Correction: Bioenergetic function is decreased in peripheral blood mononuclear cells of veterans with Gulf War Illness.

[This corrects the article DOI: 10.1371/journal.pone.0287412.].

Bioenergetic function is decreased in peripheral blood mononuclear cells of veterans with Gulf War Illness.

Gulf War Illness (GWI) is a major health problem for approximately 250,000 Gulf War (GW) veterans, but the etiology of GWI is unclear. We hypothesized that mitochondrial dysfunction is an important contributor to GWI, based on the similarity of some GWI symptoms to those occurring in some mitochondrial diseases; the plausibility that certain pollutants to which GW veterans were exposed affect mitochondria; mitochondrial effects observed in studies in laboratory models of GWI; and previous evidence of mitochondrial outcomes in studies in GW veterans. A primary role of mitochondria is generation of energy via oxidative phosphorylation. However, direct assessment of mitochondrial respiration, reflecting oxidative phosphorylation, has not been carried out in veterans with GWI. In this case-control observational study, we tested multiple measures of mitochondrial function and integrity in a cohort of 114 GW veterans, 80 with and 34 without GWI as assessed by the Kansas definition. In circulating white blood cells, we analyzed multiple measures of mitochondrial respiration and extracellular acidification, a proxy for non-aerobic energy generation; mitochondrial DNA (mtDNA) copy number; mtDNA damage; and nuclear DNA damage. We also collected detailed survey data on demographics; deployment; self-reported exposure to pesticides, pyridostigmine bromide, and chemical and biological warfare agents; and current biometrics, health and activity levels. We observed a 9% increase in mtDNA content in blood in veterans with GWI, but did not detect differences in DNA damage. Basal and ATP-linked oxygen consumption were respectively 42% and 47% higher in veterans without GWI, after adjustment for mtDNA amount. We did not find evidence for a compensatory increase in anaerobic energy generation: extracellular acidification was also lower in GWI (12% lower at baseline). A subset of 27 and 26 veterans returned for second and third visits, allowing us to measure stability of mitochondrial parameters over time. mtDNA CN, mtDNA damage, ATP-linked OCR, and spare respiratory capacity were moderately replicable over time, with intraclass correlation coefficients of 0.43, 0.44, 0.50, and 0.57, respectively. Other measures showed higher visit-to-visit variability. Many measurements showed lower replicability over time among veterans with GWI compared to veterans without GWI. Finally, we found a strong association between recalled exposure to pesticides, pyridostigmine bromide, and chemical and biological warfare agents and GWI (p < 0.01, p < 0.01, and p < 0.0001, respectively). Our results demonstrate decreased mitochondrial respiratory function as well as decreased glycolytic activity, both of which are consistent with decreased energy availability, in peripheral blood mononuclear cells in veterans with GWI.

Deployed Veterans exhibit distinct respiratory patterns and greater dyspnea during maximal cardiopulmonary exercise: A case-control study.

BACKGROUND: Exertional dyspnea and exercise intolerance are frequently endorsed in Veterans of post 9/11 conflicts in Southwest Asia (SWA). Studying the dynamic behavior of ventilation during exercise may provide mechanistic insight into these symptoms. Using maximal cardiopulmonary exercise testing (CPET) to experimentally induce exertional symptoms, we aimed to identify potential physiological differences between deployed Veterans and non-deployed controls. MATERIALS AND METHODS: Deployed (n = 31) and non-deployed (n = 17) participants performed a maximal effort CPET via the Bruce treadmill protocol. Indirect calorimetry and perceptual rating scales were used to measure rate of oxygen consumption ([Formula: see text]), rate of carbon dioxide production ([Formula: see text]), respiratory frequency (f R), tidal volume (VT), minute ventilation ([Formula: see text]), heart rate (HR), perceived exertion (RPE; 6-20 scale), and dyspnea (Borg Breathlessness Scale; 0-10 scale). A repeated measures analysis of variance (RM-ANOVA) model (2 groups: deployed vs non-deployed X 6 timepoints: 0%, 20%, 40%, 60%, 80%, and 100% [Formula: see text]) was conducted for participants meeting valid effort criteria (deployed = 25; non-deployed = 11). RESULTS: Significant group (η2partial = 0.26) and interaction (η2partial = 0.10) effects were observed such that deployed Veterans exhibited reduced f R and a greater change over time relative to non-deployed controls. There was also a significant group effect for dyspnea ratings (η2partial = 0.18) showing higher values in deployed participants. Exploratory correlational analyses revealed significant associations between dyspnea ratings and fR at 80% (R2 = 0.34) and 100% (R2 = 0.17) of [Formula: see text], but only in deployed Veterans. CONCLUSION: Relative to non-deployed controls, Veterans deployed to SWA exhibited reduced fR and greater dyspnea during maximal exercise. Further, associations between these parameters occurred only in deployed Veterans. These findings support an association between SWA deployment and affected respiratory health, and also highlight the utility of CPET in the clinical evaluation of deployment-related dyspnea in Veterans.

