RESUMEN
Neuropeptide W (NPW) is an anorectic peptide produced in the brain. Here, we showed that NPW was present in several hypothalamic nuclei, including the paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, lateral hypothalamus, and hypothalamic arcuate nucleus. NPW expression was significantly up-regulated in leptin-deficient ob/ob and leptin receptor-deficient db/db mice. The increase in NPW expression in ob/ob mice was abrogated to control levels after leptin replacement. Leptin induced suppressors of cytokine signaling-3 after phosphorylation of signal transducer and activator of transcription-3 in NPW-expressing neurons. In addition, we demonstrated that NPW reduces feeding via the melanocortin-4-receptor signaling pathway. We also showed that NPW activates proopiomelanocortin and inhibits neuropeptide Y neurons using loose-patch extracellular recording of these neurons identified by promoter-driven green fluorescent protein expression. This study indicates that NPW may play an important role in the regulation of feeding and energy metabolism under the conditions of leptin insufficiency.
Asunto(s)
Metabolismo Basal/fisiología , Hipotálamo/metabolismo , Leptina/fisiología , Neuropéptidos/metabolismo , Animales , Anorexia/metabolismo , Expresión Génica/efectos de los fármacos , Hipotálamo/citología , Hipotálamo/ultraestructura , Inmunohistoquímica , Leptina/genética , Leptina/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones Obesos , Microscopía Inmunoelectrónica , Neuronas/citología , Neuronas/metabolismo , Neuronas/fisiología , Neuropéptido Y/genética , Neuropéptido Y/metabolismo , Neuropéptidos/genética , Neuropéptidos/farmacología , Técnicas de Placa-Clamp , Fosforilación/efectos de los fármacos , Ratas , Ratas Wistar , Receptor de Melanocortina Tipo 4/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Transcripción STAT3/metabolismo , Transducción de Señal/efectos de los fármacosRESUMEN
Obestatin is a 23-amino acid peptide, initially isolated from rat stomach as an endogenous ligand for the orphan G-protein-coupled receptor. Obestatin is derived from proteolytic cleavage of a 117-amino acid precursor, preproghrelin. Ghrelin increases food intake, body weight, and gastric emptying, whereas obestatin has the opposite effects. In this study, we characterized obestatin in both rat and human stomach, and investigated the peptide's effect on feeding behavior. Using reversed-phase high-performance liquid chromatography coupled with RIAs specific for rat and human obestatin, we detected a very small amount of obestatin, compared with ghrelin, in the gastric fundi. The ratios of obestatin to ghrelin are 0.0039 and 1.94% respectively in the rat and human gastric fundi. In humans, plasma obestatin accounted for 5.21% of the ghrelin concentration, whereas it was undetectable in rat plasma. Plasma ghrelin concentration decreased after a meal in normal subjects, whereas obestatin concentration did not change. When administered centrally or peripherally, obestatin did not suppress food intake in either free-feeding or fasted rodents. Administration of obestatin did not antagonize ghrelin-induced feeding. These findings indicate that obestatin is present at very low levels compared with ghrelin in both rat and human, and has no acute effect on feeding behavior.
