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Sturgis J, Singh R, Caron Q, Samuels IS, Shiju TM, Mukkara A, Freedman P, Bonilha VL. Modeling aging and retinal degeneration with mitochondrial DNA mutation burden. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.30.569464. [PMID: 38076962 PMCID: PMC10705408 DOI: 10.1101/2023.11.30.569464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Somatic mitochondrial DNA (mtDNA) mutation accumulation has been observed in individuals with retinal degenerative disorders. To study the effects of aging and mtDNA mutation accumulation in the retina, a Polymerase gamma (POLG) deficiency model, the POLGD257A mutator mice (PolgD257A), was used. POLG is an enzyme responsible for regulating mtDNA replication and repair. Retinas of young and older mice with this mutation were analyzed in vivo and ex vivo to provide new insights into the contribution of age-related mitochondrial dysfunction due to mtDNA damage. Optical coherence tomography (OCT) image analysis revealed a decrease in retinal and photoreceptor thickness starting at 6 months of age in mice with the POLGD257A mutation compared to wild-type (WT) mice. Electroretinography (ERG) testing showed a significant decrease in all recorded responses at 6 months of age. Sections labeled with markers of different types of retinal cells, including cones, rods, and bipolar cells, exhibited decreased labeling starting at 6 months. However, electron microscopy analysis revealed differences in retinal pigment epithelium (RPE) mitochondria morphology beginning at 3 months. Interestingly, there was no increase in oxidative stress observed in the retina or RPE of POLGD257A mice. Additionally, POLGD257A RPE exhibited an accelerated rate of autofluorescence cytoplasmic granule formation and accumulation. Mitochondrial markers displayed decreased abundance in protein lysates obtained from retina and RPE samples. These findings suggest that the accumulation of mitochondrial DNA mutations leads to impaired mitochondrial function and accelerated aging, resulting in retinal degeneration.
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Affiliation(s)
- John Sturgis
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Rupesh Singh
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Quinn Caron
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Ivy S. Samuels
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Research Service, Louis Stokes Cleveland VA Medical Center, Cleveland, OH
| | - Thomas Micheal Shiju
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Aditi Mukkara
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- College of Arts and Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Paul Freedman
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Debusk College of Osteopathic Medicine, Knoxville, TN, USA
| | - Vera L. Bonilha
- Department of Ophthalmic Research, Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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Zhu Y, Zhou X, Zhu A, Xiong S, Xie J, Bai Z. Advances in exercise to alleviate sarcopenia in older adults by improving mitochondrial dysfunction. Front Physiol 2023; 14:1196426. [PMID: 37476691 PMCID: PMC10355810 DOI: 10.3389/fphys.2023.1196426] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 06/23/2023] [Indexed: 07/22/2023] Open
Abstract
Sarcopenia is a chronic degenerative disease affecting primarily older adults. A growing aging population is gradually increasing the number of patients suffering from sarcopenia, placing increasing financial pressure on patients' families and society in general. There is a strong link between mitochondrial dysfunction and sarcopenia pathogenesis. As a result, treating sarcopenia by improving mitochondrial dysfunction is an effective strategy. Numerous studies have demonstrated that exercise has a positive effect on mitochondrial dysfunction when treating sarcopenia. Exercise promotes mitochondrial biogenesis and mitochondrial fusion/division to add new mitochondria or improve dysfunctional mitochondria while maintaining mitochondrial calcium homeostasis, mitochondrial antioxidant defense system, and mitochondrial autophagy to promote normal mitochondrial function. Furthermore, exercise can reduce mitochondrial damage caused by aging by inhibiting mitochondrial oxidative stress, mitochondrial DNA damage, and mitochondrial apoptosis. Exercise effectiveness depends on several factors, including exercise duration, exercise intensity, and exercise form. Therefore, Moderate-intensity exercise over 4 weeks potentially mitigates sarcopenia in older adults by ameliorating mitochondrial dysfunction. HIIT has demonstrated potential as a viable approach to addressing sarcopenia in aged rats. However, further investigation is required to validate its efficacy in treating sarcopenia in older adults.
