bims-moremu 2024-11-24 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024–11–24
34 papers selected by
Anna Vainshtein, Craft Science Inc.

Muscle fibroblasts and stem cells stimulate motor neurons in an age and exercise-dependent manner.
Human skeletal muscle possesses an epigenetic memory of high intensity interval training.
AMPK regulates the maintenance and remodelling of the neuromuscular junction.
Mechanisms of Muscle Cells Alterations and Regeneration Decline During Aging.
Mapping aged stem cell states associated with decline in skeletal muscle regeneration.
Tenascin-C from the tissue microenvironment promotes muscle stem cell self-renewal through Annexin A2.
Transcriptomic analysis of skeletal muscle regeneration across mouse lifespan identifies altered stem cell states.
Impact of Ageing and Disuse on Neuromuscular Junction and Mitochondrial Function and Morphology: Current Evidence and Controversies.
Inducible and reversible SOD2 knockdown in mouse skeletal muscle drives impaired pyruvate oxidation and reduced metabolic flexibility.
Aerobic capacity and muscle proteome: Insights from a mouse model.
Post-sepsis chronic muscle weakness can be prevented by pharmacological protection of mitochondria.
Genetic reduction of skeletal muscle glycogen synthase 1 abundance reveals that the refeeding-induced reversal of elevated insulin-stimulated glucose uptake after exercise is not attributable to achieving a high muscle glycogen concentration.
Optimized simple culture protocol for inducing mature myotubes from MYOD1-overexpressed human iPS cells.
Personalized phosphoproteomics of skeletal muscle insulin resistance and exercise links MINDY1 to insulin action.
MOTS-c modulates skeletal muscle function by directly binding and activating CK2.
The mitochondrial-targeted peptide therapeutic elamipretide improves cardiac and skeletal muscle function during aging without detectable changes in tissue epigenetic or transcriptomic age.
Ultrastructural alterations and mitochondrial dysfunction in skeletal muscle of peripheral artery disease patients: implications for early therapeutic interventions.
Metabolic flexibility to lipid during exercise is not associated with metabolic health outcomes in individuals without obesity.
Dystrophin interacts with Msp300 to Regulate Myonuclear Positioning and Microtubule Organization.
Theabrownin/whey protein isolate complex coacervate strengthens C2C12 cell proliferation via modulation of energy metabolism and mitochondrial apoptosis.
Three-dimensional tissue engineered skeletal muscle modelling facioscapulohumeral muscular dystrophy.
Endothelial-mesenchymal transition in skeletal muscle: Opportunities and challenges from 3D microphysiological systems.
Recombinant ADAMTS1 promotes muscle cell differentiation and alleviates muscle atrophy by repressing NOTCH1.
Synaptic-like coupling of macrophages to myofibers regulates muscle repair.
FNDC1 is a myokine that promotes myogenesis and muscle regeneration.
Muscle type-specific effects of bilateral abobotulinumtoxinA injection on muscle growth and contractile function in spastic mice.
Femoral artery infusion of αMSH increases muscle thermogenesis and promotes glucose uptake in ovariectomised ewes.
Neurotization of decellularized muscle graft increases de novo type I slow muscle fiber formation and large fiber size frequency.
Ucp1 Ablation Improves Skeletal Muscle Glycolytic Function in Aging Mice.
Regulation of MiR-206 in denervated and dystrophic muscles and its effect on AChR clustering.
Knockout of the Muscle-Specific E3 Ligase MuRF1 Affects Liver Lipid Metabolism upon Dexamethasone Treatment in Mice.
Regulating translation in aging: from global to gene-specific mechanisms.
Muscle Mass, Strength, Power and Physical Performance and Their Association with Quality of Life in Older Adults, the Study of Muscle, Mobility and Aging (SOMMA).
IBS008738, a TAZ activator, facilitates muscle repair and inhibits muscle injury in a mouse model of sport-induced injury.

Aging Cell. 2024 Nov 18. e14413

Muscle fibroblasts and stem cells stimulate motor neurons in an age and exercise-dependent manner.

Casper Soendenbroe, Peter Schjerling, Cecilie J L Bechshøft, Rene B Svensson, Laurent Schaeffer, Michael Kjaer, Bénédicte Chazaud, Arnaud Jacquier, Abigail L Mackey.

  Exercise preserves neuromuscular function in aging through unknown mechanisms. Skeletal muscle fibroblasts (FIB) and stem cells (MuSC) are abundant in skeletal muscle and reside close to neuromuscular junctions, but their relative roles in motor neuron maintenance remain undescribed. Using direct cocultures of embryonic rat motor neurons with either human MuSC or FIB, RNA sequencing revealed profound differential regulation of the motor neuron transcriptome, with FIB generally favoring neuron growth and cell migration and MuSC favoring production of ribosomes and translational machinery. Conditioned medium from FIB was superior to MuSC in preserving motor neurons and increasing their maturity. Lastly, we established the importance of donor age and exercise status and found an age-related distortion of motor neuron and muscle cell interaction that was fully mitigated by lifelong physical activity. In conclusion, we show that human muscle FIB and MuSC synergistically stimulate the growth and viability of motor neurons, which is further amplified by regular exercise.

Keywords:  aging; neural plasticity; neurodegeneration; sarcopenia; satellite stem cell; skeletal muscle; training

DOI:  https://doi.org/10.1111/acel.14413
Am J Physiol Cell Physiol. 2024 Nov 21.

Human skeletal muscle possesses an epigenetic memory of high intensity interval training.

Andrea M Pilotto, Daniel C Turner, Raffaele Mazzolari, Emanuela Crea, Lorenza Brocca, Maria Antonietta Pellegrino, Danilo Miotti, Roberto Bottinelli, Adam P Sharples, Simone Porcelli.

   INTRODUCTION: Human skeletal muscle displays an epigenetic memory of resistance exercise induced by hypertrophy. It is unknown, however, whether high-intensity interval training (HIIT) also evokes an epigenetic muscle memory. This study employed repeated training intervention interspersed with a detraining period to assess epigenetic memory of HIIT.
METHODS: Twenty healthy subjects (25±5yrs) completed two HIIT interventions (training and retraining) lasting 2 months, separated by 3 months of detraining. Measurements at baseline, after training, detraining and retraining included maximal oxygen consumption (V̇ O2max). Vastus lateralis biopsies were taken for genome-wide DNA methylation and targeted gene expression analyses.
RESULTS: V̇ O2max improved during training and retraining (p<0.001) without differences between interventions (p>0.58). Thousands of differentially methylated positions (DMPs) predominantly demonstrated a hypomethylated state after training, retained even after 3-months exercise cessation and into retraining. Five genes; ADAM19, INPP5a, MTHFD1L, CAPN2, SLC16A3 possessed differentially methylated regions (DMRs) with retained hypomethylated memory profiles and increased gene expression. The retained hypomethylation during detraining was associated with an enhancement in expression of the same genes even after 3 months of detraining. SLC16A3, INPP5a, CAPN2 are involved in lactate transport and calcium signaling.
CONCLUSIONS: Despite similar physiological adaptations between training and retraining, memory profiles were found at epigenetic and gene expression level, characterized by retained hypomethylation and increased gene expression after training into long-term detraining and retraining. These genes were associated with calcium signaling and lactate transport. Whilst significant memory was not observed in physiological parameters, our novel findings indicate that human skeletal muscle possesses an epigenetic memory of HIIT.

Keywords:  DNA methylation; endurance exercise; gene transcription; muscle memory

DOI:  https://doi.org/10.1152/ajpcell.00423.2024
Mol Metab. 2024 Nov 19. pii: S2212-8778(24)00197-2. [Epub ahead of print] 102066

AMPK regulates the maintenance and remodelling of the neuromuscular junction.

Sean Y Ng, Andrew I Mikhail, Stephanie R Mattina, Salah A Mohammed, Shahzeb K Khan, Eric M Desjardins, Changhyun Lim, Stuart M Phillips, Gregory R Steinberg, Vladimir Ljubicic.

  The neuromuscular junction (NMJ) is an electrochemical signaling apparatus essential for facilitating muscle contraction and counteracting neurodegenerative processes associated with aging and neuromuscular disorders. Although our understanding of the molecular mechanisms that govern the maintenance and plasticity of the NMJ is limited, recent evidence suggests that AMP-activated protein kinase (AMPK) is an emerging, influential player. Our findings reveal an increased abundance of AMPK transcripts within the NMJ and an age-associated decline in AMPK activity and synapse-specific mitochondrial gene expression. Young mice null for skeletal muscle AMPK displayed a neuromuscular phenotype akin to aged animals. Pharmacological AMPK stimulation facilitated its localization in subsynaptic myonuclei, preceded the induction of several NMJ-related transcripts, and enhanced myotube acetylcholine receptor clustering. Exercise-induced AMPK activation in mouse muscle elicited a broad NMJ-related gene response, consistent with human exercise data. Together, these findings highlight a role for AMPK in the maintenance and remodeling of the NMJ.