Asunto(s)
Fundus Gástrico/metabolismo , Hormonas Peptídicas/sangre , Hormonas Peptídicas/metabolismo , Animales , Cromatografía Líquida de Alta Presión , Conducta Alimentaria/efectos de los fármacos , Fundus Gástrico/efectos de los fármacos , Ghrelina/sangre , Ghrelina/metabolismo , Ghrelina/farmacología , Humanos , Técnicas In Vitro , Masculino , Ratones , Ratones Endogámicos C57BL , Hormonas Peptídicas/farmacología , Radioinmunoensayo , Ratas , Ratas WistarRESUMEN
Orexin-A and -B (identical to hypocretin-1 and -2) are hypothalamic neuropeptides that regulate appetite and arousal. Orexins-producing neurons project their axons to various brain regions, including the olfactory bulb. In the present study, to understand the relationship between orexins and olfaction, we investigated the distribution of the orexin-A- and -B-immunoreactive (ir) fibers in the rat olfactory bulb and the contents of orexin-A and -B in the rat olfactory bulb after food deprivation for 48 h by using immunohistochemistry and radioimmunoassay, respectively. Both orexin-A- and -B-ir fibers are similarly wide spread from the glomerular layer of the olfactory bulb where the terminals of the peripheral olfactory nerves make synapses with the mitral cells or the tufted cells, to the piriform cortex. Dense orexin-A- and -B-ir fibers were observed mainly in the granular cell layer and anterior olfactory nucleus. The contents of orexin-A and -B (pg/10 mg wet weight tissue) in fed rats (mean+/-S.E.M., n=6) were 2.72+/-0.24 and 6.31+/-0.63, respectively. Fasting for 48 h significantly reduced the contents of orexin-B, but not orexin-A. Orexins in the rat olfactory bulb may be involved in not only olfactory system but also energy balance.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Fibras Nerviosas/metabolismo , Neuropéptidos/metabolismo , Bulbo Olfatorio/citología , Bulbo Olfatorio/metabolismo , Animales , Corteza Cerebral/citología , Corteza Cerebral/metabolismo , Interpretación Estadística de Datos , Técnica del Anticuerpo Fluorescente Indirecta , Privación de Alimentos/fisiología , Glutamato Descarboxilasa/metabolismo , Inmunohistoquímica , Masculino , Vías Nerviosas/citología , Vías Nerviosas/metabolismo , Orexinas , Radioinmunoensayo , Ratas , Ratas WistarRESUMEN
Neuropeptide W (NPW), a novel endogenous peptide for G protein-coupled receptors GPR7 and GPR8, is expressed in the gastric antral mucosa of rat, mouse, and human stomachs. Here, we studied the ontogeny of NPW in the developing rat stomach. Real-time RT-PCR showed that NPW gene expression was initially detectable in embryonic day 14 (E14) stomach and gradually increased during the progress of age until birth, postnatal day 1 (P1). NPW mRNA level in the stomach increased again from the weaning period (P21) until reaching adulthood. Immunohistochemistry using polyclonal antibodies raised against rat NPW revealed that NPW-positive cells were detected in the P1 antral stomach and gradually increased during the development of age. Furthermore, double immunohistochemistry demonstrated that NPW colocalized with gastrin in P1 rat stomach. These data will provide clues to physiological functions of NPW in the development of rat stomach.
Asunto(s)
Mucosa Gástrica/metabolismo , Regulación del Desarrollo de la Expresión Génica , Neuropéptidos/clasificación , Neuropéptidos/metabolismo , Animales , Femenino , Inmunohistoquímica , Masculino , Neuropéptidos/genética , Ratas , Ratas Wistar , Estómago/embriología , Estómago/crecimiento & desarrolloRESUMEN
Recent advances in peptidomics have enabled the identification of previously uncharacterized peptides. However, sequence information alone does not allow us to identify candidates for bioactive peptides. To increase an opportunity to discover bioactive peptides, we have focused on C-terminal amidation, a post-translational modification shared by many bioactive peptides. We analyzed peptides secreted from human medullary thyroid carcinoma TT cells that produce amidated peptides, and we identified two novel amidated peptides, designated neuroendocrine regulatory peptide (NERP)-1 and NERP-2. NERPs are derived from distinct regions of the neurosecretory protein that was originally identified as a product of a nerve growth factor-responsive gene in PC12 cells. Mass spectrometric analysis of the immunoprecipitate using specific antibodies as well as reversed phase-high performance liquid chromatography coupled with radioimmunoassay analysis of brain extract demonstrated the endogenous presence of NERP-1 and NERP-2 in the rat. NERPs are abundant in the paraventricular and supraoptic nuclei of the rat hypothalamus and colocalized frequently with vasopressin but rarely with oxytocin. NERPs dose-dependently suppressed vasopressin release induced by intracerebroventricular injection of hypertonic NaCl or angiotensin II in vivo. NERPs also suppressed basal and angiotensin II-induced vasopressin secretion from hypothalamic explants in vitro. Bioactivity of NERPs required C-terminal amidation. Anti-NERP IgGs canceled plasma vasopressin reduction in response to water loading, indicating that NERPs could be potent endogenous suppressors of vasopressin release. These findings suggest that NERPs are novel modulators in body fluid homeostasis.
