Cholesterol absorption efficiency and sterol metabolism in obesity

Pole of enterohepatic cholesterol metabolism in obesity-induced increase of cholesterol synthesis was studied in healthy lean (BMI < 24) and overweigh t (BMI > 31) subjects by measuring serum lipids (including plant sterols, c holestanol and cholesterol precursors), cholesterol absorption % (double-la bel method), sterol balance and biliary lipids. New aspects of sterol metab olism in obesity were as follows: low efficiency of cholesterol absorption, reduced ratios to cholesterol of serum and biliary plant sterols and chole stanol (5 alpha -derivative of cholesterol), and a marked increase of serum and biliary cholesterol precursor sterols. Percent of cholesterol absorpti on was positively related to serum cholestanol and plant sterols, and negat ively to cholesterol synthesis, measured by the sterol balance technique or cholesterol precursor sterols in serum or bile. Total and endogenous chole sterol fluxes into the intestine were increased, but owing to low absorptio n percent, mass of cholesterol absorption was within control limits in the obese subjects. Thus, per gram of their large liver tissue the entry of int estinal cholesterol may even be subnormal. Percent of cholesterol absorptio n was insignificantly negatively (r = - 0.256) related to intestinal choles terol pool, but significantly to biliary concentrations of cholesterol (r = - 0.581), bile acids (r = - 0.513) and phospholipids (r = - 0.469). Thus, dilution of labeled dietary cholesterol by expanded intestinal cholesterol pool could have contributed to subnormal efficiency of cholesterol absorpti on, or transfer of labeled dietary cholesterol from intestinal oil phase to micellar phase may be competitively inhibited by expanded biliary secretio n, resulting in reduced absorption of dietary cholesterol. These mechanisms could have contributed to changes in metabolism of non-cholesterol sterols , especially of cholestanol and plant sterols. (C) 2000 Elsevier Science Ir eland Ltd. All rights reserved.