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Wang Q, Liu C, Uchida A, Chuang JC, Walker A, Liu T, Osborne-Lawrence S, Mason BL, Mosher C, Berglund ED, Elmquist JK, Zigman JM. Arcuate AgRP neurons mediate orexigenic and glucoregulatory actions of ghrelin. Mol Metab 2013; 3:64-72. [PMID: 24567905 PMCID: PMC3929914 DOI: 10.1016/j.molmet.2013.10.001] [Citation(s) in RCA: 182] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 10/08/2013] [Accepted: 10/08/2013] [Indexed: 12/21/2022] Open
Abstract
The hormone ghrelin stimulates eating and helps maintain blood glucose upon caloric restriction. While previous studies have demonstrated that hypothalamic arcuate AgRP neurons are targets of ghrelin, the overall relevance of ghrelin signaling within intact AgRP neurons is unclear. Here, we tested the functional significance of ghrelin action on AgRP neurons using a new, tamoxifen-inducible AgRP-CreERT2 transgenic mouse model that allows spatiotemporally-controlled re-expression of physiological levels of ghrelin receptors (GHSRs) specifically in AgRP neurons of adult GHSR-null mice that otherwise lack GHSR expression. AgRP neuron-selective GHSR re-expression partially restored the orexigenic response to administered ghrelin and fully restored the lowered blood glucose levels observed upon caloric restriction. The normalizing glucoregulatory effect of AgRP neuron-selective GHSR expression was linked to glucagon rises and hepatic gluconeogenesis induction. Thus, our data indicate that GHSR-containing AgRP neurons are not solely responsible for ghrelin's orexigenic effects but are sufficient to mediate ghrelin's effects on glycemia.
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Key Words
- ARC, arcuate nucleus
- AgRP
- AgRP, Agouti-related peptide
- BAC, bacterial artificial chromosome
- Blood glucose homeostasis
- CNS, central nervous system
- DG, dentate gyrus
- DVC, dorsal vagal complex
- Food intake
- Foxo1, Forkhead box protein O1
- G6p, glucose-6 phosphatase
- GABA, gamma-aminobutyric acid
- GHRH, Growth-hormone-releasing hormone
- GHSR, growth hormone secretagogue receptor, ghrelin receptor
- GOAT, ghrelin O-acyltransferase
- Ghrelin
- Ghrelin receptor
- Hnf4α, hepatocyte nuclear factor 4α
- NAc, nucleus accumbens
- NPY, neuropeptide Y
- POMC, pro-opiomelanocortin
- Pcx, pyruvate carboxylase
- Pepck, phosphoenolpyruvate carboxykinase
- Phox2b, paired-like homeobox 2b
- VGAT, vesicular GABA transporter
- VTA, ventral tegmental area
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Affiliation(s)
- Qian Wang
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Chen Liu
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Aki Uchida
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jen-Chieh Chuang
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Angela Walker
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Tiemin Liu
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sherri Osborne-Lawrence
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Brittany L Mason
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Christina Mosher
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Eric D Berglund
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Joel K Elmquist
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jeffrey M Zigman
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Division of Endocrinology and Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA ; Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA
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202
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Mason BL, Wang Q, Zigman JM. The central nervous system sites mediating the orexigenic actions of ghrelin. Annu Rev Physiol 2013; 76:519-33. [PMID: 24111557 DOI: 10.1146/annurev-physiol-021113-170310] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The peptide hormone ghrelin is important for both homeostatic and hedonic eating behaviors, and its orexigenic actions occur mainly via binding to the only known ghrelin receptor, the growth hormone secretagogue receptor (GHSR). GHSRs are located in several distinct regions of the central nervous system. This review discusses those central nervous system sites that have been found to play critical roles in the orexigenic actions of ghrelin, including hypothalamic nuclei, the hippocampus, the amygdala, the caudal brain stem, and midbrain dopaminergic neurons. Hopefully, this review can be used as a stepping stone for the reader wanting to gain a clearer understanding of the central nervous system sites of direct ghrelin action on feeding behavior, and as inspiration for future studies to provide an even-more-detailed map of the neurocircuitry controlling eating and body weight.
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Affiliation(s)
- B L Mason
- Departments of Internal Medicine (Divisions of Hypothalamic Research and of Endocrinology & Metabolism) and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9077; , ,
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203
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Abstract
Many questions must be considered with regard to consuming food, including when to eat, what to eat and how much to eat. Although eating is often thought to be a homeostatic behaviour, little evidence exists to suggest that eating is an automatic response to an acute shortage of energy. Instead, food intake can be considered as an integrated response over a prolonged period of time that maintains the levels of energy stored in adipocytes. When we eat is generally determined by habit, convenience or opportunity rather than need, and meals are preceded by a neurally-controlled coordinated secretion of numerous hormones that prime the digestive system for the anticipated caloric load. How much we eat is determined by satiation hormones that are secreted in response to ingested nutrients, and these signals are in turn modified by adiposity hormones that indicate the fat content of the body. In addition, many nonhomeostatic factors, including stress, learning, palatability and social influences, interact with other controllers of food intake. If a choice of food is available, what we eat is based on pleasure and past experience. This article reviews the hormones that mediate and influence these processes.
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Affiliation(s)
- Denovan P Begg
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, 2170 East Galbraith Road, Cincinnati, OH 45237, USA
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204
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Cabral A, Fernandez G, Perello M. Analysis of brain nuclei accessible to ghrelin present in the cerebrospinal fluid. Neuroscience 2013; 253:406-15. [PMID: 24042041 DOI: 10.1016/j.neuroscience.2013.09.008] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 08/21/2013] [Accepted: 09/04/2013] [Indexed: 01/24/2023]
Abstract
Ghrelin is a stomach-derived peptide hormone that acts in the brain to regulate many important physiological functions. Ghrelin receptor, named the growth hormone secretagogue receptor (GHSR), is present in many brain areas with or without obvious direct access to ghrelin circulating in the bloodstream. Ghrelin is also present in the cerebrospinal fluid (CSF) but the brain targets of CSF ghrelin are unclear. Here, we studied which brain areas are accessible to ghrelin present in the CSF. For this purpose, we centrally injected mice with fluorescein-labeled ghrelin (F-ghrelin) peptide tracer and then systematically mapped the distribution of F-ghrelin signal through the brain. Our results indicated that centrally injected F-ghrelin labels neurons in most of the brain areas where GHSR is present. Also, we detected F-ghrelin uptake in the ependymal cells of both wild-type and GHSR-null mice. We conclude that CSF ghrelin is able to reach most of brain areas expressing GHSR. Also, we propose that the accessibility of CSF ghrelin to the brain parenchyma occurs through the ependymal cells in a GHSR-independent manner.
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Affiliation(s)
- A Cabral
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, Argentine Research Council (CONICET) and Scientific Research Commission, La Plata, Province of Buenos Aires (CIC-PBA), Argentina
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205
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Souza-Moreira L, Morell M, Delgado-Maroto V, Pedreño M, Martinez-Escudero L, Caro M, O'Valle F, Luque R, Gallo M, de Lecea L, Castaño JP, Gonzalez-Rey E. Paradoxical effect of cortistatin treatment and its deficiency on experimental autoimmune encephalomyelitis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2013; 191:2144-54. [PMID: 23918980 DOI: 10.4049/jimmunol.1300384] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cortistatin is a cyclic-neuropeptide produced by brain cortex and immune cells that shows potent anti-inflammatory activity. In this article, we investigated the effect of cortistatin in two models of experimental autoimmune encephalomyelitis (EAE) that mirror chronic and relapsing-remitting multiple sclerosis. A short-term systemic treatment with cortistatin reduced clinical severity and incidence of EAE, the appearance of inflammatory infiltrates in spinal cord, and the subsequent demyelination and axonal damage. This effect was associated with a reduction of the two deleterious components of the disease, namely, the autoimmune and inflammatory response. Cortistatin decreased the presence/activation of encephalitogenic Th1 and Th17 cells in periphery and nervous system, and downregulated various inflammatory mediators, whereas it increased the number of regulatory T cells with suppressive effects on the encephalitogenic response. Moreover, cortistatin regulated glial activity and favored an active program of neuroprotection/regeneration. We further used cortistatin-deficient mice to investigate the role of endogenous cortistatin in the control of immune responses. Surprisingly, cortistatin-deficient mice were partially resistant to EAE and other inflammatory disorders, despite showing competent inflammatory/autoreactive responses. This unexpected phenotype was associated with elevated circulating glucocorticoids and an anxiety-like behavior. Our findings provide a powerful rationale for the assessment of the efficacy of cortistatin as a novel multimodal therapeutic approach to treat multiple sclerosis and identify cortistatin as a key endogenous component of neuroimmune system.
