bims-moremu 2023-12-10 papers

bims-moremu

Biomed News

on Molecular regulators of muscle mass

Issue of 2023‒12‒10
thirty-one papers selected by
Anna Vainshtein, Craft Science Inc.

Ubiquitin-proteasome pathway in skeletal muscle atrophy.
The unique function of Runx1 in skeletal muscle differentiation and regeneration is mediated by an ETS interaction domain.
Exertional heat stroke causes long-term skeletal muscle epigenetic reprogramming, altered gene expression and impaired satellite cell function in mice.
Interaction of the C2C12 myotube contractions and glucose availability on transcriptome and extracellular vesicle microRNAs.
Contraction intensity affects NIRS-derived skeletal muscle oxidative capacity but not its relationships to mitochondrial protein content or aerobic fitness.
The YAP1/TAZ-TEAD transcriptional network regulates gene expression at neuromuscular junctions in skeletal muscle fibers.
Pulsed ultrasound promotes secretion of anti-inflammatory extracellular vesicles from skeletal myotubes via elevation of intracellular calcium level.
Exercise training modifies skeletal muscle clock gene expression but not 24-hour rhythmicity in substrate metabolism of men with insulin resistance.
Senotherapeutic drug treatment ameliorates chemotherapy-induced cachexia.
Protocol for low-input proteomic analysis of in situ fixed adult murine muscle stem cells.
FK506 bypasses the effect of erythroferrone in cancer cachexia skeletal muscle atrophy.
Muscle cofilin alters neuromuscular junction postsynaptic development to strengthen functional neurotransmission.
Lysine methylation signaling in skeletal muscle biology: from myogenesis to clinical insights.
Current limitations and future opportunities of tracer studies of muscle ageing.
Skeletal muscle mitochondria demonstrate similar respiration per cristae surface area independent of training status and sex in healthy humans.
LPS-Induced Modifications in Macrophage Transcript and Secretion Profiles Are Linked to Muscle Wasting and Glucose Intolerance.
P2Y1 and P2Y2 receptors differ in their role in the regulation of signaling pathways during unloading-induced rat soleus muscle atrophy.
CRIPTO-based micro-heterogeneity of mouse muscle satellite cells enables adaptive response to regenerative microenvironment.
Exercise intolerance in post-COVID syndrome cannot only be due to skeletal muscle impairment.
Translational mobility medicine and ugo carraro: a life of significant scientific contributions reviewed in celebration.
Metabolic Pathways for Removing Reactive Aldehydes are Diminished in Atrophic Muscle During Heart Failure.
The contribution of mitochondria to age-related skeletal muscle wasting: A sex-specific perspective.
A causative role for periarticular skeletal muscle weakness in the progression of joint damage and pain in OA.
The impact of 60 days of -6° head down tilt bed rest on mitochondrial content, respiration and regulators of mitochondrial dynamics.
Replenishing NAD+ content reduces aspects of striated muscle disease in a dog model of Duchenne muscular dystrophy.
Antioxidant effects of LEDT in dystrophic muscle cells: involvement of PGC-1α and UCP-3 pathways.
Potential regulatory role of PGC-1α within the skeletal muscle during metabolic adaptations in response to high-fat diet feeding in animal models.
Gene therapy for primary myopathies: literature review and prospects.
Exercise intolerance with ageing: Major role for vascular dysfunction?
A low-cost 2D sarcomere model to demonstrate titin related mechanisms for force production.
Resveratrol directly suppresses proteolysis possibly via PKA/CREB signaling in denervated rat skeletal muscle.

Front Physiol. 2023 ;14 1289537

Ubiquitin-proteasome pathway in skeletal muscle atrophy.

XiangSheng Pang, Peng Zhang, XiaoPing Chen, WenMing Liu.

  Skeletal muscles underpin myriad human activities, maintaining an intricate balance between protein synthesis and degradation crucial to muscle mass preservation. Historically, disruptions in this balance-where degradation overshadows synthesis-have marked the onset of muscle atrophy, a condition diminishing life quality and, in grave instances, imperiling life itself. While multiple protein degradation pathways exist-including the autophagy-lysosome, calcium-dependent calpain, and cysteine aspartate protease systems-the ubiquitin-proteasome pathway emerges as an especially cardinal avenue for intracellular protein degradation, wielding pronounced influence over the muscle atrophy trajectory. This paper ventures a panoramic view of predominant muscle atrophy types, accentuating the ubiquitin-proteasome pathway's role therein. Furthermore, by drawing from recent scholarly advancements, we draw associations between the ubiquitin-proteasome pathway and specific pathological conditions linked to muscle atrophy. Our exploration seeks to shed light on the ubiquitin-proteasome pathway's significance in skeletal muscle dynamics, aiming to pave the way for innovative therapeutic strategies against muscle atrophy and affiliated muscle disorders.

Keywords:  cachexia; muscle disuse; sarcopenia; skeletal muscle atrophy; ubiquitin-proteasom

DOI:  https://doi.org/10.3389/fphys.2023.1289537
bioRxiv. 2023 Nov 21. pii: 2023.11.21.568117. [Epub ahead of print]

The unique function of Runx1 in skeletal muscle differentiation and regeneration is mediated by an ETS interaction domain.

Meng Yu, Konrad Thorner, Sreeja Parameswaran, Wei Wei, Chuyue Yu, Xinhua Lin, Raphael Kopan, Matthew R Hass.

The conserved Runt-related (RUNX) transcription factor family are well-known master regulators of developmental and regenerative processes. Runx1 and Runx2 are both expressed in satellite cells (SC) and skeletal myotubes. Conditional deletion of Runx1 in adult SC negatively impacted self-renewal and impaired skeletal muscle maintenance. Runx1- deficient SC retain Runx2 expression but cannot support muscle regeneration in response to injury. To determine the unique molecular functions of Runx1 that cannot be compensated by Runx2 we deleted Runx1 in C2C12 that retain Runx2 expression and established that myoblasts differentiation was blocked in vitro due in part to ectopic expression of Mef2c, a target repressed by Runx1 . Structure-function analysis demonstrated that the Ets-interacting MID/EID region of Runx1, absent from Runx2, is critical to regulating myoblasts proliferation, differentiation, and fusion. Analysis of in-house and published ChIP-seq datasets from Runx1 (T-cells, muscle) versus Runx2 (preosteoblasts) dependent tissue identified enrichment for a Ets:Runx composite site in Runx1 -dependent tissues. Comparing ATACseq datasets from WT and Runx1KO C2C12 cells showed that the Ets:Runx composite motif was enriched in peaks open exclusively in WT cells compared to peaks unique to Runx1KO cells. Thus, engagement of a set of targets by the RUNX1/ETS complex define the non-redundant functions of Runx1 .

DOI: https://doi.org/10.1101/2023.11.21.568117
Am J Physiol Regul Integr Comp Physiol. 2023 Dec 04.

Exertional heat stroke causes long-term skeletal muscle epigenetic reprogramming, altered gene expression and impaired satellite cell function in mice.

Kevin O Murray, Jason O Brant, Ray A Spradlin, Trace Thome, Orlando Laitano, Terence E Ryan, Alberto Riva, Michael P Kladde, Thomas L Clanton.

