bims-moremu 2025-11-09 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2025–11–09
thirty-six papers selected by
Anna Vainshtein, Craft Science Inc.

Myoblast paracrine factors induce catabolic remodelling in electrically stimulated myotubes.
Molecular Motors Activate Skeletal Muscle.
The mitochondrial-targeted antioxidant SkQ1 prevents skeletal muscle mitochondrial-apoptotic but not necroptotic signalling during ovarian cancer.
Embedding muscle fibers in hydrogel improves viability and preserves contractile function during prolonged ex vivo culture.
Sestrin2 is Induced Upon Cellular Stress but Has No Effect on Myotube Size or Amino Acid Sensing in C2C12 Myotubes.
Transcriptional landscape of skeletal muscle in cancer patients.
Targeting ER stress in skeletal muscle through physical activity: a strategy for combating neurodegeneration-associated muscle decline.
Myosin inhibition partially rescues the myofibre proteome in X-linked myotubular myopathy.
Belt-type electrical muscle stimulation preserves muscle fiber size but does not improve muscle function in a rat model of cancer cachexia.
Myostatin deficiency blunts mechanical adaptation of soleus muscle to overload.
Endocrine, Metabolic, and Skeletal Muscle Proteomic Responses During Energy Deficit With Concomitant Aerobic Exercise in Humans.
Across the space: applications of spatial transcriptomic technology in healthy and diseased muscle.
Clenbuterol, but not Inhaled Formoterol, Upregulates the Sarcomere Stabilizer KLHL41 to a Similar Extent as Resistance Training in Human Skeletal Muscle.
Sex differences in human skeletal muscle fiber types and the influence of age, physical activity, and muscle group: A systematic review and meta-analysis.
Genetic disruption of satellite cell function underlying congenital myopathies.
Mitochondrial Activation and Therapeutics: Innovations in Cell- and Organelle-Specific Medicine.
Exercise upregulates Mitsugumin 53 and ameliorates behavioral deficits and mitochondrial biogenesis in a sporadic Alzheimer's disease model in rats.
Effects of exercise training on skeletal muscle mitochondrial outcomes in type 2 diabetes: a systematic review and meta-analysis.
Muscle-Restricted Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Knockout Partially Corrects Muscle Contractility After Spinal Cord Injury in Mice.
Adaptable Immunofluorescence Protocol for Muscle Fiber Typing in FFPE Human and Mouse Skeletal Muscle and Intact Mouse Hindlimbs.
Syntaphilin loss enhances mitochondrial axonal transport and neuromuscular junction formation in a human stem cell derived neuromuscular assembloid model.
Oligo fucoidan alleviates sarcopenia via attenuating muscle mass loss and function decline in senescence-accelerated mouse prone 8 mice.
Inter-Organ Crosstalk and Regulatory Mechanisms of Skeletal Muscle-Derived Extracellular Vesicles in Systemic Metabolic Homeostasis.
NAD depletion in skeletal muscle does not compromise muscle function or accelerate aging.
Cytosine base editor-mediated SOCS2 knockout promotes C2C12 cell differentiation via the PI3K/AKT/mTOR signaling pathway.
Zebrafish fast muscle contractions avoid the mammalian requirement for voltage-gated Na+ channels.
Retrospective transcriptomic analysis indicates temporal dysregulation of mitochondrial genes and metabolic pathways after volumetric muscle loss injury.
From Bench to Motion: Unraveling Exercise Biology Through 3D Human Organoids.
Postinactivity Exercise Training Improves Sarcopenia Traits in 40-60-Year-Old Women Regardless of Fortified Milk Supplementation.
Muscle loss and GLP-1R agonists use.
Dietary leucine intake and sarcopenia: from isolated supplementation to combined strategies.
Cistromic insight into the association of retinoid X receptor with MyoD and CTCF in proliferating myoblasts.
Weightlifting outperforms voluntary wheel running for improving adiposity and insulin sensitivity in obese mice.
Association of muscle mass and strength with blood-based epigenetic aging among middle-aged and older adults in the United States.
Inhibition of ATP citrate lyase does not affect muscle mitochondrial activity in apoE-/- mice.
A focus shift from sarcopenia to muscle health in the Asian Working Group for Sarcopenia 2025 Consensus Update.

Sci Rep. 2025 Nov 04. 15(1): 38537

Myoblast paracrine factors induce catabolic remodelling in electrically stimulated myotubes.

Magda A Lesinski, Michael J Kamal, Gianni Parise.

  Skeletal muscle plasticity is strongly influenced by a multitude of cell populations within the muscle niche. Satellite cells, or resident muscle stem cells, play an essential role in skeletal muscle remodelling after injury where they differentiate into myoblasts and directly donate myonuclei to damaged fibres thereby promoting protein synthesis. Satellite cells have also been shown to act in a paracrine fashion to influence the infiltration of immune cells and other cell types into the skeletal muscle environment to advance regeneration. However, in many degenerative muscular conditions, satellite cell activity is impaired. Moreover, their paracrine mediated signalling directly to muscle fibres remains poorly understood, highlighting a promising therapeutic target for addressing satellite cell dysfunction. The purpose of this project was two-fold: (1) develop an in vitro model of myoblast (MBL) intercellular communication following myotube damage and (2) to determine if MBL proximity alone is adequate for improving tissue repair and reducing cellular stress during recovery. C2C12-derived myotubes were exposed to 1 h of electrical pulse stimulation (EPS). Immediately following EPS, porous cell inserts containing either myoblasts (MBL+) or no cells (MBL-) were introduced to the damaged myotubes. We employed quantitative protein, mRNA, and morphological analyses of myotubes to characterize the phenotypic response to myoblast signalling. EPS produced Z line sarcomeric disorganization and creatine kinase release from the myotubes, which was mitigated in the MBL + groups (p < 0.05). A significant main effect of MBL exposure was observed in molecular indicators of muscle repair and metabolism; MBL + myotubes had greater hspa1a gene expression, calpain 3 protein and gene expression, BNIP3 and t-ULK protein expression as compared to MBL- myotubes when recovering from EPS (p < 0.05). Myotube diameter decreased significantly in MBL + myotubes post-EPS (p < 0.05). Myoblasts participate in intercellular crosstalk directly to damaged myotubes, and this signalling may increase catabolic processes through the upregulation of contraction-mediated protease activity and autophagic protein content. This research is the first to identify an early, non-fusogenic response mechanism of muscle-resident myoblasts to skeletal muscle in response to damaging stimuli.

Keywords:  Catabolism; Electrical-pulse stimulation; Exercise-induced muscle damage; Myoblast signaling

DOI:  https://doi.org/10.1038/s41598-025-21126-y
ACS Appl Bio Mater. 2025 Nov 05.

Molecular Motors Activate Skeletal Muscle.

Yuchen Rui, Dallin Arnold, Jacob L Beckham, Bowen Li, Guillaume Duret, Gautam Chaudhry, Jacob T Robinson, James M Tour.

  Precise remote control of skeletal muscle contraction could be beneficial to the study and treatment of muscular dysfunction. Recently, we reported a method regulating intracellular calcium signaling using molecular motors (MMs), molecules that rotate submolecular components unidirectionally upon absorption of light. Here, we explore the application of this methodology to skeletal muscle tissue. Our results demonstrate that MMs induce intracellular calcium release in C2C12 myoblasts and differentiated myotubes via IP3-mediated signaling in a fashion that depends on their fast unidirectional rotation. Inhibition of proteins involved in the cAMP pathway such as adenylyl cyclase and protein kinase A also reduced the magnitude of the elicited calcium responses. We further show that, in differentiated C2C12 myotubes, the calcium signaling events driven by MM activation cause localized myotube contraction. This work demonstrates the use of a molecular mechanical technique to directly control skeletal muscle contraction, expanding the scope of available tools to study muscle contraction in a single-cell regime and treat a range of myopathies.

Keywords:  C2C12 cells; calcium release; molecular motors; muscle contraction; myopathy

DOI:  https://doi.org/10.1021/acsabm.5c01450
J Physiol. 2025 Nov 02.

The mitochondrial-targeted antioxidant SkQ1 prevents skeletal muscle mitochondrial-apoptotic but not necroptotic signalling during ovarian cancer.

Shahrzad Khajehzadehshoushtar, Luca J Delfinis, Fasih A Rahman, Madison C Garibotti, Shivam Gandhi, Aditya N Brahmbhatt, Brooke A Morris, Bianca Garlisi, Sylvia Lauks, Caroline Aitken, Leslie Ogilvie, Zhu-Xu Zhang, Jeremy A Simpson, Joe Quadrilatero, Jim Petrik, Christopher G R Perry.

