heat shock proteins and whole body...

Heat Shock Proteins and Whole Body Physiology

HEAT SHOCK PROTEINS

Volume 5

Series Editors:

A. A. A. AseaEffie and Wofford Cain Centennial Endowed Chair in Clinical Pathology,Chief, Division of Investigative Pathology, Scott & White Memorial Hospital and Clinicand Texas A&M Health Science Center, College of Medicine

S. K. CalderwoodDivision of Molecular and Cellular Radiation Oncology,Beth Israel Deaconness Medical Center and Harvard Medical School

For further volumes:http://www.springer.com/series/7515

Heat Shock Proteins andWhole Body Physiology

Edited by

Alexzander A. A. AseaEffie and Wofford Cain Centennial Endowed Chair in Clinical Pathology,Chief, Division of Investigative Pathology, Scott & White Memorial Hospital and Clinicand Texas A&M Health Science Center, College of Medicine

and

Bente K. PedersenDepartment of Infectious Diseases and Copenhagen Muscle Research Centre (CMRC),Director, Centre of Inflammation and Metabolism,University of Copenhagen, Faculty of Health Sciences, Copenhagen, Denmark

123

EditorsDr. Alexzander A. A. AseaTexas A&M Health Science Center,College of MedicineScott & White MemorialHospital & Clinic1901 South 1st St.Temple TX [email protected]@medicine.tamhsc.edu

Dr. Bente K. PedersenUniversity of CopenhagenRigshospitaletDept. Internal MedicineBlegdamsvej 92100 KoebenhavnDenmark

ISSN 1877-1246 e-ISSN 1877-1254ISBN 978-90-481-3380-2 e-ISBN 978-90-481-3381-9DOI 10.1007/978-90-481-3381-9Springer Dordrecht Heidelberg London New York

Library of Congress Control Number: 2009941471

© Springer Science+Business Media B.V. 2010No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or byany means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without writtenpermission from the Publisher, with the exception of any material supplied specifically for the purpose ofbeing entered and executed on a computer system, for exclusive use by the purchaser of the work.

Printed on acid-free paper

Springer is part of Springer Science+Business Media (www.springer.com)

This book is dedicated to our children Dean,Diana, Dorte and Daffy (to B.K.P.) and Edwina,Vanessa and Alexzander Jr. (to A.A.A.)

PREFACE

The heat shock proteins (HSP) are a family of highly conserved proteins with criticalroles in maintaining cellular homeostasis and in protecting the cell from chronicallyand acutely stressful conditions. HSP are molecular chaperones that participate ina variety of physiological processes and are widespread in organisms, tissues, andcells. It follows that chaperone failure will have an impact, possibly serious, on oneor more cellular function, which may lead to disease. Activation of HSP resultsin stress tolerance and cytoprotection against otherwise lethal exposures to stress-induced molecular damage and the induction of HSP, therefore, may have broadtherapeutic benefits in the treatment of various types of tissue trauma and disease.This book provides a comprehensive review on ccontemporary knowledge on therole of heat shock proteins in whole body physiology. Using an integrative approachto understanding heat shock protein physiology, the contributors provide a synop-sis of novel mechanisms by which HSP are involved in the regulation of normalphysiological and pathophysiological conditions.

Heat Shock Proteins and Whole Body Physiology reviews current progress on heatshock proteins in relation to diseases (Part I), psychological stress (Part II), exercisephysiology and physiology of aging (Part III). Part I provides cutting edge knowl-edge regarding the regulatory role of HSP in the progression of a wide spectrumof diseases, ranging from diabetes, kidney diseases and cardiovascular diseases toinfertility. Part II reviews our recent knowledge with regard to psychological stress,including learning, posttraumatic stress disorders, Alzheimer, social isolation andprovides us with brand new information on the proteomics profile of chronicallystressed individuals. Part III provides comprehensive reviews on the role of HSP inmuscle. Increasing evidence suggests that intracellular expression of HSP has numer-ous protective effects for health and that increased muscular expression of HSP mayrepresent one among several links between physical exercise and health. In con-trast, HSP released during stress provoke pro-inflammatory responses and immuneimpairment. Finally, the “shock” of aging is presented. One of the key homeostaticresponses involved in maintaining vitality and longevity is the induction of HSP.These chaperones play an important role in the deterrence of protein damage duringaging.

Key basic and clinical research laboratories from major universities and hos-pitals around the world contribute chapters that review present research activity

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viii Preface

and importantly project the field into the future. The book is a must readfor researchers, postdoctoral fellows and graduate students in the fields ofEndocrinology, Cardiology, Rheumatology, Physiology, Molecular Medicine,Aging, Pharmacology and Pathology.

Alexzander A. A. Asea and Bente K. Pedersen

TABLE OF CONTENTS

Part I Heat Shock Proteins and Disease

1. HSP and Diabetes 3Martin Whitham and Mark A. Febbraio

2. Role of Heat Shock Proteins in Obesity and Type 2 Diabetes 19Punit Kaur, Michael D. Reis, Glen R. Couchman, Samuel N. Forjuoh,John F. Greene Jr, and Alexzander Asea

3. Multifaceted Role of Heat Stress Proteins in the Kidney 31Andrea Havasi, Jonathan M. Gall, and Steven C. Borkan

4. Heat Shock Protein and Inflammation 57Fabiano Amorim and Pope L. Moseley

5. HSP Reactive T Cells are Anti-Inflammatory and Disease Suppressive inArthritic Diseases 85Femke Broere, Suzanne E. Berlo, Teun Guichelaar, Lotte Wieten,Ruurd Van Der Zee, and Willem Van Eden

6. Heat Shock Proteins in Vascular Disease 103Tapan A. Mehta

7. Heat Shock Proteins and Cancer 121Ganachari M. Nagaraja and Alexzander Asea

8. Heat Shock Protein (HSP)-Based Immunotherapies 135Hongying Zheng and Alexzander Asea

9. Heat Shock Proteins and Fertility 151Steven S. Witkin and Iara Moreno Linhares

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x Table of contents

10. Heat Shock Proteins and Diarrhea Causing Microorganisms:Emergence of Enteroaggregative Escherichia coli 163Punit Kaur and Alexzander Asea

Part II Heat Shock Proteins and Psychological Stress

11. Heat Shock Proteins and Post-Traumatic Stress Disorder 179Lei Zhang, He Li, and Robert J. Ursano

12. In Vivo Tissue Source and Releasing Signal for EndogenousExtracellular Hsp72 193Monika Fleshner, Thomas Maslanik, and Lida A. Beninson

