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Zou W, Chezhian J, Yu T, Liu W, Vu J, Slone J, Huang T. Dissecting the Roles of the Nuclear and Mitochondrial Genomes in a Mouse Model of Autoimmune Diabetes. Diabetes 2024; 73:108-119. [PMID: 37847928 DOI: 10.2337/db23-0430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 09/25/2023] [Indexed: 10/19/2023]
Abstract
Mitochondria, the organelles responsible for generating ATP in eukaryotic cells, have been previously implicated as a contributor to diabetes. However, mitochondrial proteins are encoded by both nuclear DNA (nDNA) and mtDNA. In order to better understand the relative contribution of each of these genomes to diabetes, a chimeric mitochondrial-nuclear exchange (MNX) mouse was created via pronuclear transfer carrying nDNA from a strain susceptible to type 1 diabetes (NOD/ShiLtJ) and mtDNA from nondiabetic C57BL/6J mice. Inheritance of the resulting heteroplasmic mtDNA mixture was then tracked across multiple generations, showing that offspring heteroplasmy generally followed that of the mother, with occasional large shifts consistent with an mtDNA bottleneck in the germ line. In addition, survival and incidence of diabetes in MNX mice were tracked and compared with those in unaltered NOD/ShiLtJ control mice. The results indicated improved survival and a delay in diabetes onset in the MNX mice, demonstrating that mtDNA has a critical influence on disease phenotype. Finally, enzyme activity assays showed that the NOD/ShiLtJ mice had significant hyperactivity of complex I of the electron transport chain relative to MNX mice, suggesting that a particular mtDNA variant (m.9461T>C) may be responsible for disease causation in the original NOD/ShiLtJ strain. ARTICLE HIGHLIGHTS Mitochondria have been previously implicated in diabetes, but the specific genetic factors remain unclear. To better understand the contributions of mitochondrial genes in nuclear DNA (nDNA) versus mtDNA, we created mitochondrial-nuclear exchange (MNX) mice carrying nDNA from a diabetic strain and mtDNA from nondiabetic mice. Long-term tracking of MNX mice showed occasional large shifts in heteroplasmy consistent with an mtDNA bottleneck in the germ line. In addition, the MNX mice showed improved survival and delayed incidence of diabetes relative to the unaltered diabetic mice, which appeared to be linked to the activity of respiratory complex I.
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Affiliation(s)
- Weiwei Zou
- Department of Obstetrics and Gynecology, Reproductive Medicine Center, First Affiliated Hospital of Anhui Medical University, Hefei, Anhui Province, China
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - Janaki Chezhian
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY
| | - Tenghui Yu
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY
- Human Aging Research Institute, School of Life Science, Nanchang University, Nanchang, Jiangxi Province, China
| | - Wensheng Liu
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY
| | - Jimmy Vu
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY
| | - Jesse Slone
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY
| | - Taosheng Huang
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY
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2
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Nichols CG. Personalized Therapeutics for K ATP-Dependent Pathologies. Annu Rev Pharmacol Toxicol 2023; 63:541-563. [PMID: 36170658 PMCID: PMC9868118 DOI: 10.1146/annurev-pharmtox-051921-123023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Ubiquitously expressed throughout the body, ATP-sensitive potassium (KATP) channels couple cellular metabolism to electrical activity in multiple tissues; their unique assembly as four Kir6 pore-forming subunits and four sulfonylurea receptor (SUR) subunits has resulted in a large armory of selective channel opener and inhibitor drugs. The spectrum of monogenic pathologies that result from gain- or loss-of-function mutations in these channels, and the potential for therapeutic correction of these pathologies, is now clear. However, while available drugs can be effective treatments for specific pathologies, cross-reactivity with the other Kir6 or SUR subfamily members can result in drug-induced versions of each pathology and may limit therapeutic usefulness. This review discusses the background to KATP channel physiology, pathology, and pharmacology and considers the potential for more specific or effective therapeutic agents.
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Affiliation(s)
- Colin G. Nichols
- Center for the Investigation of Membrane Excitability Diseases and Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, USA
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3
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Early Effects of Metabolic Syndrome on ATP-Sensitive Potassium Channels from Rat Pancreatic Beta Cells. Metabolites 2022; 12:metabo12040365. [PMID: 35448552 PMCID: PMC9030496 DOI: 10.3390/metabo12040365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Revised: 04/12/2022] [Accepted: 04/16/2022] [Indexed: 11/16/2022] Open
Abstract
Metabolic syndrome (MS) is a cluster of metabolic signs that increases the risk of developing type 2 two diabetes mellitus and cardiovascular diseases. MS leads to pancreatic beta cell exhaustion and decreased insulin secretion through unknown mechanisms in a time-dependent manner. ATP-sensitive potassium channels (KATP channels), common targets of anti-diabetic drugs, participate in the glucose-stimulated insulin secretion, coupling the metabolic status and electrical activity of pancreatic beta cells. We investigated the early effects of MS on the conductance, ATP and glybenclamide sensitivity of the KATP channels. We used Wistar rats fed with a high-sucrose diet (HSD) for 8 weeks as a MS model. In excised membrane patches, control and HSD channels showed similar unitary conductance and ATP sensitivity pancreatic beta cells in their KATP channels. In contrast, MS produced variability in the sensitivity to glybenclamide of KATP channels. We observed two subpopulations of pancreatic beta cells, one with similar (Gly1) and one with increased (Gly2) glybenclamide sensitivity compared to the control group. This study shows that the early effects of MS produced by consuming high-sugar beverages can affect the pharmacological properties of KATP channels to one of the drugs used for diabetes treatment.