  The degree to which mitochondrial-linked programmed cell death pathways contribute to skeletal muscle atrophy during cancer remains unknown. Here we combined a novel and robust mouse model of metastatic ovarian cancer with chronic administration of the mitochondrial-targeted antioxidant SkQ1 to determine the time-dependent and muscle-specific relationships of mitochondrial-linked apoptotic and necroptotic signalling to the development of muscle atrophy in the type IIB-rich gastrocnemius. Early-stage ovarian cancer reduced type IIB fibre cross-sectional area in the gastrocnemius but did not alter mitochondrial H2O2 emission despite increased activities of mitochondrial-linked caspase-9 and -3 regulators of apoptosis. During late-stage ovarian cancer sustained atrophy was associated with increased mitochondrial H2O2 emission potential in vitro, a greater probability of calcium-triggered mitochondrial permeability transition and increases in downstream caspase-9 and -3 activities. SkQ1 attenuated mitochondrial H2O2 emission and caspase-9 and -3 activities in late-stage ovarian cancer but did not prevent atrophy. Necroptosis markers were heterogeneous across time with total RIPK1 increasing during early-stage cancer, which reverted to normal levels by late stages, whereas phosphorylated RIPK3 decreased below control levels. These discoveries indicate that preventing increases in mitochondrial-linked apoptotic caspase-9 and -3 activities during late-stage ovarian cancer with SkQ1 does not prevent atrophy of type II B fibres. Furthermore necroptotic markers are inconclusive during cancer in this muscle type but are not modified by SkQ1. These results do not support a causal relationship between mitochondrial H2O2-linked apoptotic or necroptotic signalling and atrophy in type IIB fibres during ovarian cancer but do not rule out potential relationships in other muscle types. KEY POINTS: Cancer increases mitochondrial reactive oxygen species (ROS) in skeletal muscle during atrophy, but the role of ROS in regulating cell death remains unknown. We show that attenuating gastrocnemius mitochondrial ROS with the mitochondrial-targeted antioxidant SkQ1 prevented mitochondrial-linked pro-apoptotic caspase 9- and -3 activities but did not affect markers of necroptosis in a mouse model of ovarian cancer. Reductions in gastrocnemius muscle fibre cross-sectional areas and the wet weights of several muscles were not prevented by SkQ1. These findings demonstrate that mitochondrial ROS regulate apoptotic caspases but not necroptotic proteins, and neither pathway is linked to gastrocnemius atrophy in mice with ovarian cancer. The degree to which mitochondrial ROS-linked cell death pathways regulate muscle mass in other muscle types and cancer models requires further investigation.

Keywords:  apoptosis; cachexia; mitochondria; necroptosis; ovarian cancer; skeletal muscle

DOI:  https://doi.org/10.1113/JP287912
J Gen Physiol. 2026 Jan 05. pii: e202513761. [Epub ahead of print]158(1):

Embedding muscle fibers in hydrogel improves viability and preserves contractile function during prolonged ex vivo culture.

Leander A Vonk, Osman Esen, Daan Hoomoedt, Rajvi M N Balesar, Coen A C Ottenheijm, Tyler J Kirby.

Ex vivo culture of isolated muscle fibers can serve as an important model for in vitro research on mature skeletal muscle fibers. Nevertheless, this model has limitations for long-term studies due to structural loss and dedifferentiation following prolonged culture periods. This study aimed to investigate how ex vivo culture affects muscle fiber contraction and to improve the culture system to preserve muscle fiber morphology and sarcomere function. Additionally, we sought to determine which culture-induced changes can negatively affect muscle fiber contraction. We cultured isolated flexor digitorum brevis (FDB) muscle fibers in several conditions for up to 7 days and investigated viability, morphology, and the unloaded sarcomere shortening in intact fibers, along with force generation in permeabilized muscle fibers. In addition, we examined changes to the microtubule network. We found a time-dependent decrease in contractility and viability in muscle fibers cultured for 7 days on a laminin-coated culture dish (2D). Conversely, we found that culturing FDB muscle fibers in a low-serum, fibrin/Geltrex hydrogel (3D) reduces markers of muscle fiber dedifferentiation (i.e., sprouting), improves viability, and retains contractility over time. We discovered that the loss of contractility of cultured muscle fibers was not the direct result of reduced sarcomere function but may be related to changes in the microtubule network. Collectively, our findings highlight the importance of providing muscle fibers with a 3D environment during ex vivo culture, particularly when testing pharmacological or genetic interventions to study viability or contractile function.

DOI: https://doi.org/10.1085/jgp.202513761
Biol Cell. 2025 Nov;117(11): e70040

Sestrin2 is Induced Upon Cellular Stress but Has No Effect on Myotube Size or Amino Acid Sensing in C2C12 Myotubes.

Jiani Qian, Stephanie D Gagnon, Vladimir Belhac, Carl J Hulston, Neil R W Martin.

  Sestrins are a stress-inducible family of proteins that function in cell survival and nutrient sensing through their regulation of mTORC1. Muscle wasting is associated with cellular stress, but to date, there is limited in vitro research investigating sestrins in skeletal muscle cells. Here we use C2C12 myotubes to understand how sestrin proteins (sestrin 1-3) are regulated by different forms of cellular stress linked to muscle wasting conditions. Furthermore, since sestrin2 is a well-characterised protein but is lowly expressed in muscle tissue in the absence of stress, we also aimed to determine if silencing this protein impacted parameters of muscle growth or nutrient sensing by mTORC1 under basal conditions. Incubating C2C12 myotubes with the endoplasmic reticulum (ER) stress-inducing agent tunicamycin, or a high concentration (1000 µM) of hydrogen peroxide (H2O2), increased sestrin2 protein levels with no change in sestrins 1 or 3. This increase was temporally associated with increased ER stress markers Ddit3 mRNA and ATF4 protein levels, and could be blocked by approximately half when myotubes were co-incubated with H2O2 and the ER-stress inhibitor 4-Phenylbutyrate. siRNA silencing of sestrin2 blunted the phosphorylation of the mTORC1 effector S6K1, but did not acutely influence protein synthesis or myotube size. Similarly, silencing sestrin2 did not affect mTORC1 signalling in response to nutrient deprivation. These data indicate that sestrin2 is stress-inducible and may play a role in protecting skeletal muscle from ER stress, but is less important in regulating mTORC1 and nutrient sensing in unstressed/basal conditions.

Keywords:  ER stress; mTORC1; myotubes; nutrient sensing; skeletal muscle

DOI:  https://doi.org/10.1111/boc.70040
Trends Mol Med. 2025 Oct 31. pii: S1471-4914(25)00255-2. [Epub ahead of print]

Transcriptional landscape of skeletal muscle in cancer patients.

Samet Agca, Serkan Kir.

  Bhatt et al. have identified two RNAome-based skeletal muscle subtypes in cancer cachexia. The first subtype is cachexia associated with weight and muscle loss, fiber atrophy, and shortened survival. Furthermore, this subtype has dysregulated post-transcriptional networks involving hub long noncoding (lnc)RNAs, neuronal, immune, and metabolic pathways. The study highlights new biomarkers and network-targeted interventions.

Keywords:  RNAome; cancer cachexia; skeletal muscle

DOI:  https://doi.org/10.1016/j.molmed.2025.10.004
Front Mol Neurosci. 2025 ;18 1639114

Targeting ER stress in skeletal muscle through physical activity: a strategy for combating neurodegeneration-associated muscle decline.

Zhanguo Su, Lijuan Xiang.

  The pathophysiology of neurodegenerative diseases is largely driven by ER stress, contributing to cellular dysfunction and inflammation. Chronic ER stress in skeletal muscle is associated with a deterioration in muscle function, particularly in diseases such as ALS, PD, and AD, which are often accompanied by muscle wasting and weakness. ER stress triggers the UPR, a cellular process designed to restore protein homeostasis, but prolonged or unresolved stress can lead to muscle degeneration. Recent studies indicate that exercise may modulate ER stress, thereby improving muscle health through the enhancement of the adaptive UPR, reducing protein misfolding, and promoting cellular repair mechanisms. This review examines the influence of exercise on the modulation of ER stress in muscle cells, with a particular focus on how physical activity influences key pathways contributed to mitochondrial function, protein folding, and quality control. We discuss how exercise-induced adaptations, including the activation of stress-resilience pathways, antioxidant responses, and autophagy, can help mitigate the negative effects of ER stress in muscle cells. Moreover, we examine the potential therapeutic implications of exercise in neurodegenerative diseases, where it may improve muscle function, reduce muscle wasting, and alleviate symptoms associated with ER stress. By integrating findings from neurobiology, muscle physiology, and cellular stress responses, this article highlights the therapeutic potential of exercise as a strategy to modulate ER stress and improve muscle function in neurodegenerative diseases.

Keywords:  ER stress; exercise; muscle function; neurodegenerative diseases; unfolded protein response

DOI:  https://doi.org/10.3389/fnmol.2025.1639114
JCI Insight. 2025 Nov 04. pii: e194868. [Epub ahead of print]

Myosin inhibition partially rescues the myofibre proteome in X-linked myotubular myopathy.

Elise Gerlach Melhedegaard, Fanny Rostedt, Charlotte Gineste, Robert Ae Seaborne, Hannah F Dugdale, Vladimir Belhac, Edmar Zanoteli, Michael W Lawlor, David L Mack, Carina Wallgren-Pettersson, Anthony L Hessel, Heinz Jungbluth, Jocelyn Laporte, Yoshihiko Saito, Ichizo Nishino, Julien Ochala, Jenni Laitila.

