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Acreman S, Ma J, Denwood G, Gao R, Tarasov A, Rorsman P, Zhang Q. The endoplasmic reticulum plays a key role in α-cell intracellular Ca 2+ dynamics and glucose-regulated glucagon secretion in mouse islets. iScience 2024; 27:109665. [PMID: 38646167 PMCID: PMC11033163 DOI: 10.1016/j.isci.2024.109665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 02/13/2024] [Accepted: 04/02/2024] [Indexed: 04/23/2024] Open
Abstract
Glucagon is secreted by pancreatic α-cells to counteract hypoglycaemia. How glucose regulates glucagon secretion remains unclear. Here, using mouse islets, we studied the role of transmembrane and endoplasmic reticulum (ER) Ca2+ on intrinsic α-cell glucagon secretion. Blocking isradipine-sensitive L-type voltage-gated Ca2+ (Cav) channels abolished α-cell electrical activity but had little impact on its cytosolic Ca2+ oscillations or low-glucose-stimulated glucagon secretion. In contrast, depleting ER Ca2+ with cyclopiazonic acid or blocking ER Ca2+-releasing ryanodine receptors abolished α-cell glucose sensitivity and low-glucose-stimulated glucagon secretion. ER Ca2+ mobilization in α-cells is regulated by intracellular ATP and likely to be coupled to Ca2+ influx through P/Q-type Cav channels. ω-Agatoxin IVA blocked α-cell ER Ca2+ release and cell exocytosis, but had no additive effect on glucagon secretion when combined with ryanodine. We conclude that glucose regulates glucagon secretion through the control of ER Ca2+ mobilization, a mechanism that can be independent of α-cell electrical activity.
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Affiliation(s)
- Samuel Acreman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Institute of Neuroscience and Physiology, Department of Physiology, Metabolic Research Unit, Sahlgrenska Academy, University of Gothenburg, Box 430, S-405 30 Gothenburg, Sweden
| | - Jinfang Ma
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Department of Endocrinology and Metabolism, West China Hospital, Sichuan University, Chengdu, China
| | - Geoffrey Denwood
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Rui Gao
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
| | - Andrei Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- Institute of Neuroscience and Physiology, Department of Physiology, Metabolic Research Unit, Sahlgrenska Academy, University of Gothenburg, Box 430, S-405 30 Gothenburg, Sweden
- Biomedical Sciences Research Institute, School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LE, UK
- CNC - Center for Neuroscience and Cell Biology, CIBB - Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal
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Arratia LM, Bermudes-Contreras JD, Juarez-Monroy JA, Romero-Macías EA, Luna-Rojas JC, López-Hidalgo M, Vega AV, Zamorano-Carrillo A. Experimental and computational evidence that Calpain-10 binds to the carboxy terminus of Na V1.2 and Na V1.6. Sci Rep 2024; 14:6761. [PMID: 38514708 PMCID: PMC10957924 DOI: 10.1038/s41598-024-57117-8] [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: 11/08/2023] [Accepted: 03/14/2024] [Indexed: 03/23/2024] Open
Abstract
Voltage-gated sodium channels (NaV) are pivotal proteins responsible for initiating and transmitting action potentials. Emerging evidence suggests that proteolytic cleavage of sodium channels by calpains is pivotal in diverse physiological scenarios, including ischemia, brain injury, and neuropathic pain associated with diabetes. Despite this significance, the precise mechanism by which calpains recognize sodium channels, especially given the multiple calpain isoforms expressed in neurons, remains elusive. In this work, we show the interaction of Calpain-10 with NaV's C-terminus through a yeast 2-hybrid assay screening of a mouse brain cDNA library and in vitro by GST-pulldown. Later, we also obtained a structural and dynamic hypothesis of this interaction by modeling, docking, and molecular dynamics simulation. These results indicate that Calpain-10 interacts differentially with the C-terminus of NaV1.2 and NaV1.6. Calpain-10 interacts with NaV1.2 through domains III and T in a stable manner. In contrast, its interaction with NaV1.6 involves domains II and III, which could promote proteolysis through the Cys-catalytic site and C2 motifs.
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Affiliation(s)
- Luis Manuel Arratia
- Carrera de Médico Cirujano, FES Iztacala, UNAM, Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Edo. Mex, Mexico
- Laboratorio de Biofísica Computacional, Doctorado en Biotecnología, SEPI-ENMH Instituto Politécnico Nacional, Av. Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Gustavo A. Madero, 07320, Mexico City, Mexico
| | - Juan David Bermudes-Contreras
- Laboratorio de Biofísica Computacional, Doctorado en Biotecnología, SEPI-ENMH Instituto Politécnico Nacional, Av. Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Gustavo A. Madero, 07320, Mexico City, Mexico
| | - Jorge Armando Juarez-Monroy
- Laboratorio de Biofísica Computacional, Doctorado en Biotecnología, SEPI-ENMH Instituto Politécnico Nacional, Av. Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Gustavo A. Madero, 07320, Mexico City, Mexico
| | - Erik Alan Romero-Macías
- Carrera de Médico Cirujano, FES Iztacala, UNAM, Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Edo. Mex, Mexico
- Doctorado en Ciencias Biomédicas, FES Iztacala, UNAM, Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla Edo, Mexico City, Mexico
| | - Julio Cesar Luna-Rojas
- Carrera de Médico Cirujano, FES Iztacala, UNAM, Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Edo. Mex, Mexico
- Maestría en Neurobiología, FES Iztacala, UNAM, Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla Edo, Mexico City, Mexico
| | - Marisol López-Hidalgo
- Laboratorio de Biofísica Computacional, Doctorado en Biotecnología, SEPI-ENMH Instituto Politécnico Nacional, Av. Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Gustavo A. Madero, 07320, Mexico City, Mexico
| | - Ana Victoria Vega
- Carrera de Médico Cirujano, FES Iztacala, UNAM, Av. de los Barrios 1, Los Reyes Iztacala, Tlalnepantla, Edo. Mex, Mexico.
| | - Absalom Zamorano-Carrillo
- Laboratorio de Biofísica Computacional, Doctorado en Biotecnología, SEPI-ENMH Instituto Politécnico Nacional, Av. Guillermo Massieu Helguera 239, Fracc. La Escalera, Ticomán, Gustavo A. Madero, 07320, Mexico City, Mexico.
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Li Q, Liu R, Lin Z, Zhang X, Silva IG, Pollock SD, Alvarez-Dominguez JR, Liu J. Cyborg islets: implanted flexible electronics reveal principles of human islet electrical maturation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.18.585551. [PMID: 38562695 PMCID: PMC10983936 DOI: 10.1101/2024.03.18.585551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Flexible electronics implanted during tissue formation enable chronic studies of tissue-wide electrophysiology. Here, we integrate tissue-like stretchable electronics during organogenesis of human stem cell-derived pancreatic islets, stably tracing single-cell extracellular spike bursting dynamics over months of functional maturation. Adapting spike sorting methods from neural studies reveals maturation-dependent electrical patterns of α and β-like (SC-α and β) cells, and their stimulus-coupled dynamics. We identified two major electrical states for both SC-α and β cells, distinguished by their glucose threshold for action potential firing. We find that improved hormone stimulation capacity during extended culture reflects increasing numbers of SC-α/β cells in low basal firing states, linked to energy and hormone metabolism gene upregulation. Continuous recording during further maturation by entrainment to daily feeding cycles reveals that circadian islet-level hormone secretion rhythms reflect sustained and coordinate oscillation of cell-level SC-α and β electrical activities. We find that this correlates with cell-cell communication and exocytic network induction, indicating a role for circadian rhythms in coordinating system-level stimulus-coupled responses. Cyborg islets thus reveal principles of electrical maturation that will be useful to build fully functional in vitro islets for research and therapeutic applications.
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Oropeza D, Herrera PL. Glucagon-producing α-cell transcriptional identity and reprogramming towards insulin production. Trends Cell Biol 2024; 34:180-197. [PMID: 37626005 DOI: 10.1016/j.tcb.2023.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/07/2023] [Accepted: 07/11/2023] [Indexed: 08/27/2023]
Abstract
β-Cell replacement by in situ reprogramming of non-β-cells is a promising diabetes therapy. Following the observation that near-total β-cell ablation in adult mice triggers the reprogramming of pancreatic α-, δ-, and γ-cells into insulin (INS)-producing cells, recent studies are delving deep into the mechanisms controlling adult α-cell identity. Systematic analyses of the α-cell transcriptome and epigenome have started to pinpoint features that could be crucial for maintaining α-cell identity. Using different transgenic and chemical approaches, significant advances have been made in reprogramming α-cells in vivo into INS-secreting cells in mice. The recent reprogramming of human α-cells in vitro is an important step forward that must now be complemented with a comprehensive molecular dissection of the mechanisms controlling α-cell identity.
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Affiliation(s)
- Daniel Oropeza
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Pedro Luis Herrera
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
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Gandasi NR, Gao R, Kothegala L, Pearce A, Santos C, Acreman S, Basco D, Benrick A, Chibalina MV, Clark A, Guida C, Harris M, Johnson PRV, Knudsen JG, Ma J, Miranda C, Shigeto M, Tarasov AI, Yeung HY, Thorens B, Asterholm IW, Zhang Q, Ramracheya R, Ladds G, Rorsman P. GLP-1 metabolite GLP-1(9-36) is a systemic inhibitor of mouse and human pancreatic islet glucagon secretion. Diabetologia 2024; 67:528-546. [PMID: 38127123 PMCID: PMC10844371 DOI: 10.1007/s00125-023-06060-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 10/18/2023] [Indexed: 12/23/2023]
Abstract
AIMS/HYPOTHESIS Diabetes mellitus is associated with impaired insulin secretion, often aggravated by oversecretion of glucagon. Therapeutic interventions should ideally correct both defects. Glucagon-like peptide 1 (GLP-1) has this capability but exactly how it exerts its glucagonostatic effect remains obscure. Following its release GLP-1 is rapidly degraded from GLP-1(7-36) to GLP-1(9-36). We hypothesised that the metabolite GLP-1(9-36) (previously believed to be biologically inactive) exerts a direct inhibitory effect on glucagon secretion and that this mechanism becomes impaired in diabetes. METHODS We used a combination of glucagon secretion measurements in mouse and human islets (including islets from donors with type 2 diabetes), total internal reflection fluorescence microscopy imaging of secretory granule dynamics, recordings of cytoplasmic Ca2+ and measurements of protein kinase A activity, immunocytochemistry, in vivo physiology and GTP-binding protein dissociation studies to explore how GLP-1 exerts its inhibitory effect on glucagon secretion and the role of the metabolite GLP-1(9-36). RESULTS GLP-1(7-36) inhibited glucagon secretion in isolated islets with an IC50 of 2.5 pmol/l. The effect was particularly strong at low glucose concentrations. The degradation product GLP-1(9-36) shared this capacity. GLP-1(9-36) retained its glucagonostatic effects after genetic/pharmacological inactivation of the GLP-1 receptor. GLP-1(9-36) also potently inhibited glucagon secretion evoked by β-adrenergic stimulation, amino acids and membrane depolarisation. In islet alpha cells, GLP-1(9-36) led to inhibition of Ca2+ entry via voltage-gated Ca2+ channels sensitive to ω-agatoxin, with consequential pertussis-toxin-sensitive depletion of the docked pool of secretory granules, effects that were prevented by the glucagon receptor antagonists REMD2.59 and L-168049. The capacity of GLP-1(9-36) to inhibit glucagon secretion and reduce the number of docked granules was lost in alpha cells from human donors with type 2 diabetes. In vivo, high exogenous concentrations of GLP-1(9-36) (>100 pmol/l) resulted in a small (30%) lowering of circulating glucagon during insulin-induced hypoglycaemia. This effect was abolished by REMD2.59, which promptly increased circulating glucagon by >225% (adjusted for the change in plasma glucose) without affecting pancreatic glucagon content. CONCLUSIONS/INTERPRETATION We conclude that the GLP-1 metabolite GLP-1(9-36) is a systemic inhibitor of glucagon secretion. We propose that the increase in circulating glucagon observed following genetic/pharmacological inactivation of glucagon signalling in mice and in people with type 2 diabetes reflects the removal of GLP-1(9-36)'s glucagonostatic action.
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Affiliation(s)
- Nikhil R Gandasi
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
- Cell Metabolism Lab (GA-08), Department of Developmental Biology and Genetics, Indian Institute of Science, Bangalore, India
| | - Rui Gao
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Lakshmi Kothegala
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
| | - Abigail Pearce
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Cristiano Santos
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
| | - Samuel Acreman
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Davide Basco
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Anna Benrick
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
| | - Margarita V Chibalina
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Anne Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Claudia Guida
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Matthew Harris
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Paul R V Johnson
- Nuffield Department of Surgical Sciences, John Radcliffe Hospital, Oxford, UK
- Biomedical Research Centre, Oxford National Institute for Health Research, Churchill Hospital, Oxford, UK
| | - Jakob G Knudsen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Jinfang Ma
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Caroline Miranda
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Makoto Shigeto
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Andrei I Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
- School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK
| | - Ho Yan Yeung
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Ingrid W Asterholm
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Reshma Ramracheya
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Graham Ladds
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Patrik Rorsman
- Metabolic Physiology Unit, Department of Physiology, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Gothenburg, Sweden.
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK.
- Biomedical Research Centre, Oxford National Institute for Health Research, Churchill Hospital, Oxford, UK.
- School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK.
