BILE ACID TRANSPORT

Bile acids are end products of cholesterol and play essential roles in a number of diverse physiologic functions.73 They are the major driving force for bile formation, are required to form micelles with fatty acids and other intraluminal hydrophobic compounds that are necessary for their uptake by enterocytes, and are the major excretory products of cholesterol. To conserve the high metabolic cost of bile acid synthesis, the bile acid pool is recirculated up to 10 to 20 times each day in a unique enterohepatic circulation.34, 73 This process allows for bile acids to be reabsorbed from their site of action in the intestinal lumen and return to the liver by way of the portal vascular system. This article summarizes current understanding of how the different components that constitute this remarkably efficient system operate and highlights advances in the molecular identification of these specific bile acid transporters. Advances in understanding of how mutations of these bile acid transporters lead to distinct clinical entities, which predominately present as familial intrahepatic cholestatic syndromes, are also summarized. Use of these bile acid transporters for enhanced intestinal absorption of drugs or targeting to the liver is also briefly reviewed.