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Skeletal Muscles Do Not Compete for Growth: Activating Additional Muscle Mass Does Not Compromise Changes in Muscle Size.

Kataoka, R, Yamada, Y, Hammert, WB, Sallberg, RW, Kang, A, Song, JS, Kassiano, W, Metcalf, EE, and Loenneke, JP. Skeletal muscles do not compete for growth: Activating additional muscle mass does not compromise changes in muscle size. J Strength Cond Res 40(9): 1043-1049, 2026-This study investigated whether the magnitude of muscle size and strength differed based on the amount of muscle recruited during training sessions. One hundred five untrained individuals were randomly assigned to 1 of 3 groups: low-load unilateral elbow flexion exercise (a) to failure (LL-Failure, n = 36), (b) to failure and low-load knee extension exercise to failure (LL-Failure + Legs, n = 33), or (c) a time-matched nonexercise control (CON, n = 36). Training groups completed 18 supervised sessions over 6 weeks (2 sets at 30% 1 repetition maximum [1RM] to failure). LL-Failure + Legs group performed 4 additional sets of knee extension exercise in each leg (20-30 RM). Muscle thickness on the anterior upper arm (60 and 70% sites) and elbow flexor 1RM strength of the trained arm were measured at pretesting and posttesting. Changes were compared using the ANCOVA function of Bayes Factors for Informative Hypotheses (prevalues as the covariate). Specific hypotheses were evaluated by comparing Bayes factors and the posterior probabilities between models. Six weeks of training led to increases in muscle size and strength. However, performing additional leg exercise did not attenuate the muscle growth in the anterior upper arm (0.19 cm) compared with performing only arm exercise to failure (0.18 cm). Changes in 1RM strength also did not differ between training groups (0.32 and 0.25 kg for LL-Failure and LL-Failure + Legs, respectively). Overall, there was no evidence for competition of adaptations in muscle size and strength under uncontrolled nutritional conditions. Whether greater training volume or limited nutrient intake induces a competition for resources warrants further investigation.

Humans

Responsiveness of muscle mass gain to different load intensities of resistance training in older women: A randomized crossover study.

BACKGROUND: Aging is associated with progressive declines in skeletal muscle mass (SMM) and substantial interindividual variability in adaptations to resistance training (RT). However, whether training load intensity influences hypertrophic responsiveness in older adults remains unclear. OBJECTIVE: To investigate the effects of two commonly prescribed RT loading schemes (15RM and 10RM) on estimated SMM adaptations and responsiveness in older women. METHODS: Twenty-seven older women (67.7 ± 4.9 years; 65.7 ± 10.6 kg; 154.5 ± 5.8 cm) completed two 8-week RT interventions performed at 15RM and 10RM in a randomized crossover design, separated by a 12-week detraining period. Estimated SMM was assessed using dual-energy X-ray absorptiometry. Responsiveness was operationally defined using the standard error of measurement, and participants were classified as responders (RP) or non-responders (N-RP) according to changes in estimated SMM. RESULTS: Both loading schemes promoted significant and comparable increases in estimated SMM (15RM: +0.62 ± 0.4 kg vs. 10RM: +0.43 ± 0.3 kg). Overall, 61.1% of participants were classified as responders in at least one condition, whereas 38.9% were classified as non-responders. Responsiveness status was consistent across conditions for most participants, with 48.1% classified as responders under both loading schemes and 25.9% as non-responders under both conditions. Only seven participants (25.9%) changed responsiveness status between interventions. No clear pattern indicated a greater likelihood of responsiveness with either loading scheme. CONCLUSIONS: Results suggest that both the 10RM and 15RM RT protocols significantly increase estimated SMM in older women, with no significant differences between training conditions. Although substantial interindividual variability in adaptive responses exists, training load intensity does not appear to meaningfully influence responsiveness status in most individuals. These findings suggest that both loading schemes can be effectively prescribed to promote SMM gains in older women.

Aged

Effects of blood flow restriction training combined with resistance training on lower-limb strength and sport-specific performance in athletes: a systematic review and meta-analysis.

