bims-moremu Biomed News
on Molecular regulators of muscle mass
Issue of 2026–07–05
39 papers selected by
Anna Vainshtein, Craft Science Inc.



  1. bioRxiv. 2026 Jun 23. pii: 2026.06.18.733224. [Epub ahead of print]
      Regular exercise induces adaptations in skeletal muscle and other organ systems to improve physical performance and overall health. Exercise results in phosphorylation of 5' AMP-activated protein kinase (AMPK) at threonine 172 (T172) of the α2 subunit; however, the role of this activation in cellular and functional adaptations has not been elucidated. To this end, we subjected non-activatable Ampkα2 ( T172A ) knock-in (KI) adult mice and wild-type (WT) littermates to 4 weeks of voluntary wheel running (VWR). Exercise training led to significant improvements in endurance capacity, maximal oxygen consumption ( O 2 max), and glucose tolerance, as well as skeletal muscle IIb-to-IIa fiber type shift in both WT and KI mice. Contrastingly, VWR resulted in increased mitochondrial OxPhos protein expression, mitochondrial volume density, and capillary density in skeletal muscle of WT but not KI mice. Exercise-induced improvements of mitochondrial respiration and conductance revealed by high-resolution respirometry of isolated mitochondria were blunted in KI mice. Therefore, for the first time, we reveal that AMPKα2 T172 activation is required for exercise training-induced mitochondrial biogenesis, improvement of mitochondrial respiratory function, and angiogenesis in skeletal muscle, but that these adaptations are not solely responsible for improved O 2 max and exercise endurance capacity.
    Significance Statement: Exercise is the most effective lifestyle intervention for promoting health and preventing chronic diseases through adaptive changes in skeletal muscle and many other tissues/organs. AMPK is an energy sensor and signaling regulator for exercise-induced skeletal muscle adaptation, yet its functional role and the impact on exercise capacity have been studied in mouse genetic models wherein protein stoichiometry is disrupted. Using non-activatable Ampkα2(T172A) knock-in mice, we ascertained that AMPKα2 activation via T172 phosphorylation is required for endurance training-induced mitochondrial and angiogenic adaptations in skeletal muscle. Importantly, these adaptations are not required for improved exercise capacity, challenging the prevailing concept that increased mitochondrial content and function and microvasculature are the sole driving factors for the performance gains with endurance training.
    DOI:  https://doi.org/10.64898/2026.06.18.733224
  2. Front Cell Dev Biol. 2026 ;14 1878702
      Skeletal muscle is a highly plastic tissue with a robust capacity for regeneration, largely driven by resident satellite cells. Muscular dystrophies comprise a heterogeneous group of inherited disorders characterized by progressive muscle degeneration, chronic inflammation, and impaired regenerative capacity. Despite well-defined genetic etiologies, effective disease-modifying therapies for these disorders, as well as many acquired myopathies, remain limited. Emerging evidence identifies nuclear receptors (NRs) as key regulators of skeletal muscle homeostasis, integrating hormonal, metabolic, and environmental signals to control transcriptional programs governing mitochondrial function, metabolism, inflammation, and myogenesis. In this review, we summarize the diverse roles and mechanisms of action of NRs in skeletal muscle biology and discuss how their dysregulation contributes to muscle wasting and disease progression. We also highlight emerging NR-targeted therapeutic strategies aimed at enhancing metabolic function, suppressing inflammation and fibrosis, and promoting muscle regeneration. Finally, we outline critical knowledge gaps and future directions to advance the translation of NR-based therapies for muscular dystrophies and related neuromuscular disorders.
    Keywords:  muscular dystrophy; myopathy; nuclear receptors; signaling; transcription factors
    DOI:  https://doi.org/10.3389/fcell.2026.1878702
  3. J Cachexia Sarcopenia Muscle. 2026 Aug;17(4): e70333
       BACKGROUND: Duchenne muscular dystrophy (DMD) is the most common and severe form of muscular dystrophy, primarily affecting skeletal muscle and leading to premature death. Although the loss of dystrophin has long been recognised as the primary cause of the disease, no definitive cure is currently available. As a consequence, therapeutic efforts have largely focused on mitigating disease progression rather than correcting the primary genetic defect. In this context, extensive research focuses on secondary pathological mechanisms, downstream cellular and molecular alterations triggered by dystrophin deficiency, that contribute to disease progression, particularly by affecting muscle degeneration and regeneration. While therapeutic strategies have traditionally aimed to enhance muscle regeneration, accumulating evidence indicates that limiting chronic degeneration and the associated degeneration-regeneration cycles may represent a more effective approach to preserve muscle integrity. Here, we examine the published evidence to delineate this shift in therapeutic perspective.
    METHODS: This narrative review summarises preclinical and clinical strategies for DMD. We considered over 100 published articles, 85% from the last 15 years and analysing 40 different approaches, grouping them based on pathways targeted. For each study, therapeutic efficacy was assessed by focusing on the impact on promoting muscle regeneration versus limiting degeneration, based on morphological features, including muscle architecture, inflammation and fibrosis, as well as functional outcomes.
    RESULTS: Our analysis revealed pathway-specific benefits in skeletal muscle. Among calcium- and mitochondrial-targeted interventions, 94.4% preserved muscle morphology and slowed down muscle regeneration. Myofibre stability approaches were evenly split, with 50% promoting regeneration and 50% delaying muscle wasting. Satellite cell-targeted therapies affecting proliferation and fusion enhanced muscle regeneration in most cases, while anti-inflammatory strategies slowed muscle degeneration in 63.6% and promoted new myofibre formation in 36.4% of cases. Oxidative stress modulation preserved muscle structure in 85.7% of cases, while boosting muscle regeneration in the remaining therapies.
    CONCLUSIONS: Emerging evidence indicates a shift in DMD therapeutic focus, from strategies aimed primarily at enhancing muscle regeneration to approaches that limit repeated degeneration-regeneration cycles. Most current interventions act by modulating pathological processes that drive chronic muscle damage rather than by directly stimulating regeneration. Importantly, targeting multiple disease-relevant pathways within skeletal muscle has shown beneficial effects in preclinical models, supporting the concept that coordinated and temporally controlled modulation of key biological processes may represent an effective strategy to stabilise muscle tissue and delay disease progression.
    Keywords:  Duchenne muscular dystrophy; anti‐inflammatory strategies; calcium homeostasis and mitochondrial function; cycles of degeneration and regeneration; myofibre stability and regeneration; oxidative stress; pharmacological treatments; satellite cell
    DOI:  https://doi.org/10.1002/jcsm.70333
  4. Circ Res. 2026 Jul 06. 139(2): e328678
      Skeletal muscle health and regeneration are highly orchestrated processes governed by a complex interplay of muscle stem cells, fibro-adipogenic progenitors, immune cells, and endothelial cells. Among these cell types, endothelial cells play a central role not only by regulating blood and nutrient flow to support metabolic and regenerative needs, but also by directly interacting with muscle stem cells and fibro-adipogenic progenitors to regulate stem cell quiescence or activation, and muscle tissue remodeling during its regeneration and growth. The current review article provides a broad overview of the crucial role of the endothelial cells during muscle health and growth, their expansion and interaction with key muscle cell types, governing signaling pathways, and their role in metabolism. Furthermore, we discuss the role of endothelial dysfunction as a pathogenic mechanism in muscular dystrophies, diabetes, peripheral artery disease, and sarcopenia. We also overview current therapeutic approaches targeting endothelial cells in the muscle and highlight biological and research barriers causing underdeveloped therapeutics in this field.
