Codonopsis lanceolata polysaccharide CLPS alleviates high fat/high sucrose diet-induced insulin resistance via anti-oxidative stress

Polysaccharide has been considered as an important bioactive compound in Codonopsis lanceolata. High fat/high sucrose (HFHS) diet-induced insulin resistance is implicated in multiple metabolic diseases, such as type 2 diabetes mellitus (T2DM) and nonalcoholic fatty liver disease (NAFLD), these metabolic diseases has become epidemic health issue worldwide. In this study, the effect of C. lanceolata polysaccharide (CLPS) on improving insulin sensitivity in chronic HFHS diet-fed mice was investigated. Our data indicates that CLPS significantly reduced fasting blood glucose (FBG), fasting serum insulin (FINS) and insulin resistance index, in parallel with improved glucose and insulin tolerance impaired by HFHS diet. Impaired phosphorylation of PKB/Akt and hyperphosphorylation of IRS-1 at Ser307 were observed in the mice fed with HFHS diet, and those defects were also rescued by CLPS administration. In addition, CLPS caused a significant decrease in the level of malondialdehyde (MDA), and an increase in reduced glutathione (GSH)/oxidised glutathione (GSSG) ratio; concurrent with enhanced expression of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT), and activated Nrf2 signaling. In summary, these findings suggest that CLPS ameliorates HFHS diet-induced insulin resistance through activating anti-oxidative signaling pathway, providing new insights into the protective effects of C. lanceolata polysaccharide in metabolic disease.