bims-moremu 2024-04-14 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024‒04‒14
35 papers selected by
Anna Vainshtein, Craft Science Inc.

Time-of-day effects on ex vivo muscle contractility following short-term satellite cell ablation.
The 24-Hour Time Course of Integrated Molecular Responses to Resistance Exercise in Human Skeletal Muscle Implicates MYC as a Hypertrophic Regulator That is Sufficient for Growth.
The BALB/c.mdx62 mouse exhibits a dystrophic muscle pathology and is a novel model of Duchenne muscular dystrophy.
The Role of TGF-β Signaling in Muscle Atrophy, Sarcopenia and Cancer Cachexia.
Temporal Single-Cell Sequencing Analysis Reveals That GPNMB-Expressing Macrophages Potentiate Muscle Regeneration.
Life-Long Aerobic Exercise is a Non-Pharmacological Approach for Inducing Autophagy and Delaying Muscle Atrophy in the Aging Population.
GDF5 as a rejuvenating treatment for age-related neuromuscular failure.
Intramuscular injection of mesenchymal stem cells augments basal muscle protein synthesis after bouts of resistance exercise in male mice.
Matrix mechanics regulates muscle regeneration by modulating kinesin-1 activity.
Endurance exercise has a negative impact on the onset of SOD1-G93A ALS in female mice and affects the entire skeletal muscle-motor neuron axis.
Effect of exercise-induced Neutrophil maturation on skeletal muscle repair in vitro.
Mitochondria and Reactive Oxygen Species: The Therapeutic Balance of Powers for Duchenne Muscular Dystrophy.
Irisin alters D-galactose-induced apoptosis by increasing caveolin-1 expression in C2C12 myoblasts and skeletal muscle fibroblasts.
PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway.
Dispase/collagenase cocktail allows for coisolation of satellite cells and fibroadipogenic progenitors from human skeletal muscle.
Collagen type VI regulates TGFβ bioavailability in skeletal muscle.
Expression of nNOS alpha and beta isoforms in skeletal muscle of mice.
Skeletal Muscle Heat Shock Protein Content and the Repeated Bout Effect.
Challenges and Considerations of Preclinical Development for iPSC-Based Myogenic Cell Therapy.
Islr regulates satellite cells asymmetric division through the SPARC/p-ERK1/2 signaling pathway.
Regulation of myogenic cell proliferation and differentiation during mammalian skeletal myogenesis.
The extracellular matrix differentially directs myoblast motility and differentiation in distinct forms of muscular dystrophy: Dystrophic matrices alter myoblast motility.
Targeting Mitochondrial Dynamics during Lower-Limb Ischemia Reperfusion in Young and Old Mice: Effect of Mitochondrial Fission Inhibitor-1 (mDivi-1).
Right place at the right time: Mitochondrial shape, distribution and inter-organelle interaction during skeletal muscle postnatal development.
The human genetic variant rs6190 unveils Foxc1 and Arid5a as novel pro-metabolic targets of the glucocorticoid receptor in muscle.
Optimization of Xenografting Methods for Generating Human Skeletal Muscle in Mice.
Photobiomodulation therapy moderates cancer cachexia-associated muscle wasting through activating PI3K/AKT/FoxO3a pathway.
Exercise training mode effects on myokine expression in healthy adults: A systematic review with meta-analysis.
The autophagy inhibitor NSC185058 suppresses mTORC1-mediated protein anabolism in cultured skeletal muscle.
Post-translational modifications of vertebrate striated muscle myosin heavy chains.
Revealing myopathy spectrum: integrating transcriptional and clinical features of human skeletal muscles with varying health conditions.
Beyond muscles: Investigating immunoregulatory myokines in acute resistance exercise - A systematic review and meta-analysis.
Hypoxia treatment and resistance training alters microRNA profiling in rats skeletal muscle.
A conserved complex lipid signature marks human muscle aging and responds to short-term exercise.
Mitochondrial respiration atlas reveals differential changes in mitochondrial function across sex and age.

Am J Physiol Cell Physiol. 2024 Apr 08.

Time-of-day effects on ex vivo muscle contractility following short-term satellite cell ablation.

Ryan Edward Kahn, Richard L Lieber, Guadalupe Meza, Fawzan Dinnunhan, Orly Lacham-Kaplan, Sudarshan Dayanidhi, John A Hawley.

  Muscle isometric torque fluctuates according to time-of-day with such variation owed to the influence of circadian molecular clock genes. Satellite cells (SC), the muscle stem cell population, also express molecular clock genes with several contractile related genes oscillating in a diurnal pattern. Currently, limited evidence exists regarding the relationship between SCs and contractility, although long-term SC ablation alters muscle contractile function. Whether there are acute alterations in contractility following SC ablation and with respect to the time-of-day is unknown. We investigated whether short-term SC ablation affected contractile function at two times of day, and whether any such alterations lead to different extents of eccentric contraction-induced injury. Utilizing an established mouse model to deplete SCs, we characterized muscle clock gene expression and ex vivo contractility at two times-of-day (morning 0700 h and afternoon, 1500 h). Morning-SC+ animals demonstrated ~25-30% reductions in tetanic/eccentric specific forces and, after eccentric injury, exhibited ~30% less force-loss and ~50% less dystrophinnegative fibers versus SC- counterparts; no differences were noted between Afternoon groups (Morning-SC+: -5.63 ± 0.61, Morning-SC-: -7.93 ± 0.61; N/cm2; p < 0.05) (Morning-SC+: 32 ± 2.1, Morning-SC-: 64 ± 10.2; dystrophinnegative fibers; p < 0.05). As Ca++ kinetics underpin force-generation, we also evaluated caffeine-induced contracture-force as an indirect marker of Ca++ availability, and found similar force reductions in Morning-SC+ vs SC- mice. We conclude that force-production is reduced in the presence of SCs in the morning but not the afternoon, suggesting that SCs may have a time-of-day influence over contractile-function.

Keywords:  contractile injury; contractility; eccentric contractions; molecular clocks; muscle stem cells

DOI:  https://doi.org/10.1152/ajpcell.00157.2024
bioRxiv. 2024 Mar 27. pii: 2024.03.26.586857. [Epub ahead of print]

The 24-Hour Time Course of Integrated Molecular Responses to Resistance Exercise in Human Skeletal Muscle Implicates MYC as a Hypertrophic Regulator That is Sufficient for Growth.

Sebastian Edman, Ronald G Jones, Paulo R Jannig, Rodrigo Fernandez-Gonzalo, Jessica Norrbom, Nicholas T Thomas, Sabin Khadgi, Pieter Jan Koopmans, Francielly Morena, Calvin S Peterson, Logan N Scott, Nicholas P Greene, Vandre C Figueiredo, Christopher S Fry, Liu Zhengye, Johanna T Lanner, Yuan Wen, Björn Alkner, Kevin A Murach, Ferdinand von Walden.

Molecular control of recovery after exercise in muscle is temporally dynamic. A time course of biopsies around resistance exercise (RE) combined with -omics is necessary to better comprehend the molecular contributions of skeletal muscle adaptation in humans. Vastus lateralis biopsies before and 30 minutes, 3-, 8-, and 24-hours after acute RE were collected. A time-point matched biopsy-only group was also included. RNA-sequencing defined the transcriptome while DNA methylomics and computational approaches complemented these data. The post-RE time course revealed: 1) DNA methylome responses at 30 minutes corresponded to upregulated genes at 3 hours, 2) a burst of translation- and transcription-initiation factor-coding transcripts occurred between 3 and 8 hours, 3) global gene expression peaked at 8 hours, 4) ribosome-related genes dominated the mRNA landscape between 8 and 24 hours, 5) methylation-regulated MYC was a highly influential transcription factor throughout the 24-hour recovery and played a primary role in ribosome-related mRNA levels between 8 and 24 hours. The influence of MYC in human muscle adaptation was strengthened by transcriptome information from acute MYC overexpression in mouse muscle. To test whether MYC was sufficient for hypertrophy, we generated a muscle fiber-specific doxycycline inducible model of pulsatile MYC induction. Periodic 48-hour pulses of MYC over 4 weeks resulted in higher muscle mass and fiber size in the soleus of adult female mice. Collectively, we present a temporally resolved resource for understanding molecular adaptations to RE in muscle and reveal MYC as a regulator of RE-induced mRNA levels and hypertrophy.

DOI: https://doi.org/10.1101/2024.03.26.586857
Dis Model Mech. 2024 Apr 11. pii: dmm.050502. [Epub ahead of print]

The BALB/c.mdx62 mouse exhibits a dystrophic muscle pathology and is a novel model of Duchenne muscular dystrophy.

