Marie-Noëlle Dieudonné

Leptin mediates a proliferative response in human MCF7 breast cancer cells.

Obesity is a risk factor of breast cancers. As leptin, a hormone mainly secreted by white adipocytes, elicits proliferative effects in some cell types, we tested the hypothesis that leptin could influence human breast cancer MCF-7 cell growth. Here we show that MCF-7 cells express leptin receptors and respond to human recombinant leptin by STAT3 and p42/p44 MAPkinase activations and by increased proliferation. These findings suggest that leptin could act in vivo as a paracrine/endocrine growth factor towards mammary epithelial cells thus contributing to explain why obesity is a risk factor of developing breast cancers.

Direct in vitro effects of androgens and estrogens on ob gene expression and leptin secretion in human adipose tissue

In the present study, we have explored, in vitro, the possibility that short exposure to androgens and estrogens for 24 h may directly influence leptin expression (ARNm and secretion) in sc adipose tissue from men and women. In men, only dihydrotestosterone at high concentration (100 nM) induced a reduction in leptin secretion and ob mRNA level. In women, 17β-estradiol (10–100 nM) increased ob mRNA expression (+180 to +500%) and leptin release (+75%). Moreover, in adipose tissue of women, the estrogen precursors testosterone (100 nM) and dehydroepiandrosterone (1 µM) also induced an increase in leptin secretion (+84 and +96%, respectively), an effect that was prevented by the aromatase inhibitor letrozole. Finally, the stimulatory effect of 17β-estradiol observed in women was antagonized by the antiestrogen ICI182780. Altogether, these results suggest that the sexual dimorphism of leptinemia in humans is mainly owing to the estrogen receptor-dependent stimulation of leptin expression in adipose tissue by estrogens and estrogen precursors in women.

Sex steroids and leptin regulate 11β-hydroxysteroid dehydrogenase I and P450 aromatase expressions in human preadipocytes: Sex specificities

Adipose tissue is an important site of steroid hormone biosynthesis, as type I 11beta-hydroxysteroid dehydrogenase (HSD1), the enzyme responsible for the conversion of cortisone into cortisol and the P450 aromatase, the enzyme catalysing androgens aromatization into estrogens, are both expressed in human adipose tissue. In the present report, we have investigated the possibility that sex steroids and leptin could regulate these two enzymes in cultured preadipocytes from men and women intra-abdominal fat depots. In women preadipocytes, human recombinant leptin down-regulates HSD1 mRNA expression (-58%) and P450 aromatase activity (-26%). Conversely, leptin up-regulates the HSD1 (2.4-fold) and the P450 aromatase (1.6-fold) mRNA expression in men preadipocytes. In women preadipocytes, 17beta-estradiol strongly stimulates HSD1 mRNA expression (10-fold) and, in contrast, decreases by half the P450 aromatase expression. In men, 17beta-estradiol has no influence on HSD1 expression but up-regulates P450 aromatase mRNA expression (2.4-fold). Finally, androgens increase by a factor of 2.5-5 the mRNA expression of both enzymes in men. These findings suggest that sex steroids and leptin either increase or decrease local cortisol and estrogens productions in men or in women preadipocytes, respectively. They also indicate that steroid metabolism in adipose tissue is controlled by a coordinated regulation of P450 aromatase and HSD1 expressions. Finally, the important sex-specific differences described herein may also contribute to explain the sexual dimorphism of body fat distribution in humans.

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.

Estrogen-related receptor gamma modulates energy metabolism target genes in human trophoblast

Placenta growth and functions depend on correct trophoblast migration, proliferation, and differentiation. The placenta has a critical role in gas and nutrient transport. To accomplish these numerous functions, the placenta depends on a highly efficient energy metabolism control. Recent studies showed that the orphan nuclear receptor Estrogen-Related Receptor gamma (ERRγ) is highly expressed in human placentas. As ERRγ has been described as a major energy metabolism regulator, we investigated ERRγ expression and putative roles on energy homeostasis in human trophoblast from first trimester placentas. First, we showed that ERRγ expression level increased during pregnancy and that ERRγ was more abundant in villous than in extravillous trophoblasts. We also observed that ERRγ expression increased during trophoblast differentiation. Second, we demonstrated that mitochondrial biogenesis and expression of some energy metabolism target genes decreased when ERRγ expression was impaired. Altogether, these results suggest that ERRγ could be implicated in the energy metabolism regulation of human trophoblasts.

