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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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2
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Bisht S, Singh MF. The triggering pathway, the metabolic amplifying pathway, and cellular transduction in regulation of glucose-dependent biphasic insulin secretion. Arch Physiol Biochem 2024:1-12. [PMID: 38196246 DOI: 10.1080/13813455.2023.2299920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Accepted: 12/16/2023] [Indexed: 01/11/2024]
Abstract
Introduction: Insulin secretion is a highly regulated process critical for maintaining glucose homeostasis. This abstract explores the intricate interplay between three essential pathways: The Triggering Pathway, The Metabolic Amplifying Pathway, and Cellular Transduction, in orchestrating glucose-dependent biphasic insulin secretion.Mechanism: During the triggering pathway, glucose metabolism in pancreatic beta-cells leads to ATP production, closing ATP-sensitive potassium channels and initiating insulin exocytosis. The metabolic amplifying pathway enhances insulin secretion via key metabolites like NADH and glutamate, enhancing calcium influx and insulin granule exocytosis. Additionally, the cellular transduction pathway involves G-protein coupled receptors and cyclic AMP, modulating insulin secretion.Result and Conclusion: These interconnected pathways ensure a dynamic insulin response to fluctuating glucose levels, with the initial rapid phase and the subsequent sustained phase. Understanding these pathways' complexities provides crucial insights into insulin dysregulation in diabetes and highlights potential therapeutic targets to restore glucose-dependent insulin secretion.
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Affiliation(s)
- Shradha Bisht
- Amity Institute of Pharmacy, Amity University, Lucknow, Uttar Pradesh, India
| | - Mamta F Singh
- School of Pharmaceutical Sciences, SBS University, Balawala, Uttarakhand, India
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3
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Lin Q, Liu J, Chen H, Hu W, Lei W, Wang M, Lin X, Zhang Y, Ai H, Chen S, Li C. A Novel Peptide COX 52-69 Inhibits High Glucose-induced Insulin Secretion by Modulating BK Channel Activity. Curr Protein Pept Sci 2024; 25:419-426. [PMID: 37885106 DOI: 10.2174/0113892037249620231010063637] [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: 02/17/2023] [Revised: 08/21/2023] [Accepted: 09/03/2023] [Indexed: 10/28/2023]
Abstract
BACKGROUND Excessive insulin is the leading cause of metabolic syndromes besides hyperinsulinemia. Insulin-lowering therapeutic peptides have been poorly studied and warrant urgent attention. OBJECTIVES The main purpose of this study, was to introduce a novel peptide COX52-69 that was initially isolated from the porcine small intestine and possessed the ability to inhibit insulin secretion under high-glucose conditions by modulating large conductance Ca2+-activated K+ channels (BK channels) activity. METHODS AND RESULTS Enzyme-linked immunosorbent assay results indicate that COX52-69 supressed insulin release induced by high glucose levels in pancreatic islets and animal models. Furthermore, electrophysiological data demonstrated that COX52-69 can increase BK channel currents and hyperpolarize cell membranes. Thus, cell excitability decreased, corresponding to a reduction in insulin secretion. CONCLUSION Our study provides a novel approach to modulate high glucose-stimulated insulin secretion in patients with hyperinsulinemia.
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Affiliation(s)
- Qian Lin
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Jingtao Liu
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Hengling Chen
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Wenwu Hu
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Weiqiong Lei
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Meijie Wang
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Xianguang Lin
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Yongning Zhang
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Huiting Ai
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Su Chen
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
| | - Chenhong Li
- Laboratory of Membrane Ion Channels and Medicine, Key Laboratory of Cognitive Science of State Ethnic Affairs Commission, Hubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis and Treatment, College of Biomedical Engineering, South-Central Minzu University, Wuhan, Hubei, 430074, China
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4
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Russell NX, Burra K, Shah RM, Bottasso-Arias N, Mohanakrishnan M, Snowball J, Ediga HH, Madala SK, Sinner D. Wnt signaling regulates ion channel expression to promote smooth muscle and cartilage formation in developing mouse trachea. Am J Physiol Lung Cell Mol Physiol 2023; 325:L788-L802. [PMID: 37873566 PMCID: PMC11068408 DOI: 10.1152/ajplung.00024.2023] [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: 01/17/2023] [Revised: 08/28/2023] [Accepted: 10/15/2023] [Indexed: 10/25/2023] Open
Abstract
Ion channels play critical roles in the physiology and function of the nervous system and contractile tissue; however, their role in noncontractile tissue and embryonic development has yet to be understood. Tracheobronchomalacia (TBM) and complete tracheal rings (CTR) are disorders affecting the muscle and cartilage of the trachea and bronchi, whose etiology remains poorly understood. We demonstrated that trachealis muscle organization and polarity are disrupted after epithelial ablation of Wntless (Wls), a cargo receptor critical for the Wnt signaling pathway, in developing trachea. The phenotype resembles the anomalous trachealis muscle observed after deletion of ion channel encoding genes in developing mouse trachea. We sought to investigate whether and how the deletion of Wls affects ion channels during tracheal development. We hypothesize that Wnt signaling influences the expression of ion channels to promote trachealis muscle cell assembly and patterning. Deleting Wls in developing trachea causes differential regulation of genes mediating actin binding, cytoskeleton organization, and potassium ion channel activity. Wnt signaling regulates the expression of Kcnj13, Kcnd3, Kcnj8, and Abcc9 as demonstrated by in vitro studies and in vivo analysis in Wnt5a and β-catenin-deficient tracheas. Pharmacological inhibition of potassium ion channels and Wnt signaling impaired contractility of developing trachealis smooth muscle and formation of cartilaginous mesenchymal condensation. Thus, in mice, epithelial-induced Wnt/β-catenin signaling mediates trachealis muscle and cartilage development via modulation of ion channel expression, promoting trachealis muscle architecture, contractility, and cartilaginous extracellular matrix. In turn, ion channel activity may influence tracheal morphogenesis underlying TBM and CTR.NEW & NOTEWORTHY Ion channels play critical roles in the physiology and function of the nervous system and contractile tissue; however, their role in noncontractile tissue and embryonic development has yet to be understood. In this study, we focused on the role of ion channels in the differentiation and patterning of the large airways of the developing respiratory tract. We identify a mechanism by which Wnt-beta-catenin signaling controls levels of ion channel-encoding genes to promote tracheal differentiation.
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Affiliation(s)
- Nicholas X Russell
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati Honors Program, Cincinnati, Ohio, United States
| | - Kaulini Burra
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
| | - Ronak M Shah
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati Honors Program, Cincinnati, Ohio, United States
| | - Natalia Bottasso-Arias
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
| | - Megha Mohanakrishnan
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati Honors Program, Cincinnati, Ohio, United States
| | - John Snowball
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
| | - Harshavardhana H Ediga
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States
| | - Satish K Madala
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States
| | - Debora Sinner
- Neonatology and Pulmonary Biology Perinatal Institute, Cincinnati Children's Hospital Medical Center, University of Cincinnati, College of Medicine, Cincinnati, Ohio, United States
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5
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Russell NX, Burra K, Shah R, Bottasso-Arias N, Mohanakrishnan M, Snowball J, Ediga HH, Madala SK, Sinner D. Wnt signaling regulates ion channel expression to promote smooth muscle and cartilage formation in developing mouse trachea. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.10.523309. [PMID: 36711918 PMCID: PMC9882072 DOI: 10.1101/2023.01.10.523309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Ion channels play critical roles in the physiology and function of the nervous system and contractile tissue; however, their role in non-contractile tissue and embryonic development has yet to be understood. Tracheobronchomalacia (TBM) and complete tracheal rings (CTR) are disorders affecting the muscle and cartilage of the trachea and bronchi, whose etiology remains poorly understood. We demonstrated that trachealis muscle organization and polarity are disrupted after epithelial ablation of Wls, a cargo receptor critical for the Wnt signaling pathway, in developing trachea. The phenotype resembles the anomalous trachealis muscle observed after deletion of ion channel encoding genes in developing mouse trachea. We sought to investigate whether and how the deletion of Wls affects ion channels during tracheal development. We hypothesize that Wnt signaling influences the expression of ion channels to promote trachealis muscle cell assembly and patterning. Deleting Wls in developing trachea causes differential regulation of genes mediating actin binding, cytoskeleton organization, and potassium ion channel activity. Wnt signaling regulated expression of Kcnj13, Kcnd3, Kcnj8, and Abcc9 as demonstrated by in vitro studies and in vivo analysis in Wnt5a and β-catenin deficient tracheas. Pharmacological inhibition of potassium ion channels and Wnt signaling impaired contractility of developing trachealis smooth muscle and formation of cartilaginous mesenchymal condensation. Thus, in mice, epithelial-induced Wnt/β-catenin signaling mediates trachealis muscle and cartilage development via modulation of ion channel expression, promoting trachealis muscle architecture, contractility, and cartilaginous extracellular matrix. In turn, ion channel activity may influence tracheal morphogenesis underlying TBM and CTR.
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Affiliation(s)
- Nicholas X. Russell
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center and University of Cincinnati Honors Program
| | - Kaulini Burra
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center. Current affiliation: Nationwide Children’s Hospital Columbus OH
| | - Ronak Shah
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center and University of Cincinnati Honors Program Current Affiliation: Renaissance School of Medicine at Stony Brook University
| | - Natalia Bottasso-Arias
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center
| | - Megha Mohanakrishnan
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center and University of Cincinnati Honors Program
| | - John Snowball
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center. Current affiliation: P&G Cincinnati, OH
| | - Harshavardhana H. Ediga
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine
| | - Satish K Madala
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, University of Cincinnati College of Medicine
| | - Debora Sinner
- Neonatology and Pulmonary Biology Perinatal Institute. Cincinnati Children’s Hospital Medical Center and University of Cincinnati, College of Medicine
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Abstract
Plasma glucose is tightly regulated via the secretion of the two glucose-regulating hormones insulin and glucagon. Situated next to the insulin-secreting β-cells, the α-cells produce and secrete glucagon-one of the body's few blood glucose-increasing hormones. Diabetes is a bihormonal disorder, resulting from both inadequate insulin secretion and dysregulation of glucagon. The year 2023 marks the 100th anniversary of the discovery of glucagon, making it particularly timely to highlight the roles of this systemic metabolic messenger in health and disease.
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Affiliation(s)
- Patrick E MacDonald
- Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK.
- Metabolic Physiology, Institute of Neuroscience and Physiology, University of Göteborg, Gothenburg, Sweden.
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7
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Pixner T, Stummer N, Schneider AM, Lukas A, Gramlinger K, Julian V, Thivel D, Mörwald K, Mangge H, Dalus C, Aigner E, Furthner D, Weghuber D, Maruszczak K. The relationship between glucose and the liver-alpha cell axis - A systematic review. Front Endocrinol (Lausanne) 2023; 13:1061682. [PMID: 36686477 PMCID: PMC9849557 DOI: 10.3389/fendo.2022.1061682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 12/13/2022] [Indexed: 01/06/2023] Open
Abstract
Until recently, glucagon was considered a mere antagonist to insulin, protecting the body from hypoglycemia. This notion changed with the discovery of the liver-alpha cell axis (LACA) as a feedback loop. The LACA describes how glucagon secretion and pancreatic alpha cell proliferation are stimulated by circulating amino acids. Glucagon in turn leads to an upregulation of amino acid metabolism and ureagenesis in the liver. Several increasingly common diseases (e.g., non-alcoholic fatty liver disease, type 2 diabetes, obesity) disrupt this feedback loop. It is important for clinicians and researchers alike to understand the liver-alpha cell axis and the metabolic sequelae of these diseases. While most of previous studies have focused on fasting concentrations of glucagon and amino acids, there is limited knowledge of their dynamics after glucose administration. The authors of this systematic review applied PRISMA guidelines and conducted PubMed searches to provide results of 8078 articles (screened and if relevant, studied in full). This systematic review aims to provide better insight into the LACA and its mediators (amino acids and glucagon), focusing on the relationship between glucose and the LACA in adult and pediatric subjects.
