Exercise Training Reverses Extrapulmonary Impairments in Smoke-exposed Mice

Diaphragm thickness and physical performance in regular smokers and non-smokers: A pilot study

BACKGROUND

Despite the understanding of the role of diaphragm role as a crucial element in trunk stabilizer performance, limited research has been carried out on the diaphragmatic features particularly in smoking population.

OBJECTIVES

It was aimed to compare the diaphragm structure beside trunk stabilizer performance & body balance of young regular smokers and non-smokers and investigate the relationship between diaphragmatic features and physical performance in regular smokers.

METHODS

Asymptomatic regular smoker (n = 22) and nonsmoker (n = 22) young male subjects (21.63 ± 2.37 years) were participated to the study. The diaphragmatic ultrasonic scanning and physical performance tests of core muscle strength and endurance & Y balance test were performed.

RESULTS

The duration of prone and lateral side bridge (t = -3.347, t = 3.477, p < 0.001), and modify push-up test repetition (Z = -2.213, p = 0.027) were detected lower in regular smokers. A positive moderate correlation was observed between the duration of the prone bridge test and the maximum inspiration thickness & the thickness difference at inspiration and expiration (r = 0.545, p = 0.009 & r = 0.468, p = 0.028) and between the number of repetitions of the modify push-up and the maximum expiration thickness (r = 0.530, p = 0.011).

CONCLUSION

While no difference was detected in terms of the diaphragm structure between groups, trunk stabilizer performance was lower and greater diaphragm thickness was associated with better trunk stability in some performance tasks in smokers. While the diaphragm muscle structure, which is the main respiratory muscle, does not differ in young smokers, the effects of the diaphragm muscle on general body biomechanics have been preliminary demonstrated.

Immune system benefits of pulmonary rehabilitation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a respiratory disease characterized by pulmonary and systemic inflammation. Inflammatory mediators show relationships with shortness of breath, exercise intolerance and health related quality of life. Pulmonary rehabilitation (PR), a comprehensive education and exercise training programme, is the most effective therapy for COPD and is associated with reduced exacerbation and hospitalization rates and increased survival. Exercise training, the primary physiological intervention within PR, is known to exert a beneficial anti-inflammatory effect in health and chronic diseases. The question of this review article is whether exercise training can also make such a beneficial anti-inflammatory effect in COPD. Experimental studies using smoke exposure mice models suggest that the response of the immune system to exercise training is favourably anti-inflammatory. However, the evidence about the response of most known inflammatory mediators (C-reactive protein, tumour necrosis factor α, interleukin 6, interleukin 10) to exercise training in COPD patients is inconsistent, making it difficult to conclude whether regular exercise training has an anti-inflammatory effect in COPD. It is also unclear whether COPD patients with more persistent inflammation are a subgroup that would benefit more from hypothesized immunomodulatory effects of exercise training (i.e., personalized treatment). Nevertheless, it seems that PR combined with maintenance exercise training (i.e., lifestyle change) might be more beneficial in controlling inflammation and slowing disease progress in COPD patients, specifically in those with early stages of disease.

Exercise Attenuate Diaphragm Atrophy in COPD Mice via Inhibiting the RhoA/ROCK Signaling

Background

Exercise is an indispensable component of pulmonary rehabilitation with strong anti-inflammatory effects. However, the mechanisms by which exercise prevents diaphragmatic atrophy in COPD (chronic obstructive pulmonary disease) remain unclear.

Methods

Forty male C57BL/6 mice were assigned to the control (n=16) and smoke (n=24) groups. Mice in the smoke group were exposed to the cigarette smoke (CS) for six months. They were then divided into model and exercise training groups for 2 months. Histological changes were observed in lung and diaphragms. Subsequently, agonist U46639 and antagonist Y27632 of RhoA/ROCK were subjected to mechanical stretching in LPS-treated C2C12 myoblasts. The expression levels of Atrogin-1, MuRF-1, MyoD, Myf5, IL-1β, TNF-α, and RhoA/ROCK were determined by Western blotting.

Results

Diaphragmatic atrophy and increased RhoA/ROCK expression were observed in COPD mice. Exercise training attenuated diaphragmatic atrophy, decreased the expression of MuRF-1, and increased MyoD expression in COPD diaphragms. Exercise also affects the upregulation of RhoA/ROCK and inflammation-related proteins. In in vitro experiments with C2C12 myoblasts, LPS remarkably increased the level of inflammation and protein degradation, whereas Y27632 or combined with mechanical stretching prevented this phenomenon considerably.

