1
|
Brubaker PL. A New Role for Endocrine Cells in the Intestinal Crypt. Cell Mol Gastroenterol Hepatol 2023; 15:1525-1526. [PMID: 36805429 DOI: 10.1016/j.jcmgh.2023.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 01/25/2023] [Accepted: 01/25/2023] [Indexed: 02/23/2023]
|
2
|
Cyranka M, Monfeuga T, Vedovato N, Larabee CM, Chandran A, Toledo EM, de Wet H. NMDA Receptor Antagonists Increase the Release of GLP-1 From Gut Endocrine Cells. Front Pharmacol 2022; 13:861311. [PMID: 35571112 PMCID: PMC9091448 DOI: 10.3389/fphar.2022.861311] [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: 01/24/2022] [Accepted: 04/04/2022] [Indexed: 11/30/2022] Open
Abstract
Type 2 diabetes mellitus (T2DM) remains one of the most pressing health issues facing modern society. Several antidiabetic drugs are currently in clinical use to treat hyperglycaemia, but there is a need for new treatments that effectively restore pancreatic islet function in patients. Recent studies reported that both murine and human pancreatic islets exhibit enhanced insulin release and β-cell viability in response to N-methyl-D-aspartate (NMDA) receptor antagonists. Furthermore, oral administration of dextromethorphan, an over-the-counter NMDA receptor antagonist, to diabetic patients in a small clinical trial showed improved glucose tolerance and increased insulin release. However, the effects of NMDA receptor antagonists on the secretion of the incretin hormone GLP-1 was not tested, and nothing is known regarding how NMDA receptor antagonists may alter the secretion of gut hormones. This study demonstrates for the first time that, similar to β-cells, the NMDA receptor antagonist MK-801 increases the release of GLP-1 from a murine L-cell enteroendocrine model cell line, GLUTag cells. Furthermore, we report the 3′ mRNA expression profiling of GLUTag cells, with a specific focus on glutamate-activated receptors. We conclude that if NMDA receptor antagonists are to be pursued as an alternative, orally administered treatment for T2DM, it is essential that the effects of these drugs on the release of gut hormones, and specifically the incretin hormones, are fully investigated.
Collapse
Affiliation(s)
- Malgorzata Cyranka
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, United Kingdom
| | - Thomas Monfeuga
- Novo Nordisk Research Centre Oxford, Innovation Building, Oxford, United Kingdom
| | - Natascia Vedovato
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, United Kingdom
| | - Chelsea M Larabee
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, United Kingdom
| | | | - Enrique M Toledo
- Novo Nordisk Research Centre Oxford, Innovation Building, Oxford, United Kingdom
| | - Heidi de Wet
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
3
|
García-Gaytán AC, Hernández-Abrego A, Díaz-Muñoz M, Méndez I. Glutamatergic system components as potential biomarkers and therapeutic targets in cancer in non-neural organs. Front Endocrinol (Lausanne) 2022; 13:1029210. [PMID: 36457557 PMCID: PMC9705578 DOI: 10.3389/fendo.2022.1029210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 10/24/2022] [Indexed: 11/17/2022] Open
Abstract
Glutamate is one of the most abundant amino acids in the blood. Besides its role as a neurotransmitter in the brain, it is a key substrate in several metabolic pathways and a primary messenger that acts through its receptors outside the central nervous system (CNS). The two main types of glutamate receptors, ionotropic and metabotropic, are well characterized in CNS and have been recently analyzed for their roles in non-neural organs. Glutamate receptor expression may be particularly important for tumor growth in organs with high concentrations of glutamate and might also influence the propensity of such tumors to set metastases in glutamate-rich organs, such as the liver. The study of glutamate transporters has also acquired relevance in the physiology and pathologies outside the CNS, especially in the field of cancer research. In this review, we address the recent findings about the expression of glutamatergic system components, such as receptors and transporters, their role in the physiology and pathology of cancer in non-neural organs, and their possible use as biomarkers and therapeutic targets.
Collapse
|
4
|
Najjar SA, Albers KM. Pain in Inflammatory Bowel Disease: Optogenetic Strategies for Study of Neural-Epithelial Signaling. CROHN'S & COLITIS 360 2021; 3:otab040. [PMID: 34805983 PMCID: PMC8600958 DOI: 10.1093/crocol/otab040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Indexed: 02/06/2023] Open
Abstract
Abdominal pain is common in patients with active inflammation of the colon but can persist even in its absence, suggesting other mechanisms of pain signaling. Recent findings suggest colon epithelial cells are direct regulators of pain-sensing neurons. Optogenetic activation of epithelial cells evoked nerve firing and pain-like behaviors. Inhibition of epithelial cells caused the opposite effect, reducing responses to colon distension and inflammatory hypersensitivity. Thus, epithelial cells alone can regulate the activation of pain circuits. Future goals are to define the anatomical and cellular mechanisms that underlie epithelial-neural pain signaling and how it is altered in response to colon inflammation.
