Characterization and expression of netrin-1 and its receptors UNC5B and DCC in human placenta.

Netrins are a family of proteins that mediate axonal guidance in the central nervous system (CNS). In addition to the CNS, netrins are involved in cell adhesion, motility, proliferation, differentiation, and survival. Because these processes occur in the placenta, we raised the question of whether netrin-1 is expressed by placental cells during development. In the present study, we analyzed the spatial and temporal distribution of netrin-1 and its two receptors, DCC (deleted in colorectal cancer) and UNC5B (uncoordinated-5 homolog) in human placenta using RT-PCR, Western blotting, and immunohistochemistry analysis. We demonstrated the presence of the proteins and transcripts of netrin-1 and its receptors in placenta and cytotrophoblasts. Furthermore, using immunohistochemistry, we localized endogenous netrin-1 protein staining to villous and extravillous cytotrophoblasts, and secreted netrin-1 outside the syncytiotrophoblasts. The DCC receptor was localized to syncytiotrophoblasts and invasive extravillous cytotrophoblasts during the first trimester and at term. On the other hand, the UNC5B receptor was localized to villous and extravillous cytotrophoblasts proximal to anchoring areas during the first trimester. At term, UNC5B was observed in decidual cells and weakly in extravillous cells. The discrete pattern of netrin-1 and netrin-1 receptor distribution suggested that netrin-1 protein functions might vary with its localization in the placenta and probably with time of gestation.

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.

Increased achondroplasia mutation frequency with advanced age and evidence for G1138A mosaicism in human testis biopsies.

OBJECTIVE: To evaluate the influence of aging on the achondroplasia mutation rate in the male germline. DESIGN: Studies in sperm and testis biopsy DNA according to donor's age. SETTING: University teaching hospital. PATIENT(S): Seventeen donors aged 30 to 65 years for sperm collection and 14 deceased donors aged 53 to 95 years for testis biopsies, all with normal stature. INTERVENTION(S): Testes were obtained from 14 deceased donors, and sperm was obtained from 17 patients who requested ART. MAIN OUTCOME MEASURE(S): Real-time polymerase chain reaction quantification of the G1138A mutation in sperm and testis biopsies. RESULT(S): The rate of G1138A mutation did not significantly vary with age in sperm, whereas in testis biopsies it increased markedly past the age of 70 years. Moreover, and for the first time, a mosaic for this mutation was detected in the testis of three subjects who were >80 years of age. CONCLUSION(S): These findings could contribute to providing a molecular explanation for the increased incidence of achondroplastic offspring with advanced paternal age.

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.

Nongenomic estrogen effects on nitric oxide synthase activity in rat adipocytes.

Estrogens exert multiple genomic effects on adipose tissue through binding to nuclear estrogen receptors. However, there is evidence for additional nongenomic mechanisms whereby estrogens may exert their control on adipose tissue metabolism through rapid activation of various membrane-initiated kinase cascades. Here, we tested rapid effects of estrogens on nitric oxide production in white adipose tissue using 17-beta estradiol (E2) and its membrane impermeant albumin conjugated form (17-beta estradiol hemisuccinate BSA, E2-BSA). We found that both E2 and E2-BSA stimulate nitric oxide synthase (NOS) activity in adipocytes. These effects were abolished by 1) ICI 182-780, a selective estrogen receptor antagonist; 2) wortmannin, an inhibitor of phosphatidylinositol 3-kinase; and 3) N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinolinesulfonamide (H-89) an inhibitor of protein kinase A. In contrast to NOS activation by E2, E2-BSA-induced NOS activity was abolished by UO126, an inhibitor of MAPK kinase/ERK (p42/p44 MAPKs). Immunoblotting studies have shown that both estrogens phosphorylate endothelial NOS (NOS III) on Ser(1179), an effect that is prevented by wortmannin and H89, suggesting that NOS III is the target for estrogen-induced NOS activity. Furthermore, only the E2-BSA-induced NOS III phosphorylation on Ser(1179) was totally abolished by UO126. These results indicate that the signaling cascades involved in adipocyte NOS stimulation by estrogens are different depending on whether estrogens are free or conjugated to albumin and therefore underline the importance of estrogen receptor locations in the nongenomic actions of estrogens in these cells.

