bims-moremu 2023-11-05 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–11–05
29 papers selected by
Anna Vainshtein, Craft Science Inc.

Muscle Bmal1 is necessary for normal transcriptomic and metabolomic adaptation to endurance exercise training.
Loss of adenosine A3 receptors accelerates skeletal muscle regeneration in mice following cardiotoxin-induced injury.
Exercise performance is not improved in mice with skeletal muscle deletion of natriuretic peptide clearance receptor.
Regenerating human skeletal muscle forms an emerging niche in vivo to support PAX7 cells.
Metabolic Consequences of Skeletal Muscle- and Liver-Specific BBSome Deficiency.
Cullin-3 intervenes in muscle atrophy in the elderly by mediating the degradation of nAchRs ubiquitination.
ALDH1A1 and ALDH1A3 paralogues of aldehyde dehydrogenase 1 control myogenic differentiation of skeletal muscle satellite cells by retinoic acid-dependent and -independent mechanisms.
Angiogenic potential of skeletal muscle derived extracellular vesicles differs between oxidative and glycolytic muscle tissue in mice.
Enhanced capacity for CaMKII signaling mitigates calcium release related contractile fatigue with high intensity exercise.
ROCK1 activates mitochondrial fission leading to oxidative stress and muscle atrophy.
Metabolomic and Lipidomic Signature of Skeletal Muscle with Constitutively Active mTORC1.
Skeletal muscle DNA methylation: Effects of exercise and HIV.
Gli1 marks a sentinel muscle stem cell population for muscle regeneration.
Receptor interacting protein kinase-3 mediates both myopathy and cardiomyopathy in preclinical animal models of Duchenne muscular dystrophy.
Glucocorticoid intermittence coordinates rescue of energy and mass in aging-related sarcopenia through the myocyte-autonomous PGC1alpha-Lipin1 transactivation.
The influence of skeletal muscle mitochondria and sex on critical torque and performance fatiguability in humans.
Muscle-targeted nanoparticles strengthen the effects of small-molecule inhibitors in ameliorating sarcopenia.
Advanced glycation end products inhibit proliferation and primary cilia formation of myoblasts through receptor for advanced glycation end products pathway.
Explore novel molecular mechanisms of FNDC5 in ischemia-reperfusion (I/R) injury by analyzing transcriptome changes in mouse model of skeletal muscle I/R injury with FNDC5 knockout.
Dystrophin- and Utrophin-Based Therapeutic Approaches for Treatment of Duchenne Muscular Dystrophy: A Comparative Review.
DNA methylation of insulin signaling pathways is associated with HOMA2-IR in primary myoblasts from older adults.
Regulatory T cells shield muscle mitochondria from interferon-γ-mediated damage to promote the beneficial effects of exercise.
The Interconnection Between Muscle and Bone: A Common Clinical Management Pathway.
In vivo cytosolic H2O2 changes and Ca2+ homeostasis in mouse skeletal muscle.
A mechano- and heat-gated two-pore domain K+ channel controls excitability in adult zebrafish skeletal muscle.
Early skeletal muscle loss in adolescent and young adult cancer patients treated with anthracycline chemotherapy.
A Kinase Interacting Protein 1 regulates mitochondrial protein levels in energy metabolism and promotes mitochondrial turnover after exercise.
Distal hereditary motor neuronopathy as a new phenotype associated with variants in BAG3.
A new hydrogel can be directly injected into muscle to help it regenerate.

bioRxiv. 2023 Oct 17. pii: 2023.10.13.562100. [Epub ahead of print]

Muscle Bmal1 is necessary for normal transcriptomic and metabolomic adaptation to endurance exercise training.

Mark R Viggars, Hannah E Berko, Miguel A Gutierrez-Monreal, Ryan A Martin, Karyn A Esser.

Objective: The skeletal muscle circadian clock plays a pivotal role in muscle homeostasis and metabolic flexibility. Recently, this clock mechanism has been linked to both transcriptional and metabolic responses to acute exercise. However, the contribution of the circadian clock mechanism to the molecular and phenotypic adaptations to exercise training have not been defined.
Methods: Inducible skeletal muscle-specific Bmal1-floxed mice were treated with tamoxifen to induce skeletal muscle specific deletion of Bmal1 (iMSBmal1KO) or given a vehicle. Mice were assigned to normal cage conditions, or 6-weeks of progressive treadmill training. Exercise performance, body composition, and tissue/serum indices of metabolic health were assessed over the timecourse of training. Gastrocnemius muscles were collected 48-hours after their last exercise bout for histological, biochemical, and molecular analyses including RNA-sequencing and untargeted metabolomics.
Results: Improvements in exercise workload and maximal performance were comparable between iMSBmal1KO mice and vehicle treated controls after 6-weeks of exercise training. However, exercise training in the absence of Bmal1 was not able to rescue the metabolic phenotype and hyperinsulinemia of the iMSBmal1KO mice, attributed to the continued dysregulation of core clock components and gene expression relating to glucose metabolism. Importantly, a much larger and divergent transcriptional reprogramming occurred in the muscle of iMSBmal1KO mice in comparison to their vehicle treated counterparts. This response included a large compensatory upregulation of genes associated with fatty acid β-oxidation, pyruvate metabolism, citric acid cycle components and oxidative phosphorylation components, including mitochondrial subunits and mitoribosome units.
Conclusions: Collectively, we propose that endurance training requires muscle Bmal1 , and the core clock network, to elicit well recognized molecular adaptations. In the absence of Bmal1 , exercise training results in a much larger and divergent re-networking of the basal skeletal muscle transcriptome and metabolome. We also demonstrate that skeletal muscle Bmal1 is indispensable for the transcriptional regulation of glucose homeostasis, even after a 6-weeks exercise training programme.

DOI: https://doi.org/10.1101/2023.10.13.562100
Cell Death Dis. 2023 Oct 28. 14(10): 706

Loss of adenosine A3 receptors accelerates skeletal muscle regeneration in mice following cardiotoxin-induced injury.

Nastaran Tarban, Albert Bálint Papp, Dávid Deák, Péter Szentesi, Hajnalka Halász, Andreas Patsalos, László Csernoch, Zsolt Sarang, Zsuzsa Szondy.

Skeletal muscle regeneration is a complex process orchestrated by multiple interacting steps. An increasing number of reports indicate that inflammatory responses play a central role in linking initial muscle injury responses to timely muscle regeneration following injury. The nucleoside adenosine has been known for a long time as an endogenously produced anti-inflammatory molecule that is generated in high amounts during tissue injury. It mediates its physiological effects via four types of adenosine receptors. From these, adenosine A3 receptors (A3Rs) are not expressed by the skeletal muscle but are present on the surface of various inflammatory cells. In the present paper, the effect of the loss of A3Rs was investigated on the regeneration of the tibialis anterior (TA) muscle in mice following cardiotoxin-induced injury. Here we report that regeneration of the skeletal muscle from A3R-/- mice is characterized by a stronger initial inflammatory response resulting in a larger number of transmigrating inflammatory cells to the injury site, faster clearance of cell debris, enhanced proliferation and faster differentiation of the satellite cells (the muscle stem cells), and increased fusion of the generated myoblasts. This leads to accelerated skeletal muscle tissue repair and the formation of larger myofibers. Though the infiltrating immune cells expressed A3Rs and showed an increased inflammatory profile in the injured A3R-/- muscles, bone marrow transplantation experiments revealed that the increased response of the tissue-resident cells to tissue injury is responsible for the observed phenomenon. Altogether our data indicate that A3Rs are negative regulators of injury-related regenerative inflammation and consequently also that of the muscle fiber growth in the TA muscle. Thus, inhibiting A3Rs might have a therapeutic value during skeletal muscle regeneration following injury.

DOI: https://doi.org/10.1038/s41419-023-06228-7
PLoS One. 2023 ;18(11): e0293636

Exercise performance is not improved in mice with skeletal muscle deletion of natriuretic peptide clearance receptor.

Brigitte Jia, Alexander Hasse, Fubiao Shi, Sheila Collins.

