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Ringuet MT, Koo A, Furness SGB, McDougall SJ, Furness JB. Sites and mechanisms of action of colokinetics at dopamine, ghrelin and serotonin receptors in the rodent lumbosacral defecation centre. J Physiol 2023; 601:5195-5211. [PMID: 37772438 PMCID: PMC10952827 DOI: 10.1113/jp285217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 09/13/2023] [Indexed: 09/30/2023] Open
Abstract
Agonists of dopamine D2 receptors (D2R), 5-hydroxytryptamine (5-HT, serotonin) receptors (5-HTR) and ghrelin receptors (GHSR) activate neurons in the lumbosacral defecation centre, and act as 'colokinetics', leading to increased propulsive colonic motility, in vivo. In the present study, we investigated which neurons in the lumbosacral defecation centre express the receptors and whether dopamine, serotonin and ghrelin receptor agonists act on the same lumbosacral preganglionic neurons (PGNs). We used whole cell electrophysiology to record responses from neurons in the lumbosacral defecation centre, following colokinetic application, and investigated their expression profiles and the chemistries of their neural inputs. Fluorescence in situ hybridisation revealed Drd2, Ghsr and Htr2C transcripts were colocalised in lumbosacral PGNs of mice, and immunohistochemistry showed that these neurons have closely associated tyrosine hydroxylase and 5-HT boutons. Previous studies showed that they do not receive ghrelin inputs. Whole cell electrophysiology in adult mice spinal cord revealed that dopamine, serotonin, α-methylserotonin and capromorelin each caused inward, excitatory currents in overlapping populations of lumbosacral PGNs. Furthermore, dopamine caused increased frequency of both IPSCs and EPSCs in a cohort of D2R neurons. Tetrodotoxin blocked the IPSCs and EPSCs, revealing a post-synaptic excitatory action of dopamine. In lumbosacral PGNs of postnatal day 7-14 rats, only dopamine's postsynaptic effects were observed. Furthermore, inward, excitatory currents evoked by dopamine were reduced by the GHSR antagonist, YIL781. We conclude that lumbosacral PGNs are the site where the action of endogenous ligands of D2R and 5-HT2R converge, and that GHSR act as a cis-modulator of D2R expressed by the same neurons. KEY POINTS: Dopamine, 5-hydroxytryptamine (5-HT, serotonin) and ghrelin (GHSR) receptor agonists increase colorectal motility and have been postulated to act at receptors on parasympathetic preganglionic neurons (PGNs) in the lumbosacral spinal cord. We aimed to determine which neurons in the lumbosacral spinal cord express dopamine, serotonin and GHSR receptors, their neural inputs, and whether agonists at these receptors excite them. We show that dopamine, serotonin and ghrelin receptor transcripts are contained in the same PGNs and that these neurons have closely associated tyrosine hydroxylase and serotonin boutons. Whole cell electrophysiology revealed that dopamine, serotonin and GHSR receptor agonists induce an inward excitatory current in overlapping populations of lumbosacral PGNs. Dopamine-induced excitation was reversed by GHSR antagonism. The present study demonstrates that lumbosacral PGNs are the site at which actions of endogenous ligands of dopamine D2 receptors and 5-HT type 2 receptors converge. Ghrelin receptors are functional, but their role appears to be as modulators of dopamine effects at D2 receptors.
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Affiliation(s)
- Mitchell T. Ringuet
- Department of Anatomy & PhysiologyUniversity of MelbourneMelbourneVICAustralia
| | - Ada Koo
- Department of Anatomy & PhysiologyUniversity of MelbourneMelbourneVICAustralia
| | - Sebastian G. B. Furness
- School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
- Monash Institute of Pharmaceutical SciencesMelbourneVICAustralia
| | - Stuart J. McDougall
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneMelbourneVICAustralia
| | - John B. Furness
- Department of Anatomy & PhysiologyUniversity of MelbourneMelbourneVICAustralia
- Florey Institute of Neuroscience and Mental HealthUniversity of MelbourneMelbourneVICAustralia
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2
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Furness JB, Pustovit RV, Syder AJ, Ringuet MT, Yoo EJ, Fanjul A, Wykosky J, Fothergill LJ, Whitfield EA, Furness SGB. Dopamine and ghrelin receptor co-expression and interaction in the spinal defecation centers. Neurogastroenterol Motil 2021; 33:e14051. [PMID: 33264473 DOI: 10.1111/nmo.14051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 10/20/2020] [Accepted: 11/12/2020] [Indexed: 12/24/2022]
Abstract
BACKGROUND Dopamine receptor 2 (DRD2) and ghrelin receptor (GHSR1a) agonists both stimulate defecation by actions at the lumbosacral defecation center. Dopamine is in nerve terminals surrounding autonomic neurons of the defecation center, whereas ghrelin is not present in the spinal cord. Dopamine at D2 receptors generally inhibits neurons, but at the defecation center, its effect is excitatory. METHODS In vivo recording of defecation and colorectal propulsion was used to investigate interaction between DRD2 and GHSR1a. Localization studies were used to determine sites of receptor expression in rat and human spinal cord. KEY RESULTS Dopamine, and the DRD2 agonist, quinpirole, directly applied to the lumbosacral cord, caused defecation. The effect of intrathecal dopamine was inhibited by the GHSR1a antagonist, YIL781, given systemically, but YIL781 was not an antagonist at DRD2. The DRD2 agonist, pramipexole, administered systemically caused colorectal propulsion that was prevented when the pelvic nerves were cut. Drd2 and Ghsr were expressed together in autonomic preganglionic neurons at the level of the defecation centers in rat and human. Behaviorally induced defecation (caused by water avoidance stress) was reduced by the DRD2 antagonist, sulpiride. We had previously shown it is reduced by YIL781. CONCLUSIONS AND INFERENCES Our observations imply that dopamine is a transmitter of the defecation pathways whose actions are exerted through interacting dopamine (D2) and ghrelin receptors on lumbosacral autonomic neurons that project to the colorectum. The results explain the excitation by dopamine agonists and the conservation of GHSR1a in the absence of ghrelin.
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Affiliation(s)
- John B Furness
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Vic., Australia
| | - Ruslan V Pustovit
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Vic., Australia
| | - Andrew J Syder
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Mitchell T Ringuet
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Vic., Australia
| | - Eun Ji Yoo
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Andrea Fanjul
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Jill Wykosky
- Gastroenterology Drug Discovery Unit, Takeda Pharmaceutical Company Limited, San Diego, CA, USA
| | - Linda J Fothergill
- Florey Institute of Neuroscience and Mental Health, Parkville, Vic., Australia.,Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia
| | - Emily A Whitfield
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia
| | - Sebastian G B Furness
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Vic., Australia
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3
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Reich N, Hölscher C. Acylated Ghrelin as a Multi-Targeted Therapy for Alzheimer's and Parkinson's Disease. Front Neurosci 2020; 14:614828. [PMID: 33381011 PMCID: PMC7767977 DOI: 10.3389/fnins.2020.614828] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 11/27/2020] [Indexed: 12/13/2022] Open
Abstract
Much thought has been given to the impact of Amyloid Beta, Tau and Alpha-Synuclein in the development of Alzheimer's disease (AD) and Parkinson's disease (PD), yet the clinical failures of the recent decades indicate that there are further pathological mechanisms at work. Indeed, besides amyloids, AD and PD are characterized by the culminative interplay of oxidative stress, mitochondrial dysfunction and hyperfission, defective autophagy and mitophagy, systemic inflammation, BBB and vascular damage, demyelination, cerebral insulin resistance, the loss of dopamine production in PD, impaired neurogenesis and, of course, widespread axonal, synaptic and neuronal degeneration that leads to cognitive and motor impediments. Interestingly, the acylated form of the hormone ghrelin has shown the potential to ameliorate the latter pathologic changes, although some studies indicate a few complications that need to be considered in the long-term administration of the hormone. As such, this review will illustrate the wide-ranging neuroprotective properties of acylated ghrelin and critically evaluate the hormone's therapeutic benefits for the treatment of AD and PD.