Conclusion

RhoA/ROCK plays an important role in the prevention of diaphragmatic atrophy in COPD.

Altered skeletal muscle function and beneficial effects of exercise training in a rat model of induced pulmonary emphysema

AIM

Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow obstruction and development of emphysema. Among the comorbidities associated with COPD, skeletal muscle dysfunction is known to affect exercise capacity and the survival rate of patients. Pulmonary rehabilitation (PR), via exercise training, is essential for COPD patients. However, the response to PR is most often moderate. An animal model that recapitulates critical features of chronic human disease and provides access to muscle function should therefore be useful to improve PR benefits.

METHODS

We used a rat model of induced emphysema based on pulmonary instillations of elastase (ELA) and lipopolysaccharides (LPS). We assessed the long-term effects of ELA/LPS and the potential effectiveness of endurance training on the skeletal muscle function. In vivo strength of the animals, and ex vivo contractility, endurance, type 1 fiber proportion, fiber cross-sectional area, and capillarization of both soleus and extensor digitorum longus (EDL) were assessed.

RESULTS

An impaired overall muscle strength with decreased force, reduced capillarization, and atrophy of type 1 fiber of EDL was observed in ELA/LPS rats. Soleus was not affected. Endurance training was able to reduce fatigability, and increase type 1 fiber proportion and capillarization of soleus, and improve force, endurance, and capillarization of EDL in control and ELA/LPS rats.

CONCLUSION

Our rat model of induced emphysema, which shares some features with the phenotype present in patients with COPD, could represent a suitable model to study skeletal muscle dysfunction and the effects of exercise training on muscle function in patients.

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.

Identification of exercise-regulated genes in mice exposed to cigarette smoke

Cigarette smoke (CS) is the major risk factor for COPD and is linked to cardiopulmonary dysfunction. Exercise training as part of pulmonary rehabilitation is recommended for all COPD patients. It has several physiological benefits, but the mechanisms involved remain poorly defined. Here, we employed transcriptomic profiling and examined lung endothelium to investigate novel interactions between exercise and CS on cardiopulmonary alterations. Mice were exposed to 20 weeks of CS, CS + 6 weeks of high-intensity interval training on a treadmill, or control. Lung and cardiac (left and right ventricle) tissue were harvested and RNA-sequencing was performed and validated with RT-qPCR. Immunohistochemistry assessed pulmonary arteriolar changes. Transcriptome analysis between groups revealed 37 significantly regulated genes in the lung, 21 genes in the left ventricle, and 43 genes in the right ventricle (likelihood-ratio test). Validated genes that showed interaction between exercise and CS included angiotensinogen (p = 0.002) and resistin-like alpha (p = 0.019) in left ventricle, with prostacyclin synthetase different in pulmonary arterioles (p = 0.004). Transcriptomic profiling revealed changes in pulmonary and cardiac tissue following exposure to CS, with exercise training exerting rescue effects. Exercise-regulated genes included angiotensinogen and resistin-like alpha, however, it remains unclear if these represent potential candidate genes or biomarkers that could play a role during pulmonary rehabilitation.

Integrating Mechanisms of Exacerbated Atrophy and Other Adverse Skeletal Muscle Impact in COPD

The normal decline in skeletal muscle mass that occurs with aging is exacerbated in patients with chronic obstructive pulmonary disease (COPD) and contributes to poor health outcomes, including a greater risk of death. There has been controversy about the causes of this exacerbated muscle atrophy, with considerable debate about the degree to which it reflects the very sedentary nature of COPD patients vs. being precipitated by various aspects of the COPD pathophysiology and its most frequent proximate cause, long-term smoking. Consistent with the latter view, recent evidence suggests that exacerbated aging muscle loss with COPD is likely initiated by decades of smoking-induced stress on the neuromuscular junction that predisposes patients to premature failure of muscle reinnervation capacity, accompanied by various alterations in mitochondrial function. Superimposed upon this are various aspects of COPD pathophysiology, such as hypercapnia, hypoxia, and inflammation, that can also contribute to muscle atrophy. This review will summarize the available knowledge concerning the mechanisms contributing to exacerbated aging muscle affect in COPD, consider the potential role of comorbidities using the specific example of chronic kidney disease, and identify emerging molecular mechanisms of muscle impairment, including mitochondrial permeability transition as a mechanism of muscle atrophy, and chronic activation of the aryl hydrocarbon receptor in driving COPD muscle pathophysiology.