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Affiliation(s)
- Luciana Souza-Moreira
- Institute of Parasitology and Biomedicine "López-Neyra," Consejo Superior Investigaciones Cientificas, Granada 18016, Spain
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206
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Smith JT, Reichenbach A, Lemus M, Mani BK, Zigman JM, Andrews ZB. An eGFP-expressing subpopulation of growth hormone secretagogue receptor cells are distinct from kisspeptin, tyrosine hydroxylase, and RFamide-related peptide neurons in mice. Peptides 2013; 47:45-53. [PMID: 23831041 PMCID: PMC3762877 DOI: 10.1016/j.peptides.2013.06.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 06/18/2013] [Accepted: 06/18/2013] [Indexed: 01/26/2023]
Abstract
Ghrelin acts on the growth hormone secretagogue receptor (GHSR) in the brain to elicit changes in physiological functions. It is associated with the neural control of appetite and metabolism, however central ghrelin also affects fertility. Central ghrelin injection in rats suppresses luteinizing hormone (LH) concentrations and pulse frequency. Although ghrelin suppresses LH and regulates kisspeptin mRNA in the anteroventral periventricular/periventricular nucleus (AVPV/PeN), there is no neuroanatomical evidence linking GHSR neural circuits to kisspeptin neurons. In this study, we first determined coexpression of GHSR and GnRH neurons using a GHSR-eGFP reporter mouse line. Using dual-label immunohistochemistry, we saw no coexpression. GHSR-eGFP expressing cells were present in the AVPV/PeN and over 90% of these expressed estrogen receptor-α (ERα). Despite this, we observed no evidence of GHSR-eGFP/kisspeptin coexpressing neurons in the AVPV/PeN. To further examine the phenotype of GHSR-eGFP cells in the AVPV/PeN, we determined coexpression with tyrosine hydroxylase (TH) and showed virtually no coexpression in the AVPV/PeN (<2%). We also observed no coexpression of GHSR-eGFP and RFamide-related peptide-3 (RFRP3) neurons in the dorsomedial hypothalamic nucleus. Importantly, we observed that approximately half of the GHSR-eGFP cells in the AVPV coexpressed Ghsr mRNA (as determined by in situ hybridization) so these data should be interpreted accordingly. Although ghrelin influences the hypothalamic reproductive axis, our data using a GHSR-eGFP reporter suggests ghrelin regulates neurons expressing ERα but does not directly act on GnRH, kisspeptin, TH, or RFRP3 neurons, as little or no GHSR-eGFP coexpression was observed.
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Affiliation(s)
- Jeremy T. Smith
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Australia 6009
- Corresponding authors: Dr Jeremy Smith & Dr Zane B. Andrews: JTS, School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Australia 6009 ; ZBA, Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia 3800; Phone: +61 3 9905 8165; Fax: + 61 3 9905 2547
| | - Alex Reichenbach
- Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia 3800
| | - Moyra Lemus
- Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia 3800
| | - Bharath K. Mani
- Departments of Internal Medicine (Divisions of Hypothalamic Research and of Endocrinology & Metabolism) and Psychiatry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390-9077
| | - Jeffrey M. Zigman
- Departments of Internal Medicine (Divisions of Hypothalamic Research and of Endocrinology & Metabolism) and Psychiatry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390-9077
| | - Zane B. Andrews
- Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia 3800
- Corresponding authors: Dr Jeremy Smith & Dr Zane B. Andrews: JTS, School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Australia 6009 ; ZBA, Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia 3800; Phone: +61 3 9905 8165; Fax: + 61 3 9905 2547
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207
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Schellekens H, Dinan TG, Cryan JF. Taking two to tango: a role for ghrelin receptor heterodimerization in stress and reward. Front Neurosci 2013; 7:148. [PMID: 24009547 PMCID: PMC3757321 DOI: 10.3389/fnins.2013.00148] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 08/01/2013] [Indexed: 12/25/2022] Open
Abstract
The gut hormone, ghrelin, is the only known peripherally derived orexigenic signal. It activates its centrally expressed receptor, the growth hormone secretagogue receptor (GHS-R1a), to stimulate food intake. The ghrelin signaling system has recently been suggested to play a key role at the interface of homeostatic control of appetite and the hedonic aspects of food intake, as a critical role for ghrelin in dopaminergic mesolimbic circuits involved in reward signaling has emerged. Moreover, enhanced plasma ghrelin levels are associated with conditions of physiological stress, which may underline the drive to eat calorie-dense "comfort-foods" and signifies a role for ghrelin in stress-induced food reward behaviors. These complex and diverse functionalities of the ghrelinergic system are not yet fully elucidated and likely involve crosstalk with additional signaling systems. Interestingly, accumulating data over the last few years has shown the GHS-R1a receptor to dimerize with several additional G-protein coupled receptors (GPCRs) involved in appetite signaling and reward, including the GHS-R1b receptor, the melanocortin 3 receptor (MC3), dopamine receptors (D1 and D2), and more recently, the serotonin 2C receptor (5-HT2C). GHS-R1a dimerization was shown to affect downstream signaling and receptor trafficking suggesting a potential novel mechanism for fine-tuning GHS-R1a receptor mediated activity. This review summarizes ghrelin's role in food reward and stress and outlines the GHS-R1a dimer pairs identified to date. In addition, the downstream signaling and potential functional consequences of dimerization of the GHS-R1a receptor in appetite and stress-induced food reward behavior are discussed. The existence of multiple GHS-R1a heterodimers has important consequences for future pharmacotherapies as it significantly increases the pharmacological diversity of the GHS-R1a receptor and has the potential to enhance specificity of novel ghrelin-targeted drugs.
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208
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Patterson ZR, Abizaid A. Stress induced obesity: lessons from rodent models of stress. Front Neurosci 2013; 7:130. [PMID: 23898237 PMCID: PMC3721047 DOI: 10.3389/fnins.2013.00130] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 07/08/2013] [Indexed: 11/15/2022] Open
Abstract
Stress was once defined as the non-specific result of the body to any demand or challenge to homeostasis. A more current view of stress is the behavioral and physiological responses generated in the face of, or in anticipation of, a perceived threat. The stress response involves activation of the sympathetic nervous system and recruitment of the hypothalamic-pituitary-adrenal (HPA) axis. When an organism encounters a stressor (social, physical, etc.), these endogenous stress systems are stimulated in order to generate a fight-or-flight response, and manage the stressful situation. As such, an organism is forced to liberate energy resources in attempt to meet the energetic demands posed by the stressor. A change in the energy homeostatic balance is thus required to exploit an appropriate resource and deliver useable energy to the target muscles and tissues involved in the stress response. Acutely, this change in energy homeostasis and the liberation of energy is considered advantageous, as it is required for the survival of the organism. However, when an organism is subjected to a prolonged stressor, as is the case during chronic stress, a continuous irregularity in energy homeostasis is considered detrimental and may lead to the development of metabolic disturbances such as cardiovascular disease, type II diabetes mellitus and obesity. This concept has been studied extensively using animal models, and the neurobiological underpinnings of stress induced metabolic disorders are beginning to surface. However, different animal models of stress continue to produce divergent metabolic phenotypes wherein some animals become anorexic and lose body mass while others increase food intake and body mass and become vulnerable to the development of metabolic disturbances. It remains unclear exactly what factors associated with stress models can be used to predict the metabolic outcome of the organism. This review will explore a variety of rodent stress models and discuss the elements that influence the metabolic outcome in order to further extend our understanding of stress-induced obesity.
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209
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Uchida A, Zigman JM, Perelló M. Ghrelin and eating behavior: evidence and insights from genetically-modified mouse models. Front Neurosci 2013; 7:121. [PMID: 23882175 PMCID: PMC3712270 DOI: 10.3389/fnins.2013.00121] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 06/25/2013] [Indexed: 01/08/2023] Open
Abstract
Ghrelin is an octanoylated peptide hormone, produced by endocrine cells of the stomach, which acts in the brain to increase food intake and body weight. Our understanding of the mechanisms underlying ghrelin's effects on eating behaviors has been greatly improved by the generation and study of several genetically manipulated mouse models. These models include mice overexpressing ghrelin and also mice with genetic deletion of ghrelin, the ghrelin receptor [the growth hormone secretagogue receptor (GHSR)] or the enzyme that post-translationally modifies ghrelin [ghrelin O-acyltransferase (GOAT)]. In addition, a GHSR-null mouse model in which GHSR transcription is globally blocked but can be cell-specifically reactivated in a Cre recombinase-mediated fashion has been generated. Here, we summarize findings obtained with these genetically manipulated mice, with the aim to highlight the significance of the ghrelin system in the regulation of both homeostatic and hedonic eating, including that occurring in the setting of chronic psychosocial stress.
