51
|
Asadi F, Dhanvantari S. Plasticity in the Glucagon Interactome Reveals Novel Proteins That Regulate Glucagon Secretion in α-TC1-6 Cells. Front Endocrinol (Lausanne) 2019; 9:792. [PMID: 30713523 PMCID: PMC6346685 DOI: 10.3389/fendo.2018.00792] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 12/17/2018] [Indexed: 12/27/2022] Open
Abstract
Glucagon is stored within the secretory granules of pancreatic alpha cells until stimuli trigger its release. The alpha cell secretory responses to the stimuli vary widely, possibly due to differences in experimental models or microenvironmental conditions. We hypothesized that the response of the alpha cell to various stimuli could be due to plasticity in the network of proteins that interact with glucagon within alpha cell secretory granules. We used tagged glucagon with Fc to pull out glucagon from the enriched preparation of secretory granules in α-TC1-6 cells. Isolation of secretory granules was validated by immunoisolation with Fc-glucagon and immunoblotting for organelle-specific proteins. Isolated enriched secretory granules were then used for affinity purification with Fc-glucagon followed by liquid chromatography/tandem mass spectrometry to identify secretory granule proteins that interact with glucagon. Proteomic analyses revealed a network of proteins containing glucose regulated protein 78 KDa (GRP78) and histone H4. The interaction between glucagon and the ER stress protein GRP78 and histone H4 was confirmed through co-immunoprecipitation of secretory granule lysates, and colocalization immunofluorescence confocal microscopy. Composition of the protein networks was altered at different glucose levels (25 vs. 5.5 mM) and in response to the paracrine inhibitors of glucagon secretion, GABA and insulin. siRNA-mediated silencing of a subset of these proteins revealed their involvement in glucagon secretion in α-TC1-6 cells. Therefore, our results show a novel and dynamic glucagon interactome within α-TC1-6 cell secretory granules. We suggest that variations in the alpha cell secretory response to stimuli may be governed by plasticity in the glucagon "interactome."
Collapse
Affiliation(s)
- Farzad Asadi
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Savita Dhanvantari
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
- Metabolism, Diabetes and Imaging Programs, Lawson Health Research Institute, London, ON, Canada
| |
Collapse
|
52
|
Zhong F, Jiang Y. Endogenous Pancreatic β Cell Regeneration: A Potential Strategy for the Recovery of β Cell Deficiency in Diabetes. Front Endocrinol (Lausanne) 2019; 10:101. [PMID: 30842756 PMCID: PMC6391341 DOI: 10.3389/fendo.2019.00101] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 02/04/2019] [Indexed: 12/11/2022] Open
Abstract
Endogenous pancreatic β cell regeneration is a potential strategy for β cell expansion or neogenesis to treat diabetes. Regeneration can occur through stimulation of existing β cell replication or conversion of other pancreatic cells into β cells. Recently, various strategies and approaches for stimulation of endogenous β cell regeneration have been evaluated, but they were not suitable for clinical application. In this paper, we comprehensively review these strategies, and further discuss various factors involved in regulation of β cell regeneration under physiological or pathological conditions, such as mediators, transcription factors, signaling pathways, and potential pharmaceutical drugs. Furthermore, we discuss possible reasons for the failure of regenerative medicines in clinical trials, and possible strategies for improving β cell regeneration. As β cell heterogeneity and plasticity determines their function and environmental adaptability, we focus on β cell subtype markers and discuss the importance of research evaluating the characteristics of new β cells. In addition, based on the autoimmunologic features of type 1 diabetes, NOD/Lt-SCID-IL2rg null (NSG) mice grafted with human immune cells and β cells are recommended for use in evaluation of antidiabetic regenerative medicines. This review will further understand current advances in endogenous β cell regeneration, and provide potential new strategies for the treatment of diabetes focused on cell therapy.
Collapse
Affiliation(s)
- Fan Zhong
- Department of Gastroenterology, Songjiang Hospital Affiliated First People's Hospital, Shanghai Jiao Tong University, Shanghai, China
- Institutes of Biomedical Sciences of Shanghai Medical College, Fudan University, Shanghai, China
| | - Yan Jiang
- Institutes of Biomedical Sciences of Shanghai Medical College, Fudan University, Shanghai, China
- *Correspondence: Yan Jiang
| |
Collapse
|
53
|
Skelin M, Bursa D, Kozina V, Winters T, Macan M, Urlin M. Key molecules in the GABA signalling pathway are present in mouse and human cervical tissue. Reprod Fertil Dev 2018; 30:1267-1275. [PMID: 29665953 DOI: 10.1071/rd17333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 03/04/2018] [Indexed: 11/23/2022] Open
Abstract
Cervical mucus modulates fertility by cyclical changes of its biophysical and functional properties. Based on an analogy with bronchial goblet cells we set out to investigate the possible role of the gamma-aminobutyric acid (GABA) signalling pathway in the mediation of oestrogen-induced mucus secretion from endocervical secretory cells. The aim of the study was to examine the existence of GABAA receptor (GABAAR), glutamic acid decarboxylase 65/67 (GAD65/67) and vesicular GABA transporter (VGAT) in human and mouse cervical tissue. The mouse cervical tissue expressed GabaAR mRNA transcripts throughout the oestrous cycle. GABAAR-positive immunolabelling was present in the superficial layer of the mouse cervico-vaginal epithelium in pro-oestrus. Human cervical tissue showed the presence of GABAAR, GAD67 and VGAT mRNA transcripts and clear immunofluorescent signals of all three molecules were detected in the endocervical secretory epithelium. The results of this study confirmed that elements of the GABA signalling pathway are present in the secretory epithelium of mouse and human cervical tissue and that GABA signalling pathway could be considered a possible mediator in oestrogen regulation of mucus secretion in the endocervical glands.
Collapse
Affiliation(s)
- Marta Skelin
- Department of Histology and Embryology, University of Zagreb School of Medicine, Šalata 3, 10000 Zagreb, Croatia
| | - Danijel Bursa
- Department of Obstetrics and Gynaecology, Merkur Clinical Hospital, Zaj?eva 19, 10000 Zagreb, Croatia
| | - Viviana Kozina
- Department of Histology and Embryology, University of Zagreb School of Medicine, Šalata 3, 10000 Zagreb, Croatia
| | - Tristan Winters
- Medical Faculty Carl Gustav Carus, Institute of Physiological Chemistry Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden, Germany
| | - Marija Macan
- Department of Gynaecological and Perinatal Pathology, University Hospital Centre Zagreb, University of Zagreb School of Medicine, Kišpati?eva 12, 10000 Zagreb, Croatia
| | - Marija Urlin
- Department of Histology and Embryology, University of Zagreb School of Medicine, Šalata 3, 10000 Zagreb, Croatia
| |
Collapse
|
54
|
Functional Characterization of Native, High-Affinity GABA A Receptors in Human Pancreatic β Cells. EBioMedicine 2018; 30:273-282. [PMID: 29606630 PMCID: PMC5952339 DOI: 10.1016/j.ebiom.2018.03.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Revised: 02/02/2018] [Accepted: 03/12/2018] [Indexed: 01/19/2023] Open
Abstract
In human pancreatic islets, the neurotransmitter γ-aminobutyric acid (GABA) is an extracellular signaling molecule synthesized by and released from the insulin-secreting β cells. The effective, physiological GABA concentration range within human islets is unknown. Here we use native GABAA receptors in human islet β cells as biological sensors and reveal that 100–1000 nM GABA elicit the maximal opening frequency of the single-channels. In saturating GABA, the channels desensitized and stopped working. GABA modulated insulin exocytosis and glucose-stimulated insulin secretion. GABAA receptor currents were enhanced by the benzodiazepine diazepam, the anesthetic propofol and the incretin glucagon-like peptide-1 (GLP-1) but not affected by the hypnotic zolpidem. In type 2 diabetes (T2D) islets, single-channel analysis revealed higher GABA affinity of the receptors. The findings reveal unique GABAA receptors signaling in human islets β cells that is GABA concentration-dependent, differentially regulated by drugs, modulates insulin secretion and is altered in T2D. In human islets GABA (≤μM) activates β cell-specific GABAA receptors that become supersensitive to GABA in type 2 diabetes. GABAA receptors activity in β cells is enhanced by diazepam, anesthetics, the incretin GLP-1 but not the hypnotic zolpidem. GABA modulates rate of insulin granule exocytosis and glucose-stimulated insulin secretion.
GABA is a signal molecule in the brain but is also secreted by the insulin-producing β cells in pancreatic islets. GABA has many roles in human islets that most aim at optimizing function and survival of β cells. In the report by Korol, Jin et al. the authors identify and characterize the molecular unit that GABA binds to in human β cells, the GABAA receptors. These receptors normally sensitive become super-sensitive to GABA in type 2 diabetes. The GABAA receptors regulate insulin secretion and can themselves be regulated by the anxiolytic diazepam, anesthetics, the incretin GLP-1 but not the hypnotic zolpidem. Targeting GABA signaling in human islets in diabetes mellitus is likely to be a part of the solution when curing diabetes.
Collapse
|
55
|
Sharma A, Varghese RT, Shah M, Man CD, Cobelli C, Rizza RA, Bailey KR, Vella A. Impaired Insulin Action Is Associated With Increased Glucagon Concentrations in Nondiabetic Humans. J Clin Endocrinol Metab 2018; 103:314-319. [PMID: 29126197 PMCID: PMC5761487 DOI: 10.1210/jc.2017-01197] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 11/01/2017] [Indexed: 01/18/2023]
Abstract
CONTEXT Abnormal glucagon concentrations contribute to hyperglycemia, but the mechanisms of α-cell dysfunction in prediabetes are unclear. OBJECTIVE We sought to determine the relative contributions of insulin secretion and action to α-cell dysfunction in nondiabetic participants across the spectrum of glucose tolerance. DESIGN This was a cross-sectional study. A subset of participants (n = 120) was studied in the presence and absence of free fatty acid (FFA) elevation, achieved by infusion of Intralipid (Baxter Healthcare, Deerfield, IL) plus heparin, to cause insulin resistance. SETTING An inpatient clinical research unit at an academic medical center. PARTICIPANTS A total of 310 nondiabetic persons participated in this study. INTERVENTIONS Participants underwent a seven-sample oral glucose tolerance test. Subsequently, 120 participants were studied on two occasions. On one day, infusion of Intralipid plus heparin raised FFA. On the other day, participants received glycerol as a control. MAIN OUTCOME MEASURE(S) We examined the relationship of glucagon concentration with indices of insulin action after adjusting for the effects of age, sex, and weight. Subsequently, we sought to determine whether an acute decrease in insulin action, produced by FFA elevation, altered glucagon concentrations in nondiabetic participants. RESULTS Fasting glucagon concentrations correlated positively with fasting insulin and C-peptide concentrations and inversely with insulin action. Fasting glucagon was not associated with any index of β-cell function in response to an oral challenge. As expected, FFA elevation decreased insulin action and also raised glucagon concentrations. CONCLUSIONS In nondiabetic participants, glucagon secretion was altered by changes in insulin action.
