bims-moremu 2023-07-23 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–07–23
twenty-two papers selected by
Anna Vainshtein, Craft Science Inc.

Class I HDAC inhibitors attenuate dexamethasone-induced muscle atrophy via increased protein kinase C (PKC) delta phosphorylation.
In vivo Electroporation of Skeletal Muscle Fibers in Mice.
Exercise-Induced Changes to the Fiber Type Specific Redox State in Human Skeletal Muscle are Associated with Aerobic Capacity.
Septin 7 Interacts With Numb To Preserve Sarcomere Structural Organization And Muscle Contractile Function.
Skeletal muscle-specific DJ-1 ablation-induced atrogenes expression and mitochondrial dysfunction contributing to muscular atrophy.
Targeting NAT10 protects against sepsis-induced skeletal muscle atrophy by inhibiting ROS/NLRP3.
Development of Assays to Measure GNE Gene Potency and Gene Replacement in Skeletal Muscle.
Clearance of defective muscle stem cells by senolytics restores myogenesis in myotonic dystrophy type 1.
Resistance training diminishes mitochondrial adaptations to subsequent endurance training in healthy untrained men.
Opposing gene regulatory programs governing myofiber development and maturation revealed at single nucleus resolution.
AAV-mediated delivery of secreted acid α-glucosidase with enhanced uptake corrects neuromuscular pathology in Pompe mice.
The dark side of shift work: circadian misalignment of skeletal muscle.
Baf155 regulates skeletal muscle metabolism via HIF-1a signaling.
A Complete Workflow for High Throughput Human Single Skeletal Muscle Fiber Proteomics.
The Role of Sympathetic Innervation in Neonatal Muscle Growth and Neuromuscular Contractures.
Pro-fibrogenic and adipogenic aspects of chronic muscle degeneration are contributed by distinct stromal cell subpopulations.
Kinin receptors regulate skeletal muscle regeneration: differential effects for B1 and B2 receptors.
Deliberation on debilitating condition of cancer cachexia: Skeletal muscle wasting.
Autophagy signaling in hypertrophied muscles of diabetic and control rats.
Spinal and bulbar muscular atrophy: From molecular pathogenesis to pharmacological intervention targeting skeletal muscle.
Skeletal Muscle-Focused Guideline Development: Hierarchal Model Incorporating Muscle Form, Function, and Clinical Outcomes.
Autophagy in sarcopenia: Possible mechanisms and novel therapies.

Cell Signal. 2023 Jul 19. pii: S0898-6568(23)00229-2. [Epub ahead of print] 110815

Class I HDAC inhibitors attenuate dexamethasone-induced muscle atrophy via increased protein kinase C (PKC) delta phosphorylation.

Justine S Habibian, Matthew Bolino, Anthony Qian, Rebekah Woolsey, David Quilici, Juli Petereit, Bradley S Ferguson.

  Skeletal muscle atrophy is defined by wasting or decrease in muscle mass owing to injury, aging, malnutrition, chronic disuse or physical consequences of chronic illness. Under normal physiological conditions, a network of signal transduction pathways serves to balance muscle protein synthesis and proteolysis; however, metabolic shifts occur from protein synthesis to protein degradation that leads to a reduction in cross-sectional myofibers and can result in loss of skeletal muscle mass (atrophy) over time. Recent evidence highlights posttranslational modifications (PTMs) such as acetylation and phosphorylation in contractile dysfunction and muscle wasting. Indeed, histone deacetylase (HDAC) inhibitors have been shown to attenuate muscle atrophy and delay muscle damage in response to nutrient deprivation, in models of metabolic dysfunction and genetic models of muscle disease (e.g., muscle dystrophy). Despite our current understanding for lysine acetylation in muscle physiology, a role for HDACs in the regulation of muscle signal transduction remains a 'black box.' Using C2C12 myotubes stimulated with dexamethasone (Dex) as a model of muscle atrophy, we report that protein kinase C delta (PKCδ) phosphorylation decreased at threonine 505 (T505) and serine 643 (S643) in myotubes in response to muscle atrophy; these residues are important for PKCδ activity. Interestingly, PKCδ phosphorylation was restored/increased in myotubes treated with a pan-HDAC inhibitor or a class I selective HDAC inhibitor targeting HDACs1, -2, and - 3 in response to Dex. Moreover, we observed that Dex induced atrophy in skeletal muscle tissue in mice; this reduction in atrophy occurred rapidly, with weight loss noted by day 3 post-Dex and muscle weight loss noted by day 7. Similar to our findings in C2C12 myotubes, Dex attenuated phosphorylation of PKCδ at S643, while HDAC inhibition restored or increased PKCδ phosphorylation at both T505 and S643 in the tibialis anterior. Consistent with this hypothesis, we report that HDAC inhibition could not restore myotube size in response to Dex in the presence of a PKCδ inhibitor or when overexpressing a dominant negative PKCδ. Additionally, the overexpression of a constitutively active PKCδ prevented Dex-induced myotube atrophy. Combined, these data suggest that HDACs regulate muscle physiology via changes in intracellular signaling, namely PKCδ phosphorylation. Whether HDACs regulate PKCδ through canonical (e.g. gene-mediated regulation of phosphatases) or non-canonical (e.g. direct deacetylation of PKCδ to change phosphorylation states) mechanisms remain unclear and future research is needed to clarify this point.

Keywords:  HDACs; Histone deacetylases; Muscle wasting; PKCδ; Protein kinase C delta; Skeletal muscle atrophy

DOI:  https://doi.org/10.1016/j.cellsig.2023.110815
Bio Protoc. 2023 Jul 05. 13(13): e4759

In vivo Electroporation of Skeletal Muscle Fibers in Mice.

