bims-moremu 2025-02-09 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2025–02–09
thirty papers selected by
Anna Vainshtein, Craft Science Inc.

Increased muscle satellite cell content and preserved telomere length in response to combined exercise training in patients with FSHD.
Skeletal Muscle Mitochondrial and Autophagic Dysregulation Are Modifiable in Spinal Muscular Atrophy.
Type-2 innate signals are dispensable for skeletal muscle regeneration and pathology linked to Duchenne muscular dystrophy.
Diurnal variation in skeletal muscle mitochondrial function dictates time-of-day-dependent exercise capacity.
Neuromuscular electrical stimulation training induces myonuclear accretion and hypertrophy in mice without overt signs of muscle damage and regeneration.
Cellular deconstruction of the human skeletal muscle microenvironment identifies an exercise-induced histaminergic crosstalk.
Skeletal muscle stem cells modulate niche function in Duchenne muscular dystrophy mouse through YY1-CCL5 axis.
FRET-Based Sensor Zebrafish Reveal Muscle Cells Do Not Undergo Apoptosis in Starvation or Natural Aging-Induced Muscle Atrophy.
The liver clock tunes transcriptional rhythms in skeletal muscle to regulate mitochondrial function.
Multitasking muscle: engineering iPSC-derived myogenic progenitors to do more.
Effect of spermidine intake on overload-induced skeletal muscle hypertrophy in male mice.
Skeletal Muscle Innervation: Reactive Oxygen Species as Regulators of Neuromuscular Junction Dynamics and Motor Unit Remodeling.
Myogenic differentiation markers in muscle tissue after aerobic training.
Muscle Cathepsin B treatment improves behavioral and neurogenic deficits in a mouse model of Alzheimer's Disease.
hBMSC-EVs alleviate weightlessness-induced skeletal muscle atrophy by suppressing oxidative stress and inflammation.
Cellular mechanisms underlying overreaching in skeletal muscle following excessive high-intensity interval training.
A window into intracellular events in myositis through subcellular proteomics.
Bifidobacterium adolescentis-derived nicotinic acid improves host skeletal muscle mitochondrial function to ameliorate sarcopenia.
Optimizing In Situ Proximity Ligation Assays for Mitochondria, ER, or MERC Markers in Skeletal Muscle Tissue and Cells.
Targeting Drug Delivery System to Skeletal Muscles: A Comprehensive Review of Different Approaches.
Turning over new ideas in human skeletal muscle proteostasis: What do we know and where to from here?
Multi-omic profiling of sarcopenia identifies disrupted branched-chain amino acid catabolism as a causal mechanism and therapeutic target.
Multiomics Analysis Reveals Therapeutic Targets for Chronic Kidney Disease With Sarcopenia.
Effect of Notch1 signaling on muscle engraftment and maturation from pluripotent stem cells.
Physiological mechanisms of neuromuscular impairment in diabetes-related complications: Can physical exercise help prevent it?
Kinetics insight into the roles of the N- and C-lobes of calmodulin in RyR1 channel regulation.
Creating Optimal Western Blot Conditions for OPA1 Isoforms in Skeletal Muscle Cells and Tissue.
Klotho is cardioprotective in the mdx mouse model of Duchenne muscular dystrophy.
Myofiber structure, sarcoplasmic reticulum Ca2+ handling, and contractile function after muscle-damaging exercise in humans.
Muscle-specific Bet1L knockdown induces neuromuscular denervation, motor neuron degeneration, and motor dysfunction in a rat model of familial ALS.

J Physiol. 2025 Feb 01.

Increased muscle satellite cell content and preserved telomere length in response to combined exercise training in patients with FSHD.

Oscar Horwath, Diego Montiel-Rojas, Elodie Ponsot, Léonard Féasson, Fawzi Kadi.

  Facioscapulohumeral muscular dystrophy (FSHD) is an inherited muscle disease characterized by weakness and muscle wasting. In the absence of available treatments, exercise training has emerged as a potential strategy to attenuate muscle tissue deterioration. However, little is known about the impact of chronic exercise on degenerative events and regenerative capacity in FSHD muscle. Muscle biopsies were obtained from 16 FSHD patients before and after a 24 week training program combining aerobic-, strength- and high-intensity exercise (Control; n = 8, Training; n = 8). Histochemical and immunohistochemical approaches were applied to assess histopathological signs, markers of regeneration, inflammatory infiltrates and satellite cell content. Muscle telomere length was measured as an indicator of the remaining regenerative capacity. The proportion of muscle fibres expressing developmental myosins and centralized myonuclei was not exacerbated after the intervention. Similarly, no alterations were observed in the number of inflammatory infiltrates (CD68+ cells). Alongside muscle hypertrophy in slow (P = 0.022) and fast fibres (P = 0.022 and P = 0.008), satellite cell content increased specifically in fast fibres (+75 %, P = 0.015), indicating a functional satellite cell pool in FSHD muscle. Importantly, exercise training was not associated with a shortening of muscle telomere length, suggesting that muscle cell turnover was not accelerated despite an expansion of the satellite cell pool. Our findings suggest that combined exercise training elicits beneficial muscular adaptations without impairing important indicators of skeletal muscle regenerative capacity in patients with FSHD. KEY POINTS: A 24 week combined exercise training program is a safe and well-tolerated strategy to attenuate skeletal muscle deterioration in facioscapulohumeral muscular dystrophy (FSHD) patients. Markers of histopathology, muscle fibre regeneration and inflammatory infiltrates were not exacerbated following exercise training in FSHD muscle. Here, we show novel data that exercise training in FSHD patients induced muscle fibre hypertrophy and triggered an expansion of the satellite cell pool specifically in fast fibres. Exercise training in these patients is not associated with a shortening of muscle telomere length thereby indicating a preserved capacity for muscle regeneration.

Keywords:  Pax7; facioscapulohumeral muscular dystrophy; muscle fibre; muscle regeneration; myogenesis

DOI:  https://doi.org/10.1113/JP287033
J Cachexia Sarcopenia Muscle. 2025 Feb;16(1): e13701

Skeletal Muscle Mitochondrial and Autophagic Dysregulation Are Modifiable in Spinal Muscular Atrophy.

Andrew I Mikhail, Sean Y Ng, Donald Xhuti, Magda A Lesinski, Jennifer Chhor, Marc-Olivier Deguise, Yves De Repentigny, Joshua P Nederveen, Rashmi Kothary, Mark A Tarnopolsky, Vladimir Ljubicic.

