The role of leptin during the development of mouse preimplantation embryos

Metabolic memory determines oviductal gene expression of underfed ewes during early gestation

Our aim was to investigate the oviduct environment by studying oviduct gene expression after undernutrition in day-5 pregnant ewes with different initial (i) BCS, and its association with the number of embryos recovered. Thirty-six ewes were divided into 2 groups with different iBCS: iBCS ≥2.75 (n = 19; high, H) and iBCS ≤2.25 (n = 17; low, L), and were randomly assigned to two nutritional treatments for 20 days: 1.5 (control, C) or 0.5 (underfed, U) times the daily maintenance requirements. Thus, the final four groups were: high-iBCS control (HC, n = 9), high-iBCS underfed (HU, n = 10), low-iBCS control (LC, n = 9) and low-iBCS underfed (LU, n = 8). Samples of oviduct were collected and the expression of target genes was quantified using real-time PCR. While high-iBCS control ewes presented more ADIPOR1 mRNA than the high-iBCS underfed group (P < 0.05) and low-iBCS control ewes (P = 0.01), high-iBCS underfed group presented higher ADIPOR2 gene expression than low-iBCS underfed ewes (P < 0.01) evidencing a differential oviductal gene expression for these receptors. In high-iBCS ewes, control animals presented higher IGFBP2 gene expression than underfed ewes (P < 0.05), associated these results with a poor oviductal environment. High-iBCS underfed ewes presented higher IGFBP4 gene expression than high-iBCS control ewes (P < 0.05). Stepwise regression models, using various combinations of data on metabolic and reproductive hormones, and oviduct gene expression as independent variables, identified a set of variables that accounted for 75% of the variation in the number of embryos recovered. In conclusion, the oviductal gene expression depends on body reserves and nutritional treatment, and the effect is gene-specific.

Adipokines Expression and Effects in Oocyte Maturation, Fertilization and Early Embryo Development: Lessons from Mammals and Birds

Some evidence shows that body mass index in humans and extreme weights in animal models, including avian species, are associated with low in vitro fertilization, bad oocyte quality, and embryo development failures. Adipokines are hormones mainly produced and released by white adipose tissue. They play a key role in the regulation of energy metabolism. However, they are also involved in many other physiological processes including reproductive functions. Indeed, leptin and adiponectin, the most studied adipokines, but also novel adipokines including visfatin and chemerin, are expressed within the reproductive tract and modulate female fertility. Much of the literature has focused on the physiological and pathological roles of these adipokines in ovary, placenta, and uterine functions. The purpose of this review is to summarize the current knowledge regarding the involvement of leptin, adiponectin, visfatin, and chemerin in the oocyte maturation, fertilization, and embryo development in both mammals and birds.

17Beta-Estradiol Regulates NUCB2/ Nesfatin-1 Expression in Mouse Oviduct

NUCB2/nesfatin-1 known to regulate appetite and energy homeostasis is expressed not only in the hypothalamus, but also in various organs and tissues. Our previous reports also demonstrated that NUCB2/nesfatin-1 was expressed in the reproductive organs, including the ovaries, uterus, and testes of mice. However, it is yet known whether NUCB2/nesfatin-1 is expressed in the oviduct and how its expression is regulated. Therefore, we investigated the expression of NUCB2/nesfatin-1 in the oviduct and its expression is regulated by gonadotropin. Immunohistochemical staining results showed that nesfatin-1 protein was localized in epithelial cells of the oviduct. As a result of quantitative real-time PCR (qRT-PCR) and Western blot, NUCB2/nesfatin-1 was detected strongly in the oviducts. During the estrus cycle, NUCB2/nesfatin-1 expression in the oviducts was markedly higher in the proestrus stage than in other estrus stages. In order to elucidate whether the expression of NUCB2 mRNA is controlled by the gonadotropins, we injected PMSG and hCG and measured NUCB2 mRNA level in the oviduct after injection. Its level was increased in the oviduct after PMSG injection, but no significant change after hCG injection. In addition, NUCB2 mRNA levels were markedly reduced after ovariectomy, while recovered after 17β-estradiol (E2) injection, but not by progesterone (P4). This study demonstrated that NUCB2/nesfatin-1 is highly expressed in the oviduct of mouse and its expression is regulated by E2 secreted by the ovaries. These results suggest that NUCB2/nesfatin-1 expressed by the oviduct may affect the function of the oviduct regulated by the ovaries.

Effects of pre-pregnancy body mass index on pregnancy and perinatal outcomes in women with PCOS undergoing frozen embryo transfer

Background

Previous studies have shown that among women with polycystic ovary syndrome who have difficulties conceiving, frozen-embryo transfer resulted in increased live birth rates and decreased ovarian hyperstimulation syndrome risk than did fresh-embryo transfer. In the present retrospective analysis, we sought to determine the effect of body mass index (BMI) on pregnancy and perinatal outcomes in women with PCOS undergoing FET.

Methods

Women with PCOS (n = 1556) undergoing FET were divided into groups based on weight, with those with normal weight having a BMI of 18.5–24.9 kg/m²,those who were overweight having a BMI of 25–29.9 kg/m², and those who were obese having a BMI ≥30 kg/m². Both pregnancy and perinatal outcomes were compared among these groups.

Results

The normal-weight, overweight, or obese groups exhibited similar pregnancy outcomes, including clinical pregnancy rate, miscarriage rate, ongoing pregnancy rate and live birth rate. In singletons, birth characteristics regarding newborn gender, gestational age, birthweight and length at birth were comparable between the three groups. For adverse neonatal outcomes, the three groups showed no significant differences on the rates of low birthweight, very low birthweight, preterm birth, and very preterm birth after adjustment. In addition, the obstetric complications and the frequencies of live-birth defects were also comparable between the three groups except that overweight and obese women were more likely than women of normal weight to have delivered via cesarean section.

Conclusion

BMI did not affect the pregnancy or perinatal outcomes in women with PCOS undergoing FET.

