Metformin improves ovarian insulin signaling alterations caused by fetal programming

A novel action of insulin sensitizing drug as a potential promotor of preovulatory follicles, ovulation rate and prolificacy in sheep

The effect of the insulin-sensitizing drug metformin on preovulatory follicle (POF) number, ovulation rate, fetal rate and prolificacy was studied in forty-six cyclic Malpura ewes. After estrus synchronization, the ewes were equally divided into two groups (n = 23). The treatment group (MET) received a daily oral dose of metformin at a rate of 500 mg/animal for approximately 12 weeks, spanning five estrous cycles, as against untreated control (CON). All the ewes were bred to proven rams at the end of treatment. Ovarian ultrasound scans were performed at each estrus and day 9 of each cycle to assess the number and diameter of POFs and corpora lutea (CL), respectively. A comprehensive assessment of circulating hormones including, estradiol, progesterone, androstenedione, and insulin as well as metabolic indicators such as glucose, and lipid profile parameters was performed. At the end of treatment on the day of estrus (E5D0), the treatment showed a stimulatory effect on follicular development with a 53.2% (P < 0.001) increase in the number of POFs. It also increased the ovulation rate by 67.4% (P < 0.01), with a higher proportion (χ2df1 = 10.7, P < 0.001) of ewes in the MET group having multiple ovulations compared to the CON group (82.6 vs. 30.4%). With 1.48 ± 0.12 prolificacy rate in MET ewes, the proportion of ewes giving birth to multiple lambs was 2.9-fold higher than in the CON group. Plasma estradiol, insulin, glucose, total cholesterol, and LDL-cholesterol concentrations were lower (P < 0.05) in the MET ewes than in the CON. The results of the present study indicate that metformin can increase the number of POF, ovulation rate, fetal rate and prolificacy in ewes, while reducing the plasma estradiol, insulin, glucose and cholesterol in MET ewes.

Association between different insulin resistance surrogates and infertility in reproductive-aged females

BACKGROUND

Obesity and metabolic syndrome are observed more frequently in infertile women, and insulin resistance (IR) is closely related to them. However, there are no studies that have examined the association between different IR surrogates and female infertility, hence we investigated the potential association between them in the general population.

METHODS

This was a cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES, 2013-2018). The association of different IR surrogates (HOMA-IR index, TyG index and TyG-BMI index) with female infertility was estimated by multivariable regression analysis.

RESULTS

After adjusting for confounders, the HOMA-IR index and TyG index did not show an association with female infertility, while the TyG-BMI index was found to have a positive association with female infertility (OR = 1.01, 95% CI: 1.00, 1.01; P < 0.0001), and the OR of the TyG-BMI group T3 (≥ 255.55) was significantly different compared to the group T1 (< 185.31) (OR = 3.02, 95% CI: 1.62, 5.60). Similar results were seen in most of the subgroup participants by stratified analysis (P-interaction > 0.05). However, different IR surrogates did not show variability in their ability to predict infertility [TyG-BMI: 0.68 (95% CI: 0.62, 0.74) vs. TyG: 0.62 (95% CI: 0.57, 0.68) vs. HOMA-IR: 0.65 (95% CI: 0.60, 0.71)].

CONCLUSIONS

Our result suggests that high levels of TyG-BMI index were positively associated with female infertility in US reproductive-aged females.

ApoC3 is expressed in oocytes and increased expression is associated with PCOS progression

BACKGROUND

Polycystic ovary syndrome (PCOS) is a lifelong metabolic disorder and the most common cause of anovulatory infertility affecting women in reproductive age. Our recent study reported that apolipoprotein C3 (ApoC3) could be a potential diagnostic serum marker for metabolism disturbance in PCOS patients, but whether it is present in the ovaries and what role it plays has not yet been described.

OBJECTIVE

Aimed to investigate ApoC3 expression in ovary of PCOS, and to discuss its potential role in PCOS progression.

METHODS

ApoC3 expression in ovarian tissue samples from 12 PCOS patients along with 12 healthy controls were measured via immunohistochemistry (IHC). Also, the level of ApoC3 in follicular fluid from 14 patients diagnosed with PCOS and 13 control subjects were detected by ELISA. The expression and location of ApoC3 in ovaries of PCOS mice were tested weekly for three consecutive weeks during PCOS formation using real time PCR, Western Blot, IHC and immunofluorescence. The relation of ApoC3 and sex hormones was analyzed in mouse plasma. Additionally, the dynamic changes of ApoC3 level in ovaries of healthy mice during postnatal development was also investigated.

