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Rathore M, Das N, Ghosh N, Guha R. Insights on discovery, efficacy, safety and clinical applications of ghrelin receptor agonist capromorelin in veterinary medicine. Vet Res Commun 2024; 48:1-10. [PMID: 37493940 DOI: 10.1007/s11259-023-10184-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 07/20/2023] [Indexed: 07/27/2023]
Abstract
Growth hormone and insulin like growth factor-1 plays an important role in the regulation of body composition and metabolism. Growth Hormone is released from the pituitary through a specific G-protein coupled receptor (GPCR) called growth hormone secretagogue receptor 1a expressed in the hypothalamus. Ghrelin is a peptide hormone released from the cells in the stomach, which stimulates appetite and food intake in mammals, regulates gut motility, gastric acid secretion, taste sensation, circadian rhythm, learning and memory, oxidative stress, autophagy, glucose metabolism etc. When the release of the endogenous ligand GHSR-1a, i.e., ghrelin is malfunctioned or stopped, external substitutes are administrated to induce the stimulation of growth hormone and appetite. A class of compound known as ghrelin receptor agonists are developed as an external substitute of ghrelin for regulation and stimulation of growth hormone in frailty, for body weight gain, muscle mass gain, prevention of cachexia and for the treatment of chronic fatigue syndromes. Capromorelin [Entyce™ (Aratana Therapeutics, Leawood, KS, USA)] is the only FDA (Food and Drug Administration) approved (May 2016) drug used for stimulating appetite in dogs and was marketed in the fall of 2017. In 2020, USFDA approved Capromorelin [Elura™ (Elanco US Inc.)] for the management of weight loss in chronic kidney disease of cats. This article reviews the discovery of the ghrelin receptor agonist capromorelin, its efficacy, safety, clinical applications and aims to delineate its further scope of use in veterinary practice.
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Affiliation(s)
- Manisha Rathore
- Laboratory Animal Facility, CSIR-Central Drug Research Institute, Lucknow, India
| | - Nabanita Das
- National Institute of Pharmaceutical Education and Research, Raebareli, India
| | - Nayan Ghosh
- Division of Medicinal and Process Chemistry, CSIR-Central Drug Research Institute, Lucknow, India
| | - Rajdeep Guha
- Laboratory Animal Facility, CSIR-Central Drug Research Institute, Lucknow, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India.
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2
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"A LEAP 2 conclusions? Targeting the ghrelin system to treat obesity and diabetes". Mol Metab 2020; 46:101128. [PMID: 33246141 PMCID: PMC8085568 DOI: 10.1016/j.molmet.2020.101128] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 11/15/2020] [Accepted: 11/20/2020] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND The hormone ghrelin stimulates food intake, promotes adiposity, increases body weight, and elevates blood glucose. Consequently, alterations in plasma ghrelin levels and the functioning of other components of the broader ghrelin system have been proposed as potential contributors to obesity and diabetes. Furthermore, targeting the ghrelin system has been proposed as a novel therapeutic strategy for obesity and diabetes. SCOPE OF REVIEW The current review focuses on the potential for targeting ghrelin and other proteins comprising the ghrelin system as a treatment for obesity and diabetes. The main components of the ghrelin system are introduced. Data supporting a role for the endogenous ghrelin system in the development of obesity and diabetes along with data that seemingly refute such a role are outlined. An argument for further research into the development of ghrelin system-targeted therapeutic agents is delineated. Also, an evidence-based discussion of potential factors and contexts that might influence the efficacy of this class of therapeutics is provided. MAJOR CONCLUSIONS It would not be a "leap to" conclusions to suggest that agents which target the ghrelin system - including those that lower acyl-ghrelin levels, raise LEAP2 levels, block GHSR activity, and/or raise desacyl-ghrelin signaling - could represent efficacious novel treatments for obesity and diabetes.
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Sinha DK, Balasubramanian A, Tatem AJ, Rivera-Mirabal J, Yu J, Kovac J, Pastuszak AW, Lipshultz LI. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Transl Androl Urol 2020; 9:S149-S159. [PMID: 32257855 PMCID: PMC7108996 DOI: 10.21037/tau.2019.11.30] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Male hypogonadism is an increasingly prevalent clinical condition that affects patients’ quality of life and overall health. Obesity and metabolic syndrome can both cause and result from hypogonadism. Although testosterone remains the gold standard for hypogonadism management, its benefits are not always conserved across different populations, especially with regards to changes in body composition. Partially in response to this, growth hormone secretagogues (GHS) have emerged as a potential novel adjunctive therapy for some of the symptoms of hypogonadism, although current data on their clinical efficacy largely remain lacking. The present review examines the existing literature on the use of GHS and explores their potential complementary role in the management of hypogonadal and eugonadal males with metabolic syndrome or subclinical hypogonadism (SH). The GHS that will be discussed include sermorelin, growth hormone-releasing peptides (GHRP)-2, GHRP-6, ibutamoren, and ipamorelin. All are potent GH and IGF-1 stimulators that can significantly improve body composition while ameliorating specific hypogonadal symptoms including fat gain and muscular atrophy. However, a paucity of data examining the clinical effects of these compounds currently limits our understanding of GHS’ role in the treatment of men with hypogonadism, but does open opportunities for future investigation.
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Affiliation(s)
| | | | | | | | - Justin Yu
- Baylor College of Medicine, Houston, TX, USA
| | - Jason Kovac
- Men's Health Center, Urology of Indiana, Greenwood, IN, USA
| | - Alexander W Pastuszak
- Division of Urology, Department of Surgery, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Larry I Lipshultz
- Scott Department of Urology, Baylor College of Medicine, Houston, TX, USA.,Center for Reproductive Medicine, Baylor College of Medicine, Houston, TX, USA
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Lee J, Kwon A, Chae HW, Lee WJ, Kim TH, Kim HS. Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats. Yonsei Med J 2018; 59:1174-1180. [PMID: 30450851 PMCID: PMC6240568 DOI: 10.3349/ymj.2018.59.10.1174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 09/20/2018] [Accepted: 09/21/2018] [Indexed: 11/27/2022] Open
Abstract
PURPOSE Growth hormone secretagogues (GHSs) possess the ability to release growth hormone (GH) in the body. This study aimed to investigate the effects of MK-677, an orally active GHS, on somatic growth in rats. MATERIALS AND METHODS The serum levels of GH were measured after oral administration of MK-677 to confirm GH stimulatory effects. Body weight, body length, tibia length, epiphyseal plate width, and serum levels of insulin-like growth factor (IGF)-I were measured after oral administration of 4 mg/kg of MK-677 for 6 weeks to investigate growth-promoting effects. RESULTS Oral administration of MK-677 at 4 mg/kg increased peak GH concentrations by 1.8-fold, compared to baseline. However, oral administration of MK-677 for 6 weeks did not increase body growth or serum levels of IGF-I. At 6 weeks after treatment, the GH response to MK-677 was abolished. Pituitary GH mRNA and hypothalamic GH-releasing hormone mRNA, and GH secretagogue receptor (GHSR) mRNA expression in the pituitary and hypothalamus did not differ between the control and treatment group. Somatostatin (SST) mRNA expression in the hypothalamus was markedly increased in the treatment group, whereas SST receptor (SSTR)-2 mRNA expression in the pituitary gland was decreased. Protein expression of hypothalamic GHSR, SST, and pituitary SSTR-2 showed patterns similar to those for mRNA expression. CONCLUSION Our results suggest that prolonged administration of MK-677 in rats does not promote growth despite the GH stimulatory effect of MK-677, which may be related to increased expression of SST in the hypothalamus. Further studies are needed to overcome the observed desensitization to GHS.
