180 Glucose versus fatty acids: Different energy supplies for the bovine oocyte

Studies show that optimal concentrations of fatty acids (FA) and glucose are crucial for proper oocyte development, maturation, and further embryo quality support (Sutton McDowall et al. 2010 Reproduction 139, 685-95, https://doi.org/10.1530/REP-09-0345; Sutton McDowall et al. 2014 Theriogenology 82, 95-103, https://doi.org/10.1016/j.theriogenology.2014.03.011). A balance between metabolism of FA and glucose in oocytes needs to be maintained; however, it is not clear what the preferable pathway of energy production is and how it affects the oocyte. The aim of the experiment was to selectively block pathways of either glucose or FA metabolism during IVM of bovine oocytes to reveal changes within oocyte lipid droplets (LD) under crucial changes in energy metabolism. Cumulus-oocyte complexes were matured under standard conditions (Warzych et al. 2007Mol. Reprod. Dev. 74, 280-289; https://doi.org/10.1002/mrd.20610) without FA and glucose supplementation. The experimental groups were (1) control (IVM in basic medium), (2) group with inhibited glucose metabolism [supplementation with 1.5 µM iodoacetate (IO, inhibitor of glycolysis) and 150 µM dehydroepiandrosterone (DHEA, inhibitor of pentose phosphate pathway)], and (3) group with inhibited FA metabolism (150 µM etomoxir supplementation, ETO). Oocytes after 24h of IVM were stained with boron-dipyrromethene (BODIPY) 493/503 dye (lipid droplets) and 4′,6-diamidino-2-phenylindole (DAPI; chromatin) and analysed using a confocal microscope (LSM 880 AiryScan FAST; Zeiss). Obtained data were analysed using the Kruskal-Wallis test. The MII rate decreased to 60.5% for IO+DHEA (P