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Otsuka M, Huang J, Tanaka T, Sakata I. Identification of glucagon like peptide-1 (GLP-1) in mice stomach. Biochem Biophys Res Commun 2024; 704:149708. [PMID: 38417346 DOI: 10.1016/j.bbrc.2024.149708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 02/18/2024] [Accepted: 02/20/2024] [Indexed: 03/01/2024]
Abstract
Glucagon like peptide-1 (GLP-1) is a peptide hormone encoded by the pre-proglucagon gene that serves multiple physiological functions, including incretin action. While GLP-1 is primarily synthesized in the L cells of the lower intestine, recent findings indicate its presence in the stomachs of both rats and humans. However, the role of gastric GLP-1 in other species remains unclear. In this study, we aimed to identify GLP-1-producing cells and examine the localization of GLP-1 production in the mouse stomach. We found that pre-proglucagon mRNA was higher in the corpus than that in the antrum of the stomach. In addition, GLP-1 immunoreactive cells were found in the gastric mucosa, and their cell number was higher in the corpus than that in the antrum. Double immunofluorescence showed that some GLP-1 immunoreactive cells displayed somatostatin immunoreactivity, whereas did not co-localize with ghrelin and gastrin. Moreover, transmembrane G protein-coupled Receptor 5 (TGR5) agonist decreased pre-proglucagon mRNA expression in SG-1 cells in a concentration-dependent manner, and in vivo experiments showed a decrease in its mRNA levels in the gastric corpus but not in the antrum. This study marks the first report of GLP-1 production in the mouse stomach. Our findings suggest that gastric pre-proglucagon mRNA expression is regulated by a distinct mechanism compared to the L cells of the lower intestine.
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Affiliation(s)
- Manami Otsuka
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Jin Huang
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama, 338-8570, Japan
| | - Toru Tanaka
- Faculty of Pharmacy and Pharmaceutical Sciences, Department of Pharmaceutical Sciences, Josai University, Saitama, 1-1 Keiyaki dai, Sakado, Saitama, 350-0295, Japan
| | - Ichiro Sakata
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama, 338-8570, Japan; Area of Research Evolutionary Molecular Design, Strategic Research Center, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 338-8570, Japan.
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Wagner S, Brierley DI, Leeson-Payne A, Jiang W, Chianese R, Lam BYH, Dowsett GKC, Cristiano C, Lyons D, Reimann F, Gribble FM, Martinez de Morentin PB, Yeo GSH, Trapp S, Heisler LK. Obesity medication lorcaserin activates brainstem GLP-1 neurons to reduce food intake and augments GLP-1 receptor agonist induced appetite suppression. Mol Metab 2023; 68:101665. [PMID: 36592795 PMCID: PMC9841057 DOI: 10.1016/j.molmet.2022.101665] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/23/2022] [Accepted: 12/26/2022] [Indexed: 01/01/2023] Open
Abstract
OBJECTIVE Overweight and obesity are endemic in developed countries, with a substantial negative impact on human health. Medications developed to treat obesity include agonists for the G-protein coupled receptors glucagon-like peptide-1 (GLP-1R; e.g. liraglutide), serotonin 2C (5-HT2CR; e.g, lorcaserin), and melanocortin4 (MC4R) which reduce body weight primarily by suppressing food intake. However, the mechanisms underlying the therapeutic food intake suppressive effects are still being defined and were investigated here. METHODS We profiled PPG neurons in the nucleus of the solitary tract (PPGNTS) using single nucleus RNA sequencing (Nuc-Seq) and histochemistry. We next examined the requirement of PPGNTS neurons for obesity medication effects on food intake by virally ablating PPGNTS neurons. Finally, we assessed the effects on food intake of the combination of liraglutide and lorcaserin. RESULTS We found that 5-HT2CRs, but not GLP-1Rs or MC4Rs, were widespread in PPGNTS clusters and that lorcaserin significantly activated PPGNTS neurons. Accordingly, ablation of PPGNTS neurons prevented the reduction of food intake by lorcaserin but not MC4R agonist melanotan-II, demonstrating the functional significance of PPGNTS 5-HT2CR expression. Finally, the combination of lorcaserin with GLP-1R agonists liraglutide or exendin-4 produced greater food intake reduction as compared to either monotherapy. CONCLUSIONS These findings identify a necessary mechanism through which obesity medication lorcaserin produces its therapeutic benefit, namely brainstem PPGNTS neurons. Moreover, these data reveal a strategy to augment the therapeutic profile of the current frontline treatment for obesity, GLP-1R agonists, via coadministration with 5-HT2CR agonists.