Collapse
Affiliation(s)
- Anu Sharma
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Ron T. Varghese
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Meera Shah
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Chiara Dalla Man
- Department of Information Engineering, Università di Padova, 35131 Padova, Italy
| | - Claudio Cobelli
- Department of Information Engineering, Università di Padova, 35131 Padova, Italy
| | - Robert A. Rizza
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Kent R. Bailey
- Biomedical Statistics and Informatics, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Adrian Vella
- Division of Endocrinology, Diabetes & Metabolism, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| |
Collapse
|
56
|
Tian J, Dang H, Hu A, Xu W, Kaufman DL. Repurposing Lesogaberan to Promote Human Islet Cell Survival and β-Cell Replication. J Diabetes Res 2017; 2017:6403539. [PMID: 29018828 PMCID: PMC5605788 DOI: 10.1155/2017/6403539] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 07/26/2017] [Indexed: 12/15/2022] Open
Abstract
The activation of β-cell's A- and B-type gamma-aminobutyric acid receptors (GABAA-Rs and GABAB-Rs) can promote their survival and replication, and the activation of α-cell GABAA-Rs promotes their conversion into β-cells. However, GABA and the most clinically applicable GABA-R ligands may be suboptimal for the long-term treatment of diabetes due to their pharmacological properties or potential side-effects on the central nervous system (CNS). Lesogaberan (AZD3355) is a peripherally restricted high-affinity GABAB-R-specific agonist, originally developed for the treatment of gastroesophageal reflux disease (GERD) that appears to be safe for human use. This study tested the hypothesis that lesogaberan could be repurposed to promote human islet cell survival and β-cell replication. Treatment with lesogaberan significantly enhanced replication of human islet cells in vitro, which was abrogated by a GABAB-R antagonist. Immunohistochemical analysis of human islets that were grafted into immune-deficient mice revealed that oral treatment with lesogaberan promoted human β-cell replication and islet cell survival in vivo as effectively as GABA (which activates both GABAA-Rs and GABAB-Rs), perhaps because of its more favorable pharmacokinetics. Lesogaberan may be a promising drug candidate for clinical studies of diabetes intervention and islet transplantation.
Collapse
Affiliation(s)
- Jide Tian
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, USA
| | - Hoa Dang
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, USA
| | - Angela Hu
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, USA
| | - Willem Xu
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, USA
| | - Daniel L. Kaufman
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, USA
| |
Collapse
|
57
|
Müller TD, Finan B, Clemmensen C, DiMarchi RD, Tschöp MH. The New Biology and Pharmacology of Glucagon. Physiol Rev 2017; 97:721-766. [PMID: 28275047 DOI: 10.1152/physrev.00025.2016] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the last two decades we have witnessed sizable progress in defining the role of gastrointestinal signals in the control of glucose and energy homeostasis. Specifically, the molecular basis of the huge metabolic benefits in bariatric surgery is emerging while novel incretin-based medicines based on endogenous hormones such as glucagon-like peptide 1 and pancreas-derived amylin are improving diabetes management. These and related developments have fostered the discovery of novel insights into endocrine control of systemic metabolism, and in particular a deeper understanding of the importance of communication across vital organs, and specifically the gut-brain-pancreas-liver network. Paradoxically, the pancreatic peptide glucagon has reemerged in this period among a plethora of newly identified metabolic macromolecules, and new data complement and challenge its historical position as a gut hormone involved in metabolic control. The synthesis of glucagon analogs that are biophysically stable and soluble in aqueous solutions has promoted biological study that has enriched our understanding of glucagon biology and ironically recruited glucagon agonism as a central element to lower body weight in the treatment of metabolic disease. This review summarizes the extensive historical record and the more recent provocative direction that integrates the prominent role of glucagon in glucose elevation with its under-acknowledged effects on lipids, body weight, and vascular health that have implications for the pathophysiology of metabolic diseases, and the emergence of precision medicines to treat metabolic diseases.
Collapse
Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - B Finan
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - C Clemmensen
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - R D DiMarchi
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - M H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| |
Collapse
|
58
|
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.
Collapse
|
59
|
Heindel JJ, Blumberg B, Cave M, Machtinger R, Mantovani A, Mendez MA, Nadal A, Palanza P, Panzica G, Sargis R, Vandenberg LN, Vom Saal F. Metabolism disrupting chemicals and metabolic disorders. Reprod Toxicol 2017; 68:3-33. [PMID: 27760374 PMCID: PMC5365353 DOI: 10.1016/j.reprotox.2016.10.001] [Citation(s) in RCA: 627] [Impact Index Per Article: 89.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 09/04/2016] [Accepted: 10/13/2016] [Indexed: 01/09/2023]
Abstract
The recent epidemics of metabolic diseases, obesity, type 2 diabetes(T2D), liver lipid disorders and metabolic syndrome have largely been attributed to genetic background and changes in diet, exercise and aging. However, there is now considerable evidence that other environmental factors may contribute to the rapid increase in the incidence of these metabolic diseases. This review will examine changes to the incidence of obesity, T2D and non-alcoholic fatty liver disease (NAFLD), the contribution of genetics to these disorders and describe the role of the endocrine system in these metabolic disorders. It will then specifically focus on the role of endocrine disrupting chemicals (EDCs) in the etiology of obesity, T2D and NAFLD while finally integrating the information on EDCs on multiple metabolic disorders that could lead to metabolic syndrome. We will specifically examine evidence linking EDC exposures during critical periods of development with metabolic diseases that manifest later in life and across generations.
Collapse
Affiliation(s)
- Jerrold J Heindel
- National Institute of Environmental Health Sciences, Division of Extramural Research and Training Research Triangle Park, NC, USA.
| | - Bruce Blumberg
- University of California, Department of Developmental and Cell Biology, Irvine CA, USA
| | - Mathew Cave
- University of Louisville, Division of Gastroenterology, Hepatology and Nutrition, Louisville KY, USA
| | | | | | - Michelle A Mendez
- University of North Carolina at Chapel Hill, School of Public Health, Chapel Hill NC, USA
| | - Angel Nadal
- Institute of Bioengineering and CIBERDEM, Miguel Hernandez University of Elche, Elche, Alicante, Spain
| | - Paola Palanza
- University of Parma, Department of Neurosciences, Parma, Italy
| | - Giancarlo Panzica
- University of Turin, Department of Neuroscience and Neuroscience Institute Cavalieri Ottolenghi (NICO), Turin, Italy
| | - Robert Sargis
- University of Chicago, Section of Endocrinology, Diabetes and Metabolism, Department of Medicine Chicago, IL, USA
| | - Laura N Vandenberg
- University of Massachusetts, Department of Environmental Health Sciences, School of Public Health & Health Sciences, Amherst, MA, USA
| | - Frederick Vom Saal
- University of Missouri, Department of Biological Sciences, Columbia, MO, USA
| |
Collapse
|
60
|
Li J, Casteels T, Frogne T, Ingvorsen C, Honoré C, Courtney M, Huber KVM, Schmitner N, Kimmel RA, Romanov RA, Sturtzel C, Lardeau CH, Klughammer J, Farlik M, Sdelci S, Vieira A, Avolio F, Briand F, Baburin I, Májek P, Pauler FM, Penz T, Stukalov A, Gridling M, Parapatics K, Barbieux C, Berishvili E, Spittler A, Colinge J, Bennett KL, Hering S, Sulpice T, Bock C, Distel M, Harkany T, Meyer D, Superti-Furga G, Collombat P, Hecksher-Sørensen J, Kubicek S. Artemisinins Target GABA A Receptor Signaling and Impair α Cell Identity. Cell 2016; 168:86-100.e15. [PMID: 27916275 PMCID: PMC5236063 DOI: 10.1016/j.cell.2016.11.010] [Citation(s) in RCA: 273] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 08/04/2016] [Accepted: 11/03/2016] [Indexed: 12/12/2022]
Abstract
Type 1 diabetes is characterized by the destruction of pancreatic β cells, and generating new insulin-producing cells from other cell types is a major aim of regenerative medicine. One promising approach is transdifferentiation of developmentally related pancreatic cell types, including glucagon-producing α cells. In a genetic model, loss of the master regulatory transcription factor Arx is sufficient to induce the conversion of α cells to functional β-like cells. Here, we identify artemisinins as small molecules that functionally repress Arx by causing its translocation to the cytoplasm. We show that the protein gephyrin is the mammalian target of these antimalarial drugs and that the mechanism of action of these molecules depends on the enhancement of GABAA receptor signaling. Our results in zebrafish, rodents, and primary human pancreatic islets identify gephyrin as a druggable target for the regeneration of pancreatic β cell mass from α cells. Artemisinins inhibit ARX function and impair α cell identity Compounds act by stabilizing gephyrin, thus enhancing GABAA receptor signaling Artemisinins increase β cell mass in zebrafish and rodent models Functional and transcriptional data indicate a conserved phenotype in human islets
Collapse
Affiliation(s)
- Jin Li
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Tamara Casteels
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Thomas Frogne
- Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Måløv, Denmark
| | | | | | - Monica Courtney
- Université Côte d'Azur, INSERM, CNRS, iBV, 06108 Nice, France
| | - Kilian V M Huber
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Nicole Schmitner
- Institute of Molecular Biology, Leopold-Franzens-University Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
| | - Robin A Kimmel
- Institute of Molecular Biology, Leopold-Franzens-University Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
| | - Roman A Romanov
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria; Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Caterina Sturtzel
- Children's Cancer Research Institute, Innovative Cancer Models, Zimmermannplatz 10, 1090 Vienna, Austria
| | - Charles-Hugues Lardeau
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria; Christian Doppler Laboratory for Chemical Epigenetics and Antiinfectives, CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090 Vienna, Austria
| | - Johanna Klughammer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Matthias Farlik
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Sara Sdelci
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Andhira Vieira
- Université Côte d'Azur, INSERM, CNRS, iBV, 06108 Nice, France
| | - Fabio Avolio
- Université Côte d'Azur, INSERM, CNRS, iBV, 06108 Nice, France
| | - François Briand
- Physiogenex S.A.S., Prologue Biotech, 516, rue Pierre et Marie Curie, 31670 Labege, France
| | - Igor Baburin
- Institute of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Peter Májek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Florian M Pauler
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Thomas Penz
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Alexey Stukalov
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Manuela Gridling
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Katja Parapatics
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Charlotte Barbieux
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, 1211 Geneva, Switzerland
| | - Ekaterine Berishvili
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, 1211 Geneva, Switzerland; Institute of Medical Research, Ilia State University, Tbilisi 0162, Georgia
| | - Andreas Spittler
- Core Facility Flow Cytometry and Department of Surgery, Research Laboratories, Medical University of Vienna, 1090 Vienna, Austria
| | - Jacques Colinge
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Keiryn L Bennett
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria
| | - Steffen Hering
- Institute of Pharmacology and Toxicology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Thierry Sulpice
- Physiogenex S.A.S., Prologue Biotech, 516, rue Pierre et Marie Curie, 31670 Labege, France
| | - Christoph Bock
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria; Department of Laboratory Medicine, Medical University of Vienna, 1090 Vienna, Austria; Max Planck Institute for Informatics, 66123 Saarbrücken, Germany
| | - Martin Distel
- Children's Cancer Research Institute, Innovative Cancer Models, Zimmermannplatz 10, 1090 Vienna, Austria
| | - Tibor Harkany
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria; Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Dirk Meyer
- Institute of Molecular Biology, Leopold-Franzens-University Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria; Center for Physiology and Pharmacology, Medical University of Vienna, 1090 Vienna, Austria
| | | | | | - Stefan Kubicek
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences. Lazarettgasse 14, 1090 Vienna, Austria; Christian Doppler Laboratory for Chemical Epigenetics and Antiinfectives, CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, 1090 Vienna, Austria.
