Marie-Ève Paré

Functional and Muscular Effects of Neuromuscular Electrical Stimulation in Patients With Severe COPD: A Randomized Clinical Trial

BACKGROUND The mechanisms through which neuromuscular electrical stimulation (NMES) training may improve limb muscle function and exercise tolerance in COPD are poorly understood. We investigated the functional and muscular effects of NMES in advanced COPD. METHODS Twenty of 22 patients with COPD were randomly assigned to NMES (n = 12) or sham (n = 8) training in a double-blind controlled study. NMES was performed on quadriceps and calf muscles, at home, 5 days per week for 6 weeks. Quadriceps and calf muscle cross-sectional area (CSA), quadriceps force and endurance, and the shuttle-walking distance with cardiorespiratory measurements were assessed before and after training. Quadriceps biopsy specimens were obtained to explore the insulin-like growth factor-1/AKT signaling pathway (70-kDa ribosomal S6 kinase [p70S6K] , atrogin-1). RESULTS NMES training improved muscle CSA (P < .05), force, and endurance (P < .03) when compared with sham training. Phosphorylated p70S6K levels (anabolism) were increased after NMES as compared with sham (P = .03), whereas atrogin-1 levels (catabolism) were reduced (P = .01). Changes in quadriceps strength and ventilation during walking contributed independently to variations in walking distance after training (r = 0.77, P < .001). Gains in walking distance were related to the ability to tolerate increasing current intensities during training (r = 0.95, P < .001). CONCLUSIONS In patients with severe COPD, NMES improved muscle CSA. This was associated with a more favorable muscle anabolic to catabolic balance. Improvement in walking distance after NMES training was associated with gains in muscle strength, reduced ventilation during walking, and the ability to tolerate higher stimulation intensity. TRIAL REGISTRY ClinicalTrials.gov; No.: NCT00874965; URL: www.clinicaltrials.gov.

Satellite cells senescence in limb muscle of severe patients with COPD.

Rationale The maintenance of peripheral muscle mass may be compromised in chronic obstructive pulmonary disease (COPD) due to premature cellular senescence and exhaustion of the regenerative potential of the muscles. Methods Vastus lateralis biopsies were obtained from patients with COPD (n = 16) and healthy subjects (n = 7). Satellite cell number and the proportion of central nuclei, as a marker of muscle regenerative events, were assessed on cryosections. Telomere lengths, used as a marker of cellular senescence, were determined using Southern blot analyses. Results Central nuclei proportion was significantly higher in patients with COPD with a preserved muscle mass compared to controls and patients with COPD with muscle atrophy (p<0.001). In COPD, maximal telomere length was significantly decreased compared to controls (p<0.05). Similarly, minimal telomere length was significantly reduced in GOLD III–IV patients with muscle atrophy compared to controls (p<0.005). Minimal, mean and maximum telomere lengths correlated with mid-thigh muscle cross-sectional area (MTCSA) (R = 0.523, p = 0.005; R = 0.435, p = 0.019 and R = 0.491, p = 0.009, respectively). Conclusions Evidence of increased regenerative events was seen in GOLD III–IV patients with preserved muscle mass. Shortening of telomeres in GOLD III–IV patients with muscle atrophy is consistent with an increased number of senescent satellite cells and an exhausted muscle regenerative capacity, compromising the maintenance of muscle mass in these individuals.

Atrophy and hypertrophy signalling of the quadriceps and diaphragm in COPD

Background Factors involved in the regulation of muscle mass in chronic obstructive pulmonary disease (COPD) are still poorly understood. Comparing the signalisation involved in muscle mass regulation between two muscles with different levels of activation within the same subjects is an interesting strategy to tease out the impact of local (muscle activity) versus systemic factors in the regulation of muscle mass. A study was undertaken to measure and compare the protein levels of p-AKT, AKT, Atrogin-1, p-p70S6K, p-4E-BP1, p-GSK3β as well as the mRNA expression of Atrogin-1, MuRF1 and FoxO-1 in the quadriceps and the diaphragm of 12 patients with COPD and 7 controls with normal lung function. Methods Diaphragm biopsies were obtained during thoracic surgery and quadriceps samples were obtained from needle biopsies. Protein content and mRNA expression were measured by western blot and quantitative PCR, respectively. Results Increased mRNA expressions of Atrogin-1, MuRF1 and FoxO-1 were found in the quadriceps compared with the diaphragm only in patients with COPD. The quadriceps/diaphragm ratio for MuRF1 was higher in COPD. The protein level of p-p70S6K was decreased in the quadriceps compared with the diaphragm in patients with COPD. The quadriceps/diaphragm ratios of p-p70S6K and p-GSK3β were lower in patients with COPD than in controls. Conclusions These results indicate a greater susceptibility to a catabolic/anabolic imbalance favouring muscle atrophy in the quadriceps compared with the diaphragm in patients with COPD. The balance between the atrophy and hypertrophy signalling is inhomogeneous between respiratory and lower limb muscles, suggesting that local factors are likely to be involved in the regulation of muscle mass in COPD.