Collapse
Affiliation(s)
- Sarah A Najjar
- Department of Neurobiology and Pittsburgh Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA,Present address: Department of Pediatrics, Columbia University Medical Center, New York, New York, USA
| | - Kathryn M Albers
- Department of Neurobiology and Pittsburgh Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA,Address correspondence to: Kathryn M. Albers, PhD, Department of Neurobiology, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15216, USA ()
| |
Collapse
|
5
|
Najjar SA, Davis BM, Albers KM. Epithelial-Neuronal Communication in the Colon: Implications for Visceral Pain. Trends Neurosci 2020; 43:170-181. [PMID: 31983457 DOI: 10.1016/j.tins.2019.12.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/18/2019] [Accepted: 12/30/2019] [Indexed: 02/07/2023]
Abstract
Visceral hypersensitivity and pain result, at least in part, from increased excitability of primary afferents that innervate the colon. In addition to intrinsic changes in these neurons, emerging evidence indicates that changes in lining epithelial cells may also contribute to increased excitability. Here we review recent studies on how colon epithelial cells communicate directly with colon afferents. Specifically, anatomical studies revealed specialized synaptic connections between epithelial cells and nerve fibers and studies using optogenetic activation of the epithelium showed initiation of pain-like responses. We review the possible mechanisms of epithelial-neuronal communication and provide an overview of the possible neurotransmitters and receptors involved. Understanding the biology of this interface and how it changes in pathological conditions may provide new treatments for visceral pain conditions.
Collapse
Affiliation(s)
- Sarah A Najjar
- Center for Neuroscience at the University of Pittsburgh, Pittsburgh Center for Pain Research and Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| | - Brian M Davis
- Center for Neuroscience at the University of Pittsburgh, Pittsburgh Center for Pain Research and Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Kathryn M Albers
- Center for Neuroscience at the University of Pittsburgh, Pittsburgh Center for Pain Research and Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| |
Collapse
|
6
|
Cyranka M, Veprik A, McKay EJ, van Loon N, Thijsse A, Cotter L, Hare N, Saibudeen A, Lingam S, Pires E, Larraufie P, Reimann F, Gribble F, Stewart M, Bentley E, Lear P, McCullagh J, Cantley J, Cox RD, de Wet H. Abcc5 Knockout Mice Have Lower Fat Mass and Increased Levels of Circulating GLP-1. Obesity (Silver Spring) 2019; 27:1292-1304. [PMID: 31338999 PMCID: PMC6658130 DOI: 10.1002/oby.22521] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 04/09/2019] [Indexed: 12/11/2022]
Abstract
OBJECTIVE A previous genome-wide association study linked overexpression of an ATP-binding cassette transporter, ABCC5, in humans with a susceptibility to developing type 2 diabetes with age. Specifically, ABCC5 gene overexpression was shown to be strongly associated with increased visceral fat mass and reduced peripheral insulin sensitivity. Currently, the role of ABCC5 in diabetes and obesity is unknown. This study reports the metabolic phenotyping of a global Abcc5 knockout mouse. METHODS A global Abcc5-/- mouse was generated by CRISPR/Cas9. Fat mass was determined by weekly EchoMRI and fat pads were dissected and weighed at week 18. Glucose homeostasis was ascertained by an oral glucose tolerance test, intraperitoneal glucose tolerance test, and intraperitoneal insulin tolerance test. Energy expenditure and locomotor activity were measured using PhenoMaster cages. Glucagon-like peptide 1 (GLP-1) levels in plasma, primary gut cell cultures, and GLUTag cells were determined by enzyme-linked immunosorbent assay. RESULTS Abcc5-/- mice had decreased fat mass and increased plasma levels of GLP-1, and they were more insulin sensitive and more active. Recombinant overexpression of ABCC5 protein in GLUTag cells decreased GLP-1 release. CONCLUSIONS ABCC5 protein expression levels are inversely related to fat mass and appear to play a role in the regulation of GLP-1 secretion from enteroendocrine cells.