Association between androgen receptor gene CAG trinucleotide repeat length and testicular histology in older men.

OBJECTIVE: To determine whether the size of CAG repeat in exon 1 of the androgen receptor (AR) gene is related to impaired spermatogenesis in older men. DESIGN: Study of two groups of older men: one with preserved spermatogenesis and the other with arrested spermatogenesis. SETTING: University teaching hospital. PATIENT(S): Twenty-eight men aged from 53 to 102 years. INTERVENTION(S): The DNA fragment encoding the AR polyglutamine tract was amplified from DNA of testis tissue. MAIN OUTCOME MEASURE(S): The size of the CAG repeat was evaluated by using fluorescent-labeled polymerase chain reaction performed on an ABI Prism 377 DNA sequencer followed by automated analysis with Genscan 3.1.2 software. RESULT(S): Mean CAG repeat length was 22.76 +/- 3 in the group of 13 aged men with preserved spermatogenesis and 21.86 +/- 2.23 in the group of 15 aged men with arrested spermatogenesis. CONCLUSION(S): Impaired spermatogenesis in elderly men does not seem to be correlated with the AR gene CAG repeat length, which therefore does not appear to be a risk factor for impaired spermatogenesis in older men.

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.

Screening for Down syndrome using first-trimester combined screening followed by second-trimester ultrasound examination in an unselected population.

OBJECTIVE: Recent studies have reported the efficacy of first-trimester combined screening for Down syndrome based on maternal age, serum markers (human chorionic gonadotropin, pregnancy-associated plasma protein A), and ultrasound measurement of fetal nuchal translucency. However, those do not incorporate the value of the widely accepted routine 20-22 weeks' anomaly scan. STUDY DESIGN: We carried out a multicenter, interventional study in the unselected population of a single health authority in order to assess the performance of first-trimester combined screening, followed by routine second trimester ultrasound examination and/or screening by maternal serum markers (free beta-hCG and alpha-fetoprotein measurement or total hCG, alpha-fetoprotein, and unconjugated estriol measurement) when incidentally performed. Detection and screen positive rates were estimated using a correction method for nonverified issues. A cost analysis was also performed. RESULTS: During the study period, 14,934 women were included. Fifty-one cases of Down syndrome were observed, giving a prevalence of 3.4 per 1000 pregnancies. Of these, 46 were diagnosed through first (n = 41) or second (n = 5) trimester screening. Among the 5 screen-negative Down syndrome cases, all were diagnosed postnatally after an uneventful pregnancy. Detection and screen positive rates of first-trimester combined screening were 79.6% and 2.7%, respectively. These features reached 89.7%, and 4.2%, respectively, when combined with second-trimester ultrasound screening. The average cost of the full screening procedure was 108 euros (120 dollars) per woman and the cost per diagnosed Down syndrome pregnancy was 7,118 euros (7909 dollars). CONCLUSION: Our findings suggest that 1 pragmatic interventional 2-step approach using first-trimester combined screening followed by second-trimester detailed ultrasound examination is a suitable and acceptable option for Down syndrome screening in pregnancy.

Sex steroids and leptin regulate 11beta-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.

Changes in progesterone-induced-blocking-factor expression rates following mifepristone administration in termination of pregnancy at 5 to 8 weeks.

OBJECTIVE: To study changes in the expression rate of PIBF by peripheral lymphocytes in healthy pregnant women after administration of mifepristone for non-surgical termination of pregnancy at 5-8 wks of gestation. METHODS: Patients requesting early social termination of pregnancy, in a 3-month period, were included. A first venous blood sample was taken before oral administration of 600 mg of mifepristone (day 0). A second venous blood sample was taken 2 days later. PIBF on lymphocytes was determined by immunocytochemistry using a PIBF-specific polyclonal antibody. RESULTS: Termination of pregnancy was successful and complete in all cases. In 17 out of 21 patients, the percentage of PIBF positive lymphocytes decreased after anti-progesterone administration. The percentage of PIBF-expressing lymphocytes significantly decreased from 52.8%+/-21.6% (day 0) to 39.8%+/-18.2% by day 2 (p=0.001). CONCLUSIONS: These data suggest a strong relationship between early termination of pregnancy induced with mifepristone and disturbances of progesterone-mediated immunosuppression.

