7-Chloroarctinone-b as a new selective PPARy antagonist potently blocks adipocyte differentiation

Aim： Peroxisome proliferator-activated receptor gamma （PPARγ） 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 PPARy antagonists with inhibitory effects on adipocyte differentiation. Methods： Surface plasmon resonance （SPR） technology and cell-based transactivation assay were used to screen for PPARy antago nists. To investigate the antagonistic mechanism of the active compound, we measured its effect on PPARy/RXRγ heterodimerization and PPARy co-activator recruitment using yeast two-hybrid assay, Ga14/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 PPARy antagonist capable of inhibiting rosiglitazone-induced PPARy transcriptional activity. SPR analysis suggested that CAB bound tightly to PPARy and considerably antagonized the potent PPARy agonist rosiglitazone-stimulated PPARγ- LBD/RXRα-LBD binding. Gal4/UAS and yeast two-hybrid assays were used to evaluate the antagonistic activity of CAB on rosiglitazoneinduced recruitment of the coactivator for PPARy. CAB could efficiently antagonize both hormone and rosiglitazone-induced adipocyte differentiation in cell culture. Conclusion： CAB shows antagonistic activity to PPARy and can block the adipocyte differentiation, indicating it may be of potential use as a lead therapeutic compound for obesity.