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Morrice N, Vainio S, Mikkola K, van Aalten L, Gallagher JR, Ashford MLJ, McNeilly AD, McCrimmon RJ, Grosfeld A, Serradas P, Koffert J, Pearson ER, Nuutila P, Sutherland C. Metformin increases the uptake of glucose into the gut from the circulation in high-fat diet-fed male mice, which is enhanced by a reduction in whole-body Slc2a2 expression. Mol Metab 2023; 77:101807. [PMID: 37717665 PMCID: PMC10550722 DOI: 10.1016/j.molmet.2023.101807] [Citation(s) in RCA: 2] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/28/2023] [Accepted: 09/12/2023] [Indexed: 09/19/2023] Open
Abstract
OBJECTIVES Metformin is the first line therapy recommended for type 2 diabetes. However, the precise mechanism of action remains unclear and up to a quarter of patients show some degree of intolerance to the drug, with a similar number showing poor response to treatment, limiting its effectiveness. A better understanding of the mechanism of action of metformin may improve its clinical use. SLC2A2 (GLUT2) is a transmembrane facilitated glucose transporter, with important roles in the liver, gut and pancreas. Our group previously identified single nucleotide polymorphisms in the human SLC2A2 gene, which were associated with reduced transporter expression and an improved response to metformin treatment. The aims of this study were to model Slc2a2 deficiency and measure the impact on glucose homoeostasis and metformin response in mice. METHODS We performed extensive metabolic phenotyping and 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG)-positron emission tomography (PET) analysis of gut glucose uptake in high-fat diet-fed (HFD) mice with whole-body reduced Slc2a2 (Slc2a2+/-) and intestinal Slc2a2 KO, to assess the impact of metformin treatment. RESULTS Slc2a2 partial deficiency had no major impact on body weight and insulin sensitivity, however mice with whole-body reduced Slc2a2 expression (Slc2a2+/-) developed an age-related decline in glucose homoeostasis (as measured by glucose tolerance test) compared to wild-type (Slc2a2+/+) littermates. Glucose uptake into the gut from the circulation was enhanced by metformin exposure in Slc2a2+/+ animals fed HFD and this action of the drug was significantly higher in Slc2a2+/- animals. However, there was no effect of specifically knocking-out Slc2a2 in the mouse intestinal epithelial cells. CONCLUSIONS Overall, this work identifies a differential metformin response, dependent on expression of the SLC2A2 glucose transporter, and also adds to the growing evidence that metformin efficacy includes modifying glucose transport in the gut. We also describe a novel and important role for this transporter in maintaining efficient glucose homoeostasis during ageing.
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Affiliation(s)
- Nicola Morrice
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Susanne Vainio
- Turku PET Centre, University of Turku, Turku, Finland; MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Kirsi Mikkola
- Turku PET Centre, University of Turku, Turku, Finland; MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Lidy van Aalten
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Jennifer R Gallagher
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Michael L J Ashford
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Alison D McNeilly
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Rory J McCrimmon
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Alexandra Grosfeld
- Sorbonne Université, Inserm, Centre de Recherche Saint-Antoine, CRSA, F-75012, Paris, France
| | - Patricia Serradas
- Sorbonne Université, INSERM, Nutrition and Obesities: Systemic approaches, NutriOmics, Research group, F-75013, Paris, France
| | - Jukka Koffert
- Turku PET Centre, University of Turku, Turku, Finland; Department of Gastroenterology, Turku University Hospital, Turku, Finland
| | - Ewan R Pearson
- Division of Population Health and Genomics, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK
| | - Pirjo Nuutila
- Turku PET Centre, University of Turku, Turku, Finland; Department of Endocrinology, Turku University Hospital, Turku, Finland
| | - Calum Sutherland
- Division of Cellular and Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland, DD1 9SY, UK.
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2
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Sri S, Greenstein A, Granata A, Collcutt A, Jochems ACC, McColl BW, Castro BD, Webber C, Reyes CA, Hall C, Lawrence CB, Hawkes C, Pegasiou-Davies CM, Gibson C, Crawford CL, Smith C, Vivien D, McLean FH, Wiseman F, Brezzo G, Lalli G, Pritchard HAT, Markus HS, Bravo-Ferrer I, Taylor J, Leiper J, Berwick J, Gan J, Gallacher J, Moss J, Goense J, McMullan L, Work L, Evans L, Stringer MS, Ashford MLJ, Abulfadl M, Conlon N, Malhotra P, Bath P, Canter R, Brown R, Ince S, Anderle S, Young S, Quick S, Szymkowiak S, Hill S, Allan S, Wang T, Quinn T, Procter T, Farr TD, Zhao X, Yang Z, Hainsworth AH, Wardlaw JM. A multi-disciplinary commentary on preclinical research to investigate vascular contributions to dementia. Cereb Circ Cogn Behav 2023; 5:100189. [PMID: 37941765 PMCID: PMC10628644 DOI: 10.1016/j.cccb.2023.100189] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/27/2023] [Accepted: 10/05/2023] [Indexed: 11/10/2023]
Abstract
Although dementia research has been dominated by Alzheimer's disease (AD), most dementia in older people is now recognised to be due to mixed pathologies, usually combining vascular and AD brain pathology. Vascular cognitive impairment (VCI), which encompasses vascular dementia (VaD) is the second most common type of dementia. Models of VCI have been delayed by limited understanding of the underlying aetiology and pathogenesis. This review by a multidisciplinary, diverse (in terms of sex, geography and career stage), cross-institute team provides a perspective on limitations to current VCI models and recommendations for improving translation and reproducibility. We discuss reproducibility, clinical features of VCI and corresponding assessments in models, human pathology, bioinformatics approaches, and data sharing. We offer recommendations for future research, particularly focusing on small vessel disease as a main underpinning disorder.
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Affiliation(s)
- Sarmi Sri
- UK Dementia Research Institute Headquarters, 6th Floor Maple House, London W1T 7NF, UK
| | - Adam Greenstein
- Division of Cardiovascular Sciences, The University of Manchester, Manchester M13 9PL, UK
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Alessandra Granata
- Department of Clinical Neurosciences, Victor Phillip Dahdaleh Heart & Lung Research Institute, University of Cambridge, Papworth Road, Cambridge Biomedical Campus, Cambridge CB2 0BB, UK
| | - Alex Collcutt
- UK Dementia Research Institute Headquarters, 6th Floor Maple House, London W1T 7NF, UK
| | - Angela C C Jochems
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
| | - Barry W McColl
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Blanca Díaz Castro
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Caleb Webber
- UK Dementia Research Institute Cardiff, Cardiff University, Cardiff CF24 4HQ, UK
| | - Carmen Arteaga Reyes
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
| | - Catherine Hall
- School of Psychology and Sussex Neuroscience, University of Sussex, Falmer, Brighton, East Sussex, UK
| | - Catherine B Lawrence
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
- Division of Neuroscience, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Cheryl Hawkes
- Biomedical and Life Sciences, Lancaster University, Lancaster, UK
| | | | - Claire Gibson
- School of Psychology, University of Nottingham, Nottingham NG7 2UH, UK
| | - Colin L Crawford
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Colin Smith
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Denis Vivien
- Physiopathology and Imaging of Neurological Disorders (PhIND), Normandie University, UNICAEN, INSERM UMR-S U1237, , GIP Cyceron, Institute Blood and Brain @ Caen-Normandie (BB@C), Caen, France
- Department of clinical research, Caen-Normandie University Hospital, Caen, France
| | - Fiona H McLean
- Division of Systems Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Frances Wiseman
- UK Dementia Research Institute, University College London, London WC1N 3BG, UK
| | - Gaia Brezzo
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Giovanna Lalli
- UK Dementia Research Institute Headquarters, 6th Floor Maple House, London W1T 7NF, UK
| | - Harry A T Pritchard
- Division of Cardiovascular Sciences, The University of Manchester, Manchester M13 9PL, UK
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Hugh S Markus
- Stroke Research Group, Clinical Neurosciences, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Isabel Bravo-Ferrer
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Jade Taylor
- Division of Cardiovascular Sciences, The University of Manchester, Manchester M13 9PL, UK
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - James Leiper
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
| | - Jason Berwick
- Department of Psychology, University of Sheffield, Sheffield, UK
- Neuroscience Institute, University of Sheffield, Sheffield, UK
- Healthy Lifespan Institute, University of Sheffield, Sheffield, UK
| | - Jian Gan
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - John Gallacher
- Department of Psychiatry, Warneford Hospital, University of Oxford, Oxford, UK
| | - Jonathan Moss
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
- The Roslin Institute, Royal (Dick) School of Veterinary Studies, The University of Edinburgh, UK
| | - Jozien Goense
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, IL, USA
- Department of Psychology, University of Illinois, Urbana-Champaign, Champaign, IL, USA
- Department of Bioengineering, University of Illinois, Urbana-Champaign, Urbana, IL, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, IL, USA
- School of Psychology and Neuroscience, University of Glasgow, UK
| | - Letitia McMullan
- School of Psychology and Sussex Neuroscience, University of Sussex, Falmer, Brighton, East Sussex, UK
| | - Lorraine Work
- School of Cardiovascular & Metabolic Health, College of Medical, Veterinary & Life Sciences, University of Glasgow; Glasgow; UK
| | - Lowri Evans
- Division of Cardiovascular Sciences, The University of Manchester, Manchester M13 9PL, UK
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Michael S Stringer
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
| | - MLJ Ashford
- Division of Systems Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Mohamed Abulfadl
- Dementia Research Group, Department of Clinical Neurosciences, Bristol Medical School, University of Bristol, Bristol BS10 5NB, UK
| | - Nina Conlon
- Division of Cardiovascular Sciences, The University of Manchester, Manchester M13 9PL, UK
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
| | - Paresh Malhotra
- Department of Brain Sciences, Imperial College London, London, UK
- Department of Neurology, Imperial College Healthcare NHS Trust, London, UK
- UK Dementia Research Institute Care Research and Technology Centre, Imperial College London and the University of Surrey, UK
| | - Philip Bath
- Stroke Trials Unit, University of Nottingham, Nottingham, UK; Stroke, Medicine Division, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | - Rebecca Canter
- Dementia Discovery Fund, SV Health Managers LLP, London, UK
| | - Rosalind Brown
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
| | - Selvi Ince
- Dementia Research Group, Department of Clinical Neurosciences, Bristol Medical School, University of Bristol, Bristol BS10 5NB, UK
| | - Silvia Anderle
- School of Psychology and Sussex Neuroscience, University of Sussex, Falmer, Brighton, East Sussex, UK
- Department of Neuroscience, Physiology and Pharmacology, University College London, UK
| | - Simon Young
- Dementias Platform UK, Department of Psychiatry, University of Oxford, Oxford OX3 7JX, UK
| | - Sophie Quick
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
| | - Stefan Szymkowiak
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
- UK Dementia Research Institute Cardiff, Cardiff University, Cardiff CF24 4HQ, UK
| | - Steve Hill
- Centre for Discovery Brain Sciences, Chancellor's Building, The University of Edinburgh, Edinburgh, UK
- UK Dementia Research Institute Cardiff, Cardiff University, Cardiff CF24 4HQ, UK
| | - Stuart Allan
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
- Division of Neuroscience, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Tao Wang
- Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, University of Manchester, Manchester, UK
- Division of Evolution, Infection and Genomic Sciences, Faculty of Biology Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester, UK
- Manchester Centre for Genomic Medicine, Manchester University NHS Foundation Trust, Manchester, UK
| | - Terry Quinn
- College of Medical Veterinary and Life Sciences, University of Glasgow, Scotland, UK
| | - Tessa Procter
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
- Centre for Regenerative Medicine, Institute for Regeneration and Repair, The University of Edinburgh, Edinburgh, UK
- Royal (Dick) School of Veterinary Studies, The University of Edinburgh, UK
| | - Tracy D Farr
- School of Life Sciences, Physiology, Pharmacology, and Neuroscience Division, Medical School, University of Nottingham, Nottingham NG7 2UH, UK
| | - Xiangjun Zhao
- Division of Evolution, Infection and Genomic Sciences, Faculty of Biology Medicine and Health, School of Biological Sciences, The University of Manchester, Manchester, UK
| | - Zhiyuan Yang
- Department of Neuroinflammation, UCL Queen Square Institute of Neurology, London, UK
| | - Atticus H Hainsworth
- Molecular and Clinical Sciences Research Institute, St George's University of London SW17 0RE, UK
- Department of Neurology, St George's University Hospitals NHS Foundation Trust, London, UK
| | - Joanna M Wardlaw
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK
- UK Dementia Research Institute Edinburgh, University of Edinburgh, Edinburgh, UK
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3
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McNeilly AD, Gallagher JR, Evans ML, de Galan BE, Pedersen-Bjergaard U, Thorens B, Dinkova-Kostova AT, Huang JT, Ashford MLJ, McCrimmon RJ. Chronic hyperglycaemia increases the vulnerability of the hippocampus to oxidative damage induced during post-hypoglycaemic hyperglycaemia in a mouse model of chemically induced type 1 diabetes. Diabetologia 2023:10.1007/s00125-023-05907-6. [PMID: 37015997 DOI: 10.1007/s00125-023-05907-6] [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] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 01/26/2023] [Indexed: 04/06/2023]
Abstract
AIMS/HYPOTHESIS Chronic hyperglycaemia and recurrent hypoglycaemia are independently associated with accelerated cognitive decline in type 1 diabetes. Recurrent hypoglycaemia in rodent models of chemically induced (streptozotocin [STZ]) diabetes leads to cognitive impairment in memory-related tasks associated with hippocampal oxidative damage. This study examined the hypothesis that post-hypoglycaemic hyperglycaemia in STZ-diabetes exacerbates hippocampal oxidative stress and explored potential contributory mechanisms. METHODS The hyperinsulinaemic glucose clamp technique was used to induce equivalent hypoglycaemia and to control post-hypoglycaemic glucose levels in mice with and without STZ-diabetes and Nrf2-/- mice (lacking Nrf2 [also known as Nfe2l2]). Subsequently, quantitative proteomics based on stable isotope labelling by amino acids in cell culture and biochemical approaches were used to assess oxidative damage and explore contributory pathways. RESULTS Evidence of hippocampal oxidative damage was most marked in mice with STZ-diabetes exposed to post-hypoglycaemic hyperglycaemia; these mice also showed induction of Nrf2 and the Nrf2 transcriptional targets Sod2 and Hmox-1. In this group, hypoglycaemia induced a significant upregulation of proteins involved in alternative fuel provision, reductive biosynthesis and degradation of damaged proteins, and a significant downregulation of proteins mediating the stress response. Key differences emerged between mice with and without STZ-diabetes following recovery from hypoglycaemia in proteins mediating the stress response and reductive biosynthesis. CONCLUSIONS/INTERPRETATION There is a disruption of the cellular response to a hypoglycaemic challenge in mice with STZ-induced diabetes that is not seen in wild-type non-diabetic animals. The chronic hyperglycaemia of diabetes and post-hypoglycaemic hyperglycaemia act synergistically to induce oxidative stress and damage in the hippocampus, possibly leading to irreversible damage/modification to proteins or synapses between cells. In conclusion, recurrent hypoglycaemia in sub-optimally controlled diabetes may contribute, at least in part, to accelerated cognitive decline through amplifying oxidative damage in key brain regions, such as the hippocampus. DATA AVAILABILITY The datasets generated during and/or analysed during the current study are available in ProteomeXchange, accession no. 1-20220824-173727 ( www.proteomexchange.org ). Additional datasets generated during and/or analysed during the present study are available from the corresponding author upon reasonable request.
