Transcriptional and translational abundance of visfatin (NAMPT) in buffalo ovary during estrous cycle and its in vitro effect on steroidogenesis

Abstract

Visfatin is a highly conserved adipokine protein having multiple biological effects, including regulation of reproduction. Evidence in recent years has shown a pivotal role of visfatin in ovarian functions. The present study was conducted to evaluate the mRNA and protein abundance of visfatin in ovarian follicles and corpora lutea (CL) during different stages of their development in the ovary of water buffalo (Bubalus bubalis) and to investigate the role of visfatin on estradiol (E₂) and progesterone (P₄) secretion. Ovarian follicles were categorized in to small (F1), medium (F2), large (F3), and preovulatory (F4) follicles, whereas the CL were categorized into early (CL1), mid (CL2), late (CL3), and regressing (CL4) CL stage. In follicles, the mRNA and protein abundance of visfatin increased with an increase in follicle size in granulosa cells (GCs) and theca interna (TI) cells. In CL, the transcript of visfatin was significantly (P < 0.05) higher in the late luteal phase (CL3) than that in other phases. The translational abundance of visfatin was significantly higher in the mid and late luteal phase. Visfatin was localized in the cytoplasm of GC and TI of ovarian follicles and small and large luteal cells of CL. GCs were cultured in vitro and treated at 0, 1, and 10 ng/mL visfatin either alone or in the presence of FSH (30 ng/mL) or IGF-I (10 ng/mL) for 48 h. The luteal cells were treated with visfatin at 0, 1, and 10 ng/mL dose for 48h. There was significant (P < 0.05) increase in estradiol (E₂) secretion from GCs at 10 ng/mL dose of visfatin and visfatin (10 ng/mL) +IGF-I (10 ng/mL). Visfatin also increased (P < 0.05) progesterone (P₄) secretion from cultured luteal cells at both 1 and 10 ng/mL dose. In GCs, visfatin in the presence of IGF-I increased the transcriptional abundance of cytochrome P45019A1 (CYP19A1), the gene for key enzyme aromatase. In luteal cells, the visfatin increased mRNA abundance of factors involved in progesterone synthesis viz. steroidogenic acute regulatory protein (StAR), cytochrome P45011A1 (CYP11A1), 3beta-hydroxysteroid dehydrogenase (HSD3B1). The present study provided evidence that visfatin is expressed in ovarian follicles and CL of buffalo ovary and visfatin has a stimulatory effect on estradiol and progesterone secretion in ovarian cells of water buffalo.

Keywords: Buffalo; Corpus luteum; Estradiol; Ovarian follicles; Visfatin.