13. The 70 kDa Heat Shock Protein Family and Learning 217Martine Ammassari-Teule, Giuseppina Mariucci, and Maria VittoriaAmbrosini

Part III Heat Shock Proteins and Exercise Physiology

14. HSP, Exercise, and Antioxidants 243Bente Klarlund Pedersen and Christian Philip Fischer

15. Exercise Intensity and Duration Affect Blood-Soluble HSP72 253Kishiko Ogawa and Elvira Fehrenbach

16. Ultra Marathon Race Competition and Immune Function 267David C. Nieman

17. HSP, Exercise and Skeletal Muscle 285Earl G. Noble, C.W. James Melling, and Kevin J. Milne

18. Circulating HSP70 as an Endogenous Cytoprotector? 317Alan Graham Pockley and Gabriele Multhoff

19. 72kDa Extracellular Heat Shock Protein (eHsp72), Norepinephrine (NE),and the Innate Immune Response Following Moderate Exercise 327Eduardo Ortega, Esther Giraldo, M. Dolores Hinchado,Leticia Martín-Cordero, and Juan J. García

20. Molecular Chaperones as Mediators of Stress Protective Effect of PlantAdaptogens 351Alexander Panossian, Georg Wikman, Punit Kaur, and Alexzander Asea

21. Biochemical Changes in Response to Intensive Resistance ExerciseTraining in the Elderly 365Ivan Bautmans, Rose Njemini, and Tony Mets

Table of contents xi

22. Heat Shock Proteins, Exercise, and Aging 387Kimberly A. Huey, Victoria Vieira, and Jeffrey A. Woods

23. Hsp60 and Hsp10 in Ageing 401Francesco Cappello, Antonino Di Stefano, Everly Conway De Macario,and Alberto J.L. Macario

Index 427

LIST OF CONTRIBUTORS

Maria Vittoria AmbrosiniDipartimento di Medicina Sperimentale e Scienze Biochimiche, University ofPerugia, Perugia, Italy

Martine Ammassari-TeuleIstituto di Neuroscienze, Consiglio Nazionale delle Ricerche and Santa LuciaFoundation, Rome, Italy

Fabiano AmorimDepartment of Internal Medicine, University of New Mexico, Albuquerque, NM,USA

Alexzander AseaDivision of Investigative Pathology, The Texas A&M Health Science Center, Collegeof Medicine, Scott & White Memorial Hospital and Clinic, Temple, TX, USA

Ivan BautmansFrailty in Ageing (FRIA) Research Group, Vrije Universiteit Brussel, Brussels,Belgium

Lida A. BeninsonDepartment of Integrative Physiology, The Center for Neuroscience, University ofColorado, Boulder, CO, USA

Suzanne E. BerloDivision of Immunology, Department of Infectious Diseases and Immunology,Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands

Steven C. BorkanRenal Section, Boston Medical Center, Evans Biomedical Research Center, BostonUniversity School of Medicine, Boston, MA, USA

Femke BroereDivision of Immunology, Department of Infectious Diseases and Immunology,Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands

Francesco CappelloDipartimento di Medicina Sperimentale, Università degli Studi di Palermo, Palermo,Italy

xiii

xiv List of contributors

Everly Conway De MacarioUniversity of Maryland Biotechnology Institute, Baltimore, MD, USA

Glen R. CouchmanDepartment of Family & Community Medicine, The Texas A&M Health ScienceCenter College of Medicine, Scott & White Memorial Hospital and Clinic, Temple,TX, USA

Antonino Di StefanoFondazione “S. Maugeri”, Centro Medico di Veruno (NO), Veruno, Italy

Mark A. FebbraioDivision of Metabolism and Obesity, Cellular & Molecular Metabolism Laboratory,Baker IDI heart & Diabetes Institute, Melbourne, VIC, Australia

Elvira FehrenbachInstitute of Clinical and Experimental Transfusion Medicine (IKET), University ofTuebingen, Tuebingen, Germany

Christian Philip FischerDepartment of Infectious Diseases and CMRC, Faculty of Health Sciences, TheCentre of Inflammation and Metabolism, University of Copenhagen, Copenhagen,Denmark

Monika FleshnerDepartment of Integrative Physiology, The Center for Neuroscience, University ofColorado, Boulder, CO, USA

Samuel N. ForjuohDepartment of Family & Community Medicine, The Texas A&M Health ScienceCenter College of Medicine, Scott & White Memorial Hospital and Clinic, Temple,TX, USA

Jonathan M. GallRenal Section, Boston Medical Center, Evans Biomedical Research Center, BostonUniversity School of Medicine, Boston, MA, USA

Juan J. GarcíaDepartment of Physiology (Immunophysiology Research Group), Faculty ofScience, University of Extremadura, Badajoz, Spain

Esther GiraldoDepartment of Physiology (Immunophysiology Research Group), Faculty ofScience, University of Extremadura, Badajoz, Spain

John F. GreeneDepartment of Pathology, The Texas A&M Health Science Center College ofMedicine, Scott & White Memorial Hospital and Clinic, Temple, TX, USA

Teun GuichelaarDivision of Immunology, Department of Infectious Diseases and Immunology,Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands

List of contributors xv

Andrea HavasiRenal Section, Boston Medical Center, Evans Biomedical Research Center, BostonUniversity School of Medicine, Boston, MA, USA

M. Dolores HinchadoDepartment of Physiology (Immunophysiology Research Group), Faculty ofScience, University of Extremadura, Badajoz, Spain

Kimberly A. HueyDepartment of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Punit KaurDivision of Investigative Pathology, The Texas A&M Health Science Center, Collegeof Medicine, Scott & White Memorial Hospital and Clinic, Temple, TX, USA

He LiDepartment of Psychiatry, Center for the Study of Traumatic Stress, UniformedServices, University of the Health Sciences, Bethesda, MD, USA

Iara Moreno LinharesDivision of Immunology and Infectious Diseases, Department of Obstetrics andGynecology, Weill Medical College of Cornell University, New York, NY, USA;Department of Gynecology, Hospital das Clinicas, University of Sao Paulo MedicalSchool, Sao Paulo, Brazil

Alberto J. L. MacarioUniversity of Maryland Biotechnology Institute, Baltimore, MD, USA

Giuseppina MariucciDipartimento di Medicina Sperimentale e Scienze Biochimiche, University ofPerugia, Perugia, Italy

Leticia Martín-CorderoDepartment of Physiology (Immunophysiology Research Group), Faculty ofScience, University of Extremadura, Badajoz, Spain

