Mitochondrial stress-induced GDF15-GFRAL axis promotes anxiety-like behavior and CRH-dependent anorexia
Growth differentiation factor 15 (GDF15) is a stress-induced cytokine that modulates food intake and energy metabolism. Until now, most mechanistic studies on GDF15 rely on pharmacological interventions using exogenous GDF15, but little is known about its mode of action when induced both chronically and endogenously. Mitochondrial stress is one of the most described physiological conditions that induces GDF151, and therefore an important model to study the underlying mechanisms of endogenous GDF15s action. Here, using a mouse model of mitochondrial dysfunction via elevated respiratory uncoupling in skeletal muscle, we show a circadian oscillation of muscle-derived GDF15 to promote a daytime-restricted anorexia without signs of nausea or reduced physical activity, contrary to findings using recombinant GDF152-5. We find that mitochondrial stress-induced GDF15 associates with increased anxiety and hypothalamic corticotropin releasing hormone (CRH) induction, without further activation of the hypothalamic-pituitary-adrenal (HPA) axis and corticosterone response. Strikingly, the daytime-restricted anorexia, lean phenotype, systemic shift in substrate metabolism and anxiety-like behavior are completely abolished in conditions of mitochondrial stress coupled with genetic ablation of the GDF15 receptor GDNF receptor alpha-like (GFRAL), which is predominantly expressed in the hindbrain. Finally, we demonstrate that stress-induced GDF15-GFRAL signaling is required for hypothalamic CRH induction to control diurnal food intake in a CRH-receptor 1 (CRHR1)-dependent manner. With this, we uncover for the first time a molecular target of the GDF15-GFRAL axis that links anxiolytic and anorectic behavior as downstream effects of the chronic activation of this pathway by mitochondrial stress.