RESULTS

ApoC3 levels in ovarian tissue and follicular fluid were significantly higher in PCOS patients than in controls (33.87 ± 4.11 vs. 27.71 ± 3.65, P < 0.01; 0.87 ± 0.09 vs. 0.51 ± 0.32 ng/mL, P < 0.05), respectively. In ovary, ApoC3 was found to be located in the cytoplasm of oocyte, and its expression gradually increased with PCOS progression (P < 0.05). Furthermore, correlation analysis showed that plasma ApoC3 level was closely associated with luteinizing hormone (r = 0.709, P = 0.001), testosterone (r = 0.627, P = 0.005) and anti-mullerian hormone (r = 0.680, P = 0.002) in PCOS mice. In addition, ApoC3 level in oocyte was physiologically increased and peaked on postnatal age 21 (P21), then decreased following P21 in healthy mice.

CONCLUSIONS

We identified ApoC3 expression in oocyte. It may be involved in PCOS progression and possibly participate in the regulation of oocyte development.

Intrauterine androgen exposure impairs gonadal adipose tissue functions of adult female rats

Prenatal androgen exposure induces fetal programming leading to alterations in offspring health and phenotypes that resemble those seen in women with Polycystic Ovary Syndrome. It has been described that prenatal androgenization affects the reproductive axis and leads to metabolic and endocrine disorders. Adipose tissue plays a crucial role in all these functions and is susceptible to programming effects. Particularly, gonadal adipose tissue is involved in reproductive functions, so dysfunctions in this tissue could be related to fertility alterations. We aimed to investigate the extent to which prenatal hyperandrogenization is able to alter the functionality of gonadal adipose tissue in female adult rats, including lipid metabolism, adipokines expression, and de novo synthesis of steroids. Pregnant rats were treated with 1 mg of testosterone from day 16 to day 19 of pregnancy, and female offspring were followed until 90 days of age, when they were euthanized. The prenatally hyperandrogenized (PH) female offspring displayed two phenotypes: irregular ovulatory (PHiov) and anovulatory (PHanov). Regarding lipid metabolism, both PH groups displayed disruptions in the main lipid pathways with altered levels of triglyceride and increased lipid peroxidation levels. In addition, we found that Peroxisome Proliferator-Activated Receptors (PPARs) alpha protein expression was decreased in both PH phenotypes (p < 0.05), but no changes were found in PPARγ protein levels. Furthermore, regarding adipokines, no changes were found in Leptin and Adiponectin protein levels, but Chemerin protein levels were decreased in the PHiov group (p < 0.05). Regarding de novo synthesis of steroids, the PHanov group showed increased protein levels of Cyp17a1 and Cyp19, while the PHiov group only showed decreased protein levels of Cyp19 (p < 0.05). These results suggest that prenatal androgen exposure affects females' gonadal adipose tissue in adulthood, disturbing different lipid pathways, Chemerin expression, and de novo synthesis of steroids.

Resveratrol regulates insulin resistance to improve the glycolytic pathway by activating SIRT2 in PCOS granulosa cells

Scope

Insulin resistance (IR) has a close relationship with the main clinical manifestations of patients with PCOS; hence, the research and development of new drugs to treat PCOS by improving IR is a desiderate task at present. Resveratrol (RES) possesses a variety of beneficial pharmacological functions, such as antioxidation, anti-inflammatory, regulating glucose, and lipid metabolism. However, whether RES could improve IR and the underlying mechanisms remained unclear in PCOS.

Methods and results

SD rats received a high-fat diet and letrozole for 30 days to establish the PCOS model and then intervened with RES for 30 days. The results demonstrated that RES played a protective role on the IR in PCOS rats, which significantly decreased the levels of blood glucose and serum insulin, up regulated the expression of IGF1R, and down regulated the expression of IGF1. In vitro, KGN cells were treated with insulin, RES, and AGK2, respectively. We found that a high dose of insulin (4μg/mL) significantly inhibited KGN cell viability, decreased the level of lactic acid, and increased the level of pyruvate, while RES (25μM) attenuated the growth-inhibitory effect, as well as increased the level of lactic acid and decreased the level of pyruvate after high levels of insulin treatment. Simultaneously, RES up regulated the expression level of the crucial rate-limiting enzymes relating to glycolytic pathways, such as LDHA, HK2, and PKM2. Furthermore, AGK2 remarkably inhibited the expression level of SIRT2, which was similar to the same negative effects processed by insulin. Meanwhile, RES overtly repaired the glycolysis process by reversing the levels of lactic acid and pyruvate, together with up regulating the expression level of LDHA, HK2, and PKM2, after AGK2 treatment.

