for esterification of fatty acids to form triglycerides, resulting in decreased triglyceride synthesis and hepatic atherogenic lipoprotein secretion. Inhibitied triglyceride synthesis results in accelerated intracellular hepatic apo B degradation and the decreased secretion of VLDL and LDL particles. Niacin also inhibits hepatic expression of beta-chain adenosine triphosphate synthase which inhibits the removal or uptake of HDL–apo A-I. It is also suggested that niacin increases vascular endothelial cell redox state, resulting in the inhibition of oxidative stress and vascular inflammatory genes or key cytokines involved in atherosclerosis. It acts as a ligand on G-protein coupled receptor 109A (HCAR2/HM74A) and 109B (HCAR3/HM74) which mediates the anti-lipolytic and lipid-lowering effects of nicotinic acid. Niacin-mediated signalling of GPR109A expressed on adipocytes and G(i)-mediated decrease in cAMP levels result in decreased lipolysis, fatty acid mobilization, and triglyceride synthesis. The action of inositol nicotinate on GPR109A expressed on skin and macrophages to cause increased prostaglandin D2/E2 activity is thought to be less significant compared to other niacin molecules as it involves sustained release that leads to less flushing.