bims-moremu 2024-10-27 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024–10–27
twenty-two papers selected by
Anna Vainshtein, Craft Science Inc.

The Acute and Chronic influence of Exercise on Mitochondrial Dynamics in Skeletal Muscle.
Decreased number of satellite cells-derived myonuclei in both fast- and slow-twitch muscles in HeyL-KO mice during voluntary running exercise.
The role of amino acids in skeletal muscle health and sarcopenia: A narrative review.
Mitochondrial pathways and sarcopenia in the geroscience era.
Nrf2 deficiency in muscle attenuates experimental autoimmune myositis-induced muscle weakness.
Exercise-induced adaptations to homeostasis of reactive oxygen species in skeletal muscle.
Effect of spermidine intake on skeletal muscle regeneration after chemical injury in male mice.
Mitochondrial Maintenance in Skeletal Muscle.
Measurement of Mitochondrial Respiration in Human and Mouse Skeletal Muscle Fibers by High-Resolution Respirometry.
Molecular determinants of skeletal muscle force loss in response to 5 days of dry immersion in human.
Sex differences in the association between skeletal muscle energetics and perceived physical fatigability: the Study of Muscle, Mobility and Aging (SOMMA).
Screening of hub genes for sepsis-induced myopathy by weighted gene co-expression network analysis and protein-protein interaction network construction.
Protocol for cell proliferation and cell death analysis of primary muscle stem cell culture using flow cytometry.
Sexual Dimorphism in Sex Hormone Metabolism in Human Skeletal Muscle Cells in Response to Different Testosterone Exposure.
Epigenetic regulation of myogenesis by vitamin C.
Rodent model intervention for prevention and optimal management of sarcopenia: A systematic review on the beneficial effects of nutrients & non-nutrients and exercise to improve skeletal muscle health.
Single-nucleus transcriptomics reveals subsets of degenerative myonuclei after rotator cuff tear-induced muscle atrophy.
Mitochondria break free: Mitochondria-derived vesicles in aging and associated conditions.
Establishment of a dexamethasone-induced zebrafish skeletal muscle atrophy model and exploration of its mechanisms.
Endothelial Beta 1 Integrins are Necessary for Microvascular Function and Glucose Uptake.
Analyzing super-enhancer temporal dynamics reveals potential critical enhancers and their gene regulatory networks underlying skeletal muscle development.
Advances in Muscle Research in Health and Disease.

Am J Physiol Endocrinol Metab. 2024 Oct 23.

The Acute and Chronic influence of Exercise on Mitochondrial Dynamics in Skeletal Muscle.

Elya Janis Ritenis, Camila S Padilha, Matthew B Cooke, Christos George Stathis, Andrew Philp, Donny M Camera.

  Exercise and nutritional modulation are potent stimuli for eliciting increases in mitochondrial mass and function. Collectively, these beneficial adaptations are increasingly recognized to coincide with improvements to skeletal muscle health. Mitochondrial dynamics of fission and fusion are increasingly implicated as having a central role in mediating aspects of key organelle adaptions that are seen with exercise. Exercise-induced mitochondrial adaptations that dynamics have been implicated in are: 1) Increases to mitochondrial turnover, resulting from elevated rates of mitochondrial synthesis (biogenesis) and degradative (mitophagy) processes. 2) Morphological changes to the 3D tubular network, known as the mitochondrial reticulum, that mitochondria form in skeletal muscle. Notably, mitochondrial fission has also been implicated in coordinating increases in mitophagy, following acute exercise. Further, increased fusion following exercise training promotes increased connectivity of the mitochondrial reticulum and is associated with improved metabolism and mitochondrial function. However, the molecular basis and fashion in which exercise infers beneficial mitochondrial adaptations through mitochondrial dynamics remains poorly understood. This review attempts to highlight recent developments investigating the effects of exercise on mitochondrial dynamics, while attempting to offer a perspective of the methodological refinements and potential variables, such as substrate/glycogen availability, which should be considered going forward.

Keywords:  Exercise; Mitochondrial Dynamics; Skeletal Muscle

DOI:  https://doi.org/10.1152/ajpendo.00311.2024
Skelet Muscle. 2024 Oct 24. 14(1): 25

Decreased number of satellite cells-derived myonuclei in both fast- and slow-twitch muscles in HeyL-KO mice during voluntary running exercise.

Kanako Iwamori, Manami Kubota, Lidan Zhang, Kazuki Kodama, Atsushi Kubo, Hiroki Kokubo, Takayuki Akimoto, So-Ichiro Fukada.

   BACKGROUND: Skeletal muscles possess unique abilities known as adaptation or plasticity. When exposed to external stimuli, such as mechanical loading, both myofiber size and myonuclear number increase. Muscle stem cells, also known as muscle satellite cells (MuSCs), play vital roles in these changes. HeyL, a direct target of Notch signaling, is crucial for efficient muscle hypertrophy because it ensures MuSC proliferation in surgically overloaded muscles by inhibiting the premature differentiation. However, it remains unclear whether HeyL is essential for MuSC expansion in physiologically exercised muscles. Additionally, the influence of myofiber type on the requirement for HeyL in MuSCs within exercised muscles remains unclear.
METHODS: We used a voluntary wheel running model and HeyL-knockout mice to investigate the impact of HeyL deficiency on MuSC-derived myonuclei, MuSC behavior, muscle weight, myofiber size, and myofiber type in the running mice.
RESULTS: The number of new MuSC-derived myonuclei was significantly lower in both slow-twitch soleus and fast-twitch plantaris muscles from exercised HeyL-knockout mice than in control mice. However, expect for the frequency of Type IIb myofiber in plantaris muscle, exercised HeyL-knockout mice exhibited similar responses to control mice regarding myofiber size and type.
CONCLUSIONS: HeyL expression is crucial for MuSC expansion during physiological exercise in both slow and fast muscles. The frequency of Type IIb myofiber in plantaris muscle of HeyL-knockout mice was not significantly reduced compared to that of control mice. However, the absence of HeyL did not affect the increased size and frequency of Type IIa myofiber in plantaris muscles. In this model, no detectable changes in myofiber size or type were observed in the soleus muscles of either control or HeyL-knockout mice. These findings imply that the requirement for MuSCs in the wheel-running model is difficult to observe due to the relatively low degree of hypertrophy compared to surgically overloaded models.