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Affiliation(s)
- Alison D McNeilly
- Division of Systems Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK
| | - Jennifer R Gallagher
- Division of Systems Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK
| | - Mark L Evans
- Wellcome-MRC Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Bastiaan E de Galan
- Radboud University Medical Center, Nijmegen, the Netherlands
- Department of Internal Medicine, Maastricht University Medical Center, Maastricht, the Netherlands
- CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, the Netherlands
| | | | - Bernard Thorens
- Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Albena T Dinkova-Kostova
- Division of Cancer Research, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK
| | - Jeffrey-T Huang
- Division of Systems Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK
- Biomarker and Drug Analysis Core Facility, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK
| | - Michael L J Ashford
- Division of Systems Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK
| | - Rory J McCrimmon
- Division of Systems Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, UK.
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Al-Mubarak BR, Bell KFS, Chowdhry S, Meakin PJ, Baxter PS, McKay S, Dando O, Ashford MLJ, Gazaryan I, Hayes JD, Hardingham GE. Non-canonical Keap1-independent activation of Nrf2 in astrocytes by mild oxidative stress. Redox Biol 2021; 47:102158. [PMID: 34626892 PMCID: PMC8512624 DOI: 10.1016/j.redox.2021.102158] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [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] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 09/29/2021] [Accepted: 09/30/2021] [Indexed: 12/30/2022] Open
Abstract
The transcription factor Nrf2 is a stress-responsive master regulator of antioxidant, detoxification and proteostasis genes. In astrocytes, Nrf2-dependent gene expression drives cell-autonomous cytoprotection and also non-cell-autonomous protection of nearby neurons, and can ameliorate pathology in several acute and chronic neurological disorders associated with oxidative stress. However, the value of astrocytic Nrf2 as a therapeutic target depends in part on whether Nrf2 activation by disease-associated oxidative stress occludes the effect of any Nrf2-activating drug. Nrf2 activation classically involves the inhibition of interactions between Nrf2's Neh2 domain and Keap1, which directs Nrf2 degradation. Keap1 inhibition is mediated by the modification of cysteine residues on Keap1, and can be triggered by electrophilic small molecules such as tBHQ. Here we show that astrocytic Nrf2 activation by oxidative stress involves Keap1-independent non-canonical signaling. Keap1 deficiency elevates basal Nrf2 target gene expression in astrocytes and occludes the effects of tBHQ, oxidative stress still induced strong Nrf2-dependent gene expression in Keap1-deficient astrocytes. Moreover, while tBHQ prevented protein degradation mediated via Nrf2's Neh2 domain, oxidative stress did not, consistent with a Keap1-independent mechanism. Moreover the effects of oxidative stress and tBHQ on Nrf2 target gene expression are additive, not occlusive. Mechanistically, oxidative stress enhances the transactivation potential of Nrf2's Neh5 domain in a manner dependent on its Cys-191 residue. Thus, astrocytic Nrf2 activation by oxidative stress involves Keap1-independent non-canonical signaling, meaning that further Nrf2 activation by Keap1-inhibiting drugs may be a viable therapeutic strategy.
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Affiliation(s)
- Bashayer R Al-Mubarak
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK; Behavioral Genetics Unit, Department of Genetics, King Faisal Specialist Hospital and Research Center, P.O Box 3354, Riyadh, 11211, Saudi Arabia
| | - Karen F S Bell
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK
| | - Sudhir Chowdhry
- Biomedical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
| | - Paul J Meakin
- Discovery & Translational Science Department, Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, LS2 9JT, UK; Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital & Medical School, Dundee, UK
| | - Paul S Baxter
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK; UK Dementia Research Institute at the University of Edinburgh, Chancellor's Building, Edinburgh Medical School, EH16 4SB, UK
| | - Sean McKay
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK; UK Dementia Research Institute at the University of Edinburgh, Chancellor's Building, Edinburgh Medical School, EH16 4SB, UK
| | - Owen Dando
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK; UK Dementia Research Institute at the University of Edinburgh, Chancellor's Building, Edinburgh Medical School, EH16 4SB, UK
| | - Michael L J Ashford
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital & Medical School, Dundee, UK
| | - Irina Gazaryan
- Department of Chemistry and Physical Sciences, Dyson College of Arts and Sciences, Pace University, Pleasantville, NY, 10570, USA
| | - John D Hayes
- Biomedical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK
| | - Giles E Hardingham
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK; UK Dementia Research Institute at the University of Edinburgh, Chancellor's Building, Edinburgh Medical School, EH16 4SB, UK.
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Gabriel JL, Tinti M, Fuller W, Ashford MLJ. Identifying the beta-site amyloid precursor protein cleaving enzyme 1 interactome through the proximity-dependent biotin identification assay. Neurosci Lett 2021; 767:136302. [PMID: 34710551 DOI: 10.1016/j.neulet.2021.136302] [Citation(s) in RCA: 1] [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] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 10/15/2021] [Accepted: 10/18/2021] [Indexed: 11/30/2022]
Abstract
Beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) is a key drug target against Alzheimer's Disease however, due to its promiscuous proteolytic activity, little is known about its physiological functions. Previous studies have analysed BACE1 cleavage products to examine BACE1 interactions and determine substrates, but these studies cannot establish non-enzymatic (and potentially functional) associations. This study used the biotin identification proximity assay to establish the BACE1 interactome in healthy neuronal cells and identified interactions involved in BACE1 trafficking, post-translational modification and substrates. Furthermore, this method has identified a putative novel role for BACE1 in sex hormone signalling and haem regulation through interaction with the progesterone receptor membrane component 2 (PGRC2). Data are available via ProteomeXchange with identifier PXD021464.
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Affiliation(s)
- Jennie L Gabriel
- Division of Systems Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Michele Tinti
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK
| | - William Fuller
- Division of Systems Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Michael L J Ashford
- Division of Systems Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK.
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Chen C, Gallagher JR, Tarlton J, van Aalten L, Bray SE, Ashford MLJ, McCrimmon RJ, Pearson ER, McNeilly AD, Sutherland C. The genetic association of the transcription factor NPAT with glycemic response to metformin involves regulation of fuel selection. PLoS One 2021; 16:e0253533. [PMID: 34197485 PMCID: PMC8248654 DOI: 10.1371/journal.pone.0253533] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 06/07/2021] [Indexed: 11/19/2022] Open
Abstract
The biguanide, metformin, is the first-choice therapeutic agent for type-2 diabetes, although the mechanisms that underpin metformin clinical efficacy remain the subject of much debate, partly due to the considerable variation in patient response to metformin. Identification of poor responders by genotype could avoid unnecessary treatment and provide clues to the underlying mechanism of action. GWAS identified SNPs associated with metformin treatment success at a locus containing the NPAT (nuclear protein, ataxia-telangiectasia locus) and ATM (ataxia-telangiectasia mutated) genes. This implies that gene sequence dictates a subsequent biological function to influence metformin action. Hence, we modified expression of NPAT in immortalized cell lines, primary mouse hepatocytes and mouse tissues, and analysed the outcomes on metformin action using confocal microscopy, immunoblotting and immunocytochemistry. In addition, we characterised the metabolic phenotype of npat heterozygous knockout mice and established the metformin response following development of insulin resistance. NPAT protein was localised in the nucleus at discrete loci in several cell types, but over-expression or depletion of NPAT in immortalised cell models did not change cellular responses to biguanides. In contrast, metformin regulation of respiratory exchange ratio (RER) was completely lost in animals lacking one allele of npat. There was also a reduction in metformin correction of impaired glucose tolerance, however no other metabolic abnormalities, or response to metformin, were found in the npat heterozygous mice. In summary, we provide methodological advancements for the detection of NPAT, demonstrate that minor reductions in NPAT mRNA levels (20–40%) influence metformin regulation of RER, and propose that the association between NPAT SNPs and metformin response observed in GWAS, could be due to loss of metformin modification of cellular fuel usage.
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Affiliation(s)
- Changwei Chen
- Division of Cellular Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Jennifer R. Gallagher
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Jamie Tarlton
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Lidy van Aalten
- Division of Cellular Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Susan E. Bray
- Tayside Tissue Bank, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Michael L. J. Ashford
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Rory J. McCrimmon
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Ewan R. Pearson
- Division of Population Health and Genomics, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Alison D. McNeilly
- Division of Systems Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
| | - Calum Sutherland
- Division of Cellular Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, James Arnott Drive, Dundee, United Kingdom
- * E-mail:
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7
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Bugler-Lamb AR, Hasib A, Weng X, Hennayake CK, Lin C, McCrimmon RJ, Stimson RH, Ashford MLJ, Wasserman DH, Kang L. Adipocyte integrin-linked kinase plays a key role in the development of diet-induced adipose insulin resistance in male mice. Mol Metab 2021; 49:101197. [PMID: 33647469 PMCID: PMC8027775 DOI: 10.1016/j.molmet.2021.101197] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [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: 11/17/2020] [Revised: 01/30/2021] [Accepted: 02/23/2021] [Indexed: 12/12/2022] Open
Abstract
Objective Increased deposition of the extracellular matrix (ECM) in adipose tissue (AT) during obesity contributes to insulin resistance. The integrin receptors transmit changes in the extracellular environment causing corresponding intracellular adaptations. Integrin-linked kinase (ILK), an adaptor protein, is a central hub for intracellular signaling of integrins. This study determined the role of ILK in adipose function and insulin resistance. Methods The pathogenic role of ILK in obesity and insulin resistance was studied in human adipose tissue and adipocyte-specific ILK-deficient mice (ILKlox/loxAdCre). ILKlox/loxAdCre mice together with wild-type littermates (ILKlox/lox) were fed a chow diet or 60% high-fat (HF) diet for 16 weeks. In vivo insulin sensitivity was determined by hyperinsulinemic-euglycemic clamps. Results AT ILK expression was increased by HF diet feeding in mice and increased in visceral fat of morbidly obese humans. The HF-fed ILKlox/loxAdCre mice displayed reduced fat mass and improved glucose tolerance relative to the HF-fed ILKlox/lox mice. During a hyperinsulinemic-euglycemic clamp, the HF-fed ILKlox/loxAdCre mice exhibited partially improved insulin resistance in AT. Lipolysis was suppressed to a greater extent by insulin and glucose uptake in brown AT (BAT) increased. Increased inhibition of lipolysis may have been attributed to increased vascularization in white AT, while increased glucose uptake in BAT was associated with increased Akt phosphorylation and P38/JNK dephosphorylation. Notably, AT insulin sensitivity in lean mice was not affected by ILK deletion. Moreover, reduced fat mass in the HF-fed ILKlox/loxAdCre mice may have been attributed to decreased free fatty acid uptake into adipocytes via the downregulation of CD36 gene expression. Consistent with the results in the mice, knockdown and knockout of ILK in 3T3-L1 cells decreased lipid accumulation and CD36 gene expression during adipogenesis. Conclusions These data show that adipocyte ILK is important for regulating HF diet-mediated insulin resistance in AT in a manner consistent with AT function. ILK protein increased in visceral adipose tissue of obese humans and mice. Mice lacking adipocyte ILK had less fat and improved glucose tolerance in obesity. Adipocyte ILK deletion improved anti-lipolytic action of insulin in obese mice. Adipocyte ILK deletion stimulated brown adipose tissue glucose uptake in obese mice.
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Affiliation(s)
- Aimée R Bugler-Lamb
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - Annie Hasib
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - Xiong Weng
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - Chandani K Hennayake
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - Chenshi Lin
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - Rory J McCrimmon
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - Roland H Stimson
- Center for Cardiovascular Science, University of Edinburgh, Edinburgh, Scotland, UK
| | - Michael L J Ashford
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK
| | - David H Wasserman
- Department of Molecular Physiology and Biophysics and Mouse Metabolic Phenotyping Center, Vanderbilt University, Nashville, TN, USA
| | - Li Kang
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, UK.
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8
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Hasib A, Hennayake CK, Bracy DP, Bugler-Lamb AR, Lantier L, Khan F, Ashford MLJ, McCrimmon RJ, Wasserman DH, Kang L. CD44 contributes to hyaluronan-mediated insulin resistance in skeletal muscle of high-fat-fed C57BL/6 mice. Am J Physiol Endocrinol Metab 2019; 317:E973-E983. [PMID: 31550181 PMCID: PMC6957377 DOI: 10.1152/ajpendo.00215.2019] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [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: 01/07/2023]
Abstract
Extracellular matrix hyaluronan is increased in skeletal muscle of high-fat-fed insulin-resistant mice, and reduction of hyaluronan by PEGPH20 hyaluronidase ameliorates diet-induced insulin resistance (IR). CD44, the main hyaluronan receptor, is positively correlated with type 2 diabetes. This study determines the role of CD44 in skeletal muscle IR. Global CD44-deficient (cd44-/-) mice and wild-type littermates (cd44+/+) were fed a chow diet or 60% high-fat diet for 16 wk. High-fat-fed cd44-/- mice were also treated with PEGPH20 to evaluate its CD44-dependent action. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp (ICv). High-fat feeding increased muscle CD44 protein expression. In the absence of differences in body weight and composition, despite lower clamp insulin during ICv, the cd44-/- mice had sustained glucose infusion rate (GIR) regardless of diet. High-fat diet-induced muscle IR as evidenced by decreased muscle glucose uptake (Rg) was exhibited in cd44+/+ mice but absent in cd44-/- mice. Moreover, gastrocnemius Rg remained unchanged between genotypes on chow diet but was increased in high-fat-fed cd44-/- compared with cd44+/+ when normalized to clamp insulin concentrations. Ameliorated muscle IR in high-fat-fed cd44-/- mice was associated with increased vascularization. In contrast to previously observed increases in wild-type mice, PEGPH20 treatment in high-fat-fed cd44-/- mice did not change GIR or muscle Rg during ICv, suggesting a CD44-dependent action. In conclusion, genetic CD44 deletion improves muscle IR, and the beneficial effects of PEGPH20 are CD44-dependent. These results suggest a critical role of CD44 in promoting hyaluronan-mediated muscle IR, therefore representing a potential therapeutic target for diabetes.
