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Dos-Santos RC, Reis LC, Perello M, Ferguson AV, Mecawi AS. The actions of ghrelin in the paraventricular nucleus: energy balance and neuroendocrine implications. Ann N Y Acad Sci 2019; 1455:81-97. [PMID: 31008525 DOI: 10.1111/nyas.14087] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 02/28/2019] [Accepted: 03/10/2019] [Indexed: 12/15/2022]
Abstract
Ghrelin is a peptide mainly produced and secreted by the stomach. Since its discovery, the impact of ghrelin on the regulation of food intake has been the most studied function of this hormone; however, ghrelin affects a wide range of physiological systems, many of which are controlled by the hypothalamic paraventricular nucleus (PVN). Several pathways may mediate the effects of ghrelin on PVN neurons, such as direct or indirect effects mediated by circumventricular organs and/or the arcuate nucleus. The ghrelin receptor is expressed in PVN neurons, and the peripheral or intracerebroventricular administration of ghrelin affects PVN neuronal activity. Intra-PVN application of ghrelin increases food intake and decreases fat oxidation, which chronically contribute to the increased adiposity. Additionally, ghrelin modulates the neuroendocrine axes controlled by the PVN, increasing the release of vasopressin and oxytocin by magnocellular neurons and corticotropin-releasing hormone by neuroendocrine parvocellular neurons, while possibly inhibiting the release of thyrotropin-releasing hormone. Thus, the PVN is an important target for the actions of ghrelin. Our review discusses the mechanisms of ghrelin actions in the PVN, and its potential implications for energy balance, neuroendocrine, and integrative physiological control.
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Affiliation(s)
- Raoni C Dos-Santos
- Department of Physiological Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Luís C Reis
- Department of Physiological Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil
| | - Mario Perello
- Laboratory of Neurophysiology, Multidisciplinary Institute of Cell Biology, La Plata, Argentina
| | - Alastair V Ferguson
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - André S Mecawi
- Laboratory of Neuroendocrinology, Department of Biophysics, Paulista Medical School, Federal University of São Paulo, São Paulo, Brazil
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Vázquez-Borrego MC, Gahete MD, Martínez-Fuentes AJ, Fuentes-Fayos AC, Castaño JP, Kineman RD, Luque RM. Multiple signaling pathways convey central and peripheral signals to regulate pituitary function: Lessons from human and non-human primate models. Mol Cell Endocrinol 2018; 463:4-22. [PMID: 29253530 DOI: 10.1016/j.mce.2017.12.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 12/14/2017] [Accepted: 12/14/2017] [Indexed: 12/12/2022]
Abstract
The anterior pituitary gland is a key organ involved in the control of multiple physiological functions including growth, reproduction, metabolism and stress. These functions are controlled by five distinct hormone-producing pituitary cell types that produce growth hormone (somatotropes), prolactin (lactotropes), adrenocorticotropin (corticotropes), thyrotropin (thyrotropes) and follicle stimulating hormone/luteinizing hormone (gonadotropes). Classically, the synthesis and release of pituitary hormones was thought to be primarily regulated by central (neuroendocrine) signals. However, it is now becoming apparent that factors produced by pituitary hormone targets (endocrine and non-endocrine organs) can feedback directly to the pituitary to adjust pituitary hormone synthesis and release. Therefore, pituitary cells serve as sensors to integrate central and peripheral signals in order to fine-tune whole-body homeostasis, although it is clear that pituitary cell regulation is species-, age- and sex-dependent. The purpose of this review is to provide a comprehensive, general overview of our current knowledge of both central and peripheral regulators of pituitary cell function and associated intracellular mechanisms, focusing on human and non-human primates.
