bims-moremu 2026-10-18 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2026–10–18
35 papers selected by
Anna Vainshtein, Craft Science Inc.

Redox resilience in skeletal muscle aging: cellular adaptations and exercise-mediated homeostasis.
Skeletal Muscle-Derived Extracellular Vesicles in Interorgan Communication During Aging.
Proximity Ligation Assay to Determine Protein-Protein Interactions in Muscle Stem Cells.
An integrative transcriptomic atlas of ALS and aging skeletal muscle defines shared and distinct molecular programs of degeneration.
High-Resolution Skeletal Muscle Fiber Typing Using Four-Color Immunofluorescence Microscopy.
Circular RNAs in Skeletal Muscle Aging and Sarcopenia: Mechanistic Evidence, Biomarker Potential, and Therapeutic Readiness.
Extracellular Vesicle Isolation and Purification from Skeletal Muscle Cells.
Physiological Reference Mapping Reveals Context-Dependent Dysregulation of Regenerative Programs in Duchenne Muscular Dystrophy.
Muscle stem cells produce a protective Fibrillin-1 matrix to prevent precocious activation.
The Role of TXNIP in Skeletal Muscle Physiology and Related Diseases: Current Perspectives.
Engineering Functional Skeletal Muscle Tissues from Human Induced Pluripotent Stem Cells.
Klhl41b orchestrates sarcomere assembly and growth to drive skeletal muscle hypertrophy in vivo.
Delphinidin induces the upregulation of miR-23a-3p expression in skeletal muscle and miR-23a-3p release from intestinal cells.
Muscle satellite cell dysfunction in critical illness: niche biology, regenerative failure, and implications for recovery.
Can Resistance Training-Induced Skeletal Muscle Growth Improve Local Muscular Endurance?
Cannabigerol Enhances Muscle Strength and Performance in Dexamethasone-Treated Mice.
Ferroptosis-related hub genes and immune infiltration characteristics in Duchenne muscular dystrophy: a molecular framework with implications for aging-related muscle degeneration.
Carnosine drives mitochondrial biogenesis and skeletal muscle regeneration via Sirt1-mediated nuclear translocation of PGC-1α.
Bulk Differentiation of Human Induced Pluripotent Stem Cells into Contractile Skeletal Muscles.
SLIT and NTRK-like family member 1 regulates muscle regeneration.
Aging concomitantly reduces skeletal muscle proteome plasticity and hypertrophic responses to resistance training in male adults.
A Hypertrophic Stimulus Drives Age-Dependent Transcript Isoform Switching With and Without Differential Gene Expression in Skeletal Muscle.
Differential alternative splicing in skeletal muscle after 14 days immobilization-induced atrophy in young men.
Integrative Multi-Omics Analysis Reveals Molecular Signatures of Age-Related Decline in Vervet Leg Skeletal Muscle.
FAPs orchestrate ANTXR2-mediated fine-tuning of collagen VI to ensure skeletal muscle function.
Measuring Skeletal Muscle Mitochondrial Architecture in 3D Using Focused Ion Beam Scanning Electron Microscopy (FIB-SEM).
Ets2 Is an Activity-Dependent Transcriptional Regulator of a Fast-Twitch Muscle Program.
Quantification of Mitochondrial Oxidative Phosphorylation in Skeletal Muscle.
GNMT alleviates heart failure-induced skeletal muscle atrophy by regulating ATP5J2-mediated mitochondrial metabolic reprogramming through succinylation.
An NAD+-responsive adipose signal coordinates inter-organ defense against muscle atrophy.
Sarcopenia beyond muscle: endocrine-metabolic regulation and inter-tissue crosstalk across the muscle-tendon unit.
Lysosomal Competence in Skeletal Muscle Aging: Autophagic Flux, Measurement Gaps, and Human Translation.
Flow Cytometric Methods for ROS Quantification in Skeletal Muscle Myotubes.
Systemic proteomic dynamics of acute exercise reveal genetic links to health and disease.
Multi-omics atlas of chronic exercise.

Free Radic Biol Med. 2026 Oct 15. pii: S0891-5849(26)01214-1. [Epub ahead of print]

Redox resilience in skeletal muscle aging: cellular adaptations and exercise-mediated homeostasis.

Eva Tamayo-Torres, Miriam Martinez-Canton, Silvana Soto-Rodriguez, Abril Gorgori-Gonzalez, Julian Carretero, Juan Ignacio Cervera-Miguel, Olga Laosa, Leocadio Rodriguez-Mañas, Maria Carmen Gomez-Cabrera.

Aging progressively impairs skeletal muscle function, leading to sarcopenia, frailty, and loss of independence. Although oxidative stress has long been considered a central driver of muscle aging, increasing evidence indicates that reactive oxygen species (ROS) also serve essential signaling functions that coordinate mitochondrial remodeling, proteostasis, metabolism, and tissue repair. Consequently, age-related muscle dysfunction is increasingly understood as reflecting impaired adaptive redox signaling rather than excessive oxidant production alone. In this review, we propose the concept of redox resilience as an integrative framework describing the capacity of skeletal muscle to preserve structural integrity and functional performance through the dynamic regulation of oxidant production, antioxidant defenses, and redox-sensitive signaling in response to physiological challenges. We discuss how aging disrupts this resilience through impaired redox-sensitive signaling, including the attenuation of exercise-induced Nrf-2 activation, together with alterations in the multicellular organization of skeletal muscle. Recent advances in single-cell and single-nucleus transcriptomics have revealed that muscle aging involves profound remodeling of specialized myonuclear populations, stromal cells, immune cells, and intercellular communication networks, highlighting the multicellular complexity of skeletal muscle aging and providing a framework to investigate how redox-dependent processes may interact with tissue-wide signaling networks. We further examine how regular physical exercise reinforces redox resilience by promoting transient ROS-mediated signaling through NADPH oxidases, activation of Nrf-2 and PGC-1α-dependent pathways, mitochondrial quality control, and metabolic remodeling. These adaptations enhance the capacity of skeletal muscle to respond to physiological stress while preserving tissue homeostasis. Finally, we discuss future perspectives for targeting adaptive redox networks to promote healthy muscle aging and propose that restoring redox resilience may preserve physiological ROS signaling while strengthening endogenous antioxidant responses and limiting excessive oxidative damage, thereby contributing to the maintenance of muscle function and health span.

DOI: https://doi.org/10.1016/j.freeradbiomed.2026.10.023
Aging Cell. 2026 Oct;25(10): e70773

Skeletal Muscle-Derived Extracellular Vesicles in Interorgan Communication During Aging.

Weiyi Jiang, Kenon Chua, Joe Young, Eng King Tan, Hong-Wen Tang.

Skeletal muscle is increasingly recognized as a secretory organ that communicates with distant tissues through the release of bioactive factors, including extracellular vesicles (EVs). During aging, muscle-derived EVs have emerged as important mediators of interorgan communication, influencing tissue homeostasis, regeneration, metabolism, and disease progression. Recent studies demonstrate that skeletal muscle EVs carry diverse cargos such as proteins, lipids, metabolites, and regulatory RNAs that can modulate the function of recipient cells in multiple organs. In particular, aging-associated alterations in EV biogenesis, cargo composition, and secretion may contribute to chronic inflammation, stem cell dysfunction, metabolic decline, and age-related pathologies. In this review, we summarize current advances in skeletal muscle-derived EV biology and their roles in interorgan communication during aging. We discuss mechanisms regulating EV formation and cargo loading, their impact on stem cell function and tissue regeneration, and their involvement in aging-related diseases. We also highlight the translational potential of muscle EVs as biomarkers and therapeutic targets. Together, these findings identify muscle-derived EVs as key regulators of systemic aging and interorgan signaling.

DOI: https://doi.org/10.1111/acel.70773
Methods Mol Biol. 2026 ;3057 235-247

Proximity Ligation Assay to Determine Protein-Protein Interactions in Muscle Stem Cells.

Marie J Catenacci, Michael A Rudnicki.

  Satellite cells are present only in skeletal muscle and are crucial for regeneration. In recent years, satellite cell heterogeneity has identified different subpopulations, such as bona fide muscle stem cells. These populations are rare and in small numbers, making studying them very difficult. Moreover, satellite cells are sensitive to the environment and niche. To avoid niche disruption and changes to the cell state, our lab developed a mix of different techniques to study protein-protein interactions ex vivo on cultured myofibers. This protocol is based on the Proximity Ligation Assay (PLA) technique and uses IMARIS software to analyze protein interactions.

