bims-moremu 2026-09-20 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2026–09–20
thirty-one papers selected by
Anna Vainshtein, Craft Science Inc.

mtDNA alterations in muscle progenitors determine myoblast differentiation and disrupt skeletal muscle architecture.
The Primary Cilium: A New Player in Muscle Stem Cell Biology.
Cellular senescence of fibro-adipogenic progenitors by STAT5A/GFPT2/O-GlcNAcylation impairs muscle recovery after glucocorticoid-induced injury.
A Biomimetic 3D Human Skeletal Muscle Microtissue for Modeling Biological and Functional Hallmarks of Aging.
Protein kinase C-λ drives third-degree burn-induced muscle wasting via STAT3-dependent catabolic pathways.
5-Fluorouracil-based chemotherapy disrupts autophagy flux and protein synthesis in cultured myotubes: a role for mTORC1 signaling.
Bifidobacterium adolescentis-derived nicotinic acid improves host skeletal muscle mitochondrial function to ameliorate sarcopenia.
Tceal7 is a BRG1-regulated target of calcineurin signaling that promotes myoblast differentiation.
KMT5A maintains muscle stem cell quiescence through epigenetic regulation of Notch signaling.
PAX3-SIX2 muscle stem cell heterogeneity drives muscle-specific repair dynamics diversification.
Piperine disrupts the OFF state of the resting thick filament of rat skeletal muscle, enhancing dynamic contractility in a fibre-type-dependent manner.
Enterovirus 71 drives TLR2-NF-κB-dependent inflammatory skeletal muscle injury in neonatal BALB/c mice.
Functional and Molecular Skeletal Muscle Responses to Aerobic Exercise in Rat Models of Acute and Chronic Doxorubicin Exposure.
Increased Insulin Action, Glucose Metabolism and Muscle Function in Supervillin-Knockout and Supervillin-Mutant Mice.
Methylome-transcriptome integration reveals molecular signatures of intrinsic aerobic capacity in aged skeletal muscle.
Endogenous calcium/calmodulin-dependent protein kinase II gamma and delta maintain Type II myofiber identity in adult mice.
Exercise-Induced Skeletal Muscle Secretory Factors and Macrophage Functional Remodeling: Mechanistic Advances.
Spatial proteomics identifies FXYD6 as a dual-site protein of neuromuscular junction in the diaphragm.
Glucocorticoid Receptor Signaling in Myeloid Cells Orchestrates Inflammation Resolution and Muscle Repair.
Magnetic Mitohormesis as a Potential Non-Invasive Restorative Therapy for X-Linked Muscular Dystrophies.
Nanoengineered GATA3+ Macrophages Transplantation Reconstitutes the Muscle Stem Cells Niche for Skeletal Muscle Regeneration.
CellSize-Clust: An Unsupervised Multi-Algorithm Method for Classifying Skeletal Muscle Cells by Feret Diameter in Mice Soleus and Gastrocnemius.
Post transcriptional modification regulation of skeletal muscle TFEB protein nuclear cytoplasmic transport based on different exercise modes in computer biomedical research.
Relaxin-2: Shaping the Proteomic Landscape of Skeletal Muscle Physiology, Glucose Trafficking, and Mitochondrial Function in Rat.
Nuclear Translocation of PFKFB3 Promotes Disuse-Induced Muscle Atrophy via Scaffolding Nedd4-Mediated JunB Ubiquitination.
Integrating and Orchestrating Multiple Components of Skeletal Muscle Injury and Regeneration.
Development of a Multi-Organ Microphysiological (MPS) Model to Study Age-Related Comorbidities.
Cancer Cell-Derived Small Extracellular Vesicles Are Associated with Impaired C2C12 Myoblast Differentiation.
Citius, Maius, Melius: Mitochondria and Endurance Performance.
Autocrine Signaling may Regulate Exercise-Induced Interleukin-6 Release from Human Skeletal Muscle.
Skeletal Muscle Dysfunction in Heart Failure: Mechanistic Insights and Therapeutic Implications.

Cell Rep. 2026 Sep 11. pii: S2211-1247(26)01057-0. [Epub ahead of print]45(9): 117979

mtDNA alterations in muscle progenitors determine myoblast differentiation and disrupt skeletal muscle architecture.

Ayesha Sen, Olivier R Baris, Yulia Schaumkessel, Sebastian Kallabis, Claudie Gabillard-Lefort, Valerie Desquiret, Rudolf J Wiesner, David Pla-Martín.

  Mitochondrial DNA (mtDNA) damage has been linked to age-related tissue decline, yet its impact on muscle stem cells (MuSCs) integrity remains unclear. Here, we used a dominant-negative variant of the mitochondrial helicase Twinkle (p.K320E) to induce mtDNA instability in C2C12 and MuSCs, and examined myogenic differentiation. In C2C12, mtDNA alterations impaired respiratory complex assembly, increased reactive oxygen species, and disrupted differentiation. Proteomic analyses of differentiated C2C12 revealed extensive remodeling of the mitochondrial proteome. In vivo, during muscle regeneration, MuSCs expressing K320E generated fibers showing mitochondrial dysfunction and elevated oxidative stress. Furthermore, when mtDNA instability was induced during early postnatal stages, mtDNA alterations were progressively transmitted to mature myofibers, resulting in persistent fiber remodeling of the skeletal muscle. Together, these findings identify mtDNA instability in muscle progenitors as a driver of skeletal muscle remodeling and reveal that even modest levels of mtDNA alterations are sufficient to compromise skeletal muscle function.

Keywords:  CP: developmental biology; mitochondria; mtDNA; muscle differentiation; satellite cells; skeletal muscle

DOI:  https://doi.org/10.1016/j.celrep.2026.117979
Stem Cell Rev Rep. 2026 Sep 12.

The Primary Cilium: A New Player in Muscle Stem Cell Biology.

Anna Rausch de Traubenberg, Ludivine Rotard, Caroline E Brun.

  Adult muscle stem cells are responsible for skeletal muscle regeneration, a process where quiescent muscle stem cells activate, enter the cell cycle, and proliferate to give rise to either lineage-committed myoblasts for new muscle fiber formation, or self-renewing cells to replenish the stem cell reservoir. The regenerative capacity of muscle stem cells relies on their precise reception of environmental cues and appropriate intracellular responses. Quiescent muscle stem cells display a primary cilium, a microtubule-based organelle that protrudes from the cell surface and acts as a hub for chemical and mechanical signal transduction. Recent work has significantly increased our understanding of this organelle, demonstrating that the primary cilium actively regulates signaling pathways that are essential for maintenance of muscle stem cell quiescence, proliferation, and fate decision. In this review, we synthesize the current knowledge and recent advances on how this sensory organelle controls muscle stem cell quiescence, enables mechano-sensation, and regulates activation following tissue injury and during asymmetric self-renewal.

Keywords:  Cilia-mediated Signaling; Fate; Muscle Stem Cell; Primary Cilium; Quiescence; Skeletal Muscle Regeneration

DOI:  https://doi.org/10.1007/s12015-026-11233-2
Pharmacol Res. 2026 Sep 16. pii: S1043-6618(26)00376-2. [Epub ahead of print]233 108461

Cellular senescence of fibro-adipogenic progenitors by STAT5A/GFPT2/O-GlcNAcylation impairs muscle recovery after glucocorticoid-induced injury.

Bingfei Li, Wei Xiang, Wanwan Qi, Xinxin Liu, Weiwen Zhu, Wei Zhang, Runze Jin, Shuo Ma, Lifeng Chen, Chuanqing Bai, Shunzheng Fang, Jiangyi Wu, Xiaoqi Zhang, Limeng Dai, Xingying Guan, Jia Li, Song Li, Yan Xiong, Xiangqin Fang, Changyue Gao, Siru Zhou, Hong Guo, Zhenhong Ni.

  The clinical use of glucocorticoids often leads to skeletal muscle injury, characterized by muscle atrophy and dysfunction. Fibro-adipogenic progenitors (FAPs) play an important role in maintaining muscle homeostasis, but their roles in the recovery of skeletal muscle after glucocorticoid-induced injury remain largely elusive. Here, we reveal that glucocorticoid induces cellular senescence of FAPs, leading to their accumulation in skeletal muscle. Mechanistically, glucocorticoid enhances the expression of GFPT2 through STAT5A, which further elevates O-GlcNAcylation in FAPs and promotes their senescence. Targeting the STAT5A-GFPT2-mediated O-GlcNAcylation can reduce the burden of senescent FAPs in glucocorticoid-treated muscle and facilitate muscle recovery after injury. Our results demonstrate that exosomes derived from senescent FAPs suppress myotube formation, greatly inhibiting the regrowth of glucocorticoid-treated skeletal muscle. Moreover, senescent FAPs reduce the muscle stem cells (MuSCs) pool by suppressing their proliferation, thereby impairing the regenerative capacity of skeletal muscle during the recovery process after glucocorticoid treatment.