  The effect of exertional heat stroke (EHS) exposure on skeletal muscles is incompletely understood. Muscle weakness is an early symptom of EHS but is not considered a major target of multiorgan injury. Previously, in a preclinical mouse model of EHS, we observed vulnerability of limb muscles to a second EHS exposure, suggesting hidden processes contributing to declines in muscle resilience. Here, we evaluated possible molecular origins of EHS-induced declines in muscle resilience. Female C57BL/6 mice [total n =56; 28/condition, i.e. EHS & exercise control (EXC)] underwent forced wheel running at 37.5°C/40% relative humidity until symptom limitation (unconsciousness). EXC mice exercised identically at room temperature (22-23°C). After one month of recovery, the following were assessed: (1) specific force and caffeine-induced contracture in soleus (SOL) and extensor digitorum longus (EDL) muscles; (2) transcriptome and DNA methylome responses in gastrocnemius (GAST); and (3) primary satellite cell function (proliferation and differentiation). There were no differences in specific force in either SOL or EDL from EXC. Only EHS solei exhibited lower caffeine sensitivity. EHS GAST exhibited higher RNA expression of genes encoding structural proteins of slow fibers, heat shock proteins, and myogenesis. A total of ~2500 differentially methylated regions of DNA that could potentially affect many cell functions were identified. Primary satellite cells exhibited suppressed proliferation rates but normal differentiation responses. Results demonstrate long-term changes in skeletal muscles one month after EHS that could contribute to declines in muscle resilience. Skeletal muscle may join other, more recognized tissues, considered vulnerable to long-term effects of EHS.

Keywords:  Calcium regulation; DNA methylation; Heat Illness; RNA-Seq; satellite cells

DOI:  https://doi.org/10.1152/ajpregu.00226.2023
Am J Physiol Cell Physiol. 2023 Dec 04.

Interaction of the C2C12 myotube contractions and glucose availability on transcriptome and extracellular vesicle microRNAs.

Juulia H Lautaoja-Kivipelto, Sira Karvinen, Tia-Marje Korhonen, Thomas M O'Connell, Marja Tiirola, Juha J Hulmi, Satu Pekkala.

  Exercise-like electrical pulse stimulation (EL-EPS) of myotubes mimics many key physiological changes induced by in vivo exercise. Besides enabling intracellular research, EL-EPS allows to study secreted factors, including muscle-specific microRNAs (myomiRs) carried in extracellular vesicles (EVs). These factors can participate in contraction-induced intercellular crosstalk and may mediate health benefits of exercise. However, the current knowledge of these responses, especially under variable nutritional conditions, is limited. We investigated the effects of EL-EPS on C2C12 myotube transcriptome in high and low glucose conditions by messenger RNA sequencing, while the expression of EV-carried miRNAs was analyzed by small RNA sequencing and RT-qPCR. We show that higher glucose availability augmented contraction-induced transcriptional changes and that the majority of the differentially expressed genes were upregulated. Furthermore, based on the pathway analyses, processes related to contractility and cytokine/inflammatory responses were upregulated. Additionally, we report that EL-EPS increased packing of miR-1-3p into EVs independent of glucose availability. Together our findings suggest that in vitro EL-EPS is a usable tool not only to study contraction-induced intracellular mechanisms, but also extracellular responses. The distinct transcriptional changes observed under variable nutritional conditions emphasize the importance of careful consideration of media composition in future exercise-mimicking studies.

Keywords:  electrical pulse stimulation; exercise; exerkine; skeletal muscle

DOI:  https://doi.org/10.1152/ajpcell.00401.2023
J Appl Physiol (1985). 2023 Dec 07.

Contraction intensity affects NIRS-derived skeletal muscle oxidative capacity but not its relationships to mitochondrial protein content or aerobic fitness.

Thomas R Tripp, Rachel M McDougall, Barnaby P Frankish, J Preston Wiley, Victor Lun, Martin J MacInnis.

  To further refine the near-infrared spectroscopy (NIRS)-derived measure of skeletal muscle oxidative capacity in humans, we sought to determine whether the exercise stimulus intensity affected the τ value and/or influenced the magnitude of correlations with in vitro measures of mitochondrial content and in vivo indices of exercise performance. Males (n=12) and females (n=12), matched for maximal aerobic fitness per fat-free mass, completed NIRS-derived skeletal muscle oxidative capacity tests for the vastus lateralis following repeated contractions at 40% (τ40) and 100% (τ100) of maximum voluntary contraction, underwent a skeletal muscle biopsy of the same muscle, and performed multiple intermittent isometric knee extension tests to task failure to establish critical torque (CT). τ100 (34.4±7.0 s) was greater than τ40 (24.2±6.9 s, p<0.001), but the values were correlated (r=0.688; p<0.001). τ40 (r=-0.692, p<0.001) and τ100 (r=-0.488, p=0.016) correlated with myosin heavy chain I percentage as well as several markers of mitochondrial content, including COX II protein content in whole muscle (τ40: r=-0.547, p=0.006; τ100: r=-0.466, p=0.022), type I pooled fibres (τ40: r=-0.547, p=0.006; τ100: r=-0.547, p=0.006), and type II pooled fibres (τ40: r=-0.516, p=0.009; τ100: r=-0.635, p=0.001). τ40 (r=-0.702, p<0.001), but not τ100 (r=-0.378, p=0.083) correlated with CT; however, neither value correlated with W' (τ40: r=0.071, p=0.753; τ100: r=0.054, p=0.812). Overall, the NIRS method of assessing skeletal muscle oxidative capacity is sensitive to the intensity of skeletal muscle contraction but maintains relationships to whole-body fitness, isolated limb critical intensity, and mitochondrial content regardless of intensity.

Keywords:  Critical torque; Fibre type; Near-infrared spectroscopy; Skeletal muscle; Western blotting

DOI:  https://doi.org/10.1152/japplphysiol.00342.2023
Nucleic Acids Res. 2023 Dec 04. pii: gkad1124. [Epub ahead of print]

The YAP1/TAZ-TEAD transcriptional network regulates gene expression at neuromuscular junctions in skeletal muscle fibers.

Lea Gessler, Danyil Huraskin, Yongzhi Jian, Nane Eiber, Zhaoyong Hu, Tomasz J Prószyński, Said Hashemolhosseini.

We examined YAP1/TAZ-TEAD signaling pathway activity at neuromuscular junctions (NMJs) of skeletal muscle fibers in adult mice. Our investigations revealed that muscle-specific knockouts of Yap1 or Taz, or both, demonstrate that these transcriptional coactivators regulate synaptic gene expression, the number and morphology of NMJs, and synaptic nuclei. Yap1 or Taz single knockout mice display reduced grip strength, fragmentation of NMJs, and accumulation of synaptic nuclei. Yap1/Taz muscle-specific double knockout mice do not survive beyond birth and possess almost no NMJs, the few detectable show severely impaired morphology and are organized in widened endplate bands; and with motor nerve endings being mostly absent. Myogenic gene expression is significantly impaired in the denervated muscles of knockout mice. We found that Tead1 and Tead4 transcription rates were increased upon incubation of control primary myotubes with AGRN-conditioned medium. Reduced AGRN-dependent acetylcholine receptor clustering and synaptic gene transcription were observed in differentiated primary Tead1 and Tead4 knockout myotubes. In silico analysis of previously reported genomic occupancy sites of TEAD1/4 revealed evolutionary conserved regions of potential TEAD binding motifs in key synaptic genes, the relevance of which was functionally confirmed by reporter assays. Collectively, our data suggest a role for YAP1/TAZ-TEAD1/TEAD4 signaling, particularly through TAZ-TEAD4, in regulating synaptic gene expression and acetylcholine receptor clustering at NMJs.

DOI: https://doi.org/10.1093/nar/gkad1124
Elife. 2023 Dec 06. pii: RP89512. [Epub ahead of print]12

Pulsed ultrasound promotes secretion of anti-inflammatory extracellular vesicles from skeletal myotubes via elevation of intracellular calcium level.

