Skeletal Muscle In Response Research Articles

The effect of body position on cardiovascular, skeletal muscle and ventilatory responses to submaximal cycling.

The completion of exercise in different body positions can impact the function of various components of the oxygen delivery pathway; however, the effect of the haemodynamic conditions induced by a semi-upright body position on the integrative physiological response to exercise is poorly understood. The purpose of this study was to explore the effect of a semi-upright body position on cardiac output (CO), vastus lateralis oxygen saturation ( ), oxygen consumption ( ) and ratings of perceived exertion (Borg RPE) during submaximal cycling. Twenty healthy individuals (22±3 years, 50% female) each completed alternating 5-min bouts of submaximal upright and semi-upright (40° incline) cycling at 50 and 100W. CO, , and RPE were assessed at rest and at each exercise intensity during steady state. There was a main effect of intensity on the increase in CO, , and RPE (all P<0.001). In a semi-upright position, the increase in CO (7.9±2.8vs. 6.4±2.6L/min, P<0.001), RPE (median (interquartile range): 11 (9-13)vs. 10 (8-12), P=0.013) and the decrease in (-38±23vs. -21%±18%, P<0.001) were greater than upright, while the increase in was attenuated (1.030±0.130vs. 1.154±0.165L/min, P<0.001). These results suggest that while a semi-upright body position produces elevations in CO, these elevations do not seem to perfuse the active skeletal muscle. This may explain the elevation in RPE despite a blunting in the increase in . Further work is required to understand the effects of a semi-upright exercise position on skeletal muscle activation and lower limb blood flow.

Circadian Rhythms, Feeding Patterns, and Metabolic Regulation: Implications for Critical Care.

Endogenous biological rhythms synchronise human physiology with daily cycles of light-dark, wake-sleep, feeding-fasting. Proper circadian alignment is crucial for physiological function, reflected in the rhythmic expression of molecular clock genes in various tissues, especially in skeletal muscle. Circadian disruption, such as misaligned feeding, dysregulates metabolism and increases the risk of metabolic disorders like type 2 diabetes. Such disturbances are common in critically ill patients, especially those who rely on enteral nutrition. Whilst continuous provision of enteral nutrition is currently the most common practice in ciritical care, this is largely dictated by convenience rather than evidence. Conversely, some findings indicate that that intermittent provision of enteral nutrition aligned with daylight may better support physiological functions and improve clinical/metabolic outcomes. However, there is a critical need for studies of skeletal muscle responses to acutely divergent feeding patterns, in addition to complementary translational research to map tissue-level physiology to whole-body and clinical outcomes.

Muscle Tissue Response to Vipera berus berus and Vipera berus nikolskii Venoms: A Study on Matrix Metalloproteinases and Cytokine Modulation

Vipera berus, also known as the common adder, is a snake species widely distributed in Europe and parts of Asia. Its venom is a mix of enzymatic and non-enzymatic components causing both local and systemic effects including edema, hemorrhage, myonecrosis, gastrointestinal disorders, and rarely – rhabdomyolysis, coagulopathy and hypovolemic shock. Matrix metalloproteinases (MMPs) and cytokines, being inflammatory mediators, participate both in the development of these reactions and in tissue regeneration after acute damage. The current study was aimed at analyzing the concentrations of important mediators of tissue damage, inflammation and regeneration, namely, MMP-1, -2, -3, -8, -10, TIMP-1 (a tissue inhibitor of MMPs), and pro- and anti-inflammatory cytokines, in rat muscle after intraperitoneal injection of venoms from two subspecies of adders – V. berus berus and V. berus nikolskii — to clarify their role in the local response of skeletal muscle to the studied venoms. Changes in muscle tissue were revealed, namely, significant increase in almost all MMPs including MMP-2, as well as TIMP-1, IFN-γ and anti-inflammatory IL-4 and IL-10 content. Moreover, a tendency for some pro-inflammatory cytokines levels to decline 24 h after venom administration was observed, which may be a sign of inflammation suppression and the beginning of reparative processes associated with extracellular matrix remodeling and formation of an optimal environment for muscle regeneration. However, to establish the exact mechanisms of the changes we found, further studies are needed. The ability of V. berus nikolskii venom to induce more pronounced changes was also shown. Our results may be useful for the development of differentiated and more effective treatment strategies for the consequences of bites by these snakes, which include myonecrosis

Astragaloside IV Improves Muscle Atrophy by Modulating the Activity of UPS and ALP via Suppressing Oxidative Stress and Inflammation in Denervated Mice.

