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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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Sadee W. Ligand-Free Signaling of G-Protein-Coupled Receptors: Physiology, Pharmacology, and Genetics. Molecules 2023; 28:6375. [PMID: 37687205 PMCID: PMC10489045 DOI: 10.3390/molecules28176375] [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: 07/29/2023] [Revised: 08/28/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) are ubiquitous sensors and regulators of cellular functions. Each GPCR exists in complex aggregates with multiple resting and active conformations. Designed to detect weak stimuli, GPCRs can also activate spontaneously, resulting in basal ligand-free signaling. Agonists trigger a cascade of events leading to an activated agonist-receptor G-protein complex with high agonist affinity. However, the ensuing signaling process can further remodel the receptor complex to reduce agonist affinity, causing rapid ligand dissociation. The acutely activated ligand-free receptor can continue signaling, as proposed for rhodopsin and μ opioid receptors, resulting in robust receptor activation at low agonist occupancy with enhanced agonist potency. Continued receptor stimulation can further modify the receptor complex, regulating sustained ligand-free signaling-proposed to play a role in opioid dependence. Basal, acutely agonist-triggered, and sustained elevated ligand-free signaling could each have distinct functions, reflecting multi-state conformations of GPCRs. This review addresses basal and stimulus-activated ligand-free signaling, its regulation, genetic factors, and pharmacological implications, focusing on opioid and serotonin receptors, and the growth hormone secretagogue receptor (GHSR). The hypothesis is proposed that ligand-free signaling of 5-HT2A receptors mediate therapeutic effects of psychedelic drugs. Research avenues are suggested to close the gaps in our knowledge of ligand-free GPCR signaling.
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Affiliation(s)
- Wolfgang Sadee
- Cancer Biology and Genetics, College of Medicine, The Ohio State University, Columbus, OH 43210, USA;
- Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
- Aether Therapeutics Inc., Austin, TX 78756, USA
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3
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Ringuet MT, Furness JB, Furness SGB. G protein-coupled receptor interactions and modification of signalling involving the ghrelin receptor, GHSR1a. J Neuroendocrinol 2022; 34:e13077. [PMID: 34931385 DOI: 10.1111/jne.13077] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/05/2021] [Indexed: 12/28/2022]
Abstract
The growth hormone secretagogue receptor 1a (GHSR1a) is intriguing because of its potential as a therapeutic target and its diverse molecular interactions. Initial studies of the receptor focused on the potential therapeutic ability for growth hormone (GH) release to reduce wasting in aging individuals, as well as food intake regulation for treatment of cachexia. Known roles of GHSR1a now extend to regulation of neurogenesis, learning and memory, gastrointestinal motility, glucose/lipid metabolism, the cardiovascular system, neuronal protection, motivational salience, and hedonic feeding. Ghrelin, the endogenous agonist of GHSR1a, is primarily located in the stomach and is absent from the central nervous system (CNS), including the spinal cord. However, ghrelin in the circulation does have access to a small number of CNS sites, including the arcuate nucleus, which is important in feeding control. At some sites, such as at somatotrophs, GHSR1a has high constitutive activity. Typically, ghrelin-dependent and constitutive GHSR1a activation occurs via Gαq/11 pathways. In vitro and in vivo data suggest that GHSR1a heterodimerises with multiple G protein-coupled receptors (GPCRs), including dopamine D1 and D2, serotonin 2C, orexin, oxytocin and melanocortin 3 receptors (MCR3), as well as the MCR3 accessory protein, MRAP2, providing possible mechanisms for its many physiological effects. In all cases, the receptor interaction changes downstream signalling and the responses to receptor agonists. This review discusses the signalling mechanisms of GHSR1a alone and in combination with other GPCRs, and explores the physiological consequences of GHSR1a coupling with other GPCRs.