Keywords:  Mitochondria; PGC-1α; acetylcholine receptors; aging; exercise

DOI:  https://doi.org/10.1016/j.molmet.2024.102066
Ageing Res Rev. 2024 Nov 18. pii: S1568-1637(24)00407-0. [Epub ahead of print] 102589

Mechanisms of Muscle Cells Alterations and Regeneration Decline During Aging.

Guntarat Chinvattanachot, Daniel Rivas, Gustavo Duque.

  Skeletal muscles are essential for locomotion and body metabolism regulation. As muscles age, they lose strength, elasticity, and metabolic capability, leading to ineffective motion and metabolic derangement. Both cellular and extracellular alterations significantly influence muscle aging. Satellite cells (SCs), the primary muscle stem cells responsible for muscle regeneration, become exhausted, resulting in diminished population and functionality during aging. This decline in SC function impairs intercellular interactions as well as extracellular matrix production, further hindering muscle regeneration. Other muscle-resident cells, such as fibro-adipogenic progenitors (FAPs), pericytes, and immune cells, also deteriorate with age, reducing local growth factor activities and responsiveness to stress or injury. Systemic signaling, including hormonal changes, contributes to muscle cellular catabolism and disrupts muscle homeostasis. Collectively, these cellular and environmental components interact, disrupting muscle homeostasis and regeneration in advancing age. Understanding these complex interactions offers insights into potential regenerative strategies to mitigate age-related muscle degeneration.

Keywords:  Fibro-adipogenic progenitors; Satellite cells; aging; geroscience; muscle regeneration; muscle side population; stem cell exhaustion

DOI:  https://doi.org/10.1016/j.arr.2024.102589
Nat Aging. 2024 Nov 22.

Mapping aged stem cell states associated with decline in skeletal muscle regeneration.

DOI: https://doi.org/10.1038/s43587-024-00768-z
bioRxiv. 2024 Nov 01. pii: 2024.10.29.620732. [Epub ahead of print]

Tenascin-C from the tissue microenvironment promotes muscle stem cell self-renewal through Annexin A2.

Mafalda Loreti, Alessandra Cecchini, Collin D Kaufman, Cedomir Stamenkovic, Alma Renero, Chiara Nicoletti, Anais Kervadec, Gabriele Guarnaccia, Daphne Mayer, Alexandre Colas, Pier Lorenzo Puri, Alessandra Sacco.

Skeletal muscle tissue self-repair occurs through the finely timed activation of resident muscle stem cells (MuSC). Following perturbation, MuSC exit quiescence, undergo myogenic commitment, and differentiate to regenerate the injured muscle. This process is coordinated by signals present in the tissue microenvironment, however the precise mechanisms by which the microenvironment regulates MuSC activation are still poorly understood. Here, we identified Tenascin-C (TnC), an extracellular matrix (ECM) glycoprotein, as a key player in promoting of MuSC self-renewal and function. We show that fibro-adipogenic progenitors (FAPs) are the primary cellular source of TnC during muscle repair, and that MuSC sense TnC signaling through cell the surface receptor Annexin A2. We provide in vivo evidence that TnC is required for efficient muscle repair, as mice lacking TnC exhibit a regeneration phenotype of premature aging. We propose that the decline of TnC in physiological aging contributes to inefficient muscle regeneration in aged muscle. Taken together, our results highlight the pivotal role of TnC signaling during muscle repair in healthy and aging skeletal muscle.

DOI: https://doi.org/10.1101/2024.10.29.620732
Nat Aging. 2024 Nov 22.

Transcriptomic analysis of skeletal muscle regeneration across mouse lifespan identifies altered stem cell states.

Lauren D Walter, Jessica L Orton, Ioannis Ntekas, Ern Hwei Hannah Fong, Viviana I Maymi, Brian D Rudd, Iwijn De Vlaminck, Jennifer H Elisseeff, Benjamin D Cosgrove.

In aging, skeletal muscle regeneration declines due to alterations in both myogenic and non-myogenic cells and their interactions. This regenerative dysfunction is not understood comprehensively or with high spatiotemporal resolution. We collected an integrated atlas of 273,923 single-cell transcriptomes and high-resolution spatial transcriptomic maps from muscles of young, old and geriatric mice (~5, 20 and 26 months old) at multiple time points following myotoxin injury. We identified eight immune cell types that displayed accelerated or delayed dynamics by age. We observed muscle stem cell states and trajectories specific to old and geriatric muscles and evaluated their association with senescence by scoring experimentally derived and curated gene signatures in both single-cell and spatial transcriptomic data. This revealed an elevation of senescent-like muscle stem cell subsets within injury zones uniquely in aged muscles. This Resource provides a holistic portrait of the altered cellular states underlying muscle regenerative decline across mouse lifespan.

DOI: https://doi.org/10.1038/s43587-024-00756-3
Ageing Res Rev. 2024 Nov 16. pii: S1568-1637(24)00404-5. [Epub ahead of print] 102586

Impact of Ageing and Disuse on Neuromuscular Junction and Mitochondrial Function and Morphology: Current Evidence and Controversies.

Evgeniia Motanova, Marco Pirazzini, Samuele Negro, Ornella Rossetto, Marco Narici.

  Inactivity and ageing can have a detrimental impact on skeletal muscle and the neuromuscular junction (NMJ). Decreased physical activity results in muscle atrophy, impaired mitochondrial function, and NMJ instability. Ageing is associated with a progressive decrease in muscle mass, deterioration of mitochondrial function in the motor axon terminals and in myofibres, NMJ instability and loss of motor units. Focusing on the impact of inactivity and ageing, this review examines the consequences on NMJ stability and the role of mitochondrial dysfunction, delving into their complex relationship with ageing and disuse. Evidence suggests that mitochondrial dysfunction can be a pathogenic driver for NMJ alterations, with studies revealing the role of mitochondrial defects in motor neuron degeneration and NMJ instability. Two perspectives behind NMJ instability are discussed: one is that mitochondrial dysfunction in skeletal muscle triggers NMJ deterioration, the other envisages dysfunction of motor terminal mitochondria as a primary contributor to NMJ instability. While evidence from these studies supports both perspectives on the relationship between NMJ dysfunction and mitochondrial impairment, gaps persist in the understanding of how mitochondrial dysfunction can cause NMJ deterioration. Further research, both in humans and in animal models, is essential for unravelling the mechanisms and potential interventions for age- and inactivity-related neuromuscular and mitochondrial alterations.

Keywords:  Ageing; Disuse; Mitochondrial Ca(2+); Mitochondrial dysfunction; Neuromuscular junction; Skeletal muscle

DOI:  https://doi.org/10.1016/j.arr.2024.102586
Free Radic Biol Med. 2024 Nov 16. pii: S0891-5849(24)01018-9. [Epub ahead of print]226 237-250

Inducible and reversible SOD2 knockdown in mouse skeletal muscle drives impaired pyruvate oxidation and reduced metabolic flexibility.

Ethan L Ostrom, Rudy Stuppard, Aurora Mattson-Hughes, David J Marcinek.

   INTRODUCTION: Skeletal muscle mitochondrial dysfunction is a key characteristic of aging muscle and contributes to age related diseases such as sarcopenia, frailty, and type 2 diabetes. Mitochondrial oxidative stress has been implicated as a driving factor in these age-related diseases, however whether it is a cause, or a consequence of mitochondrial dysfunction remains to be determined. The development of flexible genetic models is an important tool to test the mechanistic role of mitochondrial oxidative stress on skeletal muscle metabolic dysfunction. We characterize a new model of inducible and reversible mitochondrial redox stress using a tetracycline controlled skeletal muscle specific short hairpin RNA targeted to superoxide dismutase 2 (iSOD2).
METHODS: iSOD2 KD and control (CON) animals were administered doxycycline for 3- or 12- weeks and followed for up to 24 weeks and mitochondrial respiration and muscle contraction were measured to define the time course of SOD2 KD and muscle functional changes and recovery.
RESULTS: Maximum knockdown of SOD2 protein occurred by 6 weeks and recovered by 24 weeks after DOX treatment. Mitochondrial aconitase activity and maximum mitochondrial respiration declined in KD muscle by 12 weeks and recovered by 24 weeks. There were no significant differences in antioxidant or mitochondrial biogenesis genes between groups. Twelve-week KD showed a small, but significant decrease in muscle fatigue resistance. The primary phenotype was reduced metabolic flexibility characterized by impaired pyruvate driven respiration when other substrates are present. The pyruvate dehydrogenase kinase inhibitor dichloroacetate partially restored pyruvate driven respiration, while the thiol reductant DTT did not.
CONCLUSION: We use a model of inducible and reversible skeletal muscle SOD2 knockdown to demonstrate that elevated matrix superoxide reversibly impairs mitochondrial substrate flexibility characterized by impaired pyruvate oxidation. Despite the bioenergetic effect, the limited change in gene expression suggests that the elevated redox stress in this model is confined to the mitochondrial matrix.

