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Velázquez E, Le Baut Ayuso Y, Blázquez E, Ruiz-Albusac JM. Glucose and Several Mitogenic Agents Modulate the Glucagon-Like Peptide-2 Receptor Expression in Cultured Rat Astrocytes. J Alzheimers Dis Rep 2022; 6:723-732. [PMID: 36606205 PMCID: PMC9741749 DOI: 10.3233/adr-220043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 10/20/2022] [Indexed: 11/16/2022] Open
Abstract
Background Glucagon-like peptide-2 (GLP-2) is an intestinal trophic factor that induces astrocyte proliferation through its own receptor (GLP-2R), but the control of its expression is not well known. Objective To study the effects of glucose and of different mitogenic agents on the control of GLP-2R expression in cultured rat astrocytes. Methods GLP-2R mRNA content was measured by quantitative RT-PCR. Results GLP-2R expression was higher in proliferating than in resting cells. The expression was dependent of glucose concentration both in the absence and in the presence of GLP-2. In the presence of a high glucose concentration, GLP-2, PDGF, and PDGF plus GLP-2 presented opposite effects depending on the incubation time. However, insulin, IGF-1, and EGF alone, and plus GLP-2 had no effect. IGF-2, but not IGF-2 plus GLP-2, increased the expression. On the contrary, NGF decreased the GLP-2R expression, but NGF plus GLP-2 increased it even until values similar to those obtained with GLP-2 alone. Interestingly, in the presence of a low glucose concentration, leptin and NPY produced a significant reduction of GLP-2R expression. Conclusion Astrocytes are distributed throughout the brain, where GLP-2 appears to have important functions. Since these cells express the GLP-2R, the results of this study could be considered of interest to advance the knowledge of the role of GLP-2 signaling in the CNS, which should lead a better understanding of the events that occur under normal and pathophysiological conditions.
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Affiliation(s)
- Esther Velázquez
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Madrid, Spain,Health Research Institute of the San Carlos Clinical Hospital, Madrid, Spain
| | - Yannick Le Baut Ayuso
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Madrid, Spain
| | - Enrique Blázquez
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Madrid, Spain,Health Research Institute of the San Carlos Clinical Hospital, Madrid, Spain
| | - Juan Miguel Ruiz-Albusac
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Complutense University, Madrid, Spain,Health Research Institute of the San Carlos Clinical Hospital, Madrid, Spain,Correspondence to: Juan Miguel Ruiz-Albusac, Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense, 28040-Madrid, Spain. Tel.: +34 913941446; E-mail:
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Amato A, Mulè F. Protective potential of glucagon like peptide 2 (GLP-2) against the neurodegeneration. Neural Regen Res 2019; 14:1901-1902. [PMID: 31290442 PMCID: PMC6676866 DOI: 10.4103/1673-5374.259612] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Antonella Amato
- 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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Taher J, Baker C, Alvares D, Ijaz L, Hussain M, Adeli K. GLP-2 Dysregulates Hepatic Lipoprotein Metabolism, Inducing Fatty Liver and VLDL Overproduction in Male Hamsters and Mice. Endocrinology 2018; 159:3340-3350. [PMID: 30052880 DOI: 10.1210/en.2018-00416] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Accepted: 07/13/2018] [Indexed: 02/07/2023]
Abstract
Fundamental complications of insulin resistance and type 2 diabetes include the development of nonalcoholic fatty liver disease and an atherogenic fasting dyslipidemic profile, primarily due to increases in hepatic very-low-density lipoprotein (VLDL) production. Recently, central glucagon-like peptide-2 receptor (GLP2R) signaling has been implicated in regulating hepatic insulin sensitivity; however, its role in hepatic lipid and lipoprotein metabolism is unknown. We investigated the role of glucagon-like peptide-2 (GLP-2) in regulating hepatic lipid and lipoprotein metabolism in Syrian golden hamsters, C57BL/6J mice, and Glp2r-/- mice consuming either a normal chow or high-fat diet (HFD). In the chow-fed hamsters, IP GLP-2 administration significantly increased fasting dyslipidemia, hepatic VLDL production, and the expression of key genes involved in hepatic de novo lipogenesis. In HFD-fed hamsters and chow-fed mice, GLP-2 administration exacerbated or induced hepatic lipid accumulation. HFD-fed Glp2r-/- mice displayed reduced glucose tolerance, VLDL secretion, and microsomal transfer protein lipid transfer activity, as well as exacerbated fatty liver. Thus, we conclude that GLP-2 plays a lipogenic role in the liver by increasing lipogenic gene expression and inducing hepatic steatosis, fasting dyslipidemia, and VLDL overproduction. In contrast, the lack of Glp2r appears to interfere with VLDL secretion, resulting in enhanced hepatic lipid accumulation. These studies have uncovered a role for GLP-2 in maintaining hepatic lipid and lipoprotein homeostasis.
