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RESEARCH |
1 Department of Biology & Genetics of Larissa, University of Thessalia Medical School, 22 Papakyriazi, Larisa 41222, Larissa, Greece and 2 2nd Department of Obstetrics and Gynecology of Athens, University of Athens, Aretaieio hospital, 76 V. Sofias Ave, 11528, Athens, Greece
Correspondence should be addressed to Anifandis Georgios; Email: ganif{at}med.uth.gr
| Abstract |
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| Introduction |
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The quality of transferred embryos plays a crucial role in implantation and pregnancy success, although the factors affecting embryo quality are not well known. Among those, estradiol has an important role, although its value as a single prognostic IVF marker is relatively weak. Additional parameters are therefore needed to improve the prognosis of IVF outcome. The role of leptin in human reproduction and IVF with embryo transfer (IVF-ET) (Moschos et al. 2002), which is mediated through membrane receptors in the ovaries and follicles (Karlsson et al. 1997, Loffler et al. 2001), may justify its potential involvement in the control of embryo quality. In agreement with this possibility previous reports indicated that the pregnancy rates of women with high circulating serum and follicular fluid (ff) leptin levels were low (Mantzoros et al. 2000) and together with high vascular epidermal growth factor (VEGF) and NO were associated with poor embryo quality (Barroso et al. 1999).
A primary aim of the present study was to assess the role of leptin on estradiol-dependent embryo quality and elucidate its prognostic value as an additional marker of IVF outcome. Our findings suggest that estradiol and leptin interact coordinately to conditionally modulate IVF outcome at the level of embryo quality through concentration-dependent mechanisms.
| Materials and Methods |
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The women who signed a written informed consent form were enrolled in the study. Two hundred of these women with basal follicle-stimulating hormone (FSH) levels of <8.5 IU/l underwent their first IVF cycle between January 2003 and January 2004 using a long stimulation protocol with 1 mg daily s.c. gonadotrophin-releasing hormone-a leuprolide acetate (LA) administration, starting from the midluteal phase of the previous cycle. The dose was not modified for at least 10 days or until estradiol levels dropped to <50 pg/ml and no follicular activity was noted by transvaginal ultrasound examination. At that time, 36 ampoules of recombinant FSH (rFSH; Puregon, Organon Organon Pharmaceuticals, USA Inc. Roseland, NJ, USA; and Gonal F, Serono Inc. Rockland, MA, USA) were administered daily according to the ovarian response of every woman and the LA dose decreased to 0.5 mg/day s.c. rFSH administration and serum estradiol determination continued until at least two follicles a reached diameter of 1822 mm or estradiol levels increased above 500 pg/ml. At that time hCG (10 000 IU; Pregnayl®, Organon) was administered and LA injections were discontinued. The peak estradiol level was defined as the level of estradiol on the day of hCG administration. Serum leptin concentrations were also measured that day. Oocyte retrieval was scheduled for 3638 h after hCG injection and performed under light sedation. ff was aspirated, centrifuged at 1500 r.p.m. and frozen at 20 °C for future analysis. Standard luteal-phase progesterone support (Utrogestan®, Faran S. A. Greece) was given and 15 days after ET, serum ß-hCG concentrations were measured. If a viable pregnancy was confirmed, progesterone supplementation was continued until 810 weeks of gestation.
The women studied were categorized according to their peak estradiol levels in four groups: 5001000, 10012000, 20013000, and 30014000 pg/ml. The biological rationale for this classification was to identify among normal rFSH responders (>5004000 pg/ml estradiol) the optimum concentration range of estradiol conferring optimal embryo quality, implantation and pregnancy rate. Women with ovarian hyperstimulation and polycystic ovarian syndromes, which alter pregnancy rate, were identified by their elevated estradiol (>4000 pg/ml) and leptin levels and were excluded from the study.
Embryo quality was defined as the number of blastomeres (<5 and
5) and grade of fragmentation (on a scale of 14 with 34 = highest quality = A and 12 = poorest quality = B) in the second or third day after insemination. For statistical purposes embryo quality was defined as good when the majority of transferred embryos were grade A or B with five or more blastomeres and poor when they were grade A or B with less than five blastomeres. Embryos were referred as equal quality, when the same number of good- and poor-quality embryos was transferred.
The data were expressed as means±S.E.M. KruskalWallis, MannWhitney and
2 tests were used where appropriate and P < 0.05 was considered statistically significant. Pearsons test was used for the correlations between the variables.
Estradiol and leptin determinations were performed with commercial RIA and IRMA diagnostic kits (Diagnostic Systems Laboratories, Webster, TX, USA).
| Results |
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5 blastomeres (r = 0.744, P = 0.05 and r = 0.733, P = 0.048, respectively), and positively with poor-quality embryos, of grade B and with <5 blastomeres (r = 0.974, P = 0.02 and r = 0.916, P = 0.05, respectively). We observed a negative correlation (r = 0.23, P = 0.048) between estradiol and leptin in women with peak estradiol levels above 3000 pg/ml.
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Figure 1
shows the association between low ff leptin and high pregnancy and implantation rate, expressed in percentages. The range of optimal hormonal conditions needed to achieve maximum implantation and pregnancy rates is clearly defined in the figure.
