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Fausto LL, Alberti A, Kades G, de Carvalho RPD, Freiberger V, Ventura L, Dias P, Zanoni EM, Soares BH, Dutra ML, Martins DF, Comim CM. Effects of a Ketogenic Diet on the Assessment of Biochemical and Clinical Parameters in Duchenne Muscular Dystrophy: A Preclinical Investigation. Mol Neurobiol 2024:10.1007/s12035-024-04258-6. [PMID: 38816675 DOI: 10.1007/s12035-024-04258-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 05/22/2024] [Indexed: 06/01/2024]
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterized by progressive skeletal muscle degeneration and systemic effects, including the central nervous system (CNS). This study aimed to assess the impact of a 14-day ketogenic diet (DCet) on biochemical and clinical parameters in a DMD mouse model. Young adult mice (50 days old) were fed DCet, while control groups received a standard diet. On the 14th day, memory and behavior tests were conducted, followed by biochemical evaluations of oxidative stress, inflammatory biomarkers, body weight, feed intake, and brain-derived neurotrophic factor (BDNF) levels. mdx + DCet mice showed reduced mass (0.2 g ± 2.49) and improved memory retention (p < 0.05) compared to controls. Oxidative damage in muscle tissue and CNS decreased, along with a significant cytokine level reduction (p <0.05). The protocol led to an increase in hippocampal BDNF and mitochondrial respiratory complex activity in muscle tissue and the central nervous system (CNS), while also decreasing creatine kinase activity only in the striatum. Overall, a 14-day DCet showed protective effects by improving spatial learning and memory through reductions in oxidative stress and immune response, as well as increases in BDNF levels, consistent with our study's findings.
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Affiliation(s)
- Lilian Leite Fausto
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
| | - Adriano Alberti
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil.
| | | | | | - Viviane Freiberger
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
| | - Leticia Ventura
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
| | - Paula Dias
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
| | | | | | - Matheus Luchini Dutra
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
| | - Daniel Fernandes Martins
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
| | - Clarissa Martinelli Comim
- Research Group in Neurodevelopment of Childhood and Adolescence, Laboratory of Experimental Neuroscience, Postgraduate Program in Health Sciences, University of South Santa Catarina, Avenida Pedra Branca, 25, Pedra Branca, Palhoça, SC, 88137-270, Brazil
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2
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Chen Y, Ling C, Chen M, Yu L, Yang J, Fang Q. Astaxanthin Ameliorates Worsened Muscle Dysfunction of MDX Mice Fed with a High-Fat Diet through Reducing Lipotoxicity and Regulating Gut Microbiota. Nutrients 2023; 16:33. [PMID: 38201863 PMCID: PMC10780320 DOI: 10.3390/nu16010033] [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: 10/22/2023] [Revised: 12/04/2023] [Accepted: 12/08/2023] [Indexed: 01/12/2024] Open
Abstract
Duchenne muscular dystrophy (DMD), a severe X-linked inherited neuromuscular disease, has a high prevalence of obesity. Obesity exacerbates muscle damage and results in adverse clinical outcomes. Preventing obesity helps DMD patients delay disease progression and improve quality of life. Astaxanthin (AX) is a kind of carotenoid which has antioxidant and anti-adipogenesis effects. In this study, male C57BL/10ScSnDmdmdx/J mice were fed with a normal diet, a high-fat diet (HFD), and an HFD containing AX for 16 weeks, respectively. The results showed that AX significantly increased gastrocnemius fiber cross-section area and grip strength, improved treadmill endurance test and mitochondrial morphology, and reduced muscle triglyceride and malonaldehyde levels compared to the HFD. Lipidomic analysis revealed that AX decreased high levels of triglyceride, diglyceride, ceramides, and wax ester induced by HFD. Gut microbiota analysis indicated that AX supplementation failed to alleviate abnormal microbiota diversity, but increased the relative abundances of Akkermansia, Bifidobacterium, Butyricicoccus, and Staphylococcus. In conclusion, AX was expected to alleviate disease progression associated with obesity in DMD patients by reducing lipotoxicity and increasing the abundance of beneficial bacteria.
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Affiliation(s)
- Ying Chen
- Department of Neurology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China; (Y.C.); (L.Y.)
| | - Chenjie Ling
- Department of Clinical Nutrition, Dushu Lake Hospital Affiliated to Soochow University, Suzhou 215124, China;
| | - Mengting Chen
- Department of Endocrinology and Metabolism, The First Affiliated Hospital of Soochow University, Suzhou 215006, China;
| | - Liqiang Yu
- Department of Neurology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China; (Y.C.); (L.Y.)
| | - Jing Yang
- Department of Clinical Nutrition, The First Affiliated Hospital of Soochow University, Suzhou 215031, China
| | - Qi Fang
- Department of Neurology, The First Affiliated Hospital of Soochow University, Suzhou 215006, China; (Y.C.); (L.Y.)