Natriuretic peptides (NP), including atrial, brain, and C-type natriuretic peptides (ANP, BNP, and CNP), play essential roles in regulating blood pressure, cardiovascular homeostasis, and systemic metabolism. One of the major metabolic effects of NP is manifested by their capacity to stimulate lipolysis and the thermogenesis gene program in adipocytes, however, in skeletal muscle their effects on metabolism and muscle function are not as well understood. There are three NP receptors (NPR): NPRA, NPRB, and NPRC, and all three NPR genes are expressed in skeletal muscle and C2C12 myocytes. In C2C12 myocytes treatment with either ANP, BNP, or CNP evokes the cGMP signaling pathway. Since NPRC functions as a clearance receptor and the amount of NPRC in a cell type determines the signaling strength of NPs, we generated a genetic model with Nprc gene deletion in skeletal muscle and tested whether enhancing NP signaling by preventing its clearance in skeletal muscle would improve exercise performance in mice. Under sedentary conditions, Nprc skeletal muscle knockout (MKO) mice showed comparable exercise performance to their floxed littermates in terms of maximal running velocity and total endurance running time. Eight weeks of voluntary running-wheel training in a young cohort significantly increased exercise performance, but no significant differences were observed in MKO compared with floxed control mice. Furthermore, 6-weeks of treadmill training in a relatively aged cohort also increased exercise performance compared with their baseline values, but again there were no differences between genotypes. In summary, our study suggests that NP signaling is potentially important in skeletal myocytes but its function in skeletal muscle in vivo needs to be further studied in additional physiological conditions or with new genetic mouse models.

DOI: https://doi.org/10.1371/journal.pone.0293636
Nat Cell Biol. 2023 Nov 02.

Regenerating human skeletal muscle forms an emerging niche in vivo to support PAX7 cells.

Michael R Hicks, Kholoud K Saleh, Ben Clock, Devin E Gibbs, Mandee Yang, Shahab Younesi, Lily Gane, Victor Gutierrez-Garcia, Haibin Xi, April D Pyle.

Skeletal muscle stem and progenitor cells including those derived from human pluripotent stem cells (hPSCs) offer an avenue towards personalized therapies and readily fuse to form human-mouse myofibres in vivo. However, skeletal muscle progenitor cells (SMPCs) inefficiently colonize chimeric stem cell niches and instead associate with human myofibres resembling foetal niches. We hypothesized competition with mouse satellite cells (SCs) prevented SMPC engraftment into the SC niche and thus generated an SC ablation mouse compatible with human engraftment. Single-nucleus RNA sequencing of SC-ablated mice identified the absence of a transient myofibre subtype during regeneration expressing Actc1. Similarly, ACTC1+ human myofibres supporting PAX7+ SMPCs increased in SC-ablated mice, and after re-injury we found SMPCs could now repopulate into chimeric niches. To demonstrate ACTC1+ myofibres are essential to supporting PAX7 SMPCs, we generated caspase-inducible ACTC1 depletion human pluripotent stem cells, and upon SMPC engraftment we found a 90% reduction in ACTC1+ myofibres and a 100-fold decrease in PAX7 cell numbers compared with non-induced controls. We used spatial RNA sequencing to identify key factors driving emerging human niche formation between ACTC1+ myofibres and PAX7+ SMPCs in vivo. This revealed that transient regenerating human myofibres are essential for emerging niche formation in vivo to support PAX7 SMPCs.

DOI: https://doi.org/10.1038/s41556-023-01271-0
Am J Physiol Endocrinol Metab. 2023 Nov 01.

Metabolic Consequences of Skeletal Muscle- and Liver-Specific BBSome Deficiency.

Younes Rouabhi, Deng-Fu Guo, Yuying Zhao, Kamal Rahmouni.

  The BBSome is a protein complex composed of eight Bardet-Biedl syndrome (BBS) proteins including BBS1. Humans and mice lacking a functional BBSome display obesity and type 2 diabetes, highlighting the importance of this protein complex for metabolic regulation. However, the contribution of the BBSome in insulin sensitive tissues such as skeletal muscle and liver to metabolic regulation is ill defined. Here, we show that disruption of the BBSome through Bbs1 gene deletion in the skeletal muscle had no effect on body weight, glucose handling, but improved insulin sensitivity of female mice without changing insulin receptor signaling. Interestingly, when fed an obesogenic diet, male mice lacking the Bbs1 gene in skeletal muscle exhibited heightened insulin sensitivity despite the comparable weight gain and glucose tolerance relative to controls. On the other hand, normal chow-fed mice missing the Bbs1 gene in hepatocytes displayed increased body weight, as well as impaired glucose handling and insulin sensitivity. This was associated with attenuated insulin signaling in liver and hepatocytes, but not skeletal muscle and white adipose tissue. Moreover, hepatocytes lacking the Bbs1 gene displayed significant reduction in plasma membrane insulin receptor levels due to the mitochondrial dysfunction evoked by loss of the BBSome. Together, these findings demonstrate that myocyte BBSome is minimally involved in metabolic regulation whereas the hepatic BBSome plays a critical role in the control of energy homeostasis and insulin sensitivity through its requirement for insulin receptor trafficking.

Keywords:  Bardet-Biedl syndrome proteins; energy balance; insulin sensitivity; liver; skeletal muscle

DOI:  https://doi.org/10.1152/ajpendo.00174.2023
Exp Gerontol. 2023 Oct 30. pii: S0531-5565(23)00239-5. [Epub ahead of print] 112318

Cullin-3 intervenes in muscle atrophy in the elderly by mediating the degradation of nAchRs ubiquitination.

Jintao Chen, Qun Xu, Xinyi Wang, Zherong Xu, Xujiao Chen.

  Sarcopenia involves in the loss of muscle mass associated with aging, which is the major cause of progressive muscle weakness and deterioration in older adults. Muscle atrophy is a direct presentation of sarcopenia, and it greatly contributes to the decline in quality of life among older adults. Neuromuscular junction (NMJ) stability is the key link to maintain muscle function. Besides, the degenerative change of NMJ promotes the process of muscle atrophy in the elderly. Based on previous transcriptome sequencing and bioinformatics analyses of aged muscle, this study used the 18-month-old aged mouse model and the 6-month-old young mouse model to deliberate the role and underlying mechanisms of Cullin-3 (Cul3) in age-related muscle atrophy. The results of reverse transcriptase polymerase chain reaction (RT-PCR) and immunoblotting analysis showed that the expression of CUL3 increased in aged muscle tissue, while the expression level of postsynaptic membrane nicotinic acetylcholine receptors (nAChRs) decreased significantly, which manfested a negative correlation. Meanwhile, immunofluorescence demonstrated that Cul3 was highly expressed in senile muscle NMJ. The results of ubiquitin indicated that the ubiquitin level of aged muscle nAChRs was evidently increased. Co-immunoprecipitation furtherly verified the correlation between Cul3 and nAChRs. Taken together, Cul3 may mediate the ubiquitination degradation of nAChRs protein at the NMJ site in aged mice, leading to NMJ degeneration and accelerated atrophy of fast-twitch muscle fibers in aged muscle. As a prominent element to maintain the stability of NMJ, Cul3 is supposed to be one of candidate intervention targets in sarcopenia.

Keywords:  Cul3; Muscle atrophy; NMJ; Sarcopenia; nAChRs

DOI:  https://doi.org/10.1016/j.exger.2023.112318
Cell Tissue Res. 2023 Oct 31.

ALDH1A1 and ALDH1A3 paralogues of aldehyde dehydrogenase 1 control myogenic differentiation of skeletal muscle satellite cells by retinoic acid-dependent and -independent mechanisms.

Laura Steingruber, Florian Krabichler, Sophie Franzmeier, Wei Wu, Jürgen Schlegel, Marco Koch.

