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Resistance exercise training (RET) can counteract negative features of muscle ageing but older age associates with reduced adaptive capacity to RET. Altered muscle protein networks likely contribute to ageing RET adaptation; therefore, associated proteome-wide responses warrant exploration. We employed quantitative sarcoplasmic proteomics to compare age-related proteome and phosphoproteome responses to RET. Thigh muscle biopsies were collected from eight young (25 ± 1.1 years) and eight older (67.5 ± 2.6 years) adults before and after 20 weeks supervised RET. Muscle sarcoplasmic fractions were pooled for each condition and analysed using Isobaric Tags for Relative and Absolute Quantification (iTRAQ) labelling, tandem mass spectrometry and network-based hub protein identification. Older adults displayed impaired RET-induced adaptations in whole-body lean mass, body fat percentage and thigh lean mass (P > 0.05). iTRAQ identified 73 differentially expressed proteins with age and/or RET. Despite possible proteomic stochasticity, RET improved ageing profiles for mitochondrial function and glucose metabolism (top hub; PYK (pyruvate kinase)) but failed to correct altered ageing expression of cytoskeletal proteins (top hub; YWHAZ (14–3-3 protein zeta/delta)). These ageing RET proteomic profiles were generally unchanged or oppositely regulated post-RET in younger muscle. Similarly, RET corrected expression of 10 phosphoproteins altered in ageing, but these responses were again different vs. younger adults. Older muscle is characterised by RET-induced metabolic protein profiles that, whilst not present in younger muscle, improve untrained age-related proteomic deficits. Combined with impaired cytoskeletal adhesion responses, these results provide a proteomic framework for understanding and optimising ageing muscle RET adaptation.

Optimization of resistance exercise (RE) remains a hotbed of research for muscle building and maintenance. However, the interactions between the contractile components of RE (i.e. concentric (CON) and eccentric (ECC)) and age, are poorly defined. We used transcriptomics to compare age-related molecular responses to acute CON and ECC exercise. Eight young (21±1 y) and eight older (70±1 y) exercise-naïve male volunteers had vastus lateralis biopsies collected at baseline and 5 h post unilateral CON and contralateral ECC exercise. RNA was subjected to next-generation sequencing and differentially expressed (DE) genes tested for pathway enrichment using Gene Ontology (GO). The young transcriptional response to CON and ECC was highly similar and older adults displayed moderate contraction-specific profiles, with no GO enrichment. Age-specific responses to ECC revealed 104 DE genes unique to young, and 170 DE genes in older muscle, with no GO enrichment. Following CON, 15 DE genes were young muscle-specific, whereas older muscle uniquely expressed 147 up-regulated genes enriched for cell adhesion and blood vessel development, and 28 down-regulated genes involved in mitochondrial respiration, amino acid and lipid metabolism. Thus, older age is associated with contraction-specific regulation often without clear functional relevance, perhaps reflecting a degree of stochastic age-related dysregulation.

Key points: Reduced vitamin D receptor (VDR) expression prompts skeletal muscle atrophy. Atrophy occurs through catabolic processes, namely the induction of autophagy, while anabolism remains unchanged. In response to VDR-knockdown mitochondrial function and related gene-set expression is impaired. In vitro VDR knockdown induces myogenic dysregulation occurring through impaired differentiation. These results highlight the autonomous role the VDR has within skeletal muscle mass regulation. Abstract: Vitamin D deficiency is estimated to affect ?40% of the world's population and has been associated with impaired muscle maintenance. Vitamin D exerts its actions through the vitamin D receptor (VDR), the expression of which was recently confirmed in skeletal muscle, and its down-regulation is linked to reduced muscle mass and functional decline. To identify potential mechanisms underlying muscle atrophy, we studied the impact of VDR knockdown (KD) on mature skeletal muscle in vivo, and myogenic regulation in vitro in C2C12 cells. Male Wistar rats underwent in vivo electrotransfer (IVE) to knock down the VDR in hind-limb tibialis anterior (TA) muscle for 10days. Comprehensive metabolic and physiological analysis was undertaken to define the influence loss of the VDR on muscle fibre composition, protein synthesis, anabolic and catabolic signalling, mitochondrial phenotype and gene expression. Finally, in vitro lentiviral transfection was used to induce sustained VDR-KD in C2C12 cells to analyse myogenic regulation. Muscle VDR-KD elicited atrophy through a reduction in total protein content, resulting in lower myofibre area. Activation of autophagic processes was observed, with no effect upon muscle protein synthesis or anabolic signalling. Furthermore, RNA-sequencing analysis identified systematic down-regulation of multiple mitochondrial respiration-related protein and genesets. Finally, in vitro VDR-knockdown impaired myogenesis (cell cycling, differentiation and myotube formation). Together, these data indicate a fundamental regulatory role of the VDR in the regulation of myogenesis and muscle mass, whereby it acts to maintain muscle mitochondrial function and limit autophagy.