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Affiliation(s)
- Stefan Wagner
- The Rowett Institute, University of Aberdeen, Aberdeen, UK
| | - Daniel I Brierley
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | | | - Wanqing Jiang
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
| | | | - Brian Y H Lam
- Wellcome-MRC Institute of Metabolic Science-Metabolic Research Laboratories, Medical Research Council Metabolic Diseases Unit, University of Cambridge, Cambridge, UK
| | - Georgina K C Dowsett
- Wellcome-MRC Institute of Metabolic Science-Metabolic Research Laboratories, Medical Research Council Metabolic Diseases Unit, University of Cambridge, Cambridge, UK
| | | | - David Lyons
- The Rowett Institute, University of Aberdeen, Aberdeen, UK
| | - Frank Reimann
- Wellcome-MRC Institute of Metabolic Science-Metabolic Research Laboratories, Medical Research Council Metabolic Diseases Unit, University of Cambridge, Cambridge, UK
| | - Fiona M Gribble
- Wellcome-MRC Institute of Metabolic Science-Metabolic Research Laboratories, Medical Research Council Metabolic Diseases Unit, University of Cambridge, Cambridge, UK
| | | | - Giles S H Yeo
- Wellcome-MRC Institute of Metabolic Science-Metabolic Research Laboratories, Medical Research Council Metabolic Diseases Unit, University of Cambridge, Cambridge, UK
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK.
| | - Lora K Heisler
- The Rowett Institute, University of Aberdeen, Aberdeen, UK.
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Mukherjee A, DiBrog AM, Mietlicki-Baase EG. The Impact of Binge-Like Palatable Food Intake on the Endogenous Glucagon-Like Peptide-1 System in Female Rats. Behav Brain Res 2022;:113869. [PMID: 35378108 DOI: 10.1016/j.bbr.2022.113869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 03/08/2022] [Accepted: 03/29/2022] [Indexed: 11/21/2022]
Abstract
Binge eating involves consumption of large amounts of food and a loss of control over the amount consumed. The incidence of binge eating disorder is higher in females than males, hinting at important sex differences in binge eating behavior, but the neural underpinnings of binge eating still remain unresolved. Recent work in male rats has shown that a history of binge-like palatable food intake suppresses hindbrain expression of preproglucagon (PPG), the precursor for glucagon-like peptide-1 (GLP-1). Given the roles of GLP-1 in reducing feeding and food reward, this could be a mechanism underlying binge-like eating in rodents. However, whether similar effects occur in female rats is unknown. Here, we tested the hypothesis that a history of binge-like palatable food intake in female rats would reduce PPG expression in the nucleus tractus solitarius (NTS), a key central site of GLP-1 production. Female rats given access to vegetable shortening every fourth day (4D) engaged in binge-like feeding, demonstrated by consuming significantly more shortening during the first hour of fat access compared to counterparts with ad libitum (AL) fat access. After several weeks of fat access under these schedules, PPG and GLP-1 receptor (GLP-1R) expression were measured in the NTS and ileum. Surprisingly, and in contrast to previous findings in male rats, there were no significant differences in expression of PPG or GLP-1R in either site in 4D versus AL rats, nor were there effects on plasma GLP-1 levels. These findings highlight key differences in the effects of binge-like intake on the central GLP-1 system in female compared to male rats.
