Protective effects of melatonin against metabolic and reproductive disturbances in polycystic ovary syndrome in rats

Gut microbiota in diabetic-linked polycystic ovarian syndrome: Mechanisms and therapeutic insights

Polycystic ovarian syndrome (PCOS) is a complex multisystem disorder prevalent among women of reproductive age, commonly marked by insulin resistance, hyperinsulinemia, and metabolic disruptions such as hypertension and dyslipidemia, which elevate risks of cardiovascular disease and hepatic steatosis. Recent advances underscore the gut microbiome's critical role in modulating insulin resistance and metabolic homeostasis in PCOS. This review highlights novel insights into gut dysbiosis-driven inflammation, gut-brain hormonal signaling, and immune modulation as underlying mechanisms connecting PCOS with metabolic dysfunction and diabetes. We comprehensively analyzed studies up to September 2024 on gut microbiota, diabetes, PCOS, and metformin, exploring emerging perspectives on the microbiome's therapeutic potential in managing PCOS. Metformin's dual role in insulin sensitivity improvement and gut microbiome modulation is emphasized, including its indirect effects on weight management. This review also identifies gaps in current research, urging a shift toward precision therapies targeting microbiome-related pathways in PCOS. Further exploration of the gut-brain axis, pathogen-associated molecular patterns, and the need for controlled clinical trials are discussed to enhance therapeutic approaches.

Effects of melatonin in polycystic ovary syndrome: is there Hippo pathway crosstalk?

OBJECTIVE

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder among reproductive women, characterized by hyperandrogenism, oligo-ovulation and polycystic ovarian morphology. Incorporating complementary medicine alongside traditional lifestyle therapies for PCOS may offer additional benefits for affected women. Melatonin (MT), a hormone secreted by the pineal gland, has emerged as a potential treatment for regulating ovarian function in PCOS. However, the specific effects and underlying mechanisms of MT on PCOS need to be elucidated.

METHODS

This review consolidates evidence from randomized controlled trials, original research articles, systematic reviews, and meta-analyses regarding MT supplementation in PCOS, with a particular focus on its interaction with the Hippo pathway, to provide a comprehensive overview of current knowledge.

RESULTS

Current evidence suggests that MT plays a role in modulating PCOS through various mechanisms and is associated with the Hippo pathway. However, several uncertainties and key limitations in the existing literature must be addressed before these treatments can be integrated into standard clinical practice.

CLINICAL TRIAL NUMBER

Not applicable.

Exploring melatonin's multifaceted role in female reproductive health: From follicular development to lactation and its therapeutic potential in obstetric syndromes

BACKGROUND

Melatonin is mainly secreted by the pineal gland during darkness and regulates biological rhythms through its receptors in the suprachiasmatic nucleus of the hypothalamus. In addition, it also plays a role in the reproductive system by affecting the function of the hypothalamic-pituitary-gonadal axis, and by acting as a free radical scavenger thus contributing to the maintenance of the optimal physiological state of the gonads. Besides, melatonin can freely cross the placenta to influence fetal development. However, there is still a lack of overall understanding of the role of melatonin in the reproductive cycle of female mammals.

AIM OF REVIEW

Here we focus the role of melatonin in female reproduction from follicular development to delivery as well as the relationship between melatonin and lactation. We further summarize the potential role of melatonin in the treatment of preeclampsia, polycystic ovary syndrome, endometriosis, and ovarian aging.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Understanding the physiological role of melatonin in female reproductive processes will contribute to the advancement of human fertility and reproductive medicine research.

A Retrospective Review on Dysregulated Autophagy in Polycystic Ovary Syndrome: From Pathogenesis to Therapeutic Strategies

The main purpose of this article is to explore the relationship between autophagy and the pathological mechanism of PCOS, and to find potential therapeutic methods that can alleviate the pathological mechanism of PCOS by targeting autophagy. Relevant literatures were searched in the following databases, including: PubMed, MEDLINE, Web of Science, Scopus. The search terms were "autophagy", "PCOS", "polycystic ovary syndrome", "ovulation", "hyperandrogenemia", "insulin resistance", "inflammatory state", "circadian rhythm" and "treatment", which were combined according to the retrieval methods of different databases. Through analysis, we uncovered that abnormal levels of autophagy were closely related to abnormal ovulation, insulin resistance, hyperandrogenemia, and low-grade inflammation in patients with PCOS. Lifestyle intervention, melatonin, vitamin D, and probiotics, etc. were able to improve the pathological mechanism of PCOS via targeting autophagy. In conclusion, autophagy disorder is a key pathological mechanism in PCOS and is also a potential target for drug development and design.

Polycystic ovary syndrome and its management: In view of oxidative stress

In the past two decades, oxidative stress (OS) has drawn a lot of interest due to the revelation that individuals with many persistent disorders including diabetes, polycystic ovarian syndrome (PCOS), cardiovascular, and other disorders often have aberrant oxidation statuses. OS has a close interplay with PCOS features such as insulin resistance, hyperandrogenism, and chronic inflammation; there is a belief that OS might contribute to the development of PCOS. PCOS is currently recognized as not only one of the most prevalent endocrine disorders but also a significant contributor to female infertility, affecting a considerable proportion of women globally. Therefore, the understanding of the relationship between OS and PCOS is crucial to the development of therapeutic and preventive strategies for PCOS. Moreover, the mechanistic study of intracellular reactive oxygen species/ reactive nitrogen species formation and its possible interaction with women's reproductive health is required, which includes complex enzymatic and non-enzymatic antioxidant systems. Apart from that, our current review includes possible regulation of the pathogenesis of OS. A change in lifestyle, including physical activity, various supplements that boost antioxidant levels, particularly vitamins, and the usage of medicinal herbs, is thought to be the best way to combat this occurrence of OS and improve the pathophysiologic conditions associated with PCOS.

