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2.  Association of the FAM46A Gene VNTRs and BAG6 rs3117582 SNP with Non Small Cell Lung Cancer (NSCLC) in Croatian and Norwegian Populations 
PLoS ONE  2015;10(4):e0122651.
We analyzed for associations between a variable number of tandem repeat (VNTR) polymorphism in the Family with sequence similarity 46, member A (FAM46A) gene and a single nucleotide polymorphism (rs3117582) in the BCL2-Associated Athanogene 6 (BAG6) with non small cell lung cancer in Croatian and Norwegian subjects. A total of 503 (262 Croatian and 241Norwegian) non small cell lung cancer patients and 897 controls (568 Croatian and 329 Norwegian) were analyzed. We found that the frequency of allele b (three VNTR repeats) of FAM46A gene was significantly increased in the patients compared to the healthy controls in the Croatian and the combined Croatian and Norwegian subjects. Genotype frequencies of cd (four and five VNTR repeats) and cc (four VNTR repeats homozygote) of the FAM46A gene were significantly decreased in the patients compared to the healthy controls in the Croatian and Norwegian subjects, respectively. Logistic regression analyses revealed FAM46A genotype cc to be an independent predictive factor for non small cell lung cancer risk in the Norwegian subjects after adjustment for age, gender and smoking status. This is the first study to suggest an association between the FAM46A gene VNTR polymorphisms and non small cell lung cancer. We found also that BAG6 rs3117582 SNP was associated with non small cell lung cancer in the Norwegian subjects and the combined Croatian-Norwegian subjects corroborating the earlier finding that BAG6 rs3117582 SNP was associated with lung cancer in Europeans. Logistic regression analyses revealed that genotypes and alleles of BAG6 were independent predictive factor for non small cell lung cancer risk in the Norwegian and combined Croatian-Norwegian subjects, after adjustment for age and gender.
PMCID: PMC4401550  PMID: 25884493
3.  Exposure to Household Air Pollution from Wood Combustion and Association with Respiratory Symptoms and Lung Function in Nonsmoking Women: Results from the RESPIRE Trial, Guatemala 
Environmental Health Perspectives  2014;123(4):285-292.
With 40% of the world’s population relying on solid fuel, household air pollution (HAP) represents a major preventable risk factor for COPD (chronic obstructive pulmonary disease). Meta-analyses have confirmed this relationship; however, constituent studies are observational, with virtually none measuring exposure directly.
We estimated associations between HAP exposure and respiratory symptoms and lung function in young, nonsmoking women in rural Guatemala, using measured carbon monoxide (CO) concentrations in exhaled breath and personal air to assess exposure.
The Randomized Exposure Study of Pollution Indoors and Respiratory Effects (RESPIRE) Guatemala study was a trial comparing respiratory outcomes among 504 women using improved chimney stoves versus traditional cookstoves. The present analysis included 456 women with data from postintervention surveys including interviews at 6, 12, and 18 months (respiratory symptoms) and spirometry and CO (ppm) in exhaled breath measurements. Personal CO was measured using passive diffusion tubes at variable times during the study. Associations between CO concentrations and respiratory health were estimated using random intercept regression models.
Respiratory symptoms (cough, phlegm, wheeze, or chest tightness) during the previous 6 months were positively associated with breath CO measured at the same time of symptom reporting and with average personal CO concentrations during the follow-up period. CO in exhaled breath at the same time as spirometry was associated with lower lung function [average reduction in FEV1 (forced expiratory volume in 1 sec) for a 10% increase in CO was 3.33 mL (95% CI: –0.86, –5.81)]. Lung function measures were not significantly associated with average postintervention personal CO concentrations.
Our results provide further support for the effects of HAP exposures on airway inflammation. Further longitudinal research modeling continuous exposure to particulate matter against lung function will help us understand more fully the impact of HAP on COPD.
Pope D, Diaz E, Smith-Sivertsen T, Lie RT, Bakke P, Balmes JR, Smith KR, Bruce NG. 2015. Exposure to household air pollution from wood combustion and association with respiratory symptoms and lung function in nonsmoking women: results from the RESPIRE Trial, Guatemala. Environ Health Perspect 123:285–292;
PMCID: PMC4384202  PMID: 25398189
4.  Vitamin D, Vitamin D Binding Protein, and Longitudinal Outcomes in COPD 
PLoS ONE  2015;10(3):e0121622.
Associations between Vitamin D3 [25(OH)D], vitamin D binding protein (VDBP) and chronic obstructive pulmonary disease (COPD) are previously reported. We aimed to further investigate these associations on longitudinal outcomes.
426 COPD patients from western Norway, GOLD stage II-IV, aged 40–76, were followed every six-month from 2006 through 2009 with spirometry, bioelectrical impedance measurements and registration of exacerbation frequency. Serum 25(OH)D and VDBP levels were determined at study-entry by high-performance liquid chromatography coupled with mass spectrometry and enzyme immunoassays respectively. Yearly change in lung function and body composition was assessed by generalized estimating equations (GEE), yearly exacerbation rate by negative binomial regression models, and 5 years all-cause mortality by Cox proportional-hazard regression.
1/3 of the patients had vitamin D deficiency (<20ng/mL) and a greater decline in both FEV1 and FVC, compared to patients with normal levels; for FEV1 this difference only reached statistical significance in the 28 patients with the lowest levels (<10ng/mL, p = 0.01). Neither 25(OH)D nor VDBP levels predicted exacerbation rate, change in fat free mass index or risk of death.
Severe vitamin D deficiency may affect decline in lung function parameters in COPD. Neither 25(OH)D nor VDBP levels did otherwise predict markers of disease progression.
PMCID: PMC4372215  PMID: 25803709
5.  Risk loci for chronic obstructive pulmonary disease: a genome-wide association study and meta-analysis 
The Lancet. Respiratory medicine  2014;2(3):214-225.