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Affiliation(s)
| | | | | | | | | | - Zhenmin Bai
- School of Sports Medicine and Rehabilitation, Beijing Sport University, Beijing, China
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Metabolic landscape in cardiac aging: insights into molecular biology and therapeutic implications. Signal Transduct Target Ther 2023; 8:114. [PMID: 36918543 PMCID: PMC10015017 DOI: 10.1038/s41392-023-01378-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 02/06/2023] [Accepted: 02/20/2023] [Indexed: 03/16/2023] Open
Abstract
Cardiac aging is evident by a reduction in function which subsequently contributes to heart failure. The metabolic microenvironment has been identified as a hallmark of malignancy, but recent studies have shed light on its role in cardiovascular diseases (CVDs). Various metabolic pathways in cardiomyocytes and noncardiomyocytes determine cellular senescence in the aging heart. Metabolic alteration is a common process throughout cardiac degeneration. Importantly, the involvement of cellular senescence in cardiac injuries, including heart failure and myocardial ischemia and infarction, has been reported. However, metabolic complexity among human aging hearts hinders the development of strategies that targets metabolic susceptibility. Advances over the past decade have linked cellular senescence and function with their metabolic reprogramming pathway in cardiac aging, including autophagy, oxidative stress, epigenetic modifications, chronic inflammation, and myocyte systolic phenotype regulation. In addition, metabolic status is involved in crucial aspects of myocardial biology, from fibrosis to hypertrophy and chronic inflammation. However, further elucidation of the metabolism involvement in cardiac degeneration is still needed. Thus, deciphering the mechanisms underlying how metabolic reprogramming impacts cardiac aging is thought to contribute to the novel interventions to protect or even restore cardiac function in aging hearts. Here, we summarize emerging concepts about metabolic landscapes of cardiac aging, with specific focuses on why metabolic profile alters during cardiac degeneration and how we could utilize the current knowledge to improve the management of cardiac aging.
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Maclaine KD, Stebbings KA, Llano DA, Havird JC. The mtDNA mutation spectrum in the PolG mutator mouse reveals germline and somatic selection. BMC Genom Data 2021; 22:52. [PMID: 34823474 PMCID: PMC8620558 DOI: 10.1186/s12863-021-01005-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 10/25/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Mitochondrial DNA (mtDNA) codes for products necessary for electron transport and mitochondrial gene translation. mtDNA mutations can lead to human disease and influence organismal fitness. The PolG mutator mouse lacks mtDNA proofreading function and rapidly accumulates mtDNA mutations, making it a model for examining the causes and consequences of mitochondrial mutations. Premature aging in PolG mice and their physiology have been examined in depth, but the location, frequency, and diversity of their mtDNA mutations remain understudied. Identifying the locations and spectra of mtDNA mutations in PolG mice can shed light on how selection shapes mtDNA, both within and across organisms. RESULTS Here, we characterized somatic and germline mtDNA mutations in brain and liver tissue of PolG mice to quantify mutation count (number of unique mutations) and frequency (mutation prevalence). Overall, mtDNA mutation count and frequency were the lowest in the D-loop, where an mtDNA origin of replication is located, but otherwise uniform across the mitochondrial genome. Somatic mtDNA mutations have a higher mutation count than germline mutations. However, germline mutations maintain a higher frequency and were also more likely to be silent. Cytosine to thymine mutations characteristic of replication errors were the plurality of basepair changes, and missense C to T mutations primarily resulted in increased protein hydrophobicity. Unlike wild type mice, PolG mice do not appear to show strand asymmetry in mtDNA mutations. Indel mutations had a lower count and frequency than point mutations and tended to be short, frameshift deletions. CONCLUSIONS Our results provide strong evidence that purifying selection plays a major role in the mtDNA of PolG mice. Missense mutations were less likely to be passed down in the germline, and they were less likely to spread to high frequencies. The D-loop appears to have resistance to mutations, either through selection or as a by-product of replication processes. Missense mutations that decrease hydrophobicity also tend to be selected against, reflecting the membrane-bound nature of mtDNA-encoded proteins. The abundance of mutations from polymerase errors compared with reactive oxygen species (ROS) damage supports previous studies suggesting ROS plays a minimal role in exacerbating the PolG phenotype, but our findings on strand asymmetry provide discussion for the role of polymerase errors in wild type organisms. Our results provide further insight on how selection shapes mtDNA mutations and on the aging mechanisms in PolG mice.
