Developmental programming: Differing impact of prenatal testosterone and prenatal bisphenol-A -treatment on hepatic methylome in female sheep

Steroid hormones are integral to pregnancy and fetal development, regulating processes such as metabolism, inflammation, and immune responses. Excessive prenatal steroid exposure, through lifestyle choices or environmental chemicals, can lead to metabolic dysfunctions in offspring. The research focuses on how exposure to testosterone (T) and bisphenol A (BPA) affects the liver's DNA methylome, a key component of the epigenome influencing long-term health. Using Suffolk sheep, the study involved two cohorts: one exposed to prenatal-T and the other to prenatal-BPA. Whole genome bisulfite sequencing was employed to map DNA methylation across over 22 million CpG sites. Regions with p-value<10^-4 and a magnitude of difference of at least 5 % methylation between groups were considered differentially methylated. Results demonstrated substantial differential methylation in the liver tissues due to both treatments, with prenatal-T causing unique epigenetic modifications distinct from those induced by prenatal-BPA. Specifically, prenatal-T treatment resulted in 53 differentially methylated regions (DMRs), of which 31 were located in gene regions, including exons. Prenatal-BPA exposure led to 32 DMRs, with 22 associated with gene regions. These modifications were associated with genes governing lipid and glucose metabolism, potentially underlying the observed metabolic disruptions such as insulin resistance and dyslipidemia. Pathway analysis revealed that genes differentially methylated due to prenatal-T were involved in cellular organization, while those affected by prenatal-BPA were enriched in signal regulation pathways. The findings underscore how prenatal exposure to steroid excess and steroid-mimics influence epigenetic landscapes, contributing to metabolic disease programming.