Gymnemic Acids from Gymnema sylvestre. Potentially Regulates Dexamethasone-Induced Hyperglycemia in Mice

ABSTRACT

Effects of three different doses (6.7, 13.4, and 26.8 mg/kg body wt., i.p.) of gymnemic acids (GA) from the leaves of Gymnema sylvestre. R. Br. in the regulation of dexamethasone induced hyperglycemia have been investigated in mice. Simultaneously, thyroid hormone levels were estimated by radioimmunoassay (RIA) in order to find out whether the effects are mediated through alteration in the thyroid function or not. While the prestandardized dose (1 mg/kg body wt., i.m.) of dexamethasone administration for 22 days increased the serum glucose concentration, it decreased serum concentration of the thyroid hormones thyroxine (T₄) and triiodothyronine (T₃). Although the administration of all three different doses of gymnemic acid decreased the serum glucose concentration in dexamethasone-induced hyperglycemic animals, the decrease was significant only in groups receiving the two higher doses, 13.4 and 26.8 mg/kg. These effects were comparable to a standard corticosteroid-inhibiting drug, ketoconazole. However, the percentage reduction was greater in the 13.4 and 26.8 mg/kg of gymnemic acids–treated groups (28.76% and 21.71% respectively) as compared to that of ketoconazole, where it was only 9.07%. As no significant changes in thyroid hormone concentrations were observed by the administration of any of the doses of GA in dexamethasone-treated animals, it further appears that the effects of the tested material might not have been mediated through alterations in the thyroid function. The changes in hepatic lipid peroxidation (LPO), superoxide dismutase (SOD), and catalase (CAT) activity revealed a toxic effect at the highest dose (26.8 mg/kg body wt.) as evidenced by increased LPO, whereas the medium dose (13.4 mg/kg body wt.) was found to be safe and antiperoxidative. It is suggested that 13.4 mg/kg of gymnemic acids may prove to be potentially effective in the amelioration of corticosteroid-induced diabetes mellitus/hyperglycemia.

Keywords:

• Dexamethasone
• gymnemic acids
• hyperglycaemia
• lipid peroxidation
• T₃
• T₄