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Affiliation(s)
- Annie Hasib
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
| | - Chandani K Hennayake
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
| | - Deanna P Bracy
- Department of Molecular Physiology and Biophysics and Mouse Metabolic Phenotyping Centre, Vanderbilt University, Nashville, Tennessee
| | - Aimée R Bugler-Lamb
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
| | - Louise Lantier
- Department of Molecular Physiology and Biophysics and Mouse Metabolic Phenotyping Centre, Vanderbilt University, Nashville, Tennessee
| | - Faisel Khan
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
| | - Michael L J Ashford
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
| | - Rory J McCrimmon
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
| | - David H Wasserman
- Department of Molecular Physiology and Biophysics and Mouse Metabolic Phenotyping Centre, Vanderbilt University, Nashville, Tennessee
| | - Li Kang
- Division of Systems Medicine, School of Medicine, University of Dundee, Dundee, Scotland, United Kingdom
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9
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Botteri G, Salvadó L, Gumà A, Hamilton DL, Meakin PJ, Montagut G, Ashford MLJ, Ceperuelo-Mallafré V, Fernández-Veledo S, Vendrell J, Calderón-Dominguez M, Serra D, Herrero L, Pizarro J, Barroso E, Palomer X, Vázquez-Carrera M. Corrigendum to "The BACE1 product sAPPβ induces ER stress and inflammation and impairs insulin signaling" [Metab Clin Exp 85 (2018) 59-75]. Metabolism 2019; 96:101-102. [PMID: 31005247 DOI: 10.1016/j.metabol.2019.04.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Gaia Botteri
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Laia Salvadó
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Anna Gumà
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - D Lee Hamilton
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Paul J Meakin
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Gemma Montagut
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Victoria Ceperuelo-Mallafré
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Hospital Universitari de Tarragona Joan XXIII, Institut d'Investigació Sanitària Pere Virgili, Universitat Rovira i Virgili, Tarragona, Spain
| | - Sonia Fernández-Veledo
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Hospital Universitari de Tarragona Joan XXIII, Institut d'Investigació Sanitària Pere Virgili, Universitat Rovira i Virgili, Tarragona, Spain
| | - Joan Vendrell
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Hospital Universitari de Tarragona Joan XXIII, Institut d'Investigació Sanitària Pere Virgili, Universitat Rovira i Virgili, Tarragona, Spain
| | - María Calderón-Dominguez
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, Barcelona, Spain
| | - Dolors Serra
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, Barcelona, Spain
| | - Laura Herrero
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, Barcelona, Spain
| | - Javier Pizarro
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Emma Barroso
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Xavier Palomer
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Manuel Vázquez-Carrera
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain.
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10
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Smith MA, Katsouri L, Virtue S, Choudhury AI, Vidal-Puig A, Ashford MLJ, Withers DJ. Calcium Channel Ca V2.3 Subunits Regulate Hepatic Glucose Production by Modulating Leptin-Induced Excitation of Arcuate Pro-opiomelanocortin Neurons. Cell Rep 2018; 25:278-287.e4. [PMID: 30304668 PMCID: PMC6198286 DOI: 10.1016/j.celrep.2018.09.024] [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] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 07/26/2018] [Accepted: 09/07/2018] [Indexed: 11/18/2022] Open
Abstract
Leptin acts on hypothalamic pro-opiomelanocortin (POMC) neurons to regulate glucose homeostasis, but the precise mechanisms remain unclear. Here, we demonstrate that leptin-induced depolarization of POMC neurons is associated with the augmentation of a voltage-gated calcium (CaV) conductance with the properties of the "R-type" channel. Knockdown of the pore-forming subunit of the R-type (CaV2.3 or Cacna1e) conductance in hypothalamic POMC neurons prevented sustained leptin-induced depolarization. In vivo POMC-specific Cacna1e knockdown increased hepatic glucose production and insulin resistance, while body weight, feeding, or leptin-induced suppression of food intake were not changed. These findings link Cacna1e function to leptin-mediated POMC neuron excitability and glucose homeostasis and may provide a target for the treatment of diabetes.
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Affiliation(s)
- Mark A Smith
- Metabolic Signalling Group, MRC London Institute of Medical Sciences, London W12 0NN, UK.
| | - Loukia Katsouri
- Metabolic Signalling Group, MRC London Institute of Medical Sciences, London W12 0NN, UK
| | - Samuel Virtue
- Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Agharul I Choudhury
- Metabolic Signalling Group, MRC London Institute of Medical Sciences, London W12 0NN, UK
| | - Antonio Vidal-Puig
- Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Dominic J Withers
- Metabolic Signalling Group, MRC London Institute of Medical Sciences, London W12 0NN, UK; Institute of Clinical Sciences, Imperial College London, Du Cane Road, London W12 0NN, UK.
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11
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Botteri G, Salvadó L, Gumà A, Lee Hamilton D, Meakin PJ, Montagut G, Ashford MLJ, Ceperuelo-Mallafré V, Fernández-Veledo S, Vendrell J, Calderón-Dominguez M, Serra D, Herrero L, Pizarro J, Barroso E, Palomer X, Vázquez-Carrera M. The BACE1 product sAPPβ induces ER stress and inflammation and impairs insulin signaling. Metabolism 2018. [PMID: 29526536 DOI: 10.1016/j.metabol.2018.03.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [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: 02/06/2023]
Abstract
OBJECTIVE β-secretase/β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) is a key enzyme involved in Alzheimer's disease that has recently been implicated in insulin-independent glucose uptake in myotubes. However, it is presently unknown whether BACE1 and the product of its activity, soluble APPβ (sAPPβ), contribute to lipid-induced inflammation and insulin resistance in skeletal muscle cells. MATERIALS/METHODS Studies were conducted in mouse C2C12 myotubes, skeletal muscle from Bace1-/-mice and mice treated with sAPPβ and adipose tissue and plasma from obese and type 2 diabetic patients. RESULTS We show that BACE1 inhibition or knockdown attenuates palmitate-induced endoplasmic reticulum (ER) stress, inflammation, and insulin resistance and prevents the reduction in Peroxisome Proliferator-Activated Receptor γ Co-activator 1α (PGC-1α) and fatty acid oxidation caused by palmitate in myotubes. The effects of palmitate on ER stress, inflammation, insulin resistance, PGC-1α down-regulation, and fatty acid oxidation were mimicked by soluble APPβ in vitro. BACE1 expression was increased in subcutaneous adipose tissue of obese and type 2 diabetic patients and this was accompanied by a decrease in PGC-1α mRNA levels and by an increase in sAPPβ plasma levels of obese type 2 diabetic patients compared to obese non-diabetic subjects. Acute sAPPβ administration to mice reduced PGC-1α levels and increased inflammation in skeletal muscle and decreased insulin sensitivity. CONCLUSIONS Collectively, these findings indicate that the BACE1 product sAPPβ is a key determinant in ER stress, inflammation and insulin resistance in skeletal muscle and gluconeogenesis in liver.
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Affiliation(s)
- Gaia Botteri
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Laia Salvadó
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Anna Gumà
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Barcelona, Barcelona, Spain
| | - D Lee Hamilton
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Paul J Meakin
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Gemma Montagut
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
| | - Victoria Ceperuelo-Mallafré
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Hospital Universitari de Tarragona Joan XXIII, Institut d'Investigació Sanitària Pere Virgili, Universitat Rovira i Virgili, Tarragona, Spain
| | - Sonia Fernández-Veledo
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Hospital Universitari de Tarragona Joan XXIII, Institut d'Investigació Sanitària Pere Virgili, Universitat Rovira i Virgili, Tarragona, Spain
| | - Joan Vendrell
- Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Hospital Universitari de Tarragona Joan XXIII, Institut d'Investigació Sanitària Pere Virgili, Universitat Rovira i Virgili, Tarragona, Spain
| | - María Calderón-Dominguez
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, Barcelona, Spain
| | - Dolors Serra
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, Barcelona, Spain
| | - Laura Herrero
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Department of Biochemistry and Physiology, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, Barcelona, Spain
| | - Javier Pizarro
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Emma Barroso
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Xavier Palomer
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain
| | - Manuel Vázquez-Carrera
- Pharmacology Unit, Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, Spain; Institut de Biomedicina de la Universitat de Barcelona (IBUB), Spain; Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Instituto de Salud Carlos III, Barcelona, Spain; Institut de Recerca Sant Joan de Déu (IR-SJD), Esplugues de Llobregat, Barcelona, Spain.
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12
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Mills EL, Ryan DG, Prag HA, Dikovskaya D, Menon D, Zaslona Z, Jedrychowski MP, Costa ASH, Higgins M, Hams E, Szpyt J, Runtsch MC, King MS, McGouran JF, Fischer R, Kessler BM, McGettrick AF, Hughes MM, Carroll RG, Booty LM, Knatko EV, Meakin PJ, Ashford MLJ, Modis LK, Brunori G, Sévin DC, Fallon PG, Caldwell ST, Kunji ERS, Chouchani ET, Frezza C, Dinkova-Kostova AT, Hartley RC, Murphy MP, O'Neill LA. Itaconate is an anti-inflammatory metabolite that activates Nrf2 via alkylation of KEAP1. Nature 2018; 556:113-117. [PMID: 29590092 PMCID: PMC6047741 DOI: 10.1038/nature25986] [Citation(s) in RCA: 978] [Impact Index Per Article: 163.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 02/09/2018] [Indexed: 02/02/2023]
Abstract
The endogenous metabolite itaconate has recently emerged as a regulator of macrophage function, but its precise mechanism of action remains poorly understood. Here we show that itaconate is required for the activation of the anti-inflammatory transcription factor Nrf2 (also known as NFE2L2) by lipopolysaccharide in mouse and human macrophages. We find that itaconate directly modifies proteins via alkylation of cysteine residues. Itaconate alkylates cysteine residues 151, 257, 288, 273 and 297 on the protein KEAP1, enabling Nrf2 to increase the expression of downstream genes with anti-oxidant and anti-inflammatory capacities. The activation of Nrf2 is required for the anti-inflammatory action of itaconate. We describe the use of a new cell-permeable itaconate derivative, 4-octyl itaconate, which is protective against lipopolysaccharide-induced lethality in vivo and decreases cytokine production. We show that type I interferons boost the expression of Irg1 (also known as Acod1) and itaconate production. Furthermore, we find that itaconate production limits the type I interferon response, indicating a negative feedback loop that involves interferons and itaconate. Our findings demonstrate that itaconate is a crucial anti-inflammatory metabolite that acts via Nrf2 to limit inflammation and modulate type I interferons.
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Affiliation(s)
- Evanna L Mills
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
- GlaxoSmithKline, Gunnelswood Road, Stevenage, Hertfordshire, UK
| | - Dylan G Ryan
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Hiran A Prag
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Dina Dikovskaya
- Jacqui Wood Cancer Centre, Division of Cancer Research, School of Medicine, University of Dundee, Dundee DD1 9SY, UK
| | - Deepthi Menon
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Zbigniew Zaslona
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Mark P Jedrychowski
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Ana S H Costa
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK
| | - Maureen Higgins
- Jacqui Wood Cancer Centre, Division of Cancer Research, School of Medicine, University of Dundee, Dundee DD1 9SY, UK
| | - Emily Hams
- School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - John Szpyt
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Marah C Runtsch
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Martin S King
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Joanna F McGouran
- School of Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Roman Fischer
- Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford OX3 7FZ, UK
| | - Benedikt M Kessler
- Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford OX3 7FZ, UK
| | - Anne F McGettrick
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Mark M Hughes
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Richard G Carroll
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- GlaxoSmithKline, Gunnelswood Road, Stevenage, Hertfordshire, UK
| | - Lee M Booty
- GlaxoSmithKline, Gunnelswood Road, Stevenage, Hertfordshire, UK
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Elena V Knatko
- Jacqui Wood Cancer Centre, Division of Cancer Research, School of Medicine, University of Dundee, Dundee DD1 9SY, UK
| | - Paul J Meakin
- Division of Molecular and Clinical Medicine, School of Medicine, University of Dundee, Dundee DD1 9SY, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, University of Dundee, Dundee DD1 9SY, UK
| | - Louise K Modis
- GlaxoSmithKline, Gunnelswood Road, Stevenage, Hertfordshire, UK
| | - Gino Brunori
- GlaxoSmithKline, Park Road, Ware, Hertfordshire, UK
| | | | - Padraic G Fallon
- School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Stuart T Caldwell
- WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Edmund R S Kunji
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Edward T Chouchani
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Christian Frezza
- MRC Cancer Unit, University of Cambridge, Hutchison/MRC Research Centre, Box 197, Cambridge Biomedical Campus, Cambridge CB2 0XZ, UK
| | - Albena T Dinkova-Kostova
- Jacqui Wood Cancer Centre, Division of Cancer Research, School of Medicine, University of Dundee, Dundee DD1 9SY, UK
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Richard C Hartley
- WestCHEM School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK
| | - Michael P Murphy
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, UK
| | - Luke A O'Neill
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
- GlaxoSmithKline, Gunnelswood Road, Stevenage, Hertfordshire, UK
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13
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Meakin PJ, Mezzapesa A, Benabou E, Haas ME, Bonardo B, Grino M, Brunel JM, Desbois-Mouthon C, Biddinger SB, Govers R, Ashford MLJ, Peiretti F. The beta secretase BACE1 regulates the expression of insulin receptor in the liver. Nat Commun 2018; 9:1306. [PMID: 29610518 PMCID: PMC5880807 DOI: 10.1038/s41467-018-03755-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [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: 07/28/2017] [Accepted: 03/08/2018] [Indexed: 01/04/2023] Open
Abstract
Insulin receptor (IR) plays a key role in the control of glucose homeostasis; however, the regulation of its cellular expression remains poorly understood. Here we show that the amount of biologically active IR is regulated by the cleavage of its ectodomain, by the β-site amyloid precursor protein cleaving enzyme 1 (BACE1), in a glucose concentration-dependent manner. In vivo studies demonstrate that BACE1 regulates the amount of IR and insulin signaling in the liver. During diabetes, BACE1-dependent cleavage of IR is increased and the amount of IR in the liver is reduced, whereas infusion of a BACE1 inhibitor partially restores liver IR. We suggest the potential use of BACE1 inhibitors to enhance insulin signaling during diabetes. Additionally, we show that plasma levels of cleaved IR reflect IR isoform A expression levels in liver tumors, which prompts us to propose that the measurement of circulating cleaved IR may assist hepatic cancer detection and management.
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Affiliation(s)
- Paul J Meakin
- Division of Molecular & Clinical Medicine, Ninewells Hospital & Medical School, Dundee, DD19SY, UK
| | - Anna Mezzapesa
- Aix Marseille Univ, INSERM, INRA, C2VN, 13385, Marseille, France
| | - Eva Benabou
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Saint-Antoine Research Center, F-75012, Paris, France
| | - Mary E Haas
- Division of Endocrinology, Boston Children's Hospital, Boston, MA, 02115, USA
| | | | - Michel Grino
- Aix Marseille Univ, INSERM, INRA, C2VN, 13385, Marseille, France
| | - Jean-Michel Brunel
- Aix Marseille Univ, INSERM, CNRS, CRCM, Institut Paoli Calmettes, Marseille, 13385, France
| | - Christèle Desbois-Mouthon
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, Saint-Antoine Research Center, F-75012, Paris, France
| | - Sudha B Biddinger
- Division of Endocrinology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Roland Govers
- Aix Marseille Univ, INSERM, INRA, C2VN, 13385, Marseille, France
| | - Michael L J Ashford
- Division of Molecular & Clinical Medicine, Ninewells Hospital & Medical School, Dundee, DD19SY, UK
| | - Franck Peiretti
- Aix Marseille Univ, INSERM, INRA, C2VN, 13385, Marseille, France.
