Peroxisome proliferator-activated receptors: new players in the field of reproduction

IGF2BP2 and IGFBP3 Genotypes, Haplotypes, and Genetic Models Studies in Polycystic Ovary Syndrome

BACKGROUND

Insulin resistance has been correlated with the genetic diversity within the insulin-like binding proteins genes. Moreover, insulin resistance is one of the key characteristics of the widespread reproductive endocrine condition known as polycystic ovarian syndrome (PCOS). Hence, this study is aimed to determine the association between IGFBP3 and IGF2BP2 gene variants and PCOS risk.

METHODS

A total of 300 subjects (150 PCOS cases diagnosed based on Rotterdam ESHRE/ASRM consensus criteria and 150 healthy subjects) were recruited in this case-control cross-sectional study. Tetra-primer amplification refractory mutation system polymerase chain reaction (ARMS-PCR) was used for genotyping rs11705701, whereas genotyping of rs1470579 and rs2854744 was done employing PCR-restriction fragment length polymorphism (PCR-RFLP) technique.

RESULTS

The CC and AA+AC genotypes of rs1470579 conferred an increased risk of PCOS in our population. Regarding the rs2854744, an increased risk of PCOS was observed under the codominant homozygous (TT vs. GG) model by 2.54 fold. The C allele of rs1470579 and T allele of rs2854744 enhanced PCOS risk by 1.97 and 1.46 folds, respectively. Haplotype analysis showed that the Ars1470579Ars11705701 haplotype conferred a decreased risk of PCOS (odds ratio = 0.53, 95% confidence interval = 0.34-0.83, p = 0.006). The AC/GG/GT, AA/GA/GT, AC/GA/GG, and AC/GA/GT genotype combinations of rs1470579/rs11705701/rs2854744 were associated with a decreased risk of the disease.

CONCLUSIONS

IGF2BP2 rs1470579 and IGFBP3 rs2854744 enhanced PCOS susceptibility in a Southeastern Iranian population. Further investigation involving larger cohorts representing diverse ethnic backgrounds is needed to confirm the current findings.

Novel Insights into the Regulatory Role of Nuclear Factor (Erythroid-Derived 2)-Like 2 in Oxidative Stress and Inflammation of Human Fetal Membranes

Fetal membrane dysfunction in response to oxidative stress (OS) is associated with adverse pregnancy outcomes. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is one of the regulators of innate OS response. This study evaluated changes in Nrf2 expression and its downstream targets heme oxygenase (HO-1) and peroxisome proliferator-activated receptor gamma (PPARγ) in fetal membranes during OS and infection in vitro. Furthermore, we tested the roles of sulforaphane (SFN; an extract from cruciferous vegetables) and trigonelline (TRN; an aromatic compound in coffee) in regulating Nrf2 and its targets. Fetal membranes (n = 6) collected at term were placed in an organ explant system were treated with water-soluble cigarette smoke extract (CSE), an OS inducer (1:10), and lipopolysaccharide (LPS; 100 ng/mL). Nrf2 expression, expression, its enhancement by sulforaphane (SFN, 10 µM/mL) and down regulation by TRN (10uM/mL) was determined by western blots. Expression of Nrf2 response elements PPARγ (western) heme oxygenase (HO-1), and IL-6 were quantified by ELISA. CSE and LPS treatment of fetal membranes increased nrf2, but reduced HO-1 and PPARγ and increased IL-6. Co-treatment of SFN, but not with TRN, with CSE and LPS increased Nrf2 substantially, as well as increased HO-1 and PPARγ and reduced IL-6 expression. Risk factor-induced Nrf2 increase is insufficient to generate an antioxidant response in fetal membranes. Sulforaphane may enhance innate antioxidant and anti-inflammatory capacity by increasing NRF-2 expression.

Peroxisome proliferator-activated receptor β/δ and γ agonists differentially affect prostaglandin E2 and cytokine synthesis and nutrient transporter expression in porcine trophoblast cells during implantation

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor family of ligand-dependent transcription factors. PPARs have been shown to be important regulators of female reproductive functions, including conceptus development and placenta formation. This study examines the effect of PPARβ/δ and PPARγ agonists and antagonists on (1) the synthesis of prostaglandin (PG) E2, interleukin (IL) 6, interferon (IFN) γ, and tumor necrosis factor (TNF) α and (2) the mRNA expression of genes encoding nutrient transporters and/or binding proteins in Day 15 conceptus trophoblast cells. The study also examines whether PPAR agonist-modulated IL6, IFNγ, and TNFα secretion is mediated via mitogen-activated protein kinase (MAPK) pathways. Trophoblast cells were exposed to L-165,041 (a PPARβ/δ agonist) or rosiglitazone (a PPARγ agonist) in the presence or absence of GSK3787 (a PPARβ/δ antagonist) or GW9662 (a PPARγ antagonist) or in the presence or absence of U0126 (a MAPK inhibitor). Rosiglitazone stimulated PGE synthase and IFNG mRNA expression in trophoblast cells and enhanced PGE2 concentrations in the incubation medium. Moreover, cells treated with rosiglitazone exhibited increased abundance of the solute carrier organic anion transporter family member 2A1 (SLCO2A1, a PG transporter) and of fatty acid binding protein (FABP) 5 transcripts. All these effects were abolished by the addition of GW9662, which indicates that the action of rosiglitazone is PPARγ-dependent in the studied cells. L-165,041 inhibited TNFα synthesis and decreased the mRNA expression of FABP3 and IL6 in trophoblast cells. However, this effect was not abolished by the addition of GSK3787 into the incubation medium, suggesting that L-165,041 action is independent of PPARβ/δ. The inhibitory effect of L-165,041 on TNFα concentration and the stimulatory effect of rosiglitazone on IFNγ accumulation in the medium were not observed in the presence of the MAPK inhibitor, suggesting that the action of both agonists may be mediated by MAPKs. In conclusion, PPARβ/δ and PPARγ agonists are differentially involved in the trophoblast expression of genes related to conceptus development and implantation in pigs. Furthermore, L-165,041 and rosiglitazone may have PPAR-dependent and -independent effects in conceptus trophoblast cells.