Peripheral nerve injury is common clinically and can lead to neuronal degeneration and atrophy and fibrosis of the target muscle. The molecular mechanisms of muscle atrophy induced by denervation are complex and not fully understood. Inflammation and oxidative stress play an important triggering role in denervated muscle atrophy. Astragaloside IV (ASIV), a monomeric compound purified from astragalus membranaceus, has antioxidant and anti-inflammatory properties. The aim of this study was to investigate the effect of ASIV on denervated muscle atrophy and its molecular mechanism, so as to provide a new potential therapeutic target for the prevention and treatment of denervated muscle atrophy. In this study, an ICR mouse model of muscle atrophy was generated through sciatic nerve dissection. We found that ASIV significantly inhibited the reduction of tibialis anterior muscle mass and muscle fiber cross-sectional area in denervated mice, reducing ROS and oxidative stress-related protein levels. Furthermore, ASIV inhibits the increase in inflammation-associated proteins and infiltration of inflammatory cells, protecting the denervated microvessels in skeletal muscle. We also found that ASIV reduced the expression levels of MAFbx, MuRF1 and FoxO3a, while decreasing the expression levels of autophagy-related proteins, it inhibited the activation of ubiquitin-proteasome and autophagy-lysosome hydrolysis systems and the slow-to-fast myofiber shift. Our results show that ASIV inhibits oxidative stress and inflammatory responses in skeletal muscle due to denervation, inhibits mitophagy and proteolysis, improves microvascular circulation and reverses the transition of muscle fiber types; Therefore, the process of skeletal muscle atrophy caused by denervation can be effectively delayed.

MG53 Protein-Mediated biomimetic nanotherapeutics for the treatment of acute myocardial infarction by driving the impaired plasma membrane resealing

Myocardial infarction (MI) remains a leading global cause of mortality. The frequent disruptions of cardiomyocyte plasma membranes underscore the pivotal role played by MG53, a tissue repair protein secreted by skeletal muscle in response to physical exercise, in cardioprotection. However, the clinical application of recombinant human MG53 (rhMG53) is challenged by its short circulation half-life, necessitating frequent administration, and its low cell membrane permeability. Here we introduce an innovative MG53 protein-mediated biomimetic nanotherapeutic (Rm@mSiO2@MG53) to address the poor delivery. Rm@mSiO2@MG53 nanotherapeutics, attributed to the high specific surface area and adjustable pore size of mSiO2 and the expression of CD47 on erythrocyte membranes, enable sustained protein delivery, enhance their ability to evade the mononuclear phagocytic system (MPS), and extend the half-life of rhMG53 proteins in circulation. In a mouse MI model, Rm@mSiO2@MG53 demonstrated superior efficacy in protecting injured cardiomyocytes and preserving heart function post-MI. Our findings developed a novel protein biomimetic nanotherapeutics that mediates heart repair by driving cell membrane resealing, offering the potential to expedite the clinical deployment of rhMG53 as a viable therapeutic for treating MI and other tissue injuries.

The combined influences of local heat application and resistance exercise on the acute mRNA response of skeletal muscle.

The development and maintenance of the skeletal muscle is crucial for the support of daily function. Heat, when applied locally, has shown substantial promise in the maintenance of the muscle. The purpose of this study was to determine the combined effects of local heat application and acute resistance exercise on gene expression associated with the human muscle growth program. Participants (n = 12, 26 ± 7years, 1.77 ± 0.07m, 79.6 ± 15.4kg, and 16.1 ± 11.6 %BF) completed an acute bilateral bout of resistance exercise consisting of leg press (11 ± 2 reps; 170 ± 37kg) and leg extension (11 ± 1 reps; 58 ± 18kg). Participants wore a thermal wrap containing circulating fluid (40°C, exercise + heat; EX + HT) during the entire experimental period and 4h post-exercise, while the other leg served as an exercise-only (EX) control. Biopsies of the vastus lateralis were collected (Pre, Post, and 4hPost) for gene expression analyses. Intramuscular temperatures increased (Post, +2.2°C ± 0.7°C, and p < 0.001; 4hPost, +2.5°C ± 0.6°C, and p < 0.001) and were greater in the EX + HT leg post-exercise (+0.35°C ± 0.3°C, and p = 0.005) and after 4hPost (+2.1°C ± 0.8°C and p < 0.001). MYO-D1 mRNA was greater in the EX + HT leg vs. the EX (fold change = 2.74 ± 0.42 vs. 1.70 ± 0.28, p = 0.037). No other genes demonstrated temperature sensitivity when comparing both legs (p > 0.05). mRNA associated with the negative regulator, myostatin (MSTN), decreased post-exercise (p = 0.001) and after 4h (p = 0.001). mRNA associated with proteolysis decreased post-exercise (FBXO32, p = 0.001; FOXO3a, p = 0.001) and after 4h (FBXO32, p = 0.001; FOXO3a, p = 0.027). The elevated transcription of the myogenic differentiation factor 1 (MYO-D1) after exercise in the heated condition may provide a mechanism by which muscle growth could be enhanced.

