bims-moremu 2023-03-05 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–03–05
34 papers selected by
Anna Vainshtein, Craft Science Inc.

DOCK3 regulates normal skeletal muscle regeneration and glucose metabolism.
Dysfunctional mitochondria accumulate in a skeletal muscle knockout model of Smn1, the causal gene of spinal muscular atrophy.
MYTHO is a novel regulator of skeletal muscle autophagy and integrity.
Global deletion of CCL2 has adverse impacts on recovery of skeletal muscle fiber size and function and is muscle-specific.
Protein turnover in skeletal muscle: looking at molecular regulation towards active lifestyle.
Denervation Atrophy of Skeletal Muscle is Not Influenced by Numb Levels in Mice.
Six weeks of N-acetylcysteine antioxidant in drinking water decreases pathological fiber branching in MDX mouse dystrophic fast-twitch skeletal muscle.
Thyroid-stimulating hormone receptor signaling restores skeletal muscle stem cell regeneration in rats with muscular dystrophy.
Comprehensive Analyses of Muscle Function, Lean and Muscle Mass, and Myofiber Typing in Mice.
Molecular mechanisms of cancer cachexia-related loss of skeletal muscle mass: data analysis from preclinical and clinical studies.
Quantitative proteomic analysis of skeletal muscles from wild-type and transgenic mice carrying recessive Ryr1 mutations linked to congenital myopathies.
Complete Workflow for High Throughput Human Single Skeletal Muscle Fiber Proteomics.
Etiology of genetic muscle disorders induced by mutations in fast and slow skeletal MyBP-C paralogs.
Nicotinamide Phosphoribosyltransferase-elevated NAD+ biosynthesis prevents muscle disuse atrophy by reversing mitochondrial dysfunction.
Multiomics reveals glutathione metabolism as a driver of bimodality during stem cell aging.
Outside the fiber: Endomysial stromal and capillary pathology in skeletal muscle may impede infusion therapy in infantile-onset Pompe disease.
Dietary phosphate restriction prevents the appearance of sarcopenia signs in old mice.
Delivery challenges for CRISPR-Cas9 genome editing for Duchenne muscular dystrophy.
LncRNA XLOC_015548 affects the proliferation and differentiation of myoblasts via the MAPK signaling pathway.
Antagonism of TRPV4 channels partially reduces mechanotransduction in rat skeletal muscle afferents.
Quantitative model of aging-related muscle degeneration: a Drosophila study.
Effects of CX3CR1 and CXCR2 antagonists on running-dependent intramuscular neutrophil recruitments and myokine upregulation.
IRE1α arm of unfolded protein response in muscle-specific TGF-β signaling-mediated regulation of muscle cell immunological properties.
Validation of the association between MRI and gene signatures in facioscapulohumeral dystrophy muscle: implications for clinical trial design.
Dynamical modeling reveals RNA decay mediates the effect of matrix stiffness on aged muscle stem cell fate.
Quantitative analysis of myofiber type composition in human and mouse skeletal muscles.
The distinctive mechanical and structural signatures of residual force enhancement in myofibers.
Irisin: An anti-inflammatory exerkine in aging and redox-mediated comorbidities.
Regulation and mechanism of action of miRNAs on insulin resistance in skeletal muscles.
Quantification of autophagy flux in isolated mouse skeletal muscle fibers with overexpression of fluorescent protein mCherry-EGFP-LC3.
When dysbiosis meets dystrophy: an unwanted gut-muscle connection.
A spinal muscular atrophy modifier implicates the SMN protein in SNARE complex assembly at neuromuscular synapses.
Cancer cachexia: involvement of an expanding macroenvironment.
Considerations for designing trials targeting muscle dysfunction in exercise oncology.

bioRxiv. 2023 Feb 27. pii: 2023.02.22.529576. [Epub ahead of print]

DOCK3 regulates normal skeletal muscle regeneration and glucose metabolism.

Adrienne Samani, Muthukumar Karuppasamy, Katherine G English, Colin A Siler, Yimin Wang, Jeffrey J Widrick, Matthew S Alexander.

DOCK (dedicator of cytokinesis) is an 11-member family of typical guanine nucleotide exchange factors (GEFs) expressed in the brain, spinal cord, and skeletal muscle. Several DOCK proteins have been implicated in maintaining several myogenic processes such as fusion. We previously identified DOCK3 as being strongly upregulated in Duchenne muscular dystrophy (DMD), specifically in the skeletal muscles of DMD patients and dystrophic mice. Dock3 ubiquitous KO mice on the dystrophin-deficient background exacerbated skeletal muscle and cardiac phenotypes. We generated Dock3 conditional skeletal muscle knockout mice (Dock3 mKO) to characterize the role of DOCK3 protein exclusively in the adult muscle lineage. Dock3 mKO mice presented with significant hyperglycemia and increased fat mass, indicating a metabolic role in the maintenance of skeletal muscle health. Dock3 mKO mice had impaired muscle architecture, reduced locomotor activity, impaired myofiber regeneration, and metabolic dysfunction. We identified a novel DOCK3 interaction with SORBS1 through the C-terminal domain of DOCK3 that may account for its metabolic dysregulation. Together, these findings demonstrate an essential role for DOCK3 in skeletal muscle independent of DOCK3 function in neuronal lineages.

DOI: https://doi.org/10.1101/2023.02.22.529576
Cell Death Dis. 2023 Feb 27. 14(2): 162

Dysfunctional mitochondria accumulate in a skeletal muscle knockout model of Smn1, the causal gene of spinal muscular atrophy.

Francesco Chemello, Michela Pozzobon, Lorenza Iolanda Tsansizi, Tatiana Varanita, Rubèn Quintana-Cabrera, Daniele Bonesso, Martina Piccoli, Gerolamo Lanfranchi, Marta Giacomello, Luca Scorrano, Camilla Bean.

The approved gene therapies for spinal muscular atrophy (SMA), caused by loss of survival motor neuron 1 (SMN1), greatly ameliorate SMA natural history but are not curative. These therapies primarily target motor neurons, but SMN1 loss has detrimental effects beyond motor neurons and especially in muscle. Here we show that SMN loss in mouse skeletal muscle leads to accumulation of dysfunctional mitochondria. Expression profiling of single myofibers from a muscle specific Smn1 knockout mouse model revealed down-regulation of mitochondrial and lysosomal genes. Albeit levels of proteins that mark mitochondria for mitophagy were increased, morphologically deranged mitochondria with impaired complex I and IV activity and respiration and that produced excess reactive oxygen species accumulated in Smn1 knockout muscles, because of the lysosomal dysfunction highlighted by the transcriptional profiling. Amniotic fluid stem cells transplantation that corrects the SMN knockout mouse myopathic phenotype restored mitochondrial morphology and expression of mitochondrial genes. Thus, targeting muscle mitochondrial dysfunction in SMA may complement the current gene therapy.

DOI: https://doi.org/10.1038/s41419-023-05573-x
Nat Commun. 2023 Mar 02. 14(1): 1199

MYTHO is a novel regulator of skeletal muscle autophagy and integrity.

Jean-Philippe Leduc-Gaudet, Anais Franco-Romero, Marina Cefis, Alaa Moamer, Felipe E Broering, Giulia Milan, Roberta Sartori, Tomer Jordi Chaffer, Maude Dulac, Vincent Marcangeli, Dominique Mayaki, Laurent Huck, Anwar Shams, José A Morais, Elise Duchesne, Hanns Lochmuller, Marco Sandri, Sabah N A Hussain, Gilles Gouspillou.

