The relationship between chronic hypoxemia and activation of the tumor necrosis factor-alpha system in patients with chronic obstructive pulmonary disease

Molecular and biological pathways of skeletal muscle dysfunction in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) will be a major leading cause of death worldwide in the near future. Weakness and atrophy of the quadriceps are associated with a significantly poorer prognosis and increased mortality in COPD. Despite that skeletal muscle dysfunction may affect both respiratory and limb muscle groups in COPD, the latter are frequently more severely affected. Therefore, muscle dysfunction in COPD is a common systemic manifestation that should be evaluated on routine basis in clinical settings. In the present review, several aspects of COPD muscle dysfunction are being reviewed, with special emphasis on the underlying biological mechanisms. Figures on the prevalence of COPD muscle dysfunction and the most relevant etiologic contributors are also provided. Despite that ongoing research will shed light into the contribution of additional mechanisms to COPD muscle dysfunction, current knowledge points toward the involvement of a wide spectrum of cellular and molecular events that are differentially expressed in respiratory and limb muscles. Such mechanisms are thoroughly described in the article. The contribution of epigenetic events on COPD muscle dysfunction is also reviewed. We conclude that in view of the latest discoveries, from now, on new avenues of research should be designed to specifically target cellular mechanisms and pathways that impair muscle mass and function in COPD using pharmacological strategies and/or exercise training modalities.

Frailty Phenotypes, Disability, and Outcomes in Adult Candidates for Lung Transplantation

RATIONALE

Frailty is associated with morbidity and mortality in abdominal organ transplantation but has not been examined in lung transplantation.

OBJECTIVES

To examine the construct and predictive validity of frailty phenotypes in lung transplant candidates.

METHODS

In a multicenter prospective cohort, we measured frailty with the Fried Frailty Phenotype (FFP) and Short Physical Performance Battery (SPPB). We evaluated construct validity through comparisons with conceptually related factors. In a nested case-control study of frail and nonfrail subjects, we measured serum IL-6, tumor necrosis factor receptor 1, insulin-like growth factor I, and leptin. We estimated the association between frailty and disability using the Lung Transplant Valued Life Activities disability scale. We estimated the association between frailty and risk of delisting or death before transplant using multivariate logistic and Cox models, respectively.

MEASUREMENTS AND MAIN RESULTS

Of 395 subjects, 354 completed FFP assessments and 262 completed SPPB assessments; 28% were frail by FFP (95% confidence interval [CI], 24-33%) and 10% based on the SPPB (95% CI, 7-14%). By either measure, frailty correlated more strongly with exercise capacity and grip strength than with lung function. Frail subjects tended to have higher plasma IL-6 and tumor necrosis factor receptor 1 and lower insulin-like growth factor I and leptin. Frailty by either measure was associated with greater disability. After adjusting for age, sex, diagnosis, and transplant center, both FFP and SPPB were associated with increased risk of delisting or death before lung transplant. For every 1-point worsening in score, hazard ratios were 1.30 (95% CI, 1.01-1.67) for FFP and 1.53 (95% CI, 1.19-1.59) for SPPB.

CONCLUSIONS

Frailty is prevalent among lung transplant candidates and is independently associated with greater disability and an increased risk of delisting or death.

Low forced expiratory volume in one second is associated with the history of acute coronary syndrome in patients with organic coronary stenosis

BACKGROUND

Chronic obstructive pulmonary disease often coexists with cardiovascular diseases and airflow limitation has been known as a risk of cardiovascular death. However, the association between airflow limitation and the history of acute coronary syndrome (ACS) in patients with coronary stenosis remains to be determined.

METHODS

Study subjects were 271 consecutive patients (age: 70.6±9.5 years, sex: 200 males) who underwent coronary angiography and in whom organic coronary stenosis was detected. We collected spirometric data from those patients and investigated the association of the pulmonary function and the history of ACS. We also compared the prevalence of airflow limitation of the present subjects with Japanese epidemiological data that had been previously published.

RESULTS

Multivariate analysis with multiple logistic regression analysis showed that the reduced forced expiratory volume in one second (FEV_1.0) less than 80% of predicted value was significantly associated with a history of ACS (odds ratio: 2.81, 95% CI: 1.27-6.20, p<0.02) independently of age, sex, body mass index, and classic coronary risk factors including smoking habit, diabetes mellitus, hypertension, and dyslipidemia. Furthermore, the airflow limitation was more prevalent in the present subjects than in the Japanese general population (25.8% vs. 10.9%, p<0.05).

CONCLUSIONS

Reduced FEV_1.0 is associated with a history of ACS in patients with coronary arterial stenosis irrespective of any coronary risk factors. Airflow limitation is more prevalent in patients with coronary stenosis than in the general population.

Chronic obstructive pulmonary disease and obstructive sleep apnoea-the overlap syndrome

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea (OSA) are highly prevalent disorders and the co-existence of both disorders, termed the overlap syndrome, affects at least 1% of the adult population. Patients with the overlap syndrome typically experience more pronounced nocturnal oxygen desaturation and there is a high prevalence of pulmonary hypertension in such patients. Recent evidence suggests that the prevalence of each disorder together is higher than might be predicted by simple prevalence statistics, although the evidence is not clear-cut in this regard. Sleep itself can have several negative effects in patients with COPD. Sleep quality is diminished with reduced amounts of slow wave and rapid-eye-movement (REM) sleep, which may contribute to daytime symptoms such as fatigue and lethargy. Furthermore, normal physiological adaptations during sleep that result in mild hypoventilation in normal subjects are more pronounced in COPD, which can result in clinically important nocturnal oxygen desaturation. Management of sleep disorders in patients with COPD should address both sleep quality and disordered gas exchange. Non-invasive pressure support is beneficial in selected cases, particularly during acute exacerbations associated with respiratory failure, and is particularly helpful in patients with the overlap syndrome. There is limited evidence of benefit from pressure support in the chronic setting in COPD patients without OSA.

Responsiveness of blood and sputum inflammatory cells in Japanese COPD patients, non-COPD smoking controls, and non-COPD nonsmoking controls

PURPOSE

To compare pulmonary and systemic inflammatory mediator release, pre- and poststimulation, ex vivo, in cells from Japanese patients with chronic obstructive pulmonary disease (COPD), non-COPD smoking controls, and non-COPD nonsmoking controls (NSC).

PATIENTS AND METHODS

This was a nontreatment study with ten subjects per group. Inflammatory biomarker release, including interleukin (IL)-6 and -8, matrix metalloproteinase-9, and tumor necrosis factor (TNF)-α, was measured in peripheral blood mononuclear cells (PBMC) and sputum cells with and without lipopolysaccharide or TNF-α stimulation.