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Affiliation(s)
- Thomas Pixner
- Department of Pediatric and Adolescent Medicine, Salzkammergutklinikum Voecklabruck, Voecklabruck, Austria
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
| | - Nathalie Stummer
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria
| | - Anna Maria Schneider
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria
| | - Andreas Lukas
- Department of Pediatric and Adolescent Medicine, Salzkammergutklinikum Voecklabruck, Voecklabruck, Austria
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
| | - Karin Gramlinger
- Department of Pediatric and Adolescent Medicine, Salzkammergutklinikum Voecklabruck, Voecklabruck, Austria
| | - Valérie Julian
- Department of Sport Medicine and Functional Explorations, Diet and Musculoskeletal Health Team, Human Nutrition Research Center (CRNH), INRA, University Hospital of Clermont-Ferrand, University of Clermont Auvergne, Clermont-Ferrand, France
| | - David Thivel
- Laboratory of Metabolic Adaptations to Exercise under Physiological and Pathological Conditions (AME2P), University of Clermont Auvergne, Clermont-Ferrand, France
| | - Katharina Mörwald
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria
| | - Harald Mangge
- Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria
| | - Christopher Dalus
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria
| | - Elmar Aigner
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- First Department of Medicine, Paracelsus Medical University, Salzburg, Austria
| | - Dieter Furthner
- Department of Pediatric and Adolescent Medicine, Salzkammergutklinikum Voecklabruck, Voecklabruck, Austria
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
| | - Daniel Weghuber
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria
| | - Katharina Maruszczak
- Obesity Research Unit, Paracelsus Medical University, Salzburg, Austria
- Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria
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8
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Doliba NM, Rozo AV, Roman J, Qin W, Traum D, Gao L, Liu J, Manduchi E, Liu C, Golson ML, Vahedi G, Naji A, Matschinsky FM, Atkinson MA, Powers AC, Brissova M, Kaestner KH, Stoffers DA. α Cell dysfunction in islets from nondiabetic, glutamic acid decarboxylase autoantibody-positive individuals. J Clin Invest 2022; 132:156243. [PMID: 35642629 PMCID: PMC9151702 DOI: 10.1172/jci156243] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 04/14/2022] [Indexed: 01/07/2023] Open
Abstract
BACKGROUNDMultiple islet autoantibodies (AAbs) predict the development of type 1 diabetes (T1D) and hyperglycemia within 10 years. By contrast, T1D develops in only approximately 15% of individuals who are positive for single AAbs (generally against glutamic acid decarboxylase [GADA]); hence, the single GADA+ state may represent an early stage of T1D.METHODSHere, we functionally, histologically, and molecularly phenotyped human islets from nondiabetic GADA+ and T1D donors.RESULTSSimilar to the few remaining β cells in the T1D islets, GADA+ donor islets demonstrated a preserved insulin secretory response. By contrast, α cell glucagon secretion was dysregulated in both GADA+ and T1D islets, with impaired glucose suppression of glucagon secretion. Single-cell RNA-Seq of GADA+ α cells revealed distinct abnormalities in glycolysis and oxidative phosphorylation pathways and a marked downregulation of cAMP-dependent protein kinase inhibitor β (PKIB), providing a molecular basis for the loss of glucose suppression and the increased effect of 3-isobutyl-1-methylxanthine (IBMX) observed in GADA+ donor islets.CONCLUSIONWe found that α cell dysfunction was present during the early stages of islet autoimmunity at a time when β cell mass was still normal, raising important questions about the role of early α cell dysfunction in the progression of T1D.FUNDINGThis work was supported by grants from the NIH (3UC4DK112217-01S1, U01DK123594-02, UC4DK112217, UC4DK112232, U01DK123716, and P30 DK019525) and the Vanderbilt Diabetes Research and Training Center (DK20593).
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Affiliation(s)
- Nicolai M. Doliba
- Department of Biochemistry and Biophysics,,Institute for Diabetes, Obesity, and Metabolism
| | - Andrea V. Rozo
- Institute for Diabetes, Obesity, and Metabolism,,Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine
| | | | - Wei Qin
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine
| | | | | | | | | | - Chengyang Liu
- Institute for Diabetes, Obesity, and Metabolism,,Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Maria L. Golson
- Institute for Diabetes, Obesity, and Metabolism,,Department of Genetics, and
| | - Golnaz Vahedi
- Institute for Diabetes, Obesity, and Metabolism,,Department of Genetics, and
| | - Ali Naji
- Institute for Diabetes, Obesity, and Metabolism,,Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Franz M. Matschinsky
- Department of Biochemistry and Biophysics,,Institute for Diabetes, Obesity, and Metabolism
| | - Mark A. Atkinson
- Departments of Pathology, Immunology, and Laboratory Medicine, University of Florida Diabetes Institute, Gainesville, Florida, USA.,Department of Pediatrics, University of Florida Diabetes Institute, College of Medicine, Gainesville, Florida, USA
| | - Alvin C. Powers
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA.,VA Tennessee Valley Healthcare System, Nashville, Tennessee, USA
| | - Marcela Brissova
- Division of Diabetes, Endocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA
| | - Klaus H. Kaestner
- Institute for Diabetes, Obesity, and Metabolism,,Department of Genetics, and
| | - Doris A. Stoffers
- Institute for Diabetes, Obesity, and Metabolism,,Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine
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9
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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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10
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Skovsø S, Panzhinskiy E, Kolic J, Cen HH, Dionne DA, Dai XQ, Sharma RB, Elghazi L, Ellis CE, Faulkner K, Marcil SAM, Overby P, Noursadeghi N, Hutchinson D, Hu X, Li H, Modi H, Wildi JS, Botezelli JD, Noh HL, Suk S, Gablaski B, Bautista A, Kim R, Cras-Méneur C, Flibotte S, Sinha S, Luciani DS, Nislow C, Rideout EJ, Cytrynbaum EN, Kim JK, Bernal-Mizrachi E, Alonso LC, MacDonald PE, Johnson JD. Beta-cell specific Insr deletion promotes insulin hypersecretion and improves glucose tolerance prior to global insulin resistance. Nat Commun 2022; 13:735. [PMID: 35136059 PMCID: PMC8826929 DOI: 10.1038/s41467-022-28039-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 01/05/2022] [Indexed: 01/23/2023] Open
Abstract
Insulin receptor (Insr) protein is present at higher levels in pancreatic β-cells than in most other tissues, but the consequences of β-cell insulin resistance remain enigmatic. Here, we use an Ins1cre knock-in allele to delete Insr specifically in β-cells of both female and male mice. We compare experimental mice to Ins1cre-containing littermate controls at multiple ages and on multiple diets. RNA-seq of purified recombined β-cells reveals transcriptomic consequences of Insr loss, which differ between female and male mice. Action potential and calcium oscillation frequencies are increased in Insr knockout β-cells from female, but not male mice, whereas only male βInsrKO islets have reduced ATP-coupled oxygen consumption rate and reduced expression of genes involved in ATP synthesis. Female βInsrKO and βInsrHET mice exhibit elevated insulin release in ex vivo perifusion experiments, during hyperglycemic clamps, and following i.p. glucose challenge. Deletion of Insr does not alter β-cell area up to 9 months of age, nor does it impair hyperglycemia-induced proliferation. Based on our data, we adapt a mathematical model to include β-cell insulin resistance, which predicts that β-cell Insr knockout improves glucose tolerance depending on the degree of whole-body insulin resistance. Indeed, glucose tolerance is significantly improved in female βInsrKO and βInsrHET mice compared to controls at 9, 21 and 39 weeks, and also in insulin-sensitive 4-week old males. We observe no improved glucose tolerance in older male mice or in high fat diet-fed mice, corroborating the prediction that global insulin resistance obscures the effects of β-cell specific insulin resistance. The propensity for hyperinsulinemia is associated with mildly reduced fasting glucose and increased body weight. We further validate our main in vivo findings using an Ins1-CreERT transgenic line and find that male mice have improved glucose tolerance 4 weeks after tamoxifen-mediated Insr deletion. Collectively, our data show that β-cell insulin resistance in the form of reduced β-cell Insr contributes to hyperinsulinemia in the context of glucose stimulation, thereby improving glucose homeostasis in otherwise insulin sensitive sex, dietary and age contexts.
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Affiliation(s)
- Søs Skovsø
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Evgeniy Panzhinskiy
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jelena Kolic
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Haoning Howard Cen
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Derek A Dionne
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Xiao-Qing Dai
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Rohit B Sharma
- Division of Endocrinology, Diabetes and Metabolism and the Weill Center for Metabolic Health, Weill Cornell Medicine, New York, NY, USA
| | - Lynda Elghazi
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, MI, USA
| | - Cara E Ellis
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Katharine Faulkner
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Stephanie A M Marcil
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Peter Overby
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Nilou Noursadeghi
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Daria Hutchinson
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Xiaoke Hu
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Hong Li
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Honey Modi
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Jennifer S Wildi
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - J Diego Botezelli
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Hye Lim Noh
- Program in Molecular Medicine University of Massachusetts Medical School, Worcester, MA, USA
- Charles River Laboratories, Shrewsbury, MA, USA
| | - Sujin Suk
- Program in Molecular Medicine University of Massachusetts Medical School, Worcester, MA, USA
| | - Brian Gablaski
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
- Charles River Laboratories, Shrewsbury, MA, USA
| | - Austin Bautista
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Ryekjang Kim
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - Corentin Cras-Méneur
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, MI, USA
| | - Stephane Flibotte
- UBC Life Sciences Institute Bioinformatics Facility, University of British Columbia, Vancouver, BC, Canada
| | - Sunita Sinha
- UBC Sequencing and Bioinformatics Consortium, Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Dan S Luciani
- BC Children's Hospital Research Institute, Department of Surgery, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada
| | - Corey Nislow
- UBC Sequencing and Bioinformatics Consortium, Pharmaceutical Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Elizabeth J Rideout
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Eric N Cytrynbaum
- Department of Mathematics, University of British Columbia, Vancouver, BC, Canada
| | - Jason K Kim
- Program in Molecular Medicine University of Massachusetts Medical School, Worcester, MA, USA
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ernesto Bernal-Mizrachi
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine and Miami VA Health Care System, Miami, FL, USA
| | - Laura C Alonso
- Division of Endocrinology, Diabetes and Metabolism and the Weill Center for Metabolic Health, Weill Cornell Medicine, New York, NY, USA
| | - Patrick E MacDonald
- Alberta Diabetes Institute and Department of Pharmacology, University of Alberta, Edmonton, Canada
| | - James D Johnson
- Diabetes Research Group, Life Sciences Institute, and Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada.
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11
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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: 34] [Impact Index Per Article: 17.0] [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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12
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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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13
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Hughson BN. The Glucagon-Like Adipokinetic Hormone in Drosophila melanogaster - Biosynthesis and Secretion. Front Physiol 2021; 12:710652. [PMID: 35002748 PMCID: PMC8733639 DOI: 10.3389/fphys.2021.710652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
Metabolic homeostasis requires the precise regulation of circulating sugar titers. In mammals, homeostatic control of circulating sugar titers requires the coordinated secretion and systemic activities of glucagon and insulin. Metabolic homeostasis is similarly regulated in Drosophila melanogaster through the glucagon-like adipokinetic hormone (AKH) and the Drosophila insulin-like peptides (DILPs). In flies and mammals, glucagon and AKH are biosynthesized in and secreted from specialized endocrine cells. KATP channels borne on these cells respond to fluctuations in circulating glucose titers and thereby regulate glucagon secretion. The influence of glucagon in the pathogenesis of type 2 diabetes mellitus is now recognized, and a crucial mechanism that regulates glucagon secretion was reported nearly a decade ago. Ongoing efforts to develop D. melanogaster models for metabolic syndrome must build upon this seminal work. These efforts make a critical review of AKH physiology timely. This review focuses on AKH biosynthesis and the regulation of glucose-responsive AKH secretion through changes in CC cell electrical activity. Future directions for AKH research in flies are discussed, including the development of models for hyperglucagonemia and epigenetic inheritance of acquired metabolic traits. Many avenues of AKH physiology remain to be explored and thus present great potential for improving the utility of D. melanogaster in metabolic research.
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Affiliation(s)
- Bryon N. Hughson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada
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14
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Ng XW, Chung YH, Piston DW. Intercellular Communication in the Islet of Langerhans in Health and Disease. Compr Physiol 2021; 11:2191-2225. [PMID: 34190340 PMCID: PMC8985231 DOI: 10.1002/cphy.c200026] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.
