Macrophage miR-130b/301b and beige adipogenesis

Project Summary Obesityis a global health problem that increases the risk of type 2 diabetes, cardiovascular diseases,and cancer. As the main inducible thermogenic cell type capable of improving energy homeostasis in humans, beige adipocytes are a potential therapeutic target to combat obesity and related comorbidities. A critical barrier to the anti-obesity potential of beige fat is the limited understanding of the intercellular regulation of beige adipogenesis in obesity. Adipose tissue macrophages (ATMs) have emerged as a central regulator of adipose remodeling. Here, we have identified a microRNA cluster, miR-130b and miR-301b, as an important macrophage-derived suppressor of adipose tissue beigeing and energy metabolism. We found that miR-130b is upregulated in subcutaneous ATMs of both humans and mouse models with obesity. Our recent published study showed that mice lacking miR-130b/301b globally are protected from high fat diet (HFD)-induced obesity and glucose intolerance, concomitant with increased beigeing and decreased inflammation specifically in subcutaneous fat depot. Further studies using myeloid-specific miR-130b/301b knockout mice showed that deletion of miR-130b/301b specifically in myeloid cells resulted in nearly complete loss (~99%) of miR-130b in adipose stem/stromal cells (ASCs) and in circulation, indicating that myeloid cells are the major source of miR- 130b. In vitro studies demonstrated that macrophages (Mφs) release extracellular vesicles (EVs) containing miR- 130b that are taken up by ASCs, and miR-130b overexpression in ASCs suppresses beige differentiation likely via AMP-activated protein kinase (AMPK) and mitochondrial metabolism. However, detailed molecular mechanism whereby miR-130b/301b, produced in myeloid cells, impacts beige adipogenesis and adipose tissue inflammation in specific fat depots remain to be elucidated. We hypothesize that HFD increases Mφ-derived miR-130b/301b which suppresses beige adipogenesis via EV-mediated transfer of miR-130b/301b into specific ASCs and increases inflammation via modulation of Mφ polarization. Combining in vitro and in vivo studies using Mφ-specific miR-130b/301b knockout mice and EV administration, our goals are to delineate cell-specific actions of miR-130b/301b and explore therapeutic potential of EV-mediated miR-130b/301b inhibition in obesity. Aim1 will test the hypothesis that HFD, opposed to cold, increases Mφ-derived EV uptake of miR-130b/301b into the subtypes of adipose progenitors, impairing beige adipogenesis. Cell distribution of miR-130b/301b in WT versus Mφ-specific miR-130b/301b KO mice will be assessed using miRNA flow cytometry and miRNAScope. Single-cell RNAseq and Mφ/ASC co-culture will be performed. Aim2 will assess the roles of miR- 130b/30b in Mφ polarization and the underlying mechanisms. Aim3 will explore therapeutic potential of EV- mediated miR-130b/301b inhibition in obesity and associated disorders. Results of these studies will provide new knowledge about the cross-talk between macrophages and beige adipocyte development/function in obesity and pave the way for using miR-130b/301b and their gene networks as novel therapeutic targets and biomarkers.