Hyperinsulinemia and human chorionic gonadotropin synergistically promote the growth of ovarian follicular cysts in rats

A non-canonical role of somatic Cyclin D/CYD-1 in oogenesis and in maintenance of reproductive fidelity, dependent on the FOXO/DAF-16 activation state

For the optimal survival of a species, an organism coordinates its reproductive decisions with the nutrient availability of its niche. Thus, nutrient-sensing pathways like insulin-IGF-1 signaling (IIS) play an important role in modulating cell division, oogenesis, and reproductive aging. Lowering of the IIS leads to the activation of the downstream FOXO transcription factor (TF) DAF-16 in Caenorhabditis elegans which promotes oocyte quality and delays reproductive aging. However, less is known about how the IIS axis responds to changes in cell cycle proteins, particularly in the somatic tissues. Here, we show a new aspect of the regulation of the germline by this nutrient-sensing axis. First, we show that the canonical G1-S cyclin, Cyclin D/CYD-1, regulates reproductive fidelity from the uterine tissue of wild-type worms. Then, we show that knocking down cyd-1 in the uterine tissue of an IIS receptor mutant arrests oogenesis at the pachytene stage of meiosis-1 in a DAF-16-dependent manner. We observe activated DAF-16-dependent deterioration of the somatic gonadal tissues like the sheath cells, and transcriptional de-regulation of the sperm-to-oocyte switch genes which may be the underlying reason for the absence of oogenesis. Deleting DAF-16 releases the arrest and leads to restoration of the somatic gonad but poor-quality oocytes are produced. Together, our study reveals the unrecognized cell non-autonomous interaction of Cyclin D/CYD-1 and FOXO/DAF-16 in the regulation of oogenesis and reproductive fidelity.

Loureirin B Reduces Insulin Resistance and Chronic Inflammation in a Rat Model of Polycystic Ovary Syndrome by Upregulating GPR120 and Activating the LKB1/AMPK Signaling Pathway

Polycystic ovary yndrome (PCOS) is a common metabolic disorder in women, which is usually associated with insulin resistance (IR) and chronic inflammation. Loureirin B (LrB) can effectively improve insulin resistance and alleviate chronic inflammation, and in order to investigate the therapeutic effect of LrB on polycystic ovary syndrome with insulin resistance (PCOS-IR), we conducted animal experiments. A PCOS-IR rat model was established by feeding a high-fat diet combined with letrozole (1 mg/kg·d for 21 days). The rats were treated with the GPR120 agonists TUG-891 and LrB for 4 weeks. Biochemical parameters (fasting blood glucose, total cholesterol, triglycerides, high- and low-density lipoprotein), hormone levels (serum insulin, E2, T, LH, and FSH), and inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-18) were analyzed. Histopathological analyses of ovaries were performed using hematoxylin/eosin (H&E) staining. Real-time PCR and western blotting were used to assess GPR120, NLRP3, and caspase-1 expression in ovaries, and immunohistochemistry was used to evaluate LKB1 and AMPK protein expression. LrB reduced body weight, Lee's index, ovarian index, ovarian area, and volume in PCOS-IR rats. It lowered fasting blood glucose, serum insulin, and HOMA-IR. LrB decreased total serum cholesterol, triglyceride, and LDL levels and increased HDL levels. It reduced serum T, LH, and LH/FSH and raised serum E2 and FSH levels. LrB downregulated the mRNA and protein expression levels of NLRP3 and Caspase-1, increased the protein and mRNA expression levels of GPR120 in rat ovaries, and increased LKB1 and AMPK protein expression in ovaries, ameliorating ovarian histopathological changes in PCOS-IR rats. Taken together, LrB upregulated GPR120, LKB1, and AMPK protein expression, downregulated NLRP3 and Caspase-1 protein expression, reduced insulin resistance and chronic inflammation, and ameliorated histopathological changes in ovarian tissues in PCOS rats, suggesting its potential as a treatment for PCOS.

Effect of irisin on ovarian phosphatidylinositol-3-kinase/protein kinase B signaling pathway and mitogen-activated protein kinase/extracellular signal-regulated kinase pathways of rats with polycystic ovary syndrome

OBJECTIVE

To investigate the independent effects of irisin on insulin resistance (IR) in ovary of polycystic ovary syndrome (PCOS) and explore possible pathways.

METHODS

We established PCOS medel using Poretsky L's method, then PCOS rats were randomly divided into model group (M) and irisin group (I), and normal rats (N) were used as the control. Then rats in the group I were injected with recombinant irisin. Then the levels of circulating fasting blood glucose (FBG), fasting insulin (FINS), homeostasis model assessment of IR (HOMA-IR) and PI3K/AKT and MAPK/ERK pathways in each group were observed, as well as the effects of irisin on the levels of circulating HOMA-IR and PI3K/AKT and MAPK/ERK pathways in ovary of PCOS rats were evaluated.

RESULTS

Compared with normal group, levels of FBG, FINS, and HOMA-IR of model group were significantly increased (p < 0.001, p < 0.001, and p < 0.001, respectively), levels of average optical density by IHC of p-PI3K, PI3K, p-AKT, and AKT (p = 0.015, p = 0.010, p = 0.005, and p = 0.009, respectively) and levels of mRNA concentration of PI3K and AKT (p = 0.001, and p = 0.005, respectively) were decreased, while the levels of average optical density of p-ERK, ERK (p = 0.011, and p = 0.013, respectively) and level of mRNA concentration of ERK (p < 0.001) were increased in ovary. After irisin intervention, compared with model group, levels of FBG, FINS, and HOMA-IR of rats in irisin group were significantly decreased (p = 0.001, p < 0.001, and p < 0.001, respectively), levels of average optical density by IHC of p-PI3K, PI3K, p-AKT, and AKT (p = 0.030, p = 0.024, p = 0.012, and p = 0.025, respectively) and levels of mRNA concentration of PI3K and AKT (p = 0.002, and p = 0.003, respectively) were significantly increased, while the levels of average optical density of p-ERK, ERK (p = 0.004, and p = 0.026, respectively) and level of mRNA concentration of ERK (p = 0.001) were significantly decreased.

CONCLUSION

Our study demonstrated that irisin could not only improve circulating insulin resistance, but may also improve ovarian IR through an increase in the activity of PI3K/AKT signaling and a decrease of MAPK/ERK signaling.

Dehydroepiandrosterone with a high-fat diet treatment at inducing polycystic ovary syndrome in rat model

OBJECTIVE

This study aimed to evaluate the effects of dehydroepiandrosterone (DHEA) and DHEA combined with a high-fat diet (HFD) treatment of reproductive and endocrine metabolism in rats and then identify an ideal model of polycystic ovary syndrome (PCOS).

METHODS

Three-week-old female Sprague-Dawley rats were injected subcutaneously with DHEA or oil, fed with or without a HFD, for 21 days, during which body weight, feed intake, and estrous cycle monitoring were carried out. Fasting blood glucose was measured, and serum fasting insulin, testosterone, dihydrotestosterone (DHT), estradiol, progesterone, luteinizing hormone (LH), anti-Müllerian hormone (AMH), and follicle-stimulating hormone (FSH) were estimated by ELISA. Serum total cholesterol (TC), total triglycerides (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were measured by colorimetric assay. Whereas, histologic changes in rat ovaries were evaluated by H&E staining. Ovarian steroid hormone synthases and their protein levels (StAR, 3β-HSD2, 17β-HSD1, CYP11A1, CYP17A1, and CYP19A1) were examined by Western blotting.

RESULTS

Both DHEA and DHEA + HFD-treated rats lost a regular estrous cycle; had polycystic ovarian changes, significantly higher serum fasting insulin and testosterone levels; and increased ovarian StAR, 3β-HSD2, and CYP11A1 protein levels. Additionally, rats in the DHEA + HFD-treated group were obese; had elevated fasting blood glucose, TG, DHT, AMH levels and LH:FSH ratios; increased ovarian 17β-HSD1 protein levels.

CONCLUSION

DHEA combined with HFD treatment is more effective at inducing PCOS than DHEA alone. The reproductive and endocrine metabolic aspects of this method are more consistent with the clinical characteristics of PCOS patients.

