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Pandics T, Major D, Fazekas-Pongor V, Szarvas Z, Peterfi A, Mukli P, Gulej R, Ungvari A, Fekete M, Tompa A, Tarantini S, Yabluchanskiy A, Conley S, Csiszar A, Tabak AG, Benyo Z, Adany R, Ungvari Z. Exposome and unhealthy aging: environmental drivers from air pollution to occupational exposures. GeroScience 2023; 45:3381-3408. [PMID: 37688657 PMCID: PMC10643494 DOI: 10.1007/s11357-023-00913-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 08/14/2023] [Indexed: 09/11/2023] Open
Abstract
The aging population worldwide is facing a significant increase in age-related non-communicable diseases, including cardiovascular and brain pathologies. This comprehensive review paper delves into the impact of the exposome, which encompasses the totality of environmental exposures, on unhealthy aging. It explores how environmental factors contribute to the acceleration of aging processes, increase biological age, and facilitate the development and progression of a wide range of age-associated diseases. The impact of environmental factors on cognitive health and the development of chronic age-related diseases affecting the cardiovascular system and central nervous system is discussed, with a specific focus on Alzheimer's disease, Parkinson's disease, stroke, small vessel disease, and vascular cognitive impairment (VCI). Aging is a major risk factor for these diseases. Their pathogenesis involves cellular and molecular mechanisms of aging such as increased oxidative stress, impaired mitochondrial function, DNA damage, and inflammation and is influenced by environmental factors. Environmental toxicants, including ambient particulate matter, pesticides, heavy metals, and organic solvents, have been identified as significant contributors to cardiovascular and brain aging disorders. These toxicants can inflict both macro- and microvascular damage and many of them can also cross the blood-brain barrier, inducing neurotoxic effects, neuroinflammation, and neuronal dysfunction. In conclusion, environmental factors play a critical role in modulating cardiovascular and brain aging. A deeper understanding of how environmental toxicants exacerbate aging processes and contribute to the pathogenesis of neurodegenerative diseases, VCI, and dementia is crucial for the development of preventive strategies and interventions to promote cardiovascular, cerebrovascular, and brain health. By mitigating exposure to harmful environmental factors and promoting healthy aging, we can strive to reduce the burden of age-related cardiovascular and brain pathologies in the aging population.
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Affiliation(s)
- Tamas Pandics
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- Department of Public Health Laboratory, National Public Health Centre, Budapest, Hungary
- Department of Public Health Siences, Faculty of Health Sciences, Semmelweis University, Budapest, Hungary
| | - David Major
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Vince Fazekas-Pongor
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Zsofia Szarvas
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Anna Peterfi
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Peter Mukli
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Rafal Gulej
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Anna Ungvari
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Monika Fekete
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Anna Tompa
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Stefano Tarantini
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Stephenson Cancer Center, University of Oklahoma, Oklahoma City, OK, USA
- Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- International Training Program in Geroscience, Doctoral School of Basic and Translational Medicine/Department of Public Health, Semmelweis University, Budapest, Hungary
| | - Andriy Yabluchanskiy
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Stephenson Cancer Center, University of Oklahoma, Oklahoma City, OK, USA
- Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- International Training Program in Geroscience, Doctoral School of Basic and Translational Medicine/Department of Public Health, Semmelweis University, Budapest, Hungary
| | - Shannon Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Anna Csiszar
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
- Stephenson Cancer Center, University of Oklahoma, Oklahoma City, OK, USA
- Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Adam G Tabak
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- UCL Brain Sciences, University College London, London, UK
- Department of Internal Medicine and Oncology, Faculty of Medicine, Semmelweis University, Budapest, Hungary
| | - Zoltan Benyo
- Department of Translational Medicine, Semmelweis University, Budapest, Hungary
- Eötvös Loránd Research Network and Semmelweis University (ELKH-SE) Cerebrovascular and Neurocognitive Disorders Research Group, Budapest, H-1052, Hungary
| | - Roza Adany
- Department of Public Health, Faculty of Medicine, Semmelweis University, Budapest, Hungary
- ELKH-DE Public Health Research Group, Department of Public Health and Epidemiology, Faculty of Medicine, University of Debrecen, 4032, Debrecen, Hungary
- Epidemiology and Surveillance Centre, Semmelweis University, 1085, Budapest, Hungary
| | - Zoltan Ungvari
- Vascular Cognitive Impairment, Neurodegeneration and Healthy Brain Aging Program, Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- Oklahoma Center for Geroscience and Healthy Brain Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- Stephenson Cancer Center, University of Oklahoma, Oklahoma City, OK, USA.
- Department of Health Promotion Sciences, College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
- International Training Program in Geroscience, Doctoral School of Basic and Translational Medicine/Department of Public Health, Semmelweis University, Budapest, Hungary.
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2
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Mitochondrial DNA Profiling by Fractal Lacunarity to Characterize the Senescent Phenotype as Normal Aging or Pathological Aging. FRACTAL AND FRACTIONAL 2022. [DOI: 10.3390/fractalfract6040219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Biocomplexity, chaos, and fractality can explain the heterogeneity of aging individuals by regarding longevity as a “secondary product” of the evolution of a dynamic nonlinear system. Genetic-environmental interactions drive the individual senescent phenotype toward normal, pathological, or successful aging. Mitochondrial dysfunctions and mitochondrial DNA (mtDNA) mutations represent a possible mechanism shared by disease(s) and the aging process. This study aims to characterize the senescent phenotype and discriminate between normal (nA) and pathological (pA) aging by mtDNA mutation profiling. MtDNA sequences from hospitalized and non-hospitalized subjects (age-range: 65–89 years) were analyzed and compared to the revised Cambridge Reference Sequence (rCRS). Fractal properties of mtDNA sequences were displayed by chaos game representation (CGR) method, previously modified to deal with heteroplasmy. Fractal lacunarity analysis was applied to characterize the senescent phenotype on the basis of mtDNA sequence mutations. Lacunarity parameter β, from our hyperbola model function, was statistically different (p < 0.01) between the nA and pA groups. Parameter β cut-off value at 1.26 × 10−3 identifies 78% nA and 80% pA subjects. This also agrees with the presence of MT-CO gene variants, peculiar to nA (C9546m, 83%) and pA (T9900w, 80%) mtDNA, respectively. Fractal lacunarity can discriminate the senescent phenotype evolving as normal or pathological aging by individual mtDNA mutation profile.
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Abstract
Mitochondria are the main source of energy used to maintain cellular homeostasis. This aspect of mitochondrial biology underlies their putative role in age-associated tissue dysfunction. Proper functioning of the electron transport chain (ETC), which is partially encoded by the extra-nuclear mitochondrial genome (mtDNA), is key to maintaining this energy production. The acquisition of de novo somatic mutations that interrupt the function of the ETC have long been associated with aging and common diseases of the elderly. Yet, despite over 30 years of study, the exact role(s) mtDNA mutations play in driving aging and its associated pathologies remains under considerable debate. Furthermore, even fundamental aspects of age-related mtDNA mutagenesis, such as when mutations arise during aging, where and how often they occur across tissues, and the specific mechanisms that give rise to them, remain poorly understood. In this review, we address the current understanding of the somatic mtDNA mutations, with an emphasis of when, where, and how these mutations arise during aging. Additionally, we highlight current limitations in our knowledge and critically evaluate the controversies stemming from these limitations. Lastly, we highlight new and emerging technologies that offer potential ways forward in increasing our understanding of somatic mtDNA mutagenesis in the aging process.
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Affiliation(s)
- Monica Sanchez-Contreras
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States
| | - Scott R Kennedy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States
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4
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Nicoletti V, Palermo G, Del Prete E, Mancuso M, Ceravolo R. Understanding the Multiple Role of Mitochondria in Parkinson's Disease and Related Disorders: Lesson From Genetics and Protein-Interaction Network. Front Cell Dev Biol 2021; 9:636506. [PMID: 33869180 PMCID: PMC8047151 DOI: 10.3389/fcell.2021.636506] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 02/16/2021] [Indexed: 12/12/2022] Open
Abstract
As neurons are highly energy-demanding cell, increasing evidence suggests that mitochondria play a large role in several age-related neurodegenerative diseases. Synaptic damage and mitochondrial dysfunction have been associated with early events in the pathogenesis of major neurodegenerative diseases, including Parkinson’s disease, atypical parkinsonisms, and Huntington disease. Disruption of mitochondrial structure and dynamic is linked to increased levels of reactive oxygen species production, abnormal intracellular calcium levels, and reduced mitochondrial ATP production. However, recent research has uncovered a much more complex involvement of mitochondria in such disorders than has previously been appreciated, and a remarkable number of genes and proteins that contribute to the neurodegeneration cascade interact with mitochondria or affect mitochondrial function. In this review, we aim to summarize and discuss the deep interconnections between mitochondrial dysfunction and basal ganglia disorders, with an emphasis into the molecular triggers to the disease process. Understanding the regulation of mitochondrial pathways may be beneficial in finding pharmacological or non-pharmacological interventions to delay the onset of neurodegenerative diseases.
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Affiliation(s)
- Valentina Nicoletti
- Unit of Neurology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Giovanni Palermo
- Unit of Neurology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Eleonora Del Prete
- Unit of Neurology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Michelangelo Mancuso
- Unit of Neurology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Roberto Ceravolo
- Unit of Neurology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
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5
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Herbst A, Prior SJ, Lee CC, Aiken JM, McKenzie D, Hoang A, Liu N, Chen X, Xun P, Allison DB, Wanagat J. Skeletal muscle mitochondrial DNA copy number and mitochondrial DNA deletion mutation frequency as predictors of physical performance in older men and women. GeroScience 2021; 43:1253-1264. [PMID: 33740224 DOI: 10.1007/s11357-021-00351-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 03/04/2021] [Indexed: 12/31/2022] Open
Abstract
Mitochondrial DNA (mtDNA) quality and quantity relate to two hallmarks of aging-genomic instability and mitochondrial dysfunction. Physical performance relies on mitochondrial integrity and declines with age, yet the interactions between mtDNA quantity, quality, and physical performance are unclear. Using a validated digital PCR assay specific for mtDNA deletions, we tested the hypothesis that skeletal muscle mtDNA deletion mutation frequency (i.e., a measure of mtDNA quality) or mtDNA copy number predicts physical performance in older adults. Total DNA was isolated from vastus lateralis muscle biopsies and used to quantitate mtDNA copy number and mtDNA deletion frequency by digital PCR. The biopsies were obtained from a cross-sectional cohort of 53 adults aged 50 to 86 years. Before the biopsy procedure, physical performance measurements were collected, including VO2max, modified physical performance test score, 6-min walk distance, gait speed, grip strength, and total lean and leg mass. Linear regression models were used to evaluate the relationships between age, sex, and the outcomes. We found that mtDNA deletion mutation frequency increased exponentially with advancing age. On average from ages 50 to 86, deletion frequency increased from 0.008 to 0.15%, an 18-fold increase. Females may have lower deletion frequencies than males at older ages. We also measured declines in VO2max and mtDNA copy number with age in both sexes. The mtDNA deletion frequency measured from single skeletal muscle biopsies predicted 13.3% of the variation in VO2max. Copy number explained 22.6% of the variation in mtDNA deletion frequency and 10.4% of the lean mass variation. We found predictive relationships between age, mtDNA deletion mutation frequency, mtDNA copy number, and physical performance. These data are consistent with a role for mitochondrial function and genome integrity in maintaining physical performance with age. Analyses of mtDNA quality and quantity in larger cohorts and longitudinal studies could extend our understanding of the importance of mitochondrial DNA in human aging and longevity.
