bims-moremu Biomed News
on Molecular regulators of muscle mass
Issue of 2022‒11‒13
39 papers selected by
Anna Vainshtein
Craft Science Inc.
  1. Denervation induces mitochondrial decline and exacerbates lysosome dysfunction in middle-aged mice.
  2. Muscle weakness precedes atrophy during cancer cachexia and is linked to muscle-specific mitochondrial stress.
  3. Scientific Meeting report: International Biochemistry of Exercise 2022.
  4. Role of lncRNA Has2os in Skeletal Muscle Differentiation and Regeneration.
  5. Adenosine monophosphate activated protein kinase contributes to skeletal muscle health through the control of mitochondrial function.
  6. Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models.
  7. Shared and unique phosphoproteomics responses in skeletal muscle from exercise models and in hyperammonemic myotubes.
  8. Identification of underexplored mesenchymal and vascular-related cell populations in human skeletal muscle.
  9. Genes Whose Gain or Loss of Function Changes Type 1, 2A, 2X, or 2B Muscle Fibre Proportions in Mice-A Systematic Review.
  10. Loss of the Nuclear Envelope Protein LAP1B Disrupts the Myogenic Differentiation of Patient-Derived Fibroblasts.
  11. Tcf12 is required to sustain myogenic genes synergism with MyoD by remodelling the chromatin landscape.
  12. Skeletal muscle as a reservoir for nitrate and nitrite: The role of xanthine oxidase reductase (XOR).
  13. Skeletal Muscle CSE Deficiency Leads to Insulin Resistance in Mice.
  14. Duchenne muscular dystrophy progression induced by downhill running is accompanied by increased endomysial fibrosis and oxidative damage DNA in muscle of mdx mice.
  15. Thick filament activation is different in fast and slow-twitch skeletal muscle.
  16. MyoD-Induced Trans-Differentiation: A Paradigm for Dissecting the Molecular Mechanisms of Cell Commitment, Differentiation and Reprogramming.
  17. Short-time recovery skeletal muscle from dexamethasone-induced atrophy and weakness in old female rats.
  18. Loss of hepatic phosphoenolpyruvate carboxykinase 1 dysregulates metabolic responses to acute exercise but enhances adaptations to exercise training in mice.
  19. Connexin 43 Channels in Osteocytes Are Necessary for Bone Mass and Skeletal Muscle Function in Aged Male Mice.
  20. BKCa Activator NS1619 Improves the Structure and Function of Skeletal Muscle Mitochondria in Duchenne Dystrophy.
  21. Aberrant DNA and RNA Methylation Occur in Spinal Cord and Skeletal Muscle of Human SOD1 Mouse Models of ALS and in Human ALS: Targeting DNA Methylation Is Therapeutic.
  22. A link between agrin signalling and Cav3.2 at the neuromuscular junction in spinal muscular atrophy.
  23. Mitochondrial Dysfunction as an Underlying Cause of Skeletal Muscle Disorders.
  24. Irisin and ALCAT1 mediated aerobic exercise-alleviated oxidative stress and apoptosis in skeletal muscle of mice with myocardial infarction.
  25. Differential impact of ubiquitous and muscle dynamin 2 isoforms in muscle physiology and centronuclear myopathy.
  26. Energy metabolism and frailty: The potential role of exercise-induced myokines - A narrative review.
  27. Proteomic Identification of Markers of Membrane Repair, Regeneration and Fibrosis in the Aged and Dystrophic Diaphragm.
  28. Expression analysis of irisin during different development stages of skeletal muscle in mice.
  29. The impact of senescence on muscle wasting in chronic kidney disease.
  30. Downhill running induced DNA damage enhances mitochondrial membrane permeability by facilitating ER-mitochondria signaling.
  31. Understanding altered contractile properties in advanced age: insights from a systematic muscle modelling approach.
  32. Interleukin-6 initiates muscle- and adipose tissue wasting in a novel C57BL/6 model of cancer-associated cachexia.
  33. Muscle glycogen unavailability and fat oxidation rate during exercise: Insights from McArdle disease.
  34. Development of new 1, 3-dihydroxyacridone derivatives as Akt pathway inhibitors in skeletal muscle cells.
  35. The Cytokine Growth Differentiation Factor-15 and Skeletal Muscle Health: Portrait of an Emerging Widely Applicable Disease Biomarker.
  36. Functional divergence of the sarcomeric myosin, MYH7b, supports species-specific biological roles.
  37. Association of Myostatin Gene Polymorphisms with Strength and Muscle Mass in Athletes: A Systematic Review and Meta-Analysis of the MSTN rs1805086 Mutation.
  38. Molecular identity of proprioceptor subtypes innervating different muscle groups in mice.
  39. Using a multiomics approach to unravel a septic shock specific signature in skeletal muscle.
  1. Aging (Albany NY). 2022 Nov 04. 14
    Denervation induces mitochondrial decline and exacerbates lysosome dysfunction in middle-aged mice.
    Matthew Triolo, Debasmita Bhattacharya, David A Hood.
      With age, skeletal muscle undergoes a progressive decline in size and quality. Imbalanced mitochondrial turnover and the resultant dysfunction contribute to these phenotypic alterations. Motor neuron denervation (Den) is a contributor to the etiology of muscle atrophy associated with age. Further, aged muscle exhibits reduced plasticity to both enhanced and suppressed contractile activity. It remains unclear when the onset of this blunted response occurs, and how middle-aged muscle adapts to denervation. The purpose of this study was to compare mitochondrial turnover pathways in young (Y, ~5months) and middle-aged (MA, ~15months) mice, and determine the influence of Den. Transgenic mt-Keima mice were subjected to 1,3 or 7 days of Den. Muscle mass, mitochondrial content, and PGC-1α protein were not different between Y and MA mice. However, indications of enhanced mitochondrial fission and mitophagy were evident in MA muscle which were supported by a greater abundance of lysosome proteins. Den resulted in muscle atrophy and reductions in mitochondrial protein content by 7-days. These changes occurred concomitant with modest decreases in PGC-1α protein, but without further elevations in mitophagy. Although both autophagosomal and lysosomal proteins were elevated, evidence of lysosome dysfunction was present following Den in MA mice. These data suggest that increases in fission drive an acceleration of mitophagy in muscle of MA mice to preserve mitochondrial quality. Den exacerbates the aging phenotype by reducing biogenesis in the absence of a change in mitophagy, perhaps limited by lysosomal capacity, leading to an accumulation of dysfunctional mitochondria with an age-related loss of neuromuscular innervation.
    Keywords:  autophagy; lysosomes; mitochondrial biogenesis; mitophagy; muscle
    DOI:  https://doi.org/10.18632/aging.204365
  2. JCI Insight. 2022 Nov 08. pii: e155147. [Epub ahead of print]
    Muscle weakness precedes atrophy during cancer cachexia and is linked to muscle-specific mitochondrial stress.
    Luca J Delfinis, Catherine A Bellissimo, Shivam Gandhi, Sara N DiBenedetto, Madison C Garibotti, Arshdeep K Thuhan, Stavroula Tsitkanou, Megan E Rosa-Caldwell, Fasih A Rahman, Arthur J Cheng, Michael P Wiggs, Uwe Schlattner, Joe Quadrilatero, Nicholas P Greene, Christopher Gr Perry.
      Muscle weakness and wasting are defining features of cancer-induced cachexia. Mitochondrial stress occurs before atrophy in certain muscles, but the possibility of heterogeneous responses between muscles and across time remains unclear. Using mice inoculated with Colon-26 (C26) cancer, we demonstrate that specific force production was reduced in quadriceps and diaphragm at 2 weeks in the absence of atrophy. At this time, pyruvate-supported mitochondrial respiration was lower in quadriceps while mitochondrial H2O2 emission was elevated in diaphragm. By 4 weeks, atrophy occurred in both muscles, but specific force production increased to control levels in quadriceps such that reductions in absolute force were due entirely to atrophy. Specific force production remained reduced in diaphragm. Mitochondrial respiration increased and H2O2 emission was unchanged in both muscles vs control while mitochondrial creatine sensitivity was reduced in quadriceps. These findings indicate muscle weakness precedes atrophy and is linked to heterogeneous mitochondrial alterations that could involve adaptive responses to metabolic stress. Eventual muscle-specific restorations in force and bioenergetics highlight how the effects of cancer on one muscle do not predict the response in another muscle. Exploring heterogeneous responses of muscle to cancer may reveal new mechanisms underlying distinct sensitivities, or resistance, to cancer cachexia.
    Keywords:  Colorectal cancer; Metabolism; Mitochondria; Oncology; Skeletal muscle
    DOI:  https://doi.org/10.1172/jci.insight.155147
  3. J Appl Physiol (1985). 2022 Nov 10.
    Scientific Meeting report: International Biochemistry of Exercise 2022.
    Anna Vainshtein, Mikhaela B Slavin, Arthur J Cheng, Jonathan M Memme, Ashley N Oliveira, Christopher G R Perry, Ali A Abdul-Sater, Angelo N Belcastro, Michael C Riddell, Matthew Triolo, Tara L Haas, Emilie Roudier, David A Hood.
      Exercise is one of the only non-pharmacologic remedies known to counteract genetic and chronic diseases by enhancing health and improving life span. Although the many benefits of regular physical activity have been recognized for some time, the intricate and complex signalling system triggered at the onset of exercise have only recently begun to be uncovered. Exercising muscles initiate a coordinated, multisystemic, metabolic rewiring which is communicated to distant organs by various molecular mediators, including extracellular vesicles such as exosomes. The field of exercise research has been expanding beyond the musculoskeletal system, with interest from industry to provide realistic models and exercise mimetics that evoke a whole-body rejuvenation response. This year's 18th International Biochemistry of Exercise conference took place in Toronto, Canada, from May 25th to May 28th, 2022, with more than 400 attendees. Here we provide an overview of the most cutting-edge exercise-related research presented by 66 speakers, focusing on new developments in topics ranging from molecular and cellular mechanisms of exercise adaptations, diabetes, and aging. We also provide descriptions on how manipulation of these signaling pathways provide therapeutic avenues for improving human health and quality of life.
    Keywords:  adaptation; biochemistry; exercise; muscle; training
    DOI:  https://doi.org/10.1152/japplphysiol.00475.2022
  4. Cells. 2022 Nov 04. pii: 3497. [Epub ahead of print]11(21):
    Role of lncRNA Has2os in Skeletal Muscle Differentiation and Regeneration.
    Wanxin Chen, Weicai Chen, Peng Liu, Shiyu Qian, Shuang Tao, Mengchun Huang, Wanyi Xu, Cuiping Li, Xiaoyan Chen, Huizhu Lin, Zhenshu Qin, Jianxi Lu, Shujuan Xie.