Putative Complementary Compounds to Counteract Insulin-Resistance in PCOS Patients

Polycystic ovary syndrome (PCOS) is the most frequent endocrine-metabolic disorder among women at reproductive age. The diagnosis is based on the presence of at least two out of three criteria of the Rotterdam criteria (2003). In the last decades, the dysmetabolic aspect of insulin resistance and compensatory hyperinsulinemia have been taken into account as the additional key features in the etiopathology of PCOS, and they have been widely studied. Since PCOS is a complex and multifactorial syndrome with different clinical manifestations, it is difficult to find the gold standard treatment. Therefore, a great variety of integrative treatments have been reported to counteract insulin resistance. PCOS patients need a tailored therapeutic strategy, according to the patient’s BMI, the presence or absence of familiar predisposition to diabetes, and the patient’s desire to achieve pregnancy or not. The present review analyzes and discloses the main clinical insight of such complementary substances.

Clinical and Biochemical Potential of Antioxidants in Treating Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common cause of infertility in reproductive-age women. Increased reactive oxygen species levels and decreased antioxidant capacity in PCOS patients can lead to metabolic disorders and damage the ovarian tissues, resulting in the occurrence of related symptoms. Antioxidants have been used in the treatment of PCOS and have yielded satisfactory outcomes due to their ability to counter oxidative stress. Many experiments on PCOS patients have proved that antioxidants can not only improve the ovarian environment, promote follicular maturation, and elevate oocyte quantities but can also regulate lipid and glucose metabolism as well as vascular endothelial cell function in PCOS patients, thereby attenuating adiposity and reducing the occurrence rate of chronic complications to ensure that patients can obtain long-term benefits. This review describes the use of antioxidants in PCOS, which have been used in the treatment.

Evidence-based hormonal, mutational, and endocrine-disrupting chemical-induced zebrafish as an alternative model to study PCOS condition similar to mammalian PCOS model

Polycystic ovarian syndrome (PCOS) causes swollen ovaries in women at reproductive age due to hormonal disorder with small cysts on the outer edges. The cause of the disorder is still yet to be found. Multiple factors have increased PCOS prevalence, hyperandrogenism, oxidative stress, inflammation, and insulin resistance. Various animal PCOS models have been developed to imitate the pathophysiology of PCOS in humans. Zebrafish is one of the most versatile animal experimental models because of the transparency of the embryos, small size, and rapid growth. The zebrafish similarity to higher vertebrates made it a useful non-mammalian model for PCOS drug testing and screening. This review provides an insight into the usage of zebrafish, a non-mammalian model for PCOS, as an opportunity for evaluating future initiatives in such a research domain.

Melatonin alleviates insulin resistance through the PI3K/AKT signaling pathway in ovary granulosa cells of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common endocrine gynecological disorder. Insulin resistance (IR) is a major cause of PCOS. Melatonin, a critical endogenous hormone, has beneficial effects on the female reproductive system. This study aims to investigate the molecular effect of melatonin on IR in human ovarian granulosa cells (GCs). Hormone levels of the subjects were determined through clinical examination. The expression levels of insulin receptor substrate (IRS)-1 and glucose transporter (GLUT4) in GCs from PCOS patients and a human granulosa cell line (SVOG) were examined using qRT-PCR and western blot. The IR cell model was established by inducing SVOG cells with palmitic acid (PA). IR was detected in GCs of PCOS patients and SVOG by measuring glucose content and glucose uptake. Cell viability and apoptosis levels were detected by CCK-8 assay and flow cytometry. PI3K/Akt pathway expression in SVOG was assessed by western blot. PCOS patients had higher levels of luteinizing hormone (LH), testosterone, and LH/follicle-stimulating hormone. PA decreased cell viability, promoted apoptosis, and reduced glucose uptake in SVOG cells. IRS-1 and GLUT4 mRNA and protein expression was downregulated, and glucose uptake capacity was reduced in PCOS GCs and SVOG cells. Melatonin significantly upregulated IRS-1 and GLUT4 expression, downregulated p-IRS-1 (Ser307), and improved glucose uptake in PCOS patients' GCs and SVOG cells. PA decreased PI3K and Akt phosphorylation, whereas melatonin increased p-PI3K and p-Akt levels. Melatonin can reduce IR in GCs and PA-induced SVOG cells via the PI3K/Akt signaling pathway, providing more evidence for treating polycystic ovary syndrome.