Keywords:  HeyL; Hypertrophy; Muscle satellite cells; Wheel running

DOI:  https://doi.org/10.1186/s13395-024-00357-z
J Biomed Res. 2024 Oct 25. 1-14

The role of amino acids in skeletal muscle health and sarcopenia: A narrative review.

Ramendu Hom Chaudhuri.

  The skeletal muscle is the largest organ present inside the body and is responsible for mechanical activities like maintaining posture, movement, respiratory function, and support for the health and functioning of other systems of the body. Skeletal muscle atrophy is a condition associated with a reduction in muscle size, strength, and activity, which leads to an increased dependency on movement, an increased risk of falls, and a reduced quality of life. Various conditions like osteoarthritis, osteoporosis, and fractures are directly associated with an increased muscle atrophy. Additionally, numerous risk factors, like aging, malnutrition, physical inactivity, and certain disease conditions, through distinct pathways negatively affect skeletal muscle health and lead to muscle atrophy. Among the various determinants of the overall muscle health, the rate of muscle protein synthesis and degradation is an important parameter that eventually alters the fate of overall muscle health. In conditions of excessive skeletal muscle atrophy, including sarcopenia, the rate of muscle protein degradation usually exceeds the rate of protein synthesis. The availability of amino acids in the systemic circulation is a crucial step for muscle protein synthesis. The current review aimed to consolidate the existing evidence of amino acids, highlight their mechanisms of action, and assess their roles and effectiveness in enhancing skeletal muscle health.

Keywords:  essential amino acids; protein synthesis; sarcopenia.; skeletal muscle

DOI:  https://doi.org/10.7555/JBR.38.20240167
J Nutr Health Aging. 2024 Oct 19. pii: S1279-7707(24)00485-8. [Epub ahead of print]28(12): 100397

Mitochondrial pathways and sarcopenia in the geroscience era.

Emanuele Marzetti, Riccardo Calvani, Helio José Coelho-Junior, Anna Picca.

  Sarcopenia is associated with structural, ultrastructural, and molecular abnormalities of skeletal muscle. Mitochondrial dysfunction is a pivotal factor involved in muscle aging and sarcopenia. Mitochondrial bioenergetics are significantly reduced in muscles of older adults which is associated with whole-body aerobic capacity, muscle strength, and physical performance. Transcriptional profiling of muscle samples from older adults also revealed inverse correlations between gene expression patterns of autophagy and mitophagy and muscle volume and physical performance. This is in line with the proposition that mitochondrial quality control (MQC) processes are key to organellar and tissue health. MQC encompasses mitochondrial biogenesis, dynamics, and mitophagy. The latter has recently been included among the hallmarks of aging and alterations in MQC have been associated with chronic sterile inflammation as well as muscle atrophy and dysfunction. Several biomarkers spanning MQC, inflammation, metabolism, intercellular communication, and gut microbiota have been linked to sarcopenia. Findings from these initial studies hold promise to inform geroscience-based research in the field of sarcopenia by offering a plausible biological framework for developing gerotherapeutics and monitoring their effects.

Keywords:  Biology of aging; Extracellular vesicles; Inflammaging; Mitochondrial quality control; Multi-Marker; Omics

DOI:  https://doi.org/10.1016/j.jnha.2024.100397
J Physiol. 2024 Oct 21.

Nrf2 deficiency in muscle attenuates experimental autoimmune myositis-induced muscle weakness.

Koichi Himori, Mami Yamada, Takahiro Onoki, Daisuke Matsumaru, Hozumi Motohashi, Mitsuharu Okutsu.

