RESUMEN

Multiple sclerosis (MS) is the chronic inflammatory demyelinating disease of the CNS. Relapsing-remitting MS (RRMS) is the most common type of MS. However, the mechanisms of relapse and remission in MS have not been fully understood. While SJL mice immunized with proteolipid protein (PLP) develop relapsing-remitting experimental autoimmune encephalomyelitis (RR-EAE), we have recently observed that some of these mice were resistant to the active induction of relapsing EAE after initial clinical and histological symptoms of EAE with a severity similar to the relapsing EAE mice. To clarify the mechanism of relapsing, we examined myelin morphology during PLP139-151-induced RR-EAE in the SJL mice. While RR-EAE mice showed an increased EAE severity (relapse) with CNS inflammation, demyelination with abnormal myelin morphology in the spinal cord, the resistant mice exhibited a milder EAE phenotype with diminished relapse. Compared with the RR-EAE mice, the resistant mice showed less CNS inflammation, demyelination, and abnormalities of the myelin structure. In addition, scanning electron microscopic (SEM) analysis with the osmium-maceration method displayed ultrastructural abnormalities of the myelin structure in the white matter of the RR-EAE spinal cord, but not in that of the resistant mice. While the intensity of myelin staining was reduced in the relapsing EAE spinal cord, immunohistochemistry and immunoblot analysis revealed that the 21.5 kDa isoform of degenerating myelin basic protein (MBP) was specifically induced in the relapsing EAE spinal cord. Taken together, the neuroinflammation-induced degenerating 21 kDa isoform of MBP sheds light on the development of abnormal myelin on the relapse of MS pathogenesis.

Asunto(s)

Encefalomielitis Autoinmune Experimental , Esclerosis Múltiple , Ratones , Animales , Encefalomielitis Autoinmune Experimental/patología , Proteína Básica de Mielina , Proteína Proteolipídica de la Mielina , Recurrencia Local de Neoplasia/patología , Médula Espinal/patología , Esclerosis Múltiple/patología , Ratones Endogámicos , Enfermedad Crónica , Inflamación/patología , Encéfalo/patología , Isoformas de Proteínas

RESUMEN

TAR DNA-binding protein 43 (TDP-43), aggregation prone protein, is a potential target of drug discovery for amyotrophic lateral sclerosis. The molecular binders, targeting the disordered low complexity domain (LCD) relevant to the aggregation, may suppress the aggregation. Recently, Kamagata et al. developed a rational design of peptide binders targeting intrinsically disordered proteins based on contact energies between residue pairs. In this study, we designed 18 producible peptide binder candidates to TDP-43 LCD by using this method. Fluorescence anisotropy titration and surface plasmon resonance assays demonstrated that one of the designed peptides bound to TDP-43 LCD at 30 µM. Thioflavin-T fluorescence and sedimentation assays showed that the peptide binder suppressed the aggregation of TDP-43. In summary, this study highlights the potential applicability of peptide binder design for aggregation prone proteins.

Asunto(s)

Esclerosis Amiotrófica Lateral , Proteínas Intrínsecamente Desordenadas , Humanos , Péptidos/farmacología , Esclerosis Amiotrófica Lateral/metabolismo , Proteínas de Unión al ADN/metabolismo

RESUMEN

BACKGROUND: Oligodendrocytes, which form myelin, enable rapid and efficient nerve conduction. Destruction of myelin causes demyelinating diseases such as multiple sclerosis. Primary oligodendrocyte progenitor cells (OPCs) from postnatal rodents have been utilized to elucidate the developmental mechanism of oligodendrocytes in vitro. However, this process is complicated and takes up to several weeks. NEW METHOD: We established a method to culture OPCs from neonatal rat brain in DMEM/F-12 with Stem-Pro, bFGF (10 ng/mL), and rhPDGF (30 ng/mL). The culture, without shaking or immunopanning, became OPC-enriched rather than a mixed glial culture. RESULTS: Immunofluorescent analysis using cell lineage markers suggested that these cells were initially glial progenitors, which gradually changed to OPCs with a few cells further differentiating into oligodendrocytes. Using compounds that promote OPC differentiation, we confirmed that these cells were compatible for high-throughput screening in a 96-well plate format. In co-culture with dorsal root ganglion neuron, OPCs showed myelin sheath-like morphologies. This method was also applicable to mouse OPCs. COMPARISON WITH EXISTING METHODS: Although the purity of the OPCs was not comparable to that after immunopanning, most cells were of the oligodendrocyte lineage at 8 DIV, while less than 10% were astrocytes. This method requires mediums with only two growth factors without any specific equipment like antibodies or magnet and takes simple procedures. CONCLUSIONS: The simplicity and high yield of our method make it a good choice when working with oligodendrocytes/OPCs. We believe that this method is an affordable protocol for various biological applications without any special techniques or equipment.

