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Janssens JV, Raaijmakers AJA, Koutsifeli P, Weeks KL, Bell JR, Van Eyk JE, Curl CL, Mellor KM, Delbridge LMD. Mechanical loading reveals an intrinsic cardiomyocyte stiffness contribution to diastolic dysfunction in murine cardiometabolic disease. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.21.581448. [PMID: 38659933 PMCID: PMC11042179 DOI: 10.1101/2024.02.21.581448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Cardiometabolic syndromes including diabetes and obesity are associated with occurrence of heart failure with diastolic dysfunction. There are no specific treatments for diastolic dysfunction and therapies to manage symptoms have limited efficacy. Understanding of the cardiomyocyte origins of diastolic dysfunction is an important priority to identify new therapeutics. The investigative goal was to experimentally define in vitro stiffness (stress/strain) properties of isolated cardiomyocytes derived from rodent hearts exhibiting diastolic dysfunction in vivo in response to dietary induction of cardiometabolic disease. Mice fed a High Fat/Sugar Diet (HFSD vs control) for at least 25 weeks exhibited glucose intolerance, obesity and diastolic dysfunction (echo E/e'). Intact paced cardiomyocytes were functionally investigated in three conditions: non-loaded, loaded and stretched. Mean stiffness of HFSD cardiomyocytes was 70% higher than control. The E/e' doppler ratio for the origin hearts was elevated by 35%. A significant relationship was identified between in vitro cardiomyocyte stiffness and in vivo dysfunction severity. With conversion from non-loaded to loaded condition, the decrement in maximal sarcomere lengthening rate was more accentuated in HFSD cardiomyocytes (vs control). With stretch, the Ca 2+ transient decay time course was prolonged. With transition from 2-4Hz pacing, HFSD cardiomyocyte stiffness was further increased, yet diastolic Ca 2+ rise was 50% less than control. Collectively, these findings demonstrate that a component of cardiac diastolic dysfunction in cardiometabolic disease is derived from intrinsic cardiomyocyte mechanical abnormality. Differential responses to load, stretch and pacing suggest that a previously undescribed alteration in myofilament-Ca 2+ interaction contributes to cardiomyocyte stiffness in cardiometabolic disease. KEY POINTS Understanding cardiomyocyte stiffness components is an important priority for identifying new therapeutics for diastolic dysfunction, a key feature of cardiometabolic disease. In this study cardiac function was measured in vivo (echocardiography) for mice fed a high-fat/sugar diet (HFSD, ≥25weeks) and performance of intact isolated cardiomyocytes derived from the same hearts was measured during pacing under non-loaded, loaded and stretched conditions in vitro . Using a calibrated cardiomyocyte stretch protocol, stiffness (stress/strain) was elevated in HFSD cardiomyocytes in vitro and correlated with diastolic dysfunction (E/e') in vivo . The HFSD cardiomyocyte Ca 2+ transient decay was prolonged in response to stretch, and stiffness was accentuated in response to pacing increase while the rise in diastolic Ca 2+ was attenuated. These findings suggest that stretch-dependent augmentation of the myofilament-Ca 2+ response during diastole partially underlies elevated cardiomyocyte stiffness and diastolic dysfunction of hearts of animals with cardiometabolic disease.
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2
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Siddiqui SH, Rossi NF. Acute Intake of Fructose Increases Arterial Pressure in Humans: A Meta-Analysis and Systematic Review. Nutrients 2024; 16:219. [PMID: 38257112 PMCID: PMC10818414 DOI: 10.3390/nu16020219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/08/2024] [Accepted: 01/09/2024] [Indexed: 01/24/2024] Open
Abstract
Hypertension is a major cardiac risk factor. Higher blood pressures are becoming more prevalent due to changing dietary habits. Here, we evaluated the impact on blood pressure in human subjects after acutely ingesting fructose using meta-analysis. A total of 89 studies were collected from four different electronic databases from 1 January 2008 to 1 August 2023. Of these studies, 10 were selected that fulfilled all the criteria for this meta-analysis. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and blood glucose level were analyzed using the Cohen's d analysis or standardized mean difference at a confidence interval (CI) of 95%. The SBP, DBP, and MAP showed medium effect size; HR and glucose level displayed small effect size. The standardized mean difference of normal diet groups and fructose diet groups showed a significant increase in SBP (p = 0.04, REM = 2.30), and DBP (p = 0.03, REM = 1.48) with heterogeneity of 57% and 62%, respectively. Acute fructose ingestion contributes to an increase in arterial pressure in humans. The different parameters of arterial pressure in humans correlated with each other. These findings support further rigorous investigation, retrospective of necessity, into the effect of chronic dietary of fructose in humans in order to better understand the impact on long term arterial pressure.
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Affiliation(s)
| | - Noreen F. Rossi
- Department of Physiology, Wayne State University, 540 E. Canfield Ave. Scott 5473, Detroit, MI 48201, USA;
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3
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Sukiasyan L. Fructose-Induced Alteration of the Heart and Vessels Homeostasis. Curr Probl Cardiol 2023; 48:101013. [PMID: 34637847 DOI: 10.1016/j.cpcardiol.2021.101013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 10/02/2021] [Accepted: 10/04/2021] [Indexed: 01/04/2023]
Abstract
To date, the role of uncontrolled sugar consumption in the triggering and progression of cardiovascular events is undeniable. Modern concepts offer a new hypothesis regarding the direct myocardiotoxic effects of fructose. Experimental studies have demonstrated that cardiomyocytes have a unique ability to transport and use fructose along with the expression of all components involved in fructose metabolism. The purpose of this review article is to assess and analyze the available knowledge on fructose-induced cardiotoxicity detection since understanding the pathophysiological mechanisms and pathobiochemical aspects will become the basis for the determination of a rational myocardioprotection regimen.
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Affiliation(s)
- Lilit Sukiasyan
- Yerevan State Medical University after M.Heratsi, Armenia; L. A. Orbeli Institute of Human Physiology, Armenia.
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4
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Purnama U, Castro-Guarda M, Sahoo OS, Carr CA. Modelling Diabetic Cardiomyopathy: Using Human Stem Cell-Derived Cardiomyocytes to Complement Animal Models. Metabolites 2022; 12:metabo12090832. [PMID: 36144236 PMCID: PMC9503602 DOI: 10.3390/metabo12090832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 08/28/2022] [Accepted: 08/30/2022] [Indexed: 11/24/2022] Open
Abstract
Diabetes is a global epidemic, with cardiovascular disease being the leading cause of death in diabetic patients. There is a pressing need for an in vitro model to aid understanding of the mechanisms driving diabetic heart disease, and to provide an accurate, reliable tool for drug testing. Human induced-pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have potential as a disease modelling tool. There are several factors that drive molecular changes inside cardiomyocytes contributing to diabetic cardiomyopathy, including hyperglycaemia, lipotoxicity and hyperinsulinemia. Here we discuss these factors and how they can be seen in animal models and utilised in cell culture to mimic the diabetic heart. The use of human iPSC-CMs will allow for a greater understanding of disease pathogenesis and open up new avenues for drug testing.
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Affiliation(s)
- Ujang Purnama
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
| | - Marcos Castro-Guarda
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
| | - Om Saswat Sahoo
- Department of Biotechnology, National Institute of Technology Durgapur, Durgapur 713216, India
| | - Carolyn A. Carr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
- Correspondence: ; Tel.: +44-1865-282247
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5
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Prakoso D, De Blasio MJ, Tate M, Ritchie RH. Current landscape of preclinical models of diabetic cardiomyopathy. Trends Pharmacol Sci 2022; 43:940-956. [PMID: 35779966 DOI: 10.1016/j.tips.2022.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 04/04/2022] [Accepted: 04/11/2022] [Indexed: 12/01/2022]
Abstract
Patients with diabetes have an increased risk of developing heart failure, preceded by (often asymptomatic) cardiac abnormalities, collectively called diabetic cardiomyopathy (DC). Diabetic heart failure lacks effective treatment, remaining an urgent, unmet clinical need. Although structural and functional characteristics of the diabetic human heart are well defined, clinical studies lack the ability to pinpoint the specific mechanisms responsible for DC. Preclinical animal models represent a vital component for understanding disease aetiology, which is essential for the discovery of new targeted treatments for diabetes-induced heart failure. In this review, we describe the current landscape of preclinical DC models (genetic, pharmacologically induced, and diet-induced models), highlighting their strengths and weaknesses and alignment to features of the human disease. Finally, we provide tools, resources, and recommendations to assist future preclinical translation addressing this knowledge gap.
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Affiliation(s)
- Darnel Prakoso
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Miles J De Blasio
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; Department of Pharmacology, Monash University, Clayton, VIC 3800, Australia
| | - Mitchel Tate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Rebecca H Ritchie
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia; Department of Pharmacology, Monash University, Clayton, VIC 3800, Australia; Department of Diabetes, Monash University, Clayton, VIC 3800, Australia.
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6
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Heather LC, Hafstad AD, Halade GV, Harmancey R, Mellor KM, Mishra PK, Mulvihill EE, Nabben M, Nakamura M, Rider OJ, Ruiz M, Wende AR, Ussher JR. Guidelines on Models of Diabetic Heart Disease. Am J Physiol Heart Circ Physiol 2022; 323:H176-H200. [PMID: 35657616 PMCID: PMC9273269 DOI: 10.1152/ajpheart.00058.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Diabetes is a major risk factor for cardiovascular diseases, including diabetic cardiomyopathy, atherosclerosis, myocardial infarction, and heart failure. As cardiovascular disease represents the number one cause of death in people with diabetes, there has been a major emphasis on understanding the mechanisms by which diabetes promotes cardiovascular disease, and how antidiabetic therapies impact diabetic heart disease. With a wide array of models to study diabetes (both type 1 and type 2), the field has made major progress in answering these questions. However, each model has its own inherent limitations. Therefore, the purpose of this guidelines document is to provide the field with information on which aspects of cardiovascular disease in the human diabetic population are most accurately reproduced by the available models. This review aims to emphasize the advantages and disadvantages of each model, and to highlight the practical challenges and technical considerations involved. We will review the preclinical animal models of diabetes (based on their method of induction), appraise models of diabetes-related atherosclerosis and heart failure, and discuss in vitro models of diabetic heart disease. These guidelines will allow researchers to select the appropriate model of diabetic heart disease, depending on the specific research question being addressed.
