rs10732516 polymorphism at the IGF2/H19 locus associates with genotype-specific effects on placental DNA methylation and birth weight of newborns conceived by assisted reproductive technology

Background

Assisted reproductive technology (ART) has been associated with low birth weight of fresh embryo transfer (FRESH) derived and increased birth weight of frozen embryo transfer (FET)-derived newborns. Owing to that, we focused on imprinted insulin-like growth factor 2 (IGF2)/H19 locus known to be important for normal growth. This locus is regulated by H19 imprinting control region (ICR) with seven binding sites for the methylation-sensitive zinc finger regulatory protein (CTCF). A polymorphism rs10732516 G/A in the sixth binding site for CTCF, associates with a genotype-specific trend to the DNA methylation. Due to this association, 62 couples with singleton pregnancies derived from FRESH (44 IVF/18 ICSI), 24 couples from FET (15 IVF/9 ICSI), and 157 couples with spontaneously conceived pregnancies as controls were recruited in Finland and Estonia for genotype-specific examination. DNA methylation levels at the H19 ICR, H19 DMR, and long interspersed nuclear elements in placental tissue were explored by MassARRAY EpiTYPER (n = 122). Allele-specific changes in the methylation level of H19 ICR in placental tissue (n = 26) and white blood cells (WBC, n = 8) were examined by bisulfite sequencing. Newborns' (n = 243) anthropometrics was analyzed by using international growth standards.

Results

A consistent trend of genotype-specific decreased methylation level was observed in paternal allele of rs10732516 paternal A/maternal G genotype, but not in paternal G/maternal A genotype, at H19 ICR in ART placentas. This hypomethylation was not detected in WBCs. Also genotype-specific differences in FRESH-derived newborns' birth weight and head circumference were observed (P = 0.04, P = 0.004, respectively): FRESH-derived newborns with G/G genotype were heavier (P = 0.04) and had larger head circumference (P = 0.002) compared to newborns with A/A genotype. Also, the placental weight and birth weight of controls, FRESH- and FET-derived newborns differed significantly in rs10732516 A/A genotype (P = 0.024, P = 0.006, respectively): the placentas and newborns of FET-derived pregnancies were heavier compared to FRESH-derived pregnancies (P = 0.02, P = 0.004, respectively).

Conclusions

The observed DNA methylation changes together with the phenotypic findings suggest that rs10732516 polymorphism associates with the effects of ART in a parent-of-origin manner. Therefore, this polymorphism should be considered when the effects of environmental factors on embryonic development are studied.

Increasing openness in oocyte donation families regarding disclosure over 15 years

BACKGROUND

Worldwide there is an increasing number of families created by oocyte donation (OD). The aim of this study was to gather information about parents' plans of disclosure to their child and to other people, as well as parents' attitudes and level of satisfaction up to 15 years after their OD treatment.

METHODS

A questionnaire with separate material for each partner was sent to all parents (167 mothers, 163 fathers) who had had a child after treatment with donated oocytes at Väestöliitto Fertility Clinics in Helsinki during 1992-2006. These parents had a total of 231 children aged 1-14 years. Parents were asked if they had told or intended to tell their child about his/her origin and how and when they had done so and about the reasons to disclose or not. Other questions were about openness towards other people, concerns about donor characteristics, counselling and feelings towards the child.

RESULTS

Of the mothers, 61.1%, and of the fathers, 60.0%, had told or intended to tell the child of his/her conception. Of children over 3 years of age, 26% had already been informed. There was a statistically significant difference between parental telling in different age groups of children (P = 0.011, χ(2)). In the youngest age group (1-3 years), 83.3% of parents were inclined to disclosure compared with 44.4% in the oldest age group (13-14 years). A high proportion of mothers (86.7%) and fathers (71.0%) had told other people about the nature of their child's conception. The majority of parents did not have much concern about the characteristics of the donor. A higher proportion of the mothers (24%) compared with fathers (11%) thought that the psychological support had been insufficient. They thought that discussions with health professionals should be arranged routinely after delivery or when it was time to inform the child.

CONCLUSIONS

Parents with young OD children are clearly more inclined to disclosure compared with parents with older children.

In-vitro maturation of eggs: is it really useful?

In in-vitro maturation (IVM), immature oocytes are collected from small antral follicles and allowed to mature in the laboratory before routine in-vitro fertilization or micro-injection. The authors' experience in IVM is based on the treatment of two main groups of patients: women with polycystic ovaries and women with normal ovaries. Patients with polycystic ovarian syndrome have irregular, mostly anovulatory cycles and are at increased risk for ovarian hyperstimulation syndrome because of their higher sensitivity to gonadotropins. Women with normal ovarian function may wish to avoid the side-effects of hormone injections, and therefore IVM has also been offered to couples with tubal, male factor and unexplained infertility. In all these groups of patients, immature oocytes have successfully been matured, fertilized and embryos transferred. Pregnancy rates have been reported to be between 4% and 54%. More than 300 children have been born and follow-up studies have reported no major concerns about the pregnancies, deliveries or health of the babies. There are still many questions concerning IVM. As the factors regulating follicle selection are poorly understood, no specific markers for the optimal time of immature oocyte collection have been defined. Furthermore, basic knowledge on the complex intracellular processes involved in the cytoplasmic maturation of human oocyte is lacking, making the design of optimal culture conditions for maturation difficult. The possible long-term effects of IVM on the health and development of children needs future study.

Frozen embryo transfers: implications of clinical and embryological factors on the pregnancy outcome

BACKGROUND

Frozen embryo transfers are characterized by impaired pregnancy outcome and increased incidence of pregnancy loss as compared with fresh IVF/ICSI embryo transfers. In this study, we performed a retrospective analysis of clinical and embryological factors that potentially influence the outcome of frozen embryo transfer.

METHODS

We reviewed the outcome of 1242 frozen embryo transfers with respect to the age of the woman, the method of fertilization, embryo quality before and after freezing and the number of embryos transferred.

