JAK/STAT signaling and human in vitro myogenesis

<p>Abstract</p> <p>Background</p> <p>A population of satellite cells exists in skeletal muscle. These cells are thought to be primarily responsible for postnatal muscle growth and injury-induced muscle regeneration. The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling cascade has a crucial role in regulating myogenesis. In rodent skeletal muscle, STAT3 is essential for satellite cell migration and myogenic differentiation, regulating the expression of myogenic factors. The aim of the present study was to investigate and compare the expression profile of JAK/STAT family members, using cultured primary human skeletal muscle cells.</p> <p>Results</p> <p>Near confluent proliferating myoblasts were induced to differentiate for 1, 5 or 10 days. During these developmental stages, members of the JAK/STAT family were examined, along with factors known to regulate myogenesis. We demonstrate the phosphorylation of JAK1 and STAT1 only during myoblast proliferation, while JAK2 and STAT3 phosphorylation increases during differentiation. These increases were correlated with the upregulation of genes associated with muscle maturation and hypertrophy.</p> <p>Conclusions</p> <p>Taken together, these results provide insight into JAK/STAT signaling in human skeletal muscle development, and confirm recent observations in rodents.</p

Skeletal muscle satellite cells, mitochondria, and microRNAs: their involvement in the pathogenesis of ALS

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is a fatal motor neuron disorder. It results in progressive degeneration and death of upper and lower motor neurons, protein aggregation, severe muscle atrophy and respiratory insufficiency. Median survival with ALS is between 2 and 5 years from the onset of symptoms. ALS manifests as either familial ALS (FALS) (~10% of cases) or sporadic ALS (SALS), (~90% of cases). Mutations in the copper/zinc (CuZn) superoxide dismutase (SOD1) gene account for ~20% of FALS cases and the mutant SOD1 mouse model has been used extensively to help understand the ALS pathology. As the precise mechanisms causing ALS are not well understood there is presently no cure. Recent evidence suggests that motor neuron degradation may involve a cell non-autonomous phenomenon involving numerous cell types within various tissues. Skeletal muscle is now considered as an important tissue involved in the pathogenesis of ALS by activating a retrograde signaling cascade that degrades motor neurons. Skeletal muscle heath and function are regulated by numerous factors including satellite cells, mitochondria and microRNAs. Studies demonstrate that in ALS these factors show various levels of dysregulation within the skeletal muscle. This review provides an overview of their dysregulation in various ALS models as well as how they may contribute individually and/or synergistically to the ALS pathogenesis

Effect of ageing and exercise training on myokine expression responses to acute exercise

Age-related muscle loss is a major contributor to falls, fraility and mortality. It has been widely suggested that chronic, age-related inflammation contributes to the gradual loss of skeletal muscle mass that occurs with ageing. Indeed, ageing is associated with elevations in a number of circulating inflammatory proteins, many of which have detrimental effects on skeletal muscle growth and protein balance. Exercise training has been shown to reduce chronic inflammation and, therefore, may represent an appropriate means to reduce age-related inflammation and counteract sarcopenia. Yet few studies have evaluated the effect of aging on skeletal muscle expression of inflammatory proteins and the effect of acute and repeated exercise on these factors. The aim of the current study was to determine the effect of 12 weeks of resistance exercise training on the levels of myokines within skeletal muscle, both at rest and following an acute bout of exercise and to examine how these responses may vary in young and older subjects, thus evaluating the potential for exercise to reduce age-related muscle inflammation. Six healthy young (aged 18-25 years) and 8 healthy older men (aged 60-75 years) completed 12 weeks of resistance exercise training. Muscle biopsies were collected before and 2 h after an acute exercise bout at the beginning and the end of the 12 week training period. Muscle tissue was analyzed for the expression of key inflammatory (MCP-1, IL-8, IL-6 and TNF-α) and anti-inflammatory cytokines (IL-10, IL-13 and IL-4) via bead-based multiplex analysis. Acute exercise increased the expression of inflammatory myokines, while anti-inflammatory myokines remained unchanged. In contrast to the hypothesis for this study, neither age nor training had a significant effect on the expression of myokines within skeletal muscle either in the resting state or 2 hours following exercise. However, older individuals displayed an increased inflammatory response to exercise prior to training when compared to younger individuals. Twelve weeks of resistance exercise training appeared to normalize this difference. Given the variability in myokine levels between individuals and the small subject number in the current study, further research is required to confirm this findin

G-CSF does not influence C2C12 myogenesis despite receptor expression in healthy and dystrophic skeletal muscle

