Supplemental oxygen prevents exercise-induced oxidative stress in muscle-wasted patients with chronic obstructive pulmonary disease

The benefits and drawbacks of home oxygen therapy for COPD: what's next?

INTRODUCTION

Home oxygen therapy is one of the few interventions that can improve survival in patients with chronic obstructive pulmonary disease (COPD) when administered appropriately, although it may cause side effects and be an unnecessary burden for some patients.

AREAS COVERED

This narrative review summarizes the current literature on the assessment of hypoxemia, different types of home oxygen therapy, potential beneficial and adverse effects, and emerging research on home oxygen therapy in COPD. A literature search was performed using MEDLINE and EMBASE up to January 2024, with additional articles being identified through clinical guidelines.

EXPERT OPINION

Hypoxemia is common in patients with more severe COPD. Long-term oxygen therapy is established to prolong survival in patients with chronic severe resting hypoxemia. Conversely, in the absence of chronic severe resting hypoxemia, home oxygen therapy has an unclear or conflicting evidence base, including for palliation of breathlessness, and is generally not recommended. However, beneficial effects in some patients cannot be precluded. Evidence is emerging on the optimal daily duration of oxygen use, the role of high-flow and auto-titrated oxygen therapy, improved informed decision-making, and telemonitoring. Further research is needed to validate novel oxygen delivery systems and monitoring tools and establish long-term effects of ambulatory oxygen therapy in COPD.

Brief Oxygen Exposure after Traumatic Brain Injury Hastens Recovery and Promotes Adaptive Chronic Endoplasmic Reticulum Stress Responses

Traumatic brain injury (TBI) is a major public health concern, particularly in adolescents who have a higher mortality and incidence of visual pathway injury compared to adult patients. Likewise, we have found disparities between adult and adolescent TBI outcomes in rodents. Most interestingly, adolescents suffer a prolonged apneic period immediately post-injury, leading to higher mortality; therefore, we implemented a brief oxygen exposure paradigm to circumvent this increased mortality. Adolescent male mice experienced a closed-head weight-drop TBI and were then exposed to 100% O2 until normal breathing returned or recovered in room air. We followed mice for 7 and 30 days and assessed their optokinetic response; retinal ganglion cell loss; axonal degeneration; glial reactivity; and retinal ER stress protein levels. O2 reduced adolescent mortality by 40%, improved post-injury visual acuity, and reduced axonal degeneration and gliosis in optical projection regions. ER stress protein expression was altered in injured mice, and mice given O2 utilized different ER stress pathways in a time-dependent manner. Finally, O2 exposure may be mediating these ER stress responses through regulation of the redox-sensitive ER folding protein ERO1α, which has been linked to a reduction in the toxic effects of free radicals in other animal models of ER stress.

Brief oxygen exposure after traumatic brain injury speeds recovery and promotes adaptive chronic endoplasmic reticulum stress responses

Traumatic brain injury (TBI) is a major public health concern particularly in adolescents who have a higher mortality and incidence of visual pathway injury compared to adult patients. Likewise, we have found disparities between adult and adolescent TBI outcomes in rodents. Most interestingly, adolescents suffer a prolonged apneic period immediately post injury leading to higher mortality; so, we implemented a brief oxygen exposure paradigm to circumvent this increased mortality. Adolescent male mice experienced a closed-head weight-drop TBI then were exposed to 100% O ₂ until normal breathing returned or recovered in room air. We followed mice for 7- and 30-days and assessed their optokinetic response; retinal ganglion cell loss; axonal degeneration; glial reactivity; and retinal ER stress protein levels. O ₂ reduced adolescent mortality by 40%, improved post-injury visual acuity, and reduced axonal degeneration and gliosis in optic projection regions. ER stress protein expression was altered in injured mice, and mice given O ₂ utilized different ER-stress pathways in a time dependent manner. Finally, O ₂ exposure may be mediating these ER stress responses through regulation of the redox-sensitive ER folding protein ERO1α, which has been linked to a reduction in the toxic effects of free radicals in other animal models of ER stress.