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Lin H, Suzuki K, Smith N, Li X, Nalbach L, Fuentes S, Spigelman AF, Dai XQ, Bautista A, Ferdaoussi M, Aggarwal S, Pepper AR, Roma LP, Ampofo E, Li WH, MacDonald PE. A role and mechanism for redox sensing by SENP1 in β-cell responses to high fat feeding. Nat Commun 2024; 15:334. [PMID: 38184650 PMCID: PMC10771529 DOI: 10.1038/s41467-023-44589-x] [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: 02/23/2023] [Accepted: 12/21/2023] [Indexed: 01/08/2024] Open
Abstract
Pancreatic β-cells respond to metabolic stress by upregulating insulin secretion, however the underlying mechanisms remain unclear. Here we show, in β-cells from overweight humans without diabetes and mice fed a high-fat diet for 2 days, insulin exocytosis and secretion are enhanced without increased Ca2+ influx. RNA-seq of sorted β-cells suggests altered metabolic pathways early following high fat diet, where we find increased basal oxygen consumption and proton leak, but a more reduced cytosolic redox state. Increased β-cell exocytosis after 2-day high fat diet is dependent on this reduced intracellular redox state and requires the sentrin-specific SUMO-protease-1. Mice with either pancreas- or β-cell-specific deletion of this fail to up-regulate exocytosis and become rapidly glucose intolerant after 2-day high fat diet. Mechanistically, redox-sensing by the SUMO-protease requires a thiol group at C535 which together with Zn+-binding suppresses basal protease activity and unrestrained β-cell exocytosis, and increases enzyme sensitivity to regulation by redox signals.
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Affiliation(s)
- Haopeng Lin
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Guangzhou Laboratory, Guangzhou, 510005, Guangdong, China
| | - Kunimasa Suzuki
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Nancy Smith
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Xi Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX, 75390-9039, USA
| | - Lisa Nalbach
- Institute for Clinical & Experimental Surgery, Saarland University, Homburg/Saar, Germany
- Biophysics Department, Center for Human and Molecular Biology, Saarland University, Homburg/Saar, Germany
| | - Sonia Fuentes
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX, 75390-9039, USA
| | - Aliya F Spigelman
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Xiao-Qing Dai
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Austin Bautista
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Mourad Ferdaoussi
- Faculty Saint-Jean, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Saloni Aggarwal
- Department of Surgery, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Andrew R Pepper
- Department of Surgery, University of Alberta, Edmonton, AB, T6G 2E1, Canada
| | - Leticia P Roma
- Biophysics Department, Center for Human and Molecular Biology, Saarland University, Homburg/Saar, Germany
| | - Emmanuel Ampofo
- Institute for Clinical & Experimental Surgery, Saarland University, Homburg/Saar, Germany
| | - Wen-Hong Li
- Departments of Cell Biology and Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX, 75390-9039, USA
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, T6G 2E1, Canada.
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Chen D, Rehfeld JF, Watts AG, Rorsman P, Gundlach AL. History of key regulatory peptide systems and perspectives for future research. J Neuroendocrinol 2023; 35:e13251. [PMID: 37053148 DOI: 10.1111/jne.13251] [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: 01/09/2023] [Revised: 02/10/2023] [Accepted: 02/26/2023] [Indexed: 03/06/2023]
Abstract
Throughout the 20th Century, regulatory peptide discovery advanced from the identification of gut hormones to the extraction and characterization of hypothalamic hypophysiotropic factors, and to the isolation and cloning of multiple brain neuropeptides. These discoveries were followed by the discovery of G-protein-coupled and other membrane receptors for these peptides. Subsequently, the systems physiology associated with some of these multiple regulatory peptides and receptors has been comprehensively elucidated and has led to improved therapeutics and diagnostics and their approval by the US Food and Drug Administration. In light of this wealth of information and further potential, it is truly a time of renaissance for regulatory peptides. In this perspective, we review what we have learned from the pioneers in exemplified fields of gut peptides, such as cholecystokinin, enterochromaffin-like-cell peptides, and glucagon, from the trailblazing studies on the key stress hormone, corticotropin-releasing factor, as well as from more recently characterized relaxin-family peptides and receptors. The historical viewpoints are based on our understanding of these topics in light of the earliest phases of research and on subsequent studies and the evolution of knowledge, aiming to sharpen our vision of the current state-of-the-art and those studies that should be prioritized in the future.
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Affiliation(s)
- Duan Chen
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Jens F Rehfeld
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Alan G Watts
- Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
- Florey Department of Neuroscience and Mental Health and Department of Anatomy and Physiology, The University of Melbourne, Melbourne, VIC, Australia
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Brooks EP, Sussel L. Not the second fiddle: α cell development, identity, and function in health and diabetes. J Endocrinol 2023; 258:e220297. [PMID: 37171828 PMCID: PMC10524258 DOI: 10.1530/joe-22-0297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 05/12/2023] [Indexed: 05/13/2023]
Abstract
Historic and emerging studies provide evidence for the deterioration of pancreatic α cell function and identity in diabetes mellitus. Increased access to human tissue and the availability of more sophisticated molecular technologies have identified key insights into how α cell function and identity are preserved in healthy conditions and how they become dysfunctional in response to stress. These studies have revealed evidence of impaired glucagon secretion, shifts in α cell electrophysiology, changes in α cell mass, dysregulation of α cell transcription, and α-to-β cell conversion prior to and during diabetes. In this review, we outline the current state of research on α cell identity in health and disease. Evidence in model organisms and humans suggests that in addition to β cell dysfunction, diabetes is associated with a fundamental dysregulation of α cell identity. Importantly, epigenetic studies have revealed that α cells retain more poised and open chromatin at key cell-specific and diabetes-dysregulated genes, supporting the model that the inherent epigenetic plasticity of α cells makes them susceptible to the transcriptional changes that potentiate the loss of identity and function seen in diabetes. Thus, additional research into the maintenance of α cell identity and function is critical to fully understanding diabetes. Furthermore, these studies suggest α cells could represent an alternative source of new β cells for diabetes treatment.
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Affiliation(s)
- Elliott P Brooks
- Barbara Davis Center for Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, Colorado, USA
| | - Lori Sussel
- Barbara Davis Center for Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, Colorado, USA
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Turbitt J, Brennan L, Moffett RC, Flatt PR, Johnson PRV, Tarasov AI, McClenaghan NH. NKCC transport mediates the insulinotropic effects of taurine and other small neutral amino acids. Life Sci 2023; 316:121402. [PMID: 36669678 DOI: 10.1016/j.lfs.2023.121402] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 01/04/2023] [Accepted: 01/13/2023] [Indexed: 01/19/2023]
Abstract
AIMS Despite its high concentration in pancreatic islets of Langerhans and broad range of antihyperglycemic effects, the route facilitating the import of dietary taurine into pancreatic β-cell and mechanisms underlying its insulinotropic activity are unclear. We therefore studied the impact of taurine on beta-cell function, alongside that of other small neutral amino acids, L-alanine and L-proline. MAIN METHODS Pharmacological profiling of insulin secretion was conducted using clonal BRIN BD11 β-cells, the impact of taurine on the metabolic fate of glucose carbons was assessed using NMR and the findings were verified by real-time imaging of Ca2+ dynamics in the cytosol of primary mouse and human islet beta-cells. KEY FINDINGS In our hands, taurine, alanine and proline induced secretory responses that were dependent on the plasma membrane depolarisation, import of Ca2+, homeostasis of K+ and Na+ as well as on cell glycolytic and oxidative metabolism. Taurine shifted the balance between the oxidation and anaplerosis towards the latter, in BRIN BD11 beta-cells. Furthermore, the amino acid signalling was significantly attenuated by inhibition of Na+-K+-Cl- symporter (NKCC). SIGNIFICANCE These data suggest that taurine, like L-alanine and L-proline, acutely induces glucose-dependent insulin-secretory responses by modulating electrogenic Na+ transport, with potential role of intracellular K+ and Cl- in the signal transduction. The acute action delineated would be consistent with antidiabetic potential of dietary taurine supplementation.
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Affiliation(s)
- Julie Turbitt
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK
| | - Lorraine Brennan
- UCD Institute of Food and Health, UCD School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
| | - R Charlotte Moffett
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK.
| | - Peter R Flatt
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK.
| | - Paul R V Johnson
- Nuffeld Department of Surgical Sciences, Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Headington, OX3 7LE Oxford, UK; Oxford Biomedical Research Centre (OxBRC), UK.
| | - Andrei I Tarasov
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK; Nuffeld Department of Surgical Sciences, Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Headington, OX3 7LE Oxford, UK; Oxford Biomedical Research Centre (OxBRC), UK.
| | - Neville H McClenaghan
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK; Department of Life Sciences, Atlantic Technological University, Ash Lane, Sligo, F91 YW50, Ireland.
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10
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Dickerson MT, Dadi PK, Zaborska KE, Nakhe AY, Schaub CM, Dobson JR, Wright NM, Lynch JC, Scott CF, Robinson LD, Jacobson DA. G i/o protein-coupled receptor inhibition of beta-cell electrical excitability and insulin secretion depends on Na +/K + ATPase activation. Nat Commun 2022; 13:6461. [PMID: 36309517 PMCID: PMC9617941 DOI: 10.1038/s41467-022-34166-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 10/17/2022] [Indexed: 12/25/2022] Open
Abstract
Gi/o-coupled somatostatin or α2-adrenergic receptor activation stimulated β-cell NKA activity, resulting in islet Ca2+ fluctuations. Furthermore, intra-islet paracrine activation of β-cell Gi/o-GPCRs and NKAs by δ-cell somatostatin secretion slowed Ca2+ oscillations, which decreased insulin secretion. β-cell membrane potential hyperpolarization resulting from Gi/o-GPCR activation was dependent on NKA phosphorylation by Src tyrosine kinases. Whereas, β-cell NKA function was inhibited by cAMP-dependent PKA activity. These data reveal that NKA-mediated β-cell membrane potential hyperpolarization is the primary and conserved mechanism for Gi/o-GPCR control of electrical excitability, Ca2+ handling, and insulin secretion.
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Affiliation(s)
- Matthew T Dickerson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Prasanna K Dadi
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Karolina E Zaborska
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Arya Y Nakhe
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Charles M Schaub
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Jordyn R Dobson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Nicole M Wright
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Joshua C Lynch
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Claire F Scott
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - Logan D Robinson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA
| | - David A Jacobson
- Molecular Physiology and Biophysics Department, Vanderbilt University, 7425B MRB IV, 2213 Garland Ave., Nashville, TN, USA.
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11
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Ježek P, Holendová B, Jabůrek M, Dlasková A, Plecitá-Hlavatá L. Contribution of Mitochondria to Insulin Secretion by Various Secretagogues. Antioxid Redox Signal 2022; 36:920-952. [PMID: 34180254 PMCID: PMC9125579 DOI: 10.1089/ars.2021.0113] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Significance: Mitochondria determine glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells by elevating ATP synthesis. As the metabolic and redox hub, mitochondria provide numerous links to the plasma membrane channels, insulin granule vesicles (IGVs), cell redox, NADH, NADPH, and Ca2+ homeostasis, all affecting insulin secretion. Recent Advances: Mitochondrial redox signaling was implicated in several modes of insulin secretion (branched-chain ketoacid [BCKA]-, fatty acid [FA]-stimulated). Mitochondrial Ca2+ influx was found to enhance GSIS, reflecting cytosolic Ca2+ oscillations induced by action potential spikes (intermittent opening of voltage-dependent Ca2+ and K+ channels) or the superimposed Ca2+ release from the endoplasmic reticulum (ER). The ATPase inhibitory factor 1 (IF1) was reported to tune the glucose sensitivity range for GSIS. Mitochondrial protein kinase A was implicated in preventing the IF1-mediated inhibition of the ATP synthase. Critical Issues: It is unknown how the redox signal spreads up to the plasma membrane and what its targets are, what the differences in metabolic, redox, NADH/NADPH, and Ca2+ signaling, and homeostasis are between the first and second GSIS phase, and whether mitochondria can replace ER in the amplification of IGV exocytosis. Future Directions: Metabolomics studies performed to distinguish between the mitochondrial matrix and cytosolic metabolites will elucidate further details. Identifying the targets of cell signaling into mitochondria and of mitochondrial retrograde metabolic and redox signals to the cell will uncover further molecular mechanisms for insulin secretion stimulated by glucose, BCKAs, and FAs, and the amplification of secretion by glucagon-like peptide (GLP-1) and metabotropic receptors. They will identify the distinction between the hub β-cells and their followers in intact and diabetic states. Antioxid. Redox Signal. 36, 920-952.
