bims-moremu 2023-12-17 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023‒12‒17
33 papers selected by
Anna Vainshtein, Craft Science Inc.

RhoA Is a Crucial Regulator of Myoblast Fusion.
The Role of TFE3 in Mediating Skeletal Muscle Mitochondrial Adaptations to Exercise Training.
AMPKα2 is a skeletal muscle stem cell intrinsic regulator of myonuclear accretion.
Effects of chemically induced ovarian failure on single muscle fiber contractility in a mouse model of menopause.
DBC1 maintains skeletal muscle integrity by enhancing myogenesis and preventing myofibre wasting.
Fast and Slow Muscle Fiber Transcriptome Dynamics with Lifelong Endurance Exercise.
ApoE isoform does not influence skeletal muscle regeneration in adult mice.
Mustn1 ablation in skeletal muscle results in functional alterations.
Downregulation of mitochondrial metabolism is a driver for fast skeletal muscle loss during mouse aging.
BIO101 stimulates myoblast differentiation and improves muscle function in adult and old mice.
The L27 Domain of MPP7 enhances TAZ-YY1 Cooperation to Renew Muscle Stem Cells.
Secreted Metabolome of ALS-Related hSOD1(G93A) Primary Cultures of Myocytes and Implications for Myogenesis.
Division-Independent Differentiation of Muscle Stem Cells During a Growth Stimulus.
Excess PrPC inhibits muscle cell differentiation via miRNA-enhanced liquid-liquid phase separation implicated in myopathy.
Lifelong dietary protein restriction accelerates skeletal muscle loss and reduces muscle fibre size by impairing proteostasis and mitochondrial homeostasis.
Transcriptome sequencing promotes insights on the molecular mechanism of SKP-SC-EVs mitigating denervation-induced muscle atrophy.
Unlocking the Role of sMyBP-C: A Key Player in Skeletal Muscle Development and Growth.
Sex-specific increases in myostatin and SMAD3 contribute to obesity-related insulin resistance in human skeletal muscle and primary human myotubes.
DPPIV+ fibro-adipogenic progenitors form the niche of adult skeletal muscle self-renewing resident macrophages.
Ex vivo two-photon imaging of whole-mount skeletal muscles to visualize stem cell behavior.
Asperosaponin VI facilitates the regeneration of skeletal muscle injury by suppressing GSK-3β-mediated cell apoptosis.
Targeted genetic therapies for inherited disorders that affect both cardiac and skeletal muscle.
Pulsed Electromagnetic Fields Induce Skeletal Muscle Cell Repair by Sustaining the Expression of Proteins Involved in the Response to Cellular Damage and Oxidative Stress.
Adaptive changes in the DNA damage response during skeletal muscle cell differentiation.
Aerobic exercise training mitigates tumor growth and cancer-induced splenomegaly through modulation of non-platelet platelet factor 4 expression.
Calcium's Role and Signaling in Aging Muscle, Cellular Senescence, and Mineral Interactions.
How soon do metabolic alterations and oxidative distress precede the reduction of muscle mass and strength in Wistar rats in aging process?
Long term peripheral AAV9-SMN gene therapy promotes survival in a mouse model of spinal muscular atrophy.
Geroprotector drugs and exercise: friends or foes on healthy longevity?
Explainable machine learning identifies multi-omics signatures of muscle response to spaceflight in mice.
Obesity worsens mitochondrial quality control and does not protect against skeletal muscle wasting in murine cancer cachexia.
The ER stress sensor IRE1 interacts with STIM1 to promote store-operated calcium entry, T cell activation, and muscular differentiation.
Fibroblast Growth Factor 21: A Fascinating Perspective on the Regulation of Muscle Metabolism.

Cells. 2023 Nov 21. pii: 2673. [Epub ahead of print]12(23):

RhoA Is a Crucial Regulator of Myoblast Fusion.

Chiara Noviello, Kassandra Kobon, Voahangy Randrianarison-Huetz, Pascal Maire, France Pietri-Rouxel, Sestina Falcone, Athanassia Sotiropoulos.

  Satellite cells (SCs) are adult muscle stem cells that are mobilized when muscle homeostasis is perturbed. Here we show that RhoA in SCs is indispensable to have correct muscle regeneration and hypertrophy. In particular, the absence of RhoA in SCs prevents a correct SC fusion both to other RhoA-deleted SCs (regeneration context) and to growing control myofibers (hypertrophy context). We demonstrated that RhoA is dispensable for SCs proliferation and differentiation; however, RhoA-deleted SCs have an inefficient movement even if their cytoskeleton assembly is not altered. Proliferative myoblast and differentiated myotubes without RhoA display a decreased expression of Chordin, suggesting a crosstalk between these genes for myoblast fusion regulation. These findings demonstrate the importance of RhoA in SC fusion regulation and its requirement to achieve an efficient skeletal muscle homeostasis restoration.

Keywords:  adult muscle stem cells; muscle cell fusion; muscle damage; muscle hypertrophy; muscle regeneration; small GTPase proteins

DOI:  https://doi.org/10.3390/cells12232673
J Appl Physiol (1985). 2023 Dec 14.

The Role of TFE3 in Mediating Skeletal Muscle Mitochondrial Adaptations to Exercise Training.

Jenna C Wong, Ashley N Oliveira, Priyanka Khemraj, David A Hood.

  TFE3 is a transcription factor that activates the expression of lysosomal genes involved in the clearance of dysfunctional mitochondria, termed mitophagy. With exercise, TFE3 is presumed to optimize the mitochondrial pool through the removal of organelles via lysosomes. However, the molecular mechanisms of the involved pathways remain unknown. Wild-type (WT) and TFE3 knockout (KO) mice were subjected to 6 weeks of voluntary wheel running as an endurance training regimen. This was followed by a 45-minute bout of in situ stimulation of the sciatic nerve innervating hindlimb muscles to evaluate muscle fatigue and contractile properties. A subset of animals was treated with colchicine to measure autophagy and mitophagy flux. Fatigability during stimulation was reduced with training in WT animals, as seen by a 13% increase in percent of maximum force at 5 minutes of stimulation, and a 30% increase at 30 minutes. Permeabilized fiber oxygen consumption was also improved with training. Concurrent with improved muscle and mitochondrial function, COX activity and COX I protein expression were increased in trained WT animals compared to untrained animals, signifying an increase in mitochondrial content. These training adaptations were abolished with the loss of TFE3. Surprisingly, the absence of TFE3 did not affect lysosomal content, nor did it blunt the induction of mitophagy flux with contractile activity compared to WT mice. Our results suggest that the loss of TFE3 compromises beneficial training adaptations that lead to improved muscle endurance and mitochondrial function.

Keywords:  TFE3; exercise; mitochondria; mitophagy; skeletal muscle

DOI:  https://doi.org/10.1152/japplphysiol.00484.2023
iScience. 2023 Dec 15. 26(12): 108343

AMPKα2 is a skeletal muscle stem cell intrinsic regulator of myonuclear accretion.

Anita Kneppers, Sabrina Ben Larbi, Marine Theret, Audrey Saugues, Carole Dabadie, Linda Gsaier, Arnaud Ferry, Philipp Rhein, Julien Gondin, Kei Sakamoto, Rémi Mounier.

  Due to the post-mitotic nature of skeletal muscle fibers, adult muscle maintenance relies on dedicated muscle stem cells (MuSCs). In most physiological contexts, MuSCs support myofiber homeostasis by contributing to myonuclear accretion, which requires a coordination of cell-type specific events between the myofiber and MuSCs. Here, we addressed the role of the kinase AMPKα2 in the coordination of these events supporting myonuclear accretion. We demonstrate that AMPKα2 deletion impairs skeletal muscle regeneration. Through in vitro assessments of MuSC myogenic fate and EdU-based cell tracing, we reveal a MuSC-specific role of AMPKα2 in the regulation of myonuclear accretion, which is mediated by phosphorylation of the non-metabolic substrate BAIAP2. Similar cell tracing in vivo shows that AMPKα2 knockout mice have a lower rate of myonuclear accretion during regeneration, and that MuSC-specific AMPKα2 deletion decreases myonuclear accretion in response to myofiber contraction. Together, this demonstrates that AMPKα2 is a MuSC-intrinsic regulator of myonuclear accretion.