  Idiopathic inflammatory myopathies (IIMs) are systemic autoimmune diseases characterised by muscle weakness. Although multiple physiological and pathological processes are associated with IIMs, T-lymphocyte infiltration into muscle plays a key role in the development and exacerbation of IIMs. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor that regulates inflammatory responses; therefore, muscle Nrf2 may serve an important role in the development of IIMs. In this study, we demonstrated that experimental autoimmune myositis (EAM) causes loss of muscle mass and function in oxidative and glycolytic muscles in C57BL/6 mice. EAM increased CD4+ and CD8+ T-lymphocyte infiltration, as well as interferon-gamma (IFN-γ) and tumour necrosis factor-alpha (TNF-α) mRNA expression in oxidative soleus and glycolytic extensor digitorum longus muscles, along with elevated chemokine mRNA levels (i.e. CCL3, CCL5, CXCL9, CXCL10 and CXCL16). IFN-γ and TNF-α treatments increased the mRNA expression levels of these chemokines in C2C12 myotubes. EAM also increased phosphorylated Nrf2 at Ser40 in soleus and glycolytic white vastus lateralis muscle. Although the expression of several chemokines was affected by Nrf2 activation following tert-butylhydroquinone treatment or Keap1 knockdown, CCL5 mRNA expression significantly increased in C2C12 myotubes and mouse skeletal muscle. Moreover, muscle-specific Nrf2 knockout in mice attenuates EAM-induced loss of muscle mass and function, which was associated with the inhibition of CCL5 mRNA expression, CD8+ T-lymphocyte infiltration and IFN-γ mRNA expression. Collectively, these findings reveal that regulating Nrf2 activity is a promising therapeutic approach for treating IIM-mediated muscle weakness. KEY POINTS: Experimental autoimmune myositis (EAM) causes loss of muscle mass and function. Loss of muscle mass and function in EAM were associated with increased chemokine mRNA expression (i.e. CCL3, CCL5, CXCL9, CXCL10 and CXCL16), T-lymphocyte infiltration and inflammatory cytokine mRNA expression (i.e. IFN-γ and TNF-α) in the skeletal muscle. EAM activated Nrf2 in muscle and increased Nrf2 activity in vivo and in vitro increased CCL5 mRNA expression. Muscle-specific Nrf2 knockout in mice attenuated EAM-induced muscle weakness by inhibiting CCL5 mRNA expression, CD8+ T-lymphocyte migration and IFN-γ mRNA expression in muscles. These results provide further evidence for the potential therapeutic targeting of Nrf2 to mitigate EAM-induced muscle weakness.

Keywords:  T‐lymphocyte; chemokine; idiopathic inflammatory myopathy; muscle weakness; nuclear factor erythroid 2‐related factor 2

DOI:  https://doi.org/10.1113/JP286534
Free Radic Biol Med. 2024 Oct 18. pii: S0891-5849(24)00971-7. [Epub ahead of print]225 494-500

Exercise-induced adaptations to homeostasis of reactive oxygen species in skeletal muscle.

Malcolm J Jackson.

  Reactive oxygen species are generated by multiple mechanisms during contractile activity in exercising skeletal muscle and are recognised to play a role in signaling adaptations to the contractions. The sources of the superoxide and hydrogen peroxide generated are now relatively well understood but how the resulting low concentrations of hydrogen peroxide induce activation of multiple signaling pathways remains obscure. Several theories are presented together with accumulating evidence that 2-Cys peroxiredoxins may play a role of "effector" proteins in mediating the signaling actions of hydrogen peroxide. Identification of the mechanisms underlying these pathways offers the potential in the longer term for development of novel interventions to maintain exercise responses in the elderly with the potential to maintain muscle mass and function and consequent quality of life.

Keywords:  Hydrogen peroxide; Peroxiredoxin; Redox signaling; Skeletal muscle; Superoxide dismutase

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.10.270
Physiol Rep. 2024 Oct;12(20): e70092

Effect of spermidine intake on skeletal muscle regeneration after chemical injury in male mice.

Tomohiro Iwata, Takanaga Shirai, Kazuki Uemichi, Riku Tanimura, Tohru Takemasa.

  Skeletal muscle has a high regenerative ability and maintains homeostasis by rapidly regenerating from frequent damage caused by intense exercise or trauma. In sports, skeletal muscle damage occurs frequently due to intense exercise, so practical methods to promote skeletal muscle regeneration are required. Recent studies have shown that it may be possible to promote skeletal muscle regeneration through new pathways, such as promoting autophagy and improving mitochondrial function. Spermidine is a type of polyamine, and oral intake of spermidine promotes autophagy and improves mitochondrial function without inhibiting mTOR. Therefore, we evaluate the effects of spermidine intake on skeletal muscle regeneration after injury using a mouse model of cardiotoxin-induced muscle injury. Our results showed no significant change in skeletal muscle wet weight with spermidine intake at all time points. In addition, although spermidine intake significantly increased the mean fiber cross-sectional area 14 days after injury, these effects were not observed at other time points. In addition, we analyzed stem cells, autophagy, mTOR signaling, inflammation, and mitochondria, but no significant effects of spermidine intake were observed at almost all time points and protein expression levels. Therefore, spermidine intake does not affect skeletal muscle regeneration after chemical injury, and if there is any, it is very limited.

Keywords:  autophagy; mTOR signaling; mitochondria; skeletal muscle regeneration; spermidine

DOI:  https://doi.org/10.14814/phy2.70092
Cold Spring Harb Perspect Biol. 2024 Oct 21. pii: a041514. [Epub ahead of print]

Mitochondrial Maintenance in Skeletal Muscle.

Laura M de Smalen, Christoph Handschin.

Skeletal muscle is one of the tissues with the highest range of variability in metabolic rate, which, to a large extent, is critically dependent on tightly controlled and fine-tuned mitochondrial activity. Besides energy production, other mitochondrial processes, including calcium buffering, generation of heat, redox and reactive oxygen species homeostasis, intermediate metabolism, substrate biosynthesis, and anaplerosis, are essential for proper muscle contractility and performance. It is thus not surprising that adequate mitochondrial function is ensured by a plethora of mechanisms, aimed at balancing mitochondrial biogenesis, proteostasis, dynamics, and degradation. The fine-tuning of such maintenance mechanisms ranges from proper folding or degradation of individual proteins to the elimination of whole organelles, and in extremis, apoptosis of cells. In this review, the present knowledge on these processes in the context of skeletal muscle biology is summarized. Moreover, existing gaps in knowledge are highlighted, alluding to potential future studies and therapeutic implications.

DOI: https://doi.org/10.1101/cshperspect.a041514
J Vis Exp. 2024 Oct 04.