Prenatal androgen excess alters the uterine peroxisome proliferator-activated receptor (PPAR) system

It is known that androgen excess induces changes in fetal programming that affect several physiological pathways. Peroxisome proliferator-activated receptors (PPARs) α, δ and γ are key mediators of female reproductive functions, in particular in uterine tissues. Thus, we aimed to study the effect of prenatal hyperandrogenisation on the uterine PPAR system. Rats were treated with 2mg testosterone from Day 16 to 19 of pregnancy. Female offspring (PH group) were followed until 90 days of life, when they were killed. The PH group exhibited an anovulatory phenotype. We quantified uterine mRNA levels of PPARα (Ppara ), PPARδ (Ppard ), PPARγ (Pparg ), their regulators peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Ppargc1a ) and nuclear receptor co-repressor 1 (Ncor1 ) and cyclo-oxygenase (COX)-2 (Ptgs2 ), and assessed the lipid peroxidation (LP) index and levels of glutathione (GSH) and prostaglandin (PG) E2 . The PH group showed decreased levels of all uterine PPAR isoforms compared with the control group. In addition, PGE2 and Ptgs2 levels were increased in the PH group, which led to a uterine proinflammatory environment, as was LP, which led to a pro-oxidant status that GSH was not able to compensate for. These results suggest that prenatal exposure to androgen excess has a fetal programming effect that affects the gene expression of PPAR isoforms, and creates a misbalanced oxidant-antioxidant state and a proinflammatory status.

DNA methylation in the pathogenesis of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the leading endocrine and metabolic disorder in premenopausal women characterized by hyperandrogenism and abnormal development of ovarian follicles. To date, the PCOS etiology remains unclear and has been related to insulin resistance, obesity, type 2 diabetes mellitus, cardiovascular disease and infertility, among other morbidities. Substantial evidence illustrates the impact of genetic, intrauterine and environmental factors on the PCOS etiology. Lately, epigenetic factors have garnered considerable attention in the pathogenesis of PCOS considering that changes in the content of DNA methylation, histone acetylation and noncoding RNAs have been reported in various tissues of women with this disease. DNA methylation is changed in the peripheral and umbilical cord blood, as well as in ovarian and adipose tissue of women with PCOS, suggesting the involvement of this epigenetic modification in the pathogenesis of the disease. Perhaps, these defects in DNA methylation promote the deregulation of genes involved in inflammation, hormone synthesis and signaling and glucose and lipid metabolism. Research on the role of DNA methylation in the pathogenesis of PCOS is just beginning, and several issues await investigation. This review aims to provide an overview of current research focused on DNA methylation and PCOS, as well as discuss the perspectives regarding this topic.

Expression and role of peroxisome proliferator-activated receptors in the porcine early placenta trophoblast

Peroxisome proliferator-activated receptors (PPARs) are members of a nuclear receptor family of ligand-dependent transcription factors. Three isoforms of PPAR named PPARα, PPARβ/δ, and PPARγ have been described, each encoded by a separate gene: PPARA, PPARD, and PPARG, respectively. In the present study, we examined the profiles of PPAR and retinoid X receptor (RXR; PPAR heterodimer partner) mRNA expression and PPAR DNA binding activity in porcine trophoblast tissue collected on days 15, 20, 25, and 30 of pregnancy and in day-20 embryos. Placenta trophoblast cells isolated on day 25 of pregnancy were used to determine effects of (1) cytokines on PPAR and RXR mRNA expression and (2) PPAR agonists on prostaglandin (PG) E2 synthesis and the expression of genes involved in steroidogenesis, fatty acid binding, and PG transport, as well as on cell proliferation. The mRNA expression of PPARA and RXRB was greater in trophoblast tissue collected on days 25 and 30 of pregnancy compared with day 15 (P < 0.05), while DNA binding activity of PPARα decreased between day 15 and 25 (P < 0.05). Increased concentrations of PPARD and RXRA transcripts were observed in trophoblasts collected on day 20 compared to trophoblasts from days 15 and 30 (P < 0.05). Moreover, concentrations of DNA-bound PPARβ/δ and PPARγ proteins increased in day-30 trophoblasts compared to day 15 (P < 0.01) and day 20 (P < 0.05), respectively. On day 20 of gestation, the mRNA expression of PPARD, PPARG, and RXRA and protein levels of PPARα and PPARγ isoforms were greater in trophoblast than embryonic tissue (P < 0.01). Interleukin 1β and/or interferon γ, but not IL6 and leukemia inhibitory factor, upregulated PPAR and RXR mRNA expression in placenta trophoblast cells in vitro (P < 0.05). Rosiglitazone (a PPARγ agonist) stimulated prostaglandin E synthase mRNA expression in trophoblast cells and PGE2 accumulation in incubation medium (P < 0.05). Moreover, activation of PPAR isoforms differentially affected the expression of genes involved in steroidogenesis, fatty acid binding, and PG transport in studied cells. Finally, PPARα and PPARγ agonists stimulated trophoblast cell proliferation (P < 0.05), and this effect was abolished by the addition of a respective PPAR antagonist (P < 0.05). Overall, these results point to a role of PPAR isoforms in porcine placenta development and function.