Keywords:  Inducible SOD2 knockdown; Metabolic inflexibility; Mitochondrial oxidative stress; Mitochondrial respiration; Pyruvate oxidation; Skeletal muscle

DOI:  https://doi.org/10.1016/j.freeradbiomed.2024.10.310
Exp Physiol. 2024 Nov 21.

Aerobic capacity and muscle proteome: Insights from a mouse model.

Abel Plaza-Florido, Alejandro Santos-Lozano, Susana López-Ortiz, Beatriz G Gálvez, Joaquín Arenas, Miguel A Martín, Pedro L Valenzuela, Tomàs Pinós, Alejandro Lucia, Carmen Fiuza-Luces.

  We explored the association between aerobic capacity (AC) and the skeletal muscle proteome of McArdle (n = 10) and wild-type (n = 8) mice, as models of intrinsically 'low' and 'normal' AC, respectively. AC was determined as total distance achieved in treadmill running until exhaustion. The quadriceps muscle proteome was studied using liquid chromatography with tandem mass spectrometry, with the Search Tool for the Retrieval of Interacting Genes/Proteins database used to generate protein-protein interaction (PPI) networks and enrichment analyses. AC was significantly associated (P-values ranging from 0.0002 to 0.049) with 73 (McArdle) and 61 (wild-type) proteins (r-values from -0.90 to 0.94). These proteins were connected in PPI networks that enriched biological processes involved in skeletal muscle structure/function in both groups (false discovery rate <0.05). In McArdle mice, the proteins associated with AC were involved in skeletal muscle fibre differentiation/development, lipid oxidation, mitochondrial function and calcium homeostasis, whereas in wild-type animals AC-associated proteins were related to cytoskeleton structure (intermediate filaments), cell cycle regulation and endocytic trafficking. Two proteins (WEE2, THYG) were associated with AC (negatively and positively, respectively) in both groups. Only 14 of the 132 proteins (∼11%) associated with AC in McArdle or wild-type mice were also associated with those previously reported to be modified by aerobic training in these mice, providing preliminary evidence for a large divergence in the muscle proteome signature linked to aerobic training or AC, irrespective of AC (intrinsically low or normal) levels. Our findings might help to gain insight into the molecular mechanisms underlying AC at the muscle tissue level.

Keywords:  cardiorespiratory fitness; endurance; exercise; glycogenosis type V; omics; proteome

DOI:  https://doi.org/10.1113/EP092308
Mol Med. 2024 Nov 19. 30(1): 221

Post-sepsis chronic muscle weakness can be prevented by pharmacological protection of mitochondria.

Meagan S Kingren, Alexander R Keeble, Alyson M Galvan-Lara, Jodi M Ogle, Zoltán Ungvári, Daret K St Clair, Timothy A Butterfield, Allison M Owen, Christopher S Fry, Samir P Patel, Hiroshi Saito.

   BACKGROUND: Sepsis, mainly caused by bacterial infections, is the leading cause of in-patient hospitalizations. After discharge, most sepsis survivors suffer from long-term medical complications, particularly chronic skeletal muscle weakness. To investigate this medical condition in detail, we previously developed a murine severe sepsis-survival model that exhibits long-term post-sepsis skeletal muscle weakness. While mitochondrial abnormalities were present in the skeletal muscle of the sepsis surviving mice, the relationship between abnormal mitochondria and muscle weakness remained unclear. Herein, we aimed to investigate whether mitochondrial abnormalities have a causal role in chronic post-sepsis muscle weakness and could thereby serve as a therapeutic target.
METHODS: Experimental polymicrobial abdominal sepsis was induced in 16-18 months old male and female mice using cecal slurry injection with subsequent antibiotic and fluid resuscitation. To evaluate the pathological roles of mitochondrial abnormalities in post-sepsis skeletal muscle weakness, we utilized a transgenic mouse strain overexpressing the mitochondria-specific antioxidant enzyme manganese superoxide dismutase (MnSOD). Following sepsis development in C57BL/6 mice, we evaluated the effect of the mitochondria-targeting synthetic tetrapeptide SS-31 in protecting mitochondria from sepsis-induced damage and preventing skeletal muscle weakness development. In vivo and in vitro techniques were leveraged to assess muscle function at multiple timepoints throughout sepsis development and resolution. Histological and biochemical analyses including bulk mRNA sequencing were used to detect molecular changes in the muscle during and after sepsis RESULTS: Our time course study revealed that post sepsis skeletal muscle weakness develops progressively after the resolution of acute sepsis and in parallel with the accumulation of mitochondrial abnormalities and changes in the mitochondria-related gene expression profile. Transgenic mice overexpressing MnSOD were protected from mitochondrial abnormalities and muscle weakness following sepsis. Further, pharmacological protection of mitochondria utilizing SS-31 during sepsis effectively prevented the later development of muscle weakness.
CONCLUSIONS: Our study revealed that the accumulation of mitochondrial abnormalities is the major cause of post-sepsis skeletal muscle weakness. Pharmacological protection of mitochondria during acute sepsis is a potential clinical treatment strategy to prevent post-sepsis muscle weakness.

Keywords:  Critical care illness; Mitochondrial myopathy; Muscle weakness; Post-sepsis syndrome

DOI:  https://doi.org/10.1186/s10020-024-00982-w
FASEB J. 2024 Nov 30. 38(22): e70176

Genetic reduction of skeletal muscle glycogen synthase 1 abundance reveals that the refeeding-induced reversal of elevated insulin-stimulated glucose uptake after exercise is not attributable to achieving a high muscle glycogen concentration.

Seong Eun Kwak, Haiyan Wang, Xiufang Pan, Dongsheng Duan, Gregory D Cartee.

One exercise session can increase subsequent insulin-stimulated glucose uptake (ISGU) by skeletal muscle. Postexercise refeeding induces reversal of postexercise (PEX)-enhanced ISGU concomitant with attaining high muscle glycogen in rats. To test the relationship between high glycogen and reversal of PEX-ISGU, we injected one epitrochlearis muscle from each rat with adeno-associated virus (AAV) small hairpin RNA (shRNA) that targets glycogen synthase 1 (GS1) and injected contralateral muscles with AAV-shRNA-Scrambled (Scr). Muscles from PEX and sedentary rats were collected at 3-hour PEX (3hPEX) or 6-hour PEX (6hPEX). Rats were either not refed or refed rat-chow during the recovery period. Isolated muscles were incubated with [3H]-3-O-methylglucose, with or without insulin. The results revealed: (1) GS1 abundance was substantially lower for AAV-shRNA-GS1-treated versus AAV-shRNA-Scr-treated muscles; (2) reduced GS1 abundance in refed-rats induced much lower glycogen in AAV-shRNA-GS1-treated versus AAV-shRNA-Scr-treated muscles at 3hPEX or 6hPEX; (3) PEX-ISGU was elevated in not refed-rats at either 3hPEX or 6hPEX versus sedentary controls, regardless of GS1 abundance; (4) PEX-ISGU was not reversed by 3 h of refeeding, regardless of GS1 abundance; (5) despite substantially lower glycogen in AAV-shRNA-GS1-treated versus AAV-shRNA-Scr-treated muscles, elevated PEX-ISGU was eliminated at 6hPEX in both of the paired muscles of refed-rats; and (6) 3hPEX versus sedentary non-refed rats had greater AMP-activated protein kinase-γ3 activity in both paired muscles, but this exercise effect was eliminated in both paired muscles by 3 h of refeeding. In conclusion, the results provided compelling evidence that the reversal of exercise-enhanced ISGU by refeeding was not attributable to the accumulation of high muscle glycogen concentration.

DOI: https://doi.org/10.1096/fj.202401859R
Sci Rep. 2024 Nov 20. 14(1): 28783

Optimized simple culture protocol for inducing mature myotubes from MYOD1-overexpressed human iPS cells.

Eiji Wada, Nao Susumu, Yuya Okuzaki, Akitsu Hotta, Hidetoshi Sakurai, Yukiko K Hayashi.