- Department of Clinical Nutrition, Dushu Lake Hospital Affiliated to Soochow University, Suzhou 215124, China;
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3
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You JS, Kim Y, Lee S, Bashir R, Chen J. RhoA/ROCK signalling activated by ARHGEF3 promotes muscle weakness via autophagy in dystrophic mdx mice. J Cachexia Sarcopenia Muscle 2023. [PMID: 37311604 PMCID: PMC10401546 DOI: 10.1002/jcsm.13278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 03/16/2023] [Accepted: 05/01/2023] [Indexed: 06/15/2023] Open
Abstract
BACKGROUND Duchenne muscular dystrophy (DMD), caused by dystrophin deficiency, leads to progressive and fatal muscle weakness through yet-to-be-fully deciphered molecular perturbations. Emerging evidence implicates RhoA/Rho-associated protein kinase (ROCK) signalling in DMD pathology, yet its direct role in DMD muscle function, and related mechanisms, are unknown. METHODS Three-dimensionally engineered dystrophin-deficient mdx skeletal muscles and mdx mice were used to test the role of ROCK in DMD muscle function in vitro and in situ, respectively. The role of ARHGEF3, one of the RhoA guanine nucleotide exchange factors (GEFs), in RhoA/ROCK signalling and DMD pathology was examined by generating Arhgef3 knockout mdx mice. The role of RhoA/ROCK signalling in mediating the function of ARHGEF3 was determined by evaluating the effects of wild-type or GEF-inactive ARHGEF3 overexpression with ROCK inhibitor treatment. To gain more mechanistic insights, autophagy flux and the role of autophagy were assessed in various conditions with chloroquine. RESULTS Inhibition of ROCK with Y-27632 improved muscle force production in 3D-engineered mdx muscles (+25% from three independent experiments, P < 0.05) and in mice (+25%, P < 0.001). Unlike suggested by previous studies, this improvement was independent of muscle differentiation or quantity and instead related to increased muscle quality. We found that ARHGEF3 was elevated and responsible for RhoA/ROCK activation in mdx muscles, and that depleting ARHGEF3 in mdx mice restored muscle quality (up to +36%, P < 0.01) and morphology without affecting regeneration. Conversely, overexpressing ARHGEF3 further compromised mdx muscle quality (-13% vs. empty vector control, P < 0.01) in GEF activity- and ROCK-dependent manner. Notably, ARHGEF3/ROCK inhibition exerted the effects by rescuing autophagy which is commonly impaired in dystrophic muscles. CONCLUSIONS Our findings uncover a new pathological mechanism of muscle weakness in DMD involving the ARHGEF3-ROCK-autophagy pathway and the therapeutic potential of targeting ARHGEF3 in DMD.
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Affiliation(s)
- Jae-Sung You
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Nick J. Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Yongdeok Kim
- Nick J. Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Soohyun Lee
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Rashid Bashir
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Nick J. Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
- Department of Biomedical and Translational Sciences, Carle Illinois College of Medicine, Urbana, Illinois, USA
| | - Jie Chen
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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Bellissimo CA, Garibotti MC, Perry CGR. Mitochondrial Stress Responses in Duchenne muscular dystrophy: Metabolic Dysfunction or Adaptive Reprogramming? Am J Physiol Cell Physiol 2022; 323:C718-C730. [PMID: 35816642 DOI: 10.1152/ajpcell.00249.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondrial stress may be a secondary contributor to muscle weakness in inherited muscular dystrophies. Duchenne muscular dystrophy has received the majority of attention whereby most discoveries suggest mitochondrial ATP synthesis may be reduced. However, not all studies support this finding. Furthermore, some studies have reported increased mitochondrial reactive oxygen species and propensity for permeability transition pore formation as an inducer of apoptosis, although divergent findings have also been described. A closer examination of the literature suggests the degree and direction of mitochondrial stress responses may depend on the progression of the disease, the muscle type examined, the mouse model employed with regards to pre-clinical research, the precise metabolic pathways in consideration, and in some cases the in vitro technique used to assess a given mitochondrial bioenergetic function. One intent of this review is to provide careful considerations for future experimental designs to resolve the heterogeneous nature of mitochondrial stress during the progression of Duchenne muscular dystrophy. Such considerations have implications for other muscular dystrophies as well which are addressed briefly herein. A renewed perspective of the term 'mitochondrial dysfunction' is presented whereby stress responses might be re-explored in future investigations as direct contributors to myopathy vs an adaptive 'reprogramming' intended to maintain homeostasis in the face of disease stressors themselves. In so doing, the prospective development of mitochondrial enhancement therapies can be driven by advances in perspectives as much as experimental approaches when resolving the precise relationships between mitochondrial remodelling and muscle weakness in Duchenne and, indeed, other muscular dystrophies.