Kristy Swiderski, Audrey S Chan, Marco J Herold, Andrew J Kueh, Jin D Chung, Justin P Hardee, Jennifer Trieu, Annabel Chee, Timur Naim, Paul Gregorevic, Gordon S Lynch.

  Duchenne muscular dystrophy (DMD) is a devastating monogenic skeletal muscle wasting disorder. While many pharmacological and genetic interventions have been reported in preclinical studies, few have progressed to clinical trials with meaningful benefit. Identifying therapeutic potential may be limited by availability of suitable preclinical mouse models. More rigorous testing across models with varied background strains and mutations may identify treatments for clinical success. Here we report the generation of a DMD mouse model, with a CRISPR-induced deletion within exon 62 of the Dmd gene, and the first generated in BALB/c mice. Analysis of mice at 3, 6, and 12 months of age confirmed loss of Dp427 protein expression and resultant dystrophic pathology in limb muscles and the diaphragm, with evidence of centrally nucleated fibers, increased inflammatory markers and fibrosis, progressive decline in muscle function, and compromised trabecular bone development. The C.mdx62 mouse is a novel model of DMD with associated variations in the immune response and muscle phenotype, compared with existing models. It represents an important addition to the preclinical model toolbox for developing therapeutic strategies.

Keywords:  Bone; Genetic modifier; Muscular dystrophy; Pathophysiology; Preclinical; Skeletal muscle

DOI:  https://doi.org/10.1242/dmm.050502
Gen Comp Endocrinol. 2024 Apr 09. pii: S0016-6480(24)00073-X. [Epub ahead of print] 114513

The Role of TGF-β Signaling in Muscle Atrophy, Sarcopenia and Cancer Cachexia.

Xin-Qiang Lan, Cheng-Jie Deng, Qi-Quan Wang, Li-Min Zhao, Bao-Wei Jiao, Yang Xiang.

  Skeletal muscle, comprising a significant proportion (40 to 50 percent) of total body weight in humans, plays a critical role in maintaining normal physiological conditions. Muscle atrophy occurs when the rate of protein degradation exceeds protein synthesis. Sarcopenia refers to age-related muscle atrophy, while cachexia represents a more complex form of muscle wasting associated with various diseases such as cancer, heart failure, and AIDS. Recent research has highlighted the involvement of signaling pathways, including IGF1-Akt-mTOR, MuRF1-MAFbx, and FOXO, in regulating the delicate balance between muscle protein synthesis and breakdown. Myostatin, a member of the TGF-β superfamily, negatively regulates muscle growth and promotes muscle atrophy by activating Smad2 and Smad3. It also interacts with other signaling pathways in cachexia and sarcopenia. Inhibition of myostatin has emerged as a promising therapeutic approach for sarcopenia and cachexia. Additionally, other TGF-β family members, such as TGF-β1, activin A, and GDF11, have been implicated in the regulation of skeletal muscle mass. Furthermore, myostatin cooperates with these family members to impair muscle differentiation and contribute to muscle loss. This review provides an overview of the significance of myostatin and other TGF-β signaling pathway members in muscular dystrophy, sarcopenia, and cachexia. It also discusses potential novel therapeutic strategies targeting myostatin and TGF-β signaling for the treatment of muscle atrophy.

Keywords:  TGF-β; cancer cachexia; muscle atrophy; myostatin; sarcopenia

DOI:  https://doi.org/10.1016/j.ygcen.2024.114513
Res Sq. 2024 Mar 28. pii: rs.3.rs-4108866. [Epub ahead of print]

Temporal Single-Cell Sequencing Analysis Reveals That GPNMB-Expressing Macrophages Potentiate Muscle Regeneration.

Yu-Fan Chen.

Macrophages play a crucial role in coordinating the skeletal muscle repair response, but their phenotypic diversity and the transition of specialized subsets to resolution-phase macrophages remain poorly understood. To address this issue, we induced injury and performed single-cell RNA sequencing on individual cells in skeletal muscle at different time points. Our analysis revealed a distinct macrophage subset that expressed high levels of Gpnmb and that coexpressed critical factors involved in macrophage-mediated muscle regeneration, including Igf1, Mertk , and Nr1h3 . Gpnmb gene knockout inhibited macrophage-mediated efferocytosis and impaired skeletal muscle regeneration. Functional studies demonstrated that GPNMB acts directly on muscle cells in vitro and improves muscle regeneration in vivo . These findings provide a comprehensive transcriptomic atlas of macrophages during muscle injury, highlighting the key role of the GPNMB macrophage subset in regenerative processes. Targeting GPNMB signaling in macrophages could have therapeutic potential for restoring skeletal muscle integrity and homeostasis.

DOI: https://doi.org/10.21203/rs.3.rs-4108866/v1
Aging Dis. 2024 Mar 25.

Life-Long Aerobic Exercise is a Non-Pharmacological Approach for Inducing Autophagy and Delaying Muscle Atrophy in the Aging Population.

Mingwei Wang, Xiangzhi Wu, Yuyao Jiao, Wenli Yin, Lili Zhang.

Numerous bodily processes deteriorate with age, chief among them being the loss of muscle mass and function. The condition referred to as aging myasthenia gravis impairs older persons' quality of life and is linked to a higher risk of several chronic illnesses. An increasing number of studies conducted in the last several years has demonstrated that moderate exercise can halt this process. Specifically, by promoting autophagy, aerobic exercise helps to postpone the onset of senile myasthenia gravis. In this work, we will explore how aerobic exercise modulates autophagy to prevent muscle aging and examine the most recent findings in this area of study. We discovered that exercise-induced autophagy can effectively balance protein degradation and relieve skeletal muscle atrophy by looking through pertinent literature. Aerobic exercise has a direct impact on autophagy, but it can also delay the onset of senile myasthenia gravis by enhancing blood flow, lowering inflammation, and boosting muscle oxidative capacity. In order to postpone the onset of senile myasthenia gravis, research on the mechanism of action of aerobic exercise in inducing autophagy will be discussed in detail in this study.

DOI: https://doi.org/10.14336/AD.2024.0318
Brain. 2024 Apr 08. pii: awae107. [Epub ahead of print]

GDF5 as a rejuvenating treatment for age-related neuromuscular failure.

Traoré Massiré, Noviello Chiara, Vergnol Amélie, Gentil Christel, Halliez Marius, Saillard Lucile, Gelin Maxime, Forand Anne, Lemaitre Mégane, Guesmia Zoheir, Cadot Bruno, Caldas Eriky, Marty Benjamin, Mougenot Nathalie, Messéant Julien, Strochlic Laure, Sadoine Jeremy, Slimani Lofti, Jolly Ariane, De la Grange Pierre, Hogrel Jean-Yves, Pietri-Rouxel France, Falcone Sestina.

  Sarcopenia involves a progressive loss of skeletal muscle force, quality and mass during ageing, which results in increased inability and death; however, no cure has been established thus far. Growth differentiation factor 5 (GDF5) has been described to modulate muscle mass maintenance in various contexts. For our proof of concept, we overexpressed GDF5 by AAV vector injection in Tibialis Anterior (TA) muscle of adult aged (20 months) mice and performed molecular and functional analysis of skeletal muscle. We analysed human Vastus Lateralis muscle biopsies from adult young (21-42 years) and aged (77-80 years) donors, quantifying the molecular markers modified by GDF5 overexpression (OE) in mouse muscle. We validated the major effects of GDF5 overexpression using human immortalized myotubes and Schwann Cells (SCs). We established a pre-clinical study by treating chronically (for 4 months) aged mice using recombinant GDF5 protein (rGDF5) in systemic administration and evaluated the long-term effect of this treatment on muscle mass and function. Here, we demonstrated that GDF5 OE in the old TAs promoted an increase of 16.5% of muscle weight (P = 0.0471) associated with a higher percentage of 5000-6000 µm2 large fibres (P = 0.0211), without the induction of muscle regeneration. Muscle mass gain was associated with an amelioration of 26.8% of rate of force generation (P = 0.0330) and a better neuromuscular connectivity (P = 0.0098). Moreover, GDF5 OE preserved neuromuscular junction (NMJ) morphology (38.5% of nerve terminal area increase, P < 0.0001) and stimulated the expression of re-innervation-related genes, in particular markers of SCs (fold change 3.19 for S100b gene expression, P = 0.0101). To further characterize the molecular events induced by GDF5 OE during ageing, we performed a genome-wide transcriptomic analysis of treated muscles and showed that this factor leads to a "rejuvenating" transcriptomic signature in aged mice, as 42% of the transcripts dysregulated by ageing reverted to youthful expression levels upon GDF5 OE (P < 0.05). Towards a pre-clinical approach, we performed a long-term systemic treatment using rGDF5 and showed its effectiveness in counteracting age-related muscle wasting, improving muscle function (17,8% of absolute maximal force increase, P = 0.0079), ensuring neuromuscular connectivity and preventing NMJ degeneration (7,96% of AchR area increase, P = 0.0125). In addition, in human muscle biopsies, we found the same age-related alterations than those observed in mice and improved by GDF5 and reproduced its major effects on human cells, suggesting this treatment as efficient in humans. Overall, these data provide a foundation to examine the curative potential of GDF5 drug in clinical trials for sarcopenia and, eventually, other neuromuscular diseases.