Keywords:  Molecular biology experimental approach; Molecular mechanism of behavior; Specialized functions of cells; Stem cells research; cell Biology

DOI:  https://doi.org/10.1016/j.isci.2023.108343
Maturitas. 2023 Nov 11. pii: S0378-5122(23)00491-7. [Epub ahead of print]180 107885

Effects of chemically induced ovarian failure on single muscle fiber contractility in a mouse model of menopause.

Parastoo Mashouri, Jinan Saboune, W Glen Pyle, Geoffrey A Power.

  OBJECTIVE: Menopause is associated with impaired skeletal muscle contractile function. The temporal and mechanistic bases of this dysfunction are unknown. Using a mouse model of menopause, we identified how gradual ovarian failure affects single muscle fiber contractility.STUDY DESIGN: Ovarian failure was chemically induced over 120 days, representing the perimenopausal transition. Mice were sacrificed and soleus and extensor digitorum longus muscles were dissected and chemically permeabilized for single fiber mechanical testing.
MAIN OUTCOME MEASURES: Muscle fiber contractility was assessed via force, rate of force redevelopment, instantaneous stiffness, and calcium sensitivity.
RESULTS: Peak force and cross-sectional area of the soleus were, respectively, ~33 % and ~24 % greater following ovarian failure compared with controls (p < 0.05) with no differences in force produced by the extensor digitorum longus across groups (p > 0.05). Upon normalizing force to cross-sectional area there were no differences across groups (p > 0.05). Following ovarian failure, rate of force redevelopment of single fibers from the soleus was ~33 % faster compared with controls. There was no shift in the midpoint of the force‑calcium curve between groups or muscles (p > 0.05). However, following ovarian failure, Type I fibers from the soleus had a higher calcium sensitivity between pCa values of 4.5 and 6.2 compared with controls (p < 0.05), with no differences for Type II fibers or the extensor digitorum longus (p > 0.05).
CONCLUSIONS: In our model of menopause, alterations to muscle contractility were less evident than in ovariectomized models. This divergence across models highlights the importance of better approximating the natural trajectory of menopause during and after the transitional phase of ovarian failure on neuromuscular function.

Keywords:  Calcium sensitivity; Force; Instantaneous stiffness; Menopause; Ovarian failure; Single muscle fibers

DOI:  https://doi.org/10.1016/j.maturitas.2023.107885
J Cachexia Sarcopenia Muscle. 2023 Dec 07.

DBC1 maintains skeletal muscle integrity by enhancing myogenesis and preventing myofibre wasting.

Na Liang, Jia He, Jiaqi Yan, Xueying Han, Xiaoqian Zhang, Yamei Niu, Wuga Sha, Jun Li.

  BACKGROUND: Skeletal muscle atrophy, particularly ageing-related muscular atrophy such as sarcopenia, is a significant health concern. Despite its prevalence, the underlying mechanisms remain poorly understood, and specific approved medications are currently unavailable. Deleted in breast cancer 1 (DBC1) is a well-known regulator of senescence, metabolism or apoptosis. Recent reports suggest that DBC1 may also potentially regulate muscle function, as mice lacking DBC1 exhibit weakness and limpness. However, the function of DBC1 in skeletal muscle and its associated molecular mechanisms remain unknown, thus prompting the focus of this study.METHODS: Tibialis anterior (TA) muscle-specific DBC1 knockdown C57BL/6J male mice were generated through a single injection of 2.00 E + 11 vg of adeno-associated virus 9 delivering single-guide RNA for DBC1. Grip strength and endurance were assessed 2 months later, followed by skeletal muscle harvest. Muscle atrophy model was generated by cast immobilization of the mouse hindlimb for 2 weeks. Molecular markers of atrophy were probed in muscles upon termination. Cardiotoxin (CTX) was injected in TA muscles of DBC1 knockdown mice, and muscle regeneration was assessed by immunohistochemistry, quantitative PCR and western blotting. DBC1 knockdown C2C12 cells and myotubes were investigated using immunofluorescence staining, Seahorse, immunohistology, fluorescence-activated cell sorting and RNA-sequencing analyses.
RESULTS: DBC1 knockdown in skeletal muscle of young mice led to signatures of muscle atrophy, including a 28% reduction in muscle grip force (P = 0.023), a 54.4% reduction in running distance (P = 0.002), a 14.3% reduction in muscle mass (P = 0.007) and significantly smaller myofibre cross-sectional areas (P < 0.0001). DBC1 levels decrease in age-related or limb immobilization-induced atrophic mouse muscles and overexpress DBC1-attenuated atrophic phenotypes in these mice. Muscle regeneration was hampered in mice with CTX-induced muscle injury by DBC1 knockdown, as evidenced by reductions in myofibre cross-sectional areas of regenerating myofibres with centralized nuclei (P < 0.0001), percentages of MyoG+ nuclei (P < 0.0001) and fusion index (P < 0.0001). DBC1 transcriptionally regulated mouse double minute 2 (MDM2), which mediated ubiquitination and degradation of forkhead box O3 (FOXO3). Increased FOXO3 proteins hampered myogenesis in DBC1 knockdown satellite cells by compromising around 50% of mitochondrial functions (P < 0.001) and exacerbated atrophy in DBC1 knockdown myofibres by activating the ubiquitin-proteasome and autophagy-lysosome pathways.
CONCLUSIONS: DBC1 is essential in maintaining skeletal muscle integrity by protecting against myofibres wasting and enhancing muscle regeneration via FOXO3. This research highlights the significance of DBC1 for healthy skeletal muscle function and its connection to muscular atrophy.

Keywords:  DBC1; FOXO3; myogenesis; skeletal muscle atrophy

DOI:  https://doi.org/10.1002/jcsm.13398
J Appl Physiol (1985). 2023 Dec 14.

Fast and Slow Muscle Fiber Transcriptome Dynamics with Lifelong Endurance Exercise.

Ulrika Raue, Gwenaelle Begue, Kiril Minchev, Bozena Jemiolo, Kevin J Gries, Toby Chambers, Aliza Rubenstein, Elena Zaslavsky, Stuart C Sealfon, Todd Trappe, Scott Trappe.

  We investigated fast and slow muscle fiber transcriptome exercise dynamics among three groups of men: Lifelong exercisers (LLE, n=8, 74±1 y), old healthy non-exercisers (OH, n=9, 75±1 y), and young exercisers (YE, n=8, 25±1 y). Muscle biopsies were obtained pre- and 4h post-resistance exercise (3x10 knee extensions, 70% 1-RM). Fast and slow fiber size and function were assessed pre-exercise with fast and slow RNA-seq examined pre- and post-exercise. LLE fast fiber size was similar to OH, which were ~30% smaller than YE (P<0.05) with contractile function variables among groups resulting in lower power in LLE (P<0.05). LLE slow fibers were ~30% larger and more powerful compared to YE and OH (P<0.05). At the transcriptome level, fast fibers were more responsive to resistance exercise compared to slow fibers among all three cohorts (P<0.05). Exercise induced a comprehensive biological response in fast fibers (P<0.05) including transcription, signaling, skeletal muscle cell differentiation, and metabolism with vast differences among the groups. Fast fibers from YE exhibited a growth and metabolic signature, with LLE being primarily metabolic, and OH showing a strong stress related response. In slow fibers, only LLE exhibited a biological response to exercise (P<0.05), which was related to ketone and lipid metabolism. The divergent exercise transcriptome signatures provide novel insight into the molecular regulation in fast and slow fibers with age and exercise and suggest that the ~5% weekly exercise time commitment of the lifelong exercisers provided a powerful investment for fast and slow muscle fiber metabolic health at the molecular level.

Keywords:  Aging; Exercise; Masters Athletes; Skeletal Muscle; Transcriptome

DOI:  https://doi.org/10.1152/japplphysiol.00442.2023
Front Physiol. 2023 ;14 1302695

ApoE isoform does not influence skeletal muscle regeneration in adult mice.

Benjamin I Burke, Jensen Goh, Fatmah A Albathi, Taylor R Valentino, Georgia L Nolt, Jai K Joshi, Cory M Dungan, Lance A Johnson, Yuan Wen, Ahmed Ismaeel, John J McCarthy.