Hypoxia alters contractile protein homeostasis in L6 myotubes

Since hypoxia might contribute to the development of muscle atrophy, we wished to provide direct evidence linking hypoxia to muscle atrophy. By evaluating protein degradation and synthesis in hypoxic myotubes we found a significant reduction in total protein content. Using functional assays we observed protein degradation elevation in the first 24 h while synthesis was maintained during this period and then significantly decrease at 48 h. These results demonstrate a temporal regulation of protein homeostasis, whereby elevated protein degradation is followed by a reduction in synthesis. These results are comparable to the cellular adaptation seen during development of muscle atrophy.

Regenerative defect in vastus lateralis muscle of patients with chronic obstructive pulmonary disease

BackgroundImpaired skeletal muscle regeneration could contribute to the progression of muscle atrophy in patients with chronic obstructive pulmonary disease (COPD).MethodsSatellite cells and myogenesis-related proteins were compared between healthy subjects and patients with COPD, with or without muscle atrophy. Satellite cells were isolated and cultured to assess their proliferative and differentiation aptitudes.ResultsAlthough satellite cell numbers in muscle samples were similar between groups, the proportion of muscle fibers with central nuclei was increased in COPD. In muscle homogenates, increased expression of MyoD and decreased expression of myogenin and MRF4 were observed in COPD. In cultured satellite cells of patients with COPD, increased protein content was observed for Pax7, Myf5 (proliferation phase) and myogenin (differentiation phase) while myosin heavy chain protein content was significantly lower during differentiation.ConclusionIn COPD, the number of central nuclei was increased in muscle fibers suggesting a greater number of attempts to regenerate muscle tissue than in healthy subjects. Myogenesis signaling was also altered in muscle homogenates in patients with COPD and there was a profound reduction in the differentiation potential in this population as indicated by a reduced ability to incorporate myosin heavy chain into newly formed myotubes. Collectively, these results indicate that skeletal muscle regenerative capacity termination is impaired in COPD and could contribute to the progression of muscle atrophy progression in this population.

T-Cell Receptor/CD28 Engagement When Combined with Prostaglandin E2 Treatment Leads to Potent Activation of Human T-Cell Leukemia Virus Type 1

ABSTRACT Infection with human T-cell leukemia virus type 1 (HTLV-1) is characterized by long latency periods, indicating that viral gene expression is under tight control. There is presently little information available regarding the nature of extracellular stimuli that can transactivate the regulatory elements of HTLV-1 (i.e., long terminal repeat [LTR]). To gain insight into the biological importance of externally induced activation pathways in virus gene expression, primary and established T cells were transfected with HTLV-1-based reporter gene vectors and then were treated with agents that cross-linked the T-cell receptor (TCR) or the costimulatory CD28 molecule with prostaglandin E2 (PGE2). We demonstrated that a potent induction of HTLV-1 LTR-driven reporter gene activity was seen only when the three agents were used in combination. Interestingly, similar observations were made when using C91/PL, a cell line that carries integrated HTLV-1 proviral DNA. This TCR-CD28-PGE2-mediated increase in virus transcription was dependent on protein kinase A activation and induction of the cAMP response element binding protein. Experiments with a mutated reporter construct further revealed the importance of the Tax-responsive elements in the HTLV-1 LTR in the observed up regulation of virus gene expression when TCR/CD28 engagement was combined with PGE2 treatment. The protein tyrosine kinases p56lck and the transmembrane tyrosine phosphatase CD45 were all found to be involved in TCR-CD28-PGE2-directed increase in HTLV-1 LTR activity. This study presents new information on the possible mechanisms underlying reactivation of this retrovirus.