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Affiliation(s)
- Petr Ježek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Blanka Holendová
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Jabůrek
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Andrea Dlasková
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Lydie Plecitá-Hlavatá
- Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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12
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Molecular dissection of cellular response of pancreatic islet cells to Bisphenol-A (BPA): a comprehensive review. Biochem Pharmacol 2022; 201:115068. [DOI: 10.1016/j.bcp.2022.115068] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/11/2022] [Accepted: 04/25/2022] [Indexed: 12/15/2022]
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13
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Alles SRA, Smith PA. Peripheral Voltage-Gated Cation Channels in Neuropathic Pain and Their Potential as Therapeutic Targets. FRONTIERS IN PAIN RESEARCH 2022; 2:750583. [PMID: 35295464 PMCID: PMC8915663 DOI: 10.3389/fpain.2021.750583] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 11/10/2021] [Indexed: 11/25/2022] Open
Abstract
The persistence of increased excitability and spontaneous activity in injured peripheral neurons is imperative for the development and persistence of many forms of neuropathic pain. This aberrant activity involves increased activity and/or expression of voltage-gated Na+ and Ca2+ channels and hyperpolarization activated cyclic nucleotide gated (HCN) channels as well as decreased function of K+ channels. Because they display limited central side effects, peripherally restricted Na+ and Ca2+ channel blockers and K+ channel activators offer potential therapeutic approaches to pain management. This review outlines the current status and future therapeutic promise of peripherally acting channel modulators. Selective blockers of Nav1.3, Nav1.7, Nav1.8, Cav3.2, and HCN2 and activators of Kv7.2 abrogate signs of neuropathic pain in animal models. Unfortunately, their performance in the clinic has been disappointing; some substances fail to meet therapeutic end points whereas others produce dose-limiting side effects. Despite this, peripheral voltage-gated cation channels retain their promise as therapeutic targets. The way forward may include (i) further structural refinement of K+ channel activators such as retigabine and ASP0819 to improve selectivity and limit toxicity; use or modification of Na+ channel blockers such as vixotrigine, PF-05089771, A803467, PF-01247324, VX-150 or arachnid toxins such as Tap1a; the use of Ca2+ channel blockers such as TTA-P2, TTA-A2, Z 944, ACT709478, and CNCB-2; (ii) improving methods for assessing “pain” as opposed to nociception in rodent models; (iii) recognizing sex differences in pain etiology; (iv) tailoring of therapeutic approaches to meet the symptoms and etiology of pain in individual patients via quantitative sensory testing and other personalized medicine approaches; (v) targeting genetic and biochemical mechanisms controlling channel expression using anti-NGF antibodies such as tanezumab or re-purposed drugs such as vorinostat, a histone methyltransferase inhibitor used in the management of T-cell lymphoma, or cercosporamide a MNK 1/2 inhibitor used in treatment of rheumatoid arthritis; (vi) combination therapy using drugs that are selective for different channel types or regulatory processes; (vii) directing preclinical validation work toward the use of human or human-derived tissue samples; and (viii) application of molecular biological approaches such as clustered regularly interspaced short palindromic repeats (CRISPR) technology.
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Affiliation(s)
- Sascha R A Alles
- Department of Anesthesiology and Critical Care Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Peter A Smith
- Department of Pharmacology, Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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14
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Acetyl-CoA-carboxylase 1 (ACC1) plays a critical role in glucagon secretion. Commun Biol 2022; 5:238. [PMID: 35304577 PMCID: PMC8933412 DOI: 10.1038/s42003-022-03170-w] [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: 09/03/2020] [Accepted: 02/08/2022] [Indexed: 11/09/2022] Open
Abstract
Dysregulated glucagon secretion from pancreatic alpha-cells is a key feature of type-1 and type-2 diabetes (T1D and T2D), yet our mechanistic understanding of alpha-cell function is underdeveloped relative to insulin-secreting beta-cells. Here we show that the enzyme acetyl-CoA-carboxylase 1 (ACC1), which couples glucose metabolism to lipogenesis, plays a key role in the regulation of glucagon secretion. Pharmacological inhibition of ACC1 in mouse islets or αTC9 cells impaired glucagon secretion at low glucose (1 mmol/l). Likewise, deletion of ACC1 in alpha-cells in mice reduced glucagon secretion at low glucose in isolated islets, and in response to fasting or insulin-induced hypoglycaemia in vivo. Electrophysiological recordings identified impaired KATP channel activity and P/Q- and L-type calcium currents in alpha-cells lacking ACC1, explaining the loss of glucose-sensing. ACC-dependent alterations in S-acylation of the KATP channel subunit, Kir6.2, were identified by acyl-biotin exchange assays. Histological analysis identified that loss of ACC1 caused a reduction in alpha-cell area of the pancreas, glucagon content and individual alpha-cell size, further impairing secretory capacity. Loss of ACC1 also reduced the release of glucagon-like peptide 1 (GLP-1) in primary gastrointestinal crypts. Together, these data reveal a role for the ACC1-coupled pathway in proglucagon-expressing nutrient-responsive endocrine cell function and systemic glucose homeostasis.
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15
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Lubberding AF, Juhl CR, Skovhøj EZ, Kanters JK, Mandrup‐Poulsen T, Torekov SS. Celebrities in the heart, strangers in the pancreatic beta cell: Voltage-gated potassium channels K v 7.1 and K v 11.1 bridge long QT syndrome with hyperinsulinaemia as well as type 2 diabetes. Acta Physiol (Oxf) 2022; 234:e13781. [PMID: 34990074 PMCID: PMC9286829 DOI: 10.1111/apha.13781] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 12/20/2021] [Accepted: 01/02/2022] [Indexed: 12/13/2022]
Abstract
Voltage‐gated potassium (Kv) channels play an important role in the repolarization of a variety of excitable tissues, including in the cardiomyocyte and the pancreatic beta cell. Recently, individuals carrying loss‐of‐function (LoF) mutations in KCNQ1, encoding Kv7.1, and KCNH2 (hERG), encoding Kv11.1, were found to exhibit post‐prandial hyperinsulinaemia and episodes of hypoglycaemia. These LoF mutations also cause the cardiac disorder long QT syndrome (LQTS), which can be aggravated by hypoglycaemia. Interestingly, patients with LQTS also have a higher burden of diabetes compared to the background population, an apparent paradox in relation to the hyperinsulinaemic phenotype, and KCNQ1 has been identified as a type 2 diabetes risk gene. This review article summarizes the involvement of delayed rectifier K+ channels in pancreatic beta cell function, with emphasis on Kv7.1 and Kv11.1, using the cardiomyocyte for context. The functional and clinical consequences of LoF mutations and polymorphisms in these channels on blood glucose homeostasis are explored using evidence from pre‐clinical, clinical and genome‐wide association studies, thereby evaluating the link between LQTS, hyperinsulinaemia and type 2 diabetes.
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Affiliation(s)
- Anniek F. Lubberding
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Christian R. Juhl
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Emil Z. Skovhøj
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Jørgen K. Kanters
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Thomas Mandrup‐Poulsen
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
| | - Signe S. Torekov
- Department of Biomedical Sciences Faculty of Health and Medical Sciences University of Copenhagen Copenhagen Denmark
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16
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Dai XQ, Camunas-Soler J, Briant LJB, Dos Santos T, Spigelman AF, Walker EM, Arrojo E Drigo R, Bautista A, Jones RC, Avrahami D, Lyon J, Nie A, Smith N, Zhang Y, Johnson J, Manning Fox JE, Michelakis ED, Light PE, Kaestner KH, Kim SK, Rorsman P, Stein RW, Quake SR, MacDonald PE. Heterogenous impairment of α cell function in type 2 diabetes is linked to cell maturation state. Cell Metab 2022; 34:256-268.e5. [PMID: 35108513 PMCID: PMC8852281 DOI: 10.1016/j.cmet.2021.12.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 10/08/2021] [Accepted: 12/22/2021] [Indexed: 02/03/2023]
Abstract
In diabetes, glucagon secretion from pancreatic α cells is dysregulated. The underlying mechanisms, and whether dysfunction occurs uniformly among cells, remain unclear. We examined α cells from human donors and mice using electrophysiological, transcriptomic, and computational approaches. Rising glucose suppresses α cell exocytosis by reducing P/Q-type Ca2+ channel activity, and this is disrupted in type 2 diabetes (T2D). Upon high-fat feeding of mice, α cells shift toward a "β cell-like" electrophysiological profile in concert with indications of impaired identity. In human α cells we identified links between cell membrane properties and cell surface signaling receptors, mitochondrial respiratory chain complex assembly, and cell maturation. Cell-type classification using machine learning of electrophysiology data demonstrated a heterogenous loss of "electrophysiologic identity" in α cells from donors with type 2 diabetes. Indeed, a subset of α cells with impaired exocytosis is defined by an enrichment in progenitor and lineage markers and upregulation of an immature transcriptomic phenotype, suggesting important links between α cell maturation state and dysfunction.
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Affiliation(s)
- Xiao-Qing Dai
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Joan Camunas-Soler
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94518, USA
| | - Linford J B Briant
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, Churchill Hospital, Oxford OX3 7LE, UK
| | - Theodore Dos Santos
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Aliya F Spigelman
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Emily M Walker
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48105, USA
| | - Rafael Arrojo E Drigo
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Austin Bautista
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Robert C Jones
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Dana Avrahami
- Endocrinology and Metabolism Department, Hadassah-Hebrew University Medical Centre, Jerusalem, Israel
| | - James Lyon
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Aifang Nie
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Nancy Smith
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Yongneng Zhang
- Department of Medicine, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Janyne Johnson
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Jocelyn E Manning Fox
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | | | - Peter E Light
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada
| | - Klaus H Kaestner
- Department of Genetics and Institute for Diabetes, Obesity and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Seung K Kim
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Stanford Diabetes Research Center, Stanford University, Stanford, CA 94305, USA
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, Churchill Hospital, Oxford OX3 7LE, UK
| | - Roland W Stein
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Stephen R Quake
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94518, USA; Department of Applied Physics, Stanford University, Stanford, CA 94305, USA
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G2R3, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G2R3, Canada.
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17
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Göbl C, Morettini M, Salvatori B, Alsalim W, Kahleova H, Ahrén B, Tura A. Temporal Patterns of Glucagon and Its Relationships with Glucose and Insulin following Ingestion of Different Classes of Macronutrients. Nutrients 2022; 14:nu14020376. [PMID: 35057557 PMCID: PMC8780023 DOI: 10.3390/nu14020376] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Revised: 01/11/2022] [Accepted: 01/12/2022] [Indexed: 01/27/2023] Open
Abstract
Background: glucagon secretion and inhibition should be mainly determined by glucose and insulin levels, but the relative relevance of each factor is not clarified, especially following ingestion of different macronutrients. We aimed to investigate the associations between plasma glucagon, glucose, and insulin after ingestion of single macronutrients or mixed-meal. Methods: thirty-six participants underwent four metabolic tests, based on administration of glucose, protein, fat, or mixed-meal. Glucagon, glucose, insulin, and C-peptide were measured at fasting and for 300 min following food ingestion. We analyzed relationships between time samples of glucagon, glucose, and insulin in each individual, as well as between suprabasal area-under-the-curve of the same variables (ΔAUCGLUCA, ΔAUCGLU, ΔAUCINS) over the whole participants’ cohort. Results: in individuals, time samples of glucagon and glucose were related in only 26 cases (18 direct, 8 inverse relationships), whereas relationship with insulin was more frequent (60 and 5, p < 0.0001). The frequency of significant relationships was different among tests, especially for direct relationships (p ≤ 0.006). In the whole cohort, ΔAUCGLUCA was weakly related to ΔAUCGLU (p ≤ 0.02), but not to ΔAUCINS, though basal insulin secretion emerged as possible covariate. Conclusions: glucose and insulin are not general and exclusive determinants of glucagon secretion/inhibition after mixed-meal or macronutrients ingestion.
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Affiliation(s)
- Christian Göbl
- Department of Obstetrics and Gynaecology, Medical University of Vienna, 1090 Vienna, Austria;
| | - Micaela Morettini
- Department of Information Engineering, Università Politecnica delle Marche, 60131 Ancona, Italy;
| | | | - Wathik Alsalim
- Department of Clinical Sciences, Faculty of Medicine, Lund University, 22184 Lund, Sweden; (W.A.); (B.A.)
| | - Hana Kahleova
- Physicians Committee for Responsible Medicine, Washington, DC 20016, USA;
| | - Bo Ahrén
- Department of Clinical Sciences, Faculty of Medicine, Lund University, 22184 Lund, Sweden; (W.A.); (B.A.)
| | - Andrea Tura
- CNR Institute of Neuroscience, 35127 Padova, Italy;
- Correspondence: ; Tel.: +39-049-829-5786
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18
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Pharmacological Dissection of the Crosstalk between Na V and Ca V Channels in GH3b6 Cells. Int J Mol Sci 2022; 23:ijms23020827. [PMID: 35055012 PMCID: PMC8775721 DOI: 10.3390/ijms23020827] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 01/07/2022] [Accepted: 01/09/2022] [Indexed: 02/01/2023] Open
Abstract
Thanks to the crosstalk between Na+ and Ca2+ channels, Na+ and Ca2+ homeostasis interplay in so-called excitable cells enables the generation of action potential in response to electrical stimulation. Here, we investigated the impact of persistent activation of voltage-gated Na+ (NaV) channels by neurotoxins, such as veratridine (VTD), on intracellular Ca2+ concentration ([Ca2+]i) in a model of excitable cells, the rat pituitary GH3b6 cells, in order to identify the molecular actors involved in Na+-Ca2+ homeostasis crosstalk. By combining RT-qPCR, immunoblotting, immunocytochemistry, and patch-clamp techniques, we showed that GH3b6 cells predominantly express the NaV1.3 channel subtype, which likely endorses their voltage-activated Na+ currents. Notably, these Na+ currents were blocked by ICA-121431 and activated by the β-scorpion toxin Tf2, two selective NaV1.3 channel ligands. Using Fura-2, we showed that VTD induced a [Ca2+]i increase. This effect was suppressed by the selective NaV channel blocker tetrodotoxin, as well by the selective L-type CaV channel (LTCC) blocker nifedipine. We also evidenced that crobenetine, a NaV channel blocker, abolished VTD-induced [Ca2+]i elevation, while it had no effects on LTCC. Altogether, our findings highlight a crosstalk between NaV and LTCC in GH3b6 cells, providing a new insight into the mode of action of neurotoxins.