Exercise-induced changes in gene expression do not mediate post exertional malaise in Gulf War illness.

Background: Post-exertional malaise (PEM) is considered a characteristic feature of chronic multi-symptom illnesses (CMI) like Gulf War illness (GWI); however, its pathophysiology remains understudied. Previous investigations in other CMI populations (i.e., Myalgic Encephalomyelitis/Chronic Fatigue Syndrome) have reported associations between PEM and expression of genes coding for adrenergic, metabolic, and immune function. Objectives: To investigate whether PEM is meditated by gene expression in Veterans with GWI. Methods: Veterans with GWI (n = 37) and healthy control Gulf War Veterans (n = 25) provided blood samples before and after 30-min of cycling at 70% of age-predicted heart rate reserve. Relative quantification of gene expression, symptom measurements, and select cardiopulmonary parameters were compared between groups at pre-, 30 minpost-, and 24 hpost-exercise using a doubly multivariate repeated measures analysis of variance (RM-MANOVA). Mediation analyses were used to test indirect effects of changes in gene expression on symptom responses (i.e., PEM) to the standardized exercise challenge. Results: Veterans with GWI experienced large symptom exacerbations following exercise compared to controls (Cohen's d: 1.65; p < 0.05). Expression of ß -actin (ACTB), catechol-O-methyltransferase (COMT), and toll-like receptor 4 (TLR4) decreased in Veterans with GWI at 30 min (p < 0.05) and 24 h post-exercise (p < 0.05). Changes in gene expression did not mediate post-exercise symptom exacerbation in GWI (Indirect Effect Slope Coefficient: 0.06 - 0.02; 95% CI: 0.19, 0.12). Conclusion: An acute bout of moderate intensity cycling reduced the expression of select structural, adrenergic, and immune genes in Veterans with GWI, but the pathophysiological relevance to PEM is unclear.

Relationship between clinician documented blast exposure and pulmonary function: a retrospective chart review from a national specialty clinic.

BACKGROUND: Service member exposure to explosive blast overpressure waves is common with considerable attention to traumatic brain injury (TBI) and neuropsychological sequalae. Less is known about the impacts on the respiratory system, particularly long-term effects, despite vulnerability to overpressure. Using a national registry, we previously observed an independent relationship between self-reported blast exposure and respiratory symptoms; however, the impact on objective measures of pulmonary function is poorly understood. METHODS: 307 Veterans referred to our national specialty center for post-deployment health concerns underwent a comprehensive multi-day evaluation that included complete pulmonary function testing (PFT), occupational and environmental medicine history, neuropsychological or psychological evaluation. We developed an a priori chart abstraction process and template to classify Veterans into blast exposure groups: (1) none, (2) single-mild, or (3) multiple-mild. This template focused primarily on clinician documented notes of blast related TBI that were used as proxy for blast overpressure injury to thorax. PFT variables characterizing flow (FEV1%; %∆FEV1), volume (TLC%), diffusion (DLCO%) and respiratory mechanics (forced oscillometry) were selected for analysis. RESULTS: Veterans (40.5 ± 9.7 years; 16.3% female) were referred 8.6 ± 3.6 years after their last deployment and presented with considerable comorbid conditions and health problems (e.g., 62% post-traumatic stress, 55% dyspnea). After chart abstraction, Veterans were assigned to none (n = 208), single mild (n = 52) and multiple mild (n = 47) blast exposure groups. Among the blast exposed, clinicians documented 73.7% were < 50 m from the blast and 40.4% were physically moved by blast. PFT outcome measures were similar across all groups (p value range: 0.10-0.99). CONCLUSIONS: In this referred sample of deployed Veterans, PFT measures of flow, volume, diffusion, and respiratory mechanics were not associated with clinician documented blast exposure per the retrospective chart abstraction methodology applied. Yet, these clinical findings suggest future research should determine and assess distinction between Veteran recollections of perceived blast experiences versus overpressure wave exposure to the respiratory system.

Employing the Forced Oscillation Technique for the Assessment of Respiratory Mechanics in Adults.

