Validity and clinical applicability of the 60-secondecond sit-to-stand test in people with acute exacerbations of COPD

BACKGROUND

The 60-second sit-to-stand test (60STS) is a simple and increasingly popular test of physical function, however evidence to support its appropriateness for assessing people with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) is lacking.

AIMS

To evaluate the concurrent, convergent, predictive and discriminant validity, and responsiveness of the 60STS against the six-minute walk test (6MWT) in people hospitalised due to AECOPD.

METHODS

Prospective cohort study involving 54 inpatients with AECOPD (53% males, mean age 69.0 years, FEV1 46.5% predicted). 60STS was performed 30 min after a six-minute walk test (6MWT) upon discharge, with follow-up testing repeated one-month later (n = 39). Outcome measures included 60STS repetitions (60STSr), six-minute walk distance (6MWD), heart rate, oxyhaemoglobin saturation (SpO2), perceived dyspnoea (Borg scale), and rate of perceived exertion (RPE). Concurrent validity was assessed via correlation, convergent validity via Bland-Altman plots, predictive validity via multivariate linear regression (adjusted for confounders), discriminant validity via unpaired t tests and responsiveness via Chi (Jenkins, 2007) [2] tests.

RESULTS

Discharge 60STSr and 6MWD were strongly correlated (r = 0.61). Bland-Altman plots for nadir SpO2, peak HR, Borg and RPE scores showed acceptable agreement in terms of mean differences, but wide limits of agreement. Poor 60STSr performers were older, had weaker quadriceps, and had lower 6MWD than high performers (p < 0.05 for all). 60STSr was not retained as a significant predictor of 6MWD in multivariate regression analyses. 80% of 60STSr improvers also improved >30m on 6MWT at follow-up.

CONCLUSION

The 60STS demonstrates satisfactory validity and responsiveness as a measure of exercise performance in people with AECOPD.

Role of Nrf2 and exercise in alleviating COPD-induced skeletal muscle dysfunction

Chronic obstructive pulmonary disease (COPD) is a complex chronic respiratory disease with cumulative impacts on multiple systems, exhibiting significant extrapulmonary impacts, and posing a serious public health problem. Skeletal muscle dysfunction is one of the most pronounced extrapulmonary effects in patients with COPD, which severely affects patient prognosis and mortality primarily through reduced productivity resulting from muscle structural and functional alterations. Although the detailed pathogenesis of COPD has not been fully determined, some researchers agree that oxidative stress plays a significant role. Oxidative stress not only catalyzes the progression of pulmonary symptoms but also drives the development of skeletal muscle dysfunction. Nuclear factor erythroid 2-related factor 2 (Nrf2), is a key transcription factor that regulates the antioxidant response and plays an enormous role in combating oxidative stress. In this review, we have summarized current research on oxidative stress damage to COPD skeletal muscle and analyzed the role of Nrf2 in improving skeletal muscle dysfunction in COPD through exercise. The results suggest that oxidative stress drives the occurrence and development of skeletal muscle dysfunction in COPD. Exercise may improve skeletal muscle dysfunction in patients with COPD by promoting the dissociation of Kelch-like ECH-associated protein 1 (Keap1) and Nrf2, inducing sequestosome1(p62) phosphorylation to bind with Keap1 competitively leading to Nrf2 stabilization and improving dynamin-related protein 1-dependent mitochondrial fission. Nrf2 may be a key target for exercise anti-oxidative stress to alleviate skeletal muscle dysfunction in COPD.

Effects of external diaphragm pacing combined with conventional rehabilitation therapies in patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis

BACKGROUND

Numerous randomized controlled trials (RCTs) have reported the benefits of external diaphragm pacing combined with conventional rehabilitation therapies (EDP-CRTs) on pulmonary function and exercise capacity in patients with chronic obstructive pulmonary disease (COPD). However, evidence-based regarding its effects remains unclear.

OBJECTIVES

This systematic review and meta-analysis aimed to evaluate the effects of EDP-CRTs versus CRTs on patients with COPD.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES AND METHODS

We performed a systematic review and meta-analysis, searching PubMed, Embase, Cochrane Central Register of Controlled Trials, Scopus, China Biology Medicine Disc, Chinese National Knowledge Infrastructure, Wan-Fang Database, and Chinese Scientific Journal Database from inception to 10 September 2023. RCTs investigating the effects of EDP-CRTs versus CRTs on COPD patients were included. The primary outcome was pulmonary function, including forced expiratory volume in 1 s (FEV1), the percentage of predicted values of FEV1 (FEV1%pred), and FEV1/forced vital capacity (FVC)%. Secondary outcomes included arterial blood gas analysis [the partial pressure of arterial oxygen (PaO2) and the partial pressure of arterial carbon dioxide (PaCO2)]; dyspnea [modified Medical Research Council Dyspnea Scale (mMRC)]; exercise capacity [6-min walking distance (6MWD)]; and quality of life [COPD assessment test (CAT)]. RevMan 5.3 software was used for meta-analysis. The quality of the included studies was assessed using the revised Cochrane Risk of Bias tool for randomized trials (RoB 2.0). The certainty of the evidence was evaluated with the Grading of Recommendations Assessment, Development, and Evaluation system.

RESULTS

In total, 13 studies/981 participants were included. The pooled results revealed significant benefits of EDP-CRTs versus CRTs on the FEV1 [standardized mean difference (SMD) = 1.07, 95% confidence interval (CI) = 0.58-1.56], FEV1%pred [weighted mean difference (WMD) = 6.67, 95% CI = 5.69-7.64], the FEV1/FVC% (SMD = 1.24, 95% CI = 0.48-2.00), PaO2 (SMD = 1.29, 95% CI = 0.74-1.84), PaCO2 (SMD = -1.88, 95% CI = -2.71 to -1.04), mMRC (WMD = -0.55, 95% CI = -0.65 to -0.45), 6MWD (SMD = 1.63, 95% CI = 0.85-2.42), and CAT (WMD = -1.75, 95% CI = -3.16 to -0.35), respectively. Planned subgroup analysis suggested that EDP-CRTs had a better effect on FEV1, FEV1/FVC%, 6MWD, and CAT in the duration of 2-4 weeks.

CONCLUSION

EDP-CRTs have better effects on pulmonary function, PaCO2, dyspnea, exercise capacity, and quality of life in COPD patients than CRTs, and the duration to achieve the most effective treatment is 2-4 weeks.

TRIAL REGISTRATION

This systematic review and meta-analysis protocol was prospectively registered with PROSPERO (No. CRD42022355964).

Three Weeks of Pulmonary Rehabilitation Do Not Influence Oscillometry Parameters in Postoperative Lung Cancer Patients

Background: Thoracic surgery is a recommended treatment option for non-small cell lung cancer patients. An important part of a patient’s therapy, which helps to prevent postoperative complications and improve quality of life, is pulmonary rehabilitation (PR). The aim of this study was to assess whether the implementation of physical activity has an influence on forced oscillation technique (FOT) values in patients after thoracic surgery due to lung cancer. Methods: In this observational study, we enrolled 54 patients after thoracic surgery due to lung cancer, 49 patients with idiopathic interstitial fibrosis (IPF), and 54 patients with chronic obstructive pulmonary disease/asthma−COPD overlap (COPD/ACO). All patients were subjected to three weeks of in-hospital PR and assessed at the baseline as well as after completing PR by FOT, spirometry, grip strength measurement, and the 6-min walk test (6MWT). Results: We observed differences between FOT values under the influence of physical activity in studied groups, mostly between patients after thoracic surgery and COPD/ACO patients; however, no significant improvement after completing PR among FOT parameters was noticed in any group of patients. Improvements in the 6MWT distance, left hand strength, and right hand strength after PR were noticed (p < 0.001, 0.002, and 0.012, respectively). Conclusions: Three weeks of pulmonary rehabilitation had no impact on FOT values in patients after thoracic surgery due to lung cancer. Instead, we observed improvements in the 6MWT distance and the strength of both hands. Similarly, no FOT changes were observed in IPF and COPD/ACO patients after completing PR.

Exploring red cell distribution width as a biomarker for treatment efficacy in home mechanical ventilation

BACKGROUND

With the growing practice of home mechanical ventilation, there is a need to identify biological markers for adequate follow-up. Red cell distribution width (RDW) is a promising candidate because it is convenient, objective and may reflect treatment effect over a long period of time. The aim of this study was to explore the possible role of RDW as a marker for home mechanical ventilation in real-life, unselected chronic respiratory patient populations.

