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Baccari MC, Vannucchi MG, Idrizaj E. The Possible Involvement of Glucagon-like Peptide-2 in the Regulation of Food Intake through the Gut-Brain Axis. Nutrients 2024; 16:3069. [PMID: 39339669 PMCID: PMC11435434 DOI: 10.3390/nu16183069] [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: 08/09/2024] [Revised: 09/05/2024] [Accepted: 09/10/2024] [Indexed: 09/30/2024] Open
Abstract
Food intake regulation is a complex mechanism involving the interaction between central and peripheral structures. Among the latter, the gastrointestinal tract represents one of the main sources of both nervous and hormonal signals, which reach the central nervous system that integrates them and sends the resulting information downstream to effector organs involved in energy homeostasis. Gut hormones released by nutrient-sensing enteroendocrine cells can send signals to central structures involved in the regulation of food intake through more than one mechanism. One of these is through the modulation of gastric motor phenomena known to be a source of peripheral satiety signals. In the present review, our attention will be focused on the ability of the glucagon-like peptide 2 (GLP-2) hormone to modulate gastrointestinal motor activity and discuss how its effects could be related to peripheral satiety signals generated in the stomach and involved in the regulation of food intake through the gut-brain axis. A better understanding of the possible role of GLP-2 in regulating food intake through the gut-brain axis could represent a starting point for the development of new strategies to treat some pathological conditions, such as obesity.
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Affiliation(s)
- Maria Caterina Baccari
- Department of Experimental & Clinical Medicine, Section of Physiological Sciences, University of Florence, 50134 Florence, Italy;
| | - Maria Giuliana Vannucchi
- Department of Experimental & Clinical Medicine, Research Unit of Histology & Embryology, University of Florence, 50139 Florence, Italy;
| | - Eglantina Idrizaj
- Department of Experimental & Clinical Medicine, Section of Physiological Sciences, University of Florence, 50134 Florence, Italy;
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2
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Idrizaj E, Biagioni C, Traini C, Vannucchi MG, Baccari MC. Glucagon-like Peptide-2 Depresses Ileal Contractility in Preparations from Mice through Opposite Modulatory Effects on Nitrergic and Cholinergic Neurotransmission. Int J Mol Sci 2024; 25:1855. [PMID: 38339131 PMCID: PMC10855646 DOI: 10.3390/ijms25031855] [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: 12/07/2023] [Revised: 01/26/2024] [Accepted: 01/31/2024] [Indexed: 02/12/2024] Open
Abstract
Glucagon-like peptide-2 (GLP-2) has been reported to influence gastrointestinal motor responses, exerting a modulatory role on enteric neurotransmission. To our knowledge, no data on GLP-2 effects on the motility of the isolated ileum are available; therefore, we investigated whether GLP-2 affects the contractile activity of mouse ileal preparations and the neurotransmitters engaged. Ileal preparations showed tetrodotoxin (TTX)- and atropine-insensitive spontaneous contractile activity, which was unaffected by the nitric oxide synthesis inhibitor, L-NNA. GLP-2 depressed the spontaneous contractility, an effect that was abolished by TTX or L-NNA and not influenced by atropine. Electrical field stimulation induced TTX- and atropine-sensitive contractile responses, which were reduced in amplitude by GLP-2 even in the presence of L-NNA. Immunohistochemical results showed a significant increase in nNOS-positive fibers in the ileal muscle wall and a significant decrease in ChAT-positive myenteric neurons in GLP-2-exposed preparations. The present results offer the first evidence that GLP-2 acts on ileal preparations. The hormone appears to depress ileal contractility through a dual opposite modulatory effect on inhibitory nitrergic and excitatory cholinergic neurotransmission. From a physiological point of view, it could be hypothesized that GLP-2 inhibitory actions on ileal contractility can increase transit time, facilitating nutrient absorption.
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Affiliation(s)
- Eglantina Idrizaj
- Section of Physiological Sciences, Department of Experimental & Clinical Medicine, University of Florence, 50139 Florence, Italy;
| | - Cristina Biagioni
- Research Unit of Histology & Embryology, Department of Experimental & Clinical Medicine, University of Florence, 50139 Florence, Italy; (C.B.); (C.T.)
| | - Chiara Traini
- Research Unit of Histology & Embryology, Department of Experimental & Clinical Medicine, University of Florence, 50139 Florence, Italy; (C.B.); (C.T.)
| | - Maria Giuliana Vannucchi
- Research Unit of Histology & Embryology, Department of Experimental & Clinical Medicine, University of Florence, 50139 Florence, Italy; (C.B.); (C.T.)
| | - Maria Caterina Baccari
- Section of Physiological Sciences, Department of Experimental & Clinical Medicine, University of Florence, 50139 Florence, Italy;
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3
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Gadomski S, Fielding C, García-García A, Korn C, Kapeni C, Ashraf S, Villadiego J, Toro RD, Domingues O, Skepper JN, Michel T, Zimmer J, Sendtner R, Dillon S, Poole KES, Holdsworth G, Sendtner M, Toledo-Aral JJ, De Bari C, McCaskie AW, Robey PG, Méndez-Ferrer S. A cholinergic neuroskeletal interface promotes bone formation during postnatal growth and exercise. Cell Stem Cell 2022; 29:528-544.e9. [PMID: 35276096 PMCID: PMC9033279 DOI: 10.1016/j.stem.2022.02.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Revised: 12/02/2021] [Accepted: 02/10/2022] [Indexed: 11/30/2022]
Abstract
The autonomic nervous system is a master regulator of homeostatic processes and stress responses. Sympathetic noradrenergic nerve fibers decrease bone mass, but the role of cholinergic signaling in bone has remained largely unknown. Here, we describe that early postnatally, a subset of sympathetic nerve fibers undergoes an interleukin-6 (IL-6)-induced cholinergic switch upon contacting the bone. A neurotrophic dependency mediated through GDNF-family receptor-α2 (GFRα2) and its ligand, neurturin (NRTN), is established between sympathetic cholinergic fibers and bone-embedded osteocytes, which require cholinergic innervation for their survival and connectivity. Bone-lining osteoprogenitors amplify and propagate cholinergic signals in the bone marrow (BM). Moderate exercise augments trabecular bone partly through an IL-6-dependent expansion of sympathetic cholinergic nerve fibers. Consequently, loss of cholinergic skeletal innervation reduces osteocyte survival and function, causing osteopenia and impaired skeletal adaptation to moderate exercise. These results uncover a cholinergic neuro-osteocyte interface that regulates skeletogenesis and skeletal turnover through bone-anabolic effects.
