Global DNA methylation and risk of subclinical atherosclerosis in young adults: The Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study

Abstract

Objective

The association between hepatic global DNA methylation measured using pyrosequencing technology and the risk of subclinical atherosclerosis was examined in the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study. PDAY is a bi-racial investigation of the natural history of atherosclerosis and its risk factors involving 3013 individuals aged 15–34 years who underwent autopsy after dying of unrelated causes in 1987–1994.

Methods

Raised atherosclerotic lesions were defined as the sum of the percentages of intimal surface area detected in the right coronary artery and left half of the abdominal and thoracic aorta harboring fibrous plaques, complicated lesions, and calcified lesions during a postmortem pathological examination. To conduct the case–control study, 300 cases selected with the highest raised lesion scores were paired with 300 controls without raised lesions after matching for age, race, and gender.

Results

Global DNA methylation was not associated with disease risk in the study population considered as a whole using conditional logistic regression models to analyze matched pairs. Since the estimation of the risk of atherosclerosis associated with inter-individual variation in DNA methylation was similar if unconditional logistic regression was used, subgroup analyses were carried out after adjusting for matching variables. A modest association with methylation levels below the median value was found in white but not in African-American study participants (odds ratio = 1.59, 95% confidence interval = 1.02–2.49, p = 0.04).

Conclusions

Hepatic global DNA methylation does not appear to be a definitive determinant of atherosclerosis burden in a postmortem sample of young adults.

Introduction

Coronary heart disease and stroke are the first and third leading causes of death in developed countries and can be largely attributed to deposition and rupture of atherosclerotic plaques in the coronary and carotid arteries [1]. Several lines of evidence suggest that alterations in global rather than gene-specific DNA methylation patterns may be implicated in atherosclerosis. A significant reduction in global 5-methylcytosine content was found in advanced atherosclerotic lesions from patients with coronary heart disease, in smooth muscle cells, and in mice lacking apolipoprotein E (Apoe), a widely used animal model of atherosclerosis due to defective lipid metabolism [2], [3], [4], [5]. More recently, a higher level of global DNA methylation in the peripheral blood leukocytes of patients with prevalent coronary heart disease when compared to controls has been observed in two studies, while lower methylation of LINE-1 repeats has been shown to predict both baseline and incident ischemic heart disease and stroke in a cohort of elderly individuals from the Boston-area Normative Aging Study [6], [7], [8].

In this study, hepatic global methylation status was examined using a case–control design in which 600 subjects were selected from the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study. PDAY is a bi-racial investigation of the development and progression of subclinical atherosclerosis involving 3013 individuals aged 15–34 who underwent autopsy within 48 h following violent death [9], [10]. The PDAY study assessed the relationship between pathologically defined atherosclerotic lesions and postmortem risk factors for coronary heart disease including serum lipoprotein levels, smoking, hypertension, glycohemoglobin levels, and obesity. The sum of the percentages of intimal surface area detected in the right coronary artery and left half of the abdominal and thoracic aorta harboring fibrous plaques, complicated lesions, and calcified lesions was defined as a raised lesion. All of the aortas and approximately half of the coronary arteries examined in individuals 15–19 years of age had fatty streaks or raised lesions, increasing to about 75% in those 30–34 years of age, suggesting that the pathological processes leading to atherosclerosis are initiated in childhood and early adolescence [11]. For the case–control study, 300 cases with the highest raised lesion scores were paired with 300 controls free of raised lesions after matching for age, race, and gender. Global DNA methylation content was measured in genomic liver DNA derived from the PDAY study participants by a high throughput luminometric methylation assay (LUMA) using pyrosequencing technology [12].