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Affiliation(s)
- Aki Uchida
- Divisions of Hypothalamic Research and Endocrinology and Metabolism, Department of Medicine, The University of Texas Southwestern Medical Center Dallas, TX, USA ; Department of Psychiatry, The University of Texas Southwestern Medical Center Dallas, TX, USA
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210
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Abstract
The opioid system is well recognized as an important regulator of appetite and energy balance. We now hypothesized that the hypothalamic opioid system might modulate the orexigenic effect of ghrelin. Using pharmacological and gene silencing approaches, we demonstrate that ghrelin utilizes a hypothalamic κ-opioid receptor (KOR) pathway to increase food intake in rats. Pharmacological blockade of KOR decreases the acute orexigenic effect of ghrelin. Inhibition of KOR expression in the hypothalamic arcuate nucleus is sufficient to blunt ghrelin-induced food intake. By contrast, the specific inhibition of KOR expression in the ventral tegmental area does not affect central ghrelin-induced feeding. This new pathway is independent of ghrelin-induced AMP-activated protein kinase activation, but modulates the levels of the transcription factors and orexigenic neuropeptides triggered by ghrelin to finally stimulate feeding. Our novel data implicate hypothalamic KOR signaling in the orexigenic action of ghrelin.
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211
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Stress as a common risk factor for obesity and addiction. Biol Psychiatry 2013; 73:827-35. [PMID: 23541000 PMCID: PMC3658316 DOI: 10.1016/j.biopsych.2013.01.032] [Citation(s) in RCA: 354] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 01/23/2013] [Accepted: 01/26/2013] [Indexed: 11/23/2022]
Abstract
Stress is associated with obesity, and the neurobiology of stress overlaps significantly with that of appetite and energy regulation. This review will discuss stress, allostasis, the neurobiology of stress and its overlap with neural regulation of appetite, and energy homeostasis. Stress is a key risk factor in the development of addiction and in addiction relapse. High levels of stress changes eating patterns and augments consumption of highly palatable (HP) foods, which in turn increases incentive salience of HP foods and allostatic load. The neurobiological mechanisms by which stress affects reward pathways to potentiate motivation and consumption of HP foods as well as addictive drugs is discussed. With enhanced incentive salience of HP foods and overconsumption of these foods, there are adaptations in stress and reward circuits that promote stress-related and HP food-related motivation as well as concomitant metabolic adaptations, including alterations in glucose metabolism, insulin sensitivity, and other hormones related to energy homeostasis. These metabolic changes in turn might also affect dopaminergic activity to influence food motivation and intake of HP foods. An integrative heuristic model is proposed, wherein repeated high levels of stress alter the biology of stress and appetite/energy regulation, with both components directly affecting neural mechanisms contributing to stress-induced and food cue-induced HP food motivation and engagement in overeating of such foods to enhance risk of weight gain and obesity. Future directions in research are identified to increase understanding of the mechanisms by which stress might increase risk of weight gain and obesity.
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212
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Kenny R, Cai G, Bayliss JA, Clarke M, Choo YL, Miller AA, Andrews ZB, Spencer SJ. Endogenous ghrelin's role in hippocampal neuroprotection after global cerebral ischemia: does endogenous ghrelin protect against global stroke? Am J Physiol Regul Integr Comp Physiol 2013; 304:R980-90. [PMID: 23576609 DOI: 10.1152/ajpregu.00594.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ghrelin is a gastrointestinal hormone with a well-characterized role in feeding and metabolism. Recent evidence suggests that ghrelin may also be neuroprotective after injury in animal models of cerebral ischemia. Thus exogenous ghrelin treatment can improve cell survival, reduce infarct size, and rescue memory deficits in focal ischemia models, doing so by suppressing inflammation and apoptosis. Endogenous ghrelin plays a key a role in a number of physiological processes, including feeding, metabolism, stress, and anxiety. However, no study has examined whether endogenous ghrelin also contributes to neuroprotection after cerebral ischemia. Here, we aimed to determine whether endogenous ghrelin normally protects against neuronal cell death and cognitive impairments after global cerebral ischemia and whether such changes are linked with inflammation or apoptosis. We used a two-vessel occlusion (2VO) model of global cerebral ischemia in wild-type (wt) and ghrelin knockout (ghr-/-) C57/Bl6J mice. ghr-/- mice had improved cell survival in the Cornu Ammonis(CA)-2/3 region of the hippocampus-a region of significant growth hormone secretagogue receptor expression. They also displayed less cellular degeneration than wt mice after the 2VO (Fluoro-Jade) and had less cognitive impairment in the novel object-recognition test. These outcomes were despite evidence of more neuroinflammation and apoptosis in the ghr-/- and less of a postsurgery hypothermia. Finally, we found that mortality in the week following the 2VO was reduced more in ghr-/- mice than in wt. Overall, these experiments point to a neurodegenerative but antiapoptotic effect of endogenous ghrelin in this model of global ischemia, highlighting that further research is essential before we can apply ghrelin treatments to neurodegenerative insults in the clinic.
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Affiliation(s)
- Rachel Kenny
- School of Health Sciences and Health Innovations Research Institute, Royal Melbourne Institute of Technology University, Melbourne, Victoria, Australia
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213
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Characterization of gastric and neuronal histaminergic populations using a transgenic mouse model. PLoS One 2013; 8:e60276. [PMID: 23555941 PMCID: PMC3612060 DOI: 10.1371/journal.pone.0060276] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 02/24/2013] [Indexed: 01/29/2023] Open
Abstract
Histamine is a potent biogenic amine that mediates numerous physiological processes throughout the body, including digestion, sleep, and immunity. It is synthesized by gastric enterochromaffin-like cells, a specific set of hypothalamic neurons, as well as a subset of white blood cells, including mast cells. Much remains to be learned about these varied histamine-producing cell populations. Here, we report the validation of a transgenic mouse line in which Cre recombinase expression has been targeted to cells expressing histidine decarboxylase (HDC), which catalyzes the rate-limiting step in the synthesis of histamine. This was achieved by crossing the HDC-Cre mouse line with Rosa26-tdTomato reporter mice, thus resulting in the expression of the fluorescent Tomato (Tmt) signal in cells containing Cre recombinase activity. As expected, the Tmt signal co-localized with HDC-immunoreactivity within the gastric mucosa and gastric submucosa and also within the tuberomamillary nucleus of the brain. HDC expression within Tmt-positive gastric cells was further confirmed by quantitative PCR analysis of mRNA isolated from highly purified populations of Tmt-positive cells obtained by fluorescent activated cell sorting (FACS). HDC expression within these FACS-separated cells was found to coincide with other markers of both ECL cells and mast cells. Gastrin expression was co-localized with HDC expression in a subset of histaminergic gastric mucosal cells. We suggest that these transgenic mice will facilitate future studies aimed at investigating the function of histamine-producing cells.
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214
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Perello M, Raingo J. Leptin activates oxytocin neurons of the hypothalamic paraventricular nucleus in both control and diet-induced obese rodents. PLoS One 2013; 8:e59625. [PMID: 23527232 PMCID: PMC3601091 DOI: 10.1371/journal.pone.0059625] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 02/15/2013] [Indexed: 12/25/2022] Open
Abstract
The adipocyte-derived hormone leptin acts in the brain to reduce body weight and fat mass. Recent studies suggest that parvocellular oxytocin (OXT) neurons of the hypothalamic paraventricular nucleus (PVN) can mediate body weight reduction through inhibition of food intake and increased energy expenditure. However, the role of OXT neurons of the PVN as a primary target of leptin has not been investigated. Here, we studied the potential role of OXT neurons of the PVN in leptin-mediated effects on body weight regulation in fasted rats. We demonstrated that intracerebroventricular (ICV) leptin activates STAT3 phosphorylation in OXT neurons of the PVN, showed that this occurs in a subpopulation of OXT neurons that innervate the nucleus of the solitary tract (NTS), and provided further evidence suggesting a role of OXT to mediate leptin's actions on body weight. In addition, our results indicated that OXT neurons are responsive to ICV leptin and mediate leptin effects on body weight in diet induced obese (DIO) rats, which are resistant to the anorectic effects of the hormone. Thus, we conclude that leptin targets a specific subpopulation of parvocellular OXT neurons of the PVN, and that this action may be important for leptin's ability to reduce body weight in both control and obese rats.
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Affiliation(s)
- Mario Perello
- Laboratory of Neurophysiology, Argentine Research Council and Scientific Research Commission of the Province of Buenos Aires, La Plata, Buenos Aires, Argentina.
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215
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Patterson ZR, Khazall R, Mackay H, Anisman H, Abizaid A. Central ghrelin signaling mediates the metabolic response of C57BL/6 male mice to chronic social defeat stress. Endocrinology 2013; 154:1080-91. [PMID: 23341196 DOI: 10.1210/en.2012-1834] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Chronic stressors promote metabolic disturbances, including obesity and metabolic syndrome. Ghrelin, a peptide that promotes appetite and the accumulation of adipose tissue, is also secreted in response to stressors to protect the brain and peripheral tissues from the effects of these stressors. Here we demonstrate that elevated ghrelin levels produced by chronic exposure to social stress are associated with increased caloric intake and body weight gain in male C57BL mice. In contrast, stressed mice lacking ghrelin receptors (GHSR KO mice) or C57BL mice receiving chronic intracerebroventricular delivery of the ghrelin receptor antagonist [d-Lys(3)]-GHRP-6 show attenuated weight gain and feeding responses under the same social stress paradigm. Interestingly, stressed GHSR KO mice showed depleted sc and intrascapular brown fat depots, whereas stressed young wild-type mice did not. In old wild-type mice, chronic social defeat increased visceral and intrascapular brown fat depots in association with increases in obesity markers like hyperleptinemia and hyperinsulinemia along with increased hypothalamic expression of neuropeptide Y and Agouti related peptide. Importantly, the elevated expression of these peptides persisted least for 2 weeks after cessation of the stressor regimen. In contrast, old GHSR KO mice did not show these alterations after chronic social defeat. These results suggest that ghrelin plays an important role in the metabolic adaptations necessary to meet the energetic demands posed by stressors, but chronic exposure to stress-induced ghrelin elevations ultimately could lead to long lasting metabolic dysfunctions.
