bims-moremu 2022-09-11 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2022‒09‒11
thirty papers selected by
Anna Vainshtein
Craft Science Inc.

Atonal homolog 8/Math6 regulates differentiation and maintenance of skeletal muscle.
Effects of short-term unloading and active recovery on human motor unit properties, neuromuscular junction transmission and transcriptomic profile.
Lumican, an Exerkine, Protects against Skeletal Muscle Loss.
Myosin as a novel key modulator of striated muscle metabolism.
Neither myonuclear accretion nor a myonuclear domain size ceiling is a feature of the attenuated hypertrophic potential of aged human skeletal muscle.
Gomisin G improves muscle strength by enhancing mitochondrial biogenesis and function in disuse muscle atrophic mice.
Gene Ontology (GO)-Driven Inference of Candidate Proteomic Markers Associated with Muscle Atrophy Conditions.
Cathelicidin-related antimicrobial peptide mediates skeletal muscle degeneration caused by injury and Duchenne muscular dystrophy in mice.
Near-infrared light-triggered polypyrrole promotes C2C12 cell differentiation and inhibits TNF-α induced myotube atrophy.
Role of Muscle LIM Protein in Mechanotransduction Process.
Cellular and Molecular Variations in Male and Female Murine Skeletal Muscle after Long-Term Feeding with a High-Fat Diet.
Distinctive exercise-induced inflammatory response and exerkine induction in skeletal muscle of people with type 2 diabetes.
Protective Effect of Delta-Like 1 Homolog Against Muscular Atrophy in a Mouse Model.
Senolytic elimination of senescent macrophages restores muscle stem cell function in severely dystrophic muscle.
Balanced Free Essential Amino Acids and Resistance Exercise Training Synergistically Improve Dexamethasone-Induced Impairments in Muscle Strength, Endurance, and Insulin Sensitivity in Mice.
Patient-Derived Pancreatic Cancer Cells Induce C2C12 Myotube Atrophy by Releasing Hsp70 and Hsp90.
Constitutive activation of estrogen receptor α signaling in muscle prolongs exercise endurance in mice.
Global phosphoproteomic profiling of skeletal muscle in ovarian-hormone deficient mice.
Inhibition of monocarboxylate transporters (MCT) 1 and 4 reduces exercise capacity in mice.
Caveolin 3 suppresses phosphorylation-dependent activation of sarcolemmal nNOS.
Young bone marrow transplantation prevents aging-related muscle atrophy in a senescence-accelerated mouse prone 10 model.
Cancer Cachexia: Signaling and Transcriptional Regulation of Muscle Catabolic Genes.
The effects of neurogranin knockdown on SERCA pump efficiency in soleus muscles of female mice fed a high fat diet.
PPARGC1A Is a Moderator of Skeletal Muscle Development Regulated by miR-193b-3p.
THRIFTY, a novel high-throughput method for rapid fibre type identification of isolated skeletal muscle fibres.
Transcriptome changes in DM1 patients' tissues are governed by the RNA interference pathway.
Oxidation alters myosin-actin interaction and force generation in skeletal muscle filaments.
Comparison of Incorporation of Wild Type and Mutated Actins into Sarcomeres in Skeletal Muscle Cells: A Fluorescence Recovery After Photobleaching study.
Reassessing the relationship between mRNA levels and protein abundance in exercised skeletal muscles.
Transforming Growth Factor-Beta Signaling in Cancer-Induced Cachexia: From Molecular Pathways to the Clinics.

Front Cell Dev Biol. 2022 ;10 950414

Atonal homolog 8/Math6 regulates differentiation and maintenance of skeletal muscle.

Satya Srirama Karthik Divvela, Eric Bekoe Offei, Florian Suerland, David Revuelta García, Julia Kwiatkowski, Ajeesh Balakrishnan-Renuka, Pauline Bohne, Marion Böing, Gabriela Morosan-Puopolo, Melanie D Mark, Beate Brand-Saberi.

  Atonal Homolog 8 (Atoh8) belongs to a large superfamily of transcriptional regulators called basic helix-loop-helix (bHLH) transcription factors. Atoh8 (murine homolog "Math6") has been shown to be involved in organogenesis during murine embryonic development. We have previously identified the expression of Atoh8 during skeletal myogenesis in chicken where we described its involvement in hypaxial myotome formation suggesting a regulatory role of Atoh8 in skeletal muscle development. Within the current study, we analyzed the effect of the loss of function of Atoh8 in murine primary myoblasts and during differentiation of pluripotent stem cells into myotubes, and the effect of its gain of function in C2C12 cells. Based on the observed results, we conclude that Atoh8 regulates myoblast proliferation via modulating myostatin signaling. Further, our data revealed a reduced muscle mass, strength and fiber size with significant changes to the muscle fiber type suggesting atrophy in skeletal muscle of Atoh8 mutants. We further report that Atoh8 knockout mice suffer from a condition similar to ambient hypoxia which may be the primary cause of the phenotype. Altogether, this study shows the significance of Atoh8 not only in myogenesis but also in the maintenance of skeletal muscle.

Keywords:  AKT/mTOR; Atoh8; atrophy; hypoxia; math6; myostatin; regeneration; skeletal muscle

DOI:  https://doi.org/10.3389/fcell.2022.950414
J Physiol. 2022 Sep 07.

Effects of short-term unloading and active recovery on human motor unit properties, neuromuscular junction transmission and transcriptomic profile.

Fabio Sarto, Daniel W Stashuk, Martino V Franchi, Elena Monti, Sandra Zampieri, Giacomo Valli, Giuseppe Sirago, Julián Candia, Lisa M Hartnell, Matteo Paganini, Jamie S McPhee, Giuseppe De Vito, Luigi Ferrucci, Carlo Reggiani, Marco V Narici.

  KEY POINTS: We used integrative electrophysiological and molecular approaches to comprehensively investigate changes in neuromuscular integrity and function after a 10-day unilateral lower limb suspension (ULLS), followed by 21 days of active recovery (AR) in young healthy men, with a particular focus on neuromuscular junction (NMJ) and motor unit potential (MUP) properties alterations. After 10-day ULLS, we found significant NMJ molecular alterations in absence of NMJ transmission stability impairment. These findings suggest that human NMJ is functionally resilient against insults and stresses induced by short-term disuse at least at relatively low contraction intensities, at which low-threshold, slow-type MUs are recruited. Intramuscular electromyography revealed that unloading caused increased MUP complexity and decreased motor unit firing rates, and these alterations could be related to the observed changes in skeletal muscle ion channel pool and initial and partial signs of fibre denervation and axonal damage. The AR period restored these neuromuscular changes.ABSTRACT: Electrophysiological alterations of the neuromuscular junction (NMJ) and motor unit potential (MUP) with unloading are poorly studied. We aimed to investigate these aspects and the underlying molecular mechanisms with short-term unloading and active recovery (AR). Eleven healthy males underwent a 10-day unilateral lower limb suspension (ULLS) period, followed by 21-day AR based on resistance exercise. Quadriceps femoris (QF) cross-sectional area (CSA) and isometric maximum voluntary contraction (MVC) were evaluated. Intramuscular electromyographic recordings were obtained during 10% and 25% MVC isometric contractions from the vastus lateralis (VL). Biomarkers of NMJ molecular instability (serum c-terminal agrin fragment, CAF), axonal damage (neurofilament light chain) and denervation status were assessed from blood samples and VL biopsies. NMJ and ion channels transcriptomic profiles were investigated by RNA-sequencing. QF CSA and MVC decreased with ULLS. Increased CAF and altered NMJ transcriptome with unloading suggested the emergence of NMJ molecular instability, which was not associated with impaired NMJ transmission stability. Instead, increased MUP complexity and decreased motor unit firing rates were found after ULLS. Downregulation of ion channel gene expression was found together with increased neurofilament light chain concentration and partial denervation. The AR period restored most of these neuromuscular alterations. In conclusion, the human NMJ is destabilized at the molecular level but shows functional resilience to a 10-day unloading period at least at relatively low contraction intensities. However, MUP properties are altered by ULLS, possibly due to alterations in ion channel dynamics and initial axonal damage and denervation. These changes are fully reversed by 21-day AR. Abstract figure legend Eleven young males took part in a 10-day unilateral lower limb suspension (ULLS) intervention. This unloading period was followed by 21 days of subsequent active recovery (AR) based on resistance exercise. At baseline, after ULLS and after AR we evaluated muscle size by ultrasound and in vivo muscle function by isometric dynamometry. Motor unit potential (MUP) properties and neuromuscular junction (NMJ) transmission stability were assessed using intramuscular electromyography. Finally, vastus lateralis muscle biopsies and blood samples were collected. The ULLS intervention resulted in increased NMJ molecular instability in absence of NMJ transmission stability impairment. Changes in MUP properties were observed, including increased MUP complexity and decreased motor unit firing rates, possibly due to initial axonal damage, partial denervation and altered in ion channels dynamics. The AR period was effective in restoring these neuromuscular changes. LS0: baseline data collection; LS10: unilateral lower limb suspension day 10; AR21: active recovery day 21 This article is protected by copyright. All rights reserved.

