Utilization of glucose and fructose in bovine embryos assessed by metabolic flux analysis

¹³C Metabolic flux analysis (¹³C MFA) is a non-invasive methodology for the measurement of fluxes (rates of carbon flow) throughout a metabolic network and can be used to determine nutrient contributions to central metabolic pathways. ¹³C MFA was used in a systemic metabolic investigation of the nutritional physiology of preimplantation bovine blastocysts. Bovine blastocysts were cultured either singly or in groups of five in 40 μl of medium containing ¹³C labeled glucose and/or fructose, and the metabolites expelled into the spent media were identified through ¹³C MFA of heavy isotope labeling. Similarly, the metabolites in spent media following culture of a bovine trophectoderm cell line (CT-1) were monitored. Flux maps generated using ¹³C MFA suggest that less than 10 % of metabolites from the glycolytic pathway were diverted to the pentose phosphate pathway or the tricarboxylic acid cycle in either bovine blastocysts or CT-1 cells with the majority of the hexose (70-80 %) resulting in pyruvate and lactate production.