Keywords:  Niche; Protein complex; Protein interaction; Satellite cells; Skeletal muscle

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_18
Proc Natl Acad Sci U S A. 2026 Oct 20. 123(42): e2613546123

An integrative transcriptomic atlas of ALS and aging skeletal muscle defines shared and distinct molecular programs of degeneration.

Mercedes Grima-Terrén, Megan Rommelfanger, Silvia Campanario, Aina Calls-Cobos, Andrés Cisneros, Ignacio Ramírez-Pardo, Grace Chou, Yuewen Zheng, Nasun Hah, Antonio L Serrano, Eusebio Perdiguero, Joan Isern, Pura Muñoz-Cánoves.

  Skeletal muscle atrophy and weakness resulting from loss of motor neuron innervation are shared hallmarks of amyotrophic lateral sclerosis (ALS) and age-associated sarcopenia. However, muscle wasting in ALS is rapid and severe, whereas sarcopenia progresses gradually over decades, peaking at an advanced age. The molecular mechanisms underlying muscle wasting in these conditions remain incompletely defined. Here, we used the SOD1G93A ALS mouse model and wild-type mice across the lifespan to generate an integrated single-nucleus transcriptomic atlas of skeletal muscle, mapping changes associated with ALS and aging. This atlas is complemented by structural and functional analyses. Our results identify transcriptionally distinct condition-specific myonuclear states, including disease-responsive programs within synaptic myonuclei at the neuromuscular junction, that are shared or distinct between the two conditions. Notably, at early stages, muscle from ALS mice exhibits molecular hallmarks of aged muscle at the myofiber level, indicating premature aging and reinforcing aging as a risk factor in ALS. At advanced disease stages and in old age, myonuclear subpopulations follow similar degenerative pathways in fast glycolytic fibers, consistent with their loss in both conditions. However, a distinct ALS-enriched myonuclei subpopulation displays uniquely regulated genes not observed in aged muscle, potentially underlying the more rapid and severe pathology observed in ALS. This atlas maps shared and divergent mechanisms of muscle degeneration in ALS and sarcopenia and provides a resource for identifying therapeutic targets tailored to each condition.

Keywords:  aging; amyotrophic lateral sclerosis; atrophy; skeletal muscle

DOI:  https://doi.org/10.1073/pnas.2613546123
Methods Mol Biol. 2026 ;3057 127-136

High-Resolution Skeletal Muscle Fiber Typing Using Four-Color Immunofluorescence Microscopy.

Erin Allison, Mackenzie Q Graham, Fasih A Rahman, Joe Quadrilatero.

  Skeletal muscle is composed of heterogeneous fiber types defined by distinct myosin heavy chain (MYH) isoforms. Accurate fiber type identification is essential for studying skeletal muscle development, plasticity, disease, and intervention responses. Traditional fiber type classification techniques are limited by either lack of specificity or the inability to simultaneously detect all fiber types in a single section. Here, we describe a novel four-channel immunofluorescent staining protocol that enables simultaneous visualization and quantification of type I, IIA, IIX, and IIB fibers within a single cross-section of rodent skeletal muscle. This high-resolution method improves throughput and eliminates the need for serial sectioning but also allows for the identification of hybrid fibers. Moreover, membrane staining can be applied to simultaneously perform cross-sectional area analysis. This approach enhances the precision and efficiency of skeletal muscle phenotyping in both physiological and pathological contexts by capturing the full spectrum of skeletal muscle fibers in a single image, thus providing a powerful tool for investigating fiber type-specific development and adaptation.

Keywords:  Fiber typing; Hybrid fibers; Immunofluorescence; Myosin heavy chain; Skeletal muscle; Skeletal muscle development; Skeletal muscle plasticity

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_10
Int J Mol Sci. 2026 Oct 03. pii: 8844. [Epub ahead of print]27(19):

Circular RNAs in Skeletal Muscle Aging and Sarcopenia: Mechanistic Evidence, Biomarker Potential, and Therapeutic Readiness.

Thanh Huu Phan Ngo, Wan Lee.

  Skeletal muscle aging arises from interacting defects in proteostasis, mitochondrial quality control, inflammatory signaling, neuromuscular integrity, regenerative capacity, and mechanical-metabolic plasticity, and may culminate in sarcopenia. Circular RNAs (circRNAs) are plausible regulators and biomarker candidates, but most evidence derives from developmental myogenesis, expression profiling, or non-aging atrophy models. This critical review organizes the literature around skeletal muscle aging and applies a four-level framework encompassing discovery, mechanistic support, in vivo causality, and functional intervention. We assess human linkage, species, treatment timing, locus of action, and endogenous or engineered modality separately. circSnd1 and circDdb1 currently provide the strongest combination of functional preclinical evidence and association with aged human skeletal muscle. circFUT10, circBBS9, circNEB, and circGLIS3 define less mature regenerative, discovery, histological, or muscle-quality domains. Non-aging atrophy studies, including circTmeff1 and engineered circmiR-29b, test whether proposed mechanisms remain active under defined catabolic stress. Human blood and serum-vesicle studies provide discovery-level associations with strength or mobility, but clinical validation of a circulating circRNA biomarker for sarcopenia remains insufficient. Therapeutic development is constrained by quantitative target credibility, systemic skeletal-muscle exposure, post-onset functional efficacy in aged organisms, safety, reversibility, and independent replication. The field should now prioritize rigorous validation over additional descriptive cataloging.

Keywords:  RNA therapeutics; biomarkers; circular RNA; mechanotransduction; sarcopenia; skeletal muscle aging

DOI:  https://doi.org/10.3390/ijms27198844
Methods Mol Biol. 2026 ;3057 145-158

Extracellular Vesicle Isolation and Purification from Skeletal Muscle Cells.

Dongnan Yan, Emily Haughton, Ruhani Makkar, Matthew J A Wood, Dhanu Gupta.

  Extracellular vesicles (EVs) have emerged as critical mediators of intercellular communication and hold considerable promise as biomarkers and therapeutic vectors. In skeletal muscle, EVs transport proteins, RNA, and other bioactive molecules, such as myokines, making them valuable indicators of muscle physiology and pathology. This method paper presents a detailed protocol for the isolation, purification, and characterization of EVs derived from human myoblasts. Our optimized workflow ensures high yield and sample quality, enabling comprehensive downstream molecular analysis. Additionally, we describe advanced techniques for assessing EV physical characteristics, concentration, and cargo content, providing an essential toolkit for investigating skeletal muscle EV biology and potential role in disease diagnostics. This protocol facilitates the efficient exploration of skeletal muscle-derived EVs and their implications in muscle function and pathology.

Keywords:  EV characterization; EV isolation; EV purification; Extracellular vesicles; Skeletal muscle; Ultracentrifugation

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_12
Cells. 2026 Sep 24. pii: 1743. [Epub ahead of print]15(19):

Physiological Reference Mapping Reveals Context-Dependent Dysregulation of Regenerative Programs in Duchenne Muscular Dystrophy.

Laura Perin, Yan-Yun Liu, Gregory A Brent, Anna Milanesi.

  Duchenne muscular dystrophy (DMD) involves chronic degeneration and regeneration, causing dystrophic muscle stem cells (MuSCs) to differ from uninjured wild-type tissue. Conventional disease-versus-resting-control comparisons may therefore conflate dysregulation with regeneration. We developed a physiological reference-mapping framework integrating normal regeneration trajectories with replicated dystrophic datasets to estimate disease-associated deviations relative to regenerative state and spatial context. We applied it across single-cell/single-nucleus, bulk, and spatial RNA-sequencing datasets. In a replicated genotype-by-state MuSC dataset comprising wild-type (WT) and dystrophin-deficient mdx mouse samples across four lineage states, with three biological replicates per group, activated mdx MuSCs showed excessive extracellular matrix induction (standardized mdx-WT difference = 1.431; FDR = 3.69 × 10-9) and an attenuated MYC-associated response (-0.731; FDR = 2.57 × 10-4) among five prespecified programs. Spatial decomposition indicated substantial within-niche remodeling beyond altered niche composition. Physiological calibration identified extracellular matrix induction as a normal transient program that becomes excessive in dystrophy and suggested that reduced oxidative phosphorylation transcription relative to resting muscle may represent insufficient suppression relative to normal regeneration. An independent human dystrophinopathy spatial cohort supported increased whole-biopsy extracellular matrix transcription. Physiological reference mapping therefore helps distinguish regenerative adaptation from context-dependent disease dysregulation in DMD.