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Affiliation(s)
- Allen Herbst
- Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Steven J Prior
- Department of Kinesiology, University of Maryland School of Public Health, College Park, MD, USA.,Baltimore Veterans Affairs Medical Center Geriatric Research, Education and Clinical Center, Baltimore, MD, USA
| | - Cathy C Lee
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Division of Geriatrics, Department of Medicine, University of California, Los Angeles, 650 Charles E. Young Drive South, Rm 34-115, Los Angeles, CA, 90095, USA
| | - Judd M Aiken
- Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Debbie McKenzie
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Austin Hoang
- Division of Geriatrics, Department of Medicine, University of California, Los Angeles, 650 Charles E. Young Drive South, Rm 34-115, Los Angeles, CA, 90095, USA
| | - Nianjun Liu
- Department of Epidemiology and Biostatistics, Indiana University Bloomington, Bloomington, IN, USA
| | - Xiwei Chen
- Department of Epidemiology and Biostatistics, Indiana University Bloomington, Bloomington, IN, USA
| | - Pengcheng Xun
- Department of Epidemiology and Biostatistics, Indiana University Bloomington, Bloomington, IN, USA
| | - David B Allison
- Department of Epidemiology and Biostatistics, Indiana University Bloomington, Bloomington, IN, USA
| | - Jonathan Wanagat
- Veterans Administration Greater Los Angeles Healthcare System, Los Angeles, CA, USA. .,Division of Geriatrics, Department of Medicine, University of California, Los Angeles, 650 Charles E. Young Drive South, Rm 34-115, Los Angeles, CA, 90095, USA.
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6
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Saadeh K, Fazmin IT. Mitochondrial Dysfunction Increases Arrhythmic Triggers and Substrates; Potential Anti-arrhythmic Pharmacological Targets. Front Cardiovasc Med 2021; 8:646932. [PMID: 33659284 PMCID: PMC7917191 DOI: 10.3389/fcvm.2021.646932] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 01/26/2021] [Indexed: 12/31/2022] Open
Abstract
Incidence of cardiac arrhythmias increases significantly with age. In order to effectively stratify arrhythmic risk in the aging population it is crucial to elucidate the relevant underlying molecular mechanisms. The changes underlying age-related electrophysiological disruption appear to be closely associated with mitochondrial dysfunction. Thus, the present review examines the mechanisms by which age-related mitochondrial dysfunction promotes arrhythmic triggers and substrate. Namely, via alterations in plasmalemmal ionic currents (both sodium and potassium), gap junctions, cellular Ca2+ homeostasis, and cardiac fibrosis. Stratification of patients' mitochondrial function status permits application of appropriate anti-arrhythmic therapies. Here, we discuss novel potential anti-arrhythmic pharmacological interventions that specifically target upstream mitochondrial function and hence ameliorates the need for therapies targeting downstream changes which have constituted traditional antiarrhythmic therapy.
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Affiliation(s)
- Khalil Saadeh
- School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Ibrahim Talal Fazmin
- School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom.,Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,Royal Papworth Hospital NHS Foundation Trust, Cambridge, United Kingdom
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7
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Monzio Compagnoni G, Di Fonzo A, Corti S, Comi GP, Bresolin N, Masliah E. The Role of Mitochondria in Neurodegenerative Diseases: the Lesson from Alzheimer's Disease and Parkinson's Disease. Mol Neurobiol 2020; 57:2959-2980. [PMID: 32445085 DOI: 10.1007/s12035-020-01926-1] [Citation(s) in RCA: 179] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 04/22/2020] [Indexed: 12/15/2022]
Abstract
Although the pathogenesis of neurodegenerative diseases is still widely unclear, various mechanisms have been proposed and several pieces of evidence are supportive for an important role of mitochondrial dysfunction. The present review provides a comprehensive and up-to-date overview about the role of mitochondria in the two most common neurodegenerative disorders: Alzheimer's disease (AD) and Parkinson's disease (PD). Mitochondrial involvement in AD is supported by clinical features like reduced glucose and oxygen brain metabolism and by numerous microscopic and molecular findings, including altered mitochondrial morphology, impaired respiratory chain function, and altered mitochondrial DNA. Furthermore, amyloid pathology and mitochondrial dysfunction seem to be bi-directionally correlated. Mitochondria have an even more remarkable role in PD. Several hints show that respiratory chain activity, in particular complex I, is impaired in the disease. Mitochondrial DNA alterations, involving deletions, point mutations, depletion, and altered maintenance, have been described. Mutations in genes directly implicated in mitochondrial functioning (like Parkin and PINK1) are responsible for rare genetic forms of the disease. A close connection between alpha-synuclein accumulation and mitochondrial dysfunction has been observed. Finally, mitochondria are involved also in atypical parkinsonisms, in particular multiple system atrophy. The available knowledge is still not sufficient to clearly state whether mitochondrial dysfunction plays a primary role in the very initial stages of these diseases or is secondary to other phenomena. However, the presented data strongly support the hypothesis that whatever the initial cause of neurodegeneration is, mitochondrial impairment has a critical role in maintaining and fostering the neurodegenerative process.
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Affiliation(s)
- Giacomo Monzio Compagnoni
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy. .,Department of Neurology, School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy. .,Department of Neurology, Khurana Laboratory, Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
| | - Alessio Di Fonzo
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Stefania Corti
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.,Department of Pathophysiology and Transplantation, Neuroscience Section, Dino Ferrari Center, University of Milan, Milan, Italy
| | - Giacomo P Comi
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.,Department of Pathophysiology and Transplantation, Neuroscience Section, Dino Ferrari Center, University of Milan, Milan, Italy
| | - Nereo Bresolin
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.,Department of Pathophysiology and Transplantation, Neuroscience Section, Dino Ferrari Center, University of Milan, Milan, Italy
| | - Eliezer Masliah
- Division of Neuroscience and Laboratory of Neurogenetics, National Institute on Aging, National Institute of Health, Bethesda, MD, USA
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8
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Edling C, Fazmin I, Saadeh K, Chadda K, Ahmad S, Valli H, Huang CH, Jeevaratnam K. Molecular basis of arrhythmic substrate in ageing murine peroxisome proliferator-activated receptor γ co-activator deficient hearts modelling mitochondrial dysfunction. Biosci Rep 2019; 39:BSR20190403. [PMID: 31778152 PMCID: PMC6911157 DOI: 10.1042/bsr20190403] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 11/19/2019] [Accepted: 11/26/2019] [Indexed: 12/19/2022] Open
Abstract
INTRODUCTION Ageing and chronic metabolic disorders are associated with mitochondrial dysfunction and cardiac pro-arrhythmic phenotypes which were recently attributed to slowed atrial and ventricular action potential (AP) conduction in peroxisome proliferator-activated receptor γ co-activator deficient (Pgc-1β-/-) mice. METHODS We compared expression levels of voltage-gated Na+ channel (NaV1.5) and gap junction channels, Connexins 40 and 43 (Cx40 and Cx43) in the hearts of young and old, and wild-type (WT) and Pgc-1β-/- mice. This employed Western blotting (WB) for NaV1.5, Cx40 and Cx43 in atrial/ventricular tissue lysates, and immunofluorescence (IF) from Cx43 was explored in tissue sections. Results were analysed using two-way analysis of variance (ANOVA) for independent/interacting effects of age and genotype. RESULTS In atria, increased age and Pgc-1β-/- genotype each independently decreased both Cx40 and Cx43 expression without interacting effects. In IF experiments, both age and Pgc-1β deletion independently reduced Cx43 expression. In ventricles, age and genotype exerted interacting effects in WB studies of NaV1.5 expression. Young Pgc-1β-/- then showed greater NaV1.5 expression than young WT ventricles. However, neither age nor Pgc-1β deletion affected Cx43 expression, independently or through interacting effects in both WB and IF studies. CONCLUSION Similar pro-arrhythmic atrial/ventricular phenotypes arise in aged/Pgc-1β-/- from differing contributions of altered protein expression and functional effects that may arise from multiple acute mechanisms.
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Affiliation(s)
- Charlotte E. Edling
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, United Kingdom
| | - Ibrahim T. Fazmin
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, United Kingdom
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Khalil Saadeh
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, United Kingdom
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Karan R. Chadda
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, United Kingdom
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Shiraz Ahmad
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Haseeb Valli
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
| | - Christopher L.-H. Huang
- Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG, United Kingdom
- Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge CB2 1QW, United Kingdom
| | - Kamalan Jeevaratnam
- Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7AL, United Kingdom
- Department of Biochemistry, Hopkins Building, University of Cambridge, Cambridge CB2 1QW, United Kingdom
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9
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Herbst A, Hoang AN, Woo W, McKenzie D, Aiken JM, Miller RA, Allison DB, Liu N, Wanagat J. Mitochondrial DNA alterations in aged macrophage migration inhibitory factor-knockout mice. Mech Ageing Dev 2019; 182:111126. [PMID: 31381889 PMCID: PMC6718337 DOI: 10.1016/j.mad.2019.111126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Revised: 07/16/2019] [Accepted: 07/30/2019] [Indexed: 01/06/2023]
Abstract
The age-induced, exponential accumulation of mitochondrial DNA (mtDNA) deletion mutations contributes to muscle fiber loss. The causes of these mutations are not known. Systemic inflammation is associated with decreased muscle mass in older adults and is implicated in the formation of sporadic mtDNA deletions. Macrophage migration inhibitory factor knockout (MIF-KO) mice are long-lived with decreased inflammation. We hypothesized that aged MIF-KO mice would have lower mtDNA deletion frequencies and fewer electron transport chain (ETC) deficient fibers. We measured mtDNA copy number and mutation frequency as well as the number and length of ETC deficient fibers in 22-month old MIF-KO and F2 hybrid control mice. We also measured mtDNA copy number and deletion frequency in female UM-HET3 mice, a strain whose lifespan matches the MIF-KO mice. We did not observe a significant effect of MIF ablation on muscle mtDNA deletion frequency. There was a significantly lower mtDNA copy number in the MIF-KO mice and the lifespan-matched UM-HET3 mice compared to the F2 hybrids, suggesting the importance of genetic background in mtDNA copy number control. Our data do not support a definitive role for MIF in age-induced mtDNA deletions.
