Spent culture medium analysis from individually cultured bovine embryos demonstrates metabolomic differences

Spent culture medium can provide valuable information regarding the physiological state of a bovine preimplantation embryos through non-invasive analysis of the sum/depleted metabolite constituents. Metabolomics has become of great interest as an adjunct technique to morphological and cleavage-rate assessment, but more importantly, in improving our understanding of metabolism. In this study, in vitro produced bovine embryos developing at different rates were evaluated using proton nuclear magnetic resonance (1H NMR). Spent culture medium from individually cultured embryos (2-cell to blastocyst stage) were divided into two groups based on their cleavage rate fast growing (FG) and slow growing (SG; developmentally delayed by 12-24 h), then analyzed by a 600 MHz NMR spectrometer. Sixteen metabolites were detected and investigated for sum/depletion throughout development. Data indicate distinct differences between the 4-cell SG and FG embryos for pyruvate (P < 0.05, n = 9) and at the 16-cell stage for acetate, tryptophan, leucine/isoleucine, valine and histidine. Overall sum/depletion levels of metabolites demonstrated that embryos produced glutamate, but consumed histidine, tyrosine, glycine, methionine, tryptophan, phenylalanine, lysine, arginine, acetate, threonine, alanine, pyruvate, valine, isoleucine/leucine, and lactate with an overall trend of higher consumption of these metabolites by FG groups. Principal component analysis revealed distinct clustering of the plain medium, SG, and FG group, signifying the uniqueness of the metabolomic signatures of each of these groups. This study is the first of its kind to characterize the metabolomic profiles of SG and FG bovine embryos produced in vitro using 1H NMR. Elucidating differences between embryos of varying developmental rates could contribute to a better understanding of embryonic health and physiology.