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Affiliation(s)
- Junghun Lee
- Department of Pediatrics, Severance Children's Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Ahreum Kwon
- Department of Pediatrics, Severance Children's Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Hyun Wook Chae
- Department of Pediatrics, Severance Children's Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Woo Jung Lee
- Department of Pediatrics, Severance Children's Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Tae Hyuk Kim
- Department of Pediatrics, Severance Children's Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Ho Seong Kim
- Department of Pediatrics, Severance Children's Hospital, Endocrine Research Institute, Yonsei University College of Medicine, Seoul, Korea.
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MK-0677, a Ghrelin Agonist, Alleviates Amyloid Beta-Related Pathology in 5XFAD Mice, an Animal Model of Alzheimer's Disease. Int J Mol Sci 2018; 19:ijms19061800. [PMID: 29912176 PMCID: PMC6032329 DOI: 10.3390/ijms19061800] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 05/31/2018] [Accepted: 06/06/2018] [Indexed: 12/11/2022] Open
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by cognitive deficits, neuroinflammation, and neuronal death. The primary pathogenic cause is believed to be the accumulation of pathogenic amyloid beta (Aβ) assemblies in the brain. Ghrelin, which is a peptide hormone predominantly secreted from the stomach, is an endogenous ligand for the growth hormone secretagogue-receptor type 1a (GHS-R1a). MK-0677 is a ghrelin agonist that potently stimulates the GHS-R1a ghrelin receptor. Interestingly, previous studies have shown that ghrelin improves cognitive impairments and attenuates neuronal death and neuroinflammation in several neurological disorders. However, it is unknown whether MK-0677 can affect Aβ accumulation or Aβ-mediated pathology in the brains of patients with AD. Therefore, we examined the effects of MK-0677 administration on AD-related pathology in 5XFAD mice, an Aβ-overexpressing transgenic mouse model of AD. MK-0677 was intraperitoneally administered to three-month-old 5XFAD mice. To visualize Aβ accumulation, neuroinflammation, and neurodegeneration, thioflavin-S staining and immunostaining with antibodies against Aβ (4G8), ionized calcium-binding adaptor molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), neuronal nuclear antigen (NeuN), and synaptophysin were conducted in the neocortex of 5XFAD and wild-type mice, and to evaluate changes of phosphorylated cyclic adenosine monophosphate (cAMP) response element binding protein (pCREB) levels, immunostaining with antibody against pCREB was performed in dentate gyrus of the hippocampus of 5XFAD and wild-type mice. The histological analyses indicated that MK-0677-treated 5XFAD mice showed reduced Aβ deposition, gliosis, and neuronal and synaptic loss in the deep cortical layers, and inhibited the decrement of pCREB levels in dentate gyrus of the hippocampus compared to vehicle-treated 5XFAD mice. Our results showed that activation of the ghrelin receptor with MK-0677 inhibited the Aβ burden, neuroinflammation, and neurodegeneration, which suggested that MK-0677 might have potential as a treatment of the early phase of AD.
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Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev 2018; 6:45-53. [PMID: 28400207 PMCID: PMC5632578 DOI: 10.1016/j.sxmr.2017.02.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 02/22/2017] [Accepted: 02/24/2017] [Indexed: 12/28/2022]
Abstract
INTRODUCTION Growth hormone (GH) increases lean body mass, decreases fat mass, increases exercise tolerance and maximum oxygen uptake, enhances muscle strength, and improves linear growth. Long-term studies of GH administration offer conflicting results on its safety, which has led to strict Food and Drug Administration criteria for GH use. The potential drawbacks of exogenous GH use are believed to be due in part to impaired regulatory feedback. AIM To review the literature on GH secretagogues (GHSs), which include GH-releasing peptides and the orally available small-molecule drug ibutamoren mesylate. METHODS Review of clinical studies on the safety and efficacy of GHSs in human subjects. MAIN OUTCOME MEASURE Report on the physiologic changes from GHS use in human subjects including its safety profile. RESULTS GHSs promote pulsatile release of GH that is subject to negative feedback and can prevent supra-therapeutic levels of GH and their sequelae. To date, few long-term, rigorously controlled studies have examined the efficacy and safety of GHSs, although GHSs might improve growth velocity in children, stimulate appetite, improve lean mass in wasting states and in obese individuals, decrease bone turnover, increase fat-free mass, and improve sleep. Available studies indicate that GHSs are well tolerated, with some concern for increases in blood glucose because of decreases in insulin sensitivity. CONCLUSION Further work is needed to better understand the long-term impact of GHSs on human anatomy and physiology and more specifically in the context of a diversity of clinical scenarios. Furthermore, the safety of these compounds with long-term use, including evaluation of cancer incidence and mortality, is needed. Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev 2018;6:45-53.
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Affiliation(s)
| | - Alexander W Pastuszak
- Center for Reproductive Medicine, Baylor College of Medicine, Houston, TX, USA; Scott Department of Urology, Baylor College of Medicine, Houston, TX, USA.
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7
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Sigalos JT, Pastuszak AW, Allison A, Ohlander SJ, Herati A, Lindgren MC, Lipshultz LI. Growth Hormone Secretagogue Treatment in Hypogonadal Men Raises Serum Insulin-Like Growth Factor-1 Levels. Am J Mens Health 2017; 11:1752-1757. [PMID: 28830317 PMCID: PMC5675260 DOI: 10.1177/1557988317718662] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Realizing the reported misuse of human growth hormone (GH), investigation of a safe alternative mechanism for increasing endogenous GH is needed. Several GH secretagogues are available, including GH-releasing peptides (GHRPs) GHRP-2 and GHRP-6, and the GH-releasing hormone analog, sermorelin (SERM). Insulin-like growth factor 1 (IGF-1) serves as a surrogate marker for GH. Here, the effect of GHRP/SERM therapy on IGF-1 levels is evaluated. A retrospective review of medical records was performed for 105 men on testosterone (T) therapy seeking increases in lean body mass and fat loss who were prescribed 100 mcg of GHRP-6, GHRP-2, and SERM three times daily. Compliance with therapy was assessed, and 14 men met strict inclusion criteria. Serum hormone levels of IGF-1, T, free T (FT), estradiol (E), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were evaluated. Mean (SD) age of the cohort was 33.2 (2.9) years, and baseline IGF-1 level was 159.5 (26.7) ng/mL. Mean (SD) duration of continuous GHRP/SERM treatment was 134 (88) days. Mean posttreatment IGF-1 level was 239.0 (54.6) ng/mL (p < .0001). Three of the 14 men were on an aromatase inhibitor and/or tamoxifen prior to treatment and another 4 men were coadministered an aromatase inhibitor and/or tamoxifen during treatment. Inhibition of E production or estrogen receptor blockade resulted in smaller increases in IGF-1 levels. GHRP/SERM therapy increases serum IGF-1 levels with strict compliance to thrice-daily dosing. The results suggest that combination therapy may be beneficial in men with wasting conditions that can improve with increased GH secretion.
