Hypoglycemic effects of three medicinal plants in experimental diabetes: inhibition of rat intestinal alpha -glucosidase and enhanced pancreatic insulin and cardiac glut-4 mRNAs expression

ABSTRACT

Garlic [Allium sativum L., Alliaceae], Persian shallot [Allium ascalonicum L., Alliaceae] and Sage [Salvia offcinalis L., Lamiaceae] are believed to have hypoglycemic properties and have been used traditionally as antidiabetic herbal medicines in Iran. In this study, diabetes was induced by subcutaneous injection of alloxan monohydrate [100 mg kg[-1]] to male Wistar rats. Antidiabetic effects of methanolic extracts of the above mentioned three plants on alloxan-diabetic rats was investigated in comparison with the effects of antidiabetic drugs such as acarbose, glibenclamide and metformin by measuring postprandial blood glucose [PBG], oral glucose tolerance test [OGTT], inhibition of rat intestinal alpha -glucosidase enzymes activities and pancreatic Insulin and cardiac Glut-4 mRNAs expression. In short term period, hypoglycemic effects of A. sativum and A. ascalonicum showed significant reduction of PBG similar to glibenclamide [5 mg kg[-1] bw] while S. offcinalis significantly reduced PBG similar to acarbose [20 mg kg[-1] bw]. After 3 weeks of treatment by methanolic plant extracts, significant chronic decrease in the PBG was observed similar to metformin [100 mg kg[-1] bw]. For OGTT, S. offcinalis reduced PBG in a similar way as acarbose [20 mg kg[-1] bw]. Intestinal sucrase and maltase activities were inhibited significantly by A. sativum, A. ascalonicum and S. offcinalis. In addition, we observed increased expression of Insulin and Glut-4 genes in diabetic rats treated with these plants extracts. Up regulation of Insulin and Glut-4 genes expression and inhibition of alpha -glucosidaseactivities are the two mechanisms that play a considerable role in hypoglycemic action of garlic, shallot and sage