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Patel S, Yan Z, Remedi MS. Intermittent fasting protects β-cell identity and function in a type-2 diabetes model. Metabolism 2024; 153:155813. [PMID: 38307325 PMCID: PMC10985623 DOI: 10.1016/j.metabol.2024.155813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 01/28/2024] [Accepted: 01/29/2024] [Indexed: 02/04/2024]
Abstract
Type 2 diabetes (T2DM) is caused by the interaction of multiple genes and environmental factors. T2DM is characterized by hyperglycemia, insulin secretion deficiency and insulin resistance. Chronic hyperglycemia induces β-cell dysfunction, loss of β-cell mass/identity and β-cell dedifferentiation. Intermittent fasting (IF) a commonly used dietary regimen for weight-loss, also induces metabolic benefits including reduced blood glucose, improved insulin sensitivity, reduced adiposity, inflammation, oxidative-stress and increased fatty-acid oxidation; however, the mechanisms underlying these effects in pancreatic β-cells remain elusive. KK and KKAy, mouse models of polygenic T2DM spontaneously develop hyperglycemia, glucose intolerance, glucosuria, impaired insulin secretion and insulin resistance. To determine the long-term effects of IF on T2DM, 6-weeks old KK and KKAy mice were subjected to IF for 16 weeks. While KKAy mice fed ad-libitum demonstrated severe hyperglycemia (460 mg/dL) at 6 weeks of age, KK mice showed blood glucose levels of 230 mg/dL, but progressively became severely diabetic by 22-weeks. Strikingly, both KK and KKAy mice subjected to IF showed reduced blood glucose and plasma insulin levels, decreased body weight gain, reduced plasma triglycerides and cholesterol, and improved insulin sensitivity. They also demonstrated enhanced expression of the β-cell transcription factors NKX6.1, MAFA and PDX1, and decreased expression of ALDH1a3 suggesting protection from loss of β-cell identity by IF. IF normalized glucose stimulated insulin secretion in islets from KK and KKAy mice, demonstrating improved β-cell function. In addition, hepatic steatosis, gluconeogenesis and inflammation was decreased particularly in KKAy-IF mice, indicating peripheral benefits of IF. These results have important implications as an optional intervention for preservation of β-cell identity and function in T2DM.
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Affiliation(s)
- Sumit Patel
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, United States of America
| | - Zihan Yan
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, United States of America
| | - Maria S Remedi
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, United States of America; Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, United States of America; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, Saint Louis, MO, United States of America.
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Grizzanti J, Moritz WR, Pait MC, Stanley M, Kaye SD, Carroll CM, Constantino NJ, Deitelzweig LJ, Snipes JA, Kellar D, Caesar EE, Pettit-Mee RJ, Day SM, Sens JP, Nicol NI, Dhillon J, Remedi MS, Kiraly DD, Karch CM, Nichols CG, Holtzman DM, Macauley SL. KATP channels are necessary for glucose-dependent increases in amyloid-β and Alzheimer's disease-related pathology. JCI Insight 2023; 8:e162454. [PMID: 37129980 PMCID: PMC10386887 DOI: 10.1172/jci.insight.162454] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 04/18/2023] [Indexed: 05/03/2023] Open
Abstract
Elevated blood glucose levels, or hyperglycemia, can increase brain excitability and amyloid-β (Aβ) release, offering a mechanistic link between type 2 diabetes and Alzheimer's disease (AD). Since the cellular mechanisms governing this relationship are poorly understood, we explored whether ATP-sensitive potassium (KATP) channels, which couple changes in energy availability with cellular excitability, play a role in AD pathogenesis. First, we demonstrate that KATP channel subunits Kir6.2/KCNJ11 and SUR1/ABCC8 were expressed on excitatory and inhibitory neurons in the human brain, and cortical expression of KCNJ11 and ABCC8 changed with AD pathology in humans and mice. Next, we explored whether eliminating neuronal KATP channel activity uncoupled the relationship between metabolism, excitability, and Aβ pathology in a potentially novel mouse model of cerebral amyloidosis and neuronal KATP channel ablation (i.e., amyloid precursor protein [APP]/PS1 Kir6.2-/- mouse). Using both acute and chronic paradigms, we demonstrate that Kir6.2-KATP channels are metabolic sensors that regulate hyperglycemia-dependent increases in interstitial fluid levels of Aβ, amyloidogenic processing of APP, and amyloid plaque formation, which may be dependent on lactate release. These studies identify a potentially new role for Kir6.2-KATP channels in AD and suggest that pharmacological manipulation of Kir6.2-KATP channels holds therapeutic promise in reducing Aβ pathology in patients with diabetes or prediabetes.
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Affiliation(s)
- John Grizzanti
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - William R. Moritz
- Department of Neurology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Morgan C. Pait
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Molly Stanley
- Department of Neurology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
- Department of Biology, College of Arts and Sciences, University of Vermont, Burlington, Vermont, USA
| | - Sarah D. Kaye
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Caitlin M. Carroll
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Nicholas J. Constantino
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Lily J. Deitelzweig
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - James A. Snipes
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Derek Kellar
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Emily E. Caesar
- Department of Neurology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | | | | | | | - Noelle I. Nicol
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Jasmeen Dhillon
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Maria S. Remedi
- Department of Physiology and Pharmacology and
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research
| | | | - Celeste M. Karch
- Department of Psychiatry
- Hope Center for Neurological Disorders
- Knight Alzheimer’s Disease Research Center, Department of Neurology; and
| | - Colin G. Nichols
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - David M. Holtzman
- Department of Neurology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
- Hope Center for Neurological Disorders
- Knight Alzheimer’s Disease Research Center, Department of Neurology; and
| | - Shannon L. Macauley
- Department of Physiology and Pharmacology and
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
- Alzheimer’s Disease Research Center
- Center on Diabetes, Obesity and Metabolism
- Center for Precision Medicine; and
- Cardiovascular Sciences Center, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
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Dong G, Adak S, Spyropoulos G, Zhang Q, Feng C, Yin L, Speck SL, Shyr Z, Morikawa S, Kitamura RA, Kathayat RS, Dickinson BC, Ng XW, Piston DW, Urano F, Remedi MS, Wei X, Semenkovich CF. Palmitoylation couples insulin hypersecretion with β cell failure in diabetes. Cell Metab 2023; 35:332-344.e7. [PMID: 36634673 PMCID: PMC9908855 DOI: 10.1016/j.cmet.2022.12.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 10/14/2022] [Accepted: 12/15/2022] [Indexed: 01/13/2023]
Abstract
Hyperinsulinemia often precedes type 2 diabetes. Palmitoylation, implicated in exocytosis, is reversed by acyl-protein thioesterase 1 (APT1). APT1 biology was altered in pancreatic islets from humans with type 2 diabetes, and APT1 knockdown in nondiabetic islets caused insulin hypersecretion. APT1 knockout mice had islet autonomous increased glucose-stimulated insulin secretion that was associated with prolonged insulin granule fusion. Using palmitoylation proteomics, we identified Scamp1 as an APT1 substrate that localized to insulin secretory granules. Scamp1 knockdown caused insulin hypersecretion. Expression of a mutated Scamp1 incapable of being palmitoylated in APT1-deficient cells rescued insulin hypersecretion and nutrient-induced apoptosis. High-fat-fed islet-specific APT1-knockout mice and global APT1-deficient db/db mice showed increased β cell failure. These findings suggest that APT1 is regulated in human islets and that APT1 deficiency causes insulin hypersecretion leading to β cell failure, modeling the evolution of some forms of human type 2 diabetes.
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Affiliation(s)
- Guifang Dong
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Hubei Key Laboratory of Animal Nutrition and Feed Science, Wuhan Polytechnic University, Wuhan 430023, China
| | - Sangeeta Adak
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - George Spyropoulos
- Department of Pediatrics, Washington University, St. Louis, MO 63110, USA
| | - Qiang Zhang
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Chu Feng
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Li Yin
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Sarah L Speck
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Zeenat Shyr
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Shuntaro Morikawa
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Rie Asada Kitamura
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA
| | - Rahul S Kathayat
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Bryan C Dickinson
- Department of Chemistry, University of Chicago, Chicago, IL 60637, USA
| | - Xue Wen Ng
- Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA
| | - David W Piston
- Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA
| | - Fumihiko Urano
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Department of Pathology & Immunology, Washington University, St. Louis, MO 63110, USA
| | - Maria S Remedi
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA
| | - Xiaochao Wei
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA.
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism & Lipid Research, Washington University, St. Louis, MO 63110, USA; Department of Cell Biology & Physiology, Washington University, St. Louis, MO 63110, USA.
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4
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Remedi MS, Nichols CG. Glucokinase Inhibition: A Novel Treatment for Diabetes? Diabetes 2023; 72:170-174. [PMID: 36669001 PMCID: PMC9871191 DOI: 10.2337/db22-0731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/12/2022] [Indexed: 01/21/2023]
Abstract
Chronic hyperglycemia increases pancreatic β-cell metabolic activity, contributing to glucotoxicity-induced β-cell failure and loss of functional β-cell mass, potentially in multiple forms of diabetes. In this perspective we discuss the novel paradoxical and counterintuitive concept of inhibiting glycolysis, particularly by targeted inhibition of glucokinase, the first enzyme in glycolysis, as an approach to maintaining glucose sensing and preserving functional β-cell mass, thereby improving insulin secretion, in the treatment of diabetes.
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Affiliation(s)
- Maria S. Remedi
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
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Ikle JM, Tryon RC, Singareddy SS, York NW, Remedi MS, Nichols CG. Genome-edited zebrafish model of ABCC8 loss-of-function disease. Islets 2022; 14:200-209. [PMID: 36458573 PMCID: PMC9721409 DOI: 10.1080/19382014.2022.2149206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 10/25/2022] [Accepted: 11/13/2022] [Indexed: 12/03/2022] Open
Abstract
ATP-sensitive potassium channel (KATP)gain- (GOF) and loss-of-function (LOF) mutations underlie human neonatal diabetes mellitus (NDM) and hyperinsulinism (HI), respectively. While transgenic mice expressing incomplete KATP LOF do reiterate mild hyperinsulinism, KATP knockout animals do not exhibit persistent hyperinsulinism. We have shown that islet excitability and glucose homeostasis are regulated by identical KATP channels in zebrafish. SUR1 truncation mutation (K499X) was introduced into the abcc8 gene to explore the possibility of using zebrafish for modeling human HI. Patch-clamp analysis confirmed the complete absence of channel activity in β-cells from K499X (SUR1-/-) fish. No difference in random blood glucose was detected in heterozygous SUR1+/- fish nor in homozygous SUR1-/- fish, mimicking findings in SUR1 knockout mice. Mutant fish did, however, demonstrate impaired glucose tolerance, similar to partial LOF mouse models. In paralleling features of mammalian diabetes and hyperinsulinism resulting from equivalent LOF mutations, these gene-edited animals provide valid zebrafish models of KATP -dependent pancreatic diseases.
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Affiliation(s)
- Jennifer M. Ikle
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
- Department of Pediatrics, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
| | - Robert C. Tryon
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
| | - Soma S. Singareddy
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
| | - Nathaniel W. York
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
| | - Maria S. Remedi
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Lipid Research, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis School of Medicine, St. Louis, Missouri, USA
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Singh GK, McClenaghan C, Aggarwal M, Gu H, Remedi MS, Grange DK, Nichols CG. A Unique High-Output Cardiac Hypertrophy Phenotype Arising From Low Systemic Vascular Resistance in Cantu Syndrome. J Am Heart Assoc 2022; 11:e027363. [PMID: 36515236 PMCID: PMC9798820 DOI: 10.1161/jaha.122.027363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 10/25/2022] [Indexed: 12/15/2022]
Abstract
Background Cardiomegaly caused by left ventricular hypertrophy is a risk factor for development of congestive heart failure, classically associated with decreased systolic and/or diastolic ventricular function. Less attention has been given to the phenotype of left ventricular hypertrophy with enhanced ventricular function and increased cardiac output, which is potentially associated with high-output heart failure. Lack of recognition may pose diagnostic ambiguity and management complexities. Methods and Results We sought to systematically characterize high-output cardiac hypertrophy in subjects with Cantu syndrome (CS), caused by gain-of-function variants in ABCC9, which encodes cardiovascular KATP (ATP-sensitive potassium) channel subunits. We studied the cardiovascular phenotype longitudinally in 31 subjects with CS with confirmed ABCC9 variants (median [interquartile range] age 8 years [3-32 years], body mass index 19.9 [16.5-22.9], 16 male subjects). Subjects with CS presented with significant left ventricular hypertrophy (left ventricular mass index 86.7 [57.7-103.0] g/m2 in CS, n=30; 26.6 [24.1-32.8] g/m2 in controls, n=17; P<0.0001) and low blood pressure (systolic 94.5 [90-103] mm Hg in CS, n=17; 109 [98-115] mm Hg in controls, n=17; P=0.0301; diastolic 60 [56-66] mm Hg in CS, n=17; 69 [65-72] mm Hg in control, n=17; P=0.0063). Most (21/31) subjects with CS exhibited eccentric hypertrophy with normal left ventricular wall thickness. Congestive heart failure symptoms were evident in 4 of the 5 subjects with CS aged >40 years on long-term follow-up. Conclusions The data define the natural history of high-output cardiac hypertrophy resulting from decreased systemic vascular resistance in subjects with CS, a defining population for long-term consequences of high-output hypertrophy caused by low systemic vascular resistance, and the potential for progression to high-output heart failure.
