Astragalus Polysaccharides: An Effective Treatment for Diabetes Prevention in NOD Mice

Abstract

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. 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. 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. 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. 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.