bims-moremu 2023-03-12 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023–03–12
thirty-two papers selected by
Anna Vainshtein, Craft Science Inc.

The Role of Mitophagy in Skeletal Muscle Damage and Regeneration.
Urotensin II can Induce Skeletal Muscle Atrophy Associated with Upregulating Ubiquitin-Proteasome System and Inhibiting the Differentiation of Satellite Cells in CRF Mice.
Nuclear m6A reader YTHDC1 promotes muscle stem cell activation/proliferation by regulating mRNA splicing and nuclear export.
Muscle stem cells contribute to long-term tissue repletion following surgical sepsis.
Muscle group-specific skeletal muscle aging: a five-year longitudinal study in septuagenarians.
Sarcoplasmic Reticulum Ca2+ Buffer Proteins: A Focus on the Yet-To-Be-Explored Role of Sarcalumenin in Skeletal Muscle Health and Disease.
Senolytics improve muscle adaptation in old mice.
Low myoglobin concentration in skeletal muscle of elite cyclists is associated with low mRNA expression levels.
Construction of a novel lncRNA-miRNA-mRNA competing endogenous RNA network in muscle in response to exercise training.
Effects of Long-Term Physical Activity and BCAA Availability on the Subcellular Associations between Intramyocellular Lipids, Perilipins and PGC-1α.
AAV1.NT-3 gene therapy prevents age-related sarcopenia.
Longitudinal transcriptomic analysis of mouse sciatic nerve reveals pathways associated with age-related muscle pathology.
Extracellular vesicles and Duchenne muscular dystrophy pathology: Modulators of disease progression.
MicroRNA-200c-5p Regulates Migration and Differentiation of Myoblasts via Targeting Adamts5 in Skeletal Muscle Regeneration and Myogenesis.
Extracellular vesicle distribution and localization in skeletal muscle at rest and following disuse atrophy.
Skeletal muscle atrophy is exacerbated by steatotic and fibrotic liver-derived TNF-alpha in senescence-accelerated mice.
Discovery-Based Proteomics Identify Skeletal Muscle Mitochondrial Alterations as an Early Metabolic Defect in a Mouse Model of β-Thalassemia.
Human Neuromuscular Junction on a Chip: Impact of Amniotic Fluid Stem Cell Extracellular Vesicles on Muscle Atrophy and NMJ Integrity.
Histone Deacetylases: Molecular Mechanisms and Therapeutic Implications for Muscular Dystrophies.
The double homeodomain protein DUX4c is associated with regenerating muscle fibers and RNA-binding proteins.
Activation of β-catenin in mesenchymal progenitors leads to muscle mass loss.
Mimicking exercise in vitro - effects of myotube contractions and mechanical stretch on omics.
Identification of a novel small-molecule inhibitor of miR-29b attenuates muscle atrophy.
Interleukin-6 promotes skeletal muscle catabolism by activating tryptophan-indoleamine 2,3-dioxygenase 1-kynurenine pathway during intra-abdominal sepsis.
Sex Differences in Inflammation and Muscle Wasting in Aging and Disease.
Rejuvenating muscle stem cells with the glutathione system.
Enhancing the metabolic benefits of exercise: Is timing the key?
Single-leg disuse decreases skeletal muscle strength, size, and power in uninjured adults: A systematic review and meta-analysis.
Urine titin as a novel biomarker for Duchenne muscular dystrophy.
Role of SIRT3 in Microgravity Response: A New Player in Muscle Tissue Recovery.
An AMP Kinase-pathway dependent integrated stress response regulates ageing and longevity.
Experimental evidence and clinical implications of Warburg effect in the skeletal muscle of Fabry disease.

Cells. 2023 Feb 24. pii: 716. [Epub ahead of print]12(5):

The Role of Mitophagy in Skeletal Muscle Damage and Regeneration.

Eirini Chatzinikita, Maria Maridaki, Konstantinos Palikaras, Michael Koutsilieris, Anastassios Philippou.

  Mitochondria are cellular organelles that play an essential role in generating the chemical energy needed for the biochemical reactions in cells. Mitochondrial biogenesis, i.e., de novo mitochondria formation, results in enhanced cellular respiration, metabolic processes, and ATP generation, while autophagic clearance of mitochondria (mitophagy) is required to remove damaged or useless mitochondria. The balance between the opposing processes of mitochondrial biogenesis and mitophagy is highly regulated and crucial for the maintenance of the number and function of mitochondria as well as for the cellular homeostasis and adaptations to metabolic demands and extracellular stimuli. In skeletal muscle, mitochondria are essential for maintaining energy homeostasis, and the mitochondrial network exhibits complex behaviors and undergoes dynamic remodeling in response to various conditions and pathologies characterized by changes in muscle cell structure and metabolism, such as exercise, muscle damage, and myopathies. In particular, the involvement of mitochondrial remodeling in mediating skeletal muscle regeneration following damage has received increased attention, as modifications in mitophagy-related signals arise from exercise, while variations in mitochondrial restructuring pathways can lead to partial regeneration and impaired muscle function. Muscle regeneration (through myogenesis) following exercise-induced damage is characterized by a highly regulated, rapid turnover of poor-functioning mitochondria, permitting the synthesis of better-functioning mitochondria to occur. Nevertheless, essential aspects of mitochondrial remodeling during muscle regeneration remain poorly understood and warrant further characterization. In this review, we focus on the critical role of mitophagy for proper muscle cell regeneration following damage, highlighting the molecular mechanisms of the mitophagy-associated mitochondrial dynamics and network reformation.

Keywords:  exercise; mitochondrial biogenesis; mitochondrial network; mitophagy; muscle damage; myogenesis; regeneration

DOI:  https://doi.org/10.3390/cells12050716
Calcif Tissue Int. 2023 Mar 09.

Urotensin II can Induce Skeletal Muscle Atrophy Associated with Upregulating Ubiquitin-Proteasome System and Inhibiting the Differentiation of Satellite Cells in CRF Mice.

Yajing Pan, Ting Zhou, Xingtong Dong, Leiyun Wu, Peiwen Wang, Shiyuan Wang, Aihua Zhang.

  Skeletal muscle wasting and atrophy is highly prevalent in chronic renal failure (CRF) and increases the risk of mortality. According to our previous study, we speculate that urotensin II (UII) can induce skeletal muscle atrophy by upregulating ubiquitin-proteasome system(UPS) in CRF. C2C12 mouse myoblast cells were differentiated into myotubes, and myotubes were exposed to different concentrations of UII. Myotube diameters, myosin heavy chain(MHC), p-Fxo03A, skeletal muscle-specific E3 ubiquitin ligases such as muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx/atrogin1) were detected. Three animal models (the sham operation mice as normal control (NC) group, wild-type C57BL/6 mice with 5/6 nephrectomy (WT CRF) group, UII receptor gene knock out (UT KO) mice with 5/6 nephrectomy (UT KO CRF) group) were designed. Cross-sectional area (CSA) of skeletal muscle tissues in three animal models were measured, and western blot detected protein of UII, p-Fxo03A, MAFbx and MuRF1, and immunofluorescence assays explored the satellite cell marker of Myod1 and Pax7, and PCR arrays detected the muscle protein degradation genes, protein synthesis genes and the genes which were involved in muscle components. UII could decrease mouse myotube diameters, and upregulate dephosphorylated Fxo03A protein. MAFbx and MuRF1 were higher in WT CRF group than that in NC group, but after UII receptor gene was knocked out (UT KO CRF), their expressions were downregulated. UII could inhibit the expression of Myod1 but not Pax7 in animal study. We first demonstrate that skeletal muscle atrophy induced by UII associated with upregulating ubiquitin-proteasome system and inhibiting the differentiation of satellite cells in CRF mice.

Keywords:  Proteasome system; Satellite cells; Skeletal muscle atrophy; UII; Ubiquitin

DOI:  https://doi.org/10.1007/s00223-023-01073-4
Elife. 2023 Mar 09. pii: e82703. [Epub ahead of print]12

Nuclear m6A reader YTHDC1 promotes muscle stem cell activation/proliferation by regulating mRNA splicing and nuclear export.

Yulong Qiao, Qiang Sun, Xiaona Chen, Liangqiang He, Di Wang, Ruibao Su, Yuanchao Xue, Hao Sun, Huating Wang.