RESULTS

In PBMC, basal TNF-α release (mean ± standard deviation) was significantly different between COPD (81.6±111.4 pg/mL) and nonsmoking controls (9.5±5.2 pg/mL) (P<0.05). No other significant differences were observed. Poststimulation biomarker release tended to increase, with the greatest changes in the COPD group. The greatest mean increases were seen in the lipopolysaccharide-induced release of matrix metalloproteinase-9, TNF-α, and IL-6 from PBMC. Pre- and poststimulation data from sputum samples were more variable and less conclusive than from PBMC. In the COPD group, induced sputum neutrophil levels were higher and macrophage levels were lower than in either control group. Significant correlations were seen between the number of sputum cells (macrophages and neutrophils) and biomarker levels (IL-8, IL-6, and TNF-α).

CONCLUSION

This was the first study to compare cellular inflammatory mediator release before and after stimulation among Japanese COPD, smoking controls, and nonsmoking controls populations. Poststimulation levels tended to be higher in patients with COPD. The results suggest that PBMC are already preactivated in the circulation in COPD patients. This provides further evidence that COPD is a multicomponent disease, involving both airway and systemic inflammation.

Tumor necrosis factor-α driven inflammation in alpha-1 antitrypsin deficiency: a new model of pathogenesis and treatment

Alpha-1 antitrypsin (AAT) deficiency (AATD) has traditionally been thought of as a genetic disorder characterized by lung destruction and early emphysema in a low AAT, and high neutrophil elastase (NE) environment in the lungs of affected individuals. Recently, a growing body of evidence has emerged to support the hypothesis that tumor necrosis factor alpha (TNF-α) is essential in the pathogenesis of both genetic AATD and non-genetic chronic obstructive pulmonary disease (COPD). Reports have highlighted the importance of TNF-α driven immune cell dysfunction in the development of lung disease in AATD. The authors discuss the role of AAT as a key modulator of TNF-α signaling firstly in the setting of AATD and secondly in other conditions where AAT augmentation therapy has potential utility as a novel therapy.

Low arterial blood oxygenation is associated with calcification of the coronary arteries in patients with chronic obstructive pulmonary disease

BACKGROUND

Cigarette smoking is a well-known major cause of both chronic obstructive pulmonary disease (COPD) and atherosclerosis. However, few studies have investigated the correlation between COPD and coronary atherosclerosis.

METHODS

We recruited 54 patients with stable COPD (51 men, 3 women) but without angina symptoms. Arterial blood gas analyses were performed, pulmonary function was assessed, and calcification of the coronary arteries was evaluated by computed tomography (CT).

RESULTS

Calcification of the coronary arteries was noted in 25 patients. There were no significant differences in age, body mass index, respiratory function, and levels of low-density lipoprotein cholesterol, hemoglobin A1c, glucose, or C-reactive protein between patients with or without calcification of the coronary arteries. Arterial blood oxygenation was significantly lower in patients with calcification of the coronary arteries. On both univariate and multivariate analyses, low arterial blood oxygenation was an independent risk factor for calcification of the coronary arteries.

CONCLUSIONS

In patients with COPD, low arterial blood oxygenation was strongly associated with calcification of the coronary arteries and may be a significant predictor of cardiovascular disease.

Body composition and mortality after adult lung transplantation in the United States

RATIONALE

Obesity and underweight are contraindications to lung transplantation based on their associations with mortality in studies performed before implementation of the lung allocation score (LAS)-based organ allocation system in the United States Objectives: To determine the associations of body mass index (BMI) and plasma leptin levels with survival after lung transplantation.

METHODS

We used multivariable-adjusted regression models to examine associations between BMI and 1-year mortality in 9,073 adults who underwent lung transplantation in the United States between May 2005 and June 2011, and plasma leptin and mortality in 599 Lung Transplant Outcomes Group study participants. We measured body fat and skeletal muscle mass using whole-body dual X-ray absorptiometry in 142 adult lung transplant candidates.

MEASUREMENTS AND MAIN RESULTS

Adjusted mortality rates were similar among normal weight (BMI 18.5-24.9 kg/m(2)), overweight (BMI 25.0-29.9), and class I obese (BMI 30-34.9) transplant recipients. Underweight (BMI < 18.5) was associated with a 35% increased rate of death (95% confidence interval, 10-66%). Class II-III obesity (BMI ≥ 35 kg/m(2)) was associated with a nearly twofold increase in mortality (hazard ratio, 1.9; 95% confidence interval, 1.3-2.8). Higher leptin levels were associated with increased mortality after transplant surgery performed without cardiopulmonary bypass (P for interaction = 0.03). A BMI greater than or equal to 30 kg/m(2) was 26% sensitive and 97% specific for total body fat-defined obesity.

CONCLUSIONS

A BMI of 30.0-34.9 kg/m(2) is not associated with 1-year mortality after lung transplantation in the LAS era, perhaps because of its low sensitivity for obesity. The association between leptin and mortality suggests the need to validate alternative methods to measure obesity in candidates for lung transplantation. A BMI greater than or equal to 30 kg/m(2) may no longer contraindicate lung transplantation.

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.

A systems biology approach reveals a link between systemic cytokines and skeletal muscle energy metabolism in a rodent smoking model and human COPD

Background

A relatively large percentage of patients with chronic obstructive pulmonary disease (COPD) develop systemic co-morbidities that affect prognosis, among which muscle wasting is particularly debilitating. Despite significant research effort, the pathophysiology of this important extrapulmonary manifestation is still unclear. A key question that remains unanswered is to what extent systemic inflammatory mediators might play a role in this pathology.

Cigarette smoke (CS) is the main risk factor for developing COPD and therefore animal models chronically exposed to CS have been proposed for mechanistic studies and biomarker discovery. Although mice have been successfully used as a pre-clinical in vivo model to study the pulmonary effects of acute and chronic CS exposure, data suggest that they may be inadequate models for studying the effects of CS on peripheral muscle function. In contrast, recent findings indicate that the guinea pig model (Cavia porcellus) may better mimic muscle wasting.

Methods

We have used a systems biology approach to compare the transcriptional profile of hindlimb skeletal muscles from a Guinea pig rodent model exposed to CS and/or chronic hypoxia to COPD patients with muscle wasting.

Results

We show that guinea pigs exposed to long-term CS accurately reflect most of the transcriptional changes observed in dysfunctional limb muscle of severe COPD patients when compared to matched controls. Using network inference, we could then show that the expression profile in whole lung of genes encoding for soluble inflammatory mediators is informative of the molecular state of skeletal muscles in the guinea pig smoking model. Finally, we show that CXCL10 and CXCL9, two of the candidate systemic cytokines identified using this pre-clinical model, are indeed detected at significantly higher levels in serum of COPD patients, and that their serum protein level is inversely correlated with the expression of aerobic energy metabolism genes in skeletal muscle.

Conclusions

We conclude that CXCL10 and CXCL9 are promising candidate inflammatory signals linked to the regulation of central metabolism genes in skeletal muscles. On a methodological level, our work also shows that a system level analysis of animal models of diseases can be very effective to generate clinically relevant hypothesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-014-0059-5) contains supplementary material, which is available to authorized users.