Autophagy is a critical process in the regulation of muscle mass, function and integrity. The molecular mechanisms regulating autophagy are complex and still partly understood. Here, we identify and characterize a novel FoxO-dependent gene, d230025d16rik which we named Mytho (Macroautophagy and YouTH Optimizer), as a regulator of autophagy and skeletal muscle integrity in vivo. Mytho is significantly up-regulated in various mouse models of skeletal muscle atrophy. Short term depletion of MYTHO in mice attenuates muscle atrophy caused by fasting, denervation, cancer cachexia and sepsis. While MYTHO overexpression is sufficient to trigger muscle atrophy, MYTHO knockdown results in a progressive increase in muscle mass associated with a sustained activation of the mTORC1 signaling pathway. Prolonged MYTHO knockdown is associated with severe myopathic features, including impaired autophagy, muscle weakness, myofiber degeneration, and extensive ultrastructural defects, such as accumulation of autophagic vacuoles and tubular aggregates. Inhibition of the mTORC1 signaling pathway in mice using rapamycin treatment attenuates the myopathic phenotype triggered by MYTHO knockdown. Skeletal muscles from human patients diagnosed with myotonic dystrophy type 1 (DM1) display reduced Mytho expression, activation of the mTORC1 signaling pathway and impaired autophagy, raising the possibility that low Mytho expression might contribute to the progression of the disease. We conclude that MYTHO is a key regulator of muscle autophagy and integrity.

DOI: https://doi.org/10.1038/s41467-023-36817-1
J Appl Physiol (1985). 2023 Mar 02.

Global deletion of CCL2 has adverse impacts on recovery of skeletal muscle fiber size and function and is muscle-specific.

Patrick J Ferrara, Paul T Reidy, Jonathan J Petrocelli, Elena M Yee, Dennis K Fix, Ziad S Mahmassani, Jessie A Montgomery, Alec I McKenzie, Naomi M M P de Hart, Micah J Drummond.

  Timely and complete recovery of muscle mass and function following a bout of physical disuse are critical components of returning to normal activities of daily living and lifestyle. Proper cross talk between the muscle tissue and myeloid cells (e.g., macrophages) throughout the recovery period from disuse atrophy plays a significant role for complete resolution of muscle size and function. Chemokine C-C motif ligand 2 (CCL2) has a critical function of recruiting macrophages during the early phase of muscle damage. However, the importance of CCL2 has not been defined in the context of disuse and recovery; a physiologically relevant model of atrophy and regrowth. Here, we utilized a mouse model of whole-body CCL2 deletion (CCL2KO) and subjected them to a period of hindlimb unloading followed by reloading to investigate the importance of CCL2 on the regrowth of muscle following disuse atrophy using ex vivo muscle tests, immunohistochemistry and FACS approaches. We show mice that lack CCL2 display an incomplete recovery of muscle mass, myofiber cross-sectional area, and muscle function during the recovery from disuse atrophy. Mice that lack CCL2 have decreased skeletal muscle collagen turnover which may be related to defects in muscle function and stiffness. In addition, we show that the recruitment of macrophages to skeletal muscle is dramatically reduced in CCL2KO mice during the recovery from disuse atrophy, which likely precipitates poor recovery of muscle size and function and aberrant collagen remodeling.

Keywords:  atrophy; chemokine; function; macrophage; skeletal muscle

DOI:  https://doi.org/10.1152/japplphysiol.00444.2022
Int J Sports Med. 2023 Feb 28.

Protein turnover in skeletal muscle: looking at molecular regulation towards active lifestyle.

Rita Pinho Ferreira, Jose Alberto Duarte.

Skeletal muscle is a highly plastic tissue, able to change its mass and functional properties in response to several stimuli. Skeletal muscle mass is influenced by the balance between protein synthesis and breakdown, which is regulated by several signaling pathways. The relative contribution of Akt/mTOR signaling, ubiquitin-proteasome pathway, autophagy among other signaling pathways to protein turnover and, therefore, to skeletal muscle mass differs depending on the wasting or loading condition and muscle type. By modulating mitochondria biogenesis, PGC-1α has a major role in cell's bioenergetic status and, thus, on protein turnover. In fact, rates of protein turnover regulate differently the levels of distinct protein classes in response to atrophic or hypertrophic stimuli. Mitochondrial protein turnover rates may be enhanced in wasting conditions whereas the increased turnover of myofibrillar proteins triggers muscle mass gain. The present review aims to update the knowledge on the molecular pathways implicated in the regulation of protein turnover in skeletal muscle, focusing on how distinct muscle proteins may be modulated by lifestyle interventions with emphasis on exercise training. The comprehensive analysis of the anabolic effects of exercise programs will pave the way to the tailored management of muscle wasting conditions.

DOI: https://doi.org/10.1055/a-2044-8277
Int J Med Sci. 2023 ;20(3): 376-384

Denervation Atrophy of Skeletal Muscle is Not Influenced by Numb Levels in Mice.

Abdurrahman Aslan, Lauren Harlow, Xin-Hua Liu, Rita De Gasperi, William A Bauman, Marco Brotto, Christopher P Cardozo.

  Skeletal muscle undergoes rapid and extensive atrophy following nerve transection though the underlying mechanisms remain incompletely understood. We previously showed transiently elevated Notch 1 signaling in denervated skeletal muscle that was abrogated by administration of nandrolone (an anabolic steroid) combined with replacement doses of testosterone. Numb is an adaptor molecule present in myogenic precursors and skeletal muscle fibers that is vital for normal tissue repair after muscle injury and for skeletal muscle contractile function. It is unclear whether the increase in Notch signaling observed in denervated muscle contributes to denervation and whether expression of Numb in myofibers slows denervation atrophy. To address these questions, the degree of denervation atrophy, Notch signaling, and Numb expression was studied over time after denervation in C57B6J mice treated with nandrolone, nandrolone plus testosterone or vehicle. Nandrolone increased Numb expression and reduced Notch signaling. Neither nandrolone alone nor nandrolone plus testosterone changed the rate of denervation atrophy. We next compared rates of denervation atrophy between mice with conditional, tamoxifen-inducible knockout of Numb in myofibers and genetically identical mice treated with vehicle. Numb cKO had no effect on denervation atrophy in this model. Taken together, the data indicate that loss of Numb in myofibers does not alter the course of denervation atrophy and that upregulation of Numb and blunting of the denervation-atrophy induced activation of Notch do not change the course of denervation atrophy.

Keywords:  aging; denervation atrophy; nandrolone; numb; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.7150/ijms.77603
Front Physiol. 2023 ;14 1109587

Six weeks of N-acetylcysteine antioxidant in drinking water decreases pathological fiber branching in MDX mouse dystrophic fast-twitch skeletal muscle.

Asma Redwan, Leonit Kiriaev, Sindy Kueh, John W Morley, Peter Houweling, Ben D Perry, Stewart I Head.

  Introduction: It has been proposed that an increased susceptivity to oxidative stress caused by the absence of the protein dystrophin from the inner surface of the sarcolemma is a trigger of skeletal muscle necrosis in the destructive dystrophin deficient muscular dystrophies. Here we use the mdx mouse model of human Duchenne Muscular Dystrophy to test the hypothesis that adding the antioxidant NAC at 2% to drinking water for six weeks will treat the inflammatory phase of the dystrophic process and reduce pathological muscle fiber branching and splitting resulting in a reduction of mass in mdx fast-twitch EDL muscles. Methods: Animal weight and water intake was recorded during the six weeks when 2% NAC was added to the drinking water. Post NAC treatment animals were euthanised and the EDL muscles dissected out and placed in an organ bath where the muscle was attached to a force transducer to measure contractile properties and susceptibility to force loss from eccentric contractions. After the contractile measurements had been made the EDL muscle was blotted and weighed. In order to assess the degree of pathological fiber branching mdx EDL muscles were treated with collagenase to release single fibers. For counting and morphological analysis single EDL mdx skeletal muscle fibers were viewed under high magnification on an inverted microscope. Results: During the six-week treatment phase NAC reduced body weight gain in three- to nine-week-old mdx and littermate control mice without effecting fluid intake. NAC treatment also significantly reduced the mdx EDL muscle mass and abnormal fiber branching and splitting. Discussion: We propose chronic NAC treatment reduces the inflammatory response and degenerative cycles in the mdx dystrophic EDL muscles resulting in a reduction in the number of complexed branched fibers reported to be responsible for the dystrophic EDL muscle hypertrophy.