Adaptive responses of skeletal muscle to calcaneal tendon partial injury in rats: insights into remodeling and plasticity.

Skeletal muscle is a highly adaptive tissue, capable of responding to different physiological and functional demands, even in situations that may cause instability. To evaluate how partial calcaneal tendon (CT) injuries affect the remodeling and plasticity of the gastrocnemius muscle over time. The study was carried out with Wistar rats randomly divided into five groups. The control group comprised animals not subjected to partial CT damage. The remaining four groups were subjected to partial CT damage and were further categorized based on the time of euthanasia: 3, 14, 28, and 55 days after injury. The gastrocnemius muscle was collected and used for gene expression analysis, zymography, flow cytometry, and morphology. The calcaneal tendon was analyzed only to verify the presence of the partial injury. The impact of partial CT injury on the gastrocnemius homeostasis, particularly on gene expression, was more pronounced in the 3-day group compared to the other groups, especially the control group. Cytokine profile and morphologic alterations occurred in the 55 days group when compared to the other groups. The data reported here suggest that partial injury can negatively affect intracellular signaling and degradation pathways, disturbing the muscular extracellular matrix regulatory mechanisms and communication with the tendon. However, skeletal muscle seems to mitigate these harmful effects in comparison with lesions that affect muscle and tendon.

The MyoGravity project to study real microgravity effects on human muscle precursor cells and tissue

Microgravity (µG) experienced during space flights promotes adaptation in several astronauts’ organs and tissues, with skeletal muscles being the most affected. In response to reduced gravitational loading, muscles (especially, lower limb and antigravity muscles) undergo progressive mass loss and alteration in metabolism, myofiber size, and composition. Skeletal muscle precursor cells (MPCs), also known as satellite cells, are responsible for the growth and maintenance of muscle mass in adult life as well as for muscle regeneration following damage and may have a major role in µG-induced muscle wasting. Despite the great relevance for astronaut health, very few data are available about the effects of real µG on human muscles. Based on the MyoGravity project, this study aimed to analyze: (i) the cellular and transcriptional alterations induced by real µG in human MPCs (huMPCs) and (ii) the response of human skeletal muscle to normal gravitational loading after prolonged exposure to µG. We evaluated the transcriptomic changes induced by µG on board the International Space Station (ISS) in differentiating huMPCs isolated from Vastus lateralis muscle biopsies of a pre-flight astronaut and an age- and sex-matched volunteer, in comparison with the same cells cultured on the ground in standard gravity (1×g) conditions. We found that huMPCs differentiated under real µG conditions showed: (i) upregulation of genes related to cell adhesion, plasma membrane components, and ion transport; (ii) strong downregulation of genes related to the muscle contraction machinery and sarcomere organization; and (iii) downregulation of muscle-specific microRNAs (myomiRs). Moreover, we had the unique opportunity to analyze huMPCs and skeletal muscle tissue of the same astronaut before and 30 h after a long-duration space flight on board the ISS. Prolonged exposure to real µG strongly affected the biology and functionality of the astronaut’s satellite cells, which showed a dramatic reduction of responsiveness to activating stimuli and proliferation rate, morphological changes, and almost inability to fuse into myotubes. RNA-Seq analysis of post- vs. pre-flight muscle tissue showed that genes involved in muscle structure and remodeling are promptly activated after landing following a long-duration space mission. Conversely, genes involved in the myelination process or synapse and neuromuscular junction organization appeared downregulated. Although we have investigated only one astronaut, these results point to a prompt readaptation of the skeletal muscle mechanical components to the normal gravitational loading, but the inability to rapidly recover the physiological muscle myelination/innervation pattern after landing from a long-duration space flight. Together with the persistent functional deficit observed in the astronaut’s satellite cells after prolonged exposure to real µG, these results lead us to hypothesize that a condition of inefficient regeneration is likely to occur in the muscles of post-flight astronauts following damage.