    Keywords:  endothelial cells; exercise; inflammation; muscle, skeletal; sarcopenia; stem cells
    DOI:  https://doi.org/10.1161/CIRCRESAHA.126.328678
  5. Biochem Res Int. 2026 ;2026 5967706
      The physiological age-related decline in skeletal muscle mass, power, and function is challenging for humans. Skeletal muscle has been recently recognized as a secretory organ, with human myogenic progenitor cells (hMPCs) releasing extracellular vesicles (EVs). Here, we investigate the role of hMPC-derived EVs as mediators in skeletal muscle aging. This heterologous approach enables the analysis of age-related variations in EV burden and their impact on human muscle stem cell function. Therefore, we isolated EVs from hMPCs obtained from vastus lateralis muscle biopsies of young and elderly subjects. Then, we characterized EVs for specific marker, size, and concentration and analyzed their miRNA expression and proteomic profiles to delineate the bioactive cargo that influences recipient cell signaling. Next, we tested the ability of EVs to modulate on hMPCs. Specifically, we treated elderly hMPCs with young EVs and vice versa to analyze viability and differentiation. Our results demonstrate that EVs released by young hMPCs carry regenerative signals that mitigate the functional decline of aged muscle stem cells. Conversely, the EVs derived from elderly hMPCs compromise the regenerative capacity of their younger counterparts. Therefore, these results suggest that hMPCs release EVs and that their cargo is modulated by donor age. Moreover, the EVs significantly modulated hMPCs' viability and differentiation in cell culture.
    Keywords:  extracellular vesicles; human adult myogenic progenitor cells; microRNAs; senescence; skeletal muscle
    DOI:  https://doi.org/10.1155/bri/5967706
  6. J Physiol Biochem. 2026 Jun 30. pii: 60. [Epub ahead of print]82(1):
      Preservation of skeletal muscle mass and function is a key feature of healthy ageing and relies on the tight coordination between protein synthesis and breakdown to maintain proteostatic balance. These processes impose a substantial energetic demand, highlighting the importance of mitochondrial function in skeletal muscle homeostasis. Increasing evidence indicates that mitochondria and the sarcoplasmic reticulum are functionally interconnected. Effective crosstalk between these organelles contributes to the integration of bioenergetic supply, Ca²⁺ handling, and proteostasis. Disruption of this communication network may impair adaptive stress responses, compromise protein quality control, and favour the development of anabolic resistance during ageing. This review synthesizes current evidence on mitochondria-sarcoplasmic reticulum communication. It further discusses how disruption of this crosstalk may promote anabolic resistance and skeletal muscle atrophy, with particular emphasis on its implications for age-related muscle decline.
    Keywords:  Atrophy; Calcium; Endoplasmic reticulum; Organelle crosstalk; Sarcopenia; Unfolded protein response
    DOI:  https://doi.org/10.1007/s13105-026-01198-8
  7. bioRxiv. 2026 Jun 15. pii: 2026.05.15.725287. [Epub ahead of print]
      The adult skeletal muscle regenerates robustly upon injury, but this regenerative capacity rapidly declines with age. In this study, we identify the lanthionine synthetase C-Like (LanCL) proteins, mammalian homologs of the bacterial peptide cyclase LanC, as positive regulators of muscle regeneration in middle-aged mice. In a barium chloride-induced injury model, we found the protein levels of LanCL1 and LanCL2 to increase during an early phase of regeneration in middle-aged (12-month-old) but not young adult (4-month-old) mice. Utilizing a mouse line lacking all three LanCL proteins (LanCL triple KO or LTKO), we examined a potential role of LanCL in injury-induced muscle regeneration. Consistent with an age-dependent function of LanCL, we observed a delayed regeneration of the tibialis anterior (TA) muscle after injury, as reflected by reduced sizes of regenerating myofibers at day 7 after injury in middle-aged (but not young) LTKO compared to age-matched WT mice. Although the pool size of quiescent satellite cells (Pax7+) was comparable between 12-month-old LTKO and WT muscles without injury, the number of Pax7+ cells was significantly higher in regenerating LTKO muscles at day 5 after injury, accompanied by drastically decreased numbers of MyoD+ and MyoG+ cells, as well as increased numbers of proliferating cells. In addition, we detected elevated expression of pro-inflammatory cytokines in regenerating LTKO muscles, while the number of macrophages was similar comparing LTKO and WT muscles. Taken together, our observations suggest that in aging muscles LanCLs are important for proper timing of inflammation resolution and regeneration upon injury.
    New & Noteworthy: Physiological roles of the mammalian homologs of bacterial LanC, LanCLs, are poorly understood. Our work uncovers a function of LanCLs in post-injury regeneration of aging skeletal muscles. Middle-aged LanCL triple KO mice displayed a delay in satellite cell differentiation and regenerative myofiber formation, as well as persistent inflammatory cytokine expression, suggesting that LanCLs may have an age-dependent role in modulating inflammation in the injured muscles to facilitate regeneration.
    DOI:  https://doi.org/10.64898/2026.05.15.725287
  8. J Physiol. 2026 Jul 01.
      Exercise stimulates skeletal muscle signalling and mitochondrial metabolism. Emerging evidence shows that mitochondrial dynamics (i.e. fission and fusion) could be regulated by exercise. Yet, key gaps remain in identifying (i) the signals that drive fission vs. fusion; (ii) how energy status and reactive oxygen species (ROS) shift control between dynamin-related protein 1 (DRP1) and mitofusin (MFN)/optic atrophy 1 (OPA1); and (iii) which intensity-duration combinations yield similar cytosolic signals but different mitochondrial remodelling. Therefore, we developed an integrative computational framework connecting exercise regimens to mitochondria fission-fusion machinery by linking blood-myofibre energetics in cytosol and mitochondria to signalling pathways. The influence of sprint, resistance and endurance exercise regimens on mitochondrial fission and fusion has been simulated. Classified qualitative validation of the signalling network model achieved 80% accuracy. The model predicts regimen-specific dynamics starting with an acute DRP1-driven fission during exercise followed by MFN1/2-OPA1-mediated re-fusion as energy stress declines, consistent with a cyclical triage-then-rebuild paradigm. Changes are most pronounced and sustained with endurance, sharp but brief with sprint, and minimal with resistance. Global sensitivity analysis identified AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor gamma coactivator-1α→MFN1/2 as dominant fusion drivers, ROS and AMPK→mitochondrial fission factor/DRP1 as primary fission switches, and Ca2 +-calmodulin, extracellular-signal-regulated kinase and liver kinase B1/AMPK as shared regulators. The model predicts that an endurance base, augmented with one or two weekly high intensity interval training/sprint interval training sessions could maximize AMPK-ROS pulses and mitochondrial fission-fusion. This framework unifies muscle's signalling logic with energetic state to explain how intensity-volume combinations, bout spacing and kinase modulation tune mitochondrial remodelling, yielding testable predictions for optimizing training and adjuvant therapies to enhance mitochondrial quality and performance. KEY POINTS: Different exercise regimes such as sprint, resistance, and endurance can trigger different signalling pathways. Exercise also triggers mitochondrial remodelling in skeletal muscle. Using a systems biology model, we developed a systems biology model for skeletal muscle signalling and mitochondrial metabolism for exercise. Our model predicts the dynamics of mitochondrial fusion and fission in different exercise regimes and identifies which signalling pathways dominassste these remodelling mechanisms.
    Keywords:  ROS‐mediated signalling; exercise regime; metabolic signalling; mitochondrial fission; mitochondrial fusion
    DOI:  https://doi.org/10.1113/JP290424
  9. Skelet Muscle. 2026 Jul 01.
       BACKGROUND: Duchenne muscular dystrophy (DMD) is a devastating disease manifested in skeletal muscle by repetitious myonecrosis and regeneration. Because the regenerative process is closely linked to the cumulative severity of muscle damage, which is variably distributed within and between muscle groups, accurately quantifying muscle regeneration has remained a significant challenge.