Keywords:  NAC; dystrophy; fiber branching; mdx; muscle damage; oxidative stress; skeletal muscle contraction; split fiber

DOI:  https://doi.org/10.3389/fphys.2023.1109587
Sci Transl Med. 2023 Mar;15(685): eadd5275

Thyroid-stimulating hormone receptor signaling restores skeletal muscle stem cell regeneration in rats with muscular dystrophy.

Valentina Taglietti, Kaouthar Kefi, Lea Rivera, Oriane Bergiers, Nastasia Cardone, Fanny Coulpier, Stamatia Gioftsidi, Bernadette Drayton-Libotte, Cyrielle Hou, François-Jérôme Authier, France Pietri-Rouxel, Matthieu Robert, Dominique Bremond-Gignac, Claudio Bruno, Chiara Fiorillo, Edoardo Malfatti, Peggy Lafuste, Laurent Tiret, Frédéric Relaix.

Duchenne muscular dystrophy (DMD) is a severe and progressive myopathy leading to motor and cardiorespiratory impairment. We analyzed samples from patients with DMD and a preclinical rat model of severe DMD and determined that compromised repair capacity of muscle stem cells in DMD is associated with early and progressive muscle stem cell senescence. We also found that extraocular muscles (EOMs), which are spared by the disease in patients, contain muscle stem cells with long-lasting regenerative potential. Using single-cell transcriptomics analysis of muscles from a rat model of DMD, we identified the gene encoding thyroid-stimulating hormone receptor (Tshr) as highly expressed in EOM stem cells. Further, TSHR activity was involved in preventing senescence. Forskolin, which activates signaling downstream of TSHR, was found to reduce senescence of skeletal muscle stem cells, increase stem cell regenerative potential, and promote myogenesis, thereby improving muscle function in DMD rats. These findings indicate that stimulation of adenylyl cyclase leads to muscle repair in DMD, potentially providing a therapeutic approach for patients with the disease.

DOI: https://doi.org/10.1126/scitranslmed.add5275
Bio Protoc. 2023 Feb 20. 13(4): e4617

Comprehensive Analyses of Muscle Function, Lean and Muscle Mass, and Myofiber Typing in Mice.

Hima Bindu Durumutla, Chiara Villa, Manoj Panta, Michelle Wintzinger, Ashok Daniel Prabakaran Pragasam, Karen Miz, Mattia Quattrocelli.

  Skeletal muscle disorders commonly affect the function and integrity of muscles. Novel interventions bring new potential to rescue or alleviate the symptoms associated with these disorders. In vivo and in vitro testing in mouse models allows quantitative evaluation of the degree of muscle dysfunction, and therefore, the level of potential rescue/restoration by the target intervention. Several resources and methods are available to assess muscle function and lean and muscle mass, as well as myofiber typing as separate concepts; however, a technical resource unifying these methods is missing. Here, we provide detailed procedures for analyzing muscle function, lean and muscle mass, and myofiber typing in a comprehensive technical resource paper. Graphical abstract.

Keywords:  Lean and muscle mass; Muscle cross sectional area; Muscle force; Muscle function; Myofiber type; Skeletal muscle

DOI:  https://doi.org/10.21769/BioProtoc.4617
J Cachexia Sarcopenia Muscle. 2023 Mar 02.

Molecular mechanisms of cancer cachexia-related loss of skeletal muscle mass: data analysis from preclinical and clinical studies.

Agnès Martin, Yann S Gallot, Damien Freyssenet.

  Cancer cachexia is a systemic hypoanabolic and catabolic syndrome that diminishes the quality of life of cancer patients, decreases the efficiency of therapeutic strategies and ultimately contributes to decrease their lifespan. The depletion of skeletal muscle compartment, which represents the primary site of protein loss during cancer cachexia, is of very poor prognostic in cancer patients. In this review, we provide an extensive and comparative analysis of the molecular mechanisms involved in the regulation of skeletal muscle mass in human cachectic cancer patients and in animal models of cancer cachexia. We summarize data from preclinical and clinical studies investigating how the protein turnover is regulated in cachectic skeletal muscle and question to what extent the transcriptional and translational capacities, as well as the proteolytic capacity (ubiquitin-proteasome system, autophagy-lysosome system and calpains) of skeletal muscle are involved in the cachectic syndrome in human and animals. We also wonder how regulatory mechanisms such as insulin/IGF1-AKT-mTOR pathway, endoplasmic reticulum stress and unfolded protein response, oxidative stress, inflammation (cytokines and downstream IL1ß/TNFα-NF-κB and IL6-JAK-STAT3 pathways), TGF-ß signalling pathways (myostatin/activin A-SMAD2/3 and BMP-SMAD1/5/8 pathways), as well as glucocorticoid signalling, modulate skeletal muscle proteostasis in cachectic cancer patients and animals. Finally, a brief description of the effects of various therapeutic strategies in preclinical models is also provided. Differences in the molecular and biochemical responses of skeletal muscle to cancer cachexia between human and animals (protein turnover rates, regulation of ubiquitin-proteasome system and myostatin/activin A-SMAD2/3 signalling pathways) are highlighted and discussed. Identifying the various and intertwined mechanisms that are deregulated during cancer cachexia and understanding why they are decontrolled will provide therapeutic targets for the treatment of skeletal muscle wasting in cancer patients.

Keywords:  Autophagy-lysosome; Cancer cachexia; Glucocorticoids; Inflammation; Myostatin; Oxidative stress; Proteostasis; Skeletal muscle; Ubiquitin-proteasome

DOI:  https://doi.org/10.1002/jcsm.13073
Elife. 2023 Mar 02. pii: e83618. [Epub ahead of print]12

Quantitative proteomic analysis of skeletal muscles from wild-type and transgenic mice carrying recessive Ryr1 mutations linked to congenital myopathies.

Jan Eckhardt, Alexis Ruiz, Stéphane Koenig, Maud Frieden, Hervé Meier, Alexander Schmidt, Susan Treves, Francesco Zorzato.

  Skeletal muscles are a highly structured tissue responsible for movement and metabolic regulation, which can be broadly subdivided into fast and slow twitch muscles with each type expressing common as well as specific sets of proteins. Congenital myopathies are a group of muscle diseases leading to a weak muscle phenotype caused by mutations in a number of genes including RYR1. Patients carrying recessive RYR1 mutations usually present from birth and are generally more severely affected, showing preferential involvement of fast twitch muscles as well as extraocular and facial muscles. In order to gain more insight into the pathophysiology of recessive RYR1-congential myopathies, we performed relative and absolute quantitative proteomic analysis of skeletal muscles from wild-type and transgenic mice carrying p.Q1970fsX16 and p.A4329D RyR1 mutations which were identified in a child with a severe congenital myopathy. Our in-depth proteomic analysis shows that recessive RYR1 mutations not only decrease the content of RyR1 protein in muscle, but change the expression of 1130, 753 and 967 proteins EDL, soleus and extraocular muscles, respectively. Specifically, recessive RYR1 mutations affect the expression level of proteins involved in calcium signaling, extracellular matrix, metabolism and ER protein quality control. This study also reveals the stoichiometry of major proteins involved in excitation contraction coupling and identifies novel potential pharmacological targets to treat RyR1-related congenital myopathies.

Keywords:  genetics; genomics; mouse

DOI:  https://doi.org/10.7554/eLife.83618
bioRxiv. 2023 Feb 23. pii: 2023.02.23.529600. [Epub ahead of print]

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 two hours of mass spectrometry time per single muscle fiber; 50 fibers would take approximately four 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 minutes 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 hours. Adapting single cell data analysis techniques to integrate the data, we can reliably separate type 1 and 2A fibers. Sixty-five proteins were statistically different between clusters indicating alteration of proteins involved in fatty acid oxidation, muscle structure and regulation. 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/10.1101/2023.02.23.529600
Exp Mol Med. 2023 Mar 01.