Steven J Foltz, Criss H Hartzell, Hyojung J Choo.

  In vitro models are essential for investigating the molecular, biochemical, and cell-biological aspects of skeletal muscle. Still, models that utilize cell lines or embryonic cells do not fully recapitulate mature muscle fibers in vivo. Protein function is best studied in mature differentiated tissue, where biological context is maintained, but this is often difficult when reliable detection reagents, such as antibodies, are not commercially available. Exogenous expression of tagged proteins in vivo solves some of these problems, but this approach can be technically challenging because either a mouse must be engineered for each protein of interest or viral vectors are required for adequate levels of expression. While viral vectors can infect target cells following local administration, they carry the risk of genome integration that may interfere with downstream analyses. Plasmids are another accessible expression system, but they require ancillary means of cell penetration; electroporation is a simple physical method for this purpose that requires minimal training or specialized equipment. Here, we describe a method for in vivo plasmid expression in a foot muscle following electroporation.

Keywords:  Imaging; In vivo transfection; Muscle biology; Muscular dystrophy; Skeletal muscle

DOI:  https://doi.org/10.21769/BioProtoc.4759
J Appl Physiol (1985). 2023 Jul 20.

Exercise-Induced Changes to the Fiber Type Specific Redox State in Human Skeletal Muscle are Associated with Aerobic Capacity.

James Shadiow, Edwin R Miranda, Ryan K Perkins, Corey E Mazo, Zhen Lin, Kendell N Lewis, Jacob T Mey, Thomas P J Solomon, Jacob M Haus.

  The benefits of exercise involve skeletal muscle redox state alterations of nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD). We determined the fiber-specific effects of acute exercise on the skeletal muscle redox state in healthy adults. Muscle biopsies were obtained from 19 (11 M, 8 F; 26±4 yrs) at baseline (fasted), and 30-min and 3h after treadmill exercise at 80% VO2max. Muscle samples were fiber typed probed for autofluorescence of NADH (excitation at 340-360nm) and oxidized flavoproteins (Fp; excitation at 440-470nm) to quantify the redox signatures of individual muscle fibers. Redox state was calculated as the oxidation-to-reduction redox ratio: Fp/(Fp+NADH). At baseline, the redox ratio of MHC I fibers was 7.2% higher than MHC IIa (p = 0.023, 95% CI: 5.2, 9.2%) and the redox ratio of MHC IIa was 8.0% higher than MHC IIx (p = 0.035, 95% CI: 6.8, 9.2%). MHC I fibers also displayed greater NADH intensity than MHC IIx (p = 0.007) and greater Fp intensity than both MHC IIa (p = 0.019) and MHC IIx (p < 0.0001). Fp intensities increased in all fiber types (p = 0.039) but redox ratios did not change (p = 0.483) 30 min after exercise. The change in redox ratio was positively correlated with VO2max (ml/min/kg) in MHC I (rho = 0.809, p = 0.004) and MHC IIa (rho = 0.782, p = 0.006) but not MHC IIx fibers (rho = 0.571, p = 0.151). These findings support the use of redox autofluorescence to interrogate skeletal muscle metabolism.

Keywords:  NAD/NADH; autofluorescence; exercise physiology; flavoproteins; oxygen delivery

DOI:  https://doi.org/10.1152/japplphysiol.00662.2022
bioRxiv. 2023 Jul 13. pii: 2023.05.11.540467. [Epub ahead of print]

Septin 7 Interacts With Numb To Preserve Sarcomere Structural Organization And Muscle Contractile Function.

Rita De Gasperi, Laszlo Csernoch, Beatrix Dienes, Monika Gonczi, Jayanta K Chakrabarty, Shahar Goeta, Abdurrahman Aslan, Carlos A Toro, David Karasik, Lewis M Brown, Marco Brotto, Christopher P Cardozo.

Here, we investigated mechanisms by which aging-related diminished levels of Numb in skeletal muscle fibers contribute to loss of muscle strength and power, two critical features of sarcopenia. Numb is an adaptor protein best known for its critical roles in development including asymmetric cell division, cell-type specification and termination of intracellular signaling. Numb expression is reduced in old humans and mice. We previously showed that, in skeletal muscle fibers, Numb is localized to sarcomeres where it is concentrated near triads. Conditional inactivation of Numb in myofibers causes weakness, disorganization of sarcomeres and smaller mitochondria with impaired function. Proteomics analysis of protein complexes isolated from C2C12 myotubes by immunoprecipitation using antibodies against Numb indicated that Septin 7 is a potential Numb binding partner. Septin 7 is a member of the family of GTP-binding proteins that organize into filaments, sheets and rings, and is considered part of the cytoskeleton. Immunofluorescence evaluation revealed a partial overlap of staining for Numb and Septin 7 in myofibers. Conditional, inducible knockouts of Numb led to disorganization of Septin 7 staining in myofibers. These findings support the conclusion that Septin 7 is a Numb binding partner. Because prior reports showed that conditional inactivation of Septin 7 in skeletal muscle led to weakness and disorganization of sarcomeres, and altered mitochondrial size, we also conclude that interactions between Numb and Septin 7 are critical for proper structural organization of the sarcomere, for optimal muscle contractile function, and for control of the size and function of mitochondria.

DOI: https://doi.org/10.1101/2023.05.11.540467
J Cachexia Sarcopenia Muscle. 2023 Jul 19.

Skeletal muscle-specific DJ-1 ablation-induced atrogenes expression and mitochondrial dysfunction contributing to muscular atrophy.

