Ameliorative effects of glycyrrhizin on streptozotocin-induced diabetes in rats

Objectives Glycyrrhizin is the main water-soluble constituent of the root of liquorice (Glycyrrhiza glabra). The study investigates the effect of glycyrrhizin on streptozotocin (STZ)-induced diabetic changes and associated oxidative stress, including haemoglobin-induced free iron-mediated oxidative reactions. Methods Male Wistar rats were grouped as normal control, STZ-induced diabetic control, normal treated with glycyrrhizin, diabetic treated with glycyrrhizin and diabetic treated with a standard anti-hyperglycaemic drug, glibenclamide. Different parameters were studied in blood and tissue samples of the rats. Key findings Glycyrrhizin treatment improved significantly the diabetogenic effects of STZ, namely enhanced blood glucose level, glucose intolerant behaviour, decreased serum insulin level including pancreatic islet cell numbers, increased glycohaemoglobin level and enhanced levels of cholesterol and triglyceride. The treatment significantly reduced diabetes-induced abnormalities of pancreas and kidney tissues. Oxidative stress parameters, namely, serum superoxide dismutase, catalase, malondialdehyde and fructosamine in diabetic rats were reverted to respective normal values after glycyrrhizin administration. Free iron in haemoglobin, iron-mediated free radical reactions and carbonyl formation in haemoglobin were pronounced in diabetes, and were counteracted by glycyrrhizin. Effects of glycyrrhizin and glibenclamide treatments appeared comparable. Conclusion Glycyrrhizin is quite effective against hyperglycaemia, hyperlipidaemia and associated oxidative stress, and may be a potential therapeutic agent for diabetes treatment.