Nicotinic Acid Receptor (GPR109) Agonists

Hydroxycarboxylic acid (HCA) receptors, previously known as nicotinic acid receptors, are G_i/G_o protein-coupled receptors for which hydroxycarboxylic acids are endogenous ligands. Three HCA receptors are known to exist: HCA₁ (GPR81), HCA₂ (GPR109A) and HCA₃ (GPR109B).

GPR109B receptors originated from a gene duplication of GPR109A and have >95% homology. All subtypes are widely expressed throughout adipose tissue and are found at lower levels in macrophages, neutrophils, Langerhans cells and in the spleen. The human genes encoding these receptors are located on chromosome 12 (12q24.3).