bims-moremu 2024-05-05 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2024–05–05
37 papers selected by
Anna Vainshtein, Craft Science Inc.

Molecular adaptations in response to exercise training are associated with tissue-specific transcriptomic and epigenomic signatures.
Temporal dynamics of the multi-omic response to endurance exercise training.
The impact of exercise on gene regulation in association with complex trait genetics.
The mitochondrial multi-omic response to exercise training across rat tissues.
Sexual dimorphism and the multi-omic response to exercise training in rat subcutaneous white adipose tissue.
Endurance exercise causes a multi-organ full-body molecular reaction.
Not Only Protein: Dietary Supplements to Optimize the Skeletal Muscle Growth Response to Resistance Training: The Current State of Knowledge.
Building, Breaking, and Repairing Neuromuscular Synapses.
Neuromodulatory Contribution to Muscle Force Production after Short-Term Unloading and Active Recovery.
IGF1 promotes human myotube differentiation toward a mature metabolic and contractile phenotype.
Differences in thick filament activation in fast rodent skeletal muscle and slow porcine cardiac muscle.
A therapeutic leap: how myosin inhibitors moved from cardiac interventions to skeletal muscle myopathy solutions.
Metabolomic analysis of dietary-restriction-induced attenuation of sarcopenia in prematurely aging DNA repair-deficient mice.
Myospreader improves gene editing in skeletal muscle by myonuclear propagation.
Concerted regulation of skeletal muscle metabolism and contractile properties by the orphan nuclear receptor Nr2f6.
SETDB1 modulates the TGFβ response in Duchenne muscular dystrophy myotubes.
Intermittent glucocorticoid treatment improves muscle metabolism via the PGC1α/Lipin1 axis in an aging-related sarcopenia model.
Thbs1 regulates skeletal muscle mass in a TGFβ-Smad2/3-ATF4-dependent manner.
PHF2 regulates sarcomeric gene transcription in myogenesis.
High-intensity exercise training using a rotarod instrument (RotaHIIT) significantly improves exercise capacity in mice.
Lactate-induced metabolic remodeling and myofiber type transitions via activation of the Ca2+-NFATC1 signaling pathway.
Acid α-glucosidase (GAA) activity and glycogen content in muscle biopsy specimens of patients with Pompe disease: A systematic review.
Prolyl isomerase Pin1 in skeletal muscles contributes to systemic energy metabolism and exercise capacity through regulating SERCA activity.
Skeletal muscle dysfunction in amyotrophic lateral sclerosis: a mitochondrial perspective and therapeutic approaches.
ANKRD1 expression is aberrantly upregulated in the mdm mouse model of muscular dystrophy and induced by stretch through NFκB.
UBE2C promotes myoblast differentiation and skeletal muscle regeneration through the Akt signaling pathway.
Septin 7 interacts with Numb to preserve sarcomere structural organization and muscle contractile function.
MCU genetically altered mice suggest how mitochondrial Ca2+ regulates metabolism.
Mitochondrial stress response and myogenic differentiation.
Ablation of specific insulin-like growth factor I forms reveals the importance of cleavage for regenerative capacity and glycosylation for skeletal muscle storage.
Bioinformatics Analysis Identifies Key Genes in the Effect of Resistance Training on Female Skeletal Muscle Aging.
GLP-2 ameliorates D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a signaling pathway in C2C12 cells and mice.
Brain-muscle communication prevents muscle aging by maintaining daily physiology.
Exerkine FNDC5/irisin-enriched exosomes promote proliferation and inhibit ferroptosis of osteoblasts through interaction with Caveolin-1.
Neuronal innervation regulates the secretion of neurotrophic myokines and exosomes from skeletal muscle.
Temporal regulation of the Mediator complex during muscle proliferation, differentiation, regeneration, aging, and disease.
The Mediator Med23 controls a transcriptional switch for muscle stem cell proliferation and differentiation in muscle regeneration.

Cell Genom. 2024 Apr 29. pii: S2666-979X(23)00247-1. [Epub ahead of print] 100421

Molecular adaptations in response to exercise training are associated with tissue-specific transcriptomic and epigenomic signatures.

MoTrPAC Study Group

  Regular exercise has many physical and brain health benefits, yet the molecular mechanisms mediating exercise effects across tissues remain poorly understood. Here we analyzed 400 high-quality DNA methylation, ATAC-seq, and RNA-seq datasets from eight tissues from control and endurance exercise-trained (EET) rats. Integration of baseline datasets mapped the gene location dependence of epigenetic control features and identified differing regulatory landscapes in each tissue. The transcriptional responses to 8 weeks of EET showed little overlap across tissues and predominantly comprised tissue-type enriched genes. We identified sex differences in the transcriptomic and epigenomic changes induced by EET. However, the sex-biased gene responses were linked to shared signaling pathways. We found that many G protein-coupled receptor-encoding genes are regulated by EET, suggesting a role for these receptors in mediating the molecular adaptations to training across tissues. Our findings provide new insights into the mechanisms underlying EET-induced health benefits across organs.

Keywords:  ATAC-seq; DNA methylation; GPCR; RNA-seq; RRBS; chromatin accessibility; endurance training; sex differences; tissue specificity; transcriptome

DOI:  https://doi.org/10.1016/j.xgen.2023.100421
Nature. 2024 May;629(8010): 174-183

Temporal dynamics of the multi-omic response to endurance exercise training.

MoTrPAC Study Group

Regular exercise promotes whole-body health and prevents disease, but the underlying molecular mechanisms are incompletely understood1-3. Here, the Molecular Transducers of Physical Activity Consortium4 profiled the temporal transcriptome, proteome, metabolome, lipidome, phosphoproteome, acetylproteome, ubiquitylproteome, epigenome and immunome in whole blood, plasma and 18 solid tissues in male and female Rattus norvegicus over eight weeks of endurance exercise training. The resulting data compendium encompasses 9,466 assays across 19 tissues, 25 molecular platforms and 4 training time points. Thousands of shared and tissue-specific molecular alterations were identified, with sex differences found in multiple tissues. Temporal multi-omic and multi-tissue analyses revealed expansive biological insights into the adaptive responses to endurance training, including widespread regulation of immune, metabolic, stress response and mitochondrial pathways. Many changes were relevant to human health, including non-alcoholic fatty liver disease, inflammatory bowel disease, cardiovascular health and tissue injury and recovery. The data and analyses presented in this study will serve as valuable resources for understanding and exploring the multi-tissue molecular effects of endurance training and are provided in a public repository ( https://motrpac-data.org/ ).

DOI: https://doi.org/10.1038/s41586-023-06877-w
Nat Commun. 2024 May 01. 15(1): 3346

The impact of exercise on gene regulation in association with complex trait genetics.

MoTrPAC Study Group

Endurance exercise training is known to reduce risk for a range of complex diseases. However, the molecular basis of this effect has been challenging to study and largely restricted to analyses of either few or easily biopsied tissues. Extensive transcriptome data collected across 15 tissues during exercise training in rats as part of the Molecular Transducers of Physical Activity Consortium has provided a unique opportunity to clarify how exercise can affect tissue-specific gene expression and further suggest how exercise adaptation may impact complex disease-associated genes. To build this map, we integrate this multi-tissue atlas of gene expression changes with gene-disease targets, genetic regulation of expression, and trait relationship data in humans. Consensus from multiple approaches prioritizes specific tissues and genes where endurance exercise impacts disease-relevant gene expression. Specifically, we identify a total of 5523 trait-tissue-gene triplets to serve as a valuable starting point for future investigations [Exercise; Transcription; Human Phenotypic Variation].

DOI: https://doi.org/10.1038/s41467-024-45966-w
Cell Metab. 2024 Apr 15. pii: S1550-4131(23)00472-2. [Epub ahead of print]

The mitochondrial multi-omic response to exercise training across rat tissues.

MoTrPAC Study Group

  Mitochondria have diverse functions critical to whole-body metabolic homeostasis. Endurance training alters mitochondrial activity, but systematic characterization of these adaptations is lacking. Here, the Molecular Transducers of Physical Activity Consortium mapped the temporal, multi-omic changes in mitochondrial analytes across 19 tissues in male and female rats trained for 1, 2, 4, or 8 weeks. Training elicited substantial changes in the adrenal gland, brown adipose, colon, heart, and skeletal muscle. The colon showed non-linear response dynamics, whereas mitochondrial pathways were downregulated in brown adipose and adrenal tissues. Protein acetylation increased in the liver, with a shift in lipid metabolism, whereas oxidative proteins increased in striated muscles. Exercise-upregulated networks were downregulated in human diabetes and cirrhosis. Knockdown of the central network protein 17-beta-hydroxysteroid dehydrogenase 10 (HSD17B10) elevated oxygen consumption, indicative of metabolic stress. We provide a multi-omic, multi-tissue, temporal atlas of the mitochondrial response to exercise training and identify candidates linked to mitochondrial dysfunction.