BACKGROUND: In contemporary sports science, athletes and coaches continuously explore strategies to reduce training load and injury risk while increasing muscular strength and sport-specific performance. This meta-analysis evaluated the effects of blood flow restriction training (BFRT) combined with resistance training (RT) on lower-limb muscle strength and sport-specific performance in athletes. METHODS: Relevant randomized controlled trials (RCTs) were systematically searched across major databases (e.g. PubMed, Web of Science, Cochrane, CNKI, Wanfang Data, and Embase) from inception until November 2024. Two independent reviewers carefully assessed the studies. Data analysis was carried out using RevMan 5.4 software, which included heterogeneity testing, meta-analysis, subgroup analysis, and assessment of publication bias. RESULTS: Ten RCTs (181 athletes; 91 in the BFRT and RT group, 90 in the control group) were included. Outcomes determined BFRT combined with RT yielded notable enhancements in lower-limb muscle strength (SMD = 1.09, 95% CI [0.52, 1.66], p&#x2009;<&#x2009;0.05) and muscle hypertrophy (MD = 1.09, 95% CI [0.10, 2.09], p&#x2009;<&#x2009;0.05) compared to control training. However, no significant improvement in sport-specific performance was found (SMD = 0.11, 95% CI [-0.18, 0.40], p&#x2009;=&#x2009;0.46). Substantial heterogeneity was observed for strength outcomes (I2 = 75%), whereas low heterogeneity was observed for sport-specific performance and hypertrophy outcomes (I2 = 0%). No evidence of significant publication bias was detected. CONCLUSION: BFRT combined with RT appears to provide effective augmentation of lower-limb muscle strength and hypertrophy in athletes compared to RT or conventional training alone. It may be prudent to integrate this approach systematically into training cycles to optimize physiological muscle stimulation and training outcomes, despite not directly improving sport-specific performance.

Humans

Effects of Blood Flow Restriction Training at Different Levels of Arterial Occlusion Pressure on Body Composition and Athletic Performance in Youth Soccer Players: A Randomized Controlled Trial.

This study aimed to investigate the effects of low-load blood flow restriction training (BFRT) performed at different levels of arterial occlusion pressure (AOP) on body composition, maximal strength, and athletic performance in youth soccer players. Twenty-four male youth soccer players were randomly assigned to 40% AOP group, 60% AOP group, or control group. Participants in the BFRT groups performed lower-limb resistance training at 30% of one-repetition maximum (1RM) under the corresponding pressure conditions, whereas the control group trained without BFR. Training was conducted three times per week for six weeks. Body composition, back squat 1RM, countermovement jump (CMJ), T-test, and 30-m sprint performance were assessed before and after the intervention. Results showed that lower-limb muscle mass increased significantly in both the 40% AOP group (mean change = 0.55 kg, 95% CI: 0.13 to 0.97 kg, P = 0.010) and the 60% AOP group (mean change = 0.83 kg, 95% CI: 0.37 to 1.29 kg, P < 0.001), with the 60% AOP group showing significantly greater gains than the control group (between-group difference = 1.48 kg, 95% CI: 0.40 to 2.56 kg, P = 0.008). Back squat 1RM improved significantly in both the 40% AOP group (mean change = 6.50 kg, 95% CI: 3.90 to 9.10 kg, P < 0.001) and the 60% AOP group (mean change = 9.25 kg, 95% CI: 6.75 to 11.75 kg, P < 0.001), with the 60% AOP group demonstrating superior strength gains compared with the 40% AOP group (between-group difference = 2.94 kg, 95% CI: 0.20 to 5.68 kg, P = 0.048). CMJ height and T-test performance improved significantly in both the 40% AOP group (CMJ: mean change = 2.07 cm, 95% CI: 0.80 to 3.34 cm, P = 0.002; T-test: mean change = -0.23 s, 95% CI: -0.35 to -0.11 s, P = 0.001) and the 60% AOP group (CMJ: mean change = 2.65 cm, 95% CI: 1.00 to 4.30 cm, P = 0.003; T-test: mean change = -0.26 s, 95% CI: -0.38 to -0.14 s, P < 0.001), with no significant differences between the two BFRT groups (all P > 0.05). No significant changes were observed in 30-m sprint performance across groups (all P > 0.05). This study showed that six weeks of low-load (30% 1RM) blood flow restriction training performed at both 40% and 60% AOP was associated with improvements in lower-limb muscle mass, squat strength, and selected aspects of athletic performance in youth soccer players, compared with low-load training without BFR. While both pressure levels elicited comparable improvements in CMJ and agility performance, training at 60% AOP was associated with greater adaptations in lower-limb muscle mass and squat strength, with no additional benefits observed for 30-m sprint performance.