Asunto(s)

Células Precursoras de Oligodendrocitos , Animales , Encéfalo , Diferenciación Celular , Células Cultivadas , Ratones , Vaina de Mielina , Oligodendroglía , Ratas , Roedores

RESUMEN

A novel series of spiroindoline derivatives was discovered for use as inducers of oligodendrocyte progenitor cell (OPC) differentiation, resulting from optimization of screening hit 1. Exploration of structure-activity relationships led to compound 18, which showed improved potency (rOPC EC50 = 0.0032 µM). Furthermore, oral administration of compound 18 significantly decreased clinical severity in an experimental autoimmune encephalomyelitis (EAE) model.

Asunto(s)

Descubrimiento de Drogas , Encefalomielitis Autoinmune Experimental/tratamiento farmacológico , Indoles/farmacología , Células Precursoras de Oligodendrocitos/efectos de los fármacos , Compuestos de Espiro/farmacología , Animales , Diferenciación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Encefalomielitis Autoinmune Experimental/patología , Femenino , Indoles/síntesis química , Indoles/química , Ratones , Ratones Endogámicos C57BL , Estructura Molecular , Ratas , Ratas Wistar , Compuestos de Espiro/síntesis química , Compuestos de Espiro/química , Relación Estructura-Actividad

RESUMEN

Recent evidence suggests that neural pathways from the hindbrain to the hypothalamus are important for informing the hypothalamus of the body's condition with regard to energy metabolism. Here we examined energy metabolism in rats with transections of the midbrain that severed the neural pathway from the hindbrain to the hypothalamus, and then investigated the levels of various molecules associated with control of energy metabolism in these rats. Food intake and body weight were higher in the midbrain-transected rats than in sham-operated rats. In addition, the midbrain-transected rats showed insulin resistance and hyperleptinemia. Furthermore, the hypothalamic mRNA levels of anorectic proopiomelanocortin and cocaine- and amphetamine-related transcript were significantly lower in midbrain-transected rats than in sham-operated rats. Our findings elucidate the mechanisms of food intake and energy balance from the perspective of multifactorial regulatory systems that underlie functions such as neurohormonal integration.

Asunto(s)

Metabolismo Energético , Hipotálamo/fisiología , Rombencéfalo/fisiología , Animales , Peso Corporal , Ingestión de Alimentos , Prueba de Tolerancia a la Glucosa , Homeostasis , Resistencia a la Insulina , Leptina/sangre , Masculino , Vías Nerviosas , Proopiomelanocortina/metabolismo , ARN Mensajero/metabolismo , Ratas Wistar , Receptores de Leptina/genética , Receptores de Leptina/metabolismo

RESUMEN

Activation of melanocortin-4 receptors (MC4Rs) restrains feeding and prevents obesity; however, the identity, location, and axonal projections of the neurons bearing MC4Rs that control feeding remain unknown. Reexpression of MC4Rs on single-minded 1 (SIM1)(+) neurons in mice otherwise lacking MC4Rs is sufficient to abolish hyperphagia. Thus, MC4Rs on SIM1(+) neurons, possibly in the paraventricular hypothalamus (PVH) and/or amygdala, regulate food intake. It is unknown, however, whether they are also necessary, a distinction required for excluding redundant sites of action. Hence, the location and nature of obesity-preventing MC4R-expressing neurons are unknown. Here, by deleting and reexpressing MC4Rs from cre-expressing neurons, establishing both necessity and sufficiency, we demonstrate that the MC4R-expressing neurons regulating feeding are SIM1(+), located in the PVH, glutamatergic and not GABAergic, and do not express oxytocin, corticotropin-releasing hormone, vasopressin, or prodynorphin. Importantly, these excitatory MC4R-expressing PVH neurons are synaptically connected to neurons in the parabrachial nucleus, which relays visceral information to the forebrain. This suggests a basis for the feeding-regulating effects of MC4Rs.