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Affiliation(s)
- Catherine A Bellissimo
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON, Canada
| | - Madison C Garibotti
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON, Canada
| | - Christopher G R Perry
- School of Kinesiology and Health Science, Muscle Health Research Centre, York University, Toronto, ON, Canada
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5
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Nwadozi E, Rudnicki M, De Ciantis M, Milkovich S, Pulbere A, Roudier E, Birot O, Gustafsson T, Ellis CG, Haas TL. High-fat diet pre-conditioning improves microvascular remodelling during regeneration of ischaemic mouse skeletal muscle. Acta Physiol (Oxf) 2020; 229:e13449. [PMID: 32012450 DOI: 10.1111/apha.13449] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/26/2020] [Accepted: 01/28/2020] [Indexed: 12/25/2022]
Abstract
AIM Critical limb ischaemia (CLI) is characterized by inadequate angiogenesis, arteriolar remodelling and chronic myopathy, which are most severe in type 2 diabetic patients. Hypertriglyceridaemia, commonly observed in these patients, compromises macrovascular function. However, the effects of high-fat diet-induced increases in circulating lipids on microvascular remodelling are not established. Here, we investigated if high-fat diet would mimic the detrimental effect of type 2 diabetes on post-ischaemia vascular remodelling and muscle regeneration, using a mouse model of hindlimb ischaemia. METHODS Male C57Bl6/J mice were fed with normal or high-fat diets for 8 weeks prior to unilateral femoral artery ligation. Laser doppler imaging was used to assess limb perfusion recovery. Vascular recovery, inflammation, myofibre regeneration and fibrosis were assessed at 4 or 14 days post-ligation by histology and RNA analyses. Capillary-level haemodynamics were assessed by intravital microscopy of control and regenerating muscles 14 days post-ligation. RESULTS High-fat diet increased muscle succinate dehydrogenase activity and capillary-level oxygen supply. At 4 days post-ligation, no diet differences were detected in muscle damage, inflammatory infiltration or capillary activation. At 14 days post-ligation, high fat-fed mice displayed accelerated limb blood flow recovery, elevated capillary and arteriole densities as well as greater red blood cell supply rates and capillary-level oxygen supply. Regenerating muscles from high fat-fed mice displayed lower interstitial fat and collagen deposition. CONCLUSION The muscle-level adaptations to high-fat diet improved multiple aspects of muscle recovery in response to ischaemia and did not recapitulate the worse outcomes seen in diabetic CLI patients.
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Affiliation(s)
- Emmanuel Nwadozi
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
| | - Martina Rudnicki
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
| | - Matthew De Ciantis
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
| | - Stephanie Milkovich
- Department of Medical Biophysics University of Western Ontario London ON Canada
| | - Alexandru Pulbere
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
| | - Emilie Roudier
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
| | - Olivier Birot
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
| | - Thomas Gustafsson
- Division of Clinical Physiology Department of Laboratory Medicine Karolinska Institutet Stockholm Sweden
- Unit of Clinical Physiology Karolinska University Hospital Stockholm Sweden
| | | | - Tara L. Haas
- School of Kinesiology and Health Science Muscle Health Research Centre Angiogenesis Research Group York University Toronto ON Canada
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6
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Grounds MD, Terrill JR, Al-Mshhdani BA, Duong MN, Radley-Crabb HG, Arthur PG. Biomarkers for Duchenne muscular dystrophy: myonecrosis, inflammation and oxidative stress. Dis Model Mech 2020; 13:13/2/dmm043638. [PMID: 32224496 PMCID: PMC7063669 DOI: 10.1242/dmm.043638] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a lethal, X-linked disease that causes severe loss of muscle mass and function in young children. Promising therapies for DMD are being developed, but the long lead times required when using clinical outcome measures are hindering progress. This progress would be facilitated by robust molecular biomarkers in biofluids, such as blood and urine, which could be used to monitor disease progression and severity, as well as to determine optimal drug dosing before a full clinical trial. Many candidate DMD biomarkers have been identified, but there have been few follow-up studies to validate them. This Review describes the promising biomarkers for dystrophic muscle that have been identified in muscle, mainly using animal models. We strongly focus on myonecrosis and the associated inflammation and oxidative stress in DMD muscle, as the lack of dystrophin causes repeated bouts of myonecrosis, which are the key events that initiate the resultant severe dystropathology. We discuss the early events of intrinsic myonecrosis, along with early regeneration in the context of histological and other measures that are used to quantify its incidence. Molecular biomarkers linked to the closely associated events of inflammation and oxidative damage are discussed, with a focus on research related to protein thiol oxidation and to neutrophils. We summarise data linked to myonecrosis in muscle, blood and urine of dystrophic animal species, and discuss the challenge of translating such biomarkers to the clinic for DMD patients, especially to enhance the success of clinical trials. Summary: This Review discusses biomarkers in blood and urine linked to myonecrosis, inflammation and oxidative stress, to enhance development of therapies for DMD, and the challenges to be overcome for clinical translation.