  Skeletal muscle stem cells (also known as satellite cells, SCs) are essential for muscle regeneration and the regenerative activities of SCs are intrinsically governed by gene regulatory mechanisms but the post-transcriptional regulation in SCs remains largely unknown. N(6)-methyladenosine (m6A) modification of RNAs is the most pervasive and highly conserved RNA modification in eukaryotic cells and exerts powerful impact on almost all aspects of mRNA processing which is mainly endowed by its binding with m6A reader proteins. Here in this study, we investigate the previously uncharacterized regulatory roles of YTHDC1, a m6A reader in mouse SCs. Our results demonstrate YTHDC1 is an essential regulator of SC activation and proliferation upon acute injury induced muscle regeneration. The induction of YTHDC1 is indispensable for SC activation and proliferation thus inducible YTHDC1 depletion almost abolishes SC regenerative capacity. Mechanistically, transcriptome-wide profiling using LACE-seq in both SCs and mouse C2C12 myoblasts identifies m6A mediated binding targets of YTHDC1. Next, splicing analysis defines splicing mRNA targets of m6A-YTHDC1. Furthermore, nuclear export analysis also leads to identification of potential mRNA export targets of m6A-YTHDC1 in SCs and C2C12 myoblasts and interestingly some mRNAs can be regulated at both splicing and export levels. Lastly, we map YTHDC1 interacting protein partners in myoblasts and unveil a myriad of factors governing mRNA splicing, nuclear export and transcription, among which hnRNPG appears to be a bona fide interacting partner of YTHDC1. Altogether, our findings uncover YTHDC1 as an essential factor controlling SC regenerative ability through multi-faceted gene regulatory mechanisms in mouse myoblast cells.

Keywords:  cell biology; mouse; regenerative medicine; stem cells

DOI:  https://doi.org/10.7554/eLife.82703
J Cachexia Sarcopenia Muscle. 2023 Mar 08.

Muscle stem cells contribute to long-term tissue repletion following surgical sepsis.

Rebecca E Schmitt, Aneesha Dasgupta, Paige C Arneson-Wissink, Srijani Datta, Alexandra M Ducharme, Jason D Doles.

   BACKGROUND: Over the past decade, advances in sepsis identification and management have resulted in decreased sepsis mortality. This increase in survivorship has highlighted a new clinical obstacle: chronic critical illness (CCI), for which there are no effective treatment options. Up to half of sepsis survivors suffer from CCI, which can include multi-organ dysfunction, chronic inflammation, muscle wasting, physical and mental disabilities, and enhanced frailty. These symptoms prevent survivors from returning to regular day-to-day activities and are directly associated with poor quality of life.
METHODS: Mice were subjected to cecal ligation and puncture (CLP) with daily chronic stress (DCS) as an in vivo model to study sepsis late-effects/sequelae on skeletal muscle components. Longitudinal monitoring was performed via magnetic resonance imaging, skeletal muscle and/or muscle stem cell (MuSCs) assays (e.g., post-necropsy wet muscle weights, minimum Feret diameter measurements, in vitro MuSC proliferation and differentiation, number of regenerating myofibres and numbers of Pax7-positive nuclei per myofibre), post-sepsis whole muscle metabolomics and MuSC isolation and high-content transcriptional profiling.
RESULTS: We report several findings supporting the hypothesis that MuSCs/muscle regeneration are critically involved in post-sepsis muscle recovery. First, we show that genetic ablation of muscle stem cells (MuSCs) impairs post-sepsis muscle recovery (maintenance of 5-8% average lean mass loss compared with controls). Second, we observe impaired MuSCs expansion capacity and morphological defects at 26 days post-sepsis compared with control MuSCs (P < 0.001). Third, when subjected to an experimental muscle injury, sepsis-recovered mice exhibited evidence of impaired muscle regeneration compared with non-septic mice receiving the same muscle injury (CLP/DCS injured mean minimum Feret is 92.1% of control injured, P < 0.01). Fourth, we performed a longitudinal RNA sequencing study on MuSCs isolated from post-sepsis mice and found clear transcriptional differences in all post-sepsis samples compared with controls. At Day 28, CLP/DCS mice satellite cells have multiple altered metabolic pathways, such as oxidative phosphorylation, mitochondrial dysfunction, sirtuin signalling and oestrogen receptor signalling, compared with controls (P < 0.001).
CONCLUSIONS: Our data show that MuSCs and muscle regeneration are required for effective post-sepsis muscle recovery and that sepsis triggers morphological, functional, and transcriptional changes in MuSCs. Moving forward, we strive to leverage a more complete understanding of post-sepsis MuSC/regenerative defects to identify and test novel therapies that promote muscle recovery and improve quality of life in sepsis survivors.

Keywords:  muscle regeneration; muscle stem cells; muscle wasting; satellite cells; sepsis; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13214
J Appl Physiol (1985). 2023 Mar 09.

Muscle group-specific skeletal muscle aging: a five-year longitudinal study in septuagenarians.

Masatoshi Naruse, William A Fountain, Alex Claiborne, W Holmes Finch, Scott Trappe, Todd A Trappe.

  There is some evidence that the age-associated change in skeletal muscle mass is muscle specific, yet the number of specific muscles that have been studied to form our understanding in this area is limited. In addition, few aging investigations have examined multiple muscles in the same individuals. This longitudinal investigation compared changes in skeletal muscle size via computed tomography of the quadriceps (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius), hamstrings (biceps femoris short and long heads, semitendinosus, semimembranosus), psoas, rectus abdominis, lateral abdominals (obliques and transversus abdominis), and paraspinal muscles (erector spinae and multifidi) of older individuals from the Health ABC study at baseline and 5.0±0.1 years later (n=469, 73±3yr & 78±3yr, 49% women, 33% black). Skeletal muscle size decreased (p<0.05) in quadriceps (-3.3%), hamstrings (-5.9%), psoas (-0.4%), and rectus abdominis (-7.0%). The hamstrings and rectus abdominis atrophied approximately twice as much as the quadriceps (p<0.05), while the quadriceps atrophied substantially more than the psoas (p<0.05). The lateral abdominals (+5.9%) and paraspinals (+4.3%) hypertrophied (p<0.05) to a similar degree (p>0.05) over the 5 years. These data suggest that older individuals experience skeletal muscle atrophy and hypertrophy in a muscle group-specific fashion in the eighth decade, a critical time period in the aging process. A broader understanding of muscle group-specific skeletal muscle aging is needed to better guide exercise programs and other interventions that mitigate decrements in physical function with aging.

Keywords:  Muscle mass; aging; computed tomography; sarcopenia

DOI:  https://doi.org/10.1152/japplphysiol.00769.2022
Cells. 2023 Feb 24. pii: 715. [Epub ahead of print]12(5):

Sarcoplasmic Reticulum Ca2+ Buffer Proteins: A Focus on the Yet-To-Be-Explored Role of Sarcalumenin in Skeletal Muscle Health and Disease.

Elena Conte, Giorgia Dinoi, Paola Imbrici, Annamaria De Luca, Antonella Liantonio.

  Sarcalumenin (SAR) is a luminal Ca2+ buffer protein with high capacity but low affinity for calcium binding found predominantly in the longitudinal sarcoplasmic reticulum (SR) of fast- and slow-twitch skeletal muscles and the heart. Together with other luminal Ca2+ buffer proteins, SAR plays a critical role in modulation of Ca2+ uptake and Ca2+ release during excitation-contraction coupling in muscle fibers. SAR appears to be important in a wide range of other physiological functions, such as Sarco-Endoplasmic Reticulum Calcium ATPase (SERCA) stabilization, Store-Operated-Calcium-Entry (SOCE) mechanisms, muscle fatigue resistance and muscle development. The function and structural features of SAR are very similar to those of calsequestrin (CSQ), the most abundant and well-characterized Ca2+ buffer protein of junctional SR. Despite the structural and functional similarity, very few targeted studies are available in the literature. The present review provides an overview of the role of SAR in skeletal muscle physiology, as well as of its possible involvement and dysfunction in muscle wasting disorders, in order to summarize the current knowledge on SAR and drive attention to this important but still underinvestigated/neglected protein.

Keywords:  Ca2+ buffer protein; sarcalumenin; sarcalumenin-related skeletal muscle diseases; sarcoplasmic reticulum; skeletal muscle

DOI:  https://doi.org/10.3390/cells12050715
Aging (Albany NY). 2023 Mar 06. undefined

Senolytics improve muscle adaptation in old mice.

Cory M Dungan, Charlotte A Peterson.



Keywords:  aging; senescence; senolytics; skeletal muscle

DOI:  https://doi.org/10.18632/aging.204578
Eur J Appl Physiol. 2023 Mar 06.

