Alu and LINE-1 methylation and lung function in the normative ageing study

Objectives: To investigate the association between methylation of transposable elements Alu and long-interspersed nuclear elements (LINE-1) and lung function. Design: Cohort study. Setting: Outpatient Veterans Administration facilities in greater Boston, Massachusetts, USA. Participants: Individuals from the Veterans Administration Normative Aging Study, a longitudinal study of aging in men, evaluated between 1999 and 2007. The majority (97%) were white. Primary and secondary outcome measures: Primary predictor was methylation, assessed using PCR-pyrosequencing after bisulphite treatment. Primary outcome was lung function as assessed by spirometry, performed according to American Thoracic Society/European Respiratory Society guidelines at the same visit as the blood draws. Results: In multivariable models adjusted for age, height, body mass index (BMI), pack-years of smoking, current smoking and race, Alu hypomethylation was associated with lower forced expiratory volume in 1 s (FEV1) (beta=28 ml per 1% change in Alu methylation, p=0.017) and showed a trend towards association with a lower forced vital capacity (FVC) (beta=27 ml, p=0.06) and lower FEV1/FVC (beta=0.3%, p=0.058). In multivariable models adjusted for age, height, BMI, pack-years of smoking, current smoking, per cent lymphocytes, race and baseline lung function, LINE-1 hypomethylation was associated with more rapid decline of FEV1 (beta=6.9 ml/year per 1% change in LINE-1 methylation, p=0.005) and of FVC (beta=9.6 ml/year, p=0.002). Conclusions: In multiple regression analysis, Alu hypomethylation was associated with lower lung function, and LINE-1 hypomethylation was associated with more rapid lung function decline in a cohort of older and primarily white men from North America. Future studies should aim to replicate these findings and determine if Alu or LINE-1 hypomethylation may be due to specific and modifiable environmental exposures.