Asunto(s)
Química Encefálica/efectos de los fármacos , Proteínas del Tejido Nervioso/farmacología , Péptidos/farmacología , Procesamiento Proteico-Postraduccional , Equilibrio Hidroelectrolítico/efectos de los fármacos , Angiotensina II/farmacología , Animales , Anticuerpos/farmacología , Relación Dosis-Respuesta a Droga , Humanos , Masculino , Proteínas del Tejido Nervioso/antagonistas & inhibidores , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/aislamiento & purificación , Proteínas del Tejido Nervioso/metabolismo , Oxitocina/metabolismo , Células PC12 , Núcleo Hipotalámico Paraventricular/química , Núcleo Hipotalámico Paraventricular/metabolismo , Péptidos/antagonistas & inhibidores , Péptidos/genética , Péptidos/aislamiento & purificación , Péptidos/metabolismo , Ratas , Ratas Wistar , Solución Salina Hipertónica , Núcleo Supraóptico/química , Núcleo Supraóptico/metabolismo , Vasoconstrictores/farmacología , Vasopresinas/metabolismo , Agua/metabolismo , Equilibrio Hidroelectrolítico/fisiologíaRESUMEN
Age-related decreases in energy expenditure have been associated with the loss of skeletal muscle and decline of food intake, possibly through a mechanism involving changes of growth hormone (GH) secretion and feeding behavior. Age-related declines of growth hormone secretion and food intake have been termed the somatopause and anorexia of ageing, respectively. Ghrelin, a 28-amino-acid peptide, was isolated from human and rat stomachs as an endogenous ligand of growth hormone secretagogue receptor. Ghrelin stimulates growth hormone release and food intake when peripherally administered to rodents and humans. Here, we investigate the relationship between age-related decline of growth hormone secretion and/or food intake and ghrelin function. Ghrelin (10 nmol/kg body weight) was administered intravenously to male 3-, 12-, 24-and 27-month-old Long-Evans rats, after which growth hormone concentrations and 2 h food intake were measured. An intravenous administration of ghrelin to rats increased food intake in all generations. In addition, to orexigenic effect by ghrelin, intravenous administration of ghrelin elicited a marked increase in plasma GH levels, with the peak occurring 15 min after administration. These findings suggest that the aged rats maintain the reactivity to administered exogenous ghrelin.
Asunto(s)
Envejecimiento/fisiología , Ingestión de Alimentos/efectos de los fármacos , Hormona del Crecimiento/metabolismo , Hormonas Peptídicas/farmacología , Factores de Edad , Envejecimiento/efectos de los fármacos , Animales , Peso Corporal/efectos de los fármacos , Ghrelina , Masculino , Ratas , Ratas Endogámicas LECRESUMEN
Ghrelin, an acylated peptide produced predominantly in the stomach, stimulates feeding and GH secretion via interactions with the GH secretagogue type 1a receptor (GHS-R1a), the functionally active form of the GHS-R. Ghrelin molecules exist in the stomach and hypothalamus as two major endogenous forms, a form acylated at serine 3 (ghrelin) and a des-acylated form (des-acyl ghrelin). Acylation is indispensable for the binding of ghrelin to the GHS-R1a. Ghrelin enhances feeding via the neuronal pathways of neuropeptide Y and orexin, which act as orexigenic peptides in the hypothalamus. We here studied the effect of des-acyl ghrelin on feeding behavior. Intracerebroventricular (icv) administration of rat des-acyl ghrelin to rats or mice fed ad libitum stimulated feeding during the light phase; neither ip nor icv administration of des-acyl ghrelin to fasting mice suppressed feeding. The icv administration of des-acyl ghrelin induced the expression of Fos, a marker of neuronal activation, in orexin-expressing neurons of the lateral hypothalamic area, but not neuropeptide Y-expressing neurons of the arcuate nucleus. Peripheral administration of des-acyl ghrelin to rats or mice did not affect feeding. Although icv administration of ghrelin did not induce food intake in GHS-R-deficient mice, it did in orexin-deficient mice. In contrast, icv administration of des-acyl ghrelin stimulated feeding in GHS-R-deficient mice, but not orexin-deficient mice. Des-acyl ghrelin increased the intracellular calcium concentrations in isolated orexin neurons. Central des-acyl ghrelin may activate orexin-expressing neurons, perhaps functioning in feeding regulation through interactions with a target protein distinct from the GHS-R.