Regulation of expression and role of peroxisome proliferator-activated receptors (PPARs) in luminal epithelial and stromal cells of the porcine endometrium

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor family of ligand-dependent transcription factors. PPARs are important regulators of glucose and fatty acid metabolism, apoptosis, angiogenesis, cell proliferation and differentiation, and immune response. Their possible role in the female reproductive tract was demonstrated. In the present study, cultured luminal epithelial (LE) and stromal (ST) cells of the porcine endometrium were used to examine (1) the effect of conceptus exposed medium (CEM) on mRNA and protein expression and DNA binding activity of PPARA, PPARD, and PPARG isoforms, and (2) the effect of PPARA, PPARD, and PPARG agonists on the expression of selected genes, apoptosis, and cell proliferation. The addition of CEM stimulated PPARA expression and DNA binding activity of this isoform in LE and ST cells (P < 0.05). Increased expression of PPARD mRNA in the presence of CEM was detected in ST cells (P < 0.05), while the concentration of PPARG transcripts decreased in response to CEM in both cell types (P < 0.05). LE and ST cells of the pig endometrium possess PPARA, PPARD, and PPARG proteins, with clear nuclear staining visible predominately in ST cells. In LE cells, activation of PPARG with 15-deoxy-Δ12,14-prostaglandin(PG)J2 down-regulated the expression of genes encoding amino acid transporter 1 (SLC38A1), leukemia inhibitory factor (LIF) and enzymes involved in PG synthesis (P < 0.05). In ST cells, activation of PPARD isoform with both agonists used (L-165,041 and cPGI2) and PPARG isoform with 15-deoxy-Δ12,14-PGJ2 increased vascular endothelial growth factor A (VEGFA) mRNA expression (P < 0.05). Moreover, GW9578 (PPARA agonist) and 15-deoxy-Δ12,14-PGJ2 stimulated glucose transporter 1 (SLC2A1) gene expression in ST cells. 15-deoxy-Δ12,14-PGJ2 was also effective in up-regulation of the ratio of BAX/BCL2 mRNA expression and active caspase-3 concentration in ST cells (P < 0.05). Finally, GW9578 stimulated LE and ST cell proliferation, while rosiglitazone (PPARG agonist) increased the number of viable ST but not LE cells. In conclusion, this study demonstrated that conceptus products differentially modulate PPARs expression and activity in the porcine endometrium. Activation of PPARs may in turn affect nutrient transport, PG synthesis, angiogenesis, apoptosis, or cell proliferation in this tissue. Therefore, PPAR isoforms seem to play an important role in development and function of the porcine uterus.

PPARγ Expression Is Diminished in Macrophages of Recurrent Miscarriage Placentas

PPARγ belongs to the group of nuclear receptors which is expressed in the trophoblast and together with other factors is responsible for the maintenance of pregnancy. Apart from that PPARγ is also a main factor for macrophage polarization. The aim of this study was to investigate the combined expression pattern and frequency of PPARγ under physiological circumstances and in spontaneous and recurrent miscarriages in the trophoblast and in maternal macrophages of the decidua. Human placental tissues of the first trimester (15 physiologic pregnancies, 15 spontaneous abortion and 16 recurrent miscarriage placentas) were analyzed for expression of the nuclear receptor PPARγ. Expression changes were evaluated by immunohistochemistry and real time PCR (RT-PCR) in trophoblast and in maternal macrophages of the decidua. Maternal macrophages were identified by double immunofluorescence using cluster of differentiation 68 (CD68) as marker for macrophages and further characterized regarding their M1/M2 polarization status. The intermediate villous trophoblast revealed a significantly lower PPARγ expression in spontaneous and recurrent abortion. Maternal macrophages express PPARγ. Their number is significantly enhanced in the decidua of spontaneous miscarriages whereas in recurrent miscarriages maternal macrophages seem to express PPARγ only in very few cases. PPARγ is associated with an M2 polarization state that is common for decidual macrophages. The lack of PPARγ in recurrent miscarriage decidual macrophages seems to be associated with a specific inflammatory response against the fetus.

RXRα is upregulated in first trimester endometrial glands of spontaneous abortions unlike LXR and PPARγ

Nuclear receptors are necessary for uterine invasion of the trophoblast and therefore important for maintaining a viable pregnancy. The aim of this study was to investigate the expression pattern and frequency of LXR, PPARγ and RXRα under physiological circumstances and in spontaneous abortions in endometrial glands and decidual tissue cells. A total of 28 (14 physiologic pregnancies/14 spontaneous abortion) human pregnancies in first trimester were analyzed for expression of the nuclear receptors LXR, RXRα and PPARγ. Expression changes were evaluated by immunohistochemistry in decidual tissue and endometrial glands of the decidua. RXRα expression was up-regulated in the endometrial glands of spontaneous abortion (P<0.015). Similar up regulation of RXRα was found in decidual tissue (P<0.05). LXR and PPARγ expression was unchanged in spontaneous abortion. By Correlation analysis we found a trend to positive correlation of LXR and PPARγ (Spearman correlation coefficient r=0.56, P=0.07) in endometrial glands. In decidual tissue, we found significant negative correlation in the control group, for the combination of RXRα and PPARγ (Spearman correlation coefficient r=0.913, P=0.03). Our data show that RXRα expression is increased in miscarriage in endometrial glands and correlation analysis showed that negative correlation between RXRα and PPARγ disappears in miscarriage. This shift is supposable responsible for the loss of regular function in trophoblast and embryonic tissue.