    METHODS: Myofibers are delineated by immunostaining for laminin, and subsequent image analysis employed to generate a masked outline precisely within each myofiber boundary. Morphometric parameters including minimal Feret's diameter, cross-sectional area, and circularity were measured for each myofiber. In addition, the number of Pax7-expressing satellite cells were quantified. To evaluate regenerative activity, newly formed myofibers were identified by immunostaining for expression of embryonic myosin heavy chain (eMHC). Necrotic myofibers were enumerated by immunofluorescent detection of immunoglobulin G (IgG) infiltration. The Regenerative Index (RI) was calculated as the number of regenerating (eMHC+) myofibers divided by the number of necrotic (IgG+) myofibers. Determination of RI was performed on muscle biopsies obtained from 10 boys with DMD and 3 age-matched non-DMD controls.
    RESULTS: A trend toward an increasing minimal Feret's diameter, cross-sectional area and circularity was observed with increasing age in DMD boys, with circularity showing the strongest trend. Furthermore, compared to DMD boys 7- to 8-years old, the boys 9- to 11-years old had increased myofiber circularity. Pax7-expressing cells per myofiber were elevated in DMD boys compared to control boys of similar ages, without any observation of age-related changes. The Regenerative Index in DMD boys exhibited a decline between 7 and 11 years of age, with an inverse correlation between RI and age.
    CONCLUSIONS: The use of eMHC and IgG immunostaining to calculate RI appears to provide a way to assess regeneration across biopsies that differ in histopathologic severity. Using this approach, RI showed a negative correlation with age in DMD boys aged 7 to 11 years which requires further investigation.
    Keywords:  Duchenne muscular dystrophy (DMD); Dystrophin; Embryonic myosin heavy chain (eMHC); Muscle regeneration; Necrotic myofibers; Regenerating myofibers; Regenerative Index (RI)
    DOI:  https://doi.org/10.1186/s13395-026-00436-3
  10. Hum Mol Genet. 2026 Jun 26. pii: ddag060. [Epub ahead of print]35(13):
      Dystrophin links the actin cytoskeleton to the extracellular matrix through the dystrophin-glycoprotein complex (DGC), providing structural stability to muscle fibers. In mdx mice, which lack dystrophin, neuromuscular junctions (NMJs) remain largely structurally and functionally intact despite extensive muscle pathology. Here, using single- and double-mutant mice deficient in dystrophin and α-syntrophin (α-syn), we investigated how utrophin upregulation contributes to NMJ maintenance in dystrophic muscle. During early postnatal development, when dystrophic muscles are transiently resistant to degeneration, the DGC proteins α-dystrobrevin, α-syn, and β-dystroglycan are broadly distributed along both synaptic and extra-synaptic regions of the sarcolemma, although their overall levels are reduced compared with wild-type (WT) muscle. In contrast, in WT mice, utrophin is restricted to NMJs, whereas in dystrophic muscles from both mutants, it is distributed along both synaptic and extra-synaptic regions of the sarcolemma, particularly within the innervated zone of muscle fibers. As muscles mature and degeneration begins, these DGC components become highly restricted to NMJs while being markedly reduced or absent from the extra-synaptic sarcolemma in many muscle cells. Although utrophin remains highly enriched at synaptic sites in mdx:α-syn-/- muscles, their NMJs display severe structural abnormalities compared with those of mdx mice. These include a dramatic reduction in synaptic fold depth and density, a decrease in presynaptic vesicle density, retraction of nerve terminals, and axonal thinning. These findings demonstrate that utrophin localization at the NMJ is not sufficient to preserve synaptic integrity and that functional interactions between utrophin and α-syn are required to maintain the NMJ in dystrophic muscle.
    Keywords:  molecular genetics; mouse models; muscular dystrophy
    DOI:  https://doi.org/10.1093/hmg/ddag060
  11. Front Physiol. 2026 ;17 1836341
      Striated muscles exhibit remarkable structural and functional specialization that enables precise control of force production, contractile kinetics, and energetic efficiency. Although vertebrate skeletal and cardiac muscles have been extensively studied, comparative analyses across animal phyla reveal that many molecular and biophysical principles governing muscle performance are deeply conserved. Insects, in particular, possess highly differentiated muscle types that provide powerful systems for dissecting the regulation of contraction, elasticity, and force generation at the level of the sarcomere. In this review, we integrate insights from insect and vertebrate muscles to highlight conserved and divergent features of sarcomere organization and myofilament composition. We focus on major contractile and regulatory proteins, including actin, myosin, troponin, tropomyosin, and elastic proteins, emphasizing how isoform diversity fine-tunes muscle function. We discuss the biomedical relevance of invertebrate models for understanding muscle disease mechanisms, including congenital myopathies, sarcomeric protein-associated disorders, and muscular dystrophies. Finally, we examine how principles uncovered in insect muscles inform vertebrate cardiac physiology and skeletal muscle aging, positioning insect systems as complementary discovery platforms for advancing muscle biology.
    Keywords:  Drosophila models; Frank-Starling mechanism; indirect flight muscle; muscle disease; myofilament regulation; sarcomere elasticity; stretch activation; titin-like proteins
    DOI:  https://doi.org/10.3389/fphys.2026.1836341
  12. FASEB J. 2026 Jul 15. 40(13): e72109
      Myogenesis is a stepwise process encompassing myogenic progenitor proliferation, lineage commitment, differentiation, myocyte fusion, and myotube maturation, and it is orchestrated by myogenic regulatory factors (MRFs) together with signaling pathways that coordinate these transitions. Long noncoding RNAs (lncRNAs) have emerged as important regulators of muscle development and regeneration, yet how lncRNAs integrate with canonical signaling networks to shape myogenic progression remains incompletely defined. Here, we identify a novel myocyte-enriched, Notch-repressed myogenic lncRNA (NRMLncR, known as A930003A15Rik), as a previously uncharacterized regulator of mouse myogenesis. The expression of NRMLncR is robustly induced during primary myoblast activation and differentiation. Loss-of-function analyses show that knockdown of NRMLncR impairs myogenic differentiation, accompanied by reduced expression of key myogenic genes. In contrast, adenovirus-mediated overexpression of NRMLncR enhances myogenic differentiation in vitro and is associated with increased muscle fiber size in vivo. Mechanistically, MyoD and MyoG occupy the NRMLncR promoter and promote its transcription during myogenic differentiation. NRMLncR knockdown alerts the transcription of nearby genes, suggesting its function through a cis-regulatory mechanism. RNA pull-down and functional assays further identify an interaction between NRMLncR and the RNA-binding protein CELF1. Together, these findings establish NRMLncR as a novel Notch-associated lncRNA that promotes myogenic differentiation and provide insight into lncRNA-dependent regulation of the myogenic program.