Humans

Left ventricular hypertrophy in hypertension: a systematic review and meta-analysis of echocardiographic studies published from 2011 to 2025.

AIM: An updated meta-analysis targeting the prevalence of left ventricular hypertrophy (LVH), a cardinal marker of hypertensive heart disease (HHD), over the last 15&#x200a;years is lacking. Thus, we analyzed the literature in order to provide a comprehensive information on LVH prevalence, as assessed by echocardiography, in the hypertensive setting. METHODS: The PubMed, OVID-MEDLINE, and Cochrane Library databases were analyzed to search English-language articles published from 1 January 2011 up to 31 December 2025. Studies were identified by using MeSH terms and crossing the following search items: 'left ventricular hypertrophy', 'left ventricular mass', 'hypertensive heart disease', 'echocardiography', 'hypertension', and 'subclinical cardiac damage'. RESULTS: A total of 51 studies including 74&#x200a;632 hypertensive patients were considered. Overall, the prevalence of LVH in the pooled cohort, defined according to criteria recommended by echocardiographic guidelines, was 36.6% (95% CI: 33.4-40%). Data provided by 18 studies ( n &#x200a;=&#x200a;40&#x200a;108 patients) showed that the probability of having LVH was lower in men than in women (OR&#x200a;=&#x200a;0.62, CI: 0.48-0.80, P &#x200a;<&#x200a;0.0001). Among patients with LVH (17 studies), the risk of concentric LVH was almost twice as high as eccentric (OR&#x200a;=&#x200a;1.94, CI: 1.52-2.49, P &#x200a;<&#x200a;0.0001). CONCLUSION: Our meta-analysis suggests that the high contemporary prevalence of LVH reflects the failure of therapeutic strategies worldwide in the prevention and treatment of HHD. From a clinical perspective, these data imply the need for a more aggressive treatment of hypertension and related cardiovascular risk factors leading to LVH, especially in women.

Humans

Colchicine attenuates cardiac hypertrophy by targeting the macrophage-driven Interleukin-6 suppression.

Hypertrophic cardiomyopathy (HCM), the most prevalent inherited cardiovascular disease, is strongly linked to progressive heart failure and sudden cardiac death (SCD). However, its underlying pathogenic mechanisms remain incompletely understood, and effective therapeutic strategies are still lacking. Here, we established two murine HCM models harboring high SCD risk-associated mutations. Single-cell RNA sequencing revealed immune activation and enhanced fibrotic remodeling in the myocardium of these models. Therefore, we hypothesized that colchicine, a widely used anti-inflammatory drug known to reduce cardiovascular events in multiple cardiac disorders, may also represent a promising therapeutic candidate for HCM. As we expected, colchicine treatment attenuated pathological remodeling in our study, as evidenced by reduced cardiomyocyte hypertrophy, decreased fibrosis, and downregulation of cardiac stress markers (Anp, Bnp) and fibrotic mediators (Ctgf, Col1a1, Col3a1). In addition, colchicine attenuated pro-inflammatory macrophage populations and suppressed IL-6 expression, thereby contributing to the preservation of cardiac function. These findings provide the first preclinical evidence that colchicine alleviates myocardial inflammation and fibrosis in HCM, underscoring its potential as a novel therapeutic strategy to reduce fibrosis, lower SCD risk, and improve patient outcomes.

Animals

Evidence-based insights into medial pedicle reduction mammaplasty: A systematic review and meta-analysis.