Impaired function of regulatory T-cells in patients with chronic obstructive pulmonary disease (COPD)

Anti-inflammatory pathways affecting chronic obstructive pulmonary disease (COPD) are poorly understood. Regulatory T-cells (Tregs) are important negative regulators of T-cell activity and hence were investigated in COPD patients in this study. We hypothesised that functional defects in Tregs may promote increased inflammation contributing to the pathogenesis of COPD. Peripheral blood mononuclear cells (PBMC) were isolated from patients with stable COPD and age-matched non-smoking controls. Treg-mediated suppression of memory non-Treg (Foxp3(-)CD45RO(+)) CD4(+) T-cell activation was analysed by comparing PBMC responses to staphylococcal enterotoxin-B (SEB) pre- and post-depletion of Tregs (CD25(+)CD127(low)CD4(+) T-cells) by fluorescence-activated cell sorting (FACS). Activation of T-cells was assessed by HLA-DR expression. Levels of secreted cytokines were measured by ELISA. Depletion of Tregs increased SEB-induced activation of Foxp3(-)CD45RO(+) CD4(+) T-cells in samples from 15/15 healthy controls (demonstrating Treg-mediated suppression) and 9/14 COPD patients (Fisher's test, p=0.017). A screen of clinical data associated a failure of Treg-mediated suppression in the remaining five COPD patients with a higher body mass index (BMI) (33-38 kg/m(2)) compared to patients with unimpaired Treg function (20-32 kg/m(2)). In conclusion, we demonstrate impaired Treg-mediated suppression of CD4(+) T-cell activation in a subset of COPD patients, all of whom had high BMI. Obesity and/or perturbed homeostasis of Treg subsets may explain this defect and therefore contribute to increased inflammation observed in COPD.

An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease

BACKGROUND

Limb muscle dysfunction is prevalent in chronic obstructive pulmonary disease (COPD) and it has important clinical implications, such as reduced exercise tolerance, quality of life, and even survival. Since the previous American Thoracic Society/European Respiratory Society (ATS/ERS) statement on limb muscle dysfunction, important progress has been made on the characterization of this problem and on our understanding of its pathophysiology and clinical implications.

PURPOSE

The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD.

METHODS

An interdisciplinary committee of experts from the ATS and ERS Pulmonary Rehabilitation and Clinical Problems assemblies determined that the scope of this document should be limited to limb muscles. Committee members conducted focused reviews of the literature on several topics. A librarian also performed a literature search. An ATS methodologist provided advice to the committee, ensuring that the methodological approach was consistent with ATS standards.

RESULTS

We identified important advances in our understanding of the extent and nature of the structural alterations in limb muscles in patients with COPD. Since the last update, landmark studies were published on the mechanisms of development of limb muscle dysfunction in COPD and on the treatment of this condition. We now have a better understanding of the clinical implications of limb muscle dysfunction. Although exercise training is the most potent intervention to address this condition, other therapies, such as neuromuscular electrical stimulation, are emerging. Assessment of limb muscle function can identify patients who are at increased risk of poor clinical outcomes, such as exercise intolerance and premature mortality.

CONCLUSIONS

Limb muscle dysfunction is a key systemic consequence of COPD. However, there are still important gaps in our knowledge about the mechanisms of development of this problem. Strategies for early detection and specific treatments for this condition are also needed.

Functional outcomes in patients with chronic obstructive pulmonary disease: a multivariate analysis

Background

Multiple factors can influence the severity of chronic obstructive pulmonary disease (COPD) and the functioning of patients with COPD, such as personal characteristics and systemic manifestations.

Objective

To evaluate the different factors that can influence the activity and psychosocial impact domains of the Saint George's Respiratory Questionnaire (SGRQ) in COPD patients.

Method

Participants, recruited in a university-based hospital, responded to the SGRQ, and in addition, personal, anthropometric, and clinical data were collected. The study was approved by the Institutional Ethics Committee. Data were analyzed using multiple linear regression models, with the SGRQ activity and psychosocial impact scores as outcome variables, and 10 explanatory variables (age, gender, forced expiratory volume in the first second - FEV₁, smoking load, body mass index, oxygen therapy, associated diseases, regular physical activity, participation in a formal rehabilitation program, and SGRQ symptoms score) were considered.

Results

The best regression model for predicting the SGRQ activity score (r²=0.477) included gender, FEV₁, and SGRQ symptoms. In contrast, the predictive model with the highest proportion of explained variance in psychosocial impact score (r²=0.426) included the variables gender, oxygen therapy, and SGRQ symptoms.

Conclusions

The results indicate that the outcomes, while based on functioning parameters in COPD patients, could be partly explained by the personal and clinical factors analyzed, especially by the symptoms assessed by the SGRQ. Thus, it appears that the health conditions of these patients cannot be described by isolated variables, including pulmonary function parameters.

Quantitative computed tomography measures of pectoralis muscle area and disease severity in chronic obstructive pulmonary disease. A cross-sectional study

RATIONALE

Muscle wasting in chronic obstructive pulmonary disease (COPD) is associated with a poor prognosis and is not readily assessed by measures of body mass index (BMI). BMI does not discriminate between relative proportions of adipose tissue and lean muscle and may be insensitive to early pathologic changes in body composition. Computed tomography (CT)-based assessments of the pectoralis muscles may provide insight into the clinical significance of skeletal muscles in smokers.

OBJECTIVES

We hypothesized that objective assessment of the pectoralis muscle area on chest CT scans provides information that is clinically relevant and independent of BMI.

METHODS

Data from the ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints) Study (n = 73) were used to assess the relationship between pectoralis muscle area and fat-free mass. We then used data in a subset (n = 966) of a larger cohort, the COPDGene (COPD Genetic Epidemiology) Study, to explore the relationship between pectoralis muscle area and COPD-related traits.

MEASUREMENTS AND MAIN RESULTS

We first investigated the correlation between pectoralis muscle area and fat-free mass, using data from a subset of participants in the ECLIPSE Study. We then further investigated pectoralis muscle area in COPDGene Study participants and found that higher pectoralis muscle area values were associated with greater height, male sex, and younger age. On subsequent clinical correlation, compared with BMI, pectoralis muscle area was more significantly associated with COPD-related traits, including spirometric measures, dyspnea, and 6-minute-walk distance (6MWD). For example, on average, each 10-cm(2) increase in pectoralis muscle area was associated with a 0.8-unit decrease in the BODE (Body mass index, Obstruction, Dyspnea, Exercise) index (95% confidence interval, -1.0 to -0.6; P < 0.001). Furthermore, statistically significant associations between pectoralis muscle area and COPD-related traits remained even after adjustment for BMI.

CONCLUSIONS

CT-derived pectoralis muscle area provides relevant indices of COPD morbidity that may be more predictive of important COPD-related traits than BMI. However, the relationship with clinically relevant outcomes such as hospitalization and death requires additional investigation. Pectoralis muscle area is a convenient measure that can be collected in the clinical setting in addition to BMI.