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19
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Miranda C, Begum M, Vergari E, Briant LJB. Gap junction coupling and islet delta-cell function in health and disease. Peptides 2022; 147:170704. [PMID: 34826505 DOI: 10.1016/j.peptides.2021.170704] [Citation(s) in RCA: 7] [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] [Received: 08/31/2021] [Revised: 11/12/2021] [Accepted: 11/19/2021] [Indexed: 12/12/2022]
Abstract
The pancreatic islets contain beta-cells and alpha-cells, which are responsible for secreting two principal gluco-regulatory hormones; insulin and glucagon, respectively. However, they also contain delta-cells, a relatively sparse cell type that secretes somatostatin (SST). These cells have a complex morphology allowing them to establish an extensive communication network throughout the islet, despite their scarcity. Delta-cells are electrically excitable cells, and SST secretion is released in a glucose- and KATP-dependent manner. SST hyperpolarises the alpha-cell membrane and suppresses exocytosis. In this way, islet SST potently inhibits glucagon release. Recent studies investigating the activity of delta-cells have revealed they are electrically coupled to beta-cells via gap junctions, suggesting the delta-cell is more than just a paracrine inhibitor. In this Review, we summarize delta-cell morphology, function, and the role of SST signalling for regulating islet hormonal output. A distinguishing feature of this Review is that we attempt to use the discovery of this gap junction pathway, together with what is already known about delta-cells, to reframe the role of these cells in both health and disease. In particular, we argue that the discovery of gap junction communication between delta-cells and beta-cells provides new insights into the contribution of delta-cells to the islet hormonal defects observed in both type 1 and type 2 diabetes. This reappraisal of the delta-cell is important as it may offer novel insights into how the physiology of this cell can be utilised to restore islet function in diabetes.
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Affiliation(s)
- Caroline Miranda
- Institute of Neuroscience and Physiology, Metabolic Research Unit, University of Göteborg, 405 30, Göteborg, Sweden
| | - Manisha Begum
- Institute of Neuroscience and Physiology, Metabolic Research Unit, University of Göteborg, 405 30, Göteborg, Sweden; University of Skӧvde, Department of Infection Biology, Högskolevägen 1, 541 28, Skövde, Sweden
| | - Elisa Vergari
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, OX4 7LE, Oxford, UK
| | - Linford J B Briant
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, OX4 7LE, Oxford, UK; Department of Computer Science, University of Oxford, OX1 3QD, Oxford, UK.
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20
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Mourad NI, Xhema D, Gianello P. In vitro assessment of pancreatic hormone secretion from isolated porcine islets. Front Endocrinol (Lausanne) 2022; 13:935060. [PMID: 36034433 PMCID: PMC9402940 DOI: 10.3389/fendo.2022.935060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 07/25/2022] [Indexed: 11/26/2022] Open
Abstract
The potential use of porcine islets for transplantation in humans has triggered interest in understanding porcine islet physiology. However, the number of studies dedicated to this topic has remained limited, as most islet physiologists prefer to use the less time-consuming rodent model or the more clinically relevant human islet. An often-overlooked aspect of pig islet physiology is its alpha cell activity and regulation of its glucagon secretion. In vitro islet perifusion is a reliable method to study the dynamics of hormone secretion in response to different stimuli. We thus used this method to quantify and study glucagon secretion from pig islets. Pancreatic islets were isolated from 20 neonatal (14 to 21-day old) and 5 adult (>2 years) pigs and cultured in appropriate media. Islet perifusion experiments were performed 8 to 10 days post-isolation for neonatal islets and 1 to 2 days post-isolation for adult islets. Insulin and glucagon were quantified in perifusion effluent fractions as well as in islet extracts by RIA. Increasing glucose concentration from 1 mM to 15 mM markedly inhibited glucagon secretion independently of animal age. Interestingly, the effect of high glucose was more drastic on glucagon secretion compared to its effect on insulin secretion. In vivo, glucose injection during IVGTT initiated a quick (2-10 minutes) 3-fold decrease of plasmatic glucagon whereas the increase of plasmatic insulin took 20 minutes to become significant. These results suggest that regulation of glucagon secretion significantly contributes to glucose homeostasis in pigs and might compensate for the mild changes in insulin secretion in response to changes in glucose concentration.
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Lin H, Smith N, Spigelman AF, Suzuki K, Ferdaoussi M, Alghamdi TA, Lewandowski SL, Jin Y, Bautista A, Wang YW, Manning Fox JE, Merrins MJ, Buteau J, MacDonald PE. β-Cell Knockout of SENP1 Reduces Responses to Incretins and Worsens Oral Glucose Tolerance in High-Fat Diet-Fed Mice. Diabetes 2021; 70:2626-2638. [PMID: 34462260 PMCID: PMC8564408 DOI: 10.2337/db20-1235] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 08/19/2021] [Indexed: 01/17/2023]
Abstract
SUMOylation reduces oxidative stress and preserves islet mass at the expense of robust insulin secretion. To investigate a role for the deSUMOylating enzyme sentrin-specific protease 1 (SENP1) following metabolic stress, we put pancreas/gut-specific SENP1 knockout (pSENP1-KO) mice on a high-fat diet (HFD). Male pSENP1-KO mice were more glucose intolerant following HFD than littermate controls but only in response to oral glucose. A similar phenotype was observed in females. Plasma glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) responses were identical in pSENP1-KO and wild-type littermates, including the HFD-induced upregulation of GIP responses. Islet mass was not different, but insulin secretion and β-cell exocytotic responses to the GLP-1 receptor agonist exendin-4 (Ex4) and GIP were impaired in islets lacking SENP1. Glucagon secretion from pSENP1-KO islets was also reduced, so we generated β-cell-specific SENP1 KO mice. These phenocopied the pSENP1-KO mice with selective impairment in oral glucose tolerance following HFD, preserved islet mass expansion, and impaired β-cell exocytosis and insulin secretion to Ex4 and GIP without changes in cAMP or Ca2+ levels. Thus, β-cell SENP1 limits oral glucose intolerance following HFD by ensuring robust insulin secretion at a point downstream of incretin signaling.
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Affiliation(s)
- Haopeng Lin
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Nancy Smith
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Aliya F Spigelman
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Kunimasa Suzuki
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Mourad Ferdaoussi
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Tamadher A Alghamdi
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Sophie L Lewandowski
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison
| | - Yaxing Jin
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
| | - Austin Bautista
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Ying Wayne Wang
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Jocelyn E Manning Fox
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Matthew J Merrins
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Wisconsin-Madison
| | - Jean Buteau
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, Alberta, Canada
- Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
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Thompson B, Satin LS. Beta-Cell Ion Channels and Their Role in Regulating Insulin Secretion. Compr Physiol 2021; 11:1-21. [PMID: 34636409 PMCID: PMC8935893 DOI: 10.1002/cphy.c210004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Beta cells of the pancreatic islet express many different types of ion channels. These channels reside in the β-cell plasma membrane as well as subcellular organelles and their coordinated activity and sensitivity to metabolism regulate glucose-dependent insulin secretion. Here, we review the molecular nature, expression patterns, and functional roles of many β-cell channels, with an eye toward explaining the ionic basis of glucose-induced insulin secretion. Our primary focus is on KATP and voltage-gated Ca2+ channels as these primarily regulate insulin secretion; other channels in our view primarily help to sculpt the electrical patterns generated by activated β-cells or indirectly regulate metabolism. Lastly, we discuss why understanding the physiological roles played by ion channels is important for understanding the secretory defects that occur in type 2 diabetes. © 2021 American Physiological Society. Compr Physiol 11:1-21, 2021.
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Langlhofer G, Kogel A, Schaefer M. Glucose-induced [Ca2+]i oscillations in β cells are composed of trains of spikes within a subplasmalemmal microdomain. Cell Calcium 2021; 99:102469. [PMID: 34509871 DOI: 10.1016/j.ceca.2021.102469] [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] [Received: 02/15/2021] [Revised: 08/31/2021] [Accepted: 09/01/2021] [Indexed: 10/20/2022]
Abstract
Electrical activity and oscillations of cytosolic Ca2+ concentrations ([Ca2+]i) that trigger insulin release in response to glucose are key functions of pancreatic β cells. Although oscillatory Ca2+ signals have been intensively studied in β cells, their lower frequency did not match that of electrical activity. In addition, the measured peak [Ca2+]i did not reach levels that are typically required by synaptotagmins to elicit the release of insulin-containing vesicles in live-cell experiments. We therefore sought to resolve the Ca2+ dynamics in the subplasmalemmal microdomain that is critical for triggering fast exocytosis. Applying total internal reflection fluorescence (TIRF) microscopy in insulin-producing INS-1E and primary mouse β cells, we resolved extraordinary fast trains of Ca2+ spiking (frequency > 3 s-1) in response to glucose exposure. Using a low-affinity [Ca2+]i indicator dye, we provide experimental evidence that Ca2+ spikes reach low micromolar apparent concentrations in the vicinity of the plasma membrane. Analysis of Ca2+ spikes evoked by repeated depolarization for 10 ms closely matched the Ca2+ dynamics observed upon glucose application. To our knowledge, this is the first study that experimentally demonstrates Ca2+ spikes in β cells with velocities that resemble those of bursting or continuously appearing trains of action potentials (APs) in non-patched cells.
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Affiliation(s)
- Georg Langlhofer
- Rudolf-Boehm-Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| | - Alexander Kogel
- Rudolf-Boehm-Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany
| | - Michael Schaefer
- Rudolf-Boehm-Institute for Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany.
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Acreman S, Zhang Q. Regulation of α-cell glucagon secretion: The role of second messengers. Chronic Dis Transl Med 2021; 8:7-18. [PMID: 35620162 PMCID: PMC9128566 DOI: 10.1016/j.cdtm.2021.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 06/15/2021] [Indexed: 11/30/2022] Open
Abstract
Glucagon is a potent glucose‐elevating hormone that is secreted by pancreatic α‐cells. While well‐controlled glucagon secretion plays an important role in maintaining systemic glucose homeostasis and preventing hypoglycaemia, it is increasingly apparent that defects in the regulation of glucagon secretion contribute to impaired counter‐regulation and hyperglycaemia in diabetes. It has therefore been proposed that pharmacological interventions targeting glucagon secretion/signalling can have great potential in improving glycaemic control of patients with diabetes. However, despite decades of research, a consensus on the precise mechanisms of glucose regulation of glucagon secretion is yet to be reached. Second messengers are a group of small intracellular molecules that relay extracellular signals to the intracellular signalling cascade, modulating cellular functions. There is a growing body of evidence that second messengers, such as cAMP and Ca2+, play critical roles in α‐cell glucose‐sensing and glucagon secretion. In this review, we discuss the impact of second messengers on α‐cell electrical activity, intracellular Ca2+ dynamics and cell exocytosis. We highlight the possibility that the interaction between different second messengers may play a key role in the glucose‐regulation of glucagon secretion.
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25
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Lingle CJ. Slow recovery from fast inactivation of Nav1.3 channels: a common gating mechanism shared in sweet- and sour-sensing cells. Pflugers Arch 2021; 473:855-857. [PMID: 33970334 DOI: 10.1007/s00424-021-02575-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 04/23/2021] [Accepted: 05/03/2021] [Indexed: 11/24/2022]
Affiliation(s)
- Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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26
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Hong F, Yang Y, Chen B, Li P, Wang G, Jiang Y. Protein kinase C-θ knockout decreases serum IL-10 levels and inhibits insulin secretion from islet β cells. Islets 2021; 13:24-31. [PMID: 33719858 PMCID: PMC8018435 DOI: 10.1080/19382014.2021.1890963] [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] [Indexed: 10/21/2022] Open
Abstract
Various subtypes of protein kinase C (PKC) are expressed in islet β cells and regulate β cell proliferation and survival. PKC-θ is distributed in the immune system and promotes the secretion of IL-10, which manifests a critical role in the onset of diabetes, by the immune cells. However, the role of PKC-θ in islets has not been concerned. In the present study, we investigated the role of PKC-θ in the protection of islet β cells and insulin secretion. Fasting glucose and insulin measurement, glucose tolerant test, immunofluorescence, and ELISA were conducted to study the influence of PKC-θ knockout on islet β cell survival and function, and explore the mechanism underlying this regulation. PKC-θ knockout mice at 2 weeks manifested normal serum insulin levels, glucose tolerance, and β cell mass. Knockout mice at 8 weeks show decreased β cell mass, but manifested normal insulin levels and glucose tolerance. Knockout mice at 16 weeks manifested impaired glucose tolerance, β cell mass, and decreased glucose stimulated insulin secretion. Furthermore, knockout mice manifested decreased serum IL-10 level compared with normal mice since 2 weeks. IL-10 injection into knockout mice improved glucose tolerance, serum insulin level, and reduced β cell mass, and IL-10 administration into cultured pancreatic tissue increased glucose stimulated insulin secretion. PKC-θ knockout decreases the secretion of IL-10, reduces β cell mass and insulin secretion in pancreatic islets. The present study illuminates the critical role of PKC-θ in protecting the survival and function of islet β cells.
