Signal transducer and activator of transcription 3 (STAT3) regulates adipocyte differentiation via peroxisome-proliferator-activated receptor gamma (PPAR gamma)

Background information. STAT3 (signal transducer and activator of transcription 3) is an important transcription factor involved in many biological events, including apoptosis, tumorigenesis, angiogenesis and epithelial-to-mesenchymal transition. However, no direct evidence for a role of STAT3 in 3T3-L1 adipocyte differentiation has been reported. Results. In the present study, we found that rapid activation of STAT3, lasting for more than 48 h, was elicited upon induction of adipogenesis. Both the STAT3-selective inhibitor stattic and the JAK2 (Janus kinase 2)/STAT3-selective inhibitors AG490 and Go6976 inhibited STAT3 activation, leading to the suppression of adipocyte differentiation. Adipocyte differentiation was also suppressed by STAT3 siRNA (small interfering RNA) or dominant-negative STAT3. Interestingly, the PPAR gamma (peroxisome-proliferator-activated receptor gamma) agonist TAZ (troglitazone) abolished the STAT3-inhibitor- and RNAi (RNA interference)-mediated suppression of adipogenesis. However, TAZ treatment had no effect on the stattic- and AG490-mediated down-regulation of STAT3 activation, suggesting that STAT3 regulates adipocyte differentiation through signalling that occurs upstream of PPAR gamma. Conclusion. These data indicate that STAT3 functions as a critical factor for adipogenesis via a mechanism involving the PPAR gamma activation pathway.