Effect of naringin supplementation on cholesterol metabolism and antioxidant status in rats fed high cholesterol with different levels of vitamin E

Some bioflavonoids potent antioxidants and have pharmacological effects sim ilar to those of vitamin E. The interactive effect of naringin and vitamin E was studied with respect to cholesterol metabolism and antioxidant status . Naringin supplementation (0.1%, wt/wt) with comparable levels of vitamin E was given to rats with a high-cholesterol (1%, wt/wt) diet for 5 weeks. T he amount of vitamin E included in naringin-free and naringin diets was a l ow (low-E) and a normal (normal-E) level. The naringin supplementation sign ificantly lowered the concentrations of plasma cholesterol and triglyceride compared to the naringin-free group in low vitamin E-fed rats. HMG-CoA red uctase activity was significantly lowered by naringin supplementation withi n both the low vitamin E group (794.64 +/- 9.87 vs. 432.18 +/- 12.33 pmol/ min/mg protein, mean +/- SE; p < 0.05) and normal-vitamin E group (358.82 /- 11.4 vs. 218.22 +/- 9.47 pmol/min/mg protein, mean SE; p < 0.05) compare d to each of the naringin-free group. The HMG-CoA reductase activity was al so significantly lowered by increased dietary vitamin E when compared withi n the naringin and naringin-free group, respectively. Neither dietary narin gin nor vitamin E did significantly change the activities of hepatic antiox idant enzymes and plasma thiobarbituric acid-reactive substance level. Thes e data indicate that naringin lowers the plasma lipid concentrations when t he dietary vitamin E level is low. The HMG-CoA reductase-inhibitory effect of naringin was more potent when dietary vitamin E was at a normal level. T hese data may contribute to understanding the interactive effect of naringi n and vitamin E on cholesterol biosynthesis in high-cholesterol-fed rats.