RESULTS AND CONCLUSIONS

The pregnancy (positive hCG) and clinical pregnancy rates were 25.8 and 21.1%, respectively. A total of 107 (33.3%) of the 321 pregnancies identified by a positive hCG test miscarried either before (18.4%) or after (15%) the clinical recognition of gestational sac(s). The delivery rate for the frozen embryo transfers analysed was 17.2%. Our data revealed that the delivery rate after frozen embryo transfer was dependent on both the woman's age and the quality of embryos transferred, at the same time being unaffected by IVF/ICSI treatment. In addition, the increased woman's age at IVF/ICSI treatment was identified as the only parameter elevating the biochemical pregnancy rate, whereas the clinical abortion rate was found to be unrelated to the clinical or embryological parameters studied.

Obstetric and perinatal outcome and preliminary results of development of children born after in vitro maturation of oocytes

BACKGROUND

Careful follow-up of children born after in vitro maturation (IVM) of human oocytes is essential because the technique is still very new.

METHODS

Obstetric and perinatal data were collected from all deliveries after IVM treatment during 1999-2004. The growth and development of IVM children was assessed at 6, 12 and 24 months using Muenchener Funktionelle Entwicklungs Diagnostik and Bayley Scales of Infants.

RESULTS

In total, 43 women [age 31.2 +/- 3.9 (mean +/- SD) years] gave birth to 40 singleton infants and three sets of twins (multiple rate 7.0%). Obstetric complications occurred in 15 pregnancies (35%). The mean birthweight of singleton infants was 3550 +/- 441 g and that of twins 2622 +/- 194 g. The rate of preterm birth infants was 5% in singletons. No perinatal deaths occurred. At the age of 12 months, eight children (19%) expressed minor developmental problems and one girl was found to have optical glioma. At 2 years of age, neuropsychological development was within the normal range.

CONCLUSIONS

The obstetric and perinatal outcome was good, and the mean birthweight of the infants was normal. Minor developmental delay was overexpressed at 12 months, but the development of the children was normal at 2 years.

Favourable pregnancy results with insemination of in vitro matured oocytes from unstimulated patients

BACKGROUND

The purpose has been to develop an in vitro oocyte maturation (IVM) method for a wide range of patients.

METHODS

A total of 239 cycles with immature oocyte retrieval (IOC) were carried out without hormonal priming. Patients with regular cycles and normal or polycystic ovaries (PCO) and anovulatory cycles with PCOS were included. Insemination or intracytoplasmic sperm injection (ICSI) according to sperm quality was alternatively used in fertilization of the matured oocytes.

RESULTS

A total of 971 immature oocytes (mean 8.0 +/- 5.2) were collected in 122 IVM-IVF cycles and 851 oocytes (mean 7.3 +/- 4.4) in 117 IVM-ICSI cycles. The oocyte maturation and fertilization rate was 62.6% and 37.7% after insemination, and 53.9% and 69.3% after ICSI, respectively. The mean number of embryos transferred was 1.6. Clinical pregnancy rate per IOC was 23.8% in IVM-IVF and 17.1% in IVM-ICSI (ns). Implantation rate was higher in IVM-IVF (24.2%) than in IVM-ICSI (14.8%) (P < 0.05).

CONCLUSIONS

Insemination of IVM oocytes functions well, resulting in comparable pregnancy rates per IOC between IVM-IVF and IVM-ICSI. Good pregnancy results can be achieved both in patients with regular cycles and with PCO(S) by transferring only one or two embryos at a time.

Elevated incidence of chromosomally chaotic embryos among frozen-thawed preimplantation embryos

OBJECTIVE

The aim of the study was to evaluate the effect of cryopreservation on the formation of chromosomal abnormalities in human preimplantation embryos.

STUDY DESIGN

The chromosomal constitutions of cleavage stage embryos (n = 61) were assessed using fluorescent in situ hybridisation (FISH) technique, applying probes for chromosomes 13, 16, 18, 21, X and Y. Study group embryos frozen at zygote or two-cell stage (n = 29) were cultured in vitro post-thawing until they reached four- to six-cell stage, after which their chromosomal constitutions were assessed. Control group embryos frozen at four- to six-cell stage (n = 32) were analysed immediately after thawing in order to exclude any post-thaw effect. The proportions of genetically normal and abnormal embryos were compared between study and control group.

RESULTS

The proportions of normal, aneuploid and mosaic embryos were similar in both groups. However, significantly (P < 0.05) higher proportion of chaotic embryos in study (24.1%) compared to control group (6.3%) was observed.

CONCLUSION

The elevated level of chromosomally chaotic embryos among embryos that had undergone cellular division after thawing as compared to embryos analysed immediately after thawing indicates a potential negative impact of cryopreservation on the formation of chromosomal abnormalities in preimplantation embryos.

Recombinant LH is equally effective as recombinant hCG in promoting oocyte maturation in a clinical in-vitro maturation programme: a randomized study

BACKGROUND

Fertilization treatment using oocytes matured in vitro from pre-ovulatory follicles has many potential applications. It minimizes the risk of severe ovarian hyperstimulation and is an alternative for women with polycystic ovary syndrome who may have problems regarding stimulation for IVF. In-vitro maturation (IVM) may prove important for subjects needing fertility preservation, and also provides information about the final stages of oocyte maturation.

METHODS

From a randomized study of 73 women in an IVF programme, 36 subjects with 228 oocytes were allocated for oocyte maturation in culture medium with recombinant hCG, and 37 subjects with 256 oocytes for maturation with recombinant LH. The primary outcome was the rate of nuclear maturation of oocytes to metaphase II. During the same period, 32 women outside the study underwent 38 individually tailored IVM treatments.

RESULTS

The oocyte maturation rate was 54.8% with hCG and 55.9% with LH; fertilization and cleavage rates were not significantly different. Three pregnancies were achieved in the hCG group and one in the LH group. Seven pregnancies (22.6% per embryo transfer) were achieved in the parallel group.

CONCLUSIONS

Recombinant hCG or LH are equally effective in promoting oocyte maturation in a clinical IVM programme.

Effect of developmental stage of embryo at freezing on pregnancy outcome of frozen-thawed embryo transfer

BACKGROUND

The study aim was to investigate the impact of the developmental stage of embryos on pregnancy outcome of frozen embryo transfer (FET).

METHODS

The survival rates of embryos after thawing and pregnancy outcome following FET were compared retrospectively between three cryopreservation strategies utilizing either zygote, day 2 or day 3 embryo freezing.