Keywords:  Duchenne muscular dystrophy; muscle stem cells; physiological reference mapping

DOI:  https://doi.org/10.3390/cells15191743
Sci Adv. 2026 Oct 16. 12(42): eaeb8190

Muscle stem cells produce a protective Fibrillin-1 matrix to prevent precocious activation.

Eleni Chrysostomou, Oussama Smail, Artemis Vlachopoulou, Takuto Hayashi, Nicolas Tcheng, Nicol Voermans, Dieter P Reinhardt, Frederic Relaix, Philippos Mourikis.

Diverse biological mechanisms regulate muscle stem cell quiescence, including inhibition of differentiation, adhesion, and translational control. Here, we identify the matrix glycoprotein Fibrillin-1 (FBN1) as a Notch-regulated, cell-autonomous effector, essential for maintaining quiescence. Known for its causal role in Marfan syndrome (MFS), our work positions FBN1 as a critical niche component that protects muscle stem cells from aberrant growth factor signaling. Targeted deletion of Fbn1 in muscle stem cells leads to dose-dependent quiescence defects, characterized by loss of cellular projections, depletion of the stem cell pool, and progressive decline in muscle function. Consistently, human MFS muscle biopsies show abnormally activated satellite cells, implicating stem cell imbalance in the development of MFS-associated myopathy. Mechanistically, the loss of FBN1 up-regulates transforming growth factor-β (TGFβ) signaling, and pharmacological blockade of TGFβ signaling rescues the cellular and physiological defects of FBN1-deficient muscle. These findings reveal a new quiescence-preserving mechanism through extracellular matrix-mediated shielding from mitogenic signals and position stem cell dysfunction as a driver of MFS myopathy.

DOI: https://doi.org/10.1126/sciadv.aeb8190
J Inflamm Res. 2026 ;19 637774

The Role of TXNIP in Skeletal Muscle Physiology and Related Diseases: Current Perspectives.

Jiazhe Du, Xudong Gao, Sai Yao, Ludan Zhang.

  Thioredoxin-interacting protein (TXNIP) is a multifunctional regulatory protein of the α-arrestin family that acts as a redox sensor, an energy-responsive molecule, and a transcription-associated regulator. TXNIP has emerged as a key regulator of skeletal muscle homeostasis and has been implicated in the pathogenesis of multiple muscle disorders. Skeletal muscle is a principal site of systemic glucose disposal, accounting for more than 70% of insulin-stimulated glucose uptake in the human body. TXNIP has been implicated in sarcopenia, obesity-related insulin resistance, limb ischemia-induced muscle injury, disuse muscle atrophy, and hereditary muscular dystrophy through multiple mechanisms, including glutathione metabolic regulation, ferroptosis, NLRP3 inflammasome activation, impaired GLUT4 membrane translocation, and altered mitochondrial substrate oxidation. Recent advances in gene editing, single-cell sequencing, metabolomics, and human clinical research have enabled a more detailed characterization of TXNIP-related molecular mechanisms in skeletal muscle. This review provides a systematic synthesis of recent evidence on TXNIP in skeletal muscle, organized around seven themes: its molecular characteristics, expression and regulatory patterns in skeletal muscle, physiological functions, disease-specific pathogenic mechanisms, intervention-related regulatory networks, current limitations, and future perspectives. This review aims to provide a mechanistic rationale for targeting TXNIP as a potential strategy for the prevention and treatment of skeletal muscle-related diseases.

Keywords:  NLRP3; TXNIP; insulin resistance; oxidative stress; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.2147/JIR.S637774
Methods Mol Biol. 2026 ;3057 35-53

Engineering Functional Skeletal Muscle Tissues from Human Induced Pluripotent Stem Cells.

Amber Detwiler, Alastair Khodabukus, Nenad Bursać.

  In vitro cell culture models of human skeletal muscle offer a valuable platform for studies of pathology and discovery of new therapeutics. However, traditional two-dimensional cell culture models suffer from limited durability and challenges with assessment of skeletal muscle contractile function. Furthermore, finite proliferation potential and scarce availability of patient-derived primary myoblasts limit experimental throughput when using these cells. Here, we describe a method for using human induced pluripotent stem cells (hiPSCs) to generate functional three-dimensional skeletal muscle tissues. Briefly, transient overexpression of Pax7 in hiPSC-derived paraxial mesoderm cells permits efficient formation of myogenic progenitor cells (iMPCs), which are then combined with hydrogel matrix to form cylindrically shaped skeletal muscle (iSKM) "myobundles." After 2 weeks of differentiation, iSKM myobundles contain aligned and densely packed multinucleated myotubes that, in response to electrical stimulation, exhibit robust calcium transients and positive force-frequency and force-length relationships. The methods detailed here have been successfully utilized to model and study limb-girdle muscular dystrophy type R2/2B and can be applied for studies of skeletal muscle regeneration and testing of candidate gene and cell therapies for disease. Collectively, iSKM myobundle engineering is a powerful in vitro methodology expected to significantly advance human skeletal muscle research and therapy.

Keywords:  Disease modeling; Human induced pluripotent stem cells; Hydrogel; Myopathy; Skeletal muscle; Tissue engineering

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_4
Skelet Muscle. 2026 Oct 08. pii: 38. [Epub ahead of print]16(1):

Klhl41b orchestrates sarcomere assembly and growth to drive skeletal muscle hypertrophy in vivo.

Hyewon Han, Grace R Tate, Janet Shi, Alfredo H Bongiorno, Arian Mansur, Jeffrey Widrick, Sehajpreet Gill, Esmat Karimi, Henk Granzier, Jeffrey R Moore, Vandana A Gupta.

   BACKGROUND: Nemaline myopathy (NM) is a clinically and genetically heterogeneous disease caused by mutations in sarcomere-associated genes, with congenital forms representing the most severe end of the spectrum. Recessive mutations in KLHL41 underlie a severe congenital NM characterized by sarcomeric disorganization and impaired muscle growth. The in vivo mechanisms by which KLHL41 governs sarcomere assembly and growth remain poorly understood.
METHODS: We generated zebrafish models of KLHL41 deficiency by the CRISPR-Cas9 approach to examine the temporal and molecular basis of sarcomere assembly defects in NM. The phenotypic and physiological characterization of skeletal muscle defects was investigated by birefringence, spontaneous coiling, spontaneous swimming behavior, and force generation assays. Structural analyses by electron microscopy and immunofluorescence assessed myofibril organization and sarcomere structures across developmental time points. Quantitative proteomics and biochemical assays were performed to identify perturbations in sarcomeric proteins and associated molecular pathways.
RESULTS: We show that Klhl41b is essential for the formation and organization of sarcomeres, supporting both radial and longitudinal muscle growth. Loss of Klhl41b resulted in reduced sarcomere size, defective sarcomere assembly followed by progressive destabilization of sarcomeres, nemaline body formation, and reduced muscle function. Proteomic analysis in Klhl41b-deficient zebrafish revealed reduced abundance of the sarcomeric troponin complex proteins, altered abundance of components of the translational machinery, and increased abundance of components of atrophy-associated pathways.
CONCLUSIONS: These data show that Klhl41b is required for sarcomere assembly and growth, and its deficiency drives a cascade of structural and molecular changes underlying skeletal muscle hypotrophy and NM pathology. These findings advance our understanding of disease mechanisms and may inform targeted therapeutic strategies to restore sarcomere integrity and muscle function.

Keywords:  Disease Modeling; Duplicated genes; KLHL41; Kelch; Klhl41a; Klhl41b; Nemaline Myopathy; Sarcomere; Zebrafish; thin filaments

DOI:  https://doi.org/10.1186/s13395-026-00453-2
Biochem Biophys Res Commun. 2026 Oct 09. pii: S0006-291X(26)01490-7. [Epub ahead of print]839 154724

Delphinidin induces the upregulation of miR-23a-3p expression in skeletal muscle and miR-23a-3p release from intestinal cells.