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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5
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Martin GM, Sung MW, Shyng SL. Pharmacological chaperones of ATP-sensitive potassium channels: Mechanistic insight from cryoEM structures. Mol Cell Endocrinol 2020; 502:110667. [PMID: 31821855 PMCID: PMC6994177 DOI: 10.1016/j.mce.2019.110667] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/22/2019] [Accepted: 11/22/2019] [Indexed: 02/07/2023]
Abstract
ATP-sensitive potassium (KATP) channels are uniquely evolved protein complexes that couple cell energy levels to cell excitability. They govern a wide range of physiological processes including hormone secretion, neuronal transmission, vascular dilation, and cardiac and neuronal preconditioning against ischemic injuries. In pancreatic β-cells, KATP channels composed of Kir6.2 and SUR1, encoded by KCNJ11 and ABCC8, respectively, play a key role in coupling blood glucose concentration to insulin secretion. Mutations in ABCC8 or KCNJ11 that diminish channel function result in congenital hyperinsulinism. Many of these mutations principally hamper channel biogenesis and hence trafficking to the cell surface. Several small molecules have been shown to correct channel biogenesis and trafficking defects. Here, we review studies aimed at understanding how mutations impair channel biogenesis and trafficking and how pharmacological ligands overcome channel trafficking defects, particularly highlighting recent cryo-EM structural studies which have shed light on the mechanisms of channel assembly and pharmacological chaperones.
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Affiliation(s)
- Gregory M Martin
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Min Woo Sung
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Show-Ling Shyng
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA.
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6
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Emfinger CH, Lőrincz R, Wang Y, York NW, Singareddy SS, Ikle JM, Tryon RC, McClenaghan C, Shyr ZA, Huang Y, Reissaus CA, Meyer D, Piston DW, Hyrc K, Remedi MS, Nichols CG. Beta-cell excitability and excitability-driven diabetes in adult Zebrafish islets. Physiol Rep 2019; 7:e14101. [PMID: 31161721 PMCID: PMC6546968 DOI: 10.14814/phy2.14101] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 04/30/2019] [Accepted: 04/30/2019] [Indexed: 12/15/2022] Open
Abstract
Islet β-cell membrane excitability is a well-established regulator of mammalian insulin secretion, and defects in β-cell excitability are linked to multiple forms of diabetes. Evolutionary conservation of islet excitability in lower organisms is largely unexplored. Here we show that adult zebrafish islet calcium levels rise in response to elevated extracellular [glucose], with similar concentration-response relationship to mammalian β-cells. However, zebrafish islet calcium transients are nor well coupled, with a shallower glucose-dependence of cytoplasmic calcium concentration. We have also generated transgenic zebrafish that conditionally express gain-of-function mutations in ATP-sensitive K+ channels (KATP -GOF) in β-cells. Following induction, these fish become profoundly diabetic, paralleling features of mammalian diabetes resulting from equivalent mutations. KATP -GOF fish become severely hyperglycemic, with slowed growth, and their islets lose glucose-induced calcium responses. These results indicate that, although lacking tight cell-cell coupling of intracellular Ca2+ , adult zebrafish islets recapitulate similar excitability-driven β-cell glucose responsiveness to those in mammals, and exhibit profound susceptibility to diabetes as a result of inexcitability. While illustrating evolutionary conservation of islet excitability in lower vertebrates, these results also provide important validation of zebrafish as a suitable animal model in which to identify modulators of islet excitability and diabetes.