RESULTS

A total of 4006 embryos was analysed in 1657 thaw cycles. The highest (P < 0.0001) survival rate (all cells survived) was observed for zygotes (86.5%), followed by day 2 (61.7%) and day 3 (43.1%) embryos. FET was performed in 1586 (95.7%) of all thaw cycles, resulting in overall clinical pregnancy and implantation rates of 20.7 and 14.2% respectively. The delivery rate per transfer was 16.5%, and live birth rate per transferred embryo 11%. There were no significant differences in clinical pregnancy, implantation, delivery and birth rates between frozen zygote, day 2 and 3 embryo transfers. However, an elevated miscarriage rate was observed in the day 3 group (45%) compared with zygotes (21.3%; P = 0.049) and day 2 embryos (18.3%; P = 0.004). The overall efficacy of FET (birth rate per thawed embryo) was 7.3%. The efficacy was lower in day 3 group (4.2%) than in the zygote (7.1%; P = 0.082) and day 2 (7.6%; P = 0.027) groups.

CONCLUSIONS

The developmental stage of embryos at freezing has a profound effect on their post-thaw survival, but seems to have little effect on rates of clinical pregnancy, implantation, delivery and birth after FET. The elevated miscarriage rate for day 3 frozen embryo transfers may be caused by damage during freeze-thaw procedures. The low survival rate and elevated miscarriage rate were both responsible for a reduced overall efficacy for day 3 FET when compared with zygotes and day 2 embryos.

Elective single embryo transfer yields good delivery rates in oocyte donation

BACKGROUND

High pregnancy rates have been noted after oocyte donation (OD). Multiple pregnancies should be avoided, because oocyte recipients have an increased risk of obstetric complications.

METHODS

We analysed our OD results from 2000-2001 when elective single embryo transfer (eSET) was introduced as a recommended policy for all recipients if at least one good quality embryo was available. The results were compared with those achieved in 1998-1999, when usually two embryos were transferred (double embryo transfer, DET). Between 1998 and 2001, 100 healthy women donated oocytes and 135 fresh embryo transfers were carried out. The mean age of the donors was 31 years and that of the recipient women was 35 years.

RESULTS

The proportion of eSET of all OD transfers was 17.1% in 1998-1999 and 61.0% in 2000-2001. There was no statistically significant difference in clinical pregnancy (36.8 versus 45.8%) and delivery rates (31.6 versus 33.9%) per embryo transfer between the two time periods. The proportion of twins declined from 29% (1998-1999) to 10% (2000-2001). The delivery rate was similar after eSET and DET (32.6 versus 32.1% respectively).

CONCLUSIONS

By increasing the proportion of eSETs it is possible to reduce the number of twins without affecting delivery rates in oocyte recipients.

Early cleavage predicts the viability of human embryos in elective single embryo transfer procedures

BACKGROUND

The reduction of multiple pregnancies by using elective single embryo transfers (eSET) requires critical and careful selection of the embryo for transfer. The current study was undertaken to assess whether early cleavage could be used as a marker of embryo competence in eSET procedures.

METHODS

The study included analysis of 178 eSET procedures. All embryos were checked for early cleavage at 25-27 h post insemination or ICSI. The embryos that possessed two cells at 25-27 h post insemination or ICSI were designated as 'early cleavage' (EC) embryos and those that had not yet cleaved were classified as 'no early cleavage' (NEC) embryos. Selection of the embryo for transfer was based on embryo morphology and growth rate on day 2 and not early cleavage. Clinical parameters were compared between 72 EC and 106 NEC single embryo transfers.

RESULTS

A significantly higher clinical pregnancy rate was observed after transfer of EC (50%) than NEC (26.4%) embryos.

CONCLUSIONS

The current study provides compelling evidence that EC embryos possess significantly higher developmental competence than NEC embryos.

The predictive value of pronuclear morphology of zygotes in the assessment of human embryo quality

BACKGROUND

Recent studies have shown that zygote morphology could be used for the assessment of human embryo quality. Pronuclear (PN) morphology is based on certain distinct features seen in zygotes 16-18 h after fertilization. In the present study PN stage morphology was assessed and combined with a single embryo transfer in order to investigate whether currently used zygote classifications are able to predict embryo quality and implantation rates.

METHODS AND RESULTS

Zygotes were analysed according to two different classification systems. In the first, a total of 764 zygotes was analysed according to the degree of polarization of nucleolar precursor bodies (NPB). Zygotes with unpolarized PN (i.e. scattered localization of NPB) showed significantly slower (P < 0.005) cleavage rates (38.9%) than zygotes having at least one pronucleus polarized (57.3% and 54%). However, there was no difference in the pregnancy rate in 105 single embryo transfers between the groups. The appearance of a cytoplasmic halo was related to embryo morphology. Embryos derived from halo-positive zygotes had significantly better (P < 0.05) morphology (60.9%) compared to halo-negative derived embryos (52.2%), but in terms of pregnancy rates no difference was found. A total of 1520 zygotes was analysed according to a second classification system, which was based on the number and distribution of NPB. In the comparative analysis, none of the six different classes produced superior quality embryos or higher pregnancy rates in 144 single embryo transfers.

CONCLUSIONS

Our results indicate that there are no significant differences in embryo quality or implantation/pregnancy rates between proposed zygote classes.

Y-chromosomal microdeletions among infertile Finnish men

BACKGROUND

Microdeletions in the Y-chromosome are known to cause a significant proportion of azoo- and oligozoospermia in men. The reported frequency of deletions varies greatly between the studies. Probable reasons for this variation are different selection criteria and number of patients included, and possibly also methodological aspects, whereas the contribution of environmental and genetic factors is not known. The aim of this study was to determine the incidence of Y-chromosome microdeletions among infertile Finnish men.

METHODS

Two hundred and one men showing azoospermia (n=68) or severe oligozoospermia (n=133) were included. Multiplex polymerase chain reaction method was used to amplify specific sequence tagged sites (STS) along the Y chromosome.

RESULTS

Microdeletions were observed in 18 men (9%), of whom four were azoospermic and 14 oligozoospermic.

CONCLUSIONS

The incidence of Y-deletions in the study population of infertile Finnish men falls within the range published in other countries.