Conclusion

RES could effectively improve insulin resistance and restore the glycolysis pathway by regulating SIRT2, which may contribute to attenuating the ovarian damage of PCOS rats and provide a potential treatment for patients with PCOS.

Hyperandrogenism and Polycystic ovary syndrome: Effects in pregnancy and offspring development

Polycystic ovary syndrome (PCOS) is one of the major endocrine disorders affecting women of reproductive age. Its etiology remains unclear. It is suggested that environmental factors, and particularly the intrauterine environment, play key roles in PCOS development. Besides the role of androgens in PCOS pathogenesis, exposure to endocrine disruptors, as is Bisphenol A, could also contribute to its development. Although PCOS is considered one of the leading causes of ovarian infertility, many PCOS patients can get pregnant. Some of them by natural conception and others by assisted reproductive technique treatments. As hyperandrogenism (one of PCOS main features) affects ovarian and uterine functions, PCOS women, despite reaching pregnancy, could present high-risk pregnancies, including implantation failure, an increased risk of gestational diabetes, preeclampsia, and preterm birth. Moreover, hyperandrogenism may also be maintained in these women during pregnancy. Therefore, as an altered uterine milieu, including hormonal imbalance, could affect the developing organisms, monitoring these patients throughout pregnancy and their offspring development is highly relevant. The present review focuses on the impact of androgenism and PCOS on fertility issues and pregnancy-related outcomes and offspring development. The evidence suggests that the increased risk of pregnancy complications and adverse offspring outcomes of PCOS women would be due to the factors involved in the syndrome pathogenesis and the related co-morbidities. A better understanding of the involved mechanisms is still needed and could contribute to a better management of these women and their offspring. This article is categorized under: Reproductive System Diseases > Molecular and Cellular Physiology Reproductive System Diseases > Environmental Factors.

Glucose transporter 4 mRNA expression in subcutaneous adipose tissue of women with PCOS remains unchanged despite metformin withdrawal: is there a cellular metabolic treatment legacy effect?

PURPOSE

Metformin induces GLUT-4 mRNA expression in insulin target tissues in PCOS. It is unclear how long this impact is sustained after withdrawal of metformin. We aimed to compare the effect of metformin withdrawal on GLUT-4 mRNA expression in subcutaneous adipose tissue after prior short (ST, 1 year, N = 11) and long term (LT, at least 3 years, N = 13) treatment in obese PCOS women.

METHODS

At baseline and 6 months after withdrawal, biopsy of subcutaneous adipose tissue followed by quantitative PCR analysis was performed to determine GLUT-4 mRNA expression.

RESULTS

We found no time/effect differences in GLUT-4 mRNA expression in ST (2^-dCt at baseline 0.42 (0.16-0.48) vs 2^-dCt after 6 months 0.31 (0.22-0.56), p = 0.594) and no time/effect difference in LT group (2^-dCt at baseline 0.24 (0.14-0.39) vs 2^-dCt after 6 months 0.25 (0.20-0.38), p = 0.382). There was also no difference in GLUT-4 mRNA expression between both groups at baseline and after 6 months.

CONCLUSIONS

In summary, 6 months after metformin withdrawal, GLUT-4 mRNA expression in subcutaneous adipose tissue remained stable, regardless of the prior treatment duration.

Metformin and Insulin Resistance: A Review of the Underlying Mechanisms behind Changes in GLUT4-Mediated Glucose Transport

Metformin is the most commonly used treatment to increase insulin sensitivity in insulin-resistant (IR) conditions such as diabetes, prediabetes, polycystic ovary syndrome, and obesity. There is a well-documented correlation between glucose transporter 4 (GLUT4) expression and the level of IR. Therefore, the observed increase in peripheral glucose utilization after metformin treatment most likely comes from the induction of GLUT4 expression and its increased translocation to the plasma membrane. However, the mechanisms behind this effect and the critical metformin targets are still largely undefined. The present review explores the evidence for the crucial role of changes in the expression and activation of insulin signaling pathway mediators, AMPK, several GLUT4 translocation mediators, and the effect of posttranscriptional modifications based on previously published preclinical and clinical models of metformin’s mode of action in animal and human studies. Our aim is to provide a comprehensive review of the studies in this field in order to shed some light on the complex interactions between metformin action, GLUT4 expression, GLUT4 translocation, and the observed increase in peripheral insulin sensitivity.