Interaction between cigarette smoke exposure and physical training on inflammatory and oxidative profile in mice muscle

Regular physical training and cigarette smoke exposure (CSE) have opposite effects on physical performance, antioxidant, and inflammatory profile. However, the interaction between these events is not well studied. We aimed to investigate how regular physical training and CSE interact, and in what is the outcome of this interaction on the physical performance, skeletal muscle antioxidant defense and molecular profile response of pro and anti-inflammatory cytokines. Male C57BL/6 mice were randomly divided into 4 groups (n = 8/group): 1) Sedentary group (SED); 2) 4 weeks of control, followed by 4 weeks of CSE (SED + CSEG); 3) Physically active (PA) along 8 weeks (forced swim training, 5 times a week); 4) Physically active and exposed to the cigarette smoke (PA + CSEG), group submitted to forced swim training for 4 weeks, followed by 4 weeks of concomitant training and CSE. Physical performance was evaluated before and after the experimental period (8 weeks), total peroxidase and glutathione peroxidase (GPx) activities, expression of genes encoding TNF-α, MCP-1, IL1β, IL-6, IL-10, TGF-β, HO-1 and the TNF-α/IL-10 ratio were determined from gastrocnemius muscle at the end of experimental period. The CSE attenuated the aerobic capacity adaptation (time to exhaustion in swimming forced test) promoted by physical training and inhibit the improvement in local muscle resistance (inverted screen test). The regular physical training enhanced the antioxidant defense, but the CSE abrogated this benefit. The CSE induced a harmful pro-inflammatory profile in skeletal muscle from sedentary animals whereas the regular physical training induced an opposite adaptation. Likewise, the CSE abolished the protective effect of physical training. Together, these results suggest a negative effect of CSE including, at least in part, the inhibition/attenuation of beneficial adaptations from regular physical training.

High-intensity interval training and pulmonary hemodynamics in COPD with hypoxemia

Background

Exercise is recommended for all patients with COPD. Evidence for its benefit is considerably weaker in the more severe stages of the disease. The aim of this study was to investigate whether high-intensity interval training could improve exercise capacity, pulmonary hemodynamics and cardiac function in patients with severe COPD and hypoxemia.

Methods

Stable patients with COPD GOLD stage III or IV and hypoxemia were included. They underwent extensive cardiopulmonary testing including right heart catheterization, lung function tests, echocardiography and 6-minute walk test before and after completion of 10 weeks of high-intensity interval training performed with supplemental oxygen. Primary endpoint was change in pulmonary artery pressure measured by right heart catheterization.

Results

Ten patients with very severe airflow obstruction, mean FEV1 28.7% predicted and mean FEV1/VC 0.39 completed the exercise programme. Pulmonary artery pressure remained unchanged following the intervention (26,3 mmHg vs. 25,8 mmHg at baseline, p 0.673). Six-minute walk distance improved by a mean of44.8 m (p 0.010), which is also clinically significant. We found marginally improved left ventricular ejection fraction on echocardiography (54.6% vs 59.5%, p 0.046).

Conclusion

High-intensity interval training significantly improved exercise capacity while pulmonary hemodynamics remained unchanged. The improvement may therefore be due to mechanisms other than altered pulmonary artery pressure. The increase in ejection fraction is of uncertain clinical significance. The low number of patients precludes firm conclusions.

Effects of physical exercise on baroreflex sensitivity and renal sympathetic nerve activity in chronic nicotine-treated rats

Chronic nicotine exposure may increase cardiovascular risk by impairing the cardiac autonomic function. Besides, physical exercise (PE) has shown to improve cardiovascular health. Thus, we aimed to investigate the effects of PE on baroreflex sensitivity (BRS), heart rate variability (HRV), and sympathetic nerve activity (SNA) in chronically nicotine-exposed rats. Male Wistar rats were assigned to four independent groups: Control (treated with saline solution), Control+Ex (treated with saline and submitted to treadmill training), Nicotine (treated with Nicotine), and Nicotine+Ex (treated with nicotine and submitted to treadmill training). Nicotine (1 mg·kg-1) was administered daily for 28 consecutive days. PE consisted of running exercise (60%-70% of maximal aerobic capacity) for 45 min, 5 days per week, for 4 weeks. At the end of the protocol, cardiac BRS, HRV, renal SNA (rSNA), and renal BRS were assessed. Nicotine treatment decreased absolute values of HRV indexes, increased low frequency/high frequency ratio of HRV, reduced the bradycardic and sympatho-inhibitory baroreceptor reflex responses, and reduced the rSNA. PE effectively restored time-domain HRV indexes, the bradycardic and sympatho-inhibitory reflex responses, and the rSNA in chronic nicotine-treated rats. PE was effective in preventing the deterioration of time-domain parameters of HRV, arterial baroreceptor dysfunction, and the rSNA after nicotine treatment.

