Project description:Hypothalamic neurons expressing Agouti-related peptide (AgRP) are critical for initiating food intake, but druggable biochemical pathways that control this response remain elusive. Thus, genetic ablation of insulin or leptin signaling in AgRP neurons is predicted to reduce satiety but fails to do so. FoxO1 is a shared mediator of both pathways, and its inhibition is required to induce satiety. Accordingly, FoxO1 ablation in AgRP neurons of mice results in reduced food intake, leanness, improved glucose homeostasis, and increased sensitivity to insulin and leptin. Expression profiling of flow-sorted FoxO1-deficient AgRP neurons identifies G-protein-coupled receptor Gpr17 as a FoxO1 target whose expression is regulated by nutritional status. Intracerebroventricular injection of Gpr17 agonists induces food intake, whereas Gpr17 antagonist cangrelor curtails it. These effects are absent in Agrp-Foxo1 knockouts, suggesting that pharmacological modulation of this pathway has therapeutic potential to treat obesity. We used microarrays to detail the change of gene expression in AgRP neurons after knocking out FoxO1. AgRP neurons from control and KO mice were collected by FACS. Gene expression was analyzed by microarray.
Project description:Hypothalamic neurons expressing Agouti-related peptide (AgRP) are critical for initiating food intake, but druggable biochemical pathways that control this response remain elusive. Thus, genetic ablation of insulin or leptin signaling in AgRP neurons is predicted to reduce satiety but fails to do so. FoxO1 is a shared mediator of both pathways, and its inhibition is required to induce satiety. Accordingly, FoxO1 ablation in AgRP neurons of mice results in reduced food intake, leanness, improved glucose homeostasis, and increased sensitivity to insulin and leptin. Expression profiling of flow-sorted FoxO1-deficient AgRP neurons identifies G-protein-coupled receptor Gpr17 as a FoxO1 target whose expression is regulated by nutritional status. Intracerebroventricular injection of Gpr17 agonists induces food intake, whereas Gpr17 antagonist cangrelor curtails it. These effects are absent in Agrp-Foxo1 knockouts, suggesting that pharmacological modulation of this pathway has therapeutic potential to treat obesity. We used microarrays to detail the change of gene expression in AgRP neurons after knocking out FoxO1.
Project description:Agouti-related peptide (AgRP)- and proopiomelanocortin (POMC)-expressing neurons reciprocally regulate food intake. Here, we combined non-interacting recombinases to simultaneously express functionally opposing chemogenetic receptors in AgRP and POMC neurons allowing to compare metabolic responses in mice with simultaneous activation of AgRP and inhibition of POMC neurons with isolated activation of AgRP neurons or isolated inhibition of POMC neurons. These experiments revealed that food intake is regulated by the additive effect of AgRP-neuron activation and POMC-neuron inhibition, while systemic insulin sensitivity and gluconeogenesis are differentially modulated by isolated versus simultaneous regulation of AgRP and POMC neurons. We identified a neurocircuit engaging Npy1R-expressing neurons in the paraventricular nucleus of the hypothalamus (PVH), where activated AgRP- and inhibited POMC neurons synergize to promote food consumption and activate neurons in the nucleus tractus solitarii (NTS). We then performed single-nuclei RNA sequencing to define the molecular nature of Fos+ cells in the posterior NTS/AP area that respond to simultaneous chemogenetic intervention over AgRP and POMC neurons and identified TH+ neurons as candidates for receiving neuronal inputs initiated by the simultaneous and coordinated interplay between AgRP and POMC neurocircuits and relayed to the NTS area by the silenced glutamatergic Npy1R neurons.
Project description:Objective: The central melanocortin system is essential for the regulation of food intake and body weight. Agouti-related protein (AgRP) is the sole orexigenic component of the central melanocortin system and is conserved across mammalian species. AgRP is currently known to be expressed exclusively in the mediobasal hypothalamus, and hypothalamic AgRP-expressing neurons are essential for feeding. Here we characterized a previously unknown population of AgRP cells in the mouse hindbrain. Methods: Expression of AgRP in the hindbrain was investigated using gene expression analysis, single-cell RNA sequencing, immunofluorescent analysis and multiple transgenic mice with reporter expressions. Activation of AgRP neurons was achieved by Designer Receptors Exclusively Activated by Designer Drugs (DREADD) and by transcranial focal photo-stimulation using a step-function opsin with ultra-high light sensitivity (SOUL). Results: AgRP expressing cells were present in the area postrema (AP) and the adjacent subpostrema area (SubP) and commissural nucleus of the solitary tract (cNTS) of the mouse hindbrain (termed AgRPHind herein). AgRPHind cells consisted of locally projecting neurons as well as tanycyte-like cells. Food deprivation stimulated hindbrain Agrp expression as well as neuronal activity of subsets of AgRPHind cells. In adult mice that lacked hypothalamic AgRP neurons, chemogenetic activation of AgRP neurons resulted in hyperphagia and weight gain. In addition, transcranial focal photo-stimulation of hindbrain AgRP cells increased food intake in adult mice with or without hypothalamic AgRP neurons. Conclusions: Our study indicates that the central melanocortin system in the hindbrain possesses an orexigenic component, and that AgRPHind neurons stimulate feeding independently of hypothalamic AgRP neurons.