78 Prolonged heat stress impact on molecular responses of skeletal muscle and growth performance in finishing beef steers

Abstract Rising temperatures significantly impact cattle production economically, reducing feed intake, efficiency, and growth, leading to substantial losses. Despite these known effects, there remains a paucity of data on the specific responses of skeletal muscle and adipose tissue to heat stress conditions. Therefore, this study aimed to elucidate the effects of prolonged heat stress on the molecular mechanisms of skeletal muscle growth and adipose tissue deposition and physiological response. Thirty-two predominantly Angus beef steers [initial average body weight (BW) = 364 ± 4.60 kg] were subject to a 28-d heat stress period. Steers were randomly allotted to one of two treatment groups (n = 16 steers/treatment) 1) Control (CON), exposed to outdoor environmental temperature-humidity index (THI) of 60; or 2) Heat Stress (HS), subject to THI of 70 to 80 for 8 h then returned to control treatment THI to simulate typical cooldown periods exhibited in instances of HS. Feed intakes were recorded daily, while BW was measured weekly prior to feed delivery. Biopsies of the skeletal muscle from the Longissimus muscle (LM) at the area of the 13th rib and adipose tissue from the subcutaneous fat of the flank region were performed on d 1, 14, and 28 for each individual steer and used for molecular analysis. For gene expression, a repeated measures ANOVA was utilized, acknowledging the individual animal as the experimental unit. The analysis of both gene expression over time and growth performance indicators was conducted using repeated measures ANOVA, with post-hoc analysis via Tukey’s test for specific comparisons. Data presentation includes the standard error of means, with an alpha (α) level set at 0.05 for determining statistical significance. Behavioral signs of heat stress, elevated respiratory rates, were observed with HS steers exhibiting a respiratory rate of 92.92 ± 24.79 breaths per minute (bpm) compared with 60.48 ± 14.94 bpm in CON steers (P &amp;lt; 0.01). Heat stress decreased average daily gain (ADG) during d 0 to 7 (49.11%) and d 15 to 21 (59.14%) compared with the control group (P &amp;lt; 0.01). Dry Matter Intake (DMI; P &amp;gt; 0.1) and feed efficiency (P &amp;gt; 0.1) were not altered in CON vs. HS steers. In skeletal muscle, on d 28 of exposure to heat stress, there was a significant overexpression of Heat Shock Protein (HSP) isoforms 20, 27, and 90 (P &amp;lt; 0.05) relative to the control group, accompanied by increased Myf5 (P &amp;lt; 0.05) gene expression. In adipose tissue, there was upregulation of PPARγ and SCD (P &amp;lt; 0.05), both of which are implicated with adipose tissue differentiation and lipid deposition process. Our findings indicated that HS modifies the expression of genes associated with skeletal muscle growth and adipose tissue deposition, concurrently impairing overall animal growth predominantly through reduced feed intake.

KLF3 impacts insulin sensitivity and glucose uptake in skeletal muscle.

Skeletal muscle is one of the predominant sites involved in glucose disposal, accounting for ∼80% of postprandial glucose uptake, and plays a critical role in maintaining glycemic homeostasis. Dysregulation of energy metabolism in skeletal muscle is involved in developing insulin resistance and type 2 diabetes (T2D). Transcriptomic responses of skeletal muscle to exercise found that the expression of Klf3 was increased in T2D Goto-Kakizaki (GK) rats and decreased after exercise with improved hyperglycemia and insulin resistance, implying that Klf3 might be associated with insulin sensitivity and glucose metabolism. We also found that knockdown of Klf3 promoted basal and insulin-stimulated glucose uptake in L6 myotubes, whereas overexpression of Klf3 resulted in the opposite. Through pairwise comparisons of L6 myotubes transcriptome, we identified 2,256 and 1,988 differentially expressed genes in Klf3 knockdown and overexpression groups, respectively. In insulin signaling, the expression of Slc2a4, Akt2, Insr, and Sorbs1 was significantly increased by Klf3 knockdown and decreased with Klf3 overexpression; Ptprf and Fasn were markedly downregulated in Klf3 reduced group and upregulated in Klf3 overexpressed group. Moreover, downregulation of Klf3 promoted the expression of glucose transporter 4 (GLUT4) and protein kinase B (AKT) proteins, as well as the translocation of GLUT4 to the cell membrane in the basal situation, and enhanced insulin sensitivity, characterized by increased insulin-stimulated GLUT4 translocation and AKT, TBC1 domain family member 1 (TBC1D1) and TBC1 domain family member 4 (TBC1D4) phosphorylation, whereas overexpression of Klf3 showed contrary results. These results suggest that Klf3 affects glucose uptake and insulin sensitivity via insulin signal transduction and intracellular metabolism, offering a novel potential treatment strategy for T2D.NEW & NOTEWORTHY The knockdown of Klf3 increased glucose uptake and improved insulin sensitivity in L6 myotubes, whereas its overexpression had the opposite effect. To explore the underlying mechanisms, we evaluated the transcriptional profiles of L6 myotubes after Klf3 knockdown and overexpression and revealed that metabolism and insulin-related pathways were significantly impacted. Klf3 also influenced the expression or modification of glucose transporter 4 (GLUT4), protein kinase B (AKT), TBC1 domain family member 1 (TBC1D1), and TBC1 domain family member 4 (TBC1D4)in the insulin signaling pathway, affecting insulin sensitivity and glucose uptake.