Skeletal muscle mitochondrial adaptations induced by long-term cigarette smoke exposure

Because patients with chronic obstructive pulmonary disease (COPD) are often physically inactive, it is still unclear whether the lower respiratory capacity in the locomotor muscles of these patients is due to cigarette smoking per se or is secondary to physical deconditioning. Accordingly, the purpose of this study was to examine mitochondrial alterations in the quadriceps muscle of 10 mice exposed to 8 mo of cigarette smoke, a sedentary mouse model of emphysema, and 9 control mice, using immunoblotting, spectrophotometry, and high-resolution respirometry in permeabilized muscle fibers. Mice exposed to smoke displayed a twofold increase in the oxidative stress marker, 4-HNE, (P < 0.05) compared with control mice. This was accompanied by significant decrease in protein expression of UCP3 (65%), ANT (58%), and mitochondrial complexes II-V (∼60%-75%). In contrast, maximal ADP-stimulated respiration with complex I and II substrates (CON: 23.6 ± 6.6 and SMO: 19.2 ± 8.2 ρM·mg-1·s-1) or octanoylcarnitine (CON: 21.8 ± 9.0 and SMO: 16.5 ± 6.6 ρM·mg-1·s-1) measured in permeabilized muscle fibers, as well as citrate synthase activity, were not significantly different between groups. Collectively, our findings revealed that sedentary mice exposed to cigarette smoke for 8 mo, which is typically associated with pulmonary inflammation and emphysema, exhibited a preserved mitochondrial respiratory capacity for various substrates, including fatty acid, in the skeletal muscle. However, the mitochondrial adaptations induced by cigarette smoke favored the development of chronic oxidative stress, which can indirectly contribute to augment the susceptibility to muscle fatigue and exercise intolerance.NEW & NOTEWORTHY It is unclear whether the exercise intolerance and skeletal muscle mitochondrial dysfunction observed in patients with COPD is due to cigarette smoke exposure, per se, or if they are secondary consequences to inactivity. Herein, while long-term exposure to cigarette smoke induces oxidative stress and an altered skeletal muscle phenotype, cigarette smoke does not directly contribute to mitochondrial dysfunction. With this evidence, we demonstrate the critical role of physical inactivity in cigarette smoke-related skeletal muscle dysfunction.

Effect of Oxidative Stress on Diaphragm Dysfunction and Exercise Intervention in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) can cause extrapulmonary injury such as diaphragm dysfunction. Oxidative stress is one of the main factors causing diaphragm dysfunction in COPD. Exercise plays a positive role in the prevention and treatment of diaphragm dysfunction in COPD, and the changes in diaphragm structure and function induced by exercise are closely related to the regulation of oxidative stress. Therefore, on the basis of the review of oxidative stress and the changes in diaphragm structure and function in COPD, this article analyzed the effects of exercise on oxidative stress and diaphragm dysfunction in COPD and explored the possible mechanism by which exercise improves oxidative stress. Studies have found that diaphragm dysfunction in COPD includes the decline of muscle strength, endurance, and activity. Oxidative stress mainly affects the structure and function of the diaphragm in COPD through protein oxidation, protease activation and calcium sensitivity reduction. The effects of exercise on oxidative stress level and diaphragm dysfunction may differ depending on the intensity, duration, and style of exercise. The mechanism of exercise on oxidative stress in the diaphragm of COPD may include improving antioxidant capacity, reducing oxidase activity and improving mitochondrial function.

Two Weeks of Smoking Cessation Reverse Cigarette Smoke-Induced Skeletal Muscle Atrophy and Mitochondrial Dysfunction in Mice

INTRODUCTION

Apart from its adverse effects on the respiratory system, cigarette smoking also induces skeletal muscle atrophy and dysfunction. Whether short-term smoking cessation can restore muscle mass and function is unknown. We, therefore, studied the impact of 1- and 2-week smoking cessation on skeletal muscles in a mouse model.

METHODS

Male mice were divided into four groups: Air-exposed (14 weeks); cigarette smoke (CS)-exposed (14 weeks); CS-exposed (13 weeks) followed by 1-week cessation; CS-exposed (12 weeks) followed by 2 weeks cessation to examine exercise capacity, physical activity levels, body composition, muscle function, capillarization, mitochondrial function and protein expression in the soleus, plantaris, and diaphragm muscles.