Collapse
Affiliation(s)
- Malgorzata Cyranka
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Anna Veprik
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Eleanor J. McKay
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Nienke van Loon
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Amber Thijsse
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Luke Cotter
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Nisha Hare
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Affan Saibudeen
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Swathi Lingam
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | | | - Pierre Larraufie
- Wellcome Trust‐MRC Institute of Metabolic ScienceAddenbrooke's HospitalCambridgeUK
| | - Frank Reimann
- Wellcome Trust‐MRC Institute of Metabolic ScienceAddenbrooke's HospitalCambridgeUK
| | - Fiona Gribble
- Wellcome Trust‐MRC Institute of Metabolic ScienceAddenbrooke's HospitalCambridgeUK
| | - Michelle Stewart
- MRC Harwell Institute, Genetics of Type 2 DiabetesMammalian Genetics Unit, Harwell CampusOxfordshireUK
| | - Elizabeth Bentley
- MRC Harwell Institute, Genetics of Type 2 DiabetesMammalian Genetics Unit, Harwell CampusOxfordshireUK
| | - Pamela Lear
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | | | - James Cantley
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Roger D. Cox
- MRC Harwell Institute, Genetics of Type 2 DiabetesMammalian Genetics Unit, Harwell CampusOxfordshireUK
| | - Heidi de Wet
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| |
Collapse
|
7
|
Adenosine triphosphate is co-secreted with glucagon-like peptide-1 to modulate intestinal enterocytes and afferent neurons. Nat Commun 2019; 10:1029. [PMID: 30833673 PMCID: PMC6399286 DOI: 10.1038/s41467-019-09045-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 02/01/2019] [Indexed: 02/02/2023] Open
Abstract
Enteroendocrine cells are specialised sensory cells located in the intestinal epithelium and generate signals in response to food ingestion. Whilst traditionally considered hormone-producing cells, there is evidence that they also initiate activity in the afferent vagus nerve and thereby signal directly to the brainstem. We investigate whether enteroendocrine L-cells, well known for their production of the incretin hormone glucagon-like peptide-1 (GLP-1), also release other neuro-transmitters/modulators. We demonstrate regulated ATP release by ATP measurements in cell supernatants and by using sniffer patches that generate electrical currents upon ATP exposure. Employing purinergic receptor antagonists, we demonstrate that evoked ATP release from L-cells triggers electrical responses in neighbouring enterocytes through P2Y2 and nodose ganglion neurones in co-cultures through P2X2/3-receptors. We conclude that L-cells co-secrete ATP together with GLP-1 and PYY, and that ATP acts as an additional signal triggering vagal activation and potentially synergising with the actions of locally elevated peptide hormone concentrations.
Collapse
|
8
|
Card JP, Johnson AL, Llewellyn‐Smith IJ, Zheng H, Anand R, Brierley DI, Trapp S, Rinaman L. GLP-1 neurons form a local synaptic circuit within the rodent nucleus of the solitary tract. J Comp Neurol 2018; 526:2149-2164. [PMID: 30019398 PMCID: PMC6193818 DOI: 10.1002/cne.24482] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 05/16/2018] [Accepted: 05/22/2018] [Indexed: 12/30/2022]
Abstract
Glutamatergic neurons that express pre-proglucagon (PPG) and are immunopositive (+) for glucagon-like peptide-1 (i.e., GLP-1+ neurons) are located within the caudal nucleus of the solitary tract (cNTS) and medullary reticular formation in rats and mice. GLP-1 neurons give rise to an extensive central network in which GLP-1 receptor (GLP-1R) signaling suppresses food intake, attenuates rewarding, increases avoidance, and stimulates stress responses, partly via GLP-1R signaling within the cNTS. In mice, noradrenergic (A2) cNTS neurons express GLP-1R, whereas PPG neurons do not. In this study, confocal microscopy in rats confirmed that prolactin-releasing peptide (PrRP)+ A2 neurons are closely apposed by GLP-1+ axonal varicosities. Surprisingly, GLP-1+ appositions were also observed on dendrites of PPG/GLP-1+ neurons in both species, and electron microscopy in rats revealed that GLP-1+ boutons form asymmetric synaptic contacts with GLP-1+ dendrites. However, RNAscope confirmed that rat GLP-1 neurons do not express GLP-1R mRNA. Similarly, Ca2+ imaging of somatic and dendritic responses in mouse ex vivo slices confirmed that PPG neurons do not respond directly to GLP-1, and a mouse crossbreeding strategy revealed that <1% of PPG neurons co-express GLP-1R. Collectively, these data suggest that GLP-1R signaling pathways modulate the activity of PrRP+ A2 neurons, and also reveal a local "feed-forward" synaptic network among GLP-1 neurons that apparently does not use GLP-1R signaling. This local GLP-1 network may instead use glutamatergic signaling to facilitate dynamic and potentially selective recruitment of GLP-1 neural populations that shape behavioral and physiological responses to internal and external challenges.
