INFLUENCE OF URSODEOXYCHOLIC ACID ON BILIARY LIPIDS

The advent of bile acid therapy has shed some light on the mechanisms involved in determining bile lipid secretion. The administration of ch olelytic bile acids results in a lowering of cholesterol percent molar and saturation index due to a reduction in cholesterol secretion. Stu dies carried out after administration of bile acids showed initially t hat biliary cholesterol secretion rates were dependent on the hydropho bic/hydrophilic balance of the prevailing bile acid present in bile. H owever, more detailed investigations showed that some bile acids (chol ic and chenodeoxycholic acids) did not follow this rule because of the presence of other mechanisms involved in determining biliary choleste rol secretion and a possible link between cholesterol synthesis and bi liary cholesterol secretion. Several different human models have been used in more recent studies to arrive at a better understanding of the mechanisms involved in determining bile lipid secretion: obese patien ts, obese patients in rapid weight loss, patients with non-familial hy percholesterolemia and primary biliary cirrhosis. The findings in thes e studies indicate how modifications in biliary lipid secretion can ea sily be induced when there are changes in the relative amounts of bile acids. These changes may bring about modifications in intestinal abso rption, liver synthesis, and secretion of cholesterol and bile acids t hat could possibly lead to the formation of lithogenic bile and subseq uently to cholesterol gallstones.