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Affiliation(s)
- Lisa C Heather
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Anne D Hafstad
- Department of Medical Biology, Faculty of Health Sciences, UiT-The Arctic University of Norway, Tromsø, Norway
| | - Ganesh V Halade
- Department of Medicine, The University of Alabama at Birmingham, Tampa, Florida, United States
| | - Romain Harmancey
- Department of Internal Medicine, Division of Cardiology, McGovern Medical School at The University of Texas Health Science Center at Houston, Houston, TX, United States
| | | | - Paras K Mishra
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Erin E Mulvihill
- University of Ottawa Heart Institute, Ottawa, ON, Canada.,Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada
| | - Miranda Nabben
- Departments of Genetics and Cell Biology, and Clinical Genetics, Maastricht University Medical Center, CARIM School of Cardiovascular Diseases, Maastricht, the Netherlands
| | - Michinari Nakamura
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Oliver J Rider
- University of Oxford Centre for Clinical Magnetic Resonance Research, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Matthieu Ruiz
- Montreal Heart Institute, Montreal, Quebec, Canada.,Department of Nutrition, Université de Montréal, Montreal, Quebec, Canada
| | - Adam R Wende
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, United States
| | - John R Ussher
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada.,Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.,Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada
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7
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Greenman AC, Diffee GM, Power AS, Wilkins GT, Gold OMS, Erickson JR, Baldi JC. Increased myofilament calcium sensitivity is associated with decreased cardiac troponin I phosphorylation in the diabetic rat heart. Exp Physiol 2021; 106:2235-2247. [PMID: 34605091 DOI: 10.1113/ep089730] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 09/23/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? In Zucker Diabetic Fatty rats, does cardiomyocyte myofilament function change through the time course of diabetes and what are the mechanisms behind alterations in calcium sensitivity? What is the main finding and its importance? Zucker Diabetic Fatty rats had increased myofilament calcium sensitivity and reduced phosphorylation at cardiac troponin I without differential O-GlcNAcylation. ABSTRACT The diabetic heart has impaired systolic and diastolic function independent of other comorbidities. The availability of calcium is altered, but does not fully explain the cardiac dysfunction seen in the diabetic heart. Thus, we explored if myofilament calcium regulation of contraction is altered while also categorizing the levels of phosphorylation and O-GlcNAcylation in the myofilaments. Calcium sensitivity (pCa50 ) was measured in Zucker Diabetic Fatty (ZDF) rat hearts at the initial stage of diabetes (12 weeks old) and after 8 weeks of uncontrolled hyperglycaemia (20 weeks old) and in non-diabetic (nDM) littermates. Skinned cardiomyocytes were connected to a capacitance-gauge transducer and a torque motor to measure force as a function of pCa (-log[Ca2+ ]). Fluorescent gel stain (ProQ Diamond) was used to measure total protein phosphorylation. Specific phospho-sites on cardiac troponin I (cTnI) and total cTnI O-GlcNAcylation were quantified using immunoblot. pCa50 was greater in both 12- and 20-week-old diabetic (DM) rats compared to nDM littermates (P = 0.0001). Total cTnI and cTnI serine 23/24 phosphorylation were lower in DM rats (P = 0.003 and P = 0.01, respectively), but cTnI O-GlcNAc protein expression was not different. pCa50 is greater in DM rats and corresponds with an overall reduction in cTnI phosphorylation. These findings indicate that myofilament calcium sensitivity is increased and cTnI phosphorylation is reduced in ZDF DM rats and suggests an important role for cTnI phosphorylation in the DM heart.
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Affiliation(s)
- Angela C Greenman
- Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand.,Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Gary M Diffee
- Department of Kinesiology, University of Wisconsin-Madison, Madison, WI, USA
| | - Amelia S Power
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Gerard T Wilkins
- Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Olivia M S Gold
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - Jeffrey R Erickson
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
| | - James C Baldi
- Department of Medicine, Otago Medical School, University of Otago, Dunedin, New Zealand.,HeartOtago, University of Otago, Dunedin, New Zealand
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8
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Annandale M, Daniels LJ, Li X, Neale JPH, Chau AHL, Ambalawanar HA, James SL, Koutsifeli P, Delbridge LMD, Mellor KM. Fructose Metabolism and Cardiac Metabolic Stress. Front Pharmacol 2021; 12:695486. [PMID: 34267663 PMCID: PMC8277231 DOI: 10.3389/fphar.2021.695486] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022] Open
Abstract
Cardiovascular disease is one of the leading causes of mortality in diabetes. High fructose consumption has been linked with the development of diabetes and cardiovascular disease. Serum and cardiac tissue fructose levels are elevated in diabetic patients, and cardiac production of fructose via the intracellular polyol pathway is upregulated. The question of whether direct myocardial fructose exposure and upregulated fructose metabolism have potential to induce cardiac fructose toxicity in metabolic stress settings arises. Unlike tightly-regulated glucose metabolism, fructose bypasses the rate-limiting glycolytic enzyme, phosphofructokinase, and proceeds through glycolysis in an unregulated manner. In vivo rodent studies have shown that high dietary fructose induces cardiac metabolic stress and functional disturbance. In vitro, studies have demonstrated that cardiomyocytes cultured in high fructose exhibit lipid accumulation, inflammation, hypertrophy and low viability. Intracellular fructose mediates post-translational modification of proteins, and this activity provides an important mechanistic pathway for fructose-related cardiomyocyte signaling and functional effect. Additionally, fructose has been shown to provide a fuel source for the stressed myocardium. Elucidating the mechanisms of fructose toxicity in the heart may have important implications for understanding cardiac pathology in metabolic stress settings.
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Affiliation(s)
- M Annandale
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - L J Daniels
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - X Li
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - J P H Neale
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - A H L Chau
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - H A Ambalawanar
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - S L James
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - P Koutsifeli
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - L M D Delbridge
- Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, VIC, Australia
| | - K M Mellor
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,Department of Physiology, School of Biomedical Sciences, University of Melbourne, Melbourne, VIC, Australia
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9
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Daniels LJ, Annandale M, Koutsifeli P, Li X, Bussey CT, van Hout I, Bunton RW, Davis PJ, Coffey S, Katare R, Lamberts RR, Delbridge LMD, Mellor KM. Elevated myocardial fructose and sorbitol levels are associated with diastolic dysfunction in diabetic patients, and cardiomyocyte lipid inclusions in vitro. Nutr Diabetes 2021; 11:8. [PMID: 33558456 PMCID: PMC7870957 DOI: 10.1038/s41387-021-00150-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 01/05/2021] [Accepted: 01/13/2021] [Indexed: 12/22/2022] Open
Abstract
Diabetes is associated with cardiac metabolic disturbances and increased heart failure risk. Plasma fructose levels are elevated in diabetic patients. A direct role for fructose involvement in diabetic heart pathology has not been investigated. The goals of this study were to clinically evaluate links between myocardial fructose and sorbitol (a polyol pathway fructose precursor) levels with evidence of cardiac dysfunction, and to experimentally assess the cardiomyocyte mechanisms involved in mediating the metabolic effects of elevated fructose. Fructose and sorbitol levels were increased in right atrial appendage tissues of type 2 diabetic patients (2.8- and 1.5-fold increase respectively). Elevated cardiac fructose levels were confirmed in type 2 diabetic rats. Diastolic dysfunction (increased E/e’, echocardiography) was significantly correlated with cardiac sorbitol levels. Elevated myocardial mRNA expression of the fructose-specific transporter, Glut5 (43% increase), and the key fructose-metabolizing enzyme, Fructokinase-A (50% increase) was observed in type 2 diabetic rats (Zucker diabetic fatty rat). In neonatal rat ventricular myocytes, fructose increased glycolytic capacity and cytosolic lipid inclusions (28% increase in lipid droplets/cell). This study provides the first evidence that elevated myocardial fructose and sorbitol are associated with diastolic dysfunction in diabetic patients. Experimental evidence suggests that fructose promotes the formation of cardiomyocyte cytosolic lipid inclusions, and may contribute to lipotoxicity in the diabetic heart.
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Affiliation(s)
- Lorna J Daniels
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Marco Annandale
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Parisa Koutsifeli
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Xun Li
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Carol T Bussey
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Isabelle van Hout
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Richard W Bunton
- Department of Cardiothoracic Surgery, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Philip J Davis
- Department of Cardiothoracic Surgery, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Sean Coffey
- Department of Medicine and HeartOtago, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Rajesh Katare
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Regis R Lamberts
- Department of Physiology, HeartOtago, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Lea M D Delbridge
- Department of Physiology, University of Melbourne, Melbourne, Australia
| | - Kimberley M Mellor
- Department of Physiology, University of Auckland, Auckland, New Zealand. .,Department of Physiology, University of Melbourne, Melbourne, Australia. .,Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
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10
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Olaniyi KS, Olatunji LA. Preventive effects of l-glutamine on gestational fructose-induced cardiac hypertrophy: involvement of pyruvate dehydrogenase kinase-4. Appl Physiol Nutr Metab 2019; 44:1345-1354. [PMID: 31082323 DOI: 10.1139/apnm-2018-0754] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Gestational fructose exposure has detrimental health consequences on both the maternal and fetus or offspring in the early or later life, contributing to epidemic rise in cardiometabolic syndrome including cardiac events. l-Glutamine has been shown to mitigate cardiac metabolic stress. However, the effect of l-glutamine on cardiac hypertrophy induced by gestational fructose exposure is not known. We therefore hypothesized that l-glutamine would prevent gestational fructose-induced cardiac hypertrophy, possibly by suppression of pyruvate dehydrogenase kinase-4 (PDK-4). Pregnant Wistar rats were allotted into the control, l-glutamine, gestational fructose exposure, and gestational fructose exposure plus l-glutamine groups (6 rats in each group). The groups received distilled water (vehicle, per os), 1 g/kg body weight l-glutamine (per os), 10% fructose (w/v) and 10% fructose (w/v) plus 1 g/kg l-glutamine (per os), respectively, daily for 19 days. Data from this study showed that gestational fructose-enriched drink caused cardiac hypertrophy with correspondent body weight gain, glucose dysregulation, increased cardiac PDK-4, triglyceride, glycogen, lactate, and uric acid production. On the other hand, defective glutathione-dependent antioxidant barrier was also observed in pregnant rats taking fructose-enriched drink. However, the gestational fructose-induced cardiac hypertrophy and its correlates were attenuated by l-glutamine. The present results demonstrate that gestational fructose-enriched drink induces cardiac hypertrophy that is accompanied by increased PDK-4. The findings also suggest that the inhibitory effect of l-glutamine on PDK-4 prevents the development of cardiac hypertrophy, thereby implying that PDK-4 may be a potential novel therapeutic intervention for cardiac hypertrophy especially in pregnancy.
