DNA methylation informs adult cardiovascular risk and prevention for low birthweight individuals.

Background: Barker's hypothesis posits that adverse in utero exposures, often reflected by low birthweight, increase adult cardiovascular disease (CVD) risk. However, underlying mechanisms remain unclear; identifying potentially causal mediators is crucial for developing effective interventions. Emerging research suggests epigenetic modifications may influence CVD traits from early life. We aimed to identify DNA methylation (DNAm) signatures that mediate birthweight and CVD traits and to establish their biological relevance across three developmental time points using multi-omics integration. Methods: We identified DNAm mediators using epigenetic Mendelian randomisation (MR). The exposures were 261 birthweight-associated CpG sites (BW-CpGs) from epigenome-wide association studies, instrumented by cis-methylation quantitative trait loci (cis-mQTLs) in European-ancestry participants from the Accessible Resource for Integrative Epigenomic Studies measured at three developmental time points: birth (mean gestational age = 40 weeks), childhood (mean age = 7.49 years), and adolescence (mean age = 17.14 years). The outcomes included adult cardiovascular events and lipid traits from genome-wide association studies (n = 98,048-547,261). Sensitivity analyses included colocalisation, Steiger's test, Cochran's Q, and pleiotropy-robust methods. We interrogated DNAm persisting across development using omics datasets. Results: Using cis-mQTLs measured at birth, we found 230 associations between 216 BW-CpGs and CVD traits, including coronary artery disease, hypertension, stroke, cholesterol, and triglycerides (false discovery rate-corrected P < 0.05), with effect size directions consistent with Barker's hypothesis. A total of 42 associations were robust following sensitivity analyses. Persistent DNAm changes across development were observed at ASGR1 and KDM2B. Multi-omics interrogation prioritised a promising therapeutic candidate (ASGR1). Conclusions: Although Barker's hypothesis is well-established, this is the first study to explore its causal pathway using a rigorous, multi-time-point epigenetic MR framework with multi-omic integration. This represents a major advancement over previous observational and DNAm studies. The Barker-consistent hypothesis-free discovery approach identified novel and known candidate genes that, with future validation, may serve as therapeutic targets, identify high-risk individuals, and support clinical trial recruitment.