Atomu Yamaguchi, Noriaki Maeshige, Hikari Noguchi, Jiawei Yan, Xiaoqi Ma, Mikiko Uemura, Dongming Su, Hiroyo Kondo, Kristopher Sarosiek, Hidemi Fujino.

  The regulation of inflammatory responses is an important intervention in biological function and macrophages play an essential role during inflammation. Skeletal muscle is the largest organ in the human body and releases various factors which mediate anti-inflammatory/immune modulatory effects. Recently, the roles of extracellular vesicles (EVs) from a large variety of cells are reported. In particular, EVs released from skeletal muscle are attracting attention due to their therapeutic effects on dysfunctional organs and tissues. Also, ultrasound (US) promotes release of EVs from skeletal muscle. In this study, we investigated the output parameters and mechanisms of US-induced EV release enhancement and the potential of US-treated skeletal muscle-derived EVs in the regulation of inflammatory responses in macrophages. High-intensity US (3.0 W/cm2) irradiation increased EV secretion from C2C12 murine muscle cells via elevating intracellular Ca2+ level without negative effects. Moreover, US-induced EVs suppressed expression levels of pro-inflammatory factors in macrophages. miRNA sequencing analysis revealed that miR-206-3p and miR-378a-3p were especially abundant in skeletal myotube-derived EVs. In this study we demonstrated that high-intensity US promotes the release of anti-inflammatory EVs from skeletal myotubes and exert anti-inflammatory effects on macrophages.

Keywords:  extracellular vesicles; immunology; inflammation; macrophages; mouse; skeletal muscles; ultrasound

DOI:  https://doi.org/10.7554/eLife.89512
J Physiol. 2023 Dec 05.

Exercise training modifies skeletal muscle clock gene expression but not 24-hour rhythmicity in substrate metabolism of men with insulin resistance.

Jan-Frieder Harmsen, Marit Kotte, Ivo Habets, Frederieke Bosschee, Koen Frenken, Johanna A Jorgensen, Soraya de Kam, Esther Moonen-Kornips, Jochem Cissen, Daniel Doligkeit, Tineke van de Weijer, Edmundo Erazo-Tapia, Mijke Buitinga, Joris Hoeks, Patrick Schrauwen.

  Twenty-four hour rhythmicity in whole-body substrate metabolism, skeletal muscle clock gene expression and mitochondrial respiration is compromised upon insulin resistance. With exercise training known to ameliorate insulin resistance, our objective was to test if exercise training can reinforce diurnal variation in whole-body and skeletal muscle metabolism in men with insulin resistance. In a single-arm longitudinal design, 10 overweight and obese men with insulin resistance performed 12 weeks of high-intensity interval training recurrently in the afternoon (between 14.00 and 18.00 h) and were tested pre- and post-exercise training, while staying in a metabolic research unit for 2 days under free-living conditions with regular meals. On the second days, indirect calorimetry was performed at 08.00, 13.00, 18.00, 23.00 and 04.00 h, muscle biopsies were taken from the vastus lateralis at 08.30, 13.30 and 23.30 h, and blood was drawn at least bi-hourly over 24 h. Participants did not lose body weight over 12 weeks, but improved body composition and exercise capacity. Exercise training resulted in reduced 24-h plasma glucose levels, but did not modify free fatty acid and triacylglycerol levels. Diurnal variation of muscle clock gene expression was modified by exercise training with period genes showing an interaction (time × exercise) effect and reduced mRNA levels at 13.00 h. Exercise training increased mitochondrial respiration without inducing diurnal variation. Twenty-four-hour substrate metabolism and energy expenditure remained unchanged. Future studies should investigate alternative exercise strategies or types of interventions (e.g. diet or drugs aiming at improving insulin sensitivity) for their capacity to reinforce diurnal variation in substrate metabolism and mitochondrial respiration. KEY POINTS: Insulin resistance is associated with blunted 24-h flexibility in whole-body substrate metabolism and skeletal muscle mitochondrial respiration, and disruptions in the skeletal muscle molecular circadian clock. We hypothesized that exercise training modifies 24-h rhythmicity in whole-body substrate metabolism and diurnal variation in skeletal muscle molecular clock and mitochondrial respiration in men with insulin resistance. We found that metabolic inflexibility over 24 h persisted after exercise training, whereas mitochondrial respiration increased independent of time of day. Gene expression of Per1-3 and Rorα in skeletal muscle changed particularly close to the time of day at which exercise training was performed. These results provide the rationale to further investigate the differential metabolic impact of differently timed exercise to treat metabolic defects of insulin resistance that manifest at a particular time of day.

Keywords:  circadian rhythm; exercise; insulin resistance; mitochondria

DOI:  https://doi.org/10.1113/JP285523
JCI Insight. 2023 Dec 05. pii: e169512. [Epub ahead of print]

Senotherapeutic drug treatment ameliorates chemotherapy-induced cachexia.

Davis A Englund, Alyssa M Jolliffe, Gabriel J Hanson, Zaira Aversa, Xu Zhang, Xinyi Jiang, Thomas A White, Lei Zhang, David G Monroe, Paul D Robbins, Laura J Niedernhofer, Theodore M Kamenecka, Sundeep Khosla, Nathan K LeBrasseur.

  Cachexia is a debilitating skeletal muscle wasting condition for which we currently lack effective treatments. In the context of cancer, certain chemotherapeutics cause DNA damage and cellular senescence. Senescent cells exhibit chronic activation of the transcription factor nuclear factor (NF)-κB, a known mediator of the pro-inflammatory senescence-associated secretory phenotype (SASP) and skeletal muscle atrophy. Thus, targeting NF-κB represents a logical therapeutic strategy to alleviate unintended consequences of genotoxic drugs. Herein, we show that treatment with the IKK/NF-κB inhibitor SR12343 during a course of chemotherapy reduces markers of cellular senescence and the SASP in liver, skeletal muscle, and circulation and, correspondingly, attenuates features of skeletal muscle pathology. Lastly, we demonstrate SR12343 mitigates chemotherapy-induced reductions in body weight, lean mass, fat mass, and muscle strength. These findings support senescent cells as a promising druggable target to counteract the SASP and skeletal muscle wasting in the context of chemotherapy.

Keywords:  Cellular senescence; Inflammation; Muscle Biology; Skeletal muscle

DOI:  https://doi.org/10.1172/jci.insight.169512
STAR Protoc. 2023 Dec 01. pii: S2666-1667(23)00717-7. [Epub ahead of print]4(4): 102750

Protocol for low-input proteomic analysis of in situ fixed adult murine muscle stem cells.

Wenxin Zhang, Wenshu Zeng, Pui Shuen Wong, Tom H Cheung.

  Studying skeletal muscle stem cells (MuSCs) quiescence is challenging as they quickly activate within hours of isolation from muscle. Here, we present a protocol to disassociate and characterize fixed peptides from quiescent MuSCs using trapped ion-mobility time-of-flight mass spectrometry (MS). We describe steps for mouse perfusion, fluorescence-activated cell sorting preparation and sorting, protein extraction, digestion, and liquid chromatography MS analysis. This protocol can be applied to other less-abundant somatic stem cell types using mouse lines with a reporter. For complete details on the use and execution of this protocol, please refer to Zeng et al. (2022, 2023).1,2.