Luteal phase start of low-dose FSH priming of follicles results in an efficient recovery, maturation and fertilization of immature human oocytes

In this prospective study we investigated whether the maturation and fertilization of immature oocytes can be improved by administration of recombinant follicle stimulating hormone (rFSH) starting in the late luteal phase in two groups of women: group 1 (n = 6) women with regular menstrual cycles; and group 2 (n = 6) women with irregular cycles and polycystic ovaries (PCO) on ultrasound examination. Low-dose (37.5 IU) rFSH was commenced 11 days after LH surge during a spontaneous menstrual cycle and on the ninth day of progesterone administration in an irregular cycle. Recombinant FSH was continued until the leading follicle was approximately 10 mm in diameter. The oocytes were retrieved after withdrawing rFSH for 2-5 days. In total, 136 oocytes were recovered (group 1, 67 oocytes; group 2, 69 oocytes). Nine of the oocytes from PCO women were atretic at retrieval. Oocytes complete with cumulus cells were cultured for 44 h in complex tissue culture medium supplemented with gonadotrophins and fetal calf serum. After maturation, the cumulus cells were removed and metaphase II oocytes were injected with spermatozoa. Respectively, the oocyte maturation and fertilization rates were 64 and 72% in group 1, and 78 and 57% in group 2 (not significant). After fertilization, the zygotes (group 1, n = 22; group 2, n = 11) and cleavage stage embryos (group 1, n = 9; group 2, n = 15) were frozen in propanediol. All women except one (11/12) had approximately five zygotes or cleaved embryos frozen. The viability of in-vitro matured frozen-thawed embryos was generally poorer than that (81%) seen after conventional intracytoplasmic sperm injection, with 61% survival in group 1 and 23% in group 2. Fifteen embryo transfers resulted in one miscarriage at 6 weeks gestation. The late luteal start of low-dose rFSH yielded a good number of immature oocytes in women with both regular and irregular cycles. Two out of three of these oocytes matured and fertilized. However, cryosurvival of the zygotes and cleaved embryos was unsatisfactory and thus cryopreservation of in-vitro matured embryos may not be an optimal procedure.

Comparison of two recombinant follicle-stimulating hormone preparations in in-vitro fertilization: a randomized clinical study

A randomized comparison of two recombinant human follicle-stimulating hormone (recFSH) preparations (Gonal-F and Puregon) in ovarian stimulation for in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) was carried out at the Infertility Clinic of the Family Federation of Finland. A total of 348 women (aged 22-43 years) suffering from infertility due to miscellaneous causes was recruited. Of these, 344 underwent stimulation using equal starting doses (150 IU/day: Gonal-F n = 164, Puregon n = 158 or 300 IU/day: Gonal-F n = 8, Puregon n = 14) after down-regulation with intranasal buserelin from the mid-luteal phase. Similar clinical pregnancy rates were achieved with both preparations; 33.5% per cycle and 37.4% per embryo transfer (24.5% one-embryo and 75.5% two-embryo transfers, n = 147) with Gonal-F (150 IU/day) and 32.9% per cycle and 36.4% per embryo transfer (30.1% one-embryo and 69.9% two-embryo transfers, n = 145) with Puregon (150 IU/day). The ongoing cumulative pregnancy rates after frozen-thawed embryo transfer were 35.4% with Gonal-F and 37.7% with Puregon. Six cycles were cancelled because of a low response (three in each group). Similar numbers of oocytes were obtained in both groups; 13.0 with 150 IU/day and 6.1 with 300 IU/day Gonal-F, and 12.4 with 150 IU/day and 7.1 with 300 IU/day Puregon. The fertilization and cleavage rates and the incidence of moderate or severe ovarian hyperstimulation syndrome (Gonal-F, 2.0% and Puregon, 0.7%) were also similar. Gonal-F and Puregon were equally and highly effective in stimulation for IVF and ICSI.

Successful pregnancy after in-vitro fertilization and transmyometrial embryo transfer in a patient with congenital atresia of cervix: case report

A case report of a patient with congenital cervical atresia diagnosed at the age of 24 years is given. The attempts to create a neocervix were unsuccessful. Since no signs of retrograde menstruation or haematometra were observed, in agreement with the patient hysterectomy was not performed. At the age of 32 years, a successful pregnancy was achieved after an in-vitro fertilization and transmyometrial embryo transfer. Due to rapidly progressing pre-eclampsia, an elective Caesarean section was performed at 32 weeks gestation. A 1610 g healthy male infant in breech presentation was born. The post-partum period was uneventful.

Recruitment of follicles by recombinant human follicle-stimulating hormone commencing in the luteal phase of the ovarian cycle

OBJECTIVE

To investigate, in patients who previously had a suboptimal ovarian stimulation cycle, the benefit of starting ovarian stimulation before the onset of menses.

DESIGN

Prospective, randomized, controlled study.

SETTING

A tertiary referral center for infertility treatment.

PATIENT(S)

Forty patients undergoing IVF or GIFT from whom only 3-6 oocytes were retrieved in their last cycle.

INTERVENTION(S)

Recombinant human FSH was administered before the onset of the menstrual period (experimental group) or in the early follicular phase after the onset of menses (control group).

MAIN OUTCOME MEASURE(S)

The number of oocytes retrieved.

RESULT(S)

Patients in the experimental group were ready for oocyte retrieval on menstrual cycle day 11 instead of cycle day 14. The number of oocytes retrieved was not significantly different between the two groups.

CONCLUSION(S)

Poor responders do not benefit from commencing recombinant human FSH therapy in the luteal phase.

Blastocyst development and birth after in-vitro maturation of human primary oocytes, intracytoplasmic sperm injection and assisted hatching

Immature oocyte recovery followed by in-vitro oocyte maturation and in-vitro fertilization is a promising new technology for the treatment of human infertility. The technology is attractive to potential oocyte donors and infertile couples because of its reduced treatment intervention. Immature oocytes were recovered by ultrasound-guided transvaginal follicular aspiration. Oocytes were matured in vitro for 36-48 h followed by intracytoplasmic sperm injection (ICSI). Embryos were cultured in vitro for 3 or 5 days before replacement. Assisted hatching was performed on a day 5 blastocyst stage embryo. Embryo and uterine synchrony were potentially enhanced by luteinization of the dominant follicle at the time of immature oocyte recovery. Mature oocyte and embryo production from immature oocyte recovery were similar to the previous IVF results of the patients. A blastocyst stage embryo, produced as a result of in-vitro maturation, ICSI, in-vitro culture and assisted hatching, resulted in the birth of a healthy baby girl at 39 weeks of gestation.