Keywords:  endplate; musculature; therapy

DOI:  https://doi.org/10.1093/brain/awae107
Physiol Rep. 2024 Apr;12(7): e15991

Intramuscular injection of mesenchymal stem cells augments basal muscle protein synthesis after bouts of resistance exercise in male mice.

Junya Takegaki, Kohei Sase, Yusuke Kono, Takuya Fujita, Satoshi Konishi, Satoshi Fujita.

  Skeletal muscle mass is critical for activities of daily living. Resistance training maintains or increases muscle mass, and various strategies maximize the training adaptation. Mesenchymal stem cells (MSCs) are multipotent cells with differential potency in skeletal muscle cells and the capacity to secrete growth factors. However, little is known regarding the effect of intramuscular injection of MSCs on basal muscle protein synthesis and catabolic systems after resistance training. Here, we measured changes in basal muscle protein synthesis, the ubiquitin-proteasome system, and autophagy-lysosome system-related factors after bouts of resistance exercise by intramuscular injection of MSCs. Mice performed three bouts of resistance exercise (each consisting of 50 maximal isometric contractions elicited by electrical stimulation) on the right gastrocnemius muscle every 48 h, and immediately after the first bout, mice were intramuscularly injected with either MSCs (2.0 × 106 cells) labeled with green fluorescence protein (GFP) or vehicle only placebo. Seventy-two hours after the third exercise bout, GFP was detected only in the muscle injected with MSCs with concomitant elevation of muscle protein synthesis. The injection of MSCs also increased protein ubiquitination. These results suggest that the intramuscular injection of MSCs augmented muscle protein turnover at the basal state after consecutive resistance exercise.

Keywords:  insulin‐like growth factor 1; mesenchymal stem cells; muscle protein synthesis; protein ubiquitination; resistance exercise

DOI:  https://doi.org/10.14814/phy2.15991
Biomaterials. 2024 Mar 29. pii: S0142-9612(24)00085-1. [Epub ahead of print]308 122551

Matrix mechanics regulates muscle regeneration by modulating kinesin-1 activity.

Wan-Yu Chiang, Helen Wenshin Yu, Ming-Chung Wu, Yi-Man Huang, Yin-Quan Chen, Jong-Wei Lin, Yen-Wenn Liu, Li-Ru You, Arthur Chiou, Jean-Cheng Kuo.

  Sarcopenia, a prevalent muscle disease characterized by muscle mass and strength reduction, is associated with impaired skeletal muscle regeneration. However, the influence of the biomechanical properties of sarcopenic skeletal muscle on the efficiency of the myogenic program remains unclear. Herein, we established a mouse model of sarcopenia and observed a reduction in stiffness within the sarcopenic skeletal muscle in vivo. To investigate whether the biomechanical properties of skeletal muscle directly impact the myogenic program, we established an in vitro system to explore the intrinsic mechanism involving matrix stiffness control of myogenic differentiation. Our findings identify the microtubule motor protein, kinesin-1, as a mechano-transduction hub that senses and responds to matrix stiffness, crucial for myogenic differentiation and muscle regeneration. Specifically, kinesin-1 activity is positively regulated by stiff matrices, facilitating its role in transporting mitochondria and enhancing translocation of the glucose transporter GLUT4 to the cell surface for glucose uptake. Conversely, the softer matrices significantly suppress kinesin-1 activity, leading to the accumulation of mitochondria around nuclei and hindering glucose uptake by inhibiting GLUT4 membrane translocation, consequently impairing myogenic differentiation. The insights gained from the in-vitro system highlight the mechano-transduction significance of kinesin-1 motor proteins in myogenic differentiation. Furthermore, our study confirms that enhancing kinesin-1 activity in the sarcopenic mouse model restores satellite cell expansion, myogenic differentiation, and muscle regeneration. Taken together, our findings provide a potential target for improving muscle regeneration in sarcopenia.

Keywords:  Kinesin-1; Matrix stiffness; Muscle regeneration; Sarcopenia

DOI:  https://doi.org/10.1016/j.biomaterials.2024.122551
Front Pharmacol. 2024 ;15 1360099

Endurance exercise has a negative impact on the onset of SOD1-G93A ALS in female mice and affects the entire skeletal muscle-motor neuron axis.

Silvia Scaricamazza, Valentina Nesci, Illari Salvatori, Gianmarco Fenili, Marco Rosina, Michela Gloriani, Maria Paola Paronetto, Luca Madaro, Alberto Ferri, Cristiana Valle.

  Background: Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disease characterized by the degeneration of motor neurons that leads to muscle wasting and atrophy. Epidemiological and experimental evidence suggests a causal relationship between ALS and physical activity (PA). However, the impact of PA on motor neuron loss and sarcopenia is still debated, probably because of the heterogeneity and intensities of the proposed exercises. With this study, we aimed to clarify the effect of intense endurance exercise on the onset and progression of ALS in the SOD1-G93A mouse model.Methods: We randomly selected four groups of twelve 35-day-old female mice. SOD1-G93A and WT mice underwent intense endurance training on a motorized treadmill for 8 weeks, 5 days a week. During the training, we measured muscle strength, weight, and motor skills and compared them with the corresponding sedentary groups to define the disease onset. At the end of the eighth week, we analyzed the skeletal muscle-motor neuron axis by histological and molecular techniques.
Results: Intense endurance exercise anticipates the onset of the disease by 1 week (age of the onset: trained SOD1-G93A = 63.17 ± 2.25 days old; sedentary SOD1-G93A = 70.75 ± 2.45 days old). In SOD1-G93A mice, intense endurance exercise hastens the muscular switch to a more oxidative phenotype and worsens the denervation process by dismantling neuromuscular junctions in the tibialis anterior, enhancing the Wallerian degeneration in the sciatic nerve, and promoting motor neuron loss in the spinal cord. The training exacerbates neuroinflammation, causing immune cell infiltration in the sciatic nerve and a faster activation of astrocytes and microglia in the spinal cord.
Conclusion: Intense endurance exercise, acting on skeletal muscles, worsens the pathological hallmarks of ALS, such as denervation and neuroinflammation, brings the onset forward, and accelerates the progression of the disease. Our findings show the potentiality of skeletal muscle as a target for both prognostic and therapeutic strategies; the preservation of skeletal muscle health by specific intervention could counteract the dying-back process and protect motor neurons from death. The physiological characteristics and accessibility of skeletal muscle further enhance its appeal as a therapeutic target.

Keywords:  SOD1-G93A mice; amyotrophic lateral sclerosis; endurance exercise; neurodegeneration; neuroinflammation; physical activity

DOI:  https://doi.org/10.3389/fphar.2024.1360099
Biochem Biophys Rep. 2024 Jul;38 101699

Effect of exercise-induced Neutrophil maturation on skeletal muscle repair in vitro.

Jae Yeon Park, Tae Yeon Kim, Song Won Woo, Hyo Youl Moon.

  Neutrophils as first line defender initiate a cascade of healing process immediately after muscle injury. At muscle injury site, neutrophils remove damaged muscle fibers and recruit other immune cells and these functions show in mature neutrophils. In the previous study, physical exercise can mediate neutrophils' functional changes such as phagocytosis and chemotaxis, though there is no research on how exercise-induced neutrophils contribute the muscle regeneration. In this present study, we investigated the maturation of neutrophils after 4 weeks of mouse treadmill exercise and assessed wound healing assay to evaluate whether treatment with exercise-activated neutrophils is effective for skeletal muscle repair in vitro. In the exercise group, significantly higher mRNA levels of maturation markers compared to the sedentary group and exercise-activated neutrophils improved wound healing of mouse muscle cells. To confirm at the human cell level, based on the well-known fact that exercise increases circulating cortisol levels, neutrophil-like cells were treated with dexamethasone (dHL60 + dex) as exercise mimetics. dHL60 + dex had significantly higher mRNA levels of neutrophil maturation marker and improved wound healing of human skeletal muscle cells compared to the control. These findings suggest that exercise affects neutrophil maturation and that exercise-induced neutrophils contribute to skeletal muscle repair in vitro.

