Metabolic actions of insulin in ovarian granulosa cells were unaffected by hyperandrogenism

Elevated IGFBP7 expression in follicular granulosa cells promotes PCOS pathogenesis

Polycystic ovary syndrome (PCOS) can result in female infertility, menstrual irregularities, metabolic disturbances, hormonal imbalances, and significantly impact the reproductive health of women of childbearing age. Hyperandrogenism and insulin resistance are typical primary endocrine features of PCOS, which are also regarded as its core pathogenesis. In this study, IGFBP7 expression in granulosa cells (GCs) from women with and without PCOS was analyzed using bulk RNA-seq. A PCOS-like mouse model was constructed using dehydroepiandrosterone in IGFBP7 knockout and wild-type mice to explore the role of IGFBP7 in PCOS. Primary GCs from mice were cultured and transfected with IGFBP7 overexpression plasmid and siRNA fragments. Proliferation, apoptosis, and steroid hormone levels were measured to investigate the effects of IGFBP7 on granulosa cells. IGFBP7 expression was found to be elevated in patients with PCOS. Following IGFBP7 knockdown in mouse GC, there was a significant increase in GC proliferation, a decrease in GC apoptosis, and a notable decrease in testosterone secretion by GC. Conversely, overexpression of IGFBP7 in mouse granulosa cells significantly inhibited GC proliferation, significantly increased GC apoptosis, and led to a marked increase in testosterone secretion by GCs. With mouse model, a reduction in PCOS symptoms in mice after IGFBP7 deletion was observed. Elevated IGFBP7 expression in PCOS granulosa cells may induce apoptosis, hinder insulin signaling, and enhance androgen synthesis. These insights offer novel avenues for understanding and treating PCOS.

An Update on Physiopathological Roles of Akt in the ReprodAKTive Mammalian Ovary

The phosphoinositide 3-kinase (PI3K)/Akt pathway is a key signaling cascade responsible for the regulation of cell survival, proliferation, and metabolism in the ovarian microenvironment. The optimal finetuning of this pathway is essential for physiological processes concerning oogenesis, folliculogenesis, oocyte maturation, and embryo development. The dysregulation of PI3K/Akt can impair molecular and structural mechanisms that will lead to follicle atresia, or the inability of embryos to reach later stages of development. Due to its pivotal role in the control of cell proliferation, apoptosis, and survival mechanisms, the dysregulation of this molecular pathway can trigger the onset of pathological conditions. Among these, we will focus on diseases that can harm female fertility, such as polycystic ovary syndrome and premature ovarian failure, or women's general health, such as ovarian cancer. In this review, we report the functions of the PI3K/Akt pathway in both its physiological and pathological roles, and we address the existing application of inhibitors and activators for the balancing of the molecular cascade in ovarian pathological environments.

Differential Gene Expression Analysis of Human Ovarian Follicular Cumulus and Mural Granulosa Cells Under the Influence of Insulin in IVF Ovulatory Women and Polycystic Ovary Syndrome Patients Through Network Analysis

BACKGROUND

Polycystic ovarian syndrome (PCOS) is a commonly occurring reproductive disorder among the reproductive-aged women. Its global occurrence varies based on diagnostic guidelines, ethnicities, and locations of concern. Insulin resistance (IR) is commonly observed around 65-70% of women diagnosed with PCOS, representing a prevalent association. Consequently, the study was designed with an objective of illustrating the effect of insulin on mural and cumulus granulosa cells (GCs) of PCOS patients in comparison to normal ovulating women.

METHODOLOGY

This study is a case-control design, wherein a total of 80 participants were recruited meeting criterion of inclusion and exclusion, divided into 8 groups with each group consisting of 10 samples. The process involves the isolation and culturing of mural granulosa cells (MGC) and cumulus granulosa cells (CGC) with and without exposure to insulin. The proteins released by untreated GCs and insulin-treated GCs were extracted, and complex protein mixtures were digested with trypsin, followed by tandem mass spectrometry analysis and data processing using bioinformatics.