Asunto(s)
Conducta Alimentaria , Hormonas Peptídicas/farmacología , Receptores Acoplados a Proteínas G/metabolismo , Animales , Calcio/metabolismo , Cromatografía Líquida de Alta Presión , Citosol/metabolismo , Mucosa Gástrica/metabolismo , Ghrelina , Hormona del Crecimiento/metabolismo , Hipotálamo/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Movimiento , Neuronas/metabolismo , Neuropéptido Y/metabolismo , Neuropéptidos/metabolismo , Receptores de Orexina , Orexinas , Hormonas Peptídicas/metabolismo , Péptidos/química , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ratas , Receptores de Ghrelina , Receptores de Neuropéptido , Factores de TiempoRESUMEN
The CT-R [calcitonin (CT) receptor] is expressed in the central nervous system and is involved in the regulation of food intake, thermogenesis, and behaviors. CT-R-stimulating peptide-1 (CRSP-1), a potent ligand for the CT-R, was recently isolated from the porcine brain. In this study, we first confirmed that porcine CRSP-1 (pCRSP-1) enhanced the cAMP production in COS-7 cells expressing recombinant rat CT-R, and then we examined the central effects of pCRSP-1 on feeding and energy homeostasis in rats. Intracerebroventricular (icv) administration of pCRSP-1 to free-feeding rats suppressed food intake in a dose-dependent manner. Chronic icv infusion of pCRSP-1 suppressed body weight gain over the infusion period. Furthermore, icv administration of pCRSP-1 increased body temperature and decreased locomotor activity. The central effects of pCRSP-1 were more potent than those of porcine CT in rats. In contrast, ip administration of pCRSP-1 did not elicit any anorectic or catabolic effects. Administration icv of pCRSP-1 also induced mild dyskinesia of the lower extremities and decreased gastric acid output. Fos expression induced by icv administration of pCRSP-1 was detected in the neurons of the paraventricular nucleus, dorsomedial hypothalamic nucleus, arcuate nucleus, locus coeruleus, and nucleus of solitary tract, areas that are known to regulate feeding and energy homeostasis. Administration icv of pCRSP-1 increased plasma concentrations of ACTH and corticosterone, implying that the hypothalamic-pituitary-adrenocortical axis might be involved in catabolic effects of pCRSP-1. These results suggest that CRSP-1 can function as a ligand for the CT-R and may act as a catabolic signaling molecule in the central nervous system.