Shuang Zhang, Hongmei Yan, Jiyang Ding, Ruwen Wang, Yonghao Feng, Xinyi Zhang, Xingyu Kong, Hongyu Gong, Xiaodan Lu, Alice Ma, Yinghui Hua, Huan Liu, Jiani Guo, Huanqing Gao, Zhenqi Zhou, Ru Wang, Peijie Chen, Tiemin Liu, Xingxing Kong.

   BACKGROUND: DJ-1 is a causative gene for Parkinson's disease. DJ-1-deficient mice develop gait-associated progressive behavioural abnormalities and hypoactive forearm grip strength. However, underlying activity mechanisms are not fully explored.
METHODS: Western blotting and quantitative real-time polymerase chain reaction approaches were adopted to analyse DJ-1 expression in skeletal muscle from aged humans or mice and compared with young subjects. Skeletal muscle-specific-DJ-1 knockout (MDKO) mice were generated, followed by an assessment of the physical activity phenotypes (grip strength, maximal load capacity, and hanging, rotarod, and exercise capacity tests) of the MDKO and control mice on the chow diet. Muscular atrophy phenotypes (cross-sectional area and fibre types) were determined by imaging and quantitative real-time polymerase chain reaction. Mitochondrial function and skeletal muscle morphology were evaluated by oxygen consumption rate and electron microscopy, respectively. Tail suspension was applied to address disuse atrophy. RNA-seq analysis was performed to indicate molecular changes in muscles with DJ-1 ablation. Dual-luciferase reporter assays were employed to identify the promoter region of Trim63 and Fbxo32 genes, which were indirectly regulated by DJ-1 via the FoxO1 pathway. Cytoplasmic and nuclear fractions of DJ-1-deleted muscle cells were analysed by western blotting. Compound 23 was administered into the gastrocnemius muscle to mimic the of DJ-1 deletion effects.
RESULTS: DJ-1 expression decreased in atrophied muscles of aged human (young men, n = 2; old with aged men, n = 2; young women, n = 2; old with aged women, n = 2) and immobilization mice (n = 6, P < 0.01). MDKO mice exhibited no body weight difference compared with control mice on the chow diet (Flox, n = 8; MDKO, n = 9). DJ-1-deficient muscles were slightly dystrophic (Flox, n = 7; MDKO, n = 8; P < 0.05), with impaired physical activities and oxidative capacity (n = 8, P < 0.01). In disuse-atrophic conditions, MDKO mice showed smaller cross-sectional area (n = 5, P < 0.01) and more central nuclei than control mice (Flox, n = 7; MDKO, n = 6; P < 0.05), without alteration in muscle fibre types (Flox, n = 6; MDKO, n = 7). Biochemical analysis indicated that reduced mitochondrial function and upregulated of atrogenes induced these changes. Furthermore, RNA-seq analysis revealed enhanced activity of the FoxO1 signalling pathway in DJ-1-ablated muscles, which was responsible for the induction of atrogenes. Finally, compound 23 (an inhibitor of DJ-1) could mimic the effects of DJ-1 ablation in vivo.
CONCLUSIONS: Our results illuminate the crucial of skeletal muscle DJ-1 in the regulation of catabolic signals from mechanical stimulation, providing a therapeutic target for muscle wasting diseases.

Keywords:  Atrogenes; Atrophy; DJ-1; Skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13290
Life Sci. 2023 Jul 17. pii: S0024-3205(23)00583-0. [Epub ahead of print] 121948

Targeting NAT10 protects against sepsis-induced skeletal muscle atrophy by inhibiting ROS/NLRP3.

Chuntao Wang, Yukun Liu, Yongsheng Zhang, Dongfang Wang, Ligang Xu, Zhanfei Li, Xiangjun Bai, Yuchang Wang.

   AIMS: To identify N-acetyltransferase 10 (NAT10) and its downstream signaling pathways in myocytes and skeletal muscle, and to investigate its role in inflammation-induced muscle atrophy.
MATERIALS AND METHODS: Cecal ligation and puncture models were used to induce sepsis in C57BL/6 mice, which were treated with either a NAT10 inhibitor or a control agent. The therapeutic effect of NAT10 inhibitor was investigated by evaluating the mass, morphology, and molecular characteristics of mouse skeletal muscle. C2C12 cells were stimulated with LPS, and the expression of the NAT10 gene, downstream protein content, and atrophy phenotype were analyzed using a NAT10 inhibitor, to further explore the atrophic effect of NAT10 on C2C12 differentiated myotubes.
RESULTS: Gene set enrichment analysis revealed that NAT10 expression was elevated in the Lateral femoris muscle of patients with ICUAW. In vitro and in vivo experiments showed that sepsis or LPS induced the upregulation of NAT10 expression in skeletal muscles and C2C12 myotubes. Skeletal muscle mass, tissue morphology, gene expression, and protein content were associated with atrophic response in sepsis models. Remodelin ameliorated the LPS-induced skeletal muscle weight loss, as well as muscular atrophy, and improved survival. Remodelin reversed the atrophy program that was induced by inflammation through the downregulation of the ROS/NLRP3 pathway, along with the inhibition of the expression of MuRF1 and Atrogin-1.
CONCLUSION: NAT10 is closely related to skeletal muscle atrophy during sepsis. Remodelin improves the survival rate of mice by improving the systemic inflammatory response and skeletal muscle atrophy by downregulating the ROS/NLRP3 signaling pathway.

Keywords:  CLP; ICUAW; Muscle atrophy; NLRP3; ROS; Sepsis

DOI:  https://doi.org/10.1016/j.lfs.2023.121948
J Neuromuscul Dis. 2023 Jul 12.

Development of Assays to Measure GNE Gene Potency and Gene Replacement in Skeletal Muscle.