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MESH Headings
- Adipose Tissue, Brown/pathology
- Aging/pathology
- Aging/physiology
- Aging/psychology
- Animals
- Behavior, Animal/physiology
- Energy Intake/physiology
- Ghrelin/antagonists & inhibitors
- Ghrelin/blood
- Ghrelin/physiology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Models, Biological
- Obesity/pathology
- Obesity/physiopathology
- Obesity/psychology
- Receptors, Ghrelin/deficiency
- Receptors, Ghrelin/genetics
- Receptors, Ghrelin/physiology
- Signal Transduction/physiology
- Social Behavior
- Stress, Physiological
- Stress, Psychological
- Weight Gain/physiology
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Affiliation(s)
- Z R Patterson
- Department of Neuroscience, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada
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216
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Briggs DI, Lockie SH, Wu Q, Lemus MB, Stark R, Andrews ZB. Calorie-restricted weight loss reverses high-fat diet-induced ghrelin resistance, which contributes to rebound weight gain in a ghrelin-dependent manner. Endocrinology 2013; 154:709-17. [PMID: 23307790 DOI: 10.1210/en.2012-1421] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Twelve weeks of high-fat diet feeding causes ghrelin resistance in arcuate neuropeptide Y (NPY)/agouti-related protein (AgRP) neurons. In the current study, we investigated whether diet-induced weight loss could restore NPY/AgRP neuronal responsiveness to ghrelin and whether ghrelin mediates rebound weight gain after calorie-restricted (CR) weight loss. Diet-induced obese (DIO) mice were allocated to one of two dietary interventions until they reached the weight of age-matched lean controls. DIO mice received chow diet ad libitum or chow diet with 40% CR. Chow-fed and high-fat-fed mice served as controls. Both dietary interventions normalized body weight, glucose tolerance, and plasma insulin. We show that diet-induced weight loss with CR increases total plasma ghrelin, restores ghrelin sensitivity, and increases hypothalamic NPY and AgRP mRNA expression. We propose that long-term DIO creates a higher body weight set-point and that weight loss induced by CR, as seen in the high-fat CR group, provokes the brain to protect the new higher set-point. This adaptation to weight loss likely contributes to rebound weight gain by increasing peripheral ghrelin concentrations and restoring the function of ghrelin-responsive neuronal populations in the hypothalamic arcuate nucleus. Indeed, we also show that DIO ghrelin-knockout mice exhibit reduced body weight regain after CR weight loss compared with ghrelin wild-type mice, suggesting ghrelin mediates rebound weight gain after CR weight loss.
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Affiliation(s)
- Dana I Briggs
- Department of Physiology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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217
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Kenny S, Gamble J, Lyons S, Vlatkovic N, Dimaline R, Varro A, Dockray GJ. Gastric expression of plasminogen activator inhibitor (PAI)-1 is associated with hyperphagia and obesity in mice. Endocrinology 2013; 154:718-26. [PMID: 23254194 PMCID: PMC3724960 DOI: 10.1210/en.2012-1913] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The adipokine plasminogen activator inhibitor (PAI)-1 is increased in plasma of obese individuals and exhibits increased expression in the stomachs of individuals infected with Helicobacter. To investigate the relevance of gastric PAI-1, we used 1.1 kb of the H(+)/K(+)β subunit promoter to overexpress PAI-1 specifically in mouse gastric parietal cells (PAI-1-H/Kβ mice). We studied the physiological, biochemical, and behavioral characteristics of these and mice null for PAI-1 or a putative receptor, urokinase plasminogen activator receptor (uPAR). PAI-1-H/Kβ mice had increased plasma concentrations of PAI-1 and increased body mass, adiposity, and hyperphagia compared with wild-type mice. In the latter, food intake was inhibited by cholecystokinin (CCK)8s, but PAI-1-H/Kβ mice were insensitive to the satiating effects of CCK8s. PAI-1-H/Kβ mice also had significantly reduced expression of c-fos in the nucleus tractus solitarius in response to CCK8s and refeeding compared with wild-type mice. Exogenous PAI-1 reversed the effects of CCK8s on food intake and c-fos levels in the nucleus tractus solitarius of wild-type mice, but not uPAR-null mice. Infection of C57BL/6 mice with Helicobacter felis increased gastric abundance of PAI-1 and reduced the satiating effects of CCK8s, whereas the response to CCK8s was maintained in infected PAI-1-null mice. In cultured vagal afferent neurons, PAI-1 inhibited stimulation of neuropeptide Y type 2 receptor (Y2R) expression by CCK8s. Thus, gastric expression of PAI-1 is associated with hyperphagia, moderate obesity, and resistance to the satiating effects of CCK indicating a new role in suppressing signals from the upper gut that inhibit food intake.
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Affiliation(s)
- Susan Kenny
- Departments of Cell and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, United Kingdom
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218
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Kumar J, Chuang JC, Na ES, Kuperman A, Gillman AG, Mukherjee S, Zigman JM, McClung CA, Lutter M. Differential effects of chronic social stress and fluoxetine on meal patterns in mice. Appetite 2013; 64:81-8. [PMID: 23318656 DOI: 10.1016/j.appet.2012.12.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Revised: 11/09/2012] [Accepted: 12/14/2012] [Indexed: 01/03/2023]
Abstract
Both chronic stress and antidepressant medications have been associated with changes in body weight. In the current study, we investigate mechanisms by which stress and antidepressants interact to affect meal patterns. A group of mice was subjected to the chronic social defeat stress model of major depression followed by fluoxetine treatment and was subsequently analyzed for food intake using metabolic cages. We report that chronic social defeat stress increases food intake by specifically increasing meal size, an effect that is reversed by fluoxetine treatment. In an attempt to gain mechanistic insight into changes in meal patterning induced by stress and fluoxetine, fasting serum samples were collected every 4h over a 24-h period, and acyl-ghrelin, leptin, and corticosterone levels were measured. Chronic stress induces a peak in acyl-ghrelin levels just prior to the onset of the dark phase, which is shifted in mice treated with fluoxetine. Taken together, these results indicate that stress increases food intake by decreasing satiation, and that fluoxetine can reverse stress-induced changes in meal patterns.
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Affiliation(s)
- Jaswinder Kumar
- Department of Psychiatry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9070, USA.
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219
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Geliebter A, Carnell S, Gluck ME. Cortisol and ghrelin concentrations following a cold pressor stress test in overweight individuals with and without night eating. Int J Obes (Lond) 2012; 37:1104-8. [PMID: 23247680 PMCID: PMC3610846 DOI: 10.1038/ijo.2012.166] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 06/28/2012] [Accepted: 08/29/2012] [Indexed: 11/09/2022]
Abstract
OBJECTIVE To explore appetite-related hormones following stress in overweight individuals, and their relationship with night eating (NE) status. METHOD We measured plasma cortisol and ghrelin concentrations, and recorded ratings of stress and hunger in response to a physiological laboratory stressor (cold pressor test, CPT), in overweight women with (n=11; NE) and without (n=17; non-NE) NE. RESULTS Following the CPT, cortisol (P<0.001) and ghrelin (P<0.05) levels increased, as did stress and hunger ratings (all P<0.001), across all subjects (NE and non-NE). NE exhibited higher baseline cortisol (P<0.05) levels than non-NE. NE also had greater cortisol area under the curve (AUC) than non-NE (P=0.019), but not when controlling for baseline cortisol levels. Ghrelin baseline and AUC did not differ between groups. NE showed higher AUC stress (P<0.05), even when controlling for baseline stress. DISCUSSION Overweight individuals showed increased cortisol, ghrelin, stress and hunger following a laboratory stressor, and there was some evidence for greater increases in cortisol and subjective stress among NE. The greater AUC cortisol level in NE was due to higher baseline levels, but the group difference in stress was in direct response to the stressor. Our results support a role for cortisol and stress in NE.
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Affiliation(s)
- A Geliebter
- New York Obesity Nutrition Research Center, Department of Medicine, St Luke's-Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons, New York, NY, USA.