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| Discussion |
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Serum estradiol was used to monitor rFSH stimulation. Both low (<500 pg/ml) and high (>4000 pg/ml) serum estradiol concentrations, on the day of hCG administration, resulted in undesirably low and high oocyte yields, respectively. Our study confirmed the known linear correlation between high estradiol level and oocyte yield, decreased implantation and pregnancy rate (Table 1
). It also revealed that the highest numbers of good-quality embryos were produced by women with peak estradiol levels of between 1000 and 2000 pg/ml rather than between 3000 and 4000 pg/ml (Table 1
). This may result from oocyte immaturity or increased leptin production, which may reduce embryo implantation and endometrial receptivity. It appears that the mediation of high oocyte yield and implantation and pregnancy failure by high but not low ff leptin levels (Table 1
) negatively affected ovarian steroidogenesis, follicle maturation and embryo development. The negative correlation observed between a certain normal range of estradiol and leptin levels suggested that under such conditions these hormones exert a negative influence on embryo quality. In that sense, leptin may be a valuable marker of functional IVF staging (Nomikos & Vamvakopoulos 2001) at the level of embryo quality.
ff leptin, VEGF and NO have been used as markers of IVF outcome (Barroso et al. 1999). Furthermore, the elevated ratio of serum leptin to body mass index has been correlated with fewer good-quality embryos and lower implantation and pregnancy rates (Brannian et al. 2001). In our study, high leptin levels (>57.14 ± 7.9 ng/ml (serum) and >63.8 ± 9.8 ng/ml (ff)), affected negatively the quality of transferred embryos. This finding was consistent with the negative correlation observed between good-quality embryos and serum and ff leptin levels and the significantly elevated leptin of women producing high numbers of poor-quality embryos (Table 1
). We observed strong positive correlation between serum and ff leptin levels in all the groups of women examined (P < 0.001). This finding may indicate a role of leptin in subfertility via correlation with poor-quality embryos by reducing ovarian responsiveness to gonadotrophins, which may result from down-regulation of rFSH-induced estradiol production.
Higher implantation and pregnancy rates were observed at low serum leptin levels (46.49 ± 8.4 ng/ml) in women with peak estradiol of 10012000 pg/ml (Table 1
) and lower at high serum leptin levels (60.3 ± 5.8 ng/ml) in women with peak estradiol of 30014000 pg/ml (Table 1
and Fig. 1
). It is possible that high serum and ff leptin concentrations reduce endometrial receptivity and implantation ability through the leptin receptors of the endometrium (Gonzalez et al. 2000, Kitawake et al. 2000).
We conclude that the highest implantation and pregnancy rates observed in our study group resulted from the concerted action of estradiol (10012000 pg/ml, serum) and leptin (46.49 ± 8.4 ng/ml (serum) and 52 ± 9.8 ng/ml (ff)). Outside this concentration range these hormones exert negative influence on embryo quality and IVF outcome. By modulating estradiol-dependent embryo quality, leptin appears to constitute an additional prognostic indicator of IVF outcome. The conditional hormonal IVF effects observed suggest that estradiol and leptin interact coordinately in a concentration-dependent manner. Further studies are needed to substantiate and clarify the mechanism of proposed interaction between the two hormonal systems.
| Acknowledgements |
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| Footnotes |
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| References |
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Brannian J, Schmidt D, Kreger D & Hansen K 2001 Baseline non-fasting serum leptin concentrations to body mass index ratio is predictive of IVF outcomes. Human Reproduction 16 18191826.
Chenette PE, Suaer MV & Paulson RJ 1990 Very high serum oestradol levels are not detrimental to clinical outcome of in vitro fertilization. Fertility and Sterility 54 858863.[Web of Science][Medline]
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Gonzalez RR, Gabarello-Campo P, Jasper M, Mercader A, Devoto L, Pellicer A & Simon C 2000 Leptin and leptin receptors are expressed in human endometrium and endometrial leptin secretion is regulated by the human blastocyst. Journal of Clinical Endocrinology and Metabolism 85 48834888.
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Kitawake J, Koshiba H, Ishihara H, Kusuki I, Tsukamoto K & Honjo H 2000 Expression of leptin receptor in human endometrium and fluctuation during the menstrual cycle. Journal of Clinical Endocrinology and Metabolism 85 19461950.
Loffler S, Aust G, Kohler U & Spanel-Borowski K 2001 Evidence of leptin expression in normal and polycystic human ovaries. Molecular Human Reproduction 7 11431149.
Mantzoros CS, Cramer DW, Liberman RF & Barbieri RC 2000 Predictive value of serum and follicular fluid leptin concentrations during assisted reproductive cycles in normal women and in women with polycystic ovarian syndrome. Human Reproduction 15 539544.
Moschos S, Chan JL & Mantzoros CS 2002 Leptin and reproduction: a review. Fertility and Sterility 77 433444.[CrossRef][Web of Science][Medline]
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Pellicer A, Valbuena D, Cano F, Remohi J & Simon C 1996 Lower implantation rates in high responders: evidence for an altered endocrine milieu during implantation period. Fertility and Sterility 65 11901195.[Web of Science][Medline]
Sharara FI & McClamrock HD 1999 High estradiol levels and high oocyte yield are not detrimental to in vitro fertilization outcome. Fertility and Sterility 72 401405.[CrossRef][Web of Science][Medline]
Simon C, Cano F, Valbuena D, Remohi J & Pellicer A 1995 Clinical evidence for a detrimental effect on uterine receptivity of high serum estradiol levels in high responder and normal responder patients. Human Reproduction 10 24322434.
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