The genetic risk factors for susceptibility to chronic obstructive pulmonary disease (COPD) are still largely unknown. Additional genetic variants are likely to be identified by genome-wide association studies in larger cohorts or specific subgroups.
Genome-wide association analysis in COPDGene (non-Hispanic whites and African-Americans) was combined with existing data from the ECLIPSE, NETT/NAS, and GenKOLS (Norway) studies. Analyses were performed both using all moderate-to-severe cases and the subset of severe cases. Top loci not previously described as genome-wide significant were genotyped in the ICGN study, and results combined in a joint meta-analysis.
Analysis of a total of 6,633 moderate-to-severe cases and 5,704 controls confirmed association at three known loci: CHRNA3/CHRNA5/IREB2, FAM13A, and HHIP (10−12 < P < 10−14), and also showed significant evidence of association at a novel locus near RIN3 (overall P, including ICGN = 5•4×10−9). In the severe COPD analysis (n=3,497), the effects at two of three previously described loci were significantly stronger; we also identified two additional loci previously reported to affect gene expression of MMP12 and TGFB2 (overall P = 2•6x10−9 and 8•3×10−9). RIN3 and TGFB2 expression levels were reduced in a set of Lung Tissue Research Consortium COPD lung tissue samples compared with controls.
In a genome-wide study of COPD, we confirmed associations at three known loci and found additional genome-wide significant associations with moderate-to-severe COPD near RIN3 and with severe COPD near MMP12 and TGFB2. Genetic variants, apart from alpha-1 antitrypsin deficiency, increase the risk of COPD. Our analysis of severe COPD suggests additional genetic variants may be identified by focusing on this subgroup.
National Heart, Lung, and Blood Institute; the COPD Foundation through contributions from AstraZeneca, Boehringer Ingelheim, Novartis, and Sepracor; GlaxoSmithKline; Centers for Medicare and Medicaid Services; Agency for Healthcare Research and Quality; US Department of Veterans Affairs.
PMCID: PMC4176924  PMID: 24621683
6.  On the simultaneous association analysis of large genomic regions: a massive multi-locus association test 
Bioinformatics  2013;30(2):157-164.
Motivation: For samples of unrelated individuals, we propose a general analysis framework in which hundred thousands of genetic loci can be tested simultaneously for association with complex phenotypes. The approach is built on spatial-clustering methodology, assuming that genetic loci that are associated with the target phenotype cluster in certain genomic regions. In contrast to standard methodology for multilocus analysis, which has focused on the dimension reduction of the data, our multilocus association-clustering test profits from the availability of large numbers of genetic loci by detecting clusters of loci that are associated with the phenotype.
Results: The approach is computationally fast and powerful, enabling the simultaneous association testing of large genomic regions. Even the entire genome or certain chromosomes can be tested simultaneously. Using simulation studies, the properties of the approach are evaluated. In an application to a genome-wide association study for chronic obstructive pulmonary disease, we illustrate the practical relevance of the proposed method by simultaneously testing all genotyped loci of the genome-wide association study and by testing each chromosome individually. Our findings suggest that statistical methodology that incorporates spatial-clustering information will be especially useful in whole-genome sequencing studies in which millions or billions of base pairs are recorded and grouped by genomic regions or genes, and are tested jointly for association.
Availability and implementation: Implementation of the approach is available upon request.
Supplementary information: Supplementary data are available at Bioinformatics online.
PMCID: PMC3892690  PMID: 24262215
7.  Comparison of inflammatory markers in induced and spontaneous sputum in a cohort of COPD patients 
Respiratory Research  2014;15(1):138.
Sputum induction is a non-invasive method for obtaining measurements of inflammation in the airways. Whether spontaneously sampled sputum can be a valid surrogate is unknown. The aim of this study was to compare levels of six inflammatory markers in sputum pairs consisting of induced and spontaneous sputum sampled on the same consultation either in a stable state or during exacerbations of chronic obstructive pulmonary disease (COPD).
433 COPD patients aged 40–76, Global initiative for chronic Obstructive Lung Disease (GOLD) stage II-IV were enrolled in 2006/07 and followed every six months for three years. 356 patients were followed for potential exacerbations. Interleukin-6, interleukin-8, interleukin-18, interferon gamma-inducible protein-10, monokine induced by gamma interferon and tumor necrosis factor-alpha (IL-6, IL-8, IL-18, IP-10, MIG and TNF-α) were measured by bead based multiplex immunoassay in 60 paired sputum samples from 45 patients. Albumin was measured by enzyme immunoassay, for concentration correction. Culturing for bacterial growth was performed on 24 samples. Bland-Altman plots were used to assess agreement. The paired non-parametric Wilcoxon signed-rank test, the non-parametric Spearman’s rank correlation test and Kruskal-Wallis test were used for statistical analyses. For all analyses, a p-value < 0.05 was considered significant.
Agreement between the two measurements was generally low for all six markers. TNF-α was significantly higher in spontaneous sputum at exacerbations (p = 0.002) and trending higher at the steady state (p = 0.06). Correlation coefficients between the levels of markers in induced and spontaneous sputum varied between 0.58 (IL-18) to 0.83 (IP-10). In spontaneous sputum IL-18 and MIG were higher in ex-smokers (p < 0.05). The levels of all markers were higher in GOLD stage III & IV except for IL-6 in spontaneous sputum and IL-18 in induced sputum, compared with GOLD stage II, although not statistically significant. In spontaneous sputum the levels of IL-6 were significantly higher if Haemophilus influenzae (HI) was not cultured.
We observed a low agreement and significant differences in inflammatory markers between induced and spontaneous sputum, both at steady state and exacerbations. We recommend considering sampling method when reporting on inflammatory markers in sputum.
PMCID: PMC4237726  PMID: 25398249
COPD; Sputum sampling; Inflammatory markers
8.  Predictors of Exacerbations in Chronic Obstructive Pulmonary Disease - Results from the Bergen COPD Cohort Study 
PLoS ONE  2014;9(10):e109721.