RESULTS

We found 595 proteins in both control and PCOS samples, of which 310 were contributed by MGCs and 285 by CGCs. The PCOS MGCs expressed 20%, both the normal MGCs and CGCs have equal representation of 16% by each, whereas the PCOS CGCs proteins contributed 15% of the total of the proteomic expression. However, the poor expression observed with the Insulin exposure, the Insulin treated PCOS CGCs contributes 13%, PCOS MGCs contributes 8%. The normal MGCs upon the Insulin treatment give 8% then and there only 4% of proteins expressed by normal CGCs after Insulin treatment. The Venn analysis widened on their precise expression topographies. The examination of strings exhibited important protein-protein interaction pathways.

CONCLUSION

This is a pioneering investigation aimed to establish the link between hyperinsulinemia in localized follicular GCs and PCOS mechanisms by comparing them to control group. The examination of various attributes, mechanisms, and traits shown by genes and proteins in individuals with PCOS compared to control populations, alongside the investigation of the dynamics of these genes and proteins following exposure to insulin, holds promise for the formulation of novel hypotheses and strategies in the identification of new biomarkers.

Essential Role of Granulosa Cell Glucose and Lipid Metabolism on Oocytes and the Potential Metabolic Imbalance in Polycystic Ovary Syndrome

Granulosa cells are crucial for the establishment and maintenance of bidirectional communication among oocytes. Various intercellular material exchange modes, including paracrine and gap junction, are used between them to achieve the efficient delivery of granulosa cell structural components, energy substrates, and signaling molecules to oocytes. Glucose metabolism and lipid metabolism are two basic energy metabolism pathways in granulosa cells; these are involved in the normal development of oocytes. Pyruvate, produced by granulosa cell glycolysis, is an important energy substrate for oocyte development. Granulosa cells regulate changes in intrafollicular hormone levels through the processing of steroid hormones to control the development process of oocytes. This article reviews the material exchange between oocytes and granulosa cells and expounds the significance of granulosa cells in the development of oocytes through both glucose metabolism and lipid metabolism. In addition, we discuss the effects of glucose and lipid metabolism on oocytes under pathological conditions and explore its relationship to polycystic ovary syndrome (PCOS). A series of changes were found in the endogenous molecules and ncRNAs that are related to glucose and lipid metabolism in granulosa cells under PCOS conditions. These findings provide a new therapeutic target for patients with PCOS; additionally, there is potential for improving the fertility of patients with PCOS and the clinical outcomes of assisted reproduction.

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.

Chinese herbal medicine alleviates the pathogenesis of polycystic ovary syndrome by improving oxidative stress and glucose metabolism via mitochondrial Sirtuin 3 signaling

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders among women, and the curative effects of its current management are not satisfactory. A formula of Chinese herbal medicine (CHM), called Bu-Shen-Tian-Jing Formula (BSTJF), has clinically shown beneficial effects in treating PCOS.

PURPOSE

This study aimed to investigate the mechanism underlying BSTJF for treatment of PCOS.

METHODS

Whole blood samples were collected from women with PCOS treated and not treated with BSTJF (n = 5 per group). Whole transcriptome sequencing of leukocytes and untargeted metabonomic analysis of the plasma were performed. Three groups of 18 female Sprague-Dawley rats were randomly selected: control, PCOS, and BSTJF. A PCOS rat model was established using testosterone propionate. The estrous cycle; glucose tolerance; ovarian morphology; serum markers of oxidative stress; and expression of Sirtuin 3 (SIRT3), phospho-p38 mitogen-activated protein kinase, phosphatidylinositol 3-kinase (PI3K), and phospho-protein kinase B in the ovary were measured. Palmitate was initially applied to KGN cells, followed by freeze-dried BSTJF powder. The glucose uptake, reactive oxygen species (ROS) production, and protein levels of SIRT3, PI3K, and glucose transporter type 4 (GLUT4) were detected in KGN cells.