  Introduction: Apolipoprotein E (ApoE) has been shown to be necessary for proper skeletal muscle regeneration. Consistent with this finding, single-cell RNA-sequencing analyses of skeletal muscle stem cells (MuSCs) revealed that Apoe is a top marker of quiescent MuSCs that is downregulated upon activation. The purpose of this study was to determine if muscle regeneration is altered in mice which harbor one of the three common human ApoE isoforms, referred to as ApoE2, E3 and E4. Methods: Histomorphometric analyses were employed to assess muscle regeneration in ApoE2, E3, and E4 mice after 14 days of recovery from barium chloride-induced muscle damage in vivo, and primary MuSCs were isolated to assess proliferation and differentiation of ApoE2, E3, and E4 MuSCs in vitro. Results: There was no difference in the basal skeletal muscle phenotype of ApoE isoforms as evaluated by section area, myofiber cross-sectional area (CSA), and myonuclear and MuSC abundance per fiber. Although there were no differences in fiber-type frequency in the soleus, Type IIa relative frequency was significantly lower in plantaris muscles of ApoE4 mice compared to ApoE3. Moreover, ApoE isoform did not influence muscle regeneration as assessed by fiber frequency, fiber CSA, and myonuclear and MuSC abundance. Finally, there were no differences in the proliferative capacity or myogenic differentiation potential of MuSCs between any ApoE isoform. Discussion: Collectively, these data indicate nominal effects of ApoE isoform on the ability of skeletal muscle to regenerate following injury or the in vitro MuSC phenotype.

Keywords:  APOE; MuSCs; differentiation; metabolism; myogenesis; proliferation; regeneration; satellite cells

DOI:  https://doi.org/10.3389/fphys.2023.1302695
FASEB Bioadv. 2023 Dec;5(12): 541-557

Mustn1 ablation in skeletal muscle results in functional alterations.

Charles J Kim, Chanpreet Singh, Marina Kaczmarek, Madison O'Donnell, Christine Lee, Kevin DiMagno, Melody W Young, William Letsou, Raddy L Ramos, Michael C Granatosky, Michael Hadjiargyrou.

  Mustn1, a gene expressed exclusively in the musculoskeletal system, was shown in previous in vitro studies to be a key regulator of myogenic differentiation and myofusion. Other studies also showed Mustn1 expression associated with skeletal muscle development and hypertrophy. However, its specific role in skeletal muscle function remains unclear. This study sought to investigate the effects of Mustn1 in a conditional knockout (KO) mouse model in Pax7 positive skeletal muscle satellite cells. Specifically, we investigated the potential effects of Mustn1 on myogenic gene expression, grip strength, alterations in gait, ex vivo investigations of isolated skeletal muscle isometric contractions, and potential changes in the composition of muscle fiber types. Results indicate that Mustn1 KO mice did not present any substantial phenotypic changes or significant variations in genes related to myogenic differentiation and fusion. However, an approximately 10% decrease in overall grip strength was observed in the 2-month-old KO mice in comparison to the control wild type (WT), but this decrease was not significant when normalized by weight. KO mice also generated approximately 8% higher vertical force than WT at 4 months in the hindlimb. Ex vivo experiments revealed decreases in about 20 to 50% in skeletal muscle contractions and about 10%-20% fatigue in soleus of both 2- and 4-month-old KO mice, respectively. Lastly, immunofluorescent analyses showed a persistent increase of Type IIb fibers up to 15-fold in the KO mice while Type I fibers decreased about 20% and 30% at both 2 and 4 months, respectively. These findings suggest a potential adaptive or compensatory mechanism following Mustn1 loss, as well as hinting at an association between Mustn1 and muscle fiber typing. Collectively, Mustn1's complex roles in skeletal muscle physiology requires further research, particularly in terms of understanding the potential role of Mustn1 in muscle repair and regeneration, as well as with influence of exercise. Collectively, these will offer valuable insights into Mustn1's key biological functions and regulatory pathways.

Keywords:  Mustn1; Pax7; gait alterations; grip strength; isometric contraction tests; knockout mice; muscle fiber type; skeletal muscle

DOI:  https://doi.org/10.1096/fba.2023-00082
Commun Biol. 2023 Dec 08. 6(1): 1240

Downregulation of mitochondrial metabolism is a driver for fast skeletal muscle loss during mouse aging.

Raquel Fernando, Anastasia V Shindyapina, Mario Ost, Didac Santesmasses, Yan Hu, Alexander Tyshkovskiy, Sun Hee Yim, Jürgen Weiss, Vadim N Gladyshev, Tilman Grune, José Pedro Castro.

Skeletal muscle aging is characterized by the loss of muscle mass, strength and function, mainly attributed to the atrophy of glycolytic fibers. Underlying mechanisms driving the skeletal muscle functional impairment are yet to be elucidated. To unbiasedly uncover its molecular mechanisms, we recurred to gene expression and metabolite profiling in a glycolytic muscle, Extensor digitorum longus (EDL), from young and aged C57BL/6JRj mice. Employing multi-omics approaches we found that the main age-related changes are connected to mitochondria, exhibiting a downregulation in mitochondrial processes. Consistent is the altered mitochondrial morphology. We further compared our mouse EDL aging signature with human data from the GTEx database, reinforcing the idea that our model may recapitulate muscle loss in humans. We are able to show that age-related mitochondrial downregulation is likely to be detrimental, as gene expression signatures from commonly used lifespan extending interventions displayed the opposite direction compared to our EDL aging signature.

DOI: https://doi.org/10.1038/s42003-023-05595-3
J Cachexia Sarcopenia Muscle. 2023 Dec 08.

BIO101 stimulates myoblast differentiation and improves muscle function in adult and old mice.

Maria Serova, Blaise Didry-Barca, Robin Deloux, Anne-Sophie Foucault, Stanislas Veillet, René Lafont, Pierre J Dilda, Mathilde Latil.

  BACKGROUND: Muscle aging is associated with a consistent decrease in the ability of muscle tissue to regenerate following intrinsic muscle degradation, injury or overuse. Age-related imbalance of protein synthesis and degradation, mainly regulated by AKT/mTOR pathway, leads to progressive loss of muscle mass. Maintenance of anabolic and regenerative capacities of skeletal muscles may be regarded as a therapeutic option for sarcopenia and other muscle wasting diseases. Our previous studies have demonstrated that BIO101, a pharmaceutical grade 20-hydroxyecdysone, increases protein synthesis through the activation of MAS receptor involved in the protective arm of renin-angiotensin-aldosterone system. The purpose of the present study was to assess the anabolic and pro-differentiating properties of BIO101 on C2C12 muscle cells in vitro and to investigate its effects on adult and old mice models in vivo.METHODS: The effects of BIO101 on C2C12 differentiation were assessed using myogenic transcription factors and protein expression of major kinases of AKT/mTOR pathway by Western blot. The in vivo effects of BIO101 have been investigated in BIO101 orally-treated (50 mg/kg/day) adult mice (3 months) for 28 days. To demonstrate potential beneficial effect of BIO101 treatment in a sarcopenic mouse model, we use orally treated 22-month-old C57Bl6/J mice, for 14 weeks with vehicle or BIO101. Mice body and muscle weight were recorded. Physical performances were assessed using running capacity and muscle contractility tests.
RESULTS: Anabolic properties of BIO101 were confirmed by the rapid activation of AKT/mTOR, leading to an increase of C2C12 myotubes diameters (+26%, P < 0.001). Pro-differentiating effects of BIO101 on C2C12 myoblasts were revealed by increased expression of muscle-specific differentiation transcription factors (MyoD, myogenin), resulting in increased fusion index and number of nuclei per myotube (+39% and +53%, respectively, at day 6). These effects of BIO101 were like those of angiotensin (1-7) and were abolished with the use of A779, a MAS receptor specific antagonist. Chronic BIO101 oral treatment induced AKT/mTOR activation and anabolic effects accompanied with improved physical performances in adult and old animals (maximal running distance and maximal running velocity).
CONCLUSIONS: Our data suggest beneficial anabolic and pro-differentiating effects of BIO101 rendering BIO101 a potent drug candidate for treating sarcopenia and possibly other muscle wasting disorders.