METHODS

First, we identified characteristic RDW values for mixed case, unselected chronic respiratory failure and home mechanical ventilated patients through retrospective review within our institutional database. Next, we conducted a prospective observational study to identify RDW changes during the first six months of optimized home mechanical ventilation treatment. Adult patients starting home mechanical ventilation were included. Factors affecting RDW change during the first 6 months of treatment were analysed.

RESULTS

RDW was elevated in both chronic respiratory failure and home mechanical ventilation patients compared to healthy individuals in the retrospective review. In the prospective study of 70 patients, we found that 55.4% of patients starting home mechanical ventilation have abnormal RDW values which are reduced from 14.7 (IQR = 13.2-16.2)% to 13.5 (IQR = 13.1-14.6)% during the first 6 months of HMV treatment (p < 0.001). RDW improvement correlates with improvement in self-reported health-related quality of life and sleepiness scale scores, as well as physical functional status during the same time frame. RDW proved to be a comparable marker to other parameters traditionally used to evaluate treatment efficacy.

CONCLUSIONS

RDW is elevated in chronic respiratory failure patients and is significantly reduced in the first six months of optimized home mechanical ventilation. Although further research is needed to verify if RDW change reflects outcome and how comorbidities influence RDW values, our results suggest that RDW is a promising marker of home mechanical ventilation efficacy. Trial registration This study was approved by and registered at the ethics committee of Semmelweis University (TUKEB 250/2017 and TUKEB 250-1/2017, 20th of December 2017 and 1st of October 2019).

Effects of low and high resistance training intensities on clinical outcomes in patients with COPD - a randomized trial

AIM

To compare the effects of two different intensities of combined resistance and aerobic training on physical-functional aspects and perceptual aspects of health status in patients with Chronic Obstructive Pulmonary Disease (COPD).

DESIGN

This was a randomized parallel group trial.

METHODS

Thirty-one patients were assessed regarding: symptoms (COPD Assessment Test - CAT), quality of life (Saint George's Respiratory Questionnaire - SGRQ); exercise capacity (six-minute walk test and constant-workload resistance test - CWRT); and muscle strength (one-repetition maximum test and isometric muscle strength for knee extensors - Kext and elbow flexors - EFlex). Patients were randomized in two groups to perform a combined training: 1) LL/HR = Low-load/high-repetition resistance training (n = 16; 68 ± 9.3 years; FEV₁ = 50.0 ± 15.7%pred); and 2) HL/LR = High-load/low-repetition resistance training (n = 15; 70 ± 6.5 years; FEV₁ = 46.8 ± 14.5%pred), and underwent 36 sessions.

RESULTS

Symptoms, quality of life and exercise capacity presented significant improvement (p < .05) in both groups. Both intensities of resistance training improved symptoms (∆CAT: LL/HR = -3.9; HL/LR = -2.8) and exercise capacity (∆ tolerance time in CWRT: LL/HR = +450.9s; HL/LR = +583.4s) above minimal clinically important difference value. Nevertheless, improvement in quality of life (∆SGRQ: LL/HR = -3.8; HL/LR = -10) and in isometric muscle strength (∆KExt: LL/HR = +15.8 N; HL/LR = +37.7 N and (∆EFlex: LL/HR = +9.5 N; HL/LR = +29.9 N) was observed only in the HL/LR group, which also presented a larger number of responders considering isometric muscle strength.

CONCLUSION

High-intensity resistance training in a combined training was more effective in ameliorating several aspects of patients with COPD, responding more and better to physical-functional aspects and perceptual aspects of health status.

Prolonged Immobilization Exacerbates the Loss of Muscle Mass and Function Induced by Cancer-Associated Cachexia through Enhanced Proteolysis in Mice

We hypothesized that in mice with lung cancer (LC)-induced cachexia, periods of immobilization of the hindlimb (7 and 15 days) may further aggravate the process of muscle mass loss and function. Mice were divided into seven groups (n = 10/group): (1) non-immobilized control mice, (2) 7-day unloaded mice (7-day I), (3) 15-day unloaded mice (15-day I), (4) 21-day LC-cachexia group (LC 21-days), (5) 30-day LC-cachexia group (LC 30-days), (6) 21-day LC-cachexia group besides 7 days of unloading (LC 21-days + 7-day I), (7) 30-day LC-cachexia group besides 15 days of unloading (LC 30-days + 15-day I). Physiological parameters, body weight, muscle and tumor weights, phenotype and morphometry, muscle damage (including troponin I), proteolytic and autophagy markers, and muscle regeneration markers were identified in gastrocnemius muscle. In LC-induced cachexia mice exposed to hindlimb unloading, gastrocnemius weight, limb strength, fast-twitch myofiber cross-sectional area, and muscle regeneration markers significantly decreased, while tumor weight and area, muscle damage (troponin), and proteolytic and autophagy markers increased. In gastrocnemius of cancer-cachectic mice exposed to unloading, severe muscle atrophy and impaired function was observed along with increased muscle proteolysis and autophagy, muscle damage, and impaired muscle regeneration.

Regulation of Skeletal Muscle Atrophy in Cachexia by MicroRNAs and Long Non-coding RNAs

Skeletal muscle atrophy is a common complication of cachexia, characterized by progressive bodyweight loss and decreased muscle strength, and it significantly increases the risks of morbidity and mortality in the population with atrophy. Numerous complications associated with decreased muscle function can activate catabolism, reduce anabolism, and impair muscle regeneration, leading to muscle wasting. microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), types of non-coding RNAs, are important for regulation of skeletal muscle development. Few studies have specifically identified the roles of miRNAs and lncRNAs in cellular or animal models of muscular atrophy during cachexia, and the pathogenesis of skeletal muscle wasting in cachexia is not entirely understood. To develop potential approaches to improve skeletal muscle mass, strength, and function, a more comprehensive understanding of the known key pathophysiological processes leading to muscular atrophy is needed. In this review, we summarize the known miRNAs, lncRNAs, and corresponding signaling pathways involved in regulating skeletal muscle atrophy in cachexia and other diseases. A comprehensive understanding of the functions and mechanisms of miRNAs and lncRNAs during skeletal muscle wasting in cachexia and other diseases will, therefore, promote therapeutic treatments for muscle atrophy.

Reversibility of Frailty after Lung Transplantation

BACKGROUND

Frailty contributes to increased morbidity and mortality in patients referred for and undergoing lung transplantation (LTX). The study aim was to determine if frailty is reversible after LTX in those classified as frail at LTX evaluation.

METHODS

Consecutive LTX recipients were included. All patients underwent modified physical frailty assessment during LTX evaluation. For patients assessed as frail, frailty was reassessed on completion of the post-LTX rehabilitation program. Frailty was defined by the presence of ≥ 3 domains of the modified Fried Frailty Phenotype (mFFP).

RESULTS

We performed 166 lung transplants (frail patients, n = 27, 16%). Eighteen of the 27 frail patients have undergone frailty reassessment. Eight frail patients died, and one interstate recipient did not return for reassessment. In the 18 (66%) patients reassessed, there was an overall reduction in their frailty score post-LTX ((3.4 ± 0.6 to 1.0 ± 0.7), p < 0.001) with 17/18 (94%) no longer classified as frail. Improvements were seen in the following frailty domains: exhaustion, mobility, appetite, and activity. Handgrip strength did not improve posttransplant.

CONCLUSIONS

Physical frailty was largely reversible following LTX, underscoring the importance of considering frailty a dynamic, not a fixed, entity. Further work is needed to identify those patients whose frailty is modifiable and establish specific interventions to improve frailty.

The acute effects of cigarette smoke exposure on muscle fiber type dynamics in rats

Reduced exercise capacity is common in people with chronic obstructive pulmonary diseases (COPD) and chronic smokers and is suggested to be related to skeletal muscle dysfunction. Previous studies using human muscle biopsies have shown fiber-type shifting in chronic smokers particularly those with COPD. These results, however, are confounded with aging effects because people with COPD tend to be older. In the present study, we implemented an acute 7-day cigarette smoke-exposed model using Sprague-Dawley rats to evaluate early effects of cigarette smoking on soleus muscles. Rats (n = 5 per group) were randomly assigned to either a sham air (SA) or cigarette smoking (CS) groups of three different concentrations of total particulate matters (TPM) (CS_TPM2.5, CS_TPM5, CS_TPM10). Significantly lower percentages of type I and higher type IIa fiber were detected in the soleus muscle in CS groups when compared with SA group. Of these, only CS_TMP10 group exhibited significantly lower citrate synthase activity and higher muscle tumor necrosis factor-α level than that of SA group. Tumor necrosis factor-α level was correlated with the percentage of type I and IIa fibers. However, no significant between-group differences were found in fiber cross-sectional area, physical activities, or lung function assessments. In conclusion, acute smoking may directly trigger the onset of glycolytic fiber type shift in skeletal muscle independent of aging.

