Maternal obesogenic diet-induced changes in embryo and fetal DNA methylation programming

PROJECT SUMMARY Obesity in reproductive-age women has sharply increased over the past few decades and is expected to continue to rise for the foreseeable future. Besides a greater likelihood of pregnancy complications, such as preeclampsia and preterm birth, obese women are also more likely to experience severe pregnancy outcomes, including maternal death. In obese women undergoing infertility treatment, reports of poor/delayed ovarian stimulation, a higher frequency of in vitro fertilization (IVF) failure, and defects in placentation suggest that obesity negatively affects multiple reproductive processes, but the mechanisms remain largely unknown. Studying these events in humans is difficult due to ethical and technical limitations, as well as the challenge of controlling for confounding environmental factors. Through a National Centers for Translational Research in Reproduction and Infertility (NCTRI) grant, a cohort of rhesus macaque females receiving either a low-fat control diet or a high-fat Western- Style Diet (WSD) was established to study the adverse effects of obesity and diet on reproductive function. Fertility trials conducted with these females demonstrated that WSD consumption delayed the time to pregnancy and was associated with multiple placental abnormalities. Each female then underwent an IVF cycle to determine the impact of maternal diet on preimplantation embryogenesis. Blastocyst formation was significantly reduced in the WSD group and preliminary RNA-seq data from these blastocysts revealed altered expression of genes involved in critical peri-implantation processes. Considering the important role of epigenetic modifications in regulating gene expression changes during embryonic and fetal development, here we propose to investigate how maternal WSD-induced metabolic dysfunction impairs developmental programming at the molecular level and whether it can be reversed after resuming a low-fat diet. First, we will assess if there are alterations in DNA methylation, gene expression, and/or chromosome fidelity in preimplantation embryos from female macaques with increased adiposity and insulin resistance induced by WSD exposure. By examining changes that persist after a short versus long-term diet reversal, we will also determine whether it is a dietary intervention or overt weight loss that can improve IVF outcomes (Aim 1). Secondly, we will utilize the fetal thymus, spleen, liver, and kidney collected from low-fat diet and WSD-fed mothers during the NCTRI fertility trial to determine how maternal diet and metabolism influences DNA methylation and gene expression across fetal tissues. Comparing these results to the placenta, as well as maternal and cord blood, from the same subjects will help identify epigenetic signatures that are trans-generationally shared versus fetus-specific (Aim 2). Further comparison of DNA methylation and gene expression between embryos and fetuses will reveal genomic regions that are not only important for development, but also susceptible to adverse metabolic conditions. Findings from this study will provide insight into developmental reprogramming of the embryo, fetus, and placenta, as well as the reproductive consequences of stable DNA methylation changes induced by a maternal WSD.