Asunto(s)
Encéfalo/efectos de los fármacos , Péptido Relacionado con Gen de Calcitonina/farmacología , Metabolismo Energético/efectos de los fármacos , Receptores de Calcitonina/agonistas , Hormona Adrenocorticotrópica/sangre , Animales , Temperatura Corporal/efectos de los fármacos , Corticosterona/sangre , Ingestión de Alimentos/efectos de los fármacos , Homeostasis/efectos de los fármacos , Humanos , Ligandos , Masculino , Actividad Motora/efectos de los fármacos , Ratas , Ratas Wistar , Aumento de Peso/efectos de los fármacosRESUMEN
OBJECTIVES: There are contradictory reports on the relationship between Helicobacter pylori and circulating ghrelin. We sought to clarify the influence of H. pylori infection on gastric and plasma ghrelin dynamics in humans. METHODS: Using endoscopic biopsies from the corpus of 56 H. pylori-infected patients and 25 uninfected subjects, ghrelin mRNA expression levels and gastric ghrelin peptide contents were measured by real-time polymerase chain reaction and radioimmunoassay, respectively. We also measured plasma ghrelin concentrations and analyzed the numbers of ghrelin immunoreactive cells in the fundic gland area. Fifty-one patients with H. pylori infection were treated with a 7-day triple therapy consisting of lansoprazole, clarithromycin, and amoxicillin. RESULTS: The gastric ghrelin mRNA expression level of H. pylori-positive patients (1.64 +/- 1.27 in arbitrary units) was significantly lower than in H. pylori-negative subjects (4.87 +/- 4.1, p < 0.0001). A similar trend was noted for ghrelin peptide contents (31.2 +/- 27.5 vs 81.2 +/- 64.1 ng/mg protein, respectively, p < 0.0001). There was no significant difference in the number of ghrelin immunoreactive cells/mm(2) in terms of H. plyori status. Plasma ghrelin concentrations in H. pylori-infected patients (144.6 +/- 7.8.8 fmol/ml) were significantly lower than in uninfected subjects (196.1 +/- 97.2, p < 0.05) and increased following cure of the infection. Plasma ghrelin levels correlated positively with the expression levels of ghrelin mRNA (r = 0.583, p < 0.0001) and peptide products (r = 0.574, p < 0.0001). There was a significant stepwise decrease in gastric ghrelin mRNA expression (p < 0.05), peptide contents (p < 0.01) and density of ghrelin immunoreactive cells (p < 0.05) with progression of histological severity of glandular atrophy in the corpus. The histological severity of chronic inflammation also negatively influenced the ghrelin mRNA expression (p < 0.001) and peptide production (p < 0.005). CONCLUSIONS: H. pylori infection has a negative impact on gastric and plasma ghrelin dynamics. Chronic inflammatory and atrophic changes associated with the infection may affect gastric ghrelin biosynthesis and contribute to the low circulating levels.
Asunto(s)
Mucosa Gástrica/metabolismo , Gastritis/metabolismo , Infecciones por Helicobacter/metabolismo , Helicobacter pylori , Hormonas Peptídicas/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Biopsia con Aguja , Femenino , Gastritis/microbiología , Gastritis/patología , Ghrelina , Hormona del Crecimiento/metabolismo , Infecciones por Helicobacter/patología , Humanos , Masculino , Persona de Mediana Edad , Hormonas Peptídicas/sangre , Hormonas Peptídicas/inmunología , Reacción en Cadena de la Polimerasa , ARN Mensajero/análisis , Radioinmunoensayo , Estómago/patologíaRESUMEN
Ghrelin, an acylated peptide originally identified in rat stomach as the endogenous ligand for the growth hormone secretagogue receptor (GHS-R), stimulates both food intake and growth hormone (GH) secretion. Ghrelin is predominantly synthesized by a subset of endocrine cells in the oxyntic gland of human and rat stomach. Previous studies using immunohistochemistry have shown that ghrelin is also present in the hypothalamic arcuate nucleus, a region critical for the control of feeding and GH secretion, but its expression pattern in this region and the details of its molecular form has yet to be clarified. In this report, we examined the presence of ghrelin in the arcuate nucleus using reverse-phase liquid chromatography combined with radioimmunoassay (RIA) and immunohistochemistry. Neurons in the arcuate nucleus were observed to react positively to ghrelin antibodies. In addition, we confirmed the existence of ghrelin mRNA expression using the reverse-transcription polymerase chain reaction (RT-PCR). We also observed the colocalization of GHS-R with neuropeptide Y (NPY) and growth-hormone-releasing hormone (GHRH) in the arcuate nucleus. The present study clearly indicates that ghrelin is synthesized in the arcuate nucleus, which will further our understanding of ghrelin's actions in the central nervous system, including feeding behavior and GH secretion.
