1
|
Heine KB, Parry HA, Hood WR. How does density of the inner mitochondrial membrane influence mitochondrial performance? Am J Physiol Regul Integr Comp Physiol 2023; 324:R242-R248. [PMID: 36572555 PMCID: PMC9902215 DOI: 10.1152/ajpregu.00254.2022] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 12/21/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022]
Abstract
Our current understanding of variation in mitochondrial performance is incomplete. The production of ATP via oxidative phosphorylation is dependent, in part, on the structure of the inner mitochondrial membrane. Morphology of the inner membrane is crucial for the formation of the proton gradient across the inner membrane and, therefore, ATP synthesis. The inner mitochondrial membrane is dynamic, changing shape and surface area. These changes alter density (amount per volume) of the inner mitochondrial membrane within the confined space of the mitochondrion. Because the number of electron transport system proteins within the inner mitochondrial membrane changes with inner mitochondrial membrane area, a change in the amount of inner membrane alters the capacity for ATP production within the organelle. This review outlines the evidence that the association between ATP synthases, inner mitochondrial membrane density, and mitochondrial density (number of mitochondria per cell) impacts ATP production by mitochondria. Furthermore, we consider possible constraints on the capacity of mitochondria to produce ATP by increasing inner mitochondrial membrane density.
Collapse
Affiliation(s)
- Kyle B Heine
- Department of Biological Sciences, Auburn University, Auburn, Alabama
| | - Hailey A Parry
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Wendy R Hood
- Department of Biological Sciences, Auburn University, Auburn, Alabama
| |
Collapse
|
2
|
Bellanti F, Lo Buglio A, Vendemiale G. Muscle Delivery of Mitochondria-Targeted Drugs for the Treatment of Sarcopenia: Rationale and Perspectives. Pharmaceutics 2022; 14:pharmaceutics14122588. [PMID: 36559079 PMCID: PMC9782427 DOI: 10.3390/pharmaceutics14122588] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 11/18/2022] [Accepted: 11/19/2022] [Indexed: 11/27/2022] Open
Abstract
An impairment in mitochondrial homeostasis plays a crucial role in the process of aging and contributes to the incidence of age-related diseases, including sarcopenia, which is defined as an age-dependent loss of muscle mass and strength. Mitochondrial dysfunction exerts a negative impact on several cellular activities, including bioenergetics, metabolism, and apoptosis. In sarcopenia, mitochondria homeostasis is disrupted because of reduced oxidative phosphorylation and ATP generation, the enhanced production of reactive species, and impaired antioxidant defense. This review re-establishes the most recent evidence on mitochondrial defects that are thought to be relevant in the pathogenesis of sarcopenia and that may represent promising therapeutic targets for its prevention/treatment. Furthermore, we describe mechanisms of action and translational potential of promising mitochondria-targeted drug delivery systems, including molecules able to boost the metabolism and bioenergetics, counteract apoptosis, antioxidants to scavenge reactive species and decrease oxidative stress, and target mitophagy. Even though these mitochondria-delivered strategies demonstrate to be promising in preclinical models, their use needs to be promoted for clinical studies. Therefore, there is a compelling demand to further understand the mechanisms modulating mitochondrial homeostasis, to characterize powerful compounds that target muscle mitochondria to prevent sarcopenia in aged people.
Collapse
|
3
|
Chen TH, Koh KY, Lin KMC, Chou CK. Mitochondrial Dysfunction as an Underlying Cause of Skeletal Muscle Disorders. Int J Mol Sci 2022; 23:12926. [PMID: 36361713 PMCID: PMC9653750 DOI: 10.3390/ijms232112926] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/21/2022] [Accepted: 10/21/2022] [Indexed: 09/19/2023] Open
Abstract
Mitochondria are an important energy source in skeletal muscle. A main function of mitochondria is the generation of ATP for energy through oxidative phosphorylation (OXPHOS). Mitochondrial defects or abnormalities can lead to muscle disease or multisystem disease. Mitochondrial dysfunction can be caused by defective mitochondrial OXPHOS, mtDNA mutations, Ca2+ imbalances, mitochondrial-related proteins, mitochondrial chaperone proteins, and ultrastructural defects. In addition, an imbalance between mitochondrial fusion and fission, lysosomal dysfunction due to insufficient biosynthesis, and/or defects in mitophagy can result in mitochondrial damage. In this review, we explore the association between impaired mitochondrial function and skeletal muscle disorders. Furthermore, we emphasize the need for more research to determine the specific clinical benefits of mitochondrial therapy in the treatment of skeletal muscle disorders.
Collapse
Affiliation(s)
- Tsung-Hsien Chen
- Department of Internal Medicine, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi 60002, Taiwan
| | - Kok-Yean Koh
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi 60002, Taiwan
| | - Kurt Ming-Chao Lin
- Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Zhunan 35053, Taiwan
| | - Chu-Kuang Chou
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi 60002, Taiwan
- Obesity Center, Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi 60002, Taiwan
| |
Collapse
|
4
|
Ubiquitin Ligases in Longevity and Aging Skeletal Muscle. Int J Mol Sci 2022; 23:ijms23147602. [PMID: 35886949 PMCID: PMC9315556 DOI: 10.3390/ijms23147602] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 07/07/2022] [Accepted: 07/08/2022] [Indexed: 12/07/2022] Open
Abstract
The development and prevalence of diseases associated with aging presents a global health burden on society. One hallmark of aging is the loss of proteostasis which is caused in part by alterations to the ubiquitin-proteasome system (UPS) and lysosome-autophagy system leading to impaired function and maintenance of mass in tissues such as skeletal muscle. In the instance of skeletal muscle, the impairment of function occurs early in the aging process and is dependent on proteostatic mechanisms. The UPS plays a pivotal role in degradation of misfolded and aggregated proteins. For the purpose of this review, we will discuss the role of the UPS system in the context of age-related loss of muscle mass and function. We highlight the significant role that E3 ubiquitin ligases play in the turnover of key components (e.g., mitochondria and neuromuscular junction) essential to skeletal muscle function and the influence of aging. In addition, we will briefly discuss the contribution of the UPS system to lifespan. By understanding the UPS system as part of the proteostasis network in age-related diseases and disorders such as sarcopenia, new discoveries can be made and new interventions can be developed which will preserve muscle function and maintain quality of life with advancing age.
Collapse
|
5
|
Schmidt CA, Fisher-Wellman KH, Neufer PD. From OCR and ECAR to energy: Perspectives on the design and interpretation of bioenergetics studies. J Biol Chem 2021; 297:101140. [PMID: 34461088 PMCID: PMC8479256 DOI: 10.1016/j.jbc.2021.101140] [Citation(s) in RCA: 65] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 08/25/2021] [Accepted: 08/26/2021] [Indexed: 12/12/2022] Open
Abstract
Biological energy transduction underlies all physiological phenomena in cells. The metabolic systems that support energy transduction have been of great interest due to their association with numerous pathologies including diabetes, cancer, rare genetic diseases, and aberrant cell death. Commercially available bioenergetics technologies (e.g., extracellular flux analysis, high-resolution respirometry, fluorescent dye kits, etc.) have made practical assessment of metabolic parameters widely accessible. This has facilitated an explosion in the number of studies exploring, in particular, the biological implications of oxygen consumption rate (OCR) and substrate level phosphorylation via glycolysis (i.e., via extracellular acidification rate (ECAR)). Though these technologies have demonstrated substantial utility and broad applicability to cell biology research, they are also susceptible to historical assumptions, experimental limitations, and other caveats that have led to premature and/or erroneous interpretations. This review enumerates various important considerations for designing and interpreting cellular and mitochondrial bioenergetics experiments, some common challenges and pitfalls in data interpretation, and some potential "next steps" to be taken that can address these highlighted challenges.
Collapse
Affiliation(s)
- Cameron A Schmidt
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Departments of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA
| | - Kelsey H Fisher-Wellman
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Departments of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA.
| | - P Darrell Neufer
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Departments of Physiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA; Departments of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA.
| |
Collapse
|
6
|
Abstract
Barth syndrome (BTHS) is a rare, X-linked recessive, infantile-onset debilitating disorder characterized by early-onset cardiomyopathy, skeletal muscle myopathy, growth delay, and neutropenia, with a worldwide incidence of 1/300,000-400,000 live births. The high mortality rate throughout infancy in BTHS patients is related primarily to progressive cardiomyopathy and a weakened immune system. BTHS is caused by defects in the TAZ gene that encodes tafazzin, a transacylase responsible for the remodeling and maturation of the mitochondrial phospholipid cardiolipin (CL), which is critical to normal mitochondrial structure and function (i.e., ATP generation). A deficiency in tafazzin results in up to a 95% reduction in levels of structurally mature CL. Because the heart is the most metabolically active organ in the body, with the highest mitochondrial content of any tissue, mitochondrial dysfunction plays a key role in the development of heart failure in patients with BTHS. Changes in mitochondrial oxidative phosphorylation reduce the ability of mitochondria to meet the ATP demands of the human heart as well as skeletal muscle, namely ATP synthesis does not match the rate of ATP consumption. The presence of several cardiomyopathic phenotypes have been described in BTHS, including dilated cardiomyopathy, left ventricular noncompaction, either alone or in conjunction with other cardiomyopathic phenotypes, endocardial fibroelastosis, hypertrophic cardiomyopathy, and an apical form of hypertrophic cardiomyopathy, among others, all of which can be directly attributed to the lack of CL synthesis, remodeling, and maturation with subsequent mitochondrial dysfunction. Several mechanisms by which these cardiomyopathic phenotypes exist have been proposed, thereby identifying potential targets for treatment. Dysfunction of the sarcoplasmic reticulum Ca2+-ATPase pump and inflammation potentially triggered by circulating mitochondrial components have been identified. Currently, treatment modalities are aimed at addressing symptomatology of HF in BTHS, but do not address the underlying pathology. One novel therapeutic approach includes elamipretide, which crosses the mitochondrial outer membrane to localize to the inner membrane where it associates with cardiolipin to enhance ATP synthesis in several organs, including the heart. Encouraging clinical results of the use of elamipretide in treating patients with BTHS support the potential use of this drug for management of this rare disease.
Collapse
Affiliation(s)
- Hani N Sabbah
- Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Henry Ford Health System, 2799 West Grand Boulevard, Detroit, MI, 48202, USA.
| |
Collapse
|
7
|
Memme JM, Hood DA. Molecular Basis for the Therapeutic Effects of Exercise on Mitochondrial Defects. Front Physiol 2021; 11:615038. [PMID: 33584337 PMCID: PMC7874077 DOI: 10.3389/fphys.2020.615038] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 12/16/2020] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial dysfunction is common to many organ system disorders, including skeletal muscle. Aging muscle and diseases of muscle are often accompanied by defective mitochondrial ATP production. This manuscript will focus on the pre-clinical evidence supporting the use of regular exercise to improve defective mitochondrial metabolism and function in skeletal muscle, through the stimulation of mitochondrial turnover. Examples from aging muscle, muscle-specific mutations and cancer cachexia will be discussed. We will also examine the effects of exercise on the important mitochondrial regulators PGC-1α, and Parkin, and summarize the effects of exercise to reverse mitochondrial dysfunction (e.g., ROS production, apoptotic susceptibility, cardiolipin synthesis) in muscle pathology. This paper will illustrate the breadth and benefits of exercise to serve as "mitochondrial medicine" with age and disease.
Collapse
Affiliation(s)
- Jonathan M. Memme
- Muscle Health Research Centre, York University, Toronto, ON, Canada
- School of Kinesiology and Health Science, York University, Toronto, ON, Canada
| | - David A. Hood
- Muscle Health Research Centre, York University, Toronto, ON, Canada
- School of Kinesiology and Health Science, York University, Toronto, ON, Canada
| |
Collapse
|
8
|
Bellanti F, Lo Buglio A, Vendemiale G. Mitochondrial Impairment in Sarcopenia. BIOLOGY 2021; 10:biology10010031. [PMID: 33418869 PMCID: PMC7825073 DOI: 10.3390/biology10010031] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/21/2020] [Accepted: 12/25/2020] [Indexed: 02/07/2023]
Abstract
Sarcopenia is defined by the age-related loss of skeletal muscle quality, which relies on mitochondrial homeostasis. During aging, several mitochondrial features such as bioenergetics, dynamics, biogenesis, and selective autophagy (mitophagy) are altered and impinge on protein homeostasis, resulting in loss of muscle mass and function. Thus, mitochondrial dysfunction contributes significantly to the complex pathogenesis of sarcopenia, and mitochondria are indicated as potential targets to prevent and treat this age-related condition. After a concise presentation of the age-related modifications in skeletal muscle quality and mitochondrial homeostasis, the present review summarizes the most relevant findings related to mitochondrial alterations in sarcopenia.
