Effect Of Astragalus Polysaccharidde On Insulin Signal Transduction In Renal Tissue Of Type 2 Diabetic Rats

Objective: To develop a rat model of type 2 diabetes mellitus and to investigate the effect of astragalus polysaccharidde (APS) on expression of insulin signal moleculars in renal tissue of type 2 diabetic rats.Methods: 30 healthy male Wistar rats were divided into three groups at random(ten for each group): group I :normal control group (Control group) : fed chow diet; group II :diabetes mellitus group (DM group): high-calorie diet and low dose streptozotocin (STZ) induced diabetic model; group III: diabetic model plus astragalus polysaccharidde therapy group (DM+APS group) :the diabetic rats were treated with APS. After 5 weeks, the general situation of the rats was observed before they were killed. Fasting blood glucose was determined through tail vein and serum fasting insulin was determined with radioimmunoassay. Kidneys were harvested at death. After fixation with 4% paraformaldehyde and embedding with wax, tissue sections were cut into slices. Immunohistochemistry was applied to detect the expression levels of InsR, IRS— 1 , PI3K in renal tissue.Results: The levels of weight of DM group were significantly higher than those of both Control group and DM+APS group (P<0.01) ; the levels of glucose of DM group and DM+APS group were significantly higher than those of Control group (P<0.01) , and the levels of glucose of DM+APS group were significantly lower than those of DM group (P<0.01) ; the levels of insulin were not significantly different between the groups ( P>0.05 ) ; the expression levels of InsR, IRS — 1, PI3K of DM group were significantly lower than those of both Control group and DM+APS group in renal tissue (P<0.05) .Under the light microscopy, InsR> IRS— 1, PI3K stainings of Control group in renal tissue were distributed in renal tubule epithelia cellular endochylema. The degrees of InsR, IRS— 1, PI3K stainings of DM group were slighter than those of both Control group and DM+APS group in renal tubule epithelia cellular endochylema.Conclusion: 1. A rat model of type 2 diabetes mellitus was developed successfully by combination of high-calorie diet and low dose STZ. 2. APS could decrease the levels of glucose in type 2 diabetic rats, its pharmaceutical mechanisms might be closely related with the elevation of the levels of InsR> IRS— 1 > PI3K in renal tissue of diabetic rats,increase of insulin sensitivity and improvement of insulin signal transduction in target tissue.