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Affiliation(s)
- Jennifer Taher
- Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
| | - Christopher Baker
- Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Danielle Alvares
- Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
| | - Laraib Ijaz
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York
- Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, New York
| | - Mahmood Hussain
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York
- Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, New York
| | - Khosrow Adeli
- Molecular Medicine, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
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c-Fos induction by gut hormones and extracellular ATP in osteoblastic-like cell lines. Purinergic Signal 2016; 12:647-651. [PMID: 27439698 DOI: 10.1007/s11302-016-9526-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Accepted: 07/10/2016] [Indexed: 12/21/2022] Open
Abstract
It is widely accepted that the c-Fos gene has a role in proliferation and differentiation of bone cells. ATP-induced c-Fos activation is relevant to bone homeostasis, because nucleotides that are present in the environment of bone cells can contribute to autocrine/paracrine signalling. Gut hormones have previously been shown to have an effect on bone metabolism. In this study, we used the osteoblastic Saos-2 cell line transfected with a c-Fos-driven reporter stimulated with five gut hormones: glucose inhibitory peptide (GIP), glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2), ghrelin and obestatin, in the presence or absence of ATP. In addition, TE-85 cells were used to determine the time course of c-Fos transcript induction following stimulation with GLP-1, and GLP-2 with or without ATP, using reverse transcription qPCR. The significant results from the experiments are as follows: higher level of c-Fos induction in presence of GIP, obestatin (p = 0.019 and p = 0.011 respectively), and GIP combined with ATP (p < 0.001) using the luciferase assay; GLP-1 and GLP-2 combined with ATP (p = 0.034 and p = 0.002, respectively) and GLP-2 alone (p < 0.001) using qPCR. In conclusion, three of the gut peptides induced c-Fos, providing a potential mechanism underlying the actions of these hormones in bone which can be directed or enhanced by the presence of ATP.
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Iwai T, Jin K, Ohnuki T, Sasaki-Hamada S, Nakamura M, Saitoh A, Sugiyama A, Ikeda M, Tanabe M, Oka JI. Glucagon-like peptide-2-induced memory improvement and anxiolytic effects in mice. Neuropeptides 2015; 49:7-14. [PMID: 25481797 DOI: 10.1016/j.npep.2014.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 10/18/2014] [Accepted: 11/19/2014] [Indexed: 12/11/2022]
Abstract
We investigated the effectiveness of glucagon-like peptide-2 (GLP-2) on memory impairment in lipopolysaccharide (LPS)-treated mice, and anxiety-like behavior in adrenocorticotropic hormone (ACTH)-treated mice. In the Y-maze test, LPS (10 µg/mouse, i.c.v.) significantly decreased spontaneous alternation, which was prevented by pretreatment with GLP-2 (0.01-0.3 µg/mouse, i.c.v.). The GLP-2 treatment just before the Y-maze test also improved LPS-induced memory impairment. Continuous treatment with GLP-2 (3 µg/mouse, i.c.v.) had no effect on the open-field test in saline-treated or ACTH-treated mice. Chronic ACTH treatment did not cause anxiogenic effects in the elevated plus-maze test. GLP-2 showed weak anxiolytic-like effects in the elevated plus-maze test in ACTH-treated, but not saline-treated mice. Moreover, GLP-2 increased 5-HT, but not 5-HIAA and tryptophan hydroxylase 2 levels in the amygdala of ACTH-treated mice. Pharmacological depletion of 5-HT prevented the anxiolytic effects of GLP-2. These results suggest that GLP-2 protected and improved memory function in LPS-treated mice, and also had anxiolytic effects due to changes in the 5-HT system.