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Affiliation(s)
- Allen Herbst
- Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Austin N Hoang
- Department of Medicine, Division of Geriatrics, UCLA, Los Angeles, CA, USA
| | - Wendy Woo
- Department of Medicine, Division of Geriatrics, UCLA, Los Angeles, CA, USA
| | - Debbie McKenzie
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Judd M Aiken
- Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Richard A Miller
- Department of Pathology and Geriatrics Center, University of Michigan, Ann Arbor, MI, USA
| | - David B Allison
- Department of Epidemiology and Biostatistics, Indiana University Bloomington, Bloomington, IN, USA
| | - Nianjun Liu
- Department of Epidemiology and Biostatistics, Indiana University Bloomington, Bloomington, IN, USA
| | - Jonathan Wanagat
- Department of Medicine, Division of Geriatrics, UCLA, Los Angeles, CA, USA.
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10
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Hoitzing H, Gammage PA, Haute LV, Minczuk M, Johnston IG, Jones NS. Energetic costs of cellular and therapeutic control of stochastic mitochondrial DNA populations. PLoS Comput Biol 2019; 15:e1007023. [PMID: 31242175 PMCID: PMC6615642 DOI: 10.1371/journal.pcbi.1007023] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 07/09/2019] [Accepted: 04/11/2019] [Indexed: 12/28/2022] Open
Abstract
The dynamics of the cellular proportion of mutant mtDNA molecules is crucial for mitochondrial diseases. Cellular populations of mitochondria are under homeostatic control, but the details of the control mechanisms involved remain elusive. Here, we use stochastic modelling to derive general results for the impact of cellular control on mtDNA populations, the cost to the cell of different mtDNA states, and the optimisation of therapeutic control of mtDNA populations. This formalism yields a wealth of biological results, including that an increasing mtDNA variance can increase the energetic cost of maintaining a tissue, that intermediate levels of heteroplasmy can be more detrimental than homoplasmy even for a dysfunctional mutant, that heteroplasmy distribution (not mean alone) is crucial for the success of gene therapies, and that long-term rather than short intense gene therapies are more likely to beneficially impact mtDNA populations.
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Affiliation(s)
- Hanne Hoitzing
- Department of Mathematics, Imperial College London, London, SW7 2AZ, United Kingdom
| | - Payam A. Gammage
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
- CRUK Beatson Institute for Cancer Research, Glasgow, United Kingdom
| | - Lindsey Van Haute
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - Michal Minczuk
- MRC Mitochondrial Biology Unit, University of Cambridge, Cambridge, CB2 0XY, United Kingdom
| | - Iain G. Johnston
- Faculty of Mathematics and Natural Sciences, University of Bergen, Bergen, Norway
- Alan Turing Institute, London, United Kingdom
| | - Nick S. Jones
- Department of Mathematics, Imperial College London, London, SW7 2AZ, United Kingdom
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11
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Abstract
Mutations of mtDNA accumulate in aging humans and other mammals to cause mitochondrial dysfunction in a subset of cells in various tissues. Furthermore, experimental induction of mtDNA mutations causes a premature aging syndrome in the mouse. To study if mitochondrial dysfunction is universally involved in shortening life span in metazoans, we generated a series of fruit fly lines with varying levels of mtDNA mutations. Unexpectedly, we report that fruit flies are remarkably tolerant to mtDNA mutations, as exemplified by their lack of effect on physiology and lifespan. Only an artificially induced, very drastic increase of the mtDNA mutation load will lead to reduced lifespan, showing that mtDNA mutations are unlikely to limit lifespan in natural fruit fly populations. Mammals develop age-associated clonal expansion of somatic mtDNA mutations resulting in severe respiratory chain deficiency in a subset of cells in a variety of tissues. Both mathematical modeling based on descriptive data from humans and experimental data from mtDNA mutator mice suggest that the somatic mutations are formed early in life and then undergo mitotic segregation during adult life to reach very high levels in certain cells. To address whether mtDNA mutations have a universal effect on aging metazoans, we investigated their role in physiology and aging of fruit flies. To this end, we utilized genetically engineered flies expressing mutant versions of the catalytic subunit of mitochondrial DNA polymerase (DmPOLγA) as a means to introduce mtDNA mutations. We report here that lifespan and health in fruit flies are remarkably tolerant to mtDNA mutations. Our results show that the short lifespan and wide genetic bottleneck of fruit flies are limiting the extent of clonal expansion of mtDNA mutations both in individuals and between generations. However, an increase of mtDNA mutations to very high levels caused sensitivity to mechanical and starvation stress, intestinal stem cell dysfunction, and reduced lifespan under standard conditions. In addition, the effects of dietary restriction, widely considered beneficial for organismal health, were attenuated in flies with very high levels of mtDNA mutations.
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12
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Liu C, Fetterman JL, Liu P, Luo Y, Larson MG, Vasan RS, Zhu J, Levy D. Deep sequencing of the mitochondrial genome reveals common heteroplasmic sites in NADH dehydrogenase genes. Hum Genet 2018; 137:203-213. [PMID: 29423652 DOI: 10.1007/s00439-018-1873-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 01/30/2018] [Indexed: 12/17/2022]
Abstract
Increasing evidence implicates mitochondrial dysfunction in aging and age-related conditions. But little is known about the molecular basis for this connection. A possible cause may be mutations in the mitochondrial DNA (mtDNA), which are often heteroplasmic-the joint presence of different alleles at a single locus in the same individual. However, the involvement of mtDNA heteroplasmy in aging and age-related conditions has not been investigated thoroughly. We deep-sequenced the complete mtDNA genomes of 356 Framingham Heart Study participants (52% women, mean age 43, mean coverage 4570-fold), identified 2880 unique mutations and comprehensively annotated them by MITOMAP and PolyPhen-2. We discovered 11 heteroplasmic "hot" spots [NADH dehydrogenase (ND) subunit 1, 4, 5 and 6 genes, n = 7; cytochrome c oxidase I (COI), n = 2; 16S rRNA, n = 1; D-loop, n = 1] for which the alternative-to-reference allele ratios significantly increased with advancing age (Bonferroni correction p < 0.001). Four of these heteroplasmic mutations in ND and COI genes were predicted to be deleterious nonsynonymous mutations which may have direct impact on ATP production. We confirmed previous findings that healthy individuals carry many low-frequency heteroplasmy mutations with potentially deleterious effects. We hypothesize that the effect of a single deleterious heteroplasmy may be minimal due to a low mutant-to-wildtype allele ratio, whereas the aggregate effects of many deleterious mutations may cause changes in mitochondrial function and contribute to age-related diseases. The identification of age-related mtDNA mutations is an important step to understand the genetic architecture of age-related diseases and may uncover novel therapeutic targets for such diseases.
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Affiliation(s)
- Chunyu Liu
- Population Sciences Branch, NHLBI/NHI, Bethesda, MD, USA. .,Framingham Heart Study, Framingham, MA, USA. .,Department of Biostatistics, Boston University, Boston, MA, USA.
| | | | - Poching Liu
- DNA Sequencing and Genomics Core, NHLBI/NIH, Bethesda, MD, USA
| | - Yan Luo
- DNA Sequencing and Genomics Core, NHLBI/NIH, Bethesda, MD, USA
| | - Martin G Larson
- Framingham Heart Study, Framingham, MA, USA.,Department of Biostatistics, Boston University, Boston, MA, USA
| | - Ramachandran S Vasan
- Framingham Heart Study, Framingham, MA, USA.,School of Medicine, Boston University, Boston, MA, USA
| | - Jun Zhu
- System Biology Center, NHLBI/NHI, Bethesda, MD, USA
| | - Daniel Levy
- Population Sciences Branch, NHLBI/NHI, Bethesda, MD, USA. .,Framingham Heart Study, Framingham, MA, USA.
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13
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Ambeskovic M, Roseboom TJ, Metz GAS. Transgenerational effects of early environmental insults on aging and disease incidence. Neurosci Biobehav Rev 2017; 117:297-316. [PMID: 28807754 DOI: 10.1016/j.neubiorev.2017.08.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 06/18/2017] [Accepted: 08/03/2017] [Indexed: 02/06/2023]
Abstract
Adverse early life experiences are major influences on developmental trajectories with potentially life-long consequences. Prenatal or early postnatal exposure to stress, undernutrition or environmental toxicants may reprogram brain development and increase risk of behavioural and neurological disorders later in life. Not only experience within a single lifetime, but also ancestral experience affects health trajectories and chances of successful aging. The central mechanism in transgenerational programming of a disease may be the formation of epigenetic memory. This review explores transgenerational effects of early adverse experience on health and disease incidence in older age. First, we address mechanisms of developmental and transgenerational programming of disease and inheritance. Second, we discuss experimental and clinical findings linking early environmental determinants to adverse aging trajectories in association with possible parental contributions and sex-specific effects. Third, we outline the main mechanisms of age-related functional decline and suggest potential interventions to reverse negative effects of transgenerational programming. Thus, strategies that support healthy development and successful aging should take into account the potential influences of transgenerational inheritance.
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Affiliation(s)
- Mirela Ambeskovic
- Canadian Centre for Behavioural Neuroscience, Department of Neuroscience, University of Lethbridge, Lethbridge, Alberta T1K3M4, Canada
| | - Tessa J Roseboom
- Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Centre, Meibergdreef 9, University of Amsterdam, 1105 AZ Amsterdam, Netherlands; Department of Obstetrics and Gynaecology, Academic Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, Netherlands
| | - Gerlinde A S Metz
- Canadian Centre for Behavioural Neuroscience, Department of Neuroscience, University of Lethbridge, Lethbridge, Alberta T1K3M4, Canada.
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14
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Mistriotis P, Andreadis ST. Vascular aging: Molecular mechanisms and potential treatments for vascular rejuvenation. Ageing Res Rev 2017; 37:94-116. [PMID: 28579130 DOI: 10.1016/j.arr.2017.05.006] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 05/22/2017] [Accepted: 05/25/2017] [Indexed: 12/14/2022]
Abstract
Aging is the main risk factor contributing to vascular dysfunction and the progression of vascular diseases. In this review, we discuss the causes and mechanisms of vascular aging at the tissue and cellular level. We focus on Endothelial Cell (EC) and Smooth Muscle Cell (SMC) aging due to their critical role in mediating the defective vascular phenotype. We elaborate on two categories that contribute to cellular dysfunction: cell extrinsic and intrinsic factors. Extrinsic factors reflect systemic or environmental changes which alter EC and SMC homeostasis compromising vascular function. Intrinsic factors induce EC and SMC transformation resulting in cellular senescence. Replenishing or rejuvenating the aged/dysfunctional vascular cells is critical to the effective repair of the vasculature. As such, this review also elaborates on recent findings which indicate that stem cell and gene therapies may restore the impaired vascular cell function, reverse vascular aging, and prolong lifespan.
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Affiliation(s)
- Panagiotis Mistriotis
- Bioengineering Laboratory, Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Amherst, NY 14260-4200, USA
| | - Stelios T Andreadis
- Bioengineering Laboratory, Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Amherst, NY 14260-4200, USA; Department of Biomedical Engineering, University at Buffalo, The State University of New York, Amherst, NY 14260-4200, USA; Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY 14203, USA.