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220
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Hansson C, Shirazi RH, Näslund J, Vogel H, Neuber C, Holm G, Anckarsäter H, Dickson SL, Eriksson E, Skibicka KP. Ghrelin influences novelty seeking behavior in rodents and men. PLoS One 2012; 7:e50409. [PMID: 23227170 PMCID: PMC3515575 DOI: 10.1371/journal.pone.0050409] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 10/19/2012] [Indexed: 12/13/2022] Open
Abstract
Recent discoveries indicate an important role for ghrelin in drug and alcohol reward and an ability of ghrelin to regulate mesolimbic dopamine activity. The role of dopamine in novelty seeking, and the association between this trait and drug and alcohol abuse, led us to hypothesize that ghrelin may influence novelty seeking behavior. To test this possibility we applied several complementary rodent models of novelty seeking behavior, i.e. inescapable novelty-induced locomotor activity (NILA), novelty-induced place preference and novel object exploration, in rats subjected to acute ghrelin receptor (growth hormone secretagogue receptor; GHSR) stimulation or blockade. Furthermore we assessed the possible association between polymorphisms in the genes encoding ghrelin and GHSR and novelty seeking behavior in humans. The rodent studies indicate an important role for ghrelin in a wide range of novelty seeking behaviors. Ghrelin-injected rats exhibited a higher preference for a novel environment and increased novel object exploration. Conversely, those with GHSR blockade drastically reduced their preference for a novel environment and displayed decreased NILA. Importantly, the mesolimbic ventral tegmental area selective GHSR blockade was sufficient to reduce the NILA response indicating that the mesolimbic GHSRs might play an important role in the observed novelty responses. Moreover, in untreated animals, a striking positive correlation between NILA and sucrose reward behavior was detected. Two GHSR single nucleotide polymorphisms (SNPs), rs2948694 and rs495225, were significantly associated with the personality trait novelty seeking, as assessed using the Temperament and Character Inventory (TCI), in human subjects. This study provides the first evidence for a role of ghrelin in novelty seeking behavior in animals and humans, and also points to an association between food reward and novelty seeking in rodents.
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Affiliation(s)
- Caroline Hansson
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
- Department of Clinical and Molecular Medicine, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Rozita H. Shirazi
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Jakob Näslund
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Heike Vogel
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Corinna Neuber
- Department of Clinical and Molecular Medicine, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Göran Holm
- Department of Metabolism and Cardiovascular Disease, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Henrik Anckarsäter
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Suzanne L. Dickson
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Elias Eriksson
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Karolina P. Skibicka
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
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221
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Dockray GJ. Making sense of gut-brain signals. Clin Med (Lond) 2012. [DOI: 10.7861/clinmedicine.12-6-s80] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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222
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Abstract
Research into the control of energy balance has tended to focus on discrete brain regions, such as the brainstem, medulla, arcuate nucleus of the hypothalamus, and neocortex. Recently, a larger picture has begun to emerge in which the coordinated communication between these areas is proving to be critical to appropriate regulation of metabolism. By serving as a center for such communication, the paraventricular nucleus of the hypothalamus (PVH) is perhaps the most important brain nucleus regulating the physiological response to energetic challenges. Here we review recent advances in the understanding of the circuitry and function of the PVH.
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Affiliation(s)
- Jennifer W. Hill
- Department of Physiology and Pharmacology, Center for Diabetes and Endocrine Research, University of Toledo Medical Center, Obstetrics-Gynecology, University of Toledo, USA
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223
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Abstract
Peptide hormones are released from the gastrointestinal tract in response to nutrients and communicate information regarding the current state of energy balance to the brain. These hormones regulate appetite, energy expenditure and glucose homeostasis. They can act either via the circulation at target peripheral tissues, by activation of the vagus nerve or by acting on key brain regions implicated in energy homeostasis such as the hypothalamus and brainstem. This review gives an overview of the main gut hormones implicated in the regulation of food intake and how some of these are being targeted to develop anti obesity treatments.
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Affiliation(s)
- Gavin A Bewick
- Section of Investigative Medicine, Imperial College London, London, United Kingdom.
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224
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Reichenbach A, Steyn FJ, Sleeman MW, Andrews ZB. Ghrelin receptor expression and colocalization with anterior pituitary hormones using a GHSR-GFP mouse line. Endocrinology 2012; 153:5452-66. [PMID: 22962259 DOI: 10.1210/en.2012-1622] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ghrelin is the endogenous ligand for the GH secretagogue receptor (GHSR) and robustly stimulates GH release from the anterior pituitary gland. Ghrelin also regulates the secretion of anterior pituitary hormones including TSH, LH, prolactin (PRL), and ACTH. However, the relative contribution of a direct action at the GHSR in the anterior pituitary gland vs. an indirect action at the GHSR in the hypothalamus remains undefined. We used a novel GHSR-enhanced green fluorescent protein (eGFP) reporter mouse to quantify GHSR coexpression with GH, TSH, LH, PRL, and ACTH anterior pituitary cells in males vs. females and in chow-fed or calorie-restricted (CR) mice. GHSR-eGFP-expressing cells were only observed in anterior pituitary. The number of GHSR-eGFP-expressing cells was higher in male compared with females, and CR did not affect the GHSR-eGFP cell number. Double staining revealed 77% of somatotrophs expressed GHSR-eGFP in both males and females. Nineteen percent and 12.6% of corticotrophs, 21% and 9% of lactotrophs, 18% and 19% of gonadotrophs, and 3% and 9% of males and females, respectively, expressed GHSR-eGFP. CR increased the number of TSH cells, but suppressed the number of lactotrophs and gonadotrophs, expressing GHSR-eGFP compared with controls. These studies support a robust stimulatory action of ghrelin via the GHSR on GH secretion and identify a previously unknown sexual dimorphism in the GHSR expression in the anterior pituitary. CR affects GHSR-eGFP expression on lactotrophs, gonadotrophs, and thyrotrophs, which may mediate reproductive function and energy metabolism during periods of negative energy balance. The low to moderate expression of GHSR-eGFP suggests that ghrelin plays a minor direct role on remaining anterior pituitary cells.
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Affiliation(s)
- Alex Reichenbach
- Department of Physiology, Monash University, Clayton, Victoria, Australia
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225
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Walker AK, Ibia IE, Zigman JM. Disruption of cue-potentiated feeding in mice with blocked ghrelin signaling. Physiol Behav 2012; 108:34-43. [PMID: 23063723 DOI: 10.1016/j.physbeh.2012.10.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Accepted: 10/04/2012] [Indexed: 12/22/2022]
Abstract
The peptide hormone ghrelin regulates a variety of eating behaviors. Not only does it potently increase intake of freely-available food, but it also shifts food preference toward diets rich in fat, enhances operant responding for food rewards, and induces conditioned place preference for food rewards. Here, we postulated that ghrelin also enables cue-potentiated feeding, in which eating is enhanced upon presentation of a food-conditioned stimulus. To test this hypothesis, a novel cue-potentiated feeding protocol adapted for use in mice was designed and validated, and then the effects of pharmacologic ghrelin receptor (GHSR) antagonism and GHSR transcriptional blockade (as occurs in GHSR-null mice) were assessed. Sated C57BL/6J mice indeed demonstrated cue-potentiated intake of grain-based pellets specifically upon presentation of a positive conditioned stimulus (CS+) but not a negative conditioned stimulus (CS-). Treatment with a GHSR antagonist blocked potentiated feeding in sated C57BL/6J mice in response to the CS+. In contrast, while GHSR-null mice also lacked a potentiation of feeding specifically in response to the CS+, they displayed an enhanced intake of pellets in response to both the positive and negative conditioned stimuli. The pattern of immediate early gene expression within the basolateral amygdala - a brain region previously linked to cue-potentiated feeding - paralleled the observed behavior of these mice, suggesting uncharacteristic activation of the amygdala in response to negative conditioned stimuli in GHSR-null mice as compared to wild-type littermates. Thus, although the observed disruptions in cue-potentiated feeding are different depending upon whether GHSR activity or GHSR expression is blocked, a key role for GHSRs in establishing a specific positive cue-food association has now been established.