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Affiliation(s)
- Miranda D Grounds
- School of Human Sciences, the University of Western Australia, Perth, WA 6009, Australia
| | - Jessica R Terrill
- School of Molecular Sciences, the University of Western Australia, Perth, WA 6009, Australia
| | - Basma A Al-Mshhdani
- School of Molecular Sciences, the University of Western Australia, Perth, WA 6009, Australia
| | - Marisa N Duong
- School of Molecular Sciences, the University of Western Australia, Perth, WA 6009, Australia
| | - Hannah G Radley-Crabb
- School of Pharmacy and Biomedical Sciences, Curtin Health and Innovation Research Institute, Faculty of Health Sciences, Curtin University, Perth, WA 6102, Australia
| | - Peter G Arthur
- School of Molecular Sciences, the University of Western Australia, Perth, WA 6009, Australia
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7
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Reggio A, Rosina M, Krahmer N, Palma A, Petrilli LL, Maiolatesi G, Massacci G, Salvatori I, Valle C, Testa S, Gargioli C, Fuoco C, Castagnoli L, Cesareni G, Sacco F. Metabolic reprogramming of fibro/adipogenic progenitors facilitates muscle regeneration. Life Sci Alliance 2020; 3:3/3/e202000646. [PMID: 32019766 PMCID: PMC7003708 DOI: 10.26508/lsa.202000660] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 01/28/2020] [Indexed: 12/25/2022] Open
Abstract
High-fat diet ameliorates muscle dystrophic phenotype by promoting the FAP-dependent myogenesis of satellite cells. In Duchenne muscular dystrophy (DMD), the absence of the dystrophin protein causes a variety of poorly understood secondary effects. Notably, muscle fibers of dystrophic individuals are characterized by mitochondrial dysfunctions, as revealed by a reduced ATP production rate and by defective oxidative phosphorylation. Here, we show that in a mouse model of DMD (mdx), fibro/adipogenic progenitors (FAPs) are characterized by a dysfunctional mitochondrial metabolism which correlates with increased adipogenic potential. Using high-sensitivity mass spectrometry–based proteomics, we report that a short-term high-fat diet (HFD) reprograms dystrophic FAP metabolism in vivo. By combining our proteomic dataset with a literature-derived signaling network, we revealed that HFD modulates the β-catenin–follistatin axis. These changes are accompanied by significant amelioration of the histological phenotype in dystrophic mice. Transplantation of purified FAPs from HFD-fed mice into the muscles of dystrophic recipients demonstrates that modulation of FAP metabolism can be functional to ameliorate the dystrophic phenotype. Our study supports metabolic reprogramming of muscle interstitial progenitor cells as a novel approach to alleviate some of the adverse outcomes of DMD.
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Affiliation(s)
- Alessio Reggio
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Marco Rosina
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Natalie Krahmer
- Department Proteomics and Signal Transduction, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Alessandro Palma
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | | | | | - Giorgia Massacci
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Illari Salvatori
- Fondazione Santa Lucia Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Cristiana Valle
- Fondazione Santa Lucia Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy.,Institute of Translational Pharmacology, Consiglio Nazionale delle Ricerche (CNR), Rome, Italy
| | - Stefano Testa
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Cesare Gargioli
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Claudia Fuoco
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Luisa Castagnoli
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
| | - Gianni Cesareni
- Department of Biology, University of Rome Tor Vergata, Rome, Italy .,Fondazione Santa Lucia Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Rome, Italy
| | - Francesca Sacco
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
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Wood CL, Suchacki KJ, van 't Hof R, Cawthorn WP, Dillon S, Straub V, Wong SC, Ahmed SF, Farquharson C. A comparison of the bone and growth phenotype of mdx, mdx:Cmah-/- and mdx:Utrn +/- murine models with the C57BL/10 wild-type mouse. Dis Model Mech 2020; 13:dmm.040659. [PMID: 31754018 PMCID: PMC6994935 DOI: 10.1242/dmm.040659] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 11/12/2020] [Indexed: 12/20/2022] Open
Abstract
The muscular dystrophy X-linked (mdx) mouse is commonly used as a mouse model of Duchenne muscular dystrophy (DMD). Its phenotype is, however, mild, and other mouse models have been explored. The mdx:Cmah−/− mouse carries a human-like mutation in the Cmah gene and has a severe muscle phenotype, but its growth and bone development are unknown. In this study, we compared male mdx, mdx:Utrn+/−, mdx:Cmah−/− and wild-type (WT) mice at 3, 5 and 7 weeks of age to determine the suitability of the mdx:Cmah−/− mouse as a model for assessing growth and skeletal development in DMD. The mdx:Cmah−/− mice were lighter than WT mice at 3 weeks, but heavier at 7 weeks, and showed an increased growth rate at 5 weeks. Cortical bone fraction as assessed by micro-computed tomography was greater in both mdx and mdx:Cmah−/− mice versus WT mice at 7 weeks. Tissue mineral density was also higher in mdx:Cmah−/− mice at 3 and 7 weeks. Gene profiling of mdx:Cmah−/− bone identified increased expression of Igf1, Igf1r and Vegfa. Both the mdx and mdx:Cmah−/− mice showed an increased proportion of regulated bone marrow adipose tissue (BMAT) but a reduction in constitutive BMAT. The mdx:Cmah−/− mice show evidence of catch-up growth and more rapid bone development. This pattern does not mimic the typical DMD growth trajectory and therefore the utility of the mdx:Cmah−/− mouse for studying growth and skeletal development in DMD is limited. Further studies of this model may, however, shed light on the phenomenon of catch-up growth. This article has an associated First Person interview with the first author of the paper. Summary: Unlike boys with DMD, the mdx:Cmah−/− mouse shows increased weight gain and more rapid bone development; therefore, its utility for studying growth and skeletal development in DMD is limited.