Survival benefit of CPAP favors hypercapnic patients with the overlap syndrome

BACKGROUND

Patients with the combination of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), known as the "overlap syndrome," have a substantially greater risk of morbidity and mortality compared to those with either COPD or OSA alone. The study's objective was to report on the long-term outcome of hypercapnic (PaCO2 ≥ 45 mmHg) and normocapnic patients with the overlap syndrome treated with continuous positive airway pressure (CPAP).

METHODS

A nonconcurrent cohort of consecutive patients with the overlap syndrome was followed for a median duration of 71 months (range 1-100) at a VA sleep center. All patients were managed according to the prevailing recommendations of both diseases. The end point of the study was all-cause mortality.

RESULTS

Of the 271 patients identified, 104 were hypercapnic (PaCO2 = 51.6 ± 4.3 mmHg). Both normocapnic and hypercapnic patients had comparable apnea-hypopnea indexes (AHI) (29.2 ± 23.8 and 35.2 ± 29.2/h, respectively; p = 0.07) and similar adherence rates to CPAP (43 and 42 %, respectively, p = 0.9). Survival analysis revealed that hypercapnic patients who were adherent to CPAP had reduced mortality compared to nonadherent hypercapnic patients (p = 0.04). In contrast, the cumulative mortality rate for normocapnic patients was not significantly different between the adherent and the nonadherent group (p = 0.42). In multivariate analysis, the comorbidity index was the only independent predictor of mortality in normocapnic patients with the overlap syndrome [hazard ratio (HR) 1.68; p < 0.001] while CPAP adherence was associated with improved survival (HR 0.65; p = 0.04).

CONCLUSIONS

CPAP mitigates the excess risk of mortality in hypercapnic patients but not in normocapnic patients with the overlap syndrome.

Cardiovascular safety in patients receiving roflumilast for the treatment of COPD

BACKGROUND

Evaluation of cardiovascular safety for new therapies for COPD is important because of a high prevalence of cardiac comorbidities in the COPD population. Hence, we evaluated the effects of roflumilast, a novel oral phosphodiesterase 4 inhibitor developed for the treatment and prevention of COPD exacerbations, on major adverse cardiovascular events (MACEs).

METHODS

Intermediate- and long-term placebo-controlled clinical trials of roflumilast in COPD were pooled and assessed for potential cardiovascular events. Studies comprised 14 12- to 52-week placebo-controlled trials in patients with moderate to very severe COPD. All deaths and serious nonfatal cardiovascular events were evaluated by an independent adjudication committee blinded to study and treatment. The MACE composite of cardiovascular death, nonfatal myocardial infarction, and stroke was analyzed according to treatment group.

RESULTS

Of 6,563 patients receiving roflumilast, 52 experienced MACEs (14.3 per 1,000 patient-years), and of 5,491 patients receiving placebo, 76 experienced MACEs (22.3 per 1,000 patient-years). The MACE composite rate was significantly lower for roflumilast compared with placebo (hazard ratio, 0.65; 95% CI, 0.45-0.93; P = .019).

CONCLUSIONS

A lower rate of cardiovascular events was observed with roflumilast than with placebo in patients with COPD, indicating the lack of a cardiovascular safety signal when treating patients with COPD. Potential cardiovascular benefits of roflumilast should be evaluated in future controlled clinical trials.

Longitudinal association of C-reactive protein and lung function over 13 years: The EPIC-Norfolk study

Chronic obstructive pulmonary disease is known to be associated with systemic inflammation. We examined the longitudinal association of C-reactive protein (CRP) and lung function in a cohort of 18,110 men and women from the European Prospective Investigation Into Cancer in Norfolk who were 40-79 years of age at baseline (recruited in 1993-1997) and followed-up through 2011. We assessed lung function by measuring forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) at baseline, 4 years, and 13 years. Serum CRP levels were measured using a high-sensitivity assay at baseline and the 13-year follow up. Cross-sectional and longitudinal associations of loge-CRP and lung function were examined using multivariable linear mixed models. In the cross-sectional analysis, 1-standard-deviation increase in baseline loge-CRP (about 3-fold higher CRP on the original milligrams per liter scale) was associated with a -86.3 mL (95% confidence interval: -93.9, -78.6) reduction in FEV1. In longitudinal analysis, a 1-standard-deviation increase in loge-CRP over 13 years was also associated with a -64.0 mL (95% confidence interval: -72.1, -55.8) decline in FEV1 over the same period. The associations were similar for FVC and persisted among lifetime never-smokers. Baseline CRP levels were not predictive of the rate of change in FEV1 or FVC over time. In the present study, we found longitudinal observational evidence that suggested that increases in systemic inflammation are associated with declines in lung function.

The clinical significance of anaemia and disturbed iron homeostasis in chronic respiratory failure

BACKGROUND

Anaemia is a frequent, clinically relevant condition in various chronic diseases. It seems also to be prevalent in patients with chronic respiratory failure (CRF). We studied the characteristics of anaemia in CRF and its associations with clinical outcome.

METHODS

In a prospective design, 271 consecutive patients with CRF were evaluated; patients with other conditions often associated with anaemia were excluded. Haematological laboratory and physiological parameters, health-related quality of life (HRQL), dyspnoea and 48-month survival were determined. Anaemia was defined according to WHO [haemoglobin (Hb)< 13 g/l (male); Hb< 12 g/dl (female)] and using an established algorithm.

RESULTS

Among 185 patients included, 18.4% showed anaemia, not depending on chronic obstructive pulmonary disease (COPD) vs. non-COPD (17.6% vs. 19.0%; p = 0.851) or on gender [16.5% (female) vs. 19.8% (male); p = 0.702]. Anaemic patients had higher age, creatinine (p < 0.05 each) and erythropoietin levels (p < 0.001), but lower transferrin saturation (TSAT), serum iron and vitamin B12 levels (p < 0.01 each). By definition, most anaemic patients (67.6%) had disturbances in iron homeostasis according to 'anaemia of chronic disease' and/or true iron deficiency anaemia. Hb was independently related to dyspnoea and HRQL, while TSAT ≥ 20% was linked to less dyspnoea and better subjective exercise capability. Non-survivors had lower Hb and serum iron levels (p < 0.05 each). In multivariate analysis, lower serum iron levels and TSAT were independently associated with mortality (p < 0.05 each).

CONCLUSION

Anaemia was common in patients with CRF and often because of disturbed iron homeostasis. Hb and TSAT were linked to functional outcome and HRQL. Lower serum iron levels and TSAT were independent prognostic parameters.

Cellular and molecular mechanisms of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is associated with chronic inflammation affecting predominantly lung parenchyma and peripheral airways and results in largely irreversible and progressive airflow limitation. This inflammation is characterized by increased numbers of alveolar macrophages, neutrophils, and T lymphocytes, which are recruited from the circulation. Oxidative stress plays a key role in driving this inflammation. The pulmonary inflammation may enhance the development and growth of lung cancer. The peripheral inflammation extends into the circulation, resulting in systemic inflammation with the same inflammatory proteins. Systemic inflammation may worsen comorbidities. Treatment of pulmonary inflammation may therefore have beneficial effects.

