Identification of Insulin Sensitizing Activity of Gymnema sylvestre in Dexamethasone Induced Insulin Resistance in Rats

Background: Insulin resistance plays a key role in the onset of several metabolic disorders. Aim and Objectives: To determine the insulin sensitizing property of aqueous extract of Gymnema sylvestre leaves on dexamethasone induced insulin resistance in rats. Materials and Methods: Animals were divided into five groups (n=6) and the study was conducted for a period of 12 days. Insulin resistance was induced with dexamethasone (Dex) (4 mg/kg) intraperitoneal (i.p) injection. Control (Group I) and Dexamethasone group (Group II) received gum acacia orally (p.o) for 12 days. The test groups (Group III and Group IV) received Gymnema sylvestre leaves aqueous extract (1 and 2 gm/kg/p.o. respectively) and standard drug group (Group V) received rosiglitazone (8 mg/kg/p.o) for 12 days. All the groups except control group received Dex (4 mg/kg/i.p.) from 7th day to 12th day. Insulin resistance was measured by using serum glucose, insulin levels and by performing intraperitoneal glucose tolerance test (IPGTT). The degree of Insulin resistance was calculated by using indices i.e. Homeostasis model assessment for insulin resistance (HOMA-IR), insulin sensitivity (HOMA-IS) and fasting glucose to insulin ratio (FGIR). Values were analyzed by one way analysis of variance (ANOVA) followed by Scheffe’s multiple comparison posttest. Results: Dex significantly raised serum glucose and insulin levels in comparison to control group. It induced glucose intolerance and insulin resistance confirmed by HOMA-IR, IS and FGIR. Treatment with Gymnema sylvestre extract significantly prevented all the changes induced by Dex. Conclusion: To conclude, Dex has induced insulin resistance and these abnormalities associated with IR are partially prevented with pre administration of Gymnema sylvestre.