Should the Treatment of Patients with Repeated Embryo Implantation Failure Be Adapted as a Function of the Endometrial Cytokine Profile? A Single-Center Experience.

Repeated embryo implantation failures (RIF) is a source of distress and frustration for patients and clinicians alike. Today's approaches for treating RIF are largely empirical and have limited effectiveness. The main causes of RIF are poor endometrial receptivity and poor-quality embryos. Recent studies have suggested the involvement of immune dysregulation due to an imbalance between T-helper (Th) 1 and Th2 cytokines; this opens up perspectives for treating women with RIF and increasing the implantation rate. We conducted an interventional, longitudinal, prospective cohort study of the impact of correcting the cytokine imbalance on the clinical pregnancy rate in women with RIF. Seventy-seven women with RIF underwent an endometrial biopsy during the implantation window. The cytokine profile was evaluated by studying the activation and maturation of uterine natural killer (uNK) cells, the IL-15/Fn-14 mRNA ratio (a biomarker of uNK activation/maturation), and the IL-18/TWEAK mRNA ratio (a marker of angiogenesis and the Th1/Th2 balance). Personalized treatment was initiated for women with an abnormal endometrial cytokine profile (hyper-activation or hypo-activation). We documented the clinical pregnancy rate after subsequent embryo transfers. In total, 72.7% (56/77) of patients had an abnormal endometrial cytokine profile (hyper-activation in 68.8% (n = 53) and hypo-activation in 3.9% (n = 3). After treatment (or not) as a function of the endometrial profile, the overall clinical pregnancy rate was 30.2%. Our results indicated a potential positive effect of appropriate treatment on the ongoing pregnancy rate in women with RIF, despite the small number of cases analyzed. The results must now be validated in randomized studies with larger numbers of well-characterized patients. By applying a previously published decision tree, this treatment approach could be implemented in clinics worldwide.

Influence of maternal obesity on human trophoblast differentiation: The role of mitochondrial status.

Maternal obesity is associated with complications of pregnancy and increases the infant's risk of developing obesity, diabetes and cardiovascular disease later in life. The placenta has an important role in determining the pregnancy outcome, and the syncytiotrophoblast (ST) is the main component of the placenta that supports the relationship between the mother and fetus. The differentiation of the cytotrophoblast (CT) into the ST is accompanied by changes in mitochondrial functions and dynamics. The objective of the present study was to investigate the effects of maternal obesity (without gestational diabetes) on the in vitro differentiation capacities of human CT isolated from term placenta by focusing on mitochondrial status. We found that, during human CT differentiation process, maternal obesity is associated with (i) a lower progesterone secretion, (ii) a transient impairment in the ST's fusion potential (via syncytin-2 and its receptor), (iii) a lower mitochondrial content, and (iv) weaker mRNA expression of oestrogen-related receptor-gamma (a key mitobiogenesis gene). Moreover, maternal obesity altered the time course of ATP and reactive oxygen species production throughout CT differentiation. The mitochondrial dysfunctions observed in isolated human CTs of obese women might explain the observed decrease in progesterone production. Our results demonstrated that obesity in pregnancy is associated with a functional impairment of the ST which might alter the foetal-maternal dialogue.

Maternal Obesity Influences Placental Nutrient Transport, Inflammatory Status, and Morphology in Human Term Placenta.