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Affiliation(s)
- Niklas Reich
- Biomedical & Life Sciences Division, Lancaster University, Lancaster, United Kingdom
| | - Christian Hölscher
- Neurology Department, A Second Hospital, Shanxi Medical University, Taiyuan, China.,Research and Experimental Center, Henan University of Chinese Medicine, Zhengzhou, China
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4
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Chai XY, Diwakarla S, Pustovit RV, McQuade RM, Di Natale M, Ermine CM, Parish CL, Finkelstein DI, Furness JB. Investigation of nerve pathways mediating colorectal dysfunction in Parkinson's disease model produced by lesion of nigrostriatal dopaminergic neurons. Neurogastroenterol Motil 2020; 32:e13893. [PMID: 32512642 DOI: 10.1111/nmo.13893] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/02/2020] [Accepted: 05/04/2020] [Indexed: 12/20/2022]
Abstract
BACKGROUND Gastrointestinal (GI) dysfunction, including constipation, is a common non-motor symptom of Parkinson's disease (PD). The toxin 6-hydroxydopamine (6OHDA) produces the symptoms of PD, surprisingly including constipation, after it is injected into the medial forebrain bundle (MFB). However, the mechanisms involved in PD-associated constipation caused by central application of 6OHDA remain unknown. We investigated effects of 6OHDA lesioning of the MFB on motor performance and GI function. METHODS Male Sprague Dawley rats were unilaterally injected with 6OHDA in the MFB. Colorectal propulsion was assessed by bead expulsion after 4 weeks and by recording colorectal contractions and propulsion after 5 weeks. Enteric nervous system (ENS) neuropathy was examined by immunohistochemistry. KEY RESULTS When compared to shams, 6OHDA-lesioned rats had significantly increased times of bead expulsion from the colorectum, indicative of colon dysmotility. Administration of the colokinetic, capromorelin, that stimulates defecation centers in the spinal cord, increased the number of contractions and colorectal propulsion in both groups compared to baseline; however, the effectiveness of capromorelin in 6OHDA-lesioned rats was significantly reduced in comparison with shams, indicating that 6OHDA animals have reduced responsiveness of the spinal defecation centers. Enteric neuropathy was observed in the distal colon, revealing that lesion of the MFB has downstream effects at the cellular level, remote from the site of 6OHDA administration. CONCLUSIONS & INFERENCES We conclude that there are trans-synaptic effects of the proximal, forebrain, lesion of pathways from the brain that send signals down the spinal cord, at the levels of the defecation centers and the ENS.
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Affiliation(s)
- Xin-Yi Chai
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - Shanti Diwakarla
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - Ruslan V Pustovit
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
| | - Rachel M McQuade
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
| | - Madeleine Di Natale
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
| | - Charlotte M Ermine
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - Clare L Parish
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - David I Finkelstein
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia
| | - John B Furness
- Florey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Vic, Australia.,Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic, Australia
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Gruzdeva OV, Borodkina DA, Belik EV, Akbasheva OE, Palicheva EI, Barbarash OL. [Ghrelin Physiology and Pathophysiology: Focus on the Cardiovascular System]. ACTA ACUST UNITED AC 2019; 59:60-67. [PMID: 30990143 DOI: 10.18087/cardio.2019.3.10220] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Accepted: 04/13/2019] [Indexed: 11/18/2022]
Abstract
Ghrelin is a multifunctional peptide hormone, mainly synthesized by P / D1 cells of the stomach fundus mucosa. Its basic effect, which is realized via GHS-R1 α receptor in the arcuate and the ventromedial nucleuses of hypothalamus, is stimulation of the synthesis of pituitary hormones. Ghrelin is involved in control of appetite and energy balance, regulation of carbohydrate and lipid metabolism, cell proliferation and apoptosis, as well as modulation of functioning of gastrointestinal, cardiovascular, pulmonary and immune systems. It was found that cardiomyocytes are able to synthesize ghrelin. High concentrations of GHS-R1α in the heart and major blood vessels evidence for its possible participation in functioning of cardiovascular system. Ghrelin inhibits apoptosis of cardiomyocytes and endothelial cells, and improves the functioning of the left ventricle (LV) after injury of ischemia-reperfusion mechanism. In rats with heart failure (HF) ghrelin improves LV function and attenuates development of cardiac cachexia. In addition, ghrelin exerts vasodilatory effects in humans, improves cardiac function and reduces peripheral vascular resistance in patients with chronic HF. The review contains of the predictive value of ghrelin in the development and prevention of cardiovascular disease.
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Affiliation(s)
- O V Gruzdeva
- Research Institute for Complex Issues of Cardiovascular Diseases Kemerovo State Medical University
| | - D A Borodkina
- Kemerovo regional clinical hospital named after S. V. Belyaeva
| | - E V Belik
- Research Institute for Complex Issues of Cardiovascular Diseases
| | | | - E I Palicheva
- Research Institute for Complex Issues of Cardiovascular Diseases Kemerovo State Medical University
| | - O L Barbarash
- Research Institute for Complex Issues of Cardiovascular Diseases Kemerovo State Medical University
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6
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Kemp BA, Howell NL, Padia SH. Intrarenal ghrelin receptor inhibition ameliorates angiotensin II-dependent hypertension in rats. Am J Physiol Renal Physiol 2018; 315:F1058-F1066. [PMID: 29923768 DOI: 10.1152/ajprenal.00010.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The intrarenal ghrelin receptor (GR) is localized to collecting duct (CD) cells, where it increases epithelial Na+ channel (αENaC)-dependent sodium reabsorption in rodents. We hypothesized that chronic GR inhibition with intrarenal GR siRNA lowers blood pressure (BP) in angiotensin II-dependent hypertension via reductions in αENaC-dependent sodium reabsorption. Uninephrectomized Sprague-Dawley rats ( n = 121) received subcutaneous osmotic pumps for chronic systemic delivery of angiotensin II or vehicle (5% dextrose in water). Rats also received intrarenal infusion of vehicle, GR siRNA, or scrambled (SCR) siRNA. In rats receiving intrarenal vehicle or intrarenal SCR siRNA, systemic angiotensin II infusion increased sodium retention and BP on day 1, and BP remained elevated throughout the 5-day study. These rats also demonstrated increased CD GR expression after 5 days of infusion. However, intrarenal GR siRNA infusion prevented angiotensin II-mediated sodium retention on day 1, induced a continuously negative cumulative sodium balance compared with angiotensin II alone, and reduced BP chronically. Glomerular filtration rate and renal blood flow remained unchanged in GR siRNA-infused rats. Systemic angiotensin II infusion also increased serum aldosterone levels, CD αENaC, and phosphorylated serum and glucocorticoid-inducible kinase 1 expression in rats with intrarenal SCR siRNA; however, these effects were not observed in the presence of intrarenal GR siRNA, despite exposure to the same systemic angiotensin II. These data demonstrate that chronic inhibition of intrarenal GR activity significantly reduces αENaC-dependent sodium retention, resulting in a negative cumulative sodium balance, thereby ameliorating angiotensin II-induced hypertension in rats. Renal GRs represent a novel therapeutic target for the treatment of hypertension and other sodium-retaining states.
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Affiliation(s)
- Brandon A Kemp
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine , Charlottesville, Virginia
| | - Nancy L Howell
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine , Charlottesville, Virginia
| | - Shetal H Padia
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia School of Medicine , Charlottesville, Virginia
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7
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Naitou K, Shiina T, Nakamori H, Sano Y, Shimaoka H, Shimizu Y. Colokinetic effect of somatostatin in the spinal defecation center in rats. J Physiol Sci 2018; 68:243-251. [PMID: 28124286 PMCID: PMC10717079 DOI: 10.1007/s12576-017-0524-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 01/12/2017] [Indexed: 01/10/2023]
Abstract
Somatostatin and its receptors are expressed in the spinal cord, but the functional roles of the peptide remain unknown. In this study, we examined the colokinetic effect of somatostatin in the spinal defecation center in anesthetized rats. Intrathecal application of somatostatin into the lumbo-sacral cord caused propulsive contractions of the colorectum. However, somatostatin administered intravenously or intrathecally to the thoracic cord failed to enhance colorectal motility. Transection of the thoracic cord had no significant impact on the colokinetic action of somatostatin. The enhancement of colorectal motility by intrathecal administration of somatostatin was abolished by severing the pelvic nerves. Our results demonstrate that somatostatin acting on the spinal defecation center causes propulsive motility of the colorectum in rats. Considering that somatostatin is involved in nociceptive signal transmission in the spinal cord, our results provide a rational explanation for the concurrent appearance of chronic abdominal pain and colonic motility disorders in IBS patients.