  X-linked myotubular myopathy (XLMTM) due to MTM1 mutations is a rare and often lethal congenital myopathy. Its downstream molecular and cellular mechanisms are currently incompletely understood. The most abundant protein in muscle, myosin, has been implicated in the pathophysiology of other congenital myopathies. Hence, in the present study, we aimed to define whether myosin is also dysfunctional in XLMTM and whether it thus may constitute a potential drug target. To this end, we used skeletal muscle tissue from human patients and canine/mouse models; we performed Mant-ATP chase experiments coupled with X-ray diffraction analyses and LC/MS-based proteomics studies. In XLMTM humans, we found that myosin molecules are structurally disordered and preferably adopt their ATP-consuming biochemical state. This phosphorylation-related (mal)adaptation was mirrored by a striking remodelling of the myofibre energetic proteome in XLMTM dogs. In line with these, we confirmed an accrued myosin ATP consumption in mice lacking MTM1. Hence, we treated these, with a myosin ATPase inhibitor, mavacamten. After a four-week treatment period, we observed a partial restoration of the myofibre proteome, especially proteins involved in cytoskeletal, sarcomeric and energetic pathways. Altogether, our study highlights myosin inhibition as a new potential drug mechanism for the complex XLMTM muscle phenotype.

Keywords:  Metabolism; Molecular pathology; Muscle; Muscle biology; Neuromuscular disease

DOI:  https://doi.org/10.1172/jci.insight.194868
PLoS One. 2025 ;20(11): e0336391

Belt-type electrical muscle stimulation preserves muscle fiber size but does not improve muscle function in a rat model of cancer cachexia.

Karina Kouzaki, Mako Isemura, Yuki Tamura, Hiroyuki Uno, Shunta Tadano, Ryuji Akimoto, Katsu Hosoki, Koichi Nakazato.

Cancer cachexia causes severe muscle wasting, and current treatments remain limited. Belt-type electrical muscle stimulation (bEMS) has emerged as a passive rehabilitation tool capable of activating multiple lower limb muscles simultaneously. We investigated whether bEMS prevents muscle wasting and improves functional outcomes in rats with cancer cachexia. Cancer cachexia was induced in male Sprague-Dawley rats by intraperitoneal injection of AH130 Yoshida hepatoma cells. Acute and chronic effects of bEMS were tested. Muscle protein synthesis was evaluated using the SUnSET method, and muscle fiber cross-sectional area (CSA) and ankle torque were measured after chronic stimulation. bEMS increased puromycin-labeled protein levels on day 3 post-injection (~1.5-2.0 fold; p < 0.05). After 10 days, bEMS mitigated reductions in muscle CSA in the gastrocnemius and tibialis anterior compared to the cachexia group. However, muscle strength (ankle torque) was not significantly improved. bEMS preserved muscle fiber size in cancer cachexia but failed to restore muscle function. These findings suggest bEMS may serve as a supportive strategy against muscle atrophy in cachectic conditions.

DOI: https://doi.org/10.1371/journal.pone.0336391
J Muscle Res Cell Motil. 2025 Nov 03.

Myostatin deficiency blunts mechanical adaptation of soleus muscle to overload.

Leonardo Cesanelli, P Minderis, A Fokin, A Ratkevicius, D Satkunskiene, H Degens.

  The aim of this study was to determine the impact of myostatin deficiency on the mechanical and contractile adaptations of the soleus muscle to functional overload (FO). Using a cross-sectional design, we compared the control and FO soleus muscles of myostatin-deficient (BEHcc) and myostatin-functional (BEH⁺⁺) mice. FO was induced by 28 days of gastrocnemius ablation. Soleus muscles were isolated and subjected to an isometric-eccentric contraction protocol to analyse contractile performance and tissue mechanical behaviour. FO significantly increased muscle mass, tetanic force, and stiffness, in BEH⁺⁺ mice (p < 0.05), but not in BEHcc where absolute force was even reduced (p < 0.05). These findings indicate that myostatin plays an important role in successful skeletal muscle adaptations and preservation of muscle function under chronic loading.

Keywords:  ECM; Muscle mechanics; Muscle plasticity; Myostatin

DOI:  https://doi.org/10.1007/s10974-025-09715-w
FASEB J. 2025 Nov 15. 39(21): e71163

Endocrine, Metabolic, and Skeletal Muscle Proteomic Responses During Energy Deficit With Concomitant Aerobic Exercise in Humans.

Yusuke Nishimura, Carl Langan-Evans, Harry L Taylor, Wee L Foo, James P Morton, Sam Shepherd, Juliette A Strauss, Jatin G Burniston, José L Areta.

  Energy deficit is a potent physiological stressor that has shaped human evolution and can improve lifespan and healthspan in a wide range of species. Preserving locomotive capacity was likely essential for survival during the human hunter-gatherer period but surprisingly little is known about the molecular effects of energy deficit on human skeletal muscle, which is a key tissue for locomotion and metabolic health. Here we show that after a 5-day 78% reduction in energy availability with concomitant aerobic exercise in healthy men there was a profound modulation of skeletal muscle phenotype alongside increases in fat oxidation at rest and during exercise and a 2.1 ± 0.8 kg loss of fat free mass and 0.8 ± 0.6 kg of fat mass. We used stable isotope (D2O) labelling and peptide mass spectrometry to investigate the abundance and turnover rates of individual proteins. Abundance (1469 proteins) and synthesis rate (736 proteins) data discovered a shift toward a more oxidative phenotype and reorganization of cytoskeleton and extracellular matrix structure during energy deficit. Mitochondrial components: TCA, electron transport chain and beta-oxidation, were prominently represented amongst proteins that increased in abundance and synthesis rate, as well as proteins related to mitochondrial proteostasis, remodeling and quality-control such as BDH1 and LONP1. Changes in muscle metabolic pathways occurred alongside a reduction in extracellular matrix proteins, which may counteract the age-related muscle fibrosis. Our results suggest that muscle metabolic pathways are not only preserved but positively affected during periods of concomitant low energy availability and exercise.

Keywords:  aerobic exercise; dietary restriction; fibrosis; human evolution; lifespan; mitochondria; proteome; skeletal muscle; weight loss

DOI:  https://doi.org/10.1096/fj.202502384RR
Front Cell Dev Biol. 2025 ;13 1656918

Across the space: applications of spatial transcriptomic technology in healthy and diseased muscle.

Laura Virtanen, Chiara D'Ercole, Lorenzo Giordani.

  In recent years, spatial transcriptomics (ST) has emerged as a groundbreaking technology with the potential to transform and accelerate our understanding of cellular crosstalk. While single-cell approaches have uncovered an unexpected level of cellular heterogeneity in both healthy and diseased tissues, they remain limited in their ability to capture cellular interactions in the native microenvironment. ST techniques bridge this gap by preserving anatomical information, enabling a direct investigation of spatially defined cellular interactions. This feature is particularly relevant in tissues such as skeletal muscle, where syncytial myofibers coexist with a heterogeneous set of interstitial cell populations. Spatial localization is a key factor during muscle regeneration, particularly as stem cell progression is driven by complex interactions between resident and recruited cell populations. Understanding these spatial dynamics is therefore critical to better characterize the fundamental mechanisms of muscle repair and identify aberrant signaling pathways of chronic injury or impaired regeneration. In this review, we will explore the various types of ST techniques, provide a brief summary of the available analytical tools, and highlight recent advancements in the skeletal muscle field enabled by the application of ST.

Keywords:  bioinformatics; muscle disorders; muscle regeneration; skeletal muscle; spatial transcriptomics

DOI:  https://doi.org/10.3389/fcell.2025.1656918
Drug Test Anal. 2025 Nov 04.

Clenbuterol, but not Inhaled Formoterol, Upregulates the Sarcomere Stabilizer KLHL41 to a Similar Extent as Resistance Training in Human Skeletal Muscle.

Morten Hostrup, Lukas Moesgaard, Martin Thomassen, Atul Deshmukh, Søren Jessen.

  Beta2-adrenergic agonists are widely used for bronchial relief in respiratory conditions such as asthma and exercise-induced bronchoconstriction. However, this drug class has also been shown to have muscle anabolic properties. Kelch-Like Family Member 41 (KLHL41) is a sarcomeric protein implicated in muscle remodeling and hypertrophy. In this study, we examined the effects of oral clenbuterol, therapeutic inhaled formoterol, and resistance training on KLHL41 protein abundance in human skeletal muscle. KLHL41 levels were measured by immunoblotting in vastus lateralis muscle biopsies from healthy adults following 2 weeks of oral clenbuterol administration, 6 weeks of inhaled formoterol at therapeutic doses, or 8 weeks of resistance training. We also assessed sex differences and the effects of acute versus prolonged interventions. Prolonged oral clenbuterol administration significantly increased KLHL41 abundance compared to placebo (p < 0.001), with a magnitude similar to that observed after resistance training (p < 0.01), whereas therapeutic inhaled formoterol had no effect on KLHL41 levels. Neither acute clenbuterol administration nor a single resistance training session altered KLHL41 abundance, and no sex differences were observed in baseline KLHL41 levels. These findings indicate that beta2-adrenergic stimulation via oral clenbuterol, but not therapeutic inhalation of formoterol, promotes sarcomeric remodeling through KLHL41-related pathways similar to those activated by resistance training. The distinct effects of these agents on KLHL41 support current anti-doping regulations prohibiting clenbuterol use and highlight KLHL41 as a potential molecular marker of skeletal muscle adaptation to hypertrophic stimuli.