Keywords:  Dasatinib (PubChem CID: 3062316); Dexamethasone (PubChem CID: 5743); Fibro-adipogenic progenitors; GFPT2; Muscle stem cells; O-GlcNAcylation; Quercetin (PubChem CID: 5280343); STAT5A; Senescence; Skeletal muscle; UMI-77 (PubChem CID: 992586)

DOI:  https://doi.org/10.1016/j.phrs.2026.108461
Small Sci. 2026 Sep;6(9): e70386

A Biomimetic 3D Human Skeletal Muscle Microtissue for Modeling Biological and Functional Hallmarks of Aging.

Sohae Yang, Jeong Sik Kong, Hyun Young Shin, Sung Chun Cho, Aseer Intisar, Min Young Kim, Yeong-Jin Choi, Yun-Il Lee, Dong-Woo Cho, Minseok S Kim.

  Skeletal muscle is one of the largest organs in the human body, playing a central role in mobility, metabolism, and endocrine regulation. The aging global population underscores the need to understand skeletal muscle aging, which is bottlenecked by the lack of in vitro models that recapitulate biological and functional features of aged human muscle as well as discrepancies between humans and animal models. Here, we present a 3D biomimetic aged skeletal muscle model using human primary skeletal muscle cells (SkMCs) embedded in a skeletal muscle-derived decellularized extracellular matrix (dECM) scaffold. Constructs fabricated from aged and young SkMCs were systematically evaluated across structural, molecular, mitochondrial, calcium-handling, and contractile readouts. Compared with young constructs, aged constructs recapitulated several aging-associated biological and functional phenotypes, including smaller myotubes, altered myogenic and inflammatory marker expression, mitochondrial alterations, delayed calcium responses, and weakened contractile forces. This human-relevant platform enables simultaneous assessment of biological and functional aspects of muscle aging and may serve as a translational tool to study mechanisms and screen therapies for age-associated muscle disorders. This aligns with the FDA Modernization Act 2.0-which recognizes in vitro human systems as alternatives to animal testing-underscoring the practical relevance of this model.

Keywords:  3D skeletal muscle constructs; aged skeletal muscle; contractile function; decellularized extracellular matrix; human‐derived skeletal muscle cells; in vitro model

DOI:  https://doi.org/10.1002/smsc.70386
Front Pharmacol. 2026 ;17 1839235

Protein kinase C-λ drives third-degree burn-induced muscle wasting via STAT3-dependent catabolic pathways.

Peilong Li, Xinzhuang Liu, Guobao Huang.

   Objective: Severe burn injury triggers profound skeletal muscle atrophy through incompletely understood molecular mechanisms. This study investigated the role of protein kinase C (PKC) isoforms in burn-induced muscle wasting and evaluated potential therapeutic targets.
Methods: We examined PKC isoform expression in skeletal muscle biopsies from burn patients with second-degree (n = 5) and third-degree burns (n = 5) at 7 days post-injury. Mouse burn models were established to investigate PKC signaling at 14 days post-injury. Muscle-specific PKC-lambda (PKC-λ) knockout mice and pharmacological inhibition with [4-(5-amino-4-carbamoylimidazol-1-yl)-2,3-dihydroxycyclopentyl] methyl dihydrogen phosphate (ICA-1) were employed. C2C12 myotubes were used for mechanistic studies with signal transducer and activator of transcription 3 (STAT3) overexpression experiments.
Results: Among six PKC isoforms examined, only PKC-λ was selectively upregulated in third-degree versus second-degree burns in both humans and mice. Third-degree burns caused 39.5% muscle mass loss and 57.3% grip strength reduction, accompanied by PKC-λ activation and downstream STAT3-CCAAT/enhancer-binding protein delta (C/EBPδ)/myostatin catabolic signaling. Muscle-specific PKC-λ knockout mice showed significant protection against burn-induced muscle atrophy. In vitro studies demonstrated that PKC-λ regulates muscle catabolism through STAT3 activation, as STAT3 overexpression reversed protective effects of PKC-λ inhibition. Pharmacological PKC-λ inhibition with ICA-1 restored muscle mass to 85.5% and grip strength to 73.6% of control levels while suppressing the PKC-λ/STAT3-C/EBPδ catabolic cascade.
Conclusion: PKC-λ serves as a critical upstream mediator linking severe burn injury to skeletal muscle atrophy through STAT3-C/EBPδ catabolic signaling. These findings establish PKC-λ as a promising therapeutic target for preventing burn-induced muscle wasting.

Keywords:  ICA-1; STAT3 signaling; burn injury; muscle atrophy; protein kinase C-lambda

DOI:  https://doi.org/10.3389/fphar.2026.1839235
Am J Physiol Cell Physiol. 2026 Sep 14.

5-Fluorouracil-based chemotherapy disrupts autophagy flux and protein synthesis in cultured myotubes: a role for mTORC1 signaling.

Jessica L Halle, Quan Zhang, Tanner Jenkins, James A Carson.

  5-Fluorouracil-based chemotherapies, such as FOLFOX (5-fluorouracil, leucovorin, oxaliplatin), are used to treat colon cancer but also induce skeletal muscle toxicities. While FOLFOX can disrupt muscle autophagy signaling in vivo, the upstream mechanisms underlying this effect, as well as the roles of mTORC1 and AMPK signaling, require further investigation. We investigated whether 5-FU, 5-FU + leucovorin, oxaliplatin, or the combined FOLFOX regimen disrupts protein synthesis or autophagy flux through altered mTORC1/AMPK signaling in C2C12 myotubes with or without tumor cell-conditioned media, and whether these effects were readily reversible. We also examined the effects of rapamycin or metformin administration on FOLFOX-induced disruptions to muscle protein synthesis and autophagy. FOLFOX was added to myotube cultures for 24 hours; recovery was assessed by removing FOLFOX from the culture media for an additional 24 hours. Cultured Colon-26 tumor cells (CT26) were used for conditioned media. Autophagy flux was assessed using Bafilomycin A1 and LC3BII/I immunoblotting. FOLFOX and CT26 each decreased myotube diameter and protein synthesis compared to the vehicle. CT26, but not FOLFOX, increased STAT3 phosphorylation. FOLFOX, but not CT26, increased Atrogin-1 protein, while MURF-1 protein was increased by both CT26 and FOLFOX. FOLFOX reduced autophagy flux, AMPK, and ULK1(S555) phosphorylation, which did not recover upon FOLFOX removal. Rapamycin, but not metformin, altered autophagy flux in FOLFOX-treated myotubes and restored suppressed AMPK phosphorylation without increasing protein synthesis. We report that FOLFOX and oxaliplatin disrupt myotube mTORC1/AMPK regulation of autophagy flux, which was not easily reversible. However, rapamycin treatment increased autophagy flux in FOLFOX-treated myotubes.

Keywords:  Colon Cancer; FOLFOX; Muscle; Oxaliplatin; Rapamycin; metformin

DOI:  https://doi.org/10.1152/ajpcell.00321.2026
Cell Rep. 2026 Sep 15. pii: S2211-1247(26)01133-2. [Epub ahead of print]45(10): 118054

Bifidobacterium adolescentis-derived nicotinic acid improves host skeletal muscle mitochondrial function to ameliorate sarcopenia.

Zeng Zhang, Quan Guo, Zhihan Yang, Yukai Sun, Shuaiming Jiang, Yangli He, Jiahe Li, Jiachao Zhang.

DOI: https://doi.org/10.1016/j.celrep.2026.118054
PLoS One. 2026 ;21(9): e0358038

Tceal7 is a BRG1-regulated target of calcineurin signaling that promotes myoblast differentiation.

Sandhya Yadav, Tapan Sharma, Monserrat Olea-Flores, Teresita Padilla-Benavides, Anthony N Imbalzano.