Keywords:  C-terminal agrin fragment; Intramuscular electromyography; NFM jiggle; NFM jitter; disuse; motor units

DOI:  https://doi.org/10.1113/JP283381
Int J Mol Sci. 2022 Sep 02. pii: 10031. [Epub ahead of print]23(17):

Lumican, an Exerkine, Protects against Skeletal Muscle Loss.

Han Jin Cho, Young-Sun Lee, Da Ae Kim, Sung Ah Moon, Seung Eun Lee, Seung Hun Lee, Jung-Min Koh.

  Exerkines are soluble factors secreted by exercised muscles, mimicking the effects of exercise in various organs, including the muscle itself. Lumican is reportedly secreted from muscles; however, its roles in skeletal muscle remain unknown. Herein, we found that lumican mRNA expression in the extensor digitorum longus was significantly higher in exercised mice than in unloading mice, and lumican stimulated myogenesis in vitro. Additionally, lumican knockdown significantly decreased muscle mass and cross-sectional area (CSA) of the muscle fiber in the gastrocnemius muscle of exercised mice. Lumican upregulated phosphorylation of p38 mitogen-activated protein kinase (MAPK) and a p38 inhibitor near completely blocked lumican-stimulated myogenesis. Inhibitors for integrin α2β1 and integrin ανβ3 also prevented lumican-stimulated myogenesis. Systemic lumican treatment, administered via the tail vein for 4 weeks, significantly increased relative muscle masses by 36.1% in ovariectomized mice. In addition, intramuscular lumican injection into unloaded muscles for 2 weeks significantly increased muscle mass by 8.5%. Both intravenous and intramuscular lumican treatment significantly increased muscle CSA. Our in vitro and in vivo experiments indicate that lumican is a muscle-secreted exerkine that affords protection against muscle loss by activating p38 MAPK via integrin receptors.

Keywords:  exerkine; integrin; lumican; muscle loss; myogenesis

DOI:  https://doi.org/10.3390/ijms231710031
Physiology (Bethesda). 2022 Sep 06.

Myosin as a novel key modulator of striated muscle metabolism.

Christopher T A Lewis, Julien Ochala.

  After years of intense research using structural, biological, and biochemical experimental procedures, it is clear that myosin molecules are essential for striated muscle contraction. However, this is just the tip of the iceberg of their function. Interestingly, recently, it has been shown that these molecules (especially myosin heavy chains) are also crucial for cardiac and skeletal muscle relaxed state. In the present review, we first overview myosin heavy chain biochemical states and how they influence the consumption of ATP. We then detail how neighbouring partner proteins including myosin light chains and myosin binding protein C intervene in such processes, modulating energy demand in health and disease. Finally, we present current experimental drugs targeting myosin ATP consumption and how they can treat muscle diseases.

Keywords:  Heart; Metabolism; Myosin; Skeletal muscle

DOI:  https://doi.org/10.1152/physiol.00018.2022
Geroscience. 2022 Sep 09.

Neither myonuclear accretion nor a myonuclear domain size ceiling is a feature of the attenuated hypertrophic potential of aged human skeletal muscle.

Matthew S Brook, Daniel J Wilkinson, Janelle Tarum, Kyle W Mitchell, Jonathan L Lund, Bethan E Phillips, Nathaniel J Szewczyk, Fawzi Kadi, Paul L Greenhaff, Ken Smith, Philip J Atherton.

  Ageing limits growth capacity of skeletal muscle (e.g. in response to resistance exercise), but the role of satellite cell (SC) function in driving this phenomenon is poorly defined. Younger (Y) (~ 23 years) and older (O) men (~ 69 years) (normal-weight BMI) underwent 6 weeks of unilateral resistance exercise training (RET). Muscle biopsies were taken at baseline and after 3-/6-week training. We determined muscle size by fibre CSA (and type), SC number, myonuclei counts and DNA synthesis (via D2O ingestion). At baseline, there were no significant differences in fibre areas between Y and O. RET increased type I fibre area in Y from baseline at both 3 weeks and 6 weeks (baseline: 4509 ± 534 µm2, 3 weeks; 5497 ± 510 µm2 P < 0.05, 6 weeks; 5402 ± 352 µm2 P < 0.05), whilst O increased from baseline at 6 weeks only (baseline 5120 ± 403 µm2, 3 weeks; 5606 ± 620 µm2, 6 weeks; 6017 ± 482 µm2 P < 0.05). However, type II fibre area increased from baseline in Y at both 3 weeks and 6 weeks (baseline: 4949 ± 459 µm2, 3 weeks; 6145 ± 484 µm2 (P < 0.01), 6 weeks; 5992 ± 491 µm2 (P < 0.01), whilst O showed no change (baseline 5210 ± 410 µm2, 3 weeks; 5356 ± 535 µm2 (P = 0.9), 6 weeks; 5857 ± 478 µm2 (P = 0.1). At baseline, there were no differences in fibre myonuclei number between Y and O. RET increased type I fibre myonuclei number from baseline in both Y and O at 3 weeks and 6 weeks with RET (younger: baseline 2.47 ± 0.16, 3 weeks; 3.19 ± 0.16 (P < 0.001), 6 weeks; 3.70 ± 0.29 (P < 0.0001); older: baseline 2.29 ± 0.09, 3 weeks; 3.01 ± 0.09 (P < 0.001), 6 weeks; 3.65 ± 0.18 (P < 0.0001)). Similarly, type II fibre myonuclei number increased from baseline in both Y and O at 3 weeks and 6 weeks (younger: baseline 2.49 ± 0.14, 3 weeks; 3.31 ± 0.21 (P < 0.001), 6 weeks; 3.86 ± 0.29 (P < 0.0001); older: baseline 2.43 ± 0.12, 3 weeks; 3.37 ± 0.12 (P < 0.001), 6 weeks; 3.81 ± 0.15 (P < 0.0001)). DNA synthesis rates %.d-1 exhibited a main effect of training but no age discrimination. Declines in myonuclei addition do not underlie impaired muscle growth capacity in older humans, supporting ribosomal and proteostasis impairments as we have previously reported.

Keywords:  Ageing; DNA synthesis; Myonuclei; Resistance exercise; Skeletal muscle

DOI:  https://doi.org/10.1007/s11357-022-00651-y
Biomed Pharmacother. 2022 Sep;pii: S0753-3322(22)00795-8. [Epub ahead of print]153 113406

Gomisin G improves muscle strength by enhancing mitochondrial biogenesis and function in disuse muscle atrophic mice.

MyeongHoon Yeon, Hojung Choi, Kwang-Hoon Chun, Jong Han Lee, Hee-Sook Jun.