BACKGROUND: Breast reduction relieves the physical and psychosocial burden of macromastia. Medial pedicle reduction mammaplasty may enhance vascular reliability, preserve nipple-areola complex (NAC) sensation, and sustain upper pole fullness, even in large-volume reductions. The purpose of this study was to assess the outcomes of medial pedicle breast reduction. METHODS: A search across ScienceDirect, Cochrane, and PubMed was conducted. Included studies reported on perioperative outcomes and complications of medial pedicle breast reduction. Data on demographics, surgical variables, complications, sensory recovery, volumetric changes, and patient satisfaction were extracted. Proportion meta-analysis was performed, and odds ratios were calculated for comparison with inferior pedicle breast reduction. RESULTS: Twenty-five studies comprising 1033 patients met the inclusion criteria. Mean BMI ranged from 27 to 42&#xa0;kg/m2, with mean resection weights between 412 and 3828&#xa0;g. Mean surgical times ranged from 104 to 204&#xa0;min. Pooled complication rates were low: infection 1%, seroma 1%, hematoma 1%, fat necrosis 2%, NAC necrosis 1%, dehiscence 8%, and reintervention 5%. Odds of complications did not differ significantly from inferior pedicle reductions. NAC sensation typically recovered by 6-12 months, with no long-term deficits. Volumetric analyses demonstrated stable breast shape after the first postoperative year, with superior upper pole tissue maintained. Patient satisfaction ranged 75-100%, with higher ratings for scar appearance and overall aesthetics in medial pedicle reductions. CONCLUSION: Medial pedicle breast reduction is a well-established and reproducible technique, preserving NAC sensation, achieving stable long-term shape, and enhancing upper pole fullness. It offers satisfactory aesthetic outcomes compared to other traditional methods, even in large-volume reductions.

Humans

Estimated prevalence and distribution of causes of immune-mediated hypertrophic pachymeningitis in S&#xe3;o Paulo, Brazil.

BACKGROUND: The prevalence of hypertrophic pachymeningitis (HP) remains poorly defined worldwide. In Japan, the estimated prevalence is 0.949 cases per 100,000 inhabitants, with most cases related to ANCA-associated vasculitis or IgG4-related disease. In contrast, epidemiological data from other regions, including Latin America, are scarce. METHODS: This study was conducted at a tertiary referral center in the city of S&#xe3;o Paulo, Brazil. The prevalence of HP was estimated by comparison with the known prevalence of multiple sclerosis (MS), based on the number of patients with each condition followed at our institution. The etiological distribution of HP was also analyzed. In addition, HP prevalence was compared with that of tuberculous meningoencephalitis, a compulsory notifiable disease and a well-established cause of chronic meningitis in Brazil, using data from the national surveillance system (SINAN). RESULTS: We identified 55 patients with HP: 36 (65%) idiopathic, 10 (18%) IgG4-related disease, 4 (7%) ANCA-associated pachymeningitis, 4 (7%) probable or definite neurosarcoidosis, and 1 (2%) secondary to rheumatoid arthritis. Among 968 registered MS patients and assuming an MS prevalence of 15 per 100,000 inhabitants in S&#xe3;o Paulo, the estimated HP prevalence was 0.85 per 100,000 inhabitants. This estimate was comparable to the prevalence of tuberculous meningoencephalitis in the same region. CONCLUSION: The estimated prevalence of HP in S&#xe3;o Paulo (0.85 per 100,000) is consistent with reports from other regions and is comparable to that of tuberculous meningeal disease, although with a distinct etiological profile. IgG4-related disease was the most frequent systemic association, differing from previous reports. ANCA-associated HP appears to be less frequent than in other geographic regions, possibly reflecting differences in disease phenotype. Key Points &#x2022; The estimated prevalence of HP in S&#xe3;o Paulo was 0.85 per 100,000 inhabitants. &#x2022; IgG4-related disease was the most common systemic disease identified among patients with HP. &#x2022; ANCA-associated HP was less common than reported in Asian and European cohorts. &#x2022; The prevalence of HP was comparable to that of tuberculous meningoencephalitis in S&#xe3;o Paulo.

Humans

Effects of exercise on muscle strength and characteristics in rheumatic diseases and sarcopenia: Protocol for the Care for Muscle (C4M) Study.