Leptin-induced nitric oxide production in white adipocytes is mediated through PKA and MAP kinase activation.

Leptin injection increases plasma levels of nitrites and/or nitrates, an index of nitric oxide (NO) production. Because plasma levels of NO are correlated with fat mass and because adipose tissue is the main source of leptin, it seems that adipose tissue plays a major role in NO release induced by leptin. Adipocytes express both leptin receptors and nitric oxide synthase (NOS; including the endothelial isoform, NOS III, and the inducible isoform, NOS II). In this study, we have demonstrated that physiological concentrations of leptin stimulate NOS activity in adipocytes. This effect of leptin is abolished by 1) AG490, an inhibitor of Janus tyrosine kinase 2/signal transducer and activator of transcription 3; 2) U0126, an inhibitor of mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (p42/p44 MAPK); and 3) N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89) or Rp diastereomer of adenosine 3',5'-cyclic phosphorothioate, two inhibitors of protein kinase A, but not by wortmannin, an inhibitor of phosphatidylinositol 3-kinase. Immunoblotting studies have shown that leptin fails to activate Akt but increases p42/p44 MAPK phosphorylation, an effect that is prevented by U0126 but not by H-89. Furthermore, leptin induces NOS III phosphorylation at Ser(1179) and Thr(497), but not when adipocytes are pretreated with H-89 or U0126. Finally, stimulation of adipocyte NOS activity by leptin is either unaltered when protein phosphatase 2A is inhibited by 1 nM okadaic acid or completely abolished when protein phosphatase 1 (PP1) activity is inhibited by 3 nM tautomycin, which supports a crucial role for PP1 in mediating this effect of leptin. On the whole, these experiments demonstrate that NOS activity is a novel target for leptin in adipocytes and that the leptin-induced NOS activity is at least in part the result of NOS III phosphorylations via both protein kinase A and p42/p44 MAPK activation. More generally, this study also leads to the hypothesis of NO as a potentially important factor for leptin signaling in adipocytes.

cAMP-positive regulation of angiotensinogen gene expression and protein secretion in rat adipose tissue.

The adipose renin-angiotensin system (RAS) has been assigned to participate in the control of adipose tissue development and in the pathogenesis of obesity-related hypertension. In adipose cells, the biological responses to beta-adrenergic stimulation are mediated by an increase in intracellular cAMP. Because cAMP is known to promote adipogenesis and because an association exists between body fat mass, hypertension, and increased sympathetic stimulation, we examined the influence of cAMP on angiotensinogen (ATG) expression and secretion in rat adipose tissue. Exposure of primary cultured differentiated preadipocytes to the cAMP analog 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) or cAMP-stimulating agents (forskolin and IBMX) results in a significant increase in ATG mRNA levels. In adipose tissue fragments, 8-BrcAMP also increases ATG mRNA levels and protein secretion, but not in the presence of the protein kinase A inhibitor H89. The addition of isoproterenol, known to stimulate the synthesis of intracellular cAMP via beta-adrenoreceptors, had the same stimulatory effect on ATG expression and secretion. These results indicate that cAMP in vitro upregulates ATG expression and secretion in rat adipose tissue via the protein kinase A-dependent pathway. Further studies are required to determine whether this regulatory pathway is activated in human obesity, where increased sympathetic tone is frequently observed, and to elucidate the importance of adipose ATG to the elevated blood pressure observed in this pathological state.

In vitro suppression of the lipogenic pathway by the nonnucleoside reverse transcriptase inhibitor efavirenz in 3T3 and human preadipocytes or adipocytes.

