Evaluation of Antidiabetic Potential of Gymnema Sylvestre and Metformin Combination in Streptozotocin-Induced Diabetic Rats

This study evaluated the antidiabetic effects of Gymnemasylvestre and metformin, alone and in combination, in a rat model of type 2 diabetes mellitus (T2DM) induced by high-fat diet (HFD) and streptozotocin (STZ). Thirty male Sprague Dawley rats (150 ± 20 g) were housed under standard conditions and acclimatized before being randomly assigned to five groups: normal control, diabetic control, metformin-treated, Gymnemasylvestretreated, and a combination therapy group. T2DM was induced by feeding the rats an HFD for 21 days to promote insulin resistance, followed by two intraperitoneal injections of STZ at a dose of 25 mg/kg body weight in 0.1 mM citrate buffer (pH 4.5), administered five days apart. Rats with fasting blood glucose (FBG) ≥250 mg/dl were considered diabetic and included in the treatment phase. After 4 weeks of treatment, all therapy groups showed significant improvements in biochemical markers compared to diabetic controls. Metformin and combination therapy significantly reduced FBG, cholesterol, creatinine, and HbA1c levels (p<0.05). Although Gymnemasylvestre alone demonstrated a modest glucose-lowering effect, its impact was significantly enhanced when combined with metformin. Metformin alone, however, showed superior efficacy in improving glycemic control and renal function markers compared to the herbal extract. Body weight gain was reduced in diabetic controls and improved across treatment groups. These findings suggest that while Gymnemasylvestre has antidiabetic potential, its combination with metformin may enhance treatment outcomes. However, metformin remains the more potent agent in regulating glucose metabolism in STZ-induced diabetic rats.