Asunto(s)

Conducta Alimentaria , Glutamatos/metabolismo , Neuronas/metabolismo , Núcleos Parabraquiales/metabolismo , Núcleo Hipotalámico Paraventricular/metabolismo , Receptor de Melanocortina Tipo 4/metabolismo , Sinapsis/metabolismo , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Peso Corporal , Dependovirus/metabolismo , Metabolismo Energético , Neuronas GABAérgicas/metabolismo , Eliminación de Gen , Inyecciones , Integrasas/metabolismo , Ratones , Neuropéptidos/metabolismo , Proteínas Represoras/metabolismo , Reproducibilidad de los Resultados , Técnicas Estereotáxicas , Proteína 2 de Transporte Vesicular de Glutamato/metabolismo

RESUMEN

Orexin-A (a neuropeptide in the hypothalamus) plays an important role in many physiological functions, including the regulation of glucose metabolism. We have previously found that the development of post-ischemic glucose intolerance is one of the triggers of ischemic neuronal damage, which is suppressed by hypothalamic orexin-A. Other reports have shown that the communication system between brain and peripheral tissues through the autonomic nervous system (sympathetic, parasympathetic and vagus nerve) is important for maintaining glucose and energy metabolism. The aim of this study was to determine the involvement of the hepatic vagus nerve on hypothalamic orexin-A-mediated suppression of post-ischemic glucose intolerance development and ischemic neuronal damage. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO) for 2 h. Intrahypothalamic orexin-A (5 pmol/mouse) administration significantly suppressed the development of post-ischemic glucose intolerance and neuronal damage on day 1 and 3, respectively after MCAO. MCAO-induced decrease of hepatic insulin receptors and increase of hepatic gluconeogenic enzymes on day 1 after was reversed to control levels by orexin-A. This effect was reversed by intramedullary administration of the orexin-1 receptor antagonist, SB334867, or hepatic vagotomy. In the medulla oblongata, orexin-A induced the co-localization of cholin acetyltransferase (cholinergic neuronal marker used for the vagus nerve) with orexin-1 receptor and c-Fos (activated neural cells marker). These results suggest that the hepatic branch vagus nerve projecting from the medulla oblongata plays an important role in the recovery of post-ischemic glucose intolerance and mediates a neuroprotective effect by hypothalamic orexin-A.

Asunto(s)

Intolerancia a la Glucosa/metabolismo , Hipotálamo/metabolismo , Infarto de la Arteria Cerebral Media/metabolismo , Péptidos y Proteínas de Señalización Intracelular/farmacología , Hígado/inervación , Neuropéptidos/farmacología , Fármacos Neuroprotectores/farmacología , Nervio Vago/fisiología , Animales , Benzoxazoles/farmacología , Colina O-Acetiltransferasa/metabolismo , Hipotálamo/efectos de los fármacos , Masculino , Ratones , Naftiridinas , Receptores de Orexina/metabolismo , Orexinas , Proteínas Proto-Oncogénicas c-fos/metabolismo , Urea/análogos & derivados , Urea/farmacología , Nervio Vago/efectos de los fármacos

RESUMEN

Agouti-related peptide (AgRP) neurons of the hypothalamus release a fast transmitter (GABA) in addition to neuropeptides (neuropeptide Y [NPY] and Agouti-related peptide [AgRP]). This raises questions as to their respective functions. The acute activation of AgRP neurons robustly promotes food intake, while central injections of AgRP, NPY, or GABA agonist results in the marked escalation of food consumption with temporal variance. Given the orexigenic capability of all three of these neuroactive substances in conjunction with their coexpression in AgRP neurons, we looked to unravel their relative temporal role in driving food intake. After the acute stimulation of AgRP neurons with DREADD technology, we found that either GABA or NPY is required for the rapid stimulation of feeding, and the neuropeptide AgRP, through action on MC4 receptors, is sufficient to induce feeding over a delayed yet prolonged period. These studies help to elucidate the neurochemical mechanisms of AgRP neurons in controlling temporally distinct phases of eating.