Quadriceps miR-542-3p and -5p are elevated in COPD and reduce function by inhibiting ribosomal and protein synthesis

Reduced physical performance reduces quality of life in patients with chronic obstructive pulmonary disease (COPD). Impaired physical performance is, in part, a consequence of reduced muscle mass and function, which is accompanied by mitochondrial dysfunction. We recently showed that miR-542-3p and miR-542-5p were elevated in a small cohort of COPD patients and more markedly in critical care patients. In mice, these microRNAs (miRNAs) promoted mitochondrial dysfunction suggesting that they would affect physical performance in patients with COPD, but we did not explore the association of these miRNAs with disease severity or physical performance further. We therefore quantified miR-542-3p/5p and mitochondrial rRNA expression in RNA extracted from quadriceps muscle of patients with COPD and determined their association with physical performance. As miR-542-3p inhibits ribosomal protein synthesis its ability to inhibit protein synthesis was also determined in vitro. Both miR-542-3p expression and -5p expression were elevated in patients with COPD (5-fold P < 0.001) and the degree of elevation associated with impaired lung function (transfer capacity of the lung for CO in % and forced expiratory volume in 1 s in %) and physical performance (6-min walk distance in %). In COPD patients, the ratio of 12S rRNA to 16S rRNA was suppressed suggesting mitochondrial ribosomal stress and mitochondrial dysfunction and miR-542-3p/5p expression was inversely associated with mitochondrial gene expression and positively associated with p53 activity. miR-542-3p suppressed RPS23 expression and maximal protein synthesis in vitro. Our data show that miR-542-3p and -5p expression is elevated in COPD patients and may suppress physical performance at least in part by inhibiting mitochondrial and cytoplasmic ribosome synthesis and suppressing protein synthesis. NEW & NOTEWORTHY miR-542-3p and -5p are elevated in the quadriceps muscle of patients with chronic obstructive pulmonary disease (COPD) in proportion to the severity of their lung disease. These microRNAs inhibit mitochondrial and cytoplasmic protein synthesis suggesting that they contribute to impaired exercise performance in COPD.

Neuromuscular electrical stimulation improves muscle atrophy induced by chronic hypoxia-hypercapnia through the MicroRNA-486/PTEN/FoxO1 pathway

Previous work has confirmed that the chronic hypoxia-hypercapnia (CHH) associated with chronic obstructive pulmonary disease contributes to the development of skeletal muscle atrophy. Neuromuscular Electrical Stimulation (NMES) has shown some efficacy when used as a treatment to reduce skeletal muscle atrophy. The present study focuses on the MicroRNA-486/PTEN/FoxO1 pathway with the goal of identifying its physiological role in skeletal muscle atrophy induced by CHH as well as its role during NMES treatment. To test this, 32 male Sprague Dawley rats were randomly divided into four groups. After completion of the disease modeling, gastrocnemius muscles were collected from all animals and cross-sectional areas of muscular fiber were observed and analyzed via H&E staining. MiR-486 expression was further assessed by qRT-PCR, and protein levels of TNF-α, PTEN, p-Akt, Akt, FoxO1, atrogin-1 and MuRF1 were measured by immunohistochemistry and western blotting. CSA, miR-486, and the ratio p-Akt/Akt were significantly reduced in the CHH group, while the levels of TNF-α, PTEN, FoxO1, atrogin-1, and MuRF1 were markedly increased. Importantly, these findings were reversed as a result of NMES. Thus, the MicroRNA-486/PTEN/FoxO1 pathway functions in muscle protein synthesis and degradation. NEW & NOTEWORTHY: Our research provides a theoretical basis for the application of NMES as a means of improving muscle atrophy. Moreover, these therapeutic targets provide possible clues relevant to the treatment of amyotrophic diseases.

Hypoxic Preconditioning Attenuates Reoxygenation-Induced Skeletal Muscle Dysfunction in Aged Pulmonary TNF-α Overexpressing Mice

Aim: Skeletal muscle subjected to hypoxia followed by reoxygenation is susceptible to injury and subsequent muscle function decline. This phenomenon can be observed in the diaphragm during strenuous exercise or in pulmonary diseases such as chronic obstructive pulmonary diseases (COPD). Previous studies have shown that PO₂ cycling or hypoxic preconditioning (HPC), as it can also be referred to as, protects muscle function via mechanisms involving reactive oxygen species (ROS). However, this HPC protection has not been fully elucidated in aged pulmonary TNF-α overexpressing (Tg⁺) mice (a COPD-like model). We hypothesize that HPC can exert protection on the diaphragms of Tg⁺ mice during reoxygenation through pathways involving ROS/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/extracellular signal regulated kinase (ERK), as well as the downstream activation of mitochondrial ATP-sensitive potassium channel (mitoK_ATP) and inhibition of mitochondrial permeability transition pore (mPTP).

Methods: Isolated Tg⁺ diaphragm muscle strips were pre-treated with inhibitors for ROS, PI3K, Akt, ERK, or a combination of mitoK_ATP inhibitor and mPTP opener, respectively, prior to HPC. Another two groups of muscles were treated with either mitoK_ATP activator or mPTP inhibitor without HPC. Muscles were treated with 30-min hypoxia, followed by 15-min reoxygenation. Data were analyzed by multi-way ANOVA and expressed as means ± SE.

Results: Muscle treated with HPC showed improved muscle function during reoxygenation (n = 5, p < 0.01). Inhibition of ROS, PI3K, Akt, or ERK abolished the protective effect of HPC. Simultaneous inhibition of mitoK_ATP and activation of mPTP also diminished HPC effects. By contrast, either the opening of mitoK_ATP channel or the closure of mPTP provided a similar protective effect to HPC by alleviating muscle function decline, suggesting that mitochondria play a role in HPC initiation (n = 5; p < 0.05).

Conclusion: Hypoxic preconditioning may protect respiratory skeletal muscle function in Tg⁺ mice during reoxygenation through redox-sensitive signaling cascades and regulations of mitochondrial channels.

Inspiratory muscle strength, diaphragmatic mobility, and body composition in chronic obstructive pulmonary disease

BACKGROUND AND PURPOSE

Chronic obstructive pulmonary disease (COPD) is a systemic inflammatory disease that can cause repercussions on respiratory muscles and body composition. The aim of the current study was to evaluate inspiratory muscle strength, diaphragmatic mobility, and body composition in COPD subjects and to correlate these variables.

METHODS

This was a cross-sectional study performed with 21 COPD patients. Inspiratory muscle strength (manovacuometry), pulmonary function test (forced vital capacity [FVC], forced expiratory volume in 1 s [FEV₁ ], and FEV₁ /FVC ratio), diaphragmatic mobility (ultrasonography), and body composition (bioelectrical impedance analysis) were examined.

RESULTS

COPD individuals in Stages II (28.9%), III (52%), and IV (19%) according to Global Initiative for Chronic Obstructive Disease were recruited, 61.9% of which were men. Inspiratory muscle weakness was found in 47.6% of subjects, who presented a lower fat-free mass percentage (p = 0.017) and smaller fat-free mass index (p = 0.001) and greater fat mass percentage (p = 0.029) and less diaphragmatic mobility (p = 0.007) compared with the nonrespiratory weakness group. Maximal inspiratory pressure exhibited a moderately positive relationship to the fat-free mass index (r = 0.767, p < 0.001) and a weak positive relationship to diaphragmatic mobility (r = 0.496, p = 0.022).

CONCLUSION

Our study showed a high prevalence of inspiratory muscle weakness based on the severity of airway obstruction and on the presence of muscular depletion. The evaluation of body composition detected important changes. It also demonstrated that not only muscular weakness was present in these patients but also this had repercussions on the mobility of the diaphragm muscle.

Smart Vest for Respiratory Rate Monitoring of COPD Patients Based on Non-Contact Capacitive Sensing

In this paper, a first approach to the design of a portable device for non-contact monitoring of respiratory rate by capacitive sensing is presented. The sensing system is integrated into a smart vest for an untethered, low-cost and comfortable breathing monitoring of Chronic Obstructive Pulmonary Disease (COPD) patients during the rest period between respiratory rehabilitation exercises at home. To provide an extensible solution to the remote monitoring using this sensor and other devices, the design and preliminary development of an e-Health platform based on the Internet of Medical Things (IoMT) paradigm is also presented. In order to validate the proposed solution, two quasi-experimental studies have been developed, comparing the estimations with respect to the golden standard. In a first study with healthy subjects, the mean value of the respiratory rate error, the standard deviation of the error and the correlation coefficient were 0.01 breaths per minute (bpm), 0.97 bpm and 0.995 (p < 0.00001), respectively. In a second study with COPD patients, the values were −0.14 bpm, 0.28 bpm and 0.9988 (p < 0.0000001), respectively. The results for the rest period show the technical and functional feasibility of the prototype and serve as a preliminary validation of the device for respiratory rate monitoring of patients with COPD.