RESULTS

The transcriptomic and metabolomic profiles showed alterations in 572 genes and 73 metabolites in women with PCOS treated with BSTJF. The enriched pathways in women with PCOS treated with BSTJF were mainly involved in inflammation, insulin resistance, glucose and lipid metabolism, and neuro and associated signaling pathways. In PCOS rat models, BSTJF improved the estrous cycle, glucose tolerance, and ovarian morphology; relieved oxidative stress; increased ovarian SIRT3 expression; inhibited p38 MAPK activation; and promoted the activation of PI3K/AKT signaling in the ovary. In the in-vitro study with KGN cells, BSTJF rescued the palmitate-induced impaired glucose uptake and SIRT3 expression, reduced mitochondrial ROS production mediated by SIRT3, and restored the impaired insulin-induced PI3K/AKT signaling pathway.

CONCLUSION

BSTJF effectively alleviated the pathogenesis of PCOS by improving oxidative stress and glucose metabolism via mitochondrial SIRT3 and the following insulin signaling pathway. This study innovatively revealed the action mechanism of CHM in treating PCOS.

Resveratrol improves follicular development of PCOS rats via regulating glycolysis pathway and targeting SIRT1

Polycystic ovary syndrome (PCOS) is a disease characterized by metabolic disorders. This study aimed to examine the effects of resveratrol treatment on ovulation in the PCOS rat model. Quantitative real-time PCR and immunohistochemistry were used to determine the mRNA and protein expression levels. TNUEL assay was used to evaluate cell apoptosis in ovary. The metabolites were evaluated by liquid chromatography with tandem mass spectrometry. Resveratrol alleviated disrupted estrous cycle and improved granular cell layers, and reversed the decreased proliferation and increased cell apoptosis of granulosa cells in the ovarian tissues of PCOS rats. Resveratrol restored the changes in the mRNA expression levels in the rate-limiting genes of glycolysis in the PCOS ovary. The expression of lactate dehydrogenase A (LDH-A), pyruvate kinase isozyme M2 (PKM2), and sirtuin 1 (SIRT1) was significantly downregulated in ovarian tissues of the PCOS rats; while the resveratrol treatment significantly increased the expression of LDH-A, PKM2, and SIRT1 in the ovarian tissues of PCOS rats. Collectively, the protective effects of resveratrol in the PCOS rats may be associated with the regulation of glycolysis-related mediators including PKM2, LDH-A, and SIRT1. Resveratrol may represent a good candidate in alleviating the development of PCOS.

Mitochondrial and glucose metabolic dysfunctions in granulosa cells induce impaired oocytes of polycystic ovary syndrome through Sirtuin 3

Mitochondrial function and glucose metabolism play important roles in bidirectional signaling between granulosa cells (GCs) and oocytes. However, the factors associated with mitochondrial function and glucose metabolism of GCs in polycystic ovary syndrome (PCOS) are poorly understood, and their potential downstream effects on oocyte quality are still unknown. The aim of this study was to investigate whether there are alterations in mitochondrial-related functions and glucose metabolism in ovarian GCs of women with PCOS and the role of Sirtuin 3 (SIRT3) in this process. Here, we demonstrated that women with PCOS undergoing in vitro fertilization and embryo transfer had significantly lower rates of metaphase II oocytes, two-pronuclear fertilization, cleavage, and day 3 good-quality embryos. Germinal vesicle- and metaphase I-stage oocytes from women with PCOS exhibited increased mitochondrial reactive oxygen species (ROS), decreased mitochondrial membrane potential, and downregulation of glucose-6-phosphate dehydrogenase. GCs from women with PCOS presented significant alterations in mitochondrial morphology, amount, and localization, decreased membrane potential, reduced adenosine triphosphate (ATP) synthesis, increased mitochondrial ROS and oxidative stress, and insufficient oxidative phosphorylation (OXPHOS) together with decreased glycolysis. SIRT3 expression was significantly decreased in GCs of PCOS patients, and knockdown of SIRT3 in KGN cells could mimic the alterations in mitochondrial functions and glucose metabolism in PCOS GCs. SIRT3 knockdown changed the acetylation status of NDUFS1, which might induce altered mitochondrial OXPHOS, the generation of mitochondrial ROS, and eventually defects in the cellular insulin signaling pathway. These findings suggest that SIRT3 deficiency in GCs of PCOS patients may contribute to mitochondrial dysfunction, elevated oxidative stress, and defects in glucose metabolism, which potentially induce impaired oocytes in PCOS.