Expression of Thyroid Hormone Receptors in Villous Trophoblasts and Decidual Tissue at Protein and mRNA Levels Is Downregulated in Spontaneous and Recurrent Miscarriages

Thyroid hormones are essential for the maintenance of pregnancy, and a deficiency in maternal thyroid hormones has been associated with early pregnancy losses. The expression of THRα1, THRβ1 and THRα2 increases with gestational age. The aim of this study was the investigation of the protein and mRNA-levels of THR isoforms THRα1, THRα2, THRβ1 and THRβ2 in normal, spontaneous and recurrent miscarriages. The identification of THR-expressing cells in the decidua was done with double immunofluorescence. The nuclear expression of THRα1, THRα2, THRβ1 and THRβ2 is downregulated at protein level in spontaneous and recurrent miscarriages in villous trophoblast tissue. In decidual tissue, we found a significant downregulation only for THRα1 in spontaneous miscarriages. For recurrent miscarriages, THRα1 and THRβ1 were both significantly downregulated in decidual tissue. By applying HLA-G as a trophoblast marker, we found a significant co-expression only for THRβ2. The results of our study show that thyroid hormone receptors THRα1, THRα2, THRβ1 and THRβ2 are downregulated in spontaneous and recurrent miscarriages. The majority of cells expressing the thyroid hormone receptors in the decidua are decidual stromal cells.

Peroxisome proliferator-activated receptor-gamma (PPARγ) is down regulated in trophoblast cells of gestational diabetes mellitus (GDM) and in trophoblast tumour cells BeWo in vitro after stimulation with PPARγ agonists

AIMS

Peroxisome proliferator-activated receptor-gamma (PPARγ) plays an important role in insulin metabolism, trophoblast differentiation and anti-inflammatory circuits. The aim of this study was to investigate the expression of PPARγ in the placenta of patients with gestational diabetes mellitus (GDM) and the regulation of PPARγ by its agonists in trophoblast tumour cells BeWo in vitro.

METHODS

PPARγ expression in a total of 80 placentas (40 GDM/40 controls) was analysed by immunohistochemistry using the semi-quantitative immunoreactive score. Furthermore, a quantitative reverse transcription-polymerase chain reaction (PCR) was performed to determine the PPARγ mRNA-expression in both groups. We used a fused and a non-fused BeWo cell culture model for the stimulation with arachidonic acid and 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2). Afterwards PPARγ mRNA-expression was analysed by quantitative real-time PCR (RT-PCR) (TaqMan).

RESULTS

Using immunohistochemistry we identified a decreased expression of PPARγ in the syncytiotrophoblast and the extravillous trophoblast of GDM placentas compared to normal controls. Furthermore, PPARγ mRNA-expression was reduced in GDM placentas. Stimulation of BeWo cells with arachidonic acid and 15d-PGJ2 caused a downregulation of PPARγ expression.

CONCLUSION

As PPARγ is down regulated by arachidonic acid and 15d-PGJ2, the reduced PPARγ expression in GDM placentas may be due to an altered concentration of fatty acid derivates.

The effect of embryo presence on the expression of peroxisome proliferator activated receptor (PPAR) genes in the porcine reproductive system during periimplantation

This study was undertaken to determine the effect of the presence of embryos in the uterine horn on peroxisome proliferator activated receptors (PPARs; A, D, G) gene expression in the reproductive tissues of gilts subjected to a surgical procedure. The uterus consisted of one intact horn connected to the uterine corpus and the second horn detached from the uterine corpus but connected with the contiguous ovary. The gilts were hormonally stimulated and divided into two groups: the first group, inseminated (pregnant) and the second group (cyclic), with surgical procedure but not inseminated. The animals of both groups were slaughtered on day 14 of pregnancy or on day 14 of the oestrous cycle, respectively. PPARs mRNA abundance in the endometrium and the corpus luteum (CL) was analysed by quantitative real-time PCR. During pregnancy, PPARA and PPARD μmRNA abundance in the porcine endometrium was significantly higher in the horn containing embryos than in the contralateral horn, where embryos were absent. The endometrial PPARG1 mRNA abundance did not differ between the two horns during pregnancy and the oestrous cycle, but a higher level of the transcript was observed during pregnancy when compared to the oestrous cycle. In the CL, there were no significant differences in PPARA and PPARDμ mRNA abundance between horns in pregnant or cyclic sows. However, there was a significant increase of PPARA and PPARD transcript level in the CL from cyclic compared with pregnant sows. The results of our study suggest that PPARA and PPARD have regulatory functions in early pregnancy, and they indicate that increased levels of endometrial gene expression are correlated with the presence of embryos in the uterine horn. Higher levels of PPARA and PPARD expression in the porcine CL on day 14 of the oestrous cycle than on day 14 of pregnancy suggest that both forms are involved in the regulation of CL functions.

Adipokines, insulin-like growth factor binding protein-3 levels, and insulin sensitivity in women with polycystic ovary syndrome

BACKGROUND/AIMS

Many women with polycystic ovary syndrome (PCOS) exhibit insulin resistance. Adipose tissue plays an important role in insulin resistance, and adipokines including tumor necrosis factor (TNF)-α and adiponectin are altered in PCOS. Insulin-like growth factor binding protein-3 (IGFBP-3), alone or in conjunction with other adipokines, is also associated with insulin resistance. We evaluated the effects of TNF-α, adiponectin, and IGFBP-3 on insulin sensitivity and the relationships among these proteins in women with PCOS.