   BACKGROUND: Spinal muscular atrophy (SMA) is a health- and life-limiting neuromuscular disorder. Although varying degrees of mitochondrial abnormalities have been documented in SMA skeletal muscle, the influence of disease progression on pathways that govern organelle turnover and dynamics are poorly understood. Thus, the purpose of this study was to investigate skeletal muscle mitochondria during SMA disease progression and determine the effects of therapeutic modalities on organelle biology.
METHODS: Smn2B/+ and Smn2B/- severe SMA-like mice were used to investigate mitochondrial turnover and dynamics signalling. Muscles were analysed at postnatal day 9 (P9), P13 or P21 to address pre-symptomatic, early symptomatic and late symptomatic periods of the disorder. Additionally, we utilized an acute dose of exercise and urolithin A (UA) to stimulate organelle remodelling in skeletal muscle of SMA mice in vivo and in SMA patient-derived myotubes in vitro, respectively.
RESULTS: Smn2B/+ and Smn2B/- mice demonstrated similar levels of muscle mitochondrial oxidative phosphorylation (OxPhos) proteins throughout disease progression. In contrast, at P21 the mRNA levels of upstream factors important for the transcription of mitochondrial genes encoded by the nuclear and mitochondrial DNA, including nuclear respiratory factor 2, sirtuin 1, mitochondrial transcription factor A and tumour protein 53, were upregulated (+31%-195%, p < 0.05) in Smn2B/- mice relative to Smn2B/+. Early and late symptomatic skeletal muscle from SMA-like mice showed greater autophagosome formation as denoted by more phosphorylated autophagy related 16-like 1 (p-ATG16L1Ser278) puncta (+60%-80%, p < 0.05), along with a build-up of molecules indicative of damaged mitochondria such as BCL2 interacting protein 3, Parkin and PTEN-induced kinase 1 (+100%-195%, p < 0.05). Furthermore, we observed a fragmented mitochondrial phenotype at P21 that was concomitant with abnormal splicing of Optic atrophy 1 transcripts (-53%, p < 0.05). A single dose of exercise augmented the expression of citrate synthase (+43%, p < 0.05) and corrected the over-assembly of autophagosomes (-64%, p < 0.05). In patient muscle cells, UA treatment stimulated autophagic flux, increased the expression of OxPhos proteins (+15%-47%, p < 0.05) and improved maximal oxygen consumption (+84%, p < 0.05).
CONCLUSIONS: Abnormal skeletal muscle mitochondrial turnover and dynamics are associated with disease progression in Smn2B/- mice despite compensatory elevations in upstream factors important for organelle synthesis and recycling. Exercise and UA enhance mitochondrial health in skeletal muscle, which indicates that lifestyle-based and pharmacological interventions may be effective countermeasures targeting the organelle for therapeutic remodelling in SMA.

Keywords:  autophagy; biogenesis; dynamics; exercise; mitophagy; urolithin A

DOI:  https://doi.org/10.1002/jcsm.13701
EMBO Rep. 2025 Feb 03.

Type-2 innate signals are dispensable for skeletal muscle regeneration and pathology linked to Duchenne muscular dystrophy.

Melina Messing, Marine Theret, Michael R Hughes, Jiaqi Wu, Omar Husain Syed, Fang Fang Li, Yicong Li, Fabio M V Rossi, Kelly M McNagny.

  Immune responses play an integral role in skeletal muscle regeneration. In the genetically inherited muscle disease Duchenne muscular dystrophy (DMD), muscle regeneration is disrupted, leading to chronic inflammation, fibrosis, and early mortality. Previously, it has been suggested that type-2 innate immune cells, particularly eosinophils and their production of IL-4, play an essential role in effective muscle regeneration after acute injury. We here re-investigate the role of eosinophils in skeletal muscle repair using mice deficient in eosinophils (ΔdblGATA), or deficient in IL-4R/IL-13R signaling through STAT6 (Stat6-/-). We show that neither deficiency has an impact on skeletal muscle regeneration in response to acute injury as quantified by fiber size, immune cell infiltration, or muscle-resident stem cell proliferation. We also investigate the role of STAT6 signaling in mdx:Stat6-/- mice, a model of DMD and, again, find that ablation of STAT6 signaling has no effect on the rate or severity of fibrotic scar formation or disease progression. In contrast to previous models, our data suggest a negligible role for eosinophils and STAT6 signaling in skeletal muscle regeneration after acute or chronic injury.

Keywords:  Duchenne Muscular Dystrophy (DMD); Eosinophils; STAT6 Signaling; Skeletal Muscle Regeneration

DOI:  https://doi.org/10.1038/s44319-025-00383-y
FASEB J. 2025 Feb 15. 39(3): e70365

Diurnal variation in skeletal muscle mitochondrial function dictates time-of-day-dependent exercise capacity.

Subhash Khatri, Souparno Das, Anshit Singh, Shabbir Ahmad, Mohit Kashiv, Sunil Laxman, Ullas Kolthur-Seetharam.

  Exercise impinges on almost all physiological processes at an organismal level and is a potent intervention to treat various diseases. Exercise performance is well established to display diurnal rhythm, peaking during the late active phase. However, the underlying molecular/metabolic factors and mitochondrial energetics that possibly dictate time-of-day exercise capacity remain unknown. Here, we have unraveled the importance of diurnal variation in mitochondrial functions as a determinant of skeletal muscle exercise performance. Our results show that exercise-induced muscle metabolome and mitochondrial energetics are distinct at ZT3 and ZT15. Importantly, we have elucidated key diurnal differences in mitochondrial functions that are well correlated with disparate time-of-day-dependent exercise capacity. Providing causal mechanistic evidence, we illustrate that loss of Sirtuin4 (SIRT4), a well-known mitochondrial regulator, abrogates mitochondrial diurnal variation and consequently abolishes time-of-day-dependent muscle output. Therefore, our findings unequivocally demonstrate the pivotal role of baseline skeletal muscle mitochondrial functions in dictating diurnal exercise capacity.

Keywords:  Sirtuin4 (SIRT4); chronobiology; circadian exercise physiology; exercise metabolism; mitochondrial metabolism; skeletal muscle energetics; time‐of‐day exercise capacity

DOI:  https://doi.org/10.1096/fj.202402930R
Skelet Muscle. 2025 Feb 05. 15(1): 3

Neuromuscular electrical stimulation training induces myonuclear accretion and hypertrophy in mice without overt signs of muscle damage and regeneration.

Aurélie Fessard, Aliki Zavoriti, Natacha Boyer, Jules Guillemaud, Masoud Rahmati, Peggy Del Carmine, Christelle Gobet, Bénédicte Chazaud, Julien Gondin.

   BACKGROUND: Skeletal muscle is a plastic tissue that adapts to increased mechanical loading/contractile activity through fusion of muscle stem cells (MuSCs) with myofibers, a physiological process referred to as myonuclear accretion. However, it is still unclear whether myonuclear accretion is driven by increased mechanical loading per se, or occurs, at least in part, in response to muscle injury/regeneration. Here, we developed a non-damaging protocol to evaluate contractile activity-induced myonuclear accretion/hypertrophy in physiological conditions.
METHODS: Contractile activity was generated by applying repeated electrical stimuli over the mouse plantar flexor muscles. This method is commonly referred to as NeuroMuscular Electrical Simulation (NMES) in Human. Each NMES training session consisted of 80 isometric contractions delivered at ∼15% of maximal tetanic force to avoid muscle damage. C57BL/6J male mice were submitted to either a short (i.e., 6 sessions) or long (i.e., 12 sessions) individualized NMES training program while unstimulated mice were used as controls. Histological investigations were performed to assess the impact of NMES on MuSC number and status, myonuclei content and muscle tissue integrity, typology and size.
RESULTS: NMES led to a robust proliferation of MuSCs and myonuclear accretion in the absence of overt signs of muscle damage/regeneration. NMES-induced myonuclear accretion was specific to type IIB myofibers and was an early event preceding muscle hypertrophy inasmuch as a mild increase in myofiber cross-sectional area was only observed in response to the long-term NMES training protocol.
CONCLUSION: We conclude that NMES-induced myonuclear accretion and muscle hypertrophy are driven by a mild increase in mechanical loading in the absence of overt signs of muscle injury.

Keywords:  Contractile activity; Force production; Muscle stem cells; Resistance training; Skeletal muscle plasticity

DOI:  https://doi.org/10.1186/s13395-024-00372-0
Cell Metab. 2025 Feb 03. pii: S1550-4131(24)00493-5. [Epub ahead of print]

Cellular deconstruction of the human skeletal muscle microenvironment identifies an exercise-induced histaminergic crosstalk.

