Effect of Radix isatidis polysaccharide on alleviating insulin resistance in type 2 diabetes mellitus cells and rats

Objectives The objective of this paper was to explore the effects of Radix isatidis polysaccharide (RIP) extracted from Radix isatis on alleviating insulin resistance. Methods The insulin resistance models of 3T3-L1 preadipocytes and type 2 diabetic rats were established to evaluate the insulin resistance activity of RIP. Key findings Radix isatidis polysaccharide within the concentration range of 25-100 mu g/ml could reduce cell supernatant glucose and TNF-alpha levels (P < 0.01) and increase the expression of PI-3K P85, Glut4, IRS-1 and Akt protein in symptoms of IR 3T3-L1 preadipocytes. In the meantime, RIP contributed to relieve the weight loss of diabetic rats whose liver weight and liver index were decreased due to the effects of RIP. Experiments in rats also showed that RIP had capacity in reduced serum TC, TG, LDL-C, FFA, FBG, FINS, MDA, ALT, AST activities and increased serum HDL-C, SOD, ISI (P < 0.05 or 0.01). In addition, the oral glucose tolerance in rats was improved (P < 0.05) and liver damage was restored due to RIP. Conclusions Radix isatidis polysaccharide significantly alleviates insulin resistance in 3T3-L1 preadipocytes and type 2 diabetic rats. These beneficial effects of RIP may associate with their roles in improving the glucose metabolism, lipid metabolism and oxidative stress.