Exposure to electronic cigarette vapors affects pulmonary and systemic expression of circadian molecular clock genes

E‐cigarette use has exploded in the past years, especially among young adults and smokers desiring to quit. While concerns are mostly based on the presence of nicotine and flavors, pulmonary effects of propylene glycol and glycerol inhalation, the main solvents of e‐liquid have not been thoroughly investigated. In this preclinical study, mice were exposed 2 h daily for up to 8 weeks to vapors of propylene glycol and/or glycerol generated by an e‐cigarette. Lung transcriptome analysis revealed it affected the expression level of genes of the circadian molecular clock, despite causing no inflammatory response. Periodical sacrifices showed that the rhythmicity of these regulatory genes was indeed altered in the lungs, but also in the liver, kidney, skeletal muscle, and brain. E‐cigarette exposure also altered the expression of rhythmic genes (i.e., hspa1a and hspa1b), suggesting that alterations to the ‘clock genes’ could translate into systemic biological alterations. This study reveals that the major solvents used in e‐cigarettes propylene glycol and glycerol, not nicotine or flavors, have unsuspected effects on gene expression of the molecular clock that are to be taken seriously, especially considering the fundamental role of the circadian rhythm in health and disease.

Interplay between cigarette smoking and pulmonary reverse lipid transport

Reverse lipid transport is critical to maintain homeostasis. Smoking causes lipid accumulation in macrophages, therefore suggesting suboptimal reverse lipid transport mechanisms. In this study, we investigated the interplay between smoking and reverse lipid transport and the consequences on smoking-induced lung and peripheral alterations. To investigate the relationship between smoking and reverse lipid transport, we used a clinical lung gene expression dataset and a mouse model of cigarette smoke exposure. We also used ApoA-1−/− mice, with reduced reverse lipid transport capacity, and a recombinant ApoA-1 Milano/phospholipid complex (MDCO-216) to boost reverse lipid transport. Cellular and functional analyses were performed on the lungs and impact on body composition was also assessed. Smoking affects pulmonary expression of abca1, abcg1, apoe and scarb1 in both mice and humans, key genes involved in reverse lipid transport. In mice, the capacity of bronchoalveolar lavage fluid and serum to stimulate cholesterol efflux in macrophages was increased after a single exposure to cigarette smoke. ApoA-1−/− mice showed increased lung neutrophilia, larger macrophages and greater loss in lean mass in response to smoking, whereas treatment with MDCO-216 reduced the size of macrophages and increased the lean mass of mice exposed to cigarette smoke. Altogether, this study shows a functional interaction between smoking and reverse lipid transport, and opens new avenues for better understanding the link between metabolic and pulmonary diseases related to smoking. Smoking affects reverse lipid export mechanisms, represent a new pathological mechanism and therapeutic target http://ow.ly/g8pw30dWU8U

Study of the Relation between Hypoxia and Muscle Atrophy

Background : Skeletal muscle atrophy is an important feature of chronic obstructive pulmonary disease (COPD) and it is recognized to have considerable clinical impacts. Unfortunately, factors contributing to muscle wasting in COPD are poorly understood. Hypoxemia is typical in COPD and several evidences link hypoxic conditions and protein breakdown. We propose that hypoxia participate to muscle atrophy by increasing Ubiquitin-Proteasome (UP) system activity and by decreasing the activity of IGF/PI3K/Akt synthesis pathway. Methods: To test this hypothesis, L6 muscle myotubes were either exposed to hypoxia (1% O2) or normoxia (21% O2). Results: After 24 hours of hypoxic exposure, we found a significant rise in the chymotrypsin and caspase-like 20S proteasome activities. Proteolysis was confirmed by an accumulation of a 14 kDa actin fragment during hypoxia. An elevation of Atrogin-1 mRNA expression was also observed in similar conditions. A decline in Akt phosphorylation was noticed in hypoxia. These changes were attenuated by insulin treatment. Conclusion: Proteolysis is accentuated in myotubes exposed to hypoxia and the UP system appears to be involved. In addition, protein synthesis seems to be affected as a lower Akt activity was observed. However, the IGF/PI3K/Akt pathway can still be stimulated by a suitable signal suggesting that therapies targeting this pathway are conceivable.