Alterations in the protein lactylation landscape of sperm from patients with varicocele-associated asthenozoospermia.

BACKGROUNDS: Varicocele is a leading cause of male infertility, primarily manifesting as asthenozoospermia. The underlying molecular mechanisms remain unclear, and the potential role of protein lactylation in this condition is unknown.

METHODS

We performed a comprehensive lactylome analysis using data-independent acquisition (DIA) mass spectrometry on paired sperm samples collected from patients with varicocele-associated asthenozoospermia before and after treatment. Differential lactylation analysis and bioinformatic enrichment analyses were conducted.

RESULTS

Disrupted lactate metabolism was observed in asthenozoospermic sperm, with decreased intracellular L-lactate and elevated seminal plasma L-lactate. This was concomitant with a global reduction in protein lactylation, particularly in the sperm midpiece and tail. Lactylome profiling identified 2,699 lactylation sites on 1,216 proteins. Comparison of pre- and post-treatment samples revealed 133 differentially lactylated proteins, which were significantly enriched in pathways critical for sperm motility, including glycolysis/gluconeogenesis, microtubule-based movement, and flagellar assembly. Notably, lactylation abundance of key proteins (TEKT3, AKAP4, TUBA1A, AKAP3, TUBB4B) were significantly downregulated.

CONCLUSIONS

This study presents an initial characterization of the protein lactylation landscape in human sperm, revealing​ its alteration in the context of varicocele-associated asthenozoospermia. The findings suggest that dysregulation of the lactate-lactylation axis correlates with impaired sperm motility, potentially through concurrent alterations in energy metabolism and flagellar structure. This correlation underscores specific lactylation events that warrant future mechanistic investigation.