OBJECTIVE: Muscle weakness is prevalent in rheumatoid arthritis (RA), osteoarthritis (OA) and sarcopenia (SARC). Endurance exercises may improve mitochondrial function and oxidative capacity, while strength exercises are thought to stimulate myofibrillar protein synthesis. This study aims to compare the effects of strength and endurance exercise and explore the association between muscle characteristics and exercise outcomes in patients with RA, OA and SARC. We hypothesize that responses to endurance and strength exercises in patients with muscle weakness are influenced by intramuscular pathology including muscle morphology, mitochondrial function, and systemic inflammation, based on their disease pathology, potentially requiring personalized training schedules. METHODS: This two-arm, parallel-group exploratory trial will enroll 69 patients (23 RA, 23 OA, 23 SARC), randomized to endurance (n&#x2009;=&#x2009;35) or muscle strength exercises (n&#x2009;=&#x2009;34), using minimization to balance disease type and gender. The 8-week intervention includes two supervised sessions per week using a controlled cable pulley device (Reforter&#x2122;) and fitness equipment, plus one weekly home-based session. The primary outcome is isokinetic muscle strength (peak torque), measured with the Biodex system&#xae;. Secondary outcomes include muscle morphology, mitochondrial function, systemic inflammation and muscle endurance (by Biodex and 6 Minute Walk test). Muscle morphology will be assessed via 3D ultrasound imaging of the vastus lateralis. Mitochondrial function will be analyzed using high-resolution respirometry on muscle biopsies. Systemic inflammation will be measured using multiplex assays or ELISA on serum samples. DISCUSSION: This study will explore differential responses to muscle endurance and muscle strength exercises in patients with RA, OA, and SARC, offering novel insights into the molecular mechanisms of muscle weakness. The findings may help identify potential mechanisms underlying variability in exercise response and provide effect size estimates to guide future confirmatory studies and more targeted exercise interventions. TRIAL REGISTRATION: ClinicalTrials.gov NCT06480643 (date of registration28-06-24).

Humans

Comparative effects of 12-week resistance training on unstable and stable surfaces on muscle stiffness, muscle co-activation, and balance in older patients with knee osteoarthritis.

OBJECTIVE: This randomized trial compared the effects of unstable resistance training (URT), involving resistance exercises on unstable surfaces, and stable resistance training (SRT), performed on stable surfaces, on muscle stiffness, co-activation, and balance in older adults with knee osteoarthritis (KOA). We hypothesized that URT would yield greater improvements by enhancing neuromuscular adaptability. METHODS: Fifty patients with KOA were randomly assigned to the URT group (n&#x202f;=&#x202f;25) or the SRT group (n&#x202f;=&#x202f;25). After attrition, 46 participants (URT: n&#x202f;=&#x202f;23; SRT: n&#x202f;=&#x202f;23) completed the intervention and were included in the final analysis. Both groups completed a 12-week supervised lower-limb resistance training program (3 sessions/week) consisting of 10 exercises performed under either unstable or stable support conditions. RESULTS: After 12 weeks of intervention, both groups showed significant reductions in pain intensity (p&#x202f;<&#x202f;0.001). However, compared with the SRT group, the URT group demonstrated significantly greater reductions in quadriceps stiffness (p&#x202f;<&#x202f;0.05), selected hamstring stiffness outcomes (p&#x202f;<&#x202f;0.05), and quadriceps-hamstring co-activation (p&#x202f;<&#x202f;0.001), alongside superior improvements in both dynamic balance and static balance (all p&#x202f;<&#x202f;0.05). CONCLUSION: While both training modalities are effective for pain relief, URT elicited greater improvements in balance-related performance and neuromuscular-mechanical outcomes than SRT in older adults with KOA. These findings suggest that incorporating unstable support conditions into resistance training may provide additional rehabilitation benefits for this population.

Humans

Muscular fiber properties and multi-omics investigation of larval and adult locomotor muscle in Microhyla fissipes.

During metamorphosis, Microhyla fissipes undergoes a critical transition from an aquatic to a terrestrial lifestyle, accompanied by significant remodeling of skeletal muscle. Notably, larval tail muscle degenerates, while adult hindlimb muscle develops. However, the molecular mechanisms that orchestrate these muscle type-specific adaptations to the changing environment remain unclear. In this study, histological observation, transcriptomics, and metabolomics were integrated to compare locomotor muscles from two stages: larval muscle from tail versus adult muscle from hindlimb. Our results revealed that adult muscle fibers exhibited reduced diameter and shorter sarcomere length compared to those of tadpoles. Transcriptomic analysis identified 4103 differentially expressed genes (DEGs), including 2182 up-regulated and 1921 down-regulated genes. Up-regulated genes were mainly involved in energy metabolism and cellular homeostasis pathways, including PPAR signaling and oxidative phosphorylation, whereas down-regulated genes were associated with carbohydrate metabolism and cell proliferation pathways, such as glycolysis/gluconeogenesis and PI3K-Akt signaling. Metabolic profiling indicated a metabolic shift from anaerobic to aerobic energy production, with 57 differential metabolites identified, mainly involved in protein metabolism and insulin-related pathways. Integrated multi-omics analysis further highlighted the AMPK and FoxO signaling pathways play key roles in this process. In conclusion, our findings demonstrate that the metabolic and structural differences between larval and adult skeletal muscles are mediated by AMPK- and FoxO-dependent signaling pathways, providing novel insights into the molecular mechanisms underlying adaptive development and locomotor transition in anuran amphibians.

