Gene methylation is an epigenetic change that involves a heritable modification of chromatin structure that alters gene expression without a change in DNA sequence. It has previously been shown that methylation of the GATA-4 gene promoter region in sputum DNA is associated with low lung function and increased odds of chronic obstructive pulmonary disease (COPD) among smokers. Given these findings, we hypothesized that GATA-4 gene methylation in sputum DNA would be associated with low health status, as measured by the St. George's Respiratory Questionnaire (SGRQ), in subjects with COPD. Self-reported SGRQ, spirometry, and induced sputum samples were obtained from 168 COPD subjects from the Lovelace Smokers Cohort. GATA-4 gene methylation was evaluated in sputum DNA using nested methylation-specific polymerase chain reaction (PCR) assays. Using general linear model with Poisson regression, we found that GATA-4 gene methylation was significantly associated with overall lower SGRQ health status (parameter estimate = .296, p < .001). This finding remained significant even after controlling for age, lung function, and other covariates. In an additional analysis using logistic regression and comparing extreme tertiles of overall SGRQ score, we confirmed that GATA-4 gene methylation was associated with a 3-fold increase in risk of poor health status (OR 2.95 and p = .028). The unexplored links between epigenetic changes and psychosocial factors such as health status are critical gaps in the literature. This study is the first to suggest that airway GATA-4 gene methylation status may independently predict health status in individuals with COPD.
Keywords: COPD; GATA-4; gene methylation; health status.
© The Author(s) 2014.