Involvement of endometrial IGF-1R/IGF-1/Bcl-2 pathways in experimental polycystic ovary syndrome: Identification of the regulatory effect of melatonin

The involvement of endometrial IGF-1R/IGF-1/Bcl-2 pathways and the potential regulatory effects of exogenously administrated melatonin on this expression is investigated in the experimental PCOS model in the present study. Thirty-two 6-8 week old Sprague Dawley rats were divided into four groups: the Sham Control Group (1% CMC/day by oral gavage [o.g.]); the Melatonin Group (2 mg/kg/day melatonin by subcutaneous administration [s.c.]); the Experimental PCOS Group (1 mg/kg/day Letrozole by o.g.); and the Experimental PCOS + Melatonin Group (1 mg/kg/day Letrozole by o.g. and 2 mg/kg/day melatonin by s.c. administration). Vaginal smear samples were taken from the 14th day to the end of the experiment for colpocytological measurements. At the end of the 21 day experimental period, uterine tissues were taken; Hematoxylin-Eosin histochemical, IGF-1R/IGF-1/Bcl-2, PCNA immuno-histochemical stainings and western blot analyses were performed for related antibodies. All of the data was supported statistically. The epithelium of endometrium lost its single-layer structure in some parts, separation was observed between the epithelium and the basal membrane junction, intracellular edema was found in the uterine glands by the polycystic ovary-induction. Also this induction increased the expression of IGF-1R/IGF-1, Bcl-2, and PCNA proteins. Morphological degenerations returned to its normal appearance generally by the melatonin administrations and melatonin also regulated the increased expression of endometrial IGF-1R/IGF-1/Bcl-2 and PCNA pathways. It is concluded that additional studies are needed, using melatonin as a supporting agent may be appropriate in cases of PCOS.

Metabolic and hormonal effects of melatonin and/or magnesium supplementation in women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders among women of reproductive age. This study was designed to investigate the effects of melatonin and/or magnesium supplementation on metabolic profile and levels of sex hormones in PCOS women.

METHODS

In an 8-week randomized double-blind placebo-controlled trial, 84 subjects with PCOS aged 18-40 years were randomly assigned based on the random block procedure to take magnesium, melatonin, magnesium plus melatonin, and placebo. Fasting blood samples were obtained at the beginning and end of the study.

RESULTS

After intervention, the mean Pittsburg Sleep Quality Index score decreased significantly in both co-supplementation and melatonin groups (P < 0.001). Magnesium supplementation in combination with melatonin resulted in a significant greater decrease in testosterone concentrations compared with the placebo (P < 0.05). Co-supplementation of magnesium-melatonin had significantly reduced serum insulin levels (geometric means difference: - 1.11 (mIU/mL) (percent change: - 15.99)), homeostasis model of assessment-insulin resistance (HOMA-IR) (- 0.28 (- 18.66)), serum cholesterol (mean difference: - 16.08 (mg/dl) [95% CI - 24.24, - 7.92]), low-density lipoprotein cholesterol (LDL-C) - 18.96 (mg/dl) [- 28.73, - 9.20]) and testosterone levels (- 0.09 (ng/ml) (- 25.00)), as compared to the baseline values (P < 0.05). An increase in serum high-density lipoprotein cholesterol (HDL-C) levels was also observed following the administration of the melatonin alone (2.76 (mg/dl) [0.57, 4.95]) or in combination with magnesium (2.19 (mg/dl) [0.61, 3.77]) (P < 0.05).

CONCLUSIONS

Co-supplementation with magnesium and melatonin had beneficial effects on sleep quality and total testosterone. Additionally, melatonin supplementation alone was found to be associated with a significant reduction in PSQI score. Moreover, combined melatonin and magnesium supplementation was more effective in improving serum levels of cholesterol, LDL-C, HDL-C and insulin, and HOMA-IR.

TRIAL REGISTRATION

Iranian Registry of Clinical Trial. http://www.irct.ir : IRCT20191130045556N1, January 2020.

The role of melatonin in polycystic ovary syndrome: A review

Background

Polycystic ovary syndrome (PCOS) is a widespread endocrine disorder, affecting approximately 20% of women within reproductive age. It is associated with hyperandrogenism, obesity, menstrual irregularity, and anovulatory infertility. Melatonin is the main pineal gland hormone involved in the regulation of the circadian rhythm. In recent years, it has been observed that a reduction in melatonin levels of follicular fluid exists in PCOS patients. Melatonin receptors in the ovary and intra-follicular fluid adjust sex steroid secretion at different phases of ovarian follicular maturation. Moreover, melatonin is a strong antioxidant and an effective free radical scavenger, which protects ovarian follicles during follicular maturation.

Objective

In this paper, we conducted a literature review and the summary of the current research on the role of melatonin in PCOS.

Materials and Methods

Electronic databases including PubMed/MEDLINE, Web of Science, Scopus, and Reaxys were searched from their inception to October 2018 using the keywords “Melatonin” AND “Polycystic ovary syndrome” OR “PCOS.”

Results

Based on the data included in our review, it was found that the administration of melatonin can improve the oocyte and embryo quality in PCOS patients. It may also have beneficial effects in correcting the hormonal alterations in PCOS patients.

Conclusion

Since metabolic dysfunction is the major finding contributing to the initiation of PCOS, melatonin can hinder this process via its improving effects on metabolic functions.

Melatonin Reduces Androgen Production and Upregulates Heme Oxygenase-1 Expression in Granulosa Cells from PCOS Patients with Hypoestrogenia and Hyperandrogenia

Background/Aims

Polycystic ovary syndrome (PCOS) is an endocrine disorder characterized by abnormal hormone levels in peripheral blood and poor-quality oocytes. PCOS is a pathophysiological syndrome caused by chronic inflammation and oxidative stress. The aim of this study was to investigate the mechanism of melatonin regulation on androgen production and antioxidative damage in granulosa cells from PCOS patients with hypoestrogenia and hyperandrogenia.