  The forced expression system of MYOD1, a master gene for myogenic differentiation, can efficiently and rapidly reproduce muscle differentiation of human induced pluripotent stem cells (hiPSCs). Despite these advantages of the MYOD1 overexpression system, developed myotubes are relatively immature and do not recapitulate several aspects of striated muscle fibers. Here, we developed a simple optimized protocol using an alternative culture medium for maximizing the advantages of the MYOD1 overexpression system, and successfully improved the formation of multinucleated mature myotubes within 10 days. In this study, we generated hiPSCs derived from healthy donors and an individual with congenial muscular dystrophy caused by LMNA mutation (laminopathy), and compared disease-associated phenotypes in differentiated myotubes generated by the conventional method and by our new optimized culture method. Using our optimized method, abnormal myonuclear shape was pronounced in the patient-derived iPSCs. In addition, abnormal accumulation of the nuclear membrane protein emerin was observed in LMNA-mutant hiPSCs. Our new culture method is expected to be widely applicable as a MYOD1 overexpression model of hiPSC-derived skeletal muscle cells for the analysis of a variety of muscle diseases.

Keywords:  Differentiation of skeletal muscle cells; Induced pluripotent stem cells; Laminopathy; Muscular dystrophy; Newly developed culture method

DOI:  https://doi.org/10.1038/s41598-024-79745-w
Cell Metab. 2024 Nov 18. pii: S1550-4131(24)00416-9. [Epub ahead of print]

Personalized phosphoproteomics of skeletal muscle insulin resistance and exercise links MINDY1 to insulin action.

Elise J Needham, Janne R Hingst, Johan D Onslev, Alexis Diaz-Vegas, Magnus R Leandersson, Hannah Huckstep, Jonas M Kristensen, Kohei Kido, Erik A Richter, Kurt Højlund, Benjamin L Parker, Kristen Cooke, Guang Yang, Christian Pehmøller, Sean J Humphrey, David E James, Jørgen F P Wojtaszewski.

  Type 2 diabetes is preceded by a defective insulin response, yet our knowledge of the precise mechanisms is incomplete. Here, we investigate how insulin resistance alters skeletal muscle signaling and how exercise partially counteracts this effect. We measured parallel phenotypes and phosphoproteomes of insulin-resistant (IR) and insulin-sensitive (IS) men as they responded to exercise and insulin (n = 19, 114 biopsies), quantifying over 12,000 phosphopeptides in each biopsy. Insulin resistance involves selective and time-dependent alterations to signaling, including reduced insulin-stimulated mTORC1 and non-canonical signaling responses. Prior exercise promotes insulin sensitivity even in IR individuals by "priming" a portion of insulin signaling prior to insulin infusion. This includes MINDY1 S441, which we show is an AKT substrate. We found that MINDY1 knockdown enhances insulin-stimulated glucose uptake in rat myotubes. This work delineates the signaling alterations in IR skeletal muscle and identifies MINDY1 as a regulator of insulin action.

Keywords:  MINDY1; cell signaling; exercise; insulin; insulin resistance; phosphoproteomics; proteomics; skeletal muscle

DOI:  https://doi.org/10.1016/j.cmet.2024.10.020
iScience. 2024 Nov 15. 27(11): 111212

MOTS-c modulates skeletal muscle function by directly binding and activating CK2.

Hiroshi Kumagai, Su-Jeong Kim, Brendan Miller, Hirofumi Zempo, Kumpei Tanisawa, Toshiharu Natsume, Shin Hyung Lee, Junxiang Wan, Naphada Leelaprachakul, Michi Emma Kumagai, Ricardo Ramirez, Hemal H Mehta, Kevin Cao, Tae Jung Oh, James A Wohlschlegel, Jihui Sha, Yuichiro Nishida, Noriyuki Fuku, Shohei Dobashi, Eri Miyamoto-Mikami, Mizuki Takaragawa, Mizuho Fuku, Toshinori Yoshihara, Hisashi Naito, Ryoko Kawakami, Suguru Torii, Taishi Midorikawa, Koichiro Oka, Megumi Hara, Chiharu Iwasaka, Yosuke Yamada, Yasuki Higaki, Keitaro Tanaka, Kelvin Yen, Pinchas Cohen.

  MOTS-c is a mitochondrial microprotein that improves metabolism. Here, we demonstrate CK2 is a direct and functional target of MOTS-c. MOTS-c directly binds to CK2 and activates it in cell-free systems. MOTS-c administration to mice prevented skeletal muscle atrophy and enhanced muscle glucose uptake, which were blunted by suppressing CK2 activity. Interestingly, the effects of MOTS-c are tissue-specific. Systemically administered MOTS-c binds to CK2 in fat and muscle, yet stimulates CK2 activity in muscle while suppressing it in fat by differentially modifying CK2-interacting proteins. Notably, a naturally occurring MOTS-c variant, K14Q MOTS-c, has reduced binding to CK2 and does not activate it or elicit its effects. Male K14Q MOTS-c carriers exhibited a higher risk of sarcopenia and type 2 diabetes (T2D) in an age- and physical-activity-dependent manner, whereas females had an age-specific reduced risk of T2D. Altogether, these findings provide evidence that CK2 is required for MOTS-c effects.

Keywords:  Physiology; cell biology

DOI:  https://doi.org/10.1016/j.isci.2024.111212
bioRxiv. 2024 Oct 31. pii: 2024.10.30.620676. [Epub ahead of print]

The mitochondrial-targeted peptide therapeutic elamipretide improves cardiac and skeletal muscle function during aging without detectable changes in tissue epigenetic or transcriptomic age.

Wayne Mitchell, Gavin Pharaoh, Alexander Tyshkovskiy, Matthew Campbell, David J Marcinek, Vadim N Gladyshev.

Aging-related decreases in cardiac and skeletal muscle function are strongly associated with various comorbidities. Elamipretide (ELAM), a novel mitochondrial-targeted peptide, has demonstrated broad therapeutic efficacy in ameliorating disease conditions associated with mitochondrial dysfunction across both clinical and pre-clinical models. ELAM is proposed to restore mitochondrial bioenergetic function by stabilizing inner membrane structure and increasing oxidative phosphorylation coupling and efficiency. Although ELAM treatment effectively attenuates physiological declines in multiple tissues in rodent aging models, it remains unclear whether these functional improvements correlate with favorable changes in molecular biomarkers of aging. Herein, we investigated the impact of 8-week ELAM treatment on pre- and post-measures of C57BL/6J mice frailty, skeletal muscle, and cardiac muscle function, coupled with post-treatment assessments of biological age and affected molecular pathways. We found that health status, as measured by frailty index, cardiac strain, diastolic function, and skeletal muscle force are significantly diminished with age, with skeletal muscle force changing in a sex-dependent manner. Conversely, ELAM mitigated frailty accumulation and was able to partially reverse these declines, as evidenced by treatment-induced increases in cardiac strain and muscle fatigue resistance. Despite these improvements, we did not detect statistically significant changes in gene expression or DNA methylation profiles indicative of molecular reorganization or reduced biological age in most ELAM-treated groups. However, pathway analyses revealed that ELAM treatment showed pro-longevity shifts in gene expression such as upregulation of genes involved in fatty acid metabolism, mitochondrial translation and oxidative phosphorylation, and downregulation of inflammation. Together, these results indicate that ELAM treatment is effective at mitigating signs of sarcopenia and heart failure in an aging mouse model, but that these functional improvements occur independently of detectable changes in epigenetic and transcriptomic age. Thus, some age-related changes in function may be uncoupled from changes in molecular biological age.

DOI: https://doi.org/10.1101/2024.10.30.620676
EXCLI J. 2024 ;23 1208-1225

Ultrastructural alterations and mitochondrial dysfunction in skeletal muscle of peripheral artery disease patients: implications for early therapeutic interventions.

Dylan Wilburn, Emma Fletcher, Evlampia Papoutsi, William T Bohannon, Gleb Haynatzki, Bernd Zechmann, Yuqian Tian, Iraklis I Pipinos, Dimitrios Miserlis, Panagiotis Koutakis.