Thibaux Van der Stede, Alexia Van de Loock, Guillermo Turiel, Camilla Hansen, Andrea Tamariz-Ellemann, Max Ullrich, Eline Lievens, Jan Spaas, Nurten Yigit, Jasper Anckaert, Justine Nuytens, Siegrid De Baere, Ruud Van Thienen, Anneleen Weyns, Laurie De Wilde, Peter Van Eenoo, Siska Croubels, John R Halliwill, Pieter Mestdagh, Erik A Richter, Lasse Gliemann, Ylva Hellsten, Jo Vandesompele, Katrien De Bock, Wim Derave.

  Plasticity of skeletal muscle is induced by transcriptional and translational events in response to exercise, leading to multiple health and performance benefits. The skeletal muscle microenvironment harbors myofibers and mononuclear cells, but the rich cell diversity has been largely ignored in relation to exercise adaptations. Using our workflow of transcriptome profiling of individual myofibers, we observed that their exercise-induced transcriptional response was surprisingly modest compared with the bulk muscle tissue response. Through the integration of single-cell data, we identified a small mast cell population likely responsible for histamine secretion during exercise and for targeting myeloid and vascular cells rather than myofibers. We demonstrated through histamine H1 or H2 receptor blockade in humans that this paracrine histamine signaling cascade drives muscle glycogen resynthesis and coordinates the transcriptional exercise response. Altogether, our cellular deconstruction of the human skeletal muscle microenvironment uncovers a histamine-driven intercellular communication network steering muscle recovery and adaptation to exercise.

Keywords:  crosstalk; exercise; glycogen; histamine; macrophages; mast cells; metabolism; muscle fibers; skeletal muscle; transcriptomics

DOI:  https://doi.org/10.1016/j.cmet.2024.12.011
Nat Commun. 2025 Feb 03. 16(1): 1324

Skeletal muscle stem cells modulate niche function in Duchenne muscular dystrophy mouse through YY1-CCL5 axis.

Yang Li, Chuhan Li, Qiang Sun, Xingyuan Liu, Fengyuan Chen, Yeelo Cheung, Yu Zhao, Ting Xie, Bénédicte Chazaud, Hao Sun, Huating Wang.

Adult skeletal muscle stem cells (MuSCs) are indispensable for muscle regeneration and tightly regulated by macrophages (MPs) and fibro-adipogenic progenitors (FAPs) in their niche. Deregulated MuSC/MP/FAP interactions and the ensuing inflammation and fibrosis are hallmarks of dystrophic muscle. Here we demonstrate intrinsic deletion of transcription factor Yin Yang 1 (YY1) in MuSCs exacerbates dystrophic pathologies by altering composition and heterogeneity of MPs and FAPs. Further analysis reveals YY1 loss induces expression of immune genes in MuSCs, including C-C motif chemokine ligand 5 (Ccl5). Augmented CCL5 secretion promotes MP recruitment via CCL5/C-C chemokine receptor 5 (CCR5) crosstalk, which subsequently hinders FAP clearance through elevated Transforming growth factor-β1 (TGFβ1). Maraviroc-mediated pharmacological blockade of the CCL5/CCR5 axis effectively mitigates muscle dystrophy and improves muscle performance. Lastly, we demonstrate YY1 represses Ccl5 transcription by binding to its enhancer thus facilitating promoter-enhancer looping. Altogether, our study demonstrates the critical role of MuSCs in actively shaping their niche and provides novel insight into the therapeutic intervention of muscle dystrophy.

DOI: https://doi.org/10.1038/s41467-025-56474-w
Adv Sci (Weinh). 2025 Feb 04. e2416811

FRET-Based Sensor Zebrafish Reveal Muscle Cells Do Not Undergo Apoptosis in Starvation or Natural Aging-Induced Muscle Atrophy.

Hao Jia, Renfei Wu, Hongmei Yang, Kathy Qian Luo.

  Muscle atrophy occurs during natural aging and under disease conditions. Muscle cell apoptosis is considered one of the main causes of muscle atrophy, while several recent studies argued that muscle cells do not die during muscle atrophy. Here, sensor zebrafish are generated to visualize muscle cell apoptosis and the engulfment of dead muscle cells by macrophages. Using these sensor zebrafish, starvation, and natural aging-induced muscle atrophy models are established. The data showed that the diameters of muscle cells decreased in both models; however, muscle cell apoptosis is not found in the process of muscle atrophy. In starvation-induced muscle atrophy, it also showed that the number of nuclei in muscle cells remained constant, and there is no increase in the number of macrophages in muscle tissues, both of which further confirmed that muscle cells do not die. In both models, transcriptional analysis showed that the apoptosis pathway is down-regulated, and autophagy and protein degradation pathways are up-regulated. All these data indicated that although there is a great reduction of muscle mass during starvation or aging-induced muscle atrophy, muscle cells do not die by apoptosis. These findings provide new insights into muscle atrophy and can benefit the treatments for muscle atrophy-related diseases.

Keywords:  FRET; aging; apoptosis; autophagy; live imaging; muscle atrophy; starvation

DOI:  https://doi.org/10.1002/advs.202416811
bioRxiv. 2025 Jan 20. pii: 2025.01.17.633623. [Epub ahead of print]

The liver clock tunes transcriptional rhythms in skeletal muscle to regulate mitochondrial function.

Valentina Sica, Tomoki Sato, Ioannis Tsialtas, Sophia Hernandez, Siwei Chen, Pierre Baldi, Pura Muñoz Cánoves, Paolo Sassone-Corsi, Kevin B Koronowski, Jacob G Smith.

Circadian clocks present throughout the brain and body coordinate diverse physiological processes to support daily homeostasis and respond to changing environmental conditions. The local dependencies within the mammalian clock network are not well defined. We previously demonstrated that the skeletal muscle clock controls transcript oscillations of genes involved in fatty acid metabolism in the liver, yet whether the liver clock also regulates the muscle was unknown. Here, we use hepatocyte-specific Bmal1 KO mice (Bmal1 hep-/- ) and reveal that approximately one third of transcriptional rhythms in skeletal muscle are regulated by the liver clock vivo. Treatment of myotubes with serum harvested from Bmal1 hep-/- mice inhibited expression of genes involved in metabolic pathways, including oxidative phosphorylation. Overall, the transcriptional changes induced by liver clock-driven endocrine-communication revealed from our in vitro system were small in magnitude, leading us to surmise that the liver clock acts to fine-tune metabolic gene expression in muscle. Strikingly, treatment of myotubes with serum from Bmal1 hep-/- mice inhibited mitochondrial ATP production compared to WT and this effect was only observed with serum harvested during the active phase. Overall, our results reveal communication between the liver clock and skeletal muscle-uncovering a bidirectional endocrine communication pathway dependent on clocks in these two key metabolic tissues. Targeting liver and muscle circadian clocks may represent a potential avenue for exploration for diseases associated with dysregulation of metabolism in these tissues.

DOI: https://doi.org/10.1101/2025.01.17.633623
Front Cell Dev Biol. 2024 ;12 1526635

Multitasking muscle: engineering iPSC-derived myogenic progenitors to do more.

Mark Stephen Hamer, Fabio M V Rossi.

  The generation of myogenic progenitors from iPSCs (iMPs) with therapeutic potential for in vivo tissue regeneration has long been a goal in the skeletal muscle community. Today, protocols enable the production of potent, albeit immature, iMPs that resemble Pax7+ adult muscle stem cells. While muscular dystrophies are often the primary therapeutic target for these cells, an underexplored application is their use in treating traumatic muscle injuries. Notably absent from recent reviews on iMPs is the concept of engineering these cells to perform functions post-transplantation that non-transgenic cells cannot. Here, we highlight protocols to enhance the generation, purification, and maturation of iMPs, and introduce the idea of engineering these cells to perform functions beyond their normal capacities, envisioning novel therapeutic applications.