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Affiliation(s)
- Gautam K. Singh
- Division of Cardiology, Department of PediatricsWashington University School of MedicineSt. LouisMO
- Center for the Investigation of Membrane Excitability Diseases (CIMED)Washington University School of MedicineSt. LouisMO
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases (CIMED)Washington University School of MedicineSt. LouisMO
- Department of Cell Biology and PhysiologyWashington University School of MedicineSt. LouisMO
| | - Manish Aggarwal
- Division of Cardiology, Department of PediatricsWashington University School of MedicineSt. LouisMO
| | - Hongjie Gu
- Division of StatisticsWashington University School of MedicineSt. LouisMO
| | - Maria S. Remedi
- Center for the Investigation of Membrane Excitability Diseases (CIMED)Washington University School of MedicineSt. LouisMO
- Department of Medicine, Division of EndocrinologyWashington University School of MedicineSt. LouisMO
| | - Dorothy K. Grange
- Center for the Investigation of Membrane Excitability Diseases (CIMED)Washington University School of MedicineSt. LouisMO
- Department of Pediatrics, Division of GeneticsWashington University School of MedicineSt. LouisMO
| | - Colin G. Nichols
- Center for the Investigation of Membrane Excitability Diseases (CIMED)Washington University School of MedicineSt. LouisMO
- Department of Cell Biology and PhysiologyWashington University School of MedicineSt. LouisMO
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Yan Z, Fortunato M, Shyr ZA, Clark AL, Fuess M, Nichols CG, Remedi MS. Genetic Reduction of Glucose Metabolism Preserves Functional β-Cell Mass in KATP-Induced Neonatal Diabetes. Diabetes 2022; 71:1233-1245. [PMID: 35294000 PMCID: PMC9163553 DOI: 10.2337/db21-0992] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 03/09/2022] [Indexed: 11/13/2022]
Abstract
β-Cell failure and loss of β-cell mass are key events in diabetes progression. Although insulin hypersecretion in early stages has been implicated in β-cell exhaustion/failure, loss of β-cell mass still occurs in KATP gain-of-function (GOF) mouse models of human neonatal diabetes in the absence of insulin secretion. Thus, we hypothesize that hyperglycemia-induced increased β-cell metabolism is responsible for β-cell failure and that reducing glucose metabolism will prevent loss of β-cell mass. To test this, KATP-GOF mice were crossed with mice carrying β-cell-specific glucokinase haploinsufficiency (GCK+/-), to genetically reduce glucose metabolism. As expected, both KATP-GOF and KATP-GOF/GCK+/- mice showed lack of glucose-stimulated insulin secretion. However, KATP-GOF/GCK+/- mice demonstrated markedly reduced blood glucose, delayed diabetes progression, and improved glucose tolerance compared with KATP-GOF mice. In addition, decreased plasma insulin and content, increased proinsulin, and augmented plasma glucagon observed in KATP-GOF mice were normalized to control levels in KATP-GOF/GCK+/- mice. Strikingly, KATP-GOF/GCK+/- mice demonstrated preserved β-cell mass and identity compared with the marked decrease in β-cell identity and increased dedifferentiation observed in KATP-GOF mice. Moreover KATP-GOF/GCK+/- mice demonstrated restoration of body weight and liver and brown/white adipose tissue mass and function and normalization of physical activity and metabolic efficiency compared with KATP-GOF mice. These results demonstrate that decreasing β-cell glucose signaling can prevent glucotoxicity-induced loss of insulin content and β-cell failure independently of compensatory insulin hypersecretion and β-cell exhaustion.
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Affiliation(s)
- Zihan Yan
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Manuela Fortunato
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Zeenat A. Shyr
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Amy L. Clark
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO
| | - Matt Fuess
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Colin G. Nichols
- Deparment of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
| | - Maria S. Remedi
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
- Deparment of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
- Corresponding author: Maria S. Remedi,
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8
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Nichols CG, York NW, Remedi MS. ATP-Sensitive Potassium Channels in Hyperinsulinism and Type 2 Diabetes: Inconvenient Paradox or New Paradigm? Diabetes 2022; 71:367-375. [PMID: 35196393 PMCID: PMC8893938 DOI: 10.2337/db21-0755] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 11/28/2021] [Indexed: 11/13/2022]
Abstract
Secretion of insulin from pancreatic β-cells is complex, but physiological glucose-dependent secretion is dominated by electrical activity, in turn controlled by ATP-sensitive potassium (KATP) channel activity. Accordingly, loss-of-function mutations of the KATP channel Kir6.2 (KCNJ11) or SUR1 (ABCC8) subunit increase electrical excitability and secretion, resulting in congenital hyperinsulinism (CHI), whereas gain-of-function mutations cause underexcitability and undersecretion, resulting in neonatal diabetes mellitus (NDM). Thus, diazoxide, which activates KATP channels, and sulfonylureas, which inhibit KATP channels, have dramatically improved therapies for CHI and NDM, respectively. However, key findings do not fit within this simple paradigm: mice with complete absence of β-cell KATP activity are not hyperinsulinemic; instead, they are paradoxically glucose intolerant and prone to diabetes, as are older human CHI patients. Critically, despite these advances, there has been little insight into any role of KATP channel activity changes in the development of type 2 diabetes (T2D). Intriguingly, the CHI progression from hypersecretion to undersecretion actually mirrors the classical response to insulin resistance in the progression of T2D. In seeking to explain the progression of CHI, multiple lines of evidence lead us to propose that underlying mechanisms are also similar and that development of T2D may involve loss of KATP activity.
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Affiliation(s)
- Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
| | - Nathaniel W York
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO
- Division of Endocrinology Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO
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Shyr ZA, Yan Z, Ustione A, Egan EM, Remedi MS. SGLT2 inhibitors therapy protects glucotoxicity-induced β-cell failure in a mouse model of human KATP-induced diabetes through mitigation of oxidative and ER stress. PLoS One 2022; 17:e0258054. [PMID: 35180212 PMCID: PMC8856523 DOI: 10.1371/journal.pone.0258054] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 02/01/2022] [Indexed: 01/06/2023] Open
Abstract
Progressive loss of pancreatic β-cell functional mass and anti-diabetic drug responsivity are classic findings in diabetes, frequently attributed to compensatory insulin hypersecretion and β-cell exhaustion. However, loss of β-cell mass and identity still occurs in mouse models of human KATP-gain-of-function induced Neonatal Diabetes Mellitus (NDM), in the absence of insulin secretion. Here we studied the temporal progression and mechanisms underlying glucotoxicity-induced loss of functional β-cell mass in NDM mice, and the effects of sodium-glucose transporter 2 inhibitors (SGLT2i) therapy. Upon tamoxifen induction of transgene expression, NDM mice rapidly developed severe diabetes followed by an unexpected loss of insulin content, decreased proinsulin processing and increased proinsulin at 2-weeks of diabetes. These early events were accompanied by a marked increase in β-cell oxidative and ER stress, without changes in islet cell identity. Strikingly, treatment with the SGLT2 inhibitor dapagliflozin restored insulin content, decreased proinsulin:insulin ratio and reduced oxidative and ER stress. However, despite reduction of blood glucose, dapagliflozin therapy was ineffective in restoring β-cell function in NDM mice when it was initiated at >40 days of diabetes, when loss of β-cell mass and identity had already occurred. Our data from mouse models demonstrate that: i) hyperglycemia per se, and not insulin hypersecretion, drives β-cell failure in diabetes, ii) recovery of β-cell function by SGLT2 inhibitors is potentially through reduction of oxidative and ER stress, iii) SGLT2 inhibitors revert/prevent β-cell failure when used in early stages of diabetes, but not when loss of β-cell mass/identity already occurred, iv) common execution pathways may underlie loss and recovery of β-cell function in different forms of diabetes. These results may have important clinical implications for optimal therapeutic interventions in individuals with diabetes, particularly for those with long-standing diabetes.
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MESH Headings
- Administration, Oral
- Animals
- Benzhydryl Compounds/administration & dosage
- Blood Glucose/metabolism
- Diabetes Mellitus/chemically induced
- Diabetes Mellitus/drug therapy
- Diabetes Mellitus/genetics
- Diabetes Mellitus/metabolism
- Disease Models, Animal
- Endoplasmic Reticulum Stress/drug effects
- Female
- Gain of Function Mutation/drug effects
- Glucosides/administration & dosage
- Humans
- Infant, Newborn
- Infant, Newborn, Diseases/chemically induced
- Infant, Newborn, Diseases/drug therapy
- Infant, Newborn, Diseases/genetics
- Infant, Newborn, Diseases/metabolism
- Insulin-Secreting Cells/drug effects
- Insulin-Secreting Cells/metabolism
- KATP Channels/genetics
- Male
- Mice
- Mice, Transgenic
- Oxidative Stress/drug effects
- Protective Agents/administration & dosage
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Sodium-Glucose Transporter 2 Inhibitors/administration & dosage
- Treatment Outcome
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Affiliation(s)
- Zeenat A. Shyr
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States of America
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Zihan Yan
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States of America
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Alessandro Ustione
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Erin M. Egan
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Maria S. Remedi
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, Missouri, United States of America
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St. Louis, St. Louis, Missouri, United States of America
- Department of Cell Biology and Physiology, Washington University in St. Louis, St. Louis, Missouri, United States of America
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10
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Clark AL, Yan Z, Chen SX, Shi V, Kulkarni DH, Diwan A, Remedi MS. High-fat diet prevents the development of autoimmune diabetes in NOD mice. Diabetes Obes Metab 2021; 23:2455-2465. [PMID: 34212475 PMCID: PMC8490276 DOI: 10.1111/dom.14486] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 06/21/2021] [Accepted: 06/30/2021] [Indexed: 12/20/2022]
Abstract
AIMS Type 1 diabetes (T1D) has a strong genetic predisposition and requires an environmental trigger to initiate the beta-cell autoimmune destruction. The rate of childhood obesity has risen in parallel to the proportion of T1D, suggesting high-fat diet (HFD)/obesity as potential environmental triggers for autoimmune diabetes. To explore this, non-obese diabetic (NOD) mice were subjected to HFD and monitored for the development of diabetes, insulitis and beta-cell stress. MATERIALS AND METHODS Four-week-old female NOD mice were placed on HFD (HFD-NOD) or standard chow-diet. Blood glucose was monitored weekly up to 40 weeks of age, and glucose- and insulin-tolerance tests performed at 4, 10 and 15 weeks. Pancreata and islets were analysed for insulin secretion, beta-cell mass, inflammation, insulitis and endoplasmic reticulum stress markers. Immune cell levels were measured in islets and spleens. Stool microbiome was analysed at age 4, 8 and 25 weeks. RESULTS At early ages, HFD-NOD mice showed a significant increase in body weight, glucose intolerance and insulin resistance; but paradoxically, they were protected from developing diabetes. This was accompanied by increased insulin secretion and beta-cell mass, decreased insulitis, increased splenic T-regulatory cells and altered stool microbiome. CONCLUSIONS This study shows that HFD protects NOD mice from autoimmune diabetes and preserves beta-cell mass and function through alterations in gut microbiome, increased T-regulatory cells and decreased insulitis. Further studies into the exact mechanism of HFD-mediated prevention of diabetes in NOD mice could potentially lead to interventions to prevent or delay T1D development in humans.