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Affiliation(s)
| | - Alexander W Pastuszak
- 2 Center for Reproductive Medicine, Baylor College of Medicine, Houston, TX, USA.,3 Scott Department of Urology, Baylor College of Medicine, Houston, TX, USA
| | - Andrew Allison
- 2 Center for Reproductive Medicine, Baylor College of Medicine, Houston, TX, USA.,3 Scott Department of Urology, Baylor College of Medicine, Houston, TX, USA
| | - Samuel J Ohlander
- 4 University of Illinois at Chicago College of Medicine, Chicago, IL, USA
| | - Amin Herati
- 5 The Brady Urological Institut, John's Hopkins Bayview Medical Center Baltimore, MD, USA
| | - Mark C Lindgren
- 6 University of Oklahoma College of Medicine, Department of Urology, Oklahoma City, OK, USA
| | - Larry I Lipshultz
- 2 Center for Reproductive Medicine, Baylor College of Medicine, Houston, TX, USA.,3 Scott Department of Urology, Baylor College of Medicine, Houston, TX, USA
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8
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Müller TD, Nogueiras R, Andermann ML, Andrews ZB, Anker SD, Argente J, Batterham RL, Benoit SC, Bowers CY, Broglio F, Casanueva FF, D'Alessio D, Depoortere I, Geliebter A, Ghigo E, Cole PA, Cowley M, Cummings DE, Dagher A, Diano S, Dickson SL, Diéguez C, Granata R, Grill HJ, Grove K, Habegger KM, Heppner K, Heiman ML, Holsen L, Holst B, Inui A, Jansson JO, Kirchner H, Korbonits M, Laferrère B, LeRoux CW, Lopez M, Morin S, Nakazato M, Nass R, Perez-Tilve D, Pfluger PT, Schwartz TW, Seeley RJ, Sleeman M, Sun Y, Sussel L, Tong J, Thorner MO, van der Lely AJ, van der Ploeg LHT, Zigman JM, Kojima M, Kangawa K, Smith RG, Horvath T, Tschöp MH. Ghrelin. Mol Metab 2015; 4:437-60. [PMID: 26042199 PMCID: PMC4443295 DOI: 10.1016/j.molmet.2015.03.005] [Citation(s) in RCA: 680] [Impact Index Per Article: 75.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/11/2015] [Accepted: 03/11/2015] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The gastrointestinal peptide hormone ghrelin was discovered in 1999 as the endogenous ligand of the growth hormone secretagogue receptor. Increasing evidence supports more complicated and nuanced roles for the hormone, which go beyond the regulation of systemic energy metabolism. SCOPE OF REVIEW In this review, we discuss the diverse biological functions of ghrelin, the regulation of its secretion, and address questions that still remain 15 years after its discovery. MAJOR CONCLUSIONS In recent years, ghrelin has been found to have a plethora of central and peripheral actions in distinct areas including learning and memory, gut motility and gastric acid secretion, sleep/wake rhythm, reward seeking behavior, taste sensation and glucose metabolism.
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Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, München, Germany
| | - R Nogueiras
- Department of Physiology, Centro de Investigación en Medicina Molecular y Enfermedades Crónicas, University of Santiago de Compostela (CIMUS)-Instituto de Investigación Sanitaria (IDIS)-CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| | - M L Andermann
- Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Z B Andrews
- Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia
| | - S D Anker
- Applied Cachexia Research, Department of Cardiology, Charité Universitätsmedizin Berlin, Germany
| | - J Argente
- Department of Pediatrics and Pediatric Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain ; Department of Pediatrics, Universidad Autónoma de Madrid and CIBER Fisiopatología de la obesidad y nutrición, Instituto de Salud Carlos III, Madrid, Spain
| | - R L Batterham
- Centre for Obesity Research, University College London, London, United Kingdom
| | - S C Benoit
- Metabolic Disease Institute, Division of Endocrinology, Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - C Y Bowers
- Tulane University Health Sciences Center, Endocrinology and Metabolism Section, Peptide Research Section, New Orleans, LA, USA
| | - F Broglio
- Division of Endocrinology, Diabetes and Metabolism, Dept. of Medical Sciences, University of Torino, Torino, Italy
| | - F F Casanueva
- Department of Medicine, Santiago de Compostela University, Complejo Hospitalario Universitario de Santiago (CHUS), CIBER de Fisiopatologia Obesidad y Nutricion (CB06/03), Instituto Salud Carlos III, Santiago de Compostela, Spain
| | - D D'Alessio
- Duke Molecular Physiology Institute, Duke University, Durham, NC, USA
| | - I Depoortere
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium
| | - 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
| | - E Ghigo
- Department of Pharmacology & Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - P A Cole
- Monash Obesity & Diabetes Institute, Monash University, Clayton, Victoria, Australia
| | - M Cowley
- Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia ; Monash Obesity & Diabetes Institute, Monash University, Clayton, Victoria, Australia
| | - D E Cummings
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington School of Medicine, Seattle, WA, USA
| | - A Dagher
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - S Diano
- Dept of Neurobiology, Yale University School of Medicine, New Haven, CT, USA
| | - S L Dickson
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - C Diéguez
- Department of Physiology, School of Medicine, Instituto de Investigacion Sanitaria (IDIS), University of Santiago de Compostela, Spain
| | - R Granata
- Division of Endocrinology, Diabetes and Metabolism, Dept. of Medical Sciences, University of Torino, Torino, Italy
| | - H J Grill
- Department of Psychology, Institute of Diabetes, Obesity and Metabolism, University of Pennsylvania, Philadelphia, PA, USA
| | - K Grove
- Department of Diabetes, Obesity and Metabolism, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR, USA
| | - K M Habegger
- Comprehensive Diabetes Center, University of Alabama School of Medicine, Birmingham, AL, USA
| | - K Heppner
- Division of Diabetes, Obesity, and Metabolism, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR 97006, USA
| | - M L Heiman
- NuMe Health, 1441 Canal Street, New Orleans, LA 70112, USA
| | - L Holsen
- Departments of Psychiatry and Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - B Holst
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen N, Denmark
| | - A Inui
- Department of Psychosomatic Internal Medicine, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan
| | - J O Jansson
- Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - H Kirchner
- Medizinische Klinik I, Universitätsklinikum Schleswig-Holstein Campus Lübeck, Lübeck, Germany
| | - M Korbonits
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London, Queen Mary University of London, London, UK
| | - B Laferrère
- New York Obesity Research Center, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - C W LeRoux
- Diabetes Complications Research Centre, Conway Institute, University College Dublin, Ireland
| | - M Lopez
- Department of Physiology, Centro de Investigación en Medicina Molecular y Enfermedades Crónicas, University of Santiago de Compostela (CIMUS)-Instituto de Investigación Sanitaria (IDIS)-CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela, Spain
| | - S Morin
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, München, Germany
| | - M Nakazato
- Division of Neurology, Respirology, Endocrinology and Metabolism, Department of Internal Medicine, Faculty of Medicine, University of Miyazaki, Kiyotake, Miyazaki, Japan
| | - R Nass
- Division of Endocrinology and Metabolism, University of Virginia, Charlottesville, VA, USA
| | - D Perez-Tilve
- Department of Internal Medicine, Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - P T Pfluger
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, München, Germany
| | - T W Schwartz
- Department of Neuroscience and Pharmacology, Laboratory for Molecular Pharmacology, The Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - R J Seeley
- Department of Surgery, University of Michigan School of Medicine, Ann Arbor, MI, USA
| | - M Sleeman
- Department of Physiology, Faculty of Medicine, Monash University, Melbourne, Victoria, Australia
| | - Y Sun
- Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
| | - L Sussel
- Department of Genetics and Development, Columbia University, New York, NY, USA
| | - J Tong
- Duke Molecular Physiology Institute, Duke University, Durham, NC, USA
| | - M O Thorner
- Division of Endocrinology and Metabolism, University of Virginia, Charlottesville, VA, USA
| | - A J van der Lely
- Department of Medicine, Erasmus University MC, Rotterdam, The Netherlands
| | | | - J M Zigman
- Departments of Internal Medicine and Psychiatry, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - M Kojima
- Molecular Genetics, Institute of Life Science, Kurume University, Kurume, Japan
| | - K Kangawa
- National Cerebral and Cardiovascular Center Research Institute, Osaka, Japan
| | - R G Smith
- The Scripps Research Institute, Florida Department of Metabolism & Aging, Jupiter, FL, USA
| | - T Horvath
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - M H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, München, Germany ; Division of Metabolic Diseases, Department of Medicine, Technical University Munich, Munich, Germany
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Albarran-Zeckler RG, Sun Y, Smith RG. Physiological roles revealed by ghrelin and ghrelin receptor deficient mice. Peptides 2011; 32:2229-35. [PMID: 21781995 PMCID: PMC3221867 DOI: 10.1016/j.peptides.2011.07.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 05/13/2011] [Accepted: 07/05/2011] [Indexed: 02/04/2023]
Abstract
Ghrelin is a hormone made in the stomach and known primarily for its growth hormone releasing and orexigenic properties. Nevertheless, ghrelin through its receptor, the GHS-R1a, has been shown to exert many roles including regulation of glucose homeostasis, memory & learning, food addiction and neuroprotection. Furthermore, ghrelin could promote overall health and longevity by acting directly in the immune system and promoting an extended antigen repertoire. The development of mice lacking either ghrelin (ghrelin-/-) or its receptor (ghsr-/-) have provided a valuable tool for determining the relevance of ghrelin and its receptor in these multiple and diverse roles. In this review, we summarize the most important findings and lessons learned from the ghrelin-/- and ghsr-/- mice.