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Affiliation(s)
- Christopher H. Emfinger
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Department of MedicineDivision of Endocrinology, Metabolism, and Lipid ResearchWashington University in St. Louis School of MedicineSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Réka Lőrincz
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
- Institute of Molecular Biology/CMBILeopold‐Franzens‐University InnsbruckInnsbruckAustria
| | - Yixi Wang
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Nathaniel W. York
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Soma S. Singareddy
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Jennifer M. Ikle
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
- Department of PediatricsWashington University in St. Louis School of MedicineSt. LouisMissouri
- Present address:
Department of CardiologyRenmin Hospital of Wuhan UniversityWuhanChina
| | - Robert C. Tryon
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Conor McClenaghan
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Zeenat A. Shyr
- Department of MedicineDivision of Endocrinology, Metabolism, and Lipid ResearchWashington University in St. Louis School of MedicineSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Yan Huang
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
- Department of PediatricsWashington University in St. Louis School of MedicineSt. LouisMissouri
- Present address:
Department of CardiologyRenmin Hospital of Wuhan UniversityWuhanChina
| | - Christopher A. Reissaus
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
| | - Dirk Meyer
- Institute of Molecular Biology/CMBILeopold‐Franzens‐University InnsbruckInnsbruckAustria
| | - David W. Piston
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Krzysztof Hyrc
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Maria S. Remedi
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Department of MedicineDivision of Endocrinology, Metabolism, and Lipid ResearchWashington University in St. Louis School of MedicineSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
| | - Colin G. Nichols
- Department of Cell Biology and PhysiologyWashington University in St. LouisSt. LouisMissouri
- Center for the Investigation of Membrane Excitability DiseasesWashington University in St. Louis School of MedicineSt. LouisMissouri
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Shyr ZA, Wang Z, York NW, Nichols CG, Remedi MS. The role of membrane excitability in pancreatic β-cell glucotoxicity. Sci Rep 2019; 9:6952. [PMID: 31061431 PMCID: PMC6502887 DOI: 10.1038/s41598-019-43452-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 01/11/2019] [Indexed: 01/09/2023] Open
Abstract
Persistent hyperglycemia is causally associated with pancreatic β-cell dysfunction and loss of pancreatic insulin. Glucose normally enhances β-cell excitability through inhibition of KATP channels, opening of voltage-dependent calcium channels, increased [Ca2+]i, which triggers insulin secretion. Glucose-dependent excitability is lost in islets from KATP-knockout (KATP-KO) mice, in which β-cells are permanently hyperexcited, [Ca2+]i, is chronically elevated and insulin is constantly secreted. Mouse models of human neonatal diabetes in which KATP gain-of-function mutations are expressed in β-cells (KATP-GOF) also lose the link between glucose metabolism and excitation-induced insulin secretion, but in this case KATP-GOF β-cells are chronically underexcited, with permanently low [Ca2+]i and lack of glucose-dependent insulin secretion. We used KATP-GOF and KATP-KO islets to examine the role of altered-excitability in glucotoxicity. Wild-type islets showed rapid loss of insulin content when chronically incubated in high-glucose, an effect that was reversed by subsequently switching to low glucose media. In contrast, hyperexcitable KATP-KO islets lost insulin content in both low- and high-glucose, while underexcitable KATP-GOF islets maintained insulin content in both conditions. Loss of insulin content in chronic excitability was replicated by pharmacological inhibition of KATP by glibenclamide, The effects of hyperexcitable and underexcitable islets on glucotoxicity observed in in vivo animal models are directly opposite to the effects observed in vitro: we clearly demonstrate here that in vitro, hyperexcitability is detrimental to islets whereas underexcitability is protective.
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Affiliation(s)
- Zeenat A Shyr
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
| | - Zhiyu Wang
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA.,Endocrine Consultants Northwest, Franciscan Medical Group, 1628 South Mildred St. Suite 104, Tacoma, WA, 98465, USA
| | - Nathaniel W York
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA
| | - Maria S Remedi
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA. .,Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA. .,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri, 63110, USA.
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Emfinger CH, Yan Z, Welscher A, Hung P, McAllister W, Hruz PW, Nichols CG, Remedi MS. Contribution of systemic inflammation to permanence of K ATP-induced neonatal diabetes in mice. Am J Physiol Endocrinol Metab 2018; 315:E1121-E1132. [PMID: 30226997 PMCID: PMC6336961 DOI: 10.1152/ajpendo.00137.2018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Gain-of-function (GOF) mutations in the ATP-sensitive potassium (KATP) channels cause neonatal diabetes. Despite the well-established genetic root of the disease, pathways modulating disease severity and treatment effectiveness remain poorly understood. Patient phenotypes can vary from severe diabetes to remission, even in individuals with the same mutation and within the same family, suggesting that subtle modifiers can influence disease outcome. We have tested the underlying mechanism of transient vs. permanent neonatal diabetes in KATP-GOF mice treated for 14 days with glibenclamide. Some KATP-GOF mice show remission of diabetes and enhanced insulin sensitivity long after diabetes treatment has ended, while others maintain severe insulin-resistance. However, insulin sensitivity is not different between the two groups before or during diabetes induction, suggesting that improved sensitivity is a consequence, rather than the cause of, remission, implicating other factors modulating glucose early in diabetes progression. Leptin, glucagon, insulin, and glucagon-like peptide-1 are not different between remitters and nonremitters. However, liver glucose production is significantly reduced before transgene induction in remitter, relative to nonremitter and nontreated, mice. Surprisingly, while subsequent remitter animals exhibited normal serum cytokines, nonremitter mice showed increased cytokines, which paralleled the divergence in blood glucose. Together, these results suggest that systemic inflammation may play a role in the remitting versus non-remitting outcome. Supporting this conclusion, treatment with the anti-inflammatory meloxicam significantly increased the fraction of remitting animals. Beyond neonatal diabetes, the potential for inflammation and glucose production to exacerbate other forms of diabetes from a compensated state to a glucotoxic state should be considered.