Urinary vascular endothelial growth factor concentrations in women undergoing gonadotrophin treatment

A recently identified cytokine, vascular endothelial growth factor (VEGF, vascular permeability factor) has been implicated in ovarian hyperstimulation syndrome in women undergoing assisted reproduction. We postulate that circulating and urinary VEGF values increase following gonadotrophin stimulation, in parallel with the increased ovarian vascularity. A VEGF radioimmunoassay was developed using iodinated VEGF as tracer, a goat anti-VEGF serum as antiserum and recombinant human VEGF as standard. The specificity of the assay was confirmed by comparing the reverse phase high-performance liquid chromatography (HPLC) pattern of VEGF immunoactivity in urine and urine spiked with recombinant VEGF. Urine was concentrated 5-fold prior to measurement by the radioimmunoassay. VEGF:creatinine ratios in early morning urine samples were used to monitor daily urinary VEGF concentrations based on its high correlation (r = 0.77, P < 0.001) with VEGF concentrations in 24 h urine collections. No diurnal variation in VEGF:creatinine ratios was detected. VEGF:creatinine ratios were determined daily from nine women undergoing gonadotrophin-releasing hormone (GnRH) agonist/gonadotrophin treatment. In a further 16 women, early morning urine samples were collected in the peri-ovulatory period. A significant increase (P < 0.005, n = 25) was observed in VEGF:creatinine ratios following human chorionic gonadotrophin (HCG) administration. VEGF:creatinine ratios correlated poorly (r < 0.34) with plasma oestradiol, follicle number and size. It is concluded that urinary VEGF/creatinine ratios increase following HCG stimulation.

Ultrasonographic appearance of polycystic ovaries is associated with exaggerated ovarian androgen and oestradiol responses to gonadotrophin-releasing hormone agonist in women undergoing assisted reproduction treatment

While no single biochemical test is diagnostic of polycystic ovary syndrome (PCOS), most patients show a characteristic ovarian ultrasonographic appearance. It has been proposed that a dysfunction of cytochrome P-450c17 alpha in PCOS leads to an increased 17-hydroxyprogesterone (17-OHP) response to a gonadotrophin-releasing hormone (GnRH) agonist-induced gonadotrophin rise. We postulated that this abnormality of steroid metabolism might influence the ovarian response during assisted reproduction treatment. We investigated 106 patients undergoing a short 'boost' stimulation regimen for assisted reproduction treatment, including in-vitro fertilization and gamete intra-Fallopian transfers. The ovarian ultrasound pattern was correlated with serum testosterone, 17-OHP, androstenedione and oestradiol responses, and with the clinical outcome. Polycystic ovaries, defined ultrasonographically as the presence of > or = 10 follicles between 2 and 10 mm diameter in either ovary, were found in 48% of the whole study population. Dexamethasone was given to suppress adrenal androgen secretion. Functional ovarian hyperandrogenism (FOH) was defined as serum testosterone > 0.5 nmol/l after dexamethasone. There was a significantly (P < 0.001) higher prevalence of FOH in patients with polycystic ovaries (23%) compared with normal ovaries (7%). Patients with polycystic ovaries had approximately double the 17-OHP, androstenedione and oestradiol responses to a GnRH agonist as patients with non-polycystic ovaries. Exaggerated 17-OHP and oestradiol responses to GnRH agonist were found in 89% of patients with clinically diagnosed PCOS. The number of oocytes retrieved was positively correlated (r = 0.51, P < 0.001) with the oestradiol responses in all patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the binding defect in insulin-like growth factor binding protein-3 from pregnancy serum

During pregnancy, insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) undergoes proteolysis, rendering it undetectable by radioligand binding techniques. This study examines the physical and functional defect in pregnancy IGFBP-3. Ternary complex formation has been measured by the binding of the acid-labile subunit of the circulating IGFBP-3 complex, which also requires IGF-I or IGF-II binding. IGF-depleted pregnancy IGFBP-3, prepared by size-exclusion chromatography at low pH, could not form a ternary complex in the presence of [Tyr60]IGF-I or of an IGF-I analogue extensively altered in the A-domain, whereas analogues altered in the C- or D-domains complexed as well as native IGF-I. After purification by immunoaffinity chromatography, non-pregnancy and pregnancy IGFBP-3 formed ternary complexes with IGF-I equally well, although the pregnancy-proteolysed protein appeared degraded to approximately 30 kDa. On analysis by affinity labelling, cross-linked ternary complexes containing non-pregnancy or pregnancy IGFBP-3 were predominantly 135-140 kDa, with an additional complex of 110-115 kDa in the pregnancy preparation. After reverse-phase h.p.l.c., affinity-isolated pregnancy IGFBP-3 was inactive, whereas the protein from non-pregnancy serum retained activity. Thus pregnancy-proteolysed IGFBP-3 is altered in its specificity for IGF analogues, and is more labile than non-pregnancy IGFBP-3, but shows little impairment in normal IGF binding or ternary complex formation.