  Peripheral artery disease (PAD) is an atherosclerotic condition that impairs blood flow to the lower extremities, resulting in myopathy in affected skeletal muscles. Improving our understanding of PAD and developing novel treatment strategies necessitates a comprehensive examination of cellular structural alterations that occur in the muscles with disease progression. Here we aimed to employ electron microscopy to quantify skeletal muscle ultrastructural alterations responsible for the myopathy of PAD. Fifty-two participants (22 controls, 10 PAD Stage II, and 20 PAD Stage IV) were enrolled. Gastrocnemius biopsies were obtained to determine mitochondrial respiration and oxidative stress. Skeletal muscle sarcomere, mitochondria, lipid droplets, and sarcoplasm were assessed using transmission electron microscopy and focused ion beam scanning electron microscopy. Controls and PAD Stage II patients underwent walking performance tests: 6-minute walking test, 4-minute walking velocity, and maximum graded treadmill test. We identified several prominent ultrastructural modifications in PAD gastrocnemius, including reduced sarcomere dimensions, alterations in mitochondria number and localization, myofibrillar disorientation, changes in lipid droplets, and modifications in mitochondria-lipid droplet contact area. These changes correlated with impaired mitochondrial respiration and increased ROS production. We observed progressive deterioration in mitochondrial parameters across PAD stages. Stage II PAD showed impaired mitochondrial function and structure, while stage IV exhibited further deterioration, more pronounced structural alterations, and a decrease in mitochondrial content. The walking performance of Stage II PAD patients was significantly reduced. Our findings suggest that pathological mitochondria play a key role in the skeletal muscle dysfunction of PAD patients and represent an important target for therapeutic interventions aimed at improving clinical and functional outcomes in this patient population. Our data indicate that treatments should be implemented early and may include therapies designed to preserve and enhance mitochondrial biogenesis and respiration, optimize mitochondrial-lipid droplet interactions, or mitigate oxidative stress. Translational Perspective: Peripheral artery disease (PAD) is characterized by skeletal muscle and mitochondrial dysfunction. Ultrastructural changes in skeletal muscle myofibers and mitochondria morphology can provide significant information on the PAD pathophysiology. Here, we investigated skeletal muscle and mitochondria morphological and functional changes at the sarcomere level and across the disease progression and have found that sarcomere lengths and mitochondria count and function are associated with disease progression, indicating loss of skeletal muscle contractile and metabolic function. Ultrastructural changes in the PAD skeletal muscle can provide significant information in the development of new treatments.

Keywords:  intramyocellular lipids; mitochondria; muscle; peripheral artery disease; sarcomere atrophy; sarcoplasm

DOI:  https://doi.org/10.17179/excli2024-7592
Sci Rep. 2024 Nov 19. 14(1): 28642

Metabolic flexibility to lipid during exercise is not associated with metabolic health outcomes in individuals without obesity.

Rodrigo Fernández-Verdejo, Juan Gutiérrez-Pino, Thomas Hayes-Ortiz, Hermann Zbinden-Foncea, Claudio Cabello-Verrugio, Mayalen Valero-Breton, Mauro Tuñón-Suárez, Ronald Vargas-Foitzick, Jose E Galgani.

  A low metabolic flexibility to lipid (MetF-lip) in skeletal muscle may promote ectopic lipid accumulation, thus inducing metabolic disturbances. We aimed to determine the association between MetF-lip in skeletal muscle and metabolic health outcomes in individuals without obesity. We also explored the association between MetF-lip and the inflammatory signaling pathway in skeletal muscle. This was a cross-sectional study in 17 individuals aged (median [IQR]) 55.4 [48.6, 58.5] years, with a BMI of 24.4 [22.6, 26.0] kg/m2. MetF-lip was assessed as the increase in relative lipid oxidation during a single exercise session (~ 50% VO2max, 2 hours), quantified as the drop in whole-body respiratory exchange ratio (ΔRER = RER at 2 hours - maximum RER attained). HOMA-IR, metabolic syndrome z-score, fat percentage, trunk-to-appendicular fat, and VO2max were included as metabolic health outcomes. The abundance of proteins of the inflammatory pathway was analyzed in resting muscle. Acute exercise progressively increased relative lipid oxidation (ΔRER = -0.04 [-0.08, -0.02]). MetF-lip was not associated with any metabolic health outcome but correlated inversely with p-p38Thr180/Tyr182 in muscle. A low MetF-lip in skeletal muscle does not seem a major determinant of metabolic disturbances but associates with a partial activation of the inflammatory signaling in individuals without obesity.

Keywords:  Body composition; Cardiorespiratory Fitness; Insulin resistance; Mitogen-activated protein kinases

DOI:  https://doi.org/10.1038/s41598-024-79092-w
bioRxiv. 2024 Nov 08. pii: 2024.11.07.622444. [Epub ahead of print]

Dystrophin interacts with Msp300 to Regulate Myonuclear Positioning and Microtubule Organization.

Jorel R Padilla, Yunshu Qiu, Grace Aleck, Lillie Ferreria, Sharon Wu, William Gibbons, Torrey Mandigo, Eric S Folker.

During Drosophila myognesis, myonuclei are actively moved during embryogenesis, and their spacing is maintained through an anchoring mechanism in the fully differentiated myofiber. While we have identified microtubule associated proteins, motors, and nuclear envelope proteins that regulate myonuclear spacing, the developmental time during which each gene functions has not been tested. Here we have identified a Dystrophin as required only for the maintenance of myonuclear spacing. Furthermore, we demonstrate that Dystrophin genetically interacts with the KASH-domain protein Msp300 to maintain myonuclear spacing. Mechanistically, both Dystrophin and Msp300 regulate microtubule organization. Specifically, in animals with disrupted expression of both Dystrophin and Msp300 , microtubule colocalization with sarcomeres is reduced. Taken altogether, these data indicate that the peripheral membrane protein Dystrophin, and the outer nuclear membrane protein Msp300, together regulate the organization of the microtubule network which then acts as an anchor to restrict myonuclear movement in contractile myofibers. These data are consistent with growing evidence that myonuclear movement and myonuclear spacing are critical to muscle development, muscle function, and muscle repair and provide a mechanism to connect disparate muscle diseases.
Summary Statement: Here we show that Dystrophin is required to maintain the spacing of nuclei in differentiated myofibers. Furthermore, Dystrophin achieves this function via a genetic interaction with Msp300 which regulates microtubule organization.

DOI: https://doi.org/10.1101/2024.11.07.622444
Int J Biol Macromol. 2024 Nov 17. pii: S0141-8130(24)08496-4. [Epub ahead of print] 137686

Theabrownin/whey protein isolate complex coacervate strengthens C2C12 cell proliferation via modulation of energy metabolism and mitochondrial apoptosis.

Yang Wei, Yi Huang, Caican Wen, Kang Wei, Lanlan Peng, Xinlin Wei.

  Theabrownin (TB)-whey protein isolate (WPI) complex coacervates (TW) were firstly prepared to investigate the regulatory effects on skeletal muscle. The binding of TB to WPI reached saturation with the strongest electrostatic interaction at the ratio of 10:1. The formation of TW was driven by electrostatic interactions with the aid of hydrogen bonding and hydrophobic interactions, and the digestion behavior of TW was investigated based on in vitro gastrointestinal and CaCO2 cell models. The regulatory effect of TW on muscle cells was investigated by C2C12 cell assay. Cell cycle analysis showed that TW promoted the transition of skeletal muscle cells from proliferative state to differentiated state. Immunofluorescence and gene expression revealed that TW positively regulated myogenic regulatory factors, contributing to myofiber formation. Moreover, TW activated the intracellular TCA cycling and oxidative phosphorylation, providing energy for skeletal muscle regeneration and repair. Mechanistically, TW inhibited the release of cytochrome C from mitochondria to cytoplasm through the Bcl-2/Cytochrome C/Cleaved-Caspase-3 pathway, exhibiting a protective effect on skeletal muscle cells. In the future, the molecular mechanism of TW enhancing skeletal muscle function should be validated through aging animal models and clinical trials and expand its therapeutic application for muscle health in functional food and dietary supplements.

Keywords:  Formation mechanism; Skeletal muscle function; Theabrownin-whey protein isolate complex coacervate

DOI:  https://doi.org/10.1016/j.ijbiomac.2024.137686
Brain. 2024 Nov 18. pii: awae379. [Epub ahead of print]

Three-dimensional tissue engineered skeletal muscle modelling facioscapulohumeral muscular dystrophy.

Marnix Franken, Erik van der Wal, Dongxu Zheng, Bianca den Hamer, Patrick J van der Vliet, Richard J L F Lemmers, Anita van den Heuvel, Alexandra L Dorn, Cas G A Duivenvoorden, Stijn L M In't Groen, Christian Freund, Bert Eussen, Rabi Tawil, Baziel G M van Engelen, Pim W W M P Pijnappel, Silvère M van der Maarel, Jessica C de Greef.

  Facioscapulohumeral muscular dystrophy (FSHD) is caused by sporadic misexpression of the transcription factor double homeobox 4 (DUX4) in skeletal muscles. So far, monolayer cultures and animal models have been used to study the FSHD disease mechanism and for FSHD therapy development, but these models do not fully recapitulate the disease and there is a lack of knowledge on how DUX4 misexpression leads to skeletal muscle dysfunction. To overcome these barriers, we have developed a three-dimensional tissue engineered skeletal muscle (3D-TESM) model by generating genetically matched myogenic progenitors (MPs) from human induced pluripotent stem cells of three mosaic FSHD patients. 3D-TESMs derived from genetically affected MPs recapitulate pathological features including DUX4 and DUX4 target gene expression, smaller myofiber diameters, and reduced absolute forces upon electrical stimulation. RNA sequencing data illustrates increased expression of DUX4 target genes in 3D-TESMs compared to two-dimensional (2D) myotubes, and cellular differentiation was improved by 3D culture conditions. Treatment of 3D-TESMs with three different small molecules identified in drug development screens in 2D muscle cultures showed no improvements, and sometimes even declines, in contractile force and sarcomere organization. These results suggest that these compounds either have a detrimental effect on the formation of 3D-TESMs, an effect that might have been overlooked or was challenging to detect in 2D cultures and in vivo models, and/or that further development of the 3D-TESM model is needed. In conclusion, we have developed a 3D skeletal muscle model for FSHD that can be employed for preclinical research focusing on DUX4 expression and downstream pathways of FSHD in relation to contractile properties. In the future, we expect that this model can also be used for preclinical drug screening.