Keywords:  HSD17B10; acetylome; aerobic; exercise; metabolism; metabolomics; mitochondria; multi-omics; proteomics; transcriptomics

DOI:  https://doi.org/10.1016/j.cmet.2023.12.021
Nat Metab. 2024 May 01.

Sexual dimorphism and the multi-omic response to exercise training in rat subcutaneous white adipose tissue.

MoTrPAC Study Group

Subcutaneous white adipose tissue (scWAT) is a dynamic storage and secretory organ that regulates systemic homeostasis, yet the impact of endurance exercise training (ExT) and sex on its molecular landscape is not fully established. Utilizing an integrative multi-omics approach, and leveraging data generated by the Molecular Transducers of Physical Activity Consortium (MoTrPAC), we show profound sexual dimorphism in the scWAT of sedentary rats and in the dynamic response of this tissue to ExT. Specifically, the scWAT of sedentary females displays -omic signatures related to insulin signaling and adipogenesis, whereas the scWAT of sedentary males is enriched in terms related to aerobic metabolism. These sex-specific -omic signatures are preserved or amplified with ExT. Integration of multi-omic analyses with phenotypic measures identifies molecular hubs predicted to drive sexually distinct responses to training. Overall, this study underscores the powerful impact of sex on adipose tissue biology and provides a rich resource to investigate the scWAT response to ExT.

DOI: https://doi.org/10.1038/s42255-023-00959-9
Nature. 2024 May 01.

Endurance exercise causes a multi-organ full-body molecular reaction.



Keywords:  Health care; Metabolism; Molecular biology

DOI:  https://doi.org/10.1038/d41586-024-00585-9
J Hum Kinet. 2024 Mar;91(Spec Issue): 225-244

Not Only Protein: Dietary Supplements to Optimize the Skeletal Muscle Growth Response to Resistance Training: The Current State of Knowledge.

Antonio Paoli, Giuseppe Cerullo, Antonino Bianco, Marco Neri, Federico Gennaro, Davide Charrier, Tatiana Moro.

  Regarding skeletal muscle hypertrophy, resistance training and nutrition, the most often discussed and proposed supplements include proteins. Although, the correct amount, quality, and daily distribution of proteins is of paramount importance for skeletal muscle hypertrophy, there are many other nutritional supplements that can help and support the physiological response of skeletal muscle to resistance training in terms of muscle hypertrophy. A healthy muscle environment and a correct whole muscle metabolism response to the stress of training is a prerequisite for the increase in muscle protein synthesis and, therefore, muscle hypertrophy. In this review, we discuss the role of different nutritional supplements such as carbohydrates, vitamins, minerals, creatine, omega-3, polyphenols, and probiotics as a support and complementary factors to the main supplement i.e., protein. The different mechanisms are discussed in the light of recent evidence.

Keywords:  ergogenic aids; muscle hypertrophy; strength training

DOI:  https://doi.org/10.5114/jhk/18666
Cold Spring Harb Perspect Biol. 2024 May 02. pii: a041490. [Epub ahead of print]16(5):

Building, Breaking, and Repairing Neuromuscular Synapses.

Ruth Herbst, Maartje G Huijbers, Julien Oury, Steven J Burden.

A coordinated and complex interplay of signals between motor neurons, skeletal muscle cells, and Schwann cells controls the formation and maintenance of neuromuscular synapses. Deficits in the signaling pathway for building synapses, caused by mutations in critical genes or autoantibodies against key proteins, are responsible for several neuromuscular diseases, which cause muscle weakness and fatigue. Here, we describe the role that four key genes, Agrin, Lrp4, MuSK, and Dok7, play in this signaling pathway, how an understanding of their mechanisms of action has led to an understanding of several neuromuscular diseases, and how this knowledge has contributed to emerging therapies for treating neuromuscular diseases.

DOI: https://doi.org/10.1101/cshperspect.a041490
Med Sci Sports Exerc. 2024 May 01.

Neuromodulatory Contribution to Muscle Force Production after Short-Term Unloading and Active Recovery.

Giovanni Martino, Giacomo Valli, Fabio Sarto, Martino V Franchi, Marco V Narici, Giuseppe De Vito.

PURPOSE: Prior evidence has shown that neural factors contribute to the loss of muscle force after skeletal-muscle disuse. However, little is known about the specific neural mechanisms altered by disuse. Persistent inward current (PIC) is an intrinsic property of motoneurons responsible for prolonging and amplifying the synaptic input, proportionally to the level of neuromodulation, thus influencing motoneuron discharge rate and force production. Here, we hypothesized that short-term unilateral lower-limb suspension (ULLS) would reduce the neuromodulatory input associated with PICs, contributing to the reduction of force generation capacity. Additionally, we tested whether physical exercise would restore the force generation capacity by re-establishing the initial level of neuromodulatory input.
METHODS: In 12 young adults, we assessed maximal voluntary contraction (MVC) pre- and post- 10 days of ULLS and following 21 days of active recovery (AR) based on resistance exercise. PIC was estimated from high-density surface electromyograms of the vastus lateralis muscle as the delta frequency (∆F) of paired motor units calculated during isometric ramped contractions.
RESULTS: The values of ∆F were reduced after 10 days of ULLS (-33%, p < 0.001), but were fully re-established after the AR (+29.4%, p < 0.001). The changes in estimated PIC values were correlated (r = 0.63, p = 0.004) with the reduction in MVC after ULLS (-29%, p = 0.002) and its recovery after the AR (+28.5%, p = 0.003).
CONCLUSIONS: Our findings suggest that PIC estimates are reduced by muscle disuse and may contribute to the loss of force production and its recovery with exercise. Overall, this is the first study demonstrating that, in addition to peripheral neuromuscular changes, central neuromodulation is a major contributor to the loss of force generation capacity after disuse, and can be recovered after resistance exercise.

DOI: https://doi.org/10.1249/MSS.0000000000003473
Am J Physiol Cell Physiol. 2024 Mar 04.

IGF1 promotes human myotube differentiation toward a mature metabolic and contractile phenotype.

Simon I Dreher, Paul Grubba, Christine von Toerne, Alessia Moruzzi, Jennifer Maurer, Thomas Goj, Andreas L Birkenfeld, Andreas Peter, Peter Loskill, Stefanie M Hauck, Cora Weigert.

  Skeletal muscle mediates the beneficial effects of exercise, thereby improving insulin sensitivity and reducing the risk for type 2 diabetes. Current human skeletal muscle models in vitro are incapable of fully recapitulating its physiological functions especially muscle contractility. By supplementation of insulin-like growth factor 1 (IGF1), a growth factor secreted by myofibers in vivo, we aimed to overcome these limitations. We monitored the differentiation process starting from primary human CD56-positive myoblasts in the presence/absence of IGF1 in serum-free medium in daily collected samples for 10 days. IGF1-supported differentiation formed thicker multinucleated myotubes showing physiological contraction upon electrical pulse stimulation following day 6. Myotubes without IGF1 were almost incapable of contraction. IGF1-treatment shifted the proteome toward skeletal muscle-specific proteins that contribute to myofibril and sarcomere assembly, striated muscle contraction, and ATP production. Elevated PPARGC1A, MYH7 and reduced MYH1/2 suggest a more oxidative phenotype further demonstrated by higher abundance of proteins of the respiratory chain and elevated mitochondrial respiration. IGF1-treatment also upregulated GLUT4 and increased insulin-dependent glucose uptake compared to myotubes differentiated without IGF1. To conclude, addition of IGF1 to serum-free medium significantly improves the differentiation of human myotubes that showed enhanced myofibril formation, response to electrical pulse stimulation, oxidative respiratory capacity and glucose metabolism overcoming limitations of previous standards. This novel protocol enables investigation of muscular exercise on a molecular level.

Keywords:  Contraction; EPS; GLUT4; Human myotubes; Proteomics

DOI:  https://doi.org/10.1152/ajpcell.00654.2023
J Physiol. 2024 May 02.

Differences in thick filament activation in fast rodent skeletal muscle and slow porcine cardiac muscle.

Jing Zhao, Lin Qi, Shengyao Yuan, Thomas C Irving, Weikang Ma.