Measurement of Mitochondrial Respiration in Human and Mouse Skeletal Muscle Fibers by High-Resolution Respirometry.

Terri A Pietka, Rita T Brookheart.

Mitochondrial function, a cornerstone of cellular energy production, is critical for maintaining metabolic homeostasis. Its dysfunction in skeletal muscle is linked to prevalent metabolic disorders (e.g., diabetes and obesity), muscular dystrophies, and sarcopenia. While there are many techniques to evaluate mitochondrial content and morphology, the hallmark method to assess mitochondrial function is the measurement of mitochondrial oxidative phosphorylation (OXPHOS) by respirometry. Quantification of mitochondrial OXPHOS provides insight into the efficiency of mitochondrial oxidative energy production and cellular bioenergetics. A high-resolution respirometer provides highly sensitive, robust measurements of mitochondrial OXPHOS in permeabilized muscle fibers by measuring real-time changes in mitochondrial oxygen consumption rate. The use of permeabilized muscle fibers, as opposed to isolated mitochondria, preserves mitochondrial networks, maintains mitochondrial membrane integrity, and ultimately allows for more physiologically relevant measurements. This system also allows for the measurement of fuel preference and metabolic flexibility - dynamic aspects of muscle energy metabolism. Here, we provide a comprehensive guide for mitochondrial OXPHOS measurements in human and mouse skeletal muscle fibers using a high-resolution respirometer. Skeletal muscle groups are composed of different fiber types that vary in their mitochondrial fuel preference and bioenergetics. Using a high-resolution respirometer, we describe methods for evaluating both aerobic glycolytic and fatty acid substrates to assess fuel preference and metabolic flexibility in a fiber-type-dependent manner. The protocol is versatile and applicable to both human and rodent muscle fibers. The goal is to enhance the reproducibility and accuracy of mitochondrial function assessments, which will improve our understanding of an organelle important to muscle health.

DOI: https://doi.org/10.3791/66834
J Cachexia Sarcopenia Muscle. 2024 Oct 25.

Molecular determinants of skeletal muscle force loss in response to 5 days of dry immersion in human.

Mathias Velarde, Michel-Yves Sempore, Valentine Allibert, Valérie Montel, Josiane Castells, Loïc Treffel, Angèle Chopard, Thomas Brioche, Laetitia Cochon, Jérome Morel, Bruno Bastide, Anne-Cécile Durieux, Laurence Stevens, Damien Freyssenet.

   BACKGROUND: Astronauts in Earth's orbit experience microgravity, resulting in a decline of skeletal muscle mass and function. On Earth, models simulating microgravity have shown that the extent of the loss in muscle force is greater than the loss in muscle mass. The reasons behind this disproportionate loss of muscle force are still poorly understood. In the present study, we hypothesize that alongside the loss in skeletal muscle mass, modifications in the expression profile of genes encoding critical determinants of resting membrane potential, excitation-contraction coupling and Ca2+ handling contribute to the decline in skeletal muscle force.
METHODS: Healthy male volunteers (n = 18) participated in a 5-day dry immersion (DI) study, an Earth-based model of simulated microgravity. Muscle force measurement and MRI analysis of the cross-sectional area of thigh muscles were performed before and after DI. Biopsies of the vastus lateralis skeletal muscle performed before and after DI were used for the determination Ca2+ properties of isolated muscle fibres, molecular and biochemical analyses.
RESULTS: The extent of the decline in force, measured as maximal voluntary contraction of knee extensors (-11.1%, P < 0.01) was higher than the decline in muscle mass (-2.5%, P < 0.01). The decline in muscle mass was molecularly supported by a significant repression of the anabolic IGF-1/Akt/mTOR pathway (-19.9% and -40.9% in 4E-BP1 and RPS6 phosphorylation, respectively), a transcriptional downregulation of the autophagy-lysosome pathway and a downregulation in the mRNA levels of myofibrillar protein slow isoforms. At the single fibre level, biochemical and tension-pCa curve analyses showed that the loss in force was independent of fibre type (-11% and -12.3% in slow and fast fibres, respectively) and Ca2+ activation properties. Finally, we showed a significant remodelling in the expression of critical players of resting membrane potential (aquaporin 4: -24.9%, ATP1A2: +50.4%), excitation-contraction coupling (CHRNA1: +75.1%, CACNA2D1: -23.5%, JPH2: -24.2%, TRDN: -15.6%, S100A1: +27.2%), and Ca2+ handling (ATP2A2: -32.5%, CASQ1: -15%, ORAI1: -36.2%, ATP2B1: -19.1%).
CONCLUSIONS: These findings provide evidence that a deregulation in the expression profile of critical molecular determinants of resting membrane potential, excitation-contraction coupling, and Ca2+ handling could be involved in the loss of muscle force induced by DI. They also provide the paradigm for the understanding of muscle force loss during prolonged bed rest periods as those encountered in intensive care unit.

Keywords:  Excitation‐contraction coupling; Microgravity; Muscle atrophy; Muscle disuse; Slow and fast isoforms of myofibrillar proteins

DOI:  https://doi.org/10.1002/jcsm.13559
Geroscience. 2024 Oct 22.

Sex differences in the association between skeletal muscle energetics and perceived physical fatigability: the Study of Muscle, Mobility and Aging (SOMMA).

Emma L Gay, Paul M Coen, Stephanie Harrison, Reagan E Garcia, Yujia Susanna Qiao, Bret H Goodpaster, Daniel E Forman, Frederico G S Toledo, Giovanna Distefano, Philip A Kramer, Sofhia V Ramos, Anthony J A Molina, Barbara J Nicklas, Steven R Cummings, Peggy M Cawthon, Russell T Hepple, Anne B Newman, Nancy W Glynn.

