Insulinotropic effect of aqueous extract of Brassica nigra improves glucose homeostasis in streptozotocin induced diabetic rats.

Aqueous extract of BRASSICA NIGRA (AEBN) has been shown to have good antidiabetic effect along with significant decrease (p<0.01) of abnormal serum lipid levels in our previous study. To understand the mechanism of action, effect of oral administration of AEBN for two months on glycolytic and gluconeogenic enzymes was studied in liver and kidney tissues of rats with streptozotocin (STZ) induced diabetes mellitus. The activities of gluconeogenic enzymes were higher and of glycolytic enzymes were decreased in both the liver and kidney tissues during diabetes. However, in diabetic rats treated with AEBN for two months, decrease of serum glucose, increase of serum insulin and release of insulin from pancreas (shown in vitro from isolated pancreas) along with the restoration of key regulatory enzyme activities of carbohydrate metabolism and glycogen content were observed. The therapeutic role of AEBN in STZ induced diabetes as exemplified in this study can be attributed to the release of insulin from pancreas and change of glucose metabolizing enzyme activities to normal levels, thus stabilizing glucose homeostasis in the liver and kidney. The LD50 was found to be more than 15 times the effective dose (ED) implying higher margin of safety for AEBN. These biochemical effects indicate that AEBN could be a possible new therapeutic agent for the treatment of diabetes.