RESULTS

CS-induced loss of body and muscle mass was significantly improved within 1 week of cessation due to increased lean and fat mass. Mitochondrial respiration and protein levels of the respiratory complexes in the soleus were lower in CS-exposed mice, but similar to control values after 2 weeks of cessation. Exposing isolated soleus muscles to CS extracts reduced mitochondrial respiration that was reversed after removing the extract. While physical activity was reduced in all groups, exercise capacity, limb muscle force, fatigue resistance, fiber size and capillarization, and diaphragm cytoplasmic HIF-1α were unaltered by CS-exposure. However, CS-induced diaphragm atrophy and increased capillary density were not seen after 2 weeks of smoking cessation.

CONCLUSION

In male mice, 2 weeks of smoking cessation reversed smoking-induced mitochondrial dysfunction, limb muscle mass loss, and diaphragm muscle atrophy, highlighting immediate benefits of cessation on skeletal muscles.

IMPLICATIONS

Our study demonstrates that CS-induced skeletal muscle mitochondrial dysfunction and atrophy are significantly improved by 2 weeks of cessation in male mice. We show for the first time that smoking cessation as short as 1 to 2 weeks is associated with immediate beneficial effects on skeletal muscle structure and function with the diaphragm being particularly sensitive to CS-exposure and cessation. This could help motivate smokers to quit smoking as early as possible. The knowledge that smoking cessation has potential positive extrapulmonary effects is particularly relevant for patients referred to rehabilitation programs and those admitted to hospitals suffering from acute or chronic muscle deterioration yet struggling with smoking cessation.

CIMI: Classify and Itemize Medical Image System for PFT Big Data Based on Deep Learning

The value of pulmonary function test (PFT) data is increasing due to the advent of the Coronavirus Infectious Disease 19 (COVID-19) and increased respiratory disease. However, these PFT data cannot be directly used in clinical studies, because PFT results are stored in raw image files. In this study, the classification and itemization medical image (CIMI) system generates valuable data from raw PFT images by automatically classifying various PFT results, extracting texts, and storing them in the PFT database and Excel files. The deep-learning-based optical character recognition (OCR) technology was mainly used in CIMI to classify and itemize PFT images in St. Mary’s Hospital. CIMI classified seven types and itemized 913,059 texts from 14,720 PFT image sheets, which cannot be done by humans. The number, type, and location of texts that can be extracted by PFT type are all different, but CIMI solves this issue by classifying the PFT image sheets by type, allowing researchers to analyze the data. To demonstrate the superiority of CIMI, the validation results of CIMI were compared to the results of the other four algorithms. A total of 70 randomly selected sheets (ten sheets from each type) and 33,550 texts were used for the validation. The accuracy of CIMI was 95%, which was the highest accuracy among the other four algorithms.

Aerobic exercise training attenuates detrimental effects of cigarette smoke exposure on peripheral muscle through stimulation of the Nrf2 pathway and cytokines: a time-course study in mice

Cigarette smoke (CS) exposure reduces skeletal muscle function; however, the mechanisms involved have been poorly investigated. The current study evaluated the temporal effects of aerobic exercise training on oxidant and antioxidant systems as well as inflammatory markers in skeletal muscle of mice exposed to CS. Mice were randomly allocated to control, exercise, smoke, and smoke+exercise groups and 3 time points (4, 8, and 12 weeks; n = 12 per group). Exercise training and CS exposure were performed for 30 min/day, twice a day, 5 days/week for 4, 8, and 12 weeks. Aerobic exercise improved functional capacity and attenuated the increase in the cachexia index induced by CS exposure after 12 weeks. Concomitantly, exercise training downregulated tumor necrosis factor α concentration, glutathione oxidation, and messenger RNA (mRNA) expression of Keap1 (P < 0.01) and upregulated interleukin 10 concentration, total antioxidant capacity, and mRNA expression of Nrf2, Gsr, and Txn1 (P < 0.01) in muscle. Exercise increased mRNA expression of Hmox1 compared with the control after 12 weeks (P < 0.05). There were no significant differences between smoke groups for superoxide dismutase activity and Hmox1 mRNA expression. Exercise training improved the ability of skeletal muscle to adequately upregulate key antioxidant and anti-inflammatory defenses to detoxify electrophilic compounds induced by CS exposure, and these effects were more pronounced after 12 weeks. Novelty Exercise attenuates oxidative stress in skeletal muscle from animals exposed to CS via Nrf2 and glutathione pathways. Exercise is a helpful tool to control the inflammatory balance in skeletal muscle from animals exposed to CS. These beneficial effects were evident after 12 weeks.