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Affiliation(s)
- Mitchell Ty Ringuet
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
| | - John Barton Furness
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
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Chen X, Dong J, Jiao Q, Du X, Bi M, Jiang H. "Sibling" battle or harmony: crosstalk between nesfatin-1 and ghrelin. Cell Mol Life Sci 2022; 79:169. [PMID: 35239020 PMCID: PMC11072372 DOI: 10.1007/s00018-022-04193-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 02/02/2022] [Accepted: 02/04/2022] [Indexed: 12/17/2022]
Abstract
Ghrelin was first identified as an endogenous ligand of the growth hormone secretagogue receptor (GHSR) in 1999, with the function of stimulating the release of growth hormone (GH), while nesfatin-1 was identified in 2006. Both peptides are secreted by the same kind of endocrine cells, X/A-like cells in the stomach. Compared with ghrelin, nesfatin-1 exerts opposite effects on energy metabolism, glucose metabolism, gastrointestinal functions and regulation of blood pressure, but exerts similar effects on anti-inflammation and neuroprotection. Up to now, nesfatin-1 remains as an orphan ligand because its receptor has not been identified. Several studies have shown the effects of nesfatin-1 are dependent on the receptor of ghrelin. We herein compare the effects of nesfatin-1 and ghrelin in several aspects and explore the possibility of their interactions.
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Affiliation(s)
- Xi Chen
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, 266071, People's Republic of China
| | - Jing Dong
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, 266071, People's Republic of China
| | - Qian Jiao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, 266071, People's Republic of China
| | - Xixun Du
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, 266071, People's Republic of China
| | - Mingxia Bi
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, 266071, People's Republic of China
| | - Hong Jiang
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, 266071, People's Republic of China.
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5
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Gupta S, Mukhopadhyay S, Mitra A. Therapeutic potential of GHSR-1A antagonism in alcohol dependence, a review. Life Sci 2022; 291:120316. [PMID: 35016882 DOI: 10.1016/j.lfs.2022.120316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 01/05/2022] [Accepted: 01/05/2022] [Indexed: 11/28/2022]
Abstract
Growth hormone secretagogue receptor type 1A (GHSR-1A) is a functional receptor of orexigenic peptide ghrelin and is highly expressed in mesolimbic dopaminergic systems that regulate incentive value of artificial reward in substance abuse. Interestingly, GHSR-1A has also shown ligand-independent constitutive activity. Alcohol use disorder (AUD) is one of the growing concerns worldwide as it involves complex neuro-psycho-endocrinological interactions. Positive correlation of acylated ghrelin and alcohol-induced human brain response in the right and left ventral striatum are evident. In the last decade, the beneficial effects of ghrelin receptor (GHSR-1A) antagonism to suppress artificial reward circuitries and induce self-control for alcohol consumption have drawn significant attention from researchers. In this updated review, we summarize the available recent preclinical, clinical, and experimental data to discuss functional, molecular actions of central ghrelin-GHSR-1A signaling in different craving levels for alcohol as well as to promote "GHSR-1A antagonism" as one of the potential therapies in early abstinence.
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Affiliation(s)
- Shreyasi Gupta
- Department of Zoology, Triveni Devi Bhalotia College, Raniganj, Paschim Bardhaman 713 347, West Bengal, India
| | - Sanchari Mukhopadhyay
- Department of Psychiatry, National Institute of Mental Health and Neurosciences, Hombegowda Nagar, Bengaluru 560029, India
| | - Arkadeep Mitra
- Department of Zoology, City College, 102/1, Raja Rammohan Sarani, Kolkata 700 009, West Bengal, India.
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Giorgioni G, Del Bello F, Quaglia W, Botticelli L, Cifani C, Micioni Di Bonaventura E, Micioni Di Bonaventura MV, Piergentili A. Advances in the Development of Nonpeptide Small Molecules Targeting Ghrelin Receptor. J Med Chem 2022; 65:3098-3118. [PMID: 35157454 PMCID: PMC8883476 DOI: 10.1021/acs.jmedchem.1c02191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ghrelin is an octanoylated peptide acting by the activation of the growth hormone secretagogue receptor, namely, GHS-R1a. The involvement of ghrelin in several physiological processes, including stimulation of food intake, gastric emptying, body energy balance, glucose homeostasis, reduction of insulin secretion, and lipogenesis validates the considerable interest in GHS-R1a as a promising target for the treatment of numerous disorders. Over the years, several GHS-R1a ligands have been identified and some of them have been extensively studied in clinical trials. The recently resolved structures of GHS-R1a bound to ghrelin or potent ligands have provided useful information for the design of new GHS-R1a drugs. This perspective is focused on the development of recent nonpeptide small molecules acting as GHS-R1a agonists, antagonists, and inverse agonists, bearing classical or new molecular scaffolds, as well as on radiolabeled GHS-R1a ligands developed for imaging. Moreover, the pharmacological effects of the most studied ligands have been discussed.