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Affiliation(s)
- Amy L. Clark
- Department of PediatricsWashington University in St LouisSt LouisMissouriUSA
| | - Zihan Yan
- Department of Internal Medicine, Endocrinology, Metabolism and Lipid research DivisionWashington University in St LouisSt LouisMissouriUSA
| | - Sophia X. Chen
- Department of Internal Medicine, Endocrinology, Metabolism and Lipid research DivisionWashington University in St LouisSt LouisMissouriUSA
| | - Victoria Shi
- Department of Internal Medicine, Endocrinology, Metabolism and Lipid research DivisionWashington University in St LouisSt LouisMissouriUSA
| | - Devesha H. Kulkarni
- Department of Internal MedicineWashington University in St LouisSt LouisMissouriUSA
| | - Abhinav Diwan
- Department of Internal Medicine‐Cardiovascular DivisionWashington University in St LouisSt LouisMissouriUSA
- John Cochran VA Medical Center‐Cardiovascular DivisionSt LouisMissouriUSA
| | - Maria S. Remedi
- Department of Internal Medicine, Endocrinology, Metabolism and Lipid research DivisionWashington University in St LouisSt LouisMissouriUSA
- Department of Cell Biology and PhysiologyWashington University in St LouisSt LouisMissouriUSA
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11
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Leanza G, Fontana F, Lee SY, Remedi MS, Schott C, Ferron M, Hamilton-Hall M, Alippe Y, Strollo R, Napoli N, Civitelli R. Gain-of-Function Lrp5 Mutation Improves Bone Mass and Strength and Delays Hyperglycemia in a Mouse Model of Insulin-Deficient Diabetes. J Bone Miner Res 2021; 36:1403-1415. [PMID: 33831261 PMCID: PMC8360087 DOI: 10.1002/jbmr.4303] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 03/21/2021] [Accepted: 03/28/2021] [Indexed: 01/26/2023]
Abstract
High fracture rate and high circulating levels of the Wnt inhibitor, sclerostin, have been reported in diabetic patients. We studied the effects of Wnt signaling activation on bone health in a mouse model of insulin-deficient diabetes. We introduced the sclerostin-resistant Lrp5A214V mutation, associated with high bone mass, in mice carrying the Ins2Akita mutation (Akita), which results in loss of beta cells, insulin deficiency, and diabetes in males. Akita mice accrue less trabecular bone mass with age relative to wild type (WT). Double heterozygous Lrp5A214V /Akita mutants have high trabecular bone mass and cortical thickness relative to WT animals, as do Lrp5A214V single mutants. Likewise, the Lrp5A214V mutation prevents deterioration of biomechanical properties occurring in Akita mice. Notably, Lrp5A214V /Akita mice develop fasting hyperglycemia and glucose intolerance with a delay relative to Akita mice (7 to 8 vs. 5 to 6 weeks, respectively), despite lack of insulin production in both groups by 6 weeks of age. Although insulin sensitivity is partially preserved in double heterozygous Lrp5A214V /Akita relative to Akita mutants up to 30 weeks of age, insulin-dependent phosphorylated protein kinase B (pAKT) activation in vitro is not altered by the Lrp5A214V mutation. Although white adipose tissue depots are equally reduced in both compound and Akita mice, the Lrp5A214V mutation prevents brown adipose tissue whitening that occurs in Akita mice. Thus, hyperactivation of Lrp5-dependent signaling fully protects bone mass and strength in prolonged hyperglycemia and improves peripheral glucose metabolism in an insulin independent manner. Wnt signaling activation represents an ideal therapeutic approach for diabetic patients at high risk of fracture. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Giulia Leanza
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA.,Department of Medicine, Unit of Endocrinology and Diabetes, Campus Bio-Medico University of Rome, Rome, Italy
| | - Francesca Fontana
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA
| | - Seung-Yon Lee
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA
| | - Maria S Remedi
- Division of Endocrinology, Metabolism and Lipid Research, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Céline Schott
- Molecular Physiology Research Unit, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada.,Molecular Biology Programs & Department of Medicine, Université de Montréal, Montréal, Quebec, Canada
| | - Mathieu Ferron
- Molecular Physiology Research Unit, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada.,Molecular Biology Programs & Department of Medicine, Université de Montréal, Montréal, Quebec, Canada
| | - Malcolm Hamilton-Hall
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA
| | - Yael Alippe
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA
| | - Rocky Strollo
- Department of Medicine, Unit of Endocrinology and Diabetes, Campus Bio-Medico University of Rome, Rome, Italy
| | - Nicola Napoli
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA.,Department of Medicine, Unit of Endocrinology and Diabetes, Campus Bio-Medico University of Rome, Rome, Italy
| | - Roberto Civitelli
- Division of Bone and Mineral Diseases, Department of Medicine, Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA
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12
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Zhang H, Hanson A, de Almeida TS, Emfinger C, McClenaghan C, Harter T, Yan Z, Cooper PE, Brown GS, Arakel EC, Mecham RP, Kovacs A, Halabi CM, Schwappach B, Remedi MS, Nichols CG. Complex consequences of Cantu syndrome SUR2 variant R1154Q in genetically modified mice. JCI Insight 2021; 6:145934. [PMID: 33529173 PMCID: PMC8021106 DOI: 10.1172/jci.insight.145934] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 01/27/2021] [Indexed: 01/10/2023] Open
Abstract
Cantu syndrome (CS) is caused by gain-of-function (GOF) mutations in pore-forming (Kir6.1, KCNJ8) and accessory (SUR2, ABCC9) ATP-sensitive potassium (KATP) channel subunits, the most common mutations being SUR2[R1154Q] and SUR2[R1154W], carried by approximately 30% of patients. We used CRISPR/Cas9 genome engineering to introduce the equivalent of the human SUR2[R1154Q] mutation into the mouse ABCC9 gene. Along with minimal CS disease features, R1154Q cardiomyocytes and vascular smooth muscle showed much lower KATP current density and pinacidil activation than WT cells. Almost complete loss of SUR2-dependent protein and KATP in homozygous R1154Q ventricles revealed underlying diazoxide-sensitive SUR1-dependent KATP channel activity. Surprisingly, sequencing of SUR2 cDNA revealed 2 distinct transcripts, one encoding full-length SUR2 protein; and the other with an in-frame deletion of 93 bases (corresponding to 31 amino acids encoded by exon 28) that was present in approximately 40% and approximately 90% of transcripts from hetero- and homozygous R1154Q tissues, respectively. Recombinant expression of SUR2A protein lacking exon 28 resulted in nonfunctional channels. CS tissue from SUR2[R1154Q] mice and human induced pluripotent stem cell-derived (hiPSC-derived) cardiomyocytes showed only full-length SUR2 transcripts, although further studies will be required in order to fully test whether SUR2[R1154Q] or other CS mutations might result in aberrant splicing and variable expressivity of disease features in human CS.
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Affiliation(s)
- Haixia Zhang
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Alex Hanson
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Tobias Scherf de Almeida
- Department of Molecular Biology, Center for Biochemistry and Molecular Cell Biology, Heart Research Center Göttingen, University Medicine Göttingen, Göttingen, Germany
| | - Christopher Emfinger
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Theresa Harter
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Zihan Yan
- Center for the Investigation of Membrane Excitability Diseases and.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany.,Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research
| | - Paige E Cooper
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - G Schuyler Brown
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Eric C Arakel
- Department of Molecular Biology, Center for Biochemistry and Molecular Cell Biology, Heart Research Center Göttingen, University Medicine Göttingen, Göttingen, Germany
| | - Robert P Mecham
- Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | | | - Carmen M Halabi
- Department of Pediatrics, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
| | - Blanche Schwappach
- Department of Molecular Biology, Center for Biochemistry and Molecular Cell Biology, Heart Research Center Göttingen, University Medicine Göttingen, Göttingen, Germany
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases and.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases and.,Department of Cell Biology and Physiology, Washington University School of Medicine in St. Louis, St. Louis, Missouri, USA
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13
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Nichols CG, York NW, Remedi MS. Preferential Gq signaling in diabetes: an electrical switch in incretin action and in diabetes progression? J Clin Invest 2021; 130:6235-6237. [PMID: 33196460 DOI: 10.1172/jci143199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Patients with type 2 diabetes (T2D) fail to secrete insulin in response to increased glucose levels that occur with eating. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are two incretins secreted from gastrointestinal cells that amplify insulin secretion when glucose is high. In this issue of the JCI, Oduori et al. explore the role of ATP-sensitive K+ (KATP) channels in maintaining glucose homeostasis. In persistently depolarized β cells from KATP channel knockout (KO) mice, the researchers revealed a shift in G protein signaling from the Gs family to the Gq family. This shift explains why GLP-1, which signals via Gq, but not GIP, which signals preferentially via Gs, can effectively potentiate secretion in islets from the KATP channel-deficient mice and in other models of KATP deficiency, including diabetic KK-Ay mice. Their results provide one explanation for differential insulinotropic potential of incretins in human T2D and point to a potentially unifying model for T2D progression itself.
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Affiliation(s)
- Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology and Physiology
| | - Nathaniel W York
- Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology and Physiology
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases.,Division of Endocrinology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
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14
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York NW, Parker H, Xie Z, Tyus D, Waheed MA, Yan Z, Grange DK, Remedi MS, England SK, Hu H, Nichols CG. Kir6.1- and SUR2-dependent KATP over-activity disrupts intestinal motility in murine models of Cantu Syndrome. JCI Insight 2020; 5:141443. [PMID: 33170808 PMCID: PMC7714409 DOI: 10.1172/jci.insight.141443] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 10/28/2020] [Indexed: 11/17/2022] Open
Abstract
Cantύ Syndrome (CS), caused by gain-of-function (GOF) mutations in pore-forming (Kir6.1, KCNJ8) and accessory (SUR2, ABCC9) ATP-sensitive potassium (KATP) channel subunit genes, is frequently accompanied by gastrointestinal (GI) dysmotility, and we describe one CS patient who required an implanted intestinal irrigation system for successful stooling. We used gene-modified mice to assess the underlying KATP channel subunits in gut smooth muscle, and to model the consequences of altered KATP channels in CS gut. We show that Kir6.1/SUR2 subunits underlie smooth muscle KATP channels throughout the small intestine and colon. Knock-in mice, carrying human KCNJ8 and ABCC9 CS mutations in the endogenous loci, exhibit reduced intrinsic contractility throughout the intestine, resulting in death when weaned onto solid food in the most severely affected animals. Death is avoided by weaning onto a liquid gel diet, implicating intestinal insufficiency and bowel impaction as the underlying cause, and GI transit is normalized by treatment with the KATP inhibitor glibenclamide. We thus define the molecular basis of intestinal KATP channel activity, the mechanism by which overactivity results in GI insufficiency, and a viable approach to therapy.
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Affiliation(s)
- Nathaniel W York
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States of America
| | - Helen Parker
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States of America
| | - Zili Xie
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, United States of America
| | - David Tyus
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States of America
| | - Maham A Waheed
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States of America
| | - Zihan Yan
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, United States of America
| | - Dorothy K Grange
- Divison of Clinical Genetics, Washington University School of Medicine, St. Louis, United States of America
| | - Maria S Remedi
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States of America
| | - Sarah K England
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, United States of America
| | - Hongzhen Hu
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, United States of America
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States of America
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15
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McClenaghan C, Huang Y, Yan Z, Harter TM, Halabi CM, Chalk R, Kovacs A, van Haaften G, Remedi MS, Nichols CG. Glibenclamide reverses cardiovascular abnormalities of Cantu syndrome driven by KATP channel overactivity. J Clin Invest 2020; 130:1116-1121. [PMID: 31821173 DOI: 10.1172/jci130571] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 12/05/2019] [Indexed: 12/12/2022] Open
Abstract
Cantu syndrome (CS) is a complex disorder caused by gain-of-function (GoF) mutations in ABCC9 and KCNJ8, which encode the SUR2 and Kir6.1 subunits, respectively, of vascular smooth muscle (VSM) KATP channels. CS includes dilated vasculature, marked cardiac hypertrophy, and other cardiovascular abnormalities. There is currently no targeted therapy, and it is unknown whether cardiovascular features can be reversed once manifest. Using combined transgenic and pharmacological approaches in a knockin mouse model of CS, we have shown that reversal of vascular and cardiac phenotypes can be achieved by genetic downregulation of KATP channel activity specifically in VSM, and by chronic administration of the clinically used KATP channel inhibitor, glibenclamide. These findings demonstrate that VSM KATP channel GoF underlies CS cardiac enlargement and that CS-associated abnormalities are reversible, and provide evidence of in vivo efficacy of glibenclamide as a therapeutic agent in CS.