Low myoglobin concentration in skeletal muscle of elite cyclists is associated with low mRNA expression levels.

Nina Jacobs, Daniek Mos, Frank W Bloemers, Willem J van der Laarse, Richard T Jaspers, Stephan van der Zwaard.

  Myoglobin is essential for oxygen transport to the muscle fibers. However, measurements of myoglobin (Mb) protein concentrations within individual human muscle fibers are scarce. Recent observations have revealed surprisingly low Mb concentrations in elite cyclists, however it remains unclear whether this relates to Mb translation, transcription and/or myonuclear content. The aim was to compare Mb concentration, Mb messenger RNA (mRNA) expression levels and myonuclear content within muscle fibers of these elite cyclists with those of physically-active controls. Muscle biopsies were obtained from m. vastus lateralis in 29 cyclists and 20 physically-active subjects. Mb concentration was determined by peroxidase staining for both type I and type II fibers, Mb mRNA expression level was determined by quantitative PCR and myonuclear domain size (MDS) was obtained by immunofluorescence staining. Average Mb concentrations (mean ± SD: 0.38 ± 0.04 mM vs. 0.48 ± 0.19 mM; P = 0.014) and Mb mRNA expression levels (0.067 ± 0.019 vs. 0.088 ± 0.027; P = 0.002) were lower in cyclists compared to controls. In contrast, MDS and total RNA per mg muscle were not different between groups. Interestingly, in cyclists compared to controls, Mb concentration was only lower for type I fibers (P < 0.001), but not for type II fibers (P > 0.05). In conclusion, the lower Mb concentration in muscle fibers of elite cyclists is partly explained by lower Mb mRNA expression levels per myonucleus and not by a lower myonuclear content. It remains to be determined whether cyclists may benefit from strategies that upregulate Mb mRNA expression levels, particularly in type I fibers, to enhance their oxygen supply.

Keywords:  Cycling; Muscle biopsy; Muscle fiber type; Myonuclei; Oxygen transport; Satellite cells

DOI:  https://doi.org/10.1007/s00421-023-05161-z
Gen Physiol Biophys. 2023 Mar;42(2): 123-133

Construction of a novel lncRNA-miRNA-mRNA competing endogenous RNA network in muscle in response to exercise training.

Mingkun Nie, Qingling Liu, Cheng Yan.

Physical inactivity has evidently been a hazard factor for many diseases, including cardiovascular disease, diabetes, cancer, etc. Rising evidence indicates that RNA, as competitive endogenous RNA (ceRNA), plays an important role in adaptive changes in skeletal muscle in response to exercise training. Although the eﬀects of exercise-induced fitness on skeletal muscle have been well established, the mechanisms underlying are not fully understood. The purpose of this study is to construct a novel ceRNA network in skeletal muscle in response to exercise training. Skeletal muscle gene expression profiles were downloaded from the GEO database. Then, we identified differentially expressed lncRNAs, miRNAs, and mRNAs between the pre-exercise and post-exercise samples. Subsequently, we constructed lncRNA-miRNA-mRNA regulatory networks based on the ceRNA theory. 1153 mRNAs (687 upregulated and 466 downregulated), 7 miRNAs (3 upregulated and 4 downregulated), and 5 lncRNAs (3 upregulated and 2 downregulated) were identified as differentially expressed genes. 3 lncRNAs, 5 miRNAs and 227 mRNAs were obtained to build miRNA-mediated ceRNA networks. We constructed a novel ceRNA regulatory network in muscle in response to exercise training, which provides insights into molecular mechanisms underlying the health benefits brought by physical activity.

DOI: https://doi.org/10.4149/gpb_2022062
Int J Mol Sci. 2023 Feb 21. pii: 4282. [Epub ahead of print]24(5):

Effects of Long-Term Physical Activity and BCAA Availability on the Subcellular Associations between Intramyocellular Lipids, Perilipins and PGC-1α.

Vasco Fachada, Mika Silvennoinen, Ulla-Maria Sahinaho, Paavo Rahkila, Riikka Kivelä, Juha J Hulmi, Urho Kujala, Heikki Kainulainen.

  Cellular skeletal muscle lipid metabolism is of paramount importance for metabolic health, specifically through its connection to branched-chain amino acids (BCAA) metabolism and through its modulation by exercise. In this study, we aimed at better understanding intramyocellular lipids (IMCL) and their related key proteins in response to physical activity and BCAA deprivation. By means of confocal microscopy, we examined IMCL and the lipid droplet coating proteins PLIN2 and PLIN5 in human twin pairs discordant for physical activity. Additionally, in order to study IMCLs, PLINs and their association to peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in cytosolic and nuclear pools, we mimicked exercise-induced contractions in C2C12 myotubes by electrical pulse stimulation (EPS), with or without BCAA deprivation. The life-long physically active twins displayed an increased IMCL signal in type I fibers when compared to their inactive twin pair. Moreover, the inactive twins showed a decreased association between PLIN2 and IMCL. Similarly, in the C2C12 cell line, PLIN2 dissociated from IMCL when myotubes were deprived of BCAA, especially when contracting. In addition, in myotubes, EPS led to an increase in nuclear PLIN5 signal and its associations with IMCL and PGC-1α. This study demonstrates how physical activity and BCAA availability affects IMCL and their associated proteins, providing further and novel evidence for the link between the BCAA, energy and lipid metabolisms.

Keywords:  C2C12; EPS; PLIN2; PLIN5; electrical pulse stimulation; lipid droplets; physical activity; skeletal muscle; subcellular localization

DOI:  https://doi.org/10.3390/ijms24054282
Aging (Albany NY). 2023 Mar 09. 15

AAV1.NT-3 gene therapy prevents age-related sarcopenia.

Burcak Ozes, Lingying Tong, Morgan Myers, Kyle Moss, Alicia Ridgley, Zarife Sahenk.

  Sarcopenia is progressive loss of muscle mass and strength, occurring during normal aging with significant consequences on the quality of life for elderly. Neurotrophin 3 (NT-3) is an important autocrine factor supporting Schwann cell survival and differentiation and stimulating axon regeneration and myelination. NT-3 is involved in the maintenance of neuromuscular junction (NMJ) integrity, restoration of impaired radial growth of muscle fibers through activation of the Akt/mTOR pathway. We tested the efficacy of NT-3 gene transfer therapy in wild type (WT)-aged C57BL/6 mice, a model for natural aging and sarcopenia, via intramuscular injection 1 × 1011 vg AAV1.tMCK.NT-3, at 18 months of age. The treatment efficacy was assessed at 6 months post-injection using run to exhaustion and rotarod tests, in vivo muscle contractility assay, and histopathological studies of the peripheral nervous system, including NMJ connectivity and muscle. AAV1.NT-3 gene therapy in WT-aged C57BL/6 mice resulted in functional and in vivo muscle physiology improvements, supported by quantitative histology from muscle, peripheral nerves and NMJ. Hindlimb and forelimb muscles in the untreated cohort showed the presence of a muscle- and sex-dependent remodeling and fiber size decrease with aging, which was normalized toward values obtained from 10 months old WT mice with treatment. The molecular studies assessing the NT-3 effect on the oxidative state of distal hindlimb muscles, accompanied by western blot analyses for mTORC1 activation were in accordance with the histological findings. Considering the cost and quality of life to the individual, we believe our study has important implications for management of age-related sarcopenia.

Keywords:  NT-3; aging; gene therapy; muscle remodeling; sarcopenia

DOI:  https://doi.org/10.18632/aging.204577
J Cachexia Sarcopenia Muscle. 2023 Mar 10.

Longitudinal transcriptomic analysis of mouse sciatic nerve reveals pathways associated with age-related muscle pathology.

Nicole Comfort, Meethila Gade, Madeleine Strait, Samantha J Merwin, Daphne Antoniou, Chiara Parodi, Lina Marcinczyk, Lea Jean-Francois, Tessa R Bloomquist, Anna Memou, Hardy J Rideout, Stefania Corti, Shingo Kariya, Diane B Re.