Keywords:  Kelch‐like family; beta adrenergic receptor; beta agonist; doping; muscle hypertrophy; resistance training

DOI:  https://doi.org/10.1002/dta.3963
Physiol Rep. 2025 Nov;13(21): e70616

Sex differences in human skeletal muscle fiber types and the influence of age, physical activity, and muscle group: A systematic review and meta-analysis.

Jessica J James, Maddison L Mellow, Elizabeth P Bueckers, Savannah B Gutsch, David J Wrucke, Andrew G Pearson, Ashleigh E Smith, Sandra K Hunter.

  To understand the sex differences in human skeletal muscle fibers, we determined whether sex differences in fiber cross-sectional area (CSA), fiber type distribution, and proportional area remained after controlling for age, physical activity level, muscle group, and analysis technique. Meta-analysis was performed on 6222 unique participants (Males, M = 3501; Females, F = 2721) (>18 years and free of disease) extracted from 156 studies. A random-effects meta-analysis was used to determine the main effect of sex, and subgroup analyses were performed to determine the influence of age, physical activity level, muscle group biopsied, and analysis technique. Males had greater type I CSA (M = 4936 ± 1250 μm2; F = 4151 ± 1074 μm2; p < 0.001), type II CSA (M = 5272 ± 1950 μm2; F = 3483 ± 1309 μm2; p < 0.001), type II distribution (M = 51.6 ± 14.6%; F = 48.3 ± 13.0%; p < 0.001), and type II proportional area (M = 55.0 ± 14.4%; F = 47.9 ± 13.1%; p < 0.001) than females. Conversely, females had greater type I distribution (F = 51.4 ± 12.1%; M = 48.3 ± 13.3%; p = 0.01) and type I proportional area (F = 51.8 ± 12.4%; M = 44.9 ± 13.2%; p < 0.001) than males. Sex differences were moderated by muscle group biopsied in type I and II proportional area and by age in type I and II fiber type distribution but remained in all other subgroup analyses. In healthy adults, males have larger type I and type II CSA, type II fiber type distribution, and type II proportional area than females, while females have greater type I fiber type distribution and type I proportional area than males. Sex differences generally remained regardless of age, physical activity level, muscle group, and analysis technique, indicating inherent biological sex differences in muscle fiber composition of whole skeletal muscle.

Keywords:  aging; fiber types; physical activity; sex differences; skeletal muscle

DOI:  https://doi.org/10.14814/phy2.70616
J Hum Genet. 2025 Nov 05.

Genetic disruption of satellite cell function underlying congenital myopathies.

Shinichiro Hayashi.

Congenital myopathies are a group of genetically heterogeneous neuromuscular disorders characterized by early-onset hypotonia and muscle weakness. While many congenital myopathies have historically been attributed to structural defects in muscle fibers, accumulating evidence reveals that dysfunction of satellite cells-the resident stem cells essential for muscle growth and regeneration-can also cause congenital myopathy. In this review, we focus on four genes critical for satellite cell biology: PAX7, MYOD1, MEGF10, and MYMK, and discuss how pathogenic variants in these genes contribute to muscle pathology. Mutations in PAX7, a transcription factor essential for satellite cell specification and maintenance, have been identified in patients with progressive congenital myopathy and scoliosis. MYOD1 variants affect the transcriptional regulation of myogenic differentiation and have been reported in individuals with congenital muscle hypoplasia. Loss-of-function variants in MEGF10, which mediates satellite cell proliferation, result in early-onset myopathy characterized by severe weakness and areflexia. Mutations in MYMK, essential for myoblast fusion, lead to congenital myopathy with facial and axial weakness. Together, these studies illustrate that distinct steps in satellite cell function-including specification, commitment, proliferation, and fusion-are critical for normal muscle development and maintenance. Recognizing that genetic defects affecting any of these processes can lead to congenital myopathies, redefining the disease spectrum beyond purely structural muscle disorders. Expanding our understanding of satellite cell biology will be key to elucidating the full spectrum of congenital myopathies and identifying targeted therapeutic strategies.

DOI: https://doi.org/10.1038/s10038-025-01425-y
Biol Pharm Bull. 2025 ;48(11): 1652-1666

Mitochondrial Activation and Therapeutics: Innovations in Cell- and Organelle-Specific Medicine.

Itsumi Sato, Masahiro Shiraishi, Kaede Norota, Kaoru Shiraki, Yuma Yamada.

  Mitochondria are essential for cellular functions, including ATP production, calcium homeostasis, oxidative stress regulation, and apoptosis. Mitochondrial dysfunction is associated with a variety of diseases, including neurodegenerative disorders, skeletal muscle diseases, and mitochondrial diseases. This review explores the latest mitochondrial-targeted therapeutic approaches across the following key perspectives: (1) technological innovations in mitochondrial transplantation, focusing on tunnel nanotubes and extracellular vesicles; (2) the role of mitochondria in skeletal muscle diseases and therapeutic activation strategies; (3) advances in mitochondrial enhancement techniques within cell therapy, particularly in pediatric applications; and (4) the latest treatment modalities for mitochondrial diseases, such as gene and cell therapies. Taken together, these strategies demonstrate the transformative potential of mitochondrial targeting in cell- and organelle-specific medicine. Additionally, the MITO-Porter system is highlighted as an innovative drug delivery platform contributing to these advances.

Keywords:  cell therapy; drug delivery system; mitochondria; mitochondrial disease; organelle medicine; skeletal muscle disease

DOI:  https://doi.org/10.1248/bpb.b25-00218
Arch Gerontol Geriatr. 2025 Nov 03. pii: S0167-4943(25)00335-8. [Epub ahead of print]141 106078

Exercise upregulates Mitsugumin 53 and ameliorates behavioral deficits and mitochondrial biogenesis in a sporadic Alzheimer's disease model in rats.

Muaz Belviranlı, Nilsel Okudan, Tuğba Sezer.

  Chronic physical exercise is a promising non-pharmacological strategy to mitigate the progression of Alzheimer's disease (AD), yet the underlying molecular mechanisms remain incompletely understood. This study investigated the effects of chronic treadmill exercise on behavioral deficits and key molecular pathways in a d-galactose and AlCl3-induced rat model of sporadic AD. Animals were assigned to control, AD, exercise and AD + exercise (AE) groups for a ten-week intervention. Behavioral assessments included the elevated plus maze and Morris Water Maze, followed by molecular and biochemical analyses (RT-qPCR, ELISA) of the hippocampus, skeletal muscle, and plasma. Our results demonstrate that the AD model induced profound cognitive impairments, diminished locomotor activity, heightened anxiety-like behavior, and elevated plasma tau levels. These pathological changes were accompanied by a significant downregulation of the AMPK/SIRT1/PGC-1α mitochondrial biogenesis pathway and, notably, a marked suppression of the membrane repair protein Mitsugumin 53 (MG53) in both the hippocampus and skeletal muscle. The physical exercise regimen successfully ameliorated these behavioral deficits and normalized plasma tau. Mechanistically, physical exercise potently upregulated the AMPK/PGC-1α/FNDC5/BDNF axis in both central and peripheral tissues. Crucially, this study reveals for the first time that physical exercise also triggers a robust upregulation of MG53 at both the gene and protein levels in the brain, muscle, and circulation. These findings identify the physical exercise-induced mobilization of MG53 as a novel and powerful neuroprotective mechanism, linking systemic cellular repair capacity to the enhancement of cognitive resilience against AD.

Keywords:  Alzheimer's Disease; Exerkines; Hippocampal Signaling; Mitsugumin 53; Physical Exercise

DOI:  https://doi.org/10.1016/j.archger.2025.106078
Front Physiol. 2025 ;16 1671926

Effects of exercise training on skeletal muscle mitochondrial outcomes in type 2 diabetes: a systematic review and meta-analysis.

Wenning Zhu, Zhangxu Zhou, Jingyao Sun, Juncheng Si.