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Affiliation(s)
- Kiyotada Naitou
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Takahiko Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiroyuki Nakamori
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yuuki Sano
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiroki Shimaoka
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yasutake Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Center for Highly Advanced Integration of Nano and Life Sciences, Gifu University (G-CHAIN), Gifu, Japan.
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8
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Pustovit RV, Callaghan B, Ringuet MT, Kerr NF, Hunne B, Smyth IM, Pietra C, Furness JB. Evidence that central pathways that mediate defecation utilize ghrelin receptors but do not require endogenous ghrelin. Physiol Rep 2018; 5:5/15/e13385. [PMID: 28801520 PMCID: PMC5555902 DOI: 10.14814/phy2.13385] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 07/17/2017] [Accepted: 07/20/2017] [Indexed: 01/24/2023] Open
Abstract
In laboratory animals and in human, centrally penetrant ghrelin receptor agonists, given systemically or orally, cause defecation. Animal studies show that the effect is due to activation of ghrelin receptors in the spinal lumbosacral defecation centers. However, it is not known whether there is a physiological role of ghrelin or the ghrelin receptor in the control of defecation. Using immunohistochemistry and immunoassay, we detected and measured ghrelin in the stomach, but were unable to detect ghrelin by either method in the lumbosacral spinal cord, or other regions of the CNS. In rats in which the thoracic spinal cord was transected 5 weeks before, the effects of a ghrelin agonist on colorectal propulsion were significantly enhanced, but defecation caused by water avoidance stress (WAS) was reduced. In knockout rats that expressed no ghrelin and in wild‐type rats, WAS‐induced defecation was reduced by a ghrelin receptor antagonist, to similar extents. We conclude that the ghrelin receptors of the lumbosacral defecation centers have a physiological role in the control of defecation, but that their role is not dependent on ghrelin. This implies that a transmitter other than ghrelin engages the ghrelin receptor or a ghrelin receptor complex.
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Affiliation(s)
- Ruslan V Pustovit
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Brid Callaghan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Mitchell T Ringuet
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Nicole F Kerr
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Billie Hunne
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia
| | - Ian M Smyth
- Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria, Australia
| | - Claudio Pietra
- Helsinn Research and Preclinical Department, Lugano, Switzerland
| | - John B Furness
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria, Australia .,Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
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9
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Abstract
Ghrelin and motilin are released from gastrointestinal endocrine cells during hunger, to act through G protein-coupled receptors that have closely related amino acid sequences. The actions of ghrelin are more complex than motilin because ghrelin also exists outside the GI tract, it is processed to des-acyl ghrelin which has activity, ghrelin can exist in truncated forms and retain activity, the ghrelin receptor can have constitutive activity and is subject to biased agonism and finally additional ghrelin-like and des-acyl ghrelin receptors are proposed. Both ghrelin and motilin can stimulate gastric emptying, acting via different pathways, perhaps influenced by biased agonism at the receptors, but research is revealing additional pathways of activity. For example, it is becoming apparent that reduction of nausea may be a key therapeutic target for ghrelin receptor agonists and perhaps for compounds that modulate the constitutive activity of the ghrelin receptor. Reduction of nausea may be the mechanism through which gastroparesis symptoms are reduced. Intriguingly, a potential ability of motilin to influence nausea is also becoming apparent. Ghrelin interacts with digestive function through its effects on appetite, and ghrelin antagonists may have a place in treating Prader-Willi syndrome. Unlike motilin, ghrelin receptor agonists also have the potential to treat constipation by acting at the lumbosacral defecation centres. In conclusion, agonists of both ghrelin and motilin receptors hold potential as treatments for specific subsets of digestive system disorders.
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10
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Crotta K, Casnici C, Tonna N, Lattuada D, Bianco F, Marelli O. Characterization of a Monoclonal Antibody Specific for the Growth Hormone Secretagogue Receptor. Monoclon Antib Immunodiagn Immunother 2017; 36:37-43. [PMID: 28409695 DOI: 10.1089/mab.2016.0053] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Ghrelin is an orexigenic peptide hormone that primarily regulates growth hormone secretion, food intake, and energy homeostasis. It has been shown to also play a role in numerous higher brain functions, such as the regulation of inflammation and cell proliferation. Ghrelin is the endogenous ligand of the growth hormone secretagogue receptor (GHSR), a G-protein-coupled receptor highly expressed in brain and detectable in some peripheral tissues. The wide distribution of ghrelin receptor and the number of tissues and cell types known to respond to ghrelin suggest that a number of systems may be affected by treatment with this hormone or its analogues. In this study, we characterized a new GHSR specific monoclonal antibody recognizing specifically the ghrelin receptor. This could be a useful tool for immunoassays aimed at obtaining insights into the physiological and pathological significance of the GHSR/ghrelin system.
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Affiliation(s)
- Katia Crotta
- 1 Department of Medical Biotechnologies and Translational Medicine, School of Medicine, University of Milan , Milan, Italy
| | - Claudia Casnici
- 1 Department of Medical Biotechnologies and Translational Medicine, School of Medicine, University of Milan , Milan, Italy .,2 Ferdinando Santarelli Foundation , Milan, Italy
| | | | - Donatella Lattuada
- 1 Department of Medical Biotechnologies and Translational Medicine, School of Medicine, University of Milan , Milan, Italy
| | - Fabio Bianco
- 2 Ferdinando Santarelli Foundation , Milan, Italy .,4 Sanipedia srl , OpenZone, Bresso, Italy
| | - Ornella Marelli
- 1 Department of Medical Biotechnologies and Translational Medicine, School of Medicine, University of Milan , Milan, Italy
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11
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Zhang CJ, Bidlingmaier M, Altaye M, Page LC, D'Alessio D, Tschöp MH, Tong J. Acute administration of acyl, but not desacyl ghrelin, decreases blood pressure in healthy humans. Eur J Endocrinol 2017; 176:123-132. [PMID: 27913606 PMCID: PMC5325691 DOI: 10.1530/eje-16-0789] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/02/2016] [Accepted: 11/08/2016] [Indexed: 01/13/2023]
Abstract
OBJECTIVE To compare the effects of acyl ghrelin (AG) and desacyl ghrelin (DAG) on blood pressure (BP), heart rate (HR) and other autonomic parameters in healthy humans and to elucidate the hormonal mechanisms through which AG could exert its cardiovascular effects. DESIGN Seventeen healthy participants underwent frequent monitoring of systolic (sBP) and diastolic blood pressure (dBP), HR, respiratory rate (RR) and body surface temperature (Temp) during continuous infusion of AG, DAG, combined AG + DAG or saline control before and during an IV glucose tolerance test on 4 separate days. Plasma catecholamines, renin and aldosterone levels were also measured. Differences in outcome measures between treatment groups were assessed using mixed-model analysis. RESULTS Compared to the saline control, AG and combined AG + DAG infusions decreased sBP, dBP, mean arterial blood pressure (MAP), HR and Temp. In contrast, DAG infusion did not alter BP, RR or Temp, but did decrease HR. The AG and AG + DAG infusions also raised plasma aldosterone levels compared to saline (P < 0.001) without affecting renin or catecholamine levels. CONCLUSIONS The decrease in BP, HR, RR and Temp with AG infusion suggests mediation through the autonomic nervous system. The lack of response to DAG suggests that these autonomic effects require activation of the ghrelin receptor.