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Affiliation(s)
- Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology.,Department of Physiology
| | - Yan Huang
- Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology.,Department of Physiology
| | - Zihan Yan
- Center for the Investigation of Membrane Excitability Diseases.,Division of Endocrinology, Department of Medicine, and
| | - Theresa M Harter
- Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology.,Department of Physiology
| | - Carmen M Halabi
- Center for the Investigation of Membrane Excitability Diseases.,Division of Nephrology, Department of Pediatrics, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Rod Chalk
- Structural Genomics Consortium, University of Oxford, Oxford, United Kingdom
| | - Attila Kovacs
- Department of Medicine, Washington University School of Medicine, Saint Louis, Missouri, USA
| | - Gijs van Haaften
- Center for Molecular Medicine, Department of Genetics, University Medical Center Utrecht, Utrecht, Netherlands
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases.,Division of Endocrinology, Department of Medicine, and
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases.,Department of Cell Biology.,Department of Physiology
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16
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Courtney CM, Shyr ZA, Yan Z, Onufer EJ, Steinberger AE, Tecos ME, Barron LK, Guo J, Remedi MS, Warner BW. Alterations in pancreatic islet cell function in response to small bowel resection. Am J Physiol Gastrointest Liver Physiol 2020; 319:G36-G42. [PMID: 32463335 PMCID: PMC7468758 DOI: 10.1152/ajpgi.00282.2019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
After 50% proximal small bowel resection (SBR) in mice, we have demonstrated hepatic steatosis, impaired glucose metabolism without insulin resistance, and increased pancreatic islet area. We sought to determine the consequences of SBR on pancreatic β-cell morphology, proliferation, and expression of a key regulatory hormone, glucagon-like peptide-1 (GLP-1). C57BL/6 mice underwent 50% SBR or sham operation. At 10 wk, pancreatic insulin content and secretion was measured by ELISA. Immunohistochemistry was performed to determine structural alterations in pancreatic α-and β-cells. Western blot analysis was used to measure GLP-1R expression, and immunoassay was used to measure plasma insulin and GLP-1. Experiments were repeated by administering a GLP-1 agonist (exendin-4) to a cohort of mice following SBR. After SBR, there was pancreatic islet hypertrophy and impaired glucose tolerance. The proportion of α and β cells was not grossly altered. Whole pancreas and pancreatic islet insulin content was not significantly different; however, SBR mice demonstrated decreased insulin secretion in both static incubation and islet perfusion experiments. The expression of pancreatic GLP-1R was decreased approximately twofold after SBR, compared with sham and serum GLP-1, was decreased. These metabolic derangements were mitigated after administration of the GLP-1 agonist. Following massive SBR, there is significant hypertrophy of pancreatic islet cells with morphologically intact α- and β-cells. Significantly reduced pancreatic insulin release in both static and dynamic conditions demonstrate a perturbed second phase of insulin secretion. GLP-1 is a key mediator of this amplification pathway. Decreased expression of serum GLP-1 and pancreatic GLP-1R in face of no change in insulin content presents a novel pathway for enteropancreatic glucose regulation following SBR.NEW & NOTEWORTHY Metabolic changes occur following intestinal resection; however, the effects on pancreatic function are unknown. Prior studies have demonstrated that glucagon-like protein-1 (GLP-1) signaling is a crucial player in the improved insulin sensitivity after bariatric surgery. In this study, we explore the effect of massive small bowel resection on gut hormone physiology and provide novel insights into the enteropancreatic axis.
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Affiliation(s)
- Cathleen M. Courtney
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
| | - Zeenat A. Shyr
- 2Division of Endocrinology, Metabolism, and Lipid Research, Washington University in St. Louis, Missouri
| | - Zihan Yan
- 2Division of Endocrinology, Metabolism, and Lipid Research, Washington University in St. Louis, Missouri
| | - Emily Jean Onufer
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
| | - Allie E. Steinberger
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
| | - Maria E. Tecos
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
| | - Lauren K. Barron
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
| | - Jun Guo
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
| | - Maria S. Remedi
- 2Division of Endocrinology, Metabolism, and Lipid Research, Washington University in St. Louis, Missouri
| | - Brad W. Warner
- 1Division of Pediatric Surgery, Department of Surgery, St. Louis Children’s Hospital, Washington University School of Medicine, St. Louis, Missouri
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17
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McClenaghan C, Huang Y, Matkovich SJ, Kovacs A, Weinheimer CJ, Perez R, Broekelmann TJ, Harter TM, Lee JM, Remedi MS, Nichols CG. The Mechanism of High-Output Cardiac Hypertrophy Arising From Potassium Channel Gain-of-Function in Cantú Syndrome. Function (Oxf) 2020; 1:zqaa004. [PMID: 32865539 PMCID: PMC7446247 DOI: 10.1093/function/zqaa004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 01/06/2023]
Abstract
Dramatic cardiomegaly arising from gain-of-function (GoF) mutations in the ATP-sensitive potassium (KATP) channels genes, ABCC9 and KCNJ8, is a characteristic feature of Cantú syndrome (CS). How potassium channel over-activity results in cardiac hypertrophy, as well as the long-term consequences of cardiovascular remodeling in CS, is unknown. Using genome-edited mouse models of CS, we therefore sought to dissect the pathophysiological mechanisms linking KATP channel GoF to cardiac remodeling. We demonstrate that chronic reduction of systemic vascular resistance in CS is accompanied by elevated renin-angiotensin signaling, which drives cardiac enlargement and blood volume expansion. Cardiac enlargement in CS results in elevation of basal cardiac output, which is preserved in aging. However, the cardiac remodeling includes altered gene expression patterns that are associated with pathological hypertrophy and are accompanied by decreased exercise tolerance, suggestive of reduced cardiac reserve. Our results identify a high-output cardiac hypertrophy phenotype in CS which is etiologically and mechanistically distinct from other myocardial hypertrophies, and which exhibits key features of high-output heart failure (HOHF). We propose that CS is a genetically-defined HOHF disorder and that decreased vascular smooth muscle excitability is a novel mechanism for HOHF pathogenesis.
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Affiliation(s)
- Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yan Huang
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Scot J Matkovich
- Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Attila Kovacs
- Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Carla J Weinheimer
- Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ron Perez
- Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Thomas J Broekelmann
- Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Theresa M Harter
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jin-Moo Lee
- Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA,Departments of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA,Corresponding author. E-mail:
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18
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Davis MJ, Kim HJ, Zawieja SD, Castorena-Gonzalez JA, Gui P, Li M, Saunders BT, Zinselmeyer BH, Randolph GJ, Remedi MS, Nichols CG. Kir6.1-dependent K ATP channels in lymphatic smooth muscle and vessel dysfunction in mice with Kir6.1 gain-of-function. J Physiol 2020; 598:3107-3127. [PMID: 32372450 DOI: 10.1113/jp279612] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 05/01/2020] [Indexed: 02/06/2023] Open
Abstract
KEY POINTS Spontaneous contractions are essential for normal lymph transport and these contractions are exquisitely sensitive to the KATP channel activator pinacidil. KATP channel Kir6.1 and SUR2B subunits are expressed in mouse lymphatic smooth muscle (LSM) and form functional KATP channels as verified by electrophysiological techniques. Global deletion of Kir6.1 or SUR2 subunits results in severely impaired lymphatic contractile responses to pinacidil. Smooth muscle-specific expression of Kir6.1 gain-of-function mutant (GoF) subunits results in profound lymphatic contractile dysfunction and LSM hyperpolarization that is partially rescued by the KATP inhibitor glibenclamide. In contrast, lymphatic endothelial-specific expression of Kir6.1 GoF has essentially no effect on lymphatic contractile function. The high sensitivity of LSM to KATP channel GoF offers an explanation for the lymphoedema observed in patients with Cantú syndrome, a disorder caused by gain-of-function mutations in genes encoding Kir6.1 or SUR2, and suggests that glibenclamide may be an appropriate therapeutic agent. ABSTRACT This study aimed to understand the functional expression of KATP channel subunits in distinct lymphatic cell types, and assess the consequences of altered KATP channel activity on lymphatic pump function. KATP channel subunits Kir6.1 and SUR2B were expressed in mouse lymphatic muscle by PCR, but only Kir6.1 was expressed in lymphatic endothelium. Spontaneous contractions of popliteal lymphatics from wild-type (WT) (C57BL/6J) mice, assessed by pressure myography, were very sensitive to inhibition by the SUR2-specific KATP channel activator pinacidil, which hyperpolarized both mouse and human lymphatic smooth muscle (LSM). In vessels from mice with deletion of Kir6.1 (Kir6.1-/- ) or SUR2 (SUR2[STOP]) subunits, contractile parameters were not significantly different from those of WT vessels, suggesting that basal KATP channel activity in LSM is not an essential component of the lymphatic pacemaker, and does not exert a strong influence over contractile strength. However, these vessels were >100-fold less sensitive than WT vessels to pinacidil. Smooth muscle-specific expression of a Kir6.1 gain-of-function (GoF) subunit resulted in severely impaired lymphatic contractions and hyperpolarized LSM. Membrane potential and contractile activity was partially restored by the KATP channel inhibitor glibenclamide. In contrast, lymphatic endothelium-specific expression of Kir6.1 GoF subunits had negligible effects on lymphatic contraction frequency or amplitude. Our results demonstrate a high sensitivity of lymphatic contractility to KATP channel activators through activation of Kir6.1/SUR2-dependent channels in LSM. In addition, they offer an explanation for the lymphoedema observed in patients with Cantú syndrome, a disorder caused by gain-of-function mutations in genes encoding Kir6.1/SUR2.
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Affiliation(s)
- Michael J Davis
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Hae Jin Kim
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Scott D Zawieja
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Jorge A Castorena-Gonzalez
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Peichun Gui
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Min Li
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO, 65212, USA
| | - Brian T Saunders
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Bernd H Zinselmeyer
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Gwendalyn J Randolph
- Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Maria S Remedi
- Department of Medicine, Washington University School of Medicine, St Louis, MO, 63110, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO, 63110, USA
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19
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Grange DK, Roessler HI, McClenaghan C, Duran K, Shields K, Remedi MS, Knoers NVAM, Lee JM, Kirk EP, Scurr I, Smithson SF, Singh GK, van Haelst MM, Nichols CG, van Haaften G. Cantú syndrome: Findings from 74 patients in the International Cantú Syndrome Registry. Am J Med Genet C Semin Med Genet 2020; 181:658-681. [PMID: 31828977 DOI: 10.1002/ajmg.c.31753] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 10/14/2019] [Accepted: 10/18/2019] [Indexed: 11/11/2022]
Abstract
Cantú syndrome (CS), first described in 1982, is caused by pathogenic variants in ABCC9 and KCNJ8, which encode the regulatory and pore forming subunits of ATP-sensitive potassium (KATP ) channels, respectively. Multiple case reports of affected individuals have described the various clinical features of CS, but systematic studies are lacking. To define the effects of genetic variants on CS phenotypes and clinical outcomes, we have developed a standardized REDCap-based registry for CS. We report phenotypic features and associated genotypes on 74 CS subjects, with confirmed ABCC9 variants in 72 of the individuals. Hypertrichosis and a characteristic facial appearance are present in all individuals. Polyhydramnios during fetal life, hyperflexibility, edema, patent ductus arteriosus (PDA), cardiomegaly, dilated aortic root, vascular tortuosity of cerebral arteries, and migraine headaches are common features, although even with this large group of subjects, there is incomplete penetrance of CS-associated features, without clear correlation to genotype.