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Affiliation(s)
- Xue W Ng
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - Yong H Chung
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
| | - David W Piston
- Department of Cell Biology and Physiology, Washington University, St Louis, Missouri, USA
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15
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Singh B, Khattab F, Chae H, Desmet L, Herrera PL, Gilon P. K ATP channel blockers control glucagon secretion by distinct mechanisms: A direct stimulation of α-cells involving a [Ca 2+] c rise and an indirect inhibition mediated by somatostatin. Mol Metab 2021; 53:101268. [PMID: 34118477 PMCID: PMC8274344 DOI: 10.1016/j.molmet.2021.101268] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 05/10/2021] [Accepted: 06/03/2021] [Indexed: 02/06/2023] Open
Abstract
Objective Glucagon is secreted by pancreatic α-cells in response to hypoglycemia and its hyperglycemic effect helps to restore normal blood glucose. Insulin and somatostatin (SST) secretions from β- and δ-cells, respectively, are stimulated by glucose by mechanisms involving an inhibition of their ATP-sensitive K+ (KATP) channels, leading to an increase in [Ca2+]c that triggers exocytosis. Drugs that close KATP channels, such as sulfonylureas, are used to stimulate insulin release in type 2 diabetic patients. α-cells also express KATP channels. However, the mechanisms by which sulfonylureas control glucagon secretion are still largely debated and were addressed in the present study. In particular, we studied the effects of KATP channel blockers on α-cell [Ca2+]c and glucagon secretion in the presence of a low (1 mM) or a high (15 mM) glucose concentration and evaluated the role of SST in these effects. Methods Using a transgenic mouse model expressing the Ca2+-sensitive fluorescent protein, GCaMP6f, specifically in α-cells, we measured [Ca2+]c in α-cells either dispersed or within whole islets (by confocal microscopy). By measuring [Ca2+]c in α-cells within islets and glucagon secretion using the same perifusion protocols, we tested whether glucagon secretion correlated with changes in [Ca2+]c in response to sulfonylureas. We studied the role of SST in the effects of sulfonylureas using multiple approaches including genetic ablation of SST, or application of SST-14 and SST receptor antagonists. Results Application of the sulfonylureas, tolbutamide, or gliclazide, to a medium containing 1 mM or 15 mM glucose increased [Ca2+]c in α-cells by a direct effect as in β-cells. At low glucose, sulfonylureas inhibited glucagon secretion of islets despite the rise in α-cell [Ca2+]c that they triggered. This glucagonostatic effect was indirect and attributed to SST because, in the islets of SST-knockout mice, sulfonylureas induced a stimulation of glucagon secretion which correlated with an increase in α-cell [Ca2+]c. Experiments with exogenous SST-14 and SST receptor antagonists indicated that the glucagonostatic effect of sulfonylureas mainly resulted from an inhibition of the efficacy of cytosolic Ca2+ on exocytosis. Although SST-14 was also able to inhibit glucagon secretion by decreasing α-cell [Ca2+]c, no decrease in [Ca2+]c occurred during sulfonylurea application because it was largely counterbalanced by the direct stimulatory effect of these drugs on α-cell [Ca2+]c. At high glucose, i.e., in conditions where glucagon release was already low, sulfonylureas stimulated glucagon secretion because their direct stimulatory effect on α-cells exceeded the indirect effect by SST. Our results also indicated that, unexpectedly, SST-14 poorly decreased the efficacy of Ca2+ on exocytosis in β-cells. Conclusions Sulfonylureas exert two opposite actions on α-cells: a direct stimulation as in β-cells and an indirect inhibition by SST. This suggests that any alteration of SST paracrine influence, as described in diabetes, will modify the effect of sulfonylureas on glucagon release. In addition, we suggest that δ-cells inhibit α-cells more efficiently than β-cells. KATP channel blockers control glucagon secretion by two mechanisms. The first one is the direct stimulation of α-cell by a [Ca2+]c rise, as in β-cells. The second one is an indirect inhibition mediated by δ-cells releasing somatostatin. Somatostatin mainly reduces the efficacy of Ca2+ on exocytosis in α-cells. Somatostatin more potently inhibits glucagon than insulin secretion.
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Affiliation(s)
- Bilal Singh
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Firas Khattab
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Heeyoung Chae
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium
| | - Lieven Desmet
- Université Catholique de Louvain, SMCS, Louvain Institute of Data Analysis and Modeling in economics and statistics, Louvain-la-Neuve, Belgium
| | - Pedro L Herrera
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Patrick Gilon
- Université Catholique de Louvain, Institut de Recherche Expérimentale et Clinique, Pôle d'Endocrinologie, Diabète et Nutrition, Brussels, Belgium.
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16
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Perry RJ, Saunders CJ, Nelson JM, Rizzo MJ, Braco JT, Johnson EC. Regulation of Metabolism by an Ensemble of Different Ion Channel Types: Excitation-Secretion Coupling Mechanisms of Adipokinetic Hormone Producing Cells in Drosophila. Front Physiol 2020; 11:580618. [PMID: 33192586 PMCID: PMC7658370 DOI: 10.3389/fphys.2020.580618] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/07/2020] [Indexed: 12/11/2022] Open
Abstract
Adipokinetic Hormone (AKH) is the primary insect hormone that mobilizes stored energy and is functional equivalent to mammalian glucagon. While most studies have focused on exploring the functional roles of AKH, relatively little is known about how AKH secretion is regulated. We assessed the AKH cell transcriptome and mined the data set for specific insight into the identities of different ion channels expressed in this cell lineage. We found reliable expression of multiple ion channel genes with multiple members for each ionic species. Specifically, we found significant signals for 39 of the either known or suspected ion channel genes within the Drosophila genome. We next performed a targeted RNAi screen aimed to identify the functional contribution of these different ion channels that may participate in excitation-secretion coupling in AKH producing cells (APCs). We assessed starvation survival, because changes in AKH signaling have previously been shown to impact starvation sensitivity. Genetic knockdown of three genes (Ca-Beta, Sur, and sei), in AKH producing cells caused highly significant changes (P < 0.001) in both male and female lifespan, and knockdown of six other genes (Shaw, cac, Ih, NaCP60E, stj, and TASK6) caused significant changes (P < 0.05) in only female lifespan. Specifically, the genetic knockdown of Ca-Beta and Sur led to increases in starvation lifespan, whereas the knockdown of sei decreased starvation survivorship. Focusing on these three strongest candidates from the behavioral screen, we assessed other AKH-dependent phenotypes. The AKH hormone is required for starvation-induced hyperactivity, and we found that these three ion channel gene knockdowns changed activity profiles and further suggest a modulatory role of these channels in AKH release. We eliminated the possibility that these genetic elements caused AKH cell lethality, and using independent methods, we verified expression of these genes in AKH cells. Collectively, these results suggest a model of AKH-cell excitability and establish an experimental framework for evaluating intrinsic mechanisms of AKH release.
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Affiliation(s)
- Rebecca J Perry
- Department of Biology, Wake Forest University, Winston-Salem, NC, United States
| | - Cecil J Saunders
- Department of Biology, Wake Forest University, Winston-Salem, NC, United States
| | - Jonathan M Nelson
- Department of Biology, Wake Forest University, Winston-Salem, NC, United States
| | - Michael J Rizzo
- Department of Biology, Wake Forest University, Winston-Salem, NC, United States
| | - Jason T Braco
- Department of Biology, Wake Forest University, Winston-Salem, NC, United States
| | - Erik C Johnson
- Department of Biology, Wake Forest University, Winston-Salem, NC, United States
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17
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Neumaier F, Schneider T, Albanna W. Ca v2.3 channel function and Zn 2+-induced modulation: potential mechanisms and (patho)physiological relevance. Channels (Austin) 2020; 14:362-379. [PMID: 33079629 PMCID: PMC7583514 DOI: 10.1080/19336950.2020.1829842] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Voltage-gated calcium channels (VGCCs) are critical for Ca2+ influx into all types of excitable cells, but their exact function is still poorly understood. Recent reconstruction of homology models for all human VGCCs at atomic resolution provides the opportunity for a structure-based discussion of VGCC function and novel insights into the mechanisms underlying Ca2+ selective flux through these channels. In the present review, we use these data as a basis to examine the structure, function, and Zn2+-induced modulation of Cav2.3 VGCCs, which mediate native R-type currents and belong to the most enigmatic members of the family. Their unique sensitivity to Zn2+ and the existence of multiple mechanisms of Zn2+ action strongly argue for a role of these channels in the modulatory action of endogenous loosely bound Zn2+, pools of which have been detected in a number of neuronal, endocrine, and reproductive tissues. Following a description of the different mechanisms by which Zn2+ has been shown or is thought to alter the function of these channels, we discuss their potential (patho)physiological relevance, taking into account what is known about the magnitude and function of extracellular Zn2+ signals in different tissues. While still far from complete, the picture that emerges is one where Cav2.3 channel expression parallels the occurrence of loosely bound Zn2+ pools in different tissues and where these channels may serve to translate physiological Zn2+ signals into changes of electrical activity and/or intracellular Ca2+ levels.
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Affiliation(s)
- Felix Neumaier
- Forschungszentrum Jülich GmbH, Institute of Neuroscience and Medicine, Nuclear Chemistry (INM-5) , Jülich, Germany.,University of Cologne, Faculty of Medicine and University Hospital Cologne, Institute of Radiochemistry and Experimental Molecular Imaging , Cologne, Germany
| | - Toni Schneider
- Institute of Neurophysiology , Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Walid Albanna
- Department of Neurosurgery, RWTH Aachen University , Aachen, Germany
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18
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Sohn JW, Ho WK. Cellular and systemic mechanisms for glucose sensing and homeostasis. Pflugers Arch 2020; 472:1547-1561. [PMID: 32960363 DOI: 10.1007/s00424-020-02466-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 08/14/2020] [Accepted: 09/14/2020] [Indexed: 12/25/2022]
Abstract
Glucose is a major source of energy in animals. Maintaining blood glucose levels within a physiological range is important for facilitating glucose uptake by cells, as required for optimal functioning. Glucose homeostasis relies on multiple glucose-sensing cells in the body that constantly monitor blood glucose levels and respond accordingly to adjust its glycemia. These include not only pancreatic β-cells and α-cells that secrete insulin and glucagon, but also central and peripheral neurons regulating pancreatic endocrine function. Different types of cells respond distinctively to changes in blood glucose levels, and the mechanisms involved in glucose sensing are diverse. Notably, recent studies have challenged the currently held views regarding glucose-sensing mechanisms. Furthermore, peripheral and central glucose-sensing cells appear to work in concert to control blood glucose level and maintain glucose and energy homeostasis in organisms. In this review, we summarize the established concepts and recent advances in the understanding of cellular and systemic mechanisms that regulate glucose sensing and its homeostasis.
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Affiliation(s)
- Jong-Woo Sohn
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, South Korea.
| | - Won-Kyung Ho
- Department of Physiology, Seoul National University College of Medicine, 103 Daehak-ro, Jongro-gu, Seoul, 03080, South Korea.
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.
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19
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Zaborska KE, Dadi PK, Dickerson MT, Nakhe AY, Thorson AS, Schaub CM, Graff SM, Stanley JE, Kondapavuluru RS, Denton JS, Jacobson DA. Lactate activation of α-cell K ATP channels inhibits glucagon secretion by hyperpolarizing the membrane potential and reducing Ca 2+ entry. Mol Metab 2020; 42:101056. [PMID: 32736089 PMCID: PMC7479281 DOI: 10.1016/j.molmet.2020.101056] [Citation(s) in RCA: 14] [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] [Received: 07/01/2020] [Revised: 07/17/2020] [Accepted: 07/24/2020] [Indexed: 12/20/2022] Open
Abstract
Objective Elevations in pancreatic α-cell intracellular Ca2+ ([Ca2+]i) lead to glucagon (GCG) secretion. Although glucose inhibits GCG secretion, how lactate and pyruvate control α-cell Ca2+ handling is unknown. Lactate enters cells through monocarboxylate transporters (MCTs) and is also produced during glycolysis by lactate dehydrogenase A (LDHA), an enzyme expressed in α-cells. As lactate activates ATP-sensitive K+ (KATP) channels in cardiomyocytes, lactate may also modulate α-cell KATP. Therefore, this study investigated how lactate signaling controls α-cell Ca2+ handling and GCG secretion. Methods Mouse and human islets were used in combination with confocal microscopy, electrophysiology, GCG immunoassays, and fluorescent thallium flux assays to assess α-cell Ca2+ handling, Vm, KATP currents, and GCG secretion. Results Lactate-inhibited mouse (75 ± 25%) and human (47 ± 9%) α-cell [Ca2+]i fluctuations only under low-glucose conditions (1 mM) but had no effect on β- or δ-cells [Ca2+]i. Glyburide inhibition of KATP channels restored α-cell [Ca2+]i fluctuations in the presence of lactate. Lactate transport into α-cells via MCTs hyperpolarized mouse (14 ± 1 mV) and human (12 ± 1 mV) α-cell Vm and activated KATP channels. Interestingly, pyruvate showed a similar KATP activation profile and α-cell [Ca2+]i inhibition as lactate. Lactate-induced inhibition of α-cell [Ca2+]i influx resulted in reduced GCG secretion in mouse (62 ± 6%) and human (43 ± 13%) islets. Conclusions These data demonstrate for the first time that lactate entry into α-cells through MCTs results in KATP activation, Vm hyperpolarization, reduced [Ca2+]i, and inhibition of GCG secretion. Thus, taken together, these data indicate that lactate either within α-cells and/or elevated in serum could serve as important modulators of α-cell function. Lactate reduces islet α-cell Ca2+ entry under low glucose conditions. Lactate does not alter β- or δ-cell Ca2+ handling under low glucose conditions. Lactate enters islet α-cells through monocarboxylate transporters. Lactate hyperpolarizes islet α-cell membrane potential by activating KATP channels. Lactate reduces mouse and human islet glucagon secretion.