   BACKGROUND: Sarcopenia, the age-associated decline in skeletal muscle mass and strength, has long been considered a disease of muscle only, but accumulating evidence suggests that sarcopenia could originate from the neural components controlling muscles. To identify early molecular changes in nerves that may drive sarcopenia initiation, we performed a longitudinal transcriptomic analysis of the sciatic nerve, which governs lower limb muscles, in aging mice.
METHODS: Sciatic nerve and gastrocnemius muscle were obtained from female C57BL/6JN mice aged 5, 18, 21 and 24 months old (n = 6 per age group). Sciatic nerve RNA was extracted and underwent RNA sequencing (RNA-seq). Differentially expressed genes (DEGs) were validated using quantitative reverse transcription PCR (qRT-PCR). Functional enrichment analysis of clusters of genes associated with patterns of gene expression across age groups (adjusted P-value < 0.05, likelihood ratio test [LRT]) was performed. Pathological skeletal muscle aging was confirmed between 21 and 24 months by a combination of molecular and pathological biomarkers. Myofiber denervation was confirmed with qRT-PCR of Chrnd, Chrng, Myog, Runx1 and Gadd45ɑ in gastrocnemius muscle. Changes in muscle mass, cross-sectional myofiber size and percentage of fibres with centralized nuclei were analysed in a separate cohort of mice from the same colony (n = 4-6 per age group).
RESULTS: We detected 51 significant DEGs in sciatic nerve of 18-month-old mice compared with 5-month-old mice (absolute value of fold change > 2; false discovery rate [FDR] < 0.05). Up-regulated DEGs included Dbp (log2 fold change [LFC] = 2.63, FDR < 0.001) and Lmod2 (LFC = 7.52, FDR = 0.001). Down-regulated DEGs included Cdh6 (LFC = -21.38, FDR < 0.001) and Gbp1 (LFC = -21.78, FDR < 0.001). We validated RNA-seq findings with qRT-PCR of various up- and down-regulated genes including Dbp and Cdh6. Up-regulated genes (FDR < 0.1) were associated with the AMP-activated protein kinase signalling pathway (FDR = 0.02) and circadian rhythm (FDR = 0.02), whereas down-regulated DEGs were associated with biosynthesis and metabolic pathways (FDR < 0.05). We identified seven significant clusters of genes (FDR < 0.05, LRT) with similar expression patterns across groups. Functional enrichment analysis of these clusters revealed biological processes that may be implicated in age-related changes in skeletal muscles and/or sarcopenia initiation including extracellular matrix organization and an immune response (FDR < 0.05).
CONCLUSIONS: Gene expression changes in mouse peripheral nerve were detected prior to disturbances in myofiber innervation and sarcopenia onset. These early molecular changes we report shed a new light on biological processes that may be implicated in sarcopenia initiation and pathogenesis. Future studies are warranted to confirm the disease modifying and/or biomarker potential of the key changes we report here.

Keywords:  RNA-seq; aging; frailty; motor unit; sarcopenia; skeletal muscle

DOI:  https://doi.org/10.1002/jcsm.13204
Front Physiol. 2023 ;14 1130063

Extracellular vesicles and Duchenne muscular dystrophy pathology: Modulators of disease progression.

Laura Yedigaryan, Maurilio Sampaolesi.

  Duchenne muscular dystrophy (DMD) is a devastating disorder and is considered to be one of the worst forms of inherited muscular dystrophies. DMD occurs as a result of mutations in the dystrophin gene, leading to progressive muscle fiber degradation and weakness. Although DMD pathology has been studied for many years, there are aspects of disease pathogenesis and progression that have not been thoroughly explored yet. The underlying issue with this is that the development of further effective therapies becomes stalled. It is becoming more evident that extracellular vesicles (EVs) may contribute to DMD pathology. EVs are vesicles secreted by cells that exert a multitude of effects via their lipid, protein, and RNA cargo. EV cargo (especially microRNAs) is also said to be a good biomarker for identifying the status of specific pathological processes that occur in dystrophic muscle, such as fibrosis, degeneration, inflammation, adipogenic degeneration, and dilated cardiomyopathy. On the other hand, EVs are becoming more prominent vehicles for custom-engineered cargos. In this review, we will discuss the possible contribution of EVs to DMD pathology, their potential use as biomarkers, and the therapeutic efficacy of both, EV secretion inhibition and custom-engineered cargo delivery.

Keywords:  cardiomyopathy; exosomes; extracellular vesicles (EVs); induced pluripotent stem cells (iPSCs); miRNAs; muscle regeneration; muscular dystrophies; satellite cells

DOI:  https://doi.org/10.3389/fphys.2023.1130063
Int J Mol Sci. 2023 Mar 05. pii: 4995. [Epub ahead of print]24(5):

MicroRNA-200c-5p Regulates Migration and Differentiation of Myoblasts via Targeting Adamts5 in Skeletal Muscle Regeneration and Myogenesis.

Yanwen Liu, Yilong Yao, Yongsheng Zhang, Chao Yan, Mingsha Yang, Zishuai Wang, Wangzhang Li, Fanqinyu Li, Wei Wang, Yalan Yang, Xinyun Li, Zhonglin Tang.

  Skeletal muscle, as a regenerative organization, plays a vital role in physiological characteristics and homeostasis. However, the regulation mechanism of skeletal muscle regeneration is not entirely clear. miRNAs, as one of the regulatory factors, exert profound effects on regulating skeletal muscle regeneration and myogenesis. This study aimed to discover the regulatory function of important miRNA miR-200c-5p in skeletal muscle regeneration. In our study, miR-200c-5p increased at the early stage and peaked at first day during mouse skeletal muscle regeneration, which was also highly expressed in skeletal muscle of mouse tissue profile. Further, overexpression of miR-200c-5p promoted migration and inhibited differentiation of C2C12 myoblast, whereas inhibition of miR-200c-5p had the opposite effect. Bioinformatic analysis predicted that Adamts5 has potential binding sites for miR-200c-5p at 3'UTR region. Dual-luciferase and RIP assays further proved that Adamts5 is a target gene of miR-200c-5p. The expression patterns of miR-200c-5p and Adamts5 were opposite during the skeletal muscle regeneration. Moreover, miR-200c-5p can rescue the effects of Adamts5 in the C2C12 myoblast. In conclusion, miR-200c-5p might play a considerable function during skeletal muscle regeneration and myogenesis. These findings will provide a promising gene for promoting muscle health and candidate therapeutic target for skeletal muscle repair.

Keywords:  Adamts5; differentiation; miR-200c-5p; migration; regeneration; skeletal muscle

DOI:  https://doi.org/10.3390/ijms24054995
Skelet Muscle. 2023 Mar 10. 13(1): 6

Extracellular vesicle distribution and localization in skeletal muscle at rest and following disuse atrophy.

Ahmed Ismaeel, Douglas W Van Pelt, Zachary R Hettinger, Xu Fu, Christopher I Richards, Timothy A Butterfield, Jonathan J Petrocelli, Ivan J Vechetti, Amy L Confides, Micah J Drummond, Esther E Dupont-Versteegden.

   BACKGROUND: Skeletal muscle (SkM) is a large, secretory organ that produces and releases myokines that can have autocrine, paracrine, and endocrine effects. Whether extracellular vesicles (EVs) also play a role in the SkM adaptive response and ability to communicate with other tissues is not well understood. The purpose of this study was to investigate EV biogenesis factors, marker expression, and localization across cell types in the skeletal muscle. We also aimed to investigate whether EV concentrations are altered by disuse atrophy.
METHODS: To identify the potential markers of SkM-derived EVs, EVs were isolated from rat serum using density gradient ultracentrifugation, followed by fluorescence correlation spectroscopy measurements or qPCR. Single-cell RNA sequencing (scRNA-seq) data from rat SkM were analyzed to assess the EV biogenesis factor expression, and cellular localization of tetraspanins was investigated by immunohistochemistry. Finally, to assess the effects of mechanical unloading on EV expression in vivo, EV concentrations were measured in the serum by nanoparticle tracking analysis in both a rat and human model of disuse.
RESULTS: In this study, we show that the widely used markers of SkM-derived EVs, α-sarcoglycan and miR-1, are undetectable in serum EVs. We also found that EV biogenesis factors, including the tetraspanins CD63, CD9, and CD81, are expressed by a variety of cell types in SkM. SkM sections showed very low detection of CD63, CD9, and CD81 in myofibers and instead accumulation within the interstitial space. Furthermore, although there were no differences in serum EV concentrations following hindlimb suspension in rats, serum EV concentrations were elevated in human subjects after bed rest.
CONCLUSIONS: Our findings provide insight into the distribution and localization of EVs in SkM and demonstrate the importance of methodological guidelines in SkM EV research.

Keywords:  Bed rest; Disuse atrophy; Extracellular vesicles; Hindlimb suspension; Skeletal muscle

DOI:  https://doi.org/10.1186/s13395-023-00315-1
J Gastroenterol Hepatol. 2023 Mar 08.

Skeletal muscle atrophy is exacerbated by steatotic and fibrotic liver-derived TNF-alpha in senescence-accelerated mice.