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14
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Meakin PJ, Jalicy SM, Montagut G, Allsop DJP, Cavellini DL, Irvine SW, McGinley C, Liddell MK, McNeilly AD, Parmionova K, Liu YR, Bailey CLS, Dale JK, Heisler LK, McCrimmon RJ, Ashford MLJ. Bace1-dependent amyloid processing regulates hypothalamic leptin sensitivity in obese mice. Sci Rep 2018; 8:55. [PMID: 29311632 PMCID: PMC5758523 DOI: 10.1038/s41598-017-18388-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [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: 06/21/2017] [Accepted: 12/11/2017] [Indexed: 01/21/2023] Open
Abstract
Obesity places an enormous medical and economic burden on society. The principal driver appears to be central leptin resistance with hyperleptinemia. Accordingly, a compound that reverses or prevents leptin resistance should promote weight normalisation and improve glucose homeostasis. The protease Bace1 drives beta amyloid (Aβ) production with obesity elevating hypothalamic Bace1 activity and Aβ1–42 production. Pharmacological inhibition of Bace1 reduces body weight, improves glucose homeostasis and lowers plasma leptin in diet-induced obese (DIO) mice. These actions are not apparent in ob/ob or db/db mice, indicating the requirement for functional leptin signalling. Decreasing Bace1 activity normalises hypothalamic inflammation, lowers PTP1B and SOCS3 and restores hypothalamic leptin sensitivity and pSTAT3 response in obese mice, but does not affect leptin sensitivity in lean mice. Raising central Aβ1–42 levels in the early stage of DIO increases hypothalamic basal pSTAT3 and reduces the amplitude of the leptin pSTAT3 signal without increased inflammation. Thus, elevated Aβ1–42 promotes hypothalamic leptin resistance, which is associated with diminished whole-body sensitivity to exogenous leptin and exacerbated body weight gain in high fat fed mice. These results indicate that Bace1 inhibitors, currently in clinical trials for Alzheimer’s disease, may be useful agents for the treatment of obesity and associated diabetes.
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Affiliation(s)
- Paul J Meakin
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Susan M Jalicy
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Gemma Montagut
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - David J P Allsop
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Daniella L Cavellini
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Stuart W Irvine
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Christopher McGinley
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Mary K Liddell
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Alison D McNeilly
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Karolina Parmionova
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Yu-Ru Liu
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | | | - J Kim Dale
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Lora K Heisler
- Rowett Institute of Nutrition and Health, Aberdeen, AB21 9SB, UK
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, Dundee, DD1 9SY, UK.
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15
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Vlachaki Walker JM, Robb JL, Cruz AM, Malhi A, Weightman Potter PG, Ashford MLJ, McCrimmon RJ, Ellacott KLJ, Beall C. AMP-activated protein kinase (AMPK) activator A-769662 increases intracellular calcium and ATP release from astrocytes in an AMPK-independent manner. Diabetes Obes Metab 2017; 19:997-1005. [PMID: 28211632 DOI: 10.1111/dom.12912] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [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: 12/05/2016] [Revised: 02/09/2017] [Accepted: 02/14/2017] [Indexed: 12/18/2022]
Abstract
AIM To test the hypothesis that, given the role of AMP-activated protein kinase (AMPK) in regulating intracellular ATP levels, AMPK may alter ATP release from astrocytes, the main sources of extracellular ATP (eATP) within the brain. MATERIALS AND METHODS Measurements of ATP release were made from human U373 astrocytoma cells, primary mouse hypothalamic (HTAS) and cortical astrocytes (CRTAS) and wild-type and AMPK α1/α2 null mouse embryonic fibroblasts (MEFs). Cells were treated with drugs known to modulate AMPK activity: A-769662, AICAR and metformin, for up to 3 hours. Intracellular calcium was measured using Fluo4 and Fura-2 calcium-sensitive fluorescent dyes. RESULTS In U373 cells, A-769662 (100 μM) increased AMPK phosphorylation, whereas AICAR and metformin (1 mM) induced a modest increase or had no effect, respectively. Only A-769662 increased eATP levels, and this was partially blocked by AMPK inhibitor Compound C. A-769662-induced increases in eATP were preserved in AMPK α1/α2 null MEF cells. A-769662 increased intracellular calcium in U373, HTAS and CRTAS cells and chelation of intracellular calcium using BAPTA-AM reduced A-769662-induced eATP levels. A-769662 also increased ATP release from a number of other central and peripheral endocrine cell types. CONCLUSIONS AMPK is required to maintain basal eATP levels but is not required for A-769662-induced increases in eATP. A-769662 (>50 μM) enhanced intracellular calcium levels leading to ATP release in an AMPK and purinergic receptor independent pathway.
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Affiliation(s)
- Julia M Vlachaki Walker
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
- Division of Molecular and Clinical Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - Josephine L Robb
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Ana M Cruz
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Amrinder Malhi
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Paul G Weightman Potter
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
| | - Kate L J Ellacott
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
| | - Craig Beall
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, Exeter, UK
- Division of Molecular and Clinical Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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16
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McNeilly AD, Gallagher JR, Huang JTJ, Ashford MLJ, McCrimmon RJ. High-Intensity Exercise as a Dishabituating Stimulus Restores Counterregulatory Responses in Recurrently Hypoglycemic Rodents. Diabetes 2017; 66:1696-1702. [PMID: 28270522 DOI: 10.2337/db16-1533] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [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: 12/12/2016] [Accepted: 02/21/2017] [Indexed: 11/13/2022]
Abstract
Hypoglycemia is a major adverse effect of insulin therapy for people with type 1 diabetes (T1D). Profound defects in the normal counterregulatory response to hypoglycemia explain the frequency of hypoglycemia occurrence in T1D. Defective counterregulation results to a large extent from prior exposure to hypoglycemia per se, leading to a condition called impaired awareness of hypoglycemia (IAH), the cause of which is unknown. In the current study, we investigate the hypothesis that IAH develops through a special type of adaptive memory referred to as habituation. To test this hypothesis, we used a novel intense stimulus (high-intensity exercise) to demonstrate two classic features of a habituated response, namely dishabituation and response recovery. We demonstrate that after recurrent hypoglycemia the introduction of a novel dishabituating stimulus (a single burst of high-intensity exercise) in male Sprague-Dawley rats restores the defective hypoglycemia counterregulatory response. In addition, the rats showed an enhanced response to the novel stimulus (response recovery). We make the further observation using proteomic analysis of hypothalamic extracts that high-intensity exercise in recurrently hypoglycemic rats increases levels of a number of proteins linked with brain-derived neurotrophic factor signaling. These findings may lead to novel therapeutic approaches for individuals with T1D and IAH.
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Affiliation(s)
- Alison D McNeilly
- Division of Molecular and Clinical Medicine, University of Dundee, Dundee, U.K
| | | | - Jeffrey T-J Huang
- Division of Molecular and Clinical Medicine, University of Dundee, Dundee, U.K
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, University of Dundee, Dundee, U.K
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, University of Dundee, Dundee, U.K.
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17
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Dadak S, Beall C, Vlachaki Walker JM, Soutar MPM, McCrimmon RJ, Ashford MLJ. Oleate induces K ATP channel-dependent hyperpolarization in mouse hypothalamic glucose-excited neurons without altering cellular energy charge. Neuroscience 2017; 346:29-42. [PMID: 28087336 PMCID: PMC5346158 DOI: 10.1016/j.neuroscience.2016.12.053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 12/29/2016] [Indexed: 11/29/2022]
Abstract
Oleate and low glucose hyperpolarize and inhibit GT1-7 and mouse GE neurons by activation of KATP. Oleate inhibition of GT1-7 neuron activity is not mediated by AMPK or fatty acid oxidation. Activation of KATP by oleate requires ATP hydrolysis but does not reduce the levels ATP or the ATP:ADP ratio. GT1-7 hyperpolarization by oleate is not dependent on UCP2. Oleate and low glucose depolarize a subpopulation of hypothalamic GI neurons.
The unsaturated fatty acid, oleate exhibits anorexigenic properties reducing food intake and hepatic glucose output. However, its mechanism of action in the hypothalamus has not been fully determined. This study investigated the effects of oleate and glucose on GT1-7 mouse hypothalamic cells (a model of glucose-excited (GE) neurons) and mouse arcuate nucleus (ARC) neurons. Whole-cell and perforated patch-clamp recordings, immunoblotting and cell energy status measures were used to investigate oleate- and glucose-sensing properties of mouse hypothalamic neurons. Oleate or lowered glucose concentration caused hyperpolarization and inhibition of firing of GT1-7 cells by the activation of ATP-sensitive K+ channels (KATP). This effect of oleate was not dependent on fatty acid oxidation or raised AMP-activated protein kinase activity or prevented by the presence of the UCP2 inhibitor genipin. Oleate did not alter intracellular calcium, indicating that CD36/fatty acid translocase may not play a role. However, oleate activation of KATP may require ATP metabolism. The short-chain fatty acid octanoate was unable to replicate the actions of oleate on GT1-7 cells. Although oleate decreased GT1-7 cell mitochondrial membrane potential there was no change in total cellular ATP or ATP/ADP ratios. Perforated patch and whole-cell recordings from mouse hypothalamic slices demonstrated that oleate hyperpolarized a subpopulation of ARC GE neurons by KATP activation. Additionally, in a separate small population of ARC neurons, oleate application or lowered glucose concentration caused membrane depolarization. In conclusion, oleate induces KATP-dependent hyperpolarization and inhibition of firing of a subgroup of GE hypothalamic neurons without altering cellular energy charge.
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Affiliation(s)
- Selma Dadak
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Craig Beall
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK; Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK
| | - Julia M Vlachaki Walker
- Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building, Barrack Road, Exeter EX2 5DW, UK
| | - Marc P M Soutar
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK.
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18
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McNeilly AD, Gallagher JR, Dinkova-Kostova AT, Hayes JD, Sharkey J, Ashford MLJ, McCrimmon RJ. Nrf2-Mediated Neuroprotection Against Recurrent Hypoglycemia Is Insufficient to Prevent Cognitive Impairment in a Rodent Model of Type 1 Diabetes. Diabetes 2016; 65:3151-60. [PMID: 27411381 DOI: 10.2337/db15-1653] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [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: 12/09/2015] [Accepted: 07/07/2016] [Indexed: 11/13/2022]
Abstract
It remains uncertain whether recurrent nonsevere hypoglycemia (Hypo) results in long-term cognitive impairment in type 1 diabetes (T1D). This study tested the hypothesis that specifically in the T1D state, Hypo leads to cognitive impairment via a pathological response to oxidative stress. Wild-type (Control) and nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) null mice were studied. Eight groups of mice (Control and Nrf2(-/-) ± T1D and ± Hypo) were subject to recurrent, twice-weekly, insulin or saline injections over 4 weeks, after which cognitive function was assessed and brain tissue analyzed. Recurrent moderate hypoglycemia in T1D, but not Control, mice significantly impaired cognitive performance, and this was associated with hippocampal oxidative damage and inflammation despite an enhanced expression of Nrf2 and its target genes Hmox1 and Nqo1 In Nrf2(-/-) mice, both T1D and Hypo independently resulted in impaired cognitive performance, and this was associated with oxidative cell damage and marked inflammation. Together, these data suggest that Hypo induces an Nrf2-dependent antioxidant response in the hippocampus, which counteracts oxidative damage. However, in T1D, this neuroprotective mechanism is insufficient to prevent neuronal oxidative damage, resulting in chronic deficits in working and long-term memory.
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Affiliation(s)
- Alison D McNeilly
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K
| | - Jennifer R Gallagher
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K
| | - Albena T Dinkova-Kostova
- Division of Cancer Research, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K
| | - John D Hayes
- Division of Cancer Research, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K
| | - John Sharkey
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K. Division of Neuroscience, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital and Medical School, Dundee, U.K.
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19
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Haythorne E, Hamilton DL, Findlay JA, Beall C, McCrimmon RJ, Ashford MLJ. Chronic exposure to K ATP channel openers results in attenuated glucose sensing in hypothalamic GT1-7 neurons. Neuropharmacology 2016; 111:212-222. [PMID: 27618741 DOI: 10.1016/j.neuropharm.2016.09.008] [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] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 07/06/2016] [Accepted: 09/07/2016] [Indexed: 10/21/2022]
Abstract
Individuals with Type 1 diabetes (T1D) are often exposed to recurrent episodes of hypoglycaemia. This reduces hormonal and behavioural responses that normally counteract low glucose in order to maintain glucose homeostasis, with altered responsiveness of glucose sensing hypothalamic neurons implicated. Although the molecular mechanisms are unknown, pharmacological studies implicate hypothalamic ATP-sensitive potassium channel (KATP) activity, with KATP openers (KCOs) amplifying, through cell hyperpolarization, the response to hypoglycaemia. Although initial findings, using acute hypothalamic KCO delivery, in rats were promising, chronic exposure to the KCO NN414 worsened the responses to subsequent hypoglycaemic challenge. To investigate this further we used GT1-7 cells to explore how NN414 affected glucose-sensing behaviour, the metabolic response of cells to hypoglycaemia and KATP activity. GT1-7 cells exposed to 3 or 24 h NN414 exhibited an attenuated hyperpolarization to subsequent hypoglycaemic challenge or NN414, which correlated with diminished KATP activity. The reduced sensitivity to hypoglycaemia was apparent 24 h after NN414 removal, even though intrinsic KATP activity recovered. The NN414-modified glucose responsiveness was not associated with adaptations in glucose uptake, metabolism or oxidation. KATP inactivation by NN414 was prevented by the concurrent presence of tolbutamide, which maintains KATP closure. Single channel recordings indicate that NN414 alters KATP intrinsic gating inducing a stable closed or inactivated state. These data indicate that exposure of hypothalamic glucose sensing cells to chronic NN414 drives a sustained conformational change to KATP, probably by binding to SUR1, that results in loss of channel sensitivity to intrinsic metabolic factors such as MgADP and small molecule agonists.
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Affiliation(s)
- Elizabeth Haythorne
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - D Lee Hamilton
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - John A Findlay
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Craig Beall
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
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20
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McGuire VA, Ruiz-Zorrilla Diez T, Emmerich CH, Strickson S, Ritorto MS, Sutavani RV, Weiβ A, Houslay KF, Knebel A, Meakin PJ, Phair IR, Ashford MLJ, Trost M, Arthur JSC. Dimethyl fumarate blocks pro-inflammatory cytokine production via inhibition of TLR induced M1 and K63 ubiquitin chain formation. Sci Rep 2016; 6:31159. [PMID: 27498693 PMCID: PMC4976367 DOI: 10.1038/srep31159] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [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: 10/19/2015] [Accepted: 07/15/2016] [Indexed: 12/24/2022] Open
Abstract
Dimethyl fumarate (DMF) possesses anti-inflammatory properties and is approved for the treatment of psoriasis and multiple sclerosis. While clinically effective, its molecular target has remained elusive - although it is known to activate anti-oxidant pathways. We find that DMF inhibits pro-inflammatory cytokine production in response to TLR agonists independently of the Nrf2-Keap1 anti-oxidant pathway. Instead we show that DMF can inhibit the E2 conjugating enzymes involved in K63 and M1 polyubiquitin chain formation both in vitro and in cells. The formation of K63 and M1 chains is required to link TLR activation to downstream signaling, and consistent with the block in K63 and/or M1 chain formation, DMF inhibits NFκB and ERK1/2 activation, resulting in a loss of pro-inflammatory cytokine production. Together these results reveal a new molecular target for DMF and show that a clinically approved drug inhibits M1 and K63 chain formation in TLR induced signaling complexes. Selective targeting of E2s may therefore be a viable strategy for autoimmunity.