There is increasing interest in the use of the forced oscillation technique (FOT) or oscillometry to characterize respiratory mechanics in healthy and diseased individuals. FOT, a complementary method to traditional pulmonary function testing, utilizes a range of oscillatory frequencies superimposed on tidal breathing to measure the functional relationship between airway pressure and flow. This passive assessment provides an estimate of respiratory system resistance (Rrs) and reactance (Xrs) that reflect airway caliber and energy storage and dissipation, respectively. Despite the recent increase in popularity and updated Technical Standards, clinical adoption has been slow which relates, in part, to the lack of standardization regarding the acquisition and reporting of FOT data. The goal of this article is to address the lack of standardization across laboratories by providing a comprehensive written protocol for FOT and an accompanying video. To illustrate that this protocol can be utilized irrespective of a particular device, three separate FOT devices have been employed in the case examples and video demonstration. This effort is intended to standardize the use and interpretation of FOT, provide practical suggestions, as well as highlight future questions that need to be addressed.

Predicting post-exertional malaise in Gulf War Illness based on acute exercise responses.

AIMS: Post-exertional malaise (PEM) is poorly understood in Gulf War Illness (GWI). Exercise challenges have emerged as stimuli to study PEM; however, little attention has been paid to unique cardiorespiratory and perceptual responses during exercise. This study tested whether select exercise parameters explained variability in PEM responses. MAIN METHODS: Visual analog scale (0-100) versions of the Kansas questionnaire were used for daily symptom measurements one week before and one week after 30-min of cycling at 70% heart rate reserve in 43 Veterans with GWI and 31 Veteran controls (CON). Cardiopulmonary exercise testing (CPET) methods were used to measure oxygen (VO2), carbon dioxide (VCO2), ventilation (VE), heart rate, work rate, and leg muscle pain. Symptom changes and CPET parameters were compared between groups with independent samples t-tests. Linear regression (GLM) with VE/VCO2, cumulative work, leg muscle pain, and self-reported physical function treated as independent variables and peak symptom response as the dependent variable tested whether exercise responses predicted PEM. KEY FINDINGS: Compared to CON, Veterans with GWI had greater ventilatory equivalent for oxygen (VE/VO2), peak leg muscle pain, fatigue, and lower VCO2, VO2, power, and cumulative work during exercise (p < 0.05), and greater peak symptom responses (GWI = 38.90 ± 29.06, CON = 17.84 ± 28.26, g = 0.70, p < 0.01). The final GLM did not explain significant variance in PEM (Pooled R2 = 0.15, Adjusted R2 = 0.03, p = 0.34). SIGNIFICANCE: The PEM response was not related to the selected combination of cardiorespiratory and perceptual responses to exercise.

Hemorheological responses to an acute bout of maximal exercise in Veterans with Gulf War Illness.

BACKGROUND: Altered red blood cell (RBC) deformability has been reported in Veterans with Gulf War Illness (GWI) who endorse exercise-induced symptom exacerbation and fatigue. However, it is unknown whether altered RBC deformability is worsened secondary to exercise. OBJECTIVE: To evaluate RBC deformability in response to maximal exercise in individuals with and without GWI. METHODS: Seventeen Veterans with GWI and 11 controls performed maximal exercise and provided blood samples (pre-, immediately post- and 60-min post-exercise). We calculated RBC deformation at infinite stress (EIMAX), shear stress for half-deformation (SS1/2) and their ratio (SS1/2/EIMAX) via repeated measures ANOVA with group and time as factors. RESULTS: A moderate interaction effect (p = 0.08, η2p = 0.10), large main effect for group (p = 0.02, η2p = 0.19) and moderate main effect for time (p = 0.20, η2p = 0.06) were observed for EIMAX, but only the main effect for group reached statistical significance. Changes in SS1/2 and SS1/2/EIMAX over time were similar between cases and controls as were main effects. CONCLUSIONS: Veterans with GWI had more deformable RBCs in comparison to controls that was unaffected by maximal exercise. Future studies to confirm our findings and identify associated mechanisms are warranted.

An analysis of 2-day cardiopulmonary exercise testing to assess unexplained fatigue.