Thomas MaslanikDepartment of Integrative Physiology, The Center for Neuroscience, University ofColorado, Boulder, CO, USA

Tapan A. MehtaAcademic Surgical Unit, University Of Hull, Hull, UK

C. W. James MellingBachelor of Health Sciences Program, Faculty of Health Sciences, The University ofWestern Ontario, London, ON, Canada

Tony MetsGerontology and Geriatrics Department, Frailty in Ageing (FRIA) ResearchGroup, Vrije Universiteit Brussel, Brussels, Belgium; Gerontology and GeriatricsDepartment, Frailty in Ageing (FRIA) Research Group, Universitair ZiekenhuisBrussel, Brussels, Belgium

xvi List of contributors

Kevin J. MilneDepartment of Kinesiology, Faculty of Human Kinetics, University of Windsor,Windsor, ON, Canada

Pope L. MoseleyDepartment of Internal Medicine, University of New Mexico, Albuquerque, NM,USA

Gabriele MulthoffDepartment of Radiotherapy and Radiooncology, Klinikum rechts der Isar,Technische Universität München, Munich, Germany; Helmholtz Center Munich,German Research Center for Environmental Health (GmbH), Institute of Pathology,Clinical Cooperation Group ‘Innate Immunity in Tumor Biology’, Munich, Germany

Ganachari M. NagarajaDivision of Investigative Pathology, The Texas A&M Health Science Center, Collegeof Medicine, Scott & White Memorial Hospital and Clinic, Temple, TX, USA

David C. NiemanAppalachian State University, Boone, NC, USA

Rose NjeminiGerontology and Geriatrics Department, Frailty in Ageing (FRIA) Research Group,Vrije Universiteit Brussel, Brussels, Belgium

Earl G. NobleFaculty of Health Sciences, School of Kinesiology, London, ON, Canada; LawsonHealth Research Institute, The University of Western Ontario, London, ON, Canada

Kishiko OgawaResearch Team for Social Participation and Health Promotion, Tokyo MetropolitanInstitute of Gerontology, Tokyo, Japan

Eduardo OrtegaDepartment of Physiology (Immunophysiology Research Group), Faculty ofScience, University of Extremadura, Badajoz, Spain

Alexander PanossianSwedish Herbal Institute Research and Development, Åskloster, Sweden

Bente Klarlund PedersenDepartment of Infectious Diseases and CMRC, Faculty of Health Sciences, TheCentre of Inflammation and Metabolism, University of Copenhagen, Copenhagen,Denmark

Alan Graham PockleyImmunobiology Research Unit, School of Medicine and Biomedical Sciences,University of Sheffield, Sheffield, UK

Michael D. ReisDepartment of Family & Community Medicine, The Texas A&M Health ScienceCenter College of Medicine, Scott & White Memorial Hospital and Clinic, Temple,TX, USA

List of contributors xvii

Robert J. UrsanoDepartment of Psychiatry, Center for the Study of Traumatic Stress, UniformedServices, University of the Health Sciences, Bethesda, MD, USA

Ruurd Van Der ZeeDivision of Immunology, Department of Infectious Diseases and Immunology,Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands

Willem Van EdenDivision of Immunology, Department of Infectious Diseases and Immunology,Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands

Victoria VieiraDepartment of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Martin WhithamSchool of Sport, Health and Exercise Sciences, Bangor University, Gwynedd, UK

Lotte WietenDivision of Immunology, Department of Infectious Diseases and Immunology,Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands

Georg WikmanSwedish Herbal Institute Research and Development, Åskloster, Sweden

Steven S. WitkinDivision of Immunology and Infectious Diseases, Department of Obstetrics andGynecology, Weill Medical College of Cornell University, New York, NY, USA

Jeffrey A. WoodsDepartment of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Lei ZhangDepartment of Psychiatry, Center for the Study of Traumatic Stress, UniformedServices, University of the Health Sciences, Bethesda, MD, USA

Hongying ZhengDivision of Investigative Pathology, The Texas A&M Health Science Center, Collegeof Medicine, Scott & White Memorial Hospital and Clinic, Temple, TX, USA

PART I

HEAT SHOCK PROTEINS AND DISEASE

CHAPTER 1

HSP AND DIABETES

MARTIN WHITHAM1,2* AND MARK A. FEBBRAIO2

1 School of Sport, Health and Exercise Sciences, Bangor University, Gwynedd, UK2 Division of Metabolism and Obesity, Cellular & Molecular Metabolism Laboratory, Baker IDI Heart& Diabetes Institute, Melbourne, VIC, Australia

Abstract: As the prevalence of diabetes continues to rise, strategies that aim to prevent and treat thecondition continue to gain importance. Obesity is thought to induce a state of low-gradeinflammation, which ultimately disrupts insulin signalling and predisposes individuals totype II diabetes. In particular, TNFα, endoplasmic reticulum (ER) and oxidative stressall appear to be associated with obesity and stimulate inflammatory kinases such as cjun amino terminal kinase (JNK), inhibitor of NF-κβ kinase (IKK) and protein kinase C(PKC). These kinases in turn inhibit insulin signalling, predominantly through inhibitoryphosphorylation of the insulin receptor substrate (IRS). The current chapter reviews theliterature that describes this process and the potential that heat shock proteins have inpreventing inflammatory disruption of insulin signalling. In particular, data are presentedthat demonstrate the role of Hsp72 in the prevention of insulin resistance in diet and geneticmodels of murine obesity. The role of HSP in the autoimmunity of type I diabetes is alsodiscussed

Keywords: Obesity; inflammation; insulin resistance; hydroxylamine derivatives; autoimmunity

Abbreviations: β-HAD, β-hydroxyacyl-CoA-dehydrogenase; ATM, adipose tissue macrophages; BB,biobreeding; CS, citrate synthase; DAG, diacylglycerol; ER, endoplasmic reticu-lum; ERK1, extracellular signal-regulated kinases; FFA, free fatty acid; GSK-3β,glycogen synthase kinase 3β; HFD, high fat diet; HO-1, haem-oxygenase; HOMA-IR, homeostatic model assessment of insulin resistance; HT, heat therapy; HSE, heatshock element; HSF, heat shock factor; HSP, heat shock proteins; IKK, inhibitor ofNF-κβ kinase; IMTG, intramuscular triglyceride; IPGTT, intraperotineal glucose tol-erance tests; IR, insulin receptor; IRS, insulin receptor substrate; JNK, c-jun aminoterminal kinase; MEF, mouse embryonic fibroblasts; NHANES, National Healthand Nutrition Examination survey; NOD, non-obese diabetic mice; NSAID, non-steroidal anti-inflammatory drugs; OLETF, Otsuka Long-Evans Tokushima Fatty rats;