  Disuse muscle atrophy is characterized by a decrease in muscle mass and strength and an increase in glycolytic muscle fiber type. Although Schisandra chinensis extract has beneficial effects on muscle atrophy induced by various conditions (e.g., dexamethasone and aging), the effect of gomisin G, a lignan component of S. chinensis, on disuse muscle atrophy is unclear. Here, we induced disuse muscle atrophy through wire immobilization of the hind legs in mice followed by the oral administration of gomisin G. The cross-sectional area and muscle strength in disuse muscle atrophic mice were increased by gomisin G; however, the total muscle mass did not increase. Gomisin G decreased the expression of muscle atrophic factors (myostatin, atrogin-1, and MuRF1) but increased the expression of protein synthesis factors (mTOR and 4E-BP1). In H2O2-treated C2C12 myotubes, the level of puromycin incorporation (as a marker of protein synthesis) gradually increased in a dose-dependent manner by gomisin G. Furthermore, gomisin G induced a muscle fiber switch from fast-type glycolytic fibers (type 2B) to slow-type oxidative fibers (type I, 2A) in the gastrocnemius (GA) muscle as proved a decrease in the expression of TnI-FS and an increase in the expression of TnI-SS. Gomisin G increased mitochondrial DNA content and ATP levels in the GA muscle and COX activity in H2O2-treated C2C12 myotubes, improving mitochondrial function. Mechanistically, mitochondrial biogenesis is regulated by gomisin G via the Sirt 1/PGC-1α signaling pathway, targeting NRF1 and TFAM. These data suggest that gomisin G has a potential therapeutic effect on disuse muscle atrophy.

Keywords:  Disuse muscle atrophy; Gomisin G; Mitochondria biogenesis; Muscle strength; Schisandra chinensis extract

DOI:  https://doi.org/10.1016/j.biopha.2022.113406
Molecules. 2022 Aug 27. pii: 5514. [Epub ahead of print]27(17):

Gene Ontology (GO)-Driven Inference of Candidate Proteomic Markers Associated with Muscle Atrophy Conditions.

Angelique Stalmach, Ines Boehm, Marco Fernandes, Alison Rutter, Richard J E Skipworth, Holger Husi.

  Skeletal muscle homeostasis is essential for the maintenance of a healthy and active lifestyle. Imbalance in muscle homeostasis has significant consequences such as atrophy, loss of muscle mass, and progressive loss of functions. Aging-related muscle wasting, sarcopenia, and atrophy as a consequence of disease, such as cachexia, reduce the quality of life, increase morbidity and result in an overall poor prognosis. Investigating the muscle proteome related to muscle atrophy diseases has a great potential for diagnostic medicine to identify (i) potential protein biomarkers, and (ii) biological processes and functions common or unique to muscle wasting, cachexia, sarcopenia, and aging alone. We conducted a meta-analysis using gene ontology (GO) analysis of 24 human proteomic studies using tissue samples (skeletal muscle and adipose biopsies) and/or biofluids (serum, plasma, urine). Whilst there were few similarities in protein directionality across studies, biological processes common to conditions were identified. Here we demonstrate that the GO analysis of published human proteomics data can identify processes not revealed by single studies. We recommend the integration of proteomics data from tissue samples and biofluids to yield a comprehensive overview of the human skeletal muscle proteome. This will facilitate the identification of biomarkers and potential pathways of muscle-wasting conditions for use in clinics.

Keywords:  biomarker; cancer cachexia; muscle wasting; proteomics; sarcopenia

DOI:  https://doi.org/10.3390/molecules27175514
J Cachexia Sarcopenia Muscle. 2022 Sep 04.

Cathelicidin-related antimicrobial peptide mediates skeletal muscle degeneration caused by injury and Duchenne muscular dystrophy in mice.

Moon-Chang Choi, Jiwon Jo, Myeongjin Lee, Jonggwan Park, Tso-Pang Yao, Yoonkyung Park.

  BACKGROUND: Cathelicidin, an antimicrobial peptide, plays a key role in regulating bacterial killing and innate immunity; however, its role in skeletal muscle function is unknown. We investigated the potential role of cathelicidin in skeletal muscle pathology resulting from acute injury and Duchenne muscular dystrophy (DMD) in mice.METHODS: Expression changes and muscular localization of mouse cathelicidin-related antimicrobial peptide (Cramp) were examined in the skeletal muscle of normal mice treated with chemicals (cardiotoxin and BaCl2 ) or in dystrophic muscle of DMD mouse models (mdx, mdx/Utrn+/- and mdx/Utrn-/- ). Cramp penetration into myofibres and effects on muscle damage were studied by treating synthetic peptides to mouse skeletal muscles or C2C12 myotubes. Cramp knockout (KO) mice and mdx/Utrn/Cramp KO lines were used to determine whether Cramp mediates muscle degeneration. Muscle pathophysiology was assessed by histological methods, serum analysis, grip strength and lifespan. Molecular factors targeted by Cramp were identified by the pull-down assay and proteomic analysis.
RESULTS: In response to acute muscle injury, Cramp was activated in muscle-infiltrating neutrophils and internalized into myofibres. Cramp treatments of mouse skeletal muscles or C2C12 myotubes resulted in muscle degeneration and myotube damage, respectively. Genetic ablation of Cramp reduced neutrophil infiltration and ameliorated muscle pathology, such as fibre size (P < 0.001; n = 6) and fibrofatty infiltration (P < 0.05). Genetic reduction of Cramp in mdx/Utrn+/- mice not only attenuated muscle damage (35%, P < 0.05; n = 9-10), myonecrosis (53%, P < 0.05), inflammation (37-65%, P < 0.01) and fibrosis (14%, P < 0.05) but also restored muscle fibre size (14%, P < 0.05) and muscle force (18%, P < 0.05). Reducing Cramp levels led to a 63% (male, P < 0.05; n = 10-14) and a 124% (female, P < 0.001; n = 20) increase in the lifespan of mdx/Utrn-/- mice. Proteomic and mechanistic studies revealed that Cramp cross-talks with Ca2+ signalling in skeletal muscle through sarcoplasmic/endoplasmic reticulum Ca2+ -ATPase1 (SERCA1). Cramp binds and inactivates SERCA1, leading to the activation of Ca2+ -dependent calpain proteases that exacerbate DMD progression.
CONCLUSIONS: These findings identify Cramp as an immune cell-derived regulator of skeletal muscle degeneration and provide a potential therapeutic target for DMD.

Keywords:  Cathelicidin; Cramp; Duchenne muscular dystrophy; Muscle degeneration; Serca1

DOI:  https://doi.org/10.1002/jcsm.13065
Cell Signal. 2022 Sep 05. pii: S0898-6568(22)00225-X. [Epub ahead of print] 110463

Near-infrared light-triggered polypyrrole promotes C2C12 cell differentiation and inhibits TNF-α induced myotube atrophy.

Yuanyuan Wu, Ji Che, Peiyu Jia, Yantao Ma, Qi Han, Xiaolei Wang, Lei Fu, Hongjing Dou, Yongjun Zheng.