    Keywords:  CELF1; long non‐coding RNA; myoblast; myogenesis; myogenic regulatory factor; notch signaling
    DOI:  https://doi.org/10.1096/fj.202601027R
  13. Front Genet. 2026 ;17 1846707
      Identification of skeletal muscle fiber types and metabolic reprogramming are crucial for postnatal muscle maturation, but high-resolution metabolism and spatial heterogeneity of muscle fibers in mid-maturation remain poorly understood. Our study performed single-cell RNA sequencing (scRNA-seq) and single-cell nuclear RNA sequencing (snRNA-seq) on five hind limb muscles from 5-week-old mice, combined with Stereo-cell at single muscle fiber resolution, to elucidate myofiber subtype maturation and its metabolic changes. Integrating scRNA-seq and snRNA-seq data, a comprehensive mouse skeletal muscle cell atlas was constructed, demonstrating the complementary advantages of the two techniques in capturing interstitial cells and multinucleated muscle fibers. Our analysis resolved a continuous maturational lineage from type I to IIB myonuclei (IIB_1-3). Notably, the IIB_3 myonuclei subtype exhibited a dual hypermetabolic phenotype, with increased oxidative phosphorylation (OXPHOS) and glycolytic activity, which differs from the purely glycolytic phenotype observed in adult mice. Stereo-cell further validated this transitional metabolic state and revealed spatial heterogeneity within individual IIB myofibers, with localized high-oxidation regions. Furthermore, we observed a mixed myofiber phenotype, with subtype-specific myosin heavy chain expression enriched at the myofiber terminals, indicating directional transformation of myofiber during maturation. In summary, this study reveals a previously undescribed transitional metabolic feature of IIB-type myofiber during postnatal muscle maturation and elucidates the spatial metabolic heterogeneity of myofiber, providing new insights into the regulatory mechanisms of skeletal muscle developmental plasticity and metabolic specialization.
    Keywords:  metabolism; myofiber; scRNA; snRNA; stereo-cell
    DOI:  https://doi.org/10.3389/fgene.2026.1846707
  14. Mol Biol Rep. 2026 Jun 30. pii: 1032. [Epub ahead of print]53(1):
      Skeletal muscle (SkM) atrophy is an associated disorder of cachexia, sarcopenia, immobilization, and denervation and is responsible for increased mortality and morbidity. SkM atrophy is often characterized by increased protein degradation and decreased protein synthesis in skeletal muscle. Increased protein catabolism is firmly associated with protein ubiquitination, an associated post-transcriptional modification of proteins that mediate diverse cellular functions like cell growth, cell death, DNA damage repair, and protein degradation. During the SkM atrophy, the extents of ubiquitination decide the degradative pathway of proteins as well as organelles. The ubiquitination process is regulated by three enzymes, ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and an E3 ubiquitin ligase (E3) to mediate the transfer of ubiquitin to the Lys residue of the targeted protein. More than 600 E3 ligases (Reviewed Uniprot Database) known to date are tissue-specific, organ-specific, and ubiquitous. Hence, E3 ligases may be selective drug targets due to their involvement in the regulation of stabilities and functions of proteins. Muscle atrophy F-box protein (MAFbx)/atrogin-1, and E3 ubiquitin-protein ligase TRIM63 (MuRF-1) are highly explored muscle-specific E3 ligases. However, the inhibition of MAFbx and MuRF-1 cannot stop the muscle atrophy completely. Hence, the involvement of other highly expressed E3 ubiquitin-protein ligases in SkM i.e., TRIM7, UBE2O, MIB2, and CHIP are also important factors in SkM atrophy. Hence, this review aimed to highlight the interplay and importance of E3 ligases in SkM atrophy.
    Keywords:  Drug targets; E3 ligases; HECT; Muscle atrophy; RING-finger; U-box; and PHD-finger
    DOI:  https://doi.org/10.1007/s11033-026-12239-2
  15. J Toxicol Sci. 2026 ;51(7): 379-391
      Cisplatin is a widely used platinum-based chemotherapeutic agent whose dose-limiting toxicities, including nephrotoxicity, neurotoxicity, and myelosuppression, have been extensively characterized. In contrast, skeletal muscle has not traditionally been regarded as a primary target of cisplatin toxicity. However, accumulating experimental evidence indicates that cisplatin administration leads to a significant reduction in skeletal muscle mass and fiber size, even in the absence of tumor burden or overt cachexia. These findings suggest that cisplatin itself can directly induce skeletal muscle atrophy as a form of drug-induced toxicity. Animal and cell-based studies have demonstrated that cisplatin activates catabolic signaling in skeletal muscle, most notably through enhanced protein degradation via the ubiquitin-proteasome system. This response is accompanied by increased expression of muscle-specific E3 ubiquitin ligases, including muscle RING finger 1 (MuRF1) and muscle atrophy F-box protein (MAFbx/atrogin-1), which are established mediators of skeletal muscle atrophy. In parallel, suppression of anabolic signaling, particularly impairment of the insulin-like growth factor-1/Akt/mechanistic target of rapamycin complex 1 (mTORC1) pathway, has been reported, indicating a shift in muscle protein turnover toward a catabolic state. Recent studies suggest that cellular stress responses, such as endoplasmic reticulum stress, may be involved in regulating these processes. This review summarizes experimental evidence supporting cisplatin-induced skeletal muscle atrophy and discusses the underlying toxicological processes from a muscle-centered perspective. By distinguishing drug-induced muscle toxicity from cancer cachexia and other wasting conditions, we propose that skeletal muscle should be recognized as a clinically relevant but underestimated target organ of cisplatin toxicity. Improved understanding of these processes may support the development of strategies to preserve muscle mass and function during cancer chemotherapy.
    Keywords:  Atrogin-1; Cisplatin; MuRF1; Skeletal muscle atrophy; Ubiquitin–proteasome system
    DOI:  https://doi.org/10.2131/jts.51.379
  16. Nat Aging. 2026 Jul 03.
      Exercise is fundamental to healthy aging, yet how it mitigates age-related molecular changes and how fitness level shapes exercise responses remain unclear. To address these questions, we performed transcriptomics, lipidomics and metabolomics on skeletal muscle of young and older adults with differing physical function, both before and after an acute bout of submaximal exercise. At baseline, older adults exhibited reduced expression of genes associated with cellular respiration and energy metabolism compared to young adults with comparable activity levels. Here we found that 50% of these age-related differences were absent in trained older adults, resulting in profiles resembling those of young adults. Although all participants displayed transcriptional immune and stress responses upon acute exercise, the magnitude of these responses in older adults was positively correlated with their physical fitness. Integrated multiomic analyses further revealed links among mitochondrial respiration, lipid metabolism, stress responses and NAD+ biology. These findings demonstrate that sustained physical training transforms age-related molecular profiles and provide a molecular atlas for study of fitness-dependent aging mechanisms.
    DOI:  https://doi.org/10.1038/s43587-026-01150-x
  17. Spectrochim Acta A Mol Biomol Spectrosc. 2026 Jun 29. pii: S1386-1425(26)00901-7. [Epub ahead of print]363(Pt 2): 128330
      Muscle fiber types perform distinct functions within skeletal muscle tissue, enabling a wide range of physical and motor capabilities. Although specific fiber types are well characterized by their Myosin Heavy Chain isoform expression, it is highly informative to investigate these cells using further approaches. In this context, Raman spectroscopy represents a powerful tool for molecular discovery. Here, we characterized the Raman spectroscopic signatures of Type I, IIa, and IIx skeletal muscle fibers in the mouse soleus. Specific bands associated with amino acids such as tryptophan, phenylalanine, tyrosine, and the Amide I band are the main drivers of the observed variation. Interestingly, distinct spectral intensities and peak ratios particularly within the 1350 cm-1 region and 1550-1750 cm-1 range clearly differentiated Type I from Type IIa/IIx fibers. Principal Component Analysis further revealed that most of the observed variation is driven by changes near ∼1600 cm-1. Overall, the detection of these spectral patterns provides valuable insights into the biochemical characteristics of muscle fibers and highlights the potential of Raman spectroscopy to identify fiber-type-specific signatures under various physiological and pathological conditions, including atrophy, hypertrophy, and sarcopenia.
