Tumour necrosis factor-α inhibits adipogenesis via a β-catenin/TCF4(TCF7L2)-dependent pathway

Abstract

Tumour necrosis factor-α (TNF-α), a proinflammatory cytokine, is a potent negative regulator of adipocyte differentiation. However, the mechanism of TNF-α-mediated antiadipogenesis remains incompletely understood. In this study, we first confirm that TNF-α inhibits adipogenesis of 3T3-L1 preadipocytes by preventing the early induction of the adipogenic transcription factors peroxisome proliferator-activated receptor-γ (PPARγ) and CCAATαenhancer binding protein-α (C/EBPα). This suppression coincides with enhanced expression of several reported mediators of antiadipogenesis that are also targets of the Wnt/ β-catenin/T-cell factor 4 (TCF4) pathway. Indeed, we found that TNF-α enhanced TCF4-dependent transcriptional activity during early antiadipogenesis, and promoted the stabilisation of β-catenin throughout antiadipogenesis. We analysed the effect of TNF-α on adipogenesis in 3T3-L1 cells in which β-catenin/TCF signalling was impaired, either via stable knockdown of β-catenin, or by overexpression of dominant-negative TCF4 (dnTCF4). The knockdown of β-catenin enhanced the adipogenic potential of 3T3-L1 preadipocytes and attenuated TNF-α-induced antiadipogenesis. However, β-catenin knockdown also promoted TNF-α-induced apoptosis in these cells. In contrast, overexpression of dnTCF4 prevented TNF-α-induced antiadipogenesis but showed no apparent effect on cell survival. Finally, we show that TNF-α-induced antiadipogenesis and stabilisation of β-catenin requires a functional death domain of TNF-α receptor 1 (TNFR1). Taken together these data suggest that TNFR1-mediated death domain signals can inhibit adipogenesis via a β-catenin/TCF4-dependent pathway.