Keywords:  Mass Spectrometry; Proteomics; Stem Cells

DOI:  https://doi.org/10.1016/j.xpro.2023.102750
Cell Rep Med. 2023 Nov 28. pii: S2666-3791(23)00500-1. [Epub ahead of print] 101306

FK506 bypasses the effect of erythroferrone in cancer cachexia skeletal muscle atrophy.

Erica Mina, Elisabeth Wyart, Roberta Sartori, Elia Angelino, Ivan Zaggia, Valentina Rausch, Mara Maldotti, Alessia Pagani, Myriam Y Hsu, Alberto Friziero, Cosimo Sperti, Alessio Menga, Andrea Graziani, Emilio Hirsch, Salvatore Oliviero, Marco Sandri, Laura Conti, Léon Kautz, Laura Silvestri, Paolo E Porporato.

  Skeletal muscle atrophy is a hallmark of cachexia, a wasting condition typical of chronic pathologies, that still represents an unmet medical need. Bone morphogenetic protein (BMP)-Smad1/5/8 signaling alterations are emerging drivers of muscle catabolism, hence, characterizing these perturbations is pivotal to develop therapeutic approaches. We identified two promoters of "BMP resistance" in cancer cachexia, specifically the BMP scavenger erythroferrone (ERFE) and the intracellular inhibitor FKBP12. ERFE is upregulated in cachectic cancer patients' muscle biopsies and in murine cachexia models, where its expression is driven by STAT3. Moreover, the knock down of Erfe or Fkbp12 reduces muscle wasting in cachectic mice. To bypass the BMP resistance mediated by ERFE and release the brake on the signaling, we targeted FKBP12 with low-dose FK506. FK506 restores BMP-Smad1/5/8 signaling, rescuing myotube atrophy by inducing protein synthesis. In cachectic tumor-bearing mice, FK506 prevents muscle and body weight loss and protects from neuromuscular junction alteration, suggesting therapeutic potential for targeting the ERFE-FKBP12 axis.

Keywords:  ERFE; FK506; FKBP12; cachexia; cancer; cancer cachexia; erythroferrone; skeletal muscle atrophy; tacrolimus; wasting

DOI:  https://doi.org/10.1016/j.xcrm.2023.101306
bioRxiv. 2023 Nov 22. pii: 2023.11.21.568166. [Epub ahead of print]

Muscle cofilin alters neuromuscular junction postsynaptic development to strengthen functional neurotransmission.

Briana Christophers, Shannon N Leahy, David B Soffar, Victoria E von Saucken, Kendal Broadie, Mary K Baylies.

Cofilin, an actin severing protein, plays critical roles in muscle sarcomere addition and maintenance. Our previous work has shown Drosophila cofilin ( DmCFL ) knockdown causes progressive deterioration of muscle structure and function and produces features seen in nemaline myopathy (NM) caused by cofilin mutations. We hypothesized that disruption of actin cytoskeleton dynamics by DmCFL knockdown would impact other aspects of muscle development, and, thus, conducted an RNA sequencing analysis which unexpectedly revealed upregulated expression of numerous neuromuscular junction (NMJ) genes. We found that DmCFL is enriched in the muscle postsynaptic compartment and that DmCFL deficiency causes F-actin disorganization in this subcellular domain prior to the sarcomere defects observed later in development. Despite NMJ gene expression changes, we found no significant changes in gross presynaptic Bruchpilot active zones or total postsynaptic glutamate receptor levels. However, DmCFL knockdown results in mislocalization of glutamate receptors containing the GluRIIA subunit in more deteriorated muscles and neurotransmission strength is strongly impaired. These findings expand our understanding of cofilin's roles in muscle to include NMJ structural development and suggest that NMJ defects may contribute to NM pathophysiology.Summary statement: Cofilin regulates muscle postsynaptic actin organization, structural maintenance, glutamate receptor composition, and neuromuscular junction function in a Drosophila nemaline myopathy disease model.

DOI: https://doi.org/10.1101/2023.11.21.568166
Biochem J. 2023 Dec 13. 480(23): 1969-1986

Lysine methylation signaling in skeletal muscle biology: from myogenesis to clinical insights.

Eric Cordeiro-Spinetti, Scott B Rothbart.

  Lysine methylation signaling is well studied for its key roles in the regulation of transcription states through modifications on histone proteins. While histone lysine methylation has been extensively studied, recent discoveries of lysine methylation on thousands of non-histone proteins has broadened our appreciation for this small chemical modification in the regulation of protein function. In this review, we highlight the significance of histone and non-histone lysine methylation signaling in skeletal muscle biology, spanning development, maintenance, regeneration, and disease progression. Furthermore, we discuss potential future implications for its roles in skeletal muscle biology as well as clinical applications for the treatment of skeletal muscle-related diseases.

Keywords:  epigenetics; lysine methylation; myogenesis

DOI:  https://doi.org/10.1042/BCJ20230223
J Physiol. 2023 Dec 05.

Current limitations and future opportunities of tracer studies of muscle ageing.

Colleen L O'Reilly, Sue C Bodine, Benjamin F Miller.



Keywords:  ageing; deuterium oxide; sarcopenia; skeletal muscle; stable isotopes

DOI:  https://doi.org/10.1113/JP285616
J Physiol. 2023 Dec 05.

Skeletal muscle mitochondria demonstrate similar respiration per cristae surface area independent of training status and sex in healthy humans.

Camilla Tvede Schytz, Niels Ørtenblad, Anne-Kristine Meinild Lundby, Robert Acton Jacobs, Joachim Nielsen, Carsten Lundby.

  The impact of training status and sex on intrinsic skeletal muscle mitochondrial respiratory capacity remains unclear. We examined this by analysing human skeletal muscle mitochondrial respiration relative to mitochondrial volume and cristae density across training statuses and sexes. Mitochondrial cristae density was estimated in skeletal muscle biopsies originating from previous independent studies. Participants included females (n = 12) and males (n = 41) across training statuses ranging from untrained (UT, n = 8), recreationally active (RA, n = 9), active-to-elite runners (RUN, n = 27) and cross-country skiers (XC, n = 9). The XC and RUN groups demonstrated higher mitochondrial volume density than the RA and UT groups while all active groups (RA, RUN and XC) displayed higher mass-specific capacity of oxidative phosphorylation (OXPHOS) and mitochondrial cristae density than UT. Differences in OXPHOS diminished between active groups and UT when normalising to mitochondrial volume density and were lost when normalising to muscle cristae surface area density. Moreover, active females (n = 6-9) and males (n = 15-18) did not differ in mitochondrial volume and cristae density, OXPHOS, or when normalising OXPHOS to mitochondrial volume density and muscle cristae surface area density. These findings demonstrate: (1) differences in OXPHOS between active and untrained individuals may be explained by both higher mitochondrial volume and cristae density in active individuals, with no difference in intrinsic mitochondrial respiratory capacity (OXPHOS per muscle cristae surface area density); and (2) no sex differences in mitochondrial volume and cristae density or mass-specific and normalised OXPHOS. This highlights the importance of normalising OXPHOS to muscle cristae surface area density when studying skeletal muscle mitochondrial biology. KEY POINTS: Oxidative phosphorylation is the mitochondrial process by which ATP is produced, governed by the electrochemical gradient across the inner mitochondrial membrane with infoldings named cristae. In human skeletal muscle, the mass-specific capacity of oxidative phosphorylation (OXPHOS) can change independently of shifts in mitochondrial volume density, which may be attributed to variations in cristae density. We demonstrate that differences in skeletal muscle OXPHOS between healthy females and males, ranging from untrained to elite endurance athletes, are matched by differences in cristae density. This suggests that higher OXPHOS in skeletal muscles of active individuals is attributable to an increase in the density of cristae. These findings broaden our understanding of the variability in human skeletal muscle OXPHOS and highlight the significance of cristae, specific to mitochondrial respiration.