Abnormal renal resistive index in patients with mild-to-moderate chronic obstructive pulmonary disease

BACKGROUND

Arterial rigidity and endothelial dysfunction are systemic manifestations of chronic obstructive pulmonary disease (COPD). The decrease in renal vascular resistance in order to adapt the increase in glomerular filtration rate after oral protein loading is known as normal renal functional reserve. We tested the hypothesis that COPD patients, even in those with mild-to-moderate airflow obstruction, are affected by systemic inflammation associated with abnormal renal functional reserve.

MATERIALS AND METHODS

The study enrolled 24 current smokers with a cigarette smoking history ≥ 25 pack-years and 8 nonsmokers with normal spirometry as control. Doppler sonography detected the renal resistive index (RRI) before and after oral protein loading to determine the renal functional reserve. Pulmonary function and serum tumor necrosis factor α (TNF-α) levels were analyzed to compare with the renal functional reserve.

RESULTS

The smokers were stratified into 3 groups (Group 1: smokers with normal spirometry, Group 2: mild COPD, Group 3: moderate COPD); nonsmokers as Group 4. The baseline RRI levels were similar in Group 1 and Group 4. After protein loading, the RRI elevated in all smoking groups; moreover, Group 3 had the highest RRI and with longer duration than other groups. The smokers with higher serum TNF-α levels had a longer RRI elevation. Multiple linear regression revealed forced expiratory volume in one second (FEV1), serum TNF-α levels and aging were independently predictive factors of impaired renal functional reserve.

CONCLUSIONS

A greater impairment in renal functional reserve of COPD patients was correlated with more severe airway obstruction and inflammation.

Superoxide release from contracting skeletal muscle in pulmonary TNF-α overexpression mice

Chronic obstructive pulmonary disease (COPD) often results in increased levels of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, which circulates in the blood. However, it is not clear whether pulmonary TNF-α overexpression (a COPD mimic) induces excessive reactive oxygen species (ROS) formation in skeletal muscle and thereby may contribute to the muscle impairment often seen in COPD. We hypothesized that ROS generation in contracting skeletal muscle is elevated when there is TNF-α overproduction in the lung and that this can induce muscle dysfunction. Cytochrome c (cyt c) in the perfusate was used to assay superoxide (O2(·-)) release from isolated contracting soleus muscles from transgenic mice of pulmonary TNF-α overexpression (Tg(+)) and wild-type (WT) mice. Our results showed that Tg(+) muscle released significantly higher levels of O2(·-) than WT during a period of intense contractile activity (in nmol/mg wt; 17.5 ± 2.3 vs. 4.4 ± 1.3, respectively; n = 5; P < 0.05). In addition, the soleus muscle demonstrated a significantly reduced fatigue resistance in Tg(+) mice compared with WT mice. Perfusion of the contracting soleus muscle with superoxide dismutase, which specifically scavenges O2(·-) in the perfusate, resulted in significantly less cyt c reduction, thereby indicating that the type of ROS released from the Tg(+) muscles is O2(·-). Our results demonstrate that pulmonary TNF-α overexpression leads to a greater O2(·-) release from contracting soleus muscle in Tg(+) compared with WT and that the excessive formation of O2(·-) in the contracting muscle of Tg(+) mice leads to earlier fatigue.

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.

Pathophysiologic mechanisms of cardiovascular disease in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a highly prevalent sleep disorder, characterized by repeated disruptions of breathing during sleep. This disease has many potential consequences including excessive daytime sleepiness, neurocognitive deterioration, endocrinologic and metabolic effects, and decreased quality of life. Patients with OSAS experience repetitive episodes of hypoxia and reoxygenation during transient cessation of breathing that provoke systemic effects. Furthermore, there may be increased levels of biomarkers linked to endocrine-metabolic and cardiovascular alterations. Epidemiological studies have identified OSAS as an independent comorbid factor in cardiovascular and cerebrovascular diseases, and physiopathological links may exist with onset and progression of heart failure. In addition, OSAS is associated with other disorders and comorbidities which worsen cardiovascular consequences, such as obesity, diabetes, and metabolic syndrome. Metabolic syndrome is an emerging public health problem that represents a constellation of cardiovascular risk factors. Both OSAS and metabolic syndrome may exert negative synergistic effects on the cardiovascular system through multiple mechanisms (e.g., hypoxemia, sleep disruption, activation of the sympathetic nervous system, and inflammatory activation). It has been found that CPAP therapy for OSAS provides an objective improvement in symptoms and cardiac function, decreases cardiovascular risk, improves insulin sensitivity, and normalises biomarkers. OSAS contributes to the pathogenesis of cardiovascular disease independently and by interaction with comorbidities. The present review focuses on indirect and direct evidence regarding mechanisms implicated in cardiovascular disease among OSAS patients.

Pathophysiology of muscle dysfunction in COPD

Muscle dysfunction often occurs in patients with chronic obstructive pulmonary disease (COPD) and may involve both respiratory and locomotor (peripheral) muscles. The loss of strength and/or endurance in the former can lead to ventilatory insufficiency, whereas in the latter it limits exercise capacity and activities of daily life. Muscle dysfunction is the consequence of complex interactions between local and systemic factors, frequently coexisting in COPD patients. Pulmonary hyperinflation along with the increase in work of breathing that occur in COPD appear as the main contributing factors to respiratory muscle dysfunction. By contrast, deconditioning seems to play a key role in peripheral muscle dysfunction. However, additional systemic factors, including tobacco smoking, systemic inflammation, exercise, exacerbations, nutritional and gas exchange abnormalities, anabolic insufficiency, comorbidities and drugs, can also influence the function of both respiratory and peripheral muscles, by inducing modifications in their local microenvironment. Under all these circumstances, protein metabolism imbalance, oxidative stress, inflammatory events, as well as muscle injury may occur, determining the final structure and modulating the function of different muscle groups. Respiratory muscles show signs of injury as well as an increase in several elements involved in aerobic metabolism (proportion of type I fibers, capillary density, and aerobic enzyme activity) whereas limb muscles exhibit a loss of the same elements, injury, and a reduction in fiber size. In the present review we examine the current state of the art of the pathophysiology of muscle dysfunction in COPD.

