Effect of alpha-lipoic acid supplementation on oxidative protein damage inthe streptozotocin-diabetic rat

An increase in oxidative stress may contribute to the development of oxidat ive protein damage in streptozotocin diabetic rats. In the present study, t he influence of alpha-lipoic acid supplementation on plasma protein carbony l, plasma thiol, and plasma lipid hydroperoxide levels was examined in orde r to characterize the relationship between the oxidative stress and the oxi dative protein damage. Rats were randomly divided into three groups of equa l body weight. Chronic hyperglycemia was induced by intravenous streptozoto cin injection in both the group of male Wistar rats to be supplemented with alpha-lipoic acid and the group that was not to receive alpha-lipoic acid. Nondiabetic rats formed the control group and received a saline injection. In streptozotocin diabetic rats with and without alpha-lipoic acid supplem entation, plasma carbonyl levels were significantly increased, while plasma thiol levels were significantly decreased compared with those of the contr ol group. Plasma lipid hydroperoxide levels were significantly increased in diabetic rats without alpha-lipoic acid supplementation compared with thos e of the controls, but the lipid hydroperoxide levels in the alpha-lipoic a cid supplemented group were no different from those of the controls. In str eptozotocin-diabetic rats, oxidative stress was significantly decreased in the alpha-lipoic acid-supplemented group. The results of this study suggest that alpha-lipoic acid, by decreasing oxidative stress, may be effective i n preventing oxidative protein damage, which may contribute to the developm ent of diabetic complications.