*Cellular & Molecular Metabolism Laboratory, Baker IDI Heart & Diabetes Institute, 75 CommercialRoad, Melbourne, VIC 3004, Australia, Tel: + 61(0)3 8532 1170, Fax: + 61(0)3 8532 1100, E-mail:[email protected]

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A.A.A. Asea and B.K. Pedersen (eds.), Heat Shock Proteins and Whole Body Physiology, 3–18.DOI 10.1007/978-90-481-3381-9_1, C© Springer Science+Business Media B.V. 2010

4 Whitham and Febbraio

PBA, 4-phenyl butyric acid; PERK, PKR-like kinase; PI, phosphatidylinositol; PIP3,phosphatidilinositol 3, 4, 5 triphosphate; PKA, protein kinase A; PKC, protein kinaseC; ROS, reactive oxygen species; TNFα, tumor necrosis factor α

INTRODUCTION

Diabetes is characterised by a chronic elevation of blood glucose (hyperglycaemia).The condition is broadly categorised into two types; type 1 is associated with insuf-ficient insulin production, due to the destruction of pancreatic beta cells and type 2encompasses a wide range of disorders that ultimately lead to hyperglycaemia. Thepersistent hyperglycaemia that results from these conditions can lead to further com-plications associated with the cardiovascular system, such as coronary artery disease,stroke and peripheral vascular disease. Although research into the pathogenesis ofdiabetes has progressed over the last 20 years, our understanding of this condition isstill far from complete. Furthermore, the prevalence of diabetes is gradually increas-ing globally. Estimates report an incidence of 2.8% in the year 2000 and predict thisvalue to grow to 4.4% by the year 2030 (Wild et al. 2004). Moreover, these projec-tions assume other risk factors such as physical inactivity and obesity will remainconstant, suggesting these figures could underestimate the global burden of diabetes.Given the apparent ubiquity of the highly conserved heat shock proteins (HSP), it isperhaps unsurprising that these chaperone proteins have been associated with a num-ber of clinical conditions, including diabetes. HSP have been implicated in both theaetiology of immune mediated type I diabetes (Elias et al. 1990) and in the treatmentof insulin resistance and obesity associated type 2 diabetes (Chung et al. 2008). Theaim of this chapter is to review the current literature that implicates HSP as potentialtherapeutic targets for diabetes.

HSP derived their name following their apparent accidental discovery in the sali-vary glands of Drosophila melanogaster following transient heat stress (5◦C abovenormal temperature) (Ritossa 1996). This heat shock response was characterisedby the appearance of inducible proteins, which transiently gave rise to increasedtolerance to high and otherwise lethal temperatures. Subsequently, the heat shockprotein response has shown similar behaviour when faced with stressors such asoxidative stress, glucose deprivation and infection, which ultimately lead to themis-folding of intracellular proteins. Therefore, the abundantly expressed HSP areprimarily involved in cytoprotection, prevention of apoptosis and protein mis-foldingand promoting signalling pathways during periods of cellular stress (Westerheideand Morimoto 2005). The heat shock protein superfamily have been traditionallyorganised by size and functional class. These include (alternative names in brackets(Kampinga et al. 2008)) Hsp100 (HSPH), Hsp70 (HSPA), Hsp60 (HSPD), Hsp40(DNAJ), small HSP (HSPB) and haem oxygenase. The HSP60 and HSP70 familieshave received particular attention with regard to diabetes.

HSP MECHANISM OF INDUCTION

Hsp gene transcription is effectuated via a transcription factor called HSF1. In theunstressed state, HSP are bound to HSF1 maintaining it in an inactive, monomeric

HSP and diabetes 5

state. Cellular stress causes dissociation of the HSP/HSF1 complex, which allowsunbound HSF1 to translocate to the nucleus, convert to a trimeric complex and acti-vate DNA binding activity at the heat shock element (HSE) promoter region of thehsp genes (Amin et al. 1988; Sarge et al. 1993). While this process is clearly keyto hsp gene transcription, overexpression of HSF1 leads to heightened HSF1-HSEDNA binding in the absence of hsp70 gene expression (Zuo et al. 1995), suggest-ing further regulatory input is required. In particular, numerous protein kinases arethought to potentially phosphorylate HSF1 at various serine residues, through whichthe heat shock response can be influenced by cellular stress. For example, in responseto thermal stress in human embryonic kidney cells, Polo-like kinase 1 phospho-rylates HSF1 on Ser419 and is thought to regulate its nuclear translocation (Kimet al. 2005). Furthermore, non-steroidal anti-inflammatory drugs (NSAID) such assodium salicylate cause the monomer to trimer transition (Jurivich et al. 1992), sug-gesting that kinases that are inhibited by NSAIDs such as RSK2, ERK, and IKKα

might negatively regulate HSF1 activation (Wang et al. 2006). Indeed, Melling et al.(2006) were able to demonstrate a role for protein kinase A (PKA) in the suppres-sion of ERK phosphorylation of HSF1 at Ser307 in rat cardiac tissue following thestress of exercise. Since ERK phosphorylation participates in the down-regulationof HSF1 transcriptional activity (He et al. 1998), this implicates PKA and ERK askey mediators of hsp gene expression, particularly following exercise. Moreover,both in vitro and in vivo experiments imply a facilitatory role of Glycogen synthasekinase 3β (GSK-3β) in the negative regulation of HSF1 (Chu et al. 1996; He et al.1998).