Keywords:  intrinsic mitochondrial respiratory capacity; mitochondria; mitochondrial cristae density; oxidative phosphorylation; sex; skeletal muscle; training status

DOI:  https://doi.org/10.1113/JP285091
J Microbiol Biotechnol. 2023 Dec 01. 34(3): 1-10

LPS-Induced Modifications in Macrophage Transcript and Secretion Profiles Are Linked to Muscle Wasting and Glucose Intolerance.

Heeyeon Ryu, Hyeon Hak Jeong, Seungjun Lee, Min-Kyeong Lee, Myeong-Jin Kim, Bonggi Lee.

  Macrophages are versatile immune cells that play crucial roles in tissue repair, immune defense, and the regulation of immune responses. In the context of skeletal muscle, they are vital for maintaining muscle homeostasis but macrophage-induced chronic inflammation can lead to muscle dysfunction, resulting in skeletal muscle atrophy characterized by reduced muscle mass and impaired insulin regulation and glucose uptake. Although the involvement of macrophage-secreted factors in inflammation-induced muscle atrophy is well-established, the precise intracellular signaling pathways and secretion factors affecting skeletal muscle homeostasis require further investigation. This study aimed to explore the regulation of macrophage-secreted factors and their impact on muscle atrophy and glucose metabolism. By employing RNA sequencing (RNA-seq) and proteome array, we uncovered that factors secreted by lipopolysaccharide (LPS)-stimulated macrophages upregulated markers of muscle atrophy and pro-inflammatory cytokines, while concurrently reducing glucose uptake in muscle cells. The RNA-seq analysis identified alterations in gene expression patterns associated with immune system pathways and nutrient metabolism. The utilization of gene ontology (GO) analysis and proteome array with macrophage-conditioned media revealed the involvement of macrophage-secreted cytokines and chemokines associated with muscle atrophy. These findings offer valuable insights into the regulatory mechanisms of macrophage-secreted factors and their contributions to muscle-related diseases.

Keywords:  Macrophages; RNA Seq; cytokine; proteome array; skeletal muscle

DOI:  https://doi.org/10.4014/jmb.2309.09037
Arch Biochem Biophys. 2023 Dec 02. pii: S0003-9861(23)00343-0. [Epub ahead of print]751 109844

P2Y1 and P2Y2 receptors differ in their role in the regulation of signaling pathways during unloading-induced rat soleus muscle atrophy.

Ksenia A Zaripova, Svetlana P Belova, Tatiana Y Kostrominova, Boris S Shenkman, Tatiana L Nemirovskaya.

  The current study aimed to investigate the hypothesis that purinergic receptors P2Y1 and P2Y2 play a regulatory role in gene expression in unloaded muscle. ATP is released from cells through pannexin channels, and it interacts with P2Y1 and P2Y2 receptors, leading to the activation of markers of protein catabolism and a reduction in protein synthesis. To test this hypothesis thirty-two rats were randomly divided into four groups (8 per group): a non-treated control group (C), a group subjected to three days of hindlimb unloading with a placebo (HS), a group subjected to three days of hindlimb unloading treated with a P2Y1 receptor inhibitor, MRS2179 (HSM), and a group subjected to three days of hindlimb unloading treated with a P2Y2 receptor inhibitor, AR-C 118925XX (HSA). This study revealed several key findings following three days of soleus muscle unloading: 1: Inhibition of P2Y1 or P2Y2 receptors prevented the accumulation of ATP, the increase in IP3 receptor content, and the decrease in the phosphorylation of GSK-3beta. This inhibition also mitigated the reduction in the rate of protein synthesis. However, it had no significant effect on the markers of mTORC1-dependent signaling. 2: Blocking P2Y1 receptors prevented the unloading-induced upregulation of phosphorylated p38MAPK and partially reduced the increase in MuRF1mRNA expression. 3: Blocking P2Y2 receptors prevented muscle atrophy during unloading, partially maintained the levels of phosphorylated ERK1/2, reduced the increase in mRNA expression of MAFbx, ubiquitin, and IL-6 receptor, prevented the decrease in phosphorylated AMPK, and attenuated the increase in phosphorylated p70S6K. Taken together, these results suggest that the prevention of muscle atrophy during unloading, as achieved by the P2Y2 receptor inhibitor, is likely mediated through a reduction in catabolic processes and maintenance of energy homeostasis. In contrast, the P2Y1 receptor appears to play a relatively minor role in muscle atrophy during unloading.

Keywords:  ATP; MAFbx; Muscle atrophy; Muscle unloading; P2Y1 and P2Y2 receptors

DOI:  https://doi.org/10.1016/j.abb.2023.109844
Dev Cell. 2023 Nov 30. pii: S1534-5807(23)00585-3. [Epub ahead of print]

CRIPTO-based micro-heterogeneity of mouse muscle satellite cells enables adaptive response to regenerative microenvironment.

Ombretta Guardiola, Francescopaolo Iavarone, Chiara Nicoletti, Maurizio Ventre, Cristina Rodríguez, Laura Pisapia, Gennaro Andolfi, Valentina Saccone, Eduardo J Patriarca, Pier Lorenzo Puri, Gabriella Minchiotti.

  Skeletal muscle repair relies on heterogeneous populations of satellite cells (SCs). The mechanisms that regulate SC homeostasis and state transition during activation are currently unknown. Here, we investigated the emerging role of non-genetic micro-heterogeneity, i.e., intrinsic cell-to-cell variability of a population, in this process. We demonstrate that micro-heterogeneity of the membrane protein CRIPTO in mouse-activated SCs (ASCs) identifies metastable cell states that allow a rapid response of the population to environmental changes. Mechanistically, CRIPTO micro-heterogeneity is generated and maintained through a process of intracellular trafficking coupled with active shedding of CRIPTO from the plasma membrane. Irreversible perturbation of CRIPTO micro-heterogeneity affects the balance of proliferation, self-renewal, and myogenic commitment in ASCs, resulting in increased self-renewal in vivo. Our findings demonstrate that CRIPTO micro-heterogeneity regulates the adaptative response of ASCs to microenvironmental changes, providing insights into the role of intrinsic heterogeneity in preserving stem cell population diversity during tissue repair.

Keywords:  CRIPTO; cell fate determination; cell state transition; membrane trafficking; micro-heterogeneity; non-genetic heterogeneity; phospholipase C; satellite cell population dynamics; self-renewal; skeletal muscle regeneration

DOI:  https://doi.org/10.1016/j.devcel.2023.11.009
J Appl Physiol (1985). 2023 Dec 01. 135(6): 1384-1385

Exercise intolerance in post-COVID syndrome cannot only be due to skeletal muscle impairment.

Josef Finsterer, Fulvio Alexandre Scorza.



Keywords:  exercise intolerance; muscle biopsy; myositis; oxidative capacity; post-COVID syndrome

DOI:  https://doi.org/10.1152/japplphysiol.00734.2023
Neurol Res. 2023 Dec 03. 1-18

Translational mobility medicine and ugo carraro: a life of significant scientific contributions reviewed in celebration.

Barbara Ravara, Walter Giuriati, Sandra Zampieri, Helmut Kern, Amber L Pond.