Polycystic ovarian syndrome: signs and feedback effects of hyperandrogenism and insulin resistance

Polycystic ovary syndrome (PCOS) is a disease whose diagnosis is based on the detection of hyperandrogenism (HA) and ovulatory dysfunction. Women with PCOS frequently develop insulin resistance (IR), which generates a metabolic condition that involves a decrease in the action of insulin at the cellular level and is linked to compensatory hyperinsulinemia (HI). In PCOS, the ovary remains sensitive to the action of insulin. Additionally, it has been observed that the main effect of insulin in the ovary is the stimulation of androgen synthesis, resulting in HA, one of the fundamental characteristics of the PCOS. In this sense, the excess of androgens favors the development of IR, thus perpetuating the cycle of IR-HI-HA, and therefore PCOS. Moreover, mitochondrial dysfunction is present in PCOS patients and is a common feature in both IR and HA. This review places electron transfer as a key element in HA and IR development, with emphasis on the relationship between androgen biosynthesis and mitochondrial function. Indeed, metformin has been involved in repair mitochondrial dysfunction, decrease of oxidative stress, reduction of androgens levels and the enhancing of insulin sensitivity. Therefore, we propose that treatment with metformin could decrease HI and consequently HA, restoring, at least in part, the metabolic and hormonal disorders of PCOS.

Investigation of the Mechanism of Zishen Yutai Pills on Polycystic Ovary Syndrome: A Network Pharmacology and Molecular Docking Approach

BACKGROUND

Zishen Yutai Pills (ZSYTP) is a prescription based on traditional Chinese medicine used to treat kidney-deficient pattern in traditional Chinese medicine. It is also widely used clinically for the treatment of polycystic ovary syndrome (PCOS) with positive results. This study aims to explore the potential pharmacological mechanism of ZSYTP for the treatment of PCOS by a network pharmacology approach.

METHODS

Compounds were collected from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform and Bioinformatics Analysis Tool for Molecular mechanism of Traditional Chinese Medicine and TCM Database@ Taiwan, and the corresponding targets were retrieved from PubChem, Swiss Target Prediction, STITCH, and DrugBank. Meanwhile, PCOS targets were retrieved from the GeneCards database, the Online Mendelian Inheritance in Man database, National Center for Biotechnology Information Database, and DrugBank. Subsequently, multiple network construction and gene enrichment analyses were conducted with Cytoscape 3.8.2 software. Based on the previous results in the study, molecular docking simulations were done.

RESULTS

205 active compounds and 478 ZSYTP target genes were obtained after screening by ADME consideration. 1881 disease-related targets were obtained after removing duplicates. 148 intersection target genes between drug and disease targets were isolated. Gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes analysis highlighted multiple gene functions and different signaling pathways to treat PCOS. Further molecular docking demonstrated the practicality of in vivo action of ZSYTP to a certain extent.

CONCLUSIONS

It is possible that the pharmacological effect of ZSYTP on PCOS is linked to the hypoxia-inducible factor 1 (HIF-1) signaling pathway, improving insulin resistance, the variation on gene expression such as RNA splicing, and regulation of mRNA metabolic process. This study paves the way for further research investigating its mechanisms.

Fetal programming by androgen excess impairs liver lipid content and PPARg expression in adult rats

It is known that prenatal hyperandrogenization induces alterations since early stages of life, contributing to the development of polycystic ovary syndrome affecting the reproductive axis and the metabolic status, thus promoting others associated disorders, such as dyslipidemia, insulin resistance, liver dysfunction, and even steatosis. In this study, we aimed to evaluate the effect of fetal programming by androgen excess on the hepatic lipid content and metabolic mediators at adult life. Pregnant rats were hyperandrogenized with daily subcutaneous injections of 1 mg of free testosterone from days 16 to 19 of pregnancy. The prenatally hyperandrogenized (PH) female offspring displayed two phenotypes: irregular ovulatory phenotype (PHiov) and anovulatory phenotype (PHanov), with different metabolic and endocrine features. We evaluated the liver lipid content and the main aspect of the balance between fatty acid (FA) synthesis and oxidation. We investigated the status of the peroxisomal proliferator-activated receptors (PPARs) alpha and gamma, which act as lipid mediators, and the adipokine chemerin, one marker of liver alterations. We found that prenatal hyperandrogenization altered the liver lipid profile with increased FAs levels in the PHanov phenotype and decreased cholesterol content in the PHiov phenotype. FA metabolism was also disturbed, including decreased mRNA and protein PPARgamma levels and impaired gene expression of the main enzymes involved in lipid metabolism. Moreover, we found low chemerin protein levels in both PH phenotypes. In conclusion, these data suggest that prenatal hyperandrogenization exerts a negative effect on the liver and alters lipid content and metabolic mediators' expression at adult age.