  ALDH1A1 and ALDH1A3 paralogues of aldehyde dehydrogenase 1 (ALDH1) control myogenic differentiation of skeletal muscle satellite cells (SC) by formation of retinoic acid (RA) and subsequent cell cycle adjustments. The respective relevance of each paralogue for myogenic differentiation and the mechanistic interaction of each paralogue within RA-dependent and RA-independent pathways remain elusive.We analysed the impact of ALDH1A1 and ALDH1A3 activity on myogenesis of murine C2C12 myoblasts. Both paralogues are pivotal factors in myogenic differentiation, since CRISPR/Cas9-edited single paralogue knock-out impaired serum withdrawal-induced myogenic differentiation, while successive recombinant re-expression of ALDH1A1 or ALDH1A3, respectively, in the corresponding ALDH1 paralogue single knock-out cell lines, recovered the differentiation potential. Loss of differentiation in single knock-out cell lines was restored by treatment with RA-analogue TTNPB, while RA-receptor antagonization by AGN 193109 inhibited differentiation of wildtype cell lines, supporting the idea that RA-dependent pathway is pivotal for myogenic differentiation which is accomplished by both paralogues.However, overexpression of ALDH1-paralogues or disulfiram-mediated inhibition of ALDH1 enzymatic activity not only increased ALDH1A1 and ALDH1A3 protein levels but also induced subsequent differentiation of C2C12 myoblasts independently from serum withdrawal, indicating that ALDH1-dependent myogenic differentiation relies on different cellular conditions. Remarkably, ALDH1-paralogue knock-out impaired the autophagic flux, namely autophagosome cargo protein p62 formation and LC3B-I to LC3B-II conversion, demonstrating that ALDH1-paralogues interact with autophagy in myogenesis. Together, ALDH1 paralogues play a crucial role in myogenesis by orchestration of complex RA-dependent and RA-independent pathways.

Keywords:  ALDH1A1/ALDH1A3 paralogue; Autophagy; CRISPR/Cas9 knock-out; Myogenic differentiation; Retinoic acid

DOI:  https://doi.org/10.1007/s00441-023-03838-7
Sci Rep. 2023 Nov 02. 13(1): 18943

Angiogenic potential of skeletal muscle derived extracellular vesicles differs between oxidative and glycolytic muscle tissue in mice.

Christopher K Kargl, Zhihao Jia, Deborah A Shera, Brian P Sullivan, Lundon C Burton, Kun Ho Kim, Yaohui Nie, Monica J Hubal, Jonathan H Shannahan, Shihuan Kuang, Timothy P Gavin.

Skeletal muscle fibers regulate surrounding endothelial cells (EC) via secretion of numerous angiogenic factors, including extracellular vesicles (SkM-EV). Muscle fibers are broadly classified as oxidative (OXI) or glycolytic (GLY) depending on their metabolic characteristics. OXI fibers secrete more pro-angiogenic factors and have greater capillary densities than GLY fibers. OXI muscle secretes more EV than GLY, however it is unknown whether muscle metabolic characteristics regulate EV contents and signaling potential. EVs were isolated from primarily oxidative or glycolytic muscle tissue from mice. MicroRNA (miR) contents were determined and endothelial cells were treated with OXI- and GLY-EV to investigate angiogenic signaling potential. There were considerable differences in miR contents between OXI- and GLY-EV and pathway analysis identified that OXI-EV miR were predicted to positively regulate multiple endothelial-specific pathways, compared to GLY-EV. OXI-EV improved in vitro angiogenesis, which may have been mediated through nitric oxide synthase (NOS) related pathways, as treatment of endothelial cells with a non-selective NOS inhibitor abolished the angiogenic benefits of OXI-EV. This is the first report to show widespread differences in miR contents between SkM-EV isolated from metabolically different muscle tissue and the first to demonstrate that oxidative muscle tissue secretes EV with greater angiogenic signaling potential than glycolytic muscle tissue.

DOI: https://doi.org/10.1038/s41598-023-45787-9
Biochim Biophys Acta Mol Cell Res. 2023 Oct 30. pii: S0167-4889(23)00183-0. [Epub ahead of print] 119610

Enhanced capacity for CaMKII signaling mitigates calcium release related contractile fatigue with high intensity exercise.

Martin Flück, Colline Sanchez, Vincent Jacquemond, Christine Berthier, Marie-Noëlle Giraud, Daniel Jacko, Käthe Bersiner, Sebastian Gehlert, Guus Baan, Richard T Jaspers.

   BACKGROUND: We tested whether enhancing the capacity for calcium/calmodulin-dependent protein kinase type II (CaMKII) signaling would delay fatigue of excitation-induced calcium release and improve contractile characteristics of skeletal muscle during fatiguing exercise.
METHODS: Fast and slow type muscle, gastrocnemius medialis (GM) and soleus (SOL), of rats and mouse interosseus (IO) muscle fibers, were transfected with pcDNA3-based plasmids for rat α and β CaMKII or empty controls. Levels of CaMKII, its T287-phosphorylation (pT287-CaMKII), and phosphorylation of components of calcium release and re-uptake, ryanodine receptor 1 (pS2843-RyR1) and phospholamban (pT17-PLN), were quantified biochemically. Sarcoplasmic calcium in transfected muscle fibers was monitored microscopically during trains of electrical excitation based on Fluo-4 FF fluorescence (n = 5-7). Effects of low- (n = 6) and high- (n = 8) intensity exercise on pT287-CaMKII and contractile characteristics were studied in situ.
RESULTS: Co-transfection with αCaMKII-pcDNA3/βCaMKII-pcDNA3 increased α and βCaMKII levels in SOL (+45.8 %, +250.5 %) and GM (+40.4 %, +89.9 %) muscle fibers compared to control transfection. High-intensity exercise increased pT287-βCaMKII and pS2843-RyR1 levels in SOL (+269 %, +151 %) and GM (+354 %, +119 %), but decreased pT287-αCaMKII and p17-PLN levels in GM compared to SOL (-76 % vs. +166 %; 0 % vs. +128 %). α/β CaMKII overexpression attenuated the decline of calcium release in muscle fibers with repeated excitation, and mitigated exercise-induced deterioration of rates in force production, and passive force, in a muscle-dependent manner, in correlation with pS2843-RyR1 and pT17-PLN levels (|r| > 0.7).
CONCLUSION: Enhanced capacity for α/β CaMKII signaling improves fatigue-resistance of active and passive contractile muscle properties in association with RyR1- and PLN-related improvements in sarcoplasmic calcium release.

Keywords:  Contraction; Fatigue; Force; Phosphorylation; Ryanodine receptor; Velocity

DOI:  https://doi.org/10.1016/j.bbamcr.2023.119610
bioRxiv. 2023 Oct 22. pii: 2023.10.22.563469. [Epub ahead of print]

ROCK1 activates mitochondrial fission leading to oxidative stress and muscle atrophy.

Meijun Si, Rizhen Yu, Hongchun Lin, Feng Li, Sungyun Jung, Sandhya S Thomas, Farhard S Danesh, Yanlin Wang, Hui Peng, Zhaoyong Hu.

Chronic kidney disease (CKD) is often associated with protein-energy wasting (PEW), which is characterized by a reduction in muscle mass and strength. Although mitochondrial dysfunction and oxidative stress have been implicated to play a role in the pathogenesis of muscle wasting, the underlying mechanisms remain unclear. In this study, we used transcriptomics, metabolomics analyses and mouse gene manipulating approaches to investigate the effects of mitochondrial plasticity and oxidative stress on muscle wasting in mouse CKD models. Our results showed that the expression of oxidative stress response genes was increased, and that of oxidative phosphorylation genes was decreased in the muscles of mice with CKD. This was accompanied by reduced oxygen consumption rates, decreased levels of mitochondrial electron transport chain proteins, and increased cellular oxidative damage. Excessive mitochondrial fission was also observed, and we found that the activation of ROCK1 was responsible for this process. Inducible expression of muscle-specific constitutively active ROCK1 (mROCK1 ca ) exacerbated mitochondrial fragmentation and muscle wasting in CKD mice. Conversely, ROCK1 depletion (ROCK1-/-) alleviated these phenomena. Mechanistically, ROCK1 activation promoted the recruitment of Drp1 to mitochondria, thereby facilitating fragmentation. Notably, the pharmacological inhibition of ROCK1 mitigated muscle wasting by suppressing mitochondrial fission and oxidative stress. Our findings demonstrate that ROCK1 participates in CKD-induced muscle wasting by promoting mitochondrial fission and oxidative stress, and pharmacological suppression of ROCK1 could be a therapeutic strategy for combating muscle wasting in CKD conditions.
Translational Statement: Protein-energy wasting (PEW) is a prevalent issue among patients with chronic kidney disease (CKD) and is characterized by the loss of muscle mass. Our research uncovers a critical role that ROCK1 activation plays in muscle wasting induced by CKD. We found that ROCK1 is instrumental in causing mitochondrial fission, which leads to increased oxidative stress in muscle cells. By employing a pharmacological inhibitor, hydroxyfasudil, we were able to effectively curb ROCK1 activity, which in turn mitigated muscle wasting by reducing both mitochondrial fission and oxidative stress. These findings suggest that pharmacological inhibition of ROCK1 presents a promising therapeutic strategy for combating the muscle wasting associated with CKD.