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Affiliation(s)
- Karolina E Zaborska
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew T Dickerson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Arya Y Nakhe
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Ariel S Thorson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Charles M Schaub
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Sarah M Graff
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Jade E Stanley
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Roy S Kondapavuluru
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Jerod S Denton
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, USA
| | - David A Jacobson
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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20
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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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21
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Grubelnik V, Zmazek J, Markovič R, Gosak M, Marhl M. Modelling of energy-driven switch for glucagon and insulin secretion. J Theor Biol 2020; 493:110213. [PMID: 32109481 DOI: 10.1016/j.jtbi.2020.110213] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 02/19/2020] [Accepted: 02/24/2020] [Indexed: 12/14/2022]
Abstract
We present a mathematical model of the energy-driven metabolic switch for glucagon and insulin secretion from pancreatic alpha and beta cells, respectively. The energy status related to hormone secretion is studied for various glucose concentrations. Additionally, the physiological response is studied with regards to the presence of other metabolites, particularly the free-fatty acids. At low glucose, the ATP production in alpha cells is high due to free-fatty acids oxidation in mitochondria, which enables glucagon secretion. When the glucose concentration is elevated above the threshold value, the glucagon secretion is switched off due to the contribution of glycolytic ATP production, representing an "anaerobic switch". On the other hand, during hypoglycemia, the ATP production in beta cells is low, reflecting a "waiting state" for glucose as the main metabolite. When glucose is elevated above the threshold value, the oxidative fate of glucose in mitochondria is the main source of energy required for effective insulin secretion, i.e. the "aerobic switch". Our results show the importance of well-regulated and fine-tuned energetic processes in pancreatic alpha and beta cells required for efficient hormone secretion and hence effective blood glucose regulation. These energetic processes have to be appropriately switched on and off based on the sensing of different metabolites by alpha and beta cells. Our computational results indicate that disturbances in cell energetics (e.g. mitochondrial dysfunction), and dysfunctional metabolite sensing and distribution throughout the cell might be related to pathologies such as metabolic syndrome and diabetes.
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Affiliation(s)
- Vladimir Grubelnik
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor SI-2000, Slovenia
| | - Jan Zmazek
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia
| | - Rene Markovič
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia
| | - Marko Gosak
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Medicine, University of Maribor, Maribor SI-2000, Slovenia
| | - Marko Marhl
- Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Medicine, University of Maribor, Maribor SI-2000, Slovenia; Faculty of Education, University of Maribor, Maribor SI-2000, Slovenia.
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22
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Grubelnik V, Markovič R, Lipovšek S, Leitinger G, Gosak M, Dolenšek J, Valladolid-Acebes I, Berggren PO, Stožer A, Perc M, Marhl M. Modelling of dysregulated glucagon secretion in type 2 diabetes by considering mitochondrial alterations in pancreatic α-cells. ROYAL SOCIETY OPEN SCIENCE 2020; 7:191171. [PMID: 32218947 PMCID: PMC7029933 DOI: 10.1098/rsos.191171] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 12/16/2019] [Indexed: 05/15/2023]
Abstract
Type 2 diabetes mellitus (T2DM) has been associated with insulin resistance and the failure of β-cells to produce and secrete enough insulin as the disease progresses. However, clinical treatments based solely on insulin secretion and action have had limited success. The focus is therefore shifting towards α-cells, in particular to the dysregulated secretion of glucagon. Our qualitative electron-microscopy-based observations gave an indication that mitochondria in α-cells are altered in Western-diet-induced T2DM. In particular, α-cells extracted from mouse pancreatic tissue showed a lower density of mitochondria, a less expressed matrix and a lower number of cristae. These deformities in mitochondrial ultrastructure imply a decreased efficiency in mitochondrial ATP production, which prompted us to theoretically explore and clarify one of the most challenging problems associated with T2DM, namely the lack of glucagon secretion in hypoglycaemia and its oversecretion at high blood glucose concentrations. To this purpose, we constructed a novel computational model that links α-cell metabolism with their electrical activity and glucagon secretion. Our results show that defective mitochondrial metabolism in α-cells can account for dysregulated glucagon secretion in T2DM, thus improving our understanding of T2DM pathophysiology and indicating possibilities for new clinical treatments.
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Affiliation(s)
- Vladimir Grubelnik
- Faculty of Electrical Engineering and Computer Science, University of Maribor, 2000 Maribor, Slovenia
| | - Rene Markovič
- Faculty of Electrical Engineering and Computer Science, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
| | - Saška Lipovšek
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor, Slovenia
- Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical University of Graz, Neue Stiftingtalstrasse 6, 8010 Graz, Austria
| | - Gerd Leitinger
- Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical University of Graz, Neue Stiftingtalstrasse 6, 8010 Graz, Austria
| | - Marko Gosak
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
| | - Jurij Dolenšek
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
| | - Ismael Valladolid-Acebes
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, 171 76 Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, 171 76 Stockholm, Sweden
| | - Andraž Stožer
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
| | - Matjaž Perc
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan
- Complexity Science Hub Vienna, 1080 Vienna, Austria
- Authors for correspondence: Matjač Perc e-mail:
| | - Marko Marhl
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Education, University of Maribor, 2000 Maribor, Slovenia
- Authors for correspondence: Marko Marhl e-mail:
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23
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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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24
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Grubelnik V, Markovič R, Lipovšek S, Leitinger G, Gosak M, Dolenšek J, Valladolid-Acebes I, Berggren PO, Stožer A, Perc M, Marhl M. Modelling of dysregulated glucagon secretion in type 2 diabetes by considering mitochondrial alterations in pancreatic α-cells. ROYAL SOCIETY OPEN SCIENCE 2020. [PMID: 32218947 DOI: 10.5061/dryad.9n2k1vk] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Type 2 diabetes mellitus (T2DM) has been associated with insulin resistance and the failure of β-cells to produce and secrete enough insulin as the disease progresses. However, clinical treatments based solely on insulin secretion and action have had limited success. The focus is therefore shifting towards α-cells, in particular to the dysregulated secretion of glucagon. Our qualitative electron-microscopy-based observations gave an indication that mitochondria in α-cells are altered in Western-diet-induced T2DM. In particular, α-cells extracted from mouse pancreatic tissue showed a lower density of mitochondria, a less expressed matrix and a lower number of cristae. These deformities in mitochondrial ultrastructure imply a decreased efficiency in mitochondrial ATP production, which prompted us to theoretically explore and clarify one of the most challenging problems associated with T2DM, namely the lack of glucagon secretion in hypoglycaemia and its oversecretion at high blood glucose concentrations. To this purpose, we constructed a novel computational model that links α-cell metabolism with their electrical activity and glucagon secretion. Our results show that defective mitochondrial metabolism in α-cells can account for dysregulated glucagon secretion in T2DM, thus improving our understanding of T2DM pathophysiology and indicating possibilities for new clinical treatments.
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Affiliation(s)
- Vladimir Grubelnik
- Faculty of Electrical Engineering and Computer Science, University of Maribor, 2000 Maribor, Slovenia
| | - Rene Markovič
- Faculty of Electrical Engineering and Computer Science, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
| | - Saška Lipovšek
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor, Slovenia
- Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical University of Graz, Neue Stiftingtalstrasse 6, 8010 Graz, Austria
| | - Gerd Leitinger
- Division of Cell Biology, Histology and Embryology, Gottfried Schatz Research Center for Cell Signaling, Metabolism and Aging, Medical University of Graz, Neue Stiftingtalstrasse 6, 8010 Graz, Austria
| | - Marko Gosak
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
| | - Jurij Dolenšek
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
| | - Ismael Valladolid-Acebes
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, 171 76 Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital L1, 171 76 Stockholm, Sweden
| | - Andraž Stožer
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
| | - Matjaž Perc
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan
- Complexity Science Hub Vienna, 1080 Vienna, Austria
| | - Marko Marhl
- Faculty of Natural Sciences and Mathematics, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
- Faculty of Education, University of Maribor, 2000 Maribor, Slovenia
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25
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Montefusco F, Cortese G, Pedersen MG. Heterogeneous alpha-cell population modeling of glucose-induced inhibition of electrical activity. J Theor Biol 2019; 485:110036. [PMID: 31585105 DOI: 10.1016/j.jtbi.2019.110036] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 09/12/2019] [Accepted: 09/28/2019] [Indexed: 12/22/2022]
Abstract
Glucagon release from the pancreatic alpha-cells is regulated by glucose, but the underlying mechanisms are far from understood. It is known that the alpha-cell population is very heterogeneous, but - compared to the insulin-secreting beta-cells - the consequences of this cell-to-cell variation are much less studied. Since the alpha-cells are not electrically coupled, large differences in the single cell responses are to be expected, and this variation may contribute to the confusion regarding the mechanisms of glucose-induced suppression of glucagon release. Using mathematical modeling of alpha-cells with realistic cell-to-cell parameter variation based on recent experimental results, we show that the simulated alpha-cells exhibit great diversity in their electrophysiological behavior. To robustly reproduce experimental recordings from alpha-cell exposed to a rise in glucose levels, we must assume that both intrinsic mechanisms and paracrine signals contribute to glucose-induced changes in electrical activity. Our simulations suggest that the sum of different electrophysiological responses due to alpha-cell heterogeneity is involved in glucose-suppressed glucagon secretion, and that more than one mechanism contribute to control the alpha-cell populations' behavior. Finally, we apply regression analysis to our synthetic alpha-cell population to infer which membrane currents influence electrical activity in alpha-cells at different glucose levels. The results from such statistical modeling suggest possible disturbances underlying defect regulation of alpha-cell electrical behavior in diabetics. Thus, although alpha-cells appear to be inherently complex and heterogeneous as reflected in published data, realistic modeling of the alpha-cells at the population level provides insight into the mechanisms of glucagon release.
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Affiliation(s)
| | - Giuliana Cortese
- Department of Statistical Sciences, University of Padova, Padova, Italy
| | - Morten G Pedersen
- Department of Information Engineering, University of Padova, Padova, Italy; Department of Mathematics "Tullio Levi-Civita", University of Padova, Padova, Italy; Padova Neuroscience Center, University of Padova, Padova, Italy.
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26
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Janah L, Kjeldsen S, Galsgaard KD, Winther-Sørensen M, Stojanovska E, Pedersen J, Knop FK, Holst JJ, Wewer Albrechtsen NJ. Glucagon Receptor Signaling and Glucagon Resistance. Int J Mol Sci 2019; 20:E3314. [PMID: 31284506 PMCID: PMC6651628 DOI: 10.3390/ijms20133314] [Citation(s) in RCA: 104] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 06/28/2019] [Accepted: 07/03/2019] [Indexed: 02/08/2023] Open
Abstract
Hundred years after the discovery of glucagon, its biology remains enigmatic. Accurate measurement of glucagon has been essential for uncovering its pathological hypersecretion that underlies various metabolic diseases including not only diabetes and liver diseases but also cancers (glucagonomas). The suggested key role of glucagon in the development of diabetes has been termed the bihormonal hypothesis. However, studying tissue-specific knockout of the glucagon receptor has revealed that the physiological role of glucagon may extend beyond blood-glucose regulation. Decades ago, animal and human studies reported an important role of glucagon in amino acid metabolism through ureagenesis. Using modern technologies such as metabolomic profiling, knowledge about the effects of glucagon on amino acid metabolism has been expanded and the mechanisms involved further delineated. Glucagon receptor antagonists have indirectly put focus on glucagon's potential role in lipid metabolism, as individuals treated with these antagonists showed dyslipidemia and increased hepatic fat. One emerging field in glucagon biology now seems to include the concept of hepatic glucagon resistance. Here, we discuss the roles of glucagon in glucose homeostasis, amino acid metabolism, and lipid metabolism and present speculations on the molecular pathways causing and associating with postulated hepatic glucagon resistance.
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Affiliation(s)
- Lina Janah
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Sasha Kjeldsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Katrine D Galsgaard
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Marie Winther-Sørensen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Elena Stojanovska
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Jens Pedersen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Department of Cardiology, Nephrology and Endocrinology, Nordsjællands Hospital Hillerød, University of Copenhagen, 3400 Hillerød, Denmark
| | - Filip K Knop
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, 2900 Hellerup, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Steno Diabetes Center Copenhagen, 2820 Gentofte, Denmark
| | - Jens J Holst
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Nicolai J Wewer Albrechtsen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark.
- Department of Clinical Biochemistry, Rigshospitalet, 2100 Copenhagen, Denmark.
- Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, 2100 Copenhagen, Denmark.