Collapse
|
9
|
Urbina-Varela R, Castillo N, Videla LA, del Campo A. Impact of Mitophagy and Mitochondrial Unfolded Protein Response as New Adaptive Mechanisms Underlying Old Pathologies: Sarcopenia and Non-Alcoholic Fatty Liver Disease. Int J Mol Sci 2020; 21:E7704. [PMID: 33081022 PMCID: PMC7589512 DOI: 10.3390/ijms21207704] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/08/2020] [Accepted: 10/12/2020] [Indexed: 12/12/2022] Open
Abstract
Mitochondria are the first-line defense of the cell in the presence of stressing processes that can induce mitochondrial dysfunction. Under these conditions, the activation of two axes is accomplished, namely, (i) the mitochondrial unfolded protein response (UPRmt) to promote cell recovery and survival of the mitochondrial network; (ii) the mitophagy process to eliminate altered or dysfunctional mitochondria. For these purposes, the former response induces the expression of chaperones, proteases, antioxidant components and protein import and assembly factors, whereas the latter is signaled through the activation of the PINK1/Parkin and BNIP3/NIX pathways. These adaptive mechanisms may be compromised during aging, leading to the development of several pathologies including sarcopenia, defined as the loss of skeletal muscle mass and performance; and non-alcoholic fatty liver disease (NAFLD). These age-associated diseases are characterized by the progressive loss of organ function due to the accumulation of reactive oxygen species (ROS)-induced damage to biomolecules, since the ability to counteract the continuous and large generation of ROS becomes increasingly inefficient with aging, resulting in mitochondrial dysfunction as a central pathogenic mechanism. Nevertheless, the role of the integrated stress response (ISR) involving UPRmt and mitophagy in the development and progression of these illnesses is still a matter of debate, considering that some studies indicate that the prolonged exposure to low levels of stress may trigger these mechanisms to maintain mitohormesis, whereas others sustain that chronic activation of them could lead to cell death. In this review, we discuss the available research that contributes to unveil the role of the mitochondrial UPR in the development of sarcopenia, in an attempt to describe changes prior to the manifestation of severe symptoms; and in NAFLD, in order to prevent or reverse fat accumulation and its progression by means of suitable protocols to be addressed in future studies.
Collapse
Affiliation(s)
- Rodrigo Urbina-Varela
- Laboratorio de Fisiología y Bioenergética Celular, Departamento de Farmacia, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Santiago 7810000, Chile; (R.U.-V.); (N.C.)
| | - Nataly Castillo
- Laboratorio de Fisiología y Bioenergética Celular, Departamento de Farmacia, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Santiago 7810000, Chile; (R.U.-V.); (N.C.)
| | - Luis A. Videla
- Molecular and Clinical Pharmacology Program, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago 8380453, Chile;
| | - Andrea del Campo
- Laboratorio de Fisiología y Bioenergética Celular, Departamento de Farmacia, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Santiago 7810000, Chile; (R.U.-V.); (N.C.)
| |
Collapse
|
10
|
Towarnicki SG, Kok LM, Ballard JWO. Yin and Yang of mitochondrial ROS in Drosophila. JOURNAL OF INSECT PHYSIOLOGY 2020; 122:104022. [PMID: 32045573 DOI: 10.1016/j.jinsphys.2020.104022] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 12/12/2019] [Accepted: 02/07/2020] [Indexed: 06/10/2023]
Abstract
In this study, we test the hypothesis that Drosophila larvae producing mildly elevated levels of endogenous mitochondrial reactive oxygen species (ROS) benefit in stressful environmental conditions due to the priming of antioxidant responses. Reactive oxygen species (ROS) are produced as a by-product of oxidative phosphorylation and may be elevated when mutations decrease the efficiency of ATP production. In moderation, ROS are necessary for cell signaling and organismal health, but in excess can damage DNA, proteins, and lipids. We utilize two Drosophila melanogaster strains (Dahomey and Alstonville) that share the same nuclear genetic background but differ in their mitochondrial DNA haplotypes. Previously, we reported that Dahomey larvae harboring the V161L ND4 mtDNA mutation have reduced proton pumping and higher levels of mitochondrial ROS than Alstonville larvae when they are fed a 1:2 protein: carbohydrate (P:C) diet. Here, we explore the potential for mitochondrial ROS to provide resistance to dietary stressors by feeding larvae 1:2 P:C food supplemented with ethanol or hydrogen peroxide (H2O2). When fed a diet supplemented with ethanol or H2O2, Dahomey develop more quickly than Alstonville into larger pupae, while Alstonville developed faster on the control. Dahomey larvae displayed higher antioxidant capacity than Alstonville on all diets, with mitochondrial H2O2 levels unchanged after the addition of stressors. Addition of stressors to the diet did not affect the mitochondrial functions of Dahomey larvae as measured by mitochondrial membrane potential, respiratory control ratio, or larval survival after bacterial challenge. In contrast, Alstonville larvae developed slower, had lower pupal weight, higher cytosolic H2O2, and had reduced mitochondrial functions. Further, Alstonville larvae fed the ethanol treated diet had lower survival after bacterial infection than those fed the control diet. Surprisingly, they had greater survival when fed diet with H2O2 indicating a mitotype by stressor interaction that influences the immune response. Overall, these data suggest that elevated mitochondrial ROS in Dahomey can result in greater antioxidant capacity that prevents oxidative damage from exogenous stressors and may be a conserved response to high ethanol found in rotting fruit.
Collapse
Affiliation(s)
- Samuel G Towarnicki
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
| | - Leanne M Kok
- Saxion University of Applied Sciences Maarten Harpertszoon Tromplaan 28, 7513 AB Enschede, The Netherlands.
| | - J William O Ballard
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
| |
Collapse
|
11
|
Sabbah HN. Targeting the Mitochondria in Heart Failure: A Translational Perspective. JACC Basic Transl Sci 2020; 5:88-106. [PMID: 32043022 PMCID: PMC7000886 DOI: 10.1016/j.jacbts.2019.07.009] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 07/19/2019] [Accepted: 07/21/2019] [Indexed: 12/12/2022]
Abstract
The burden of heart failure (HF) in terms of health care expenditures, hospitalizations, and mortality is substantial and growing. The failing heart has been described as "energy-deprived" and mitochondrial dysfunction is a driving force associated with this energy supply-demand imbalance. Existing HF therapies provide symptomatic and longevity benefit by reducing cardiac workload through heart rate reduction and reduction of preload and afterload but do not address the underlying causes of abnormal myocardial energetic nor directly target mitochondrial abnormalities. Numerous studies in animal models of HF as well as myocardial tissue from explanted failed human hearts have shown that the failing heart manifests abnormalities of mitochondrial structure, dynamics, and function that lead to a marked increase in the formation of damaging reactive oxygen species and a marked reduction in on demand adenosine triphosphate synthesis. Correcting mitochondrial dysfunction therefore offers considerable potential as a new therapeutic approach to improve overall cardiac function, quality of life, and survival for patients with HF.
Collapse
Key Words
- ADP, adenosine diphosphate
- ATP, adenosine triphosphate
- CI (to V), complex I (to V)
- Drp, dynamin-related protein
- ETC, electron transport chain
- HF, heart failure
- HFpEF, heart failure with preserved ejection fraction
- HFrEF, heart failure with reduced ejection fraction
- LV, left ventricular
- MPTP, mitochondrial permeability transition pore
- Mfn, mitofusin
- OPA, optic atrophy
- PGC, peroxisome proliferator-activated receptor coactivator
- PINK, phosphatase and tensin homolog–inducible kinase
- ROS, reactive oxygen species
- TAZ, tafazzin
- cardiolipin
- heart failure
- mitochondria
- mtDNA, mitochondrial deoxyribonucleic acid
- myocardial energetics
- oxidative phosphorylation
Collapse
Affiliation(s)
- Hani N Sabbah
- Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, Michigan
| |
Collapse
|
12
|
Memme JM, Erlich AT, Phukan G, Hood DA. Exercise and mitochondrial health. J Physiol 2019; 599:803-817. [PMID: 31674658 DOI: 10.1113/jp278853] [Citation(s) in RCA: 128] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 10/28/2019] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial health is an important mediator of cellular function across a range of tissues, and as a result contributes to whole-body vitality in health and disease. Our understanding of the regulation and function of these organelles is of great interest to scientists and clinicians across many disciplines within our healthcare system. Skeletal muscle is a useful model tissue for the study of mitochondrial adaptations because of its mass and contribution to whole body metabolism. The remarkable plasticity of mitochondria allows them to adjust their volume, structure and capacity under conditions such as exercise, which is useful or improving metabolic health in individuals with various diseases and/or advancing age. Mitochondria exist within muscle as a functional reticulum which is maintained by dynamic processes of biogenesis and fusion, and is balanced by opposing processes of fission and mitophagy. The sophisticated coordination of these events is incompletely understood, but is imperative for organelle function and essential for the maintenance of an interconnected organelle network that is finely tuned to the metabolic needs of the cell. Further elucidation of the mechanisms of mitochondrial turnover in muscle could offer potential therapeutic targets for the advancement of health and longevity among our ageing populations. As well, investigating exercise modalities that are both convenient and capable of inducing robust mitochondrial adaptations are useful in fostering more widespread global adherence. To this point, exercise remains the most potent behavioural therapeutic approach for the improvement of mitochondrial health, not only in muscle, but potentially also in other tissues.
Collapse
Affiliation(s)
- Jonathan M Memme
- Muscle Health Research Centre, York University, Toronto, Ontario, Canada, M3J 1P3.,School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada, M3J 1P3
| | - Avigail T Erlich
- Muscle Health Research Centre, York University, Toronto, Ontario, Canada, M3J 1P3.,School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada, M3J 1P3
| | - Geetika Phukan
- Muscle Health Research Centre, York University, Toronto, Ontario, Canada, M3J 1P3.,School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada, M3J 1P3
| | - David A Hood
- Muscle Health Research Centre, York University, Toronto, Ontario, Canada, M3J 1P3.,School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada, M3J 1P3
| |
Collapse
|
13
|
Holloway GP, Holwerda AM, Miotto PM, Dirks ML, Verdijk LB, van Loon LJC. Age-Associated Impairments in Mitochondrial ADP Sensitivity Contribute to Redox Stress in Senescent Human Skeletal Muscle. Cell Rep 2019. [PMID: 29539414 DOI: 10.1016/j.celrep.2018.02.069] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
It remains unknown if mitochondrial bioenergetics are altered with aging in humans. We established an in vitro method to simultaneously determine mitochondrial respiration and H2O2 emission in skeletal muscle tissue across a range of biologically relevant ADP concentrations. Using this approach, we provide evidence that, although the capacity for mitochondrial H2O2 emission is not increased with aging, mitochondrial ADP sensitivity is impaired. This resulted in an increase in mitochondrial H2O2 and the fraction of electron leak to H2O2, in the presence of virtually all ADP concentrations examined. Moreover, although prolonged resistance training in older individuals increased muscle mass, strength, and maximal mitochondrial respiration, exercise training did not alter H2O2 emission rates in the presence of ADP, the fraction of electron leak to H2O2, or the redox state of the muscle. These data establish that a reduction in mitochondrial ADP sensitivity increases mitochondrial H2O2 emission and contributes to age-associated redox stress.
Collapse
Affiliation(s)
- Graham P Holloway
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
| | - Andrew M Holwerda
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, 6200 Maastricht, the Netherlands
| | - Paula M Miotto
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Marlou L Dirks
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, 6200 Maastricht, the Netherlands
| | - Lex B Verdijk
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, 6200 Maastricht, the Netherlands
| | - Luc J C van Loon
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, 6200 Maastricht, the Netherlands
| |
Collapse
|
14
|
Sabbah HN, Gupta RC, Singh‐Gupta V, Zhang K. Effects of elamipretide on skeletal muscle in dogs with experimentally induced heart failure. ESC Heart Fail 2019; 6:328-335. [PMID: 30688415 PMCID: PMC6437430 DOI: 10.1002/ehf2.12408] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 12/12/2018] [Indexed: 12/04/2022] Open
Abstract
AIMS Elamipretide (ELAM), an aromatic-cationic tetrapeptide, interacts with cardiolipin and normalizes dysfunctional mitochondria of cardiomyocytes. This study examined the effects of ELAM on skeletal muscle mitochondria function in dogs with chronic heart failure (HF). METHODS AND RESULTS Studies were performed in skeletal muscle biopsy specimens obtained from normal dogs (n = 7) and dogs with chronic intracoronary microembolization-induced HF (n = 14) treated with subcutaneous ELAM 0.5 mg/kg (HF + ELAM, n = 7) or vehicle (normal saline control, HF-CON, n = 7). After 3 months of therapy, triceps skeletal muscle samples were obtained from all dogs, and the proportion of type 1 and type 2 fibres was assessed. Mitochondria isolated from myofibrils of the vastus lateralis skeletal muscle exposed in vitro to ELAM for 1 h were used to assess mitochondrial function. The proportion of skeletal muscle type 1 fibres was lower in HF-CON dogs compared with normal dogs (23 ± 4 vs. 32 ± 5%, P < 0.05). Treatment with ELAM restored a near-normal fibre-type composition (31 ± 7%, P < 0.05 vs. HF-CON). Skeletal muscle mitochondria showed significantly lower levels of adenosine diphosphate-dependent mitochondrial respiration (100 ± 9 vs. 164 ± 15 natom O/min/mg protein, P < 0.05), mitochondrial membrane potential (0.17 ± 0.03 vs. 0.53 ± 0.03 red/green fluorescence ratio, P < 0.05), mitochondrial permeability transition pore (38 ± 3 vs. 62 ± 2 relative light units, P < 0.05), maximum rate of adenosine triphosphate synthesis (3284 ± 418 vs. 8835 ± 423 RLU/μg protein, P < 0.05), and cytochrome c oxidase activity (1390 ± 108 vs. 2459 ± 210 natom O/min/mg protein, P < 0.05) compared with normal dogs. Exposure of skeletal muscle myofibrillar mitochondria from HF dogs to ELAM showed a dose-dependent improvement/normalization of all measures of mitochondrial function. In mitochondria from skeletal muscle of HF dogs exposed to 0.10 μM ELAM, adenosine diphosphate-dependent mitochondrial respiration increased to 183 ± 18 natom O/min/mg protein, membrane potential increased to 0.30 ± 0.03 red/green fluorescence ratio, mitochondrial permeability transition pore increased to 54 ± 4 RLU, maximum rate of adenosine triphosphate synthesis increased to 4423 ± 414, and cytochrome c oxidase activity increased to 2033 ± 191 natom O/min/mg protein. Exposure of skeletal muscle myofibrillar mitochondria from normal dogs to ELAM had no effect on mitochondrial function parameters. CONCLUSIONS The results indicate that ELAM, previously shown to positively influence mitochondrial function of the failing heart, can also positively impact mitochondrial function of skeletal muscle and potentially help restore skeletal muscle function and improve exercise tolerance.