Asunto(s)
Núcleo Arqueado del Hipotálamo/fisiología , Neuronas/fisiología , Hormonas Peptídicas/biosíntesis , ARN Mensajero/biosíntesis , Receptores Acoplados a Proteínas G/biosíntesis , Animales , Núcleo Arqueado del Hipotálamo/citología , Ghrelina , Hormona Liberadora de Hormona del Crecimiento/biosíntesis , Inmunohistoquímica , Masculino , Neuronas/citología , Neuropéptido Y/biosíntesis , Hormonas Peptídicas/genética , ARN Mensajero/genética , Ratas , Ratas Wistar , Receptores Acoplados a Proteínas G/genética , Receptores de GhrelinaRESUMEN
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 TiempoRESUMEN
Neuropeptide W (NPW) is a novel hypothalamic peptide that activates the previously described orphan G protein-coupled receptors, GPR7 and GPR8. Two endogenous molecular forms of NPW that consist of 23- and 30-amino acid residues were identified. The localization of GPR7 and GPR8 in some hypothalamic regions of primary importance in the regulation of feeding behavior has provided a springboard for investigation of the role of NPW in the central nervous system. In this study we examined the effects of NPW on feeding and energy expenditure in rats. Single intracerebroventricular (i.c.v.) administration of NPW23 and NPW30 to free-feeding rats suppressed dark phase and fasting-induced food intake at similar effective doses. Continuous i.c.v. infusion of NPW using an osmotic minipump suppressed feeding and body weight gain over the infusion period. Conversely, i.c.v. administration of anti-NPW IgG stimulated feeding. Furthermore, i.c.v. administration of NPW increased body temperature and heat production. These data raise the possibility that NPW functions as an endogenous catabolic signaling molecule in the brain. Further investigation of the biochemical and physiological functions of NPW will help us to better understand the hypothalamic regulation of energy homeostasis.
Asunto(s)
Conducta Alimentaria/fisiología , Neuropéptidos/fisiología , Animales , Ingestión de Alimentos/efectos de los fármacos , Metabolismo Energético/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Humanos , Inyecciones Intraventriculares , Masculino , Neuropéptidos/administración & dosificación , Ratas , Ratas WistarRESUMEN
Ghrelin is an acylated peptide that stimulates food intake and the secretion of growth hormone. While ghrelin is predominantly synthesized in a subset of endocrine cells in the oxyntic gland of the human and rat stomach, the mechanism regulating ghrelin secretion remains unknown. Somatostatin, a peptide produced in the gastric oxyntic mucosa, is known to suppress secretion of several gastrointestinal peptides in a paracrine fashion. By double immunohistochemistry, we demonstrated that somatostatin-immunoreactive cells contact ghrelin-immunoreactive cells. A single intravenous injection of somatostatin reduced the systemic plasma concentration of ghrelin in rats. Continuous infusion of somatostatin into the gastric artery of the vascularly perfused rat stomach suppressed ghrelin secretion in both dose- and time-dependent manner. These findings indicate that ghrelin secretion from the stomach is regulated by gastric somatostatin.
Asunto(s)
Mucosa Gástrica/metabolismo , Hormonas Peptídicas/antagonistas & inhibidores , Hormonas Peptídicas/metabolismo , Somatostatina/farmacología , Somatostatina/fisiología , Animales , Área Bajo la Curva , Cromatografía Líquida de Alta Presión , Relación Dosis-Respuesta a Droga , Ghrelina , Inmunohistoquímica , Masculino , Octreótido/farmacología , Perfusión , Radioinmunoensayo , Ratas , Ratas Wistar , Estómago/efectos de los fármacos , Factores de TiempoRESUMEN
The hypothalamus regulates energy intake by integrating the degree of starvation or satiation with the status of the environment through a variety of neuronal and blood-derived signals. Ghrelin, a peptide produced in the stomach and hypothalamus, stimulates feeding and GH secretion. Centrally administered ghrelin exerts an orexigenic activity through the neuropeptide Y (NPY) and agouti-related protein systems. The interaction between ghrelin and other hypothalamic orexigenic peptides, however, has not been clarified. Here, we investigated the anatomical interactions and functional relationship between ghrelin and two orexigenic peptides, orexin and melanin-concentrating hormone (MCH), present in the lateral hypothalamus. Ghrelin-immunoreactive axonal terminals made direct synaptic contacts with orexin-producing neurons. Intracerebroventricular administration of ghrelin induced Fos expression, a marker of neuronal activation, in orexin-producing neurons but not in MCH-producing neurons. Ghrelin remained competent to induce Fos expression in orexin-producing neurons following pretreatment with anti-NPY IgG. Pretreatment with anti-orexin-A IgG and anti-orexin-B IgG, but not anti-MCH IgG, attenuated ghrelin-induced feeding. Administration of NPY receptor antagonist further attenuated ghrelin-induced feeding in rats treated with anti-orexin-IgGs. Ghrelin-induced feeding was also suppressed in orexin knockout mice. This study identifies a novel hypothalamic pathway that links ghrelin and orexin in the regulation of feeding behavior and energy homeostasis.