Mechanism of cryptotanshinone to improve endocrine and metabolic functions in the endometrium of PCOS rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cryptotanshinone is the main bioactive component of Salvia miltiorrhiza, with various mechanisms of action, including antioxidant, anti-inflammatory, cardiovascular protection, neuroprotection, and hepatoprotection. Salvia miltiorrhiza is used clinically by gynecologists in China.

AIM OF THE STUDY

Polycystic ovary syndrome (PCOS) has a significant impact on women's quality of life, leading to infertility and reproductive disorders. Hence, this study aims to assess the pharmacological activity of cryptotanshinone in the treatment of PCOS and investigate its therapeutic mechanism.

MATERIALS AND METHODS

Human chorionic gonadotropin (HCG) combined with insulin is used to simulate a PCOS-like rat model and attempt to discover the abnormal changes that occur and the means by which the pathway acts in this model.

RESULTS

The transcriptome sequencing method is used to identify 292 differential genes that undergo significant changes, of which 219 were upregulated and 73 were downregulated. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the signaling pathways reveals that differential expressed genes are significantly enriched in 23 typical pathways. Estrogen signaling pathways are screened in the cryptotanshinone and model groups, and significant differential changes in Fos, ALOX12, and AQP8 are found. This suggests that these signaling pathways and molecules may be the main signaling targets for regulating the differences in endometrial tissue.

CONCLUSION

These results indicate that cryptotanshinone has targets for regulating the proliferation of endometrial tissue via estrogen signaling pathways in PCOS-like rats, providing an experimental basis for the clinical application of cryptotanshinone in the treatment of PCOS.

Development and evaluation of novel rodent model of PCOS mimicking clinical phenotype in human disease

Background

Polycystic ovary syndrome is a most common female reproductive disorder, involving endocrine and metabolic disorders with unclear etiology. Androgen-based rodent animal models like DHEA and DHT are most suitable for PCOS induction, but still, these models fail to produce non-lean PCOS phenotypes such as hyperandrogenism, hyperinsulinemia, elevated estrogen levels, and ovary weight. Excess fructose consumption leads to hyperandrogenism, hyperinsulinemia, and insulin resistance. The purpose of this study is to investigate, whether fructose consumption along with androgens in rats, could develop all metabolic and endocrine phenotypes of non-lean human PCOS disease. 

Methods

Prepubertal SD rats were administered with DHT (83ug, s.c.) and fructose (20%, p.o.) for 90 days whereas DHEA (7 mg/kg, s.c) and fructose (20%, p.o.) for 30 days. During study duration, the blood glucose level for oral glucose tolerance test, estrus cyclicity, and ultrasonography was observed. Reproductive hormones LH, FSH, insulin, testosterone, and estradiol levels were assessed using ELISA. The ovary, uterus, abdominal fat, and subcutaneous fat were collected and weighed, and histopathology was done for any anomaly’s findings.

Results

DHT + fructose-treated rats showed significant (p < 0.05) increase in serum testosterone, LH, estradiol, decreased FSH levels, and caused multiple cystic follicles. Abdominal fat, subcutaneous fat, ovary, and uterine weight were higher in DHT + F and DHEA + F when compared to control groups. OGTT reveals impaired insulin sensitivity and glucose tolerance in both model groups. Ovarian histopathology of DHT + F shows more cysts than the DHEA + F groups. No significant changes in uterine histology of DHT + F and DHEA + F-treated rats.

Conclusion

DHT + F-treated rats mimic all clinical phenotypes and could be used as novel rodent model for non-lean type PCOS.

Effects of N-acetylcysteine and metformin treatment on the stereopathological characteristics of uterus and ovary

In this study, the stereo-pathological effect of metformin and N-acetyl cysteine is evaluated on the uterus and ovary of polycystic ovary syndrome (PCOS) mice. 96 mature females (8-weekold, weight of 20–30 gr) BALB/c mice were classified into 6 groups including the control group (n= 16), letrozole-induced PCOS group (n=16), PCOS + metformin (n=16), PCOS+NAC (n=16) and a separate control group for NAC (n=16). Another PCOS group was maintained for a month to make sure that features remain till the end of the study. Testosterone level, vaginal cytology and stereological evaluations were assessed. Vaginal cytology in letrozole-receiving mice showed a diestrus phase continuity. Testosterone level, body weight, uterine weight, endometrial volume, myometrial volume, gland volume, stromal volume, epithelial volume, vessel volume, daughter and conglomerate glands, endometrial thickness, and myometrial thickness exhibited an increasing trend in the uterus of PCOS mice. While normal gland and vessel length decreased in the PCOS group. Ovarian volume, corticomedullary volume, primary follicles, secondary follicles, and ovarian cysts were increased in PCOS ovaries. While corpus luteum, primordial, graafian, and atretic follicles showed a decline in the PCOS group. NAC and metformin, however, managed to restore the condition to normal. Given the prevalence of PCOS and its impact on fertility, the use of noninvasive methods is of crucial significance. NAC can control and treat pathological parameters and help as a harmless drug in the treatment of women with PCOS.

Experimentally Induced Hyperinsulinemia Fails to Induce Polycystic Ovary Syndrome-like Traits in Female Rhesus Macaques

As in women with polycystic ovary syndrome (PCOS), hyperinsulinemia is associated with anovulation in PCOS-like female rhesus monkeys. Insulin sensitizers ameliorate hyperinsulinemia and stimulate ovulatory menstrual cycles in PCOS-like monkeys. To determine whether hyperinsulinemia (>694 pmol/L), alone, induces PCOS-like traits, five PCOS-like female rhesus monkeys with minimal PCOS-like traits, and four control females of similar mid-to-late reproductive years and body mass index, received daily subcutaneous injections of recombinant human insulin or diluent for 6−7 months. A cross-over experimental design enabled use of the same monkeys in each treatment phase. Insulin treatment unexpectedly normalized follicular phase duration in PCOS-like, but not control, females. In response to an intramuscular injection of 200 IU hCG, neither prenatally androgenized nor control females demonstrated ovarian hyperandrogenic responses while receiving insulin. An intravenous GnRH (100 ng/kg) injection also did not reveal evidence of hypergonadotropism. Taken together, these results suggest that experimentally induced adult hyperinsulinemia, alone, is insufficient to induce PCOS-like traits in female rhesus monkeys and to amplify intrinsic PCOS-like pathophysiology.

The Goto-Kakizaki rat is a spontaneous prototypical rodent model of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is characterized by an oligo-anovulation, hyperandrogenism and polycystic ovarian morphology combined with major metabolic disturbances. However, despite the high prevalence and the human and economic consequences of this syndrome, its etiology remains unknown. In this study, we show that female Goto-Kakizaki (GK) rats, a type 2 diabetes mellitus model, encapsulate naturally all the reproductive and metabolic hallmarks of lean women with PCOS at puberty and in adulthood. The analysis of their gestation and of their fetuses demonstrates that this PCOS-like phenotype is developmentally programmed. GK rats also develop features of ovarian hyperstimulation syndrome. Lastly, a comparison between GK rats and a cohort of women with PCOS reveals a similar reproductive signature. Thus, this spontaneous rodent model of PCOS represents an original tool for the identification of the mechanisms involved in its pathogenesis and for the development of novel strategies for its treatment.

Cryptotanshinone alleviates polycystic ovary syndrome in rats by regulating the HMGB1/TLR4/NF‑κB signaling pathway

Cryptotanshinone (CRY) has been demonstrated to reverse reproductive disorders. However, whether CRY is effective in the treatment of polycystic ovary syndrome (PCOS) remains unknown. The aim of the present study was to evaluate the therapeutic potential of CRY in PCOS. A rat model of PCOS was established by daily injection of human chorionic gonadotropin and insulin for 22 days. Total body weight and ovarian weight, as well as the levels of luteinizing hormone (LH) and the LH to follicle-stimulating hormone (FSH) ratio (LH/FSH) significantly increased in rats with PCOS, compared with controls. Moreover, the levels of testosterone (T), tumor necrosis factor (TNF)-α and high-mobility group box 1 protein (HMGB1) also increased. However, CRY treatment attenuated the increase in body weight, ovarian weight, LH, LH/FSH ratio, T, TNF-α and HMGB1 levels, compared with the PCOS group. Treatment with CRY also reduced NF-κB/p65, HMGB1 and toll-like receptor (TLR)4 mRNA and protein expression levels in the ovarian tissue and granulosa cells, both in vitro and in vivo. Thus, CRY significantly mitigated the changes in body weight, ovary weight, hormone levels and inflammatory factor levels observed in rats with PCOS. Thus, CRY protects against PCOS-induced damage of ovarian tissue, possibly through a regulatory pathway involving HMGB1, TLR4 and NF-κB.