Oxidative Stress and Total Phenolics Concentration in COPD Patients-The Effect of Exercises: A Randomized Controlled Trial

Patients with chronic obstructive pulmonary disease (COPD) suffer from exercise intolerance, the sensation of dyspnea, and fatigue, which are the main reasons for limiting their physical activity. In addition to changes in the respiratory and circulatory systems in patients with COPD, peripheral muscle dysfunction, with numerous metabolic dysfunctions, is observed. One of the symptoms of the described anomalies, among others, is an antioxidative and prooxidative imbalance. The aim of the study was to demonstrate the impact of endurance training, carried out in the extended pulmonary rehabilitation program in COPD patients, on the imbalance between prooxidants and antioxidants in their bodies. Methods: The tests were carried out on a group of patients (n = 32) with COPD; 20 randomly selected people underwent a modified rehabilitation program during their rehabilitation stay, and the obtained results were compared with the results of 12 patients (control group) who were treated without endurance training. At the beginning and at the end of the study, spirometry and cardiopulmonary exercise tests (CPET) were performed. Oxidative stress (allantoin (All) and substances which react with thiobarbituric acid) and antioxidant (ferric reducing ability of plasma and total phenolics) parameters’ concentrations were determined in the venous blood. Results: In the study group, greater post-training increases of VO2max (p = 0.0702) and FEV1/FVC (p < 0.05; ES: 0.436) were reported. The applied CPET at each time caused an increase in the All concentration (p < 0.05) in the study and control groups. Conclusions: Endurance training applied as a part of the rehabilitation process did not cause the additional aggravation of oxidative stress and blood total phenolics concentration.

A Feasibility and Efficacy Randomized Controlled Trial of Two Exercise Programs in Severe AECOPD Patients with Resting Hypoxemia

Resting hypoxemia is the most severe stage of Chronic Obstructive Pulmonary Disease (COPD). Due to their impairments during the exacerbation, these patients are limited to traditional exercise rehabilitation and are excluded from the majority of the studies. The aim of this study was to assess the feasibility and the efficacy of two exercise programs in Acute Exacerbation of COPD (AECOPD) patients with resting hypoxemia. In this randomized clinical trial, patients hospitalized due to an acute exacerbation of COPD with hypoxemia at rest were included. Patients were randomly assigned into three groups. A Control Group (pharmacological treatment), a Global Exercise Group (GEG), and a Functional Electrostimulation Group (FEG). Patients were treated during the hospitalization period. The main outcomes were lower limb strength (assessed by a dynamometer), balance (assessed by the one leg standing balance test), health related quality of life (assessed by the EQ-5D), adverse events and adherence. At the end of the intervention, there were significant differences in all the variables in favour of the experimental groups (p < 0.05). We concluded that conducting an exercise program is feasible and improves lower limb strength, balance, and health related quality of life in AECOPD patients with resting hypoxemia.

Ascorbate attenuates cycling exercise-induced neuromuscular fatigue but fails to improve exertional dyspnea and exercise tolerance in COPD

We examined the effect of intravenous ascorbate (VitC) administration on exercise-induced redox balance, inflammation, exertional dyspnea, neuromuscular fatigue, and exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). Eight COPD patients completed constant-load cycling (∼80% of peak power output, 83 ± 10 W) to task failure after intravenous VitC (2 g) or saline (placebo, PL) infusion. All participants repeated the shorter of the two exercise trials (isotime) with the other infusate. Quadriceps fatigue was determined by pre- to postexercise changes in quadriceps twitch torque (ΔQtw, electrical femoral nerve stimulation). Corticospinal excitability before, during, and after exercise was assessed by changes in motor evoked potentials triggered by transcranial magnetic stimulation. VitC increased superoxide dismutase (marker for endogenous antioxidant capacity) by 129% and mitigated C-reactive protein (marker for inflammation) in the plasma during exercise but failed to alter the exercise-induced increase in lipid peroxidation (malondialdehyde) and free radicals [electron paramagnetic resonance (EPR)-spectroscopy]. Although VitC did, indeed, decrease neuromuscular fatigue (ΔQtw: PL -29 ± 5%, VitC -23 ± 6%, P < 0.05), there was no impact on corticospinal excitability and time to task failure (∼8 min, P = 0.8). Interestingly, in terms of pulmonary limitations to exercise, VitC had no effect on perceived exertional dyspnea (∼8.5/10) and its determinants, including oxygen saturation ([Formula: see text]) (∼92%) and respiratory muscle work (∼650 cmH2O·s·min-1) (P > 0.3). Thus, although VitC facilitated indicators for antioxidant capacity, diminished inflammatory markers, and improved neuromuscular fatigue resistance, it failed to improve exertional dyspnea and cycling exercise tolerance in patients with COPD. As dyspnea is recognized to limit exercise tolerance in COPD, the otherwise beneficial effects of VitC may have been impacted by this unaltered sensation.NEW & NOTEWORTHY We investigated the effect of intravenous vitamin C on redox balance, exertional dyspnea, neuromuscular fatigue, and exercise tolerance in chronic obstructive pulmonary disease (COPD) patients. Acute vitamin C administration increased superoxide dismutase (marker of antioxidant capacity) and attenuated fatigue development but failed to improve exertional dyspnea and exercise tolerance. These findings suggest that a compromised redox balance plays a critical role in the development of fatigue in COPD but also highlight the significance of exertional dyspnea as an important symptom limiting the patients' exercise tolerance.