  There is a growing appreciation that regulation of muscle contraction requires both thin filament and thick filament activation in order to fully activate the sarcomere. The prevailing mechano-sensing model for thick filament activation was derived from experiments on fast-twitch muscle. We address the question whether, or to what extent, this mechanism can be extrapolated to the slow muscle in the hearts of large mammals, including humans. We investigated the similarities and differences in structural signatures of thick filament activation in porcine myocardium as compared to fast rat extensor digitorum longus (EDL) skeletal muscle under relaxed conditions and sub-maximal contraction using small angle X-ray diffraction. Thick and thin filaments were found to adopt different structural configurations under relaxing conditions, and myosin heads showed different changes in configuration upon sub-maximal activation, when comparing the two muscle types. Titin was found to have an X-ray diffraction signature distinct from those of the overall thick filament backbone, and its spacing change appeared to be positively correlated to the force exerted on the thick filament. Structural changes in fast EDL muscle were found to be consistent with the mechano-sensing model. In porcine myocardium, however, the structural basis of mechano-sensing is blunted suggesting the need for additional activation mechanism(s) in slow cardiac muscle. These differences in thick filament regulation can be related to their different physiological roles where fast muscle is optimized for rapid, burst-like, contractions, and the slow cardiac muscle in large mammalian hearts adopts a more finely tuned, graded response to allow for their substantial functional reserve. KEY POINTS: Both thin filament and thick filament activation are required to fully activate the sarcomere. Thick and thin filaments adopt different structural configurations under relaxing conditions, and myosin heads show different changes in configuration upon sub-maximal activation in fast extensor digitorum longus muscle and slow porcine cardiac muscle. Titin has an X-ray diffraction signature distinct from those of the overall thick filament backbone and this titin reflection spacing change appeared to be directly proportional to the force exerted on the thick filament. Mechano-sensing is blunted in porcine myocardium suggesting the need for additional activation mechanism(s) in slow cardiac muscle. Fast skeletal muscle is optimized for rapid, burst-like contractions, and the slow cardiac muscle in large mammalian hearts adopts a more finely tuned graded response to allow for their substantial functional reserve.

Keywords:  X‐ray diffraction; porcine heart; skeletal muscle; thick filament activation

DOI:  https://doi.org/10.1113/JP286072
J Clin Invest. 2024 May 01. pii: e179958. [Epub ahead of print]134(9):

A therapeutic leap: how myosin inhibitors moved from cardiac interventions to skeletal muscle myopathy solutions.

Julius Bogomolovas, Ju Chen.

The myosin inhibitor mavacamten has transformed the management of obstructive hypertrophic cardiomyopathy (HCM) by targeting myosin ATPase activity to mitigate cardiac hypercontractility. This therapeutic mechanism has proven effective for patients with HCM independent of having a primary gene mutation in myosin. In this issue of the JCI, Buvoli et al. report that muscle hypercontractility is a mechanism of pathogenesis underlying muscle dysfunction in Laing distal myopathy, a disorder characterized by mutations altering the rod domain of β myosin heavy chain. The authors performed detailed physiological, molecular, and biomechanical analyses and demonstrated that myosin ATPase inhibition can correct a large extent of muscle abnormalities. The findings offer a therapeutic avenue for Laing distal myopathy and potentially other myopathies. This Commentary underscores the importance of reevaluating myosin activity's role across myopathies in general for the potential development of targeted myosin inhibitors to treat skeletal muscle disorders.

DOI: https://doi.org/10.1172/JCI179958
J Cachexia Sarcopenia Muscle. 2024 Apr 30.

Metabolomic analysis of dietary-restriction-induced attenuation of sarcopenia in prematurely aging DNA repair-deficient mice.

Yupeng He, Wei Yang, Luojiao Huang, Marlien Admiraal-van Mever, Rawi Ramautar, Amy Harms, Yvonne Rijksen, Renata M C Brandt, Sander Barnhoorn, Kimberly Smit, Dick Jaarsma, Peter Lindenburg, Jan H J Hoeijmakers, Wilbert P Vermeij, Thomas Hankemeier.

   BACKGROUND: Sarcopenia is characterized by loss of skeletal muscle mass and function, and is a major risk factor for disability and independence in the elderly. Effective medication is not available. Dietary restriction (DR) has been found to attenuate aging and aging-related diseases, including sarcopenia, but the mechanism of both DR and sarcopenia are incompletely understood.
METHODS: In this study, mice body weight, fore and all limb grip strength, and motor learning and coordination performance were first analysed to evaluate the DR effects on muscle functioning. Liquid chromatography-mass spectrometry (LC-MS) was utilized for the metabolomics study of the DR effects on sarcopenia in progeroid DNA repair-deficient Ercc1∆/- and Xpg-/- mice, to identify potential biomarkers for attenuation of sarcopenia.
RESULTS: Muscle mass was significantly (P < 0.05) decreased (13-20%) by DR; however, the muscle quality was improved with retained fore limbs and all limbs grip strength in Ercc1∆/- and Xpg-/- mice. The LC-MS results revealed that metabolites and pathways related to oxidative-stress, that is, GSSG/GSH (P < 0.01); inflammation, that is, 9-HODE, 11-HETE (P < 0.05), PGE2, PGD2, and TXB2 (P < 0.01); and muscle growth (PGF2α) (P < 0.01) and regeneration stimulation (PGE2) (P < 0.05) are significantly downregulated by DR. On the other hand, anti-inflammatory indicator and several related metabolites, that is, β-hydroxybutyrate (P < 0.01), 14,15-DiHETE (P < 0.0001), 8,9-EET, 12,13-DiHODE, and PGF1 (P < 0.05); consumption of sources of energy (i.e., muscle and liver glycogen); and energy production pathways, that is, glycolysis (glucose, glucose-6-P, fructose-6-P) (P < 0.01), tricarboxylic acid cycle (succinyl-CoA, malate) (P < 0.001), and gluconeogenesis-related metabolite, alanine (P < 0.01), are significantly upregulated by DR. The notably (P < 0.01) down-modulated muscle growth (PGF2α) and regeneration (PGE2) stimulation metabolite and the increased consumption of glycogen in muscle and liver may be related to the significantly (P < 0.01) lower body weight and muscle mass by DR. The downregulated oxidative stress, pro-inflammatory mediators, and upregulated anti-inflammatory metabolites resulted in a lower energy expenditure, which contributed to enhanced muscle quality together with upregulated energy production pathways by DR. The improved muscle quality may explain why grip strength is maintained and motor coordination and learning performance are improved by DR in Ercc1∆/- and Xpg-/- mice.
CONCLUSIONS: This study provides fundamental supporting information on biomarkers and pathways related to the attenuation of sarcopenia, which might facilitate its diagnosis, prevention, and clinical therapy.

Keywords:  Dietary restriction; Energy generation; Inflammation; Muscle aging; Oxidative stress; Progeria

DOI:  https://doi.org/10.1002/jcsm.13433
Proc Natl Acad Sci U S A. 2024 May 07. 121(19): e2321438121

Myospreader improves gene editing in skeletal muscle by myonuclear propagation.

Kiril K Poukalov, M Carmen Valero, Derek R Muscato, Leanne M Adams, Heejae Chun, Young Il Lee, Nadja S Andrade, Zane Zeier, H Lee Sweeney, Eric T Wang.

  Successful CRISPR/Cas9-based gene editing in skeletal muscle is dependent on efficient propagation of Cas9 to all myonuclei in the myofiber. However, nuclear-targeted gene therapy cargos are strongly restricted to their myonuclear domain of origin. By screening nuclear localization signals and nuclear export signals, we identify "Myospreader," a combination of short peptide sequences that promotes myonuclear propagation. Appending Myospreader to Cas9 enhances protein stability and myonuclear propagation in myoblasts and myofibers. AAV-delivered Myospreader dCas9 better inhibits transcription of toxic RNA in a myotonic dystrophy mouse model. Furthermore, Myospreader Cas9 achieves higher rates of gene editing in CRISPR reporter and Duchenne muscular dystrophy mouse models. Myospreader reveals design principles relevant to all nuclear-targeted gene therapies and highlights the importance of the spatial dimension in therapeutic development.

Keywords:  CRISPR; adeno-associated virus; gene therapy; myonuclear domains; spatial gene regulation

DOI:  https://doi.org/10.1073/pnas.2321438121
J Cachexia Sarcopenia Muscle. 2024 Apr 29.

Concerted regulation of skeletal muscle metabolism and contractile properties by the orphan nuclear receptor Nr2f6.

Dimitrius Santiago P S F Guimarães, Ninon M F Barrios, André Gustavo de Oliveira, David Rizo-Roca, Maxence Jollet, Jonathon A B Smith, Thiago R Araujo, Marcos Vinicius da Cruz, Emilio Marconato, Sandro M Hirabara, André S Vieira, Anna Krook, Juleen R Zierath, Leonardo R Silveira.