The influence of body composition assessed by dual-energy x-ray absorptiometry on functional capacity of patients with chronic obstructive pulmonary disease

INTRODUCTION: The individual with chronic obstructive pulmonary disease (COPD) can experience a significant reduction of body composition, peripheral muscle dysfunction, resulting in a negative influence on functional capacity. OBJECTIVES: To analyze the influence of body composition assessed by dual-energy x-ray absorptiometry on functional capacity of patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: Eleven male patients with COPD (COPDG), seven presenting moderate obstruction and four severe, and 11 sedentary male subjects (CG) were evaluated by dual-energy x-ray absorptiometry to assess their body composition. All subjects also performed the 6-minute walk test (6MWT) and Step Test (6MST) to assess their functional capacity. RESULTS: No significant differences were found between groups for anthropometric data such as age, weight, height and body mass index (BMI). However, the COPDG presented Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1), FEV1/FVC ratio, Maximal Voluntary Ventilation (MVV), Walked Distance (WD) and Number of Steps (NS) significantly lower than the CG (p < 0.05, Student's t-test). The Body Bone Mass (BBM), BBM%, Lean Mass (LM), LM%, and Right Lower Limb (RLL) and Left Lower Limb (LLL) were significantly lower in the COPDG when compared with the CG, presenting statistically significant positive correlations with 6MWT's WD and 6MST's NS (p < 0.05, Pearson's test). CONCLUSION: We conclude that body composition is an important prognostic factor for patients with COPD, which reinforces the importance of assessing body composition by dual-energy absorptiometry since it has demonstrated with satisfactory accuracy in clinical practice. Moreover, it is a useful parameter for evaluation and reassessment in pulmonary rehabilitation programs.

Delayed resolution of inflammatory response compared with clinical recovery in patients with acute exacerbations of chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVE

The temporal profile of inflammatory markers during acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and their relationship to clinical response are not well characterized. The aim was to assess the changes in levels of inflammatory markers in AECOPD and correlate these with clinical and laboratory indices of recovery.

METHODS

Serum levels of C-reactive protein (CRP), interleukin (IL)-6 and fibrinogen were measured in patients with AECOPD within 24 h of hospitalization and pre-discharge (stable state).

RESULTS

Ninety-seven patients were evaluated (79 males; mean (SD) age, 61.4 (10.3) years). Eighty eight (90.7%) were current or former smokers, with a median consumption of 15 (0-75) packs/year. The median duration of COPD was 8 (2-25) years. Forty-six patients (56.9%) required mechanical ventilation for a median of 5 days (1-34) while in hospital. The median duration of hospital stay was 13 days (1-77). At reassessment before planned discharge, the levels of dyspnoea, leucocyte counts, erythrocyte sedimentation rate, creatinine, partial pressure of oxygen, and albumin normalized. The levels of CRP, IL-6 and fibrinogen reduced significantly but did not reach the normal range. Changes in IL-6 and fibrinogen levels correlated significantly with the acute physiologic assessment and chronic health evaluation II score, smoking history, blood pressure and leucocyte counts. Baseline IL-6 and fibrinogen levels significantly predicted a prolonged duration of mechanical ventilation.

CONCLUSIONS

During AECOPD, the inflammatory response lags behind clinical and biochemical improvement. Fibrinogen and IL-6 are potentially useful markers for monitoring clinical response following an acute episode.

Angiogenesis-related factors in skeletal muscles of COPD patients: roles of angiopoietin-2

The role of angiogenesis factors in skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease (COPD) is unknown. The first objective of this study was to assess various pro- and antiangiogenic factor and receptor expressions in the vastus lateralis muscles of control subjects and COPD patients. Preliminary inquiries revealed that angiopoietin-2 (ANGPT2) is overexpressed in limb muscles of COPD patients. ANGPT2 promotes skeletal satellite cell survival and differentiation. Factors that are involved in regulating muscle ANGPT2 production are unknown. The second objective of this study was to evaluate how oxidants and proinflammatory cytokines influence muscle-derived ANGPT2 expression. Angiogenic gene expressions in human vastus lateralis biopsies were quantified with low-density real-time PCR arrays. ANGPT2 mRNA expressions in cultured skeletal myoblasts were quantified in response to proinflammatory cytokine and H2O2 exposure. Ten proangiogenesis genes, including ANGPT2, were significantly upregulated in the vastus lateralis muscles of COPD patients. ANGPT2 mRNA levels correlated negatively with forced expiratory volume in 1 s and positively with muscle wasting. Immunoblotting confirmed that ANGPT2 protein levels were significantly greater in muscles of COPD patients compared with control subjects. ANGPT2 expression was induced by interferon-γ and -β and by hydrogen peroxide, but not by tumor necrosis factor. We conclude that upregulation of ANGPT2 expression in vastus lateralis muscles of COPD patients is likely due to oxidative stress and represents a positive adaptive response aimed at facilitating myogenesis and angiogenesis.

Monoclonal antibodies for asthma and chronic obstructive pulmonary disease

INTRODUCTION

In asthma and chronic obstructive pulmonary disease (COPD), the inflammation in the airways cannot always be controlled with conventional therapies, such as inhaled corticosteroids. Addition of more specific anti-inflammatory therapies, such as monoclonal antibodies, against inflammation pathways might improve the disease outcome.

AREAS COVERED

This review individually discusses the major inflammation pathways and their potential blocking monoclonal antibodies in asthma and COPD.

EXPERT OPINION

The current use of omalizumab in asthma provides a good example on the potential therapeutic role of monoclonal antibodies in both asthma and COPD. There are many other monoclonal antibodies which are currently investigated as possible therapies in these diseases. The identification of the disease subsets in which such antibodies might exert the maximum benefit opens the door for personalized medicine and for targeted biological therapy in asthma and COPD.

Chronic obstructive pulmonary disease: an update of treatment related to frequently associated comorbidities

Chronic obstructive pulmonary disease (COPD) is associated with a pulmonary inflammatory response to inhaled substances, and individuals with COPD often have raised levels of several circulating inflammatory markers indicating the presence of systemic inflammation. Recently, there has been increasing interest in comorbidities associated with COPD such as skeletal muscle dysfunction, cardiovascular disease, osteoporosis, diabetes and lung cancer. These conditions are associated with a similar inflammation-based patho-physiology to COPD, and may represent a lung inflammatory 'overspill' to distant organs. Cardiovascular disease is a significant cause of mortality in COPD, and the concepts of an inflammatory link raise the possibility that treatment for one organ may show benefits to comorbidities in other organs. When considering treatment of COPD and its comorbidities, one approach is to target the pulmonary inflammation and hence reduce any 'overspill' effect of inflammatory mediators systemically as suggested by response to inhaled corticosteroids. Alternatively, treatment targeted towards comorbid organs may alter features of pulmonary disease as statins, angiotensin-converting enzyme (ACE) inhibitors and peroxisome proliferator-activated receptor (PPAR) agonists may have beneficial effects on COPD by reducing exacerbations and mortality. Newer anti-inflammatory treatments, such as phosphodiesterase 4 (PDE4), nuclear factor(NF)-kB, and p38 mitogen-activated protein kinase (MAPK) inhibitors, are given systemically and may confer benefits to both COPD and its comorbidities. With common inflammatory pathways it might be expected that successful anti-inflammatory therapy in one organ may also influence others. In this review we explore the concepts of systemic inflammation in COPD and current evidence for treatment of its related comorbidities.

