Pieter Zanen

Genome-Wide Association Studies Identify CHRNA5/3 and HTR4 in the Development of Airflow Obstruction

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 FEV(1) and its ratio to FVC (FEV(1)/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 FEV(1)/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.

Common and different genetic background for rheumatoid arthritis and coeliac disease

Recent genome-wide association studies (GWAS) have revealed genetic risk factors in autoimmune and inflammatory disorders. Several of the associated genes and underlying pathways are shared by various autoimmune diseases. Rheumatoid arthritis (RA) and coeliac disease (CD) are two autoimmune disorders which have commonalities in their pathogenesis. We aimed to replicate known RA loci in a Dutch RA population, and to investigate whether the effect of known RA and CD risk factors generalize across the two diseases. We selected all loci associated to either RA or CD in a GWAS and confirmed in an independent cohort, with a combined P-value cut-off P < 5 x 10(-6). We genotyped 11 RA and 11 CD loci in 1368 RA patients, 795 CD patients and 1683 Dutch controls. We combined our results in a meta-analysis with UK GWAS on RA (1860 cases; 2938 controls) and CD (767 cases; 1422 controls). In the Dutch RA cohort, the PTPN22 and IL2/IL21 variants showed convincing association (P = 3.4 x 10(-12) and P = 2.8 x 10(-4), respectively). Association of RA with the known CD risk variant in the SH2B3 was also observed, predominantly in the subgroup of rheumatoid factor-positive RA patients (P = 0.0055). In a meta-analysis of Dutch and UK data sets, shared association with six loci (TNFAIP3, IL2/IL21, SH2B3, LPP, MMEL1/TNFRSF14 and PFKFB3/PRKCQ) was observed in both RA and CD cohorts. We confirmed two known loci and identified four novel ones for shared CD-RA genetic risk. Most of the shared loci further emphasize a role for adaptive and innate immunity in these diseases.

CT-quantified emphysema in male heavy smokers: association with lung function decline

Background Emphysema and small airway disease both contribute to chronic obstructive pulmonary disease (COPD), a disease characterised by accelerated decline in lung function. The association between the extent of emphysema in male current and former smokers and lung function decline was investigated. Methods Current and former heavy smokers participating in a lung cancer screening trial were recruited to the study and all underwent CT. Spirometry was performed at baseline and at 3-year follow-up. The 15th percentile (Perc15) was used to assess the severity of emphysema. Results 2085 men of mean age 59.8 years participated in the study. Mean (SD) baseline Perc15 was −934.9 (19.5) HU. A lower Perc15 value correlated with a lower forced expiratory volume in 1 s (FEV1) at baseline (r=0.12, p<0.001). Linear mixed model analysis showed that a lower Perc15 was significantly related to a greater decline in FEV1 after follow-up (p<0.001). Participants without baseline airway obstruction who developed it after follow-up had significantly lower mean (SD) Perc15 values at baseline than those who did not develop obstruction (−934.2 (17.1) HU vs −930.2 (19.7) HU, p<0.001). Conclusion Greater baseline severity of CT-detected emphysema is related to lower baseline lung function and greater rates of lung function decline, even in those without airway obstruction. CT-detected emphysema aids in identifying non-obstructed male smokers who will develop airflow obstruction.

The optimal particle size for β-adrenergic aerosols in mild asthmatics

Abstract Background: the optimal particle size of a β 2 -mimetic aerosol is not known. Methods: eight stable asthmatics with a FEV 1 (forced expiratory volume) of 72% of the predicted value inhaled three types of monodisperse salbutamol aerosols, with particle sizes of 1.5, 2.8 and 5 μm, respectively, and a placebo aerosol. The volunteers inhaled cumulative dosages of 5, 10, 20 and 40 μg salbutamol, after which lung function improvement was determined. The four resulting dose-response curves (one for each type of aerosol) were analysed with repeated measurements ANOVA. Results: for the FEV 1 and the MEF 75/50/25 (maximum expiratory flow) the 2.8 μm aerosol induced a significantly better dilation than the 5 μm aerosol. In the case of the PEF (peak expiratory flow) the 1.5 μm aerosol elicited a significantly smaller improvement than the 2.8 μm aerosol. No particle size effect was noticeable in the case of the VC (vital capacity), FVC (forced vital capacity) and the R tot . Conclusions: in mild asthmatics the particle size of choice for a β 2 -mimetic aerosol should be around 2.8 μm.