    Keywords:  Fibers; Raman spectroscopy; Skeletal muscle
    DOI:  https://doi.org/10.1016/j.saa.2026.128330
  18. Histol Histopathol. 2026 Jul 03. 25119
      Satellite cells (SCs) are recognized as the resident stem cells of adult skeletal muscles, essential for post-natal skeletal muscle growth and regeneration following focal myotrauma. In healthy muscle, SCs are quiescent, but in response to damage or growth signals, they become activated to proliferate and differentiate to form new myofibers. A small population self-renews to replenish the basal pool for future demands. The ability of SCs to precisely balance quiescence, self-renewal, and myogenic commitment/differentiation is essential for ensuring long-term muscle homeostasis and tissue maintenance. Their state and functionality are strictly regulated by different intrinsic and extrinsic cues, the latter deriving from the microenvironment in which SCs reside, known as the niche. The niche is a dynamic compartment where extracellular matrix components, soluble factors, mechanical stimuli, and multiple interacting cell populations modulate the morphological, molecular, and electrophysiological properties of SCs. This review provides an updated overview of the morpho-functional features of SCs and of non-myogenic stromal interstitial cells, highlighting their reciprocal crosstalk within the regenerative niche. Such stromal cells play a dual role, acting as "good" or "bad" cells: while functioning as nursing cells for SCs during muscle repair/regeneration via juxtracrine and paracrine interactions, their excessive accumulation and adoption of a fibrotic/fat phenotype may lead to aberrant tissue repair, compromising muscle function. A deeper understanding of SC biology and of collaborative spatiotemporal cell interactions in the healthy, damaged, and regenerative niche is essential to identify potential novel targets and to better address interventions for maintaining, restoring, or enhancing muscle regeneration capacity and mitigating the deleterious effects of extended, severe, or pathological muscle damage.
    DOI:  https://doi.org/10.14670/HH-25-119
  19. Diabetes. 2026 Jul 02. pii: db260229. [Epub ahead of print]
       ARTICLE HIGHLIGHTS: Female C57BL/6 J mice are relatively resistant to weight gain, which complicates the study of sex-specific metabolic responses. So, we used ob/ob mice to examine semaglutide-induced weight loss in both sexes. We wanted to determine whether semaglutide-induced weight loss produces sex-specific effects on skeletal muscle mass and function in ob/ob mice. Semaglutide had minimal effects on skeletal muscle mass and strength in ob/ob mice. In particular, females were completely resistant to loss of muscle mass. These findings reveal that semaglutide exerts sex-specific effects, highlighting a need for further research into the molecular mechanisms driving these distinct protective outcomes.
    DOI:  https://doi.org/10.2337/db26-0229
  20. Front Immunol. 2026 ;17 1843626
      Macrophage polarization has a significant influence on the immune microenvironment of skeletal muscle, regulating metabolic and repair homeostasis. Meteorin-like protein (Metrnl), a recently identified myokine, is implicated in immunity, metabolism, and tissue remodeling. It regulates macrophage polarization through a complex, integrated signaling network, conferring multiple metabolic benefits on skeletal muscle. This review outlines the dynamics of macrophage polarization in maintaining skeletal muscle homeostasis and discusses the signaling pathways through which Metrnl exerts its effects. Drawing on human and rodent in vivo studies, the focus is on the pivotal role of this regulatory axis in skeletal muscle destabilization, particularly in glucose metabolic disorders and age-related sarcopenia. Notably, Metrnl acts as a bidirectional regulator whose biological effects are highly tissue- and disease-dependent. The review further concludes by examining potential pathological mechanisms linking Metrnl-modulated macrophage polarization to skeletal muscle microenvironmental homeostasis, and highlights unresolved questions regarding Metrnl receptor distribution and subset-specific macrophage regulation, putting forward multi-omics and in vivo imaging technologies as core avenues for subsequent exploration.
    Keywords:  glucose metabolism; inflammation; macrophage polarization; meteorin-like protein; myokines; sarcopenia; skeletal muscle homeostasis
    DOI:  https://doi.org/10.3389/fimmu.2026.1843626
  21. Acta Physiol (Oxf). 2026 Aug;242(8): e70274
       BACKGROUND: Resistance training has been shown to activate the protein synthesis pathway, leading to muscle growth in humans. However, this type of exercise has shown equivocal results in animal studies due to the difficulty of mimicking muscle overload in vivo. This study aimed to determine whether ladder-based exercise in mice induces canonical molecular, cellular, and functional adaptations to training.
    METHODS: Mice performed a single exercise session or 6 weeks of training in the ladder climb. Acute responses included mTOR phosphorylation, puromycin incorporation, and mRNA levels of myogenic regulatory factors (MRF). Chronic adaptations were assessed by strength, fat-free mass, physical performance, and blood lactate levels to confirm the training load. Sarcomeric proteins were analyzed using Western blot, while histology measured muscle fiber diameter and satellite cell (SC) fusion. The SC amount was quantified by flow cytometry.
    RESULTS: After a single exercise bout, mTOR phosphorylation increased at one and 3 h, with puromycin incorporation and MRF mRNA levels elevated at 8 h. After 6 weeks of training, the mice showed increased skeletal muscle strength and fat-free mass, with no changes in physical performance. Muscle-specific adaptations included increases in sarcomeric proteins and fiber diameters. SC adaptations were associated with an increased pool and enhanced capacity to fuse with muscle fibers.
    CONCLUSIONS: Our results demonstrate that ladder-based resistance exercise in mice induces molecular, cellular, and functional responses that are directionally consistent with adaptations reported after human resistance training, supporting its value for investigating the molecular and cellular mechanisms underlying this training.
    Keywords:  acute responses; chronic adaptations; exercise; ladder climb; resistance training; skeletal muscle
    DOI:  https://doi.org/10.1111/apha.70274
  22. Bone Res. 2026 Jun 29. pii: 68. [Epub ahead of print]14(1):
      Cell-cell fusion, essential for diverse physiological events, requires high ATP levels. While mitochondrial activity increases in fusing cells, the mechanism driving mitochondrial ribosome (mitoribosome) biogenesis to support these energy demands remains unclear. Here, we identify angiogenin (ANG) as a mitochondrial tRNA (mt-tRNA) processing enzyme critical for mitoribosome biogenesis during myoblast and osteoclast fusion. Upon fusion initiation, ANG translocates to mitochondria, promoting mitoribosome biogenesis to support translation of respiratory complex proteins for ATP production. Using transcriptome-wide PARE and 5' RACE analyses, we show that ANG cleaves the tRNA 3'-end in mitochondrial pre-RNA transcripts bordering rRNAs and mRNAs, enabling their release for translation. Loss of ANG or disruption of its ribonucleolytic activity impairs osteoclast and myoblast fusion, disrupting bone and muscle homeostasis and skeletal muscle regeneration post-injury. Our findings establish ANG as an essential mitoribosome biogenesis regulator and highlight a novel mechanism of mitochondria energy regulation in high-energy-demand biological processes.
    DOI:  https://doi.org/10.1038/s41413-026-00545-1
  23. Front Neurol. 2026 ;17 1861632
       Background: Lipid storage myopathy (LSM) is characterized by abnormal lipid accumulation in skeletal muscle. Emerging evidence suggests that environmental factors, including the use of antidepressants such as sertraline, may trigger LSM. Given the established link between hyperhomocysteinemia (HHcy) and disrupted lipid metabolism, we investigated its potential role in skeletal muscle lipid deposition.
    Methods: We enrolled six patients with HHcy undergoing muscle biopsy and explored their clinical and pathological characteristics of skeletal muscle. The mechanistic link was explored in muscle tissues from patients through transcriptomic profiling, quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and enzymatic assays, and validated in C2C12 myotubes.