Keywords:  Exercise; Maturation; Muscle regeneration; Neutrophil; Skeletal muscle repair; Wound healing

DOI:  https://doi.org/10.1016/j.bbrep.2024.101699
Cells. 2024 Mar 26. pii: 574. [Epub ahead of print]13(7):

Mitochondria and Reactive Oxygen Species: The Therapeutic Balance of Powers for Duchenne Muscular Dystrophy.

Silvia Rosanna Casati, Davide Cervia, Paulina Roux-Biejat, Claudia Moscheni, Cristiana Perrotta, Clara De Palma.

  Duchenne muscular dystrophy (DMD) is a genetic progressive muscle-wasting disorder that leads to rapid loss of mobility and premature death. The absence of functional dystrophin in DMD patients reduces sarcolemma stiffness and increases contraction damage, triggering a cascade of events leading to muscle cell degeneration, chronic inflammation, and deposition of fibrotic and adipose tissue. Efforts in the last decade have led to the clinical approval of novel drugs for DMD that aim to restore dystrophin function. However, combination therapies able to restore dystrophin expression and target the myriad of cellular events found impaired in dystrophic muscle are desirable. Muscles are higher energy consumers susceptible to mitochondrial defects. Mitochondria generate a significant source of reactive oxygen species (ROS), and they are, in turn, sensitive to proper redox balance. In both DMD patients and animal models there is compelling evidence that mitochondrial impairments have a key role in the failure of energy homeostasis. Here, we highlighted the main aspects of mitochondrial dysfunction and oxidative stress in DMD and discussed the recent findings linked to mitochondria/ROS-targeted molecules as a therapeutic approach. In this respect, dual targeting of both mitochondria and redox homeostasis emerges as a potential clinical option in DMD.

Keywords:  DMD therapies; Duchenne muscular dystrophy; antioxidant defense; mitochondria; mitophagy; oxidative stress; redox homeostasis; skeletal muscle

DOI:  https://doi.org/10.3390/cells13070574
Mol Cell Biochem. 2024 Apr 06.

Irisin alters D-galactose-induced apoptosis by increasing caveolin-1 expression in C2C12 myoblasts and skeletal muscle fibroblasts.

Yaoxuan Wu, Yongxin Wu, Jing Yu, Yingxiao Zhang, Xin Dai, Jinliang Chen, Yue Sun, Yongxue Yang, Kexiang Zhao, Qian Xiao.

  Muscle atrophy and skeletal muscle fibrosis are significant pathological manifestations of primary sarcopenia. The regulation of C2C12 myoblast and skeletal muscle fibroblast apoptosis is associated with these pathological changes. Previous studies have indicated that irisin, the cleaved form of fibronectin type III domain-containing protein 5 (FNDC5), can alleviate primary sarcopenia. However, the mechanisms of the effect of irisin in age-related apoptosis remain unknown. Our present research aimed to explore the effect of irisin and the underlying mechanism of D-galactose (D-gal)-induced apoptosis in skeletal muscle fibroblasts and C2C12 myoblasts. We found the opposite effects of D-gal on C2C12 myoblasts and fibroblasts. We also found that irisin suppressed C2C12 cell apoptosis and promoted fibroblast apoptosis. Mechanistically, irisin altered D-gal-induced apoptosis by increasing caveolin-1 expression. Taken together, these findings further demonstrated that irisin is a potential agent that can treat aged-relative muscle atrophy and fibrosis.

Keywords:  Apoptosis; C2C12; Fibroblast; Irisin; Sarcopenia

DOI:  https://doi.org/10.1007/s11010-024-04990-6
Exp Gerontol. 2024 Apr 11. pii: S0531-5565(24)00070-6. [Epub ahead of print]190 112428

PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway.

Yimin Fu, Lei Tao, Xiaojun Wang, Binyou Wang, Weilin Qin, Lei Song.

  BACKGROUND: Mitochondrial dysregulation in skeletal myocytes is considered a major factor in aged sarcopenia. In this study, we aimed to study the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on Sestrin2-mediated mechanistic target of rapamycin complex 1 (mTORC1) in aged skeletal muscles.METHODS: C2C12 myoblasts were stimulated by 50 μM 7β-hydroxycholesterol (7β-OHC) to observe the changes of DNA damage, mitochondrial membrane potential (Δψm), mitochondrial ROS and PGC-1α protein. The PGC-1α silence in the C2C12 cells was established by siRNA transfection. The levels of DNA damage, Δψm, mitochondrial ROS, Sestrin2 and p-S6K1/S6K1 proteins were observed after the PGC-1α silence in the C2C12 cells. Recombinant Sestrin2 treatment was used to observe the changes of DNA damage, Δψm, mitochondrial ROS and p-S6K1/S6K1 protein in the 7β-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. Wild-type (WT) mice and muscle-specific PGC-1α conditional knockout (MKO) mice, including young and old, were used to analyse the effects of PGC-1α on muscle function and the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles. Recombinant Sestrin2 was administrated to analyse its effects on muscle function in the old WT mice and old MKO mice.
RESULTS: 7β-OHC treatment induced DNA damage, mitochondrial dysfunction and decrease of PGC-1α protein in the C2C12 cells. PGC-1α silence also induced DNA damage and mitochondrial dysfunction in the C2C12 cells. Additionally, PGC-1α silence or 7β-OHC treatment decreased the levels of Sestrin2 and p-S6K1/S6K1 protein in the C2C12 cells. Recombinant Sestrin2 treatment significantly improved the DNA damage and mitochondrial dysfunction in the 7β-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia and decreased the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles when compared to the WT mice. Recombinant Sestrin2 treatment improved muscle function and increased p-S6K1 levels in the old two genotypes.
CONCLUSION: This research demonstrates that PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway.

Keywords:  7β-hydroxycholesterol; Mitochondrial dysregulation; Muscle function; PGC-1α conditional knockout

DOI:  https://doi.org/10.1016/j.exger.2024.112428
Am J Physiol Cell Physiol. 2024 Apr 01. 326(4): C1193-C1202

Dispase/collagenase cocktail allows for coisolation of satellite cells and fibroadipogenic progenitors from human skeletal muscle.

Alis Balayan, Marie DeBoutray, Thomas G Molley, Severin Ruoss, Matthew Maceda, Ashley Sevier, Catherine M Robertson, Samuel R Ward, Adam J Engler.

  Satellite cells (SCs) and fibroadipogenic progenitors (FAPs) are progenitor populations found in muscle that form new myofibers postinjury. Muscle development, regeneration, and tissue-engineering experiments require robust progenitor populations, yet their isolation and expansion are difficult given their scarcity in muscle, limited muscle biopsy sizes in humans, and lack of methodological detail in the literature. Here, we investigated whether a dispase and collagenase type 1 and 2 cocktail could allow dual isolation of SCs and FAPs, enabling significantly increased yield from human skeletal muscle. Postdissociation, we found that single cells could be sorted into CD56 + CD31-CD45- (SC) and CD56-CD31-CD45- (FAP) cell populations, expanded in culture, and characterized for lineage-specific marker expression and differentiation capacity; we obtained ∼10% SCs and ∼40% FAPs, with yields twofold better than what is reported in current literature. SCs were PAX7+ and retained CD56 expression and myogenic fusion potential after multiple passages, expanding up to 1012 cells. Conversely, FAPs expressed CD140a and differentiated into either fibroblasts or adipocytes upon induction. This study demonstrates robust isolation of both SCs and FAPs from the same muscle sample with SC recovery more than two times higher than previously reported, which could enable translational studies for muscle injuries.NEW & NOTEWORTHY We demonstrated that a dispase/collagenase cocktail allows for simultaneous isolation of SCs and FAPs with 2× higher SC yield compared with other studies. We provide a thorough characterization of SC and FAP in vitro expansion that other studies have not reported. Following our dissociation, SCs and FAPs were able to expand by up to 1012 cells before reaching senescence and maintained differentiation capacity in vitro demonstrating their efficacy for clinical translation for muscle injury.

Keywords:  coisolation; fibroadipogenic progenitors; human skeletal muscle; satellite cells

DOI:  https://doi.org/10.1152/ajpcell.00023.2024
bioRxiv. 2023 Jun 24. pii: 2023.06.22.545964. [Epub ahead of print]

Collagen type VI regulates TGFβ bioavailability in skeletal muscle.