The kidney-skeletal muscle-heart axis in chronic kidney disease: implications for myokines.

Myokines are signalling moieties released by the skeletal muscle in response to acute and/or chronic exercise, which exert their beneficial or detrimental effects through paracrine and/or autocrine pathways on the own muscle and through endocrine pathways in many other organs (e.g. the heart). Interestingly, alterations in myokines have been described in patients with heart failure (HF) that are associated with adverse structural and functional left ventricular remodelling and poor cardiac outcomes. Recent experimental and clinical studies have shown that the muscle regulation of a number of myokines is altered in chronic kidney disease (CKD) thus representing a new molecular aspect of the pathophysiology of skeletal myopathy present in patients with CKD. Muscle dysregulation of myokines may contribute to a number of disorders in non-dialysis and dialysis patients with CKD, including the high risk of developing HF. This possibility would translate into a range of new diagnostic and therapeutic options. In fact, the measurement of circulating myokines opens their possible usefulness as biomarkers to personalize exercise training and pharmacological therapies for the prevetion and treatment of HF in patients with CKD and skeletal myopathy. This review will analyze information on some myokines that target the heart and are altered at the level of skeletal muscle and circulation in patients with CKD.

Irisin-Encapsulated Mitochondria-Targeted Biomimetic Nanotherapeutics for Alleviating Acute Kidney Injury.

Acute kidney injury (AKI) is the sudden decrease in renal function that can be attributed to dysregulated reactive oxygen species (ROS) production and impaired mitochondrial function. Irisin, a type I membrane protein secreted by skeletal muscles in response to physical activity, has been reported to alleviate kidney damage through regulation of mitochondrial biogenesis and oxidative metabolism. In this study, a macrophage membrane-coated metal-organic framework (MCM@MOF) is developed as a nanocarrier for encapsulating irisin to overcome the inherent characteristics of irisin, including a short circulation time, limited kidney-targeting ability, and low membrane permeability. The engineered irisin-mediated biomimetic nanotherapeutics have extended circulation time and enhanced targeting capability toward injured kidneys due to the preservation of macrophage membrane proteins. The irisin-encapsulated biomimetic nanotherapeutics effectively mitigate acute ischemia-reperfusion injury by protecting mitochondrial function and modulating SOD2 levels in renal tubular epithelial cells. The present study provides novel insights to advance the development of irisin as a potential therapeutic approach for AKI.

The role of interleukin-10 in mitigating endoplasmic reticulum stress in aged mice through exercise.

Although unfolded protein response (UPR) is essential for cellular protection, its prolonged activation may induce apoptosis, compromising cellular longevity. The aging process increases the endoplasmic reticulum (ER) stress in skeletal muscle. However, whether combined exercise can prevent age-induced ER stress in skeletal muscle remains unknown. Evidence suggests that ER stress may increase inflammation by counteracting the positive effects of interleukin-10 (IL-10), whereas its administration in cells inhibits ER stress and apoptosis. This study verified the effects of aging and combined exercise on physical performance, ER stress markers, and inflammation in the quadriceps of mice. Moreover, we verified the effects of IL-10 on ER stress markers. C57BL/6 mice were distributed into young (Y, 6 mo old), old sedentary (OS, sedentary, 24 mo old), and old trained group (OT, submitted to short-term combined exercise, 24 mo old). To clarify the role of IL-10 in UPR pathways, knockout mice lacking IL-10 were used. The OS mice presented worse physical performance and higher ER stress-related proteins, such as C/EBP homologous protein (CHOP) and phospho-eukaryotic translation initiation factor 2 alpha (p-eIF2α/eIF2α). The exercise protocol increased muscle strength and IL-10 protein levels in OT while inducing the downregulation of CHOP protein levels compared with OS. Furthermore, mice lacking IL-10 increased BiP, CHOP, and p-eIF2α/eIF2α protein levels, indicating this cytokine can regulate the ER stress response in skeletal muscle. Bioinformatics analysis showed that endurance and resistance training downregulated DNA damage inducible transcript 3 (DDIT3) and XBP1 gene expression in the vastus lateralis of older people, reinforcing our findings. Thus, combined exercise is a potential therapeutic intervention for promoting adjustments in ER stress markers in aged skeletal muscle.NEW & NOTEWORTHY Aging elevates endoplasmic reticulum (ER) stress in skeletal muscle, potentially heightening inflammation by opposing interleukin-10 (IL-10) effects. This study found that short-term combined exercise boosted strength and IL-10 protein levels while reducing CHOP protein levels in older mice. In addition, IL-10-deficient mice exhibited increased ER stress markers, highlighting IL-10's role in regulating ER stress in skeletal muscle. Consequently, combined exercise emerges as a therapeutic intervention to elevate IL-10 and adjust ER stress markers in aging.

