Effects of nicotinamide on follicular development and the quality of oocytes

BACKGROUND: Nicotinamide (NAM) is an important antioxidant, which is closely related to female fertility, but its role has not been clearly elucidated. The purpose of the present study was to investigate the effects of NAM on follicular development at different stages and the quality of oocytes. METHODS: The concentration of NAM in follicular fluid (FF) of 236 women undergoing in vitro fertilization (IVF) was ascertained by enzyme-linked immunosorbent assay (ELISA), and the correlation between NAM and clinical indexes was analyzed. During the in vitro maturation (IVM) of mice cumulus-oocyte complexes (COCs), different concentrations of NAM were added to check the maturation rate and fertilization rate. The reactive oxygen species (ROS) levels in the oocytes treated with different hydrogen peroxide (H(2)O(2)) and NAM were assessed. Immunofluorescence staining was performed to measure the proportion of abnormal spindles. RESULTS: The level of NAM in large follicles was significantly higher than that in small follicles. In mature FF, the NAM concentration was positively correlated with the rates of oocyte maturation and fertilization. Five mM NAM treatment during IVM increased maturation rate and fertilization rate in the oxidative stress model, and significantly reduced the increase of ROS levels induced by H(2)O(2) in mice oocytes. CONCLUSIONS: Higher levels of NAM in FF are associated with larger follicle development. The supplement of 5 mM NAM during IVM may improve mice oocyte quality, reducing damage caused by oxidative stress. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12958-022-00938-x.