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Affiliation(s)
- Kehinde Samuel Olaniyi
- HOPE Cardiometabolic Research Team and Department of Physiology, College of Health Sciences, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria.,Department of Physiology, College of Medicine and Health Sciences, Afe Babalola University, Ado-Ekiti, Nigeria
| | - Lawrence Aderemi Olatunji
- HOPE Cardiometabolic Research Team and Department of Physiology, College of Health Sciences, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria
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11
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Cardiac molecular pathways influenced by doxorubicin treatment in mice. Sci Rep 2019; 9:2514. [PMID: 30792528 PMCID: PMC6385261 DOI: 10.1038/s41598-019-38986-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 01/14/2019] [Indexed: 11/08/2022] Open
Abstract
Doxorubicin (DOX) is a potent chemotherapeutic with distinct cardiotoxic properties. Understanding the underlying cardiotoxic mechanisms on a molecular level would enable the early detection of cardiotoxicity and implementation of prophylactic treatment. Our goal was to map the patterns of different radiopharmaceuticals as surrogate markers of specific metabolic pathways induced by chemotherapy. Therefore, cardiac distribution of 99mTc-sestamibi, 99mTc-Annexin V, 99mTc-glucaric acid and [18F]FDG and cardiac expression of Bcl-2, caspase-3 and -8, TUNEL, HIF-1α, and p53 were assessed in response to DOX exposure in mice. A total of 80 mice (64 treated, 16 controls) were evaluated. All radiopharmaceuticals showed significantly increased uptake compared to controls, with peak cardiac uptake after one (99mTc-Annexin V), two (99mTc-sestamibi), three ([18F]FDG), or four (99mTc-glucaric acid) cycles of DOX. Strong correlations (p < 0.01) were observed between 99mTc-Annexin V, caspase 3 and 8, and TUNEL, and between [18F]FDG and HIF-1α. This suggests that the cardiac DOX response starts with apoptosis at low exposure levels, as indicated by 99mTc-Annexin V and histological apoptosis markers. Late process membrane disintegration can possibly be detected by 99mTc-sestamibi and 99mTc-glucaric acid. [18F]FDG signifies an early adaptive response to DOX, which can be further exploited clinically in the near future.
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12
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Molecular mechanisms of cardiac pathology in diabetes - Experimental insights. Biochim Biophys Acta Mol Basis Dis 2017; 1864:1949-1959. [PMID: 29109032 DOI: 10.1016/j.bbadis.2017.10.035] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/09/2017] [Accepted: 10/27/2017] [Indexed: 12/11/2022]
Abstract
Diabetic cardiomyopathy is a distinct pathology independent of co-morbidities such as coronary artery disease and hypertension. Diminished glucose uptake due to impaired insulin signaling and decreased expression of glucose transporters is associated with a shift towards increased reliance on fatty acid oxidation and reduced cardiac efficiency in diabetic hearts. The cardiac metabolic profile in diabetes is influenced by disturbances in circulating glucose, insulin and fatty acids, and alterations in cardiomyocyte signaling. In this review, we focus on recent preclinical advances in understanding the molecular mechanisms of diabetic cardiomyopathy. Genetic manipulation of cardiomyocyte insulin signaling intermediates has demonstrated that partial cardiac functional rescue can be achieved by upregulation of the insulin signaling pathway in diabetic hearts. Inconsistent findings have been reported relating to the role of cardiac AMPK and β-adrenergic signaling in diabetes, and systemic administration of agents targeting these pathways appear to elicit some cardiac benefit, but whether these effects are related to direct cardiac actions is uncertain. Overload of cardiomyocyte fuel storage is evident in the diabetic heart, with accumulation of glycogen and lipid droplets. Cardiac metabolic dysregulation in diabetes has been linked with oxidative stress and autophagy disturbance, which may lead to cell death induction, fibrotic 'backfill' and cardiac dysfunction. This review examines the weight of evidence relating to the molecular mechanisms of diabetic cardiomyopathy, with a particular focus on metabolic and signaling pathways. Areas of uncertainty in the field are highlighted and important knowledge gaps for further investigation are identified. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.
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de Oliveira Sá G, dos Santos Neves V, de Oliveira Fraga SR, Souza-Mello V, Barbosa-da-Silva S. High-intensity interval training has beneficial effects on cardiac remodeling through local renin-angiotensin system modulation in mice fed high-fat or high-fructose diets. Life Sci 2017; 189:8-17. [DOI: 10.1016/j.lfs.2017.09.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 08/30/2017] [Accepted: 09/07/2017] [Indexed: 12/14/2022]
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Bundalo M, Romic S, Tepavcevic S, Stojiljkovic M, Stankovic A, Zivkovic M, Koricanac G. Fructose-rich diet and insulin action in female rat heart: Estradiol friend or foe? Eur J Pharmacol 2017; 811:141-147. [PMID: 28601616 DOI: 10.1016/j.ejphar.2017.06.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 05/26/2017] [Accepted: 06/06/2017] [Indexed: 01/01/2023]
Abstract
Increased intake of fructose in humans and laboratory animals is demonstrated to be a risk factor for development of metabolic disorders (insulin resistance, metabolic syndrome, type 2 diabetes) and cardiovascular diseases. On the other hand, estradiol is emphasized as a cardioprotective agent. The main goal of this review is to summarize recent findings on damaging cardiac effects of fructose-rich diet in females, mostly experimental animals, and to evaluate protective capacity of estradiol. Published results of our and other research groups indicate mostly detrimental effects of fructose-rich diet on cardiac insulin signaling molecules, glucose and fatty acid metabolism, nitric oxide production and ion transport, as well as renin-angiotensin system and inflammation. Some of these processes are involved in cardiac insulin signal transmission, others are regulated by insulin or have an influence on insulin action. Administration of estradiol to ovariectomized female rats, exposed to increased intake of fructose, was mostly beneficial to the heart, but sometimes it was ineffective or even detrimental, depending on the particular processes. We believe that these data, carefully translated to human population, could be useful for clinicians dealing with postmenopausal women susceptible to metabolic diseases and hormone replacement therapy.
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Affiliation(s)
- Maja Bundalo
- Laboratory for Radiobiology and Molecular Genetics, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
| | - Snjezana Romic
- Laboratory for Molecular Biology and Endocrinology, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
| | - Snezana Tepavcevic
- Laboratory for Molecular Biology and Endocrinology, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
| | - Mojca Stojiljkovic
- Laboratory for Molecular Biology and Endocrinology, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
| | - Aleksandra Stankovic
- Laboratory for Radiobiology and Molecular Genetics, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
| | - Maja Zivkovic
- Laboratory for Radiobiology and Molecular Genetics, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia
| | - Goran Koricanac
- Laboratory for Molecular Biology and Endocrinology, Vinca Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
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Maarman GJ, Mendham AE, Lamont K, George C. Review of a causal role of fructose-containing sugars in myocardial susceptibility to ischemia/reperfusion injury. Nutr Res 2017. [PMID: 28633867 DOI: 10.1016/j.nutres.2017.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In 2012, the World Health Organization Global Status Report on noncommunicable diseases showed that 7.4 million deaths were due to ischemic heart disease. Consequently, cardiovascular disease is a significant health burden, especially when partnered with comorbidities such as obesity, metabolic syndrome, and type 2 diabetes mellitus. Of note, these diseases can all be induced or exacerbated by diet. Carbohydrates, in particular, fructose and glucose, generally form the largest part of the human diet. Accumulating evidence from animal studies suggests that if large amounts of fructose are consumed either in isolation or in combination with glucose (fructose-containing sugars), myocardial susceptibility to ischemia/reperfusion (I/R) injury increases. However, the underlying mechanisms that predisposes the myocardium to I/R injury in the fructose model are not elucidated, and no single mechanistic pathway has been described. Based on all available data on this topic, this review describes previously investigated mechanisms and highlights 3 main mechanistic pathways whereby fructose has shown to increase myocardial susceptibility to I/R injury. These pathways include (1) increased reactive oxygen species, resulting in reduced nitric oxide synthase and coronary flow; (2) elevated plasma fatty acids and insulin, leading to increased cardiac triglyceride content and lipotoxicity; and (3) disrupted myocardial calcium handling/homeostasis. Moreover, we highlight various factors that should be taken into account when the fructose animal model is used, such as rat strain, treatment periods, and doses. We argue that failure to do so would result in erratic inferences drawn from the existing body of evidence on fructose animal models.
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Affiliation(s)
- Gerald J Maarman
- Division of Exercise Science and Sports Medicine (ESSM), Department of Human Biology, University of Cape Town, PO Box 115, 7725, Cape Town, South Africa.
| | - Amy E Mendham
- Division of Exercise Science and Sports Medicine (ESSM), Department of Human Biology, University of Cape Town, PO Box 115, 7725, Cape Town, South Africa.
| | - Kim Lamont
- Soweto Cardiovascular Research Unit, University of the Witwatersrand, 3Q05, 7 York Rd, Parktown, 2193, Johannesburg, South Africa.
| | - Cindy George
- Non-Communicable Diseases Research Unit, South African Medical Research Council, PO Box 19070, Tygerberg, Cape Town, South Africa.
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Liquiritigenin attenuates cardiac injury induced by high fructose-feeding through fibrosis and inflammation suppression. Biomed Pharmacother 2016; 86:694-704. [PMID: 28039849 DOI: 10.1016/j.biopha.2016.12.066] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 12/10/2016] [Accepted: 12/16/2016] [Indexed: 12/22/2022] Open
Abstract
Diabetes combined with cardiomyopathy is considered as an essential complication, showing diastolic persistently and causing cardiac injury, which is linked to fibrosis progression and inflammation response. Fibrosis and inflammation response are two markers for cardiomyopathy. Liquiritigenin is a flavanone, isolated from Radix glycyrrhiza, which exhibits various biological properties, including anti-cancer and anti-inflammatory activities. Here, in our study, the protective effects and anti-inflammatory activity of liquiritigenin were explored in mice and cardiac muscle cells treated by fructose to reveal the possible mechanism by which liquiritigenin attenuates cardiac injury. The mice were separated into five groups. The diabetic model of mouse was established with 30% high fructose feeding. Liquiritigenin dramatically reduced the lipid accumulation induced by high fructose diet. Compared to mice only treated with high fructose, mice in the presence of liquiritigenin after fructose feeding developed less cardiac fibrosis with lower levels of alpha smooth muscle-actin (α-SMA), Collagen type I, Collagen type II, TGF-β1 and Procol1a1. Additionally, liquiritigenin markedly down-regulated inflammatory cytokines secretion and phosphorylated NF-κB via inhibiting IKKα/IκBα signaling pathway. Our results indicate that liquiritigenin has a protective role in high fructose feeding-triggered cardiac injury through fibrosis and inflammation response suppression by inactivating NF-κB signaling pathway. Thus, liquiritigenin may be a potential candidate for diabetes-associated cardiac injury.