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Affiliation(s)
- Dorothy K Grange
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.,Center for the Investigation of Membrane Excitability Diseases (CIMED)
| | - Helen I Roessler
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases (CIMED).,Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri
| | - Karen Duran
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Kathleen Shields
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases (CIMED).,Department of Medicine, Division of Endocrinology, Washington University School of Medicine, St. Louis, Missouri
| | - Nine V A M Knoers
- Department of Genetics, University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands.,Department of Genetics, University Medical Center Groningen, Groningen, the Netherlands
| | - Jin-Moo Lee
- Department of Neurology and Radiology, Washington University School of Medicine, St. Louis, Missouri
| | - Edwin P Kirk
- Centre for Clinical Genetics, Sydney Children's Hospital, Randwick, New South Wales, Australia.,School of Women's and Children's Health, University of New South Wales, Randwick, New South Wales, Australia
| | - Ingrid Scurr
- Department of Clinical Genetics, University Hospitals, Bristol, UK
| | - Sarah F Smithson
- Department of Clinical Genetics, University Hospitals, Bristol, UK
| | - Gautam K Singh
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.,Center for the Investigation of Membrane Excitability Diseases (CIMED)
| | - Mieke M van Haelst
- Department of Clinical Genetics, VU Medical Center, VU University Amsterdam, Amsterdam, The Netherlands.,Department of Clinical Genetics, Amsterdam Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases (CIMED).,Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri
| | - Gijs van Haaften
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
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20
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McClenaghan C, Huang Y, Yan Z, Roeglin J, Harter T, Halabi C, Remedi MS, Nichols CG. Pharmacological Approaches for Targeting Cardiovascular and Skeletal Muscle KATP Channelopathies. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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21
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Maqoud F, Scala R, Mele A, McClenaghan C, Remedi MS, Nichols CC, Tricarico D. Biophysical and Pharmacological Characterization of Atp-Sensitive Potassium Channels in Mice Kir6.1WT/V65M Mirroring the Human Cantu′ Syndrome. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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22
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York NW, Parker H, Tyus D, Xie Z, Akbar M, Yan Z, Hu H, Remedi MS, Nichols CG. KATP Activity in Intestinal Smooth Muscle Regulates Motility. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.3193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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23
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Smeland MF, McClenaghan C, Roessler HI, Savelberg S, Hansen GÅM, Hjellnes H, Arntzen KA, Müller KI, Dybesland AR, Harter T, Sala-Rabanal M, Emfinger CH, Huang Y, Singareddy SS, Gunn J, Wozniak DF, Kovacs A, Massink M, Tessadori F, Kamel SM, Bakkers J, Remedi MS, Van Ghelue M, Nichols CG, van Haaften G. ABCC9-related Intellectual disability Myopathy Syndrome is a K ATP channelopathy with loss-of-function mutations in ABCC9. Nat Commun 2019; 10:4457. [PMID: 31575858 PMCID: PMC6773855 DOI: 10.1038/s41467-019-12428-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 08/30/2019] [Indexed: 11/30/2022] Open
Abstract
Mutations in genes encoding KATP channel subunits have been reported for pancreatic disorders and Cantú syndrome. Here, we report a syndrome in six patients from two families with a consistent phenotype of mild intellectual disability, similar facies, myopathy, and cerebral white matter hyperintensities, with cardiac systolic dysfunction present in the two oldest patients. Patients are homozygous for a splice-site mutation in ABCC9 (c.1320 + 1 G > A), which encodes the sulfonylurea receptor 2 (SUR2) subunit of KATP channels. This mutation results in an in-frame deletion of exon 8, which results in non-functional KATP channels in recombinant assays. SUR2 loss-of-function causes fatigability and cardiac dysfunction in mice, and reduced activity, cardiac dysfunction and ventricular enlargement in zebrafish. We term this channelopathy resulting from loss-of-function of SUR2-containing KATP channels ABCC9-related Intellectual disability Myopathy Syndrome (AIMS). The phenotype differs from Cantú syndrome, which is caused by gain-of-function ABCC9 mutations, reflecting the opposing consequences of KATP loss- versus gain-of-function.
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Affiliation(s)
- Marie F Smeland
- Department of Medical Genetics, University Hospital of North Norway, 9019, Tromsø, Norway.
| | - Conor McClenaghan
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Helen I Roessler
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | - Sanne Savelberg
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | | | - Helene Hjellnes
- Department of Medical Genetics, University Hospital of North Norway, 9019, Tromsø, Norway
| | - Kjell Arne Arntzen
- Department of Neurology, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Clinical Medicine, UiT-The Arctic University of Norway, 9019, Tromsø, Norway
- The National Neuromuscular Centre of Norway, University Hospital of North Norway, 9019, Tromsø, Norway
| | - Kai Ivar Müller
- Department of Neurology, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Clinical Medicine, UiT-The Arctic University of Norway, 9019, Tromsø, Norway
| | - Andreas Rosenberger Dybesland
- The National Neuromuscular Centre of Norway, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Physiotherapy, University Hospital of North Norway, 9019, Tromsø, Norway
| | - Theresa Harter
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Monica Sala-Rabanal
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University, St Louis, MO, 63110, USA
| | - Chris H Emfinger
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Yan Huang
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Soma S Singareddy
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Jamie Gunn
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - David F Wozniak
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Attila Kovacs
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Maarten Massink
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | - Federico Tessadori
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT, Utrecht, the Netherlands
| | - Sarah M Kamel
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT, Utrecht, the Netherlands
| | - Jeroen Bakkers
- Hubrecht Institute-KNAW and UMC Utrecht, 3584 CT, Utrecht, the Netherlands
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands
| | - Maria S Remedi
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University, St Louis, MO, 63110, USA
| | - Marijke Van Ghelue
- Department of Medical Genetics, University Hospital of North Norway, 9019, Tromsø, Norway
- Department of Medical Genetics, the Arctic University of Norway, 9019, Tromsø, Norway
| | - Colin G Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University, St Louis, MO, 63110, USA
| | - Gijs van Haaften
- Department of Genetics, Center for Molecular Medicine, University Medical Center Utrecht, 3584 CX, Utrecht, the Netherlands.
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24
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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25
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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] [What about the content of this article? (0)] [Affiliation(s)] [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] [What about the content of this article? (0)] [Affiliation(s)] [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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Yan Z, Shyr ZA, Fortunato M, Welscher A, Alisio M, Martino M, Finck BN, Conway H, Remedi MS. High-fat-diet-induced remission of diabetes in a subset of K ATP -GOF insulin-secretory-deficient mice. Diabetes Obes Metab 2018; 20:2574-2584. [PMID: 29896801 PMCID: PMC6407888 DOI: 10.1111/dom.13423] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 06/04/2018] [Accepted: 06/09/2018] [Indexed: 02/06/2023]
Abstract
AIMS To examine the effects of a high-fat-diet (HFD) on monogenic neonatal diabetes, without the confounding effects of compensatory hyperinsulinaemia. METHODS Mice expressing KATP channel gain-of-function (KATP -GOF) mutations, which models human neonatal diabetes, were fed an HFD. RESULTS Surprisingly, KATP -GOF mice exhibited resistance to HFD-induced obesity, accompanied by markedly divergent blood glucose control, with some KATP -GOF mice showing persistent diabetes (KATP -GOF-non-remitter [NR] mice) and others showing remission of diabetes (KATP -GOF-remitter [R] mice). Compared with the severely diabetic and insulin-resistant KATP -GOF-NR mice, HFD-fed KATP -GOF-R mice had lower blood glucose, improved insulin sensitivity, and increased circulating plasma insulin and glucagon-like peptide-1 concentrations. Strikingly, while HFD-fed KATP -GOF-NR mice showed increased food intake and decreased physical activity, reduced whole body fat mass and increased plasma lipids, KATP -GOF-R mice showed similar features to those of control littermates. Importantly, KATP -GOF-R mice had restored insulin content and β-cell mass compared with the marked loss observed in both HFD-fed KATP -GOF-NR and chow-fed KATP -GOF mice. CONCLUSION Together, our results suggest that restriction of dietary carbohydrates and caloric replacement by fat can induce metabolic changes that are beneficial in reducing glucotoxicity and secondary consequences of diabetes in a mouse model of insulin-secretory deficiency.
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Affiliation(s)
- Zihan Yan
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - 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
| | - Manuela Fortunato
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - Alecia Welscher
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - Mariana Alisio
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - Michael Martino
- Department of Medicine, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - Brian N. Finck
- Department of Medicine, Division of Geriatrics and Nutritional Science, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA
| | - Hannah Conway
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, 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
- Address all correspondence and reprint requests to MSR: Ph: (314) 362-6636,
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Huang Y, McClenaghan C, Harter TM, Hinman K, Halabi CM, Matkovich SJ, Zhang H, Brown GS, Mecham RP, England SK, Kovacs A, Remedi MS, Nichols CG. Cardiovascular consequences of KATP overactivity in Cantu syndrome. JCI Insight 2018; 3:121153. [PMID: 30089727 DOI: 10.1172/jci.insight.121153] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 06/28/2018] [Indexed: 11/17/2022] Open
Abstract
Cantu syndrome (CS) is characterized by multiple vascular and cardiac abnormalities including vascular dilation and tortuosity, systemic hypotension, and cardiomegaly. The disorder is caused by gain-of-function (GOF) mutations in genes encoding pore-forming (Kir6.1, KCNJ8) and accessory (SUR2, ABCC9) ATP-sensitive potassium (KATP) channel subunits. However, there is little understanding of the link between molecular dysfunction and the complex pathophysiology observed, and there is no known treatment, in large part due to the lack of appropriate preclinical disease models in which to test therapies. Notably, expression of Kir6.1 and SUR2 does not fully overlap, and the relative contribution of KATP GOF in various cardiovascular tissues remains to be elucidated. To investigate pathophysiologic mechanisms in CS we have used CRISPR/Cas9 engineering to introduce CS-associated SUR2[A478V] and Kir6.1[V65M] mutations to the equivalent endogenous loci in mice. Mirroring human CS, both of these animals exhibit low systemic blood pressure and dilated, compliant blood vessels, as well dramatic cardiac enlargement, the effects being more severe in V65M animals than in A478V animals. In both animals, whole-cell patch-clamp recordings reveal enhanced basal KATP conductance in vascular smooth muscle, explaining vasodilation and lower blood pressure, and demonstrating a cardinal role for smooth muscle KATP dysfunction in CS etiology. Echocardiography confirms in situ cardiac enlargement and increased cardiac output in both animals. Patch-clamp recordings reveal reduced ATP sensitivity of ventricular myocyte KATP channels in A478V, but normal ATP sensitivity in V65M, suggesting that cardiac remodeling occurs secondary to KATP overactivity outside of the heart. These SUR2[A478V] and Kir6.1[V65M] animals thus reiterate the key cardiovascular features seen in human CS. They establish the molecular basis of the pathophysiological consequences of reduced smooth muscle excitability resulting from SUR2/Kir6.1-dependent KATP GOF, and provide a validated animal model in which to examine potential therapeutic approaches to treating CS.
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Affiliation(s)
- Yan Huang
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | - Conor McClenaghan
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | - Theresa M Harter
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | | | | | | | - Haixia Zhang
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | - G Schuyler Brown
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
| | | | - Sarah K England
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Obstetrics and Gynecology, and
| | - Attila Kovacs
- Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Maria S Remedi
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G Nichols
- Center for the Investigation of Membrane Excitability Diseases, and Departments of.,Cell Biology and Physiology
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McClenaghan C, Huang Y, Harter T, Brown GS, Hinman K, Halabi C, Matkovich S, Mecham RP, Weinheimer CJ, Kovacs A, England S, Remedi MS, Nichols CG. Abstract 011: Cardiovascular Consequences of Cantu Syndrome and Response to Glibenclamide Treatment in Two Novel KATP Channel Mutant Mouse Models. Arterioscler Thromb Vasc Biol 2018. [DOI: 10.1161/atvb.38.suppl_1.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The rare heritable disorder Cantů syndrome (CS) arises from gain-of-function mutations in the genes encoding the cardiovascular KATP channel subunits Kir6.1 and SUR2 (
KCNJ8
and
ABCC9
, respectively). CS is characterized by diverse features including hypertrichosis, osteochondrodysplasia and craniofacial dysmorphology. Multiple cardiovascular abnormalities are also reported in CS including vascular dilation and tortuosity, dramatic cardiomegaly, pulmonary hypertension and low systemic blood pressure. We have developed and characterized two novel mouse models of Cantu Syndrome in which disease causing amino acid substitutions have been engineered into either Kir6.1 (p.V65M) or SUR2 (p.A478V) using CRISPR/Cas9 genome editing. Electrophysiological assessment of isolated vascular smooth muscle cells (VSMCs) showed that both mutations result in increased basal activity of VSM KATP channels. Mutant mice also exhibit vascular dilation, low blood pressure, and pulmonary hypertension. In addition, mutant mice exhibited hypertrophic, hyper-contractile hearts. The latter findings are not trivially predictable as a consequence of KATP gain-of-function, but also recapitulates key clinical features of CS. The severity of pathophysiological remodeling correlated with the molecular effects of the substitution. These models provide novel insights to the cardiovascular consequences of KATP over-activity. Little is known about the long-term effects of human CS, nor reversibility of pathophysiological consequences. Chronic administration of the sulfonylurea KATP inhibitor glibenclamide (glyburide) by slow-release pellets implanted under the skin resulted in normalization of vascular consequences and reversal of cardiac hypertrophy in SUR2(A478V) mice over 3 weeks. Kir6.1(V65M) mice are less sensitive to glibenclamide treatment, as predicted from studies of recombinant channels. These results suggest that glibenclamide represents a promising pharmacotherapy for CS (but that sensitivity may be patient- and mutation-dependent), and perhaps for diverse cardiovascular conditions arising from decreased smooth muscle excitability in general.
