Free Fatty Acid Receptor

Free fatty acid receptors (FFARs) are G protein-coupled receptors (GPCRs) activated by free fatty acids (FFAs). The four well-characterized FFARs are FFAR1/GPR40, FFAR2/GPR43, FFAR3/GPR41, and FFAR4/GPR120. FFARs are categorized according to the chain length of FFA ligands that activate each FFAR; FFA2 and FFA3 are activated by short chain FFAs, mainly acetate, butyrate, and propionate. GPR84 is activated by medium-chain FFAs, whereas FFA1 and GPR120 are activated by medium- or long-chain FFAs. Thus, each FFAR can act as an FFA sensor with selectivity for a particular FFA carbon chain length derived from food or food derived metabolites. FFARs have been reported to have physiological functions such as facilitation of insulin and incretin hormone secretion, adipocyte differentiation, anti-inflammatory effects, neuronal responses, and taste preferences. These physiological functions of FFARs could be considered to regulate energy and immune homeostasis. Therefore, FFARs have been targeted in therapeutic strategies for the treatment of metabolic disorders including type 2 diabetes and metabolic syndrome.