Effect of vitamin E supplementation on plasma lipids and oxidized low-density lipoprotein in hypercholesterolemic rats

Coronary artery disease is the leading cause of death in the United States. A major risk factor for atherosclerosis is elevated levels of semm cholesterol, particularly lowdensity lipoprotein (LDL) cholesterol in the blood. It has become increasingly evident that LDL must undergo oxidative modification before giving rise to foam cells, one of the earliest stages in the development of atherosclerosis.

Micronutrient antioxidants can protect LDL from oxidation and can thus delay or prevent the development of fatty streaks in the arterial wall. The purpose of the present study was to determine the effect of graded doses of vitamin E and selenium on plasma total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides and oxidized LDL cholesterol in rats fed control and cholesterol/cholic acid (l%)/0.3%)) enriched diets for five months. Eighty-two female Fischer rats were randomly assigned to seven treatment groups and fed experimental diets containing vitamin E supplementation ranging from 60 mg/kg basal diet (adequate level) to 2400 mg (high level). Six groups of rats were given adequate levels of selenium (0.2 mg/kg diet) and one group was given excess (4,0 mg/kg) selenium.

At the end of the study period there was progressive weight gain in all the animals, but the vitamin E deficient group and the selenium excess group consistently showed lower weight gain compared to other treatment groups. Plasma lipids were elevated in all the treatment groups fed cholesterol. A positive association between HDL levels and increasing levels of vitamin E supplementation was noted. The liver weights of animals fed cholesterol were higher than that of the control group. Determination of total plasma oxidation based on malondialdehyde (MDA) formation showed that there was decreased formation of MDA at high levels of vitamin E supplementation. There was a positive association between increasing amoimts of dietary vitamin E supplementation and plasma a-tocopherol levels with the highest concentration found in the treatment group fed the highest amount of vitamin E. The oxidation kinetics of LDL based on the thiobarbituric acid reacting substances assay and conjugated diene assay revealed that the treatment group fed high levels of vitamin E had prolonged lag phase of oxidation compared to the other treatment groups. High levels of vitamin E supplementation did not produce any adverse effects in the rats.