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Affiliation(s)
- Stephen Gadomski
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Hematology, University of Cambridge, Cambridge CB2 0AW, UK; National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0AW, UK; Skeletal Biology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA; NIH Oxford-Cambridge Scholars Program in Partnership with Medical University of South Carolina, Charleston, SC 29425, USA
| | - Claire Fielding
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Hematology, University of Cambridge, Cambridge CB2 0AW, UK; National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0AW, UK
| | - Andrés García-García
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Hematology, University of Cambridge, Cambridge CB2 0AW, UK; National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0AW, UK
| | - Claudia Korn
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Hematology, University of Cambridge, Cambridge CB2 0AW, UK; National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0AW, UK
| | - Chrysa Kapeni
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Hematology, University of Cambridge, Cambridge CB2 0AW, UK; National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0AW, UK
| | - Sadaf Ashraf
- Arthritis and Regenerative Medicine Laboratory, Aberdeen Centre for Arthritis and Musculoskeletal Health, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Javier Villadiego
- Instituto de Biomedicina de Sevilla-IBiS (Hospitales Universitarios Virgen del Rocío y Macarena/CSIC/Universidad de Sevilla), 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, (CIBERNED), Madrid 28029, Spain
| | - Raquel Del Toro
- Instituto de Biomedicina de Sevilla-IBiS (Hospitales Universitarios Virgen del Rocío y Macarena/CSIC/Universidad de Sevilla), 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, 41009 Seville, Spain
| | - Olivia Domingues
- Department of Infection and Immunity, Luxembourg Institute of Health, 4354 Esch-sur Alzette, Luxembourg
| | - Jeremy N Skepper
- Department of Physiology, Development, and Neuroscience, Cambridge Advanced Imaging Centre, University of Cambridge, Cambridge CB2 3DY, UK
| | - Tatiana Michel
- Department of Infection and Immunity, Luxembourg Institute of Health, 4354 Esch-sur Alzette, Luxembourg
| | - Jacques Zimmer
- Department of Infection and Immunity, Luxembourg Institute of Health, 4354 Esch-sur Alzette, Luxembourg
| | - Regine Sendtner
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, 97080 Wuerzburg, Germany
| | - Scott Dillon
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK
| | - Kenneth E S Poole
- Cambridge NIHR Biomedical Research Centre, Department of Medicine, University of Cambridge, Cambridge CB2 0QQ, UK
| | | | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, 97080 Wuerzburg, Germany
| | - Juan J Toledo-Aral
- Instituto de Biomedicina de Sevilla-IBiS (Hospitales Universitarios Virgen del Rocío y Macarena/CSIC/Universidad de Sevilla), 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, 41009 Seville, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, (CIBERNED), Madrid 28029, Spain
| | - Cosimo De Bari
- Arthritis and Regenerative Medicine Laboratory, Aberdeen Centre for Arthritis and Musculoskeletal Health, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Andrew W McCaskie
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Surgery, School of Clinical Medicine, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Pamela G Robey
- Skeletal Biology Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
| | - Simón Méndez-Ferrer
- Wellcome-MRC Cambridge Stem Cell Institute, Cambridge CB2 0AW, UK; Department of Hematology, University of Cambridge, Cambridge CB2 0AW, UK; National Health Service Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0AW, UK; Instituto de Biomedicina de Sevilla-IBiS (Hospitales Universitarios Virgen del Rocío y Macarena/CSIC/Universidad de Sevilla), 41013 Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, 41009 Seville, Spain.
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Srikrishnaraj A, Jeong H, Brubaker PL. Complementary and antagonistic effects of combined glucagon-like peptide-2 and glucagon-like peptide-1 receptor agonist administration on parameters relevant to short bowel syndrome. JPEN J Parenter Enteral Nutr 2021; 46:1361-1370. [PMID: 34826336 DOI: 10.1002/jpen.2307] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Short Bowel Syndrome (SBS) is characterized by debilitating malabsorption requiring parenteral nutrition. The intestinotrophic glucagon-like peptide-2 receptor agonist, h[Gly2]GLP2, is currently used to treat patients with SBS. Recent evidence suggests that GLP-1 receptor agonists such as Exendin-4 (Ex4) may also be beneficial in SBS given their ability to increase intestinal growth and delay gastric emptying (GE). METHODS Intestinal growth, body weight (BW), food intake (FI), GE, gastrointestinal (GI) transit, intestinal permeability, and glucose tolerance were investigated in male and female C57/BL6 mice following vehicle, h[Gly2]GLP2 or Ex4 treatment, alone or in combination at "low", "medium", and "high" doses (0.1, 0.5, 1.0 and 0.01, 0.05, 0.1 μg/g, respectively). RESULTS Only the h[Gly2]GLP2 low/Ex4 high-dose combination increased small intestinal (SI) weight, in an additive manner, compared to vehicle and both mono-agonists (P<0.01-0.001), via increases in villus height (P<0.01) and SI length (P<0.05), respectively. This combination had no effects on BW, FI and fat, liver, spleen, heart and kidney weights, but reduced GI transit (P<0.001) compared to low-dose h[Gly2]GLP2 mono-treatment, and abrogated the inhibitory effects of high-dose Ex4 on GE (P<0.01) and of low-dose h[Gly2]GLP2 on intestinal permeability (P<0.05). Ex4-induced improvements in glucose homeostasis were maintained upon combination with h[Gly2]GLP2 (P<0.001). CONCLUSIONS These findings suggest that combining specific doses of GLP-2-based therapies and GLP-1 receptor agonists additively improves SI growth and GI transit without detrimental effects on BW, FI, GE, and glucose homeostasis, and may therefore be a useful approach to the treatment of patients with SBS. This article is protected by copyright. All rights reserved.