Association of TNF-α -308G/A, SP-B 1580 C/T, IL-13 -1055 C/T gene polymorphisms and latent adenoviral infection with chronic obstructive pulmonary disease in an Egyptian population

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a leading cause of disability and death. The most common cause of COPD is smoking. There is evidence suggesting that genetic factors influence COPD susceptibility and variants in several candidate genes have been significantly associated with COPD. In this study, we aimed to investigate the possible association of the TNF-α -308, SPB+1580, IL-13 -1055 gene polymorphisms and latent adenovirus C infection with COPD in an Egyptian population.

MATERIAL AND METHODS

Our study included 115 subjects (75 smokers with COPD, 25 resistant smokers and 15 non-smokers) who were subjected to spirometric measurements, identification of adenovirus C and genotyping of TNF-α -308G/A, SP-B+1580 C/T and IL-13 -1055 C/T polymorphisms by real-time PCR.

RESULTS

The adenovirus C gene was identified in all subjects. The distribution of TNF-α genotypes showed no significant differences between different groups. However, homozygous A genotype was associated with a significant decrease in FEV(1), FEV(1)/FVC and FEF25/75% of predicted in COPD (p < 0.05). As regards SP-B genotypes, resistant smokers had a significantly higher homozygous T genotype frequency compared to COPD and non smokers (p = 0.005). Interleukin 13 genotypes showed no significant difference between different groups. There was a significant decrease in FEF25/75% of predicted in T allele carriers in COPD patients (p = 0.001).

CONCLUSIONS

The COPD is a disease caused by the interaction of combined genes and environmental influences, in the presence of smoking and latent adenovirus C infection, TNF-α -308A, SPB +1580 T and IL-13 -1055 T polymorphisms predispose to the development of COPD.

Effects of peripheral neuropathy on exercise capacity and quality of life in patients with chronic obstructive pulmonary diseases

INTRODUCTION

Chronic obstructive pulmonary diseases (COPD) have some systemic effects including systemic inflammation, nutritional abnormalities, skeletal muscle dysfunction, and cardiovascular, skeletal and neurological disorders. Some studies have reported the presence of peripheral neuropathy (PNP) at an incidence of 28-94% in patients with COPD. Our study aimed to identify whether PNP affects exercise performance and quality of life in COPD patients.

MATERIAL AND METHODS

Thirty mild-very severe patients with COPD (male/female = 29/1, mean age = 64 ±10 years) and 14 normal subjects (male/female = 11/5, mean age = 61 ±8 years) were included in the present study. All subjects underwent pulmonary function testing (PFT), cardiopulmonary exercise testing, electroneuromyography and short form 36 (SF-36).

RESULTS

Peak oxygen uptake (PeakVO(2)) was lower in COPD patients (1.15 ±0.53 l/min) than healthy subjects (2.02 ±0.46 l/min) (p = 0.0001). There was no PNP in healthy subjects while 16 (53%) of the COPD patients had PNP. Forced expiratory volume in 1 s (FEV(1)) and PeakVO(2) were significantly different between patients with PNP and those without (p = 0.009, p = 0.03 respectively). Quality of life of patients with PNP was lower than that of patients without PNP (p < 0.05).

CONCLUSIONS

The present study demonstrates the exercise limitation in COPD patients with PNP. Thus, presence of PNP has a poor effect on exercise capacity and quality of life in patients with COPD. Furthermore, treatment modalities for PNP can be recommended to these patients in order to improve exercise capacity and quality of life.

Cigarette smoke-induced oxidative stress in skeletal muscles of mice

Cigarette smoke (CS)-induced oxidative stress may cause muscle alterations in chronic conditions such as chronic obstructive pulmonary disease (COPD). We sought to explore in AKR/J mice exposed to CS for 6 months and in control animals, levels of protein oxidation, oxidized proteins (immunoblotting, proteomics) and antioxidant mechanisms in both respiratory and limb muscles, body weight modifications, systemic inflammation, and lung structure. Compared to control mice, CS-exposed animals exhibited a reduction in body weight gain at 3 months and thereafter, showed lung emphysema, and exhibited increased oxidative stress levels in their diaphragms and gastrocnemius at 6 months. Proteins involved in glycolysis, ATP production and distribution, carbon dioxide hydration, and muscle contraction were carbonylated in respiratory and limb muscles. Blood tumor necrosis factor (TNF)-alpha levels were significantly greater in CS-exposed mice than in control animals. In AKR/J mice, chronic exposure to CS induces lung emphysema concomitantly with greater oxidative modifications on muscle proteins in both respiratory and limb muscles, and systemic inflammation.

Molecular mechanisms of cachexia in chronic disease

Cachexia is a metabolic syndrome that manifests with excessive weight loss and disproportionate muscle wasting. It is related to many different chronic diseases, such as cancer, infections, liver disease, inflammatory bowel disease, cardiac disease, chronic obstructive pulmonary disease, chronic renal failure and rheumatoid arthritis. Cachexia is linked with poor outcome for the patients. In this article, we explore the role of the hypothalamus, liver, muscle tissue and adipose tissue in the pathogenesis of this syndrome, particularly concentrating on the role of cytokines, hormones and cell energy-controlling pathways (such as AMPK, PI3K/Akt and mTOR). We also look at possible future directions for therapeutic strategies.

Use of cluster analysis to describe desaturator phenotypes in COPD: correlations between pulmonary function tests and nocturnal oxygen desaturation

BACKGROUND

Significant heterogeneity of clinical presentation and disease progression exists within chronic obstructive pulmonary disease (COPD). Although forced expiratory volume in 1 second (FEV(1)) inadequately describes this heterogeneity, a clear alternative has not emerged. This article discusses and refines the concept of phenotyping desaturators in COPD and shows a possible pattern which could be used as a framework for future research.

RECENT FINDINGS

COPD is a complex condition with pulmonary and extrapulmonary manifestations. We suggest that COPD phenotypes should be associated with clinically meaningful outcomes. The innovation of COPD phenotyping is defined as COPD desaturators. Sleep-related hypoxemia and hypercapnia are well recognized in COPD and the development of systemic inflammation during sleep. These sleep-related changes predispose to nocturnal cardiac arrhythmias, pulmonary hypertension, and possibly death, particularly during acute exacerbations.

CONCLUSION

A more focused definition makes possible a classification of patients into two distinct subgroups for both clinical and research purposes. Establishing a common language for future research will facilitate our understanding and management of such diseases. Even if different treatment strategies have different outcomes for these groups, we will have confirmation, or otherwise, of the clinical value of cluster analysis. This knowledge could lead to pharmacological treatment and other interventions directed to specific phenotypic groups.

Hypoxia and muscle maintenance regulation: implications for chronic respiratory disease

PURPOSE OF REVIEW

Muscle wasting and impaired muscle oxidative metabolism are common extrapulmonary features of chronic respiratory failure (CRF) that significantly increase disease burden. This review aims to address the question whether hypoxia, an obvious consequence of this disease, actually plays a causal role in these muscle impairments.