   Background: Skeletal muscle mitochondrial dysfunction is a key driver of insulin resistance and disease progression in type 2 diabetes mellitus (T2DM), while exercise training has shown potential to improve mitochondrial function. However, existing studies focus on single exercise modalities, lack systematic synthesis of mitochondrial mechanisms, and exhibit conflicting results, highlighting the need for a comprehensive meta-analysis.
Methods: Systematic searches were conducted in PubMed, Web of Science, and Scopus for studies involving T2DM patients (≥40 years) with exercise as the primary intervention and mitochondrial outcomes. Methodological quality was assessed via the TESTEX scale, with meta-analysis performed using Stata 17.0.
Results: A total of 18 studies (394 participants, 272 in training groups) were included. Exercise significantly enhanced mitochondrial oxidative capacity (SMD = 0.61, 95% CI [0.30, 0.92], driven by citrate synthase [CS] and COX-II), antioxidant capacity (SMD = 1.18, 95% CI [0.50, 1.86], mainly via SOD2), and fusion marker MFN2 (SMD = 0.96, 95% CI [0.63, 1.29]). It tended to increase mitochondrial content (SMD = 0.50, p = 0.091) but with no significant mtDNA/PGC-1α changes. Effective modalities included long-term moderate aerobic training, short-term HIIT, and long-term resistance/combined training. Antidiabetic medications' potential interference was underassessed.
Conclusion: Moderate-to-high intensity exercise selectively improves skeletal muscle mitochondrial function in T2DM, particularly oxidative capacity (via CS/COX-II), antioxidant capacity (via SOD2), and mitochondrial fusion (via MFN2). The effect on mitochondrial content is non-significant, and the influence of antidiabetic medications requires further investigation.
Systematic Review Registration: Identifier CRD42024579581.

Keywords:  exercise training; meta-analysis; mitochondrial function; skeletal muscle; type 2 diabetes mellitus

DOI:  https://doi.org/10.3389/fphys.2025.1671926
Neurotrauma Rep. 2024 ;5(1): 304-316

Muscle-Restricted Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Knockout Partially Corrects Muscle Contractility After Spinal Cord Injury in Mice.

Carlos A Toro, Rita De Gasperi, Abdurrahman Aslan, Nicholas Johnson, Mustafa M Siddiq, Christine Chow, Wei Zhao, Lauren Harlow, Zachary Graham, Xin-Hua Liu, Junichi Sadoshima, Ravi Iyengar, Christopher P Cardozo.

  Spinal cord injury (SCI) results in severe atrophy of skeletal muscle in paralyzed regions, and a decrease in the force generated by muscle per unit of cross-sectional area. Oxidation of skeletal muscle ryanodine 1 receptors (RyR1) reduces contractile force as a result of reduced binding of calstabin 1 to RyR1. One cause of RyR1 oxidation is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (Nox4). We have previously shown that, in rats, RyR1 was oxidized and bound less to calstabin 1 at 56 days after SCI by spinal cord transection. Here, we used a conditional knockout (KO) mouse model of Nox4 in skeletal muscle to investigate the role of Nox4 in reduced muscle specific force after SCI. Peak twitch force of extensor digitorum longus muscles in control mice after SCI was reduced by 42% compared with sham-operated controls, but was increased by ∼43% in SCI Nox4 conditional KO mice compared with SCI controls, although it remained less than that for sham-operated controls. Unlike what was previously observed in rats after SCI, the expression of Nox4 was not increased in gastrocnemius muscle, and binding of calstabin 1 to RyR1 was not reduced in this muscle. The results suggest that Nox4 is directly involved in reduction in muscle twitch force after SCI, although further studies are needed to understand the mechanistic basis for this linkage.

Keywords:  Nox4; SCI mouse models; muscle cKO; muscle contractility; transection SCI

DOI:  https://doi.org/10.1089/neur.2023.0089
Curr Protoc. 2025 Nov;5(11): e70246

Adaptable Immunofluorescence Protocol for Muscle Fiber Typing in FFPE Human and Mouse Skeletal Muscle and Intact Mouse Hindlimbs.

Connor Thomas, Lainey M Hibbard, Kenneth E White, Steven S Welc.

  Skeletal muscle fiber type composition affects muscle function, metabolism, and disease vulnerability. In addition, muscle fiber type analysis informs disease diagnosis and underlying pathophysiology. Multiple methodologies can be used to assess muscle fiber type; however, immunofluorescence (IF) for myosin heavy chain (MyHC) isoforms is the most widely used modern approach due to its relative ease, time-effectiveness, single-cell resolution, and capacity to preserve spatial positioning within the native tissue architecture. Here, we present a protocol for IF for MyHC labeling on formalin-fixed paraffin-embedded (FFPE) mouse and human muscle sections. We then describe a modified procedure for fiber type analysis of the intact mouse lower hindlimb, enabling high-throughput muscle composition and morphological analysis across distinct muscles on a single tissue section. Traditionally, IF labeling for MyHC isoforms required fresh tissue flash-frozen in liquid nitrogen-cooled isopentane, which, while effective, presents challenges for sample processing and preservation, long-term storage, transport, and biosafety. Comparatively, embedding tissue in paraffin after formalin fixation streamlines clinical workflows, preserves morphology, improves long-term sample stability, and simplifies sample storage and transport. Furthermore, FFPE effectively inactivates most infectious agents, which can be retained in frozen sections. Thus, FFPE samples are typically safe for standard laboratory handling and are not classified as biohazardous. This approach can be adapted for use with a range of downstream applications, including integration of fiber type analysis with emerging next-generation techniques that favor FFPE samples. In sum, this method offers a robust alternative to traditional fresh-frozen protocols and allows for simultaneous fiber type analysis across multiple muscle tissues. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Multiplex Immunofluorescence for MyHC Labeling in FFPE Skeletal Muscle Tissues Alternate Protocol 1: Immunofluorescence for MyHC 2x Labeling in FFPE Skeletal Muscle Tissues Alternate Protocol 2: Multiplex Immunofluorescence for MyHC Labeling in FFPE Whole Hindlimb Sections.

Keywords:  formalin‐fixed paraffin‐embedded; immunofluorescence; myosin heavy chain; skeletal muscle fiber type

DOI:  https://doi.org/10.1002/cpz1.70246
Mol Med. 2025 Nov 05. 31(1): 328

Syntaphilin loss enhances mitochondrial axonal transport and neuromuscular junction formation in a human stem cell derived neuromuscular assembloid model.

Andrea Salzinger, Esra Özkan, Vidya Ramesh, Jyoti Nanda, Karen Burr, David Story, Nhan T Pham, Siddharthan Chandran, Bhuvaneish T Selvaraj.

   BACKGROUND: The neuromuscular junction (NMJ) is the synapse between motor neurons and skeletal muscle and controlls movement. Impaired synaptic transmission and NMJ degeneration has been observed during healthy ageing and is also implicated in several neuromuscular diseases. On account of the high energy demands of being distally located and large sized, NMJs are enriched with mitochondria. This enrichment is dependent on transport of mitochondria across the axon to the NMJ.
METHODS: We first established a human 3D neuromuscular assembloid model to study in-vitro NMJs, by fusing human stem cell derived spinal cord organoids and primary skeletal muscle organoids. To determine whether enhancing axonal mitochondrial transport modulates NMJ formation and maintenance, we generated a CRISPR-Cas9 meditated knock-out of syntaphilin in human stem cells.
RESULTS: Firstly, we characterised the neuromuscular assembloid model which showed functional innervated NMJs as measured by juxtaposed neurofilament+ axons and α-bungarotoxin+ acetylcholine receptors. Secondly, we showed that spinal cord selective genetic ablation of syntaphilin - an axonally localised mitochondrial anchor protein - resulted in increased mitochondrial motility in motor neurons, and consequently increased axonal density and NMJ formation.
CONCLUSION: This proof-of-concept study demonstrated that enhancing mitochondrial mobility could provide a therapeutic target to prevent NMJ degeneration.

Keywords:  Assembloid; Axonal transport; Mitochondria; Neuromuscular diseases; Neuromuscular junction; Organoid; Stem cells

DOI:  https://doi.org/10.1186/s10020-025-01319-x
Exp Gerontol. 2025 Oct 31. pii: S0531-5565(25)00283-9. [Epub ahead of print]212 112954

Oligo fucoidan alleviates sarcopenia via attenuating muscle mass loss and function decline in senescence-accelerated mouse prone 8 mice.

Yun-Ching Chang, Yin-Ching Chan, Yu-Chi Chen, Ching-Yu Huang, Sue-Joan Chang.

   OBJECTIVE: Sarcopenia, the progressive loss of skeletal muscle mass and function with age, presents a significant health challenge for older adults. Fucoidan, a bioactive polysaccharide from brown seaweed, has attracted attention for its physiological benefits. We aimed to evaluate the potential of oligo fucoidan (OliFuco) as a nutritional intervention to mitigate sarcopenia.
METHOD: We assessed senescence-associated β-galactosidase activity and myotube formation in senescent C2C12 myoblasts with or without OliFuco treatment. In senescence-accelerated mouse-prone 8 (SAMP8) mice, an in vivo model of sarcopenia, OliFuco was administered from the asymptomatic stage (preventive model) or the pre-sarcopenia stage (treatment model). We evaluated muscle mass, strength, histology, inflammatory cytokines, and key molecular pathways.
RESULTS: OliFuco delayed cellular senescence and improved myotube formation in C2C12 myoblasts. In vivo, OliFuco significantly increased muscle mass, strength, and myofiber cross-sectional area in SAMP8 mice, particularly in the preventive model. OliFuco promoted protein synthesis through AKT/mTOR/p70sk6 up-regulation, inhibited protein degradation via FoxO1/MuRF1 down-regulation, and reduced pro-inflammatory cytokines IL-6, TNF-α, and myostatin by suppressing NF-κB. Compared with branched-chain amino acids, a well-known nutritional supplement for stimulating muscle protein synthesis, OliFuco was more effective in ameliorating sarcopenia in SAMP8 mice. OliFuco alleviates sarcopenia by delaying cellular senescence, supporting positive muscle protein turnover, and reducing chronic inflammation during aging.
CONCLUSION: Our findings show that OliFuco is a promising nutritional intervention for mitigating sarcopenia by preserving muscle mass and function in aging populations, offering a novel strategy to address age-related muscle decline.