Keywords:  20-hydroxyecdysone (20E); Ecdysteroids; MAS receptor; Muscle cell differentiation; Renin-angiotensin-aldosterone system (RAAS); Sarcopenia

DOI:  https://doi.org/10.1002/jcsm.13326
Res Sq. 2023 Nov 30. pii: rs.3.rs-3673774. [Epub ahead of print]

The L27 Domain of MPP7 enhances TAZ-YY1 Cooperation to Renew Muscle Stem Cells.

Chen-Ming Fan, Anwen Shao, Joseph Kissil.

Stem cells regenerate differentiated cells to maintain and repair tissues and organs. They also replenish themselves, i.e. self-renewal, for the regenerative process to last a lifetime. How stem cells renew is of critical biological and medical significance. Here we use the skeletal muscle stem cell (MuSC) to study this process. Using a combination of genetic, molecular, and biochemical approaches, we show that MPP7, AMOT, and TAZ/YAP form a complex that activates a common set of target genes. Among these targets, Carm1 can direct MuSC renewal. In the absence of MPP7, TAZ can support regenerative progenitors and activate Carm1 expression, but not to a level needed for self-renewal. Facilitated by the actin polymerization-responsive AMOT, TAZ recruits the L27 domain of MPP7 to up-regulate Carm1 to the level necessary to drive MuSC renewal. The promoter of Carm1, and those of other common downstream genes, also contain binding site(s) for YY1. We further demonstrate that the L27 domain of MPP7 enhances the interaction between TAZ and YY1 to activate Carm1 . Our results define a renewal transcriptional program embedded within the progenitor program, by selectively up-regulating key gene(s) within the latter, through the combination of protein interactions and in a manner dependent on the promoter context.

DOI: https://doi.org/10.21203/rs.3.rs-3673774/v1
Cells. 2023 Nov 30. pii: 2751. [Epub ahead of print]12(23):

Secreted Metabolome of ALS-Related hSOD1(G93A) Primary Cultures of Myocytes and Implications for Myogenesis.

Roberto Stella, Raphael Severino Bonadio, Stefano Cagnin, Roberta Andreotti, Maria Lina Massimino, Alessandro Bertoli, Caterina Peggion.

  Amyotrophic lateral sclerosis (ALS) is a motor neuron (MN) disease associated with progressive muscle atrophy, paralysis, and eventually death. Growing evidence demonstrates that the pathological process leading to ALS is the result of multiple altered mechanisms occurring not only in MNs but also in other cell types inside and outside the central nervous system. In this context, the involvement of skeletal muscle has been the subject of a few studies on patients and ALS animal models. In this work, by using primary myocytes derived from the ALS transgenic hSOD1(G93A) mouse model, we observed that the myogenic capability of such cells was defective compared to cells derived from control mice expressing the nonpathogenic hSOD1(WT) isoform. The correct in vitro myogenesis of hSOD1(G93A) primary skeletal muscle cells was rescued by the addition of a conditioned medium from healthy hSOD1(WT) myocytes, suggesting the existence of an in trans activity of secreted factors. To define a dataset of molecules participating in such safeguard action, we conducted comparative metabolomic profiling of a culture medium collected from hSOD1(G93A) and hSOD1(WT) primary myocytes and report here an altered secretion of amino acids and lipid-based signaling molecules. These findings support the urgency of better understanding the role of the skeletal muscle secretome in the regulation of the myogenic program and mechanisms of ALS pathogenesis and progression.

Keywords:  SOD1; amyotrophic lateral sclerosis; metabolomic profiling; myocytes; myogenesis; neuromuscular disorders

DOI:  https://doi.org/10.3390/cells12232751
Stem Cells. 2023 Dec 08. pii: sxad091. [Epub ahead of print]

Division-Independent Differentiation of Muscle Stem Cells During a Growth Stimulus.

Ahmed Ismaeel, Jensen Goh, C Brooks Mobley, Kevin A Murach, Jamie O Brett, Antoine de Morrée, Thomas A Rando, Charlotte A Peterson, Yuan Wen, John J McCarthy.

  Adult muscle stem cells (MuSCs) are known to replicate upon activation before differentiating and fusing to regenerate myofibers. It is unclear whether MuSC differentiation is intrinsically linked to cell division, which has implications for stem cell population maintenance. We use single-cell RNA-seq (scRNA-seq) to identify transcriptionally diverse subpopulations of MuSCs after 5 days of a growth stimulus in adult muscle. Trajectory inference in combination with a novel mouse model for tracking MuSC-derived myonuclei and in vivo labeling of DNA replication revealed a MuSC population that exhibited division-independent differentiation and fusion. These findings demonstrate that in response to a growth stimulus in the presence of intact myofibers, MuSC division is not obligatory.

Keywords:  Adult Stem Cells; Cell Division; DNA Replication; Single-Cell Gene Expression Analysis

DOI:  https://doi.org/10.1093/stmcls/sxad091
Nat Commun. 2023 Dec 08. 14(1): 8131

Excess PrPC inhibits muscle cell differentiation via miRNA-enhanced liquid-liquid phase separation implicated in myopathy.

Jing Tao, Yanping Zeng, Bin Dai, Yin Liu, Xiaohan Pan, Li-Qiang Wang, Jie Chen, Yu Zhou, Zuneng Lu, Liwei Xie, Yi Liang.

The cellular prion protein (PrPC) is required for skeletal muscle function. Here, we report that a higher level of PrPC accumulates in the cytoplasm of the skeletal muscle of six myopathy patients compared to controls. PrPC inhibits skeletal muscle cell autophagy, and blocks myoblast differentiation. PrPC selectively binds to a subset of miRNAs during myoblast differentiation, and the colocalization of PrPC and miR-214-3p was observed in the skeletal muscle of six myopathy patients with excessive PrPC. We demonstrate that PrPC is overexpressed in skeletal muscle cells under pathological conditions, inhibits muscle cell differentiation by physically interacting with a subset of miRNAs, and selectively recruits these miRNAs into its phase-separated condensate in living myoblasts, which in turn enhances liquid-liquid phase separation of PrPC, promotes pathological aggregation of PrP, and results in the inhibition of autophagy-related protein 5-dependent autophagy and muscle bundle formation in myopathy patients characterized by incomplete muscle regeneration.

DOI: https://doi.org/10.1038/s41467-023-43826-7
Redox Biol. 2023 Dec 02. pii: S2213-2317(23)00381-6. [Epub ahead of print]69 102980

Lifelong dietary protein restriction accelerates skeletal muscle loss and reduces muscle fibre size by impairing proteostasis and mitochondrial homeostasis.

Ufuk Ersoy, Ioannis Kanakis, Moussira Alameddine, Gibran Pedraza-Vazquez, Susan E Ozanne, Mandy Jayne Peffers, Malcolm J Jackson, Katarzyna Goljanek-Whysall, Aphrodite Vasilaki.

  The early life environment significantly affects the development of age-related skeletal muscle disorders. However, the long-term effects of lactational protein restriction on skeletal muscle are still poorly defined. Our study revealed that male mice nursed by dams fed a low-protein diet during lactation exhibited skeletal muscle growth restriction. This was associated with a dysregulation in the expression levels of genes related to the ribosome, mitochondria and skeletal muscle development. We reported that lifelong protein restriction accelerated loss of type-IIa muscle fibres and reduced muscle fibre size by impairing mitochondrial homeostasis and proteostasis at 18 months of age. However, feeding a normal-protein diet following lactational protein restriction prevented accelerated fibre loss and fibre size reduction in later life. These findings provide novel insight into the mechanisms by which lactational protein restriction hinders skeletal muscle growth and includes evidence that lifelong dietary protein restriction accelerated skeletal muscle loss in later life.

Keywords:  Maternal nutrition; Mitochondrial homeostasis; Protein restriction; Proteostasis; Sarcopenia; Skeletal muscle

DOI:  https://doi.org/10.1016/j.redox.2023.102980
Mol Biol Rep. 2023 Dec 12. 51(1): 9

Transcriptome sequencing promotes insights on the molecular mechanism of SKP-SC-EVs mitigating denervation-induced muscle atrophy.