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Affiliation(s)
- Cecilia J Zhang
- Division of EndocrinologyMetabolism and Nutrition, Department of Medicine, Duke University, Durham, North Carolina, USA
| | - Martin Bidlingmaier
- Medizinische Klinik und Poliklinik IVLudwig-Maximilians-Universität, Munich, Germany
| | - Mekibib Altaye
- BiostatisticsClinical Translational Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Laura C Page
- Division of Pediatric Endocrinology and DiabetesDepartment of Pediatrics, Duke University, Durham, North Carolina, USA
| | - David D'Alessio
- Division of EndocrinologyDiabetes and Metabolism, Department of Medicine, University of Cincinnati, Cincinnati, Ohio, USA
- Division of EndocrinologyMetabolism and Nutrition, Department of Medicine, Duke University, Durham, North Carolina, USA
- Cincinnati Veterans Affairs Medical CenterCincinnati, Ohio, USA
| | - Matthias H Tschöp
- Division of EndocrinologyDiabetes and Metabolism, Department of Medicine, University of Cincinnati, Cincinnati, Ohio, USA
- Institute for Obesity and DiabetesHelmholtz Diabetes Center Munich and Division of Metabolic Diseases, Technical University, Munich, Germany
| | - Jenny Tong
- Division of EndocrinologyDiabetes and Metabolism, Department of Medicine, University of Cincinnati, Cincinnati, Ohio, USA
- Division of EndocrinologyMetabolism and Nutrition, Department of Medicine, Duke University, Durham, North Carolina, USA
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12
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Yanagimoto Y, Takiguchi S, Miyazaki Y, Makino T, Takahashi T, Kurokawa Y, Yamasaki M, Miyata H, Nakajima K, Mori M, Doki Y. Plasma ghrelin levels as a predictor of adverse renal events due to cisplatin-based chemotherapy in patients with esophageal cancer. Jpn J Clin Oncol 2016; 46:421-6. [DOI: 10.1093/jjco/hyw004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/04/2016] [Indexed: 12/15/2022] Open
Affiliation(s)
- Yoshitomo Yanagimoto
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Shuji Takiguchi
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Yasuhiro Miyazaki
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Tomoki Makino
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Tsuyoshi Takahashi
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Yukinori Kurokawa
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Makoto Yamasaki
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Hiroshi Miyata
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Kiyokazu Nakajima
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Masaki Mori
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
| | - Yuichiro Doki
- Department of Gastroenterological Surgery, Osaka University Graduate School of Medicine, Suita-city, Osaka, Japan
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13
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Deuchars SA, Lall VK. Sympathetic preganglionic neurons: properties and inputs. Compr Physiol 2016; 5:829-69. [PMID: 25880515 DOI: 10.1002/cphy.c140020] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The sympathetic nervous system comprises one half of the autonomic nervous system and participates in maintaining homeostasis and enabling organisms to respond in an appropriate manner to perturbations in their environment, either internal or external. The sympathetic preganglionic neurons (SPNs) lie within the spinal cord and their axons traverse the ventral horn to exit in ventral roots where they form synapses onto postganglionic neurons. Thus, these neurons are the last point at which the central nervous system can exert an effect to enable changes in sympathetic outflow. This review considers the degree of complexity of sympathetic control occurring at the level of the spinal cord. The morphology and targets of SPNs illustrate the diversity within this group, as do their diverse intrinsic properties which reveal some functional significance of these properties. SPNs show high degrees of coupled activity, mediated through gap junctions, that enables rapid and coordinated responses; these gap junctions contribute to the rhythmic activity so critical to sympathetic outflow. The main inputs onto SPNs are considered; these comprise afferent, descending, and interneuronal influences that themselves enable functionally appropriate changes in SPN activity. The complexity of inputs is further demonstrated by the plethora of receptors that mediate the different responses in SPNs; their origins and effects are plentiful and diverse. Together these different inputs and the intrinsic and coupled activity of SPNs result in the rhythmic nature of sympathetic outflow from the spinal cord, which has a variety of frequencies that can be altered in different conditions.
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Affiliation(s)
- Susan A Deuchars
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
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Abstract
The gastrointestinal tract is the major source of the related hormones ghrelin and motilin, which act on structurally similar G protein-coupled receptors. Nevertheless, selective receptor agonists are available. The primary roles of endogenous ghrelin and motilin in the digestive system are to increase appetite or hedonic eating (ghrelin) and initiate phase III of gastric migrating myoelectric complexes (motilin). Ghrelin and motilin also both inhibit nausea. In clinical trials, the motilin receptor agonist camicinal increased gastric emptying, but at lower doses reduced gastroparesis symptoms and improved appetite. Ghrelin receptor agonists have been trialled for the treatment of diabetic gastroparesis because of their ability to increase gastric emptying, but with mixed results; however, relamorelin, a ghrelin agonist, reduced nausea and vomiting in patients with this disorder. Treatment of postoperative ileus with a ghrelin receptor agonist proved unsuccessful. Centrally penetrant ghrelin receptor agonists stimulate defecation in animals and humans, although ghrelin itself does not seem to control colorectal function. Thus, the most promising uses of motilin receptor agonists are the treatment of gastroparesis or conditions with slow gastric emptying, and ghrelin receptor agonists hold potential for the reduction of nausea and vomiting, and the treatment of constipation. Therapeutic, gastrointestinal roles for receptor antagonists or inverse agonists have not been identified.
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Naitou K, Mamerto TP, Pustovit RV, Callaghan B, Rivera LR, Chan AJ, Ringuet MT, Pietra C, Furness JB. Site and mechanism of the colokinetic action of the ghrelin receptor agonist, HM01. Neurogastroenterol Motil 2015; 27:1764-71. [PMID: 26416336 DOI: 10.1111/nmo.12688] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 08/23/2015] [Indexed: 02/06/2023]
Abstract
BACKGROUND It has been recently demonstrated that the ghrelin receptor agonist, HM01, caused defecation in rats that were treated to provide a model for the constipation of Parkinson's disease. HM01 significantly increased fecal output and increased Fos activity in neurons of the hypothalamus and hindbrain, but not in the spinal defecation center. Other ghrelin agonists act on the defecation center. METHODS Receptor pharmacology was examined in ghrelin receptor (GHSR1a) transfected cells. Anesthetized rats were used to investigate sites and mechanisms of action. KEY RESULTS HM01 activated rat GHSR1a at nanomolar concentrations and was antagonized by the GHSR1a antagonist, YIL781. HM01, intravenous, was potent to activate propulsive colorectal contractions. This was prevented by pelvic nerve section and by intravenous YIL781, but not by spinal cord section rostral to the defecation centers. Direct intrathecal application of HM01 to the defecation center at spinal level L6-S1 initiated propulsive contractions of the colorectum. CONCLUSIONS & INFERENCES HM01 stimulates GHSR1a receptors on neurons in the lumbosacral defecation centers to cause propulsive contractions and emptying of the colorectum. It has greater potency when given systemically, compared with other GHSR1a agonists.
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Affiliation(s)
- K Naitou
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia.,Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - T P Mamerto
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - R V Pustovit
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - B Callaghan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - L R Rivera
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - A J Chan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - M T Ringuet
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
| | - C Pietra
- Helsinn Research and Preclinical Department, Lugano, Switzerland
| | - J B Furness
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia.,Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
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Naitou K, Shiina T, Sugita R, Nakamori H, Shimizu Y. Characterization of ghrelin-sensitive neurons in the lumbosacral defecation center in rats. Neurogastroenterol Motil 2015; 27:147-55. [PMID: 25557226 DOI: 10.1111/nmo.12492] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 11/21/2014] [Indexed: 01/06/2023]
Abstract
BACKGROUND Ghrelin is involved in the regulation of somatic growth, feeding behavior and energy homeostasis. Ghrelin stimulates neuropeptide Y (NPY) neurons and activates intracellular AMP-activated protein kinase (AMPK) in the hypothalamus. These NPY neurons also express the leptin receptor and leptin inhibits ghrelin-induced activation of NPY neurons. In the spinal cord, we have demonstrated colokinetic action of ghrelin. However, the precise characteristics of the ghrelin-sensitive neurons remain to be clarified. The aim of this study was firstly to confirm that the action of ghrelin is mediated via a neurogenic pathway in the spinal cord, and secondly to characterize the ghrelin-sensitive neurons by comparing with hypothalamic ghrelin-sensitive neurons. METHODS Rats were anesthetised with alpha-chloralose and ketamine, and colorectal intraluminal pressure and expelled volume were recorded in vivo. Drugs were applied intrathecally. KEY RESULTS Ghrelin caused enhancement of propulsive contractions. Tetrodotoxin completely blocked the colokinetic effect of ghrelin. An AMPK activator, aminoimidazole carboxamide ribonucleotide, failed to mimic the ghrelin effect. Leptin had no effect on the spontaneous contractions and did not exert a suppressive effect on the ghrelin-enhanced colorectal motility. An NPY Y1 receptor antagonist did not affect the action of ghrelin. NPY had no effect on the colorectal motility. CONCLUSIONS & INFERENCES This study showed that intrathecal injection of ghrelin stimulates colorectal motility by acting on ghrelin-sensitive neurons in the lumbosacral defecation center. The characteristics of ghrelin-sensitive neurons in the spinal cord are quite different from those of ghrelin-sensitive neurons in the hypothalamus.