Collapse
Affiliation(s)
- J. Patrick Card
- Department of NeuroscienceUniversity of PittsburghPittsburghPennsylvania
| | - Aaron L. Johnson
- Department of NeuroscienceUniversity of PittsburghPittsburghPennsylvania
- Systems Neuroscience CenterUniversity of PittsburghPittsburghPennsylvania
| | - Ida J. Llewellyn‐Smith
- Cardiovascular Medicine, Human Physiology and Centre for NeuroscienceCollege of Medicine and Public Health, Flinders UniversityBedford ParkSouth AustraliaAustralia
| | - Huiyuan Zheng
- Department of PsychologyFlorida State UniversityTallahasseeFlorida
| | - Rishi Anand
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & PharmacologyUniversity College LondonLondonUnited Kingdom
| | - Daniel I. Brierley
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & PharmacologyUniversity College LondonLondonUnited Kingdom
| | - Stefan Trapp
- Centre for Cardiovascular and Metabolic Neuroscience, Department of Neuroscience, Physiology & PharmacologyUniversity College LondonLondonUnited Kingdom
| | - Linda Rinaman
- Department of PsychologyFlorida State UniversityTallahasseeFlorida
| |
Collapse
|
9
|
Andersson LE, Shcherbina L, Al-Majdoub M, Vishnu N, Arroyo CB, Aste Carrara J, Wollheim CB, Fex M, Mulder H, Wierup N, Spégel P. Glutamine-Elicited Secretion of Glucagon-Like Peptide 1 Is Governed by an Activated Glutamate Dehydrogenase. Diabetes 2018; 67:372-384. [PMID: 29229616 DOI: 10.2337/db16-1441] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 12/07/2017] [Indexed: 11/13/2022]
Abstract
Glucagon-like peptide 1 (GLP-1), secreted from intestinal L cells, glucose dependently stimulates insulin secretion from β-cells. This glucose dependence prevents hypoglycemia, rendering GLP-1 analogs a useful and safe treatment modality in type 2 diabetes. Although the amino acid glutamine is a potent elicitor of GLP-1 secretion, the responsible mechanism remains unclear. We investigated how GLP-1 secretion is metabolically coupled in L cells (GLUTag) and in vivo in mice using the insulin-secreting cell line INS-1 832/13 as reference. A membrane-permeable glutamate analog (dimethylglutamate [DMG]), acting downstream of electrogenic transporters, elicited similar alterations in metabolism as glutamine in both cell lines. Both DMG and glutamine alone elicited GLP-1 secretion in GLUTag cells and in vivo, whereas activation of glutamate dehydrogenase (GDH) was required to stimulate insulin secretion from INS-1 832/13 cells. Pharmacological inhibition in vivo of GDH blocked secretion of GLP-1 in response to DMG. In conclusion, our results suggest that nonelectrogenic nutrient uptake and metabolism play an important role in L cell stimulus-secretion coupling. Metabolism of glutamine and related analogs by GDH in the L cell may explain why GLP-1 secretion, but not that of insulin, is activated by these secretagogues in vivo.
