Bile Acid Metabolism

Bile acids are synthesised from cholesterol by the liver and are the major end products of cholesterol catabolism. Bile acid homoeostasis is dependent on hepatic de novo synthesis and an intact enterohepatic circulation, by means of which bile acids emptied into the small intestine are efficiently reabsorbed and sent back to the liver for resecretion into bile. As such, most of the biliary bile acids were previously secreted and had undergone enterohepatic cycling. In addition to acting as detergents to facilitate digestion and absorption of dietary lipids, bile acids play important roles in cholesterol homoeostasis, in hepatic bile formation and biliary excretion of lipids, and as signalling molecules to regulate lipid and glucose metabolism. This chapter reviews the pathways for biosynthesis, transport and metabolism of bile acids. The regulation of bile acid homoeostasis and their role as signalling molecules is also discussed.