There is growing evidence that in utero and early developmental exposures to environmental chemicals may play a role in the development of obesity and related metabolic diseases later in life. Endocrine disrupting compounds are exogenous substances that mimic endogenous hormones in the endocrine pathway. Bisphenol-A (BPA) is a chemical plasticizer and xenoestrogen used in the production of polycarbonate plastics and epoxy resins. Human exposure to BPA is ubiquitous at low levels and occurs primarily through the diet. Studies in our laboratory and other investigators have shown that exposure of rodents to BPA during pregnancy results in increased adiposity and impaired glucose tolerance in adulthood. An important mechanism for in utero and early developmental effects of BPA is thought to be altered epigenetic regulation of gene expression. In support of this hypothesis is our preliminary data in mouse that BPA exposure during pregnancy results in loss of imprinting at two genes critical for development and obesity, Igf2 and Snrpn, in the embryo and placenta. These findings lead us to hypothesize that BPA exposure during development alters the epigenetic profile in key cells including the germline, resulting in altered gene expression, an abnormal phenotype, and transgenerational transmission of the phenotype. Other than the placenta, we cannot obtain target tissues such as islets, liver, or fat from humans during development. Thus an animal model can provide insight into mechanisms that can be later explored in the human. We propose the following specific aims:
Specific Aim 1 will assess the epigenome of F1 offspring exposed to BPA in utero as well as the F2-F3 generations. In addition to testing the expression and DNA methylation of imprinted genes, we will assay genome-wide DNA methylation changes and key histone modifications in F1-F3 offspring. The F1-F3 generations will also be metabolically phenotyped and germline of F2 and F3 epigenetically assayed.
Specific Aim 2 will ascertain whether BPA exposure of males during puberty and early adulthood alters the germline and leads to transgenerational transmission of an altered epigenotype and abnormal phenotype.
In Specific Aim 3 we will determine whether low dose BPA exposure in combination with DEHP, and vinclozolin alters the epigenome in the germline and leads to transgenerational transmission of an abnormal phenotype. Through the comprehensive analyses in the in vivo model, the results of the proposed project will build a solid standard for extrapolation of effects and mode of action to other classes of endocrine disrupting chemicals that are present in food and are identified as potential inducers of obesity and related metabolic diseases later in life. The proof of the principle of prenatal programming by environmental contaminants may change our awareness of critical assessment of the risk of such compounds.
The proposed studies will provide new information regarding the association of BPA exposure with epigenetic changes and adverse phenotypes in the adult and whether these changes can be transmitted transgenerationally. The work will also assess the effects of combinations of endocrine disrupting compounds. The results of these studies will impact our assessment of risks due to environmental exposure of endocrine disrupting compounds.