Oxygen supplementation increases the total work and muscle damage markers but reduces the inflammatory response in COPD patients

INTRODUCTION

Oxygen supplementation (O₂-Suppl) is recommended for pulmonary rehabilitation with higher exercise intensities. However, high-intensity exercise tends toward muscle damage and a greater inflammatory response. We aimed to investigate the effect of O₂-Suppl during exercise test (EET) on CRP level and muscle damage (CPK, LDH, lactate) in non-hypoxemic COPD patients.

METHODS

Eleven non-depleted patients with COPD (FEV₁ 65.5 ± 4.3 %) performed two EET (room-air or O₂-Suppl-100 %), through a blind, randomized, and placebo-controlled crossover design. CPK, LDH and CRP were measured before, immediately after and 24 h after EET.

RESULTS

Exercise time was higher with O₂-Suppl (49.9 ± 37.3 %; p = 0.001) and increases in CPK and LDH were observed compared to basal values in the O₂-Suppl (28.4UI/L and 28.3 UI/L). The O₂-Suppl protocol resulted in a lower increase in CRP (92.1 ± 112.4 % vs. 400.1 ± 384.9 %; p = 0.003).

CONCLUSIONS

O₂-Suppl increases exercise-tolerance, resulting in increased muscle injury markers in COPD. However, oxygen supplementation attenuates the inflammatory response, even upon increased physical exercise.

Oxygen therapy improves cerebral oxygen delivery and neurovascular function in hypoxaemic chronic obstructive pulmonary disease patients

NEW FINDINGS

What is the central question of this study? How does oxygen therapy influence cerebral blood flow, cerebral oxygen delivery and neurovascular function in chronic obstructive pulmonary disease patients? What is the main finding and its importance? Oxygen therapy improves cerebral oxygen delivery and neurovascular function in chronic obstructive pulmonary disease patients. This improvement in cerebral oxygen delivery and neurovascular function might provide a physiological link between oxygen therapy and a reduced risk of cerebrovascular disease (e.g. stroke, mild cognitive impairment and dementia) in chronic obstructive pulmonary disease.

ABSTRACT

We investigated the role of hypoxaemia in cerebral blood flow (CBF), oxygen delivery (CDO₂ ) and neurovascular coupling (coupling of CBF to neural activity; NVC) in hypoxaemic chronic obstructive pulmonary disease (COPD) patients (n = 14). Resting CBF (duplex ultrasound), peripheral oxyhaemoglobin saturation (SpO2; pulse-oximetry) and NVC (transcranial Doppler) were assessed before and after a 20 min wash-in of supplemental oxygen (∼3 l min^-1 ). The peripheral oxyhaemoglobin saturation increased from 91.0 ± 3.3 to 97.4 ± 3.0% (P < 0.01), whereas CBF was unaltered (593.0 ± 162.8 versus 590.1 ± 138.5 ml min^-1 ; P = 0.91) with supplemental O₂ . In contrast, both CDO₂ (98.1 ± 25.7 versus 108.7 ± 28.4 ml dl^-1 ; P = 0.02) and NVC were improved. Specifically, the posterior cerebral artery cerebrovascular conductance was increased to a greater extent after O₂ normalization (+40%, from 20.4 ± 9.9 to 28.0 ± 10.4% increase in conductance; P = 0.04), whereas the posterior cerebral artery cerebrovascular resistance decreased to a greater extent during O₂ normalization (+22%, from -16.7 ± 7.3 to -21.4 ± 6.6% decrease in resistance; P = 0.04). The cerebral vasculature of COPD patients appears insensitive to oxygen, because CBF was unaltered in response to O₂ supplementation leading to improved CDO₂ . In patients, the improvements in CDO₂ and neurovascular function with supplemental O₂ may underlie the cognitive benefits associated with O₂ therapy.