Junfei Lin, Yong Cai, Jian Wang, Ruiqi Liu, Chong Qiu, Yan Huang, Boya Liu, Xiaoming Yang, Songlin Zhou, Yuntian Shen, Wei Wang, Jianwei Zhu.

  BACKGROUND: Complex pathophysiological changes accompany denervation-induced skeletal muscle atrophy, but no effective treatment strategies exist. Our previous study indicated that extracellular vesicles derived from skin-derived precursors-derived Schwann cells (SKP-SC-EVs) can effectively mitigate denervation-induced muscle atrophy. However, the specific molecular mechanism remains unclear.METHODS AND RESULTS: In this study, we used bioinformatics methods to scrutinize the impact of SKP-SC-EVs on gene expression in denervation-induced skeletal muscle atrophy. We found that SKP-SC-EVs altered the expression of 358 genes in denervated skeletal muscles. The differentially expressed genes were predominantly participated in biological processes, including cell cycle, inflammation, immunity, and adhesion, and signaling pathways, such as FoxO and PI3K.Using the Molecular Complex Detection (MCODE) plugin, we identified the two clusters with the highest score: cluster 1 comprised 37 genes, and Cluster 2 consisted of 24 genes. Then, fifty hub genes were identified using CytoHubba. The intersection of Hub genes and genes obtained by MCODE showed that all 23 genes related to the cell cycle in Cluster 1 were hub genes, and 5 genes in Cluster 2 were hub genes and associated with inflammation.
CONCLUSIONS: Overall, the differentially expressed genes in denervated skeletal muscle following SKP-SC-EVs treatment are primarily linked to the cell cycle and inflammation. Consequently, promoting proliferation and inhibiting inflammation may be the critical process in which SKP-SC-EVs delay denervation-induced muscle atrophy. Our findings contribute to a better understanding of the molecular mechanism of SKP-SC-EVs delaying denervation-induced muscle atrophy, offering a promising new avenue for muscle atrophy treatment.

Keywords:  Cell cycle; Denervation muscular atrophy; Inflammation; SKP-SC-EVs; Transcriptome sequencing

DOI:  https://doi.org/10.1007/s11033-023-08952-x
bioRxiv. 2023 Nov 30. pii: 2023.10.23.563591. [Epub ahead of print]

Unlocking the Role of sMyBP-C: A Key Player in Skeletal Muscle Development and Growth.

Taejeong Song, James W McNamara, Akhil Baby, Weikang Ma, Maicon Landim-Vieira, Sankar Natesan, Jose Renato Pinto, John N Lorenz, Thomas C Irving, Sakthivel Sadayappan.

Skeletal muscle is the largest organ in the body, responsible for gross movement and metabolic regulation. Recently, variants in the MYBPC1 gene have been implicated in a variety of developmental muscle diseases, such as distal arthrogryposis. How MYBPC1 variants cause disease is not well understood. Here, through a collection of novel gene-edited mouse models, we define a critical role for slow myosin binding protein-C (sMyBP-C), encoded by MYBPC1 , across muscle development, growth, and maintenance during prenatal, perinatal, postnatal and adult stages. Specifically, Mybpc1 knockout mice exhibited early postnatal lethality and impaired skeletal muscle formation and structure, skeletal deformity, and respiratory failure. Moreover, a conditional knockout of Mybpc1 in perinatal, postnatal and adult stages demonstrates impaired postnatal muscle growth and function secondary to disrupted actomyosin interaction and sarcomere structural integrity. These findings confirm the essential role of sMyBP-C in skeletal muscle and reveal specific functions in both prenatal embryonic musculoskeletal development and postnatal muscle growth and function.

DOI: https://doi.org/10.1101/2023.10.23.563591
Am J Physiol Endocrinol Metab. 2023 Dec 13.

Sex-specific increases in myostatin and SMAD3 contribute to obesity-related insulin resistance in human skeletal muscle and primary human myotubes.

Gunjan Saxena, Sean Gallagher, Timothy D Law, Dominic Maschari, Erin Walsh, Courtney Dudley, Jeffrey J Brault, Leslie A Consitt.

  The purpose of the present study was to determine the effects of obesity and biological sex on myostatin expression in humans, and to examine the direct effects of myostatin, SMAD2 and SMAD3 on insulin signaling in primary human skeletal muscle cells (HSkMCs). Cohort 1: Fifteen lean (BMI: 22.1 ± 0.5 kg/m2, n=8 males, n=7 females) and fourteen obese (BMI: 40.6 ± 1.4 kg/m2, n=7 males, n=7 females) individuals underwent skeletal muscle biopsies and an oral glucose tolerance test (OGTT). Cohort 2: Fifteen young lean (BMI: 22.4 ± 1.9 kg/m2, n=6 males, n=8 females) and fourteen obese (BMI: 39.3 ± 7.9 kg/m2, n=6 males, n=8 females) individuals underwent muscle biopsies for primary HSkMC experiments. Plasma mature myostatin (P=0.041), skeletal muscle precursor myostatin (P=0.048) and skeletal muscle SMAD3 (P=0.029) were elevated in obese females compared to lean females, and plasma mature myostatin (r=0.58, P=0.029) and skeletal muscle SMAD3 (r=0.56, P=0.037) were associated with insulin resistance in females, but not males. Twenty-four hours of myostatin treatment impaired insulin signaling in primary HSkMC derived from females (P<0.024) but not males. Overexpression of SMAD3, but not SMAD2, impaired insulin-stimulated AS160 phosphorylation in HSkMC derived from lean females (-27%, P=0.040); whereas silencing SMAD3, improved insulin-stimulated AS160 phosphorylation and insulin-stimulated glucose uptake (25%, P<0.014) in HSkMC derived from obese females. These results suggest for the first time that myostatin-induced impairments in skeletal muscle insulin signaling are sex-specific and that increased body fat in females is associated with detrimental elevations in myostatin and SMAD3, which contribute to obesity-related insulin resistance.

Keywords:  SMAD3; insulin sensitivity; myostatin; obesity; skeletal muscle

DOI:  https://doi.org/10.1152/ajpendo.00199.2023
Nat Commun. 2023 Dec 13. 14(1): 8273

DPPIV+ fibro-adipogenic progenitors form the niche of adult skeletal muscle self-renewing resident macrophages.

Farshad Babaeijandaghi, Nasim Kajabadi, Reece Long, Lin Wei Tung, Chun Wai Cheung, Morten Ritso, Chih-Kai Chang, Ryan Cheng, Tiffany Huang, Elena Groppa, Jean X Jiang, Fabio M V Rossi.

Adult tissue-resident macrophages (RMs) are either maintained by blood monocytes or through self-renewal. While the presence of a nurturing niche is likely crucial to support the survival and function of self-renewing RMs, evidence regarding its nature is limited. Here, we identify fibro-adipogenic progenitors (FAPs) as the main source of colony-stimulating factor 1 (CSF1) in resting skeletal muscle. Using parabiosis in combination with FAP-deficient transgenic mice (PdgfrαCreERT2 × DTA) or mice lacking FAP-derived CSF1 (PdgfrαCreERT2 × Csf1flox/null), we show that local CSF1 from FAPs is required for the survival of both TIM4- monocyte-derived and TIM4+ self-renewing RMs in adult skeletal muscle. The spatial distribution and number of TIM4+ RMs coincide with those of dipeptidyl peptidase IV (DPPIV)+ FAPs, suggesting their role as CSF1-producing niche cells for self-renewing RMs. This finding identifies opportunities to precisely manipulate the function of self-renewing RMs in situ to further unravel their role in health and disease.

DOI: https://doi.org/10.1038/s41467-023-43579-3
STAR Protoc. 2023 Dec 11. pii: S2666-1667(23)00739-6. [Epub ahead of print]5(1): 102772

Ex vivo two-photon imaging of whole-mount skeletal muscles to visualize stem cell behavior.

Nuoying Ma, Foteini Mourkioti.

  Quiescent skeletal muscle stem cells (MuSCs) are morphologically and functionally heterogeneous and exhibit different lengths of cellular extensions, which we call protrusions. Here, we present a protocol for ex vivo two-photon imaging of MuSCs in their native environment. We describe steps for muscle dissection, fixation, embedding, imaging, and analysis of datasets. This protocol allows the examination of MuSC morphology and protrusions at the single-cell level as well as stem cell numbers. For complete details on the use and execution of this protocol, please refer to Ma et al. (2022).1.