microRNA-103 Contributes to Progression of Polycystic Ovary Syndrome Through Modulating the IRS1/PI3K/AKT Signal Axis

BACKGROUND

Polycystic ovary syndrome (PCOS) is a frequent gynecological endocrine disorder, and the majority of PCOS patients experience different degrees of insulin resistance (IR). Nevertheless, the functions of microRNAs (miRNAs) in IR of PCOS remain unclear. In this study, we desired to elucidate the mechanisms of miR-103 in IR of PCOS.

METHODS

The ovarian pathological morphology of established PCOS rats was detected by HE staining. Following miR-103 expression determination in the ovarian tissues of PCOS rats, the relationship between its expression and IR was studied. A PCOS/IR cell model was established, and the effect of miR-103 on granulosa cells was determined by CCK-8 assay and flow cytometry. Through online website prediction and consulting related literatures, the target gene of miR-103 and the pathway regulated by the target genes were discovered, which was verified by further experiments.

RESULTS

PCOS rats showed polycystic changes in the ovary and a decrease in granulosa cells, and these symptoms were more pronounced in rats showed IR. miR-103 expressed highly in PCOS and was positively related to IR. miR-103 inhibitor led to improved PCOS-related symptoms. In addition, miR-103 directly targeted IRS1, which was poorly expressed in PCOS, and IRS1 silencing promoted PCOS development. Furthermore, miR-103 regulated the PI3K/AKT pathway by targeting IRS1, and PI3K/AKT pathway suppression reduced the therapeutic effect of miR-103 inhibitor.

CONCLUSION

This study indicates that miR-103 disrupts the PI3K/AKT pathway activation by targeting IRS1, thereby aggravating PCOS development. miR-103 inhibition may be a promising molecular target for treatment of PCOS.

LNK promotes granulosa cell apoptosis in PCOS via negatively regulating insulin-stimulated AKT-FOXO3 pathway

BACKGROUND

Polycystic ovary syndrome (PCOS), which is often accompanied by insulin resistance, is closely related to increased apoptosis of ovarian granulosa cells. LNK is an important regulator of the insulin signaling pathway. When insulin binds to the receptor, the PI3K/AKT/FOXO signaling pathway is activated, and FOXO translocates from the nucleus to the cytoplasm, thereby inhibiting the expression of pro-apoptotic genes.

METHODS

Granulosa cells were collected from PCOS patients to investigate the relationship between LNK, cell apoptosis and insulin resistance. KGN cells underwent LNK overexpression/silence and insulin stimulation. The AKT/FOXO3 pathway was studied by western blot and immunofluorescence. LNK knockout mice were used to investigate the effect of LNK on the pathogenesis of PCOS.

RESULTS

The level of LNK was higher in PCOS group than control group. LNK was positively correlated with granulosa cell apoptosis and insulin resistance, and negatively correlated with oocyte maturation rate. LNK overexpression in KGN cells inhibited insulin-induced AKT/FOXO3 signaling pathway, causing nucleus translocation of FOXO3 and promoting granulosa cell apoptosis. LNK knockout partially restored estrous cycle and improved glucose metabolism in PCOS mice.

CONCLUSIONS

LNK was closely related to insulin resistance and apoptosis of granulosa cells via the AKT/FOXO3 pathway. LNK knockout partially restored estrous cycle and improved glucose metabolism in PCOS mice, suggesting LNK might become a potential biological target for the clinical treatment of PCOS.