Growth hormone and insulin-like growth factor regulate insulin-like growth factor-binding protein-1 in Laron type dwarfism, growth hormone deficiency and constitutional short stature

Insulin-like growth factors (IGFs) mediate the effects of growth hormone (GH), and the insulin-like growth factor-binding proteins (IGFBPs) modulate the actions of IGFs in tissues. We studied the circulating levels of IGFBP-1 in 6 children and 9 adults with Laron type dwarfism (LTD), in 11 children and 21 adults with growth hormone deficiency (GHD), and in 8 children with constitutional short stature. Compared with the situation in healthy children, the basal serum IGFBP-1 concentration was 5.4-fold higher in LTD children, 4.1-fold higher in GHD children, and 3.8-fold higher in children with short stature (p < 0.02 vs controls in all groups). In adult patients with multiple pituitary hormone deficiency (MPHD), the IGFBP-1 concentration was 2-fold elevated, but it was normal in adult LTD patients. Intravenous (N = 10) or subcutaneous (N = 9) administration of IGF-I (75 micrograms.kg-1 and 150 micrograms.kg-1, respectively) in LTD children resulted in a rapid 50-60% fall in serum insulin (p < 0.02), a decline in blood glucose and a concomitant 40-60% rise of IGFBP-1 levels (p < 0.05). Treatment for seven days with IGF-I (150 micrograms.kg-1 x d-1) resulted in a decrease by 34% and 44% of serum IGFBP-1 level in two out of three children with LTD. After prolonged GH therapy, the IGFBP-1 level fell in GHD children by 29% (p < 0.05), in GHD adults by 52% (p < 0.02) and in children with constitutional short stature by 17% (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of insulin-like growth factor binding protein-1 mRNA in human fetal kidney

Expression of insulin-like growth factor binding protein-1 (IGFBP-1) messenger RNA (mRNA) was studied in tissues of human fetuses from 15 to 23 weeks of gestation. Northern blot analysis revealed IGFBP-1 mRNA in the fetal liver and kidney but not in other fetal tissues, including the brain, heart, lung, skeletal muscle and spleen. Studies by in situ hybridization histochemistry showed that, in all fetal kidneys tested, the IGFBP-1 mRNA was localized preferentially to the epithelial cells of the collecting ducts, as well as to the cells of developing glomeruli and in the subcapsular nephrogenic mesenchyme. Less intense labeling for IGFBP-1 mRNA was seen in the connective tissue stroma of the medullary pyramids. A weak signal was detected in the mature glomeruli, and in the cells of the medullary mesenchyme and capsular connective tissue. IGFBP-1 protein was detected by immunoperoxidase staining mostly around small blood vessels but not in the respective endothelium. The protein was also present in many epithelial cells of the collecting ducts and in stromal connective tissue. These results show that the predominant sites of IGFBP-1 transcription in the developing kidney are those with most active differentiation.

Insulin-like growth factor-binding protein-3 is functionally normal in pregnancy serum

Insulin-like growth factor-binding protein-3 (IGFBP-3) carries most of the serum IGFs as a 150K ternary complex which increases during pregnancy. However, recent studies have demonstrated that IGFBP-3 is absent in pregnancy serum when measured by ligand blotting after electrophoresis. In the present study we demonstrate that, by several criteria, IGFBP-3 appears functionally intact in pregnancy serum. Serum samples were collected from pregnant women between 2-40 weeks gestation. Serum immunoreactive IGFBP-3 and acid-labile (alpha) subunit increased linearly throughout pregnancy. Ligand blotting confirmed diminution of IGFBP-3 at 2 weeks gestation and complete absence after 4 weeks gestation or when nonpregnancy serum was preincubated with amniotic fluid. When less harsh methods (neutral chromatography or transient acidification) were used, IGFBP-3 appeared functionally normal in pregnancy serum. Fractionation of pregnancy serum by Superose-12 gel permeation chromatography showed similar elution profiles for both IGFBP-3 and alpha-subunit compared to those for nonpregnancy serum. Preincubation of nonpregnancy serum with pregnancy serum or amniotic fluid had no effect on IGFBP-3 recovery. After acidification and neutralization of serum to destroy endogenous alpha-subunit, ternary complex formation, measured by radiolabeled alpha-subunit binding, was essentially identical in all nonpregnancy and pregnancy serum, except for a slight loss of activity in first trimester serum. Since the 150K complex cannot form unless IGFBP-3 binds IGFs and alpha-subunit normally, these results suggest that IGFBP-3 in native pregnancy serum is functionally normal.

Insulin-like growth factor (IGF) binding protein-3 in pregnancy serum binds native IGF-I but not iodo-IGF-I

Although serum immunoreactive insulin-like growth factor binding protein-3 (IGFBP-3) increases during pregnancy, radioligand binding methods such as ligand blotting with iodinated IGFs fail to detect the protein in pregnancy serum. Since IGFBP-3 must bind IGF-I or IGF-II to form a complex with the acid-labile subunit (alpha-subunit), we have used ternary complex formation from [125I]alpha-subunit as a measure of IGF binding to serum IGFBP-3. High-pressure liquid chromatography fractions containing IGFBP-3 from pregnancy serum did not bind [125I]IGF-I, although the equivalent fractions from nonpregnancy serum showed dose-dependent binding. In contrast, IGFBP-3 fractions from nonpregnancy and pregnancy sera both bound [125I]alpha-subunit in the presence of either exogenous IGF-I or endogenous serum IGFs, implying that non-iodinated IGFs could bind to the IGFBP-3. Substitution of nonradioactive iodo-IGF-I for native IGF-I in the complex formation assay confirmed that the pregnancy-induced alteration in IGFBP-3, probably resulting from proteolysis, prevents it from binding iodo-IGF-I while having little effect on its binding of the native peptide. This provides an explanation for the failure to detect IGFBP-3 in pregnancy by radioligand binding methods, and raises the question of the significance of proteolysis of IGFBP-3.

Insulin-like growth factor binding protein-1 inhibits the DNA amplification induced by insulin-like growth factor I in human granulosa-luteal cells

In order to study the effects of insulin-like growth factor (IGF-I) and insulin-like growth factor binding protein (IGFBP-1) on human granulosa cell proliferation after in vitro fertilization, cells were obtained after oocyte retrieval and cultured in the presence or absence of graded amounts of recombinant IGF-I, purified IGFBP-1 and [3H]thymidine. Physiological concentrations of IGF-I (2-200 ng/ml) were found to stimulate [3H]thymidine incorporation into the cells in a concentration-dependent manner. Half-maximal stimulation of [3H]thymidine incorporation was obtained with 10 ng/ml exogenous IGF-I, which was chosen for suppression experiments with graded amounts of purified IGFBP-1. Suppression of IGF-stimulated thymidine incorporation was observed when 200 ng/ml or more of IGFBP-1 was added to the culture medium. The same concentration of IGFBP-1 also markedly inhibited binding of [125I]iodotyrosyl IGF-I to the cells. It is concluded that: (i) after a refractory period, granulosa cells from hyperstimulated follicles retained their mitogenic activity; (ii) IGF-I is capable of stimulating DNA amplification in granulosa cells; and (iii) IGFBP-1 inhibits the IGF-I stimulated proliferation in these cells. In view of our previous studies showing that IGFBP-1 is synthesized by the granulosa cells as they luteinize, the present results suggest that IGFBP-1 is one of the endogenous factors locally regulating the growth and differentiation of granulosa cells.