Methods

Cumulus-oocyte complexes were collected from PCOS patients who had low levels of estrogen in follicular fluids.

Results

Melatonin triggered upregulation of cytochrome P450 family 19 subfamily A member 1 (CYP19A1) expression via the extracellular signal-regulated kinase pathway in luteinized granulosa cells. As a result, conversion of androgen to 17β-estradiol was accelerated. We also found that melatonin significantly reduced the levels of inducible nitric oxide (NO) synthetase and NO in luteinized granulosa cells. Levels of transcripts encoding NF-E2-related factor-2 and its downstream target heme oxygenase-1 were also increased, leading to anti-inflammatory and antioxidant effects. We also found that melatonin could improve oocyte development potential.

Conclusion

Our preliminary results showed that melatonin had a positive impact on oocyte quality in PCOS patients with hypoestrogenia and hyperandrogenia.

The Effect of Interleukin-6 (IL-6), Interleukin-11 (IL-11), Signal Transducer and Activator of Transcription 3 (STAT3), and AKT Signaling on Adipocyte Proliferation in a Rat Model of Polycystic Ovary Syndrome

Background

Polycystic ovary syndrome (PCOS) is associated with low-grade inflammation, adipocyte hypertrophy, hyperglycemia, increased serum testosterone levels, and reduced lipolysis. This study aimed to investigate the role of interleukin-6 (IL-6) and IL-11 in the pathophysiology of adipocyte hypertrophy in a rat model of PCOS.

Material/Methods

The rat model of PCOS was developed using a subcutaneous injection of dehydroepiandrosterone (DHEA). Histology of the rat ovaries was used to confirm the development of PCOS. Serum levels of testosterone and glucose were measured. Immunohistochemistry, immunofluorescence, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot were performed to measure IL-6 and IL-11 in the rat model of PCOS. Cell proliferation was measured using the cell counting kit-8 (CCK-8) assay.

Results

Serum levels of testosterone and glucose and the expression of IL-6 and IL-11 were significantly increased in the rat model of PCOS via the activation of AKT/STAT3 signaling. Following IL-6 and IL-11 stimulation of mesenchymal adipocytes isolated from adipose tissue, IL-6 and IL-11 induced cell proliferation through the STAT3/AKT signaling pathway.

Conclusions

In a rat model of PCOS, increased expression of IL-6 and IL-11 was associated with the AKT/STAT3 pathway. Increased levels of IL-6 and IL-11 stimulated adipocytes from adipose tissue of the rat model, which promoted cell proliferation by activating AKT/STAT3 signaling.

Morning Circadian Misalignment Is Associated With Insulin Resistance in Girls With Obesity and Polycystic Ovarian Syndrome

CONTEXT

To our knowledge, circadian rhythms have not been examined in girls with polycystic ovarian syndrome (PCOS), despite the typical delayed circadian timing of adolescence, which is an emerging link between circadian health and insulin sensitivity (SI), and decreased SI in PCOS.

OBJECTIVE

To examine differences in the circadian melatonin rhythm between obese adolescent girls with PCOS and control subjects, and evaluate relationships between circadian variables and SI.

DESIGN

Cross-sectional study.

PARTICIPANTS

Obese adolescent girls with PCOS (n = 59) or without PCOS (n = 33).

OUTCOME MEASURES

Estimated sleep duration and timing from home actigraphy monitoring, in-laboratory hourly sampled dim-light, salivary-melatonin and fasting hormone analysis.

RESULTS

All participants obtained insufficient sleep. Girls with PCOS had later clock-hour of melatonin offset, later melatonin offset relative to sleep timing, and longer duration of melatonin secretion than control subjects. A later melatonin offset after wake time (i.e., morning wakefulness occurring during the biological night) was associated with higher serum free testosterone levels and worse SI regardless of group. Analyses remained significant after controlling for daytime sleepiness and sleep-disordered breathing.

CONCLUSION

Circadian misalignment in girls with PCOS is characterized by later melatonin offset relative to clock time and sleep timing. Morning circadian misalignment was associated with metabolic dysregulation in girls with PCOS and obesity. Clinical care of girls with PCOS and obesity would benefit from assessment of sleep and circadian health. Additional research is needed to understand mechanisms underlying the relationship between morning circadian misalignment and SI in this population.

Very low dose spironolactone protects experimentally-induced polycystic ovarian syndrome from insulin-resistant metabolic disturbances by suppressing elevated circulating testosterone

Polycystic ovarian syndrome (PCOS) is the most common endocrinological disorder in women of reproductive age and hyperandrogenism is a prominent feature of PCOS resulting in infertility and increased risk of developing metabolic disorders including insulin resistance (IR), abdominal adiposity, glucose intolerance and cardiovascular diseases. Spironolactone (SPL), a non-selective mineralocorticoid receptor (MR) antagonist, has been in wide clinical use for several decades. In this study, we investigated the effects of SPL on IR and metabolic disturbances in letrozole-induced PCOS rats. Eighteen adults female Wistar rats were randomly divided into 3 groups and treated with vehicle, letrozole (LET; 1 mg/kg) and LET + SPL (SPL; 0.25 mg/kg), p.o. once daily for 21 consecutive days. Results showed that LET treatment induced PCOS characterised by elevated plasma testosterone and luteinizing hormone (LH) accompanied with increased body weight and visceral adiposity, IR, glucose intolerance, dyslipidemia and altered histomorphological ovaries. Treatment with SPL however attenuated the elevated testosterone in LET-induced PCOS model accompanied with a reversal in all the observed alterations. Taken together, analysis of the physical, biochemical and histological evidences shows that the protective effect of this very low dose spironolactone may be through its anti-androgenic mechanism.