Keywords:  Cellular senescence; Chronic inflammation; Oligo fucoidan; Protein turnover; Sarcopenia

DOI:  https://doi.org/10.1016/j.exger.2025.112954
J Cell Mol Med. 2025 Nov;29(21): e70896

Inter-Organ Crosstalk and Regulatory Mechanisms of Skeletal Muscle-Derived Extracellular Vesicles in Systemic Metabolic Homeostasis.

Zhuoying Wu, Yuanyuan Gao, Qi Chen, Li Yuan.

  Extracellular vesicles (EVs), including exosomes, play a pivotal role in intercellular communication by facilitating the transfer of bioactive molecules between cells. These vesicles, which encompass a variety of subtypes such as exosomes, microvesicles and apoptotic bodies, carry functional proteins, mRNAs, miRNAs and other molecular cargo that influence various physiological processes. In particular, skeletal muscle-derived EVs have recently emerged as a novel category of myokines, contributing to muscle homeostasis through paracrine signalling and exerting systemic endocrine effects on metabolic tissues, including the pancreas, adipose tissue and liver. This review systematically examines the regulatory mechanisms of skeletal muscle-derived EVs, with particular focus on exosomes, in mediating inter-organ crosstalk. Additionally, it examines the factors that influence the release of skeletal muscle-derived EVs, particularly exosomes and their subsequent effects on metabolism.

Keywords:  adipose tissue; extracellular vesicles; liver; pancreas; skeletal muscle

DOI:  https://doi.org/10.1111/jcmm.70896
Cell Metab. 2025 Nov 04. pii: S1550-4131(25)00480-2. [Epub ahead of print]

NAD depletion in skeletal muscle does not compromise muscle function or accelerate aging.

Sabina Chubanava, Iuliia Karavaeva, Amy M Ehrlich, Roger M Justicia, Astrid L Basse, Ivan Kulik, Emilie Dalbram, Danial Ahwazi, Samuel R Heaselgrave, Kajetan Trošt, Ben Stocks, Ondřej Hodek, Raissa N Rodrigues, Jesper F Havelund, Farina L Schlabs, Steen Larsen, Caio Y Yonamine, Carlos Henriquez-Olguín, Daniela Giustarini, Ranieri Rossi, Zachary Gerhart-Hines, Thomas Moritz, Juleen R Zierath, Kei Sakamoto, Thomas E Jensen, Nils J Færgeman, Gareth G Lavery, Atul S Deshmukh, Jonas T Treebak.

DOI: https://doi.org/10.1016/j.cmet.2025.10.020
Funct Integr Genomics. 2025 Nov 06. 25(1): 231

Cytosine base editor-mediated SOCS2 knockout promotes C2C12 cell differentiation via the PI3K/AKT/mTOR signaling pathway.

Y Wang, C J Zhang, Y X Li, W J Liu, P Liu, Y P Liu, J Zhang, S X Cao, H X Li.

  Skeletal muscle development depends on the directed differentiation of myoblasts and their fusion into myotubes. Elucidating the mechanisms governing myoblast differentiation is essential for understanding muscle formation. Although suppressor of cytokine signaling 2 (SOCS2) has been implicated in this process, its precise regulatory role remains unclear. Here, the Cytosine Base Editor (CBE) system, offers a powerful approach for studying gene-specific functions, was used to investigate SOCS2 specific functions. sgRNAs targeting the murine SOCS2 gene were designed and expression plasmids were constructed. In C2C12 myoblasts, one sgRNA (sg1) mediated efficient base editing (53.0%), introducing a point mutation at amino acid 19 that generated a premature stop codon. Monoclonal cell lines with this mutation were established using limiting dilution. Western blot (WB) analysis confirmed a significant (P < 0.01) reduction in SOCS2 protein expression in the edited cells, accompanied by elevated levels of Growth Hormone Receptor (GHR). Immunofluorescence (IF) staining further validated increased GHR expression following SOCS2 knockdown. Differentiation assays indicated that SOCS2 knockout promoted C2C12 differentiation, with significantly (P < 0.01) upregulated expression of the myogenic markers MyoD1, MyoG and MYH1. Proteomic sequencing revealed enrichment of differentially expressed proteins in the PI3K/AKT and mTOR signaling pathways. Correspondingly, WB results showed that SOCS2 knockout significantly (P < 0.05) increased the expression of AKT, mTOR, and the phosphorylated forms of PI3K, AKT, and mTOR. Together, these findings demonstrate that CBE-mediated SOCS2 knockout enhances C2C12 differentiation and activates the PI3K/AKT/mTOR signaling pathway, thereby contributing new insights into the molecular regulation of skeletal muscle development.

Keywords:  C2C12 cell; Cytosine base editor; Differentiation; PI3K/AKT/mTOR pathway; SOCS2

DOI:  https://doi.org/10.1007/s10142-025-01754-3
PLoS Biol. 2025 Nov 04. 23(11): e3003484

Zebrafish fast muscle contractions avoid the mammalian requirement for voltage-gated Na+ channels.

Léa Demesmay, Romane Idoux, Christine Berthier, Claire Bernat, Léon Espinosa, Vincent Jacquemond, Frédéric Brunet, Angel Maunier-Mercier, Philippe Lory, Sophie Nicole, Bruno Allard.

Fast skeletal muscle fibers from zebrafish share a number of functional properties with mammalian twitch muscle fibers, making this vertebrate a precious model to investigate the pathophysiology of neuromuscular disorders. We previously reported that action potentials (APs) from zebrafish fast fibers exhibit low amplitude and require unusually strong negative resting membrane voltage levels to be elicited. In this study, using voltage-clamp and current-clamp techniques, we explored the properties of voltage-gated Na+ channels (NaV) responsible for initiation and propagation of AP in isolated adult zebrafish fast skeletal muscle fibers and compared them to mouse fast-twitch muscle fibers using the same experimental conditions. We found that kinetics of activation and inactivation of NaV were faster in zebrafish fibers and, overall, that the voltage-dependence of inactivation was shifted by 25 mV toward negative voltages as compared to mouse fibers, yielding a mean half-inactivation potential of -90 mV. In agreement with these findings, recording of APs at various resting membrane potentials indicated that APs vanished for resting membrane potentials less negative than -80 mV in zebrafish, whereas APs could still be elicited from resting membrane potentials as low as -60 mV in mice. In addition, Ca2+ transients induced by field stimulation were insensitive to Na+ current blockade in zebrafish but not in mouse fibers. Fluorescence labeling of nicotinic acetylcholine receptors showed that zebrafish fast fibers were multi-innervated with a mean distance between extra-synaptic sarcolemma and motor endplates of 14 µm, expected to lead to negligible attenuation of depolarization propagated from endplates. Finally, knock out of the two genes encoding pore-forming NaV subunits in zebrafish muscles did not induce any change in locomotion and escape behavior of the animals. Taken together, these data question the role of NaV and the occurrence of APs in zebrafish fast muscle.

DOI: https://doi.org/10.1371/journal.pbio.3003484
Physiol Rep. 2025 Nov;13(21): e70612

Retrospective transcriptomic analysis indicates temporal dysregulation of mitochondrial genes and metabolic pathways after volumetric muscle loss injury.

David L Miller, Sarah M Greising, Eugene F Douglas, Jarrod A Call.

  Volumetric muscle loss (VML) injury results in the irrecoverable loss of muscle mass and strength and alters the metabolic capacity of the remaining muscle tissue. The primary objective of this retrospective study was to leverage existing RNA-seq datasets to investigate mitochondria and metabolic transcriptome changes after VML injury. The datasets were extracted from publicly available sources and included a bulk RNA-seq dataset (Rattus norvegicus) and a single-cell RNA-seq dataset (Mus musculus) that combined provided a transcriptional landscape out to 42 days post-injury (dpi). The Broad Institute's MitoCarta3.0 database was used to identify mitochondrial-associated genes and pathways for the analysis. There was a robust downregulation of genes in the bulk RNA-seq dataset out to 28 dpi. Gene set enrichment analysis revealed that these genes contributed to oxidative phosphorylation, fatty-acid oxidation, and carbohydrate metabolism. A changing metabolic transcriptional landscape was evident in the single-cell RNA-seq dataset as several cell types (e.g., satellite cells, macrophages, and fibro-adipogenic cells) had upregulated gene sets (e.g., oxidative phosphorylation) that switched to downregulated after 14 dpi. Results from this study complement physiological studies that report dysfunctional mitochondrial bioenergetics, particularly for carbohydrate and free-fatty acid carbon sources, both immediately and chronically after VML injury. These findings also provide targets for monitoring the success of future interventions or directly manipulating in attempts to improve whole-muscle metabolic function.