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Affiliation(s)
- Victoria A McGuire
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Tamara Ruiz-Zorrilla Diez
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK.,Department of Chemistry and Biochemistry, Faculty of Pharmacy, CEU San Pablo University, Urbanización Montepríncipe, 28668 Madrid, Spain
| | - Christoph H Emmerich
- MRC Protein Phosphorylation and ubiquitylation Unit, School of Life Sciences, Sir James Black Centre, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Sam Strickson
- MRC Protein Phosphorylation and ubiquitylation Unit, School of Life Sciences, Sir James Black Centre, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Maria Stella Ritorto
- MRC Protein Phosphorylation and ubiquitylation Unit, School of Life Sciences, Sir James Black Centre, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Ruhcha V Sutavani
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Anne Weiβ
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Kirsty F Houslay
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Axel Knebel
- MRC Protein Phosphorylation and ubiquitylation Unit, School of Life Sciences, Sir James Black Centre, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Paul J Meakin
- Cardiovascular and Diabetes Medicine, Medical Research Institute, School of Medicine, University of Dundee, Ninewells Hospital, Dundee, DD1 9SY, UK
| | - Iain R Phair
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Michael L J Ashford
- Cardiovascular and Diabetes Medicine, Medical Research Institute, School of Medicine, University of Dundee, Ninewells Hospital, Dundee, DD1 9SY, UK
| | - Matthias Trost
- MRC Protein Phosphorylation and ubiquitylation Unit, School of Life Sciences, Sir James Black Centre, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - J Simon C Arthur
- Division of Cell Signaling and Immunology, School of Life Sciences, Wellcome Trust Building, University of Dundee, Dow St, Dundee, DD1 5EH, UK
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21
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Findlay JA, Hamilton DL, Ashford MLJ. BACE1 activity impairs neuronal glucose oxidation: rescue by beta-hydroxybutyrate and lipoic acid. Front Cell Neurosci 2015; 9:382. [PMID: 26483636 PMCID: PMC4589671 DOI: 10.3389/fncel.2015.00382] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [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: 07/14/2015] [Accepted: 09/14/2015] [Indexed: 11/13/2022] Open
Abstract
Glucose hypometabolism and impaired mitochondrial function in neurons have been suggested to play early and perhaps causative roles in Alzheimer's disease (AD) pathogenesis. Activity of the aspartic acid protease, beta-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), responsible for beta amyloid peptide generation, has recently been demonstrated to modify glucose metabolism. We therefore examined, using a human neuroblastoma (SH-SY5Y) cell line, whether increased BACE1 activity is responsible for a reduction in cellular glucose metabolism. Overexpression of active BACE1, but not a protease-dead mutant BACE1, protein in SH-SY5Y cells reduced glucose oxidation and the basal oxygen consumption rate, which was associated with a compensatory increase in glycolysis. Increased BACE1 activity had no effect on the mitochondrial electron transfer process but was found to diminish substrate delivery to the mitochondria by inhibition of key mitochondrial decarboxylation reaction enzymes. This BACE1 activity-dependent deficit in glucose oxidation was alleviated by the presence of beta hydroxybutyrate or α-lipoic acid. Consequently our data indicate that raised cellular BACE1 activity drives reduced glucose oxidation in a human neuronal cell line through impairments in the activity of specific tricarboxylic acid cycle enzymes. Because this bioenergetic deficit is recoverable by neutraceutical compounds we suggest that such agents, perhaps in conjunction with BACE1 inhibitors, may be an effective therapeutic strategy in the early-stage management or treatment of AD.
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Affiliation(s)
- John A Findlay
- Division of Cardiovascular and Diabetes Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee Dundee, UK
| | - David L Hamilton
- Division of Cardiovascular and Diabetes Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee Dundee, UK
| | - Michael L J Ashford
- Division of Cardiovascular and Diabetes Medicine, School of Medicine, Ninewells Hospital and Medical School, University of Dundee Dundee, UK
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22
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Meakin PJ, Morrison VL, Sneddon CC, Savinko T, Uotila L, Jalicy SM, Gabriel JL, Kang L, Ashford MLJ, Fagerholm SC. Mice Lacking beta2-Integrin Function Remain Glucose Tolerant in Spite of Insulin Resistance, Neutrophil Infiltration and Inflammation. PLoS One 2015; 10:e0138872. [PMID: 26405763 PMCID: PMC4583187 DOI: 10.1371/journal.pone.0138872] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [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: 01/27/2015] [Accepted: 09/06/2015] [Indexed: 12/16/2022] Open
Abstract
Beta2-integrins are important in leukocyte trafficking and function, and are regulated through the binding of cytoplasmic proteins, such as kindlin-3, to their intracellular domain. Here, we investigate the involvement of beta2-integrins in the regulation of metabolic disease using mice where the kindlin-3 binding site in the beta2-integrin cytoplasmic tail has been mutated (TTT/AAA-beta2-integrin knock-in (KI) mice), leading to expressed but dysfunctional beta2-integrins and significant neutrophilia in vivo. Beta2-integrin KI mice fed on a high fat diet showed normal weight gain, and normal accumulation of macrophages and lymphocytes in white adipose tissue (WAT) and liver, but increased neutrophil numbers especially in WAT. In addition, beta2-integrin KI mice fed on a high fat diet showed significantly increased peripheral insulin resistance in response to high-fat feeding. However, this was associated with improved glucose disposal following glucose load. Interestingly, beta2-integrin KI neutrophils produced more elastase in vitro, in response to stimulation. Beta2-integrin KI mice displayed variability of tissue inflammatory status, with liver and WAT exhibiting little or no difference in inflammation compared to high fat fed controls, whereas skeletal muscle demonstrated a raised inflammatory profile in association with higher elastase levels and diminished signalling through the IRS1-PKB pathway. In conclusion, although expression of dysfunctional beta2-integrins increased neutrophil production and infiltration into tissue, skeletal muscle was the most affected tissue exhibiting evidence of higher neutrophil activity and insulin resistance. Thus, beta2-integrins modulate glucose homeostasis during high fat feeding predominantly through actions on skeletal muscle to affect metabolic phenotype in vivo.
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Affiliation(s)
- Paul J. Meakin
- Divison of Cardiovascular & Diabetes Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
| | - Vicky L. Morrison
- Division of Cancer Research, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Claire C. Sneddon
- Divison of Cardiovascular & Diabetes Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
| | - Terhi Savinko
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Liisa Uotila
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Susan M. Jalicy
- Divison of Cardiovascular & Diabetes Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
| | - Jennie L. Gabriel
- Divison of Cardiovascular & Diabetes Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
| | - Li Kang
- Divison of Cardiovascular & Diabetes Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
| | - Michael L. J. Ashford
- Divison of Cardiovascular & Diabetes Medicine, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
- * E-mail: (SCF); (MLJA)
| | - Susanna C. Fagerholm
- Division of Cancer Research, School of Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
- * E-mail: (SCF); (MLJA)
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23
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Reilly L, Howie J, Wypijewski K, Ashford MLJ, Hilgemann DW, Fuller W. Palmitoylation of the Na/Ca exchanger cytoplasmic loop controls its inactivation and internalization during stress signaling. FASEB J 2015; 29:4532-43. [PMID: 26174834 PMCID: PMC4608915 DOI: 10.1096/fj.15-276493] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 06/30/2015] [Indexed: 01/02/2023]
Abstract
The electrogenic Na/Ca exchanger (NCX) mediates bidirectional Ca movements that are highly sensitive to changes of Na gradients in many cells. NCX1 is implicated in the pathogenesis of heart failure and a number of cardiac arrhythmias. We measured NCX1 palmitoylation using resin-assisted capture, the subcellular location of yellow fluorescent protein–NCX1 fusion proteins, and NCX1 currents using whole-cell voltage clamping. Rat NCX1 is substantially palmitoylated in all tissues examined. Cysteine 739 in the NCX1 large intracellular loop is necessary and sufficient for NCX1 palmitoylation. Palmitoylation of NCX1 occurs in the Golgi and anchors the NCX1 large regulatory intracellular loop to membranes. Surprisingly, palmitoylation does not influence trafficking or localization of NCX1 to surface membranes, nor does it strongly affect the normal forward or reverse transport modes of NCX1. However, exchangers that cannot be palmitoylated do not inactivate normally (leading to substantial activity in conditions when wild-type exchangers are inactive) and do not promote cargo-dependent endocytosis that internalizes 50% of the cell surface following strong G-protein activation or large Ca transients. The palmitoylated cysteine in NCX1 is found in all vertebrate and some invertebrate NCX homologs. Thus, NCX palmitoylation ubiquitously modulates Ca homeostasis and membrane domain function in cells that express NCX proteins.—Reilly, L., Howie, J., Wypijewski, K., Ashford, M. L. J., Hilgemann, D. W., Fuller, W. Palmitoylation of the Na/Ca exchanger cytoplasmic loop controls its inactivation and internalization during stress signaling.
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Affiliation(s)
- Louise Reilly
- *Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry, and Nursing, University of Dundee, Dundee, United Kingdom; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Jacqueline Howie
- *Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry, and Nursing, University of Dundee, Dundee, United Kingdom; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Krzysztof Wypijewski
- *Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry, and Nursing, University of Dundee, Dundee, United Kingdom; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Michael L J Ashford
- *Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry, and Nursing, University of Dundee, Dundee, United Kingdom; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Donald W Hilgemann
- *Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry, and Nursing, University of Dundee, Dundee, United Kingdom; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - William Fuller
- *Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, College of Medicine, Dentistry, and Nursing, University of Dundee, Dundee, United Kingdom; and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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24
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Bell KFS, Al-Mubarak B, Martel MA, McKay S, Wheelan N, Hasel P, Márkus NM, Baxter P, Deighton RF, Serio A, Bilican B, Chowdhry S, Meakin PJ, Ashford MLJ, Wyllie DJA, Scannevin RH, Chandran S, Hayes JD, Hardingham GE. Neuronal development is promoted by weakened intrinsic antioxidant defences due to epigenetic repression of Nrf2. Nat Commun 2015; 6:7066. [PMID: 25967870 PMCID: PMC4441249 DOI: 10.1038/ncomms8066] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [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: 08/07/2014] [Accepted: 03/30/2015] [Indexed: 12/13/2022] Open
Abstract
Forebrain neurons have weak intrinsic antioxidant defences compared with astrocytes, but the molecular basis and purpose of this is poorly understood. We show that early in mouse cortical neuronal development in vitro and in vivo, expression of the master-regulator of antioxidant genes, transcription factor NF-E2-related-factor-2 (Nrf2), is repressed by epigenetic inactivation of its promoter. Consequently, in contrast to astrocytes or young neurons, maturing neurons possess negligible Nrf2-dependent antioxidant defences, and exhibit no transcriptional responses to Nrf2 activators, or to ablation of Nrf2's inhibitor Keap1. Neuronal Nrf2 inactivation seems to be required for proper development: in maturing neurons, ectopic Nrf2 expression inhibits neurite outgrowth and aborization, and electrophysiological maturation, including synaptogenesis. These defects arise because Nrf2 activity buffers neuronal redox status, inhibiting maturation processes dependent on redox-sensitive JNK and Wnt pathways. Thus, developmental epigenetic Nrf2 repression weakens neuronal antioxidant defences but is necessary to create an environment that supports neuronal development.
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Affiliation(s)
- Karen F S Bell
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Bashayer Al-Mubarak
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Marc-André Martel
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Sean McKay
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Nicola Wheelan
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Philip Hasel
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Nóra M Márkus
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Paul Baxter
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Ruth F Deighton
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | - Andrea Serio
- MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Bilada Bilican
- MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - Sudhir Chowdhry
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Paul J Meakin
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Michael L J Ashford
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - David J A Wyllie
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
| | | | - Siddharthan Chandran
- MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh EH16 4SB, UK
| | - John D Hayes
- Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
| | - Giles E Hardingham
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
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Wypijewski KJ, Tinti M, Chen W, Lamont D, Ashford MLJ, Calaghan SC, Fuller W. Identification of caveolar resident proteins in ventricular myocytes using a quantitative proteomic approach: dynamic changes in caveolar composition following adrenoceptor activation. Mol Cell Proteomics 2015; 14:596-608. [PMID: 25561500 PMCID: PMC4349980 DOI: 10.1074/mcp.m114.038570] [Citation(s) in RCA: 23] [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] [Indexed: 11/16/2022] Open
Abstract
The lipid raft concept proposes that membrane environments enriched in cholesterol and sphingolipids cluster certain proteins and form platforms to integrate cell signaling. In cardiac muscle, caveolae concentrate signaling molecules and ion transporters, and play a vital role in adrenergic regulation of excitation–contraction coupling, and consequently cardiac contractility. Proteomic analysis of cardiac caveolae is hampered by the presence of contaminants that have sometimes, erroneously, been proposed to be resident in these domains. Here we present the first unbiased analysis of the proteome of cardiac caveolae, and investigate dynamic changes in their protein constituents following adrenoreceptor (AR) stimulation. Rat ventricular myocytes were treated with methyl-β-cyclodextrin (MβCD) to deplete cholesterol and disrupt caveolae. Buoyant caveolin-enriched microdomains (BCEMs) were prepared from MβCD-treated and control cell lysates using a standard discontinuous sucrose gradient. BCEMs were harvested, pelleted, and resolubilized, then alkylated, digested, and labeled with iTRAQ reagents, and proteins identified by LC-MS/MS on a LTQ Orbitrap Velos Pro. Proteins were defined as BCEM resident if they were consistently depleted from the BCEM fraction following MβCD treatment. Selective activation of α-, β1-, and β2-AR prior to preparation of BCEMs was achieved by application of agonist/antagonist pairs for 10 min in populations of field-stimulated myocytes. We typically identified 600–850 proteins per experiment, of which, 249 were defined as high-confidence BCEM residents. Functional annotation clustering indicates cardiac BCEMs are enriched in integrin signaling, guanine nucleotide binding, ion transport, and insulin signaling clusters. Proteins possessing a caveolin binding motif were poorly enriched in BCEMs, suggesting this is not the only mechanism that targets proteins to caveolae. With the notable exception of the cavin family, very few proteins show altered abundance in BCEMs following AR activation, suggesting signaling complexes are preformed in BCEMs to ensure a rapid and high fidelity response to adrenergic stimulation in cardiac muscle.