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Affiliation(s)
| | - Hyerin Jeong
- Departments of Physiology, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Patricia L Brubaker
- Departments of Physiology, University of Toronto, Toronto, ON, M5S 1A8, Canada.,Departments of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
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5
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Traini C, Idrizaj E, Garella R, Squecco R, Vannucchi MG, Baccari MC. Glucagon-like peptide-2 interferes with the neurally-induced relaxant responses in the mouse gastric strips through VIP release. Neuropeptides 2020; 81:102031. [PMID: 32143816 DOI: 10.1016/j.npep.2020.102031] [Citation(s) in RCA: 2] [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: 09/27/2019] [Revised: 01/20/2020] [Accepted: 02/16/2020] [Indexed: 02/07/2023]
Abstract
Glucagon-like peptide-2 (GLP-2) has been reported to indirectly relax gastric smooth muscle. In the present study we investigated, through a combined mechanical and immunohistochemical approach, whether GLP-2 interferes with the electrical field stimulation (EFS)-induced vipergic relaxant responses and the mechanism through which it occurs. For functional experiments, strips from the mouse gastric fundus were mounted in organ baths for isometric recording of the mechanical activity. Vasoactive intestinal peptide (VIP) immunoreactivity in GLP-2 exposed specimens was also evaluated by immunohistochemistry. In carbachol pre-contracted strips, GLP-2 (20 nM) evoked a tetrodotoxin (TTX)-sensitive relaxation, similar in shape to the TTX-insensitive of 100 nM VIP. In the presence of GLP-2, VIP had no longer effects and no more response to GLP-2 was observed following VIP receptor saturation. EFS (4-16 Hz) induced a fast relaxant response followed, at the higher stimulation frequencies (≥ 8 Hz), by a slow one. This latter was abolished either by GLP-2 or VIP receptor saturation as well as by the VIP receptor antagonist, VIP 6-28 (10 μM). A decrease of VIP-immunoreactive nerve structures in the GLP-2 exposed specimens was observed. These results suggest that, in the mouse gastric fundus, GLP-2 influences the EFS-induced slow relaxant response by promoting neuronal VIP release.
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Affiliation(s)
- Chiara Traini
- Department of Experimental and Clinical Medicine, Histology and Embryology Research Unit, University of Florence, 50134 Florence, Italy
| | - Eglantina Idrizaj
- Department of Experimental and Clinical Medicine, Section of Physiological Sciences, University of Florence, 50134 Florence, Italy
| | - Rachele Garella
- Department of Experimental and Clinical Medicine, Section of Physiological Sciences, University of Florence, 50134 Florence, Italy
| | - Roberta Squecco
- Department of Experimental and Clinical Medicine, Section of Physiological Sciences, University of Florence, 50134 Florence, Italy
| | - Maria Giuliana Vannucchi
- Department of Experimental and Clinical Medicine, Histology and Embryology Research Unit, University of Florence, 50134 Florence, Italy
| | - Maria Caterina Baccari
- Department of Experimental and Clinical Medicine, Section of Physiological Sciences, University of Florence, 50134 Florence, Italy.
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6
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Brubaker PL. Glucagon‐like Peptide‐2 and the Regulation of Intestinal Growth and Function. Compr Physiol 2018; 8:1185-1210. [DOI: 10.1002/cphy.c170055] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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7
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Garella R, Idrizaj E, Traini C, Squecco R, Vannucchi MG, Baccari MC. Glucagon-like peptide-2 modulates the nitrergic neurotransmission in strips from the mouse gastric fundus. World J Gastroenterol 2017; 23:7211-7220. [PMID: 29142468 PMCID: PMC5677198 DOI: 10.3748/wjg.v23.i40.7211] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/19/2017] [Accepted: 09/26/2017] [Indexed: 02/06/2023] Open
Abstract
AIM To investigate whether glucagon-like peptide-2 (GLP-2) influences the neurally-induced responses in gastric strips from mice, since no data are available.
METHODS For functional experiments, gastric fundal strips were mounted in organ baths containing Krebs-Henseleit solution. Mechanical responses were recorded via force-displacement transducers, which were coupled to a polygraph for continuous recording of isometric tension. Electrical field stimulation (EFS) was applied via two platinum wire rings through which the preparation was threaded. The effects of GLP-2 (2 and 20 nmol/L) were evaluated on the neurally-induced contractile and relaxant responses elicited by EFS. Neuronal nitric oxide synthase (nNOS) enzyme was evaluated by immunohistochemistry.
RESULTS In the functional experiments, electrical field stimulation (EFS, 4-16 Hz) induced tetrodotoxin (TTX)-sensitive contractile responses, which were reduced in amplitude by GLP-2 (P < 0.05). In the presence of the nitric oxide (NO) synthesis inhibitor L-NNA, GLP-2 no longer influenced the neurally-evoked contractile responses (P > 0.05). The direct smooth muscle response to methacholine was not influenced by GLP-2 (P > 0.05). In the presence of guanethidine and carbachol, the addition of GLP-2 to the bath medium evoked TTX-sensitive relaxant responses that were unaffected by L-NNA (P > 0.05). EFS induced a fast NO-mediated relaxation, whose amplitude was enhanced in the presence of the hormone (P < 0.05). Immunohistochemical experiments showed a significant increase (P < 0.05) in nNOS immunoreactivity in the nerve structures after GLP-2 exposure.
CONCLUSION The results demonstrate that in gastric fundal strips, GLP-2 influences the amplitude of neurally-induced responses through the modulation of the nitrergic neurotransmission and increases nNOS expression.