Effect of irisin on endometrial receptivity of rats with polycystic ovary syndrome

To investigate the influence of irisin on endometrial receptivity of rats with polycystic ovarian syndrome (PCOS). PCOS rats were randomly divided into PCOS group and irisin group, and normal rats were used as control group. The PCOS group and control group were injected intraperitoneally with normal saline while the irisin group with recombinant irisin. The serum and uterus were obtained. Detect serum sex hormones, including Testosterone (T), Estradiol (E₂), Progesterone (P), and glucose, insulin levels. Observe endometrial morphology by hematoxylin-eosin staining. Then evaluate the expression of leukemia inhibitory factor (LIF) and integrin αvβ3 in endometrium using ELISA, immunohistochemistry and Real-time PCR. (1) Levels of serum T, glucose and insulin in PCOS group were significantly higher than those in control and irisin group. (2) For the endometrial morphology, levels of equivalent diameter, area of uterine glands and gland cavity and endometrial average thickness were lower in PCOS group than those in control and irisin group. (3) LIF and integrin αvβ3 mRNA were basically consistent with protein expression. Levels of LIF and integrin αvβ3 were decreased in PCOS group when compared with control and irisin group. Irisin may improve endometrial receptivity by promoting expression of LIF and integrin αvβ3.

Effects of Nigella sativa oil on ovarian volume, oxidant systems, XIAP and NF-kB expression in an experimental model of diabetes

We investigated the effects of Nigella sativa oil on ovary volume, nuclear factor-kappaB (NF-κB), X-linked inhibitor of apoptosis protein (XIAP) expression, and serum malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant status (TAS) and total oxidant status (TOS) levels in diabetic rats. We divided 21 adult female rats into three groups: controls, diabetics and diabetics + N. sativa oil. The diabetics + N. sativa oil group was given 0.2 mg/kg/day N. sativa oil 6 days/week for 4 weeks. NF-κB and XIAP expression was assessed in ovarian sections using immunohistochemistry. The right and left ovary volumes were calculated using stereology. We also measured serum MDA, SOD, TAS and TOS levels. We found that N. sativa oil reduced hyperglycemia, but not to control levels. N. sativa oil also exhibited antioxidant properties as demonstrated by reduced serum TOS and MDA levels, and increased SOD and TAS levels compared to controls. We found no significant difference in total ovarian volume, XIAP or NF-κB expression among the groups, which may be due to the short study period. Our findings suggest that N. sativa oil may be useful for reducing blood glucose levels and elevated oxidant activity in diabetic patients.

Effect of Vitex negundo L. seeds in letrozole induced polycystic ovarian syndrome

The clinical management of PCOS is multifaceted but often unsatisfactory. The aim of the current study is to evaluate the effect of Vitex negundo L. in the letrozole-induced polycystic ovarian syndrome. Female Sprague-Dawley rats were divided into six groups, each containing 6 animals. Group I (Control) daily received 1% carboxymethylcellulose (CMC) suspension as a vehicle control. Letrozole (1 mg/kg) was administered per orally (p.o) for a period of 21 days for the induction of PCOS in Group II to VI. PCOS induced animals were treated with aqueous (Group III - 200 mg/kg and IV- 400 mg/kg) and hydroalcoholic extract (Group V- 200 mg/kg and VI- 400 mg/kg) of Vitex negundo up to 66 days using 0.5% w/v CMC as the vehicle. Body weight and estrous cycle phase were measured every day. Blood samples were collected on 0, 21 and 66 days for the measurement of fasting blood glucose, lipid profile, LH, FSH and hormonal level. Oral glucose tolerance test was performed to study insulin resistance effect. Toxicity markers; SGOT, SGPT, and creatinine also measured at the end of the study. The administration of Letrozole led to an abnormality in serum sex steroid profile, lipid profile, glucose and estrous cycle. It was able to successfully exert its protective effect by restoring parameters to the normal level and disappearance of cysts in ovaries. This can be attributed to phyto-components present in the extract. The aqueous and hydro-alcoholic extracts of seeds of Vitex negundo showed significant amelioration of Letrozole induced PCOS.

The regulatory effect of Genistein on granulosa cell in ovary of rat with PCOS through Bcl-2 and Bax signaling pathways

The effect of genistein on Bcl-2 and Bax protein expression in the ovarian tissue of rats with polycystic ovarian syndrome (PCOS) was evaluated. Sixty rats were divided into six groups. Rats in the Dose group received genistein at a concentration of either 5 (L-gen), 10 (M-Gen) or 20 (H-Gen) mg per kg of body weight per day. The expression of Bcl-2 mRNA and Bax mRNA was determined by in situ hybridization. Bcl-2 and Bax protein concentration was quantified by ELISA. The results showed that the expression of Bcl-2 mRNA and Bcl-2 protein was significantly higher in the high genistein Dose group (H-Gen) when compared to the Model group (MG) (P<0.05). Genistein induced higher expression of the Bcl-2 gene at the transcriptional and translational level. Treatment with genistein resulted in an improvement of ovarian function with Bcl-2 expression being enhanced and Bax expression being suppressed. These alterations may be due to the structural and functional modifications that take place in these cells, and could be related to apoptotic changes that occur in rats with PCOS.

Uterine progesterone signaling is a target for metformin therapy in PCOS-like rats

Impaired progesterone (P4) signaling is linked to endometrial dysfunction and infertility in women with polycystic ovary syndrome (PCOS). Here, we report for the first time that elevated expression of progesterone receptor (PGR) isoforms A and B parallels increased estrogen receptor (ER) expression in PCOS-like rat uteri. The aberrant PGR-targeted gene expression in PCOS-like rats before and after implantation overlaps with dysregulated expression of Fkbp52 and Ncoa2, two genes that contribute to the development of uterine P4 resistance. In vivo and in vitro studies of the effects of metformin on the regulation of the uterine P4 signaling pathway under PCOS conditions showed that metformin directly inhibits the expression of PGR and ER along with the regulation of several genes that are targeted dependently or independently of PGR-mediated uterine implantation. Functionally, metformin treatment corrected the abnormal expression of cell-specific PGR and ER and some PGR-target genes in PCOS-like rats with implantation. Additionally, we documented how metformin contributes to the regulation of the PGR-associated MAPK/ERK/p38 signaling pathway in the PCOS-like rat uterus. Our data provide novel insights into how metformin therapy regulates uterine P4 signaling molecules under PCOS conditions.

Hyperandrogenism and insulin resistance contribute to hepatic steatosis and inflammation in female rat liver

Women with polycystic ovary syndrome (PCOS) are at high risk for nonalcoholic fatty liver disease (NAFLD). While insulin resistance is a common trait for both PCOS and NAFLD, hyperandrogenism is also considered to be a key factor contributing to PCOS, and the molecular mechanisms behind the interactions between insulin resistance and hyperandrogenism in the female liver remain largely unexplored. Using chronic treatment with insulin and/or human chorionic gonadotropin (hCG), we showed that all female rats with different treatments induced imbalance between de novo lipogenesis and mitochondrial β-oxidation via the Pparα/β–Srebp1/2–Acc1 axis, resulting in varying degrees of hepatic steatosis. Given the fact that hepatic lipid metabolism and inflammation are tightly linked processes, we found that hCG-induced hyperandrogenic rats had strongly aggravated hepatic inflammation. Further mechanistic investigations revealed that dysregulation of the IRS–PI3K–Akt signaling axis that integrated aberrant inflammatory, apoptotic and autophagic responses in the liver was strongly associated with hyperandrogenism itself or combined with insulin resistance. Additionally, we found that hCG-treated and insulin+hCG-induced rats developed visceral adipose tissue inflammation characterized by the presence of “crown like” structure and increased inflammatory gene expression. Because a more pronounced hepatic steatosis, inflammatory responses, and hepatocyte cell damage were observed in insulin+hCG-induced PCOS-like rats, our finding suggest that NAFLD seen in PCOS patients is dependent of hyperandrogenism and insulin resistance.

