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Nakamura-Utsunomiya A. Autoimmunity Related to Adipsic Hypernatremia and ROHHAD Syndrome. Int J Mol Sci 2022; 23:ijms23136899. [PMID: 35805903 PMCID: PMC9266522 DOI: 10.3390/ijms23136899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/18/2022] [Accepted: 06/20/2022] [Indexed: 11/16/2022] Open
Abstract
Specific antibody responses to subfornical organs, including Nax antibody, have been reported in patients with adipsic hypernatremia of unknown etiology who do not have structural lesions in the hypothalamic–pituitary gland. The subfornical organ, also referred to as the window of the brain, is a sensing site that monitors sodium and osmotic pressure levels. On the other hand, ROHHAD syndrome is a rare disease for which the etiology of the hypothalamic disorder is unknown, and there have been some reports in recent years describing its association with autoimmune mechanisms. In addition, abnormal Na levels, including hypernatremia, are likely to occur in this syndrome. When comparing the clinical features of adipsic hypernatremia due to autoimmune mechanisms and ROHHAD syndrome, there are similar hypothalamic–pituitary dysfunction symptoms in addition to abnormal Na levels. Since clinical diagnoses of autoimmunological adipsic hypernatremia and ROHAD syndrome might overlap, we need to understand the essential etiology and carry out precise assessments to accurately diagnose patients and provide effective treatment. In this review, I review the literature on the autoimmune mechanism reported in recent years and describe the findings obtained so far and future directions.
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Affiliation(s)
- Akari Nakamura-Utsunomiya
- Department of Genetic Medicine, Hiroshima University Graduate School, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8511, Japan;
- Department of Pediatrics, Hiroshima University Graduate School, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8511, Japan
- Division of Neonatal Screening, National Center for Child Health and Development, 2 Chome-10-1 Okura, Setagaya, Tokyo 157-8535, Japan
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Hagemann CA, Zhang C, Hansen HH, Jorsal T, Rigbolt KTG, Madsen MR, Bergmann NC, Heimbürger SMN, Falkenhahn M, Theis S, Breitschopf K, Holm S, Hedegaard MA, Christensen MB, Vilsbøll T, Holst B, Vrang N, Jelsing J, Knop FK. Identification and Metabolic Profiling of a Novel Human Gut-derived LEAP2 Fragment. J Clin Endocrinol Metab 2021; 106:e966-e981. [PMID: 33135737 DOI: 10.1210/clinem/dgaa803] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Indexed: 02/06/2023]
Abstract
CONTEXT The mechanisms underlying Roux-en-Y gastric bypass (RYGB) surgery-induced weight loss and the immediate postoperative beneficial metabolic effects associated with the operation remain uncertain. Enteroendocrine cell (EEC) secretory function has been proposed as a key factor in the marked metabolic benefits from RYGB surgery. OBJECTIVE To identify novel gut-derived peptides with therapeutic potential in obesity and/or diabetes by profiling EEC-specific molecular changes in obese patients following RYGB-induced weight loss. SUBJECTS AND METHODS Genome-wide expression analysis was performed in isolated human small intestinal EECs obtained from 20 gut-biopsied obese subjects before and after RYGB. Targets of interest were profiled for preclinical and clinical metabolic effects. RESULTS Roux-en-Y gastric bypass consistently increased expression levels of the inverse ghrelin receptor agonist, liver-expressed antimicrobial peptide 2 (LEAP2). A secreted endogenous LEAP2 fragment (LEAP238-47) demonstrated robust insulinotropic properties, stimulating insulin release in human pancreatic islets comparable to the gut hormone glucagon-like peptide-1. LEAP238-47 showed reciprocal effects on growth hormone secretagogue receptor (GHSR) activity, suggesting that the insulinotropic action of the peptide may be directly linked to attenuation of tonic GHSR activity. The fragment was infused in healthy human individuals (n = 10), but no glucoregulatory effect was observed in the chosen dose as compared to placebo. CONCLUSIONS Small intestinal LEAP2 expression was upregulated after RYGB. The corresponding circulating LEAP238-47 fragment demonstrated strong insulinotropic action in vitro but failed to elicit glucoregulatory effects in healthy human subjects.
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Affiliation(s)
- Christoffer A Hagemann
- Gubra Aps, Hørsholm, Denmark
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | | | | | - Tina Jorsal
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | | | | | - Natasha C Bergmann
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
| | - Sebastian M N Heimbürger
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Steno Diabetes Center Copenhagen, Gentofte, Denmark
| | | | | | | | - Stephanie Holm
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Morten A Hedegaard
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mikkel B Christensen
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Clinical Pharmacology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark
| | - Tina Vilsbøll
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Steno Diabetes Center Copenhagen, Gentofte, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Birgitte Holst
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Filip K Knop
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark
- Steno Diabetes Center Copenhagen, Gentofte, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Dos-Santos RC, Reis LC, Perello M, Ferguson AV, Mecawi AS. The actions of ghrelin in the paraventricular nucleus: energy balance and neuroendocrine implications. Ann N Y Acad Sci 2019; 1455:81-97. [PMID: 31008525 DOI: 10.1111/nyas.14087] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 02/28/2019] [Accepted: 03/10/2019] [Indexed: 12/15/2022]
Abstract
Ghrelin is a peptide mainly produced and secreted by the stomach. Since its discovery, the impact of ghrelin on the regulation of food intake has been the most studied function of this hormone; however, ghrelin affects a wide range of physiological systems, many of which are controlled by the hypothalamic paraventricular nucleus (PVN). Several pathways may mediate the effects of ghrelin on PVN neurons, such as direct or indirect effects mediated by circumventricular organs and/or the arcuate nucleus. The ghrelin receptor is expressed in PVN neurons, and the peripheral or intracerebroventricular administration of ghrelin affects PVN neuronal activity. Intra-PVN application of ghrelin increases food intake and decreases fat oxidation, which chronically contribute to the increased adiposity. Additionally, ghrelin modulates the neuroendocrine axes controlled by the PVN, increasing the release of vasopressin and oxytocin by magnocellular neurons and corticotropin-releasing hormone by neuroendocrine parvocellular neurons, while possibly inhibiting the release of thyrotropin-releasing hormone. Thus, the PVN is an important target for the actions of ghrelin. Our review discusses the mechanisms of ghrelin actions in the PVN, and its potential implications for energy balance, neuroendocrine, and integrative physiological control.