Payam Mohassel, Jachinta Rooney, Yaqun Zou, Kory Johnson, Gina Norato, Hailey Hearn, Matthew A Nalls, Pomi Yun, Tracy Ogata, Sarah Silverstein, David A Sleboda, Thomas J Roberts, Daniel B Rifkin, Carsten G Bönnemann.

Collagen VI-related disorders ( COL6 -RDs) are a group of rare muscular dystrophies caused by pathogenic variants in collagen VI genes ( COL6A1, COL6A2, and COL6A3 ). Collagen type VI is a heterotrimeric, microfibrillar component of the muscle extracellular matrix (ECM), predominantly secreted by resident fibroadipogenic precursor cells in skeletal muscle. The absence or mislocalizatoion of collagen VI in the ECM underlies the non-cell autonomous dysfunction and dystrophic changes in skeletal muscle with an as of yet elusive direct mechanistic link between the ECM and myofiber dysfunction. Here, we conduct a comprehensive natural history and outcome study in a novel mouse model of COL6 -RDs ( Col6a2 -/- mice) using standardized (Treat-NMD) functional, histological, and physiologic parameter. Notably, we identify a conspicuous dysregulation of the TGFβ pathway early in the disease process and propose that the collagen VI deficient matrix is not capable of regulating the dynamic TGFβ bioavailability at baseline and also in response to muscle injury. Thus, we propose a new mechanism for pathogenesis of the disease that links the ECM regulation of TGFβ with downstream skeletal muscle abnormalities, paving the way for developing and validating therapeutics that target this pathway.

DOI: https://doi.org/10.1101/2023.06.22.545964
Biochem J. 2024 Apr 09. pii: BCJ20230458. [Epub ahead of print]

Expression of nNOS alpha and beta isoforms in skeletal muscle of mice.

Oliver Baum.

  Knowledge of the primary structure of neuronal NO synthase (nNOS) in skeletal muscle is still conflicting and needs further clarification. To elucidate the expression patterns of nNOS isoforms at both mRNA and protein level, systematic RT-PCR and epitope mapping by qualitative immunoblot analysis on skeletal muscle of C57/BL6 mice were performed. The ability of the nNOS isoforms to form aggregates was characterized by native low-temperature polyacrylamide electrophoresis (LT-PAGE). The molecular analysis was focused on the rectus femoris (RF) muscle, a skeletal muscle with a nearly balanced ratio of nNOS alpha- and beta-isoforms. RT-PCR amplificates from RF muscles showed exclusive exon-1d mRNA expression, either with or without exon-mu. Epitope mapping demonstrated the simultaneous expression of the nNOS splice variants alpha/mu, alpha/non-mu, beta/mu and beta/non-mu. Furthermore, immunoblotting suggests that the transition between nNOS alpha- and beta-isoforms lies within exon-3. In LT-PAGE, three protein nNOS associated aggregates iwere detected in homogenates of RF muscle and tibialis anterior muscle: a 320 kDa band containing nNOS alpha-isoforms, while 250 kDa and 300 kDa bands consist of nNOS beta-isoforms that form homodimers or heterodimers with non-nNOS proteins.

Keywords:  gene expression and regulation; nitric oxide synthases; skeletal muscle

DOI:  https://doi.org/10.1042/BCJ20230458
Int J Mol Sci. 2024 Apr 04. pii: 4017. [Epub ahead of print]25(7):

Skeletal Muscle Heat Shock Protein Content and the Repeated Bout Effect.

Marius Locke, Giovanni Bruccoleri.

  The "Repeated Bout Effect" (RBE) occurs when a skeletal muscle is preconditioned with a few lengthening contractions (LC) prior to exposing the muscle to a greater number of LC. The preconditioning (PC) results in significantly less damage and preservation of force. Since it takes only a few LC to increase muscle heat shock protein (HSP) content, it was of interest to examine the relationship between HSPs and the RBE. To do this, one tibialis anterior (TA) muscle from Sprague-Dawley rats (n = 5/group) was preconditioned with either 0, 5, or 15 lengthening contractions (LC) and exposed to a treatment of 60 LC 48 h later. Preconditioning TA muscles with 15 LC, but not 5 LC, significantly elevated muscle αB-crystallin (p < 0.05), HSP25 (p < 0.05), and HSP72 content (p < 0.001). These preconditioned TA muscles also showed a significantly (p < 0.05) reduced loss of active torque throughout the subsequent 60 LC. While there was a trend for all preconditioned muscles to maintain higher peak torque levels throughout the 60 LC, no significant differences were detected between the groups. Morphologically, preconditioned muscles appeared to show less discernible muscle fiber damage. In conclusion, an elevated skeletal muscle HSP content from preconditioning may contribute to the RBE.

Keywords:  heat shock proteins; lengthening contractions; rodent; skeletal muscle damage; tibialis anterior

DOI:  https://doi.org/10.3390/ijms25074017
Cells. 2024 Mar 29. pii: 596. [Epub ahead of print]13(7):

Challenges and Considerations of Preclinical Development for iPSC-Based Myogenic Cell Therapy.

Congshan Sun, Carlo Serra, Brianna Harley Kalicharan, Jeffrey Harding, Mahendra Rao.

  Cell therapies derived from induced pluripotent stem cells (iPSCs) offer a promising avenue in the field of regenerative medicine due to iPSCs' expandability, immune compatibility, and pluripotent potential. An increasing number of preclinical and clinical trials have been carried out, exploring the application of iPSC-based therapies for challenging diseases, such as muscular dystrophies. The unique syncytial nature of skeletal muscle allows stem/progenitor cells to integrate, forming new myonuclei and restoring the expression of genes affected by myopathies. This characteristic makes genome-editing techniques especially attractive in these therapies. With genetic modification and iPSC lineage specification methodologies, immune-compatible healthy iPSC-derived muscle cells can be manufactured to reverse the progression of muscle diseases or facilitate tissue regeneration. Despite this exciting advancement, much of the development of iPSC-based therapies for muscle diseases and tissue regeneration is limited to academic settings, with no successful clinical translation reported. The unknown differentiation process in vivo, potential tumorigenicity, and epigenetic abnormality of transplanted cells are preventing their clinical application. In this review, we give an overview on preclinical development of iPSC-derived myogenic cell transplantation therapies including processes related to iPSC-derived myogenic cells such as differentiation, scaling-up, delivery, and cGMP compliance. And we discuss the potential challenges of each step of clinical translation. Additionally, preclinical model systems for testing myogenic cells intended for clinical applications are described.

Keywords:  disease models; genetic modification; iPSC; muscular dystrophy; preclinical studies; stem cell therapy

DOI:  https://doi.org/10.3390/cells13070596
FASEB J. 2024 Apr 15. 38(7): e23534

Islr regulates satellite cells asymmetric division through the SPARC/p-ERK1/2 signaling pathway.

Fan Liu, Yuxin Cao, Xiong Wang, Kuo Zhang, Na Li, Yang Su, Yali Zhang, Qingyong Meng.

Satellite cells (SCs) are adult muscle stem cells responsible for muscle regeneration after acute and chronic muscle injuries. The balance between stem cell self-renewal and differentiation determines the kinetics and efficiency of skeletal muscle regeneration. This study assessed the function of Islr in SC asymmetric division. The deletion of Islr reduced muscle regeneration in adult mice by decreasing the SC pool. Islr is pivotal for SC proliferation, and its deletion promoted the asymmetric division of SCs. A mechanistic search revealed that Islr bound to and degraded secreted protein acidic and rich in cysteine (SPARC), which activated p-ERK1/2 signaling required for asymmetric division. These findings demonstrate that Islr is a key regulator of SC division through the SPARC/p-ERK1/2 signaling pathway. These data provide a basis for treating myopathy.

DOI: https://doi.org/10.1096/fj.202302614R
Biomed Pharmacother. 2024 Apr 06. pii: S0753-3322(24)00447-5. [Epub ahead of print]174 116563

Regulation of myogenic cell proliferation and differentiation during mammalian skeletal myogenesis.

Jiyao Wu, Binglin Yue.

  Mammalian skeletal myogenesis is a complex process that allows precise control of myogenic cells' proliferation, differentiation, and fusion to form multinucleated, contractile, and functional muscle fibers. Typically, myogenic progenitors continue growth and division until acquiring a differentiated state, which then permanently leaves the cell cycle and enters terminal differentiation. These processes have been intensively studied using the skeletal muscle developing models in vitro and in vivo, uncovering a complex cellular intrinsic network during mammalian skeletal myogenesis containing transcription factors, translation factors, extracellular matrix, metabolites, and mechano-sensors. Examining the events and how they are knitted together will better understand skeletal myogenesis's molecular basis. This review describes various regulatory mechanisms and recent advances in myogenic cell proliferation and differentiation during mammalian skeletal myogenesis. We focus on significant cell cycle regulators, myogenic factors, and chromatin regulators impacting the coordination of the cell proliferation versus differentiation decision, which will better clarify the complex signaling underlying skeletal myogenesis.