Keywords:  Cell Biology; Microscopy; Model Organisms; Single Cell; Stem Cells

DOI:  https://doi.org/10.1016/j.xpro.2023.102772
J Cell Biochem. 2023 Dec 11.

Asperosaponin VI facilitates the regeneration of skeletal muscle injury by suppressing GSK-3β-mediated cell apoptosis.

Xinru Yang, Jian Liang, Yue Shu, Linlin Wei, Cailing Wen, Hui Luo, Liqing Ma, Tian Qin, Bin Wang, Siyu Zeng, Ying Liu, Chun Zhou.

  Asperosaponin VI (ASA VI) is a bioactive triterpenoid saponin extracted from Diptychus roots, of Diptyl, and has previously shown protective functions in rheumatoid arthritis and sepsis. This study investigates the effects and molecular mechanisms of ASA VI on skeletal muscle regeneration in a cardiotoxin (CTX)-induced skeletal muscle injury mouse model. Mice were subjected to CTX-induced injury in the tibialis anterior and C2C12 myotubes were treated with CTX. Muscle fiber histology was analyzed at 7 and 14 days postinjury. Apoptosis and autophagy-related protein expression were evaluated t s by Western blot, and muscle regeneration markers were quantified by quantitative polymerase chain reaction. Docking studies, cell viability assessments, and glycogen synthase kinase-3β (GSK-3β) activation analyses were performed to elucidate the mechanism. ASA VI was observed to improve muscle interstitial fibrosis, remodeling, and performance in CTX-treated mice, thereby increased skeletal muscle size, weight, and locomotion. Furthermore, ASA VI modulated the expression of apoptosis and autophagy-related proteins through GSK-3β inhibition and activated the transcription of regeneration genes. Our results suggest that ASA VI mitigates skeletal muscle injury by modulating apoptosis and autophagy via GSK-3β signaling and promotes regeneration, thus presenting a probable therapeutic agent for skeletal muscle injury.

Keywords:  GSK-3β; asperosaponin VI; injury; regeneration; skeletal muscle

DOI:  https://doi.org/10.1002/jcb.30510
Exp Physiol. 2023 Dec 14.

Targeted genetic therapies for inherited disorders that affect both cardiac and skeletal muscle.

Yiangos Psaras, Christopher N Toepfer.

  Skeletal myopathies and ataxias with secondary cardiac involvement are complex, progressive and debilitating conditions. As life expectancy increases across these conditions, cardiac involvement often becomes more prominent. This highlights the need for targeted therapies that address these evolving cardiac pathologies. Musculopathies by and large lack cures that directly target the genetic basis of the diseases; however, as our understanding of the genetic causes of these conditions has evolved, it has become tractable to develop targeted therapies using biologics, to design precision approaches to target the primary genetic causes of these varied diseases. Using the examples of Duchenne muscular dystrophy, Friedreich ataxia and Pompe disease, we discuss how the genetic causes of such diseases derail diverse homeostatic, energetic and signalling pathways, which span multiple cellular systems in varied tissues across the body. We outline existing therapeutics and treatments in the context of emerging novel genetic approaches. We discuss the hurdles that the field must overcome to deliver targeted therapies across the many tissue types affected in primary myopathies. NEW FINDINGS: What is the topic of this review? Overlapping disease pathomechanisms and therapeutic opportunities in neuromuscular, skeletal and cardiac muscle diseases in the context of novel genetic therapies. What advances does it highlight? This review outlines the diverse genetic changes that drive pathomechanism across a set of neuromuscular conditions and highlight the emerging targeted biological therapies that are being developed to treat these conditions, with additional discussion of the hurdles to actualising genetically targeted precision medicine.

Keywords:  Duchenne muscular dystrophy; Friedreich's ataxia; Pompe disease; gene therapy; skeletal and cardiac muscle disease; therapeutics

DOI:  https://doi.org/10.1113/EP090436
Int J Mol Sci. 2023 Nov 23. pii: 16631. [Epub ahead of print]24(23):

Pulsed Electromagnetic Fields Induce Skeletal Muscle Cell Repair by Sustaining the Expression of Proteins Involved in the Response to Cellular Damage and Oxidative Stress.

Silvia Maiullari, Antonella Cicirelli, Angela Picerno, Francesca Giannuzzi, Loreto Gesualdo, Angela Notarnicola, Fabio Sallustio, Biagio Moretti.

  Pulsed electromagnetic fields (PEMF) are employed as a non-invasive medicinal therapy, especially in the orthopedic field to stimulate bone regeneration. However, the effect of PEMF on skeletal muscle cells (SkMC) has been understudied. Here, we studied the potentiality of 1.5 mT PEMF to stimulate early regeneration of human SkMC. We showed that human SkMC stimulated with 1.5 mT PEMF for four hours repeated for two days can stimulate cell proliferation without inducing cell apoptosis or significant impairment of the metabolic activity. Interestingly, when we simulated physical damage of the muscle tissue by a scratch, we found that the same PEMF treatment can speed up the regenerative process, inducing a more complete cell migration to close the scratch and wound healing. Moreover, we investigated the molecular pattern induced by PEMF among 26 stress-related cell proteins. We found that the expression of 10 proteins increased after two consecutive days of PEMF stimulation for 4 h, and most of them were involved in response processes to oxidative stress. Among these proteins, we found that heat shock protein 70 (HSP70), which can promote muscle recovery, inhibits apoptosis and decreases inflammation in skeletal muscle, together with thioredoxin, paraoxonase, and superoxide dismutase (SOD2), which can also promote skeletal muscle regeneration following injury. Altogether, these data support the possibility of using PEMF to increase SkMC regeneration and, for the first time, suggest a possible molecular mechanism, which consists of sustaining the expression of antioxidant enzymes to control the important inflammatory and oxidative process occurring following muscle damage.

Keywords:  PEMF; cellular damage; skeletal muscle cells

DOI:  https://doi.org/10.3390/ijms242316631
Front Cell Dev Biol. 2023 ;11 1239138

Adaptive changes in the DNA damage response during skeletal muscle cell differentiation.

Inês Faleiro, Ana I Afonso, André Balsinha, Beatriz Lucas, Robert M Martin, Edgar R Gomes, Sérgio F de Almeida.

  DNA double-strand breaks (DSBs) trigger specialized cellular mechanisms that collectively form the DNA damage response (DDR). In proliferating cells, the DDR serves the function of mending DNA breaks and satisfying the cell-cycle checkpoints. Distinct goals exist in differentiated cells that are postmitotic and do not face cell-cycle checkpoints. Nonetheless, the distinctive requirements and mechanistic details of the DDR in differentiated cells are still poorly understood. In this study, we set an in vitro differentiation model of human skeletal muscle myoblasts into multinucleated myotubes that allowed monitoring DDR dynamics during cell differentiation. Our results demonstrate that myotubes have a prolonged DDR, which is nonetheless competent to repair DSBs and render them significantly more resistant to cell death than their progenitors. Using live-cell microscopy and single-molecule kinetic measurements of transcriptional activity, we observed that myotubes respond to DNA damage by rapidly and transiently suppressing global gene expression and rewiring the epigenetic landscape of the damaged nucleus. Our findings provide novel insights into the DDR dynamics during cellular differentiation and shed light on the strategy employed by human skeletal muscle to preserve the integrity of the genetic information and sustain long-term organ function after DNA damage.

Keywords:  DNA damage response; cell cycle; cell death; cellular differentiation; skeletal muscle

DOI:  https://doi.org/10.3389/fcell.2023.1239138
Sci Rep. 2023 Dec 11. 13(1): 21970

Aerobic exercise training mitigates tumor growth and cancer-induced splenomegaly through modulation of non-platelet platelet factor 4 expression.

Gabriel C Tobias, João L P Gomes, Larissa G Fernandes, Vanessa A Voltarelli, Ney R de Almeida, Paulo R Jannig, Rodrigo W Alves de Souza, Carlos E Negrão, Edilamar M Oliveira, Roger Chammas, Christiano R R Alves, Patricia C Brum.

