Hepatic cholesterogenesis and cholesterol 7 alpha-hydroxylase activity in hamsters fed diets enriched with pectins...

Cholesterol 7 alpha-hydroxylase activity was determined in parallel with the rate of cholesterogenesis from acetate and mevalonate in the liver of hamsters fed diets enriched with pectins (5%) and/or cholesterol (0.1%). Cholesterol feeding reduced the rate of incorporation of the precursors into cholesterol. Moreover, the radioactivity derived from mevalonate was found mainly in the esterified form of the newly synthesized molecules. In parallel, cholesterol 7 alpha-hydroxylation decreased by 50%. Pectins did not greatly affect hepatic cholesterogenesis or 7 alpha-hydroxycholesterol formation. In contrast, the fibers prevented to a large extent the metabolic alterations resulting from cholesterol feeding. Cholesterogenesis from mevalonate remained active; ester formation declined and the activity of cholesterol 7 alpha-hydroxylase persisted. Pectins could maintain the activity of this enzyme through multiple mechanisms, one of them being the channeling of substrate into the specific compartment of cholesterol which is destined to form bile acids.