Pulmonary disorders impact 40% to 80% of individuals with obesity. Respiratory muscle dysfunction is linked to these conditions; however, its pathophysiology remains largely undefined. Mice subjected to diet-induced obesity (DIO) develop diaphragmatic weakness. Increased intra-diaphragmatic adiposity and extracellular matrix (ECM) content correlate with reductions in contractile force. Thrombospondin-1 (THBS1) is an obesity-associated matricellular protein linked with muscular damage in genetic myopathies. THBS1 induces proliferation of fibro-adipogenic progenitors (FAPs) - mesenchymal cells that differentiate into adipocytes and fibroblasts. We hypothesized that THBS1 drives FAP-mediated diaphragm remodeling and contractile dysfunction in DIO. We tested this by comparing the effects of dietary challenge on diaphragms of wild-type (WT) and Thbs1 knockout (Thbs1-/-) mice. Bulk and single-cell transcriptomics demonstrated DIO-induced stromal expansion in WT diaphragms. Diaphragm FAPs displayed upregulation of ECM and TGF β-related expression signatures and augmentation of a Thy1-expressing sub-population previously linked to type 2 diabetes. Despite similar weight gain, Thbs1-/- mice were protected from these transcriptomic changes and from obesity-induced increases in diaphragm adiposity and ECM deposition. Unlike WT controls, Thbs1-/- diaphragms maintained normal contractile force and motion after DIO challenge. These findings establish THBS1 as a necessary mediator of diaphragm stromal remodeling and contractile dysfunction in overnutrition and a potential therapeutic target in obesity-associated respiratory dysfunction.

To assess malnutrition contribution to the functional status and health related quality of life after hospitalization due to COVID-19 pneumonia, 66 selected adults referred for physical rehabilitation accepted to participate in the study; none of them required oxygen supply or had history of lung/musculoskeletal/neurological/immune/rheumatic disease or trauma, or contraindication for respiratory-function tests. At three evaluations, with 3 months in-between, assessments included: self-report of functional status, the St. George\'s Respiratory Questionnaire, spirometry, the 6-min-walk-test, the MRC-scale, the 30-s sit-to-stand-test, the timed-up-and-go-test, nutritional status, and ultrasound imaging (vastus medialis and diaphragm). At referral, patients had nutritional deficits with protein deficiency, which gradually improved; while muscle thickness (of both vastus medialis and diaphragm) increased, along with muscle strength and mobility (ANOVA, p < 0.05). Contrarywise, the distance covered during the 6-min-walk-test decreased (ANOVA, p < 0.05), with a negative influence from excess body mass. During rehabilitation, health-related quality of life and functional status improved, with negative influence from a history of tobacco use and referral delay, respectively. After hospitalization due to COVID-19, early diagnosis of both protein deficiency and decrease of skeletal muscle thickness could be relevant for rehabilitation, while pondering the negative impact of excess body mass on submaximal exercise performance.

BACKGROUND: The phenotypic consequences of the p.Arg577Ter variant in the α-actinin-3 (ACTN3) gene are suggestive of a trade-off between performance traits for speed and endurance sports. Although there is a consistent association of the c.1729C allele (aka R allele) with strength/power traits, there is still a debate on whether the null allele (c.1729T allele; aka X allele) influences endurance performance. The present study aimed to test the association of the ACTN3 p.Arg577Ter variant with long-distance endurance athlete status, using previously published data with the Brazilian population.
METHODS: Genotypic data from 203 long-distance athletes and 1724 controls were analysed in a case-control approach.
RESULTS: The frequency of the X allele was significantly higher in long-distance athletes than in the control group (51.5% vs. 41.4%; p = 0.000095). The R/X and X/X genotypes were overrepresented in the athlete group. Individuals with the R/X genotype instead of the R/R genotype had a 1.6 increase in the odds of being a long-distance athlete (p = 0.012), whereas individuals with the X/X genotype instead of the R/R genotype had a 2.2 increase in the odds of being a long-distance athlete (p = 0.00017).
CONCLUSIONS: The X allele, mainly the X/X genotype, was associated with long-distance athlete status in Brazilians.