Effects of Melatonin Supplementation on Hormonal, Inflammatory, Genetic, and Oxidative Stress Parameters in Women With Polycystic Ovary Syndrome

Purpose: The aim of the current study was to evaluate the effect of melatonin administration on clinical, hormonal, inflammatory, and genetic parameters in women with polycystic ovarian syndrome (PCOS). Methods: The present randomized, double-blinded, placebo-controlled clinical trial was conducted among 56 patients with PCOS, aged 18-40 years old. Subjects were randomly allocated to take either 5 mg melatonin supplements (n = 28) or placebo (n = 28) twice a day for 12 weeks. Results: Melatonin administration significantly reduced hirsutism (β -0.47; 95% CI, -0.86, -0.09; P = 0.01), serum total testosterone (β -0.11 ng/mL; 95% CI, -0.21, -0.02; P = 0.01), high-sensitivity C-reactive protein (hs-CRP) (β -0.61 mg/L; 95% CI, -0.95, -0.26; P = 0.001), and plasma malondialdehyde (MDA) levels (β -0.25 μmol/L; 95% CI, -0.38, -0.11; P < 0.001), and significantly increased plasma total antioxidant capacity (TAC) levels (β 106.07 mmol/L; 95% CI, 62.87, 149.28; P < 0.001) and total glutathione (GSH) (β 81.05 μmol/L; 95% CI, 36.08, 126.03; P = 0.001) compared with the placebo. Moreover, melatonin supplementation downregulated gene expression of interleukin-1 (IL-1) (P = 0.03) and tumor necrosis factor alpha (TNF-α) (P = 0.01) compared with the placebo. Conclusions: Overall, melatonin administration for 12 weeks to women with PCOS significantly reduced hirsutism, total testosterone, hs-CRP, and MDA, while increasing TAC and GSH levels. In addition, melatonin administration reduced gene expression of IL-1 and TNF-α. Clinical Trial Registration: www.irct.ir, identifier IRCT2017082733941N9, Available online at: https://www.irct.ir/trial/26051.

Pathophysiological changes in experimental polycystic ovary syndrome in female albino rats: Using either hemin or L-arginine

Polycystic ovary syndrome (PCOS), one of the important endocrine disorders affecting females in the reproductive age, is caused mainly by an abnormal oxidation status that subsequently causes inflammatory conditions. Thus, this study aims to examine the possible individual prophylactic effects of gasotransmitters, hemin, or L-arginine in letrozole-induced PCOS. Fifty adult female albino rats were used and separated into a control group, which received the vehicle; a letrozole-induced PCOS group (L), which received letrozole orally at a dose level of 1 mg/kg for 21 days; a letrozole+hemin (L+H) group, which received letrozole plus hemin at a dose level of 25 mg/kg injected IP twice per week for 21 days; and a letrozole+L-arginine (L+A) group, which received letrozole plus L-arginine at a dose level of 200 mg/kg orally for 21 days. During PCO induction, the body weight and Lee index were measured. Serum glucose, insulin, lipid profile, gonadotrophic hormones, testosterone, estrogen, and tumor necrosis factor alpha were assayed, while ovarian tissues were analyzed to measure the oxidative state and histopathological changes. Our results proved that either hemin or L-arginine administration could improve the oxidative state, the inflammatory reaction, the hormonal imbalance, and the metabolic disturbances in PCO rats, which was confirmed by a histopathological examination of the rats' ovaries. In conclusion, either hemin or L-arginine had protective effects against PCOS with better pathophysiological changes with hemin.

Histopathological changes in androgenized ovaries are recovered by melatonin treatment

Nandrolone decanoate (ND) is a synthetic steroid, which promotes adverse effects on the ovarian tissue, and melatonin (MLT) exhibits a number of beneficial properties in the reproductive system. This study evaluated the general features of the ovarian tissue and the immunoexpression of sex steroid receptors in ND-treated rats that were submitted to short-term melatonin treatment. Adult rats received mineral oil (control group) and ND at doses of 7.5 mg/kg for 15 days (ND-treated group). The treatment with MLT (10mg/kg for 7 days) was given alone, before or in combination with ND. All ND-treated animals showed persistent dioestrus. In the androgenized groups that received MLT, ovarian morphology and size, and the number/area of corpora lutea were recovered. The number of healthy and atretic follicles was recovered when MLT was administered prior to ND; this was similar to the ovaries of control and MLT groups. There was a decrease in estrogen receptors immunostaining in the follicles of androgenized rats that were treated with MLT, and pretreatment with MLT reduced the expression of androgen receptor in atretic follicles and corpora lutea, when compared with ND-treated group. We conclude that MLT treatment recovered the histopathological aspects of the androgenized ovaries, and MLT pretreatment was the most effective.

How to choose the suitable animal model of polycystic ovary syndrome?