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Affiliation(s)
- Christopher H Emfinger
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis , St. Louis, Missouri
| | - Zihan Yan
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
| | - Alecia Welscher
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
| | - Peter Hung
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
| | - William McAllister
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
| | - Paul W Hruz
- Department of Pediatrics, Washington University in St. Louis , St. Louis, Missouri
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis , St. Louis, Missouri
| | - Maria S Remedi
- Department of Medicine, Washington University in St. Louis , St. Louis, Missouri
- Department of Cell Biology and Physiology, Washington University in St. Louis , St. Louis, Missouri
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis , St. Louis, Missouri
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9
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Viji D, Aswathi P, Pricilla Charmine P, Akram Husain R, Noorul Ameen S, Ahmed SS, Ramakrishnan V. Genetic association of ABCC8 rs757110 polymorphism with Type 2 Diabetes Mellitus risk: A case-control study in South India and a meta-analysis. GENE REPORTS 2018. [DOI: 10.1016/j.genrep.2018.10.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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10
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Wang DD, Chen X, Yang Y, Liu CX. Association of K ir6.2 gene rs5219 variation with type 2 diabetes: A meta-analysis of 21,464 individuals. Prim Care Diabetes 2018; 12:345-353. [PMID: 29685723 DOI: 10.1016/j.pcd.2018.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 03/01/2018] [Accepted: 03/24/2018] [Indexed: 12/16/2022]
Abstract
AIMS rs5219 is in Potassium inwardly-rectifying channel, subfamily J, member 11 (KCNJ11) E23K gene, located at 11p15.1. Researches on the association between rs5219 gene polymorphism with type 2 diabetes mellitus (T2DM) were performed extensively, but the results remain controversial. To investigate the relationship, a meta-analysis involving 21,464 individuals was conducted. METHODS Odds ratios (OR) and 95% confidence intervals (CI) were used to assess the strength of this association. Publication bias was evaluated with Begg's test. Our research includes three gene models: allelic genetic model (K-allele vs. E-allele), recessive genetic model (KK vs. EK+EE) and dominant genetic model (EE vs. EK+KK). RESULTS In allelic genetic model, subgroup analysis demonstrated rs5219 K-allele was relevant to T2DM risk in Caucasian (OR: 1.16, 95% CI: 1.09-1.24, P=0.000) and East Asian (OR: 1.19, 95% CI: 1.13-1.26, P=0.000), recessive genetic model indicated rs5219 KK genotype was related to T2DM risk in Caucasian, East Asian, South Asian, and North African (OR: 1.27, 95% CI: 1.17-1.38, P=0.000), dominant genetic model pointed out rs5219 EE genotype was an opposite association with T2DM risk in Caucasian (OR: 0.86, 95% CI: 0.78-0.94, P=0.001). No obvious evidence of publication bias was found. CONCLUSIONS There was a believable evidence to verify that rs5219 variation was associated with T2DM.
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Affiliation(s)
- Dong-Dong Wang
- Department of Pharmacy, Children's Hospital of Fudan University, Shanghai, 201102, PR China
| | - Xiao Chen
- Department of Pharmacy, The People's Hospital of Jiangyin, Jiangyin, Jiangsu 214400, PR China.
| | - Yang Yang
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical University, Xuzhou, Jiangsu 221004, PR China
| | - Chen-Xu Liu
- Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical University, Xuzhou, Jiangsu 221004, PR China
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11
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Ramu Y, Xu Y, Lu Z. A novel high-affinity inhibitor against the human ATP-sensitive Kir6.2 channel. J Gen Physiol 2018; 150:969-976. [PMID: 29844136 DOI: 10.1085/jgp.201812017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/27/2018] [Indexed: 01/29/2023] Open
Abstract
The adenosine triphosphate (ATP)-sensitive (KATP) channels in pancreatic β cells couple the blood glucose level to insulin secretion. KATP channels in pancreatic β cells comprise the pore-forming Kir6.2 and the modulatory sulfonylurea receptor 1 (SUR1) subunits. Currently, there is no high-affinity and relatively specific inhibitor for the Kir6.2 pore. The importance of developing such inhibitors is twofold. First, in many cases, the lack of such an inhibitor precludes an unambiguous determination of the Kir6.2's role in certain physiological and pathological processes. This problem is exacerbated because Kir6.2 knockout mice do not yield the expected phenotypes of hyperinsulinemia and hypoglycemia, which in part, may reflect developmental adaptation. Second, mutations in Kir6.2 or SUR1 that increase the KATP current cause permanent neonatal diabetes mellitus (PNDM). Many patients who have PNDM have been successfully treated with sulphonylureas, a common class of antidiabetic drugs that bind to SUR1 and indirectly inhibit Kir6.2, thereby promoting insulin secretion. However, some PNDM-causing mutations render KATP channels insensitive to sulphonylureas. Conceptually, because these mutations are located intracellularly, an inhibitor blocking the Kir6.2 pore from the extracellular side might provide another approach to this problem. Here, by screening the venoms from >200 animals against human Kir6.2 coexpressed with SUR1, we discovered a small protein of 54 residues (SpTx-1) that inhibits the KATP channel from the extracellular side. It inhibits the channel with a dissociation constant value of 15 nM in a relatively specific manner and with an apparent one-to-one stoichiometry. SpTx-1 evidently inhibits the channel by primarily targeting Kir6.2 rather than SUR1; it inhibits not only wild-type Kir6.2 coexpressed with SUR1 but also a Kir6.2 mutant expressed without SUR1. Importantly, SpTx-1 suppresses both sulfonylurea-sensitive and -insensitive, PNDM-causing Kir6.2 mutants. Thus, it will be a valuable tool to investigate the channel's physiological and biophysical properties and to test a new strategy for treating sulfonylurea-resistant PNDM.
