X-box binding protein 1 enhances adipogenic differentiation of 3T3-L1 cells through the downregulation of Wnt10b expression.

Differentiation of preadipocytes into adipocytes is controlled by various transcription factors. Recently, the pro-adipogenic function of XBP1, a transcription factor upregulated by endoplasmic reticulum stress, has been reported. In this study, we demonstrated that XBP1 suppresses the expression of Wnt10b, an anti-adipogenic Wnt, during the differentiation of 3T3-L1 preadipocytes. The expression pattern of XBP1 was reciprocal to that of Wnt10b during the early stage of adipogenesis. The intracellular protein levels of β-catenin were negatively regulated by XBP1. Direct binding of XBP1 to the Wnt10b promoter and the subsequent decrease of the β-catenin signalling pathway represent a novel adipogenic differentiation mechanism.