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Affiliation(s)
- Raoni C Dos-Santos
- Department of Physiological Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Luís C Reis
- Department of Physiological Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Mario Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology, La Plata, Argentina
| | - Alastair V Ferguson
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - André S Mecawi
- Laboratory of Neuroendocrinology, Department of Biophysics, Paulista Medical School, Federal University of São Paulo, São Paulo, Brazil
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New Metabolic Influencer on Oxytocin Release: The Ghrelin. Molecules 2019; 24:molecules24040735. [PMID: 30781678 PMCID: PMC6413225 DOI: 10.3390/molecules24040735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 02/11/2019] [Accepted: 02/13/2019] [Indexed: 11/16/2022] Open
Abstract
Background: The hypothalamic–pituitary axis by secreting neuropeptides plays a key role in metabolic homeostasis. In light of the metabolic regulation, oxytocin is a potential neuropeptide for therapies against obesity and related disorders. The aim of our study is to measure ghrelin-induced oxytocin secretion in rats and to detect the changes after administration of ghrelin antagonist. Methods: Ghrelin was administrated centrally (intracerebroventricular, i.c.v., 1.0, 10.0, and 100.0 pmol) or systemically (intravenous, i.v., 1.0, and 10.0 nmol). [d-Lys3]-GHRP-6 ghrelin antagonist was injected 15 min before ghrelin injection in a dose of 10.0 pmol i.c.v. and 10.0 nmol i.v. Results: Either i.c.v. or i.v. administration of ghrelin dose-dependently increased the plasma oxytocin concentration. Following pretreatment with the ghrelin antagonist [d-Lys3]-GHRP-6, the high plasma oxytocin level induced by ghrelin was significantly reduced. Conclusion: The results indicate that the release of oxytocin is influenced directly by the ghrelin system. Examination of the mechanism of ghrelin-induced oxytocin secretion is a new horizon for potential therapeutic options.
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Koutouratsas T, Kalli T, Karamanolis G, Gazouli M. Contribution of ghrelin to functional gastrointestinal disorders’ pathogenesis. World J Gastroenterol 2019; 25:539-551. [PMID: 30774270 PMCID: PMC6371003 DOI: 10.3748/wjg.v25.i5.539] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 12/20/2018] [Accepted: 01/15/2019] [Indexed: 02/06/2023] Open
Abstract
Functional gastrointestinal disorders (FGID) are heterogeneous disorders with a variety of clinical manifestations, primarily defined by signs and symptoms rather than a definite underlying cause. Their pathophysiology remains obscure and, although it is expected to differ according to the specific FGID, disruptions in the brain-gut axis are now thought to be a common denominator in their pathogenesis. The hormone ghrelin is an important component of this axis, exerting a wide repertoire of physiological actions, including regulation of gastrointestinal motility and protection of mucosal tissue. Ghrelin’s gene shows genetic polymorphism, while its protein product undergoes complex regulation and metabolism in the human body. Numerous studies have studied ghrelin’s relation to the emergence of FGIDs, its potential value as an index of disease severity and as a predictive marker for symptom relief during attempted treatment. Despite the mixed results currently available in scientific literature, the plethora of statistically significant findings shows that disruptions in ghrelin genetics and expression are plausibly related to FGID pathogenesis. The aim of this paper is to review current literature studying these associations, in an effort to uncover certain patterns of alterations in both genetics and expression, which could delineate its true contribution to FGID emergence, either as a causative agent or as a pathogenetic intermediate.
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Affiliation(s)
- Tilemachos Koutouratsas
- Department of Basic Medical Science, Laboratory of Biology, School of Medicine, University of Athens, Athens 11527, Greece
| | - Theodora Kalli
- Gastroenterology Department, Larnaca General Hospital, Larnaca 6301, Cyprus
| | - Georgios Karamanolis
- Gastroenterology Unit, 2nd Department of Surgery, “Aretaieio” University Hospital, School of Medicine, University of Athens, Athens 11527, Greece
| | - Maria Gazouli
- Department of Basic Medical Science, Laboratory of Biology, School of Medicine, University of Athens, Athens 11527, Greece
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Administration of ghrelin associated with decreased expression of matrix metalloproteinase-9 following normobaric systemic hypoxia in the brain. Endocr Regul 2018; 52:152-158. [PMID: 31517605 DOI: 10.2478/enr-2018-0019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE According to our previous studies, ghrelin protects blood brain barrier (BBB) integrity and it attenuates hypoxia-induced brain edema in the hypoxic conditions. However, the underlying mechanisms remain poorly understood. Several studies suggest a role for matrix metal-loproteinase-9 (MMP9) in the BBB disruption and cerebral edema formation. The present study was conducted to determine the effect of ghrelin on MMP9 protein expression in the model of acute and chronic systemic hypoxia. METHODS Adult male Wistar rats were divided into acute or chronic controls, acute or chronic hypoxia and ghrelin-treated acute or chronic hypoxia groups. The hypoxic groups were kept in the hypoxic chamber (10-11% O2) for two (acute) or ten days (chronic). Effect of ghrelin on MMP9 protein expression was assessed using immunoblotting. RESULTS Our results showed that acute and chronic systemic hypoxia increased the MMP9 protein expression in the brain (p<0.001). Treatment with ghrelin significantly attenuated this expression in the cerebral hypoxia (p<0.05). CONCLUSION Our results demonstrate that the neuroprotective effects of ghrelin may be mediated, in part, by decreasing in MMP9 production in the hypoxic brain.
