It is widely accepted that diet and other lifestyle factors contribute significantly to the pathogenesis of cardiovascular disease, however the precise mechanisms for many of these factors remains poorly understood. Epigenetics refers to heritable changes in gene function that are not dependent on DNA sequence variation and includes the covalent modification of the DNA by methylation. Epigenetic factors provide a heritable, reversible and dynamic mechanism for regulating gene expression in response to the external stimuli induced by lifestyle/environment including nutrition. In this study we propose to explore epigenetic changes that occur in the progression to cardiovascular disease with a focus on dietary intake as the mediator in a well-characterized epidemiologic cohort of older adults, the Cardiovascular Health Study (CHS). Specifically, we will investigate:
AIM 1 : Is DNA methylation of specific loci associated with an increased risk of total mortality and, specifically, cardiovascular disease mortality, in older adults? AIM 2: Is DNA methylation of specific loci associated with an increased risk of incident cardiovascular disease, specifically myocardial infarction, angina pectoris, heart failure, and stroke? AIM 3: Is DNA methylation related to dietary intake prior to and after adjustment for other CVD risk factors such as hypertension and diabetes, subclinical disease, and behaviors/factors related to CVD risk? Are association independent or does methylation appears to be along the pathway to CVD? AIM 4: How are dietary factors related to epigenetic drift in persons with and without CVD? Does change in dietary intake correspond with change in DNA methylation? Does change in methylation mediate the association with CVD? We will measure DNA methylation in 30 pre-selected loci previously demonstrated to be related to CVD disease in stored blood samples of 500 CHS participants. To measure epigenetic drift, DNA methylation will be analyzed on blood samples taken 6 years apart to correspond with the food frequency questionnaires administered during CHS clinical evaluations. Disease outcomes will include total and cardiovascular mortality, incident myocardial infarction, angina pectoris, heart failure and stroke. Dietary data to be assessed will include estimated carbohydrate quality, including glycemix index, glycemic load, and cereal fiber intake;dietary saturated fat, linoleic acid, and oleic acid (energy-corrected);and weekly servings of whole grains, vegetables, fruits, meats, tuna/other fish, fried fish, and alcohol. Associations will be evaluated using Cox proportional hazards regression for incidence of CVD and mortality, and multiple linear regression and reduced rank regression for continuous measures of dietary intake. Models will be adjusted for other CVD risk factors to assess the role of diet in epigenetic drift and CVD. Results will lead to a better understanding of mechanisms controlling epigenomic variation allowing for identification of crucial disease-related alterations that may ultimately be targeted for novel treatment.
DNA methylation represents a gene regulatory mechanism affected by environmental exposures that may be implicated in complex diseases with both genetic and environmental components that are heritable. In this study we will investigate associations between DNA methylation and cardiovascular disease (CVD) with a focus on the role of dietary intake using data collected in the Cardiovascular Health Study (CHS) and conducting new analysis of stored DNA. By investigating associations between methylation in specific loci and nutrient intake, we can assess epigenetic drift and better understand the pathogenesis and mechanisms involved in the progression to CVD.
