Human obesity is associated with insulin resistance and hyperinsulinemia, increased risk of atherosclerosis, and increased incidence of endometrial carcinoma. The atherosclerosis may be mediated by the growth effects of insulin, which could potentially also contribute to growth and oncogenic changes in endometrial epithelial cells. The renin angiotensin system (RAS) is also prominent in the uterus. Large amounts of prorenin are secreted by human endometrial stromal cells, and there is local production of angiotensin II. However, the exact mechanism of AII generation and its function is unknown. The primary risk of estrogen replacement therapy is endometrial carcinoma. Estrogen is known to enhance the circulating RAS, but its effects on the tissue RAS are unknown. In addition, estrogen stimulates endometrial stromal production of insulin-like growth factor 1 (IGF1). We hypothesize that: 1) human renin production by uterine lining regulates activity of the uterine renin angiotensin system (RAS), 2) gonadal steroids and possibly growth factors such as IGF1, and insulin contribute to regulation of endometrial renin production, and 3) locally generated AII may promote growth of stromal or epithelial cells in the uterine lining and insulin may enhance this effect.
Specific Aims i nclude: 1. Identification of renin mRNA and components of the RAS cascade (prorenin, cathepsin D, angiotensinogen, angiotensin converting enzyme, AII, AT1 receptor) in cultures of human endometrial stroma vs epithelial cells to define a pathway of AII production and action. 2. Determination of whether estrogen, progesterone or insulin or IGF1 affect a) renin or AT1 receptor gene expression, b) growth of endometrial stroma or epithelial cells with and without gonadal steroids and the insulin growth factors, c) prorenin uptake by epithelial cells. 3. Investigation of elements on the promotor area of the human renin gene which contribute to tissue-specific regulation in the endometrium and which can be used to identify trans-acting factors in the endometrium involved in renin gene regulation. 4. Assessment of the effects of AII on cultured stromal and epithelial cell growth parameters including: cell number, H3 thymidine incorporation, protein synthesis, H3 leucine incorporation, proto- oncogene and early growth response (Egr) gene expression and prolactin gene expression. This investigation will allow us to determine whether insulin-like growth factors or the RAS are paracrine mediators between endometrial stroma and epithelial cells, define the effect of gonadal steroids on this relationship, and to assess whether these factors could play a role in abnormal epithelial cell growth.