Collapse
Affiliation(s)
- Hani N. Sabbah
- Department of Medicine, Division of Cardiovascular MedicineHenry Ford Hospital2799 West Grand BoulevardDetroitMI48202USA
| | - Ramesh C. Gupta
- Department of Medicine, Division of Cardiovascular MedicineHenry Ford Hospital2799 West Grand BoulevardDetroitMI48202USA
| | - Vinita Singh‐Gupta
- Department of Medicine, Division of Cardiovascular MedicineHenry Ford Hospital2799 West Grand BoulevardDetroitMI48202USA
| | - Kefei Zhang
- Department of Medicine, Division of Cardiovascular MedicineHenry Ford Hospital2799 West Grand BoulevardDetroitMI48202USA
| |
Collapse
|
15
|
Mitochondrial Theory of Skeletal Muscle Ageing - New Facts, New Doubts. J Vet Res 2019; 63:149-160. [PMID: 30989147 PMCID: PMC6458556 DOI: 10.2478/jvetres-2019-0015] [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: 07/16/2018] [Accepted: 02/27/2019] [Indexed: 11/21/2022] Open
Abstract
For many years, scientists have been pursuing research on skeletal muscle ageing both in humans and animals. Studies on animal models have extended our knowledge of this mechanism in humans. Most researchers agree that the major processes of muscle ageing occur in the mitochondria as the major energy production centres in muscle cells. It is believed that decisive changes occur at the enzymatic activity level as well as in protein synthesis and turnover ability. Deregulation of ion channels and oxidative stress also play significant roles. In particular, in recent years the free radical theory of ageing has undergone considerable modification; researchers are increasingly highlighting the partly positive effects of free radicals on processes occurring in cells. In addition, the influence of diet and physical activity on the rate of muscle cell ageing is widely debated as well as the possibility of delaying it through appropriate physical exercise and diet programmes. Numerous studies, especially those related to genetic processes, are still being conducted, and in the near future the findings could provide valuable information on muscle ageing. The results of ongoing research could answer the perennial question of whether and how we can influence the rate of ageing both in animals and humans.
Collapse
|
16
|
Szeto HH, Liu S. Cardiolipin-targeted peptides rejuvenate mitochondrial function, remodel mitochondria, and promote tissue regeneration during aging. Arch Biochem Biophys 2018; 660:137-148. [DOI: 10.1016/j.abb.2018.10.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 10/13/2018] [Accepted: 10/18/2018] [Indexed: 12/21/2022]
|
17
|
Gouspillou G, Godin R, Piquereau J, Picard M, Mofarrahi M, Mathew J, Purves-Smith FM, Sgarioto N, Hepple RT, Burelle Y, Hussain SNA. Protective role of Parkin in skeletal muscle contractile and mitochondrial function. J Physiol 2018; 596:2565-2579. [PMID: 29682760 DOI: 10.1113/jp275604] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 04/06/2018] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Parkin, an E3 ubiquitin ligase encoded by the Park2 gene, has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are degraded. The exact physiological significance of Parkin in regulating mitochondrial function and contractility in skeletal muscle remains largely unexplored. Using Park2-/- mice, we show that Parkin ablation causes a decrease in muscle specific force, a severe decrease in mitochondrial respiration, mitochondrial uncoupling and an increased susceptibility to opening of the permeability transition pore. These results demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in skeletal muscles. ABSTRACT Parkin is an E3 ubiquitin ligase encoded by the Park2 gene. Parkin has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are sequestered in autophagosomes and delivered to lysosomes for degradation. Although Parkin has been mainly studied for its implication in neuronal degeneration in Parkinson disease, its role in other tissues remains largely unknown. In the present study, we investigated the skeletal muscles of Park2 knockout (Park2-/- ) mice to test the hypothesis that Parkin plays a physiological role in mitochondrial quality control in normal skeletal muscle, a tissue highly reliant on mitochondrial content and function. We first show that the tibialis anterior (TA) of Park2-/- mice display a slight but significant decrease in its specific force. Park2-/- muscles also show a trend for type IIB fibre hypertrophy without alteration in muscle fibre type proportion. Compared to Park2+/+ muscles, the mitochondrial function of Park2-/- skeletal muscles was significantly impaired, as indicated by the significant decrease in ADP-stimulated mitochondrial respiratory rates, uncoupling, reduced activities of respiratory chain complexes containing mitochondrial DNA (mtDNA)-encoded subunits and increased susceptibility to opening of the permeability transition pore. Muscles of Park2-/- mice also displayed a decrease in the content of the mitochondrial pro-fusion protein Mfn2 and an increase in the pro-fission protein Drp1 suggesting an increase in mitochondrial fragmentation. Finally, Park2 ablation resulted in an increase in basal autophagic flux in skeletal muscles. Overall, the results of the present study demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in normal skeletal muscles.
Collapse
Affiliation(s)
- Gilles Gouspillou
- Département des sciences de l'activité physique, Faculté des Sciences, UQAM, Montréal, Quebec, Canada.,Groupe de recherche en Activité Physique Adaptée, Montréal, Quebec, Canada.,Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montréal, Quebec, Canada
| | - Richard Godin
- Faculty of Pharmacy, Université de Montréal, Chemin de la polytechnique, Quebec, Canada
| | - Jérome Piquereau
- Faculty of Pharmacy, Université de Montréal, Chemin de la polytechnique, Quebec, Canada.,Inserm, Université Paris-Sud, UMR-S 1180, Châtenay-Malabry, France
| | - Martin Picard
- Division of Behavioral Medicine, Department of Psychiatry, Columbia University Medical Center, New York, NY, USA.,Department of Neurology, The Merritt Center and Columbia Translational Neuroscience Initiative, Columbia University Medical Center, New York, NY, USA.,Columbia Aging Center, Columbia University Mailman School of Public Health, New York, NY, USA
| | - Mahroo Mofarrahi
- Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Jasmin Mathew
- Faculty of Pharmacy, Université de Montréal, Chemin de la polytechnique, Quebec, Canada
| | - Fennigje M Purves-Smith
- Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Nicolas Sgarioto
- Faculty of Pharmacy, Université de Montréal, Chemin de la polytechnique, Quebec, Canada.,Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada
| | - Russell T Hepple
- Department of Physical Therapy, College of Health & Health Professions, University of Florida, Gainesville, FL, USA
| | - Yan Burelle
- Interdisciplinary School of Health Sciences, Faculty of Health Sciences, University of Ottawa, Ottawa, Ontario, Canada
| | - Sabah N A Hussain
- Departments of Critical Care and Medicine, McGill University Health Centre and Meakins-Christie Laboratories, Department of Medicine, McGill University, Montreal, Quebec, Canada
| |
Collapse
|
18
|
Abstract
Changes in mitochondrial capacity and quality play a critical role in skeletal and cardiac muscle dysfunction. In vivo measurements of mitochondrial capacity provide a clear link between physical activity and mitochondrial function in aging and heart failure, although the cause and effect relationship remains unclear. Age-related decline in mitochondrial quality leads to mitochondrial defects that affect redox, calcium, and energy-sensitive signaling by altering the cellular environment that can result in skeletal muscle dysfunction independent of reduced mitochondrial capacity. This reduced mitochondrial quality with age is also likely to sensitize skeletal muscle mitochondria to elevated angiotensin or beta-adrenergic signaling associated with heart failure. This synergy between aging and heart failure could further disrupt cell energy and redox homeostasis and contribute to exercise intolerance in this patient population. Therefore, the interaction between aging and heart failure, particularly with respect to mitochondrial dysfunction, should be a consideration when developing strategies to improve quality of life in heart failure patients. Given the central role of the mitochondria in skeletal and cardiac muscle dysfunction, mitochondrial quality may provide a common link for targeted interventions in these populations.
Collapse
Affiliation(s)
- Sophia Z Liu
- Department of Radiology, University of Washington, Box 358050, Seattle, WA, 98109, USA
| | - David J Marcinek
- Department of Radiology, University of Washington, Box 358050, Seattle, WA, 98109, USA. .,Department of Pathology, University of Washington, Seattle, WA, 98109, USA. .,Department of Bioengineering, University of Washington, Seattle, WA, 98109, USA.
| |
Collapse
|
19
|
Musci RV, Hamilton KL, Miller BF. Targeting mitochondrial function and proteostasis to mitigate dynapenia. Eur J Appl Physiol 2018; 118:1-9. [PMID: 28986697 PMCID: PMC5756099 DOI: 10.1007/s00421-017-3730-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 09/30/2017] [Indexed: 12/25/2022]
Abstract
Traditionally, interventions to treat skeletal muscle aging have largely targeted sarcopenia-the age-related loss of skeletal muscle mass. Dynapenia refers to the age-related loss in skeletal muscle function due to factors outside of muscle mass, which helps to inform treatment strategies for aging skeletal muscle. There is evidence that mechanisms to maintain protein homeostasis and proteostasis, deteriorate with age. One key mechanism to maintain proteostasis is protein turnover, which is an energetically costly process. When there is a mismatch between cellular energy demands and energy provision, inelastic processes related to metabolism are maintained, but there is competition for the remaining energy between the elastic processes of somatic maintenance and growth. With aging, mitochondrial dysfunction reduces ATP generation capacity, constraining the instantaneous supply of energy, thus compromising growth and somatic maintenance processes. Further, with age the need for somatic maintenance increases because of the accumulation of protein damage. In this review, we highlight the significant role mitochondria have in maintaining skeletal muscle proteostasis through increased energy provision, protein turnover, and substrate flux. In addition, we provide evidence that improving mitochondrial function could promote a cellular environment that is conducive to somatic maintenance, and consequently for mitigating dynapenia. Finally, we highlight interventions, such as aerobic exercise, that could be used to improve mitochondrial function and improve outcomes related to dynapenia.
Collapse
Affiliation(s)
- Robert V Musci
- Translational Research on Aging and Chronic Disease Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80523-1582, USA
| | - Karyn L Hamilton
- Translational Research on Aging and Chronic Disease Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80523-1582, USA
| | - Benjamin F Miller
- Translational Research on Aging and Chronic Disease Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, 80523-1582, USA.
| |
Collapse
|
20
|
Faitg J, Reynaud O, Leduc-Gaudet JP, Gouspillou G. [Skeletal muscle aging and mitochondrial dysfunction: an update]. Med Sci (Paris) 2017; 33:955-962. [PMID: 29200393 DOI: 10.1051/medsci/20173311012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
One of the most obvious and deleterious changes occurring with aging is a progressive loss of skeletal muscle mass and strength, a physiological process named sarcopenia. Amongst the multiple theories that have been put forward to explain sarcopenia, the mitochondrial theory of aging, which postulates that the accumulation of mitochondrial dysfunctions with aging plays a causal role in muscle atrophy, has focused intense research effort and attention in the past decades. The generally accepted view of this theory is that, due to the reactive oxygen species (ROS) production inherent to respiratory chain activity, oxidative damage to mitochondrial proteins, lipids and DNA accumulates with aging. This damage is thought to (i) exacerbate mitochondrial ROS production, (ii) impair the capacity of mitochondria to adequately match the cellular ATP demand and (iii) trigger mitochondrial-mediated apoptosis. Although very appealing, this theory remains controversial. The aims of the present review are (i) to provide the reader with a short, but comprehensive review of the current literature linking mitochondrial dysfunction and sarcopenia and (ii) to briefly discuss the potential mechanisms underlying the accumulation of mitochondrial dysfunction with muscle aging.
