Insulin sensitization via partial agonism of PPARγ and glucose uptake through translocation and activation of GLUT4 in PI3K/p-Akt signaling pathway by embelin in type 2 diabetic rats

Background: The present study was aimed at isolating an antidiabetic molecule from a herbal source and assessing its mechanism of action. Methods: Embelin, isolated from Embelia ribes Burm. (Myrsinaceae) fruit, was evaluated for its potential to regulate insulin resistance, alter beta-cell dysfunction and modulate key markers involved in insulin sensitivity and glucose transport using high-fat diet (HFD) fed-streptozotocin (STZ) (40 mg/kg)-induced type 2 diabetic rats. Molecular-dockings were performed to investigate the binding modes of embelin into PPAR gamma, PI3K, p-Akt and GLUT4 active sites. Results: Embelin (50 mg/kg b wt.) reduced body weight gain, blood glucose and plasma insulin in treated diabetic rats. It further modulated the altered lipid profiles and antioxidant enzymes with cytoprotective action on beta-cell. Embelin significantly increased the PPAR gamma expression in epididymal adipose tissue compared to diabetic control group: it also inhibited adipogenic activity; it mildly activated PPAR gamma levels in the liver and skeletal muscle. It also regulated insulin mediated glucose uptake in epididymal adipose tissue through translocation and activation of GLUT4 in PI3K/p-Akt signaling cascade. Embelin bound to PPAR gamma; it disclosed stable binding affinities to the active sites of PI3K p-Akt and GLUT4. Conclusions: These findings show that embelin could improve adipose tissue insulin sensitivity without increasing weight gain, enhance glycemic control, protect beta-cell from damage and maintain glucose homeostasis in adipose tissue. General significance: Embelin can be used in the prevention and treatment of type 2 diabetes mellitus caused due to obesity. (C) 2012 Elsevier B.V. All rights reserved.