Animals

Muscle mechanical and architectural adaptations in response to different endurance training modalities in older adults.

INTRODUCTION: This study examined the effects of various cycling endurance training modalities, matched for total workload, on muscle mechanical and architectural characteristics in older adults. METHODS: Fifty healthy participants (25 females, 59-79&#xa0;yrs) were randomly assigned to five age and sex matched groups: one control and four workload-matched training groups (moderate-intensity continuous, heavy-intensity continuous, high-intensity interval, and heavy-intensity continuous in eccentric cycling). Training consisted of three weekly sessions over 8&#xa0;weeks, with evaluations conducted at the beginning and end of the intervention with maximal voluntary isometric contractions at five different knee angles (90, 75, 60, 45, 30&#xb0;) and maximal concentric and eccentric isokinetic contractions at five different knee angular velocities (45, 90, 150, 210, 250&#xb0;/s). Maximum voluntary isometric torque (Tmax) and optimal knee angle (KAopt) were obtained from the isometric contractions; eccentric torque (Tecc) and maximum concentric knee angular velocity (Vmax) were obtained from the isokinetic contractions. The muscle architecture of vastus lateralis (VL) at rest (muscle thickness, pennation angle, and fascicle length) was investigated as well. RESULTS: No statistical differences were detected between groups or time points in VL architecture, in KAopt and in Vmax. A main effect of time was observed for Tmax (p&#xa0;<&#xa0;0.001, &#x3b7;2p&#xa0;=&#xa0;0.458) and Tecc (p&#xa0;=&#xa0;0.002, &#x3b7;2p&#xa0;=&#xa0;0.191) in all the investigated training groups. The within-group comparisons indicate significant increases in Tmax in the training groups, but not in the control group. CONCLUSIONS: Commonly applied endurance exercises improve muscle mechanical capacity (Tmax and Tecc) in older adults, with no structural (architectural) muscle remodelling, when matched for workload.

Humans

Genome-wide characterisation of the myosin light chain gene family in Chinese perch (Siniperca chuatsi) and its expression patterns in muscle fibre types and injury response.

The Class II myosin light chain (myl) genes in Chinese perch (Siniperca chuatsi) have not yet been systematically characterised, and relationships with muscle fibre specification, development, and injury-associated remodelling remain unclear. In this study, fast and slow muscle fibres were initially distinguished using myofibrillar ATPase histochemistry. Subsequently, genome-wide mining identified 16 Class II myl genes, comprising eight essential and eight regulatory light-chain subunits. Their conserved-domain features, chromosomal distribution, phylogenetic relationships and expression profiles were analysed. Transcriptomic profiling showed that summed myl transcript abundance was higher in fast muscle than in slow muscle, accounting for 67.2% of the pooled myl transcript pool across the two muscle types (paired t-test, raw P&#xa0;=&#xa0;0.036). mylpfa, myl1 and mylz3 were the major fast-muscle-associated genes, whereas myl10, myl2b and myl13 were preferentially expressed in slow muscle at the transcript level. These patterns support these genes as candidate fibre-type-associated expression markers. Developmental profiling identified stage-associated myl expression patterns, including a possible expression shift between mylpfb and mylpfa. In the descriptive injury-repair time course (d0-d7), FPKM profiles indicated that fast-muscle-associated genes (mylpfa, mylz3 and myl1) were lower at d1 and recovered by d3, whereas several slow-muscle-associated genes showed biphasic transcript-level increases. The slow-muscle-associated RLC gene mylpfb showed a delayed expression peak at d7. Notably, the embryonic isoform myl6l showed a modest increase from approximately 2 FPKM at d0 to 4-5 FPKM after injury, suggesting a possible injury-associated expression pattern that requires further validation. Together, these findings provide a genome-wide description of the Chinese perch myl gene family and identify candidate fibre-type-associated genes and descriptive injury-associated isoform expression patterns.