Methylglyoxal reduces resistance exercise-induced protein synthesis and anabolic signaling in rat tibialis anterior muscle.

Resistance exercise provides significant benefits to skeletal muscle, including hypertrophy and metabolic enhancements, supporting overall health and disease management. However, skeletal muscle responsiveness to resistance exercise is significantly reduced in conditions such as aging and diabetes. Recent reports suggest that glycation stress contributes to muscle atrophy and impaired exercise-induced muscle adaptation; however, its role in the muscle response to resistance exercise remains unclear. Therefore, in this study, we investigated whether methylglyoxal (MGO), a key factor in glycation stress, affects the acute responsiveness of skeletal muscles to resistance exercise, focusing on protein synthesis and the key signaling molecules. This study included 12 8-week-old male Sprague-Dawley rats divided into two groups: one received 0.5% MGO-supplemented drinking water (MGO group) and the other received regular water (control group). After 10 weeks, the left tibialis anterior muscle of each rat was subjected to electrical stimulation (ES) to mimic resistance exercise, with the right muscle serving as a non-stimulated control. Muscle protein-synthesis rates were evaluated with SUnSET, and phosphorylation levels of key signaling molecules (p70S6K and S6rp) were quantified using western blotting. In the control group, stimulated muscles exhibited significantly increased muscle protein synthesis and phosphorylation levels of p70S6K and S6rp. In the MGO group, these increases were attenuated, indicating that MGO treatment suppresses the adaptive response to resistance exercise. MGO diminishes the skeletal muscle's adaptive response to ES-simulated resistance exercise, affecting both muscle protein synthesis and key signaling molecules. The potential influence of glycation stress on the effectiveness of resistance exercise or ES emphasizes the need for individualized interventions in conditions of elevated glycation stress, such as diabetes and aging.

Transcriptomic and Epigenomic Responses to Cortisol-Mediated Stress in Rainbow Trout (Oncorhynchus mykiss) Skeletal Muscle.

The production and release of cortisol during stress responses are key regulators of growth in teleosts. Understanding the molecular responses to cortisol is crucial for the sustainable farming of rainbow trout (Oncorhynchus mykiss) and other salmonid species. While several studies have explored the genomic and non-genomic impacts of cortisol on fish growth and skeletal muscle development, the long-term effects driven by epigenetic mechanisms, such as cortisol-induced DNA methylation, remain unexplored. In this study, we analyzed the transcriptome and genome-wide DNA methylation in the skeletal muscle of rainbow trout seven days after cortisol administration. We identified 550 differentially expressed genes (DEGs) by RNA-seq and 9059 differentially methylated genes (DMGs) via whole-genome bisulfite sequencing (WGBS) analysis. KEGG enrichment analysis showed that cortisol modulates the differential expression of genes associated with nucleotide metabolism, ECM-receptor interaction, and the regulation of actin cytoskeleton pathways. Similarly, cortisol induced the differential methylation of genes associated with focal adhesion, adrenergic signaling in cardiomyocytes, and Wnt signaling. Through integrative analyses, we determined that 126 genes showed a negative correlation between up-regulated expression and down-regulated methylation. KEGG enrichment analysis of these genes indicated participation in ECM-receptor interaction, regulation of actin cytoskeleton, and focal adhesion. Using RT-qPCR, we confirmed the differential expression of lamb3, itga6, limk2, itgb4, capn2, and thbs1. This study revealed for the first time the molecular responses of skeletal muscle to cortisol at the transcriptomic and whole-genome DNA methylation levels in rainbow trout.

Maintaining mitochondrial NAD+ homeostasis is key for heat-induced skeletal muscle injury prevention despite presence of intracellular cation alterations.