METHODS

We recruited 40 women with PCOS and 40 age- and body mass index (BMI)-matched regular cycling women (controls). The women were divided into obese (BMI ≥ 25 kg/m(2)) and nonobese (BMI < 25 kg/m(2)) groups. Anthropometric measurements were performed, and serum levels of TNF-α, adiponectin, and IGFBP-3 were determined. Insulin sensitivity was estimated using the metabolic clearance rate (MCR) of glucose calculated from the oral glucose tolerance test.

RESULTS

Serum levels of TNF-α and IGFBP-3 did not differ between the PCOS and control groups, but adiponectin levels in the PCOS group were lower than those in control women in the nonobese group (p < 0.05). TNF-α, adiponectin, and IGFBP-3 levels were not correlated with each other in women with PCOS, but a significant positive correlation was observed between adiponectin levels and MCR (p < 0.05). Multiple regression analysis revealed that adiponectin levels were significantly associated with insulin sensitivity (p < 0.05) in women with PCOS.

CONCLUSIONS

IGFBP-3 and TNF-α levels were not associated with insulin sensitivity, but adiponectin levels were related to insulin sensitivity in women with PCOS.

Peroxisome proliferator activated receptor gamma gene variants influence susceptibility and insulin related traits in Indian women with polycystic ovary syndrome

PURPOSE

Peroxisome proliferator activated receptor gamma (PPARγ), a transcription factor involved in glucose and lipid metabolism is one of the candidate genes associated with polycystic ovary syndrome (PCOS). We investigated individual and combined associations of Pro12Ala and His447His polymorphisms of PPARγ with PCOS susceptibility and its related traits (hyperinsulinemia, hyperandrogenemia and lipid parameters) in Indian women.

METHOD

Genotyping of PPARγ polymorphisms in this case-control study was performed in PCOS (n = 450) and age-matched controls (n = 300) by direct sequencing. Clinical, anthropometric, hormonal and metabolic parameters were estimated in 275 women with PCOS and 169 controls. Chi-square test was used to compare the categorical data while regression analysis was used to evaluate association of genotypes with PCOS as well as its related phenotypes.

RESULTS

The frequencies of CC and CG + GG genotypes of Pro12Ala (χ² = 15.3, p < 0.0001) and CC and CT + TT genotypes of His447His (χ² = 12.7, p = 0.0004) polymorphisms were significantly different between PCOS and controls. Logistic regression analysis revealed a significant association of PCOS with Pro12Ala but not the His447His polymorphism. Carriers of variant genotypes at both PPARγ loci showed significantly reduced 2 h glucose levels while carriers of variant His447His genotype showed lower fasting insulin and HOMA-IR levels in PCOS women.

CONCLUSIONS

Pro12Ala polymorphism of PPARγ showed significant association with decreased PCOS susceptibility. Both polymorphisms influenced insulin related traits (2 h glucose, fasting insulin and HOMA-IR) and improved glucose metabolism in these women. This is the first report to establish that variations in PPARγ gene influence the insulin resistance pathophysiology in Indian women with PCOS.

The liver x receptor in correlation with other nuclear receptors in spontaneous and recurrent abortions

The liver X receptors (LXRs) have been shown to be crucially involved in maternal-fetal cholesterol transport and placentation. The aim of this study was to investigate the expression pattern and frequency of LXR under normal physiological circumstances and in spontaneous abortion and/or recurrent miscarriage. A total of 29 (12 physiologic pregnancies/10 spontaneous abortions/7 recurrent miscarriages) human pregnancies in first trimester were analysed for LXR expression. Expression changes were evaluated by immunohistochemistry for receptor and quantitative RT-PCR (TaqMan) was performed to determine the level of LXR mRNA expression. We also stained for RXRα and PPARγ as possible heterodimers of LXR. LXR expression was downregulated in the syncytiotrophoblast of spontaneous abortion placentas compared to normal pregnancy. In recurrent miscarriage there was a trend for a downregulation. Decidua showed an even stronger downregulation in both groups. In the syncytiotrophoblast we found a positive correlation for the combination of LXR/PPARγ in abortions and a negative correlation for LXR/RXRα. In addition, double-immunofluorescence staining showed that LXR as well as RXRα and PPARγ are expressed by the extravillous trophoblast. Finally, RXRα and LXR showed coexpression in the same extravillous trophoblast cells. To conclude, our data show that LXR expression is decreased in miscarriage.

Evaluation of an alternative in vitro test battery for detecting reproductive toxicants

The application of alternative methods in developmental and reproductive toxicology is challenging in view of the complexity of mechanisms involved. A battery of complementary test systems may provide a better prediction of developmental and reproductive toxicity than single assays. We tested twelve compounds with varying mechanisms of toxic action in an assay battery including 24 CALUX transcriptional activation assays, mouse cardiac embryonic stem cell test, ReProGlo assay, zebrafish embryotoxicity assay, and two CYP17 and two CYP19 activity assays. The battery correctly detected 11/12 compounds tested, with one false negative occurring, which could be explained by the absence of the specific mechanism of action of this compound in the battery. Toxicokinetic modeling revealed that toxic concentrations were in the range expected from in vivo reproductive toxicity data. This study illustrates added value of combining assays that contain complementary biological processes and mechanisms, increasing predictive value of the battery over individual assays.

