Long-term outdoor air pollution and DNA methylation in circulating monocytes: results from the Multi-Ethnic Study of Atherosclerosis (MESA).

BACKGROUND: DNA methylation may mediate effects of air pollution on cardiovascular disease. The association between long-term air pollution exposure and DNA methylation in monocytes, which are central to atherosclerosis, has not been studied. We investigated the association between long-term ambient air pollution exposure and DNA methylation (candidate sites and global) in monocytes of adults (aged ≥55). METHODS: One-year average ambient fine particulate matter (PM2.5) and oxides of nitrogen (NOX) concentrations were predicted at participants' (n = 1,207) addresses using spatiotemporal models. We assessed DNA methylation in circulating monocytes at 1) 2,713 CpG sites associated with mRNA expression of nearby genes and 2) probes mapping to Alu and LINE-1 repetitive elements (surrogates for global DNA methylation) using Illumina's Infinium HumanMethylation450 BeadChip. We used linear regression models adjusted for demographics, smoking, physical activity, socioeconomic status, methyl-nutrients, and technical variables. For significant air pollution-associated methylation sites, we also assessed the association between expression of gene transcripts previously associated with these CpG sites and air pollution. RESULTS: At a false discovery rate of 0.05, five candidate CpGs (cg20455854, cg07855639, cg07598385, cg17360854, and cg23599683) had methylation significantly associated with PM2.5 and none were associated with NOX. Cg20455854 had the smallest p-value for the association with PM2.5 (p = 2.77 × 10-5). mRNA expression profiles of genes near three of the PM2.5-associated CpGs (ANKHD1, LGALS2, and ANKRD11) were also significantly associated with PM2.5 exposure. Alu and LINE-1 methylation were not associated with long-term air pollution exposure. CONCLUSIONS: We observed novel associations between long-term ambient air pollution exposure and site-specific DNA methylation, but not global DNA methylation, in purified monocytes of a multi-ethnic adult population. Epigenetic markers may provide insights into mechanisms underlying environmental factors in complex diseases like atherosclerosis.

A Longitudinal Study of Changes in Prenatal Care Utilization Between First and Second Births and Low Birth Weight.

OBJECTIVES: Because previous analyses of prenatal care (PNC) utilization and risk of low birth weight (LBW) may have been influenced by selection bias, we conducted a study using longitudinal data of women with repeat pregnancies. METHODS: We analyzed Washington State birth certificates of first and second live births (2003-2012). We estimated relative risk (RR) of LBW at second birth associated with Kotelchuck Index PNC level among women stratified by level of PNC in their first birth (n = 67,571). RESULTS: Among women with inadequate PNC prior to their first birth (n = 10,355), women with intermediate or adequate PNC before their second birth (n = 7464) had a reduced risk of LBW (adjusted RR 0.61, 95% CI: 0.48, 0.78) compared to those whose PNC level remained inadequate. Likewise, among women with intermediate or adequate PNC prior to their first birth (n = 57,216), those with inadequate PNC before the second birth (n = 7095) had higher risk of LBW (adjusted RR 1.59, 95% CI: 1.36, 1.85) compared to those who remained at intermediate or adequate PNC. CONCLUSIONS: Our findings support the hypothesis that PNC decreases LBW risk at second birth, independent of factors related to the utilization of PNC at first birth.