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Affiliation(s)
- Rachele Garella
- Department of Experimental and Clinical Medicine, Section of Physiology, University of Florence, 50134 Florence, Italy
| | - Eglantina Idrizaj
- Department of Experimental and Clinical Medicine, Section of Physiology, University of Florence, 50134 Florence, Italy
| | - Chiara Traini
- Department of Experimental and Clinical Medicine, Histology and Embryology Research Unit, University of Florence, 50134 Florence, Italy
| | - Roberta Squecco
- Department of Experimental and Clinical Medicine, Section of Physiology, University of Florence, 50134 Florence, Italy
| | - Maria Giuliana Vannucchi
- Department of Experimental and Clinical Medicine, Histology and Embryology Research Unit, University of Florence, 50134 Florence, Italy
| | - Maria Caterina Baccari
- Department of Experimental and Clinical Medicine, Section of Physiology, University of Florence, 50134 Florence, Italy
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8
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Amato A, Baldassano S, Mulè F. GLP2: an underestimated signal for improving glycaemic control and insulin sensitivity. J Endocrinol 2016; 229:R57-66. [PMID: 27048234 DOI: 10.1530/joe-16-0035] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 02/24/2016] [Indexed: 12/12/2022]
Abstract
Glucagon-like peptide 2 (GLP2) is a proglucagon-derived peptide produced by intestinal enteroendocrine L-cells and by a discrete population of neurons in the brainstem, which projects mainly to the hypothalamus. The main biological actions of GLP2 are related to the regulation of energy absorption and maintenance of mucosal morphology, function and integrity of the intestine; however, recent experimental data suggest that GLP2 exerts beneficial effects on glucose metabolism, especially in conditions related to increased uptake of energy, such as obesity, at least in the animal model. Indeed, mice lacking GLP2 receptor selectively in hypothalamic neurons that express proopiomelanocortin show impaired postprandial glucose tolerance and hepatic insulin resistance (by increased gluconeogenesis). Moreover, GLP2 acts as a beneficial factor for glucose metabolism in mice with high-fat diet-induced obesity. Thus, the aim of this review is to update and summarize current knowledge about the role of GLP2 in the control of glucose homeostasis and to discuss how this molecule could exert protective effects against the onset of related obesity type 2 diabetes.
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Affiliation(s)
- Antonella Amato
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF)Università di Palermo, Palermo, Italy
| | - Sara Baldassano
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF)Università di Palermo, Palermo, Italy
| | - Flavia Mulè
- Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF)Università di Palermo, Palermo, Italy
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9
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Fleming MS, Vysochan A, Paixão S, Niu J, Klein R, Savitt JM, Luo W. Cis and trans RET signaling control the survival and central projection growth of rapidly adapting mechanoreceptors. eLife 2015; 4:e06828. [PMID: 25838128 PMCID: PMC4408446 DOI: 10.7554/elife.06828] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 04/01/2015] [Indexed: 01/26/2023] Open
Abstract
RET can be activated in cis or trans by its co-receptors and ligands in vitro, but the physiological roles of trans signaling are unclear. Rapidly adapting (RA) mechanoreceptors in dorsal root ganglia (DRGs) express Ret and the co-receptor Gfrα2 and depend on Ret for survival and central projection growth. Here, we show that Ret and Gfrα2 null mice display comparable early central projection deficits, but Gfrα2 null RA mechanoreceptors recover later. Loss of Gfrα1, the co-receptor implicated in activating RET in trans, causes no significant central projection or cell survival deficit, but Gfrα1;Gfrα2 double nulls phenocopy Ret nulls. Finally, we demonstrate that GFRα1 produced by neighboring DRG neurons activates RET in RA mechanoreceptors. Taken together, our results suggest that trans and cis RET signaling could function in the same developmental process and that the availability of both forms of activation likely enhances but not diversifies outcomes of RET signaling.
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Affiliation(s)
- Michael S Fleming
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Anna Vysochan
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Sόnia Paixão
- Molecules - Signals - Development, Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Jingwen Niu
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Rüdiger Klein
- Molecules - Signals - Development, Max Planck Institute of Neurobiology, Martinsried, Germany
| | - Joseph M Savitt
- Parkinson's Disease and Movement Disorder Center of Maryland, Elkridge, United States
| | - Wenqin Luo
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
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10
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Baldassano S, Amato A. GLP-2: what do we know? What are we going to discover? ACTA ACUST UNITED AC 2014; 194-195:6-10. [PMID: 25218018 DOI: 10.1016/j.regpep.2014.09.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 08/22/2014] [Accepted: 09/03/2014] [Indexed: 12/17/2022]
Abstract
Glucagon-like peptide 2 [GLP-2] is a 33-amino acid peptide released from the mucosal enteroendocrine L-cells of the intestine. The actions of GLP-2 are transduced by the GLP-2 receptor [GLP-2R], which is localized in the neurons of the enteric nervous system but not in the intestinal epithelium, indicating an indirect mechanism of action. GLP-2 is well known for its trophic role within the intestine and interest in GLP-2 is now reviving based on the approval of the GLP-2R agonist for treatment of short bowel syndrome [SBS]. Recently it also seems to be involved in glucose homeostasis. The aim of this review is to outline the importance of neuroendocrine peptides, specifically of GLP-2 in the enteric modulation of the gastrointestinal function and to focus on new works in order to present an innovative picture of GLP-2.
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Affiliation(s)
- Sara Baldassano
- Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche [STEBICEF], Italy.
| | - Antonella Amato
- Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche [STEBICEF], Italy
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11
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Bohórquez DV, Samsa LA, Roholt A, Medicetty S, Chandra R, Liddle RA. An enteroendocrine cell-enteric glia connection revealed by 3D electron microscopy. PLoS One 2014; 9:e89881. [PMID: 24587096 PMCID: PMC3935946 DOI: 10.1371/journal.pone.0089881] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 01/28/2014] [Indexed: 11/25/2022] Open
Abstract
The enteroendocrine cell is the cornerstone of gastrointestinal chemosensation. In the intestine and colon, this cell is stimulated by nutrients, tastants that elicit the perception of flavor, and bacterial by-products; and in response, the cell secretes hormones like cholecystokinin and peptide YY – both potent regulators of appetite. The development of transgenic mice with enteroendocrine cells expressing green fluorescent protein has allowed for the elucidation of the apical nutrient sensing mechanisms of the cell. However, the basal secretory aspects of the enteroendocrine cell remain largely unexplored, particularly because a complete account of the enteroendocrine cell ultrastructure does not exist. Today, the fine ultrastructure of a specific cell can be revealed in the third dimension thanks to the invention of serial block face scanning electron microscopy (SBEM). Here, we bridged confocal microscopy with SBEM to identify the enteroendocrine cell of the mouse and study its ultrastructure in the third dimension. The results demonstrated that 73.5% of the peptide-secreting vesicles in the enteroendocrine cell are contained within an axon-like basal process. We called this process a neuropod. This neuropod contains neurofilaments, which are typical structural proteins of axons. Surprisingly, the SBEM data also demonstrated that the enteroendocrine cell neuropod is escorted by enteric glia – the cells that nurture enteric neurons. We extended these structural findings into an in vitro intestinal organoid system, in which the addition of glial derived neurotrophic factors enhanced the development of neuropods in enteroendocrine cells. These findings open a new avenue of exploration in gastrointestinal chemosensation by unveiling an unforeseen physical relationship between enteric glia and enteroendocrine cells.