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Affiliation(s)
- K Naitou
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
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17
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Callaghan B, Kosari S, Pustovit RV, Sartor DM, Ferens D, Ban K, Baell J, Nguyen TV, Rivera LR, Brock JA, Furness JB. Hypotensive effects of ghrelin receptor agonists mediated through a novel receptor. Br J Pharmacol 2014; 171:1275-86. [PMID: 24670149 DOI: 10.1111/bph.12527] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2013] [Revised: 09/27/2013] [Accepted: 11/12/2013] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE Some agonists of ghrelin receptors cause rapid decreases in BP. The mechanisms by which they cause hypotension and the pharmacology of the receptors are unknown. EXPERIMENTAL APPROACH The effects of ligands of ghrelin receptors were investigated in rats in vivo, on isolated blood vessels and on cells transfected with the only molecularly defined ghrelin receptor, growth hormone secretagogue receptor 1a (GHSR1a). KEY RESULTS Three agonists of GHSR1a receptors, ulimorelin, capromorelin and CP464709, caused a rapid decrease in BP in the anaesthetized rat. The effect was not reduced by either of two GHSR1a antagonists, JMV2959 or YIL781, at doses that blocked effects on colorectal motility, in vivo. The rapid hypotension was not mimicked by ghrelin, unacylated ghrelin or the unacylated ghrelin receptor agonist, AZP531. The early hypotension preceded a decrease in sympathetic nerve activity. Early hypotension was not reduced by hexamethonium or by baroreceptor (sino-aortic) denervation. Ulimorelin also relaxed isolated segments of rat mesenteric artery, and, less potently, relaxed aorta segments. The vascular relaxation was not reduced by JMV2959 or YIL781. Ulimorelin, capromorelin and CP464709 activated GHSR1a in transfected HEK293 cells at nanomolar concentrations. JMV2959 and YIL781 both antagonized effects in these cells, with their pA2 values at the GHSR1a receptor being 6.55 and 7.84. CONCLUSIONS AND IMPLICATIONS Our results indicate a novel vascular receptor or receptors whose activation by ulimorelin, capromorelin and CP464709 lowered BP. This receptor is activated by low MW GHSR1a agonists, but is not activated by ghrelin.
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Affiliation(s)
- Brid Callaghan
- Department of Anatomy and Neuroscience, University of Melbourne, Parkville, Vic., Australia
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18
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Kemp BA, Howell NL, Gildea JJ, Padia SH. Intrarenal ghrelin receptor antagonism prevents high-fat diet-induced hypertension in male rats. Endocrinology 2014; 155:2658-66. [PMID: 24797629 DOI: 10.1210/en.2013-2177] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Excess weight gain contributes up to 65% of the risk of primary hypertension, and the increase in blood pressure in response to high-fat diet (HFD) is preceded by significant increases in renal tubular sodium (Na(+)) reabsorption. In normal rats, intrarenal ghrelin infusion increases distal nephron-dependent Na(+) reabsorption via activation of the intrarenal ghrelin receptor (GHSR). This study focusses on the role of intrarenal GHSR-mediated Na(+) reabsorption in HFD-induced hypertension. Dahl salt-sensitive rats received standard diet or HFD for 6 weeks. Rats underwent uninephrectomy and osmotic minipump implantation for chronic intrarenal delivery of vehicle (0.25 μL/h × 28 d), selective GHSR antagonist [D-Lys-3]-growth hormone releasing peptide-6 (0.2μM/d), or GHSR inverse agonist [D-Arg(1), D-Phe(5), D-Trp(7,9), Leu(11)]-substance P (SUB-P) (3.6μM/d). HFD rats with vehicle pumps had significantly increased renal GHSR expression compared with standard diet (0.092 ± 0.005 vs 0.065 ± 0.004 arbitrary units; P < .05), whereas acyl ghrelin levels were similar (16.3±6.2 vs 15.7±8.7 pg/g tissue). HFD rats with vehicle pumps became hypertensive after 2 weeks (P < .05) and showed a significant reduction in 24-hour urine Na(+) before hypertension. At this time, these rats showed an increase in collecting duct α-epithelial Na(+) channel, thereby providing a potential mechanism for the excess Na(+) reabsorption. In contrast, HFD rats with [D-Lys-3]-growth hormone releasing peptide-6 or SUB-P pumps never became hypertensive and did not show the reduction in urine Na(+). Because SUB-P blocks the constitutive, but not ghrelin-dependent, activity of the GHSR, and HFD-induced α-epithelial Na(+) channel up-regulation was abolished during GHSR antagonism, these data suggest that HFD increases the constitutive activity of renal GHSR to increase Na(+) reabsorption and induce hypertension in rats.
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Affiliation(s)
- Brandon A Kemp
- Division of Endocrinology and Metabolism (B.A.K., N.L.H., S.H.P.), Department of Medicine, and Department of Pathology (J.J.G.), University of Virginia School of Medicine, Charlottesville, Virginia 22908-1414
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19
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Hirayama H, Mominoki K, Shiina T, Shimizu Y. [Effect of ghrelin on colonic motility]. Nihon Yakurigaku Zasshi 2014; 143:270-274. [PMID: 24919551 DOI: 10.1254/fpj.143.270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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20
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Sim YB, Park SH, Kim SS, Kim CH, Kim SJ, Lim SM, Jung JS, Suh HW. Ghrelin administered spinally increases the blood glucose level in mice. Peptides 2014; 54:162-5. [PMID: 24472858 DOI: 10.1016/j.peptides.2014.01.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 01/17/2014] [Accepted: 01/17/2014] [Indexed: 02/07/2023]
Abstract
Ghrelin is known as a regulator of the blood glucose homeostasis and food intake. In the present study, the possible roles of ghrelin located in the spinal cord in the regulation of the blood glucose level were investigated in ICR mice. We found that intrathecal (i.t.) injection with ghrelin (from 1 to 10 μg) caused an elevation of the blood glucose level. In addition, i.t. pretreatment with YIL781 (ghrelin receptor antagonist; from 0.1 to 5 μg) markedly attenuated ghrelin-induced hyperglycemic effect. The plasma insulin level was increased by ghrelin. The enhanced plasma insulin level by ghrelin was reduced by i.t. pretreatment with YIL781. However, i.t. pretreatment with glucagon-like peptide-1 (GLP-1; 5 μg) did not affect the ghrelin-induced hyperglycemia. Furthermore, i.t. administration with ghrelin also elevated the blood glucose level, but in an additive manner, in d-glucose-fed model. Our results suggest that the activation of ghrelin receptors located in the spinal cord plays important roles for the elevation of the blood glucose level.
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Affiliation(s)
- Yun-Beom Sim
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Soo-Hyun Park
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Sung-Su Kim
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Chea-Ha Kim
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Su-Jin Kim
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Su-Min Lim
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Jun-Sub Jung
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea
| | - Hong-Won Suh
- Department of Pharmacology, Institute of Natural Medicine, College of Medicine, Hallym University, 39 Hallymdaehak-gil, Chuncheon, Gangwon-do 200-702, Republic of Korea.
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21
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Sanger GJ. Ghrelin and motilin receptor agonists: time to introduce bias into drug design. Neurogastroenterol Motil 2014; 26:149-55. [PMID: 24438586 DOI: 10.1111/nmo.12300] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 12/11/2013] [Indexed: 02/08/2023]
Abstract
Ghrelin and motilin receptor agonists increase gastric motility and are attractive drug targets. However, 14 years after the receptors were described (18-24 years since ligands became available) the inactivity of the ghrelin agonist TZP-102 in patients with gastroparesis joins the list of unsuccessful motilin agonists. Fundamental questions must be asked. Pustovit et al., have now shown that the ghrelin agonist ulimorelin evokes prolonged increases in rat colorectal propulsion yet responses to other ghrelin agonists fade. Similarly, different motilin agonists induce short- or long-lasting effects in a cell-dependent manner. Together, these and other data create the hypothesis that the receptors can be induced to preferentially signal ('biased agonism') via particular pathways to evoke different responses with therapeutic advantages/disadvantages. Biased agonism has been demonstrated for ghrelin. Are motilin agonists which cause long-lasting facilitation of human stomach cholinergic function (compared with motilin) biased agonists (e.g., camicinal, under development for patients with gastric hypo-motility)? For ghrelin, additional complications exist because the therapeutic aims/mechanisms of action are uncertain, making it difficult to select the best (biased) agonist. Will ghrelin agonists be useful treatments of nausea and/or as suggested by Pustovit et al., chronic constipation? How does ghrelin increase gastric motility? As gastroparesis symptoms poorly correlate with delayed gastric emptying (yet gastro-prokinetic drugs can provide relief: e.g., low-dose erythromycin), would low doses of ghrelin and motilin agonists relieve symptoms simply by restoring neuromuscular rhythm? These questions on design and functions need addressing if ghrelin and motilin agonists are to reach patients as drugs.