CONTEXT: Maternal obesity has a significant impact on placental development. However, this impact on the placenta's structure and function (ie, nutrient transport and hormone and cytokine production) is a controversial subject. OBJECTIVE: We hypothesized that maternal obesity is associated with morphologic, secretory, and nutrient-related changes and elevated levels of inflammation in the placenta. DESIGN: We collected samples of placental tissue from 2 well-defined groups of pregnant women from 2017 to 2019. We compared the 2 groups regarding placental cytokine and hormone secretion, immune cell content, morphology, and placental nutrient transporter expressions. SETTING: Placenta were collected after caesarean section performed by experienced clinicians at Centre Hospitalier Intercommunal (CHI) of Poissy-Saint-Germain-en-Laye. PATIENTS: The main inclusion criteria were an age between 27 and 37 years old, no complications of pregnancy, and a first-trimester body mass index of 18-25 kg/m2 for the nonobese (control) group and 30-40 kg/m2 for the obese group. RESULTS: In contrast to our starting hypothesis, we observed that maternal obesity was associated with (1) lower placental IL-6 expression and macrophage/leukocyte infiltration, (2) lower placental expression of GLUT1 and SNAT1-2, (3) a lower placental vessel density, and (4) lower levels of placental leptin and human chorionic gonadotropin production. CONCLUSION: These results suggest that the placenta is a plastic organ and could optimize fetal growth. A better understanding of placental adaptation is required because these changes may partly determine the fetal outcome in cases of maternal obesity.

Maternal obesity influences expression and DNA methylation of the adiponectin and leptin systems in human third-trimester placenta.

BACKGROUND: It is well established that obesity is associated with dysregulation of the ratio between the two major adipokines leptin and adiponectin. Furthermore, it was recently reported that maternal obesity has a significant impact on placental development. Leptin and adiponectin are present at the fetal-maternal interface and are involved in the development of a functional placenta. However, less is known about leptin and adiponectin's involvement in the placental alterations described in obese women. Hence, the objective of the present study was to characterize the placental expression and DNA methylation of these two adipokine systems (ligands and receptors) in obese women. RESULTS: Biopsies were collected from the fetal and maternal sides of third-trimester placenta in obese and non-obese (control) women. In both groups, leptin levels were higher on the fetal side than the maternal side, suggesting that this cytokine has a pivotal role in fetal growth. Secondly, maternal obesity (in the absence of gestational diabetes) was associated with (i) elevated DNA methylation of the leptin promoter on fetal side only, (ii) hypomethylation of the adiponectin promoter on the maternal side only, (iii) significantly low levels of leptin receptor protein (albeit in the absence of differences in mRNA levels and promoter DNA methylation), (iv) significantly low levels of adiponectin receptor 1 mRNA expression on the maternal side only, and (v) elevated DNA methylation of the adiponectin receptor 2 promoter on the maternal side only. CONCLUSION: Our present results showed that maternal obesity is associated with the downregulation of both leptin/adiponectin systems in term placenta, and thus a loss of the beneficial effects of these two adipokines on placental development. Maternal obesity was also associated with epigenetic changes in leptin and adiponectin systems; this highlighted the molecular mechanisms involved in the placenta's adaptation to a harmful maternal environment.

Adiponectin regulates glycogen metabolism at the human fetal­maternal interface

Throughout the entire first trimester of pregnancy, fetal growth is sustained by endometrial secretions, i.e. histiotrophic nutrition. Endometrial stromal cells (EnSCs) accumulate and secrete a variety of nutritive molecules that are absorbed by trophoblastic cells and transmitted to the fetus. Glycogen appears to have a critical role in the early stages of fetal development, since infertile women have low endometrial glycogen levels. However, the molecular mechanisms underlying glycogen metabolism and trafficking at the fetal­maternal interface have not yet been characterized. Among the various factors acting at the fetal­maternal interface, we focused on adiponectin ­ an adipocyte-secreted cytokine involved in the control of carbohydrate and lipid homeostasis. Our results clearly demonstrated that adiponectin controls glycogen metabolism in EnSCs by (i) increasing glucose transporter 1 expression, (ii) inhibiting glucose catabolism via a decrease in lactate and ATP productions, (iii) increasing glycogen synthesis, (iv) promoting glycogen accumulation via phosphoinositide-3 kinase activation and (v) enhancing glycogen secretion. Furthermore, our results revealed that adiponectin significantly limits glycogen endocytosis by human villous trophoblasts. Lastly, we demonstrated that once glycogen has been endocytosed into placental cells, it is degraded into glucose molecules in lysosomes. Taken as a whole, the present results demonstrate that adiponectin exerts a dual role at the fetal­maternal interface by promoting glycogen synthesis in the endometrium and conversely reducing trophoblastic glycogen uptake. We conclude that adiponectin may be involved in feeding the conceptus during the first trimester of pregnancy by controlling glycogen metabolism in both the uterus and the placenta.