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Affiliation(s)
- Krzysztof J Wypijewski
- From the ‡Division of Cardiovascular and Diabetes Medicine, College of Medicine, Dentistry and Nursing, University of Dundee, Dundee, United Kingdom
| | - Michele Tinti
- §College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Wenzhang Chen
- §College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Douglas Lamont
- §College of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Michael L J Ashford
- From the ‡Division of Cardiovascular and Diabetes Medicine, College of Medicine, Dentistry and Nursing, University of Dundee, Dundee, United Kingdom
| | - Sarah C Calaghan
- ¶School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - William Fuller
- From the ‡Division of Cardiovascular and Diabetes Medicine, College of Medicine, Dentistry and Nursing, University of Dundee, Dundee, United Kingdom;
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26
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Abstract
AMP-activated protein kinase appears to have evolved in single-celled eukaryotes as an adenine nucleotide sensor that maintains energy homeostasis at the cellular level. However, during evolution of more complex multicellular organisms, the system has adapted to interact with hormones so that it also plays a key role in balancing energy intake and expenditure at the whole body level.
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Affiliation(s)
- D Grahame Hardie
- Division of Cell Signalling & Immunology, College of Life Sciences, and Division of Cardiovascular and Diabetes Medicine, College of Medicine, Dentistry & Nursing, University of Dundee, Dundee, Scotland, United Kingdom
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Hamilton DL, Findlay JA, Montagut G, Meakin PJ, Bestow D, Jalicy SM, Ashford MLJ. Altered amyloid precursor protein processing regulates glucose uptake and oxidation in cultured rodent myotubes. Diabetologia 2014; 57:1684-92. [PMID: 24849570 PMCID: PMC4079947 DOI: 10.1007/s00125-014-3269-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [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: 03/17/2014] [Accepted: 04/29/2014] [Indexed: 12/19/2022]
Abstract
AIMS/HYPOTHESIS Impaired glucose uptake in skeletal muscle is an important contributor to glucose intolerance in type 2 diabetes. The aspartate protease, beta-site APP-cleaving enzyme 1 (BACE1), a critical regulator of amyloid precursor protein (APP) processing, modulates in vivo glucose disposal and insulin sensitivity in mice. Insulin-independent pathways to stimulate glucose uptake and GLUT4 translocation may offer alternative therapeutic avenues for the treatment of diabetes. We therefore addressed whether BACE1 activity, via APP processing, in skeletal muscle modifies glucose uptake and oxidation independently of insulin. METHODS Skeletal muscle cell lines were used to investigate the effects of BACE1 and α-secretase inhibition and BACE1 and APP overexpression on glucose uptake, GLUT4 cell surface translocation, glucose oxidation and cellular respiration. RESULTS In the absence of insulin, reduction of BACE1 activity increased glucose uptake and oxidation, GLUT4myc cell surface translocation, and basal rate of oxygen consumption. In contrast, overexpressing BACE1 in C2C12 myotubes decreased glucose uptake, glucose oxidation and oxygen consumption rate. APP overexpression increased and α-secretase inhibition decreased glucose uptake in C2C12 myotubes. The increase in glucose uptake elicited by BACE1 inhibition is dependent on phosphoinositide 3-kinase (PI3K) and mimicked by soluble APPα (sAPPα). CONCLUSIONS/INTERPRETATION Inhibition of muscle BACE1 activity increases insulin-independent, PI3K-dependent glucose uptake and cell surface translocation of GLUT4. As APP overexpression raises basal glucose uptake, and direct application of sAPPα increases PI3K-protein kinase B signalling and glucose uptake in myotubes, we suggest that α-secretase-dependent shedding of sAPPα regulates insulin-independent glucose uptake in skeletal muscle.
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Affiliation(s)
- D. Lee Hamilton
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
| | - John A. Findlay
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
| | - Gemma Montagut
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
| | - Paul J. Meakin
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
| | - Dawn Bestow
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
| | - Susan M. Jalicy
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
| | - Michael L. J. Ashford
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY Scotland UK
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28
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Hamilton DL, Beall C, Jeromson S, Chevtzoff C, Cuthbertson DJ, Ashford MLJ. Kv1.3 inhibitors have differential effects on glucose uptake and AMPK activity in skeletal muscle cell lines and mouse ex vivo skeletal muscle. J Physiol Sci 2014; 64:13-20. [PMID: 24043354 PMCID: PMC10717203 DOI: 10.1007/s12576-013-0285-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 08/21/2013] [Indexed: 11/26/2022]
Abstract
Knockout of Kv1.3 improves glucose homeostasis and confers resistance to obesity. Additionally, Kv1.3 inhibition enhances glucose uptake. This is thought to occur through calcium release. Kv1.3 inhibition in T-lymphocytes alters mitochondrial membrane potential, and, as many agents that induce Ca(2+) release or inhibit mitochondrial function activate AMPK, we hypothesised that Kv1.3 inhibition would activate AMPK and increase glucose uptake. We screened cultured muscle with a range of Kv1.3 inhibitors for their ability to alter glucose uptake. Only Psora4 increased glucose uptake in C2C12 myotubes. None of the inhibitors had any impact on L6 myotubes. Magratoxin activated AMPK in C2C12 myotubes and only Pap1 activated AMPK in the SOL. Kv1.3 inhibitors did not alter cellular respiration, indicating a lack of effect on mitochondrial function. In conclusion, AMPK does not mediate the effects of Kv1.3 inhibitors and they display differential effects in different skeletal muscle cell lines without impairing mitochondrial function.
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Affiliation(s)
- D Lee Hamilton
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, UK,
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29
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Beall C, Haythorne E, Fan X, Du Q, Jovanovic S, Sherwin RS, Ashford MLJ, McCrimmon RJ. Continuous hypothalamic K(ATP) activation blunts glucose counter-regulation in vivo in rats and suppresses K(ATP) conductance in vitro. Diabetologia 2013; 56:2088-92. [PMID: 23793715 DOI: 10.1007/s00125-013-2970-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [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: 04/26/2013] [Accepted: 05/23/2013] [Indexed: 11/28/2022]
Abstract
AIMS/HYPOTHESIS Acute systemic delivery of the sulfonylurea receptor (SUR)-1-specific ATP-sensitive K(+) channel (K(ATP)) opener, NN414, has been reported to amplify glucose counter-regulatory responses (CRRs) in rats exposed to hypoglycaemia. Thus, we determined whether continuous NN414 could prevent hypoglycaemia-induced defective counter-regulation. METHODS Chronically catheterised male Sprague-Dawley rats received a continuous infusion of NN414 into the third ventricle for 8 days after implantation of osmotic minipumps. Counter-regulation was examined by hyperinsulinaemic-hypoglycaemic clamp on day 8 after three episodes of insulin-induced hypoglycaemia (recurrent hypoglycaemia [RH]) on days 5, 6 and 7. In a subset of rats exposed to RH, NN414 infusion was terminated on day 7 to wash out NN414 before examination of counter-regulation on day 8. To determine whether continuous NN414 exposure altered K(ATP) function, we used the hypothalamic glucose-sensing GT1-7 cell line, which expresses the SUR-1-containing K(ATP) channel. RESULTS Continuous exposure to NN414 in the setting of RH increased, rather than decreased, the glucose infusion rate (GIR), as exemplified by attenuated adrenaline (epinephrine) secretion. Termination of NN414 on day 7 with subsequent washout for 24 h partially diminished the GIR. The same duration of exposure of GT1-7 cells to NN414 substantially reduced K(ATP) conductance, which was also reversed on washout of the agonist. The suppression of K(ATP) current was not associated with reduced channel subunit mRNA or protein levels. CONCLUSIONS/INTERPRETATION These data indicate that continuous K(ATP) activation results in suppressed CRRs to hypoglycaemia in vivo, which in vitro is associated with the reversible conversion of KATP into a stable inactive state.
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Affiliation(s)
- Craig Beall
- Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY Scotland, UK
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30
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Beall C, Watterson KR, McCrimmon RJ, Ashford MLJ. AMPK modulates glucose-sensing in insulin-secreting cells by altered phosphotransfer to KATP channels. J Bioenerg Biomembr 2013; 45:229-41. [PMID: 23575945 DOI: 10.1007/s10863-013-9509-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 03/22/2013] [Indexed: 10/27/2022]
Abstract
Glucose-sensing (GS) behaviour in pancreatic β-cells is dependent on ATP-sensitive K(+) channel (KATP) activity, which is controlled by the relative levels of the KATP ligands ATP and ADP, responsible for closing and opening KATP, respectively. However, the mechanism by which β-cells transfer energy status from mitochondria to KATP, and hence to altered electrical excitability and insulin secretion, is presently unclear. Recent work has demonstrated a critical role for AMP-activated protein kinase (AMPK) in GS behaviour of cells. Electrophysiological recordings, coupled with measurements of gene and protein expression were made from rat insulinoma cells to investigate whether AMPK activity regulates this energy transfer process. Using the whole-cell recording configuration with sufficient intracellular ATP to keep KATP closed, raised AMPK activity induced GS electrical behaviour. This effect was prevented by the AMPK inhibitor, compound C and required a phosphotransfer process. Indeed, high levels of intracellular phosphocreatine or the presence of the adenylate kinase (AK) inhibitor AP5A blocked this action of AMPK. Using conditions that maximised AMPK-induced KATP opening, there was a significant increase in AK1, AK2 and UCP2 mRNA expression. Thus we propose that KATP opening in response to lowered glucose concentration requires AMPK activity, perhaps in concert with increased AK and UCP2 to enable mitochondrial-derived ADP signals to be transferred to plasma membrane KATP by phosphotransfer cascades.
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Affiliation(s)
- Craig Beall
- Division of Cardiovascular and Diabetes Medicine, Medical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland, UK
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31
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Abstract
Why upregulation of the transcription factor Nrf2 increases tumor cell proliferation is unclear. Mitsuishi et al. (2012) now provide evidence that Nrf2 augments purine nucleotide synthesis, thus supporting tissue hypertrophy. This change in cellular metabolism requires loss of Nrf2 repression by Keap1 as well as costimulation via the PI3K-Akt pathway.
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Affiliation(s)
- John D Hayes
- Jacqui Wood Cancer Centre, Division of Cancer Research, Medical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK.
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Watterson KR, Bestow D, Gallagher J, Hamilton DL, Ashford FB, Meakin PJ, Ashford MLJ. Anorexigenic and orexigenic hormone modulation of mammalian target of rapamycin complex 1 activity and the regulation of hypothalamic agouti-related protein mRNA expression. Neurosignals 2012; 21:28-41. [PMID: 22456226 PMCID: PMC3704126 DOI: 10.1159/000334144] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 09/30/2011] [Indexed: 12/16/2022] Open
Abstract
Activation of mammalian target of rapamycin 1 (mTORC1) by nutrients, insulin and leptin leads to appetite suppression (anorexia). Contrastingly, increased AMP-activated protein kinase (AMPK) activity by ghrelin promotes appetite (orexia). However, the interplay between these mechanisms remains poorly defined. The relationship between the anorexigenic hormones, insulin and leptin, and the orexigenic hormone, ghrelin, on mTORC1 signalling was examined using S6 kinase phosphorylation as a marker for changes in mTORC1 activity in mouse hypothalamic GT1-7 cells. Additionally, the contribution of AMPK and mTORC1 signalling in relation to insulin-, leptin- and ghrelin-driven alterations to mouse hypothalamic agouti-related protein (AgRP) mRNA levels was examined. Insulin and leptin increase mTORC1 activity in a phosphoinositide-3-kinase (PI3K)- and protein kinase B (PKB)-dependent manner, compared to vehicle controls, whereas increasing AMPK activity inhibits mTORC1 activity and blocks the actions of the anorexigenic hormones. Ghrelin mediates an AMPK-dependent decrease in mTORC1 activity and increases hypothalamic AgRP mRNA levels, the latter effect being prevented by insulin in an mTORC1-dependent manner. In conclusion, mTORC1 acts as an integration node in hypothalamic neurons for hormone-derived PI3K and AMPK signalling and mediates at least part of the assimilated output of anorexigenic and orexigenic hormone actions in the hypothalamus.
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Affiliation(s)
- Kenneth R Watterson
- Medical Research Institute, Division of Cardiovascular and Diabetes Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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33
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Deldicque L, Cani PD, Philp A, Raymackers JM, Meakin PJ, Ashford MLJ, Delzenne NM, Francaux M, Baar K. The unfolded protein response is activated in skeletal muscle by high-fat feeding: potential role in the downregulation of protein synthesis. Am J Physiol Endocrinol Metab 2010; 299:E695-705. [PMID: 20501874 DOI: 10.1152/ajpendo.00038.2010] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [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] [Indexed: 11/22/2022]
Abstract
High-fat diets are known to decrease muscle protein synthesis, the adaptation to overload, and insulin sensitivity. Conditions that disrupt endoplasmic reticulum (ER) homeostasis lead to the activation of the unfolded protein response (UPR) that is associated with decreases in protein synthesis, chronic inflammation, and insulin resistance. The purpose of the present study was to establish whether ER stress is induced by a high-fat diet in skeletal muscle and whether ER stress can decrease mTORC1 activity and protein synthesis in muscle cells. Two independent protocols of high-fat feeding activated the UPR in mice. In the first study, mice consuming a high-fat diet containing 70% fat and <1% carbohydrates for 6 wk showed higher markers of the UPR (BiP, IRE1α, and MBTPS2) in the soleus and in the tibialis anterior muscles and ATF4 in the tibialis anterior (P < 0.05). In the second study, a 20-wk high-fat diet containing 46% fat and 36% carbohydrates also increased BiP, IRE1α, and phospho-PERK protein and the expression of ATF4, CHOP, and both the spliced and unspliced forms of XBP1 in the plantar flexors (P < 0.05). In C(2)C(12) muscle cells, tunicamycin, thapsigargin, and palmitic acid all increased UPR markers and decreased phosphorylation of S6K1 (P < 0.05). Collectively, these data show that a high-fat diet activates the UPR in mouse skeletal muscle in vivo. In addition, in vitro studies indicate that palmitic acid, and other well-known ER stress inducers, triggered the UPR in myogenic cells and led to a decrease in protein synthesis and mTORC1 activity.