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Delbridge LMD, Benson VL, Ritchie RH, Mellor KM. Diabetic Cardiomyopathy: The Case for a Role of Fructose in Disease Etiology. Diabetes 2016; 65:3521-3528. [PMID: 27879401 DOI: 10.2337/db16-0682] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 09/09/2016] [Indexed: 11/13/2022]
Abstract
A link between excess dietary sugar and cardiac disease is clearly evident and has been largely attributed to systemic metabolic dysregulation. Now a new paradigm is emerging, and a compelling case can be made that fructose-associated heart injury may be attributed to the direct actions of fructose on cardiomyocytes. Plasma and cardiac fructose levels are elevated in patients with diabetes, and evidence suggests that some unique properties of fructose (vs. glucose) have specific cardiomyocyte consequences. Investigations to date have demonstrated that cardiomyocytes have the capacity to transport and utilize fructose and express all of the necessary proteins for fructose metabolism. When dietary fructose intake is elevated and myocardial glucose uptake compromised by insulin resistance, increased cardiomyocyte fructose flux represents a hazard involving unregulated glycolysis and oxidative stress. The high reactivity of fructose supports the contention that fructose accelerates subcellular hexose sugar-related protein modifications, such as O-GlcNAcylation and advanced glycation end product formation. Exciting recent discoveries link heart failure to induction of the specific high-affinity fructose-metabolizing enzyme, fructokinase, in an experimental setting. In this Perspective, we review key recent findings to synthesize a novel view of fructose as a cardiopathogenic agent in diabetes and to identify important knowledge gaps for urgent research focus.
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Affiliation(s)
- Lea M D Delbridge
- Department of Physiology, University of Melbourne, Victoria, Australia
| | - Vicky L Benson
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Rebecca H Ritchie
- Heart Failure Pharmacology, Baker IDI Heart and Diabetes Institute, Victoria, Australia
| | - Kimberley M Mellor
- Department of Physiology, University of Melbourne, Victoria, Australia
- Department of Physiology, University of Auckland, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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Okatan EN, Durak AT, Turan B. Electrophysiological basis of metabolic-syndrome-induced cardiac dysfunction. Can J Physiol Pharmacol 2016; 94:1064-1073. [DOI: 10.1139/cjpp-2015-0531] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Myocardial contractility is controlled by intracellular Ca2+ cycling with the contribution of sarcoplasmic reticulum (SR). In this study, we aimed to investigate the role of altered SR function in defective regulation of intracellular Ca2+ levels in rats with metabolic syndrome (MetS) induced by a 16-week high-sucrose drinking-water diet. Electric-field stimulated transient intracellular Ca2+ changes in MetS cardiomyocytes exhibited significantly reduced amplitude (∼30%) and prolonged time courses (2-fold), as well as depressed SR Ca2+ loading (∼55%) with increased basal Ca2+ level. Consistent with these data, altered ryanodine receptor (RyR2) function and SERCA2a activity were found in MetS cardiomyocytes through Ca2+ spark measurements and caffeine application assay in a state in which sodium calcium exchanger was inhibited. Furthermore, tetracaine application assay results and hyperphosphorylated level of RyR2 also support the “leaky RyR2” hypothesis. Moreover, altered phosphorylation levels of phospholamban (PLN) support the depressed SERCA2a-activity thesis and these alterations in the phosphorylation of Ca2+-handling proteins are correlated with altered protein kinase and phosphatase activity in MetS cardiomyocytes. In conclusion, MetS-rat heart exhibits altered Ca2+ signaling largely due to altered SR function via changes in RyR2 and SERCA2a activity. These results point to RyR2 and SERCA2a as potential pharmacological targets for restoring intracellular Ca2+ homeostasis and, thereby, combatting dysfunction in MetS-rat heart.
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Affiliation(s)
- Esma N. Okatan
- Department of Biophysics, Ankara University, Faculty of Medicine, 06100 Ankara, Turkey
- Department of Biophysics, Ankara University, Faculty of Medicine, 06100 Ankara, Turkey
| | - Aysegul Toy Durak
- Department of Biophysics, Ankara University, Faculty of Medicine, 06100 Ankara, Turkey
- Department of Biophysics, Ankara University, Faculty of Medicine, 06100 Ankara, Turkey
| | - Belma Turan
- Department of Biophysics, Ankara University, Faculty of Medicine, 06100 Ankara, Turkey
- Department of Biophysics, Ankara University, Faculty of Medicine, 06100 Ankara, Turkey
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Priyadarshini E, Anuradha CV. Glucocorticoid Antagonism Reduces Insulin Resistance and Associated Lipid Abnormalities in High-Fructose-Fed Mice. Can J Diabetes 2016; 41:41-51. [PMID: 27614803 DOI: 10.1016/j.jcjd.2016.06.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 06/07/2016] [Accepted: 06/13/2016] [Indexed: 01/17/2023]
Abstract
OBJECTIVES High intake of dietary fructose causes perturbation in lipid metabolism and provokes lipid-induced insulin resistance. A rise in glucocorticoids (GCs) has recently been suggested to be involved in fructose-induced insulin resistance. The objective of the study was to investigate the effect of GC blockade on lipid abnormalities in insulin-resistant mice. METHODS Insulin resistance was induced in mice by administering a high-fructose diet (HFrD) for 60 days. Mifepristone (RU486), a GC antagonist, was administered to HFrD-fed mice for the last 18 days, and the intracellular and extracellular GC levels, the glucocorticoid receptor (GR) activation and the expression of GC-regulated genes involved in lipid metabolism were examined. RESULTS HFrD elevated the intracellular GC content in both liver and adipose tissue and enhanced the GR nuclear translocation. The plasma GC level remained unchanged. The levels of free fatty acids and triglycerides in plasma were elevated, accompanied by increased plasma insulin and glucose levels and decreased hepatic glycogen content. Treatment with RU486 reduced plasma lipid levels, tissue GC levels and the expression of GC-targeted genes involved in lipid accumulation, and it improved insulin sensitivity. CONCLUSIONS This study demonstrated that HFrD-induced lipid accumulation and insulin resistance are mediated by enhanced GC in liver and adipose tissue and that GC antagonism might reduce fructose-induced lipid abnormalities and insulin resistance.
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Ip WTK, McAlindon A, Miller SE, Bell JR, Curl CL, Huggins CE, Mellor KM, Raaijmakers AJA, Bienvenu LA, McLennan PL, Pepe S, Delbridge LMD. Dietary omega-6 fatty acid replacement selectively impairs cardiac functional recovery after ischemia in female (but not male) rats. Am J Physiol Heart Circ Physiol 2016; 311:H768-80. [PMID: 27422989 DOI: 10.1152/ajpheart.00690.2015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 07/12/2016] [Indexed: 02/05/2023]
Abstract
A definitive understanding of the role of dietary lipids in determining cardioprotection (or cardiodetriment) has been elusive. Randomized trial findings have been variable and sex specificity of dietary interventions has not been determined. In this investigation the sex-selective cardiac functional effects of three diets enriched by omega-3 or omega-6 polyunsaturated fatty acids (PUFA) or enriched to an equivalent extent in saturated fatty acid components were examined in rats after an 8-wk treatment period. In females the myocardial membrane omega-6:omega-3 PUFA ratio was twofold higher than males in the omega-6 diet replacement group. In diets specified to be high in omega-3 PUFA or in saturated fat, this sex difference was not apparent. Isolated cardiomyocyte and heart Langendorff perfusion experiments were performed, and molecular measures of cell viability were assessed. Under basal conditions the contractile performance of omega-6 fed female cardiomyocytes and hearts was reduced compared with males. Omega-6 fed females exhibited impaired systolic resilience after ischemic insult. This response was associated with increased postischemia necrotic cell damage evaluated by coronary lactate dehydrogenase during reperfusion in omega-6 fed females. Cardiac and myocyte functional parameters were not different between omega-3 and saturated fat dietary groups and within these groups there were no discernible sex differences. Our data provide evidence at both the cardiac and cardiomyocyte levels that dietary saturated fatty acid intake replacement with an omega-6 (but not omega-3) enriched diet has selective adverse cardiac effect in females. This finding has potential relevance in relation to women, cardiac risk, and dietary management.
