EFFECT OF HIGH CHOLESTEROL DIET ON RAT LIVER PEROXISOMAL ENZYMES

Abstract

The effect of a high cholesterol diet on rat liver peroxisomal enzymes was investigated. Chow containing 2% cholesterol was given for 14 days to rats initially weighing ca. 200 g. The cholesterol levels of the blood and liver were elevated and the activities of the hepatic peroxisomal fatty acyl-CoA β-oxidizing system (FAOS) and fatty acyl-CoA oxidase (FAO), a rate-limiting enzyme, were significantly increased (approximately 1.4- and 1.5-fold, respectively). Other groups of the rats were fed a normal diet or a 2% cholesterol diet for 7 days. Then clofibrate (40 mg) was intraperitoneally administered daily to both groups for 7 days, all the while the rats continued to receive the same diet as before. Though clofibrate treatment alone enhanced the peroxisomal FAOS and FAO activities of the liver (4.3-fold for FAOS and 13.5- fold for FAO), both activities were further increased significantly in rats on the 2% cholesterol diet (approximately further 1.4- and 1.3-fold, respectively). The high cholesterol diet failed to increase catalase and urate oxidase activities, which are not directly related to fatty acid β-oxidation. Cholesterol is a probable physiological substrate for liver peroxisomes, and thus the particles are considered to be induced by various substrates : not only long-chain fatty acids, but also cholesterol.