Animals

Intestinal content accelerates muscle protein degradation in red shrimp (Solenocera crassicornis) during refrigeration: Insights from metagenomics and metabolomics.

This study systematically explored the effects of intestinal components on muscle quality deterioration and protein degradation of red shrimp during refrigerated storage. The results demonstrated that refrigeration induced continuous quality degradation and muscle protein breakdown in red shrimp, whereas eliminating intestinal tissues effectively retarded muscle spoilage and protein degradation, and optimized muscle texture. The intestinal microorganisms could secrete extracellular proteases to promote muscle protein degradation were primarily Vibrio, Bacillus, Pseudomonas, Photobacterium, and Shewanella. These microorganisms promote protein degradation by secreting zinc proteases, serine proteases, and aspartyl proteases. This study elucidates the molecular mechanisms of intestinal microbial metabolism influences the muscle protein degradation of red shrimp during refrigeration. The findings provide a theoretical foundation for precise regulation of intestinal-targeted microorganisms, thereby maintaining optimal quality of shrimps during refrigeration.

Animals

Effects of rumen fluid transplantation on longissimus dorsi muscle development in Xizang sheep: An association analysis based on transcriptomic and serum metabolomic profiles.

This study aimed to investigate the effects of rumen fluid transplantation (RFT) on the growth and development of the longissimus dorsi muscle in female Xizang sheep. After RFT, muscle lightness differed significantly between the two groups, with the LDC group showing significantly higher lightness than the LDT group. In contrast, no significant differences were observed between groups in other muscle phenotypic traits, including drip loss, pH, cooking loss, shear force, redness, and yellowness. Antioxidant-related indices (SOD, GSH-PX, MDA, CAT, and T-AOC) also showed no significant differences between groups. Histological analysis revealed that muscle fiber length, width, and density were significantly greater in the experimental group than in the control group. Transcriptomic analysis identified 515 differentially expressed genes (DEGs), of which 419 were downregulated. KEGG analysis indicated that genes involved in muscle development-related pathways, such as cell adhesion and the PI3K-Akt signaling pathway, were predominantly downregulated. Key serum metabolites (L-kynurenine, IPA, allantoin, and propionylcarnitine) showed highly significant positive correlations with muscle fiber growth indices. In contrast, metabolites such as l-carnitine, acetylcarnitine, and citrulline were negatively correlated with muscle fiber growth, but positively correlated with the expression of muscle structure-related genes (COL11A1 and EFNA5) and with meat lightness. Overall, this study provides new insights into the potential molecular basis by which RFT influences muscle growth and development. However, the mechanisms by which RFT affects muscle development and meat quality-related traits remain unclear and warrant further investigation.

Animals

Comparative transcriptome analysis reveals ncRNA-mediated regulatory networks associated with muscle crispiness in grass carp.

Non-coding RNAs (ncRNAs) have been demonstrated to be involved in muscle development and to function as key regulators. However, the molecular mechanism underlying muscle crispiness in grass carp (GC) remains poorly understood, and whether these ncRNAs are involved in its regulation is still unknown. In the current investigation, differentially expressed (DE) RNAs (including lncRNAs, circRNAs, miRNAs, and mRNAs) were identified; concomitantly, target genes prediction was conducted, and functional and signaling pathway enrichment analyses were performed. Pathways related to muscle crispiness were identified, and the competitive endogenous RNA (ceRNA) (lncRNA/circRNA-miRNA-mRNA) regulatory network was further constructed. The results showed that a total of 126 DE-lncRNAs, 17 DE-circRNAs, 329 DE-miRNAs, and 442 DE-mRNAs were identified in muscle tissues of both the GC and crisp grass carp (CGC). GO and KEGG enrichment analyses revealed that target genes of DE-ncRNAs were significantly enriched in signaling pathways, including structural constituents of muscle, apoptosis, oxidative phosphorylation, and regulation of actin cytoskeleton, suggesting that these pathways may be involved in muscle texture remodeling. Subsequently, DE-RNAs enriched in related pathways were identified, and a core ceRNA regulation network comprising 3 lncRNAs, 4 circRNAs, 3 miRNAs, and 17 mRNAs was constructed. Additionally, 10 DE-RNAs from randomly selected groups were validated by qRT-PCR. Our findings not only provide scientific evidence elucidating the molecular mechanisms underlying muscle crispiness in GC but also establish a foundation for studying changes in muscle textural qualities across other fish species.

