Bioscientifica Proceedings

Summary. The progress in understanding the metabolism of the ruminant cumulus-oocyte complex (COC) from large antral follicles has progressed significantly in the past decade. In particular, new insights in the importance of lipid metabolism, ß-oxidation and its relationship to oxidative phosphorylation within oocytes have emerged. This provides opportunities for tapping into the potential yield of ATP from lipid metabolism, as ATP content is a major determinant of oocyte competence. However, this new appreciation of lipid metabolism also includes the damaging influence of some free-fatty acids, the non-esterified fatty acids, which are particularly high in the follicular fluid of dairy cows during peak lactation. Historically, studies have focussed on carbohydrate metabolism, which occupies a central significance, especially for cumulus cell metabolism. Glucose has multiple roles; one still largely unexplored is its requirement for extracellular matrix production, via the hexosamine biosynthesis pathway. The availability of oxygen for oocytes in large antral follicles remains to be resolved, and requires new tools to measure intra-follicular O₂ levels to determine its significance. For in vitro oocyte maturation, new strategies for improving oocyte competence includes: cAMP management, oocyte secreted factor supplementation, protection against reactive oxygen species with glutathione, and utilizing the endogenous maturation signalling molecules, the EGF-like peptides, during maturation - all of which influence metabolism. The introduction of existing platforms, such as metabolomics, to ruminant oocyte metabolism will broaden our understanding. Ultimately, to appreciate the dynamic nature of metabolism in oocytes of all species requires the development of new nano-scale sensing platforms that will allow us to measure activity in single oocytes and early embryos in situ in real time.

© 2014 Society for Reproduction and Fertility