Nicotinic acid: recent developments.

PURPOSE OF REVIEW: To review the recent progress in niacin research that is made in two major areas: new preparations to decrease flushing and niacin's mechanism of action. RECENT FINDINGS: Flushing, an adverse effect of niacin, results from GPR109A-mediated production of prostaglandin D2 and E2 in Langerhans' cells which act on DP1 and EP2/4 receptors in dermal capillaries causing their vasodilatation. DP1 receptor antagonist (laropiprant) attenuates the niacin flush in animals and humans. A reformulated preparation of extended-release niacin lowers flushing compared with the extended-release niacin (Niaspan, Abbott Laboratories, Chicago, Illinois, USA). Aspirin pretreatment attenuates flushing from Niaspan. Recent data on niacin's mechanism of action indicate that it directly inhibits hepatic diacylglycerolacyl transferase 2 resulting in an inhibition of triglyceride synthesis and decreased apolipoprotein B-containing lipoproteins; niacin, by inhibiting the surface expression of hepatic ATP synthase beta chain, decreases the hepatic holoparticle high-density lipoprotein catabolism and raises high-density lipoprotein levels; and niacin increases redox potential in arterial endothelial cells resulting in the inhibition of redox-sensitive genes. SUMMARY: Recent developments suggest that the niacin receptor GPR109A is involved in flushing, but it does not explain multiple actions of niacin. Actions of niacin on diacylglycerolacyl transferase 2, ATP synthase beta chain, and redox state may explain the multiple actions of niacin.