Deborah A Zygmunt, Patricia Lam, Anna Ashbrook, Katherine Koczwara, Angela Lek, Monkol Lek, Paul T Martin.

   BACKGROUND: GNE myopathy (GNEM) is a severe muscle disease caused by mutations in the UDP-GlcNAc-2-epimerase/ManNAc-6-kinase (GNE) gene, which encodes a bifunctional enzyme required for sialic acid (Sia) biosynthesis.
OBJECTIVE: To develop assays to demonstrate the potency of AAV gene therapy vectors in making Sia and to define the dose required for replacement of endogenous mouse Gne gene expression with human GNE in skeletal muscles.
METHODS: A MyoD-inducible Gne-deficient cell line, Lec3MyoDI, and a GNE-deficient human muscle cell line, were made and tested to define the potency of various AAV vectors to increase binding of Sia-specific lectins, including MAA and SNA. qPCR and qRT-PCR methods were used to quantify AAV biodistribution and GNE gene expression after intravenous delivery of AAV vectors designed with different promoters in wild-type mice.
RESULTS: Lec3 cells showed a strong deficit in MAA binding, while GNE-/-MB135 cells did not. Overexpressing GNE in Lec3 and Lec3MyoDI cells by AAV infection stimulated MAA binding in a dose-dependent manner. Use of a constitutive promoter, CMV, showed higher induction of MAA binding than use of muscle-specific promoters (MCK, MHCK7). rAAVrh74.CMV.GNE stimulated human GNE expression in muscles at levels equivalent to endogenous mouse Gne at a dose of 1×1013vg/kg, while AAVs with muscle-specific promoters required higher doses. AAV biodistribution in skeletal muscles trended higher when CMV was used as the promoter, and this correlated with increased sialylation of its viral capsid.
CONCLUSIONS: Lec3 and Lec3MyoDI cells work well to assay the potency of AAV vectors in making Sia. Systemic delivery of rAAVrh74.CMV.GNE can deliver GNE gene replacement to skeletal muscles at doses that do not overwhelm non-muscle tissues, suggesting that AAV vectors that drive constitutive organ expression could be used to treat GNEM.

Keywords:  AAV; GNE myopathy; gene therapy; muscular dystrophy; sialic acid

DOI:  https://doi.org/10.3233/JND-221596
Nat Commun. 2023 07 19. 14(1): 4033

Clearance of defective muscle stem cells by senolytics restores myogenesis in myotonic dystrophy type 1.

Talita C Conte, Gilberto Duran-Bishop, Zakaria Orfi, Inès Mokhtari, Alyson Deprez, Isabelle Côté, Thomas Molina, Tae-Yeon Kim, Lydia Tellier, Marie-Pier Roussel, Damien Maggiorani, Basma Benabdallah, Severine Leclerc, Lara Feulner, Ornella Pellerito, Jean Mathieu, Gregor Andelfinger, Cynthia Gagnon, Christian Beauséjour, Serge McGraw, Elise Duchesne, Nicolas A Dumont.

Muscle stem cells, the engine of muscle repair, are affected in myotonic dystrophy type 1 (DM1); however, the underlying molecular mechanism and the impact on the disease severity are still elusive. Here, we show using patients' samples that muscle stem cells/myoblasts exhibit signs of cellular senescence in vitro and in situ. Single cell RNAseq uncovers a subset of senescent myoblasts expressing high levels of genes related to the senescence-associated secretory phenotype (SASP). We show that the levels of interleukin-6, a prominent SASP cytokine, in the serum of DM1 patients correlate with muscle weakness and functional capacity limitations. Drug screening revealed that the senolytic BCL-XL inhibitor (A1155463) can specifically remove senescent DM1 myoblasts by inducing their apoptosis. Clearance of senescent cells reduced the expression of SASP, which rescued the proliferation and differentiation capacity of DM1 myoblasts in vitro and enhanced their engraftment following transplantation in vivo. Altogether, this study identifies the pathogenic mechanism associated with muscle stem cell defects in DM1 and opens a therapeutic avenue that targets these defective cells to restore myogenesis.

DOI: https://doi.org/10.1038/s41467-023-39663-3
J Physiol. 2023 Jul 20.

Resistance training diminishes mitochondrial adaptations to subsequent endurance training in healthy untrained men.

Paulo H C Mesquita, Joshua S Godwin, Bradley A Ruple, Casey L Sexton, Mason C McIntosh, Breanna J Mueller, Shelby C Osburn, C Brooks Mobley, Cleiton A Libardi, Kaelin C Young, L Bruce Gladden, Michael D Roberts, Andreas N Kavazis.

  We investigated the effects of performing a period of resistance training (RT) on the performance and molecular adaptations to a subsequent period of endurance training (ET). Twenty-five young adults were divided into an RT+ET group (n = 13), which underwent 7 weeks of RT followed by 7 weeks of ET, and an ET-only group (n = 12), which performed 7 weeks of ET. Body composition, endurance performance and muscle biopsies were collected before RT (T1, baseline for RT+ET), before ET (T2, after RT for RT+ET and baseline for ET) and after ET (T3). Immunohistochemistry was performed to determine fibre cross-sectional area (fCSA), myonuclear content, myonuclear domain size, satellite cell number and mitochondrial content. Western blots were used to quantify markers of mitochondrial remodelling. Citrate synthase activity and markers of ribosome content were also investigated. RT improved body composition and strength, increased vastus lateralis thickness, mixed and type II fCSA, myonuclear number, markers of ribosome content, and satellite cell content (P < 0.050). In response to ET, both groups similarly decreased body fat percentage (P < 0.0001) and improved endurance performance (e.g. V̇O2max${\dot V_{{{\mathrm{O}}_2}\max }}$ , and speed at which the onset of blood lactate accumulation occurred, P < 0.0001). Levels of mitochondrial complexes I-IV in the ET-only group increased 32-66%, while those in the RT+ET group increased 1-11% (time, P < 0.050). Additionally, mixed fibre relative mitochondrial content increased 15% in the ET-only group but decreased 13% in the RT+ET group (interaction, P = 0.043). In conclusion, RT performed prior to ET had no additional benefits to ET adaptations. Moreover, prior RT seemed to impair mitochondrial adaptations to ET. KEY POINTS: Resistance training is largely underappreciated as a method to improve endurance performance, despite reports showing it may improve mitochondrial function. Although several concurrent training studies are available, in this study we investigated the effects of performing a period of resistance training on the performance and molecular adaptations to subsequent endurance training. Prior resistance training did not improve endurance performance and impaired most mitochondrial adaptations to subsequent endurance training, but this effect may have been a result of detraining from resistance training.