The Responses of Mouse Preimplantation Embryos to Leptin In Vitro in a Transgenerational Model for Obesity

The aim of the present study was to test the hypothesis that leptin can directly mediate the negative effect of maternal obesity on preimplantation embryos. As previously shown, maternal obesity retards early embryonic development in vivo and increases the incidence of apoptosis in blastocysts. When two-cell embryos isolated from control and obese mice were transferred to identical (leptin free) conditions in vitro, no differences in any growth or quality parameters were recorded, including apoptosis incidence in blastocysts. Embryos isolated from control mice responded to transfer to environments with a high concentration of leptin (10 ng/mL) with a significant increase in arrest at the first or subsequent cell cycle. However, the majority of non-arrested embryos developed into blastocysts, showing morphology comparable to those cultured in the leptin-free group. On the other hand, the exposure of embryos isolated from obese mice to high leptin concentration in vitro did not retard their development. Furthermore, these embryos developed into blastocysts, showing a lower incidence of apoptosis. In vivo-developed blastocysts recovered from obese mice showed elevated expression levels of the proapoptotic gene BAX and the insulin-responsive glucose transporter gene SLC2A4. In conclusion, elevated leptin levels have both positive and negative effects on preimplantation embryo development in vitro, a response that likely depends on the body condition of the embryo donor. Moreover, these results suggest that leptin acts as a survival factor rather than an apoptotic inductor in embryonic cells. Since no elevations in the expression of the leptin receptor gene (LEPR) or fat metabolism-associated genes (PLIN2, SLC27A4) were recorded in blastocysts recovered from obese mice, the role of leptin in mediating the effects of obesity on embryos at the peripheral level is likely lower than expected.

Expression of leptin receptor in the oviduct of Chinese brown frog (Rana dybowskii)

The oviduct of Chinese brown frog ( Rana dybowskii) expands specifically during prehibernation instead of in the breeding period. In this study, we investigated the expression of leptin receptor (Ob-Rb) in Rana dybowskii oviduct during the breeding period and prehibernation. Histologically, the oviduct of Rana dybowskii consists of glandular cells, tubule lumen, and epithelial cells. The oviductal weight and pipe diameter also revealed significant differences, which were higher in prehibernation than that of the breeding period. Ob-Rb was observed in stromal cells of oviductal tissue in both the breeding period and prehibernation. The mean protein and mRNA levels of the Ob-Rb were significantly higher in prehibernation as compared with the breeding period. In addition, oviductal content of leptin was also higher in prehibernation than that of the breeding period. These results suggested that oviduct of Rana dybowskii might be a target organ of leptin, and leptin may play an autocrine/paracrine role mediated by Ob-Rb in regulating the oviductal hypertrophy during prehibernation.

Molecular biology of the stress response in the early embryo and its stem cells

Stress is normal during early embryogenesis and transient, elevated stress is commonplace. Stress in the milieu of the peri-implantation embryo is a summation of maternal hormones, and other elements of the maternal milieu, that signal preparedness for development and implantation. Examples discussed here are leptin, adrenaline, cortisol, and progesterone. These hormones signal maternal nutritional status and provide energy, but also signal stress that diverts maternal and embryonic energy from an optimal embryonic developmental trajectory. These hormones communicate endocrine maternal effects and local embryonic effects although signaling mechanisms are not well understood. Other in vivo stresses affect the embryo such as local infection and inflammation, hypoxia, environmental toxins such as benzopyrene, dioxin, or metals, heat shock, and hyperosmotic stress due to dehydration or diabetes. In vitro, stresses include shear during handling, improper culture media and oxygen levels, cryopreservation, and manipulations of the embryo to introduce sperm or mitochondria. We define stress as any stimulus that slows stem cell accumulation or diminishes the ability of cells to produce normal and sufficient parenchymal products upon differentiation. Thus stress deflects downwards the normal trajectories of development, growth and differentiation. Typically stress is inversely proportional to embryonic developmental and proliferative rates, but can be proportional to induction of differentiation of stem cells in the peri-implantation embryo. When modeling stress it is most interesting to produce a 'runting model' where stress exposures slow accumulation but do not create excessive apoptosis or morbidity. Windows of stress sensitivity may occur when major new embryonic developmental programs require large amounts of energy and are exacerbated if nutritional flow decreases and removes energy from the normal developmental programs and stress responses. These windows correspond to zygotic genome activation, the large mRNA program initiated at compaction, ion pumping required for cavitation, the differentiation of the first lineages, integration with the uterine environment at implantation, rapid proliferation of stem cells, and production of certain lineages which require the highest energy and are most sensitive to mitochondrial inhibition. Stress response mechanisms insure that stem cells for the early embryo and placenta survive at lower stress exposures, and that the organism survives through compensatory and prioritized stem cell differentiation, at higher stress exposures. These servomechanisms include a small set of stress enzymes from the 500 protein kinases in the kinome; the part of the genome coding for protein kinases that hierarchically regulate the activity of other proteins and enzymes. Important protein kinases that mediate the stress response of embryos and their stem cells are SAPK, p38MAPK, AMPK, PI3K, Akt, MEK1/2, MEKK4, PKA, IRE1 and PERK. These stress enzymes have cytosolic function in cell survival at low stress exposures and nuclear function in modifying transcription factor activity at higher stress exposures. Some of the transcription factors (TFs) that are most important in the stress response are JunC, JunB, MAPKAPs, ATF4, XBP1, Oct1, Oct4, HIFs, Nrf2/KEAP, NFKB, MT1, Nfat5, HSF1/2 and potency-maintaining factors Id2, Cdx2, Eomes, Sox2, Nanog, Rex1, and Oct4. Clearly the stress enzymes have a large number of cytosolic and nuclear substrates and the TFs regulate large numbers of genes. The interaction of stress enzymes and TFs in the early embryo and its stem cells are a continuing central focus of research. In vitro regulation of TFs by stress enzymes leads to reprogramming of the stem cell when stress diminishes stem cell accumulation. Since more differentiated product is produced by fewer cells, the process compensates for fewer cells. Coupled with stress-induced compensatory differentiation of stem cells is a tendency to prioritize differentiation by increasing the first essential lineage and decreasing later lineages. These mechanisms include stress enzymes that regulate TFs and provide stress-specific, shared homeostatic cellular and organismal responses of prioritized differentiation.

