Fig. 5.

Butein inhibits adipocyte differentiation through STAT3 signaling. A: Transient transfection of 3T3-L1 cells with two independent STAT3 siRNAs (si #1 or si #2) reduced STAT3 expression. B, C: Silencing the expression of STAT3 impaired adipocyte differentiation. Transient transfection of 3T3-L1 cells with two independent STAT3 siRNAs inhibited adipocyte differentiation as assessed by Oil Red O staining after 6 days (B) and quantification of lipid accumulation by measuring the extracted dye at 520 nm (C). D: Knockdown of STAT3 attenuated the effects on expression of STAT3 target genes by butein. Expression of STAT3 target genes KLF5, C/EBPδ, and CycD1 in control and siRNA-transfected cells treated with DMSO or butein (10 μM) for 12 h was measured by real-time PCR. E, F: Silencing expression of STAT3 blunted butein's inhibitory effects on adipocyte differentiation in 3T3-L1 cells. E: Knockdown of STAT3 attenuated the effects of butein on expression of adipocyte markers. Expression of PPARγ and its target gene aP2 in control nonspecific siRNA- and specific siRNA-transfected cells treated with DMSO or butein (10 μM) for 6 days was measured by real-time PCR. F: Silencing STAT3 compromised butein's inhibitory effects on lipid accumulation in 3T3-L1 cells. Control and siRNA-transfected cells were treated with DMSO or butein (10 μM) and then differentiated for 6 days. Differentiated cells were stained with Oil Red O. Data shown represent the mean ± SEM from three independent experiments. Statistical significance was determined relative to a control by the Student's t-test (*P < 0.05; **P < 0.005; ***P < 0.0005). Ctrl, control; Norm., normailzed; But, butein.