HSP EXPRESSION IN INSULIN RESISTANCE AND DIABETES

Perhaps the first link between HSP and diabetes was introduced with the observa-tion that in insulin resistant and diabetic patients, HSP expression was markedlyaltered. Muscle biopsies taken from type 2 diabetic patients showed significantlylower mRNA levels of the inducible isoform of HSP70, Hsp72, than those takenfrom non-diabetic controls (Kurucz et al. 2002). Furthermore, data collected in ourlaboratory supported this finding and demonstrated a marked relationship betweenboth Hsp72 and Haem-oxygenase (HO-1) mRNA and insulin stimulated glucoseuptake during a hyperinsulemic-euglycemic clamp in type 2 diabetic patients (Bruceet al. 2003). Interestingly, Kurucz et al. (2002) assessed the Hsp72 mRNA con-centrations in monozygotic twins discordant for diabetes in an attempt to estimatethe contribution of genetic or acquired factors in the relationship between Hsp72and diabetes. Hsp72 mRNA was significantly lower in non-diabetic co-twins thanaged matched healthy controls. However, these non-diabetic twin “halves” were alsoinsulin resistant, making conclusions on the influence of genetic inheritance of lowHsp72 difficult. Furthermore, the authors were able to show a progressive declinein Hsp72 mRNA from insulin resistance, to impaired glucose tolerance, to diabetes,suggesting this defect in Hsp72 mRNA is an acquired abnormality rather than aninherited one. Assuming that Hsp72 mRNA levels reflect protein expression, these


data suggest that Hsp72 expression is low in type II diabetic patients. A key questionthat arises, is whether decreased Hsp72 expression is the cause or consequence ofmetabolic complications in diabetes?

EARLY SIGNS OF AN INVOLVEMENT OF HSP72 IN THE ETIOLOGYOF TYPE 2 DIABETES

Early reports of a decreased expression of Hsp72 in type 2 diabetes (Bruce et al.2003; Kurucz et al. 2002) were supported by a preliminary study identifying Hsp72as only 1 of 17 genes out of >5000, that were markedly lower in insulin resistancepatients versus healthy controls (Patti et al. 2001, Abstract). Since no correlationis evident between skeletal muscle Hsp72 mRNA and fasting plasma glucose andinsulin concentration (Kurucz et al. 2002), it is unlikely that altered Hsp72 expres-sion is due to the chronic elevation of plasma glucose in diabetes. Instead, thereare data that support the hypothesis that lowered Hsp72 expression is causallyinvolved, at least in part, in the development of insulin resistance and type 2 dia-betes. Early speculation considered that Hsp72 expression might be affecting insulinsensitivity through a direct interaction with GLUT4 (Kurucz et al. 2002). However,we have shown no reduction in GLUT4 gene expression in diabetic patients ver-sus aged matched controls (Bruce et al. 2003). In the same study, we directlymeasured intramuscular triglyceride (IMTG) content in the muscle biopsy samplesderived from type 2 diabetes patients and aged matched healthy controls. IMTGcontent was ∼150% higher in the patient group. Allied to the finding of loweredHsp72 mRNA expression in diabetes, these data provided a rationale for the exam-ination of the role of HSP expression in the etiology of obesity induced insulinresistance.

OBESITY, INFLAMMATION AND INSULIN RESISTANCE

Before examining how HSP might alter obesity induced insulin resistance, it is firstworth noting the magnitude of the problem of obesity and the potential mechanisticlinks between over-nourishment and diabetes. The most recently published surveyssuggest that, in affluent and well-nourished societies, obesity levels have reachedepidemic proportions. For example, figures from the National Health and NutritionExamination survey (NHANES) in the USA suggested that the prevalence of obe-sity (BMI >30) in 2000 was 30.5%. This represents an increase of 7.6% from thefigures collected during 1988–1994 (Flegal et al. 2002). Similarly, the prevalence ofobesity is as high as 36.5% in some areas of Europe (Berghoefer et al. 2008). Thecauses of these trends are unclear, although it is likely that social, economic, andcultural changes lead to an imbalance in energy intake and expenditure. Given thefact that the prevalence of obesity and diabetes appear to be rising in tandem, it isunsurprising that obesity is identified as a significant risk factor for diabetes. The

HSP and diabetes 7

exact mechanisms by which this connection is made have been the subject of a greatdeal of research in recent years.

Numerous lines of evidence suggest a link between obesity and inflammation.However, the traditional characteristics of inflammation do not apply to the obesecondition. Inflammation is a classical response to injury, characterised by swelling,redness, pain and fever (tumor, rubor, dolor and calor). As such, the inflamma-tory processes are seen as acutely beneficial to the host. However, prolonged orchronic inflammation is associated with a cluster of metabolic diseases, includ-ing diabetes. Therefore, this aspect of inflammation is often referred to as “lowgrade” or meta-inflammation (Hotamisligil 2006). While the cascade of moleculesinvolved in inflammation is complex, the pro-inflammatory cytokine, TNFα has con-ferred a prominent role in mediating downstream transduction cascades that affectinsulin signalling. In landmark studies, Hotamisligil and colleagues were the firstto demonstrate that TNFα was overexpressed in the adipose tissue of obese mice(Hotamisligil et al. 1993). Moreover, in loss-of-function experiments in obese mice,null mutations in the gene encoding TNFα and its’ receptors, resulted in improvedinsulin sensitivity (Uysal et al. 1997). Experiments that involve the adipose tissueare of particular relevance, as it appears that this is the predominant site of obesity-associated meta-inflammation. Indeed, both functionally and biologically, adipocytesand immune system macrophages show a high degree of similarity (Wellen andHotamisligil 2005). Perhaps most significantly, both these cell types co-localise inadipose tissue in obesity, and in rodents and humans, adipose tissue macrophages(ATM) accumulate with increasing body weight (Weisberg et al. 2003; Xu et al.2003). Furthermore, after surgery-induced weight loss in morbidly obese patients,ATM infiltration decreased significantly (Cancello et al. 2005). Of added interest isthe high correlation between ATM accumulation and measures of insulin resistance(Xu et al. 2003), adding further support to the contention that obesity induced insulinresistance is determined, at least in part, by inflammation originating from adiposetissue.

A multitude of metabolic stressors appear capable of inducing inflammatory sig-nalling pathways. In addition to the established influence of extracellular TNFα

(Hotamisligil et al. 1996), stressors originating from within the cell appear influ-ential. For example, obesity places overload on the endoplasmic reticulum due toan accumulation of misfolded proteins, lipid oversupply and increased demand onthe synthetic machinery (Ozcan et al. 2004). Indeed, in both high fat diet andgenetic (ob/ob) models of murine obesity, indicators of ER stress such as PKR-like kinase (PERK) and eIF2α are significantly phosphorylated in liver extracts fromobese animals versus lean controls (Ozcan et al. 2006). Elevated glucose metabolismcan also cause an increase in reactive oxygen species (ROS) in the mitochondria.Interestingly, gene expression analysis has suggested a role for ROS in both TNFα

and glucocorticoid models of insulin resistance (Houstis et al. 2006). Given thatboth ER and oxidative stress are known to induce inflammatory signalling cascades(Kamata et al. 2005; Ozcan et al. 2004), these stressors provide additional means bywhich obesity disrupts insulin signalling.