Polycystic ovary syndrome (PCOS) is a gynecological metabolic and endocrine disorder with uncertain etiology. To understand the etiology of PCOS or the evaluation of various therapeutic agents, different animal models have been introduced. Considering this fact that is difficult to develop an animal model that mimics all aspects of this syndrome, but, similarity of biological, anatomical, and/or biochemical features of animal model to the human PCOS phenotypes can increase its application. This review paper evaluates the recently researched animal models and introduced the best models for different research purposes in PCOS studies. During January 2013 to January 2017, 162 studies were identified which applied various kinds of animal models of PCOS including rodent, primate, ruminant and fish. Between these models, prenatal and pre-pubertal androgen rat models and then prenatal androgen mouse model have been studied in detail than others. The comparison of main features of these models with women PCOS demonstrates higher similarity of these three models to human conditions. Thereafter, letrozole models can be recommended for the investigation of various aspects of PCOS. Interestingly, similarity of PCOS features of post-pubertal insulin and human chorionic gonadotropin rat models with women PCOS were considerable which can make it as a good choice for future investigations.

Evidence from animal models on the pathogenesis of PCOS

Polycystic ovarian syndrome (PCOS) is the most common endocrine condition in women, and is characterized by reproductive, endocrine and metabolic features. However, there is no simple unequivocal diagnostic test for PCOS, its etiology remains unknown and there is no cure. Hence, the management of PCOS is suboptimal as it relies on the ad hoc empirical management of its symptoms only. Decisive studies are required to unravel the origins of PCOS, but due to ethical and logistical reasons these are not possible in humans. Experimental animal models for PCOS have been established which have enhanced our understanding of the mechanisms underlying PCOS and propose novel mechanism-based therapies to treat the condition. This review examines the findings from various animal models to reveal the current knowledge of the mechanisms underpinning the development of PCOS, and also provides insights into the implications from these studies for improved clinical management of this disorder.

Eicosapentaenoic Acid Improves Polycystic Ovary Syndrome in Rats via Sterol Regulatory Element-Binding Protein 1 (SREBP-1)/Toll-Like Receptor 4 (TLR4) Pathway

BACKGROUND This study aimed to investigate the protective effect of eicosapentaenoic acid (EPA) on rats with polycystic ovary syndrome (PCOS). MATERIAL AND METHODS Rats with PCOS were intraperitoneally injected with different doses of EPA. Levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) were measured using corresponding kits. HE staining was used to observe lesions in ovarian tissue. Levels of inflammatory factors in ovarian tissue of rats were detected by ELISA. RT-PCR was to detect the expression of SREBP1 mRNA and Western blot was used to detect the expression of SREBP1 and TLR4 protein. RESULTS The levels of LH and T were significantly higher and FDH was significantly lower in the Model group compared with the Control group. EPA treatment increased the number of follicular cell layers and promoted maturation of oocytes. Levels of IL-1β, TNF-α, and IL-18 were significantly reduced after EPA treatment. Content of IL-10 was significantly increased after EPA treatment. Expression levels of SREBP1 and TLR4 were significantly deceased after EPA treatment. CONCLUSIONS EPA can improve PCOS through the SREBP1/TLR4 pathway.

Protective effect of melatonin on cadmium-induced changes in some maturation and reproductive parameters of female Prussian carp (Carassius gibelio B.)

The aim of this study was to determine whether melatonin (Mel), which is a known antioxidant and free radical scavenger, could perform the role of a preventive agent against the toxic effects of cadmium (Cd²⁺) on mortality, fish growth, gonadosomatic index (GSI), luteinizing hormone (LH) secretion, the response to hormonal stimulation of spawning, and also tissue accumulation of Cd in Prussian carp females. These females received melatonin implants and were exposed to 0.4 or 4.0 mg/L of Cd (as CdCl₂·2.5H₂O) over either a 5- or 3-month period, followed by further 2 months of purification in clear water. Negative changes caused by exposure to cadmium in the water were as follows: higher fish mortality, lower body weight, increased accumulation of cadmium in the brain and ovary, lowered GSI, impaired spontaneous LH secretion during exposure, and impaired LH secretion during stimulation of spawning. All of these effects were observed in the group of fish exposed to 0.4 and/or 4.0 mg Cd/L but did not occur or were less pronounced in the groups exposed to cadmium in the presence of melatonin released from the implants. During depuration, in the group of fish which had been exposed to the highest Cd concentration, we observed a significant improvement in fish survival rate, body growth, inhibition of further cadmium accumulation in tissues, and gradual return of spontaneous LH secretion as well as normalization of the GSI value to the control group levels. In conclusion, these findings indicate that melatonin can be a preventive agent for some toxic effects on fish reproduction induced by environmental cadmium contamination.

Pleiotropic roles of melatonin in endometriosis, recurrent spontaneous abortion, and polycystic ovary syndrome

Melatonin is a neurohormone synthesized from the aromatic amino acid tryptophan mainly by the pineal gland of mammals. Melatonin acts as a broad-spectrum antioxidant, powerful free radical scavenger, anti-inflammatory agent, anticarcinogenic factor, sleep inducer and regulator of the circadian rhythm, and potential immunoregulator. Melatonin and reproductive system are interrelated under both physiological and pathological conditions. Oxidative stress, inflammation, and immune dysregulation are associated with the pathogenesis of the female reproductive system which causes endometriosis (EMS), recurrent spontaneous abortion (RSA), and polycystic ovary syndrome (PCOS). Accumulating studies have indicated that melatonin plays pleiotropic and essential roles in these obstetrical and gynecological disorders and would be a candidate therapeutic drug to regulate inflammation and immune function and protect special cells or organs. Here, we systematically review the pleiotropic roles of melatonin in EMS, RSA, and PCOS to explore its pathological implications and treatment potential.