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Affiliation(s)
- M C Vázquez-Borrego
- Maimonides Institute of Biomedical Research of Cordoba (IMIBIC), 14004 Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, 14004 Cordoba, Spain; Reina Sofia University Hospital (HURS), 14004 Cordoba, Spain; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 14004 Cordoba, Spain; Agrifood Campus of International Excellence (ceiA3), 14004 Cordoba, Spain
| | - M D Gahete
- Maimonides Institute of Biomedical Research of Cordoba (IMIBIC), 14004 Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, 14004 Cordoba, Spain; Reina Sofia University Hospital (HURS), 14004 Cordoba, Spain; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 14004 Cordoba, Spain; Agrifood Campus of International Excellence (ceiA3), 14004 Cordoba, Spain
| | - A J Martínez-Fuentes
- Maimonides Institute of Biomedical Research of Cordoba (IMIBIC), 14004 Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, 14004 Cordoba, Spain; Reina Sofia University Hospital (HURS), 14004 Cordoba, Spain; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 14004 Cordoba, Spain; Agrifood Campus of International Excellence (ceiA3), 14004 Cordoba, Spain
| | - A C Fuentes-Fayos
- Maimonides Institute of Biomedical Research of Cordoba (IMIBIC), 14004 Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, 14004 Cordoba, Spain; Reina Sofia University Hospital (HURS), 14004 Cordoba, Spain; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 14004 Cordoba, Spain; Agrifood Campus of International Excellence (ceiA3), 14004 Cordoba, Spain
| | - J P Castaño
- Maimonides Institute of Biomedical Research of Cordoba (IMIBIC), 14004 Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, 14004 Cordoba, Spain; Reina Sofia University Hospital (HURS), 14004 Cordoba, Spain; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 14004 Cordoba, Spain; Agrifood Campus of International Excellence (ceiA3), 14004 Cordoba, Spain
| | - R D Kineman
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA; Jesse Brown Veterans Affairs Medical Center, Research and Development Division, Chicago, IL, USA
| | - R M Luque
- Maimonides Institute of Biomedical Research of Cordoba (IMIBIC), 14004 Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, 14004 Cordoba, Spain; Reina Sofia University Hospital (HURS), 14004 Cordoba, Spain; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 14004 Cordoba, Spain; Agrifood Campus of International Excellence (ceiA3), 14004 Cordoba, Spain.
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Ghrelin Actions on Somatotropic and Gonadotropic Function in Humans. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 138:3-25. [PMID: 26940384 DOI: 10.1016/bs.pmbts.2015.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ghrelin, a 28 amino-acid octanoylated peptide predominantly produced by the stomach, was discovered to be the natural ligand of the type 1a GH secretagogue receptor (GHS-R1a). It was thus considered as a natural GHS additional to GHRH, although later on ghrelin has mostly been considered a major orexigenic factor. The GH-releasing action of ghrelin takes place both directly on pituitary cells and through modulation of GHRH from the hypothalamus; some functional antisomatostatin action has also been shown. However, ghrelin is much more than a natural GH secretagogue. In fact, it also modulates lactotroph and corticotroph secretion in humans as well as in animals and plays a relevant role in the modulation of the hypothalamic-pituitary-gonadal function. Several studies have indicated that ghrelin plays an inhibitory effect on gonadotropin pulsatility, is involved in the regulation of puberty onset in animals, and may regulate spermatogenesis, follicular development and ovarian cell functions in humans. In this chapter ghrelin actions on the GH/IGF-I and the gonadal axes will be revised. The potential therapeutic role of ghrelin as a treatment of catabolic conditions will also be discussed.