Keywords:  HIIT; aerobic training; mitochondrial remodelling; skeletal muscle; strength training

DOI:  https://doi.org/10.1113/JP284822
Nat Commun. 2023 07 19. 14(1): 4333

Opposing gene regulatory programs governing myofiber development and maturation revealed at single nucleus resolution.

Matthieu Dos Santos, Akansha M Shah, Yichi Zhang, Svetlana Bezprozvannaya, Kenian Chen, Lin Xu, Weichun Lin, John R McAnally, Rhonda Bassel-Duby, Ning Liu, Eric N Olson.

Skeletal muscle fibers express distinct gene programs during development and maturation, but the underlying gene regulatory networks that confer stage-specific myofiber properties remain unknown. To decipher these distinctive gene programs and how they respond to neural activity, we generated a combined multi-omic single-nucleus RNA-seq and ATAC-seq atlas of mouse skeletal muscle development at multiple stages of embryonic, fetal, and postnatal life. We found that Myogenin, Klf5, and Tead4 form a transcriptional complex that synergistically activates the expression of muscle genes in developing myofibers. During myofiber maturation, the transcription factor Maf acts as a transcriptional switch to activate the mature fast muscle gene program. In skeletal muscles of mutant mice lacking voltage-gated L-type Ca2+ channels (Cav1.1), Maf expression and myofiber maturation are impaired. These findings provide a transcriptional atlas of muscle development and reveal genetic links between myofiber formation, maturation, and contraction.

DOI: https://doi.org/10.1038/s41467-023-40073-8
JCI Insight. 2023 Jul 18. pii: e170199. [Epub ahead of print]

AAV-mediated delivery of secreted acid α-glucosidase with enhanced uptake corrects neuromuscular pathology in Pompe mice.

Naresh K Meena, Davide Randazzo, Nina Raben, Rosa Puertollano.

  Gene therapy is under advanced clinical development for several lysosomal storage disorders. Pompe disease, a debilitating neuromuscular illness that affects infants, children, and adults with different degrees of severity, is caused by a deficiency of lysosomal glycogen-degrading enzyme acid alpha-glucosidase (GAA). Here, we demonstrated that adeno-associated virus (AAV9)-mediated systemic gene transfer fully reversed glycogen storage in all key therapeutic targets - skeletal and cardiac muscles, the diaphragm, and the central nervous system (CNS) - in both young and severely affected old Gaa knockout mice. Furthermore, the therapy reversed secondary cellular abnormalities in skeletal muscle, such as autophagy and mTORC1/AMPK signaling. We used a newly developed AAV9 vector encoding a chimeric human GAA protein with enhanced uptake and secretion to facilitate efficient spread of the expressed protein among multiple target tissues. These results lay the groundwork for future clinical development strategy in Pompe disease.

Keywords:  Autophagy; Gene therapy; Muscle Biology; Skeletal muscle

DOI:  https://doi.org/10.1172/jci.insight.170199
Nat Rev Endocrinol. 2023 Jul 20.

The dark side of shift work: circadian misalignment of skeletal muscle.

Ronan Lordan.

DOI: https://doi.org/10.1038/s41574-023-00875-8
PLoS Biol. 2023 Jul 21. 21(7): e3002192

Baf155 regulates skeletal muscle metabolism via HIF-1a signaling.

Jong-Seol Kang, Dongha Kim, Joonwoo Rhee, Ji-Yun Seo, Inkuk Park, Ji-Hoon Kim, Daewon Lee, WonUk Lee, Ye Lynne Kim, Kyusang Yoo, Sunghwan Bae, Jongkyeong Chung, Rho Hyun Seong, Young-Yun Kong.

During exercise, skeletal muscle is exposed to a low oxygen condition, hypoxia. Under hypoxia, the transcription factor hypoxia-inducible factor-1α (HIF-1α) is stabilized and induces expressions of its target genes regulating glycolytic metabolism. Here, using a skeletal muscle-specific gene ablation mouse model, we show that Brg1/Brm-associated factor 155 (Baf155), a core subunit of the switch/sucrose non-fermentable (SWI/SNF) complex, is essential for HIF-1α signaling in skeletal muscle. Muscle-specific ablation of Baf155 increases oxidative metabolism by reducing HIF-1α function, which accompanies the decreased lactate production during exercise. Furthermore, the augmented oxidation leads to high intramuscular adenosine triphosphate (ATP) level and results in the enhancement of endurance exercise capacity. Mechanistically, our chromatin immunoprecipitation (ChIP) analysis reveals that Baf155 modulates DNA-binding activity of HIF-1α to the promoters of its target genes. In addition, for this regulatory function, Baf155 requires a phospho-signal transducer and activator of transcription 3 (pSTAT3), which forms a coactivator complex with HIF-1α, to activate HIF-1α signaling. Our findings reveal the crucial role of Baf155 in energy metabolism of skeletal muscle and the interaction between Baf155 and hypoxia signaling.