Yuki Marugame, Motoki Murata, Riku Migihashi, Megumi Goto, Mai Morozumi, Motofumi Kumazoe, Yoshinori Fujimura, Hirofumi Tachibana.

  Delphinidin, one of the major anthocyanidins, inhibits disuse muscle atrophy by increasing the expression of miR-23a-3p in mouse skeletal muscle. However, delphinidin is less stable and poorly absorbed in vivo, so its mechanism of function remains unclear. In this study, we aimed to elucidate the mechanism by which delphinidin increases miR-23a-3p expression in skeletal muscle. miRNAs can be packaged into extracellular vesicles (EVs) and secreted from cells. We investigated whether delphinidin induces the release of miR-23a-3p encapsulated in EVs from intestinal cells and whether these EVs increase miR-23a-3p expression in skeletal muscle cells. A single dose of delphinidin increased the expression of miR-23a-3p in the small intestine of mice. To examine whether delphinidin affects the secretion of miR-23a-3p in intestinal cells, we used differentiated Caco-2 cells as an in vitro model. Results showed that delphinidin increases the expression of miR-23a-3p in EVs secreted from differentiated Caco-2 cells. In addition, EVs derived from delphinidin-treated Caco-2 cells were taken up by differentiated C2C12 myotubes, resulting in increased intracellular miR-23a-3p expression. Our in vitro results suggest that intestinal cell-derived EVs may contribute to the antimuscle atrophy activity of delphinidin through the delivery of miR-23a-3p to skeletal muscle cells.

Keywords:  Anthocyanidin; Extracellular vesicles; Intestine; Skeletal muscle; microRNA

DOI:  https://doi.org/10.1016/j.bbrc.2026.154724
Front Cell Dev Biol. 2026 ;14 1984134

Muscle satellite cell dysfunction in critical illness: niche biology, regenerative failure, and implications for recovery.

Takafumi Ono, Atsushi Asakura.

  Adult skeletal muscle can regenerate. After muscle injury, muscle stem cells (satellite cells) can generate new muscle fibers. Under normal conditions, satellite cells are mitotically quiescent and located beneath the basal lamina of muscle fibers. In response to regenerative stimuli, satellite cells activate and proliferate as myogenic precursor cells. After several rounds of cell division, these precursor cells differentiate and fuse to form new muscle fibers. A subset of proliferating myogenic precursor cells returns to a quiescent state to replenish the satellite cell pool through self-renewal. Intensive care unit-acquired weakness (ICU-AW) affects many critically ill patients partly due to acute muscle loss. It is a major physical component of post-intensive care syndrome. Current explanations of ICU-AW focus on rapid protein breakdown and impaired energy metabolism during the early catabolic phase, but these mechanisms do not fully explain why some survivors fail to rebuild muscle once the initial catabolic stress has subsided. In this review, we argue that persistent weakness may also reflect defective muscle regeneration, with satellite cell dysfunction and niche abnormalities as plausible contributors. Recent serial-biopsy studies suggest that dysfunction can occur without stem-cell depletion: satellite cell number can be preserved even when differentiation or later proliferative capacity is impaired in culture. We first review the normal satellite cell niche, including the parent fiber, microvasculature and perivascular cells, extracellular matrix, resident immune and interstitial cells, and systemic signals, with separate consideration of the diaphragm. We then examine how critical illness affects these compartments and how cell-intrinsic defects may additionally impair regeneration. We use this evidence to develop three working hypotheses (niche-detached activation, abortive myogenesis, and niche locking) and treat them as testable models rather than recognized mechanisms. Finally, we consider how future studies might measure, target, and test these processes.

Keywords:  Notch pathway; critical illness; intensive care unit–acquired weakness (ICU-AW); muscle satellite cells; myogenesis; post-intensive care syndrome; skeletal muscle regeneration; stem cell niche

DOI:  https://doi.org/10.3389/fcell.2026.1984134
Sports Med. 2026 Oct 13.

Can Resistance Training-Induced Skeletal Muscle Growth Improve Local Muscular Endurance?

Matthew A Chatlaong, William B Hammert, Kealey J Wohlgemuth, Jeremy P Loenneke, Matthew B Jessee.

Skeletal muscle growth occurs in response to training with a wide range of loads, despite traditionally being linked to high-load resistance training and maximal strength development. A body of literature suggests that with lower loads, training near fatigue/task failure is an important stimulus for muscle growth. We consider that training-induced adaptations often improve performance in the specific activity that stimulated them (e.g., increased cardiac output and endurance exercise). Accordingly, we explore skeletal muscle growth as a compensatory adaptation to intense fatiguing exercise, possibly serving a functional role in maintaining/prolonging force generation during disruptive fatigue-related processes. Our aims were to: (1) contextualize a possible relationship between training-induced skeletal muscle growth and fatigue resistance given the common framing of muscle growth driving greater strength, (2) examine previous resistance training studies assessing both muscle growth and endurance to evaluate whether their changes coincide with one another, and (3) consider speculatively the physiological condition(s) in which training-induced muscle growth could contribute to local muscular endurance. We highlight that absolute muscular endurance and muscle growth frequently improve together, discuss potential mechanisms (e.g., increased myofilament content, enhanced oxygen delivery, and metabolic adaptations), and consider the critical power/force framework to identify loading conditions where training-induced growth may have beneficial effects. Although muscle growth and absolute muscular endurance adaptations often co-occur, no causal relationship can currently be established between them. For example, neural and metabolic changes inherent to resistance training may be driving increased endurance. Future research clarifying this relationship could refine resistance training approaches and broaden our understanding of skeletal muscle growth's functional role.

DOI: https://doi.org/10.1007/s40279-026-02539-9
ACS Pharmacol Transl Sci. 2026 Oct 09. 9(10): 2772-2782

Cannabigerol Enhances Muscle Strength and Performance in Dexamethasone-Treated Mice.

Izabel Feltrin Fabro, Tatyana Nery, Ana Paula Pinto de Araújo, Amanda Leite Bastos Pereira, Francielly Andressa Felipetti, Aderbal Silva Aguiar.

  Sarcopenia is a major clinical condition associated with aging and is characterized by progressive loss of skeletal muscle mass and function. Resistance training is an effective intervention to counteract muscle atrophy; however, strategies that selectively enhance functional performance remain limited. Cannabigerol, a phytocannabinoid that is not a CB1 receptor agonist and therefore lacks psychotomimetic activity, has emerged as a potential modulator of neuromuscular function, although its role in skeletal muscle adaptation remains poorly understood. Here, we investigated the effects of resistance exercise and cannabigerol, alone and in combination, in a dexamethasone-induced model of muscle atrophy in mice. Animals received dexamethasone (20 mg/kg, i.p.) for 12 days and were subsequently subjected to a 4-week ladder-based resistance exercise protocol. Cannabigerol (10 mg/kg, i.p.) was administered on training days. Resistance exercise restored muscle morphology and improved fatigue resistance. In contrast, cannabigerol acted mainly on neuromuscular performance, increasing muscle power while producing only a small increase in fiber cross-sectional area. Cannabigerol potentiated training-induced power output, increasing performance by ∼55% in the first week and up to ∼87% after 4 weeks compared to exercise alone. In addition, cannabigerol increased peak grip strength (∼10%) and lowered post-exercise blood lactate in sedentary animals (∼48%). These findings show that resistance exercise and cannabigerol exert complementary effects on skeletal muscleexercise promoting structural recovery and cannabigerol enhancing neuromuscular performance and lowering post-exercise lactateand support further investigation of cannabigerol as an adjunct to exercise in glucocorticoid-induced muscle atrophy.

Keywords:  cannabinoids; energy metabolism; glucocorticoids; muscle fatigue; resistance exercise; skeletal muscle

DOI:  https://doi.org/10.1021/acsptsci.6c00187
Aging (Albany NY). 2026 Oct 14. 18(1): 1426-1447

Ferroptosis-related hub genes and immune infiltration characteristics in Duchenne muscular dystrophy: a molecular framework with implications for aging-related muscle degeneration.

Juanjuan Peng, Jing Hu, Mianhua Wu, Houxi Xu.