Asunto(s)

Proteína Relacionada con Agouti/metabolismo , Neuronas/metabolismo , Neuropéptido Y/metabolismo , Ácido gamma-Aminobutírico/metabolismo , Proteína Relacionada con Agouti/genética , Animales , Clozapina/análogos & derivados , Clozapina/farmacología , Ingestión de Alimentos/efectos de los fármacos , Masculino , Ratones , Ratones Noqueados , Ratones Transgénicos , Neuronas/efectos de los fármacos , Neuropéptido Y/deficiencia , Neuropéptido Y/genética , Receptor de Melanocortina Tipo 4/deficiencia , Receptor de Melanocortina Tipo 4/genética , Receptor de Melanocortina Tipo 4/metabolismo , Transducción de Señal , Proteínas del Transporte Vesicular de Aminoácidos Inhibidores/deficiencia , Proteínas del Transporte Vesicular de Aminoácidos Inhibidores/genética , Proteínas del Transporte Vesicular de Aminoácidos Inhibidores/metabolismo

RESUMEN

Simple and efficient cross coupling of alcohols was developed in the presence of NaHSO4/SiO2 to give the corresponding substituted olefins. Direct coupling of alcohols and alkenes was also achieved to give substituted olefins. NaHSO4/SiO2 could be recycled 7 times without loss of catalytic activity.

Asunto(s)

Alcoholes/química , Alquenos/síntesis química , Dióxido de Silicio/química , Sulfatos/química , Alquenos/química , Estructura Molecular

RESUMEN

A high-fat diet (HFD) is a well-known contributing factor in the development of obesity. Most rats fed HFDs become obese. Those that avoid obesity when fed HFDs are considered diet resistant (DR). We performed a microarray screen to identify genes specific to the mesenteric fat of DR rats and revealed high expression of guanylin and guanylyl cyclase C (GC-C) in some subjects. Our histologic studies revealed that the cellular source of guanylin and GC-C is macrophages. Therefore, we developed double-transgenic (Tg) rats overexpressing guanylin and GC-C in macrophages and found that they were resistant to the effects of HFDs. In the mesenteric fat of HFD-fed Tg rats, Fas and perilipin mRNAs were downregulated, and those of genes involved in fatty acid oxidation were upregulated, compared with the levels in HFD-fed wild-type rats. In vitro studies demonstrated that lipid accumulation was markedly inhibited in adipocytes cocultured with macrophages expressing guanylin and GC-C and that this inhibition was reduced after treatment with guanylin- and GC-C-specific siRNAs. Our results suggest that the macrophagic guanylin-GC-C system contributes to the altered expression of genes involved in lipid metabolism, leading to resistance to obesity.

Asunto(s)

Dieta Alta en Grasa/efectos adversos , Hormonas Gastrointestinales/metabolismo , Macrófagos/metabolismo , Mesenterio/citología , Péptidos Natriuréticos/metabolismo , Receptores Acoplados a la Guanilato-Ciclasa/metabolismo , Receptores de Péptidos/metabolismo , Adipocitos/metabolismo , Animales , Colesterol/sangre , Ácidos Grasos no Esterificados/sangre , Hormonas Gastrointestinales/deficiencia , Hormonas Gastrointestinales/genética , Regulación de la Expresión Génica , Técnicas de Sustitución del Gen , Insulina/sangre , Hígado/metabolismo , Macrófagos/enzimología , Macrófagos Peritoneales/enzimología , Macrófagos Peritoneales/metabolismo , Masculino , Péptidos Natriuréticos/deficiencia , Péptidos Natriuréticos/genética , Oxidación-Reducción , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN Interferente Pequeño/genética , Ratas , Ratas Transgénicas , Receptores de Enterotoxina , Receptores Acoplados a la Guanilato-Ciclasa/deficiencia , Receptores Acoplados a la Guanilato-Ciclasa/genética , Receptores de Péptidos/deficiencia , Receptores de Péptidos/genética , Triglicéridos/sangre , Triglicéridos/metabolismo

