Pravastatin lowers serum cholesterol, cholesterol-precursor sterols, fecal steroids, and cholesterol absorption in man

Abstract

Serum lipids, and absorption, intestinal fluxes, fecal elimination, and synthesis of cholesterol were studied before and during 4 weeks of pravastatin treatment at a dose of 40 mg/d in heterozygous familial hypercholesterolemic (FH) patients without (control group, n = 7) and with an ileal bypass (IBP group, n = 6). The drug reduced serum total and low-density lipoprotein (LDL) cholesterol and LDL-apoprotein (apo)B levels up to 34%. Less-consistent decreases in intermediate-density lipoprotein (IDL) and very-low-density lipoprotein (VLDL) cholesterol were also seen. None of the control patients and two of the IBP patients became normolipidemic (LDL <4 mmol/L). Marked transient reductions in serum free-methylated-cholesterol precursors, and more-constant decreases in the esterified and total fractions, suggested that cholesterol synthesis was reduced shortly after the start of treatment. The decreases in total lathosterol and methylsterols were more extensive in the IBP group than in the control group. Serum plant sterol levels were slightly increased, with inconsistent elevations of cholestanol. Reduced fecal elimination of cholesterol and its precursors suggests that decreased cholesterol synthesis was mainly due to lowered bile acid production, particularly in the IBP group with markedly enhanced basal bile acid and cholesterol synthesis. The serum and fecal levels of cholesterol precursors, lathosterol in particular, were related to each other and were proportionate to the serum level and fecal elimination of cholesterol. Absorption efficiency of cholesterol tended to be decreased, and mass calculations showed that biliary secretion and total absorption of cholesterol were clearly reduced in both groups by pravastatin. The findings suggest that the pravastatin-induced reduction of cholesterol synthesis and absorption are mainly balanced by lowered biliary and fecal output of cholesterol and bile acids. Determination of total lathosterol by gas-liquid chromatography (GLC) from nonsaponifiable serum lipids seems suitable for monitoring cholesterol metabolism during pravastatin treatment.