| |
Collapse
|
61
|
Watts M, Ha J, Kimchi O, Sherman A. Paracrine regulation of glucagon secretion: the β/α/δ model. Am J Physiol Endocrinol Metab 2016; 310:E597-E611. [PMID: 26837808 PMCID: PMC4835945 DOI: 10.1152/ajpendo.00415.2015] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 01/19/2016] [Indexed: 01/17/2023]
Abstract
The regulation of glucagon secretion in the pancreatic α-cell is not well understood. It has been proposed that glucose suppresses glucagon secretion either directly through an intrinsic mechanism within the α-cell or indirectly through an extrinsic mechanism. Previously, we described a mathematical model for isolated pancreatic α-cells and used it to investigate possible intrinsic mechanisms of regulating glucagon secretion. We demonstrated that glucose can suppress glucagon secretion through both ATP-dependent potassium channels (KATP) and a store-operated current (SOC). We have now developed an islet model that combines previously published mathematical models of α- and β-cells with a new model of δ-cells and use it to explore the effects of insulin and somatostatin on glucagon secretion. We show that the model can reproduce experimental observations that the inhibitory effect of glucose remains even when paracrine modulators are no longer acting on the α-cell. We demonstrate how paracrine interactions can either synchronize α- and δ-cells to produce pulsatile oscillations in glucagon and somatostatin secretion or fail to do so. The model can also account for the paradoxical observation that glucagon can be out of phase with insulin, whereas α-cell calcium is in phase with insulin. We conclude that both paracrine interactions and the α-cell's intrinsic mechanisms are needed to explain the response of glucagon secretion to glucose.
Collapse
Affiliation(s)
- Margaret Watts
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland; and
| | - Joon Ha
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland; and
| | - Ofer Kimchi
- Department of Physics, Princeton University, Princeton, New Jersey
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland; and
| |
Collapse
|
62
|
Abstract
OBJECTIVE There is general recognition that insulin and glucagon are the main hormones involved in the pathophysiology of diabetes, but the role of glucagon in diabetes is complex and in some circumstances controversial. The increasing appreciation of the role of glucagon in currently used hypoglycemic agents and the ongoing development of glucagon-targeted therapies underscores glucagon's important contribution in optimizing diabetes management. The current review provides a background on glucagon physiology and pathophysiology and an update for investigators, endocrinologists, and other healthcare providers on glucagon-modulating therapies. METHODS A literature review was conducted utilizing published literature in PubMed and AccessMedicine including the years 1922-2015 using the following key words: glucagon, bihormonal, diabetes mellitus, glucagon antagonists, glucagon-targeted therapies. RESULTS Glucagon is a counterregulatory hormone that promotes hepatic glucose production, thus preventing hypoglycemia in normal physiology. In patients with diabetes mellitus, glucagon secretion may be unregulated, which contributes to problems with glucose homeostasis. Several of the most effective therapies for diabetes have been found to suppress glucagon secretion or action, which may contribute to their success. Additionally, glucagon-specific targeted therapies, such as glucagon receptor antagonists, are being studied at a basic and clinical level. CONCLUSION Glucagon plays an important role in contributing to hyperglycemia in patients with diabetes. Utilizing hypoglycemic agents that decrease glucagon secretion or inhibit glucagon action can help improve glycemic control, making these agents a valuable resource in diabetes therapy.
Collapse
|
63
|
Hoang Do O, Thorn P. Insulin secretion from beta cells within intact islets: location matters. Clin Exp Pharmacol Physiol 2015; 42:406-14. [PMID: 25676261 PMCID: PMC4418378 DOI: 10.1111/1440-1681.12368] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 12/21/2014] [Accepted: 01/06/2015] [Indexed: 12/17/2022]
Abstract
The control of hormone secretion is central to body homeostasis, and its dysfunction is important in many diseases. The key cellular steps that lead to hormone secretion have been identified, and the stimulus-secretion pathway is understood in outline for many endocrine cells. In the case of insulin secretion from pancreatic beta cells, this pathway involves the uptake of glucose, cell depolarization, calcium entry, and the triggering of the fusion of insulin-containing granules with the cell membrane. The wealth of information on the control of insulin secretion has largely been obtained from isolated single-cell studies. However, physiologically, beta cells exist within the islets of Langerhans, with structural and functional specializations that are not preserved in single-cell cultures. This review focuses on recent work that is revealing distinct aspects of insulin secretion from beta cells within the islet.
Collapse
Affiliation(s)
- Oanh Hoang Do
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Qld, Australia
| | | |
Collapse
|
64
|
Li J, Zhang Z, Liu X, Wang Y, Mao F, Mao J, Lu X, Jiang D, Wan Y, Lv JY, Cao G, Zhang J, Zhao N, Atkinson M, Greiner DL, Prud'homme GJ, Jiao Z, Li Y, Wang Q. Study of GABA in Healthy Volunteers: Pharmacokinetics and Pharmacodynamics. Front Pharmacol 2015; 6:260. [PMID: 26617516 PMCID: PMC4639630 DOI: 10.3389/fphar.2015.00260] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 10/20/2015] [Indexed: 01/13/2023] Open
Abstract
Preclinical studies show that GABA exerts anti-diabetic effects in rodent models of type 1 diabetes. Because little is known about its absorption and effects in humans, we investigated the pharmacokinetics and pharmacodynamics of GABA in healthy volunteers. Twelve subjects were subjected to an open-labeled, three-period trial involving sequential oral administration of placebo, 2 g GABA once, and 2 g GABA three times/day for 7 days, with a 7-day washout between each period. GABA was rapidly absorbed (Tmax: 0.5 ~ 1 h) with the half-life (t1/2) of 5 h. No accumulation was observed after repeated oral GABA administration for 7 days. Remarkably, GABA significantly increased circulating insulin levels in the subjects under either fasting (1.6-fold, single dose; 2.0-fold, repeated dose; p < 0.01) or fed conditions (1.4-fold, single dose; 1.6-fold, repeated dose; p < 0.01). GABA also increased glucagon levels only under fasting conditions (1.3-fold, single dose, p < 0.05; 1.5-fold, repeated dose, p < 0.01). However, there were no significant differences in the insulin-to-glucagon ratio and no significant change in glucose levels in these healthy subjects during the study period. Importantly, GABA significantly decreased glycated albumin levels in the repeated dosing period. Subjects with repeated dosing showed an elevated incidence of minor adverse events in comparison to placebo or the single dosing period, most notably transient discomforts such as dizziness and sore throat. However, there were no serious adverse events observed throughout the study. Our data show that GABA is rapidly absorbed and tolerated in human beings; its endocrine effects, exemplified by increasing islet hormonal secretion, suggest potential therapeutic benefits for diabetes.
Collapse
Affiliation(s)
- Junfeng Li
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Zhaoyun Zhang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Xiaoxia Liu
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Yi Wang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Fei Mao
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Junjun Mao
- Department of Pharmacy, Huashan Hospital, Fudan University Shanghai, China
| | - Xiaolan Lu
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Dongdong Jiang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Yun Wan
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Jia-Ying Lv
- Department of Biostatistics, School of Public Health, Fudan University Shanghai, China
| | - Guoying Cao
- Key Laboratory of Clinical Pharmacology of Antibiotics, Ministry of Health, Institute of Antibiotics, Huashan Hospital, Fudan University Shanghai, China
| | - Jing Zhang
- Key Laboratory of Clinical Pharmacology of Antibiotics, Ministry of Health, Institute of Antibiotics, Huashan Hospital, Fudan University Shanghai, China
| | - Naiqing Zhao
- Department of Biostatistics, School of Public Health, Fudan University Shanghai, China
| | - Mark Atkinson
- Department of Pathology, College of Medicine, University of Florida Gainesville, FL, USA
| | - Dale L Greiner
- Department of Molecular Medicine, University of Massachusetts Medical School Worcester, MA, USA
| | - Gerald J Prud'homme
- Department of Laboratory Medicine and Pathobiology, Keenan Research Centre for Biomedical Science of St. Michael's Hospital, University of Toronto Toronto, ON, Canada
| | - Zheng Jiao
- Department of Pharmacy, Huashan Hospital, Fudan University Shanghai, China
| | - Yiming Li
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China
| | - Qinghua Wang
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University Shanghai, China ; Division of Endocrinology and Metabolism, The Keenan Research Centre in the Li Ka Shing Knowledge Institute, St. Michael's Hospital Toronto, ON, Canada ; Department of Physiology and Medicine, University of Toronto ON, Canada
| |
Collapse
|
65
|
Akaishi T, Jin K, Kato K, Itabashi H, Misu T, Tateyama M, Iwasaki M, Aoki M, Nakasato N. [Clinical characteristics of four patients with temporal lobe epilepsy associated with elevated anti-GAD antibodies]. Rinsho Shinkeigaku 2015; 55:804-9. [PMID: 26369378 DOI: 10.5692/clinicalneurol.cn-000740] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Anti-glutamic acid decarboxylase (GAD) antibodies are known to be associated with insulin-dependent diabetes mellitus (IDDM), stiff-person syndrome, and other neurological symptoms including temporal lobe epilepsy (TLE), known as autoimmune epilepsy. We treated four patients with TLE who had elevated titers of serum anti-GAD antibody (anti-GAD-Ab), higher than 100 U/ml. Three of the four patients started to have epileptic seizures in their 5th or 6th decade. Characteristic symptoms suggesting encephalitis or encephalopathy were absent at onset of these symptoms, which led to delayed diagnosis. All four patients developed two or three of cerebellar ataxia, neuropsychological impairment, and IDDM, by several years or decades after onset of TLE, even after seizure freedom in two patients. These abnormalities were indicators for suspecting the involvement of anti-GAD-Ab in the pathogenesis. Anti-GAD-Ab levels in the cerebrospinal fluid (CSF) were measured, which detected elevated CSF/serum anti-GAD-Ab ratio (≥ 1.0), suggesting intrathecal anti-GAD-Ab synthesis, in three of the four patients. The TLE symptoms were somewhat prolonged, but three of the four patients eventually achieved seizure freedom after immunotherapies with combinations of two or three anti-epileptic drugs. Serum anti-GAD Ab is recommended to be measured in patients with middle-aged onset TLE. Moreover, immune-modulating therapies including steroid pulse and intravenous immunoglobulin therapies could have ameliorated neurological complications, even in the chronic phase.