RECENT FINDINGS

In experimental models, a causal role for hypoxia in muscle atrophy and metabolic impairments has clearly been shown. Although the hypoxia-inducible factors and nuclear factor kappa B are putative mediators of these hypoxia-induced alterations, their true involvement remains to be proven. Molecular signatures of disrupted regulation of muscle mass and oxidative metabolism observed in these experimental models also have been shown in muscles of patients suffering from CRF, suggestive of but not conclusive for a causal role of hypoxia. Therapies, including but not restricted to those aimed at alleviating hypoxia, have been shown to partially but not completely restore muscle mass and oxidative capacity in CRF patients, which may imply an additive effect of nutritional modulation of substrate metabolism.

SUMMARY

Although hypoxia clearly affects skeletal muscle maintenance, it remains to be confirmed whether and by which underlying molecular mechanisms hypoxia is causally involved in CRF-related muscle atrophy and impaired oxidative capacity.

Elastase-induced pulmonary emphysema: insights from experimental models

Several distinct stimuli can be used to reproduce histological and functional features of human emphysema, a leading cause of disability and death. Since cigarette smoke is the main cause of emphysema in humans, experimental researches have attempted to reproduce this situation. However, this is an expensive and cumbersome method of emphysema induction, and simpler, more efficacious alternatives have been sought. Among these approaches, elastolytic enzymes have been widely used to reproduce some characteristics of human cigarette smoke-induced disease, such as: augmentation of airspaces, inflammatory cell influx into the lungs, and systemic inflammation. Nevertheless, the use of elastase-induced emphysema models is still controversial, since the disease pathways involved in elastase induction may differ from those occurring in smoke-induced emphysema. This indicates that the choice of an emphysema model may impact the results of new therapies or drugs being tested. The aim of this review is to compare the mechanisms of disease induction in smoke and elastase emphysema models, to describe the differences among various elastase models, and to establish the advantages and disadvantages of elastase-induced emphysema models. More studies are required to shed light on the mechanisms of elastase-induced emphysema.

A unique protein profile of peripheral neutrophils from COPD patients does not reflect cytokine-induced protein profiles of neutrophils in vitro

Background

Inflammation, both local and systemic, is a hallmark of chronic obstructive pulmonary disease (COPD). Inflammatory mediators such as TNFα and GM-CSF are secreted by lung epithelium, alveolar macrophages and other inflammatory cells and are thought to be important contributors in the pathogenesis of COPD. Indeed, neutrophils are activated by these cytokines and these cells are one of the major inflammatory cell types recruited to the pulmonary compartment of COPD patients. Furthermore, these inflammatory mediators are found in the peripheral blood of COPD patients and, therefore, we hypothesized that TNFα/GM-CSF-induced protein profiles can be found in peripheral neutrophils of COPD patients.

Methods

Using fluorescence 2-dimensional difference gel electrophoresis we investigated differentially regulated proteins in peripheral neutrophils from COPD patients and healthy age-matched control subjects. Furthermore, protein profiles from COPD patients were compared with those of neutrophils of healthy age-matched controls that were stimulated with TNFα and/or GM-CSF in vitro. Protein gels were compared using DeCyder 7.0 software.

Results

We identified 7 significantly regulated protein spots between peripheral neutrophils from COPD patients and age-matched healthy control subjects. Stimulation of peripheral neutrophils with TNFα, GM-CSF or TNFα + GM-CSF in vitro resulted in 13, 20 and 22 regulated protein spots, respectively. However, these cytokine-induced protein differences did not correspond with the protein differences found in neutrophils from COPD patients.

Conclusion

These results show that neutrophils from COPD patients have a unique protein profile compared to neutrophils from healthy age-matched controls. Furthermore, the neutrophil profiles of COPD patients do not reflect putative dominant signals induced by TNFα, GM-CSF or their combination. Our results indicate that systemic neutrophil responses in COPD patients are caused by a unique but subtle interplay between multiple inflammatory signals.

Inflammatory cells and apoptosis in respiratory and limb muscles of patients with COPD

Discrepancies exist regarding the involvement of cellular inflammation and apoptosis in the muscle dysfunction of chronic obstructive pulmonary disease (COPD) patients with preserved body composition. We explored whether levels of inflammatory cells and apoptosis were increased in both respiratory and limb muscles of COPD patients without nutritional abnormalities. In the vastus lateralis, external intercostals, and diaphragms of severe and moderate COPD patients with normal body composition, and in healthy subjects, intramuscular leukocytes and macrophage levels were determined (immunohistochemistry). Muscle structure was also evaluated. In the diaphragm and vastus lateralis of severe and moderate COPD patients and controls, apoptotic nuclei were explored using the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, electron microscopy, and caspase-3 expression. In COPD patients compared with controls, diaphragm and intercostal levels of inflammatory cells were extremely low and not significantly different. However, in the vastus lateralis of the severe patients, inflammatory cell counts, although also very low, were significantly greater. In those patients, TUNEL-positive nuclei levels were also significantly greater in diaphragms and vastus lateralis. A significant inverse relationship was found between quadriceps TUNEL-positive nuclei levels and muscle force. Ultrastructural apoptotic nuclei revealed no differences in respiratory or limb muscles between COPD patients and controls. Muscle caspase-3 expression did not differ between patients and controls. In severe COPD patients with preserved body composition, while increased apoptotic nuclei seems to be a contributor to their muscle dysfunction, cellular inflammation does not. The increased numbers of TUNEL-positive nuclei in their muscles suggest that they may also be exposed to a continuous repair/remodeling process.

Respiratory and skeletal muscle strength in chronic obstructive pulmonary disease: impact on exercise capacity and lower extremity function

PURPOSE

We sought to quantify the impact of respiratory muscle and lower extremity strength on exercise capacity and lower extremity function (LEF) in patients with chronic obstructive pulmonary disease (COPD).

METHODS

In 828 persons with COPD, we assessed the impact of reduced respiratory (maximum inspiratory pressure, MIP) and lower extremity muscle strength (quadriceps strength, QS) on exercise capacity (6-minute walk test, 6MWT), and LEF (short physical performance battery). Multiple regression analyses taking into account key covariates, including lung function and smoking, tested the associations between muscle strength and exercise and functional capacity.

RESULTS

For each 0.5 SD decrement in QS, men walked 18.3 m less during 6MWT (95% confidence interval [CI], -24.1 to -12.4); women 25.1 m less (95% CI, -31.1 to -12.4). For each 0.5 SD decrement in MIP, men walked 9.4 m less during 6MWT (95% CI, -15.2 to -3.6); women 8.7 m less (95% CI, -14.1 to -3.4). For each 0.5 SD decrease in QS, men had a 1.32 higher odds (95% CI, 1.11-1.15) of poor LEF; women had a 1.87 higher odds (95% CI, 1.54-2.27). Lower MIP (per 0.5 SD) was associated with increased odds of poor LEF in women (odds ratio = 1.18; 95% CI, 1.00-1.39), but not in men (odds ratio = 1.10; 95% CI, 0.93-1.31).

CONCLUSIONS

In COPD, reduced respiratory and lower extremity muscle strength are associated with decreased exercise and functional capacity. Muscle weakness is likely an important component of impairment and disability in patients with COPD.