Asunto(s)
Proteínas Portadoras/metabolismo , Ingestión de Alimentos/efectos de los fármacos , Péptidos y Proteínas de Señalización Intracelular , Neuropéptidos/metabolismo , Hormonas Peptídicas/farmacología , Animales , Anticuerpos/farmacología , Proteínas Portadoras/genética , Proteínas Portadoras/inmunología , Ingestión de Alimentos/fisiología , Técnica del Anticuerpo Fluorescente , Ghrelina , Hormonas Hipotalámicas/inmunología , Hormonas Hipotalámicas/metabolismo , Masculino , Melaninas/inmunología , Melaninas/metabolismo , Ratones , Ratones Noqueados , Microscopía Inmunoelectrónica , Neuronas/química , Neuronas/metabolismo , Neuronas/ultraestructura , Neuropéptidos/genética , Neuropéptidos/inmunología , Orexinas , Hormonas Peptídicas/análisis , Hormonas Hipofisarias/inmunología , Hormonas Hipofisarias/metabolismo , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Ratas , Ratas WistarRESUMEN
Neuromedin U (NMU) is a hypothalamic peptide involved in energy homeostasis and stress responses. NMU, when administered intracerebroventricularly, decreases food intake and body weight while increasing body temperature and heat production. In addition, NMU, acting via the corticotropin-releasing hormone (CRH) system, induces gross locomotor activity and stress responses. We studied the effect of intracerebroventricularly administered NMU (0.5-4 nmol) in the regulation of gastric functions in conscious rats. Intracerebroventricular administration of NMU significantly decreased gastric acid output to 30-60% and gastric emptying to 35-70% in a dose-dependent manner. Vagotomy did not abolish the inhibitory effect of NMU on pentagastrin-induced gastric acid secretion. Pretreatment with indomethacin (10 mg/kg), an inhibitor of prostaglandin synthesis, also did not affect NMU-induced acid inhibition. Pretreatment with anti-CRH IgG (1 microg/rat), however, completely blocked NMU-induced acid inhibition (P < 0.01). Administration of yohimbine (4 mg/kg), an alpha(2)-adrenergic receptor antagonist, also abolished NMU-induced acid inhibition (P < 0.01). These findings suggest that NMU is critical in the central regulation of gastric acid secretion via CRH.
Asunto(s)
Sistema Nervioso Central/efectos de los fármacos , Hormona Liberadora de Corticotropina/metabolismo , Ácido Gástrico/metabolismo , Neuropéptidos/farmacología , Animales , Hormona Liberadora de Corticotropina/inmunología , Vaciamiento Gástrico/efectos de los fármacos , Mucosa Gástrica/metabolismo , Inmunoglobulina G/inmunología , Inmunoglobulina G/farmacología , Indometacina/farmacología , Masculino , Pentagastrina/farmacología , Ratas , Ratas Sprague-Dawley , Transducción de Señal/efectos de los fármacos , Estómago/efectos de los fármacos , Vagotomía , Nervio Vago/fisiología , Yohimbina/farmacologíaRESUMEN
Orexins (hypocretins) and the melanin-concentrating hormone (MCH) are neuropeptides localized to the lateral hypothalamic area and are potential regulators of energy homeostasis. Using highly sensitive radioimmunoassay for orexins and MCH, we determined their contents in the lateral hypothalamus (LH) of genetically obese ob/ob and db/db mice and their controls, C57BL/6J and C57BL/KSJ. The orexin contents in the lateral hypothalamus significantly increased in the ob/ob mice, whereas the orexin contents significantly decreased in the db/db mice. Mature orexin-A and -B peptides were the major endogenous orexin molecules in the lateral hypothalamus. Conversely, the MCH contents in the lateral hypothalamus of both obese mice increased compared to the control mice. MCH contents in the lateral hypothalamus were two- to five-fold higher than that of orexin contents. These results suggest that the regulatory mechanism of orexin and MCH may be different in the genetically obese mice.