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15
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Ross JM, Olson L, Coppotelli G. Mitochondrial and Ubiquitin Proteasome System Dysfunction in Ageing and Disease: Two Sides of the Same Coin? Int J Mol Sci 2015; 16:19458-76. [PMID: 26287188 PMCID: PMC4581307 DOI: 10.3390/ijms160819458] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 07/23/2015] [Accepted: 08/07/2015] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial dysfunction and impairment of the ubiquitin proteasome system have been described as two hallmarks of the ageing process. Additionally, both systems have been implicated in the etiopathogenesis of many age-related diseases, particularly neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. Interestingly, these two systems are closely interconnected, with the ubiquitin proteasome system maintaining mitochondrial homeostasis by regulating organelle dynamics, the proteome, and mitophagy, and mitochondrial dysfunction impairing cellular protein homeostasis by oxidative damage. Here, we review the current literature and argue that the interplay of the two systems should be considered in order to better understand the cellular dysfunction observed in ageing and age-related diseases. Such an approach may provide valuable insights into molecular mechanisms underlying the ageing process, and further discovery of treatments to counteract ageing and its associated diseases. Furthermore, we provide a hypothetical model for the heterogeneity described among individuals during ageing.
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Affiliation(s)
- Jaime M Ross
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, Stockholm 171 77, Sweden.
| | - Lars Olson
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, Stockholm 171 77, Sweden.
| | - Giuseppe Coppotelli
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, Stockholm 171 77, Sweden.
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16
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Khrapko K, Turnbull D. Mitochondrial DNA mutations in aging. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 127:29-62. [PMID: 25149213 DOI: 10.1016/b978-0-12-394625-6.00002-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The relationship of mitochondrial DNA mutations to aging is still debated. Most mtDNA mutations are recessive: there are multiple copies per cell and mutation needs to clonally expand to cause respiratory deficiency. Overall mtDNA mutant loads are low, so effects of mutations are limited to critical areas where mutations locally reach high fractions. This includes respiratory chain deficient zones in muscle fibers, respiratory-deficient crypts in colon, and massive expansions of deleted mtDNA in substantia nigra neurons. mtDNA "mutator" mouse with increased rate of mtDNA mutations is a useful model, although rates and distribution of mutations may significantly deviate from what is observed in human aging. Comparison of species with different longevity reveals intriguing longevity-related traits in mtDNA sequence, although their significance is yet to be evaluated. The impact of somatic mtDNA mutations rapidly increases with age, so their importance is expected to grow as human life expectancy increases.
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Affiliation(s)
- Konstantin Khrapko
- Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
| | - Doug Turnbull
- LLHW Centre for Ageing and Vitality, Newcastle University, Newcastle, United Kingdom
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17
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Zapico SC, Ubelaker DH. mtDNA Mutations and Their Role in Aging, Diseases and Forensic Sciences. Aging Dis 2013; 4:364-80. [PMID: 24307969 DOI: 10.14336/ad.2013.0400364] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Revised: 10/02/2013] [Accepted: 10/02/2013] [Indexed: 12/28/2022] Open
Abstract
Mitochondria are independent organelles with their own DNA. As a primary function, mitochondria produce the energy for the cell through Oxidative Phosphorylation (OXPHOS) in the Electron Transport Chain (ETC). One of the toxic products of this process is Reactive Oxygen Species (ROS), which can induce oxidative damage in macromolecules like lipids, proteins and DNA. Mitochondrial DNA (mtDNA) is less protected and has fewer reparation mechanisms than nuclear DNA (nDNA), and as such is more exposed to oxidative, mutation-inducing damage. This review analyzes the causes and consequences of mtDNA mutations and their relationship with the aging process. Neurodegenerative diseases, related with the aging, are consequences of mtDNA mutations resulting in a decrease in mitochondrial function. Also described are "mitochondrial diseases", pathologies produced by mtDNA mutations and whose symptoms are related with mitochondrial dysfunction. Finally, mtDNA haplogroups are defined in this review; these groups are important for determination of geographical origin of an individual. Additionally, different haplogroups exhibit variably longevity and risk of certain diseases. mtDNA mutations in aging and haplogroups are of special interest to forensic science research. Therefore this review will help to clarify the key role of mtDNA mutations in these processes and support further research in this area.
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Affiliation(s)
- Sara C Zapico
- Smithsonian Institution, National Museum of Natural History, Department of Anthropology, Washington, DC 20560, USA
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18
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Dhillon VS, Fenech M. Mutations that affect mitochondrial functions and their association with neurodegenerative diseases. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2013; 759:1-13. [PMID: 24055911 DOI: 10.1016/j.mrrev.2013.09.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 09/05/2013] [Accepted: 09/08/2013] [Indexed: 12/20/2022]
Abstract
Mitochondria are essential for mammalian and human cell function as they generate ATP via aerobic respiration. The proteins required in the electron transport chain are mainly encoded by the circular mitochondrial genome but other essential mitochondrial proteins such as DNA repair genes, are coded in the nuclear genome and require transport into the mitochondria. In this review we summarize current knowledge on the association of point mutations and deletions in the mitochondrial genome that are detrimental to mitochondrial function and are associated with accelerated ageing and neurological disorders including Alzheimer's, Parkinson's, Huntington's and Amyotrophic lateral sclerosis (ALS). Mutations in the nuclear encoded genes that disrupt mitochondrial functions are also discussed. It is evident that a greater understanding of the causes of mutations that adversely affect mitochondrial metabolism is required to develop preventive measures against accelerated ageing and neurological disorders caused by mitochondrial dysfunction.
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Affiliation(s)
- Varinderpal S Dhillon
- Preventative-Health Flagship, Gate 13, Kintore Avenue, Adelaide, SA 5000, Australia; CSIRO Animal, Food and Health Sciences, Gate 13, Kintore Avenue, Adelaide, SA 5000, Australia.
| | - Michael Fenech
- Preventative-Health Flagship, Gate 13, Kintore Avenue, Adelaide, SA 5000, Australia; CSIRO Animal, Food and Health Sciences, Gate 13, Kintore Avenue, Adelaide, SA 5000, Australia
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19
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Johnson ML, Robinson MM, Nair KS. Skeletal muscle aging and the mitochondrion. Trends Endocrinol Metab 2013; 24:247-56. [PMID: 23375520 PMCID: PMC3641176 DOI: 10.1016/j.tem.2012.12.003] [Citation(s) in RCA: 152] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 12/19/2012] [Accepted: 12/19/2012] [Indexed: 01/06/2023]
Abstract
Decline in human muscle mass and strength (sarcopenia) is a hallmark of the aging process. A growing body of research in the areas of bioenergetics and protein turnover has placed the mitochondria at the center of this process. It is now clear that, unless an active lifestyle is rigorously followed, skeletal muscle mitochondrial decline occurs as humans age. Increasing research on mitochondrial biology has elucidated the regulatory pathways involved in mitochondrial biogenesis, many of which are potential therapeutic targets, and highlight the beneficial effects of vigorous physical activity on skeletal muscle health for an aging population.
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Affiliation(s)
- Matthew L Johnson
- Mayo Clinic, Division of Endocrinology, 200 First Street SW, Joseph 5-194, Rochester, MN 55905, USA
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20
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Abstract
Protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage is well known to be necessary to longevity. The relevance of mitochondrial DNA (mtDNA) to aging is suggested by the fact that the two most commonly measured forms of mtDNA damage, deletions and the oxidatively induced lesion 8-oxo-dG, increase with age. The rate of increase is species-specific and correlates with maximum lifespan. It is less clear that failure or inadequacies in the protection from reactive oxygen species (ROS) and from mitochondrial oxidative damage are sufficient to explain senescence. DNA containing 8-oxo-dG is repaired by mitochondria, and the high ratio of mitochondrial to nuclear levels of 8-oxo-dG previously reported are now suspected to be due to methodological difficulties. Furthermore, MnSOD -/+ mice incur higher than wild type levels of oxidative damage, but do not display an aging phenotype. Together, these findings suggest that oxidative damage to mitochondria is lower than previously thought, and that higher levels can be tolerated without physiological consequence. A great deal of work remains before it will be known whether mitochondrial oxidative damage is a "clock" which controls the rate of aging. The increased level of 8-oxo-dG seen with age in isolated mitochondria needs explanation. It could be that a subset of cells lose the ability to protect or repair mitochondria, resulting in their incurring disproportionate levels of damage. Such an uneven distribution could exceed the reserve capacity of these cells and have serious physiological consequences. Measurements of damage need to focus more on distribution, both within tissues and within cells. In addition, study must be given to the incidence and repair of other DNA lesions, and to the possibility that repair varies from species to species, tissue to tissue, and young to old.
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Affiliation(s)
- R M Anson
- Laboratory of Molecular Genetics, National Institute on Aging, Baltimore, MD
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21
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Gouspillou G, Hepple RT. Facts and controversies in our understanding of how caloric restriction impacts the mitochondrion. Exp Gerontol 2013; 48:1075-84. [PMID: 23523973 DOI: 10.1016/j.exger.2013.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 02/26/2013] [Accepted: 03/11/2013] [Indexed: 12/11/2022]
Abstract
Caloric restriction (CR) has pronounced benefits in promoting healthy aging. Amongst the most frequently implicated physiological mechanisms implicated in this benefit is altered mitochondrial function. Whereas a reduction in mitochondrial reactive oxygen species (ROS) production is a widely consistent effect of CR, an increase in mitochondrial biogenesis, which is accepted by many as fact, is contradicted on several levels, most critically by a lack of increase in mitochondrial protein synthesis rate in vivo. Furthermore, an increase in PGC-1α protein and markers of mitochondrial content with CR is a highly variable observation between studies. On the other hand, deacetylation of several mitochondrial proteins by the sirtuin, Sirt3, is an increasingly reported observation and at least so far, this observation is consistent between studies. Notwithstanding this point, the controversies evident in the published literature underscore the significant questions that remain in our understanding of how CR impacts the mitochondrion and suggest we have yet to fully understand the complexities herein.
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Affiliation(s)
- Gilles Gouspillou
- McGill University Health Center, Department of Kinesiology, McGill University, Montreal, QC, Canada
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22
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Abstract
Over the last decade, accumulating evidence has suggested a causative link between mitochondrial dysfunction and major phenotypes associated with aging. Somatic mitochondrial DNA (mtDNA) mutations and respiratory chain dysfunction accompany normal aging, but the first direct experimental evidence that increased mtDNA mutation levels contribute to progeroid phenotypes came from the mtDNA mutator mouse. Recent evidence suggests that increases in aging-associated mtDNA mutations are not caused by damage accumulation, but rather are due to clonal expansion of mtDNA replication errors that occur during development. Here we discuss the caveats of the traditional mitochondrial free radical theory of aging and highlight other possible mechanisms, including insulin/IGF-1 signaling (IIS) and the target of rapamycin pathways, that underlie the central role of mitochondria in the aging process.
