Acta Pharmacologica Sinica (2009) 30: 1351–1358; doi: 10.1038/aps.2009.113; published online 17 August 2009

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 PPARγ antagonists with inhibitory effects on adipocyte differentiation.

Methods: Surface plasmon resonance (SPR) technology and cell-based transactivation assay were used to screen for PPARγ antagonists.  To investigate the antagonistic mechanism of the active compound, we measured its effect on PPARγ/RXRα heterodimerization and PPARγ 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 PPARγ antagonist capable of inhibiting rosiglitazone-induced PPARγ transcriptional activity.  SPR analysis suggested that CAB bound tightly to PPARγ and considerably antagonized the potent PPARγ 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 rosiglitazone-induced recruitment of the coactivator for PPARγ.  CAB could efficiently antagonize both hormone and rosiglitazone-induced adipocyte differentiation in cell culture.

Conclusion: CAB shows antagonistic activity to PPARγ and can block the adipocyte differentiation, indicating it may be of potential use as a lead therapeutic compound for obesity.

Keywords: peroxisome proliferator-activated receptor; antagonist; surface plasmon resonance; recruitment of the coactivator; adipocyte differentiation