Swertisin rich fraction from Enicostema littorale ameliorates hyperglycemia and hyperlipidemia in high-fat fed diet and low dose streptozotacin induced type 2 diabetes mellitus in rats.

INTRODUCTION: Enicostema littorale blume (A. Raynal) is a traditional Indian plant belongs to the Gentianaceae family. A lot of research has been done on this plant for its antidiabetic activity. However, there are no reports on flavonoids from E. littorale for its antidiabetic activity and their mechanism of action. Thus, the aim of this study is to evaluate the antidiabetic activity of Swertisin rich flavonoid fraction (SRF) from Enicostema littorale blume and their mechanism of action.

MATERIALS & METHODS: Type 2 Diabetes Mellitus rat model was established by inducing insulin resistance using high fat diet and low dose of streptozotacin injection and was authenticated by HOMA index. The antidiabetic effect of SRF was evaluated on diabetic rats to investigate its long term effects on fasting blood glucose, OGTT, weight of rats, insulin, liver profile, lipid profile, kidney profile, histopathology of liver and pancreas. In addition, antioxidant activity by lipid peroxidation and catalase assay, ex vivo assays and hepatic glycogen content were performed to determine its effect on glycogenesis and hepatic glucose production. Furthermore, the mechanism of action of SRF was evaluated by Real time PCR and the mRNA expression was quantified for Glucokinase (GCK), Insulin receptor substrate (IRS-1), Glucose transporter-2 (GLUT-2) and Glucose transporter-4 (GLUT-4) genes.

RESULTS: Treatment of diabetic rats with SRF demonstrated significant (p<0.0001) dose dependant hypoglycemic activity as compared to positive control metformin group. A decrease in liver, lipid and kidney function tests was seen as compared to diabetic control indicating normalization of organ function tests. Also, antioxidant activity showed significant decrease in malondialdehyde (MDA) content in liver (p<0.001) as compared to pancreas and increased catalytic activity in liver, kidney, spleen and pancreas. The hepatic glycogen content was significantly (p<0.001) increased in SRF treated rats indicating its inhibition of hepatic glucose production. Furthermore, ex vivo assays showed the significant (p<0.05) increase in glucose uptake by diaphragm. The mRNA expression for GCK, IRS-1, GLUT-2 and GLUT-4 genes showed significant up regulation as compared to diabetic control indicating its mechanism via insulin signalling pathway.

CONCLUSION: The studies suggest that SRF ameliorates the insulin resistance by increasing glucose uptake and sensitizing cells towards insulin via IRS1/PI3K/Akt2 pathway.