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Affiliation(s)
- G J Sanger
- Neurogastroenterology Group, Blizard Institute, Barts & The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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22
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Pustovit RV, Callaghan B, Kosari S, Rivera LR, Thomas H, Brock JA, Furness JB. The mechanism of enhanced defecation caused by the ghrelin receptor agonist, ulimorelin. Neurogastroenterol Motil 2014; 26:264-71. [PMID: 24304447 DOI: 10.1111/nmo.12259] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 10/11/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND Discovery of adequate pharmacological treatments for constipation has proven elusive. Increased numbers of bowel movements were reported as a side-effect of ulimorelin treatment of gastroparesis, but there has been no investigation of the site of action. METHODS Anesthetized rats were used to investigate sites and mechanisms of action of ulimorelin. KEY RESULTS Intravenous ulimorelin (1-5 mg/kg) caused a substantial and prolonged (~1 h) increase in colorectal propulsive activity and expulsion of colonic contents. This was prevented by cutting the nerves emerging from the lumbosacral cord, by the nicotinic receptor antagonist hexamethonium and by antagonists of the ghrelin receptor. The effect of intravenous ulimorelin was mimicked by direct application of ulimorelin (5 μg) to the lumbosacral spinal cord. CONCLUSIONS & INFERENCES Ulimorelin is a potent prokinetic that causes propulsive contractions of the colorectum by activating ghrelin receptors of the lumbosacral defecation centers. Its effects are long-lasting, in contrast with other colokinetics that target ghrelin receptors.
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Affiliation(s)
- R V Pustovit
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, VIC, Australia
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Bron R, Yin L, Russo D, Furness JB. Expression of the ghrelin receptor gene in neurons of the medulla oblongata of the rat. J Comp Neurol 2013; 521:2680-702. [DOI: 10.1002/cne.23309] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 12/12/2012] [Accepted: 01/17/2013] [Indexed: 01/29/2023]
Affiliation(s)
- Romke Bron
- Department of Anatomy & Neuroscience; University of Melbourne; Parkville; Victoria 3010; Australia
| | - Lei Yin
- Department of Anatomy & Neuroscience; University of Melbourne; Parkville; Victoria 3010; Australia
| | - Domenico Russo
- Department of Veterinary Morphophysiology and Animal Production; University of Bologna; 40064 Ozzano Emilia; Bologna; Italy
| | - John B. Furness
- Department of Anatomy & Neuroscience; University of Melbourne; Parkville; Victoria 3010; Australia
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Freeman JN, do Carmo JM, Adi AH, da Silva AA. Chronic central ghrelin infusion reduces blood pressure and heart rate despite increasing appetite and promoting weight gain in normotensive and hypertensive rats. Peptides 2013; 42:35-42. [PMID: 23416021 PMCID: PMC3654065 DOI: 10.1016/j.peptides.2013.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/04/2013] [Accepted: 02/05/2013] [Indexed: 11/29/2022]
Abstract
Acute studies showed that ghrelin acts on the central nervous system (CNS) to reduce blood pressure (BP), heart rate (HR) and sympathetic activity. However, the long-term CNS cardiovascular actions of ghrelin are still unclear. We tested whether chronic intracerebroventricular (ICV) infusion of ghrelin causes sustained reductions in BP, HR and whether it alters baroreceptor sensitivity (BRS) and autonomic input to the heart. A cannula was placed in the lateral ventricle of male Sprague-Dawley (SD) rats for ICV infusions via osmotic minipump (0.5 μl/h). BP and HR were measured 24-h/day by telemetry. After 5 days of control measurements, ghrelin (0.21 nmol/h) or saline vehicle were infused ICV for 10 days followed by a 5-day post-treatment period. Chronic ICV ghrelin infusion increased food intake (22±3 to 26±1 g/day) leading to ~50 g body weight gain. BP fell slightly during ghrelin infusion while HR decreased by ~26 bpm. In control animals BP and HR increased modestly. ICV Ghrelin infusion caused a 50% reduction in sympathetic tone to the heart but did not alter BRS. We also tested if the depressor responses to ICV ghrelin infusion were enhanced in spontaneously hypertensive rats (SHR) due to their high basal sympathetic tone. However, we observed similar BP and HR responses compared to normotensive rats. These results indicate that ghrelin, acting via direct actions on the CNS, has a sustained effect to lower HR and a modest impact to reduce BP in normotensive and hypertensive animals despite increasing appetite and body weight.
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Affiliation(s)
- John N Freeman
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS 39216-4505, United States
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25
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Callaghan B, Hunne B, Hirayama H, Sartor DM, Nguyen TV, Abogadie FC, Ferens D, McIntyre P, Ban K, Baell J, Furness JB, Brock JA. Sites of action of ghrelin receptor ligands in cardiovascular control. Am J Physiol Heart Circ Physiol 2012; 303:H1011-21. [PMID: 22886413 DOI: 10.1152/ajpheart.00418.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Circulating ghrelin reduces blood pressure, but the mechanism for this action is unknown. This study investigated whether ghrelin has direct vasodilator effects mediated through the growth hormone secretagogue receptor 1a (GHSR1a) and whether ghrelin reduces sympathetic nerve activity. Mice expressing enhanced green fluorescent protein under control of the promoter for growth hormone secretagogue receptor (GHSR) and RT-PCR were used to locate sites of receptor expression. Effects of ghrelin and the nonpeptide GHSR1a agonist capromorelin on rat arteries and on transmission in sympathetic ganglia were measured in vitro. In addition, rat blood pressure and sympathetic nerve activity responses to ghrelin were determined in vivo. In reporter mice, expression of GHSR was revealed at sites where it has been previously demonstrated (hypothalamic neurons, renal tubules, sympathetic preganglionic neurons) but not in any artery studied, including mesenteric, cerebral, and coronary arteries. In rat, RT-PCR detected GHSR1a mRNA expression in spinal cord and kidney but not in the aorta or in mesenteric arteries. Moreover, the aorta and mesenteric arteries from rats were not dilated by ghrelin or capromorelin at concentrations >100 times their EC(50) determined in cells transfected with human or rat GHSR1a. These agonists did not affect transmission from preganglionic sympathetic neurons that express GHSR1a. Intravenous application of ghrelin lowered blood pressure and decreased splanchnic nerve activity. It is concluded that the blood pressure reduction to ghrelin occurs concomitantly with a decrease in sympathetic nerve activity and is not caused by direct actions on blood vessels or by inhibition of transmission in sympathetic ganglia.
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Affiliation(s)
- Brid Callaghan
- Department of Anatomy & Neuroscience, University of Melbourne, Parkville, Victoria 3010, Australia
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Zhang Q, Huang C, Meng B, Tang T, Shi Q, Yang H. Acute effect of Ghrelin on ischemia/reperfusion injury in the rat spinal cord. Int J Mol Sci 2012; 13:9864-9876. [PMID: 22949835 PMCID: PMC3431833 DOI: 10.3390/ijms13089864] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/17/2012] [Accepted: 07/19/2012] [Indexed: 01/25/2023] Open
Abstract
Ghrelin, a 28-amino acid peptide, is mainly secreted by the stomach. Ghrelin has been shown to have neuroprotective effects. However, whether ghrelin protects the spinal cord from ischemia/reperfusion (I/R) injury is unknown. To investigate this, 60 rats were randomly divided into three different groups: the sham group (n = 20), the vehicle group (n = 20), and the Ghrelin group (100 μg/kg, n = 20). Rats were sacrificed 12, 24, 48 and 72 h after ischemia. After the evaluation of neurologic function (48 h), the spinal cords were immediately removed for the determination of myeloperoxidase (MPO) activity (12-72 h). Apoptosis was quantitatively measured using the terminal transferase UTP nick end-labeling (TUNEL) method (24 h). The expression of bax and bcl-2 were evaluated by Western blot analysis (1 h), and GHSR-1a mRNA expression was detected using reverse transcriptase polymerase chain reaction (24 h). The neurological motor function was evaluated by 'Tarlov's score'. The neurologic outcomes in the ghrelin-group were significantly better than those in the vehicle group (p < 0.05). Serum tumor necrosis factor (TNF-α) levels were assessed in the peripheral venous blood. Ghrelin decreased the serum TNF-α levels and ameliorated the down regulation of spinal cord MPO activity. The expression of ghrelin receptors (GHSR-1a) in the rat spinal cord was decreased by I/R injury and increased by ghrelin. Ghrelin reduced the TUNEL-positive rate. Greater bcl-2, HSP27, HSP70, and attenuated bax expression were observed in the ghrelin-treated rats. Our results suggest that ghrelin administration may inhibit spinal I/R injury. Moreover, the improvement of neurologic function in rats was increased after the ghrelin treatment.