Keywords:  cell therapeutic; iPSCs (induced pluripotent stem cells); muscle regeneration; muscle stem cell (MuSC); myogenic progenitor cells; synthetic biology (synbio)

DOI:  https://doi.org/10.3389/fcell.2024.1526635
Physiol Rep. 2025 Feb;13(3): e70209

Effect of spermidine intake on overload-induced skeletal muscle hypertrophy in male mice.

Tomohiro Iwata, Takanaga Shirai, Riku Tanimura, Ryoto Iwai, Tohru Takemasa.

  Skeletal muscles exhibit high plasticity, such as overload-induced hypertrophy or immobilization-induced atrophy. During sports, skeletal muscle hypertrophy is induced by training to improve performance. Spermidine is a type of polyamine and oral intake of spermidine exerts many beneficial effects on health through various mechanisms, such as promoting autophagy and improving mitochondrial function. In a recent study, we showed that spermidine intake activates mTOR signaling and significantly increases the mean fiber cross-sectional area (CSA) 14 days after injury. This suggests that spermidine promotes the anabolic growth of differentiated muscle (i.e., muscle hypertrophy); however, calorie restriction, which has been reported to have effects on the same molecular mechanisms as spermidine (promoting autophagy and improving mitochondrial function), promotes skeletal muscle regeneration, while inhibiting skeletal muscle hypertrophy. Therefore, we evaluated the effect of spermidine intake on skeletal muscle hypertrophy in mice using a synergistic ablation-induced muscle hypertrophy model. Our results showed that spermidine intake significantly decreased mean myofiber of CSA, but this was not consistent with the change in skeletal muscle wet weight. We also analyzed autophagy, mTOR signaling, inflammation, and mitochondria, but no significant effects of spermidine intake were observed at most protein expression levels. Therefore, spermidine intake does not affect overload-induced skeletal muscle hypertrophy, and even if it does, the effect is suppressive.

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

DOI:  https://doi.org/10.14814/phy2.70209
Free Radic Biol Med. 2025 Jan 30. pii: S0891-5849(25)00072-3. [Epub ahead of print]

Skeletal Muscle Innervation: Reactive Oxygen Species as Regulators of Neuromuscular Junction Dynamics and Motor Unit Remodeling.

Steve D Guzman, Susan V Brooks.

  This review explores the intricate processes of motor unit remodeling with a specific focus on the influence of reactive oxygen species (ROS) and oxidative stress on the primary cellular components: nerves/axons, muscle fibers, and muscle-resident glial cells. Emphasizing the role of redox biology, we highlight how oxidative stress impacts motor unit adaptation, injury response, and aging. By synthesizing findings from recent studies with seminal works, including investigations of myelin and terminal Schwann cells and neuromuscular junction (NMJ) dynamics, this review provides a comprehensive understanding of the molecular mechanisms underpinning motor unit maintenance and repair. The goal is to elucidate how oxidative stress influences these processes and to explore potential therapeutic strategies for neuromuscular disorders.

Keywords:  Denervation; Oxidative Stress; Reinnervation; Sarcopenia; Schwann Cell

DOI:  https://doi.org/10.1016/j.freeradbiomed.2025.01.053
Heliyon. 2025 Jan 30. 11(2): e41888

Myogenic differentiation markers in muscle tissue after aerobic training.

Rastegar Hoseini, Zahra Hoseini, Ayob Kamangar.

  Aerobic training induces a myriad of adaptations in muscle tissue, encompassing alterations in muscle fiber type composition, hypertrophy, and metabolic capacity. Understanding the potential role of myogenic differentiation markers (MDFs), such as Pax7, MyoD, Myogenin, and myosin heavy chain (MHC) isoforms, in mediating these adaptations is of paramount importance. The review delves into the intricate molecular mechanisms underlying the regulation of MDFs following aerobic training, elucidating the role of key signaling pathways including the MAPK/ERK, PI3K/Akt, and AMPK pathways, among others. These pathways play pivotal roles in orchestrating the expression and activity of MDFs, ultimately influencing muscle adaptation and regeneration. The comprehension of MDFs in the context of aerobic training is far-reaching, offering the potential for targeted interventions to optimize muscle adaptation and regeneration. This review identifies the need for further research to unveil the precise molecular mechanisms of the activation and interaction of myogenic differentiation markers with other signaling pathways, as well as to explore their potential as therapeutic targets for muscle-related conditions. This review article also provides a thorough analysis of MDFs in muscle tissue after aerobic training, highlighting their potential clinical implications and outlining future research directions in this area.

Keywords:  Aerobic training; Muscle adaptation; Muscle regeneration; Myogenic differentiation markers; Signaling pathways

DOI:  https://doi.org/10.1016/j.heliyon.2025.e41888
bioRxiv. 2025 Jan 22. pii: 2025.01.20.633414. [Epub ahead of print]

Muscle Cathepsin B treatment improves behavioral and neurogenic deficits in a mouse model of Alzheimer's Disease.

Alejandro Pinto, Hazal Haytural, Cassio Loss, Claudia Alvarez, Asude Ertas, Olivia Curtis, Alyssa R Williams, Grayson Murphy, Ken Salleng, Sylvia Gografe, Ali Altintas, Tal Kafri, Romain Barres, Atul Shahaji Deshmukh, Henriette van Praag.

Muscle secretes factors during exercise that enhance cognition. Myokine Cathepsin B (Ctsb) is linked to memory function, but its role in neurodegenerative disease is unclear. Here we show that AAV-vector-mediated Ctsb overexpression in skeletal muscle in an Alzheimer's Disease (AD) mouse model (APP/PS1), improves motor coordination, memory function and adult hippocampal neurogenesis, while plaque pathology and neuroinflammation remain unchanged. Additionally, in AD mice, Ctsb treatment modifies hippocampal, muscle and plasma proteomic profiles to resemble that of wildtype controls. Conversely, in wildtype mice, Ctsb expression causes memory deficits and results in protein profiles across tissues that are comparable to AD control mice. In AD mice, Ctsb treatment increases the abundance of hippocampal proteins involved in mRNA metabolism and protein synthesis, including those relevant to adult hippocampal neurogenesis and memory function. Furthermore, Ctsb treatment enhances plasma metabolic and mitochondrial processes, and reduces inflammatory responses. In muscle, Ctsb expression elevates protein translation in AD mice, whereas in wildtype mice mitochondrial proteins decrease. Overall, the biological changes in the treatment groups are consistent with effects on memory function. Thus, skeletal muscle Ctsb application has potential as an AD therapeutic intervention.

DOI: https://doi.org/10.1101/2025.01.20.633414
Stem Cell Res Ther. 2025 Feb 04. 16(1): 46

hBMSC-EVs alleviate weightlessness-induced skeletal muscle atrophy by suppressing oxidative stress and inflammation.

Mengyuan Chang, Ruiqi Liu, Bingqian Chen, Jin Xu, Wei Wang, Yanan Ji, Zihui Gao, Boya Liu, Xinlei Yao, Hualin Sun, Feng Xu, Yuntian Shen.

