DNA methylation mediates the association between organochlorine pesticides and MASLD: An epigenome-wide association study with integrated AOP framework.

Chronic exposure to organochlorine pesticides (OCPs) is associated with altered DNA methylation and metabolic diseases, but their specific methylation patterns and mediating role in metabolic dysfunction-associated steatotic liver disease (MASLD) remain unclear. We conducted an epigenome-wide association study among 2905 adults, measuring 19 serum OCPs and blood DNA methylation using the Illumina EPIC array. Differentially methylated probes (DMPs) were identified via linear regression, and mediation analyses assessed their mediating effects on MASLD. We also constructed an integrated adverse outcome pathway (AOP) network to illustrate the underlying mechanisms. Eighteen novel OCP-associated DMPs were identified, of which 11 DMPs were related to prevalent MASLD and four to incident MASLD, with three overlapping (cg17075888, cg27402362, and cg11024682). In the cross-sectional analysis, eight DMPs (e.g., ABCG1, CPT1A, SREBF1) statistically mediated 15.90% of the association between β-HCH and prevalent MASLD. Furthermore, the longitudinal analysis provided stronger evidence, suggesting that cg27402362 (RUNX3) mediated 5.22% of the β-HCH and incident MASLD association. The AOP network included six molecular initiating events and 19 key events, implicating lipid metabolism, oxidative stress, and immune and inflammatory pathways. This study provides novel population-based evidence that OCP exposure may be associated with MASLD development through DNA methylation mechanisms. The AOP framework further strengthens the mechanistic plausibility of OCP-induced hepatotoxicity and improves our understanding of OCP-associated MASLD.