Immunoreactivities of PPARγ2, leptin and leptin receptor in oviduct of Chinese brown frog during breeding period and pre-hibernation

The Chinese brown frog (Rana dybowskii) is a special amphibian with one unique physiological phenomenon, which is that its oviduct expands prior to hibernation, instead of during the breeding period. In this study, we investigate the localization and expression level of PPARγ2, leptin and leptin receptor proteins in oviduct of Rana dybowskii during breeding period and pre-hibernation. There were significant variations in oviductal weight and size, with values much lower in the breeding period than in pre-hibernation. PPARγ2 was observed in stromal and epithelial cells in both periods. Leptin was immunolocalized in epithelial cells in both periods, whereas leptin receptor was detected only in stromal cells. Consistently, the protein levels of PPARγ2, leptin and leptin receptor were higher in pre-hibernation as compared to the breeding period. These results suggested that oviduct was the target organ of leptin, which may play an important paracrine role in regulating the oviductal hypertrophy during prehibernation.

An updated view of leptin on implantation and pregnancy: a review

The hormone leptin, which is thought to be primarily produced by adipose tissue, is a polypeptide that was initially characterized by its ability to regulate food intake and energy metabolism. Leptin appears to signal the status of body energy stores to the brain, resulting in the regulation of food intake and whole-body energy expenditure. Subsequently, it was recognized as a cytokine with a wide range of peripheral actions and is involved in the regulation of a number of physiological systems including reproduction. In the fed state, leptin circulates in the plasma in proportion to body adiposity in all species studied to date. However other factors such as sex, age, body mass index (BMI), sex steroids and pregnancy may also affect leptin levels in plasma. In pregnant mice and humans, the placenta is also a major site of leptin expression. Leptin circulates in biological fluids both as free protein and in a form that is bound to the soluble isoform of its receptor or other binding proteins such as one of the immunoglobulin superfamily members Siglec-6 (OB-BP1). Although the actions of leptin in the control of reproductive function are thought to be exerted mainly via the hypothalamic-pituitary-gonadal axis, there have also been reports of local direct effects of leptin at the peripheral level, however, these data appear contradictory. Therefore, there is a need to summarize the current status of research outcomes and analyze the possible reasons for differing results and thus provide researchers with new insight in designing experiments to investigate leptin effect on reproduction. Most importantly, our recent experimental data suggesting that reproductive performance is improved by decreasing concentrations of peripheral leptin was unexpected and cannot be explained by hypotheses drawn from the experiments of excessive exogenous leptin administration to normal animals or ob/ob mice.

Follicular fluid leptin concentrations and expression of leptin and leptin receptor in the equine ovary and in vitro-matured oocyte with reference to pubertal development and breeds

There is no published information about follicular-fluid leptin concentrations or the presence of leptin and leptin receptor in the equine ovary or oocyte. Three groups of mares - adult draft mares, draft fillies and adult Standardbred mares - were included in the study. Leptin and leptin receptor were detected in all immature oocytes by immunofluorescence with higher intensity in oocytes from draft mares compared with draft fillies and Standardbred mares. After in vitro maturation a higher proportion of oocytes reached metaphase II in draft mares than in draft fillies and Standardbred mares, and in all groups both leptin and leptin receptor became localised in the oocyte cortex but with higher immunopositivity in draft mares compared with draft fillies and Standardbred mares. These intensities were confirmed by the expression profiles of leptin and leptin receptor mRNA. Moreover, leptin was detected in ovarian blood vessels in all three types of animal and within the corpora lutea in adult mares. Serum and follicular-fluid concentrations of leptin were similar in draft and Standardbred mares but higher in draft mares than in draft fillies. This study supports the hypothesis that expression of leptin and leptin receptor mRNA and the rate of maturation can be related either to adiposity or to puberty.

Stress responses at the endometrial-placental interface regulate labyrinthine placental differentiation from trophoblast stem cells

Development can happen in one of two ways. Cells performing a necessary function can differentiate from stem cells before the need for it arises and stress does not develop. Or need arises before function, stress develops and stress signals are part of the normal stimuli that regulate developmental mechanisms. These mechanisms adjust stem cell differentiation to produce function in a timely and proportional manner. In this review, we will interpret data from studies of null lethal mutants for placental stress genes that suggest the latter possibility. Acknowledged stress pathways participate in stress-induced and -regulated differentiation in two ways. These pathways manage the homeostatic response to maintain stem cells during the stress. Stress pathways also direct stem cell differentiation to increase the first essential lineage and suppress later lineages when stem cell accumulation is diminished. This stress-induced differentiation maintains the conceptus during stress. Pathogenic outcomes arise because population sizes of normal stem cells are first depleted by decreased accumulation. The fraction of stem cells is further decreased by differentiation that is induced to compensate for smaller stem cell populations. Analysis of placental lethal null mutant genes known to mediate stress responses suggests that the labyrinthine placenta develops during, and is regulated by, hypoxic stress.

Characterization of foamy epithelial surface cells in the canine endometrium

In mature bitches, endometrial epithelial surface cells modify function and corresponding morphology during the oestrous cycle. During late metoestrous, endometrial epithelial surface cells frequently accumulate fat and thereby adopt a foamy morphology. This cyclic appearance of foamy endometrial epithelial cells (fEECs) seems to be physiological in the dog, whereas in other species, it indicates pathological changes. Function of these fEECs has not been identified until now. Therefore, the aim of the study was to characterize the fEECs by means of transmission electron microscopy and immunohistochemistry. Different manifestations of fEECs were observed and analysed with regard to proliferative activity and presence of different epithelial adhesion molecules including PLEKHA7, β-catenin and E-cadherin. PLEKHA7 was restricted to the apical regions of the fEECs, whereas E-cadherin and β-catenin were demonstrated basolateral. The immunohistochemical detection of steroid hormone receptors demonstrated the responsiveness of the fEECs to steroid hormones. Intense progesterone receptor expression was observed in the fEECs indicating a high responsiveness to this hormone. Considering a potential function of the fEECs, we hypothesized that leptin, a hormone produced by other lipid-accumulating cells and described to be involved in reproduction, in particular during implantation, might also originate from the fEECs which was confirmed by immunohistochemical methods. Moreover, leptin receptor was found in fEECs indicating the fEECs as both, source and target for leptin. Therefore, we conclude that fEECs in the canine uterus have a potential role in early pregnancy events and that the different observed manifestations might simply reflect the variations of signs of pseudopregnancy among bitches.

