Antidiabetic effects of polysaccharide from azuki bean (Vigna angularis) in type 2 diabetic rats via insulin/PI3K/AKT signaling pathway

The prevalence of type 2 diabetes mellitus (T2DM) is increasing year by year worldwide, which threatens human health severely. This study aimed to investigate the antidiabetic effects and the potential mechanism of polysaccharide from azuki bean (ABP) in high fat diet and STZ-induced type 2 diabetic rats. Results showed that oral administration of ABP could significantly reduce weight loss and fasting blood glucose (FBG) levels and concentration of serum triglyceride (TG) compared with those of the untreated diabetic rats (p < 0.05). Furthermore, improved glucose tolerance ability, increased hepatic glycogen levels and ameliorated insulin resistance (HOMA-IR) were observed in ABP treatment groups. ABP also significantly reversed the dyslipidemia caused by diabetes as indicated by decreased triglyceride (TG) and elevated high density lipoprotein-cholesterol (HDL-C). Histopathological observation confirmed that ABP could maintain the integrity of islet structure by inhibiting β-cell apoptosis. In addition, ABP treatment significantly enhanced the antioxidant capacity of diabetic rats. Real-time Quantitative PCR (RT-PCR) and western blotting analysis showed that ABP significantly increased the expression of insulin receptor (INSR), insulin receptor substrate-1 (IRS-1), phosphoinositide 3-kinase (PI3K), protein kinase B (AKT) and glucose transporter-2 (GLUT-2), indicating that ABP regulates glucose metabolism and oxidative stress by activating the PI3K/AKT signaling pathway. This study provided new insights for investigating the antidiabetic effects of ABP and suggests that ABP could be a promising nutraceutical for treating T2DM.