Bile acids are endogenous ligands for TGR5, a G-protein coupled receptor. Bile acids are important amphipathic biomolecules which can help absorption of dietary lipids and fat-soluble vitamins in the intestine. The TGR5 receptor is the first known G-protein coupled receptor specific for bile acids¹.

The coding sequence of the TGR5 gene contains 993 base pairs, encoding a protein of 330 amino acids. The receptor comprises seven transmembrane helices, three extracellular loops contributing to ligand binding, and three intracellular loops involved in mediating the signal to downstream signaling molecules².

TGR5 gene expression is widely distributed, including endocrine glands, adipocytes, muscles, immune organs, spinal cord, and the enteric nervous system³.

Animal studies suggest that TGR5 activation influences energy production and thereby may be involved in obesity and diabetes. TGR5 activation also influences intestinal motility. TGR5 is now recognized as a potential target for the treatment of metabolic disorders, such as type 2 diabetes¹. In addition, the ability of TGR5 to lower the levels of proinflammatory cytokines in monocytes has opened new insights into the modulatory role of bile acids in pathology where inflammatory processes play a central role, including colitis and atheroma development^4,5.