Genetic coding variants in the niacin receptor, hydroxyl-carboxylic acid receptor 2, and response to niacin therapy

Niacin has been used for seven decades to modulate plasma lipids, but its mechanism of action is still unclear. We sought to determine whether variants in the niacin receptor gene, hydroxyl–carboxylic receptor 2 (HCAR2), are associated with lipid response to treatment. Coding variants, rs7314976 (p.R311C) and rs2454727 (p.M317I), were genotyped in 2067 participants from the Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes (AIM-HIGH) trial. AIM-HIGH was a randomized, placebo-controlled trial that was conducted to assess the effect of extended-release niacin in patients with cardiovascular disease aggressively treated with low-density lipoprotein cholesterol-lowering therapy. There was no association of p.R311C or p.M317I with changes in low-density lipoprotein cholesterol, triglycerides, or high-density lipoprotein cholesterol at 1 year in groups receiving placebo or extended-release niacin. In White patients, the reduction in lipoprotein (a) [Lp(a)] in response to niacin was greater in homozygous carriers of the major 317M allele (−22.7%; P=0.005) compared with minor allele carriers (−15.3%). This was directionally consistent in the Black participants. Upon combining both groups, the reduction in Lp(a) in response to niacin was significantly greater in the homozygous major allele carriers (−23.0%; P=0.003) compared with minor allele carriers (−15.2%). Understanding the genetic contribution toward variation in response to niacin therapy, including Lp(a) reduction, could uncover mechanisms by which niacin decreases Lp(a), an important independent risk factor for cardiovascular disease.