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Affiliation(s)
- Gianfabio Giorgioni
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
| | - Fabio Del Bello
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
| | - Wilma Quaglia
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
| | - Luca Botticelli
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - Carlo Cifani
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - E Micioni Di Bonaventura
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - M V Micioni Di Bonaventura
- School of Pharmacy, Pharmacology Unit, University of Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy
| | - Alessandro Piergentili
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy
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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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8
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Tang ZQ, Zhao L, Chen GX, Chen CYC. Novel and versatile artificial intelligence algorithms for investigating possible GHSR1α and DRD1 agonists for Alzheimer's disease. RSC Adv 2021; 11:6423-6446. [PMID: 35423219 PMCID: PMC8694922 DOI: 10.1039/d0ra10077c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Accepted: 01/18/2021] [Indexed: 11/21/2022] Open
Abstract
Hippocampal lesions are recognized as the earliest pathological changes in Alzheimer's disease (AD). Recent researches have shown that the co-activation of growth hormone secretagogue receptor 1α (GHSR1α) and dopamine receptor D1 (DRD1) could recover the function of hippocampal synaptic and cognition. We combined traditional virtual screening technology with artificial intelligence models to screen multi-target agonists for target proteins from TCM database and a novel boost Generalized Regression Neural Network (GRNN) model was proposed in this article to improve the poor adjustability of GRNN. R-square was chosen to evaluate the accuracy of these artificial intelligent models. For the GHSR1α agonist dataset, Adaptive Boosting (AdaBoost), Linear Ridge Regression (LRR), Support Vector Machine (SVM), and boost GRNN achieved good results; the R-square of the test set of these models reached 0.900, 0.813, 0.708, and 0.802, respectively. For the DRD1 agonist dataset, Gradient Boosting (GB), Random Forest (RF), SVM, and boost GRNN achieved good results; the R-square of the test set of these models reached 0.839, 0.781, 0.763, and 0.815, respectively. According to these values of R-square, it is obvious that boost GRNN and SVM have better adaptability for different data sets and boost GRNN is more accurate than SVM. To evaluate the reliability of screening results, molecular dynamics (MD) simulation experiments were performed to make sure that candidates were docked well in the protein binding site. By analyzing the results of these artificial intelligent models and MD experiments, we suggest that 2007_17103 and 2007_13380 are the possible dual-target drugs for Alzheimer's disease (AD).
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Affiliation(s)
- Zi-Qiang Tang
- Artificial Intelligence Medical Center, School of Intelligent Systems Engineering, Sun Yat-sen University Shenzhen Guangzhou 510275 China
| | - Lu Zhao
- Artificial Intelligence Medical Center, School of Intelligent Systems Engineering, Sun Yat-sen University Shenzhen Guangzhou 510275 China
- Department of Clinical Laboratory, The Sixth Affiliated Hospital, Sun Yat-sen University Guangzhou 510655 China
| | - Guan-Xing Chen
- Artificial Intelligence Medical Center, School of Intelligent Systems Engineering, Sun Yat-sen University Shenzhen Guangzhou 510275 China
| | - Calvin Yu-Chian Chen
- Artificial Intelligence Medical Center, School of Intelligent Systems Engineering, Sun Yat-sen University Shenzhen Guangzhou 510275 China
- Department of Medical Research, China Medical University Hospital Taichung 40447 Taiwan
- Department of Bioinformatics and Medical Engineering, Asia University Taichung 41354 Taiwan
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9
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Xiao X, Bi M, Jiao Q, Chen X, Du X, Jiang H. A new understanding of GHSR1a--independent of ghrelin activation. Ageing Res Rev 2020; 64:101187. [PMID: 33007437 DOI: 10.1016/j.arr.2020.101187] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 09/13/2020] [Accepted: 09/21/2020] [Indexed: 12/13/2022]
Abstract
Growth hormone secretagogue receptor 1a (GHSR1a), a member of the G protein-coupled receptor (GPCR) family, is a functional receptor of ghrelin. The expression levels and activities of GHSR1a are affected by various factors. In past years, it has been found that the ghrelin-GHSR1a system can perform biological functions such as anti-inflammation, anti-apoptosis, and anti-oxidative stress. In addition to mediating the effect of ghrelin, GHSR1a also has abnormally high constitutive activity; that is, it can still transmit intracellular signals without activation of the ghrelin ligand. This constitutive activity affects brain functions, growth and development of the body; therefore, it has profound impacts on neurodegenerative diseases and some other age-related diseases. In addition, GHSR1a can also form homodimers or heterodimers with other GPCRs, affecting the release of neurotransmitters, appetite regulation, cell proliferation and insulin release. Therefore, further understanding of the constitutive activities and dimerization of GHSR1a will enable us to better clarify the characteristics of GHSR1a and provide more therapeutic targets for drug development. Here, we focus on the roles of GHSR1a in various biological functions and provide a comprehensive summary of the current research on GHSR1a to provide broader therapeutic prospects for age-related disease treatment.