   BACKGROUND: The maintenance of skeletal muscle plasticity upon changes in the environment, nutrient supply, and exercise depends on regulatory mechanisms that couple structural and metabolic adaptations. The mechanisms that interconnect both processes at the transcriptional level remain underexplored. Nr2f6, a nuclear receptor, regulates metabolism and cell differentiation in peripheral tissues. However, its role in the skeletal muscle is still elusive. Here, we aimed to investigate the effects of Nr2f6 modulation on muscle biology in vivo and in vitro.
METHODS: Global RNA-seq was performed in Nr2f6 knockdown C2C12 myocytes (N = 4-5). Molecular and metabolic assays and proliferation experiments were performed using stable Nr2f6 knockdown and Nr2f6 overexpression C2C12 cell lines (N = 3-6). Nr2f6 content was evaluated in lipid overload models in vitro and in vivo (N = 3-6). In vivo experiments included Nr2f6 overexpression in mouse tibialis anterior muscle, followed by gene array transcriptomics and molecular assays (N = 4), ex vivo contractility experiments (N = 5), and histological analysis (N = 7). The conservation of Nr2f6 depletion effects was confirmed in primary skeletal muscle cells of humans and mice.
RESULTS: Nr2f6 knockdown upregulated genes associated with muscle differentiation, metabolism, and contraction, while cell cycle-related genes were downregulated. In human skeletal muscle cells, Nr2f6 knockdown significantly increased the expression of myosin heavy chain genes (two-fold to three-fold) and siRNA-mediated depletion of Nr2f6 increased maximal C2C12 myocyte's lipid oxidative capacity by 75% and protected against lipid-induced cell death. Nr2f6 content decreased by 40% in lipid-overloaded myotubes and by 50% in the skeletal muscle of mice fed a high-fat diet. Nr2f6 overexpression in mice resulted in an atrophic and hypoplastic state, characterized by a significant reduction in muscle mass (15%) and myofibre content (18%), followed by an impairment (50%) in force production. These functional phenotypes were accompanied by the establishment of an inflammation-like molecular signature and a decrease in the expression of genes involved in muscle contractility and oxidative metabolism, which was associated with the repression of the uncoupling protein 3 (20%) and PGC-1α (30%) promoters activity following Nr2f6 overexpression in vitro. Additionally, Nr2f6 regulated core components of the cell division machinery, effectively decoupling muscle cell proliferation from differentiation.
CONCLUSIONS: Our findings reveal a novel role for Nr2f6 as a molecular transducer that plays a crucial role in maintaining the balance between skeletal muscle contractile function and oxidative capacity. These results have significant implications for the development of potential therapeutic strategies for metabolic diseases and myopathies.

Keywords:  Metabolism; Muscle atrophy; Nr2f6; Skeletal muscle; Transcription

DOI:  https://doi.org/10.1002/jcsm.13480
Sci Adv. 2024 May 03. 10(18): eadj8042

SETDB1 modulates the TGFβ response in Duchenne muscular dystrophy myotubes.

Alice Granados, Maeva Zamperoni, Roberta Rapone, Maryline Moulin, Ekaterina Boyarchuk, Costas Bouyioukos, Laurence Del Maestro, Véronique Joliot, Elisa Negroni, Myriame Mohamed, Sandra Piquet, Anne Bigot, Fabien Le Grand, Sonia Albini, Slimane Ait-Si-Ali.

Overactivation of the transforming growth factor-β (TGFβ) signaling in Duchenne muscular dystrophy (DMD) is a major hallmark of disease progression, leading to fibrosis and muscle dysfunction. Here, we investigated the role of SETDB1 (SET domain, bifurcated 1), a histone lysine methyltransferase involved in muscle differentiation. Our data show that, following TGFβ induction, SETDB1 accumulates in the nuclei of healthy myotubes while being already present in the nuclei of DMD myotubes where TGFβ signaling is constitutively activated. Transcriptomics revealed that depletion of SETDB1 in DMD myotubes leads to down-regulation of TGFβ target genes coding for secreted factors involved in extracellular matrix remodeling and inflammation. Consequently, SETDB1 silencing in DMD myotubes abrogates the deleterious effect of their secretome on myoblast differentiation by impairing myoblast pro-fibrotic response. Our findings indicate that SETDB1 potentiates the TGFβ-driven fibrotic response in DMD muscles, providing an additional axis for therapeutic intervention.

DOI: https://doi.org/10.1126/sciadv.adj8042
J Clin Invest. 2024 May 03. pii: e177427. [Epub ahead of print]

Intermittent glucocorticoid treatment improves muscle metabolism via the PGC1α/Lipin1 axis in an aging-related sarcopenia model.

Ashok Daniel Prabakaran, Kevin McFarland, Karen Miz, Hima Bindu Durumutla, Kevin Piczer, Fadoua El Abdellaoui-Soussi, Hannah Latimer, Cole Werbrich, Hyun-Jy Chung, N Scott Blair, Douglas P Millay, Andrew J Morris, Brendan Prideaux, Brian N Finck, Mattia Quattrocelli.

  Sarcopenia burdens the elderly population through loss of muscle energy and mass, yet treatments to functionally rescue both parameters are missing. The glucocorticoid prednisone remodels muscle metabolism based on frequency of intake, but its mechanisms in sarcopenia are unknown. We found that once-weekly intermittent prednisone rescued muscle quality in aged 24-month-old mice to levels comparable to young 4-month-old mice. We discovered an age- and sex-independent glucocorticoid receptor transactivation program in muscle encompassing PGC1α and its co-factor Lipin1. Treatment coordinately improved mitochondrial abundance through isoform 1 and muscle mass through isoform 4 of the myocyte-specific PGC1α, which was required for the treatment-driven increase in carbon shuttling from glucose to amino acid biogenesis. We also probed the myocyte-specific Lipin1 as non-redundant factor coaxing PGC1α upregulation to the stimulation of both oxidative and anabolic effects. Our study unveils an aging-resistant druggable program in myocytes to coordinately rescue energy and mass in sarcopenia.

Keywords:  Aging; Epigenetics; Mitochondria; Muscle; Muscle biology

DOI:  https://doi.org/10.1172/JCI177427
Cell Rep. 2024 Apr 26. pii: S2211-1247(24)00477-7. [Epub ahead of print]43(5): 114149

Thbs1 regulates skeletal muscle mass in a TGFβ-Smad2/3-ATF4-dependent manner.

Davy Vanhoutte, Tobias G Schips, Rachel A Minerath, Jiuzhou Huo, Naga Swathi Sree Kavuri, Vikram Prasad, Suh-Chin Lin, Michael J Bround, Michelle A Sargent, Christopher M Adams, Jeffery D Molkentin.

  Loss of muscle mass is a feature of chronic illness and aging. Here, we report that skeletal muscle-specific thrombospondin-1 transgenic mice (Thbs1 Tg) have profound muscle atrophy with age-dependent decreases in exercise capacity and premature lethality. Mechanistically, Thbs1 activates transforming growth factor β (TGFβ)-Smad2/3 signaling, which also induces activating transcription factor 4 (ATF4) expression that together modulates the autophagy-lysosomal pathway (ALP) and ubiquitin-proteasome system (UPS) to facilitate muscle atrophy. Indeed, myofiber-specific inhibition of TGFβ-receptor signaling represses the induction of ATF4, normalizes ALP and UPS, and partially restores muscle mass in Thbs1 Tg mice. Similarly, myofiber-specific deletion of Smad2 and Smad3 or the Atf4 gene antagonizes Thbs1-induced muscle atrophy. More importantly, Thbs1-/- mice show significantly reduced levels of denervation- and caloric restriction-mediated muscle atrophy, along with blunted TGFβ-Smad3-ATF4 signaling. Thus, Thbs1-mediated TGFβ-Smad3-ATF4 signaling in skeletal muscle regulates tissue rarefaction, suggesting a target for atrophy-based muscle diseases and sarcopenia with aging.

Keywords:  ATF4; CP: Metabolism; TGFβ; atrophy; autophagy; extracellular matrix; proteasome; skeletal muscle; thrombospondin

DOI:  https://doi.org/10.1016/j.celrep.2024.114149
PLoS One. 2024 ;19(5): e0301690

PHF2 regulates sarcomeric gene transcription in myogenesis.

Taku Fukushima, Yuka Hasegawa, Sachi Kuse, Taiju Fujioka, Takeshi Nikawa, Satoru Masubuchi, Iori Sakakibara.