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Affiliation(s)
- Feng Hong
- School of Preclinical Medicine, Wannan Medical College, Wuhu, China
- Hong Feng School of Preclinical Medicine, Wannan Medical College; No.22 Wenchang West Road, Wuhu 241002, China
| | - Yang Yang
- School of Preclinical Medicine, Wannan Medical College, Wuhu, China
| | - Baiyi Chen
- School of Preclinical Medicine, Wannan Medical College, Wuhu, China
| | - Peng Li
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Guoguang Wang
- School of Preclinical Medicine, Wannan Medical College, Wuhu, China
- CONTACT Yuxin Jiang School of Medicine, Jiaxing University, No.118 Jiahang Road, Jiaxing 341001, China
| | - Yuxin Jiang
- College of Medicine, Jiaxing University, Jiaxing, China
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27
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Martinez-Espinosa PL, Yang C, Xia XM, Lingle CJ. Nav1.3 and FGF14 are primary determinants of the TTX-sensitive sodium current in mouse adrenal chromaffin cells. J Gen Physiol 2021; 153:211839. [PMID: 33651884 PMCID: PMC8020717 DOI: 10.1085/jgp.202012785] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 01/07/2021] [Accepted: 01/19/2021] [Indexed: 12/29/2022] Open
Abstract
Adrenal chromaffin cells (CCs) in rodents express rapidly inactivating, tetrodotoxin (TTX)-sensitive sodium channels. The resulting current has generally been attributed to Nav1.7, although a possible role for Nav1.3 has also been suggested. Nav channels in rat CCs rapidly inactivate via two independent pathways which differ in their time course of recovery. One subpopulation recovers with time constants similar to traditional fast inactivation and the other ∼10-fold slower, but both pathways can act within a single homogenous population of channels. Here, we use Nav1.3 KO mice to probe the properties and molecular components of Nav current in CCs. We find that the absence of Nav1.3 abolishes all Nav current in about half of CCs examined, while a small, fast inactivating Nav current is still observed in the rest. To probe possible molecular components underlying slow recovery from inactivation, we used mice null for fibroblast growth factor homology factor 14 (FGF14). In these cells, the slow component of recovery from fast inactivation is completely absent in most CCs, with no change in the time constant of fast recovery. The use dependence of Nav current reduction during trains of stimuli in WT cells is completely abolished in FGF14 KO mice, directly demonstrating a role for slow recovery from inactivation in determining Nav current availability. Our results indicate that FGF14-mediated inactivation is the major determinant defining use-dependent changes in Nav availability in CCs. These results establish that Nav1.3, like other Nav isoforms, can also partner with FGF subunits, strongly regulating Nav channel function.
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Affiliation(s)
| | - Chengtao Yang
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO
| | - Xiao-Ming Xia
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO
| | - Christopher J Lingle
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO
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28
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Ježek P, Holendová B, Jabůrek M, Tauber J, Dlasková A, Plecitá-Hlavatá L. The Pancreatic β-Cell: The Perfect Redox System. Antioxidants (Basel) 2021; 10:antiox10020197. [PMID: 33572903 PMCID: PMC7912581 DOI: 10.3390/antiox10020197] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/20/2021] [Accepted: 01/25/2021] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β-cell insulin secretion, which responds to various secretagogues and hormonal regulations, is reviewed here, emphasizing the fundamental redox signaling by NADPH oxidase 4- (NOX4-) mediated H2O2 production for glucose-stimulated insulin secretion (GSIS). There is a logical summation that integrates both metabolic plus redox homeostasis because the ATP-sensitive K+ channel (KATP) can only be closed when both ATP and H2O2 are elevated. Otherwise ATP would block KATP, while H2O2 would activate any of the redox-sensitive nonspecific calcium channels (NSCCs), such as TRPM2. Notably, a 100%-closed KATP ensemble is insufficient to reach the -50 mV threshold plasma membrane depolarization required for the activation of voltage-dependent Ca2+ channels. Open synergic NSCCs or Cl- channels have to act simultaneously to reach this threshold. The resulting intermittent cytosolic Ca2+-increases lead to the pulsatile exocytosis of insulin granule vesicles (IGVs). The incretin (e.g., GLP-1) amplification of GSIS stems from receptor signaling leading to activating the phosphorylation of TRPM channels and effects on other channels to intensify integral Ca2+-influx (fortified by endoplasmic reticulum Ca2+). ATP plus H2O2 are also required for branched-chain ketoacids (BCKAs); and partly for fatty acids (FAs) to secrete insulin, while BCKA or FA β-oxidation provide redox signaling from mitochondria, which proceeds by H2O2 diffusion or hypothetical SH relay via peroxiredoxin "redox kiss" to target proteins.
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29
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Zhang Q, Dou H, Rorsman P. 'Resistance is futile?' - paradoxical inhibitory effects of K ATP channel closure in glucagon-secreting α-cells. J Physiol 2020; 598:4765-4780. [PMID: 32716554 PMCID: PMC7689873 DOI: 10.1113/jp279775] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 07/24/2020] [Indexed: 12/12/2022] Open
Abstract
By secreting insulin and glucagon, the β- and α-cells of the pancreatic islets play a central role in the regulation of systemic metabolism. Both cells are equipped with ATP-regulated potassium (KATP ) channels that are regulated by the intracellular ATP/ADP ratio. In β-cells, KATP channels are active at low (non-insulin-releasing) glucose concentrations. An increase in glucose leads to KATP channel closure, membrane depolarization and electrical activity that culminates in elevation of [Ca2+ ]i and initiation of exocytosis of the insulin-containing secretory granules. The α-cells are also equipped with KATP channels but they are under strong tonic inhibition at low glucose, explaining why α-cells are electrically active under hypoglycaemic conditions and generate large Na+ - and Ca2+ -dependent action potentials. Closure of residual KATP channel activity leads to membrane depolarization and an increase in action potential firing but this stimulation of electrical activity is associated with inhibition rather than acceleration of glucagon secretion. This paradox arises because membrane depolarization reduces the amplitude of the action potentials by voltage-dependent inactivation of the Na+ channels involved in action potential generation. Exocytosis in α-cells is tightly linked to the opening of voltage-gated P/Q-type Ca2+ channels, the activation of which is steeply voltage-dependent. Accordingly, the inhibitory effect of the reduced action potential amplitude exceeds the stimulatory effect resulting from the increased action potential frequency. These observations highlight a previously unrecognised role of the action potential amplitude as a key regulator of pancreatic islet hormone secretion.
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Affiliation(s)
- Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Haiqiang Dou
- Metabolic Physiology Unit, Institute of Neuroscience and Physiology, University of Göteborg, PO Box 430, Göteborg, SE-405 30, Sweden
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, OX3 7LE, UK.,Metabolic Physiology Unit, Institute of Neuroscience and Physiology, University of Göteborg, PO Box 430, Göteborg, SE-405 30, Sweden
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30
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Drissi I, Woods WA, Woods CG. Understanding the genetic basis of congenital insensitivity to pain. Br Med Bull 2020; 133:65-78. [PMID: 32219415 PMCID: PMC7227775 DOI: 10.1093/bmb/ldaa003] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/21/2020] [Accepted: 01/31/2020] [Indexed: 12/15/2022]
Abstract
INTRODUCTION OR BACKGROUND Congenital insensitivity to pain (CIP) is caused by extremely rare Mendelian genetic disorders. CIP individuals demonstrate the unexpectedly severe consequences of painlessness. Although only a small number of causative conditions and genes are known, most have led to profound insights into human nociception. CIP gene discovery is catalyzing the manufacture of completely new classes of analgesics, and these are needed as alternatives to synthetic highly potent opioids. SOURCES OF DATA Pubmed.gov peer-reviewed journal articles and reviews. AREAS OF AGREEMENT The importance of nerve growth factor-tropomyosin receptor kinase A (NGF-TRKA) signalling for nociceptor genesis and subsequent pain sensing.New analgesics can be generated from knowledge of the NGF-TRKA nociceptor pathway.Increased susceptibility to Staphylococcus aureus infection is a consequence of deficient NGF-TRKA signalling.Mutations in the voltage-gated sodium channels SCN9A and SCN11A can cause congenital painlessness, and in contradistinction, other mutations can cause episodic neuropathic pain. SCN9A/Nav1.7 is an analgesic target. SCN11A/Nav1.9 is unlikely to be an analgesic target.There are further Mendelian causes of painlessness to be discovered. AREAS OF CONTROVERSY Which NGF-TRKA intracellular signalling pathways operate in nociceptor development and which in post-natal pain sensing?Why have no clinically effective Nav1.7 antagonist been generated? SCN9A-CIP causes analgesia, at least in part, through endogenous opioids.Why do all CIP phenotypes involve a complete loss of all types of nociception? AREAS TIMELY FOR DEVELOPING RESEARCH PRDM12 as an analgesic target.Discovery of the function and analgesic potential of new CIP genes.Can NGF-TRKA be used in the treatment of S. aureus?
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Affiliation(s)
- Ichrak Drissi
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - William Aidan Woods
- School of Medicine, David Weatherall building, University Road, Keele University, Staffordshire ST5 5BG, UK
| | - Christopher Geoffrey Woods
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
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Camunas-Soler J, Dai XQ, Hang Y, Bautista A, Lyon J, Suzuki K, Kim SK, Quake SR, MacDonald PE. Patch-Seq Links Single-Cell Transcriptomes to Human Islet Dysfunction in Diabetes. Cell Metab 2020; 31:1017-1031.e4. [PMID: 32302527 PMCID: PMC7398125 DOI: 10.1016/j.cmet.2020.04.005] [Citation(s) in RCA: 161] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 01/23/2020] [Accepted: 04/02/2020] [Indexed: 12/16/2022]
Abstract
Impaired function of pancreatic islet cells is a major cause of metabolic dysregulation and disease in humans. Despite this, it remains challenging to directly link physiological dysfunction in islet cells to precise changes in gene expression. Here we show that single-cell RNA sequencing combined with electrophysiological measurements of exocytosis and channel activity (patch-seq) can be used to link endocrine physiology and transcriptomes at the single-cell level. We collected 1,369 patch-seq cells from the pancreata of 34 human donors with and without diabetes. An analysis of function and gene expression networks identified a gene set associated with functional heterogeneity in β cells that can be used to predict electrophysiology. We also report transcriptional programs underlying dysfunction in type 2 diabetes and extend this approach to cryopreserved cells from donors with type 1 diabetes, generating a valuable resource for understanding islet cell heterogeneity in health and disease.
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Affiliation(s)
- Joan Camunas-Soler
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94518, USA
| | - Xiao-Qing Dai
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G 2E1, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Yan Hang
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Austin Bautista
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G 2E1, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - James Lyon
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Kunimasa Suzuki
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Seung K Kim
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, USA; Stanford Diabetes Research Center, Stanford University, Stanford, CA 94305, USA.
| | - Stephen R Quake
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94518, USA; Stanford Diabetes Research Center, Stanford University, Stanford, CA 94305, USA; Department of Applied Physics, Stanford University, Stanford, CA 94305, USA.
| | - Patrick E MacDonald
- Department of Pharmacology, University of Alberta, Edmonton, AB T6G 2E1, Canada; Alberta Diabetes Institute, University of Alberta, Edmonton, AB T6G 2E1, Canada.
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32
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Omar-Hmeadi M, Lund PE, Gandasi NR, Tengholm A, Barg S. Paracrine control of α-cell glucagon exocytosis is compromised in human type-2 diabetes. Nat Commun 2020; 11:1896. [PMID: 32312960 PMCID: PMC7171169 DOI: 10.1038/s41467-020-15717-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 03/23/2020] [Indexed: 01/05/2023] Open
Abstract
Glucagon is released from pancreatic α-cells to activate pathways that raise blood glucose. Its secretion is regulated by α-cell-intrinsic glucose sensing and paracrine control through insulin and somatostatin. To understand the inadequately high glucagon levels that contribute to hyperglycemia in type-2 diabetes (T2D), we analyzed granule behavior, exocytosis and membrane excitability in α-cells of 68 non-diabetic and 21 T2D human donors. We report that exocytosis is moderately reduced in α-cells of T2D donors, without changes in voltage-dependent ion currents or granule trafficking. Dispersed α-cells have a non-physiological V-shaped dose response to glucose, with maximal exocytosis at hyperglycemia. Within intact islets, hyperglycemia instead inhibits α-cell exocytosis, but not in T2D or when paracrine inhibition by insulin or somatostatin is blocked. Surface expression of somatostatin-receptor-2 is reduced in T2D, suggesting a mechanism for the observed somatostatin resistance. Thus, elevated glucagon in human T2D may reflect α-cell insensitivity to paracrine inhibition at hyperglycemia. Glucagon is elevated Type-2 diabetes, which contributes to poor glucose control in patients with the disease. Here the authors report that secretion of the hormone is controlled by paracrine inhibition, and that resistance of α-cells to somatostatin can explain hyperglucagonemia in type-2 diabetes.
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Affiliation(s)
- Muhmmad Omar-Hmeadi
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Per-Eric Lund
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Nikhil R Gandasi
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Anders Tengholm
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden
| | - Sebastian Barg
- Medical Cell Biology, Uppsala University, Box 571, BMC, 751 23, Uppsala, Sweden.
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Wendt A, Eliasson L. Pancreatic α-cells - The unsung heroes in islet function. Semin Cell Dev Biol 2020; 103:41-50. [PMID: 31983511 DOI: 10.1016/j.semcdb.2020.01.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/17/2020] [Accepted: 01/20/2020] [Indexed: 01/15/2023]
Abstract
The pancreatic islets of Langerhans consist of several hormone-secreting cell types important for blood glucose control. The insulin secreting β-cells are the best studied of these cell types, but less is known about the glucagon secreting α-cells. The α-cells secrete glucagon as a response to low blood glucose. The major function of glucagon is to release glucose from the glycogen stores in the liver. In both type 1 and type 2 diabetes, glucagon secretion is dysregulated further exaggerating the hyperglycaemia, and in type 1 diabetes α-cells fail to counter regulate hypoglycaemia. Although glucagon has been recognized for almost 100 years, the understanding of how glucagon secretion is regulated and how glucagon act within the islet is far from complete. However, α-cell research has taken off lately which is promising for future knowledge. In this review we aim to highlight α-cell regulation and glucagon secretion with a special focus on recent discoveries from human islets. We will present some novel aspects of glucagon function and effects of selected glucose lowering agents on glucagon secretion.