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Affiliation(s)
- Rosie G Albarran-Zeckler
- Department of Metabolism and Aging, Scripps Research Institute Florida, 130 Scripps Way B3B, Jupiter, FL 33458, United States.
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10
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Effect of ghrelin on glucose-insulin homeostasis: therapeutic implications. INTERNATIONAL JOURNAL OF PEPTIDES 2010; 2010. [PMID: 20700401 PMCID: PMC2911604 DOI: 10.1155/2010/234709] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 11/23/2009] [Indexed: 12/17/2022]
Abstract
Ghrelin is a 28-amino-acid peptide that displays a strong growth hormone- (GH-) releasing activity through the activation of the growth hormone secretagogue receptor (GHSR). The first studies about role of ghrelin were focused on its orexigenic ability, but despite indisputable pharmacological data, the evidence for a physiological role for ghrelin in the control of appetite is much less clear. Mice with targeted deletion of either ghrelin or the GHSR exhibit an essentially normal metabolic phenotype when fed a regular chow diet, suggesting that ghrelin may have a redundant role in the regulation of food intake. RNAs for ghrelin as well as GHSR are expressed in the pancreas of rats and humans and several studies propose that ghrelin could have an important function in glucose homeostasis and insulin release, independent of GH secretion. Low plasma ghrelin levels are associated with elevated fasting insulin levels and insulin resistance, suggesting both physiological and pathophysiological roles for ghrelin. For this reason, at least theoretically, ghrelin and/or its signalling manipulation could be useful for the treatment or prevention of diseases of glucose homeostasis such as type 2 diabetes.
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Nass R, Pezzoli SS, Oliveri MC, Patrie JT, Harrell FE, Clasey JL, Heymsfield SB, Bach MA, Vance ML, Thorner MO. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med 2008; 149:601-11. [PMID: 18981485 PMCID: PMC2757071 DOI: 10.7326/0003-4819-149-9-200811040-00003] [Citation(s) in RCA: 166] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Growth hormone secretion and muscle mass decline from midpuberty throughout life, culminating in sarcopenia, frailty, decreased function, and loss of independence. The decline of growth hormone in the development of sarcopenia is one of many factors, and its etiologic role needs to be demonstrated. OBJECTIVE To determine whether MK-677, an oral ghrelin mimetic, increases growth hormone secretion into the young-adult range without serious adverse effects, prevents the decline of fat-free mass, and decreases abdominal visceral fat in healthy older adults. DESIGN 2-year, double-blind, randomized, placebo-controlled, modified-crossover clinical trial. SETTING General clinical research center study performed at a university hospital. PARTICIPANTS 65 healthy adults (men, women receiving hormone replacement therapy, and women not receiving hormone replacement therapy) ranging from 60 to 81 years of age. INTERVENTION Oral administration of MK-677, 25 mg, or placebo once daily. MEASUREMENTS Growth hormone and insulin-like growth factor I levels. Fat-free mass and abdominal visceral fat were the primary end points after 1 year of treatment. Other end points were body weight, fat mass, insulin sensitivity, lipid and cortisol levels, bone mineral density, limb lean and fat mass, isokinetic strength, function, and quality of life. All end points were assessed at baseline and every 6 months. RESULTS Daily administration of MK-677 significantly increased growth hormone and insulin-like growth factor I levels to those of healthy young adults without serious adverse effects. Mean fat-free mass decreased in the placebo group but increased in the MK-677 group (change, -0.5 kg [95% CI, -1.1 to 0.2 kg] vs. 1.1 kg [CI, 0.7 to 1.5 kg], respectively; P < 0.001), as did body cell mass, as reflected by intracellular water (change, -1.0 kg [CI, -2.1 to 0.2 kg] vs. 0.8 kg [CI, -0.1 to 1.6 kg], respectively; P = 0.021). No significant differences were observed in abdominal visceral fat or total fat mass; however, the average increase in limb fat was greater in the MK-677 group than the placebo group (1.1 kg vs. 0.24 kg; P = 0.001). Body weight increased 0.8 kg (CI, -0.3 to 1.8 kg) in the placebo group and 2.7 kg (CI, 2.0 to 3.5 kg) in the MK-677 group (P = 0.003). Fasting blood glucose level increased an average of 0.3 mmol/L (5 mg/dL) in the MK-677 group (P = 0.015), and insulin sensitivity decreased. The most frequent side effects were an increase in appetite that subsided in a few months and transient, mild lower-extremity edema and muscle pain. Low-density lipoprotein cholesterol levels decreased in the MK-677 group relative to baseline values (change, -0.14 mmol/L [CI, -0.27 to -0.01 mmol/L]; -5.4 mg/dL [CI, -10.4 to -0.4 mg/dL]; P = 0.026); no differences between groups were observed in total or high-density lipoprotein cholesterol levels. Cortisol levels increased 47 nmol/L (CI, 28 to 71 nmol/L (1.7 microg/dL [CI, 1.0 to 2.6 microg/dL]) in MK-677 recipients (P = 0.020). Changes in bone mineral density consistent with increased bone remodeling occurred in MK-677 recipients. Increased fat-free mass did not result in changes in strength or function. Two-year exploratory analyses confirmed the 1-year results. LIMITATION Study power (duration and participant number) was insufficient to evaluate functional end points in healthy elderly persons. CONCLUSION Over 12 months, the ghrelin mimetic MK-677 enhanced pulsatile growth hormone secretion, significantly increased fat-free mass, and was generally well tolerated. Long-term functional and, ultimately, pharmacoeconomic, studies in elderly persons are indicated.