Keywords:  3D tissue engineering; DUX4; FSHD; disease modelling; hiPSC; mosaic

DOI:  https://doi.org/10.1093/brain/awae379
Bioeng Transl Med. 2024 Sep;9(5): e10644

Endothelial-mesenchymal transition in skeletal muscle: Opportunities and challenges from 3D microphysiological systems.

Riccardo Francescato, Matteo Moretti, Simone Bersini.

  Fibrosis is a pathological condition that in the muscular context is linked to primary diseases such as dystrophies, laminopathies, neuromuscular disorders, and volumetric muscle loss following traumas, accidents, and surgeries. Although some basic mechanisms regarding the role of myofibroblasts in the progression of muscle fibrosis have been discovered, our knowledge of the complex cell-cell, and cell-matrix interactions occurring in the fibrotic microenvironment is still rudimentary. Recently, vascular dysfunction has been emerging as a key hallmark of fibrosis through a process called endothelial-mesenchymal transition (EndoMT). Nevertheless, no effective therapeutic options are currently available for the treatment of muscle fibrosis. This lack is partially due to the absence of advanced in vitro models that can recapitulate the 3D architecture and functionality of a vascularized muscle microenvironment in a human context. These models could be employed for the identification of novel targets and for the screening of potential drugs blocking the progression of the disease. In this review, we explore the potential of 3D human muscle models in studying the role of endothelial cells and EndoMT in muscle fibrotic tissues and identify limitations and opportunities for optimizing the next generation of these microphysiological systems. Starting from the biology of muscle fibrosis and EndoMT, we highlight the synergistic links between different cell populations of the fibrotic microenvironment and how to recapitulate them through microphysiological systems.

Keywords:  biofabrication; fibrosis; in vitro 3D modeling; organ‐on‐a‐chip; vascularization

DOI:  https://doi.org/10.1002/btm2.10644
BMB Rep. 2024 Nov 21. pii: 6299. [Epub ahead of print]

Recombinant ADAMTS1 promotes muscle cell differentiation and alleviates muscle atrophy by repressing NOTCH1.

Sang Hyup Lee, Sang Yoon Kim, Yun Gu Gwon, Chanwoo Lee, Changhwan Kim, Ick Hyun Cho, Tae-Won Kim, Bong-Keun Choi.

A disintegrin and metalloproteinase with thrombospondin motifs 1 (ADAMTS1) plays crucial roles in various biological processes, including myogenesis, by modulating the neurogenic locus notch homolog protein 1 (NOTCH1) signaling pathway. However, the mechanisms through which ADAMTS1 regulates myogenesis remain unclear. In this study, we generated recombinant ADAMTS1 mutants and determined their effects on muscle cell differentiation, focusing on the regulation of NOTCH1 signaling. Treatment of C2C12 cells with recombinant ADAMTS1 protein enhanced muscle cell differentiation. Meanwhile, ADAM10 treatment inhibited muscle differentiation through the activation of NOTCH1 cleavage. Recombinant ADAMTS1 reversed ADAM10-induced muscle cell atrophy by suppressing NOTCH1 activation and downregulating its target gene. Recombinant ADAMTS1 also alleviated dexamethasoneinduced muscle atrophy in a mouse model. In summary, our findings suggest that recombinant ADAMTS1 promotes muscle regeneration by suppressing NOTCH1 and highlight the potential of recombinant ADAMTS1 proteins in the treatment of muscle wasting disease.
Res Sq. 2024 Oct 28. pii: rs.3.rs-5290399. [Epub ahead of print]

Synaptic-like coupling of macrophages to myofibers regulates muscle repair.

Gyanesh Tripathi, Adam Dourson, Jennifer Wayland, Sahana Khanna, Megan Hoffmann, Thirupugal Govindarajan, Fabian Montecino Morales, Luis Queme, Douglas Millay, Michael P Jankowski.

Peripheral injury responses essential for muscle repair and nociception require complex interactions of target tissues, immune cells and primary sensory neurons. Nociceptors and myofibers both react robustly to signals generated from circulating immune cells, which promote repair, growth, and regeneration of muscle while simultaneously modulating peripheral sensitization. Here, we found that macrophages form a synaptic-like contact with myofibers to hasten repair after acute incision injury and to facilitate regeneration after major muscle damage. Transient chemogenetic activation of macrophages enhanced calcium dependent membrane repair, induced muscle calcium waves in vivo , elicited low level electrical activity in the muscles and enhanced myonuclear accretion. Under severe injury, macrophage activation could also modulate pain-like behaviors. This study identifies a novel mechanism by which synaptic-like functions of macrophages impacts muscle repair after tissue damage.

DOI: https://doi.org/10.21203/rs.3.rs-5290399/v1
EMBO J. 2024 Nov 20.

FNDC1 is a myokine that promotes myogenesis and muscle regeneration.

Rui Xin Zhang, Yuan Yuan Zhai, Rong Rong Ding, Jia He Huang, Xiao Chen Shi, Huan Liu, Xiao Peng Liu, Jian Feng Zhang, Jun Feng Lu, Zhe Zhang, Xiang Kai Leng, De Fu Li, Jun Ying Xiao, Bo Xia, Jiang Wei Wu.

  Myogenesis is essential for skeletal muscle formation and regeneration after injury, yet its regulators are largely unknown. Here we identified fibronectin type III domain containing 1 (FNDC1) as a previously uncharacterized myokine. In vitro studies showed that knockdown of Fndc1 in myoblasts reduces myotube formation, while overexpression of Fndc1 promotes myogenic differentiation. We further generated recombinant truncated mouse FNDC1 (mFNDC1), which retains reliable activity in promoting myoblast differentiation in vitro. Gain- and loss-of-function studies collectively showed that FNDC1 promotes cardiotoxin (CTX)-induced muscle regeneration in adult mice. Furthermore, recombinant FNDC1 treatment ameliorated pathological muscle phenotypes in the mdx mouse model of Duchenne muscular dystrophy. Mechanistically, FNDC1 bound to the integrin α5β1 and activated the downstream FAK/PI3K/AKT/mTOR pathway to promote myogenic differentiation. Pharmacological inhibition of integrin α5β1 or of the downstream FAK/PI3K/AKT/mTOR pathway abolished the pro-myogenic effect of FNDC1. Collectively, these results suggested that myokine FNDC1 might be used as a therapeutic agent to regulate myogenic differentiation and muscle regeneration for the treatment of acute and chronic muscle disease.

Keywords:  FNDC1; Integrin α5β1; Muscle Regeneration; Myogenic Differentiation

DOI:  https://doi.org/10.1038/s44318-024-00285-0
FASEB J. 2024 Nov 30. 38(22): e70141

Muscle type-specific effects of bilateral abobotulinumtoxinA injection on muscle growth and contractile function in spastic mice.

Cintia Rivares, Alban Vignaud, Wendy Noort, Guus Baan, Bastijn Koopmans, Maarten Loos, Rob C I Wüst, Mikhail Kalinichev, Richard T Jaspers.

  Intramuscular injection of botulinum neurotoxin type A (BoNT-A) is commonly used to improve or maintain the joint range of motion in young children with spasticity. However, the effectiveness of BoNT-A treatment is variable and movement limitations are recurrent. Here we show long-term effects of a single, bilateral abobotulinumtoxinA (aboBoNT-A) injection in the gastrocnemius medialis and soleus muscles of wild-type and spastic (B6.Cg-Glrbspa/J with a mutation in the glycine receptor) mice at a young age (6-7 days). Specifically, we evaluated the impact of aboBoNT-A-A on gait, physical performance, and spontaneous physical behavior, as well as on contractile force characteristics, morphology, and histological phenotype of soleus and gastrocnemius muscles by comparing their results to those of saline-injected controls up to 9 weeks after the injection. The detailed time course of the study specifies the timing of the aboBoNT-A injection at 1 week, the period of behavioral studies from 4-9 weeks, and the age of the mice (10 weeks) at the time of contractile force characteristics and histology assessments. In spastic mice, aboBoNT-A injection had a minor and very specific effect on physical performance, by only modestly increasing stride length as a function of age. aboBoNT-A injection caused a reduction in the force-generating capacity and a slightly smaller physiological cross-sectional area in gastrocnemius medialis, but not in soleus. Reduced physiological cross-sectional area in aboBoNT-A-injected muscles was due to a lower number of muscle fibers, rather than reduced muscle fiber cross-sectional area. The percentage of slow-type muscle fibers and mitochondrial succinate dehydrogenase activity were increased, which was associated with an improved muscle endurance capacity. In conclusion, aboBoNT-A injection reduced the number of muscle fibers, causing muscle hypertrophy in remaining fibers and a shift towards more oxidative fibers, resulting in an improved endurance capacity and gait. This study proposed potential cellular mechanisms for the therapeutic efficacy of aboBoNT-A in spasticity.