Neuroactive steroids and diabetic complications in the nervous system

Important complications of diabetes mellitus in the nervous system are represented by diabetic peripheral neuropathy and diabetic encephalopathy. In this context, an important link is represented by neuroactive steroids (i.e., steroids coming from peripheral glands and affecting nervous functionality as well as directly synthesized in the nervous system). Indeed, diabetes does not only affect the reproductive axis and consequently the levels of sex steroid hormones, but also those of neuroactive steroids. Indeed, as will be here summarized, the levels of these neuromodulators present in the central and peripheral nervous system are affected by the pathology in a sex-dimorphic way. In addition, some of these neuroactive steroids, such as the metabolites of progesterone or testosterone, as well as pharmacological tools able to increase their levels have been demonstrated, in experimental models, to be promising protective agents against diabetic peripheral neuropathy and diabetic encephalopathy.

High-Fat, High-Sugar Diet Disrupts the Preovulatory Hormone Surge and Induces Cystic Ovaries in Cycling Female Rats

Diet-induced obesity has been associated with various metabolic and reproductive disorders, including polycystic ovary syndrome. However, the mechanisms by which obesity influences the reproductive system are still not fully known. Studies have suggested that impairments in hormone signaling are associated with the development of symptoms such as acyclicity and ovarian cysts. However, these studies have often failed to address how these hormonal changes arise and how they might contribute to the progression of reproductive diseases. In the present study, we used a high-fat, high-sugar (HFHS) diet to induce obesity in a female rodent model to determine the changes in critical reproductive hormones that might contribute to the development of irregular estrous cycling and reproductive cycle termination. The HFHS animals exhibited impaired estradiol, progesterone (P4), and luteinizing hormone (LH) surges before ovulation. The HFHS diet also resulted in altered basal levels of testosterone (T) and LH. Furthermore, alterations in the basal P4/T ratio correlated strongly with ovarian cyst formation in HFHS rats. Thus, this model provides a method to assess the underlying etiology of obesity-related reproductive dysfunction and to examine an acyclic reproductive phenotype as it develops.

Conserved insulin signaling in the regulation of oocyte growth, development, and maturation

Insulin signaling regulates various aspects of physiology, such as glucose homeostasis and aging, and is a key determinant of female reproduction in metazoans. That insulin signaling is crucial for female reproductive health is clear from clinical data linking hyperinsulinemic and hypoinsulinemic condition with certain types of ovarian dysfunction, such as altered steroidogenesis, polycystic ovary syndrome, and infertility. Thus, understanding the signaling mechanisms that underlie the control of insulin-mediated ovarian development is important for the accurate diagnosis of and intervention for female infertility. Studies of invertebrate and vertebrate model systems have revealed the molecular determinants that transduce insulin signaling as well as which biological processes are regulated by the insulin-signaling pathway. The molecular determinants of the insulin-signaling pathway, from the insulin receptor to its downstream signaling components, are structurally and functionally conserved across evolution, from worms to mammals-yet, physiological differences in signaling still exist. Insulin signaling acts cooperatively with gonadotropins in mammals and lower vertebrates to mediate various aspects of ovarian development, mainly owing to evolution of the endocrine system in vertebrates. In contrast, insulin signaling in Drosophila and Caenorhabditis elegans directly regulates oocyte growth and maturation. In this review, we compare and contrast insulin-mediated regulation of ovarian functions in mammals, lower vertebrates, C. elegans, and Drosophila, and highlight conserved signaling pathways and regulatory mechanisms in general while illustrating insulin's unique role in specific reproductive processes.

Metformin Ameliorates Uterine Defects in a Rat Model of Polycystic Ovary Syndrome

Adult rats treated concomitantly with insulin and human chorionic gonadotropin exhibit endocrine, metabolic, and reproductive abnormalities that are very similar to those observed in polycystic ovary syndrome (PCOS) patients. In this study, we used this rat model to assess the effects of metformin on PCOS-related uterine dysfunction. In addition to reducing androgen levels, improving insulin sensitivity, and correcting the reproductive cycle, metformin treatment induced morphological changes in the PCOS-like uterus. At the molecular and cellular levels, metformin normalized the androgen receptor-mediated transcriptional program and restored epithelial–stromal interactions. In contrast to glucose transport, uterine inflammatory gene expression was suppressed through the PI3K–Akt–NFκB network, but without affecting apoptosis. These effects appeared to be independent of AMPK subunit and autophagy-related protein regulation. We found that when metformin treatment partially restored implantation, several implantation-related genes were normalized in the PCOS-like rat uterus. These results improve our understanding of how metformin rescues the disruption of the implantation process due to the uterine defects that result from hyperandrogenism and insulin resistance. Our data provide insights into the molecular and functional clues that might help explain, at least in part, the potential therapeutic options of metformin in PCOS patients with uterine dysfunction.

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The therapeutic dose of metformin sufficiently suppresses hyperandrogenism and insulin resistance.

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Metformin inhibits uterine androgen receptor (AR)-dependent gene expression to restore epithelial–stromal interactions.

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Metformin reduces uterine inflammation through the PI3K–Akt–NFκB pathway.

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Metformin partially restores implantation in PCOS-like rats.

The systemic benefits of metformin therapy for women with polycystic ovary syndrome (PCOS) are widely appreciated, but knowledge of the molecular mechanisms of its action and to what extent it beneficially affects uterine function is limited. Using a PCOS-like rat model, we show that treatment with metformin can reverse the negative effects of androgenic and inflammatory conditions in the rat uterus. Importantly, we find that the sustained benefit of metformin is to rescue implantation failure in some PCOS-like rats. Thus, our data will be of translational value in the clinical management of metformin treatment in PCOS patients with uterine dysfunction.

Mice endometrium receptivity in early pregnancy is impaired by maternal hyperinsulinemia

Previous studies have investigated the lower embryo implantation rates in women with polycystic ovary syndrome, obesity and type 2 diabetes, and specifically the association between the abnormal oocyte and embryo and hyperinsulinemia. The importance of hyperinsulinemia on maternal endometrium receptivity remains to be elucidated. The present study used a hyperinsulinemic mouse model to determine whether hyperinsulinemia may affect endometrial receptivity. An insulin intervention mouse model was first established. The serum levels of insulin, progesterone and estradiol were subsequently detected by ELISA assay analysis. The number of implantation sites was recorded using Trypan blue dye and the morphology of mice uteri was investigated using hematoxylin and eosin staining. The expression levels of molecular markers associated with endometrial receptivity were detected by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemistry analyses. Finally, the importance of mechanistic target of rapamycin (mTOR) expression following insulin treatment was determined. Mice treated with insulin developed insulin resistance and hyperinsulinemia. The number of implantation sites following insulin treatment did not differ between the control and insulin‑treated groups. Additionally, no significant morphological alterations in mice uteri between control and insulin‑treated groups were observed. However, the expression levels of estrogen receptor (Esr) 1, Esr2, progesterone receptor and homeobox A10 associated with endometrial receptivity, were imbalanced during endometrium receptivity when maternal hyperinsulinemia was induced. Western blot analysis revealed that expression levels of endometrial phosphorylated (p)‑mTOR and p‑ribosomal protein S6 kinase β‑1 were significantly greater in the insulin‑treated group. These results demonstrated that although an embryo may implant into endometrium, mice endometrium receptivity in early pregnancy may be impaired by maternal hyperinsulinemia. In addition, mTOR signaling may be involved in this process. The present study provides preliminary results demonstrating that female reproduction may be compromised during hyperinsulinemia, which requires further investigation in future studies.

High-fat high-sugar diet induces polycystic ovary syndrome in a rodent model

Obesity has been linked with a host of metabolic and reproductive disorders including polycystic ovary syndrome (PCOS). While a clear association exists between obesity and PCOS, the exact nature of this relationship remains unexplained. The primary symptoms of PCOS include hyperandrogenism, anovulation, and polycystic ovaries. Most animal models utilize androgen treatments to induce PCOS. However, these models often fail to address the underlying causes of the disease and do not effectively reproduce key metabolic features such as hyperinsulinemia. Here, we present a novel rodent model of diet-induced obesity that recapitulates both the metabolic and reproductive phenotypes of human PCOS. Rats on a high-fat high-sugar (HFHS) diet not only demonstrated signs of metabolic impairment, but they also developed polycystic ovaries and experienced irregular estrous cycling. Though hyperandrogenism was not characteristic of HFHS animals as a group, elevated testosterone levels were predictive of high numbers of ovarian cysts. Alterations in steroidogenesis and folliculogenesis gene expression were also found via RNA sequencing of ovarian tissue. Importantly, the PCOS-like symptoms induced in these rats may share a similar etiology to PCOS in humans. Therefore, this model offers a unique opportunity to study PCOS at its genesis rather than following the development of disease symptoms.