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Affiliation(s)
- Ralf Nass
- University of Virginia, Charlottesville, Virginia 22908, USA
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12
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Reduction in hypophyseal growth hormone and prolactin expression due to deficiency in ghrelin receptor signaling is associated with Pit-1 suppression: relevance to the immune system. Brain Behav Immun 2008; 22:1138-45. [PMID: 18602461 PMCID: PMC2783985 DOI: 10.1016/j.bbi.2008.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2007] [Revised: 06/06/2008] [Accepted: 06/07/2008] [Indexed: 10/21/2022] Open
Abstract
In mice and in rats, reduced levels of the growth hormone secretagogue receptor (GHS-R1a) results in reduced body weight and lower levels of serum insulin-like growth factor I (IGF-I). However, the mechanism leading to these impairments has not been elucidated. Studies in primary cultures of pituitary cells from very young mice have shown that GHS-R1a agonists, including ghrelin, increase expression of the pituitary-specific transcription factor (Pit-1) that is critical for differentiation of pituitary cells into somatotrophs, lactotrophs, and thyrotrophs. Hence, we hypothesized that ablation of Ghsr would reduce Pit-1 expression and as a consequence reduce growth hormone (GH) production explaining the lower body weight of Ghsr-/- mice. Here, we now show that Pit-1 mRNA levels are significantly lower in the pituitary gland of Ghsr-/- mice compared to wild-type littermates and also with advancing age. This Pit-1 loss is associated with reduced GH mRNA and fewer GH producing cells. To determine whether reduced GH is caused by reduced expression of Pit-1 in Ghsr-/- mice, we also measured prolactin (PRL) expression in the pituitary gland and in the circulation. PRL mRNA was significantly reduced in Ghsr-/- mice compared to wild-type littermates and fewer cells expressed PRL. The reduction in expression of both GH and PRL is consistent with a Pit-1 regulated pathway and demonstrates that the GHS-R has an important role in the pituitary gland as a modulator of Pit-1 expression and provides a possible mechanism to explain the lower plasma IGF-1 and modestly reduced body weight exhibited by Ghsr-/- mice. We also believe that lower systemic and lymphoid hormone expression may also account, in part, for the enhanced thymic involution and reduced thymic output in Ghsr-/- mice.
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Veldhuis JD, Reynolds GA, Iranmanesh A, Bowers CY. Twenty-four hour continuous ghrelin infusion augments physiologically pulsatile, nycthemeral, and entropic (feedback-regulated) modes of growth hormone secretion. J Clin Endocrinol Metab 2008; 93:3597-603. [PMID: 18593763 PMCID: PMC2567861 DOI: 10.1210/jc.2008-0620] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Ghrelin is a 28-amino acid acylated peptide that potentiates GHRH stimulation and opposes somatostatin inhibition acutely. Whether prolonged ghrelin administration can sustain physiological patterns of GH secretion remains unknown. HYPOTHESIS Continuous delivery of ghrelin will amplify physiological patterns of GH secretion over 24 h. SUBJECTS Men and women ages 29-69 yr, body mass indices 23-52 kg/m2, were included in the study. LOCATION The study was performed at an academic medical center. METHODS Twenty-four hour continuous sc infusion of saline vs. ghrelin (1 microg/kg.h) with frequent sampling was examined. Deconvolution and entropy analyses were performed. OUTCOMES IGF-I concentrations were determined. Basal, pulsatile, nycthemeral, and entropic measures of GH secretion were calculated. RESULTS Ghrelin infusion compared with saline infusion for 24 h elevated (median) acylated ghrelin, GH, and IGF-I concentrations by 8.1-fold (P < 0.001),11-fold (P < 0.001), and 1.4-fold (P = 0.002). GH secretory-burst mass and frequency increased by 6.6-fold (P = 0.004) and 1.7-fold (P < 0.001), respectively, resulting in a 12-fold increase in pulsatile GH secretion (P < 0.001). Interpulse variability decreased significantly (P = 0.046), whereas GH secretory-burst shape and half-life did not change. The amplitude of the nycthemeral GH rhythm increased by 3.4-fold (P < 0.001), and GH patterns became more irregular (higher approximate entropy P < 0.001). Combining GHRH with ghrelin was not an additive in driving GH secretion. CONCLUSIONS Continuous ghrelin infusion for 24 h elevates acylated ghrelin, GH and IGF-I concentrations, and stimulates pulsatile, nycthemeral, and entropic modes of GH secretion. The consistency of outcomes in a heterogeneous cohort of adults suggests potentially broad utility of this physiological secretagogue in hyposomatotropic states.
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Affiliation(s)
- Johannes D Veldhuis
- Endocrine Research Unit, Department of Internal Medicine, Clinical Translational Science Unit, Mayo Medical and Graduate Schools of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA.
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Nass R, Farhy LS, Liu J, Prudom CE, Johnson ML, Veldhuis P, Pezzoli SS, Oliveri MC, Gaylinn BD, Geysen HM, Thorner MO. Evidence for acyl-ghrelin modulation of growth hormone release in the fed state. J Clin Endocrinol Metab 2008; 93:1988-94. [PMID: 18334589 PMCID: PMC2386275 DOI: 10.1210/jc.2007-2234] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
CONTEXT The timing and frequency of GH secretory episodes is regulated by GHRH and somatostatin. This study provides evidence for amplification of these GH pulses by endogenous acyl-ghrelin. DESIGN Blood was sampled every 10 min for 26.5 h during a fed admission with standardized meals and also during the final 24 h of a 61.5-h fast. GH secretion profiles were derived from deconvolution of 10-min sampling data, and full-length acyl-ghrelin levels were measured using a newly developed two-site sandwich assay. SETTING The study was conducted at a university hospital general clinical research center. PARTICIPANTS Participants included eight men with mean (+/- sd) age 24.5 +/- 3.7 yr (body mass index 24 +/- 2.1 kg/m(2)). RESULTS Correlations were computed between amplitudes of individual GH secretory events and the average acyl-ghrelin concentration in the 60-min interval preceding each GH burst. In the fed state, the peak correlations were positive for all subjects and significantly higher than in the fasting state when acyl-ghrelin levels declined [mean (+/- sem): 0.7 (0.04) vs. 0.29 (0.08), P = 0.017]. In addition, long-term fasting was associated with an increase in the GH secretory pulse mass and amplitude but not frequency [fed vs. fasting pulse mass: 0.22 (0.05) vs. 0.44 (0.06) microg/liter, P = 0.002; amplitude: 5.2 (1.3) vs. 11.8 (1.9) microg/liter/min, P = 0.034; pulses per 24 h: 19.4 (0.5) vs. 22.0 (1.4), P = 0.1]. CONCLUSION Our data support the hypothesis that under normal conditions in subjects given regular meals endogenous acyl-ghrelin acts to increase the amplitude of GH pulses.
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Affiliation(s)
- Ralf Nass
- Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA
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15
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Sun Y, Butte NF, Garcia JM, Smith RG. Characterization of adult ghrelin and ghrelin receptor knockout mice under positive and negative energy balance. Endocrinology 2008; 149:843-50. [PMID: 18006636 PMCID: PMC2219310 DOI: 10.1210/en.2007-0271] [Citation(s) in RCA: 207] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Accepted: 11/07/2007] [Indexed: 12/20/2022]
Abstract
Ghrelin and the ghrelin receptor (GH secretagogue receptor, GHS-R), are believed to have important roles in energy homeostasis. We describe results from the first studies to be conducted in congenic (N10) adult ghrelin(-/-) and Ghsr(-/-) mice under conditions of both positive (high-fat diet) and negative (caloric restriction) energy balance. In contrast to results from young N2 mutant mice, changes in body weight and energy expenditure are not clearly distinguishable across genotypes. Although respiratory quotient was lower in mice fed a high-fat diet, no differences were evident between littermate wild-type and null genotypes. With normal chow, a modest decrease trend in respiratory quotient was detected in ghrelin(-/-) mice but not in Ghsr(-/-) mice. Under caloric restriction, the weight loss of ghrelin(-/-) and Ghsr(-/-) mice was identical to wild-type littermates, but blood glucose levels were significantly lower. We conclude that adult congenic ghrelin(-/-) and Ghsr(-/-) mice are not resistant to diet-induced obesity but under conditions of negative energy balance show impairment in maintaining glucose homeostasis. These results support our hypothesis that the primary metabolic function of ghrelin in adult mice is to modulate glucose sensing and insulin sensitivity, rather than directly regulate energy intake and energy expenditure.
