Effect of Energy Substrate Dynamics on Mitochondrial Activity and Oxidative Stress Levels of in vitro Maturing Bovine Oocytes

This study was conducted to explore the effect of energy substrates in the culture medium during in vitro maturation of bovine oocytes. A modified TCM199 medium (M-7528) was used to mature bovine oocytes in vitro. Oocytes were supplemented with different pyruvate (0.1, 0.2, 0.4 mM) and glucose (1.5, 5.6, 20.0 mM) concentrations for 48 hours at 38.5 °C under 5% CO2 atmosphere with 95% humidity. Their maturity was checked at 24 and 48 hours. After 48 hours, the denuded oocytes were stained with fluorescent dye JC-1 and avidin-FITC. Fluorescent dye JC-1 is a membrane permeable to the cell and would indicates membrane activity or its organization. Fluorescence intensity of avidin-FITC determination using corrected total cell fluorescence (CTCF) expressed oxidative stress level. There is a significant contribution of energy substrates towards oocyte maturation. Pyruvate at 0.2 mM produced mature oocytes with a diameter of ≥ 120 μm, promoted oocytes maturation to metaphase II (MII) stage faster and reduced cell’s oxidative stress levels. In comparison, 5.6 mM glucose is the optimum concentration for glucose to reduce cell stress level. Unfortunately, this concentration only produced mature oocytes with a small diameter of up to 116 μm. All changes were significant at the level of p < 0.05. As a conclusion, pyruvate at 0.2 mM is the optimum concentration for in vitro maturation after taking cell’s stress level into consideration.