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Williams DL, Lilly NA, Edwards IJ, Yao P, Richards JE, Trapp S. GLP-1 action in the mouse bed nucleus of the stria terminalis. Neuropharmacology 2018; 131:83-95. [PMID: 29221794 PMCID: PMC5840513 DOI: 10.1016/j.neuropharm.2017.12.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 10/13/2017] [Accepted: 12/03/2017] [Indexed: 01/07/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) injected into the brain reduces food intake. Similarly, activation of preproglucagon (PPG) cells in the hindbrain which synthesize GLP-1, reduces food intake. However, it is far from clear whether this happens because of satiety, nausea, reduced reward, or even stress. Here we explore the role of the bed nucleus of the stria terminalis (BNST), an area involved in feeding control as well as stress responses, in GLP-1 responses. Using cre-expressing mice we visualized projections of NTS PPG neurons and GLP-1R-expressing BNST cells with AAV-driven Channelrhodopsin-YFP expression. The BNST displayed many varicose YFP+ PPG axons in the ventral and less in the dorsal regions. Mice which express RFP in GLP-1R neurons had RFP+ cells throughout the BNST with the highest density in the dorsal part, suggesting that PPG neuron-derived GLP-1 acts in the BNST. Indeed, injection of GLP-1 into the BNST reduced chow intake during the dark phase, whereas injection of the GLP-1 receptor antagonist Ex9 increased feeding. BNST-specific GLP-1-induced food suppression was less effective in mice on high fat (HF, 60%) diet, and Ex9 had no effect. Restraint stress-induced hypophagia was attenuated by BNST Ex9 treatment, further supporting a role for endogenous brain GLP-1. Finally, whole-cell patch clamp recordings of RFP+ BNST neurons demonstrated that GLP-1 elicited either a depolarizing or hyperpolarizing reversible response that was of opposite polarity to that under dopamine. Our data support a physiological role for BNST GLP-1R in feeding, and suggest complex cellular responses to GLP-1 in this nucleus.
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Affiliation(s)
- Diana L Williams
- Psychology Department & Program in Neuroscience, Florida State University, USA
| | - Nicole A Lilly
- Psychology Department & Program in Neuroscience, Florida State University, USA
| | - Ian J Edwards
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, UK
| | - Pallas Yao
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, UK
| | - James E Richards
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, UK
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, UK.
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Wismann P, Barkholt P, Secher T, Vrang N, Hansen HB, Jeppesen PB, Baggio LL, Koehler JA, Drucker DJ, Sandoval DA, Jelsing J. The endogenous preproglucagon system is not essential for gut growth homeostasis in mice. Mol Metab 2017; 6:681-692. [PMID: 28702324 PMCID: PMC5485241 DOI: 10.1016/j.molmet.2017.04.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 04/21/2017] [Accepted: 04/24/2017] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVE The prevalence of obesity and related co-morbidities is reaching pandemic proportions. Today, the most effective obesity treatments are glucagon-like peptide 1 (GLP-1) analogs and bariatric surgery. Interestingly, both intervention paradigms have been associated with adaptive growth responses in the gut; however, intestinotrophic mechanisms associated with or secondary to medical or surgical obesity therapies are poorly understood. Therefore, the objective of this study was to assess the local basal endogenous and pharmacological intestinotrophic effects of glucagon-like peptides and bariatric surgery in mice. METHODS We used in situ hybridization to provide a detailed and comparative anatomical map of the local distribution of GLP-1 receptor (Glp1r), GLP-2 receptor (Glp2r), and preproglucagon (Gcg) mRNA expression throughout the mouse gastrointestinal tract. Gut development in GLP-1R-, GLP-2R-, or GCG-deficient mice was compared to their corresponding wild-type controls, and intestinotrophic effects of GLP-1 and GLP-2 analogs were assessed in wild-type mice. Lastly, gut volume was determined in a mouse model of vertical sleeve gastrectomy (VSG). RESULTS Comparison of Glp1r, Glp2r, and Gcg mRNA expression indicated a widespread, but distinct, distribution of these three transcripts throughout all compartments of the mouse gastrointestinal tract. While mice null for Glp1r or Gcg showed normal intestinal morphology, Glp2r-/- mice exhibited a slight reduction in small intestinal mucosa volume. Pharmacological treatment with GLP-1 and GLP-2 analogs significantly increased gut volume. In contrast, VSG surgery had no effect on intestinal morphology. CONCLUSION The present study indicates that the endogenous preproglucagon system, exemplified by the entire GCG gene and the receptors for GLP-1 and GLP-2, does not play a major role in normal gut development in the mouse. Furthermore, elevation in local intestinal and circulating levels of GLP-1 and GLP-2 achieved after VSG has limited impact on intestinal morphometry. Hence, although exogenous treatment with GLP-1 and GLP-2 analogs enhances gut growth, the contributions of endogenously-secreted GLP-1 and GLP-2 to gut growth may be more modest and highly context-dependent.