Oral contraceptives increase insulin-like growth factor binding protein-1 concentration in women with polycystic ovarian disease

Insulin-like growth factor-I (IGF-I) stimulates ovarian androgen production. Insulin-like growth factor binding protein-1 (IGFBP-1) inhibits IGF actions in vitro.

OBJECTIVE

To investigate the effect of oral contraceptive (OC) pills, given for 3 months, on serum gonadotropin, androgen, IGF-I, and IGFBP-1 concentrations, and glucose tolerance in seven women with polycystic ovarian disease (PCOD) and in five healthy control subjects.

PATIENTS

Seven women with PCOD and five healthy control subjects.

INTERVENTIONS

An oral glucose tolerance test (OGTT) was performed before and after treatment with OC.

RESULTS

After treatment with OC, serum luteinizing hormone, androstenedione, and free testosterone levels decreased, and sex hormone-binding globulin concentration increased in the women with PCOD as well as in the control subjects. The cumulative response of serum insulin to OGTT was larger in the women with PCOD than in the control subjects both before and after treatment. Serum IGF-I concentration, which was unchanged during OGTT, decreased from basal level of 326 +/- 70 micrograms/L to 199 +/- 28 micrograms/L after treatment with OC in the women with PCOD, whereas no change was found in the control subjects (from 235 +/- 11 micrograms/L to 226 +/- 11 micrograms/L). Treatment with OC caused an increase of the mean basal IGFBP-1 concentration from 24 +/- 7 micrograms/L to 73 +/- 14 micrograms/L in the women with PCOD. This increase was constant during the OGTT. In the control subjects, treatment with OC did not result in any significant change in IGFBP-1 concentrations (from 44 +/- 11 micrograms/L to 61 +/- 9 micrograms/L).

CONCLUSION

The combination of decreased total IGF-I concentration and increased IGFBP-1 concentration induced by OC may decrease ovarian androgen production in PCOD.

Effect of naloxone on plasma insulin, insulin-like growth factor I, and its binding protein 1 in patients with polycystic ovarian disease

Insulin and insulin-like growth factors (IGFs) stimulate ovarian steroidogenesis, and hyperinsulinemia is often accompanied by hyperandrogenemia in women with polycystic ovarian disease (PCOD). Because opioid peptides are involved in the regulation of insulin secretion, we studied the effect of naloxone-induced opiate receptor blockade on the circulating levels of insulin, IGF-I, and IGF binding protein 1 (IGFBP-1) in 13 nonobese and 7 obese PCOD patients and in 6 healthy subjects. In obese PCOD patients, the mean basal insulin concentration was significantly higher and the IGFBP-1 concentration lower than in nonobese PCOD patients. Plasma IGF-I levels were elevated both in obese and nonobese PCOD patients. After an intravenous bolus of 10 mg naloxone, no significant changes were found in the circulating insulin or IGF-I levels, whereas IGFBP-1 levels decreased in nonobese PCOD patients and remained low in obese PCOD patients. No significant decrease was found in healthy subjects. These results suggest that, in addition to insulin, endogenous opioids are involved in the regulation of serum IGFBP-1 level.

Human granulosa cells contain insulin-like growth factor-binding protein (IGF BP-1) mRNA

Previous studies have demonstrated expression of insulin-like growth factor-binding protein (IGF BP-1) in secretory and decidualized endometrium, in adult and fetal liver, and in HepG2 liver cancer cells. We have studied the expression of IGF BP-1 in various types of ovarian neoplasias, normal ovary, and granulosa cells from hyperstimulated human ovarian follicles by RNA blot hybridization. A single 1.6 kb mRNA species, similar to that present in human decidua, was identified in poly(A)RNA-containing preparations of granulosa cells and of a borderline malignant ovarian cystadenoma. This finding verifies the postulated production of IGF BP-1 by the human ovary.

Identification by hybridization histochemistry of human endometrial cells expressing mRNAs encoding a uterine beta-lactoglobulin homologue and insulin-like growth factor-binding protein-1

A beta-lactoglobulin homologue (beta LG/PP14) and insulin-like growth factor-binding protein-1 (IGFBP-1) are two major secretory proteins of the human endometrium. In the present study, we have shown that beta LG/PP14 mRNA is expressed in the endometrium in a cyclic manner, being hardly detectable in midcycle and most abundant during the late secretory phase. IGFBP-1 mRNA is also expressed in endometrium, but in amounts smaller than those encoding beta LG/PP14 and with maximal accumulation earlier in the secretory phase. The expression of these two mRNAs occurs in different cell types of the endometrium, as revealed by in situ hybridization techniques using single-stranded RNA probes. The glandular epithelial cells accumulate beta LG/PP14 mRNA during the late secretory phase of the cycle, whereas only the stromal cells of the late secretory endometrium express IGFBP-1 mRNA. In contrast to the endometrium, the two mRNAs are present at very low abundance in the fallopian tubes where they are expressed in the epithelial cells of the mucosa.

Concentrations of somatomedin-C and triiodothyronine in patients with thyroid dysfunction and nonthyroidal illnesses

We studied the possibility of an association between serum somatomedin-C (Sm-C) and thyroid hormone concentrations. For this purpose 34 hyperthyroid patients, 39 patients with primary hypothyroidism, 36 patients with severe nonthyroidal illnesses (NTI), and 63 euthyroid healthy control subjects were examined. The mean concentration of serum dialyzable free triiodothyronine (FT3) was 26.6 +/- 15.4 pmol/l (+/- SD) in hyperthyroidism, 2.8 +/- 1.2 in hypothyroidism, 4.2 +/- 1.1 in NTI, and 5.3 +/- 0.7 in controls. The lowest mean concentration of serum Sm-C (10.1 +/- 3.0 nmol/l) was found in the NTI group and the highest in the hyperthyroid group (16.8 +/- 3.2): these concentrations differed significantly from the mean control level (12.2 +/- 2.2). In NTI patients the serum FT3 and T3 levels correlated significantly with the serum Sm-C levels (r = 0.63; p less than 0.001, r = 0.65; p less than 0.001, respectively). In hypothyroid patients there was a weak correlation between the serum FT3 and Sm-C levels (r = 0.36; p less than 0.05), but no correlations were found in hyperthyroid and healthy subjects. We conclude that the lowered Sm-C levels in NTI do not reflect a hypothyroid state, as normal Sm-C levels were found in hypothyroidism, and that impaired nutritional state of the patients is the most likely explanation for the association between Sm-C and FT3 (and T3) in NTI.