Collapse
Affiliation(s)
- Lotta E Andersson
- Unit of Molecular Metabolism, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | - Liliya Shcherbina
- Neuroendocrine Cell Biology, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | - Mahmoud Al-Majdoub
- Unit of Molecular Metabolism, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | - Neelanjan Vishnu
- Unit of Molecular Metabolism, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | | | - Jonathan Aste Carrara
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
| | - Claes B Wollheim
- Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
- Department of Cell Physiology and Metabolism, University Medical Centre, Geneva, Switzerland
| | - Malin Fex
- Unit of Molecular Metabolism, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | - Hindrik Mulder
- Unit of Molecular Metabolism, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | - Nils Wierup
- Neuroendocrine Cell Biology, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
| | - Peter Spégel
- Unit of Molecular Metabolism, Department of Clinical Sciences, Lund University Diabetes Centre, Clinical Research Centre, Skåne University Hospital, Malmö, Sweden
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
| |
Collapse
|
10
|
Zhang H, Liu R, Deng T, Wang X, Lang H, Qu Y, Duan J, Huang D, Ying G, Ba Y. The microRNA-124-iGluR2/3 pathway regulates glucagon release from alpha cells. Oncotarget 2017; 7:24734-43. [PMID: 27013590 PMCID: PMC5029737 DOI: 10.18632/oncotarget.8270] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/07/2016] [Indexed: 01/30/2023] Open
Abstract
Glucagon, secreted from islet alpha cells, plays an important role in regulating glucose homeostasis; however, the molecular mechanism underlying this process is not fully understood. Previous studies have demonstrated that miRNAs are involved in the function of alpha cells. Glutamate promotes glucagon secretion by mediating the opening of Ca2+ channels. In this present, iGluR2 and iGluR3 levels were significantly increased in fasting-treated mouse islets. Additional studies showed that miR-124-3p simultaneously regulates the expression of iGluR2 and iGluR3 through the direct targeting of mRNA 3’UTR of these two genes. The miR-124-iGluRs pathway also contributed to the high level of glucagon secretion through long-term high glucose levels. Thus, a novel pathway comprising miRNA, glutamate and iGluRs has been demonstrated to regulate the biological process of glucagon release.
Collapse
Affiliation(s)
- Haiyang Zhang
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Rui Liu
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Ting Deng
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Xia Wang
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Hongmei Lang
- Department of Endocrinology, Chengdu Military General Hospital, Chengdu, Sichuan 610083, China
| | - Yanjun Qu
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Jingjing Duan
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Dingzhi Huang
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Guoguang Ying
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| | - Yi Ba
- Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin 300060, China
| |
Collapse
|
11
|
|
12
|
Glutamate acts as a key signal linking glucose metabolism to incretin/cAMP action to amplify insulin secretion. Cell Rep 2014; 9:661-73. [PMID: 25373904 PMCID: PMC4536302 DOI: 10.1016/j.celrep.2014.09.030] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 08/19/2014] [Accepted: 09/15/2014] [Indexed: 11/29/2022] Open
Abstract
Incretins, hormones released by the gut after meal ingestion, are essential for maintaining systemic glucose homeostasis by stimulating insulin secretion. The effect of incretins on insulin secretion occurs only at elevated glucose concentrations and is mediated by cAMP signaling, but the mechanism linking glucose metabolism and cAMP action in insulin secretion is unknown. We show here, using a metabolomics-based approach, that cytosolic glutamate derived from the malate-aspartate shuttle upon glucose stimulation underlies the stimulatory effect of incretins and that glutamate uptake into insulin granules mediated by cAMP/PKA signaling amplifies insulin release. Glutamate production is diminished in an incretin-unresponsive, insulin-secreting β cell line and pancreatic islets of animal models of human diabetes and obesity. Conversely, a membrane-permeable glutamate precursor restores amplification of insulin secretion in these models. Thus, cytosolic glutamate represents the elusive link between glucose metabolism and cAMP action in incretin-induced insulin secretion. Glutamate is derived from the malate-aspartate shuttle upon glucose stimulation Shuttle-derived glutamate is crucial for incretin-induced insulin secretion Cytosolic glutamate is transported into insulin granules via cAMP/PKA signaling Glutamate production by glucose is defective in incretin-unresponsive β cells
Collapse
|
13
|
Zheng H, Stornetta RL, Agassandian K, Rinaman L. Glutamatergic phenotype of glucagon-like peptide 1 neurons in the caudal nucleus of the solitary tract in rats. Brain Struct Funct 2014; 220:3011-22. [PMID: 25012114 DOI: 10.1007/s00429-014-0841-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 07/02/2014] [Indexed: 01/30/2023]
Abstract
The expression of a vesicular glutamate transporter (VGLUT) suffices to assign a glutamatergic phenotype to neurons and other secretory cells. For example, intestinal L cells express VGLUT2 and secrete glutamate along with glucagon-like peptide 1 (GLP1). We hypothesized that GLP1-positive neurons within the caudal (visceral) nucleus of the solitary tract (cNST) also are glutamatergic. To test this, the axonal projections of GLP1 and other neurons within the cNST were labeled in rats via iontophoretic delivery of anterograde tracer. Dual immunofluorescence and confocal microscopy was used to visualize tracer-, GLP1-, and VGLUT2-positive fibers within brainstem, hypothalamic, and limbic forebrain nuclei that receive input from the cNST. Electron microscopy was used to confirm GLP1 and VGLUT2 immunolabeling within the same axon varicosities, and fluorescent in situ hybridization was used to examine VGLUT2 mRNA expression by GLP1-positive neurons. Most anterograde tracer-labeled fibers displayed VGLUT2-positive varicosities, providing new evidence that ascending axonal projections from the cNST are primarily glutamatergic. Virtually all GLP1-positive varicosities also were VGLUT2-positive. Electron microscopy confirmed the colocalization of GLP1 and VGLUT2 immunolabeling in axon terminals that formed asymmetric (excitatory-type) synapses with unlabeled dendrites in the hypothalamus. Finally, in situ hybridization confirmed that GLP1-positive cNST neurons express VGLUT2 mRNA. Thus, hindbrain GLP1 neurons in rats are equipped to store glutamate in synaptic vesicles, and likely co-release both glutamate and GLP1 from axon varicosities and terminals in the hypothalamus and other brain regions.