   BACKGROUND: Muscle disuse and offloading in microgravity are likely the primary factors mediating spaceflight-induced muscle atrophy, for which there is currently no effective treatment other than exercise. Extracellular vesicles derived from bone marrow mesenchymal stem cells (BMSC-EVs) possess anti-inflammatory and antioxidant properties, offering a potential strategy for combating weightless muscular atrophy.
METHODS: In this study, human BMSCs-EVs (hBMSC-EVs) were isolated using super-centrifugation and characterized. C2C12 myotube nutrition-deprivation and mice tail suspension models were established. Subsequently, the diameter of C2C12 myotubes, Soleus mass, cross-sectional area (CSA) of muscle fibers, and grip strength in mice were assessed to investigate the impact of hBMSC-EVs on muscle atrophy. Immunostaining, transmission electron microscopy observation, and western blot analysis were employed to assess the impact of hBMSC-EVs on muscle fiber types, ROS levels, inflammation, ubiquitin-proteasome system activity, and autophagy lysosome pathway activation in skeletal muscle atrophy.
RESULTS: The active hBMSC-EVs can be internalized by C2C12 myotubes and skeletal muscle. hBMSC-EVs can effectively reduce C2C12 myotube atrophy caused by nutritional deprivation, with a concentration of 10 × 108 particles/mL showing the best effect (P < 0.001). Additionally, hBMSC-EVs can down-regulate the protein levels associated with UPS and oxidative stress. Moreover, intravenous administration of hBMSC-EVs at a concentration of 1 × 1010 particles/mL can effectively reverse the reduction in soleus mass (P < 0.001), CSA (P < 0.01), and grip strength (P < 0.001) in mice caused by weightlessness. They demonstrate the ability to inhibit protein degradation mediated by UPS and autophagy lysosome pathway, along with the suppression of oxidative stress and inflammatory responses. Furthermore, hBMSC-EVs impede the transition of slow muscle fibers to fast muscle fibers via upregulation of Sirt1 and PGC-1α protein levels.
CONCLUSIONS: Our findings indicate that hBMSC-EVs are capable of inhibiting excessive activation of the UPS and autophagy lysosome pathway, suppressing oxidative stress and inflammatory response, reversing muscle fiber type transformation, effectively delaying hindlimb unloading-induced muscle atrophy and enhancing muscle function. Our study has further advanced the understanding of the molecular mechanism underlying muscle atrophy in weightlessness and has demonstrated the protective effect of hBMSC-EVs on muscle atrophy.

Keywords:  Bone marrow mesenchymal stem cells; Extracellular vesicles; Inflammation; Muscle atrophy; Oxidative stress

DOI:  https://doi.org/10.1186/s13287-025-04175-y
Am J Physiol Cell Physiol. 2025 Feb 04.

Cellular mechanisms underlying overreaching in skeletal muscle following excessive high-intensity interval training.

Daiki Watanabe, Masanobu Wada.

  Overreaching (OR) can be defined as a decline in physical performance resulting from excessive exercise training, necessitating days to weeks recovery. Impairments in the contractile function of skeletal muscle are believed to be a primary factor contributing to OR. However, the cellular mechanism triggering OR remains unclear. The purpose of this study was to elu idate the mechanisms underlying OR. Rats' plantar flexor muscles were subjected to repeated electrical stimulations mimicking excessive high-intensity interval training (HIIT) daily for 13 consecutive days, and isometric torques were monitored. The torque was measured one day after HIIT, and subsequently, the physiological function of type II fibers was analyzed by using mechanically-skinned-fiber technique. Eleven out of 17 rats exhibited torque decline, while others did not. Thus, the rats were divided into OR and non-overreaching (NOR) groups. Skinned fibers from the gastrocnemius (GAS) muscles of both groups showed decreased depolarization-induced force and increased myofibrillar Ca2+ sensitivity.However, the fibers from the OR group, but not the NOR group, exhibited a decrease in myofibrillar maximal force. Biochemical analyses of a superficial region of GAS muscle revealed that α-actinin 2 content was increased in the NOR group, but not the OR group, whereas calpain-3 autolysis was increased in the OR group, but not the NOR group. These findings shed light on the cellular mechanism underlying OR: OR following excessive HIIT was induced by a decreased myofibrillar maximal force, while Ca2+ sensitivity was increased.

Keywords:  myofibril; overtraining; sarcoplasmic reticulum; skinned fiber

DOI:  https://doi.org/10.1152/ajpcell.00623.2024
Inflamm Res. 2025 Jan 31. 74(1): 31

A window into intracellular events in myositis through subcellular proteomics.

Jennifer M Peterson, Valérie Leclair, Olumide E Oyebode, Dema M Herzallah, Andrea L Nestor-Kalinoski, Jose Morais, René P Zahedi, Mazen Alamr, John A Di Battista, Marie Hudson.

   OBJECTIVE AND DESIGN: Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of inflammatory muscle disorders of unknown etiology. It is postulated that mitochondrial dysfunction and protein aggregation in skeletal muscle contribute to myofiber degeneration. However, molecular pathways that lead to protein aggregation in skeletal muscle are not well defined.
SUBJECTS: Here we have isolated membrane-bound organelles (e.g., nuclei, mitochondria, sarcoplasmic/endoplasmic reticulum, Golgi apparatus, and plasma membrane) from muscle biopsies of normal (n = 3) and muscle disease patients (n = 11). Of the myopathy group, 10 patients displayed mitochondrial abnormalities (IIM (n = 9); mitochondrial myopathy (n = 1)), and one IIM patient did not show mitochondrial abnormalities (polymyositis).
METHODS: Global proteomic analysis was performed using an Orbitrap Fusion mass spectrometer. Upon unsupervised clustering, normal and mitochondrial myopathy muscle samples clustered separately from IIM samples.
RESULTS: We have confirmed previously known protein alterations in IIM and identified several new ones. For example, we found differential expression of (i) nuclear proteins that control cell division, transcription, RNA regulation, and stability, (ii) ER and Golgi proteins involved in protein folding, degradation, and protein trafficking in the cytosol, and (iii) mitochondrial proteins involved in energy production/metabolism and alterations in cytoskeletal and contractile machinery of the muscle.
CONCLUSIONS: Our data demonstrates that molecular alterations are not limited to protein aggregations in the cytosol (inclusions) and occur in nuclear, mitochondrial, and membrane compartments of IIM skeletal muscle.

Keywords:  Biopsy; Human; Muscle; Myositis; Proteomics

DOI:  https://doi.org/10.1007/s00011-025-01996-8
Cell Rep. 2025 Feb 04. pii: S2211-1247(25)00036-1. [Epub ahead of print]44(2): 115265

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

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

  Sarcopenia significantly diminishes quality of life and increases mortality risk in older adults. While the connection between the gut microbiome and muscle health is recognized, the underlying mechanisms are poorly understood. In this study, shotgun metagenomics revealed that Bifidobacterium adolescentis is notably depleted in individuals with sarcopenia, correlating with reduced muscle mass and function. This finding was validated in aged mice. Metabolomics analysis identified nicotinic acid as a key metabolite produced by B. adolescentis, linked to improvements in muscle mass and functionality in individuals with sarcopenia. Mechanistically, nicotinic acid restores nicotinamide adenine dinucleotide (NAD+) levels in muscle, inhibits the FoxO3/Atrogin-1/Murf-1 axis, and promotes satellite cell proliferation, reducing muscle atrophy. Additionally, NAD+ activation enhances the silent-information-regulator 1 (SIRT1)/peroxisome-proliferator-activated-receptor-γ-coactivator 1-alpha (PGC-1α) axis, stimulating mitochondrial biogenesis and promoting oxidative metabolism in slow-twitch fibers, ultimately improving muscle function. Our findings suggest that B. adolescentis-derived nicotinic acid could be a promising therapeutic strategy for individuals with sarcopenia.

Keywords:  Bifidobacterium adolescentis; CP: Metabolism; CP: Microbiology; NAD+; gut microbiome; mitochondria biogenesis; multi-omics; nicotinic acid; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.1016/j.celrep.2025.115265
Curr Protoc. 2025 Feb;5(2): e70043

Optimizing In Situ Proximity Ligation Assays for Mitochondria, ER, or MERC Markers in Skeletal Muscle Tissue and Cells.