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Affiliation(s)
- Yajamana Ramu
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Yanping Xu
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Zhe Lu
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
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12
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Remedi MS, Thomas M, Nichols CG, Marshall BA. Sulfonylurea challenge test in subjects diagnosed with type 1 diabetes mellitus. Pediatr Diabetes 2017; 18:777-784. [PMID: 28111849 PMCID: PMC5522783 DOI: 10.1111/pedi.12489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 11/14/2016] [Accepted: 11/22/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Patients with early onset diabetes because of defects in glucose-stimulated insulin secretion (GSIS) may respond better to sulfonylureas than insulin treatment. Such patients include those with monogenic disorders, who can be differentiated from autoimmune type 1 diabetes mellitus (T1DM) by genetic testing. Genetic testing is expensive and unknown defects in GSIS would not be diagnosed. AIMS We propose a sulfonylurea challenge test to identify patients who have been clinically diagnosed with T1DM, but those who maintain a preferentially sulfonylurea-responsive insulin secretion. MATERIALS & METHODS A total of 3 healthy controls, 2 neonatal diabetes mellitus (NDM) subjects, 3 antibody-positive (Ab+T1DM), and 12 antibody-negative (Ab-T1DM) subjects with type 1 diabetes, were given an intravenous bolus of glucose followed by an oral dose of glipizide. RESULTS Healthy controls showed a robust C-peptide increase after both glucose and glipizide, but NDM subjects showed a large increase in C-peptide only following glipizide. As expected, 2 of 3 Ab+T1DM, as well as 11 of 12 Ab-T1DM showed no response to either glucose or glipizide. However, 1 Ab-T1DM and 1 Ab+T1DM showed a small C-peptide response to glucose and a marked positive response to glipizide, suggesting defects in GSIS rather than typical autoimmune diabetes. DISCUSSION These data demonstrate the feasibility of the sulfonylurea challenge test, and suggest that responder individuals may be identified. CONCLUSIONS We propose that this sulfonylurea challenge test should be explored more extensively, as it may prove useful as a clinical and scientific tool.
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Affiliation(s)
- Maria S. Remedi
- Department of Medicine, Washington University Medical School, St. Louis, MO,Department of Cell Biology and Physiology, Washington University Medical School, St. Louis, MO,Department of Center for the Investigation of Membrane Excitability Diseases, Washington University Medical School, St. Louis, MO
| | - Mareen Thomas
- Department of Pediatrics, Washington University Medical School, St. Louis, MO
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University Medical School, St. Louis, MO,Department of Center for the Investigation of Membrane Excitability Diseases, Washington University Medical School, St. Louis, MO
| | - Bess A. Marshall
- Department of Pediatrics, Washington University Medical School, St. Louis, MO,Department of Cell Biology and Physiology, Washington University Medical School, St. Louis, MO,Department of Center for the Investigation of Membrane Excitability Diseases, Washington University Medical School, St. Louis, MO,Correspondence should be addressed to: Bess A. Marshall. One Children’s Place, Box 8116, St. Louis, MO, 63110. Phone: (314) 454-6051, Fax: (314) 454-6225.
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Velasco M, Díaz-García CM, Larqué C, Hiriart M. Modulation of Ionic Channels and Insulin Secretion by Drugs and Hormones in Pancreatic Beta Cells. Mol Pharmacol 2016; 90:341-57. [PMID: 27436126 DOI: 10.1124/mol.116.103861] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/18/2016] [Indexed: 12/11/2022] Open
Abstract
Pancreatic beta cells, unique cells that secrete insulin in response to an increase in glucose levels, play a significant role in glucose homeostasis. Glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells has been extensively explored. In this mechanism, glucose enters the cells and subsequently the metabolic cycle. During this process, the ATP/ADP ratio increases, leading to ATP-sensitive potassium (KATP) channel closure, which initiates depolarization that is also dependent on the activity of TRP nonselective ion channels. Depolarization leads to the opening of voltage-gated Na(+) channels (Nav) and subsequently voltage-dependent Ca(2+) channels (Cav). The increase in intracellular Ca(2+) triggers the exocytosis of insulin-containing vesicles. Thus, electrical activity of pancreatic beta cells plays a central role in GSIS. Moreover, many growth factors, incretins, neurotransmitters, and hormones can modulate GSIS, and the channels that participate in GSIS are highly regulated. In this review, we focus on the principal ionic channels (KATP, Nav, and Cav channels) involved in GSIS and how classic and new proteins, hormones, and drugs regulate it. Moreover, we also discuss advances on how metabolic disorders such as metabolic syndrome and diabetes mellitus change channel activity leading to changes in insulin secretion.