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Affiliation(s)
- Qin Zhang
- Department of Orthopedics, Yuncheng Central Hospital, Yuncheng 044000, China; E-Mail:
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Soochow 215007, China; E-Mails: (C.H.); (B.M.); (T.T.); (Q.S.)
| | - Chen Huang
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Soochow 215007, China; E-Mails: (C.H.); (B.M.); (T.T.); (Q.S.)
| | - Bin Meng
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Soochow 215007, China; E-Mails: (C.H.); (B.M.); (T.T.); (Q.S.)
| | - Tiansi Tang
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Soochow 215007, China; E-Mails: (C.H.); (B.M.); (T.T.); (Q.S.)
| | - Qin Shi
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Soochow 215007, China; E-Mails: (C.H.); (B.M.); (T.T.); (Q.S.)
| | - Huilin Yang
- Department of Orthopedics, The First Affiliated Hospital of Soochow University, Soochow 215007, China; E-Mails: (C.H.); (B.M.); (T.T.); (Q.S.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +86-512-6778-1169; Fax: +86-512-6778-0999
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Furness JB, Cho HJ, Hunne B, Hirayama H, Callaghan BP, Lomax AE, Brock JA. Identification of neurons that express ghrelin receptors in autonomic pathways originating from the spinal cord. Cell Tissue Res 2012; 348:397-405. [DOI: 10.1007/s00441-012-1405-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 03/08/2012] [Indexed: 12/26/2022]
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Liu B, Garcia EA, Korbonits M. Genetic studies on the ghrelin, growth hormone secretagogue receptor (GHSR) and ghrelin O-acyl transferase (GOAT) genes. Peptides 2011; 32:2191-207. [PMID: 21930173 DOI: 10.1016/j.peptides.2011.09.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 09/03/2011] [Accepted: 09/06/2011] [Indexed: 12/15/2022]
Abstract
Ghrelin is a 28 amino acid peptide hormone that is produced both centrally and peripherally. Regulated by the ghrelin O-acyl transferase enzyme, ghrelin exerts its action through the growth hormone secretagogue receptor, and is implicated in a diverse range of physiological processes. These implications have placed the ghrelin signaling pathway at the center of a large number of candidate gene and genome-wide studies which aim to identify the genetic basis of human heterogeneity. In this review we summarize the available data on the genetic variability of ghrelin, its receptor and its regulatory enzyme, and their association with obesity, stature, type 2 diabetes, cardiovascular disease, eating disorders, and reward seeking behavior.
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Affiliation(s)
- Boyang Liu
- Department of Endocrinology, Barts and the London School of Medicine, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK
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Venables G, Hunne B, Bron R, Cho HJ, Brock JA, Furness JB. Ghrelin receptors are expressed by distal tubules of the mouse kidney. Cell Tissue Res 2011; 346:135-9. [PMID: 21956643 DOI: 10.1007/s00441-011-1240-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 09/02/2011] [Indexed: 11/25/2022]
Abstract
Ghrelin, a peptide hormone from the stomach, has been recently discovered to reduce sodium excretion from the kidney. Although the effects on the kidney suggest actions in the distal nephron, the sites of expression of ghrelin receptors have not been localised. In the present work we have used a mouse that expresses green fluorescent protein under the control of the ghrelin receptor promoter to locate sites of receptor expression in the kidney. Receptor expression was confined to the straight parts of the distal tubules and the thin limbs of the loops of Henle. No expression was detected in other structures, including the glomeruli, proximal tubules and collecting ducts. Ghrelin receptors were not found in extra-renal or intra-renal arteries, despite observations that ghrelin is a vasodilator. The distribution revealed by in situ hybridisation histochemistry was the same as that revealed by the reporter. In conclusion, ghrelin receptors have a restricted distribution in the kidney. The location in the straight parts of the distal tubules accords with observations that ghrelin promotes sodium retention.
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Affiliation(s)
- Gene Venables
- Department of Anatomy & Cell Biology, University of Melbourne, Parkville, Victoria, Australia
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30
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Frago LM, Baquedano E, Argente J, Chowen JA. Neuroprotective actions of ghrelin and growth hormone secretagogues. Front Mol Neurosci 2011; 4:23. [PMID: 21994488 PMCID: PMC3182030 DOI: 10.3389/fnmol.2011.00023] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 08/29/2011] [Indexed: 11/21/2022] Open
Abstract
The brain incorporates and coordinates information based on the hormonal environment, receiving information from peripheral tissues through the circulation. Although it was initially thought that hormones only acted on the hypothalamus to perform endocrine functions, it is now known that they in fact exert diverse actions on many different brain regions including the hypothalamus. Ghrelin is a gastric hormone that stimulates growth hormone secretion and food intake to regulate energy homeostasis and body weight by binding to its receptor, growth hormone secretagogues–GH secretagogue-receptor, which is most highly expressed in the pituitary and hypothalamus. In addition, ghrelin has effects on learning and memory, reward and motivation, anxiety, and depression, and could be a potential therapeutic agent in neurodegenerative disorders where excitotoxic neuronal cell death and inflammatory processes are involved.
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Affiliation(s)
- Laura M Frago
- Department of Pediatrics, Universidad Autónoma de Madrid Madrid, Spain
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Furness JB, Hunne B, Matsuda N, Yin L, Russo D, Kato I, Fujimiya M, Patterson M, McLeod J, Andrews ZB, Bron R. Investigation of the presence of ghrelin in the central nervous system of the rat and mouse. Neuroscience 2011; 193:1-9. [PMID: 21835225 DOI: 10.1016/j.neuroscience.2011.07.063] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 07/25/2011] [Accepted: 07/25/2011] [Indexed: 11/25/2022]
Abstract
Ghrelin and ghrelin receptor agonist have effects on central neurons in many locations, including the hypothalamus, caudal brain stem, and spinal cord. However, descriptions of the distributions of ghrelin-like immunoreactivity in the CNS in published work are inconsistent. We have used three well-characterized anti-ghrelin antibodies, an antibody to the unacylated form of ghrelin, and a ghrelin peptide assay in rats, mice, ghrelin knockout mice, and ghrelin receptor reporter mice to re-evaluate ghrelin presence in the rodent CNS. The stomach served as a positive control. All antibodies were effective in revealing gastric endocrine cells. However, no specific staining could be found in the brain or spinal cord. Concentrations of antibody 10 to 30 times those effective in the stomach bound to nerve cells in rat and mouse brain, but this binding was not reduced by absorbing concentrations of ghrelin peptide, or by use of ghrelin gene knockout mice. Concentrations of ghrelin-like peptide, detected by enzyme-linked immunosorbent assay in extracts of hypothalamus, were 1% of gastric concentrations. Ghrelin receptor-expressing neurons had no adjacent ghrelin immunoreactive terminals. It is concluded that there are insignificant amounts of authentic ghrelin in neurons in the mouse or rat CNS and that ghrelin receptor-expressing neurons do not receive synaptic inputs from ghrelin-immunoreactive nerve terminals in these species.