COPD exacerbations accelerate disease progression.
To examine if COPD characteristics and systemic inflammatory markers predict the risk for acute COPD exacerbation (AECOPD) frequency and duration.
403 COPD patients, GOLD stage II-IV, aged 44–76 years were included in the Bergen COPD Cohort Study in 2006/07, and followed for 3 years. Examined baseline predictors were sex, age, body composition, smoking, AECOPD the last year, GOLD stage, Charlson comorbidity score (CCS), hypoxemia (PaO2<8 kPa), cough, use of inhaled steroids, and the inflammatory markers leucocytes, C-reactive protein (CRP), neutrophil gelatinase associated lipocalin (NGAL), soluble tumor necrosis factor receptor 1 (sTNF-R1), and osteoprotegrin (OPG). Negative binomial models with random effects were fitted to estimate the annual incidence rate ratios (IRR). For analysis of AECOPD duration, a generalized estimation equation logistic regression model was fitted, also adjusting for season, time since inclusion and AECOPD severity.
After multivariate adjustment, significant predictors of AECOPD were: female sex [IRR 1.45 (1.14–1.84)], age per 10 year increase [1.23 (1.03–1.47)], >1 AECOPD last year before baseline [1.65 (1.24–2.21)], GOLD III [1.36 (1.07–1.74)], GOLD IV [2.90 (1.98–4.25)], chronic cough [1.64 (1.30–2.06)] and use of inhaled steroids [1.57 (1.21–2.05)]. For AECOPD duration more than three weeks, significant predictors after adjustment were: hypoxemia [0.60 (0.39–0.92)], years since inclusion [1.19 (1.03–1.37)], AECOPD severity; moderate [OR 1.58 (1.14–2.18)] and severe [2.34 (1.58–3.49)], season; winter [1.51 (1.08–2.12)], spring [1.45 (1.02–2.05)] and sTNF-R1 per SD increase [1.16 (1.00–1.35)].
Several COPD characteristics were independent predictors of both AECOPD frequency and duration.
PMCID: PMC4184893  PMID: 25279458
9.  Genetic susceptibility for chronic bronchitis in chronic obstructive pulmonary disease 
Respiratory Research  2014;15(1):113.
Chronic bronchitis (CB) is one of the classic phenotypes of COPD. The aims of our study were to investigate genetic variants associated with COPD subjects with CB relative to smokers with normal spirometry, and to assess for genetic differences between subjects with CB and without CB within the COPD population.
We analyzed data from current and former smokers from three cohorts: the COPDGene Study; GenKOLS (Bergen, Norway); and the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE). CB was defined as having a cough productive of phlegm on most days for at least 3 consecutive months per year for at least 2 consecutive years. CB COPD cases were defined as having both CB and at least moderate COPD based on spirometry. Our primary analysis used smokers with normal spirometry as controls; secondary analysis was performed using COPD subjects without CB as controls. Genotyping was performed on Illumina platforms; results were summarized using fixed-effect meta-analysis.
For CB COPD relative to smoking controls, we identified a new genome-wide significant locus on chromosome 11p15.5 (rs34391416, OR = 1.93, P = 4.99 × 10-8) as well as significant associations of known COPD SNPs within FAM13A. In addition, a GWAS of CB relative to those without CB within COPD subjects showed suggestive evidence for association on 1q23.3 (rs114931935, OR = 1.88, P = 4.99 × 10-7).
We found genome-wide significant associations with CB COPD on 4q22.1 (FAM13A) and 11p15.5 (EFCAB4A, CHID1 and AP2A2), and a locus associated with CB within COPD subjects on 1q23.3 (RPL31P11 and ATF6). This study provides further evidence that genetic variants may contribute to phenotypic heterogeneity of COPD.
Trial registration NCT00608764, NCT00292552
Electronic supplementary material
The online version of this article (doi:10.1186/s12931-014-0113-2) contains supplementary material, which is available to authorized users.
PMCID: PMC4190389  PMID: 25241909
Pulmonary disease; Chronic obstructive; Chronic bronchitis; Genome-wide association study
10.  DNAH5 is associated with total lung capacity in chronic obstructive pulmonary disease 
Respiratory Research  2014;15(1):97.
Chronic obstructive pulmonary disease (COPD) is characterized by expiratory flow limitation, causing air trapping and lung hyperinflation. Hyperinflation leads to reduced exercise tolerance and poor quality of life in COPD patients. Total lung capacity (TLC) is an indicator of hyperinflation particularly in subjects with moderate-to-severe airflow obstruction. The aim of our study was to identify genetic variants associated with TLC in COPD.
We performed genome-wide association studies (GWASs) in white subjects from three cohorts: the COPDGene Study; the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); and GenKOLS (Bergen, Norway). All subjects were current or ex-smokers with at least moderate airflow obstruction, defined by a ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC) <0.7 and FEV1 < 80% predicted on post-bronchodilator spirometry. TLC was calculated by using volumetric computed tomography scans at full inspiration (TLCCT). Genotyping in each cohort was completed, with statistical imputation of additional markers. To find genetic variants associated with TLCCT, linear regression models were used, with adjustment for age, sex, pack-years of smoking, height, and principal components for genetic ancestry. Results were summarized using fixed-effect meta-analysis.
Analysis of a total of 4,543 COPD subjects identified one genome-wide significant locus on chromosome 5p15.2 (rs114929486, β = 0.42L, P = 4.66 × 10−8).
In COPD, TLCCT was associated with a SNP in dynein, axonemal, heavy chain 5 (DNAH5), a gene in which genetic variants can cause primary ciliary dyskinesia. DNAH5 could have an effect on hyperinflation in COPD.
Electronic supplementary material
The online version of this article (doi:10.1186/s12931-014-0097-y) contains supplementary material, which is available to authorized users.