Despite over 30 years of microbiome and skeletal muscle research, no quantitative analysis of sarcopenia and the microbiome literature had been conducted. Our bibliometric study examined research status, hotspots, and future trends. We utilized bibliometric techniques to search the Science Citation Index Extended Database on February 27, 2023, using the Bibliometrix package in R to create a map displaying scientific production and subject categories. Collaborative network maps between countries/regions were visualized using Scimago Graphica, while VOSviewer explored collaboration modes among individuals and institutions. We analyzed the top 25 emerging keywords, top co-occurring keyword networks, and co-occurring keyword clusters using CiteSpace. A total of 997 articles were retrieved for sarcopenia and microbiome, of which 633 papers were analyzed. Both the number of publications and total citation frequency had been continuously increasing. The United States had the highest total citation frequency, while China had the highest number of publications. Research on the impact of the microbiome on sarcopenia was in its nascent stage and spans multiple disciplines, including nutrition, microbiology, geriatrics, immunology, endocrinology and metabolism, molecular biology, and sports medicine. The University of Copenhagen contributed the most to the number of publications (n=16), with Tibbett M (n=7) and Hulver MW (n=7) among the top authors. The most published journal was \"Nutrients\" (n=24). Analysis of keywords and clusters revealed new research hotspots in microbes and sarcopenia, such as malnutrition, dietary fiber, signaling pathways, frailty, and intestinal permeability. Research on the impact of the microbiome on sarcopenia is in its infancy and spans multiple disciplines. Malnutrition, dietary fiber, signaling pathways, frailty, and intestinal microbes are currently research hotspots. Furthermore, the visual atlas analysis of research on microbes and sarcopenia helps to track the knowledge structure in research fields related to sarcopenia and microbes, providing direction for future research.

UNASSIGNED: Skeletal muscle injury (SMI) is often treated conservatively, although it can lead to scar tissue formation, which impedes muscle function and increases muscle re-injury risk. However, effective interventions for SMIs are yet to be established.
UNASSIGNED: The administration of Silk Elastin® (SE), a novel artificial protein, to the SMI site can suppress scar formation and promote tissue repair.
UNASSIGNED: A controlled laboratory study.
UNASSIGNED: In vitro: Fibroblast migration ability was assessed using a scratch assay. SE solution was added to the culture medium, and the fibroblast migration ability was compared across different concentrations. In vivo: An SMI model was established with Sprague-Dawley rats, which were assigned to three groups based on the material injected to the SMI site: SE gel (SE group; n = 8), atelocollagen gel (Atelo group; n = 8), and phosphate buffer saline (PBS group; n = 8). Histological evaluations were performed at weeks 1 and 4 following the SMI induction. In the 1-week model, we detected the expression of transforming growth factor (TGF)-β1 in the stroma using immunohistological evaluation and real-time polymerase chain reaction analysis. In the 4-week model, we measured tibialis anterior muscle strength upon peroneal nerve stimulation as a functional assessment.
UNASSIGNED: In vitro: The fibroblast migration ability was suppressed by SE added at a concentration of 10⁴ μg/mL in the culture medium. In vivo: In the 1-week model, the SE group exhibited significantly lower TGFβ -1 expression than the PBS group. In the 4-week model, the SE group had a significantly larger regenerated muscle fiber diameter and smaller scar formation area ratio than the other two groups. Moreover, the SE group was superior to the other two groups in terms of regenerative muscle strength.
UNASSIGNED: Injection of SE gel to the SMI site may inhibit tissue scarring by reducing excessive fibroblast migration, thereby enhancing tissue repair.
UNASSIGNED: The findings of this study may contribute to the development of an early intervention method for SMIs.