RESUMEN

Neural regulation of energy expenditure is incompletely understood. By genetically disrupting GABAergic transmission in a cell-specific fashion, and by combining this with selective pharmacogenetic activation and optogenetic mapping techniques, we have uncovered an arcuate-based circuit that selectively drives energy expenditure. Specifically, mice lacking synaptic GABA release from RIP-Cre neurons have reduced energy expenditure, become obese and are extremely sensitive to high-fat diet-induced obesity, the latter due to defective diet-induced thermogenesis. Leptin's ability to stimulate thermogenesis, but not to reduce feeding, is markedly attenuated. Acute, selective activation of arcuate GABAergic RIP-Cre neurons, which monosynaptically innervate PVH neurons projecting to the NTS, rapidly stimulates brown fat and increases energy expenditure but does not affect feeding. Importantly, this response is dependent upon GABA release from RIP-Cre neurons. Thus, GABAergic RIP-Cre neurons in the arcuate selectively drive energy expenditure, contribute to leptin's stimulatory effect on thermogenesis, and protect against diet-induced obesity.

Asunto(s)

Núcleo Arqueado del Hipotálamo/metabolismo , Metabolismo Energético , Neuronas GABAérgicas/metabolismo , Vías Nerviosas , Tejido Adiposo Pardo/metabolismo , Animales , Núcleo Arqueado del Hipotálamo/citología , Dieta , Integrasas/metabolismo , Leptina/metabolismo , Ratones , Obesidad/metabolismo , Núcleo Hipotalámico Paraventricular/citología , Núcleo Hipotalámico Paraventricular/metabolismo , Proteína 2 de Transporte Vesicular de Glutamato/metabolismo , Proteínas del Transporte Vesicular de Aminoácidos Inhibidores/genética , Proteínas del Transporte Vesicular de Aminoácidos Inhibidores/metabolismo

RESUMEN

Leptin regulates energy balance. However, knowledge of the critical intracellular transducers of leptin signaling remains incomplete. We found that Rho-kinase 1 (ROCK1) regulates leptin action on body weight homeostasis by activating JAK2, an initial trigger of leptin receptor signaling. Leptin promoted the physical interaction of JAK2 and ROCK1, thereby increasing phosphorylation of JAK2 and downstream activation of Stat3 and FOXO1. Mice lacking ROCK1 in either pro-opiomelanocortin (POMC) or agouti-related protein neurons, mediators of leptin action, displayed obesity and impaired leptin sensitivity. In addition, deletion of ROCK1 in the arcuate nucleus markedly enhanced food intake, resulting in severe obesity. Notably, ROCK1 was a specific mediator of leptin, but not insulin, regulation of POMC neuronal activity. Our data identify ROCK1 as a key regulator of leptin action on energy homeostasis.

Asunto(s)

Metabolismo Energético/fisiología , Hipotálamo/metabolismo , Leptina/fisiología , Receptores de Leptina/fisiología , Quinasas Asociadas a rho/fisiología , Potenciales de Acción/genética , Potenciales de Acción/fisiología , Proteína Relacionada con Agouti/fisiología , Animales , Regulación del Apetito/genética , Regulación del Apetito/fisiología , Núcleo Arqueado del Hipotálamo/metabolismo , Células Cultivadas , Ingestión de Alimentos , Janus Quinasa 2/metabolismo , Leptina/farmacología , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Ratones Transgénicos , Neuronas/metabolismo , Obesidad/genética , Fosforilación , Proopiomelanocortina/metabolismo , Receptores de Leptina/agonistas , Receptores de Leptina/antagonistas & inhibidores , Factor de Transcripción STAT3/metabolismo , Quinasas Asociadas a rho/genética

RESUMEN

Glucagon-like peptide-1 (GLP-1) and leptin are anorectic hormones produced in the small intestine and white adipose tissue, respectively. Investigating how these hormones act together as an integrated anorectic signal is important to elucidate a mechanism to maintain energy balance. In the present study, coadministration of subthreshold GLP-1 and leptin dramatically reduced feeding in rats. Although coadministration of GLP-1 with leptin did not enhance leptin signal transduction in the hypothalamus, it significantly decreased phosphorylation of AMP-activated protein kinase (AMPK). In addition, coadministration of GLP-1 with leptin significantly increased proopiomelanocortin (POMC) mRNA levels. Considering that α-melanocortin stimulating hormone (α-MSH) is derived from POMC and functions through the melanocortin-4-receptor (MC4-R) as a key molecule involved in feeding reduction, the interaction of GLP-1 and leptin on feeding reduction may be mediated through the α-MSH/MC4-R system. As expected, the interaction of GLP-1 and leptin was abolished by intracerebroventricular preadministration of the MC4-R antagonists agouti-related peptide and SHU9119. Taken together, GLP-1 and leptin cooperatively reduce feeding at least in part via inhibition of AMPK following binding of α-MSH to MC4-R.