Yohei Shirakami, Junichi Kato, Toshihide Maeda, Takayasu Ideta, Kenji Imai, Hiroyasu Sakai, Makoto Shiraki, Masahito Shimizu.

   BACKGROUND AND AIM: Although liver diseases, including non-alcoholic steatohepatitis, are associated with skeletal muscle atrophy, the mechanism behind their association has not been fully elucidated. In this study, the effects of aging and non-alcoholic steatohepatitis on the skeletal muscle and the interaction between the liver and muscle were investigated using a diet-induced non-alcoholic steatohepatitis model in senescence-accelerated mice.
METHODS: A total of four groups of senescence-accelerated mice and the control mice were fed either a non-alcoholic steatohepatitis-inducing or control diet, and their livers and skeletal muscles were removed for examinations.
RESULTS: In the senescence-accelerated/non-alcoholic steatohepatitis group, serum level of alanine aminotransferase was markedly elevated and histopathology of non-alcoholic steatohepatitis was significant. Skeletal muscles were also markedly atrophied. The expression of the ubiquitin ligase Murf1 in the muscle was significantly increased with muscle atrophy, while that of Tnfa was not significantly different. In contrast, the hepatic Tnfa expression and serum TNF-α levels were significantly increased in the senescence-accelerated/non-alcoholic steatohepatitis group. These results suggest that liver-derived TNF-α might promote muscle atrophy associated with steatohepatitis and aging through Murf-1. The metabolomic analysis of skeletal muscle indicated higher spermidine and lower tryptophan levels in the steatohepatitis-diet group.
CONCLUSIONS: The findings of this study revealed an aspect of liver-muscle interaction, which might be important in developing treatments for sarcopenia associated with liver diseases.

Keywords:  NASH; TNF-alpha; sarcopenia; skeletal muscle; steatohepatitis

DOI:  https://doi.org/10.1111/jgh.16171
Int J Mol Sci. 2023 Feb 23. pii: 4402. [Epub ahead of print]24(5):

Discovery-Based Proteomics Identify Skeletal Muscle Mitochondrial Alterations as an Early Metabolic Defect in a Mouse Model of β-Thalassemia.

Patricia Reboucas, Carine Fillebeen, Amy Botta, Riley Cleverdon, Alexandra P Steele, Vincent Richard, René P Zahedi, Christoph H Borchers, Yan Burelle, Thomas J Hawke, Kostas Pantopoulos, Gary Sweeney.

  Although metabolic complications are common in thalassemia patients, there is still an unmet need to better understand underlying mechanisms. We used unbiased global proteomics to reveal molecular differences between the th3/+ mouse model of thalassemia and wild-type control animals focusing on skeletal muscles at 8 weeks of age. Our data point toward a significantly impaired mitochondrial oxidative phosphorylation. Furthermore, we observed a shift from oxidative fibre types toward more glycolytic fibre types in these animals, which was further supported by larger fibre-type cross-sectional areas in the more oxidative type fibres (type I/type IIa/type IIax hybrid). We also observed an increase in capillary density in th3/+ mice, indicative of a compensatory response. Western blotting for mitochondrial oxidative phosphorylation complex proteins and PCR analysis of mitochondrial genes indicated reduced mitochondrial content in the skeletal muscle but not the hearts of th3/+ mice. The phenotypic manifestation of these alterations was a small but significant reduction in glucose handling capacity. Overall, this study identified many important alterations in the proteome of th3/+ mice, amongst which mitochondrial defects leading to skeletal muscle remodelling and metabolic dysfunction were paramount.

Keywords:  iron; mitochondria; proteomics; skeletal muscle; thalassemia

DOI:  https://doi.org/10.3390/ijms24054402
Int J Mol Sci. 2023 Mar 03. pii: 4944. [Epub ahead of print]24(5):

Human Neuromuscular Junction on a Chip: Impact of Amniotic Fluid Stem Cell Extracellular Vesicles on Muscle Atrophy and NMJ Integrity.

Martina Gatti, Katarina Stoklund Dittlau, Francesca Beretti, Laura Yedigaryan, Manuela Zavatti, Pietro Cortelli, Carla Palumbo, Emma Bertucci, Ludo Van Den Bosch, Maurilio Sampaolesi, Tullia Maraldi.

  Neuromuscular junctions (NMJs) are specialized synapses, crucial for the communication between spinal motor neurons (MNs) and skeletal muscle. NMJs become vulnerable in degenerative diseases, such as muscle atrophy, where the crosstalk between the different cell populations fails, and the regenerative ability of the entire tissue is hampered. How skeletal muscle sends retrograde signals to MNs through NMJs represents an intriguing field of research, and the role of oxidative stress and its sources remain poorly understood. Recent works demonstrate the myofiber regeneration potential of stem cells, including amniotic fluid stem cells (AFSC), and secreted extracellular vesicles (EVs) as cell-free therapy. To study NMJ perturbations during muscle atrophy, we generated an MN/myotube co-culture system through XonaTM microfluidic devices, and muscle atrophy was induced in vitro by Dexamethasone (Dexa). After atrophy induction, we treated muscle and MN compartments with AFSC-derived EVs (AFSC-EVs) to investigate their regenerative and anti-oxidative potential in counteracting NMJ alterations. We found that the presence of EVs reduced morphological and functional in vitro defects induced by Dexa. Interestingly, oxidative stress, occurring in atrophic myotubes and thus involving neurites as well, was prevented by EV treatment. Here, we provided and validated a fluidically isolated system represented by microfluidic devices for studying human MN and myotube interactions in healthy and Dexa-induced atrophic conditions-allowing the isolation of subcellular compartments for region-specific analyses-and demonstrated the efficacy of AFSC-EVs in counteracting NMJ perturbations.

Keywords:  amniotic fluid stem cells; extracellular vesicles; muscle atrophy; neuromuscular junction; oxidative stress

DOI:  https://doi.org/10.3390/ijms24054944
Int J Mol Sci. 2023 Feb 21. pii: 4306. [Epub ahead of print]24(5):

Histone Deacetylases: Molecular Mechanisms and Therapeutic Implications for Muscular Dystrophies.

Martina Sandonà, Giorgia Cavioli, Alessandra Renzini, Alessia Cedola, Giuseppe Gigli, Dario Coletti, Timothy A McKinsey, Viviana Moresi, Valentina Saccone.

  Histone deacetylases (HDACs) are enzymes that regulate the deacetylation of numerous histone and non-histone proteins, thereby affecting a wide range of cellular processes. Deregulation of HDAC expression or activity is often associated with several pathologies, suggesting potential for targeting these enzymes for therapeutic purposes. For example, HDAC expression and activity are higher in dystrophic skeletal muscles. General pharmacological blockade of HDACs, by means of pan-HDAC inhibitors (HDACi), ameliorates both muscle histological abnormalities and function in preclinical studies. A phase II clinical trial of the pan-HDACi givinostat revealed partial histological improvement and functional recovery of Duchenne Muscular Dystrophy (DMD) muscles; results of an ongoing phase III clinical trial that is assessing the long-term safety and efficacy of givinostat in DMD patients are pending. Here we review the current knowledge about the HDAC functions in distinct cell types in skeletal muscle, identified by genetic and -omic approaches. We describe the signaling events that are affected by HDACs and contribute to muscular dystrophy pathogenesis by altering muscle regeneration and/or repair processes. Reviewing recent insights into HDAC cellular functions in dystrophic muscles provides new perspectives for the development of more effective therapeutic approaches based on drugs that target these critical enzymes.

Keywords:  Duchenne Muscular Dystrophy; clinical trials; histone deacetylase; muscular dystrophies

DOI:  https://doi.org/10.3390/ijms24054306
Skelet Muscle. 2023 Mar 07. 13(1): 5

The double homeodomain protein DUX4c is associated with regenerating muscle fibers and RNA-binding proteins.

Clothilde Claus, Moriya Slavin, Eugénie Ansseau, Céline Lancelot, Karimatou Bah, Saskia Lassche, Manon Fiévet, Anna Greco, Sara Tomaiuolo, Alexandra Tassin, Virginie Dudome, Benno Kusters, Anne-Emilie Declèves, Dalila Laoudj-Chenivesse, Baziel G M van Engelen, Denis Nonclercq, Alexandra Belayew, Nir Kalisman, Frédérique Coppée.