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Abstract
Ghrelin and motilin are released from gastrointestinal endocrine cells during hunger, to act through G protein-coupled receptors that have closely related amino acid sequences. The actions of ghrelin are more complex than motilin because ghrelin also exists outside the GI tract, it is processed to des-acyl ghrelin which has activity, ghrelin can exist in truncated forms and retain activity, the ghrelin receptor can have constitutive activity and is subject to biased agonism and finally additional ghrelin-like and des-acyl ghrelin receptors are proposed. Both ghrelin and motilin can stimulate gastric emptying, acting via different pathways, perhaps influenced by biased agonism at the receptors, but research is revealing additional pathways of activity. For example, it is becoming apparent that reduction of nausea may be a key therapeutic target for ghrelin receptor agonists and perhaps for compounds that modulate the constitutive activity of the ghrelin receptor. Reduction of nausea may be the mechanism through which gastroparesis symptoms are reduced. Intriguingly, a potential ability of motilin to influence nausea is also becoming apparent. Ghrelin interacts with digestive function through its effects on appetite, and ghrelin antagonists may have a place in treating Prader-Willi syndrome. Unlike motilin, ghrelin receptor agonists also have the potential to treat constipation by acting at the lumbosacral defecation centres. In conclusion, agonists of both ghrelin and motilin receptors hold potential as treatments for specific subsets of digestive system disorders.
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Nakamura-Utsunomiya A, Hiyama TY, Okada S, Noda M, Kobayashi M. Characteristic clinical features of adipsic hypernatremia patients with subfornical organ-targeting antibody. Clin Pediatr Endocrinol 2017; 26:197-205. [PMID: 29026268 PMCID: PMC5627220 DOI: 10.1297/cpe.26.197] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 04/15/2017] [Indexed: 12/11/2022] Open
Abstract
Adipsic hypernatremia is a rare disease presenting as persistent hypernatremia with disturbance of thirst regulation and hypothalamic dysfunction. As a result of congenital disease, tumors, or inflammation, most cases are accompanied by structural abnormalities in the hypothalamic-pituitary area. While cases with no hypothalamic-pituitary structural lesion have been reported, their etiology has not been elucidated. Recently, we reported three patients with adipsic hypernatremia whose serum-derived immunoglobulin (Ig) specifically reacted with mouse subfornical organ (SFO) tissue. As one of the circumventricular organs (CVOs) that form a sensory interface between the blood and brain, the SFO is a critical site for generating physiological responses to dehydration and hypernatremia. Intravenous injection of the patient's Ig fraction induced hypernatremia in mice, along with inflammation and apoptosis in the SFO. These results support a new autoimmunity-related mechanism for inducing adipsic hypernatremia without demonstrable hypothalamic-pituitary structural lesions. In this review, we aim to highlight the characteristic clinical features of these patients, in addition to etiological mechanisms related to SFO function. These findings may be useful for diagnosing adipsic hypernatremia caused by an autoimmune response to the SFO, and support development of new strategies for prevention and treatment.
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Affiliation(s)
| | - Takeshi Y Hiyama
- Division of Molecular Neurobiology, National Institute for Basic Biology (NIBB), Aichi, Japan.,School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Aichi, Japan
| | - Satoshi Okada
- Department of Pediatrics, Hiroshima University Hospital, Hiroshima, Japan
| | - Masaharu Noda
- Division of Molecular Neurobiology, National Institute for Basic Biology (NIBB), Aichi, Japan.,School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Aichi, Japan
| | - Masao Kobayashi
- Department of Pediatrics, Hiroshima University Hospital, Hiroshima, Japan
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Clarifying the Ghrelin System's Ability to Regulate Feeding Behaviours Despite Enigmatic Spatial Separation of the GHSR and Its Endogenous Ligand. Int J Mol Sci 2017; 18:ijms18040859. [PMID: 28422060 PMCID: PMC5412441 DOI: 10.3390/ijms18040859] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/04/2017] [Accepted: 04/11/2017] [Indexed: 12/23/2022] Open
Abstract
Ghrelin is a hormone predominantly produced in and secreted from the stomach. Ghrelin is involved in many physiological processes including feeding, the stress response, and in modulating learning, memory and motivational processes. Ghrelin does this by binding to its receptor, the growth hormone secretagogue receptor (GHSR), a receptor found in relatively high concentrations in hypothalamic and mesolimbic brain regions. While the feeding and metabolic effects of ghrelin can be explained by the effects of this hormone on regions of the brain that have a more permeable blood brain barrier (BBB), ghrelin produced within the periphery demonstrates a limited ability to reach extrahypothalamic regions where GHSRs are expressed. Therefore, one of the most pressing unanswered questions plaguing ghrelin research is how GHSRs, distributed in brain regions protected by the BBB, are activated despite ghrelin’s predominant peripheral production and poor ability to transverse the BBB. This manuscript will describe how peripheral ghrelin activates central GHSRs to encourage feeding, and how central ghrelin synthesis and ghrelin independent activation of GHSRs may also contribute to the modulation of feeding behaviours.