      Long non-coding RNAs (lncRNAs) regulate a series of physiological processes and play an important role in development, metabolism and disease. Our previous studies showed that lncRNAs involved in skeletal muscle differentiation. Here, we demonstrated that lncRNA Has2os is highly expressed in skeletal muscle and significantly elevated during skeletal cell differentiation. The knockdown of Has2os inhibited myocyte fusion and impeded the expression of the myogenic factors MyHC and Mef2C. Mechanically, Has2os regulates skeletal muscle differentiation by inhibiting the JNK/MAPK signaling pathway. Furthermore, we also revealed that Has2os is involved in the early stage of regeneration after muscle injury, and the JNK/MAPK signaling pathway is activated at both protein and mRNA levels during early repair. Our results demonstrate the new function of lncRNA Has2os, which plays crucial roles during skeletal muscle differentiation and muscle regeneration, providing a basis for the therapy of lncRNA-related muscle diseases.
    Keywords:  Has2os; JNK/MAPK; lncRNA; regeneration; skeletal muscle differentiation
    DOI:  https://doi.org/10.3390/cells11213497
  5. Front Pharmacol. 2022 ;13 947387
    Adenosine monophosphate activated protein kinase contributes to skeletal muscle health through the control of mitochondrial function.
    Yan Yan, Ming Li, Jie Lin, Yanan Ji, Kexin Wang, Dajun Yan, Yuntian Shen, Wei Wang, Zhongwei Huang, Haiyan Jiang, Hualin Sun, Lei Qi.
      Skeletal muscle is one of the largest organs in the body and the largest protein repository. Mitochondria are the main energy-producing organelles in cells and play an important role in skeletal muscle health and function. They participate in several biological processes related to skeletal muscle metabolism, growth, and regeneration. Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor and regulator of systemic energy balance. AMPK is involved in the control of energy metabolism by regulating many downstream targets. In this review, we propose that AMPK directly controls several facets of mitochondrial function, which in turn controls skeletal muscle metabolism and health. This review is divided into four parts. First, we summarize the properties of AMPK signal transduction and its upstream activators. Second, we discuss the role of mitochondria in myogenesis, muscle atrophy, regeneration post-injury of skeletal muscle cells. Third, we elaborate the effects of AMPK on mitochondrial biogenesis, fusion, fission and mitochondrial autophagy, and discuss how AMPK regulates the metabolism of skeletal muscle by regulating mitochondrial function. Finally, we discuss the effects of AMPK activators on muscle disease status. This review thus represents a foundation for understanding this biological process of mitochondrial dynamics regulated by AMPK in the metabolism of skeletal muscle. A better understanding of the role of AMPK on mitochondrial dynamic is essential to improve mitochondrial function, and hence promote skeletal muscle health and function.
    Keywords:  AMPK; mitochondria; muscle atrophy; muscle regeneration; skeletal muscle
    DOI:  https://doi.org/10.3389/fphar.2022.947387
  6. Int J Mol Sci. 2022 Nov 02. pii: 13380. [Epub ahead of print]23(21):
    Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models.
    Yanjie Wang, Jianqiang Lu, Yujian Liu.
      Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.
    Keywords:  cardiotoxin injury; mechanism; mice; regeneration; skeletal muscle
    DOI:  https://doi.org/10.3390/ijms232113380
  7. iScience. 2022 Nov 18. 25(11): 105325
    Shared and unique phosphoproteomics responses in skeletal muscle from exercise models and in hyperammonemic myotubes.
    Nicole Welch, Shashi Shekhar Singh, Ryan Musich, M Shahid Mansuri, Annette Bellar, Saurabh Mishra, Aruna K Chelluboyina, Jinendiran Sekar, Amy H Attaway, Ling Li, Belinda Willard, Troy A Hornberger, Srinivasan Dasarathy.
      Skeletal muscle generation of ammonia, an endogenous cytotoxin, is increased during exercise. Perturbations in ammonia metabolism consistently occur in chronic diseases, and may blunt beneficial skeletal muscle molecular responses and protein homeostasis with exercise. Phosphorylation of skeletal muscle proteins mediates cellular signaling responses to hyperammonemia and exercise. Comparative bioinformatics and machine learning-based analyses of published and experimentally derived phosphoproteomics data identified differentially expressed phosphoproteins that were unique and shared between hyperammonemic murine myotubes and skeletal muscle from exercise models. Enriched processes identified in both hyperammonemic myotubes and muscle from exercise models with selected experimental validation included protein kinase A (PKA), calcium signaling, mitogen-activated protein kinase (MAPK) signaling, and protein homeostasis. Our approach of feature extraction from comparative untargeted "omics" data allows for selection of preclinical models that recapitulate specific human exercise responses and potentially optimize functional capacity and skeletal muscle protein homeostasis with exercise in chronic diseases.
    Keywords:  Biological sciences; Cell biology; Functional aspects of cell biology; Omics; Proteomics
    DOI:  https://doi.org/10.1016/j.isci.2022.105325
  8. Am J Physiol Cell Physiol. 2022 Nov 07.
    Identification of underexplored mesenchymal and vascular-related cell populations in human skeletal muscle.
    Alasdair Cameron, Griffen Wakelin, Nicholas Gaulton, Laura V Young, Scott Wotherspoon, Nathan Hodson, Matthew J Lees, Daniel R Moore, Adam P Johnston.
      Skeletal muscle repair and maintenance are directly and indirectly supported by stromal populations such as vascular cells and fibro-adipogenic progenitors (FAPs), a subset of which express Twist2 and possess direct myogenic potential in rodents. However, less is understood of the complexity and heterogeneity of human skeletal muscle stromal cells. To this end, we performed single-cell RNA sequencing (scRNAseq) on ~2000 cells isolated from the human semitendinosus muscle of young individuals. This demonstrated the presence of two poorly described cell populations. First, we detected a vascular-related cell type that expressed pericyte and pan-endothelial genes that we localized to large blood vessels within skeletal muscle cross-sections and termed stromal pericytes. RNA velocity analysis demonstrated that stromal pericytes may represent a "transition state" between endothelial cells and pericytes. Analysis of published scRNAseq datasets revealed evidence for stromal pericytes in trunk and heart musculature, which showed transcriptional similarity. Additionally, we identified a subset of FAPs expressing TWIST2 mRNA and protein. Human TWIST2-expressing cells were anatomically and transcriptionally comparable to mouse Twist2 cells as they were restricted to the myofiber interstitium, expressed fibrogenic genes but lacked satellite cell markers and colocalized with the FAPs marker PDGFRα in human muscle cross-sections. Taken together, these results highlight the complexity of stromal cells residing in human skeletal muscle and support the utility of scRNAseq for discovery and characterization of poorly described cell populations.
    Keywords:  Single-cell RNA sequencing; Skeletal muscle; Stem cell; Twist2
    DOI:  https://doi.org/10.1152/ajpcell.00364.2022
  9. Int J Mol Sci. 2022 Oct 26. pii: 12933. [Epub ahead of print]23(21):
    Genes Whose Gain or Loss of Function Changes Type 1, 2A, 2X, or 2B Muscle Fibre Proportions in Mice-A Systematic Review.
    Gabryela Kuhnen, Tiago Guedes Russomanno, Marta Murgia, Nicolas J Pillon, Martin Schönfelder, Henning Wackerhage.
      Adult skeletal muscle fibres are classified as type 1, 2A, 2X, and 2B. These classifications are based on the expression of the dominant myosin heavy chain isoform. Muscle fibre-specific gene expression and proportions of muscle fibre types change during development and in response to exercise, chronic electrical stimulation, or inactivity. To identify genes whose gain or loss-of-function alters type 1, 2A, 2X, or 2B muscle fibre proportions in mice, we conducted a systematic review of transgenic mouse studies. The systematic review was conducted in accordance with the 2009 PRISMA guidelines and the PICO framework. We identified 25 "muscle fibre genes" (Akirin1, Bdkrb2, Bdnf, Camk4, Ccnd3, Cpt1a, Epas1, Esrrg, Foxj3, Foxo1, Il15, Mapk12, Mstn, Myod1, Ncor1, Nfatc1, Nol3, Ppargc1a, Ppargc1b, Sirt1, Sirt3, Thra, Thrb, Trib3, and Vgll2) whose gain or loss-of-function significantly changes type 1, 2A, 2X or 2B muscle fibre proportions in mice. The fact that 15 of the 25 muscle fibre genes are transcriptional regulators suggests that muscle fibre-specific gene expression is primarily regulated transcriptionally. A reanalysis of existing datasets revealed that the expression of Ppargc1a and Vgll2 increases and Mstn decreases after exercise, respectively. This suggests that these genes help to regulate the muscle fibre adaptation to exercise. Finally, there are many known DNA sequence variants of muscle fibre genes. It seems likely that such DNA sequence variants contribute to the large variation of muscle fibre type proportions in the human population.
    Keywords:  muscle fibre proportions; myosin heavy chain; skeletal muscle fibre
    DOI:  https://doi.org/10.3390/ijms232112933
  10. Int J Mol Sci. 2022 Nov 06. pii: 13615. [Epub ahead of print]23(21):
    Loss of the Nuclear Envelope Protein LAP1B Disrupts the Myogenic Differentiation of Patient-Derived Fibroblasts.
    Gülsüm Kayman Kürekçi, Aybar C Acar, Pervin R Dinçer.
      Lamina-associated polypeptide 1 (LAP1) is a ubiquitously expressed inner nuclear membrane protein encoded by TOR1AIP1, and presents as two isoforms in humans, LAP1B and LAP1C. While loss of both isoforms results in a multisystemic progeroid-like syndrome, specific loss of LAP1B causes muscular dystrophy and cardiomyopathy, suggesting that LAP1B has a critical role in striated muscle. To gain more insight into the molecular pathophysiology underlying muscular dystrophy caused by LAP1B, we established a patient-derived fibroblast line that was transdifferentiated into myogenic cells using inducible MyoD expression. Compared to the controls, we observed strongly reduced myogenic differentiation and fusion potentials. Similar defects were observed in the C2C12 murine myoblasts carrying loss-of-function LAP1A/B mutations. Using RNA sequencing, we found that, despite MyoD overexpression and efficient cell cycle exit, transcriptional reprogramming of the LAP1B-deficient cells into the myogenic lineage is impaired with delayed activation of MYOG and muscle-specific genes. Gene set enrichment analyses suggested dysregulations of protein metabolism, extracellular matrix, and chromosome organization. Finally, we found that the LAP1B-deficient cells exhibit nuclear deformations, such as an increased number of micronuclei and altered morphometric parameters. This study uncovers the phenotypic and transcriptomic changes occurring during myoconversion of patient-derived LAP1B-deficient fibroblasts and provides a useful resource to gain insights into the mechanisms implicated in LAP1B-associated nuclear envelopathies.