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Affiliation(s)
| | | | - Thomas Secher
- Gubra Aps, Hørsholm Kongevej 11B, DK-2970 Hørsholm, Denmark
| | - Niels Vrang
- Gubra Aps, Hørsholm Kongevej 11B, DK-2970 Hørsholm, Denmark
| | | | | | - Laurie L. Baggio
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, M5G1X5, Canada
| | - Jacqueline A. Koehler
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, M5G1X5, Canada
| | - Daniel J. Drucker
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, M5G1X5, Canada
| | | | - Jacob Jelsing
- Gubra Aps, Hørsholm Kongevej 11B, DK-2970 Hørsholm, Denmark
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Holt MK, Llewellyn-Smith IJ, Reimann F, Gribble FM, Trapp S. Serotonergic modulation of the activity of GLP-1 producing neurons in the nucleus of the solitary tract in mouse. Mol Metab 2017; 6:909-921. [PMID: 28752054 PMCID: PMC5518719 DOI: 10.1016/j.molmet.2017.06.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 06/01/2017] [Accepted: 06/05/2017] [Indexed: 12/21/2022] Open
Abstract
Objective Glucagon-like peptide-1 (GLP-1) and 5-HT are potent regulators of food intake within the brain. GLP-1 is expressed by preproglucagon (PPG) neurons in the nucleus tractus solitarius (NTS). We have previously shown that PPG neurons innervate 5-HT neurons in the ventral brainstem. Here, we investigate whether PPG neurons receive serotonergic input and respond to 5-HT. Methods We employed immunohistochemistry to reveal serotonergic innervation of PPG neurons. We investigated the responsiveness of PPG neurons to 5-HT using in vitro Ca2+ imaging in brainstem slices from transgenic mice expressing the Ca2+ indicator, GCaMP3, in PPG neurons, and cell-attached patch-clamp recordings. Results Close appositions from 5-HT-immunoreactive axons occurred on many PPG neurons. Application of 20 μM 5-HT produced robust Ca2+ responses in NTS PPG dendrites but little change in somata. Dendritic Ca2+ spikes were concentration-dependent (2, 20, and 200 μM) and unaffected by blockade of glutamatergic transmission, suggesting 5-HT receptors on PPG neurons. Neither activation nor blockade of 5-HT3 receptors affected [Ca2+]i. In contrast, inhibition of 5-HT2 receptors attenuated increases in intracellular Ca2+ and 5-HT2C receptor activation produced Ca2+ spikes. Patch-clamp recordings revealed that 44% of cells decreased their firing rate under 5-HT, an effect blocked by 5-HT1A receptor antagonism. Conclusions PPG neurons respond directly to 5-HT with a 5-HT2C receptor-dependent increase in dendritic [Ca2+]i. Electrical responses to 5-HT revealed additional inhibitory effects due to somatic 5-HT1A receptors. Reciprocal innervation between 5-HT and PPG neurons suggests that the coordinated activity of these brainstem neurons may play a role in the regulation of food intake. Brainstem PPG neurons receive close appositions from 5-HT-containing axons. 5-HT activates NTS PPG dendrites directly via 5-HT2 receptors. 5-HT inhibits a subset of somata via 5-HT1A receptors. Activation of 5-HT3 receptors does not affect PPG cell [Ca2+]i. 5-HT2C receptor activation induces spatially confined Ca2+ spikes in PPG neurons.
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Key Words
- 5-HT, 5-hydroxytryptamine
- CCK-8, cholecystokinin-8
- CNS, central nervous system
- Dendritic calcium
- GCaMP
- GLP-1, glucagon-like peptide-1
- HPA, hypothalamic–pituitary–adrenal
- IRT, intermediate reticular nucleus
- NTS
- NTS, nucleus tractus solitarius
- PBN, parabrachial nucleus
- PPG, preproglucagon
- Preproglucagon
- Serotonin
- YFP, yellow fluorescent protein
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Affiliation(s)
- Marie K Holt
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, UK
| | - Ida J Llewellyn-Smith
- Cardiovascular Medicine, Human Physiology and Centre for Neuroscience, Flinders University, Bedford Park, SA 5042, Australia
| | - Frank Reimann
- Cambridge Institute for Medical Research, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0QQ, UK
| | - Fiona M Gribble
- Cambridge Institute for Medical Research, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0QQ, UK
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & Pharmacology, University College London, London, WC1E 6BT, UK.