Two consecutive maximal cardiopulmonary exercise tests (CPETs) performed 24 hr apart (2-day CPET protocol) are increasingly used to evaluate post-exertional malaise (PEM) and related disability among individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This protocol may extend to other fatiguing illnesses with similar characteristics to ME/CFS; however, 2-day CPET protocol reliability and minimum change required to be considered clinically meaningful (i.e., exceeding the standard error of the measure) are not well characterized. To address this gap, we evaluated the 2-day CPET protocol in Gulf War Illness (GWI) by quantifying repeatability of seven CPET parameters, establishing their thresholds of clinically significant change, and determining whether changes differed between veterans with GWI and controls. Excluding those not attaining peak effort criteria (n = 15), we calculated intraclass correlation coefficients (ICCs), the smallest real difference (SRD%), and repeated measures analysis of variance (RM-ANOVA) at the ventilatory anaerobic threshold (VAT) and peak exercise in 15 veterans with GWI and eight controls. ICC values at peak ranged from moderate to excellent for veterans with GWI (mean [range]; 0.84 [0.65 - 0.92]) and were reduced at the VAT (0.68 [0.37 - 0.78]). Across CPET variables, the SRD% at peak exercise for veterans with GWI (18.8 [8.8 - 28.8]) was generally lower than at the VAT (28.1 [9.5 - 34.8]). RM-ANOVAs did not detect any significant group-by-time interactions (all p > .05). The methods and findings reported here provide a framework for evaluating 2-day CPET reliability, and reinforce the importance of carefully considering measurement error in the population of interest when interpreting findings.

Exercise-Induced Bronchoconstriction in Iraq and Afghanistan Veterans With Deployment-Related Exposures.

INTRODUCTION: Acute exposure to high-levels of ambient fine particulate matter while exercising results in airway narrowing, but the long-term effects of repeated exposure on exercise-induced bronchoconstriction (EIB) are not well known. The goal of this preliminary study is to determine the rate of EIB among a sample of non-treatment seeking veterans deployed to Iraq and Afghanistan. MATERIALS AND METHODS: Twenty-four veterans (median [interquartile range]: 35.0 [27.3, 45] years) without history of asthma volunteered for this study. Spirometry was assessed before and after a standardized exercise challenge. A positive EIB response was defined as an exercise-induced fall in forced expiatory volume in 1 second ≥10%. Secondary criteria (peak flow ≥10% or mid-expiratory flow ≥15%) were also considered as an estimate of probable EIB. RESULTS: A positive EIB response was observed in 16.7% and probable EIB response was observed in 41.7% of our sample. Median deployment length to Iraq or Afghanistan was 13.0 [10.3, 17.5] months and the median time since deployment was 4.2 [2.7, 7.7] years. At the time of testing, veterans reported persistent cough (58.3%), wheeze (37.5%), and shortness of breath (37.5%). During deployment, veterans reported exposure to dust and sand (70.8%), smoke from burn pits (66.7%), vehicle exhaust (83.3%), and regional air pollution (26.0%) on most days or daily. CONCLUSIONS: Approximately 17% of our sample of non-treatment seeking deployed Iraq and Afghanistan veterans demonstrated EIB, similar to the general population prevalence. However, persistent respiratory symptoms and alternative indices of probable EIB supports continued monitoring of this population.

Post-exertional malaise in veterans with gulf war illness.

Post-exertional malaise (PEM) is a potentially debilitating aspect of Gulf War Illness (GWI) that has received limited research attention. The purpose of the present investigation was to determine symptom severity changes following exercise in Veterans with GWI compared to control Veterans without GWI (CO). Sixty-seven Veterans (n = 39 GWI; n = 28 CO) underwent a 30-minute submaximal exercise challenge at 70% of heart rate reserve. Symptom measurements (e.g. fatigue, pain) occurred pre-, immediately post-, and 24-hour post-exercise. Self-reported physical and mental health, and physiological and perceptual responses to exercise were compared between groups using descriptive statistics, independent samples t-tests and repeated measures Analysis of Variance (RM-ANOVA). Post-exertional malaise was modeled using Group by Time (2 × 3) doubly-multivariate, RM-MANOVAs for (1) mood, (2) pain and (3) GWI-related symptoms, respectively (α = 0.05). Data were analyzed for the full sample of Veterans with GWI (n = 39) compared to CO (n = 28) and a subsample of Veterans (n = 18) who endorsed "feeling unwell after physical exercise or exertion" ("PEM endorsers") during screening. Veterans with GWI reported significantly lower physical and mental health. Groups exercised at similar relative exercise intensities, but GWI perceived exercise as more painful and fatiguing. Group-by-Time interactions were not significant for the entire sample for the three PEM models, however limiting the GWI sample to "PEM endorsers" resulted in significant interactions for Pain- and GWI-related PEM models. These results indicate that not all GVs with GWI experience PEM 24 h after exercise, and that more research is needed to determine the extent that exercise worsens symptoms in GWI.

