Effect of a-lipoic Acid Supplementation on Lipid Peroxidation and Expression of SOD Protein Dependent on Skeletal Muscle Types in Rats Fed a High-fat Diet

Journal of Exercise Nutrition & Biochemistry 2009;13(4):257-264.

Abstract

This study was examined the effects of a-lipoic acid (ALA) supplementation and swimming exercise on lipid peroxidation and superoxide dismutase(SOD) protein expression, dependent on skeletal muscle types, in rats fed a high-fat diet. Thirty-two male rats were randomly divided into 4 groups: HS (high-fat diet sedentary group, n = 8), HE (high-fat diet exercised group, n = 8), AS (ALA supplemented diet sedentary group, n = 8), and AE (ALA supplemented diet exercised group, n = 8). The high-fat diet was composed of 35% carbohydrate, 20% protein, and 35% fat. In the exercised groups, the rats swam for 60 min/day, 5 days/week for 4 weeks. The results showed that the serum glucose, triglyceride(TG), insulin, Homeostasis model assessment of insulin resistance(HOMA-IR), and leptin levels of the AS group were significantly decreased compared to those of the HS group. In the extensor digitorum longus (EDL) and gastrocnemius muscles, the malondialdehyde (MDA) levels of HE and AE were slightly decreased compared to HS and AS, respectively. In addition, the MDA levels in the EDL and gastrocnemius muscles of the AS group were slightly decreased compared to that of the HS group despite no significant difference between the groups. However, for the MDA levels in soleus muscle, the HE rats had significantly lower contents compared to the HS group, and the MDA levels of the AS group were also significantly lower than that of the HS. However, there was no significant difference between the AS and AE groups. For Cu,Zn-SOD expression in the EDL and soleus muscles, no significant differences were found among the groups. However, Cu,Zn-SOD expression in the gastrocnemius muscle of the AS group was significantly increased compared to that of the HS group. For Mn-SOD expression in the soleus muscle, the AS and AE groups had significantly greater values compared to that of the HS and the HE, respectively. However, Mn-SOD expressions in the EDL and gastrocnemius muscles were not significantly different among the groups. From these results, it is suggested that a-lipoic acid supplementation and swimming exercise for 4 weeks had a crucial role in the inhibition of lipid peroxidation and increased SOD protein expression, dependent on skeletal muscle types, in rats fed a high-fat diet.

Key Words: α-lipoic acid, swimming, lipid peroxidation, SOD protein expression, muscle types