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Affiliation(s)
- Takashi Iwai
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan; Department of Neuropsychopharmacology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo 187-8553, Japan; Department of Pharmacology, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Kazushi Jin
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Tomoko Ohnuki
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Sachie Sasaki-Hamada
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Minami Nakamura
- Department of Pharmacology, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Akiyoshi Saitoh
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan; Department of Neuropsychopharmacology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo 187-8553, Japan
| | - Azusa Sugiyama
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan; Department of Neuropsychopharmacology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Tokyo 187-8553, Japan
| | - Masaatsu Ikeda
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Mitsuo Tanabe
- Department of Pharmacology, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Jun-Ichiro Oka
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
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Blázquez E, Velázquez E, Hurtado-Carneiro V, Ruiz-Albusac JM. Insulin in the brain: its pathophysiological implications for States related with central insulin resistance, type 2 diabetes and Alzheimer's disease. Front Endocrinol (Lausanne) 2014; 5:161. [PMID: 25346723 PMCID: PMC4191295 DOI: 10.3389/fendo.2014.00161] [Citation(s) in RCA: 316] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/21/2014] [Indexed: 12/21/2022] Open
Abstract
Although the brain has been considered an insulin-insensitive organ, recent reports on the location of insulin and its receptors in the brain have introduced new ways of considering this hormone responsible for several functions. The origin of insulin in the brain has been explained from peripheral or central sources, or both. Regardless of whether insulin is of peripheral origin or produced in the brain, this hormone may act through its own receptors present in the brain. The molecular events through which insulin functions in the brain are the same as those operating in the periphery. However, certain insulin actions are different in the central nervous system, such as hormone-induced glucose uptake due to a low insulin-sensitive GLUT-4 activity, and because of the predominant presence of GLUT-1 and GLUT-3. In addition, insulin in the brain contributes to the control of nutrient homeostasis, reproduction, cognition, and memory, as well as to neurotrophic, neuromodulatory, and neuroprotective effects. Alterations of these functional activities may contribute to the manifestation of several clinical entities, such as central insulin resistance, type 2 diabetes mellitus (T2DM), and Alzheimer's disease (AD). A close association between T2DM and AD has been reported, to the extent that AD is twice more frequent in diabetic patients, and some authors have proposed the name "type 3 diabetes" for this association. There are links between AD and T2DM through mitochondrial alterations and oxidative stress, altered energy and glucose metabolism, cholesterol modifications, dysfunctional protein O-GlcNAcylation, formation of amyloid plaques, altered Aβ metabolism, and tau hyperphosphorylation. Advances in the knowledge of preclinical AD and T2DM may be a major stimulus for the development of treatment for preventing the pathogenic events of these disorders, mainly those focused on reducing brain insulin resistance, which is seems to be a common ground for both pathological entities.