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Affiliation(s)
- Diego V. Bohórquez
- Departments of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
| | - Leigh A. Samsa
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Andrew Roholt
- Renovo Neural Incorporation, Cleveland, Ohio, United States of America
| | - Satish Medicetty
- Renovo Neural Incorporation, Cleveland, Ohio, United States of America
| | - Rashmi Chandra
- Departments of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Rodger A. Liddle
- Departments of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
- Veterans Affairs Medical Center, Durham, North Carolina, United States of America
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12
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Baldassano S, Amato A, Cappello F, Rappa F, Mulè F. Glucagon-like peptide-2 and mouse intestinal adaptation to a high-fat diet. J Endocrinol 2013; 217:11-20. [PMID: 23308022 DOI: 10.1530/joe-12-0500] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Endogenous glucagon-like peptide-2 (GLP2) is a key mediator of refeeding-induced and resection-induced intestinal adaptive growth. This study investigated the potential role of GLP2 in mediating the mucosal responses to a chronic high-fat diet (HFD). In this view, the murine small intestine adaptive response to a HFD was analyzed and a possible involvement of endogenous GLP2 was verified using GLP2 (3-33) as GLP2 receptor (GLP2R) antagonist. In comparison with animals fed a standard diet, mice fed a HFD for 14 weeks exhibited an increase in crypt-villus mean height (duodenum, 27.5±3.0%; jejunum, 36.5±2.9%; P<0.01), in the cell number per villus (duodenum, 28.4±2.2%; jejunum, 32.0±2.9%; P<0.01), and in Ki67-positive cell number per crypt. No change in the percent of caspase-3-positive cell in the villus-crypt was observed. The chronic exposure to a HFD also caused a significant increase in GLP2 plasma levels and in GLP2R intestinal expression. Daily administration of GLP2 (3-33) (30-60 ng) for 4 weeks did not modify the crypt-villus height in control mice. In HFD-fed mice, chronic treatment with GLP2 (3-33) reduced the increase in crypt-villus height and in the cell number per villus through reduction of cell proliferation and increase in apoptosis. This study provides the first experimental evidence for a role of endogenous GLP2 in the intestinal adaptation to HFD in obese mice and for a dysregulation of the GLP2/GLP2R system after a prolonged HFD.
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Affiliation(s)
- Sara Baldassano
- Laboratorio di Fisiologia generale, Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari (STEMBIO), Università di Palermo, 90128 Palermo, Italy
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13
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Chen Y, Li Z, Yang Y, Lin L, Zhang H. Role of glucagon-like peptide-1 in the pathogenesis of experimental irritable bowel syndrome rat models. Int J Mol Med 2013; 31:607-13. [PMID: 23338623 DOI: 10.3892/ijmm.2013.1252] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Accepted: 11/01/2012] [Indexed: 12/17/2022] Open
Abstract
Alterations in gut motility and visceral hypersensitivity are two major features of irritable bowel syndrome (IBS). The aim of this study was to investigate the roles of glucagon-like peptide-1 (GLP-1) in the pathogenesis of experimental IBS. Rat models of constipation-predominant IBS (IBS-C) and diarrhea-predominant IBS (IBS-D) were established. Fecal water content and behavioral responses to colorectal distention (CRD), using electromyography (EMG), were measured. The expression of glucagon-like peptide-1 receptor (GLP-1R) in the colon was detected by immunohistochemistry, and the serum concentration of GLP-1 was measured by ELISA assay. The movement of circular and longitudinal colonic muscle was detected using an organ bath recording technique. Compared to controls, the fecal water contents were lower in the IBS-C group, while they were higher in the IBS-D group (P<0.05). EMG response to CRD in the experimental IBS groups was increased compared with their respective controls (P<0.05). GLP-1R was localized in the mucosa layer, circular muscle and myenteric nerve plexus of the colon. Notably, the expression of GLP-1R in the IBS-C group was higher, but in the IBS-D group, it was lower compared with controls. The serum levels of GLP-1 in the IBS-C group were higher compared to those in the IBS-D group (P<0.05). In addition, administration of exogenous GLP-1 and exendin-4 inhibited colonic circular muscle contraction, particularly in the IBS-C group, while there was no significant effect on longitudinal muscle contraction. In conclusion, these results indicated that GLP-1 and GLP-1R are implicated in the pathogenesis of IBS-C and IBS-D.
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Affiliation(s)
- Yan Chen
- Department of Gastroenterology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210029, PR China
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14
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Janssen P, Rotondo A, Mulé F, Tack J. Review article: a comparison of glucagon-like peptides 1 and 2. Aliment Pharmacol Ther 2013; 37:18-36. [PMID: 23121085 DOI: 10.1111/apt.12092] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 07/09/2012] [Accepted: 09/29/2012] [Indexed: 12/18/2022]
Abstract
BACKGROUND Recent advancements in understanding the roles and functions of glucagon-like peptide 1 (GLP-1) and 2 (GLP-2) have provided a basis for targeting these peptides in therapeutic strategies. AIM To summarise the preclinical and clinical research supporting the discovery of new therapeutic molecules targeting GLP-1 and GLP-2. METHODS This review is based on a comprehensive PubMed search, representing literature published during the past 30 years related to GLP-1 and GLP-2. RESULTS Although produced and secreted together primarily from L cells of the intestine in response to ingestion of nutrients, GLP-1 and GLP-2 exhibit distinctive biological functions that are governed by the expression of their respective receptors, GLP-1R and GLP-2R. Through widespread expression in the pancreas, intestine, nervous tissue, et cetera, GLP-1Rs facilitates an incretin effect along with effects on appetite and satiety. GLP-1 analogues resistant to degradation by dipeptidyl peptidase-IV and inhibitors of dipeptidyl peptidase-IV have been developed to aid treatment of diabetes and obesity. The GLP-2R is expressed almost exclusively in the stomach and bowel. The most apparent role for GLP-2 is its promotion of growth and function of intestinal mucosa, which has been targeted for therapies that promote repair and adaptive growth. These are used as treatments for intestinal failure and related conditions. CONCLUSIONS Our growing understanding of the biology and function of GLP-1, GLP-2 and corresponding receptors has fostered further discovery of fundamental biological function as well as new categories of potent therapeutic medicines.
