Acta Pharmacologica Sinica (2009) 30: 1607–1615; doi: 10.1038/aps.2009.168

Aim:To establish the mechanism underlying the improvement of glucose toxicity by Astragalus polysaccharide (APS), which occurred via an AMP activated protein kinase (AMPK)-dependent pathway.

Methods: In vivo and in vitro effects of APS on glucose homeostasis were examined in a type 2 diabetes mellitus (T2DM) rat model. The T2DM rat model was duplicated by a high-fat diet (58% fat, 25.6% carbohydrate, and 16.4% protein) and a small dose of streptozotocin (STZ, 25 mg/kg, ip).  After APS therapy (700 mg·kg^-1·d^-1, ig) for 8 weeks, blood glucose, glycosylated hemoglobin, and serum insulin were measured.  Insulin sensitivity was evaluated by the comprehensive analysis of oral glucose tolerance tests (OGTT) and HOMA IR index.  Hepatic glycogen was observed by the PAS staining method.  The expression and activity of skeletal muscle AMPKα and acetyl-CoA carboxylase (ACC), and the phosphorylation of hepatic glycogen synthase (GS), the glycogen synthase (GS),were measured by Western blotting.  Glucose uptake was measured with the 2-deoxy-[³H]-D-glucose method in C 2C 12 cells.

Results: The hyperglycemia status, insulin sensitivity, glucose uptake, and activation level of AMPK in diabetic rats were improved in response to APS administration.  APS could also alleviate glucose toxicity in cultured mouse cells by the activation of AMPK.

Conclusion: APS can alleviate glucose toxicity by increasing liver glycogen synthesis and skeletal muscle glucose translocation in the T2DM rat model, via activation of AMPK.  

Keywords: Astragalus polysaccharides; T2DM; AMPK; glucose; toxicity