The transcriptional control of skeletal muscle differentiation requires the coordinated activity of lineage-defining transcription factors, signal-responsive regulators, chromatin modifiers, and ATP-dependent chromatin remodeling enzymes. Here, we identify TCEAL7, a member of the X-linked, poorly characterized TCEAL family of proteins, as a direct downstream target of BRG1-containing mammalian SWI/SNF (mSWI/SNF) complexes and calcineurin signaling during myoblast differentiation. Analyses of previously published datasets showed that pharmacological inhibition of mSWI/SNF bromodomains or knockdown of the BRG1 ATPase, but not knockdown of the homologue BRM ATPase, significantly reduced Tceal7 expression in differentiating C2C12 myoblasts. We demonstrate that BRG1 occupancy at the Tceal7 promoter increased during differentiation, paralleling the induction of Tceal7 expression and nuclear accumulation of TCEAL7 protein. BRG1 functions in part by integrating calcium-dependent cues via the phosphatase calcineurin (Cn); we also determined that Cn knockdown or pharmacological inhibition of Cn suppressed Tceal7 expression and impaired myoblast differentiation. The data suggest that both BRG1-driven chromatin remodeling and Cn signaling converge on Tceal7 regulation. Functionally, Tceal7 knockdown altered cell proliferation and disrupted myoblast differentiation, at least in part due to reduced expression of Myogenin, which encodes a transcription factor that is an essential differentiation determinant. RNA-seq analysis revealed broad dysregulation of myogenic, metabolic, and cell-cycle gene programs in Tceal7-deficient cells, including changes in cyclin-dependent kinase-regulated pathways consistent with prior reports linking TCEAL7 to cell-cycle control. Together, these findings identify TCEAL7 as a necessary component of the myogenic regulatory network whose expression is controlled by BRG1-dependent chromatin remodeling and Cn activity.

DOI: https://doi.org/10.1371/journal.pone.0358038
iScience. 2026 Sep 18. 29(9): 117424

KMT5A maintains muscle stem cell quiescence through epigenetic regulation of Notch signaling.

Jeonghye Hannah Hwang, Adam Y Chu, Roméo S Blanc.

  Quiescence preserves muscle stem cell (MuSC) identity and regenerative capacity, but the chromatin mechanisms that support this state remain incompletely understood. Here, we show that the H4K20 monomethyltransferase KMT5A sustains canonical Notch signaling in quiescent MuSCs through catalytic deposition of H4K20me1. Loss of Kmt5a led to delayed reduction of Rbpj and other canonical Notch pathway genes, whereas acute catalytic inhibition of KMT5A was sufficient to suppress their expression, indicating that H4K20me1 supports transcriptional competence at Notch loci. Genetic restoration of Notch signaling rescued quiescence-associated features in Kmt5a-deficient MuSCs but did not restore post-activation survival or regenerative output. During physiological activation after injury, H4K20me1 at Notch loci remained largely preserved while H4K20me3 accumulated. Together, these findings identify KMT5A-dependent H4K20me1 as a chromatin mechanism that maintains the Notch-dependent quiescence program and distinguish homeostatic Kmt5a loss from physiological MuSC activation.

Keywords:  H4K20 methylation; KMT5A; SETD8; activation; epigenetics; muscle stem cells; notch signaling; quiescence; regeneration

DOI:  https://doi.org/10.1016/j.isci.2026.117424
Sci Adv. 2026 Sep 18. 12(38): eaed0880

PAX3-SIX2 muscle stem cell heterogeneity drives muscle-specific repair dynamics diversification.

Virginia Zoglio, Sarah Chebouti, Fayez Issa, Théo Massard, Benjamin Polin, Sylvie Manin, Pascal Maire, Dawon Choi, Indigo T C Chan, Tom H Cheung, Joana Esteves de Lima, Frederic Relaix.

The human body contains around 640 distinct muscles, each capable of regeneration following injury through the action of muscle-specific stem cells (MuSCs), that express the transcription factor PAX7. Its paralog, PAX3, a master regulator of embryonic myogenesis, is selectively expressed in a subset of adult quiescent MuSCs. The proportion of PAX3-pos MuSCs varies across muscles. By combining lineage tracing and skeletal muscle injury, we demonstrate that PAX3 drives MuSC diversity and muscle-specific regeneration rates. PAX3-expressing MuSCs display enhanced proliferation and differentiation capacities, enabling a faster response following injury, whereas loss of PAX3 leads to proliferation arrest and cell death. Single-cell RNA-sequencing analyses revealed the specific expression of Six2 in PAX3-pos MuSCs. We show that PAX3 is required for SIX2 expression, and loss of SIX2 in MuSCs reduces proliferation and differentiation rates. Conversely, ectopic Six2 expression promotes proliferation of PAX3-neg MuSCs by directly activating cell cycle pathways. With this work, we establish that PAX3-SIX2 expression correlates with distinct MuSCs behavior, influencing regeneration rates in a muscle-type-dependent context. Our findings highlight a previously unrecognized layer of regulation in MuSC behaviour and muscle repair and suggest that PAX3-SIX2 heterogeneity could be leveraged for targeted therapeutic strategies in muscle-wasting diseases.

DOI: https://doi.org/10.1126/sciadv.aed0880
J Physiol. 2026 Sep;604(18): 7739-7771

Piperine disrupts the OFF state of the resting thick filament of rat skeletal muscle, enhancing dynamic contractility in a fibre-type-dependent manner.

Daniel Z Kruse, Jon Herskind, Michel N Kuehn, Annika J Klotz, Anthony L Hessel, Kristian Overgaard.

  The myosin-containing thick filament has been shown to alter its resting structure in response to multiple diseases and therapeutics. Changes in thick filament resting structure are caused by myosin heads transitioning between ordered and disordered OFF conformational states. Functionally, this modulation of thick filament structure is a key regulatory step in muscle contraction and a promising therapeutic target. The availability of disordered myosin heads governs dynamic contractility, which is critical to physical function and well-being. At present, there is a lack of compounds favouring this disordered state in resting skeletal muscle. Piperine is a molecule known to bind to myosin and increase submaximal isometric contractility in fast and slow skeletal muscle. However, the effects on dynamic contractility and the underlying mechanism responsible for the observed effects in skeletal muscles remain unclear. Here, we used fibre small-angle X-ray diffraction and intact-muscle ex vivo contractility experiments to determine the effects of piperine on resting myosin structure and dynamic contractility in fast and slow rat muscles. X-ray diffraction data suggest that piperine promotes a priming of myosin in resting skeletal muscle from an ordered OFF state to a disordered OFF state, increasing the availability of myosin heads for force generation. Functionally, piperine substantially enhanced submaximal dynamic contractility in both muscle types, while only leading to improvements in slow muscle during maximal electrical stimulation. These findings establish piperine as a tool for priming the thick filament in skeletal muscle, highlighting muscle-type-specific effects of thick-filament modulation on the recruitment of the contractile reserve capacity. KEY POINTS: Piperine is a compound known to bind to skeletal muscle myosin and enhance isometric contractility in fast and slow muscles, but its effect on dynamic muscle function and the underlying molecular mechanism remain unknown. We show that piperine disrupts the ordered OFF state of the myosin-containing thick filament in resting fast and slow skeletal muscle, which likely explains the effect of piperine on contractile function. Piperine substantially increases contractile power of both fast and slow skeletal muscles at low-frequency stimulation; however, it only enhances power in slow skeletal muscle at high-frequency stimulation. Our data reveal potentiation of dynamic contractility with fibre-type-dependent magnitudes in response to piperine-induced priming of the resting thick filament, which is a phenomenon requiring further investigation. Dynamic contractility drives locomotion in vivo; therefore, thick-filament priming may ultimately be exploited in the treatment of diseases characterised by skeletal muscle weakness.

Keywords:  contractile power; force–velocity curve; skeletal muscle phenotype; skeletal‐muscle myosin; small‐angle X‐ray diffraction; thick‐filament activation

DOI:  https://doi.org/10.1113/JP290962
Microbiol Spectr. 2026 Sep 15. e0038326

Enterovirus 71 drives TLR2-NF-κB-dependent inflammatory skeletal muscle injury in neonatal BALB/c mice.

Xinhong Zou, YaXin Li, Xiaomeng Zhang, Honglin Niu, Hairui Zhou, Lei Liu, Guoli Cui, Baixin Wang, Rui Wu.