Keywords:  Cell cycle; Cell differentiation; Cell proliferation; Epigenetic modifications; Skeletal myogenesis; Transcription factor

DOI:  https://doi.org/10.1016/j.biopha.2024.116563
Matrix Biol. 2024 Apr 04. pii: S0945-053X(24)00051-9. [Epub ahead of print]

The extracellular matrix differentially directs myoblast motility and differentiation in distinct forms of muscular dystrophy: Dystrophic matrices alter myoblast motility.

Ashlee M Long, Jason M Kwon, GaHyun Lee, Nina L Reiser, Lauren A Vaught, Joseph G O'Brien, Patrick G T Page, Michele Hadhazy, Joseph C Reynolds, Rachelle H Crosbie, Alexis R Demonbreun, Elizabeth M McNally.

  Extracellular matrix (ECM) pathologic remodeling underlies many disorders, including muscular dystrophy. Tissue decellularization removes cellular components while leaving behind ECM components. We generated "on-slide" decellularized tissue slices from genetically distinct dystrophic mouse models. The ECM of dystrophin- and sarcoglycan-deficient muscles had marked thrombospondin 4 deposition, while dysferlin-deficient muscle had excess decorin. Annexins A2 and A6 were present on all dystrophic decellularized ECMs, but annexin matrix deposition was excessive in dysferlin-deficient muscular dystrophy. Muscle-directed viral expression of annexin A6 resulted in annexin A6 in the ECM. C2C12 myoblasts seeded onto decellularized matrices displayed differential myoblast mobility and fusion. Dystrophin-deficient decellularized matrices inhibited myoblast mobility, while dysferlin-deficient decellularized matrices enhanced myoblast movement and differentiation. Myoblasts treated with recombinant annexin A6 increased mobility and fusion like that seen on dysferlin-deficient decellularized matrix and demonstrated upregulation of ECM and muscle cell differentiation genes. These findings demonstrate specific fibrotic signatures elicit effects on myoblast activity.

Keywords:  Duchenne muscular dystrophy; Extracellular matrix; Limb Girdle muscular dystrophy; annexin; dysferlin; muscle; myoblast

DOI:  https://doi.org/10.1016/j.matbio.2024.04.001
Int J Mol Sci. 2024 Apr 04. pii: 4025. [Epub ahead of print]25(7):

Targeting Mitochondrial Dynamics during Lower-Limb Ischemia Reperfusion in Young and Old Mice: Effect of Mitochondrial Fission Inhibitor-1 (mDivi-1).

Stéphanie Paradis, Anne-Laure Charles, Margherita Giannini, Alain Meyer, Anne Lejay, Samy Talha, Gilles Laverny, Anne Charloux, Bernard Geny.

  Peripheral arterial disease (PAD) strikes more than 200 million people worldwide and has a severe prognosis by potentially leading to limb amputation and/or death, particularly in older patients. Skeletal muscle mitochondrial dysfunctions and oxidative stress play major roles in this disease in relation with ischemia-reperfusion (IR) cycles. Mitochondrial dynamics through impairment of fission-fusion balance may contribute to skeletal muscle pathophysiology, but no data were reported in the setting of lower-limb IR despite the need for new therapeutic options. We, therefore, investigated the potential protective effect of mitochondrial division inhibitor-1 (mDivi-1; 50 mg/kg) in young (23 weeks) and old (83 weeks) mice submitted to two-hour ischemia followed by two-hour reperfusion on systemic lactate, muscle mitochondrial respiration and calcium retention capacity, and on transcripts specific for oxidative stress and mitochondrial dynamics. At the systemic levels, an IR-related increase in circulating lactate was still major despite mDivi-1 use (+305.9% p < 0.0001, and +269.4% p < 0.0001 in young and old mice, respectively). Further, IR-induced skeletal muscle mitochondrial dysfunctions (more severely impaired mitochondrial respiration in old mice (OXPHOS CI state, -68.2% p < 0.0001 and -84.9% p < 0.0001 in 23- and 83-week mice) and reduced calcium retention capacity (-46.1% p < 0.001 and -48.2% p = 0.09, respectively) were not corrected by mDivi-1 preconditioning, whatever the age. Further, mDivi-1 treatment did not oppose superoxide anion production (+71.4% p < 0.0001 and +37.5% p < 0.05, respectively). At the transcript level, markers of antioxidant enzymes (SOD 1, SOD 2, catalase, and GPx) and fission markers (Drp1, Fis) remained unchanged or tended to be decreased in the ischemic leg. Fusion markers such as mitofusin 1 or 2 decreased significantly after IR in both groups. In conclusion, aging enhanced the deleterious effects or IR on muscle mitochondrial respiration, and in this setting of lower-limb IR, mDivi-1 failed to protect the skeletal muscle both in young and old mice.

Keywords:  aging; ischemia reperfusion; lactate; mitochondria; mitochondrial dynamics; muscle; peripheral arterial disease; reactive oxygen species

DOI:  https://doi.org/10.3390/ijms25074025
J Physiol. 2024 Apr 11.

Right place at the right time: Mitochondrial shape, distribution and inter-organelle interaction during skeletal muscle postnatal development.

Itamar C G Jesus, Marcos Eliezeck, Débora L Scheffer.



Keywords:  inter‐organelle interaction; lipid droplet; mitochondria; postnatal development; skeletal muscle

DOI:  https://doi.org/10.1113/JP286517
bioRxiv. 2024 Mar 31. pii: 2024.03.28.586997. [Epub ahead of print]

The human genetic variant rs6190 unveils Foxc1 and Arid5a as novel pro-metabolic targets of the glucocorticoid receptor in muscle.

Ashok Daniel Prabakaran, Hyun-Jy Chung, Kevin McFarland, Thirupugal Govindarajan, Fadoua El Abdellaoui Soussi, Hima Bindu Durumutla, Chiara Villa, Kevin Piczer, Hannah Latimer, Cole Werbrich, Olukunle Akinborewa, Robert Horning, Mattia Quattrocelli.

Genetic variations in the glucocorticoid receptor (GR) gene NR3C1 can impact metabolism. The single nucleotide polymorphism (SNP) rs6190 (p.R23K) has been associated in humans with enhanced metabolic health, but the SNP mechanism of action remains completely unknown. We generated a transgenic knock-in mice genocopying this polymorphism to elucidate how the mutant GR impacts metabolism. Compared to non-mutant littermates, mutant mice showed increased muscle insulin sensitivity and strength on regular chow and high-fat diet, blunting the diet-induced adverse effects on weight gain and exercise intolerance. Overlay of RNA-seq and ChIP-seq profiling in skeletal muscle revealed increased transactivation of Foxc1 and Arid5A genes by the mutant GR. Using adeno-associated viruses for in vivo overexpression in muscle, we found that Foxc1 was sufficient to transcriptionally activate the insulin response pathway genes Insr and Irs1. In parallel, Arid5a was sufficient to transcriptionally repress the lipid uptake genes Cd36 and Fabp4, reducing muscle triacylglycerol accumulation. Collectively, our findings identify a muscle-autonomous epigenetic mechanism of action for the rs6190 SNP effect on metabolic homeostasis, while leveraging a human nuclear receptor coding variant to unveil Foxc1 and Arid5a as novel epigenetic regulators of muscle metabolism.

DOI: https://doi.org/10.1101/2024.03.28.586997
Cell Transplant. 2024 Jan-Dec;33:33 9636897241242624

Optimization of Xenografting Methods for Generating Human Skeletal Muscle in Mice.

Andrea O'Neill, Anna Llach Martinez, Amber L Mueller, Weiliang Huang, Anthony Accorsi, Maureen A Kane, David Eyerman, Robert J Bloch.

