Single Nucleotide Polymorphisms in the NOS Genes as Predictors of the Levels of Exhaled Nitric Oxide

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1 Single Nucleotide Polymorphisms in the NOS Genes as Predictors of the Levels of Exhaled Nitric Oxide Santosh Dahgam, Anna-Carin Olin, Lars Modig, Åsa Torinsson Naluai, Fredrik Nyberg Occupational and Environmental Medicine, Sahlgrenska Academy at University of Gothenburg Gothenburg, Sweden

2 Conflict of interest This research/authors does not have a financial relationship with any commercial entity that has an interest in this study

3 Background Nitric oxide is produced by nitric oxide synthase (NOS) enzymes 3 genes coding for 3 isoforms of NOS NOS1 (neuronal NOS) 12q24 NOS2 (inducible NOS) 17q12 NOS3 (endothelial NOS) 7q35-36 Chemiluminescence method, NIOX system (Aerocrine AB) Fractional exhaled nitric oxide (FENO) - is a noninvasive biomarker of airway inflammation Tool for diagnosis and management of asthma

4 Background Sputum eosinophils correlate with FENO Berry MA et al.2006 Age, height and atopy were shown to predict only 11% of the variability in FENO Olin AC et al.2006

5 Some studies have investigated associations between genetic variants in the NOS genes and FENO Background Locus Polymorphism Association population Reference NOS1 Intron 20 AAT repeat FENO Hispanic Wechsler M, et al., 2000 NOS1 Intron 20 AAT repeat Atopy Not FENO Australian astmatic children Ali M, et al., 2003 NOS3 G894T FENO White American adults Strom Van's GK, et al., 2003

6 Aim To comprehensively investigate the associations between single nucleotide polymorphisms (SNPs) in all three NOS genes and FENO levels in an adult Swedish population

7 The ADONIX study The Adult onset asthma and nitric oxide (ADONIX) study is a population-based study Subjects were recruited from the city of Gothenburg and the Västra Götaland region in Sweden from 2001 to 2003 Subject characteristics N=1737 Male, n (%) 853 (49.1%) Age, years; mean (SD) 49.2 (13.6) Height, cm; mean (SD) (9.1) FENO50, ppb; mean (SD) 15.9 (1.7) Never-smokers, n (%) 878 (50.5%) Wheeze, n (%) 319 (18.3%) Atopics, n (%) 434 (24.9%) Asthmatics, n (%) 136 (7.8%)

8 SNP selection and Genotyping 54 SNPs in the NOS genes were selected based on literature and the HapMap 5 SNPs were excluded after genotyping QC 49 SNPs were included in the analysis Chromosome 12 SNPs in NOS1 (n=20) Chromosome 17 SNPs in NOS2 (n=17) Chromosome 7 SNPs in NOS3 (n=12)

9 Genetic models Additive effect: Each copy of the minor allele increases the risk by same degree Dominant effect: one or two minor alleles have same influence Recessive effect: 2 copies of minor allele are necessary for risk increase

10 Single-SNP association analysis: FENO and each of the 49 SNPs with different genetic models Statistical analysis Adjusted for age, sex, height, atopy and smoking habits

11 13 SNPs with p 0.2 Forward stepwise analysis stage I Only one independent significant SNP: rs

12 Forward stepwise analysis stage II 7 SNPs with p 0.05 from the non-additive genetic models rs and 7 SNPs were categorized into 5 genetic models

13 Three SNPs were independently associated with higher levels of FENO 50 Two SNPs in NOS2 (rs and rs ) One SNP in NOS3 (rs7830) Gene/SNP Genetic model Result Genotypes (n=1737) Prevalence Difference in FENO50 (%) p-value NOS2 rs Dominant CC+CT 83% TT(ref) 17% rs Additive GG 5% 10.7 CG 36% CC (ref) 59% NOS3 rs7830 Dominant GT+TT 60% GG (ref) 40% Adjusted for age, sex, height, atopy and smoking habits

14 Conclusions Three polymorphisms in the NOS2 and NOS3 genes were independently associated with elevated levels of FENO Clearest result for inducible NOS (NOS2) Suggestive independent effect also for endothelial NOS (NOS3) No independent association with FENO for neuronal NOS (NOS1) These genetic variants are common in the population Minor allele frequencies 20-40% NOS genetics accounts for approx. 20% of the variability in FENO

15 Thank you