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Affiliation(s)
- Wendy T K Ip
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Andrew McAlindon
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Sarah E Miller
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - James R Bell
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Claire L Curl
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Catherine E Huggins
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Kimberley M Mellor
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Antonia J A Raaijmakers
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Laura A Bienvenu
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia
| | - Peter L McLennan
- Graduate School of Medicine, Centre for Human Applied Physiology, University of Wollongong, Wollongong, Australia; and
| | - Salvatore Pepe
- Murdoch Children's Research Institute, Department of Paediatrics, University of Melbourne, Melbourne, Australia
| | - Lea M D Delbridge
- Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Parkville, Australia;
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Bell JR, Curl CL, Harding TW, Vila Petroff M, Harrap SB, Delbridge LMD. Male and female hypertrophic rat cardiac myocyte functional responses to ischemic stress and β-adrenergic challenge are different. Biol Sex Differ 2016; 7:32. [PMID: 27390618 PMCID: PMC4936311 DOI: 10.1186/s13293-016-0084-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 06/22/2016] [Indexed: 01/19/2023] Open
Abstract
Background Cardiac hypertrophy is the most potent cardiovascular risk factor after age, and relative mortality risk linked with cardiac hypertrophy is greater in women. Ischemic heart disease is the most common form of cardiovascular pathology for both men and women, yet significant differences in incidence and outcomes exist between the sexes. Cardiac hypertrophy and ischemia are frequently occurring dual pathologies. Whether the cellular (cardiomyocyte) mechanisms underlying myocardial damage differ in women and men remains to be determined. In this study, utilizing an in vitro experimental approach, our goal was to examine the proposition that responses of male/female cardiomyocytes to ischemic (and adrenergic) stress may be differentially modulated by the presence of pre-existing cardiac hypertrophy. Methods We used a novel normotensive custom-derived hypertrophic heart rat (HHR; vs control strain normal heart rat (NHR)). Cardiomyocyte morphologic and electromechanical functional studies were performed using microfluorimetric techniques involving simulated ischemia/reperfusion protocols. Results HHR females exhibited pronounced cardiac/cardiomyocyte enlargement, equivalent to males. Under basal conditions, a lower twitch amplitude in female myocytes was prominent in normal but not in hypertrophic myocytes. The cardiomyocyte Ca2+ responses to β-adrenergic challenge differed in hypertrophic male and female cardiomyocytes, with the accentuated response in males abrogated in females—even while contractile responses were similar. In simulated ischemia, a marked and selective elevation of end-ischemia Ca2+ in normal female myocytes was completely suppressed in hypertrophic female myocytes—even though all groups demonstrated similar shifts in myocyte contractile performance. After 30 min of simulated reperfusion, the Ca2+ desensitization characterizing the male response was distinctively absent in female cardiomyocytes. Conclusions Our data demonstrate that cardiac hypertrophy produces dramatically different basal and stress-induced pathophenotypes in female- and male-origin cardiomyocytes. The lower Ca2+ operational status characteristic of female (vs male) cardiomyocytes comprising normal hearts is not exhibited by myocytes of hypertrophic hearts. After ischemia/reperfusion, availability of activator Ca2+ is suppressed in female hypertrophic myocytes, whereas sensitivity to Ca2+ is blunted in male hypertrophic myocytes. These findings demonstrate that selective intervention strategies should be pursued to optimize post-ischemic electromechanical support for male and female hypertrophic hearts. Electronic supplementary material The online version of this article (doi:10.1186/s13293-016-0084-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- James R Bell
- Department of Physiology, University of Melbourne, Melbourne, Victoria Australia
| | - Claire L Curl
- Department of Physiology, University of Melbourne, Melbourne, Victoria Australia
| | - Tristan W Harding
- Department of Physiology, University of Melbourne, Melbourne, Victoria Australia
| | - Martin Vila Petroff
- Centro de Investigaciones Cardiovasculares, Centro Cientifico Tecnologico La Plata, Facultad de Ciencias Medicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Stephen B Harrap
- Department of Physiology, University of Melbourne, Melbourne, Victoria Australia
| | - Lea M D Delbridge
- Department of Physiology, University of Melbourne, Melbourne, Victoria Australia.,Cardiac Phenomics Laboratory, Department of Physiology, University of Melbourne, Melbourne, Victoria 3010 Australia
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Mirtschink P, Krek W. Hypoxia-driven glycolytic and fructolytic metabolic programs: Pivotal to hypertrophic heart disease. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1822-8. [DOI: 10.1016/j.bbamcr.2016.02.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/28/2016] [Accepted: 02/13/2016] [Indexed: 01/21/2023]
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High fructose diet suppresses exercise-induced increase in AQP7 expression in the in vivo rat heart. Anatol J Cardiol 2016; 16:916-922. [PMID: 27182614 PMCID: PMC5324910 DOI: 10.14744/anatoljcardiol.2016.6958] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Objective: Cardiac uptake of fructose is thought to be mediated by glucose transporter 5 (GLUT5), whereas the uptake of glycerol is facilitated by aquaporin 7 (AQP7). We aimed to investigate the effect of a high-fructose diet (HFD) on GLUT5 and AQP7 levels in the rat heart subjected to exercise. Methods: Male Sprague–Dawley rats were allocated to control (C; n=11), exercise (E; n=10), HFD (n=12), and HFD plus exercise (HFD-E; n=12) groups. HFD was started 28 days before euthanasia. From day 24 to 27, rats were subjected to moderate exercise, followed by vigorous exercise on day 28 (groups E and HFD-E). Cardiac GLUT5 and AQP7 mRNA levels were determined using RT-PCR. The protein contents of GLUT5 and AQP7 were immunohistochemically assessed. Paired-t, ANOVA with Bonferroni, Kruskal–Wallis, and Bonferroni-corrected Mann–Whitney U tests were used for statistical analysis. Results: GLUT5 mRNA expression and protein content did not differ between the groups. AQP7 mRNA levels significantly increased (4.8-fold) in group E compared with in group C (p<0.001). Compared with group C, no significant change was observed in AQP7 mRNA levels in groups HFD and HFD-E. The AQP7 staining score in group E was significantly higher than that in groups C (p<0.001), E (p<0.001), and HFD-E (p<0.001). Conclusion: Our study indicates that exercise enhances cardiac AQP7 mRNA expression and protein content. However, HFD prevents the exercise-induced increase in cardiac AQP7 expression. This inhibitory effect may be related to the competition between fructose and glycerol as energy substrates in the rat heart subjected to 5 days of physical exercise. (Anatol J Cardiol 2016; 16: 916-22)
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Taegtmeyer H, Young ME, Lopaschuk GD, Abel ED, Brunengraber H, Darley-Usmar V, Des Rosiers C, Gerszten R, Glatz JF, Griffin JL, Gropler RJ, Holzhuetter HG, Kizer JR, Lewandowski ED, Malloy CR, Neubauer S, Peterson LR, Portman MA, Recchia FA, Van Eyk JE, Wang TJ. Assessing Cardiac Metabolism: A Scientific Statement From the American Heart Association. Circ Res 2016; 118:1659-701. [PMID: 27012580 DOI: 10.1161/res.0000000000000097] [Citation(s) in RCA: 185] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In a complex system of interrelated reactions, the heart converts chemical energy to mechanical energy. Energy transfer is achieved through coordinated activation of enzymes, ion channels, and contractile elements, as well as structural and membrane proteins. The heart's needs for energy are difficult to overestimate. At a time when the cardiovascular research community is discovering a plethora of new molecular methods to assess cardiac metabolism, the methods remain scattered in the literature. The present statement on "Assessing Cardiac Metabolism" seeks to provide a collective and curated resource on methods and models used to investigate established and emerging aspects of cardiac metabolism. Some of those methods are refinements of classic biochemical tools, whereas most others are recent additions from the powerful tools of molecular biology. The aim of this statement is to be useful to many and to do justice to a dynamic field of great complexity.
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Schaible N, Han YS, Hoang T, Arteaga G, Tveita T, Sieck G. Hypothermia/rewarming disrupts excitation-contraction coupling in cardiomyocytes. Am J Physiol Heart Circ Physiol 2016; 310:H1533-40. [PMID: 26993227 DOI: 10.1152/ajpheart.00840.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 03/16/2016] [Indexed: 12/25/2022]
Abstract
Hypothermia/rewarming (H/R) is poorly tolerated by the myocardium; however, the underlying intracellular basis of H/R-induced cardiac dysfunction remains elusive. We hypothesized that in cardiomyocytes, H/R disrupts excitation-contraction coupling by reducing myofilament Ca(2+) sensitivity due to an increase in cardiac troponin I (cTnI) phosphorylation. To test this hypothesis, isolated rat cardiomyocytes (13-15 cells from 6 rats per group) were electrically stimulated to evoke both cytosolic Ca(2+) ([Ca(2+)]cyto) and contractile (sarcomere shortening) responses that were simultaneously measured using an IonOptix system. Cardiomyocytes were divided into two groups: 1) those exposed to hypothermia (15°C for 2 h) followed by rewarming (35°C; H/R); or 2) time-matched normothermic (35°C) controls (CTL). Contractile dysfunction after H/R was indicated by reduced velocity and extent of sarcomere length (SL) shortening compared with time-matched controls. Throughout hypothermia, basal [Ca(2+)]cyto increased and the duration of evoked [Ca(2+)]cyto transients was prolonged. Phase-loop plots of [Ca(2+)]cyto vs. contraction were shifted rightward in cardiomyocytes during hypothermia compared with CTL, indicating a decrease in Ca(2+) sensitivity. Using Western blot, we found that H/R increases cTnI phosphorylation. These results support our overall hypothesis and suggest that H/R disrupts excitation-contraction coupling of cardiomyocytes due to increased cTnI phosphorylation and reduced Ca(2+) sensitivity.
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Affiliation(s)
- Niccole Schaible
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Young Soo Han
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Thuy Hoang
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Grace Arteaga
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
| | - Torkjel Tveita
- Departments of Anesthesiology and Physiology, University of Tromsø-The Arctic University of Norway, Tromsø, Norway
| | - Gary Sieck
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota; and
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Sommese L, Valverde CA, Blanco P, Castro MC, Rueda OV, Kaetzel M, Dedman J, Anderson ME, Mattiazzi A, Palomeque J. Ryanodine receptor phosphorylation by CaMKII promotes spontaneous Ca(2+) release events in a rodent model of early stage diabetes: The arrhythmogenic substrate. Int J Cardiol 2016; 202:394-406. [PMID: 26432489 PMCID: PMC4872299 DOI: 10.1016/j.ijcard.2015.09.022] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 08/31/2015] [Accepted: 09/19/2015] [Indexed: 12/13/2022]
Abstract
BACKGROUND Heart failure and arrhythmias occur more frequently in patients with type 2 diabetes (T2DM) than in the general population. T2DM is preceded by a prediabetic condition marked by elevated reactive oxygen species (ROS) and subclinical cardiovascular defects. Although multifunctional Ca2+ calmodulin-dependent protein kinase II (CaMKII) is ROS-activated and CaMKII hyperactivity promotes cardiac diseases, a link between prediabetes and CaMKII in the heart is unprecedented. OBJECTIVES To prove the hypothesis that increased ROS and CaMKII activity contribute to heart failure and arrhythmogenic mechanisms in early stage diabetes. METHODS-RESULTS Echocardiography, electrocardiography, biochemical and intracellular Ca2+ (Ca2+i) determinations were performed in fructose-rich diet-induced impaired glucose tolerance, a prediabetes model, in rodents. Fructose-rich diet rats showed decreased contractility and hypertrophy associated with increased CaMKII activity, ROS production, oxidized CaMKII and enhanced CaMKII-dependent ryanodine receptor (RyR2) phosphorylation compared to rats fed with control diet. Isolated cardiomyocytes from fructose-rich diet showed increased spontaneous Ca2+i release events associated with spontaneous contractions, which were prevented by KN-93, a CaMKII inhibitor, or addition of Tempol, a ROS scavenger, to the diet. Moreover, fructose-rich diet myocytes showed increased diastolic Ca2+ during the burst of spontaneous Ca2+i release events. Mice treated with Tempol or with sarcoplasmic reticulum-targeted CaMKII-inhibition by transgenic expression of the CaMKII inhibitory peptide AIP, were protected from fructose-rich diet-induced spontaneous Ca2+i release events, spontaneous contractions and arrhythmogenesis in vivo, despite ROS increases. CONCLUSIONS RyR2 phosphorylation by ROS-activated CaMKII, contributes to impaired glucose tolerance-induced arrhythmogenic mechanisms, suggesting that CaMKII inhibition could prevent prediabetic cardiovascular complications and/or evolution.