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Affiliation(s)
- Angela K Walker
- Department of Internal Medicine (Divisions of Hypothalamic Research and of Endocrinology & Metabolism), The University of Texas Southwestern Medical Center, Dallas, TX 75390-9077, United States
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226
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Ghrelin regulates the hypothalamic-pituitary-adrenal axis and restricts anxiety after acute stress. Biol Psychiatry 2012; 72:457-65. [PMID: 22521145 DOI: 10.1016/j.biopsych.2012.03.010] [Citation(s) in RCA: 169] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 03/05/2012] [Accepted: 03/05/2012] [Indexed: 12/17/2022]
Abstract
BACKGROUND Ghrelin plays important roles in glucose metabolism, appetite, and body weight regulation, and recent evidence suggests ghrelin prevents excessive anxiety under conditions of chronic stress. METHODS We used ghrelin knockout (ghr-/-) mice to examine the role of endogenous ghrelin in anxious behavior and hypothalamic-pituitary-adrenal axis (HPA) responses to acute stress. RESULTS Ghr-/- mice are more anxious after acute restraint stress, compared with wild-type (WT) mice, with three independent behavioral tests. Acute restraint stress exacerbated neuronal activation in the hypothalamic paraventricular nucleus and medial nucleus of the amygdala in ghr-/- mice compared with WT, and exogenous ghrelin reversed this effect. Acute stress increased neuronal activation in the centrally projecting Edinger-Westphal nucleus in WT but not ghr-/- mice. Ghr-/- mice exhibited a lower corticosterone response after stress, suggesting dysfunctional glucocorticoid negative feedback in the absence of ghrelin. We found no differences in dexamethasone-induced Fos expression between ghr-/- and WT mice, suggesting central feedback was not impaired. Adrenocorticotropic hormone replacement elevated plasma corticosterone in ghr-/-, compared with WT mice, indicating increased adrenal sensitivity. The adrenocorticotropic hormone response to acute stress was significantly reduced in ghr-/- mice, compared with control subjects. Pro-opiomelanocortin anterior pituitary cells express significant growth hormone secretagogue receptor. CONCLUSIONS Ghrelin reduces anxiety after acute stress by stimulating the HPA axis at the level of the anterior pituitary. A novel neuronal growth hormone secretagogue receptor circuit involving urocortin 1 neurons in the centrally projecting Edinger-Westphal nucleus promotes an appropriate stress response. Thus, ghrelin regulates acute stress and offers potential therapeutic efficacy in human mood and stress disorders.
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227
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Els S, Schild E, Petersen PS, Kilian TM, Mokrosinski J, Frimurer TM, Chollet C, Schwartz TW, Holst B, Beck-Sickinger AG. An aromatic region to induce a switch between agonism and inverse agonism at the ghrelin receptor. J Med Chem 2012; 55:7437-49. [PMID: 22920150 DOI: 10.1021/jm300414b] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The ghrelin receptor displays a high constitutive activity suggested to be involved in the regulation of appetite and food intake. Here, we have created peptides with small changes in the core binding motif -wFw- of the hexapeptide KwFwLL-NH(2) that can swap the peptide behavior from inverse agonism to agonism, indicating the importance of this sequence. Introduction of β-(3-benzothienyl)-d-alanine (d-Bth), 3,3-diphenyl-d-alanine (d-Dip) and 1-naphthyl-d-alanine (d-1-Nal) at position 2 resulted in highly potent and efficient inverse agonists, whereas the substitution of d-tryptophane at position 4 with 1-naphthyl-d-alanine (d-1-Nal) and 2-naphthyl-d-alanine (d-2-Nal) induces agonism in functional assays. Competitive binding studies showed a high affinity of the inverse agonist K-(d-1-Nal)-FwLL-NH(2) at the ghrelin receptor. Moreover, mutagenesis studies of the receptor revealed key positions for the switch between inverse agonist and agonist response. Hence, only minor changes in the peptide sequence can decide between agonism and inverse agonism and have a major impact on the biological activity.
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Affiliation(s)
- Sylvia Els
- Institute of Biochemistry, Universität Leipzig, Brüderstraße 34, 04103 Leipzig, Germany
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228
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Perelló M, Zigman JM. The role of ghrelin in reward-based eating. Biol Psychiatry 2012; 72:347-53. [PMID: 22458951 PMCID: PMC3388148 DOI: 10.1016/j.biopsych.2012.02.016] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 02/03/2012] [Accepted: 02/17/2012] [Indexed: 01/18/2023]
Abstract
The peptide hormone ghrelin acts in the central nervous system as a potent orexigenic signal. Not only is ghrelin recognized as playing an important role in feeding circuits traditionally thought of as affecting body weight homeostasis, but also an accumulating number of scientific studies have identified ghrelin as being a key regulator of reward-based, hedonic eating behaviors. In the current article, we review ghrelin's orexigenic actions, the evidence linking ghrelin to food reward behavior, potential mechanisms by which ghrelin mediates reward-based eating behavior, and those studies suggesting an obligatory role for ghrelin in the changed eating behaviors induced by stress.
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Affiliation(s)
- Mario Perelló
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology (IMBICE-CONICET/CICPBA), Calle 526 s/n entre 10 y 11, La Plata, Buenos Aires, Argentina 1900
| | - Jeffrey M. Zigman
- Department of Internal Medicine (Divisions of Hypothalamic Research and of Endocrinology & Metabolism), The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390-9077,Department of Psychiatry, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390-9077
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229
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Tremblay F, Huard C, Dow J, Gareski T, Will S, Richard AM, Syed J, Bailey S, Brenneman KA, Martinez RV, Perreault M, Lin Q, Gimeno RE. Loss of coiled-coil domain containing 80 negatively modulates glucose homeostasis in diet-induced obese mice. Endocrinology 2012; 153:4290-303. [PMID: 22753645 DOI: 10.1210/en.2012-1242] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Coiled-coil domain containing 80 (Ccdc80) is a secreted protein highly enriched in mouse and human white adipose tissue (WAT) that plays an important role during adipocyte differentiation in vitro. To investigate the physiological function of Ccdc80 in energy and glucose homeostasis, we generated mice in which the gene encoding Ccdc80 was disrupted. Mice lacking Ccdc80 showed increased sensitivity to diet-induced hyperglycemia and glucose intolerance while displaying reduced glucose-stimulated insulin secretion in vivo. Gene expression analysis by microarray revealed that only 10 transcripts were simultaneously altered in pancreas, skeletal muscle, and WAT from Ccdc80(-/-) mice, including some components of the circadian clock. Expression of the core clock member Arntl/Bmal1 was reduced whereas that of the oscillating transcription factors Dbp and Tef was increased in all tissues examined. Furthermore, knockdown of Ccdc80 in 3T3-L1 cells led to an increase of Dbp mRNA levels during adipocyte differentiation, suggesting that Ccdc80 might be involved in the regulation of this gene in a cell-autonomous manner. Importantly, transcriptional alterations in Ccdc80(-/-) mice were associated with changes in feeding behavior, increased caloric intake, decreased energy expenditure, and obesity. Taken together, our results suggest that Ccdc80 is a novel modulator of glucose and energy homeostasis during diet-induced obesity.
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Affiliation(s)
- Frédéric Tremblay
- Centers for Therapeutic Innovation, Pfizer Inc., 3 Blackfan Circle, Boston, Massachusetts 02115, USA.
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230
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Scott MM, Perello M, Chuang JC, Sakata I, Gautron L, Lee CE, Lauzon D, Elmquist JK, Zigman JM. Hindbrain ghrelin receptor signaling is sufficient to maintain fasting glucose. PLoS One 2012; 7:e44089. [PMID: 22952883 PMCID: PMC3432098 DOI: 10.1371/journal.pone.0044089] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 08/01/2012] [Indexed: 11/19/2022] Open
Abstract
The neuronal coordination of metabolic homeostasis requires the integration of hormonal signals with multiple interrelated central neuronal circuits to produce appropriate levels of food intake, energy expenditure and fuel availability. Ghrelin, a peripherally produced peptide hormone, circulates at high concentrations during nutrient scarcity. Ghrelin promotes food intake, an action lost in ghrelin receptor null mice and also helps maintain fasting blood glucose levels, ensuring an adequate supply of nutrients to the central nervous system. To better understand mechanisms of ghrelin action, we have examined the roles of ghrelin receptor (GHSR) expression in the mouse hindbrain. Notably, selective hindbrain ghrelin receptor expression was not sufficient to restore ghrelin-stimulated food intake. In contrast, the lowered fasting blood glucose levels observed in ghrelin receptor-deficient mice were returned to wild-type levels by selective re-expression of the ghrelin receptor in the hindbrain. Our results demonstrate the distributed nature of the neurons mediating ghrelin action.
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Affiliation(s)
- Michael M. Scott
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Mario Perello
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Jen-Chieh Chuang
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Ichiro Sakata
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Laurent Gautron
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Charlotte E. Lee
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Danielle Lauzon
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Joel K. Elmquist
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Division of Endocrinology & Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Department of Psychiatry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Department of Pharmacology, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- * E-mail: (JKE); (JMZ)
| | - Jeffrey M. Zigman
- Division of Hypothalamic Research, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Division of Endocrinology & Metabolism, Department of Internal Medicine, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- Department of Psychiatry, The University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
- * E-mail: (JKE); (JMZ)
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231
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Schellekens H, Finger BC, Dinan TG, Cryan JF. Ghrelin signalling and obesity: at the interface of stress, mood and food reward. Pharmacol Ther 2012; 135:316-26. [PMID: 22749794 DOI: 10.1016/j.pharmthera.2012.06.004] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 06/07/2012] [Indexed: 12/14/2022]
Abstract
The neuronal circuitry underlying the complex relationship between stress, mood and food intake are slowly being unravelled and several studies suggest a key role herein for the peripherally derived hormone, ghrelin. Evidence is accumulating linking obesity as an environmental risk factor to psychiatric disorders such as stress, anxiety and depression. Ghrelin is the only known orexigenic hormone from the periphery to stimulate food intake. Plasma ghrelin levels are enhanced under conditions of physiological stress and ghrelin has recently been suggested to play an important role in stress-induced food reward behaviour. In addition, chronic stress or atypical depression has often demonstrated to correlate with an increase in ingestion of caloric dense 'comfort foods' and have been implicated as one of the major contributor to the increased prevalence of obesity. Recent evidence suggests ghrelin as a critical factor at the interface of homeostatic control of appetite and reward circuitries, modulating the hedonic aspects of food intake. Therefore, the reward-related feeding of ghrelin may reveal itself as an important factor in the development of addiction to certain foods, similar to its involvement in the dependence to drugs of abuse, including alcohol. This review will highlight the accumulating evidence demonstrating the close interaction between food, mood and stress and the development of obesity. We consider the ghrelinergic system as an effective target for the development of successful anti-obesity pharmacotherapies, which not only affects appetite but also selectively modulates the rewarding properties of food and impact on psychological well-being in conditions of stress, anxiety and depression.
