BS33 BMP signalling in brown and white adipocytes

Introduction Adipose tissue dysfunction constitutes a significant risk factor for cardiovascular diseases. Adipocyte function and adipose tissue thermogenesis are regulated by many factors, including bone morphogenetic proteins (BMPs). BMP4 promotes a beige phenotype in brown and white adipocytes and angiogenesis in adipose tissue. BMP9 and BMP10, two vascular quiescence factors that signal potently in vascular endothelial cells, also signal in mature brown and white adipocytes, but their functions are less well-understood. This study aims to compare the potency and signalling outcomes of BMP9 and BMP10 to BMP4 to elucidate how the signalling and regulation of BMP family ligands impact the functions of brown and white adipocytes. Methods 3T3-L1 white preadipocytes and p-BAT brown preadipocytes were differentiated into mature white and brown adipocytes, respectively. Signalling assays were carried out by restricting serum for 16 hours to quiesce the cells before treatment by BMP4, BMP9 or BMP10 in dose-dependent assays and time-course assays. RNAseq experiments were performed to identify the shared and unique target genes regulated by BMP4, BMP9 and BMP10. RNAseq sample flow and preparation are shown in the diagrams below. Results and Conclusions BMP4 and BMP9 signal more potently than BMP10 in both brown and white adipocytes. All three BMPs can induce the canonical BMP target genes such as Id1, Id3, Id4 and Smad6, and the key adipogenesis regulator PPARgamma in both adipocyte types. Yet, each BMP exerts unique effects on the regulation of genes associated with adipogenesis, lipogenesis, neurogenesis, and angiogenesis. Furthermore, the same BMP induces overlapping but not identical target genes in brown and white adipocytes. In brown adipocytes, genes associated with nervous system development, such as Fabp7, Cdc24a, and Nrn1, were upregulated independent of the BMP used. In white adipocytes, BMP4 and BMP9 upregulated the expression of genes related to the positive regulation of SMAD signalling, including Tgfb3, Acvrl1 (Alk1), and Acvr1b (Alk4). BMP9 also upregulated the expression of Bmp4, suggesting a potential feedback mechanism for sustained signalling activation. Conflict of Interest None