Molecular characterization of insulin resistance and glycolytic metabolism in the rat uterus

Peripheral insulin resistance and hyperandrogenism are the primary features of polycystic ovary syndrome (PCOS). However, how insulin resistance and hyperandrogenism affect uterine function and contribute to the pathogenesis of PCOS are open questions. We treated rats with insulin alone or in combination with human chorionic gonadotropin (hCG) and showed that peripheral insulin resistance and hyperandrogenism alter uterine morphology, cell phenotype, and cell function, especially in glandular epithelial cells. These defects are associated with an aberration in the PI3K/Akt signaling pathway that is used as an indicator for the onset of insulin resistance in classical metabolic tissues. Concomitantly, increased GSK3β (Ser-9) phosphorylation and decreased ERK1/2 phosphorylation in rats treated with insulin and hCG were also observed. We also profiled the expression of glucose transporter (Glut) isoform genes in the uterus under conditions of insulin resistance and/or hyperandrogenism. Finally, we determined the expression pattern of glycolytic enzymes and intermediates during insulin resistance and hyperandrogenism in the uterus. These findings suggest that the PI3K/Akt and MAPK/ERK signaling pathways play a role in the onset of uterine insulin resistance, and they also suggest that changes in specific Glut isoform expression and alterations to glycolytic metabolism contribute to the endometrial dysfunction observed in PCOS patients.

Thecal cell sensitivity to luteinizing hormone and insulin in polycystic ovarian syndrome

This study examined whether a defect of steroid synthesis in ovarian theca cells may lead to the development of PCOS, through contributions to excess androgen secretion. Polycystic ovarian syndrome (PCOS) is one of the leading causes of infertility worldwide affecting around 1 in 10 of women of a reproductive age. One of the fundamental abnormalities in this syndrome is the presence of hormonal irregularities, including hyperandrogenemia, hyperinsulinemia and hypersecretion of luteinizing hormone (LH). Studies suggest that insulin treatment increases progesterone and androstenedione secretion in PCOS theca cells when compared to insulin treated normal theca cells. Furthermore the augmented effects of LH and insulin have been seen to increase ovarian androgen synthesis in non-PCOS theca cultures whilst also increasing the expression of steroidogenic enzymes specific to the PI3-K pathway. Our examination of primary thecal cultures showed an increase in both the expression of the steroidogenic enzyme CYP17 and androgen secretion in PCOS theca cells under basal conditions, when compared to non-PCOS cells. This was increased significantly under treatments of LH and insulin combined. Our results support the previous reported hypothesis that a dysfunction may exist within the PI3-K pathway. Specifically, that sensitivity exists to physiological symptoms including hyperinsulinemia and hyper secretion of LH found in PCOS through co-stimulation. The impact of these findings may allow the development of a therapeutic target in PCOS.

Genetic Rodent Models of Obesity-Associated Ovarian Dysfunction and Subfertility: Insights into Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting women and a leading cause of female infertility worldwide. Defined clinically by the presence of hyperandrogenemia and oligomenorrhoea, PCOS represents a state of hormonal dysregulation, disrupted ovarian follicle dynamics, and subsequent oligo- or anovulation. The syndrome's prevalence is attributed, at least partly, to a well-established association with obesity and insulin resistance (IR). Indeed, the presence of severe PCOS in human genetic obesity and IR syndromes supports a causal role for IR in the pathogenesis of PCOS. However, the molecular mechanisms underlying this causality, as well as the important role of hyperandrogenemia, remain poorly elucidated. As such, treatment of PCOS is necessarily empirical, focusing on symptom alleviation. The generation of knockout and transgenic rodent models of obesity and IR offers a promising platform in which to address mechanistic questions about reproductive dysfunction in the context of metabolic disease. Similarly, the impact of primary perturbations in rodent gonadotrophin or androgen signaling has been interrogated. However, the insights gained from such models have been limited by the relatively poor fidelity of rodent models to human PCOS. In this mini review, we evaluate the ovarian phenotypes associated with rodent models of obesity and IR, including the extent of endocrine disturbance, ovarian dysmorphology, and subfertility. We compare them to both human PCOS and other animal models of the syndrome (genetic and hormonal), explore reasons for their discordance, and consider the new opportunities that are emerging to better understand and treat this important condition.

Scientific Statement on the Diagnostic Criteria, Epidemiology, Pathophysiology, and Molecular Genetics of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous and complex disorder that has both adverse reproductive and metabolic implications for affected women. However, there is generally poor understanding of its etiology. Varying expert-based diagnostic criteria utilize some combination of oligo-ovulation, hyperandrogenism, and the presence of polycystic ovaries. Criteria that require hyperandrogenism tend to identify a more severe reproductive and metabolic phenotype. The phenotype can vary by race and ethnicity, is difficult to define in the perimenarchal and perimenopausal period, and is exacerbated by obesity. The pathophysiology involves abnormal gonadotropin secretion from a reduced hypothalamic feedback response to circulating sex steroids, altered ovarian morphology and functional changes, and disordered insulin action in a variety of target tissues. PCOS clusters in families and both female and male relatives can show stigmata of the syndrome, including metabolic abnormalities. Genome-wide association studies have identified a number of candidate regions, although their role in contributing to PCOS is still largely unknown.

Expression and clinical significance of the HIF-1a/ET-2 signaling pathway during the development and treatment of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a major health problem in reproductive-aged women worldwide, but the precise pathogenesis of PCOS remains unclear. Our previous study revealed that hypoxia-inducible factor (HIF)-1a mediated endothelin (ET)-2 signaling plays an important role in ovulation in rats. Therefore, the present study used a PCOS rat model to test the hypotheses that HIF-1a signaling is expressed and inhibited in ovaries during PCOS formation and that the HIF-1a/ET-2 signaling pathway is a target of dimethyldiguanide (DMBG) in the clinical treatment of PCOS. First, the development of a PCOS model and the effect of DMBG treatment were examined through ovarian histology and serum hormone levels, which were consistent with previous reports. Second, HIF-1a and ET-2 expression were detected by immunohistochemistry and western blot. The results showed decreased HIF-1a/ET-2 expression in the ovaries of PCOS rats, whereas DMBG treatment reversed the protein decreases and improved the PCOS symptoms. Third, to understand the molecular mechanism, HIF-1a/ET-2 mRNA expression was also examined. Interestingly, HIF-1a mRNA increased in the ovaries of PCOS rats, while ET-2 mRNA decreased, indicating that HIF-1a protein degradation may be involved in POCS development and treatment. Finally, HIF prolyl hydroxylase (PHD) activity was examined to further clarify the contribution of HIF-1a signaling to the development and treatment of PCOS. The results suggested that the inhibition of HIF-1a/ET-2 signaling may be caused by increased PHD activity in PCOS. DMBG-treated PCOS may further activate HIF-1a signaling at least partly through inhibiting PHD activity. Taken together, these results indicate that HIF-1a signaling is inhibited in a PCOS rat model through increasing PHD activity. DMBG treatment improved PCOS by rescuing this pathway, suggesting that HIF-1a signaling plays an important role in the development and treatment of PCOS. This HIF-1a-mediated ET-2 signaling pathway may be an important mechanism regulating PCOS formation and treatment in mammalian ovaries in vivo and should be a new clinical target for PCOS prevention and treatment in the future.