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Johnson L, Manzardo AM, Miller JL, Driscoll DJ, Butler MG. Elevated plasma oxytocin levels in children with Prader-Willi syndrome compared with healthy unrelated siblings. Am J Med Genet A 2015; 170:594-601. [PMID: 26615966 DOI: 10.1002/ajmg.a.37488] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/05/2015] [Indexed: 11/07/2022]
Abstract
Prader-Willi syndrome (PWS) is a rare genetic disorder associated with distinct abnormal behaviors including hyperphagia, profound social deficits, and obsessive-compulsive tendencies. PWS males showed reduced oxytocin receptor (OTR) gene expression and density in the hypothalamic paraventricular nucleus that may play a role in PWS psychopathology. Oxytocin is an anorexigenic neuropeptide similar to vasopressin that is associated with social cognition and obsessive-compulsive behavior. To evaluate oxytocin biology in PWS, we examined overnight fasting plasma oxytocin levels in 23 children with PWS (mean ± SD age: 8.2 ± 2.0 year) having genetic confirmation and 18 age matched healthy unrelated siblings without PWS (mean ± SD age: 8.2 ± 2.3 year) and a similar gender ratio under the same clinical assessments, specimen processing and laboratory conditions. Multiplex immune assays were carried out using the Milliplex Human Neuropeptide Magnetic panel and the Luminex system. Natural log-transformed oxytocin levels were analyzed using general linear model adjusting for diagnosis, gender, age and body mass index (BMI). Oxytocin plasma levels were significantly elevated in children with PWS (168 ± 121 pg/ml) compared with unrelated and unaffected siblings without the diagnosis of PWS (64.8 ± 83.8 pg/ml, F = 8.8, P < 0.01) and the diagnosis of PWS predicted oxytocin level (F = 9.5, P < 0.003) in controlled regression analysis with an overall model fit R(2) = 0.33 (P < 0.01). The symptoms of hyperphagia, anxiety and repetitive behaviors classically seen in PWS may be related to the disruption of oxytocin responsivity or feedback in the hypothalamic paraventricular nucleus possibly influencing vasopressin signaling. Further study is needed to characterize oxytocin function in PWS.
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Affiliation(s)
- Lisa Johnson
- Departments of Psychiatry and Behavioral Sciences and Pediatrics, University of Kansas Medical Center, Kansas City, Kansas
| | - Ann M Manzardo
- Departments of Psychiatry and Behavioral Sciences and Pediatrics, University of Kansas Medical Center, Kansas City, Kansas
| | - Jennifer L Miller
- Department of Pediatrics, University of Florida Medical Center, Gainesville, Florida
| | - Daniel J Driscoll
- Department of Pediatrics, University of Florida Medical Center, Gainesville, Florida
| | - Merlin G Butler
- Departments of Psychiatry and Behavioral Sciences and Pediatrics, University of Kansas Medical Center, Kansas City, Kansas
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Ibrahim Abdalla MM. Ghrelin - Physiological Functions and Regulation. EUROPEAN ENDOCRINOLOGY 2015; 11:90-95. [PMID: 29632576 DOI: 10.17925/ee.2015.11.02.90] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/13/2015] [Indexed: 01/01/2023]
Abstract
Ghrelin is an orexigenic peptide predominantly secreted from the stomach and stimulates appetite and growth hormone (GH) release. Studies have provided evidence that ghrelin exercises a wide range of functions, including regulation of food intake and energy metabolism, modulation of cardiovascular function, stimulation of osteoblast proliferation and bone formation and stimulation of neurogenesis and myogenesis. In the gastrointestinal system, ghrelin affects multiple functions, including secretion of gastric acid, gastric motility and pancreatic protein output. Most of these functions have been attributed to the actions of acylated ghrelin. The balance among its secretion rate, degradation rate and clearance rate determines the circulating level of ghrelin. This review explains what ghrelin is, its physiological functions and the factors that influence its level.
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Gahete MD, Rincón-Fernández D, Villa-Osaba A, Hormaechea-Agulla D, Ibáñez-Costa A, Martínez-Fuentes AJ, Gracia-Navarro F, Castaño JP, Luque RM. Ghrelin gene products, receptors, and GOAT enzyme: biological and pathophysiological insight. J Endocrinol 2014; 220:R1-24. [PMID: 24194510 DOI: 10.1530/joe-13-0391] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ghrelin is a 28-amino acid acylated hormone, highly expressed in the stomach, which binds to its cognate receptor (GHSR1a) to regulate a plethora of relevant biological processes, including food intake, energy balance, hormonal secretions, learning, inflammation, etc. However, ghrelin is, in fact, the most notorious component of a complex, intricate regulatory system comprised of a growing number of alternative peptides (e.g. obestatin, unacylated ghrelin, and In1-ghrelin, etc.), known (GHSRs) and, necessarily unknown receptors, as well as modifying enzymes (e.g. ghrelin-O-acyl-transferase), which interact among them as well as with other regulatory systems in order to tightly modulate key (patho)-physiological processes. This multiplicity of functions and versatility of the ghrelin system arise from a dual, genetic and functional, complexity. Importantly, a growing body of evidence suggests that dysregulation in some of the components of the ghrelin system can lead to or influence the development and/or progression of highly concerning pathologies such as endocrine-related tumors, inflammatory/cardiovascular diseases, and neurodegeneration, wherein these altered components could be used as diagnostic, prognostic, or therapeutic targets. In this context, the aim of this review is to integrate and comprehensively analyze the multiple components and functions of the ghrelin system described to date in order to define and understand its biological and (patho)-physiological significance.