Objective Vitamin‐D deficiency is estimated to affect ∼40% of the world's population and has been associated with impaired muscle maintenance. Vitamin‐D exerts its actions through the Vitamin‐D‐receptor (VDR), the expression of which was recently confirmed in skeletal muscle, and its down‐regulation is linked to reduced muscle mass and functional decline. To identify potential mechanisms underlying muscle atrophy, we studied the impact of VDR knockdown (KD) on mature skeletal muscle in vivo, and myogenic regulation in vitro in C2C12 cells. Methods Male Wistar rats underwent in vivo electrotransfer (IVE) to knock down the VDR in hind‐limb tibialis anterior (TA) muscle for 10 days. Comprehensive metabolic and physiological analysis was undertaken to define the influence loss of the VDR on muscle fibre composition, protein synthesis, anabolic and catabolic signalling, mitochondrial phenotype, and gene expression. Finally, in vitro lentiviral transfection was used to induce sustained VDR‐KD in C2C12 cells to analyse myogenic regulation. Results Muscle VDR‐KD elicited atrophy through a reduction in total protein content, resulting in lower myofibre area. Activation of autophagic processes was observed, with no effect upon muscle protein synthesis or anabolic signalling. Furthermore, RNA‐Seq analysis identified systematic down‐regulation of multiple mitochondrial respiration related protein and genesets. Finally, in vitro VDR‐knockdown impaired myogenesis (cell cycling, differentiation and myotube formation). Conclusion Taken together, these data indicate a fundamental regulatory role of the VDR in the regulation of myogenesis and muscle mass; whereby it acts to maintain muscle mitochondrial function and limit autophagy. Joseph Bass completed his PhD in Medicine and Health in 2017 at The University of Nottingham, where he is currently a Research Fellow. Joe is interested in examining the mechanistic regulation of musculoskeletal health, particularly factors impacting muscle atrophy susceptibility.

著者人数: 12名, 形態: カラー図版あり, Number of authors: 12, Physical characteristics: Original contains color illustrations, Accepted: 2022-01-10, 資料番号: PA2210079000

Additional file 1: Table S1. Costs associated with each recruitment method. Figure S1. Facebook campaigns. Figure S2. Mailshot template.

Muscle strength is a key clinical parameter used to monitor the progression of human muscular dystrophies, including Duchenne and Becker muscular dystrophies. Although Caenorhabditis elegans is an established genetic model for studying the mechanisms and treatments of muscular dystrophies, analogous strength-based measurements in this disease model are lacking. Here, we describe the first demonstration of the direct measurement of muscular strength in dystrophin-deficient C. elegans mutants using a micropillar-based force measurement system called NemaFlex. We show that dys-1(eg33) mutants, but not dys-1(cx18) mutants, are significantly weaker than their wild-type counterparts in early adulthood, cannot thrash in liquid at wild-type rates, display mitochondrial network fragmentation in the body wall muscles, and have an abnormally high baseline mitochondrial respiration. Furthermore, treatment with prednisone, the standard treatment for muscular dystrophy in humans, and melatonin both improve muscular strength, thrashing rate and mitochondrial network integrity in dys-1(eg33), and prednisone treatment also returns baseline respiration to normal levels. Thus, our results demonstrate that the dys-1(eg33) strain is more clinically relevant than dys-1(cx18) for muscular dystrophy studies in C. elegans. This finding, in combination with the novel NemaFlex platform, can be used as an efficient workflow for identifying candidate compounds that can improve strength in the C. elegans muscular dystrophy model. Our study also lays the foundation for further probing of the mechanism of muscle function loss in dystrophin-deficient C. elegans, leading to knowledge translatable to human muscular dystrophy.