  Prof. Ugo Carraro reached 80 years of age on 23 February 2023, and we wish to celebrate him and his work by reviewing his lifetime of scientific achievements in Translational Myology. Currently, he is a Senior Scholar with the University of Padova, Italy, where, as a tenured faculty member, he founded the Interdepartmental Research Center of Myology. Prof. Carraro, a pioneer in skeletal muscle research, is a world-class expert in structural and molecular investigations of skeletal muscle biology, physiology, pathology, and care. An authority in bidimensional gel electrophoresis for myosin light chains, he was the first to separate mammalian muscle myosin heavy chain isoforms by SDS-gel electrophoresis. He has demonstrated that long-term denervated muscle can survive denervation by myofiber regeneration, and shown that an athletic lifestyle has beneficial impacts on muscle reinnervation. He has utilized his expertise in translational myology to develop and validate rehabilitative treatments for denervated and ageing skeletal muscle. He has authored more than 160 PubMed listed papers and numerous scholarly books, including his recent autobiography. Prof. Carraro founded and serves as Editor-in-Chief of the European Journal of Translational Myology and Mobility Medicine. He has organized more than 40 Padua Muscle Days Meetings and continues this, encouraging students and young scientists to participate. As he dreams endlessly, he is currently validating non-invasive analyses on saliva, a promising approach that will allow increased frequency sampling to analyze systemic factors during the transient effects of training and rehabilitation by his proposed Full-Body in- Bed Gym for bed-ridden elderly.

Keywords:  CIR-Myo; European Journal of Translational Myology; Ugo carraro; mobility medicine; padua muscle days; skeletal muscle

DOI:  https://doi.org/10.1080/01616412.2023.2258041
Res Sq. 2023 Nov 21. pii: rs.3.rs-3621159. [Epub ahead of print]

Metabolic Pathways for Removing Reactive Aldehydes are Diminished in Atrophic Muscle During Heart Failure.

Mamata Chaudhari, Igor Zelko, Pawel Lorkiewicz, David Hoetker, Benjamin Doelling, Kenneth Brittian, Aruni Bhatnagar, Sanjay Srivast, Shahid P Baba.

Background : Muscle wasting is a serious complication in heart failure patients, and oxidative stress is involved in the pathogenesis of muscle wasting. Oxidative stress leads to the formation of toxic lipid peroxidation products, such as 4-hydroxy-2-nonenal (HNE) and acrolein, which causemuscle wasting. In tissues, these toxic aldehydes are metabolically removed by enzymes such asaldo keto reductases and endogenous nucleophiles, such as glutathione and carnosine. Whether these metabolic pathways could be affected in skeletal muscle during heart failure has never been studied. Methods : Male wild-type C57BL/6J mice were subjected to a pressure overload model of hypertrophy by transaortic constriction (TAC) surgery, and echocardiography was performed after 14 weeks. Different skeletal muscle beds were weighed and analyzed for atrophic and inflammatory markers, Atrogin1 and TRIM63, TNF-α and IL-6 , respectively, by RT‒PCR. Levels of acrolein and HNE-protein adducts, aldehyde-removing enzymes, aldose reductase (AKR1B1) and aldehyde dehydrogenase 2 (ALDH2) were measured by Western blotting, and histidyl dipeptides and histidyl dipeptide aldehyde conjugates were analyzed by LC/MS-MS in the gastrocnemius and soleus muscles of sham- and TAC-operated mice. Furthermore, histidyl dipeptide synthesizing enzyme carnosine synthase (CARNS) and amino acid transporters (PEPT2 and TAUT)wasmeasured in the gastrocnemius muscles of the sham and TAC-operated mice. Results : TAC-induced heart failure decreases body weight and gastrocnemius and soleus muscle weights. The expression of the atrophic and inflammatory markers Atrogin1 and TNF-α, respectively, wasincreased (~1.5-2-fold), and the formation of HNE and acrolein-protein adducts was increased in the gastrocnemius muscle of TAC-operated mice. The expression of AKR1B1 remained unchanged, whereas ALDH2 was decreased, in the gastrocnemius muscle of TAC mice. Similarly, in the atrophic gastrocnemius muscle, levels of total histidyl dipeptides (carnosine and anserine) and, in particular,carnosine were decreased. Depletion of histidyl dipeptides diminished the aldehyde removal capacity of the atrophic gastrocnemius muscle. Furthermore, the expression of CARNS and TAUT wasdecreased in the atrophic gastrocnemius muscle. Conclusions : Collectively, these results show that metabolic pathways involved in the removal of lipid peroxidation products and synthesis of histidyl dipeptides are diminished in atrophic skeletal muscle during heart failure, which could contribute to muscle atrophy.

DOI: https://doi.org/10.21203/rs.3.rs-3621159/v1
Life Sci. 2023 Nov 30. pii: S0024-3205(23)00959-1. [Epub ahead of print]336 122324

The contribution of mitochondria to age-related skeletal muscle wasting: A sex-specific perspective.

Alessandro Nuccio, Rita Nogueira-Ferreira, Alexandra Moreira-Pais, Alessandro Attanzio, José Alberto Duarte, Claudio Luparello, Rita Ferreira.

  As people age, their skeletal muscle (SkM) experiences a decline in mitochondrial functionality and density, which leads to decreased energy production and increased generation of reactive oxygen species. This cascade of events, in turn, might determine the loss of SkM mass, strength and quality. Even though the mitochondrial processes dysregulated by aging, such as oxidative phosphorylation, mitophagy, antioxidant defenses and mtDNA transcription, are the same in both sexes, mitochondria age differently in the SkM of men and women. Indeed, the onset and magnitude of the impairment of these processes seem to be influenced by sex-specific factors. Sexual hormones play a pivotal role in the regulation of SkM mass through both genomic and non-genomic mechanisms. However, the precise mechanisms by which these hormones regulate mitochondrial plasticity in SkM are not fully understood. Although the presence of estrogen receptors in mitochondria is recognized, it remains unclear whether androgen receptors affect mitochondrial function. This comprehensive review critically dissects the current knowledge on the interplay of sex in the aging of SkM, focusing on the role of sex hormones and the corresponding signaling pathways in shaping mitochondrial plasticity. Improved knowledge on the sex dimorphism of mitochondrial aging may lead to sex-tailored interventions that target mitochondrial health, which could be effective in slowing or preventing age-related muscle loss.

Keywords:  Androgens; Estrogens; Mitochondria remodeling; Sarcopenia; Sexual dimorphism

DOI:  https://doi.org/10.1016/j.lfs.2023.122324
Sci Rep. 2023 Dec 04. 13(1): 21349

A causative role for periarticular skeletal muscle weakness in the progression of joint damage and pain in OA.

Ju-Ryoung Kim, Thi Hong Nhung Pham, Wan-Uk Kim, Hyun Ah Kim.

Although osteoarthritis (OA) is regarded as a disease of the articular cartilage, recent research has demonstrated alterations in periarticular muscles that surround the affected joint. Here, we investigated changes in periarticular muscle during the progression of OA, as well as the cause-and-effect relationship between muscle weakness and OA, in a mouse model of OA by destabilization of the medial meniscus (DMM). Pathological phenotypes in the periarticular muscles were assessed in the early and late stages of OA by DMM. OA pathology and pain behavior in the mice after DMM induction were examined in response to periarticular muscle weakness induced by multiple rounds of barium chloride (BaCl2) injections. The examinations were also performed in myostatin knockout mice with strengthened muscle phenotypes by muscle hypertrophy. Morphological alterations in the tibialis anterior (TA) and quadriceps muscles in DMM mice included variations in muscle-fiber size, aberrant extracellular matrix (ECM) deposition, inflammatory cell infiltration, and decreased muscle mass. Periarticular muscle fibers isolated from DMM mice showed reductions in the number of satellite cells and myogenic capacity of primary myoblast, as well as proliferation. DMM + muscle injury mice also showed exacerbated joint degeneration compared to the DMM vehicles. Myostatin knockout mice were characterized by attenuated OA and the complete abrogation of pain behavior after DMM. Our results suggest an association between muscle weakness and OA progression and pain.