Collapse
Affiliation(s)
- H Zheng
- Department of Neuroscience, University of Pittsburgh, A210 Langley Hall, Pittsburgh, PA, 15260, USA
| | | | | | | |
Collapse
|
14
|
Li SK, Zhu D, Gaisano HY, Brubaker PL. Role of vesicle-associated membrane protein 2 in exocytosis of glucagon-like peptide-1 from the murine intestinal L cell. Diabetologia 2014; 57:809-18. [PMID: 24356748 DOI: 10.1007/s00125-013-3143-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 11/22/2013] [Indexed: 12/27/2022]
Abstract
AIMS/HYPOTHESIS Glucagon-like peptide-1 (GLP-1), secreted by the enteroendocrine L cell, is an incretin hormone that potently stimulates insulin secretion. Although signalling pathways promoting GLP-1 release are well characterised, the mechanisms by which GLP-1-containing granules fuse to the L cell membrane are unknown. As soluble NSF attachment proteins (SNAREs) are known to mediate granule-membrane fusion, the role of vesicle-associated membrane proteins (VAMPs) in GLP-1 exocytosis was examined. METHODS SNARE expression was determined in murine GLUTag L cells by RT-PCR and immunoblot and in primary murine L cells by immunofluorescence. Co-immunoprecipitation was used to examine SNARE interactions, while tetanus toxin (TetX)-mediated cleavage of VAMP was used with a GLP-1 secretion assay and total internal reflection fluorescence microscopy to determine the role of VAMP2 in exocytosis. RESULTS VAMP2 was expressed in murine L cells and localised to secretory granules in GLUTag cells. VAMP1/3 and the core membrane proteins syntaxin1a and synaptosomal-associated protein 25 kDa (SNAP25) were also detected. TetX cleaved VAMPs in GLUTag cells. However, only VAMP2 interacted with syntaxin1a, as did SNAP25 and Munc18-1. TetX treatment of GLUTag cells prevented glucose-dependent insulinotrophic peptide- and oleic-acid-stimulated GLP-1 secretion (p < 0.05-0.01), as well as K(+)-stimulated single-cell exocytosis (p < 0.05-0.001), while TetX-resistant VAMP2 expression rescued GLP-1 secretion (p < 0.01-0.001). CONCLUSIONS/INTERPRETATION Together, these findings indicate an essential role for VAMP2 in GLP-1 exocytosis from the GLUTag L cell in response to a variety of established secretagogues. An improved understanding of the mechanisms governing the release of GLP-1 may lead to new therapeutic approaches to enhance the levels of this incretin hormone in patients with type 2 diabetes.
Collapse
Affiliation(s)
- Samantha K Li
- Department of Physiology, Medical Sciences Building, 1 King's College Circle, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | | | | | | |
Collapse
|
15
|
Ritter RC. A tale of two endings: modulation of satiation by NMDA receptors on or near central and peripheral vagal afferent terminals. Physiol Behav 2011; 105:94-9. [PMID: 21382391 PMCID: PMC3181280 DOI: 10.1016/j.physbeh.2011.02.042] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 02/28/2011] [Indexed: 10/18/2022]
Abstract
Glutamate is the neurotransmitter responsible for fast excitatory transmission from vagal afferents to second order neurons in the NTS. Antagonism of NMDA-type glutamate receptors in the NTS increases food intake and attenuates reduction of food intake by vagally mediated satiation signals, such as cholecystokinin. Although, the cellular location(s) of NMDA receptors that participate in satiation is uncertain, recent findings suggest that attenuation of satiation by NMDA receptor antagonists is due, at least in part, to their action on primary vagal afferents themselves. While evidence is accumulating that NMDA receptors located on vagal afferent endings in the hindbrain are involved in control of food intake, there also is preliminary evidence that peripheral NMDA receptors also may influence vagal control of food intake. Hence, NMDA receptor expression on central and perhaps peripheral vagal afferent endings could provide a parsimonious mechanism for modulation of satiation signals by endogenously released glutamate.