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Affiliation(s)
- Anna Wendt
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden
| | - Lena Eliasson
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden.
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34
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Gilon P. The Role of α-Cells in Islet Function and Glucose Homeostasis in Health and Type 2 Diabetes. J Mol Biol 2020; 432:1367-1394. [PMID: 31954131 DOI: 10.1016/j.jmb.2020.01.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/23/2019] [Accepted: 01/06/2020] [Indexed: 01/09/2023]
Abstract
Pancreatic α-cells are the major source of glucagon, a hormone that counteracts the hypoglycemic action of insulin and strongly contributes to the correction of acute hypoglycemia. The mechanisms by which glucose controls glucagon secretion are hotly debated, and it is still unclear to what extent this control results from a direct action of glucose on α-cells or is indirectly mediated by β- and/or δ-cells. Besides its hyperglycemic action, glucagon has many other effects, in particular on lipid and amino acid metabolism. Counterintuitively, glucagon seems also required for an optimal insulin secretion in response to glucose by acting on its cognate receptor and, even more importantly, on GLP-1 receptors. Patients with diabetes mellitus display two main alterations of glucagon secretion: a relative hyperglucagonemia that aggravates hyperglycemia, and an impaired glucagon response to hypoglycemia. Under metabolic stress states, such as diabetes, pancreatic α-cells also secrete GLP-1, a glucose-lowering hormone, whereas the gut can produce glucagon. The contribution of extrapancreatic glucagon to the abnormal glucose homeostasis is unclear. Here, I review the possible mechanisms of control of glucagon secretion and the role of α-cells on islet function in healthy state. I discuss the possible causes of the abnormal glucagonemia in diabetes, with particular emphasis on type 2 diabetes, and I briefly comment the current antidiabetic therapies affecting α-cells.
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Affiliation(s)
- Patrick Gilon
- Université Catholique de Louvain, Institute of Experimental and Clinical Research, Pole of Endocrinology, Diabetes and Nutrition, Avenue Hippocrate 55 (B1.55.06), Brussels, B-1200, Belgium.
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35
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Selvaraj C, Selvaraj G, Kaliamurthi S, Cho WC, Wei DQ, Singh SK. Ion Channels as Therapeutic Targets for Type 1 Diabetes Mellitus. Curr Drug Targets 2020; 21:132-147. [PMID: 31538892 DOI: 10.2174/1389450119666190920152249] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 02/07/2023]
Abstract
Ion channels are integral proteins expressed in almost all living cells and are involved in muscle contraction and nutrient transport. They play a critical role in the normal functioning of the excitable tissues of the nervous system and regulate the action potential and contraction events. Dysfunction of genes encodes ion channel proteins, which disrupt the channel function and lead to a number of diseases, among which is type 1 diabetes mellitus (T1DM). Therefore, understanding the complex mechanism of ion channel receptors is necessary to facilitate the diagnosis and management of treatment. In this review, we summarize the mechanism of important ion channels and their potential role in the regulation of insulin secretion along with the limitations of ion channels as therapeutic targets. Furthermore, we discuss the recent investigations of the mechanism regulating the ion channels in pancreatic beta cells, which suggest that ion channels are active participants in the regulation of insulin secretion.
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Affiliation(s)
- Chandrabose Selvaraj
- Department of Bioinformatics, Computer-Aided Drug Design, and Molecular Modeling Lab, Science Block, Alagappa University, Karaikudi, Tamil Nadu, 630004, India
| | - Gurudeeban Selvaraj
- Center of Interdisciplinary Sciences-Computational Life Sciences, College of Food Science and Engineering, Henan University of Technology, Zhengzhou, 450001, China
- Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nanshan District, Shenzhen, Guangdong, 518055, China
| | - Satyavani Kaliamurthi
- Center of Interdisciplinary Sciences-Computational Life Sciences, College of Food Science and Engineering, Henan University of Technology, Zhengzhou, 450001, China
- Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nanshan District, Shenzhen, Guangdong, 518055, China
| | - William C Cho
- Department of Clinical Oncology, Queen Elizabeth Hospital, Kowloon, Hong Kong
| | - Dong-Qing Wei
- Center of Interdisciplinary Sciences-Computational Life Sciences, College of Food Science and Engineering, Henan University of Technology, Zhengzhou, 450001, China
- Peng Cheng Laboratory, Vanke Cloud City Phase I Building 8, Xili Street, Nanshan District, Shenzhen, Guangdong, 518055, China
- Department of Bioinformatics, The State Key Laboratory of Microbial Metabolism, College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Sanjeev Kumar Singh
- Department of Bioinformatics, Computer-Aided Drug Design, and Molecular Modeling Lab, Science Block, Alagappa University, Karaikudi, Tamil Nadu, 630004, India
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36
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Denwood G, Tarasov A, Salehi A, Vergari E, Ramracheya R, Takahashi H, Nikolaev VO, Seino S, Gribble F, Reimann F, Rorsman P, Zhang Q. Glucose stimulates somatostatin secretion in pancreatic δ-cells by cAMP-dependent intracellular Ca 2+ release. J Gen Physiol 2019; 151:1094-1115. [PMID: 31358556 PMCID: PMC6719402 DOI: 10.1085/jgp.201912351] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 05/11/2019] [Accepted: 07/09/2019] [Indexed: 12/12/2022] Open
Abstract
Somatostatin secretion from pancreatic islet δ-cells is stimulated by elevated glucose levels, but the underlying mechanisms have only partially been elucidated. Here we show that glucose-induced somatostatin secretion (GISS) involves both membrane potential-dependent and -independent pathways. Although glucose-induced electrical activity triggers somatostatin release, the sugar also stimulates GISS via a cAMP-dependent stimulation of CICR and exocytosis of somatostatin. The latter effect is more quantitatively important and in mouse islets depolarized by 70 mM extracellular K+ , increasing glucose from 1 mM to 20 mM produced an ∼3.5-fold stimulation of somatostatin secretion, an effect that was mimicked by the application of the adenylyl cyclase activator forskolin. Inhibiting cAMP-dependent pathways with PKI or ESI-05, which inhibit PKA and exchange protein directly activated by cAMP 2 (Epac2), respectively, reduced glucose/forskolin-induced somatostatin secretion. Ryanodine produced a similar effect that was not additive to that of the PKA or Epac2 inhibitors. Intracellular application of cAMP produced a concentration-dependent stimulation of somatostatin exocytosis and elevation of cytoplasmic Ca2+ ([Ca2+]i). Both effects were inhibited by ESI-05 and thapsigargin (an inhibitor of SERCA). By contrast, inhibition of PKA suppressed δ-cell exocytosis without affecting [Ca2+]i Simultaneous recordings of electrical activity and [Ca2+]i in δ-cells expressing the genetically encoded Ca2+ indicator GCaMP3 revealed that the majority of glucose-induced [Ca2+]i spikes did not correlate with δ-cell electrical activity but instead reflected Ca2+ release from the ER. These spontaneous [Ca2+]i spikes are resistant to PKI but sensitive to ESI-05 or thapsigargin. We propose that cAMP links an increase in plasma glucose to stimulation of somatostatin secretion by promoting CICR, thus evoking exocytosis of somatostatin-containing secretory vesicles in the δ-cell.
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Affiliation(s)
- Geoffrey Denwood
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Andrei Tarasov
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
- School of Life and Medical Sciences, University of Hertfordshire, Hatfield, UK
| | - Albert Salehi
- Institute of Neuroscience and Physiology, Department of Physiology, Metabolic Research Unit, University of Goteborg, Göteborg, Sweden
| | - Elisa Vergari
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Reshma Ramracheya
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
| | - Harumi Takahashi
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Viacheslav O Nikolaev
- Institute of Experimental Cardiovascular Research, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Susumo Seino
- Division of Molecular and Metabolic Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Fiona Gribble
- Institute of Metabolic Science, University of Cambridge, Addenbrook's Hospital, Cambridge, UK
| | - Frank Reimann
- Institute of Metabolic Science, University of Cambridge, Addenbrook's Hospital, Cambridge, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
- Institute of Neuroscience and Physiology, Department of Physiology, Metabolic Research Unit, University of Goteborg, Göteborg, Sweden
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, UK
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Martinez-Pinna J, Marroqui L, Hmadcha A, Lopez-Beas J, Soriano S, Villar-Pazos S, Alonso-Magdalena P, Dos Santos RS, Quesada I, Martin F, Soria B, Gustafsson JÅ, Nadal A. Oestrogen receptor β mediates the actions of bisphenol-A on ion channel expression in mouse pancreatic beta cells. Diabetologia 2019; 62:1667-1680. [PMID: 31250031 DOI: 10.1007/s00125-019-4925-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 04/26/2019] [Indexed: 10/26/2022]
Abstract
AIMS/HYPOTHESIS Bisphenol-A (BPA) is a widespread endocrine-disrupting chemical that has been associated with type 2 diabetes development. Low doses of BPA modify pancreatic beta cell function and induce insulin resistance; some of these effects are mediated via activation of oestrogen receptors α (ERα) and β (ERβ). Here we investigated whether low doses of BPA regulate the expression and function of ion channel subunits involved in beta cell function. METHODS Microarray gene profiling of isolated islets from vehicle- and BPA-treated (100 μg/kg per day for 4 days) mice was performed using Affymetrix GeneChip Mouse Genome 430.2 Array. Expression level analysis was performed using the normalisation method based on the processing algorithm 'robust multi-array average'. Whole islets or dispersed islets from C57BL/6J or oestrogen receptor β (ERβ) knockout (Erβ-/-) mice were treated with vehicle or BPA (1 nmol/l) for 48 h. Whole-cell patch-clamp recordings were used to measure Na+ and K+ currents. mRNA expression was evaluated by quantitative real-time PCR. RESULTS Microarray analysis showed that BPA modulated the expression of 1440 probe sets (1192 upregulated and 248 downregulated genes). Of these, more than 50 genes, including Scn9a, Kcnb2, Kcnma1 and Kcnip1, encoded important Na+ and K+ channel subunits. These findings were confirmed by quantitative RT-PCR in islets from C57BL/6J BPA-treated mice or whole islets treated ex vivo. Electrophysiological measurements showed a decrease in both Na+ and K+ currents in BPA-treated islets. The pharmacological profile indicated that BPA reduced currents mediated by voltage-activated K+ channels (Kv2.1/2.2 channels) and large-conductance Ca2+-activated K+ channels (KCa1.1 channels), which agrees with BPA's effects on gene expression. Beta cells from ERβ-/- mice did not present BPA-induced changes, suggesting that ERβ mediates BPA's effects in pancreatic islets. Finally, BPA increased burst duration, reduced the amplitude of the action potential and enlarged the action potential half-width, leading to alteration in beta cell electrical activity. CONCLUSIONS/INTERPRETATION Our data suggest that BPA modulates the expression and function of Na+ and K+ channels via ERβ in mouse pancreatic islets. Furthermore, BPA alters beta cell electrical activity. Altogether, these BPA-induced changes in beta cells might play a role in the diabetogenic action of BPA described in animal models.
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Affiliation(s)
- Juan Martinez-Pinna
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Laura Marroqui
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Abdelkrim Hmadcha
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
- Department of Cell Regeneration and Advanced Therapies, Andalusian Center for Molecular Biology and Regenerative Medicine-CABIMER, University of Pablo Olavide-University of Seville-CSIC, Seville, Spain
| | - Javier Lopez-Beas
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
- Department of Cell Regeneration and Advanced Therapies, Andalusian Center for Molecular Biology and Regenerative Medicine-CABIMER, University of Pablo Olavide-University of Seville-CSIC, Seville, Spain
| | - Sergi Soriano
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Alicante, Spain
| | - Sabrina Villar-Pazos
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Paloma Alonso-Magdalena
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Reinaldo S Dos Santos
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Ivan Quesada
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
| | - Franz Martin
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
- Department of Cell Regeneration and Advanced Therapies, Andalusian Center for Molecular Biology and Regenerative Medicine-CABIMER, University of Pablo Olavide-University of Seville-CSIC, Seville, Spain
| | - Bernat Soria
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain
- Department of Cell Regeneration and Advanced Therapies, Andalusian Center for Molecular Biology and Regenerative Medicine-CABIMER, University of Pablo Olavide-University of Seville-CSIC, Seville, Spain
| | - Jan-Åke Gustafsson
- Department of Cell Biology and Biochemistry, Center for Nuclear Receptors and Cell Signaling, University of Houston, Houston, TX, USA
- Department of Biosciences and Nutrition, Karolinska Institut, Huddinge, Sweden
| | - Angel Nadal
- Instituto de Biología Molecular y Celular (IBMC), Universitas Miguel Hernández, 03202, Elche, Spain.
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universitas Miguel Hernández, Elche, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Spain, .
