Alpha-ketoglutarate restraints the mitochondrial DNA reprogramming impairing the first events of cell differentiation in bovine embryos

During the pre-implantation embryonic development, metabolic and epigenomic remodeling are crucial events that can be significantly impacted even by minor environmental changes. Right after fertilization, nuclear DNA undergoes demethylation, reaching the lowest levels at the 8-16 cell stage, marking the onset of mitochondrial metabolism and genome activation. This coincides with de novo DNA methylation events guiding cell lineage differentiation at the blastocyst stage. High levels of alpha-Ketoglutarate (AKG) in cancer and pluripotent stem cells promote a more undifferentiated state, acting as a cofactor for TET demethylases. In this study we examined the metaboloepigenetic adaptations from AKG supplementation during the in vitro culture in a bovine model. AKG during the early stages of development led to the expected increase in the activity of TET family enzymes, resulting in a decrease in nuclear 5mC levels. Additionally, the blastocysts derived from the AKG group exhibited reduced mitochondrial activity in the inner cell mass (ICM), along with increased methylation levels of mitochondrial DNA which, surprisingly, led to hypomethylation and upregulation of genes related to the trophectoderm. These results indicate that minor metabolic alterations early in development, such as AKG supplementation, have a significant impact on the embryo's metabolism and molecular control, compromising the differentiation process and future development.