Are leptin and adiponectin involved in recurrent pregnancy loss?

AIM: The aim of this study was to investigate whether recurrent pregnancy loss (RPL) is associated with adipokine gene polymorphisms (namely the leptin -2548 (G/A), adiponectin 276 (G/T), and adiponectin 45 (T/G) polymorphisms) and/or adipokine serum levels. METHODS: A total of 145 women participated in the study. For the analysis of serum adipokine levels, 19 healthy fertile women (control group) and 60 women suffering from RPL were included. For the polymorphism analysis, 126 women suffering from RPL were included. Serum adipokine levels were determined using a commercial radioimmunoassay kit. Adipokine polymorphisms were analyzed using an allele-specific polymerase chain reaction (PCR). RESULTS: Our immunoassays revealed that serum leptin levels were similar in control and RPL groups (17.34 and 20.16 ng/mL, respectively). In contrast, serum adiponectin levels were significantly higher in women with RPL than in controls (9.83 and 6.89 µg/mL, respectively; P < 0.05). Unfortunately, our allele-specific PCR experiments did not reveal any significant differences in allele frequency between women with RPL and NCBI allele frequencies. CONCLUSION: This study demonstrates that adiponectinemia is increased in patients suffering from RPL. However, association of adiponectin with adverse pregnancy outcomes remains to be elucidated.

Adiponectin limits differentiation and trophoblast invasion in human endometrial cells.

Successful human embryo implantation requires a proper differentiation of endometrial stromal cells (ESCs) into decidual cells, during a process called decidualization. ESCs express specific molecules, such as prolactin, insulin-like growth factor-binding protein-1 (IGFBP-1) and connexin-43. Decidual cells are also involved in the control of trophoblast invasion, by secreting various factors, such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Adiponectin is an adipokine with insulin-sensitizing, anti-inflammatory and anti-proliferative effects. At the embryo-maternal interface, adiponectin promotes differentiation and invasion of human trophoblastic cells. We hypothesize that the effects of adiponectin on endometrium could counteract its pro-invasive effects previously described in the human trophoblast. In this context, we have firstly demonstrated that adiponectin downregulates IGFBP-1 and connexin-43 mRNA expressions, as well as prolactin secretion in ESCs, suggesting an anti-differentiative effect of adiponectin. Secondly, we found that invasive capacities of trophoblastic cell line HTR-8/SVneo are reduced in the presence of conditioned media from ESC cultured in the presence of adiponectin. Adiponectin's anti-invasive action is associated with a decreased activity of MMP-2 and MMP-9, and an increased TIMP-3 mRNA expression in ESCs. Finally, adiponectin receptors (ADIPOR1 and ADIPOR2) knockdown abolishes the anti-differentiative and anti-invasive effects of adiponectin in human ESCs. Altogether, our results suggest that adiponectin reduces the decidualization process and inversely induces the production of endometrial factors that limit trophoblast invasion. Thus, through a dual control in trophoblast and endometrial cells, adiponectin appears as a pivotal actor of the embryo implantation process.

The roles of leptin and adiponectin at the fetal-maternal interface in humans.

Infertility now affects one in seven couples, and the prevalence of this condition continues to increase. Ovulatory defects and unknown causes account for more than half of the cases of infertility. It has been postulated that a significant proportion of these cases are directly or indirectly related to obesity, since the presence of excess adipose tissue has a variety of effects on reproductive function. Here, we review on the effects of the two major adipokines (leptin and adiponectin) on fertility, with a focus on the first steps in embryo implantation and the key components of fetal-maternal interface (the placenta and the endometrium). These adipokines are reportedly involved in the regulation of cell proliferation and differentiation, and as such affect local angiogenesis, immune tolerance and inflammatory processes in placental and endometrial tissues. In placental cells, leptin and adiponectin also modulate trophoblast invasiveness and the nutrient supply. These observations strongly suggest by interfering with the placenta and endometrium, adipokines can create a favorable environment for embryo implantation and have a key role in fetal-maternal metabolism, fetal-maternal communication, and gestation. Given that reproductive functions are tightly coupled to the energy balance, metabolic abnormalities may lead to the development of complications of pregnancy and changes in fetal growth. In this context, we suggest that the leptin/adiponectin ratio may be a clinically valuable marker for detecting a number of pathologies in pregnancy.