It is well known that the adaptations of muscular antioxidant system to aerobic exercise depend on the frequency, intensity, duration, type of the exercise. Nonetheless, the timing of aerobic exercise, related to circadian rhythms or biological clock, may also affect the antioxidant defense system, but its impact remains uncertain. Bain and muscle ARNT-like 1 (BMAL1) is the core orchestrator of molecular clock, which can maintain cellular redox homeostasis by directly controlling the transcriptional activity of nuclear factor erythroid 2-related factor 2 (NRF2). So, our research objective was to evaluate the impacts of aerobic exercise training at various time points of the day on BMAL1 and NRF2-mediated antioxidant system in skeletal muscle. C57BL/6J mice were assigned to the control group, the group exercising at Zeitgeber Time 12 (ZT12), and the group exercising at ZT24. Control mice were not intervened, while ZT12 and ZT24 mice were trained for four weeks at the early and late time point of their active phase, respectively. We observed that the skeletal muscle of ZT12 mice exhibited higher total antioxidant capacity and lower reactive oxygen species compared to ZT24 mice. Furthermore, ZT12 mice improved the colocalization of BMAL1 with nucleus, the protein expression of BMAL1, NRF2, NAD(P)H quinone oxidoreductase 1, heme oxygenase 1, glutamate-cysteine ligase modifier subunit and glutathione reductase in comparison to those of ZT24 mice. In conclusion, the 4-week aerobic training performed at ZT12 is more effective for enhancing NRF2-mediated antioxidant responses of skeletal muscle, which may be attributed to the specific activation of BMAL1.

Skeletal muscle injury affects the quality of life in many pathologies, including volumetric muscle loss, contusion injury, and aging. We hypothesized that the nicotinamide phosphoribosyltransferase (Nampt) activator P7C3 improves muscle repair following injury. In the present study, we tested the effect of P7C3 (1-anilino-3-(3,6-dibromocarbazol-9-yl) propan-2-ol) on chemically induced muscle injury. Muscle injury was induced by injecting 50 µL 1.2% barium chloride (BaCl2) into the tibialis anterior (TA) muscle in C57Bl/6J wild-type male mice. Mice were then treated with either 10 mg/kg body weight of P7C3 or Vehicle intraperitoneally for 7 days and assessed for histological, biochemical, and molecular changes. In the present study, we show that the acute BaCl2-induced TA muscle injury was robust and the P7C3-treated mice displayed a significant increase in the total number of myonuclei and blood vessels, and decreased serum CK activity compared with vehicle-treated mice. The specificity of P7C3 was evaluated using Nampt+/- mice, which did not display any significant difference in muscle repair capacity among treated groups. RNA-sequencing analysis of the injured TA muscles displayed 368 and 212 genes to be exclusively expressed in P7C3 and Veh-treated mice, respectively. There was an increase in the expression of genes involved in cellular processes, inflammatory response, angiogenesis, and muscle development in P7C3 versus Veh-treated mice. Conversely, there is a decrease in muscle structure and function, myeloid cell differentiation, glutathione, and oxidation-reduction, drug metabolism, and circadian rhythm signaling pathways. Chromatin immunoprecipitation-quantitative polymerase chain reaction (qPCR) and reverse transcription-qPCR analyses identified increased Pax7, Myf5, MyoD, and Myogenin expression in P7C3-treated mice. Increased histone lysine (H3K) methylation and acetylation were observed in P7C3-treated mice, with significant upregulation in inflammatory markers. Moreover, P7C3 treatment significantly increased the myotube fusion index in the BaCl2-injured human skeletal muscle in vitro. P7C3 also inhibited the lipopolysaccharide-induced inflammatory response and mitochondrial membrane potential of RAW 264.7 macrophage cells. Overall, we demonstrate that P7C3 activates muscle stem cells and enhances muscle injury repair with increased angiogenesis.

Microplastics (MPs) pose a significant threat to livestock health. Yet, the roles of polystyrene MPs (PS-MPs) on meat quality and skeletal muscle development in pigs have not been fully determined. To investigate the effect of PS-MPs on skeletal muscle, piglets were given diets supplementation with 0 mg/kg (CON group), 75 mg/kg (75 mg/kg PS-MPs group), and 150 mg/kg PS-MPs (150 mg/kg PS-MPs group), respectively. The results indicated that the average daily gain (ADG) of piglets in the 150 mg/kg PS-MPs group was significantly lower than that in the CON group. No significant differences were observed in the final body weight and ADG between the CON group and the 75 mg/kg PS-MPs group. Piglets in the 150 mg/kg PS-MPs group exhibited decreased meat redness index and type I muscle fiber density. Metabolomic analysis revealed that the contents of meat flavor compounds carnosine, beta-alanine, palmitic acid, and niacinamide in muscle were lower in the 150 mg/kg PS-MPs group than in the CON group. Additionally, piglets subjected to 150 mg/kg PS-MPs exhibited impaired muscle angiogenesis. Further analysis indicated that PS-MPs exposure up-regulated thrombospondin 1 (THBS1) expression by inhibiting THBS1 mRNA and protein degradation, thereby disrupting skeletal muscle angiogenesis. These findings indicate that PS-MPs exposure adversely affects meat quality and hinders skeletal muscle angiogenesis in pigs, providing deeper insights into the detrimental effects of PS-MPs on meat quality and skeletal muscle development.