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Affiliation(s)
- Claire L Wood
- Division of Developmental Biology, Roslin Institute, University of Edinburgh, Midlothian, EH25 9RG, UK .,John Walton Muscular Dystrophy Research Centre, Newcastle University and Newcastle Hospitals NHS Foundation Trust, Newcastle, NE1 3BZ, UK
| | - Karla J Suchacki
- BHF Centre for Cardiovascular Science, University of Edinburgh, Midlothian, EH25 9RG, UK
| | - Rob van 't Hof
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, L7 8TX, UK
| | - Will P Cawthorn
- BHF Centre for Cardiovascular Science, University of Edinburgh, Midlothian, EH25 9RG, UK
| | - Scott Dillon
- Division of Developmental Biology, Roslin Institute, University of Edinburgh, Midlothian, EH25 9RG, UK
| | - Volker Straub
- John Walton Muscular Dystrophy Research Centre, Newcastle University and Newcastle Hospitals NHS Foundation Trust, Newcastle, NE1 3BZ, UK
| | - Sze Choong Wong
- Developmental Endocrinology Research Group, School of Medicine, University of Glasgow, Glasgow, G51 4TF, UK
| | - Syed F Ahmed
- Developmental Endocrinology Research Group, School of Medicine, University of Glasgow, Glasgow, G51 4TF, UK
| | - Colin Farquharson
- Division of Developmental Biology, Roslin Institute, University of Edinburgh, Midlothian, EH25 9RG, UK
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Fajardo VA, Chambers PJ, Juracic ES, Rietze BA, Gamu D, Bellissimo C, Kwon F, Quadrilatero J, Russell Tupling A. Sarcolipin deletion in mdx mice impairs calcineurin signalling and worsens dystrophic pathology. Hum Mol Genet 2019; 27:4094-4102. [PMID: 30137316 DOI: 10.1093/hmg/ddy302] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 08/15/2018] [Indexed: 12/11/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is the most severe form of muscular dystrophy affecting 1 in 3500 live male births. Although there is no cure for DMD, therapeutic strategies aimed at enhancing calcineurin signalling and promoting the slow fibre phenotype have shown promise in mdx mice, which is the classical mouse model for DMD. Sarcolipin (SLN) is a small protein that regulates the sarco(endo)plasmic reticulum Ca2+-ATPase pump and its expression is highly upregulated in dystrophic skeletal muscle. We have recently shown that SLN in skeletal muscle amplifies calcineurin signalling thereby increasing myofibre size and the slow fibre phenotype. Therefore, in the present study we sought to determine the physiological impact of genetic Sln deletion in mdx mice, particularly on calcineurin signalling, fibre-type distribution and size and dystrophic pathology. We generated an mdx/Sln-null (mdx/SlnKO) mouse colony and hypothesized that the soleus and diaphragm muscles from these mice would display blunted calcineurin signalling, smaller myofibre sizes, an increased proportion of fast fibres and worsened dystrophic pathology compared with mdx mice. Our results show that calcineurin signalling was impaired in mdx/SlnKO mice as indicated by reductions in utrophin, stabilin-2 and calcineurin expression. In addition, mdx/SlnKO muscles contained smaller myofibres, exhibited a slow-to-fast fibre-type switch that corresponded with reduced expression of mitochondrial proteins and displayed a worsened dystrophic pathology compared with mdx muscles. Altogether, our findings demonstrate a critical role for SLN upregulation in dystrophic muscles and suggest that SLN can be viewed as a potential therapeutic target.
