Hepatic cholesterol and bile acid synthesis in Japanese patients with cholesterol gallstones

In Japan the composition of gallstones is changing rapidly from the once-predominant brownpigment stones to cholesterol ones. The present work was undertaken to clarify the mechanism of cholesterol supersaturated bile production in Japanese patients with cholesterol gallstones. In 26 non-obese and normolipidemic patients (11 with cholesterol gallstones, 8 with black- or brown-pigment gallstones, 7 without gallstones) a liver biopsy and hepatic bile were surgically obtained under standardized conditions. The cholesterol saturation of hepatic bile was significantly higher in cholesterol gallstone patients than in gallstone-free controls (195 ±10 vs. 146 ±8%, respectively; P < 0.01). The microsomal activities of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme for cholesterol synthesis, cholesterol 7 α-hydroxylase, the rate-limiting enzyme for bile acid synthesis, and 7 α-hydroxy-4-cholesten-3-one 12 α-hydroxylase (12 α-hydroxylase), the rate-limiting enzyme for cholic acid synthesis, were assayed simultaneously in the same subjects. There were positive correlations between HMG-CoA reductase and cholesterol 7 α-hydroxylase activities (Rs = 0.62, P < 0.005), and between cholesterol 7 α-hydroxylase and 12 α-hydroxylase activities (Rs = 0.44, P < 0.05) in all subjects, irrespective of the existence of gallstones. The activities of the three rate-limiting enzymes did not differ significantly among the three groups (cholesterol stone, pigment stone and stone-free). In conclusion, the cholesterol supersaturation of hepatic bile in nonobese and normolipidemic Japanese patients with cholesterol gallstones does not result from an increased hepatic cholesterol synthesis or a decreased bile acid synthesis. This study was supported in part by a Grant-in-Aid for Scientific Research (No. 02454226) from the Ministry of Education, Science and Culture of Japan, and a grant from University of Tsukuba Project Research.