Etiology of genetic muscle disorders induced by mutations in fast and slow skeletal MyBP-C paralogs.

Taejeong Song, Maicon Landim-Vieira, Mustafa Ozdemir, Caroline Gott, Onur Kanisicak, Jose Renato Pinto, Sakthivel Sadayappan.

Skeletal muscle, a highly complex muscle type in the eukaryotic system, is characterized by different muscle subtypes and functions associated with specific myosin isoforms. As a result, skeletal muscle is the target of numerous diseases, including distal arthrogryposes (DAs). Clinically, DAs are a distinct disorder characterized by variation in the presence of contractures in two or more distal limb joints without neurological issues. DAs are inherited, and up to 40% of patients with this condition have mutations in genes that encode sarcomeric protein, including myosin heavy chains, troponins, and tropomyosin, as well as myosin binding protein-C (MYBPC). Our research group and others are actively studying the specific role of MYBPC in skeletal muscles. The MYBPC family of proteins plays a critical role in the contraction of striated muscles. More specifically, three paralogs of the MYBPC gene exist, and these are named after their predominant expression in slow-skeletal, fast-skeletal, and cardiac muscle as sMyBP-C, fMyBP-C, and cMyBP-C, respectively, and encoded by the MYBPC1, MYBPC2, and MYBPC3 genes, respectively. Although the physiology of various types of skeletal muscle diseases is well defined, the molecular mechanism underlying the pathological regulation of DAs remains to be elucidated. In this review article, we aim to highlight recent discoveries involving the role of skeletal muscle-specific sMyBP-C and fMyBP-C as well as their expression profile, localization in the sarcomere, and potential role(s) in regulating muscle contractility. Thus, this review provides an overall summary of MYBPC skeletal paralogs, their potential roles in skeletal muscle function, and future research directions.

DOI: https://doi.org/10.1038/s12276-023-00953-x
J Cachexia Sarcopenia Muscle. 2023 Mar 02.

Nicotinamide Phosphoribosyltransferase-elevated NAD+ biosynthesis prevents muscle disuse atrophy by reversing mitochondrial dysfunction.

Yao Zhang, Yingming Wang, Shuai Lu, Rui Zhong, Zhilin Liu, Qichun Zhao, Chongyang Wang.

   BACKGROUND: It is well known that muscle disuse atrophy is associated with mitochondrial dysfunction, which is implicated in reduced nicotinamide adenine dinucleotide (NAD+ ) levels. Nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in NAD+ biosynthesis, may serve as a novel strategy to treat muscle disuse atrophy by reversing mitochondrial dysfunction.
METHODS: To investigate the effects of NAMPT on the prevention of disuse atrophy of skeletal muscles predominantly composed of slow-twitch (type I) or fast-twitch (type II) fibres, rabbit models of rotator cuff tear-induced supraspinatus muscle atrophy and anterior cruciate ligament (ACL) transection-induced extensor digitorum longus (EDL) atrophy were established and then administered NAMPT therapy. Muscle mass, fibre cross-sectional area (CSA), fibre type, fatty infiltration, western blot, and mitochondrial function were assayed to analyse the effects and molecular mechanisms of NAMPT in preventing muscle disuse atrophy.
RESULTS: Acute disuse of the supraspinatus muscle exhibited significant loss of mass (8.86 ± 0.25 to 5.10 ± 0.79 g; P < 0.001) and decreased fibre CSA (3939.6 ± 136.1 to 2773.4 ± 217.6 μm2 , P < 0.001), which were reversed by NAMPT (muscle mass 6.17 ± 0.54 g, P = 0.0033; fibre CSA, 3219.8 ± 289.4 μm2 , P = 0.0018). Disuse-induced impairment of mitochondrial function were significantly improved by NAMPT, including citrate synthase activity (40.8 ± 6.3 to 50.5 ± 5.6 nmol/min/mg, P = 0.0043), and NAD+ biosynthesis (279.9 ± 48.7 to 392.2 ± 43.2 pmol/mg, P = 0.0023). Western blot revealed that NAMPT increases NAD+ levels by activating NAMPT-dependent NAD+ salvage synthesis pathway. In supraspinatus muscle atrophy due to chronic disuse, a combination of NAMPT injection and repair surgery was more effective than repair in reversing muscle atrophy. Although the predominant composition of EDL muscle is fast-twitch (type II) fibre type that differ from supraspinatus muscle, its mitochondrial function and NAD+ levels are also susceptible to disuse. Similar to the supraspinatus muscle, NAMPT-elevated NAD+ biosynthesis was also efficient in preventing EDL disuse atrophy by reversing mitochondrial dysfunction.
CONCLUSIONS: NAMPT-elevated NAD+ biosynthesis can prevent disuse atrophy of skeletal muscles that predominantly composed with either slow-twitch (type I) or fast-twitch (type II) fibres by reversing mitochondrial dysfunction.

Keywords:  Fatty infiltration; Mitochondrial dysfunction; Muscle disuse atrophy; NAMPT; Rotator cuff tear

DOI:  https://doi.org/10.1002/jcsm.13182
Cell Metab. 2023 Feb 18. pii: S1550-4131(23)00037-2. [Epub ahead of print]

Multiomics reveals glutathione metabolism as a driver of bimodality during stem cell aging.

Daniel I Benjamin, Jamie O Brett, Pieter Both, Joel S Benjamin, Heather L Ishak, Jengmin Kang, Soochi Kim, Mingyu Chung, Marina Arjona, Christopher W Nutter, Jenna H Tan, Ananya K Krishnan, Hunter Dulay, Sharon M Louie, Antoine de Morree, Daniel K Nomura, Thomas A Rando.

  With age, skeletal muscle stem cells (MuSCs) activate out of quiescence more slowly and with increased death, leading to defective muscle repair. To explore the molecular underpinnings of these defects, we combined multiomics, single-cell measurements, and functional testing of MuSCs from young and old mice. The multiomics approach allowed us to assess which changes are causal, which are compensatory, and which are simply correlative. We identified glutathione (GSH) metabolism as perturbed in old MuSCs, with both causal and compensatory components. Contrary to young MuSCs, old MuSCs exhibit a population dichotomy composed of GSHhigh cells (comparable with young MuSCs) and GSHlow cells with impaired functionality. Mechanistically, we show that antagonism between NRF2 and NF-κB maintains this bimodality. Experimental manipulation of GSH levels altered the functional dichotomy of aged MuSCs. These findings identify a novel mechanism of stem cell aging and highlight glutathione metabolism as an accessible target for reversing MuSC aging.

Keywords:  GSH; MuSC; NAC; aging; bimodality; multiomics; satellite cells; stem cells

DOI:  https://doi.org/10.1016/j.cmet.2023.02.001
J Neuropathol Exp Neurol. 2023 Mar 02. pii: nlad012. [Epub ahead of print]

Outside the fiber: Endomysial stromal and capillary pathology in skeletal muscle may impede infusion therapy in infantile-onset Pompe disease.

Anne F Buckley, Ankit K Desai, Christine I Ha, Maureen A Petersen, Januario C Estrada, Justin R Waterﬁeld, Edward H Bossen, Priya S Kishnani.

  The survival of infantile-onset Pompe disease (IOPD) patients has improved dramatically since the introduction of enzyme replacement therapy (ERT) with a1glucosidase alfa. However, long-term IOPD survivors on ERT demonstrate motor deficits indicating that current therapy cannot completely prevent disease progression in skeletal muscle. We hypothesized that in IOPD, skeletal muscle endomysial stroma and capillaries would show consistent changes that could impede the movement of infused ERT from blood to muscle fibers. We retrospectively examined 9 skeletal muscle biopsies from 6 treated IOPD patients using light and electron microscopy. We found consistent ultrastructural endomysial stromal and capillary changes. The endomysial interstitium was expanded by lysosomal material, glycosomes/glycogen, cellular debris, and organelles, some exocytosed by viable muscle fibers and some released on fiber lysis. Endomysial scavenger cells phagocytosed this material. Mature fibrillary collagen was seen in the endomysium, and both muscle fibers and endomysial capillaries showed basal laminar reduplication and/or expansion. Capillary endothelial cells showed hypertrophy and degeneration, with narrowing of the vascular lumen. Ultrastructurally defined stromal and vascular changes likely constitute obstacles to movement of infused ERT from capillary lumen to muscle fiber sarcolemma, contributing to the incomplete efficacy of infused ERT in skeletal muscle. Our observations can inform approaches to overcoming these barriers to therapy.

