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Lipid and Lipoprotein Research Group and Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
2To whom correspondence should be addressed. LBA is a Senior Scholar of the Alberta Heritage Foundation for Medical Research.
We examined whether the degree of saturation of C-18 fatty acids influenced hepatic cholesterol metabolism in C3H mice. The mice were fed diets containing 20 g/100 g fat, enriched in stearic (18:0), oleic (18:1) or linoleic acid (18:2) with or without 1 g/100 g cholesterol. Plasma total cholesterol concentration was lower in mice fed the 18:0 diet relative to those fed the 18:1- or 18:2-enriched diets (P < 0.05) regardless of dietary cholesterol supplementation. Dietary cholesterol significantly raised hepatic total cholesterol concentration (P < 0.05) in those fed the 18:1- and 18:2-enriched diets, but not in mice fed the 18:0-enriched diet. Dietary cholesterol raised biliary cholesterol concentration (P < 0.05) in mice fed the 18:1- and 18:2-enriched diets, but not in mice fed the 18:0-enriched diet. The cholesterol saturation index was variably affected by the fat diets. Feeding diets containing cholesterol suppressed the hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity and induced acyl coenzyme A:cholesterol acyl transferase (ACAT) activity compared with feeding diets without cholesterol (P < 0.05), indicating that the liver was exposed to dietary cholesterol. Hepatic ACAT activity was lower in mice fed the 18:0-enriched diet compared with those fed the 18:1- or 18:2-enriched diets (P < 0.05). Addition of cholesterol to the 18:1 diet induced the largest increase of hepatic ACAT activity, and this was associated with the enrichment of VLDL with cholesterol. Varying the degree of saturation of C-18 fatty acids influences the metabolism and disposition of hepatic cholesterol.
KEY WORDS: acyl CoA cholesterol acyl transferase bile composition cholesterol 7
-hydroxylase 3-hydroxy-3-methylglutaryl coenzyme A reductase mice stearic acid
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