Amber Crabtree, Han Le, Chanel Harris, Ashton Oliver, Andy Barillas, Johnathan Moore, Desiree Ngoc-Ha Nguyen, Izabella Marie Rabago, Benjamin Rodriguez, Dominique C Stephens, Heather K Beasley, Edgar Garza-Lopez, Kit Neikirk, Margaret Mungai, Larry Vang, Zer Vue, Neng Vue, Andrea G Marshall, Kyrin Turner, Jianqiang Shao, Sandra Murray, Jennifer A Gaddy, Celestine Wanjalla, Jamaine Davis, Steven Damo, Antentor O Hinton.

  Proximity ligation assays (PLAs) use specific antibodies to detect endogenous protein-protein interactions. PLAs are a highly useful biochemical technique that allow two proteins within proximity to be visualized with fluorescent probes amplified by PCR. While this technique has gained prominence, the use of a PLA in mouse skeletal muscle (SkM) is novel. In this article, we discuss how the PLA method can be used in SkM to study the protein-protein interactions within mitochondria-endoplasmic reticulum contact sites (MERCs). © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Proximity ligation assay for skeletal muscle tissue and myoblast for MERC proteins.

Keywords:  MERCs; Mfn1; Mfn2; mitochondria; protein‐protein interactions; proximity ligation assays; skeletal muscles

DOI:  https://doi.org/10.1002/cpz1.70043
J Cachexia Sarcopenia Muscle. 2025 Feb;16(1): e13691

Targeting Drug Delivery System to Skeletal Muscles: A Comprehensive Review of Different Approaches.

Xiaofang Li, Jintao Xu, Shanshan Yao, Ning Zhang, Bao-Ting Zhang, Zong-Kang Zhang.

  The skeletal muscle is one of the largest organs in the body and is responsible for the mechanical activity required for posture, movement and breathing. The effects of current pharmaceutical therapies for skeletal muscle diseases are far from satisfactory; approximately 24% of Duchenne muscular dystrophy (DMD) trials have been terminated because of unsatisfactory outcomes. The lack of a skeletal muscle-targeting strategy is a major reason for these unsuccessful trials, contributing to low efficiency and severe side effects. The development of targeting strategies for skeletal muscle-specific drug delivery has shown the potential for increasing drug concentrations in the skeletal muscle, minimising off-target effects, and thereby improving the therapeutic effects of drugs. Over the past few decades, novel methods for specifically delivering cargo to skeletal muscles have been developed. In this review, we categorise targeting methods into four types: peptides, antibodies, small molecules and aptamers. Most research has focused on peptide and antibody ligands, and there are several well-established drugs in this category; however, drawbacks such as protease degradation and immunogenicity limit their use. Aptamers and small molecules have low immunogenicity and are simple to chemically produce. However, small molecule ligands generally exhibit lower affinity because of their small size and high mobility. Aptamers are promising ligands for skeletal muscle-targeting delivery systems. Additionally, if the active site of the cargo is located inside the cell, an internalisation pathway becomes necessary. The order of internalisation ligands and targeting ligands in the complex is a crucial factor, because an inappropriate order could lead to much lower targeting and internalisation efficiencies. Moreover, ligand density also merits consideration, as increasing the density of the targeting ligands may result in steric hindrance, which could impact the accessibility of the receptor and cause enlargement of the targeted ligands. More efforts are required to optimise drug delivery systems that specifically recognise skeletal muscle, with the aim of enhancing quality of life and promoting patient well-being.

Keywords:  aptamer; internalisation; nanocarrier; peptide; skeletal muscle; targeting delivery

DOI:  https://doi.org/10.1002/jcsm.13691
Exp Physiol. 2025 Feb 05.

Turning over new ideas in human skeletal muscle proteostasis: What do we know and where to from here?

Changhyun Lim, James McKendry, Matthew Lees, Philip J Atherton, Nicholas A Burd, Andrew M Holwerda, Luc J C van Loon, Chris McGlory, Cameron J Mitchell, Kenneth Smith, Daniel J Wilkinson, Tanner Stokes, Stuart M Phillips.

  Understanding the turnover of proteins in tissues gives information as to how external stimuli result in phenotypic change. Nowhere is such phenotypic change more conspicuous than skeletal muscle, which can be effectively remodelled by increased loading, ageing and unloading (disuse), all of which are subject to modification by nutrition and other environmental stimuli. The understanding of muscle proteome remodelling has undergone a renaissance recently with the reintroduction of deuterated water (D2O) and its ingestion to label amino acids and measure their incorporation into proteins. However, there is confusion around the use of the deuterated water methodology and the interpretation of the data it provides. Here, we provide a short review of some of the more salient features of the method and clarify some of the confusion around the method of deuterated water methods and its use in humans and how the interpretation of the data is in contrast to that of rodents.

Keywords:  deuterium oxide; human; phenotype; skeletal muscle; stable isotope tracer

DOI:  https://doi.org/10.1113/EP092353
Nat Aging. 2025 Feb 05.

Multi-omic profiling of sarcopenia identifies disrupted branched-chain amino acid catabolism as a causal mechanism and therapeutic target.

Xinrong Zuo, Rui Zhao, Minming Wu, Yanyan Wang, Shisheng Wang, Kuo Tang, Yang Wang, Jie Chen, Xiaoxiang Yan, Yang Cao, Tao Li.

Sarcopenia is a geriatric disorder characterized by a gradual loss of muscle mass and function. Despite its prevalence, the underlying mechanisms remain unclear, and there are currently no approved treatments. In this study, we conducted a comprehensive analysis of the molecular and metabolic signatures of skeletal muscle in patients with impaired muscle strength and sarcopenia using multi-omics approaches. Across discovery and replication cohorts, we found that disrupted branched-chain amino acid (BCAA) catabolism is a prominent pathway in sarcopenia, which leads to BCAA accumulation and decreased muscle health. Machine learning analysis further supported the causal role of BCAA catabolic dysfunction in sarcopenia. Using mouse models, we validated that defective BCAA catabolism impairs muscle mass and strength through dysregulated mTOR signaling, and enhancing BCAA catabolism by BT2 protects against sarcopenia in aged mice and in mice lacking Ppm1k, a positive regulator of BCAA catabolism in skeletal muscle. This study highlights improving BCAA catabolism as a potential treatment of sarcopenia.

DOI: https://doi.org/10.1038/s43587-024-00797-8
J Cachexia Sarcopenia Muscle. 2025 Feb;16(1): e13696

Multiomics Analysis Reveals Therapeutic Targets for Chronic Kidney Disease With Sarcopenia.

Meiqiu Wang, Lianghui You, Xu He, Yingchao Peng, Ren Wang, Zhiqiang Zhang, Jiaping Shu, Pei Zhang, Xiaoyi Sun, LiLi Jia, Zhengkun Xia, Chenbo Ji, Chunlin Gao.