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Affiliation(s)
| | - Yan Huang
- Washington Univ in St Louis, Saint Louis, MO
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Abstract
Assessing the response of pancreatic islet cells to glucose stimulation is important for understanding β-cell function. Zebrafish are a promising model for studies of metabolism in general, including stimulus-secretion coupling in the pancreas. We used transgenic zebrafish embryos expressing a genetically-encoded Ca2+ sensor in pancreatic β-cells to monitor a key step in glucose induced insulin secretion; the elevations of intracellular [Ca2+]i. In vivo and ex vivo analyses of [Ca2+]i demonstrate that β-cell responsiveness to glucose is well established in late embryogenesis and that embryonic β-cells also respond to free fatty acid and amino acid challenges. In vivo imaging of whole embryos further shows that indirect glucose administration, for example by yolk injection, results in a slow and asynchronous induction of β-cell [Ca2+]i responses, while intravenous glucose injections cause immediate and islet-wide synchronized [Ca2+]i fluctuations. Finally, we demonstrate that embryos with disrupted mutation of the CaV1.2 channel gene cacna1c are hyperglycemic and that this phenotype is associated with glucose-independent [Ca2+]i fluctuation in β-cells. The data reveal a novel central role of cacna1c in β-cell specific stimulus-secretion coupling in zebrafish and demonstrate that the novel approach we propose - to monitor the [Ca2+]i dynamics in embryonic β-cells in vivo - will help to expand the understanding of β-cell physiological functions in healthy and diseased states.
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Affiliation(s)
- Reka Lorincz
- Institute of Molecular Biology/CMBI, University of Innsbruck, Innsbruck, Austria
| | - Christopher H. Emfinger
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University School of Medicine, St. Louis, MO, USA
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Andrea Walcher
- Institute of Molecular Biology/CMBI, University of Innsbruck, Innsbruck, Austria
| | - Michael Giolai
- Institute of Molecular Biology/CMBI, University of Innsbruck, Innsbruck, Austria
| | - Claudia Krautgasser
- Institute of Molecular Biology/CMBI, University of Innsbruck, Innsbruck, Austria
| | - Maria S. Remedi
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases (CIMED), Washington University School of Medicine, St. Louis, MO, USA
| | - Dirk Meyer
- Institute of Molecular Biology/CMBI, University of Innsbruck, Innsbruck, Austria
- CONTACT Dirk Meyer Institute of Molecular Biology/CMBI, University of Innsbruck, Technikerstrasse 25, Innsbruck 6020, Austria
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Liu H, Javaheri A, Godar RJ, Murphy J, Ma X, Rohatgi N, Mahadevan J, Hyrc K, Saftig P, Marshall C, McDaniel ML, Remedi MS, Razani B, Urano F, Diwan A. Intermittent fasting preserves beta-cell mass in obesity-induced diabetes via the autophagy-lysosome pathway. Autophagy 2017; 13:1952-1968. [PMID: 28853981 DOI: 10.1080/15548627.2017.1368596] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Obesity-induced diabetes is characterized by hyperglycemia, insulin resistance, and progressive beta cell failure. In islets of mice with obesity-induced diabetes, we observe increased beta cell death and impaired autophagic flux. We hypothesized that intermittent fasting, a clinically sustainable therapeutic strategy, stimulates autophagic flux to ameliorate obesity-induced diabetes. Our data show that despite continued high-fat intake, intermittent fasting restores autophagic flux in islets and improves glucose tolerance by enhancing glucose-stimulated insulin secretion, beta cell survival, and nuclear expression of NEUROG3, a marker of pancreatic regeneration. In contrast, intermittent fasting does not rescue beta-cell death or induce NEUROG3 expression in obese mice with lysosomal dysfunction secondary to deficiency of the lysosomal membrane protein, LAMP2 or haplo-insufficiency of BECN1/Beclin 1, a protein critical for autophagosome formation. Moreover, intermittent fasting is sufficient to provoke beta cell death in nonobese lamp2 null mice, attesting to a critical role for lysosome function in beta cell homeostasis under fasting conditions. Beta cells in intermittently-fasted LAMP2- or BECN1-deficient mice exhibit markers of autophagic failure with accumulation of damaged mitochondria and upregulation of oxidative stress. Thus, intermittent fasting preserves organelle quality via the autophagy-lysosome pathway to enhance beta cell survival and stimulates markers of regeneration in obesity-induced diabetes.
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Affiliation(s)
- Haiyan Liu
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA.,b John Cochran VA Medical Center , St. Louis , MO , USA
| | - Ali Javaheri
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA
| | - Rebecca J Godar
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA
| | - John Murphy
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA
| | - Xiucui Ma
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA.,b John Cochran VA Medical Center , St. Louis , MO , USA
| | - Nidhi Rohatgi
- c Department of Pathology and Immunology , Washington University School of Medicine , St. Louis , MO , USA
| | - Jana Mahadevan
- d Division of Endocrinology , Department of Internal Medicine , Washington University School of Medicine , St. Louis , MO , USA
| | - Krzysztof Hyrc
- e Department of Neurology , Washington University School of Medicine , St. Louis , MO , USA
| | - Paul Saftig
- f Institut für Biochemie, Christian-Albrechts-Universität zu Kiel , Kiel , Germany
| | - Connie Marshall
- c Department of Pathology and Immunology , Washington University School of Medicine , St. Louis , MO , USA
| | - Michael L McDaniel
- c Department of Pathology and Immunology , Washington University School of Medicine , St. Louis , MO , USA
| | - Maria S Remedi
- d Division of Endocrinology , Department of Internal Medicine , Washington University School of Medicine , St. Louis , MO , USA
| | - Babak Razani
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA
| | - Fumihiko Urano
- d Division of Endocrinology , Department of Internal Medicine , Washington University School of Medicine , St. Louis , MO , USA
| | - Abhinav Diwan
- a Center for Cardiovascular Research and Division of Cardiology , Washington University School of Medicine , St. Louis , MO , USA.,b John Cochran VA Medical Center , St. Louis , MO , USA.,g Department of Cell Biology and Physiology , Washington University School of Medicine , St. Louis , MO , USA
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Abstract
Understanding mechanisms for maintaining pancreatic islet cell fate and function is important for addressing the urgent challenge of restoring islet β- and α-cell function in T1DM. In this issue of Cell Metabolism, Chakravarthy et al. (2017) identify a genetic mechanism by which mouse β-cells are spontaneously regenerated from adult α-cells.
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Affiliation(s)
- Maria S Remedi
- Department of Medicine, Division of Endocrinology, Metabolism and Lipid Research, School of Medicine, Washington University in Saint Louis, Saint Louis, MO 63110, USA.
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Emfinger CH, Welscher A, Yan Z, Wang Y, Conway H, Moss JB, Moss LG, Remedi MS, Nichols CG. Expression and function of ATP-dependent potassium channels in zebrafish islet β-cells. R Soc Open Sci 2017; 4:160808. [PMID: 28386438 PMCID: PMC5367309 DOI: 10.1098/rsos.160808] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/06/2017] [Indexed: 05/04/2023]
Abstract
ATP-sensitive potassium channels (KATP channels) are critical nutrient sensors in many mammalian tissues. In the pancreas, KATP channels are essential for coupling glucose metabolism to insulin secretion. While orthologous genes for many components of metabolism-secretion coupling in mammals are present in lower vertebrates, their expression, functionality and ultimate impact on body glucose homeostasis are unclear. In this paper, we demonstrate that zebrafish islet β-cells express functional KATP channels of similar subunit composition, structure and metabolic sensitivity to their mammalian counterparts. We further show that pharmacological activation of native zebrafish KATP using diazoxide, a specific KATP channel opener, is sufficient to disturb glucose tolerance in adult zebrafish. That β-cell KATP channel expression and function are conserved between zebrafish and mammals illustrates the evolutionary conservation of islet metabolic sensing from fish to humans, and lends relevance to the use of zebrafish to model islet glucose sensing and diseases of membrane excitability such as neonatal diabetes.
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Affiliation(s)
- Christopher H. Emfinger
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Alecia Welscher
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Zihan Yan
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Yixi Wang
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Hannah Conway
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
| | - Jennifer B. Moss
- Division of Endocrinology, Metabolism, and Nutrition and DMPI, Duke University Medical Center, Durham, NC, USA
| | - Larry G. Moss
- Division of Endocrinology, Metabolism, and Nutrition and DMPI, Duke University Medical Center, Durham, NC, USA
| | - Maria S. Remedi
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
| | - Colin G. Nichols
- Department of Cell Biology and Physiology, Washington University in St Louis, St Louis, MO, USA
- Center for the Investigation of Membrane Excitability Diseases, Washington University in St Louis, St Louis, MO, USA
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35
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Asghar ZA, Cusumano A, Yan Z, Remedi MS, Moley KH. Reduced islet function contributes to impaired glucose homeostasis in fructose-fed mice. Am J Physiol Endocrinol Metab 2017; 312:E109-E116. [PMID: 28028036 PMCID: PMC5336566 DOI: 10.1152/ajpendo.00279.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 12/19/2016] [Accepted: 12/19/2016] [Indexed: 01/09/2023]
Abstract
Increased sugar consumption, particularly fructose, in the form of sweetened beverages and sweeteners in our diet adversely affects metabolic health. Because these effects are associated with features of the metabolic syndrome in humans, the direct effect of fructose on pancreatic islet function is unknown. Therefore, we examined the islet phenotype of mice fed excess fructose. Fructose-fed mice exhibited fasting hyperglycemia and glucose intolerance but not hyperinsulinemia, dyslipidemia, or hyperuricemia. Islet function was impaired, with decreased glucose-stimulated insulin secretion and increased glucagon secretion and high fructose consumption leading to α-cell proliferation and upregulation of the fructose transporter GLUT5, which was localized only in α-cells. Our studies demonstrate that excess fructose consumption contributes to hyperglycemia by affecting both β- and α-cells of islets in mice.