Myogenesis is regulated mainly by transcription factors known as Myogenic Regulatory Factors (MRFs), and the transcription is affected by epigenetic modifications. However, the epigenetic regulation of myogenesis is poorly understood. Here, we focused on the epigenomic modification enzyme, PHF2, which demethylates histone 3 lysine 9 dimethyl (H3K9me2) during myogenesis. Phf2 mRNA was expressed during myogenesis, and PHF2 was localized in the nuclei of myoblasts and myotubes. We generated Phf2 knockout C2C12 myoblasts using the CRISPR/Cas9 system and analyzed global transcriptional changes via RNA-sequencing. Phf2 knockout (KO) cells 2 d post differentiation were subjected to RNA sequencing. Gene ontology (GO) analysis revealed that Phf2 KO impaired the expression of the genes related to skeletal muscle fiber formation and muscle cell development. The expression levels of sarcomeric genes such as Myhs and Mybpc2 were severely reduced in Phf2 KO cells at 7 d post differentiation, and H3K9me2 modification of Mybpc2, Mef2c and Myh7 was increased in Phf2 KO cells at 4 d post differentiation. These findings suggest that PHF2 regulates sarcomeric gene expression via epigenetic modification.

DOI: https://doi.org/10.1371/journal.pone.0301690
Physiol Rep. 2024 May;12(9): e15997

High-intensity exercise training using a rotarod instrument (RotaHIIT) significantly improves exercise capacity in mice.

Jonathan J Herrera, Christopher M McAllister, Danielle Szczesniak, Rose-Carmel Goddard, Sharlene M Day.

  Voluntary or forced exercise training in mice is used to assess functional capacity as well as potential disease-modifying effects of exercise over a range of cardiovascular disease phenotypes. Compared to voluntary wheel running, forced exercise training enables precise control of exercise workload and volume, and results in superior changes in cardiovascular performance. However, the use of a shock grid with treadmill-based training is associated with stress and risk of injury, and declining compliance with longer periods of training time for many mouse strains. With these limitations in mind, we designed a novel, high-intensity interval training modality (HIIT) for mice that is carried out on a rotarod. Abbreviated as RotaHIIT, this protocol establishes interval workload intensities that are not time or resource intensive, maintains excellent training compliance over time, and results in improved exercise capacity independent of sex when measured by treadmill graded exercise testing (GXT) and rotarod specific acceleration and endurance testing. This protocol may therefore be useful and easily implemented for a broad range of research investigations. As RotaHIIT training was not associated cardiac structural or functional changes, or changes in oxidative capacity in cardiac or skeletal muscle tissue, further studies will be needed to define the physiological adaptations and molecular transducers that are driving the training effect of this exercise modality.

Keywords:  exercise capacity; exercise training; mice; rotarod

DOI:  https://doi.org/10.14814/phy2.15997
J Cell Physiol. 2024 Apr 30.

Lactate-induced metabolic remodeling and myofiber type transitions via activation of the Ca2+-NFATC1 signaling pathway.

Yu Zhou, Xi Liu, Zhen Qi, Caihua Huang, Longhe Yang, Donghai Lin.

  Lactate can serve as both an energy substrate and a signaling molecule, exerting diverse effects on skeletal muscle physiology. Due to the apparently positive effects, it would be interesting to consider it as a sports supplement. However, the mechanism behind these effects are yet to be comprehensively understood. In this study, we observed that lactate administration could improve the ability of antifatigue, and we further found that lactate upregulated the expression of myosin heavy chain (MYHC I) and MYHC IIa, while downregulating the expression of MYHC IIb. Besides, transcriptomics and metabolomics revealed significant changes in the metabolic profile of gastrocnemius muscle following lactate administration. Furthermore, lactate enhanced the activities of metabolic enzymes, including HK, LDHB, IDH, SDM, and MDH, and promoted the expression of lactate transport-related proteins MCT1 and CD147, thereby improving the transport and utilization of lactate in both vivo and vitro. More importantly, lactate administration increased cellular Ca2+ concentration and facilitated nuclear translocation of nuclear factor of activated T cells (NFATC1) in myotubes, whereas inhibition of NFATC1 significantly attenuated the effects of lactate treatment on NFATC1 nuclear translocation and MyHC expression. Our results elucidate the ability of lactate to induce metabolic remodeling in skeletal muscle and promote myofiber-type transitions by activating the Ca2+-NFATC1 signaling pathway. This study is useful in exploring the potential of lactate as a nutritional supplement for skeletal muscle adaptation and contributing to a mechanistic understanding of the central role of lactate in exercise physiology.

Keywords:  Ca2+‐NAFTC1 signaling pathway; lactate; metabolic remodeling; myofiber type transitions

DOI:  https://doi.org/10.1002/jcp.31290
Mol Genet Metab Rep. 2024 Jun;39 101085

Acid α-glucosidase (GAA) activity and glycogen content in muscle biopsy specimens of patients with Pompe disease: A systematic review.

Benedikt Schoser, Nina Raben, Fatbardha Varfaj, Mark Walzer, Antonio Toscano.

  Pompe disease is a rare genetic disorder characterized by a deficiency of acid α-glucosidase (GAA), leading to the accumulation of glycogen in various tissues, especially in skeletal muscles. The disease manifests as a large spectrum of phenotypes from infantile-onset Pompe disease (IOPD) to late-onset Pompe disease (LOPD), depending on the age of symptoms onset. Quantifying GAA activity and glycogen content in skeletal muscle provides important information about the disease severity. However, the distribution of GAA and glycogen levels in skeletal muscles from healthy individuals and those impacted by Pompe disease remains poorly understood, and there is currently no universally accepted standard assay for GAA activity measurement. This systematic literature review aims to provide an overview of the available information on GAA activity and glycogen content levels in skeletal muscle biopsies from patients with Pompe disease. A structured review of PubMed and Google Scholar literature (with the latter used to check that no additional publications were identified) was conducted to identify peer-reviewed publications on glycogen storage disease type II [MeSH term] + GAA, protein human (supplementary concept), Pompe, muscle; and muscle, acid alpha-glucosidase. A limit of English language was applied. Results were grouped by methodologies used to quantify GAA activity and glycogen content in skeletal muscle. The search and selection strategy were devised and carried out in line with Preferred Reporting of Items in Systematic Reviews and Meta-Analysis guidelines and documented using a flowchart. Bibliographies of papers included in the analysis were reviewed and applicable publications not already identified in the search were included. Of the 158 articles retrieved, 24 (comprising >100 muscle biopsies from >100 patients) were included in the analysis, with four different assays. Analysis revealed that patients with IOPD exhibited markedly lower GAA activity in skeletal muscles than those with LOPD, regardless of the measurement method employed. Additionally, patients with IOPD had notably higher glycogen content levels in skeletal muscles than those with LOPD. In general, however, it was difficult to fully characterize GAA activity because of the different methods used. The findings underscore the challenges in the interpretation and comparison of the results across studies because of the substantial methodological variations. There is a need to establish standardized reference ranges of GAA activity and glycogen content in healthy individuals and in Pompe disease patients based on globally standardized methods to improve comparability and reliability in assessing this rare disease.

Keywords:  Acid α-glucosidase; Glycogen; Pompe disease; Skeletal muscle biopsy

DOI:  https://doi.org/10.1016/j.ymgmr.2024.101085
Biochem Biophys Res Commun. 2024 Apr 24. pii: S0006-291X(24)00537-0. [Epub ahead of print]715 150001

Prolyl isomerase Pin1 in skeletal muscles contributes to systemic energy metabolism and exercise capacity through regulating SERCA activity.

Yusuke Nakatsu, Yasuka Matsunaga, Mikako Nakanishi, Takeshi Yamamotoya, Tomomi Sano, Takashi Kanematsu, Tomoichiro Asano.

  The skeletal muscle is a pivotal organ involved in the regulation of both energy metabolism and exercise capacity. There is no doubt that exercise contributes to a healthy life through the consumption of excessive energy or the release of myokines. Skeletal muscles exhibit insulin sensitivity and can rapidly uptake blood glucose. In addition, they can undergo non-shivering thermogenesis through actions of both the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) and small peptide, sarcolipin, resulting in systemic energy metabolism. Accordingly, the maintenance of skeletal muscles is important for both metabolism and exercise. Prolyl isomerase Pin1 is an enzyme that converts the cis-trans form of proline residues and controls substrate function. We have previously reported that Pin1 plays important roles in insulin release, thermogenesis, and lipolysis. However, the roles of Pin1 in skeletal muscles remains unknown. To clarify this issue, we generated skeletal muscle-specific Pin1 knockout mice. Pin1 deficiency had no effects on muscle weights, morphology and ratio of fiber types. However, they showed exacerbated obesity or insulin resistance when fed with a high-fat diet. They also showed a lower ability to exercise than wild type mice did. We also found that Pin1 interacted with SERCA and elevated its activity, resulting in the upregulation of oxygen consumption. Overall, our study reveals that Pin1 in skeletal muscles contributes to both systemic energy metabolism and exercise capacity.