A serious metabolic syndrome combining insulin-resistance, dyslipidemia, central adiposity, and peripheral lipoatrophy has arisen in HIV-infected patients receiving highly active antiretroviral therapy. The aim of this work was to examine the effects of the nonnucleoside reverse transcriptase inhibitor (NNRTI) efavirenz on adipocyte differentiation and metabolism. When induced to differentiate in the presence of efavirenz (5-50 microm), 3T3-F442A preadipocytes failed to accumulate cytoplasmic triacylglycerol droplets. This phenomenon was rapidly reversible and was also readily detectable in the 3T3-L1 preadipose cell line and in primary cultures of human preadipocytes. When applied to mature 3T3-F442A adipocytes, efavirenz induced a delayed and moderate reduction in cell triglyceride content. Measurement of [(3)H]deoxyglucose uptake, basal and agonist-stimulated lipolysis, and cell viability indicated that these pathways are not involved in efavirenz effects on triacylglycerol accumulation. By contrast, we found that the NNRTI induced a dramatic dose- and time-dependent decrease in gene and protein expression of the lipogenic transcription factor sterol regulatory element-binding protein-1c (SREBP-1c). Adipose conversion was only altered at the highest efavirenz concentrations, as suggested by the mild reduction in peroxisome proliferator-activated receptor-gamma and CCAAT/enhancer-binding protein-alpha. CCAAT/enhancer-binding protein-beta remained unchanged. The inhibition of SREBP-1c expression was accompanied by a sharp reduction in the expression of SREBP-1c target genes and in the adipocyte lipogenic activity in efavirenz-treated cells. Finally, the inhibitory effect of efavirenz on cell triglyceride accumulation was prevented by directly providing free fatty acids to the cells and was reversed by overexpression of a dominant positive form of SREBP-1c, reinforcing the implication of this transcription factor in the antilipogenic effect of the drug. When considered together, these results demonstrate for the first time that the NNRTI efavirenz induces a strong inhibition of the SREBP-1c-dependent lipogenic pathway that might contribute to adipose tissue atrophy.

Human adipose angiotensinogen gene expression and secretion are stimulated by cyclic AMP via increased DNA cyclic AMP responsive element binding activity.

Components of the adipose renin-angiotensin system (RAS) have been suggested as providing a potential path-way linking obesity to hypertension. In adipose cells, the biological responses to beta-adrenergic stimulation are mediated by an increase in intracellular cAMP. Because an association exists among body fat mass, hypertension, and increased sympathetic stimulation, we examined the influence of cAMP on angiotensinogen (ATG) expression and secretion in human adipose tissue and in parallel we studied the DNA binding activity of CRE transcriptional factors. A 24 h exposure to the cAMP analog 8Br-cAMP resulted in significant increases in ATG mRNA levels (+176+/-60%) and protein secretion (+40+/-27%). The ability of 8Br-cAMP to promote ATG gene expression was unaltered by H89, a protein kinase A inhibitor, because H89 per se was found to stimulate ATG mRNA levels and protein secretion. Moreover, 8Br-cAMP stimulated the specific CRE DNA binding activity (+115+/-14%) in human adipocyte nuclear extracts as assessed by electrophoretic mobility shift assays. These results indicate that cAMP upregulates in vitro ATG expression and secretion in human adipose tissue and that the induction in ATG mRNA levels appears to result, at least in part, from positive effects on the DNA binding activity of CRE transcription factors. Further studies are required to determine whether this regulatory pathway is activated in human obesity and to elucidate the importance of adipose ATG to the elevated blood pressure observed in this pathological state.

Hypothalamic leptin receptor and signaling molecule expressions in cafeteria diet-fed rats.

Although obesity is associated with a state of leptin resistance, it has been suggested that leptin may contribute to the pathogenesis of obesity-related hypertension. In previous studies, we reported that cafeteria diet feeding induces hyperleptinaemia and hyperinsulinemia in both male and female rats, with hypertension occurring only in male rats. However, when female rats were neonatally treated with testosterone (T), these animals develop hypertension when fed the cafeteria diet. These observations led us to investigate leptin signaling and some neuropeptides that are leptin targets in the hypothalamus of male, intact female, and T-treated female cafeteria diet-fed rats. A decrease in the hypothalamic leptin receptors (Ob-Ra and Ob-Rb) and pro-opiomelanocortin (POMC) mRNA was observed only in male hypertensive cafeteria diet-fed rats. Although no alterations in Ob-R occurred in both groups of female cafeteria diet-fed rats, the hyperleptinaemic state of these animals had no influence on POMC mRNA levels. In intact female rats, expression of the suppressors of cytokines signaling SOCS-1, SOCS-2, SOCS-3, and cytokine inhibitor signaling were unaltered, whereas in T-treated females SOCS-3 was overexpressed. Finally SOCS-1 mRNA level was increased only in male rats. Because hyperinsulinemia was reported to counteract the leptin-induced stimulation of the sympathetic tone and because SOCS-1 and -3 are potential inhibitors of insulin signaling, our results suggest that the hypothalamic overexpression of SOCS-1 or SOCS-3 found in male or T-treated female rats after cafeteria diet feeding could block the negative influence of the hyperinsulinemia on the central pressor action of leptin, thereby contributing to their hypertensive state.

