The effect of folic acid supplementation in the ovary and upon embryo development

Altered maternal nutrition around conception can affect oocyte and embryo development which influences later-life health outcomes. Low folate is related to poor reproductive outcomes. Folic acid (FA) supplementation and fortification have been effective strategies to avoid NTD. On the other hand, the FA levels in women of reproductive age are increased more than recommended, with unknown consequences. This project aims to determine the effect of high FA diet on the ovary and embryo development. C57BL/6 female mice at PND74 were fed with control (1mg FA/kg food) or high (5mg FA/kg food) FA diet for four weeks and culled at diestrus stage (PND102). In parallel, a group of animals were maintained on the control diet for another four weeks (PND130) or either mated and culled at 3.5 days post coitum (dpc). Ovaries and embryos were collected, RNA extracted and analysed by qPCR. Morphological and immunostaining analyses were also performed to determine the effect of FA in the ovary and blastocyst. High FA diet reduced expression of follicle developmental control genes at PND102 such as Fshr and Oct4, but also epigenetic writers like Ezh2 and Bmi1. In contrast, four weeks after FA diet release, the same genes were upregulated in the ovary. Females with a preconceptional high FA diet showed an increased mating period compared to the control group. The embryos of these mice showed reduced TE cells and lower expression of CDX2. In parallel, embryos exposed to high FA diet exclusively during preimplantation showed delayed development with decreased total cell number and lower expression of lineage markers (Oct4, NANOG and Gata6). High FA diet not only altered follicle growth factors during and after supplementation in a different pattern but also affected blastocyst biogenesis. This could impact on later-life health outcomes of the offspring.