PMCID: PMC4169636  PMID: 25134640
Pulmonary disease; Chronic obstructive; Hyperinflation; Genome-wide association analysis; Total lung capacity; DNAH5
11.  On the Follow-Up of Genome-Wide Association Studies: An Overall Test for the Most Promising S.N.P.’s 
Genetic epidemiology  2011;35(5):303-309.
Even in large-scale genome-wide association studies, only a fraction of the true associations are detected at the genome-wide significance level. When few or no associations reach the significance threshold, one strategy is to follow-up on the most promising candidates, i.e. the single nucleotide polymorphisms with the smallest association-test p-values, by genotyping them in additional studies. In this communication, we propose an overall test for genome-wide association studies that analyzes the SNP’s with the most promising p-values simultaneously and thereby allows an early assessment of whether the follow- up of the selected SNP’s is likely promising. We theoretically derive the properties of the proposed overall test under the null hypothesis and assess its power based on simulation studies. An application to a GWAS for chronic obstructive pulmonary disease suggests that there are true association signals among the top SNPs and that an additional follow-up study is promising.
PMCID: PMC4096304  PMID: 21374717
genome wide association studies; snps association tests; chronic obstructive pulmonary disease; statistical genetics; multiple testing
12.  Gene expression analysis uncovers novel Hedgehog interacting protein (HHIP) effects in human bronchial epithelial cells 
Genomics  2013;101(5):263-272.
Hedgehog Interacting Protein (HHIP) was implicated in chronic obstructive pulmonary disease (COPD) by genome-wide association studies (GWAS). However, it remains unclear how HHIP contributes to COPD pathogenesis. To identify genes regulated by HHIP, we performed gene expression microarray analysis in a human bronchial epithelial cell line (Beas-2B) stably infected with HHIP shRNAs. HHIP silencing led to differential expression of 296 genes; enrichment for variants nominally associated with COPD was found. Eighteen of the differentially expressed genes were validated by real-time PCR in Beas-2B cells. Seven of 11 validated genes tested in human COPD and control lung tissues demonstrated significant gene expression differences. Functional annotation indicated enrichment for extracellular matrix and cell growth genes. Network modeling demonstrated that the extracellular matrix and cell proliferation genes influenced by HHIP tended to be interconnected. Thus, we identified potential HHIP targets in human bronchial epithelial cells that may contribute to COPD pathogenesis.
PMCID: PMC3659826  PMID: 23459001
Hedgehog interacting protein (HHIP); Gene expression profiling; COPD (Chronic obstructive pulmonary disease); extracellular matrix (ECM); network modeling
13.  Predictors of health-related quality of life changes after lifestyle intervention in persons at risk of type 2 diabetes mellitus 
Quality of Life Research  2014;23(9):2585-2593.
To assess health-related quality of life (HRQOL) of subjects at risk of type 2 diabetes undergoing lifestyle intervention, and predictors for improved HRQOL.
The Finnish Diabetes Risk Score was used by general practitioners to identify individuals at risk. Low-intensity interventions with an 18-month follow-up were employed. HRQOL was assessed using the SF-36 at baseline and compared with results from a general Norwegian population survey and further at 6 and 18 months. Simple and multiple linear regression analyses were applied to identify predictors of changes in HRQOL of clinical importance.
Two hundred and thirteen participants (50 % women; mean age: 46 years, mean body mass index: 37) were included: 182 returned for 18-month follow-up, of whom 172 completed the HRQOL questionnaire. HRQOL was reduced with clinical significance compared with general Norwegians. The mean changes in HRQOL from the baseline to the follow-up were not of clinical importance. However, one out of three individuals achieved a moderate or large clinical improvement in HRQOL. The best determinant for improved HRQOL was obtained for a composite, clinically significant lifestyle change, i.e. both a weight reduction of at least 5 % and an improvement in exercise capacity of at least 10 %, which was associated with an improvement in five out of the eight SF-36 domains.
Subjects at risk of type 2 diabetes report a clinically important reduction in HRQOL compared with general Norwegians. The best predictor of improved HRQOL was a small weight loss combined with a small improvement in aerobic capacity.
PMCID: PMC4186973  PMID: 24789668
Quality of life; Type 2 diabetes mellitus; Prevention; Lifestyle; Obesity
14.  Susceptibility to Chronic Mucus Hypersecretion, a Genome Wide Association Study 
PLoS ONE  2014;9(4):e91621.
Chronic mucus hypersecretion (CMH) is associated with an increased frequency of respiratory infections, excess lung function decline, and increased hospitalisation and mortality rates in the general population. It is associated with smoking, but it is unknown why only a minority of smokers develops CMH. A plausible explanation for this phenomenon is a predisposing genetic constitution. Therefore, we performed a genome wide association (GWA) study of CMH in Caucasian populations.
GWA analysis was performed in the NELSON-study using the Illumina 610 array, followed by replication and meta-analysis in 11 additional cohorts. In total 2,704 subjects with, and 7,624 subjects without CMH were included, all current or former heavy smokers (≥20 pack-years). Additional studies were performed to test the functional relevance of the most significant single nucleotide polymorphism (SNP).
A strong association with CMH, consistent across all cohorts, was observed with rs6577641 (p = 4.25×10−6, OR = 1.17), located in intron 9 of the special AT-rich sequence-binding protein 1 locus (SATB1) on chromosome 3. The risk allele (G) was associated with higher mRNA expression of SATB1 (4.3×10−9) in lung tissue. Presence of CMH was associated with increased SATB1 mRNA expression in bronchial biopsies from COPD patients. SATB1 expression was induced during differentiation of primary human bronchial epithelial cells in culture.
Our findings, that SNP rs6577641 is associated with CMH in multiple cohorts and is a cis-eQTL for SATB1, together with our additional observation that SATB1 expression increases during epithelial differentiation provide suggestive evidence that SATB1 is a gene that affects CMH.
PMCID: PMC3979657  PMID: 24714607
15.  Dissecting direct and indirect genetic effects on chronic obstructive pulmonary disease (COPD) susceptibility 
Human genetics  2013;132(4):431-441.