  Sarcopenia, the age-related loss of skeletal muscle mass and function, is a major driver of frailty in older adults, yet its molecular basis remains incompletely defined. Ferroptosis, an iron-dependent regulated cell death, has emerged as a link between iron dysregulation and muscle wasting in aging. However, ferroptosis-related signatures and their interplay with immune remodeling in degenerating muscle remain uncharacterized. DMD shares selected molecular and pathological features with aging-related muscle degeneration, including iron overload, oxidative stress, and impaired regenerative capacity, and may provide a disease-accelerated context for exploring ferroptosis-associated muscle pathology. We integrated two DMD transcriptomic datasets from GEO to identify 35 ferroptosis-related differentially expressed genes. Protein-protein interaction analysis identified three hub genes (HIF1A, CDKN1A, and CD44), which are related to hypoxic responses, cellular senescence, and iron-associated cellular processes, respectively. ROC analysis showed high internal discriminatory performance within the integrated dataset. CIBERSORT-based analysis suggested altered immune cell composition, including increased estimated proportions of γδ T cells and M2 macrophages and decreased regulatory T cells. Correlations between hub gene expression and estimated immune cell populations suggested a potential association between ferroptosis-related transcriptional changes and immune remodeling. Reverse transcription-quantitative PCR (RT-qPCR) validated the upregulation of HIF1A, CDKN1A, and CD44 mRNA, whereas western blotting (WB) confirmed significantly increased protein levels of HIF-1α and CD44 in mdx mice. These findings suggest a ferroptosis-related and immune-associated transcriptional and expression-level signature in dystrophic muscle that may be relevant to aging-related muscle degeneration and warrants further validation using direct ferroptosis assays, aged muscle models, and clinical sarcopenia cohorts.

Keywords:  aging; ferroptosis; inflammaging; muscle degeneration; sarcopenia

DOI:  https://doi.org/10.18632/aging.206429
Biochim Biophys Acta Mol Cell Res. 2026 Oct 15. pii: S0167-4889(26)00136-9. [Epub ahead of print] 120237

Carnosine drives mitochondrial biogenesis and skeletal muscle regeneration via Sirt1-mediated nuclear translocation of PGC-1α.

Yanyan Liang, Chenjin Song, Lei Xing, Yuxin Chen, Huaixin Teng, Bo Tian, Shuang Li, Xin Jin, Huili Tong.

  Post-injury skeletal muscle regeneration depends on the proliferation and differentiation of satellite cells, and mitochondrial function acts as an essential prerequisite for this biological process. This study shows carnosine promotes mouse C2C12 myoblast proliferation, up-regulates mitochondrial genes, and activates oxidative phosphorylation and ATP synthesis. In mechanism, it promotes PGC-1α nuclear translocation, TFAM expression, mitochondrial biogenesis and ATP production. The pharmacological inhibition of Sirt1 by EX-527 eliminated the nuclear accumulation of Sirt1 and PGC-1α induced by carnosine, which confirmed that Sirt1 is an important mediator. Animal experiments confirmed that oral carnosine could accelerate the repair of injury, increase regenerated muscle fibers on the 7th day, and up regulate Pax7, myogenic differentiation 1 (MyoD) and myogenin (MyoG). Molecular docking showed that carnosine could bind to Sirt1 protein. This study clarified that carnosine can drive mitochondrial biogenesis by targeting Sirt1/PGC-1α/TFAM signaling axis, thus promoting myogenesis and muscle repair, providing a theoretical basis for the clinical application of carnosine.

Keywords:  Carnosine; Cell proliferation; PGC-1α; Sirt1; Skeletal muscle injury and regeneration

DOI:  https://doi.org/10.1016/j.bbamcr.2026.120237
Methods Mol Biol. 2026 ;3057 55-67

Bulk Differentiation of Human Induced Pluripotent Stem Cells into Contractile Skeletal Muscles.

Yu-Shen Cheng, Farah Ulfat Jamee, Muhammad Irfanur Rashid, Hidetoshi Sakurai, Kazunori Shimizu, Yohei Okada.

  Effective treatments for various muscular disorders and a clear understanding of their disease pathology remain lacking owing to the limitations of traditional animal models and two-dimensional (2D) cell cultures. Human induced pluripotent stem cells (hiPSCs) offer promising platforms for disease modeling and regenerative medicine. However, existing protocols for skeletal muscle differentiation are often labor-intensive and yield inconsistent results. Here, we utilized a piggyBac transposon-based system to generate bulk MYOD1-hiPSCs, eliminating the need for clonal selection and enabling rapid, efficient, and reproducible skeletal muscle differentiation. Furthermore, we established a protocol for generating functional three-dimensional (3D) skeletal muscle tissues that exert contractile force in response to electrical stimulation, highlighting their physiological relevance. This system provides a simple and valuable tool for disease modeling, drug screening, and the study of sporadic muscle disorders using patient-derived hiPSCs.

Keywords:  3D culture; Bulk culture; Contraction; Disease modeling; MYOD1-hiPSC; Skeletal muscle differentiation

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_5
Biochem Biophys Res Commun. 2026 Oct 08. pii: S0006-291X(26)01479-8. [Epub ahead of print]839 154713

SLIT and NTRK-like family member 1 regulates muscle regeneration.

Moyuri Inoue, Tomohiko Shirakawa, Takumi Ito, Jun J Miyamoto, Kayoko N Kuroishi, Kaori K Gunjigake, Takuma Matsubara, Tsuyoshi Sato, Anna Yoshimura, Minoru Hatayama, Jun Aruga, Yusuke Ono, William N Addison, Tatsuo Kawamoto, Shoichiro Kokabu.

  Muscle satellite cells play a major role in skeletal muscle regeneration following skeletal muscle injury. However, our understanding of the molecular mechanisms that coordinate the proliferation and myogenic differentiation of muscle satellite cells remains incomplete. SLIT and NTRK-like family member 1 (SLITRK1) is a transmembrane protein. We previously reported that Slitrk1 is involved in osteoblast differentiation. In contrast, the function of Slitrk1 in muscle, a closely related mesenchymal lineage, remains largely unknown. In this study, we demonstrated that muscle regeneration in Slitrk1-null mice is impaired following injury whereas Slitrk1-null mice exhibit no significant differences compared to wild-type mice in intact muscles. Furthermore, we revealed that deletion of Slitrk1 led to reduced cell proliferation and premature myogenic differentiation of muscle satellite cells ex vivo. Additionally, Slitrk1 deletion resulted in increased expression of RhoA, a small GTPase protein known to inhibit muscle fiber fusion. These findings suggest that Slitrk1 may play an important role in the proliferation and myogenic differentiation of muscle satellite cells.

Keywords:  Muscle proliferation; Muscle regeneration; Myoblast; Satellite cell; Slitrk1; muscle differentiation

DOI:  https://doi.org/10.1016/j.bbrc.2026.154713
Physiol Rep. 2026 Oct;14(19): e71141

Aging concomitantly reduces skeletal muscle proteome plasticity and hypertrophic responses to resistance training in male adults.

Dustyn T Lewis, J Max Michel, Mason C McIntosh, Dakota R Tiede, Daniel L Plotkin, Madison L Mattingly, Nicholas J Kontos, George Kontos, Breanna J Mueller, Samuel C Norton, Joshua S Godwin, Brad J Schoenfeld, Melissa D Boersma, Andrew D Frugé, C Brooks Mobley, Andreas N Kavazis, Michael D Roberts.

  Resistance training (RT)-induced hypertrophy is attenuated with aging, albeit the proteomic basis of this attenuation remains unclear. We thus determined whether reduced skeletal muscle proteome plasticity accompanies age-related blunted hypertrophic responses. Seventeen younger (21.9 ± 2.5 years) and 15 older (57.5 ± 6.9 years) untrained males completed 10-12 weeks of RT, and the vastus lateralis (VL) soluble proteome was profiled pre- and post-training using data-independent acquisition mass spectrometry (2106 proteins). Despite similar training volume (p = 0.771), younger adults gained more lean body mass (+2.73 vs. +1.18 kg, p = 0.009) and VL thickness (+0.49 vs. +0.20 cm, p = 0.002) than older adults. Proteome plasticity paralleled this divergence, as RT altered 135 proteins (FDR < 0.05) in younger adults and none in older adults. This attenuation was one of magnitude rather than direction, as 81.5% of the 135 younger-adult proteins shifted concordantly in older adults (ρ = 0.711), and 75 gene sets were enriched with RT in older adults, led by translational machinery (NES up to +2.85). At baseline, 278 proteins differed between age groups (FDR <0.05), and age dominated the co-expression network (Turquoise module AUC = 0.96). In conclusion, the blunted hypertrophic response of older males coincides with a loss of RT-induced proteome plasticity, reflecting a compressed rather than qualitatively altered RT adaptation.