DOI: https://doi.org/10.1038/s41598-023-46599-7
J Physiol. 2023 Dec 04.

The impact of 60 days of -6° head down tilt bed rest on mitochondrial content, respiration and regulators of mitochondrial dynamics.

John Noone, Anthony Damiot, Helena Kenny, Isabelle Chery, Alexandre Zahariev, Sylvie Normand, François Crampes, Isabelle de Glisezinski, Keith D Rochfort, Claire Laurens, Marie-Pierre Bareille, Chantal Simon, Audrey Bergouignan, Stéphane Blanc, Donal J O'Gorman.

  It is unclear how skeletal muscle metabolism and mitochondrial function adapt to long duration bed rest and whether changes can be prevented by nutritional intervention. The present study aimed (1) to assess the effect of prolonged bed rest on skeletal muscle mitochondrial function and dynamics and (2) to determine whether micronutrient supplementation would mitigate the adverse metabolic effect of bed rest. Participants were maintained in energy balance throughout 60 days of bed rest with micronutrient supplementation (INT) (body mass index: 23.747 ± 1.877 kg m-2 ; 34.80 ± 7.451 years; n = 10) or without (control) (body mass index: 24.087 ± 2.088 kg m-2 ; 33.50 ± 8.541 years; n = 10). Indirect calorimetry and dual-energy x-ray absorptiometry were used for measures of energy expenditure, exercise capacity and body composition. Mitochondrial respiration was determined by high-resolution respirometry in permeabilized muscle fibre bundles from vastus lateralis biopsies. Protein and mRNA analysis further examined the metabolic changes relating to regulators of mitochondrial dynamics induced by bed rest. INT was not sufficient in preserving whole body metabolic changes conducive of a decrease in body mass, fat-free mass and exercise capacity within both groups. Mitochondrial respiration, OPA1 and Drp1 protein expression decreased with bed rest, with an increase pDrp1s616 . This reduction in mitochondrial respiration was explained through an observed decrease in mitochondrial content (mtDNA:nDNA). Changes in regulators of mitochondrial dynamics indicate an increase in mitochondrial fission driven by a decrease in inner mitochondrial membrane fusion (OPA1) and increased pDrp1s616 . KEY POINTS: Sixty days of -6° head down tilt bed rest leads to significant changes in body composition, exercise capacity and whole-body substrate metabolism. Micronutrient supplementation throughout bed rest did not preserve whole body metabolic changes. Bed rest results in a decrease in skeletal muscle mitochondrial respiratory capacity, mainly as a result of an observed decrease in mitochondrial content. Prolonged bed rest ensues changes in key regulators of mitochondrial dynamics. OPA1 and Drp1 are significantly reduced, with an increase in pDrp1s616 following bed rest indicative of an increase in mitochondrial fission. Given the reduction in mitochondrial content following 60 days of bed rest, the maintenance of regulators of mitophagy in line with the increase in regulators of mitochondrial fission may act to maintain mitochondrial respiration to meet energy demands.

Keywords:  OPA1; bed rest; energy expenditure; metabolism; mitochondrial dynamics; mitochondrial function; skeletal muscle

DOI:  https://doi.org/10.1113/JP284734
Skelet Muscle. 2023 Dec 04. 13(1): 20

Replenishing NAD+ content reduces aspects of striated muscle disease in a dog model of Duchenne muscular dystrophy.

Déborah Cardoso, Inès Barthélémy, Stéphane Blot, Antoine Muchir.

  Duchenne muscular dystrophy (DMD) is an X-linked disease caused by mutations in DMD gene and loss of the protein dystrophin, which ultimately leads to myofiber membrane fragility and necrosis, with eventual muscle atrophy and contractures. Affected boys typically die in their second or third decade due to either respiratory failure or cardiomyopathy. Among the developed therapeutic strategies for DMD, gene therapy approaches partially restore micro-dystrophin or quasi-dystrophin expression. However, despite extensive attempts to develop definitive therapies for DMD, the standard of care remains corticosteroid, which has only palliative benefits. Animal models have played a key role in studies of DMD pathogenesis and treatment development. The golden retriever muscular dystrophy (GRMD) dog displays a phenotype aligning with the progressive course of DMD. Therefore, canine studies may translate better to humans. Recent studies suggested that nicotinamide adenine dinucleotide (NAD+) cellular content could be a critical determinant for striated muscle function. We showed here that NAD+ content was decreased in the striated muscles of GRMD, leading to an alteration of one of NAD+ co-substrate enzymes, PARP-1. Moreover, we showed that boosting NAD+ content using nicotinamide (NAM), a natural NAD+ precursor, modestly reduces aspects of striated muscle disease. Collectively, our results provide mechanistic insights into DMD.

Keywords:  Duchenne muscular dystrophy; GRMD; NAD+; Nicotinamide

DOI:  https://doi.org/10.1186/s13395-023-00328-w
Photochem Photobiol Sci. 2023 Dec 06.

Antioxidant effects of LEDT in dystrophic muscle cells: involvement of PGC-1α and UCP-3 pathways.

Guilherme Luiz da Rocha, Dimitrius Santiago Passos Simões Fróes Guimarães, Marcos Vinicius da Cruz, Daniela Sayuri Mizobuti, Heloina Nathalliê Mariano da Silva, Elaine Cristina Leite Pereira, Leonardo Reis Silveira, Elaine Minatel.

  PURPOSE: Reactive oxygen species and mitochondrial dysfunction play a crucial role in the pathophysiology of Duchenne muscular dystrophy (DMD). The light-emitting diode therapy (LEDT) showed beneficial effects on the dystrophic muscles. However, the mechanisms of this therapy influence the molecular pathways in the dystrophic muscles, particularly related to antioxidant effects, which still needs to be elucidated. The current study provides muscle cell-specific insights into the effect of LEDT, 48 h post-irradiation, on oxidative stress and mitochondrial parameters in the dystrophic primary muscle cells in culture.METHODS: Dystrophic primary muscle cells were submitted to LEDT, at multiple wavelengths (420 nm, 470 nm, 660 nm and 850 nm), 0.5 J dose, and evaluated after 48 h based on oxidative stress markers, antioxidant enzymatic system and biogenesis, and functional mitochondrial parameters.
RESULTS: The mdx muscle cells treated with LEDT showed a significant reduction of H2O2 production and 4-HNE, catalase, SOD-2, and GR levels. Upregulation of UCP3 was observed with all wavelengths while upregulation of PGC-1α and a slight upregulation of electron transport chain complexes III and V was only observed following 850 nm LEDT. In addition, the mitochondrial membrane potential and mitochondrial mass mostly tended to be increased following LEDT, while parameters like O2·- production tended to be decreased.
CONCLUSION: The data shown here highlight the potential of LEDT as a therapeutic agent for DMD through its antioxidant action by modulating PGC-1α and UCP3 levels.

Keywords:  Dystrophic muscle cells; Mitochondrial parameters; Oxidative stress; Photobiomodulation

DOI:  https://doi.org/10.1007/s43630-023-00506-1
Pflugers Arch. 2023 Dec 04.