Keywords:  chemical denervation; gait; muscle endurance; muscle fiber typing; muscle oxidative capacity; physiological cross‐sectional area; plantar flexor muscles; sarcomeres

DOI:  https://doi.org/10.1096/fj.202302258R
Endocrinology. 2024 Nov 19. pii: bqae156. [Epub ahead of print]

Femoral artery infusion of αMSH increases muscle thermogenesis and promotes glucose uptake in ovariectomised ewes.

Belinda A Henry, Michael A Cowley, Zane B Andrews, Iain J Clarke.

  The melanocortin system is fundamental to neural control of energy balance and long-term weight regulation. Recent evidence shows that melanocortins also act at peripheral tissues to regulate metabolism, independent of the brain or the sympathetic nervous system (SNS). One such target is skeletal muscle, which contributes to energy expenditure through changes in adaptive thermogenesis. We aimed to determine 1. whether direct femoral infusion of αMSH could increase muscle heat production independent of SNS activation and 2. if α-MSH-induced skeletal muscle heat production was associated with altered mitochondrial function. Dataloggers were implanted into one hind-leg of ovariectomised ewes and set to record vastus lateralis temperature every 15 mins. A cannula was inserted into one femoral artery for infusion of either αMSH (0.1 μg/ h) or saline. Femoral infusion of αMSH increased (P<0.0001) skeletal muscle heat production, without effect on food intake. State 4 respiration increased (P<0.05) and the respiratory control ratio decreased (P<0.05) in mitochondria isolated from αMSH-treated animals. In addition, femoral infusion of αMSH reduced plasma glucose concentration in the femoral, but not the jugular vein; there was no effect of αMSH treatment on non-esterified fatty acid concentrations. These data suggest that αMSH can act locally to increase glucose uptake. We further show that blockade of the α- and β-adrenergic limbs of the SNS with either phentolamine or propranolol infusion, had no effect on αMSH-induced skeletal muscle heat production. Overall, we show that αMSH acts directly at skeletal muscle to promote glucose uptake and increase energy expenditure via mitochondrial thermogenesis.

Keywords:  Skeletal muscle; energy expenditure; melanocortins; mitochondria

DOI:  https://doi.org/10.1210/endocr/bqae156
Acta Biomater. 2024 Nov 17. pii: S1742-7061(24)00677-9. [Epub ahead of print]

Neurotization of decellularized muscle graft increases de novo type I slow muscle fiber formation and large fiber size frequency.

James T Redden, David J Cohen, Lucas C Olson, Geetanjali Bendale, Jonathan E Isaacs, Zvi Schwartz, Michael J McClure.

  Volumetric muscle loss (VML) injuries are the result of extreme trauma from battlefield injuries, tumor ablations, and other physical traumas such as car crash injuries. The abrupt loss of muscle restricts the tissue's remaining regenerative capacity, leading to loss of satellite cells, peripheral nerve connections, and aberrant fibrosis. Prior research from our lab demonstrated that decellularized muscle matrix (DMM) supported regeneration of de novo fibers within the graft. The goal of this study was to determine whether DMM treated with a peripheral nerve using neurotization surgeries would enhance muscle regeneration and innervation. Forty-eight male Sprague Dawley rats were randomized and received a 1.5×1 cm defect treated with no treatment empty defect (ED), DMM, or autograft with a direct peroneal (antagonist) neurotization or tibial via end to side graft (agonist) neurotization. DMM grafts treated with neurotization utilizing either peroneal or tibial nerve axons increased fast twitch fibers within the grafted area compared to untreated DMM or ED. Additionally, the frequency distribution of myofiber size shifted toward a healthier morphology in the tibial nerve axon neurotized DMM compared to the uninjured medial head. Lastly, Nanostring gene results showed DMM treated with a neurotization shifted expression towards a more regenerative phenotype with some myogenic markers returning to sham levels. These data indicate that injured muscle treated with DMM and neurotization becomes pro-regenerative and can contribute to the functionalization of DMM. STATEMENT OF SIGNIFICANCE: Extremity soft tissue trauma like volumetric muscle loss (VML) can result in permanent loss of skeletal muscle mass, denervation, and ischemia posing a significant clinical challenge. VML injuries disrupt normal tissue architecture in addition to intramuscular axons which are critical elements in muscle function and regeneration. The overall objective of this study was to enhance axon growth into a VML injury treated with decellularized muscle matrix (DMM) using neurotization. DMM is an acellular biomaterial capable of regenerating skeletal muscle; however, without bona fide neuromuscular connections, functional gains are small. This study demonstrates that introducing motor axons into an acellular regenerative material using neurotization enhanced muscle regeneration and promoted slow twitch fiber formation.

Keywords:  Atrophy; Decellularized muscle matrix; Extracellular matrix; Peripheral nerve

DOI:  https://doi.org/10.1016/j.actbio.2024.11.022
Adv Sci (Weinh). 2024 Nov 21. e2411015

Ucp1 Ablation Improves Skeletal Muscle Glycolytic Function in Aging Mice.

Jin Qiu, Yuhan Guo, Xiaozhen Guo, Ziqi Liu, Zixuan Li, Jun Zhang, Yutang Cao, Jiaqi Li, Shuwu Yu, Sainan Xu, Juntong Chen, Dongmei Wang, Jian Yu, Mingwei Guo, Wenhao Zhou, Sainan Wang, Yiwen Wang, Xinran Ma, Cen Xie, Lingyan Xu.

  Muscular atrophy is among the systematic decline in organ functions in aging, while defective thermogenic fat functionality precedes these anomalies. The potential crosstalk between adipose tissue and muscle during aging is poorly understood. In this study, it is showed that UCP1 knockout (KO) mice characterized deteriorated brown adipose tissue (BAT) function in aging, yet their glucose homeostasis is sustained and energy expenditure is increased, possibly compensated by improved inguinal adipose tissue (iWAT) and muscle functionality compared to age-matched WT mice. To understand the potential crosstalk, RNA-seq and metabolomic analysis were performed on adipose tissue and muscle in aging mice and revealed that creatine levels are increased both in iWAT and muscle of UCP1 KO mice. Interestingly, molecular analysis and metabolite tracing revealed that creatine biosynthesis is increased in iWAT while creatine uptake is increased in muscle in UCP1 KO mice, suggesting creatine transportation from iWAT to muscle. Importantly, creatine analog β-GPA abolished the differences in muscle functions between aging WT and UCP1 KO mice, while UCP1 inhibitor α-CD improved muscle glycolytic function and glucose metabolism in aging mice. Overall, these results suggested that iWAT and skeletal muscle compensate for declined BAT function during aging via creatine metabolism to sustain metabolic homeostasis.

Keywords:  aging; creatine; glycolytic function; skeletal muscle; thermogenic adipose tissue

DOI:  https://doi.org/10.1002/advs.202411015
J Cell Sci. 2024 Nov 22. pii: jcs.262303. [Epub ahead of print]

Regulation of MiR-206 in denervated and dystrophic muscles and its effect on AChR clustering.

Joseph Barden, Olivia Kosloski, Amir Jadidian, Mohammed Akaaboune.

  Muscle-specific microRNA miR-206 has recently emerged as a potential regulator of genes involved in the formation and regeneration of the neuromuscular junction (NMJ). This study investigated miR-206-3p (miR-206) expression in synaptic and non-synaptic regions of denervated and in alpha-dystrobrevin (Dtnb) knockout mice, as well as its impact on the formation and/or maintenance of agrin-induced acetylcholine receptor (AChR) clusters. In denervated, Dtnb-deficient, and crushed muscles, miR-206 expression significantly increased compared to innervated muscles. While miR-206 expression is slightly elevated in the synaptic regions of innervated muscles, it dramatically rises in non-synaptic areas of denervated muscles. miR-206 targets transcripts of essential NMJ proteins such as Dtnb, alpha-syntrophin (Snta1), and rapsyn, but not AchRα subunit or Lrp4 in innervated muscles. However, in denervated muscles, AChRα transcripts, which increase significantly, become a target of miR-206. Co-expression of miR-206 with rapsyn, Dtnb, and Snta1 in C2C12 myoblasts significantly reduced their protein levels, and overexpression of miR-206 in myotubes disrupted agrin-induced AChR clustering. These results indicate that miR-206 fine-tunes NMJ signaling proteins by regulating transcripts of various proteins with different localizations under normal and pathological conditions.

