D-Mannose-Mediated metabolic pathways sustain the molecular signatures of sperm function and fertilization.

INTRODUCTION: Mammalian sperm within a single ejaculate exhibit significant heterogeneity, with only a subset possessing the molecular characteristics required for successful fertilization. Identifying the defining traits of these high-fertility sperm remains an open question. OBJECTIVES: To elucidate the molecular markers and mechanisms underlying the fertilization potential of sperm in both mice and humans, with a focus on the role of D-mannose. METHODS: Sperm morphology and functionality were analyzed using flow cytometry, biochemical assays, and immunofluorescence. Multi-omics analyses, including proteomics, metabolomics, and lipidomics, were conducted to identify distinct molecular signatures. Pharmacological interventions were employed to validate the role of key pathways, particularly Akt/mTOR signaling. RESULTS: Sperm with longer flagella demonstrated enhanced motility, mitochondrial activity, and fertilization potential in both mice and humans. Multi-omics analyses revealed distinct molecular profiles in high-fertility sperm, characterized by specific proteins, lipids, and metabolites. Notably, D-mannose supplementation enhanced sperm motility and fertilization capacity, even in asthenozoospermic sperm, by activating the Akt/mTOR pathway. This effect was not replicated by D-glucose or ATP supplementation. Mechanistically, D-mannose bypassed glycolytic rate-limiting steps, increasing ATP production and promoting mitochondrial and acrosomal integrity. CONCLUSION: This study identifies key molecular signatures of fertilization-competent sperm and highlights D-mannose as a novel modulator of sperm quality and function. These findings provide valuable insights into sperm biology and propose innovative therapeutic strategies for treating male infertility and optimizing assisted reproduction technologies.