Muscle strength is a key clinical parameter used to monitor the progression of human muscular dystrophies, including Duchenne and Becker muscular dystrophies. Although Caenorhabditis elegans is an established genetic model for studying the mechanisms and treatments of muscular dystrophies, analogous strength-based measurements in this disease model are lacking. Here, we describe the first demonstration of the direct measurement of muscular strength in dystrophin-deficient C. elegans mutants using a micropillar-based force measurement system called NemaFlex. We show that dys-1(eg33) mutants, but not dys-1(cx18) mutants, are significantly weaker than their wild-type counterparts in early adulthood, cannot thrash in liquid at wild-type rates, display mitochondrial network fragmentation in the body wall muscles, and have an abnormally high baseline mitochondrial respiration. Furthermore, treatment with prednisone, the standard treatment for muscular dystrophy in humans, and melatonin both improve muscular strength, thrashing rate and mitochondrial network integrity in dys-1(eg33), and prednisone treatment also returns baseline respiration to normal levels. Thus, our results demonstrate that the dys-1(eg33) strain is more clinically relevant than dys-1(cx18) for muscular dystrophy studies in C. elegans. This finding, in combination with the novel NemaFlex platform, can be used as an efficient workflow for identifying candidate compounds that can improve strength in the C. elegans muscular dystrophy model. Our study also lays the foundation for further probing of the mechanism of muscle function loss in dystrophin-deficient C. elegans, leading to knowledge translatable to human muscular dystrophy. This article has an associated First Person interview with the first author of the paper., Editor's choice: Dystrophin-deficient Caenorhabditis elegans have measurably weak muscle strength and mitochondrial dysfunction, and they respond to drug treatments standard in treating human Duchenne muscular dystrophy.

Long term spaceflight is associated with the loss of skeletal muscle mass and function. The Molecular Muscle Experiment (MME) seeks to identify the causes of muscle decline in space and test potential therapies to attenuate this in the microscopic worm,C. elegans. This is the first UK-led experiment in the almost two-decade history of the International Space Station. We therefore intend to complete significant and widespread educational outreach activities to promote interest in science, technology, engineering and maths (STEM), and to increase engagement with our space life science experiment. This paper describes three education outreach activities relating to our MME experiment that are suitable for use in the classroom, including: (i) observing normal and mutant worms; (ii) observing the effect of unloading (simulation of microgravity); and (iii) handling spaceflight hardware. Activity packs are provided at a ‘starter’ and ‘advanced’ level to support these activities. This paper also provides three posters that may be used as learning resources for educators that give information on: (i) why worms are used for research; (ii) spaceflight human physiology; and (iii) the specifics of our MME. Details of further planned engagement activities are outlined to increase the awareness of the MME.