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232
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Hussain SS, Bloom SR. The regulation of food intake by the gut-brain axis: implications for obesity. Int J Obes (Lond) 2012; 37:625-33. [PMID: 22710925 DOI: 10.1038/ijo.2012.93] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Our understanding of the regulation of appetite has improved considerably over the last few decades. Recent work, stimulated by efforts aimed at curbing the current obesity epidemic, has unravelled some of the complex pathways regulating energy homeostasis. Key factors to this progress have been the discovery of leptin and the neuronal circuitry involved in mediating its effects, as well as the identification of gut hormones that have important physiological roles relating to energy homeostasis. Despite these advances in research, there are currently no effective treatments for the growing problem of obesity. In this article, we summarise the regulatory pathways controlling appetite with a special focus on gut hormones. We detail how recent findings have contributed to our knowledge regarding the pathogenesis and treatment of common obesity. A number of barriers still need to be overcome to develop safe and effective anti-obesity treatments. We outline problems highlighted by historical failures and discuss the potential of augmenting natural satiety signals, such as gut hormones, to treat obesity.
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Affiliation(s)
- S S Hussain
- Department of Diabetes, Endocrinology and Metabolism, Hammersmith Hospital, Imperial College London, London, UK
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233
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Tomiyama AJ, Schamarek I, Lustig RH, Kirschbaum C, Puterman E, Havel PJ, Epel ES. Leptin concentrations in response to acute stress predict subsequent intake of comfort foods. Physiol Behav 2012; 107:34-9. [PMID: 22579988 DOI: 10.1016/j.physbeh.2012.04.021] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 04/03/2012] [Accepted: 04/24/2012] [Indexed: 01/07/2023]
Abstract
Both animals and humans show a tendency toward eating more "comfort food" (high fat, sweet food) after acute stress. Such stress eating may be contributing to the obesity epidemic, and it is important to understand the underlying psychobiological mechanisms. Prior investigations have studied what makes individuals eat more after stress; this study investigates what might make individuals eat less. Leptin has been shown to increase following a laboratory stressor, and is known to regulate satiety. This study examined whether leptin reactivity accounts for individual differences in stress eating. To test this, we exposed forty women to standardized acute psychological laboratory stress (Trier Social Stress Test) while blood was sampled repeatedly for measurements of plasma leptin. We then measured food intake after the stressor. Increasing leptin during the stressor predicted lower intake of comfort food. These initial findings suggest that acute changes in leptin may be one of the factors modulating down the consumption of comfort food following stress.
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234
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Rosini TC, da Silva ASR, Moraes CD. Obesidade induzida por consumo de dieta: modelo em roedores para o estudo dos distúrbios relacionados com a obesidade. Rev Assoc Med Bras (1992) 2012. [DOI: 10.1590/s0104-42302012000300021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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235
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Diet-induced obesity: rodent model for the study of obesity-related disorders. Rev Assoc Med Bras (1992) 2012. [DOI: 10.1016/s0104-4230(12)70211-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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236
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Sakata I, Park WM, Walker AK, Piper PK, Chuang JC, Osborne-Lawrence S, Zigman JM. Glucose-mediated control of ghrelin release from primary cultures of gastric mucosal cells. Am J Physiol Endocrinol Metab 2012; 302:E1300-10. [PMID: 22414807 PMCID: PMC3361986 DOI: 10.1152/ajpendo.00041.2012] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The peptide hormone ghrelin is released from a distinct group of gastrointestinal cells in response to caloric restriction, whereas its levels fall after eating. The mechanisms by which ghrelin secretion is regulated remain largely unknown. Here, we have used primary cultures of mouse gastric mucosal cells to investigate ghrelin secretion, with an emphasis on the role of glucose. Ghrelin secretion from these cells upon exposure to different d-glucose concentrations, the glucose antimetabolite 2-deoxy-d-glucose, and other potential secretagogues was assessed. The expression profile of proteins involved in glucose transport, metabolism, and utilization within highly enriched pools of mouse ghrelin cells and within cultured ghrelinoma cells was also determined. Ghrelin release negatively correlated with d-glucose concentration. Insulin blocked ghrelin release, but only in a low d-glucose environment. 2-Deoxy-d-glucose prevented the inhibitory effect of high d-glucose exposure on ghrelin release. mRNAs encoding several facilitative glucose transporters, hexokinases, the ATP-sensitive potassium channel subunit Kir6.2, and sulfonylurea type 1 receptor were expressed highly within ghrelin cells, although neither tolbutamide nor diazoxide exerted direct effects on ghrelin secretion. These findings suggest that direct exposure of ghrelin cells to low ambient d-glucose stimulates ghrelin release, whereas high d-glucose and glucose metabolism within ghrelin cells block ghrelin release. Also, low d-glucose sensitizes ghrelin cells to insulin. Various glucose transporters, channels, and enzymes that mediate glucose responsiveness in other cell types may contribute to the ghrelin cell machinery involved in regulating ghrelin secretion under these different glucose environments, although their exact roles in ghrelin release remain uncertain.
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Affiliation(s)
- Ichiro Sakata
- Division of Hypothalamic Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9077, USA
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237
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Maniam J, Morris MJ. The link between stress and feeding behaviour. Neuropharmacology 2012; 63:97-110. [PMID: 22710442 DOI: 10.1016/j.neuropharm.2012.04.017] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 04/11/2012] [Accepted: 04/20/2012] [Indexed: 02/06/2023]
Abstract
Exposure to stress is inevitable, and it may occur, to varying degrees, at different phases throughout the lifespan. The impact of stress experienced in later life has been well documented as many populations in modern society experience increasing socio-economic demands. The effects of stress early in life are less well known, partly as the impact of an early exposure may be difficult to quantify, however emerging evidence shows it can impact later in life. One of the major impacts of stress besides changes in psychosocial behaviour is altered feeding responses. The system that regulates stress responses, the hypothalamo-pituitary-adrenal axis, also regulates feeding responses because the neural circuits that regulate food intake converge on the paraventricular nucleus, which contains corticotrophin releasing hormone (CRH), and urocortin containing neurons. In other words the systems that control food intake and stress responses share the same anatomy and thus each system can influence each other in eliciting a response. Stress is known to alter feeding responses in a bidirectional pattern, with both increases and decreases in intake observed. Stress-induced bidirectional feeding responses underline the complex mechanisms and multiple contributing factors, including the levels of glucocorticoids (dependent on the severity of a stressor), the interaction between glucocorticoids and feeding related neuropeptides such as neuropeptide Y (NPY), alpha-melanocyte stimulating hormone (α-MSH), agouti-related protein (AgRP), melanocortins and their receptors, CRH, urocortin and peripheral signals (leptin, insulin and ghrelin). This review discusses the neuropeptides that regulate feeding behaviour and how their function can be altered through cross-talk with hormones and neuropeptides that also regulate the hypothalamo-pituitary-adrenal axis. In addition, long-term stress induced alterations in feeding behaviour, and changes in gene expression of neuropeptides regulating stress and food intake through epigenetic modifications will be discussed. This article is part of a Special Issue entitled 'SI: Central Control of Food Intake'.
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Affiliation(s)
- Jayanthi Maniam
- Pharmacology, School of Medical Sciences, University of New South Wales, Sydney NSW 2052, Australia
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238
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Coppari R. Metabolic actions of hypothalamic SIRT1. Trends Endocrinol Metab 2012; 23:179-85. [PMID: 22382036 PMCID: PMC3312933 DOI: 10.1016/j.tem.2012.01.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 01/19/2012] [Accepted: 01/23/2012] [Indexed: 11/16/2022]
Abstract
The hypothalamus is a small structure located in the ventral diencephalon. Hypothalamic neurons sense changes in circulating metabolic cues (e.g. leptin, insulin, glucose), and coordinate responses aimed at maintaining normal body weight and glucose homeostasis. Recent findings indicate that a nicotinamide adenine dinucleotide (NAD(+))-dependent protein deacetylase (namely SIRT1) expressed by hypothalamic neurons is crucial for mounting responses against diet-induced obesity and type 2 diabetes mellitus (T2DM). Here, the repercussions of these findings will be discussed and particular emphasis will be given to the potential exploitation of hypothalamic SIRT1 as a target for the treatment of the rapidly-spreading metabolic disorders of obesity and T2DM. The possible roles of hypothalamic SIRT1 in regulating metabolic ageing processes will also be addressed.