  Xenografts of human skeletal muscle generated in mice can be used to study muscle pathology and to test drugs designed to treat myopathies and muscular dystrophies for their efficacy and specificity in human tissue. We previously developed methods to generate mature human skeletal muscles in immunocompromised mice starting with human myogenic precursor cells (hMPCs) from healthy individuals and individuals with facioscapulohumeral muscular dystrophy (FSHD). Here, we examine a series of alternative treatments at each stage in order to optimize engraftment. We show that (i) X-irradiation at 25Gy is optimal in preventing regeneration of murine muscle while supporting robust engraftment and the formation of human fibers without significant murine contamination; (ii) hMPC lines differ in their capacity to engraft; (iii) some hMPC lines yield grafts that respond better to intermittent neuromuscular electrical stimulation (iNMES) than others; (iv) some lines engraft better in male than in female mice; (v) coinjection of hMPCs with laminin, gelatin, Matrigel, or Growdex does not improve engraftment; (vi) BaCl2 is an acceptable replacement for cardiotoxin, but other snake venom preparations and toxins, including the major component of cardiotoxin, cytotoxin 5, are not; and (vii) generating grafts in both hindlimbs followed by iNMES of each limb yields more robust grafts than housing mice in cages with running wheels. Our results suggest that replacing cardiotoxin with BaCl2 and engrafting both tibialis anterior muscles generates robust grafts of adult human muscle tissue in mice.

Keywords:  X-irradiation; electrical stimulation; exercise; immortalized muscle cells; myotoxin

DOI:  https://doi.org/10.1177/09636897241242624
Apoptosis. 2024 Apr 10.

Photobiomodulation therapy moderates cancer cachexia-associated muscle wasting through activating PI3K/AKT/FoxO3a pathway.

Yonghua Li, Yibing Chen, Yuan Liao, Ting Huang, Qing Tang, Chengsi He, Liu Xu, Haocai Chang, Hongsheng Li, Quentin Liu, Dongming Lai, Qing Xia, Zhengzhi Zou.

  Cancer cachexia-associated muscle wasting as a multifactorial wasting syndrome, is an important factor affecting the long-term survival rate of tumor patients. Photobiomodulation therapy (PBMT) has emerged as a promising tool to cure and prevent many diseases. However, the effect of PBMT on skeletal muscle atrophy during cancer progression has not been fully demonstrated yet. Here, we found PBMT alleviated the atrophy of myotube diameter induced by cancer cells in vitro, and prevented cancer-associated muscle atrophy in mice bearing tumor. Mechanistically, the alleviation of muscle wasting by PBMT was found to be involved in inhibiting E3 ubiquitin ligases MAFbx and MuRF-1. In addition, transcriptomic analysis using RNA-seq and GSEA revealed that PI3K/AKT pathway might be involved in PBMT-prevented muscle cachexia. Next, we showed the protective effect of PBMT against muscle cachexia was totally blocked by AKT inhibitor in vitro and in vivo. Moreover, PBMT-activated AKT promoted FoxO3a phosphorylation and thus inhibiting the nucleus entry of FoxO3a. Lastly, in cisplatin-treated muscle cachexia model, PBMT had also been shown to ameliorate muscle atrophy through enhancing PI3K/AKT pathway to suppress MAFbx and MuRF-1 expression. These novel findings revealed that PBMT could be a promising therapeutic approach in treating muscle cachexia induced by cancer.

Keywords:  Cancer cachexia; E3 ubiquitin ligases; Muscle wasting; PBMT; PI3K/AKT pathway

DOI:  https://doi.org/10.1007/s10495-024-01949-2
J Sport Health Sci. 2024 Apr 09. pii: S2095-2546(24)00049-8. [Epub ahead of print]

Exercise training mode effects on myokine expression in healthy adults: A systematic review with meta-analysis.

Francesco Bettariga, Dennis R Taaffe, Daniel A Galvão, Pedro Lopez, Chris Bishop, Anna Maria Markarian, Valentina Natalucci, Jin-Soo Kim, Robert U Newton.

  BACKGROUND: The benefits of exercise are well known; however, many of the underlying molecular mechanisms are not fully understood. Skeletal muscle secretes myokines, which mediate muscle-organ crosstalk. Myokines regulate satellite-cell proliferation and migration, inflammatory cascade, insulin secretion, angiogenesis, fatty oxidation, and cancer suppression. To date, the effects of different exercise modes (namely, aerobic and resistance exercise) on myokine response remain to be elucidated. This is crucial considering the clinical implementation of exercise to enhance general health and wellbeing and as a medical treatment.METHODS: A systematic search was undertaken in PubMed, Medline, CINAHL, Embase, SPORTDiscus, and Web of Science in April 2023. Eligible studies examining the effects of a single bout of exercise on IL-15, irisin, SPARC, OSM, and decorin were included. A random-effects meta-analysis was also undertaken to quantify the magnitude of change.
RESULTS: Sixty-two studies were included (n = 1193). Overall, exercise appeared to induce small to large increases in myokine expression, with effects observed immediately after to 60 min post-exercise, although these were mostly not statistically significant. Both aerobic and resistance exercise resulted in changes in myokine levels, without any significant difference between training modes, and with the magnitude of change differing across myokines. Myokine levels returned to baseline levels within 180 min to 24 h post-exercise. However, owing to potential sources of heterogeneity, most changes were not statistically significant, indicating that precise conclusions cannot be drawn.
CONCLUSION: Knowledge is limited but expanding with respect to the impact of overall and specific effects of exercise on myokine expression at different time points in the systemic circulation. Further research is required to investigate the effects of different exercise modes at multiple time points on myokine response.

Keywords:  Aerobic exercise; Cytokine; Myokine; Resistance exercise; Systemic circulation

DOI:  https://doi.org/10.1016/j.jshs.2024.04.005
Sci Rep. 2024 04 06. 14(1): 8094

The autophagy inhibitor NSC185058 suppresses mTORC1-mediated protein anabolism in cultured skeletal muscle.

Patrick J Ryan, Selina Uranga, Sean T Stanelle, Megan H Lewis, Colleen L O'Reilly, Jessica M Cardin, J William Deaver, Aaron B Morton, James D Fluckey.

The mammalian target of rapamycin (mTOR), and specifically the mTOR complex 1 (mTORC1) is the central regulator of anabolism in skeletal muscle. Among the many functions of this kinase complex is the inhibition of the catabolic process of autophagy; however, less work has been done in investigating the role of autophagy in regulating mTORC1 signaling. Using an in vitro model to better understand the pathways involved, we activated mTORC1 by several different means (growth factors, leucine supplementation, or muscle contraction), alone or with the autophagy inhibitor NSC185058. We found that inhibiting autophagy with NSC185058 suppresses mTORC1 activity, preventing any increase in cellular protein anabolism. These decrements were the direct result of action on the mTORC1 kinase, which we demonstrate, for the first time, cannot function when autophagy is inhibited by NSC185058. Our results indicate that, far from being a matter of unidirectional action, the relationship between mTORC1 and the autophagic cascade is more nuanced, with autophagy serving as an mTORC1 input, and mTORC1 inhibition of autophagy as a form of homeostatic feedback to regulate anabolic signaling. Future studies of cellular metabolism will have to consider this fundamental intertwining of protein anabolism and catabolism, and how it ultimately serves to regulate muscle proteostasis.

DOI: https://doi.org/10.1038/s41598-024-58716-1
Cytoskeleton (Hoboken). 2024 Apr 08.

Post-translational modifications of vertebrate striated muscle myosin heavy chains.

Paula Nieto Morales, Arianna N Coons, Amelia J Koopman, Sonu Patel, P Bryant Chase, Michelle S Parvatiyar, Jose R Pinto.

  Post-translational modifications (PTMs) play a crucial role in regulating the function of many sarcomeric proteins, including myosin. Myosins comprise a family of motor proteins that play fundamental roles in cell motility in general and muscle contraction in particular. A myosin molecule consists of two myosin heavy chains (MyHCs) and two pairs of myosin light chains (MLCs); two MLCs are associated with the neck region of each MyHC's N-terminal head domain, while the two MyHC C-terminal tails form a coiled-coil that polymerizes with other MyHCs to form the thick filament backbone. Myosin undergoes extensive PTMs, and dysregulation of these PTMs may lead to abnormal muscle function and contribute to the development of myopathies and cardiovascular disorders. Recent studies have uncovered the significance of PTMs in regulating MyHC function and showed how these PTMs may provide additional modulation of contractile processes. Here, we discuss MyHC PTMs that have been biochemically and/or functionally studied in mammals' and rodents' striated muscle. We have identified hotspots or specific regions in three isoforms of myosin (MYH2, MYH6, and MYH7) where the prevalence of PTMs is more frequent and could potentially play a significant role in fine-tuning the activity of these proteins.

Keywords:  acetylation; cardiac muscle; myosin heavy chain; phosphorylation; post‐translational modifications; skeletal muscle

DOI:  https://doi.org/10.1002/cm.21857
Commun Biol. 2024 Apr 10. 7(1): 438

Revealing myopathy spectrum: integrating transcriptional and clinical features of human skeletal muscles with varying health conditions.