  Treatment of skeletal muscle atrophy and strengthening the muscles remain a challenge in modern medicine. Studies have shown that photobiomodulation can inhibit skeletal muscle atrophy and aid in functional recovery. Near-infrared radiation (NIR) therapy has emerged as a complementary therapy for the treatment of skeletal muscle atrophy, but its underlying mechanism remains unclear. Polypyrrole (PPy) is an organic polymer with strong near-infrared absorption, which can generate heat from absorbed NIR. In this study, MHC immunofluorescence staining was performed on C2C12 myoblasts to investigate the differentiation of C2C12 cells after NIR-triggered PPy exposure. As TNF-α-induced C2C12 myotubes were used as a model of muscular atrophy. Giemsa staining was used to determine the myotube diameter. Western blot analysis was performed to examine the proteins involved in the differentiation and atrophy of muscle cells, as well as in the Akt/P70S6K signaling pathway. PPy triggered by NIR promoted the differentiation of C2C12 cells, inhibited C2C12 myotube atrophy caused by TNF-α, and downregulated the expression levels of Atrogin-1 and MuRF 1 protein. In addition, we determined that Akt/P70S6K signaling pathway activity plays a crucial role in the therapeutic effect of NIR-triggered polypyrrole, which was further confirmed by the administration of the Akt inhibitor GDC0068. The optimal conditions for these effects were a PPy concentration of 0.125 mg/ml and NIR exposure for 80 s. We show that the photothermal effect of PPy triggered by near-infrared light can increase the beneficial effects of NIR, promote the differentiation of C2C12 cells, and improve C2C12 myotube atrophy, laying a foundation for its future clinical use.

Keywords:  Atrophy; C2C12; Differentiation; Near-infrared radiation; Polypyrrole

DOI:  https://doi.org/10.1016/j.cellsig.2022.110463
Int J Mol Sci. 2022 Aug 29. pii: 9785. [Epub ahead of print]23(17):

Role of Muscle LIM Protein in Mechanotransduction Process.

Philippe Germain, Anthony Delalande, Chantal Pichon.

  The induction of protein synthesis is crucial to counteract the deconditioning of neuromuscular system and its atrophy. In the past, hormones and cytokines acting as growth factors involved in the intracellular events of these processes have been identified, while the implications of signaling pathways associated with the anabolism/catabolism ratio in reference to the molecular mechanism of skeletal muscle hypertrophy have been recently identified. Among them, the mechanotransduction resulting from a mechanical stress applied to the cell appears increasingly interesting as a potential pathway for therapeutic intervention. At present, there is an open question regarding the type of stress to apply in order to induce anabolic events or the type of mechanical strain with respect to the possible mechanosensing and mechanotransduction processes involved in muscle cells protein synthesis. This review is focused on the muscle LIM protein (MLP), a structural and mechanosensing protein with a LIM domain, which is expressed in the sarcomere and costamere of striated muscle cells. It acts as a transcriptional cofactor during cell proliferation after its nuclear translocation during the anabolic process of differentiation and rebuilding. Moreover, we discuss the possible opportunity of stimulating this mechanotransduction process to counteract the muscle atrophy induced by anabolic versus catabolic disorders coming from the environment, aging or myopathies.

Keywords:  MLP; atrophy; mechanotransduction; prophylaxis; striated muscle; ultrasound stimulation

DOI:  https://doi.org/10.3390/ijms23179785
Int J Mol Sci. 2022 Aug 23. pii: 9547. [Epub ahead of print]23(17):

Cellular and Molecular Variations in Male and Female Murine Skeletal Muscle after Long-Term Feeding with a High-Fat Diet.

Bright Starling Emerald, Mohammed A Al Jailani, Marwa F Ibrahim, Challagandla Anil Kumar, Mohammed Z Allouh.

  Current information regarding the effects of a high-fat diet (HFD) on skeletal muscle is contradictory. This study aimed to investigate the effects of a long-term HFD on skeletal muscle in male and female mice at the morphological, cellular, and molecular levels. Adult mice of the C57BL/6 strain were fed standard chow or an HFD for 20 weeks. The tibialis anterior muscles were dissected, weighed, and processed for cellular and molecular analyses. Immunocytochemical and morphometric techniques were applied to quantify fiber size, satellite cells (SCs), and myonuclei. Additionally, PCR array and RT-qPCR tests were performed to determine the expression levels of key muscle genes. Muscles from HFD mice showed decreases in weight, SCs, and myonuclei, consistent with the atrophic phenotype. This atrophy was associated with a decrease in the percentage of oxidative fibers within the muscle. These findings were further confirmed by molecular analyses that showed significant reductions in the expression of Pax7, Myh1, and Myh2 genes and increased Mstn gene expression. Male and female mice showed similar trends in response to HFD-induced obesity. These findings indicate that the long-term effects of obesity on skeletal muscle resemble those of age-related sarcopenia.

Keywords:  Myh; Pax7; fiber type; myonuclei; myosin; myostatin; satellite cells

DOI:  https://doi.org/10.3390/ijms23179547
Sci Adv. 2022 Sep 09. 8(36): eabo3192

Distinctive exercise-induced inflammatory response and exerkine induction in skeletal muscle of people with type 2 diabetes.

Nicolas J Pillon, Jonathon A B Smith, Petter S Alm, Alexander V Chibalin, Julia Alhusen, Erik Arner, Piero Carninci, Tomas Fritz, Julia Otten, Tommy Olsson, Sophie van Doorslaer de Ten Ryen, Louise Deldicque, Kenneth Caidahl, Harriet Wallberg-Henriksson, Anna Krook, Juleen R Zierath.

Mechanistic insights into the molecular events by which exercise enhances the skeletal muscle phenotype are lacking, particularly in the context of type 2 diabetes. Here, we unravel a fundamental role for exercise-responsive cytokines (exerkines) on skeletal muscle development and growth in individuals with normal glucose tolerance or type 2 diabetes. Acute exercise triggered an inflammatory response in skeletal muscle, concomitant with an infiltration of immune cells. These exercise effects were potentiated in type 2 diabetes. In response to contraction or hypoxia, cytokines were mainly produced by endothelial cells and macrophages. The chemokine CXCL12 was induced by hypoxia in endothelial cells, as well as by conditioned medium from contracted myotubes in macrophages. We found that CXCL12 was associated with skeletal muscle remodeling after exercise and differentiation of cultured muscle. Collectively, acute aerobic exercise mounts a noncanonical inflammatory response, with an atypical production of exerkines, which is potentiated in type 2 diabetes.

DOI: https://doi.org/10.1126/sciadv.abo3192
Endocrinol Metab (Seoul). 2022 Aug;37(4): 684-697

Protective Effect of Delta-Like 1 Homolog Against Muscular Atrophy in a Mouse Model.

Ji Young Lee, Minyoung Lee, Dong-Hee Lee, Yong-Ho Lee, Byung-Wan Lee, Eun Seok Kang, Bong-Soo Cha.

  BACKGRUOUND: Muscle atrophy is caused by an imbalance between muscle growth and wasting. Delta-like 1 homolog (DLK1), a protein that modulates adipogenesis and muscle development, is a crucial regulator of myogenic programming. Thus, we investigated the effect of exogenous DLK1 on muscular atrophy.METHODS: We used muscular atrophy mouse model induced by dexamethasone (Dex). The mice were randomly divided into three groups: (1) control group, (2) Dex-induced muscle atrophy group, and (3) Dex-induced muscle atrophy group treated with DLK1. The effects of DLK1 were also investigated in an in vitro model using C2C12 myotubes.
RESULTS: Dex-induced muscular atrophy in mice was associated with increased expression of muscle atrophy markers and decreased expression of muscle differentiation markers, while DLK1 treatment attenuated these degenerative changes together with reduced expression of the muscle growth inhibitor, myostatin. In addition, electron microscopy revealed that DLK1 treatment improved mitochondrial dynamics in the Dex-induced atrophy model. In the in vitro model of muscle atrophy, normalized expression of muscle differentiation markers by DLK1 treatment was mitigated by myostatin knockdown, implying that DLK1 attenuates muscle atrophy through the myostatin pathway.
CONCLUSION: DLK1 treatment inhibited muscular atrophy by suppressing myostatin-driven signaling and improving mitochondrial biogenesis. Thus, DLK1 might be a promising candidate to treat sarcopenia, characterized by muscle atrophy and degeneration.

Keywords:  DLK1 protein, human; Myostatin; Sarcopenia

DOI:  https://doi.org/10.3803/EnM.2022.1446
Aging (Albany NY). 2022 Sep 08. 14(undefined):

Senolytic elimination of senescent macrophages restores muscle stem cell function in severely dystrophic muscle.