Disturbed blood flow worsens endothelial dysfunction in moderate-severe chronic obstructive pulmonary disease

The aims of this study were: (1) to test whether oscillatory shear stress further exacerbates endothelial dysfunction in patients with moderate-severe COPD, and (2) to test whether low flow oxygen administration improves endothelial function and is protective against oscillatory shear stress-induced endothelial dysfunction in patients with moderate-severe COPD. In 17 patients and 10 age-matched non-smoking control subjects we examined brachial artery flow-mediated dilation (FMD) and circulating microparticles before and after 20 minutes of experimentally-induced oscillatory shear stress. COPD patients performed this intervention a second time following a 20-minute wash in period of low flow supplemental oxygen to normalize arterial oxygen saturation. COPD patients had ~six-fold greater baseline retrograde shear rate (P < 0.05) and lower FMD (P < 0.05). The oscillatory shear stress intervention induced significant decreases in brachial artery FMD of all groups (P < 0.05). Oscillatory shear stress elevated circulating markers of endothelial cell apoptosis (CD31+/CD41b- microparticles) in COPD patients, but not age-matched controls. Supplemental oxygen administration abrogated the oscillatory shear stress-induced increase in CD31+/CD41b- microparticles, and improved FMD after accounting for the shear stress stimulus. We have demonstrated that acutely disturbed blood flow with increased retrograde shear stress further deteriorates the already impaired endothelial function with attendant endothelial apoptosis in patients with moderate-severe COPD.

Short-term Effects of Supplemental Oxygen on 6-Min Walk Test Outcomes in Patients With COPD: A Randomized, Placebo-Controlled, Single-blind, Crossover Trial

BACKGROUND

The acute effect of supplemental oxygen during exercise has been shown to differ largely among patients with COPD. It is unknown what factors influence oxygen response.

METHODS

In a randomized, single-blind fashion, 124 patients with COPD underwent one 6-min walk test on supplemental oxygen (6MWT_O2) and one 6-min walk test on room air after a practice 6-min walk test. Both gases were delivered via standard nasal prongs (2 L/min). For analyses, patients were stratified on the basis of PaO₂ values and compared: (1) 34 patients with resting hypoxemia (HYX); (2) 43 patients with exercise-induced hypoxemia (EIH); and (3) 31 patients with normoxemia (NOX).

RESULTS

Oxygen supplementation resulted in an increase in the 6-min walk distance in the total cohort (27 ± 42 meters; P < .001) and in the subgroups of HYX (37 ± 40 meters; P < .001) and EIH (28 ± 44 meters; P < .001) but not in the NOX subgroup (15 ± 43 meters; P = .065). Forty-two percent of patients with HYX and 47% of patients with EIH improved their 6-min walk distance to a clinically relevant extent (≥ 30 meters) by using oxygen. These oxygen responders were characterized by significantly lower 6-min walk distance using room air compared with patients without a relevant response (306 ± 106 meters vs 358 ± 113 meters; P < .05). Although oxygen saturation was significantly higher during 6MWT_O2 compared with the 6-min walk test on room air in all 3 subgroups, it dropped to < 88% during 6MWT_O2 in 73.5% of patients with HYX.

CONCLUSIONS

In contrast to patients with NOX, patients with HYX and EIH generally benefit from supplemental oxygen by increasing exercise capacity. However, less than one-half of patients reached the threshold of clinically relevant improvements. These oxygen responders were characterized by significantly lower exercise capacity levels.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00886639; URL: www.clinicaltrials.gov.

Hyperoxia increases arterial oxygen pressure during exercise in type 2 diabetes patients: a feasibility study

Objective

The study investigated the feasibility and potential outcome measures during acute hyperoxia in type 2 diabetes patients (DM2).

Methods

Eleven DM2 patients (7 men and 4 women) were included in the study. The patients cycled (30 min at 20 % W_max) whilst breathing three different supplemental oxygen flows (SOF, 5, 10, 15 L min⁻¹). During hyperoxic exercise, arterial blood gases and intra-arterial blood pressure measurements were obtained.

Results

Arterial pO₂ levels increased significantly (ANOVA, p < 0.05) with SOF: 13.9 ± 1.2 (0 L min⁻¹); 18.5 ± 1.5 (5 L min⁻¹); 21.7 ± 1.7 (10 L min⁻¹); 24.0 ± 2.3 (15 L min⁻¹). Heart rate (HR) and pH increased significantly after terminating administration of hyperoxic air.

Conclusions

An SOF of 15 L min⁻¹ appears to be more effective than 5 or 10 L min⁻¹. Moreover, HR, blood pressure, blood lactate and pH are not recommended as primary outcome measures.