Asunto(s)
Glucemia/análisis , Proteínas Portadoras/metabolismo , Área Hipotalámica Lateral/metabolismo , Hormonas Hipotalámicas/metabolismo , Péptidos y Proteínas de Señalización Intracelular , Melaninas/metabolismo , Neuropéptidos/metabolismo , Obesidad/metabolismo , Hormonas Hipofisarias/metabolismo , Animales , Peso Corporal , Química Encefálica/fisiología , Proteínas Portadoras/análisis , Cromatografía Líquida de Alta Presión , Área Hipotalámica Lateral/química , Hormonas Hipotalámicas/análisis , Masculino , Melaninas/análisis , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos , Neuropéptidos/análisis , Obesidad/genética , Orexinas , Hormonas Hipofisarias/análisisRESUMEN
Ghrelin, a novel GH-releasing peptide isolated from human and rat stomach, stimulates food intake and GH secretion. We determined plasma ghrelin concentrations in patients with simple obesity, anorexia nervosa, and type 2 diabetes mellitus by RIA. We also studied plasma ghrelin responses to glucose load and meal intake and obtained a 24-h profile of circulating ghrelin in humans. Plasma ghrelin concentrations in patients with simple obesity and anorexia nervosa were lower and higher, respectively, than those of healthy subjects with normal body weight. Among those with type 2 diabetes mellitus, obese patients had lower and lean patients higher fasting plasma ghrelin concentrations than normal-weight patients. Fasting plasma ghrelin concentration was negatively correlated with body mass index in both nondiabetic and diabetic patients. Plasma ghrelin concentrations of normal subjects decreased significantly after oral and iv glucose administration; a similar response was also observed in diabetic patients after a meal tolerance test, reaching a nadir of 69% of the basal level after the meal. Circulating plasma ghrelin showed a diurnal pattern with preprandial increases, postprandial decreases, and a maximum peak at 0200 h. This study demonstrates that nutritional state is a determinant of plasma ghrelin in humans. Ghrelin secretion is up-regulated under conditions of negative energy balance and down-regulated in the setting of positive energy balance. These findings suggest the involvement of ghrelin in the regulation of feeding behavior and energy homeostasis.
Asunto(s)
Glucosa/farmacología , Obesidad/sangre , Hormonas Peptídicas , Péptidos/metabolismo , Adulto , Anorexia Nerviosa/sangre , Ritmo Circadiano , Diabetes Mellitus Tipo 2/sangre , Femenino , Ghrelina , Prueba de Tolerancia a la Glucosa , Humanos , Masculino , Péptidos/sangre , Periodo Posprandial , Estómago/efectos de los fármacosRESUMEN
Ghrelin, a novel growth hormone-releasing peptide isolated from human and rat stomach, is a 28-amino acid peptide with a posttranslational acylation modification that is indispensable for stimulating growth hormone secretion by increasing intracellular Ca(2+) concentration. It also functions in the regulation of feeding behavior, energy metabolism, and gastric acid secretion and motility. Using two different antibodies against the NH(2)- and COOH-terminal regions of ghrelin, we studied its localization in human and rat pancreas by immunohistochemistry. Ghrelin-immunoreactive cells were identified at the periphery of pancreatic islets in both species. Ghrelin co-localized exclusively with glucagon in rat islets, indicating that it is produced in alpha-cells. We identified ghrelin and des-acyl ghrelin in the rat pancreas using reverse-phase high-performance liquid chromatography combined with two radioimmunoassays. We also detected mRNA encoding ghrelin and its receptor in the rat pancreatic islets. Ghrelin increased the cytosolic free Ca(2+) concentration in beta-cells and stimulated insulin secretion when it was added to isolated rat pancreatic islets. These findings indicate that ghrelin may regulate islet function in an endocrine and/or paracrine manner.