RESUMO
Astrocytes represent central regulators of brain glucose metabolism and neuronal function. They have recently been shown to adapt their function in response to alterations in nutritional state through responding to the energy state-sensing hormones leptin and insulin. Here, we demonstrate that glucagon-like peptide (GLP)-1 inhibits glucose uptake and promotes ß-oxidation in cultured astrocytes. Conversely, postnatal GLP-1 receptor (GLP-1R) deletion in glial fibrillary acidic protein (GFAP)-expressing astrocytes impairs astrocyte mitochondrial integrity and activates an integrated stress response with enhanced fibroblast growth factor (FGF)21 production and increased brain glucose uptake. Accordingly, central neutralization of FGF21 or astrocyte-specific FGF21 inactivation abrogates the improvements in glucose tolerance and learning in mice lacking GLP-1R expression in astrocytes. Collectively, these experiments reveal a role for astrocyte GLP-1R signaling in maintaining mitochondrial integrity, and lack of GLP-1R signaling mounts an adaptive stress response resulting in an improvement of systemic glucose homeostasis and memory formation.
Assuntos
Astrócitos/metabolismo , Ácidos Graxos/metabolismo , Receptor do Peptídeo Semelhante ao Glucagon 1/metabolismo , Mitocôndrias/metabolismo , Animais , Feminino , Receptor do Peptídeo Semelhante ao Glucagon 1/deficiência , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Oxirredução , Transdução de SinaisRESUMO
Melanin-concentrating hormone (MCH)-expressing neurons are key regulators of energy and glucose homeostasis. Here, we demonstrate that they provide dense projections to the median eminence (ME) in close proximity to tanycytes and fenestrated vessels. Chemogenetic activation of MCH neurons as well as optogenetic stimulation of their projections in the ME enhance permeability of the ME by increasing fenestrated vascular loops and enhance leptin action in the arcuate nucleus of the hypothalamus (ARC). Unbiased phosphoRiboTrap-based assessment of cell activation upon chemogenetic MCH neuron activation reveals MCH-neuron-dependent regulation of endothelial cells. MCH neurons express the vascular endothelial growth factor A (VEGFA), and blocking VEGF-R signaling attenuates the leptin-sensitizing effect of MCH neuron activation. Our experiments reveal that MCH neurons directly regulate permeability of the ME barrier, linking the activity of energy state and sleep regulatory neurons to the regulation of hormone accessibility to the ARC.
Assuntos
Permeabilidade da Membrana Celular/fisiologia , Hormônios Hipotalâmicos/fisiologia , Eminência Mediana/fisiologia , Melaninas/fisiologia , Neurônios/fisiologia , Hormônios Hipofisários/fisiologia , Animais , Núcleo Arqueado do Hipotálamo/fisiologia , Vasos Sanguíneos/fisiologia , Capilares/fisiologia , Núcleo Celular/fisiologia , Núcleo Celular/ultraestrutura , Células Endoteliais/fisiologia , Leptina/fisiologia , Eminência Mediana/irrigação sanguínea , Camundongos , Cultura Primária de Células , Ratos , Ratos Sprague-Dawley , Receptores de Fatores de Crescimento do Endotélio Vascular/antagonistas & inibidores , Fator A de Crescimento do Endotélio Vascular/biossínteseRESUMO
Mitochondrial oxidative phosphorylation (OXPHOS) and substrate utilization critically regulate the function of hypothalamic proopiomelanocortin (POMC)-expressing neurons. Here, we demonstrate that inactivation of apoptosis-inducing factor (AIF) in POMC neurons mildly impairs mitochondrial respiration and decreases firing of POMC neurons in lean mice. In contrast, under diet-induced obese conditions, POMC-Cre-specific inactivation of AIF prevents obesity-induced silencing of POMC neurons, translating into improved glucose metabolism, improved leptin, and insulin sensitivity, as well as increased energy expenditure in AIFΔPOMC mice. On a cellular level, AIF deficiency improves mitochondrial morphology, facilitates the utilization of fatty acids for mitochondrial respiration, and increases reactive oxygen species (ROS) formation in POMC neurons from obese mice, ultimately leading to restored POMC firing upon HFD feeding. Collectively, partial impairment of mitochondrial function shifts substrate utilization of POMC neurons from glucose to fatty acid metabolism and restores their firing properties, resulting in improved systemic glucose and energy metabolism in obesity.
Assuntos
Ácidos Graxos/metabolismo , Glucose/metabolismo , Homeostase , Mitocôndrias/patologia , Neurônios/metabolismo , Obesidade/prevenção & controle , Fosforilação Oxidativa , Pró-Opiomelanocortina/metabolismo , Animais , Fator de Indução de Apoptose/fisiologia , Dieta Hiperlipídica/efeitos adversos , Metabolismo Energético , Intolerância à Glucose , Hipotálamo/metabolismo , Hipotálamo/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Obesos , Mitocôndrias/metabolismo , Neurônios/patologia , Obesidade/etiologia , Obesidade/metabolismo , Obesidade/patologiaRESUMO
Natural killer (NK) cells contribute to the development of obesity-associated insulin resistance. We demonstrate that in mice obesity promotes expansion of a distinct, interleukin-6 receptor (IL6R)a-expressing NK subpopulation, which also expresses a number of other myeloid lineage genes such as the colony-stimulating factor 1 receptor (Csf1r). Selective ablation of this Csf1r-expressing NK cell population prevents obesity and insulin resistance. Moreover, conditional inactivation of IL6Ra or Stat3 in NK cells limits obesity-associated formation of these myeloid signature NK cells, protecting from obesity, insulin resistance, and obesity-associated inflammation. Also in humans IL6Ra+ NK cells increase in obesity and correlate with markers of systemic low-grade inflammation, and their gene expression profile overlaps with characteristic gene sets of NK cells in obese mice. Collectively, we demonstrate that obesity-associated inflammation and metabolic disturbances depend on interleukin-6/Stat3-dependent formation of a distinct NK population, which may provide a target for the treatment of obesity, metaflammation-associated pathologies, and diabetes.
Assuntos
Metabolismo Energético , Glucose/metabolismo , Inflamação/metabolismo , Interleucina-6/metabolismo , Células Matadoras Naturais/patologia , Obesidade/metabolismo , Fator de Transcrição STAT3/metabolismo , Adulto , Animais , Homeostase , Humanos , Inflamação/complicações , Inflamação/patologia , Resistência à Insulina , Células Matadoras Naturais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Obesos , Obesidade/complicações , Obesidade/patologia , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos/metabolismo , Receptores de Interleucina-6/metabolismo , Transdução de Sinais , Adulto JovemRESUMO
Interleukin (IL)-6 engages similar signaling mechanisms to leptin. Here, we find that central application of IL-6 in mice suppresses feeding and improves glucose tolerance. In contrast to leptin, whose action is attenuated in obesity, the ability of IL-6 to suppress feeding is enhanced in obese mice. IL-6 suppresses feeding in the absence of neuronal IL-6-receptor (IL-6R) expression in hypothalamic or all forebrain neurons of mice. Conversely, obese mice exhibit increased soluble IL-6R levels in the cerebrospinal fluid. Blocking IL-6 trans-signaling in the CNS abrogates the ability of IL-6 to suppress feeding. Furthermore, gp130 expression is enhanced in the paraventricular nucleus of the hypothalamus (PVH) of obese mice, and deletion of gp130 in the PVH attenuates the beneficial central IL-6 effects on metabolism. Collectively, these experiments indicate that IL-6 trans-signaling is enhanced in the CNS of obese mice, allowing IL-6 to exert its beneficial metabolic effects even under conditions of leptin resistance.