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Affiliation(s)
- Louise Deldicque
- Institute of Neurosciences, UCLouvain, Louvain-la-Neuve, Belgium
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34
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Chowdhry S, Nazmy MH, Meakin PJ, Dinkova-Kostova AT, Walsh SV, Tsujita T, Dillon JF, Ashford MLJ, Hayes JD. Loss of Nrf2 markedly exacerbates nonalcoholic steatohepatitis. Free Radic Biol Med 2010; 48:357-71. [PMID: 19914374 DOI: 10.1016/j.freeradbiomed.2009.11.007] [Citation(s) in RCA: 204] [Impact Index Per Article: 14.6] [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: 09/24/2009] [Revised: 11/02/2009] [Accepted: 11/10/2009] [Indexed: 02/07/2023]
Abstract
Nonalcoholic steatohepatitis (NASH) arises from nonalcoholic fatty liver disease (NAFLD) as a consequence of oxidative stress. Herein we report that the development of NASH is greatly accelerated in mice lacking transcription factor Nrf2 when they are challenged with a methionine- and choline-deficient (MCD) diet. After 14 days of feeding on an MCD diet, livers from Nrf2(-/-) mice showed a substantial increase in macro- and microvesicular steatosis and a massive increase in the number of neutrophil polymorphs, compared to livers from wild-type mice treated similarly. Livers of Nrf2(-/-) mice on the MCD diet suffered more oxidative stress than their wild-type counterparts as assessed by a significant depletion of reduced glutathione that was coupled with increases in oxidized glutathione and malondialdehyde. Furthermore, livers from Nrf2(-/-) mice on the MCD diet suffered heightened inflammation as judged by an approximately 10-fold increase in the amount of nuclear NF-kappaB p65 protein and approximately 5-fold increases in the levels of mRNA for interleukin-1beta, tumor necrosis factor alpha, cyclooxygenase 2, and inducible nitric oxide synthase compared with livers from similarly treated wild-type mice. Thus, impairment of Nrf2 activity may represent a major risk factor for the evolution of NAFLD to NASH.
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Affiliation(s)
- Sudhir Chowdhry
- Biomedical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, UK
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35
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Al-Qassab H, Smith MA, Irvine EE, Guillermet-Guibert J, Claret M, Choudhury AI, Selman C, Piipari K, Clements M, Lingard S, Chandarana K, Bell JD, Barsh GS, Smith AJH, Batterham RL, Ashford MLJ, Vanhaesebroeck B, Withers DJ. Dominant role of the p110beta isoform of PI3K over p110alpha in energy homeostasis regulation by POMC and AgRP neurons. Cell Metab 2009; 10:343-54. [PMID: 19883613 PMCID: PMC2806524 DOI: 10.1016/j.cmet.2009.09.008] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2009] [Revised: 08/10/2009] [Accepted: 09/16/2009] [Indexed: 11/20/2022]
Abstract
PI3K signaling is thought to mediate leptin and insulin action in hypothalamic pro-opiomelanocortin (POMC) and agouti-related protein (AgRP) neurons, key regulators of energy homeostasis, through largely unknown mechanisms. We inactivated either p110alpha or p110beta PI3K catalytic subunits in these neurons and demonstrate a dominant role for the latter in energy homeostasis regulation. In POMC neurons, p110beta inactivation prevented insulin- and leptin-stimulated electrophysiological responses. POMCp110beta null mice exhibited central leptin resistance, increased adiposity, and diet-induced obesity. In contrast, the response to leptin was not blocked in p110alpha-deficient POMC neurons. Accordingly, POMCp110alpha null mice displayed minimal energy homeostasis abnormalities. Similarly, in AgRP neurons, p110beta had a more important role than p110alpha. AgRPp110alpha null mice displayed normal energy homeostasis regulation, whereas AgRPp110beta null mice were lean, with increased leptin sensitivity and resistance to diet-induced obesity. These results demonstrate distinct metabolic roles for the p110alpha and p110beta isoforms of PI3K in hypothalamic energy regulation.
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Affiliation(s)
- Hind Al-Qassab
- Centre for Diabetes and Endocrinology, Rayne Institute, University College London, London WC1E 6JJ, UK
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36
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Ning K, Miller LC, Laidlaw HA, Watterson KR, Gallagher J, Sutherland C, Ashford MLJ. Leptin-dependent phosphorylation of PTEN mediates actin restructuring and activation of ATP-sensitive K+ channels. J Biol Chem 2009; 284:9331-40. [PMID: 19208634 PMCID: PMC2666585 DOI: 10.1074/jbc.m806774200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [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: 09/02/2008] [Revised: 02/04/2009] [Indexed: 11/08/2022] Open
Abstract
Leptin activates multiple signaling pathways in cells, including the phosphatidylinositol 3-kinase pathway, indicating a degree of cross-talk with insulin signaling. The exact mechanisms by which leptin alters this signaling pathway and how it relates to functional outputs are unclear at present. A previous study has established that leptin inhibits the activity of the phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome 10), an important tumor suppressor and modifier of phosphoinositide signaling. In this study we demonstrate that leptin phosphorylates multiple sites on the C-terminal tail of PTEN in hypothalamic and pancreatic beta-cells, an action not replicated by insulin. Inhibitors of the protein kinases CK2 and glycogen synthase kinase 3 (GSK3) block leptin-mediated PTEN phosphorylation. PTEN phosphorylation mutants reveal the critical role these sites play in transmission of the leptin signal to F-actin depolymerization. CK2 and GSK3 inhibitors also prevent leptin-mediated F-actin depolymerization and consequent ATP-sensitive K(+) channel opening. GSK3 kinase activity is inhibited by insulin but not leptin in hypothalamic cells. Both hormones increase N-terminal GSK3 serine phosphorylation, but in hypothalamic cells this action of leptin is transient. Leptin, not insulin, increases GSK3 tyrosine phosphorylation in both cell types. These results demonstrate a significant role for PTEN in leptin signal transmission and identify GSK3 as a potential important signaling node contributing to divergent outputs for these hormones.
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Affiliation(s)
- Ke Ning
- Biomedical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, United Kingdom
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37
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Hisadome K, Smith MA, Choudhury AI, Claret M, Withers DJ, Ashford MLJ. 5-HT inhibition of rat insulin 2 promoter Cre recombinase transgene and proopiomelanocortin neuron excitability in the mouse arcuate nucleus. Neuroscience 2008; 159:83-93. [PMID: 19135134 PMCID: PMC2661429 DOI: 10.1016/j.neuroscience.2008.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 11/28/2008] [Accepted: 12/02/2008] [Indexed: 11/28/2022]
Abstract
A number of anti-obesity agents have been developed that enhance hypothalamic 5-HT transmission. Various studies have demonstrated that arcuate neurons, which express proopiomelanocortin peptides (POMC neurons), and neuropeptide Y with agouti-related protein (NPY/AgRP) neurons, are components of the hypothalamic circuits responsible for energy homeostasis. An additional arcuate neuron population, rat insulin 2 promoter Cre recombinase transgene (RIPCre) neurons, has recently been implicated in hypothalamic melanocortin circuits involved in energy balance. It is currently unclear how 5-HT modifies neuron excitability in these local arcuate neuronal circuits. We show that 5-HT alters the excitability of the majority of mouse arcuate RIPCre neurons, by either hyperpolarization and inhibition or depolarization and excitation. RIPCre neurons sensitive to 5-HT, predominantly exhibit hyperpolarization and pharmacological studies indicate that inhibition of neuronal firing is likely to be through 5-HT1F receptors increasing current through a voltage-dependent potassium conductance. Indeed, 5-HT1F receptor immunoreactivity co-localizes with RIPCre green fluorescent protein expression. A minority population of POMC neurons also respond to 5-HT by hyperpolarization, and this appears to be mediated by the same receptor-channel mechanism. As neither POMC nor RIPCre neuronal populations display a common electrical response to 5-HT, this may indicate that sub-divisions of POMC and RIPCre neurons exist, perhaps serving different outputs.
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Affiliation(s)
- K Hisadome
- Biomedical Research Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, Scotland, UK
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38
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Mirshamsi S, Olsson M, Arnelo U, Kinsella JM, Permert J, Ashford MLJ. BVT.3531 reduces body weight and activates K(ATP) channels in isolated arcuate neurons in rats. ACTA ACUST UNITED AC 2006; 141:19-24. [PMID: 17346811 DOI: 10.1016/j.regpep.2006.12.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Revised: 11/16/2006] [Accepted: 12/01/2006] [Indexed: 11/21/2022]
Abstract
A number of hormones, including leptin, have been shown to inhibit food intake in humans and animals. Analogues of 3-guanidinopropionic acid have also been found to reduce total food intake, but their mechanisms of action have not been well studied. The present study investigated the effects of intracerebroventricular infusion of the analogue BVT.3531 on food intake, meal pattern, and body weight in rats during 7 days. Single channel recordings from arcuate neurons and insulinoma cells were used to determine the effects of BVT.3531 on K(ATP) activity. Data analysis showed that BVT.3531 significantly decreased body weight and food intake, primarily by reducing meal size. BVT.3531 activated K(ATP) channels in cell-attached recordings from insulin-secreting cells and rat arcuate neurons but had no effect on K(ATP) channel activity in inside-out membrane patches from either cell type. BVT.3531 did not alter the firing rate or K(+) channel activity of arcuate neurons devoid of K(ATP). The study suggests that small molecules capable of mimicking the effects of leptin on food intake and body weight may utilize output mechanisms similar to those of leptin to elicit changes in arcuate neuron excitability.
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Affiliation(s)
- Shirin Mirshamsi
- Division of Pathology & Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
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Smith MA, Hisadome K, Al-Qassab H, Heffron H, Withers DJ, Ashford MLJ. Melanocortins and agouti-related protein modulate the excitability of two arcuate nucleus neuron populations by alteration of resting potassium conductances. J Physiol 2006; 578:425-38. [PMID: 17068101 PMCID: PMC1864999 DOI: 10.1113/jphysiol.2006.119479] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The hypothalamic melanocortin system is crucial for the control of appetite and body weight. Two of the five melanocortin receptors, MC3R and MC4R are involved in hypothalamic control of energy homeostasis, with the MC4R having the major influence. It is generally thought that the main impact of the melanocortin system on hypothalamic circuits is external to the arcuate nucleus, and that any effect locally in the arcuate nucleus is inhibitory on proopiomelanocortin-expressing (POMC) neurons. In contrast, using current- and voltage-clamp recordings from identified neurons, we demonstrate that MC3R and MC4R agonists depolarize arcuate POMC neurons and a separate arcuate neuronal population identified by the rat insulin 2 promoter (RIPCre) transgene expression. Furthermore, the endogenous MC3R and MC4R antagonist, agouti-related protein (AgRP), hyperpolarizes POMC and RIPCre neurons in the absence of melanocortin agonist, consistent with inverse agonism at the MC4R. A decreased transient outward (I(A)) potassium conductance, and to a lesser extent the inward rectifier (K(IR)) conductance, underlies neuronal depolarization, whereas an increase in I(A) mediates AgRP-induced hyperpolarization. Accordingly, POMC and RIPCre neurons may be targets for peptide transmitters that are possibly released locally from AgRP-expressing and POMC neurons in the arcuate nucleus, adding further previously unappreciated complexity to the arcuate system.
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MESH Headings
- 4-Aminopyridine/pharmacology
- Action Potentials/drug effects
- Adenylyl Cyclase Inhibitors
- Agouti-Related Protein
- Animals
- Arcuate Nucleus of Hypothalamus/cytology
- Arcuate Nucleus of Hypothalamus/drug effects
- Arcuate Nucleus of Hypothalamus/physiology
- Barium/pharmacology
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- Integrases/genetics
- Integrases/metabolism
- Intercellular Signaling Peptides and Proteins/pharmacology
- Melanocortins/pharmacology
- Melanocyte-Stimulating Hormones/pharmacology
- Mice
- Mice, Transgenic
- Neurons/drug effects
- Neurons/physiology
- Patch-Clamp Techniques
- Peptides, Cyclic/pharmacology
- Potassium Channel Blockers/pharmacology
- Potassium Channels/physiology
- Receptor, Melanocortin, Type 3/agonists
- Receptor, Melanocortin, Type 3/antagonists & inhibitors
- Receptor, Melanocortin, Type 4/agonists
- Receptor, Melanocortin, Type 4/antagonists & inhibitors
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- alpha-MSH/analogs & derivatives
- alpha-MSH/pharmacology
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Affiliation(s)
- Mark A Smith
- Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, UK
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40
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Abstract
Derivatives of 3-guanidinopropionic acid, such as leptin, reduce body weight in obese, diabetic mice. We have assessed whether one of these analogues, BVT.12777 activates intracellular signalling pathways in the arcuate nucleus in a manner analogous to leptin and insulin. In addition, because these hormones have been shown to activate K(ATP) channels in a subset of arcuate neurones, we examined whether this channel is also a functional endpoint for BVT.12777 in the arcuate nucleus. BVT.12777 transiently increased phosphorylation of MAPK, STAT3, PKB and GSK3, in a manner identical to that observed for leptin and insulin. BVT.12777 also hyperpolarized glucose-responsive neurones by increasing the activity of K(ATP) channels. The increase in K(ATP) activity driven by BVT.12777 was PI3-kinase independent, unlike leptin and insulin activation of this channel, and could also be elicited in isolated patches. However, K(ATP) activity induced by BVT.12777 was dependent on actin filament dynamics, both in intact neurones and isolated patches. Thus, BVT.12777 modulates arcuate neurone K(ATP) activity by re-organization of the cytoskeleton, a mechanism that has also been ascribed to leptin and insulin. Consequently, BVT.12777 appears to act as a leptin and insulin mimetic with respect to at least some elements of arcuate neurone intracellular signalling and the activation of K(ATP) channels. Resistance to leptin and insulin, associated with obesity has, at least in part, been postulated to be due to aberrant intracellular signalling in arcuate neurones. The data presented here indicate that it may be possible to develop drugs, which by-pass up-stream signalling components associated with adiposity hormone resistance, such as PI3-kinase, but can still induce functional outputs from arcuate neurones by targeting downstream components of the leptin and insulin signalling cascades.
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Affiliation(s)
- S Mirshamsi
- Division of Pathology and Neuroscience, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK
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41
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Choudhury AI, Heffron H, Smith MA, Al-Qassab H, Xu AW, Selman C, Simmgen M, Clements M, Claret M, Maccoll G, Bedford DC, Hisadome K, Diakonov I, Moosajee V, Bell JD, Speakman JR, Batterham RL, Barsh GS, Ashford MLJ, Withers DJ. The role of insulin receptor substrate 2 in hypothalamic and beta cell function. J Clin Invest 2005; 115:940-50. [PMID: 15841180 PMCID: PMC1069106 DOI: 10.1172/jci24445] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Accepted: 02/22/2005] [Indexed: 11/17/2022] Open
Abstract
Insulin receptor substrate 2 (Irs2) plays complex roles in energy homeostasis. We generated mice lacking Irs2 in beta cells and a population of hypothalamic neurons (RIPCreIrs2KO), in all neurons (NesCreIrs2KO), and in proopiomelanocortin neurons (POMCCreIrs2KO) to determine the role of Irs2 in the CNS and beta cell. RIPCreIrs2KO mice displayed impaired glucose tolerance and reduced beta cell mass. Overt diabetes did not ensue, because beta cells escaping Cre-mediated recombination progressively populated islets. RIPCreIrs2KO and NesCreIrs2KO mice displayed hyperphagia, obesity, and increased body length, which suggests altered melanocortin action. POMCCreIrs2KO mice did not display this phenotype. RIPCreIrs2KO and NesCreIrs2KO mice retained leptin sensitivity, which suggests that CNS Irs2 pathways are not required for leptin action. NesCreIrs2KO and POMCCreIrs2KO mice did not display reduced beta cell mass, but NesCreIrs2KO mice displayed mild abnormalities of glucose homeostasis. RIPCre neurons did not express POMC or neuropeptide Y. Insulin and a melanocortin agonist depolarized RIPCre neurons, whereas leptin was ineffective. Insulin hyperpolarized and leptin depolarized POMC neurons. Our findings demonstrate a critical role for IRS2 in beta cell and hypothalamic function and provide insights into the role of RIPCre neurons, a distinct hypothalamic neuronal population, in growth and energy homeostasis.