The Polycystic Ovary Syndrome and the Metabolic Syndrome: A Possible Chronobiotic-Cytoprotective Adjuvant Therapy

Polycystic ovary syndrome is a highly frequent reproductive-endocrine disorder affecting up to 8-10% of women worldwide at reproductive age. Although its etiology is not fully understood, evidence suggests that insulin resistance, with or without compensatory hyperinsulinemia, and hyperandrogenism are very common features of the polycystic ovary syndrome phenotype. Dysfunctional white adipose tissue has been identified as a major contributing factor for insulin resistance in polycystic ovary syndrome. Environmental (e.g., chronodisruption) and genetic/epigenetic factors may also play relevant roles in syndrome development. Overweight and/or obesity are very common in women with polycystic ovary syndrome, thus suggesting that some polycystic ovary syndrome and metabolic syndrome female phenotypes share common characteristics. Sleep disturbances have been reported to double in women with PCOS and obstructive sleep apnea is a common feature in polycystic ovary syndrome patients. Maturation of the luteinizing hormone-releasing hormone secretion pattern in girls in puberty is closely related to changes in the sleep-wake cycle and could have relevance in the pathogenesis of polycystic ovary syndrome. This review article focuses on two main issues in the polycystic ovary syndrome-metabolic syndrome phenotype development: (a) the impact of androgen excess on white adipose tissue function and (b) the possible efficacy of adjuvant melatonin therapy to improve the chronobiologic profile in polycystic ovary syndrome-metabolic syndrome individuals. Genetic variants in melatonin receptor have been linked to increased risk of developing polycystic ovary syndrome, to impairments in insulin secretion, and to increased fasting glucose levels. Melatonin therapy may protect against several metabolic syndrome comorbidities in polycystic ovary syndrome and could be applied from the initial phases of patients' treatment.

Melatonin, mitochondria, and the metabolic syndrome

A number of risk factors for cardiovascular disease including hyperinsulinemia, glucose intolerance, dyslipidemia, obesity, and elevated blood pressure are collectively known as metabolic syndrome (MS). Since mitochondrial activity is modulated by the availability of energy in cells, the disruption of key regulators of metabolism in MS not only affects the activity of mitochondria but also their dynamics and turnover. Therefore, a link of MS with mitochondrial dysfunction has been suspected since long. As a chronobiotic/cytoprotective agent, melatonin has a special place in prevention and treatment of MS. Melatonin levels are reduced in diseases associated with insulin resistance like MS. Melatonin improves sleep efficiency and has antioxidant and anti-inflammatory properties, partly for its role as a metabolic regulator and mitochondrial protector. We discuss in the present review the several cytoprotective melatonin actions that attenuate inflammatory responses in MS. The clinical data that support the potential therapeutical value of melatonin in human MS are reviewed.

Chronomedicine and type 2 diabetes: shining some light on melatonin

In mammals, the circadian timing system drives rhythms of physiology and behaviour, including the daily rhythms of feeding and activity. The timing system coordinates temporal variation in the biochemical landscape with changes in nutrient intake in order to optimise energy balance and maintain metabolic homeostasis. Circadian disruption (e.g. as a result of shift work or jet lag) can disturb this continuity and increase the risk of cardiometabolic disease. Obesity and metabolic disease can also disturb the timing and amplitude of the clock in multiple organ systems, further exacerbating disease progression. As our understanding of the synergy between the timing system and metabolism has grown, an interest has emerged in the development of novel clock-targeting pharmaceuticals or nutraceuticals for the treatment of metabolic dysfunction. Recently, the pineal hormone melatonin has received some attention as a potential chronotherapeutic drug for metabolic disease. Melatonin is well known for its sleep-promoting effects and putative activity as a chronobiotic drug, stimulating coordination of biochemical oscillations through targeting the internal timing system. Melatonin affects the insulin secretory activity of the pancreatic beta cell, hepatic glucose metabolism and insulin sensitivity. Individuals with type 2 diabetes mellitus have lower night-time serum melatonin levels and increased risk of comorbid sleep disturbances compared with healthy individuals. Further, reduced melatonin levels, and mutations and/or genetic polymorphisms of the melatonin receptors are associated with an increased risk of developing type 2 diabetes. Herein we review our understanding of molecular clock control of glucose homeostasis, detail the influence of circadian disruption on glucose metabolism in critical peripheral tissues, explore the contribution of melatonin signalling to the aetiology of type 2 diabetes, and discuss the pros and cons of melatonin chronopharmacotherapy in disease management.

Melatonin and the pathologies of weakened or dysregulated circadian oscillators

Dynamic aspects of melatonin's actions merit increasing future attention. This concerns particularly entirely different effects in senescent, weakened oscillators and in dysregulated oscillators of cancer cells that may be epigenetically blocked. This is especially obvious in the case of sirtuin 1, which is upregulated by melatonin in aged tissues, but strongly downregulated in several cancer cells. These findings are not at all controversial, but are explained on the basis of divergent changes in weakened and dysregulated oscillators. Similar findings can be expected to occur in other accessory oscillator components that are modulated by melatonin, among them several transcription factors and metabolic sensors. Another cause of opposite effects concerns differences between nocturnally active laboratory rodents and the diurnally active human. This should be more thoroughly considered in the field of metabolic syndrome and related pathologies, especially with regard to type 2 diabetes and other aspects of insulin resistance. Melatonin was reported to impair glucose tolerance in humans, especially in carriers of the risk allele of the MT₂ receptor gene, MTNR1B, that contains the SNP rs10830963. These findings contrast with numerous reports on improvements of glucose tolerance in preclinical studies. However, the relationship between melatonin and insulin may be more complex, as indicated by loss-of-function mutants of the MT₂ receptor that are also prodiabetic, by the age-dependent time course of risk allele overexpression, by progressive reduction in circadian amplitudes and melatonin secretion, which are aggravated in diabetes. By supporting high-amplitude rhythms, melatonin may be beneficial in preventing or delaying diabetes.