Lei Liu, Xianlin Yue, Zewei Sun, William S Hambright, Qi Feng, Yan Cui, Johnny Huard, Paul D Robbins, Zhihui Wang, Xiaodong Mu.

  The aging of the immune system, or immunosenescence, was recently verified to have a causal role in driving the aging of solid organs, while the senolytic elimination of senescent immune cells was found to effectively delay systemic aging. Our recent study also showed that immune cells in severely dystrophic muscles develop senescence-like phenotypes, including the increased expression of senescence-associated secretory phenotype (SASP) factors and senescence markers. Here we further investigated whether the specific clearance of senescent immune cells in dystrophic muscle may effectively improve the function of muscle stem cells and the phenotypes of dystrophic muscle. We observed increased percentage of senescent cells in macrophages from mdx/utro(-/-) mice (a murine model for muscular dystrophy disease, dystrophin-/-; utrophin-/-), while the treatment of mdx/utro(-/-) macrophages with senolytic drug fisetin resulted in reduced number of senescent cells. We administrated fisetin to mdx/utro(-/-) mice for 4 weeks, and observed obviously reduced number of senescent immune cells, restored number of muscle cells, and improve muscle phenotypes. In conclusion, our results reveal that senescent immune cells, such as macrophages, are greatly involved in the development of muscle dystrophy by impacting the function of muscle stem cells, and the senolytic ablation of these senescent cells with fisetin can be an effective therapeutic strategy for improving function of muscle stem cells and phenotypes of dystrophic muscles.

Keywords:  cellular senescence; immunosenescence; muscular dystrophy; senolytics; stem cells

DOI:  https://doi.org/10.18632/aging.204275
Int J Mol Sci. 2022 Aug 27. pii: 9735. [Epub ahead of print]23(17):

Balanced Free Essential Amino Acids and Resistance Exercise Training Synergistically Improve Dexamethasone-Induced Impairments in Muscle Strength, Endurance, and Insulin Sensitivity in Mice.

Jiwoong Jang, Jin-Ho Koh, Yeongmin Kim, Hee-Joo Kim, Sanghee Park, Yewon Chang, Jiyeon Jung, Robert R Wolfe, Il-Young Kim.

  Our previous study shows that an essential amino acid (EAA)-enriched diet attenuates dexamethasone (DEX)-induced declines in muscle mass and strength, as well as insulin sensitivity, but does not affect endurance. In the present study, we hypothesized that the beneficial effects will be synergized by adding resistance exercise training (RET) to EAA, and diet-free EAA would improve endurance. To test hypotheses, mice were randomized into the following four groups: control, EAA, RET, and EAA+RET. All mice except the control were subjected to DEX treatment. We evaluated the cumulative rate of myofibrillar protein synthesis (MPS) using 2H2O labeling and mass spectrometry. Neuromuscular junction (NMJ) stability, mitochondrial contents, and molecular signaling were demonstrated in skeletal muscle. Insulin sensitivity and glucose metabolism using 13C6-glucose tracing during oral glucose tolerance tests were analyzed. We found that EAA and RET synergistically improve muscle mass and/or strength, and endurance capacity, as well as insulin sensitivity, and glucose metabolism in DEX-treated muscle. These improvements are accomplished, in part, through improvements in myofibrillar protein synthesis, NMJ, fiber type preservation, and/or mitochondrial biogenesis. In conclusion, free EAA supplementation, particularly when combined with RET, can serve as an effective means that counteracts the adverse effects on muscle of DEX that are found frequently in clinical settings.

Keywords:  dexamethasone; essential amino acids; glucose metabolic flux; mitochondrial biogenesis; muscle atrophy; neuromuscular junction stability; physical performance; protein turnover; resistance exercise training

DOI:  https://doi.org/10.3390/ijms23179735
Cells. 2022 Sep 03. pii: 2756. [Epub ahead of print]11(17):

Patient-Derived Pancreatic Cancer Cells Induce C2C12 Myotube Atrophy by Releasing Hsp70 and Hsp90.

Hong-Yu Wu, Jose G Trevino, Bing-Liang Fang, Andrea N Riner, Vignesh Vudatha, Guo-Hua Zhang, Yi-Ping Li.

  Pancreatic cancer (PC) patients are highly prone to cachexia, a lethal wasting syndrome featuring muscle wasting with an undefined etiology. Recent data indicate that certain murine cancer cells induce muscle wasting by releasing Hsp70 and Hsp90 through extracellular vesicles (EVs) to activate p38β MAPK-mediated catabolic pathways primarily through Toll-like receptor 4 (TLR4). However, whether human PC induces cachexia through releasing Hsp70 and Hsp90 is undetermined. Here, we investigated whether patient-derived PC cells induce muscle cell atrophy directly through this mechanism. We compared cancer cells isolated from patient-derived xenografts (PDX) from three PC patients who had cachexia (PCC) with those of three early-stage lung cancer patients without cachexia (LCC) and two renal cancer patients who were not prone to cachexia (RCC). We observed small increases of Hsp70 and Hsp90 released by LCC and RCC in comparison to non-cancer control cells (NCC). However, PCC released markedly higher levels of Hsp70 and Hsp90 (~ 6-fold on average) than LCC and RCC. In addition, PCC released similarly increased levels of Hsp70/90-containing EVs. In contrast to RCC and LCC, PCC-conditioned media induced a potent catabolic response in C2C12 myotubes including the activation of p38 MAPK and transcription factor C/EBPβ, upregulation of E3 ligases UBR2 and MAFbx, and increase of autophagy marker LC3-II, resulting in the loss of the myosin heavy chain (MHC ~50%) and myotube diameter (~60%). Importantly, the catabolic response was attenuated by Hsp70- and Hsp90-neutralizing antibodies in a dose-dependent manner. These data suggest that human PC cells release high levels of Hsp70 and Hsp90 that induce muscle atrophy through a direct action on muscle cells.

Keywords:  Hsp70; Hsp90; myotube atrophy; pancreatic cancer; patient-derived xenografts

DOI:  https://doi.org/10.3390/cells11172756
Biochem Biophys Res Commun. 2022 Aug 26. pii: S0006-291X(22)01201-3. [Epub ahead of print]628 11-17

Constitutive activation of estrogen receptor α signaling in muscle prolongs exercise endurance in mice.

Kenta Yoh, Kazuhiro Ikeda, Saki Nagai, Kuniko Horie, Satoru Takeda, Satoshi Inoue.

  Estrogen is a female hormone that plays a role in various tissues, although the mechanism in skeletal muscle has not been fully clarified. We previously showed that systemic administration of estrogen for 10 weeks ameliorated decreased exercise endurance in ovariectomized mice. To assess whether a long-term and muscle-specific activation of estrogen signaling modulates muscle function, we constructed an expression plasmid for a constitutively active estrogen receptor α (caERα) under the control of muscle creatine kinase (Mck) gene promoter/enhancer. In C2C12 mouse myoblastic cells, transfection of the Mck-caERα plasmid elevated the estrogen response element-driven transcription in a ligand-independent manner. Using this construct, we generated Mck-caERα transgenic mice, in which caERα is predominantly expressed in muscle. Treadmill running test revealed that female Mck-caERα mice exhibit a prolonged running time and distance compared with the wild-type mice. Moreover, microarray expression analysis revealed that the genes related to lipid metabolism, insulin signaling, and growth factor signaling were particularly upregulated in the quadriceps femoris muscle of Mck-caERα mice. These results suggest that estrogen signaling potentiates exercise endurance in skeletal muscle through modulating the expression of metabolism-associated genes.

Keywords:  Endurance; Estrogen receptor; Gene expression; Mouse; Muscle

DOI:  https://doi.org/10.1016/j.bbrc.2022.08.064
Physiol Genomics. 2022 Sep 05.

Global phosphoproteomic profiling of skeletal muscle in ovarian-hormone deficient mice.

