Integrated profiling of semen microbiota and metabolome reveals dysregulation in primary idiopathic male infertility.

BACKGROUND: Primary idiopathic male infertility remains a significant challenge due to its complex etiology and the lack of effective diagnostic tools. This study characterized seminal microbiota and metabolome alterations in this condition and their association with sperm quality, aiming to identify potential biomarkers. METHODS: We conducted an integrated microbiota-metabolome profiling study, enrolling 26 men with primary idiopathic infertility and 14 fertile controls. Semen samples were evaluated according to WHO guidelines. Microbiota composition was assessed by 5R 16S rRNA sequencing, and metabolites were profiled using an untargeted liquid chromatography-mass spectrometry (LC-MS) metabolomics approach. Statistical analyses included diversity assessment, differential abundance testing, correlation analysis, and ROC curve evaluation for potential biomarkers. RESULTS: Infertile men exhibited significantly lower seminal microbiota α-diversity, with 45 differentially abundant taxa identified. Metabolomics identified 147 differentially expressed metabolites (DEMs). Four DEMs (γ-Glu-Tyr, Indalone, Lys-Glu, γ-Glu-Phe) showed exceptional diagnostic potential (AUC > 0.97). Providencia rettgeri, Pediococcus pentosaceus, and Streptococcus pneumoniae abundance correlated positively with sperm quality, whereas Proteus penneri correlated negatively. Metabolites Arg-Arg, Fumarate, and Lpc 18:2 positively correlated with sperm motility, whereas Lys-Glu and Indalone showed negative correlations. CONCLUSION: This integrated analysis reveals distinct dysbiosis of the seminal microbiota and metabolic disruptions in idiopathic male infertility, offering novel insights into its mechanisms and biomarker discovery.