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Affiliation(s)
- P Janssen
- Translational Research Center for Gastrointestinal Disorders, University of Leuven, Belgium
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15
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Baldassano S, Bellanca AL, Serio R, Mulè F. Food intake in lean and obese mice after peripheral administration of glucagon-like peptide 2. J Endocrinol 2012; 213:277-84. [PMID: 22457516 DOI: 10.1530/joe-12-0092] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We investigated the potential anorectic action of peripherally administered glucagon-like peptide 2 (GLP2) in lean and diet-induced obese (DIO) mice. Mice, fasted for 16 h, were injected i.p. with native GLP2 or [Gly2]GLP2, stable analog of GLP2, before or after GLP2 (3-33), a GLP2 receptor (GLP2R) antagonist, or exendin (9-39), a GLP1R antagonist. Food intake was measured at intervals 1, 2, 4, 8, and 24 h postinjection. In addition, we tested in lean mice the influence of [Gly2]GLP2 on gastric emptying and the effects of GLP1 alone or in combination with [Gly2]GLP2 on food intake. [Gly2]GLP2 dose dependently and significantly inhibited food intake in lean and DIO mice. The reduction of food intake occurred in the first hour postinjection and it was sustained until 4 h postinjection in lean mice while it was sustained until 2 h postinjection in DIO mice. GLP2 significantly inhibited food intake in both lean and DIO mice but only in the first hour postinjection. The efficiency of [Gly2]GLP2 or GLP2 in suppressing food intake was significantly weaker in DIO mice compared with lean animals. The [Gly2]GLP2 anorectic actions were blocked by the GLP2R antagonist GLP2 (3-33) or by the GLP1R antagonist exendin (9-39). The coadministration of [Gly2]GLP2 and GLP1 did not cause additive effects. [Gly2]GLP2 decreased the gastric emptying rate. Results suggest that GLP2 can reduce food intake in mice in the short term, likely acting at a peripheral level. DIO mice are less sensitive to the anorectic effect of the peptide.
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Affiliation(s)
- Sara Baldassano
- Laboratorio di Fisiologia Generale, Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari (STEMBIO), Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy
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Rowland KJ, Trivedi S, Lee D, Wan K, Kulkarni RN, Holzenberger M, Brubaker PL. Loss of glucagon-like peptide-2-induced proliferation following intestinal epithelial insulin-like growth factor-1-receptor deletion. Gastroenterology 2011; 141:2166-2175.e7. [PMID: 21925122 DOI: 10.1053/j.gastro.2011.09.014] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Revised: 08/18/2011] [Accepted: 09/01/2011] [Indexed: 01/16/2023]
Abstract
BACKGROUND & AIMS Glucagon-like peptide-2 (GLP-2) is an intestinal hormone that promotes growth of the gastrointestinal tract. Although insulin-like growth factor (IGF)-1 and the IGF-1 receptor (IGF-1R) are required for GLP-2-induced proliferation of crypt cells, little is known about localization of the IGF-1R which mediates the intestinotropic actions of GLP-2. METHODS We examined intestinal growth and proliferative responses in mice with conditional deletion of IGF-1R from intestinal epithelial cells (IE-igf1rKO) after acute administration (30-90 min) of GLP-2, in response to 24-hour fasting and re-feeding (to induce GLP-2-dependent adaptation), and after chronic exposure (10 days) to GLP-2. RESULTS IE-igf1rKO mice had normal small intestinal weight, morphometric parameters, proliferative indices, and distribution of differentiated epithelial cell lineages. Acute administration of GLP-2 increased nuclear translocation of β-catenin in non-Paneth crypt cells and stimulated the crypt-cell proliferative marker c-Myc in control but not IE-igf1rKO mice. Small intestinal weight, crypt depth, villus height, and crypt-cell proliferation were decreased in control and IE-igf1rKO mice after 24-hour fasting. Although re-feeding control mice restored all of these parameters, re-fed IE-igf1rKO mice had reductions in adaptive regrowth of the villi and crypt-cell proliferation. Control mice that were given chronic GLP-2 had increases in small intestinal weight, mucosal cross-sectional area, crypt depth, villus height, and crypt-cell proliferation. However, the GLP-2-induced increase in crypt-cell proliferation was not observed in IE-igf1rKO mice, and growth of the crypt-villus axis was reduced. CONCLUSIONS The proliferative responses of the intestinal epithelium to exogenous GLP-2 administration and conditions of GLP-2-dependent adaptive re-growth require the intestinal epithelial IGF-1R.