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Affiliation(s)
- Ana Bratic
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, Cologne, Germany
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23
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Molecular mechanisms for age-associated mitochondrial deficiency in skeletal muscle. J Aging Res 2012; 2012:768304. [PMID: 22548174 PMCID: PMC3324903 DOI: 10.1155/2012/768304] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 01/23/2012] [Indexed: 01/01/2023] Open
Abstract
The abundance, morphology, and functional properties of mitochondria decay in skeletal muscle during the process of ageing. Although the precise mechanisms remain to be elucidated, these mechanisms include decreased mitochondrial DNA (mtDNA) repair and mitochondrial biogenesis. Mitochondria possess their own protection system to repair mtDNA damage, which leads to defects of mtDNA-encoded gene expression and respiratory chain complex enzymes. However, mtDNA mutations have shown to be accumulated with age in skeletal muscle. When damaged mitochondria are eliminated by autophagy, mitochondrial biogenesis plays an important role in sustaining energy production and physiological homeostasis. The capacity for mitochondrial biogenesis has shown to decrease with age in skeletal muscle, contributing to progressive mitochondrial deficiency. Understanding how these endogenous systems adapt to altered physiological conditions during the process of ageing will provide a valuable insight into the underlying mechanisms that regulate cellular homeostasis. Here we will summarize the current knowledge about the molecular mechanisms responsible for age-associated mitochondrial deficiency in skeletal muscle. In particular, recent findings on the role of mtDNA repair and mitochondrial biogenesis in maintaining mitochondrial functionality in aged skeletal muscle will be highlighted.
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24
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Kennedy SR, Loeb LA, Herr AJ. Somatic mutations in aging, cancer and neurodegeneration. Mech Ageing Dev 2012; 133:118-26. [PMID: 22079405 PMCID: PMC3325357 DOI: 10.1016/j.mad.2011.10.009] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 10/05/2011] [Accepted: 10/22/2011] [Indexed: 10/15/2022]
Abstract
The somatic mutation theory of aging posits that the accumulation of mutations in the genetic material of somatic cells as a function of time results in a decrease in cellular function. In particular, the accumulation of random mutations may inactivate genes that are important for the functioning of the somatic cells of various organ systems of the adult, result in a decrease in organ function. When the organ function decreases below a critical level, death occurs. A significant amount of research has shown that somatic mutations play an important role in aging and a number of age related pathologies. In this review, we explore evidence for increases in somatic nuclear mutation burden with age and the consequences for aging, cancer, and neurodegeneration. We then review evidence for increases in mitochondrial mutation burden and the consequences for dysfunction in the disease processes.
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Affiliation(s)
- Scott R. Kennedy
- Department of Pathology, University of Washington School of Medicine, Seattle, Washington, 98195-7705
| | - Lawrence A. Loeb
- Department of Pathology, University of Washington School of Medicine, Seattle, Washington, 98195-7705
- Department of Biochemistry, University of Washington School of Medicine, Seattle, Washington, 98195-7705
| | - Alan J. Herr
- Department of Pathology, University of Washington School of Medicine, Seattle, Washington, 98195-7705
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25
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Mao P, Gallagher P, Nedungadi S, Manczak M, shirendeb UP, Kohama SG, Ferguson B, Park BS, Reddy PH. Mitochondrial DNA deletions and differential mitochondrial DNA content in Rhesus monkeys: implications for aging. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1822:111-9. [PMID: 22056405 PMCID: PMC3249524 DOI: 10.1016/j.bbadis.2011.10.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 10/19/2011] [Accepted: 10/19/2011] [Indexed: 12/26/2022]
Abstract
The purpose of this study was to determine the relationship between mitochondrial DNA (mtDNA) deletions, mtDNA content and aging in rhesus monkeys. Using 2 sets of specific primers, we amplified an 8 kb mtDNA fragment covering a common 5.7 kb deletion and the entire 16.5 kb mitochondrial genome in the brain and buffy-coats of young and aged monkeys. We studied a total of 66 DNA samples: 39 were prepared from a buffy-coat and 27 were prepared from occipital cortex tissues. The mtDNA data were assessed using a permutation test to identify differences in mtDNA, in the different monkey groups. Using real-time RT-PCR strategy, we also assessed both mtDNA and nuclear DNA levels for young, aged and male and female monkeys. We found a 5.7 kb mtDNA deletion in 81.8% (54 of 66) of the total tested samples. In the young group of buffy-coat DNA, we found 5.7 kb deletions in 7 of 17 (41%), and in the aged group, we found 5.7 kb deletions in 12 of 22 (54%), suggesting that the prevalence of mtDNA deletions is related to age. We found decreased mRNA levels of mtDNA in aged monkeys relative to young monkeys. The increases in mtDNA deletions and mtDNA levels in aged rhesus monkeys suggest that damaged DNA accumulates as rhesus monkeys age and these altered mtDNA changes may have physiological relevance to compensate decreased mitochondrial function.
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Affiliation(s)
- Peizhong Mao
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Patience Gallagher
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Samira Nedungadi
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Maria Manczak
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Ulziibat P. shirendeb
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Steven G. Kohama
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Betsy Ferguson
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
| | - Byung S. Park
- Byung S. Park, Division of Biostatistics, Department of Public Health and Preventive Medicine, Oregon Health & Science University, Portland, OR 97239
| | - P. Hemachandra Reddy
- Neuroscience Division, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006
- Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, OR 97201
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26
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Lee HC, Wei YH. Mitochondria and Aging. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 942:311-27. [DOI: 10.1007/978-94-007-2869-1_14] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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27
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Oxidative stress, mitochondrial dysfunction, and aging. JOURNAL OF SIGNAL TRANSDUCTION 2011; 2012:646354. [PMID: 21977319 PMCID: PMC3184498 DOI: 10.1155/2012/646354] [Citation(s) in RCA: 592] [Impact Index Per Article: 45.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Accepted: 08/03/2011] [Indexed: 12/31/2022]
Abstract
Aging is an intricate phenomenon characterized by progressive decline in physiological functions and increase in mortality that is often accompanied by many pathological diseases. Although aging is almost universally conserved among all organisms, the underlying molecular mechanisms of aging remain largely elusive. Many theories of aging have been proposed, including the free-radical and mitochondrial theories of aging. Both theories speculate that cumulative damage to mitochondria and mitochondrial DNA (mtDNA) caused by reactive oxygen species (ROS) is one of the causes of aging. Oxidative damage affects replication and transcription of mtDNA and results in a decline in mitochondrial function which in turn leads to enhanced ROS production and further damage to mtDNA. In this paper, we will present the current understanding of the interplay between ROS and mitochondria and will discuss their potential impact on aging and age-related diseases.
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28
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Rowan SL, Purves-Smith FM, Solbak NM, Hepple RT. Accumulation of severely atrophic myofibers marks the acceleration of sarcopenia in slow and fast twitch muscles. Exp Gerontol 2011; 46:660-9. [PMID: 21513786 DOI: 10.1016/j.exger.2011.03.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 03/03/2011] [Accepted: 03/31/2011] [Indexed: 01/07/2023]
Abstract
The age-related decline in muscle mass, known as sarcopenia, exhibits a marked acceleration in advanced age. Although many studies have remarked upon the accumulation of very small myofibers, particularly at advanced stages of sarcopenia, the significance of this phenomenon in the acceleration of sarcopenia has never been examined. Furthermore, although mitochondrial dysfunction characterized by a lack of cytochrome oxidase (COX) activity has been implicated in myofiber atrophy in sarcopenia, the contribution of this phenotype to the accumulation of severely atrophied fibers in aged muscles has never been determined. To this end, we examined the fiber size distribution in the slow twitch soleus (Sol) and fast twitch gastrocnemius (Gas) muscles between young adulthood (YA) and senescence (SEN). We also quantified the abundance of COX deficient myocytes and their size attributes to gain insight into the contribution of this phenotype to myofiber atrophy with aging. Our data showed that the progression of muscle atrophy, particularly its striking acceleration between late middle age and SEN, was paralleled by an accumulation of severely atrophic myofibers (≤ 1000 μm(2) in size) in both Sol and Gas. On the other hand, we observed no COX deficient myofibers in Sol, despite nearly 20% of the myofibers being severely atrophic. Similarly, only 0.17 ± 0.06% of all fibers in Gas were COX deficient, and their size was generally larger (2375 ± 319 μm(2)) than the severely atrophied myofibers noted above. Collectively, our results suggest that similar processes likely contribute to the acceleration of sarcopenia in both slow twitch and fast twitch muscles, and that COX deficiency is not a major contributor to this phenomenon.
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Affiliation(s)
- Sharon L Rowan
- Muscle & Aging Laboratory, Faculty of Kinesiology and Faculty of Medicine, University of Calgary, Calgary, AB, Canada
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Ameur A, Stewart JB, Freyer C, Hagström E, Ingman M, Larsson NG, Gyllensten U. Ultra-deep sequencing of mouse mitochondrial DNA: mutational patterns and their origins. PLoS Genet 2011; 7:e1002028. [PMID: 21455489 PMCID: PMC3063763 DOI: 10.1371/journal.pgen.1002028] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 02/01/2011] [Indexed: 01/12/2023] Open
Abstract
Somatic mutations of mtDNA are implicated in the aging process, but there is no universally accepted method for their accurate quantification. We have used ultra-deep sequencing to study genome-wide mtDNA mutation load in the liver of normally- and prematurely-aging mice. Mice that are homozygous for an allele expressing a proof-reading–deficient mtDNA polymerase (mtDNA mutator mice) have 10-times-higher point mutation loads than their wildtype siblings. In addition, the mtDNA mutator mice have increased levels of a truncated linear mtDNA molecule, resulting in decreased sequence coverage in the deleted region. In contrast, circular mtDNA molecules with large deletions occur at extremely low frequencies in mtDNA mutator mice and can therefore not drive the premature aging phenotype. Sequence analysis shows that the main proportion of the mutation load in heterozygous mtDNA mutator mice and their wildtype siblings is inherited from their heterozygous mothers consistent with germline transmission. We found no increase in levels of point mutations or deletions in wildtype C57Bl/6N mice with increasing age, thus questioning the causative role of these changes in aging. In addition, there was no increased frequency of transversion mutations with time in any of the studied genotypes, arguing against oxidative damage as a major cause of mtDNA mutations. Our results from studies of mice thus indicate that most somatic mtDNA mutations occur as replication errors during development and do not result from damage accumulation in adult life. Mitochondria represent the powerhouses of cells and have their own DNA. Mutations in the mitochondrial genome are associated with a range of human diseases and have also been implicated as a driving force behind the aging process. We have used ultra-deep sequencing to study the genome-wide mutation load in the mitochondrial DNA (mtDNA) of liver from normal inbred mice and mice that express a proof-reading–deficient mtDNA polymerase (mtDNA mutator mice) that cause premature aging. The mtDNA mutator mice show a dramatic increase of point mutations with age and have 10-times-higher point mutation levels than wildtype siblings or normal C57Bl/6N mice. Circular mtDNA molecules with large deletions occur at very low frequencies in mtDNA mutator mice and are therefore unlikely to contribute to the premature aging phenotype. We found no increase in levels of point mutations or deletions in normal mice with increasing age, arguing against the accumulation of mtDNA mutations as contributing to aging. Our results indicate that most somatic mtDNA mutations occur as replication errors during the rapid amplification of mtDNA during embryogenesis and do not result from damage accumulation in adult life.