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Affiliation(s)
- Kendra D Maclaine
- Department of Integrative Biology, The University of Texas at Austin, 2415 Speedway #C0930, Austin, TX, 78712, USA.
| | - Kevin A Stebbings
- Neuroscience Program, The University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, IL, 61801, USA
- Beckman Institute for Advanced Science and Technology, 405 North Mathews Avenue, Urbana, IL, 61801, USA
| | - Daniel A Llano
- Neuroscience Program, The University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, IL, 61801, USA
- Beckman Institute for Advanced Science and Technology, 405 North Mathews Avenue, Urbana, IL, 61801, USA
- Department of Molecular an Integrative Physiology, 524 Burrill Hall, MC-114, 407 South Goodwin Avenue, Urbana, IL, 61801, USA
| | - Justin C Havird
- Department of Integrative Biology, The University of Texas at Austin, 2415 Speedway #C0930, Austin, TX, 78712, USA
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Emerging methods for and novel insights gained by absolute quantification of mitochondrial DNA copy number and its clinical applications. Pharmacol Ther 2021; 232:107995. [PMID: 34592204 DOI: 10.1016/j.pharmthera.2021.107995] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 08/26/2021] [Accepted: 09/01/2021] [Indexed: 02/07/2023]
Abstract
The past thirty years have seen a surge in interest in pathophysiological roles of mitochondria, and the accurate quantification of mitochondrial DNA copy number (mCN) in cells and tissue samples is a fundamental aspect of assessing changes in mitochondrial health and biogenesis. Quantification of mCN between studies is surprisingly variable due to a combination of physiological variability and diverse protocols being used to measure this endpoint. The advent of novel methods to quantify nucleic acids like digital polymerase chain reaction (dPCR) and high throughput sequencing offer the ability to measure absolute values of mCN. We conducted an in-depth survey of articles published between 1969 -- 2020 to create an overview of mCN values, to assess consensus values of tissue-specific mCN, and to evaluate consistency between methods of assessing mCN. We identify best practices for methods used to assess mCN, and we address the impact of using specific loci on the mitochondrial genome to determine mCN. Current data suggest that clinical measurement of mCN can provide diagnostic and prognostic value in a range of diseases and health conditions, with emphasis on cancer and cardiovascular disease, and the advent of means to measure absolute mCN should improve future clinical applications of mCN measurements.
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LaFave ER, Tarpey MD, Balestrieri NP, Spangenburg EE, Hvastkovs EG. Complementary Square-Wave Voltammetry and LC-MS/MS Analysis to Elucidate Induced Damaged and Mutated Mitochondrial and Nuclear DNA from in Vivo Knockdown of the BRCA1 Gene in the Mouse Skeletal Muscle. Anal Chem 2021; 93:11592-11600. [PMID: 34383484 PMCID: PMC8796311 DOI: 10.1021/acs.analchem.1c02249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Breast cancer 1 gene (BRCA1) DNA mutations impact skeletal muscle functions. Inducible skeletal muscle specific Brca1 homozygote knockout (Brca1KOsmi, KO) mice accumulate mitochondrial DNA (mtDNA) mutations resulting in loss of muscle quality.1 Complementary electrochemical andmass spectrometry analyses were utilized to rapidly assess mtDNA or nuclear DNA (nDNA) extracted directly from mouse skeletal muscles. Oxidative peak currents (Ip) from DNA immobilized layer by layer (LbL) were monitored using square-wave voltammetry (SWV) via Ru(bpy)32+ electrocatalysis. Ip significantly decreased (p < 0.05) for KO mtDNA compared to heterozygous KO (Het) or wild type (WT), indicative of decreases in the guanine content. nDNA Ip significantly increased in KO compared to WT (p < 0.05), suggesting an accumulation of damaged nDNA. Guanine or oxidatively damaged guanine content was monitored via appropriate m/z mass transitions using liquid chromatography-tandem mass spectroscopy (LC-MS/MS). Guanine in both KO mtDNA and nDNA was significantly lower, while oxidatively damaged guanine in KO nDNA was significantly elevated versus WT. These data demonstrate a loss of guanine content consistent with mtDNA mutation accumulation. Oxidative damage in KO nDNA suggests that repair processes associated with Brca1 are impacted. Overall, electrochemical and LC-MS/MS analysis can provide chemical-level answers to biological model phenotypic responses as a rapid and cost-effective analysis alternative to established assays.