Animals

Comprehensive multi-post-translational modifications profiling reveals age-associated remodeling in skeletal muscle.

Sarcopenia, characterized by the progressive loss of skeletal muscle mass and function, is a major hallmark of aging. Post-translational modifications (PTMs) play essential roles in regulating protein activity and cellular homeostasis; however, how multiple PTMs are remodeled during skeletal muscle aging remains incompletely characterized. Here, we performed comprehensive multi-layered proteomic profiling of skeletal muscle from young (3-month-old) and aged (24-month-old) mice, systematically quantifying the global proteome together with five major PTMs: acetylation, phosphorylation, N-glycosylation, O-glycosylation, and ubiquitination. In total, we identified 5 337 proteins and mapped thousands of PTM sites, generating an integrated atlas of age-associated proteomic and PTM remodeling in skeletal muscle. Pathway enrichment analyses revealed distinct modification-specific patterns: acetylation and phosphorylation were predominantly associated with metabolic and mitochondrial-related pathways; N-glycosylation was enriched in immune- and secretory pathway-related processes; O-glycosylation was associated with muscle contraction-related pathways; and ubiquitination was preferentially linked to cytoskeletal organization in muscle cells. Correlation analyses further uncovered diverse association patterns among different PTMs across protein- and modification-level datasets. Phosphorylation and ubiquitination exhibited consistent positive associations, whereas acetylation and ubiquitination showed both inverse and concordant co-variation patterns across subsets of proteins. Phosphorylation and O-glycosylation displayed heterogeneous association patterns across different proteins, and acetylation and phosphorylation demonstrated positive correlations with distinct age-associated directional changes across protein subsets. Together, these results provide a comprehensive, multi-dimensional view of age-associated remodeling of the skeletal muscle proteome and multiple PTM layers, offering a valuable resource for understanding molecular alterations accompanying muscle aging and sarcopenia.

Animals

Transcriptomic insights into temperature regulation of proliferation and differentiation in skeletal muscle cells of Nibea albiflora.

Myogenesis involves sequential stages of muscle satellite cell activation, myoblast proliferation, differentiation, and fusion into multinucleated myotubes. Teleost muscle exhibits indeterminate growth and is highly sensitive to environmental temperature, yet the underlying mechanisms by which temperature regulate proliferation and differentiation remain poorly understood. In this study, we established a primary skeletal muscle cell culture from the yellow drum (Nibea albiflora), an economically important marine fish, and integrated morphological observations with comparative transcriptomics analysis to characterize cellular and molecular responses at 28&#xa0;&#xb0;C and 20&#xa0;&#xb0;C during both proliferation and differentiation stages. Phenotypic analysis revealed that 28&#xa0;&#xb0;C significantly enhanced both myoblast proliferation and myogenic differentiation ability compared with 20&#xa0;&#xb0;C. Transcriptomic profiling revealed that at 28&#xa0;&#xb0;C, differentiation upregulated extracellular matrix(ECM) organization, calcium signaling, and sarcomere assembly, while proliferation enhanced focal adhesion, growth factor signaling, and lipid metabolism. At 20&#xa0;&#xb0;C, differentiation was characterized by glutathione metabolism, and ferroptosis, while proliferation involved cytokine-cytokine receptor interaction and negative regulation of signal transduction. Core myogenic regulatory factors (MRFs), particularly myogenin, were strongly upregulated at 28&#xa0;&#xb0;C during the differentiation stage, serving as an internal control. Based on these findings, we propose a testable model that elevated temperature coordinates Ca2+-dependent MRF activation with ECM-integrin signaling to drive sarcomere assembly and muscle growth. Key differentially expressed genes (DEGs) regulating myogenesis in N. albiflora were also identified. This study provides a mechanistic framework for temperature adaptation in teleost skeletal muscle and identifies candidate genes for functional validation and marker-assisted selection, as well as a rationale for temperature management strategies to improve aquaculture yield of N. albiflora.

Animals