Transcriptional Control of High-thermogenic Adipocyte Development

Brown adipose tissue is composed of heterogenous adipocyte populations evidenced by the coexistence of low-thermogenic adipocytes (mitochondria content low and uncoupling protein 1 (UCP1) low) and high- thermogenic adipocytes within the tissue, a fundamental feature of adipocyte heterogeneity and plasticity. However, the mechanisms underlying adipocyte heterogeneity and its significance in metabolic physiology and disease remain poorly defined. In our preliminary study, we discovered a population of JunB-enriched adipocytes (JunB+ adipocytes) within the brown fat depot that exhibits lower thermogenic capacity and less lipid droplets compared to high-thermogenic adipocytes. The abundance of JunB+ adipocytes is increased during obesity. Through snRNA-seq and functional assays, we observed that inactivation of JunB in adipocytes increased the fraction of adipocytes exhibiting high mitochondrial content and thermogenic capacity. Importantly, JunB ablation in UCP1+ adipocytes resulted in enhanced basal and cold-induced energy expenditure and protected mice against diet-induced obesity. Based upon these novel findings, we hypothesize that JunB serves a critical role in governing adipocyte heterogeneity and systemic energy and glucose homeostasis. We will elucidate the mechanisms by which JunB suppresses high-thermogenic cell differentiation and explore the regulation of JunB+ adipocyte development by examining the identity, origin, and fate of this distinct subpopulation. We will also use Diphtheria toxin gene A chain (DTA)- mediated approach to ablate JunB+ adipocytes within adipose tissue to determine the physiological role of this subpopulation in regulating energy and glucose metabolism. Characterization of JunB in regulating adipocyte heterogeneity and plasticity will provide novel knowledge to the biology of brown adipocyte and a solid foundation to aid in the development of therapeutic interventions for obesity and its associated disorders.