The Evaluation of Dietary Black Soybean and Purple Sweet Potato on Insulin Sensitivity in Streptozotocin - Induced Diabetic Rats

Introduction: Hyperglycemia mediates the production of excess free radicals and reduces endogenous antioxidant in type 2 diabetes mellitus (T2DM). Black soybean (BSB) is rich in antioxidant mainly from isoflavones, whereas the antioxidant of purple sweet potato (PSP) comes from high anthocyanin. The study aimed to evaluate the efficacy of BSB, PSP, and its combination on malondialdehyde (MDA), superoxide dismutase (SOD) concentrations, insulin and insulin receptor substrate-1 (IRS-1) expression in T2DM rats. Methods: T2DM induced by high-calorie diet for five weeks and then injected with a low dose of streptozotocin (30 mg/kg BW) intraperitoneally. The DM rats then treated with black soybean (DM + BSB), purple sweet potato (DM + PSP) and the combination of BSB and PSP 1:3, 2:2, 3:1 respectively (DM + C1- 3). Treatments were given for thirty days. The effect of BSB, PSP and its combination evaluated by measuring SOD and MDA, necrosis in pancreas evaluated through hematoxylin-eosin (HE) and insulin and IRS-1 expression in pancreas through immunohistochemistry-fluorescence (IHC-F). Results: Our result indicated that there were no significant differences of BSB and the combination in decreasing MDA concentrations. The ratio of BSB and PSP combination of 2:2 increase SOD towards near normal, decrease necrosis, and improve insulin and IRS-1. Conclusion: The combination of BSB and PSP had the potential to improve insulin sensitivity through the increase of SOD, reduce necrosis, and improve insulin and IRS-1 expression.