Collapse
Affiliation(s)
- Tetsuya Akaishi
- Department of Epileptology, Tohoku University, Graduate School of Medicine
| | | | | | | | | | | | | | | | | |
Collapse
|
66
|
Ren HZ, Zheng MY, Shan CY, Yang JH, Xu YG, Yang YH, Wang Y, Chen LM, Chang BC. Relationship between circadian blood pressure variability and function of islet α and β cell in type 2 diabetes with dyssomnia. J Diabetes Complications 2015; 29:675-8. [PMID: 25957006 DOI: 10.1016/j.jdiacomp.2015.03.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Revised: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 01/24/2023]
Abstract
AIMS To investigate the relationship between circadian blood pressure (BP) variability and function of islet α and β cell in type 2 diabetes (T2D) with dyssomnia. METHODS Patients with T2D were divided into dyssomnia group and non-dyssomnia group by PSQI. OGTT, insulin and glucagon-releasing test were tested, and ambulatory BP was monitored for 24 hours to compare two groups with α and β cell, circadian BP variability and fasting and post-meal BP variability. The correlation and regression analysis were made between PSQI and other indicators. RESULTS In dyssomnia group, ① Glucagon, glucagon/insulin ratio and AUCG were significantly higher (P < 0.05). ② Fasting insulin (13.32 ± 4.54 mIU/L), AUCI (8.51 ± 0.54) and HOMA-IR (4.62 ± 1.11) were high (P < 0.05). But ISI (-4.27 ± 0.77) was low (P < 0.05). ③ Mean 24-hour and nighttime SBP and DBP, as well as their standard deviations and coefficients of variation, were all higher in the dyssomnia group (P < 0.05). Multiple stepwise regression analysis showed that PSQI score was positively related to AUCG, HOMA-IR, nighttime SBP, and negatively related to ISI and nocturnal BP fall (P < 0.05). CONCLUSION Dyssomnia may cause abnormal circadian BP variability through various mechanisms. Improving dyssomnia can help to better function the islet α and β cell and restore normal circadian BP variability.
Collapse
Affiliation(s)
- Hui-Zhu Ren
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Miao-Yan Zheng
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Chun-Yan Shan
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Ju-Hong Yang
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Yan-Guang Xu
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Yan-Hui Yang
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Ying Wang
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China
| | - Li-Ming Chen
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China.
| | - Bao-Cheng Chang
- Department of Nephrology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Key Laboratory of Hormone and Development (Ministry of Health), Metabolic Disease Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin 300070, China.
| |
Collapse
|
67
|
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: 53] [Impact Index Per Article: 5.9] [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.
Collapse
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
| |
Collapse
|
68
|
Kanaani J, Cianciaruso C, Phelps EA, Pasquier M, Brioudes E, Billestrup N, Baekkeskov S. Compartmentalization of GABA synthesis by GAD67 differs between pancreatic beta cells and neurons. PLoS One 2015; 10:e0117130. [PMID: 25647668 PMCID: PMC4315522 DOI: 10.1371/journal.pone.0117130] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 12/19/2014] [Indexed: 11/22/2022] Open
Abstract
The inhibitory neurotransmitter GABA is synthesized by the enzyme glutamic acid decarboxylase (GAD) in neurons and in pancreatic β-cells in islets of Langerhans where it functions as a paracrine and autocrine signaling molecule regulating the function of islet endocrine cells. The localization of the two non-allelic isoforms GAD65 and GAD67 to vesicular membranes is important for rapid delivery and accumulation of GABA for regulated secretion. While the membrane anchoring and trafficking of GAD65 are mediated by intrinsic hydrophobic modifications, GAD67 remains hydrophilic, and yet is targeted to vesicular membrane pathways and synaptic clusters in neurons by both a GAD65-dependent and a distinct GAD65-independent mechanism. Herein we have investigated the membrane association and targeting of GAD67 and GAD65 in monolayer cultures of primary rat, human, and mouse islets and in insulinoma cells. GAD65 is primarily detected in Golgi membranes and in peripheral vesicles distinct from insulin vesicles in β-cells. In the absence of GAD65, GAD67 is in contrast primarily cytosolic in β-cells; its co-expression with GAD65 is necessary for targeting to Golgi membranes and vesicular compartments. Thus, the GAD65-independent mechanism for targeting of GAD67 to synaptic vesicles in neurons is not functional in islet β-cells. Therefore, only GAD65:GAD65 homodimers and GAD67:GAD65 heterodimers, but not the GAD67:GAD67 homodimer gain access to vesicular compartments in β-cells to facilitate rapid accumulation of newly synthesized GABA for regulated secretion and fine tuning of GABA-signaling in islets of Langerhans.
Collapse
Affiliation(s)
- Jamil Kanaani
- Departments of Medicine and Microbiology/Immunology, Diabetes Center, University of California San Francisco, San Francisco, California, United States of America
| | - Chiara Cianciaruso
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Edward A. Phelps
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Miriella Pasquier
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Estelle Brioudes
- Cell Isolation and Transplantation Center, Department of Surgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
| | - Nils Billestrup
- Institute of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Steinunn Baekkeskov
- Departments of Medicine and Microbiology/Immunology, Diabetes Center, University of California San Francisco, San Francisco, California, United States of America
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| |
Collapse
|
69
|
Abstract
Type 2 diabetes (T2D) has been known as 'bi-hormonal disorder' since decades ago, the role of glucagon from α-cell has languished whereas β-cell taking center stage. Recently, numerous findings indicate that the defects of glucagon secretion get involve with development and exacerbation of hyperglycemia in T2D. Aberrant α-cell responses exhibit both fasting and postprandial states: hyperglucagonemia contributes to fasting hyperglycemia caused by inappropriate hepatic glucose production, and to postprandial hyperglycemia owing to blunted α-cell suppression. During hypoglycemia, insufficient counter-regulation response is also observed in advanced T2D. Though many debates still remained for exact mechanisms behind the dysregulation of α-cell in T2D, it is clear that the blockade of glucagon receptor or suppression of glucagon secretion from α-cell would be novel therapeutic targets for control of hyperglycemia. Whereas there have not been remarkable advances in developing new class of drugs, currently available glucagon-like peptide-1 and dipeptidyl peptidase-IV inhibitors could be options for treatment of hyperglucagonemia. In this review, we focus on α-cell dysfunction and therapeutic potentials of targeting α-cell in T2D.
Collapse
Affiliation(s)
- Jun Sung Moon
- Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Korea
| | - Kyu Chang Won
- Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Korea
| |
Collapse
|
70
|
Shen KP, Hao CL, Yen HW, Chen CY, Wu BN, Lin HL. Pre-germinated brown rice prevents high-fat diet induced hyperglycemia through elevated insulin secretion and glucose metabolism pathway in C57BL/6J strain mice. J Clin Biochem Nutr 2014; 56:28-34. [PMID: 25834303 PMCID: PMC4306661 DOI: 10.3164/jcbn.14-50] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Accepted: 08/03/2014] [Indexed: 12/27/2022] Open
Abstract
This study investigated the effect and mechanism of pre-germinated brown rice (PGBR) prevented hyperglycemia in C57BL/6J mice fed high-fat-diet (HFD). Normal six-week-old mice were randomly divided into three groups. Group 1 was fed standard-regular-diet (SRD) and group 2 was fed HFD for 16 weeks. In group 3, the mice were fed a HFD with its carbohydrate replaced with PGBR for 16 weeks. Comparing the SRD and HFD groups, we found the HFD group had higher blood pressure, higher concentrations of blood glucose and HbA1c. The HFD group had less protein expression of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), phosphatidylinositol-3-kinase (PI3K), glucose transporter-4 (GLUT-4) and glucokinase (GCK) and greater expression of glucogen synthase kinase (GSK) in skeletal muscle. The HFD group also had less expression of IR, serine/threonine kinase PI3K-linked protein kinase B (Akt/PKB), AMP-activated protein kinase (AMPK), GCK and peroxisome proliferator-activated receptor γ (PPARγ) in liver. In the HFD + PGBR group, the PGBR could reverse the disorders of blood pressure, blood glucose, HbA1c and increase insulin concentration. PGBR increased the IR, IRS-1, PI3K, Akt, GLUT-1 and GLUT-4 proteins, and ameliorated AMPK, GCK, GSK and PPARγ proteins. Together, PGBR prevented HFD-induced hyperglycemia through improving insulin levels, insulin receptor, glucose transporters and enhancing glucose metabolism.
