Mediating effects of BMI on the association between DNA methylation regions and 24-h blood pressure in African Americans

Background: DNA methylation is an important epigenetic mechanism that may influence blood pressure (BP) regulation and hypertension risk. Obesity, a major lifestyle factor associated with hypertension, may interact with DNA methylation to affect BP. However, the indirect effect of DNA methylation on 24-hBP measurements mediated by obesity-related phenotypes such as BMI has not been investigated. Methods: Causal mediation analysis was applied to examine the mediating role of BMI in the relation between DNA methylation and 24-h BP phenotypes, including SBP, DBP and mean arterial blood pressure (MAP), in 281 African American participants. Results: Analysis of 38 215 DNA methylation regions, derived from 1,549,368 CpG sites across the genome, identified up to 138 methylation regions that were significantly associated with 24-h BP measurements through BMI mediation. Among them, 38 (19.2%) methylation regions were concurrently associated with SBP, DBP and MAP. Genes associated with BMI-mediated methylation regions are potentially involved in various chronic diseases such as coronary artery disease and renal disease, which are often caused or exacerbated by hypertension. Notably, three genes ( CDH4 , NOTCH1 and COLGALT1 ) showed both direct associations with 24-h BP measurements and indirect associations through BMI after adjusting for age and sex covariates. Conclusion: Our findings suggest that DNA methylation may contribute to the regulation of 24-h BP in African Americans both directly and indirectly through BMI mediation.