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Affiliation(s)
- Manuel D Gahete
- Department of Cell Biology, Physiology and Immunology, Campus Universitario de Rabanales, Edificio Severo Ochoa (C6), Planta 3, University of Córdoba, 14014-Córdoba; Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), University of Córdoba; Reina Sofia University Hospital, Córdoba; and CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Córdoba, Spain
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Roh SG, Koiwa K, Sato K, Ohtani Y, Takahashi T, Katoh K. Actions of intravenous injections of AVP and oxytocin on plasma ACTH, GH, insulin and glucagon concentrations in goats. Anim Sci J 2013; 85:286-92. [DOI: 10.1111/asj.12142] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/23/2013] [Indexed: 12/17/2022]
Affiliation(s)
- Sang-gun Roh
- Laboratory of Animal Physiology; Graduate School of Agricultural Science; Tohoku University; Sendai Japan
| | - Kohta Koiwa
- Laboratory of Animal Physiology; Graduate School of Agricultural Science; Tohoku University; Sendai Japan
| | - Katsuyoshi Sato
- Laboratory of Animal Physiology; Graduate School of Agricultural Science; Tohoku University; Sendai Japan
| | | | | | - Kazuo Katoh
- Laboratory of Animal Physiology; Graduate School of Agricultural Science; Tohoku University; Sendai Japan
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Garin MC, Burns CM, Kaul S, Cappola AR. Clinical review: The human experience with ghrelin administration. J Clin Endocrinol Metab 2013; 98:1826-37. [PMID: 23533240 PMCID: PMC3644599 DOI: 10.1210/jc.2012-4247] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
CONTEXT Ghrelin is an endogenous stimulator of GH and is implicated in a number of physiological processes. Clinical trials have been performed in a variety of patient populations, but there is no comprehensive review of the beneficial and adverse consequences of ghrelin administration to humans. EVIDENCE ACQUISITION PubMed was utilized, and the reference list of each article was screened. We included 121 published articles in which ghrelin was administered to humans. EVIDENCE SYNTHESIS Ghrelin has been administered as an infusion or a bolus in a variety of doses to 1850 study participants, including healthy participants and patients with obesity, prior gastrectomy, cancer, pituitary disease, diabetes mellitus, eating disorders, and other conditions. There is strong evidence that ghrelin stimulates appetite and increases circulating GH, ACTH, cortisol, prolactin, and glucose across varied patient populations. There is a paucity of evidence regarding the effects of ghrelin on LH, FSH, TSH, insulin, lipolysis, body composition, cardiac function, pulmonary function, the vasculature, and sleep. Adverse effects occurred in 20% of participants, with a predominance of flushing and gastric rumbles and a mild degree of severity. The few serious adverse events occurred in patients with advanced illness and were not clearly attributable to ghrelin. Route of administration may affect the pattern of adverse effects. CONCLUSIONS Existing literature supports the short-term safety of ghrelin administration and its efficacy as an appetite stimulant in diverse patient populations. There is some evidence to suggest that ghrelin has wider ranging therapeutic effects, although these areas require further investigation.
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Affiliation(s)
- Margaret C Garin
- Division of Endocrinology, Diabetes, and Metabolism, Perelman School of Medicine at the University of Pennsylvania, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104-5160, USA
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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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