    Keywords:  LAP1; TOR1AIP1; muscular dystrophy; myogenic differentiation; nuclear envelope
    DOI:  https://doi.org/10.3390/ijms232113615
  11. Commun Biol. 2022 Nov 09. 5(1): 1201
    Tcf12 is required to sustain myogenic genes synergism with MyoD by remodelling the chromatin landscape.
    Sheng Wang, Yinlong Liao, Haoyuan Zhang, Yunqi Jiang, Zhelun Peng, Ruimin Ren, Xinyun Li, Heng Wang.
      Muscle stem cells (MuSCs) are essential for skeletal muscle development and regeneration, ensuring muscle integrity and normal function. The myogenic proliferation and differentiation of MuSCs are orchestrated by a cascade of transcription factors. In this study, we elucidate the specific role of transcription factor 12 (Tcf12) in muscle development and regeneration based on loss-of-function studies. Muscle-specific deletion of Tcf12 cause muscle weight loss owing to the reduction of myofiber size during development. Inducible deletion of Tcf12 specifically in adult MuSCs delayed muscle regeneration. The examination of MuSCs reveal that Tcf12 deletion resulted in cell-autonomous defects during myogenesis and Tcf12 is necessary for proper myogenic gene expression. Mechanistically, TCF12 and MYOD work together to stabilise chromatin conformation and sustain muscle cell fate commitment-related gene and chromatin architectural factor expressions. Altogether, our findings identify Tcf12 as a crucial regulator of MuSCs chromatin remodelling that regulates muscle cell determination and participates in skeletal muscle development and regeneration.
    DOI:  https://doi.org/10.1038/s42003-022-04176-0
  12. Nitric Oxide. 2022 Oct 28. pii: S1089-8603(22)00112-4. [Epub ahead of print]129 102-109
    Skeletal muscle as a reservoir for nitrate and nitrite: The role of xanthine oxidase reductase (XOR).
    Joaquin Ortiz de Zevallos, Mary N Woessner, Eric E Kelley.
      Recent studies have identified skeletal muscle as a tissue compartment where nitrate and nitrite can be stored and utilized to potentially maintain nitric oxide (NO) homeostasis. Given its capacity to reduce nitrate and nitrite, the molybdopterin-containing enzyme, xanthine oxidoreductase (XOR) has been suggested as a key enzyme within skeletal muscle which catalytically reduces these N-oxides; however, there remains limited insight into the role of XOR in this process as well as how different conditions (e.g. health vs disease and rest vs exercise) may determine when and where, within skeletal muscle, XOR could serve as a significant source of NO. A key factor that determines the extent by which XOR may or may not contribute to NO generation in a biologically relevant manner is the biochemical landscape (e.g. oxygen tension, pH, isoform of XOR (XDH vs. XO) and substrate levels of the microenvironment in normal versus stressed skeletal muscle. As such, a critical focus of this review is the evaluation of the biochemical and physiologic data supporting the role of XOR within skeletal muscle for supplying nitrite and/or NO from endogenous and exogenous sources during pathophysiologic conditions and/or exercise stress.
    Keywords:  Exercise; Nitrate; Nitrite; Skeletal muscle; Xanthine dehydrogenase; Xanthine oxidase; Xanthine oxidoreductase
    DOI:  https://doi.org/10.1016/j.niox.2022.10.004
  13. Antioxidants (Basel). 2022 Nov 09. pii: 2216. [Epub ahead of print]11(11):
    Skeletal Muscle CSE Deficiency Leads to Insulin Resistance in Mice.
    Miaomiao Xu, Xiaoguang Liu, Peng Bao, Yanjie Wang, Xiaoyan Zhu, Yujian Liu, Xin Ni, Jianqiang Lu.
      Cystathionine-γ-lyase (CSE) is expressed in various tissues and generates H2S via an alternative desulfuration reaction. We sought to explore the functions of skeletal muscle CSE using skeletal muscle conditional knockout CSE (MCSEKO) mice. It was found that body weight, muscle morphology, and exercise capacity were not altered in MCSEKO mice compared with littermate wild-type mice. RNA-seq-based transcriptome analysis showed that 275 genes were differentially regulated in skeletal muscle and multiple signaling pathways including insulin signaling and mTOR, PI3K-AKT, and cGMP-PKG signaling pathways were enriched in MCSEKO mice. The intraperitoneal glucose tolerance test and insulin tolerance test showed that glucose tolerance and insulin sensitivity were reduced in MCSEKO mice. Glucose transporter 4 (GLU4) and PKG-1 expression levels and insulin receptor substrate-1(IRS1)/PI3K/Akt signaling pathway were downregulated whilst the mTOR/S6K/S6 pathway was enhanced in MCSEKO mice. These effects were reversed by the H2S supplement. Aerobic treadmill training significantly promoted glucose tolerance and insulin sensitivity and improved GLU4 and PKG-1 levels, promoted IRS1/PI3K/Akt signaling and suppressed mTOR/S6K/S6 signaling pathway in MCSEKO mice. Our data suggest that skeletal muscle CSE/H2S signaling is critical for the maintenance of insulin sensitivity, which is associated with maintaining the balance in PKG, PI3K/Akt, and mTOR/S6K/S6 signaling pathways in skeletal muscle.
    Keywords:  H2S; cystathionine-γ-lyase; exercise; glucose tolerance; insulin resistance; skeletal muscle
    DOI:  https://doi.org/10.3390/antiox11112216
  14. J Mol Histol. 2022 Nov 08.
    Duchenne muscular dystrophy progression induced by downhill running is accompanied by increased endomysial fibrosis and oxidative damage DNA in muscle of mdx mice.
    Mariana Cruz Lazzarin, José Fontes Dos Santos, Hananiah Tardivo Quintana, Flavia Andressa Mazzuco Pidone, Flavia de Oliveira.
      Duchenne muscular dystrophy (DMD) is characterized by progressive muscle necrosis. One of the major challenges for prescribing physical rehabilitation exercises for DMD patients is associated with the lack of a thorough knowledge of dystrophic muscle responsiveness to exercise. This study aims to understand the relationship between myogenic regulation, inflammation and oxidative stress parameters, and disease progression induced by downhill running in the skeletal muscle of an experimental model of DMD. Six-month-old C57BL/10 and C57BL/10-DMDmdx male mice were distributed into three groups: Control (C), mdx, and mdx + Exercise (mdx + Ex). Animals were trained in a downhill running protocol for seven weeks. The gastrocnemius muscle was subjected to histopathology, muscle regeneration (myoD and myogenin), inflammation (COX-2), oxidative stress (8-OHdG) immunohistochemistry markers, and gene expression (qPCR) of NF-kB and NADP(H)Oxidase 2 (NOX-2) analysis. In the mdx + Ex group, the gastrocnemius muscle showed a higher incidence of endomysial fibrosis and a lower myonecrosis percentage area. Immunohistochemical analysis revealed decreased myogenin immunoexpression in the mdx group, as well as accentuated immunoexpression of nuclear 8-OHdG in both mdx groups and increase in cytoplasmic 8-OHdG only in the mdx + Ex. COX-2 immunoexpression was related to areas of regeneration process and inflammatory infiltrate in the mdx group, while associated with areas of muscle fibrosis in the mdx + Ex. Moreover, the NF-kB gene expression was not influenced by exercise; however, a NAD(P)HOxidase 2 increase was observed. Oxidative stress and oxidative DNA damage play a significant role in the DMD phenotype progression induced by exercise, compromising cellular patterns resulting in increased endomysial fibrosis.
    Keywords:  8-hydroxy-2-deoxyguanosine; Connective tissue; Exercise-induced muscle damage; Mdx mice; cyclooxygenase-2
    DOI:  https://doi.org/10.1007/s10735-022-10109-2
  15. J Physiol. 2022 Nov 07.
    Thick filament activation is different in fast and slow-twitch skeletal muscle.
    Henry M Gong, Weikang Ma, Michael Regnier, Thomas C Irving.
      Fast-twitch muscle and slow-twitch muscle are optimized for strong, short duration contractions and for tonic postural activity respectively. Structural events (OFF to ON transitions) in the myosin containing thick filaments in fast muscle help determine the timing and strength of contractions but these have not been studied in slow-twitch muscle. The X-ray diffraction signatures of structural OFF to ON transitions are different in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle, being completely absent during twitches in soleus muscle and blunted during tetanic contractions SOL as compared to EDL Quasi-stepwise thick filament structural OFF to ON transitions in fast twitch muscle may be an adaptation for rapid, ballistic movements whereas more graded OFF to ON structural transitions in slow-twitch muscle may be an adaptation for slower, finer motions. ABSTRACT: The contractile properties of fast-twitch and slow-twitch skeletal muscles are primarily determined by the myosin isoform content and modulated by a variety of sarcomere proteins. X-ray diffraction studies of regulatory mechanisms in muscle contraction have focused predominately on fast- or mixed-fiber muscle with slow muscle being much less studied. Here, we used time-resolved x-ray diffraction to investigate the dynamic behavior of the myofilament proteins in relatively pure slow-twitch fiber rat soleus (SOL) and pure fast-twitch fiber rat extensor digitorum longus (EDL) muscle during twitch and tetanic contractions at optimal length. During twitch contractions the diffraction signatures indicating a transition in the myosin heads from ordered OFF states, where heads are held close to the thick filament backbone, to disordered ON states, where heads are free to bind to thin filaments, were found in EDL and not in SOL muscle. During tetanic contraction, changes in the disposition of myosin heads as active tension develops is a quasi-stepwise process in EDL muscle whereas in SOL muscle this relationship appears to be linear. The observed reduced extensibility of the thick filaments in SOL muscle as compared to EDL muscles indicate a molecular basis for this behavior. These data indicate that for the EDL thick filament activation is a cooperative strain-induced mechano-sensing mechanism, whereas for the SOL thick filament activation has a more graded response. These different approaches to thick filament regulation in fast- and slow-twitch muscles may be adaptations for short-duration, strong contractions versus sustained, finely controlled contractions, respectively. Abstract figure legend Time-resolved x-ray diffraction was used to investigate the dynamic behavior of the myofilament proteins in relatively pure slow-twitch fiber rat soleus (SOL) and pure fast-twitch fiber rat extensor digitorum longus (EDL) muscle. Both actin-containing thin filaments and myosin-containing thick filaments are in the OFF state under resting conditions. During twitch contractions of EDL muscle the diffraction signatures indicating a transition in the myosin heads from ordered OFF states (Grey heads), where heads are held close to the thick filament backbone, to disordered ON states (Green heads). In contrast, twitch contraction of SOL muscle did not trigger an OFF to ON transition of the myosin heads. Structural dynamics during tetanic contraction showed that thick filament activation in EDL is a cooperative strain-induced mechano-sensing process, whereas thick filament activation in SOL has a more graded response. These data indicate that thick filament regulation is not the same in all muscle types. This article is protected by copyright. All rights reserved.
