ABSTRACT
Niacin, also known as vitamin B3, has a pivotal role in energy metabolism, cellular signaling cascades regulating gene expression, and apoptosis. However, the effect of Niacin on porcine early embryo developmental competence remains to be elucidated. The present study aimed to assess the effects of Niacin treatment during in vitro maturation (IVM) on the nuclear maturation of porcine oocytes and subsequent development of in vitro embryos. In addition, the expression profiles of selected genes related to lipid metabolism, oxidative stress, and apoptosis were assessed. The IVM medium was supplemented with different concentrations of Niacin (0, 300, 600, and 900 µM). The results showed that a high concentration of Niacin (900 µM) significantly decreased cumulus expansion compared to the other groups (p < 0.05). No significant difference was observed among the experimental groups for nuclear maturation rate. Niacin treatments (300, 600, and 900 µM) during IVM significantly (p < 0.05) enhanced glutathione levels. Treatment with 300 and 600 µM significantly (p < 0.05) lowered the reactive oxygen species levels compared to treatment with 900 µM and the control group. Niacin supplementation to the IVM media significantly improved the cleavage and blastocyst rates compared to the control group. Supplementation with 300 and 600 µM of Niacin significantly increased the total cell number of blastocysts compared to supplementation with 900 µM or the control groups. Cytoplasmic lipid droplets were significantly reduced after 600 µM treatment. Supplementation of Niacin to IVM media positively affected the relative expression of genes related to energy and oxidative status (SIRT1), pro-apoptosis (BAX), anti-apoptosis (BCL2), and lipid metabolism (ACACA and PNPLA2) in cumulus cells and oocytes. Taken together, Niacin supplementation to porcine IVM media improved the developmental competence of early embryos mainly through protection against oxidative stress and its influence on energy metabolism and apoptosis pathways.