Keywords:  Capillary; Endomysium; Glycogen; Muscle; Pompe; Stroma; Ultrastructure

DOI:  https://doi.org/10.1093/jnen/nlad012
J Cachexia Sarcopenia Muscle. 2023 Feb 28.

Dietary phosphate restriction prevents the appearance of sarcopenia signs in old mice.

Elena Alcalde-Estévez, Patricia Sosa, Ana Asenjo-Bueno, Patricia Plaza, Pedro L Valenzuela, Manuel Naves-Díaz, Gemma Olmos, Susana López-Ongil, María P Ruiz-Torres.

   BACKGROUND: Sarcopenia is defined by the progressive and generalized loss of muscle mass and function associated with aging. We have previously proposed that aging-related hyperphosphataemia is linked with the appearance of sarcopenia signs. Because there are not effective treatments to prevent sarcopenia, except for resistance exercise, we propose here to analyse whether the dietary restriction of phosphate could be a useful strategy to improve muscle function and structure in an animal model of aging.
METHODS: Five-month-old (young), 24-month-old (old) and 28-month-old (geriatric) male C57BL6 mice were used. Old and geriatric mice were divided into two groups, one fed with a standard diet (0.6% phosphate) and the other fed with a low-phosphate (low-P) diet (0.2% phosphate) for 3 or 7 months, respectively. A phosphate binder, Velphoro®, was also supplemented in a group of old mice, mixed with a standard milled diet for 3 months. Muscle mass was measured by the weight of gastrocnemius and tibial muscles, and quality by nuclear magnetic resonance imaging (NMRI) and histological staining assays. Muscle strength was measured by grip test and contractile properties of the tibialis muscle by electrical stimulation of the common peroneal nerve. Gait parameters were analysed during the spontaneous locomotion of the mice with footprinting. Orientation and motor coordination were evaluated using a static rod test.
RESULTS: Old mice fed with low-P diet showed reduced serum phosphate concentration (16.46 ± 0.77 mg/dL young; 21.24 ± 0.95 mg/dL old; 17.46 ± 0.82 mg/dL low-P diet). Old mice fed with low-P diet displayed 44% more mass in gastrocnemius muscles with respect to old mice (P = 0.004). NMRI revealed a significant reduction in T2 relaxation time (P = 0.014) and increased magnetization transfer (P = 0.045) and mean diffusivity (P = 0.045) in low-P diet-treated mice compared with their coetaneous. The hypophosphataemic diet increased the fibre size and reduced the fibrotic area by 52% in gastrocnemius muscle with respect to old mice (P = 0.002). Twitch force and tetanic force were significantly increased in old mice fed with the hypophosphataemic diet (P = 0.004 and P = 0.014, respectively). Physical performance was also improved, increasing gait speed by 30% (P = 0.032) and reducing transition time in the static rod by 55% (P = 0.012). Similar results were found when diet was supplemented with Velphoro®.
CONCLUSIONS: The dietary restriction of phosphate in old mice improves muscle quantity and quality, muscle strength and physical performance. Similar results were found using the phosphate binder Velphoro®, supporting the role of phosphate in the impairment of muscle structure and function that occurs during aging.

Keywords:  aging; hyperphosphataemia; phosphate binders; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13194
Biophys Rev (Melville). 2023 Mar;4(1): 011307

Delivery challenges for CRISPR-Cas9 genome editing for Duchenne muscular dystrophy.

Made Harumi Padmaswari, Shilpi Agrawal, Mary S Jia, Allie Ivy, Daniel A Maxenberger, Landon A Burcham, Christopher E Nelson.

Duchene muscular dystrophy (DMD) is an X-linked neuromuscular disorder that affects about one in every 5000 live male births. DMD is caused by mutations in the gene that codes for dystrophin, which is required for muscle membrane stabilization. The loss of functional dystrophin causes muscle degradation that leads to weakness, loss of ambulation, cardiac and respiratory complications, and eventually, premature death. Therapies to treat DMD have advanced in the past decade, with treatments in clinical trials and four exon-skipping drugs receiving conditional Food and Drug Administration approval. However, to date, no treatment has provided long-term correction. Gene editing has emerged as a promising approach to treating DMD. There is a wide range of tools, including meganucleases, zinc finger nucleases, transcription activator-like effector nucleases, and, most notably, RNA-guided enzymes from the bacterial adaptive immune system clustered regularly interspaced short palindromic repeats (CRISPR). Although challenges in using CRISPR for gene therapy in humans still abound, including safety and efficiency of delivery, the future for CRISPR gene editing for DMD is promising. This review will summarize the progress in CRISPR gene editing for DMD including key summaries of current approaches, delivery methodologies, and the challenges that gene editing still faces as well as prospective solutions.

DOI: https://doi.org/10.1063/5.0131452
Exp Biol Med (Maywood). 2023 Feb 27. 15353702231151963

LncRNA XLOC_015548 affects the proliferation and differentiation of myoblasts via the MAPK signaling pathway.

Yihao Wei, Tiantian Qi, Siyang Cao, Weifei Zhang, Fei Yu, Hui Zeng, Jian Weng.

  In recent years, an increasing number of studies have reported that long non-coding RNAs (lncRNAs) play essential regulatory roles in myogenic differentiation. In this study, a specific LncRNA XLOC_015548 (Lnc000280) was identified. However, little research has explored its mechanism of action by constructing XLOC_015548 gene editing cell models. In this study, relevant sequences were obtained according to the RNA-seq results. Subsequently, XLOC_015548 knockdown and over-expression lentiviral vectors were constructed, and the C2C12 myoblast cell line was transfected to prepare the XLOC_015548 gene-edited myoblast model. The in vitro analysis revealed that over-expression of XLOC_015548 significantly promoted the proliferation and differentiation of myoblasts and the formation of myotubes, whereas the opposite result was obtained in the knockdown group. XLOC_015548 regulated myogenic differentiation and affected the expression of myogenic differentiation regulators such as Myod, myogenin, and MyHC. Regarding the signaling pathway, we found that XLOC_015548 correlated with the phosphorylation level of MAPK/MEK/ERK pathway proteins. And the degree of phosphorylation was positively correlated with the protein expression of myogenic differentiation regulators. In conclusion, a new gene-edited myoblast model was constructed based on the lncRNA regulator XLOC_015548. The in vitro cell experiments verified that XLOC_015548 had regulatory effects on muscle growth and myoblast differentiation. These findings provide a laboratory foundation for the clinical application of lncRNAs as regulatory factors in the treatment of disuse muscle atrophy.

Keywords:  Long non-coding RNA XLOC_015548; MAPK signaling pathway; RNA sequencing; muscle; myoblast differentiation; myogenesis

DOI:  https://doi.org/10.1177/15353702231151963
J Physiol. 2023 Mar 03.

Antagonism of TRPV4 channels partially reduces mechanotransduction in rat skeletal muscle afferents.

Ayumi Fukazawa, Amane Hori, Hotta Norio, Kimiaki Katanosaka, Juan A Estrada, Rie Ishizawa, Han-Kyul Kim, Gary A Iwamoto, Scott A Smith, Wanpen Vongpatanasin, Masaki Mizuno.