Collapse
Affiliation(s)
- Robert C Ritter
- Dept of VCAPP and Programs in Neuroscience, Washington State University, Pullman, WA 99164-6520, United States.
| |
Collapse
|
16
|
Gunawardene AR, Corfe BM, Staton CA. Classification and functions of enteroendocrine cells of the lower gastrointestinal tract. Int J Exp Pathol 2011; 92:219-31. [PMID: 21518048 DOI: 10.1111/j.1365-2613.2011.00767.x] [Citation(s) in RCA: 189] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
With over thirty different hormones identified as being produced in the gastrointestinal (GI) tract, the gut has been described as 'the largest endocrine organ in the body' (Ann. Oncol., 12, 2003, S63). The classification of these hormones and the cells that produce them, the enteroendocrine cells (EECs), has provided the foundation for digestive physiology. Furthermore, alterations in the composition and function of EEC may influence digestive physiology and thereby associate with GI pathologies. Whilst there is a rapidly increasing body of data on the role and function of EEC in the upper GI tract, there is a less clear-cut understanding of the function of EEC in the lower GI. Nonetheless, their presence and diversity are indicative of a role. This review focuses on the EECs of the lower GI where new evidence also suggests a possible relationship with the development and progression of primary adenocarcinoma.
Collapse
Affiliation(s)
- Ashok R Gunawardene
- Department of Oncology, The Medical School, University of Sheffield, Sheffield, UK
| | | | | |
Collapse
|
17
|
Mace OJ, Lister N, Morgan E, Shepherd E, Affleck J, Helliwell P, Bronk JR, Kellett GL, Meredith D, Boyd R, Pieri M, Bailey PD, Pettcrew R, Foley D. An energy supply network of nutrient absorption coordinated by calcium and T1R taste receptors in rat small intestine. J Physiol 2008; 587:195-210. [PMID: 19001049 DOI: 10.1113/jphysiol.2008.159616] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
T1R taste receptors are present throughout the gastrointestinal tract. Glucose absorption comprises active absorption via SGLT1 and facilitated absorption via GLUT2 in the apical membrane. Trafficking of apical GLUT2 is rapidly up-regulated by glucose and artificial sweeteners, which act through T1R2 + T1R3/alpha-gustducin to activate PLC beta2 and PKC betaII. We therefore investigated whether non-sugar nutrients are regulated by taste receptors using perfused rat jejunum in vivo. Under different conditions, we observed a Ca(2+)-dependent reciprocal relationship between the H(+)/oligopeptide transporter PepT1 and apical GLUT2, reflecting the fact that trafficking of PepT1 and GLUT2 to the apical membrane is inhibited and activated by PKC betaII, respectively. Addition of L-glutamate or sucralose to a perfusate containing low glucose (20 mM) each activated PKC betaII and decreased apical PepT1 levels and absorption of the hydrolysis-resistant dipeptide L-Phe(PsiS)-L-Ala (1 mM), while increasing apical GLUT2 and glucose absorption within minutes. Switching perfusion from mannitol to glucose (75 mM) exerted similar effects. c-glutamate induced rapid GPCR internalization of T1R1, T1R3 and transducin, whereas sucralose internalized T1R2, T1R3 and alpha-gustducin. We conclude that L-glutamate acts via amino acid and glucose via sweet taste receptors to coordinate regulation of PepT1 and apical GLUT2 reciprocally through a common enterocytic pool of PKC betaII. These data suggest the existence of a wider Ca(2+) and taste receptor-coordinated transport network incorporating other nutrients and/or other stimuli capable of activating PKC betaII and additional transporters, such as the aspartate/glutamate transporter, EAAC1, whose level was doubled by L-glutamate. The network may control energy supply.