Involvement of estrogen-related receptor-γ and mitochondrial content in intrauterine growth restriction and preeclampsia.

OBJECTIVE: To measure mitochondrial content and the expression of estrogen-related receptor-γ (ERRγ, a major inducer of mitochondrial biogenesis) in placentas from women with intrauterine growth restriction (IUGR) associated or not with pre-eclampsia (PE), relative to control placentas. DESIGN: Case-control study. SETTING: Teaching hospital and university research laboratory. PATIENT(S): Thirty-nine placentas from women with IUGR, 8 IUGR+PE, and 30 controls. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Mitochondrial DNA and protein content, gene and protein expression. RESULT(S): We observed significantly lower placental mitochondrial DNA and protein contents (associated with down-regulation of ERRγ expression) in IUGR and IUGR+PE placentas, relative to control placentas. Our results also revealed that the placental mitochondrial DNA content was directly correlated with fetal weight. Moreover, we observed significantly lower peroxisome proliferator-activated receptor-γ coactivator-1α and sirtuin 1 messenger RNA expression levels in IUGR+PE placentas, relative to control placentas. CONCLUSION(S): The low mitochondrial DNA and protein contents observed in IUGR placentas are probably due to down-regulation of ERRγ expression. This finding suggests that ERRγ has a major role in the control of placental development.

Trophoblast syncytialisation necessitates mitochondrial function through estrogen-related receptor-γ activation.

Human pregnancy needs a correct placentation which depends on adequate cytotrophoblast proliferation, differentiation and invasion. In this study, using specific mitochondrial respiratory chain inhibitors, we observed a decrease of hormone production (hCG and leptin) and cell fusion of human primary villous cytotrophoblasts (CT). These results demonstrated that mitochondria are involved in the control of CT differentiation process. Moreover, we also observed a decrease of mitochondrial mass associated with an increase of mitochondrial DNA during CT differentiation. Furthermore, lactate production increased during CT differentiation suggesting that anaerobic metabolism was enhanced in differentiated CTs, and that the role of mitochondria in CT fusion is not only related to its energetic function. Otherwise, the orphan nuclear receptor, estrogen-related receptor γ (ERRγ) is known to orchestrate transcriptional control of energy metabolism genes. In this study, using RNA knockdown and transcriptional activation with DY131 (an ERRγ agonist), we clearly demonstrated that ERRγ promotes hormone production and cell fusion indicating that ERRγ is a key positive transcriptional factor involved in CT differentiation. Finally, we showed that ERRγ promotes mitochondrial biogenesis and function during CT differentiation, and that the role of ERRγ during trophoblast differentiation is mainly mediated by the control of mitochondrial functions.

Associations between Individual and Combined Polymorphisms of the TNF and VEGF Genes and the Embryo Implantation Rate in Patients Undergoing In Vitro Fertilization (IVF) Programs.