MECHANISMS OF INSULIN SIGNALLING

Insulin itself is the most potent physiological anabolic agent that promotes stor-age and synthesis of lipids, protein and of course, carbohydrates. While the basicregulated transport of glucose into the cell is mediated by the GLUT4 receptor,a complex cascade of signalling cascades exists that effects the actions of insulin(Chang et al. 2004). The foremost step of this process is the initial binding of insulinreceptor (IR). The IR itself is a heterotetrameric transmembrane complex, the α

unit of which binds insulin, and initiates phosphorylation of the IR β units on tyro-sine residues. The resulting activation of the kinase associated with the β units setsforth a web of phosphatidylinositol (PI) 3 kinase dependent and independent down-stream signalling cascades (Chang et al. 2004; Taniguchi et al. 2006). Briefly, IRSstimulation of PI-3 kinase produces phosphatidilinositol 3, 4, 5 triphosphate (PIP3)which stimulates kinases such as PDK. PDK in turn activates a series of kinasesthat results in the activation of Akt and PKC and subsequent regulation of GLUT4mediated glucose transport. It is thought that this process can also be stimulated vialipid raft microdomains through activation of Cbl and APS (Chang et al. 2004). Sowhile the process of insulin signalling is clearly complex, the initial tyrosine phos-phorylation of the insulin receptor substrate family (IRS 1–6) is highly significant(Chang et al. 2004). For example, IRS-1 and IRS-2 knock-out mice are markedlyinsulin resistant, underscoring the importance of the IRS family on insulin signalling(White 2002). Indeed, the tyrosine phosphorylation of IRS proteins appears defectivein experimental and human models of insulin resistance (Wellen and Hotamisligil2005).

INFLAMMATORY KINASES AND THE DISRUPTIONOF INSULIN SIGNALLING

While it is becoming increasingly established that fatty acids, proinflammatorycytokines, ER stress and ROS can disrupt insulin signalling, in order to developvarious therapeutic avenues, it is important to determine the specific mechanismsby which these stressors induce insulin resistance. In this regard, the inflamma-tory serine/threonine kinases c jun amino terminal kinase (JNK), inhibitor of NF-κβ

kinase (IKK) and protein kinase C (PKC) have received attention. JNK belongs tothe MAPK family of kinases and has emerged as a key regulator of metabolic alter-ations in insulin sensitivity. Indeed, three lines of evidence highlight this. (1) JNKactivity appears elevated in both dietary and genetic models of obesity (Hirosumiet al. 2002; Prada et al. 2005). For example, rats fed a high fat “western” diet for30 days showed significantly higher JNK activity in liver, muscle and hypothalamustissue, versus controls (Prada et al. 2005). In addition, JNK phosphorylation is ele-vated in liver, muscle and adipose tissues taken from leptin deficient (ob/ob) mice,a commonly used genetic model of murine obesity (Hirosumi et al. 2002). (2) JNKis activated by FFA, TNFα, ER stress and ROS (Kamata et al. 2005; Nguyen et al.2005; Ozcan et al. 2004; Yuasa et al. 1998), all of which are known to contribute to

HSP and diabetes 9

insulin resistance. (3) Finally, JNK serine phosphorylates IRS-1 (ser307) which dis-rupts IRS-1 and IR interaction (Aguirre et al. 2002; Hotamisligil et al. 1996). Indeed,the importance of JNK in the development of insulin resistance is emphasised by datafrom JNK-1 knock-out animal experiments, that show markedly decreased ser307

IRS-1 phosphorylation in obese JNK-1–/– versus obese wild-type mice. Significantly,obese JNK-1–/– mice also demonstrated markedly improved measures of wholebody insulin sensitivity versus obese wild type controls (Hirosumi et al. 2002).Taken together, these findings suggest that JNK inhibition might provide a promisingtherapeutic avenue for diabetes.

Other inflammatory kinases that inhibit insulin signalling are IKK and PKC.Indeed, high doses of salicylates, which inhibit IKKβ and NFκβ, reverses insulinresistance in genetic and diet models of animal obesity (Yuan et al. 2001). Moreover,IKKβ+/– transgenic mice showed consistently lower fasting glucose and insulin con-centrations following a high fat diet when compared to wild-type counterparts. Inkeeping with the inhibitory effects of other inflammatory kinases such as JNK, over-expression of IKKβ in hepatocytes resulted in decreased insulin-stimulated IR andIRS-1 phosphorylation (Cai et al. 2005). Infusion of lipid emulsions in rats, a modelfor fatty acid induced insulin resistance, causes an increase in intracellular fatty acyl-CoA and diacylglycerol (DAG) (Yu et al. 2002). Raised concentrations of these lipidspecies is associated with an increased activation of PKCθ and heightened IRS-1ser307 phosphorylation (Yu et al. 2002), suggesting a role for PKCθ in direct dis-ruption of insulin signalling. Collectively therefore, these data outline a potentialmechanism mediated predominantly by inflammatory kinases, which accounts forTNFα, fatty acid, ROS and ER stress induced insulin resistance. Therapies aimed tolimit this meta-inflammation thus require further investigation.

HSP AND INFLAMMATION

A key feature of HSP is their ability to provide cytoprotection. Early experimentsdemonstrated that if cells were heat treated at 43◦C, the number of cells survivinga subsequent insult of heat shock increased. Furthermore, this “acquired thermo-tolerance” was associated with the synthesis of HSP (Landry et al. 1982). Once itbecame understood that HSP could provide cytoprotection against other stressors,interest in their therapeutic value increased. For example, an upregulation of HSP hasbeen associated with improved recovery from ischemia in cardiac tissue (Snoeckxet al. 2001) and protection against acute respiratory distress syndrome (Weiss et al.2007). Of particular interest are data that imply a role for HSP in the inhibition ofstress activated kinases and subsequent apoptotic pathways. For example, preheat-ing of human leukemic cells led to reduced cell death following a subsequent heatshock, which was associated with an inhibition of JNK and p38 activation (Gabaiet al. 1997). That this effect might be mediated by HSP was assessed using ectopicover-expression of Hsp72 in the human PEER cell line. Indeed, overexpression ofHsp72 suppressed the apoptotic and stress kinase activating effects of heat, osmotic


shock, H2O2 and UV irradiation (Gabai et al. 1997). Subsequent work using Hsp72transfected mouse embryonic fibroblasts (MEF), suggested that Hsp72 suppressesthe JNK signalling pathway through physical association and prevention of JNKphosphorylation by its upstream kinase SEK1 (Park et al. 2001). Similarly, HSP70proteins have been implicated in the inhibition of IKKγ and subsequent formationof IKK complexes (Salminen et al. 2008). Given the importance of NFκβ in inflam-mation, the inhibition of its kinase IKK has particular therapeutic significance. Forexample, overexpression of Hsp70 protects rats against sepsis induced lung injurythrough an inhibition of the IKK complex (Weiss et al. 2007). Finally, Ozcan et al.(2006) have demonstrated that chemical chaperones such as 4-phenyl butyric acid(PBA) can limit ER stress and subsequent JNK mediated insulin resistance in geneticmodels of murine obesity and diabetes.