Retinoid X receptor α and retinoids are key regulators in apoptosis of trophoblasts of patients with recurrent miscarriages

The retinoid X receptor α (RXRα) is a nuclear hormone receptor that is able to bind other nuclear receptors in a heterodimeric complex, thereby activating gene transcription. Recently, we identified enhanced expression of RXRα in extravillous trophoblasts (EVT) and villous trophoblasts (VT) of miscarried placentas. In addition, an increased number of apoptotic EVT was present in miscarried placentas. In this study, on the basis of immunocytochemical analysis, western blots, and quantitative real-time reverse transcription PCR, we could demonstrate a reduced expression of RXRα in choriocarcinoma cell lines and in human VTs after stimulation with the retinoids 9-cis-retinoic acid and all-trans-retinoic acid and the prostaglandin 15-deoxy-Δ(12,14)-prostaglandin J(2). Furthermore, a simultaneous expression of RXRα and the apoptotic marker M30 CytoDEATH in EVT of miscarried placentas from the first trimester was shown. In EVT of control placentas from legal termination of pregnancies, no co-expression of RXRα and M30 could be detected. A likely conclusion is that RXRα plays an important role in the induction of apoptosis. Downregulation of RXRα, as observed in the tested choriocarcinoma cells and trophoblasts, might serve as a protection against apoptosis and miscarriage. In conclusion, RXRα represents a potential target in the treatment of recurrent miscarriages.

Association of placental inflammation with fetomaternal hemorrhage and loss of placental mucin-1

BACKGROUND

Fetomaternal hemorrhage (FMH) poses an immediate risk to the fetus and, in case of Rhesus-immunization, to future pregnancies. Given that altered endothelial permeability is part of the pathophysiology of inflammation, in this study we investigated whether placental inflammatory processes like chorioamnionitis (ChoA) or preeclampsia (PE) lead to increased rates of FMH compared to the established risk factor of placenta previa (PP). Putative accompanying markers of trophoblastic damage were also explored.

METHODS

40 patients (14 PE; 6 ChoA; 9 PP; 11 normal controls) were evaluated for FMH using a flowcytometric test kit, which is able to quantify FMH of 0.06% fetal cells. Placental tissue samples were immunostained for human placental lactogen (hPL), human chorionic gonadotropin (hCG), and mucin-1 (MUC1). MUC1 was evaluated as a potential serum marker of FMH.

RESULTS

Patients with ChoA had a mean calculated FMH volume of 29 ml, compared to 4 ml in PE and 1 ml in PP and controls. MUC1 staining was reduced in PE and ChoA placenta samples, while elevated MUC1 serum concentration correlated positively with FMH.

CONCLUSION

Diseases of placental inflammation are associated with FMH. Placental MUC1 staining is reduced and serum concentrations are increased in cases of FMH.

Placental implications of peroxisome proliferator-activated receptors in gestation and parturition

The placenta is a transitory structure indispensable for the proper development of the embryo and fetus during mammalian gestation. Like other members of the nuclear receptor family, the peroxisome proliferator-activated receptors (PPARs) are known to be involved in the physiological and pathological events occurring during the placentation. This placental involvement has been recently reviewed focusing on the early stages of placental development (implantation and invasion, etc.), mouse PPARs knockout phenotypes, and cytotrophoblast physiology. In this review, we describe the placental involvement of PPARs (e.g., fat transport and metabolism, etc.) during the late stages of gestation and in the amniotic membranes, highlighting their roles in the inflammation process (e.g., chorioamnionitis), metabolic disorders (e.g., diabetes), and parturition.

Relaxin causes selective outward remodeling of brain parenchymal arterioles via activation of peroxisome proliferator-activated receptor-γ

Brain parenchymal arterioles (PAs), but not pial arteries, undergo hypotrophic outward remodeling during pregnancy that involves peroxisome proliferator-activated receptor-γ (PPARγ) activation. Relaxin, a peptide hormone produced during pregnancy, is involved in systemic and renal artery remodeling and activates PPARγ in vitro. Thus, we hypothesized that relaxin is involved in the selective outward remodeling of PAs through a PPARγ-dependent mechanism. Nonpregnant rats were treated with relaxin (4 μg/h, osmotic minipump), relaxin plus PPARγ inhibitor GW9662 (10 mg/kg/d), or vehicle for 10 d. Vascular function and structure were compared in isolated and pressurized middle cerebral arteries (MCAs) and PAs taken from the same animals. Relaxin treatment increased serum relaxin to the level of pregnancy (54 ng/ml) and increased passive wall thickness (hypertrophy; 70 ± 5 vs. 54 ± 4 μm in vehicle; P<0.05) and inner diameter (outward remodeling; 10.6 ± 0.5 vs. 8.0 ± 0.6 μm in vehicle; P<0.05) in PAs, but not in MCAs. This hypertrophic outward remodeling was prevented by GW9662 that had diameters (57 ± 3 μm) and wall thickness (8.6 ± 1.0 μm) similar to vehicle. GW9662 also prevented relaxin-induced changes in PPARγ target gene expression. These results suggest that relaxin produced during pregnancy may be partly responsible for selective remodeling of PAs during pregnancy through a mechanism involving PPARγ

Hematopoietic-Prostaglandin D2 synthase through PGD2 production is involved in the adult ovarian physiology

Background

The prostaglandin D2 (PGD2) pathway is involved in numerous biological processes and while it has been identified as a partner of the embryonic sex determining male cascade, the roles it plays in ovarian function remain largely unknown. PGD2 is secreted by two prostaglandin D synthases (Pgds); the male-specific lipocalin (L)-Pgds and the hematopoietic (H)-Pgds.

Methods

To study the expression of the Pgds in the adult ovary, in situ hybridization were performed. Then, to evaluate the role of H-Pgds produced PGD2 in the ovarian physiology, adult female mice were treated with HQL-79, a specific inhibitor of H-Pgds enzymatic activity. The effects on expression of the gonadotrophin receptors FshR and LhR, steroidogenic genes Cyp11A1, StAR and on circulating progesterone and estradiol, were observed.

