The research on the effects of APS increased insulin sensitivity and reduced ER stress in a STZ induced rat model of type 2 diabetes

Abstract

Recent researches have identified that endoplasmic reticulum stress (ERS) is involved in the development of type 2 diabetes. Astragalus polysaccharide (APS) is extracted from Astragalus membranaceus (Huangqi) and has the potential as a immunomodulator with wide clinical applications. Our research is to investigate the effects of APS on ERS and insulin sensitivity in a rat model of type 2 diabetes. We established animal models of type 2 diabetes by high fat forage associated with small dosage of STZ(25mg/kg) injection through abdominal cavity and randomly divided animals into four groups: diabetes group(DM group), diabetes+APS group(DA group, control group(C group), control+APS group(CA group). CA group and DA group were administered with APS(700mg/kg/day) while the other two groups were administered with the same dose of sodium chloride for 8 weeks. We found that the FBG and RBG of DA group were markedly lower than those of DM group, the index for each time point of oral glucose tolerance test were increased than those of the DM group(p<0.01). The expression of PTP1B, p‐IRE‐1 were significantly increased in DM group to compare with C group(p<0.01), but the expression in DA group was decreased than DM group(p<0.05). The expression of uncleaved ATF6 in DM group was lower than C group, but it increased after treatment with APS(p<0.01). These results indicate that treatment with APS can lower the level of blood glucose and increase insulin sensitivity probably through decreasing the level of expression of PTP1B, and APS can relieve ERS through reducing the expression of activated ATF6 and phosphorylated IRE‐1, the relief of ERS by APS was also probably one of the mechanisms of its effects on enhancement of insulin sensitivity.(This research is supported by national science foundation of China granted NO: 30771023)