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Affiliation(s)
- J B Furness
- Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
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Stimulation of defecation in spinal cord-injured rats by a centrally acting ghrelin receptor agonist. Spinal Cord 2011; 49:1036-41. [DOI: 10.1038/sc.2011.60] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Granata R, Isgaard J, Alloatti G, Ghigo E. Cardiovascular actions of the ghrelin gene-derived peptides and growth hormone-releasing hormone. Exp Biol Med (Maywood) 2011; 236:505-514. [DOI: 10.1258/ebm.2011.010365] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
Abstract
In 1976, small peptide growth hormone secretagogues (GHSs) were discovered and found to promote growth hormone (GH) release from the pituitary. The GHS receptor (GHS-R) was subsequently cloned, and its endogenous ligand ghrelin was later isolated from the stomach. Ghrelin is a 28-amino acid peptide, whose acylation is essential for binding to GHS-R type 1a and for the endocrine functions, including stimulation of GH secretion and subsequent food intake. Unacylated ghrelin, the other ghrelin form, although devoid of GHS-R binding is an active peptide, sharing many peripheral effects with acylated ghrelin (AG). The ghrelin system is broadly expressed in myocardial tissues, where it exerts different functions. Indeed, ghrelin inhibits cardiomyocyte and endothelial cell apoptosis, and improves left ventricular (LV) function during ischemia–reperfusion (I/R) injury. In rats with heart failure (HF), ghrelin improves LV dysfunction and attenuates the development of cardiac cachexia. Similarly, ghrelin exerts vasodilatory effects in humans, improves cardiac function and decreases systemic vascular resistance in patients with chronic HF. Obestatin is a recently identified ghrelin gene peptide. The physiological role of obestatin and its binding to the putative GPR39 receptor are still unclear, although protective effects have been demonstrated in the pancreas and heart. Similarly to AG, the hypothalamic peptide growth hormone-releasing hormone (GHRH) stimulates GH release from the pituitary, through binding to the GHRH-receptor. Besides its proliferative effects in different cell types, at the cardiovascular level GHRH inhibits cardiomyocyte apoptosis, and reduces infarct size in both isolated rat heart after I/R and in vivo after myocardial infarction. Therefore, both ghrelin and GHRH exert cardioprotective effects, which make them candidate targets for therapeutic intervention in cardiovascular dysfunctions.
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Affiliation(s)
- Riccarda Granata
- Laboratory of Molecular and Cellular Endocrinology, Division of Endocrinology, Diabetology and Metabolism, Department of Internal Medicine, University of Turin, Corso Dogliotti, 14-10126 Turin, Italy
| | - Jörgen Isgaard
- Department of Internal Medicine, The Sahlgrenska Academy at the University of Gothenburg, 413 46 Gothenburg, Sweden
| | - Giuseppe Alloatti
- Department of Animal and Human Biology, University of Turin, 10123 Turin, Italy
| | - Ezio Ghigo
- Laboratory of Molecular and Cellular Endocrinology, Division of Endocrinology, Diabetology and Metabolism, Department of Internal Medicine, University of Turin, Corso Dogliotti, 14-10126 Turin, Italy
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Current world literature. Curr Opin Endocrinol Diabetes Obes 2011; 18:83-98. [PMID: 21178692 DOI: 10.1097/med.0b013e3283432fa7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Kemp BA, Howell NL, Gray JT, Keller SR, Nass RM, Padia SH. Intrarenal ghrelin infusion stimulates distal nephron-dependent sodium reabsorption in normal rats. Hypertension 2011; 57:633-9. [PMID: 21220707 DOI: 10.1161/hypertensionaha.110.166413] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Ghrelin is a 28-amino acid peptide hormone that exerts powerful orexigenic effects. Ghrelin receptor expression has been reported in the kidney, but the role of ghrelin in the kidney is unknown. The present studies confirmed ghrelin receptor mRNA expression in the kidneys of normal Sprague Dawley rats (n=6) using reverse transcription polymerase chain reaction (PCR) and sequencing of the 588-bp PCR product. To test intrarenal ghrelin action, uninephrectomized rats received 3 cumulative 1-hour renal interstitial (RI) infusions of 5% dextrose in water (vehicle, n=21), ghrelin (n=10), ghrelin plus specific ghrelin receptor antagonist [D-Lys-3]-GHRP-6 (n=24), or [D-Lys-3]-GHRP-6 alone (n=32). Mean arterial pressure (MAP), urine sodium excretion rate (U(Na)V), glomerular filtration rate (GFR), fractional excretion of sodium (FE(Na)), and fractional excretion of lithium (FE(Li)) were calculated for each period. RI ghrelin infusion significantly decreased U(Na)V to 86 ± 4.9% (P<0.05), 74 ± 6.5% (P<0.01), and 62 ± 10% (P<0.01) of baseline during periods 1 to 3, respectively. Ghrelin also significantly decreased FE(Na) to 68 ± 11% (P<0.05), 57 ± 8.6% (P<0.001), and 59 ± 12% (P<0.01) of baseline, without changing GFR or FE(Li). Identical ghrelin infusions in the presence of [D-Lys-3]-GHRP-6 failed to permit reductions in U(Na)V or FE(Na). Following [D-Lys-3]-GHRP-6 infusion alone, U(Na)V increased from 0.06 ± 0.01 to 0.18 ± 0.03 μmol/min (P<0.0001). Concomitant increases in FE(Na) were also observed (0.23 ± 0.03% to 0.51 ± 0.06% [P<0.001]), without changes in MAP, GFR, or FE(Li). Together, these data introduce a novel intrarenal ghrelin-ghrelin receptor system, which, on activation, significantly increases Na(+) reabsorption at the level of the distal nephron.
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Affiliation(s)
- Brandon A Kemp
- Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia Health System, Charlottesville, VA 22908-1414, USA
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Andrews ZB. The extra-hypothalamic actions of ghrelin on neuronal function. Trends Neurosci 2010; 34:31-40. [PMID: 21035199 DOI: 10.1016/j.tins.2010.10.001] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 09/30/2010] [Accepted: 10/01/2010] [Indexed: 12/20/2022]
Abstract
Ghrelin is a peptide hormone produced and secreted in the stomach. Numerous studies over the past decade demonstrate its importance in food intake, body-weight regulation and glucose homeostasis. These effects are driven largely by the high expression of the ghrelin receptor (GHSR1a) in the hypothalamus. However, GHSR1a is also expressed in numerous extra-hypothalamic neuronal populations, suggesting that ghrelin has physiological functions besides those involved in metabolic functions. In this review, I focus on increasing evidence that ghrelin has important roles in extra-hypothalamic functions, including learning and memory, reward and motivation, anxiety and depression, and neuroprotection. Furthermore, I discuss how the recently demonstrated role of ghrelin in promoting survival during periods of caloric restriction could contribute to its inherent neuroprotective and neuromodulatory properties.
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Affiliation(s)
- Zane B Andrews
- Department of Physiology, Monash University, Clayton, VIC 3183, Australia.
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Hirayama H, Shiina T, Shima T, Kuramoto H, Takewaki T, B Furness J, Shimizu Y. Contrasting effects of ghrelin and des-acyl ghrelin on the lumbo-sacral defecation center and regulation of colorectal motility in rats. Neurogastroenterol Motil 2010; 22:1124-31. [PMID: 20584261 DOI: 10.1111/j.1365-2982.2010.01553.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND We have previously demonstrated that a centrally penetrant ghrelin receptor agonist enhances colorectal motility, through activation of the lumbo-sacral defecation center (L6-S1 region of the spinal cord) in rats. In the present study, we examined the effects of the native peptide and its non-acylated counterpart in eliciting this stimulatory effect on colorectal motility. METHODS Rats were anesthetised with α-chloralose and ketamine, and colorectal intraluminal pressure and propelled intraluminal liquid volume were recorded in vivo. KEY RESULTS Intrathecal application of acylated ghrelin to the L6-S1 region of the spinal cord, but not intravenous application, elicited groups of phasic increases in colorectal intraluminal pressure that were associated with increased fluid output through the anal cannula. The effect was dose-dependent. The colokinetic effects of ghrelin were prevented if the pelvic nerves were severed. Reverse transcription polymerase chain reaction revealed the expression of the ghrelin and ghrelin receptor genes in the lumbo-sacral spinal cord. In contrast to acylated ghrelin, des-acyl ghrelin failed to cause changes in colorectal motility. However, when des-acyl ghrelin and ghrelin were applied simultaneously at the L6-S1 region, the ghrelin-induced enhancement of colorectal motility was significantly attenuated. CONCLUSION & INFERENCES It is concluded that acylation of the ghrelin peptide is essential to promote propulsive contractions of the colorectum and that des-acyl ghrelin opposes this effect. At most other sites of ghrelin action, des-acyl ghrelin either has no effect or it mimics ghrelin. This is the first evidence that non-acylated ghrelin opposes the action of the acylated peptide in the spinal cord.
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Affiliation(s)
- H Hirayama
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University, Yanagido, Gifu, Japan
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Ferens DM, Yin L, Ohashi-Doi K, Habgood M, Bron R, Brock JA, Gale JD, Furness JB. Evidence for functional ghrelin receptors on parasympathetic preganglionic neurons of micturition control pathways in the rat. Clin Exp Pharmacol Physiol 2010; 37:926-32. [DOI: 10.1111/j.1440-1681.2010.05409.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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