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Gastrointestinal Spatiotemporal mRNA Expression of Ghrelin vs Growth Hormone Receptor and New Growth Yield Machine Learning Model Based on Perturbation Theory. Sci Rep 2016; 6:30174. [PMID: 27460882 PMCID: PMC4962052 DOI: 10.1038/srep30174] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 06/28/2016] [Indexed: 12/16/2022] Open
Abstract
The management of ruminant growth yield has economic importance. The current work presents a study of the spatiotemporal dynamic expression of Ghrelin and GHR at mRNA levels throughout the gastrointestinal tract (GIT) of kid goats under housing and grazing systems. The experiments show that the feeding system and age affected the expression of either Ghrelin or GHR with different mechanisms. Furthermore, the experimental data are used to build new Machine Learning models based on the Perturbation Theory, which can predict the effects of perturbations of Ghrelin and GHR mRNA expression on the growth yield. The models consider eight longitudinal GIT segments (rumen, abomasum, duodenum, jejunum, ileum, cecum, colon and rectum), seven time points (0, 7, 14, 28, 42, 56 and 70 d) and two feeding systems (Supplemental and Grazing feeding) as perturbations from the expected values of the growth yield. The best regression model was obtained using Random Forest, with the coefficient of determination R2 of 0.781 for the test subset. The current results indicate that the non-linear regression model can accurately predict the growth yield and the key nodes during gastrointestinal development, which is helpful to optimize the feeding management strategies in ruminant production system.
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Abstract
The gastrointestinal tract is the major source of the related hormones ghrelin and motilin, which act on structurally similar G protein-coupled receptors. Nevertheless, selective receptor agonists are available. The primary roles of endogenous ghrelin and motilin in the digestive system are to increase appetite or hedonic eating (ghrelin) and initiate phase III of gastric migrating myoelectric complexes (motilin). Ghrelin and motilin also both inhibit nausea. In clinical trials, the motilin receptor agonist camicinal increased gastric emptying, but at lower doses reduced gastroparesis symptoms and improved appetite. Ghrelin receptor agonists have been trialled for the treatment of diabetic gastroparesis because of their ability to increase gastric emptying, but with mixed results; however, relamorelin, a ghrelin agonist, reduced nausea and vomiting in patients with this disorder. Treatment of postoperative ileus with a ghrelin receptor agonist proved unsuccessful. Centrally penetrant ghrelin receptor agonists stimulate defecation in animals and humans, although ghrelin itself does not seem to control colorectal function. Thus, the most promising uses of motilin receptor agonists are the treatment of gastroparesis or conditions with slow gastric emptying, and ghrelin receptor agonists hold potential for the reduction of nausea and vomiting, and the treatment of constipation. Therapeutic, gastrointestinal roles for receptor antagonists or inverse agonists have not been identified.
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Perello M, Dickson SL. Ghrelin signalling on food reward: a salient link between the gut and the mesolimbic system. J Neuroendocrinol 2015; 27:424-34. [PMID: 25377898 PMCID: PMC5033008 DOI: 10.1111/jne.12236] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 10/29/2014] [Accepted: 11/02/2014] [Indexed: 12/12/2022]
Abstract
'Hunger is the best spice' is an old and wise saying that acknowledges the fact that almost any food tastes better when we are hungry. The neurobiological underpinnings of this lore include activation of the brain's reward system and the stimulation of this system by the hunger-promoting hormone ghrelin. Ghrelin is produced largely from the stomach and levels are higher preprandially. The ghrelin receptor is expressed in many brain areas important for feeding control, including not only the hypothalamic nuclei involved in energy balance regulation, but also reward-linked areas such as the ventral tegmental area. By targeting the mesoaccumbal dopamine neurones of the ventral tegmental area, ghrelin recruits pathways important for food reward-related behaviours that show overlap with but are also distinct from those important for food intake. We review a variety of studies that support the notion that ghrelin signalling at the level of the mesolimbic system is one of the key molecular substrates that provides a physiological signal connecting gut and reward pathways.
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Affiliation(s)
- M. Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research CommissionProvince of Buenos Aires (CIC‐PBA)]La PlataBuenos AiresArgentina
| | - S. L. Dickson
- Department of Physiology/EndocrinologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
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Ghrelin: a link between ageing, metabolism and neurodegenerative disorders. Neurobiol Dis 2014; 72 Pt A:72-83. [PMID: 25173805 DOI: 10.1016/j.nbd.2014.08.026] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 06/28/2014] [Accepted: 08/20/2014] [Indexed: 12/13/2022] Open
Abstract
Along with the increase in life expectancy over the last century comes the increased risk for development of age-related disorders, including metabolic and neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's diseases. These chronic disorders share two main characteristics: 1) neuronal loss in motor, sensory or cognitive systems, leading to cognitive and motor decline; and 2) a strong correlation between metabolic changes and neurodegeneration. In order to treat them, a better understanding of their complexity is required: it is necessary to interpret the neuronal damage in light of the metabolic changes, and to find the disrupted link between the peripheral organs governing energy metabolism and the CNS. This review is an attempt to present ghrelin as part of molecular regulatory interface between energy metabolism, neuroendocrine and neurodegenerative processes. Ghrelin takes part in lipid and glucose metabolism, in higher brain functions such as sleep-wake state, learning and memory consolidation; it influences mitochondrial respiration and shows neuroprotective effect. All these make ghrelin an attractive target for development of biomarkers or therapeutics for prevention or treatment of disorders, in which cell protection and recruitment of new neurons or synapses are needed.