Heterogeneity of Systemic Oxidative Stress Profiles in COPD: A Potential Role of Gender

Oxidative stress (OS) plays a key role in the muscle impairment and exercise capacity of COPD patients. However, the literature reveals that systemic OS markers show great heterogeneity, which may hinder the prescription of effective antioxidant supplementation. This study therefore aimed to identify OS markers imbalance of COPD patients, relative to validated normal reference values, and to investigate the possibility of systemic OS profiles. We measured systemic enzymatic/nonenzymatic antioxidant and lipid peroxidation (LP) levels in 54 stable COPD patients referred for a rehabilitation program. The main systemic antioxidant deficits in these patients concerned vitamins and trace elements. Fully 89% of the COPD patients showed a systemic antioxidant imbalance which may have caused the elevated systemic LP levels in 69% of them. Interestingly, two patient profiles (clusters 3 and 4) had a more elevated increase in LP combined with increased copper and/or decreased vitamin C, GSH, and GPx. Further analysis revealed that the systemic LP level was higher in COPD women and associated with exercise capacity. Our present data therefore support future supplementations with antioxidant vitamins and trace elements to improve exercise capacity, but COPD patients will probably show different positive responses.

Palliative care for patients with chronic obstructive pulmonary disease: current perspectives

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory illness with a myriad of disabling symptoms and a decline in the functional parameters that affect the quality of life. The mortality and morbidity associated with severe COPD is high and the patients are mostly housebound and in need of continuous care and support. The uncertain nature of its prognosis makes the commencement of palliative care and discussion of end-of-life issues difficult even in the advanced stage of the disease. This is often compounded by inadequate communication and counseling with patients and their relatives. The areas that may improve the quality of care include the management of dyspnea, oxygen therapy, nutritional support, antianxiety, and antidepressant treatment, and advance care planning. Hence, it is necessary to pursue a holistic care approach for palliative care services along with disease-specific medical management in all such patients to improve the quality of life in end-stage COPD.

Effect of supplemental oxygen on post-exercise inflammatory response and oxidative stress

This investigation explored the influence of supplemental oxygen administered during the recovery periods of an interval-based running session on the post-exercise markers of reactive oxygen species (ROS) and inflammation. Ten well-trained male endurance athletes completed two sessions of 10 × 3 min running intervals at 85 % of the maximal oxygen consumption velocity (vVO(2)peak) on a motorised treadmill. A 90-s recovery period was given between each interval, during which time the participants were administered either a hyperoxic (HYP) (Fraction of Inspired Oxygen (FIO2) 99.5 %) or normoxic (NORM) (FIO2 21 %) gas, in a randomized, single-blind fashion. Pulse oximetry (SpO(2)), heart rate (HR), blood lactate (BLa), perceived exertion (RPE), and perceived recovery (TQRper) were recorded during each trial. Venous blood samples were taken pre-exercise, post-exercise and 1 h post-exercise to measure Interleukin-6 (IL-6) and Isoprostanes (F2-IsoP). The S(p)O(2) was significantly lower than baseline following all interval repetitions in both experimental trials (p < 0.05). The S(p)O(2) recovery time was significantly quicker in the HYP when compared to the NORM (p < 0.05), with a trend for improved perceptual recovery. The IL-6 and F2-IsoP were significantly elevated immediately post-exercise, but had significantly decreased by 1 h post-exercise in both trials (p < 0.05). There were no differences in IL-6 or F2-IsoP levels between trials. Supplemental oxygen provided during the recovery periods of interval based exercise improves the recovery time of SPO(2) but has no effect on post-exercise ROS or inflammatory responses.

Pulmonary rehabilitation improves exercise capacity and quality of life in underweight patients with chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVE

An estimated 20-40% of COPD patients are underweight. We sought to confirm the physiological and psychosocial benefits of pulmonary rehabilitation programmes (PRP) in underweight compared with non-underweight patients with COPD.

METHODS

Twenty-two underweight COPD patients with BMI <20 kg/m(2), and 22 non-underweight COPD patients, who were matched for FEV(1) and age, were studied. All patients had moderate-to-very severe COPD. All patients participated in 12-week, hospital-based outpatient PRP consisting of two sessions per week. Baseline and post-PRP status were evaluated by spirometry, cardiopulmonary exercise testing, ventilatory muscle strength and the St. George's Respiratory Questionnaire (SGRQ).

RESULTS

At baseline, the age distribution and airflow obstruction were similar in underweight and non-underweight patients with COPD. Baseline exercise capacity, inspiratory muscle strength and SGRQ total and symptoms scores were significantly lower in the underweight patients (all P < 0.05). After the PRP, there was significant weight gain in the underweight COPD patients (mean increase 0.8 kg, P = 0.01). There were also significant improvements in peak oxygen uptake, peak workload and the SGRQ total, symptoms, activity and impact scores in both underweight and non-underweight patients with COPD (all P < 0.05).