DOI: https://doi.org/10.1101/2023.10.22.563469
J Nutr. 2023 Oct 26. pii: S0022-3166(23)72670-9. [Epub ahead of print]

Metabolomic and Lipidomic Signature of Skeletal Muscle with Constitutively Active mTORC1.

Rosario Maroto, Ted G Graber, Trevor B Romsdahl, Andrzej Kudlicki, William K Russell, Blake B Rasmussen.

   BACKGROUND: Regulation of mTORC1 plays an important role in aging and nutrition. For example, caloric restriction reduces mTORC1 signaling and extends lifespan, whereas nutrient abundance and obesity increase mTORC1 signaling and reduce lifespan. Skeletal muscle specific knockout of DEP domain-containing 5 protein (DEPDC5) results in constitutively active mTORC1 signaling, muscle hypertrophy and an increase in mitochondrial respiratory capacity. The metabolic profile of skeletal muscle, in the setting of hyperactive mTORC1 signaling, is not well known.
OBJECTIVES: To determine the metabolomic and lipidomic signature in skeletal muscle from female and male wildtype and DEPDC5 knockout mice.
METHODS: Tibialis anterior (TA) muscles from wildtype (WT) and transgenic (conditional skeletal muscle specific DEPDC5 knockout, KO) were obtained from female (F) and male (M) adult mice. Polar metabolites and lipids were extracted using a Bligh-Dyer extraction from 5 samples per group and identified and quantified by LC-MS/MS. Resulting analyte peak areas were analyzed with t-test, ANOVA, and volcano plots for group comparisons (e.g., WT vs KO) and multivariate statistical analysis for genotype and sex comparisons.
RESULTS: A total of 162 polar metabolites (organic acids, amino acids and amines and acyl carnitines) and 1141 lipid metabolites were detected in TA samples by LC-MS/MS. Few polar metabolites showed significant differences in KO muscles compared to WT within the same sex group. P-aminobenzoic acid, β-alanine and dopamine were significantly higher in KO male muscle whereas erythrose- 4-phosphate and oxoglutaric acid were significantly reduced in KO females. The lipidomic profile of the KO groups revealed an increase of muscle phospholipids and reduced triacylglycerol and diacylglycerol compared to the WT groups.
CONCLUSIONS: Sex differences were detected in polar metabolome and lipids were dependent on genotype. Metabolomic profile of mice with hyperactive skeletal muscle mTORC1 is consistent with an upregulation of mitochondrial function and amino acid utilization for protein synthesis.

Keywords:  DEPDC5; metabolites; sexual dimorphism; skeletal muscle

DOI:  https://doi.org/10.1016/j.tjnut.2023.10.016
Aging Cell. 2023 Nov 03. e14025

Skeletal muscle DNA methylation: Effects of exercise and HIV.

Catherine M Jankowski, Iain R Konigsberg, Melissa P Wilson, Jing Sun, Todd T Brown, Colleen G Julian, Kristine M Erlandson.

  Aging, human immunodeficiency virus (HIV) infection, and antiretroviral therapy modify the epigenetic profile and function of cells and tissues, including skeletal muscle (SkM). In some cells, accelerated epigenetic aging begins very soon after the initial HIV infection, potentially setting the stage for the early onset of frailty. Exercise imparts epigenetic modifications in SkM that may underpin some health benefits, including delayed frailty, in people living with HIV (PWH). In this first report of exercise-related changes in SkM DNA methylation among PWH, we investigated the impact of 24 weeks of aerobic and resistance exercise training on SkM (vastus lateralis) DNA methylation profiles and epigenetic age acceleration (EAA) in older, virally suppressed PWH (n = 12) and uninfected controls (n = 18), and associations of EAA with physical function at baseline. We identified 983 differentially methylated positions (DMPs) in PWH and controls at baseline and 237 DMPs after training. The influence of HIV serostatus on SkM methylation was more pronounced than that of exercise training. There was little overlap in the genes associated with the probes most significantly differentiated by exercise training within each group. Baseline EAA (mean ± SD) was similar between PWH (-0.4 ± 2.5 years) and controls (0.2 ± 2.6 years), and the exercise effect was not significant (p = 0.79). EAA and physical function at baseline were not significantly correlated (all p ≥ 0.10). This preliminary investigation suggests HIV-specific epigenetic adaptations in SkM with exercise training but confirmation in a larger study that includes transcriptomic analysis is warranted.

Keywords:  DNA methylation; HIV; aging; epigenetic; epigenetic clock; exercise training; skeletal muscle

DOI:  https://doi.org/10.1111/acel.14025
Nat Commun. 2023 Nov 01. 14(1): 6993

Gli1 marks a sentinel muscle stem cell population for muscle regeneration.

Jiayin Peng, Lili Han, Biao Liu, Jiawen Song, Yuang Wang, Kunpeng Wang, Qian Guo, XinYan Liu, Yu Li, Jujin Zhang, Wenqing Wu, Sheng Li, Xin Fu, Cheng-le Zhuang, Weikang Zhang, Shengbao Suo, Ping Hu, Yun Zhao.

Adult skeletal muscle regeneration is mainly driven by muscle stem cells (MuSCs), which are highly heterogeneous. Although recent studies have started to characterize the heterogeneity of MuSCs, whether a subset of cells with distinct exists within MuSCs remains unanswered. Here, we find that a population of MuSCs, marked by Gli1 expression, is required for muscle regeneration. The Gli1+ MuSC population displays advantages in proliferation and differentiation both in vitro and in vivo. Depletion of this population leads to delayed muscle regeneration, while transplanted Gli1+ MuSCs support muscle regeneration more effectively than Gli1- MuSCs. Further analysis reveals that even in the uninjured muscle, Gli1+ MuSCs have elevated mTOR signaling activity, increased cell size and mitochondrial numbers compared to Gli1- MuSCs, indicating Gli1+ MuSCs are displaying the features of primed MuSCs. Moreover, Gli1+ MuSCs greatly contribute to the formation of GAlert cells after muscle injury. Collectively, our findings demonstrate that Gli1+ MuSCs represents a distinct MuSC population which is more active in the homeostatic muscle and enters the cell cycle shortly after injury. This population functions as the tissue-resident sentinel that rapidly responds to injury and initiates muscle regeneration.

DOI: https://doi.org/10.1038/s41467-023-42837-8
J Cachexia Sarcopenia Muscle. 2023 Nov 01.

Receptor interacting protein kinase-3 mediates both myopathy and cardiomyopathy in preclinical animal models of Duchenne muscular dystrophy.

Maximilien Bencze, Baptiste Periou, Isabel Punzón, Inès Barthélémy, Valentina Taglietti, Cyrielle Hou, Louai Zaidan, Kaouthar Kefi, Stéphane Blot, Onnik Agbulut, Marianne Gervais, Geneviève Derumeaux, François-Jérôme Authier, Laurent Tiret, Fréderic Relaix.