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Cabral A, Valdivia S, Fernandez G, Reynaldo M, Perello M. Divergent neuronal circuitries underlying acute orexigenic effects of peripheral or central ghrelin: critical role of brain accessibility. J Neuroendocrinol 2014; 26:542-54. [PMID: 24888783 PMCID: PMC4108543 DOI: 10.1111/jne.12168] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Revised: 05/15/2014] [Accepted: 05/23/2014] [Indexed: 11/27/2022]
Abstract
Ghrelin is an octanoylated peptide hormone that potently and rapidly increases food intake. The orexigenic action of ghrelin involves the hypothalamic arcuate nucleus (ARC), which is accessible to plasma ghrelin and expresses high levels of the ghrelin receptor. Local administration of ghrelin in a variety of other brain nuclei also increases food intake. It is currently unclear, however, whether these non-ARC ghrelin brain targets are impacted by physiological increases of plasma ghrelin. Thus, the present study aimed to clarify which ghrelin brain targets participate in the short-term orexigenic actions of ghrelin. First, c-Fos induction into mouse brains centrally or peripherally treated with ghrelin was analysed. It was confirmed that peripherally administered ghrelin dose-dependently increases food intake and mainly activates c-Fos in ARC neurones. By contrast, centrally administered ghrelin activates c-Fos in a larger number of brain nuclei. To determine which nuclei are directly accessible to ghrelin, mice were centrally or peripherally injected with a fluorescent ghrelin tracer. It was found that peripherally injected tracer mainly accesses the ARC, whereas centrally injected tracer reaches most brain areas known to express ghrelin receptors. Subsequently, the effects of ghrelin were tested in ARC-ablated mice and it was found that these mice failed to increase food intake in response to peripherally administered ghrelin but fully responded to centrally administered ghrelin. ARC-ablated mice showed patterns of ghrelin-induced c-Fos expression similar to those seen in control mice with the exception of the ARC, where no c-Fos was found. Thus, peripheral ghrelin mainly accesses the ARC, which is required for the orexigenic effects of the hormone. Central ghrelin accesses a variety of nuclei, which can mediate the orexigenic effects of the hormone, even in the absence of an intact ARC.
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Affiliation(s)
- Agustina Cabral
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - Spring Valdivia
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - Gimena Fernandez
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - Mirta Reynaldo
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - Mario Perello
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology [Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
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Date Y, Kangawa K. Ghrelin as a starvation signal. Obes Res Clin Pract 2013; 6:e263-346. [PMID: 24331586 DOI: 10.1016/j.orcp.2012.08.195] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 08/28/2012] [Indexed: 10/27/2022]
Abstract
SUMMARY Ghrelin, a gastrointestinal hormone, functions as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). It comprises 28 amino acids, of which the Ser-3 residue is post-translationally modified by the addition of octanoyl acid. Ghrelin stimulates feeding and the secretion of growth hormone; it is also thought to function in energy conservation. Here, we provide an overview of the discovery of ghrelin, its pathophysiological significance, and the mechanism of ghrelin-induced feeding.:
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Affiliation(s)
- Yukari Date
- Frontier Science Research Center, University of Miyazaki, Miyazaki 889-1692, Japan.
| | - Kenji Kangawa
- National Cerebral and Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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Bron R, Yin L, Russo D, Furness JB. Expression of the ghrelin receptor gene in neurons of the medulla oblongata of the rat. J Comp Neurol 2013; 521:2680-702. [DOI: 10.1002/cne.23309] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 12/12/2012] [Accepted: 01/17/2013] [Indexed: 01/29/2023]
Affiliation(s)
- Romke Bron
- Department of Anatomy & Neuroscience; University of Melbourne; Parkville; Victoria 3010; Australia
| | - Lei Yin
- Department of Anatomy & Neuroscience; University of Melbourne; Parkville; Victoria 3010; Australia
| | - Domenico Russo
- Department of Veterinary Morphophysiology and Animal Production; University of Bologna; 40064 Ozzano Emilia; Bologna; Italy
| | - John B. Furness
- Department of Anatomy & Neuroscience; University of Melbourne; Parkville; Victoria 3010; Australia
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Laeger T, Sauerwein H, Tuchscherer A, Bellmann O, Metges C, Kuhla B. Concentrations of hormones and metabolites in cerebrospinal fluid and plasma of dairy cows during the periparturient period. J Dairy Sci 2013; 96:2883-93. [DOI: 10.3168/jds.2012-5909] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 01/09/2013] [Indexed: 01/18/2023]
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Morita S, Hourai A, Miyata S. Changes in pericytic expression of NG2 and PDGFRB and vascular permeability in the sensory circumventricular organs of adult mouse by osmotic stimulation. Cell Biochem Funct 2013; 32:51-61. [PMID: 23629811 DOI: 10.1002/cbf.2971] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 02/22/2013] [Accepted: 02/25/2013] [Indexed: 01/27/2023]
Abstract
The blood-brain barrier (BBB) is a barrier that prevents free access of blood-derived substances to the brain through the tight junctions and maintains a specialized brain environment. Circumventricular organs (CVOs) lack the typical BBB. The fenestrated vasculature of the sensory CVOs, including the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO) and area postrema (AP), allows parenchyma cells to sense a variety of blood-derived information, including osmotic ones. In the present study, we utilized immunohistochemistry to examine changes in the expression of NG2 and platelet-derived growth factor receptor beta (PDGFRB) in the OVLT, SFO and AP of adult mice during chronic osmotic stimulation. The expression of NG2 and PDGFRB was remarkably prominent in pericytes, although these angiogenesis-associated proteins are highly expressed at pericytes of developing immature vasculature. The chronic salt loading prominently increased the expression of NG2 in the OVLT and SFO and that of PDGFRB in the OVLT, SFO and AP. The vascular permeability of low-molecular-mass tracer fluorescein isothiocyanate was increased significantly by chronic salt loading in the OVLT and SFO but not AP. In conclusion, the present study demonstrates changes in pericyte expression of NG2 and PDGFRB and vascular permeability in the sensory CVOs by chronic osmotic stimulation, indicating active participation of the vascular system in osmotic homeostasis.