Aberrant elevation of GDF8 impairs granulosa cell glucose metabolism via upregulating SERPINE1 expression in patients with PCOS

Clinical investigations have demonstrated that polycystic ovary syndrome (PCOS) is often accompanied by insulin resistance (IR) in more than 70% of women with PCOS. However, the etiology of PCOS with IR remains to be characterized. Growth differentiation factor 8 (GDF8) is an intraovarian factor that plays a vital role in the regulation of follicle development and ovulation. Previous studies have reported that GDF8 is a pathogenic factor in glucose metabolism disorder in IR patients. To date, the role of GDF8 on glucose metabolism of granulosa cell in PCOS patients remains to be determined. In the current study, we demonstrated that the expression and accumulation of GDF8 in human granulosa-lutein (hGL) cells and follicular fluid from PCOS patients were higher compared with those of non-PCOS women. GDF8 treatment caused glucose metabolism defects in hGL cells. Transcriptome sequencing results showed that SERPINE1 mediated GDF8-induced impairment of hGL glucose metabolism defects. Using pharmacological and small interfering RNA (siRNA)-mediated knockdown approaches, we demonstrated that GDF8 upregulated the expression of SERPINE1 via the ALK5-mediated SMAD2/3-SMAD4 signaling pathway. Interestingly, the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway was also activated with GDF8 treatment but did not participate in the effect of GDF8 on SERPINE1 expression. Our results also showed that TP53 was required for the GDF8-stimulated increase in SERPINE1 expression. Importantly, our study demonstrated that SB-431542 treatment significantly improved DHEA-induced PCOS-like ovaries. These findings support a potential role for GDF8 in metabolic disorders in PCOS.

Combined use of Diane-35 and metformin improves the ovulation in the PCOS rat model possibly via regulating glycolysis pathway

BACKGROUND

Polycystic ovary syndrome (PCOS) is a complex endocrine and metabolic disease with unknown pathogenesis. However, the treatment of Diane-35 combined with metformin can improve the endocrine and ovulation of PCOS. In this study, we investigated the effects of Diane-35 combined with metformin (DM) treatment on ovulation and glucose metabolism in a PCOS rat model.

METHODS

Sprague Dawley rats were divided into 3 groups, control group, model group (PCOS group) and Diane-35 combined with metformin (PCOS + DM group). The mRNA expression levels were determined by qRT-PCR. The hormone levels were determined by enzyme-linked immunosorbent assay. Immunostaining detected the protein levels of lactate dehydrogenase A (LDH-A), pyruvate kinase isozyme M2 (PKM2) and sirtuin 1 (SIRT1) in the ovarian tissues. TNUEL assay was performed to determine cell apoptosis in the PCOS rats. The metabolites in the ovarian tissues were analyzed by liquid chromatography with tandem mass spectrometry.

RESULTS

PCOS rats showed an increased in body weight, levels of luteinizing hormone and testosterone and insulin resistance, which was significantly attenuated by the DM treatment. The DM treatment improved disrupted estrous cycle and increased the granulosa cells of the ovary in the PCOS rats. The decreased proliferation and increased cell apoptosis of granulosa cells in the ovarian tissues of PCOS rats were significantly reversed by the DM treatment. The analysis of metabolics revealed that ATP and lactate levels were significantly decreased in PCOS rats, which was recovered by the DM treatment. Furthermore, the expression of LDH-A, PKM2 and SIRT1 was significantly down-regulated in ovarian tissues of the PCOS rats; while the DM treatment significantly increased the expression of LDH-A, PKM2 and SIRT1 in the ovarian tissues of the PCOS rats.

CONCLUSION

In conclusion, our study demonstrated that Diane-35 plus metformin treatment improved the pathological changes in the PCOS rats. Further studies suggest that Diane-35 plus metformin can improve the energy metabolism of the ovary via regulating the glycolysis pathway. The mechanistic studies indicated that the therapeutic effects of Diane-35 plus metformin treatment in the PCOS rats may be associated with the regulation of glycolysis-related mediators including PKM2, LDH-A and SIRT1.