   BACKGROUND: Duchenne muscular dystrophy (DMD) is a progressive muscle degenerative disorder, culminating in a complete loss of ambulation, hypertrophic cardiomyopathy and a fatal cardiorespiratory failure. Necroptosis is the form of necrosis that is dependent upon the receptor-interacting protein kinase (RIPK) 3; it is involved in several inflammatory and neurodegenerative conditions. We previously identified RIPK3 as a key player in the acute myonecrosis affecting the hindlimb muscles of the mdx dystrophic mouse model. Whether necroptosis also mediates respiratory and heart disorders in DMD is currently unknown.
METHODS: Evidence of activation of the necroptotic axis was examined in dystrophic tissues from Golden retriever muscular dystrophy (GRMD) dogs and R-DMDdel52 rats. A functional assessment of the involvement of necroptosis in dystrophic animals was performed on mdx mice that were genetically depleted for RIPK3. Dystrophic mice aged from 12 to 18 months were analysed by histology and molecular biology to compare the phenotype of muscles from mdxRipk3+/+ and mdxRipk3-/- mice. Heart function was also examined by echocardiography in 40-week-old mice.
RESULTS: RIPK3 expression in sartorius and biceps femoris muscles from GRMD dogs positively correlated to myonecrosis levels (r = 0.81; P = 0.0076). RIPK3 was also found elevated in the diaphragm (P ≤ 0.05). In the slow-progressing heart phenotype of GRMD dogs, the phosphorylated form of RIPK1 at the Serine 161 site was dramatically increased in cardiomyocytes. A similar p-RIPK1 upregulation characterized the cardiomyocytes of the severe DMDdel52 rat model, associated with a marked overexpression of Ripk1 (P = 0.007) and Ripk3 (P = 0.008), indicating primed activation of the necroptotic pathway in the dystrophic heart. MdxRipk3-/- mice displayed decreased compensatory hypertrophy of the heart (P = 0.014), and echocardiography showed a 19% increase in the relative wall thickness (P < 0.05) and 29% reduction in the left ventricle mass (P = 0.0144). Besides, mdxRipk3-/- mice presented no evidence of a regenerative default or sarcopenia in skeletal muscles, moreover around 50% less affected by fibrosis (P < 0.05).
CONCLUSIONS: Our data highlight molecular and histological evidence that the necroptotic pathway is activated in degenerative tissues from dystrophic animal models, including the diaphragm and the heart. We also provide the genetic proof of concept that selective inhibition of necroptosis in dystrophic condition improves both histological features of muscles and cardiac function, suggesting that prevention of necroptosis is susceptible to providing multiorgan beneficial effects for DMD.

Keywords:  Animal model; Cardiac failure; Duchenne muscular dystrophy; Fibrosis; Myogenesis; Myonecrosis; Necroptosis; Programmed cell death

DOI:  https://doi.org/10.1002/jcsm.13265
bioRxiv. 2023 Oct 19. pii: 2023.10.16.562573. [Epub ahead of print]

Glucocorticoid intermittence coordinates rescue of energy and mass in aging-related sarcopenia through the myocyte-autonomous PGC1alpha-Lipin1 transactivation.

Ashok Daniel Prabakaran, Kevin McFarland, Karen Miz, Hima Bindu Durumutla, Kevin Piczer, Fadoua El Abdellaoui Soussi, Hannah Latimer, Cole Werbrich, N Scott Blair, Douglas P Millay, 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 PGC1alpha and its co-factor Lipin1. Treatment coordinately improved mitochondrial abundance through isoform 1 and muscle mass through isoform 4 of the myocyte-specific PGC1alpha, which was required for the treatment-driven increase in carbon shuttling from glucose oxidation to amino acid biogenesis. We also probed the myocyte-specific Lipin1 as non-redundant factor coaxing PGC1alpha upregulation to the stimulation of both oxidative and anabolic capacities. Our study unveils an aging-resistant druggable program in myocytes to coordinately rescue energy and mass in sarcopenia.

DOI: https://doi.org/10.1101/2023.10.16.562573
J Physiol. 2023 Oct 30.

The influence of skeletal muscle mitochondria and sex on critical torque and performance fatiguability in humans.

Rachel M McDougall, Thomas R Tripp, Barnaby P Frankish, Patricia K Doyle-Baker, Victor Lun, J Preston Wiley, S Jalal Aboodarda, Martin J MacInnis.

  Critical torque (CT) represents the highest oxidative steady state for intermittent knee extensor exercise, but the extent to which it is influenced by skeletal muscle mitochondria and sex is unclear. Vastus lateralis muscle biopsy samples were collected from 12 females and 12 males -matched for relative maximal oxygen uptake normalized to fat-free mass (FFM) (F: 57.3 (7.5) ml (kg FFM)-1 min-1 ; M: 56.8 (7.6) ml (kg FFM)-1 min-1 ; P = 0.856) - prior to CT determination and performance fatiguability trials. Males had a lower proportion of myosin heavy chain (MHC) I isoform (40.6 (18.4)%) compared to females (59.5 (18.9)%; P = 0.021), but MHC IIa and IIx isoform distributions and protein markers of mitochondrial content were not different between sexes (P > 0.05). When normalized to maximum voluntary contraction (MVC), the relative CT (F: 42.9 (8.3)%; M: 37.9 (9.0)%; P = 0.172) and curvature constant, W' (F: 26.6 (11.0) N m s (N m)-1 ; M: 26.4 (6.5) N m s (N m)-1 ; P = 0.962) were not significantly different between sexes. All protein biomarkers of skeletal muscle mitochondrial content, as well as the proportion of MHC I isoform, positively correlated with relative CT (0.48 < r < 0.70; P < 0.05), and the proportion of MHC IIx isoform correlated positively with relative W' (r = 0.57; P = 0.007). Indices of performance fatiguability were not different between males and females for MVC- and CT-controlled trials (P > 0.05). Greater mitochondrial protein abundance was associated with attenuated declines in potentiated twitch torque for exercise at 60% MVC (P < 0.05); however, the influence of mitochondrial protein abundance on performance fatiguability was reduced when exercise was prescribed relative to CT. Whether these findings translate to whole-body exercise requires additional research. KEY POINTS: The quadriceps critical torque represents the highest intensity of intermittent knee extensor exercise for which an oxidative steady state is attainable, but its relationship with skeletal muscle mitochondrial protein abundance is unknown. Matching males and females for maximal oxygen uptake relative to fat-free mass facilitates investigations of sex differences in exercise physiology, but studies that have compared critical torque and performance fatiguability during intermittent knee extensor exercise have not ensured equal aerobic fitness between sexes. Skeletal muscle mitochondrial protein abundance was correlated with critical torque and fatigue resistance for exercise prescribed relative to maximum voluntary contraction but not for exercise performed relative to the critical torque. Differences between sexes in critical torque, skeletal muscle mitochondrial protein abundance and performance fatiguability were not statistically significant. Our results suggest that skeletal muscle mitochondrial protein abundance may contribute to fatigue resistance by influencing the critical intensity of exercise.

Keywords:  aerobic fitness; critical intensity; exercise; exercise prescription; fatigue; quadriceps; sex differences; small muscle mass

DOI:  https://doi.org/10.1113/JP284958
Nanomedicine (Lond). 2023 Nov 01.

Muscle-targeted nanoparticles strengthen the effects of small-molecule inhibitors in ameliorating sarcopenia.

Jinyu Wang, Yikang He, Baoyue Wang, Ruian Yin, Biao Chen, Hongxing Wang.

  Background: Sarcopenia is an aging-related degeneration of muscle mass and strength. Small-molecule inhibitor SW033291 has been shown to attenuate muscle atrophy. Targeted nanodrug-delivery systems can improve the efficacy of small-molecule inhibitors. Methods: The skeletal muscle cell-targeted nanoparticle was called AP@SW033291, which consisted of SW033291, modular peptide ASSLNIAGGRRRRRG and PEG-DSPE. Nanoparticles were featured with particle size, fluorescence emission spectra and targeting ability. We also investigated their effects on muscle mass and function. Results: The size of AP@SW033291 was 125.7 nm and it demonstrated targeting effects on skeletal muscle; thus, it could improve muscle mass and muscle function. Conclusion: Nanoparticle AP@SW033291 could become a potential strategy to strengthen the treatment effects of small-molecule inhibitors in sarcopenia.

