The free fatty acid receptor (FFAR) is a G protein-coupled receptor (GPCR) activated by free fatty acids (FFAs), which play important roles not only as essential nutritional components but also as signaling molecules in numerous physiological processes. Free fatty acids (FFAs) are an important energy source for most body tissues, and are categorized by the length of their aliphatic tails; short-chain fatty acids (SCFAs) have less than 6 carbons, medium-chain fatty acids have 6–12 carbons, and long-chain fatty acids have 12 or more carbons. Five free fatty acid receptors (FFARs) have received considerable attention as a result of their physiological importance in various biological processes. Among the FFARs that have been identified, FFA1 (GPR40) and GPR120 are activated by medium- and long-chain FFAs, and GPR84 is activated by medium-chain FFAs. In contrast, FFA2 (GPR43) and FFA3 (GPR41) are activated by SCFAs. Each FFAR may act as a sensor for FFAs with selectivity for a particular FFA carbon chain length that is derived from food or food-derived metabolites. Physiological functions of FFARs have been reported to include the secretion of insulin and incretin hormones, adipocyte differentiation, anti-inflammatory effect, nerve activation, and taste preferences.


1.Hara T, et al. Rev Physiol Biochem Pharmacol. 2013;164:77–116.