The rat model of COPD skeletal muscle dysfunction induced by progressive cigarette smoke exposure: a pilot study

Background

Chronic obstructive pulmonary disease (COPD) skeletal muscle dysfunction is a prevalent malady that significantly affects patients’ prognosis and quality of life. Although the study of this disease has attracted considerable attention, a definite animal model is yet to be established. This study investigates whether smoke exposure could lead to the development of a COPD skeletal muscle dysfunction model in rats.

Methods

Sprague Dawley rats were randomly divided into model (MG, n = 8) and control groups (CG, n = 6). The MG was exposed to cigarette smoke for 16 weeks while the CG was not. The body weight and forelimb grip strength of rats were monitored monthly. The pulmonary function and the strength of tibialis anterior muscle were assessed in vitro and compared after establishing the model. The histological changes in lung and gastrocnemius muscles were observed. The expressions of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α were detected by ELISA, while the expressions of Atrogin-1 and MuRF1 in the gastrocnemius muscle were determined by Western blotting.

Results

Smoke exposure slowly increases the body weight and forelimb grip strength of MG rats, compared to CG rats. However, it significantly decreases the pulmonary ventilation function and the skeletal muscle contractility of the MG in vitro. Histologically, the lung tissues of MG show typical pathological manifestations of emphysema, while the skeletal muscles present muscular atrophy. The expressions of IL-6, IL-8, and TNF-α in MG rats are significantly higher than those measured in CG rats. Increased levels of Atrogin-1 and MuRF1 were also detected in the gastrocnemius muscle tissue of MG.

Conclusion

Progressive smoking exposure decreases the contractile function of skeletal muscles, leading to muscular atrophy. It also increases the expressions of inflammatory and muscle protein degradation factors in COPD rats. This indicates that smoke exposure could be used to establish a COPD skeletal muscle dysfunction model in rats.

Muscle metabolomics analysis reveals potential biomarkers of exercise‑dependent improvement of the diaphragm function in chronic obstructive pulmonary disease

Decreased diaphragm function is a crucial factor leading to reduced ventilatory efficiency and worsening of quality of life in chronic obstructive pulmonary disease (COPD). Exercise training has been demonstrated to effectively improve the function of the diaphragm. However, the mechanism of this process has not been identified. The emergence of metabolomics has allowed the exploration of new ideas. The present study aimed to analyze the potential biomarkers of exercise-dependent enhancement of diaphragm function in COPD using metabolomics. Sprague Dawley rats were divided into three groups: COPD + exercise group (CEG); COPD model group (CMG); and control group (CG). The first two groups were exposed to cigarette smoke for 16 weeks to establish a COPD model. Then, the rats in the CEG underwent aerobic exercise training for 9 weeks. Following confirmation that exercise effectively improved the diaphragm function, a gas chromatography tandem time-of-flight mass spectrometry analysis system was used to detect the differential metabolites and associated pathways in the diaphragm muscles of the different groups. Following exercise intervention, the pulmonary function and diaphragm contractility of the CEG rats were significantly improved compared with those of the CMG rats. A total of 36 different metabolites were identified in the comparison between the CMG and the CG. Pathway enrichment analysis indicated that these different metabolites were involved in 17 pathways. A total of 29 different metabolites were identified in the comparison between the CMG and the CEG, which are involved in 14 pathways. Candidate biomarkers were selected, and the pathways analysis of these metabolites demonstrated that 2 types of metabolic pathways, the nicotinic acid and nicotinamide metabolism and arginine and proline metabolism pathways, were associated with exercise-induced pulmonary rehabilitation.

Comparison of morphometry and ventricular function of healthy and smoking young people

Background

Tobacco smoke is one of the most significant risk factors for cardiovascular diseases and damages in the myocardial tissue directly. Cardiac magnetic resonance (CMR) has been used and is a promising tool to evaluate morphometry and cardiac function in humans. The objective of this study was to evaluate associations of smoking with morphometry and cardiac function by CMR technique in young adult smokers.

Methods

Altogether, 49 volunteers (22 smokers and 27 non-smokers) were included in the study. The comparisons between groups were performed by multiple linear regression adjusting for body mass index and gender.

Results

In the morphometric and functional evaluation of the left ventricle, we observed statistical significant lower values of end-diastolic volume (EDV) (p = 0.02), ejection volume (EV) (p = 0.001) and indexed ejection volume (IEV) (p = 0.007) in smokers when compared to no-smoker group. Right ventricle showed statistical significant lower values of EDV (p = < 0.001), end-systolic volume (p = 0.01), EV (p = < 0.001), IEV (p = 0.001), indexed end-diastolic volume (p = 0.001) and major axis (p = 0.01) in smokers when compared to non-smokers group.