Leptin and interleukin-6 alter the function of mesolimbic dopamine neurons in a rodent model of prenatal inflammation

Maternal inflammation during critical stages of gestation is thought to underlie the link between prenatal infection and several neurodevelopmental psychiatric disorders in the offspring, including schizophrenia. Increased activity of mesolimbic dopamine (DA) neurons, a hallmark of psychosis, is found in offspring of rodents exposed to a prenatal inflammatory challenge but it is unclear how this effect is elicited. Using an experimental model of localized aseptic inflammation with turpentine oil (TURP) we sought to establish whether circulating interleukin-6 (IL-6) and leptin play a role in the effects of prenatal inflammation on DA neurons. Both mediators are involved in the systemic inflammatory response to immunogens, with IL-6 mediating the early phase, followed by leptin in the late phase of the response. Maternal treatment with TURP at gestational day (GD) 15 enhanced the locomotor response to the DA indirect agonist, amphetamine (AMPH), increased the expression of tyrosine hydroxylase (TH), an enzyme involved in DA synthesis, DA levels and the expression of the post-synaptic protein spinophilin in the nucleus accumbens (NAcc) in the adult offspring. All of these alterations were totally abolished by co-treating the pregnant dams with a neutralizing IL-6 antiserum. Neutralization of maternal leptin prevented the enhanced behavioral sensitization and elevation of DA and spinophilin in the NAcc but spared other changes regulated by IL-6, such as increased NAcc TH levels and acute locomotor response to AMPH. Our results provide novel evidence to suggest that prenatal surges in both maternal circulating IL-6 and leptin contribute to the appearance of sensitized DA function in the adult offspring.

Pluripotency factor-mediated expression of the leptin receptor (OB-R) links obesity to oncogenesis through tumor-initiating stem cells. Proc Natl Acad Sci U S A. 2012;109:829-834. [PMID: 22207628 DOI: 10.1073/pnas.1114438109]

Misregulation of a pluripotency-associated transcription factor network in adult tissues is associated with the expansion of rare, highly malignant tumor-initiating stem cells (TISCs) through poorly understood mechanisms. We demonstrate that robust and selective expression of the receptor for the adipocyte-derived peptide hormone leptin (OB-R) is a characteristic feature of TISCs and of a broad array of embryonic and induced pluripotent stem cells and is mediated directly by the core pluripotency-associated transcription factors OCT4 and SOX2. TISCs exhibit sensitized responses to leptin, including the phosphorylation and activation of the pluripotency-associated oncogene STAT3 and induction of Oct4 and Sox2, thereby establishing a self-reinforcing signaling module. Exposure of cultured mouse embryonic stem cells to leptin sustains pluripotency in the absence of leukemia inhibitory factor. By implanting TISCs into leptin-deficient ob/ob mice or into comparably overweight Lepr(db/db) mice that produce leptin, we provide evidence of a central role for the leptin-TISC-signaling axis in promoting obesity-induced tumor growth. Differential responses to extrinsic, adipocyte-derived cues may promote the expansion of tumor cell subpopulations and contribute to oncogenesis.

Effect of bariatric surgery on obesity-related infertility

BACKGROUND

There is a strong association between obesity and infertility, and weight loss can increase fecundity in obese women. In an attempt to determine the effect of bariatric surgery on obesity-related infertility, we reviewed the fertility outcomes after intragastric balloon placement, adjustable gastric banding, sleeve gastrectomy, and gastric bypass in childbearing women with a diagnosis of infertility at a university hospital in Italy.

METHODS

This was a retrospective study of 110 obese infertile women. We evaluated the effectiveness of bariatric surgery in improving fertility, assessing the influence of age, surgical technique, co-morbidities (hypertension and diabetes), weight loss, and body mass index before and after surgery.

RESULTS

Of these 110 women who had tried unsuccessfully to become pregnant before weight loss, 69 became pregnant afterward. The pregnancies proceeded without complications and ended with a live birth. Only the weight loss (odds ratio 20.2, P = .001) and the achieved body mass index (P = .001) after surgery were the predictors of pregnancy.

CONCLUSION

Bariatric surgery might be effective in young infertile obese women who wish to become pregnant. Weight loss appears to be independent from the surgical technique in determining the increase in the pregnancy rate as well as the body mass index achieved at pregnancy.

The potential role of intragastric balloon in the treatment of obese-related infertility: personal experience

The prevalence of people who are overweight or obese has increased dramatically in high-income countries over the past 20 years. There is a strong association between obesity and infertility, and weight loss can result in increased fecundity in obese women. The aim of this study is to demonstrate the potential role of intragastric balloon in the treatment of obese-related infertility. This is a retrospective study. A chart review of 27 obese women seen between September 2003 and July 2008 was performed. They all presented with the diagnosis of infertility and had undergone endoscopic intragastric balloon positioning. Among these women who tried unsuccessfully to become pregnant before weight loss, 15 became pregnant afterward. The pregnancies proceeded without complications and ended with live births. An improvement in the fertility status after weight loss has been described, although data on fertility after weight loss following bariatric surgery are still limited. The results obtained in our experience are not different from data reported in literature for bariatric surgery. Therefore, balloon treatment might be effective in young infertile obese women who wish to become pregnant.