Results

We report the localization of H-Pgds mRNA in the granulosa cells from the primary to pre-ovulatory follicles. We provide evidence of the role of H-Pgds-produced PGD2 signaling in the FSH signaling through increased FshR and LhR receptor expression. This leads to the activation of steroidogenic Cyp11A1 and StAR gene expression leading to progesterone secretion, independently on other prostanoid-synthetizing mechanisms. We also identify a role whereby H-Pgds-produced PGD2 is involved in the regulation of follicular growth through inhibition of granulosa cell proliferation in the growing follicles.

Conclusions

Together, these results show PGD2 signaling to interfere with FSH action within granulosa cells, thus identifying an important and unappreciated role for PGD2 signaling in modulating the balance of proliferation, differentiation and steroidogenic activity of granulosa cells.

Effect of polymorphism in the peroxisome proliferator-activated receptor gamma gene on litter size of pigs

The association of polymorphisms in peroxisome proliferator-activated receptor γ (PPARγ) gene with litter size was studied in Large White and Landrace pig. Three SNP loci (P1, P2 and P7) on PPARγ(2) gene were determined by PCR-SSCP and the results showed that there were A → G mutations at 220 and 324 bp in 5'-regulator region and at 147 bp in exon 6, respectively. Allele frequencies were analysed in two breeds. Information on 2341 litter records from 564 sows was used to analyse the trait total number born (TNB) and number born alive (NBA). In Large White, TNB and NBA of genotype BB for P2 locus were the lowest, and the TNB and NBA of third and following parities and all parities were 0.74 and 0.51 piglets per litter less (P < 0.001) than those of the highest genotype AB, respectively, but for P1 and P7 locus the beneficial genotype AA were more 0.4-0.8 piglets per litter (P < 0.05) than the inferior genotype AB. In landrace, TNB and NBA of the first parity of genotype BB for P1 locus were 2.0 piglets per litter higher than AA (P < 0.05), but for all parities the TNB and NBA of genotype BB were 0.66 and 0.97 piglets per litter (P < 0.05) higher than AA, respectively. At P2 locus, the TNB and NBA of the second parity of genotype AA were obviously higher than those of AB (P < 0.05). And at P7 locus, the TNB and NBA of each parity of genotype AA were both about 2 piglets per litter more than those of BB (P < 0.05). The results indicated that PPARγ gene was significantly associated with litter size in pigs.

Nuclear receptors of the peroxisome proliferator-activated receptor (PPAR) family in gestational diabetes: from animal models to clinical trials

Gestational diabetes mellitus (GDM) is defined as impaired glucose tolerance and affects 2%-8% of all pregnancies. Among other complications, GDM can lead to the development of type 2 diabetes mellitus (DM 2) in both mother and child. Peroxisome proliferator-activated receptors (PPARs) are major regulators of glucose and lipid metabolism. Furthermore, PPARs are mediators of inflammation and angiogenesis and are involved in the maternal adaptational dynamics during pregnancy to serve the requirements of the growing fetus. PPARs were originally named for their ability to induce hepatic peroxisome proliferation in mice in response to xenobiotic stimuli. The expression of three PPAR isoforms, alpha, beta/delta, and gamma, have been described. Each of them is encoded by different genes; however, they share 60%-80% homology in their ligand-binding and DNA-binding domains. PPARs are involved in trophoblast differentiation, invasion, metabolism, and parturition and are expressed in invasive extravillous trophoblast and villous trophoblast cells. Nuclear receptors, to which PPARs belong, are promising targets for disease-specific treatment strategies because they act as transcription factors controlling cellular processes at the level of gene expression and may produce selective alterations in downstream gene expression. To date, PPAR agonists are therapeutically used in patients with DM 2 and in patients with reproductive disorders such as polycystic ovary syndrome. Because of safety concerns and limited data, PPAR agonists are not yet included in GDM-related treatment strategies. Our objective herein is to review newly emerging generations of selective PPAR modulators and panagonists, which may have potent therapeutic implications in the context of GDM.

Recurrent miscarriage: current concepts in diagnosis and treatment

Although recurrent miscarriage (RM) affects only 1-3% of couples, it has a major influence on the wellbeing and psychosocial status of patients. Therefore, research into improved diagnosis and development of new treatment strategies is essential. In this review, we summarize current concepts on diagnosis and treatment in RM, drawing upon research reports and international guidelines to provide insights into the pathophysiology of pregnancy disrupted by repeated miscarriage. Anatomical malformations, infectious diseases, endocrine disorders, autoimmune defects as well as acquired and inherited thrombophilia are established risk factors in RM. In addition, our recent findings indicate an impact on miscarriage incidence of glycoproteins such as glycodelin, and nuclear hormone receptors such as the peroxisome proliferator-activated receptors (PPARs). Significantly reduced glycodelin expression is associated with miscarriage, whereas up-regulation of PPARs appears to compensate for either the activated immune response or the disturbed cytotrophoblast differentiation in RM patients. There is also evidence that circulating placental microparticles are increased in a subgroup of RM patients, indicating an acquired procoagulant state even outside pregnancy. Treatment strategies like aspirin and low molecular weight heparin (LMWH) are standard medications in RM, although only a few placebo-controlled trials have proven their benefit in respect to live birth rate. There is emerging evidence that new treatment options, including drugs like TNFalpha inhibitors and granulocyte colony-stimulating factor (G-CSF) might be beneficial in some cases of RM. However, larger clinical trials must be completed to further prove or disprove benefits of these drugs in the treatment of RM patients.