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Affiliation(s)
- Myrian Velasco
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Manlio Díaz-García
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Carlos Larqué
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Marcia Hiriart
- Department of Neurodevelopment and Physiology, Neuroscience Division, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
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14
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Wang C, Geng B, Cui Q, Guan Y, Yang J. Intracellular and extracellular adenosine triphosphate in regulation of insulin secretion from pancreatic β cells (β). J Diabetes 2014; 6:113-9. [PMID: 24134160 DOI: 10.1111/1753-0407.12098] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 09/27/2013] [Accepted: 10/11/2013] [Indexed: 01/09/2023] Open
Abstract
Adenosine triphosphate (ATP) synthesis and release in mitochondria play critical roles in regulating insulin secretion in pancreatic β cells. Mitochondrial dysfunction is mainly characterized by a decrease in ATP production, which is a central event in the progression of pancreatic β cell dysfunction and diabetes. ATP has been demonstrated to regulate insulin secretion via several pathways: (i) Intracellular ATP directly closes ATP-sensitive potassium channel to open L-type calcium channel, leading to an increase in free cytosolic calcium levels and exocytosis of insulin granules; (ii) A decrease in ATP production is always associated with an increase in production of reactive oxygen species, which exerts deleterious effects on pancreatic β cell survival and insulin secretion; and (iii) ATP can be co-secreted with insulin from pancreatic β cells, and the released ATP functions as an autocrine signal to modulate insulin secretory process via P2 receptors on the cell membrane. In this review, the recent findings regarding the role and mechanism of ATP synthesis and release in regulation of insulin secretion from pancreatic β cells will be summarized and discussed.
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Affiliation(s)
- Chunjiong Wang
- Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China
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15
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Abstract
Ion channels and transporters are expressed in every living cell, where they participate in controlling a plethora of biological processes and physiological functions, such as excitation of cells in response to stimulation, electrical activities of cells, excitation-contraction coupling, cellular osmolarity, and even cell growth and death. Alterations of ion channels/transporters can have profound impacts on the cellular physiology associated with these proteins. Expression of ion channels/transporters is tightly regulated and expression deregulation can trigger abnormal processes, leading to pathogenesis, the channelopathies. While transcription factors play a critical role in controlling the transcriptome of ion channels/transporters at the transcriptional level by acting on the 5'-flanking region of the genes, microribonucleic acids (miRNAs), a newly discovered class of regulators in the gene network, are also crucial for expression regulation at the posttranscriptional level through binding to the 3'untranslated region of the genes. These small noncoding RNAs fine tune expression of genes involved in a wide variety of cellular processes. Recent studies revealed the role of miRNAs in regulating expression of ion channels/transporters and the associated physiological functions. miRNAs can target ion channel genes to alter cardiac excitability (conduction, repolarization, and automaticity) and affect arrhythmogenic potential of heart. They can modulate circadian rhythm, pain threshold, neuroadaptation to alcohol, brain edema, etc., through targeting ion channel genes in the neuronal systems. miRNAs can also control cell growth and tumorigenesis by acting on the relevant ion channel genes. Future studies are expected to rapidly increase to unravel a new repertoire of ion channels/transporters for miRNA regulation.
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Affiliation(s)
- Zhiguo Wang
- Harbin Medical University, Harbin, Heilongjiang, People's Republic of China.
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16
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Park SH, Ho WK, Jeon JH. AMPK regulates K(ATP) channel trafficking via PTEN inhibition in leptin-treated pancreatic β-cells. Biochem Biophys Res Commun 2013; 440:539-44. [PMID: 24103758 DOI: 10.1016/j.bbrc.2013.09.099] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 09/19/2013] [Indexed: 02/08/2023]
Abstract
Leptin regulates pancreatic β-cell excitability through AMP-activated protein kinase (AMPK)-mediated ATP-sensitive potassium (KATP) channel trafficking. However, the signaling components connecting AMPK to KATP channel trafficking are not identified. In this study, we discovered that AMPK inhibits phosphatase and tensin homologue (PTEN) via glycogen synthase kinase 3β (GSK3β) and this signaling pathway is crucial for KATP channel trafficking in leptin-treated pancreatic β-cells. Pharmacologic or genetic inhibition of AMPK or GSK3β, but not casein kinase 2 (CK2), impaired leptin-induced PTEN inactivation and thereby KATP channel trafficking. The PTEN mutant lacking both protein and lipid phosphatase activity is sufficient to induce KATP channel trafficking without leptin. These results present a novel signaling mechanism that underlies leptin regulation of KATP channel trafficking in pancreatic β-cells. Our findings assist in gaining a broader perspective on the peripheral action of leptin on pancreatic β-cell physiology and glucose homeostasis.