DOI: https://doi.org/10.1371/journal.pbio.3002192
J Am Soc Mass Spectrom. 2023 Jul 18.

A Complete Workflow for High Throughput Human Single Skeletal Muscle Fiber Proteomics.

Amanda Momenzadeh, Yuming Jiang, Simion Kreimer, Laura E Teigen, Carlos S Zepeda, Ali Haghani, Mitra Mastali, Yang Song, Alexandre Hutton, Sarah J Parker, Jennifer E Van Eyk, Christopher W Sundberg, Jesse G Meyer.

Skeletal muscle is a major regulatory tissue of whole-body metabolism and is composed of a diverse mixture of cell (fiber) types. Aging and several diseases differentially affect the various fiber types, and therefore, investigating the changes in the proteome in a fiber-type specific manner is essential. Recent breakthroughs in isolated single muscle fiber proteomics have started to reveal heterogeneity among fibers. However, existing procedures are slow and laborious, requiring 2 h of mass spectrometry time per single muscle fiber; 50 fibers would take approximately 4 days to analyze. Thus, to capture the high variability in fibers both within and between individuals requires advancements in high throughput single muscle fiber proteomics. Here we use a single cell proteomics method to enable quantification of single muscle fiber proteomes in 15 min total instrument time. As proof of concept, we present data from 53 isolated skeletal muscle fibers obtained from two healthy individuals analyzed in 13.25 h. Adapting single cell data analysis techniques to integrate the data, we can reliably separate type 1 and 2A fibers. Ninety-four proteins were statistically different between clusters indicating alteration of proteins involved in fatty acid oxidation, oxidative phosphorylation, and muscle structure and contractile function. Our results indicate that this method is significantly faster than prior single fiber methods in both data collection and sample preparation while maintaining sufficient proteome depth. We anticipate this assay will enable future studies of single muscle fibers across hundreds of individuals, which has not been possible previously due to limitations in throughput.

DOI: https://doi.org/10.1021/jasms.3c00072
FEBS J. 2023 Jul 18.

The Role of Sympathetic Innervation in Neonatal Muscle Growth and Neuromuscular Contractures.

Mason T Runkel, Albaraa Tarabishi, Kritton Shay-Winkler, Marianne E Emmert, Qingnian Goh, Roger Cornwall.

  Neonatal brachial plexus injury (NBPI), a leading cause of pediatric upper limb paralysis, results in disabling and incurable muscle contractures that are driven by impaired longitudinal growth of denervated muscles. A rare form of NBPI, which maintains both afferent and sympathetic muscle innervation despite motor denervation, protects against contractures. We have previously ruled out a role for NRG/ErbB signaling, the predominant pathway governing antegrade afferent neuromuscular transmission, in modulating the formation of contractures. Our current study therefore investigated the contributions of sympathetic innervation of skeletal muscle in modulating NBPI-induced contractures. Through chemical sympathectomy and pharmacologic modification with a β2 -adrenergic agonist, we discovered that sympathetic innervation alone is neither required nor sufficient to modulate contracture formation in neonatal mice. Despite this, sympathetic innervation plays an intriguing sex-specific role in mediating neonatal muscle growth, as the cross-sectional area (CSA) and volume of normally innervated male muscles were diminished by ablation of sympathetic neurons and increased by β-adrenergic stimulation. Intriguingly, the robust alterations in CSA occurred with minimal changes to normal longitudinal muscle growth as determined by sarcomere length. Instead, β-adrenergic stimulation exacerbated sarcomere overstretch in denervated male muscles, indicating potentially discrete regulation of muscle width and length. Future investigations into the mechanistic underpinnings of these distinct aspects of muscle growth are thus essential for improving clinical outcomes in patients affected by muscle disorders in which both length and width are affected.

Keywords:  Beta-adrenergic signaling; Beta2 agonist; Denervation; Muscle Atrophy; Muscle Growth; Neonatal Brachial Plexus Injury; Neuromuscular Contractures; Sympathectomy; Sympathetic Innervation

DOI:  https://doi.org/10.1111/febs.16908
PLoS One. 2023 ;18(7): e0288800

Pro-fibrogenic and adipogenic aspects of chronic muscle degeneration are contributed by distinct stromal cell subpopulations.

Cansu Özdemir, Duygu Akçay, Diğdem Yöyen-Ermiş, Ekim Zihni Taşkıran, Rana Soylu-Kucharz, Güneş Esendağlı, Yusuf Çetin Kocaefe.

Chronic skeletal muscle degeneration is characterized by fiber atrophy accompanied by deposition of extracellular matrix (ECM) components and fatty infiltration. Excessive accumulation of ECM leads to fibrosis via the contribution of fibro-adipogenic precursors (FAPs). Fibrosis also accompanies disuse atrophy and sarcopenia without significant inflammation. The present study aimed to comparatively analyze heterogeneous population of FAPs during acute injury and immobilization (tenotomy and denervation). The comparative analysis was accomplished based on the following 3 stromal cell subpopulations: i) CD140a(+)/Sca1(+); ii) CD140a(+)/Sca1(-); iii) CD140a(-)/Sca1(+). RNASeq analysis was employed to characterize and compare their quiescent and activated states. Whereas CD140a(-)/Sca1(+) was the most predominant activated subpopulation in tenotomy, denervation stimulated the CD140a(+)/Sca1(+) subpopulation. Immobilization models lacked myofiber damage and exhibited a minute increase in CD45(+) cells, as compared to acute injury. Transcriptome analysis showed common and discordant regulation of ECM components, without profound proliferative activation. Herein, we suggest unique surface markers for further identification of the investigated cell subpopulations. FAP subpopulations show similar activation kinetics in an inflammatory environment but the present findings highlight the fact that inflammation may not be a prerequisite for FAP activation. Delayed proliferation kinetics indicate that signals beyond inflammation might trigger FAP activation, leading to irreversible stromal changes.