Downhill walking influence on physical condition and quality of life in patients with COPD: A randomized controlled trial

Background: Chronic Obstructive Pulmonary Disease (COPD), in addition to its respiratory problems, is accompanied by several musculoskeletal consequences. The aim of this study is to investigate the effectiveness of eccentric exercise in the form of downhill walking (DW) on respiratory capacity, physical function and quality of life (QOL) in patients with COPD. Methods: The randomized controlled trial was carried out during 2014 - 2015 in Hazrat-e-Rasool Hospital in Tehran, Iran. The study design was as an assessor blind RCT on 32 patients with COPD that randomly assigned to the eccentric training (ET) and control (CON) groups. Patients in ET group received a 12-week DW exercise on the treadmill while the patients in the control group were only treated by COPD conventional medications and walked on paved surfaces. Functional tests, FEV1, FEV1 to FVC and St. George's Respiratory Questionnaire (SGRQ) were used to assess the subject's physical status and QOL pre and post-intervention. Results: The FEV1 (p=0.008), FEV1/FVC (p=0.002), six-minute walk test (p=0.029), timed up & go test (p=0.023), SGRQ symptom (p=0.022), SGRQ activity (p=0.007), SGRQ impact (p=0.033) and total score of SGRQ (p=0.013) improved significantly in the ET group compare to the CON group. Conclusion: DW could have positive influence on physical status and QOL of patients with COPD.

Altered skeletal muscle mitochondrial phenotype in COPD: disease vs. disuse

Patients with chronic obstructive pulmonary disease (COPD) exhibit an altered skeletal muscle mitochondrial phenotype, which often includes reduced mitochondrial density, altered respiratory function, and elevated oxidative stress. As this phenotype may be explained by the sedentary lifestyle that commonly accompanies this disease, the aim of this study was to determine whether such alterations are still evident when patients with COPD are compared to control subjects matched for objectively measured physical activity (PA; accelerometry). Indexes of mitochondrial density [citrate synthase (CS) activity], respiratory function (respirometry in permeabilized fibers), and muscle oxidative stress [4-hydroxynonenal (4-HNE) content] were assessed in muscle fibers biopsied from the vastus lateralis of nine patients with COPD and nine PA-matched control subjects (CON). Despite performing similar levels of PA (CON: 18 ± 3, COPD: 20 ± 7 daily minutes moderate-to-vigorous PA; CON: 4,596 ± 683, COPD: 4,219 ± 763 steps per day, P > 0.70), patients with COPD still exhibited several alterations in their mitochondrial phenotype, including attenuated skeletal muscle mitochondrial density (CS activity; CON 70.6 ± 3.8, COPD 52.7 ± 6.5 U/mg, P < 0.05), altered mitochondrial respiration [e.g., ratio of complex I-driven state 3 to complex II-driven state 3 (CI/CII); CON: 1.20 ± 0.11, COPD: 0.90 ± 0.05, P < 0.05), and oxidative stress (4-HNE; CON: 1.35 ± 0.19, COPD: 2.26 ± 0.25 relative to β-actin, P < 0.05). Furthermore, CS activity ( r = 0.55), CI/CII ( r = 0.60), and 4-HNE ( r = 0.49) were all correlated with pulmonary function, assessed as forced expiratory volume in 1 s ( P < 0.05), but not PA ( P > 0.05). In conclusion, the altered mitochondrial phenotype in COPD is present even in the absence of differing levels of PA and appears to be related to the disease itself. NEW & NOTEWORTHY Chronic obstructive pulmonary disease (COPD) is associated with debilitating alterations in the function of skeletal muscle mitochondria. By comparing the mitochondrial phenotype of patients with COPD to that of healthy control subjects who perform the same amount of physical activity each day, this study provides evidence that many aspects of the dysfunctional mitochondrial phenotype observed in COPD are not merely due to reduced physical activity but are likely related to the disease itself.

miR-422a suppresses SMAD4 protein expression and promotes resistance to muscle loss

BACKGROUND

Loss of muscle mass and strength are important sequelae of chronic disease, but the response of individuals is remarkably variable, suggesting important genetic and epigenetic modulators of muscle homeostasis. Such factors are likely to modify the activity of pathways that regulate wasting, but to date, few such factors have been identified.

METHODS

The effect of miR-422a on SMAD4 expression and transforming growth factor (TGF)-β signalling were determined by western blotting and luciferase assay. miRNA expression was determined by qPCR in plasma and muscle biopsy samples from a cross-sectional study of patients with chronic obstructive pulmonary disease (COPD) and a longitudinal study of patients undergoing aortic surgery, who were subsequently admitted to the intensive care unit (ICU).

RESULTS

miR-422a was identified, by a screen, as a microRNA that was present in the plasma of patients with COPD and negatively associated with muscle strength as well as being readily detectable in the muscle of patients. In vitro, miR-422a suppressed SMAD4 expression and inhibited TGF-beta and bone morphogenetic protein-dependent luciferase activity in muscle cells. In male patients with COPD and those undergoing aortic surgery and on the ICU, a model of ICU-associated muscle weakness, quadriceps expression of miR-422a was positively associated with muscle strength (maximal voluntary contraction r = 0.59, P < 0.001 and r = 0.51, P = 0.004, for COPD and aortic surgery, respectively). Furthermore, pre-surgery levels of miR-422a were inversely associated with the amount of muscle that would be lost in the first post-operative week (r = -0.57, P < 0.001).

CONCLUSIONS

These data suggest that differences in miR-422a expression contribute to the susceptibility to muscle wasting associated with chronic and acute disease and that at least part of this activity may be mediated by reduced TGF-beta signalling in skeletal muscle.

MicroRNA-542 Promotes Mitochondrial Dysfunction and SMAD Activity and Is Elevated in Intensive Care Unit-acquired Weakness

RATIONALE

Loss of skeletal muscle mass and function is a common consequence of critical illness and a range of chronic diseases, but the mechanisms by which this occurs are unclear.

OBJECTIVES

To identify microRNAs (miRNAs) that were increased in the quadriceps of patients with muscle wasting and to determine the molecular pathways by which they contributed to muscle dysfunction.

METHODS

miRNA-542-3p/5p (miR-542-3p/5p) were quantified in the quadriceps of patients with chronic obstructive pulmonary disease and intensive care unit-acquired weakness (ICUAW). The effect of miR-542-3p/5p was determined on mitochondrial function and transforming growth factor-β signaling in vitro and in vivo.

MEASUREMENTS AND MAIN RESULTS

miR-542-3p/5p were elevated in patients with chronic obstructive pulmonary disease but more markedly in patients with ICUAW. In vitro, miR-542-3p suppressed the expression of the mitochondrial ribosomal protein MRPS10 and reduced 12S ribosomal RNA (rRNA) expression, suggesting mitochondrial ribosomal stress. miR-542-5p increased nuclear phospho-SMAD2/3 and suppressed expression of SMAD7, SMURF1, and PPP2CA, proteins that inhibit or reduce SMAD2/3 phosphorylation, suggesting that miR-542-5p increased transforming growth factor-β signaling. In mice, miR-542 overexpression caused muscle wasting, and reduced mitochondrial function, 12S rRNA expression, and SMAD7 expression, consistent with the effects of the miRNAs in vitro. Similarly, in patients with ICUAW, the expression of 12S rRNA and of the inhibitors of SMAD2/3 phosphorylation were reduced, indicative of mitochondrial ribosomal stress and increased transforming growth factor-β signaling. In patients undergoing aortic surgery, preoperative levels of miR-542-3p/5p were positively correlated with muscle loss after surgery.

CONCLUSIONS

Elevated miR-542-3p/5p may cause muscle atrophy in intensive care unit patients through the promotion of mitochondrial dysfunction and activation of SMAD2/3 phosphorylation.

Measurement Properties of Short Lower Extremity Functional Exercise Tests in People With Chronic Obstructive Pulmonary Disease: Systematic Review

BACKGROUND

An increasing variety of short functional exercise tests are reported in people with chronic obstructive pulmonary disease (COPD). Systematic review of the psychometric properties of these exercise tests is indicated.