  Enterovirus 71 (EV-A71) can cause inflammatory injury beyond the central nervous system, yet the host pathways driving EV-A71-associated skeletal muscle pathology remain poorly defined. Toll-like receptor 2 (TLR2) is a key innate immune sensor capable of amplifying inflammatory signaling during infection. Here, we established an EV-A71 infection model in 1-day-old BALB/c suckling mice by intraperitoneal inoculation for 3 consecutive days and administered the TLR2 inhibitor C29 intraperitoneally at 6 h post-inoculation. EV-A71 infection induced prominent skeletal muscle pathology characterized by inflammatory cell infiltration, muscle bundle disruption, and dissolution, and reduced myofiber cross-sectional area. Consistently, EV-A71 increased the levels of TLR2, nuclear factor-κB (NF-κB) signaling markers (p65 and phosphorylated p65), the pro-inflammatory cytokine IL-6, and the viral protein VP1 in skeletal muscle. EV-A71 infection was also associated with elevated α-SMA and collagen III, suggesting tissue remodeling in injured muscle. Notably, pharmacological inhibition of TLR2 with C29 markedly alleviated histopathological damage and reduced IL-6 expression in skeletal muscle. Collectively, these findings support a model in which EV-A71 activates a TLR2-NF-κB-linked inflammatory program that contributes to skeletal muscle immunopathology and highlights TLR2 as a tractable host-directed target for mitigating virus-associated skeletal muscle injury.IMPORTANCEVirus-associated skeletal muscle injury can cause functional impairment and may worsen outcomes, but actionable host determinants remain limited. Using a neonatal mouse model, we show that enterovirus 71 (EV-A71) infection is accompanied by activation of a Toll-like receptor 2 (TLR2)-linked inflammatory program in skeletal muscle and that pharmacological TLR2 inhibition reduces IL-6 expression and alleviates muscle pathology. These results support the concept that excessive innate immune signaling contributes to muscle immunopathology and identify TLR2 as a potential host-directed intervention point. This work provides a mechanistic framework for understanding and targeting skeletal muscle injury associated with EV-A71 and potentially other viral infections.

Keywords:  EV-A71; NF-κB; TLR2; inflammation; skeletal muscle; suckling mouse

DOI:  https://doi.org/10.1128/spectrum.00383-26
Am J Physiol Regul Integr Comp Physiol. 2026 Sep 14.

Functional and Molecular Skeletal Muscle Responses to Aerobic Exercise in Rat Models of Acute and Chronic Doxorubicin Exposure.

Carolina R Tonon, Bertha F Polegato, Daniela S Inoue, Quinten W Pigg, Dillon R Harris, Riya Meka, Advait Dadi, Mariana Janini Gomes.

  This study examined the effects of aerobic exercise on skeletal muscle function, structure, and molecular markers following acute and chronic doxorubicin (DOX) exposure. Fifty-six male Wistar rats were assigned to acute (20 mg/kg, single dose) or chronic DOX (5 mg/kg/week, 3 doses) protocols. In both protocols, rats were allocated in 4 groups: Control (C, n=6), Control Exercise (Control Ex, n=6), DOX (DOX, n=8), and DOX Exercise (DOX Ex, n=8). A 4-week aerobic exercise was performed on a treadmill before acute DOX (preconditioning) or during chronic DOX treatment (concomitant). Muscle function was assessed by electrical stimulation and tibialis anterior muscle was analyzed. Data were analyzed using two-way ANOVA (p<0.05). Acute DOX significantly reduced body and muscle mass, increased low-frequency muscle torque, and impaired muscle relaxation, accompanied by calpain-mediated proteolysis and increased p67phox and catalase expression. Exercise preconditioning significantly reduced circulating basal creatine kinase and modulated SERCA1 expression in skeletal muscle. Chronic DOX significantly reduced body mass, muscle mass, size and function, with a significant increase in plasma malondialdehyde. Inflammatory cytokines were significantly elevated only acutely. Concomitant exercise significantly attenuated calpain-mediated proteolysis in DOX-treated rats and increased glutathione peroxidase expression in control animals. In conclusion, DOX induced skeletal muscle dysfunction with acute alterations in proteins involved in calcium regulation. In the chronic model, DOX induced muscle atrophy, muscle dysfunction, and systemic oxidative stress. While aerobic exercise attenuated calpain-mediated proteolysis in both acute and chronic models, only exercise preconditioning increased SERCA1 expression, highlighting the importance of exercise timing for mitigating DOX-induced muscle alterations.

Keywords:  aerobic training; calcium handling; chemotherapy; muscle function; myotoxicity

DOI:  https://doi.org/10.1152/ajpregu.00108.2026
Cytoskeleton (Hoboken). 2026 Sep 16.

Increased Insulin Action, Glucose Metabolism and Muscle Function in Supervillin-Knockout and Supervillin-Mutant Mice.

Tara C Smith, Lauren A Tauer, Randall H Friedline, Xiaodi Hu, Duy Tran, Yangyi E Luo, Nacima Hadjout-Rabi, Elisabeth R Barton, Jason K Kim, Elizabeth J Luna.

  We here describe mouse models with complementary homozygous Svil mutations. In skeletal muscle, Svil-Mut mice express the Svil-encoded N-terminus fused to the βgal-neo gene-trap tag and lack the highly conserved archvillin C-terminus; Svil-KO mice lack expression of all known Svil-encoded proteins; and Svil-LoxP mice contain loxP sites for tissue-specific disruption of protein expression. Older Svil-KO male mice showed decreased levels of markers for type 1, 2a, and 2b muscle fibers. Male mice showed elevated P-ERK/ERK signaling during lengthening contractions, consistent with low-level muscle damage such as that in myofibrillar myopathy-10 (MFM10) in humans lacking SVIL proteins. Female mice lacking full-length Svil-encoded proteins, including supervillin and archvillin, exhibited reduced body weights and reduced fat mass. Females in both strains exhibited improved glucose tolerance and lower insulin levels following intraperitoneal glucose injections. Hyperinsulinemic-euglycemic clamp experiments showed increased insulin sensitivity in both strains and increased glucose metabolism in adipose tissues in female Svil-Mut mice. The GLUT4 glucose transporter was increased in skeletal muscle in breeder-aged female Svil-KO and Svil-Mut mice. RNA-Seq revealed transcriptional differences in adult male homeostatic muscles that supported roles in muscle differentiation, ERK signaling, and lipid metabolism. A yeast two-hybrid screen identified new Svil candidate interactors, including CH1 domains of muscle Z-line proteins, a potential dimerization site, and Rho GTPase-activating protein (ARHGAP21), a negative regulator of glucose-stimulated insulin secretion in pancreatic beta cells. We suggest that the Svil-Mut, Svil-KO, and Svil-LoxP strains described here will be useful models for understanding signaling within and between tissues regulating glucose metabolism.

Keywords:  adipose tissue; costameres; inbred C57BL; mice; muscle; muscular diseases; myofibrillar myopathy; skeletal

DOI:  https://doi.org/10.1002/cm.70196
J Sport Health Sci. 2026 Sep 17. pii: S2095-2546(26)00069-4. [Epub ahead of print] 101178

Methylome-transcriptome integration reveals molecular signatures of intrinsic aerobic capacity in aged skeletal muscle.

Lei Zhou, Soroosh Mozaffaritabar, Ferenc Torma, Erika Koltai, Takuji Kawamura, Mitsuru Higuchi, Zhentao Zhong, Lauren Gerard Koch, Steven Loyal Britton, Zsolt Radák.

   BACKGROUND: Intrinsic aerobic capacity is a critical determinant of metabolic health and healthy aging, yet its epigenomic and transcriptomic features in aged skeletal muscle, and whether these intrinsic differences are accompanied by distinct exercise-related molecular responses, remain unclear.
METHODS: Soleus muscle from aged selectively bred high- and low-running capacity rats (HCR and LCR; 23-24 months) was profiled by reduced representation bisulfite sequencing (RRBS) and RNA sequencing (RNA-seq). Differentially methylated regions (DMRs) were annotated, functionally enriched, integrated with differentially expressed genes (DEGs), and correlated with maximal oxygen uptake (VO₂max). An age-comparable voluntary-running cohort was further analyzed by RNA-seq and selected protein profiling to assess exercise adaptation.
RESULTS: RRBS identified broad baseline methylome remodeling, including 7196 significant DMRs, with a higher proportion of hypermethylated regions in HCR muscle. These DMRs were mainly localized to open-sea CpGs, while gene-associated DMRs were predominantly intronic and exonic, and showed context-dependent functional enrichment. Baseline RNA-seq identified 322 DEGs between HCR and LCR muscle. Methylome-transcriptome integration revealed 72 DMR-DEG pairs representing 53 unique genes, mostly located in open-sea, intronic, and exonic regions. Exploratory VO2max analysis identified 63 DMRs associated with aerobic capacity. Chronic voluntary running induced more DEGs in HCR than in LCR muscle, while pathway-level responses in both lines converged on mitochondrial and oxidative metabolism. Selected protein profiling further revealed mainly baseline LCR-HCR differences, with limited additional exercise-associated changes.
CONCLUSION: Intrinsic high aerobic capacity in aged skeletal muscle is associated with hypermethylation-enriched methylome remodeling, feature-dependent functional enrichment, distinct transcriptional signatures, and oxidative-metabolic protein differences. These findings provide a multi-layer molecular framework for understanding intrinsic aerobic-capacity divergence in aged skeletal muscle and highlight candidate regulatory regions for future functional validation.

