Metformin treatment decreases ovarian VEGF and Angiopoietin-1 levels, improves follicular development and decreases cyst formation in a rat model of Polycystic Ovary Syndrome.

DI PIETRO MARIANA; PARBORELL FERNANDA; IRUSTA GRISELDA; ACCIALINI PAULA; TESONE MARTA; ABRAMOVICH DALHIA

Chicago

Congreso; ICE-ENDO 2014; 2014

Endocrine Society

PCOS is the most common endocrine disorder among women of reproductive age. The main features of this heterogeneous syndrome are anovulation, oligo- or amenorrhea, hyperandrogenism and polycystic ovaries. In addition, PCOS is often associated with obesity and insulin resistance. It has been widely demonstrated that PCOS women have elevated levels of serum and follicular fluid VEGF, leading to an increase in ovarian blood flow. This increase in the levels of VEGF may be involved in the higher risk of developing Ovarian Hyperstimulation Syndrome (OHSS) when these patients are stimulated with gonadotropins in assisted reproductive techniques. In a previous work, we have demonstrated that in a PCOS rat model developed by administration of the androgen dehydroepiandrosterone (DHEA), the levels of VEGF were increased compared to control rats and, interestingly, the levels of Angiopoietin-1 (ANGPT-1) were also increased. Metformin is the most widely insulin sensitizer used in the therapeutic management of type 2 diabetes. Because of the metabolic disturbances that are often present in PCOS patients, metformin has been introduced as a therapy that targets not only insulin resistance but also other aspects of the pathology including reproductive alterations. In several studies was demonstrated that metformin is able to reduce the levels of VEGF in different types of cancer, regulating tumour angiogenesis. The use of metformin in PCOS patients has been associated with an increase in menstrual cycles and ovulation rates, and with the decrease in the levels of circulating androgens and in the rate of first-trimester spontaneous abortions. However, these observations are controversial and the mechanisms of action of metformin in the ovary are not known yet. Our hypothesis was that metformin may act in the ovary at least in part by regulating the levels of angiogenic factors. This would improve ovarian angiogenesis leading to an enhancement in follicular development and the selection of the dominant follicle, a decrease in cyst formation and an increase in ovulation rates. We used a rat PCOS model developed by dehydroepiandrostrone (DHEA) administration (6mg/ 100g weight) to 21 days old rats for 15 days. Control rats received vehicle. One PCOS group of rats received metformin (300 mg/ Kg) diluted in drink water during the 15 days of treatment. At day 16 rats were killed and the ovaries processed for western blot or immunohistological assays. Metformin administration decreased the levels of ovarian VEGF (PCOS: 81.8±12.2 pg/mg protein; PCOS + metformin: 28.6±5.8 pg/mg protein; p<0.01) and ANGPT-1 (PCOS: 0.47±0.04 arbitrary units; PCOS + metformin: 0.33±0.02 arbitrary units; p<0.05) in PCOS rats. Furthermore, the increase in periendothelial cell area observed in the ovaries of PCOS rats was reversed by metformin (PCOS: 7.7±0.3%; PCOS + metformin: 5.6±0.4%; p<0.05). Regarding follicular development, we observed that metformin decreased the percentage of primary and atretic follicles (PCOS: 36.8±4.0%; PCOS + metformin: 19.5±3.1%; p<0.01) while increased the percentage of antral follicles (PCOS: 46.7±2.7%; PCOS + metformin: 62.5±5.0%; p<0.01). Interestingly, administration of metformin decreased the percentage of cystic structures (PCOS: 4.6±0.5%; PCOS + metformin: 2.9±0.5%; p<0.05) and increased the percentage of corpora lutea (PCOS: 0.1±0.1%; PCOS + metformin: 1.5±1.0%; p<0.05) in PCOS rat ovaries. These results suggest that the treatment with metformin to the PCOS rats decreases VEGF and ANGPT-1 ovarian levels, improving follicular angiogenesis. This may contribute to a better follicular development, with an increase in ovulation and a decrease in cyst formation.