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Affiliation(s)
- Zeenat A Asghar
- Department of Obstetrics and Gynecology, Washington University in St. Louis School of Medicine, St. Louis, Missouri; and
| | - Andrew Cusumano
- Department of Obstetrics and Gynecology, Washington University in St. Louis School of Medicine, St. Louis, Missouri; and
| | - Zihan Yan
- Department of Medicine, Washington University in St. Louis School of Medicine, St. Louis, Missouri
| | - Maria S Remedi
- Department of Medicine, Washington University in St. Louis School of Medicine, St. Louis, Missouri
| | - Kelle H Moley
- Department of Obstetrics and Gynecology, Washington University in St. Louis School of Medicine, St. Louis, Missouri; and
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Remedi MS, Friedman JB, Nichols CG. Diabetes induced by gain-of-function mutations in the Kir6.1 subunit of the KATP channel. J Gen Physiol 2016; 149:75-84. [PMID: 27956473 PMCID: PMC5217086 DOI: 10.1085/jgp.201611653] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 11/28/2016] [Indexed: 12/13/2022] Open
Abstract
Kir6.2-containing KATP channels are prominent in pancreatic β cells, and gain-of-function mutations in these channels are the most common cause of human neonatal diabetes mellitus. Remedi et al. find that Kir6.1 subunits are also present in pancreatic KATP channels and that gain-of-function mutations can also cause impaired glucose tolerance and insulin secretion. Gain-of-function (GOF) mutations in the pore-forming (Kir6.2) and regulatory (SUR1) subunits of KATP channels have been identified as the most common cause of human neonatal diabetes mellitus. The critical effect of these mutations is confirmed in mice expressing Kir6.2-GOF mutations in pancreatic β cells. A second KATP channel pore-forming subunit, Kir6.1, was originally cloned from the pancreas. Although the prominence of this subunit in the vascular system is well documented, a potential role in pancreatic β cells has not been considered. Here, we show that mice expressing Kir6.1-GOF mutations (Kir6.1[G343D] or Kir6.1[G343D,Q53R]) in pancreatic β cells (under rat-insulin-promoter [Rip] control) develop glucose intolerance and diabetes caused by reduced insulin secretion. We also generated transgenic mice in which a bacterial artificial chromosome (BAC) containing Kir6.1[G343D] is incorporated such that the transgene is only expressed in tissues where Kir6.1 is normally present. Strikingly, BAC-Kir6.1[G343D] mice also show impaired glucose tolerance, as well as reduced glucose- and sulfonylurea-dependent insulin secretion. However, the response to K+ depolarization is intact in Kir6.1-GOF mice compared with control islets. The presence of native Kir6.1 transcripts was demonstrated in both human and wild-type mouse islets using quantitative real-time PCR. Together, these results implicate the incorporation of native Kir6.1 subunits into pancreatic KATP channels and a contributory role for these subunits in the control of insulin secretion.
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Affiliation(s)
- Maria S Remedi
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110 .,Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
| | - Jonathan B Friedman
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110
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Lee J, Harris AN, Holley CL, Mahadevan J, Pyles KD, Lavagnino Z, Scherrer DE, Fujiwara H, Sidhu R, Zhang J, Huang SCC, Piston DW, Remedi MS, Urano F, Ory DS, Schaffer JE. Rpl13a small nucleolar RNAs regulate systemic glucose metabolism. J Clin Invest 2016; 126:4616-4625. [PMID: 27820699 DOI: 10.1172/jci88069] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 09/29/2016] [Indexed: 12/22/2022] Open
Abstract
Small nucleolar RNAs (snoRNAs) are non-coding RNAs that form ribonucleoproteins to guide covalent modifications of ribosomal and small nuclear RNAs in the nucleus. Recent studies have also uncovered additional non-canonical roles for snoRNAs. However, the physiological contributions of these small RNAs are largely unknown. Here, we selectively deleted four snoRNAs encoded within the introns of the ribosomal protein L13a (Rpl13a) locus in a mouse model. Loss of Rpl13a snoRNAs altered mitochondrial metabolism and lowered reactive oxygen species tone, leading to increased glucose-stimulated insulin secretion from pancreatic islets and enhanced systemic glucose tolerance. Islets from mice lacking Rpl13a snoRNAs demonstrated blunted oxidative stress responses. Furthermore, these mice were protected against diabetogenic stimuli that cause oxidative stress damage to islets. Our study illuminates a previously unrecognized role for snoRNAs in metabolic regulation.
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Abstract
Recovery of functional β-cell mass continues to be an ongoing challenge in treating diabetes. Initial work studying β-cells suggested apoptotic β-cell death as a main contributor for the loss of β-cell mass in diabetes. Restoration of β-cells either by transplant or stimulating proliferation of remaining β-cells or precursors would then logically be a viable therapeutic option for diabetes. However, recent work has highlighted the inherent β-cell plasticity and the critical role of loss of β-cell identity in diabetes, and has suggested that β-cells fail to maintain a fully differentiated glucose-responsive and drug-responsive state, particularly in diabetic individuals with poorly controlled, long-lasting periods of hyperglycaemia. Understanding the underlying mechanisms of loss of β-cell identity and conversion in other cell types, as well as how to regain their mature differentiated functional state, is critical to develop novel therapeutic strategies to prevent or reverse these processes. In this review, we discuss the role of plasticity and loss of β-cell identity in diabetes, the current understanding of mechanisms involved in altering this mature functional β-cell state and potential progresses to identify novel therapeutic targets providing better opportunities for slowing or preventing diabetes progression.
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Affiliation(s)
- M S Remedi
- Department of Medicine and Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri.
| | - C Emfinger
- Department of Medicine and Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
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McCommis KS, Hodges WT, Bricker DK, Wisidagama DR, Compan V, Remedi MS, Thummel CS, Finck BN. An ancestral role for the mitochondrial pyruvate carrier in glucose-stimulated insulin secretion. Mol Metab 2016; 5:602-614. [PMID: 27656398 PMCID: PMC5021712 DOI: 10.1016/j.molmet.2016.06.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 06/24/2016] [Accepted: 06/30/2016] [Indexed: 11/27/2022] Open
Abstract
OBJECTIVE Transport of pyruvate into the mitochondrial matrix by the Mitochondrial Pyruvate Carrier (MPC) is an important and rate-limiting step in its metabolism. In pancreatic β-cells, mitochondrial pyruvate metabolism is thought to be important for glucose sensing and glucose-stimulated insulin secretion. METHODS To evaluate the role that the MPC plays in maintaining systemic glucose homeostasis, we used genetically-engineered Drosophila and mice with loss of MPC activity in insulin-producing cells. RESULTS In both species, MPC deficiency results in elevated blood sugar concentrations and glucose intolerance accompanied by impaired glucose-stimulated insulin secretion. In mouse islets, β-cell MPC-deficiency resulted in decreased respiration with glucose, ATP-sensitive potassium (KATP) channel hyperactivity, and impaired insulin release. Moreover, treatment of pancreas-specific MPC knockout mice with glibenclamide, a sulfonylurea KATP channel inhibitor, improved defects in islet insulin secretion and abnormalities in glucose homeostasis in vivo. Finally, using a recently-developed biosensor for MPC activity, we show that the MPC is rapidly stimulated by glucose treatment in INS-1 insulinoma cells suggesting that glucose sensing is coupled to mitochondrial pyruvate carrier activity. CONCLUSIONS Altogether, these studies suggest that the MPC plays an important and ancestral role in insulin-secreting cells in mediating glucose sensing, regulating insulin secretion, and controlling systemic glycemia.
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Key Words
- DILP2, Drosophila insulin-like peptide 2
- Diabetes
- Drosophila
- GSIS, glucose-stimulated insulin secretion
- GTT, glucose tolerance test
- IMM, inner mitochondrial membrane
- IPCs, Insulin-producing Cells
- ITT, insulin tolerance test
- Insulin
- MPC1 and MPC2, Mitochondrial Pyruvate Carrier 1 and 2
- Mitochondria
- OCR, oxygen consumption rates
- Pdx1, pancreatic and duodenal homeobox 1
- Pyruvate
- RESPYR, REporter Sensitive to PYRuvate
- Stimulus-coupled secretion
- β-Cell
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Affiliation(s)
- Kyle S McCommis
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Wesley T Hodges
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Daniel K Bricker
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Dona R Wisidagama
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Vincent Compan
- Institute of Functional Genomics, Labex ICST; INSERM U1191, CNRS UMR5203; University of Montpellier, Montpellier, France
| | - Maria S Remedi
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Carl S Thummel
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.
| | - Brian N Finck
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Affiliation(s)
- Bess A Marshall
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO Department of Cell Biology, Washington University School of Medicine, St. Louis, MO
| | | | - Jennifer Wambach
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO
| | - Neil H White
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO
| | - Maria S Remedi
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO
| | - Colin G Nichols
- Department of Cell Biology, Washington University School of Medicine, St. Louis, MO
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Wang Z, York NW, Nichols CG, Remedi MS. Pancreatic β cell dedifferentiation in diabetes and redifferentiation following insulin therapy. Cell Metab 2014; 19:872-82. [PMID: 24746806 PMCID: PMC4067979 DOI: 10.1016/j.cmet.2014.03.010] [Citation(s) in RCA: 289] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 02/06/2014] [Accepted: 02/26/2014] [Indexed: 01/09/2023]
Abstract
Diabetes is characterized by "glucotoxic" loss of pancreatic β cell function and insulin content, but underlying mechanisms remain unclear. A mouse model of insulin-secretory deficiency induced by β cell inexcitability (K(ATP) gain of function) demonstrates development of diabetes and reiterates the features of human neonatal diabetes. In the diabetic state, β cells lose their mature identity and dedifferentiate to neurogenin3-positive and insulin-negative cells. Lineage-tracing experiments show that dedifferentiated cells can subsequently redifferentiate to mature neurogenin3-negative, insulin-positive β cells after lowering of blood glucose by insulin therapy. We demonstrate here that β cell dedifferentiation, rather than apoptosis, is the main mechanism of loss of insulin-positive cells, and redifferentiation accounts for restoration of insulin content and antidiabetic drug responsivity in these animals. These results may help explain gradual decrease in β cell mass in long-standing diabetes and recovery of β cell function and drug responsivity in type 2 diabetic patients following insulin therapy, and they suggest an approach to rescuing "exhausted" β cells in diabetes.
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Affiliation(s)
- Zhiyu Wang
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Nathaniel W York
- Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | - Maria S Remedi
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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Li A, Knutsen RH, Zhang H, Osei-Owusu P, Moreno-Dominguez A, Harter TM, Uchida K, Remedi MS, Dietrich HH, Bernal-Mizrachi C, Blumer KJ, Mecham RP, Koster JC, Nichols CG. Hypotension due to Kir6.1 gain-of-function in vascular smooth muscle. J Am Heart Assoc 2013; 2:e000365. [PMID: 23974906 PMCID: PMC3828800 DOI: 10.1161/jaha.113.000365] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background KATP channels, assembled from pore‐forming (Kir6.1 or Kir6.2) and regulatory (SUR1 or SUR2) subunits, link metabolism to excitability. Loss of Kir6.2 results in hypoglycemia and hyperinsulinemia, whereas loss of Kir6.1 causes Prinzmetal angina–like symptoms in mice. Conversely, overactivity of Kir6.2 induces neonatal diabetes in mice and humans, but consequences of Kir6.1 overactivity are unknown. Methods and Results We generated transgenic mice expressing wild‐type (WT), ATP‐insensitive Kir6.1 [Gly343Asp] (GD), and ATP‐insensitive Kir6.1 [Gly343Asp,Gln53Arg] (GD‐QR) subunits, under Cre‐recombinase control. Expression was induced in smooth muscle cells by crossing with smooth muscle myosin heavy chain promoter–driven tamoxifen‐inducible Cre‐recombinase (SMMHC‐Cre‐ER) mice. Three weeks after tamoxifen induction, we assessed blood pressure in anesthetized and conscious animals, as well as contractility of mesenteric artery smooth muscle and KATP currents in isolated mesenteric artery myocytes. Both systolic and diastolic blood pressures were significantly reduced in GD and GD‐QR mice but normal in mice expressing the WT transgene and elevated in Kir6.1 knockout mice as well as in mice expressing dominant‐negative Kir6.1 [AAA] in smooth muscle. Contractile response of isolated GD‐QR mesenteric arteries was blunted relative to WT controls, but nitroprusside relaxation was unaffected. Basal KATP conductance and pinacidil‐activated conductance were elevated in GD but not in WT myocytes. Conclusions KATP overactivity in vascular muscle can lead directly to reduced vascular contractility and lower blood pressure. We predict that gain of vascular KATP function in humans would lead to a chronic vasodilatory phenotype, as indeed has recently been demonstrated in Cantu syndrome.
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Affiliation(s)
- Anlong Li
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO
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Abstract
Hyperglycaemia has multiple effects on β-cells, some clearly prosecretory, including hyperplasia and elevated insulin content, but eventually, a 'glucotoxic' effect which leads to pancreatic β-cell dysfunction, reduced β-cell mass and insulin deficiency, is an important part of diabetes pathophysiology. Myriad underlying cellular and molecular processes could lead to such dysfunction. High glucose will stimulate glycolysis and oxidative phosphorylation, which will in turn increase β-cell membrane excitability through K(ATP) channel closure. Chronic hyperexcitability will then lead to persistently elevated [Ca(2+)](i), a key trigger to insulin secretion. Thus, at least a part of the consequence of 'hyperstimulation' by glucose has been suggested to be a result of 'hyperexcitability' and chronically elevated [Ca(2+)](i). This link is lost when the [glucose], K(ATP) -channel activity link is broken, either pharmacologically or genetically. In isolated islets, such studies reveal that hyperexcitability causes a largely reversible chronic loss of insulin content, but in vivo chronic hyperexcitability per se does not lead to β-cell death or loss of insulin content. On the other hand, chronic inexcitability in vivo leads to systemic diabetes and consequential β-cell death, even while [Ca(2+)](i) remains low.