    Results: Four of the six patients presented with clinical myopathic manifestations, including progressive muscle weakness and exercise intolerance, which resolved completely after B-vitamin supplementation, while abnormal skeletal muscle lipid deposition was observed in all six patients. Transcriptome and qRT-PCR analyses demonstrated a significant upregulation of the acetyl-CoA carboxylase β (ACACB) gene (p < 0.001), which encodes acetyl-CoA carboxylase 2 (ACC2), in the muscle tissues from patients. Furthermore, ACC2 protein expression was markedly elevated (p < 0.01), thereby raising cellular malonyl-CoA levels (p < 0.01). This metabolite potently inhibits carnitine palmitoyltransferase 1 (CPT1), impairing fatty acid oxidative metabolism in skeletal muscle. The key molecular cascade involving ACACB upregulation and subsequent CPT1 inhibition (p < 0.05), was further verified in C2C12 myotubes.
    Conclusion: This study indicates that HHcy is closely associated with abnormal skeletal muscle lipid deposition. HHcy may correlate with increased ACC2 expression, which elevates malonyl-CoA levels. This, in turn, suppresses CPT1 activity and facilitates abnormal lipid accumulation in skeletal muscle.
    Keywords:  ACC2; C2C12 myotubes; CPT1 enzyme activity; hyperhomocysteinemia; lipid deposition; malonyl-CoA
    DOI:  https://doi.org/10.3389/fneur.2026.1861632
  24. Exp Mol Med. 2026 Jul 03.
      Sarcopenia and neuromuscular degeneration are key drivers of functional decline during ageing and arise not solely from muscle loss but also from failure of mitochondrial and metabolic stress adaptation across the neuromuscular system. Mitochondrial dysfunction, characterized by impaired oxidative phosphorylation, defective quality control and redox imbalance, contributes directly to muscle weakness, neuromuscular junction instability and motor unit degeneration. However, the upstream mechanisms governing the transition from adaptive remodelling to degenerative collapse remain incompletely defined. Protein arginine methyltransferases (PRMTs) have emerged as critical modulators of mitochondrial and metabolic stress signalling. Beyond epigenetic regulation, PRMTs influence signalling pathways that intersect with AMP-activated protein kinase (AMPK)-Forkhead box O (FOXO) and mechanistic target of rapamycin (mTOR), thereby regulating mitochondrial biogenesis, selective autophagy and mitophagy, proteostatic balance, and anabolic restraint. Distinct PRMT family members exert non-redundant functions across muscle fibres, satellite cells and motor neurons, collectively shaping neuromuscular stress resilience. We propose that PRMTs act as molecular rheostats that bias cellular responses to mitochondrial stress towards adaptive resolution or progression to neuromuscular degeneration, thereby positioning PRMT-regulated metabolic signalling as a unifying mechanism underlying sarcopenia and compromised healthspan.
    DOI:  https://doi.org/10.1038/s12276-026-01762-8
  25. Hum Mol Genet. 2026 Jun 26. pii: ddag059. [Epub ahead of print]35(13):
      Tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK) are clinically overlapping disorders characterized by muscle weakness, thrombocytopenia, spleen anomalies and short stature. They are due to mutations affecting the Ca2+ sensor STIM1 or the Ca2+ channel ORAI1 and leading to aberrant Ca2+ homeostasis. Therapeutic approaches aiming to rebalance intracellular Ca2+ levels largely rescued the multi-systemic phenotype in Stim1R304W/+ mice harboring the most common TAM/STRMK mutation. However, the currently used biomarkers to follow disease progression are costly and inadequate for longitudinal studies. Here, we investigated the suitability of MYOM3 to serve as a robust blood-based biomarker for TAM/STRMK. Using only minimal blood volumes, we detected highly elevated circulating MYOM3 levels in plasma samples from Stim1R304W/+ mice and TAM/STRMK patients with different mutations, and we found that the MYOM3 levels were normalized in Stim1R304W/+ mice undergoing efficient therapies. We also identified skeletal muscle as the primary source of circulating MYOM3, a structural protein of the contractile unit in myofibers, and uncovered that MYOM3 is primarily expressed in regenerating muscle fibers and in fast-twitch type IIa fibers. Overall, this work emphasizes the utility of MYOM3 as a minimally-invasive biomarker for disorders involving myofiber degeneration, and highlights the ability of MYOM3 to detect early muscle dysfunction in TAM/STRMK and evaluate therapeutic efficiency.
    Keywords:  MYOM3; STIM1; Stormorken syndrome; TAM; calcium; myomesin; tubular aggregate myopathy
    DOI:  https://doi.org/10.1093/hmg/ddag059
  26. Commun Biol. 2026 Jul 03.
      Transforming growth factor-β (TGF-β) signaling is associated with progressive skeletal muscle wasting. It is unknown whether myofibre-specific knockout of TGF-β type I receptors affects muscle transcriptome, mass, contractile force and oxidative metabolism. Here we show that 3 months after myofibre-specific knockout of TGF-β type I receptors (dKO) in male mice, transcriptomics demonstrate substantially more differentially expressed genes in gastrocnemius medialis (GM) than in soleus, mainly related to muscle contraction, hypertrophy and oxidative metabolism. GM mass of dKO mice increases substantially more than maximal force. Conversely, soleus mass of dKO mice increases in proportion to maximal force. Myofibre hypertrophy in dKO mice is accompanied by a proportional increase in succinate dehydrogenase enzyme activity. These adaptations are associated with a simultaneous decrease in β1-syntrophin and increases in sarcolipin, hepatocyte growth factor gene expression and anabolic signalling. Single receptor knockout causes minor phenotypical and transcriptional alterations. Our study highlights that myofibre-specific interference with both TGF-β type I receptors concurrently stimulates myofibre hypertrophy, enhances absolute force and simultaneously augments oxidative capacity.
    DOI:  https://doi.org/10.1038/s42003-026-10501-8
  27. Autophagy. 2026 Jun 28. 1-17
      Accelerated CHRN/AChR/nicotinic acetylcholine receptor internalization induced by auto-antibodies impairs neuromuscular junction transmission and contributes to myasthenia gravis (MG), a typical autoimmune disease. Although CHRN internalization is well established in MG pathogenesis, the downstream cellular events, especially those related to autophagy, remain poorly described. Here, we report that RAPSN/rapsyn, an intracellular CHRN-binding protein essential for its clustering, accumulates as aggregates in experimental autoimmune myasthenia gravis (EAMG) mice. In CHRN antibody-treated myotubes, RAPSN dissociates from internalized CHRN and forms aggregates due to exposure of its hydrophobic domains. These aggregates in turn impair the trafficking and membrane incorporation of newly synthesized CHRN, thereby exacerbating CHRN loss. Notably, the accumulation of RAPSN aggregates facilitates formation of HSPA/HSP70-BAG3 complex, which recognizes and transports the aggregates along microtubules to form perinuclear aggresomes for subsequent lysosomal degradation. Accordingly, pharmacological inhibition or knockdown of HSPA-BAG3 complex increases RAPSN aggregation, which participates in enhanced CHRN loss and worsened muscle weakness in EAMG mice. This study identifies HSPA-BAG3 aggrephagy as a protective mechanism that clears RAPSN aggregates to maintain CHRN integrity and suggests a potential therapeutic strategy for MG.Abbreviation: 3-MA: 3-methyladenine; AAV: adeno-associated virus; CASA: chaperone-assisted selective autophagy; CHRN/nicotinic acetylcholine receptor: cholinergic receptor nicotinic; CHRN-ab: CHRN antibodies; CHX: cycloheximide; CMAP: compound muscle action potential; CQ: chloroquine; EAMG: experimental autoimmune myasthenia gravis; ER: endoplasmic reticulum; GAS: gastrocnemius; MAP1LC3A/B: microtubule associated protein 1 light chain 3 alpha/beta; MG: myasthenia gravis; NMJ: neuromuscular junction; Rapa: rapamycin; RAPSN/rapsyn: receptor associated protein of the synapse; SQSTM1: sequestosome 1; TA: tibialis anterior; αBTX-A594: α-bungarotoxin-Alexa-594.
