Lack of heritability of exhaled volatile compound pattern: an electronic nose twin study

Electronic noses can distinguish various disorders by analyzing exhaled volatile organic compound (VOC) pattern; however it is unclear how hereditary and environmental backgrounds affect the exhaled VOC pattern. A twin study enrolling monozygotic (MZ) and dizygotic (DZ) twins is an ideal tool to separate the influence of these factors on the exhaled breath pattern. Exhaled breath samples were collected in duplicates from 28 never smoking twin pairs (in total 112 samples) without lung diseases and processed with an electronic nose (Cyranose 320). Univariate quantitative hereditary modeling (ACE analysis) adjusted for age and gender was performed to decompose the phenotypic variance of the exhaled volatile compound pattern (assessing principal components (PCs) derived from electronic nose data) into hereditary (A), shared (C), and unshared (E) environmental effects. Exhaled VOC pattern showed good intra-subject reproducibility as assessed with the Bland–Altman plot. Significant correlations were found between exhaled VOC patterns of both MZ and DZ twins. The hereditary background did not influence the VOC pattern. The shared environmental effect on PC 1, 2 and 3 was estimated to be 93%, 94% and 54%, respectively. The unshared (unique) environmental influence explained a smaller variance (7%, 6% and 46%). For the first time using the twin design, we have shown that the environmental background largely affects the exhaled volatile compound pattern in never smoking volunteers without respiratory disorders. Further studies should identify these environmental factors and also assess their influence on exhaled breath patterns in patients with lung diseases.