PURPOSE

The aim of this study was to determine the reliability, validity, and responsiveness of short (duration < 6 min) lower extremity functional exercise tests in people with COPD.

DATA SOURCES

Five databases were searched: MEDLINE, Embase, Scopus, AMED, and CINAHL.

STUDY SELECTION

Studies reporting psychometric properties of short functional exercise tests in people with COPD were included.

DATA EXTRACTION

Two reviewers independently extracted data and rated the quality of each measurement property using the COnsensus-based Standards for the Selection of Health Measurement INstrument (COSMIN).

DATA SYNTHESIS

Twenty-nine studies were identified reporting properties of 11 different tests. Four-meter gait speed [4MGS] and 5 repetition sit-to-stand [5STS] demonstrated high reliability (ICC = .95-.99; .97) with no learning effect (COSMIN study ratings = good--excellent). Their validity for use as a stratification tool anchored against an established prognostic indicator (area under receiver operator characteristics curve [AUC] = 0.72-0.87; 0.82) and responsiveness to change after pulmonary rehabilitation was greatest in more frail people with COPD. Studies of the Timed "Up and Go" [TUG] test support use of a practice test and show discriminative ability to detect falls history and low six-minute walk distance (AUC = 0.77; 0.82, COSMIN ratings = fair-excellent).

LIMITATIONS

Earlier studies were limited by small sample size. Limited data of lower study quality was identified for step tests and the Two-Minute Walk Test.

CONCLUSIONS

Selected short functional exercise tests can complement established exercise capacity measures, in stratification and measuring responsiveness to change especially in people with COPD and lower functional ability.

Reduced HDAC2 in skeletal muscle of COPD patients

Background

Skeletal muscle weakness in chronic obstructive pulmonary disease (COPD) is an important predictor of poor prognosis, but the molecular mechanisms of muscle weakness in COPD have not been fully elucidated. The aim of this study was to investigate the role of histone deacetylases(HDAC) in skeletal muscle weakness in COPD.

Methods and results

Twelve COPD patients, 8 smokers without COPD (SM) and 4 healthy non-smokers (NS) were recruited to the study. HDAC2 protein expression in quadriceps muscle biopsies of COPD patients (HDAC2/β-actin: 0.59 ± 0.34) was significantly lower than that in SM (1.9 ± 1.1, p = 0.0007) and NS (1.2 ± 0.7, p = 0.029). HDAC2 protein in skeletal muscle was significantly correlated with forced expiratory volume in 1 s % predicted (FEV₁ % pred) (r_s = 0.53, p = 0.008) and quadriceps maximum voluntary contraction force (MVC) (r_s = 0.42, p = 0.029). HDAC5 protein in muscle biopsies of COPD patients (HDAC5/β-actin: 0.44 ± 0.26) was also significantly lower than that in SM (1.29 ± 0.39, p = 0.0001) and NS (0.98 ± 0.43, p = 0.020). HDAC5 protein in muscle was significantly correlated with FEV₁ % pred (r_s = 0.64, p = 0.0007) but not with MVC (r_s = 0.30, p = 0.180). Nuclear factor-kappa B (NF-κB) DNA binding activity in muscle biopsies of COPD patients (10.1 ± 7.4) was significantly higher than that in SM (3.9 ± 7.3, p = 0.020) and NS (1.0 ± 1.2, p = 0.004and significantly correlated with HDAC2 decrease (r_s = −0.59, p = 0.003) and HDAC5 (r_s = 0.050, p = 0.012). HDAC2 knockdown by RNA interference in primary skeletal muscle cells caused an increase in NF-κB activity, NF-κB acetylation and basal tumour necrosis factor (TNF)-α production, as well as progressive cell death through apoptosis.

Conclusion

Skeletal muscle weakness in COPD may result from HDAC2 down-regulation in skeletal muscle via acetylation and activation of NF-κB. The restoration of HDAC2 levels might be a therapeutic target for improving skeletal muscle weakness in COPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0588-8) contains supplementary material, which is available to authorized users.

Using laser capture microdissection to study fiber specific signaling in locomotor muscle in COPD: A pilot study

INTRODUCTION

Quadriceps dysfunction is important in chronic obstructive pulmonary disease (COPD), with an associated increased proportion of type II fibers. Investigation of protein synthesis and degradation has yielded conflicting results, possibly due to study of whole biopsy samples, whereas signaling may be fiber-specific. Our objective was to develop a method for fiber-specific gene expression analysis.

METHODS

12 COPD and 6 healthy subjects underwent quadriceps biopsy. Cryosections were immunostained for type II fibers, which were separated using laser capture microdissection (LCM). Whole muscle and different fiber populations were subject to quantitative polymerase chain reaction.

RESULTS

Levels of muscle-RING-finger-protein-1 and Atrogin-1 were lower in type II fibers of COPD versus healthy subjects (P = 0.02 and P = 0.03, respectively), but differences were not apparent in whole muscle or type I fibers.

CONCLUSIONS

We describe a novel method for studying fiber-specific gene expression in optimum cutting temperature compound-embedded muscle specimens. LCM offers a more sensitive way to identify molecular changes in COPD muscle. Muscle Nerve 55: 902-912, 2017.

Growth differentiation factor-15 is associated with muscle mass in chronic obstructive pulmonary disease and promotes muscle wasting in vivo

BACKGROUND

Loss of muscle mass is a co-morbidity common to a range of chronic diseases including chronic obstructive pulmonary disease (COPD). Several systemic features of COPD including increased inflammatory signalling, oxidative stress, and hypoxia are known to increase the expression of growth differentiation factor-15 (GDF-15), a protein associated with muscle wasting in other diseases. We therefore hypothesized that GDF-15 may contribute to muscle wasting in COPD.

METHODS

We determined the expression of GDF-15 in the serum and muscle of patients with COPD and analysed the association of GDF-15 expression with muscle mass and exercise performance. To determine whether GDF-15 had a direct effect on muscle, we also determined the effect of increased GDF-15 expression on the tibialis anterior of mice by electroporation.

RESULTS

Growth differentiation factor-15 was increased in the circulation and muscle of COPD patients compared with controls. Circulating GDF-15 was inversely correlated with rectus femoris cross-sectional area (P < 0.001) and exercise capacity (P < 0.001) in two separate cohorts of patients but was not associated with body mass index. GDF-15 levels were associated with 8-oxo-dG in the circulation of patients consistent with a role for oxidative stress in the production of this protein. Local over-expression of GDF-15 in mice caused wasting of the tibialis anterior muscle that expressed it but not in the contralateral muscle suggesting a direct effect of GDF-15 on muscle mass (P < 0.001).

CONCLUSIONS

Together, the data suggest that GDF-15 contributes to the loss of muscle mass in COPD.

Electrical stimulation influences chronic intermittent hypoxia-hypercapnia induction of muscle fibre transformation by regulating the microRNA/Sox6 pathway

Chronic obstructive pulmonary disease can cause muscle fibre transformation due to chronic intermittent hypoxia-hypercapnia (CIHH). Studies have shown that high expression of Sox6 in muscle could suppress type-I fibres through downregulating the PPARβ (peroxisome proliferator-activated receptor β)/ERRγ (oestrogen-related receptor γ)/microRNA pathway. However, whether this pathway is involved in CIHH-induced muscle fibre transformation is unknown. Electrical stimulation (ES) is an effective approach to ameliorate muscle dysfunction. Here, we explored the effects of ES on CIHH-induced muscle fibre transformation and the microRNA/Sox6 pathway. After CIHH exposure, both the soleus (SOL) and gastrocnemius (GC) muscles showed decreased type-I fibres. The PPARβ/ERRγ/mir-499&208b (PEM, for GC) and PPARβ/mir-499&208b (PM, for SOL) signalling cascades were suppressed, followed by elevated Sox6 expression. Low frequency electrical stimulation (LFES) activated the PEM/PM pathway and enhanced type-I fibre numbers through suppressing Sox6 in SOL and GC. High frequency electrical stimulation (HFES) promoted type-I fibre expression through activating the PEM pathway in GC. Although PPARβ expression and type-I fibres were suppressed in SOL after HFES, no significant change was found in mir-499&208b/Sox6 expression. These results suggest that the microRNA/Sox6 pathway is disturbed after CIHH. Both low and high frequency electrical stimulations induce muscle fibre transformation partly through regulating the microRNA/Sox6 pathway.