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Affiliation(s)
- Xue Xiao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Mingxia Bi
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Qian Jiao
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Xi Chen
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Xixun Du
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China.
| | - Hong Jiang
- Department of Physiology, Shandong Provincial Key Laboratory of Pathogenesis and Prevention of Neurological Disorders and State Key Disciplines: Physiology, School of Basic Medicine, Qingdao University, Qingdao, China.
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10
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Reiner D, Seifert L, Deck C, Schüle R, Jung M, Stark H. Epigenetics meets GPCR: inhibition of histone H3 methyltransferase (G9a) and histamine H 3 receptor for Prader-Willi Syndrome. Sci Rep 2020; 10:13558. [PMID: 32782417 PMCID: PMC7419559 DOI: 10.1038/s41598-020-70523-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 07/28/2020] [Indexed: 02/08/2023] Open
Abstract
The role of epigenetic regulation is in large parts connected to cancer, but additionally, its therapeutic claim in neurological disorders has emerged. Inhibition of histone H3 lysine N-methyltransferase, especially G9a, has been recently shown to restore candidate genes from silenced parental chromosomes in the imprinting disorder Prader-Willi syndrome (PWS). In addition to this epigenetic approach, pitolisant as G-protein coupled histamine H3 receptor (H3R) antagonist has demonstrated promising therapeutic effects for Prader-Willi syndrome. To combine these pioneering principles of drug action, we aimed to identify compounds that combine both activities, guided by the pharmacophore blueprint for both targets. However, pitolisant as selective H3R inverse agonist with FDA and EMA-approval did not show the required inhibition at G9a. Pharmacological characterization of the prominent G9a inhibitor A-366, that is as well an inhibitor of the epigenetic reader protein Spindlin1, revealed its high affinity at H3R while showing subtype selectivity among subsets of the histaminergic and dopaminergic receptor families. This work moves prominent G9a ligands forward as pharmacological tools to prove for a potentially combined, symptomatic and causal, therapy in PWS by bridging the gap between drug development for G-protein coupled receptors and G9a as an epigenetic effector in a multi-targeting approach.
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Affiliation(s)
- David Reiner
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany
| | - Ludwig Seifert
- Institute of Pharmaceutical Sciences, University of Freiburg, 79104, Freiburg, Germany
| | - Caroline Deck
- Institute of Pharmaceutical Sciences, University of Freiburg, 79104, Freiburg, Germany
| | - Roland Schüle
- Department of Urology, Center for Clinical Research, Medical Center, Signalling Research Centres BIOSS and CIBSS, University of Freiburg, 79106, Freiburg, Germany
| | - Manfred Jung
- Institute of Pharmaceutical Sciences, University of Freiburg, 79104, Freiburg, Germany
| | - Holger Stark
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University Duesseldorf, Universitaetsstr. 1, 40225, Duesseldorf, Germany.
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11
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Tian J, Guo L, Sui S, Driskill C, Phensy A, Wang Q, Gauba E, Zigman JM, Swerdlow RH, Kroener S, Du H. Disrupted hippocampal growth hormone secretagogue receptor 1α interaction with dopamine receptor D1 plays a role in Alzheimer's disease. Sci Transl Med 2020; 11:11/505/eaav6278. [PMID: 31413143 PMCID: PMC6776822 DOI: 10.1126/scitranslmed.aav6278] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 06/24/2019] [Indexed: 12/12/2022]
Abstract
Hippocampal lesions are a defining pathology of Alzheimer's disease (AD). However, the molecular mechanisms that underlie hippocampal synaptic injury in AD have not been fully elucidated. Current therapeutic efforts for AD treatment are not effective in correcting hippocampal synaptic deficits. Growth hormone secretagogue receptor 1α (GHSR1α) is critical for hippocampal synaptic physiology. Here, we report that GHSR1α interaction with β-amyloid (Aβ) suppresses GHSR1α activation, leading to compromised GHSR1α regulation of dopamine receptor D1 (DRD1) in the hippocampus from patients with AD. The simultaneous application of the selective GHSR1α agonist MK0677 with the selective DRD1 agonist SKF81297 rescued Ghsr1α function from Aβ inhibition, mitigating hippocampal synaptic injury and improving spatial memory in an AD mouse model. Our data reveal a mechanism of hippocampal vulnerability in AD and suggest that a combined activation of GHSR1α and DRD1 may be a promising approach for treating AD.