Keywords:  Exercise capacity; Prolyl isomerase Pin1; SERCA; Skeletal muscles; Systemic energy metabolism

DOI:  https://doi.org/10.1016/j.bbrc.2024.150001
Neurol Sci. 2024 Apr 27.

Skeletal muscle dysfunction in amyotrophic lateral sclerosis: a mitochondrial perspective and therapeutic approaches.

Gokhan Burcin Kubat, Pasquale Picone.

  Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disease that results in the loss of motor neurons and severe skeletal muscle atrophy. The etiology of ALS is linked to skeletal muscle, which can activate a retrograde signaling cascade that destroys motor neurons. This is why satellite cells and mitochondria play a crucial role in the health and performance of skeletal muscles. This review presents current knowledge on the involvement of mitochondrial dysfunction, skeletal muscle atrophy, muscle satellite cells, and neuromuscular junction (NMJ) in ALS. It also discusses current therapeutic strategies, including exercise, drugs, stem cells, gene therapy, and the prospective use of mitochondrial transplantation as a viable therapeutic strategy.

Keywords:  Amyotrophic lateral sclerosis; Mitochondria; Mitochondrial transplantation; Skeletal muscle dysfunction

DOI:  https://doi.org/10.1007/s10072-024-07508-6
J Muscle Res Cell Motil. 2024 Apr 29.

ANKRD1 expression is aberrantly upregulated in the mdm mouse model of muscular dystrophy and induced by stretch through NFκB.

Michael A Lopez, Patricia S Pardo, Junaith S Mohamed, Aladin M Boriek.

  The muscular dystrophy with myositis (mdm) mouse model results in a severe muscular dystrophy due to an 83-amino-acid deletion in the N2A region of titin, an expanded sarcomeric protein that functions as a molecular spring which senses and modulates the response to mechanical forces in cardiac and skeletal muscles. ANKRD1 is one of the muscle ankyrin repeat domain proteins (MARPs) a family of titin-associated, stress-response molecules and putative transducers of stretch-induced signaling in skeletal muscle. The aberrant over-activation of Nuclear factor Kappa B (NF-κB) and the Ankyrin-repeat domain containing protein 1 (ANKRD1) occurs in several models of progressive muscle disease including Duchenne muscular dystrophy. We hypothesized that mechanical regulation of ANKRD1 is mediated by NF-κB activation in skeletal muscles and that this mechanism is perturbed by small deletion of the stretch-sensing titin N2A region in the mdm mouse. We applied static mechanical stretch of the mdm mouse diaphragm and cyclic mechanical stretch of C2C12 myotubes to examine the interaction between NF-κΒ and ANKRD1 expression utilizing Western blot and qRTPCR. As seen in skeletal muscles of other severe muscular dystrophies, an aberrant increased basal expression of NF-κB and ANKRD1 were observed in the diaphragm muscles of the mdm mice. Our data show that in the mdm diaphragm, basal levels of NF-κB are increased, and pharmacological inhibition of NF-κB does not alter basal levels of ANKRD1. Alternatively, NF-κB inhibition did alter stretch-induced ANKRD1 upregulation. These data show that NF-κB activity is at least partially responsible for the stretch-induced expression of ANKRD1.

Keywords:  ANKRD1; Mechanotransduction; Muscular dystrophy; NF-κB; Titin N2A

DOI:  https://doi.org/10.1007/s10974-024-09671-x
Acta Biochim Biophys Sin (Shanghai). 2024 Apr 30.

UBE2C promotes myoblast differentiation and skeletal muscle regeneration through the Akt signaling pathway.

Renqiang Yuan, Xiaorong Luo, Ziyun Liang, Shufang Cai, Yunxiang Zhao, Qi Zhu, Enru Li, Xiaohong Liu, Delin Mo, Yaosheng Chen.

  Ubiquitin-conjugation enzyme E2C (UBE2C) is a crucial component of the ubiquitin-proteasome system that is involved in numerous cancers. In this study, we find that UBE2C expression is significantly increased in mouse embryos, a critical stage during skeletal muscle development. We further investigate the function of UBE2C in myogenesis. Knockdown of UBE2C inhibits C2C12 cell differentiation and decreases the expressions of MyoG and MyHC, while overexpression of UBE2C promotes C2C12 cell differentiation. Additionally, knockdown of UBE2C, specifically in the tibialis anterior muscle (TA), severely impedes muscle regeneration in vivo. Mechanistically, we show that UBE2C knockdown reduces the level of phosphorylated protein kinase B (p-Akt) and promotes the degradation of Akt. These findings suggest that UBE2C plays a critical role in myoblast differentiation and muscle regeneration and that UBE2C regulates myogenesis through the Akt signaling pathway.

Keywords:  Akt; UBE2C; muscle; myoblast differentiation

DOI:  https://doi.org/10.3724/abbs.2024062
Elife. 2024 May 02. pii: RP89424. [Epub ahead of print]12

Septin 7 interacts with Numb to preserve sarcomere structural organization and muscle contractile function.

Rita De Gasperi, Laszlo Csernoch, Beatrix Dienes, Monika Gonczi, Jayanta K Chakrabarty, Shahar Goeta, Abdurrahman Aslan, Carlos A Toro, David Karasik, Lewis M Brown, Marco Brotto, Christopher P Cardozo.

  Here, we investigated the mechanisms by which aging-related reductions of the levels of Numb in skeletal muscle fibers contribute to loss of muscle strength and power, two critical features of sarcopenia. Numb is an adaptor protein best known for its critical roles in development, including asymmetric cell division, cell-type specification, and termination of intracellular signaling. Numb expression is reduced in old humans and mice. We previously showed that, in mouse skeletal muscle fibers, Numb is localized to sarcomeres where it is concentrated near triads; conditional inactivation of Numb and a closely related protein Numb-like (Numbl) in mouse myofibers caused weakness, disorganization of sarcomeres, and smaller mitochondria with impaired function. Here, we found that a single knockout of Numb in myofibers causes reduction in tetanic force comparable to a double Numb, Numbl knockout. We found by proteomics analysis of protein complexes isolated from C2C12 myotubes by immunoprecipitation using antibodies against Numb that Septin 7 is a potential Numb-binding partner. Septin 7 is a member of the family of GTP-binding proteins that organize into filaments, sheets, and rings, and is considered part of the cytoskeleton. Immunofluorescence evaluation revealed a partial overlap of staining for Numb and Septin 7 in myofibers. Conditional, inducible knockouts of Numb led to disorganization of Septin 7 staining in myofibers. These findings indicate that Septin 7 is a Numb-binding partner and suggest that interactions between Numb and Septin 7 are critical for structural organization of the sarcomere and muscle contractile function.

Keywords:  Numb; Septin; cell biology; cytoskeleton; excitation–contraction coupling; mouse; sarcomere structure; skeletal muscle

DOI:  https://doi.org/10.7554/eLife.89424
Trends Endocrinol Metab. 2024 Apr 29. pii: S1043-2760(24)00088-2. [Epub ahead of print]

MCU genetically altered mice suggest how mitochondrial Ca2+ regulates metabolism.

Jiuzhou Huo, Jeffery D Molkentin.

  Skeletal muscle has a major impact on total body metabolism and obesity, and is characterized by dynamic regulation of substrate utilization. While it is accepted that acute increases in mitochondrial matrix Ca2+ increase carbohydrate usage to augment ATP production, recent studies in mice with deleted genes for components of the mitochondrial Ca2+ uniporter (MCU) complex have suggested a more complicated regulatory scenario. Indeed, mice with a deleted Mcu gene in muscle, which lack acute mitochondrial Ca2+ uptake, have greater fatty acid oxidation (FAO) and less adiposity. By contrast, mice deleted for the inhibitory Mcub gene in skeletal muscle, which have greater acute mitochondrial Ca2+ uptake, antithetically display reduced FAO and progressive obesity. In this review we discuss the emerging concept that dynamic fluxing of mitochondrial matrix Ca2+ regulates metabolism.

Keywords:  Ca(2+) signaling; metabolism; mitochondria; obesity; skeletal muscle

DOI:  https://doi.org/10.1016/j.tem.2024.04.005
Front Cell Dev Biol. 2024 ;12 1381417

Mitochondrial stress response and myogenic differentiation.

Fu Lin, Liankun Sun, Yu Zhang, Weinan Gao, Zihan Chen, Yanan Liu, Kai Tian, Xuyu Han, Ruize Liu, Yang Li, Luyan Shen.

