Differential release of cell-signaling metabolites by male and female bovine embryos cultured in vitro

Abstract

Male and female early bovine embryos show dimorphic transcription that impacts metabolism. Individual release of metabolites was examined in a 24h single culture medium from Day-6 male and female morulae that developed to Day-7 expanded blastocysts. Embryos were produced in vitro, fertilized with a single bull and cultured in SOFaaci+6 g/L BSA. The embryonic sex was identified (amelogenin gene amplification). Embryos (N = 10 males and N = 10 females) and N = 6 blank samples (i.e. SOFaaci+6 g/L BSA incubated with no embryos) were collected from 3 replicates. Metabolome was analyzed by UHPLC-TOF-MS in spent culture medium. After tentative identification, N = 13 metabolites significantly (P < 0.05; ANOVA) differed in their concentrations between male and female embryos, although N = 10 of these metabolites showed heterogeneity (Levene's test; P > 0.05). LysoPC(15:0) was the only metabolite found at higher concentration in females (fold change [FC] male to female = 0.766). FC of metabolites more abundant in male culture medium (N = 12) varied from 1.069 to 1.604. Chemical taxonomy grouped metabolites as amino-acids and related compounds (DL-2 aminooctanoic acid, arginine, 5-hydroxy-l-tryptophan, and palmitoylglycine); lipids (2-hexenoylcarnitine; Lauroyl diethanolamide; 5,6 dihydroxyprostaglandin F1a; LysoPC(15:0); DG(14:0/14:1(9Z)/0:0) and triterpenoid); endogenous amine ((S)-N-Methylsalsolinol/(R)-N-Methylsalsolinol); n-acyl-alpha-hexosamine (N-acetyl-alpha-d-galactosamine 1-phosphate); and dUMP, a product of pyrimidine metabolism. Among the compounds originally contained in CM, female embryos significantly depleted more arginine than males and blank controls (P < 0.001). Male and female embryos induce different concentrations of metabolites with potential signaling effects. The increased abundance of metabolites released from males is consistent with the higher metabolic activity attributed to such blastocysts.