Mina P Peyton, Tzu-Yi Yang, LeeAnn Higgins, Todd W Markowski, Cha Vue, Laurie L Parker, Dawn A Lowe.

  Protein phosphorylation is important in skeletal muscle development, growth, regeneration, and contractile function. Alterations in the skeletal muscle phosphoproteome due to aging have been reported in males; however, studies in females are lacking. We have demonstrated that estrogen deficiency decreases muscle force which correlates with decreased myosin regulatory light chain phosphorylation. Thus, we questioned whether the decline of estrogen in females that occurs with aging might alter the skeletal muscle phosphoproteome. C57BL/6J female mice (6 mo) were randomly assigned to a sham-operated (Sham) or ovariectomy (Ovx) group to investigate the effects of estrogen deficiency on skeletal muscle protein phosphorylation in a resting, non-contracting condition. After 16 weeks of estrogen deficiency, the tibialis anterior muscle was dissected and prepped for label-free nano-liquid chromatography tandem mass spectrometry phosphoproteomic analysis. We identified 4,780 phosphopeptides in tibialis anterior muscles of ovariectomized (Ovx) and Sham-operated (Sham) control mice. Further analysis revealed 647 differentially regulated phosphopeptides (Benjamini - Hochberg adjusted p-value < 0.05 and 1.5-fold change ratio) that corresponded to 130 proteins with 22 proteins differentially phosphorylated (3 unique to Ovx, two unique to Sham, six upregulated, and 11 downregulated). Differentially phosphorylated proteins associated with the sarcomere, cytoplasm, and metabolic and calcium signaling pathways were identified. Our work provides the first global phosphoproteomic analysis in females and how estrogen deficiency impacts the skeletal muscle phosphoproteome.

Keywords:  AMPK; calcium signaling; females; ovariectomy; sarcomere

DOI:  https://doi.org/10.1152/physiolgenomics.00104.2022
Physiol Rep. 2022 Sep;10(17): e15457

Inhibition of monocarboxylate transporters (MCT) 1 and 4 reduces exercise capacity in mice.

Yu Kitaoka, Kenya Takahashi, Hideo Hatta.

  The concept of lactate shuttle is widely accepted in exercise physiology. Lactate transport is mediated by monocarboxylate transporters (MCT), which enable cells to take up and release lactate. However, the role of lactate during exercise has not yet been fully elucidated. In this study, we investigated the effects of lactate transport inhibition on exercise capacity and metabolism in mice. Here, we demonstrated that MCT1 inhibition by α-cyano-4-hydroxycinnamate administration (4-CIN, 200 mg/g of body weight) reduced the treadmill running duration at 20 m/min. The administration of 4-CIN increased the blood lactate concentration immediately after exercise. With matched exercise duration, the muscle lactate concentration was higher while muscle glycogen content was lower in 4-CIN-administered mice. Further, we showed that MCT4 inhibition by bindarit administration (50 mg/kg of body weight) reduced the treadmill running duration at 40 m/min. Bindarit administration increased the muscle lactate but did not alter the blood lactate and glucose concentrations, as well as muscle glycogen content, immediately after exercise. A negative correlation was observed between exercise duration at 40 m/min and muscle lactate concentration immediately after exercise. Our results suggest that lactate transport via MCT1 and MCT4 plays a pivotal role in sustaining exercise.

Keywords:  MCT; exercise; lactate; skeletal muscle

DOI:  https://doi.org/10.14814/phy2.15457
Biochem Biophys Res Commun. 2022 Aug 27. pii: S0006-291X(22)01203-7. [Epub ahead of print]628 84-90

Caveolin 3 suppresses phosphorylation-dependent activation of sarcolemmal nNOS.

Yutaka Ohsawa, Hideaki Ohtsubo, Yoshihiko Saito, Shin-Ichiro Nishimatsu, Hiroki Hagiwara, Tatsufumi Murakami, Ichizo Nishino, Yoshihide Sunada.

  Mutations of the caveolin 3 gene cause autosomal dominant limb-girdle muscular dystrophy (LGMD)1C. In mice, overexpression of mutant caveolin 3 leads to loss of caveolin 3 and results in myofiber hypotrophy in association with activation of neuronal nitric oxide synthase (nNOS) at the sarcolemma. Here, we show that caveolin 3 directly bound to nNOS and suppressed its phosphorylation-dependent activation at a specific residue, Ser1412 in the nicotinamide adenine dinucleotide phosphate (NADPH)-flavin adenine dinucleotide (FAD) module near the C-terminus of the reduction domain, in vitro. Constitutively active nNOS enhanced myoblast fusion, but not myogenesis, in vitro. Phosphorylation-dependent activation of nNOS occurred in muscles from caveolin 3-mutant mice and LGMD1C patients. Mating with nNOS-mutant mice exacerbated myofiber hypotrophy in the caveolin 3-mutant mice. In nNOS-mutant mice, regenerating myofibers after cardiotoxin injury became hypotrophic with reduced myoblast fusion. Administration of NO donor increased myofiber size and the number of myonuclei in the caveolin 3-mutant mice. Exercise also increased myofiber size accompanied by phosphorylation-dependent activation of nNOS in wild-type and caveolin 3-mutant mice. These data indicate that caveolin 3 inhibits phosphorylation-dependent activation of nNOS, which leads to myofiber hypertrophy via enhancing myoblast fusion. Hypertrophic signaling by nNOS phosphorylation could act in a compensatory manner in caveolin 3-deficient muscles.

Keywords:  Exercise; Limb-girdle muscular dystrophy 1C; Myoblast fusion; Myofiber hypertrophy; Neuronal nitric oxide synthase; caveolin 3

DOI:  https://doi.org/10.1016/j.bbrc.2022.08.066
J Cachexia Sarcopenia Muscle. 2022 Sep 04.

Young bone marrow transplantation prevents aging-related muscle atrophy in a senescence-accelerated mouse prone 10 model.

Aiko Inoue, Limei Piao, Xueling Yue, Zhe Huang, Lina Hu, Hongxian Wu, Xiangkun Meng, Wenhu Xu, Chenglin Yu, Takeshi Sasaki, Kohji Itakura, Hiroyuki Umegaki, Masafumi Kuzuya, Xian Wu Cheng.

  BACKGROUND: Young bone marrow transplantation (YBMT) has been shown to stimulate vascular regeneration in pathological conditions, including ageing. Here, we investigated the benefits and mechanisms of the preventive effects of YBMT on loss of muscle mass and function in a senescence-associated mouse prone 10 (SAMP10) model, with a special focus on the role of growth differentiation factor 11 (GDF-11).METHODS: Nine-week-old male SAMP10 mice were randomly assigned to a non-YBMT group (n = 6) and a YBMT group (n = 7) that received the bone marrow of 8-week-old C57BL/6 mice.
RESULTS: Compared to the non-YBMT mice, the YBMT mice showed the following significant increases (all P < 0.05 in 6-7 mice): endurance capacity (>61.3%); grip strength (>37.9%), percentage of slow myosin heavy chain fibres (>14.9-15.9%). The YBMT also increased the amounts of proteins or mRNAs for insulin receptor substrate 1, p-Akt, p-extracellular signal-regulated protein kinase1/2, p-mammalian target of rapamycin, Bcl-2, peroxisom proliferator-activated receptor-γ coactivator (PGC-1α), plus cytochrome c oxidase IV and the numbers of proliferating cells (n = 5-7, P < 0.05) and CD34+/integrin-α7+ muscle stem cells (n = 5-6, P < 0.05). The YMBT significantly decreased the levels of gp91phox, caspase-9 proteins and apoptotic cells (n = 5-7, P < 0.05) in both muscles; these beneficial changes were diminished by the blocking of GDF-11 (n = 5-6, P < 0.05). An administration of mouse recombinant GDF-11 improved the YBMT-mediated muscle benefits (n = 5-6, P < 0.05). Cell therapy with young bone marrow from green fluorescent protein (GFP) transgenic mice exhibited GFP+ myofibres in aged muscle tissues.
CONCLUSIONS: These findings suggest that YBMT can prevent muscle wasting and dysfunction by mitigating apoptosis and proliferation via a modulation of GDF-11 signalling and mitochondrial dysfunction in SAMP10 mice.