Segregation during cleavage in the mammalian embryo? A critical comparison of whole-mount/CLSM and section immunohistochemistry casts doubts on segregation of axis-relevant leptin domains in the rabbit

Segregation of certain cytoplasmic molecules during cleavage and blastocyst formation that was previously reported to occur in the human and the mouse (Antczak and Van Blerkom Mol Hum Reprod 3:1067-1086, 1997; Antczak and Van Blerkom Hum Reprod 14:429-447, 1999) has been reinvestigated in the rabbit model. Additional methodology was used and two approaches were compared: (1) whole-mount immunohistochemistry followed by confocal laser scanning microscopy (WM-IHC/CLSM) versus (2) IHC performed on histological sections of resin-embedded material (S-IHC). This study concentrates on leptin and cytoskeletal proteins (actin and cytokeratins). With S-IHC, leptin was localized predominantly on the surface of blastomeres which is facing the perivitelline space, and in the extracellular embryonic coats, without any polar asymmetry being detectable along (presumptive) embryonic axes. A polar distribution of leptin with a pattern that could be interpreted as predictive of the prospective embryonic-abembryonic axis was seen only with WM-IHC/CLSM, not with S-IHC, although the latter gave excellent resolution. With both techniques, no differences between blastomeres were detected with respect to actin and cytokeratin patterns, an increased expression of cytokeratin in trophoblast cells occurring no earlier than at blastocyst formation. Artifacts that can occur with the two methodological approaches are critically discussed, as is the possible significance of the findings for theories on the differentiation of trophoblast versus embryoblast and on axis formation in early mammalian development. It is concluded that these data call for cautioning when studying distribution patterns of diffusible molecules with WM-IHC/CLSM technology, whereas patterns obtained with S-IHC are more reliable. Specifically these data cast doubts on previous claims that leptin IHC would allow to monitor cytoplasmic domain segregation occurring during cleavage as an element of early embryonic pattern/axis formation.

Contraceptive vaccines targeting factors involved in establishment of pregnancy

Current methods of contraception lack specificity and are accompanied with serious side effects. A more specific method of contraception is needed. Contraceptive vaccines can provide most, if not all, the desired characteristics of an ideal contraceptive. This article reviews several factors involved in the establishment of pregnancy, focusing on those that are essential for successful implantation. Factors that are both essential and pregnancy-specific can provide potential targets for contraception. Using database search, 76 factors (cytokines/chemokines/growth factors/others) were identified that are involved in various steps of the establishment of pregnancy. Among these factors, three, namely chorionic gonadotropin (CG), leukemia inhibitory factor (LIF), and pre-implantation factor (PIF), are found to be unique and exciting molecules. Human CG is a well-known pregnancy-specific protein that has undergone phase I and phase II clinical trials, in women, as a contraceptive vaccine with encouraging results. LIF and PIF are pregnancy-specific and essential for successful implantation. These molecules are intriguing and may provide viable targets for immunocontraception. A multiepitope vaccine combining factors/antigens involved in various steps of the fertilization cascade and pregnancy establishment may provide a highly immunogenic and efficacious modality for contraception in humans.

Dynamic changes in leptin distribution in the progression from ovum to blastocyst of the pre-implantation mouse embryo

The hormone leptin, which is primarily produced by adipose tissue, is a critical permissive factor for multiple reproductive events in the mouse, including implantation. In the CD1 strain, maternally derived leptin from the oocyte becomes differentially distributed among the blastomeres of pre-implantation embryos to create a polarized pattern, a feature consistent with a model of development in which blastomeres are biased toward a particular fate as early as the two-cell stage. In this study, we have confirmed that embryonic leptin is of maternal origin and re-examined leptin distribution in two distinct strains in which embryos were derived after either normal ovulation or superovulation. A polarized pattern of leptin distribution was found in the majority of both CD1 and CF1 embryos (79.1 and 76.9% respectively) collected following superovulation but was reduced, particularly in CF1 embryos (29.8%; P<0.0001), after natural ovulation. The difference in leptin asymmetries in the CF1 strain arose between ovulation and the first cleavage division and was not affected by removal of the zona pellucida. The presence or absence of leptin polarization was not linked to differences in the ability of embryos to normally develop to blastocyst. In the early blastocyst, leptin was confined subcortically to trophectoderm, but on blastocoel expansion, it was lost from the cells. Throughout development, leptin co-localized with LRP2, a multi-ligand transport protein, and its patterning resembled that noted for the maternal-effect proteins OOEP, NLRP5, and PADI6, suggesting that it is a component of the subcortical maternal complex with as yet unknown significance in pre-implantation development.

Women, weight, and fertility: the effect of body mass index on the outcome of superovulation/intrauterine insemination cycles

OBJECTIVE

To determine the fecundity of overweight and obese infertile women treated with gonadotropins and undergoing intrauterine insemination (IUI).

DESIGN

Retrospective study.

SETTING

Academic infertility clinic.

PATIENT(S)

Four hundred seventy-seven women undergoing 1,189 ovulation induction (OI)/IUI cycles stratified by body mass index (BMI).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

BMI groups were compared regarding the following: gonadotropin dose, duration of treatment, peak E(2), number of follicles (total, large, and medium size), E(2)/follicle, endometrial thickness, spontaneous abortion, and clinical and multiple pregnancy rates.

RESULT(S)

There was a significant trend toward higher medication requirements and lower E(2) levels with increasing BMI. BMI was inversely associated with [1] the E(2) level per produced preovulatory follicle and [2] the number of medium-size follicles. Furthermore, BMI was inversely associated with the number of medium, large, and total follicles divided by total FSH dose, suggesting that women with a higher BMI develop a lower number of medium and/or large follicles at a given total FSH dose. BMI was positively associated with endometrial thickness, and endometrial thickness was positively associated with pregnancy. Mean number of cycles required to conceive, clinical pregnancy, and spontaneous abortion rates did not differ significantly among the different BMI categories.

CONCLUSION(S)

Obese women require higher doses of medication and produce fewer follicles for a given dose, but once medication and response are adjusted to overcome the weight effect, the success of the treatment cycle is comparable to that of normal weight women.