Mitochondrial dysfunction is implicated in heat-induced skeletal muscle (SKM) injury and its underlying mechanisms remain unclear. Evidence suggests that cellular ions and molecules, including divalent cations and adenine nucleotides, are involved in the regulation of mitochondrial function. In this study, we examined Ca2+, Mg2+, and NAD+ levels in mouse C2C12 myoblasts and SKM in response to heat exposure. During heat exposure, mitochondrial Ca2+ levels increased significantly, whereas cytosolic Ca2+ levels remained unaltered. The mitochondrial Ca2+ levels in the SKM of heat-exposed mice were 28% higher compared to control mice. No changes in cytosolic Ca2+ were detected between the two groups. Following heat exposure, cytosolic and mitochondrial Mg2+ levels were reduced by 47% and 23% in C2C12 myoblasts, and by 51% and 44% in mouse SKMs, respectively. In addition, heat exposure decreased mitochondrial NAD+ levels by 32% and 26% in C2C12 myoblasts and mouse SKMs, respectively. Treatment with the NAD+ precursor nicotinamide riboside (NR) partially prevented heat-induced depletion of NAD+. Additionally, NR significantly reduced heat-increased mitochondrial fission, mitochondrial depolarization, and apoptosis in C2C12 myoblasts and mouse SKMs. No effects of NR on heat-induced changes in intracellular Ca2+ and Mg2+ levels were observed. This study provides in vitro and in vivo evidence that acute heat stress causes alterations in mitochondrial Ca2+, Mg2+, and NAD+ homeostasis. Our results suggest mitochondrial NAD+ homeostasis as a therapeutic target for the prevention of heat-induced SKM injury.

The Role of Cardiopulmonary Exercise Testing in Assessment of Patients with Interstitial Lung Disease

Abstract Background Cardiopulmonary exercise testing (CPET) is considered as the gold standard for evaluating the causes of exercise intolerance in patients with pulmonary and cardiac disease, and is based on the principle that system failure typically occurs while the system (e.g muscle-energetic, cardiovascular or pulmonary) is under stress. Objective To evaluate the role of cardiopulmonary exercise test in assessment of patients with interstitial lung disease. Patients and Methods This is observational study included 30 consecutive examined with the diagnosis of ILDs in Kobry El Kopa military hospital. The study was carried out over the period from February 2016 to August 2019. All patients with dyspnea to be investigated and ILDs diagnosed and assessed in rehabilitation department who undergo cardio pulmonary exercise test. Results Reduction on the compliance of the lung and/ or chest wall cause change in lung volumes and tachypnea during exercise. Also agreed with harris EzeAo Who showed that alterations on breathing pattern such as lower Vt, increased respiratory effort, rapid shallow breathing were reported in individual with interstitial lung diseases. Conclusion The pathophysiology of ILD has a negative impact on the ventilatory, cardiovascular, and skeletal muscle responses to exercise, thereby leading to exertional dyspnea and reduced exercise capacity. CPET is an excellent tool for assessing the severity of exertional dyspnea and mechanisms of exercise limitation in patients with various forms of cardiorespiratory disease; however, its application in ILD has remained limited. A growing body of evidence supports the use of CPET in patients with ILD. CPET is currently used to assess functional capacity, to inform exercise prescription, and to evaluate the effects of various interventions. Recent findings highlight that, in addition to its current uses, CPET-derived measures may help improve the management of patients with ILD. Despite these recent advances, additional research is required in order to confirm the utility of CPET in this population.

Proteomic and transcriptomic response of human skeletal muscle to 12-week resistance training