The underlying mechanisms regulating the ability of skeletal muscle to regenerate after acute “damaging” eccentric or “non-damaging” concentric exercise in young human skeletal muscle is poorly defined. Age-related impairments in the regenerative mechanisms may contribute to the age-related loss of muscle mass and function, which has negative consequences for overall health and disease. Thus, the first aim of this thesis was to initially investigate multiple targeted mechanisms previously implicated in the regeneration process, over a comprehensive time-course following eccentric versus concentric exercise in young adults. Within this study it was found that post-exercise, in general, increased anabolic and repressed catabolic signalling preceded functional decline, whereas inflammation and ubiquitin proteasome system-related breakdown increased once functional recovery was initiated/achieved. Eccentric exercise led to greater anabolic signalling and inflammatory signalling response. As such, this study has provided a benchmark of muscle regeneration in young skeletal muscle, which implicates early anabolic and catabolic regulation in the rapid adaptation of muscle, whereas inflammation and ubiquitin proteasome system-related breakdown likely mediate longer term remodelling/adaptations, which may be greater following eccentric exercise. Using this benchmark, the aim of the second study was to identify age-related changes in targeted regenerative mechanisms. Concentric exercise did not cause a molecular regenerative response, whilst eccentric exercise induced anabolic signalling and satellite cell activation, prior to and at the nadir of force, respectively. Compared to the younger adults, ageing per se was associated with increased inflammation, whilst anabolic and catabolic signalling post-eccentric and concentric exercise was blunted. Interestingly, satellite cell activity was induced in the old only following eccentric exercise. These data suggest that eccentric exercise is potentially more advantageous for promoting muscle growth versus concentric exercise in older adults. Whilst, compared to the young, the old displayed blunted molecular responses which might underlie blunted muscle growth during ageing. Furthermore, the activation of satellite cells in the old might be the result of the impaired molecular mechanisms being suboptimal for repair thus, requiring additional regenerative means. In order to further characterise ageing muscle and the mechanisms of muscle regeneration, RNA sequencing was performed at the time of peak anabolic signalling to highlight more global and novel molecular networks. Ageing per se revealed genes involved in blood vessel development, plasma membrane and cell-cell junction expression were down-regulated, thus implicating these processes in age-related muscle loss. Following concentric exercise in older adults, there was an up-regulation of structural transcripts whilst there was a general down-regulation of genes related to metabolism, which might suggest impaired metabolism post-concentric exercise. Perhaps the blunted transcript responses contribute to the often observed age-related blunting of muscle mass adaptations in response to exercise training. Collectively, the data from this thesis has important implications for developing interventions for maximising hypertrophic responses and for counteracting the suboptimal regenerative responses observed in older adults.

18 p.-3 fig.-1 graph. abst., The European research community, via European Space Agency (ESA) spaceflight opportunities, has significantly contributed towards our current understanding of spaceflight biology. Recent molecular biology experiments include “omic” analysis, which provides a holistic and systems level understanding of the mechanisms underlying phenotypic adaptation. Despite vast interest in, and the immense quantity of biological information gained from space omics research, the knowledge of ESA-related space omics works as a collective remains poorly defined due to the recent exponential application of omics approaches in space and the limited search capabilities of pre-existing records. Thus, a review of such contributions is necessary to clarify and promote the development of space omics among ESA and ESA state members. To address this gap, in this review we: i) identified and summarised omics works led by European researchers, ii) geographically described these omics works, and iii) highlighted potential caveats in complex funding scenarios among ESA member states., All listed authors are members of the ESA Space Omics Topical Team, funded by the ESA grant/contract 4000131202/20/NL/PG/pt “Space Omics: Towards an integrated ESA/NASA –omics database for spaceflight and ground facilities experiments” awarded to RH, which was the main funding source for this work. Individual authors also acknowledge support from: the Medical Research Council part of a Skills Development Fellowship [grant number MR/T026014/1] awarded to CSD; the Spanish CAM TALENTO program project 2020-5A_BIO-19724 to MAFR; the Spanish Plan Estatal de Investigación Científica y Desarrollo Tecnológico Grant RTI2018-099309-B-I00 to FJM, the Swedish Research Council VR grant 2020-04864 to SG and the French Centre National d'Etudes Spatiales grant DAR 2020-4800001004, 2021-4800001117 to ECD. This research was also funded in part by the Wellcome Trust [110182/Z/15/Z] to KS.

6 p., The authors belong to the ESA Space Omics Topical Team funded by the ESA grant/contract 4000131202/20/NL/PG/pt “Space Omics: Towards an integrated ESA/NASA –omics database for spaceflight and ground facilities experiments” to RH.