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Affiliation(s)
- Adam Ameur
- Department of Immunology, Genetics, and Pathology, SciLifeLab Uppsala, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
| | | | | | - Erik Hagström
- Division of Metabolic Diseases, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Max Ingman
- Department of Immunology, Genetics, and Pathology, SciLifeLab Uppsala, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
| | - Nils-Göran Larsson
- Max Planck Institute for Biology of Ageing, Cologne, Germany
- Division of Metabolic Diseases, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Ulf Gyllensten
- Department of Immunology, Genetics, and Pathology, SciLifeLab Uppsala, Rudbeck Laboratory, Uppsala University, Uppsala, Sweden
- * E-mail:
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Mitochondrial Dysfunction and Oxidative Stress in Asthma: Implications for Mitochondria-Targeted Antioxidant Therapeutics. Pharmaceuticals (Basel) 2011; 4:429-456. [PMID: 21461182 PMCID: PMC3066010 DOI: 10.3390/ph4030429] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Asthma is a complex, inflammatory disorder characterized by airflow obstruction of variable degrees, bronchial hyper-responsiveness, and airway inflammation. Asthma is caused by environmental factors and a combination of genetic and environmental stimuli. Genetic studies have revealed that multiple loci are involved in the etiology of asthma. Recent cellular, molecular, and animal-model studies have revealed several cellular events that are involved in the progression of asthma, including: increased Th2 cytokines leading to the recruitment of inflammatory cells to the airway, and an increase in the production of reactive oxygen species and mitochondrial dysfunction in the activated inflammatory cells, leading to tissue injury in the bronchial epithelium. Further, aging and animal model studies have revealed that mitochondrial dysfunction and oxidative stress are involved and play a large role in asthma. Recent studies using experimental allergic asthmatic mouse models and peripheral cells and tissues from asthmatic humans have revealed antioxidants as promising treatments for people with asthma. This article summarizes the latest research findings on the involvement of inflammatory changes, and mitochondrial dysfunction/oxidative stress in the development and progression of asthma. This article also addresses the relationship between aging and age-related immunity in triggering asthma, the antioxidant therapeutic strategies in treating people with asthma.
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Endurance exercise rescues progeroid aging and induces systemic mitochondrial rejuvenation in mtDNA mutator mice. Proc Natl Acad Sci U S A 2011; 108:4135-40. [PMID: 21368114 DOI: 10.1073/pnas.1019581108] [Citation(s) in RCA: 269] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A causal role for mitochondrial DNA (mtDNA) mutagenesis in mammalian aging is supported by recent studies demonstrating that the mtDNA mutator mouse, harboring a defect in the proofreading-exonuclease activity of mitochondrial polymerase gamma, exhibits accelerated aging phenotypes characteristic of human aging, systemic mitochondrial dysfunction, multisystem pathology, and reduced lifespan. Epidemiologic studies in humans have demonstrated that endurance training reduces the risk of chronic diseases and extends life expectancy. Whether endurance exercise can attenuate the cumulative systemic decline observed in aging remains elusive. Here we show that 5 mo of endurance exercise induced systemic mitochondrial biogenesis, prevented mtDNA depletion and mutations, increased mitochondrial oxidative capacity and respiratory chain assembly, restored mitochondrial morphology, and blunted pathological levels of apoptosis in multiple tissues of mtDNA mutator mice. These adaptations conferred complete phenotypic protection, reduced multisystem pathology, and prevented premature mortality in these mice. The systemic mitochondrial rejuvenation through endurance exercise promises to be an effective therapeutic approach to mitigating mitochondrial dysfunction in aging and related comorbidities.
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Lee HC, Chang CM, Chi CW. Somatic mutations of mitochondrial DNA in aging and cancer progression. Ageing Res Rev 2010; 9 Suppl 1:S47-58. [PMID: 20816876 DOI: 10.1016/j.arr.2010.08.009] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mitochondria are intracellular organelles responsible for generating ATP through respiration and oxidative phosphorylation (OXPHOS), producing reactive oxygen species, and initiating and executing apoptosis. Mitochondrial dysfunction has been observed to be an important hallmark of aging and cancer. Because mitochondrial DNA (mtDNA) is important in maintaining functionally competent organelles, accumulation of mtDNA mutations can affect energy production, oxidative stress, and cell survival, which may contribute to aging and/or carcinogenesis. This review outlines a variety of somatic mtDNA mutations identified in aging tissues and human cancers, as well as recent advances in understanding the causal role of mtDNA mutations in the aging process and cancer progression. Mitochondrial dysfunction elicited by somatic mutations in mtDNA could induce apoptosis in aging cells and some cancer cells with severe mtDNA mutations. In addition, it could activate mitochondria-to-nucleus retrograde signaling to modulate the expression of nuclear genes involved in a metabolic shift from OXPHOS to glycolysis, facilitate cells to adapt to altered environments and develop resistance to chemotherapeutic agents, or promote metastatic properties of cancer cells. These findings suggest that accumulation of somatic mtDNA mutations is not only an important contributor to human aging but also plays a critical role in cancer progression.
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High brain lactate is a hallmark of aging and caused by a shift in the lactate dehydrogenase A/B ratio. Proc Natl Acad Sci U S A 2010; 107:20087-92. [PMID: 21041631 DOI: 10.1073/pnas.1008189107] [Citation(s) in RCA: 193] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
At present, there are few means to track symptomatic stages of CNS aging. Thus, although metabolic changes are implicated in mtDNA mutation-driven aging, the manifestations remain unclear. Here, we used normally aging and prematurely aging mtDNA mutator mice to establish a molecular link between mitochondrial dysfunction and abnormal metabolism in the aging process. Using proton magnetic resonance spectroscopy and HPLC, we found that brain lactate levels were increased twofold in both normally and prematurely aging mice during aging. To correlate the striking increase in lactate with tissue pathology, we investigated the respiratory chain enzymes and detected mitochondrial failure in key brain areas from both normally and prematurely aging mice. We used in situ hybridization to show that increased brain lactate levels were caused by a shift in transcriptional activities of the lactate dehydrogenases to promote pyruvate to lactate conversion. Separation of the five tetrameric lactate dehydrogenase (LDH) isoenzymes revealed an increase of those dominated by the Ldh-A product and a decrease of those rich in the Ldh-B product, which, in turn, increases pyruvate to lactate conversion. Spectrophotometric assays measuring LDH activity from the pyruvate and lactate sides of the reaction showed a higher pyruvate → lactate activity in the brain. We argue for the use of lactate proton magnetic resonance spectroscopy as a noninvasive strategy for monitoring this hallmark of the aging process. The mtDNA mutator mouse allows us to conclude that the increased LDH-A/LDH-B ratio causes high brain lactate levels, which, in turn, are predictive of aging phenotypes.
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Weber TA, Reichert AS. Impaired quality control of mitochondria: aging from a new perspective. Exp Gerontol 2010; 45:503-11. [PMID: 20451598 DOI: 10.1016/j.exger.2010.03.018] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 03/15/2010] [Accepted: 03/16/2010] [Indexed: 11/30/2022]
Abstract
Mitochondria fulfill a number of essential cellular functions and play a key role in the aging process. Reactive oxygen species (ROS) are predominantly generated in this organelle but next to inducing oxidative damage they act as signaling molecules. Autophagy is regulated by signaling ROS and is known to affect aging as well as neurodegenerative diseases. Many cellular components that influence autophagy are linked to longevity such as members of the sirtuin protein family. Recent studies further link mitochondrial dynamics to the removal of dysfunctional mitochondria by mitophagy, thereby representing a novel mechanism for the quality control of mitochondria. Here we summarize the current views on how mitochondrial function is linked to aging and we propose that quality control of mitochondria has a crucial role in counteracting the aging process.
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Affiliation(s)
- Tobias A Weber
- CEF Makromolekulare Komplexe, Mitochondriale Biologie, Fachbereich Medizin, Goethe-Universität Frankfurt am Main, Theodor-Stern-Kai 7, Frankfurt/Main, Germany
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Ylikallio E, Tyynismaa H, Tsutsui H, Ide T, Suomalainen A. High mitochondrial DNA copy number has detrimental effects in mice. Hum Mol Genet 2010; 19:2695-705. [PMID: 20413656 DOI: 10.1093/hmg/ddq163] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mitochondrial DNA (mtDNA) is an essential multicopy genome, compacted into protein-DNA clusters called nucleoids. Maintaining an adequate mtDNA copy number is crucial for cellular viability. Loss of mtDNA results in severe human syndromes, whereas increased mtDNA copy number has been suggested to improve survival from myocardial infarction in mice and to be a promising therapeutic strategy for mitochondrial disease. The mechanisms that regulate mtDNA amount and organization are, however, not fully understood. Of the proteins required for mtDNA existence, only the mitochondrial helicase Twinkle and mitochondrial transcription factor A (TFAM) have been shown to increase mtDNA copy number in vivo, when expressed in physiological levels. Here we studied how Twinkle and TFAM affect mtDNA synthesis and nucleoid structure in mice. Using in vivo BrdU labeling, we show that Twinkle specifically regulates de novo mtDNA synthesis. Remarkably, high mtDNA copy number in mice is accompanied by nucleoid enlargement, which in turn correlates with defective transcription, age-related accumulation of mtDNA deletions and respiratory chain (RC) deficiency. Simultaneous overexpression of Twinkle and TFAM in bitransgenic mice has an additive effect on mtDNA copy number, increasing it up to 6-fold in skeletal muscle. Bitransgenic mice also exhibit further enlargement of nucleoids and aggravation of the RC defect. In conclusion, we show that Twinkle acts as a regulator of mtDNA replication initiation, and provide evidence that high mtDNA copy number and alteration of nucleoid architecture may be detrimental to mitochondrial function.
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Affiliation(s)
- Emil Ylikallio
- Biomedicum Helsinki, Research Program of Molecular Neurology, University of Helsinki, and Department of Neurology, Helsinki University Central Hospital, Helsinki, Finland
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Abstract
Mitochondrial dysfunction is heavily implicated in the multifactorial aging process. Aging humans have increased levels of somatic mtDNA mutations that tend to undergo clonal expansion to cause mosaic respiratory chain deficiency in various tissues, such as heart, brain, skeletal muscle, and gut. Genetic mouse models have shown that somatic mtDNA mutations and cell type-specific respiratory chain dysfunction can cause a variety of phenotypes associated with aging and age-related disease. There is thus strong observational and experimental evidence to implicate somatic mtDNA mutations and mosaic respiratory chain dysfunction in the mammalian aging process. The hypothesis that somatic mtDNA mutations are generated by oxidative damage has not been conclusively proven. Emerging data instead suggest that the inherent error rate of mitochondrial DNA (mtDNA) polymerase gamma (Pol gamma) may be responsible for the majority of somatic mtDNA mutations. The roles for mtDNA damage and replication errors in aging need to be further experimentally addressed.