Veterans with Gulf War Illness exhibit distinct respiratory patterns during maximal cardiopulmonary exercise.

INTRODUCTION: The components of minute ventilation, respiratory frequency and tidal volume, appear differentially regulated and thereby afford unique insight into the ventilatory response to exercise. However, respiratory frequency and tidal volume are infrequently reported, and have not previously been considered among military veterans with Gulf War Illness. Our purpose was to evaluate respiratory frequency and tidal volume in response to a maximal cardiopulmonary exercise test in individuals with and without Gulf War Illness. MATERIALS AND METHODS: 20 cases with Gulf War Illness and 14 controls participated in this study and performed maximal cardiopulmonary exercise test on a cycle ergometer. Ventilatory variables (minute ventilation, respiratory frequency and tidal volume) were obtained and normalized to peak exercise capacity. Using mixed-design analysis of variance models, with group and time as factors, we analyzed exercise ventilatory patterns for the entire sample and for 11 subjects from each group matched for race, age, sex, and height. RESULTS: Despite similar minute ventilation (p = 0.57, η2p = 0.01), tidal volume was greater (p = 0.02, η2p = 0.16) and respiratory frequency was lower (p = 0.004, η2p = 0.24) in Veterans with Gulf War Illness than controls. The findings for respiratory frequency remained significant in the matched subgroup (p = 0.004, η2p = 0.35). CONCLUSION: In our sample, veterans with Gulf War Illness adopt a unique exercise ventilatory pattern characterized by reduced respiratory frequency, despite similar ventilation relative to controls. Although the mechanism(s) by which this pattern is achieved remains unresolved, our findings suggest that the components of ventilation should be considered when evaluating clinical conditions with unexplained exertional symptoms.

Forced oscillation technique in veterans with preserved spirometry and chronic respiratory symptoms.

PURPOSE: To evaluate the utility of the forced oscillation technique (FOT) among military veterans with preserved spirometry and chronic unexplained respiratory symptoms. METHODS: 178 veterans referred for evaluation of unexplained respiratory symptoms completed pulmonary function testing and FOT. Preserved spirometry was defined as FEV1/FVC, FEV1 and FVC ≥ 5th percentile. Frequency dependence of resistance (R4-R20) and reactance area (AX) were assessed via FOT, and R4-R20 ≥ 20% and AX ≥ 95th percentile were considered abnormal. RESULTS: Spirometry was preserved in 71.3%, of whom 124 had acceptable FOT data. 93 of 124 (75.0%) veterans with preserved spirometry had one or more abnormal findings on FOT. Veterans with abnormal R4-R20 and/or AX had reduced FVC, FEV1, FEF25-75, and diffusing capacity (% predicted) in comparison to those with Normal FOT (p = 0.030 to p < 0.001). CONCLUSIONS: In our referral sample, distal airway dysfunction in the presence of preserved spirometry appears common and may represent an at-risk group requiring closer surveillance.

Effects of Exercise Training on Pulmonary Function in Adults With Chronic Lung Disease: A Meta-Analysis of Randomized Controlled Trials.

OBJECTIVE: To quantify the effect of exercise training on indices of pulmonary function in adults with chronic lung disease using meta-analytic techniques. DATA SOURCES: Eligible trials were identified using a systematic search of MEDLINE, Web of Science, Physiotherapy Evidence Database, and GoogleScholar databases. STUDY SELECTION: Randomized controlled trials that evaluated pulmonary function before and after whole-body exercise training among adult patients (aged ≥19y) with chronic lung disease were included. DATA EXTRACTION: Data were independently extracted from each study by 3 authors. Random-effects models were used to aggregate a mean effect size (Hedges' d; Δ) and 95% confidence interval (CI), and multilevel linear regression with robust maximum likelihood estimation was used to adjust for potential nesting effects. DATA SYNTHESIS: Among 2923 citations, a total of 105 weighted effects from 21 randomized controlled trials were included. After adjusting for nesting effects, exercise training resulted in a small (Δ=.18; 95% CI, .07-.30) and significant (P=.002) improvement in a composite measure of pulmonary function. Tests of heterogeneity of the mean effect size were nonsignificant. CONCLUSIONS: Contrary to prior assumptions, whole-body exercise training is effective for improving pulmonary function in adults with chronic lung disease, particularly spirometric indices. Subsequent studies are necessary to determine the optimal exercise training characteristics to maximize functional improvement.