Insulin and hyperandrogenism in women with polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a very common endocrine disorder characterized by chronic anovulation, clinical and/or biochemical hyperandrogenism, and/or polycystic ovaries. But most experts consider that hyperandrogenism is the main characteristic of PCOS. Several theories propose different mechanisms to explain PCOS manifestations: (1) a primary enzymatic default in the ovarian and/or adrenal steroidogenesis; (2) an impairment in gonadotropin releasing hormone (GnRH) secretion that promotes luteal hormone (LH) secretion; or (3) alterations in insulin actions that lead to insulin resistance with compensatory hyperinsulinemia. However, in the past 20 years there has been growing evidence supporting that defects in insulin actions or in the insulin signalling pathways are central in the pathogenesis of the syndrome. Indeed, most women with PCOS are metabolically insulin resistant, in part due to genetic predisposition and in part secondary to obesity. But some women with typical PCOS do not display insulin resistance, which supports the hypothesis of a genetic predisposition specific to PCOS that would be revealed by the development of insulin resistance and compensatory hyperinsulinemia in most, but not all, women with PCOS. However, these hypotheses are not yet appropriately confirmed, and more research is still needed to unravel the true pathogenesis underlying this syndrome. The present review thus aims at discussing new concepts and findings regarding insulin actions in PCOS women and how it is related to hyperandrogenemia.

Invasiveness of breast cancer cells MDA-MB-231 through extracellular matrix is increased by the estradiol metabolite 4-hydroxyestradiol.

In malignant breast cancer, estrogen metabolism is altered, favoring the accumulation of hydroxyestradiols, which can generate free radicals. These reactive species can activate matrix metalloproteinases (MMPs), which in turn can hydrolyze the proteins of the extracellular matrix (ECM) that act as a barrier to tumor cell passage. The aim of this study was to determine whether reactive oxygen species generated by 4-hydroxyestradiol (4-OHE(2)) can activate MMP-2 and then enhance the invasiveness of breast cancer cells MDA-MB-231 in vitro. Enzymatic assay and gel zymography demonstrated that 4-OHE(2) at a concentration as low as 10(-8) M led to the conversion of proMMP-2 to active MMP-2. Activation of proMMP-2 by 4-OHE(2) was inhibited by the Cu,Zn-SOD supporting the involvement of the free radical superoxide anion (O(2)(*-)). Using invasion chambers coated with matrigel (artificial ECM), 4-OHE(2) (10(-8) M) enhanced the invasiveness of MDA-MB-231 breast cancer cells by 3-fold. The addition of Cu,Zn-SOD reduced the invasiveness of MDA-MB-231 cells by more than 2-fold, supporting the involvement of O(2)(*-) generated by 4-OHE(2). Addition of an MMP-2 inhibitor completely inhibited the enhancement of invasiveness induced by 4-OHE(2), which demonstrates the importance of activating MMP-2 by 4-OHE(2). On the other hand, estradiol, which does not have a catechol structure, did not generate free radicals, and it could not activate proMMP-2 or enhance the invasiveness of beast cancer cells. Although these data need to be confirmed in an animal model, this study suggests that the accumulation of 4-OHE(2) in breast tumors could enhance the invasiveness of breast cancer cells.