Keywords:  Aging; DNA methylation; Intrinsic aerobic capacity; Skeletal muscle; Transcriptomics

DOI:  https://doi.org/10.1016/j.jshs.2026.101178
Am J Physiol Cell Physiol. 2026 Sep 16.

Endogenous calcium/calmodulin-dependent protein kinase II gamma and delta maintain Type II myofiber identity in adult mice.

Hikaru Iwase, Yuka Ichihashi, Ryoka Tsukahara, Takuma Kunieda, Yuki Maeda, Yasuo Uchida, Tomoharu Yasuda, Yasuo Kitajima.

  Skeletal muscle fiber identity is commonly characterized by coordinated contractile and metabolic programs, but the mechanisms that preserve this coordination in adult muscle remain unclear. We tested whether endogenous calcium/calmodulin-dependent protein kinase II γ and δ (CaMKIIγ/δ) maintain type II myofiber identity. Tamoxifen-inducible, skeletal muscle-specific Camk2g/Camk2d double-knockout mice were analyzed 1 and 3 mo after deletion using soleus fiber typing, laser microdissection proteomics, and immunofluorescence. CaMKIIγ/δ deletion was not associated with detectable changes in body weight or muscle mass but increased type I fibers and reduced total type II fibers at both time points, with a transient increase in type I/II hybrid fibers. Within mKO muscles, the type IIa fiber proportion declined over time. Fiber type-resolved proteomics revealed remodeling within fibers retaining a type II myosin heavy chain profile. Proteins enriched in control type I fibers shifted upward in knockout type II fibers, whereas type II-enriched proteins shifted downward. Consistently, a type I-like score derived from an independent single-myofiber proteomic dataset increased selectively in knockout type II fibers, supporting remodeling beyond myosin isoform switching. CaMKII abundance was higher in type II than in type I fibers. Unexpectedly, this type I-like remodeling was not accompanied by an oxidative shift: oxidative phosphorylation-related protein programs were reduced across type I, type II, and hybrid fibers. These findings identify endogenous CaMKIIγ/δ as a homeostatic regulator of adult type II myofiber identity and show that fiber identity-associated proteomic features and mitochondrial oxidative programs can be remodeled in divergent directions.

Keywords:  Calcium/calmodulin-dependent protein kinase II; Laser microdissection; Muscle fiber type; Proteomics; Skeletal muscle

DOI:  https://doi.org/10.1152/ajpcell.00464.2026
Int J Mol Sci. 2026 Aug 22. pii: 7527. [Epub ahead of print]27(17):

Exercise-Induced Skeletal Muscle Secretory Factors and Macrophage Functional Remodeling: Mechanistic Advances.

Ziyan Li, Chenyu Lin, Linjia Tang, Yiyao Xu, Jieming Liang, Dehui Pan, Ziran Huang, Xianyan Xie, Yu Wang, Shuqi Qin, Gaoyuan Yang, Xiaoguang Liu, Huiguo Wang.

  Regular exercise mediates inter-tissue communication between skeletal muscle and the immune system through skeletal muscle-derived secretory factors, providing an important molecular basis for the beneficial effects of exercise on chronic inflammation, metabolic dysregulation, and impaired tissue repair. As key effector cells of the innate immune system, macrophages do not simply conform to a dichotomous classification of classically activated M1 macrophages and alternatively activated M2 macrophages; rather, their functional states constitute a dynamic spectrum shaped by exercise load, recovery time window, tissue microenvironment, and disease context. This review focuses on recent advances in exercise-induced skeletal muscle secretory factors involved in macrophage functional remodeling. Representative signals, including interleukin-6 (IL-6), irisin, meteorin-like protein (METRNL), fibroblast growth factor 21 (FGF21), oncostatin M (OSM), decorin, myostatin, chemokines, and extracellular vesicles, are systematically summarized in terms of their exercise responsiveness, evidence for skeletal muscle origin, and evidence supporting macrophage regulation. Based on these dimensions, an evidence-strength grading framework is further proposed. Moreover, this review integrates key signaling axes, including glycoprotein 130 (gp130)/Janus kinase (JAK)/signal transducer and activator of transcription (STAT), signal transducer and activator of transcription 6 (STAT6)/peroxisome proliferator-activated receptor gamma (PPARγ), AMP-activated protein kinase (AMPK)/nuclear factor erythroid 2-related factor 2 (Nrf2)/nuclear factor kappa B (NF-κB), transforming growth factor beta (TGF-β)/Smad, and chemokine receptor pathways, to explain how exercise-induced secretory networks participate in the dynamic regulation of the macrophage functional spectrum through immune cell recruitment, inflammatory clearance, immunometabolic reprogramming, matrix remodeling, and repair-niche formation. Current evidence indicates the translational potential of exercise-induced skeletal muscle secretory factors in skeletal muscle repair, metabolic inflammation, aging-related functional decline, and cancer rehabilitation. However, this field still faces several major challenges, including insufficient tracing of skeletal muscle-derived signals, limited direct causal validation, a lack of human tissue-level evidence, and unclear exercise dose-response relationships. Future studies should combine tissue-specific genetic interventions, receptor blockade, single-cell and spatial omics, metabolic flux analysis, and standardized human exercise interventions to further clarify the mechanistic basis and application boundaries of exercise-induced skeletal muscle-macrophage communication, thereby providing a theoretical foundation for precision exercise prescription and chronic inflammation intervention.

Keywords:  exercise; immunometabolism; inflammation resolution; macrophage functional spectrum; myokines; skeletal muscle secretory factors; tissue repair

DOI:  https://doi.org/10.3390/ijms27177527
Commun Biol. 2026 Sep 18. pii: 1220. [Epub ahead of print]9(1):

Spatial proteomics identifies FXYD6 as a dual-site protein of neuromuscular junction in the diaphragm.

Nitin Eapen, Luisa Schmidt, Michael Saynisch, Jan-Wilm Lackmann, Christian Hoegsbjerg, Abigail L Mackey, Manuel Koch, Bent Brachvogel, Philipp Antczak, Marcus Krüger.

Morphological studies of the diaphragm have provided a detailed view of its architecture, which consists of parallel skeletal muscle fibers and a central ring of neuronal innervation that includes neuromuscular junction (NMJ) units. NMJs are disease-vulnerable synapses; thus, analysis of the NMJ is essential to understand its function in both healthy and disease-related conditions. The diaphragm was analyzed by spatial proteomics and 115 proteins were enriched at the NMJ. Comparison of the protein signatures of the NMJ and myotendinous junction (MTJ) revealed 31 shared proteins, suggesting partially conserved structures between these junctions. Key mediators of synaptic transmission and extracellular matrix organization were observed among the NMJ-enriched components, which indicates the molecular complexity and regulatory potential of the NMJ. A focused study of the uncharacterized NMJ protein FXYD6 demonstrate enhanced FXYD6 expression in type IIa fibers of the diaphragm, which exhibit a unique balance of oxidative and glycolytic capacity. FXYD6 interacts with Na⁺/K⁺-ATPase subunits in the diaphragm, which supports the function of FXYD6 in the ionic homeostasis required for continuous, fatigue-resistant contraction. Overall, the dataset provides a comprehensive molecular atlas of the NMJ in the diaphragm and opens new opportunities to dissect the synaptic mechanisms underlying respiratory function and neuromuscular diseases.

DOI: https://doi.org/10.1038/s42003-026-10884-8
Adv Sci (Weinh). 2026 Sep 13. e77653

Glucocorticoid Receptor Signaling in Myeloid Cells Orchestrates Inflammation Resolution and Muscle Repair.

Sirine Souali-Crespo, Joe G Rizk, Emilia Calvano, Rajesh Sahu, Emina Colovic, Imane Chabba, Valentine Gilbart, Erwan Grandgirard, Bastien Morlet, Qingshuang Cai, Daniel Metzger, Delphine Duteil.

  Glucocorticoids are key regulators of inflammation and tissue repair, yet their precise role in muscle regeneration remains incompletely understood. Here, we investigate the impact of myeloid-specific glucocorticoid receptor (GR) invalidation on macrophage dynamics and muscle stem cell function following acute injury. We demonstrate that the loss of GR in myeloid cells leads to increased macrophage accumulation, driven by altered proliferation and recruitment, without affecting fibro-adipogenic progenitor differentiation or satellite cell proliferation and differentiation under steady-state conditions. Transcriptomic and cistrome analyses at early regeneration stages reveal that GR directly regulates gene networks involved in cell cycle control in myeloid cells. Importantly, administration of dexamethasone during the pro-inflammatory phase markedly delays muscle regeneration by impairing monocyte-to-macrophage transition and promoting macrophage proliferation in a myeloid-GR-dependent manner, ultimately reducing satellite cell proliferation and myogenesis. In contrast, dexamethasone treatment during the anti-inflammatory phase exerts limited effects on muscle recovery. Together, our findings uncover a critical temporal role of GR signaling in myeloid cells in coordinating inflammatory resolution and stem cell function during muscle repair, and highlight the complexity of glucocorticoid actions in regenerative contexts.