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27
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Abstract
Controlling the excess and shortage of energy is a fundamental task for living organisms. Diabetes is a representative metabolic disease caused by the malfunction of energy homeostasis. The islets of Langerhans in the pancreas release long-range messengers, hormones, into the blood to regulate the homeostasis of the primary energy fuel, glucose. The hormone and glucose levels in the blood show rhythmic oscillations with a characteristic period of 5-10 min, and the functional roles of the oscillations are not clear. Each islet has [Formula: see text] and [Formula: see text] cells that secrete glucagon and insulin, respectively. These two counter-regulatory hormones appear sufficient to increase and decrease glucose levels. However, pancreatic islets have a third cell type, [Formula: see text] cells, which secrete somatostatin. The three cell populations have a unique spatial organization in islets, and they interact to perturb their hormone secretions. The mini-organs of islets are scattered throughout the exocrine pancreas. Considering that the human pancreas contains approximately a million islets, the coordination of hormone secretion from the multiple sources of islets and cells within the islets should have a significant effect on human physiology. In this review, we introduce the hierarchical organization of tripartite cell networks, and recent biophysical modeling to systematically understand the oscillations and interactions of [Formula: see text], [Formula: see text], and [Formula: see text] cells. Furthermore, we discuss the functional roles and clinical implications of hormonal oscillations and their phase coordination for the diagnosis of type II diabetes.
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Affiliation(s)
- Taegeun Song
- Department of Physics, Pohang University of Science and Technology, Pohang, Gyeongbuk 37673, Republic of Korea
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28
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Ojha A, Ojha U, Mohammed R, Chandrashekar A, Ojha H. Current perspective on the role of insulin and glucagon in the pathogenesis and treatment of type 2 diabetes mellitus. Clin Pharmacol 2019; 11:57-65. [PMID: 31191043 PMCID: PMC6515536 DOI: 10.2147/cpaa.s202614] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 03/28/2019] [Indexed: 01/17/2023] Open
Abstract
According to the World Health Organization, 422 million adults worldwide live with diabetes mellitus (DM), a significant portion of whom have type 2 diabetes. The discovery of insulin as a key regulator of glucose metabolism has revolutionized our understanding of DM and provided several therapeutic avenues. Most studies have so far predominantly focused on the role of insulin in type 2 diabetes. However, the balance between insulin and glucagon is essential in ensuring glucose homeostasis. In this review, we begin by evaluating the principal differences between insulin and glucagon with regard to their mechanism and control of their secretion. Next, we discuss their mode of action and effects on metabolism. We further explore how the two hormones impact the natural history of type 2 diabetes. Finally, we outline how current and emerging pharmacological agents attempt to exploit the properties of insulin and glucagon to benefit patients with type 2 diabetes.
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Affiliation(s)
- Ashutosh Ojha
- Shobhaben Pratapbhai Patel School Of Pharmacy & Technology Management, SVKM's Narsee Monjee Institute of Management Studies, Mumbai, India
| | - Utkarsh Ojha
- Faculty of Medicine, Imperial College London, London, UK
| | - Raihan Mohammed
- Department of Medicine, University of Cambridge, Cambridge, UK
| | | | - Harsh Ojha
- Department of Life Sciences, University of Warwick, Coventry, UK
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29
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Edlund A, Barghouth M, Huhn M, Abels M, Esguerra J, Mollet I, Svedin E, Wendt A, Renstrom E, Zhang E, Wierup N, Scholte BJ, Flodström-Tullberg M, Eliasson L. Defective exocytosis and processing of insulin in a cystic fibrosis mouse model. J Endocrinol 2019; 241:JOE-18-0570.R1. [PMID: 30721137 DOI: 10.1530/joe-18-0570] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 02/05/2019] [Indexed: 01/21/2023]
Abstract
Cystic fibrosis-related diabetes (CFRD) is a common complication for patients with cystic fibrosis (CF), a disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). The cause of CFRD is unclear, but a commonly observed reduction in first-phase insulin secretion suggests defects at the beta cell level. Here we aimed to examine beta- and alpha-cell function in the Cftrtm1EUR/F508del mouse model (C57BL/6J), which carries the most common human mutation in CFTR, the F508del mutation. CFTR expression, beta cell mass, insulin granule distribution, hormone secretion and single cell capacitance changes were evaluated using islets (or beta cells) from F508del mice and age-matched wild-type mice aged 7-10 weeks. Granular pH was measured with DND-189 fluorescence. Serum glucose, insulin and glucagon levels were measured in vivo, and glucose tolerance was assessed using IPGTT. We show increased secretion of proinsulin and concomitant reduced secretion of C-peptide in islets from F508del mice compared to WT mice. Exocytosis and number of docked granules was reduced. We confirmed reduced granular pH by CFTR stimulation. We detected decreased pancreatic beta cell area, but unchanged beta cell number. Moreover, the F508del mutation caused failure to suppress glucagon secretion leading to hyperglucagonemia. In conclusion, F508del mice have beta cell defects resulting in 1) reduced number of docked insulin granules and reduced exocytosis, and 2) potential defective proinsulin cleavage and secretion of immature insulin. These observations provide insight into the functional role of CFTR in pancreatic islets and contribute to increased understanding of the pathogenesis of CFRD.
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Affiliation(s)
- Anna Edlund
- A Edlund, Clinical sciences in Malmo, Lund University, Malmo, 21428, Sweden
| | - Mohammad Barghouth
- M Barghouth, Dept Clinical Sciences in Malmö, Lunds Universitet, Malmö, Sweden
| | - Michael Huhn
- M Huhn, of medicine Huddinge, Karolinska institute, Center for infectious medicine, Stockholm, Sweden
| | - Mia Abels
- M Abels, Department of clinical sciencies in Malmo, Lunds Universitet Institutionen for kliniska vetenskaper i Malmo, Malmo, Sweden
| | - Jonathan Esguerra
- J Esguerra, Clinical Sciences - Malmö, Lund University, Malmö, 21428, Sweden
| | - Ines Mollet
- I Mollet, CEDOC - Chronic Diseases Research Center, NOVA Medical School - Faculdade de Ciências Médicas, Lisboa, 1150-082, Portugal
| | - Emma Svedin
- E Svedin, Department of Medicine Huddinge, Karolinska Institutet Department of Medicine Huddinge, Stockholm, Sweden
| | - Anna Wendt
- A Wendt, Dept Clinical Sciences in Malmö, Lunds Universitet, Malmö, Sweden
| | - Erik Renstrom
- E Renstrom, Clinical Sciences Malmo, Lund University, Malmo, SE-20502, Sweden
| | - Enming Zhang
- E Zhang, Department of Clinical Science, Lund Uinversity, Malmö, 20502, Sweden
| | - Nils Wierup
- N Wierup, Department of Clinical Sciences, Lund University Diabetes Centre, Malmö, 20502, Sweden
| | - Bob J Scholte
- B Scholte, Department of Cellbiology, Pediatric Pulmonology, Erasmus MC, Rotterdam, Netherlands
| | - Malin Flodström-Tullberg
- M Flodström-Tullberg, Dept of Medicine Huddinge, Karolinska institute, Center for Infectious Medicine, Stockholm, Sweden
| | - Lena Eliasson
- L Eliasson, Dept Clinical Sciences in Malmö, Lunds Universitet, Malmö, 214 28, Sweden
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30
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Ramracheya R, Chapman C, Chibalina M, Dou H, Miranda C, González A, Moritoh Y, Shigeto M, Zhang Q, Braun M, Clark A, Johnson PR, Rorsman P, Briant LJB. GLP-1 suppresses glucagon secretion in human pancreatic alpha-cells by inhibition of P/Q-type Ca 2+ channels. Physiol Rep 2018; 6:e13852. [PMID: 30187652 PMCID: PMC6125244 DOI: 10.14814/phy2.13852] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/31/2018] [Accepted: 08/07/2018] [Indexed: 01/13/2023] Open
Abstract
Glucagon is the body's main hyperglycemic hormone, and its secretion is dysregulated in type 2 diabetes mellitus (T2DM). The incretin hormone glucagon-like peptide-1 (GLP-1) is released from the gut and is used in T2DM therapy. Uniquely, it both stimulates insulin and inhibits glucagon secretion and thereby lowers plasma glucose levels. In this study, we have investigated the action of GLP-1 on glucagon release from human pancreatic islets. Immunocytochemistry revealed that only <0.5% of the α-cells possess detectable GLP-1R immunoreactivity. Despite this, GLP-1 inhibited glucagon secretion by 50-70%. This was due to a direct effect on α-cells, rather than paracrine signaling, because the inhibition was not reversed by the insulin receptor antagonist S961 or the somatostatin receptor-2 antagonist CYN154806. The inhibitory effect of GLP-1 on glucagon secretion was prevented by the PKA-inhibitor Rp-cAMPS and mimicked by the adenylate cyclase activator forskolin. Electrophysiological measurements revealed that GLP-1 decreased action potential height and depolarized interspike membrane potential. Mathematical modeling suggests both effects could result from inhibition of P/Q-type Ca2+ channels. In agreement with this, GLP-1 and ω-agatoxin (a blocker of P/Q-type channels) inhibited glucagon secretion in islets depolarized by 70 mmol/L [K+ ]o , and these effects were not additive. Intracellular application of cAMP inhibited depolarization-evoked exocytosis in individual α-cells by a PKA-dependent (Rp-cAMPS-sensitive) mechanism. We propose that inhibition of glucagon secretion by GLP-1 involves activation of the few GLP-1 receptors present in the α-cell membrane. The resulting small elevation of cAMP leads to PKA-dependent inhibition of P/Q-type Ca2+ channels and suppression of glucagon exocytosis.
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Affiliation(s)
- Reshma Ramracheya
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Caroline Chapman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Margarita Chibalina
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Haiqiang Dou
- Institute of Neuroscience and PhysiologyMetabolic Research UnitUniversity of GöteborgGöteborgSweden
| | - Caroline Miranda
- Institute of Neuroscience and PhysiologyMetabolic Research UnitUniversity of GöteborgGöteborgSweden
| | - Alejandro González
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Yusuke Moritoh
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Makoto Shigeto
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Matthias Braun
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Anne Clark
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
| | - Paul R. Johnson
- Nuffield Department of SurgeryUniversity of OxfordJohn Radcliffe HospitalOxfordUnited Kingdom
- NIHR Oxford Biomedical Research CentreOxfordUnited Kingdom
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
- Institute of Neuroscience and PhysiologyMetabolic Research UnitUniversity of GöteborgGöteborgSweden
- NIHR Oxford Biomedical Research CentreOxfordUnited Kingdom
| | - Linford J. B. Briant
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of MedicineUniversity of OxfordOxfordUnited Kingdom
- Department of Computer ScienceUniversity of OxfordOxfordUnited Kingdom
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31
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Proks P, Kramer H, Haythorne E, Ashcroft FM. Binding of sulphonylureas to plasma proteins - A KATP channel perspective. PLoS One 2018; 13:e0197634. [PMID: 29772022 PMCID: PMC5957440 DOI: 10.1371/journal.pone.0197634] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 05/04/2018] [Indexed: 12/25/2022] Open
Abstract
Sulphonylurea drugs stimulate insulin secretion from pancreatic β-cells primarily by inhibiting ATP sensitive potassium (KATP) channels in the β-cell membrane. The effective sulphonylurea concentration at its site of action is significantly attenuated by binding to serum albumin, which makes it difficult to compare in vitro and in vivo data. We therefore measured the ability of gliclazide and glibenclamide to inhibit KATP channels and stimulate insulin secretion in the presence of serum albumin. We used this data, together with estimates of free drug concentrations from binding studies, to predict the extent of sulphonylurea inhibition of KATP channels at therapeutic concentrations in vivo. KATP currents from mouse pancreatic β-cells and Xenopus oocytes were measured using the patch-clamp technique. Gliclazide and glibenclamide binding to human plasma were determined in spiked plasma samples using an ultrafiltration-mass spectrometry approach. Bovine serum albumin (60g/l) produced a mild, non-significant reduction of gliclazide block of KATP currents in pancreatic β-cells and Xenopus oocytes. In contrast, glibenclamide inhibition of recombinant KATP channels was dramatically suppressed by albumin (predicted free drug concentration <0.1%). Insulin secretion was also reduced. Free concentrations of gliclazide and glibenclamide in the presence of human plasma measured in binding experiments were 15% and 0.05%, respectively. Our data suggest the free concentration of glibenclamide in plasma is too low to account for the drug’s therapeutic effect. In contrast, the free gliclazide concentration in plasma is high enough to close KATP channels and stimulate insulin secretion.