  Regeneration and repair are prerequisites for maintaining effective function of skeletal muscle under high energy demands, and myogenic differentiation is one of the key steps in the regeneration and repair process. A striking feature of the process of myogenic differentiation is the alteration of mitochondria in number and function. Mitochondrial dysfunction can activate a number of transcriptional, translational and post-translational programmes and pathways to maintain cellular homeostasis under different types and degrees of stress, either through its own signaling or through constant signaling interactions with the nucleus and cytoplasm, a process known as the mitochondrial stress responses (MSRs). It is now believed that mitochondrial dysfunction is closely associated with a variety of muscle diseases caused by reduced levels of myogenic differentiation, suggesting the possibility that MSRs are involved in messaging during myogenic differentiation. Also, MSRs may be involved in myogenesis by promoting bioenergetic remodeling and assisting myoblast survival during myogenic differentiation. In this review, we will take MSRs as an entry point to explore its concrete regulatory mechanisms during myogenic differentiation, with a perspective to provide a theoretical basis for the treatment and repair of related muscle diseases.

Keywords:  ISR; UPRmt; apoptosis; mitochondrial biogenesis; mitochondrial fusion and fission; mitophagy; myogenic differentiation

DOI:  https://doi.org/10.3389/fcell.2024.1381417
FASEB J. 2024 May 15. 38(9): e23634

Ablation of specific insulin-like growth factor I forms reveals the importance of cleavage for regenerative capacity and glycosylation for skeletal muscle storage.

Yangyi E Luo, Katelyn R Villani, Hanqin Lei, Li-Ying Kuo, Ian Imery, Bradley E Stoker, Naureen Fatima, Steven M Noles, Cara M Moore, Elisabeth R Barton.

  Insulin-like growth factor-I (IGF-I) facilitates mitotic and anabolic actions in all tissues. In skeletal muscle, IGF-I can promote growth and resolution of damage by promoting satellite cell proliferation and differentiation, suppressing inflammation, and enhancing fiber formation. While the most well-characterized form of IGF-I is the mature protein, alternative splicing and post-translational modification complexity lead to several additional forms of IGF-I. Previous studies showed muscle efficiently stores glycosylated pro-IGF-I. However, non-glycosylated forms display more efficient IGF-I receptor activation in vitro, suggesting that the removal of the glycosylated C terminus is a necessary step to enable increased activity. We employed CRISPR-Cas9 gene editing to ablate IGF-I glycosylation sites (2ND) or its cleavage site (3RA) in mice to determine the necessity of glycosylation or cleavage for IGF-I function in postnatal growth and during muscle regeneration. 3RA mice had the highest circulating and muscle IGF-I content, whereas 2ND mice had the lowest levels compared to wild-type mice. After weaning, 4-week-old 2ND mice exhibited higher body and skeletal muscle mass than other strains. However, by 16 weeks of age, muscle and body size differences disappeared. Even though 3RA mice had more IGF-I stored in muscle in homeostatic conditions, regeneration was delayed after cardiotoxin-induced injury, with prolonged necrosis most evident at 5 days post injury (dpi). In contrast, 2ND displayed improved regeneration with reduced necrosis, and greater fiber size and muscle mass at 11 and 21 dpi. Overall, these results demonstrate that while IGF-I glycosylation may be important for storage, cleavage is needed to enable IGF-I to be used for efficient activity in postnatal growth and following acute injury.

Keywords:  anabolic signaling; muscle injury; postnatal growth; post‐translational processing; proprotein convertase

DOI:  https://doi.org/10.1096/fj.202302512RR
J Aging Phys Act. 2024 Apr 29. 1-10

Bioinformatics Analysis Identifies Key Genes in the Effect of Resistance Training on Female Skeletal Muscle Aging.

Jiacheng Ma, Xiaoli Pang, Ismail Laher, Shunchang Li.

  Resistance training is used to combat skeletal muscle function decline in older adults. Few studies have been designed specific for females, resulting in very limited treatment options for skeletal muscle atrophy in aging women. Here, we analyzed the gene expression profiles of skeletal muscle samples from sedentary young women, sedentary older women, and resistance-trained older women, using microarray data from public database. A total of 45 genes that were differentially expressed during female muscle aging and reversed by resistance training were identified. Functional and pathway enrichment analysis, protein-protein interaction network analysis, and receiver operating characteristic analysis were performed to reveal the key genes and pathways involved in the effects of resistance training on female muscle aging. The collagen genes COL1A1, COL3A1, and COL4A1 were identified important regulators of female muscle aging and resistance training, by modulating multiple signaling pathways, such as PI3 kinase-Akt signaling, focal adhesions, extracellular matrix-receptor interactions, and relaxin signaling. Interestingly, the expression of CDKN1A and TP63 were increased during aging, and further upregulated by resistance training in older women, suggesting they may negatively affect resistance training outcomes. Our findings provide novel insights into the molecular mechanisms of resistance training on female muscle aging and identify potential biomarkers and targets for clinical intervention.

Keywords:  differentially expressed genes; protein–protein interaction; signaling pathways

DOI:  https://doi.org/10.1123/japa.2023-0178
Arch Gerontol Geriatr. 2024 Apr 26. pii: S0167-4943(24)00138-9. [Epub ahead of print]124 105462

GLP-2 ameliorates D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a signaling pathway in C2C12 cells and mice.

Yang-Li Ye, Zheng Kuai, Dian-Dian Qian, Yu-Ting He, Ji-Ping Shen, Ke-Fen Wu, Wei-Ying Ren, Yu Hu.

   BACKGROUND: The study aimed to investigate the effect of Glucagon-like peptide-2 (GLP-2) on muscle aging in vivo and in vitro.
METHODS: Six-week-old C57BL/6J mice were administered with D-galactose (200 mg/kg/day, intraperitoneally) for 8weeks, followed by daily subcutaneous injections of GLP-2 (300 or 600 μg/kg/day) for 4weeks. Skeletal muscle function and mass were evaluated using relative grip strength and muscle weight. The sizes and types of muscle fibers and apoptosis were assessed through histological analysis, immunofluorescence staining, and TUNEL staining, respectively. C2C12 myotubes were treated with D-galactose (40 mg/mL) and GLP-2. Protein expression of differentiation-related myogenic differentiation factor D (MyoD), myogenin (MyoG), and myosin heavy chain (Myhc), degradation-related Muscle RING finger 1 (MuRF-1), and muscle atrophy F-box (MAFbx)/Atrogin-1, and apoptosis-related B-cell leukemia/lymphoma 2 (Bcl-2) and Bax, were assessed using western blots. The Pi3k inhibitor LY294002 was applied to investigate whether GLP-2 regulated myogenesis and myotube aging via IGF-1/Pi3k/Akt/FoxO3a signaling pathway.
RESULTS: The results demonstrated that GLP-2 significantly reversed the decline in muscles weight, relative grip strength, diameter, and cross-sectional area of muscle fibers induced by D-galactose in mice. Apart from suppressing the expressions of MuRF-1 and Atrogin-1 in the muscles and C2C12 myotubes, GLP-2 significantly increased the expressions of MyoD, MyoG, and Myhc compared to the D-galactose. GLP-2 significantly suppressed cell apoptosis. Western blot analysis indicated that the regulation of GLP-2 may be attributed to the activation of theIGF-1/Pi3k/Akt/FoxO3a phosphorylation pathway.
CONCLUSIONS: This study suggested that GLP-2 ameliorated D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a pathway.

Keywords:  D-galactose; Glucagon-like peptide-2; Myogenesis; Skeletal muscle aging

DOI:  https://doi.org/10.1016/j.archger.2024.105462
Science. 2024 May 03. 384(6695): 563-572

Brain-muscle communication prevents muscle aging by maintaining daily physiology.

Arun Kumar, Mireia Vaca-Dempere, Thomas Mortimer, Oleg Deryagin, Jacob G Smith, Paul Petrus, Kevin B Koronowski, Carolina M Greco, Jessica Segalés, Eva Andrés, Vera Lukesova, Valentina M Zinna, Patrick-Simon Welz, Antonio L Serrano, Eusebio Perdiguero, Paolo Sassone-Corsi, Salvador Aznar Benitah, Pura Muñoz-Cánoves.

A molecular clock network is crucial for daily physiology and maintaining organismal health. We examined the interactions and importance of intratissue clock networks in muscle tissue maintenance. In arrhythmic mice showing premature aging, we created a basic clock module involving a central and a peripheral (muscle) clock. Reconstituting the brain-muscle clock network is sufficient to preserve fundamental daily homeostatic functions and prevent premature muscle aging. However, achieving whole muscle physiology requires contributions from other peripheral clocks. Mechanistically, the muscle peripheral clock acts as a gatekeeper, selectively suppressing detrimental signals from the central clock while integrating important muscle homeostatic functions. Our research reveals the interplay between the central and peripheral clocks in daily muscle function and underscores the impact of eating patterns on these interactions.