CONCLUSIONS

Underweight patients with COPD have impaired exercise capacity and health-related quality of life (HRQL). Exercise training with supplemental oxygen may result in significant weight gains and improvements in exercise capacity and HRQL. Exercise training is indicated for underweight patients with COPD.

Hypoxemia in patients with COPD: cause, effects, and disease progression

Chronic obstructive pulmonary disease (COPD) is a leading cause of death and disability internationally. Alveolar hypoxia and consequent hypoxemia increase in prevalence as disease severity increases. Ventilation/perfusion mismatch resulting from progressive airflow limitation and emphysema is the key driver of this hypoxia, which may be exacerbated by sleep and exercise. Uncorrected chronic hypoxemia is associated with the development of adverse sequelae of COPD, including pulmonary hypertension, secondary polycythemia, systemic inflammation, and skeletal muscle dysfunction. A combination of these factors leads to diminished quality of life, reduced exercise tolerance, increased risk of cardiovascular morbidity, and greater risk of death. Concomitant sleep-disordered breathing may place a small but significant subset of COPD patients at increased risk of these complications. Long-term oxygen therapy has been shown to improve pulmonary hemodynamics, reduce erythrocytosis, and improve survival in selected patients with severe hypoxemic respiratory failure. However, the optimal treatment for patients with exertional oxyhemoglobin desaturation, isolated nocturnal hypoxemia, or mild-to-moderate resting daytime hypoxemia remains uncertain.

Structural and functional changes of peripheral muscles in chronic obstructive pulmonary disease patients

PURPOSE OF REVIEW

The purpose of this review is to identify new advances in our understanding of skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease (COPD).

RECENT FINDINGS

Recent studies have confirmed the relevance of muscle dysfunction as an independent prognosis factor in COPD. Animal studies have shed light on the molecular mechanisms governing skeletal muscle hypertrophy/atrophy. Recent evidence in patients with COPD highlighted the contribution of protein breakdown and mitochondrial dysfunction as pathogenic mechanisms leading to muscle dysfunction in these patients.

SUMMARY

COPD is a debilitating disease impacting negatively on health status and the functional capacity of patients. COPD goes beyond the lungs and incurs significant systemic effects among which muscle dysfunction/wasting is one of the most important. Muscle dysfunction is a prominent contributor to exercise limitation, healthcare utilization and an independent predictor of morbidity and mortality. Gaining more insight into the molecular mechanisms leading to muscle dysfunction/wasting is key for the development of new and tailored therapeutic strategies to tackle skeletal muscle dysfunction/wasting in COPD patients.

Muscle as an endocrine organ: focus on muscle-derived interleukin-6

Skeletal muscle has recently been identified as an endocrine organ. It has, therefore, been suggested that cytokines and other peptides that are produced, expressed, and released by muscle fibers and exert paracrine, autocrine, or endocrine effects should be classified as "myokines." Recent research demonstrates that skeletal muscles can produce and express cytokines belonging to distinctly different families. However, the first identified and most studied myokine is the gp130 receptor cytokine interleukin-6 (IL-6). IL-6 was discovered as a myokine because of the observation that it increases up to 100-fold in the circulation during physical exercise. Identification of IL-6 production by skeletal muscle during physical activity generated renewed interest in the metabolic role of IL-6 because it created a paradox. On one hand, IL-6 is markedly produced and released in the postexercise period when insulin action is enhanced but, on the other hand, IL-6 has been associated with obesity and reduced insulin action. This review focuses on the myokine IL-6, its regulation by exercise, its signaling pathways in skeletal muscle, and its role in metabolism in both health and disease.

Oxygen therapy in chronic obstructive pulmonary disease

Since the introduction of oxygen as a therapeutic agent 70 years ago, much has been learned regarding the detrimental effects of hypoxemia and the beneficial impact of oxygen therapy. It is projected that there are close to 800,000 patients receiving long-term oxygen therapy (LTOT) in the United States, at a cost of approximately $1.8 billion annually. The large numbers of patients receiving supplemental oxygen as treatment and the high costs incurred in providing oxygen therapy necessitate the practitioner to know the indications for LTOT as well its effects on survival, pulmonary hemodynamics, sleep, and exercise capacity. It is now recognized that the basis for LTOT prescription for all patients is founded on data that are over 25 years old and that only involve a very select cohort of patients. It is clear that further studies are required to assess the effects of oxygen on patients with chronic obstructive pulmonary disease with only mild hypoxemia, not only survival but also on neurocognitive function, quality of life, exercise physiology, and sleep quality. In addition, although proven to be safe when prescribed long term to individuals with lung disease, there are some concerns about worsening carbon dioxide retention and increased oxidant injury. The goals of this article are to briefly describe the indications for chronic oxygen administration, the physiologic effects of treatment, and potential toxicities, as well as its effect on morbidity and mortality.