Obesity-induced infertility and hyperandrogenism are corrected by deletion of the insulin receptor in the ovarian theca cell

Women with polycystic ovary syndrome (PCOS) exhibit elevated androgen levels, oligoanovulation, infertility, and insulin resistance in metabolic tissues. The aims of these studies were to determine the role of insulin signaling in the development and function of ovarian theca cells and the pathophysiologic effects of hyperinsulinism on ovarian function in obesity. We disrupted the insulin receptor (IR) gene specifically in the theca-interstitial (TI) cells of the ovaries (Cyp17IRKO). No changes in reproductive development or function were observed in lean Cyp17IRKO female mice, suggesting that insulin signaling in TI cell is not essential for reproduction. However, when females were fed a high-fat diet, diet-induced obesity (DIO) wild-type (DIO-WT) mice were infertile and experienced increased circulating testosterone levels, whereas DIO-Cyp17IRKO mice exhibited improved fertility and testosterone levels comparable to those found in lean mice. The levels of phosphorylated IRS1 and CYP17 protein were higher in the ovary of DIO-WT compared with DIO-Cyp17IRKO or lean mice. Ex vivo studies using a whole ovary culture model demonstrated that insulin acts independently or additively with human chorionic gonadotropin to enhance androstenedione secretion. These studies reveal the causal pathway linking hyperinsulinism with ovarian hyperandrogenism and the infertility of obesity.

Ovarian aging-like phenotype in the hyperandrogenism-induced murine model of polycystic ovary

There are prominently similar symptoms, effectors, and commonalities in the majority of characteristics between ovarian aging and polycystic ovarian syndrome (PCOS). Despite the approved role of oxidative stress in the pathogenesis of PCOS and aging, to our knowledge, the link between the PCO(S) and aging has not been investigated yet. In this study we investigated the possible exhibition of ovarian aging phenotype in murine model of PCO induced by daily oral administration of letrozole (1 mg/kg body weight) for 21 consecutive days in the female Wistar rats. Hyperandrogenization showed irregular cycles and histopathological characteristics of PCO which was associated with a significant increase in lipid peroxidation (LPO) and reactive oxygen species (ROS) and decrease in total antioxidant capacity (TAC) in serum and ovary. Moreover, serum testosterone, insulin and tumor necrosis factor-alpha (TNF-α) levels, and ovarian matrix metalloproteinase-2 (MMP-2) were increased in PCO rats compared with healthy controls, while estradiol and progesterone diminished. Almost all of these findings are interestingly found to be common with the characteristics identified with (ovarian) aging showing that hyperandrogenism-induced PCO in rat is associated with ovarian aging-like phenotypes. To our knowledge, this is the first report that provides evidence regarding the phenomenon of aging in PCO.

Diabetes and the female reproductive system

The insulin/insulin-like growth factor (IGF) pathways and glucose metabolism act as mediators of human ovarian function and female fertility. In normal insulin action, insulin binds to its own receptors in the ovary to mediate steroidogenesis and act as a co-gonadotropin. Insulin with other factors may influence ovarian growth and cyst formation. The IGF pathway also seems to influence normal ovarian function. Insulin signaling affects reproductive function. Dysregulation of this pathway leads to altered puberty, ovulation, and fertility. Better understanding of the normal physiology and pathophysiology of insulin, IGF, and glucose effects on the human reproductive system will allow for better outcomes.

Increased expression of P450scc and CYP17 in development of endogenous hyperandrogenism in a rat model of PCOS

The objective of the present study was to characterize the effect of insulin plus hCG on the expression of steroidogenic enzymes (P450scc and CYP17) in polycystic ovaries of rats. Changes in estrous cycle, ovarian morphology, hormonal levels, and protein levels by immunohistochemistry and western-blot were determined. Rats treated with insulin plus hCG displayed abnormal estrous cycles with increasing androgen biosynthesis. Meanwhile, insulin plus hCG resulted in multiple large cysts with diminished granulosa layers and increased thecal layers and stromal-interstitial tissue. Moreover, there was an increase in the expression of P450scc and CYP17 in thecal and stromal cells in our PCOS rat model compared with control rats. These results indicate that administration of insulin with hCG can synergistically result in endogenous hyperandrogenism which may partially upregulate the expression of steroidogenic enzymes in ovarian tissue.

Obesity management in women with polycystic ovary syndrome

Obesity and insulin resistance play an important role in initiating or maintaining ill health in polycystic ovary syndrome (PCOS). This implies that treatment that reduces body weight and insulin resistance would alleviate the symptoms of PCOS. Lifestyle modification has been found to be effective in restoring reproductive function in up to 80% of individuals who achieve at least 5% weight loss. However, long-term weight maintenance is a challenge. This article provides a review of reduced glycemic load diets, including low glycemic index, very low carbohydrate, high-protein and high monounsaturated fat diets, on metabolic and reproductive health in PCOS and non-PCOS populations. Dietary trials in non-PCOS women suggest that higher-protein, reduced glycemic load diets were probably more beneficial than the conventional low-fat, high-carbohydrate diet but further studies are required to confirm this in PCOS women. Similarly, the optimal exercise regime for PCOS women remains to be investigated.

Female reproduction and type 1 diabetes: from mechanisms to clinical findings

BACKGROUND

The functional reproductive alterations seen in women with type 1 diabetes (T1D) have changed as therapy has improved. Historically, patients with T1D and insufficient metabolic control exhibited a high prevalence of amenorrhea, hypogonadism and infertility. This paper reviews the impact of diabetes on the reproductive axis of female T1D patients treated with modern insulin therapy, with special attention to the mechanisms by which diabetes disrupts hypothalamic-pituitary-ovarian function, as documented mainly by animal model studies.

METHODS

A comprehensive MEDLINE search of articles published from 1966 to 2012 was performed. Animal model studies on experimental diabetes and human studies on T1D were examined and cross-referenced with terms that referred to different aspects of the gonadotropic axis, gonadotrophins and gonadal steroids.

RESULTS

Recent studies have shown that women with T1D still display delayed puberty and menarche, menstrual irregularities (especially oligomenorrhoea), mild hyperandrogenism, polycystic ovarian syndrome, fewer live born children and possibly earlier menopause. Animal models have helped us to decipher the underlying basis of these conditions and have highlighted the variable contributions of defective leptin, insulin and kisspeptin signalling to the mechanisms of perturbed reproduction in T1D.

CONCLUSIONS

Despite improvements in insulin therapy, T1D patients still suffer many reproductive problems that warrant specific diagnoses and therapeutic management. Similar to other states of metabolic stress, T1D represents a challenge to the correct functioning of the reproductive axis.

High fat diet affects reproductive functions in female diet-induced obese and dietary resistant rats

The incidence of ovulatory disorders is common in obese animal models. The mechanism behind this effect is unclear. We hypothesised that a high-fat (HF) diet induces alterations in neuroendocrine mechanisms resulting in anovulation in diet-induced obese (DIO) animals. Adult female DIO and diet-resistant (DR) rats were fed either chow or a HF diet (45% calories from fat) for 6 weeks. Oestrous cyclicity and body weight were monitored regularly. At the end of treatment, rats were implanted with a jugular catheter to monitor luteinising hormone (LH) levels on the day of pro-oestrous. Rats were sacrificed on the next pro-oestrous, and their brains and ovaries were collected. Plasma from trunk blood was analysed for oestradiol and leptin concentrations. Ovaries were fixed and sectioned for histological analysis. Brains were removed, frozen and sectioned, and norepinephrine (NE) concentrations in discrete hypothalamic areas were measured using high-performance liquid chromatography with electrochemical detection. A HF diet exposure affected oestrous cyclicity in both DIO and DR rats, with the effect being more pronounced in DIO animals. HF diet exposure increased leptin levels in both DIO and DR rats. Oestradiol levels were low in the DIO-HF group. NE levels in the hypothalamus were unaffected by HF diet or genotype. A normal LH surge was observed in DR-Chow rats and LH levels were low in the remaining groups. These results lead to the conclusion that DIO rats have an inherently reduced reproductive capacity and exposure to a HF diet decreases it further. A reduction in oestradiol and LH surge levels could contribute to this effect; however, the underlying mechanisms need to be investigated further.