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Affiliation(s)
- Leandro Sommese
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata 1900, Facultad de Medicina, UNLP, Argentina
| | - Carlos A Valverde
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata 1900, Facultad de Medicina, UNLP, Argentina
| | - Paula Blanco
- Servicio de Ecocardiografía, Facultad de Veterinaria, UNLP, La Plata 1900, Argentina
| | - María Cecilia Castro
- CENEXA, Centro Experimental de Endocrinología y Aplicada (UNLP-CONICET La Plata), Facultad de Ciencias Médicas, UNLP, La Plata 1900, Argentina
| | - Omar Velez Rueda
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata 1900, Facultad de Medicina, UNLP, Argentina
| | - Marcia Kaetzel
- Department of Genome Science, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575, USA
| | - John Dedman
- Department of Genome Science, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575, USA
| | - Mark E Anderson
- University of Iowa, 285 Newton Rd, CBRB 2256, Iowa City, IA 52242, USA
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata 1900, Facultad de Medicina, UNLP, Argentina
| | - Julieta Palomeque
- Centro de Investigaciones Cardiovasculares, CONICET-La Plata 1900, Facultad de Medicina, UNLP, Argentina.
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Affiliation(s)
- Lea M D Delbridge
- Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
| | - Kimberley M Mellor
- Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia; Department of Physiology, University of Auckland, New Zealand
| | - Loren E Wold
- College of Nursing, The Ohio State University, Columbus, OH, USA; Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA.
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Mellor KM, Brimble MA, Delbridge LM. Glucose as an agent of post-translational modification in diabetes — New cardiac epigenetic insights. Life Sci 2015; 129:48-53. [DOI: 10.1016/j.lfs.2014.03.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 03/11/2014] [Accepted: 03/17/2014] [Indexed: 01/07/2023]
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Han J, Tan C, Wang Y, Yang S, Tan D. Betanin reduces the accumulation and cross-links of collagen in high-fructose-fed rat heart through inhibiting non-enzymatic glycation. Chem Biol Interact 2015; 227:37-44. [DOI: 10.1016/j.cbi.2014.12.032] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 12/17/2014] [Accepted: 12/19/2014] [Indexed: 10/24/2022]
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Fuentes-Antrás J, Picatoste B, Gómez-Hernández A, Egido J, Tuñón J, Lorenzo Ó. Updating experimental models of diabetic cardiomyopathy. J Diabetes Res 2015; 2015:656795. [PMID: 25973429 PMCID: PMC4417999 DOI: 10.1155/2015/656795] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 03/26/2015] [Accepted: 03/29/2015] [Indexed: 11/17/2022] Open
Abstract
Diabetic cardiomyopathy entails a serious cardiac dysfunction induced by alterations in structure and contractility of the myocardium. This pathology is initiated by changes in energy substrates and occurs in the absence of atherothrombosis, hypertension, or other cardiomyopathies. Inflammation, hypertrophy, fibrosis, steatosis, and apoptosis in the myocardium have been studied in numerous diabetic experimental models in animals, mostly rodents. Type I and type II diabetes were induced by genetic manipulation, pancreatic toxins, and fat and sweet diets, and animals recapitulate the main features of human diabetes and related cardiomyopathy. In this review we update and discuss the main experimental models of diabetic cardiomyopathy, analysing the associated metabolic, structural, and functional abnormalities, and including current tools for detection of these responses. Also, novel experimental models based on genetic modifications of specific related genes have been discussed. The study of specific pathways or factors responsible for cardiac failures may be useful to design new pharmacological strategies for diabetic patients.
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Affiliation(s)
- J. Fuentes-Antrás
- IIS-Fundación Jiménez Díaz, Autónoma University, 28040 Madrid, Spain
| | - B. Picatoste
- IIS-Fundación Jiménez Díaz, Autónoma University, 28040 Madrid, Spain
- Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM) Network, 28040 Madrid, Spain
| | - A. Gómez-Hernández
- Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM) Network, 28040 Madrid, Spain
- Biochemistry and Molecular Biology Department, School of Pharmacy, Complutense University of Madrid, 28040 Madrid, Spain
| | - J. Egido
- IIS-Fundación Jiménez Díaz, Autónoma University, 28040 Madrid, Spain
- Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM) Network, 28040 Madrid, Spain
| | - J. Tuñón
- IIS-Fundación Jiménez Díaz, Autónoma University, 28040 Madrid, Spain
| | - Ó. Lorenzo
- IIS-Fundación Jiménez Díaz, Autónoma University, 28040 Madrid, Spain
- Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM) Network, 28040 Madrid, Spain
- *Ó. Lorenzo:
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31
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Regulation of SERCA pumps expression in diabetes. Cell Calcium 2014; 56:302-10. [DOI: 10.1016/j.ceca.2014.09.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 09/11/2014] [Accepted: 09/12/2014] [Indexed: 11/22/2022]
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Mellor KM, Curl CL, Chandramouli C, Pedrazzini T, Wendt IR, Delbridge LMD. Ageing-related cardiomyocyte functional decline is sex and angiotensin II dependent. AGE (DORDRECHT, NETHERLANDS) 2014; 36:9630. [PMID: 24566994 PMCID: PMC4082583 DOI: 10.1007/s11357-014-9630-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 02/07/2014] [Indexed: 05/19/2023]
Abstract
Clinically, heart failure is an age-dependent pathological phenomenon and displays sex-specific characteristics. The renin-angiotensin system mediates cardiac pathology in heart failure. This study investigated the sexually dimorphic functional effects of ageing combined with angiotensin II (AngII) on cardiac muscle cell function, twitch and Ca(2+)-handling characteristics of isolated cardiomyocytes from young (~13 weeks) and aged (~87 weeks) adult wild type (WT) and AngII-transgenic (TG) mice. We hypothesised that AngII-induced contractile impairment would be exacerbated in aged female cardiomyocytes and linked to Ca(2+)-handling disturbances. AngII-induced cardiomyocyte hypertrophy was evident in young adult mice of both sexes and accentuated by age (aged adult ~21-23 % increases in cell length relative to WT). In female AngII-TG mice, ageing was associated with suppressed cardiomyocyte contractility (% shortening, maximum rate of shortening, maximum rate of relaxation). This was associated with delayed cytosolic Ca(2+) removal during twitch relaxation (Tau ~20 % increase relative to young adult female WT), and myofilament responsiveness to Ca(2+) was maintained. In contrast, aged AngII-TG male cardiomyocytes exhibited peak shortening equivalent to young TG; yet, myofilament Ca(2+) responsiveness was profoundly reduced with ageing. Increased pro-arrhythmogenic spontaneous activity was evident with age and cardiac AngII overexpression in male mice (42-55 % of myocytes) but relatively suppressed in female aged transgenic mice. Female myocytes with elevated AngII appear more susceptible to an age-related contractile deficit, whereas male AngII-TG myocytes preserve contractile function with age but exhibit desensitisation of myofilaments to Ca(2+) and a heightened vulnerability to arrhythmic activity. These findings support the contention that sex-specific therapies are required for the treatment of age-progressive heart failure.
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Affiliation(s)
- Kimberley M. Mellor
- />Department of Physiology, University of Melbourne, Melbourne, VIC Australia
- />Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Claire L. Curl
- />Department of Physiology, University of Melbourne, Melbourne, VIC Australia
| | | | | | - Igor R. Wendt
- />Department of Physiology, Monash University, Melbourne, VIC Australia
| | - Lea M. D. Delbridge
- />Department of Physiology, University of Melbourne, Melbourne, VIC Australia
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MacDonald JK, Pyle WG, Reitz CJ, Howlett SE. Cardiac contraction, calcium transients, and myofilament calcium sensitivity fluctuate with the estrous cycle in young adult female mice. Am J Physiol Heart Circ Physiol 2014; 306:H938-53. [DOI: 10.1152/ajpheart.00730.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
This study established conditions to induce regular estrous cycles in female C57BL/6J mice and investigated the impact of the estrous cycle on contractions, Ca2+ transients, and underlying cardiac excitation-contraction (EC)-coupling mechanisms. Daily vaginal smears from group-housed virgin female mice were stained to distinguish estrous stage (proestrus, estrus, metestrus, diestrus). Ventricular myocytes were isolated from anesthetized mice. Contractions and Ca2+ transients were measured simultaneously (4 Hz, 37°C). Interestingly, mice did not exhibit regular cycles unless they were exposed to male pheromones in bedding added to their cages. Field-stimulated myocytes from mice in estrus had larger contractions (∼2-fold increase), larger Ca2+ transients (∼1.11-fold increase), and longer action potentials (>2-fold increase) compared with other stages. Larger contractions and Ca2+ transients were not observed in estrus myocytes voltage-clamped with shorter action potentials. Voltage-clamp experiments also demonstrated that estrous stage had no effect on Ca2+ current, EC-coupling gain, diastolic Ca2+, sarcoplasmic reticulum (SR) Ca2+ content, or fractional release. Although contractions were largest in estrus, myofilament Ca2+ sensitivity was lowest (EC50 values ∼1.15-fold higher) in conjunction with increased phosphorylation of myosin binding protein C in estrus. Contractions were enhanced in ventricular myocytes from mice in estrus because action potential prolongation increased SR Ca2+ release. These findings demonstrate that cyclical changes in reproductive hormones associated with the estrous cycle can influence myocardial electrical and contractile function and modify Ca2+ homeostasis. However, such changes are unlikely to occur in female mice housed in groups under conventional conditions, since these mice do not exhibit regular estrous cycles.