Cigarette smoking is the major environmental risk factor for chronic obstructive pulmonary disease (COPD). Genome-wide association studies have provided compelling associations for three loci with COPD. In this study, we aimed to estimate direct, i.e., independent from smoking, and indirect effects of those loci on COPD development using mediation analysis. We included a total of 3,424 COPD cases and 1,872 unaffected controls with data on two smoking-related phenotypes: lifetime average smoking intensity and cumulative exposure to tobacco smoke (pack years). Our analysis revealed that effects of two linked variants (rs1051730 and rs8034191) in the AGPHD1/CHRNA3 cluster on COPD development are significantly, yet not entirely, mediated by the smoking-related phenotypes. Approximately 30 % of the total effect of variants in the AGPHD1/CHRNA3 cluster on COPD development was mediated by pack years. Simultaneous analysis of modestly (r2 = 0.21) linked markers in CHRNA3 and IREB2 revealed that an even larger (~42 %) proportion of the total effect of the CHRNA3 locus on COPD was mediated by pack years after adjustment for an IREB2 single nucleotide polymorphism. This study confirms the existence of direct effects of the AGPHD1/CHRNA3, IREB2, FAM13A and HHIP loci on COPD development. While the association of the AGPHD1/CHRNA3 locus with COPD is significantly mediated by smoking-related phenotypes, IREB2 appears to affect COPD independently of smoking.
PMCID: PMC3600068  PMID: 23299987
16.  Airway obstruction, dynamic hyperinflation, and breathing pattern during incremental exercise in COPD patients 
Physiological Reports  2014;2(2):e00222.
Ventilatory capacity is reduced in chronic obstructive pulmonary disease (COPD) patients. Tidal volume (VT) is lower and breathing frequency higher at a given ventilation (VE) compared to healthy subjects. We examined whether airflow limitation and dynamic hyperinflation in COPD patients were related to breathing pattern. An incremental treadmill exercise test was performed in 63 COPD patients (35 men), aged 65 years (48–79 years) with a mean forced expiratory volume in 1 sec (FEV1) of 48% of predicted (SD = 15%). Data were averaged over 20‐sec intervals. The relationship between VE and VT was described by the quadratic equation VT = a + bVE + cVE2 for each subject. The relationships between the curve parameters b and c, and spirometric variables and dynamic hyperinflation measured as the difference in inspiratory capacity from start to end of exercise, were analyzed by multivariate linear regression. The relationship between VE and VT could be described by a quadratic model in 59 patients with median R2 of 0.90 (0.40–0.98). The linear coefficient (b) was negatively (P = 0.001) and the quadratic coefficient (c) positively (P < 0.001) related to FEV1. Forced vital capacity, gender, height, weight, age, inspiratory reserve volume, and dynamic hyperinflation were not associated with the curve parameters after adjusting for FEV1. We concluded that a quadratic model could satisfactorily describe the relationship between VE and VT in most COPD patients. The curve parameters were related to FEV1. With a lower FEV1, maximal VT was lower and achieved at a lower VE. Dynamic hyperinflation was not related to breathing pattern when adjusting for FEV1.
The relationship between minute ventilation and tidal volume during incremental treadmill exercise could be described by a quadratic model in COPD patients. The curve parameters were related to airway obstruction, but not to dynamic hyperinflation or inspiratory reserve volume by the end of exercise.
PMCID: PMC3966235  PMID: 24744891
Chronic obstructive pulmonary disease; exercise; inspiratory capacity; spirometry
17.  Genome-Wide Association Analysis of Blood Biomarkers in Chronic Obstructive Pulmonary Disease 
Rationale: A genome-wide association study (GWAS) for circulating chronic obstructive pulmonary disease (COPD) biomarkers could identify genetic determinants of biomarker levels and COPD susceptibility.
Objectives: To identify genetic variants of circulating protein biomarkers and novel genetic determinants of COPD.
Methods: GWAS was performed for two pneumoproteins, Clara cell secretory protein (CC16) and surfactant protein D (SP-D), and five systemic inflammatory markers (C-reactive protein, fibrinogen, IL-6, IL-8, and tumor necrosis factor-α) in 1,951 subjects with COPD. For genome-wide significant single nucleotide polymorphisms (SNPs) (P < 1 × 10−8), association with COPD susceptibility was tested in 2,939 cases with COPD and 1,380 smoking control subjects. The association of candidate SNPs with mRNA expression in induced sputum was also elucidated.
Measurements and Main Results: Genome-wide significant susceptibility loci affecting biomarker levels were found only for the two pneumoproteins. Two discrete loci affecting CC16, one region near the CC16 coding gene (SCGB1A1) on chromosome 11 and another locus approximately 25 Mb away from SCGB1A1, were identified, whereas multiple SNPs on chromosomes 6 and 16, in addition to SNPs near SFTPD, had genome-wide significant associations with SP-D levels. Several SNPs affecting circulating CC16 levels were significantly associated with sputum mRNA expression of SCGB1A1 (P = 0.009–0.03). Several SNPs highly associated with CC16 or SP-D levels were nominally associated with COPD in a collaborative GWAS (P = 0.001–0.049), although these COPD associations were not replicated in two additional cohorts.
Conclusions: Distant genetic loci and biomarker-coding genes affect circulating levels of COPD-related pneumoproteins. A subset of these protein quantitative trait loci may influence their gene expression in the lung and/or COPD susceptibility.
Clinical trial registered with (NCT 00292552).
PMCID: PMC3622441  PMID: 23144326
biomarker; chronic obstructive pulmonary disease; genome-wide association study
18.  Nitric oxide synthase polymorphisms, gene expression and lung function in chronic obstructive pulmonary disease 
Due to the pleiotropic effects of nitric oxide (NO) within the lungs, it is likely that NO is a significant factor in the pathogenesis of chronic obstructive pulmonary disease (COPD). The aim of this study was to test for association between single nucleotide polymorphisms (SNPs) in three NO synthase (NOS) genes and lung function, as well as to examine gene expression and protein levels in relation to the genetic variation.