Keywords:  Aging; Bone marrow transplantation; Mouse model; Muscle stem cell; SAMP10; Sarcopenia

DOI:  https://doi.org/10.1002/jcsm.13058
Cancers (Basel). 2022 Aug 31. pii: 4258. [Epub ahead of print]14(17):

Cancer Cachexia: Signaling and Transcriptional Regulation of Muscle Catabolic Genes.

Vinay Kumar Rao, Dipanwita Das, Reshma Taneja.

  Cancer cachexia (CC) is a multifactorial syndrome characterized by a significant reduction in body weight that is predominantly caused by the loss of skeletal muscle and adipose tissue. Although the ill effects of cachexia are well known, the condition has been largely overlooked, in part due to its complex etiology, heterogeneity in mediators, and the involvement of diverse signaling pathways. For a long time, inflammatory factors have been the focus when developing therapeutics for the treatment of CC. Despite promising pre-clinical results, they have not yet advanced to the clinic. Developing new therapies requires a comprehensive understanding of how deregulated signaling leads to catabolic gene expression that underlies muscle wasting. Here, we review CC-associated signaling pathways and the transcriptional cascade triggered by inflammatory cytokines. Further, we highlight epigenetic factors involved in the transcription of catabolic genes in muscle wasting. We conclude with reflections on the directions that might pave the way for new therapeutic approaches to treat CC.

Keywords:  cancer; cytokine signaling; epigenetics; muscle wasting; transcription factors

DOI:  https://doi.org/10.3390/cancers14174258
Front Endocrinol (Lausanne). 2022 ;13 957182

The effects of neurogranin knockdown on SERCA pump efficiency in soleus muscles of female mice fed a high fat diet.

Jessica L Braun, Jisook Ryoo, Kyle Goodwin, Emily N Copeland, Mia S Geromella, Ryan W Baranowski, Rebecca E K MacPherson, Val A Fajardo.

  The sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA) pump is responsible for the transport of Ca2+ from the cytosol into the sarcoplasmic reticulum at the expense of ATP, making it a regulator of both muscle relaxation and muscle-based energy expenditure. Neurogranin (Ng) is a small protein that negatively regulates calcineurin signaling. Calcineurin is Ca2+/calmodulin dependent phosphatase that promotes the oxidative fibre type in skeletal muscle and regulates muscle-based energy expenditure. A recent study has shown that calcineurin activation reduces SERCA Ca2+ transport efficiency, ultimately raising energy expenditure. Since the biomedical view of obesity states that it arises as an imbalance between energy intake and expenditure which favors the former, we questioned whether heterozygous Ng deletion (Ng+/- ) would reduce SERCA efficiency and increase energy expenditure in female mice fed a high-fat diet (HFD). Young (3-4-month-old) female wild type (WT) and Ng+/- mice were fed a HFD for 12 weeks with their metabolic profile being analyzed using metabolic cages and DXA scanning, while soleus SERCA efficiency was measured using SERCA specific Ca2+ uptake and ATPase activity assays. Ng+/- mice showed significantly less cage ambulation compared to WT mice but this did not lead to any added weight gain nor changes in daily energy expenditure, glucose or insulin tolerance despite a similar level of food intake. Furthermore, we observed significant reductions in SERCA's apparent coupling ratio which were associated with significant reductions in SERCA1 and phospholamban content. Thus, our results show that Ng regulates SERCA pump efficiency, and future studies should further investigate the potential cellular mechanisms.

Keywords:  calcineurin; calmodulin; neuronatin; obesity; phospholamban; sarcolipin

DOI:  https://doi.org/10.3389/fendo.2022.957182
Int J Mol Sci. 2022 Aug 24. pii: 9575. [Epub ahead of print]23(17):

PPARGC1A Is a Moderator of Skeletal Muscle Development Regulated by miR-193b-3p.

Manting Ma, Bolin Cai, Shaofen Kong, Zhen Zhou, Jing Zhang, Xiquan Zhang, Qinghua Nie.

  Meat production performance is one of the most important factors in determining the economic value of poultry. Myofiber is the basic unit of skeletal muscle, and its physical and chemical properties determine the meat quality of livestock and poultry to a certain extent. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) as a transcriptional coactivator has been found to be widely involved in a series of biological processes. However, PPARGC1A is still poorly understood in chickens. In this manuscript, we reported that PPARGC1A was highly expressed in slow-twitch myofibers. PPARGC1A facilitated mitochondrial biogenesis and regulated skeletal muscle metabolism by mediating the flux of glycolysis and the TCA cycle. Gain- and loss-of-function analyses revealed that PPARGC1A promoted intramuscular fatty acid oxidation, drove the transformation of fast-twitch to slow-twitch myofibers, and increased chicken skeletal muscle mass. Mechanistically, the expression level of PPARGC1A is regulated by miR-193b-3p. Our findings help to understand the genetic regulation of skeletal muscle development and provide a molecular basis for further research on the antagonism of skeletal muscle development and fat deposition in chickens.

Keywords:  PPARGC1A; miR-193b-3p; mitochondrial biogenesis; muscle metabolism; skeletal muscle development

DOI:  https://doi.org/10.3390/ijms23179575
J Physiol. 2022 Sep 07.

THRIFTY, a novel high-throughput method for rapid fibre type identification of isolated skeletal muscle fibres.

Oscar Horwath, Sebastian Edman, Alva Andersson, Filip J Larsen, William Apró.

  KEY POINTS: Skeletal muscle is composed of different fibre types, each with distinct physiological properties. To fully understand how skeletal muscle adapts to external cues such as exercise, nutrition and ageing, fibre type specific investigations are required. Such investigations are however very difficult to conduct due to the extreme time requirements related to classifying individually isolated muscle fibres. To bypass this issue, we have developed a rapid and reliable method named THRIFTY which is cheap as well as versatile and which can easily be implemented in most laboratories. THRIFTY increases the feasibility to conduct larger fibre-type specific studies and enables time-sensitive assays where measurements need to be carried out in close connection with tissue sampling By using THRIFTY, new insights into fibre type-specific muscle physiology can be gained which may have broad implications in health and disease ABSTRACT: Fibre type-specific analyses are required for broader understanding of muscle physiology, but such analyses are difficult to conduct due to the extreme time requirements of dissecting and fibre typing individual fibres. Investigations are often confined to a small number of fibres from few participants with low representativeness of the entire fibre population and the participant population. To increase the feasibility of conducting large-scale fibre type-specific studies, a valid and rapid method for high-throughput fibre typing of individually dissected fibres was developed. Employing THRIFTY (High-Throughput Immunofluorescence Fibre Typing), 400 fibre segments were fixed onto microscope slides with a pre-printed coordinated grid system, probed with antibodies against MyHC-I and MyHC-II and classified using a fluorescence microscope. The validity and speed of THRIFTY was compared to a previously validated protocol (dot blot) on a fibre-to-fibre basis. Fibre pool purity was evaluated using 'gold standard' SDS-PAGE and silver staining. A modified THRIFTY-protocol using fluorescent western blot equipment was also validated. THRIFTY displayed excellent agreement with the dot blot protocol, κ = 0,955 (95% CI, 0,928 to 0,982), P < 0.001. Both the original and modified THRIFTY protocols generated type I and type II fibre pools of absolute purity. Using THRIFTY, 400 fibres were typed just under 11 hours, which was approximately 3 times faster than dot blot. THRIFTY is a novel and valid method with high versatility for very rapid fibre typing of individual fibres. THRIFTY can therefore facilitate the generation of large fibre pools for more extensive mechanistic studies into skeletal muscle physiology. Absract figure legend Large scale investigations into fibre type-specific physiology are limited by the extreme time requirements related to classifying individually isolated muscle fibres. To increase the feasibility of such studies, we developed a rapid and reliable fibre-typing method which we have named THRIFTY. Additional benefits of THRIFTY, beyond high speed and validity, include high versatility, excellent scalability, and low cost. The many benefits of THRIFTY increase the feasibility to generate large pools of pure type I and type II muscle fibres which can be used for multiple downstream analyses. The high speed of THRIFTY also enables time-sensitive assays where measurements need to be carried out in close connection with tissue sampling. Employing THRIFTY may therefore provide new insights into fibre type-specific muscle physiology which may have broad implications in health and disease. This article is protected by copyright. All rights reserved.