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Affiliation(s)
| | - W. Glen Pyle
- Cardiovascular Research Group, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Cristine J. Reitz
- Cardiovascular Research Group, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Susan E. Howlett
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Medicine (Geriatric Medicine), Dalhousie University, Halifax, Nova Scotia, Canada
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Huynh K, Bernardo BC, McMullen JR, Ritchie RH. Diabetic cardiomyopathy: mechanisms and new treatment strategies targeting antioxidant signaling pathways. Pharmacol Ther 2014; 142:375-415. [PMID: 24462787 DOI: 10.1016/j.pharmthera.2014.01.003] [Citation(s) in RCA: 400] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 01/08/2014] [Indexed: 12/14/2022]
Abstract
Cardiovascular disease is the primary cause of morbidity and mortality among the diabetic population. Both experimental and clinical evidence suggest that diabetic subjects are predisposed to a distinct cardiomyopathy, independent of concomitant macro- and microvascular disorders. 'Diabetic cardiomyopathy' is characterized by early impairments in diastolic function, accompanied by the development of cardiomyocyte hypertrophy, myocardial fibrosis and cardiomyocyte apoptosis. The pathophysiology underlying diabetes-induced cardiac damage is complex and multifactorial, with elevated oxidative stress as a key contributor. We now review the current evidence of molecular disturbances present in the diabetic heart, and their role in the development of diabetes-induced impairments in myocardial function and structure. Our focus incorporates both the contribution of increased reactive oxygen species production and reduced antioxidant defenses to diabetic cardiomyopathy, together with modulation of protein signaling pathways and the emerging role of protein O-GlcNAcylation and miRNA dysregulation in the progression of diabetic heart disease. Lastly, we discuss both conventional and novel therapeutic approaches for the treatment of left ventricular dysfunction in diabetic patients, from inhibition of the renin-angiotensin-aldosterone-system, through recent evidence favoring supplementation of endogenous antioxidants for the treatment of diabetic cardiomyopathy. Novel therapeutic strategies, such as gene therapy targeting the phosphoinositide 3-kinase PI3K(p110α) signaling pathway, and miRNA dysregulation, are also reviewed. Targeting redox stress and protective protein signaling pathways may represent a future strategy for combating the ever-increasing incidence of heart failure in the diabetic population.
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Affiliation(s)
- Karina Huynh
- Baker IDI Heart & Diabetes Institute, Melbourne, Australia; Department of Medicine, Monash University, Clayton, Victoria, Australia
| | | | - Julie R McMullen
- Baker IDI Heart & Diabetes Institute, Melbourne, Australia; Department of Medicine, Monash University, Clayton, Victoria, Australia; Department of Physiology, Monash University, Clayton, Victoria, Australia.
| | - Rebecca H Ritchie
- Baker IDI Heart & Diabetes Institute, Melbourne, Australia; Department of Medicine, Monash University, Clayton, Victoria, Australia.
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35
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Myocardial glycophagy - a specific glycogen handling response to metabolic stress is accentuated in the female heart. J Mol Cell Cardiol 2013; 65:67-75. [PMID: 24080183 DOI: 10.1016/j.yjmcc.2013.09.014] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Revised: 09/19/2013] [Accepted: 09/21/2013] [Indexed: 01/03/2023]
Abstract
Cardiac metabolic stress is a hallmark of many cardiac pathologies, including diabetes. Cardiac glycogen mis-handling is a frequent manifestation of various cardiopathologies. Diabetic females have a higher risk of heart disease than males, yet sex disparities in cardiac metabolic stress settings are not well understood. Oestrogen acts on key glycogen regulatory proteins. The goal of this study was to evaluate sex-specific metabolic stress-triggered cardiac glycogen handling responses. Male and female adult C57Bl/6J mice were fasted for 48h. Cardiac glycogen content, particle size, regulatory enzymes, signalling intermediates and autophagic processes were evaluated. Female hearts exhibited 51% lower basal glycogen content than males associated with lower AMP-activated-kinase (AMPK) activity (35% decrease in pAMPK:AMPK). With fasting, glycogen accumulated in female hearts linked with decreased particle size and upregulation of Akt and AMPK signalling, activation of glycogen synthase and inactivation of glycogen phosphorylase. Fasting did not alter glycogen content or regulatory proteins in male hearts. Expression of glycogen autophagy marker, starch-binding-protein-domain-1 (STBD1), was 63% lower in female hearts than males and increased by 69% with fasting in females only. Macro-autophagy markers, p62 and LC3BII:I ratio, increased with fasting in male and female hearts. This study identifies glycogen autophagy ('glycophagy') as a potentially important component of the response to cardiac metabolic stress. Glycogen autophagy occurs in association with a marked and selective accumulation of glycogen in the female myocardium. Our findings suggest that sex-specific differences in glycogen handling may have cardiopathologic consequences in various settings, including diabetic cardiomyopathy.
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36
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Fares E, Pyle WG, Ray G, Rose RA, Denovan-Wright EM, Chen RP, Howlett SE. The impact of ovariectomy on calcium homeostasis and myofilament calcium sensitivity in the aging mouse heart. PLoS One 2013; 8:e74719. [PMID: 24058623 PMCID: PMC3776741 DOI: 10.1371/journal.pone.0074719] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 08/05/2013] [Indexed: 12/20/2022] Open
Abstract
This study determined whether deficiency of ovarian estrogen starting very early in life promoted age-associated Ca(2+) dysregulation and contractile dysfunction in isolated ventricular myocytes. Myocytes were isolated from anesthetized C57BL/6 female mice. Animals received an ovariectomy or sham-operation at one month and were aged to ~24 months. Excitation-contraction coupling parameters were compared in fura-2 loaded myocytes (37°C). While Ca(2+) transients were larger and faster in field-stimulated myocytes from ovariectomized mice, ovariectomy had no effect on peak fractional shortening. Similarly, ovariectomy had no effect on fractional shortening measured in vivo by echocardiography (values were 60.5 ± 2.9 vs. 60.3 ± 2.5% in sham and ovariectomized, respectively; n=5 mice/group). Ovariectomy did decrease myofilament Ca(2+) sensitivity, as evidenced by a 26% increase in the Ca(2+) required to activate actomyosin MgATPase in ovariectomized hearts. Larger Ca(2+) transients were attributable to a 48% increase in peak Ca(2+) current, along with an increase in the amplitude, width and frequency of Ca(2+) sparks measured in fluo-4 loaded myocytes. These changes in Ca(2+) handling were not due to increased expression of Ca(2+) channels (Cav1.2), sarcoplasmic reticulum Ca(2+) ATPase (SERCA2) or Na(+)-Ca(2+) exchanger in ovariectomized hearts. However, ovariectomy increased sarcoplasmic reticulum Ca(2+) stores by ~90% and promoted spontaneous Ca(2+) release from the sarcoplasmic reticulum when compared to sham controls. These observations demonstrate that long-term ovariectomy promotes intracellular Ca(2+) dysregulation, reduces myofilament Ca(2+) sensitivity and increases spontaneous Ca(2+) release in the aging female heart.
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Affiliation(s)
- Elias Fares
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - W. Glen Pyle
- Cardiovascular Research Group, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Gibanananda Ray
- Department of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Robert A. Rose
- Department of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
| | | | - Robert P. Chen
- Pediatric Cardiology, IWK Health Centre and Dalhousie University, Halifax, Nova Scotia, Canada
| | - Susan E. Howlett
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Medicine (Geriatric Medicine), Dalhousie University, Halifax, Nova Scotia, Canada
- * E-mail:
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Mellor KM, Bell JR, Ritchie RH, Delbridge LMD. Myocardial insulin resistance, metabolic stress and autophagy in diabetes. Clin Exp Pharmacol Physiol 2013; 40:56-61. [PMID: 22804725 DOI: 10.1111/j.1440-1681.2012.05738.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 06/15/2012] [Accepted: 06/18/2012] [Indexed: 01/19/2023]
Abstract
Clinical studies in humans strongly support a link between insulin resistance and non-ischaemic heart failure. The occurrence of a specific insulin-resistant cardiomyopathy, independent of vascular abnormalities, is now recognized. The progression of cardiac pathology linked with insulin resistance is poorly understood. Cardiac insulin resistance is characterized by reduced availability of sarcolemmal Glut-4 transporters and consequent lower glucose uptake. A shift away from glycolysis towards fatty acid oxidation for ATP supply is apparent and is associated with myocardial oxidative stress. Reliance of cardiomyocyte excitation-contraction coupling on glycolytically derived ATP supply potentially renders cardiac function vulnerable to the metabolic remodelling adaptations observed in diabetes development. Findings from Glut-4-knockout mice demonstrate that cardiomyocytes with extreme glucose uptake deficiency exhibit cardiac hypertrophy and marked excitation-contraction coupling abnormalities characterized by reduced sarcolemmal Ca(2+) influx and sarcoplasmic reticulum Ca(2+) uptake. The 'milder' phenotype fructose-fed mouse model of type 2 diabetes does not show evidence of cardiac hypertrophy, but cardiomyocyte loss linked with autophagic activation is evident. Fructose feeding induces a marked reduction in intracellular Ca(2+) availability with myofilament adaptation to preserve contractile function in this setting. The cardiac metabolic adaptations of two load-independent models of diabetes, namely the Glut-4-deficient mouse and the fructose-fed mouse are contrasted. The role of autophagy in diabetic cardiopathology is evaluated and anomalies of type 1 versus type 2 diabetic autophagic responses are highlighted.