Project description:Energy homeostasis requires precise measurement of the quantity and quality of ingested food. The vagus nerve innervates the gut and can detect diverse interoceptive cues, but the identity of the key sensory neurons and corresponding signals that regulate food intake remains unknown. Here we use an approach for target-specific, single-cell RNA sequencing to generate a map of the vagal cell types that innervate the gastrointestinal tract. We show that unique molecular markers identify vagal neurons with distinct innervation patterns, sensory endings, and function. Surprisingly, we find that food intake is most sensitive to stimulation of mechanoreceptors in the intestine, whereas nutrient-activated mucosal afferents have no effect. Peripheral manipulations combined with central recordings reveal that intestinal mechanoreceptors, but not other cell types, potently and durably inhibit hunger-promoting AgRP neurons in the hypothalamus. These findings identify a key role for intestinal mechanoreceptors in the regulation of feeding.
Project description:Overconsumption of energy-rich food is a key driver of the obesity epidemic. However, the neural circuits that regulate food overconsumption are highly complex and many molecular components of these circuits remain unknown. Our recent studies attribute a novel role of Clic1 as a driver of food intake and overconsumption. Clic1 is expressed in the arcuate nucleus of the hypothalamus and expression specifically increases in Agrp/Npy neurons in the fasted state. Importantly, Clic1 exists in two forms and fasting induces a transformation from the predominant soluble enzymatic form to the membrane-associated ion channel form. Clic1KO mice eat significantly less and have a lower body weight than WT littermates when either fed chow or high fat diet. Furthermore, pharmacological inhibition of Clic1 inhibition results in suppression of food intake and promotes highly efficacious weight loss in obese mice.
Project description:Autophagy represents a key regulator of aging and metabolism upon cell autonomous sensing of energy deprivation. We find that fasting in mice activates autophagy in liver paralleled by activation of hypothalamic AgRP neurons. Optogenetic and chemogenetic activation of AgRP neurons induces autophagy, alters phosphorylation of autophagy regulators and promotes ß-oxidation in the liver. AgRP neuron dependent induction of liver autophagy relies on NPY expression in these neurons. AgRP neuron projections in the paraventricular nucleus of the hypothalamus (PVH) and the lateral hypothalamus (LHA) mediate AgRP neuron-dependent control of liver autophagy. Conversely, inhibiting AgRP neurons during energy deprivation abrogates induction of hepatic autophagy and re-wiring of metabolism. Finally, AgRP neuron activation increases circulating corticosterone concentrations, and reduction of hepatic glucocorticoid receptor expression attenuates AgRP neuron-dependent activation of hepatic autophagy. Collectively, our study reveals a fundamental regulatory principle of non-cell autonomous control of liver autophagy in control of metabolic adaptation during nutrient deprivation.
Project description:The paraventricular hypothalamus (PVH) is crucial for food intake control, yet the presynaptic mechanisms underlying PVH neurons remain unclear. Here, we show that RUVBL2 in the PVH is significantly reduced during energy deficit, and knockout (KO) of PVH RUVBL2 results in hyperphagic obesity in mice. RUVBL2-expressing neurons in the PVH (PVHRUVBL2) exert the anorexigenic effect by projecting to the arcuate hypothalamus, the dorsomedial hypothalamus, and the parabrachial complex. We further demonstrate that PVHRUVBL2 neurons form the synaptic connections with POMC and AgRP neurons in the ARC. PVH RUVBL2 KO impairs the excitatory synaptic transmission by reducing presynaptic boutons and synaptic vesicles near active zone. Finally, RUVBL2 overexpression in the PVH suppresses food intake and protects against diet induced obesity. Together, this study demonstrates an essential role for PVH RUVBL2 in food intake control, and suggests that modulation of synaptic plasticity could be an effective way to curb appetite and obesity.
Project description:The arcuate nucleus of the hypothalamus (ARH) is one key structure controlling energy homeostasis. While it has been shown that the biogenic amines dopamine and serotonin modulate food intake controlling NPY/AgRP and/or POMC neurons in the ARH, the neural substrates that mediate the effect of noradrenaline (NA) on energy homeostasis remain elusive. By electrophysiological recordings and cell type-specific transcriptomics we show that the main neuronal populations in the ARH, NPY/AgRP and POMC neurons express a combination of excitatory and inhibitory adrenergic receptors (ARs). Surprisingly, NA had a clear differential effect on these neurons. Activation of NPY/AgRP neurons is mediated by _1A - and _- ARs, while POMC neurons are inhibited via _2A ARs. Collectively, our data indicate an orexigenic influence of NA on the ARH circuitry that controls energy balance