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Affiliation(s)
- Peter Proks
- Oxford Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Holger Kramer
- Oxford Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Elizabeth Haythorne
- Oxford Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M. Ashcroft
- Oxford Centre for Gene Function, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- * E-mail:
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32
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Abstract
Type 1 diabetes is characterized by selective loss of beta cells and insulin secretion, which significantly impact glucose homeostasis. However, this progressive disease is also associated with dysfunction of the alpha cell component of the islet, which can exacerbate hyperglycemia due to paradoxical hyperglucagonemia or lead to severe hypoglycemia as a result of failed counterregulation. In this review, the physiology of alpha cell secretion and the potential mechanisms underlying alpha cell dysfunction in type 1 diabetes will be explored. Because type 1 diabetes is a progressive disease, a synthesized timeline of aberrant alpha cell function will be presented as an attempt to delineate the natural history of type 1 diabetes with respect to the alpha cell.
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Affiliation(s)
- Gina L C Yosten
- Department of Pharmacology and Physiology, Saint Louis University School of Medicine, 1402 S. Grand Blvd, Saint Louis, MO 63104, United States.
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33
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Yu T, Jiang Z, Liu L, Fan Z. Decrease of γ-aminobutyric acid and zinc ions in the islet periportal circulation stimulates glucagon secretion during hypoglycemia. Exp Ther Med 2017; 15:2507-2511. [PMID: 29467850 DOI: 10.3892/etm.2017.5670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 07/07/2017] [Indexed: 11/05/2022] Open
Abstract
The present study assessed the effects of γ-aminobutyric acid (GABA) from β-cells on glucose levels and glucagon secretion, and identified channels via which glucagon secretion is initiated. An in vivo experiment was performed containing three groups: Intrapancreatic artery infusion of GABA alone, GABA plus insulin or insulin alone in rats with diabetes. Rats infused with GABA and insulin were also subdivided in groups receiving additional infusion of K+-channel activator diazoxide (DIA), K+-channel blocker tolbutamide (TLB) and calcium channel blocker nifedipine (NIF). In the hypoglycemic state, termination of infusion of insulin and insulin plus GABA resulted in signaling to the α-cells to secrete glycogen, while that of GABA alone did not. However, intrapancreatic artery infusion of K+-channel activator DIA, K+-channel blocker TLB or calcium channel blocker NIF in addition to GABA and insulin had no effect on glucagon secretion. In conclusion, if the delivery of insulin or GABA plus insulin in rats with hypoglycemia is terminated, β-cells are stimulated and signal the α-cells to secrete glucagon. Thus, the detection of a sudden decrease in zinc levels by β-cells as well as a decrease in GABA in the periportal circulation induces signaling to α-cells to stimulate them to secrete glucagon.
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Affiliation(s)
- Tingting Yu
- Department of Digestive Medicine, Institute of Digestive Endoscopy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210000, P.R. China.,Department of Gastroenterology, The First People's Hospital of Yancheng, Yancheng, Jiangsu 224000, P.R. China
| | - Zhonghua Jiang
- Department of Gastroenterology, The First People's Hospital of Yancheng, Yancheng, Jiangsu 224000, P.R. China
| | - Li Liu
- Department of Digestive Medicine, Institute of Digestive Endoscopy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210000, P.R. China
| | - Zhining Fan
- Department of Digestive Medicine, Institute of Digestive Endoscopy, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu 210000, P.R. China
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34
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Bozadjieva N, Blandino-Rosano M, Chase J, Dai XQ, Cummings K, Gimeno J, Dean D, Powers AC, Gittes GK, Rüegg MA, Hall MN, MacDonald PE, Bernal-Mizrachi E. Loss of mTORC1 signaling alters pancreatic α cell mass and impairs glucagon secretion. J Clin Invest 2017; 127:4379-4393. [PMID: 29106387 DOI: 10.1172/jci90004] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 09/26/2017] [Indexed: 01/19/2023] Open
Abstract
Glucagon plays a major role in the regulation of glucose homeostasis during fed and fasting states. However, the mechanisms responsible for the regulation of pancreatic α cell mass and function are not completely understood. In the current study, we identified mTOR complex 1 (mTORC1) as a major regulator of α cell mass and glucagon secretion. Using mice with tissue-specific deletion of the mTORC1 regulator Raptor in α cells (αRaptorKO), we showed that mTORC1 signaling is dispensable for α cell development, but essential for α cell maturation during the transition from a milk-based diet to a chow-based diet after weaning. Moreover, inhibition of mTORC1 signaling in αRaptorKO mice and in WT animals exposed to chronic rapamycin administration decreased glucagon content and glucagon secretion. In αRaptorKO mice, impaired glucagon secretion occurred in response to different secretagogues and was mediated by alterations in KATP channel subunit expression and activity. Additionally, our data identify the mTORC1/FoxA2 axis as a link between mTORC1 and transcriptional regulation of key genes responsible for α cell function. Thus, our results reveal a potential function of mTORC1 in nutrient-dependent regulation of glucagon secretion and identify a role for mTORC1 in controlling α cell-mass maintenance.
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Affiliation(s)
- Nadejda Bozadjieva
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and.,Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Manuel Blandino-Rosano
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and.,Department of Internal Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Jennifer Chase
- Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Xiao-Qing Dai
- Alberta Diabetes Institute and Department of Pharmacology, Edmonton, Alberta, Canada
| | - Kelsey Cummings
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and
| | - Jennifer Gimeno
- Department of Internal Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA
| | - Danielle Dean
- Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, and
| | - Alvin C Powers
- Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, and.,Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, Tennessee, USA.,VA Tennessee Valley Healthcare, Nashville, Tennessee, USA
| | - George K Gittes
- Children's Hospital, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | | | | | - Patrick E MacDonald
- Alberta Diabetes Institute and Department of Pharmacology, Edmonton, Alberta, Canada
| | - Ernesto Bernal-Mizrachi
- Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, and.,Graduate Program in Cellular and Molecular Biology, University of Michigan, Ann Arbor, Michigan, USA.,Department of Internal Medicine, Division Endocrinology, Metabolism and Diabetes, Miller School of Medicine, University of Miami, Miami, Florida, USA.,Veterans Affairs Medical Center, Miami, Florida, USA
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35
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Reissaus CA, Piston DW. Reestablishment of Glucose Inhibition of Glucagon Secretion in Small Pseudoislets. Diabetes 2017; 66:960-969. [PMID: 28130310 PMCID: PMC5360306 DOI: 10.2337/db16-1291] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 01/23/2017] [Indexed: 12/12/2022]
Abstract
Misregulated hormone secretion from the islet of Langerhans is central to the pathophysiology of diabetes. Although insulin plays a key role in glucose regulation, the importance of glucagon is increasingly acknowledged. However, the mechanisms that regulate glucagon secretion from α-cells are still unclear. We used pseudoislets reconstituted from dispersed islet cells to study α-cells with and without various indirect effects from other islet cells. Dispersed islet cells secrete aberrant levels of glucagon and insulin at basal and elevated glucose levels. When cultured, murine islet cells reassociate to form pseudoislets, which recover normal glucose-regulated hormone secretion, and human islet cells follow a similar pattern. We created small (∼40-µm) pseudoislets using all of the islet cells or only some of the cell types, which allowed us to characterize novel aspects of regulated hormone secretion. The recovery of regulated glucagon secretion from α-cells in small pseudoislets depends upon the combined action of paracrine factors, such as insulin and somatostatin, and juxtacrine signals between EphA4/7 on α-cells and ephrins on β-cells. Although these signals modulate different pathways, both appear to be required for proper inhibition of glucagon secretion in response to glucose. This improved understanding of the modulation of glucagon secretion can provide novel therapeutic routes for the treatment of some individuals with diabetes.
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Affiliation(s)
- Christopher A Reissaus
- Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, MO, and Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - David W Piston
- Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, MO, and Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
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36
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Converting Adult Pancreatic Islet α Cells into β Cells by Targeting Both Dnmt1 and Arx. Cell Metab 2017; 25:622-634. [PMID: 28215845 PMCID: PMC5358097 DOI: 10.1016/j.cmet.2017.01.009] [Citation(s) in RCA: 153] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 10/21/2016] [Accepted: 01/17/2017] [Indexed: 02/06/2023]
Abstract
Insulin-producing pancreatic β cells in mice can slowly regenerate from glucagon-producing α cells in settings like β cell loss, but the basis of this conversion is unknown. Moreover, it remains unclear if this intra-islet cell conversion is relevant to diseases like type 1 diabetes (T1D). We show that the α cell regulators Aristaless-related homeobox (Arx) and DNA methyltransferase 1 (Dnmt1) maintain α cell identity in mice. Within 3 months of Dnmt1 and Arx loss, lineage tracing and single-cell RNA sequencing revealed extensive α cell conversion into progeny resembling native β cells. Physiological studies demonstrated that converted α cells acquire hallmark β cell electrophysiology and show glucose-stimulated insulin secretion. In T1D patients, subsets of glucagon-expressing cells show loss of DNMT1 and ARX and produce insulin and other β cell factors, suggesting that DNMT1 and ARX maintain α cell identity in humans. Our work reveals pathways regulated by Arx and Dnmt1 that are sufficient for achieving targeted generation of β cells from adult pancreatic α cells.
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37
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CFTR is involved in the regulation of glucagon secretion in human and rodent alpha cells. Sci Rep 2017; 7:90. [PMID: 28273890 PMCID: PMC5428348 DOI: 10.1038/s41598-017-00098-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 02/07/2017] [Indexed: 12/15/2022] Open
Abstract
Glucagon is the main counterregulatory hormone in the body. Still, the mechanism involved in the regulation of glucagon secretion from pancreatic alpha cells remains elusive. Dysregulated glucagon secretion is common in patients with Cystic Fibrosis (CF) that develop CF related diabetes (CFRD). CF is caused by a mutation in the Cl- channel Cystic fibrosis transmembrane conductance regulator (CFTR), but whether CFTR is present in human alpha cells and regulate glucagon secretion has not been investigated in detail. Here, both human and mouse alpha cells showed CFTR protein expression, whereas CFTR was absent in somatostatin secreting delta cells. CFTR-current activity induced by cAMP was measured in single alpha cells. Glucagon secretion at different glucose levels and in the presence of forskolin was increased by CFTR-inhibition in human islets, whereas depolarization-induced glucagon secretion was unaffected. CFTR is suggested to mainly regulate the membrane potential through an intrinsic alpha cell effect, as supported by a mathematical model of alpha cell electrophysiology. In conclusion, CFTR channels are present in alpha cells and act as important negative regulators of cAMP-enhanced glucagon secretion through effects on alpha cell membrane potential. Our data support that loss-of-function mutations in CFTR contributes to dysregulated glucagon secretion in CFRD.
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38
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Briant LJB, Zhang Q, Vergari E, Kellard JA, Rodriguez B, Ashcroft FM, Rorsman P. Functional identification of islet cell types by electrophysiological fingerprinting. J R Soc Interface 2017; 14:20160999. [PMID: 28275121 PMCID: PMC5378133 DOI: 10.1098/rsif.2016.0999] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 02/15/2017] [Indexed: 01/18/2023] Open
Abstract
The α-, β- and δ-cells of the pancreatic islet exhibit different electrophysiological features. We used a large dataset of whole-cell patch-clamp recordings from cells in intact mouse islets (N = 288 recordings) to investigate whether it is possible to reliably identify cell type (α, β or δ) based on their electrophysiological characteristics. We quantified 15 electrophysiological variables in each recorded cell. Individually, none of the variables could reliably distinguish the cell types. We therefore constructed a logistic regression model that included all quantified variables, to determine whether they could together identify cell type. The model identified cell type with 94% accuracy. This model was applied to a dataset of cells recorded from hyperglycaemic βV59M mice; it correctly identified cell type in all cells and was able to distinguish cells that co-expressed insulin and glucagon. Based on this revised functional identification, we were able to improve conductance-based models of the electrical activity in α-cells and generate a model of δ-cell electrical activity. These new models could faithfully emulate α- and δ-cell electrical activity recorded experimentally.
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Affiliation(s)
- Linford J B Briant
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
| | - Quan Zhang
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
| | - Elisa Vergari
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
| | - Joely A Kellard
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
| | - Blanca Rodriguez
- Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
| | - Frances M Ashcroft
- Department of Physiology, Anatomy, and Genetics, University of Oxford, South Parks Road, Oxford OX1 3PT, UK
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology, and Metabolism, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LE, UK
- Metabolic Research, Department of Physiology, Institute of Neuroscience and Physiology, University of Göteborg, SE-405 30 Göteborg, Sweden
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39
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Yang L, Li Q, Liu X, Liu S. Roles of Voltage-Gated Tetrodotoxin-Sensitive Sodium Channels NaV1.3 and NaV1.7 in Diabetes and Painful Diabetic Neuropathy. Int J Mol Sci 2016; 17:ijms17091479. [PMID: 27608006 PMCID: PMC5037757 DOI: 10.3390/ijms17091479] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/24/2016] [Accepted: 08/25/2016] [Indexed: 02/07/2023] Open
Abstract
Diabetes mellitus (DM) is a common chronic medical problem worldwide; one of its complications is painful peripheral neuropathy, which can substantially erode quality of life and increase the cost of management. Despite its clinical importance, the pathogenesis of painful diabetic neuropathy (PDN) is complex and incompletely understood. Voltage-gated sodium channels (VGSCs) link many physiological processes to electrical activity by controlling action potentials in all types of excitable cells. Two isoforms of VGSCs, NaV1.3 and NaV1.7, which are encoded by the sodium voltage-gated channel alpha subunit 3 and 9 (Scn3A and Scn9A) genes, respectively, have been identified in both peripheral nociceptive neurons of dorsal root ganglion (DRG) and pancreatic islet cells. Recent advances in our understanding of tetrodotoxin-sensitive (TTX-S) sodium channels NaV1.3 and NaV1.7 lead to the rational doubt about the cause–effect relation between diabetes and painful neuropathy. In this review, we summarize the roles of NaV1.3 and NaV1.7 in islet cells and DRG neurons, discuss the link between DM and painful neuropathy, and present a model, which may provide a starting point for further studies aimed at identifying the mechanisms underlying diabetes and painful neuropathy.
