Epidemiologic approaches to understanding mechanisms of cardiovascular diseases: Genes, environment, and DNA methylation by Min A Jhun A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Epidemiological Science) in the University of Michigan 2015 Doctoral Committee: Assistant Professor Sung Kyun Park, Co-Chair Professor Patricia A. Peyser, Co-Chair Emeritus Professor John D. Kalbfleisch Professor Sharon L.R. Kardia Assistant Research Scientist Jennifer A. Smith © 2015 Min A Jhun All Rights Reserved Acknowledgements Heartfelt appreciation to my advisors, Dr. Patricia Peyser and Dr. Sung Kyun Park, friends, and family ii Table of Contents Acknowledgements ......................................................................................................................... ii Table of Contents ........................................................................................................................... iii List of figures ................................................................................................................................. ix List of tables ................................................................................................................................... xi List of abbreviations .................................................................................................................... xiv Abstract ....................................................................................................................................... xvii Chapter 1 Introduction .................................................................................................................... 1 Importance of Cardiovascular Disease ................................................................................... 1 Inflammation and Cardiovascular Disease ............................................................................. 2 C-reactive Protein ............................................................................................................... 3 Interleukin-6 ........................................................................................................................ 3 Interkeukin-18 ..................................................................................................................... 4 Fibrinogen ........................................................................................................................... 4 Selected Subclinical Markers of Cardiovascular Disease ....................................................... 5 Pulse Pressure and Arterial Stiffness .................................................................................. 5 Left Ventricular Ejection Fraction and Systolic Function .................................................. 6 Left Ventricular Mass Index and Hypertrophy ................................................................... 7 iii Genetics of Cardiovascular Disease........................................................................................ 8 SNPs in Cardiovascular Disease ......................................................................................... 8 DNA Methylation and Cardiovascular Disease Risks ........................................................ 9 Vitamin D, Vitamin D receptor, and Cardiovascular Disease .............................................. 10 Vitamin D and VDR ......................................................................................................... 11 VDR and Cardiovascular Disease ..................................................................................... 12 Genetics of the VDR ......................................................................................................... 13 Lead....................................................................................................................................... 13 Importance and measurement of Lead .............................................................................. 13 Lead and Cardiovascular Disease ..................................................................................... 14 Lead and VDR .................................................................................................................. 15 Mendelian Randomization .................................................................................................... 16 Two-Step Epigenetic Mendelian Randomization ............................................................. 17 Network Mendelian Randomization ................................................................................. 18 Gene by Environment Interaction in Cardiovascular Disease .............................................. 19 Overarching goal ....................................................................................................................... 19 Hypothesis for Aim 1 ............................................................................................................ 20 Hypothesis for Aim 2 ............................................................................................................ 20 Hypothesis for Aim 3 ............................................................................................................ 20 Tables ........................................................................................................................................ 22 iv References ................................................................................................................................. 23 Chapter 2 Effect modification by Vitamin D receptor genetic polymorphisms in the association between cumulative lead exposure and pulse pressure: a longitudinal study .............................. 37 Introduction ............................................................................................................................... 37 Methods..................................................................................................................................... 39 Study population ................................................................................................................... 39 Blood pressure ...................................................................................................................... 40 Lead exposure ....................................................................................................................... 40 Genotyping ............................................................................................................................ 40 Statistical analysis ................................................................................................................. 41 Results ....................................................................................................................................... 42 Discussion ................................................................................................................................. 45 Conclusion ................................................................................................................................ 50 Tables ........................................................................................................................................ 52 References ................................................................................................................................. 58 Chapter 3 Modeling the causal role of DNA methylation in the association between smoking and inflammation in African Americans ...................................................................................... 62 Introduction ............................................................................................................................... 62 Methods..................................................................................................................................... 64 Study population ................................................................................................................... 64 v Genotypes ............................................................................................................................. 65 DNA methylation .................................................................................................................. 66 Smoking variable .................................................................................................................. 66 Inflammatory markers ........................................................................................................... 67 Assumption checking ............................................................................................................ 67 Two-step epigenetic Mendelian randomization .................................................................... 69 Results ....................................................................................................................................... 73 Study population descriptive................................................................................................. 73 Assumption checking ............................................................................................................ 73 Step 1 Mendelian randomization: Smoking -> DNA methylation ....................................... 74 Step 2 Mendelian randomization: DNA methylation -> Inflammation ................................ 76 Discussion ................................................................................................................................