Methanol and Water Extracts of Costus Speciosus (j.könig) sm. Leaves Reverse the High-Fat-Diet Induced Peripheral Insulin Resistance in Experimental Wistar Rats

Abstract

Worldwide prevalence of insulin resistance is growing rapidly and there is no specific treatment for this condition. Medicinal plants are being used as sources of novel drug discovery. The objective of this study was to investigate the effect of methanol and water extracts of Costus speciosus leaf on insulin resistant experimental Wistar rats. Male Wistar rats were divided into five groups (n = 6) and IR was induced by a high fat diet (19.13 % fats). CS leaf methanol extract and water extract were prepared. Rats were treated daily for four weeks with the extracts. Group 1: 0.5 % CMC 1 ml, Group 2: 500 mg/kg/day methanol extract in CMC, Group 3: 500 mg/kg/day water extract in CMC, Group 4: 1500 mg/kg/day water extract in CMC, Group 5: Pioglitazone 10 mg/kg/day. Serum was analysed for glucose, triglycerides and insulin at baseline and after the therapy. Insulin resistance was calculated using indirect indices; HOMA, QUICKI and McAuley. Data were analysed by one- way ANOVA followed by Bonferroni post-hoc test and student’s t-test. Test values of p < 0.05 were considered statistically significant. Both CSlwex (at doses 500 and 1500 mg/kg) and CSlmex (500 mg/kg) significantly reduced (p < 0.05) insulin resistance and serum insulin level within four weeks therapy. Further, 500 mg/kg CSlmex reduced serum triglyceride level by 8.98 % in IR rats. Both Costus speciosus leaf water and methanol extracts have potent effect on reducing IR in experimental rats. Therefore, Costus speciosus leaf might be useful as a good source of insulin sensitizing chemical compounds.