  Greater perceived physical fatigability and lower skeletal muscle energetics are both predictors of mobility decline. Characterizing associations between muscle energetics and perceived fatigability may provide insight into potential targets to prevent mobility decline. We examined associations of in vivo (maximal ATP production, ATPmax) and ex vivo (maximal carbohydrate supported oxidative phosphorylation [max OXPHOS] and maximal fatty acid supported OXPHOS [max FAO OXPHOS]) measures of mitochondrial energetics with two measures of perceived physical fatigability, Pittsburgh Fatigability Scale (PFS, 0-50, higher = greater) and Rating of Perceived Exertion (RPE Fatigability, 6-20, higher = greater) after a slow treadmill walk. Participants from the Study of Muscle, Mobility and Aging (N = 873) were 76.3 ± 5.0 years old, 59.2% women, and 85.3% White. Higher muscle energetics (both in vivo and ex vivo) were associated with lower perceived physical fatigability, all p < 0.03. When stratified by sex, higher ATPmax was associated with lower PFS Physical for men only; higher max OXPHOS and max FAO OXPHOS were associated with lower RPE Fatigability for both sexes. Higher skeletal muscle energetics were associated with 40-55% lower odds of being in the most (PFS ≥ 25, RPE Fatigability ≥ 12) vs least (PFS 0-4, RPE Fatigability 6-7) severe fatigability strata, all p < 0.03. Being a woman was associated with 2-3 times higher odds of being in the most severe fatigability strata when controlling for ATPmax but not the ex vivo measures (p < 0.05). Better mitochondrial energetics were linked to lower fatigability and less severe fatigability in older adults. Findings imply that improving skeletal muscle energetics may mitigate perceived physical fatigability and prolong healthy aging.

Keywords:  Aging; Epidemiology; Fatigue; Mitochondria; Oxidative phosphorylation

DOI:  https://doi.org/10.1007/s11357-024-01373-z
BMC Musculoskelet Disord. 2024 Oct 22. 25(1): 834

Screening of hub genes for sepsis-induced myopathy by weighted gene co-expression network analysis and protein-protein interaction network construction.

Jianhao Wang, Kun Han, Jinshuai Lu.

  Sepsis-induced myopathy is one of the serious complications of sepsis, which severely affects the respiratory and peripheral motor systems of patients, reduces their quality of life, and jeopardizes their lives, as evidenced by muscle atrophy, loss of strength, and impaired regeneration after injury. The pathogenesis of sepsis-induced myopathy is complex, mainly including cytokine action, enhances free radical production in muscle, increases muscle protein hydrolysis, and decreases skeletal muscle protein synthesis, etc. The above mechanisms have been demonstrated in existing studies. However, it is still unclear how the overall pattern of gene co-expression affects the pathological process of sepsis-induced myopathy. Therefore, we intend to identify hub genes and signaling pathways. Weighted gene co-expression network analysis was our main approach to study gene expression profiles: skeletal muscle transcriptome in ICU patients with sepsis-induced multi-organ failure (GSE13205). After data pre-processing, about 15,181 genes were used to identify 13 co-expression modules. Then, 16 genes (FEM1B, KLHDC3, GPX3, NIFK, GNL2, EBNA1BP2, PES1, FBP2, PFKP, BYSL, HEATR1, WDR75, TBL3, and WDR43) were selected as the hub genes including 3 up-regulated genes and 13 down-regulated genes. Then, Gene Set Enrichment Analysis was performed to show that the hub genes were closely associated with skeletal muscle dysfunction, necrotic and apoptotic skeletal myoblasts, and apoptosis in sepsis-induced myopathy. Overall, 16 candidate biomarkers were certified as reliable features for more in-depth exploration of sepsis-induced myopathy in basic and clinical studies.

Keywords:  Gene set enrichment analysis (GSEA); Protein-protein interaction network (PPI); Sepsis; Sepsis-induced myopathy (SIM); Weighted gene co-expression network analysis (WGCNA)

DOI:  https://doi.org/10.1186/s12891-024-07967-0
STAR Protoc. 2024 Oct 23. pii: S2666-1667(24)00576-8. [Epub ahead of print]5(4): 103411

Protocol for cell proliferation and cell death analysis of primary muscle stem cell culture using flow cytometry.

Pauline Garcia, Orane Mercier, Jade Ravent, Fabien Le Grand.

  Skeletal muscle is critically dependent on the function of muscle stem cells (MuSCs) for effective muscle repair following injury. Here, we detail a protocol for the isolation of primary muscle cells and subsequent analysis of proliferation capacity in vitro using EdU (5-ethynyl-2'-deoxyuridine) on fixed cells. We also describe a cell death analysis on living cells with the identification of early- and late-apoptotic cells, as well as necrotic cells, through the incorporation of propidium iodide and YO-PRO-1 staining. For complete details on the use and execution of this protocol, please refer to Garcia et al.1.

Keywords:  cell biology; cell culture; cell isolation; flow cytometry; microscopy; stem cells

DOI:  https://doi.org/10.1016/j.xpro.2024.103411
Biology (Basel). 2024 Oct 05. pii: 796. [Epub ahead of print]13(10):

Sexual Dimorphism in Sex Hormone Metabolism in Human Skeletal Muscle Cells in Response to Different Testosterone Exposure.

