Niacin improves maturation and cryo-tolerance of bovine in vitro matured oocytes: An experimental study

Background: Nicotinic acid (niacin) is a broad-spectrum lipid-modifying agent that has potent antioxidant properties and reduces the production of lipid peroxidation. Objective: The purpose of the present study was to investigate the maturation, embryo development and cryo-tolerance merit, and levels of malondialdehyde (MDA), total oxidant status, and total antioxidant capacity following the supplementation of bovine oocytes maturation medium with different concentrations of niacin. Materials and Methods: Immature cumulus-oocyte complexes were cultured in tissue culture medium-199 maturation media supplemented with 0, 100, 200, and 400 (mu)M niacin under a standard in vitro culture condition. After 24 hr of culture, the nuclear maturation rate was assessed. Then, two groups of immature cumulus-oocyte complexes were cultured in TCM-199 either with or without 400 (mu)M niacin and evaluated for embryo development. Also, matured cumulus-oocyte complexes in both groups were frozen using a standard vitrification procedure. After vitrification, oocytes were warmed in two steps and evaluated for embryo development. In addition, the level of total antioxidant capacity, total oxidant status, and MDA were measured. Results: The results indicated that although the treatment with 400(mu)Mniacin increased in vitro nuclear maturation (87.6 ± 5.3), it did not improved the embryo development to the blastocyst stage. Higher cleavage and blastocyst rates were observed in vitrified oocytes that were cultured with supplemented 400 (mu)M niacin compared to the control group (without niacin) (53.6 ± 2.7 and 10.6 ± 1.6 vs. 46.2 ± 4.1 and 6.3 ± 2.4, respectively). Also, the addition of 400 (mu)Mniacin to the maturation media could decrease MDA levels after maturation. Conclusion: Niacin could improve the quality of in vitro embryo production (IVP) embryos and tolerance of bovine oocytes to vitrification.