Collapse
Affiliation(s)
- Oliver J Mace
- Department of Biology (Area 3), The University of York, Heslington, York YO10 5YW, UK
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Moriyama Y, Omote H. Vesicular Glutamate Transporter Acts as a Metabolic Regulator. Biol Pharm Bull 2008; 31:1844-6. [DOI: 10.1248/bpb.31.1844] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Yoshinori Moriyama
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences
| | - Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences
| |
Collapse
|
19
|
Morimoto R, Uehara S, Yatsushiro S, Juge N, Hua Z, Senoh S, Echigo N, Hayashi M, Mizoguchi T, Ninomiya T, Udagawa N, Omote H, Yamamoto A, Edwards RH, Moriyama Y. Secretion of L-glutamate from osteoclasts through transcytosis. EMBO J 2006; 25:4175-86. [PMID: 16957773 PMCID: PMC1570443 DOI: 10.1038/sj.emboj.7601317] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2005] [Accepted: 08/08/2006] [Indexed: 01/11/2023] Open
Abstract
Osteoclasts are involved in the catabolism of the bone matrix and eliminate the resulting degradation products through transcytosis, but the molecular mechanism and regulation of transcytosis remain poorly understood. Upon differentiation, osteoclasts express vesicular glutamate transporter 1 (VGLUT1), which is essential for vesicular storage and subsequent exocytosis of glutamate in neurons. VGLUT1 is localized in transcytotic vesicles and accumulates L-glutamate. Osteoclasts secrete L-glutamate and the bone degradation products upon stimulation with KCl or ATP in a Ca2+-dependent manner. KCl- and ATP-dependent secretion of L-glutamate was absent in osteoclasts prepared from VGLUT1-/- knockout mice. Osteoclasts express mGluR8, a class III metabotropic glutamate receptor. Its stimulation by a specific agonist inhibits secretion of L-glutamate and bone degradation products, whereas its suppression by a specific antagonist stimulates bone resorption. Finally, it was found that VGLUT1-/- mice develop osteoporosis. Thus, in bone-resorbing osteoclasts, L-glutamate and bone degradation products are secreted through transcytosis and the released L-glutamate is involved in autoregulation of transcytosis. Glutamate signaling may play an important role in the bone homeostasis.
Collapse
Affiliation(s)
- Riyo Morimoto
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Shunsuke Uehara
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Shouki Yatsushiro
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Narinobu Juge
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Zhaolin Hua
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, University of California San Francisco School of Medicine, CA, USA
| | - Shigenori Senoh
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Noriko Echigo
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Mitsuko Hayashi
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | | | - Tadashi Ninomiya
- Institute for Oral Science, Matsumoto Dental University, Shiojiri, Japan
| | - Nobuyuki Udagawa
- Department of Biochemistry, Matsumoto Dental University, Shiojiri, Japan
| | - Hiroshi Omote
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Akitsugu Yamamoto
- Department of Cell Biology, Nagahama Institute of Bioscience and Technology, Nagahama, Japan
| | - Robert H Edwards
- Departments of Neurology and Physiology, Graduate Programs in Neuroscience and Cell Biology, University of California San Francisco School of Medicine, CA, USA
| | - Yoshinori Moriyama
- Laboratory of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
- Department of Membrane Biochemistry, Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan. Tel.: +81 86 251 7933/7934; Fax: +81 86 251 7935; E-mail:
| |
Collapse
|
20
|
Tremolizzo L, DiFrancesco JC, Rodriguez-Menendez V, Sirtori E, Longoni M, Cassetti A, Bossi M, El Mestikawy S, Cavaletti G, Ferrarese C. Human platelets express the synaptic markers VGLUT1 and 2 and release glutamate following aggregation. Neurosci Lett 2006; 404:262-5. [PMID: 16814469 DOI: 10.1016/j.neulet.2006.06.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2006] [Revised: 06/04/2006] [Accepted: 06/05/2006] [Indexed: 11/20/2022]
Abstract
Vesicular glutamate transporters (VGLUTs) are involved in storing glutamate for secretion at the level of glutamatergic axon terminals, and for this reason they have been extensively used as markers to identify glutamate-releasing cells. Platelets have been considered as a suitable model for studying glutamatergic dysfunction because they perform glutamate uptake and express both external transporters, and NMDA-like receptors. Here, we show that platelets express the pre-synaptic markers VGLUT1 and VGLUT2 and release glutamate following aggregation, implying a possible contributory role in the pathophysiology of stroke, migraine, and other excitotoxic disorders.
Collapse
Affiliation(s)
- L Tremolizzo
- Department of Neuroscience and Biomedical Technologies, University of Milano-Bicocca, Italy
| | | | | | | | | | | | | | | | | | | |
Collapse
|