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Affiliation(s)
- C G Nichols
- Department of Cell Biology and Physiology and Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA.
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Toib A, Zhang HX, Broekelmann TJ, Hyrc KL, Guo Q, Chen F, Remedi MS, Nichols CG. Cardiac specific ATP-sensitive K+ channel (KATP) overexpression results in embryonic lethality. J Mol Cell Cardiol 2012; 53:437-45. [PMID: 22796573 DOI: 10.1016/j.yjmcc.2012.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2012] [Revised: 06/23/2012] [Accepted: 07/02/2012] [Indexed: 11/26/2022]
Abstract
Transgenic mice overexpressing SUR1 and gain of function Kir6.2[∆N30, K185Q] K(ATP) channel subunits, under cardiac α-myosin heavy chain (αMHC) promoter control, demonstrate arrhythmia susceptibility and premature death. Pregnant mice, crossed to carry double transgenic progeny, which harbor high levels of both overexpressed subunits, exhibit the most extreme phenotype and do not deliver any double transgenic pups. To explore the fetal lethality and embryonic phenotype that result from K(ATP) overexpression, wild type (WT) and K(ATP) overexpressing embryonic cardiomyocytes were isolated, cultured and voltage-clamped using whole cell and excised patch clamp techniques. Whole mount embryonic imaging, Hematoxylin and Eosin (H&E) and α smooth muscle actin (αSMA) immunostaining were used to assess anatomy, histology and cardiac development in K(ATP) overexpressing and WT embryos. Double transgenic embryos developed in utero heart failure and 100% embryonic lethality by 11.5 days post conception (dpc). K(ATP) currents were detectable in both WT and K(ATP)-overexpressing embryonic cardiomyocytes, starting at early stages of cardiac development (9.5 dpc). In contrast to adult cardiomyocytes, WT and K(ATP)-overexpressing embryonic cardiomyocytes exhibit basal and spontaneous K(ATP) current, implying that these channels may be open and active under physiological conditions. At 9.5 dpc, live double transgenic embryos demonstrated normal looping pattern, although all cardiac structures were collapsed, probably representing failed, non-contractile chambers. In conclusion, K(ATP) channels are present and active in embryonic myocytes, and overexpression causes in utero heart failure and results in embryonic lethality. These results suggest that the K(ATP) channel may have an important physiological role during early cardiac development.
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Affiliation(s)
- Amir Toib
- Department of Pediatrics, St. Louis, MO, 63110, USA.
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Finol-Urdaneta RK, Remedi MS, Raasch W, Becker S, Clark RB, Strüver N, Pavlov E, Nichols CG, French RJ, Terlau H. Block of Kv1.7 potassium currents increases glucose-stimulated insulin secretion. EMBO Mol Med 2012; 4:424-34. [PMID: 22438204 PMCID: PMC3403299 DOI: 10.1002/emmm.201200218] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 01/12/2012] [Accepted: 01/13/2012] [Indexed: 01/26/2023] Open
Abstract
Glucose-stimulated insulin secretion (GSIS) relies on repetitive, electrical spiking activity of the beta cell membrane. Cyclic activation of voltage-gated potassium channels (Kv) generates an outward, ‘delayed rectifier’ potassium current, which drives the repolarizing phase of each spike and modulates insulin release. Although several Kv channels are expressed in pancreatic islets, their individual contributions to GSIS remain incompletely understood. We take advantage of a naturally occurring cone-snail peptide toxin, Conkunitzin-S1 (Conk-S1), which selectively blocks Kv1.7 channels to provide an intrinsically limited, finely graded control of total beta cell delayed rectifier current and hence of GSIS. Conk-S1 increases GSIS in isolated rat islets, likely by reducing Kv1.7-mediated delayed rectifier currents in beta cells, which yields increases in action potential firing and cytoplasmic free calcium. In rats, Conk-S1 increases glucose-dependent insulin secretion without decreasing basal glucose. Thus, we conclude that Kv1.7 contributes to the membrane-repolarizing current of beta cells during GSIS and that block of this specific component of beta cell Kv current offers a potential strategy for enhancing GSIS with minimal risk of hypoglycaemia during metabolic disorders such as Type 2 diabetes.
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Affiliation(s)
- Rocio K Finol-Urdaneta
- Department of Physiology and Pharmacology, and HBI, University of Calgary, Calgary, AB, Canada
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Benninger RKP, Remedi MS, Head WS, Ustione A, Piston DW, Nichols CG. Defects in beta cell Ca²+ signalling, glucose metabolism and insulin secretion in a murine model of K(ATP) channel-induced neonatal diabetes mellitus. Diabetologia 2011; 54:1087-97. [PMID: 21271337 PMCID: PMC3245714 DOI: 10.1007/s00125-010-2039-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 12/03/2010] [Indexed: 10/18/2022]
Abstract
AIMS/HYPOTHESIS Mutations that render ATP-sensitive potassium (K(ATP)) channels insensitive to ATP inhibition cause neonatal diabetes mellitus. In mice, these mutations cause insulin secretion to be lost initially and, as the disease progresses, beta cell mass and insulin content also disappear. We investigated whether defects in calcium signalling alone are sufficient to explain short-term and long-term islet dysfunction. METHODS We examined the metabolic, electrical and insulin secretion response in islets from mice that become diabetic after induction of ATP-insensitive Kir6.2 expression. To separate direct effects of K(ATP) overactivity on beta cell function from indirect effects of prolonged hyperglycaemia, normal glycaemia was maintained by protective exogenous islet transplantation. RESULTS In endogenous islets from protected animals, glucose-dependent elevations of intracellular free-calcium activity ([Ca(2+)](i)) were severely blunted. Insulin content of these islets was normal, and sulfonylureas and KCl stimulated increased [Ca(2+)](i). In the absence of transplant protection, [Ca(2+)](i) responses were similar, but glucose metabolism and redox state were dramatically altered; sulfonylurea- and KCl-stimulated insulin secretion was also lost, because of systemic effects induced by long-term hyperglycaemia and/or hypoinsulinaemia. In both cases, [Ca(2+)](i) dynamics were synchronous across the islet. After reduction of gap-junction coupling, glucose-dependent [Ca(2+)](i) and insulin secretion was partially restored, indicating that excitability of weakly expressing cells is suppressed by cells expressing mutants, via gap-junctions. CONCLUSIONS/INTERPRETATION The primary defect in K(ATP)-induced neonatal diabetes mellitus is failure of glucose metabolism to elevate [Ca(2+)](i), which suppresses insulin secretion and mildly alters islet glucose metabolism. Loss of insulin content and mitochondrial dysfunction are secondary to the long-term hyperglycaemia and/or hypoinsulinaemia that result from the absence of glucose-dependent insulin secretion.
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Affiliation(s)
- R K P Benninger
- Molecular Physiology and Biophysics, Vanderbilt University, 2215 Garland Avenue, Nashville, TN 37232, USA
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Rohatgi N, Remedi MS, Kwon G, Pappan KL, Marshall CA, McDaniel ML. Therapeutic Strategies to Increase Human β-Cell Growth and Proliferation by Regulating mTOR and GSK-3/β-Catenin Pathways. ACTA ACUST UNITED AC 2010; 4. [PMID: 24339841 DOI: 10.2174/1874216501004010040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
This perspective delineates approaches to develop therapeutic strategies to stimulate the proliferative potential of adult human β-cells in vitro. Previous findings demonstrated that nutrients, through regulation of mTOR signaling, promote regenerative processes including DNA synthesis, cell cycle progression and β-cell proliferation in rodent islets but rarely in human islets. Recently, we discovered that regulation of the Wnt/GSK-3/β-catenin pathway by directly inhibiting GSK-3 with pharmacologic agents, in combination with nutrient activation of mTOR, was required to increase growth and proliferation in human islets. Studies also revealed that nuclear translocation of β-catenin in response to GSK-3 inhibition regulated these processes and was rapamycin sensitive, indicating a role for mTOR. Human islets displayed a high level of insulin resistance consistent with the inability of exogenous insulin to activate Akt and engage the Wnt pathway by GSK-3 inhibition. This insulin resistance in human islets is not present in rodent islets and may explain the differential requirement in human islets to inhibit GSK-3 to enhance these regenerative processes. Human islets exhibited normal insulin secretion but a loss of insulin content, which was independent of all treatment conditions. The loss of insulin content may be related to insulin resistance, the isolation process or culture conditions. In this perspective, we provide strategies to enhance the proliferative capacity of adult human β-cells and highlight important differences between human and rodent islets: the lack of a nutrient response, requirement for direct GSK-3 inhibition, insulin resistance and loss of insulin content that emphasize the physiological significance of conducting studies in human islets.
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Affiliation(s)
- Nidhi Rohatgi
- Department of Pathology and Immunology, Washington University in St. Louis, St. Louis, Missouri, USA
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Benninger RK, Remedi MS, Ustione A, Head WS, Nichols CG, Piston DW. Metabolism-Excitation Coupling in a Model of KATP Channel Neonatal Diabetes Mellitus. Biophys J 2010. [DOI: 10.1016/j.bpj.2009.12.3140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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Abstract
Adenosine-triphosphate-sensitive potassium channels (KATP) are regulated by adenosine nucleotides, and, thereby, couple cellular metabolism with electrical activity in multiple tissues including the pancreatic beta-cell. The critical involvement of KATP in insulin secretion is confirmed by the demonstration that inactivating and activating mutations in KATP underlie persistent hyperinsulinemia and neonatal diabetes mellitus, respectively, in both animal models and humans. In addition, a common variant in KATP represents a risk factor in the etiology of type 2 diabetes. This review focuses on the mechanistic basis by which KATP mutations underlie insulin secretory disorders and the implications of these findings for successful clinical intervention.
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Affiliation(s)
- Maria S Remedi
- Department of Cell Biology and Physiology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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Liu H, Remedi MS, Pappan KL, Kwon G, Rohatgi N, Marshall CA, McDaniel ML. Glycogen synthase kinase-3 and mammalian target of rapamycin pathways contribute to DNA synthesis, cell cycle progression, and proliferation in human islets. Diabetes 2009; 58:663-72. [PMID: 19073772 PMCID: PMC2646065 DOI: 10.2337/db07-1208] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Our previous studies demonstrated that nutrient regulation of mammalian target of rapamycin (mTOR) signaling promotes regenerative processes in rodent islets but rarely in human islets. Our objective was to extend these findings by using therapeutic agents to determine whether the regulation of glycogen synthase kinase-3 (GSK-3)/beta-catenin and mTOR signaling represent key components necessary for effecting a positive impact on human beta-cell mass relevant to type 1 and 2 diabetes. RESEARCH DESIGN AND METHODS Primary adult human and rat islets were treated with the GSK-3 inhibitors, LiCl and the highly potent 1-azakenpaullone (1-Akp), and with nutrients. DNA synthesis, cell cycle progression, and proliferation of beta-cells were assessed. Measurement of insulin secretion and content and Western blot analysis of GSK-3 and mTOR signaling components were performed. RESULTS Human islets treated for 4 days with LiCl or 1-Akp exhibited significant increases in DNA synthesis, cell cycle progression, and proliferation of beta-cells that displayed varying degrees of sensitivity to rapamycin. Intermediate glucose (8 mmol/l) produced a striking degree of synergism in combination with GSK-3 inhibition to enhance bromodeoxyuridine (BrdU) incorporation and Ki-67 expression in human beta-cells. Nuclear translocation of beta-catenin responsible for cell proliferation was found to be particularly sensitive to rapamycin. CONCLUSIONS A combination of GSK-3 inhibition and nutrient activation of mTOR contributes to enhanced DNA synthesis, cell cycle progression, and proliferation of human beta-cells. Identification of therapeutic agents that appropriately regulate GSK-3 and mTOR signaling may provide a feasible and available approach to enhance human islet growth and proliferation.
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Affiliation(s)
- Hui Liu
- Department of Pathology and Immunology, Washington University, St. Louis, Missouri, USA
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