METHODS: The ethanol extract and its subfractions, and isolated compounds from T. indica stems were subjected to cytotoxicity test using MTT viability assay on 3T3-L1 pre-adipocytes. Then, the test groups were subjected to the in vitro antidiabetic investigation using 3T3-L1 pre-adipocytes and differentiated adipocytes to determine the insulin-like and insulin sensitizing activities. Rosiglitazone was used as a standard antidiabetic agent. All compounds were also subjected to fluorescence glucose (2-NBDG) uptake test on differentiated adipocytes. Test solutions were introduced to the cells in different safe concentrations as well as in different adipogenic cocktails, which were modified by the addition of compounds to be investigated and in the presence or absence of insulin. Isolation of bioactive compounds from the most effective subfraction (ethyl acetate) was performed through repeated silica gel and sephadex LH-20 column chromatographies and their structures were elucidated through (1)H-and (13)C-NMR spectroscopy.

METHODS: Diabetes was induced by intraperitoneal (i.p.) injection of streptozotocin (55 mg/kg) in to male Sprague-Dawley rats. Rats were divided into six different groups; normal control rats were not induced with STZ and served as reference, STZ diabetic control rats were given normal saline. Three groups were treated with OS aqueous extract at 0.2, 0.3 and 0.5 g/kg, orally twice daily continuously for 21 d. The fifth group was treated with glibenclamide (6 mg/kg) in aqueous solution orally continuously for 21 d. After completion of the treatment period, biochemical parameters and expression levels of glucose transporter 2 (Slc2a2), glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PCK1) were determined in liver by quantitative real time PCR.

RESULTS: Administration of OS at different doses to STZ induced diabetic rats, resulted in significant decrease (P<0.05) in blood glucose level in a dose dependent manner by 36%, 48%, and 64% at doses of 0.2, 0.3 and 0.5 g/kg, respectively, in comparison to the STZ control values. Treatment with OS elicited an increase in the expression level of Slc2a2 gene but reduced the expression of G6Pase and PCK1 genes. Morefore, OS treated rats, showed significantly lower levels of serum alanine transaminase (ALT), aspartate aminotransferase (AST) and urea levels compared to STZ untreated rats. The extract at different doses elicited signs of recovery in body weight gain when compared to STZ diabetic controls although food and water consumption were significantly lower in treated groups compared to STZ diabetic control group.