Comparative evaluation of chenodeoxycholic and ursodeoxycholic acids in obese patients. Effects on biliary lipid metabolism during weight maintenance and weight reduction

Obesity is a condition associated with an increased frequency of gallstone disease. This study attempted to evaluate the comparative effects of two gallstonedissolving agents, chenodeoxycholic acid and ursodeoxycholic acid, on bile acid metabolism and biliary lipid secretion in obese subjects in order to identify the bile acid of choice in preventing and treating gallstone disease in obesity. Twenty obese subjects (> 120% ideal body wt) were randomly treated with ursodeoxycholic acid (10 mg · kg^-1 · day^-1 · 1 mo^-1) and then with chenodeoxycholic acid (15 mg · kg^-1 · day^-1 · 1 mo^-1) or with chenodeoxycholic acid first and then with ursodeoxycholic acid. Patients 1-10 were studied while eating an unrestricted weightmaintenance diet, whereas patients 11-20 were eating a 1080-kcal/d hypocaloric diet. Biliary lipid composition, cholesterol saturation index, and biliary bile acid pattern were evaluated in all subjects before and after each treatment period; in subjects 6-10 and 16-20, biliary lipid secretion rates and bile acid pool size were also evaluated. Both ursodeoxycholic acid and chenodeoxycholic acid decreased cholesterol outputs and cholesterol saturation index. However, during the weight-maintenance period the decrease induced by chenodeoxycholic acid was not significant. Biliary cholesterol outputs and cholesterol saturation index were always lower during ursodeoxycholic acid administration than during chenodeoxycholic acid therapy. Ursodeoxycholic acid levels during ursodeoxycholic acid administration and chenodeoxycholic acid levels during chenodeoxycholic acid administration increased in bile to 50% and 77%, respectively, of total bile acid levels. Bile acid pool size remained unchanged during chenodeoxycholic acid administration and was significantly reduced by ursodeoxycholic acid administration during the weight-reduction period. In conclusion, ursodeoxycholic acid in obese subjects seems more effective than chenodeoxycholic acid, at least during weight maintenance, in reducing cholesterol saturation of bile. This effect is related to a significant decrease of biliary cholesterol output.