Metabolic enhancement of the one carbon metabolism (OCM) in bovine oocytes IVM increases the blastocyst rate: evidences for a OCM checkpoint

Abstract

The one carbon metabolism (OCM) has a primary role in the process of oocyte maturation. In this study bovine oocytes were cultured for 24 h, up to MII stage, with standard medium supplemented or not with 8 metabolic enhancers of the OCM and the MII and blastocyst rate were compared. Additional analyses were performed on matured oocytes, cumulus cells, zygotes and blastocysts. The OCM supplementation increased the blastocyst rate derived from in vitro fertilization. The mitochondrial mass and DNMT3a protein expression were increased whereas DNA fragmentation decreased in matured oocytes. DNA methylation in female pronucleus of zygotes was increased. The supplementation did not directly affect the redox balance as ROS and GSH in matured oocytes and homocysteine in the spent medium were unchanged. The supplementation of the oocytes with metabolic enhancers of the OCM may increase the yield from the culture, likely due to improved DNA methylation and epigenetic programming. The lack of effects on MII rate with huge differences appearing at the blastocyst stage suggest the existence of a OCM metabolic check point that hampers oocytes progression to blastocyst post-fertilization, if they were not properly primed at the time of maturation.

Follicular homocysteine as a marker of oocyte quality in PCOS and the role of micronutrients

“…In spite of no detectable differences in oocyte number, maturation and fertilization, the zygotes from supplemented follicles resulted in a blastocyst rate that was almost double the one in their controls. Our experimental model does not allow to infer on the reasons for this difference; however, these findings overlap with the one resulting from a recent study based on the use of comparable amounts of the same micronutrients supplemented during the 24-h in vitro maturation of bovine oocytes [ 23 ]. Also, in this case, after overlapping maturation and fertilization rate, the supplemented oocytes exerted a double blastocyst rate as compared to their controls (32.5% vs 15.7%; p < 0.001).…”

Heat-Stress Impacts on Developing Bovine Oocytes: Unraveling Epigenetic Changes, Oxidative Stress, and Developmental Resilience

“…Thus, our results completely align with the previously reported finding. In addition, it has been shown that the addition of one-carbon metabolism (OCM) enhancers during oocyte maturation significantly increased oocyte mitochondrial mass, DNMT3A protein expression, and blastocyst rate, possibly due to improved epigenetic programming [30]. OCM consists of three related pathways: the folate and methionine cycles, and the trans-sulphuration pathway [30].…”