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Affiliation(s)
- Yuxiang Sun
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA
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16
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Frutos MGS, Cacicedo L, Fernández C, Vicent D, Velasco B, Zapatero H, Sánchez-Franco F. Insights into a role of GH secretagogues in reversing the age-related decline in the GH/IGF-I axis. Am J Physiol Endocrinol Metab 2007; 293:E1140-52. [PMID: 17684105 DOI: 10.1152/ajpendo.00236.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Growth hormone (GH) secretion and serum insulin-like growth factor-I (IGF-I) decline with aging. This study addresses the role played by the hypothalamic regulators in the aging GH decline and investigates the mechanisms through which growth hormone secretagogues (GHS) activate GH secretion in the aging rats. Two groups of male Wistar rats were studied: young-adult (3 mo) and old (24 mo). Hypothalamic growth hormone-releasing hormone (GHRH) mRNA and immunoreactive (IR) GHRH dramatically decreased (P < 0.01 and P < 0.001) in the old rats, as did median eminence IR-GHRH. Decreases of hypothalamic IR-somatostatin (SS; P < 0.001) and SS mRNA (P < 0.01), and median eminence IR-SS were found in old rats as were GHS receptor and IGF-I mRNA (P < 0.01 and P < 0.05). Hypothalamic IGF-I receptor mRNA and protein were unmodified. Both young and old pituitary cells, cultured alone or cocultured with fetal hypothalamic cells, responded to ghrelin. Only in the presence of fetal hypothalamic cells did ghrelin elevate the age-related decrease of GH secretion to within normal adult range. In old rats, growth hormone-releasing peptide-6 returned the levels of GH and IGF-I secretion and liver IGF-I mRNA, and partially restored the lower pituitary IR-GH and GH mRNA levels to those of young untreated rats. These results suggest that the aging GH decline may result from decreased GHRH function rather than from increased SS action. The reduction of hypothalamic GHS-R gene expression might impair the action of ghrelin on GH release. The role of IGF-I is not altered. The aging GH/IGF-I axis decline could be rejuvenated by GHS treatment.
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17
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Gola M, Bonadonna S, Doga M, Mazziotti G, Giustina A. Cardiovascular risk in aging and obesity: is there a role for GH. J Endocrinol Invest 2005; 28:759-67. [PMID: 16277174 DOI: 10.1007/bf03347561] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
GH has significant impact in adults. In fact, patients with the GH deficiency (GHD) syndrome are now recognized as having an increased cardiovascular risk. The effects of human aging on GH secretion have been evaluated by a number of researchers. Studies of 24 h secretion of GH have shown variable reductions in most 24-h GH secretory parameters in middle-aged and in older men and women, resulting in a decrease in plasma levels of its anabolic mediator IGF-I. Obesity is also associated with several endocrine and metabolic abnormalities. These include decreased serum GH concentrations, reduced GH half-life, frequency of GH secretory episodes and daily GH production rate. The mechanism of the low GH in obesity is not completely understood nor is it clear whether its relationship with visceral adiposity is causal. The aim of this article will be to review the available clinical data concerning the potential involvement of "subclinical" or perhaps better "functional" GHD, which is observed in aging and obesity, in the increase in cardiovascular risk which characterizes these two conditions.
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Affiliation(s)
- M Gola
- Endocrine Section, Department of Internal Medicine, University of Brescia, Brescia, Italy
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18
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Sun Y, Wang P, Zheng H, Smith RG. Ghrelin stimulation of growth hormone release and appetite is mediated through the growth hormone secretagogue receptor. Proc Natl Acad Sci U S A 2004; 101:4679-84. [PMID: 15070777 PMCID: PMC384806 DOI: 10.1073/pnas.0305930101] [Citation(s) in RCA: 520] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Synthetic agonists of the growth hormone secretagogue receptor (GHSR) rejuvenate the pulsatile pattern of GH-release in the elderly, and increase lean but not fat mass in obese subjects. Screening of tissue extracts in a cell line engineered to overexpress the GHSR led to the identification of a natural agonist called ghrelin. Paradoxically, this hormone was linked to obesity. However, it had not been directly shown that the GHSR is a physiologically relevant ghrelin receptor. Furthermore, ghrelin's structure is significantly different from the synthetic agonist (MK-0677) used to expression-clone the GHSR. To address whether the GHSR mediates ghrelin's stimulatory effects on GH release and appetite, we generated Ghsr-null mice. In contrast to wild-type mice, acute treatment of Ghsr-null mice with ghrelin stimulated neither GH release nor food intake, showing that the GHSR is a biologically relevant ghrelin receptor. Nevertheless, Ghsr-null mice are not dwarfs; their appetite and body composition are comparable to that of wild-type littermates. Furthermore, in contrast to suggestions that ghrelin regulates leptin and insulin secretion, fasting-induced changes in serum levels of leptin and insulin are identical in wild-type and null mice. Serum insulin-like growth factor 1 levels and body weights of mature Ghsr-null mice are modestly reduced compared to wild-type littermates, which is consistent with ghrelin's property as an amplifier of GH pulsatility and its speculated role in establishing an insulin-like growth factor 1 set-point for maintaining anabolic metabolism. Our results suggest that chronic treatment with ghrelin antagonists will have little effect on growth or appetite.
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Affiliation(s)
- Yuxiang Sun
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030, USA
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19
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Abstract
Pharmacological studies show that ghrelin stimulates growth hormone release, appetite, and fat deposition, but ghrelin's physiological role in energy homeostasis has not been established. Ghrelin was also proposed to regulate leptin and insulin release and to be important for the normal function of stomach, heart, kidney, lung, testis, and placenta. To help determine a definable physiological role for ghrelin, we generated ghrelin-null mice. In contrast to predictions made from the pharmacology of ghrelin, ghrelin-null mice are not anorexic dwarfs; their size, growth rate, food intake, body composition, reproduction, gross behavior, and tissue pathology are indistinguishable from wild-type littermates. Fasting produces identical decreases in serum leptin and insulin in null and wild-type mice. Ghrelin-null mice display normal responses to starvation and diet-induced obesity. As in wild-type mice, the administration of exogenous ghrelin stimulates appetite in null mice. Our data show that ghrelin is not critically required for viability, fertility, growth, appetite, bone density, and fat deposition and not likely to be a direct regulator of leptin and insulin. Therefore, antagonists of ghrelin are unlikely to have broad utility as antiobesity agents.
