Euonymus alatus Extract Reduces Insulin Resistance in db/db Mice by Regulating the PI3K–AKT Pathway

In accordance with the usage of Euonymus alatus (EA) as folk medicine in diabetes, the present study employed water and 70% ethanol twig extract to assess its antidiabetic effects in C57BL/KsJ-db/db mice. These effects were then compared with those observed in normal C57BL/6J Jms Slc mice. After 4 weeks of supplementation with 70% ethanolic EA extract or water EA extract by oral gavage at a dose of 500 mg/kg with distilled water (DW) per day, body weight was measured and compared with the diabetic group (Db). HPLC demonstrated that the maximum flavonoids were extracted in the Et.EA extract rather than in the water EA extract. The supplementation of the Et.EA extract significantly increased liver and muscle glycogen content with respect to the Db group. Additionally, the Et.EA extract modulated the expression of glycogen synthase (GS) in the liver and muscles of Db mice, indicating that it plays a promotive role in glycogen synthesis. Mechanistically, Et.EA extract activates insulin receptor substrate (IRS1/IRS2)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) in the liver and muscles of Db mice. In conclusion, Et.EA extract attenuates insulin resistance by regulating the expression of metabolic enzymes and signaling pathways.