Keywords:  mitochondria; muscle injury; muscle recovery; muscle regeneration; secondary data analysis

DOI:  https://doi.org/10.14814/phy2.70612
Front Biosci (Landmark Ed). 2025 Oct 28. 30(10): 40854

From Bench to Motion: Unraveling Exercise Biology Through 3D Human Organoids.

Limin Xu, Yu Wang, Chenshi Xi, Jingqi Liu, Weijian Xu, Mutong Han, Jiahao Wu, Jianyu Pang, Chong Gao, Lina Sun.

  Despite extensive research, the systemic biological mechanisms underlying exercise-induced physiological adaptations remain incompletely understood. While animal models (e.g., rodents, non-human primates) have been instrumental in elucidating exercise-mediated benefits in aging and disease, interspecies differences in genomics, epigenetics, and metabolic regulation limit their translational relevance. The advent of induced pluripotent stem cell (iPSC)-derived 3D organoids revolutionizes exercise biology research by enabling human-specific modeling of tissue architecture and donor genomic/epigenetic profiles. This review highlights three transformative strategies: (1) Athlete-derived organoids preserving exercise-induced epigenetic memory to study muscle/neural adaptations; (2) Engineered systems integrating optogenetics and microfluidics to simulate mechanical forces (e.g., muscle contraction) and systemic signals (e.g., cytokines); (3) multi-omics mapping revealing exercise-responsive pathways like mitochondrial biogenesis. Collectively, these patient-specific models bridge pathophysiology with high-throughput screening, advancing precision medicine-from personalized training regimens to therapies counteracting sedentary-related diseases.

Keywords:  exercise; induced pluripotent stem cells; organoids; precision medicine

DOI:  https://doi.org/10.31083/FBL40854
J Cachexia Sarcopenia Muscle. 2025 Dec;16(6): e70080

Postinactivity Exercise Training Improves Sarcopenia Traits in 40-60-Year-Old Women Regardless of Fortified Milk Supplementation.

Joanne Trezise, Ricardo M Lima, Sally D Poppitt, Aaron C Fanning, Amanda Devine, Anthony J Blazevich.

   BACKGROUND: The term sarcopenia was introduced to describe the age-related decline in muscle mass, but current definitions also include measures of muscle strength and function. Menopause increases sarcopenia risk and may exacerbate the adverse effects of physical inactivity. Exercise training is a potent stimulus to restore muscle health, and nutritional supplementation can further improve the outcomes. The purposes of this study were to examine the changes in a set of sarcopenia-related phenotypes induced by a 14-day step-reduction period followed by a 12-week exercise training programme, with or without fortified milk supplementation in healthy 40-60-year-old females, and to determine whether menopausal status interacted with these changes.
METHODS: In this double-blind, placebo-controlled randomized trial, females aged 40-60 years were evaluated before and after 2 weeks of reduced activity monitored through pedometer and after a subsequent 12-week exercise + nutrition programme with ingestion of a fortified milk product (FMP) or placebo. Muscle volume (dual-energy X-ray absorptiometry [DXA] and peripheral quantitative computed tomography), handgrip (hydraulic handheld dynamometer), knee extensor and plantar flexor strength (isokinetic dynamometer) and a variety of physical function measures were assessed at all timepoints.
RESULTS: Eighty-three self-reported healthy females (50.7 ± 5.3 years; 52 postmenopausal) completed the reduced-activity period, and 67 completed the subsequent exercise training + nutrition phase. At baseline, participants averaged 8323 ± 3077 daily steps and then decreased to 1876 ± 729 during the reduced-activity period. Mean sarcopenia outcomes declined after 2 weeks of activity restriction, with significant changes (p < 0.05) in shank muscle cross-sectional area (CSA) (67.7 ± 9.9 to 66.5 ± 9.9 cm2), handgrip strength (25.3 ± 5.0 to 24.0 ± 5.3 kg), knee extensor peak torque (134.7 ± 36.2 to 122.7 ± 34.5 Nm) and stair ascending time (3.6 ± 0.6 to 3.7 ± 0.6 s) and power (367.6 ± 67.6 to 356.7 ± 67.7 W), with no significant time × menopause interactions (p > 0.05 for all variables). All muscle mass, strength and function outcomes were not only improved after exercise training + nutrition but also significantly increased compared to preintervention baseline (all p < 0.05). No training × menopause or training × supplementation interactions were observed for any variable (both p > 0.05).
CONCLUSIONS: Two weeks of step reduction negatively affected muscle mass, strength and physical function in 40-60-year-old females. A 12-week training programme including strength exercises and dietary supplementation not only recovered muscular health but also promoted improvements above the baseline before the physical activity restriction. Menopause status did not influence changes in response to step reduction or exercise, and the addition of a fortified milk product during the training period did not influence the induced adaptations.

Keywords:  disuse; fortified milk product; menopause; physical function; sarcopenia; step count

DOI:  https://doi.org/10.1002/jcsm.70080
Acta Diabetol. 2025 Nov 07.

Muscle loss and GLP-1R agonists use.

Giada Rossi, Loredana Bucciarelli, Chyrell-Lyn Mananguite, Matteo Giovarelli, Paolo Fiorina.

  Skeletal muscle wasting is a major yet often overlooked determinant of adverse outcomes in diabetes mellitus and obesity. Loss of muscle mass and strength not only impairs mobility and quality of life, but also worsens insulin resistance, accelerates cardiometabolic decline and increases mortality risk. The convergence of chronic inflammation, mitochondrial dysfunction and altered protein metabolism makes individuals with metabolic diseases particularly vulnerable to sarcopenia. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have transformed the therapeutic landscape of type 2 diabetes (T2D) and obesity by offering substantial weight loss and cardiometabolic protection. However, clinical trials and real-world evidence consistently show that weight reduction with GLP-1RAs is accompanied by decrease in lean body mass, raising concern in patients already predisposed to muscle wasting and underscoring the need for integrated management strategies. By including all English-language studies on muscle mass loss during GLP-1RA therapy in T2D and obesity from major scientific databases and clinical trial registries, this narrative review synthesizes the current knowledge on the epidemiology and mechanisms of muscle loss in diabetes and obesity, with a focus on the impact of GLP-1RAs therapy. It further examines preventive and therapeutic strategies to preserve muscle health during pharmacological weight loss, with the ultimate aim of providing clinicians and researchers with practical insights and future directions to maximize the benefits of GLP-1RAs while mitigating the risk of sarcopenia.

Keywords:  Diabetes mellitus; GLP-1RA; Muscle loss; Obesity; Prevention; Treatment

DOI:  https://doi.org/10.1007/s00592-025-02611-2
Curr Opin Clin Nutr Metab Care. 2025 Nov 10.

Dietary leucine intake and sarcopenia: from isolated supplementation to combined strategies.

Stéphane Walrand, Olivier Le Bacquer.

   PURPOSE OF REVIEW: Sarcopenia, the age-related loss of skeletal muscle mass and function, poses a major health challenge. While leucine's anabolic properties are well documented, its clinical efficacy as a standalone intervention remains limited. This review explores the potential of integrated strategies combining leucine with other nutrients, physical activity, and gut microbiota modulation to enhance sarcopenia prevention and treatment.
RECENT FINDINGS: Recent studies confirm that leucine supplementation alone fails to significantly improve muscle mass or strength in older adults. However, its benefits emerge when combined with resistance training, or gut microbiota-targeted interventions. The gut-muscle axis has gained attention as a key modulator of muscle health. Additionally, leucine supports the resumption of physical activity in sarcopenic patients by mitigating exercise-induced muscle damage and inflammation.
SUMMARY: These findings underscore the need for multimodal approaches, leucine, optimized nutrition, exercise, and microbiota modulation, to maximize therapeutic benefits. Future research should focus on defining optimal dosages, personalized protocols, and clinical feasibility. Such strategies could revolutionize sarcopenia management by integrating innovative, patient-centred care.

Keywords:  gut-muscle axis; leucine; microbiota; physical activity; sarcopenia

DOI:  https://doi.org/10.1097/MCO.0000000000001180
Sci Rep. 2025 Nov 06. 15(1): 38919

Cistromic insight into the association of retinoid X receptor with MyoD and CTCF in proliferating myoblasts.

Jean-Thomas Clément, Qiao Li.