   BACKGROUND: The presence of sarcopenia in patients with chronic kidney disease (CKD) is associated with poor prognosis. The mechanism underlying CKD-induced muscle wasting has not yet been fully explored. This study investigates the influence of renal secretions on muscles using multiomics sequencing.
METHODS: The kidney transcriptome analysis by RNA-seq and protein profiling by tandem mass tag (TMT), serum TMT and muscle TMT were performed in CKD established using 0.2% adenine and control mice. Spp1 recombinant protein was used to study its effect on myotube atrophy in vitro. In animal experiments on CKD, pharmacological inhibition of Spp1 was used to explore the role of Spp1 in skeletal muscle wasting. Transcriptome analysis was performed to identify differentially expressed genes (DEGs) in the gastrocnemius muscle following Spp1 pharmacological inhibition.
RESULTS: In the renal transcriptome and TMT, 503 and 377 proteins/genes respectively were co-upregulated and co-downregulated. In the serum TMT of CKD and normal control (NC) mice, 22 upregulated and 7 downregulated differentially expressed proteins (DEPs) showed the same expression patterns as those in the kidney transcriptome and TMT analysis. Based on bioinformatics analysis and reported studies, we selected Spp1 for further validation. Spp1 recombinant protein was added to C2C12 myotubes in vitro, and the results indicated that Spp1 significantly increased the protein levels of the muscle atrophy marker (Murf-1) and promoted the smaller myotubes (all p < 0.05). Compared with NC mice, Spp1 mRNA and protein levels were significantly upregulated in the kidneys of CKD mice, and the serum concentration of Spp1 was also markedly increased (all p < 0.05). In animal experiments, pharmacological inhibition of Spp1 increased the weights of gastrocnemius and tibialis anterior muscles (p < 0.05) and improved muscle atrophy phenotype. Transcriptome analysis showed that DEGs in the gastrocnemius muscle following Spp1 pharmacological inhibition were enriched in protein digestion and absorption, glucagon signalling pathway, apelin signalling pathway and ECM-receptor interaction pathway.
CONCLUSIONS: Our study is the first to establish a regulatory network of kidney-muscle crosstalk to explore the potential mechanism of CKD-related sarcopenia. Employing multiomics analysis, cellular assessment and animal experiments, we have identified that Spp1 could potentialy serve as a promising therapeutic target for CKD patients with sarcopenia.

Keywords:  Spp1; chronic kidney disease; multiomics analysis; myotube; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13696
Stem Cell Reports. 2025 Jan 18. pii: S2213-6711(24)00356-4. [Epub ahead of print] 102396

Effect of Notch1 signaling on muscle engraftment and maturation from pluripotent stem cells.

Aline M S Yamashita, Bayardo I Garay, Hyunkee Kim, Darko Bosnakovski, Juan E Abrahante, Karim Azzag, Phablo Abreu, Aaron Ahlquist, Rita C R Perlingeiro.

  Pax3-induced pluripotent stem cell-derived myogenic progenitors display an embryonic molecular signature but become postnatal upon transplantation. Because this correlates with upregulation of Notch signaling, here we probed whether NOTCH1 is required for in vivo maturation by performing gain- and loss-of-function studies in inducible Pax3 (iPax3) myogenic progenitors. Transplantation studies revealed that Notch1 signaling did not change the number of donor-derived fibers; however, the NOTCH1 overexpression cohorts showed enhanced satellite cell engraftment and more mature fibers, as indicated by fewer fibers expressing the embryonic myosin heavy-chain isoform and more type IIX fibers. While donor-derived Pax7+ cells were detected in all transplants, in the absence of Notch1, secondary grafts exhibited a high fraction of these cells in the interstitial space, indicating that NOTCH1 is required for proper satellite cell homing. Transcriptional profiling of NOTCH1-modified donor-derived satellite cells suggests that this may be due to changes in the extracellular matrix organization, cell cycle, and metabolism.

Keywords:  NOTCH1; Pax3; fiber type; muscle regeneration; myogenic progenitors; pluripotent stem cells; satellite cells; secondary transplantation

DOI:  https://doi.org/10.1016/j.stemcr.2024.102396
J Physiol. 2025 Feb 03.

Physiological mechanisms of neuromuscular impairment in diabetes-related complications: Can physical exercise help prevent it?

Edoardo Lecce, Alessio Bellini, Giuseppe Greco, Fiorella Martire, Alessandro Scotto di Palumbo, Massimo Sacchetti, Ilenia Bazzucchi.

  Diabetes mellitus is a chronic disorder that progressively induces complications, compromising daily independence. Among these, diabetic neuropathy is particularly prevalent and contributes to substantial neuromuscular impairments in both types 1 and 2 diabetes. This condition leads to structural damage affecting both the central and peripheral nervous systems, resulting in a significant decline in sensorimotor functions. Alongside neuropathy, diabetic myopathy also contributes to muscle impairment and reduced motor performance, intensifying the neuromuscular decline. Diabetic neuropathy typically implicates neurogenic muscle atrophy, motoneuron loss and clustering of muscle fibres as a result of aberrant denervation-reinervation processes. These complications are associated with compromised neuromuscular junctions, where alterations occur in pre-synaptic vesicles, mitochondrial content and post-synaptic signalling. Neural damage is intensified by chronic hyperglycaemia and oxidative stress, exacerbating vascular dysfunction and reducing oxygen delivery. These complications imply a severe decline in neuromuscular performance, evidenced by reductions in maximal force and power output, rate of force development and muscle endurance. Furthermore, diabetes-related complications are compounded by age-related degenerative changes in long-term patients. Aerobic and resistance training offer promising approaches for managing blood glucose levels and neuromuscular function. Aerobic exercise promotes mitochondrial biogenesis and angiogenesis, supporting metabolic and cardiovascular health. Resistance training primarily enhances neural plasticity, muscle strength and hypertrophy, which are crucial factors for mitigating sarcopenia and preserving functional independence. This topical review examines current evidence on the physiological mechanisms underlying diabetic neuropathy and the potential impact of physical activity in counteracting this decline.

Keywords:  diabetes mellitus; exercise physiology; glucose; metabolism; motor control; skeletal muscle; training

DOI:  https://doi.org/10.1113/JP287589
J Biol Chem. 2025 Feb 02. pii: S0021-9258(25)00105-X. [Epub ahead of print] 108258

Kinetics insight into the roles of the N- and C-lobes of calmodulin in RyR1 channel regulation.

Jingyan Zhang, Levy M Treinen, Skylar J Mast, Megan R McCarthy, Bengt Svensson, David D Thomas, Razvan L Cornea.

  Calmodulin (CaM) activates the skeletal muscle Ca2+ release channel (ryanodine receptor, RyR1) at nanomolar Ca2+ and inhibits it at micromolar Ca2+. CaM conversion from RyR1 activator to inhibitor is due to structural changes induced by Ca2+ binding at CaM's two lobes. However, it remains unclear which lobe provides the switch for this conversion. Here, we attached the environment-sensitive fluorophore acrylodan (Acr) at either lobe of intact CaM or lobe-specific Ca2+-sensitive CaM mutants, and monitored the effects of Ca2+ binding via the fluorescence change of free or RyR1-bound AcrCaM. Using steady state measurements, we found that Ca2+ binding to free CaM causes a dramatic structural change in the N-lobe, but only a slight effect on the C-lobe of the Ca2+-sensitive lobe-specific mutants, in addition to the previously known higher Ca2+ affinity at the C-lobe vs. the N-lobe. Using stopped-flow measurements, we found ∼30x faster Ca2+ dissociation from the N- vs. C-lobe, and ∼20x slower Ca2+ association to the N-lobe vs. C-lobe. These Ca2+ binding properties hold for the CaM/RyR1 complex, and Ca2+ affinity is enhanced at the CaM C-lobe but decreased at the N-lobe by RyR1 binding. We propose that fast Ca2+-binding at the C-lobe of CaM initiates its inhibition to RyR1 at high [Ca2+], while slow Ca2+ binding to the N-lobe is necessary for timely enhancement of the inhibitory effect. The dysregulation of RyR1 by M124Q-CaM may be explained by the lower Ca2+ affinity vs. WT-CaM, as suggested by both steady-state and transient kinetics results.

Keywords:  Ca(2+) binding; calcium release channel; fluorescence labeling; oximimetic; ryanodine receptor

DOI:  https://doi.org/10.1016/j.jbc.2025.108258
Curr Protoc. 2025 Feb;5(2): e70004

Creating Optimal Western Blot Conditions for OPA1 Isoforms in Skeletal Muscle Cells and Tissue.

