The sedimentable sterols in gallstone patients before and during ursodeoxycholic acid and simvastatin treatments

The insoluble material in supersaturated bile is prerequisite for the formation of gallstones. We therefore studied the biliary precipitable and soluble cholesterol and noncholesterol sterols, including the cholesterol precursor sterols (including lanosterol and lathosterols), and the plant sterols campesterol and sitosterol, and cholestanol, which usually reflect cholesterol synthesis and absorption, respectively, before and after a 6-month treatment with ursodeoxycholic acid (UCDA), 15.4 +/- 4 mg/kg/day (standard error of the mean) or simvastatin (40 mg/day) in 21 patients with cholesterol gallstones, to obtain further information about the factors contributing to the formation of gallstones.

The sediment and supernatant fractions of duodenal bile samples were separated by ultracentrifugation and analyzed with gas-liquid chromatography.

At the base line (n = 21) 50% +/- 3% of biliary cholesterol and a variable amount of the noncholesterol sterols (from 14% of lanosterol to 62% of cholestanol) were in the sediment fraction. The pattern of the noncholesterol sterols in the sediment resembled that of gallstones described previously. At base line body mass index was positively related to the percentage of precipitable cholesterol in bile (r = 0.46, P < 0.05), and the serum sitosterol proportion negatively related to the molar percentage of biliary cholesterol and positively to that of bile acids (r = -0.46 and r = 0.50, P < 0.05 for both). UDCA decreased the precipitable percentage of cholesterol from 46% to 31% (P < 0.03) and simvastatin from 57% to 42% (P = 0.05). Both drugs also decreased the precipitable percentages of lathosterols and cholestanol while increasing that of lanosterol. In relation to cholesterol, the sediment to supernatant ratios of all methylsterols were increased, whereas those of polar lathosterols tended to decrease during UDCA treatment.

Patients with high body mass index have more precipitable cholesterol in their bile. Although both UDCA and simvastatin decreased the precipitable cholesterol, the bile still contained one-third of its cholesterol in the sedimentable form.