Potential regulatory role of PGC-1α within the skeletal muscle during metabolic adaptations in response to high-fat diet feeding in animal models.

Sinenhlanhla X H Mthembu, Sithandiwe E Mazibuko-Mbeje, Khanyisani Ziqubu, Ndivhuwo Muvhulawa, Fabio Marcheggiani, Ilenia Cirilli, Bongani B Nkambule, Christo J F Muller, Albertus K Basson, Luca Tiano, Phiwayinkosi V Dludla.

  High-fat diet (HFD) feeding in rodents has become an essential tool to critically analyze and study the pathological effects of obesity, including mitochondrial dysfunction and insulin resistance. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) regulates cellular energy metabolism to influence insulin sensitivity, beyond its active role in stimulating mitochondrial biogenesis to facilitate skeletal muscle adaptations in response to HFD feeding. Here, some of the major electronic databases like PubMed, Embase, and Web of Science were accessed to update and critically discuss information on the potential role of PGC-1α during metabolic adaptations within the skeletal muscle in response to HFD feeding in rodents. In fact, available evidence suggests that partial exposure to HFD feeding (potentially during the early stages of disease development) is associated with impaired metabolic adaptations within the skeletal muscle, including mitochondrial dysfunction and reduced insulin sensitivity. In terms of implicated molecular mechanisms, these negative effects are partially associated with reduced activity of PGC-1α, together with the phosphorylation of protein kinase B and altered expression of genes involving nuclear respiratory factor 1 and mitochondrial transcription factor A within the skeletal muscle. Notably, metabolic abnormalities observed with chronic exposure to HFD (likely during the late stages of disease development) may potentially occur independently of PGC-1α regulation within the muscle of rodents. Summarized evidence suggests the causal relationship between PGC-1α regulation and effective modulations of mitochondrial biogenesis and metabolic flexibility during the different stages of disease development. It further indicates that prominent interventions like caloric restriction and physical exercise may affect PGC-1α regulation during effective modulation of metabolic processes.

Keywords:  High-fat diet; Insulin resistance; Mitochondrial function; Obesity; PGC-1α; Skeletal muscle

DOI:  https://doi.org/10.1007/s00424-023-02890-0
Arch Pediatr. 2023 Nov;pii: S0929-693X(23)00223-3. [Epub ahead of print]30(8S1): 8S18-8S23

Gene therapy for primary myopathies: literature review and prospects.

Giorgia Querin, Marina Colella.

  Gene therapy has emerged as a promising frontier in the pursuit of effective treatments for primary myopathies. This scientific review explores the application of viral vectors and more specifically of recombinant adeno-associated virus (rAAV) vectors as a potent gene delivery tool in the context of primary myopathies, highlighting its transformative potential. Focusing on primary myopathies, including Duchenne muscular dystrophy (DMD), limb-girdle muscular dystrophies (LGMDs), X-linked myotubular myopathy (XLMTM), and Pompe disease, we review the ongoing pre-clinical and clinical trials that underscore the therapeutic promise of rAAV-based gene therapies. Recent developments in gene therapy have unveiled innovative gene transfer approaches, particularly with rAAV vectors. These vectors offer a well-tolerated and efficient means of delivering corrective genetic material to diseased muscles, thereby addressing the root causes of primary myopathies. Encouraging data from pre-clinical studies and early clinical trials have demonstrated the potential to ameliorate muscle function, reduce pathological manifestations, and enhance the quality of life for patients afflicted with these devastating diseases. However, the transition from bench to bedside is not without challenges. This review emphasizes the critical need for a comprehensive risk management strategy to better handle potential side effects and immune responses associated with gene therapy. As the field of gene therapy for primary myopathies is advancing, it is imperative to refine and optimize safety measures, ensuring that the transformative potential of these therapies is realized while the risks are minimized. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.

Keywords:  Gene therapy; Gene transfer; Innovative treatments; Primary myopathies; rAAV

DOI:  https://doi.org/10.1016/S0929-693X(23)00223-3
Exp Physiol. 2023 Dec 06.

Exercise intolerance with ageing: Major role for vascular dysfunction?

David C Poole, Glenn A Gaesser.



Keywords:  aging; critical power; exhaustion; healthspan; muscle function; vascular control

DOI:  https://doi.org/10.1113/EP091606
Adv Physiol Educ. 2023 Dec 07.

A low-cost 2D sarcomere model to demonstrate titin related mechanisms for force production.

Heron Baptista de Oliveira Medeiros, Heiliane de Brito Fontana, Walter Herzog.

  Given the recently proposed three-filament theory of muscle contraction, we present a low-cost physical sarcomere model aimed at illustrating the role of titin in the production of active force in skeletal muscle. Using inexpensive materials, it is possible to illustrate actin-myosin cross-bridge interactions between the thick and thin filaments and demonstrate the two different mechanisms by which titin is thought to contribute to active and passive muscle force. Specifically, the model illustrates how titin, a molecule with spring-like properties, may increase its stiffness by binding free calcium upon muscle activation and reducing its extensible length by attaching itself to actin, resulting in the greater force generating capacity after an active than a passive elongation that has been observed experimentally. The model is simple to build and manipulate, and demonstration to high school students was shown to result in positive perception and improved understanding of the otherwise complex titin related mechanisms of force production in skeletal and cardiac muscles.

Keywords:  cross-bridge theory; learning tools; muscle contraction; muscle stretching; three-filament sarcomere model

DOI:  https://doi.org/10.1152/advan.00090.2023
An Acad Bras Cienc. 2023 ;pii: S0001-37652023000500802. [Epub ahead of print]95(suppl 2): e20220877

Resveratrol directly suppresses proteolysis possibly via PKA/CREB signaling in denervated rat skeletal muscle.

Ivanildo I S Júnior, Gustavo O Zanetti, Tales S Vieira, Flávia P Albuquerque, Dayane A Gomes, Silva Paula-Gomes, Rafael R Valentim, Flavia A Graça, Isis C Kettlhut, Luiz C C Navegantes, Dawit A P Gonçalves, Eduardo C Lira.

Although there are reports that polyphenol resveratrol (Rsv) may cause muscle hypertrophy in basal conditions and attenuate muscle wasting in catabolic situations, its mechanism of action is still unclear. Our study evaluated the ex vivo effects of Rsv on protein metabolism and intracellular signaling in innervated (sham-operated; Sham) and 3-day sciatic denervated (Den) rat skeletal muscles. Rsv (10-4 M) reduced total proteolysis (40%) in sham muscles. Den increased total proteolysis (~40%) in muscle, which was accompanied by an increase in the activities of ubiquitin-proteasome (~3-fold) and lysosomal (100%) proteolytic systems. Rsv reduced total proteolysis (59%) in Den muscles by inhibiting the hyperactivation of ubiquitin-proteasome (50%) and lysosomal (~70%) systems. Neither Rsv nor Den altered calcium-dependent proteolysis in muscles. Mechanistically, Rsv stimulated PKA/CREB signaling in Den muscles, and PKA blockage by H89 (50μM) abolished the antiproteolytic action of the polyphenol. Rsv reduced FoxO4 phosphorylation (~60%) in both Sham and Den muscles and Akt phosphorylation (36%) in Den muscles. Rsv also caused a homeostatic effect in Den muscles by returning their protein synthesis rates to levels similar to Sham muscles. These data indicate that Rsv directly inhibits the proteolytic activity of lysosomal and ubiquitin-proteasome systems, mainly in Den muscles through, at least in part, the activation of PKA/CREB signaling.

DOI: https://doi.org/10.1590/0001-3765202320220877