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Miller F, Nagley P, Mariani JA, Ou R, Liu VWS, Zhang C, Linnane AW, Pepe S, Rosenfeldt F. Age-related decline in stress responses of human myocardium may not be explained by changes in mtDNA. Mech Ageing Dev 2010; 130:742-7. [PMID: 19819254 DOI: 10.1016/j.mad.2009.09.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2008] [Revised: 09/03/2009] [Accepted: 09/20/2009] [Indexed: 01/07/2023]
Abstract
Elderly patients undergoing cardiac surgery are more likely to suffer postoperative heart failure than younger patients. This phenomenon is mirrored by an age-related loss of mitochondrial function and by an in vitro loss of myocardial contractile force following a stress. To examine the possibility that loss of mtDNA integrity may be responsible, we quantified representative age-associated mtDNA mutations (mtDNA(4977) and mtDNA(A3243G)) and mtDNA copy number using quantitative polymerase chain reaction in atrial samples obtained during cardiac surgery. The myocardium underwent organ bath contractility testing before and after either an ischaemic or hypoxic stress. We found that with age, recovery of developed force after either stressor significantly declined (p<0.0001). The abundance of mtDNA(4977) correlated weakly with loss of contractility (R(2)=0.09, p=0.047). However, the abundance level was low (average 0.0075% of total mtDNA) and the correlation disappeared when age was included in a multivariate analysis. Neither the abundance of mtDNA(A3243G) nor mtDNA copy number correlated with reduced recovery of developed force after stress. We conclude that, although mtDNA mutations (as exemplified by mtDNA(4977)) accumulate in the ageing heart, they are unlikely to make a major contribution to loss of contractile function.
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Affiliation(s)
- Francis Miller
- Cardiac Surgical Research Unit, Alfred Hospital, Dept of Surgery, Monash University, and Baker Heart Research Institute, Commercial Road Prahran, Victoria 3181, Australia.
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Lanza IR, Nair KS. Mitochondrial function as a determinant of life span. Pflugers Arch 2009; 459:277-89. [PMID: 19756719 PMCID: PMC2801852 DOI: 10.1007/s00424-009-0724-5] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Accepted: 08/26/2009] [Indexed: 12/31/2022]
Abstract
Average human life expectancy has progressively increased over many decades largely due to improvements in nutrition, vaccination, antimicrobial agents, and effective treatment/prevention of cardiovascular disease, cancer, etc. Maximal life span, in contrast, has changed very little. Caloric restriction (CR) increases maximal life span in many species, in concert with improvements in mitochondrial function. These effects have yet to be demonstrated in humans, and the duration and level of CR required to extend life span in animals is not realistic in humans. Physical activity (voluntary exercise) continues to hold much promise for increasing healthy life expectancy in humans, but remains to show any impact to increase maximal life span. However, longevity in Caenorhabditis elegans is related to activity levels, possibly through maintenance of mitochondrial function throughout the life span. In humans, we reported a progressive decline in muscle mitochondrial DNA abundance and protein synthesis with age. Other investigators also noted age-related declines in muscle mitochondrial function, which are related to peak oxygen uptake. Long-term aerobic exercise largely prevented age-related declines in mitochondrial DNA abundance and function in humans and may increase spontaneous activity levels in mice. Notwithstanding, the impact of aerobic exercise and activity levels on maximal life span is uncertain. It is proposed that age-related declines in mitochondrial content and function not only affect physical function, but also play a major role in regulation of life span. Regular aerobic exercise and prevention of adiposity by healthy diet may increase healthy life expectancy and prolong life span through beneficial effects at the level of the mitochondrion.
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Affiliation(s)
- Ian R Lanza
- Division of Endocrinology, Endocrinology Research Unit, Mayo Clinic College of Medicine, Rochester, MN, USA
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Nicholas A, Kraytsberg Y, Guo X, Khrapko K. On the timing and the extent of clonal expansion of mtDNA deletions: evidence from single-molecule PCR. Exp Neurol 2009; 218:316-9. [PMID: 19426731 DOI: 10.1016/j.expneurol.2009.04.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Revised: 04/27/2009] [Accepted: 04/28/2009] [Indexed: 01/07/2023]
Abstract
mtDNA deletions are pathogenic mutations that remove substantial portions of the mitochondrial genome. mtDNA deletions accumulate with age and have been implicated in various degenerative diseases. There are multiple mtDNA per cell and mtDNA mutations become toxic only if they accumulate to substantial intracellular levels, i.e. exceed so-called "phenotypic threshold". This is usually achieved via clonal expansion of a single initial mutated molecule. Intracellular mitochondrial genomes are analogous to a population of individuals in that mitochondria are born by division and die by degradation. Clonal expansion within cells is thus analogous to genetic drift within populations and is driven by a combination of random processes and selection. mtDNA mutations occurring early in development are expected to end up spread across tissues, while mutations of late origin are expected to be localized, i.e. limited a single post-mitotic cell or progeny of a single stem cell. We have explored the extent and timing of clonality of mtDNA deletion in human muscle using single-molecule PCR. We analyzed deletions from two nearby locations within the same tissue sample. Altogether we analyzed over 130 mutant molecules, but almost every deletion type detected was represented by several identical mutant molecules, so that altogether there were only 21 different kinds of deletions, implying that essentially all deletions were clonal. At the same time the sets of deletions in the two locations were completely different. This observation implies that all of the clonal expansions spanned very small areas and therefore that the corresponding mutations were likely events of older age. More studies are necessary to further validate these findings in muscle and to explore the other tissues.
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Affiliation(s)
- Alexander Nicholas
- Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
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Maynard S, Schurman SH, Harboe C, de Souza-Pinto NC, Bohr VA. Base excision repair of oxidative DNA damage and association with cancer and aging. Carcinogenesis 2008; 30:2-10. [PMID: 18978338 DOI: 10.1093/carcin/bgn250] [Citation(s) in RCA: 445] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Aging has been associated with damage accumulation in the genome and with increased cancer incidence. Reactive oxygen species (ROS) are produced from endogenous sources, most notably the oxidative metabolism in the mitochondria, and from exogenous sources, such as ionizing radiation. ROS attack DNA readily, generating a variety of DNA lesions, such as oxidized bases and strand breaks. If not properly removed, DNA damage can be potentially devastating to normal cell physiology, leading to mutagenesis and/or cell death, especially in the case of cytotoxic lesions that block the progression of DNA/RNA polymerases. Damage-induced mutagenesis has been linked to various malignancies. The major mechanism that cells use to repair oxidative damage lesions, such as 8-hydroxyguanine, formamidopyrimidines, and 5-hydroxyuracil, is base excision repair (BER). The BER pathway in the nucleus is well elucidated. More recently, BER was shown to also exist in the mitochondria. Here, we review the association of BER of oxidative DNA damage with aging, cancer and other diseases.
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Affiliation(s)
- Scott Maynard
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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Druzhyna NM, Wilson GL, LeDoux SP. Mitochondrial DNA repair in aging and disease. Mech Ageing Dev 2008; 129:383-90. [PMID: 18417187 DOI: 10.1016/j.mad.2008.03.002] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 02/29/2008] [Accepted: 03/05/2008] [Indexed: 11/16/2022]
Abstract
Mitochondria are organelles which, according to the endosymbiosis theory, evolved from purpurbacteria approximately 1.5 billion years ago. One of the unique features of mitochondria is that they have their own genome. Mitochondria replicate and transcribe their DNA semiautonomously. Like nuclear DNA, mitochondrial DNA (mtDNA) is constantly exposed to DNA damaging agents. Regarding the repair of mtDNA, the prevailing concept for many years was that mtDNA molecules suffering an excess of damage would simply be degraded to be replaced by newly generated successors copied from undamaged genomes. However, evidence now clearly shows that mitochondria contain the machinery to repair the damage to their genomes caused by certain endogenous or exogenous damaging agents. The link between mtDNA damage and repair to aging, neurodegeneration, and carcinogenesis-associated processes is the subject of this review.
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Affiliation(s)
- Nadiya M Druzhyna
- Department of Cell Biology and Neuroscience, University of South Alabama, 307 University Boulevard, Mobile, AL 36688, USA
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Dufour E, Terzioglu M, Sterky FH, Sörensen L, Galter D, Olson L, Wilbertz J, Larsson NG. Age-associated mosaic respiratory chain deficiency causes trans-neuronal degeneration. Hum Mol Genet 2008; 17:1418-26. [PMID: 18245781 PMCID: PMC2367695 DOI: 10.1093/hmg/ddn030] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Heteroplasmic mitochondrial DNA (mtDNA) mutations (mutations present only in a subset of cellular mtDNA copies) arise de novo during the normal ageing process or may be maternally inherited in pedigrees with mitochondrial disease syndromes. A pathogenic mtDNA mutation causes respiratory chain deficiency only if the fraction of mutated mtDNA exceeds a certain threshold level. These mutations often undergo apparently random mitotic segregation and the levels of normal and mutated mtDNA can vary considerably between cells of the same tissue. In human ageing, segregation of somatic mtDNA mutations leads to mosaic respiratory chain deficiency in a variety of tissues, such as brain, heart and skeletal muscle. A similar pattern of mutation segregation with mosaic respiratory chain deficiency is seen in patients with mitochondrial disease syndromes caused by inherited pathogenic mtDNA mutations. We have experimentally addressed the role of mosaic respiratory chain deficiency in ageing and mitochondrial disease by creating mouse chimeras with a mixture of normal and respiratory chain-deficient neurons in cerebral cortex. We report here that a low proportion (>20%) of respiratory chain-deficient neurons in the forebrain are sufficient to cause symptoms, whereas premature death of the animal occurs only if the proportion is high (>60–80%). The presence of neurons with normal respiratory chain function does not only prevent mortality but also delays the age at which onset of disease symptoms occur. Unexpectedly, respiratory chain-deficient neurons have adverse effect on normal adjacent neurons and induce trans-neuronal degeneration. In summary, our study defines the minimal threshold level of respiratory chain-deficient neurons needed to cause symptoms and also demonstrate that neurons with normal respiratory chain function ameliorate disease progression. Finally, we show that respiratory chain-deficient neurons induce death of normal neurons by a trans-neuronal degeneration mechanism. These findings provide novel insights into the pathogenesis of mosaic respiratory chain deficiency in ageing and mitochondrial disease.