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Affiliation(s)
- Yuxiang Sun
- Department of Molecular and Cellular Biology, Huffington Center on Aging, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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20
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Broglio F, Gottero C, Benso A, Prodam F, Volante M, Destefanis S, Gauna C, Muccioli G, Papotti M, van der Lely AJ, Ghigo E. Ghrelin and the endocrine pancreas. Endocrine 2003; 22:19-24. [PMID: 14610295 DOI: 10.1385/endo:22:1:19] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Accepted: 04/14/2003] [Indexed: 12/25/2022]
Abstract
Ghrelin is a 28-amino-acid peptide predominantly produced by the stomach, while substantially lower amounts derive from other tissues including the pancreas. It is a natural ligand of the GH secretagogue (GHS) receptor (GHS-R1a) and strongly stimulates GH secretion, but acylation in serine 3 is needed for its activity. Ghrelin also possesses other endocrine and nonendocrine actions reflecting central and peripheral GHS-R distribution including the pancreas. The wide spectrum of ghrelin activities includes orexigenic effect, control of energy expenditure, and peripheral gastroenteropancreatic actions. Circulating ghrelin levels mostly reflect gastric secretion as indicated by evidence that they are reduced by 80% after gastrectomy and even after gastric by-pass surgery. Ghrelin secretion is increased in anorexia and cachexia but reduced in obesity, a notable exception being Prader-Willi syndrome. The negative association between ghrelin secretion and body weight is emphasized by evidence that weight increase and decrease reduces and augments circulating ghrelin levels in anorexia and obesity, respectively, and agrees with the clear negative association between ghrelin and insulin levels. In fact, ghrelin secretion is increased by fasting whereas it is decreased by glucose load as well as during euglycemic clamp but not after arginine or free fatty acid load in normal subjects; in physiological conditions, however, the most remarkable inhibitory input on ghrelin secretion is represented by somatostatin as well as by its natural analog cortistatin that concomitantly reduce beta-cell secretion. This evidence indicates that the endocrine pancreas plays a role in directly or indirectly modulating ghrelin secretion.
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Affiliation(s)
- Fabio Broglio
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Turin, Ospedale Molinette, Corso Dogliotti 14, 10126 Turin, Italy
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Lanfranco F, Gianotti L, Giordano R, Pellegrino M, Maccario M, Arvat E. Ageing, growth hormone and physical performance. J Endocrinol Invest 2003; 26:861-72. [PMID: 14964439 DOI: 10.1007/bf03345237] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Human ageing is associated to a declining activity of the GH/IGF-I axis and to several changes in body composition, function and metabolism which show strict similarities with those of younger adults with pathological GH deficiency. The age-related changes of the GH/IGF-I axis activity are mainly dependent on age-related variations in the hypothalamic control of somatotroph function, which is also affected by changes in peripheral hormones and metabolic input. The term "somatopause" indicates the potential link between the age-related decline in GH and IGF-I levels and changes in body composition, structural functions and metabolism which characterise ageing. Physical exercise is an important environmental regulator of the GH/IGF-I axis activity. Increased physical fitness and regular training increase GH production in adults, while the GH response to aerobic or resistance exercise is reduced with age. In older subjects regular exercise has the potential to improve overall fitness and quality of life and is also associated to decreased morbidity and increased longevity. Similar effects are seen following GH therapy in adult deficiency. This assumption led to clinical trials focusing on rhGH and/or rhlGF-I as potential anabolic drug interventions in elderly subjects. To restore the activity of GH/IGF-I axis with anabolic, anti-ageing purposes, attention has been also paid to GH-releasing molecules such as GHRH, orally active synthetic GH-secretagogues (GHS) and, more recently, to the endogenous natural GHS, ghrelin, which exerts several important biological actions, including the regulation of metabolic balance and orexigenic effects. At present, however, there is no definite evidence that "frail" elderly subjects really benefit from restoring GH and IGF-I levels within the young adult range by treatment with rhGH, rhlGF-I, GHRH or GHS. In this article the alteration of the GH/IGF-I axis activity during ageing is revised taking into account the role of physical activity as a regulator of the axis function and considering the effects of the restoration of GH and IGF-I circulating levels on body composition and physical performance.
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Affiliation(s)
- F Lanfranco
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Turin, Turin, Italy
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22
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Abstract
There is growing evidence to indicate that age-related declines in growth hormone (GH), insulin-like growth factor (IGF)-1, and androgen and estrogen production play a role in the pathogenesis of sarcopenia (an age-related decline in muscle mass and quality). Although GH supplementation has been reported to increase lean body mass in elderly individuals, the high incidence of adverse effects combined with a very high cost has limited the applicability of this form of therapy. The assessment of an alternative approach to enhance the GH/IGF-1 axis in the elderly by using GH-releasing hormone and other secretagogues is currently under way and is showing some promise. Testosterone replacement therapy may increase muscle mass and strength and decrease body fat in hypogonadal elderly men. Long-term randomised, controlled trials are needed, however, to better define the risk-benefit ratio of this form of therapy before it can be recommended. Available data are currently insufficient to decide what role estrogen replacement therapy may play in the management of sarcopenia. Therefore, although the evidence linking age-related hormonal changes to the development of sarcopenia is rapidly growing, it is still too early to determine the clinical utility of hormonal supplementation in the management of sarcopenia.
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Affiliation(s)
- Hosam K Kamel
- Division of Geriatrics, Department of Medicine, Medical College of Wisconsin, and the Clement J Zablocki VAMC, Milwaukee, Wisconsin 53295, USA.
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Kamegai J, Tamura H, Shimizu T, Ishii S, Sugihara H, Wakabayashi I. Chronic central infusion of ghrelin increases hypothalamic neuropeptide Y and Agouti-related protein mRNA levels and body weight in rats. Diabetes 2001; 50:2438-43. [PMID: 11679419 DOI: 10.2337/diabetes.50.11.2438] [Citation(s) in RCA: 391] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor (GHS-R), was originally purified from the rat stomach. Like the synthetic growth hormone secretagogues (GHSs), ghrelin specifically releases growth hormone (GH) after intravenous administration. Also consistent with the central actions of GHSs, ghrelin-immunoreactive cells were shown to be located in the hypothalamic arcuate nucleus as well as the stomach. Recently, we showed that a single central administration of ghrelin increased food intake and hypothalamic agouti-related protein (AGRP) gene expression in rodents, and the orexigenic effect of this peptide seems to be independent of its GH-releasing activity. However, the effect of chronic infusion of ghrelin on food consumption and body weight and their possible mechanisms have not been elucidated. In this study, we determined the effects of chronic intracerebroventricular treatment with ghrelin on metabolic factors and on neuropeptide genes that are expressed in hypothalamic neurons that have been previously shown to express the GHS-R and to regulate food consumption. Chronic central administration of rat ghrelin (1 microg/rat every 12 h for 72 h) significantly increased food intake and body weight. However, it did not affect plasma insulin, glucose, leptin, or GH concentrations. We also found that chronic central administration of ghrelin increased both neuropeptide Y (NPY) mRNA levels (151.0 +/- 10.1% of saline-treated controls; P < 0.05) and AGRP mRNA levels (160.0 +/- 22.5% of saline-treated controls; P < 0.05) in the arcuate nucleus. Thus, the primary hypothalamic targets of ghrelin are NPY/AGRP-containing neurons, and ghrelin is a newly discovered orexigenic peptide in the brain and stomach.
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Affiliation(s)
- J Kamegai
- Department of Medicine, Nippon Medical School, Tokyo, Japan.
