Introduction: Pediatric hypertension is a significant public health burden. Although the association between genetic variants and blood pressure (BP) has been extensively investigated, the relationship between DNA methylation and BP, especially in adolescents, has not been characterized.
Hypothesis: DNA methylation of previously reported BP-related genes is associated with BP levels in adolescents.
Methods: We examined this relationship in 263 adolescents from the Penn State Child Cohort follow-up exam. We extracted peripheral leukocytes DNA and subjected it to enhanced, reduced representation bisulfite sequencing. A high-throughput assay provided single nucleotide resolution of DNA methylation in cytosine-phosphate-guanine (CpG) sites and surrounding regions. Bases with less than 10x coverage or available from less than 50% of the participants were excluded, resulting in a total of 165,297 analyzable sites. For each participant, 3 seated-BP measurements were taken and the average of 2nd and 3rd measurements was used to represent the participant’s BP. We used robust linear regression to associate site-specific methylation level with systolic BP (SBP) and diastolic BP (DBP). All regression models were adjusted for age, race, sex, and body mass index percentile. All intragenic sites were then mapped to the hg19 assembly and subjected to enrichment analyses. Significance of the enrichment analyses was assessed by hypergeometric and permutation tests. False discovery rate (FDR)-corrected p values were used to determine the significance between site-specific methylation and BP measures.
Results: The mean (SD) age of the participants was 16.7 (2.2) years. It consisted of 55% male, 79% white and 16% obese. Among the 5,551 and 5,890 sites related to SBP and DBP at p<0.05 level, 35 and 38 were intragenic to BP genes. BP genes were significantly enriched among
intragenic sites for both SBP (P(hypergeometric)c=0.015; P(permutation)=0.019) and DBP (P(hypergeometric)c=0.008; P(permutation)=0.012). At individual site level, two sites within MECOM were significantly related to SBP (FDR-corrected P=0.02 and 0.03).
Conclusion: Despite the need of external validation from other independent cohorts, data from this exploratory study suggests that DNA methylation of BP-related genes is associated with BP regulation in adolescents and, consequently, with the pathogenesis of hypertension in early developmental periods.