Changes in biliary lipid secretion and cholic acid kinetics induced by diet, diet plus simvastatin and diet plus ursodeoxycholic acid in obese subjects

The aim of this work was to evaluate and compare the effects of a low calorie diet (1026 kcal), simvastatin and ursodeoxycholic acid administration on biliary lipid secretion and cholic acid kinetics in dieting obese subjects. We studied 6 obese subjects before and after four weeks of a hypocaloric diet alone, after four weeks of diet plus ursodeoxycholic acid (900 mg/day) and after four weeks of diet plus simvastatin (40 mg/day), according to a Latin square design. The cholesterol saturation index was increased after diet alone, significantly reduced with diet plus ursodeoxycholic acid (p < 0.01), and unchanged during simvastatin administration. While the cholesterol output was reduced by all three regimens, diet plus ursodeoxycholic acid caused a significantly greater decrease than diet alone (p < 0.01). Cholic acid synthesis and bile acid secretion were decreased by diet and diet plus simvastatin (p < 0.05), but neither was affected by ursodeoxycholic acid. For cholic acid, all three treatments, but especially diet alone and diet plus simvastatin (p < 0.05), reduced the pool size; all three regimens also increased the turnover rate, but this was significant only for ursodeoxycholic acid (p < 0.01). Our study shows that, in obese patients, a hypocaloric diet reduces cholesterol-holding biliary lipid output and consequently increases the cholesterol saturation index. The addition of simvastatin to a hypocaloric dietary regimen reduces cholesterol secretion, but without variation in bile acid and phospholipid output thus the cholesterol saturation index remains unchanged. When ursodeoxycholic acid is added to the dietary regimen, it reduces cholesterol secretion, while maintaining bile acid output and, thus, lowers the cholesterol saturation index. Unlike simvastatin, ursodeoxycholic acid prevents the drop in cholic acid synthesis induced by a low calorie diet.