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Affiliation(s)
- Val A Fajardo
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | - Paige J Chambers
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | - Emma S Juracic
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | - Bradley A Rietze
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | - Daniel Gamu
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | | | - Frenk Kwon
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | - Joe Quadrilatero
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
| | - A Russell Tupling
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada
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10
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Verhaart IEC, van de Vijver D, Boertje-van der Meulen JW, Putker K, Adamzek K, Aartsma-Rus A, van Putten M. A modified diet does not ameliorate muscle pathology in a mouse model for Duchenne muscular dystrophy. PLoS One 2019; 14:e0215335. [PMID: 31017936 PMCID: PMC6481797 DOI: 10.1371/journal.pone.0215335] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 03/29/2019] [Indexed: 12/19/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is caused by a lack of dystrophin protein. Next to direct effects on the muscles, this has also metabolic consequences. The influence of nutrition on disease progression becomes more and more recognized. Protein intake by DMD patients may be insufficient to meet the increased demand of the constantly regenerating muscle fibers. This led to the hypothesis that improving protein uptake by the muscles could have therapeutic effects. The present study examined the effects of a modified diet, which composition might stimulate muscle growth, on disease pathology in the D2-mdx mouse model. D2-mdx males were fed with either a control diet or modified diet, containing high amounts of branched-chain amino acids, vitamin D3 and ursolic acid, for six weeks. Our study indicates that the modified diet could not ameliorate the muscle pathology. No effects on bodyweight or weight of individual muscles were observed. Neither did the diet affect severity of fibrosis or calcification of the muscles.
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Affiliation(s)
- Ingrid E. C. Verhaart
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Davy van de Vijver
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Kayleigh Putker
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Kevin Adamzek
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Annemieke Aartsma-Rus
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
| | - Maaike van Putten
- Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
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11
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Integrative effects of dystrophin loss on metabolic function of the mdx mouse. Sci Rep 2018; 8:13624. [PMID: 30206270 PMCID: PMC6134145 DOI: 10.1038/s41598-018-31753-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 08/13/2018] [Indexed: 11/23/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a disease marked by the development of skeletal muscle weakness and wasting. DMD results from mutations in the gene for the cytoskeletal protein dystrophin. The loss of dystrophin expression is not limited to muscle weakness but has multiple systemic consequences. Managing the nutritional requirements is an important aspect of the clinical care of DMD patients and is complicated by the poor understanding of the role of dystrophin, and dystrophic processes, in regulating metabolism. Here, we show that mdx mice, a genetic model of DMD, have significantly reduced fat mass relative to wild type C57BL/10. The alteration in body composition is independent of the presence of skeletal muscle disease, as it is still present in mice with transgenic expression of a fully-functional dystrophin in skeletal muscle. Furthermore, mdx mice do not increase their fat mass or body weight when housed under thermoneutral conditions, in marked contrast to C57BL/10 mice. We also demonstrated that mdx mice have significantly reduced fat metabolism and altered glucose uptake. These significant metabolic changes in dystrophic mice implicate dystrophin as an important regulator of metabolism. Understanding the metabolic functions of dystrophin is important for managing the nutritional needs of DMD patients.
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12
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Nutrition in Duchenne muscular dystrophy 16–18 March 2018, Zaandam, the Netherlands. Neuromuscul Disord 2018; 28:680-689. [DOI: 10.1016/j.nmd.2018.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 05/09/2018] [Indexed: 11/17/2022]
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13
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Utrophin up-regulation by artificial transcription factors induces muscle rescue and impacts the neuromuscular junction in mdx mice. Biochim Biophys Acta Mol Basis Dis 2018; 1864:1172-1182. [PMID: 29408646 PMCID: PMC5851675 DOI: 10.1016/j.bbadis.2018.01.030] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 01/16/2018] [Accepted: 01/25/2018] [Indexed: 01/31/2023]
Abstract
Up-regulation of the dystrophin-related gene utrophin represents a promising therapeutic strategy for the treatment of Duchenne Muscular Dystrophy (DMD). In order to re-program the utrophin expression level in muscle, we engineered artificial zinc finger transcription factors (ZF-ATFs) that target the utrophin 'A' promoter. We have previously shown that the ZF-ATF "Jazz", either by transgenic manipulation or by systemic adeno-associated viral delivery, induces significant rescue of muscle function in dystrophic "mdx" mice. We present the full characterization of an upgraded version of Jazz gene named "JZif1" designed to minimize any possible host immune response. JZif1 was engineered on the Zif268 gene-backbone using selective amino acid substitutions to address JZif1 to the utrophin 'A' promoter. Here, we show that JZif1 induces remarkable amelioration of the pathological phenotype in mdx mice. To investigate the molecular mechanisms underlying Jazz and JZif1 induced muscle functional rescue, we focused on utrophin related pathways. Coherently with utrophin subcellular localization and role in neuromuscular junction (NMJ) plasticity, we found that our ZF-ATFs positively impact the NMJ. We report on ZF-ATF effects on post-synaptic membranes in myogenic cell line, as well as in wild type and mdx mice. These results candidate our ZF-ATFs as novel therapeutic molecules for DMD treatment.