DOI: https://doi.org/10.1126/science.adj8533
Aging Cell. 2024 Apr 30. e14181

Exerkine FNDC5/irisin-enriched exosomes promote proliferation and inhibit ferroptosis of osteoblasts through interaction with Caveolin-1.

Lin Tao, Jinpeng Wang, Ke Wang, Qichang Liu, Hongyang Li, Site Xu, Chunjian Gu, Yue Zhu.

  Postmenopausal osteoporosis is a prevalent metabolic bone disorder characterized by a decrease in bone mineral density and deterioration of bone microstructure. Despite the high prevalence of this disease, no effective treatment for osteoporosis has been developed. Exercise has long been considered a potent anabolic factor that promotes bone mass via upregulation of myokines secreted by skeletal muscle, exerting long-term osteoprotective effects and few side effects. Irisin was recently identified as a novel myokine that is significantly upregulated by exercise and could increase bone mass. However, the mechanisms underlying exercise-induced muscle-bone crosstalk remain unclear. Here, we identified that polyunsaturated fatty acids (arachidonic acid and docosahexaenoic acid) are increased in skeletal muscles following a 10-week treadmill exercise programme, which then promotes the expression and release of FNDC5/irisin. In osteoblasts, irisin binds directly to Cav1, which recruits and interacts with AMP-activated protein kinase α (AMPKα) to activate the AMPK pathway. Nrf2 is the downstream target of the AMPK pathway and increases the transcription of HMOX1 and Fpn. HMOX1 is involved in regulating the cell cycle and promotes the proliferation of osteoblasts. Moreover, upregulation of Fpn in osteoblasts enhanced iron removal, thereby suppressing ferroptosis in osteoblasts. Additionally, we confirmed that myotube-derived exosomes are involved in the transportation of irisin and enter osteoblasts through caveolae-mediated endocytosis. In conclusion, our findings highlight the crucial role of irisin, present in myotube-derived exosomes, as a crucial regulator of exercise-induced protective effects on bone, which provides novel insights into the mechanisms underlying exercise-dependent treatment of osteoporosis.

Keywords:  Caveolin 1; exercise; exosome; ferroptosis; irisin; osteoporosis

DOI:  https://doi.org/10.1111/acel.14181
Proc Natl Acad Sci U S A. 2024 May 07. 121(19): e2313590121

Neuronal innervation regulates the secretion of neurotrophic myokines and exosomes from skeletal muscle.

Kai-Yu Huang, Gaurav Upadhyay, Yujin Ahn, Masayoshoi Sakakura, Gelson J Pagan-Diaz, Younghak Cho, Amanda C Weiss, Chen Huang, Jennifer W Mitchell, Jiahui Li, Yanqi Tan, Yu-Heng Deng, Austin Ellis-Mohr, Zhi Dou, Xiaotain Zhang, Sehong Kang, Qian Chen, Jonathan V Sweedler, Sung Gap Im, Rashid Bashir, Hee Jung Chung, Gabriel Popescu, Martha U Gillette, Mattia Gazzola, Hyunjoon Kong.

  Myokines and exosomes, originating from skeletal muscle, are shown to play a significant role in maintaining brain homeostasis. While exercise has been reported to promote muscle secretion, little is known about the effects of neuronal innervation and activity on the yield and molecular composition of biologically active molecules from muscle. As neuromuscular diseases and disabilities associated with denervation impact muscle metabolism, we hypothesize that neuronal innervation and firing may play a pivotal role in regulating secretion activities of skeletal muscles. We examined this hypothesis using an engineered neuromuscular tissue model consisting of skeletal muscles innervated by motor neurons. The innervated muscles displayed elevated expression of mRNAs encoding neurotrophic myokines, such as interleukin-6, brain-derived neurotrophic factor, and FDNC5, as well as the mRNA of peroxisome-proliferator-activated receptor γ coactivator 1α, a key regulator of muscle metabolism. Upon glutamate stimulation, the innervated muscles secreted higher levels of irisin and exosomes containing more diverse neurotrophic microRNAs than neuron-free muscles. Consequently, biological factors secreted by innervated muscles enhanced branching, axonal transport, and, ultimately, spontaneous network activities of primary hippocampal neurons in vitro. Overall, these results reveal the importance of neuronal innervation in modulating muscle-derived factors that promote neuronal function and suggest that the engineered neuromuscular tissue model holds significant promise as a platform for producing neurotrophic molecules.

Keywords:  exosome; innervation; myokine; neuromuscular junction; skeletal muscle

DOI:  https://doi.org/10.1073/pnas.2313590121
Front Cell Dev Biol. 2024 ;12 1331563

Temporal regulation of the Mediator complex during muscle proliferation, differentiation, regeneration, aging, and disease.

Dominic W Kolonay, Kristina M Sattler, Corinne Strawser, Jill Rafael-Fortney, Maria M Mihaylova, Katherine E Miller, Christoph Lepper, Kedryn K Baskin.

  Genesis of skeletal muscle relies on the differentiation and fusion of mono-nucleated muscle progenitor cells into the multi-nucleated muscle fiber syncytium. The temporally-controlled cellular and morphogenetic changes underlying this process are initiated by a series of highly coordinated transcription programs. At the core, the myogenic differentiation cascade is driven by muscle-specific transcription factors, i.e., the Myogenic Regulatory Factors (MRFs). Despite extensive knowledge on the function of individual MRFs, very little is known about how they are coordinated. Ultimately, highly specific coordination of these transcription programs is critical for their masterfully timed transitions, which in turn facilitates the intricate generation of skeletal muscle fibers from a naïve pool of progenitor cells. The Mediator complex links basal transcriptional machinery and transcription factors to regulate transcription and could be the integral component that coordinates transcription factor function during muscle differentiation, growth, and maturation. In this study, we systematically deciphered the changes in Mediator complex subunit expression in skeletal muscle development, regeneration, aging, and disease. We incorporated our in vitro and in vivo experimental results with analysis of publicly available RNA-seq and single nuclei RNA-seq datasets and uncovered the regulation of Mediator subunits in different physiological and temporal contexts. Our experimental results revealed that Mediator subunit expression during myogenesis is highly dynamic. We also discovered unique temporal patterns of Mediator expression in muscle stem cells after injury and during the early regeneration period, suggesting that Mediator subunits may have unique contributions to directing muscle stem cell fate. Although we observed few changes in Mediator subunit expression in aging muscles compared to younger muscles, we uncovered extensive heterogeneity of Mediator subunit expression in dystrophic muscle nuclei, characteristic of chronic muscle degeneration and regeneration cycles. Taken together, our study provides a glimpse of the complex regulation of Mediator subunit expression in the skeletal muscle cell lineage and serves as a springboard for mechanistic studies into the function of individual Mediator subunits in skeletal muscle.

Keywords:  Mediator complex; cell differentiation; myogenesis; skeletal muscle regeneration; transcription

DOI:  https://doi.org/10.3389/fcell.2024.1331563
Cell Rep. 2024 Apr 30. pii: S2211-1247(24)00505-9. [Epub ahead of print]43(5): 114177

The Mediator Med23 controls a transcriptional switch for muscle stem cell proliferation and differentiation in muscle regeneration.

Yi Fang, Chunlei Yuan, Chonghui Li, Chengjiang Lu, Wei Yu, Gang Wang.

  Muscle stem cells (MuSCs) contribute to a robust muscle regeneration process after injury, which is highly orchestrated by the sequential expression of multiple key transcription factors. However, it remains unclear how key transcription factors and cofactors such as the Mediator complex cooperate to regulate myogenesis. Here, we show that the Mediator Med23 is critically important for MuSC-mediated muscle regeneration. Med23 is increasingly expressed in activated/proliferating MuSCs on isolated myofibers or in response to muscle injury. Med23 deficiency reduced MuSC proliferation and enhanced its precocious differentiation, ultimately compromising muscle regeneration. Integrative analysis revealed that Med23 oppositely impacts Ternary complex factor (TCF)-targeted MuSC proliferation genes and myocardin-related transcription factor (MRTF)-targeted myogenic differentiation genes. Consistently, Med23 deficiency decreases the ETS-like transcription factor 1 (Elk1)/serum response factor (SRF) binding at proliferation gene promoters but promotes MRTF-A/SRF binding at myogenic gene promoters. Overall, our study reveals the important transcriptional control mechanism of Med23 in balancing MuSC proliferation and differentiation in muscle regeneration.

Keywords:  CP: Stem cell research; Elk1; MRTF-A; Med23; Mediator; differentiation; muscle regeneration; muscle stem cell; proliferation

DOI:  https://doi.org/10.1016/j.celrep.2024.114177