Lipotoxicity Impairs Granulosa Cell Function Through Activated Endoplasmic Reticulum Stress Pathway

Obesity is closely related to reproductive disorders, which may eventually lead to infertility in both males and females. Ovarian granulosa cells play a critical role during the maintenance of oocyte development through the generation of sex steroids (mainly estradiol and progesterone) and different kinds of growth factors. However, the molecular mechanism of obesity-induced granulosa cell dysfunction remains poorly investigated. In our current study, we observed that high-fat diet feeding significantly increased the level of glucose-regulated protein 78 kDa (GRP78) protein expression in mouse granulosa cells; testosterone-induced estradiol generation was impaired accordingly. To further evaluate the precise mechanism of lipotoxicity-induced granulosa cell dysfunction, mouse primary granulosa cells were treated with palmitate, and the expression levels of ER stress markers were evaluated by real-time PCR and western blot. Lipotoxicity significantly increased ER stress but impaired the mRNA expression of granulosa cell function-related makers, including androgen receptor (Ar), cytochrome P450 family 19 subfamily A member 1 (Cyp19a1), hydroxysteroid 17-beta dehydrogenase 1 (Hsd17b1), and insulin receptor substrate 1 (Irs1). Impaired testosterone-induced estradiol generation was also observed in cultured mouse granulosa cells after palmitate treatment. Insulin augmented testosterone induced estradiol generation through activation of the AKT pathway. However, palmitate treatment abolished insulin-promoted aromatase expression and estradiol generation by the stimulation of ER stress. Overexpression of IRS1 significantly ameliorated palmitate- or tunicamycin-induced impairment of aromatase expression and estradiol generation. Taken together, our current study demonstrated that lipotoxicity impaired insulin-stimulated estradiol generation through activated ER stress and inhibited IRS1 pathway.

Insulin mitigates apoptosis of porcine follicular granulosa cells by downregulating BimEL

Follicular growth or atresia is governed by the survival and apoptosis of granulosa cells. Increasing evidence shows that follicle growth is influenced by energy intake, which is positively related to insulin levels. However, the function of insulin in granulosa cell survival is poorly understood. This study focused on the effects of insulin on porcine medium follicle granulosa cell survival. In the present study, we showed that insulin markedly mitigated the apoptosis of porcine granulosa cells following serum starvation. Moreover, insulin activated the PI3K/Akt pathway to downregulate bim mRNA expression and simultaneously promoted the phosphorylation of BimEL through activating ERK 1/2, both of which reduced the level of BimEL. The results demonstrate that insulin protected the granulosa cells against apoptosis by reducing levels of the pro-apoptotic protein BimEL. However, the concentration of insulin (1 μg/ml) was relatively high. High levels of insulin partly combined with the IGF-1 receptor to play its roles in granulosa cells. This experiment provides new insight into the role of insulin in granulosa cells and sheds light on nutrition-reproduction interactions.

microRNA-126 Is a Tumor Suppressor of Granulosa Cell Tumor Mediated by Its Host Gene EGFL7

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at a post-transcriptional level. We examined the role of miR-126 in granulosa cell tumor (GCT) of the ovaries. In tissues from malignant GCT patients miR-126 expression was repressed. We showed that miR-126 could inhibit proliferation, migration, hormone production and promote apoptosis of cancerous granulosa cells (GCs) in vitro. The role of miR-126 as “tumor suppressor” was confirmed by using a tumor formation model in vivo. By RNA-seq, immunohistochemical staining (IHC), Western blot and luciferase reporter assay, we identified and confirmed EGFL7 as a direct functional target of miR-126 in cancer GCs. Furthermore, we found that the AKT signaling pathway was associated with miR-126 and EGFL7 in cancer GCs. Taken together, our results demonstrate a function of miR-126 in the suppression of GCT development via the regulation of EGFL7.