Huahua Zhong, Veronica Sian, Mridul Johari, Shintaro Katayama, Ali Oghabian, Per Harald Jonson, Peter Hackman, Marco Savarese, Bjarne Udd.

Myopathy refers to a large group of heterogeneous, rare muscle diseases. Bulk RNA-sequencing has been utilized for the diagnosis and research of these diseases for many years. However, the existing valuable sequencing data often lack integration and clinical interpretation. In this study, we integrated bulk RNA-sequencing data from 1221 human skeletal muscles (292 with myopathies, 929 controls) from both databases and our local samples. By applying a method similar to single-cell analysis, we revealed a general spectrum of muscle diseases, ranging from healthy to mild disease, moderate muscle wasting, and severe muscle disease. This spectrum was further partly validated in three specific myopathies (97 muscles) through clinical features including trinucleotide repeat expansion, magnetic resonance imaging fat fraction, pathology, and clinical severity scores. This spectrum helped us identify 234 genuinely healthy muscles as unprecedented controls, providing a new perspective for deciphering the hallmark genes and pathways among different myopathies. The newly identified featured genes of general myopathy, inclusion body myositis, and titinopathy were highly expressed in our local muscles, as validated by quantitative polymerase chain reaction.

DOI: https://doi.org/10.1038/s42003-024-06143-3
FASEB J. 2024 Apr 15. 38(7): e23596

Beyond muscles: Investigating immunoregulatory myokines in acute resistance exercise - A systematic review and meta-analysis.

Miriam Ringleb, Florian Javelle, Simon Haunhorst, Wilhelm Bloch, Lena Fennen, Sabine Baumgart, Sebastian Drube, Philipp A Reuken, Mathias W Pletz, Heiko Wagner, Holger H W Gabriel, Christian Puta.

  Myokines, released from the muscle, enable communication between the working muscles and other tissues. Their release during physical exercise is assumed to depend on immune-hormonal-metabolic interactions concerning mode (endurance or resistance exercise), duration, and intensity. This meta-analysis aims to examine the acute changes of circulating myokines inducing immunoregulatory effects caused by a bout of resistance exercise and to consider potential moderators of the results. Based on this selection strategy, a systematic literature search was conducted for resistance exercise intervention studies measuring interleukin (IL-) 6, IL-10, IL-1ra, tumor necrosis factor (TNF-) α, IL-15, IL-7, transforming growth factor (TGF-) β1, and fractalkines (FKN) before and immediately after resistance exercise in healthy individuals. Random-effects meta-analysis was performed for each myokine. We identified a moderate positive effect of resistance exercise for IL-6 and IL-1ra. Regarding IL-15 and TNF-α, small to moderate effects were found. For IL-10, no significant effect was observed. Due to no data, meta-analyses for IL-7, TGF-β1, and FKN could not be performed. No moderators (training status, type of exercise, risk of bias, age, sex, time of day, exercise volume, exercise intensity, exercise dose) of the results were detected for all tested myokines. Taken together, this systematic review and meta-analysis showed immediate positive effects of an acute resistance exercise session on IL-6, IL-1ra, TNF-α, and IL-15 levels.

Keywords:  acute effects; exerkines; immune system; inflammation; myokines; resistance exercise

DOI:  https://doi.org/10.1096/fj.202301619R
Sci Rep. 2024 04 10. 14(1): 8388

Hypoxia treatment and resistance training alters microRNA profiling in rats skeletal muscle.

Tao Mei, Yang Hu, Ying Zhang, Yanchun Li.

  MicroRNAs (miRNAs) may play a crucial regulatory role in the process of muscle atrophy induced by high-altitude hypoxia and its amelioration through resistance training. However, research in this aspect is still lacking. Therefore, this study aimed to employ miRNA microarray analysis to investigate the expression profile of miRNAs in skeletal muscle from an animal model of hypoxia-induced muscle atrophy and resistance training aimed at mitigating muscle atrophy. The study utilized a simulated hypoxic environment (oxygen concentration at 11.2%) to induce muscle atrophy and established a rat model of resistance training using ladder climbing, with a total intervention period of 4 weeks. The miRNA expression profile revealed 9 differentially expressed miRNAs influenced by hypoxia (e.g., miR-341, miR-32-5p, miR-465-5p) and 14 differentially expressed miRNAs influenced by resistance training under hypoxic conditions (e.g., miR-338-5p, miR-203a-3p, miR-92b-3p) (∣log2(FC)∣ ≥ 1.5, p < 0.05). The differentially expressed miRNAs were found to target genes involved in muscle protein synthesis and degradation (such as Utrn, mdm2, eIF4E), biological processes (such as negative regulation of transcription from RNA polymerase II promoter, regulation of transcription, DNA-dependent), and signaling pathways (such as Wnt signaling pathway, MAPK signaling pathway, ubiquitin-mediated proteolysis, mTOR signaling pathway). This study provides a foundation for understanding and further exploring the molecular mechanisms underlying hypoxia-induced rats muscle atrophy and the mitigation of atrophy through resistance training.

Keywords:  Bioinformatics analysis; Hypoxia; MiRNA expression profile; Resistance training; Skeletal muscle atrophy

DOI:  https://doi.org/10.1038/s41598-024-58996-7
Nat Aging. 2024 Apr 12.

A conserved complex lipid signature marks human muscle aging and responds to short-term exercise.

Georges E Janssens, Marte Molenaars, Katharina Herzog, Lotte Grevendonk, Carlijn M E Remie, Martin A T Vervaart, Hyung L Elfrink, Eric J M Wever, Bauke V Schomakers, Simone W Denis, Hans R Waterham, Mia L Pras-Raves, Michel van Weeghel, Antoine H C van Kampen, Alessandra Tammaro, Loes M Butter, Sanne van der Rijt, Sandrine Florquin, Aldo Jongejan, Perry D Moerland, Joris Hoeks, Patrick Schrauwen, Frédéric M Vaz, Riekelt H Houtkooper.

Studies in preclinical models suggest that complex lipids, such as phospholipids, play a role in the regulation of longevity. However, identification of universally conserved complex lipid changes that occur during aging, and how these respond to interventions, is lacking. Here, to comprehensively map how complex lipids change during aging, we profiled ten tissues in young versus aged mice using a lipidomics platform. Strikingly, from >1,200 unique lipids, we found a tissue-wide accumulation of bis(monoacylglycero)phosphate (BMP) during mouse aging. To investigate translational value, we assessed muscle tissue of young and older people, and found a similar marked BMP accumulation in the human aging lipidome. Furthermore, we found that a healthy-aging intervention consisting of moderate-to-vigorous exercise was able to lower BMP levels in postmenopausal female research participants. Our work implicates complex lipid biology as central to aging, identifying a conserved aging lipid signature of BMP accumulation that is modifiable upon a short-term healthy-aging intervention.

DOI: https://doi.org/10.1038/s43587-024-00595-2
bioRxiv. 2024 Mar 29. pii: 2024.03.26.586781. [Epub ahead of print]

Mitochondrial respiration atlas reveals differential changes in mitochondrial function across sex and age.

Dylan C Sarver, Muzna Saqib, Fangluo Chen, G William Wong.

Organ function declines with age, and large-scale transcriptomic analyses have highlighted differential aging trajectories across tissues. The mechanisms underlying shared and organ-selective functional changes across the lifespan, however, still remains poorly understood. Given the central role of mitochondria in powering cellular processes needed to maintain tissue health, we therefore undertook a systematic assessment of respiratory activity across 33 different tissues in young (2.5 months) and old (20 months) mice of both sexes. Our high-resolution mitochondrial respiration atlas reveals: 1) within any group of mice, mitochondrial activity varies widely across tissues, with the highest values consistently seen in heart, brown fat, and kidney; 2) biological sex is a significant but minor contributor to mitochondrial respiration, and its contributions are tissue-specific, with major differences seen in the pancreas, stomach, and white adipose tissue; 3) age is a dominant factor affecting mitochondrial activity, especially across different fat depots and skeletal muscle groups, and most brain regions; 4) age-effects can be sex- and tissue-specific, with some of the largest effects seen in pancreas, heart, adipose tissue, and skeletal muscle; and 5) while aging alters the functional trajectories of mitochondria in a majority of tissues, some are remarkably resilient to age-induced changes. Altogether, our data provide the most comprehensive compendium of mitochondrial respiration and illuminate functional signatures of aging across diverse tissues and organ systems.

DOI: https://doi.org/10.1101/2024.03.26.586781