Asunto(s)

Proteínas Quinasas Activadas por AMP/metabolismo , Interacciones Farmacológicas , Ingestión de Alimentos/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Péptido 1 Similar al Glucagón/administración & dosificación , Leptina/administración & dosificación , Receptor de Melanocortina Tipo 4/metabolismo , Animales , Masculino , Hormonas Estimuladoras de los Melanocitos/farmacología , Ratas , Ratas Wistar , Receptor de Melanocortina Tipo 4/antagonistas & inhibidores , alfa-MSH/metabolismo

RESUMEN

AgRP neuron activity drives feeding and weight gain whereas that of nearby POMC neurons does the opposite. However, the role of excitatory glutamatergic input in controlling these neurons is unknown. To address this question, we generated mice lacking NMDA receptors (NMDARs) on either AgRP or POMC neurons. Deletion of NMDARs from AgRP neurons markedly reduced weight, body fat and food intake whereas deletion from POMC neurons had no effect. Activation of AgRP neurons by fasting, as assessed by c-Fos, Agrp and Npy mRNA expression, AMPA receptor-mediated EPSCs, depolarization and firing rates, required NMDARs. Furthermore, AgRP but not POMC neurons have dendritic spines and increased glutamatergic input onto AgRP neurons caused by fasting was paralleled by an increase in spines, suggesting fasting induced synaptogenesis and spinogenesis. Thus glutamatergic synaptic transmission and its modulation by NMDARs play key roles in controlling AgRP neurons and determining the cellular and behavioral response to fasting.

Asunto(s)

Proteína Relacionada con Agouti/metabolismo , Espinas Dendríticas/fisiología , Ayuno , Neuronas/citología , 2-Amino-5-fosfonovalerato/farmacología , 6-Ciano 7-nitroquinoxalina 2,3-diona/farmacología , Factores de Edad , Proteína Relacionada con Agouti/deficiencia , Animales , Composición Corporal/efectos de los fármacos , Composición Corporal/genética , Encéfalo/citología , Proteínas Portadoras/genética , Espinas Dendríticas/efectos de los fármacos , Ingestión de Alimentos/efectos de los fármacos , Ingestión de Alimentos/fisiología , Metabolismo Energético/efectos de los fármacos , Metabolismo Energético/genética , Antagonistas de Aminoácidos Excitadores/farmacología , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Potenciales Postsinápticos Excitadores/genética , Femenino , Antagonistas del GABA/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Proteínas Fluorescentes Verdes/genética , Técnicas In Vitro , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/genética , Ratones , Ratones Transgénicos , Proteínas del Tejido Nervioso/deficiencia , Proteínas del Tejido Nervioso/genética , Neuronas/efectos de los fármacos , Neuropéptido Y/genética , Técnicas de Placa-Clamp , Picrotoxina/farmacología , Proopiomelanocortina/genética , Proteínas Proto-Oncogénicas c-fos/metabolismo , ARN Mensajero , Receptores de N-Metil-D-Aspartato/deficiencia , Factores de Tiempo

RESUMEN

Several different neuronal populations are involved in regulating energy homeostasis. Among these, agouti-related protein (AgRP) neurons are thought to promote feeding and weight gain; however, the evidence supporting this view is incomplete. Using designer receptors exclusively activated by designer drugs (DREADD) technology to provide specific and reversible regulation of neuronal activity in mice, we have demonstrated that acute activation of AgRP neurons rapidly and dramatically induces feeding, reduces energy expenditure, and ultimately increases fat stores. All these effects returned to baseline after stimulation was withdrawn. In contrast, inhibiting AgRP neuronal activity in hungry mice reduced food intake. Together, these findings demonstrate that AgRP neuron activity is both necessary and sufficient for feeding. Of interest, activating AgRP neurons potently increased motivation for feeding and also drove intense food-seeking behavior, demonstrating that AgRP neurons engage brain sites controlling multiple levels of feeding behavior. Due to its ease of use and suitability for both acute and chronic regulation, DREADD technology is ideally suited for investigating the neural circuits hypothesized to regulate energy balance.