Collapse
Affiliation(s)
- Kuo-Ping Shen
- Department of Nursing, Meiho University, 23 Ping-Kuang Road, Neipu, Pingtung 91202, Taiwan
| | - Chi-Long Hao
- Division of Cardiology, Department of Internal Medicine, Pingtung Christian Hospital, 60 Da-Lian Road, Pingtung 90059, Taiwan
| | - Hsueh-Wei Yen
- Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, 100 Shin-Chuan 1st Road, Kaohsiung 807, Taiwan
| | - Chun-Yen Chen
- MS program for Applied Health and Biotechnology, Meiho University, 23 Ping-Kuang Road, Neipu, Pingtung 91202, Taiwan
| | - Bin-Nan Wu
- Department of Pharmacology, School of Medicine, College of Medicine, Kaohsiung Medical University, 100 Shin-Chuan 1st Road, Kaohsiung 807, Taiwan
| | - Hui-Li Lin
- Department of Food Science and Nutrition, Meiho University, 23 Ping-Kuang Road, Neipu, Pingtung 91202, Taiwan
| |
Collapse
|
71
|
Bessho M, Murase-Mishiba Y, Imagawa A, Terasaki J, Hanafusa T. Possible contribution of taurine to distorted glucagon secretion in intra-islet insulin deficiency: a metabolome analysis using a novel α-cell model of insulin-deficient diabetes. PLoS One 2014; 9:e113254. [PMID: 25393115 PMCID: PMC4231115 DOI: 10.1371/journal.pone.0113254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 10/24/2014] [Indexed: 01/30/2023] Open
Abstract
Glycemic instability is a serious problem in patients with insulin-deficient diabetes, and it may be due in part to abnormal endogenous glucagon secretion. However, the intracellular metabolic mechanism(s) involved in the aberrant glucagon response under the condition of insulin deficiency has not yet been elucidated. To investigate the metabolic traits that underlie the distortion of glucagon secretion under insulin deficient conditions, we generated an αTC1-6 cell line with stable knockdown of the insulin receptor (IRKD), i.e., an in vitro α-cell model for insulin-deficient diabetes, which exhibits an abnormal glucagon response to glucose. A comprehensive metabolomic analysis of the IRKD αTC1-6 cells (IRKD cells) revealed some candidate metabolites whose levels differed markedly compared to those in control αTC1-6 cells, but also which could affect the glucagon release in IRKD cells. Of these candidates, taurine was remarkably increased in the IRKD cells and was identified as a stimulator of glucagon in αTC1-6 cells. Taurine also paradoxically exaggerated the glucagon secretion at a high glucose concentration in IRKD cells and islets with IRKD. These results indicate that the metabolic alterations induced by IRKD in α-cells, especially the increase of taurine, may lead to the distorted glucagon response in IRKD cells, suggesting the importance of taurine in the paradoxical glucagon response and the resultant glucose instability in insulin-deficient diabetes.
Collapse
Affiliation(s)
- Megumi Bessho
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan
| | | | - Akihisa Imagawa
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan; Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Jungo Terasaki
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan
| | - Toshiaki Hanafusa
- Department of Internal Medicine (I), Osaka Medical College, Osaka, Japan
| |
Collapse
|
72
|
Watts M, Sherman A. Modeling the pancreatic α-cell: dual mechanisms of glucose suppression of glucagon secretion. Biophys J 2014; 106:741-51. [PMID: 24507615 DOI: 10.1016/j.bpj.2013.11.4504] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 12/11/2022] Open
Abstract
The mechanism by which glucose induces insulin secretion in β-cells is fairly well understood. Despite years of research, however, the mechanism of glucagon secretion in α-cells is still not well established. It has been proposed that glucose regulates glucagon secretion by decreasing the conductance of either outward ATP-dependent potassium channels (K(ATP)) or an inward store-operated current (SOC). We have developed a mathematical model based on mouse data to test these hypotheses and found that both mechanisms are possible. Glucose metabolism closes K(ATP) channels, which depolarizes the cell but paradoxically reduces calcium influx by inactivating voltage-dependent calcium and sodium channels and decreases secretion. Glucose metabolism also activates SERCA pumps, which fills the endoplasmic reticulum and hyperpolarizes the cells by reducing the inward current through SOC channels and again suppresses glucagon secretion. We find further that the two mechanisms can combine to account for the nonmonotonic dependence of secretion on glucose observed in some studies, an effect that cannot be obtained with either mechanism alone.
Collapse
Affiliation(s)
- Margaret Watts
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Arthur Sherman
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland.
| |
Collapse
|
73
|
Williams DB. Inhibitory effects of insulin on GABAAcurrents modulated by the GABAAalpha subunit. J Recept Signal Transduct Res 2014; 35:516-22. [DOI: 10.3109/10799893.2014.960935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
74
|
Rorsman P, Ramracheya R, Rorsman NJG, Zhang Q. ATP-regulated potassium channels and voltage-gated calcium channels in pancreatic alpha and beta cells: similar functions but reciprocal effects on secretion. Diabetologia 2014; 57:1749-61. [PMID: 24906950 DOI: 10.1007/s00125-014-3279-8] [Citation(s) in RCA: 51] [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: 01/16/2014] [Accepted: 04/25/2014] [Indexed: 12/13/2022]
Abstract
Closure of ATP-regulated K(+) channels (K(ATP) channels) plays a central role in glucose-stimulated insulin secretion in beta cells. K(ATP) channels are also highly expressed in glucagon-producing alpha cells, where their function remains unresolved. Under hypoglycaemic conditions, K(ATP) channels are open in alpha cells but their activity is low and only ~1% of that in beta cells. Like beta cells, alpha cells respond to hyperglycaemia with K(ATP) channel closure, membrane depolarisation and stimulation of action potential firing. Yet, hyperglycaemia reciprocally regulates glucagon (inhibition) and insulin secretion (stimulation). Here we discuss how this conundrum can be resolved and how reduced K(ATP) channel activity, via membrane depolarisation, paradoxically reduces alpha cell Ca(2+) entry and glucagon exocytosis. Finally, we consider whether the glucagon secretory defects associated with diabetes can be attributed to impaired K(ATP) channel regulation and discuss the potential for remedial pharmacological intervention using sulfonylureas.
Collapse
Affiliation(s)
- Patrik Rorsman
- Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, OX3 7LJ, UK,
| | | | | | | |
Collapse
|
75
|
Low JT, Zavortink M, Mitchell JM, Gan WJ, Do OH, Schwiening CJ, Gaisano HY, Thorn P. Insulin secretion from beta cells in intact mouse islets is targeted towards the vasculature. Diabetologia 2014; 57:1655-63. [PMID: 24795086 PMCID: PMC4079948 DOI: 10.1007/s00125-014-3252-6] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 04/03/2014] [Indexed: 12/28/2022]
Abstract
AIMS/HYPOTHESIS We set out to test the hypothesis that insulin secretion from beta cells is targeted towards the vasculature. METHODS The spatial location of granule fusion was identified by live-cell two-photon imaging of mouse pancreatic beta cells within intact islets, using sulforhodamine B labelling. Three-dimensional (3D) immunofluorescence of pancreatic slices was used to identify the location of proteins associated with neuronal synapses. RESULTS We demonstrated an asymmetric, non-random, distribution of sites of insulin granule fusion in response to glucose and focal targeting of insulin granule secretion to the beta cell membrane facing the vasculature. 3D immunofluorescence of islets showed that structural proteins, such as liprin, piccolo and Rab2-interacting molecule, normally associated with neuronal presynaptic targeting, were present in beta cells and enriched at the vascular face. In contrast, we found that syntaxin 1A and synaptosomal-associated protein 25 kDa (SNAP25) were relatively evenly distributed across the beta cells. CONCLUSIONS/INTERPRETATION Our results show that beta cells in situ, within intact islets, are polarised and target insulin secretion. This evidence for an 'endocrine synapse' has wide implications for our understanding of stimulus-secretion coupling in healthy islets and in disease.
Collapse
Affiliation(s)
- Jiun T Low
- School of Biomedical Sciences, University of Queensland, St Lucia, QLD, 4072, Australia
| | | | | | | | | | | | | | | |
Collapse
|
76
|
Abstract
Zinc is an essential nutrient with tremendous importance for human health, and zinc deficiency is a severe risk factor for increased mortality and morbidity. As abnormal zinc homeostasis causes diabetes, and because the pancreatic β-cell contains the highest zinc content of any known cell type, it is of interest to know how zinc fluxes are controlled in β-cells. The understanding of zinc homeostasis has been boosted by the discovery of multiprotein families of zinc transporters, and one of them - zinc transporter 8 (ZnT8) - is abundantly and specifically expressed in the pancreatic islets of Langerhans. In this review, we discuss the evidence for a physiological role of ZnT8 in the formation of zinc-insulin crystals, the physical form in which most insulin is stored in secretory granules. In addition, we cross-examine this information, collected in genetically modified mouse strains, to the knowledge that genetic variants of the human ZnT8 gene predispose to the onset of type 2 diabetes and that epitopes on the ZnT8 protein trigger autoimmunity in patients with type 1 diabetes. The overall conclusion is that we are still at the dawn of a complete understanding of how zinc homeostasis operates in normal β-cells and how abnormalities lead to β-cell dysfunction and diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2012.00199.x, 2012).
Collapse
Affiliation(s)
- Katleen Lemaire
- Gene Expression Unit, Department of Molecular Cell Biology, KU Leuven, Leuven, Belgium
| | | | - Frans Schuit
- Gene Expression Unit, Department of Molecular Cell Biology, KU Leuven, Leuven, Belgium
| |
Collapse
|
77
|
Zarrin M, Wellnitz O, van Dorland H, Gross J, Bruckmaier R. Hyperketonemia during lipopolysaccharide-induced mastitis affects systemic and local intramammary metabolism in dairy cows. J Dairy Sci 2014; 97:3531-41. [DOI: 10.3168/jds.2013-7480] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 02/10/2014] [Indexed: 01/14/2023]
|
78
|
Distinctive expression and cellular distribution of dopamine receptors in the pancreatic islets of rats. Cell Tissue Res 2014; 357:597-606. [DOI: 10.1007/s00441-014-1894-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 04/10/2014] [Indexed: 11/27/2022]
|
79
|
Inoue M, Harada K, Nakamura J, Matsuoka H. Regulation of α3-containing GABAA receptors in guinea-pig adrenal medullary cells by adrenal steroids. Neuroscience 2013; 253:245-55. [DOI: 10.1016/j.neuroscience.2013.08.046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Revised: 08/23/2013] [Accepted: 08/24/2013] [Indexed: 12/14/2022]
|
80
|
Cura AJ, Carruthers A. Role of monosaccharide transport proteins in carbohydrate assimilation, distribution, metabolism, and homeostasis. Compr Physiol 2013; 2:863-914. [PMID: 22943001 DOI: 10.1002/cphy.c110024] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The facilitated diffusion of glucose, galactose, fructose, urate, myoinositol, and dehydroascorbicacid in mammals is catalyzed by a family of 14 monosaccharide transport proteins called GLUTs. These transporters may be divided into three classes according to sequence similarity and function/substrate specificity. GLUT1 appears to be highly expressed in glycolytically active cells and has been coopted in vitamin C auxotrophs to maintain the redox state of the blood through transport of dehydroascorbate. Several GLUTs are definitive glucose/galactose transporters, GLUT2 and GLUT5 are physiologically important fructose transporters, GLUT9 appears to be a urate transporter while GLUT13 is a proton/myoinositol cotransporter. The physiologic substrates of some GLUTs remain to be established. The GLUTs are expressed in a tissue specific manner where affinity, specificity, and capacity for substrate transport are paramount for tissue function. Although great strides have been made in characterizing GLUT-catalyzed monosaccharide transport and mapping GLUT membrane topography and determinants of substrate specificity, a unifying model for GLUT structure and function remains elusive. The GLUTs play a major role in carbohydrate homeostasis and the redistribution of sugar-derived carbons among the various organ systems. This is accomplished through a multiplicity of GLUT-dependent glucose sensing and effector mechanisms that regulate monosaccharide ingestion, absorption,distribution, cellular transport and metabolism, and recovery/retention. Glucose transport and metabolism have coevolved in mammals to support cerebral glucose utilization.
