Changes in the localization of ovarian visfatin protein and its possible role during estrous cycle of mice

Visfatin is a crucial adipokine, which also regulates ovarian functions in many animals. Mice estrous cycle is characterized by a dynamic complex physiological process in the reproductive system. Expression of various factors changes during the estrous cycle in the ovary. To the best of our knowledge, no previous study has been conducted on the expression of visfatin in mice ovaries during the estrous cycle. Therefore, we investigated the localization and expression of visfatin protein in the ovary of mice during the estrous cycle. Western blot analysis showed the elevated expression of visfatin in proestrus and lowest in diestrus. Immunohistochemical localization of visfatin showed intense staining in the corpus luteum of proestrus and diestrus ovaries. Thecal cells, granulosa cells, and oocytes also showed the presence of visfatin. Expression of ovarian visfatin was correlated to BCL2 and active caspase3 expression and exhibited a significant positive correlation. Furthermore, in vivo inhibition of visfatin by FK866 in the proestrus ovary down-regulated active caspase3 and PCNA expression, and up-regulated the BCL2 expression. These results suggest the role of visfatin in the proliferation and apoptosis of the follicles and specific localization of visfatin in the corpus luteum also indicate its role in corpus luteum function, which may be in progesterone biosynthesis and regression of old corpus luteum. However, further study is required to support these findings. In conclusion, visfatin may also be regulating follicular growth during the estrous cycle by regulating proliferation and apoptosis.