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Affiliation(s)
- Jing Tian
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Lan Guo
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Shaomei Sui
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA.,Department of Neurology, Qianfoshan Hospital, Shandong First Medical University, Jinan, Shandong 250014, China
| | - Christopher Driskill
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Aarron Phensy
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Qi Wang
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA.,Department of Neurology, Qianfoshan Hospital, Shandong First Medical University, Jinan, Shandong 250014, China
| | - Esha Gauba
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Jeffrey M Zigman
- Department of Internal Medicine, Division of Hypothalamic Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Russell H Swerdlow
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Sven Kroener
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Heng Du
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA.
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12
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Hedegaard MA, Holst B. The Complex Signaling Pathways of the Ghrelin Receptor. Endocrinology 2020; 161:5734640. [PMID: 32049280 DOI: 10.1210/endocr/bqaa020] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/10/2020] [Indexed: 12/13/2022]
Abstract
The ghrelin receptor (GhrR) is known for its strong orexigenic effects in pharmacological doses and has long been considered as a promising target for the treatment of obesity. Several antagonists have been developed to decrease the orexigenic signaling, but none of these have been approved for the treatment of obesity because of adverse effects and lack of efficacy. Heterodimerization and biased signaling are important concepts for G-protein coupled receptor (GPCR) signaling, and the influence of these aspects on the GhrR may be important for feeding behavior and obesity. GhrR has been described to heterodimerize with other GPCRs, such as the dopamine receptors 1 and 2, leading to a modulation of the signaling properties of both dimerization partners. Another complicating factor of GhrR-mediated signaling is its ability to activate several different signaling pathways on ligand stimulation. Importantly, some ligands have shown to be "biased" or "functionally selective," implying that the ligand favors a particular signaling pathway. These unique signaling properties could have a sizeable impact on the physiological functions of the GhrR system. Importantly, heterodimerization may explain why the GhrR is expressed in areas of the brain that are difficult for peptide ligands to access. One possibility is that the purpose of GhrR expression is to modulate the function of other receptors in addition to merely being independently activated. We suggest that a deeper understanding of the signaling properties of the GhrR will facilitate future drug discovery in the areas of obesity and weight management.
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Affiliation(s)
- Morten Adler Hedegaard
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Birgitte Holst
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
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13
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Liu Y, Yan M, Guo Y, Niu Z, Sun R, Jin H, Gong Y. Ghrelin and electrical stimulating the lateral hypothalamus area regulated the discharges of gastric distention neurons via the dorsal vagal complex in cisplatin-treated rats. Gen Comp Endocrinol 2019; 279:174-183. [PMID: 30914266 DOI: 10.1016/j.ygcen.2019.03.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 03/22/2019] [Accepted: 03/22/2019] [Indexed: 12/16/2022]
Abstract
OBJECTIVE Cisplatin is an important antineoplastic drug and has side effects such as nausea, vomiting, and dyspepsia. The detailed mechanisms for its side effects are yet not well be illustrated. Our purpose was to investigate the discharges of gastric distention (GD) sensitive neurons regulated by ghrelin and electrical stimulation of the lateral hypothalamus area (LHA) via the dorsal vagal complex (DVC) in cisplatin-treated rats. MATERIALS AND METHODS Extracellular discharge recording was performed to observe the effects of ghrelin and electrical stimulation of the LHA on discharges of GD neurons in the DVC. RESULTS GD neurons were recorded in DVC in saline-treated and cisplatin-treated rats and identified as GD-excitatory (GD-E) neurons, which are excited by gastric distension, and GD-inhibitory (GE-I) neurons, which are inhibited by gastric distension. Microinjection of ghrelin into the DVC increased the firing frequency of most GD neurons, while the ratios of excited GD-E and GD-I neurons in cisplatin-treated rats were significantly lower than those in saline-treated rats. The excitatory effect of ghrelin was eliminated completely by DVC pretreatment with ghrelin receptor antagonist [D-Lys-3]-GHRP-6. After electrical stimulation of the LHA, the firing frequency of these neurons significantly increased. This excitatory effect was weaker in cisplatin-treated rats than in saline-treated rats and could be partly blocked by DVC pretreatment with [D-Lys-3]-GHRP-6. CONCLUSION GD neurons in the DVC could be excited by microinjecting ghrelin into the DVC and electrical stimulation of the LHA, respectively. The excitatory effect was attenuated by cisplatin injected intraperitoneally.
