Effects of β-catenin deficiency on adipose tissue physiology

Objective: Compelling evidence from investigation of preclinical models and humans links canonical Wnt/β-catenin signaling to regulation of many aspects of white adipose tissue development and physiology. Dysregulation of this ancient pathway alters adiposity and metabolic homeostasis. Herein we explore how disruption of adipocyte Wnt signaling affects gene expression and crosstalk between cell types within adipose tissue. Methods: To investigate mechanisms through which adipose tissue attempts to maintain homeostasis in the absence of β-catenin in adipocytes, we employed standard methods of metabolic phenotyping as well as bulk RNA sequencing, flow cytometry, single-cell RNA sequencing, and isolation of secreted extracellular vesicles. Results: Our experiments reveal that male, but not female Ctnnb1AdKO mice have an increase in adiposity and insulin resistance. Whereas metabolic processes including fatty acid metabolism were suppressed in adipocytes, mitochondrial metabolism of immune cells was made more efficient, resulting in reduced reactive oxygen species in macrophages and dendritic cells. Deficiency of β-catenin in adipocytes altered the transcriptome of numerous stromal-vascular cell populations including adipose stem and progenitor cells, macrophages, and other immune cells. Homeostasis in white adipose tissue of Ctnnb1AdKO mice is maintained in part by elevated expression of Ctnnb1 mRNA in endothelial cells and in secreted small extracellular vesicles. Conclusions: Our studies demonstrate the importance of adipocyte Wnt signaling for regulation of lipid and mitochondrial metabolic processes in stromal-vascular cells and adipocytes in adipose tissues. This research provides further support for an intercellular Wnt signaling network with compensatory capability to maintain homeostasis, and underscores importance of Wnt/β-catenin signaling for understanding adipose tissue physiology and pathophysiology.