Asunto(s)

Proteína Relacionada con Agouti/fisiología , Conducta Alimentaria/fisiología , Neuronas/fisiología , Proteína Relacionada con Agouti/genética , Animales , Núcleo Arqueado del Hipotálamo/efectos de los fármacos , Núcleo Arqueado del Hipotálamo/fisiología , Encéfalo/efectos de los fármacos , Encéfalo/fisiología , Clozapina/análogos & derivados , Clozapina/farmacología , Ingestión de Alimentos/fisiología , Metabolismo Energético , Conducta Alimentaria/efectos de los fármacos , Femenino , Masculino , Ratones , Ratones Transgénicos , Neuronas/efectos de los fármacos , Aumento de Peso/efectos de los fármacos , Aumento de Peso/fisiología

RESUMEN

Ghrelin, a gastrointestinal peptide, stimulates feeding when administered peripherally. Blockade of the vagal afferent pathway abolishes ghrelin-induced feeding, indicating that the vagal afferent pathway may be a route conveying orexigenic ghrelin signals to the brain. Here, we demonstrate that peripheral ghrelin signaling, which travels to the nucleus tractus solitarius (NTS) at least in part via the vagus nerve, increases noradrenaline (NA) in the arcuate nucleus of the hypothalamus, thereby stimulating feeding at least partially through alpha-1 and beta-2 noradrenergic receptors. In addition, bilateral midbrain transections rostral to the NTS, or toxin-induced loss of neurons in the hindbrain that express dopamine beta hydroxylase (an NA synthetic enzyme), abolished ghrelin-induced feeding. These findings provide new evidence that the noradrenergic system is necessary in the central control of feeding behavior by peripherally administered ghrelin.

Asunto(s)

Hipotálamo/metabolismo , Norepinefrina/metabolismo , Hormonas Peptídicas/metabolismo , Rombencéfalo/metabolismo , Transducción de Señal/fisiología , Animales , Dopamina beta-Hidroxilasa/metabolismo , Relación Dosis-Respuesta a Droga , Ingestión de Alimentos , Conducta Alimentaria/efectos de los fármacos , Conducta Alimentaria/fisiología , Ghrelina , Masculino , Neuronas/metabolismo , Neuropéptido Y/metabolismo , Hormonas Peptídicas/farmacología , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Receptores Adrenérgicos alfa 1/metabolismo , Receptores Adrenérgicos beta 2/metabolismo

RESUMEN

Ghrelin and cholecystokinin (CCK) are gastrointestinal hormones regulating feeding. Both transmitted via the vagal afferent, ghrelin elicits starvation signals, whereas CCK induces satiety signals. We investigated the interaction between ghrelin and CCK functioning in short-term regulation of feeding in Otsuka Long-Evans Tokushima fatty (OLETF) rats, which have a disrupted CCK type A receptor (CCK-AR), and their lean littermates, Long-Evans Tokushima Otsuka (LETO) rats. Intravenous administration of ghrelin increased 2-h food intake in both OLETF and LETO rats. Because OLETF rats are CCK insensitive, iv-administered CCK decreased 2-h food intake in LETO, but not in OLETF, rats. Although preadministration of CCK to LETO rats blocked food intake induced by ghrelin, CCK preadministration to OLETF rats did not affect ghrelin-induced food intake. Conversely, preadministration of ghrelin to LETO rats blocked feeding reductions induced by CCK. In electrophysiological studies, once gastric vagal afferent discharges were altered by ghrelin or CCK administration, they could not be additionally affected by serial administrations of either CCK or ghrelin, respectively. The induction of Fos expression in the hypothalamic arcuate nucleus by ghrelin was also attenuated by CCK preadministration. Using immunohistochemistry, we also demonstrated the colocalization of GH secretagogue receptor (GHS-R), the cellular receptor for ghrelin, with CCK-AR in vagal afferent neurons. These results indicate that the vagus nerve plays a crucial role in determining peripheral energy balance. The efficiency of ghrelin and CCK signal transduction may depend on the balance of their respective plasma concentration and/or on interactions between GHS-R and CCK-AR.