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Affiliation(s)
- Shoko Morita
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, Japan; Department of Anatomy and Neuroscience, Faculty of Medicine, Nara Medical University, 840 Shijo-cho, Kashihara, Nara, Japan
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Schwartz GJ, Zeltser LM. Functional organization of neuronal and humoral signals regulating feeding behavior. Annu Rev Nutr 2013; 33:1-21. [PMID: 23642202 DOI: 10.1146/annurev-nutr-071812-161125] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Energy homeostasis--ensuring that energy availability matches energy requirements--is essential for survival. One way that energy balance is achieved is through coordinated action of neural and neuroendocrine feeding circuits, which promote energy intake when energy supply is limited. Feeding behavior engages multiple somatic and visceral tissues distributed throughout the body--contraction of skeletal and smooth muscles in the head and along the upper digestive tract required to consume and digest food, as well as stimulation of endocrine and exocrine secretions from a wide range of organs. Accordingly, neurons that contribute to feeding behaviors are localized to central, peripheral, and enteric nervous systems. To promote energy balance, feeding circuits must be able to identify and respond to energy requirements, as well as the amount of energy available from internal and external sources, and then direct appropriate coordinated responses throughout the body.
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Affiliation(s)
- Gary J Schwartz
- Department of Medicine, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY 10461, USA
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20
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Hourai A, Miyata S. Neurogenesis in the circumventricular organs of adult mouse brains. J Neurosci Res 2013; 91:757-70. [PMID: 23526379 DOI: 10.1002/jnr.23206] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 12/10/2012] [Accepted: 12/21/2012] [Indexed: 12/20/2022]
Abstract
The circumventricular organs (CVOs), including the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), median eminence (ME), and area postrema (AP), allow parenchyma cells to sense a variety of blood-derived substances and/or secreted peptides into blood circulation. In the present study, we examined continuous neurogenesis in the CVOs of adult mice. The immunohistochemistry of neural progenitor cell (NPC) marker proteins revealed that Math1- and Mash1-positive cells were observed in the discrete regions of CVOs, including the capillary plexus in the OVLT, the internal zone of the ME, and the lateral zone in the AP. A few Mash1- and Math1-positive cells were seen throughout the SFO, and many Math1- but not Mash1-positive cells were observed at the arcuate nucleus. Math-positive cells were often seen to localize in close proximity to the vasculature. Bromodeoxyuridine (BrdU) immunohistochemistry revealed the incorporation of BrdU in a subpopulation of Mash1-, Math1-, HuC/D-, and microtubule-associated protein 2 (MAP2)-positive cells. Mash1- and Math1-positive cells expressed exclusively high level of plasminogen, whereas a subpopulation of HuC/D- and MAP2-positive neurons expressed low or undetectable level of plasminogen. Thus, the present study demonstrates that newborn cells express NPC marker proteins and plasminogen to localize closely at vascular matrix and moreover differentiate into neurons expressing mature neuron marker proteins, indicating that new neurons are possibly generated to integrate into new neural circuits.
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Affiliation(s)
- Atsushi Hourai
- Department of Applied Biology, Kyoto Institute of Technology, Kyoto, Japan
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Monajemzadeh M, Mokhtari S, Motamed F, Shams S, Ashtiani MTH, Abbasi A, Sani MN, Sadrian E. Plasma ghrelin levels in children with cystic fibrosis and healthy children. Arch Med Sci 2013; 9:93-7. [PMID: 23515113 PMCID: PMC3598153 DOI: 10.5114/aoms.2012.28599] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2011] [Revised: 04/11/2011] [Accepted: 04/21/2011] [Indexed: 01/23/2023] Open
Abstract
INTRODUCTION Cystic fibrosis (CF) is a common genetic disorder as a result of mutation in the CF transmembrane conductance regulator gene. Weight loss in CF patients seems to be multifactorial and metabolic factors, inflammation, recurrent infections and poor appetite are possible candidates. Ghrelin affects energy hemostasis by stimulating growth hormone secretion, glucose and lipid metabolism alteration and inhibition of the inflammatory system. Data on the role of ghrelin in energy deficiency in CF patients are sparse and controversial. The study was done to compare the plasma levels of the acylated form of ghrelin in CF patients with healthy participants. MATERIAL AND METHODS Thirty cystic fibrosis patients (aged 1-168 months) and thirty healthy matched participants were enrolled in the study. Plasma ghrelin and albumin levels were measured and body mass index (BMI) was calculated as well. RESULTS Plasma levels of acylated ghrelin in CF patients were significantly higher than the control group (mean 25-75%: 14.5 vs. 2.7, p = 0.032). Body mass index measurements in CF patients were significantly lower than the control group (p < 0.001). Using regression analysis there was no statistically significant correlation between plasma ghrelin levels and serum albumin, weight, height or BMI values in CF patients and controls. CONCLUSIONS The acylated ghrelin levels are increased in CF. So plasma levels of acylated ghrelin could be used as an indicator of food uptake and energy balance in them. Further studies should be established to find out the exact role of factors affecting energy metabolism.
