The Biliary System, Second Edition

Abstract The liver is a vital organ involved in numerous metabolic processes such as cholesterol and bile acid metabolism, biliary lipid secretion, and bile formation. Cholesterol balance across the liver has a crucial effect on influencing plasma total and LDL cholesterol levels and biliary cholesterol concentrations. Cholesterol and bile acid biosyntheses are primarily modulated by negative feedback regulatory mechanisms through the sterol regulatory element-binding protein isoform 2 (SREBP-2) and the farnesoid X receptor (FXR) pathways, respectively. The conversion of cholesterol to bile acids in the liver can balance the fecal excretion of bile acids, which is an important route for the removal of cholesterol from the body. Bile formation begins in the bile canaliculi, and maintenance of the enterohepatic circulation of bile acids results in a continuous secretion of bile. Hepatic secretion of biliary lipids is determined mainly by a group of ATP-binding cassette (ABC) transporters that are located on...