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14
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Evaluation of the behavioral characteristics of the mdx mouse model of duchenne muscular dystrophy through operant conditioning procedures. Behav Processes 2017; 142:8-20. [PMID: 28532665 DOI: 10.1016/j.beproc.2017.05.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 05/15/2017] [Accepted: 05/16/2017] [Indexed: 11/20/2022]
Abstract
The mdx mouse is an important nonhuman model for Duchenne muscular dystrophy (DMD) research. Characterizing the behavioral traits of the strain relative to congenic wild-type (WT) mice may enhance our understanding of the cognitive deficits observed in some humans with DMD and contribute to treatment development and evaluation. In this paper we report the results of a number of experiments comparing the behavior of mdx to WT mice in operant conditioning procedures designed to assess learning and memory. We found that mdx outperformed WT in all learning and memory tasks involving food reinforcement, and this appeared to be related to the differential effects of the food deprivation motivating operation on mdx mice. Conversely, WT outperformed mdx in an escape/avoidance learning task. These results suggest motivational differences between the strains and demonstrate the potential utility of operant conditioning procedures in the assessment of the behavioral characteristics of the mdx mouse.
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15
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Fajardo VA, Gamu D, Mitchell A, Bloemberg D, Bombardier E, Chambers PJ, Bellissimo C, Quadrilatero J, Tupling AR. Sarcolipin deletion exacerbates soleus muscle atrophy and weakness in phospholamban overexpressing mice. PLoS One 2017; 12:e0173708. [PMID: 28278204 PMCID: PMC5344511 DOI: 10.1371/journal.pone.0173708] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 02/24/2017] [Indexed: 11/18/2022] Open
Abstract
Sarcolipin (SLN) and phospholamban (PLN) are two small proteins that regulate the sarco(endo)plasmic reticulum Ca2+-ATPase pumps. In a recent study, we discovered that Pln overexpression (PlnOE) in slow-twitch type I skeletal muscle fibers drastically impaired SERCA function and caused a centronuclear myopathy-like phenotype, severe muscle atrophy and weakness, and an 8 to 9-fold upregulation of SLN protein in the soleus muscles. Here, we sought to determine the physiological role of SLN upregulation, and based on its role as a SERCA inhibitor, we hypothesized that it would represent a maladaptive response that contributes to the SERCA dysfunction and the overall myopathy observed in the PlnOE mice. To this end, we crossed Sln-null (SlnKO) mice with PlnOE mice to generate a PlnOE/SlnKO mouse colony and assessed SERCA function, CNM pathology, in vitro contractility, muscle mass, calcineurin signaling, daily activity and food intake, and proteolytic enzyme activity. Our results indicate that genetic deletion of Sln did not improve SERCA function nor rescue the CNM phenotype, but did result in exacerbated muscle atrophy and weakness, due to a failure to induce type II fiber compensatory hypertrophy and a reduction in total myofiber count. Mechanistically, our findings suggest that impaired calcineurin activation and resultant decreased expression of stabilin-2, and/or impaired autophagic signaling could be involved. Future studies should examine these possibilities. In conclusion, our study demonstrates the importance of SLN upregulation in combating muscle myopathy in the PlnOE mice, and since SLN is upregulated across several myopathies, our findings may reveal SLN as a novel and universal therapeutic target.
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Affiliation(s)
- Val A. Fajardo
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Daniel Gamu
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Andrew Mitchell
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Darin Bloemberg
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Eric Bombardier
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Paige J. Chambers
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Catherine Bellissimo
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - Joe Quadrilatero
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
| | - A. Russell Tupling
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1
- * E-mail:
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16
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Vulin A, Wein N, Simmons TR, Rutherford AM, Findlay AR, Yurkoski JA, Kaminoh Y, Flanigan KM. The first exon duplication mouse model of Duchenne muscular dystrophy: A tool for therapeutic development. Neuromuscul Disord 2015; 25:827-34. [PMID: 26365037 DOI: 10.1016/j.nmd.2015.08.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 12/27/2022]
Abstract
Exon duplication mutations account for up to 11% of all cases of Duchenne muscular dystrophy (DMD), and a duplication of exon 2 is the most common duplication in patients. For use as a platform for testing of duplication-specific therapies, we developed a mouse model that carries a Dmd exon 2 duplication. By using homologous recombination we duplicated exon 2 within intron 2 at a location consistent with a human duplication hotspot. mRNA analysis confirms the inclusion of a duplicated exon 2 in mouse muscle. Dystrophin expression is essentially absent by immunofluorescent and immunoblot analysis, although some muscle specimens show very low-level trace dystrophin expression. Phenotypically, the mouse shows similarities to mdx, the standard laboratory model of DMD. In skeletal muscle, areas of necrosis and phagocytosis are seen at 3 weeks, with central nucleation prominent by four weeks, recapitulating the "crisis" period in mdx. Marked diaphragm fibrosis is noted by 6 months, and remains unchanged at 12 months. Our results show that the Dup2 mouse is both pathologically (in degree and distribution) and physiologically similar to mdx. As it recapitulates the most common single exon duplication found in DMD patients, this new model will be a useful tool to assess the potential of duplicated exon skipping.
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Affiliation(s)
- Adeline Vulin
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Nicolas Wein
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Tabatha R Simmons
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Andrea M Rutherford
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Andrew R Findlay
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Jacqueline A Yurkoski
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Yuuki Kaminoh
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Kevin M Flanigan
- The Center for Gene Therapy, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA; Department of Pediatrics, The Ohio State University, Columbus, OH, USA; Department of Neurology, The Ohio State University, Columbus, OH, USA.