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Jacobson DA, Shyng SL. Ion Channels of the Islets in Type 2 Diabetes. J Mol Biol 2019; 432:1326-1346. [PMID: 31473158 DOI: 10.1016/j.jmb.2019.08.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/19/2019] [Accepted: 08/21/2019] [Indexed: 02/06/2023]
Abstract
Ca2+ is an essential signal for pancreatic β-cell function. Ca2+ plays critical roles in numerous β-cell pathways such as insulin secretion, transcription, metabolism, endoplasmic reticulum function, and the stress response. Therefore, β-cell Ca2+ handling is tightly controlled. At the plasma membrane, Ca2+ entry primarily occurs through voltage-dependent Ca2+ channels. Voltage-dependent Ca2+ channel activity is dependent on orchestrated fluctuations in the plasma membrane potential or voltage, which are mediated via the activity of many ion channels. During the pathogenesis of type 2 diabetes the β-cell is exposed to stressful conditions, which result in alterations of Ca2+ handling. Some of the changes in β-cell Ca2+ handling that occur under stress result from perturbations in ion channel activity, expression or localization. Defective Ca2+ signaling in the diabetic β-cell alters function, limits insulin secretion and exacerbates hyperglycemia. In this review, we focus on the β-cell ion channels that control Ca2+ handling and how they impact β-cell dysfunction in type 2 diabetes.
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Affiliation(s)
- David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, 7415 MRB4 (Langford), 2213 Garland Avenue, Nashville, TN 37232, USA.
| | - Show-Ling Shyng
- Department of Biochemistry and Molecular Biology, Oregon Health & Science University, L224, MRB 624, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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Cell Autonomous Dysfunction and Insulin Resistance in Pancreatic α Cells. Int J Mol Sci 2019; 20:ijms20153699. [PMID: 31357734 PMCID: PMC6695724 DOI: 10.3390/ijms20153699] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 07/23/2019] [Accepted: 07/26/2019] [Indexed: 12/23/2022] Open
Abstract
To date, type 2 diabetes is considered to be a "bi-hormonal disorder" rather than an "insulin-centric disorder," suggesting that glucagon is as important as insulin. Although glucagon increases hepatic glucose production and blood glucose levels, paradoxical glucagon hypersecretion is observed in diabetes. Recently, insulin resistance in pancreatic α cells has been proposed to be associated with glucagon dysregulation. Moreover, cell autonomous dysfunction of α cells is involved in the etiology of diabetes. In this review, we summarize the current knowledge about the physiological and pathological roles of glucagon.
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40
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Sarmiento BE, Santos Menezes LF, Schwartz EF. Insulin Release Mechanism Modulated by Toxins Isolated from Animal Venoms: From Basic Research to Drug Development Prospects. Molecules 2019; 24:E1846. [PMID: 31091684 PMCID: PMC6571724 DOI: 10.3390/molecules24101846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 04/23/2019] [Accepted: 05/09/2019] [Indexed: 12/12/2022] Open
Abstract
Venom from mammals, amphibians, snakes, arachnids, sea anemones and insects provides diverse sources of peptides with different potential medical applications. Several of these peptides have already been converted into drugs and some are still in the clinical phase. Diabetes type 2 is one of the diseases with the highest mortality rate worldwide, requiring specific attention. Diverse drugs are available (e.g., Sulfonylureas) for effective treatment, but with several adverse secondary effects, most of them related to the low specificity of these compounds to the target. In this context, the search for specific and high-affinity compounds for the management of this metabolic disease is growing. Toxins isolated from animal venom have high specificity and affinity for different molecular targets, of which the most important are ion channels. This review will present an overview about the electrical activity of the ion channels present in pancreatic β cells that are involved in the insulin secretion process, in addition to the diversity of peptides that can interact and modulate the electrical activity of pancreatic β cells. The importance of prospecting bioactive peptides for therapeutic use is also reinforced.
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Affiliation(s)
- Beatriz Elena Sarmiento
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Luis Felipe Santos Menezes
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
| | - Elisabeth F Schwartz
- Departamento de Ciências Fisiológicas, Instituto de Ciências Biológicas, Universidade de Brasília, Brasília, DF 70910-900, Brazil.
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41
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Fuente-Martín E, Mellado-Gil JM, Cobo-Vuilleumier N, Martín-Montalvo A, Romero-Zerbo SY, Diaz Contreras I, Hmadcha A, Soria B, Martin Bermudo F, Reyes JC, Bermúdez-Silva FJ, Lorenzo PI, Gauthier BR. Dissecting the Brain/Islet Axis in Metabesity. Genes (Basel) 2019; 10:genes10050350. [PMID: 31072002 PMCID: PMC6562925 DOI: 10.3390/genes10050350] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 05/02/2019] [Accepted: 05/02/2019] [Indexed: 12/17/2022] Open
Abstract
The high prevalence of type 2 diabetes mellitus (T2DM), together with the fact that current treatments are only palliative and do not avoid major secondary complications, reveals the need for novel approaches to treat the cause of this disease. Efforts are currently underway to identify therapeutic targets implicated in either the regeneration or re-differentiation of a functional pancreatic islet β-cell mass to restore insulin levels and normoglycemia. However, T2DM is not only caused by failures in β-cells but also by dysfunctions in the central nervous system (CNS), especially in the hypothalamus and brainstem. Herein, we review the physiological contribution of hypothalamic neuronal and glial populations, particularly astrocytes, in the control of the systemic response that regulates blood glucose levels. The glucosensing capacity of hypothalamic astrocytes, together with their regulation by metabolic hormones, highlights the relevance of these cells in the control of glucose homeostasis. Moreover, the critical role of astrocytes in the response to inflammation, a process associated with obesity and T2DM, further emphasizes the importance of these cells as novel targets to stimulate the CNS in response to metabesity (over-nutrition-derived metabolic dysfunctions). We suggest that novel T2DM therapies should aim at stimulating the CNS astrocytic response, as well as recovering the functional pancreatic β-cell mass. Whether or not a common factor expressed in both cell types can be feasibly targeted is also discussed.
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Affiliation(s)
- Esther Fuente-Martín
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
| | - Jose M Mellado-Gil
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
| | - Nadia Cobo-Vuilleumier
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
| | - Alejandro Martín-Montalvo
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
| | - Silvana Y Romero-Zerbo
- Instituto de Investigación Biomédica de Málaga-IBIMA, UGC Endocrinología y Nutrición. Hospital Regional Universitario de Málaga, 29009 Málaga, Spain.
| | - Irene Diaz Contreras
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
| | - Abdelkrim Hmadcha
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
| | - Bernat Soria
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
| | - Francisco Martin Bermudo
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
| | - Jose C Reyes
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
| | - Francisco J Bermúdez-Silva
- Instituto de Investigación Biomédica de Málaga-IBIMA, UGC Endocrinología y Nutrición. Hospital Regional Universitario de Málaga, 29009 Málaga, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
| | - Petra I Lorenzo
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
| | - Benoit R Gauthier
- Andalusian Center of Molecular Biology and Regenerative Medicine-CABIMER, Junta de Andalucia-University of Pablo de Olavide-University of Seville-CSIC, 41092 Seville, Spain.
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), 28029 Madrid, Spain.
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Vergari E, Knudsen JG, Ramracheya R, Salehi A, Zhang Q, Adam J, Asterholm IW, Benrick A, Briant LJB, Chibalina MV, Gribble FM, Hamilton A, Hastoy B, Reimann F, Rorsman NJG, Spiliotis II, Tarasov A, Wu Y, Ashcroft FM, Rorsman P. Insulin inhibits glucagon release by SGLT2-induced stimulation of somatostatin secretion. Nat Commun 2019; 10:139. [PMID: 30635569 PMCID: PMC6329806 DOI: 10.1038/s41467-018-08193-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 12/18/2018] [Indexed: 02/08/2023] Open
Abstract
Hypoglycaemia (low plasma glucose) is a serious and potentially fatal complication of insulin-treated diabetes. In healthy individuals, hypoglycaemia triggers glucagon secretion, which restores normal plasma glucose levels by stimulation of hepatic glucose production. This counterregulatory mechanism is impaired in diabetes. Here we show in mice that therapeutic concentrations of insulin inhibit glucagon secretion by an indirect (paracrine) mechanism mediated by stimulation of intra-islet somatostatin release. Insulin’s capacity to inhibit glucagon secretion is lost following genetic ablation of insulin receptors in the somatostatin-secreting δ-cells, when insulin-induced somatostatin secretion is suppressed by dapagliflozin (an inhibitor of sodium-glucose co-tranporter-2; SGLT2) or when the action of secreted somatostatin is prevented by somatostatin receptor (SSTR) antagonists. Administration of these compounds in vivo antagonises insulin’s hypoglycaemic effect. We extend these data to isolated human islets. We propose that SSTR or SGLT2 antagonists should be considered as adjuncts to insulin in diabetes therapy. Impaired glucagon secretion in patients with diabetes causes hypoglycemia. Here the authors show that therapeutic concentrations of insulin inhibit alpha-cell glucagon secretion by stimulating delta-cell insulin receptor and the release of somatostatin. Blocking somatostatin secretion or action ameliorates this effect.
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Affiliation(s)
- Elisa Vergari
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Jakob G Knudsen
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Reshma Ramracheya
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Albert Salehi
- Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, Göteborg, SE40530, Sweden
| | - Quan Zhang
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Julie Adam
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Ingrid Wernstedt Asterholm
- Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, Göteborg, SE40530, Sweden
| | - Anna Benrick
- Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, Göteborg, SE40530, Sweden
| | - Linford J B Briant
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Margarita V Chibalina
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Fiona M Gribble
- Cambridge Institute of Metabolic Science and MRC Metabolic Diseases Unit, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0QQ, UK
| | - Alexander Hamilton
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Benoit Hastoy
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Frank Reimann
- Cambridge Institute of Metabolic Science and MRC Metabolic Diseases Unit, University of Cambridge School of Clinical Medicine, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0QQ, UK
| | - Nils J G Rorsman
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Ioannis I Spiliotis
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK.,Oxford National Institute for Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Andrei Tarasov
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK.,Oxford National Institute for Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, OX3 7LE, UK
| | - Yanling Wu
- Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, Göteborg, SE40530, Sweden
| | - Frances M Ashcroft
- Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, Göteborg, SE40530, Sweden.,Department of Physiology, Anatomy and Genetics, Henry Wellcome Centre for Gene Function, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Patrik Rorsman
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, OX3 7LE, UK. .,Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Box 430, Göteborg, SE40530, Sweden. .,Oxford National Institute for Health Research, Biomedical Research Centre, Churchill Hospital, Oxford, OX3 7LE, UK.
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43
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Teoh IH, Banerjee M. Effect of ranolazine on glycaemia in adults with and without diabetes: a meta-analysis of randomised controlled trials. Open Heart 2019; 5:e000706. [PMID: 30613407 PMCID: PMC6307613 DOI: 10.1136/openhrt-2017-000706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 12/15/2017] [Accepted: 02/14/2018] [Indexed: 12/19/2022] Open
Abstract
Background Ranolazine is an antianginal drug reported to have hypoglycaemic effects. Objectives To assess the effect of ranolazine versus placebo on glycaemic control for adults with and without diabetes. Methods A systematic search of seven databases was conducted to identify all randomised controlled trials that compared the effect of ranolazine versus placebo on haemoglobin A1c (HbA1c) and/or fasting plasma glucose (FPG) and/or incidence of hypoglycaemia. We used mean differences in HbA1c and FPG to express intervention effect estimates and analysed the data with random-effects model for meta-analyses using Revman 5.3. Results We identified seven trials including 6543 subjects to assess the effect of ranolazine on HbA1c and/or FPG. A separate trial that included 944 subjects was included to assess the effect of ranolazine on hypoglycaemia. The change in HbA1c for all patients was −0.36% (95% CI −0.57% to −0.15%; p=0.0004, I2=78%). In patients with diabetes, the change in HbA1c was −0.41% (95% CI −0.58% to −0.25%; p<0.00001, I2=65%). There was no significant difference in FPG between ranolazine and placebo groups (−2.58 mmol/L, 95% CI −7.02 to 1.85; p=0.25; I2=49%) or incidence of hypoglycaemia between ranolazine and placebo groups (OR 1.70, 95% CI 0.89 to 3.26; p=0.61, I2=0%). Conclusions Our meta-analytic findings support the fact that ranolazine improves HbA1c without increasing the risk of hypoglycaemia. It therefore has a potential of having an additional benefit of improving glycaemic control in patients with chronic stable angina and diabetes.
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Affiliation(s)
- Ik Hur Teoh
- Department of Diabetes and Endocrinology, Royal Bolton Hospital, Bolton, UK
| | - Moulinath Banerjee
- Department of Diabetes and Endocrinology, Royal Bolton Hospital, Bolton, UK.,Endocrine Sciences Research Group, Manchester University, Manchester, UK
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44
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Hastoy B, Godazgar M, Clark A, Nylander V, Spiliotis I, van de Bunt M, Chibalina MV, Barrett A, Burrows C, Tarasov AI, Scharfmann R, Gloyn AL, Rorsman P. Electrophysiological properties of human beta-cell lines EndoC-βH1 and -βH2 conform with human beta-cells. Sci Rep 2018; 8:16994. [PMID: 30451893 PMCID: PMC6242937 DOI: 10.1038/s41598-018-34743-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 10/19/2018] [Indexed: 12/30/2022] Open
Abstract
Limited access to human islets has prompted the development of human beta cell models. The human beta cell lines EndoC-βH1 and EndoC-βH2 are increasingly used by the research community. However, little is known of their electrophysiological and secretory properties. Here, we monitored parameters that constitute the glucose-triggering pathway of insulin release. Both cell lines respond to glucose (6 and 20 mM) with 2- to 3-fold stimulation of insulin secretion which correlated with an elevation of [Ca2+]i, membrane depolarisation and increased action potential firing. Similar to human primary beta cells, KATP channel activity is low at 1 mM glucose and is further reduced upon increasing glucose concentration; an effect that was mimicked by the KATP channel blocker tolbutamide. The upstroke of the action potentials reflects the activation of Ca2+ channels with some small contribution of TTX-sensitive Na+ channels. The repolarisation involves activation of voltage-gated Kv2.2 channels and large-conductance Ca2+-activated K+ channels. Exocytosis presented a similar kinetics to human primary beta cells. The ultrastructure of these cells shows insulin vesicles composed of an electron-dense core surrounded by a thin clear halo. We conclude that the EndoC-βH1 and -βH2 cells share many features of primary human β-cells and thus represent a useful experimental model.