  Mechanical distortion of working skeletal muscle induces sympathoexcitation via thin fibre afferents, a reflex response known as the skeletal muscle mechanoreflex. However, to date, the receptor ion channels responsible for mechanotransduction in skeletal muscle remain largely undetermined. Transient receptor potential vanilloid 4 (TRPV4) is known to sense mechanical stimuli such as shear stress or osmotic pressure in various organs. It is hypothesized that TRPV4 in thin-fibre primary afferents innervating skeletal muscle is involved in mechanotransduction. Fluorescence immunostaining revealed that 20.1 ± 10.1% of TRPV4 positive neurons were expressed with DiI-labeled small dorsal root ganglia (DRG) neurons, and 9.5 ± 6.1% of TRPV4 were co-localized with C-fibre marker, peripherin-positive neurons. In vitro whole-cell patch clamp recordings from cultured rat DRG neurons demonstrated that mechanically-activated current amplitude was significantly attenuated after the application of the TRPV4 antagonist, HC067047 compared to control (P = 0.004). Such reductions were also observed in single-fibre recordings from a muscle-nerve ex vivo preparation where HC067047 significantly decreased afferent discharge to mechanical stimulation (P = 0.007). Likewise, in an in vivo decerebrate rat preparation, the renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) responses to passive stretch of hindlimb muscle were significantly reduced by intraarterial injection of HC067047 (ΔRSNA: P = 0.019, ΔMAP: P = 0.002). The findings suggest that TRPV4 plays an important role in mechanotransduction contributing to the cardiovascular responses evoked by the skeletal muscle mechanoreflex during exercise. KEY POINTS: Although a mechanical stimulus to skeletal muscle reflexively activates the sympathetic nervous system, the receptors responsible for mechanotransduction in skeletal muscle thin fibre afferents have not been fully identified. Evidence suggests that TRPV4 is mechanosensitive channel that plays an important role in mechanotransduction within various organs. Immunocytochemical staining demonstrates that TRPV4 is expressed in group IV skeletal muscle afferents. In addition, we show that the TRPV4 antagonist, HC067047, decreases the responsiveness of thin fibre afferents to mechanical stimulation at the muscle tissue level as well as at the level of dorsal root ganglion neurons. Moreover, we demonstrate that intraarterial HC067047 injection attenuates the sympathetic and pressor responses to passive muscle stretch in decerebrate rats. These data suggests that antagonism of TRPV4 attenuates mechanotransduction in skeletal muscle afferents. The present study demonstrates a probable physiological role for TRPV4 in the regulation of mechanical sensation in somatosensory thin fibre muscle afferents. Abstract figure legend Blocking transient receptor potential vanilloid 4 (TRPV4) channels has an inhibitory effect on sympathetic and pressor responses to mechanical stimulation by attenuating mechanotransduction in sensory afferents innervating skeletal muscle. The TRPV4 antagonist, HC067047, reduces the responsiveness of thin fibre muscle afferents and small dorsal root ganglion neurons to mechanical stimulation. Furthermore, it is demonstrated that intraarterial injection of HC067047 suppresses the sympathetic nerve activity and blood pressure responses to passive hindlimb muscle stretch in vivo. These findings suggest that TRPV4 may play a crucial role in mechanotransduction contributing to the cardiovascular responses evoked by the skeletal muscle mechanoreflex during exercise. Design made in BioRender. This article is protected by copyright. All rights reserved.

Keywords:  group IV muscle afferents; mechanotransduction; muscle mechanoreflex; primary sensory neuron; transient receptor potential vanilloid 4

DOI:  https://doi.org/10.1113/JP284026
bioRxiv. 2023 Feb 21. pii: 2023.02.19.529145. [Epub ahead of print]

Quantitative model of aging-related muscle degeneration: a Drosophila study.

Maria Chechenova, Hannah Stratton, Kaveh Kiani, Erik Gerberich, Alesia Alekseyenko, Natasya Tamba, SooBin An, Lizzet Castillo, Emily Czajkowski, Christina Talley, Anton Bryantsev.

Changes in the composition and functionality of somatic muscles is a universal hallmark of aging that is displayed by a wide range of species. In humans, complications arising from muscle decline due to sarcopenia aggravate morbidity and mortality rates. The genetics of aging-related deterioration of muscle tissue is not well understood, which prompted us to characterize aging-related muscle degeneration in Drosophila melanogaster (fruit fly), a leading model organism in experimental genetics. Adult flies demonstrate spontaneous degeneration of muscle fibers in all types of somatic muscles, which correlates with functional, chronological, and populational aging. Morphological data imply that individual muscle fibers die by necrosis. Using quantitative analysis, we demonstrate that muscle degeneration in aging flies has a genetic component. Chronic neuronal overstimulation of muscles promotes fiber degeneration rates, suggesting a role for the nervous system in muscle aging. From the other hand, muscles decoupled from neuronal stimulation retain a basal level of spontaneous degeneration, suggesting the presence of intrinsic factors. Based on our characterization, Drosophila can be adopted for systematic screening and validation of genetic factors linked to aging-related muscle loss.

DOI: https://doi.org/10.1101/2023.02.19.529145
Am J Physiol Endocrinol Metab. 2023 Mar 01.

Effects of CX3CR1 and CXCR2 antagonists on running-dependent intramuscular neutrophil recruitments and myokine upregulation.

Mazvita R Nyasha, Weijian Chen, Haopeng Wang, Fukie Yaoita, Masashi Aoki, Ryoichi Nagatomi, Makoto Kanzaki.

  Muscle contractile activity stimulates intramuscular recruitment of immune cells including neutrophils emerging to serve as a prerequisite for exerting proper muscular performance, although the underlying mechanisms and their contributions to myokine upregulation remain ill-defined. We previously reported that pharmacological inhibition of CX3CR1, a fractalkine receptor, dampens gnawing-dependent neutrophil recruitment into masseter muscles along with compromising their masticatory activity. By employing a running exercise model, we herein demonstrated that hindlimb muscles require collaborative actions of both CX3CR1- and CXCR2-mediated signals for achieving neutrophil recruitment, upregulation of myokines including interleukin (IL)-6, enhanced GLUT4 translocation, and adequate endurance capability. Mechanistically, we revealed that a combination of CX3CR1 and CXCR2 antagonists, i.e., AZD8797 and SB2205002, inhibits exercise-inducible ICAM-1 and fractalkine upregulations in the area of the endothelium and muscle-derived CXCL1 upregulation, both of which apparently contribute to the intramuscular neutrophil accumulation in working muscles. Intriguingly, we also observed that 2 h of running results in intramuscular augmentation of innate lymphoid type 2 cells (ILC2s) markers, i.e., Bcl11b mRNA levels and anti-GATA-3-antibody-positive signals, and that these effects are completely abolished by administration of the combination of CX3CR1 and CXCR2 antagonists. Taken together, our findings strongly suggest that the exercise-evoked regional interplay among working myofibers, the adjacent endothelium and recruited immune cells including neutrophils and possibly ILC2s, mediated through these local factors, plays a key role in organization of the intramuscular microenvironment supporting the performance of hindlimb muscles during running.

Keywords:  endothelium; exercise; immunometabolic niche; myokine; neutrophil

DOI:  https://doi.org/10.1152/ajpendo.00196.2022
Cell Mol Biol Lett. 2023 Feb 27. 28(1): 15

IRE1α arm of unfolded protein response in muscle-specific TGF-β signaling-mediated regulation of muscle cell immunological properties.

Jiangwei Xiao, Jingwen Huang, Xiaoting Jian, Han Wang, Haiqiang Lan, Zhaohong Liao, Ruicai Gu, Jijie Hu, Hua Liao.

