Effects of beta-Carotene Supplementation on Lipid Peroxide Levels and Antioxidative Enzyme Activities in Diabetic Rats

ABSTRACT

This study investigated the effect of dietary beta-carotene supplementation on lipid peroxidation and anti oxidative enzyme activity as indices of oxidative stress in diabetic rats. Fifty Sprague-Dawley male rats aging 7 weeks were used as experimental animals, which were divided into the non-diabetic control group and the diabetic group. The diabetic group received an intraperitoneal injection with streptozotocin to induce diabetes. Then the diabetic rats were divided into four dietary groups which contained different amounts of beta-carotene; 0%, 0.002%, 0.02%, or 0.2% of the diet. The diabetic rats were fed the experimental diets and the non-diabetic rats were fed the basal diet without beta-carotene supplementation for 2 weeks and then sacrificed. The diabetic group had a significantly higher blood glucose level than the non-diabetic group. However, blood glucose level were not significantly changed by the level of dietary beta-carotene supplementation. Compared to the non-diabetic control group, the diabetic control group indicated a significant increase of plasma thiobarbituric acid reactive substance (TBARS). Liver TBARS level also tended to be higher in diabetic control group, although it was not significant. The beta-carotene supplementation did not reduce plasma TBARS level. However, Liver TBARS level was significantly decreased when 0.02% or more beta-carotene was supplemented in the diet. The liver lipofuscin level in the diabetic control group was higher than in the non-diabetic control group, but the effect of beta-carotene supplementation did not show any differences. Superoxide dismutase activity was significantly lower in the diabetic group, but it was increased in groups receiving 0.02% or more beta-carotene. Compared to the non-diabetic control group, lower activities of catalase and glutathione peroxidase were observed in the diabetic control group, although it was not significant. Catalase and glutathione peroxidase activities tended to increase as the levels of beta-carotene supplementation increased, although it was not statistically significant. Therefore, it seems that dietary beta-carotene supplementation might reduce diabetic complications by partly decreasing the lipid peroxidation and increasing the activity of antioxidative enzyme in diabetes.