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Affiliation(s)
- Yang Liu
- Department of Pharmacy, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China; Shandong Xiandai University, Jinan, Shandong, China
| | - Meixing Yan
- Qingdao Women and Children's Hospital, Qingdao, Shandong, China
| | - Yaoyao Guo
- Department of Pharmacy, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China
| | - Zhenzhen Niu
- Department of Pharmacy, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China
| | - Runzhou Sun
- Department of Pharmacy, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China
| | - Hong Jin
- Department of Pharmacy, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China
| | - Yanling Gong
- Department of Pharmacy, College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, Shandong, China.
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14
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Wenthur CJ, Gautam R, Zhou B, Vendruscolo LF, Leggio L, Janda KD. Ghrelin Receptor Influence on Cocaine Reward is Not Directly Dependent on Peripheral Acyl-Ghrelin. Sci Rep 2019; 9:1841. [PMID: 30755699 PMCID: PMC6372697 DOI: 10.1038/s41598-019-38549-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 12/31/2018] [Indexed: 12/30/2022] Open
Abstract
The peptide hormone acyl-ghrelin and its receptor, GHSR1a, represent intriguing therapeutic targets due to their actions in metabolic homeostasis and reward activity. However, this pleotropic activity makes it difficult to intervene in this system without inducing unwanted effects. Thus, it is desirable to identify passive and active regulatory mechanisms that allow differentiation between functional domains. Anatomical restriction by the blood brain barrier represents one major passive regulatory mechanism. However, it is likely that the ghrelin system is subject to additional passive mechanisms that promote independent regulation of orexigenic behavior and reward processing. By applying acyl-ghrelin sequestering antibodies, it was determined that peripheral sequestration of acyl-ghrelin is sufficient to blunt weight gain, but not cocaine rewarding effects. However, both weight gain and reward-associated behaviors were shown to be blocked by direct antagonism of GHSR1a. Overall, these data indicate that GHSR1a effects on reward are independent from peripheral acyl-ghrelin binding, whereas centrally-mediated alteration of energy storage requires peripheral acyl-ghrelin binding. This demonstration of variable ligand-dependence amongst functionally-distinct GHSR1a populations is used to generate a regulatory model for functional manipulation of specific effects when attempting to therapeutically target the ghrelin system.
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Affiliation(s)
- Cody J Wenthur
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, USA
- Department of Pharmacy, University of Wisconsin - Madison, Madison, WI, USA
| | - Ritika Gautam
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, USA
| | - Bin Zhou
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, USA
| | - Leandro F Vendruscolo
- Neurobiology of Addiction Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | - Lorenzo Leggio
- Section on Clinical Psychoneuroendocrinology and Neuropsychopharmacology, National Institute on Alcohol Abuse and Alcoholism Division of Intramural Clinical and Biological Research and National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Bethesda, MD, USA
- Center for Alcohol and Addiction Studies, Department of Behavioral and Social Sciences, Brown University, Providence, RI, USA
| | - Kim D Janda
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA, USA.
- Department of Immunology and Microbial Science, The Skaggs Institute for Chemical Biology, and The Worm Institute for Research and Medicine (WIRM), The Scripps Research Institute, La Jolla, CA, USA.
