Objective: To investigate the difference in the levels of metabolites in the seminal plasma exosomes (SPE) of men with a high sperm DNA fragmentation index (DFI) from those with a low DFI.
Methods: We performed a sperm exosomal metabolomics analysis of 5 healthy married men with DFI ≤15% (the control group) and another 5 with DFI ≥30% and matched in marital status, age and body mass index with the controls (the case group). Using high-performance liquid chromatography and mass spectrum, we examined the metabolites, observed their difference, and analyzed the metabolite enrichment pathway by Kyoto encyclopedia of genes and genomes (KEGG). According to the inclusion and exclusion criteria, we also selected 11 men in the control group and 20 men in the case group, and detected the differences in the seminal plasma amino acid and carnitine between the two groups using liquid measurement systems.
Results: After primary and secondary analyses and qualified screening, 23 metabolites related to sperm DNA integrity were obtained, including 9 organic acids, 2 amino acid intermediate metabolites, and 11 acylcarnitine, purine, niacin and other intermediate products. KEGG enrichment analysis showed that 23 metabolites were mainly involved in the sphingoid signaling pathway, niacin and niacinamide metabolic pathway, and arginine and proline metabolic pathway. Further verification revealed no difference in the level of seminal plasma amino acid between the two groups, and significantly lower levels of seminal plasma acylcarnitine, free carnitine, propionylcarnitine, 3-hydroxybutyrylcarnitine and malonylcarnitine, 3-hydroxyisovalerylcarnitine and succinylcarnitine, and isoamyl (enylcarnitine) in the case group than in the controls (P<0.05).
Conclusion: There are significant differences in the levels of the metabolites organic acids, amino acids and acylcarnitine in the SPE of males with a high DFI from those with a low DFI. The level of seminal plasma acylcarnitine is significantly correlated with sperm DFI, which can be used as an indicator in quantitative and rapid assessment of the degree of sperm DNA damage.
Keywords: seminal plasma exosome; DNA damage; sperm DNA fragmentation index; metabolomics; acylcarnitine.