Lower limit of normal or FEV1/FVC <0.70 in diagnosing COPD: An evidence-based review

AIM To review the currently available literature comparing the FEV1/FVC 40 years. METHODS A structured MEDLINE, EMBASE and Cochrane search of English-language literature was conducted. Studies comparing prevalence rates according to the LLN and a fixed value were included. Attention was paid to the choice of the reference test or gold standard used. RESULTS Eighteen studies met the inclusion criteria. Sixteen studies compared the rates of subjects diagnosed with airflow obstruction by either definition of airflow obstruction without using a non-independent reference standard (level 4 studies). Using a fixed value of FEV1/FVC, an overall higher number of subjects were diagnosed with airflow obstruction that increased with age. Two studies included a follow-up phase comparing risks of either hospitalization or occurrence of respiratory symptoms and mortality (level 2b studies). Adjusted risks of hospitalization (HR 2.6) or mortality (HR 1.3) were significantly larger in subjects with an FEV1/FVC below 0.70 but above the LLN (in-between group) compared to subjects with normal lung function. CONCLUSION The prevalence of spirometry-based COPD is greater when using the fixed value of FEV1/FVC in comparison to using the LLN. Based on one longitudinal study the in-between group appears to have a higher risk of hospitalization and mortality; therefore it seems that using the LLN of FEV1/FVC underestimates COPD. In absence of a gold standard of COPD longitudinal research will be necessary to determine which criterion is better and more clinically relevant.

Analysis of SNPs with an effect on gene expression identifies UBE2L3 and BCL3 as potential new risk genes for Crohn's disease

Genome-wide association studies (GWAS) for Crohns disease (CD) have identified loci explaining approximately 20% of the total genetic risk of CD. Part of the other genetic risk loci is probably partly hidden among signals discarded by the multiple testing correction needed in the analysis of GWAS data. Strategies for finding these hidden loci require large replication cohorts and are costly to perform. We adopted a strategy of selecting SNPs for follow-up that showed a correlation to gene expression [cis-expression quantitative trait loci (eQTLs)] since these have been shown more likely to be trait-associated. First we show that there is an overrepresentation of cis-eQTLs in the known CD-associated loci. Then SNPs were selected for follow-up by screening the top 500 SNP hits from a CD GWAS data set. We identified 10 cis-eQTL SNPs. These 10 SNPs were tested for association with CD in two independent cohorts of Dutch CD patients (1539) and healthy controls (2648). In a combined analysis, we identified two cis-eQTL SNPs that were associated with CD rs2298428 in UBE2L3 (P=5.22x10(-5)) and rs2927488 in BCL3 (P=2.94x10(-4)). After adding additional publicly available data from a previously reported meta-analysis, the association with rs2298428 almost reached genome-wide significance (P=2.40x10(-7)) and the association with rs2927488 was corroborated (P=6.46x10(-4)). We have identified UBE2L3 and BCL3 as likely novel risk genes for CD. UBE2L3 is also associated with other immune-mediated diseases. These results show that eQTL-based pre-selection for follow-up is a useful approach for identifying risk loci from a moderately sized GWAS.

The 15q24/25 Susceptibility Variant for Lung Cancer and Chronic Obstructive Pulmonary Disease Is Associated with Emphysema

RATIONALE Genome-wide association studies have identified genetic variants in the nicotinic acetylcholine receptor (nAChR) on chromosome 15q24/25 as a risk for nicotine dependence, lung cancer, and chronic obstructive pulmonary disease (COPD). Assessment of bronchial obstruction by spirometry, typically used for diagnosing COPD, fails, however, to detect emphysema. OBJECTIVES To determine the association of the 15q24/25 locus with emphysema. METHODS The rs1051730 variant on 15q24/25 was genotyped in two independent white cohorts of 661 and 456 heavy smokers. Participants underwent pulmonary function tests and computed tomography (CT) of the chest, and took questionnaires assessing smoking behavior and health status. MEASUREMENTS AND MAIN RESULTS The rs1051730 A-allele correlated with reduced FEV(1) and with increased susceptibility for bronchial obstruction with a pooled odds ratio (OR) of 1.33 (95% confidence interval [CI] = 1.11-1.61; P = 0.0026). In both studies a correlation between the rs1051730 A-allele and lung diffusing capacity (Dl(CO)) and diffusing capacity per unit alveolar volume (Kco) was observed. Consistently, the rs1051730 A-allele conferred increased risk for emphysema as assessed by CT (P = 0.0097 and P = 0.019), with a pooled OR of 1.39 (CI = 1.15-1.68; P = 0.00051). Visual emphysema scores and scores based on densities quantified on CT were more pronounced in A-allele carriers, indicating that rs1051730 correlates with the severity of emphysema. CONCLUSIONS The 15q24/25 locus in nAChR is associated with the presence and severity of emphysema. This association was independent of pack-years smoking, suggesting that nAChR is causally involved in alveolar destruction as a potentially shared pathogenic mechanism in lung cancer and COPD.

Identification of chronic obstructive pulmonary disease in lung cancer screening computed tomographic scans.

