An Ayurvedic formulation of Emblica officinalis and Curcuma longa alleviates insulin resistance in diabetic rats: Involvement of curcuminoids and polyphenolics

Abstract

Background: Nishamalaki is an Ayurvedic herbal formulation used to treat type 2 diabetes mellitus (T2DM), comprises Emblica officinalis and Curcuma longa. Objective(s): One of the main cause of T2DM is Insulin Resistance (IR) hence, this study was planned to evaluate IR lowering effect of a standardized Nishamalaki extract “EmbliQur” in high-fat diet (HFD) and streptozotocin (STZ) induced T2DM rats. Materials and methods: Curcuminoids (23.89% w/w), gallic acid (5.27% w/w) and tannins (25.44% w/w) were quantified from EmbliQur. Rats were fed HFD throughout the study of 45 days and received STZ (40 mg/kg, i.p) on the 15th day of the study. Rats with more than 250 mg/dl of fasting blood glucose level (FBGL) were considered diabetic and selected for administration of EmbliQur (500 mg and 1000 mg/kg) or the standard drug metformin (120 mg/kg, p.o) from the 18th day of the study for the next 27 days. FBGL and insulin levels of all rats were measured weekly and an oral glucose tolerance test (OGTT) was done at the end of the study. The values of FBGL and insulin were used to calculate IR by the HOMA-IR, QUICKI and Matsuda methods. Results: Rats treated with STZ/HFD had significantly higher than normal FBGL and insulin levels throughout the study and exhibited skewed IR indices in the above three methods of IR assessment. EmbliQur treatment successfully lowered the HFD/STZ-elevated BGL and insulin levels, and ameliorated IR in all models of IR evaluation. Conclusion: EmbliQur 1000 mg/kg was noted to be more effective than EmbliQur 500 mg/kg in alleviating IR.

Keywords

• Diabetes
• High-fat diet
• Streptozotocin
• Insulin resistance
• Curcuma longa
• Emblica officinalis