Molecular Targets of Combined Natural Antioxidants Against Diabetes in Streptozotocin-induced Diabetic Mice

Natural antioxidants, due to the different chemical structures and their unique biological protection effects on islet cell, have been received much attention in applied chemistry field for developing a new diabetic drug. However, the molecular targets of the islet cell protection have been remained obscure. For investigating molecular targets of combined natural antioxidant's(CNA) roles in against diabetes, type 1 diabetic mouse model was made by multiple injection of low doses of streptozotocin into C57BL mice. Two combinations of natural antioxidants were orally supplemented to the mice. Blood glucose level, glutathione peroxidase(GSH-Px) and superoxide dismutase (SOD) activities, and malondialdehyde(MDA) contents were measured via biochemical assays. Tumor necrosis factor α(TNF-α), interferon γ(IFN-γ) and Interleukin-12(IL-12) in CD4⁺ Peripheral blood mononuclear cells(PBMC) were evaluated with flow cytometry(FCM). In situ hybridization(ISH) and immunohistochemistry(IHC) were used to detect insulin gene expression. The results demonstrate both the combinations significantly: increased GSH-px and SOD, but decreased MDA levels in pancreas(p<0.05―0.01); up-regulated insulin expression at both mRNA and protein levels in islet cells(p<0.05―0.01); down-regulated TNF-α and IL-12 expression in PBMC(p<0.05―0.01). Our data suggest that the CAN may regulate multiple key molecular targets related to β cell function, including reduction of oxidative stress and pre-inflammatory cytokines, and upregulate insulin gene expression to reduce the development of diabetes.