Wnt/Wingless signaling promotes lipid mobilization through signal-induced transcriptional repression

The Wnt/Wingless signaling pathway plays critical roles in metazoan development and energy metabolism, but its involvement in lipid mobilization has remained unclear. Here, we report that canonical Wnt/Wg signaling reduces lipid accumulation in both larval and adult adipocytes, as well as cultured S2R+ cells, in Drosophila. This reduction occurs through promoting lipolysis while concurrently repressing lipogenesis and fatty acid ß-oxidation. Leveraging RNA-sequencing and CUT&RUN assays, we have identified a set of Wnt target genes responsible for intracellular lipid homeostasis. Notably, active Wnt signaling directly represses the transcription of these genes, resulting in decreased triglyceride accumulation in lipid droplets, increased lipolysis, and reduced fatty acid ß-oxidation. These changes lead to elevated free fatty acids and reduced triglyceride accumulation in adipocytes with active Wnt signaling. Conversely, downregulation of Wnt signaling in the fat body promotes triglyceride accumulation in both larval and adult stages. The attenuation of Wnt signaling also increases the expression of specific lipid metabolism-related genes in larval adipocytes, wing discs, and adult intestines. Collectively, our findings suggest that Wnt signaling-induced transcriptional repression plays an important role in regulating lipid homeostasis by enhancing lipolysis while simultaneously suppressing lipogenesis and fatty acid ß-oxidation processes. Overall design: To gain insights into the molecular mechanism underlying Wnt signaling-stimulated lipid catabolism and reduced lipogenesis, we conducted bulk RNA sequencing (RNA-seq) analyses on dissected larval fat body with specific depletions of Axn or slmb, and BTZ treated animals. To investigate potential direct targets of Wnt signaling, we performed CUT&Run on EGFP tagged Pan.