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Affiliation(s)
- Maryam Monajemzadeh
- Department of Pathology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Shahrzad Mokhtari
- Department of Pathology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Farzaneh Motamed
- Department of Pediatric Gastroenterology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Sedigheh Shams
- Department of Pathology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Mohammad Taghi Haghi Ashtiani
- Department of Pathology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Ata Abbasi
- Department of Pathology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Mehri Najafi Sani
- Department of Pediatric Gastroenterology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
| | - Ehsan Sadrian
- Department of Pathology, Children's Medical Center Hospital, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran
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Schaeffer M, Langlet F, Lafont C, Molino F, Hodson DJ, Roux T, Lamarque L, Verdié P, Bourrier E, Dehouck B, Banères JL, Martinez J, Méry PF, Marie J, Trinquet E, Fehrentz JA, Prévot V, Mollard P. Rapid sensing of circulating ghrelin by hypothalamic appetite-modifying neurons. Proc Natl Acad Sci U S A 2013; 110:1512-7. [PMID: 23297228 PMCID: PMC3557016 DOI: 10.1073/pnas.1212137110] [Citation(s) in RCA: 213] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
To maintain homeostasis, hypothalamic neurons in the arcuate nucleus must dynamically sense and integrate a multitude of peripheral signals. Blood-borne molecules must therefore be able to circumvent the tightly sealed vasculature of the blood-brain barrier to rapidly access their target neurons. However, how information encoded by circulating appetite-modifying hormones is conveyed to central hypothalamic neurons remains largely unexplored. Using in vivo multiphoton microscopy together with fluorescently labeled ligands, we demonstrate that circulating ghrelin, a versatile regulator of energy expenditure and feeding behavior, rapidly binds neurons in the vicinity of fenestrated capillaries, and that the number of labeled cell bodies varies with feeding status. Thus, by virtue of its vascular connections, the hypothalamus is able to directly sense peripheral signals, modifying energy status accordingly.
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Affiliation(s)
- Marie Schaeffer
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34000 Montpellier, France
- Universities of Montpellier 1 and 2, Unité Mixte de Recherche 5203, F-34000 Montpellier, France
| | - Fanny Langlet
- Institut National de la Santé et de la Recherche Médicale, Jean-Pierre Aubert Research Center, Unité 837, F-59000 Lille, France
- Faculté de Médecine, Université Droit et Santé de Lille, F-59000 Lille, France
| | - Chrystel Lafont
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34000 Montpellier, France
- Universities of Montpellier 1 and 2, Unité Mixte de Recherche 5203, F-34000 Montpellier, France
| | - François Molino
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34000 Montpellier, France
- Universities of Montpellier 1 and 2, Unité Mixte de Recherche 5203, F-34000 Montpellier, France
- University Montpellier 2, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5221, Laboratoire Charles Coulomb, F-34095 Montpellier, France
| | - David J. Hodson
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34000 Montpellier, France
- Universities of Montpellier 1 and 2, Unité Mixte de Recherche 5203, F-34000 Montpellier, France
| | | | | | - Pascal Verdié
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5247, Institut des Biomolécules Max Mousseron, Faculty of Pharmacy, Universities of Montpellier 1 and 2, F-34093 Montpellier Cedex 5, France; and
| | | | - Bénédicte Dehouck
- Institut National de la Santé et de la Recherche Médicale, Jean-Pierre Aubert Research Center, Unité 837, F-59000 Lille, France
- Faculté de Médecine, Université Droit et Santé de Lille, F-59000 Lille, France
- Université d’Artois, F-62800 Liévin, France
| | - Jean-Louis Banères
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5247, Institut des Biomolécules Max Mousseron, Faculty of Pharmacy, Universities of Montpellier 1 and 2, F-34093 Montpellier Cedex 5, France; and
| | - Jean Martinez
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5247, Institut des Biomolécules Max Mousseron, Faculty of Pharmacy, Universities of Montpellier 1 and 2, F-34093 Montpellier Cedex 5, France; and
| | - Pierre-François Méry
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34000 Montpellier, France
- Universities of Montpellier 1 and 2, Unité Mixte de Recherche 5203, F-34000 Montpellier, France
| | | | | | - Jean-Alain Fehrentz
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5247, Institut des Biomolécules Max Mousseron, Faculty of Pharmacy, Universities of Montpellier 1 and 2, F-34093 Montpellier Cedex 5, France; and
| | - Vincent Prévot
- Institut National de la Santé et de la Recherche Médicale, Jean-Pierre Aubert Research Center, Unité 837, F-59000 Lille, France
- Faculté de Médecine, Université Droit et Santé de Lille, F-59000 Lille, France
| | - Patrice Mollard
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
- Institut National de la Santé et de la Recherche Médicale, Unité 661, F-34000 Montpellier, France
- Universities of Montpellier 1 and 2, Unité Mixte de Recherche 5203, F-34000 Montpellier, France
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Ogaya M, Kim J, Sasaki K. Ghrelin postsynaptically depolarizes dorsal raphe neurons in rats in vitro. Peptides 2011; 32:1606-16. [PMID: 21763741 DOI: 10.1016/j.peptides.2011.07.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 07/01/2011] [Accepted: 07/01/2011] [Indexed: 01/03/2023]
Abstract
