Aim
Peroxisome proliferator-activated receptor gamma (PPARgamma) is a therapeutic target for obesity, cancer and diabetes mellitus. In order to develop potent lead compounds for obesity treatment, we screened a natural product library for novel PPARgamma antagonists with inhibitory effects on adipocyte differentiation.
Conclusion
CAB shows antagonistic activity to PPARgamma and can block the adipocyte differentiation, indicating it may be of potential use as a lead therapeutic compound for obesity.
Methods
Surface plasmon resonance (SPR) technology and cell-based transactivation assay were used to screen for PPARgamma antagonists. To investigate the antagonistic mechanism of the active compound, we measured its effect on PPARgamma/RXRalpha heterodimerization and PPARgamma co-activator recruitment using yeast two-hybrid assay, Gal4/UAS cell-based assay and SPR based assay. The 3T3-L1 cell differentiation assay was used to evaluate the effect of the active compound on adipocyte differentiation.
Results
A new thiophene-acetylene type of natural product, 7-chloroarctinone-b (CAB), isolated from the roots of Rhaponticum uniflorum, was discovered as a novel PPARgamma antagonist capable of inhibiting rosiglitazone-induced PPARgamma transcriptional activity. SPR analysis suggested that CAB bound tightly to PPARgamma and considerably antagonized the potent PPARgamma agonist rosiglitazone-stimulated PPARgamma-LBD/RXRalpha-LBD binding. Gal4/UAS and yeast two-hybrid assays were used to evaluate the antagonistic activity of CAB on rosiglitazone-induced recruitment of the coactivator for PPARgamma. CAB could efficiently antagonize both hormone and rosiglitazone-induced adipocyte differentiation in cell culture.