   BACKGROUND: We have previously demonstrated that double homeobox 4 centromeric (DUX4C) encoded for a functional DUX4c protein upregulated in dystrophic skeletal muscles. Based on gain- and loss-of-function studies we have proposed DUX4c involvement in muscle regeneration. Here, we provide further evidence for such a role in skeletal muscles from patients affected with facioscapulohumeral muscular dystrophy (FSHD).
METHODS: DUX4c was studied at RNA and protein levels in FSHD muscle cell cultures and biopsies. Its protein partners were co-purified and identified by mass spectrometry. Endogenous DUX4c was detected in FSHD muscle sections with either its partners or regeneration markers using co-immunofluorescence or in situ proximity ligation assay.
RESULTS: We identified new alternatively spliced DUX4C transcripts and confirmed DUX4c immunodetection in rare FSHD muscle cells in primary culture. DUX4c was detected in nuclei, cytoplasm or at cell-cell contacts between myocytes and interacted sporadically with specific RNA-binding proteins involved, a.o., in muscle differentiation, repair, and mass maintenance. In FSHD muscle sections, DUX4c was found in fibers with unusual shape or central/delocalized nuclei (a regeneration feature) staining for developmental myosin heavy chain, MYOD or presenting intense desmin labeling. Some couples of myocytes/fibers locally exhibited peripheral DUX4c-positive areas that were very close to each other, but in distinct cells. MYOD or intense desmin staining at these locations suggested an imminent muscle cell fusion. We further demonstrated DUX4c interaction with its major protein partner, C1qBP, inside myocytes/myofibers that presented features of regeneration. On adjacent muscle sections, we could unexpectedly detect DUX4 (the FSHD causal protein) and its interaction with C1qBP in fusing myocytes/fibers.
CONCLUSIONS: DUX4c upregulation in FSHD muscles suggests it contributes not only to the pathology but also, based on its protein partners and specific markers, to attempts at muscle regeneration. The presence of both DUX4 and DUX4c in regenerating FSHD muscle cells suggests DUX4 could compete with normal DUX4c functions, thus explaining why skeletal muscle is particularly sensitive to DUX4 toxicity. Caution should be exerted with therapeutic agents aiming for DUX4 suppression because they might also repress the highly similar DUX4c and interfere with its physiological role.

Keywords:  DUX genes; Differentiation; FUS; Fibrosis; HA-binding protein C1qBP; M1/M2 macrophages; Muscle regeneration; RNA-binding interactors; SFPQ; Testis

DOI:  https://doi.org/10.1186/s13395-022-00310-y
Dev Cell. 2023 Mar 03. pii: S1534-5807(23)00051-5. [Epub ahead of print]

Activation of β-catenin in mesenchymal progenitors leads to muscle mass loss.

Nasim Kajabadi, Marcela Low, Erik Jacques, Heta Lad, Lin Wei Tung, Farshad Babaeijandaghi, Daniel Gamu, Diego Zelada, Chi Kin Wong, Chihkai Chang, Lin Yi, Michael N Wosczyna, Thomas A Rando, Juan Pablo Henríquez, William T Gibson, Penney M Gilbert, Fabio M V Rossi.

  Loss of muscle mass is a common manifestation of chronic disease. We find the canonical Wnt pathway to be activated in mesenchymal progenitors (MPs) from cancer-induced cachectic mouse muscle. Next, we induce β-catenin transcriptional activity in murine MPs. As a result, we observe expansion of MPs in the absence of tissue damage, as well as rapid loss of muscle mass. Because MPs are present throughout the organism, we use spatially restricted CRE activation and show that the induction of tissue-resident MP activation is sufficient to induce muscle atrophy. We further identify increased expression of stromal NOGGIN and ACTIVIN-A as key drivers of atrophic processes in myofibers, and we verify their expression by MPs in cachectic muscle. Finally, we show that blocking ACTIVIN-A rescues the mass loss phenotype triggered by β-catenin activation in MPs, confirming its key functional role and strengthening the rationale for targeting this pathway in chronic disease.

Keywords:  cancer-associated cachexia; canonical Wnt signaling; mesenchymal progenitors; muscle atrophy

DOI:  https://doi.org/10.1016/j.devcel.2023.02.009
Am J Physiol Cell Physiol. 2023 Mar 07.

Mimicking exercise in vitro - effects of myotube contractions and mechanical stretch on omics.

Juulia H Lautaoja, Daniel C Turner, Adam P Sharples, Riikka Kivelä, Satu Pekkala, Juha J Hulmi, Laura Ylä-Outinen.

  The number of studies using skeletal muscle (SkM) cell culture models to study exercise in vitro are rapidly expanding. Progressively, more comprehensive analysis methods, such as different omics approaches including transcriptomics, proteomics and metabolomics have been used to examine the intra- and extracellular molecular responses to exercise mimicking stimuli in cultured myotubes. Among other techniques, exercise-like electrical pulse stimulation (EL-EPS) and mechanical stretch of SkM cells are the two most commonly used methods to mimic exercise in vitro. In this mini-review we focus on these two approaches and their effects on the omics of myotubes and/or cell culture media. Furthermore, besides traditional two-dimensional (2D) methods, the use of three-dimensional (3D) SkM approaches are increasing in the field of in vitro exercise mimicry. Our aim with this mini-review is to provide the reader with an up-to-date overview of the 2D and 3D models and the use of omics approaches to study the molecular response to exercise in vitro.

Keywords:  electrical pulse stimulation; metabolomics; proteomics; skeletal muscle; transcriptomics

DOI:  https://doi.org/10.1152/ajpcell.00586.2022
Mol Ther Nucleic Acids. 2023 Mar 14. 31 527-540

Identification of a novel small-molecule inhibitor of miR-29b attenuates muscle atrophy.

Qi Liu, Weilin Yuan, Yuwei Yan, Bing Jin, Mengke You, Tianqi Liu, Mingchun Gao, Jin Li, Priyanka Gokulnath, Gururaja Vulugundam, Guoping Li, Bin Xu, Junjie Xiao.

  Muscle atrophy is debilitating and can be induced by several stressors. Unfortunately, there are no effective pharmacological treatment until now. MicroRNA (miR)-29b is an important target that we identified to be commonly involved in multiple types of muscle atrophy. Although sequence-specific inhibition of miR-29b has been developed, in this study, we report a novel small-molecule miR-29b inhibitor that targets miR-29b hairpin precursor (pre-miR-29b) (Targapremir-29b-066 [TGP-29b-066]) considering both its three-dimensional structure and the thermodynamics of interaction between pre-miR-29b and the small molecule. This novel small-molecule inhibitor has been demonstrated to attenuate muscle atrophy induced by angiotensin II (Ang II), dexamethasone (Dex), and tumor necrosis factor α (TNF-α) in C2C12 myotubes, as evidenced by increase in the diameter of myotube and decrease in the expression of Atrogin-1 and MuRF-1. Moreover, it can also attenuate Ang II-induced muscle atrophy in mice, as evidenced by a similar increase in the diameter of myotube, reduced Atrogin-1 and MuRF-1 expression, AKT-FOXO3A-mTOR signaling activation, and decreased apoptosis and autophagy. In summary, we experimentally identified and demonstrated a novel small-molecule inhibitor of miR-29b that could act as a potential therapeutic agent for muscle atrophy.

Keywords:  Ang II; C2C12 myotubes; Dex; MT: Non-coding RNAs; TNF-α; miR-29b; muscle atrophy; small-molecule inhibitor

DOI:  https://doi.org/10.1016/j.omtn.2023.02.003
J Cachexia Sarcopenia Muscle. 2023 Mar 07.

Interleukin-6 promotes skeletal muscle catabolism by activating tryptophan-indoleamine 2,3-dioxygenase 1-kynurenine pathway during intra-abdominal sepsis.

Tingbin Xie, Tengfei Lv, Tenghui Zhang, Dengyu Feng, Feng Zhu, Yi Xu, Liang Zhang, Lili Gu, Zhen Guo, Chao Ding, Jianfeng Gong.

