β-Nicotinamide mononucleotide improves chilled ram sperm quality in vitro by reducing oxidative stress damage

The present study aimed to investigate the effect of β-nicotinamide mononucleotide (NMN) supplementation on ram sperm quality during storage at 4°C in vitro.

Tris-citric acid-glucose solution containing different doses of NMN (0, 30, 60, 90, and 120 μM) was used to dilute semen collected from rams and it was stored at 4°C. Sperm motility, plasma membrane integrity as well as acrosome integrity were evaluated at 0, 24, and 48 h time points after storage at 4°C. In addition, sperm mitochondrial activity, lipid peroxidation (LPO), malondialdehyde (MDA) content, reactive oxygen species (ROS) content, glutathione (GSH) content, superoxide dismutase (SOD) activity, and apoptosis were measured at 48 h time point after storage at 4°C.

Results demonstrate that the values obtained for sperm motility, acrosome integrity, and plasma membrane integrity in the NMN treatments were significantly higher than control (p<0.05). The addition of 60 μM NMN significantly improved ram sperm mitochondrial activity and reduced LPO, MDA content, and ROS content compared to control (p<0.05). Interestingly, sperm GSH content and SOD activity for the 60 μM NMN treatment were much higher than those observed for control. NMN treatment also decreased the level of Cleaved-Caspase 3, Cleaved-Caspase 9, and Bax while increasing Bcl-2 level in sperm at 48 h time point after storage at 4°C.

Ram sperm quality can be maintained during storage at 4°C with the addition of NMN at 60 μM to the semen extender. NMN also reduces oxidative stress and apoptosis. Overall, these findings suggest that NMN is efficient in improving the viability of ram sperm during storage at 4°C in vitro.