Blood flow-restricted strength training displays high functional and biological efficacy in women: a within-subject comparison with high-load strength training

Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 ± 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone. On the cellular level, 12 wk of BFR and HST resulted in similar shifts in muscle fiber composition in musculus vastus lateralis, evident as increased MyHC2A proportions and decreased MyHC2X proportions. They also resulted in similar changes of the expression of 29 genes involved in skeletal muscle function, measured both in a rested state following 12 wk of training and subsequent to singular training sessions. Training had no effect on myonuclei proportions. Of particular interest, 1) gross adaptations to BFR and HST were greater in individuals with higher proportions of type 2 fibers, 2) both BFR and HST resulted in approximately four-fold increases in the expression of the novel exercise-responsive gene Syndecan-4, and 3) BFR provided lesser hypertrophy than HST in the proximal half of musculus quadriceps femoris and also in CSApeak, potentially being a consequence of pressure from the tourniquet utilized to achieve blood flow restriction. In conclusion, BFR and HST of knee extensors resulted in similar adaptations in functional, physiological, and cell biological parameters in untrained women.

Diagnosis and pharmacotherapy of stable chronic obstructive pulmonary disease: the finnish guidelines

The Finnish Medical Society Duodecim initiated and managed the update of the Finnish national guideline for chronic obstructive pulmonary disease (COPD). The Finnish COPD guideline was revised to acknowledge the progress in diagnosis and management of COPD. This Finnish COPD guideline in English language is a part of the original guideline and focuses on the diagnosis, assessment and pharmacotherapy of stable COPD. It is intended to be used mainly in primary health care but not forgetting respiratory specialists and other healthcare workers. The new recommendations and statements are based on the best evidence available from the medical literature, other published national guidelines and the GOLD (Global Initiative for Chronic Obstructive Lung Disease) report. This guideline introduces the diagnostic approach, differential diagnostics towards asthma, assessment and treatment strategy to control symptoms and to prevent exacerbations. The pharmacotherapy is based on the symptoms and a clinical phenotype of the individual patient. The guideline defines three clinically relevant phenotypes including the low and high exacerbation risk phenotypes and the neglected asthma-COPD overlap syndrome (ACOS). These clinical phenotypes can help clinicians to identify patients that respond to specific pharmacological interventions. For the low exacerbation risk phenotype, pharmacotherapy with short-acting β2 -agonists (salbutamol, terbutaline) or anticholinergics (ipratropium) or their combination (fenoterol-ipratropium) is recommended in patients with less symptoms. If short-acting bronchodilators are not enough to control symptoms, a long-acting β2 -agonist (formoterol, indacaterol, olodaterol or salmeterol) or a long-acting anticholinergic (muscarinic receptor antagonists; aclidinium, glycopyrronium, tiotropium, umeclidinium) or their combination is recommended. For the high exacerbation risk phenotype, pharmacotherapy with a long-acting anticholinergic or a fixed combination of an inhaled glucocorticoid and a long-acting β2 -agonist (budesonide-formoterol, beclomethasone dipropionate-formoterol, fluticasone propionate-salmeterol or fluticasone furoate-vilanterol) is recommended as a first choice. Other treatment options for this phenotype include combination of long-acting bronchodilators given from separate inhalers or as a fixed combination (glycopyrronium-indacaterol or umeclidinium-vilanterol) or a triple combination of an inhaled glucocorticoid, a long-acting β2 -agonist and a long-acting anticholinergic. If the patient has severe-to-very severe COPD (FEV1  < 50% predicted), chronic bronchitis and frequent exacerbations despite long-acting bronchodilators, the pharmacotherapy may include also roflumilast. ACOS is a phenotype of COPD in which there are features that comply with both asthma and COPD. Patients belonging to this phenotype have usually been excluded from studies evaluating the effects of drugs both in asthma and in COPD. Thus, evidence-based recommendation of treatment cannot be given. The treatment should cover both diseases. Generally, the therapy should include at least inhaled glucocorticoids (beclomethasone dipropionate, budesonide, ciclesonide, fluticasone furoate, fluticasone propionate or mometasone) combined with a long-acting bronchodilator (β2 -agonist or anticholinergic or both).

Influência da força muscular isométrica de membros inferiores sobre equilíbrio e índice BODE em pacientes com DPOC: estudo transversal

Introdução Força muscular de membros inferiores (MMII) diminuída associa-se à limitação da capacidade funcional; entretanto, existem poucas evidências sobre a repercussão direta da fraqueza muscular periférica sobre tarefas de equilíbrio, bem como com o prognóstico de mortalidade nos pacientes com doença pulmonar obstrutiva crônica (DPOC). Objetivos Verificar se há relação da força isométrica de MMII com Índice BODE e equilíbrio funcional de pacientes com DPOC em reabilitação pulmonar (RP), além de investigar se esses pacientes apresentam fraqueza muscular, e se tal característica é capaz de influenciar nessas variáveis. Materiais e métodos Trata-se de um estudo transversal, onde avaliou-se 24 pacientes (idade > 50 anos) de ambos os gêneros, com DPOC moderada a muito grave (VEF1 = 44 (31 - 62,8)% previsto), por meio de:modified Medical Research Council (mMRC), Teste de Caminhada de 6 minutos (TC6), Índice BODE, TesteTimed “Up and Go” (TUG), Escala de Equilíbrio de Berg (EEB),Dynamic Gait Index (DGI) e Teste de Força Isométrica de Extensores de Joelho (ExtJ) e Abdutores de Quadril (AbdQ). Resultados Na amostra estudada, 54% dos pacientes apresentaram fraqueza muscular em ExtJ, com correlações moderadas da força de MMII com Índice BODE (AbdQ = -0,58) e mMRC (ExtJ = -0,48; AbdQ = -0,49). Foram encontradas diferenças para DPTC6 e mMRC quando a força dos ExtJ foi classificada em normal ou diminuída. Conclusão A força de AbdQ está associada ao prognóstico de mortalidade e a força de MMII está associada à sintomatologia em pacientes com DPOC em RP. Embora a força de MMII apresente impacto negativo na capacidade funcional e na dispneia, os pacientes desse estudo mantiveram preservado o equilíbrio e mobilidade funcional.

Systemic and pulmonary inflammation is independent of skeletal muscle changes in patients with chronic obstructive pulmonary disease

Background

Nutritional depletion is an important manifestation of chronic obstructive pulmonary disease (COPD), which has been related to systemic inflammation. It remains unclear to what degree airway inflammation contributes to the presence or progression of nutritional depletion.

Objectives

To determine whether airway inflammation and lung bacterial colonization are related to nutritional status or predict progressive weight loss and muscle atrophy in patients with COPD.

Methods

Body composition using dual energy X-ray absorptiometry, indices of airway inflammation, and bacterial colonization were measured in 234 COPD patients. Systemic inflammation was assessed from serum C reactive protein (CRP) and circulating total and differential leukocyte counts. Nutritional depletion was defined as a body mass index (BMI) less than 21 kg/m² and/or fat-free mass index (FFMI) less than 15 or 17 kg/m² in women and men, respectively. FFMI was calculated as the fat-free mass (FFM) corrected for body surface area. Measurements were repeated in 94 patients after a median 16-month follow-up. Regression analysis was used to assess the relationships of weight change and FFM change with indices of bacterial colonization and airway and systemic inflammation.

Results

Nutritional depletion occurred in 37% of patients. Lung function was worsened in patients with nutritional depletion compared to those without (forced expiratory volume in 1 second 1.17 L versus 1.41 L, mean difference 0.24, 95% confidence interval 0.10 to 0.38, P<0.01). There were no differences in airway inflammation and bacterial colonization in patients with and without nutritional depletion. At baseline, BMI correlated positively with serum CRP (r_s=0.14, P=0.04). Change in weight and change in FFM over time could not be predicted from baseline patient characteristics.

Conclusion

Nutritional depletion and progressive muscle atrophy are not related to airway inflammation or bacterial colonization. Overspill of pulmonary inflammation is not a key driver of muscle atrophy in COPD.

Pharmacological inhibition of GSK-3 in a guinea pig model of LPS-induced pulmonary inflammation: II. Effects on skeletal muscle atrophy

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is accompanied by pulmonary inflammation and associated with extra-pulmonary manifestations, including skeletal muscle atrophy. Glycogen synthase kinase-3 (GSK-3) has been implicated in the regulation of muscle protein- and myonuclear turnover; two crucial processes that determine muscle mass. In the present study we investigated the effect of the selective GSK-3 inhibitor SB216763 on muscle mass in a guinea pig model of lipopolysaccharide (LPS)-induced pulmonary inflammation-associated muscle atrophy.