CONTEXT Smoking is a major risk factor for both cancer and chronic obstructive pulmonary disease (COPD). Computed tomography (CT)-based lung cancer screening may provide an opportunity to detect additional individuals with COPD at an early stage. OBJECTIVE To determine whether low-dose lung cancer screening CT scans can be used to identify participants with COPD. DESIGN, SETTING, AND PATIENTS Single-center prospective cross-sectional study within an ongoing lung cancer screening trial. Prebronchodilator pulmonary function testing with inspiratory and expiratory CT on the same day was obtained from 1140 male participants between July 2007 and September 2008. Computed tomographic emphysema was defined as percentage of voxels less than -950 Hounsfield units (HU), and CT air trapping was defined as the expiratory:inspiratory ratio of mean lung density. Chronic obstructive pulmonary disease was defined as the ratio of forced expiratory volume in the first second to forced vital capacity (FEV(1)/FVC) of less than 70%. Logistic regression was used to develop a diagnostic prediction model for airflow limitation. MAIN OUTCOME MEASURES Diagnostic accuracy of COPD diagnosis using pulmonary function tests as the reference standard. RESULTS Four hundred thirty-seven participants (38%) had COPD according to lung function testing. A diagnostic model with CT emphysema, CT air trapping, body mass index, pack-years, and smoking status corrected for overoptimism (internal validation) yielded an area under the receiver operating characteristic curve of 0.83 (95% CI, 0.81-0.86). Using the point of optimal accuracy, the model identified 274 participants with COPD with 85 false-positives, a sensitivity of 63% (95% CI, 58%-67%), specificity of 88% (95% CI, 85%-90%), positive predictive value of 76% (95% CI, 72%-81%); and negative predictive value of 79% (95% CI, 76%-82%). The diagnostic model showed an area under the receiver operating characteristic curve of 0.87 (95% CI, 0.86-0.88) for participants with symptoms and 0.78 (95% CI, 0.76-0.80) for those without symptoms. CONCLUSION Among men who are current and former heavy smokers, low-dose inspiratory and expiratory CT scans obtained for lung cancer screening can identify participants with COPD, with a sensitivity of 63% and a specificity of 88%.

Methotrexate vs Azathioprine in Second-line Therapy of Sarcoidosis

BACKGROUND Steroids remain the first-choice therapeutic in sarcoidosis; however, long-term use is associated with toxicity. Evidence defining the best second-line therapeutic is currently lacking. The aim of this study was to compare the effect of methotrexate and azathioprine on prednisone tapering, pulmonary function, and side effects in the second-line treatment of sarcoidosis. METHODS An international retrospective cohort study was performed, reviewing all patients with sarcoidosis who started methotrexate or azathioprine until 2 years after initiation or discontinuation. A linear mixed model with FEV1, vital capacity (VC), diffusing capacity of lung for carbon monoxide (DLCO), and prednisone dose changes over time as end points was used. Side effects were compared with χ2 tests. RESULTS Two hundred patients were included, of whom 145 received methotrexate and 55 azathioprine. Prednisone daily dose decreased a mean of 6.32 mg/y (P < .0001) while on therapy, with a similar steroid-sparing capacity for methotrexate and azathioprine. Of all patients completing 1 year of therapy, 70% had a reduction in daily prednisone dose of at least 10 mg. FEV1 showed a mean increase of 52 mL/y (P = .006) and VC of 95 mL/y (P = .001) in both treatment groups. DLCO % predicted increased, with a mean of 1.23%/y (P = .018). There were more patients with infections in the azathioprine group (34.6% vs 18.1%, P = .01), but no differences regarding other side effects. CONCLUSIONS This retrospective study comparing the effect of second-line therapy in sarcoidosis shows that both methotrexate and azathioprine have significant steroid-sparing potency, a similar positive effect on lung function, and comparable side effects, except for a higher infection rate in the azathioprine group.

The optimal particle size for parasympathicolytic aerosols in mild asthmatics

Abstract Background: the optimal particle size of a parasympathicolytic aerosol is unknown. Methods: eight stable asthmatics with a mean FEV 1 of 72% of the predicted value inhaled three types of monodisperse ipratropium bromide aerosols, with particle sizes of 1.5, 2.8 and 5 μm, respectively, and a placebo aerosol. The volunteers inhaled 8 μg ipratropium bromide, after which lung function improvement was determined. The changes in lung function were analysed with repeated measurements ANOVA. Results: according to the changes in FEV 1 and MEF 50/25 the 1.5/2.8 μm aerosol induced significantly better bronchodilatation than the 5 μm aerosol. No particle size effect was noticeable with regard to changes in R cot , VC, FVC and PEF. Conclusions: in mild asthmatics the particle size of choice for a parasympathicolytic aerosol should be ≤ 2.8 μm.