DOI: https://doi.org/10.1371/journal.pone.0288800
Inflamm Res. 2023 Jul 18.

Kinin receptors regulate skeletal muscle regeneration: differential effects for B1 and B2 receptors.

Leonardo Martins, Weslley Wallace Amorim, Marcos Fernandes Gregnani, Ronaldo de Carvalho Araújo, Fatimunnisa Qadri, Michael Bader, João Bosco Pesquero.

   OBJECTIVE AND DESIGN: After traumatic skeletal muscle injury, muscle healing is often incomplete and produces extensive fibrosis. Bradykinin (BK) reduces fibrosis in renal and cardiac damage models through the B2 receptor. The B1 receptor expression is induced by damage, and blocking of the kallikrein-kinin system seems to affect the progression of muscular dystrophy. We hypothesized that both kinin B1 and B2 receptors could play a differential role after traumatic muscle injury, and the lack of the B1 receptor could produce more cellular and molecular substrates for myogenesis and fewer substrates for fibrosis, leading to better muscle healing.
MATERIAL AND METHODS: To test this hypothesis, tibialis anterior muscles of kinin receptor knockout animals were subjected to traumatic injury. Myogenesis, angiogenesis, fibrosis, and muscle functioning were evaluated.
RESULTS: Injured B1KO mice showed a faster healing progression of the injured area with a larger amount of central nucleated fiber post-injury when compared to control mice. In addition, they exhibited higher neovasculogenic capacity, maintaining optimal tissue perfusion for the post-injury phase; had higher amounts of myogenic markers with less inflammatory infiltrate and tissue destruction. This was followed by higher amounts of SMAD7 and lower amounts of p-SMAD2/3, which resulted in less fibrosis. In contrast, B2KO and B1B2KO mice showed more severe tissue destruction and excessive fibrosis. B1KO animals had better results in post-injury functional tests compared to control animals.
CONCLUSIONS: We demonstrate that injured skeletal muscle tissues have a better repair capacity with less fibrosis in the presence of B2 receptor and absence of B1 receptor, including better performances in functional tests.

Keywords:  Contusion; Fibrosis; Injury; Kinin; Myogenesis; Skeletal muscle

DOI:  https://doi.org/10.1007/s00011-023-01766-4
Fundam Clin Pharmacol. 2023 Jul 20.

Deliberation on debilitating condition of cancer cachexia: Skeletal muscle wasting.

Srusti Dave, Bhoomika M Patel.

   BACKGROUND: Cancer cachexia is a debilitating syndrome associated with marked body loss because of muscular atrophy and fat loss. There are several mechanisms contributing to the pathogenesis of cachexia. The presence of the tumor releases cytokines from inflammatory and immune cells, which play a significant role in activating and deactivating certain pathways associated with protein, carbohydrate, and lipid metabolism. This review focuses on various cascades involving an imbalance between protein synthesis and degradation in the skeletal muscles.
OBJECTIVES: This study aimed to elucidate the mechanisms involved in skeletal muscle wasting phenomenon over the last few years.
METHODS: This article briefly overviews different pathways responsible for muscle atrophy in cancer cachexia. Studies published up to April 2023 were included. Important findings and study contributions were chosen and compiled using several databases including PubMed, Google Scholar, Science Direct, and ClinicalTrials.gov using relevant keywords.
RESULTS: Cancer cachexia is a complex disease involving multiple factors resulting in atrophy of skeletal muscles. Systemic inflammation, altered energy balance and carbohydrate metabolism, altered lipid and protein metabolism, and adipose tissue browning are some of the major culprits in cancer cachexia. Increased protein degradation and decreased protein synthesis lead to muscle atrophy. Changes in signaling pathway like ubiquitin-proteasome, autophagy, mTOR, AMPK, and IGF-1 also lead to muscle wasting. Physical exercise, nutritional supplementation, steroids, myostatin inhibitors, and interventions targeting on inflammation have been investigated to treat cancer cachexia. Some therapy showed positive results in preclinical and clinical settings, although more research on the efficacy and safety of the treatment should be done.
CONCLUSION: Muscle atrophy in cancer cachexia is the result of multiple complex mechanisms; as a result, a lot more research has been done to describe the pathophysiology of the disease. Targeted therapy and multimodal interventions can improve clinical outcomes for patients.

Keywords:  cancer-associated cachexia; inflammation; protein breakdown; protein synthesis; skeletal muscle wasting; weight loss

DOI:  https://doi.org/10.1111/fcp.12931
FEBS Open Bio. 2023 Jul 20.

Autophagy signaling in hypertrophied muscles of diabetic and control rats.

M V M Scervino, M A S Fortes, K F Vitzel, D R de Souza, G M Murata, G O Santana, E B da Silva, A C Levada-Pires, W M T Kuwabara, T C A Loureiro, R Curi.

