Cholesterol absorption and synthesis during pravastatin, gemfibrozil and their combination

The study evaluates cholesterol metabolism off and on treatment with pravastatin (P), gemfibrozil (G) and their combination (PG) in 38 middle-age hyperlipidemic primary care patients with serum cholesterol > 6 mmol/l and serum triglycerides < 4 mmol/l after a low-fat low-cholesterol diet. The subjects were randomized to P (40 mg/g), G (1200 mg/day), PG (40 + 1200 mg/day) or placebo for 12 weeks. We analyzed serum lipids, apolipoproteins A-I, B and E, serum cholesterol precursors (markers of cholesterol synthesis), serum plant sterols and cholestanol (markers of cholesterol absorption) and cholesterol metabolism by the sterol balance technique and cholesterol absorption efficiency. P alone or in combination with G lowered apoprotein E concentration, and serum cholesterol levels by inhibiting cholesterol synthesis measured by the precursor/cholesterol proportions with inconsistent change in fecal output of cholesterol. G alone decreased bile acid synthesis and increased biliary cholesterol secretion which were associated with reduced cholesterol absorption efficiency and the serum plant sterol and cholestanol proportions, and increased synthesis of cholesterol as measured both by the sterol balance technique and the precursor sterol proportions. A combination of PG also lowered LDL cholesterol similarly but triglyceride-rich lipoproteins significantly more than P alone, and otherwise inhibited the changes caused by G in cholesterol metabolism except that the precursor sterol proportions still indicated reduced cholesterol synthesis. Overall, the changes of the cholesterol precursor proportions were negatively related to that of cholesterol absorption efficiency and positively to that of cholesterol synthesis. The respective plant sterol and cholestanol values correlated oppositely to cholesterol absorption efficiency and synthesis. Serum precursor sterols reflected changes in cholesterol synthesis more sensitively than the sterol balance technique, even though only the latter method can quantitate cholesterol synthesis.