Integrated metabolomic and microbiota analysis of semen: seasonal and morphological associations

Recent studies have begun to investigate the metabolic and microbiota profiles in semen, yet their association with abnormal sperm morphology, particularly in teratozoospermia, remains insufficiently characterized. Identifying specific metabolites and microbial taxa linked to this condition could improve diagnostics and management for male infertility. This study analyzed semen samples from 231 patients, including 30 patients with teratozoospermia and 30 patients with normal sperm morphology, collected over four seasons in Chongqing, China. Metabolomic profiling by gas chromatography-mass spectrometry (GC-MS) and microbiota composition analysis via 16S ribosomal ribonucleic acid (rRNA) sequencing revealed distinct seasonal metabolomic shifts, with significant changes in summer and autumn. After excluding seasonally affected metabolites, 14 key metabolites were associated with teratozoospermia, including reduced levels of 4-hydroxyphenylpyruvic acid, phenylpyruvic acid, and N-acetyl-L-aspartic acid. These metabolites are involved in pathways related to oxidative stress and energy metabolism in spermatozoa, suggesting that their depletion may contribute to sperm abnormalities. Proteobacteria, Firmicutes, and Actinobacteriota were predominant phyla across all seasons and groups, but significant genus-level fluctuations, such as Acinetobacter and Staphylococcus, were observed. In teratozoospermia, genera such as Lactobacillus and Limnochordaceae showed differential abundance, correlating with key metabolites and suggesting potential functional interactions. Limnochordaceae showed a significant positive correlation with undecanoic acid, whereas Lactobacillus showed a negative correlation. These findings highlight that while seasonal changes significantly influence semen metabolomics and microbiota composition, teratozoospermia is characterized by specific, season-independent metabolic and microbial signatures. Our study provides insights into the metabolic and microbial dynamics of semen, suggesting the possibility of developing novel diagnostic tools and therapeutic strategies for male infertility.