    Keywords:  Aggregate; CHRN; HSPA; RAPSN; autophagy; myasthenia gravis
    DOI:  https://doi.org/10.1080/15548627.2026.2693778
  28. Sci Adv. 2026 Jul 03. 12(27): eaej2301
      Legs use diverse muscles to perform movements. A study on insect leg muscle development shows that the environment instructs cellular diversity before muscles form.
    DOI:  https://doi.org/10.1126/sciadv.aej2301
  29. Sci Rep. 2026 Jun 30.
      Myostatin and growth differentiation factor 11 (GDF11) are closely related members of the transforming growth factor-β superfamily (TGF-β) that negatively regulate skeletal muscle growth. Pharmacologic inhibition of myostatin has been shown to preserve lean mass during glucagon-like peptide-1 receptor agonist (GLP-1RA) -mediated weight loss in persons with obesity. We developed IBIO-600, a long-acting monoclonal antibody which was engineered for dual neutralization of myostatin and GDF11. We evaluated IBIO-600 activity across cellular and preclinical models. Our evaluation of IBIO-600 demonstrated it reverses ligand-mediated suppression of myoblast differentiation in primary human skeletal myoblasts. In mechanistic in vitro studies, we further observed that GDF11 more potently modulates human myocyte and adipocyte biology than myostatin. In diet-induced obese mice treated with GLP-1RA, IBIO-600 preserves lean mass relative to GLP-1RA monotherapy. In aged, obese cynomolgus monkeys, a single administration of IBIO-600 demonstrates an elimination half-life of approximately 52 days and produces sustained improvements in body composition. These findings support further development of IBIO-600 as a differentiated approach to enhance muscle preservation and improve the quality of weight loss achieved with GLP-1RA-based therapies.
    Keywords:  Antibody therapy; GDF11; Half-life extension; Muscle loss; Myostatin; Obesity
    DOI:  https://doi.org/10.1038/s41598-026-59882-0
  30. Skelet Muscle. 2026 Jul 03.
       BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used by athletes and those who exercise, yet their influence on the molecular responses to exercise remains unclear. Prior studies have often focused on a limited set of molecular pathways, potentially overlooking broader regulator effects of NSAIDs on skeletal muscle signaling. Therefore, we conducted a systems biology study of skeletal muscle biopsies taken before and after exercise, in combination with NSAID consumption, using transcriptomics and metabolomics, to identify differentially enriched pathways and biofunctions.
    METHODS: We conducted a randomized, counterbalanced, double-masked, crossover trial (NCT05512013) in which 12 healthy adults ingested ibuprofen (IBU, 800 mg), celecoxib (CEL, 200 mg), flurbiprofen (FLU, 100 mg), or placebo (PLA) before a 10 × 10 bout of plyometric exercise. Skeletal muscle biopsies were collected before NSAID consumption and three hours post-exercise. Whole transcriptome profiling was performed using RNA-seq, and the metabolomics profile was assessed via untargeted mass spectrometry. Differential expression analysis and pathway enrichment were used to evaluate NSAID-specific effects across biological domains.
    RESULTS: FLU regulated the largest number of differentially expressed transcripts, followed by IBU and CEL. All NSAIDs activated immune-related gene networks and reversed exercise-induced lipid catabolism, with IBU enhancing adaptive immune signaling and CEL modulating both innate and adaptive pathways. Muscle remodeling pathways, including angiogenesis and cell migration, were activated across all NSAIDs, though cachexia-related genes were also upregulated. Interestingly, FLU uniquely upregulated transcripts involved in neuritogenesis.
    CONCLUSION: NSAIDs trigger drug-specific molecular responses in skeletal muscle post-exercise, affecting early recovery through changes in immune, metabolic, and neuronal signaling.
    Keywords:  Exercise; Inflammation; Metabolomics; Musculoskeletal; Myokines; Signaling
    DOI:  https://doi.org/10.1186/s13395-026-00435-4
  31. Physiol Rep. 2026 Jul;14(13): e70994
      Respiratory and muscular systems must integrate ventilation, oxygen delivery, and muscle activation to meet exercise demands. While decades of research have provided understanding of how these systems function individually, the principles regulating their dynamic coupling as a network remain unexplored. Our goal was to investigate how respiratory dynamics synchronize and integrate as a network with the activity of muscles during exercise, and assess how it responds to fatigue. Nine adults performed two graded cycling tests until exhaustion, starting at 0 W with 25 W·min-1 increments. Continuous synchronous recordings included electromyography (EMG) from right and left vastus lateralis and erector spinae, and respiration waveform via chest belt. Respiratory-muscular coupling was measured using the amplitude-amplitude cross-frequency coupling (ACFC) method. First, breathing rate was extracted from the respiration waveform. Second, EMG signals were decomposed into ten frequency bands [F1-F10], representing distinct neuromuscular processes. Last, cross-correlation coefficients (C) were computed as the ACFC outcome. We uncover novel network maps of respiratory-muscular dynamic interactions. We find that respiratory-muscular networks exhibit a complex hierarchical structure which depends on the role muscles play during exercise. Further, cross-correlations significantly increase with fatigue accumulation during exercise, indicating stronger integration between breathing and muscle activation under rising metabolic demand. This network-level adaptation shows that physiological responses to exercise arise not only from isolated systems, but also from their dynamic interactions as an integrated network. The network physiology approach utilized here contributes to the development of a new class of network-based markers to quantify multisystem interactions underlying human function during exercise.
    Keywords:  breathing rate; complex systems; dynamic networks; electromyography; network physiology
    DOI:  https://doi.org/10.14814/phy2.70994
  32. Theranostics. 2026 ;16(13): 7660-7697
      Cellular senescence is a persistent state of irreversible growth arrest that occurs when cells encounter various stress signals. It is marked by elevated expression of cell cycle inhibitors, dysregulated gene transcription, and secretion of the senescence-associated secretory phenotype (SASP). These senescent features may exert both detrimental and beneficial effects on tissue homeostasis and systemic physiological integrity. In this review, the relevant pathological processes are categorized into three tissue types: skeletal muscle, bone, and cartilaginous tissue. We systematically delineate the mechanisms of cellular senescence underlying seven musculoskeletal diseases, including skeletal muscle injury and regeneration, sarcopenia, osteoporosis, fracture, osteonecrosis of the femoral head (ONFH), osteoarthritis (OA), and intervertebral disc degeneration (IDD), with a particular focus on the heterogeneity of senescent cells across distinct musculoskeletal diseases. On this basis, we further elaborated on relevant mechanisms and senescence-related targets, and analyzed senescence heterogeneity in diverse musculoskeletal tissues, senescence identification and integrated diagnostic approaches. Moreover, we discussed convergent pathways, the dual roles of senescent cells, and the critical evaluation of disease-specific versus common therapeutic vulnerabilities.