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Affiliation(s)
- Roberto Coppari
- Department of Internal Medicine, Division of Hypothalamic Research, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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239
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Cabral A, Suescun O, Zigman JM, Perello M. Ghrelin indirectly activates hypophysiotropic CRF neurons in rodents. PLoS One 2012; 7:e31462. [PMID: 22363652 PMCID: PMC3282735 DOI: 10.1371/journal.pone.0031462] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 01/08/2012] [Indexed: 01/30/2023] Open
Abstract
Ghrelin is a stomach-derived hormone that regulates food intake and neuroendocrine function by acting on its receptor, GHSR (Growth Hormone Secretagogue Receptor). Recent evidence indicates that a key function of ghrelin is to signal stress to the brain. It has been suggested that one of the potential stress-related ghrelin targets is the CRF (Corticotropin-Releasing Factor)-producing neurons of the hypothalamic paraventricular nucleus, which secrete the CRF neuropeptide into the median eminence and activate the hypothalamic-pituitary-adrenal axis. However, the neural circuits that mediate the ghrelin-induced activation of this neuroendocrine axis are mostly uncharacterized. In the current study, we characterized in vivo the mechanism by which ghrelin activates the hypophysiotropic CRF neurons in mice. We found that peripheral or intra-cerebro-ventricular administration of ghrelin strongly activates c-fos – a marker of cellular activation – in CRF-producing neurons. Also, ghrelin activates CRF gene expression in the paraventricular nucleus of the hypothalamus and the hypothalamic-pituitary-adrenal axis at peripheral level. Ghrelin administration directly into the paraventricular nucleus of the hypothalamus also induces c-fos within the CRF-producing neurons and the hypothalamic-pituitary-adrenal axis, without any significant effect on the food intake. Interestingly, dual-label immunohistochemical analysis and ghrelin binding studies failed to show GHSR expression in CRF neurons. Thus, we conclude that ghrelin activates hypophysiotropic CRF neurons, albeit indirectly.
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Affiliation(s)
- Agustina Cabral
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), La Plata, Buenos Aires, Argentina
| | - Olga Suescun
- Laboratory of Reproductive Endocrinology, Multidisciplinary Institute of Cell Biology, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), La Plata, Buenos Aires, Argentina
| | - Jeffrey M. Zigman
- Divisions of Hypothalamic Research and Endocrinology and Metabolism, Department of Medicine, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Mario Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), La Plata, Buenos Aires, Argentina
- * E-mail:
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240
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Stengel A, Taché Y. Ghrelin - a pleiotropic hormone secreted from endocrine x/a-like cells of the stomach. Front Neurosci 2012; 6:24. [PMID: 22355282 PMCID: PMC3280431 DOI: 10.3389/fnins.2012.00024] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Accepted: 01/29/2012] [Indexed: 12/13/2022] Open
Abstract
The gastric X/A-like endocrine cell receives growing attention due to its peptide products with ghrelin being the best characterized. This peptide hormone was identified a decade ago as a stimulator of food intake and to date remains the only known peripherally produced and centrally acting orexigenic hormone. In addition, subsequent studies identified numerous other functions of this peptide including the stimulation of gastrointestinal motility, the maintenance of energy homeostasis and an impact on reproduction. Moreover, ghrelin is also involved in the response to stress and assumed to play a role in coping functions and exert a modulatory action on immune pathways. Our knowledge on the regulation of ghrelin has markedly advanced during the past years by the identification of the ghrelin acylating enzyme, ghrelin-O-acyltransferase, and by the description of changes in expression, activation, and release under different metabolic as well as physically and psychically challenging conditions. However, our insight on regulatory processes of ghrelin at the cellular and subcellular levels is still very limited and warrants further investigation.
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Affiliation(s)
- Andreas Stengel
- Division Psychosomatic Medicine and Psychotherapy, Department of Medicine, Charité - Universitätsmedizin Berlin Berlin, Germany
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241
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Ladenheim EE. Gastrointestinal regulatory peptides and central nervous system mechanisms of weight control. Curr Opin Endocrinol Diabetes Obes 2012; 19:13-8. [PMID: 22157396 DOI: 10.1097/med.0b013e32834ea723] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE OF REVIEW This review focuses on recent advances in understanding the multiple roles of gastrointestinal peptides in the control of food intake and body weight with specific emphasis on ghrelin, amylin and glucagon-like peptide 1. RECENT FINDINGS Recent studies support a role for ghrelin, amylin and glucagon-like peptide 1 in short-term and long-term effects on food intake and body weight. Apart from contributing to energy homeostasis, ghrelin's participation in reward and sensory processing has been the focus of much recent work. New findings on amylin's effects on food intake and energy balance provide further support for its role in meal-related food intake and suggest that it may also function as an adiposity signal. New investigations on the role of central and peripheral glucagon-like peptide 1 receptors in mediating the anorexic effects of glucagon-like peptide 1 have suggested that they differentially contribute to short-term and long term effects on food intake. SUMMARY Gastrointestinal peptides can influence food intake through mechanisms that involve short-term meal-related effects or through activation of central pathways involved in energy balance. An appreciation of the multiple actions of gastrointestinal peptides on food intake will aid in developing new strategies for weight management.
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Affiliation(s)
- Ellen E Ladenheim
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
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242
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Sam AH, Troke RC, Tan TM, Bewick GA. The role of the gut/brain axis in modulating food intake. Neuropharmacology 2011; 63:46-56. [PMID: 22037149 DOI: 10.1016/j.neuropharm.2011.10.008] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 09/28/2011] [Accepted: 10/13/2011] [Indexed: 12/12/2022]
Abstract
Peptide hormones released from the gastrointestinal tract communicate information about the current state of energy balance to the brain. These hormones regulate appetite and energy expenditure via the vagus nerve or by acting on key brain regions implicated in energy homeostasis such as the hypothalamus and brainstem. This review gives an overview of the main gut hormones implicated in the regulation of food intake. Research in this area has provided novel targets for the pharmacological treatment of obesity. This article is part of a Special Issue entitled 'Central Control Food Intake'
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Affiliation(s)
- Amir H Sam
- Section of Investigative Medicine, Imperial College London, London W12 0NN, UK
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243
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Furness JB, Hunne B, Matsuda N, Yin L, Russo D, Kato I, Fujimiya M, Patterson M, McLeod J, Andrews ZB, Bron R. Investigation of the presence of ghrelin in the central nervous system of the rat and mouse. Neuroscience 2011; 193:1-9. [PMID: 21835225 DOI: 10.1016/j.neuroscience.2011.07.063] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 07/25/2011] [Accepted: 07/25/2011] [Indexed: 11/25/2022]
Abstract
Ghrelin and ghrelin receptor agonist have effects on central neurons in many locations, including the hypothalamus, caudal brain stem, and spinal cord. However, descriptions of the distributions of ghrelin-like immunoreactivity in the CNS in published work are inconsistent. We have used three well-characterized anti-ghrelin antibodies, an antibody to the unacylated form of ghrelin, and a ghrelin peptide assay in rats, mice, ghrelin knockout mice, and ghrelin receptor reporter mice to re-evaluate ghrelin presence in the rodent CNS. The stomach served as a positive control. All antibodies were effective in revealing gastric endocrine cells. However, no specific staining could be found in the brain or spinal cord. Concentrations of antibody 10 to 30 times those effective in the stomach bound to nerve cells in rat and mouse brain, but this binding was not reduced by absorbing concentrations of ghrelin peptide, or by use of ghrelin gene knockout mice. Concentrations of ghrelin-like peptide, detected by enzyme-linked immunosorbent assay in extracts of hypothalamus, were 1% of gastric concentrations. Ghrelin receptor-expressing neurons had no adjacent ghrelin immunoreactive terminals. It is concluded that there are insignificant amounts of authentic ghrelin in neurons in the mouse or rat CNS and that ghrelin receptor-expressing neurons do not receive synaptic inputs from ghrelin-immunoreactive nerve terminals in these species.
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Affiliation(s)
- J B Furness
- Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
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244
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Abstract
Food and stress are powerful modulators of the body-mind connection, which is imbalanced in obese individuals. Why do we choose chocolate over an apple when overworked and stressed, and why does comfort food make us feel better? Two independent studies in the JCI, one in this issue, home in on the role of stress on gut hormones and food choices and, conversely, on the effect of the intestinal system on modulation of brain activity by sadness. These studies broaden our understanding of the ties between food and mood and underscore promising targets for obesity treatments.
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