Biliary lipid composition in heterozygous familial hypercholesterolemia and influence of treatment with probucol

The lipid composition of fasting duodenal bile was determined in 11 healthy subjects with normolipidemia and 15 patients with heterozygous familial hypercholesterolemia (FH) (12 with type IIa, three with type IIb). The age distribution among the groups of subjects was similar. In the patients with heterozygous FH type IIa, the mean value for molar percentage of cholesterol and lithogenic index (LI) of bile were significantly higher than those of controls (8.4 +/- 1.0%, 1.47 +/- 0.18 calculated by Hegard, Dam, and Holzbach vs 4.3 +/- 0.4%, 0.81 +/- 0.07, respectively). The value of LI in the patients with FH type IIb was also found to be significantly higher than that of the controls. In the patients with heterozygous FH type IIa, we observed both a significant decrease in the molar percentages of glycochenodeoxycholic acid, glycoursodeoxycholic acid, and glycolithocholic acid, and a significant increase of taurochenodeoxycholic acid compared to the corresponding values in the controls. Bile analysis of six patients was reexamined during probucol treatment after 16 weeks. Probucol significantly lowered serum cholesterol levels. However, biliary lipid composition and individual bile acid proportions was not altered by the treatment. The results suggest that most of the patients with heterozygous FH have supersaturated bile and are predisposed to cholesterol gallstone formation. In addition, the mechanism by which probucol lowers serum cholesterol appears to be independent of any change in the metabolism of biliary lipid.