Antioxidative activity of naringin and lovastatin in high cholesterol-fed rabbits

The consumption of a cholesterol-enriched diet increases the degree of lipi d peroxidation, which is one of the early processes of atherosclerosis. The aim of this trial was to determine the antioxidative effects of the citrus bioflavonoid, naringin, a potent cholesterol-lowering agent, compared to t he cholesterol-lowering drug, lovastatin, in rabbits fed a high cholesterol diet. Male rabbits were served a high-cholesterol (0.5%, w/w) diet or high -cholesterol diet supplemented with either naringin (0.5% cholesterol, 0.05 % naringin, w/w) or lovastatin (0.5% cholesterol, 0.03% lovastatin, w/w) fo r 8 weeks to determine the plasma and hepatic lipid peroxide, plasma vitami n A and E levels, and hepatic hydrogen peroxide levels, along with the hepa tic antioxidant enzyme activities and gene expressions. Only the lovastatin group showed significantly lower plasma and hepatic lipid peroxide levels compared to the control group. The naringin supplementation significantly i ncreased the activities of both hepatic SOD and catalase by 33% and 20%, re spectively, whereas the lovastatin supplementation only increased the catal ase activity by 23% compared to control group. There was no difference in t he GSH-Px. activities between the various groups. Content of H2O2 in hepati c mitochondria was significantly lower in groups supplemented with lovastat in and naringin than in control group. However, there was no difference in cytosolic H2O2 content in liver between groups. The concentration of plasma vitamin E was significantly increased by the naringin supplementation. Whe n comparing the antioxidant enzyme gene expression, the mRNA expression of SOD, catalase and GSH-Px was significantly up-regulated in the naringin-sup plemented group. Accordingly, these results would appear to indicate that n aringin, a citrus bioflavonoid, plays an important role in regulating antio xidative capacities by increasing the SOD and catalase activities, up-regul ating the gene expressions of SOD, catalase, and GSH-Px, and protecting the plasma vitamin E. In contrast, lovastatin exhibited an inhibitory effect o n the plasma and hepatic lipid peroxidation and increased the hepatic catal ase activity in high-cholesterol fed rabbits. (C) 2001 Elsevier Science Inc . All rights reserved.