Loss of PKBβ/Akt2 predisposes mice to ovarian cyst formation and increases the severity of polycystic ovary formation in vivo

Ovarian cysts affect women of all ages and decrease fertility. In particular, polycystic ovarian syndrome (PCOS), in which multiple follicular cysts develop, affects 5–10% of women of reproductive age and can result in infertility. Current non-invasive treatments for PCOS can resolve cysts and restore fertility, but unresponsive patients must undergo severe ovarian wedge resection and resort to in vitro fertilization. PCOS is related to the deregulation of leutinizing hormone (LH) signaling at various levels of the hypothalamic-pituitary-ovarian axis and resultant hyperproduction of androgens. Because insulin resistance and compensatory hyperinsulinemia are observed in 50–70% of individuals with PCOS, deregulated insulin signaling in the ovary is considered an important factor in the disease. Here we report that aged mice specifically lacking the PKBβ (also known as Akt2) isoform that is crucial for insulin signaling develop increased testosterone levels and ovarian cysts, both of which are also observed in insulin-resistant PCOS patients. Young PKBβ knockout mice were used to model PCOS by treatment with LH and exhibited a cyst area that was threefold greater than in controls, but without hyperinsulinemia. Thus, loss of PKBβ might predispose mice to ovarian cysts independently of hyperactive insulin signaling. Targeted therapeutic augmentation of specific PKBβ signaling could therefore provide a new avenue for the treatment and management of ovarian cysts.

Achieving a successful pregnancy in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a disease of complex and still poorly understood cause and of variable phenotypes. It is characterized by anovulation, hyperandrogenism, and polycystic ovaries. Infertility is commonly present. A variety of methods has been used successfully to achieve pregnancy in women with PCOS. Maintenance of pregnancy is complicated by a higher rate of premature spontaneous abortions and high risk of gestational diabetes, hypertension, and preeclampsia. However, with careful monitoring and treatment, the outcome of pregnancy in most women with PCOS is excellent.

PPAR Gamma: Coordinating Metabolic and Immune Contributions to Female Fertility

Peroxisome proliferator-activated receptor gamma (PPARG) regulates cellular functions such as adipogenesis and immune cell activation. However, new information has indicated additional roles of PPARG directing the cyclic changes that occur within ovarian tissue of female mammals, including those that facilitate the release of oocytes each estrous cycle. In addition to ovarian PPARG expression and function, many PPARG actions within adipocytes and macrophages have additional direct and indirect implications for ovarian function and female fertility. This encompasses the regulation of lipid uptake and transport, insulin sensitivity, glucose metabolism, and the regulation of inflammatory mediator synthesis and release. This review discusses the developing links between PPARG activity and female reproductive function, and highlights several mechanisms that may facilitate such a relationship.

Elevated anti-Müllerian hormone (AMH) and inhibin B levels in prepubertal girls with type 1 diabetes mellitus

OBJECTIVE

Elevated anti-Müllerian hormone (AMH) and adrenal androgen levels have been observed during childhood in girls at risk of developing polycystic ovarian syndrome (PCOS). The aim of this study was to evaluate ovarian function and adrenal steroid levels in prepubertal girls with type 1 diabetes mellitus (T1D).

DESIGN

Cross-sectional study. PATIENTS/MEASUREMENTS: We evaluated hormonal and ultrasonographic characteristics in girls with T1D (N = 73) and compared them to characteristics found in a control group of healthy girls (N = 86). Data are reported as geometric means (95% CI).

RESULTS

Prepubertal girls with T1D had higher levels of AMH (29·1 pmol/l (23·2-36·3) vs 20·9 pmol/l (16·6-26·1), P = 0·038), inhibin B (arithmetic mean: 16·7 pg/ml (11·6-21·7) vs 11·7 pg/ml (10·0-13·5), P = 0·044) and dehydroepiandrosterone sulphate (DHEAS) (0·3 nmol/l (0·2-0·6) vs 0·2 nmol/l (0·1-0·3)) than controls (P = 0·045). During puberty, decreasing AMH levels were observed in girls with T1D only (P < 0·0001). Girls with T1D in Tanner stages 4-5 had lower AMH levels than their paired healthy controls (10·1 pmol/l (7·4-13·9) vs 15·7 pmol/l (11·6-21·3), respectively, P = 0·047).

CONCLUSIONS

Our observations indicate that prepubertal girls with T1D may exhibit similar endocrine findings to those of other girls at risk of developing PCOS. The elevated levels of AMH and inhibin B suggest that higher numbers of follicles are present in the ovary during childhood in these patients and that insulin treatment may act as a local growth factor. In addition, AMH levels differed in prepubertal and pubertal girls, suggesting that the effect of T1D on ovarian folliculogenesis changes once gonadotrophin levels rise during puberty.

Selective impairment in glycogen synthase kinase-3 and mitogen-activated protein kinase phosphorylation: comparisons with the hyperandrogenic and the hyperinsulinemic rats

OBJECTIVE

To characterize and compare the effect of DHEA and insulin plus hCG on ovarian morphology, estrous cycle, hormonal levels, insulin sensitivity, and the regulation of insulin signaling in rats.

DESIGN

Animal model study.

SETTING

University laboratory.

ANIMAL(S)

Female Sprague-Dawley rats.

INTERVENTION(S)

Female rats received DHEA or insulin plus hCG by continuous administration.

MAIN OUTCOME MEASURE(S)

Ovarian morphology, estrous cycle, hormonal levels, insulin sensitivity, protein levels, and phosphorylation state of glycogen synthase kinase-3beta and extracellular regulated kinase 1/2 in the ovary.

RESULT(S)

Rats treated with DHEA displayed anovulation, insulin resistance, and polycystic ovaries characterized by cysts and a diminished granulosa layer. In contrast, insulin plus hCG results in acyclicity with increasing androgen biosynthesis and ovarian morphology different from that in DHEA-treated rats. Moreover, we found that insulin-stimulated serine-phosphorylation of glycogen synthase kinase-3beta was higher in insulin plus hCG-treated rats but lower in DHEA-treated rats. Furthermore, basal and insulin-stimulated tyrosine-phosphorylation of extracellular regulated kinase 1/2 was higher in DHEA-treated rats than in controls.

CONCLUSION(S)

Notwithstanding that both the hyperandrogenism and the hyperinsulinemia synergistic with hCG-treated rats displayed the typical traits of human polycystic ovary syndrome, there is a divergence in the insulin-signaling pathway in the ovarian tissue, which may have a role in the pathogenesis of polycystic ovary syndrome.

Morphological changes in the ovaries during modeling of functional cysts of hormonal genesis

Morphological study of ovarian follicular cysts induced by chorionic gonadotropin (300 U) and insulin (Protafane HM; 2.5 U) in adult rats showed that superovulatory dose of chorionic gonadotropin and moderate hyperinsulinemia induced the development of ovarian cysts on days 3-5 in 100% cases. Dynamic study of ovarian morphology showed that changes were reversible and the cysts regressed within 60 days, which confirmed their functional nature.

Peroxisome proliferator-activated receptor-gamma agonist rosiglitazone reverses the adverse effects of diet-induced obesity on oocyte quality

Obesity and its physiological consequences are increasingly prevalent among women of reproductive age and are associated with infertility. To investigate, female mice were fed a high-fat diet until the onset of insulin resistance, followed by assessments of ovarian gene expression, ovulation, fertilization, and oocyte developmental competence. We report defects to ovarian function associated with diet-induced obesity (DIO) that result in poor oocyte quality, subsequently reduced blastocyst survival rates, and abnormal embryonic cellular differentiation. To identify critical cellular mediators of ovarian responses to obesity induced insulin resistance, DIO females were treated for 4 d before mating with an insulin-sensitizing pharmaceutical: glucose and lipid-lowering AMP kinase activator, 5-aminoimidazole 4-carboxamide-riboside, 30 mg/kg.d; sodium salicylate, IkappaK inhibitor that reverses insulin resistance, 50 mg/kg.d; or peroxisome proliferator activated receptor-gamma agonist rosiglitazone, 10 mg/kg.d. 5-aminoimidazole 4-carboxamide-riboside or sodium salicylate treatment did not have significant effects on the reproductive parameters examined. However, embryonic development to the blastocyst stage was significantly improved when DIO mice were treated with rosiglitazone, effectively repairing development rates. Rosiglitazone also normalized DIO-associated abnormal blastomere allocation to the inner cell mass. Such improvements to oocyte quality were coupled with weight loss, improved glucose metabolism, and changes in ovarian mRNA expression of peroxisome proliferator activated receptor-regulated genes, Cd36, Scarb1, and Fabp4 cholesterol transporters. These studies demonstrate that peri-conception treatment with select insulin-sensitizing pharmaceuticals can directly influence ovarian functions and ultimately exert positive effects on oocyte developmental competence. Improved blastocyst quality in obese females treated with rosiglitazone before mating indicates that peroxisome proliferator activated receptor-gamma is a key target for metabolic regulation of ovarian function and oocyte quality.