Keywords:  Cell culture; Dystrophin-glycoprotein complex; Fluorescence; Mouse; Neuromuscular junction; Nicotinic acetylcholine receptors (nAChR); microRNA (miRNA)

DOI:  https://doi.org/10.1242/jcs.262303
ACS Omega. 2024 Nov 12. 9(45): 45610-45623

Knockout of the Muscle-Specific E3 Ligase MuRF1 Affects Liver Lipid Metabolism upon Dexamethasone Treatment in Mice.

Laurent Mosoni, Arno Germond, Cécile Coudy-Gandilhon, Mélodie Malige, Agnès Claustre, Coralie Delabrise, Mehdi Djelloul-Mazouz, Yoann Delorme, Julien Hermet, Pierre Fafournoux, Lydie Combaret, Cécile Polge, Anne-Catherine Maurin, Daniel Taillandier.

In order to preserve muscle mass during catabolic states, investigators are actively searching for a specific inhibitor of MuRF1, the only known E3 ligase that can target muscle contractile proteins for their degradation. However, what would be the consequences of such inhibitors on other organs, both in the short and long term? Indeed, skeletal muscles can provide amino acids for liver gluconeogenesis, which is a crucial adaptation for maintaining glucose homeostasis upon elevated energy demands (e.g., during prolonged starvation). Comparing 3-month-old wild-type and MuRF1-KO mice, we measured tissue weights, liver glycogen, lipid and protein content, and liver biochemical composition using Fourier transform infrared (FTIR) spectrometry in control animals and in dexamethasone (Dex)-treated animals. Dex induces a catabolic situation with muscle atrophy and lipid deposits in the liver. In response to Dex treatment, liver glycogen, lipid, and protein content increased in wild type (WT) and MuRF1-KO mice. We found that MuRF1 deletion differentially affected organ weights, the liver of KO mice being hypertrophied upon Dex treatment when compared to WT mice. Upon Dex treatment, muscle mass was preserved in MuRF1-KO mice, and by contrast, liver lipid content increased more in these animals than in WT mice. PLS-DA analysis of FTIR showed that the levels of 13 markers were significantly altered in KO vs WT mice, witnessing profound alterations of lipid, protein, and glycogen content in the liver due to the absence of MuRF1. Using Nile red and oil red lipid staining, we also found that both membrane-linked lipids and intracellular lipid droplets were altered due to the absence of MuRF1. Altogether, it seems that when the liver is deprived of the possibility of obtaining amino acids from muscle upon Dex treatment, there is a concomitant increase in tissue weight and anabolic activity.

DOI: https://doi.org/10.1021/acsomega.4c08501
EMBO Rep. 2024 Nov 19.

Regulating translation in aging: from global to gene-specific mechanisms.

Mathilde Solyga, Amitabha Majumdar, Florence Besse.

  Aging is characterized by a decline in various biological functions that is associated with changes in gene expression programs. Recent transcriptome-wide integrative studies in diverse organisms and tissues have revealed a gradual uncoupling between RNA and protein levels with aging, which highlights the importance of post-transcriptional regulatory processes. Here, we provide an overview of multi-omics analyses that show the progressive uncorrelation of transcriptomes and proteomes during the course of healthy aging. We then describe the molecular changes leading to global downregulation of protein synthesis with age and review recent work dissecting the mechanisms involved in gene-specific translational regulation in complementary model organisms. These mechanisms include the recognition of regulated mRNAs by trans-acting factors such as miRNA and RNA-binding proteins, the condensation of mRNAs into repressive cytoplasmic RNP granules, and the pausing of ribosomes at specific residues. Lastly, we mention future challenges of this emerging field, possible buffering functions as well as potential links with disease.

Keywords:  Aging; Post-transcriptional Regulation; RNA; RNA-Binding Proteins; Tanslation

DOI:  https://doi.org/10.1038/s44319-024-00315-2
J Frailty Aging. 2024 ;13(4): 384-390

Muscle Mass, Strength, Power and Physical Performance and Their Association with Quality of Life in Older Adults, the Study of Muscle, Mobility and Aging (SOMMA).

N Petnehazy, H N Barnes, A B Newman, S B Kritchevsky, S R Cummings, R T Hepplen, P M Cawthon.

   BACKGROUND: Sarcopenia negatively impacts quality of life. It is unclear whether different measures of muscle size, strength, physical performance, and fitness have similar associations with quality of life.
OBJECTIVE: To describe associations of sarcopenia metrics with quality of life outcomes.
PARTICIPANTS: Community-dwelling adults aged 70+ years participating in the SOMMA (Study of Muscle, Mobility and Aging) study, (N=875 ((women: 519, men:356)), age, years 76.3±5.0).
DESIGN AND SETTINGS: Two academic medical centers.
MEASUREMENTS: Measures included muscle size (MRI- muscle volume. D3Cr muscle mass); strength and power (grip strength, leg extension power and strength, stair climb); walking and physical performance (4m and 400m walk, SPPB (Short Physical Performance Battery), chair stand); fitness (VO2 peak); health related quality of life (EQ-5D); and anthropometrics (weight, height, and body mass index). Results were stratified by sex. Correlations, scatterplots and linear regression models described the association between various measures of sarcopenia and fitness with overall quality of life score (EQ5D VAS) as a continuous variable. We also quantified differences between sarcopenia and fitness measures by overall QOL (Quality of Life) as a categorical variable (low, medium, high) and by QOL subcomponents (pain and discomfort, problems with usual activities, mobility, anxiety and depression, and problems with self-care) using distributionally appropriate methods.
RESULTS: Walking tests and physical performance were most consistently (but modestly) associated with overall quality of life (r~0.2, p<.001) and its subcomponents. For both men and women, several sarcopenia and fitness measures were more strongly associated with pain and usual activity than other QOL components.
CONCLUSIONS: Poor performance, lower fitness and lower strength are related to worse quality of life, particularly pain, in older adults. Future studies should quantify these relationships longitudinally.

Keywords:   quality of life; D3Cr muscle mass; EQ5D; SPPB; Sarcopenia; VO2max; aging; muscle

DOI:  https://doi.org/10.14283/jfa.2024.45
Cytotechnology. 2025 Feb;77(1): 2

IBS008738, a TAZ activator, facilitates muscle repair and inhibits muscle injury in a mouse model of sport-induced injury.

Yiming Wang, Datian Liu, Sining Wang, Yiliang Li, Guanming Liu.

  High-intensity exercise can cause excessive generation of ROS and induce oxidative stress injury in the body, which is a major reason accounting for muscle damage following exercise. The previous study demonstrated that IBS008738, the activator of TZA, was able to enhance myogenesis in mouse myogenic C2C12 cells, prevent dexamethasone-induced muscle atrophy, and facilitate muscle repair in cardiotoxin-induced muscle injury. Accordingly, our study was designed to probe into the potential role of IBS008738 in muscle damage in mouse models induced by high-intensity exercise. Mice were first administrated with IBS008738, and then subjected to high-intensity eccentric exercise to induce muscle damage after 24 h. During the experiment, mouse weight change and food take were recorded. At the end of the experiment, blood samples were collected through cardiac puncture and centrifugated. Serum levels of blood urea nitrogen (BUN), creatinine, glucose, lactate dehydrogenase (LDH), creatinine kinase (CK), and C-related protein were evaluated using an autoanalyzer. After mice were sacrificed, the gastrocnemius muscles were dissected for DCFH-DA assay of ROS generation, thiobarbituric acid-reactive substances (TBARS) assay of MDA content, hematoxylin-eosin (H&E) staining of histological examination, and western blotting analysis of Akt/mTOR/S6K1 signaling expression. IBS008738 and/or exercise exert significant effects on mouse weight and food take. High-intensity exercise markedly increased ROS generation and lipid peroxidation, upregulated serum levels of CK, LDH, and C-related protein, ameliorated muscle histological damage, and reduced TAZ, phosphorylated (p)-Akt, p-mTOR, and p-S6K1 protein levels in mice. However, IBS008738 administration reversed the above changes induced by high-intensity exercise in mice. IBS008738 alleviates oxidative stress and muscle damage in mice after high-intensity exercise by activating TAZ and the Akt/mTOR/S6K1 signaling pathway.
Supplementary Information: The online version contains supplementary material available at 10.1007/s10616-024-00667-6.

Keywords:  Akt/mTOR/S6K1 signaling pathway; High-intensity exercise; IBS008738; Muscle injury; Oxidative stress; TAZ

DOI:  https://doi.org/10.1007/s10616-024-00667-6