| Background and objectives: Polycystic ovary syndrome (PCOS) is a common endocrine disorder of reproductive aged women, characterized by anovulation,hyperandrogenism, polycystic ovarian changes and insulin resistance. So far,treatments for PCOS majorly focus on ovulation induction, lowering blood androgen and improving insulin sensitivity. Clinicians are still looking for a strategy which could both regulate sexual hormones and metabolism disturbance.GLP-1 analogue has already been successfully used in type 2 diabetes mellitus and insulin resistance relevant diseases. The appliance of GLP-1 analogue in treatment for PCOS is still in the early stage. Though few clinical trials of liraglutide have proven the beneficial effects on PCOS patients, the mechanism is still vague. PI3K/AKT/FoxO1 is a pathway highly associated with glycometabolism and FoxO1 is reported to participate in the cell apoptosis of granulosa cells. This study is designed to use letrozole to make PCOS rat models,and further use liraglutide to explore its effects on PCOS rats’models and also the possibility of PI3K/AKT/FoxO1 pathway on this process.Methods: Divide the 21-day Westar rats into normal group and PCOS model group. PCOS group rats are intragastric administrated by letrozole for 21 days.Vaginal smear examination were taken every day to estimate the estrous cycle changes. OGTT was tested in the end of 21-days-intervention. The plasma testosterone and insulin were measured. Six rats from PCOS group and 7 rats from control group were executed for the morphology and histological changes of their ovaries. Determine the effect of PCOS rat model though the estrous cycle, hormonal changes, ovarian pathology. The remained PCOS rats are divided into liraglutide group (0.4mg/kg liraglutide with subcutaneous injection,qd)、liraglutide+PI3K inhibitor LY294002 group (LY group for short) ( 0.4mg/kg liraglutide with subcutaneous injection, qd and 0.3mg/kg LY with intraperitoneal injection, qd) and PCOS model group. Both PCOS model group and normal group are of no special intervention. After intervention for 3 weeks, fastingplasma glucose (FPG), fasting insulin (FINS), testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were detected. The phosphatidylinositol 3-kinase (PI3K), serine / threonine kinase (AKT) and FoxO1mRNA expression in ovary were measured by RT-PCR. AKT, p-AKT,FoxO1 and p-Foxo1 protein expression in ovary were measured by western blot method.Result: After letrozole gavage for 21 days, all the PCOS rats lost their estrous cycle. Weight increased compared to the control group (p <0.05). Multiple follicles under the capsule were observed in HE stained ovary slice. Oocyte and corpus luteum disappeared mostly arid granular cell layer decreased. Plasma testosterone, 60min and 120min glucose, and Omin and 30min plasma insulin and HOMA-IR in OGTT are significantly higher than that in the normal group.Area under curve of glucose in OGTT was significantly higher than normal group, and modified beta-cell function index (MBCI) and insulin sensitivity index (ISI) were significantly lower. As compared to PCOS model group, weight,serum LH, FPG, FINS and HOMA-IR were significantly lower in liraglutide and LY group(p <0.05). Three rats in liraglutide group recover to normal estrous cycle and their granular cell layer improved. In the LY group, estrous cycle was still abnormal. Weight, serum LH, and HOMA-IR were significantly higher than that in liraglutide group (P<0.05). FoxO1 protein mainly expressed in the nucleus of granular cells. PI3K, AKT and FoxO1 mRNA levels all decreased in PCOS models compared to normal group, but only PI3K had statistically difference (P<0.05). AKT, FoxO1 mRNA in liraglutide group were significantly higher than that in PCOS model group. LY group had lower AKT and FoxO1Mrna than that in liraglutide group, with only AKT mRNA of statistically difference (P<0.05).In Western Blot we found p-AKT and p-FoxO1 expression in PCOS group significantly decreased compared to normal group and increased remarkably after intervene with liraglutide. However, in LY group the p-AKT and p-FoxO1 significantly decreased compared to liraglutide group.Conclusion: The PCOS rats’ model induced by letrozole was able to present stable similar changes with human PCOS, which include irregular ovulation,excessive androgen, high LH and polycystic ovarian feature. Liraglutide was able to partly recover the estrous cycle, lower serum LH, decrease FPG and FINS, and decrease insulin resistance. The PI3K inhibitor LY294002 help to prove the PI3K/AKT/Fox01 pathway participate in the liraglutide affection.This study explore the possible mechanism of liraglutide in PCOS for the first time and found liraglutide can activate PI3K/AKT pathway in ovary and therefore activate the phosphorylation of FoxO1 and may further influence the follicular development. |
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