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17
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Oron A, Oron U, Sadeh M. Low-Level Laser Therapy During Postnatal Development Modulates Degeneration and Enhances Regeneration Processes in the Hindlimb Muscles of Dystrophic Mice. Photomed Laser Surg 2014; 32:606-11. [DOI: 10.1089/pho.2014.3757] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Amir Oron
- Department of Hand Surgery, Kaplan Medical Center, Rehovot, Israel
| | - Uri Oron
- Department of Zoology, The George S. Wise Faculty of Life Sciences, Tel-Aviv, University, Tel-Aviv, Israel
| | - Menahem Sadeh
- Department of Neurology, Wolfson Medical Center, Holon, Israel
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18
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Dystropathology increases energy expenditure and protein turnover in the mdx mouse model of duchenne muscular dystrophy. PLoS One 2014; 9:e89277. [PMID: 24586653 PMCID: PMC3929705 DOI: 10.1371/journal.pone.0089277] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 01/17/2014] [Indexed: 11/19/2022] Open
Abstract
The skeletal muscles in Duchenne muscular dystrophy and the mdx mouse model lack functional dystrophin and undergo repeated bouts of necrosis, regeneration, and growth. These processes have a high metabolic cost. However, the consequences for whole body energy and protein metabolism, and on the dietary requirements for these macronutrients at different stages of the disease, are not well-understood. This study used juvenile (4- to 5- wk-old) and adult (12- to 14-wk-old) male dystrophic C57BL/10ScSn-mdx/J and age-matched C57BL/10ScSn/J control male mice to measure total and resting energy expenditure, food intake, spontaneous activity, body composition, whole body protein turnover, and muscle protein synthesis rates. In juvenile mdx mice that have extensive muscle damage, energy expenditure, muscle protein synthesis, and whole body protein turnover rates were higher than in age-matched controls. Adaptations in food intake and decreased activity were insufficient to meet the increased energy and protein needs of juvenile mdx mice and resulted in stunted growth. In (non-growing) adult mdx mice with less severe dystropathology, energy expenditure, muscle protein synthesis, and whole body protein turnover rates were also higher than in age-matched controls. Food intake was sufficient to meet their protein and energy needs, but insufficient to result in fat deposition. These data show that dystropathology impacts the protein and energy needs of mdx mice and that tailored dietary interventions are necessary to redress this imbalance. If not met, the resultant imbalance blunts growth, and may limit the benefits of therapies designed to protect and repair dystrophic muscles.
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19
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Percival JM, Siegel MP, Knowels G, Marcinek DJ. Defects in mitochondrial localization and ATP synthesis in the mdx mouse model of Duchenne muscular dystrophy are not alleviated by PDE5 inhibition. Hum Mol Genet 2012; 22:153-67. [PMID: 23049075 DOI: 10.1093/hmg/dds415] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Given the crucial roles for mitochondria in ATP energy supply, Ca(2+) handling and cell death, mitochondrial dysfunction has long been suspected to be an important pathogenic feature in Duchenne muscular dystrophy (DMD). Despite this foresight, mitochondrial function in dystrophin-deficient muscles has remained poorly defined and unknown in vivo. Here, we used the mdx mouse model of DMD and non-invasive spectroscopy to determine the impact of dystrophin-deficiency on skeletal muscle mitochondrial localization and oxidative phosphorylation function in vivo. Mdx mitochondria exhibited significant uncoupling of oxidative phosphorylation (reduced P/O) and a reduction in maximal ATP synthesis capacity that together decreased intramuscular ATP levels. Uncoupling was not driven by increased UCP3 or ANT1 expression. Dystrophin was required to maintain subsarcolemmal mitochondria (SSM) pool density, implicating it in the spatial control of mitochondrial localization. Given that nitric oxide-cGMP pathways regulate mitochondria and that sildenafil-mediated phosphodiesterase 5 inhibition ameliorates dystrophic pathology, we tested whether sildenafil's benefits result from decreased mitochondrial dysfunction in mdx mice. Unexpectedly, sildenafil treatment did not affect mitochondrial content or oxidative phosphorylation defects in mdx mice. Rather, PDE5 inhibition decreased resting levels of ATP, phosphocreatine and myoglobin, suggesting that sildenafil improves dystrophic pathology through other mechanisms. Overall, these data indicate that dystrophin-deficiency disrupts SSM localization, promotes mitochondrial inefficiency and restricts maximal mitochondrial ATP-generating capacity. Together these defects decrease intramuscular ATP and the ability of mdx muscle mitochondria to meet ATP demand. These findings further understanding of how mitochondrial bioenergetic dysfunction contributes to disease pathogenesis in dystrophin-deficient skeletal muscle in vivo.
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Affiliation(s)
- Justin M Percival
- Department of Physiology and Biophysics, University of Washington Medical School, Seattle, WA, USA.
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