PreImplantation Factor (PIF) Promotes Human Trophoblast Invasion

ABSTRACT Preimplantation factor (PIF) is a peptide secreted by viable mammalian embryos. Moreover, it can be detected in the circulation of pregnant women. Recently, it was shown that PIF promotes invasion in trophoblast cell lines in vitro. Successful human embryo implantation depends on a deep and highly controlled invasion of extravillous trophoblast (EVT) in the maternal endometrium. Trophoblast invasion is regulated in part by matrix metalloproteinase (MMP) activity and integrin expression. The present study demonstrates the presence of PIF in early pregnancy and characterizes its effects on primary human trophoblast invasion. At the fetomaternal interface, intense PIF labeling by immunohistochemistry was present during early gestation in villous trophoblasts and EVTs. A decrease of labeling was observed at term. Furthermore, PIF significantly promoted invasion of human EVT isolated from first-trimester placenta. The proinvasive regulatory effect of PIF in EVT was associated with 1) increased MMP9 activity and 2) reduced tissue inhibitor of metalloproteinase-1 (TIMP1) mRNA expression. PIF also regulated alpha v and alpha 1 integrin mRNA expressions. Last, the proinvasive effect of PIF appeared to be mediated by the mitogen-activated protein kinase (MAPK), phosphoinositide-3-kinase (PI3K), and Janus-kinase signal transducer and activator of transcription (JAK-STAT) signaling pathways. In summary, this work describes the direct, positive effect of PIF on the control of human trophoblastic cell invasion by modulation of MMP/TIMP balance and integrin expression. Moreover, these results suggest that PIF is involved in pathological pregnancies characterized by insufficient or excessive trophoblast invasion.

Androgen receptors in cultured rat adipose precursor cells during proliferation and differentiation: regional specificities and regulation by testosterone

Different studies suggest that sex hormones affect adipose tissue metabolism and deposition. To investigate the possibility that androgens may play a role in adipose tissue development, we have studied androgen receptors (AR) in rat adipose precursor cells from two different anatomical fat deposits, one deep intraabdominal (epididymal) and one subcutaneous (inguinal) during the proliferation and differentiation processes. AR were quantified by [3H]R1881 specific binding in whole cells and the nuclear fraction and were localized by immunocytofluorimetry in both the cytosol and the nucleus. During the proliferative phase, total AR level decreased from D3 to D6. At confluence (D5), AR were higher in epididymal (64±4 fmol/mg protein) than in subcutaneous (33±3 fmoles/mg proteins) preadipocytes and were up-regulated by testosterone but not by 5α-dihydrotestosterone or by 17β-estradiol. At differentiation (D10-11), nuclear AR decreased by 50% in both precursor fat cell populations when compared to the confluent state (D5) and AR were no more up-regulated but rather down-regulated by testosterone. Because AR are present in preadipocytes and are differently regulated by testosterone depending on the stage of proliferation and differentiation, this study suggests that testosterone may play a role in the control of the adipogenic process.

Regulation of white adipocyte guanine nucleotide binding proteins Gsα and Giα1–2 by testosterone in vivo: Influence of regional fat distribution

Abstract The influence of the androgenic status on the steady-state amounts of Gi α 1–2 and Gsα subunits was compared in hamster fat cell membranes from the femoral subcutaneous (FSC) and epididymal (EP) adipose tissues, using immunoblotting experiments. In sham-operated hamsters, Gi α 1–2 and Gsα steady-state amounts found in FSC fat cells were 38% and 40% reduced, respectively, as compared to EP adipocytes. In EP fat cells, castration induced a down-regulation of both Gi α 1–2 (−39%) and Gsα (−33%), whereas testosterone replacement restored Gsα, but not Gi α 1–2 levels, to control values. In contrast, these G protein α-subunits were insensitive to the androgenic status in FSC fat cells. These data provide the first evidence that the androgenic status can modulate the expression of both the Gi α 1–2 and Gsα subunits of the fat cell adenylate cyclase regulatory Gi and Gs proteins and that this modulation depends on the anatomical origin of these cells.

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.

PreImplantation Factor (PIF*) endogenously prevents preeclampsia: Promotes trophoblast invasion and reduces oxidative stress.

Preeclampsia is a unique pregnancy disorder whose patho-physiology is initiated early in gestation, while clinical manifestations typically occur in mid-to-late pregnancy. Thus, prevention should optimally be initiated in early gestation. The intimate interaction between PIF, secreted early by viable embryos, and its host-mother provides insight into putative mechanisms of preeclampsia prevention. PIF is instrumental at the two critical events underlying preeclampsia. At first, shallow implantation leads to impaired placentation, oxidative stress, protein misfolding, and endothelial dysfunction. Later in gestation, hyper-oxygenation due to overflow of maternally derived oxygenated blood compromises the placenta. The first is likely involved in early preeclampsia occurrence due to reduced effectiveness of trophoblast/uterus interaction. The latter is observed with later-onset preeclampsia, caused by a breakdown in placental blood flow regulation. We reported that 1. PIF promotes implantation, endometrium receptivity, trophoblast invasion and increases pro-tolerance trophoblastic HLA-G expression and, 2. PIF protects against oxidative stress and protein misfolding, interacting with specific targets in embryo, 3. PIF regulates systemic immunity to reduce oxidative stress. Using PIF as an early preventative preeclampsia intervention could ameliorate or even prevent the disease, whose current main solution is early delivery.