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Affiliation(s)
- Benoît Hastoy
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Mahdieh Godazgar
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Anne Clark
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Vibe Nylander
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Ioannis Spiliotis
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Martijn van de Bunt
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 1936 8948grid.4991.5Wellcome Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Margarita V. Chibalina
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Amy Barrett
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Carla Burrows
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Andrei I. Tarasov
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Raphael Scharfmann
- 0000 0001 2188 0914grid.10992.33INSERM U1016, Cochin Institute, Université Paris Descartes, Paris, France
| | - Anna L. Gloyn
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 1936 8948grid.4991.5Wellcome Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 0488 9484grid.415719.fNational Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom
| | - Patrik Rorsman
- 0000 0004 1936 8948grid.4991.5Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom ,0000 0004 0488 9484grid.415719.fNational Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Churchill Hospital, Oxford, United Kingdom ,0000 0000 9919 9582grid.8761.8Department of Physiology, Institute of Neuroscience and Physiology, University of Goteborg, Goteborg, Sweden
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45
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Hu Q, Niu Q, Song H, Wei S, Wang S, Yao L, Li YP. Polysaccharides from Portulaca oleracea L. regulated insulin secretion in INS-1 cells through voltage-gated Na + channel. Biomed Pharmacother 2018; 109:876-885. [PMID: 30551541 DOI: 10.1016/j.biopha.2018.10.113] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 10/19/2018] [Accepted: 10/20/2018] [Indexed: 12/23/2022] Open
Abstract
The present study was undertaken to determine the involvement of voltage-gated Na+ channel (VGSC) and other mechanism related to insulin secretion in polysaccharides from Portulaca oleracea L. (POP)-induced secretion of insulin from insulin-secreting β-cell line cells (INS-1) cells. Our results showed that the concentration of insulin both in culture medium and inside INS-1 cells were increased under the existing of different concentration of glucose by POP or TTX, respectively. However, the effect POP on insulin secretion and production were blocked by TTX, a VGSC blocker. Meanwhile, POP improved the mitochondrial membrane potential (Δψm), increased adenosine triphosphate (ATP) production, depolarized cell membrane potential (MP) and increased intracellular Ca2+ levels ([Ca2+]i). Furthermore, POP treatment increased the expression level of Nav1.3 and decreased the expression level of Nav1.7. TTX treatment decreased the expression level of Nav1.3 and Nav1.7. On the other hand, POP also elevated the survival of INS-1 cells. These results suggested that POP induced-secretion/production of insulin in INS-1 cells were mediated by VGSC through its change of function and subunits expression and subsequent VGSC- dependent events such as change of intracellular Ca2+ releasing, ATP metabolism, cell membrane and mitochondrial membrane potential, and also improvement of INS-1 cell survival. Meanwhile, our data indicated the potentiality of developing POP to be a drug for diabetes treatment and VGSC as a therapeutic target in diabetes treatment is valuable to be investigated further.
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Affiliation(s)
- Qingjuan Hu
- School of Life science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China
| | - Qingchuan Niu
- School of Life science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China
| | - Hao Song
- School of Life science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China
| | - Shanshan Wei
- School of Life science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China
| | - Songhua Wang
- Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China
| | - Lihua Yao
- School of Life science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China
| | - Yu-Ping Li
- School of Life science, Jiangxi Science & Technology Normal University, Nanchang, Jiangxi, 330013, PR China.
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46
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Esguerra JLS, Nagao M, Ofori JK, Wendt A, Eliasson L. MicroRNAs in islet hormone secretion. Diabetes Obes Metab 2018; 20 Suppl 2:11-19. [PMID: 30230181 DOI: 10.1111/dom.13382] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 05/10/2018] [Accepted: 05/23/2018] [Indexed: 12/12/2022]
Abstract
Pancreatic islet hormone secretion is central in the maintenance of blood glucose homeostasis. During development of hyperglycaemia, the β-cell is under pressure to release more insulin to compensate for increased insulin resistance. Failure of the β-cells to secrete enough insulin results in type 2 diabetes (T2D). MicroRNAs (miRNAs) are short non-coding RNA molecules suitable for rapid regulation of the changes in target gene expression needed in β-cell adaptations. Moreover, miRNAs are involved in the maintenance of α-cell and β-cell phenotypic identities via cell-specific, or cell-enriched expression. Although many of the abundant miRNAs are highly expressed in both cell types, recent research has focused on the role of miRNAs in β-cells. It has been shown that highly abundant miRNAs, such as miR-375, are involved in several cellular functions indispensable in maintaining β-cell phenotypic identity, almost acting as "housekeeping genes" in the context of hormone secretion. Despite the abundance and importance of miR-375, it has not been shown to be differentially expressed in T2D islets. On the contrary, the less abundant miRNAs such as miR-212/miR-132, miR-335, miR-130a/b and miR-152 are deregulated in T2D islets, wherein the latter three miRNAs were shown to play key roles in regulating β-cell metabolism. In this review, we focus on β-cell function and describe miRNAs involved in insulin biosynthesis and processing, glucose uptake and metabolism, electrical activity and Ca2+ -influx and exocytosis of the insulin granules. We present current status on miRNA regulation in α-cells, and finally we discuss the involvement of miRNAs in β-cell dysfunction underlying T2D pathogenesis.
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Affiliation(s)
- Jonathan L S Esguerra
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden
| | - Mototsugu Nagao
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden
| | - Jones K Ofori
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden
| | - Anna Wendt
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden
| | - Lena Eliasson
- Islet Cell Exocytosis, Lund University Diabetes Centre, Department of Clinical Sciences Malmö, Lund University, Clinical Research Centre, SUS, Malmö, Sweden
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47
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Abstract
The somatostatin-secreting δ-cells comprise ~5% of the cells of the pancreatic islets. The δ-cells have complex morphology and might interact with many more islet cells than suggested by their low numbers. δ-Cells contain ATP-sensitive potassium channels, which open at low levels of glucose but close when glucose is elevated. This closure initiates membrane depolarization and electrical activity and increased somatostatin secretion. Factors released by neighbouring α-cells or β-cells amplify the glucose-induced effects on somatostatin secretion from δ-cells, which act locally within the islets as paracrine or autocrine inhibitors of insulin, glucagon and somatostatin secretion. The effects of somatostatin are mediated by activation of somatostatin receptors coupled to the inhibitory G protein, which culminates in suppression of the electrical activity and exocytosis in α-cells and β-cells. Somatostatin secretion is perturbed in animal models of diabetes mellitus, which might explain the loss of appropriate hypoglycaemia-induced glucagon secretion, a defect that could be mitigated by somatostatin receptor 2 antagonists. Somatostatin antagonists or agents that suppress somatostatin secretion have been proposed as an adjunct to insulin therapy. In this Review, we summarize the cell physiology of somatostatin secretion, what might go wrong in diabetes mellitus and the therapeutic potential of agents targeting somatostatin secretion or action.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, Churchill Hospital, University of Oxford, Oxford, UK.
- Department of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden.
| | - Mark O Huising
- Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis, Davis, CA, USA
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, Davis, CA, USA
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48
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The somatostatin-secreting pancreatic δ-cell in health and disease. NATURE REVIEWS. ENDOCRINOLOGY 2018. [PMID: 29773871 DOI: 10.1038/s41574‐018‐0020‐6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The somatostatin-secreting δ-cells comprise ~5% of the cells of the pancreatic islets. The δ-cells have complex morphology and might interact with many more islet cells than suggested by their low numbers. δ-Cells contain ATP-sensitive potassium channels, which open at low levels of glucose but close when glucose is elevated. This closure initiates membrane depolarization and electrical activity and increased somatostatin secretion. Factors released by neighbouring α-cells or β-cells amplify the glucose-induced effects on somatostatin secretion from δ-cells, which act locally within the islets as paracrine or autocrine inhibitors of insulin, glucagon and somatostatin secretion. The effects of somatostatin are mediated by activation of somatostatin receptors coupled to the inhibitory G protein, which culminates in suppression of the electrical activity and exocytosis in α-cells and β-cells. Somatostatin secretion is perturbed in animal models of diabetes mellitus, which might explain the loss of appropriate hypoglycaemia-induced glucagon secretion, a defect that could be mitigated by somatostatin receptor 2 antagonists. Somatostatin antagonists or agents that suppress somatostatin secretion have been proposed as an adjunct to insulin therapy. In this Review, we summarize the cell physiology of somatostatin secretion, what might go wrong in diabetes mellitus and the therapeutic potential of agents targeting somatostatin secretion or action.
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49
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Godazgar M, Zhang Q, Chibalina MV, Rorsman P. Biphasic voltage-dependent inactivation of human Na V 1.3, 1.6 and 1.7 Na + channels expressed in rodent insulin-secreting cells. J Physiol 2018; 596:1601-1626. [PMID: 29441586 PMCID: PMC5924821 DOI: 10.1113/jp275587] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 02/06/2018] [Indexed: 12/12/2022] Open
Abstract
KEY POINTS Na+ current inactivation is biphasic in insulin-secreting cells, proceeding with two voltage dependences that are half-maximal at ∼-100 mV and -60 mV. Inactivation of voltage-gated Na+ (NaV ) channels occurs at ∼30 mV more negative voltages in insulin-secreting Ins1 and primary β-cells than in HEK, CHO or glucagon-secreting αTC1-6 cells. The difference in inactivation between Ins1 and non-β-cells persists in the inside-out patch configuration, discounting an involvement of a diffusible factor. In Ins1 cells and primary β-cells, but not in HEK cells, inactivation of a single NaV subtype is biphasic and follows two voltage dependences separated by 30-40 mV. We propose that NaV channels adopt different inactivation behaviours depending on the local membrane environment. ABSTRACT Pancreatic β-cells are equipped with voltage-gated Na+ channels that undergo biphasic voltage-dependent steady-state inactivation. A small Na+ current component (10-15%) inactivates over physiological membrane potentials and contributes to action potential firing. However, the major Na+ channel component is completely inactivated at -90 to -80 mV and is therefore inactive in the β-cell. It has been proposed that the biphasic inactivation reflects the contribution of different NaV α-subunits. We tested this possibility by expression of TTX-resistant variants of the NaV subunits found in β-cells (NaV 1.3, NaV 1.6 and NaV 1.7) in insulin-secreting Ins1 cells and in non-β-cells (including HEK and CHO cells). We found that all NaV subunits inactivated at 20-30 mV more negative membrane potentials in Ins1 cells than in HEK or CHO cells. The more negative inactivation in Ins1 cells does not involve a diffusible intracellular factor because the difference between Ins1 and CHO persisted after excision of the membrane. NaV 1.7 inactivated at 15--20 mV more negative membrane potentials than NaV 1.3 and NaV 1.6 in Ins1 cells but this small difference is insufficient to solely explain the biphasic inactivation in Ins1 cells. In Ins1 cells, but never in the other cell types, widely different components of NaV inactivation (separated by 30 mV) were also observed following expression of a single type of NaV α-subunit. The more positive component exhibited a voltage dependence of inactivation similar to that found in HEK and CHO cells. We propose that biphasic NaV inactivation in insulin-secreting cells reflects insertion of channels in membrane domains that differ with regard to lipid and/or membrane protein composition.
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Affiliation(s)
- Mahdieh Godazgar
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordChurchill HospitalOxfordOX3 7LEUK
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordChurchill HospitalOxfordOX3 7LEUK
| | - Margarita V. Chibalina
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordChurchill HospitalOxfordOX3 7LEUK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordChurchill HospitalOxfordOX3 7LEUK
- Metabolic PhysiologyDepartment of Neuroscience and PhysiologyMedicinaregatan 11GothenburgS‐413 09Sweden
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50
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Carbamazepine, a beta-cell protecting drug, reduces type 1 diabetes incidence in NOD mice. Sci Rep 2018; 8:4588. [PMID: 29545618 PMCID: PMC5854601 DOI: 10.1038/s41598-018-23026-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 03/06/2018] [Indexed: 01/01/2023] Open
Abstract
Pancreatic beta-cells are selectively destroyed by the host immune system in type 1 diabetes. Thus, drugs that preserve beta-cell mass and/or function have the potential to prevent or slow the progression of this disease. We recently reported that the use-dependent sodium channel blocker, carbamazepine, protects beta-cells from inflammatory cytokines in vitro. Here, we tested the effects of carbamazepine treatment in female non-obese diabetic (NOD) mice by supplementing LabDiet 5053 with 0.5% w/w carbamazepine to achieve serum carbamazepine levels of 14.98 ± 3.19 µM. Remarkably, diabetes incidence over 25 weeks, as determined by fasting blood glucose, was ~50% lower in carbamazepine treated animals. Partial protection from diabetes in carbamazepine-fed NOD mice was also associated with improved glucose tolerance at 6 weeks of age, prior to the onset of diabetes in our colony. Less insulitis was detected in carbamazepine treated NOD mice at 6 weeks of age, but we did not observe differences in CD4+ and CD8+ T cell composition in the pancreatic lymph node, as well as circulating markers of inflammation. Taken together, our results demonstrate that carbamazepine reduces the development of type 1 diabetes in NOD mice by maintaining functional beta-cell mass.
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