To highlight potential epigenetic risk factors for blood pressure (BP) and ischemic stroke (IS) in loci identified by genome-wide association studies (GWASs).

We detected DNA methylation for BP (317,756 individuals from UK Biobank) and IS (521,612 individuals from MEGASTROKE) in Europeans by using the summary data–based mendelian randomization (SMR) method. We selected the most relevant gene to validate the association in 1,207 patients with hypertensive IS and 1,269 controls from the Chinese populations.

We first identified 173 CpG sites in 90 genes, 337 CpG sites in 142 genes, and 9 CpG sites in 7 genes that were significantly associated with systolic, diastolic BP, and IS, respectively. The methylation level of cg12760995 in CASZ1 was associated with systolic (P_SMR = 1.74 x 10^–12), diastolic BP (P_SMR = 2.48 x 10^–10), and IS (odds ratio [OR] = 0.92 [95% confidence interval [CI]: 0.91–0.94]; P_SMR = 2.28 x 10^–8) in Europeans. The methylation levels of 17 sites in the promoter of CASZ1 were measured in the Chinese individuals, and 10 of them were significantly associated with IS. The higher methylation level of CASZ1 was associated with a lower risk of IS (adjusted OR = 0.97 [95% CI: 0.96–0.99]). CASZ1 seemed to be hypomethylated in hypertensive cases, and the level was negatively correlated with BP. Systolic and diastolic BP mediated approximately 61.2% (p = 3.49 x 10^–6) and 45.0% (p = 0.0029) of the association between CASZ1 methylation and IS, respectively.

This study identified DNA methylations that were associated with BP and IS. CASZ1 was hypomethylated in Chinese patients with hypertensive IS.