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Arvat E, Gianotti L, Giordano R, Broglio F, Maccario M, Lanfranco F, Muccioli G, Papotti M, Graziani A, Ghigo E, Deghenghi R. Growth hormone-releasing hormone and growth hormone secretagogue-receptor ligands: focus on reproductive system. Endocrine 2001; 14:35-43. [PMID: 11322500 DOI: 10.1385/endo:14:1:035] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Growth hormone-releasing hormone (GHRH) and somatostatin are the most important hypothalamic neurohormones controlling growth hormone (GH) secretion. Several neurotransmitters and neuropeptides also play an important role in the control of GH secretion, mainly acting via modulation of GHRH and somatostatin. In the past two decades, particular attention has been given to a new family of substances showing a strong GH-releasing effect: GH secretagogues (GHSs). GHSs increase GH secretion in a dose- and age-related manner after iv and even oral administration. The endocrine effects of GHSs, are not fully specific for GH; they show, in fact, prolactin- (PRL), adenocorticotropic hormone- and cortisol-releasing effects. Specific GHS receptors are present in both the central nervous system and peripheral tissues, where they mediate several extraendocrine effects of GHSs. The isolation of these "orphan" receptors suggested the existence of an endogenous GHS-like ligand that could be represented by a recently discovered gastric peptide, named ghrelin. The interaction between GHSs and GHRH at the central level and in the pituitary gland, but not at peripheral level, has clearly been shown. Because GHRH and GHS receptors share the same localization in some peripheral tissues, they may have some interactions even at this level.
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Affiliation(s)
- E Arvat
- Department of Internal Medicine, University of Turin, Italy
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25
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Abstract
According to the somatomedin model, growth hormone (GH)-dependent hepatic synthesis is responsible for maintaining circulating insulin-like growth factor (IGF)-I levels. On the other hand, the local autocrine/paracrine IGF-I expression in peripheral tissue is generally GH-independent and reflects the effects of various and tissue-specific trophic hormones. Circulating IGF-I levels undergo important age-related variations increasing at puberty and decreasing, thereafter, to low levels in the elderly. Low IGF-I levels in the elderly mainly reflect impaired somatotroph secretion but the decline in gonadal sex steroid levels, some protein and micronutrients malnutrition as well as age-dependent variations in IGF-binding proteins may also play a role in the age-related decrease in IGF-I activity. This, in turn, partially accounts for age-related changes in bones, muscles, cardiovascular system, central nervous system and the immune system. However, it is currently unclear whether treatment with exogenous IGF-I can retard or reverse age-related changes in body structure and function.
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Affiliation(s)
- E Arvat
- Division of Endocrinology, Department of Internal Medicine, University of Turin, Italy
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26
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Arvat E, Ceda GP, Di Vito L, Ramunni J, Gianotti L, Broglio F, Deghenghi R, Ghigo E. Age-related variations in the neuroendocrine control, more than impaired receptor sensitivity, cause the reduction in the GH-releasing activity of GHRPs in human aging. Pituitary 1998; 1:51-8. [PMID: 11081183 DOI: 10.1023/a:1009970909015] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The mechanisms underlying the reduction in the GH-releasing activity of GHRPs in aging are still unclear. Aim of our study was to verify in man whether age-related impairment of the neurohormonal control of GH secretion and/or receptor alterations are involved in the reduced GH response to GHRPs in aging. To this goal, in 16 normal elderly subjects (E, 66-81 yr) and 12 young controls (Y, 24-28 yr) we studied the effects of 1.0, 2.0 and 3.0 micrograms/kg i.v. Hexarelin (HEX), a synthetic hexapeptide, or GHRH, as well as the interaction among HEX (2.0 micrograms/kg), GHRH (2.0 micrograms/kg) and arginine (ARG, 0.5 gr/kg) on GH secretion. In Y the GH response to increasing doses of HEX (1.0 vs. 2.0 vs. 3.0 micrograms/kg; AUC0;v-120 +/- SEM: 1728.4 +/- 406.4 vs. 2265.9 +/- 298.4 vs. 2934.3 +/- 482.2 micrograms/L/h, p < 0.05 for 1.0 vs. 2.0 micrograms/kg) and GHRH (649.6 +/- 111.4 vs. 792.2 +/- 117.6 vs. 1402.6 +/- 363.0 micrograms/L/h) showed a progressive increase. Two micrograms/kg HEX and 1 microgram/kg GHRH were the maximal effective doses. Similarly, in E the GH response to increasing doses of HEX (336.7 +/- 50.0 vs. 742.8 +/- 157.9 vs. 1205.1 +/- 178.1 micrograms/L/h, p < 0.05 for 1.0 vs. 2 micrograms/kg, p < 0.001 for 1.0 vs. 3.0 micrograms/kg and p < 0.03 for 2.0 vs. 3.0 micrograms/kg) and GHRH (183.8 +/- 27.3 vs. 260.9 +/- 17.3 vs. 356.1 +/- 46.3 micrograms/L/h, p < 0.005 for 1.0 vs. 3.0 micrograms/kg and p < 0.05 for 2.0 vs. 3.0 micrograms/kg) showed a progressive increase. In E the GH response to 3 micrograms/kg HEX or GHRH were clearly higher than those to 2 micrograms/kg. However, at each dose the GH responses to HEX or GHRH in E were lower (p < 0.05) than those in Y. In Y the GH response to HEX + GHRH was synergistical (4259.2 +/- 308.0 micrograms/L/h, p < 0.05). ARG strikingly potentiated the GHRH-induced GH rise (2640.8 +/- 273.6 micrograms/L/h, p < 0.01) but not the HEX-induced one (2371.7 +/- 387.2 micrograms/L/h) as well as the synergistical effect of HEX and GHRH (4009.1 +/- 360.8 micrograms/L/h). In E the GH response to HEX and GHRH was still synergistical (1947.7 +/- 306.0 micrograms/L/h, p < 0.05) but these responses were lower than those in young (p < 0.01). On the other hand, in E ARG restored the GH response to GHRH (1858.9 +/- 172.8 micrograms/L/h, p < 0.01) and even those to HEX (2069.5 +/- 528.7 micrograms/L/h, p < 0.01) and HEX + GHRH (4406.0 +/- 1079.2 micrograms/L/h, p < 0.05). Our present results indicate that the impairment of GHRP and GHRH receptor activity may have a role in the reduction of the somatotrope responsiveness in aging. However, the age-related reduction in the GH-releasing activity of GHRPs seems mainly dependent on age-related variations in the neural control, i.e. concomitant GHRH hypoactivity and somatostatinergic hyperactivity.
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Affiliation(s)
- E Arvat
- Department of Internal Medicine, University of Turin, Italy
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27
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Van Cauter E, Plat L, Scharf MB, Leproult R, Cespedes S, L'Hermite-Balériaux M, Copinschi G. Simultaneous stimulation of slow-wave sleep and growth hormone secretion by gamma-hydroxybutyrate in normal young Men. J Clin Invest 1997; 100:745-53. [PMID: 9239423 PMCID: PMC508244 DOI: 10.1172/jci119587] [Citation(s) in RCA: 177] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The aim of this study was to investigate, in normal young men, whether gamma-hydroxybutyrate (GHB), a reliable stimulant of slow-wave (SW) sleep in normal subjects, would simultaneously enhance sleep related growth hormone (GH) secretion. Eight healthy young men participated each in four experiments involving bedtime oral administration of placebo, 2.5, 3.0, and 3.5 g of GHB. Polygraphic sleep recordings were performed every night, and blood samples were obtained at 15-min intervals from 2000 to 0800. GHB effects were mainly observed during the first 2 h after sleep onset. There was a doubling of GH secretion, resulting from an increase of the amplitude and the duration of the first GH pulse after sleep onset. This stimulation of GH secretion was significantly correlated to a simultaneous increase in the amount of sleep stage IV. Abrupt but transient elevations of prolactin and cortisol were also observed, but did not appear to be associated with the concomitant stimulation of SW sleep. Thyrotropin and melatonin profiles were not altered by GHB administration. These data suggest that pharmacological agents that reliably stimulate SW sleep, such as GHB, may represent a novel class of powerful GH secretagogues.
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Affiliation(s)
- E Van Cauter
- Department of Medicine, University of Chicago, Illinois 60637, USA.
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