    Keywords:  muscle activation; skeletal muscle; tetanus; thick filament regulation; twitch; x-ray diffraction
    DOI:  https://doi.org/10.1113/JP283574
  16. Cells. 2022 Oct 31. pii: 3435. [Epub ahead of print]11(21):
    MyoD-Induced Trans-Differentiation: A Paradigm for Dissecting the Molecular Mechanisms of Cell Commitment, Differentiation and Reprogramming.
    Cecilia Battistelli, Sabrina Garbo, Rossella Maione.
      The discovery of the skeletal muscle-specific transcription factor MyoD represents a milestone in the field of transcriptional regulation during differentiation and cell-fate reprogramming. MyoD was the first tissue-specific factor found capable of converting non-muscle somatic cells into skeletal muscle cells. A unique feature of MyoD, with respect to other lineage-specific factors able to drive trans-differentiation processes, is its ability to dramatically change the cell fate even when expressed alone. The present review will outline the molecular strategies by which MyoD reprograms the transcriptional regulation of the cell of origin during the myogenic conversion, focusing on the activation and coordination of a complex network of co-factors and epigenetic mechanisms. Some molecular roadblocks, found to restrain MyoD-dependent trans-differentiation, and the possible ways for overcoming these barriers, will also be discussed. Indeed, they are of critical importance not only to expand our knowledge of basic muscle biology but also to improve the generation skeletal muscle cells for translational research.
    Keywords:  MyoD; chromatin regulation; forced differentiation; myogenic conversion
    DOI:  https://doi.org/10.3390/cells11213435
  17. Clin Biomech (Bristol, Avon). 2022 Oct 25. pii: S0268-0033(22)00238-8. [Epub ahead of print]100 105808
    Short-time recovery skeletal muscle from dexamethasone-induced atrophy and weakness in old female rats.
    Karin Alev, Maire Aru, Arved Vain, Ando Pehme, Priit Kaasik, Teet Seene.
      BACKGROUND: Several pathological conditions (atrophy, dystrophy, spasticity, inflammation) can change muscle biomechanical parameters. Our previous works have shown that dexamethasone treatment changes skeletal muscle tone, stiffness, elasticity. Exercise training may oppose the side effects observed during dexamethasone treatment. The purpose of this study was to examine the changes in biomechanical parameters (tone, stiffness, elasticity) of skeletal muscle occurring during dexamethasone treatment and subsequent short-time recovery from glucocorticoid-induced muscle atrophy and weakness, as well as the effect of mild therapeutic exercise.METHODS: 17 old female rats, aged 22 months were used in this study. The hand-held and non-invasive device (MyotonPRO, Myoton Ltd., Tallinn, Estonia) was used to study changes in biomechanical properties of muscle. Additionally, body and muscle mass, hind limb grip strength were assessed.
    FINDINGS: Results showed that dexamethasone treatment alters muscle tone, stiffness and elasticity. During 20-day recovery period all measured parameters gradually improved towards the average baseline, however, remaining significantly lower than these values. The body and muscle mass, hind limb grip strength of the rats decreased considerably in the groups that received glucocorticoids. After 20 days of recovery, hind limb grip strength of the animals was slightly lower than the baseline value and mild therapeutic exercise had a slight but not significant effect on hind limb grip strength. Biomechanical parameters improved during the recovery period, but only dynamic stiffness and decrement retuned to baseline value.
    INTERPRETATION: The study results show that monitoring muscle biomechanical parameters allows to assess the recovery of atrophied muscle from steroid myopathy.
    Keywords:  Glucocorticoids myopathy; Muscle elasticity; Muscle stiffness; Muscle tone; Therapeutic exercise
    DOI:  https://doi.org/10.1016/j.clinbiomech.2022.105808
  18. Am J Physiol Endocrinol Metab. 2022 Nov 09.
    Loss of hepatic phosphoenolpyruvate carboxykinase 1 dysregulates metabolic responses to acute exercise but enhances adaptations to exercise training in mice.
    Ferrol I Rome, Gregory L Shobert, William C Voigt, David B Stagg, Patrycja Puchalska, Shawn C Burgess, Peter A Crawford, Curtis C Hughey.
      Acute exercise increases liver gluconeogenesis to supply glucose to working muscle. Concurrently, elevated liver lipid breakdown fuels the high energetic cost of gluconeogenesis. This functional coupling between liver gluconeogenesis and lipid oxidation has been proposed to underlie the ability of regular exercise to enhance liver mitochondrial oxidative metabolism and decrease liver steatosis in individuals with non-alcoholic fatty liver disease. Herein we tested whether repeated bouts of increased hepatic gluconeogenesis are necessary for exercise training to lower liver lipids. Experiments used diet-induced obese mice lacking hepatic phosphoenolpyruvate carboxykinase 1 (KO) to inhibit gluconeogenesis and wild type (WT) littermates. 2H/13C metabolic flux analysis quantified glucose and mitochondrial oxidative fluxes in untrained mice at rest and during acute exercise. Circulating and tissue metabolite levels were determined during sedentary conditions, acute exercise, and refeeding post-exercise. Mice also underwent six weeks of treadmill running protocols to define hepatic and extrahepatic adaptations to exercise training. Untrained KO mice were unable to maintain euglycemia during acute exercise resulting from an inability to increase gluconeogenesis. Liver triacylglycerides were elevated following acute exercise and circulating β-hydroxybutyrate was higher during post-exercise refeeding in untrained KO mice. In contrast, exercise training prevented liver triacylglyceride accumulation in KO mice. This was accompanied by pronounced increases in indices of skeletal muscle mitochondrial oxidative metabolism in KO mice. Together, these results show that hepatic gluconeogenesis is dispensable for exercise training to reduce liver lipids. This may be due to responses in ketone body metabolism and/or metabolic adaptations in skeletal muscle to exercise.
    Keywords:  gluconeogenesis; glycogenolysis; ketone bodies; mitochondria; skeletal muscle
    DOI:  https://doi.org/10.1152/ajpendo.00222.2022
  19. Int J Mol Sci. 2022 Nov 04. pii: 13506. [Epub ahead of print]23(21):
    Connexin 43 Channels in Osteocytes Are Necessary for Bone Mass and Skeletal Muscle Function in Aged Male Mice.
    Guobin Li, Lan Zhang, Zhe Lu, Baoqiang Yang, Hui Yang, Peng Shang, Jean X Jiang, Dong'en Wang, Huiyun Xu.
      Osteoporosis and sarcopenia (termed "Osteosarcopenia"), the twin-aging diseases, are major contributors to reduced bone mass and muscle weakness in the elderly population. Connexin 43 (Cx43) in osteocytes has been previously reported to play vital roles in bone homeostasis and muscle function in mature mice. The Cx43-formed gap junctions (GJs) and hemichannels (HCs) in osteocytes are important portals for the exchange of small molecules in cell-to-cell and cell-to-extracellular matrix, respectively. However, the roles of Cx43-based GJs and HCs in both bone and muscle aging are still unclear. Here, we used two transgenic mouse models with overexpression of the dominant negative Cx43 mutants primarily in osteocytes driven by the 10-kb Dmp1 promoter, R76W mice (inhibited gap junctions but enhanced hemichannels) and Δ130-136 mice (both gap junction and hemichannels are inhibited), to determine the actions of Cx43-based hemichannels (HCs) and gap junctions (GJs) in the regulation of bone and skeletal muscle from aged mice (18 months) as compared with those from adult mice (10 months). We demonstrated that enhancement of Cx43 HCs reduces bone mass due to increased osteoclast surfaces while the impairment of Cx43 HCs increases osteocyte apoptosis in aged mice caused by reduced PGE2 levels. Furthermore, altered mitochondrial homeostasis with reduced expression of Sirt-1, OPA-1, and Drp-1 resulted in excessive ROS level in muscle soleus (SL) of aged transgenic mice. In vitro, the impairment of Cx43 HCs in osteocytes from aged mice also promoted muscle collagen synthesis through activation of TGFβ/smad2/3 signaling because of reduced PGE2 levels in the PO CM. These findings indicate that the enhancement of Cx43 HCs while GJs are inhibited reduces bone mass, and the impairment of Cx43 HCs inhibits PGE2 level in osteocytes and this reduction promotes muscle collagen synthesis in skeletal muscle through activation of TGFβ/smad2/3 signaling, which together with increased ROS level contributes to reduced muscle force in aged mice.
    Keywords:  aging; bone-muscle crosstalk; gap junctions; hemichannels; osteocytes
    DOI:  https://doi.org/10.3390/ijms232113506
  20. Pharmaceutics. 2022 Oct 29. pii: 2336. [Epub ahead of print]14(11):
    BKCa Activator NS1619 Improves the Structure and Function of Skeletal Muscle Mitochondria in Duchenne Dystrophy.
    Mikhail V Dubinin, Vlada S Starinets, Natalia V Belosludtseva, Irina B Mikheeva, Yuliya A Chelyadnikova, Anastasia D Igoshkina, Aliya B Vafina, Alexander A Vedernikov, Konstantin N Belosludtsev.
      Duchenne muscular dystrophy (DMD) is a progressive hereditary disease caused by the absence of the dystrophin protein. This is secondarily accompanied by a dysregulation of ion homeostasis, in which mitochondria play an important role. In the present work, we show that mitochondrial dysfunction in the skeletal muscles of dystrophin-deficient mdx mice is accompanied by a reduction in K+ transport and a decrease in its content in the matrix. This is associated with a decrease in the expression of the mitochondrial large-conductance calcium-activated potassium channel (mitoBKCa) in the muscles of mdx mice, which play an important role in cytoprotection. We observed that the BKCa activator NS1619 caused a normalization of mitoBKCa expression and potassium homeostasis in the muscle mitochondria of these animals, which was accompanied by an increase in the calcium retention capacity, mitigation of oxidative stress, and improvement in mitochondrial ultrastructure. This effect of NS1619 contributed to the reduction of degeneration/regeneration cycles and fibrosis in the skeletal muscles of mdx mice as well as a normalization of sarcomere size, but had no effect on the leakage of muscle enzymes and muscle strength loss. In the case of wild-type mice, we noted the negative effect of NS1619 manifested in the inhibition of the functional activity of mitochondria and disruption of their structure, which, however, did not significantly affect the state of the skeletal muscles of the animals. This article discusses the role of mitoBKCa in the development of DMD and the prospects of the approach associated with the correction of its function in treatments of this secondary channelopathy.
