The Role of DNA Methylation in Cardiovascular Risk and Disease: Methodological Aspects, Study Design, and Data Analysis for Epidemiological Studies

Abstract

Epidemiological studies have demonstrated that genetic, environmental, behavioral, and clinical factors contribute to cardiovascular disease development. How these risk factors interact at the cellular level to cause cardiovascular disease is not well known. Epigenetic epidemiology enables researchers to explore critical links between genomic coding, modifiable exposures, and manifestation of disease phenotype. One epigenetic link, DNA methylation, is potentially an important mechanism underlying these associations. In the past decade, there has been a significant increase in the number of epidemiological studies investigating cardiovascular risk factors and outcomes in relation to DNA methylation, but many gaps remain in our understanding of the underlying cause and biological implications. In this review, we provide a brief overview of the biology and mechanisms of DNA methylation and its role in cardiovascular disease. In addition, we summarize the current evidence base in epigenetic epidemiology studies relevant to cardiovascular health and disease and discuss the limitations, challenges, and future directions of the field. Finally, we provide guidelines for well-designed epigenetic epidemiology studies, with particular focus on methodological aspects, study design, and analytical challenges.

Keywords: 5-methylcytosine; DNA methylation; cardiovascular diseases; epidemiology; risk factors.

Figure 1

DNA methylation is usually associated with inactive transcription and suppressed gene expression. The figure depicts the molecular mechanism linking DNA methylation and inactive transcription. Cytosine is methylated to 5-methylcytosine by DNMT. Binding of a methyl CpG-binding protein to methylated sequences prevents access to this sequence by TFs, thereby suppressing transcription. DNMT = DNA methyltransferase. SAM = S-adenosylmethionine. SAH = S-adenosylhomocysteine. TF = transcription factor. MBP = methyl CpG-binding protein.

Figure 2

Processing and analysis pipeline for an array-based DNA methylation study.

Figure 3

Two-step epigenetic Mendelian randomization. In Mendelian randomization, step 1 uses a genetic proxy for the modifiable exposure in order to assess the causal impact of the modifiable exposure on DNA methylation (the mediator). In step 2, a genetic proxy for DNA methylation is needed to evaluate the causal relationship between the methylation mediator and disease outcome (Figure adapted from Relton and Davey Smith, Int J Epidemiol 2012).

Figure 4

Design and analysis of an epidemiological DNA methylation study.