Exercise training reduces the incidence of several cancers, but the mechanisms underlying these effects are not fully understood. Exercise training can affect the spleen function, which controls the hematopoiesis and immune response. Analyzing different cancer models, we identified that 4T1, LLC, and CT26 tumor-bearing mice displayed enlarged spleen (splenomegaly), and exercise training reduced spleen mass toward control levels in two of these models (LLC and CT26). Exercise training also slowed tumor growth in melanoma B16F10, colon tumor 26 (CT26), and Lewis lung carcinoma (LLC) tumor-bearing mice, with minor effects in mammary carcinoma 4T1, MDA-MB-231, and MMTV-PyMT mice. In silico analyses using transcriptome profiles derived from these models revealed that platelet factor 4 (Pf4) is one of the main upregulated genes associated with splenomegaly during cancer progression. To understand whether exercise training would modulate the expression of these genes in the tumor and spleen, we investigated particularly the CT26 model, which displayed splenomegaly and had a clear response to the exercise training effects. RT-qPCR analysis confirmed that trained CT26 tumor-bearing mice had decreased Pf4 mRNA levels in both the tumor and spleen when compared to untrained CT26 tumor-bearing mice. Furthermore, exercise training specifically decreased Pf4 mRNA levels in the CT26 tumor cells. Aspirin treatment did not change tumor growth, splenomegaly, and tumor Pf4 mRNA levels, confirming that exercise decreased non-platelet Pf4 mRNA levels. Finally, tumor Pf4 mRNA levels are deregulated in The Cancer Genome Atlas Program (TCGA) samples and predict survival in multiple cancer types. This highlights the potential therapeutic value of exercise as a complementary approach to cancer treatment and underscores the importance of understanding the exercise-induced transcriptional changes in the spleen for the development of novel cancer therapies.

DOI: https://doi.org/10.1038/s41598-023-47217-2
Int J Mol Sci. 2023 Dec 01. pii: 17034. [Epub ahead of print]24(23):

Calcium's Role and Signaling in Aging Muscle, Cellular Senescence, and Mineral Interactions.

Kristofer Terrell, Suyun Choi, Sangyong Choi.

  Calcium research, since its pivotal discovery in the early 1800s through the heating of limestone, has led to the identification of its multi-functional roles. These include its functions as a reducing agent in chemical processes, structural properties in shells and bones, and significant role in cells relating to this review: cellular signaling. Calcium signaling involves the movement of calcium ions within or between cells, which can affect the electrochemical gradients between intra- and extracellular membranes, ligand binding, enzyme activity, and other mechanisms that determine cell fate. Calcium signaling in muscle, as elucidated by the sliding filament model, plays a significant role in muscle contraction. However, as organisms age, alterations occur within muscle tissue. These changes include sarcopenia, loss of neuromuscular junctions, and changes in mineral concentration, all of which have implications for calcium's role. Additionally, a field of study that has gained recent attention, cellular senescence, is associated with aging and disturbed calcium homeostasis, and is thought to affect sarcopenia progression. Changes seen in calcium upon aging may also be influenced by its crosstalk with other minerals such as iron and zinc. This review investigates the role of calcium signaling in aging muscle and cellular senescence. We also aim to elucidate the interactions among calcium, iron, and zinc across various cells and conditions, ultimately deepening our understanding of calcium signaling in muscle aging.

Keywords:  aging muscle; calcium; iron; senescence; zinc

DOI:  https://doi.org/10.3390/ijms242317034
Biogerontology. 2023 Dec 08.

How soon do metabolic alterations and oxidative distress precede the reduction of muscle mass and strength in Wistar rats in aging process?

Malu Cristina de Araújo Montoro Lima, Matheus Felipe Zazula, Luiz Fernando Martins, Stephanie Rubiane Carvalhal, Ana Tereza Bittencourt Guimarães, Luiz Claudio Fernandes, Katya Naliwaiko.

  Here we investigate metabolic changes, the antioxidant system and the accumulation of oxidative damage in muscles with different fiber types during the aging process in Wistar rats and try to map how sooner the changes occur. To do so, 30 male Wistar rats were submitted to behavioral evaluation to determine voluntary strength in the 11, 15, and 19 month old rats, measuring the energy metabolism, antioxidant system, oxidative damage and structure in the soleus and extensor digitorum longus muscles. We detected structural and metabolic changes in both muscles, especially in the EDL of 15 month old rats and in the soleus of 19 month old rats. In the 15 month old rats, there was a reduction in the cross-sectional area of the fibers, and a reduction in the proportion of type I fibers, accompanied by an increase in fiber density and the amount of type IIA fibers. This change in the fiber profile was followed by an increase in the activity of anaerobic metabolism enzymes, suggesting a reduction in the oxidative capacity of the muscle. In addition, there was an increase in the rate of lipid peroxidation, accompanied by a reduced antioxidant capacity. In the 19 month old rats, these disturbances got stronger. In summary, the present study demonstrated that before functional disturbances, there was an accumulation of oxidative damage and structural changes in the skeletal muscle beginning at 15 months old in the EDL and the soleus only in the biochemical parameters. Therefore, the metabolic alterations occurred at 15 months old and not before.

Keywords:  Aging process; Antioxidant system; Damage accumulation; Energy metabolism

DOI:  https://doi.org/10.1007/s10522-023-10078-3
Hum Mol Genet. 2023 Dec 09. pii: ddad202. [Epub ahead of print]

Long term peripheral AAV9-SMN gene therapy promotes survival in a mouse model of spinal muscular atrophy.

Aoife Reilly, Rebecca Yaworski, Ariane Beauvais, Bernard L Schneider, Rashmi Kothary.

  Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease characterized by motor neuron loss and skeletal muscle atrophy. SMA is caused by the loss of the SMN1 gene and low SMN protein levels. Current SMA therapies work by increasing SMN protein in the body. Although SMA is regarded as a motor neuron disorder, growing evidence shows that several peripheral organs contribute to SMA pathology. A gene therapy treatment, onasemnogene abeparvovec, is being explored in clinical trials via both systemic and central nervous system (CNS) specific delivery, but the ideal route of delivery as well as the long-term effectiveness is unclear. To investigate the impact of gene therapy long term, we assessed SMA mice at 6 months after treatment of either intravenous (IV) or intracerebroventricular (ICV) delivery of scAAV9-cba-SMN. Interestingly, we observed that SMN protein levels were restored in the peripheral tissues but not in the spinal cord at 6 months of age. However, ICV injections provided better motor neuron and motor function protection than IV injection, while IV-injected mice demonstrated better protection of neuromuscular junctions and muscle fiber size. Surprisingly, both delivery routes resulted in an equal rescue on survival, weight, and liver and pancreatic defects. These results demonstrate that continued peripheral AAV9-SMN gene therapy is beneficial for disease improvement even in the absence of SMN restoration in the spinal cord.

Keywords:  adeno-associated virus; gene therapy; mouse model; neuromuscular disease

DOI:  https://doi.org/10.1093/hmg/ddad202
BMC Biol. 2023 Dec 08. 21(1): 287

Geroprotector drugs and exercise: friends or foes on healthy longevity?

Christian J Elliehausen, Rozalyn M Anderson, Gary M Diffee, Timothy W Rhoads, Dudley W Lamming, Troy A Hornberger, Adam R Konopka.

  Physical activity and several pharmacological approaches individually combat age-associated conditions and extend healthy longevity in model systems. It is tantalizing to extrapolate that combining geroprotector drugs with exercise could extend healthy longevity beyond any individual treatment. However, the current dogma suggests that taking leading geroprotector drugs on the same day as exercise may limit several health benefits. Here, we review leading candidate geroprotector drugs and their interactions with exercise and highlight salient gaps in knowledge that need to be addressed to identify if geroprotector drugs can have a harmonious relationship with exercise.

Keywords:  Acarbose; Aging; Geroscience; Healthspan; Metformin; Physical activity; Rapamycin; SGLT2 inhibitors; Skeletal muscle

DOI:  https://doi.org/10.1186/s12915-023-01779-9
NPJ Microgravity. 2023 Dec 13. 9(1): 90

Explainable machine learning identifies multi-omics signatures of muscle response to spaceflight in mice.