Extracellular vesicles (EVs) have the potential to provide new insights into skeletal muscle (SM) physiology and pathophysiology. However, current isolation protocols often do not eliminate co-isolated components such as lipoproteins and RNA binding proteins that could confound outcomes and hinder downstream clinical translation. In this study, we validated an EV isolation protocol that combined size-exclusion chromatography (SEC) with ultrafiltration (UF) to increase sample throughput, scalability and purity, while providing the very first analysis of the effects of UF column choice and fraction window on EV recovery. C2C12 myotube conditioned medium was pre-concentrated using either Amicon® Ultra 15 or Vivaspin®20 100 KDa UF columns and processed by SEC (IZON, qEV 70 nm). The resulting thirty fractions obtained were individually analysed to identify an optimal fraction window for EV recovery. The EV marker TSG101 could be detected from fractions 5 to 14, while CD9 and Annexin A2 only up to fraction 6. ApoA1+ lipoprotein co-isolates were detected from fraction 6 onwards for both protocols. Strikingly, Amicon and Vivaspin UF concentration protocols led to qualitative and quantitative variations in EV marker profiles and purity. Eliminating lipoprotein co-isolation by reducing the SEC fraction window resulted in a net loss of particles, but increased measures of sample purity and had only a negligible impact on the presence of EV marker proteins. In conclusion, our study developed an effective UF+SEC protocol for the isolation of EVs based on sample purity (fractions 1-5) and total EV abundance (fractions 2-10). We provide evidence to demonstrate that the choice of UF column can affect the composition of the resulting EV preparation and needs to be considered when being applied in EV isolation studies in SM. The resulting protocols will be valuable in isolating highly pure EV preparations for applications in a range of therapeutic and diagnostic studies.

BACKGROUND: Computed Tomography (CT) has an underutilized potential for evaluating body composition in clinical settings. Often conducted with intravenous contrast (IVC), CT scans yield unused body composition data due to unclear effects on skeletal muscle area (SMA), skeletal muscle index (SMI), and muscle density (SMD).
OBJECTIVE: This study investigates whether weight-adjusted IVC influences SMA, SMI, and SMD differently in female and male compared to non-contrast abdominal CT. Additionally, the study explores associations between contrast and non-contrast assessed SMA, SMI, SMD, and demographic factors.
METHODS: A comparative observational retrospective study was conducted on Danish patients who underwent consecutive four-phased contrast-enhanced abdominal CT scans (non-contrast, arterial, venous, and late venous phases). Muscle measures were evaluated using validated semi-automated threshold-based software by three independent raters.
RESULTS: The study included 72 patients (51 male, 21 female) with a mean age of 59 (55, 62) years. Weight-adjusted IVC increased SMA by up to 3.28 cm2 (CI: 2.58, 3.98) corresponding to 2.4% (1.8, 2.9) in late venous phase compared to non-contrast CT. Analysis between sexes showed no difference in the effects of IVC on SMA and SMI between female and male. However, females exhibited a higher increase in SMD during the venous by a mean of 1.7 HU 0.9; 2.5) and late venous phases with a mean HU of 1.80 (1.0; 2.6) compared to males. Multivariate regression analysis indicated an association between the differences in SMD and sex during venous (-1.38 , 95%CI: - 2.48, -0.48) and late venous phases (-1.23, 95% CI: -2.27, -0.19) CONCLUSION: Weight-adjusted IVC leads to increased SMA, SMI, and SMD. While SMA and SMI differences were consistent across the sexes, females exhibited a significantly higher SMD increase than male in the venous and late venous phases. Further investigations are necessary to determine the applicability of SMD as a muscle quality proxy in IVC CT scans.