Effect of dietary fats on susceptibility of low-density lipoproteins to lipid peroxidation in pigs

The present study investigated the effect of dietary fats rich in polyunsaturated fatty acids (soybean oil), mono-unsaturated fatty acids (olive oil) and saturated fatty acids (beef tallow) on the susceptibility of low-density lipoproteins (LDL) to lipid peroxidation in pigs. In a cross-over design with three periods, nine pigs were fed each of the fats in daily amounts of 250 g for two weeks. The susceptibility of LDL to lipid peroxidation was determined by Cu2+-catalysed oxidation. The lag phase before onset of oxidation, the rate of diene formation during propagation phase and the maximal amount of dienes produced during oxidation were considered for assessing the oxidative susceptibility. The LDL of pigs fed soybean oil had a higher oxidative susceptibility than the LDL of pigs fed beef tallow or olive oil. Probably, the increased susceptibility of LDL from pigs fed soybean oil to lipid peroxidation is due to an enrichment of LDL with linoleic acid whereas an enrichment of LDL with oleic acid in pigs fed olive oil or beef tallow reduced its oxidative susceptibility. The concentration of total tocopherols in plasma, expressed per mol lipid, was not influenced and that in LDL was only slightly influenced by the dietary fat, indicating that the dietary fat had only a small effect on vitamin E status. Pigs fed soybean oil had increased concentrations (expressed per mol lipid) of thiobarbituric acid reactive substances in plasma, suggesting an enhanced lipid peroxidation relative to pigs fed olive oil or beef tallow. The effect of dietary fats on the susceptibility of LDL to lipid peroxidation might be of physiological relevance because oxidatively modified LDL play an important role in the progress of atherosclerosis.