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Affiliation(s)
- Kimberley M Mellor
- Department of Physiology, University of Melbourne, Melbourne, Victoria, Australia
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38
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Stanley WC, Keehan KH. Update on innovative initiatives for the American Journal of Physiology-Heart and Circulatory Physiology. Am J Physiol Heart Circ Physiol 2013; 304:H1045-9. [PMID: 23457015 DOI: 10.1152/ajpheart.00082.2013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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39
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Sips PY, Irie T, Zou L, Shinozaki S, Sakai M, Shimizu N, Nguyen R, Stamler JS, Chao W, Kaneki M, Ichinose F. Reduction of cardiomyocyte S-nitrosylation by S-nitrosoglutathione reductase protects against sepsis-induced myocardial depression. Am J Physiol Heart Circ Physiol 2013; 304:H1134-46. [PMID: 23417863 DOI: 10.1152/ajpheart.00887.2012] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Myocardial depression is an important contributor to morbidity and mortality in septic patients. Nitric oxide (NO) plays an important role in the development of septic cardiomyopathy, but also has protective effects. Recent evidence has indicated that NO exerts many of its downstream effects on the cardiovascular system via protein S-nitrosylation, which is negatively regulated by S-nitrosoglutathione reductase (GSNOR), an enzyme promoting denitrosylation. We tested the hypothesis that reducing cardiomyocyte S-nitrosylation by increasing GSNOR activity can improve myocardial dysfunction during sepsis. Therefore, we generated mice with a cardiomyocyte-specific overexpression of GSNOR (GSNOR-CMTg mice) and subjected them to endotoxic shock. Measurements of cardiac function in vivo and ex vivo showed that GSNOR-CMTg mice had a significantly improved cardiac function after lipopolysaccharide challenge (LPS, 50 mg/kg) compared with wild-type (WT) mice. Cardiomyocytes isolated from septic GSNOR-CMTg mice showed a corresponding improvement in contractility compared with WT cells. However, systolic Ca(2+) release was similarly depressed in both genotypes after LPS, indicating that GSNOR-CMTg cardiomyocytes have increased Ca(2+) sensitivity during sepsis. Parameters of inflammation were equally increased in LPS-treated hearts of both genotypes, and no compensatory changes in NO synthase expression levels were found in GSNOR-overexpressing hearts before or after LPS challenge. GSNOR overexpression however significantly reduced total cardiac protein S-nitrosylation during sepsis. Taken together, our results indicate that increasing the denitrosylation capacity of cardiomyocytes protects against sepsis-induced myocardial depression. Our findings suggest that specifically reducing protein S-nitrosylation during sepsis improves cardiac function by increasing cardiac myofilament sensitivity to Ca(2+).
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Affiliation(s)
- Patrick Y Sips
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
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40
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Kagota S, Maruyama K, Tada Y, Wakuda H, Nakamura K, Kunitomo M, Shinozuka K. Abnormal amounts of intracellular calcium regulatory proteins in SHRSP.Z-Leprfa/IzmDmcr rats with metabolic syndrome and cardiac dysfunction. Can J Physiol Pharmacol 2013; 91:124-33. [DOI: 10.1139/cjpp-2012-0226] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Metabolic syndrome is known to increase the risk of abnormal cardiac structure and function, which are considered to contribute to increased incidence of cardiovascular disease and mortality. We previously demonstrated that ventricular hypertrophy and diastolic dysfunction occur in SHRSP.Z-Leprfa/IzmDmcr (SHRSP fatty) rats with metabolic syndrome. The aim of this study was to investigate the possible mechanisms underlying abnormal heart function in SHRSP fatty rats. The amount of sarcoplasmic reticulum Ca2+-ATPase (SERCA) 2a, phospholamban (PLB) protein, and Ser16-phosphorylated PLB was decreased in cardiomyocytes from SHRSP fatty rats compared with those from control Wistar–Kyoto rats at 18 weeks of age, and the PLB-to-SERCA2a ratio was increased. Left ventricular developed pressure was unchanged, and coronary flow rate and maximum rate of left ventricular pressure decline (−dP/dt) was decreased in SHRSP fatty rats. Treatment with telmisartan reversed the abnormalities of PLB amount, coronary flow rate, and −dP/dt in SHRSP fatty rats. These results indicate that abnormal amounts of intracellular Ca2+ regulatory proteins in cardiomyocytes, leading to reduced intracellular Ca2+ reuptake into the sarcoplasmic reticulum, may play a role in the diastolic dysfunction in SHRSP fatty rats and that these effects are partially related to decreased coronary circulation. Telmisartan may be beneficial in protecting against disturbances in cardiac function associated with metabolic syndrome.
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Affiliation(s)
- Satomi Kagota
- Department of Pharmacology II, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
| | - Kana Maruyama
- Department of Pharmacology II, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
| | - Yukari Tada
- Department of Pharmacology II, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
| | - Hirokazu Wakuda
- Department of Pharmacology II, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
| | - Kazuki Nakamura
- Department of Pharmacology I2, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Koshien Kyuban-cho, Nishinomiya 663-8179, Japan
| | - Masaru Kunitomo
- Department of Pharmacology I2, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Koshien Kyuban-cho, Nishinomiya 663-8179, Japan
| | - Kazumasa Shinozuka
- Department of Pharmacology II, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan
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Douard V, Ferraris RP. The role of fructose transporters in diseases linked to excessive fructose intake. J Physiol 2012; 591:401-14. [PMID: 23129794 DOI: 10.1113/jphysiol.2011.215731] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fructose intake has increased dramatically since humans were hunter-gatherers, probably outpacing the capacity of human evolution to make physiologically healthy adaptations. Epidemiological data indicate that this increasing trend continued until recently. Excessive intakes that chronically increase portal and peripheral blood fructose concentrations to >1 and 0.1 mm, respectively, are now associated with numerous diseases and syndromes. The role of the fructose transporters GLUT5 and GLUT2 in causing, contributing to or exacerbating these diseases is not well known. GLUT5 expression seems extremely low in neonatal intestines, and limited absorptive capacities for fructose may explain the high incidence of malabsorption in infants and cause problems in adults unable to upregulate GLUT5 levels to match fructose concentrations in the diet. GLUT5- and GLUT2-mediated fructose effects on intestinal electrolyte transporters, hepatic uric acid metabolism, as well as renal and cardiomyocyte function, may play a role in fructose-induced hypertension. Likewise, GLUT2 may contribute to the development of non-alcoholic fatty liver disease by facilitating the uptake of fructose. Finally, GLUT5 may play a role in the atypical growth of certain cancers and fat tissues. We also highlight research areas that should yield information needed to better understand the role of these GLUTs in fructose-induced diseases.
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Affiliation(s)
- Veronique Douard
- Department of Pharmacology & Physiology, UMDNJ – New Jersey Medical School, 185 S. Orange Avenue, Newark, NJ 07101-1749, USA
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Parks RJ, Howlett SE. H-89 decreases the gain of excitation-contraction coupling and attenuates calcium sparks in the absence of beta-adrenergic stimulation. Eur J Pharmacol 2012; 691:163-72. [PMID: 22796673 DOI: 10.1016/j.ejphar.2012.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/27/2012] [Accepted: 07/03/2012] [Indexed: 01/11/2023]
Abstract
This study used the selective protein kinase A (PKA) inhibitor H-89 (N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide) to determine the role of basal PKA activity in modulating cardiac excitation-contraction coupling in the absence of β-adrenergic stimulation. Basal intracellular cyclic AMP (cAMP) levels measured in isolated murine ventricular myocytes with an enzyme immunoassay were increased upon adenylyl cyclase activation (forskolin; 1 and 10 μM) or phosphodiesterase inhibition (3-isobutyl-1-methylxanthine, IBMX; 300 μM). Forskolin and IBMX also caused concentration-dependent increases in peak Ca(2+) transients (fura-2) and cell shortening (edge-detector) measured simultaneously in field-stimulated myocytes (37 °C). Similar effects were seen upon application of dibutyryl cAMP. In voltage-clamped myocytes, H-89 (2 μM) decreased basal Ca(2+) transients, contractions and underlying Ca(2+) currents. H-89 also decreased diastolic Ca(2+) and the gain of excitation-contraction coupling (Ca(2+) release/Ca(2+) current), especially at negative membrane potentials. This was independent of alterations in sarcoplasmic reticulum (SR) Ca(2+) loading, as SR stores were unchanged by PKA inhibition. H-89 also decreased the frequency, amplitude and width of spontaneous Ca(2+) sparks measured in quiescent myocytes (loaded with fluo-4), but increased time-to-peak. Thus, H-89 suppressed SR Ca(2+) release by decreasing Ca(2+) current and by reducing the gain of excitation-contraction coupling, in part by decreasing the size of individual Ca(2+) release units. These data suggest that basal PKA activity enhances SR Ca(2+) release in the absence of ß-adrenergic stimulation. This may depress contractile function in models such as aging, where the cAMP/PKA pathway is altered due to low basal cAMP levels.
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Affiliation(s)
- Randi J Parks
- Departments of Pharmacology, 1459 Oxford Street, PO Box 15000 Dalhousie University Halifax, Nova Scotia, Canada B3H 4R2.
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Cheng YJ, Lang D, Caruthers SD, Efimov IR, Chen J, Wickline SA. Focal but reversible diastolic sheet dysfunction reflects regional calcium mishandling in dystrophic mdx mouse hearts. Am J Physiol Heart Circ Physiol 2012; 303:H559-68. [PMID: 22777417 DOI: 10.1152/ajpheart.00321.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Cardiac dysfunction is a primary cause of patient mortality in Duchenne muscular dystrophy, potentially related to elevated cytosolic calcium. However, the regional versus global functional consequences of cellular calcium mishandling have not been defined in the whole heart. Here we sought for the first time to elucidate potential regional dependencies between calcium mishandling and myocardial fiber/sheet function as a manifestation of dystrophin-deficient (mdx) cardiomyopathy. Isolated-perfused hearts from 16-mo-old mdx (N = 10) and wild-type (WT; N = 10) were arrested sequentially in diastole and systole for diffusion tensor MRI quantification of myocardial sheet architecture and function. When compared with WT hearts, mdx hearts exhibited normal systolic sheet architecture but a lower diastolic sheet angle magnitude (|β|) in the basal region. The regional diastolic sheet dysfunction was normalized by reducing perfusate calcium concentrations. Optical mapping of calcium transients in isolated hearts (3 mdx and 4 WT) revealed a stretch-inducible regional defect of intracellular calcium reuptake, reflected by a 25% increase of decay times (T(50)) and decay constants, at the base of mdx hearts. The basal region of mdx hearts also exhibited greater fibrosis than did the apex, which matched the regional sheet dysfunction. We conclude that myocardial diastolic sheet dysfunction is observed initially in basal segments along with calcium mishandling, ultimately culminating in increased fibrosis. The preservation of relatively normal calcium reuptake and diastolic/systolic sheet mechanics throughout the rest of the heart, together with the rapid reversibility of functional defects by reducing cytosolic calcium, points to the significance of regional mechanical factors in the progression of the disease.
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Affiliation(s)
- Ya-Jian Cheng
- Cardiovascular Division, Washington University School of Medicine, Saint Louis, Missouri 63110, USA
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