Granulocyte-colony stimulating factor (G-CSF) increases recovery of rodent skeletal muscles after injury, and increases muscle function in rodent models of neuromuscular disease. However, the mechanisms by which G-CSF mediates these effects are poorly understood. G-CSF acts by binding to the membrane spanning G-CSFR and activating multiple intracellular signaling pathways. Expression of the G-CSFR within the haematopoietic system is well known, but more recently it has been demonstrated to be expressed in other tissues. However, comprehensive characterization of G-CSFR expression in healthy and diseased skeletal muscle, imperative before implementing G-CSF as a therapeutic agent for skeletal muscle conditions, has been lacking. Here we show that the G-CSFR is expressed in proliferating C2C12 myoblasts, differentiated C2C12 myotubes, human primary skeletal muscle cell cultures and in mouse and human skeletal muscle. In mdx mice, a model of human Duchenne muscular dystrophy (DMD), G-CSF mRNA and protein was down-regulated in limb and diaphragm muscle, but circulating G-CSF ligand levels were elevated. G-CSFR mRNA in the muscles of mdx mice was up-regulated however steady-state levels of the protein were down-regulated. We show that G-CSF does not influence C2C12 myoblast proliferation, differentiation or phosphorylation of Akt, STAT3, and Erk1/2. Media change alone was sufficient to elicit increases in Akt, STAT3, and Erk1/2 phosphorylation in C2C12 muscle cells and suggest previous observations showing a G-CSF increase in phosphoprotein signaling be viewed with caution. These results suggest that the actions of G-CSF may require the interaction with other cytokines and growth factors in vivo, however these data provides preliminary evidence supporting the investigation of G-CSF for the management of muscular dystrophy

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Chemoattractive myokines : impact of exercise, training & ageing

Chemoattractive myokines are inflammatory molecules released from muscle that are important in muscle repair and recovery. Exercise increased these factors, enabling the infiltration of immune cells, while ageing blunted this response. This work provides new insights into the complex regulation of inflammatory responses that are important for growth and function

Muscle damage and inflammation during recovery from exercise

Unaccustomed exercise consisting of eccentric (i.e., lengthening) muscle contractions often results in muscle damage characterized by ultrastructural alterations in muscle tissue, clinical signs, and symptoms (e.g., reduced muscle strength and range of motion, increased muscle soreness and swelling, efflux of myocellular proteins). The time course of recovery following exercise-induced muscle damage depends on the extent of initial muscle damage, which in turn is influenced by the intensity and duration of exercise, joint angle/muscle length, and muscle groups used during exercise. The effects of these factors on muscle strength, soreness, and swelling are well characterized. By contrast, much less is known about how they affect intramuscular inflammation and molecular aspects of muscle adaptation/remodeling. Although inflammation has historically been viewed as detrimental for recovery from exercise, it is now generally accepted that inflammatory responses, if tightly regulated, are integral to muscle repair and regeneration. Animal studies have revealed that various cell types, including neutrophils, macrophages, mast cells, eosinophils, CD8 and T-regulatory lymphocytes, fibro-adipogenic progenitors, and pericytes help to facilitate muscle tissue regeneration. However, more research is required to determine whether these cells respond to exercise-induced muscle damage. A large body of research has investigated the efficacy of physicotherapeutic, pharmacological, and nutritional interventions for reducing the signs and symptoms of exercise-induced muscle damage, with mixed results. More research is needed to examine if/how these treatments influence inflammation and muscle remodeling during recovery from exercise

High dose vitamin C supplementation increases skeletal muscle vitamin C concentration and SVCT2 transporter expression but does not alter redox status in healthy males.

Antioxidant vitamin C (VC) supplementation is of potential clinical benefit to individuals with skeletal muscle oxidative stress. However there is a paucity of data reporting on the bioavailability of high dose oral VC in human skeletal muscle. We aimed to establish the time-course accumulation of VC in skeletal muscle and plasma during high dose VC supplementation in healthy individuals. Concurrently we investigated effects of VC supplementation on expression levels of the key skeletal muscle VC transporter, sodium-dependent vitamin C transporter 2 (SVCT2) and intramuscular redox and mitochondrial measures. Eight healthy males completed a randomized placebo-controlled, cross-over trial involving supplementation with ascorbic acid (2&times;500mg/day) over 42 days. Participants underwent muscle and blood sampling on days 0, 1, 7 and 42 during each treatment. VC supplementation significantly increased skeletal muscle VC concentration after 7 days, which was maintained at 42 days (VC: 3.0&plusmn;0.2 [mean&plusmn;SEM] mg/100gwet weight [ww] to 3.9&plusmn;0.4mg/100g ww versus placebo: 3.1&plusmn;0.3mg/100g ww to 2.9&plusmn;0.2mg/100g ww, p=0.001). Plasma VC increased after 1 day, which was maintained at 42 days (VC: 61.0&plusmn;6.1&mu;mol/l to 111.5&plusmn;10.4&mu;mol/l versus placebo: 60.7&plusmn;5.3&mu;mol/l to 59.2&plusmn;4.8&mu;mol/l, p&lt;0.001). VC supplementation significantly increased skeletal muscle SVCT2 protein expression (main treatment effect p=0.006) but did not alter skeletal muscle redox measures or citrate synthase activity. A main finding of our study was that 7 days of high dose VC supplementation was required to significantly increase skeletal muscle vitamin C concentration in healthy males. Our findings implicate regular high dose vitamin C supplementation as a means to safely increase skeletal muscle vitamin C concentration without impairing intramuscular ascorbic acid transport, antioxidant concentrations or citrate synthase activity