Protective role of nicotinamide mononucleotide in porcine oocyte maturation and fertilization against sodium metabisulfite-induced oxidative stress and apoptosis.

Sodium metabisulfite (SMB) is commonly utilized in food to preserve freshness by acting as an antioxidant and antimicrobial agent. However, when SMB interacts with water in biological systems, it produces harmful byproducts such as sulfite and sulfur dioxide. These byproducts induce cellular stress and programmed cell death, known as apoptosis, by triggering excessive production of reactive oxygen species. Our study demonstrates that supplementation with nicotinamide mononucleotide (NMN) effectively mitigates the damage caused by SMB to porcine oocytes during their cultivation in laboratory conditions. NMN supplementation not only preserves the oocytes' ability to undergo meiosis with intact spindle and chromosome structures but also enhances their capacity for fertilization by promoting the activity of cortical granule component protease. The protective effects of NMN on porcine oocytes exposed to SMB involve the restoration of mitochondrial function and the reduction of accumulated reactive oxygen species, leading to inhibition of apoptosis. These findings suggest that excessive SMB will impair mitochondrial function in porcine oocytes, which in turn causes oxidative stress and apoptosis, and impedes maturation of porcine oocytes and development of post-fertilised embryos, and that supplementation with NMN is a promising strategy to protect oocytes from the deleterious effects of SMB exposure.