Keywords:  SAMP8; nanoparticle; sarcopenia; small-molecule inhibitor; targeted therapy

DOI:  https://doi.org/10.2217/nnm-2023-0201
Biochem Biophys Res Commun. 2023 Oct 21. pii: S0006-291X(23)01235-4. [Epub ahead of print]684 149141

Advanced glycation end products inhibit proliferation and primary cilia formation of myoblasts through receptor for advanced glycation end products pathway.

Shinichiro Suzuki, Tatsuya Hayashi, Tatsuro Egawa.

  The loss of skeletal muscle mass leads to various adverse conditions and shortened lifespan. The inhibition of myoblast proliferation is one of the causes that trigger muscle atrophy. Advanced glycation end products (AGEs) contribute to muscle atrophy. Since primary cilia are crucial organelles for proliferation, AGEs may inhibit primary cilia formation of myoblasts, thereby leading to impaired proliferation. Therefore, we aimed to clarify whether AGEs impeded the proliferation and formation of primary cilia of C2C12 skeletal muscle cells. AGE treatment inhibited the proliferation and formation of primary cilia. However, the inhibitor of the receptor for advanced glycosylation end products (RAGEs) abolished the inhibition of the proliferation and the primary cilia formation of C2C12 cells by AGEs, suggesting that AGEs cause these inhibitions through the RAGE pathway. In summary, our findings suggested that AGEs suppress the proliferation and formation of primary cilia of myoblasts through the RAGE pathway.

Keywords:  AGEs; Myoblast; Primary cilia; Proliferation

DOI:  https://doi.org/10.1016/j.bbrc.2023.149141
Cell Signal. 2023 Oct 31. pii: S0898-6568(23)00374-1. [Epub ahead of print] 110959

Explore novel molecular mechanisms of FNDC5 in ischemia-reperfusion (I/R) injury by analyzing transcriptome changes in mouse model of skeletal muscle I/R injury with FNDC5 knockout.

Ming Zhou, Kai Wang, Yesheng Jin, Jinquan Liu, Yapeng Wang, Yuan Xue, Hao Liu, Qun Chen, Zhihai Cao, Xueyuan Jia, Yongjun Rui.

   BACKGROUND: Irisin, a myokine derived from proteolytic cleavage of the fibronectin type III domain-containing protein 5 (FNDC5) protein, is crucial in protecting tissues and organs from ischemia-reperfusion (I/R) injury. However, the underlying mechanism of its action remains elusive. In this study, we investigated the expression patterns of genes associated with FNDC5 knockout to gain insights into its molecular functions.
METHODS: We employed a mouse model of skeletal muscle I/R injury with FNDC5 knockout to examine the transcriptional profiles using RNA sequencing. Differentially expressed genes (DEGs) were identified and subjected to further analyses, including gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, protein-protein interaction (PPI) network analysis, and miRNA-transcription factor network analysis. The bioinformatics findings were validated using qRT-PCR and Western blotting.
RESULTS: Comparative analysis of skeletal muscle transcriptomes between wild-type (WT; C57BL/6), WT-I/R, FNDC5 knockout (KO), and KO-I/R mice highlighted the significance of FNDC5 in both physiological conditions and I/R injury. Through PPI network analysis, we identified seven key genes (Col6a2, Acta2, Col4a5, Fap, Enpep, Mmp11, and Fosl1), which facilitated the construction of a TF-hub genes-miRNA regulatory network. Additionally, our results suggested that the PI3K-Akt pathway is predominantly involved in FNDC5 deletion-mediated I/R injury in skeletal muscle. Animal studies revealed reduced FNDC5 expression in skeletal muscle following I/R injury, and the gastrocnemius muscle with FNDC5 knockout exhibited larger infarct size and more severe tissue damage after I/R. Moreover, Western blot analysis confirmed the upregulation of Col6a2, Enpep, and Mmp11 protein levels following I/R, particularly in the KO-I/R group. Furthermore, FNDC5 deletion inhibited the PI3K-Akt signaling pathway.
CONCLUSION: This study demonstrates that FNDC5 deletion exacerbates skeletal muscle I/R injury, potentially involving the upregulation of Col6a2, Enpep, and Mmp11. Additionally, the findings suggest the involvement of the PI3K-Akt pathway in FNDC5 deletion-mediated skeletal muscle I/R injury, providing novel insights into the molecular mechanisms underlying FNDC5's role in this pathological process.

Keywords:  Bioinformatics; Fibronectin type III domain-containing protein 5 (FNDC5); Ischemia-reperfusion injury; RNA sequencing; Skeletal muscle

DOI:  https://doi.org/10.1016/j.cellsig.2023.110959
BioDrugs. 2023 Nov 02.

Dystrophin- and Utrophin-Based Therapeutic Approaches for Treatment of Duchenne Muscular Dystrophy: A Comparative Review.

Sylwia Szwec, Zuzanna Kapłucha, Jeffrey S Chamberlain, Patryk Konieczny.

Duchenne muscular dystrophy is a devastating disease that leads to progressive muscle loss and premature death. While medical management focuses mostly on symptomatic treatment, decades of research have resulted in first therapeutics able to restore the affected reading frame of dystrophin transcripts or induce synthesis of a truncated dystrophin protein from a vector, with other strategies based on gene therapy and cell signaling in preclinical or clinical development. Nevertheless, recent reports show that potentially therapeutic dystrophins can be immunogenic in patients. This raises the question of whether a dystrophin paralog, utrophin, could be a more suitable therapeutic protein. Here, we compare dystrophin and utrophin amino acid sequences and structures, combining published data with our extended in silico analyses. We then discuss these results in the context of therapeutic approaches for Duchenne muscular dystrophy. Specifically, we focus on strategies based on delivery of micro-dystrophin and micro-utrophin genes with recombinant adeno-associated viral vectors, exon skipping of the mutated dystrophin pre-mRNAs, reading through termination codons with small molecules that mask premature stop codons, dystrophin gene repair by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9)-mediated genetic engineering, and increasing utrophin levels. Our analyses highlight the importance of various dystrophin and utrophin domains in Duchenne muscular dystrophy treatment, providing insights into designing novel therapeutic compounds with improved efficacy and decreased immunoreactivity. While the necessary actin and β-dystroglycan binding sites are present in both proteins, important functional distinctions can be identified in these domains and some other parts of truncated dystrophins might need redesigning due to their potentially immunogenic qualities. Alternatively, therapies based on utrophins might provide a safer and more effective approach.

DOI: https://doi.org/10.1007/s40259-023-00632-3
Skelet Muscle. 2023 Oct 28. 13(1): 17

DNA methylation of insulin signaling pathways is associated with HOMA2-IR in primary myoblasts from older adults.

Mark A Burton, Emma S Garratt, Matthew O Hewitt, Hanan Y Sharkh, Elie Antoun, Leo D Westbury, Elaine M Dennison, Nicholas C Harvey, Cyrus Cooper, Julia L MacIsaac, Michael S Kobor, Harnish P Patel, Keith M Godfrey, Karen A Lillycrop.