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15
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You ZB, Wang B, Gardner EL, Wise RA. Cocaine and cocaine expectancy increase growth hormone, ghrelin, GLP-1, IGF-1, adiponectin, and corticosterone while decreasing leptin, insulin, GIP, and prolactin. Pharmacol Biochem Behav 2019; 176:53-56. [DOI: 10.1016/j.pbb.2018.11.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/12/2018] [Accepted: 11/07/2018] [Indexed: 12/23/2022]
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16
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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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17
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Novelle MG, Diéguez C. Food Addiction and Binge Eating: Lessons Learned from Animal Models. Nutrients 2018; 10:E71. [PMID: 29324652 PMCID: PMC5793299 DOI: 10.3390/nu10010071] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 12/26/2017] [Accepted: 01/09/2018] [Indexed: 01/10/2023] Open
Abstract
The feeding process is required for basic life, influenced by environment cues and tightly regulated according to demands of the internal milieu by regulatory brain circuits. Although eating behaviour cannot be considered "addictive" under normal circumstances, people can become "addicted" to this behaviour, similarly to how some people are addicted to drugs. The symptoms, cravings and causes of "eating addiction" are remarkably similar to those experienced by drug addicts, and both drug-seeking behaviour as eating addiction share the same neural pathways. However, while the drug addiction process has been highly characterised, eating addiction is a nascent field. In fact, there is still a great controversy over the concept of "food addiction". This review aims to summarize the most relevant animal models of "eating addictive behaviour", emphasising binge eating disorder, that could help us to understand the neurobiological mechanisms hidden under this behaviour, and to improve the psychotherapy and pharmacological treatment in patients suffering from these pathologies.
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Affiliation(s)
- Marta G Novelle
- Department of Physiology, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), University of Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 15786 Santiago de Compostela, Spain.
| | - Carlos Diéguez
- Department of Physiology, Center for Research in Molecular Medicine and Chronic Diseases (CIMUS), University of Santiago de Compostela-Instituto de Investigación Sanitaria (IDIS), CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Instituto de Salud Carlos III, 15786 Santiago de Compostela, Spain.
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18
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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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19
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Clarifying the Ghrelin System's Ability to Regulate Feeding Behaviours Despite Enigmatic Spatial Separation of the GHSR and Its Endogenous Ligand. Int J Mol Sci 2017; 18:ijms18040859. [PMID: 28422060 PMCID: PMC5412441 DOI: 10.3390/ijms18040859] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/04/2017] [Accepted: 04/11/2017] [Indexed: 12/23/2022] Open
Abstract
Ghrelin is a hormone predominantly produced in and secreted from the stomach. Ghrelin is involved in many physiological processes including feeding, the stress response, and in modulating learning, memory and motivational processes. Ghrelin does this by binding to its receptor, the growth hormone secretagogue receptor (GHSR), a receptor found in relatively high concentrations in hypothalamic and mesolimbic brain regions. While the feeding and metabolic effects of ghrelin can be explained by the effects of this hormone on regions of the brain that have a more permeable blood brain barrier (BBB), ghrelin produced within the periphery demonstrates a limited ability to reach extrahypothalamic regions where GHSRs are expressed. Therefore, one of the most pressing unanswered questions plaguing ghrelin research is how GHSRs, distributed in brain regions protected by the BBB, are activated despite ghrelin’s predominant peripheral production and poor ability to transverse the BBB. This manuscript will describe how peripheral ghrelin activates central GHSRs to encourage feeding, and how central ghrelin synthesis and ghrelin independent activation of GHSRs may also contribute to the modulation of feeding behaviours.
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20
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Jastreboff AM, Sinha R, Arora J, Giannini C, Kubat J, Malik S, Van Name MA, Santoro N, Savoye M, Duran EJ, Pierpont B, Cline G, Constable RT, Sherwin RS, Caprio S. Altered Brain Response to Drinking Glucose and Fructose in Obese Adolescents. Diabetes 2016; 65:1929-39. [PMID: 27207544 PMCID: PMC5384636 DOI: 10.2337/db15-1216] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 03/23/2016] [Indexed: 02/06/2023]
Abstract
Increased sugar-sweetened beverage consumption has been linked to higher rates of obesity. Using functional MRI, we assessed brain perfusion responses to drinking two commonly consumed monosaccharides, glucose and fructose, in obese and lean adolescents. Marked differences were observed. In response to drinking glucose, obese adolescents exhibited decreased brain perfusion in brain regions involved in executive function (prefrontal cortex [PFC]) and increased perfusion in homeostatic appetite regions of the brain (hypothalamus). Conversely, in response to drinking glucose, lean adolescents demonstrated increased PFC brain perfusion and no change in perfusion in the hypothalamus. In addition, obese adolescents demonstrated attenuated suppression of serum acyl-ghrelin and increased circulating insulin level after glucose ingestion; furthermore, the change in acyl-ghrelin and insulin levels after both glucose and fructose ingestion was associated with increased hypothalamic, thalamic, and hippocampal blood flow in obese relative to lean adolescents. Additionally, in all subjects there was greater perfusion in the ventral striatum with fructose relative to glucose ingestion. Finally, reduced connectivity between executive, homeostatic, and hedonic brain regions was observed in obese adolescents. These data demonstrate that obese adolescents have impaired prefrontal executive control responses to drinking glucose and fructose, while their homeostatic and hedonic responses appear to be heightened. Thus, obesity-related brain adaptations to glucose and fructose consumption in obese adolescents may contribute to excessive consumption of glucose and fructose, thereby promoting further weight gain.
