mTORC1-dependent increase in oxidative metabolism in POMC neurons regulates food intake and action of leptin Magalie Haissaguerre 1, 2, 3 , Amandine Ferrière 1, 2, 3 , Vincent Simon 1, 2 , Nicolas Saucisse 1, 2 , Nathalie Dupuy 1, 2 , Caroline André 1, 2 , Samantha Clark 1, 2 , Omar Guzman-Quevedo 1, 2 , Antoine Tabarin 1, 2, 3 , Daniela Cota 1, 2, * ABSTRACT Objective: Nutrient availability modulates reactive oxygen species (ROS) production in the hypothalamus. In turn, ROS regulate hypothalamic neuronal activity and feeding behavior. The mechanistic target of rapamycin complex 1 (mTORC1) pathway is an important cellular integrator of the action of nutrients and hormones. Here we tested the hypothesis that modulation of mTORC1 activity, particularly in Proopiomelanocortin (POMC)-expressing neurons, mediates the cellular and behavioral effects of ROS. Methods: C57BL/6J mice or controls and their knockout (KO) littermates deficient either for the mTORC1 downstream target 70-kDa ribosomal protein S6 kinase 1 (S6K1) or for the mTORC1 component Rptor specifically in POMC neurons (POMC-rptor-KO) were treated with an intracerebroventricular (icv) injection of the ROS hydrogen peroxide (H 2 O 2 ) or the ROS scavenger honokiol, alone or, respectively, in combination with the mTORC1 inhibitor rapamycin or the mTORC1 activator leptin. Oxidant-related signal in POMC neurons was assessed using dihydroethidium (DHE) fluorescence. Results: Icv administration of H 2 O 2 decreased food intake, while co-administration of rapamycin, whole-body deletion of S6K1, or deletion of rptor in POMC neurons impeded the anorectic action of H 2 O 2 .H 2 O 2 also increased oxidant levels in POMC neurons, an effect that hinged on functional mTORC1 in these neurons. Finally, scavenging ROS prevented the hypophagic action of leptin, which in turn required mTORC1 to increase oxidant levels in POMC neurons and to inhibit food intake. Conclusions: Our results demonstrate that ROS and leptin require mTORC1 pathway activity in POMC neurons to increase oxidant levels in POMC neurons and consequently decrease food intake. Ó 2018 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Keywords Hypothalamus; Reactive oxygen species; mTORC1; Leptin; Food intake; POMC 1. INTRODUCTION Cells use different type of signals to convey information about energy availability and coordinate cellular functions. In mammalian cells, adenosine-triphosphate (ATP) production encompasses mitochondrial oxygen consumption, which leads to the production of reactive oxygen species (ROS). ROS, including hydrogen peroxide (H 2 O 2 ) and the superoxide anion (O 2 ), are oxidant radical species derived from oxygen acting as signal molecules able to modulate numerous intracellular pathways [1,2]. Hypothalamic neurons can sense, transmit, and convert ROS signals into appropriate intracellular responses [2,3]. Among these, increased ROS production has been involved in determining hypothalamic glucose and lipid sensing [4e6] and in mediating the central appetite- suppressant action of insulin [7]. Remarkably, nutrient availability directly impacts ROS levels in Neuropeptide Y/Agouti-related protein (NPY/AgRP) and proopiomelanocortin (POMC) expressing neurons of the hypothalamic arcuate nucleus (ARC) [8,9]. In turn, ROS modify the activity of these two neuronal populations [8,9], which control feeding behavior and peripheral metabolism by integrating information related to energy availability through neuronal inputs [10] and circulating metabolic cues [11e13]. Specifically, during fasting, ROS levels are not increased in NPY/AgRP neurons despite increased neuronal firing, thanks to a feed-forward ROS buffering mechanism involving mito- chondrial uncoupling protein 2 (UCP2) [8]. However, if ROS generation is uncontrolled, firing of NPY/AgRP cells is impaired [8]. In contrast, while in fasting, ROS levels are low in hypothalamic POMC neurons, they are high upon refeeding in the same neuronal population [8,9]. Moreover, POMC neurons are depolarized and fire more in response to H 2 O 2 , while application of the H 2 O 2 scavenging enzyme catalase during patch-clamp recordings hyperpolarizes and inhibits them [9,14]. Thus, a transient increase in ROS levels in POMC neurons 1 INSERM, Neurocentre Magendie, Physiopathologie de la Plasticité Neuronale, U1215, F-33000 Bordeaux, France 2 University of Bordeaux, Neurocentre Magendie, Phys- iopathologie de la Plasticité Neuronale, U1215, F-33000 Bordeaux, France 3 Department of Endocrinology, Hôpital Haut Lévèque, CHU Bordeaux, F-33600 Pessac, France *Corresponding author. Group “Energy Balance and Obesity”, INSERM U1215, Neurocentre Magendie, 146 Rue Léo Saignat, 33077 Bordeaux, France. Fax: þ33 5 5757 3669. E-mail: daniela.cota@inserm.fr (D. Cota). Received March 14, 2018  Revision received April 5, 2018  Accepted April 7, 2018  Available online 13 April 2018 https://doi.org/10.1016/j.molmet.2018.04.002 Brief Communication 98 MOLECULAR METABOLISM 12 (2018) 98e106 Ó 2018 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). www.molecularmetabolism.com