Palmitic acid causes insulin resistance in granulosa cells via activation of JNK

Obesity is a worldwide health problem with rising incidence and results in reproductive difficulties. Elevated saturated free fatty acids (FFAs) in obesity can cause insulin resistance (IR) in peripheral tissues. The high intra-follicular saturated FFAs may also account for IR in ovarian granulosa cells (GCs). In the present study, we investigated the relationship between saturated FFAs and IR in GCs by the use of palmitic acid (PA). We demonstrated that the glucose uptake in cultured GCs and lactate accumulation in the culture medium were stimulated by insulin, but the effects of insulin were attenuated by PA treatment. Besides, insulin-induced phosphorylation of Akt was reduced by PA in a dose- and time-dependent manner. Furthermore, PA increased phosphorylation of JNK and JNK blockage rescued the phosphorylation of Akt which was downregulated by PA. These findings highlighted the negative effect of PA on GCs metabolism and may partially account for the obesity-related reproductive disorders.

Metformin improves ovarian insulin signaling alterations caused by fetal programming

Insulin resistance is the decreased ability of insulin to mediate metabolic actions. In the ovary, insulin controls ovulation and oocyte quality. Alterations in ovarian insulin signaling pathway could compromise ovarian physiology. Here, we aimed to investigate the effects of fetal programming on ovarian insulin signaling and evaluate the effect of metformin treatment. Pregnant rats were hyperandrogenized with testosterone and female offspring born to those dams were employed; at adulthood, prenatally hyperandrogenized (PH) offspring presented two phenotypes: irregular ovulatory (PHiov) and anovulatory (PHanov). Half of each group was orally treated with metformin. Metformin treatment improved the estrous cyclicity in both PH groups. Both PH groups showed low mRNA levels of IR, IRS1 and Glut4. IRS2 was decreased only in PHanov. Metformin upregulated the mRNA levels of some of the mediators studied. Protein expression of IR, IRS1/2 and GLUT4 was decreased in both PH groups. In PHiov, metformin restored the expression of all the mediators, whereas, in PHanov, metformin restored only that of IR and IRS1/2. IRS1 phosphorylation was measured in tyrosine residues, which activates the pathway, and in serine residues, which impairs insulin action. PHiov presented high IRS1 phosphorylation on tyrosine and serine residues, whereas PHanov showed high serine phosphorylation and low tyrosine phosphorylation. Metformin treatment lowered serine phosphorylation only in PHanov rats. Our results suggest that PHanov rats have a defective insulin action, partially restored with metformin. PHiov rats had less severe alterations, and metformin treatment was more effective in this phenotype.

Follicular hyperandrogenism and insulin resistance in polycystic ovary syndrome patients with normal circulating testosterone levels

Polycystic ovary syndrome (PCOS) is a common reproductive disease with high heterogeneity. The role of excess androgen in PCOS etiology remains disputed, since around 20%-50% of PCOS women do not display hyperandrogenemia. The microenvironment of the ovary critically influences follicular development. In the present study, we assessed the role of androgen in PCOS by investigating whether excessive follicular fluid androgen was present in PCOS patients with normal serum androgen levels and influenced by follicular fluid insulin resistance (IR). Follicular fluid samples of 105 women with PCOS and 105 controls were collected. Levels of steroid hormones, glucose and insulin in the follicular fluid were examined and compared with data from serum biochemistry tests. We found that 64.9% (63/97) of PCOS patients with normal serum androgen levels displayed abnormally high follicular fluid androgen level. The follicular fluid androgen level was positively correlated with follicular fluid IR within a certain range and follicular fluid estrogen-to-testosterone (E2/T) ratio was significantly reduced in these patients. These results indicated that there existed a subgroup of PCOS patients who displayed excessive follicular fluid androgen and IR despite their normal circulating testosterone (T) levels. Our study highlights the importance of ovary hyperandrogenism and IR in the etiology of PCOS.