  Endoplasmic reticulum stress (ERS) and the unfolded protein response (UPR) are involved in various muscle pathological states. The IRE1α arm of UPR can affect immunological properties of myofiber through restraining p38 mitogen-activated protein kinases (MAPK) activation under inflammatory milieu. However, the relevant pathway molecules regulating the initiation of the IRE1α arm in myofiber remain unclear. In this work, expression of transforming growth factor-beta (TGF-β) and TGF-β receptor II (TGF-βr2), and UPR pathway activation were examined in cardiotoxin (CTX)-damaged mouse muscle, which revealed the activation of TGF-β signaling and UPR in CTX-damaged muscle and in regenerating myofibers. Using control or transgenic mice with TGF-βr2 deleted in skeletal muscle (SM TGF-βr2-/-) and the derived primary differentiating myogenic precursor cells (MPCs) treated with/without ERS activator or inhibitor, IRE1α pathway inhibitor, or TGF-β signaling activator, this study further revealed an essential role of intrinsic TGF-β signaling in regulating muscle cell to express inflammation-related molecules including H-2Kb, H2-Eα, TLR3, and special myokines. TGF-β signaling prompted UPR IRE1α arm and restrained p38 MAPK activation in myofiber under inflammatory milieu. This study uncovers a previously unrecognized function of TGF-β signaling acting as an upstream factor controlling myofiber immune capacities in the inflamed state through the UPR-IRE1α-p38 MAPK pathway.

Keywords:  IRE1α; Inflammation; Myofiber; TGF-β; UPR; p38 MAPK

DOI:  https://doi.org/10.1186/s11658-023-00429-w
bioRxiv. 2023 Feb 20. pii: 2023.02.20.529303. [Epub ahead of print]

Validation of the association between MRI and gene signatures in facioscapulohumeral dystrophy muscle: implications for clinical trial design.

Chao-Jen Wong, Seth D Friedman, Lauren Snider, Sean R Bennett, Takako I Jones, Peter L Jones, Dennis W W Shaw, Silvia S Blemker, Lara Riem, Olivia DuCharme, Richard J F L Lemmers, Silv Re M van der Maarel, Leo H Wang, Rabi Tawil, Jeffrey M Statland, Stephen J Tapscott.

Identifying the aberrant expression of DUX4 in skeletal muscle as the cause of facioscapulohumeral dystrophy (FSHD) has led to rational therapeutic development and clinical trials. Several studies support the use of MRI characteristics and the expression of DUX4-regulated genes in muscle biopsies as biomarkers of FSHD disease activity and progression, but reproducibility across studies needs further validation. We performed lower-extremity MRI and muscle biopsies in the mid-portion of the tibialis anterior (TA) muscles bilaterally in FSHD subjects and validated our prior reports of the strong association between MRI characteristics and expression of genes regulated by DUX4 and other gene categories associated with FSHD disease activity. We further show that measurements of normalized fat content in the entire TA muscle strongly predict molecular signatures in the mid-portion of the TA. Together with moderate-to-strong correlations of gene signatures and MRI characteristics between the TA muscles bilaterally, these results suggest a whole muscle model of disease progression and provide a strong basis for inclusion of MRI and molecular biomarkers in clinical trial design.

DOI: https://doi.org/10.1101/2023.02.20.529303
bioRxiv. 2023 Feb 25. pii: 2023.02.24.529950. [Epub ahead of print]

Dynamical modeling reveals RNA decay mediates the effect of matrix stiffness on aged muscle stem cell fate.

Zachary R Hettinger, Sophia Hu, Hikaru Mamiya, Amrita Sahu, Hirotaka Iijima, Kai Wang, Gabrielle Gilmer, Amanda Miller, Gabriele Nasello, Antonio Dâ Amore, David Vorp, Thomas A Rando, Jianhua Xing, Fabrisia Ambrosio.

Loss of muscle stem cell (MuSC) self-renewal with aging reflects a combination of influences from the intracellular (e.g., post-transcriptional modifications) and extracellular (e.g., matrix stiffness) environment. Whereas conventional single cell analyses have revealed valuable insights into factors contributing to impaired self-renewal with age, most are limited by static measurements that fail to capture nonlinear dynamics. Using bioengineered matrices mimicking the stiffness of young and old muscle, we showed that while young MuSCs were unaffected by aged matrices, old MuSCs were phenotypically rejuvenated by young matrices. Dynamical modeling of RNA velocity vector fields in silico revealed that soft matrices promoted a self-renewing state in old MuSCs by attenuating RNA decay. Vector field perturbations demonstrated that the effects of matrix stiffness on MuSC self-renewal could be circumvented by fine-tuning the expression of the RNA decay machinery. These results demonstrate that post-transcriptional dynamics dictate the negative effect of aged matrices on MuSC self-renewal.

DOI: https://doi.org/10.1101/2023.02.24.529950
STAR Protoc. 2023 Jan 29. pii: S2666-1667(23)00033-3. [Epub ahead of print]4(1): 102075

Quantitative analysis of myofiber type composition in human and mouse skeletal muscles.

Tooba Abbassi-Daloii, Salma El Abdellaoui, Hermien E Kan, Erik van den Akker, Peter A C 't Hoen, Vered Raz, Lenard M Voortman.

  Skeletal muscles are composed of different myofiber types characterized by the expression of myosin heavy chain isoforms, which can be affected by physical activity, aging, and pathological conditions. Here, we present a step-by-step high-throughput semi-automated approach for performing myofiber type quantification of entire human or mouse muscle tissue sections, including immunofluorescence staining, image acquisition, processing, and quantification. For complete details on the use and execution of this protocol, please refer to Abbassi-Daloii et al. (2022).1.

Keywords:  High-Throughput Screening; Microscopy

DOI:  https://doi.org/10.1016/j.xpro.2023.102075
bioRxiv. 2023 Feb 21. pii: 2023.02.19.529125. [Epub ahead of print]

The distinctive mechanical and structural signatures of residual force enhancement in myofibers.

Anthony L Hessel, Michel Kuehn, Bradley M Palmer, Devin Nissen, Dhruv Mishra, Venus Joumaa, Johanna Freundt, Weikang Ma, Kiisa C Nishikawa, Thomas Irving, Wolfgang A Linke.

In muscle, titin proteins connect myofilaments together and are thought to be critical for contraction, especially during residual force enhancement (RFE) when force is elevated after an active stretch. We investigated titinâ€™s function during contraction using small-angle X-ray diffraction to track structural changes before and after 50% titin cleavage and in the RFE-deficient, mdm titin mutant. We report that the RFE state is structurally distinct from pure isometric contractions, with increased thick filament strain and decreased lattice spacing, most likely caused by elevated titin-based forces. Furthermore, no RFE structural state was detected in mdm muscle. We posit that decreased lattice spacing, increased thick filament stiffness, and increased non-crossbridge forces are the major contributors to RFE. We conclude that titin directly contributes to RFE.
One-Sentence Summary: Titin contributes to active force production and residual force enhancement in skeletal muscles.

DOI: https://doi.org/10.1101/2023.02.19.529125
Front Endocrinol (Lausanne). 2023 ;14 1106529

Irisin: An anti-inflammatory exerkine in aging and redox-mediated comorbidities.

Caio Dos Santos Trettel, Bruno Rocha de Avila Pelozin, Marcelo Paes Barros, André Luis Lacerda Bachi, Pedro Gabriel Senger Braga, César Miguel Momesso, Guilherme Eustáquio Furtado, Pedro Afonso Valente, Edilamar Menezes Oliveira, Eef Hogervorst, Tiago Fernandes.

  Human beings lead largely sedentary lives. From an evolutionary perspective, such lifestyle is not beneficial to health. Exercise can promote many enabling pathways, particularly through circulating exerkines, to optimize individual health and quality of life. Such benefits might explain the protective effects of exercise against aging and noncommunicable diseases. Nevertheless, the miRNA-mediated molecular mechanisms and exerkine interorgan crosstalk that underlie the beneficial effects of exercise remain poorly understood. In this mini review, we focused on the exerkine, irisin, mainly produced by muscle contraction during adaptation to exercise and its beneficial effects on body homeostasis. Herein, the complex role of irisin in metabolism and inflammation is described, including its subsequent effects on thermogenesis through browning to control obesity and improve glycemic regulation for diabetes mellitus control, its potential to improve cognitive function (via brain derived neurotrophic factor), and its pathways of action and role in aging.

Keywords:  exercise; exerkines; inflammaging; myokines; oxidative stress; skeletal muscle

DOI:  https://doi.org/10.3389/fendo.2023.1106529
Noncoding RNA Res. 2023 Jun;8(2): 218-223

Regulation and mechanism of action of miRNAs on insulin resistance in skeletal muscles.

