Abstract
BackgroundSubfertility decreases the efficiency of the cattle industry because artificial insemination employs spermatozoa from a single bull to inseminate thousands of cows. Variation in bull fertility has been demonstrated even among those animals exhibiting normal sperm numbers, motility, and morphology. Despite advances in research, molecular and cellular mechanisms underlying the causes of low fertility in some bulls have not been fully elucidated. In this study, we investigated the metabolic profile of bull spermatozoa using non-targeted metabolomics. Statistical analysis and bioinformatic tools were employed to evaluate the metabolic profiles high and low fertility groups. Metabolic pathways associated with the sperm metabolome were also reported.ResultsA total of 22 distinct metabolites were detected in spermatozoa from bulls with high fertility (HF) or low fertility (LF) phenotype. The major metabolite classes of bovine sperm were organic acids/derivatives and fatty acids/conjugates. We demonstrated that the abundance ratios of five sperm metabolites were statistically different between HF and LF groups including gamma-aminobutyric acid (GABA), carbamate, benzoic acid, lactic acid, and palmitic acid. Metabolites with different abundances in HF and LF bulls had also VIP scores of greater than 1.5 and AUC- ROC curves of more than 80%. In addition, four metabolic pathways associated with differential metabolites namely alanine, aspartate and glutamate metabolism, β-alanine metabolism, glycolysis or gluconeogenesis, and pyruvate metabolism were also explored.ConclusionsThis is the first study aimed at ascertaining the metabolome of spermatozoa from bulls with different fertility phenotype using gas chromatography-mass spectrometry. We identified five metabolites in the two groups of sires and such molecules can be used, in the future, as key indicators of bull fertility.
Highlights
Subfertility decreases the efficiency of the cattle industry because artificial insemination employs spermatozoa from a single bull to inseminate thousands of cows
We reported the identification of 63 compounds in bull seminal plasma by using gas chromatography-mass spectroscopy (GC-MS)
Metabolome profile of bull spermatozoa Twenty-two metabolites were structurally identified in the bull spermatozoa, regardless of fertility phenotype of the animals
Summary
Subfertility decreases the efficiency of the cattle industry because artificial insemination employs spermatozoa from a single bull to inseminate thousands of cows. Metabolic pathways associated with the sperm metabolome were reported. Some studies reported that a significant percentage of reproductive failure (i.e., low numbers of pregnant females) is caused by the low fertilizing. The complex nature of events involved in fertilization is affected by the fluctuating concentrations of macromolecules found in the spermatozoon itself [11, 12], seminal plasma [13], and by the microenvironment of female reproductive tract [14]. Several studies have reported that seminal plasma proteins improve the fertilizing capacity of sperm [15,16,17,18,19]. Growing evidence suggests that spermatozoa metabolize a wide spectrum of exogenous substrates that directly or indirectly regulate the signaling pathways involved in sperm motility, hyperactivation, capacitation, acrosome reaction, and sperm-oocyte fusion [26]
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