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Affiliation(s)
- Elizabeth R. LaFave
- East Carolina University Department of Chemistry, 300 Science and Technology Bldg., Greenville, NC 27858
| | - Michael D. Tarpey
- East Carolina University Department of Physiology, Brody School of Medicine, Greenville, NC 27834
| | - Nicholas P. Balestrieri
- East Carolina University Department of Physiology, Brody School of Medicine, Greenville, NC 27834
| | - Espen E. Spangenburg
- East Carolina University Department of Physiology, Brody School of Medicine, Greenville, NC 27834
- East Carolina Diabetes and Obesity Institute, 115 Heart Dr, East Carolina University, Greenville NC, 27834
| | - Eli G. Hvastkovs
- East Carolina University Department of Chemistry, 300 Science and Technology Bldg., Greenville, NC 27858
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Arbeithuber B, Hester J, Cremona MA, Stoler N, Zaidi A, Higgins B, Anthony K, Chiaromonte F, Diaz FJ, Makova KD. Age-related accumulation of de novo mitochondrial mutations in mammalian oocytes and somatic tissues. PLoS Biol 2020; 18:e3000745. [PMID: 32667908 PMCID: PMC7363077 DOI: 10.1371/journal.pbio.3000745] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 05/27/2020] [Indexed: 12/21/2022] Open
Abstract
Mutations create genetic variation for other evolutionary forces to operate on and cause numerous genetic diseases. Nevertheless, how de novo mutations arise remains poorly understood. Progress in the area is hindered by the fact that error rates of conventional sequencing technologies (1 in 100 or 1,000 base pairs) are several orders of magnitude higher than de novo mutation rates (1 in 10,000,000 or 100,000,000 base pairs per generation). Moreover, previous analyses of germline de novo mutations examined pedigrees (and not germ cells) and thus were likely affected by selection. Here, we applied highly accurate duplex sequencing to detect low-frequency, de novo mutations in mitochondrial DNA (mtDNA) directly from oocytes and from somatic tissues (brain and muscle) of 36 mice from two independent pedigrees. We found mtDNA mutation frequencies 2- to 3-fold higher in 10-month-old than in 1-month-old mice, demonstrating mutation accumulation during the period of only 9 mo. Mutation frequencies and patterns differed between germline and somatic tissues and among mtDNA regions, suggestive of distinct mutagenesis mechanisms. Additionally, we discovered a more pronounced genetic drift of mitochondrial genetic variants in the germline of older versus younger mice, arguing for mtDNA turnover during oocyte meiotic arrest. Our study deciphered for the first time the intricacies of germline de novo mutagenesis using duplex sequencing directly in oocytes, which provided unprecedented resolution and minimized selection effects present in pedigree studies. Moreover, our work provides important information about the origins and accumulation of mutations with aging/maturation and has implications for delayed reproduction in modern human societies. Furthermore, the duplex sequencing method we optimized for single cells opens avenues for investigating low-frequency mutations in other studies.
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Affiliation(s)
- Barbara Arbeithuber
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - James Hester
- Department of Animal Science, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Marzia A. Cremona
- Department of Statistics, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Nicholas Stoler
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Arslan Zaidi
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Bonnie Higgins
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Kate Anthony
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Francesca Chiaromonte
- Department of Statistics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- EMbeDS, Sant’Anna School of Advanced Studies, Pisa, Italy
| | - Francisco J. Diaz
- Department of Animal Science, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Kateryna D. Makova
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
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