Role of leptin in delayed embryonic development in the Indian short-nosed fruit bat, Cynopterus sphinx

An adiposity-associated rise in leptin occurs at the time of delayed embryonic development in Cynopterus sphinx. The aim of present study was to examine the mechanism by which leptin may inhibit progesterone, and therefore could be responsible for delayed development. The study showed a significant increase in circulating leptin level during the period of increased fat accumulation, which coincided with significant decrease in serum progesterone level and delayed embryonic development in C. sphinx. The study showed increased Ob-R expression in the corpus luteum and in the utero-embryonic unit during the period of delayed embryonic development. The in vitro study showed suppressive effect of leptin on progesterone synthesis. The effect of high dose of leptin on ovarian steroidogenesis was found to be mediated through decreased expression of StAR and LH-R proteins in the ovary. The treatment with leptin caused increased expression of STAT 3 and iNOS proteins in the ovary, which correlated with decreased expression of StAR protein in the ovary. The inhibitory effects of leptin on progesterone synthesis in the ovary are thus mediated through STAT 3 and iNOS-NO signaling pathways. This study further demonstrated low expression of PCNA coinciding with the increased concentration of the leptin receptor in the utero-embryonic unit and high circulating leptin level during November. In conclusion, adiposity associated increased leptin level during November-December might play role in suppressing progesterone synthesis in the corpus luteum as well as suppressing the rate of cell-proliferation in the utero-embryonic unit thereby causing delayed embryonic development in C. sphinx.

The adverse effects of obesity on conception and implantation

Whilst many multiparous women are obese (body mass index >30 kg/m(2)), obesity has been associated with impaired fecundity; however, the mechanism which links obesity to reduced fertility remains to be fully elucidated. Obese women, particularly those with central obesity, are less likely to conceive per cycle. Obese women suffer perturbations to the hypothalamic-pituitary-ovarian axis, menstrual cycle disturbance and are up to three times more likely to suffer oligo-/anovulation. A fine hormonal balance regulates follicular development and oocyte maturation, and it has been observed that obesity can alter the hormonal milieu. Leptin, a hormone produced by adipocytes, is elevated in obese women, and raised leptin has been associated with impaired fecundity. Obesity impairs ovulation but has also been observed to detrimentally affect endometrial development and implantation. The expression of polycystic ovary syndrome (PCOS) is regulated, in part, by weight, and so obese women with PCOS often have a more severe phenotype and experience more subfertility. Obesity also impairs the response of women to assisted conception treatments. Weight loss through lifestyle modification or bariatric surgery has been demonstrated to restore menstrual cyclicity and ovulation and improve the likelihood of conception. In this article, we will discuss the effect of obesity upon key reproductive mechanisms and its relation to fertility treatments.

Leptin gene and protein expression in the ovary during the oestrous cycle and early pregnancy in pigs

Leptin, the product of the obese gene, is the hormone originally identified in adipocytes. It is involved in the control of satiety and energy metabolism. More recent observations suggest that leptin plays an important role in reproduction. Leptin mRNA and protein have been found in the human and the murine ovary. However, the expression of leptin in the porcine ovary has not been examined. Therefore, the aim of the present work was to compare the expression levels of porcine leptin mRNA by semiquantitative RT-PCR and in situ hybridization, as well as leptin protein by Western blotting in the corpus luteum (CL) and ovarian stroma (OS) during mid- and late-luteal phase of the oestrous cycle as well as during days 14-16 and 30-32 of pregnancy. Leptin gene and protein expression in CL was increased on days 14-16 of the cycle compared with pregnant animals. Leptin gene expression in OS was higher during the late-luteal phase of the cycle than on days 30-32 after conception. However, comparison of leptin protein expression in OS between days 14-16 of the cycle and days 30-32 of pregnancy indicates a higher protein expression during pregnancy. Moreover, leptin gene expression was higher in porcine CL and OS on days 14-16 of pregnancy in comparison to days 30-32. Contrary to leptin mRNA expression, a higher leptin protein expression was observed on days 30-32 compared with days 14-16 after conception. In summary, the present study provides the first evidence that leptin mRNA and protein occur in porcine ovary and vary during the oestrous cycle and pregnancy. Moreover, the obtained results indicate that also locally synthesized leptin may participate in the control of pig reproduction by exercising its action at the ovarian level.

Effects of leptin on in vitro maturation, fertilization and embryonic cleavage after ICSI and early developmental expression of leptin (Ob) and leptin receptor (ObR) proteins in the horse

BACKGROUND

The identification of the adipocyte-derived obesity gene product, leptin (Ob), and subsequently its association with reproduction in rodents and humans led to speculations that leptin may be involved in the regulation of oocyte and preimplantation embryo development. In mice and pigs, in vitro leptin addition significantly increased meiotic resumption and promoted preimplantation embryo development in a dose-dependent manner. This study was conducted to determine whether leptin supplementation during in vitro maturation (IVM) to horse oocytes could have effects on their developmental capacity after fertilization by IntraCytoplasmic Sperm Injection (ICSI).

METHODS

Compact and expanded-cumulus horse oocytes were matured in medium containing different concentrations (1, 10, 100, 1000 ng/ml) of recombinant human leptin and the effects on maturation, fertilization and embryo cleavage were evaluated. Furthermore, early developmental expression of Ob and leptin receptor (Ob-R) was investigated by immunocytochemical staining.

RESULTS

In expanded-cumulus oocytes, the addition of leptin in IVM medium improved maturation (74% vs 44%, for 100 ng/ml leptin-treated and control groups, respectively; P < 0.05) and fertilization after ICSI (56% vs 23% for 10 ng/ml leptin-treated and control groups, respectively; P < 0.05). However, the developmental rate and quality of 8-cell stage embryos derived from leptin-treated oocytes (100 ng/ml) was significantly reduced, in contrast to previous data in other species where leptin increased embryo cleavage. Ob and Ob-R proteins were detected up to the 8-cell stage with cortical and cytoplasmic granule-like distribution pattern in each blastomere.

CONCLUSION

Leptin plays a cumulus cell-mediated role in the regulation of oocyte maturation in the mare. Species-specific differences may exist in oocyte sensitivity to leptin.

The impact of body mass index on assisted reproduction

PURPOSE OF REVIEW

Obesity is a worldwide problem. The effect of obesity on the outcome of assisted reproductive techniques is quite controversial.

