Rat vitamin E status and heart lipid peroxidation: Effect of dietary α-Linolenic acid and marine n−3 fatty acids

Abstract

Three groups of sixteen male rats each were fed semipurified diets containing 15% by weight of lipid for a period of 4 wk. The diets contained the same amount of polyunsaturated fatty acids (PUFA) (20% of total fatty acids) and saturated fatty acids (19% of total fatty acids). Dietary PUFA were represented exclusively by linoleic acid (18∶2 diet), or 10% linoleic acid and 10% linolenic acid (18∶3 diet), or 10% linoleic acid and 10% long-chain n−3 fatty acids (LCn−3 diet). The overall amount of vitamin E was similar in the three diets,i.e, 140, 133 and 129 mg/kg diet, respectively. Following appropriate extraction, tocopherol levels in heart, liver, brain, adipose tissue (AT) and plasma were measured by high-performance liquid chromatography. The level of vitamin E in the heart decreased with n−3 PUFA diets, most markedly with LCn−3 PUFA. Liver and AT vitamin E contents also decreased with n−3 PUFA diets when expressed as μg/mg total lipids and μg/mg phospholipids, respectively. Total plasma vitamin E was lower in rats fed the LCn−3 diet, but there was no significant difference when expressed as μg/mg total lipids. Brain vitamin E was not affected by the various diets.In vitro cardiac lipid peroxidation was quantified by the thiobarbituric acid reactive substances (TBARS) test. Heart homogenates were incubated at 37°C for 15 and 30 min in both the absence (uninduced) or presence (induced) of a free radical generating system (1 mM xanthine, 0.1 IU per mL xanthine oxidase, 0.2 mM/0.4 mM Fe/ethylenediaminetetraacetic acid). TBARS release was time-independent but significantly higher when LCn−3 fatty acids were fed to rats in either the uninduced or induced system. The study demonstrated that n−3 PUFA diets can influence vitamin E status of rats even in short-term experiments and can change the susceptibility of the heart toin vitro lipid peroxidation.