METHODS

Guinea pigs were pretreated with either intranasally instilled SB216763 or corresponding vehicle prior to each LPS/saline challenge twice weekly. Pulmonary inflammation was confirmed and indices of muscle mass were determined after 12 weeks. Additionally, cultured skeletal muscle cells were incubated with tumor necrosis factor α (TNF-α) or glucocorticoids (GCs) to model the systemic effects of pulmonary inflammation on myogenesis, in the presence or absence of GSK-3 inhibitors.

RESULTS

Repeated LPS instillation induced muscle atrophy based on muscle weight and muscle fiber cross sectional area. Intriguingly, GSK-3 inhibition using SB216763 prevented the LPS-induced muscle mass decreases and myofiber atrophy. Indices of protein turnover signaling were unaltered in guinea pig muscle. Interestingly, inhibition of myogenesis of cultured muscle cells by TNF-α or synthetic GCs was prevented by GSK-3 inhibitors.

CONCLUSIONS

In a guinea pig model of LPS-induced pulmonary inflammation, GSK-3 inhibition prevents skeletal muscle atrophy without affecting pulmonary inflammation. Resistance to inflammation- or GC-induced impairment of myogenic differentiation, imposed by GSK-3 inhibition, suggests that sustained myogenesis may contribute to muscle mass maintenance despite persistent pulmonary inflammation. Collectively, these results warrant further exploration of GSK-3 as a potential novel drug target to prevent or reverse muscle wasting in COPD.

Ventilatory chemosensory drive is blunted in the mdx mouse model of Duchenne Muscular Dystrophy (DMD)

Duchenne Muscular Dystrophy (DMD) is caused by mutations in the DMD gene resulting in an absence of dystrophin in neurons and muscle. Respiratory failure is the most common cause of mortality and previous studies have largely concentrated on diaphragmatic muscle necrosis and respiratory failure component. Here, we investigated the integrity of respiratory control mechanisms in the mdx mouse model of DMD. Whole body plethysmograph in parallel with phrenic nerve activity recordings revealed a lower respiratory rate and minute ventilation during normoxia and a blunting of the hypoxic ventilatory reflex in response to mild levels of hypoxia together with a poor performance on a hypoxic stress test in mdx mice. Arterial blood gas analysis revealed low PaO2 and pH and high PaCO2 in mdx mice. To investigate chemosensory respiratory drive, we analyzed the carotid body by molecular and functional means. Dystrophin mRNA and protein was expressed in normal mice carotid bodies however, they are absent in mdx mice. Functional analysis revealed abnormalities in Dejours test and the early component of the hypercapnic ventilatory reflex in mdx mice. Together, these results demonstrate a malfunction in the peripheral chemosensory drive that would be predicted to contribute to the respiratory failure in mdx mice. These data suggest that investigating and monitoring peripheral chemosensory drive function may be useful for improving the management of DMD patients with respiratory failure.

Neuromuscular transmission in hypoxemic patients with chronic obstructive pulmonary disease

Many studies have focused on the systemic effects of chronic obstructive pulmonary disease (COPD), but none has examined neuromuscular junction transmission (NMT). We evaluated NMT dysfunction using single-fiber electromyography (SFEMG) in patients with COPD. Twenty patients with COPD and 20 age-matched healthy controls were included in the study. All patients and controls underwent SFEMG. Abnormal NMT was found in seven of 20 patients (35%), but in none of the control subjects. The COPD patients were subgrouped according to the presence of hypoxemia. The patients with normoxemia were classified as Group 1, and the patients with hypoxemia were classified as Group 2. Abnormal NMT was found in six patients in Group 2 and in one in Group 1. While there was significant difference in terms of abnormal NMT between Group 2 and the controls, there was none between Group 1 and the controls. Our results show that NMT abnormalities can be present in hypoxemic patients with COPD.

The relationship between pulmonary emphysema and kidney function in smokers

BACKGROUND

It has been reported that the prevalence of kidney dysfunction may be increased in patients exposed to tobacco with airflow obstruction. We hypothesized that kidney dysfunction would associate with emphysema rather than with airflow obstruction measured by the FEV₁.

METHODS

Five hundred eight current and former smokers completed a chest CT scan, pulmonary function tests, medical questionnaires, and measurement of serum creatinine. Glomerular filtration rates (eGFRs) were estimated using the method of the Chronic Kidney Disease Epidemiology Collaboration. Quantitative determinants of emphysema and airway dimension were measured from multidetector chest CT scans.

RESULTS

The mean age was 66 ± 7 years, and mean eGFR was 101 ± 22 mL/min/1.73 m². Univariate and multivariate analysis showed a significant association between radiographically measured emphysema and eGFR: Participants with 10% more emphysema had an eGFR that was lower by 4.4 mL/min/1.73 m² (P = .01), independent of airflow obstruction (FEV₁), age, sex, race, height, BMI, diabetes mellitus, hypertension, coronary artery disease, patient-reported dyspnea, pack-years of smoking, and current smoking. There was no association between eGFR and either FEV₁ or quantitative CT scan measures of airway dimension.

CONCLUSIONS

More severe emphysema, rather than airflow obstruction, is associated with kidney dysfunction in tobacco smokers, independent of common risk factors for kidney disease. This finding adds to recent observations of associations between emphysema and comorbidities of COPD, including osteoporosis and lung cancer, which are independent of the traditional measure of reduced FEV₁. The mechanisms and clinical implications of kidney dysfunction in patients with emphysema need further investigation.

Intraperitoneal injection of cigarette smoke extract induced emphysema, and injury of cardiac and skeletal muscles in BALB/C mice

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic, progressive, airway disease. In order to recognize mechanisms of COPD, various types of COPD animal models have been established, and the pathogenesis are different. The present study was designed to establish a COPD animal model by intraperitoneal injection of cigarette smoke extract (CSE) in BALB/C mice.

METHODS

Mice were injected intraperitoneally with PBS/CSE and sacrificed at day 28. Pulmonary function, pathology of lung tissue, morphology of hearts and skeletal muscle, leukocytes count and antioxidant activity of bronchoalveolar lavage fluid (BALF), pulmonary parenchymal apoptosis index (AI), expression of cleaved caspase-3, expression of MMP-2 and MMP-9 mRNA, and activity of MMP-2 and MMP-9 in lung tissue were measured.

RESULTS

Intraperitoneal injection of CSE induced pulmonary parenchymal destruction, pulmonary function reduction, leukocytes count, injury of cardiac and peripheral muscles, and increased pulmonary parenchymal AI, cleaved caspase-3 protein, expression of MMP-2 and MMP-9 mRNA, activity of MMP-2 and MMP-9 protein in lung tissue, and suppressed antioxidant activity in BALF (P < 0.05).

CONCLUSIONS

Intraperitoneal injection of CSE produced emphysema, pulmonary parenchymal apoptosis, and injury of cardiac and skeletal muscles in mice. All pathobiologically relevant mechanisms in this model are shared with the COPD patients.

Renin-angiotensin system blockade: a novel therapeutic approach in chronic obstructive pulmonary disease

ACE (angiotensin-converting enzyme) inhibitors and ARBs (angiotensin II receptor blockers) are already widely used for the treatment and prevention of cardiovascular disease and their potential role in other disease states has become increasingly recognized. COPD (chronic obstructive pulmonary disease) is characterized by pathological inflammatory processes involving the lung parenchyma, airways and vascular bed. The aim of the present review is to outline the role of the RAS (renin-angiotensin system) in the pathogenesis of COPD, including reference to results from fibrotic lung conditions and pulmonary hypertension. The review will, in particular, address the emerging evidence that ACE inhibition could have a beneficial effect on skeletal muscle function and cardiovascular co-morbidity in COPD patients. The evidence to support the effect of RAS blockade as a novel therapeutic approach in COPD will be discussed.

Muscle function in COPD: a complex interplay

The skeletal muscles play an essential role in life, providing the mechanical basis for respiration and movement. Skeletal muscle dysfunction is prevalent in all stages of chronic obstructive pulmonary disease (COPD), and significantly influences symptoms, functional capacity, health related quality of life, health resource usage and even mortality. Furthermore, in contrast to the lungs, the skeletal muscles are potentially remedial with existing therapy, namely exercise-training. This review summarizes clinical and laboratory observations of the respiratory and peripheral skeletal muscles (in particular the diaphragm and quadriceps), and current understanding of the underlying etiological processes. As further progress is made in the elucidation of the molecular mechanisms of skeletal muscle dysfunction, new pharmacological therapies are likely to emerge to treat this important extra-pulmonary manifestation of COPD.

