Astragalus polysaccharides: an effective treatment for diabetes prevention in NOD mice

BACKGROUND: Type 1 diabetes mellitus (DM) is a chronic autoimmune disease that is related to the disequilibrium state of Th1 and Th2 subgroups of helper T lymphocyte (Th) and their cytokines. Astragalus polysaccharides (APS) are bioactive components extracted from one of the traditional Chinese herbs, used to enhance the function of human immune system. OBJECTIVE: To investigate the effects of APS on preventing type 1 DM and Th1/Th2-subtype cytokines, we compared the results of administration of APS and normal saline (NS) on non-obese diabetic (NOD) mice. SUBJECTS AND METHODS: APS or NS was administered to 4-week-old mice at a dose of 2.0 g/kg per day for 10 weeks. At 40 weeks, blood glucose, serum C-peptide (C-P) and GAD antibody were measured; pancreas was examined histologically; the intra-islet lymphocyte infiltration and T lymphocyte subsets in the spleen were analysed; the gene expression of IL-1 beta, IL-2, IL-6, IL-12, TNF-alpha, INF-gamma, IL-4, IL-5, IL-10, TGF-beta, Bcl-2, SOD, Fas and iNOS were measured by RT-PCR. RESULTS: The results showed that APS-administered NOD mice had a lower incidence rate of type 1 DM, lower serum C-P level, better histologic findings of pancreatic islets, and a lower D4+/CD8+ ratio of T lymphocytes from the spleen and the infiltrated islets. RT-PCR analysis showed gene expression levels are lower in IL-1 beta, IL-2, IL-6, IL-12, TNF-alpha, INF-gamma, Fas, iNOS, and higher in IL-4, IL-5, IL-10, TGF-beta, Bcl-2, SOD in the pancreatic tissue from APS-administered NOD mice as compared to the NS group.CONCLUSIONS: These results demonstrated the effects of Astragalus polysaccharides on the prevention of type 1 DM in NOD mice by correcting the imbalance between the Th1/Th2 cytokines.