BACKGROUND: A multiple pregnancy is now considered to be the most common adverse outcome associated with in vitro fertilization (IVF). As a consequence, the identification of women with the best chances of embryo implantation is a challenge in IVF program, in which the objective is to offer elective single-embryo transfer (eSET) without decreasing the pregnancy rate. To date, a range of hormonal and clinical parameters have been used to optimize eSET but none have significant predictive value. This variability could be due to genetic predispositions related to single-nucleotide polymorphisms (SNPs). Here, we assessed the individual and combined impacts of thirteen SNPs that reportedly influence the outcome of in vitro fertilisation (IVF) on the embryo implantation rate for patients undergoing intracytoplasmic sperm injection program (ICSI). MATERIALS AND METHODS: A 13 gene polymorphisms: FSHR(Asn680Ser), p53(Arg72Pro), AMH(Ile49Ser), ESR2(+1730G>A), ESR1(-397T>C), BMP15(-9C>G), MTHFR1(677C>T), MTHFR2(1298A>C), HLA-G(-725C>G), VEGF(+405G>C), TNFα(-308A>G), AMHR(-482A>G), PAI-1(4G/5G), multiplex PCR assay was designed to genotype women undergoing ICSI program. We analyzed the total patients population (n = 428) and a subgroup with homogeneous characteristics (n = 112). RESULTS: Only the VEGF(+405G>C) and TNFα(-308A>G) polymorphisms impacted fertilization, embryo implantation and pregnancy rates. Moreover, the combined VEGF+405.GG and TNFα-308.AG or AA genotype occurred significantly more frequently in women with high implantation potential. In contrast, the VEGF+405.CC and TNFα-308.GG combination was associated with a low implantation rate. CONCLUSION: We identified associations between VEGF(+405G>C) and TNFα(-308A>G) polymorphisms (when considered singly or as combinations) and the embryo implantation rate. These associations may be predictive of embryo implantation and could help to define populations in which elective single-embryo transfer should be recommended (or, conversely, ruled out). However, the mechanism underlying the function of these polymorphisms in embryo implantation remains to be determined and the associations observed here must be confirmed in a larger, more heterogeneous cohort.

Adiponectin and reproduction.

Adiponectin is an adipocyte-derived cytokine that acts as a major regulator of insulin sensitivity. Adiponectin deficiency can result in severe diabetes and metabolic disorders in humans. Since its discovery, our understanding of adiponectin's biological functions has expanded from insulin sensitization properties to new effects on inflammation, immunology, and human reproduction. Indeed, both obesity and excessive leanness are associated with reproductive dysfunction. The objective of this chapter is to review such biological actions and the potential roles of adiponectin on human reproduction. There is accumulative evidence for direct effects of this adipokine on the late stages of folliculogenesis and on the development of a functional placenta. In addition, clinical and genomic studies associate hypoadiponectinemia with pregnancy-related disorders, including polycystic ovarian syndrome.

Adiponectin and leptin systems in human endometrium during window of implantation.

OBJECTIVE: To measure the expression of adiponectin, leptin, and their respective receptors in the human endometria of fertile women compared with women with unexplained recurrent implantation failure (IF) during the window of implantation. DESIGN: Controlled, prospective, clinical study. SETTING: Teaching hospital and university research laboratory. PATIENT(S): Thirty-one endometrial biopsies from women with IF and 19 fertile controls. INTERVENTION(S): Human endometrial biopsies. MAIN OUTCOME MEASURE(S): Gene and protein expression of endometrial biopsies. RESULT(S): Endometrial leptin expression was significantly lower in the IF group compared with fertile women. In contrast, leptin receptor (Ob-R) expression was higher in endometria of women with IF. Concerning the adiponectin system, adiponectin was expressed to the same extent in both groups. Conversely, the expression of its two receptors, AdipoR1 and AdipoR2, was reduced in endometria of women with IF compared with fertile women. CONCLUSION(S): Although progesterone resistance seems to be a common state of the endometrium in some human reproductive disorders, such as endometriosis or polycystic ovary syndrome, modification in leptin endometrial expression seems to be specific to IF. These results strongly suggest that changes in Ob-R and AdipoR expression profiles [1] should be implicated in the development of uterine receptivity, and [2] may therefore be potential new targets for prediction of IF.

Antiproliferative and proapoptotic effects of bisphenol A on human trophoblastic JEG-3 cells.

