possible cytoprotectiye effect of vitamins C and E and L-carnitine on monosodium glutamate induced oxidative stress in the rat

ABSTRACT

Monosodium glutamate [MSG] consumption has increased throughout the world as flavoring agent in cooking. However, consumption of a highly palatable diet has been shown to cause endothelial dysfunction, cardiovascular disease and various age-related degenerative disease processes long before development of any significant obesity. The major purpose of the present study was to investigate the effects of MSG on glucose metabolism, lipid profile and oxidative stress. A secondary purpose was to determine the possible protective effect of vitamin C, vitamin E and L-carnitine [LC], separately or in combination in MSG inducing oxidative stress in the rat. Sixty male albino rats weighing from 100-150 g were included in this study. Rats were divided into two main groups. Group 1, [10 rats] served as a control group for group II, and were received 1 ml of physiological saline [0.9%], daily subcutaneously [s.c.] for eight weeks. Group II MSG -induced oxidative stress [50 rats] injected s.c. MSG in a dose of 200 mg/kg.b.wt. daily for eight weeks. Rats were further subdivided into A, B, C, D and E, each of ten rats. Group- A, received 1 ml of 2% gum acacia daily orally for eight weeks starting from the first day of MSG administration. Groups B, C, D treated with orally daily vitamin C in a dose of 100 mg/kg.b.wt. or vitamin E in a dose of 10 mg/kg.b.wt. or L-carnitine in a dose of 200 mg/kg.b.wt for the same previous duration. Group-E, received vitamins C, E and LC in the same previous doses and durations. S.C. injections of MSG produced significant increases in body weight, serum levels of glucose, insulin, leptin, total cholesterol, LDL-cholesterol and triglycerides, while HDL- cholesterol and Apo A 1 were significantly decreased. There were insignificant changes in serum iron, ferrritin and total iron binding capacity [TIBC] The levels of glutathione and the activities of both catalase and superoxide dismutase [SOD] in heart, liver and kidney were significantly decreased. In addition, there were significant decreases in both basal arid insulin stimulated glucose uptake by the soleus muscle and fatty tissue of the rat. Intake of vit. C or vit. E or LC, reduced the abnormalities in body weight, glucose metabolism, lipid profile and antioxidant enzymes. Also, they procducd a significant increase in both basal and insulin stimulated glucose uptake by the soleus muscle and fatty tissue of the rat. Still vit. C revealed better effects as compared to the corresponding groups. The combination of vit. C and E and LC was found to be the best as shown by the correction of glucose metabolism, lipid profile and highest levels of antioxidant enzymes as compared to the corresponding groups. MSG enhanced food intake. Overfeeding induced metabolic disorders associated with oxidative stress. The present study provides evidence that combination of antioxidant vitamins C and E with LC combat metabolic disorders and oxidative stress induced by MSG. Thus, sufficient dietary intake of these vitamins with LC is beneficial in combating MSG adverse effects