BACKGROUND: Decreased skeletal muscle mass and properties lead to the development of various pathologies and increased risk for injuries. Studies of the molecular mechanisms of skeletal muscle adaptation to resistance training to increase muscle mass and strength appear imperative for medicine and sports. AIM: To assess changes in the proteomic profile (quantitative panoramic mass spectrometric analysis) of skeletal muscles and the correlation of these changes with the expression of the corresponding mRNAs (RNA-sequencing) before and after 12 weeks of strength training and changes in the transcriptome 8 and 24 h after an acute resistance exercise with one leg. METHODS: Ten untrained men (aged 23 [20.8–25.9] years; body mass index, 22 [20.9–25.1] kg/m2) performed a two-legged seated platform press for 12 weeks (3 times/week, 50–75% of maximum voluntary contraction [MVC]). After training, the volunteers performed an acute strength exercise with one leg. Before and after 12 weeks of training, the MVC and volume of the quadriceps femoris muscle were assessed. Before and after training, as well as 8 and 24 h after the acute resistance exercise, a biopsy of the vastus lateralis muscle was performed from the loaded and contralateral limbs for immunohistochemical, proteomic (high-performance liquid chromatography-tandem mass spectrometry), and transcriptomic (RNA-sequencing) analyses. RESULTS: The 12-week strength training increased the MVC by 19%, quadriceps femoris volume by 12%, cross-sectional area of type 2 (fast) fibers by 29%, minimum Feret diameter of type 2 fibers by 10%, and type 1 (slow) fibers by 13%. Of the 1174 detected proteins, 24 increased, and 83 decreased in content. Strength training resulted in an increase in the expression levels of 142 and a decrease in 65 of the 12,112 mRNAs detected, with enrichment for the functional terms of the extracellular environment, matrix, basement membrane, etc. Changes in the contents of 433 mRNAs after 8 h and 639 mRNAs after 24 h were found when comparing the once-loaded muscle with the contralateral one (genes associated with contractile activity). Changes in the content of only a small part of proteins (5–9 out of 107) correlated with the changes in the corresponding mRNAs. CONCLUSION: Proteomic analysis showed that the 12-week resistance training had little effect on the relative abundance of high-abundance proteins in muscles. The increase in muscle mass induced by training appears to be explained by a similar change in the synthesis/degradation rates of the detected proteins. In the comparison of proteomic data with changes in mRNA expression after 12 weeks of training and 8 and 24 h after a single load (gene response specific to contractile activity), changes in protein contents caused by strength training were regulated mainly at the post-transcriptional level.

The Influence of Aging on the Unfolded Protein Response in Human Skeletal Muscle at Rest and after Acute Exercise.

The unfolded protein response (UPR) is a proteostatic process that is activated in response to endoplasmic reticulum stress. It is currently unclear how aging influences the chronic and adaptive UPR in human skeletal muscle. Here we determined the effect of aging on UPR activation at rest, in response to exercise, and the associations with muscle function. Thirty young (20-35 yr) and 50 older (65-85 yr) individuals were enrolled. Vastus lateralis biopsies were performed at rest and 3 and 48 h after a single bout of resistance exercise. The abundance of UPR-related transcripts and proteins was measured by RNA sequencing and Western blotting, respectively. Fractional synthetic rates of muscle protein were determined by mass spectrometry after intravenous infusion of 13 C 6 phenylalanine. Older adults demonstrated elevated transcriptional and proteomic markers of UPR activation in resting muscle. Resting UPR gene expression was negatively associated with muscle strength and power in older adults. The UPR is similarly activated by acute resistance exercise in young and older adults and positively associated with muscle function but not the anabolic response to exercise. Skeletal muscle from older adults exhibits chronically activated UPR, which accompanies functional decline. The adaptive UPR is a proteostatic mechanism that is upregulated in response to exercise in young and older adults and positively associated with muscle function.

Unraveling radiation-induced skeletal muscle damage: Insights from a 3D human skeletal muscle organoid model

BackgroundThree-dimensional (3D) organoids derived from human pluripotent stem cells (hPSCs) have revolutionized in vitro tissue modeling, offering a unique opportunity to replicate physiological tissue organization and functionality. This study investigates the impact of radiation on skeletal muscle response using an innovative in vitro human 3D skeletal muscle organoids (hSMOs) model derived from hPSCs. MethodsThe hSMOs model was established through a differentiation protocol faithfully recapitulating embryonic myogenesis and maturation via paraxial mesodermal differentiation of hPSCs. Key skeletal muscle characteristics were confirmed using immunofluorescent staining and RT-qPCR. Subsequently, the hSMOs were exposed to a clinically relevant dose of 2 Gy of radiation, and their response was analyzed using immunofluorescent staining and RNA-seq. ResultsThe hSMO model faithfully recapitulated embryonic myogenesis and maturation, maintaining key skeletal muscle characteristics. Following exposure to 2 Gy of radiation, histopathological analysis revealed deficits in hSMOs expansion, differentiation, and repair response across various cell types at early (30 min) and intermediate (18 h) time points post-radiation. Immunofluorescent staining targeting γH2AX and 53BP1 demonstrated elevated levels of foci per cell, particularly in PAX7+ cells, during early and intermediate time points, with a distinct kinetic pattern showing a decrease at 72 h. RNA-seq data provided comprehensive insights into the DNA damage response within the hSMOs. ConclusionsOur findings highlight deficits in expansion, differentiation, and repair response in hSMOs following radiation exposure, enhancing our understanding of radiation effects on skeletal muscle and contributing to strategies for mitigating radiation-induced damage in this context.