One SNP in each NOS gene (neuronal NOS (NOS1), inducible NOS (NOS2), and endothelial NOS (NOS3)) was genotyped in the Lung Health Study (LHS) and correlated with lung function. One SNP (rs1800779) was also analyzed for association with COPD and lung function in four COPD case–control populations. Lung tissue expression of NOS3 mRNA and protein was tested in individuals of known genotype for rs1800779. Immunohistochemistry of lung tissue was used to localize NOS3 expression.
For the NOS3 rs1800779 SNP, the baseline forced expiratory volume in one second in the LHS was significantly higher in the combined AG + GG genotypic groups compared with the AA genotypic group. Gene expression and protein levels in lung tissue were significantly lower in subjects with the AG + GG genotypes than in AA subjects. NOS3 protein was expressed in the airway epithelium and subjects with the AA genotype demonstrated higher NOS3 expression compared with AG and GG individuals. However, we were not able to replicate the associations with COPD or lung function in the other COPD study groups.
Variants in the NOS genes were not associated with lung function or COPD status. However, the G allele of rs1800779 resulted in a decrease of NOS3 gene expression and protein levels and this has implications for the numerous disease states that have been associated with this polymorphism.
PMCID: PMC3827989  PMID: 24192154
Chronic obstructive pulmonary disease; Nitric oxide synthase; Polymorphism; Gene expression
19.  Genome-Wide Association Studies Identify CHRNA5/3 and HTR4 in the Development of Airflow Obstruction 
Wilk, Jemma B. | Shrine, Nick R. G. | Loehr, Laura R. | Zhao, Jing Hua | Manichaikul, Ani | Lopez, Lorna M. | Smith, Albert Vernon | Heckbert, Susan R. | Smolonska, Joanna | Tang, Wenbo | Loth, Daan W. | Curjuric, Ivan | Hui, Jennie | Cho, Michael H. | Latourelle, Jeanne C. | Henry, Amanda P. | Aldrich, Melinda | Bakke, Per | Beaty, Terri H. | Bentley, Amy R. | Borecki, Ingrid B. | Brusselle, Guy G. | Burkart, Kristin M. | Chen, Ting-hsu | Couper, David | Crapo, James D. | Davies, Gail | Dupuis, Josée | Franceschini, Nora | Gulsvik, Amund | Hancock, Dana B. | Harris, Tamara B. | Hofman, Albert | Imboden, Medea | James, Alan L. | Khaw, Kay-Tee | Lahousse, Lies | Launer, Lenore J. | Litonjua, Augusto | Liu, Yongmei | Lohman, Kurt K. | Lomas, David A. | Lumley, Thomas | Marciante, Kristin D. | McArdle, Wendy L. | Meibohm, Bernd | Morrison, Alanna C. | Musk, Arthur W. | Myers, Richard H. | North, Kari E. | Postma, Dirkje S. | Psaty, Bruce M. | Rich, Stephen S. | Rivadeneira, Fernando | Rochat, Thierry | Rotter, Jerome I. | Artigas, María Soler | Starr, John M. | Uitterlinden, André G. | Wareham, Nicholas J. | Wijmenga, Cisca | Zanen, Pieter | Province, Michael A. | Silverman, Edwin K. | Deary, Ian J. | Palmer, Lyle J. | Cassano, Patricia A. | Gudnason, Vilmundur | Barr, R. Graham | Loos, Ruth J. F. | Strachan, David P. | London, Stephanie J. | Boezen, H. Marike | Probst-Hensch, Nicole | Gharib, Sina A. | Hall, Ian P. | O’Connor, George T. | Tobin, Martin D. | Stricker, Bruno H.
Rationale: Genome-wide association studies (GWAS) have identified loci influencing lung function, but fewer genes influencing chronic obstructive pulmonary disease (COPD) are known.
Objectives: Perform meta-analyses of GWAS for airflow obstruction, a key pathophysiologic characteristic of COPD assessed by spirometry, in population-based cohorts examining all participants, ever smokers, never smokers, asthma-free participants, and more severe cases.
Methods: Fifteen cohorts were studied for discovery (3,368 affected; 29,507 unaffected), and a population-based family study and a meta-analysis of case-control studies were used for replication and regional follow-up (3,837 cases; 4,479 control subjects). Airflow obstruction was defined as FEV1 and its ratio to FVC (FEV1/FVC) both less than their respective lower limits of normal as determined by published reference equations.
Measurements and Main Results: The discovery meta-analyses identified one region on chromosome 15q25.1 meeting genome-wide significance in ever smokers that includes AGPHD1, IREB2, and CHRNA5/CHRNA3 genes. The region was also modestly associated among never smokers. Gene expression studies confirmed the presence of CHRNA5/3 in lung, airway smooth muscle, and bronchial epithelial cells. A single-nucleotide polymorphism in HTR4, a gene previously related to FEV1/FVC, achieved genome-wide statistical significance in combined meta-analysis. Top single-nucleotide polymorphisms in ADAM19, RARB, PPAP2B, and ADAMTS19 were nominally replicated in the COPD meta-analysis.
Conclusions: These results suggest an important role for the CHRNA5/3 region as a genetic risk factor for airflow obstruction that may be independent of smoking and implicate the HTR4 gene in the etiology of airflow obstruction.