Neuromuscular electrical stimulation prevents muscle function deterioration in exacerbated COPD: a pilot study

PURPOSE

COPD is a condition with systemic effects of which peripheral muscle dysfunction is a prominent contributor to exercise limitation, health related quality of life (HRQoL) impairment, and is an independent predictor of morbidity and mortality. Pulmonary rehabilitation (PR) is a successful strategy to improve exercise tolerance and HRQoL through the improvement of muscle function in patients with stable COPD or early after severe exacerbations of COPD (SECOPD). However, muscle function further deteriorates during SECOPD before early PR programmes commence. We aimed to investigate the feasibility and efficacy of quadriceps neuromuscular electrical stimulation (NMES) applied during a SECOPD to prevent muscle function deterioration.

METHODS

We have conducted a pilot study in eleven COPD patients (FEV(1) 41.3 ± 5.6 % pred) admitted to hospital with a SECOPD. We randomly allocated one leg to receive NMES (once a day for 14 days) with the other leg as a control (non-stimulated leg). We measured the change in quadriceps maximal voluntary contraction (ΔQMVC) as the main outcome.

RESULTS

Mean quadriceps muscle strength decreased in control legs (ΔQMVC -2.9 ± 5.3 N, p = ns) but increased in the stimulated legs (ΔQMVC 19.2 ± 6.1 N, p < 0.01). The difference in ΔQMVC between groups was statistically significant (p < 0.05). The effect of NMES was directly related to the stimulation intensity (∑mA) applied throughout the 14 sessions (r = 0.76, p < 0.01). All patients tolerated NMES without any side effects.

CONCLUSIONS

NMES is a feasible and effective treatment to prevent quadriceps muscle strength derangement during severe exacerbations of COPD and may be used to compliment early post-exacerbation pulmonary rehabilitation.

Muscle wasting in animal models of severe illness

Muscle wasting is a serious complication of various clinical conditions that significantly worsens the prognosis of the illnesses. Clinically relevant models of muscle wasting are essential for understanding its pathogenesis and for selective preclinical testing of potential therapeutic agents. The data presented here indicate that muscle wasting has been well characterized in rat models of sepsis (endotoxaemia, and caecal ligation and puncture), in rat models of chronic renal failure (partial nephrectomy), in animal models of intensive care unit patients (corticosteroid treatment combined with peripheral denervation or with administration of neuromuscular blocking drugs) and in murine and rat models of cancer (tumour cell transplantation). There is a need to explore genetically engineered mouse models of cancer. The degree of protein degradation in skeletal muscle is not well characterized in animal models of liver cirrhosis, chronic heart failure and chronic obstructive pulmonary disease. The major difficulties with all models are standardization and high variation in disease progression and a lack of reflection of clinical reality in some of the models. The translation of the information obtained by using these models to clinical practice may be problematic.

Increased steady-state VO2 and larger O2 deficit with CO2 inhalation during exercise

AIM

To examine whether inhalation of CO(2) -enriched gas would increase steady-state VO(2) during exercise and enlarge O(2) deficit.

METHODS

Ten physically active men (VO(2) 53.7 ± 3.6 mL min(-1) kg(-1) ; x ± SD) performed transitions from low-load cycling (baseline; 40 W) to work rates representing light (≈ 45% VO(2); 122 ± 15 W) and heavy (≈ 80% VO(2); 253 ± 29 W) exercise while inhaling normal air (air) or a CO(2) mixture (4.2% CO(2) , 21% O(2) , balance N(2) ). Gas exchange was measured with Douglas bag technique at baseline and at min 0-2, 2-3 and 5-6.

RESULTS

Inhalation of CO(2) -enriched air consistently induced respiratory acidosis with increases in PCO(2) and decreases in capillary blood pH (P < 0.01). Hypercapnic steady-state VO(2) was on average about 6% greater (P < 0.01) than with air in both light and heavy exercise, presumably because of increased cost of breathing (ΔVE 40-50 L min(-1) ; P < 0.01), and a substrate shift towards increased lipid oxidation (decline in R 0.12; P < 0.01). VO(2) during the first 2 min of exercise were not significantly different whereas the increase in VO(2) from min 2-3 to min 5-6 in heavy exercise was larger with CO(2) than with air suggesting a greater VO(2) slow component. As a result, O(2) deficit was greater with hypercapnia in heavy exercise (2.24 ± 0.51 L vs. 1.91 ± 0.45 L; P < 0.05) but not in light (0.64 ± 0.21 L vs. 0.54 ± 0.20 L; ns).

CONCLUSION

Inhalation of CO(2)-enriched air and the ensuing respiratory acidosis increase steady-state VO(2) in both light and heavy exercise and enlarges O(2) deficit in heavy exercise.

Chronic hypobaric hypoxia increases isolated rat fast-twitch and slow-twitch limb muscle force and fatigue

Chronic hypoxia alters respiratory muscle force and fatigue, effects that could be attributed to hypoxia and/or increased activation due to hyperventilation. We hypothesized that chronic hypoxia is associated with phenotypic change in non-respiratory muscles and therefore we tested the hypothesis that chronic hypobaric hypoxia increases limb muscle force and fatigue. Adult male Wistar rats were exposed to normoxia or hypobaric hypoxia (PB=450 mm Hg) for 6 weeks. At the end of the treatment period, soleus (SOL) and extensor digitorum longus (EDL) muscles were removed under pentobarbitone anaesthesia and strips were mounted for isometric force determination in Krebs solution in standard water-jacketed organ baths at 25 °C. Isometric twitch and tetanic force, contractile kinetics, force-frequency relationship and fatigue characteristics were determined in response to electrical field stimulation. Chronic hypoxia increased specific force in SOL and EDL compared to age-matched normoxic controls. Furthermore, chronic hypoxia decreased endurance in both limb muscles. We conclude that hypoxia elicits functional plasticity in limb muscles perhaps due to oxidative stress. Our results may have implications for respiratory disorders that are characterized by prolonged hypoxia such as chronic obstructive pulmonary disease (COPD).

Cigarette smoke-induced skeletal muscle atrophy is associated with up-regulation of USP-19 via p38 and ERK MAPKs

Ubiquitin-specific proteases (USPs) deubiquitinate ubiquitin-protein conjugates in the ubiquitin-proteasome system. Previous research shows that ubiquitin-specific protease-19 (USP-19) is up-regulated in mammalian skeletal muscle in some degradative conditions, such as including fasting, diabetes, dexamethasone treatment, and cancer, and its function is associated with muscle atrophy. However, it is still unclear whether USP-19 is involved in muscle atrophy induced by chronic obstructive pulmonary disease. Rats exposed to chronic cigarette smoke and L6 myotubes incubated with cigarette smoke extract (CSE) were studied here. Using western blot analysis and quantitative real-time polymerase chain reaction (qPCR), we observed over-expression of USP-19 and down-regulation of myosin heavy chain (MHC) in both models. Moreover, CSE exposure inhibited myogenic differentiation and myotube formation in L6 myotubes. To explore the mechanism underlying these effects, we investigated the levels of phosphorylated mitogen-activated protein kinases (MAPKs) and total MAPKs. Exposing myotubes to CSE resulted in the general activation of MAPKs such as p38, JNK, and ERK1/2. The ERK inhibitor PD98059 and the p38 inhibitor SB203580 significantly blocked the increase in USP-19 gene expression induced by CSE. Our findings suggest that USP-19 is associated with muscle atrophy in response to cigarette smoke and is a potential therapeutic target. CSE promotes myotube wasting in culture partly by inhibiting myogenic differentiation and acts via p38 and ERK MAPK to stimulate expression of USP-19 in vitro.

Lung transplantation and lung volume reduction surgery

Since the publication of the last edition of the Handbook of Physiology, lung transplantation has become widely available, via specialized centers, for a variety of end-stage lung diseases. Lung volume reduction surgery, a procedure for emphysema first conceptualized in the 1950s, electrified the pulmonary medicine community when it was rediscovered in the 1990s. In parallel with their technical and clinical refinement, extensive investigation has explored the unique physiology of these procedures. In the case of lung transplantation, relevant issues include the discrepant mechanical function of the donor lungs and recipient thorax, the effects of surgical denervation, acute and chronic rejection, respiratory, chest wall, and limb muscle function, and response to exercise. For lung volume reduction surgery, there have been new insights into the counterintuitive observation that lung function in severe emphysema can be improved by resecting the most diseased portions of the lungs. For both procedures, insights from physiology have fed back to clinicians to refine patient selection and to scientists to design clinical trials. This section will first provide an overview of the clinical aspects of these procedures, including patient selection, surgical techniques, complications, and outcomes. It then reviews the extensive data on lung and muscle function following transplantation and its complications. Finally, it reviews the insights from the last 15 years on the mechanisms whereby removal of lung from an emphysema patient can improve the function of the lung left behind.