Nicotinamide Mononucleotide Enhances Boar Sperm Quality via Maintaining Mitochondrial Function During Liquid Storage

Nicotinamide mononucleotide (NMN), a key precursor of nicotinamide adenine dinucleotide (NAD⁺), plays a central role in cellular energy metabolism. This study investigated the effect of NMN supplementation on boar sperm quality during liquid storage. Semen samples diluted with Modena extender containing 0 to 80 μM NMN were stored at 17 °C for 7 days. Results demonstrate that supplementation with 20 μM NMN significantly improved sperm motility, acrosome integrity, and mitochondrial activity compared with the control group, accompanied by markedly elevated intracellular NAD⁺ and ATP level (<i>p</i> < 0.05). Also, Western blot analysis confirmed the presence of nicotinamide mononucleotide adenylyltransferase 3 (NMNAT3) in boar sperm. Furthermore, sperm treated with 20 μM NMN exhibited a higher level of protein tyrosine phosphorylation and an increased capacitation rate following storage. Tissue explant assays further revealed a significant increase in the number of sperm attached to oviductal epithelial fragments, indicating enhanced sperm-oviduct interactions. The present findings demonstrate that 20 μM NMN supplementation effectively preserves the metabolic activity and functional competence of boar sperm during liquid storage. It provides a promising strategy for improving boar semen preservation.