   BACKGROUND: While ageing is associated with increased insulin resistance (IR), the molecular mechanisms underlying increased IR in the muscle, the primary organ for glucose clearance, have yet to be elucidated in older individuals. As epigenetic processes are suggested to contribute to the development of ageing-associated diseases, we investigated whether differential DNA methylation was associated with IR in human primary muscle stem cells (myoblasts) from community-dwelling older individuals.
METHODS: We measured DNA methylation (Infinium HumanMethylationEPIC BeadChip) in myoblast cultures from vastus lateralis biopsies (119 males/females, mean age 78.24 years) from the Hertfordshire Sarcopenia Study extension (HSSe) and examined differentially methylated cytosine phosphate guanine (CpG) sites (dmCpG), regions (DMRs) and gene pathways associated with HOMA2-IR, an index for the assessment of insulin resistance, and levels of glycated hemoglobin HbA1c.
RESULTS: Thirty-eight dmCpGs (false discovery rate (FDR) < 0.05) were associated with HOMA2-IR, with dmCpGs enriched in genes linked with JNK, AMPK and insulin signaling. The methylation signal associated with HOMA2-IR was attenuated after the addition of either BMI (6 dmCpGs), appendicular lean mass index (ALMi) (7 dmCpGs), grip strength (15 dmCpGs) or gait speed (23 dmCpGs) as covariates in the model. There were 8 DMRs (Stouffer < 0.05) associated with HOMA2-IR, including DMRs within T-box transcription factor (TBX1) and nuclear receptor subfamily-2 group F member-2 (NR2F2); the DMRs within TBX1 and NR2F2 remained associated with HOMA2-IR after adjustment for BMI, ALMi, grip strength or gait speed. Forty-nine dmCpGs and 21 DMRs were associated with HbA1c, with cg13451048, located within exoribonuclease family member 3 (ERI3) associated with both HOMA2-IR and HbA1c. HOMA2-IR and HbA1c were not associated with accelerated epigenetic ageing.
CONCLUSIONS: These findings suggest that insulin resistance is associated with differential DNA methylation in human primary myoblasts with both muscle mass and body composition making a significant contribution to the methylation changes associated with IR.

Keywords:  DNA methylation; HOMA2-IR; Insulin resistance; Skeletal muscle

DOI:  https://doi.org/10.1186/s13395-023-00326-y
Sci Immunol. 2023 Nov 03. 8(89): eadi5377

Regulatory T cells shield muscle mitochondria from interferon-γ-mediated damage to promote the beneficial effects of exercise.

P Kent Langston, Yizhi Sun, Birgitta A Ryback, Amber L Mueller, Bruce M Spiegelman, Christophe Benoist, Diane Mathis.

Exercise enhances physical performance and reduces the risk of many disorders such as cardiovascular disease, type 2 diabetes, dementia, and cancer. Exercise characteristically incites an inflammatory response, notably in skeletal muscles. Although some effector mechanisms have been identified, regulatory elements activated in response to exercise remain obscure. Here, we have addressed the roles of Foxp3+CD4+ regulatory T cells (Tregs) in the healthful activities of exercise via immunologic, transcriptomic, histologic, metabolic, and biochemical analyses of acute and chronic exercise models in mice. Exercise rapidly induced expansion of the muscle Treg compartment, thereby guarding against overexuberant production of interferon-γ and consequent metabolic disruptions, particularly mitochondrial aberrancies. The performance-enhancing effects of exercise training were dampened in the absence of Tregs. Thus, exercise is a natural Treg booster with therapeutic potential in disease and aging contexts.

DOI: https://doi.org/10.1126/sciimmunol.adi5377
Calcif Tissue Int. 2023 Nov 03.

The Interconnection Between Muscle and Bone: A Common Clinical Management Pathway.

Cassandra Smith, Marc Sim, Jack Dalla Via, Itamar Levinger, Gustavo Duque.

  Often observed with aging, the loss of skeletal muscle (sarcopenia) and bone (osteoporosis) mass, strength, and quality, is associated with reduced physical function contributing to falls and fractures. Such events can lead to a loss of independence and poorer quality of life. Physical inactivity (mechanical unloading), especially in older adults, has detrimental effects on the mass and quality of bone as well as muscle, while increases in activity (mechanical loading) have positive effects. Emerging evidence suggests that the relationship between bone and muscle is driven, at least in part, by bone-muscle crosstalk. Bone and muscle are closely linked anatomically, mechanically, and biochemically, and both have the capacity to function with paracrine and endocrine-like action. However, the exact mechanisms involved in this crosstalk remain only partially explored. Given older adults with lower bone mass are more likely to present with impaired muscle function, and vice versa, strategies capable of targeting both bone and muscle are critical. Exercise is the primary evidence-based prevention strategy capable of simultaneously improving muscle and bone health. Unfortunately, holistic treatment plans including exercise in conjunction with other allied health services to prevent or treat musculoskeletal disease remain underutilized. With a focus on sarcopenia and osteoporosis, the aim of this review is to (i) briefly describe the mechanical and biochemical interactions between bone and muscle; (ii) provide a summary of therapeutic strategies, specifically exercise, nutrition and pharmacological approaches; and (iii) highlight a holistic clinical pathway for the assessment and management of sarcopenia and osteoporosis.

Keywords:  Allied health; Bone–muscle crosstalk; Diet; Exercise; Osteosarcopenia

DOI:  https://doi.org/10.1007/s00223-023-01146-4
Am J Physiol Regul Integr Comp Physiol. 2023 Oct 30.

In vivo cytosolic H2O2 changes and Ca2+ homeostasis in mouse skeletal muscle.

Ryotaro Kano, Ayaka Tabuchi, Yoshinori Tanaka, Hideki Shirakawa, Daisuke Hoshino, David C Poole, Yutaka Kano.

  Hydrogen peroxide (H2O2) and calcium ions (Ca2+) are functional regulators of skeletal muscle contraction and metabolism. Although H2O2 is one of the activators of the type-1 ryanodine receptor (RyR1) in the Ca2+ release channel, the interdependence between H2O2 and Ca2+ dynamics remains unclear. This study tested the following hypotheses using an in vivo model of mouse tibialis anterior (TA) skeletal muscle. 1. Under resting conditions, elevated cytosolic H2O2 concentration ([H2O2]cyto) leads to a concentration-dependent increase in cytosolic Ca2+concentration ([Ca2+]cyto) through its effect on RyR1. 2. In hypoxia (cardiac arrest) and muscle contractions (electrical stimulation), increased [H2O2]cyto induce Ca2+ accumulation. Cytosolic H2O2 (HyPer7) and Ca2+ (Fura-2) dynamics were resolved by TA bioimaging in C57BL/6J male mice under four conditions: Elevated exogenous H2O2, Cardiac arrest, Twitch and Tetanic contractions. Exogenous H2O2 (0.1-100mM) induced a concentration-dependent increase in [H2O2]cyto (+55%,0.1mM; +280%,100mM) and an increase in [Ca2+]cyto (+3%,1.0mM; +8%,10mM). This increase in [Ca2+]cyto was inhibited by pharmacological inhibition of RyR1 by dantrolene. Cardiac arrest-induced hypoxia increased [H2O2]cyto (+33%) and [Ca2+]cyto (+20%) 50min post-cardiac arrest. Compared to exogenous 1.0mM H2O2 condition, [H2O2]cyto after tetanic contractions rose less than one-tenth as much, while [Ca2+]cyto was 4.7-fold higher. In conclusion, substantial increases in [H2O2]cyto levels evoke only modest Ca2+ accumulation via their effect on the sarcoplasmic reticulum RyR1. On the other hand, contrary to hypoxia secondary to cardiac arrest, increases in [H2O2]cyto from contractions are small, indicating that H2O2 generation is unlikely to be a primary factor driving the significant Ca2+ accumulation after, especially tetanic, muscle contractions.

Keywords:  calcium ion; muscle contraction; reactive oxygen species; sarcoplasmic reticulum

DOI:  https://doi.org/10.1152/ajpregu.00152.2023
Proc Natl Acad Sci U S A. 2023 Nov 07. 120(45): e2305959120

A mechano- and heat-gated two-pore domain K+ channel controls excitability in adult zebrafish skeletal muscle.

Romane Idoux, Chloé Exbrayat-Héritier, Frédéric Sohm, Francisco Jaque-Fernandez, Elisabeth Vaganay, Christine Berthier, Sandrine Bretaud, Vincent Jacquemond, Florence Ruggiero, Bruno Allard.