Ameliorative effects of rutin against metabolic, biochemical and hormonal disturbances in polycystic ovary syndrome in rats

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most prevalent endocrinopathy in women of reproductive age. The study was commenced to assess the favorable effects of Rutin against metabolic, biochemical, histological, and androgenic aspects of polycystic ovary syndrome in rats.

METHODS

Female Sprague-Dawley rats were administered letrozole (1 mg/kg) per orally (p.o) for a period of 21 days for the induction of PCOS, followed by dose of rutin (100 mg/kg and 150 mg/kg, p.o) for 15 days using 0.5% w/v CMC as vehicle. Metformin was also given as a standard control to one of the rat groups. Serum estradiol, progesterone, testosterone, serum lipid parameters, CRP and glucose levels were evaluated. Furthermore, antioxidant activity was tested using superoxide dismutase, catalase, glutathione per-oxidase and reactive-oxygen species level.

RESULTS

Rutin flavonoid had a dose-dependent effect on androgenic levels depicting more recovery in the rutin-I treated group, while rutin-II treated groups showed better antioxidant and lipid profiles as compared with PCOS groups. A decrease in the value of C reactive protein (CRP) and a restoration in the proportion of estrous phase smears were observed in the rutin treated groups. Histopathological examination of ovary revealed a significant decrease in the number of cystic follicles in post treated groups. The effects observed with rutin were moderately similar to that with standard metformin, a widely used treatment drug for PCOS.

CONCLUSION

The study provides evidence for the potential ameliorative effects of rutin against clinical and biochemical features of PCOS.

The Circadian Timing System and Environmental Circadian Disruption: From Follicles to Fertility

The internal or circadian timing system is deeply integrated in female reproductive physiology. Considerable details of rheostatic timing function in the neuroendocrine control of pituitary hormone secretion, adenohypophyseal hormone gene expression and secretion, gonadal steroid hormone biosynthesis and secretion, ovulation, implantation, and parturition have been reported. The molecular clock, an autonomous feedback loop oscillator of interacting transcriptional regulators, dictates the timing and amplitude of gene expression in each tissue of the female hypothalamic-pituitary-gonadal (HPG) axis. Although multiple targets of the molecular clock have been identified, many associated with critical physiological functions in the HPG axis, the full extent of clock-driven gene expression and physiology in this critical system remains unknown. Environmental circadian disruption (ECD), the disturbance of temporal relationships within and between internal clocks (brain and periphery), and external timing cues (eg, light, nutrients, social cues) due to rotating/night shift work or transmeridian travel have been linked to reproductive dysfunction and subfertility. Moreover, ECD resulting from exposure to endocrine disrupting chemicals, environmental toxins, and/or irregular hormone levels during sexual development can also reduce fertility. Thus, perturbations that disturb clock function at the molecular, cellular or systemic level correlate with significant declines in female reproductive function. Here we briefly review the evidence for molecular clock function in each tissue of the female HPG axis (GnRH neuron, pituitary, uterus, oviduct, and ovary), describe the human epidemiological and animal data supporting the negative effects of ECD on fertility, and explore the potential for novel chronotherapeutics in women's health and fertility.

Manipulating the circadian and sleep cycles to protect against metabolic disease

Modernization of human society parallels an epidemic of metabolic disorders including obesity. Apart from excess caloric intake, a 24/7 lifestyle poses another important challenge to our metabolic health. Recent research under both laboratory and epidemiological settings has indicated that abnormal temporal organization of sleep and wakeful activities including food intake is a significant risk factor for metabolic disease. The circadian clock system is our intrinsic biological timer that regulates internal rhythms such as the sleep/wake cycle and also responses to external stimuli including light and food. Initially thought to be mainly involved in the timing of sleep, the clock, and/or clock genes may also play a role in sleep architecture and homeostasis. Importantly, an extensive body of evidence has firmly established a master regulatory role of the clock in energy balance. Together, a close relationship between well-timed circadian/sleep cycles and metabolic health is emerging. Exploiting this functional connection, an important holistic strategy toward curbing the epidemic of metabolic disorders (e.g., obesity) involves corrective measures on the circadian clock and sleep. In addition to behavioral and environmental interventions including meal timing and light control, pharmacological agents targeting sleep and circadian clocks promise convenient and effective applications. Recent studies, for example, have reported small molecules targeting specific clock components and displaying robust beneficial effects on sleep and metabolism. Furthermore, a group of clock-amplitude-enhancing small molecules (CEMs) identified via high-throughput chemical screens are of particular interest for future in vivo studies of their metabolic and sleep efficacies. Elucidating the functional relationship between clock, sleep, and metabolism will also have far-reaching implications for various chronic human diseases and aging.