Activation of PPARγ by Rosiglitazone does not negatively impact male sex steroid hormones in diabetic rats

Peroxisome proliferator-activated receptor gamma (PPARγ) activation decreased serum testosterone (T) in women with hyperthecosis and/or polycystic ovary syndrome and reduced the conversion of androgens to estradiol (E2) in female rats. This implies modulation of female sex steroid hormones by PPARγ. It is not clear if PPARγ modulates sex steroid hormones in diabetic males. Because PPARγ activation by thiazolidinedione increased insulin sensitivity in type 2 diabetes, understanding the long term impact of PPARγ activation on steroid sex hormones in males is critical. Our objective was to determine the effect of PPARγ activation on serum and intratesticular T, luteinizing hormone (LH), follicle stimulating hormone (FSH) and E2 concentrations in male Zucker diabetic fatty (ZDF) rats treated with the PPARγ agonist rosiglitazone (a thiazolidinedione). Treatment for eight weeks increased PPARγ mRNA and protein in the testis and elevated serum adiponectin, an adipokine marker for PPARγ activation. PPARγ activation did not alter serum or intratesticular T concentrations. In contrast, serum T level but not intratesticular T was reduced by diabetes. Neither diabetes nor PPARγ activation altered serum E2 or gonadotropins FSH and LH concentrations. The results suggest that activation of PPARγ by rosiglitazone has no negative impact on sex hormones in male ZDF rats.

Small molecule activators of SIRT1 replicate signaling pathways triggered by calorie restriction in vivo

Background

Calorie restriction (CR) produces a number of health benefits and ameliorates diseases of aging such as type 2 diabetes. The components of the pathways downstream of CR may provide intervention points for developing therapeutics for treating diseases of aging. The NAD⁺-dependent protein deacetylase SIRT1 has been implicated as one of the key downstream regulators of CR in yeast, rodents, and humans. Small molecule activators of SIRT1 have been identified that exhibit efficacy in animal models of diseases typically associated with aging including type 2 diabetes. To identify molecular processes induced in the liver of mice treated with two structurally distinct SIRT1 activators, SIRT501 (formulated resveratrol) and SRT1720, for three days, we utilized a systems biology approach and applied Causal Network Modeling (CNM) on gene expression data to elucidate downstream effects of SIRT1 activation.

Results

Here we demonstrate that SIRT1 activators recapitulate many of the molecular events downstream of CR in vivo, such as enhancing mitochondrial biogenesis, improving metabolic signaling pathways, and blunting pro-inflammatory pathways in mice fed a high fat, high calorie diet.

Conclusion

CNM of gene expression data from mice treated with SRT501 or SRT1720 in combination with supporting in vitro and in vivo data demonstrates that SRT501 and SRT1720 produce a signaling profile that mirrors CR, improves glucose and insulin homeostasis, and acts via SIRT1 activation in vivo. Taken together these results are encouraging regarding the use of small molecule activators of SIRT1 for therapeutic intervention into type 2 diabetes, a strategy which is currently being investigated in multiple clinical trials.

Transcriptional regulation of the processes of human labour and delivery

Preterm birth is the most important complication contributing to poor pregnancy and neonatal outcome. A critical issue that must be resolved is how spontaneous onset labour is initiated both at term and preterm. Over the past decade, we and others have provided evidence in support of the hypothesis that labour onset is regulated by specific nuclear regulatory factor (NR) pathways, involving an interplay between transcription factors (TFs) and nuclear hormone receptors, that control the expression of many of the effector pathways requisite for labour and delivery. There is now compelling evidence implicating NRs, including the nuclear factor-kappaB (NF-kappaB) family of nuclear TFs, the nuclear hormone receptor superfamily of peroxisome proliferator activated receptors (PPARs), and the steroid receptors for progesterone (PRA, PRB and PRC), as candidate upstream regulators of labour-associated processes. Based on these studies and recent data obtained in our laboratory, we provide a new model of how the multiple pathways involved in spontaneous onset labour and delivery are coordinated at a nuclear level. We propose that spontaneous onset labour and delivery are consequent upon withdrawal of the repressive effect of nuclear receptors (PPAR and PR) on pro-labour TF pathways (NF-kappaB). The withdrawal of NR-mediated repression is affected by competition between TFs and NRs for a limited pool of nuclear cofactors. We also propose that coordination of these different pathways is achieved by competition for common cofactors that control the activity of NRs in human gestational tissues.

PPAR-gamma signaling pathway in placental development and function: a potential therapeutic target in the treatment of gestational diseases

BACKGROUND

PPAR-gamma is a target for the treatment of metabolic disorders, as Pioglitazone and Rosiglitazone are already used against type 2 diabetes. Pleiotropic functions, such as antiproliferative and anti-inflammatory effects against several pathological states, including cardiovascular disease and cancer, are currently being explored in clinical studies.

OBJECTIVE

Evidence indicates that PPAR-gamma is expressed in the placenta, playing a crucial role in placental development and function, while PPAR-gamma ligands appear to modulate fetal membrane signals. Thus, in the last few years, the pivotal role of PPAR-gamma in placental biology has been the focus of extensive research, as diabetes appears to be the most common metabolic dysfunction in pregnancy.

METHODS

We aim to present data concerning the expression of PPAR-gamma in animal and human placenta, underlining its significance in normal placental development and several gestational diseases. The effects of PPAR-gamma ligands as modulators of placental biology in normal and certain pathological conditions are also discussed.

RESULTS/CONCLUSION

Current research provides substantial evidence that PPAR-gamma plays a pivotal role in placental biology and may reveal new perspectives in the treatment of gestational diseases.