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Affiliation(s)
- Sun-Hyun Park
- Cell Physiology Laboratory and Biomembrane Plasticity Research Center, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Republic of Korea; Department of Physiology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul 110-799, Republic of Korea
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17
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Denton JS, Jacobson DA. Channeling dysglycemia: ion-channel variations perturbing glucose homeostasis. Trends Endocrinol Metab 2012; 23:41-8. [PMID: 22134088 PMCID: PMC3733341 DOI: 10.1016/j.tem.2011.09.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 09/22/2011] [Accepted: 09/23/2011] [Indexed: 01/26/2023]
Abstract
Maintaining blood glucose homeostasis is a complex process that depends on pancreatic islet hormone secretion. Hormone secretion from islets is coupled to calcium entry which results from regenerative islet cell electrical activity. Therefore, the ionic mechanisms that regulate calcium entry into islet cells are crucial for maintaining normal glucose homeostasis. Genome-wide association studies (GWAS) have identified single-nucleotide polymorphisms (SNPs), including five located in or near ion-channel or associated subunit genes, which show an association with human diseases characterized by dysglycemia. This review focuses on polymorphisms and mutations in ion-channel genes that are associated with perturbations in human glucose homeostasis and discusses their potential roles in modulating pancreatic islet hormone secretion.
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Affiliation(s)
- Jerod Scott Denton
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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18
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Terzic A, Alekseev AE, Yamada S, Reyes S, Olson TM. Advances in cardiac ATP-sensitive K+ channelopathies from molecules to populations. Circ Arrhythm Electrophysiol 2011; 4:577-85. [PMID: 21846889 DOI: 10.1161/circep.110.957662] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Andre Terzic
- Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Department of Internal Medicine, Department of Molecular Pharmacology and Experimental Therapeutics, Department of Medical Genetics, Mayo Clinic, Rochester, MN, USA.
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Remedi MS, Agapova SE, Vyas AK, Hruz PW, Nichols CG. Acute sulfonylurea therapy at disease onset can cause permanent remission of KATP-induced diabetes. Diabetes 2011; 60:2515-22. [PMID: 21813803 PMCID: PMC3178299 DOI: 10.2337/db11-0538] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
OBJECTIVE Neonatal diabetes mellitus (NDM) can be caused by gain-of-function ATP-sensitive K(+) (K(ATP)) channel mutations. This realization has led to sulfonylurea therapy replacing insulin injections in many patients. In a murine model of K(ATP)-dependent NDM, hyperglycemia and consequent loss of β-cells are both avoided by chronic sulfonylurea treatment. Interestingly, K(ATP) mutations may underlie remitting-relapsing, transient, or permanent forms of the disease in different patients, but the reason for the different outcomes is unknown. RESEARCH DESIGN AND METHODS To gain further insight into disease progression and outcome, we examined the effects of very early intervention by injecting NDM mice with high-dose glibenclamide for only 6 days, at the beginning of disease onset, then after the subsequent progression with measurements of blood glucose, islet function, and insulin sensitivity. RESULTS Although ∼70% of mice developed severe diabetes after treatment cessation, ∼30% were essentially cured, maintaining near-normal blood glucose until killed. Another group of NDM mice was initiated on oral glibenclamide (in the drinking water), and the dose was titrated daily, to maintain blood glucose <200 mg/dL. In this case, ∼30% were also essentially cured; they were weaned from the drug after ∼4 weeks and again subsequently maintained near-normal blood glucose. These cured mice maintain normal insulin content and were more sensitive to insulin than control mice, a compensatory mechanism that together with basal insulin secretion may be sufficient to maintain near-normal glucose levels. CONCLUSIONS At least in a subset of animals, early sulfonylurea treatment leads to permanent remission of NDM. These cured animals exhibit insulin-hypersensitivity. Although untreated NDM mice rapidly lose insulin content and progress to permanently extremely elevated blood glucose levels, early tight control of blood glucose may permit this insulin-hypersensitivity, in combination with maintained basal insulin secretion, to provide long-term remission.
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Affiliation(s)
- Maria Sara Remedi
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Sophia E. Agapova
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
| | - Arpita K. Vyas
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Paul W. Hruz
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri
- Corresponding author: Colin G. Nichols,
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Schäfer SA, Machicao F, Fritsche A, Häring HU, Kantartzis K. New type 2 diabetes risk genes provide new insights in insulin secretion mechanisms. Diabetes Res Clin Pract 2011; 93 Suppl 1:S9-24. [PMID: 21864758 DOI: 10.1016/s0168-8227(11)70008-0] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Type 2 diabetes results from the inability of beta cells to increase insulin secretion sufficiently to compensate for insulin resistance. Insulin resistance is thought to result mainly from environmental factors, such as obesity. However, there is compelling evidence that the decline of both insulin sensitivity and insulin secretion have also a genetic component. Recent genome-wide association studies identified several novel risk genes for type 2 diabetes. The vast majority of these genes affect beta cell function by molecular mechanisms that remain unknown in detail. Nevertheless, we and others could show that a group of genes affect glucose-stimulated insulin secretion, a group incretin-stimulated insulin secretion (incretin sensitivity or secretion) and a group proinsulin-to-insulin conversion. The most important so far type 2 diabetes risk gene, TCF7L2, interferes with all three mechanisms. In addition to advancing knowledge in the pathophysiology of type 2 diabetes, the discovery of novel genetic determinants of diabetes susceptibility may help understanding of gene-environment, gene-therapy and gene-gene interactions. It was also hoped that it could make determination of the individual risk for type 2 diabetes feasible. However, the allelic relative risks of most genetic variants discovered so far are relatively low. Thus, at present, clinical criteria assess the risk for type 2 diabetes with greater sensitivity and specificity than the combination of all known genetic variants.