Conclusions

There is a strongly association of smoking in young adult and cardiac function decline, even adjusted by cofounders, which compromises the proper functioning of the heart. Evidence confirms that smoking can directly influence the cardiac function, even without atherosclerosis or other chronic comorbidities, associated with increased risk of cardiovascular diseases.

Skeletal myofiber VEGF deficiency leads to mitochondrial, structural, and contractile alterations in mouse diaphragm

Diaphragm dysfunction accompanies cardiopulmonary disease and impaired oxygen delivery. Vascular endothelial growth factor (VEGF) regulates oxygen delivery through angiogenesis, capillary maintenance, and contraction-induced perfusion. We hypothesized that myofiber-specific VEGF deficiency contributes to diaphragm weakness and fatigability. Diaphragm protein expression, capillarity and fiber morphology, mitochondrial respiration and hydrogen peroxide (H₂O₂) generation, and contractile function were compared between adult mice with conditional gene ablation of skeletal myofiber VEGF (SkmVEGF^-/-; n = 12) and littermate controls (n = 13). Diaphragm VEGF protein was ~50% lower in SkmVEGF^-/- than littermate controls (1.45 ± 0.65 vs. 3.04 ± 1.41 pg/total protein; P = 0.001). This was accompanied by an ~15% impairment in maximal isometric specific force (F[1,23] = 15.01, P = 0.001) and a trend for improved fatigue resistance (P = 0.053). Mean fiber cross-sectional area and type I fiber cross-sectional area were lower in SkmVEGF^-/- by ~40% and ~25% (P < 0.05). Capillary-to-fiber ratio was also lower in SkmVEGF^-/- by ~40% (P < 0.05), and thus capillary density was not different. Sarcomeric actin expression was ~30% lower in SkmVEGF^-/- (P < 0.05), whereas myosin heavy chain and MAFbx were similar (measured via immunoblot). Mitochondrial respiration, citrate synthase activity, PGC-1α, and hypoxia-inducible factor 1α were not different in SkmVEGF^-/- (P > 0.05). However, mitochondrial-derived reactive oxygen species (ROS) flux was lower in SkmVEGF^-/- (P = 0.0003). In conclusion, myofiber-specific VEGF gene deletion resulted in a lower capillary-to-fiber ratio, type I fiber atrophy, actin loss, and contractile dysfunction in the diaphragm. In contrast, mitochondrial respiratory function was preserved alongside lower ROS generation, which may play a compensatory role to preserve fatigue resistance in the diaphragm.NEW & NOTEWORTHY Diaphragm weakness is a hallmark of diseases in which oxygen delivery is compromised. Vascular endothelial growth factor (VEGF) modulates muscle perfusion; however, it remains unclear whether VEGF deficiency contributes to the onset of diaphragm dysfunction. Conditional skeletal myofiber VEGF gene ablation impaired diaphragm contractile function and resulted in type I fiber atrophy, a lower number of capillaries per fiber, and contractile protein content. Mitochondrial function was similar and reactive oxygen species flux was lower. Diaphragm VEGF deficiency may contribute to the onset of respiratory muscle weakness.

Molecular signalling towards mitochondrial breakdown is enhanced in skeletal muscle of patients with chronic obstructive pulmonary disease (COPD)

Loss of skeletal muscle mitochondrial oxidative capacity is well-established in patients with COPD, but the role of mitochondrial breakdown herein is largely unexplored. Currently, we studied if mitochondrial breakdown signalling is increased in skeletal muscle of COPD patients and associates with the loss of mitochondrial content, and whether it is affected in patients with iron deficiency (ID) or systemic inflammation. Therefore, mitophagy, autophagy, mitochondrial dynamics and content markers were analysed in vastus lateralis biopsies of COPD patients (N = 95, FEV₁% predicted: 39.0 [31.0–53.6]) and healthy controls (N = 15, FEV₁% predicted: 112.8 [107.5–125.5]). Sub-analyses were performed on patients stratified by ID or C-reactive protein (CRP). Compared with controls, COPD patients had lower muscle mitochondrial content, higher BNIP3L and lower FUNDC1 protein, and higher Parkin protein and gene-expression. BNIP3L and Parkin protein levels inversely correlated with mtDNA/gDNA ratio and FEV₁% predicted. ID-COPD patients had lower BNIP3L protein and higher BNIP3 gene-expression, while high CRP patients had higher BNIP3 and autophagy-related protein levels. In conclusion, our data indicates that mitochondrial breakdown signalling is increased in skeletal muscle of COPD patients, and is related to disease severity and loss of mitochondrial content. Moreover, systemic inflammation is associated with higher BNIP3 and autophagy-related protein levels.