Abdominal adiposity and the polycystic ovary syndrome

Abdominal adiposity, overweightness and obesity are frequently present in patients with polycystic ovary syndrome (PCOS). A large body of evidence suggests that abdominal adiposity and the resulting insulin resistance contribute to ovarian and, possibly, adrenal hyperandrogenism. However, androgen excess itself might also contribute to abdominal fat deposition in hyperandrogenic women. Recent genomic and proteomic analyses of visceral fat from PCOS patients have detected differences in gene expression and protein content compared with those of non-hyperandrogenic women. Here we review the existing evidence for a vicious circle whereby androgen excess favoring the abdominal deposition of fat further facilitates androgen secretion by the ovaries and adrenals in PCOS patients.

Obligatory roles for follicle-stimulating hormone (FSH), estradiol and androgens in the induction of small polyfollicular ovarian cysts in hypophysectomized immature rats

Immature hypophysectomized (HYPOXD) rats develop large, polyfollicular ovarian cysts in response to unabated, combined stimulation by subovulatory doses of human chorionic gonadotropin (hCG) and highly purified ovine follicle-stimulating hormone (FSH). Further, circulating amounts of androstenedione (A4) and estradiol (E2), but not testosterone or dihydrotestosterone (DHT), change in parallel with the development of these cysts. To determine the potential roles of either A4 or E2 at the level of the ovary in the induction of ovarian cysts, pellets containing either (1) cholesterol (placebo; controls); (2) A4; or (3) E2 were administered subcutaneously (sc) to immature HYPOXD rats. Some of these animals also received either twice-daily sc injections of 1 IU hCG, or daily s.c. injections of 2 microg FSH, for 13 days. Ovaries and sera were harvested from all treatment groups on the morning of day 14 of the combined-hormone treatment schedule. As expected, ovaries from HYPOXD rats treated with placebo, A4, or E2 pellets (with or without hCG) failed to display antral follicles. Ovaries from HYPOXD rats treated with FSH and a placebo pellet displayed polyfollicular, atretic, small antral follicles with unstimulated thecal shells. In addition, the ovarian stromal-interstitial tissue had an unstimulated appearance. In contrast, ovaries from HYPOXD rats treated with FSH plus either A4 or E2 implants displayed stimulated stromal-interstitial tissue as well as small follicular cysts and precysts with stimulated thecal shells. The number of cysts and precysts observed in the largest ovarian cross-sections for animals treated with FSH + A4 (17.0 +/- 3.0) was less than that observed in the largest ovarian cross-sections for HYPOXD rats treated with FSH + E2 (40.2 +/- 10.1; p < 0.05). To determine if the development of ovarian cysts in response to FSH + A4 was due, at least in part, to the metabolism of A4 to E2, HYPOXD rats were treated with either (1) placebo pellets; (2) pellets containing dihydrotestosterone (DHT) which cannot be metabolized to estrogen; (3) E2 pellets plus DHT pellets (E2 + DHT); (4) FSH + DHT; or (5) FSH + E2 + DHT. The largest ovarian cross-sections from FSH + DHT-treated HYPOXD rats displayed 18.3 +/- 4.1 small follicles with a mean diameter of approximately 0.437 mm which possessed few granulosa cells. The thecal and stromal-interstitial tissues in these ovaries were unstimulated, which indicates that these small degenerating follicles were atretic rather than cystic. In contrast, the largest ovarian cross-sections from FSH + E2 + DHT-treated HYPOXD rats displayed 51.6 +/- 2.4 cysts with stimulated thecal shells and a mean diameter of approximately 0.634 mm. Further, these cysts were arranged in a "string of pearls" pattern and the ovarian stromal-interstitial tissue possessed a stimulated appearance. These data demonstrate a direct, unambiguous role at the level of the ovary for unabated tonic stimulation by FSH plus estrogen in the development of small polyfollicular cysts in HYPOXD rats. Further, the data also indicate that, at least in HYPOXD rats, combined, tonic stimulation by FSH plus estrogen and androgen is sufficient for the development of small, polyfollicular ovarian cysts in a "string of pearls" pattern. These observations are in distinct contrast to our previous observations that tonic stimulation by FSH + hCG results in the induction of large ovarian cysts in HYPOXD rats and provide tantalizing new insights regarding the potential importance of specific hormones at the level of the ovary in the induction of specific types of cystic follicles.

Clinical review: Hyperandrogenism and polycystic ovary syndrome in women with type 1 diabetes mellitus

CONTEXT

At present, women with type 1 diabetes (DM1) are being treated with supraphysiological doses of exogenous insulin with the aim of providing a strict metabolic control, thereby avoiding the long-term complications of this disease. We hypothesized that PCOS would be especially prevalent in DM1, as might happen in any condition in which the ovary and the adrenals are exposed to excessive insulin concentrations. As will be seen in the present review, androgen excess and PCOS are very frequent complaints in women with DM1, yet nowadays hyperandrogenism is seldom diagnosed in these patients.

EVIDENCE ACQUISITION

We conducted a systematic review of all the published studies addressing hyperandrogenic symptoms in women with DM1, identified through the Entrez-PubMed search engine, followed by a comprehensive review of the pathophysiology and clinical and laboratory features of PCOS in women with DM1.

EVIDENCE SYNTHESIS

The prevalence of PCOS in adult women with DM1 is 12-18, 40, and 31% using National Institute for Child Health and Human Development, Rotterdam, and Androgen Excess Society criteria, respectively. Mild hirsutism and biochemical hyperandrogenism are present in 30 and 20% of the patients, respectively. In addition, menstrual abnormalities are observed in 20% of adult women with DM1, and a prevalence of 50% of polycystic ovarian morphology is reported.

CONCLUSIONS

Physicians treating women with DM1 should be aware of the risk of hyperandrogenism in them and should include evaluation of hirsutism, menstrual abnormalities, and biochemical hyperandrogenism in their routine examinations. Future studies are needed to determine the best preventive and therapeutic options for the hyperandrogenism of these patients.

Effects of chronic hyperandrogenism and/or administered central nervous system insulin on ovarian manifestation and gonadotropin and steroid secretion

OBJECTIVE

Polycystic ovarian syndrome is characterized by hyperandrogenism and insulin resistance. We studied the effects of central hyperinsulinemia and peripheral hyperandrogenism on gonadotropin secretion, steroid secretion, and ovarian histology in female rats.

DESIGN

Experimental in vivo animal study.

SETTING

University research center.

ANIMAL(S)

250-300 g female Wistar rats.

INTERVENTION(S)

Insertion of testosterone pellets and/or administration of intracerebroventricular (ICV) insulin.

MAIN OUTCOME MEASURE(S)

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels before and after GnRH administration; testosterone, insulin, and glucose levels; and ovarian histology.

RESULT(S)

Compared with control, rats with testosterone implant had a lower LH and higher FSH while rats with testosterone plus insulin had a higher FSH. Intracerebroventricular (ICV) insulin alone increased LH in response to GnRH. Ovarian histology indicated that testosterone-implanted rats had larger ovaries and an increased number of cystic follicles >50 microm as well as substantial theca enlargement. The administration of testosterone did not alter serum insulin, and ICV insulin did not increase testosterone levels.

CONCLUSION(S)

We suggest that ICV insulin acts either directly or indirectly to increase the LH responsiveness to GnRH. ICV insulin arrested the maturation of follicles leading to an increase in the number of small follicles. Peripheral androgens stimulated theca enlargement with cystic follicles. The combination of ICV insulin and peripheral androgens attenuated ovarian histologic changes and gonadotropin secretion. Thus, central hyperinsulinemia and peripheral hyperandrogenism may play a role in gonadotropin secretion as well as ovarian morphology.

Pathogenesis of polycystic ovary syndrome: what is the role of obesity?

Both obesity and the polycystic ovary syndrome (PCOS) are commonly seen in women of reproductive age. Fifty percent of all patients with PCOS are obese, and the presence of obesity affects the clinical manifestations of PCOS. The underlying pathogenetic mechanisms appear to involve insulin resistance and hyperinsulinemia, the magnitude of which is greater in obese than in non-obese women with PCOS. Specific effects of obesity on the manifestations of PCOS, underlying mechanisms of the interactions between obesity and PCOS, and therapeutic implications of these interactions are discussed in this article.