PMCID: PMC3480517  PMID: 22837378
chronic obstructive pulmonary disease; single-nucleotide polymorphism; genes
20.  Meta-analysis and imputation refines the association of 15q25 with smoking quantity 
Liu, Jason Z. | Tozzi, Federica | Waterworth, Dawn M. | Pillai, Sreekumar G. | Muglia, Pierandrea | Middleton, Lefkos | Berrettini, Wade | Knouff, Christopher W. | Yuan, Xin | Waeber, Gérard | Vollenweider, Peter | Preisig, Martin | Wareham, Nicholas J | Zhao, Jing Hua | Loos, Ruth J.F. | Barroso, Inês | Khaw, Kay-Tee | Grundy, Scott | Barter, Philip | Mahley, Robert | Kesaniemi, Antero | McPherson, Ruth | Vincent, John B. | Strauss, John | Kennedy, James L. | Farmer, Anne | McGuffin, Peter | Day, Richard | Matthews, Keith | Bakke, Per | Gulsvik, Amund | Lucae, Susanne | Ising, Marcus | Brueckl, Tanja | Horstmann, Sonja | Wichmann, H.-Erich | Rawal, Rajesh | Dahmen, Norbert | Lamina, Claudia | Polasek, Ozren | Zgaga, Lina | Huffman, Jennifer | Campbell, Susan | Kooner, Jaspal | Chambers, John C | Burnett, Mary Susan | Devaney, Joseph M. | Pichard, Augusto D. | Kent, Kenneth M. | Satler, Lowell | Lindsay, Joseph M. | Waksman, Ron | Epstein, Stephen | Wilson, James F. | Wild, Sarah H. | Campbell, Harry | Vitart, Veronique | Reilly, Muredach P. | Li, Mingyao | Qu, Liming | Wilensky, Robert | Matthai, William | Hakonarson, Hakon H. | Rader, Daniel J. | Franke, Andre | Wittig, Michael | Schäfer, Arne | Uda, Manuela | Terracciano, Antonio | Xiao, Xiangjun | Busonero, Fabio | Scheet, Paul | Schlessinger, David | St Clair, David | Rujescu, Dan | Abecasis, Gonçalo R. | Grabe, Hans Jörgen | Teumer, Alexander | Völzke, Henry | Petersmann, Astrid | John, Ulrich | Rudan, Igor | Hayward, Caroline | Wright, Alan F. | Kolcic, Ivana | Wright, Benjamin J | Thompson, John R | Balmforth, Anthony J. | Hall, Alistair S. | Samani, Nilesh J. | Anderson, Carl A. | Ahmad, Tariq | Mathew, Christopher G. | Parkes, Miles | Satsangi, Jack | Caulfield, Mark | Munroe, Patricia B. | Farrall, Martin | Dominiczak, Anna | Worthington, Jane | Thomson, Wendy | Eyre, Steve | Barton, Anne | Mooser, Vincent | Francks, Clyde | Marchini, Jonathan
Nature genetics  2010;42(5):436-440.
Smoking is a leading global cause of disease and mortality1. We performed a genomewide meta-analytic association study of smoking-related behavioral traits in a total sample of 41,150 individuals drawn from 20 disease, population, and control cohorts. Our analysis confirmed an effect on smoking quantity (SQ) at a locus on 15q25 (P=9.45e-19) that includes three genes encoding neuronal nicotinic acetylcholine receptor subunits (CHRNA5, CHRNA3, CHRNB4). We used data from the 1000 Genomes project to investigate the region using imputation, which allowed analysis of virtually all common variants in the region and offered a five-fold increase in coverage over the HapMap. This increased the spectrum of potentially causal single nucleotide polymorphisms (SNPs), which included a novel SNP that showed the highest significance, rs55853698, located within the promoter region of CHRNA5. Conditional analysis also identified a secondary locus (rs6495308) in CHRNA3.
PMCID: PMC3612983  PMID: 20418889
21.  A genome-wide association study of COPD identifies a susceptibility locus on chromosome 19q13 
Human Molecular Genetics  2011;21(4):947-957.
The genetic risk factors for chronic obstructive pulmonary disease (COPD) are still largely unknown. To date, genome-wide association studies (GWASs) of limited size have identified several novel risk loci for COPD at CHRNA3/CHRNA5/IREB2, HHIP and FAM13A; additional loci may be identified through larger studies. We performed a GWAS using a total of 3499 cases and 1922 control subjects from four cohorts: the Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE); the Normative Aging Study (NAS) and National Emphysema Treatment Trial (NETT); Bergen, Norway (GenKOLS); and the COPDGene study. Genotyping was performed on Illumina platforms with additional markers imputed using 1000 Genomes data; results were summarized using fixed-effect meta-analysis. We identified a new genome-wide significant locus on chromosome 19q13 (rs7937, OR = 0.74, P = 2.9 × 10−9). Genotyping this single nucleotide polymorphism (SNP) and another nearby SNP in linkage disequilibrium (rs2604894) in 2859 subjects from the family-based International COPD Genetics Network study (ICGN) demonstrated supportive evidence for association for COPD (P = 0.28 and 0.11 for rs7937 and rs2604894), pre-bronchodilator FEV1 (P = 0.08 and 0.04) and severe (GOLD 3&4) COPD (P = 0.09 and 0.017). This region includes RAB4B, EGLN2, MIA and CYP2A6, and has previously been identified in association with cigarette smoking behavior.
PMCID: PMC3298111  PMID: 22080838
22.  The Association of Genome-Wide Significant Spirometric Loci with Chronic Obstructive Pulmonary Disease Susceptibility 
Two recent metaanalyses of genome-wide association studies conducted by the CHARGE and SpiroMeta consortia identified novel loci yielding evidence of association at or near genome-wide significance (GWS) with FEV1 and FEV1/FVC. We hypothesized that a subset of these markers would also be associated with chronic obstructive pulmonary disease (COPD) susceptibility. Thirty-two single-nucleotide polymorphisms (SNPs) in or near 17 genes in 11 previously identified GWS spirometric genomic regions were tested for association with COPD status in four COPD case-control study samples (NETT/NAS, the Norway case-control study, ECLIPSE, and the first 1,000 subjects in COPDGene; total sample size, 3,456 cases and 1,906 controls). In addition to testing the 32 spirometric GWS SNPs, we tested a dense panel of imputed HapMap2 SNP markers from the 17 genes located near the 32 GWS SNPs and in a set of 21 well studied COPD candidate genes. Of the previously identified GWS spirometric genomic regions, three loci harbored SNPs associated with COPD susceptibility at a 5% false discovery rate: the 4q24 locus including FLJ20184/INTS12/GSTCD/NPNT, the 6p21 locus including AGER and PPT2, and the 5q33 locus including ADAM19. In conclusion, markers previously associated at or near GWS with spirometric measures were tested for association with COPD status in data from four COPD case-control studies, and three loci showed evidence of association with COPD susceptibility at a 5% false discovery rate.