Keywords:  MyHC; SDS-PAGE; fibre typing; high-throughput; immunofluorescence

DOI:  https://doi.org/10.1113/JP282959
Front Mol Biosci. 2022 ;9 955753

Transcriptome changes in DM1 patients' tissues are governed by the RNA interference pathway.

Maya Braun, Shachar Shoshani, Yuval Tabach.

  Myotonic dystrophy type 1 (DM1) is a multisystemic disease caused by pathogenic expansions of CTG repeats. The expanded repeats are transcribed to long RNA and induce cellular toxicity. Recent studies suggest that the CUG repeats are processed by the RNA interference (RNAi) pathway to generate small interfering repeated RNA (siRNA). However, the effects of the CTG repeat-derived siRNAs remain unclear. We hypothesize that the RNAi machinery in DM1 patients generates distinct gene expression patterns that determine the disease phenotype in the individual patient. The abundance of genes with complementary repeats that are targeted by siRNAs in each tissue determines the way that the tissue is affected in DM1. We integrated and analyzed published transcriptome data from muscle, heart, and brain biopsies of DM1 patients, and revealed shared, characteristic changes that correlated with disease phenotype. These signatures are overrepresented by genes and transcription factors bearing endogenous CTG/CAG repeats and are governed by aberrant activity of the RNAi machinery, miRNAs, and a specific gain-of-function of the CTG repeats. Computational analysis of the DM1 transcriptome enhances our understanding of the complex pathophysiology of the disease and may reveal a path for cure.

Keywords:  RNA interference; expansion repeat disorders; gene signature; myotonic dystrophy type 1; small RNAs; trinucleotide repeats

DOI:  https://doi.org/10.3389/fmolb.2022.955753
Am J Physiol Cell Physiol. 2022 Sep 05.

Oxidation alters myosin-actin interaction and force generation in skeletal muscle filaments.

Daren Elkrief, Yu-Shu Cheng, Oleg S Matusovsky, Dilson E Rassier.

  The interaction between actin and myosin is the basis of contraction and force production in muscle fibers. Studies have shown that actin and myosin oxidation cause myofibrillar weakness in healthy and diseased muscles. The degree to which oxidation of each of these proteins contributes to an attenuated force in myofibrils is unclear. In this study, we show that exposure of actin and myosin to the chemical 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium chloride (SIN-1), a NO and O2-• donor, affected actin-myosin interactions, as shown by a decreased myosin-propelled actin velocity in the in vitromotility assay. We also observed that oxidation of actin and myosin resulted in a decrease in force generated by myosin and actin filaments, as determined by a system of micro-fabricated cantilevers. While myosin is more sensitive to oxidative modifications than actin, as indicated by a steeper decrease in velocity and force by the filaments, modifications on actin are sufficient to affect force and velocity and also contribute to a decrease in contractile activity in muscles.

Keywords:  actin; contraction; muscle; myosin; oxidation

DOI:  https://doi.org/10.1152/ajpcell.00427.2021
Cytoskeleton (Hoboken). 2022 Sep 09.

Comparison of Incorporation of Wild Type and Mutated Actins into Sarcomeres in Skeletal Muscle Cells: A Fluorescence Recovery After Photobleaching study.

Jushuo Wang, Yingli Fan, Balraj Mittal, Jean M Sanger, Joseph W Sanger.

  The α-actin mutation G15R in the nucleotide-binding pocket of skeletal muscle, causes severe actin myopathy in human skeletal muscles. Expressed in cultured embryonic quail skeletal myotubes, YFP-G15R-α-actin incorporates in sarcomeres in a pattern indistinguishable from wildtype YFP-α-actin. However, patches of YFP-G15R-α-actin form, resembling those in patients. Analyses with FRAP of incorporation of YFP-G15R-α-actin showed major differences between fast-exchanging plus ends of overlapping actin filaments in Z-bands, versus slow exchanging ends of overlapping thin filaments in the middle of sarcomeres. Wildtype skeletal muscle YFP-α-actin shows a faster rate of incorporation at plus ends of F-actin than at their minus ends. Incorporation of YFP-G15R-α-actin molecules is reduced at plus ends, increased at minus ends. The same relationship of wildtype YFP-α-actin incorporation is seen in myofibrils treated with cytochalasin-D: decreased dynamics at plus ends, increased dynamics at minus ends and F-actin aggregates. Speculation: imbalance of normal polarized assembly of F-actin creates excess monomers that form F-actin aggregates. Two other severe skeletal muscle YFP-α-actin mutations (H40Y and V163L) not in the nucleotide pocket do not affect actin dynamics, and lack F-actin aggregates. These results indicate that normal α-actin plus and minus end dynamics are needed to maintain actin filament stability, and avoid F-actin patches. This article is protected by copyright. All rights reserved.

Keywords:  FRAP; actin dynamics; actin mutations; cytochalasin-D; mature myofibrils

DOI:  https://doi.org/10.1002/cm.21725
Nat Rev Mol Cell Biol. 2022 Sep 07.

Reassessing the relationship between mRNA levels and protein abundance in exercised skeletal muscles.

David J Bishop, John A Hawley.

DOI: https://doi.org/10.1038/s41580-022-00541-3
Cells. 2022 Aug 28. pii: 2671. [Epub ahead of print]11(17):

Transforming Growth Factor-Beta Signaling in Cancer-Induced Cachexia: From Molecular Pathways to the Clinics.

Rita Balsano, Zita Kruize, Martina Lunardi, Annalisa Comandatore, Mara Barone, Andrea Cavazzoni, Andrea David Re Cecconi, Luca Morelli, Hanneke Wilmink, Marcello Tiseo, Ingrid Garajovà, Lia van Zuylen, Elisa Giovannetti, Rosanna Piccirillo.

  Cachexia is a metabolic syndrome consisting of massive loss of muscle mass and function that has a severe impact on the quality of life and survival of cancer patients. Up to 20% of lung cancer patients and up to 80% of pancreatic cancer patients are diagnosed with cachexia, leading to death in 20% of them. The main drivers of cachexia are cytokines such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), macrophage inhibitory cytokine 1 (MIC-1/GDF15) and transforming growth factor-beta (TGF-β). Besides its double-edged role as a tumor suppressor and activator, TGF-β causes muscle loss through myostatin-based signaling, involved in the reduction in protein synthesis and enhanced protein degradation. Additionally, TGF-β induces inhibin and activin, causing weight loss and muscle depletion, while MIC-1/GDF15, a member of the TGF-β superfamily, leads to anorexia and so, indirectly, to muscle wasting, acting on the hypothalamus center. Against this background, the blockade of TGF-β is tested as a potential mechanism to revert cachexia, and antibodies against TGF-β reduced weight and muscle loss in murine models of pancreatic cancer. This article reviews the role of the TGF-β pathway and to a minor extent of other molecules including microRNA in cancer onset and progression with a special focus on their involvement in cachexia, to enlighten whether TGF-β and such other players could be potential targets for therapy.

Keywords:  TGF-β; cachexia; cancer-related syndrome

DOI:  https://doi.org/10.3390/cells11172671