Activity of hepatic fatty acid oxidation enzymes in rats fed α-linolenic acid

Abstract

The activity of hepatic fatty acid oxidation enzymes in rats fed linseed and perilla oils rich in α-linolenic acid ( α-18:3) was compared to that in rats fed safflower oil rich in linoleic acid (18:2) and a saturated fat (palm oil). Palm and safflower oils were essentially devoid of α-18:3. The palmitoyl-CoA oxidation rates both in mitochondrial and peroxisomal pathways in liver homogenates were significantly higher in rats fed linseed oil than in those fed palm and safflower oils. Among rats fed diets containing palm oil, safflower oil, fat mixtures composed of safflower and perilla oils (2:1, w/w and 1:2, w/w), and perilla oil, mitochondrial and peroxisomal fatty oxidation rates increased with increasing dietary levels of perilla oil. Compared to palm and safflower oils, dietary α-18:3 either in the form of linseed or perilla oils profoundly increased the activity of carnitine palmitoyltransferase, acyl-CoA oxidase, 3-ketoacyl-CoA thiolase, and 2,4-dienoyl-CoA reductase. Smaller but significant increases by dietary α-18:3 of the activity of acyl-CoA dehydrogenase, enoyl-CoA hydratase, and Δ 3, Δ 2-enoyl-CoA isomerase were also observed. Unexpectedly, dietary α-18:3 greatly reduced the activity of 3-hydroxyacyl-CoA dehydrogenase. Compared to palm oil, dietary polyunsaturated fats significantly reduced the activity of fatty acid synthetase and glucose-6-phosphate dehydrogenase to the same levels. The activity of pyruvate kinase was significantly higher in rats fed palm oil than in those fed polyunsaturated fats. The extent of reduction was more prominent with polyunsaturated fats containing α-18:3 than with safflower oil devoid of α-18:3. Thus, compared to linoleic acid and saturated fatty acids, dietary α-18:3 caused characteristic changes in the activity of hepatic enzymes in fatty acid and glucose metabolism in rats.