    Keywords:  BKCa; Duchenne muscular dystrophy; MPT pore; NS1619; mdx; potassium transport; skeletal muscle mitochondria
    DOI:  https://doi.org/10.3390/pharmaceutics14112336
  21. Cells. 2022 Oct 31. pii: 3448. [Epub ahead of print]11(21):
    Aberrant DNA and RNA Methylation Occur in Spinal Cord and Skeletal Muscle of Human SOD1 Mouse Models of ALS and in Human ALS: Targeting DNA Methylation Is Therapeutic.
    Lee J Martin, Danya A Adams, Mark V Niedzwiecki, Margaret Wong.
      Amyotrophic lateral sclerosis (ALS) is a fatal disease. Skeletal muscles and motor neurons (MNs) degenerate. ALS is a complex disease involving many genes in multiple tissues, the environment, cellular metabolism, and lifestyles. We hypothesized that epigenetic anomalies in DNA and RNA occur in ALS and examined this idea in: (1) mouse models of ALS, (2) human ALS, and (3) mouse ALS with therapeutic targeting of DNA methylation. Human superoxide dismutase-1 (hSOD1) transgenic (tg) mice were used. They expressed nonconditionally wildtype (WT) and the G93A and G37R mutant variants or skeletal muscle-restricted WT and G93A and G37R mutated forms. Age-matched non-tg mice were controls. hSOD1 mutant mice had increased DNA methyltransferase enzyme activity in spinal cord and skeletal muscle and increased 5-methylcytosine (5mC) levels. Genome-wide promoter CpG DNA methylation profiling in skeletal muscle of ALS mice identified hypermethylation notably in cytoskeletal genes. 5mC accumulated in spinal cord MNs and skeletal muscle satellite cells in mice. Significant increases in DNA methyltransferase-1 (DNMT1) and DNA methyltransferase-3A (DNMT3A) levels occurred in spinal cord nuclear and chromatin bound extracts of the different hSOD1 mouse lines. Mutant hSOD1 interacted with DNMT3A in skeletal muscle. 6-methyladenosine (6mA) RNA methylation was markedly increased or decreased in mouse spinal cord depending on hSOD1-G93A model, while fat mass and obesity associated protein was depleted and methyltransferase-like protein 3 was increased in spinal cord and skeletal muscle. Human ALS spinal cord had increased numbers of MNs and interneurons with nuclear 5mC, motor cortex had increased 5mC-positive neurons, while 6mA was severely depleted. Treatment of hSOD1-G93A mice with DNMT inhibitor improved motor function and extended lifespan by 25%. We conclude that DNA and RNA epigenetic anomalies are prominent in mouse and human ALS and are potentially targetable for disease-modifying therapeutics.
    Keywords:  6-methyladenosine; CpG island; Dnmt3A; FTO; cytosine methylation; motor neuron
    DOI:  https://doi.org/10.3390/cells11213448
  22. Sci Rep. 2022 Nov 08. 12(1): 18960
    A link between agrin signalling and Cav3.2 at the neuromuscular junction in spinal muscular atrophy.
    Perrine Delers, Delphine Sapaly, Badih Salman, Stephan De Waard, Michel De Waard, Suzie Lefebvre.
      SMN protein deficiency causes motoneuron disease spinal muscular atrophy (SMA). SMN-based therapies improve patient motor symptoms to variable degrees. An early hallmark of SMA is the perturbation of the neuromuscular junction (NMJ), a synapse between a motoneuron and muscle cell. NMJ formation depends on acetylcholine receptor (AChR) clustering triggered by agrin and its co-receptors lipoprotein receptor-related protein 4 (LRP4) and transmembrane muscle-specific kinase (MuSK) signalling pathway. We have previously shown that flunarizine improves NMJs in SMA model mice, but the mechanisms remain elusive. We show here that flunarizine promotes AChR clustering in cell-autonomous, dose- and agrin-dependent manners in C2C12 myotubes. This is associated with an increase in protein levels of LRP4, integrin-beta-1 and alpha-dystroglycan, three agrin co-receptors. Furthermore, flunarizine enhances MuSK interaction with integrin-beta-1 and phosphotyrosines. Moreover, the drug acts on the expression and splicing of Agrn and Cacna1h genes in a muscle-specific manner. We reveal that the Cacna1h encoded protein Cav3.2 closely associates in vitro with the agrin co-receptor LRP4. In vivo, it is enriched nearby NMJs during neonatal development and the drug increases this immunolabelling in SMA muscles. Thus, flunarizine modulates key players of the NMJ and identifies Cav3.2 as a new protein involved in the NMJ biology.
    DOI:  https://doi.org/10.1038/s41598-022-23703-x
  23. Int J Mol Sci. 2022 Oct 26. pii: 12926. [Epub ahead of print]23(21):
    Mitochondrial Dysfunction as an Underlying Cause of Skeletal Muscle Disorders.
    Tsung-Hsien Chen, Kok-Yean Koh, Kurt Ming-Chao Lin, Chu-Kuang Chou.
      Mitochondria are an important energy source in skeletal muscle. A main function of mitochondria is the generation of ATP for energy through oxidative phosphorylation (OXPHOS). Mitochondrial defects or abnormalities can lead to muscle disease or multisystem disease. Mitochondrial dysfunction can be caused by defective mitochondrial OXPHOS, mtDNA mutations, Ca2+ imbalances, mitochondrial-related proteins, mitochondrial chaperone proteins, and ultrastructural defects. In addition, an imbalance between mitochondrial fusion and fission, lysosomal dysfunction due to insufficient biosynthesis, and/or defects in mitophagy can result in mitochondrial damage. In this review, we explore the association between impaired mitochondrial function and skeletal muscle disorders. Furthermore, we emphasize the need for more research to determine the specific clinical benefits of mitochondrial therapy in the treatment of skeletal muscle disorders.
    Keywords:  OXPHOS; mitochondrial chaperone protein; mitochondrial dynamics; mitochondrial dysfunction; mitophagy; mtDNA mutation; skeletal muscle disorders
    DOI:  https://doi.org/10.3390/ijms232112926
  24. Free Radic Biol Med. 2022 Nov 03. pii: S0891-5849(22)00952-2. [Epub ahead of print]
    Irisin and ALCAT1 mediated aerobic exercise-alleviated oxidative stress and apoptosis in skeletal muscle of mice with myocardial infarction.
    Wujing Ren, Zujie Xu, Shou Pan, Yixuan Ma, Hangzhuo Li, Fangnan Wu, Wenyan Bo, Mengxin Cai, Zhenjun Tian.
      Skeletal muscle in patients with heart failure (HF) exhibits altered structure, function and metabolism. Myocardial infarction (MI) is the most common cause of HF, and oxidative stress and cell apoptosis are involved in the pathophysiology of MI/HF-induced skeletal muscle atrophy. It is well recognized that aerobic exercise (AE) could prevent skeletal muscle atrophy after MI, but the underlying mechanism and molecular targets are still not fully clarified. In this study, Fndc5-/- and Alcat1-/- mice were used to establish the MI model and subjected to six weeks of moderate-intensity AE. C2C12 cells were treated with H2O2 and recombinant human Irisin (rhIrisin), or transduced with a lentiviral vector to mediated overexpression of ALCAT1 (LV-Alcat1). Results showed that MI reduced Irisin expression and antioxidant capacity of skeletal muscle, increased ALCAT1 expression, induced protein degradation and cell apoptosis, which were reversed by AE; Knockout of Fndc5 further aggravated MI-induced oxidative stress and cell apoptosis in skeletal muscle, and partly weakened the beneficial effects of AE. In contrast, knockout of Alcat1 reduced MI-induced oxidative stress and cell apoptosis and strengthened the beneficial effects of AE. Irisin and AICAR intervention increased ALCAT1 expression and inhibited oxidative stress and cell apoptosis induced by H2O2 or LV-Alcat1 in C2C12 cells. These findings reveal that AE could alleviate the levels of oxidative stress and apoptosis in skeletal muscle following MI, partly via up-regulating Irisin and inhibiting ALCAT1 expression.
    Keywords:  ALCAT1; Aerobic exercise; Irisin; Myocardial infarction; Skeletal muscle
    DOI:  https://doi.org/10.1016/j.freeradbiomed.2022.10.321
  25. Nat Commun. 2022 Nov 11. 13(1): 6849
    Differential impact of ubiquitous and muscle dynamin 2 isoforms in muscle physiology and centronuclear myopathy.
    Raquel Gómez-Oca, Evelina Edelweiss, Sarah Djeddi, Mathias Gerbier, Xènia Massana-Muñoz, Mustapha Oulad-Abdelghani, Corinne Crucifix, Coralie Spiegelhalter, Nadia Messaddeq, Pierre Poussin-Courmontagne, Pascale Koebel, Belinda S Cowling, Jocelyn Laporte.
      Dynamin 2 mechanoenzyme is a key regulator of membrane remodeling and gain-of-function mutations in its gene cause centronuclear myopathies. Here, we investigate the functions of dynamin 2 isoforms and their associated phenotypes and, specifically, the ubiquitous and muscle-specific dynamin 2 isoforms expressed in skeletal muscle. In cell-based assays, we show that a centronuclear myopathy-related mutation in the ubiquitous but not the muscle-specific dynamin 2 isoform causes increased membrane fission. In vivo, overexpressing the ubiquitous dynamin 2 isoform correlates with severe forms of centronuclear myopathy, while overexpressing the muscle-specific isoform leads to hallmarks seen in milder cases of the disease. Previous mouse studies suggested that reduction of the total dynamin 2 pool could be therapeutic for centronuclear myopathies. Here, dynamin 2 splice switching from muscle-specific to ubiquitous dynamin 2 aggravated the phenotype of a severe X-linked form of centronuclear myopathy caused by loss-of-function of the MTM1 phosphatase, supporting the importance of targeting the ubiquitous isoform for efficient therapy in muscle. Our results highlight that the ubiquitous and not the muscle-specific dynamin 2 isoform is the main modifier contributing to centronuclear myopathy pathology.