Different studies performed in rodents revealed that bisphenol-A (BPA), an environmental compound, altered early embryonic development. However, little is known concerning the direct effects of BPA on human implantation process. Thus, we decided to study in vitro BPA's effects on proliferative capacities of the human trophoblastic cell line, JEG-3. For this purpose, we first have shown that JEG-3 cells express the specific BPA receptor, namely estrogen-related receptor γ1 (ERRγ1). Secondly, we demonstrated that BPA did not exert any cytotoxic action in JEG-3 cells up to 10(-6)M. Moreover [(3)H]-thymidine incorporation experiments revealed that BPA significantly reduced cell proliferation. The results also showed that BPA induced JEG-3 apoptosis capacity as reflected by DNA fragmentation experiments. In conclusion, we describe here the direct impact of BPA on trophoblastic cell number mediated through both anti-proliferative and pro-apoptotic effects.

Adiponectin promotes syncytialisation of BeWo cell line and primary trophoblast cells.

BACKGROUND: In human pregnancy, a correct placentation depends on trophoblast proliferation, differentiation, migration and invasion. These processes are highly regulated by placental hormones, growth factors and cytokines. Recently, we have shown that adiponectin, an adipokine, has anti-proliferative effects on trophoblastic cells. Here, we complete this study by demonstrating that adiponectin modulates BeWo and human villous cytotrophoblast cell differentiation. RESULTS: We showed that hCG secretion was up-regulated by adiponectin treatment in both BeWo cells and human cytotrophoblasts from very early placentas (5-6 weeks). The expression of two trophoblast differentiation markers, leptin and syncytin 2, was also up-regulated by adiponectin in BeWo cells. Moreover, adiponectin treatment induced a loss of E-cadherin staining in these cells. In parallel, we demonstrated that AdipoR1 and AdipoR2 are up-regulated during forskolin induced BeWo cell differentiation, reinforcing the role of adiponectin in trophoblast syncytialization. SiRNA mediated down-regulation of AdipoR1 and AdipoR2 was used to demonstrate that adiponectin effects on differentiation were essentially mediated by these receptors. Finally, using a specific inhibitor, we demonstrated that the PKA signalling pathway could be one pathway involved in adiponectin effects on trophoblast differentiation. CONCLUSION: Adiponectin enhances the differentiation process of trophoblast cells and could thus be involved in functional syncytiotrophoblast formation.

Effects of adiponectin on human trophoblast invasion.

Adiponectin is an adipokine with insulin-sensitizing, anti-inflammatory, anti-atherogenic, and anti-proliferative effects. The expression of specific adiponectin receptors in the placenta and in the endometrium suggests a role for this cytokine in placental development, but this role has not yet been elucidated. The invasion of trophoblast cells during the first trimester of pregnancy being crucial to placentation process, we have studied adiponectin effects on human trophoblast invasive capacities. We found that adiponectin stimulated human trophoblast cell migration in HTR-8/SVneo cells in a dose-independent manner. In addition, adiponectin also significantly enhanced invasion of HTR-8/SVneo cells and of human extravillous trophoblast from first trimester placenta. These pro-invasive effects of adiponectin in human trophoblasts seem to be mediated in part via increased matrix metalloproteinases (MMP2 and MMP9) activities and via repression of TIMP2 mRNA expression. Our results suggest that adiponectin could be a positive regulator of the early invasion process by modulating the MMP/TIMP balance. Moreover, these results provide an insight into the role of adiponectin in pathological conditions characterized by insufficient or excessive trophoblast invasion.

Antiproliferative effects of adiponectin on human trophoblastic cell lines JEG-3 and BeWo.

During embryo implantation, a complex dialog exists between the mother and the fetus. However, little is known about the molecules that participate in this process. Among various factors secreted at the maternal-fetal interface, the adipose tissue-derived leptin is now considered a placental growth factor. Adiponectin is another adipocyte-derived signaling molecule known to exert antiproliferative effects in various cell types. In this work, we studied adiponectin sensitivity and effects on JEG-3 and BeWo choriocarcinoma cell lines. First, we showed that JEG-3 and BeWo cells express the specific adiponectin receptors ADIPOR1 and ADIPOR2 and respond to human recombinant adiponectin by AMP-activated protein kinase (PRKA, also known as AMPK) activation. Second, we demonstrated that adiponectin induces a reduction in cell number and in [(3)H]-thymidine incorporation, demonstrating that adiponectin has antiproliferative effects on trophoblastic cells. Furthermore, these effects of adiponectin seem to be, at least in part, mediated by the mitogen-activated protein kinase (MAPK) and phosphoinositide-3-kinase (PI3K) signaling pathways. We describe herein the direct effects of adiponectin in the control of trophoblastic cell proliferation.

