ORF20-02 - Determining the Role of Creb in Pituitary Gonadotropin Regulation in a PCOS Mouse Model

Pituitary gonadotropin regulation by pulsatile GnRH is critical in maintaining optimal reproductive function. Greater induction of FSH beta subunit gene expression occurring at low pulse frequencies of GnRH is mediated in part by cAMP response element binding protein (Creb). Disruption of gonadotropin regulation can lead to reproductive disorders such as polycystic ovary syndrome (PCOS), one of the most common endocrinopathies affecting women of reproductive age. Disruption of GnRH pulsatility is a hallmark feature of PCOS, resulting in excessive LH secretion and an altered LH:FSH ratio. However, the contributions of pituitary regulatory mechanisms remain largely unexplored. Using our gonadotrope-specific Creb deletion mouse model, we have previously observed a decrease in pituitary Fshb expression, therefore, utilizing a PCOS mouse model with gonadotrope-specific deletion of Creb, we hypothesize that the PCOS-like reproductive phenotype will be exacerbated and LH pulsatility increased. A mouse model with gonadotrope-specific deletion of Creb (KO) was generated by crossing GnrhrGRIC/+ mice with Crebfl/fl (control; C) mice. Pregnant females were treated with either dihydrotestosterone or vehicle (V) on days 16-18 of gestation, a well-established prenatal androgenization (PNA) model of PCOS. Offspring underwent reproductive phenotyping and assessment of LH pulsatility. PNAKO and PNAC mice had delayed vaginal opening (VO) compared to VKO (P < 0.0001) and VC (P < 0.0001) mice, respectively. Body weight (BW) at VO did not differ between PNAKO and VKO mice, whereas BW at VO was greater (P=0.0009) in PNAC compared to VC mice. PNAKO and PNAC mice had delayed first estrus (FE) compared to VKO (P < 0.0008) and VC (P < 0.0001) mice, respectively. BW at FE did not differ between PNAKO and VKO mice but was greater (P=0.0018) in PNAC compared to VC mice. Post-pubertally, PNAKO and PNAC mice spent more time in diestrus and less time in estrus compared to their respective V controls. PNAKO and PNAC mice had fewer cycles during a 15-day monitoring period, compared to VKO (P < 0.001) and VC (P < 0.0001) mice, respectively. In adult gonad-intact mice, LH pulse frequency and amplitude did not differ between groups, but PNAKO mice had higher (P < 0.05) mean concentrations of LH than VC mice. Mean LH concentrations also trended to be higher in PNAKO than PNAC mice (P=0.06). We successfully generated a PCOS-like mouse model that exhibited delayed VO and FE, as well as impaired estrous cyclicity (Vehicle vs. PNA), but no differences were observed between genotypes (KO vs. Control). We did, however, observe that PNAKO mice had increased mean LH concentrations, compared to PNAC and VKO mice. The increased LH concentrations in PNAKO females in our PCOS model indicates that gonadotropin secretion is further disrupted, suggesting a role for Creb in the regulation of pituitary gonadotropins in the pathophysiology of PCOS.