RECENT FINDINGS

Although there is not an absolute consensus based on evidence, obesity may lengthen the duration of ovulation induction, increase the gonadotrophin dose, decrease the peak estradiol levels, number of mature follicles and number of oocytes retrieved, and increase the cycle cancellation rate. Moreover, obesity may have a negative impact on oocyte and embryo quality. Thus, fertilization, embryo transfer, implantation and pregnancy rates have been usually found to be low in many studies. In addition, oocyte retrieval and embryo transfer procedures can be difficult due to obesity itself. Finally, miscarriage rate is found to be high. None of the studies related with obesity and assisted reproduction has been designed as a randomized controlled trial, yet. Definition of obesity, cause of infertility, protocols used for ovulation induction, starting dose for gonadotrophins, oocyte and embryo-grading systems are not standardized among the studies. Some confounding factors, such as polycystic ovary syndrome status and age, are not taken into consideration.

SUMMARY

Obesity has a negative impact on the outcomes of assisted reproductive techniques.

Adiponectin enhances in vitro development of swine embryos

Recent studies have shown that factors from adipose tissue influence and regulate the reproductive system. Hormones such as leptin and resistin are now known to regulate several reproductive processes. Adiponectin is the most abundant protein secreted by adipose tissue, and its circulating concentration is inversely related to adiposity and body mass index. Little is known about the involvement of adiponectin in reproduction. In the present study, the effect of recombinant adiponectin on the meiotic maturation and early embryo development in vitro was investigated, using porcine oocytes. Adiponectin receptors, AdipoR1 and AdipoR2, were found to be expressed in porcine oocytes and cumulus cells of both small and large follicles. Both AdipoR1 and AdipoR2 were immunolocalized to cumulus-oocyte complexes (COCs), oocytes, and early developing embryos. When included in oocyte maturation medium for 46 h, adiponectin significantly decreased the frequency of meiotic immature oocytes derived from large follicles (3-6 mm) but not from small follicles (<3mm). From studies of oocytes matured in the presence of adiponectin and mitogen-activated protein kinase (MAPK) pathway inhibitors MEK1 (PD98059), MEK1/2 (U0126), and p38MAPK (SB203580) it was concluded that adiponectin enhances oocyte maturation thought the p38MAPK pathway. Finally, a superior rate of embryo development to the blastocyst stage was achieved by embryos cultured in the presence of adiponectin. These results indicate that adiponectin has a positive effect on the meiotic maturation and in vitro embryo development of porcine oocytes and suggests a physiological role for this adipokine in early development in mammals.

Expression of leptin and adiponectin in the rat oviduct

In mammals, the oviduct is an important source of factors that play key roles in reproductive and developmental events. The major components of oviduct fluid are oviduct-specific glycoproteins, but other proteins are synthesized and secreted by the oviduct epithelium. Leptin and adiponectin are two hormones originally identified in adipocytes that play a critical role not only in the control of energy balance and metabolism but also in diverse functions such as reproduction. This study investigates the presence and distribution of leptin and adiponectin in the rat oviduct through a combination of immunohistochemistry and reverse transcription-polymerase chain reaction techniques. Using both techniques, it has been detected that the oviduct of cycling rats expresses leptin and adiponectin. Immunoreactivity for both adipokines appears in the apical region of the secretory epithelial cells, only in the isthmus and ampulla. The immunostain is stronger in the isthmus and changes throughout the estrous cycle in the ampulla, increasing from proestrous to estrous. The results presented here are a further contribution to the identification of leptin and adiponectin produced and secreted by the oviduct epithelium, which must be taken into account for a better understanding of the reproductive events that take place in this organ.

Leptin has concentration and stage-dependent effects on embryonic development in vitro

There is accumulating evidence that leptin may be directly involved in pre-implantation embryonic development, however, it is unclear whether there is a concentration and stage-dependent regulatory pattern. In this study, the addition of 10 ng/ml human recombinant leptin to the culture medium significantly increased the percentage of two-cell mouse embryos that developed into blastocysts and hatched blastocysts, whereas in the presence of 100 ng/ml leptin, the development rate was significantly inhibited. The total cell numbers in the hatched blastocysts were significantly higher in the presence of 10 ng/ml leptin compared with controls and higher concentrations. The differential sensitivity to leptin was found to vary among embryos at different stages of development. Supplementation of leptin (10 ng/ml) to culture medium at two- to eight-cell stages resulted in a consistent stimulatory effect on embryo development. Most interestingly, the inhibitory effect of high leptin concentration (100 ng/ml) on embryo development was diminished when it was added to the culture medium at the eight-cell stage of development. The concentration-dependent regulation pattern was confirmed using sheep embryos, under similar conditions although sheep embryos appeared to be more sensitive in responding to leptin. Having established the effect of exogenous leptin on embryo development, the expression pattern of leptin and its receptors were also investigated. Leptin mRNA was not detected in mouse two-, four-, eight-cell and blastocyst stage embryos, whereas three isoforms of leptin receptor (Ob-Ra, Ob-Rb and Ob-Re) were identified in these cells, indicating that leptin is likely to modulate embryo development via a paracrine signalling system.

Leptin in pregnancy: an update

Leptin influences satiety, adiposity, and metabolism and is associated with mechanisms regulating puberty onset, fertility, and pregnancy in various species. Maternal hyperleptinemia is a hallmark of mammalian pregnancy, although both the roles of leptin and the mechanisms regulating its synthesis appear to be taxa specific. In pregnant humans and nonhuman primates, leptin is produced by both maternal and fetal adipose tissues, as well as by the placental trophoblast. Specific receptors in the uterine endometrium, trophoblast, and fetus facilitate direct effects of the polypeptide on implantation, placental endocrine function, and conceptus development. A soluble isoform of the receptor may be responsible for inducing maternal leptin resistance during pregnancy and/or may facilitate the transplacental passage of leptin for the purpose of directly regulating fetal development. The steroid hormones are linked to the regulation of leptin and the leptin receptor and probably interact with other pregnancy-specific, serum-borne factors to regulate leptin dynamics during pregnancy. In addition to its effects on normal conceptus development, leptin is linked to mechanisms affecting a diverse array of pregnancy-specific pathologies that include preeclampsia, gestational diabetes, and intrauterine growth restriction. Association with these anomalies and with mechanisms pointing to a fetal origin for a range of conditions affecting the individual's health in adult life, such as obesity, diabetes mellitus, and cardiovascular disease, reiterate the need for continued research dedicated to elucidating leptin's roles and regulation throughout gestation.