Prenatal testosterone exposure induces insulin resistance, uterine oxidative stress and pro-inflammatory status in rats

Prenatal androgen excess is considered one of the main causes of the development of polycystic ovary syndrome. In this study, we investigated the effect of prenatal hyperandrogenization (PH) on the physiology of the adult uterine tissue using a murine model of fetal programming caused by androgen excess in adult female rats. Pregnant rats were hyperandrogenized with testosterone and female offspring were studied when adult. Our results showed that PH leads to hyperglycemia and hyperinsulinemia. Consequently, PH developed insulin resistance and a systemic inflammatory state reflected by increased C-reactive protein. In the uterine tissue, levels of PPAR gamma-an important metabolic sensor in the endometrium-were found to be impaired. Moreover, PH induced a pro-inflammatory and an unbalanced oxidative state in the uterus reflected by increased COX-2, lipid peroxidation, and NF-κB. In summary, our results revealed that PH leads to a compromised metabolic state likely consequence of fetal reprogramming.

The effects of assisted reproduction technologies on metabolic health and disease†

The increasing prevalence of metabolic diseases places a substantial burden on human health throughout the world. It is believed that predisposition to metabolic disease starts early in life, a period of great susceptibility to epigenetic reprogramming due to environmental insults. Assisted reproductive technologies (ART), i.e., treatments for infertility, may affect embryo development, resulting in multiple adverse health outcomes in postnatal life. The most frequently observed alteration in ART pregnancies is impaired placental nutrient transfer. Moreover, consequent intrauterine growth restriction and low birth weight followed by catch-up growth can all predict future obesity, insulin resistance, and chronic metabolic diseases. In this review, we have focused on evidence of adverse metabolic alterations associated with ART, which can contribute to the development of chronic adult-onset diseases, such as metabolic syndrome, type 2 diabetes, and cardiovascular disease. Due to high phenotypic plasticity, ART pregnancies can produce both offspring with adverse health outcomes, as well as healthy individuals. We further discuss the sex-specific and age-dependent metabolic alterations reflected in ART offspring, and how the degree of interference of a given ART procedure (from mild to more severe manipulation of the egg) affects the occurrence and degree of offspring alterations. Over the last few years, studies have reported signs of cardiometabolic alterations in ART offspring that are detectable at a young age but that do not appear to constitute a high risk of disease and morbidity per se. These abnormal phenotypes could be early indicators of the development of chronic diseases, including metabolic syndrome, in adulthood. The early detection of metabolic alterations could contribute to preventing the onset of disease in adulthood. Such early interventions may counteract the risk factors and improve the long-term health of the individual.

Prenatally androgenized female rats develop uterine hyperplasia when adult

Prenatal hyperandrogenization (PH) is hypothesized as one of the main factors contributing to the development of polycystic ovary syndrome (PCOS). In this study, we aimed to investigate the impact of prenatal exposure to androgen excess on the uterus when animals reach their adulthood. We found that PH altered the morphology of the uteri that show a hyperplastic morphology with increased total uterine thickness as well as luminal epithelium thickness, with both enhanced and altered distribution of glands as compared with controls. Morphological alterations were associated with an unbalanced homeostasis as assessed by the expression of regulators of cell cycle progression and cell death dynamics. PH also causes disturbances in the cell cycle of the uterine tissue and dysregulates cell death and survival pathways leading to the development of uterine hyperplasia. These findings suggest that PH may have a deleterious effect on the uterus.

Effects of in utero androgen excess and metformin treatment on hepatic functions

This study aimed to evaluate the role of prenatal hyperandrogenization in liver functions and the extent of metformin as treatment. Pregnant rats were hyperandrogenized with subcutaneous testosterone (1mg/rat) between 16 and 19 of pregnancy. Prenatally hyperandrogenized (PH) female offspring displayed, at the adult life, two phenotypes; a PH irregular ovulatory phenotype (PHiov) and a PH anovulatory (PHanov) phenotype. From day 70 to the moment of sacrifice (90 days of age), 50% of the animals of each group received a daily oral dose of 50 mg/kg of metformin. We found that both PH phenotypes displayed a hepatic disruptions of insulin and glucose pathway and that metformin treatment reversed some of these alterations in a specific-phenotype manner. Our findings show, for the first time, that androgen excess in utero promotes hepatic dysfunctions and that metformin treatment is able to specifically reverse those hepatic alterations and sheds light on the possible mechanisms of metformin action.