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Affiliation(s)
- Linlin Yang
- Department of Endocrinology, The General Hospital of the PLA Rocket Force, Beijing 100088, China.
| | - Quanmin Li
- Department of Endocrinology, The General Hospital of the PLA Rocket Force, Beijing 100088, China.
| | - Xinming Liu
- Department of Endocrinology, The General Hospital of the PLA Rocket Force, Beijing 100088, China.
| | - Shiguang Liu
- Department of Endocrinology, The General Hospital of the PLA Rocket Force, Beijing 100088, China.
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40
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Semplici F, Mondragon A, Macintyre B, Madeyski-Bengston K, Persson-Kry A, Barr S, Ramne A, Marley A, McGinty J, French P, Soedling H, Yokosuka R, Gaitan J, Lang J, Migrenne-Li S, Philippe E, Herrera PL, Magnan C, da Silva Xavier G, Rutter GA. Cell type-specific deletion in mice reveals roles for PAS kinase in insulin and glucagon production. Diabetologia 2016; 59:1938-47. [PMID: 27338626 PMCID: PMC4969360 DOI: 10.1007/s00125-016-4025-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 06/01/2016] [Indexed: 12/12/2022]
Abstract
AIMS/HYPOTHESIS Per-Arnt-Sim kinase (PASK) is a nutrient-regulated domain-containing protein kinase previously implicated in the control of insulin gene expression and glucagon secretion. Here, we explore the roles of PASK in the control of islet hormone release, by generating mice with selective deletion of the Pask gene in pancreatic beta or alpha cells. METHODS Floxed alleles of Pask were produced by homologous recombination and animals bred with mice bearing beta (Ins1 (Cre); PaskBKO) or alpha (Ppg (Cre) [also known as Gcg]; PaskAKO) cell-selective Cre recombinase alleles. Glucose homeostasis and hormone secretion in vivo and in vitro, gene expression and islet cell mass were measured using standard techniques. RESULTS Ins1 (Cre)-based recombination led to efficient beta cell-targeted deletion of Pask. Beta cell mass was reduced by 36.5% (p < 0.05) compared with controls in PaskBKO mice, as well as in global Pask-null mice (38%, p < 0.05). PaskBKO mice displayed normal body weight and fasting glycaemia, but slightly impaired glucose tolerance, and beta cell proliferation, after maintenance on a high-fat diet. Whilst glucose tolerance was unaffected in PaskAKO mice, glucose infusion rates were increased, and glucagon secretion tended to be lower, during hypoglycaemic clamps. Although alpha cell mass was increased (21.9%, p < 0.05), glucagon release at low glucose was impaired (p < 0.05) in PaskAKO islets. CONCLUSIONS/INTERPRETATION The findings demonstrate cell-autonomous roles for PASK in the control of pancreatic endocrine hormone secretion. Differences between the glycaemic phenotype of global vs cell type-specific null mice suggest important roles for tissue interactions in the control of glycaemia by PASK.
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Affiliation(s)
- Francesca Semplici
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK
| | - Angeles Mondragon
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK
| | - Benedict Macintyre
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK
| | - Katja Madeyski-Bengston
- AstraZeneca R&D, DECS, AstraZeneca R&D, Mölndal, Sweden
- AstraZeneca R&D, HC3020, AstraZeneca R&D, Mölndal, Sweden
| | - Anette Persson-Kry
- AstraZeneca R&D, DECS, AstraZeneca R&D, Mölndal, Sweden
- AstraZeneca R&D, HC3020, AstraZeneca R&D, Mölndal, Sweden
| | - Sara Barr
- AstraZeneca R&D, DECS, AstraZeneca R&D, Mölndal, Sweden
- AstraZeneca R&D, HC3020, AstraZeneca R&D, Mölndal, Sweden
| | - Anna Ramne
- AstraZeneca R&D, DECS, AstraZeneca R&D, Mölndal, Sweden
- AstraZeneca R&D, HC3020, AstraZeneca R&D, Mölndal, Sweden
| | | | - James McGinty
- Photonics Group, Department of Physics, Imperial College London, London, UK
| | - Paul French
- Photonics Group, Department of Physics, Imperial College London, London, UK
| | - Helen Soedling
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK
| | - Ryohsuke Yokosuka
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK
| | - Julien Gaitan
- Université de Bordeaux, Institut de Chimie et Biologie des Membranes et des Nano-objets, CNRS UMR 5248, Pessac, France
| | - Jochen Lang
- Université de Bordeaux, Institut de Chimie et Biologie des Membranes et des Nano-objets, CNRS UMR 5248, Pessac, France
| | - Stephanie Migrenne-Li
- Paris Diderot University, Unit of Functional and Adaptive Biology (BFA), CNRS UMR 8251, Paris, France
| | - Erwann Philippe
- Paris Diderot University, Unit of Functional and Adaptive Biology (BFA), CNRS UMR 8251, Paris, France
| | - Pedro L Herrera
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Christophe Magnan
- Paris Diderot University, Unit of Functional and Adaptive Biology (BFA), CNRS UMR 8251, Paris, France
| | - Gabriela da Silva Xavier
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK.
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, Imperial Centre for Translational and Experimental Medicine, Hammersmith Hospital, du Cane Road, London, W12 0NN, UK.
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41
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Dapagliflozin stimulates glucagon secretion at high glucose: experiments and mathematical simulations of human A-cells. Sci Rep 2016; 6:31214. [PMID: 27535321 PMCID: PMC4989223 DOI: 10.1038/srep31214] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Accepted: 06/07/2016] [Indexed: 01/10/2023] Open
Abstract
Glucagon is one of the main regulators of blood glucose levels and dysfunctional stimulus secretion coupling in pancreatic A-cells is believed to be an important factor during development of diabetes. However, regulation of glucagon secretion is poorly understood. Recently it has been shown that Na+/glucose co-transporter (SGLT) inhibitors used for the treatment of diabetes increase glucagon levels in man. Here, we show experimentally that the SGLT2 inhibitor dapagliflozin increases glucagon secretion at high glucose levels both in human and mouse islets, but has little effect at low glucose concentrations. Because glucagon secretion is regulated by electrical activity we developed a mathematical model of A-cell electrical activity based on published data from human A-cells. With operating SGLT2, simulated glucose application leads to cell depolarization and inactivation of the voltage-gated ion channels carrying the action potential, and hence to reduce action potential height. According to our model, inhibition of SGLT2 reduces glucose-induced depolarization via electrical mechanisms. We suggest that blocking SGLTs partly relieves glucose suppression of glucagon secretion by allowing full-scale action potentials to develop. Based on our simulations we propose that SGLT2 is a glucose sensor and actively contributes to regulation of glucagon levels in humans which has clinical implications.
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42
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Stern JH, Rutkowski JM, Scherer PE. Adiponectin, Leptin, and Fatty Acids in the Maintenance of Metabolic Homeostasis through Adipose Tissue Crosstalk. Cell Metab 2016; 23:770-84. [PMID: 27166942 PMCID: PMC4864949 DOI: 10.1016/j.cmet.2016.04.011] [Citation(s) in RCA: 677] [Impact Index Per Article: 84.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Metabolism research has made tremendous progress over the last several decades in establishing the adipocyte as a central rheostat in the regulation of systemic nutrient and energy homeostasis. Operating at multiple levels of control, the adipocyte communicates with organ systems to adjust gene expression, glucoregulatory hormone exocytosis, enzymatic reactions, and nutrient flux to equilibrate the metabolic demands of a positive or negative energy balance. The identification of these mechanisms has great potential to identify novel targets for the treatment of diabetes and related metabolic disorders. Herein, we review the central role of the adipocyte in the maintenance of metabolic homeostasis, highlighting three critical mediators: adiponectin, leptin, and fatty acids.
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Affiliation(s)
- Jennifer H Stern
- Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Joseph M Rutkowski
- Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Philipp E Scherer
- Touchstone Diabetes Center, Department of Internal Medicine, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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43
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Gylfe E. Glucose control of glucagon secretion-'There's a brand-new gimmick every year'. Ups J Med Sci 2016; 121:120-32. [PMID: 27044660 PMCID: PMC4900067 DOI: 10.3109/03009734.2016.1154905] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 11/13/2022] Open
Abstract
Glucagon from the pancreatic α-cells is a major blood glucose-regulating hormone whose most important role is to prevent hypoglycaemia that can be life-threatening due to the brain's strong dependence on glucose as energy source. Lack of blood glucose-lowering insulin after malfunction or autoimmune destruction of the pancreatic β-cells is the recognized cause of diabetes, but recent evidence indicates that diabetic hyperglycaemia would not develop unless lack of insulin was accompanied by hypersecretion of glucagon. Glucagon release has therefore become an increasingly important target in diabetes management. Despite decades of research, an understanding of how glucagon secretion is regulated remains elusive, and fundamentally different mechanisms continue to be proposed. The autonomous nervous system is an important determinant of glucagon release, but it is clear that secretion is also directly regulated within the pancreatic islets. The present review focuses on pancreatic islet mechanisms involved in glucose regulation of glucagon release. It will be argued that α-cell-intrinsic processes are most important for regulation of glucagon release during recovery from hypoglycaemia and that paracrine inhibition by somatostatin from the δ-cells shapes pulsatile glucagon release in hyperglycaemia. The electrically coupled β-cells ultimately determine islet hormone pulsatility by releasing synchronizing factors that affect the α- and δ-cells.
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Affiliation(s)
- Erik Gylfe
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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44
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Montefusco F, Pedersen MG. Mathematical modelling of local calcium and regulated exocytosis during inhibition and stimulation of glucagon secretion from pancreatic alpha-cells. J Physiol 2015; 593:4519-30. [PMID: 26236035 DOI: 10.1113/jp270777] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 07/28/2015] [Indexed: 02/06/2023] Open
Abstract
Glucagon secretion from pancreatic alpha-cells is dysregulated in diabetes. Despite decades of investigations of the control of glucagon release by glucose and hormones, the underlying mechanisms are still debated. Recently, mathematical models have been applied to investigate the modification of electrical activity in alpha-cells as a result of glucose application. However, recent studies have shown that paracrine effects such as inhibition of glucagon secretion by glucagon-like peptide 1 (GLP-1) or stimulation of release by adrenaline involve cAMP-mediated effects downstream of electrical activity. In particular, depending of the intracellular cAMP concentration, specific types of Ca(2+) channels are inhibited or activated, which interacts with mobilization of secretory granules. To investigate these aspects of alpha-cell function theoretically, we carefully developed a mathematical model of Ca(2+) levels near open or closed Ca(2+) channels of various types, which was linked to a description of Ca(2+) below the plasma membrane, in the bulk cytosol and in the endoplasmic reticulum. We investigated how the various subcellular Ca(2+) compartments contribute to control of glucagon-exocytosis in response to glucose, GLP-1 or adrenaline. Our studies refine previous modelling studies of alpha-cell function, and provide deeper insight into the control of glucagon secretion.