Collapse
Affiliation(s)
- Julie Faitg
- Département des sciences de l'activité physique, faculté des sciences, Université du Québec à Montréal (UQAM), 141, avenue du Président Kennedy, H2X 1Y4 Montréal, Canada - Groupe de recherche en activité physique adaptée, Montréal, Canada
| | - Olivier Reynaud
- Département des sciences de l'activité physique, faculté des sciences, Université du Québec à Montréal (UQAM), 141, avenue du Président Kennedy, H2X 1Y4 Montréal, Canada - Groupe de recherche en activité physique adaptée, Montréal, Canada
| | - Jean-Philippe Leduc-Gaudet
- Département des sciences de l'activité physique, faculté des sciences, Université du Québec à Montréal (UQAM), 141, avenue du Président Kennedy, H2X 1Y4 Montréal, Canada - Groupe de recherche en activité physique adaptée, Montréal, Canada - McGill University, Montréal, Canada
| | - Gilles Gouspillou
- Département des sciences de l'activité physique, faculté des sciences, Université du Québec à Montréal (UQAM), 141, avenue du Président Kennedy, H2X 1Y4 Montréal, Canada - Groupe de recherche en activité physique adaptée, Montréal, Canada - Centre de recherche de l'institut universitaire de gériatrie de Montréal, Montréal, Canada
| |
Collapse
|
21
|
Drake JC, Yan Z. Mitophagy in maintaining skeletal muscle mitochondrial proteostasis and metabolic health with ageing. J Physiol 2017; 595:6391-6399. [PMID: 28795394 PMCID: PMC5638883 DOI: 10.1113/jp274337] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 08/05/2017] [Indexed: 12/26/2022] Open
Abstract
Skeletal muscle is important for overall functionality and health. Ageing is associated with an accumulation of damage to mitochondrial DNA and proteins. In particular, damage to mitochondrial proteins in skeletal muscle, which is a loss of mitochondrial proteostasis, contributes to tissue dysfunction and negatively impacts systemic health. Therefore, understanding the mechanisms underlying the regulation of mitochondrial proteostasis and how those mechanisms change with age is important for the development of interventions to promote healthy ageing. Herein, we examine how impairment in the selective degradation of damaged/dysfunctional mitochondria through mitophagy may play a central role in the loss of mitochondrial proteostasis in skeletal muscle ageing, as well as its broader implications for systemic health. Further, we explore how stimulating mitophagy through exercise may promote healthy ageing.
Collapse
Affiliation(s)
- Joshua C. Drake
- Department of MedicineUniversity of Virginia School of MedicineCharlottesvilleVA22908USA
- Center for Skeletal Muscle Research at Robert M. Berne Cardiovascular Research CenterUniversity of Virginia School of MedicineCharlottesvilleVA22908USA
| | - Zhen Yan
- Department of MedicineUniversity of Virginia School of MedicineCharlottesvilleVA22908USA
- Center for Skeletal Muscle Research at Robert M. Berne Cardiovascular Research CenterUniversity of Virginia School of MedicineCharlottesvilleVA22908USA
- Department of PharmacologyUniversity of Virginia School of MedicineCharlottesvilleVA22908USA
- Department of Molecular Physiology and Biological PhysicsUniversity of Virginia School of MedicineCharlottesvilleVA22908USA
| |
Collapse
|
22
|
St-Jean-Pelletier F, Pion CH, Leduc-Gaudet JP, Sgarioto N, Zovilé I, Barbat-Artigas S, Reynaud O, Alkaterji F, Lemieux FC, Grenon A, Gaudreau P, Hepple RT, Chevalier S, Belanger M, Morais JA, Aubertin-Leheudre M, Gouspillou G. The impact of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, mitochondrial content, and intramyocellular lipids in men. J Cachexia Sarcopenia Muscle 2017; 8:213-228. [PMID: 27897402 PMCID: PMC5377417 DOI: 10.1002/jcsm.12139] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 06/20/2016] [Accepted: 07/12/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND The exact impact of ageing on skeletal muscle phenotype and mitochondrial and lipid content remains controversial, probably because physical activity, which greatly influences muscle physiology, is rarely accounted for. The present study was therefore designed to investigate the effects of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, and mitochondrial and intramyocellular lipid content in men. METHODS Recreationally active young adult (20-30 yo; YA); active (ACT) and sedentary (SED) middle-age (50-65 yo; MA-ACT and MA-SED); and older (65 + yo; 65 + ACT and 65 + SED) and pre-frail older (65 + PF) men were recruited. Muscle biopsies from the vastus lateralis were collected to assess, on muscle cross sections, muscle phenotype (using myosin heavy chain isoforms immunolabelling), the fibre type-specific content of mitochondria (by quantifying the succinate dehydrogenase stain intensity), and the fibre type-specific lipid content (by quantifying the Oil Red O stain intensity). RESULTS Only 65 + SED and 65 + PF displayed significantly lower overall and type IIa fibre sizes vs. YA. 65 + SED displayed a lower type IIa fibre proportion vs. YA. MA-SED and 65 + SED displayed a higher hybrid type IIa/IIx fibre proportion vs. YA. Sedentary and pre-frail, but not active, men displayed lower mitochondrial content irrespective of fibre type vs. YA. 65 + SED, but not 65 + ACT, displayed a higher lipid content in type I fibres vs. YA. Finally, mitochondrial content, but not lipid content, was positively correlated with indices of muscle function, functional capacity, and insulin sensitivity across all subjects. CONCLUSIONS Taken altogether, our results indicate that ageing in sedentary men is associated with (i) complex changes in muscle phenotype preferentially affecting type IIa fibres; (ii) a decline in mitochondrial content affecting all fibre types; and (iii) an increase in lipid content in type I fibres. They also indicate that physical activity partially protects from the effects of ageing on muscle phenotype, mitochondrial content, and lipid accumulation. No skeletal specific muscle phenotype of pre-frailty was observed.
Collapse
Affiliation(s)
- Félix St-Jean-Pelletier
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Québec, Canada
| | - Charlotte H Pion
- Groupe de Recherche en Activité Physique Adaptée, Québec, Canada.,Département de Biologie, Faculté des Sciences, UQAM, Quebec, Canada
| | - Jean-Philippe Leduc-Gaudet
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Québec, Canada
| | - Nicolas Sgarioto
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada
| | - Igor Zovilé
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada
| | - Sébastien Barbat-Artigas
- Groupe de Recherche en Activité Physique Adaptée, Québec, Canada.,Département de Biologie, Faculté des Sciences, UQAM, Quebec, Canada.,Département de Neurosciences, Faculté de Médecine, Université de Montréal, Québec, Canada
| | - Olivier Reynaud
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada
| | - Feras Alkaterji
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada
| | - François C Lemieux
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Québec, Canada
| | - Alexis Grenon
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada
| | - Pierrette Gaudreau
- Département de Médecine, UdeM, et Centre de Recherche du Centre Hospitalier de l'UdeM, Quebec, Canada
| | - Russell T Hepple
- Department of Kinesiology and Division of Critical Care Medicine, McGill University, Quebec, Canada.,McGill University Health Centre-Research Institute, Quebec, Canada
| | - Stéphanie Chevalier
- McGill University Health Centre-Research Institute, Quebec, Canada.,Division of Geriatric Medicine, McGill University, Quebec, Canada
| | - Marc Belanger
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Québec, Canada
| | - José A Morais
- McGill University Health Centre-Research Institute, Quebec, Canada.,Division of Geriatric Medicine, McGill University, Quebec, Canada
| | - Mylène Aubertin-Leheudre
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Québec, Canada.,Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Quebec, Canada
| | - Gilles Gouspillou
- Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.,Groupe de Recherche en Activité Physique Adaptée, Québec, Canada.,Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Quebec, Canada
| |
Collapse
|
23
|
Fiogbé E, de Vassimon-Barroso V, de Medeiros Takahashi AC. Exercise training in older adults, what effects on muscle oxygenation? A systematic review. Arch Gerontol Geriatr 2017; 71:89-98. [PMID: 28410504 DOI: 10.1016/j.archger.2017.03.001] [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: 09/09/2016] [Revised: 02/20/2017] [Accepted: 03/01/2017] [Indexed: 12/15/2022]
Abstract
AIM To determine the effects of different modality of exercise training programs on muscle oxygenation in older adults. METHODS Relevant articles were searched in PubMed, Web of Science, Science Direct and Scopus, using the keywords: "Aged" AND "Muscle oxygenation" AND (Exercise OR "Exercise therapy" OR "Exercise Movement Techniques" OR Hydrotherapy), without limitation concerning the publication date. To be included in the full analysis, the study had to be a randomized controlled trial in which older adults participants (mean age: 65 years at least) were submitted to an exercise-training program and muscle oxygenation assessment. RESULTS The searches resulted in 1238 articles from which 7 met all the inclusion criteria. The trials involved 370 older adults (68.7±1.7years), healthy and with peripheral arterial disease. Studies included resistance and endurance exercises as well as walking sessions. Training sessions were 2-6 time per week, lasted 3-24 months and with different training intensity throughout studies. After a long-term resistance training, healthy older adults showed enhanced muscle oxygen extraction capacity, regulation of vessels and vascular endothelium function; endurance training is reported to improve microvascular blood flow and matching of oxygen delivery to oxygen utilization, muscle oxidative capacity and muscle saturation, and walking sessions results in better muscle oxygen availability and muscle oxygen extraction capacity in older adults with peripheral arterial disease. CONCLUSIONS This review supports the fact that depending on the clinical status of the participants and the modality, exercise training improves different aspects of the muscle oxygenation in older adults.
Collapse
Affiliation(s)
- Elie Fiogbé
- Department of Physiotherapy, Federal University of Sao Carlos, São Carlos, SP, Brazil.
| | | | | |
Collapse
|
24
|
Sparks LM, Redman LM, Conley KE, Harper ME, Yi F, Hodges A, Eroshkin A, Costford SR, Gabriel ME, Shook C, Cornnell HH, Ravussin E, Smith SR. Effects of 12 Months of Caloric Restriction on Muscle Mitochondrial Function in Healthy Individuals. J Clin Endocrinol Metab 2017; 102:111-121. [PMID: 27778643 PMCID: PMC5413108 DOI: 10.1210/jc.2016-3211] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 10/21/2016] [Indexed: 11/19/2022]
Abstract
CONTEXT The effects of caloric restriction (CR) on in vivo muscle mitochondrial function in humans are controversial. OBJECTIVE We evaluated muscle mitochondrial function and associated transcriptional profiles in nonobese humans after 12 months of CR. DESIGN Individuals from an ancillary study of the CALERIE 2 randomized controlled trial were assessed at baseline and 12 months after a 25% CR or ad libitum (control) diet. SETTING The study was performed at Pennington Biomedical Research Center in Baton Rouge, LA. PARTICIPANTS Study participants included 51 (34 female subjects, 25 to 50 years of age) healthy nonobese individuals randomized to 1 of 2 groups (CR or control). INTERVENTION This study included 12 months of a 25% CR or ad libitum (control) diet. MAIN OUTCOMES In vivo mitochondrial function [maximal ATP synthesis rate (ATPmax), ATPflux/O2 (P/O)] was determined by 31P-magnetic resonance spectroscopy and optical spectroscopy, and body composition was determined by dual-energy X-ray absorptiometry. In a subset of individuals, a muscle biopsy was performed for transcriptional profiling via quantitative reverse transcription polymerase chain reaction and microarrays. RESULTS Weight, body mass index (BMI), fat, and fat-free mass (P < 0.001 for all) significantly decreased at month 12 after CR vs control. In vivo ATPmax and P/O were unaffected by 12 months of CR. Targeted transcriptional profiling showed no effects on pathways involved in mitochondrial biogenesis, function, or oxidative stress. A subgroup analysis according to baseline P/O demonstrated that a higher (vs lower) P/O was associated with notable improvements in ATPmax and P/O after CR. CONCLUSIONS In healthy nonobese humans, CR has no effect on muscle mitochondrial function; however, having a "more coupled" (versus "less coupled") phenotype enables CR-induced improvements in muscle mitochondrial function.
