Free fatty acids (FFAs) were for long believed to influence cellular metabolism. Hoever, the discovery that FFAs actually mediate their effects through one of three G-protein coupled receptors (GPCRs) - Free Fatty Acid Receptors 1-3 (FFAR1-3), has initiated a number of studies in order to assess their implication in health and disease¹.

Like all other GPCRs, FFAR1-3 have seven transmembrane domains, an extracellular N-terminal tail and an intracellular C-terminus.

FFAR1 is activated by either medium or long, saturated or unsaturated fatty acids^2,3, whereas FFAR2 and FFAR3 are activated by short chain fatty acids^4,5. FFAR1 is coupled to Gq and leads to Ca2+ mobilization upon activation. FFAR2 couples to both pertussis-sensitive and insensitive G-proteins and also leads to increased intracellular Ca²⁺ levels. FFAR3 coupling to G-protein induces an increase in cAMP¹.

Distribution studies of all three FFA Receptors indicate that FFAR1 mRNA is quite elevated in the pancreas^2,3. FFAR1 is also detected in the liver, heart, skeletal muscle, and brain; although this broad localization pattern is supported only by one study². FFAR2 is expressed in many tissues like liver and colon⁶. FFAR3 is expressed in many tissues but shows highest expression in adipose tissue⁴. Relatively high expression of the receptor could be detected in pancreas, spleen, lymph nodes and bone marrow^4,5.

As mentioned above, the finding that FFAs’ actions are mediated by GPCRs, prompted many studies in order to elucidate their roles in healthy and disease states. Such studies stipulate that FFAR1 may be involved in obesity and type 2 diabetes since circulating free fatty acid levels in the plasma are significantly elevated. On the other hand, FFAR2 and FFAR3 could be potential targets for treating irritable bowel disease and appetite control¹.