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Affiliation(s)
- Silke A Schäfer
- Department of Internal Medicine, Division of Endocrinology, Diabetology, Nephrology, Vascular Disease and Clinical Chemistry, University of Tübingen, Germany
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21
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Quan Y, Barszczyk A, Feng ZP, Sun HS. Current understanding of K ATP channels in neonatal diseases: focus on insulin secretion disorders. Acta Pharmacol Sin 2011; 32:765-80. [PMID: 21602835 PMCID: PMC4009965 DOI: 10.1038/aps.2011.57] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 04/13/2011] [Indexed: 12/25/2022] Open
Abstract
ATP-sensitive potassium (K(ATP)) channels are cell metabolic sensors that couple cell metabolic status to electric activity, thus regulating many cellular functions. In pancreatic beta cells, K(ATP) channels modulate insulin secretion in response to fluctuations in plasma glucose level, and play an important role in glucose homeostasis. Recent studies show that gain-of-function and loss-of-function mutations in K(ATP) channel subunits cause neonatal diabetes mellitus and congenital hyperinsulinism respectively. These findings lead to significant changes in the diagnosis and treatment for neonatal insulin secretion disorders. This review describes the physiological and pathophysiological functions of K(ATP) channels in glucose homeostasis, their specific roles in neonatal diabetes mellitus and congenital hyperinsulinism, as well as future perspectives of K(ATP) channels in neonatal diseases.
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Affiliation(s)
- Yi Quan
- Departments of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Andrew Barszczyk
- Departments of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Zhong-ping Feng
- Departments of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
| | - Hong-shuo Sun
- Departments of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
- Departments of Surgery, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
- Departments of Pharmacology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
- Institute of Medical Science, Faculty of Medicine, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada, M5S 1A8
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22
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Schieder M, Rötzer K, Brüggemann A, Biel M, Wahl-Schott C. Planar patch clamp approach to characterize ionic currents from intact lysosomes. Sci Signal 2010; 3:pl3. [PMID: 21139138 DOI: 10.1126/scisignal.3151pl3] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Since its launch in the early 1980s, the patch clamp method has been extensively used to study ion channels in the plasma membrane, but its application to the study of intracellular ion channels has been limited. Unlike the plasma membrane, intracellular membranes are usually not stable enough to withstand mechanical manipulation by glass electrodes during seal formation and rupturing of the membrane. To circumvent these problems, we developed a method involving the immobilization of isolated organelles on a solid matrix planar glass chip. This glass chip contains a microstructured hole that supports the formation of gigaseals and subsequent electrophysiological recordings despite the high fragility of intracellular membranes. Here, we report the experimental details of this method using lysosomes, which are the smallest cellular organelles, as a model system. We demonstrate that we can record endogenous ionic currents from wild-type lysosomes, as well as from lysosomes overexpressing ion channels, and expect that this method will provide electrophysiological access to a broad range of intracellular ion channels.
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Affiliation(s)
- Michael Schieder
- Center for Integrated Protein Science CIPS-M and Zentrum für Pharmaforschung-Department Pharmazie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5 -13, D-81377 München, Germany
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23
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Edghill EL, Flanagan SE, Ellard S. Permanent neonatal diabetes due to activating mutations in ABCC8 and KCNJ11. Rev Endocr Metab Disord 2010; 11:193-8. [PMID: 20922570 DOI: 10.1007/s11154-010-9149-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The ATP-sensitive potassium (K(ATP)) channel is composed of two subunits SUR1 and Kir6.2. The channel is key for glucose stimulated insulin release from the pancreatic beta cell. Activating mutations have been identified in the genes encoding these subunits, ABCC8 and KCNJ11, and account for approximately 40% of permanent neonatal diabetes cases. The majority of patients with a K(ATP) mutation present with isolated diabetes however some have presented with the Developmental delay, Epilepsy and Neonatal Diabetes syndrome. This review focuses on mutations in the K(ATP) channel which result in permanent neonatal diabetes, we review the clinical and functional effects as well as the implications for treatment.
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MESH Headings
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- ATP-Binding Cassette Transporters/physiology
- Diabetes Mellitus/congenital
- Diabetes Mellitus/genetics
- Diabetes Mellitus/therapy
- Genetic Association Studies
- Humans
- Infant, Newborn
- Infant, Newborn, Diseases/genetics
- Infant, Newborn, Diseases/therapy
- KATP Channels/genetics
- KATP Channels/metabolism
- KATP Channels/physiology
- Models, Biological
- Mutation/physiology
- Potassium Channels, Inwardly Rectifying/genetics
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium Channels, Inwardly Rectifying/physiology
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Receptors, Drug/physiology
- Sulfonylurea Receptors
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Affiliation(s)
- Emma L Edghill
- Institute of Biomedical and Clinical Science, Peninsula College of Medicine and Dentistry, University of Exeter, Barrack Road, Exeter, UK
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