Collapse
Affiliation(s)
- Lauren M. Sparks
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, Florida 32804;
- Clinical and Molecular Origins of Disease, Sanford Burnham Prebys Medical Discovery Institute, Orlando, Florida 32827;
| | - Leanne M. Redman
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana 70808;
| | - Kevin E. Conley
- Radiology,
- Physiology & Biophysics, and
- Bioengineering, University of Washington Medical Center, Seattle, Washington 98195;
| | - Mary-Ellen Harper
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Ontario ON K1N 6N5, Canada;
| | - Fanchao Yi
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, Florida 32804;
| | - Andrew Hodges
- Bioinformatics Core, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037; and
| | - Alexey Eroshkin
- Bioinformatics Core, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037; and
| | | | - Meghan E. Gabriel
- Clinical and Molecular Origins of Disease, Sanford Burnham Prebys Medical Discovery Institute, Orlando, Florida 32827;
| | - Cherie Shook
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, Florida 32804;
| | - Heather H. Cornnell
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, Florida 32804;
| | - Eric Ravussin
- Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana 70808;
| | - Steven R. Smith
- Translational Research Institute for Metabolism and Diabetes, Florida Hospital, Orlando, Florida 32804;
- Clinical and Molecular Origins of Disease, Sanford Burnham Prebys Medical Discovery Institute, Orlando, Florida 32827;
| |
Collapse
|
25
|
Conley KE. Mitochondria to motion: optimizing oxidative phosphorylation to improve exercise performance. ACTA ACUST UNITED AC 2016; 219:243-9. [PMID: 26792336 DOI: 10.1242/jeb.126623] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Mitochondria oxidize substrates to generate the ATP that fuels muscle contraction and locomotion. This review focuses on three steps in oxidative phosphorylation that have independent roles in setting the overall mitochondrial ATP flux and thereby have direct impact on locomotion. The first is the electron transport chain, which sets the pace for oxidation. New studies indicate that the electron transport chain capacity per mitochondria declines with age and disease, but can be revived by both acute and chronic treatments. The resulting higher ATP production is reflected in improved muscle power output and locomotory performance. The second step is the coupling of ATP supply from O2 uptake (mitochondrial coupling efficiency). Treatments that elevate mitochondrial coupling raise both exercise efficiency and the capacity for sustained exercise in both young and old muscle. The final step is ATP synthesis itself, which is under dynamic control at multiple sites to provide the 50-fold range of ATP flux between resting muscle and exercise at the mitochondrial capacity. Thus, malleability at sites in these subsystems of oxidative phosphorylation has an impact on ATP flux, with direct effects on exercise performance. Interventions are emerging that target these three independent subsystems to provide many paths to improve ATP flux and elevate the muscle performance lost to inactivity, age or disease.
Collapse
Affiliation(s)
- Kevin E Conley
- Departments of Radiology, Physiology & Biophysics, and Bioengineering, University of Washington Medical Center, Seattle, WA 98195, USA
| |
Collapse
|
26
|
Hepple RT. Impact of aging on mitochondrial function in cardiac and skeletal muscle. Free Radic Biol Med 2016; 98:177-186. [PMID: 27033952 DOI: 10.1016/j.freeradbiomed.2016.03.017] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 03/12/2016] [Indexed: 12/13/2022]
Abstract
Both skeletal muscle and cardiac muscle are subject to marked structural and functional impairment with aging and these changes contribute to the reduced capacity for exercise as we age. Since mitochondria are involved in multiple aspects of cellular homeostasis including energetics, reactive oxygen species signaling, and regulation of intrinsic apoptotic pathways, defects in this organelle are frequently implicated in the deterioration of skeletal and cardiac muscle with aging. On this basis, the purpose of this review is to evaluate the evidence that aging causes dysfunction in mitochondria in striated muscle with a view towards drawing conclusions about the potential of these changes to contribute to the deterioration seen in striated muscle with aging. As will be shown, impairment in respiration and reactive oxygen species emission with aging are highly variable between studies and seem to be largely a consequence of physical inactivity. On the other hand, both skeletal and cardiac muscle mitochondria are more susceptible to permeability transition and this seems a likely cause of the increased recruitment of mitochondrial-mediated pathways of apoptosis seen in striated muscle. The review concludes by examining the role of degeneration of mitochondrial DNA versus impaired mitochondrial quality control mechanisms in the accumulation of mitochondria that are sensitized to permeability transition, whereby the latter mechanism is favored as the most likely cause.
Collapse
Affiliation(s)
- R T Hepple
- Department of Kinesiology, Centre for Translational Biology, McGill University Health Center, Canada; Meakins Christie Laboratories, Canada; Department of Medicine, McGill University, Canada
| |
Collapse
|
27
|
Exercise Promotes Healthy Aging of Skeletal Muscle. Cell Metab 2016; 23:1034-1047. [PMID: 27304505 PMCID: PMC5045036 DOI: 10.1016/j.cmet.2016.05.007] [Citation(s) in RCA: 289] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 05/18/2016] [Accepted: 05/24/2016] [Indexed: 02/08/2023]
Abstract
Primary aging is the progressive and inevitable process of bodily deterioration during adulthood. In skeletal muscle, primary aging causes defective mitochondrial energetics and reduced muscle mass. Secondary aging refers to additional deleterious structural and functional age-related changes caused by diseases and lifestyle factors. Secondary aging can exacerbate deficits in mitochondrial function and muscle mass, concomitant with the development of skeletal muscle insulin resistance. Exercise opposes deleterious effects of secondary aging by preventing the decline in mitochondrial respiration, mitigating aging-related loss of muscle mass and enhancing insulin sensitivity. This review focuses on mechanisms by which exercise promotes "healthy aging" by inducing modifications in skeletal muscle.
Collapse
|
28
|
Sabbah HN, Gupta RC, Kohli S, Wang M, Hachem S, Zhang K. Chronic Therapy With Elamipretide (MTP-131), a Novel Mitochondria-Targeting Peptide, Improves Left Ventricular and Mitochondrial Function in Dogs With Advanced Heart Failure. Circ Heart Fail 2016; 9:e002206. [PMID: 26839394 DOI: 10.1161/circheartfailure.115.002206] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND Elamipretide (MTP-131), a novel mitochondria-targeting peptide, was shown to reduce infarct size in animals with myocardial infarction and improve renal function in pigs with acute and chronic kidney injury. This study examined the effects of chronic therapy with elamipretide on left ventricular (LV) and mitochondrial function in dogs with heart failure (HF). METHODS AND RESULTS Fourteen dogs with microembolization-induced HF were randomized to 3 months monotherapy with subcutaneous injections of elamipretide (0.5 mg/kg once daily, HF+ELA, n=7) or saline (control, HF-CON, n=7). LV ejection fraction, plasma n-terminal pro-brain natriuretic peptide, tumor necrosis factor-α, and C-reactive protein were measured before (pretreatment) and 3 months after initiating therapy (post-treatment). Mitochondrial respiration, membrane potential (Δψm), maximum rate of ATP synthesis, and ATP/ADP ratio were measured in isolated LV cardiomyocytes obtained at post-treatment. In HF-CON dogs, ejection fraction decreased at post-treatment compared with pretreatment (29 ± 1% versus 31 ± 2%), whereas in HF+ELA dogs, ejection fraction significantly increased at post-treatment compared with pretreatment (36 ± 2% versus 30 ± 2%; P<0.05). In HF-CON, n-terminal pro-brain natriuretic peptide increased by 88 ± 120 pg/mL during follow-up but decreased significantly by 774 ± 85 pg/mL in HF+ELA dogs (P<0.001). Treatment with elamipretide also normalized plasma tumor necrosis factor-α and C-reactive protein and restored mitochondrial state-3 respiration, Δψm, rate of ATP synthesis, and ATP/ADP ratio (ATP/ADP: 0.38 ± 0.04 HF-CON versus 1.16 ± 0.15 HF+ELA; P<0.001). CONCLUSIONS Long-term therapy with elamipretide improves LV systolic function, normalizes plasma biomarkers, and reverses mitochondrial abnormalities in LV myocardium of dogs with advanced HF. The results support the development of elamipretide for the treatment of HF.
Collapse
Affiliation(s)
- Hani N Sabbah
- From the Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI.
| | - Ramesh C Gupta
- From the Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI
| | - Smita Kohli
- From the Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI
| | - Mengjun Wang
- From the Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI
| | - Souheila Hachem
- From the Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI
| | - Kefei Zhang
- From the Department of Medicine, Division of Cardiovascular Medicine, Henry Ford Hospital, Detroit, MI
| |
Collapse
|
29
|
Carter HN, Chen CCW, Hood DA. Mitochondria, muscle health, and exercise with advancing age. Physiology (Bethesda) 2016; 30:208-23. [PMID: 25933821 DOI: 10.1152/physiol.00039.2014] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Skeletal muscle health is dependent on the optimal function of its mitochondria. With advancing age, decrements in numerous mitochondrial variables are evident in muscle. Part of this decline is due to reduced physical activity, whereas the remainder appears to be attributed to age-related alterations in mitochondrial synthesis and degradation. Exercise is an important strategy to stimulate mitochondrial adaptations in older individuals to foster improvements in muscle function and quality of life.
Collapse
Affiliation(s)
- Heather N Carter
- Muscle Health Research Centre, School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada
| | - Chris C W Chen
- Muscle Health Research Centre, School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada
| | - David A Hood
- Muscle Health Research Centre, School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada
| |
Collapse
|
30
|
Campbell MD, Marcinek DJ. Evaluation of in vivo mitochondrial bioenergetics in skeletal muscle using NMR and optical methods. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1862:716-724. [PMID: 26708941 PMCID: PMC4788529 DOI: 10.1016/j.bbadis.2015.12.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 11/20/2015] [Accepted: 12/16/2015] [Indexed: 12/13/2022]
Abstract
It is now clear that mitochondria are involved as either a cause or consequence of many chronic diseases. This central role of the mitochondria is due to their position in the cell as important integrators of cellular energetics and signaling. Mitochondrial function affects many aspects of the cellular environment such as redox homeostasis and calcium signaling, which then also exert control over mitochondrial function. This complex dynamic between mitochondrial function and the cellular environment highlights the value of examining mitochondria in vivo in the intact physiological environment. This review discusses NMR and optical approaches used to measure mitochondria ATP and oxygen fluxes that provide in vivo measures of mitochondrial capacity and quality in animal and human models. Combining these in vivo measurements with more traditional ex vivo analyses can lead to new insights into the importance of the cellular environment in controlling mitochondrial function under pathological conditions. Interpretation and underlying assumptions for each technique are discussed with the goal of providing an overview of some of the most common approaches used to measure in vivo mitochondrial function encountered in the literature.
Collapse
Affiliation(s)
- Matthew D Campbell
- University of Washington, Seattle, 850 Republican St., Brotman D142, Seattle, WA 98109, USA.
| | - David J Marcinek
- University of Washington, Seattle, 850 Republican St., Brotman D142, Seattle, WA 98109, USA.
| |
Collapse
|
31
|
Diolez P, Bourdel-Marchasson I, Calmettes G, Pasdois P, Detaille D, Rouland R, Gouspillou G. Hypothesis on Skeletal Muscle Aging: Mitochondrial Adenine Nucleotide Translocator Decreases Reactive Oxygen Species Production While Preserving Coupling Efficiency. Front Physiol 2015; 6:369. [PMID: 26733871 PMCID: PMC4679911 DOI: 10.3389/fphys.2015.00369] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 11/19/2015] [Indexed: 01/07/2023] Open
Abstract
Mitochondrial membrane potential is the major regulator of mitochondrial functions, including coupling efficiency and production of reactive oxygen species (ROS). Both functions are crucial for cell bioenergetics. We previously presented evidences for a specific modulation of adenine nucleotide translocase (ANT) appearing during aging that results in a decrease in membrane potential - and therefore ROS production-but surprisingly increases coupling efficiency under conditions of low ATP turnover. Careful study of the bioenergetic parameters (oxidation and phosphorylation rates, membrane potential) of isolated mitochondria from skeletal muscles (gastrocnemius) of aged and young rats revealed a remodeling at the level of the phosphorylation system, in the absence of alteration of the inner mitochondrial membrane (uncoupling) or respiratory chain complexes regulation. We further observed a decrease in mitochondrial affinity for ADP in aged isolated mitochondria, and higher sensitivity of ANT to its specific inhibitor atractyloside. This age-induced modification of ANT results in an increase in the ADP concentration required to sustain the same ATP turnover as compared to young muscle, and therefore in a lower membrane potential under phosphorylating-in vivo-conditions. Thus, for equivalent ATP turnover (cellular ATP demand), coupling efficiency is even higher in aged muscle mitochondria, due to the down-regulation of inner membrane proton leak caused by the decrease in membrane potential. In the framework of the radical theory of aging, these modifications in ANT function may be the result of oxidative damage caused by intra mitochondrial ROS and may appear like a virtuous circle where ROS induce a mechanism that reduces their production, without causing uncoupling, and even leading in improved efficiency. Because of the importance of ROS as therapeutic targets, this new mechanism deserves further studies.
