Oleanolic acid derivative NPLC441 potently stimulates glucose transport in 3T3-L1 adipocytes via a multi-target mechanism

The natural product oleanolic acid (OA) has been discovered to exhibit varied pharmacological functions including anti-inflammation, anti-tumor and anti-diabetes, while appropriate synthetic oleanolic acid derivatives seem to possess more potent activities. Here we identified a new oleanolic acid derivative, 3-β-(2-carboxybenzoyloxy)-oleanolic acid (NPLC441), which functioned as a competitive PTP1B inhibitor and enhanced insulin-stimulated phosphorylation of IR and AKT in HepG2 cells. As an RXRα antagonist, it could selectively activate LXRα:RXRα heterodimer and increase the promoter activities of ABCA1 and ABCG1 genes in transient transfection assays. Quantitative RT-PCR and Western blot analyses suggested that NPLC441 could up-regulate GLUT4 expression in 3T3-L1 adipocytes, and such effect was further proved to be dependent on LXRα:RXRα activation. Moreover, 2-deoxyglucose uptake technology-based characterization demonstrated that this compound could stimulate glucose uptake in 3T3-L1 adipocytes. Finally, NPLC441 was observed to be able to suppress 11β-HSD1 expression in HepG2 cells, following the discovery that activation of LXRα:RXRα could repress the expression of 11β-HSD1. Compared with NPLC441, OA showed no effects on the transactivation of either LXRα:RXRα heterodimer or RXRα-LBD. Our work is thus expected to provide a new insight into the anti-diabetic application for oleanolic acid derivatives via multi-target mechanism, and NPLC441 could be used as a potential lead compound for further research.