Collapse
Affiliation(s)
- Anthony J Cura
- Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | | |
Collapse
|
81
|
Amisten S, Salehi A, Rorsman P, Jones PM, Persaud SJ. An atlas and functional analysis of G-protein coupled receptors in human islets of Langerhans. Pharmacol Ther 2013; 139:359-91. [DOI: 10.1016/j.pharmthera.2013.05.004] [Citation(s) in RCA: 143] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 05/03/2013] [Indexed: 12/17/2022]
|
82
|
Harris KD, Zahavi A. The evolution of ACh and GABA as neurotransmitters: a hypothesis. Med Hypotheses 2013; 81:760-2. [PMID: 23942033 DOI: 10.1016/j.mehy.2013.07.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Revised: 07/17/2013] [Accepted: 07/22/2013] [Indexed: 11/16/2022]
Abstract
The development of a signaling system requires the evolution of a mechanism for producing signals, receptors and adaptive reactions to the signal. It is reasonable to assume that the evolution of such a system cannot be the consequence of a coordinated set of mutations resulting in a complete signaling system. It is more likely that each component evolved due to an advantage that was independent of its role in the signaling system. We hypothesize how the neurotransmitters acetylcholine (ACh) and gamma-aminobutyric acid (GABA) evolved gradually, from an initial stage in which the efflux of these molecules from the cell was an inevitable consequence of specific metabolic activities of the cell. The efflux later served as a cue that reflects the activity of the cell that released the molecules. These cues can later evolve into paracrine signals. We further suggest that the signals used in paracrine signaling were adopted by the central nervous system, as peripheral cells were already attentive to these signals. Signaling molecules released by the target cells of neurons, as an inevitable consequence of the activities of the target cells, could function as retrograde signals of the activity of the target cell. We hypothesize that ACh released by innervated myocytes functions as a retrograde signal of myocyte response to neuronal stimulation.
Collapse
Affiliation(s)
- K D Harris
- Tel-Aviv University, Department of Zoology, Tel Aviv, Israel
| | | |
Collapse
|
83
|
Wendt A, Eliasson L. Progesterone metabolite influence feeding behaviour. Acta Physiol (Oxf) 2013; 208:296-7. [PMID: 23710705 DOI: 10.1111/apha.12122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
84
|
Vieira E, Marroquí L, Figueroa ALC, Merino B, Fernandez-Ruiz R, Nadal A, Burris TP, Gomis R, Quesada I. Involvement of the clock gene Rev-erb alpha in the regulation of glucagon secretion in pancreatic alpha-cells. PLoS One 2013; 8:e69939. [PMID: 23936124 PMCID: PMC3723646 DOI: 10.1371/journal.pone.0069939] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 06/13/2013] [Indexed: 11/19/2022] Open
Abstract
Disruption of pancreatic clock genes impairs pancreatic beta-cell function, leading to the onset of diabetes. Despite the importance of pancreatic alpha-cells in the regulation of glucose homeostasis and in diabetes pathophysiology, nothing is known about the role of clock genes in these cells. Here, we identify the clock gene Rev-erb alpha as a new intracellular regulator of glucagon secretion. Rev-erb alpha down-regulation by siRNA (60–70% inhibition) in alphaTC1-9 cells inhibited low-glucose induced glucagon secretion (p<0.05) and led to a decrease in key genes of the exocytotic machinery. The Rev-erb alpha agonist GSK4112 increased glucagon secretion (1.6 fold) and intracellular calcium signals in alphaTC1-9 cells and mouse primary alpha-cells, whereas the Rev-erb alpha antagonist SR8278 produced the opposite effect. At 0.5 mM glucose, alphaTC1-9 cells exhibited intrinsic circadian Rev-erb alpha expression oscillations that were inhibited by 11 mM glucose. In mouse primary alpha-cells, glucose induced similar effects (p<0.001). High glucose inhibited key genes controlled by AMPK such as Nampt, Sirt1 and PGC-1 alpha in alphaTC1-9 cells (p<0.05). AMPK activation by metformin completely reversed the inhibitory effect of glucose on Nampt-Sirt1-PGC-1 alpha and Rev-erb alpha. Nampt inhibition decreased Sirt1, PGC-1 alpha and Rev-erb alpha mRNA expression (p<0.01) and glucagon release (p<0.05). These findings identify Rev-erb alpha as a new intracellular regulator of glucagon secretion via AMPK/Nampt/Sirt1 pathway.
Collapse
MESH Headings
- AMP-Activated Protein Kinases/genetics
- AMP-Activated Protein Kinases/metabolism
- Animals
- Cell Line
- Circadian Rhythm/genetics
- Cytokines/genetics
- Cytokines/metabolism
- Gene Expression Regulation
- Glucagon/genetics
- Glucagon/metabolism
- Glucagon-Secreting Cells/cytology
- Glucagon-Secreting Cells/drug effects
- Glucagon-Secreting Cells/metabolism
- Glucose/metabolism
- Glucose/pharmacology
- Glycine/analogs & derivatives
- Glycine/pharmacology
- Isoquinolines/pharmacology
- Metformin/pharmacology
- Mice
- Nicotinamide Phosphoribosyltransferase/genetics
- Nicotinamide Phosphoribosyltransferase/metabolism
- Nuclear Receptor Subfamily 1, Group D, Member 1/agonists
- Nuclear Receptor Subfamily 1, Group D, Member 1/antagonists & inhibitors
- Nuclear Receptor Subfamily 1, Group D, Member 1/genetics
- Nuclear Receptor Subfamily 1, Group D, Member 1/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Signal Transduction
- Sirtuin 1/genetics
- Sirtuin 1/metabolism
- Thiophenes/pharmacology
Collapse
Affiliation(s)
- Elaine Vieira
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- * E-mail: (EV); (IQ)
| | - Laura Marroquí
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Ana Lucia C. Figueroa
- Diabetes and Obesity Laboratory, Institut d'investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Beatriz Merino
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Rebeca Fernandez-Ruiz
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- Diabetes and Obesity Laboratory, Institut d'investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
| | - Angel Nadal
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
| | - Thomas P. Burris
- Department of Molecular Therapeutics, The Scripps Research Institute, Jupiter, Florida, United States of America
| | - Ramon Gomis
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- Diabetes and Obesity Laboratory, Institut d'investigacions Biomèdiques August Pi i Sunyer, Barcelona, Spain
- Endocrinology and Diabetes Unit, Hospital Clinic, Universitat de Barcelona, Barcelona, Spain
| | - Ivan Quesada
- Instituto de Bioingeniería, Universidad Miguel Hernandez de Elche, Elche, Spain
- CIBER de Diabetes y Enfermedades Metabólicas Asociadas, Barcelona, Spain
- * E-mail: (EV); (IQ)
| |
Collapse
|
85
|
In intact islets interstitial GABA activates GABA(A) receptors that generate tonic currents in α-cells. PLoS One 2013; 8:e67228. [PMID: 23826240 PMCID: PMC3691163 DOI: 10.1371/journal.pone.0067228] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 05/15/2013] [Indexed: 11/19/2022] Open
Abstract
In the rat islets γ-aminobutyric acid (GABA) is produced by the β-cells and, at least, the α-cells express the GABAA receptors (GABAA channels). In this study, we examined in intact islets if the interstitial GABA activated the GABAA receptors. We used the patch-clamp technique to record whole-cell and single-channel currents and single-cell RT-PCR to identify the cell-type we recorded from, in the intact rat islets. We further identified which GABAA receptor subunits were expressed. We determined the cell-type of 43 cells we recorded from and of these 49%, 28% and 7% were α, β and δ-cells, respectively. In the remaining 16% of the cells, mRNA transcripts of more than one hormone gene were detected. The results show that in rat islets interstitial GABA activates tonic current in the α-cells but not in the β-cells. Seventeen different GABAA receptor subunits are expressed with high expression of α1, α2, α4, α6, β3, γ1, δ, ρ1, ρ2 and ρ3 subunits whereas no expression was detected for α5 or ε subunits. The abundance of the GABAA receptor subunits detected suggests that a number of GABAA receptor subtypes are formed in the islets. The single-channel and tonic currents were enhanced by pentobarbital and inhibited by the GABAA receptor antagonist SR-95531. The single-channel conductance ranged from 24 to 105 pS. Whether the single-channel conductance is related to subtypes of the GABAA receptor or variable interstitial GABA concentrations remains to be determined. Our results reveal that GABA is an extracellular signaling molecule in rat pancreatic islets and reaches concentration levels that activate GABAA receptors on the glucagon-releasing α-cells.
Collapse
|
86
|
Crivello M, Bonaventura MM, Chamson-Reig A, Arany E, Bettler B, Libertun C, Lux-Lantos V. Postnatal development of the endocrine pancreas in mice lacking functional GABAB receptors. Am J Physiol Endocrinol Metab 2013; 304:E1064-76. [PMID: 23531612 DOI: 10.1152/ajpendo.00569.2012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adult mice lacking functional GABAB receptors (GABAB1KO) have glucose metabolism alterations. Since GABAB receptors (GABABRs) are expressed in progenitor cells, we evaluated islet development in GABAB1KO mice. Postnatal day 4 (PND4) and adult, male and female, GABAB1KO, and wild-type littermates (WT) were weighed and euthanized, and serum insulin and glucagon was measured. Pancreatic glucagon and insulin content were assessed, and pancreas insulin, glucagon, PCNA, and GAD65/67 were determined by immunohistochemistry. RNA from PND4 pancreata and adult isolated islets was obtained, and Ins1, Ins2, Gcg, Sst, Ppy, Nes, Pdx1, and Gad1 transcription levels were determined by quantitative PCR. The main results were as follows: 1) insulin content was increased in PND4 GABAB1KO females and in both sexes in adult GABAB1KOs; 2) GABAB1KO females had more clusters (<500 μm(2)) and less islets than WT females; 3) cluster proliferation was decreased at PND4 and increased in adult GABAB1KO mice; 4) increased β-area at the expense of the α-cell area was present in GABAB1KO islets; 5) Ins2, Sst, and Ppy transcription were decreased in PND4 GABAB1KO pancreata, adult GABAB1KO female islets showed increased Ins1, Ins2, and Sst expression, Pdx1 was increased in male and female GABAB1KO islets; and 6) GAD65/67 was increased in adult GABAB1KO pancreata. We demonstrate that several islet parameters are altered in GABAB1KO mice, further pinpointing the importance of GABABRs in islet physiology. Some changes persist from neonatal ages to adulthood (e.g., insulin content in GABAB1KO females), whereas other features are differentially regulated according to age (e.g., Ins2 was reduced in PND4, whereas it was upregulated in adult GABAB1KO females).