   BACKGROUND: Inflammatory cytokine interleukin-6 (IL-6) plays a pivotal role in skeletal muscle degradation after intra-abdominal sepsis (IAS), with mechanism remained to be elucidated. Indoleamine 2,3-dioxygenase 1 (IDO-1), a key enzyme in converting tryptophan into kynurenine, could be activated by IL-6, and kynurenine has been shown to be involved in muscle degradation. We hypothesized that IL-6 could promote muscle degradation via tryptophan-IDO-1-kynurenine pathway in IAS patients.
METHODS: Serum and rectus abdominis (RA) were obtained from IAS or non-IAS patients. Mouse model of IAS-induced muscle wasting was generated by caecal ligation and puncture (CLP) and lipopolysaccharide (LPS) injection. IL-6 signalling was blocked by anti-mouse IL-6 antibody (IL-6-AB), and the IDO-1 pathway was blocked by navoximod. To elucidate the role of kynurenine in muscle mass and physiology, kynurenine was administered to IAS mice treated with IL-6-AB.
RESULTS: Compared to non-IAS patients, kynurenine levels in serum (+2.30-fold vs. non-IAS, P < 0.001) and RA (+3.11-fold vs. non-IAS, P < 0.001) were elevated, whereas tryptophan levels in serum (-53.65% vs. non-IAS, P < 0.01) and RA (-61.39% vs. non-IAS, P < 0.01) were decreased. Serum IL-6 level of the IAS group was significantly higher compared to non-IAS patients (+5.82-fold vs. non-IAS, P = 0.01), and muscle cross-sectional area (MCSA) was markedly reduced compared to non-IAS patients (-27.73% vs. non-IAS, P < 0.01). In animal experiments, IDO-1 expression was up-regulated in the small intestine, colon and blood for CLP or LPS-treated mice, and there was correlation (R2 = 0.66, P < 0.01) between serum and muscle kynurenine concentrations. Navoximod significantly mitigated IAS-induced skeletal muscle loss according to MCSA analysis (+22.94% vs. CLP, P < 0.05; +23.71% vs. LPS, P < 0.01) and increased the phosphorylated AKT (+2.15-fold vs. CLP, P < 0.01; +3.44-fold vs. LPS, P < 0.01) and myosin heavy chain (+3.64-fold vs. CLP, P < 0.01; +2.13-fold vs. LPS, P < 0.01) protein expression in myocytes. In the presence of anti-IL-6 antibody, a significantly decreased IDO-1 expression was observed in the small intestine, colon and blood in CLP or LPS mice (all P < 0.01), whereas the decrease of MCSA was alleviated (+37.43% vs. CLP + IgG, P < 0.001; +30.72% vs. LPS + IgG, P < 0.001). In contrast, additional supplementation of kynurenine decreased the MCSA in septic mice treated with IL-6-AB (both P < 0.01).
CONCLUSIONS: This study provided novel insights into the tryptophan-IDO-1-kynurenine-dependent mechanisms that underlie inflammatory cytokine-induced skeletal muscle catabolism during intra-abdominal sepsis.

Keywords:  indoleamine 2,3-dioxygenase 1; interleukin-6; intra-abdominal sepsis; muscle wasting; tryptophan

DOI:  https://doi.org/10.1002/jcsm.13193
Int J Mol Sci. 2023 Feb 28. pii: 4651. [Epub ahead of print]24(5):

Sex Differences in Inflammation and Muscle Wasting in Aging and Disease.

Chiara Della Peruta, Biliana Lozanoska-Ochser, Alessandra Renzini, Viviana Moresi, Carles Sanchez Riera, Marina Bouché, Dario Coletti.

  Only in recent years, thanks to a precision medicine-based approach, have treatments tailored to the sex of each patient emerged in clinical trials. In this regard, both striated muscle tissues present significant differences between the two sexes, which may have important consequences for diagnosis and therapy in aging and chronic illness. In fact, preservation of muscle mass in disease conditions correlates with survival; however, sex should be considered when protocols for the maintenance of muscle mass are designed. One obvious difference is that men have more muscle than women. Moreover, the two sexes differ in inflammation parameters, particularly in response to infection and disease. Therefore, unsurprisingly, men and women respond differently to therapies. In this review, we present an up-to-date overview on what is known about sex differences in skeletal muscle physiology and disfunction, such as disuse atrophy, age-related sarcopenia, and cachexia. In addition, we summarize sex differences in inflammation which may underly the aforementioned conditions because pro-inflammatory cytokines deeply affect muscle homeostasis. The comparison of these three conditions and their sex-related bases is interesting because different forms of muscle atrophy share common mechanisms; for instance, those responsible for protein dismantling are similar although differing in terms of kinetics, severity, and regulatory mechanisms. In pre-clinical research, exploring sexual dimorphism in disease conditions could highlight new efficacious treatments or recommend implementation of an existing one. Any protective factors discovered in one sex could be exploited to achieve lower morbidity, reduce the severity of the disease, or avoid mortality in the opposite sex. Thus, the understanding of sex-dependent responses to different forms of muscle atrophy and inflammation is of pivotal importance to design innovative, tailored, and efficient interventions.

Keywords:  aging; bed rest; cachexia; inflammation; microgravity; sarcopenia; sex differences

DOI:  https://doi.org/10.3390/ijms24054651
Cell Metab. 2023 Mar 07. pii: S1550-4131(23)00045-1. [Epub ahead of print]35(3): 379-381

Rejuvenating muscle stem cells with the glutathione system.

Laura Forcina, Antonio Musarò.

Aging results from the combination of complex processes still largely undefined. In this issue, Benjamin et al. use multiomic analysis to reveal a causative role of altered glutathione (GSH) synthesis and metabolism in age-dependent muscle stem cell (MuSC) dysfunction, casting light on novel mechanisms regulating stem cell function and on therapeutic approaches to improve defective regeneration in the aged muscle.

DOI: https://doi.org/10.1016/j.cmet.2023.02.009
Front Endocrinol (Lausanne). 2023 ;14 987208

Enhancing the metabolic benefits of exercise: Is timing the key?

Samuel Bennett, Shogo Sato.

  Physical activity represents a potent, non-pharmacological intervention delaying the onset of over 40 chronic metabolic and cardiovascular diseases, including type 2 diabetes, coronary heart disease, and reducing all-cause mortality. Acute exercise improves glucose homeostasis, with regular participation in physical activity promoting long-term improvements in insulin sensitivity spanning healthy and disease population groups. At the skeletal muscle level, exercise promotes significant cellular reprogramming of metabolic pathways through the activation of mechano- and metabolic sensors, which coordinate downstream activation of transcription factors, augmenting target gene transcription associated with substrate metabolism and mitochondrial biogenesis. It is well established that frequency, intensity, duration, and modality of exercise play a critical role in the type and magnitude of adaptation; albeit, exercise is increasingly considered a vital lifestyle factor with a critical role in the entrainment of the biological clock. Recent research efforts revealed the time-of-day-dependent impact of exercise on metabolism, adaptation, performance, and subsequent health outcomes. The synchrony between external environmental and behavioural cues with internal molecular circadian clock activity is a crucial regulator of circadian homeostasis in physiology and metabolism, defining distinct metabolic and physiological responses to exercise unique to the time of day. Optimising exercise outcomes following when to exercise would be essential to establishing personalised exercise medicine depending on exercise objectives linked to disease states. We aim to provide an overview of the bimodal impact of exercise timing, i.e. the role of exercise as a time-giver (zeitgeber) to improve circadian clock alignment and the underpinning clock control of metabolism and the temporal impact of exercise timing on the metabolic and functional outcomes associated with exercise. We will propose research opportunities that may further our understanding of the metabolic rewiring induced by specific exercise timing.

Keywords:  cardiometabolic health; circadian biology; exercise; high-throughput omics data; metabolic diseases; metabolism; physical activity; time-of-exercise

DOI:  https://doi.org/10.3389/fendo.2023.987208
J Cachexia Sarcopenia Muscle. 2023 Mar 07.

Single-leg disuse decreases skeletal muscle strength, size, and power in uninjured adults: A systematic review and meta-analysis.

Nicholas Preobrazenski, Joel Seigel, Sandra Halliday, Ian Janssen, Chris McGlory.