Margaret Mungai, Amber Crabtree, Han Le, Johnathan Moore, Desiree Nguyen, Benjamin Rodriguez, Chanel Harris, Dominique C Stephens, Heather K Beasley, Edgar Garza-Lopez, Kit Neikirk, Bryanna Shao, Ashton Oliver, Genesis Wilson, Serif Bacevac, Larry Vang, Zer Vue, Neng Vue, Andrea G Marshall, Kyrin Turner, Elma Zaganjor, Jianqiang Shao, Sandra Murray, Jennifer A Gaddy, Celestine Wanjalla, Jamaine Davis, Steven M Damo, Lori D Banks, Antentor Hinton.

  OPA1 is a dynamin-related GTPase that modulates mitochondrial dynamics and cristae integrity. Humans carry eight different isoforms of OPA1 and mice carry five, all of which are expressed as short- or long-form isoforms. These isoforms contribute to OPA1's ability to control mitochondrial energetics and DNA maintenance. However, western blot isolation of all long and short isoforms of OPA1 can be difficult. To address this issue, we developed an optimized western blot protocol based on improving running time to isolate five different isoforms of OPA1 in mouse cells and tissues. This protocol can be applied to study changes in mitochondrial structure and function. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Western Blot Protocol for Isolating OPA1 Isoforms in Mouse Primary Skeletal Muscle Cells.

Keywords:  isoforms; mitochondria; muscle tissue; optic atrophy‐1 (OPA1); western blot

DOI:  https://doi.org/10.1002/cpz1.70004
Am J Pathol. 2025 Jan 29. pii: S0002-9440(25)00035-5. [Epub ahead of print]

Klotho is cardioprotective in the mdx mouse model of Duchenne muscular dystrophy.

Areli Jannes S Javier, Felicia M Kennedy, Xin Yi, Michelle Wehling-Henricks, James G Tidball, Kenneth E White, Carol A Witczak, Makoto Kuro-O, Steven S Welc.

Duchenne muscular dystrophy (DMD) is a lethal, progressive skeletal and cardiac myopathy. Cardiomyopathy is the leading cause of death in DMD patients but the molecular basis for heart failure is incompletely understood. Like humans, in the mdx mouse model of DMD cardiac function is impaired after the onset of skeletal muscle pathology. Dysregulation of Klotho gene regulation in dystrophic skeletal muscles occurs at disease onset affecting pathogenesis. Whether Klotho is protective against dystrophin-deficient cardiomyopathy is unknown. Here, we showed that expression of a Klotho transgene prevented deficits in left ventricular ejection fraction and fractional shortening in mdx mice. Improvements in cardiac performance were associated with reductions in adverse cardiac remodeling, cardiac myocyte hypertrophy and fibrosis. In addition, mdx mice expressed high concentrations of plasma fibroblast growth factor 23 (FGF23) and expression was increased locally in hearts. The cardioprotective effects of Klotho were not associated with differences in renal function or serum biochemistries, but transgene expression prevented increased expression of plasma FGF23 and cardiac Fgf23 mRNA expression. Cardiac reactive oxygen species, oxidative damage, mitochondrial damage, and apoptosis were reduced in transgenic hearts. Our findings also showed that FGF23 stimulates hypertrophic growth in dystrophic neonatal mouse ventricular myocytes in vitro, which was inhibited by co-stimulation with soluble Klotho. Taken together, these results demonstrate that Klotho prevented dystrophic cardiac remodeling and improved function.

DOI: https://doi.org/10.1016/j.ajpath.2024.12.017
Physiol Rep. 2025 Feb;13(3): e70204

Myofiber structure, sarcoplasmic reticulum Ca2+ handling, and contractile function after muscle-damaging exercise in humans.

V Handegard, P K Lunde, M Frisk, O Seynnes, N Ørtenblad, W E Louch, G Paulsen, T Raastad.

  Exercise-induced muscle damage (EIMD) is characterized by a severe and prolonged decline in force-generating capacity. However, the precise cellular mechanisms underlying the observed long-lasting decline in force-generating capacity associated with EIMD are still unclear. We investigated in vivo force generation and ex vivo Ca2+-activated force generation, Ca2+ sensitivity, and myofiber Ca2+ handling systems (SR and t-tubules) in human biceps brachii before and 2, 48, and 96 h after eccentrically muscle-damaging contractions and in non-exercised control arm. The force-generating capacity declined by 50 ± 13% 3 h after exercise and was still not recovered after 96 h. The force-Ca relationship of skinned myofibers revealed an impaired maximal Ca2+-activated force in MHC I-fibers, but not MHC II-fibers 48 h after exercise. Further, Ca2+ sensitivity was increased in MHC II-fibers, which was reversed after incubation with a strong reductant. There was a biphasic increase in SERCA sulfonylation, and a parallel reduction in the SR Ca2+ uptake rate, with no effects on SR vesicle leak or SR vesicle Ca2+ release rate. T-tubules showed a progressive increase in the density of longitudinal tubules by 96 h after exercise. In conclusion, MHC II-fiber Ca2+ sensitivity was increased 48 h after exercise, attributed to changes in the REDOX status. 96 h after exercise SR vesicle Ca2+ uptake was impaired, and an increased number of longitudinal tubules were observed. These alterations may contribute to the impaired force generation evident at the late stage of recovery.

Keywords:  Ca2+ sensitivity; SR vesicle Ca2+ handling; contractile function; exercise‐induced muscle damage; t‐tubules

DOI:  https://doi.org/10.14814/phy2.70204
Front Neurosci. 2025 ;19 1527181

Muscle-specific Bet1L knockdown induces neuromuscular denervation, motor neuron degeneration, and motor dysfunction in a rat model of familial ALS.

Adam Eckardt, Charles Marble, Bradley Fern, Henry Moritz, Charles Kotula, Jiayi Ke, Clarisse Rebancos, Samantha Robertson, Hiroshi Nishimune, Masatoshi Suzuki.

  Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by specific loss of motor neurons in the spinal cord and brain stem. Although ALS has historically been characterized as a motor neuron disease, there is evidence that motor neurons degenerate in a retrograde manner, beginning in the periphery at the neuromuscular junctions (NMJs) and skeletal muscle. We recently reported a vesicle trafficking protein Bet1L (Bet1 Golgi Vesicular Membrane Trafficking Protein Like) as a new molecule possibly linked to NMJ degeneration in ALS. In this study, we tested the hypothesis that Bet1L gene silencing in skeletal muscle could influence NMJ integrity, motor neuron function, and survival in a rat model of familial ALS (SOD1G93A transgenic). Small interfering RNA (siRNA) targeting the Bet1L gene was injected on a weekly basis into the hindlimb muscle of pre-symptomatic ALS and wild-type (WT) rats. After 3 weeks, intramuscular Bet1L siRNA injection significantly increased the number of denervated NMJs in the injected muscle. Bet1L knockdown decreased motor neuron size in the lumbar spinal cord, which innervated the siRNA-injected hindlimb. Impaired motor function was identified in the hindlimbs of Bet1L siRNA-injected rats. Notably, the effects of Bet1L knockdown on NMJ and motor neuron degeneration were more significant in ALS rats when compared to WT rats. Together, Bet1L knockdown induces denervation of NMJs, but also this knockdown accelerates the disease progression in ALS. Our results provide new evidence to support the potential roles of Bet1L as a key molecule in NMJ maintenance and ALS pathogenesis.

Keywords:  Bet1L; SOD1G93A rats; amyotrophic lateral sclerosis (ALS); distal axonopathy; motor neuron; neuromuscular junction; skeletal muscle; small interfering RNA (siRNA)

DOI:  https://doi.org/10.3389/fnins.2025.1527181