Mechanisms of atherothrombosis in chronic obstructive pulmonary disease

Patients affected by chronic obstructive pulmonary disease (COPD) have an increased risk of atherothrombotic acute events, independent of smoking and other cardiovascular risk factors. As a consequence, myocardial ischemia is a relevant cause of death in these patients. We reviewed studies concerning the potential mechanisms of atherothrombosis in COPD. Bronchial inflammation spreads to the systemic circulation and is known to play a key role in plaque formation and rupture. In fact, C-reactive protein blood levels increase in COPD and provide independent prognostic information. Systemic inflammation is the first cause of the hypercoagulable state commonly observed in COPD. Furthermore, hypoxia is supposed to activate platelets, thus accounting for the increased urinary excretion of platelet-derived thromboxane in COPD. The potential metabolic risk in COPD is still debated, in that recent studies do not support an association between COPD and diabetes mellitus. Finally, oxidative stress contributes to the pathogenesis of COPD and may promote oxidation of low-density-lipoproteins with foam cells formation. Retrospective observations suggest that inhaled corticosteroids may reduce atherothrombotic mortality by attenuating systemic inflammation, but this benefit needs confirmation in ongoing randomized controlled trials. Physicians approaching COPD patients should always be aware of the systemic vascular implications of this disease.

Targeting systemic inflammation: novel therapies for the treatment of chronic obstructive pulmonary disease

The increasing evidence that inflammation in the lungs leads to the structural changes observed in chronic obstructive pulmonary disease, whereas extrapulmonary symptoms and comorbidities may be systemic manifestations of these inflammatory processes, highlights an urgent need to discover novel, effective anti-inflammatory treatments for this disease. Some studies are suggesting that, by decreasing dynamic hyperinflation, bronchodilators might reduce systemic inflammation; inhaled corticosteroids and their combination with long-acting beta2-agonists might contribute to this goal. Even so, the opinion that suppression of the inflammatory response might improve systemic complications is stimulating a search for novel anti-inflammatory therapies. Many drugs include those that inhibit the recruitment and activation of inflammatory cells and/or antagonise their products. However, many of these therapeutic strategies are not specific for neutrophilic inflammation because they affect other cell types, thus, it is difficult to interpret whether any clinical benefit observed is a result of a reduction in airway neutrophils. In any case, there is some evidence that drugs used to treat a co-morbid condition, such as statins, angiotensin converting enzyme (ACE) inhibitors and angiontensin II type 1 (AT1) receptor blockers as well as glycosaminoglycans and peroxisome proliferator-activated receptor (PPAR) agonists, might benefit chronic obstructive pulmonary disease patients because they deal with the extrapulmonary, systemic component of chronic obstructive pulmonary disease.

New Approaches in Pulmonary Rehabilitation

Patients who have mild to severe chronic obstructive pulmonary disease may obtain improvement in dyspnea, exercise capacity, and health-related quality of life as a result of exercise training. The type and intensity of training is of key importance in determining outcomes. High-intensity aerobic training leads to physiologic gains in aerobic fitness. Nevertheless, extreme breathlessness or peripheral muscle fatigue may prevent some patients from performing high-intensity exercise; therefore, new tools are needed to improve the effectiveness of pulmonary rehabilitation.

The clinical management in extremely severe COPD

Chronic obstructive pulmonary disease (COPD) affects 6% of the general population and is the fourth-leading cause of death in the United States with severe and very severe disease accounting for 15% and 3% of physician diagnoses of COPD. Guidelines make few recommendations regarding providing the provision of care for the most severe stages of disease, namely Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages III and IV with chronic respiratory failure. The effectiveness of inhaled drug therapy in very severe patients has not been assessed yet. Health care systems in many countries include public funding of long-term oxygen therapy for eligible candidates. Currently, there is little evidence for the use of mechanical ventilatory support in the routine management of hypercapnic patients. Pulmonary rehabilitation should be considered as a significant component of therapy, even in the most severe patients. Although Lung Volume Reduction Surgery has been shown to improve mortality, exercise capacity, and quality of life in selected patients, this modality is associated with significant morbidity and an early mortality rate in the most severe patients. Despite significant progress over the past 25 years, both short- and long-term outcomes remain significantly inferior for lung transplantation relative to other "solid" organ recipients. Nutritional assessment and management is an important therapeutic option in patients with chronic respiratory diseases. Morphine may significantly reduce dyspnoea and does not significantly accelerate death. No consistent improvement in dyspnoea over placebo has been shown with anxiolytics. Supplemental oxygen during exercise reduces exertional breathlessness and improves exercise tolerance of the hypoxaemic patient. Non-invasive ventilation has been used as a palliative treatment to reduce dyspnoea. Hypoxaemic COPD patients, on long-term oxygen therapy, may show reduced health-related quality of life, cognitive function, and depression. Only a small proportion of patients with severe COPD discuss end-of-life issues with their physicians.

