Epigenetics of type 2 diabetes and diabetes-related outcomes in the Strong Heart Study

Background: The prevalence of type 2 diabetes has dramatically increased in the past years. Increasing evidence supports that blood DNA methylation, the best studied epigenetic mark, is related to diabetes risk. Few prospective studies, however, are available. We studied the association of blood DNA methylation with diabetes in the Strong Heart Study. We used limma, Iterative Sure Independence Screening and Cox regression to study the association of blood DNA methylation with fasting glucose, HOMA-IR and incident type 2 diabetes among 1312 American Indians from the Strong Heart Study. DNA methylation was measured using Illumina's MethylationEPIC beadchip. We also assessed the biological relevance of our findings using bioinformatics analyses. Results: Among the 358 differentially methylated positions (DMPs) that were cross-sectionally associated either with fasting glucose or HOMA-IR, 49 were prospectively associated with incident type 2 diabetes, although no DMPs remained significant after multiple comparisons correction. Multiple of the top DMPs were annotated to genes with relevant functions for diabetes including SREBF1, associated with obesity, type 2 diabetes and insulin sensitivity; ABCG1, involved in cholesterol and phospholipids transport; and HDAC1, of the HDAC family. (HDAC inhibitors have been proposed as an emerging treatment for diabetes and its complications). Conclusions: Our results suggest that differences in peripheral blood DNA methylation are related to cross-sectional markers of glucose metabolism and insulin activity. While some of these DMPs were modestly associated with prospective incident type 2 diabetes, they did not survive multiple testing. Common DMPs with diabetes epigenome-wide association studies from other populations suggest a partially common epigenomic signature of glucose and insulin activity. The Strong Heart Study was supported by Grants from the National Heart, Lung, and Blood Institute (NHLBI) (contract numbers 75N92019D00027, 75N92019D00028, 75N92019D00029 and 75N92019D00030) and previous Grants (R01HL090863, R01HL109315, R01HL109301, R01HL109284, R01HL109282 and R01HL109319 and cooperative agreements: U01HL41642, U01HL41652, U01HL41654, U01HL65520 and U01HL65521) and by the National Institute of Environmental Health Sciences (Grant numbers R01ES021367, R01ES025216, P42ES033719, P30ES009089). ADR was supported by a fellowship from “la Caixa” Foundation (ID 100010434) (fellowship code “LCF/BQ/DR19/11740016”). MTP was supported by the Strategic Action for Research in Health sciences (PI15/00071) and CIBERCV, which are initiatives from Instituto de Salud Carlos III and the Spanish Ministry of Science and Innovation and co-funded with European Funds for Regional Development (FEDER), by the Third AstraZeneca Award for Spanish Young Researchers and by the State Agency for Research (PID2019-108973RB-C21). The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health (USA) or the National Health Institute Carlos III (Spain). The funders had no role in the planning, conducting, analysis, interpretation or writing of this study. Sí