Keywords:  glucocorticoid receptor; inflammation; macrophage polarization; muscle regeneration; myeloid cells; satellite cells

DOI:  https://doi.org/10.1002/advs.77653
Int J Mol Sci. 2026 Aug 28. pii: 7700. [Epub ahead of print]27(17):

Magnetic Mitohormesis as a Potential Non-Invasive Restorative Therapy for X-Linked Muscular Dystrophies.

Jan Nikolas Iversen, Alfredo Franco-Obregón.

  Duchenne and Becker X-linked muscular dystrophies are no longer viewed as disorders arising solely from passive sarcolemmal fragility but as diseases that progress because of disruption of cellular mechanotransduction. Evidence is accumulating that the gating of TRPC1 and TRPC3 mechanosensitive channels is altered in the absence of dystrophin, resulting in a breakdown of sarcoplasmic calcium homeostasis and preferential loss of type II glycolytic muscle fibres, while type I oxidative fibres are spared. TRPC1-mediated Ca2+ influx is known to activate the calcineurin-NFAT pathway, upregulating PGC-1α transcriptional activity to promote mitochondriogenesis, antioxidant defences, and the oxidative muscle phenotype. Calcineurin signalling also activates a compensatory pathway in dystrophinless muscle by inducing the expression of utrophin, a dystrophin autosomal homologue, capable of substituting for dystrophin at the muscle surface. This perspective explores the possibility that non-mechanical biophysical stimuli can be used to restore calcineurin signalling by non-invasively activating TRPC1. Pulsed electromagnetic field (PEMF) exposure has been shown to stimulate TRPC1-mediated Ca2+ entry and calcineurin-dependent signalling in skeletal muscle and may serve as a gentle method to induce utrophin expression in X-linked muscular dystrophies. By activating calcineurin compensatory mechanisms in these disorders, PEMF-based paradigms warrant future investigation as mechanistically grounded adjuvants to conventional therapies.

Keywords:  Duchenne muscular dystrophy; PGC-1α; TRPC1; X-linked muscular dystrophy; calcineurin signalling; magnetic mitohormesis; mechanotransduction; utrophin

DOI:  https://doi.org/10.3390/ijms27177700
Int J Nanomedicine. 2026 ;21 623194

Nanoengineered GATA3+ Macrophages Transplantation Reconstitutes the Muscle Stem Cells Niche for Skeletal Muscle Regeneration.

Peiwen Zhang, Yahong Xu, Yimeng Zhang, Jing Yang, Shuyun Liu, Yujia Yuan, Younan Chen, Chunhong Li, Yanrong Lu, Hui Wang, Jingping Liu.

   Introduction: Severe skeletal muscle injury is a serious disease worldwide, but current clinical treatments are unsatisfactory because of the limited ability of these treatments to repair muscle; thus, novel therapies that can efficiently promote muscle regeneration are desirable.
Methods: Nanoengineered GATA3+ macrophages (nanoGMφs) were constructed by loading IL-33-induced GATA3+ Mφs with PLGA nanoparticles encapsulating the efferocytosis agonist (aEffero) VU534 (a small molecule that enhances efferocytosis by activating the N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD) pathway), and their ability to reestablish the pro-regenerative muscle stem cell (MuSC) niche was evaluated both in vitro and in vivo.
Results: Our data revealed that dysregulation of GATA3⁺ macrophage subsets and the accumulation of harmful dead cells compromised the MuSC niche after severe skeletal muscle injury. In vitro, GATA3+ Mφs promoted MuSC activation (eg, proliferation, migration, and differentiation) via metabolic regulation. The average diameter of the VU534-loaded PLGA nanoparticles was ~200 nm, with an encapsulation efficiency of ~94.7% and a drug-loading capacity of ~7.3%. Moreover, nanoGMφs secrete EVs that regulate the immune microenvironment locally. In vivo, adoptive nanoGMφ transplantation effectively promoted MuSC activation and the clearance of dead cells and debris, thereby enhancing MuSC niche restoration and skeletal muscle regeneration in two models of acute chemically induced muscle injury. On day 7, the proportions of centrally nucleated myofibers in the nanoGMφ-treated muscles were 1.52 and 1.38 times greater than those in the untreated controls in the CTX and BaCl2 models, respectively. On day 21, compared with the control treatment, the nanoGMφ treatment increased the mean myofiber CSA by 29.38% and 17.42% in the CTX and BaCl2 models, respectively.
Conclusion: This study highlights that the tailored design of engineered immune cell therapy is a promising strategy for promoting MuSC niche restoration and regeneration following acute chemically induced skeletal muscle injury.

Keywords:  drug delivery; efferocytosis; macrophage; regenerative medicine; skeletal muscle injury

DOI:  https://doi.org/10.2147/IJN.S623194
Comput Methods Programs Biomed. 2026 Sep 08. pii: S0169-2607(26)00392-5. [Epub ahead of print]287 109643

CellSize-Clust: An Unsupervised Multi-Algorithm Method for Classifying Skeletal Muscle Cells by Feret Diameter in Mice Soleus and Gastrocnemius.

Paola Llanos, Javier Russell-Guzmán, Matías Monsalves-Álvarez, Matías Aravena, Martín Maturana, Rodrigo Olivares, Pablo Olivares, José Francisco López-Gil, Rodrigo Yáñez-Sepúlveda, Sonja Buvinic.

  The minimum Feret diameter is widely used for muscle fiber-size assessment, but identifying discrete size subpopulations remains challenging because conventional thresholds are subjective. We benchmarked CellSize-Clust, an antibody-free clustering framework that integrates eight algorithms with formal K-selection criteria and silhouette voting, using 14,655 fibers from soleus and gastrocnemius muscles of 42 male C57BL/6J mice, segmented with a U-Net deep-learning model from cryosections stained with wheat germ agglutinin (WGA). Internal validation combined Silhouette, Calinski-Harabasz, and Davies-Bouldin indices, while animal-stratified cross-validation and bootstrapping assessed stability. Most criteria supported K = 2, with Agglomerative Clustering with Ward linkage achieving the highest composite score in both muscles and strong agreement with Gaussian Mixture Models (GMM), Spectral Clustering, and K-Means. Cluster proportions were muscle-specific and showed stable cross-validated silhouettes. External validation in 6435 masseter fibers from 12 mice reproduced the two-cluster structure, proportions, and stability, although algorithm rankings did not generalize and the composite score was vulnerable to degenerate partitions. Hartigan's dip test did not reject unimodality, and separation from a unimodal null was limited. CellSize-Clust therefore provides a reproducible method for thresholding a continuous muscle fiber-size distribution rather than evidence of two biologically distinct subpopulations. Associations with myosin heavy chain isoforms require immunohistochemical confirmation. STATEMENT OF SIGNIFICANCE: CellSize-Clust addresses a persistent gap in muscle morphometry: the absence of reproducible, antibody-free frameworks for classifying skeletal muscle fibers by size. Traditional fiber typing relies on costly immunohistochemistry and is subject to inter-laboratory variability. By combining systematic multi-algorithm benchmarking, formal cluster-number justification, animal-level inferential statistics, and fully open data and code, our framework provides a transparent and reproducible pipeline for screening large morphometric datasets and identifying size-based fiber subpopulations before undertaking more resource-intensive immunohistochemical fiber typing. Although CellSize-Clust does not replace myosin heavy chain (MHC) isoform typing - which remains the gold standard - it complements it as a first-pass screening tool, particularly valuable in longitudinal studies of disuse atrophy, obesity, sarcopenia, and neuromuscular disease among others, where thousands of fibers must be phenotyped efficiently.

Keywords:  Minimum feret diameter; Morphometric analysis; Myofiber classification; Skeletal muscle; Unsupervised clustering

DOI:  https://doi.org/10.1016/j.cmpb.2026.109643
Arch Physiol Biochem. 2026 Sep 17. 1-9

Post transcriptional modification regulation of skeletal muscle TFEB protein nuclear cytoplasmic transport based on different exercise modes in computer biomedical research.

Wang Dan.