Collapse
Affiliation(s)
- Philippe Diolez
- INSERM U1045 - Centre de Recherche Cardio-Thoracique de Bordeaux and LIRYC, Institut de Rythmologie et Modélisation Cardiaque, Université de Bordeaux, CHU de Bordeaux Pessac, France
| | - Isabelle Bourdel-Marchasson
- CHU de Bordeaux, Pôle de Gérontologie CliniqueBordeaux, France; Résonance Magnétique des Systèmes Biologiques, UMR 5536 Centre National de la Recherche Scientifique, Université de BordeauxBordeaux, France
| | - Guillaume Calmettes
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles Los Angeles, CA, USA
| | - Philippe Pasdois
- INSERM U1045 - Centre de Recherche Cardio-Thoracique de Bordeaux and LIRYC, Institut de Rythmologie et Modélisation Cardiaque, Université de Bordeaux, CHU de Bordeaux Pessac, France
| | - Dominique Detaille
- INSERM U1045 - Centre de Recherche Cardio-Thoracique de Bordeaux and LIRYC, Institut de Rythmologie et Modélisation Cardiaque, Université de Bordeaux, CHU de Bordeaux Pessac, France
| | - Richard Rouland
- Résonance Magnétique des Systèmes Biologiques, UMR 5536 Centre National de la Recherche Scientifique, Université de Bordeaux Bordeaux, France
| | - Gilles Gouspillou
- Département des Sciences de l'activité Physique, Université du Québec À Montréal Montréal, QC, Canada
| |
Collapse
|
32
|
Skeletal muscle mitochondrial energetic efficiency and aging. Int J Mol Sci 2015; 16:10674-85. [PMID: 25970752 PMCID: PMC4463669 DOI: 10.3390/ijms160510674] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/05/2015] [Accepted: 05/05/2015] [Indexed: 02/06/2023] Open
Abstract
Aging is associated with a progressive loss of maximal cell functionality, and mitochondria are considered a key factor in aging process, since they determine the ATP availability in the cells. Mitochondrial performance during aging in skeletal muscle is reported to be either decreased or unchanged. This heterogeneity of results could partly be due to the method used to assess mitochondrial performance. In addition, in skeletal muscle the mitochondrial population is heterogeneous, composed of subsarcolemmal and intermyofibrillar mitochondria. Therefore, the purpose of the present review is to summarize the results obtained on the functionality of the above mitochondrial populations during aging, taking into account that the mitochondrial performance depends on organelle number, organelle activity, and energetic efficiency of the mitochondrial machinery in synthesizing ATP from the oxidation of fuels.
Collapse
|
33
|
Ortega JD, Farley CT. Effects of aging on mechanical efficiency and muscle activation during level and uphill walking. J Electromyogr Kinesiol 2015; 25:193-8. [PMID: 25263547 PMCID: PMC4306638 DOI: 10.1016/j.jelekin.2014.09.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 08/28/2014] [Accepted: 09/01/2014] [Indexed: 10/24/2022] Open
Abstract
PURPOSE The metabolic cost of walking is greater in old compared to young adults. This study examines the relation between metabolic cost, muscular efficiency, and leg muscle co-activation during level and uphill walking in young and older adults. PROCEDURES Metabolic cost and leg muscle activation were measured in young (22.3 ± 3.6 years) and older adults (74.5 ± 2.9 years) walking on a treadmill at six different slopes (0.0-7.5% grade) and a speed of 1.3 ms(-1). Across the range of slopes, 'delta mechanical efficiency' of the muscular system and antagonist muscle co-activation were quantified. MAIN FINDINGS Across all slopes, older adults walked with a 13-17% greater metabolic cost, 12% lower efficiency, and 25% more leg muscle co-activation than young adults. Among older adults, co-activation was weakly correlated to metabolic cost (r=.233) and not correlated to the lower delta efficiency. CONCLUSION Lower muscular efficiency and increased leg muscle co-activation contribute to the greater metabolic cost of uphill slope walking among older adults but are unrelated to one another.
Collapse
Affiliation(s)
- Justus D Ortega
- Biomechanics Laboratory, Department of Kinesiology and Recreation Administration, Humboldt State University, CA, United States.
| | - Claire T Farley
- Locomtion Laboratory, Department of Integrative Physiology, University of Colorado, CO, United States
| |
Collapse
|
34
|
Hepple RT. Mitochondrial involvement and impact in aging skeletal muscle. Front Aging Neurosci 2014; 6:211. [PMID: 25309422 PMCID: PMC4159998 DOI: 10.3389/fnagi.2014.00211] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 07/30/2014] [Indexed: 01/07/2023] Open
Abstract
Atrophy is a defining feature of aging skeletal muscle that contributes to progressive weakness and an increased risk of mobility impairment, falls, and physical frailty in very advanced age. Amongst the most frequently implicated mechanisms of aging muscle atrophy is mitochondrial dysfunction. Recent studies employing methods that are well-suited to interrogating intrinsic mitochondrial function find that mitochondrial respiration and reactive oxygen species emission changes are inconsistent between aging rat muscles undergoing atrophy and appear normal in human skeletal muscle from septuagenarian physically active subjects. On the other hand, a sensitization to permeability transition seems to be a general property of atrophying muscle with aging and this effect is even seen in atrophying muscle from physically active septuagenarian subjects. In addition to this intrinsic alteration in mitochondrial function, factors extrinsic to the mitochondria may also modulate mitochondrial function in aging muscle. In particular, recent evidence implicates oxidative stress in the aging milieu as a factor that depresses respiratory function in vivo (an effect that is not present ex vivo). Furthermore, in very advanced age, not only does muscle atrophy become more severe and clinically relevant in terms of its impact, but also there is evidence that this is driven by an accumulation of severely atrophied denervated myofibers. As denervation can itself modulate mitochondrial function and recruit mitochondrial-mediated atrophy pathways, future investigations need to address the degree to which skeletal muscle mitochondrial alterations in very advanced age are a consequence of denervation, rather than a primary organelle defect, to refine our understanding of the relevance of mitochondria as a therapeutic target at this more advanced age.
Collapse
Affiliation(s)
- Russell T Hepple
- Department of Kinesiology, McGill University Health Center, McGill University , Montreal, QC , Canada
| |
Collapse
|
35
|
Szeto HH, Birk AV. Serendipity and the discovery of novel compounds that restore mitochondrial plasticity. Clin Pharmacol Ther 2014; 96:672-83. [PMID: 25188726 DOI: 10.1038/clpt.2014.174] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 08/23/2014] [Indexed: 01/10/2023]
Abstract
The mitochondrial electron transport chain (ETC) plays a central role in energy generation in the cell. Mitochondrial dysfunctions diminish adenosine triphosphate (ATP) production and result in insufficient energy to maintain cell function. As energy output declines, the most energetic tissues are preferentially affected. To satisfy cellular energy demands, the mitochondrial ETC needs to be able to elevate its capacity to produce ATP at times of increased metabolic demand or decreased fuel supply. This mitochondrial plasticity is reduced in many age-associated diseases. In this review, we describe the serendipitous discovery of a novel class of compounds that selectively target cardiolipin on the inner mitochondrial membrane to optimize efficiency of the ETC and thereby restore cellular bioenergetics in aging and diverse disease models, without any effect on the normal healthy organism. The first of these compounds, SS-31, is currently in multiple clinical trials.
Collapse
Affiliation(s)
- H H Szeto
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA
| | - A V Birk
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Weill Cornell Medical College, New York, New York, USA
| |
Collapse
|
36
|
Transient receptor potential melastatin 8 channel inhibition potentiates the hypothermic response to transient receptor potential vanilloid 1 activation in the conscious mouse. Crit Care Med 2014; 42:e355-63. [PMID: 24595220 DOI: 10.1097/ccm.0000000000000229] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVES Mild decrease in core temperature (therapeutic hypothermia) provides lasting neuroprotection following cardiac arrest or cerebral ischemia. However, current methods for producing therapeutic hypothermia trigger a cold-defense response that must be countered by sedatives, muscle paralytics, and mechanical ventilation. We aimed to determine methods for producing hypothermia in the conscious mouse by targeting two transient receptor potential channels involved in thermoregulation, two transient receptor potential (TRP) channels involved in thermoregulation, TRP vanilloid 1 (TRPV1) and TRP melastatin 8 (TRPM8). DESIGN Controlled prospective animal study. SETTING Research laboratory at academic medical center. SUBJECTS Conscious unrestrained young and aged male mice. INTERVENTIONS Mice were treated with the TRPV1 agonist dihydrocapsaicin, a TRPM8 inhibitor ("compound 5"), or their combination and the effects on core temperature (Tcore) were measured by implanted thermocouples and wireless transponders. MEASUREMENTS AND MAIN RESULTS TRPV1 agonist dihydrocapsaicin produced a dose-dependent (2-4 mg/kg s.c.) drop in Tcore. A loading dose followed by continuous infusion of dihydrocapsaicin produced a rapid and prolonged (> 6 hr) drop of Tcore within the therapeutic range (32-34°C). The hypothermic effect of dihydrocapsaicin was augmented in aged mice and was not desensitized with repeated administration. TRPM8 inhibitor "compound 5" (20 mg/kg s.c.) augmented the drop in core temperature during cold exposure (8°C). When "compound 5" (30 mg/kg) was combined with dihydrocapsaicin (1.25-2.5 mg/kg), the drop in Tcore was amplified and prolonged. CONCLUSIONS Activating warm receptors (TRPV1) produced rapid and lasting hypothermia in young and old mice. Furthermore, hypothermia induced by TRPV1 agonists was potentiated and prolonged by simultaneous inhibition of TRPM8.
Collapse
|
37
|
Dai DF, Chiao YA, Marcinek DJ, Szeto HH, Rabinovitch PS. Mitochondrial oxidative stress in aging and healthspan. LONGEVITY & HEALTHSPAN 2014; 3:6. [PMID: 24860647 DOI: 10.1201/b21905] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 03/10/2014] [Indexed: 05/26/2023]
Abstract
The free radical theory of aging proposes that reactive oxygen species (ROS)-induced accumulation of damage to cellular macromolecules is a primary driving force of aging and a major determinant of lifespan. Although this theory is one of the most popular explanations for the cause of aging, several experimental rodent models of antioxidant manipulation have failed to affect lifespan. Moreover, antioxidant supplementation clinical trials have been largely disappointing. The mitochondrial theory of aging specifies more particularly that mitochondria are both the primary sources of ROS and the primary targets of ROS damage. In addition to effects on lifespan and aging, mitochondrial ROS have been shown to play a central role in healthspan of many vital organ systems. In this article we review the evidence supporting the role of mitochondrial oxidative stress, mitochondrial damage and dysfunction in aging and healthspan, including cardiac aging, age-dependent cardiovascular diseases, skeletal muscle aging, neurodegenerative diseases, insulin resistance and diabetes as well as age-related cancers. The crosstalk of mitochondrial ROS, redox, and other cellular signaling is briefly presented. Potential therapeutic strategies to improve mitochondrial function in aging and healthspan are reviewed, with a focus on mitochondrial protective drugs, such as the mitochondrial antioxidants MitoQ, SkQ1, and the mitochondrial protective peptide SS-31.
Collapse
Affiliation(s)
- Dao-Fu Dai
- Department of Pathology, University of Washington, 1959 Pacific Ave NE, HSB-K081, Seattle, WA 98195, USA
| | - Ying Ann Chiao
- Department of Pathology, University of Washington, 1959 Pacific Ave NE, HSB-K081, Seattle, WA 98195, USA
| | - David J Marcinek
- Department of Radiology, University of Washington, Seattle, WA, USA
| | - Hazel H Szeto
- Department of Pharmacology, Weill Cornell Medical College, New York, NY, USA
| | - Peter S Rabinovitch
- Department of Pathology, University of Washington, 1959 Pacific Ave NE, HSB-K081, Seattle, WA 98195, USA
| |
Collapse
|
38
|
Mitochondrial oxidative stress in aging and healthspan. LONGEVITY & HEALTHSPAN 2014; 3:6. [PMID: 24860647 PMCID: PMC4013820 DOI: 10.1186/2046-2395-3-6] [Citation(s) in RCA: 300] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 03/10/2014] [Indexed: 02/07/2023]
Abstract
The free radical theory of aging proposes that reactive oxygen species (ROS)-induced accumulation of damage to cellular macromolecules is a primary driving force of aging and a major determinant of lifespan. Although this theory is one of the most popular explanations for the cause of aging, several experimental rodent models of antioxidant manipulation have failed to affect lifespan. Moreover, antioxidant supplementation clinical trials have been largely disappointing. The mitochondrial theory of aging specifies more particularly that mitochondria are both the primary sources of ROS and the primary targets of ROS damage. In addition to effects on lifespan and aging, mitochondrial ROS have been shown to play a central role in healthspan of many vital organ systems. In this article we review the evidence supporting the role of mitochondrial oxidative stress, mitochondrial damage and dysfunction in aging and healthspan, including cardiac aging, age-dependent cardiovascular diseases, skeletal muscle aging, neurodegenerative diseases, insulin resistance and diabetes as well as age-related cancers. The crosstalk of mitochondrial ROS, redox, and other cellular signaling is briefly presented. Potential therapeutic strategies to improve mitochondrial function in aging and healthspan are reviewed, with a focus on mitochondrial protective drugs, such as the mitochondrial antioxidants MitoQ, SkQ1, and the mitochondrial protective peptide SS-31.