Salvianolic acid B as an anti-emphysema agent II: In vivo reversal activities in two rat models of emphysema

Emphysema progressively destroys alveolar structures, leading to disability and death, yet remains irreversible and incurable to date. Impaired vascular endothelial growth factor (VEGF) signaling is an emerging pathogenic mechanism, thereby proposing a hypothesis that VEGF stimulation/elevation enables recovery from alveolar structural destruction and loss of emphysema. Our previous in vitro study identified that salvianolic acid B (Sal-B), a polyphenol of traditional Chinese herbal danshen, stimulated lung cell proliferation and migration, and protected against induced lung cell death, by virtue of signal transducer and activator of transcription 3 (STAT3) activation and VEGF stimulation/elevation. Thus, this study examined Sal-B for in vivo therapeutic reversal of established emphysema in two rat models. Emphysema was induced with porcine pancreatic elastase (PPE) and cigarette smoke extract (CSE), and established by day 21. Sal-B was then spray-dosed to the lung three times weekly for three weeks. Functional treadmill exercise endurance; morphological airspace enlargement and alveolar destruction; apoptosis, cell proliferation and tissue matrix proteins; phosphorylated STAT3 (pSTAT3) and VEGF expressions; neutrophil accumulation; and lipid peroxidation were determined. In both models, Sal-B at 0.2 mg/kg significantly reversed impaired exercise endurance by 80 and 64%; airspace enlargement [mean linear intercept (MLI)] by 56 and 67%; and alveolar destructive index (%DI) by 63 and 66%, respectively. Induced apoptosis activity [cleaved caspase-3] was normalized by 94 and 82%; and cell proliferation activity [proliferative cell nuclear antigen (PCNA)] was stimulated by 1.6 and 2.1-fold. In the PPE-induced model, Sal-B reduced induction of lung's matrix metalloproteinase (MMP)-9 and MMP-2 activities by 59 and 94%, respectively, and restored pSTAT3 and VEGF expressions to the healthy lung levels, while leaving neutrophil accumulation unchecked [myeloperoxidase (MPO) activity]. In the CSE-induced model, Sal-B elevated pSTAT3 and VEGF expressions both by 1.8-fold over the healthy lung levels, and normalized induced lipid peroxidation [malondialdehyde (MDA) activity] by 68%. These results provide an in vivo proof-of-concept for Sal-B as one of the first anti-emphysema agents enabling reversal of alveolar structural destruction and loss via local lung treatment by virtue of its STAT3 activation and VEGF stimulation.

Exercise training reverses inflammation and muscle wasting after tobacco smoke exposure

Long-term cigarette smoking induces inflammatory processes in the pulmonary system that are suggested to "spill over" into systemic inflammation. Regular exercise has been shown to have anti-inflammatory properties. The aim of the study was to investigate the effects of therapeutic exercise on inflammation and muscle wasting in smoke-exposed mice. C57BL/6J mice ( n = 30) were separated into three groups to receive either 1) no specific treatment (control group), 2) 8-mo exposure to cigarette smoke [smoke-exposed (SE) group], or 3) 8 mo of cigarette smoke combined with exercise training during the last 2 mo (SEex group). The inflammatory status was analyzed by quantifying levels of various plasma proteins using multiplex ELISA and detection of lymphocyte surface markers by flow cytometry. Muscle tissue was analyzed by histological techniques and measurements of RNA/protein expression. SE led to decreased maximal O₂ uptake (V̇o_2max) and maximal running speed ( V_max), which was reversed by exercise ( P < 0.05). Expression of ICAM-1, VCAM-1, and CD62L on T cells increased and was reversed by exercise ( P < 0.05). Similarly, SE induced an increase of various inflammatory cytokines, which were downregulated by exercise. In muscle, exercise improved the structure, oxidative capacity, and metabolism by reducing ubiquitin proteasome system activation, stimulating insulin-like growth factor 1 expression, and the SE-induced inhibition of mammalian target of rapamycin signaling pathway ( P < 0.05). Exercise training reverses smoke-induced decline in exercise capacity, systemic inflammation, and muscle wasting by addressing immune-regulating, anabolic, and metabolic pathways.