Antidiabetic effect of secoisolariciresinol diglucoside in streptozotocin-induced diabetic rats

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycaemia. Its complications such as neuropathy, cardiopathy, nephropathy, and micro and macro vascular diseases are believed to be due to the increase in oxidative stress and decrease in the level of antioxidants. The aim of this study was to determine the antihyperglycemic activity of synthetic Secoisolariciresinol diglucoside (SDG) in streptozotocin (STZ)-induced diabetic rats. The synthetic SDG in a single-dose (20 mg/kg b.w.) two-day study showed dose-dependent reduction in glucose levels with maximum effect of 64.62% at 48 h post drug treatment (p < 0.05), which is comparable to that of the standard drug tolbutamide (20 mg/kg b.w.). In a multi-dose fourteen-day study, lower doses of SDG (5 and 10 mg/kg b.w.) exhibited moderate reduction in glucose levels, lipid profile, restoration of antioxidant enzymes and improvement of the insulin and c-peptide levels which shows the regeneration of β-cell which secretes insulin. Altered levels of lipids and enzymatic antioxidants were also restored by the SDG to the considerable levels in diabetic rats.Results of the present investigation suggest that diabetes is associated with an increase in oxidative stress as shown by increase in serum malondialdehyde (MDA), decreased levels of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH). Also, diabetes is associated with an increase in serum total cholesterol as well as triglycerides levels and decrease in insulin and c-peptide levels.SDG is effective in retarding the development of diabetic complications. We propose that synthetic SDG exerts anti hyperglycemic effect by preventing the liver from peroxidation damage through inhibition of ROS level mediated increased level of enzymatic and non-enzymatic antioxidants. And, also maintaining tissue function which results in improving the sensitivity and response of target cells in STZ-induced diabetic rats to insulin.