Running title: VISFATIN or NAMPT in bovine follicles

VISFATIN is a novel adipokine, also known as a Nicotinamide phosphorybosyltransferase (NAMPT) that is able to modulate different processes including lipid and glucose metabolism, oxidative stress, inflammation and insulin resistance. Recent data suggest that it also plays a role in reproductive function in rats, humans and chickens Here we identified VISFATIN in the bovine ovary and investigated the in vitro effects of this hormone on granulosa cell steroidogenesis and proliferation and oocyte maturation. By RT-PCR, immunoblotting and immunohistochemistry, we found VISFATIN in various ovarian cells, including granulosa and theca cells, corpus luteum, and oocytes. In cultured bovine granulosa cells, we showed that IGF1 (10 -8 M) and VISFATIN (10 and 100 ng/ml) but not FSH (10 -8 M) increased mRNA expression levels of NAMPT after 48h of stimulation. Moreover, we observed that human recombinant VISFATIN (hVisf, 10 ng/ml, 48 h) increased the release of progesterone and estradiol secretion and this was associated with an increase in the protein level of STAR, the HSD3B activity and the phosphorylation levels of IGF1R and MAPK ERK1/2 in the presence or absence of IGF1 (10 −8 M). All these effects were abolished when NAMPT was knocked down and when the sirtuin pharmacological inhibitors, CHIC-35 (60 nM) and EX-527 (0.5 μM) were pre-incubated in bovine granulosa cells. Thus, in cultured bovine granulosa cells, VISFATIN improves basal and IGF1-induced steroidogenesis and IGF1 receptor signaling through SIRT1. Summary sentence: The VISFATIN adipokine is present in bovine ovarian follicular cells, it increases in vitro bovine granulosa cell steroidogenesis, the protein level of cholesterol carrier named STAR and IGF1 receptor signaling through the deacetylase SIRT1.