Keywords:  aging; hypertrophy; proteomics; resistance training; skeletal muscle

DOI:  https://doi.org/10.14814/phy2.71141
Aging Cell. 2026 Oct;25(10): e70761

A Hypertrophic Stimulus Drives Age-Dependent Transcript Isoform Switching With and Without Differential Gene Expression in Skeletal Muscle.

Pieter J Koopmans, Abbey L Stokes, Christopher E Nelson, Yuan Wen, Ahmed Ismaeel, Kevin A Murach.

Aged skeletal muscle has a reduced ability to adapt to hypertrophic stimuli concomitant with dysregulation across several molecular layers. Whether altered RNA splicing associates with impaired adaptive potential is not well studied. We hypothesized that aging disrupts the splicing response to involuntary muscle mechanical loading. Using deep short-read Illumina RNA-sequencing (SRS, 60 million read pairs) and third generation Oxford Nanopore long-read RNA-sequencing (LRS) combined with a murine model of acute muscle mechanical overload (MOV), we illustrate how aged muscle has a reduced or possibly delayed potential for isoform switching in response to stress. SRS identified hundreds of genes with isoform switching events in adult MOV relative to sham but only 37 in aged MOV. LRS identified 19 genes (including Cacnb1, Naca, Psap) with true isoform switching in adult MOV and none in aged MOV. A subset of genes showed significant isoform switching without corresponding changes in overall gene expression, suggesting post-transcriptional regulation in response to MOV. These data highlight the importance of analyzing the transcriptome at the isoform level to uncover transcript diversity and "unseen genes" that may have unique functions and mechanisms influencing hypertrophic adaptations.

DOI: https://doi.org/10.1111/acel.70761
Pflugers Arch. 2026 Oct 12. pii: 90. [Epub ahead of print]478(11):

Differential alternative splicing in skeletal muscle after 14 days immobilization-induced atrophy in young men.

Aliah Y Aziz, Jamie-Lee M Thompson, Thomas M Doering, Paul J Dunn, Vernon G Coffey.

  Skeletal muscle disuse during injury decreases muscle mass and function. Previous studies have determined differential gene expression associated with atrophy, but changes in alternative splicing (AS) in response to unloading is poorly defined. This study aimed to identify global changes in differential alternative splicing (DAS) in skeletal muscle following unloading. Twenty-one healthy males (26.0 ± 5.7 years; 81.2 ± 11.6 kg) underwent 14 days unilateral knee-brace immobilization. Participants underwent strength and muscle mass assessment before and after the immobilization and vastus lateralis muscle biopsies were taken pre-immobilization, and on days 3 and 14. RNA-sequencing was performed, and DAS events were identified using the rMATS package. Leg strength decreased - 21.5 kg (P < 0.0001) while mid-thigh circumference was reduced ~ 2% (P = 0.016). A total of 157,464 and 159,395 splicing events affecting 15,219 and 15,374 genes identified on day 3 and 14, respectively. Most DAS events occurred in coding sequence regions and were primarily due to exon skipping. A higher number of DAS events were observed by day 14 than day 3, indicating time-dependent regulation. Gene Ontology analysis of DAS at day 14 revealed 37 enriched GO biological processes related to MAPK signalling, mitochondrial function, and organelle organization. Unloading-induced atrophy was associated with widespread changes in AS, particularly in genes linked to muscle maintenance and protein synthesis. AS appears to promote down-regulation of target genes and subsequent differentially enriched biological pathways associated with the functional outcomes of decreased muscle mass and strength. These findings indicate changes in alternative splicing is a regulatory mechanism in muscle wasting during immobilization.

Keywords:  Catabolic; Disuse; Genes; Muscle wasting; Unloading

DOI:  https://doi.org/10.1007/s00424-026-03221-9
bioRxiv. 2026 Oct 01. pii: 2026.09.25.754162. [Epub ahead of print]

Integrative Multi-Omics Analysis Reveals Molecular Signatures of Age-Related Decline in Vervet Leg Skeletal Muscle.

Maitree Patel, Eleanor V Rudasi, Brett Frye, Jacob D Negrey, Laura A Cox, Ge Li, Matthew Jorgensen, Thomas C Register, Kylie Kavanagh, Carol A Shively, Ellen E Quillen.

Age-related decline in skeletal muscle function, often manifesting as slower gait speed, contributes significantly to frailty and loss of independence. To uncover the molecular basis of this decline, we investigated coordinated changes across the transcriptome, miRNome, and methylome in vastus lateralis muscle from female vervet monkeys ( Chlorocebus aethiops sabaeus ), contrasting middle-aged animals with normal gait speed versus older animals with declining gait speed. Through multi-omics integration, we identified a molecular signature that sharply distinguishes these two groups. This signature involves key regulatory molecules, including miR-181a-5p, miR-320b and miR-425 control of SYNCRIP , miR-193b-3p regulation of MCL1 and PLAU , as well as a multi-omic regulatory network governing ZNF274 and ANP32E gene expression, and altered levels of mRNAs such as VEZT . Functional annotation implicates miRNA signatures with inverse expression of their mRNA targets operating within systems of skeletal muscle biology, metabolism, and potential immune-inflammation mechanisms. Collectively, these findings reveal an interconnected network of epigenetic, post-transcriptional, and transcriptional alterations associated with impaired muscle function during aging. This molecular signature provides novel insights into potential mechanisms driving sarcopenia and highlights specific molecules as potential targets for interventions aimed at preserving muscle health.

DOI: https://doi.org/10.64898/2026.09.25.754162
J Cell Biol. 2026 Nov 02. pii: e202606056. [Epub ahead of print]225(11):

FAPs orchestrate ANTXR2-mediated fine-tuning of collagen VI to ensure skeletal muscle function.

Samuele Metti, Lucie Bracq, Matteo Signor, Nicola Facchinello, Lisa Gambarotto, Leonardo Nogara, Giulia Pigato, Laurence Abrami, Béatrice Kunz, Julien Duc, Patrizia Sabatelli, Aurora De Acutis, Gabriele Maria Fortunato, Giovanni Vozzi, Paola Braghetta, Bert Blaauw, F Gisou van der Goot, Paolo Bonaldo.

Tissue function relies on the ECM, which surrounds cells and provides structural and biochemical support. Maintaining ECM homeostasis requires a tightly regulated balance between deposition and degradation of its components, and disruption of this equilibrium can lead to disease. Here, we examined the role of anthrax toxin receptor 2 (ANTXR2/CMG2), an ECM turnover receptor whose loss-of-function mutations cause hyaline fibromatosis syndrome (HFS), a multisystem connective tissue disorder. We show that ANTXR2 is expressed predominantly by fibro-adipogenic progenitors (FAPs) and mediates internalization of the major ECM component collagen VI (COL6). ANTXR2-null (Antxr2-/-) mice exhibit premature COL6 accumulation within intramuscular connective tissue, leading to tissue stiffening and progressive, maladaptive muscle hypertrophy with impaired locomotion and myopathic features. Using Antxr2-/-::Col6a1-/- double-knockout mice, we demonstrate that these phenotypes are COL6-dependent, highlighting the essential role of ANTXR2-mediated COL6 remodeling in preserving ECM homeostasis and skeletal muscle function and establishing a mechanistic basis for muscle pathology in HFS.

DOI: https://doi.org/10.1083/jcb.202606056
Methods Mol Biol. 2026 ;3057 171-187

Measuring Skeletal Muscle Mitochondrial Architecture in 3D Using Focused Ion Beam Scanning Electron Microscopy (FIB-SEM).

Hailey A Parry, Brian Glancy.

  Recent advances in volume electron microscopy have permitted unprecedented visualizations and in-depth quantitative analyses of mitochondrial network structure in skeletal muscle. Nanoscale, 3D analyses of skeletal muscle mitochondria have provided novel insights into how mitochondria interact among themselves and with other skeletal muscle cell organelles, such as the sarcoplasmic reticulum and the sarcomere. The identification of mitochondria within volume electron microscopy datasets and the downstream analyses of segmented structures remain two major bottlenecks in the analysis of 3D mitochondrial network structure at the nanoscale. Here, we provide a step-by-step guide on how to use machine learning programs to segment skeletal muscle mitochondria from volume electron microscopy datasets, followed by instructions on several types of 3D analyses of individual mitochondria and mitochondrial network structure that can be performed using ImageJ. We highlight key quality-control steps to ensure precise and accurate segmentation and analyses and to enhance reproducibility across groups.

