Characterization of the stimulatory effect of high-fat diets on peroxisomal β-oxidation in rat liver

Abstract

The effect on rat liver peroxisomal .beta.-oxidation of feeding diets containing various amounts of dietary oils was investigated. With increasing amounts(5-25% wt/wt) of soybean oil an apparent, but not statistically significant, increase of 1.5-fold was found both in specific activity and in total liver activity. Increasing amounts of partially hydrogenated marine oil revealed a sigmoidal dose-response-curve, giving a 4- to 6-fold increase in the peroxisomal .beta.-oxidation activity at .gtoreq. 20% of this oil in the diet. Addition of small amounts of soybean oil to the marine-oil diet had no effect on the peroxisomal .beta.-oxidation activity, but decreased the C20:3(5,8,11) fatty acid/C20:4(5,8,11,14) fatty acid ratio in liver phospholipids from 0.74 to 0.01. Starvation for 2 days led to a 1.5- to 1.8-fold increase in the peroxisomal .beta.-oxidation activity in rats previously fed on a standard pelleted diet, but had no effect in rats given high-fat diets. Feeding partially hydrogenated marine oil or partially hydrogenated rape-seed oil resulted in higher activities than the corresponding unhydrogenated oils. No significant differences in the effect on peroxisomal .beta.-oxidation was detected between diets containing rape-seed oils with 15 or 45% erucic acid, respectively. These findings are discussed in relation to the possible effects of C22:1 and trans fatty acids in the process leading to increased peroxisomal .beta.-oxidation activity in the liver.