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Affiliation(s)
- Katherine J Rowland
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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Rotondo A, Amato A, Baldassano S, Lentini L, Mulè F. Gastric relaxation induced by glucagon-like peptide-2 in mice fed a high-fat diet or fasted. Peptides 2011; 32:1587-92. [PMID: 21771622 DOI: 10.1016/j.peptides.2011.06.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/29/2011] [Accepted: 06/29/2011] [Indexed: 12/17/2022]
Abstract
Glucagon-like peptide-2 (GLP-2) is a nutrient-responsive gut hormone that increases the intestinal absorption. Exogenous GLP-2 also induces gastric fundus relaxation with possible implications for emptying rate or feeling of satiety. GLP-2 actions are mediated by GLP-2 receptor (GLP-2R), located on enteric neurons and myofibroblasts in murine gastrointestinal tract. Because it is not known whether changes in the endogenous GLP-2R levels occur in different nutritional states, we examined the GLP-2R gene and protein expression in gastric fundus from standard diet (STD)-fed, 12-h and 24-h fasted and re-fed, or high-fat diet (HFD)-fed mice and we analyzed the mechanical responses to exogenous GLP-2 in the stomach from different groups of animals. GLP-2 expression was examined using real-time reverse-transcription polymerase chain reaction and western blotting. The gastric mechanical activity from whole-organ was recorded in vitro as changes of intraluminal pressure. GLP-2R expression in fundic region from 12-h or 24-h fasted mice was reduced in comparison with STD-fed animals and returned to control values in re-fed mice, while it was increased in HFD-fed mice. The exogenous GLP-2 efficacy in inducing gastric relaxation, normalized to isoproterenol response, was decreased in stomach from fasted mice and it was increased in stomach from HFD-fed mice in comparison with STD-fed mice. In conclusion, the nutritional state influences GLP-2R expression in murine gastric preparations. The changes in the GLP-2R expression are associated with modifications of GLP-2 gastric relaxant efficacy. This could represent an adaptive response to reduced or increased nutrient intake.
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Affiliation(s)
- Alessandra Rotondo
- Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari (STEMBIO), Università di Palermo, 90128 Palermo, Italy
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Amato A, Rotondo A, Cinci L, Baldassano S, Vannucchi MG, Mulè F. Role of cholinergic neurons in the motor effects of glucagon-like peptide-2 in mouse colon. Am J Physiol Gastrointest Liver Physiol 2010; 299:G1038-44. [PMID: 20705903 DOI: 10.1152/ajpgi.00282.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glucagon-like peptide-2 (GLP-2) reduces mouse gastric tone and small intestine transit, but its action on large intestine motility is still unknown. The purposes of the present study were 1) to examine the influence of GLP-2 on spontaneous mechanical activity and on neurally evoked responses, by recording intraluminal pressure from mouse isolated colonic segments; 2) to characterize GLP-2 mechanism of action; and 3) to determine the distribution of GLP-2 receptor (GLP-2R) in the mouse colonic muscle coat by immunohistochemistry. Exogenous GLP-2 (0.1-300 nM) induced a concentration-dependent reduction of the spontaneous mechanical activity, which was abolished by the desensitization of GLP-2 receptor or by tetrodotoxin, a voltage-dependent Na(+)-channel blocker. GLP-2 inhibitory effect was not affected by N(ω)-nitro-l-arginine methyl ester (a nitric oxide synthase inhibitor), apamin (a blocker of small conductance Ca(2+)-dependent K(+) channels), or [Lys1,Pro2,5,Arg3,4,Tyr6]VIP(7-28) (a VIP receptor antagonist), but it was prevented by atropine or pertussis toxin (PTX), a G(i/o) protein inhibitor. Proximal colon responses to electrical field stimulation were characterized by nitrergic relaxation, which was followed by cholinergic contraction. GLP-2 reduced only the cholinergic evoked contractions. This effect was almost abolished by GLP-2 receptor desensitization or PTX. GLP-2 failed to affect the contractile responses to exogenous carbachol. GLP-2R immunoreactivity (IR) was detected only in the neuronal cells of both plexuses of the colonic muscle coat. More than 50% of myenteric GLP-2R-IR neurons shared the choline acetyltransferase IR. In conclusion, the activation of GLP-2R located on cholinergic neurons may modulate negatively the colonic spontaneous and electrically evoked contractions through inhibition of acetylcholine release. The effect is mediated by G(i) protein.
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Affiliation(s)
- Antonella Amato
- Dipartimento di Biologia cellulare e dello Sviluppo, Università di Palermo, Palermo, Italy
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19
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Amato A, Cinci L, Rotondo A, Serio R, Faussone-Pellegrini MS, Vannucchi MG, Mulè F. Peripheral motor action of glucagon-like peptide-1 through enteric neuronal receptors. Neurogastroenterol Motil 2010; 22:664-e203. [PMID: 20158614 DOI: 10.1111/j.1365-2982.2010.01476.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Glucagon-like peptide-1 (GLP-1) is a proglucagon-derived peptide expressed in the enteroendocrine-L cells of small and large intestine and released in response to meal ingestion. Glucagon-like peptide-1 exerts inhibitory effects on gastrointestinal motility through vagal afferents and central nervous mechanisms; however, no data is available about a direct influence on the gastrointestinal wall. Our aim was to investigate the effects of GLP-1 on the spontaneous and evoked mechanical activity of mouse duodenum and colon and to identify the presence and distribution of GLP-1 receptors (GLP-1R) in the muscle coat. METHODS Organ bath recording technique and immunohistochemistry were used. KEY RESULTS Glucagon-like peptide-1 (up to the concentration of 1 mumol L(-1)) failed to affect spontaneous mechanical activity. It caused concentration-dependent reduction of the electrically evoked cholinergic contractions in circular smooth muscle of both intestinal segments, without affecting the longitudinal muscle responses. Glucagon-like peptide-1 inhibitory effect was significantly antagonized by exendin (9-39), an antagonist of GLP-1R. In both intestinal preparations, GLP-1 effect was not affected by guanethidine, a blocker of adrenergic neurotransmission, but it was significantly reduced by N(omega)-nitro-l-arginine methyl ester, inhibitor of nitric oxide (NO) synthase. Glucagon-like peptide-1 failed to affect the contractions evoked by exogenous carbachol. Immunohistochemistry demonstrated GLP-1R expression in the enteric neurons. Furthermore, 27% of GLP-1R immunoreactive (IR) neurons in the duodenum and 79% of GLP-1R-IR neurons in the colon, co-expressed nNOS. CONCLUSIONS & INFERENCES The present results suggest that GLP-1 is able to act in the enteric nervous system by decreasing the excitatory cholinergic neurotransmission through presynaptic GLP-1Rs, which modulate NO release.