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Affiliation(s)
- Enrique Blázquez
- Departamento de Bioquímica y Biología Molecular III, Facultad de Medicina, Universidad Complutense, Madrid, Spain
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdiSSC), Madrid, Spain
- *Correspondence: Enrique Blázquez, Departamento de Bioquímica y Biología Molecular III, Facultad de Medicina, Universidad Complutense de Madrid, Plaza Ramón y Cajal s/n, Madrid 28040, Spain e-mail:
| | - Esther Velázquez
- Departamento de Bioquímica y Biología Molecular III, Facultad de Medicina, Universidad Complutense, Madrid, Spain
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdiSSC), Madrid, Spain
| | - Verónica Hurtado-Carneiro
- Departamento de Bioquímica y Biología Molecular III, Facultad de Medicina, Universidad Complutense, Madrid, Spain
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdiSSC), Madrid, Spain
| | - Juan Miguel Ruiz-Albusac
- Departamento de Bioquímica y Biología Molecular III, Facultad de Medicina, Universidad Complutense, Madrid, Spain
- The Center for Biomedical Research in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
- Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdiSSC), Madrid, Spain
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Glucagon-like peptide 2 in colon carcinogenesis: Possible target for anti-cancer therapy? Pharmacol Ther 2013; 139:87-94. [DOI: 10.1016/j.pharmthera.2013.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 03/21/2013] [Indexed: 12/18/2022]
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8
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Iwai T, Ohnuki T, Sasaki-Hamada S, Saitoh A, Sugiyama A, Oka JI. Glucagon-like peptide-2 but not imipramine exhibits antidepressant-like effects in ACTH-treated mice. Behav Brain Res 2013; 243:153-7. [DOI: 10.1016/j.bbr.2013.01.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2012] [Revised: 01/07/2013] [Accepted: 01/09/2013] [Indexed: 01/19/2023]
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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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de Heuvel E, Wallace L, Sharkey KA, Sigalet DL. Glucagon-like peptide 2 induces vasoactive intestinal polypeptide expression in enteric neurons via phophatidylinositol 3-kinase-γ signaling. Am J Physiol Endocrinol Metab 2012; 303:E994-1005. [PMID: 22895780 PMCID: PMC3469609 DOI: 10.1152/ajpendo.00291.2012] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Glucagon-like peptide 2 (GLP-2) is an enteroendocrine hormone trophic for intestinal mucosa; it has been shown to increase enteric neuronal expression of vasoactive intestinal polypeptide (VIP) in vivo. We hypothesized that GLP-2 would regulate VIP expression in enteric neurons via a phosphatidylinositol-3 kinase-γ (PI3Kγ) pathway. The mechanism of action of GLP-2 was investigated using primary cultures derived from the submucosal plexus (SMP) of the rat and mouse colon. GLP-2 (10(-8) M) stimulation for 24 h increased the proportion of enteric neurons expressing VIP (GLP-2: 40 ± 6% vs. control: 22 ± 5%). GLP-2 receptor expression was identified by immunohistochemistry on neurons (HuC/D+) and glial cells (GFAP+) but not on smooth muscle or fibroblasts in culture. Over 1-4 h, GLP-2 stimulation of SMP increased phosphorylated Akt/Akt ratios 6.1-fold, phosphorylated ERK/ERK 2.5-fold, and p70S6K 2.2-fold but did not affect intracellular cAMP. PI3Kγ gene deletion or pharmacological blockade of PI3Kγ, mammalian target of rapamycin (mTOR), and MEK/ERK pathways blocked the increase in VIP expression by GLP-2. GLP-2 increased the expression of growth factors and their receptors in SMP cells in culture [IGF-1r (3.2-fold increase), EGFr (5-fold), and ErbB-2-4r (6- to 7-fold)] and ligands [IGF-I (1.5-fold), amphiregulin (2.5-fold), epiregulin (3.2-fold), EGF (7.5-fold), heparin-bound EGF (2.0-fold), β-cellulin (50-fold increase), and neuregulins 2-4 (300-fold increase) (by qRT-PCR)]. We conclude that GLP-2 acts on enteric neurons and glial cells in culture via a PI3Kγ/Akt pathway, stimulating neuronal differentiation via mTOR and ERK pathways, and expression of receptors and ligands for the IGF-I and ErbB pathways.