In eukaryotic cells, histone acetylation and chromatin states affect gene expression programs in broad spectrum of cellular function. Comprehending the genomic signature of retinoid X receptor (RXR) will provide crucial insight into the molecular signaling pathways underlying stem cell fate transition. Here, we employ an integrative ChIP-seq approach to investigate the interplay of RXR with MyoD and CTCF in proliferating myoblasts. Our findings suggest an active enhancer distribution of RXR along with MyoD, marked by H3K18 and H3K27 acetylation, potentially mediated by histone acetyltransferase p300. On the other hand, RXR together with CTCF were mainly distributed to active promoters, marked by H3K9 acetylation. CTCF in proximity to RXR was also associated to nuclear receptor regulator NCOA1 and N-COR, suggesting a potential role in chromatin organization. Taken together, our analyses indicate a crucial interplay of MyoD and CTCF with RXR in the regulation of stem cell function.

DOI: https://doi.org/10.1038/s41598-025-22895-2
J Sport Health Sci. 2025 Oct 30. pii: S2095-2546(25)00082-1. [Epub ahead of print] 101100

Weightlifting outperforms voluntary wheel running for improving adiposity and insulin sensitivity in obese mice.

Robert J Shute, Ryan N Montalvo, Wenqing Shen, Yuntian Guan, Qing Yu, Mei Zhang, Zhen Yan.

   BACKGROUND: Exercise is an effective intervention for obesity and type 2 diabetes, with significant physiological benefits over pharmacological interventions. However, there is limited preclinical data available comparing endurance and resistance exercise for the impacts on obesogenic pathology and glycemic control.
METHODS: Male mice were subjected to 8 weeks of diet-induced obesity (DIO) by high-fat diet (HFD) feeding concurrent with voluntary wheel running (endurance exercise (EEX)) or weightlifting (resistance exercise (REX)). Sedentary (SED) mice fed on normal chow (NC) or HFD were used as controls.
RESULTS: EEX and REX interventions significantly attenuated weight gain vs. HFD-SED due to reduction of fat mass, not changes in lean mass, as assessed by EchoMRI. While REX suppressed visceral and subcutaneous fat accumulation significantly, only EEX enlarged brown fat mass. Exercise tolerance testing (i.e., run-to-fatigue) revealed significantly improved exercise capacity in EEX group vs. NC-SED. Interestingly, although HFD led to trends of increased skeletal muscle mass, only EEX with HFD led to significant muscle weight gain. Neither exercise modality resulted in significant changes of hindlimb skeletal muscle contractile properties and cardiac function compared to SED mice on HFD. Importantly, REX showed significantly enhanced benefits over EEX in improving homeostatic model assessment of insulin resistance (HOMA-IR), glucose tolerance, and insulin tolerance.
CONCLUSION: These results provide a direct and translatable comparison of endurance and resistance exercise training in a preclinical context of obesity and hyperglycemia. The current data set demonstrates an advantage of resistance exercise over endurance exercise in improving glucose and insulin tolerance under the condition of obesity, and that these improvements are independent of significant alterations of muscle weight gain and exercise performance.

Keywords:  Diabetes; High-fat diet; Hyperglycemia; Obesity; Skeletal muscle

DOI:  https://doi.org/10.1016/j.jshs.2025.101100
Geroscience. 2025 Nov 07.

Association of muscle mass and strength with blood-based epigenetic aging among middle-aged and older adults in the United States.

Hye-Ji Seo, Yoosoo Chang, Seungho Ryu, Kyeezu Kim.

  Muscle mass and strength influence various age-related health outcomes, however their individual and joint associations with biological aging remain understudied. This study investigated the associations of muscle health with epigenetic aging based on DNA methylation in blood samples, among middle-aged and older adults. We analyzed data from 1,121 individuals from the 1999-2002 cycles of the National Health and Nutrition Examination Survey. Muscle mass was assessed using the appendicular skeletal muscle mass index, with low muscle mass defined as < 7.0 kg/m2 in males and < 5.5 kg/m2 in females. Muscle strength was evaluated using isokinetic knee extensor force, and categorized into high or low strength based on the sample sex-specific median. Three epigenetic age acceleration measures-PhenoAA, Grim2AA and DunedinPoAm-were examined using multivariable linear regression models. Individual and joint associations were assessed, with analyses stratified by race/ethnicity and sex. Compared to individuals with lower muscle mass, those with higher mass had lower EAA (β: -1.25 for Grim2AA; β: -3.01 for DunedinPoAm; P < 0.01). Similarly, participants with higher muscle strength showed lower EAA compared to those with lower strength (β: -1.66 to -1.01, P < 0.01). Associations were more pronounced in males but not in non-Hispanic Whites. Individuals with better muscle health (higher muscle mass and strength) had lower EAA compared to those with poorer muscle health, across all EAA measures (β: -4.07 to -1.56, P < 0.05). Greater muscle mass and strength were associated with slower biological aging, suggesting the potential importance of maintaining muscle health in promoting healthy aging.

Keywords:  Biological aging; Epigenetic age; Muscle mass; Muscle strength

DOI:  https://doi.org/10.1007/s11357-025-01961-7
Biomed Pharmacother. 2025 Nov 04. pii: S0753-3322(25)00920-5. [Epub ahead of print]193 118726

Inhibition of ATP citrate lyase does not affect muscle mitochondrial activity in apoE-/- mice.

Chiara Macchi, Isabella Fichtner, Tasnim Mohamed, Elsa Franchi, Alessandra Stefania Rizzuto, Chiara Pavanello, Jurgen Gindlhuber, Simone Nerini, Cesare R Sirtori, Elena Osto, Stefano Carugo, Marco Busnelli, Giulia Chiesa, Valerio Magnaghi, Alberto Corsini, Massimiliano Ruscica.

   INTRODUCTION: Lipid-lowering therapy is a cornerstone in preventing coronary disease. Bempedoic acid is recommended in patients who are unable to take statin therapy to achieve the low-density lipoprotein cholesterol goal. Based on the hypothesis that statins impact skeletal mitochondrial activity, this study aimed to evaluate the effect of bempedoic acid on this aspect in apoE-/- mice fed a high-fat high-cholesterol (HFHC) diet and compare it to the results obtained using atorvastatin.
METHODS: Female apoE-/- mice. The following techniques were used: En face analysis of aorta, mitostress analysis of skeletal muscles mitochondria, and transmission electron microscopy analysis of muscle fibres.
RESULTS: After 12 weeks, body weight, food intake, glycaemic profile, and liver enzymes were unaffected by bempedoic acid. However, the treatment significantly reduced the plaque in thoracic and abdominal segments, as well as the necrotic core area. Mitochondrial functionality of skeletal muscles (tibialis anterior, extensor digitorum longus, soleus, gastrocnemius, quadriceps, biceps brachii) in mice receiving bempedoic acid was not reduced compared to mice fed only HFHC diet, whereas mice receiving HFHC plus atorvastatin showed a significant reduction in basal and maximal mitochondrial respiration. Cumulative energy expenditure and oxygen consumption were reduced in the atorvastatin group compared to control and bempedoic acid groups. Transmission electron microscopy analysis of muscle fibres of tibialis anterior showed that bempedoic acid did not affect the morphology and distribution of mitochondria. The same analysis in mice fed HFHC plus atorvastatin showed fragmented mitochondria.
CONCLUSIONS: In apoE-/- mice, bempedoic acid positively impacts plaque burden while preventing skeletal muscle mitochondrial dysfunction.

Keywords:  Atherosclerosis; Bempedoic acid; Mitochondrial activity; Skeletal muscles; Statins

DOI:  https://doi.org/10.1016/j.biopha.2025.118726
Nat Aging. 2025 Nov 04.

A focus shift from sarcopenia to muscle health in the Asian Working Group for Sarcopenia 2025 Consensus Update.

Liang-Kung Chen, Fei-Yuan Hsiao, Masahiro Akishita, Prasert Assantachai, Wei-Ju Lee, Wee Shiong Lim, Weerasak Muangpaisan, Miji Kim, Reshma Aziz Merchant, Li-Ning Peng, Maw Pin Tan, Chang Won Won, Minoru Yamada, Jean Woo, Hidenori Arai.

The Asian Working Group for Sarcopenia (AWGS) presents an updated 2025 consensus reframing sarcopenia management through a life-course approach to muscle health promotion. While aligning with the Global Leadership Initiative in Sarcopenia (GLIS), this update provides healthcare providers with Asia-specific guidance. The consensus introduces three key refinements: first, expanding sarcopenia diagnosis to middle-aged adults (50‒64 years) with validated diagnostic thresholds; second, simplifying the diagnostic algorithm to require only concurrent low muscle mass and strength, with physical performance as an outcome measure; and third, introducing an enhanced muscle health framework recognizing skeletal muscle as vital for healthy longevity, emphasizing cross-talk with brain, bone, adipose tissue and immune systems. This framework leverages the World Health Organization's Integrated Care for Older People (ICOPE) implementation for enhanced case-finding through natural overlap between muscle health and ICOPE's intrinsic capacity domains. The consensus provides evidence-based recommendations for multimodal interventions that combine resistance exercise with nutritional supplementation, representing advancement toward proactive muscle health promotion and establishing a framework for reducing age-related decline in Asian populations.

DOI: https://doi.org/10.1038/s43587-025-01004-y