Six-Minute Walking-Induced Systemic Inflammation and Oxidative Stress in Muscle-Wasted COPD Patients

BACKGROUND

Systemic inflammation and oxidative stress are potential mechanisms for muscle wasting in COPD patients. Six-minute walking testing (6MWT) has been suggested as simple and valid exercise test in COPD that is well tolerated, and reflective of activities of daily living. The present study investigated physiologic and systemic immunologic responses to a 6MWT in muscle-wasted patients with COPD and compared them with maximal cardiopulmonary exercise testing (CPET).

METHODS

Ten patients with muscle-wasted COPD were included (fat-free mass index [FFMI]: men, < 16 kg/m2; women, < 15 kg/m2). 6MWT and CPET were performed in random order. The physiologic response was followed by a mobile oxycon. Arterial blood was obtained at rest and after exercise to measure blood gases and markers of systemic inflammation and oxidative stress.

RESULTS

In these patients (FEV1 55 +/- 4% of predicted [mean +/- SE]), the 6MWT was a submaximal, albeit intense, exercise as reflected by oxygen uptake (VO2), minute ventilation, heart rate, and lactate values. Leukocytosis was less intense after 6MWT compared to CPET. Contrary, the increase in interleukin-6, free radical release by neutrophils, oxidation of proteins and lipids, and the reduction in antioxidant capacity were similar after both exercises. FFMI was inversely related to 6MWT-induced increases in protein and lipid peroxidation.

CONCLUSIONS

This study shows that a 6MWT induces a systemic immunologic response in muscle-wasted patients with COPD, which is comparable to CPET-induced responses. The correlation between systemic oxidative stress and the degree of muscle wasting supports a possible causal relation between systemic inflammation, oxidative stress, and muscle wasting.

Exercise-induced systemic effects in muscle-wasted patients with COPD

PURPOSE

Physical exercise is known to induce an acute inflammatory response and oxidative stress in healthy subjects and patients with chronic obstructive pulmonary disease (COPD). Increasing evidence associates systemic inflammation and oxidative stress with muscle wasting and muscle dysfunction in COPD. In the present study, it was hypothesized that exercise-induced systemic inflammatory and oxidative responses in muscle-wasted COPD patients are increased compared with non-muscle-wasted patients and healthy subjects.

METHODS

Pulmonary function, body composition, and quadriceps muscle strength were measured in 10 muscle-wasted (fat-free mass index (FFMI) < 16 kg x m(-2) (men), < 15 kg x m(-2) (women)), 10 non-muscle-wasted COPD patients, and 10 healthy subjects. Systemic inflammation (C-reactive protein (CRP), leukocytes, cytokines) and oxidative stress (production of reactive oxygen species (ROS) by neutrophils, plasma antioxidant capacity, protein oxidation, lipid peroxidation, oxidized to reduced glutathione ratio (GSSG/GSH)) were determined before and after maximal and submaximal (50% of maximal work rate) cycle ergometry.

RESULTS

Low-grade systemic inflammation was significantly (P < 0.05) elevated in all COPD patients and tended to be highest in muscle-wasted patients. A decreased antioxidant status (plasma antioxidant capacity, P < 0.05; GSH, P < 0.05) and increased protein oxidation (P < 0.001) reflected increased basal oxidative stress in muscle-wasted COPD patients compared with both other groups. Both maximal and submaximal exercise caused increased inflammatory (IL-6, +1.1 pg. x mL(-1) vs rest, P < 0.05) and oxidative responses (ROS release by neutrophils, + 32%; GSSG/GSH + 29%; lipid peroxidation, + 30% vs rest) in muscle-wasted COPD patients, which were less pronounced or not observed in non-muscle-wasted patients and healthy subjects.

CONCLUSIONS

These data indicate that both maximal and submaximal exercise induce increased systemic inflammatory and oxidative responses in muscle-wasted COPD patients compared with non-muscle-wasted patients and healthy subjects.