    DOI:  https://doi.org/10.1038/s41467-022-34490-4
  26. Ageing Res Rev. 2022 Nov 04. pii: S1568-1637(22)00222-7. [Epub ahead of print]82 101780
    Energy metabolism and frailty: The potential role of exercise-induced myokines - A narrative review.
    Duarte Barros, Elisa A Marques, José Magalhães, Joana Carvalho.
      Frailty is a complex condition that emerges from dysregulation in multiple physiological systems. Increasing evidence suggests the potential role of age-related energy dysregulation as a key driver of frailty. Exercise is considered the most efficacious intervention to prevent and even ameliorate frailty as it up-tunes and improves the function of several related systems. However, the mechanisms and molecules responsible for these intersystem benefits are not fully understood. The skeletal muscle is considered a secretory organ with endocrine functions that can produce and secrete exercise-related molecules such as myokines. These molecules are cytokines and other peptides released by muscle fibers in response to acute and/or chronic exercise. The available evidence supports that several myokines can elicit autocrine, paracrine, or endocrine effects, partly mediating inter-organ crosstalk and also having a critical role in improving cardiovascular, metabolic, immune, and neurological health. This review describes the current evidence about the potential link between energy metabolism dysregulation and frailty and provides a theoretical framework for the potential role of myokines (via exercise) in counteracting frailty. It also summarizes the physiological role of selected myokines and their response to different acute and chronic exercise protocols in older adults.
    Keywords:  Exercise; Exerkines; Frailty; Glucose metabolism; Mitochondrial dysfunction
    DOI:  https://doi.org/10.1016/j.arr.2022.101780
  27. Life (Basel). 2022 Oct 22. pii: 1679. [Epub ahead of print]12(11):
    Proteomic Identification of Markers of Membrane Repair, Regeneration and Fibrosis in the Aged and Dystrophic Diaphragm.
    Stephen Gargan, Paul Dowling, Margit Zweyer, Michael Henry, Paula Meleady, Dieter Swandulla, Kay Ohlendieck.
      Deficiency in the membrane cytoskeletal protein dystrophin is the underlying cause of the progressive muscle wasting disease named Duchenne muscular dystrophy. In order to detect novel disease marker candidates and confirm the complexity of the pathobiochemical signature of dystrophinopathy, mass spectrometric screening approaches represent ideal tools for comprehensive biomarker discovery studies. In this report, we describe the comparative proteomic analysis of young versus aged diaphragm muscles from wild type versus the dystrophic mdx-4cv mouse model of X-linked muscular dystrophy. The survey confirmed the drastic reduction of the dystrophin-glycoprotein complex in the mdx-4cv diaphragm muscle and concomitant age-dependent changes in key markers of muscular dystrophy, including proteins involved in cytoskeletal organization, metabolite transportation, the cellular stress response and excitation-contraction coupling. Importantly, proteomic markers of the regulation of membrane repair, tissue regeneration and reactive myofibrosis were detected by mass spectrometry and changes in key proteins were confirmed by immunoblotting. Potential disease marker candidates include various isoforms of annexin, the matricellular protein periostin and a large number of collagens. Alterations in these proteoforms can be useful to evaluate adaptive, compensatory and pathobiochemical changes in the intracellular cytoskeleton, myofiber membrane integrity and the extracellular matrix in dystrophin-deficient skeletal muscle tissues.
    Keywords:  annexin; biomarker; collagen; degeneration; dystrophinopathy; fibrosis; membrane repair; muscular dystrophy; periostin; regeneration
    DOI:  https://doi.org/10.3390/life12111679
  28. Gene Expr Patterns. 2022 Oct 28. pii: S1567-133X(22)00057-6. [Epub ahead of print]46 119287
    Expression analysis of irisin during different development stages of skeletal muscle in mice.
    Yi Yan, Ding Yang, Pei Wen, Yilei Li, Yufang Ge, Pei Ma, Jiahui Yuan, Pengxiang Zhang, Zhiwei Zhu, Xiaomao Luo, Xiuju Yu, Haidong Wang.
      BACKGROUND: As a newly discovered muscle factor secreted by skeletal muscle cells, irisin is a polypeptide fragment formed from hydrolysis of fibronectin type Ⅲ domain-containing protein 5 (FNDC5). Irisin can promote beigeing of white adipose tissue (WAT) and regulate glucose and lipid metabolisms. However, the functions of irisin in skeletal muscle development remain largely unknown. In order to characterize the expression of irisin, this study investigated the expression of irisin precursor FNDC5 in myoblasts and skeletal muscles during different developmental stages of SPF mice.RESULTS: The Western blot, quantitative real-time PCR (qRT-PCR), and immunofluorescence assay results showed that FNDC5 was expressed in all the developmental stages of myoblasts and gastrocnemius, but its expression differed at different stages. FNDC5 protein exhibited the highest expression in gastrocnemius of sexually mature mice, followed by elderly mice and adolescent mice, and it displayed the lowest expression in pups. Additionally, FNDC5 protein was mainly expressed in cytoplasm, and it had the highest expression in primary myoblasts, followed by the myotubes with the lowest expression in C2C12 myogenic cells.
    CONCLUSIONS: Overall, FNDC5 was mainly expressed in cytoplasm and extracellular matrix with different expression levels at different developmental stages of skeletal muscle cells and tissues in mice. This study will provide new strategies for promoting skeletal muscle development and treating muscle- and metabolism-related disease by using irisin.
    Keywords:  Expression; FNDC5; Irisin; Skeletal muscle cell
    DOI:  https://doi.org/10.1016/j.gep.2022.119287
  29. J Cachexia Sarcopenia Muscle. 2022 Nov 09.
    The impact of senescence on muscle wasting in chronic kidney disease.
    Ying Huang, Bin Wang, Faten Hassounah, S Russ Price, Janet Klein, Tamer M A Mohamed, Yanhua Wang, Jeanie Park, Hui Cai, Xuemei Zhang, Xiaonan H Wang.
      BACKGROUND: Muscle wasting is a common complication of chronic kidney disease (CKD) that is associated with higher mortality. Although the mechanisms of myofibre loss in CKD has been widely studied, the contribution of muscle precursor cell (MPC) senescence remains poorly understood. Senescent MPCs no longer proliferate and can produce proinflammatory factors or cytokines. In this study, we tested the hypothesis that the senescence associated secretory phenotype (SASP) of MPCs contributes to CKD-induced muscle atrophy and weakness.METHODS: CKD was induced in mice by 5/6th nephrectomy. Kidney function, muscle size, and function were measured, and markers of atrophy, inflammation, and senescence were evaluated using immunohistochemistry, immunoblots, or qPCR. To study the impact of senescence, a senolytics cocktail of dasatinib + quercetin (D&Q) was given orally to mice for 8 weeks. To investigate CKD-induced senescence at the cellular level, primary MPCs were incubated with serum from CKD or control subjects. The roles of specific proteins in MPC senescence were studied using adenoviral transduction, siRNA, and plasmid transfection.
    RESULTS: In the hindlimb muscles of CKD mice, (i) the senescence biomarker SA-β-gal was sharply increased (~30-fold); (ii) the DNA damage response marker γ-H2AX was increased 1.9-fold; and (iii) the senescence pathway markers p21 and p16INK4a were increased 1.99-fold and 2.82-fold, respectively (all values, P < 0.05), whereas p53 was unchanged. γ-H2AX, p21, and p16INK4A were negatively correlated at P < 0.05 with gastrocnemius weight, suggesting a causal relationship with muscle atrophy. Administration of the senolytics cocktail to CKD mice for 8 weeks eliminated the disease-related elevation of p21, p16INK4a , and γ-H2AX, abolished positive SA-β-gal, and depressed the high levels of the SASP cytokines, TNF-α, IL-6, IL-1β, and IFN (all values, P < 0.05). Skeletal muscle weight, myofibre cross-sectional area, and grip function were improved in CKD mice receiving D&Q. Markers of protein degradation, inflammation, and MPCs dysfunction were also attenuated by D&Q treatment compared with the vehicle treatment in 5/6th nephrectomy mice (all values, P < 0.05). Uraemic serum induced senescence in cultured MPCs. Overexpression of FoxO1a in MPCs increased the number of p21+ senescent cells, and p21 siRNA prevented uraemic serum-induced senescence (P < 0.05).
    CONCLUSIONS: Senescent MPCs are likely to contribute to the development of muscle wasting during CKD by producing inflammatory cytokines. Limiting senescence with senolytics ameliorated muscle wasting and improved muscle strength in vivo and restored cultured MPC functions. These results suggest potential new therapeutic targets to improve muscle health and function in CKD.
    Keywords:  CDK (cyclin-dependent kinase); CKD; Cachexia; DNA damage; Muscle precursor cells; Senescence
    DOI:  https://doi.org/10.1002/jcsm.13112
  30. J Muscle Res Cell Motil. 2022 Nov 09.
    Downhill running induced DNA damage enhances mitochondrial membrane permeability by facilitating ER-mitochondria signaling.
    Junping Li, Binting Zhao, Shengju Chen, Zhen Wang, Kexin Shi, Binkai Lei, Chunxia Cao, Zhifei Ke, Ruiyuan Wang.
      To observe whether downhill running can lead to DNA damage in skeletal muscle cells and changes in mitochondrial membrane permeability and to explore whether the DNA damage caused by downhill running can lead to changes in mitochondrial membrane permeability by regulating the components of the endoplasmic reticulum mitochondrial coupling structure (MAM). A total of 48 male adult Sprague-Dawley rats were randomly divided into a control group (C, n = 8) and a motor group (E, n = 40). Rats in Group E were further divided into 0 h (E0), 12 h (E12), 24 h (E24), 48 h (E48) and 72 h (E72) after prescribed exercise, with 8 rats in each group. At each time point, flounder muscle was collected under general anaesthesia. The DNA oxidative damage marker 8-hydroxydeoxyguanosine (8-OHdG) was detected by immunofluorescence. The expression levels of the DNA damage-related protein p53 in the nucleus and the EI24 protein and reep1 protein in whole cells were detected by Western blot. The colocalization coefficients of the endoplasmic reticulum protein EI24 and the mitochondrial protein Vdac2 were determined by immunofluorescence double staining, and the concentration of Ca2+ in skeletal muscle mitochondria was detected by a fluorescent probe. Finally, the opening of the mitochondrial membrane permeability transition pore (mPTP) was detected by immunofluorescence. Twelve hours after downhill running, the mitochondrial membrane permeability of the mPTP opened the most (P < 0.05), the content of 8-OHdG in skeletal muscle peaked (P < 0.05), and the levels of the regulatory protein p53, mitochondrial Ca2+, and the EI24 and reep1 proteins peaked (P < 0.01). Moreover, the colocalization coefficients of EI24 and Vdac2 and the Mandes coefficients of the two proteins increased first and then recovered 72 h after exercise (P < 0.05). (1) Downhill running can lead to DNA damage in skeletal muscle cells, overload of mitochondrial Ca2+ and large opening of membrane permeability transformation pores. (2) The DNA damage caused by downhill running may result in p53 promoting the transcriptional activation of reep1 and EI24, enhancing the interaction between EI24 and Vdac2, and then leading to an increase in Ca2+ in skeletal muscle mitochondria and the opening of membrane permeability transition pores.