Collapse
Affiliation(s)
- Martín Crivello
- Neuroendocrinology Laboratory, Instituto de Biología y Medicina Experimental-Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | | | | | | | | | | | | |
Collapse
|
87
|
Zarrin M, De Matteis L, Vernay M, Wellnitz O, van Dorland H, Bruckmaier R. Long-term elevation of β-hydroxybutyrate in dairy cows through infusion: Effects on feed intake, milk production, and metabolism. J Dairy Sci 2013; 96:2960-72. [DOI: 10.3168/jds.2012-6224] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 01/27/2013] [Indexed: 11/19/2022]
|
88
|
Bonaventura MM, Rodriguez D, Ferreira ML, Crivello M, Repetto EM, Bettler B, Libertun C, Lux-Lantos VA. Sex differences in insulin resistance in GABAB1 knockout mice. Life Sci 2013; 92:175-82. [PMID: 23178152 DOI: 10.1016/j.lfs.2012.11.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 10/16/2012] [Accepted: 11/07/2012] [Indexed: 11/17/2022]
Abstract
AIMS We have previously demonstrated that the absence of functional GABA B receptors (GABABRs) disturbs glucose homeostasis in GABAB1KO mice. The aim of this work was to extend our studies of these alterations in GABAB1KO mice and investigate the sexual differences therein. MAIN METHODS Male and female, GABAB1KO and WT mice were used. Glucose and insulin tolerance tests (GTT and ITT), and insulin and glucagon secretion tests (IST and GST) were performed. Blood glucose, serum insulin and hyperglycemic hormones were determined, and HOMA-IR calculated. Skeletal muscle insulin receptor β subunit (IRβ), insulin receptor substrates 1/2 (IRS1, IRS2) and hexokinase-II levels were determined by Western blot. Skeletal muscle insulin sensitivity was assessed by in vivo insulin-induced Akt phosphorylation (Western blot). Food intake and hypothalamic NPY mRNA expression (by qPCR) were also evaluated. KEY FINDINGS Fasted insulin and HOMA-IR were augmented in GABAB1KO males, with no alterations in females. Areas under the curve (AUC) for GTT and ITT were increased in GABAB1KO mice of both genders, indicating compromised insulin sensitivity. No genotype differences were observed in IST, GST or in IRβ, IRS1, IRS2 and hexokinase-II expression. Akt activation was severely impaired in GABAB1KO males while no alterations were observed in females. GABAB1KO mice showed increased food intake and NPY expression. SIGNIFICANCE Glucose metabolism and energy balance disruptions were more pronounced in GABAB1KO males, which develop peripheral insulin resistance probably due to augmented insulin secretion. Metabolic alterations in females were milder and possibly due to previously described reproductive disorders, such as persistent estrus.
Collapse
Affiliation(s)
- M M Bonaventura
- Instituto de Biología y Medicina Experimental-CONICET, Buenos Aires, Argentina
| | | | | | | | | | | | | | | |
Collapse
|
89
|
Huang YC, Rupnik MS, Karimian N, Herrera PL, Gilon P, Feng ZP, Gaisano HY. In situ electrophysiological examination of pancreatic α cells in the streptozotocin-induced diabetes model, revealing the cellular basis of glucagon hypersecretion. Diabetes 2013; 62:519-30. [PMID: 23043159 PMCID: PMC3554363 DOI: 10.2337/db11-0786] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Early-stage type 1 diabetes (T1D) exhibits hyperglucagonemia by undefined cellular mechanisms. Here we characterized α-cell voltage-gated ion channels in a streptozotocin (STZ)-induced diabetes model that lead to increased glucagon secretion mimicking T1D. GYY mice expressing enhanced yellow fluorescence protein in α cells were used to identify α cells within pancreas slices. Mice treated with low-dose STZ exhibited hyperglucagonemia, hyperglycemia, and glucose intolerance, with 71% reduction of β-cell mass. Although α-cell mass of STZ-treated mice remained unchanged, total pancreatic glucagon content was elevated, coinciding with increase in size of glucagon granules. Pancreas tissue slices enabled in situ examination of α-cell electrophysiology. α cells of STZ-treated mice exhibited the following: 1) increased exocytosis (serial depolarization-induced capacitance), 2) enhanced voltage-gated Na(+) current density, 3) reduced voltage-gated K(+) current density, and 4) increased action potential (AP) amplitude and firing frequency. Hyperglucagonemia in STZ-induced diabetes is thus likely due to increased glucagon content arising from enlarged glucagon granules and increased AP firing frequency and amplitude coinciding with enhanced Na(+) and reduced K(+) currents. These alterations may prime α cells in STZ-treated mice for more glucagon release per cell in response to low glucose stimulation. Thus, our study provides the first insight that STZ treatment sensitizes release mechanisms of α cells.
Collapse
Affiliation(s)
- Ya-Chi Huang
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Marjan S. Rupnik
- Faculty of Medicine, Institute of Physiology/CIPKEBIP, University of Maribor, Maribor, Slovenia
| | - Negar Karimian
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Pedro L. Herrera
- Cell Physiology & Metabolism, University of Geneva, Geneva, Switzerland
| | - Patrick Gilon
- Pole d’Endocrinologie, Diabète et Nutrition, Université Catholique de Louvain, Brussels, Belgium
| | - Zhong-Ping Feng
- Physiology and Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Herbert Y. Gaisano
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
- Physiology and Medicine, University of Toronto, Toronto, Ontario, Canada
- Corresponding author: Herbert Y. Gaisano,
| |
Collapse
|
90
|
Li C, Liu C, Nissim I, Chen J, Chen P, Doliba N, Zhang T, Nissim I, Daikhin Y, Stokes D, Yudkoff M, Bennett MJ, Stanley CA, Matschinsky FM, Naji A. Regulation of glucagon secretion in normal and diabetic human islets by γ-hydroxybutyrate and glycine. J Biol Chem 2012; 288:3938-51. [PMID: 23266825 DOI: 10.1074/jbc.m112.385682] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Paracrine signaling between pancreatic islet β-cells and α-cells has been proposed to play a role in regulating glucagon responses to elevated glucose and hypoglycemia. To examine this possibility in human islets, we used a metabolomic approach to trace the responses of amino acids and other potential neurotransmitters to stimulation with [U-(13)C]glucose in both normal individuals and type 2 diabetics. Islets from type 2 diabetics uniformly showed decreased glucose stimulation of insulin secretion and respiratory rate but demonstrated two different patterns of glucagon responses to glucose: one group responded normally to suppression of glucagon by glucose, but the second group was non-responsive. The non-responsive group showed evidence of suppressed islet GABA levels and of GABA shunt activity. In further studies with normal human islets, we found that γ-hydroxybutyrate (GHB), a potent inhibitory neurotransmitter, is generated in β-cells by an extension of the GABA shunt during glucose stimulation and interacts with α-cell GHB receptors, thus mediating the suppressive effect of glucose on glucagon release. We also identified glycine, acting via α-cell glycine receptors, as the predominant amino acid stimulator of glucagon release. The results suggest that glycine and GHB provide a counterbalancing receptor-based mechanism for controlling α-cell secretory responses to metabolic fuels.
Collapse
Affiliation(s)
- Changhong Li
- Division of Endocrinology, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
91
|
Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
Collapse
Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| |
Collapse
|
92
|
Israël M. A possible primary cause of cancer: deficient cellular interactions in endocrine pancreas. Mol Cancer 2012; 11:63. [PMID: 22954255 PMCID: PMC3438135 DOI: 10.1186/1476-4598-11-63] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 09/03/2012] [Indexed: 02/07/2023] Open
Abstract
Background Cancer is a devastating type of disease. New and innovative ways to tackle cancers that have so far proved refractive to conventional therapies is urgently needed. It is becoming increasingly clear that, in addition to conventional therapeutics targeting by small molecules, that tumor cell metabolism presents new opportunities to target selectively specific cancer cell populations. Metabolic defects in cancer cells can be manifested in many ways that might not be readily apparent, such as altering epigenetic gene regulation for example. The complex rewiring of metabolic pathways gives tumor cells a special advantage over differentiated cells, since they deplete body stores as fuel for their growth and proliferation. Tumor metabolism looks simpler when we consider that some enzymatic switches are in a neoglucogenic direction thereby depleting body stores. However, these pathways may be inadequately switched on by catabolic hormones (glucagon, epinephrine and cortisol) in a specific situation where anabolism is activated by, for example insulin released from beta pancreatic cells or IGF, inducing mitosis and synthesis that are powered by glucose catabolism. Such a hybrid metabolic situation would be reached if a pancreatic beta cell mechanism, mediated by GABA, failed to silence neighboring alpha cells and delta cells. The inhibitory transmitter GABA hyperpolarizes alpha and delta cells via their GABA A receptors, and blocks the release of glucagon and somatostatin. Alternatively, an anomaly of alpha cell channels, would lead to a similar situation. Whatever is the alteration, anabolism fails to silence catabolism and enzymatic switches controlled by kinases and phosphatases adopt an inadequate direction, leading to a hybrid metabolic rewiring found in cancer. It is daring to formulate such a hypothesis as this. However, it is quite possible that the starting point in cancer is an alteration of the endocrine pancreas, suppressing the mechanism by which beta cells silence the neighboring alpha and delta cells, with GABA and Zn2+.
Collapse
|
93
|
Gaisano HY, Macdonald PE, Vranic M. Glucagon secretion and signaling in the development of diabetes. Front Physiol 2012; 3:349. [PMID: 22969729 PMCID: PMC3432929 DOI: 10.3389/fphys.2012.00349] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 08/10/2012] [Indexed: 12/19/2022] Open
Abstract
Normal release of glucagon from pancreatic islet α-cells promotes glucose mobilization, which counteracts the hypoglycemic actions of insulin, thereby ensuring glucose homeostasis. In treatment of diabetes aimed at rigorously reducing hyperglycemia to avoid chronic complications, the resulting hypoglycemia triggering glucagon release from α-cells is frequently impaired, with ensuing hypoglycemic complications. This review integrates the physiology of glucagon secretion regulating glucose homeostasis in vivo to single α-cell signaling, and how both become perturbed in diabetes. α-cells within the social milieu of the islet micro-organ are regulated not only by intrinsic signaling events but also by paracrine regulation, particularly by adjacent insulin-secreting β-cells and somatostatin-secreting δ-cells. We discuss the intrinsic α-cell signaling events, including glucose sensing and ion channel regulation leading to glucagon secretion. We then discuss the complex crosstalk between the islet cells and the breakdown of this crosstalk in diabetes contributing to the dysregulated glucagon secretion. Whereas, there are many secretory products released by β- and δ-cells that become deficient or excess in diabetes, we discuss the major ones, including the better known insulin and lesser known somatostatin, which act as putative paracrine on/off switches that very finely regulate α-cell secretory responses in health and diabetes. Of note in several type 1 diabetes (T1D) rodent models, blockade of excess somatostatin actions on α-cell could normalize glucagon secretion sufficient to attain normoglycemia in response to hypoglycemic assaults. There has been slow progress in fully elucidating the pathophysiology of the α-cell in diabetes because of the small number of α-cells within an islet and the islet mass becomes severely reduced and inflamed in diabetes. These limitations are just now being surmounted by new approaches.