Keywords:  Focus Ion Beam Scanning Electron Microscopy; Mitochondria; Skeletal muscle; Volume electron microscopy

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_14
FASEB J. 2026 Oct 31. 40(20): e72211

Ets2 Is an Activity-Dependent Transcriptional Regulator of a Fast-Twitch Muscle Program.

Zaheer A Rana, Jo C Bruusgaard, Jens R Wendland, Ivan Winje, Ingrid M Egner, Irina Karavanova, Einar Eftestøl, Detlef Vullhorst, Kristian Gundersen, Andres Buonanno.

  The functional properties of excitable cells, including skeletal muscle, are regulated by electrical activity. Distinct motoneuron firing patterns control contraction speed, strength, and endurance of fast- and slow-twitch myofibers by activating transcriptional programs that specify contractile and metabolic protein isoforms. Although transcriptional regulators of slow muscle adaptation are well characterized, less is known about activity-dependent mechanisms controlling expression of fast muscle genes. We previously showed that the quail fast troponin I (TnIf) intronic regulatory element (FIRE) is both necessary and sufficient for fast-muscle-specific transcription and responds selectively to brief, high-frequency (150 Hz) stimulation rather than to sustained low-frequency (20 Hz) activity. In this study, using mRNA microarray analysis of muscles subjected to different stimulation patterns, we identified E26 transformation-specific homolog 2 (Ets2) as a transcription factor rapidly and selectively induced by fast-patterned activity. Ets2 accumulates in nuclei of slow soleus muscle following fast, but not slow, stimulation, and it is expressed more abundantly in fast muscle. Ets2 binds a consensus Ets site within the TnIf FIRE, and mutation of this site abolishes enhancer activation by fast-patterned activity. Furthermore, Ets2 knockdown reduces transcription from both a trimerized Ets2-responsive reporter and a TnIf FIRE reporter specifically in fast muscles. To our knowledge, these findings identify Ets2 as the first transcription factor shown to selectively promote fast muscle gene expression in response to fast-patterned activity. Together with NFATc1, Ets2 may contribute to a dynamic regulatory mechanism that enables skeletal muscles to adapt their functional properties to changing physiological demands.

Keywords:  adaptation; metabolic syndrome; plasticity

DOI:  https://doi.org/10.1096/fj.202602267R
Methods Mol Biol. 2026 ;3057 201-223

Quantification of Mitochondrial Oxidative Phosphorylation in Skeletal Muscle.

Aditya N Brahmbhatt, Christopher G R Perry.

  Mitochondrial oxygen consumption stimulated by ADP and inorganic phosphate is often measured as an index of ATP synthesis derived from oxidative phosphorylation. This measurement is typically performed by monitoring the rate at which oxygen disappears from a solution containing isolated mitochondria or either intact or permeabilized cells and tissue. Termed "respirometry," this method has become increasingly popular in numerous research disciplines focused on cellular metabolism, including the broader field of skeletal muscle physiology. Here, we describe how respirometry is performed in permeabilized skeletal muscle fiber bundles. This technique involves mechanically separating skeletal muscle fibers followed by exposure to a cell membrane-permeabilizing agent (e.g., saponin). This technique is thought to preserve the mitochondrial network, morphology, and interactions with surrounding intracellular structures. The method can be performed on small tissue samples and permits flexibility in designing substrate titration protocols to target specific mitochondrial pathways.

Keywords:  Mitochondria; Permeabilized fibers bundles; Polarographic oxygen sensor; Respirometry; Skeletal muscle

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_16
Apoptosis. 2026 Oct 15. pii: 250. [Epub ahead of print]31(11):

GNMT alleviates heart failure-induced skeletal muscle atrophy by regulating ATP5J2-mediated mitochondrial metabolic reprogramming through succinylation.

Ying Zhao, Ying He, Rui Song, Jimin Chen, Mingxuan Yang, Jinting Liu, Yuan Song, Ying Zhang, Liqing Yao.

  Heart failure (HF) is defined as a condition characterized by abnormalities in the heart's structure or function, which lead to the heart's inability to deliver oxygen to tissues in a timely manner, and it may progress to symptoms such as muscle atrophy of skeletal muscles. Our research primarily focuses on Glycine N-methyltransferase (GNMT), an enzyme that utilizes S-adenosylmethionine (SAM) to catalyze glycine, in order to explore its specific role in HF-induced skeletal muscle atrophy. In this study, an HF rat model induced by abdominal aortic constriction (AAC) and a C2C12 muscle atrophy cell model induced by angiotensin Ⅱ (Ang Ⅱ) were established. Echocardiography, ELISA, and HE staining were used to evaluate the damage of myocardial and gastrocnemius tissues. Immunofluorescence staining was used to assess skeletal muscle atrophy. Western blot, IP, and Co-IP were used to determine the molecular mechanism. In HF rats, the expressions of GNMT and Mitochondrial Fo complex subunit F2 (ATP5J2) were significantly decreased. Overexpression of GNMT/ATP5J2 contributed to alleviate HF-induced skeletal muscle atrophy. GNMT elevated the succinylation level and protein stability of ATP5J2 at lysine 22 (K22) by consuming glycine, and simultaneously reduced its ubiquitination level. Succinylated ATP5J2 improved mitochondrial homeostasis to mitigate HF-induced skeletal muscle atrophy. This study elucidated the function of the GNMT-ATP5J2 axis in HF-induced skeletal muscle atrophy and clarified the underlying molecular mechanism, providing a new theoretical basis for the treatment of HF-induced skeletal muscle atrophy.

Keywords:  ATP5J2; GNMT; Heart failure; Skeletal muscle atrophy; Succinylation

DOI:  https://doi.org/10.1007/s10495-026-02404-0
Cell Metab. 2026 Oct 14. pii: S1550-4131(26)00391-8. [Epub ahead of print]

An NAD+-responsive adipose signal coordinates inter-organ defense against muscle atrophy.

Na Liang, Jia He, Xiangji Guo, Jiaqi Yan, Xiaoqian Zhang, Xiaozhong Peng, Jun Li.

  Loss of skeletal muscle mass is a major driver of frailty and disability, yet how systemic metabolic cues protect muscle integrity remains unclear. We identify Serpina3n, an adipose-derived adipokine, as a key mediator of the protective effects of nicotinamide adenine dinucleotide (NAD+) supplementation against muscle atrophy. Elevation of NAD+ in adipose tissue activates signal transducer and activator of transcription (STAT)1-dependent transcription of Serpina3n, leading to its systemic release and muscle protection across models of aging, disuse, and cancer cachexia. In muscle, Serpina3n preserves pyruvate carboxylase protein level, promoting anaplerosis, oxidative metabolism, and protein synthesis. These findings define an NAD+-responsive adipose-to-muscle signaling axis that links metabolic status to tissue preservation, defining a systemic mechanism by which inter-organ communication maintains muscle integrity and suggesting potential strategies to counteract muscle degeneration.

Keywords:  NAD(+); adipokine; aging; inter-organ communication; muscle atrophy

DOI:  https://doi.org/10.1016/j.cmet.2026.09.016
Front Endocrinol (Lausanne). 2026 ;17 1935289

Sarcopenia beyond muscle: endocrine-metabolic regulation and inter-tissue crosstalk across the muscle-tendon unit.

Guang Ta, Li Li, Cai Jing, Xinxu Chen, Seung-Jun Jeong, Dongryeol Ryu, Shibo Wei.