Ghrelin promotes growth hormone (GH) secretion and feeding. Recent studies further showed that ghrelin displayed a defending effect against the depressive-like symptoms and affected sleep in animals and humans. Serotonergic system is considered to be implicated in feeding, depression and other mood disorders, and sleep. The dorsal raphe nucleus (DRN) utilizes serotonin (5-HT) as its major neurotransmitter and expresses GH secretagogue receptors (GHS-Rs). Therefore, the present study was carried out to examine the electrophysiological effect of ghrelin on rat DRN neurons in vitro and determine the ionic mechanism involved. Whole-cell recording revealed that ghrelin depolarized DRN neurons dose-dependently in tetrodotoxin-containing artificial cerebrospinal fluid (TTX ACSF). Pretreatment with [D-Lys(3)]-GHRP-6, a selective antagonist for GHS-Rs, antagonized the ghrelin-induced depolarization. The depolarization was significantly reduced in a low-Na(+) TTX ACSF and in a high-K(+) TTX ACSF and was abolished in the combination of both ACSFs, suggesting that the ghrelin-induced depolarization is mediated by a dual ionic mechanism including an increase in nonselective cationic conductance and a decrease in K(+) conductance. The experiments on the reversal potential also supported an involvement of the dual ionic mechanism in the ghrelin-induced depolarization. On the basis of their electrophysiological and pharmacological properties, approximately 80% of DRN neurons were classified as putative 5-HT-containing neurons and ghrelin depolarized 75% of them. These results suggest that DRN neurons, especially 5-HT-containing neurons, might be involved in the neural mechanisms through which ghrelin participates in the development and/or regulation of feeding behavior, sleep-wake states and depressive-like symptoms.
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Affiliation(s)
- Masaki Ogaya
- Division of Bio-Information Engineering, Faculty of Engineering, University of Toyama, 3190 Gofuku, Toyama City, Toyama 930-8555, Japan
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Ghrelin inhibits visceral afferent activation of catecholamine neurons in the solitary tract nucleus. J Neurosci 2011; 31:3484-92. [PMID: 21368060 DOI: 10.1523/jneurosci.3187-10.2011] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Brainstem A2/C2 catecholamine (CA) neurons in the solitary tract nucleus (NTS) are thought to play an important role in the control of food intake and other homeostatic functions. We have previously demonstrated that these neurons, which send extensive projections to brain regions involved in the regulation of appetite, are strongly and directly activated by solitary tract (ST) visceral afferents. Ghrelin, a potent orexigenic peptide released from the stomach, is proposed to act in part through modulating NTS CA neurons but the underlying cellular mechanisms are unknown. Here, we identified CA neurons using transgenic mice that express enhanced green fluorescent protein driven by the tyrosine hydroxylase promoter (TH-EGFP). We then determined how ghrelin modulates TH-EGFP neurons using patch-clamp techniques in a horizontal brain slice preparation. Ghrelin inhibited the frequency of spontaneous glutamate inputs (spontaneous EPSCs) onto TH-EGFP neurons, including cholecystokinin-sensitive neurons, an effect blocked by the GHSR1 antagonist, d-Lys-3-GHRP-6. This resulted in a decrease in the basal firing rate of NTS TH-EGFP neurons, an effect blocked by the glutamate antagonist NBQX. Ghrelin also dose-dependently inhibited the amplitude of ST afferent evoked EPSCs (ST-EPSCs) in TH-EGFP NTS neurons, decreasing the success rate for ST-evoked action potentials. In addition, ghrelin decreased the frequency of mini-EPSCs suggesting its actions are presynaptic to reduce glutamate release. Last, inhibition by ghrelin of the ST-EPSCs was significantly increased by an 18 h fast. These results demonstrate a potential mechanism by which ghrelin inhibits NTS TH neurons through a pathway whose responsiveness is increased during fasting.
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Abstract
The growing worldwide obesity epidemic and obesity-related disorders present a huge unmet medical need for safe and effective anti-obesity medications. The discovery of leptin in 1994 was rapidly succeeded by a wave of related discoveries leading to the elaboration of a hypothalamic melanocortinergic neuronal circuit regulated by leptin and other central and peripheral signaling molecules to control energy homeostasis. The identification of specific neuronal subtypes along with their unique connections and expression products generated a rich target menu for anti-obesity drug discovery programs. Over the course of the last decade, several new chemical entities aimed at these targets have reached various stages or successfully completed the drug discovery/regulatory process only to be dropped or taken off the market. There are now in fact fewer options for anti-obesity drug therapies in late 2010 than were available in 2000. The challenge to discover safe and effective anti-obesity drugs is alive and well.
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Affiliation(s)
| | - Robert George MacKenzie
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-313-577-0677; Fax: +1-313-577-9469
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Fetissov SO, Laviano A, Kalra S, Inui A. Update on ghrelin. INTERNATIONAL JOURNAL OF PEPTIDES 2010; 2010:963501. [PMID: 20798849 PMCID: PMC2925383 DOI: 10.1155/2010/963501] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 04/14/2010] [Indexed: 12/18/2022]
Affiliation(s)
- Sergueï O. Fetissov
- Digestive System and Nutrition Laboratory (ADEN EA4311), Biomedical Research Institute, IFR23, Rouen 76183, France
| | | | - Satya Kalra
- Department of Neuroscience, McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL 32611, USA
| | - Akio Inui
- Department of Behavioral Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima 890-8520, Japan
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