    Keywords:  DNA damage; Downhill running; MAM; Mitochondrial membrane permeability transition pore; Skeletal muscle
    DOI:  https://doi.org/10.1007/s10974-022-09634-0
  31. Biomech Model Mechanobiol. 2022 Nov 06.
    Understanding altered contractile properties in advanced age: insights from a systematic muscle modelling approach.
    Dean L Mayfield, Neil J Cronin, Glen A Lichtwark.
      Age-related alterations of skeletal muscle are numerous and present inconsistently, and the effect of their interaction on contractile performance can be nonintuitive. Hill-type muscle models predict muscle force according to well-characterised contractile phenomena. Coupled with simple, yet reasonably realistic activation dynamics, such models consist of parameters that are meaningfully linked to fundamental aspects of muscle excitation and contraction. We aimed to illustrate the utility of a muscle model for elucidating relevant mechanisms and predicting changes in output by simulating the individual and combined effects on isometric force of several known ageing-related adaptations. Simulating literature-informed reductions in free Ca2+ concentration and Ca2+ sensitivity generated predictions at odds qualitatively with the characteristic slowing of contraction speed. Conversely, incorporating slower Ca2+ removal or a fractional increase in type I fibre area emulated expected changes; the former was required to simulate slowing of the twitch measured experimentally. Slower Ca2+ removal more than compensated for force loss arising from a large reduction in Ca2+ sensitivity or moderate reduction in Ca2+ release, producing realistic age-related shifts in the force-frequency relationship. Consistent with empirical data, reductions in free Ca2+ concentration and Ca2+ sensitivity reduced maximum tetanic force only slightly, even when acting in concert, suggesting a modest contribution to lower specific force. Lower tendon stiffness and slower intrinsic shortening speed slowed and prolonged force development in a compliance-dependent manner without affecting force decay. This work demonstrates the advantages of muscle modelling for exploring sources of variation and identifying mechanisms underpinning the altered contractile properties of aged muscle.
    Keywords:  Ageing; Calcium sensitivity; Calcium uptake and release; Force-frequency relationship; Specific force; Twitch
    DOI:  https://doi.org/10.1007/s10237-022-01651-9
  32. J Cachexia Sarcopenia Muscle. 2022 Nov 09.
    Interleukin-6 initiates muscle- and adipose tissue wasting in a novel C57BL/6 model of cancer-associated cachexia.
    Isabella Pototschnig, Ursula Feiler, Clemens Diwoky, Paul W Vesely, Thomas Rauchenwald, Margret Paar, Latifa Bakiri, Laura Pajed, Peter Hofer, Karl Kashofer, Nyamdelger Sukhbaatar, Gabriele Schoiswohl, Thomas Weichhart, Gerald Hoefler, Christoph Bock, Martin Pichler, Erwin F Wagner, Rudolf Zechner, Martina Schweiger.
      BACKGROUND: Cancer-associated cachexia (CAC) is a wasting syndrome drastically reducing efficacy of chemotherapy and life expectancy of patients. CAC affects up to 80% of cancer patients, yet the mechanisms underlying the disease are not well understood and no approved disease-specific medication exists. As a multiorgan disorder, CAC can only be studied on an organismal level. To cover the diverse aetiologies of CAC, researchers rely on the availability of a multifaceted pool of cancer models with varying degrees of cachexia symptoms. So far, no tumour model syngeneic to C57BL/6 mice exists that allows direct comparison between cachexigenic- and non-cachexigenic tumours.METHODS: MCA207 and CHX207 fibrosarcoma cells were intramuscularly implanted into male or female, 10-11-week-old C57BL/6J mice. Tumour tissues were subjected to magnetic resonance imaging, immunohistochemical-, and transcriptomic analysis. Mice were analysed for tumour growth, body weight and -composition, food- and water intake, locomotor activity, O2 consumption, CO2 production, circulating blood cells, metabolites, and tumourkines. Mice were sacrificed with same tumour weights in all groups. Adipose tissues were examined using high-resolution respirometry, lipolysis measurements in vitro and ex vivo, and radioactive tracer studies in vivo. Gene expression was determined in adipose- and muscle tissues by quantitative PCR and Western blotting analyses. Muscles and cultured myotubes were analysed histologically and by immunofluorescence microscopy for myofibre cross sectional area and myofibre diameter, respectively. Interleukin-6 (Il-6) was deleted from cancer cells using CRISPR/Cas9 mediated gene editing.
    RESULTS: CHX207, but not MCA207-tumour-bearing mice exhibited major clinical features of CAC, including systemic inflammation, increased plasma IL-6 concentrations (190 pg/mL, P ≤ 0.0001), increased energy expenditure (+28%, P ≤ 0.01), adipose tissue loss (-47%, P ≤ 0.0001), skeletal muscle wasting (-18%, P ≤ 0.001), and body weight reduction (-13%, P ≤ 0.01) 13 days after cancer cell inoculation. Adipose tissue loss resulted from reduced lipid uptake and -synthesis combined with increased lipolysis but was not associated with elevated beta-adrenergic signalling or adipose tissue browning. Muscle atrophy was evident by reduced myofibre cross sectional area (-21.8%, P ≤ 0.001), increased catabolic- and reduced anabolic signalling. Deletion of IL-6 from CHX207 cancer cells completely protected CHX207IL6KO -tumour-bearing mice from CAC.
    CONCLUSIONS: In this study, we present CHX207 fibrosarcoma cells as a novel tool to investigate the mediators and metabolic consequences of CAC in C57BL/6 mice in comparison to non-cachectic MCA207-tumour-bearing mice. IL-6 represents an essential trigger for CAC development in CHX207-tumour-bearing mice.
    Keywords:  Adipose tissue; C57BL/6; Cachexia; Cancer; Interleukin-6
    DOI:  https://doi.org/10.1002/jcsm.13109
  33. J Physiol. 2022 Nov 12.
    Muscle glycogen unavailability and fat oxidation rate during exercise: Insights from McArdle disease.
    Carlos Rodriguez-Lopez, Alfredo Santalla, Pedro L Valenzuela, Alberto Real-Martínez, Mónica Villarreal-Salazar, Irene Rodriguez-Gomez, Tomàs Pinós, Ignacio Ara, Alejandro Lucia.
      KEY POINTS: Physically active McArdle patients shown an exceptional fat oxidation capacity. Maximal fat oxidation rate occurs near-maximal exercise capacity in these patients. McArdle patients' exercise tolerance might rely on maximal fat oxidation rate capacity. Hyperpnoea patients might, however, cloud substrate oxidation measurements in some patients. An animal model revealed overall no higher molecular markers of lipid transport/metabolism.ABSTRACT: Carbohydrate availability affects fat metabolism during exercise; however, the effects of complete muscle glycogen unavailability on maximal fat oxidation (MFO) rate remain unknown. Our purpose was to examine MFO rate in patients with McArdle disease-an inherited condition caused by complete blockade of muscle glycogen metabolism-compared to healthy controls. Nine patients (3 women, 36 ± 12yrs) and 12 healthy controls (4 women, 40 ± 13yrs) were studied. Several molecular markers of lipid transport/metabolism were also determined in skeletal muscle (gastrocnemius) and white adipose tissue of McArdle (Pygm p.50R*/p.50R*) and wild-type mice. Peak oxygen uptake (VO2 peak), MFO rate, the exercise intensity eliciting MFO rate (FATmax), and the MFO rate-associated workload were determined by indirect calorimetry during an incremental cycle-ergometer test. Despite having a much lower V̇O2 peak (24.7 ± 4 vs. 42.5  ±  11.4 ml·kg-1 ·min-1 , respectively; P < 0.0001), patients showed considerably higher values of MFO rate (0.53 ± 0.12 vs. 0.33 ± 0.10 g·min-1 , P = 0.001), FATmax (94.4 ± 7.2 vs. 41.3 ± 9.1 % of V̇O2 peak, P < 0.0001) and MFO rate-associated workload (1.33 ± 0.35 vs. 0.81 ± 0.54 watts·kg-1 , P = 0.020) than controls. No between-group differences were found overall in molecular markers of lipid transport/metabolism in mice. In summary, patients with McArdle disease show an exceptionally high MFO rate, which they attained at near-maximal exercise capacity. Pending more mechanistic explanations, these findings support the influence of glycogen availability on MFO rate and suggest that these patients develop a unique fat oxidation capacity, possibly as an adaptation to compensate for the inherited blockade in glycogen metabolism, and point to MFO rate as a potential limiting factor of exercise tolerance in this disease. Abstract figure legend McArdle disease is caused by inherited blockade of glycogen breakdown in skeletal muscle fibers, with subsequent intolerance to most exercise tasks as well as a substantial impairment of peak aerobic capacity. This study supports that the exercise capacity of these patients is mainly sustained by fat oxidation, with active patients showing an exceptional maximal fat oxidation rate (similar in fact to athletes) during endurance exercise, possibly as an adaptation to muscle glycogen unavailability. On the other hand, data in the (untrained) mouse model of the disease revealed overall no major differences at baseline in molecular markers of lipid transport/metabolism, compared with wild-type mice.
    ABBREVIATIONS: AMPK, AMP-activated protein kinase; CD36, transmembrane glycoprotein cluster of differentiation 36; HADH, 3-hydroxyacyl-CoA dehydrogenase; HSL, hormone-sensitive lipase (total or phosphorylated); MFO, maximum fat oxidation; NS, 'no significant' (for between-group comparisons). pAMPK, phosphorylated AMPK; pATGL, phosphorylated adipose triglyceride lipase; Plin5, perilipin 5; VO2 peak, peak oxygen uptake. Data presented as mean (SD). This article is protected by copyright. All rights reserved.
    Keywords:  anaplerotic; fatty acids; glycogen depletion; glycogen store disease; lactate; muscle fatigue; substrate oxidation; tricarboxylic acid cycle
    DOI:  https://doi.org/10.1113/JP283743
  34. Bioorg Chem. 2022 Oct 31. pii: S0045-2068(22)00628-9. [Epub ahead of print]130 106222
    Development of new 1, 3-dihydroxyacridone derivatives as Akt pathway inhibitors in skeletal muscle cells.