   BACKGROUND: The nuclear cytoplasmic transport and post transcriptional modification of TFEB protein in skeletal muscle are the core links regulating the autophagy lysosome system and mitochondrial function, and their response mechanisms to different motor modes are not fully understood.
METHODS: The study analysed the subcellular localisation of TFEB using immunofluorescence technology, detected TFEB phosphorylation (Ser142/Ser211) levels and mTOR, AMPK/ULK1 signalling pathway related protein expression by Western blot, detected autophagy related genes (LC3B, Beclin-1, Atg5, etc.) mRNA levels by qPCR, and simultaneously detected lysosome and mitochondrial functional indicators.
RESULTS: After exercise intervention, the expression of autophagy related genes was upregulated, lysosome function was enhanced. The above changes were most significant in the high-intensity interval group (P < 0.01).
CONCLUSION: Different exercise modes differentially regulate TFEB phosphorylation modification and nuclear cytoplasmic transport, mediate mTOR-AMPK/ULK1 signalling pathway imbalance. Among them, high-intensity interval exercise has significant advantages in regulating TFEB signalling pathway and enhancing skeletal muscle metabolic adaptation.

Keywords:  Computer biomedical; TFEB protein; after transcription; modification regulation; nuclear plasma transport; skeletal muscle; sports mode

DOI:  https://doi.org/10.1080/13813455.2026.2734604
FASEB J. 2026 Sep 30. 40(18): e72291

Relaxin-2: Shaping the Proteomic Landscape of Skeletal Muscle Physiology, Glucose Trafficking, and Mitochondrial Function in Rat.

Xocas Vázquez-Abuín, Lucía Gómez-Cibeira, Javier García-Seara, Pablo de la Fuente-López, Carlos Minguito-Carazo, Susana B Bravo, Manuel Otero-Santiago, Oreste Gualillo, José Ramón González-Juanatey, Francisca Lago, Sandra Feijóo-Bandín, Alana Aragón-Herrera.

  Relaxin-2 is a hormone with robust beneficial effects on the heart and blood vessels and potential as a therapy for cardiovascular (CV) disease. Considering the interorgan communication between skeletal muscle and heart, and the relation between muscle quality/composition and CV events, we hypothesize that relaxin-2 may regulate skeletal muscle physiology and metabolism. We aim to evaluate the impact of relaxin-2 on the proteome of skeletal muscle from healthy Sprague-Dawley rats. Animals were treated with 0.4 mg/kg/day of serelaxin (recombinant form of human relaxin-2) or vehicle (PBS) for 2 weeks employing subcutaneous osmotic minipumps. Skeletal muscle protein identification and quantification were performed by LC-MS/MS using a Data-Independent Acquisition (DIA)-Sequential Window Acquisition of All Theoretical Fragment Ion Spectra (SWATH) method. SWATH/MS quantitative analysis identified that relaxin-2 significantly decreased 95 proteins and significantly increased 32 proteins in rat skeletal muscle when compared to control rats. From these, 34 proteins were associated with muscle function, myogenesis, muscle differentiation and/or regeneration, 20 are mitochondrial proteins (six from the complexes of the electron transport chain), and 10 proteins participate in glucose metabolism. Qualitative data-dependent workflow analysis identified 35 proteins exclusive to the skeletal muscle of the relaxin-2-treated group: eight proteins related to processes of skeletal muscle function (size, ion homeostasis or organization of caveolae structures and cytoskeleton) and myogenesis, and two proteins involved in muscle differentiation. Our work highlighted for the first time the role of relaxin-2 in crucial processes of muscle physiology and energetic metabolism, which could influence several processes involved in myopathy and CV.

Keywords:  energetic metabolism; glucose transport; mitochondrial respiration; myogenesis; proteome; proteomics; relaxin‐2; serelaxin; skeletal muscle

DOI:  https://doi.org/10.1096/fj.202602643R
Adv Sci (Weinh). 2026 Sep 16. e77854

Nuclear Translocation of PFKFB3 Promotes Disuse-Induced Muscle Atrophy via Scaffolding Nedd4-Mediated JunB Ubiquitination.

Mengjun Ma, Yinliang Liu, Wangchang Wu, Biao Yang, Jiahao Zhuang, Haoye Yu, Rujia Mi, Yixuan Lu, Wen Yang, Hanting Yi, Chenglong Yuan, Yinfeng Gu, Hongyu Li.

  Disuse-induced muscle atrophy is characterized by coordinated metabolic remodeling and enhanced protein degradation, yet the molecular link between these processes remains unclear. Here, we identify 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) as a critical regulator of this condition. Using a unilateral hindlimb immobilization mouse model, metabolomics, and functional assays in vivo and in vitro, we demonstrate that PFKFB3 is markedly upregulated during muscle atrophy and promotes myofiber wasting. Mechanistically, PFKFB3 predominantly localizes to the nucleus and functions independently of its canonical glycolytic activity. It acts as a scaffold protein to facilitate the interaction between the E3 ubiquitin ligase Nedd4 and the transcription factor JunB, thereby enhancing JunB ubiquitination and proteasomal degradation. Loss of JunB, a known anti-atrophy factor, contributes to atrophic progression. In turn, JunB transcriptionally represses PFKFB3, forming a regulatory feedback loop. Pharmacological and genetic inhibition of the PFKFB3-Nedd4-JunB axis significantly attenuates muscle atrophy in vivo. Collectively, these findings reveal a noncanonical nuclear function of PFKFB3 in coordinating protein stability during muscle atrophy and highlight this signaling axis as a potential therapeutic target for disuse-induced muscle wasting.

Keywords:  PFKFB3; disuse; muscle atrophy; nuclear translocation; ubiquitination

DOI:  https://doi.org/10.1002/advs.77854
Am J Physiol Cell Physiol. 2026 Sep 16.

Integrating and Orchestrating Multiple Components of Skeletal Muscle Injury and Regeneration.

Steven S Segal.

  As a soft tissue comprising nearly half of body mass, skeletal muscle is vulnerable to injury from many sources. Healthy muscle can regenerate from resident stem cells known as satellite cells (SCs). During homeostasis, individual SCs reside within a niche sandwiched between basal lamina (BL) and sarcolemma, dispersed along the periphery of mature myofibers. The SC niche abuts capillaries embedded in extracellular matrix (ECM) containing fibroblasts and immune cells. With integral roles for each component of muscle tissue, cellular responses to injury are integrated and orchestrated during regeneration. Following physical trauma, chemical damage, or myotoxin exposure, inflammation ensues with efferocytosis removing debris and creating space for new growth. Residual BL selectively guide regeneration of myofibers, capillaries, and nerves. SCs transition from quiescence to activation, proliferate as myoblasts, differentiate into myocytes, fuse into multinucleated myotubes (or undergo self-renewal) and return to quiescence while nascent myofibers mature. In parallel, fibroadipogenic progenitor cells transiently proliferate to support regeneration of healthy tissue. Endothelial tip cells sprout filopodia to orient capillary growth with microvascular networks remodeling as muscle blood flow is restored. Following Wallerian degeneration, axons extend filopodia to orient their regrowth within the neurolemma along tracks of endothelial cells; cues from myofibers guide reinnervation of neuromuscular junctions. Coordinated through autocrine, paracrine, and juxtacrine signaling with guidance from the immune system and ECM, interactions between myogenesis, angiogenesis, and reinnervation provide synergistic support as muscle structure and function are restored. Failure of regeneration leads to fibrosis, loss of strength, and impaired mobility.

Keywords:  angiogenesis; extracellular matrix; inflammation; myogenesis; neuromuscular

DOI:  https://doi.org/10.1152/ajpcell.00873.2025
Adv Biol (Weinh). 2026 Sep;10(9): e70147

Development of a Multi-Organ Microphysiological (MPS) Model to Study Age-Related Comorbidities.

Gaurav Srivastava, Aakash Patel, Alice Rodriguez-Fuguet, Akanksh Jambagi, Himanshi Jangir, Ahmad Nawaz, Afeef Mahmud, Camden Dwelle, Xiufang Guo, James Hickman.

  Comorbidities, the concurrent presence of two or more medical conditions, present significant challenges for diagnosis and treatment. Skeletal muscle sarcopenia and hypertrophic cardiomyopathy (HCM) are two distinct yet interrelated conditions, often co-existing in elderly individuals and exacerbating disease progression. Mechanistic understanding of sarcopenia-HCM comorbidity is limited, largely based on clinical correlation analyses and a few available mouse models. To facilitate pathophysiological research and accelerate therapeutic development, a more efficient human-relevant in vitro model is needed. This study presents a human-based sarcopenia-HCM comorbidity model in a multi-organ microphysiological system (MPS) that incorporates primary human hepatocytes, human induced pluripotent stem cells (hiPSC)-derived skeletal muscle and cardiomyocytes. The phenotypes for sarcopenia and HCM were first induced and characterized in single-organ systems, then assembled and analyzed in a multi-organ MPS, maintained in circulated serum-free medium. The functional phenotypes of skeletal muscle, cardiomyocytes, and hepatocytes, as well as inter-organ interactions in this organ-chip system align with clinical reports. This MPS comorbidity platform will enable pathophysiological investigation of sarcopenia, HCM, their comorbidity, and testing of therapeutic efficacy, toxicity, and pharmacokinetics. This study highlights how multi-organ MPS can revolutionize preclinical research as a human-relevant, cost-effective, and ethical alternative for studying comorbidities.