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Affiliation(s)
- Francesco Montefusco
- Department of Information Engineering, University of Padova, Via Gradenigo 6/B, 35131, Padova, Italy
| | - Morten Gram Pedersen
- Department of Information Engineering, University of Padova, Via Gradenigo 6/B, 35131, Padova, Italy
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45
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Grabauskas G, Wu X, Lu Y, Heldsinger A, Song I, Zhou SY, Owyang C. KATP channels in the nodose ganglia mediate the orexigenic actions of ghrelin. J Physiol 2015; 593:3973-89. [PMID: 26174421 PMCID: PMC4575581 DOI: 10.1113/jp270788] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 06/26/2015] [Indexed: 12/21/2022] Open
Abstract
Ghrelin, a hunger signalling peptide derived from the peripheral tissues, overcomes the satiety signals evoked by anorexigenic molecules, such as cholecystokinin (CCK) and leptin, to stimulate feeding. Using in vivo and in vitro electrophysiological techniques, we show that ghrelin hyperpolarizes neurons and inhibits currents evoked by leptin and CCK-8. Administering a KATP channel antagonist or silencing Kir6.2, a major subunit of the KATP channel, abolished ghrelin inhibition. The inhibitory actions of ghrelin were also abolished by treating the vagal ganglia neurons with pertussis toxin, as well as phosphatidylinositol 3-kinase (PI3K) or extracellular signal-regulated kinase 1 and 2 (Erk1/2) small interfering RNA. Feeding experiments showed that silencing Kir6.2 in the vagal ganglia abolished the orexigenic actions of ghrelin. These data indicate that ghrelin modulates vagal ganglia neuron excitability by activating KATP conductance via the growth hormone secretagogue receptor subtype 1a-Gαi -PI3K-Erk1/2-KATP pathway. This provides a mechanism to explain the actions of ghrelin with respect to overcoming anorexigenic signals that act via the vagal afferent pathways. Ghrelin is the only known hunger signal derived from the peripheral tissues. Ghrelin overcomes the satiety signals evoked by anorexigenic molecules, such as cholecystokinin (CCK) and leptin, to stimulate feeding. The mechanisms by which ghrelin reduces the sensory signals evoked by anorexigenic hormones, which act via the vagus nerve to stimulate feeding, are unknown. Patch clamp recordings of isolated rat vagal neurons show that ghrelin hyperpolarizes neurons by activating K(+) conductance. Administering a KATP channel antagonist or silencing Kir6.2, a major subunit of the KATP channel, abolished ghrelin inhibition in vitro and in vivo. Patch clamp studies show that ghrelin inhibits currents evoked by leptin and CCK-8, which operate through independent ionic channels. The inhibitory actions of ghrelin were abolished by treating the vagal ganglia neurons with pertussis toxin, as well as phosphatidylinositol 3-kinase (PI3K) or extracellular signal-regulated kinase 1 and 2 (Erk1/2) small interfering RNA. In vivo gene silencing of PI3K and Erk1/2 in the nodose ganglia prevented ghrelin inhibition of leptin- or CCK-8-evoked vagal firing. Feeding experiments showed that silencing Kir6.2 in the vagal ganglia abolished the orexigenic actions of ghrelin. These data indicate that ghrelin modulates vagal ganglia neuron excitability by activating KATP conductance via the growth hormone secretagogue receptor subtype 1a-Gαi -PI3K-Erk1/2-KATP pathway. The resulting hyperpolarization renders the neurons less responsive to signals evoked by anorexigenic hormones. This provides a mechanism to explain the actions of ghrelin with respect to overcoming anorexigenic signals that act via the vagal afferent pathways.
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Affiliation(s)
- Gintautas Grabauskas
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
| | - Xiaoyin Wu
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
| | - Yuanxu Lu
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
| | - Andrea Heldsinger
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
| | - Il Song
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
| | - Shi-Yi Zhou
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
| | - Chung Owyang
- Division of Gastroenterology, Department of Internal Medicine, University of Michigan Health SystemAnn Arbor, MI, USA
- Corresponding author C. Owyang: 3912 Taubman Center, SPC 5362, 1500 East Medical Center Drive, University of Michigan Health System, Ann Arbor, MI 48109, USA.
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Inhibition of the malate-aspartate shuttle in mouse pancreatic islets abolishes glucagon secretion without affecting insulin secretion. Biochem J 2015; 468:49-63. [PMID: 25731850 DOI: 10.1042/bj20140697] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Altered secretion of insulin as well as glucagon has been implicated in the pathogenesis of Type 2 diabetes (T2D), but the mechanisms controlling glucagon secretion from α-cells largely remain unresolved. Therefore, we studied the regulation of glucagon secretion from αTC1-6 (αTC1 clone 6) cells and compared it with insulin release from INS-1 832/13 cells. We found that INS-1 832/13 and αTC1-6 cells respectively secreted insulin and glucagon concentration-dependently in response to glucose. In contrast, tight coupling of glycolytic and mitochondrial metabolism was observed only in INS-1 832/13 cells. Although glycolytic metabolism was similar in the two cell lines, TCA (tricarboxylic acid) cycle metabolism, respiration and ATP levels were less glucose-responsive in αTC1-6 cells. Inhibition of the malate-aspartate shuttle, using phenyl succinate (PhS), abolished glucose-provoked ATP production and hormone secretion from αTC1-6 but not INS-1 832/13 cells. Blocking the malate-aspartate shuttle increased levels of glycerol 3-phosphate only in INS-1 832/13 cells. Accordingly, relative expression of constituents in the glycerol phosphate shuttle compared with malate-aspartate shuttle was lower in αTC1-6 cells. Our data suggest that the glycerol phosphate shuttle augments the malate-aspartate shuttle in INS-1 832/13 but not αTC1-6 cells. These results were confirmed in mouse islets, where PhS abrogated secretion of glucagon but not insulin. Furthermore, expression of the rate-limiting enzyme of the glycerol phosphate shuttle was higher in sorted primary β- than in α-cells. Thus, suppressed glycerol phosphate shuttle activity in the α-cell may prevent a high rate of glycolysis and consequently glucagon secretion in response to glucose. Accordingly, pyruvate- and lactate-elicited glucagon secretion remains unaffected since their signalling is independent of mitochondrial shuttles.
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Oya M, Kitaguchi T, Harada K, Numano R, Sato T, Kojima M, Tsuboi T. Low glucose-induced ghrelin secretion is mediated by an ATP-sensitive potassium channel. J Endocrinol 2015; 226:25-34. [PMID: 26099355 DOI: 10.1530/joe-15-0090] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ghrelin is synthesized in X/A-like cells of the gastric mucosa, which plays an important role in the regulation of energy homeostasis. Although ghrelin secretion is known to be induced by neurotransmitters or hormones or by nutrient sensing in the ghrelin-secreting cells themselves, the mechanism of ghrelin secretion is not clearly understood. In the present study, we found that changing the extracellular glucose concentration from elevated (25 mM) to optimal (10 mM) caused an increase in the intracellular Ca2+ concentration ([Ca2+]i) in ghrelin-secreting mouse ghrelinoma 3-1 (MGN3-1) cells (n=32, P<0.01), whereas changing the glucose concentration from elevated to lowered (5 or 1 mM) had little effect on [Ca2+]i increase. Overexpression of a closed form of an ATP-sensitive K+ (KATP) channel mutant suppressed the 10 mM glucose-induced [Ca2+]i increase (n=8, P<0.01) and exocytotic events (n=6, P<0.01). We also found that a low concentration of a KATP channel opener, diazoxide, with 25 mM glucose induced [Ca2+]i increase (n=23, P<0.01) and ghrelin secretion (n≥3, P<0.05). In contrast, the application of a low concentration of a KATP channel blocker, tolbutamide, significantly induced [Ca2+]i increase (n=15, P<0.01) and ghrelin secretion (n≥3, P<0.05) under 5 mM glucose. Furthermore, the application of voltage-dependent Ca2+ channel inhibitors suppressed the 10 mM glucose-induced [Ca2+]i increase (n≥26, P<0.01) and ghrelin secretion (n≥5, P<0.05). These findings suggest that KATP and voltage-dependent Ca2+ channels are involved in glucose-dependent ghrelin secretion in MGN3-1 cells.
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Affiliation(s)
- Manami Oya
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Tetsuya Kitaguchi
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Kazuki Harada
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Rika Numano
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Takahiro Sato
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Masayasu Kojima
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
| | - Takashi Tsuboi
- Department of Life SciencesGraduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, JapanCell Signaling GroupWASEDA Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, #05-02 Helios, Singapore 138667, SingaporeOrganization for University Research InitiativesWaseda University, #304, Block 120-4, 513 Wasedatsurumaki-cho, Shinjuku-ku, Tokyo 162-0041, JapanDepartment of Environmental and Life SciencesElectronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, 1-1 Hibarigaoka, Tennpaku-cho, Toyohashi, Aichi 441-8580, JapanMolecular GeneticsInstitute of Life Sciences, Kurume University, 1-1 Hyakunen Kohen, Kurume, Fukuoka 839-0864, Japan
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Christensen GL, Jacobsen MLB, Wendt A, Mollet IG, Friberg J, Frederiksen KS, Meyer M, Bruun C, Eliasson L, Billestrup N. Bone morphogenetic protein 4 inhibits insulin secretion from rodent beta cells through regulation of calbindin1 expression and reduced voltage-dependent calcium currents. Diabetologia 2015; 58:1282-90. [PMID: 25828920 DOI: 10.1007/s00125-015-3568-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 03/04/2015] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Type 2 diabetes is characterised by progressive loss of pancreatic beta cell mass and function. Therefore, it is of therapeutic interest to identify factors with the potential to improve beta cell proliferation and insulin secretion. Bone morphogenetic protein 4 (BMP4) expression is increased in diabetic animals and BMP4 reduces glucose-stimulated insulin secretion (GSIS). Here, we investigate the molecular mechanism behind this inhibition. METHODS BMP4-mediated inhibition of GSIS was investigated in detail using single cell electrophysiological measurements and live cell Ca(2+) imaging. BMP4-mediated gene expression changes were investigated by microarray profiling, quantitative PCR and western blotting. RESULTS Prolonged exposure to BMP4 reduced GSIS from rodent pancreatic islets. This inhibition was associated with decreased exocytosis due to a reduced Ca(2+) current through voltage-dependent Ca(2+) channels. To identify proteins involved in the inhibition of GSIS, we investigated global gene expression changes induced by BMP4 in neonatal rat pancreatic islets. Expression of the Ca(2+)-binding protein calbindin1 was significantly induced by BMP4. Overexpression of calbindin1 in primary islet cells reduced GSIS, and the effect of BMP4 on GSIS was lost in islets from calbindin1 (Calb1) knockout mice. CONCLUSIONS/INTERPRETATION We found BMP4 treatment to markedly inhibit GSIS from rodent pancreatic islets in a calbindin1-dependent manner. Calbindin1 is suggested to mediate the effect of BMP4 by buffering Ca(2+) and decreasing Ca(2+) channel activity, resulting in diminished insulin exocytosis. Both BMP4 and calbindin1 are potential pharmacological targets for the treatment of beta cell dysfunction.
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Affiliation(s)
- Gitte L Christensen
- Department of Biomedical Sciences, University of Copenhagen, Nørre Alle 20, 2100, Copenhagen, Denmark
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49
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Diethyldithiocarbamate-mediated zinc ion chelation reveals role of Cav2.3 channels in glucagon secretion. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:953-64. [DOI: 10.1016/j.bbamcr.2015.01.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 12/28/2014] [Accepted: 01/03/2015] [Indexed: 12/13/2022]
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Li J, Yu Q, Ahooghalandari P, Gribble FM, Reimann F, Tengholm A, Gylfe E. Submembrane ATP and Ca2+ kinetics in α-cells: unexpected signaling for glucagon secretion. FASEB J 2015; 29:3379-88. [PMID: 25911612 PMCID: PMC4539996 DOI: 10.1096/fj.14-265918] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 04/16/2015] [Indexed: 11/11/2022]
Abstract
Cytoplasmic ATP and Ca(2+) are implicated in current models of glucose's control of glucagon and insulin secretion from pancreatic α- and β-cells, respectively, but little is known about ATP and its relation to Ca(2+) in α-cells. We therefore expressed the fluorescent ATP biosensor Perceval in mouse pancreatic islets and loaded them with a Ca(2+) indicator. With total internal reflection fluorescence microscopy, we recorded subplasma membrane concentrations of Ca(2+) and ATP ([Ca(2+)]pm; [ATP]pm) in superficial α- and β-cells of intact islets and related signaling to glucagon and insulin secretion by immunoassay. Consistent with ATP's controlling glucagon and insulin secretion during hypo- and hyperglycemia, respectively, the dose-response relationship for glucose-induced [ATP]pm generation was left shifted in α-cells compared to β-cells. Both cell types showed [Ca(2+)]pm and [ATP]pm oscillations in opposite phase, probably reflecting energy-consuming Ca(2+) transport. Although pulsatile insulin and glucagon release are in opposite phase, [Ca(2+)]pm synchronized in the same phase between α- and β-cells. This paradox can be explained by the overriding of Ca(2+) stimulation by paracrine inhibition, because somatostatin receptor blockade potently stimulated glucagon release with little effect on Ca(2+). The data indicate that an α-cell-intrinsic mechanism controls glucagon in hypoglycemia and that paracrine factors shape pulsatile secretion in hyperglycemia.
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Affiliation(s)
- Jia Li
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Qian Yu
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Parvin Ahooghalandari
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Fiona M Gribble
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Frank Reimann
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Anders Tengholm
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Erik Gylfe
- *Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden; and Cambridge Institute for Medical Research, Addenbrooke's Hospital, Cambridge, United Kingdom
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