Folate supplementation during oocyte maturation positively impacts the folate-methionine metabolism in pre-implantation embryos.

Folic acid is vital for DNA synthesis and methylations through one-carbon (C1) metabolism. Thus, it is essential for cell division during embryonic development. Although the oocytes contain endogenous pool of folates for development, the present study investigated the effect of external folic acid supplementation on oocyte maturation, blastocyst development and the expression of folate transporters as well as folate metabolism enzymes in oocytes and pre-implantation embryos of goat. Immature goat oocytes, matured in maturation medium comprising different folic acid concentrations (0, 10, 50, 100 and 150 μM), were in vitro fertilized and cultured. Cumulus expansion markers (PTX3 and PTGS2) in cumulus cells were highly upregulated after 50 μM folic acid supplementation indicating higher degree of maturation. Supplementation of 50 μM folic acid during oocyte maturation resulted in significantly higher blastocyst production rate, reduction in intracellular ROS levels as well as upregulation of the transcripts for folate transporters and key folate-methionine cycle enzymes in comparison to control. The present study demonstrates the existence of active folate-methionine cycle in oocytes and pre-implantation goat embryos. Supplementation of 50 μM folic acid in maturation medium improves oocyte maturation, the blastocyst production rate, reduces ROS production as well as upregulate the expression of FOLR1 and folate metabolism enzyme, MTR.