Paolo Sgrò, Cristina Antinozzi, Christopher W Wasson, Francesco Del Galdo, Ivan Dimauro, Luigi Di Luigi.

  Muscle tissue is an important target of sex steroids, and particularly, testosterone plays essential roles in muscle cell metabolism. Wide ranges of studies have reported sex differences in basal muscle steroidogenesis, and recently several genes have been identified to be regulated by androgen response elements that show innate sex differences in muscle. However, studies accounting for and demonstrating cell sexual dimorphism in vitro are still scarce and not well characterized. Here, we demonstrated the ability of 46XX and 46XY human primary skeletal muscle cells to differently activate steroidogenesis in vitro, likely related to sex-chromosome onset, and to differently induce hormone release after increasing doses of testosterone exposure. Cells were treated with testosterone at concentrations of 0.5, 2, 5, 10, 32, and 100 nmol/L for 24 h. Variations in 17β-HSD, 5α-R2, CYP-19 expression, DHT, estradiol, and androstenedione release, as well as IL6 and IL8 release, were analyzed, respectively, by RT-PCR, ELISA, and luminex-assay. Following testosterone treatments, and potentially at any concentration level, an increase in the expression of 17β-HSD, 5α-R2, and CYP-19 was observed in 46XY cells, accompanied by elevated levels of DHT, androstenedione, and IL6/IL8 release. Following the same treatment, 46XX cells exhibited an increase in 5α-R2 and CYP-19 expression, a conversion of androgens to estrogens, and a reduction in IL6 and IL8 release. In conclusion, this study demonstrated that sex-chromosome differences may influence in vitro muscle cell steroidogenesis and hormone homeostasis, which are pivotal for skeletal muscle metabolism.

Keywords:  gender dimorphism; muscle steroidogenesis; myokines; sex-chromosome; sex-related health status

DOI:  https://doi.org/10.3390/biology13100796
J Cell Physiol. 2024 Oct 24. e31472

Epigenetic regulation of myogenesis by vitamin C.

Sachiko Yamashita Takeuchi, Chirada Dusadeemeelap, Tatsuo Kawamoto, Takuma Matsubara, Shoichiro Kokabu, William N Addison.

  The micronutrient vitamin C is essential for the maintenance of skeletal muscle health and homeostasis. The pro-myogenic effects of vitamin C have long been attributed to its role as a general antioxidant agent, as well as its role in collagen matrix synthesis and carnitine biosynthesis. Here, we show that vitamin C also functions as an epigenetic compound, facilitating chromatin landscape transitions during myogenesis through its activity as an enzymatic cofactor for histone H3 and DNA demethylation. Utilizing C2C12 myoblast cells to investigate the epigenetic effects of vitamin C on myogenesis, we observe that treatment of cells with vitamin C decreases global H3K9 methylation and increases 5-hmC levels. Furthermore, vitamin C treatment enhances myoblast marker gene expression and myotube formation during differentiation. We identify KDM7A as a histone lysine demethylase markedly upregulated during myogenesis. Accordingly, knockdown of Kdm7a prevents the pro-myogenic effects of vitamin C. Chromatin immunoprecipitation analysis showed that KDM7A occupies the promoter region of the myogenic transcription factor MyoD1 where it facilitates histone demethylation. We also confirm that the methylcytosine dioxygenases TET1 and TET2 are required for myogenic differentiation and that their loss blunts stimulation of myogenesis by vitamin C. In conclusion, our data suggest that an epigenetic mode of action plays a major role in the myogenic effects of vitamin C.

Keywords:  DNA methylation; KDM7A; TET; histone methylation; myogenesis; vitamin C

DOI:  https://doi.org/10.1002/jcp.31472
Ageing Res Rev. 2024 Oct 18. pii: S1568-1637(24)00361-1. [Epub ahead of print] 102543

Rodent model intervention for prevention and optimal management of sarcopenia: A systematic review on the beneficial effects of nutrients & non-nutrients and exercise to improve skeletal muscle health.

Vijayakumar Mayakrishnan, Priya Kannappan, Janani Balakarthikeyan, Choon Young Kim.

  Sarcopenia is a common musculoskeletal disorder characterized by degenerative processes and is strongly linked to an increased susceptibility to falls, fractures, physical limitations, and mortality. Several models have been used to explore therapeutic and preventative measures as well as to gain insight into the molecular mechanisms behind sarcopenia. With novel experimental methodologies emerging to design foods or novel versions of conventional foods, understanding the impact of nutrition on the prevention and management of sarcopenia has become important. This review provides a thorough assessment of the use of rodent models of sarcopenia for understanding the aging process, focusing the effects of nutrients, plant extracts, exercise, and combined interventions on skeletal muscle health. According to empirical research, nutraceuticals and functional foods have demonstrated potential benefits in enhancing physical performance. In preclinical investigations, the administration of herbal extracts and naturally occurring bioactive compounds yielded advantageous outcomes such as augmented muscle mass and strength generation. Furthermore, herbal treatments exhibited inhibitory effects on muscle atrophy and sarcopenia. A substantial body of information establishes a connection between diet and the muscle mass, strength, and functionality of older individuals. This suggests that nutrition has a major impact in both the prevention and treatment of sarcopenia.

Keywords:  Sarcopenia; age; exercise; nutrient; plant extracts; rodent; skeletal muscle

DOI:  https://doi.org/10.1016/j.arr.2024.102543
Cell Prolif. 2024 Oct 22. e13763

Single-nucleus transcriptomics reveals subsets of degenerative myonuclei after rotator cuff tear-induced muscle atrophy.