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Affiliation(s)
- Elaine de Heuvel
- Gastrointestinal Research Group, Snyder Institute for Chronic Diseases
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Velázquez E, Blázquez E, Ruiz-Albusac JM. Glucagon-like peptide-2 (GLP-2) modulates the cGMP signalling pathway by regulating the expression of the soluble guanylyl cyclase receptor subunits in cultured rat astrocytes. Mol Neurobiol 2012; 46:242-50. [PMID: 22806360 DOI: 10.1007/s12035-012-8298-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 06/26/2012] [Indexed: 01/23/2023]
Abstract
The aim of this work was to study the effect of glucagon-like peptide-2 (GLP-2) on the cyclic guanosine monophosphate (cGMP) signalling pathway and whether insulin or epidermal growth factor (EGF) might modulate the effects of GLP-2. GLP-2 produced a dose-dependent decrease in intracellular sodium nitroprusside-induced cGMP production. However, insulin induced an increase in the levels of cGMP that was dose-dependently decreased by the addition of GLP-2. By contrast, EGF induced a decrease in cGMP production, which was further reduced by the addition of GLP-2. To assess whether variations in cGMP production might be related with changes in some component of soluble guanylyl cyclase (sGC), the expression of the α1, α2, and β1 subunits were determined by Western blot analysis. At 1 h, GLP-2 produced a decrease in the expression of both α1 and β1 in the cytosolic fraction, but at 24 h only β1was reduced. As expected, insulin induced an increase in the expression of both subunits after 1 h of incubation; this was decreased by the addition of GLP-2. Likewise, incubation with EGF for 24 h produced a decrease in the expression of both subunits that was maximal when GLP-2 was added. In addition, incubation with insulin for 1 h produced an increase in the expression of the α2 subunit, which was reduced by the addition of GLP-2. These results suggest that GLP-2 inhibits cGMP production by decreasing the cellular content of at least one subunit of the heterodimeric active form of the sGC, independently of the presence of insulin or EFG. This may open new insights into the actions of this neuropeptide.
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Affiliation(s)
- Esther Velázquez
- Department of Biochemistry and Molecular Biology, Complutense University Plaza S. Ramón y Cajal s/n, 28040 Madrid, Spain
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Cinci L, Faussone-Pellegrini MS, Rotondo A, Mulè F, Vannucchi MG. GLP-2 receptor expression in excitatory and inhibitory enteric neurons and its role in mouse duodenum contractility. Neurogastroenterol Motil 2011; 23:e383-92. [PMID: 21752156 DOI: 10.1111/j.1365-2982.2011.01750.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Glucagon-like peptide 2 (GLP-2), a nutrient-responsive hormone, exerts various actions in the gastrointestinal tract that are mediated by a G-protein coupled receptor called GLP-2R. A little information is available on GLP-2R expression in enteric neurons and nothing on the interstitial cells of Cajal (ICC). METHODS We investigated presence and distribution of the GLP-2R in the mouse duodenum by immunohistochemistry and the potential motor effects of GLP-2 on the spontaneous and neurally evoked mechanical activity. KEY RESULTS The GLP-2R was expressed by the myenteric and submucosal neurons. Labelling was also present in nerve varicosities within the circular muscular layer and at the deep muscular plexus (DMP). No immunoreactive nerve fiber was seen within the longitudinal muscle layer. The GLP-2R-positive neurons were either excitatory (SP- and choline-acetyltransferase-positive) or inhibitory (vasoactive intestinal polypeptide and nNOS-positive). The ICC, both at the myenteric plexus and at the DMP, never expressed GLP-2R but, especially those at the DMP, were surrounded by GLP-2R-positive nerve varicosities co-expressing either excitatory or inhibitory neurotransmitters. Quantitative analysis demonstrated a consistent prevalence of GLP-2R on the excitatory pathways. In agreement, the functional results showed that the administration of GLP-2 in vitro caused decrease of the spontaneous contractions mediated by nitric oxide release and reduction of the evoked cholinergic contractions. CONCLUSIONS & INFERENCES The present findings indicate that the GLP-2R is expressed by inhibitory and excitatory neurons, the GLP-2 inhibits the muscle contractility likely decreasing cholinergic neurotransmission and increasing nitric oxide production, and this effect is possibly mediated by the ICC-DMP recruitment.
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Affiliation(s)
- L Cinci
- Department of Anatomy, Histology and Forensic Medicine, Section of Histology, University of Florence, Viale G. Pieraccini 6, Florence, Italy
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