A cold-induced GDF15-secreting adipocyte subpopulation regulates energy homeostasis through endocrine signaling

Brown adipose tissue (BAT) regulates whole-body energy balance through uncoupling protein 1 (UCP1)-dependent thermogenesis and secretion of metabolic factors. Recent studies suggest UCP1-independent mechanisms contribute to energy balance, with UCP1 being conditionally dispensable. However, how adaptation to UCP1 deficiency is regulated remains unclear. Our single-nucleus RNA sequencing of BAT from cold-exposed Ucp1 knockout mice reveals a distinct brown adipocyte subpopulation (U2). U2 adipocytes exhibit a secretory profile enriched in batokines like growth differentiation factor 15 (GDF15), suggesting a shift toward an endocrine role. Functional analyses reveal that GDF15-GFRAL signaling is required to sustain energy expenditure in adipose tissue (AT). The Ucp1/Gfral knockout increased food intake to compensate for decreased energy expenditure in AT. Additionally, a conserved UCP1-GDF15 regulatory axis in human AT is observed. These findings identify a regulatory brown adipocyte subpopulation emerging in response to UCP1 deficiency, representing a compensatory mechanism for maintaining energy homeostasis in mammals.