No abstract

The aim of this study was to investigate the mechanisms by which N,N'-dimethylbiguanide metformin (50 mg/100 g body weight (BW) in 0.05 ml of water, given orally with a cannula) prevents the ovarian disorders provoked by the hyperandrogenization with dehydroepiandrosterone (DHEA) in prepuberal BALB/c mice. The injection of DHEA (6 mg/100 g BW in 0.1 ml of oil) for 20 consecutive days re-creates a mouse model that resembles some aspects of the human polycystic ovary syndrome (PCOS). The treatment with DHEA increased ovarian oxidative stress because it enhanced lipid peroxidation (LPO) and diminished both catalase (CAT) activity and glutathione (GSH) content. Therefore, the treatment with DHEA diminished both ovarian nitric oxide synthase (NOS) activity and prostaglandin E (PGE) production. When metformin was administered together with DHEA, the ovarian GSH content, NOS activity and PGE production did not differ when compared with controls. However, metformin was not able to prevent the effect of DHEA on ovarian LPO or CAT activity. Finally, DHEA increased the ovarian protein expressions of inducible NOS (iNOS), inducible cyclooxygenase (COX2) and the phosphorylated AMP-dependent kinase alpha (AMPK-alpha) (Thr172). Metformin administered together with DHEA was able to prevent the increase of ovarian iNOS and COX2 expressions and to enhance the activation of phosphorylated AMPK-alpha expression.

The present study investigated the role of the N, N{ 0 }-dimethylbiguanide metformin (50 mg/100 g body weight in 0.05 ml water, given orally with a canulla) in the prevention of endocrine and immune disorders provoked by the hyperandrogenization with dehydroepiandrosterone (DHEA) in prepuberal BALB/c mice. The treatment with DHEA (6 mg/100 g body weight in 0.1 ml oil) for 20 consecutive days, recreates a mouse model that resembles some aspects of the human polycystic ovary syndrome (PCOS). The treatment with DHEA did not modify either body mass index (BMI) or blood glucose levels, but did increase fasting insulin levels when compared with controls. Markers of ovarian function -serum estradiol (E), progesterone (P) and ovarian prostaglandin E (PGE) -were evaluated. The treatment with DHEA increased serum E and P levels while ovarian PGE diminished. When metformin was administered together with DHEA, serum insulin, E and P levels, and ovarian PGE values did not differ when compared with controls. Using flow cytometry assays we found that the treatment with DHEA diminished the percentage of the CD4 1 T lymphocyte population and increased the percentage of the CD8 1 T lymphocyte population from both ovarian tissue and retroperitoneal lymph nodes. However, when metformin was administered together with DHEA, the percentages of CD4 1 and CD8 1 T lymphocyte populations from both ovarian tissue and retroperitoneal lymph nodes were similar to those observed in controls. Finally, when DHEA was administered alone it increased the serum tumor necrosis factor-alpha (TNF-a) levels when compared with controls; however, when metformin was administered together with DHEA, serum TNF-a levels were similar to controls. These results indicate that metformin is able, directly or indirectly, to avoid the endocrine and immune alterations produced when mice are hyperandrogenized with DHEA.

The present study examined the mechanism by which metformin prevents dehydroepiandrosterone (DHEA)-induced embryonic resorption in mice. Treatment with DHEA (6 mg/100 g bodyweight, 24 and 48 h post implantation) induced 88 +/- 1 % embryonic resorption and the diminution of both serum oestradiol (E) and progesterone (P) levels. However, when metformin (50 mg/kg bodyweight) was given together with DHEA, embryo resorption (43 +/- 3% v. 35 +/- 5% in controls) and both serum E and P levels were not significantly different from controls. Glucose and insulin levels were increased in the DHEA-treated mice but when metformin was administered together with DHEA these parameters were similar to control values. Treatment with DHEA increased ovarian oxidative stress and diminished uterine nitric oxide synthase (NOS) activity; however, when metformin was administered together with DHEA, both ovarian oxidative stress and uterine NOS activity were not different from controls. Metformin treatment did not modify the percentage of CD4(+) and CD8(+) T cells from both axillar and retroperitoneal lymph nodes but prevented the increase of serum tumour necrosis factor +/- produced in DHEA-treated mice. These results show that metformin acts in DHEA-induced embryonic resorption in mice by modulating endocrine parameters, ovarian oxidative stress and uterine NOS activity.

The aim of the present report was to study the role of high levels of dehydroepiandrosterone (DHEA) on the ovarian function and embryonic resorption during early pregnancy in BALB/c mice. Pregnant animals were injected with DHEA following both the post-implantatory (DHEA-2) and peri-implantatory (DHEA-6) models. Morphological studies of implantation sites showed 40% of embryonic resorption in the DHEA-2 group while 100% of resorption was observed in the DHEA-6 group. Serum samples of both DHEA-2 and DHEA-6 groups showed higher estradiol levels and a lower progesterone concentration than those of control groups. Ovarian prostaglandin E levels after both DHEA-2 and DHEA-6 treatments increased when compared to control groups. The antioxidant metabolite glutathione diminished during both DHEA treatments. In summary, the data presented here suggest that DHEA treatment during early pregnancy modulates the ovarian function and is responsible for embryonic resorption with different degrees depending on when it is administered.

No abstract

No abstract

Corpus luteum regression has been described in terms of: (i) functional luteolysis -a reversible decline in serum progesterone concentration; and (ii) structural luteolysisirreversible morphological changes and tissue remodelling events within the cellular membrane. In rats, PGF 2␣ and interleukin 1␤ (IL-1␤) are involved in structural luteolysis, PGF 2␣ by increasing ovarian lipid peroxidation, and IL-1␤ by reducing progesterone and increasing PGF 2␣ concentrations. The aim of the present report was to determine whether by an early action IL-1␤ is able to regulate functional luteolysis. Thus, ovarian explants from rats at the mid-stage of corpus luteum development were incubated during short periods with either 15 or 25 ng IL-1␤ ml −1 . At 15 ng ml −1 , IL-1␤ inhibited progesterone after 4 and 8 h of culture without affecting PGF 2␣ production, and a longer incubation (21 h) was needed to increase PGF 2␣ production. In contrast, IL-1␤ enhanced PGF 2␣ concentrations at 8 h only at the higher dose (25 ng ml −1 ). The observed reduction in progesterone synthesis at the lower dose of IL-1␤ before the increase in PGF 2␣ concentrations led to the hypothesis that IL-1␤ regulates functional luteolysis (progesterone diminution) before it affects structural luteolysis (PGF 2␣ increase). The fact that the early IL-1␤ action was described at 4 h but no effects on inducible nitric oxide synthase and inducible cyclooxygenase expression were found before this time led to the suggestion that these inductions were not necessary for the early IL-1␤ action described.