  We aimed to quantify declines from baseline in lower limb skeletal muscle size and strength of uninjured adults following single-leg disuse. We searched EMBASE, Medline, CINAHL, and CCRCT up to 30 January 2022. Studies were included in the systematic review if they (1) recruited uninjured participants; (2) were an original experimental study; (3) employed a single-leg disuse model; and (4) reported muscle strength, size, or power data following a period of single-leg disuse for at least one group without a countermeasure. Studies were excluded if they (1) did not meet all inclusion criteria; (2) were not in English; (3) reported previously published muscle strength, size, or power data; or (4) could not be sourced from two different libraries, repeated online searches, and the authors. We used the Cochrane Risk of Bias Assessment Tool to assess risk of bias. We then performed random-effects meta-analyses on studies reporting measures of leg extension strength and extensor size. Our search revealed 6548 studies, and 86 were included in our systematic review. Data from 35 and 20 studies were then included in the meta-analyses for measures of leg extensor strength and size, respectively (40 different studies). No meta-analysis for muscle power was performed due to insufficient homogenous data. Effect sizes (Hedges' gav ) with 95% confidence intervals for leg extensor strength were all durations = -0.80 [-0.92, -0.68] (n = 429 participants; n = 68 aged 40 years or older; n ≥ 78 females); ≤7 days of disuse = -0.57 [-0.75, -0.40] (n = 151); >7 days and ≤14 days = -0.93 [-1.12, -0.74] (n = 206); and >14 days = -0.95 [-1.20, -0.70] (n = 72). Effect sizes for measures of leg extensor size were all durations = -0.41 [-0.51, -0.31] (n = 233; n = 32 aged 40 years or older; n ≥ 42 females); ≤7 days = -0.26 [-0.36, -0.16] (n = 84); >7 days and ≤14 days = -0.49 [-0.67, -0.30] (n = 102); and >14 days = -0.52 [-0.74, -0.30] (n = 47). Decreases in leg extensor strength (cast: -0.94 [-1.30, -0.59] (n = 73); brace: -0.90 [-1.18, -0.63] (n = 106)) and size (cast: -0.61[-0.87, -0.35] (n = 41); brace: (-0.48 [-1.04, 0.07] (n = 41)) following 14 days of disuse did not differ for cast and brace disuse models. Single-leg disuse in adults resulted in a decline in leg extensor strength and size that reached a nadir beyond 14 days. Bracing and casting led to similar declines in leg extensor strength and size following 14 days of disuse. Studies including females and males and adults over 40 years of age are lacking.

Keywords:  Atrophy; Immobilization; Muscle disuse; Single-leg disuse; Skeletal muscle; Unloading

DOI:  https://doi.org/10.1002/jcsm.13201
Neuromuscul Disord. 2023 Feb 13. pii: S0960-8966(23)00023-8. [Epub ahead of print]33(4): 302-308

Urine titin as a novel biomarker for Duchenne muscular dystrophy.

Misawa Niki Ishii, Masato Nakashima, Hidenori Kamiguchi, Neta Zach, Ryosuke Kuboki, Rina Baba, Takeshi Hirakawa, Kazunori Suzuki, Maria Quinton.

  Duchenne muscular dystrophy (DMD) is the most severe form of muscular dystrophy that is caused by lack of dystrophin, a critical structural protein in skeletal muscle. DMD treatments, and quantitative biomarkers to assess the efficacy of potential treatments, are urgently needed. Previous evidence has shown that titin, a muscle cell protein, is increased in the urine of patients with DMD, suggesting its usefulness as a DMD biomarker. Here, we demonstrated that the elevated titin in urine is directly associated with the lack of dystrophin and urine titin responses to drug treatment. We performed a drug intervention study using mdx mice, a DMD mouse model. We showed that mdx mice, which lack dystrophin due to a mutation in exon 23 of the Dmd gene, have elevated urine titin. Treatment with an exon skipper that targets exon 23 rescued muscle dystrophin level and dramatically decreased urine titin in mdx mice and correlates with dystrophin expression. We also demonstrated that titin levels were significantly increased in the urine of patients with DMD. This suggests that elevated urine titin level might be a hallmark of DMD and a useful pharmacodynamic marker for therapies designed to restore dystrophin levels.

Keywords:  Duchenne muscular dystrophy; Exon skipper; Mdx mice; Titin; Urine biomarker

DOI:  https://doi.org/10.1016/j.nmd.2023.02.003
Cells. 2023 Feb 22. pii: 691. [Epub ahead of print]12(5):

Role of SIRT3 in Microgravity Response: A New Player in Muscle Tissue Recovery.

Michele Aventaggiato, Federica Barreca, Laura Vitiello, Simone Vespa, Sergio Valente, Dante Rotili, Antonello Mai, Lavinia Vittoria Lotti, Luigi Sansone, Matteo A Russo, Mariano Bizzarri, Elisabetta Ferretti, Marco Tafani.

  Life on Earth has evolved in the presence of a gravity constraint. Any change in the value of such a constraint has important physiological effects. Gravity reduction (microgravity) alters the performance of muscle, bone and, immune systems among others. Therefore, countermeasures to limit such deleterious effects of microgravity are needed considering future Lunar and Martian missions. Our study aims to demonstrate that the activation of mitochondrial Sirtuin 3 (SIRT3) can be exploited to reduce muscle damage and to maintain muscle differentiation following microgravity exposure. To this effect, we used a RCCS machine to simulate microgravity on ground on a muscle and cardiac cell line. During microgravity, cells were treated with a newly synthesized SIRT3 activator, called MC2791 and vitality, differentiation, ROS and, autophagy/mitophagy were measured. Our results indicate that SIRT3 activation reduces microgravity-induced cell death while maintaining the expression of muscle cell differentiation markers. In conclusion, our study demonstrates that SIRT3 activation could represent a targeted molecular strategy to reduce muscle tissue damage caused by microgravity.

Keywords:  ROS; SIRT3; mitochondria; molecular rehabilitation; muscle tissue; simulated microgravity; sirtuins

DOI:  https://doi.org/10.3390/cells12050691
Biogerontology. 2023 Mar 06.

An AMP Kinase-pathway dependent integrated stress response regulates ageing and longevity.

H G Keizer, R Brands, W Seinen.

  The purpose of this article is to investigate the role of the AMP-kinase pathway (AMPK pathway) in the induction of a concomitant set of health benefits by exercise, numerous drugs, and health ingredients, all of which are adversely affected by ageing. Despite the AMPK pathway being frequently mentioned in relation to both these health effects and ageing, it appears challenging to understand how the activation of a single biochemical pathway by various treatments can produce such a diverse range of concurrent health benefits, involving so many organs. We discovered that the AMPK pathway functions as an integrated stress response system because of the presence of a feedback loop in it. This evolutionary conserved stress response system detects changes in AMP/ATP and NAD/NADH ratios, as well as the presence of potential toxins, and responds by activating a common protective transcriptional response that protects against aging and promotes longevity. The inactivation of the AMPK pathway with age most likely explains why ageing has a negative impact on the above-mentioned set of health benefits. We conclude that the presence of a feedback loop in the AMP-kinase pathway positions this pathway as an AMPK-ISR (AMP Kinase-dependent integrated stress response) system that responds to almost any type of (moderate) environmental stress by inducing various age-related health benefits and longevity.

Keywords:  AMPK; Ageing; Biochemistry; Feedback-loop; Longevity; Pathway

DOI:  https://doi.org/10.1007/s10522-023-10024-3
iScience. 2023 Mar 17. 26(3): 106074

Experimental evidence and clinical implications of Warburg effect in the skeletal muscle of Fabry disease.

Jessica Gambardella, Antonella Fiordelisi, Federica Andrea Cerasuolo, Antonietta Buonaiuto, Roberta Avvisato, Alessandro Viti, Eduardo Sommella, Fabrizio Merciai, Emanuela Salviati, Pietro Campiglia, Valeria D'Argenio, Silvia Parisi, Antonio Bianco, Letizia Spinelli, Eugenio Di Vaia, Alberto Cuocolo, Antonio Pisani, Eleonora Riccio, Teodolinda Di Risi, Michele Ciccarelli, Gaetano Santulli, Daniela Sorriento, Guido Iaccarino.

  Skeletal muscle (SM) pain and fatigue are common in Fabry disease (FD). Here, we undertook the investigation of the energetic mechanisms related to FD-SM phenotype. A reduced tolerance to aerobic activity and lactate accumulation occurred in FD-mice and patients. Accordingly, in murine FD-SM we detected an increase in fast/glycolytic fibers, mirrored by glycolysis upregulation. In FD-patients, we confirmed a high glycolytic rate and the underutilization of lipids as fuel. In the quest for a tentative mechanism, we found HIF-1 upregulated in FD-mice and patients. This finding goes with miR-17 upregulation that is responsible for metabolic remodeling and HIF-1 accumulation. Accordingly, miR-17 antagomir inhibited HIF-1 accumulation, reverting the metabolic-remodeling in FD-cells. Our findings unveil a Warburg effect in FD, an anaerobic-glycolytic switch under normoxia induced by miR-17-mediated HIF-1 upregulation. Exercise-intolerance, blood-lactate increase, and the underlying miR-17/HIF-1 pathway may become useful therapeutic targets and diagnostic/monitoring tools in FD.

Keywords:  Cell biology; Cellular physiology; Health sciences; Pathophysiology

DOI:  https://doi.org/10.1016/j.isci.2023.106074