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Affiliation(s)
- Ania M Jastreboff
- Division of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Rajita Sinha
- Department of Psychiatry, Yale Stress Center, Yale University School of Medicine, New Haven, CT Child Study Center, Yale University School of Medicine, New Haven, CT
| | - Jagriti Arora
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT
| | - Cosimo Giannini
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Jessica Kubat
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Saima Malik
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT
| | - Michelle A Van Name
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Nicola Santoro
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Mary Savoye
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Elvira J Duran
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Bridget Pierpont
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
| | - Gary Cline
- Division of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - R Todd Constable
- Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT
| | - Robert S Sherwin
- Division of Endocrinology, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Sonia Caprio
- Division of Pediatric Endocrinology, Department of Pediatrics, Yale University School of Medicine, New Haven, CT
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21
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Li S, Liu J, Lv Q, Zhang C, Xu S, Yang D, Huang B, Zeng Y, Gao Y, Wang W. AG and UAG induce β-casein expression via activation of ERK1/2 and AKT pathways. J Mol Endocrinol 2016; 56:213-25. [PMID: 26873999 PMCID: PMC5064986 DOI: 10.1530/jme-15-0287] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 02/12/2016] [Indexed: 01/14/2023]
Abstract
The ghrelin peptides were found to circulate in two major forms: acylated ghrelin (AG) and unacylated ghrelin (UAG). Previous studies showed that AG regulates β-casein (CSN2) expression in mammary epithelial cells. However, little is known about the mechanisms by which AG regulates CSN2 gene and protein expression. Evidence suggests that UAG has biological activity through GHSR1a-independent mechanisms. Here, we investigated the possible GHSR1a-mediated effect of UAG on the expression of CSN2 in primary bovine mammary epithelial cells (pbMECs) isolated from lactating cow. We found that both AG and UAG increase the expression of CSN2 in a dose-dependent manner in pbMECs in comparison with the control group. Increased expression of CSN2 was blocked by [D-Lys3]-GHRP-6 (an antagonist of the GHSR1a) and NF449 (a Gs-α subunit inhibitor) in pbMECs. In addition, both AG and UAG activated AKT/protein kinase B (AKT) and extracellular signal-regulated kinase 1/2 (ERK1/2) pathways, whereas [D-Lys3]-GHRP-6 and NF449 inhibited the phosphorylation of AKT and ERK1/2 in pbMECs respectively. Blockade of ERK1/2 and AKT signaling pathways prevented the expression of CSN2 induced by AG or UAG. Finally, we found that both AG and UAG cause cell proliferation through identical signaling pathways. Taken together, these results demonstrate that both AG and UAG act on ERK1/2 and AKT signaling pathways to facilitate the expression of CSN2 in a GHSR1a-dependent manner.
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Affiliation(s)
- Sunan Li
- College of Veterinary MedicineJilin University
| | - Juxiong Liu
- College of Veterinary MedicineJilin University
| | - Qingkang Lv
- College of Veterinary MedicineJilin University
| | - Chuan Zhang
- Department of Endocrinology and MetabolismThe Second Hospital of Jilin University, Changchun, China
| | - Shiyao Xu
- College of Veterinary MedicineJilin University
| | | | | | - Yalong Zeng
- College of Veterinary MedicineJilin University
| | - Yingjie Gao
- College of Veterinary MedicineJilin University
| | - Wei Wang
- College of Veterinary MedicineJilin University
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