Asunto(s)

Colecistoquinina/farmacología , Ingestión de Energía/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Obesidad/fisiopatología , Hormonas Peptídicas/farmacología , Vías Aferentes/efectos de los fármacos , Vías Aferentes/fisiología , Animales , Electrofisiología/métodos , Ghrelina , Obesidad/genética , Ratas , Ratas Mutantes

RESUMEN

Peptide YY (PYY), an anorectic peptide, is secreted postprandially from the distal gastrointestinal tract. PYY(3-36), the major form of circulating PYY, binds to the hypothalamic neuropeptide Y Y2 receptor (Y2-R) with a high-affinity, reducing food intake in rodents and humans. Additional gastrointestinal hormones involved in feeding, including cholecystokinin, glucagon-like peptide 1, and ghrelin, transmit satiety or hunger signals to the brain via the vagal afferent nerve and/or the blood stream. Here we determined the role of the afferent vagus nerve in PYY function. Abdominal vagotomy abolished the anorectic effect of PYY(3-36) in rats. Peripheral administration of PYY(3-36) induced Fos expression in the arcuate nucleus of sham-operated rats but not vagotomized rats. We showed that Y2-R is synthesized in the rat nodose ganglion and transported to the vagal afferent terminals. PYY(3-36) stimulated firing of the gastric vagal afferent nerve when administered iv. Considering that Y2-R is present in the vagal afferent fibers, PYY(3-36) could directly alter the firing rate of the vagal afferent nerve via Y2-R. We also investigated the effect of ascending fibers from the nucleus of the solitary tract on the transmission of PYY(3-36)-mediated satiety signals. In rats, bilateral midbrain transections rostral to the nucleus of the solitary tract also abolished PYY(3-36)-induced reductions in feeding. This study indicates that peripheral PYY(3-36) may transmit satiety signals to the brain in part via the vagal afferent pathway.

Asunto(s)

Núcleo Arqueado del Hipotálamo/química , Ingestión de Alimentos/efectos de los fármacos , Péptido YY/farmacología , Receptores de Neuropéptido Y/biosíntesis , Nervio Vago/fisiología , Vías Aferentes/química , Vías Aferentes/fisiología , Animales , Electrofisiología , Técnica del Anticuerpo Fluorescente , Masculino , Ganglio Nudoso/química , Ganglio Nudoso/metabolismo , Fragmentos de Péptidos , Proteínas Proto-Oncogénicas c-fos/análisis , Ratas , Ratas Wistar , Receptores de Neuropéptido Y/análisis , Receptores de Neuropéptido Y/metabolismo , Saciedad/fisiología , Vagotomía

RESUMEN

Ghrelin, a brain-gut peptide discovered from the stomach, stimulates growth hormone release, food intake, adiposity, and weight gain. Circulating ghrelin levels are modulated under conditions of positive and negative energy balance, however its effect on macronutrient selection is not known. The present experiment investigates the effect of ghrelin on single and two-diet feeding paradigms in high-carbohydrate (HC) and high-fat (HF) preferring rats. In the macronutrient selection test in which rats were given free access to either high-carbohydrate or high-fat diet, an intracerebroventricular (i.c.v.) administration of ghrelin potently enhanced fat intake over carbohydrate intake in both HC- and HF-preferring rats. In the diet preference test in which rats were given free access to both high-carbohydrate and high-fat diets simultaneously, an i.c.v. administration of ghrelin also preferentially enhanced fat consumption over carbohydrate in both HF- and HC-preferring rats. Intracerebroventricular administrations of galanin and neuropeptide Y enhanced fat and carbohydrate ingestion, respectively. Centrally administered ghrelin enhanced fat ingestion. These results provide further insights for the role of ghrelin in feeding behavior and the development of obesity.

Asunto(s)

Ingestión de Alimentos/efectos de los fármacos , Grasas/metabolismo , Preferencias Alimentarias/efectos de los fármacos , Hormonas Peptídicas/farmacología , Animales , Conducta Animal/efectos de los fármacos , Galanina/farmacología , Ghrelina , Inyecciones Intraventriculares/métodos , Masculino , Neuropéptido Y/farmacología , Ratas , Ratas Wistar , Factores de Tiempo