Ziying Sun, Xi Cheng, Zheng Wang, Chenfeng Qiao, Hong Qian, Tao Yuan, Zhongyang Lv, Wenshuang Sun, Hanwen Zhang, Yuan Liu, Zhihao Lu, Jintao Lin, Chengteng Lai, Yang Wang, Xiaojiang Yang, Xingyun Wang, Jia Meng, Nirong Bao.

Rotator cuff tear (RCT) is the primary cause of shoulder pain and disability and frequently trigger muscle degeneration characterised by muscle atrophy, fatty infiltration and fibrosis. Single-nucleus RNA sequencing (snRNA-seq) was used to reveal the transcriptional changes in the supraspinatus muscle after RCT. Supraspinatus muscles were obtained from patients with habitual shoulder dislocation (n = 3) and RCT (n = 3). In response to the RCT, trajectory analysis showed progression from normal myonuclei to ANKRD1+ myonuclei, which captured atrophy-and fatty infiltration-related regulons (KLF5, KLF10, FOSL1 and BHLHE40). Transcriptomic alterations in fibro/adipogenic progenitors (FAPs) and muscle satellite cells (MuSCs) have also been studied. By predicting cell-cell interactions, we observed communication alterations between myofibers and muscle-resident cells following RCT. Our findings reveal the plasticity of muscle cells in response to RCT and offer valuable insights into the molecular mechanisms and potential therapeutic targets of RCT.

DOI: https://doi.org/10.1111/cpr.13763
Ageing Res Rev. 2024 Oct 19. pii: S1568-1637(24)00367-2. [Epub ahead of print]102 102549

Mitochondria break free: Mitochondria-derived vesicles in aging and associated conditions.

Luigi Ferrucci, Flora Guerra, Cecilia Bucci, Emanuele Marzetti, Anna Picca.

  Mitophagy is the intracellular recycling system that disposes damaged/inefficient mitochondria and allows biogenesis of new organelles to ensure mitochondrial quality is optimized. Dysfunctional mitophagy has been implicated in human aging and diseases. Multiple evolutionarily selected, redundant mechanisms of mitophagy have been identified, but their specific roles in human health and their potential exploitation as therapeutic targets are unclear. Recently, the characterization of the endosomal-lysosomal system has revealed additional mechanisms of mitophagy and mitochondrial quality control that operate via the production of mitochondria-derived vesicles (MDVs). Circulating MDVs can be isolated and characterized to provide an unprecedented opportunity to study this type of mitochondrial recycling in vivo and to relate it to human physiology and pathology. Defining the role of MDVs in human physiology, pathology, and aging is hampered by the lack of standardized methods to isolate, validate, and characterize these vesicles. Hence, some basic questions about MDVs remain unanswered. While MDVs are generated directly through the extrusion of mitochondrial membranes within the cell, a set of circulating extracellular vesicles leaking from the endosomal-lysosomal system and containing mitochondrial portions have also been identified and warrant investigation. Preliminary research indicates that MDV generation serves multiple biological roles and contributes to restoring cell homeostasis. However, studies have shown that MDVs may also be involved in pathological conditions. Therefore, further research is warranted to establish when/whether MDVs are supporting disease progression and/or are extracting damaged mitochondrial components to alleviate cellular oxidative burden and restore redox homeoastasis. This information will be relevant for exploiting these vesicles for therapeutic purpose. Herein, we provide an overview of preclinical and clinical studies on MDVs in aging and associated conditions and discuss the interplay between MDVs and some of the hallmarks of aging (mitophagy, inflammation, and proteostasis). We also outline open questions on MDV research that should be prioritized by future investigations.

Keywords:  Exosomes; Extracellular vesicles; Inflammaging; Mitochondrial DNA; Mitochondrial quality control; Mitophagy

DOI:  https://doi.org/10.1016/j.arr.2024.102549
Exp Gerontol. 2024 Oct 21. pii: S0531-5565(24)00261-4. [Epub ahead of print] 112615

Establishment of a dexamethasone-induced zebrafish skeletal muscle atrophy model and exploration of its mechanisms.

Chen-Chen Sun, Ye-Jun Li, Dan-Ting Zhu, Zhang-Lin Chen, Jiang-Ling Xiao, Xiang-Tao Chen, Lan Zheng, Xi-Yang Peng, Chang-Fa Tang.

   BACKGROUND: Skeletal muscle atrophy is one of the main side effects of high-dose or continuous use of glucocorticoids (such as dexamethasone). However, there are limited studies on dexamethasone-induced skeletal muscle atrophy in zebrafish and even fewer explorations of the underlying molecular mechanisms. This study aimed to construct a model of dexamethasone-induced skeletal muscle atrophy in zebrafish and to investigate the molecular mechanisms.
METHODS: Zebrafish soaked in 0.01 % dexamethasone solution for 10 days. Loli Track (Denmark) and Loligo Swimming Respirometer were used to observe the effect of dexamethasone on swimming ability. The effects of dexamethasone on zebrafish skeletal muscle were observed by Transmission electron microscopy, H&E, and wheat germ agglutinin techniques. Enriched genes and signaling pathways were analyzed using Transcriptome sequencing. Further, the levels of mitochondrial and endoplasmic reticulum-related proteins were examined to investigate possible mechanisms.
RESULTS: 0.01 % dexamethasone reduced zebrafish skeletal muscle mass (p < 0.05), myofibre size and cross-sectional area (p < 0.001), and increased protein degradation (ubiquitination and autophagy) (p < 0.05). In addition, 0.01 % dexamethasone reduced the swimming ability of zebrafish, as evidenced by the reluctance to move, fewer movement trajectories, decreased total distance traveled (p < 0.001), average velocity of movement (p < 0.001), oxygen consumption (p < 0.001), critical swimming speed (p < 0.01) and increased exhaustive swimming time (p < 0.001). Further, 0.01 % dexamethasone-induced mitochondrial dysfunction (decreased mitochondrial biogenesis, disturbs kinetic homeostasis, increased autophagy) and endoplasmic reticulum stress.
CONCLUSIONS: 0.01 % dexamethasone induces skeletal muscle atrophy and impairs the swimming ability of zebrafish through mitochondrial dysfunction and endoplasmic reticulum stress.

