The effects of a dietary oxidized oil on lipid metabolism in rats

Abstract

This study was carried out to investigate the effects of a dietary oxidized oil on lipid metabolism in rats, particularly the desaturation of fatty acids. Two groups of rats were fed initially for a period of 35 d diets containing 10% of either fresh oil or thermally treated oil (150 degrees C, 6 d). The dietary fats used were markedly different for lipid peroxidation products (peroxide value: 94.5 vs. 3.1 meq O2/kg; thiobarbituric acid-reactive substances: 230 vs. 7 micromol/kg) but were equalized for their fatty acid composition by using different mixtures of lard and safflower oil and for tocopherol concentrations by individual supplementation with DL-alpha-tocopherol acetate. In the second period which lasted 16 d, the same diets were supplemented with 10% linseed oil to study the effect of the oxidized oil on the desaturation of alpha-linolenic acid. During the whole period, all the rats were fed identical quantities of diet by a restrictive feeding system in order to avoid a reduced food intake in the rats fed the oxidized oil. Body weight gains and food conversion rates were only slightly lower in the rats fed the oxidized oil compared to the rats fed the fresh oil. Hence, the effects of lipid peroxidation products could be studied without a distortion by a marked reduced food intake and growth. To assess the rate of fatty acid desaturation, the fatty acid composition of liver and heart total lipids and phospholipids was determined and ratios between product and precursor of individual desaturation reactions were calculated. Rats fed the oxidized oil had reduced ratios of 20:4n-6/18:2n-6, 20:5n-3/18:3n-3, 20:4n-6/20:3n-6, and 22:6n-3/22:5n-3 in liver phospholipids and reduced ratios of 20:4n-6/18:2n-6, 22:5n-3/18:3n-3, and 22:6n-3/18:3n-3 in heart phospholipids. Those results suggest a reduced rate of desaturation of linoleic acid and alpha-linolenic acid by microsomal delta4-, delta5-, and delta6-desaturases. Furthermore, liver total lipids of rats fed the oxidized oil exhibited a reduced ratio between total monounsaturated fatty acids and total saturated fatty acids, suggesting a reduced delta9-desaturation. Besides those effects, the study observed a slightly increased liver weight, markedly reduced tocopherol concentrations in liver and plasma, reduced lipid concentrations in plasma, and an increased ratio between phospholipids and cholesterol in the liver. Thus, the study demonstrates that feeding an oxidized oil causes several alterations of lipid and fatty acid metabolism which might be of great physiologic relevance.

Characterization of an alcoholic hepatic steatosis model induced by ethanol and high-fat diet in rats

“…Hochgraf et al (Hochgraf et al 1997) demonstrated that oxidized linoleic acid, which is present in sunflower seeds, promotes a significant increase in the plasma cholesterol levels in rats. In contrast, some other studies reported reduced levels of plasma cholesterol and triglycerides in rats and pigs in response to the consumption of oxidized dietary oil (Eder and Kirchgessner 1999;Eder 1999;Eder and Stangl 2000;Eder et al 2003;Acikgoz et al 2011). In this context, our results demonstrated increased cholesterol levels with HFD, which agrees with the proposed of Hochgraf et al (Hochgraf et al 1997).…”

A Novel Body Weight-loss Promoting Oil Prepared with Vegetable Protein

“…It is very important to keep in our mind the relation between oil and lipids/energy metabolism. Koch et al 13) and Eder 14) showed that feeding thermally oxidized oils to rats caused a reduction in the concentration of triacylglycerols and cholesterol in liver and plasma. They explain that the reduction of triacylglycerols may be due to stimulation of hepatic b-oxidation triggered by activation of peroxisome proliferators-activated receptor a (PPARa) and reduced hepatic de novo fatty acid synthesis [15][16][17] .…”

Cytotoxic Compounds Generated in Heated Oil and Assimilation of Oil in Wistar Rats

“…Koch et al 20) and Eder 21) showed that feeding thermally oxidized oils to rats caused a reduction in the concentrations of triacylglycerols and cholesterol in liver and plasma. They explain that the reduction of triacylglycerols may be due to stimulation of hepatic b-oxidation triggered by activation of peroxisome proliferators-activated receptor a (PPARa) and reduced hepatic de novo fatty acid synthesis [22][23][24] .…”