Hepatic fatty acid metabolism in rats fed diets with different contents of C18:0, C18:1cisand C18:1transisomers

Abstract

In the present study the effects of some C18fatty acids on hepatic fatty acid metabolism have been compared. Male rats were fed cholesterol-free diets containing either C18:0, C18:1cisor C18:1transisomers as the variables. In accordance with previous work, oleic acid in the diet caused an increase in cholesterol concentration in the liver and in the lipoprotein fraction of density (d; kg/l)<1·006. Oleic acid also reduced the triacylglycerol:cholesterol value in this fraction. Surprisingly, the C18:1transisomers diet induced a decrease in the amount of cholesterol in total plasma as well as in the 1·019<d<1·063 lipoprotein fraction. Both oleic acid and C18:1transisomers increased the concentration of triacylglycerols in the liver. The two C18:1fatty acids differently influenced the hepatic activities of carnitine palmitoyltransferase-I and 3-hydroxy-acyl-CoA dehydrogenase; both enzymes were inhibited by C18:1transisomers, while no change was induced by oleic acid. The activity of the citrate carrier was lower in the oleic acid- and C18:1transisomers-fed rats, when compared with the rats fed stearic acid. No diet effects were seen for the activities of acetyl-CoA carboxylase, fatty acid synthase, diacylglycerol acyltransferase, citrate synthase and phosphofructokinase. The results are interpreted in that oleic acid raised liver triacylglycerol by reducing the secretion of it with thed<1·006 lipoprotein fraction whereas the C18:1transisomers enhanced liver triacylglycerol by lowering the hepatic oxidation of fatty acids.