  Sarcopenia is characterized by a progressive loss of muscle strength and physical performance that frequently exceeds the decline predicted by muscle mass alone. This discrepancy indicates that functional deterioration is shaped not only by the force-generating capacity of skeletal muscle, but also by the tissues responsible for transmitting and integrating that force. In this Review, we examine sarcopenia through the biology of the muscle-tendon unit, encompassing skeletal muscle, tendon, and their specialized interface. We discuss how systemic aging processes, including metabolic dysfunction, inflammaging, and vascular insufficiency, produce tissue-specific and potentially asynchronous effects on muscle contractile capacity, tendon matrix remodeling, and myotendinous junction (MTJ) integrity. Much of the evidence for tendon and MTJ remodeling derives from physiological aging and experimental models, whereas their characteristic phenotypes in clinically defined sarcopenia remain insufficiently characterized. Since muscle, the MTJ, and tendon form a serial force-transmission pathway, differential remodeling across these components may create a mismatch between force-generating and force-transmitting capacities. We further evaluate the strength of evidence for inter-tissue communication, distinguishing experimentally supported muscle-to-tendon regulation from emerging tendon-to-muscle effects demonstrated primarily in co-culture, conditioned-medium, and engineered-interface systems. Particular emphasis is placed on the myotendinous junction as a structurally specialized interface where mechanical forces, extracellular matrix organization, and local signaling converge. Age-related disruption of this interface may reduce force-transfer efficiency and magnify the functional consequences of muscle weakness. Finally, we consider how the muscle-tendon unit framework may refine exercise prescription, functional phenotyping, and the evaluation of future tissue-specific interventions while remaining complementary to established diagnostic criteria and current exercise-based management. Together, these observations identify impaired coordination across the muscle-tendon unit as a potentially important contributor to loss of strength and physical performance in sarcopenia.

Keywords:  extracellular matrix remodeling; muscle aging; muscle-tendon crosstalk; myotendinous junction; sarcopenia; tendon aging

DOI:  https://doi.org/10.3389/fendo.2026.1935289
Aging Dis. 2026 09 28.

Lysosomal Competence in Skeletal Muscle Aging: Autophagic Flux, Measurement Gaps, and Human Translation.

Oyungerel Dogsom, Jae Gyu Kim, Yeon-Hee Lee, Holger Jahr, Sang-Soo Lee.

Age-related deterioration of skeletal muscle contributes to loss of mobility, frailty, and disability. Altered autophagy-lysosome competence has been proposed as a mechanism linking impaired proteostasis, mitochondrial damage, inflammation, and regenerative failure to sarcopenia. Chronological muscle aging and clinically defined sarcopenia overlap, but evidence from healthy aging, frailty, disuse, cachexia, obesity, or chronic disease cannot be treated as interchangeable. This narrative review examines how lysosomal acidification, degradative capacity, biogenesis, and turnover influences autophagic flux in aging muscle and evaluates the strength of evidence across experimental models and human studies. Genetic and pharmacological studies show that severe disruption of autophagy or specific lysosomal functions can cause myofiber damage, mitochondrial impairment, defective regeneration, and weakness. However, direct evidence that lysosomal acidification, fusion, hydrolase activity, membrane integrity, recycling, cargo degradation, or completed autophagic flux is impaired in aging human muscle remains limited. Much of the human literature relies on static abundance of LC3-II, SQSTM1/p62, lysosomal proteins, or transcriptional signatures, which cannot distinguish increased autophagosome formation from impaired degradation. We therefore separate causal experimental evidence from human associations and focus on V-ATPase, TMEM175, LAMP proteins, TFEB/TFE3, lysophagy, and crosstalk with mitophagy and the ubiquitin-proteasome system. Exercise improves clinically relevant outcomes in older adults, but mediation through completed autophagic flux has not been established. Recent trials of metformin and once-weekly sirolimus did not improve prespecified functional outcomes in the tested populations and regimens, whereas urolithin A produced endpoint-specific signals while missing key primary outcomes.

DOI: https://doi.org/10.14336/AD.2026.1047
Methods Mol Biol. 2026 ;3057 159-169

Flow Cytometric Methods for ROS Quantification in Skeletal Muscle Myotubes.

Andy Nolan, Paige Cole, Darren W Sexton.

  Flow cytometry is a high-throughput technique which can be used to analyze and quantify characteristics of individual cells. Flow cytometry hydrodynamically focuses cells past a series of size and fluorescent detectors to characterise cellular morphology and phenotype. This process of hydrodynamic focusing has previously been shown to be incompatible with myotubes due to their larger size relative to other cell types. Here, we describe the culture and differentiation of myotubes and how myotubes can be analyzed via flow cytometry to quantify changes in cellular and mitochondrial-specific ROS production.

Keywords:  C2C12 myotubes; Flow cytometry; Mitochondria; Reactive oxygen species; Skeletal muscle

DOI:  https://doi.org/10.1007/978-1-0716-5396-8_13
Nat Metab. 2026 Oct 12.

Systemic proteomic dynamics of acute exercise reveal genetic links to health and disease.

Nigel Kurgan, Jeppe Kjærgaard, Naja Zenius Jespersen, Virginia Díez-Obrero, Victor Svenstrup, Roger Moreno-Justicia, Sarah Elizabeth Heywood, Cecilie Bergmann Lindqvist, Lisa Ottander, Diana Samodova-Sommer, Alina Malita, Olga Kubrak, Nadja Ahrentløv, Nina Sloth Nielsen, Cody Garett Durrer, Michael Texada, Mathias Ried-Larsen, Simon Rasmussen, Kim Rewitz, Ruth J F Loos, Roelof Adriaan Johan Smit, Bente Klarlund Pedersen, Atul Shahaji Deshmukh.

Physical activity improves metabolic health, but the molecular responses that mediate its benefits are not fully characterized. Here we present a high-resolution, time-resolved proteomics atlas across plasma, saliva and urine from 25 healthy men in response to acute exercise. We find that exercise regulates more than 3,000 proteins through distinct, fluid-specific temporal dynamics. Network analysis uncovers coordinated remodelling of protein secretion, extracellular matrix and immune activation across body fluids. Replication in an independent cohort shows that many exercise-responsive plasma proteins exhibit consistent responses across age, sex and exercise modalities. Integration with human genome-wide association study data links secreted, exercise-responsive proteins to cardiometabolic diseases. Functional validation of genetically prioritized muscle-specific secreted proteins in Drosophila confirms their role in endurance, behaviour and metabolism. Overall, this open-access atlas ( https://cbmr.ku.dk/research/research-groups/deshmukh-group/shiny-apps/ ) provides a multifluid resource that complements existing exercise-omics efforts for defining molecular adaptations to exercise and for prioritizing candidate exerkines.

DOI: https://doi.org/10.1038/s42255-026-01621-w
Cell. 2026 Oct 15. pii: S0092-8674(26)01185-2. [Epub ahead of print]

Multi-omics atlas of chronic exercise.

Geraldine Maier, Manoj Hariharan, Ramesh K Ramasamy, Aidan Glina, Laura van Rosmalen, Suraj J Pathak, Shaunak Deota, Sahil Patel, Terry Lin, Michael Tun Yin Lam, Hiep D Le, Krushali Powale, Takashi Shimomura, Yuta Otobe, Vince Rothenberg, Ming Sun, Takeshi Sakurai, Tiffany Chin, Yue Wu, Rosa Castanon, Anna Bartlett, Huaming Chen, Joseph R Nery, Cesar Barragan, Swetha Devulapalli, Hemal H Patel, Alan Saghatelian, Hikari Yoshitane, Debashis Sahoo, Susan M Keach, Joseph R Ecker, Satchidananda Panda.

  Exercise reduces all-cause mortality, yet its molecular effects across organs, sexes, and circadian phases remain incompletely understood. We subjected mice to 8 weeks of voluntary wheel running and collected 22 tissues and plasma during active and inactive phases for bulk RNA sequencing, metabolomics, proteomics, and single-nucleus RNA and methylation sequencing. Exercise induced canonical fiber-type switching and widespread, tissue-specific remodeling, with the largest transcriptomic changes in skeletal muscle. Except for the hypothalamus, kidney, and lung, most tissues changed more during the active phase. Females showed broader transcriptional responses, with distinct downregulation. Pairing single-nucleus methylomes with transcriptomes resolved the cell types driving exercise-induced epigenetic remodeling-changes undetectable by bulk studies. These included coordinated gene-body demethylation and transcription that tracked with fiber-type switching in specific myonuclei. Cell-type-resolved methylation, including partially methylated domains characterized in muscle, revealed a strong, sex-biased epigenetic response to training. Machine learning identified conserved exercise signatures across mammalian species.

Keywords:  metabolomics; multi-omics; muscle; proteomics; sex difference; single-nucleus DNA methylation; single-nucleus RNA seqencing; tendon; transcriptomics; voluntary exercise

DOI:  https://doi.org/10.1016/j.cell.2026.09.044