Potent Effects of the Total Saponins from Dioscorea nipponica Makino Against Streptozotocin‐Induced Type 2 Diabetes Mellitus in Rats

The aim of the present paper was to investigate the effects and possible mechanisms of the total saponins from Dioscorea nipponica Makino (TSDN) against type 2 diabetes mellitus. Streptozotocin (STZ) with high‐fat diet induced type 2 diabetes mellitus (T2DM) rats were treated with TSDN. Some biochemical parameters, target proteins and genes were investigated. The results showed that TSDN decreased the levels of food/water intake, fasting blood glucose and serum lipid parameters, ameliorated oral glucose and insulin tolerance test levels, markedly increased body weight and serum insulin, reduced excess free radicals and affected ossification and renal protection. Histopathological examination indicated that TSDN increased liver glycogen, decreased the production of lipid vacuoles and lightened liver damage. Further investigation showed that TSDN down‐regulated the protein expressions of NF‐κB, GRP78, ATF6, eIF2 and the levels of MAPK phosphorylation and up‐regulated the protein expressions of IRS‐1, GLUT‐4, p‐Akt and p‐AMPK. In addition, TSDN obviously decreased the gene expressions of TNF‐a, IL‐6, PEPCK, G6Pase, GSK‐3β and GSK‐3β activity, and increased the gene expressions of PFK, PK and GK activity. These findings show the anti‐diabetic activity of total saponins from D. nipponica Makino, which should be developed as a new potent drug for treatment of diabetes mellitus in future. Copyright © 2014 John Wiley & Sons, Ltd.