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Affiliation(s)
- A Amato
- Dipartimento di Biologia cellulare e dello Sviluppo, Università di Palermo, 90128 Palermo, Italy
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Luo W, Enomoto H, Rice FL, Milbrandt J, Ginty DD. Molecular identification of rapidly adapting mechanoreceptors and their developmental dependence on ret signaling. Neuron 2009; 64:841-56. [PMID: 20064391 PMCID: PMC2813518 DOI: 10.1016/j.neuron.2009.11.003] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2009] [Indexed: 01/09/2023]
Abstract
In mammals, the first step in the perception of form and texture is the activation of trigeminal or dorsal root ganglion (DRG) mechanosensory neurons, which are classified as either rapidly (RA) or slowly adapting (SA) according to their rates of adaptation to sustained stimuli. The molecular identities and mechanisms of development of RA and SA mechanoreceptors are largely unknown. We found that the "early Ret(+)" DRG neurons are RA mechanoreceptors, which form Meissner corpuscles, Pacinian corpuscles, and longitudinal lanceolate endings. The central projections of these RA mechanoreceptors innervate layers III through V of the spinal cord and terminate within discrete subdomains of the dorsal column nuclei. Moreover, mice lacking Ret signaling components are devoid of Pacinian corpuscles and exhibit a dramatic disruption of RA mechanoreceptor projections to both the spinal cord and medulla. Thus, the early Ret(+) neurons are RA mechanoreceptors and Ret signaling is required for the assembly of neural circuits underlying touch perception.
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Affiliation(s)
- Wenqin Luo
- Solomon H. Snyder Department of Neuroscience, Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205-2185
| | - Hideki Enomoto
- Laboratory for Neuronal Differentiation and Regeneration, RIKEN Center for Developmental Biology, Kobe, Japan
| | - Frank L. Rice
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY, 12208; Integrated Tissue Dynamics, LLC, Renssalaer, NY 12144
| | - Jeffrey Milbrandt
- Department of Pathology, Washington University School of Medicine, St. Louis, MO, 63110
| | - David D. Ginty
- Solomon H. Snyder Department of Neuroscience, Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, 21205-2185
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Velázquez E, Blázquez E, Ruiz-Albusac JM. Synergistic effect of glucagon-like peptide 2 (GLP-2) and of key growth factors on the proliferation of cultured rat astrocytes. Evidence for reciprocal upregulation of the mRNAs for GLP-2 and IGF-I receptors. Mol Neurobiol 2009; 40:183-93. [PMID: 19672727 DOI: 10.1007/s12035-009-8080-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 07/27/2009] [Indexed: 12/29/2022]
Abstract
The aim of this work was to determine whether the stimulating effect of glucagon-like peptide (GLP)-2 on astrocyte proliferation could be reinforced by proliferating substances, including growth factors such as EGF, platelet-derived growth factor, insulin-like growth factor type I (IGF-I) or a hormone such as insulin. Both DNA synthesis and astrocyte density, as well as the expression of c-Fos, Ki-67, proliferating cell nuclear antigen and glial fibrillary acidic proteins, were found to be higher in the presence of GLP-2 than in its absence. In an attempt to get a better understanding of this process, intracellular cyclic adenosine monophosphate (cAMP) production, extracellular signal-regulated kinase (ERK) 1/2 phosphorylation and the expression of GLP-2R and IGF-I receptor (IGF-IR) mRNAs were studied in response to growth factors. Our results indicate that, in the presence of different growth factors, GLP-2 does not increase cAMP production but raises ERK 1/2 phosphorylation. In addition, GLP-2R mRNA expression was increased by IGF-I, whilst mRNA expression of IGF-IR was higher in cells incubated with GLP-2 than in control cells. These results suggest for the first time that GLP-2 and several growth factors show synergistic effects on the proliferation of rat astrocytes, a process in which an enhanced expression of GLP-2R and IGF-IR may be involved, providing additional insights into the physiological role of this novel neuropeptide, specially during astroglial regeneration.
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Affiliation(s)
- Esther Velázquez
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Madrid, Spain
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22
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Brantley MA, Jain S, Barr EE, Johnson EM, Milbrandt J. Neurturin-mediated ret activation is required for retinal function. J Neurosci 2008; 28:4123-35. [PMID: 18417692 PMCID: PMC2704905 DOI: 10.1523/jneurosci.0249-08.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2008] [Revised: 02/24/2008] [Accepted: 03/04/2008] [Indexed: 12/26/2022] Open
Abstract
The glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) [GDNF, NRTN (neurturin), ARTN (artemin), and PSPN (persephin)] interact with GDNF family receptors (GFRalphas) and activate intracellular signaling through the Ret receptor tyrosine kinase. To characterize the role of Ret signaling in retinal activity, we examined Ret hypomorphic and Ret conditional mice using electroretinography. We found that aberrant Ret function resulted in markedly diminished scotopic and photopic responses. Using mice deficient in individual GFLs, we found that only NRTN deficiency led to reduced retinal activity. To determine the potential target cell type for NRTN, we examined the retinal expression of its coreceptors (GFRalpha1 and GFRalpha2) and Ret using mice expressing fluorescence reporter enhanced green fluorescent protein from their respective loci. We found robust GFRalpha1 and Ret expression in horizontal, amacrine, and ganglion cells, whereas GFRalpha2 expression was only detected in a subset of amacrine and ganglion cells. In contrast to previous studies, no expression of GFRalpha1, GFRalpha2, or Ret was detected in photoreceptors or Müller cells, suggesting that these cells are not directly affected by Ret. Finally, detailed morphologic analyses of retinas from NRTN- and Ret-deficient mice demonstrated a reduction in normal horizontal cell dendrites and axons, abnormal extensions of horizontal cell and bipolar cell processes into the outer nuclear layer, and mislocalized synaptic complexes. These anatomic abnormalities indicate a possible basis for the abnormal retinal activity in the Ret and NRTN mutant mice.
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Affiliation(s)
| | - Sanjay Jain
- Department of Medicine, Renal Division
- Hope Center for Neurological Disorders, and
| | | | - Eugene M. Johnson
- Hope Center for Neurological Disorders, and
- Departments of Molecular Biology and Pharmacology
- Neurology, and
| | - Jeffrey Milbrandt
- Hope Center for Neurological Disorders, and
- Neurology, and
- Pathology, Washington University School of Medicine, St. Louis, Missouri 63110
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