PMCID: PMC3262664  PMID: 21659657
23.  Identification of FGF7 as a novel susceptibility locus for chronic obstructive pulmonary disease 
Thorax  2011;66(12):1085-1090.
Traditional genome-wide association studies (GWAS) of large cohort of subjects with chronic obstructive pulmonary disease (COPD) have successfully identified novel candidate genes, but several other plausible loci do not meet strict criteria for genome-wide significance after correction for multiple testing.
We hypothesize that by applying unbiased weights derived from unique populations we can identify additional COPD susceptibility loci.
We performed a homozygosity haplotype analysis on a group of subjects with and without COPD to identify regions of conserved homozygosity (RCHH). Weights were constructed based on the frequency of these RCHH in case vs. controls, and used to adjust the P values from a large collaborative GWAS of COPD.
We identified 2,318 regions of conserved homozygosity, of which 576 were significantly (P < .05) overrepresented in cases. After applying the weights constructed from these regions to a collaborative GWAS of COPD, we identified two single nucleotide polymorphisms in a novel gene (FGF7) that gained genome-wide significance by the false discovery rate method. In a follow-up analysis, both SNPs (rs12591300 and rs4480740) were significantly associated with COPD in an independent population (combined P values of 7.9E-07 and 2.8E-06 respectively). In another independent population, increased lung tissue FGF7 expression was associated with worse measures of lung function.
Weights constructed from a homozygosity haplotype analysis of an isolated population successfully identify novel genetic associations from a GWAS on a separate population. This method can be used to identify promising candidate genes that fail to meet strict correction for multiple testing.
PMCID: PMC3348619  PMID: 21921092
24.  Genome-wide association study of smoking behaviors in COPD patients 
Thorax  2011;66(10):894-902.
Cigarette smoking is a major risk factor for COPD and COPD severity. Previous genome-wide association studies (GWAS) have identified numerous single nucleotide polymorphisms (SNPs) associated with the number of cigarettes smoked per day (CPD) and a Dopamine Beta-Hydroxylase (DBH) locus associated with smoking cessation in multiple populations.
To identify SNPs associated with lifetime average and current CPD, age at smoking initiation, and smoking cessation in COPD subjects.
GWAS were conducted in 4 independent cohorts encompassing 3,441 ever-smoking COPD subjects (GOLD stage II or higher). Untyped SNPs were imputed using HapMap (phase II) panel. Results from all cohorts were meta-analyzed.
Several SNPs near the HLA region on chromosome 6p21 and in an intergenic region on chromosome 2q21 showed associations with age at smoking initiation, both with the lowest p=2×10−7. No SNPs were associated with lifetime average CPD, current CPD or smoking cessation with p<10−6. Nominally significant associations with candidate SNPs within alpha-nicotinic acetylcholine receptors 3/5 (CHRNA3/CHRNA5; e.g. p=0.00011 for SNP rs1051730) and Cytochrome P450 2A6 (CYP2A6; e.g. p=2.78×10−5 for a nonsynonymous SNP rs1801272) regions were observed for lifetime average CPD, however only CYP2A6 showed evidence of significant association with current CPD. A candidate SNP (rs3025343) in the DBH was significantly (p=0.015) associated with smoking cessation.
We identified two candidate regions associated with age at smoking initiation in COPD subjects. Associations of CHRNA3/CHRNA5 and CYP2A6 loci with CPD and DBH with smoking cessation are also likely of importance in the smoking behaviors of COPD patients.
PMCID: PMC3302576  PMID: 21685187
Chronic Obstructive Pulmonary Disease (COPD); Genome Wide Association study (GWAS); smoking behaviors; Single Nucleotide Polymorphism (SNP)
25.  Long-term survival in patients hospitalized for chronic obstructive pulmonary disease: a prospective observational study in the Nordic countries 
Background and aim
Mortality rate is high in patients with chronic obstructive pulmonary disease (COPD). Our aim was to investigate long-term mortality and associated risk factors in COPD patients previously hospitalized for a COPD exacerbation.
A total of 256 patients from the Nordic countries were followed for 8.7 ± 0.4 years after the index hospitalization in 2000–2001. Prior to discharge, the St George’s Respiratory Questionnaire was administered and data on therapy and comorbidities were obtained. Information on long-term mortality was obtained from national registries in each of the Nordic countries.
In total, 202 patients (79%) died during the follow up period, whereas 54 (21%) were still alive. Primary cause of death was respiratory (n = 116), cardiovascular (n = 43), malignancy (n = 28), other (n = 10), or unknown (n = 5). Mortality was related to older age, with a hazard risk ratio (HRR) of 1.75 per 10 years, lower forced expiratory volume in 1 second (FEV1) (HRR 0.80), body mass index (BMI) <20 kg/m2 (HRR 3.21), and diabetes (HRR 3.02). Older age, lower BMI, and diabetes were related to both respiratory and cardiovascular mortality. An association was also found between lower FEV1 and respiratory mortality, whereas mortality was not significantly associated with therapy, anxiety, or depression.
Almost four out of five patients died within 9 years following an admission for COPD exacerbation. Increased mortality was associated with older age, lower lung function, low BMI, and diabetes, and these factors should be taken into account when making clinical decisions about patients who have been admitted to hospital for a COPD exacerbation.
PMCID: PMC3459657  PMID: 23055707
acute exacerbation; long-term mortality; co-morbidity; diabetes; lung function

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