Abstract
Bile acids are most abundant organic compounds in the bile, and are biosynthesized from cholesterol. Bile acids play an important role on bile formation as well as the solubilization of cholesterol in the bile. Recent studies elucidated the mechanism of metabolism and transport of bile acids and its regulatory system. As the mechanism of the action of UDCA, the theory of biliary bicarbonate umbrella has recently been postulated. Itching observed in cholestasis has been reported to be caused by lysophosphatidic acid produced from lysophsphatidylcholine, not by bile acids or opioids. FXR is a nuclear receptor with bile acids as ligands, and TGR5 is a membrane receptor with bile acids as ligands. Recently, bile acids have been reported to play an important role in the metabolism of sugars, lipids and energy through these receptors, and the development of new drugs for various diseases have been conducted with these bile acid receptors as targets.