Leptin-directed embryo implantation: leptin regulates adhesion and outgrowth of mouse blastocysts and receptivity of endometrial epithelial cells

Leptin is a 16-kDa multifunctional protein. Recent reports indicate that leptin is an important molecule during implantation and placentation, implicated in embryonic-maternal cross-talk and cytotrophoblast invasiveness, however, the role of leptin playing in the process of normal blastocyst implantation has not been well characterized. In the present study, the possible mechanisms of leptin playing in mouse blastocyst implantation were investigated. Leptin and receptor isoforms mRNAs were detected in whole mouse uteri during estrous cycle and peri-implantation periods. Immunofluorescent analysis further confirmed Ob-R protein was present in mouse uterus. The differential amounts of leptin and Ob-R isoforms suggested a role for leptin in such endometrial issues as blastocyst implantation. In vitro culture model for studying embryo implantation, leptin promoted mouse blastocyst adhesion and blastocyst outgrowth on fibronectin. Blastocysts treated with 300 ng/ml leptin had the greatest adhesion rate of 76.58+/-6.41% (P=0.046), and blastocysts treated with 30 ng/ml leptin had the greatest outgrowth rate of 78.64+/-8.48% (P=0.005). In isolated endometrial epithelial cells, leptin upregulated amounts of alpha v and beta 3 integrin, and promoted cell adhesion to such extracellular matrix proteins as fibronectin, laminin and type IV collagen, showing a dose- and time-dependent cell-adhesive capacity. Collectively, the information from the present study may partly account for leptin-induced mouse blatocyst implantation.

Up-regulation of the endocannabinoid system in the uterus of leptin knockout (ob/ob) mice and implications for fertility

The levels of the endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) are under the negative control of leptin in the rodent hypothalamus. As leptin and endocannabinoids play opposite roles in the control of reproduction, we have investigated whether the impaired fertility typical of leptin-defective ob/ob mice is due, in part, to enhanced uterine endocannabinoid levels. We found that levels of both anandamide and 2-AG in the uterus of ob/ob mice are significantly elevated with respect to wild-type littermates, due to reduced hydrolase activity in the case of anandamide, and to reduced monoacylglycerol lipase and enhanced diacylglycerol lipase activity in the case of 2-AG. Furthermore, the process mediating endocannabinoid cellular uptake was also impaired in ob/ob mice, whereas the levels of cannabinoid and anandamide receptors were not modified. Although ineffective in wild-type mice, treatment of ob/ob mice with leptin re-established endocannabinoid levels and enzyme activities back to the values observed in wild-type littermates. Finally, treatment of ob/ob females with the CB1 receptor antagonist SR141716A did not improve their fertility, and inhibition of endocannabinoid inactivation with the endocannabinoid uptake inhibitor OMDM-1 in wild-type females did not result in impaired fertility.

Embryotropic effect of insulin-like growth factor (IGF)-I and its receptor on development of porcine preimplantation embryos produced by in vitro fertilization and somatic cell nuclear transfer

Insulin-like growth factor (IGF)-I is a receptor-mediated autocrine/paracrine growth/survival factor for mammalian embryo development. The present study investigated the temporal expression and regulation of porcine IGF-I receptor (IGF-IR) mRNA and the role of IGF-I on development of porcine in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos. As assessed by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR), the level of IGF-IR mRNA expression was high in unfertilized oocytes, 2-cell and 4-cell embryos and gradually decreased in 8-cell embryos, morulae, and blastocysts in both IVF and SCNT series. The IVF or SCNT embryos were cultured with 0, 1, 10, 50, or 100 ng/ml IGF-I for 168 hr. Supplementing with 50 ng/ml IGF-I increased blastocyst formation and the number of cells in inner cell masses (ICMs) in both IVF and SCNT embryos. In a second experiment, more blastocysts were obtained when IVF or SCNT embryos were cultured for the first 48 hr or for the entire 168 hr with 50 ng/ml IGF-I compared to culturing without IGF-I for 48 hr or with IGF-I for the last 120 hr or without IGF-I for the entire 168 hr. Treating IVF or SCNT embryos with 50 ng/ml IGF-I significantly up-regulated IGF-IR mRNA compared to untreated control embryos. In conclusion, the present study demonstrated that IGF-IR mRNA is expressed in porcine IVF and SCNT embryos, and that IGF-I improved the developmental competence of IVF and SCNT embryos through its specific receptors.

Expression of Smac/DIABLO in mouse preimplantation embryos and its correlation to apoptosis and fragmentation

Regulation of early embryonal development during fertilization and implantation is crucial for mammalian reproduction. Several studies have described cell death during preimplantation embryogenesis in a range of mammalian species, both in vivo and in vitro. Therefore, apoptosis may be involved in early embryonic arrest and the characteristic cytoplasmic fragments are the equivalents of apoptotic bodies, the end-product of apoptosis. Although apoptosis is expected to associate with fragmentation in early preimplantation embryos, the mechanism through which this fragmentation occurs has not been elucidated. Recently, second mitochondria-derived activator of caspase/Direct IAP Binding Protein with Low pI (Smac/DIABLO) was identified as a mitochondrial protein that is released into the cytosol during apoptosis. Once released, the Smac/DIABLO blocks the anti-apoptotic activity of inhibitor of apoptosis proteins (IAPs). We hypothesized that the Smac/DIABLO may be involved in the fragmentation of mouse preimplantation embryos. Therefore, we investigated the expression of Smac/DIABLO mRNA and protein and its localization in mouse oocytes and preimplantation embryos. Smac/DIABLO mRNA was detected by RT-PCR in the oocytes and the preimplantation embryos. Immunohistochemistry studies showed that the Smac/DIABLO protein localized in mitochondria and was released into the cytosol in both fragmented embryos and embryos in which apoptosis was induced by staurosporine. These observations indicate that the Smac/DIABLO is involved in the fragmentation and apoptosis of preimplantation embryos.