    Keywords:  IDD; OA; cellular senescence; fracture; osteoporosis; sarcopenia; skeletal muscle
    DOI:  https://doi.org/10.7150/thno.130018
  33. Exp Physiol. 2026 Jul 02.
      Skeletal muscle hypertrophy requires a substantial nutrient influx for biomass accretion, but global metabolite exchange during growth is poorly characterized. Therefore, we profiled the metabolite uptake and release in insulin-like growth factor-1 (IGF-1)-stimulated C2C12 myotubes and human muscle 24 h after resistance exercise. Differentiated C2C12 myotubes were stimulated to grow with IGF-1 (100 ng/mL, 24 h) or received vehicle control. To measure metabolite exchange, we analysed fresh and spent media by gas chromatography-mass spectroscopy metabolomics. In a second experiment, seven untrained adults (three males and four females; age 25.6 ± 3.2 years; body mass index 23.8 ± 2.8 kg/m2) performed single-leg hypertrophy-oriented resistance exercise, with the contralateral leg serving as the control. After 24 h, we obtained arteriovenous blood samples in the postabsorptive state and analysed plasma by untargeted liquid chromatography-mass spectroscopy metabolomics, characterizing the directionality of metabolite exchange across the human leg. In vitro, IGF-1 increased uptake of serine, arginine and pyridoxamine, while enhancing lactate release (all P < 0.05), reflecting anabolic, Warburg-like reprogramming. In vivo, 24 h postexercise there were modest global shifts (principal components analysis: PC1 8.8%, PC2 6.3% variance) and no significant essential amino acid uptake. Nominal differences (P < 0.05) included increased uptake of peptide-related metabolites (acisoga and 2-amino-4-CP) and α-ketoglutarate, alongside release of C12:0 and C16:0 acylcarnitines. No in vivo differences persisted after false discovery rate correction. Although IGF-1 stimulation in vitro promotes coordinated nitrogen-rich metabolite uptake and lactate release, human muscle 24 h postexercise in a postabsorptive state is characterized by increased peptide turnover and lipid release rather than net amino acid uptake. This indicates limited substrate accumulation and net biomass accretion in the absence of exogenous nutrients.
    Keywords:  C2C12 myotubes; Warburg‐like metabolism; anabolic reprogramming; arteriovenous metabolomics; skeletal muscle hypertrophy
    DOI:  https://doi.org/10.1113/EP094096
  34. Dev Cell. 2026 Jun 29. pii: S1534-5807(26)00218-2. [Epub ahead of print]
      The systemic coordination of autophagy during development remains poorly understood. Here, we identify two parallel neuronal circuits that regulate the autophagy-lysosome pathway in the body wall muscle of C. elegans. One circuit, utilizing UNC-7/UNC-9 electrical synapses between AVA interneurons and A-type motor neurons (A-MNs), promotes autophagy by inhibiting neuropeptide release from A-MNs. The other employs the TGF-β-like molecule DAF-7, secreted from ASI sensory neurons, which activates autophagy via the canonical TGF-β pathway. These pathways converge to regulate cytosolic Ca²⁺ levels in the muscle, thereby maintaining lysosomal integrity. Disruption of either circuit elevates Ca²⁺, overactivating calpain. This leads to the accumulation of non-degradative autolysosomes and accelerates muscle degeneration. Our findings elucidate a neuronal mechanism for controlling muscle autophagy and provide insights into the pathogenesis of neurogenic myopathy.
    Keywords:  C. elegans; TGF-β; autophagy; calpain; electrical synapse; lysosome; muscle degeneration; neurogenic myopathy; neuropeptide
    DOI:  https://doi.org/10.1016/j.devcel.2026.06.001
  35. Front Physiol. 2026 ;17 1839695
       Objective: The extracellular matrix is essential for skeletal muscle function, providing structural support and facilitating force transmission from muscle fibers to tendons and the skeletal system. Collagen structures, known for their high plasticity, adapt to various stimuli, including mechanical loading during high-load resistance training. The present study aimed to assess the impact of specific collagen peptide (SCP) supplementation, combined with resistance training, on the levels of intramuscular collagen (COL) types I, III, and IV, and to assess the change in intramuscular fibroblast content.
    Methods: In a randomized, placebo-controlled study, 29 healthy male participants completed 12-week high-load resistance training (70-85% of 1 repetition maximum) with daily supplementation of 15g of SCP or placebo (PLA). Before and after the intervention period, muscle biopsies from the vastus lateralis muscle were obtained to quantify intramuscular collagen amount and fibroblast density.
    Results: SCP supplementation together with exercise led to increased (p = 0.026) collagen type I content (29.8%) compared to training with placebo (9.9%). Collagen types III and IV content increased significantly across the pooled sample (p < 0.05) with no significant group x time interaction. Fibroblast density did not change over the time course of intervention, either within or between groups.
    Conclusion: Endomysial collagen type I content increased in response to resistance training when supplemented with SCP compared to placebo. The observed increase in intramuscular collagen content may contribute to improved structural support of skeletal myofibers.
    Keywords:  collagen; extracellular matrix; intramuscular connective tissue; resistance training; skeletal muscle; specific collagen peptides
    DOI:  https://doi.org/10.3389/fphys.2026.1839695
  36. Muscle Nerve. 2026 Jul 01.
      The function of the neuromuscular junction (NMJ) is compromised in many neuromuscular diseases (NMDs) such as autoimmune or congenital myasthenia gravis (MG), amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and muscular dystrophies. The NMJ contains muscle-specific kinase (MuSK), which is a critical regulator of NMJ integrity and function. Activating the MuSK signaling cascade may have therapeutic potential in several of these NMDs that are characterized by impaired neuromuscular communication. The MuSK signaling cascade consists of different components and can be activated with interventions at different levels. In the past years, different therapeutic strategies using an engineered recombinant agrin comprised of the C-terminal fragment of the protein (mini-agrin), gene therapy of key proteins in this pathway, agonist MuSK antibodies, and SRC homology 2 domain-containing phosphotyrosine phosphatase 2 (SHP2) inhibitors have been further developed for this purpose. Each of these strategies engages distinct signaling components: mini-agrin, both as recombinant protein and gene therapy, enhances agrin-Lrp4-MuSK interaction; Dok7 gene therapy amplifies MuSK phosphorylation; Lrp4 gene therapy enhances agrin responsiveness; MuSK agonist antibodies bypass upstream defects and promote downstream signaling; SHP2 inhibitors prolong the duration of active MuSK signaling. These therapeutic strategies have ameliorated NMJ integrity and function in several preclinical models of MG, motor neuron diseases, and muscular dystrophies. In this review, we highlight MuSK signaling as a possible therapeutic target, describe the therapeutic efficacy of intervention in MuSK signaling in different NMDs, and present an outlook on future clinical development.
    Keywords:  MuSK; myasthenia gravis; neuromuscular disease; neuromuscular junction; therapy
    DOI:  https://doi.org/10.1002/mus.70129
  37. Int J Biol Macromol. 2026 Jul 03. pii: S0141-8130(26)03291-5. [Epub ahead of print] 153351
      Although Mettl3-mediated N6-methyladenosine (m6A) modification has confirmed to regulate mammalian development, the precise mechanisms by which it controls myoblast differentiation and fusion remain unclear. Here, we found that Mettl3 expression and global m6A levels decreased during myogenic differentiation. Mettl3 knockdown inhibited myoblast proliferation, promoted myoblast differentiation and fusion, and reduced protein degradation in myotubes, whereas its overexpression had the opposite effects. High-throughput sequencing identified forkhead box O1 (FOXO1) as a potential target of Mettl3-mediated myogenesis. Mechanically, Mettl3-mediated methylation of FOXO1 3'untranslated region (3'UTR) promotes its translation in a Ythdf3-dependent manner, thereby suppressing the MyoD1-Myomaker/Myomixer axis and activating the ubiquitin-proteasome system (UPS). Furthermore, FOXO1 knockdown alleviates the impaired myoblast differentiation and fusion induced by Mettl3 overexpression by upregulating the MyoD1-Myomaker/Myomixer axis and suppressing the UPS. Collectively, these findings indicate that Mettl3 inhibits myoblast differentiation and fusion via the FOXO1-mediated MyoD1-Myomaker/Myomixer axis and UPS in an m6A-Ythdf3-dependent manner.
    Keywords:  FOXO1; Mettl3; MyoD1-Myomaker/Myomixer axis; Myogenesis; m(6)A modification
    DOI:  https://doi.org/10.1016/j.ijbiomac.2026.153351