Aferin Beilerli, Valentin Kudriashov, Albert Sufianov, Andrey Kostin, Sema Begliarzade, Tatiana Ilyasova, Yanchao Liang, Albert Mukhamedzyanov, Ozal Beylerli.

  The term "insulin resistance" is commonly understood as a decrease in the response of insulin-sensitive tissues to insulin at its sufficient concentration, leading to chronic compensatory hyperinsulinemia. Type 2 diabetes mellitus is based on mechanisms consisting in the development of resistance to insulin in target cells (hepatocytes, adipocytes, skeletal muscle cells), resulting in the termination of an adequate response of these tissues to interaction with insulin. Since in healthy people 75-80% of glucose is utilized by skeletal muscle, it is more likely that the main cause of insulin resistance is impaired insulin-stimulated glucose utilization by skeletal muscle. With insulin resistance, skeletal muscles do not respond to insulin at its normal concentration, thereby determining an increase in glucose levels and a compensatory increase in insulin production in response to this. Despite many years of studying diabetes mellitus (DM) and insulin resistance, the molecular genetic basis for the development of these pathological conditions is still the subject of numerous studies. Recent studies point to the involvement of microRNAs (miRNAs) as dynamic modifiers in the pathogenesis of various diseases. MiRNAs are a separate class of RNA molecules that play a key role in the post-transcriptional regulation of gene expression. Recent studies have shown that miRNAs dysregulation in DM is closely related to miRNAs regulatory abilities in skeletal muscle insulin resistance. This gave grounds to consider an increase or decrease in the expression of individual microRNAs in muscle tissue and consider them as new biomarkers for diagnosing and monitoring insulin resistance and promising directions for targeted therapy. This review presents the results of scientific studies examining the role of miRNAs in skeletal muscle insulin resistance.

Keywords:  Diabetes mellitus; Diagnosis; Insulin resistance; Mechanism; Therapy; microRNAs

DOI:  https://doi.org/10.1016/j.ncrna.2023.02.005
STAR Protoc. 2023 Jan 23. pii: S2666-1667(22)00751-1. [Epub ahead of print]4(1): 101871

Quantification of autophagy flux in isolated mouse skeletal muscle fibers with overexpression of fluorescent protein mCherry-EGFP-LC3.

Xinyu Zhou, Ju Hwan Cho, Jianxun Yi, Kyounghan Choi, Ki Ho Park, Hua Zhu, Chuanxi Cai, Erin Haggard, Jingsong Zhou, Jae-Kyun Ko, Jianjie Ma.

  Evaluation of autophagy flux could be challenging for muscle fibers due to the baseline expression of mCherry-EGFP-LC3 along the Z-line. We established a protocol to overcome this difficulty. We overexpress mChery-EGFP-LC3 in the FDB muscle of an adult mouse via electroporation. Then, we enzymatically digest FDB muscle to yield individual fibers for live cell imaging. Finally, we develop an ImageJ-based program to eliminate the baseline striation pattern and semi-automatically quantify autophagosomes (APs) and autolysosomes (ALs) for autophagy flux analysis.

Keywords:  Cell Biology; Microscopy; Model Organisms

DOI:  https://doi.org/10.1016/j.xpro.2022.101871
EMBO Mol Med. 2023 Feb 27. e17324

When dysbiosis meets dystrophy: an unwanted gut-muscle connection.

Anusha Jayaraman, Sven Pettersson.

Duchenne muscular dystrophy (DMD) is a devastating neuromuscular degenerative disease with no known cure to date. In recent years, the hypothesis of a "gut-muscle axis" has emerged suggesting that bidirectional communication between the gut microbiota and the muscular system regulates the muscular function and may be perturbed in several muscular disorders. In addition, the excessive consumption of sugar and of lipid-rich processed food products are factors that further aggravate the phenotype for such diseases and accelerate biological aging. However, these unhealthy microbiota profiles can be reversed by individualized dietary changes to not only alter the microbiota composition but also to reset the production of microbial metabolites known to trigger beneficial effects typically associated with prolonged health span. Two recent studies (in this issue of EMBO Mol Med) highlight the interesting potential of microbiota-informed next-generation dietary intervention programs to be considered in genetically linked muscle disorders like DMD.

DOI: https://doi.org/10.15252/emmm.202217324
Neuron. 2023 Feb 22. pii: S0896-6273(23)00082-X. [Epub ahead of print]

A spinal muscular atrophy modifier implicates the SMN protein in SNARE complex assembly at neuromuscular synapses.

Jeong-Ki Kim, Narendra N Jha, Tomoyuki Awano, Charlotte Caine, Kishore Gollapalli, Emily Welby, Seung-Soo Kim, Andrea Fuentes-Moliz, Xueyong Wang, Zhihua Feng, Fusako Sera, Taishi Takeda, Shunichi Homma, Chien-Ping Ko, Lucia Tabares, Allison D Ebert, Mark M Rich, Umrao R Monani.

  Reduced survival motor neuron (SMN) protein triggers the motor neuron disease, spinal muscular atrophy (SMA). Restoring SMN prevents disease, but it is not known how neuromuscular function is preserved. We used model mice to map and identify an Hspa8G470R synaptic chaperone variant, which suppressed SMA. Expression of the variant in the severely affected mutant mice increased lifespan >10-fold, improved motor performance, and mitigated neuromuscular pathology. Mechanistically, Hspa8G470R altered SMN2 splicing and simultaneously stimulated formation of a tripartite chaperone complex, critical for synaptic homeostasis, by augmenting its interaction with other complex members. Concomitantly, synaptic vesicular SNARE complex formation, which relies on chaperone activity for sustained neuromuscular synaptic transmission, was found perturbed in SMA mice and patient-derived motor neurons and was restored in modified mutants. Identification of the Hspa8G470R SMA modifier implicates SMN in SNARE complex assembly and casts new light on how deficiency of the ubiquitous protein causes motor neuron disease.

Keywords:  Hspa8; SNARE complex assembly; modifiers; spinal muscular atrophy; survival motor neuron protein

DOI:  https://doi.org/10.1016/j.neuron.2023.02.004
Cancer Cell. 2023 Feb 25. pii: S1535-6108(23)00035-1. [Epub ahead of print]

Cancer cachexia: involvement of an expanding macroenvironment.

Benjamin R Pryce, David J Wang, Teresa A Zimmers, Michael C Ostrowski, Denis C Guttridge.

Advanced cancers often present with the cachexia syndrome that impacts peripheral tissues, leading to involuntary weight loss and reduced prognosis. The central tissues undergoing depletion are skeletal muscle and adipose, but recent findings reveal an expanding tumor macroenvironment involving organ crosstalks that underlie the cachectic state.

DOI: https://doi.org/10.1016/j.ccell.2023.02.007
Front Physiol. 2023 ;14 1120223

Considerations for designing trials targeting muscle dysfunction in exercise oncology.

Alexander Brooks, Alec Schumpp, Jake Dawson, Emily Andriello, Ciaran Michael Fairman.

  Individuals diagnosed with cancer commonly experience a significant decline in muscle mass and physical function collectively referred to as cancer related muscle dysfunction. This is concerning because impairments in functional capacity are associated with an increased risk for the development of disability and subsequent mortality. Notably, exercise offers a potential intervention to combat cancer related muscle dysfunction. Despite this, research is limited on the efficacy of exercise when implemented in such a population. Thus, the purpose of this mini review is to offer critical considerations for researchers seeking to design studies pertaining to cancer related muscle dysfunction. Namely, 1) defining the condition of interest, 2) determining the most appropriate outcome and methods of assessment, 3) establishing the best timepoint (along the cancer continuum) to intervene, and 4) understanding how exercise prescription can be configured to optimize outcomes.

Keywords:  cachexia; frailty; muscle mass; muscle strength; sarcopenia

DOI:  https://doi.org/10.3389/fphys.2023.1120223