  Autophagy plays a vital role in cell homeostasis by eliminating nonfunctional components and promoting cell survival. Here, we examined the levels of autophagy signaling proteins after seven days of overload hypertrophy in the extensor digitorum longus (EDL) and soleus muscles of control and diabetic rats. We compared control and 3-day streptozotocin-induced diabetic rats, an experimental model for type 1 diabetes mellitus (T1DM). EDL muscles showed increased levels of basal autophagy signaling proteins. The diabetic state did not affect the extent of overload-induced hypertrophy or the levels of autophagy signaling proteins (p-ULK1, Beclin-1, Atg5, Atg12-5, Atg7, Atg3, LC3-I and II, and p62) in either muscle. The p-ULK-1, Beclin-1, and p62 protein expression levels were higher in the EDL muscle than in the soleus before the hypertrophic stimulus. On the other hand, the soleus muscle exhibited increased autophagic signaling after overload-induced hypertrophy, with increases in Beclin-1, Atg5, Atg12-5, Atg7, Atg3, and LC3-I expression in the control and diabetic groups, in addition to p-ULK-1 in the control groups. After hypertrophy, Beclin-1 and Atg5 levels increased in the EDL muscle of both groups, while p-ULK1 and LC3-I increased in the control group. In conclusion, the baseline EDL muscle exhibited higher autophagy than the soleus muscle. Although TDM1 promotes skeletal muscle mass loss and strength reduction, it did not significantly alter the extent of overload-induced hypertrophy and autophagy signaling proteins in EDL and soleus muscles, with the two groups exhibiting different patterns of autophagy activation.

Keywords:  Autolysosome; Autophagosome; Autophagy-related genes; Hyperglycemia; Protein degradation

DOI:  https://doi.org/10.1002/2211-5463.13677
Curr Opin Pharmacol. 2023 Jul 16. pii: S1471-4892(23)00049-8. [Epub ahead of print]71 102394

Spinal and bulbar muscular atrophy: From molecular pathogenesis to pharmacological intervention targeting skeletal muscle.

Caterina Marchioretti, Roberta Andreotti, Emanuela Zuccaro, Andrew P Lieberman, Manuela Basso, Maria Pennuto.

The clinical characteristics of SBMA, also known as Kennedy's disease (OMIM 313200), were initially documented by Dr. H Kawahara in the 18th century and a hundred years later by Dr. W. Kennedy. SBMA is a neuromuscular disease caused by expansions of a CAG microsatellite tandem repeat in exon 1 of the androgen receptor (AR) gene located on the X chromosome. These expansions result in the production of AR with an aberrantly expanded polyglutamine (polyQ) tract. In this review, we explore recent advancements in the significance of gene expression changes in skeletal muscle and discuss how pharmacological interventions targeting this aspect of disease pathogenesis can potentially be translated into therapies for SBMA patients.

DOI: https://doi.org/10.1016/j.coph.2023.102394
Appl Physiol Nutr Metab. 2023 Jul 20.

Skeletal Muscle-Focused Guideline Development: Hierarchal Model Incorporating Muscle Form, Function, and Clinical Outcomes.

Steven Heymsfield, Carla M Prado, Maria Cristina Gonzalez.

Sarcopenia, sarcopenic obesity, malnutrition, and cachexia clinical guidelines were created by expert consensus over the past decade. These pathological states all share in common deficits in skeletal muscle mass, and in some cases muscle function, that adversely impact patient outcomes. Early identification is key as some detrimental outcomes are potentially preventable with available treatments. The four guidelines share common design features: patient's suspected of having the condition are first screened with a focused clinical history; if positive, the next step is evaluation with either a measure of body "form" (e.g., mass, shape, composition) or function (e.g., mechanical, endurance, metabolic); combined form and functional criteria are also recognized. The form and functional "gateway" nodes establish whether or not to proceed with further evaluations and treatments. Intensive discussions among experts focus on selection of these gateway nodes and the final choice is made when consensus is reached. Form and functional measures are often treated as equivalent alternatives when framed in the context of "outcomes" for which they are intended to predict. Here we adapt a classic biological concept stating that "function follows form" to show that pathophysiological links are present between these two different muscle qualities and clinical outcomes. We argue that a hierarchy exists such that outcomes closely follow function that, in turn, follow form…the OFF rule. The OFF rule: explains why functional measures often show stronger associations with outcomes than those quantifying form; helps to frame debates on how to structure the gateway nodes used to identify patients for further evaluation and treatment; and sets out a pathophysiological structure for developing future outcome prediction models.

DOI: https://doi.org/10.1139/apnm-2023-0176
Biomed Pharmacother. 2023 Jul 18. pii: S0753-3322(23)00938-1. [Epub ahead of print]165 115147

Autophagy in sarcopenia: Possible mechanisms and novel therapies.

Guangyang Xie, Hongfu Jin, Herasimenka Mikhail, Volotovski Pavel, Guang Yang, Bingzhou Ji, Bangbao Lu, Yusheng Li.

  With global population aging, age-related diseases, especially sarcopenia, have attracted much attention in recent years. Characterized by low muscle strength, low muscle quantity or quality and low physical performance, sarcopenia is one of the major factors associated with an increased risk of falls and disability. Much effort has been made to understand the cellular biological and physiological mechanisms underlying sarcopenia. Autophagy is an important cellular self-protection mechanism that relies on lysosomes to degrade misfolded proteins and damaged organelles. Research designed to obtain new insight into human diseases from the autophagic aspect has been carried out and has made new progress, which encourages relevant studies on the relationship between autophagy and sarcopenia. Autophagy plays a protective role in sarcopenia by modulating the regenerative capability of satellite cells, relieving oxidative stress and suppressing the inflammatory response. This review aims to reveal the specific interaction between sarcopenia and autophagy and explore possible therapies in hopes of encouraging more specific research in need and unlocking novel promising therapies to ameliorate sarcopenia.

Keywords:  Autophagy; Inflammation; Oxidative stress; Sarcopenia; Satellite cell

DOI:  https://doi.org/10.1016/j.biopha.2023.115147