Keywords:  Dexamethasone; Endoplasmic reticulum stress; Mitochondrial dysfunction; Skeletal muscle atrophy; Zebrafish

DOI:  https://doi.org/10.1016/j.exger.2024.112615
Am J Physiol Endocrinol Metab. 2024 Oct 23.

Endothelial Beta 1 Integrins are Necessary for Microvascular Function and Glucose Uptake.

Nathan C Winn, Deborah A Roby, Penn Mason McClatchey, Ian M Williams, Deanna P Bracy, Michelle N Bedenbaugh, Louise Lantier, Erin Plosa, Ambra Pozzi, Roy Zent, David H Wasserman.

  Microvascular insulin delivery to myocytes is rate limiting for the onset of insulin-stimulated muscle glucose uptake. The structural integrity of capillaries of the microvasculature is regulated, in part, by a family of transmembrane adhesion receptors known as integrins, which are composed of an α and β subunit. The integrin β1 (itgb1) subunit is highly expressed in endothelial cells (EC). EC itgb1 is necessary for the formation of capillary networks during embryonic during development and its knockdown blunts the reactive hyperemia that manifests during ischemia reperfusion. We investigated the contribution of EC itgb1 in microcirculatory function and glucose uptake with emphasis in skeletal muscle. We hypothesized that loss of EC itgb1 would impair microvascular hemodynamics and glucose uptake during insulin stimulation, creating 'delivery'-mediated insulin resistance. An itgβ1 knockdown mouse model was developed to avoid lethality of embryonic gene knockout and the deteriorating health resulting from early post-natal inducible gene deletion. Mice with (itgb1fl/flSCLcre) and without (itgb1fl/fl) tamoxifen inducible stem cell leukemia cre recombinase (SLCcre) expression at 10 days post cre induction had comparable exercise tolerance and pulmonary and cardiac functions. Using robust in vivo experimental platforms (i.e., intravital microscopy and hyperinsulinemic-euglycemic clamp), we show that itgb1fl/flSCLcre mice compared to itgb1fl/fl littermates have, i) deficits in capillary flow rate, flow heterogeneity, and capillary density; ii) impaired insulin-stimulated glucose uptake despite sufficient transcapillary insulin efflux; and iii) reduced insulin-stimulated glucose uptake due to perfusion-limited glucose delivery. Thus, EC itgb1 is necessary for microcirculatory function and to meet the metabolic challenge of insulin stimulation.

Keywords:  Endothelial; Glucose uptake; Integrin; Microcirculation; Skeletal muscle

DOI:  https://doi.org/10.1152/ajpendo.00322.2024
Genome Res. 2024 Oct 21. pii: gr.278344.123. [Epub ahead of print]

Analyzing super-enhancer temporal dynamics reveals potential critical enhancers and their gene regulatory networks underlying skeletal muscle development.

Song Zhang, Chao Wang, Shenghua Qin, Choulin Chen, Yongzhou Bao, Yuanyuan Zhang, Lingna Xu, Qingyou Liu, Yunxiang Zhao, Kui Li, Zhonglin Tang, Yuwen Liu.

Super-enhancers (SEs) govern the expression of genes defining cell identity. However, the dynamic landscape of SEs and their critical constituent enhancers involved in skeletal muscle development remains unclear. In this study, using pig as a model, we employed CUT&Tag to profile the enhancer-associated histone modification marker H3K27ac in skeletal muscle across two prenatal and three postnatal stages and investigated how SEs influence skeletal muscle development. We identified three SE families with distinct temporal dynamics: continuous (Con, 397), transient (TS, 434), and de novo (DN, 756). These SE families are associated with different temporal gene expression trajectories, biological functions, and DNA methylation levels. Notably, several lines of evidence suggest a potential prominent role of Con SEs in regulating porcine muscle development and meat traits. To pinpoint key cis-regulatory units in Con SEs, we developed an integrative approach that leverages information from eRNA annotation, GWAS signals and high-throughput capture STARR-seq experiments. Within Con SEs, we identified 20 candidate critical enhancers with meat and carcass-associated DNA variations that affect enhancer activity and inferred their upstream TFs and downstream target genes. As a proof of concept, we experimentally validated the role of one such enhancer and its potential target gene during myogenesis. Our findings reveal the dynamic regulatory features of SEs in skeletal muscle development and provide a general integrative framework for identifying critical enhancers underlying the formation of complex traits.

DOI: https://doi.org/10.1101/gr.278344.123
Cells. 2024 Oct 14. pii: 1694. [Epub ahead of print]13(20):

Advances in Muscle Research in Health and Disease.

Wan Lee.

Muscle tissue plays a vital role in the maintenance of overall health, contributing to essential body functions such as locomotion, respiration, blood circulation, and metabolic regulation [...].

DOI: https://doi.org/10.3390/cells13201694