  TRAAK channels are mechano-gated two-pore-domain K+ channels. Up to now, activity of these channels has been reported in neurons but not in skeletal muscle, yet an archetype of tissue challenged by mechanical stress. Using patch clamp methods on isolated skeletal muscle fibers from adult zebrafish, we show here that single channels sharing properties of TRAAK channels, i.e., selective to K+ ions, of 56 pS unitary conductance in the presence of 5 mM external K+, activated by membrane stretch, heat, arachidonic acid, and internal alkaline pH, are present in enzymatically isolated fast skeletal muscle fibers from adult zebrafish. The kcnk4b transcript encoding for TRAAK channels was cloned and found, concomitantly with activity of mechano-gated K+ channels, to be absent in zebrafish fast skeletal muscles at the larval stage but arising around 1 mo of age. The transfer of the kcnk4b gene in HEK cells and in the adult mouse muscle, that do not express functional TRAAK channels, led to expression and activity of mechano-gated K+ channels displaying properties comparable to native zebrafish TRAAK channels. In whole-cell voltage-clamp and current-clamp conditions, membrane stretch and heat led to activation of macroscopic K+ currents and to acceleration of the repolarization phase of action potentials respectively, suggesting that heat production and membrane deformation associated with skeletal muscle activity can control muscle excitability through TRAAK channel activation. TRAAK channels may represent a teleost-specific evolutionary product contributing to improve swimming performance for escaping predators and capturing prey at a critical stage of development.

Keywords:  K+ channel; single-channel recording; skeletal muscle fiber; voltage-clamp; zebrafish

DOI:  https://doi.org/10.1073/pnas.2305959120
Cancer Med. 2023 Oct 30.

Early skeletal muscle loss in adolescent and young adult cancer patients treated with anthracycline chemotherapy.

Savannah V Wooten, Fei Wang, Michael E Roth, Guanshu Liu, J Andrew Livingston, Behrang Amini, Susan C Gilchrist, Michelle Hildebrandt, Eugenie S Kleinerman.

   BACKGROUND: Early skeletal muscle loss has been observed in adolescent and young adult (AYA) sarcoma patients undergoing treatment. Identification of individuals within the AYA populace that are at greatest risk of anthracycline-induced skeletal muscle loss is unknown. Moreover, investigations which seek out underlying causes of skeletal muscle degradation during chemotherapy are critical for understanding, preventing, and reducing chronic health conditions associated with poor skeletal muscle status.
METHODS: Computed tomography (CT) scans were used to investigate changes in skeletal muscle of 153 AYA sarcoma and Hodgkin lymphoma patients at thoracic vertebra 4 after anthracycline treatment. Images were examined at three time points during the first year of treatment. In parallel, we used translational juvenile mouse models to assess the impact of doxorubicin (DOX) in the soleus and gastrocnemius on muscle wasting.
RESULTS: Significant reductions in total skeletal muscle index and density were seen after chemotherapy in AYA cancer patients (p < 0.01 & p = 0.04, respectively). The severity of skeletal muscle loss varied by subgroup (i.e., cancer type, sex, and treatment). Murine models demonstrated a reduction in skeletal muscle fiber cross-sectional area, increased apoptosis and collagen volume for both the soleus and gastrocnemius after DOX treatment (all p < 0.05). After DOX, hindlimb skeletal muscle blood flow was significantly reduced (p < 0.01).
CONCLUSION: Significant skeletal muscle loss is experienced early during treatment in AYA cancer patients. Reductions in skeletal muscle blood flow may be a key contributing factor to anthracycline doxorubicin induced skeletal muscle loss.

Keywords:  Hodgkin's lymphoma; chemotherapy; clinical observations; pediatric cancer

DOI:  https://doi.org/10.1002/cam4.6646
Sci Rep. 2023 Nov 01. 13(1): 18822

A Kinase Interacting Protein 1 regulates mitochondrial protein levels in energy metabolism and promotes mitochondrial turnover after exercise.

Kirsten T Nijholt, Pablo I Sánchez-Aguilera, Belend Mahmoud, Albert Gerding, Justina C Wolters, Anouk H G Wolters, Ben N G Giepmans, Herman H W Silljé, Rudolf A de Boer, Barbara M Bakker, B Daan Westenbrink.

A Kinase Interacting Protein 1 (AKIP1) is a signalling adaptor that promotes mitochondrial respiration and attenuates mitochondrial oxidative stress in cultured cardiomyocytes. We sought to determine whether AKIP1 influences mitochondrial function and the mitochondrial adaptation in response to exercise in vivo. We assessed mitochondrial respiratory capacity, as well as electron microscopy and mitochondrial targeted-proteomics in hearts from mice with cardiomyocyte-specific overexpression of AKIP1 (AKIP1-TG) and their wild type (WT) littermates. These parameters were also assessed after four weeks of voluntary wheel running. In contrast to our previous in vitro study, respiratory capacity measured as state 3 respiration on palmitoyl carnitine was significantly lower in AKIP1-TG compared to WT mice, whereas state 3 respiration on pyruvate remained unaltered. Similar findings were observed for maximal respiration, after addition of FCCP. Mitochondrial DNA damage and oxidative stress markers were not elevated in AKIP1-TG mice and gross mitochondrial morphology was similar. Mitochondrial targeted-proteomics did reveal reductions in mitochondrial proteins involved in energy metabolism. Exercise performance was comparable between genotypes, whereas exercise-induced cardiac hypertrophy was significantly increased in AKIP1-TG mice. After exercise, mitochondrial state 3 respiration on pyruvate substrates was significantly lower in AKIP1-TG compared with WT mice, while respiration on palmitoyl carnitine was not further decreased. This was associated with increased mitochondrial fission on electron microscopy, and the activation of pathways associated with mitochondrial fission and mitophagy. This study suggests that AKIP1 regulates the mitochondrial proteome involved in energy metabolism and promotes mitochondrial turnover after exercise. Future studies are required to unravel the mechanistic underpinnings and whether the mitochondrial changes are required for the AKIP1-induced physiological cardiac growth.

DOI: https://doi.org/10.1038/s41598-023-45961-z
J Neurol. 2023 Oct 31.

Distal hereditary motor neuronopathy as a new phenotype associated with variants in BAG3.

Carlos Pablo de Fuenmayor-Fernández de la Hoz, Vincenzo Lupo, Laura Bermejo-Guerrero, Paloma Martín-Jiménez, Aurelio Hernández-Laín, Montse Olivé, Eduard Gallardo, Jesús Esteban-Pérez, Carmen Espinós, Cristina Domínguez-González.

   OBJECTIVE: To describe a new phenotype associated with a novel variant in BAG3: autosomal dominant adult-onset distal hereditary motor neuronopathy.
METHODS: This study enrolled eight affected individuals from a single family and included a comprehensive evaluation of the clinical phenotype, neurophysiologic testing, muscle MRI, muscle biopsy and western blot of BAG3 protein in skeletal muscle. Genetic workup included whole exome sequencing and segregation analysis of the detected variant in BAG3.
RESULTS: Seven patients developed slowly progressive and symmetric distal weakness and atrophy of lower limb muscles, along with absent Achilles reflexes. The mean age of onset was 46 years. The neurophysiological examination was consistent with the diagnosis of distal motor neuronopathy. One 57-year-old female patient was minimally symptomatic. The pattern of inheritance was autosomal dominant, with one caveat: one female patient who was an obligate carrier of the variant died at the age of 73 years without exhibiting any muscle weakness. The muscle biopsies revealed neurogenic changes. A novel heterozygous truncating variant c.1513_1514insGGAC (p.Val505GlyfsTer6) in the gene BAG3 was identified in all affected family members.
CONCLUSIONS: We report an autosomal dominant adult-onset distal hereditary motor neuronopathy with incomplete penetrance in women as a new phenotype related to a truncating variant in the BAG3 gene. Our findings expand the phenotypic spectrum of BAG3-related disorders, which previously included dilated cardiomyopathy, myofibrillar myopathy and adult-onset Charcot-Marie-Tooth type 2 neuropathy. Variants in BAG3 should be considered in the differential diagnosis of distal hereditary motor neuronopathies.

Keywords:  BAG3; Distal hereditary motor neuronopathies; Neuromuscular diseases

DOI:  https://doi.org/10.1007/s00415-023-12039-9
Nature. 2023 Nov 01.

A new hydrogel can be directly injected into muscle to help it regenerate.

Nick Petrić Howe, Shamini Bundell.



Keywords:  Epidemiology; Genetics; History; Medical research; Physiology

DOI:  https://doi.org/10.1038/d41586-023-03441-4