Collapse
|
39
|
Szeto HH. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol 2014; 171:2029-50. [PMID: 24117165 PMCID: PMC3976620 DOI: 10.1111/bph.12461] [Citation(s) in RCA: 356] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 09/06/2013] [Accepted: 10/01/2013] [Indexed: 12/16/2022] Open
Abstract
A decline in energy is common in aging, and the restoration of mitochondrial bioenergetics may offer a common approach for the treatment of numerous age-associated diseases. Cardiolipin is a unique phospholipid that is exclusively expressed on the inner mitochondrial membrane where it plays an important structural role in cristae formation and the organization of the respiratory complexes into supercomplexes for optimal oxidative phosphorylation. The interaction between cardiolipin and cytochrome c determines whether cytochrome c acts as an electron carrier or peroxidase. Cardiolipin peroxidation and depletion have been reported in a variety of pathological conditions associated with energy deficiency, and cardiolipin has been identified as a target for drug development. This review focuses on the discovery and development of the first cardiolipin-protective compound as a therapeutic agent. SS-31 is a member of the Szeto-Schiller (SS) peptides known to selectively target the inner mitochondrial membrane. SS-31 binds selectively to cardiolipin via electrostatic and hydrophobic interactions. By interacting with cardiolipin, SS-31 prevents cardiolipin from converting cytochrome c into a peroxidase while protecting its electron carrying function. As a result, SS-31 protects the structure of mitochondrial cristae and promotes oxidative phosphorylation. SS-31 represents a new class of compounds that can recharge the cellular powerhouse and restore bioenergetics. Extensive animal studies have shown that targeting such a fundamental mechanism can benefit highly complex diseases that share a common pathogenesis of bioenergetics failure. This review summarizes the mechanisms of action and therapeutic potential of SS-31 and provides an update of its clinical development programme.
Collapse
Affiliation(s)
- Hazel H Szeto
- Research Program in Mitochondrial Therapeutics, Department of Pharmacology, Joan and Sanford I. Weill Medical College of Cornell UniversityNew York, NY, USA
| |
Collapse
|
40
|
Gouspillou G, Bourdel-Marchasson I, Rouland R, Calmettes G, Biran M, Deschodt-Arsac V, Miraux S, Thiaudiere E, Pasdois P, Detaille D, Franconi JM, Babot M, Trézéguet V, Arsac L, Diolez P. Mitochondrial energetics is impaired in vivo in aged skeletal muscle. Aging Cell 2014; 13:39-48. [PMID: 23919652 PMCID: PMC4326861 DOI: 10.1111/acel.12147] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/25/2013] [Indexed: 12/25/2022] Open
Abstract
With aging, most skeletal muscles undergo a progressive loss of mass and strength, a process termed sarcopenia. Aging-related defects in mitochondrial energetics have been proposed to be causally involved in sarcopenia. However, changes in muscle mitochondrial oxidative phosphorylation with aging remain a highly controversial issue, creating a pressing need for integrative approaches to determine whether mitochondrial bioenergetics are impaired in aged skeletal muscle. To address this issue, mitochondrial bioenergetics was first investigated in vivo in the gastrocnemius muscle of adult (6 months) and aged (21 months) male Wistar rats by combining a modular control analysis approach with 31P magnetic resonance spectroscopy measurements of energetic metabolites. Using this innovative approach, we revealed that the in vivo responsiveness (‘elasticity’) of mitochondrial oxidative phosphorylation to contraction-induced increase in ATP demand is significantly reduced in aged skeletal muscle, a reduction especially pronounced under low contractile activities. In line with this in vivo aging-related defect in mitochondrial energetics, we found that the mitochondrial affinity for ADP is significantly decreased in mitochondria isolated from aged skeletal muscle. Collectively, the results of this study demonstrate that mitochondrial bioenergetics are effectively altered in vivo in aged skeletal muscle and provide a novel cellular basis for this phenomenon.
Collapse
Affiliation(s)
- Gilles Gouspillou
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
- Département de Kinanthropologie; Université du Québec à Montréal; Montreal Quebec Canada
| | - Isabelle Bourdel-Marchasson
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
- CHU de Bordeaux; Pôle de gérontologie clinique; Bordeaux France
| | - Richard Rouland
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
| | - Guillaume Calmettes
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
- Department of Medicine (Cardiology); David Geffen School of Medicine; University of California; Los Angeles CA USA
| | - Marc Biran
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
| | - Véronique Deschodt-Arsac
- INSERM U1045 - Cardio-Thoracic Research Centre - and Rhythmology and Heart Modeling Institute (LIRYC); Bordeaux University; Bordeaux France
| | - Sylvain Miraux
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
| | - Eric Thiaudiere
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
| | - Philippe Pasdois
- INSERM U1045 - Cardio-Thoracic Research Centre - and Rhythmology and Heart Modeling Institute (LIRYC); Bordeaux University; Bordeaux France
| | - Dominique Detaille
- INSERM U1045 - Cardio-Thoracic Research Centre - and Rhythmology and Heart Modeling Institute (LIRYC); Bordeaux University; Bordeaux France
| | - Jean-Michel Franconi
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
| | - Marion Babot
- Laboratoire de Physiologie Moléculaire et Cellulaire; Institut de Biochimie et Génétique Cellulaires; UMR 5095; CNRS-Université Bordeaux 2; Bordeaux Cedex France
| | - Véronique Trézéguet
- Laboratoire de Physiologie Moléculaire et Cellulaire; Institut de Biochimie et Génétique Cellulaires; UMR 5095; CNRS-Université Bordeaux 2; Bordeaux Cedex France
| | - Laurent Arsac
- Résonance Magnétique des Systèmes Biologiques; UMR 5536 CNRS - Bordeaux Segalen University; Bordeaux France
| | - Philippe Diolez
- INSERM U1045 - Cardio-Thoracic Research Centre - and Rhythmology and Heart Modeling Institute (LIRYC); Bordeaux University; Bordeaux France
| |
Collapse
|
41
|
Vogiatzis I, Zakynthinos S. Factors limiting exercise tolerance in chronic lung diseases. Compr Physiol 2013; 2:1779-817. [PMID: 23723024 DOI: 10.1002/cphy.c110015] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The major limitation to exercise performance in patients with chronic lung diseases is an issue of great importance since identifying the factors that prevent these patients from carrying out activities of daily living provides an important perspective for the choice of the appropriate therapeutic strategy. The factors that limit exercise capacity may be different in patients with different disease entities (i.e., chronic obstructive, restrictive or pulmonary vascular lung disease) or disease severity and ultimately depend on the degree of malfunction or miss coordination between the different physiological systems (i.e., respiratory, cardiovascular and peripheral muscles). This review focuses on patients with chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD) and pulmonary vascular disease (PVD). ILD and PVD are included because there is sufficient experimental evidence for the factors that limit exercise capacity and because these disorders are representative of restrictive and pulmonary vascular disorders, respectively. A great deal of emphasis is given, however, to causes of exercise intolerance in COPD mainly because of the plethora of research findings that have been published in this area and also because exercise intolerance in COPD has been used as a model for understanding the interactions of different pathophysiologic mechanisms in exercise limitation. As exercise intolerance in COPD is recognized as being multifactorial, the impacts of the following factors on patients' exercise capacity are explored from an integrative physiological perspective: (i) imbalance between the ventilatory capacity and requirement; (ii) imbalance between energy demands and supplies to working respiratory and peripheral muscles; and (iii) peripheral muscle intrinsic dysfunction/weakness.
Collapse
Affiliation(s)
- Ioannis Vogiatzis
- Department of Physical Education and Sport Sciences, National and Kapodistrian University of Athens, Greece.
| | | |
Collapse
|
42
|
Ortega JD. Counterpoint: skeletal muscle mechanical efficiency does not increase with age. J Appl Physiol (1985) 2013; 114:1109-11. [PMID: 23588538 DOI: 10.1152/japplphysiol.01438.2012a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Affiliation(s)
- Justus D Ortega
- Department of Kinesiology, Humboldt State University, Arcata, CA, USA.
| |
Collapse
|
43
|
Siegel MP, Kruse SE, Percival JM, Goh J, White CC, Hopkins HC, Kavanagh TJ, Szeto HH, Rabinovitch PS, Marcinek DJ. Mitochondrial-targeted peptide rapidly improves mitochondrial energetics and skeletal muscle performance in aged mice. Aging Cell 2013; 12:763-71. [PMID: 23692570 PMCID: PMC3772966 DOI: 10.1111/acel.12102] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/10/2013] [Indexed: 12/25/2022] Open
Abstract
Mitochondrial dysfunction plays a key pathogenic role in aging skeletal muscle resulting in significant healthcare costs in the developed world. However, there is no pharmacologic treatment to rapidly reverse mitochondrial deficits in the elderly. Here, we demonstrate that a single treatment with the mitochondrial-targeted peptide SS-31 restores in vivo mitochondrial energetics to young levels in aged mice after only one hour. Young (5 month old) and old (27 month old) mice were injected intraperitoneally with either saline or 3 mg kg(-1) of SS-31. Skeletal muscle mitochondrial energetics were measured in vivo one hour after injection using a unique combination of optical and (31) P magnetic resonance spectroscopy. Age-related declines in resting and maximal mitochondrial ATP production, coupling of oxidative phosphorylation (P/O), and cell energy state (PCr/ATP) were rapidly reversed after SS-31 treatment, while SS-31 had no observable effect on young muscle. These effects of SS-31 on mitochondrial energetics in aged muscle were also associated with a more reduced glutathione redox status and lower mitochondrial H2 O2 emission. Skeletal muscle of aged mice was more fatigue resistant in situ one hour after SS-31 treatment, and eight days of SS-31 treatment led to increased whole-animal endurance capacity. These data demonstrate that SS-31 represents a new strategy for reversing age-related deficits in skeletal muscle with potential for translation into human use.
Collapse
Affiliation(s)
- M. P. Siegel
- Department of Bioengineering, University of Washington, Seattle, WA 98195
| | - S. E. Kruse
- Department of Radiology, University of Washington, Seattle, WA 98195
| | - J. M. Percival
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - J. Goh
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
- Department of Nutritional Science, University of Washington, Seattle, WA 98195
| | - C. C. White
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195
| | - H. C. Hopkins
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195
| | - T. J. Kavanagh
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195
| | - H. H. Szeto
- Department of Pharmacology, Weill Cornell Medical College, New York, NY 10021
| | - P. S. Rabinovitch
- Department of Pathology, University of Washington, Seattle, WA 98195
| | - D. J. Marcinek
- Department of Bioengineering, University of Washington, Seattle, WA 98195
- Department of Radiology, University of Washington, Seattle, WA 98195
| |
Collapse
|
44
|
Conley KE, Amara CE, Bajpeyi S, Costford SR, Murray K, Jubrias SA, Arakaki L, Marcinek DJ, Smith SR. Higher mitochondrial respiration and uncoupling with reduced electron transport chain content in vivo in muscle of sedentary versus active subjects. J Clin Endocrinol Metab 2013; 98:129-36. [PMID: 23150693 PMCID: PMC3537085 DOI: 10.1210/jc.2012-2967] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
OBJECTIVE This study investigated the disparity between muscle metabolic rate and mitochondrial metabolism in human muscle of sedentary vs. active individuals. RESEARCH DESIGN AND METHODS Chronic activity level was characterized by a physical activity questionnaire and a triaxial accelerometer as well as a maximal oxygen uptake test. The ATP and O(2) fluxes and mitochondrial coupling (ATP/O(2) or P/O) in resting muscle as well as mitochondrial capacity (ATP(max)) were determined in vivo in human vastus lateralis muscle using magnetic resonance and optical spectroscopy on 24 sedentary and seven active subjects. Muscle biopsies were analyzed for electron transport chain content (using complex III as a representative marker) and mitochondrial proteins associated with antioxidant protection. RESULTS Sedentary muscle had lower electron transport chain complex content (65% of the active group) in proportion to the reduction in ATP(max) (0.69 ± 0.07 vs. 1.07 ± 0.06 mM sec(-1)) as compared with active subjects. This lower ATP(max) paired with an unchanged O(2) flux in resting muscle between groups resulted in a doubling of O(2) flux per ATP(max) (3.3 ± 0.3 vs. 1.7 ± 0.2 μM O(2) per mM ATP) that reflected mitochondrial uncoupling (P/O = 1.41 ± 0.1 vs. 2.1 ± 0.3) and greater UCP3/complex III (6.0 ± 0.7 vs. 3.8 ± 0.3) in sedentary vs. active subjects. CONCLUSION A smaller mitochondrial pool serving the same O(2) flux resulted in elevated mitochondrial respiration in sedentary muscle. In addition, uncoupling contributed to this higher mitochondrial respiration. This finding resolves the paradox of stable muscle metabolism but greater mitochondrial respiration in muscle of inactive vs. active subjects.
Collapse
Affiliation(s)
- Kevin E Conley
- Department of Radiology, University of Washington Medical Center, Box 357115, Seattle, Washington 98195-7115, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Sutherland GT, Chami B, Youssef P, Witting PK. Oxidative stress in Alzheimer's disease: Primary villain or physiological by-product? Redox Rep 2013; 18:134-41. [PMID: 23849337 PMCID: PMC6837641 DOI: 10.1179/1351000213y.0000000052] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The prevalence of Alzheimer's disease (AD) is increasing rapidly worldwide due to an ageing population and largely ineffective treatments. In AD cognitive decline is due to progressive neuron loss that begins in the medial temporal lobe and spreads through many brain regions. Despite intense research the pathogenesis of the common sporadic form of AD remains largely unknown. The popular amyloid cascade hypothesis suggests that the accumulation of soluble oligomers of beta amyloid peptides (Aβ) initiates a series of events that cause neuronal loss. Among their putative toxic effects, Aβ oligomers are thought to act as pro-oxidants combining with redox-active metals to produce excessive reactive oxygen and nitrogen species. However, to date the experimental therapies that reduce Aβ load in AD have failed to halt cognitive decline. Another hypothesis proposed by the late Mark Smith and colleagues is that oxidative stress, rather than Aβ, precipitates the pathogenesis of AD. That is, Aβ and microtubule-associated protein tau are upregulated to address the redox imbalance in the AD brain. As the disease progresses, excess Aβ and tau oligomerise to further accelerate the disease process. Here, we discuss redox balance in the human brain and how this balance is affected by ageing. We then discuss where oxidative stress is most likely to act in the disease process and the potential for intervention to reduce its effects.