Keywords:  aging; cardiomyopathy; comorbidity; human‐on‐a‐chip; microphysiological systems; new approach methods (NAMs); sarcopenia

DOI:  https://doi.org/10.1002/adbi.70147
Int J Mol Sci. 2026 Sep 04. pii: 7894. [Epub ahead of print]27(17):

Cancer Cell-Derived Small Extracellular Vesicles Are Associated with Impaired C2C12 Myoblast Differentiation.

Woojin Lee, Seongjae Yang, Hyeonseo Yu, Yeongmin Kim, Seongmin Cho, Hyeong Yun Kim, Uijoo Kim, Hyunseok Kong, Sang Bum Kim.

  Cancer cachexia is a complex metabolic syndrome characterized by progressive skeletal muscle wasting and poor clinical outcomes. Previous studies have mainly focused on the association between cancer-derived extracellular vesicles and atrophy of differentiated myotubes, whereas their effects on myoblast differentiation markers have not been sufficiently elucidated. In this exploratory in vitro study, vesicle fractions isolated from MC38, CT26, MCA205, and B16F10 cancer cell lines under serum-deprived conditions were referred to as small extracellular vesicles (sEVs) and used to treat C2C12 myoblasts during differentiation. Compared with the control group, the sEV-treated groups showed reduced myotube diameter and differentiation area on day 6, while the mRNA expression patterns of MyoD, MyoG (Myogenin), MRF4, Myf5, Pax7, and several MHC isoforms showed time-dependent changes. GO/KEGG analysis of commonly identified proteins revealed enrichment of terms related to mRNA metabolism, the cell cycle, and the proteasome. These findings suggest that treatment with cancer cell-derived sEVs may be associated with impaired in vitro differentiation of C2C12 myoblasts.

Keywords:  cancer cachexia; myoblast differentiation; myogenic regulatory factors; myosin heavy chain; small extracellular vesicles

DOI:  https://doi.org/10.3390/ijms27177894
Sports Med. 2026 Sep 12.

Citius, Maius, Melius: Mitochondria and Endurance Performance.

Javier Botella, David J Bishop, Cesare Granata.

Endurance performance relies on a range of physiological adaptations classified as central or peripheral depending on whether the remodeling occurs in the cardiovascular system or in the skeletal muscle, respectively. One of the goals of these adaptations is to enhance oxygen transport and its utilization by mitochondria to sustain ATP resynthesis. While a link between skeletal muscle mitochondrial characteristics and endurance performance may seem obvious, there is no consensus on whether mitochondrial characteristics are key determinants of endurance performance. In this narrative review, we examine cross-sectional, correlational, and intervention studies conducted in humans that support or challenge the role of mitochondria in endurance performance. Cross-section studies suggest that individuals with superior endurance performance exhibit greater mitochondrial content and respiratory function than those with lower fitness levels. Correlation studies have shown positive associations between multiple mitochondrial characteristics and markers of endurance performance. However, a lack of correlation between training-induced changes in mitochondrial characteristics and endurance performance has also been reported. Intervention studies indicate that changes in mitochondrial characteristics following training, phlebotomy, or detraining are often associated with changes in markers of endurance performance. Conversely, increasing oxygen delivery to the working muscle (i.e., via increasing oxygen concentration) has been shown to improve performance markers, suggesting these improvements are not limited by mitochondrial characteristics. In conclusion, while substantial evidence associates mitochondrial characteristics with endurance performance, this relationship is not universal; central factors display an equally strong influence independently of mitochondrial characteristics. We propose that enhanced mitochondrial characteristics represent an important and often necessary, but not sufficient, adaptation that is required to support endurance performance.

DOI: https://doi.org/10.1007/s40279-026-02530-4
Mol Metab. 2026 Sep 18. pii: S2212-8778(26)00125-0. [Epub ahead of print] 102441

Autocrine Signaling may Regulate Exercise-Induced Interleukin-6 Release from Human Skeletal Muscle.

Jonas Osted Hvidemose, Beckey Trinh, Alexandra Vassilieva, Anne-Sophie Worm Fenger, Peter Nissen Bjerring, Matthijs van Hall, Jens Otto Clemmesen, Sigurður Þór Sigurðsson, Kirsten Møller, Gerrit van Hall, Mark A Febbraio, Bente K Pedersen, Peter Plomgaard, Helga Ellingsgaard.

   BACKGROUND: Contracting skeletal muscle releases interleukin-6 (IL-6) which is primarily cleared by the liver. The tissue-specific regulation of IL-6 and soluble IL-6 receptor (sIL-6R) kinetics remains, however, poorly understood. To characterize tissue-specific IL-6 and sIL-6R exchange during exercise, we combined simultaneous arteriovenous measurements across the contracting leg, splanchnic region, and the brain with, or without, pharmacological IL-6 receptor (IL-6R) blockade.
METHODS: Thirty young, well-trained men were randomized in a double-blind, placebo-controlled design to receive either tocilizumab (IL-6R blockade) or placebo before performing moderate-intensity cycling exercise. Net tissue flux of IL-6 and sIL-6R was determined from arteriovenous concentration differences across the femoral, hepatic, and internal jugular circulation.
RESULTS: During exercise, leg IL-6 release increased with both placebo and IL-6R blockade but was significantly augmented by IL-6R blockade, suggesting a potential role for autocrine regulation of local IL-6 release . Under control conditions, the splanchnic bed was the predominant site of IL-6 clearance; however, IL-6R blockade shifted splanchnic IL-6 net balance from uptake to release. In addition, the exercising leg was identified as the source of circulating sIL-6R during exercise, whereas no consistent sIL-6R exchange occurred across the splanchnic bed or brain.
CONCLUSION: These findings suggest a potential role for IL-6 signaling in the autocrine regulation of IL-6 release from the contracting leg during exercise. Furthermore, exercise increases leg-derived sIL-6R, thereby contributing to increased circulating sIL-6R concentrations, while receptor-mediated splanchnic clearance appears to be a major determinant of systemic IL-6 availability during exercise in humans.
CLINICAL TRIAL REGISTRATION NUMBER: Clinicaltrials.gov (NCT06334653).

Keywords:  arteriovenous balance; autocrine signaling; interleukin-6; skeletal muscle; soluble IL-6 receptor; tocilizumab

DOI:  https://doi.org/10.1016/j.molmet.2026.102441
JACC Heart Fail. 2026 Sep 11. pii: S2213-1779(26)00456-7. [Epub ahead of print] 103353

Skeletal Muscle Dysfunction in Heart Failure: Mechanistic Insights and Therapeutic Implications.

Azariyas A Challa, Ambarish Pandey, Peter H Brubaker, Dalane W Kitzman, Biykem Bozkurt, Dinesh K Kalra.

  Exercise intolerance is a hallmark of heart failure (HF) and a strong predictor of morbidity and mortality. Accumulating evidence suggests that alterations in skeletal muscle (SkM) structure and metabolism are key contributors to exercise intolerance in patients with HF. These alterations include reduced muscle mass, increased intermuscular adipose tissue, capillary rarefaction, altered fiber-type composition, reduced mitochondrial content, and impaired oxidative phosphorylation. In parallel, an increase in oxidative stress and a decrease in antioxidant defenses, along with derangements in pathways that remove toxic lipid peroxidation products, heighten oxidative stress, perpetuate injury, and establish a vicious cycle of progressive muscle dysfunction. Although exercise training remains the most effective strategy to mitigate SkM dysfunction and improve exercise capacity in patients with HF, novel pharmacotherapies targeting the SkM dysfunction are emerging as potential approaches to treat exercise intolerance in HF. Future studies should delineate the contribution of SkM dysfunction to exercise intolerance in HF, help improve our understanding of its mechanistic underpinnings, and explore the clinical utility of novel SkM-targeted therapies to alleviate exercise intolerance in HF.

Keywords:  exercise intolerance; heart failure; metabolic; skeletal muscle; structural; therapy

DOI:  https://doi.org/10.1016/j.jchf.2026.103353