Effects and mechanisms of iridoid glycosides from Patrinia scabiosaefolia on improving insulin resistance in 3T3-L1 adipocytes.

Insulin resistance causes several adverse effects such as hypertension, diabetes and different aspects of cardiovascular diseases. Patrinia scabiosaefolia Fisch. ex Trev. is a traditional Chinese edible herbal, whose n-BuOH extract significantly increased glucose transportin 3T3-L1 adipocytes at the concentration of 12.5 μM. To determine its active constituent, its chemical components and bioactivities were investigated. Two compounds (1-2) could significantly improve insulin resistance in 3T3-L1 adipocytes at concentrations around 25.0 μM (P < 0.001). Compound 2 was more effective to lower the content of glucose content at 12.5 μM (P < 0.001). Compound 1 was a new compound identified by spectroscopic methods. Western-blot experiment demonstrated an upregulation of p-IRS-1, p-Akt, and GLUT4 induced by compounds 1 and 2. Hence, we speculated that compounds 1 and 2 could activate PI3K and Akt signaling by up-regulating of p-IRS-1 which resulted in the activation of PI3K before phosphorylating Akt, ultimately led to translocation of GLUT4. These events finally improve glucose transport. Our results may provide the scientific basis for the development and effective use of P. scabiosaefolia against type 2 diabetes.