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Affiliation(s)
- Eric Dufour
- Department of Laboratory Medicine, Karolinska Institutet, S-17177 Stockholm, Sweden
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The role of mitochondrial DNA mutations in aging and sarcopenia: implications for the mitochondrial vicious cycle theory of aging. Exp Gerontol 2007; 43:24-33. [PMID: 17997255 DOI: 10.1016/j.exger.2007.10.001] [Citation(s) in RCA: 171] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 09/28/2007] [Accepted: 10/01/2007] [Indexed: 01/07/2023]
Abstract
Aging is associated with a progressive loss of skeletal muscle mass and strength and the mechanisms mediating these effects likely involve mitochondrial DNA (mtDNA) mutations, mitochondrial dysfunction and the activation of mitochondrial-mediated apoptosis. Because the mitochondrial genome is densely packed and close to the main generator of reactive oxygen species (ROS) in the cell, the electron transport chain (ETC), an important role for mtDNA mutations in aging has been proposed. Point mutations and deletions in mtDNA accumulate with age in a wide variety of tissues in mammals, including humans, and often coincide with significant tissue dysfunction. Here, we examine the evidence supporting a causative role for mtDNA mutations in aging and sarcopenia. We review experimental outcomes showing that mtDNA mutations, leading to mitochondrial dysfunction and possibly apoptosis, are causal to the process of sarcopenia. Moreover, we critically discuss and dispute an important part of the mitochondrial 'vicious cycle' theory of aging which proposes that accumulation of mtDNA mutations may lead to an enhanced mitochondrial ROS production and ever increasing oxidative stress which ultimately leads to tissue deterioration and aging. Potential mechanism(s) by which mtDNA mutations may mediate their pathological consequences in skeletal muscle are also discussed.
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Herbst A, Pak JW, McKenzie D, Bua E, Bassiouni M, Aiken JM. Accumulation of mitochondrial DNA deletion mutations in aged muscle fibers: evidence for a causal role in muscle fiber loss. J Gerontol A Biol Sci Med Sci 2007; 62:235-45. [PMID: 17389720 PMCID: PMC2846622 DOI: 10.1093/gerona/62.3.235] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Although mitochondrial mutation abundance has been recognized to increase in an age-dependent manner, the impact of mutation has been more difficult to establish. Using quantitative polymerase chain reaction, we measured the intracellular abundance of mutant and wild-type mitochondrial genomes along the length of individual laser-captured microdissected muscle fibers from aged rat quadriceps. Aged muscle fibers possessed segmental, clonal intracellular expansions of unique somatically derived mitochondrial DNA (mtDNA) deletion mutations. When the mutation abundance surpassed 90% of the total mitochondrial genomes, the fiber lost cytochrome c oxidase activity and exhibited an increase in succinate dehydrogenase activity. In addition to the mitochondrial enzymatic abnormalities, some fibers displayed abnormal morphology such as fiber splitting, atrophy, and breakage. Deletion mutation accumulation was linked to these aberrant morphologies with more severe cellular pathologies resulting from higher deletion mutation abundance. In summary, our measurements indicate that age-induced mtDNA deletion mutations expand within individual muscle fibers, eliciting fiber dysfunction and breakage.
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Harvey AJ, Gibson TC, Quebedeaux TM, Brenner CA. Impact of Assisted Reproductive Technologies: A Mitochondrial Perspective of Cytoplasmic Transplantation. Curr Top Dev Biol 2007; 77:229-49. [PMID: 17222706 DOI: 10.1016/s0070-2153(06)77009-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Many of the assisted reproductive techniques associated with maternal aging, disease states, or implantation failure aim to correct poor developmental capacity. These techniques are highly invasive and require the exchange of nuclear or cytoplasmic material from a donor oocyte to compensate for deficiencies inherent in the affected individual. These techniques are based on the assumption that the cytoplasm of the donor oocyte can effectively substitute the necessary component(s) to enable development to proceed. Several studies have attempted to inject cytoplasm from "normal" (young) donors, into aged eggs, again assuming that beneficial components of the cytoplasm are transferred to restore developmental capacity. These invasive assisted reproduction technology (ART) procedures aim to eliminate chromosomal abnormalities, improve the quality of oocytes deficient in some important cytoplasmic factors necessary for maturation and/or subsequent development, and eliminate maternally inherited diseases (particularly mitochondrial myopathies). However, in order to develop such ART, understanding the processes involving mitochondrial DNA replication and transcription is imperative, as asynchrony between mitochondrial and nuclear genomes may cause problems in mitochondrial function, localization, and biogenesis.
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Affiliation(s)
- A J Harvey
- Department of Biology, University of New Orleans New Orleans, Louisiana 70148, USA
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Baker DJ, Betik AC, Krause DJ, Hepple RT. No decline in skeletal muscle oxidative capacity with aging in long-term calorically restricted rats: effects are independent of mitochondrial DNA integrity. J Gerontol A Biol Sci Med Sci 2006; 61:675-84. [PMID: 16870628 DOI: 10.1093/gerona/61.7.675] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigated if calorie restriction (CR) preserved skeletal muscle oxidative capacity with aging after accounting for life span extension by CR, and determined if mitochondrial content, mitochondrial DNA integrity, and peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) were involved. Ad libitum-fed (AL) and CR animals representing young adult, late middle age, and senescence were studied. Whereas citrate synthase and complex IV activities were lower in plantaris and gastrocnemius muscle of young adult CR animals, in contrast to the 15%-40% decline in senescent AL animals, there was no decline with aging in CR animals. There was no decline in citrate synthase protein in gastrocnemius with aging in either group, suggesting that CR preserves oxidative capacity with aging by protecting mitochondrial function rather than content. This protection was independent of mitochondrial DNA damage between groups. However, there was a slower decline in PGC-1alpha gene expression with aging in CR versus AL animals, suggesting a better maintenance of mitochondrial biogenesis with aging in CR animals.
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Affiliation(s)
- David J Baker
- Faculty of Medicine, University of Calgary, Calgary, AB, T2N 1N4, Canada
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Bua E, Johnson J, Herbst A, Delong B, McKenzie D, Salamat S, Aiken JM. Mitochondrial DNA-deletion mutations accumulate intracellularly to detrimental levels in aged human skeletal muscle fibers. Am J Hum Genet 2006; 79:469-80. [PMID: 16909385 PMCID: PMC1559550 DOI: 10.1086/507132] [Citation(s) in RCA: 316] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 06/12/2006] [Indexed: 12/18/2022] Open
Abstract
Skeletal muscle-mass loss with age has severe health consequences, yet the molecular basis of the loss remains obscure. Although mitochondrial DNA (mtDNA)-deletion mutations have been shown to accumulate with age, for these aberrant genomes to be physiologically relevant, they must accumulate to high levels intracellularly and be present in a significant number of cells. We examined mtDNA-deletion mutations in vastus lateralis (VL) muscle of human subjects aged 49-93 years, using both histologic and polymerase-chain-reaction (PCR) analyses, to determine the physiological and genomic integrity of mitochondria in aging human muscle. The number of VL muscle fibers exhibiting mitochondrial electron-transport-system (ETS) abnormalities increased from an estimated 6% at age 49 years to 31% at age 92 years. We analyzed the mitochondrial genotype of 48 single ETS-abnormal, cytochrome c oxidase-negative/succinate dehydrogenase-hyperreactive (COX-/SDH++) fibers from normal aging human subjects and identified mtDNA-deletion mutations in all abnormal fibers. Deletion mutations were clonal within a fiber and concomitant to the COX-/SDH++ region. Quantitative PCR analysis of wild-type and deletion-containing mtDNA genomes within ETS-abnormal regions of single fibers demonstrated that these deletion mutations accumulate to detrimental levels (>90% of the total mtDNA).
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MESH Headings
- Aged
- Aged, 80 and over
- Aging/genetics
- DNA, Mitochondrial/analysis
- DNA, Mitochondrial/genetics
- Electron Transport/genetics
- Electron Transport Chain Complex Proteins/genetics
- Electron Transport Complex IV/genetics
- Female
- Humans
- Male
- Middle Aged
- Mitochondria, Muscle/enzymology
- Mitochondria, Muscle/genetics
- Muscle Fibers, Skeletal/chemistry
- Muscle Fibers, Skeletal/cytology
- Muscle Fibers, Skeletal/enzymology
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/cytology
- Muscle, Skeletal/enzymology
- Sequence Deletion
- Succinate Dehydrogenase/genetics
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Affiliation(s)
- Entela Bua
- Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, WI 53706, USA
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Lorin S, Dufour E, Sainsard-Chanet A. Mitochondrial metabolism and aging in the filamentous fungus Podospora anserina. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:604-10. [PMID: 16624249 DOI: 10.1016/j.bbabio.2006.03.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2005] [Revised: 03/06/2006] [Accepted: 03/07/2006] [Indexed: 11/18/2022]
Abstract
The filamentous fungus Podospora anserina has a limited lifespan. In this organism, aging is systematically associated to mitochondrial DNA instability. We recently provided evidence that the respiratory function is a key determinant of its lifespan. Loss of function of the cytochrome pathway leads to the compensatory induction of an alternative oxidase, to a decreased production of reactive oxygen species and to a striking increase in lifespan. These changes are associated to the stabilization of the mitochondrial DNA. Here we review and discuss the links between these different parameters and their implication in the control of lifespan. Since we demonstrated the central role of mitochondrial metabolism in aging, the same relationship has been evidenced in several model systems from yeast to mice, confirming the usefulness of simple organisms as P. anserina for studying lifespan regulation.
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Affiliation(s)
- Séverine Lorin
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette Cedex, France
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Bavister BD. The mitochondrial contribution to stem cell biology. Reprod Fertil Dev 2006; 18:829-38. [PMID: 17147931 DOI: 10.1071/rd06111] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 09/04/2006] [Indexed: 12/30/2022] Open
Abstract
The distribution and functions of mitochondria in stem cells have not been examined, yet the contributions of these organelles to stem cell viability and differentiation must be vitally important in view of their critical roles in all other cell types. A key role for mitochondria in stem cells is indicated by reports that they translocate in the oocyte during fertilisation to cluster around the pronuclei and can remain in a perinuclear pattern during embryo development. This clustering appears to be essential for normal embryonic development. Because embryonic stem cells are derived from fertilised oocytes, and eventually can differentiate into ‘adult’ stem cells, it was hypothesised that mitochondrial perinuclear clustering persists through preimplantation embryo development into the stem cells, and that this localisation is indicative of stem cell pluripotency. Further, it was predicted that mitochondrial activity, as measured by respiration and adenosine triphosphate (ATP) content, would correlate with the degree of perinuclear clustering. It was also predicted that these morphological and metabolic measurements could serve as indicators of ‘stemness.’ This article reviews the distribution and metabolism of mitochondria in a model stem cell line and how this information is related to passage number, differentiation and/or senescence. In addition, it describes mitochondrial DNA deletions in oocytes and embryos that could adversely affect stem cell performance.
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Affiliation(s)
- Barry D Bavister
- Department of Biological Sciences, University of New Orleans, 200 Computer Center, New Orleans, LA 70148-2960, USA.
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