Kevin Li, Riya Desai, Ryan T Scott, Joel Ricky Steele, Meera Machado, Samuel Demharter, Adrienne Hoarfrost, Jessica L Braun, Val A Fajardo, Lauren M Sanders, Sylvain V Costes.

The adverse effects of microgravity exposure on mammalian physiology during spaceflight necessitate a deep understanding of the underlying mechanisms to develop effective countermeasures. One such concern is muscle atrophy, which is partly attributed to the dysregulation of calcium levels due to abnormalities in SERCA pump functioning. To identify potential biomarkers for this condition, multi-omics data and physiological data available on the NASA Open Science Data Repository (osdr.nasa.gov) were used, and machine learning methods were employed. Specifically, we used multi-omics (transcriptomic, proteomic, and DNA methylation) data and calcium reuptake data collected from C57BL/6 J mouse soleus and tibialis anterior tissues during several 30+ day-long missions on the international space station. The QLattice symbolic regression algorithm was introduced to generate highly explainable models that predict either experimental conditions or calcium reuptake levels based on multi-omics features. The list of candidate models established by QLattice was used to identify key features contributing to the predictive capability of these models, with Acyp1 and Rps7 proteins found to be the most predictive biomarkers related to the resilience of the tibialis anterior muscle in space. These findings could serve as targets for future interventions aiming to reduce the extent of muscle atrophy during space travel.

DOI: https://doi.org/10.1038/s41526-023-00337-5
J Cachexia Sarcopenia Muscle. 2023 Dec 07.

Obesity worsens mitochondrial quality control and does not protect against skeletal muscle wasting in murine cancer cachexia.

Thomas D Cardaci, Brandon N VanderVeen, Brooke M Bullard, Sierra J McDonald, Christian A Unger, Reilly T Enos, Daping Fan, Kandy T Velázquez, Norma Frizzell, Espen E Spangenburg, E Angela Murphy.

  BACKGROUND: More than 650 million people are obese (BMI > 30) worldwide, which increases their risk for several metabolic diseases and cancer. While cachexia and obesity are at opposite ends of the weight spectrum, leading many to suggest a protective effect of obesity against cachexia, mechanistic support for obesity's benefit is lacking. Given that obesity and cachexia are both accompanied by metabolic dysregulation, we sought to investigate the impact of obesity on skeletal muscle mass loss and mitochondrial dysfunction in murine cancer cachexia.METHODS: Male C57BL/6 mice were given a purified high fat or standard diet for 16 weeks before being implanted with 106 Lewis lung carcinoma (LLC) cells. Mice were monitored for 25 days, and hindlimb muscles were collected for cachexia indices and mitochondrial assessment via western blotting, high-resolution respirometry and transmission electron microscopy (TEM).
RESULTS: Obese LLC mice experienced significant tumour-free body weight loss similar to lean (-12.8% vs. -11.8%, P = 0.0001) but had reduced survival (33.3% vs. 6.67%, χ2 = 10.04, P = 0.0182). Obese LLC mice had reduced muscle weights (-24%, P < 0.0354) and mCSA (-16%, P = 0.0004) with similar activation of muscle p65 (P = 0.0337), and p38 (P = 0.0008). ADP-dependent coupled respiration was reduced in both Obese and Obese LLC muscle (-30%, P = 0.0072) consistent with reductions in volitional cage activity (-39%, P < 0.0001) and grip strength (-41%, P < 0.0001). TEM revealed stepwise reductions in intermyofibrillar and subsarcolemmal mitochondrial size with Obese (IMF: -37%, P = 0.0009; SS: -21%, P = 0.0101) and LLC (IMF: -40%, P = 0.0019; SS: -27%, P = 0.0383) mice. Obese LLC mice had increased pAMPK (T172; P = 0.0103) and reduced FIS1 (P = 0.0029) and DRP1 (P < 0.0001) mitochondrial fission proteins, which were each unchanged in Lean LLC. Further, mitochondrial TEM analysis revealed that Obese LLC mice had an accumulation of damaged and dysfunctional mitochondria (IMF: 357%, P = 0.0395; SS: 138%, P = 0.0174) in concert with an accumulation of p62 (P = 0.0328) suggesting impaired autophagy and clearance of damaged mitochondria. Moreover, we observed increases in electron lucent vacuoles only in Obese LLC muscle (IMF: 421%, P = 0.0260; SS: 392%, P = 0.0192), further supporting an accumulation of damaged materials that cannot be properly cleared in the obese cachectic muscle.
CONCLUSIONS: Taken together, these results demonstrate that obesity is not protective against cachexia and suggest exacerbated impairments to mitochondrial function and quality control with a particular disruption in the removal of damaged mitochondria. Our findings highlight the need for consideration of the severity of obesity and pre-existing metabolic conditions when determining the impact of weight status on cancer-induced cachexia and functional mitochondrial deficits.

Keywords:  Autophagy; High fat diet; Lewis lung carcinoma; Mitochondrial dysfunction; Mitophagy; Muscle atrophy

DOI:  https://doi.org/10.1002/jcsm.13391
Cell Rep. 2023 Dec 05. pii: S2211-1247(23)01552-8. [Epub ahead of print]42(12): 113540

The ER stress sensor IRE1 interacts with STIM1 to promote store-operated calcium entry, T cell activation, and muscular differentiation.

Amado Carreras-Sureda, Xin Zhang, Loann Laubry, Jessica Brunetti, Stéphane Koenig, Xiaoxia Wang, Cyril Castelbou, Claudio Hetz, Yong Liu, Maud Frieden, Nicolas Demaurex.

  Store-operated Ca2+ entry (SOCE) mediated by stromal interacting molecule (STIM)-gated ORAI channels at endoplasmic reticulum (ER) and plasma membrane (PM) contact sites maintains adequate levels of Ca2+ within the ER lumen during Ca2+ signaling. Disruption of ER Ca2+ homeostasis activates the unfolded protein response (UPR) to restore proteostasis. Here, we report that the UPR transducer inositol-requiring enzyme 1 (IRE1) interacts with STIM1, promotes ER-PM contact sites, and enhances SOCE. IRE1 deficiency reduces T cell activation and human myoblast differentiation. In turn, STIM1 deficiency reduces IRE1 signaling after store depletion. Using a CaMPARI2-based Ca2+ genome-wide screen, we identify CAMKG2 and slc105a as SOCE enhancers during ER stress. Our findings unveil a direct crosstalk between SOCE and UPR via IRE1, acting as key regulator of ER Ca2+ and proteostasis in T cells and muscles. Under ER stress, this IRE1-STIM1 axis boosts SOCE to preserve immune cell functions, a pathway that could be targeted for cancer immunotherapy.

Keywords:  CP: Cell biology; CP: Immunology; CRISPR screening; CaMPARI; ER stress; IRE1; SOCE; STIM1; T cells; calcium; muscle

DOI:  https://doi.org/10.1016/j.celrep.2023.113540
Int J Mol Sci. 2023 Nov 29. pii: 16951. [Epub ahead of print]24(23):

Fibroblast Growth Factor 21: A Fascinating Perspective on the Regulation of Muscle Metabolism.

Shuo Li, Jun Chen, Panting Wei, Tiande Zou, Jinming You.

  Fibroblast growth factor 21 (FGF21) plays a vital role in normal eukaryotic organism development and homeostatic metabolism under the influence of internal and external factors such as endogenous hormone changes and exogenous stimuli. Over the last few decades, comprehensive studies have revealed the key role of FGF21 in regulating many fundamental metabolic pathways, including the muscle stress response, insulin signaling transmission, and muscle development. By coordinating these metabolic pathways, FGF21 is thought to contribute to acclimating to a stressful environment and the subsequent recovery of cell and tissue homeostasis. With the emphasis on FGF21, we extensively reviewed the research findings on the production and regulation of FGF21 and its role in muscle metabolism. We also emphasize how the FGF21 metabolic networks mediate mitochondrial dysfunction, glycogen consumption, and myogenic development and investigate prospective directions for the functional exploitation of FGF21 and its downstream effectors, such as the mammalian target of rapamycin (mTOR).

Keywords:  FGF21; insulin signaling; muscle metabolism; myogenic development; stress response

DOI:  https://doi.org/10.3390/ijms242316951