Adiponectin mediates an antiproliferative response in human MDA-MB 231 breast cancer cells.

Numerous epidemiological studies have documented that obesity is a risk factor for breast cancer especially in post-menopausal women. However, the molecular basis of this association is not well known. In contrast to leptin, plasma levels of adiponectin, another major adipokine, are decreased in obese subjects. Therefore, we and others hypothesized that adiponectin may be a paracrine factor negatively controlling mammary tumor development. We recently demonstrated growth inhibition of the estrogen-sensitive breast cancer MCF-7 cell line by adiponectin. The purpose of the present study was to determine whether this anti-proliferative effect of adiponectin also applies to the MDA-MB 231 estrogen-insensitive breast epithelial cancer cell line. Our results demonstrate that i) the adiponectin-specific receptors AdipoR1 and R2 are expressed in these cells, and ii) the subphysiological concentrations of recombinant adiponectin inhibit MDA-MB 231 cell growth and concomitantly enhance the expression of Bax and p53, two pro-apoptotic genes. Moreover, the invalidation of AdipoR1 and R2 mRNA experiments demonstrated that the anti-proliferative and pro-apoptotic effects of adiponectin were partially mediated via AdipoR1 and R2. We describe, for the first time, that AdipoR mRNA expression was down-regulated by adiponectin and leptin in MDA-MB 231 cells. Taken altogether, these results strongly suggest that the two adipokines should be considered as i) additional factors of breast cancer risk, and ii) may therefore be potential targets in breast cancer therapy.

In vitro effects of chorionic gonadotropin hormone on human adipose development.

It is well known that pregnancy is associated with fat weight gain. However, the mechanisms whereby fat mass accumulation is controlled during this period are poorly understood. Therefore, we attempted to determine whether human chorionic gonadotropin (HCG), in vitro, influences human adipose tissue development and/or metabolism. For the first time, HCG/LH receptor was characterized in human adipose cells. We also demonstrated that physiological concentrations of HCG, while unaltering both lipolysis and expression of two markers of lipogenesis (FAS and ADD1) in human mature adipocytes, stimulate human preadipocyte growth via the activation of a protein kinase A-independent mitogen-activated protein kinase/c-fos signaling pathway. HCG also moderately increases the preadipocyte differentiation capacity as reflected by enhanced glycerophosphate dehydrogenase activity and expression of key adipogenic transcriptional factors (C/enhancer-binding protein alpha and peroxisome proliferator-activated receptor gamma 2). Finally, HCG significantly stimulates the secretion of the pro-adipogenic factor, leptin, from human adipose tissue. Taken altogether, these data suggest that the pro-adipogenic effect of HCG in human preadipocytes contributes to explain why increased fat storage occurs during the first trimester of pregnancy.

Adiponectin mediates antiproliferative and apoptotic responses in human MCF7 breast cancer cells.

It is well established that obesity is a risk factor for breast cancer and that blood levels of adiponectin, a hormone mainly secreted by white adipocytes, are inversely correlated with the body fat mass. As adiponectin elicits anti-proliferative effects in some cell types, we tested the hypothesis that adiponectin could influence human breast cancer MCF-7 cell growth. Here we show that MCF-7 cells express adiponectin receptors and respond to human recombinant adiponectin by reducing their growth, AMPkinase activation, and p42/p44 MAPkinase inactivation. Further, we demonstrate that the anti-proliferative effect of adiponectin involves activation of cell apoptosis and inhibition of cell cycle. These findings suggest that adiponectin could act in vivo as a paracrine/endocrine growth inhibitor towards mammary epithelial cells. Moreover, adipose adiponectin production being strongly reduced in obesity, this study may help to explain why obesity is a risk factor of developing breast cancers.