INSULIN AND IGF-1 SIGNALING IN OVARIAN CELLS

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DESCRIPTION (Adapted from applicant's description): Our preliminary studies of ovaries from transgenic mice with a knockout of the insulin receptor substrate-1 gene (IRS-1 KO) showed entrapment of the oocyte in luteal tissue and that the number of animals ovulating was about one-third that of the wild- type (WT) control group. The IRS-1 KO ovaries also exhibited a rare phenotype, polyovular (bi-oocyte) follicles. These findings imply a relationship between compromised insulin signaling and phenotypic change in ovarian function which have not been previously recognized. Accordingly, the overall study objective is to validate and extend these findings to establish the role of insulin signaling pathway components at the ovarian level in vivo. With this background, detailed studies of how these effectors help execute the insulin- and Follicle-stimulating hormone-FSH) regulated end point alternatives of cell survival, apoptosis, or mitosis will proceed in an expanded application. The ovaries of WT and IRS-1 KO mice will be compared in various aspects in the following specific aims: 1) to evaluate oocyte numbers and biochemical markers in neonatal animals and the ovulatory response to exogenous gonadotropins in prepubertal animals, and 2) to assess levels and/or activity of early effectors in the insulin signaling pathway (IRS-1, IRS-2, P13-K, Akt) during gonadotropin-regulated follicular cell mitosis and apoptosis. Specific Aim 3 will extend the in vivo studies to in vitro analysis in cultured porcine granulosa cells (pGCs) to: a) examine possible connections between the FSH receptor and insulin/IGF-1 receptor signaling pathways, and b) develop improved methods to detect BAD (Bcl-2-associated death promoter), a critical regulator of cell fate which can be phosphorylated by Akt. The results obtained may also contribute information basic to a more complete understanding of an important clinical entity, polycystic ovarian syndrome (PCOS), which is characterized in part by accelerated follicle atresia (apoptosis), insulin resistance, and virilism.