HSP72 AND THE PREVENTION OF INSULIN RESISTANCE

Meta-inflammation appears to disrupt insulin signalling and HSP appear to have thepotential to inhibit inflammatory kinases. Therefore, there is a strong rationale toinvestigate the potential therapeutic role of HSP in insulin resistance. In particu-lar, the inducible isoform of the HSP70 family, Hsp72 has been a specific focus.Interestingly, one preliminary report has suggested that heat therapy in general mighthave potential in the treatment of diabetes. Type 2 diabetic patients using a hot tubdaily for 3 weeks have shown improvements in glycaemia by unknown mechanisms(Hooper 1999). In order to investigate the effects of heat therapy and Hsp72 induc-tion on insulin resistance, we recently carried out a number of experiments (Chunget al. 2008).

Heat Therapy, JNK Phosphorylation and Insulin Sensitivity

Mice were subjected to either heat or sham therapy (control) whilst consuming a highfat diet (HFD). HT (heat therapy) involved raising the core temperature to 41◦C for15 min, once a week, for 16 weeks, which transiently increased Hsp72 expression inmuscle, liver and adipose tissue. As expected, in response to the HFD, control micedeveloped hyperglycaemia, hyperinsulinemia and insulin resistance as indicated bythe homeostatic model assessment of insulin resistance (HOMA-IR). Furthermore,intraperotineal glucose tolerance tests (IPGTT) revealed glucose intolerance in thesemice. Conversely, mice exposed to HT were protected against insulin resistance, andthis protection was associated with an attenuation of JNK phosphorylation in muscle.

Genetic Over-Expression of Hsp72 and HFD-Induced Insulin Resistance

While heat treatment showed improvements in insulin signalling in a high fat dietmodel of insulin resistance, the rather general nature of heat as a global stressorprecludes firm conclusions on the involvement of HSP. Therefore, muscle specific

HSP and diabetes 11

transgenic mice, overexpressing Hsp72 (Hsp72+/+) were placed on HFD or standardchow diets and compared to wild type controls to determine the specific effects ofHsp72 expression on diet induced insulin resistance. In keeping with the heat therapydata, the development of hyperglycaemia, hyperinsulinemia, insulin resistance andglucose intolerance was prevented in Hsp72+/+ mice as opposed to the WT controls.Given the role of inflammatory kinases in the disruption of insulin signalling, JNKand IKK phosphorylation was assessed in Hsp72+/+ and WT mice. While neither thediet nor treatment altered IKKαβ serine phosphorylation, JNK (Thr183/Tyr185) phos-phorylation was increased in WT mice following the HFD. Again, in keeping withthe hypothesis, JNK phosphorylation was completely prevented in Hsp72+/+ mice.Furthermore, when stimulated with insulin, akt phosphorylation was elevated inHsp72+/+ but not WT mice following the HFD. These data, therefore, indicated thatoverexpression of Hsp72 inhibited fatty acid disrupted insulin signalling, through theinhibition of the JNK pathway of inflammation.

Pharmacological Induction of Hsp72, JNK Phosphorylationand Insulin Resistance

Given the significance of the presented findings, it is important from a therapeuticpoint of view to determine ways in which Hsp72 can be induced. In this regard,hydroxylamine derivatives are thought to stimulate HSP expression by prolong-ing activation of HSF1 (Hargitai et al. 2003) and alteration of membrane lipidmicrodomains (Vigh et al. 2007). Therefore, the therapeutic value of the hydroxy-lamine derivative, BGP-15 was determined in a well-known model of obesity anddiabetes, the ob/ob mice. Mice treated with BGP-15 by oral gavage demonstrateda significant increase in intramuscular Hsp72 compared with mice receiving con-trol treatment (saline). In keeping with numerous previous findings, the increasedHsp72 expression was associated with decreased activation of JNK phosphoryla-tion. Furthermore, BGP-15 treated mice presented with improved fasting glucose andinsulin concentrations than control mice and a hyperinsulinemic euglycaemic clamprevealed markedly improved glucose disposal rate in the pharmacologically treatedmice. These data demonstrate that BGP-15 is able to induce heightened expressionof Hsp72 in genetic models of obesity and that this increased protection is associatedwith improved glycaemia and insulin signalling via suppression of JNK activation.

HSP72, Mitochondria and Insulin Resistance

Hsp72 is known to protect cardiac muscle against mitochondrial damage caused byischemia reperfusion injury (Suzuki et al. 2002). In addition, heat therapy increasesboth mitochondrial enzyme activity and exercise endurance capacity in rats (Chenet al. 1999). Interestingly, a significant positive correlation between the mRNAexpression of Hsp72 and mitochondrial enzyme activity has been observed in human


skeletal muscle (Bruce et al. 2003). It is important to note that in our recent study(Chung et al. 2008), we observed smaller fat pads in HSP72+/+ mice compared withWT mice, even though the daily food intake was the same when comparing strains.This prompted us to examine the oxidative capacity in skeletal muscle of WT andHSP72+/+ mice by measuring the maximal activities of two important mitochondrialenzymes, citrate synthase (CS) and β-hydroxyacyl-CoA-dehydrogenase (β-HAD).Interestingly, the maximal activities of these enzymes was higher in HSP72+/+ com-pared with WT mice. These data may suggest that Hsp72 increases the fatty acidoxidative capacity in skeletal muscle, which may account for the protection againstincreases in body weight and resultant insulin resistance.

To summarise, these data collectively imply Hsp72 as a potential target for thetreatment of obesity induced insulin resistance. Regardless of the method used tooverexpress Hsp72, heat treatment, genetic and pharmacological manipulation ofthis protein resulted in improved measures of insulin sensitivity in both high fatdiet and genetic models of obesity. Furthermore, these improvements appeared to betightly linked with a reduction in JNK phosphorylation. Therefore, it appears likelythat Hsp72 may act to limit inflammatory kinase disruption of insulin signalling.Pharmacological induction of Hsp72 may therefore provide an attractive avenue forinsulin resistance treatment in obese individuals (Fig. 1.).