Collapse
|
46
|
Suetta C, Frandsen U, Jensen L, Jensen MM, Jespersen JG, Hvid LG, Bayer M, Petersson SJ, Schrøder HD, Andersen JL, Heinemeier KM, Aagaard P, Schjerling P, Kjaer M. Aging affects the transcriptional regulation of human skeletal muscle disuse atrophy. PLoS One 2012; 7:e51238. [PMID: 23284670 PMCID: PMC3526599 DOI: 10.1371/journal.pone.0051238] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 11/05/2012] [Indexed: 12/24/2022] Open
Abstract
Important insights concerning the molecular basis of skeletal muscle disuse-atrophy and aging related muscle loss have been obtained in cell culture and animal models, but these regulatory signaling pathways have not previously been studied in aging human muscle. In the present study, muscle atrophy was induced by immobilization in healthy old and young individuals to study the time-course and transcriptional factors underlying human skeletal muscle atrophy. The results reveal that irrespectively of age, mRNA expression levels of MuRF-1 and Atrogin-1 increased in the very initial phase (2–4 days) of human disuse-muscle atrophy along with a marked reduction in PGC-1α and PGC-1β (1–4 days) and a ∼10% decrease in myofiber size (4 days). Further, an age-specific decrease in Akt and S6 phosphorylation was observed in young muscle within the first days (1–4 days) of immobilization. In contrast, Akt phosphorylation was unchanged in old muscle after 2 days and increased after 4 days of immobilization. Further, an age-specific down-regulation of MuRF-1 and Atrogin-1 expression levels was observed following 2 weeks of immobilization, along with a slowing atrophy response in aged skeletal muscle. Neither the immediate loss of muscle mass, nor the subsequent age-differentiated signaling responses could be explained by changes in inflammatory mediators, apoptosis markers or autophagy indicators. Collectively, these findings indicate that the time-course and regulation of human skeletal muscle atrophy is age dependent, leading to an attenuated loss in aging skeletal muscle when exposed to longer periods of immobility-induced disuse.
Collapse
MESH Headings
- Adult
- Aged
- Aging/genetics
- Aging/metabolism
- Aging/pathology
- Aging/physiology
- Apoptosis/genetics
- Autophagy/genetics
- Cytokines/metabolism
- Forkhead Transcription Factors/genetics
- Heat-Shock Proteins/genetics
- Humans
- Insulin-Like Growth Factor I/metabolism
- Male
- Middle Aged
- Muscle Contraction/genetics
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle Proteins/genetics
- Muscle Strength/genetics
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Muscular Disorders, Atrophic/genetics
- Muscular Disorders, Atrophic/metabolism
- Muscular Disorders, Atrophic/pathology
- Muscular Disorders, Atrophic/physiopathology
- NF-kappa B/metabolism
- Organ Size
- Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
- Proto-Oncogene Proteins c-akt/metabolism
- Signal Transduction/genetics
- Transcription Factors/genetics
- Transcription, Genetic/genetics
- Transcriptome
- Tripartite Motif Proteins
- Ubiquitin-Protein Ligases/genetics
- Young Adult
Collapse
Affiliation(s)
- Charlotte Suetta
- Institute of Sports Medicine and Center for Healthy Aging, University of Copenhagen, Bispebjerg Hospital, Copenhagen, Denmark.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Conley KE, Jubrias SA, Cress ME, Esselman P. Exercise efficiency is reduced by mitochondrial uncoupling in the elderly. Exp Physiol 2012; 98:768-77. [PMID: 23085769 DOI: 10.1113/expphysiol.2012.067314] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A reduction in exercise efficiency accompanies ageing in humans. Here we evaluated the impact of changes in the contractile-coupling and mitochondrial-coupling efficiencies on the reduction in exercise efficiency in the elderly. Nine adult (mean, 38.8 years old) and 40 elderly subjects (mean, 68.8 years old) performed a cycle ergometer test to measure O2 uptake and leg power output up to the aerobic limit ( ). Reduced leg power output per unit O2 uptake was reflected in a drop in delta efficiency (εD) from 0.27 ± 0.01 (mean ± SEM) in adults to 0.22 ± 0.01 in the elderly group. Similar declines with age were apparent for both the leg power output at and the ATP generation capacity (ATPmax) determined in vivo using (31)P magnetic resonance spectroscopy. These similar declines resulted in unchanged contractile-coupling efficiency values (εC) in the adult (0.50 ± 0.05) versus the elderly group (0.58 ± 0.04) and agreed with independent measures of muscle contractile-coupling efficiency in human quadriceps (0.5). The mitochondrial-coupling efficiency calculated from the ratio of delta to contractile-coupling efficiencies in the adults (εD/εC = 0.58 ± 0.08) corresponded to values for well-coupled mitochondria (0.6); however, εD/εC was significantly lower in the elderly subjects (0.44 ± 0.03). Conversion of ATPmax per mitochondrial volume (ATPmax/Vv[mt,f]) reported in these groups into thermodynamic units confirmed this drop in mitochondrial-coupling efficiency from 0.57 ± 0.08 in adults to 0.41 ± 0.03 in elderly subjects. Thus, two independent methods revealed that reduced mitochondrial-coupling efficiency was a key part of the drop in exercise efficiency in these elderly subjects and may be an important part of the loss of exercise performance with age.
Collapse
Affiliation(s)
- Kevin E Conley
- Department of Radiology, Box 357115, University of Washington Medical Center, Seattle, WA 98195-7115, USA.
| | | | | | | |
Collapse
|
48
|
Coen PM, Jubrias SA, Distefano G, Amati F, Mackey DC, Glynn NW, Manini TM, Wohlgemuth SE, Leeuwenburgh C, Cummings SR, Newman AB, Ferrucci L, Toledo FGS, Shankland E, Conley KE, Goodpaster BH. Skeletal muscle mitochondrial energetics are associated with maximal aerobic capacity and walking speed in older adults. J Gerontol A Biol Sci Med Sci 2012; 68:447-55. [PMID: 23051977 DOI: 10.1093/gerona/gls196] [Citation(s) in RCA: 225] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Lower ambulatory performance with aging may be related to a reduced oxidative capacity within skeletal muscle. This study examined the associations between skeletal muscle mitochondrial capacity and efficiency with walking performance in a group of older adults. METHODS Thirty-seven older adults (mean age 78 years; 21 men and 16 women) completed an aerobic capacity (VO2 peak) test and measurement of preferred walking speed over 400 m. Maximal coupled (State 3; St3) mitochondrial respiration was determined by high-resolution respirometry in saponin-permeabilized myofibers obtained from percutanous biopsies of vastus lateralis (n = 22). Maximal phosphorylation capacity (ATPmax) of vastus lateralis was determined in vivo by (31)P magnetic resonance spectroscopy (n = 30). Quadriceps contractile volume was determined by magnetic resonance imaging. Mitochondrial efficiency (max ATP production/max O2 consumption) was characterized using ATPmax per St3 respiration (ATPmax/St3). RESULTS In vitro St3 respiration was significantly correlated with in vivo ATPmax (r (2) = .47, p = .004). Total oxidative capacity of the quadriceps (St3*quadriceps contractile volume) was a determinant of VO2 peak (r (2) = .33, p = .006). ATPmax (r (2) = .158, p = .03) and VO2 peak (r (2) = .475, p < .0001) were correlated with preferred walking speed. Inclusion of both ATPmax/St3 and VO2 peak in a multiple linear regression model improved the prediction of preferred walking speed (r (2) = .647, p < .0001), suggesting that mitochondrial efficiency is an important determinant for preferred walking speed. CONCLUSIONS Lower mitochondrial capacity and efficiency were both associated with slower walking speed within a group of older participants with a wide range of function. In addition to aerobic capacity, lower mitochondrial capacity and efficiency likely play roles in slowing gait speed with age.
Collapse
Affiliation(s)
- Paul M Coen
- Department of Health and Physical Activity, University of Pittsburgh, Trees Hall Rm 134D, Allequippa St. and Darragh St., Pittsburgh, PA 15260, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Percival JM, Siegel MP, Knowels G, Marcinek DJ. Defects in mitochondrial localization and ATP synthesis in the mdx mouse model of Duchenne muscular dystrophy are not alleviated by PDE5 inhibition. Hum Mol Genet 2012; 22:153-67. [PMID: 23049075 DOI: 10.1093/hmg/dds415] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Given the crucial roles for mitochondria in ATP energy supply, Ca(2+) handling and cell death, mitochondrial dysfunction has long been suspected to be an important pathogenic feature in Duchenne muscular dystrophy (DMD). Despite this foresight, mitochondrial function in dystrophin-deficient muscles has remained poorly defined and unknown in vivo. Here, we used the mdx mouse model of DMD and non-invasive spectroscopy to determine the impact of dystrophin-deficiency on skeletal muscle mitochondrial localization and oxidative phosphorylation function in vivo. Mdx mitochondria exhibited significant uncoupling of oxidative phosphorylation (reduced P/O) and a reduction in maximal ATP synthesis capacity that together decreased intramuscular ATP levels. Uncoupling was not driven by increased UCP3 or ANT1 expression. Dystrophin was required to maintain subsarcolemmal mitochondria (SSM) pool density, implicating it in the spatial control of mitochondrial localization. Given that nitric oxide-cGMP pathways regulate mitochondria and that sildenafil-mediated phosphodiesterase 5 inhibition ameliorates dystrophic pathology, we tested whether sildenafil's benefits result from decreased mitochondrial dysfunction in mdx mice. Unexpectedly, sildenafil treatment did not affect mitochondrial content or oxidative phosphorylation defects in mdx mice. Rather, PDE5 inhibition decreased resting levels of ATP, phosphocreatine and myoglobin, suggesting that sildenafil improves dystrophic pathology through other mechanisms. Overall, these data indicate that dystrophin-deficiency disrupts SSM localization, promotes mitochondrial inefficiency and restricts maximal mitochondrial ATP-generating capacity. Together these defects decrease intramuscular ATP and the ability of mdx muscle mitochondria to meet ATP demand. These findings further understanding of how mitochondrial bioenergetic dysfunction contributes to disease pathogenesis in dystrophin-deficient skeletal muscle in vivo.
Collapse
Affiliation(s)
- Justin M Percival
- Department of Physiology and Biophysics, University of Washington Medical School, Seattle, WA, USA.
| | | | | | | |
Collapse
|
50
|
Su X, Floyd DH, Hughes A, Xiang J, Schneider JG, Uluckan O, Heller E, Deng H, Zou W, Craft CS, Wu K, Hirbe AC, Grabowska D, Eagleton MC, Townsley S, Collins L, Piwnica-Worms D, Steinberg TH, Novack DV, Conley PB, Hurchla MA, Rogers M, Weilbaecher KN. The ADP receptor P2RY12 regulates osteoclast function and pathologic bone remodeling. J Clin Invest 2012; 122:3579-92. [PMID: 22996695 DOI: 10.1172/jci38576] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 07/26/2012] [Indexed: 12/16/2022] Open
Abstract
The adenosine diphosphate (ADP) receptor P2RY12 (purinergic receptor P2Y, G protein coupled, 12) plays a critical role in platelet aggregation, and P2RY12 inhibitors are used clinically to prevent cardiac and cerebral thrombotic events. Extracellular ADP has also been shown to increase osteoclast (OC) activity, but the role of P2RY12 in OC biology is unknown. Here, we examined the role of mouse P2RY12 in OC function. Mice lacking P2ry12 had decreased OC activity and were partially protected from age-associated bone loss. P2ry12-/- OCs exhibited intact differentiation markers, but diminished resorptive function. Extracellular ADP enhanced OC adhesion and resorptive activity of WT, but not P2ry12-/-, OCs. In platelets, ADP stimulation of P2RY12 resulted in GTPase Ras-related protein (RAP1) activation and subsequent αIIbβ3 integrin activation. Likewise, we found that ADP stimulation induced RAP1 activation in WT and integrin β3 gene knockout (Itgb3-/-) OCs, but its effects were substantially blunted in P2ry12-/- OCs. In vivo, P2ry12-/- mice were partially protected from pathologic bone loss associated with serum transfer arthritis, tumor growth in bone, and ovariectomy-induced osteoporosis: all conditions associated with increased extracellular ADP. Finally, mice treated with the clinical inhibitor of P2RY12, clopidogrel, were protected from pathologic osteolysis. These results demonstrate that P2RY12 is the primary ADP receptor in OCs and suggest that P2RY12 inhibition is a potential therapeutic target for pathologic bone loss.
Collapse
Affiliation(s)
- Xinming Su
- Department of Medicine, Division of Oncology, Washington University in St. Louis School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|