Abstract P146: Telomere Length, DNA Methylation, and Risk of Cardiovascular Diseases: Meta-EWAS of Four Multi-ethnic Prospective Cohorts
Authors: Subedi Pooja , Qin Huaizhen , Cole Shelley A , Plaza Maria T , Domingo-Relloso Arce , Haack Karin , Fallin Danielle , Tang Wan-Yee , Liu Simin , Needham Belinda L , Lee Elisa T , Umans Jason G , Howard Barbara V , Liu Yongmei , Aviv Abraham , Levy Daniel , Vasan Ramachandran S , Navas-Acien Ana , Zhao Jinying 
Published: March 2020

Background:
Biological aging assessed by both leukocyte telomere length (LTL) and DNA methylation (DNAm) has been associated with CVD and its risk factors. Moreover, LTL is epigenetically regulated. We hypothesized that LTL-associated epigenetic changes are associated with risk of CVD in the community.

Objective:
To test whether LTL-associated loci are associated with incident CVD, independent of standard risk factors in multi-ethnic cohorts.

Method:
We evaluated 3,628 participants with complete LTL and DNAm data in four prospective cohorts, including 1,531 American Indians from the Strong Heart Study (SHS, mean age 56, 60% women), 821 non-Hispanic Whites (NHW) from the Framingham Heart Study (FHS, mean age 60, 51% women), 471 NHW, 150 Hispanics, and 162 African Americans from the Multi-ethnic Study of Atherosclerosis (MESA, mean age 70 , 55% women), and 471 NHW and 342 African Americans from the Women’s Health Initiative (WHI, mean age 65 , all women). LTL was quantified by qPCR (SHS, MESA) or Southern blot (FHS, WHI). DNAm was assayed by Illumina EPIC (SHS) or 450K (FHS, MESA and WHI) arrays. We imputed 450K to 850K using random forest algorithms. CVD events included fatal and nonfatal MI, CHD, heart failure, stroke, peripheral artery diseases, and cardiovascular deaths. Cohort-specific EWAS was conducted to identify CpGs associated with LTL, adjusting for age, sex, race/ethnicity, smoking, alcohol, BMI, site, cell proportion, and batch. Multiple testing was Bonferroni-corrected (genome-wide
P
< 2.4 x10
-7
). Results across studies were combined by random-effects meta-analysis. To examine whether LTL-associated epigenetic loci are associated with CVD risk, we used a weighted methylation score to predict incident CVD by Cox regression, adjusting for age, sex, site, smoking, alcohol, BMI, glucose, SBP, LDL-C, and total cholesterol.

Results:
We ascertained 2,001 CVD events, including 986 in the SHS (average follow-up 15.2 years), 208 in FHS (average follow-up 7.7 years), 74 in MESA (average follow-up 4.9 years), and 733 in WHI (average follow-up 12.2 years). Meta-EWAS identified 22 CpGs (mapped to 17 unique genes) associated with LTL. Of these, 19 loci (15 negatively and 4 positively associated with LTL) had consistent directionality of association across four cohorts. The most significant genes harboring altered CpG sites included
TLL2
(cg10549018,
P=
2.42 x 10
-12
) and
TPST1 (
cg10691866,
P
=8.6 x 10
-10
). A higher composite methylation score, which reflects longer LTL (
P
<0.0001), was significantly associated with a reduced risk of CVD in the SHS (HR=0.16, 95% CI: 0.07–0.37), FHS (HR=0.08, 95% CI: 0.01–0.40), and WHI (HR=0.32, 95%CI: 0.13–0.82), but not MESA (HR=0.47, 95% CI: 0.04–5.09).

Conclusion:
Altered DNA methylation at 19 CpG loci was significantly associated with LTL. Their combined effects may predict a reduced risk of CVD. The observed associations warrant further investigation.