    A Paula Irazoqui, Cintia A Menéndez, H Sebastián Steingruber, Agustina Gonzalez, Gustavo A Appignanesi, Claudia G Buitrago, Darío C Gerbino.
      In the present work, four new compounds based on the privileged structure acridone were efficiently synthesized following simple operational techniques and biologically tested on proliferative skeletal muscle cells (C2C12) and rhabdomyosarcoma cells (RD) showing no significant changes in the number of dead or viable cells at 1 µM during 24 or 48 h of treatment. Of relevance, acridone derivatives 3a-3d at 0.5 µM for 24 h effectively inhibited Akt activation in C2C12, while at 1 µM only compounds 3a and 3b have effect. RD cells showed a different response pattern. These cells treated with 3a (0.5 µM), 3b (0.5 µM) or 3d (0.5 or 1 µM) for 24 h shown significant Akt inhibition. In addition, 3a-3d assayed at 1 µM for 48 h were highly successful in inhibiting Akt phosphorylation. Finally, based on molecular docking and molecular dynamics simulations, we rationalize the experimental results mentioned above and propose that 3-phosphoinositide-dependent kinase-1 (PDK1) could be one of the molecular targets of this new series of 1, 3-dihydroxyacridone derivatives. Biological and in silico studies revealed that 3b could be considered as the most promising prototype for the development of new antitumor agents.
    Keywords:  Acridones; Akt pathway inhibitors; Skeletal muscle cells
    DOI:  https://doi.org/10.1016/j.bioorg.2022.106222
  35. Int J Mol Sci. 2022 Oct 29. pii: 13180. [Epub ahead of print]23(21):
    The Cytokine Growth Differentiation Factor-15 and Skeletal Muscle Health: Portrait of an Emerging Widely Applicable Disease Biomarker.
    Boel De Paepe.
      Growth differentiation factor 15 (GDF-15) is a stress-induced transforming growth factor-β superfamily cytokine with versatile functions in human health. Elevated GDF-15 blood levels associate with multiple pathological conditions, and are currently extensively explored for diagnosis, and as a means to monitor disease progression and evaluate therapeutic responses. This review analyzes GDF-15 in human conditions specifically focusing on its association with muscle manifestations of sarcopenia, mitochondrial myopathy, and autoimmune and viral myositis. The use of GDF-15 as a widely applicable health biomarker to monitor muscle disease is discussed, and its potential as a therapeutic target is explored.
    Keywords:  biomarker; growth differentiation factor-15; muscle disorders
    DOI:  https://doi.org/10.3390/ijms232113180
  36. J Biol Chem. 2022 Nov 02. pii: S0021-9258(22)01100-0. [Epub ahead of print] 102657
    Functional divergence of the sarcomeric myosin, MYH7b, supports species-specific biological roles.
    Lindsey A Lee, Samantha K Barrick, Artur Meller, Jonathan Walklate, Jeffrey M Lotthammer, Jian Wei Tay, W Tom Stump, Gregory Bowman, Michael A Geeves, Michael J Greenberg, Leslie A Leinwand.
      Myosin heavy chain 7b (MYH7b) is an evolutionarily ancient member of the sarcomeric myosin family, which typically supports striated muscle function. However, in mammals alternative splicing prevents MYH7b protein production in cardiac and most skeletal muscles and limits expression to a subset of specialized muscles and certain non-muscle environments. In contrast, MYH7b protein is abundant in python cardiac and skeletal muscles. Although the MYH7b expression pattern diverges in mammals versus reptiles, MYH7b shares high sequence identity across species. So, it remains unclear how mammalian MYH7b function may differ from that of other sarcomeric myosins and whether human and python MYH7b motor functions diverge as their expression patterns suggest. Thus, we generated recombinant human and python MYH7b protein and measured their motor properties to investigate any species-specific differences in activity. Our results reveal that despite having similar working strokes, the MYH7b isoforms have slower actin-activated ATPase cycles and actin sliding velocities than human cardiac β-MyHC. Furthermore, python MYH7b is tuned to have slower motor activity than human MYH7b due to slower kinetics of the mechanochemical cycle. We found that the MYH7b isoforms adopt a higher proportion of myosin heads in the ultra-slow, super-relaxed state compared to human cardiac β-MyHC. These findings are supported by molecular dynamics simulations that predict MYH7b preferentially occupies myosin active site conformations similar to those observed in the structurally inactive state. Together, these results suggest that MYH7b is specialized for slow, energy-conserving motor activity and that differential tuning of MYH7b orthologs contributes to species-specific biological roles.
    Keywords:  Actin; Cardiac muscle; IHM (interacting heads motif); Kinetics; Molecular motor; Myosin; SRX (super-relaxed state); Skeletal muscle; Structure-function
    DOI:  https://doi.org/10.1016/j.jbc.2022.102657
  37. Genes (Basel). 2022 Nov 07. pii: 2055. [Epub ahead of print]13(11):
    Association of Myostatin Gene Polymorphisms with Strength and Muscle Mass in Athletes: A Systematic Review and Meta-Analysis of the MSTN rs1805086 Mutation.
    Marek Kruszewski, Maksim Olegovich Aksenov.
      Polymorphism (rs1805086), c.458A&gt;G, p.Lys(K)153Arg(R), (K153R) of the myostatin gene (MSTN) has been associated with a skeletal muscle phenotype (hypertrophic response in muscles due to strength training). However, there are not enough reliable data to demonstrate whether MSTN rs1805086 K and R allelic variants are valid genetic factors that can affect the strength phenotype of athletes' skeletal muscles. The aim is to conduct a systematic review and meta-analysis of the association of MSTN rs1805086 polymorphism with the strength phenotype of athletes. This study analyzed 71 research articles on MSTN and performed a meta-analysis of MSTN&amp;nbsp;K153R rs1805086 polymorphism in strength-oriented athletes and a control (non-athletes) group. It was found that athletes in the strength-oriented athlete group had a higher frequency of the R minor variant than that in the control group (OR = 2.02, P = 0.05). Thus, the obtained results convincingly demonstrate that there is an association between the studied polymorphism and strength phenotype of athletes; therefore, further studies on this association are scientifically warranted.
    Keywords:  MSTN; hyperplasia; hypertrophy; meta-analysis; muscle; myostatin; strength; training
    DOI:  https://doi.org/10.3390/genes13112055
  38. Nat Commun. 2022 Nov 11. 13(1): 6867
    Molecular identity of proprioceptor subtypes innervating different muscle groups in mice.
    Stephan Dietrich, Carlos Company, Kun Song, Elijah David Lowenstein, Levin Riedel, Carmen Birchmeier, Gaetano Gargiulo, Niccolò Zampieri.
      The precise execution of coordinated movements depends on proprioception, the sense of body position in space. However, the molecular underpinnings of proprioceptive neuron subtype identities are not fully understood. Here we used a single-cell transcriptomic approach to define mouse proprioceptor subtypes according to the identity of the muscle they innervate. We identified and validated molecular signatures associated with proprioceptors innervating back (Tox, Epha3), abdominal (C1ql2), and hindlimb (Gabrg1, Efna5) muscles. We also found that proprioceptor muscle identity precedes acquisition of receptor character and comprise programs controlling wiring specificity. These findings indicate that muscle-type identity is a fundamental aspect of proprioceptor subtype differentiation that is acquired during early development and includes molecular programs involved in the control of muscle target specificity.
    DOI:  https://doi.org/10.1038/s41467-022-34589-8
  39. Sci Rep. 2022 Nov 05. 12(1): 18776
    Using a multiomics approach to unravel a septic shock specific signature in skeletal muscle.
    Baptiste Duceau, Michael Blatzer, Jean Bardon, Thibault Chaze, Quentin Giai Gianetto, Florence Castelli, François Fenaille, Lucie Duarte, Thomas Lescot, Christophe Tresallet, Bruno Riou, Mariette Matondo, Olivier Langeron, Pierre Rocheteau, Fabrice Chrétien, Adrien Bouglé.
      Sepsis is defined as a dysregulated host response to infection leading to organs failure. Among them, sepsis induces skeletal muscle (SM) alterations that contribute to acquired-weakness in critically ill patients. Proteomics and metabolomics could unravel biological mechanisms in sepsis-related organ dysfunction. Our objective was to characterize a distinctive signature of septic shock in human SM by using an integrative multi-omics approach. Muscle biopsies were obtained as part of a multicenter non-interventional prospective study. Study population included patients in septic shock (S group, with intra-abdominal source of sepsis) and two critically ill control populations: cardiogenic shock (C group) and brain dead (BD group). The proteins and metabolites were extracted and analyzed by High-Performance Liquid Chromatography-coupled to tandem Mass Spectrometry, respectively. Fifty patients were included, 19 for the S group (53% male, 64 ± 17 years, SAPS II 45 ± 14), 12 for the C group (75% male, 63 ± 4 years, SAPS II 43 ± 15), 19 for the BD group (63% male, 58 ± 10 years, SAPS II 58 ± 9). Biopsies were performed in median 3 days [interquartile range 1-4]) after intensive care unit admission. Respectively 31 patients and 40 patients were included in the proteomics and metabolomics analyses of 2264 proteins and 259 annotated metabolites. Enrichment analysis revealed that mitochondrial pathways were significantly decreased in the S group at protein level: oxidative phosphorylation (adjusted p = 0.008); branched chained amino acids degradation (adjusted p = 0.005); citrate cycle (adjusted p = 0.005); ketone body metabolism (adjusted p = 0.003) or fatty acid degradation (adjusted p = 0.008). Metabolic reprogramming was also suggested (i) by the differential abundance of the peroxisome proliferator-activated receptors signaling pathway (adjusted p = 0.007), and (ii) by the accumulation of fatty acids like octanedioic acid dimethyl or hydroxydecanoic. Increased polyamines and depletion of mitochondrial thioredoxin or mitochondrial peroxiredoxin indicated a high level of oxidative stress in the S group. Coordinated alterations in the proteomic and metabolomic profiles reveal a septic shock signature in SM, highlighting a global impairment of mitochondria-related metabolic pathways, the depletion of antioxidant capacities, and a metabolic shift towards lipid accumulation.ClinicalTrial registration: NCT02789995. Date of first registration 03/06/2016.
    DOI:  https://doi.org/10.1038/s41598-022-23544-8
This page is being maintained by Thomas Krichel. It was last updated on 2022‒11‒13 at 19:07:51.