Fibrinogen Poissy II (gammaN361K): a novel dysfibrinogenemia associated with defective polymerization and peptide B release.

A fibrinogen variant was identified in a pregnant patient with disseminated intravascular coagulation and abruptio placentae. This dysfibrinogen was also found in four asymptomatic members of the patient's family. Coagulation studies showed prolongation of both the thrombin and reptilase times, and discrepancy was noted between the levels of plasma fibrinogen as determined by a kinetic versus an immunological determination or light-scattering assay. Studies on purified fibrinogen revealed an impaired release of fibrinopeptide B by thrombin related to a delayed thrombin-induced fibrin polymerization. DNA sequencing revealed a heterozygous T <-- A point mutation in position 9373 of the gamma-chain gene (exon 9), which substituted a K for an N at position 361.

Sexual dimorphism in cafeteria diet-induced hypertension is associated with gender-related difference in renal leptin receptor down-regulation.

Plasma leptin levels are elevated in obesity suggesting a pathophysiologic role of this hormone in obesity and related disorders, such as hypertension. Furthermore, despite excess leptin levels, leptin satiety action is blunted in obesity suggesting the occurrence of central leptin resistance. As leptin acts on the kidney to induce natriuresis, renal leptin receptor alterations could lead to a defect in sodium excretion and hence to hypertension. Therefore, the present study investigated renal leptin receptor (Ob-Ra and Ob-Rb) mRNA and leptin binding capacities in diet-induced hypertension. Feeding male, female, and testosterone-treated female rats a cafeteria diet for 10 weeks increased body fat mass, plasma insulin, and leptin levels. Furthermore, although male and testosterone-treated female cafeteria-fed rats were hypertensive, the female rats fed the same diet failed to develop elevated blood pressure. In renal medulla, Ob-Ra and Ob-Rb mRNA levels were unchanged after cafeteria diet feeding in all groups; however, binding analysis revealed Ob-R protein down-regulation exclusively in hypertensive rats. Moreover, renal Ob-R densities were inversely correlated to plasma leptin concentrations in male rats and testosterone-treated female rats but not in female rats. These findings demonstrate the existence of differences in renal Ob-R binding capacities, which are correlated to hypertension.

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, 17beta-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 microM) 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 17beta-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.

Gender differences in hypothalamic tyrosine hydroxylase and alpha(2)-adrenoceptor subtype gene expression in cafeteria diet-induced hypertension and consequences of neonatal androgenization.

This study investigated the incidence of cafeteria-diet induced hypertension on hypothalamic tyrosine hydroxylase (TH) and alpha(2)-adrenoceptor subtype gene expression in male, female, and neonatally testosterone-imprinted female rats. After 10 weeks of cafeteria diet, all these rats were hyperleptinemic. In contrast, males and testosterone-treated females developed hypertension, whereas intact females remained normotensive. In these rats, cafeteria diet up-regulated TH gene expression only in males and testosterone-treated females. On the other hand, cafeteria diet differentially affected hypothalamic gene expression of alpha(2)-adrenoceptor subtypes. In fact, this diet increased alpha(2A)-adrenoceptor mRNA levels only in intact normotensive females. In contrast, gene expression of the alpha(2B)-adrenoceptor was up-regulated only in male and testosterone-treated female cafeteria-fed rats. Furthermore, an alpha(2C)-adrenoceptor gene over-expression was also induced, but only in male cafeteria-fed rats. If one assumes that the up-regulations in TH and alpha(2B)-adrenoceptor gene expression are indicative of increased sympathetic nervous activity, then, these altered gene expressions could be responsible for the maintenance of high blood pressure in male and testosterone-treated female cafeteria-fed rats. Conversely, in intact females, the absence of these over-expressions and the up-regulation of the alpha(2A)-adrenoceptor gene expression could reflect an adaptive response to the diet and, consequently, could be protective against cafeteria diet-induced hypertension. Moreover, neonatal testosterone imprinting in females could have induced an irreversible android susceptibility to the cafeteria diet, leading to the onset of hypertension.

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.