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Cork SC, Richards JE, Holt MK, Gribble FM, Reimann F, Trapp S. Distribution and characterisation of Glucagon-like peptide-1 receptor expressing cells in the mouse brain. Mol Metab 2015; 4:718-31. [PMID: 26500843 DOI: 10.1016/j.molmet.2015.07.008] [Citation(s) in RCA: 275] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 07/24/2015] [Accepted: 07/28/2015] [Indexed: 12/19/2022] Open
Abstract
Objective Although Glucagon-like peptide 1 is a key regulator of energy metabolism and food intake, the precise location of GLP-1 receptors and the physiological relevance of certain populations is debatable. This study investigated the novel GLP-1R-Cre mouse as a functional tool to address this question. Methods Mice expressing Cre-recombinase under the Glp1r promoter were crossed with either a ROSA26 eYFP or tdRFP reporter strain to identify GLP-1R expressing cells. Patch-clamp recordings were performed on tdRFP-positive neurons in acute coronal brain slices from adult mice and selective targeting of GLP-1R cells in vivo was achieved using viral gene delivery. Results Large numbers of eYFP or tdRFP immunoreactive cells were found in the circumventricular organs, amygdala, hypothalamic nuclei and the ventrolateral medulla. Smaller numbers were observed in the nucleus of the solitary tract and the thalamic paraventricular nucleus. However, tdRFP positive neurons were also found in areas without preproglucagon-neuronal projections like hippocampus and cortex. GLP-1R cells were not immunoreactive for GFAP or parvalbumin although some were catecholaminergic. GLP-1R expression was confirmed in whole-cell recordings from BNST, hippocampus and PVN, where 100 nM GLP-1 elicited a reversible inward current or depolarisation. Additionally, a unilateral stereotaxic injection of a cre-dependent AAV into the PVN demonstrated that tdRFP-positive cells express cre-recombinase facilitating virally-mediated eYFP expression. Conclusions This study is a comprehensive description and phenotypic analysis of GLP-1R expression in the mouse CNS. We demonstrate the power of combining the GLP-1R-CRE mouse with a virus to generate a selective molecular handle enabling future in vivo investigation as to their physiological importance. This transgenic mouse allows accurate evaluation of the distribution of GLP-1 receptor expressing cells. GLP-1 depolarises PVN, BNST and hippocampus neurons. GLP-1R expressing cells can be manipulated in vivo using this transgenic mouse.
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Key Words
- AP, area postrema
- BNST, bed nucleus stria terminalis
- Channelrhodopsin
- DMH, dorsomedial nucleus of the hypothalamus
- DMV, dorsal motor nucleus of the vagus
- Electrophysiology
- Ex-4, Exendin-4
- GFAP, glial fibrillary acidic protein
- GFP, green fluorescent protein
- GLP-1
- GLP-1, Glucagon-like peptide-1
- GLP-1R, Glucagon-like peptide-1 receptor
- Glucagon-like peptide-1 receptor
- NAc, nucleus accumbens
- NTS, nucleus of the solitary tract
- PARV, parvalbumin
- PPG
- PPG, preproglucagon
- PVN, paraventricular nucleus of the hypothalamus
- Preproglucagon
- TH, tyrosine hydroxylase
- VTA, ventral tegmental area
- YFP, yellow fluorescent protein
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Abstract
Glucagon-like peptide 1 (GLP-1) is best known as an incretin hormone, secreted from L cells in the intestine in response to nutrient ingestion to stimulate glucose-dependent insulin secretion. However, GLP-1 is also expressed in neurons, and plays a major role in regulation of homeostatic function within the central nervous system (CNS). This review summarizes our current state of knowledge on the role GLP-1 plays in neural coordination of the organismal stress response. In the brain, the primary locus of GLP-1 production is in the caudal nucleus of the solitary tract (NTS) and the ventrolateral medulla of the hindbrain. GLP-1 immunoreactive fibers directly innervate hypophysiotrophic corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN), placing GLP-1 in prime position to integrate hypothalamo-pituitary-adrenocortical responses. Exogenous central GLP-1 activates HPA axis stress responses, and responses to a variety of stressors can be blocked by a GLP-1 receptor (GLP-1R) antagonist, confirming an excitatory role in glucocorticoid secretion. In addition, central infusion of GLP-1R agonist increases heart rate and blood pressure, and activates hypothalamic and brainstem neurons innervating sympathetic preganglionic neurons, suggesting a sympathoexcitatory role of GLP-1 in the CNS. Bioavailability of preproglucagon (PPG) mRNA and GLP-1 peptide is reduced by exogenous or endogenous glucocorticoid secretion, perhaps as a mechanism to reduce GLP-1-mediated stress excitation. Altogether, the data suggest that GLP-1 plays a key role in activation of stress responses, which may be connected with its role in central regulation of energy homeostasis.
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Affiliation(s)
- Sriparna Ghosal
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Reading Campus, OH 45237-0506, USA.
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