The protective effects of Chinese yam polysaccharide against obesity-induced insulin resistance

Chinese yam polysaccharide (CYP), a bioactive compound of Chinese yam, has been proven to exhibit many pharmacological effects, such as anti-inflammatory, anti-oxidation and immune-modulation activities. However, little is known about its effect on modulating blood fat level and its protective effect against insulin resistance. The present study aims to evaluate the protective effect against obesity-induced insulin resistance and the anti-hyperlipidemia activity of CYP in vivo. In this study, we fed C57BL/6 mice with high fat diet for 14 consecutive weeks to create a diet-induced obesity model. To validate this model, we performed the insulin tolerance test by measuring the levels of blood glucose at different time points. Blood samples were collected by orbital vein pricking. Ingredients such as total cholesterol (TC), triglycerides (TG), low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C) in blood plasma were detected by auto biochemistry analyzer. The levels of IL-1β, IL-10 and leptin were quantified by ELISA kits. The content of MMP-3 and NF-КB (P65) was determined by western-blot. Our results showed that CYP is able to reduce body weight of mice and ameliorate insulin resistance. In addition, CYP is able to lower the level of LDL and total cholesterol significantly. Mechanically, our immunohistochemistry experiments demonstrated that CYP is able to decrease the levels of IL-1β, IL-10 and leptin in serum and the expression of MMP-3 and NF-КB (P65) in white adipose tissue. Our in vivo study showed that CYP is able to improve the sensitivity of insulin and exert protective effect against hyperlipidemia.