Background: Epigenetic features such as DNA hypomethylation have been associated with conditions related to cardiovascular risk. We evaluated whether lower blood DNA methylation in heavily methylated repetitive sequences predicts the risk of ischemic heart disease and stroke.
Methods: We quantified blood DNA methylation of Long Interspersed Nucleotide Element-1 (LINE-1) repetitive elements through PCR-pyrosequencing in 712 elderly individuals from the Boston-area Normative Aging Study. We estimated risk-factor adjusted relative risks (RRs) for ischemic heart disease and stroke at baseline (242 prevalent cases), and during follow-up (44 new cases; median follow-up, 63 months), as well as subsequent mortality from ischemic heart disease (86 deaths; median follow-up, 75 months).
Results: Blood LINE-1 hypomethylation was associated with baseline ischemic heart disease (RR = 2.1 [95% confidence interval = 1.2-4.0] for lowest vs. highest methylation quartile) and for stroke (2.5 [0.9-7.5]). Among participants free of baseline disease, individuals with methylation below the median also had higher risk of developing ischemic heart disease (4.0 [1.8-8.9]) or stroke (5.7 [0.8-39.5]). In the entire cohort, persons with methylation below the median had higher mortality from ischemic heart disease (3.3 [1.3-8.4]) and stroke (2.8 [0.6-14.3]). Total mortality was also increased (2.0 [1.2-3.3]). These results were confirmed in additional regression models using LINE-1 methylation as a continuous variable.
Conclusions: Subjects with prevalent IHD and stroke exhibited lower LINE-1 methylation. In longitudinal analyses, persons with lower LINE-1 methylation were at higher risk for incident ischemic heart disease and stroke, and for total mortality.
From the aCenter of Molecular and Genetic Epidemiology, Università degli Studi di Milano & IRCCS Ca′, Granda Policlinico Maggiore Hospital Foundation, Milan, Italy; bExposure Epidemiology and Risk Program, Harvard School of Public Health, Boston, MA; cChanning Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA; dVA Normative Aging Study, Veterans Affairs Boston Healthcare System, Boston, MA; and eDepartment of Medicine, Boston University School of Medicine, Boston, MA.
Submitted 11 November 2009; accepted 26 May 2010; posted 30 August 2010.
Department of Veterans Affairs and is a component of the Massachusetts Veterans Epidemiology Research and Information Center (MAVERIC).
Supported by the National Institute of Environmental Health Sciences (NIEHS) grants ES015172-01, ES00002; Environmental Protection Agency (EPA) grants EPA R83241601 and R827353; CARIPLO Foundation grant 2007-5469, and MIUR PRIN2007 grant 2S2HT8. The VA Normative Aging Study is supported by the Cooperative Studies Program/Epidemiology Research and Information Center of the US.
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Correspondence: Andrea Baccarelli, Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, 401 Park Dr., Landmark Center, Suite 412F West, P.O. Box 15698, Boston, MA 02215. E-mail: email@example.com.