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Affiliation(s)
- Agharul I Choudhury
- Centre for Diabetes and Endocrinology, Rayne Institute, University College London, London, United Kingdom
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Hartness ME, Brazier SP, Peers C, Bateson AN, Ashford MLJ, Kemp PJ. Post-transcriptional Control of Human maxiK Potassium Channel Activity and Acute Oxygen Sensitivity by Chronic Hypoxia. J Biol Chem 2003; 278:51422-32. [PMID: 14522958 DOI: 10.1074/jbc.m309463200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Various cardiorespiratory diseases (e.g. congestive heart failure, emphysema) result in systemic hypoxia and patients consequently demonstrate adaptive cellular responses which predispose them to conditions such as pulmonary hypertension and stroke. Central to many affected excitable tissues is activity of large conductance, Ca2+-activated K+ (maxiK) channels. We have studied maxiK channel activity in HEK293 cells stably co-expressing the most widely distributed of the human alpha- and beta-subunits that constitute these channel following maneuvers which mimic severe hypoxia. At all [Ca2+]i, chronic hypoxia (approximately 18 mm Hg, 72 h) increased K+ current density, most markedly at physiological [Ca2+]i K+ currents in cells cultured in normoxia showed a [Ca2+]i-dependent sensitivity to acute hypoxic inhibition ( approximately 25 mm Hg, 3 min). However, chronic hypoxia dramatically changed the Ca2+ sensitivity of this acute hypoxic inhibitory profile such that low [Ca2+]i could sustain an acute hypoxic inhibitory response. Chronic hypoxia caused no change in alpha-subunit immunoreactivity with Western blotting but evoked a 3-fold increase in beta-subunit expression. These observations were fully supported by immunocytochemistry, which also suggested that chronic hypoxia augmented alpha/beta-subunit co-localization at the plasma membrane. Using a novel nuclear run-on assay and RNase protection we found that chronic hypoxia did not alter mRNA production rates or steady-state levels, which suggests that this important environmental cue modulates maxiK channel function via post-transcriptional mechanisms.
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Affiliation(s)
- Matthew E Hartness
- School of Biomedical Sciences, Worsley Building, University of Leeds, Leeds LS2 9JT, United Kingdom
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Abstract
The discovery of the obese gene product, leptin has generated enormous interest in how the periphery signals the status of nutritional stores to specific hypothalamic nuclei involved in regulating feeding and energy balance. However it is emerging that leptin, in addition to its role as a circulating satiety factor, is a multi-faceted hormone that plays a key role in a variety of CNS functions. In this review, we summarise recent progress in leptin biology, with particular focus on its diversity of actions within the CNS, ranging from satiety signal, to regulator of bone formation and inhibitor of neuronal excitability.
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Affiliation(s)
- J Harvey
- Department of Pharmacology and Neuroscience, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK.
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Matharoo-Ball B, Ashford MLJ, Arulkumaran S, Khan RN. Down-regulation of the alpha- and beta-subunits of the calcium-activated potassium channel in human myometrium with parturition. Biol Reprod 2003; 68:2135-41. [PMID: 12606455 DOI: 10.1095/biolreprod.102.010454] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Large-conductance, calcium-dependent potassium (BKCa) channels are implicated in maintaining uterine quiescence during pregnancy. The mechanisms whereby calcium sensitivity of the BKCa channel is dramatically removed at parturition remain unknown. The aim of the present study was to investigate whether this loss of calcium sensitivity of the BKCa channel with the onset of labor is associated with changes in the protein expression of the alpha- and/or beta-subunit or arises from a physical dissociation of the alpha-subunit from the beta-subunit. The beta-subunit is a key determinant of BKCa-channel Ca2+ sensitivity. Western blot analysis, using alpha- and beta-subunit-specific antibodies, detected bands of 110-125 and 36 kDa, respectively. Protein expression levels of the alpha-subunit in term labor myometrium were significantly reduced compared with term pregnancy without labor. Furthermore, alpha-subunit levels at term pregnancy were significantly increased relative to the nonpregnant state, whereas levels at preterm gestations were unchanged. Densitometric analysis demonstrated significantly decreased beta-subunit levels in term and preterm labor samples compared with term nonlabor samples. Immunoprecipitation studies revealed the presence of both the alpha- and beta-subunits in samples taken before or after the onset of labor. We conclude that during labor, the alpha-subunit is not physically uncoupled from the beta-subunit, but a decline occurs in the level of beta-subunit protein, which may underlie the loss of calcium and voltage sensitivity of the BKCa channel with labor. Furthermore, reduced beta-subunit protein in preterm labor myometrium implies that ion channels may also contribute to pathophysiological labor.
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Affiliation(s)
- B Matharoo-Ball
- Academic Division of Obstetrics & Gynaecology, University of Nottingham, Derby City General Hospital, Derby DE22 3NE, United Kingdom
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45
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Smith MA, Herson PS, Lee K, Pinnock RD, Ashford MLJ. Hydrogen-peroxide-induced toxicity of rat striatal neurones involves activation of a non-selective cation channel. J Physiol 2003; 547:417-25. [PMID: 12562896 PMCID: PMC2342643 DOI: 10.1113/jphysiol.2002.034561] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Striatal neurones are particularly vulnerable to hypoxia/ischaemia-induced damage, and free radicals are thought to be prime mediators of this neuronal destruction. It has been shown that hydrogen peroxide (H2O2), through the production of free radicals, induces rat insulinoma cell death by activation of a non-selective cation channel, which leads to irreversible cell depolarization and unregulated Ca2+ entry into the cell. In the study presented here, we demonstrate that a subpopulation of striatal neurones (medium spiny neurones) is depolarized by H2O2 through the production of free radicals. Cell-attached recordings from rat cultured striatal neurones demonstrate that exposure to H2O2 opens a large-conductance channel that is characterized by extremely long open times (seconds). Inside-out recordings show that cytoplasmically applied beta-nicotinamide adenine dinucleotide activates a channel with little voltage dependence, a linear current-voltage relationship and a single-channel conductance of between 70 and 90 pS. This channel is permeable to Na+, K+ and Ca2+ ions. Fura-2 imaging from cultured striatal neurones reveals that H2O2 exposure induces a biphasic intracellular Ca2+ increase in a subpopulation of neurones, the second, later phase resulting in Ca2+ overload. This later component of the Ca2+ response is dependent on the presence of extracellular Ca2+ and is independent of synaptic activity or voltage-gated Ca2+ channel opening. Consequently, this channel may be an important contributor to free radical-induced selective striatal neurone destruction. These results are remarkably similar to those observed for insulinoma cells and suggest that this family of non-selective cation channels has a widespread distribution in mammalian tissues.
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Affiliation(s)
- M A Smith
- Department of Biomedical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD, UK
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Ainscow EK, Mirshamsi S, Tang T, Ashford MLJ, Rutter GA. Dynamic imaging of free cytosolic ATP concentration during fuel sensing by rat hypothalamic neurones: evidence for ATP-independent control of ATP-sensitive K(+) channels. J Physiol 2002; 544:429-45. [PMID: 12381816 PMCID: PMC2290605 DOI: 10.1113/jphysiol.2002.022434] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Glucose-responsive (GR) neurons from hypothalamic nuclei are implicated in the regulation of feeding and satiety. To determine the role of intracellular ATP in the closure of ATP-sensitive K(+) (K(ATP)) channels in these cells and associated glia, the cytosolic ATP concentration ([ATP](c)) was monitored in vivo using adenoviral-driven expression of recombinant targeted luciferases and bioluminescence imaging. Arguing against a role for ATP in the closure of K(ATP) channels in GR neurons, glucose (3 or 15 mM) caused no detectable increase in [ATP](c), monitored with cytosolic luciferase, and only a small decrease in the concentration of ATP immediately beneath the plasma membrane, monitored with a SNAP25-luciferase fusion protein. In contrast to hypothalamic neurons, hypothalamic glia responded to glucose (3 and 15 mM) with a significant increase in [ATP](c). Both neurons and glia from the cerebellum, a glucose-unresponsive region of the brain, responded robustly to 3 or 15 mM glucose with increases in [ATP](c). Further implicating an ATP-independent mechanism of K(ATP) channel closure in hypothalamic neurons, removal of extracellular glucose (10 mM) suppressed the electrical activity of GR neurons in the presence of a fixed, high concentration (3 mM) of intracellular ATP. Neurons from both brain regions responded to 5 mM lactate (but not pyruvate) with an oligomycin-sensitive increase in [ATP](c). High levels of the plasma membrane lactate-monocarboxylate transporter, MCT1, were found in both cell types, and exogenous lactate efficiently closed K(ATP) channels in GR neurons. These data suggest that (1) ATP-independent intracellular signalling mechanisms lead to the stimulation of hypothalamic neurons by glucose, and (2) these effects may be potentiated in vivo by the release of lactate from neighbouring glial cells.
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Affiliation(s)
- Edward K Ainscow
- Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, Bristol BS8 1TD, UK
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Lewis A, Peers C, Ashford MLJ, Kemp PJ. Hypoxia inhibits human recombinant large conductance, Ca(2+)-activated K(+) (maxi-K) channels by a mechanism which is membrane delimited and Ca(2+) sensitive. J Physiol 2002; 540:771-80. [PMID: 11986367 PMCID: PMC2290273 DOI: 10.1113/jphysiol.2001.013888] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Large conductance, Ca(2+)-activated K(+) (maxi-K ) channel activity was recorded in excised, inside-out patches from HEK 293 cells stably co-expressing the alpha- and beta-subunits of human brain maxi-K channels. At +50 mV, and in the presence of 300 nM Ca2+i, single channel activity was acutely and reversibly suppressed upon reducing P(O(2)) from 150 to > 40 mmHg by over 30 %. The hypoxia-evoked reduction in current was due predominantly to suppression in NP(o), although a minor component was attributable to reduced unitary conductance of 8-12 %. Hypoxia caused an approximate doubling of the time constant for activation but was without effect on deactivation. At lower levels of Ca2+i(30 and 100 nM), hypoxic inhibition did not reach significance. In contrast, 300 nM and 1 microM Ca2+i both sustained significant hypoxic suppression of activity over the entire activating voltage range. At these two Ca2+i levels, hypoxia evoked a positive shift in the activating voltage (by approximately 10 mV at 300 nM and approximately 25 mV at 1 microM). At saturating [Ca(2+)](i) (100 microM), hypoxic inhibition was absent. Distinguishing between hypoxia-evoked changes in voltage- and/or Ca2+i-sensitivity was achieved by evoking maximal channel activity using high depolarising potentials (up to +200 mV) in the presence of 300 nM or 100 microM Ca2+i or in its virtual absence (> 1 nM). Under these experimental conditions, hypoxia caused significant channel inhibition only in the presence of 300 nM Ca2+i. Thus, since regulation was observed in excised patches, maxi-K channel inhibition by hypoxia does not require soluble intracellular components and, mechanistically, is voltage independent and Ca2+i sensitive.
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Affiliation(s)
- A Lewis
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
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Anavi-Goffer S, McKay NG, Ashford MLJ, Coutts AA. Vanilloid receptor type 1-immunoreactivity is expressed by intrinsic afferent neurones in the guinea-pig myenteric plexus. Neurosci Lett 2002; 319:53-7. [PMID: 11814652 DOI: 10.1016/s0304-3940(01)02480-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The enteric sensory nervous system consists of extrinsic and intrinsic components. The cellular distribution of vanilloid receptor type 1 (VR1) and its relation to the intrinsic sensory neurones were studied in myenteric plexus-longitudinal muscle preparations of rat ileum and guinea-pig ileum and colon. VR1-immunoreactivity was localized on fine fibres and expressed by ganglionic cells. In the guinea-pig myenteric plexus, a proportion of VR1-immunoreactive cells co-localized with calbindin, a marker for intrinsic afferent neurones. Reverse transcription-polymerase chain reaction with rat VR1-specific primers detected VR1 mRNA in rat but not in guinea-pig preparations. We conclude that VR1 is expressed on fibres and by myenteric neurones. In the guinea-pig, VR1 is expressed by intrinsic afferent neurones but its mRNA may differ from the rat sequence in the region of the primers.
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Affiliation(s)
- Sharon Anavi-Goffer
- Department of Biomedical Science, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK
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49
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Harvey J, Hardy SC, Ashford MLJ. Dual actions of the metabolic inhibitor, sodium azide on K(ATP) channel currents in the rat CRI-G1 insulinoma cell line. Br J Pharmacol 1999; 126:51-60. [PMID: 10051120 PMCID: PMC1565778 DOI: 10.1038/sj.bjp.0702267] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The effects of various inhibitors of the mitochondrial electron transport chain on the activity of ATP-sensitive K+ channels were examined in the Cambridge rat insulinoma G1 (CRI-G1) cell line using a combination of whole cell and single channel recording techniques. 2. Whole cell current clamp recordings, with 5 mM ATP in the pipette, demonstrate that the mitochondrial uncoupler sodium azide (3 mM) rapidly hyperpolarizes CRI-G1 cells with a concomitant increase in K+ conductance. This is due to activation of K(ATP) channels as the sulphonylurea tolbutamide (100 microM) completely reversed the actions of azide. Other inhibitors of the mitochondrial electron transport chain, rotenone (10 microM) or oligomycin (2 microM) did not hyperpolarize CRI-G1 cells or increase K+ conductance. 3. In cell-attached recordings, bath application of 3 mM sodium azide (in the absence of glucose) resulted in a rapid increase in K(ATP) channel activity, an action readily reversible by tolbutamide (100 microM). Application of sodium azide (3 mM), in the presence of Mg-ATP, to the intracellular surface of excised inside-out patches also increased K(ATP) channel activity, in a reversible manner. 4. In contrast, rotenone (10 microM) or oligomycin (2 microM) did not increase K(ATP) channel activity in either cell-attached, in the absence of glucose, or inside-out membrane patch recordings. 5. Addition of sodium azide (3 mM) to the intracellular surface of inside-out membrane patches in the presence of Mg-free ATP or the non-hydrolysable analogue 5'-adenylylimidodiphosphate (AMP-PNP) inhibited, rather than increased, K(ATP) channel activity. 6. In conclusion, sodium azide, but not rotenone or oligomycin, directly activates K(ATP) channels in CRI-G1 insulin secreting cells. This action of azide is similar to that reported previously for diazoxide.
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Affiliation(s)
- J Harvey
- Department of Biomedical Sciences, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD
| | - S C Hardy
- Department of Biomedical Sciences, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD
| | - M L J Ashford
- Department of Biomedical Sciences, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen AB25 2ZD
- Author for correspondence:
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