Collapse
Affiliation(s)
- Herbert Y Gaisano
- Departments of Medicine and Physiology, University of Toronto Toronto, ON, Canada
| | | | | |
Collapse
|
94
|
Arvan P, Pietropaolo M, Ostrov D, Rhodes CJ. Islet autoantigens: structure, function, localization, and regulation. Cold Spring Harb Perspect Med 2012; 2:cshperspect.a007658. [PMID: 22908193 DOI: 10.1101/cshperspect.a007658] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Islet autoantigens associated with autoimmune type 1 diabetes (T1D) are expressed in pancreatic β cells, although many show wider patterns of expression in the neuroendocrine system. Within pancreatic β cells, every T1D autoantigen is in one way or another linked to the secretory pathway. Together, these autoantigens play diverse roles in glucose regulation, metabolism of biogenic amines, as well as the regulation, formation, and packaging of secretory granules. The mechanism(s) by which immune tolerance to islet-cell antigens is lost during the development of T1D, remains unclear. Antigenic peptide creation for immune presentation may potentially link to the secretory biology of β cells in a number of ways, including proteasomal digestion of misfolded products, exocytosis and endocytosis of cell-surface products, or antigen release from dying β cells during normal or pathological turnover. In this context, we evaluate the biochemical nature and immunogenicity of the major autoantigens in T1D including (pro)insulin, GAD65, ZnT8, IA2, and ICA69.
Collapse
Affiliation(s)
- Peter Arvan
- Division of Metabolism, Endocrinology & Diabetes, University of Michigan Medical School, Ann Arbor, MI 48105, USA.
| | | | | | | |
Collapse
|
95
|
Abstract
Glucagon, a peptide hormone secreted from the α-cells of the pancreatic islets, is critical for blood glucose homeostasis. We reviewed the literature and employed a computational systems analysis of intracellular metabolic and electrical regulation of glucagon secretion to better understand these processes. The mathematical model of α-cell metabolic parameters is based on our previous model for pancreatic β-cells. We also formulated an ionic model for action potentials that incorporates Ca ( 2+) , K (+) , Na (+) and Cl (-) currents. Metabolic and ionic models are coupled to the equations describing Ca ( 2+) homeostasis and glucagon secretion that depends on activation of specific voltage-gated Ca ( 2+) channels. Paracrine and endocrine regulations were analyzed with an emphasis on their effects on a hyperpolarization of membrane potential. This general model simulates and gives insight into the mechanisms of regulation of glucagon secretion under a wide range of experimental conditions. We also reviewed and analyzed dysfunctional mechanisms in α-cells to determine key pharmacological targets for modulating glucagon secretion in type 1 and 2 diabetes.
Collapse
Affiliation(s)
- Leonid E Fridlyand
- The Kovler Diabetes Center, Departments of Medicine and Pediatrics, The University of Chicago, Chicago, IL, USA.
| | | |
Collapse
|
96
|
Taneera J, Jin Z, Jin Y, Muhammed SJ, Zhang E, Lang S, Salehi A, Korsgren O, Renström E, Groop L, Birnir B. γ-Aminobutyric acid (GABA) signalling in human pancreatic islets is altered in type 2 diabetes. Diabetologia 2012; 55:1985-94. [PMID: 22538358 PMCID: PMC3369140 DOI: 10.1007/s00125-012-2548-7] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 03/07/2012] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS γ-Aminobutyric acid (GABA) is a signalling molecule in the interstitial space in pancreatic islets. We examined the expression and function of the GABA signalling system components in human pancreatic islets from normoglycaemic and type 2 diabetic individuals. METHODS Expression of GABA signalling system components was studied by microarray, quantitative PCR analysis, immunohistochemistry and patch-clamp experiments on cells in intact islets. Hormone release was measured from intact islets. RESULTS The GABA signalling system was compromised in islets from type 2 diabetic individuals, where the expression of the genes encoding the α1, α2, β2 and β3 GABA(A) channel subunits was downregulated. GABA originating within the islets evoked tonic currents in the cells. The currents were enhanced by pentobarbital and inhibited by the GABA(A) receptor antagonist, SR95531. The effects of SR95531 on hormone release revealed that activation of GABA(A) channels (GABA(A) receptors) decreased both insulin and glucagon secretion. The GABA(B) receptor antagonist, CPG55845, increased insulin release in islets (16.7 mmol/l glucose) from normoglycaemic and type 2 diabetic individuals. CONCLUSIONS/INTERPRETATION Interstitial GABA activates GABA(A) channels and GABA(B) receptors and effectively modulates hormone release in islets from type 2 diabetic and normoglycaemic individuals.
Collapse
Affiliation(s)
- J. Taneera
- Lund University Diabetes Center, Department of Clinical Sciences, Diabetes & Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - Z. Jin
- Department of Neuroscience, Uppsala University, Box 593, 75124 Uppsala, Sweden
| | - Y. Jin
- Department of Neuroscience, Uppsala University, Box 593, 75124 Uppsala, Sweden
| | - S. J. Muhammed
- Department of Clinical Sciences, Islet Cell physiology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - E. Zhang
- Department of Clinical Sciences, Islet Pathophysiology, University Hospital Malmö, Lund University, Malmö, 20502 Sweden
| | - S. Lang
- Department of Neuroscience, Uppsala University, Box 593, 75124 Uppsala, Sweden
- Lund University Diabetes Center, Department of Clinical Sciences, Diabetes & Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - A. Salehi
- Department of Clinical Sciences, Islet Cell physiology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - O. Korsgren
- Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, 75185 Sweden
| | - E. Renström
- Department of Clinical Sciences, Islet Pathophysiology, University Hospital Malmö, Lund University, Malmö, 20502 Sweden
| | - L. Groop
- Lund University Diabetes Center, Department of Clinical Sciences, Diabetes & Endocrinology, University Hospital Malmö, Lund University, Malmö, Sweden
| | - B. Birnir
- Department of Neuroscience, Uppsala University, Box 593, 75124 Uppsala, Sweden
| |
Collapse
|
97
|
Durst MA, Lux-Lantos VA, Hardy DB, Hill DJ, Arany EJ. Protein Restriction during Early Life in Rats Alters Pancreatic GABAA Receptor Subunit Expression and Glucagon Secretion in Adulthood. Can J Diabetes 2012. [DOI: 10.1016/j.jcjd.2012.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
|
98
|
Koh DS, Cho JH, Chen L. Paracrine interactions within islets of Langerhans. J Mol Neurosci 2012; 48:429-40. [PMID: 22528452 DOI: 10.1007/s12031-012-9752-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 03/12/2012] [Indexed: 01/05/2023]
Abstract
Glucose supply fluctuates between meal and fasting periods and its consumption by the body varies greatly depending on bodily metabolism. Pancreatic islets of Langerhans secrete various endocrine hormones including insulin and glucagon to keep blood glucose level relatively constant. Additionally, islet hormones regulate activity of neighboring cells as local autocrine or paracrine modulators. Moreover, islet cells release neurotransmitters such as glutamate and γ-aminobutyric acid (GABA) to gain more precise regulation of hormones release kinetics. Excitatory glutamate is co-released with glucagon from α-cells and activates glutamate receptors in the neighboring cells. GABA released from β-cells was shown to inhibit α-cells but to activate β-cells by acting GABA(A) receptors. This review summarizes the recent progress in understanding the paracrine/autocrine interactions in islets.
Collapse
Affiliation(s)
- Duk-Su Koh
- University of Washington, Seattle, WA, USA.
| | | | | |
Collapse
|
99
|
Abstract
Insulin secretion is one of the most characteristic features of β-cell physiology. As it plays a central role in glucose regulation, a number of experimental and theoretical studies have been performed since the discovery of the pancreatic β-cell. This review article aims to give an overview of the mathematical approaches to insulin secretion. Beginning with the bursting electrical activity in pancreatic β-cells, we describe effects of the gap-junction coupling between β-cells on the dynamics of insulin secretion. Then, implications of paracrine interactions among such islet cells as α-, β-, and δ-cells are discussed. Finally, we present mathematical models which incorporate effects of glycolysis and mitochondrial glucose metabolism on the control of insulin secretion.
Collapse
Affiliation(s)
- Kyungreem Han
- College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul, South Korea
| | | | | | | |
Collapse
|
100
|
Shen XX, Li HL, Pan L, Hong J, Xiao J, Hermansen K, Jeppesen PB, Li GW. Glucotoxicity and α cell dysfunction: involvement of the PI3K/Akt pathway in glucose-induced insulin resistance in rat islets and clonal αTC1-6 cells. Endocr Res 2012; 37:12-24. [PMID: 22007944 DOI: 10.3109/07435800.2011.610855] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AIM/HYPOTHESIS The objective of this study was to assess how long-term exposure to high glucose affects the α cell function and whether the increased glucagon secretion is mediated via insulin resistance. MATERIALS AND METHODS We established a β cell-depleted rat model to obtain pure primary α cells. Furthermore, isolated rat islets and TC1-6 cells (a clonal α cell line) were exposed to high glucose (25 or 30 mmol/L) and low glucose (5.5 mmol/L) for up to 5 days to evaluate the influence of chronic glucose toxicity on glucagon secretion and glucagon gene expression. Moreover, we added insulin and/or Wortmannin to examine if the inhibitory effect of insulin on glucagon secretion was impaired by high glucose via the phosphatidylinositol 3 kinase/PKB protein kinase B pathway. RESULTS Both glucagon secretion and glucagon gene expression were increased in response to 5 days exposure to high glucose. While a moderate insulin concentration slightly inhibits glucagon secretion from rat islets and α TC1-6 cells at high glucose, a pronounced increase in glucagon secretion was observed at low glucose. We found that the insulin-mediated activity of the phosphatidylinositol 3 kinase/PKB protein kinase B pathway in the α cell was markedly impaired by chronic exposure to high glucose. CONCLUSION The hypersecretion of glucagon induced by glucotoxicity may be secondary to insulin resistance of the α cell induced by impaired activity of the insulin signaling pathway.
Collapse
Affiliation(s)
- Xiao-Xia Shen
- Endocrinology and Cardiac Disease Clinical Center, Fuwai Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, PR China.
| | | | | | | | | | | | | | | |
Collapse
|