description) During the last decade it has become apparent that insulin and insulin-like growth factors (IGFs) I & II participate in the regulation of ovarian function. The roles of insulin and IGF-I in the ovary have been studied extensively in both human and animal ovarian cells. There is less information regarding the role of IGF-II in the regulation of normal ovarian function or about its role in the pathogenesis of chronic anovulatory states, such as polycystic ovary syndrome. Receptor mechanisms of IGF-II action in the ovary are particularly poorly understood. IGF-II may be an important regulator of human ovarian function since it is expressed in the human ovary more widely than IGF-I, which seems to be the predominant IGF in the animal ovaries (rat, porcine or bovine). Thus, the overall goal of this proposal is to explore the feasibility of studies which examine the receptor mechanisms of IGF-II action in human ovary. The """"""""representative"""""""" IGF-II effect which will be used to explore the receptor mechanisms of IGF action in this initial set of experiments is the IGF-II induced suppression of insulin-like growth factor binding protein I (IGFBP-1) production in human granulosa cells. The following hypotheses will be tested: 1. Type 1 IGF-receptor mediates the inhibitory effect of IGF-II on IGFBP-1 production in human granulosa cells; and 2. Activation of postbinding receptor pathways which are important for insulin-dependent transmembrane glucose transport (specifically, tyrosine kinase and phosphoinositide-3 [PI-3] kinase) is not necessary for the inhibition of IGFBP-I production by IGF-II in human granulosa cells.
Specific aims are: 1) to establish which receptor (insulin receptor, type I or type II IGF receptor) mediates the inhibitory effect of IGF-II on IGFBP-1 production in human granulosa cells; 2) to establish whether insulin receptor or type I IGF-receptor tyrosine kinase plays a role in mediating this effect of IGF-II in human ovarian cells; and 3) to establish whether PI-3 kinase activation is necessary for the mediation of this effect of IGF-II in human ovarian cells. The studies will be carried out in human granulosa cells obtained during in vitro fertilization. The cells will be incubated with increasing concentrations of insulin, IGF-I or IGF-II in the presence or absence of the following inhibitors: a) anti-insulin receptor antibodies B-2 and IR-47 and anti-IGF-1 receptor monoclonal antibody & IR-3; b) specific inhibitor of PI-3 kinase, worthmanin; and c) an inhibitor of tyrosine-kinase-tumor necrosis factor-& (TNF-&). It is hoped that this work will allow the development of preliminary data that will enable these investigators to explore the role of IGF-II and its mechanisms of action in the human ovary in a systematic way in the future. This work may ultimately lead to the therapeutic use of IGF-II, its agonists or antagonists in anovulatory states or in other ovarian abnormalities.
| Bloomgarden, Z T; Futterweit, W; Poretsky, L (2001) Use of insulin-sensitizing agents in patients with polycystic ovary syndrome. Endocr Pract 7:279-86 |