IncreasedFatty Acids

Elevated LipidIntermediates

InflammatoryCytokines

IRS-1

Serine Kinase Activation

(JNK and IKK- β)

HSF-1

NF-κB HSF-1

Serine phosphorylation

TNF-α, IL-1β, IL-6

HSP72

X

Insulin Action

Figure 1. Schematic showing the interaction between inflammation, HSP regulation and insulin action.Bold arrows indicate pathway activation. Blocked lines indicate impaired signalling. Stress kinases areproposed to phosphorylate HSF-1 on specific serine residues preventing HSF-1 nuclear translocation (X)thus rendering HSF-1 transcriptionally silent. Increased HSF-1 activation and transcriptional competencyleading to increased cellular Hsp72 levels strongly correlate with insulin sensitivity

HSP and diabetes 13

HSP, JNK, & β CELL APOPTOSIS

Both type I and overt type 2 diabetes are essentially characterised by pancreatic β

cell destruction or failure. For example, in non-obese diabetic mice (NOD), whichquickly develop type I diabetes, apoptotic destruction of pancreatic cells is criticalstep in the development of the disease (Lee et al. 2004). To a lesser extent, reductionof β cell mass is also an issue in overt type II diabetes. Inadequate β cells may lead tothe onset of diabetes in patients that have increased demand for insulin (e.g., obeseand insulin resistant individuals) (Zhao et al. 2008). Interestingly, in Otsuka Long-Evans Tokushima Fatty (OLETF) rats that are often used as a model of obesity andtype II diabetes, the rate of β cell apoptosis was significantly increased versus con-trol rats (Zhao et al. 2008). While overall β cell mass increased, insulin signallingin these cells was impaired, suggesting that increased cell mass was a compen-satory mechanism for overall β cell incompetence and peripheral insulin resistance.Interestingly, heat-induced apoptosis is correlated with activation of the SAPK/JNKpathway (Mosser et al. 1997), and cell death mediated by the sphingomyelin path-way can be prevented via inhibition of JNK (Verheij et al. 1996). Given the data thatsuggest HSP are able to disrupt the inflammatory kinases such as JNK (Gabai et al.1997), treatments that improve HSP expression may help prevent β cell apoptosisin diabetes. Indeed, overexpression of Hsp72 in renal cells (Meldrum et al. 2003), Tlymphocytes (Mosser et al. 1997) and sympathetic neurones (Bienemann et al. 2008)protects against apoptosis induced by ischemia, heat and growth factor withdrawal.

HEAT SHOCK PROTEINS AND THE “STRESS” OF DIABETES

That essential cells might be vulnerable in diabetes is another potential therapeuticavenue for HSP. For example, islet cells taken from the autoimmune diabetes-pronebiobreeding (BB) rat show an increased vulnerability to oxidative stress, an alterationthat can be limited by prior heat conditioning (Bellmann et al. 1997). Indeed, the heatshock protein response is a key aspect of cellular defence and therefore HSP expres-sion might be important when attempting to deal with the “stress” of overt diabetes.For example, experimental induction of type I diabetes via streptozotocin treatmentdecreased Hsp60 expression in the myocardium of rats (Chen et al. 2005). Indeed,this decrease in HSP expression and cellular protection may well be an underly-ing mechanism behind diabetic cardiomyopathy (Shan et al. 2003). Reductions inHsp72 have also been observed in liver and skeletal muscles from experimentallyinduced diabetic rats (Atalay et al. 2004). Interestingly, the decreases in HSP expres-sion associated with diabetes can be offset by endurance exercise (Atalay et al. 2004)and antioxidant supplementation (Oksala et al. 2006). Given that similar decreases inHSP expression have been observed in human diabetes patients (Bruce et al. 2003),the maintenance of HSP expression in diabetes might be a further aspect of theacknowledged benefit of exercise on insulin resistance (Hawley 2004) and diabetes(Ostergard et al. 2007).


HSP AND AUTOIMMUNITY OF TYPE I DIABETES

The drop in insulin production associated with type I diabetes is essentially broughtabout by an autoimmune event that culminates in the destruction of the pancreaticislet β cells (Bach 1994). Interestingly, heat shock proteins have been mentioned asone of the potential antigens to which the autoimmunity develops. For example, ina mouse model of spontaneous autoimmune diabetes (NOD mice), the onset of β

cell destruction was associated with anti-Hsp60 immunity (Elias et al. 1990) and Tcell clones that recognise Hsp60 are able to transfer the development of insulinitisand hyperglycaemia in young prediabetic NOD mice (Elias et al. 1990). Identifyingthe target antigens that induce the autoimmune event is important in order to trycombating the development of β cell destruction through immunotherapy. Indeed,vaccination with Hsp60 and an associated peptide, p277, has been successful in pre-venting spontaneous diabetes in NOD mice (Birk et al. 1996; Elias et al. 1991) andstreptozotocin treated animals (Elias et al. 1994; Szebeni et al. 2008). It is thoughtthat this immunotherapy might be utilised to alter the balance of immunity awayfrom the Th1 pathogenic autoimmune response and toward a protective Th2 antibodyresponse. Significantly, newly diagnosed child and adult patients with type I diabetes,also show a similar heightened autoimmunity to Hsp60, Hsp70 and p277 (Abulafia-Lapid et al. 1999, 2003). Although it should be acknowledged that the autoimmuneevent predisposing diabetes is asymptomatic, manipulation of HSP autoimmunitymay provide future treatment avenues for diabetes. Indeed, Raz et al. have demon-strated improved preservation of β cell function in type I diabetes patients receivingregular doses of p277 derived from Hsp60 (Raz et al. 2001, 2007). Furthermorepatients receiving p277 used 20% less insulin than non treated controls and thetreatment caused no ill side effects. While it should be noted that the benefits ofthis treatment required constant doses, these data suggest that alteration of HSPauto-immunity has treatment potential in type 1 diabetes.

CONCLUSION

Diabetes and obesity are of a major public health concern. We have summarisedhere some of the currently known pathways through which obesity leads to insulinresistance and diabetes. While these mechanisms are clearly complex, current datasuggests that HSP have the potential to alter obesity induced insulin resistance(Chung et al. 2008). HSP are also thought to be targets in autoimmune type I dia-betes and an alteration of this autoimmune response can lead to improved clinicalsymptoms (Raz et al. 2007).

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