Regulation of insulin-like growth factor-binding protein-1 production in human granulosa-luteal cells

Human follicular fluid contains the insulin-like growth factor-binding protein (IGFBP-1) synthesized by ovarian granulosa cells. We studied the regulation of IGFBP-1 production by the granulosa-luteal cells from the hyperstimulated follicles of patients attending an in vitro fertilization program. The cells were first allowed to attach and recover from the hyperstimulation for 2 days. Then, a protein kinase-C activator, 12-O-tetradecanoyl phorbol-13-acetate (TPA), and adenylate cyclase activators, gonadotropins, FSH, hCG, cholera toxin, or prostaglandin E2 (PGE2) were added to the cells. The gonadotropins failed to increase IGFBP-1 production, whereas it was enhanced by TPA and to a lesser extent by cholera toxin and PGE2. The maximal response to TPA occurred at the concentration of 1.0 ng/mL, and the enhancing effect of TPA was detected at 24 h. PGE2 stimulated IGFBP-1 production; the lowest effective concentration was 10(-8) mol/L. The mean highest response was 4.3-fold and occurred at the PGE2 concentration of 10(-5) mol/L. The effect of PGE2 on IGFBP-1 production became detectable at 24 h, and it continued to increase up to 72 h. PGE2 also increased granulosa-luteal cell progesterone production in a dose- and time-dependent manner. Incorporation of [35S]methionine into immunoreactive IGFBP-1, as detected by sodium dodecyl sulfate-polyacrylamide electrophoresis and fluorography, was also increased by TPA. This suggests that TPA accelerated the synthesis of IGFBP-1. Our results indicate that the production of IGFBP-1 by human granulosa-luteal cells can be regulated both via protein kinase-C- and adenylate cyclase-dependent pathways.

Elevated serum levels of endometrial secretory protein PP14 in patients with advanced endometriosis. Suppression by treatment with danazol and high-dose medroxyprogesterone acetate

The circulating concentration of endometrial protein PP14 varied during the menstrual cycle in patients with endometriosis. The highest levels were found on days 1 to 4 of the cycle (176 +/- 123 micrograms/L; mean +/- SD), and the lowest on days 5 to 20 (44.1 +/- 29.7 micrograms/L). Rising levels were observed on days 21 to 30 (58.3 +/- 62.6 micrograms/L). On days 5 to 20 (i.e., during period of the lowest levels) patients with advanced endometriosis had higher PP14 levels (63.9 +/- 39.0 micrograms/L) than those with mild endometriosis (29.3 +/- 18.2 micrograms/L; p less than 0.01). Patients with mild endometriosis had slightly higher serum PP14 levels than apparently healthy control subjects (p less than 0.05), but overlapping of values between the two groups is remarkable. Conservative surgical elimination of endometriosis significantly decreased the serum PP14 levels. Treatment with danazol (600 mg/day), or with medroxyprogesterone acetate (100 mg/day) after laparoscopy also resulted in significant decreases in the serum PP14 concentration. After 6 months of treatment, conservative surgery in combination with danazol or with medroxyprogesterone acetate, yielded more pronounced declines in serum PP14 level than conservative surgery plus placebo. No significant difference was observed between the effects of danazol and medroxyprogesterone acetate. We conclude that endometriosis tissue contributes to the circulating PP14 level, and the decline in PP14 level during danazol and medroxyprogesterone acetate treatments reflects regression of intrauterine and ectopic endometrial tissues.

Time-resolved immunofluorometric assay for placental protein 14

A sandwich-type solid phase time-resolved immunofluorometric assay (IFMA) was developed for endometrial protein PP14 (placental protein 14). The assay utilizes affinity-purified polyclonal antibodies for coating the microtiter wells and for labelling with europium (III) chelate. Maintaining specificity, the 0.6 micrograms/l sensitivity of IFMA is over 25 times higher than that of RIA. The immunofluorometric method enables detection and accurate quantitation of PP14 in all those samples in which PP14 is undetectable by RIA. The method is suitable for quantitative measurement of low PP14 levels in serum of postmenopausal and fertile-aged women and men, as well as in follicular fluid. At 14-16 micrograms/l, which is the sensitivity of radioimmunoassay, the intra-assay variation of IFMA is 6.6% and inter-assay variation 11.4%. In postmenopausal women the PP14 levels are 12.7-56.7 micrograms/l, in fertile-aged women 13.7-113.4 micrograms/l, and in men 3.1-53.1 micrograms/l. The levels in preovulatory follicular fluid are 1.2-20.5 micrograms/l. It is concluded that PP14 IFMA is highly sensitive, accurate and suitable for measurement of protein levels undetectable by other currently available methods.

Low levels of low molecular weight insulin-like growth factor-binding protein in patients with polycystic ovarian disease

Insulin-like growth factors IGF-I and IGF-II are bound to specific binding proteins in serum. The lower mol. wt binding protein (IGF-BP) has been detected in various tissues, including secretory endometrium and preovulatory follicles of the ovary. This group studied the circulating levels of IGF-BP in the serum of 23 patients with polycystic ovarian disease (PCOD) and found that one-third of them have a subnormal level. In comparison with PCOD patients with a normal level, those with a subnormal level had a higher degree of obesity and a tendency to be more hirsute. They also had a higher serum insulin concentration and testosterone/sex hormone-binding globulin (SHBG) ratio, but lower serum SHBG concentration than those with a normal IGF-BP level. PCOD is the second abnormal clinical condition, after insulinoma, in which subnormal serum IGF-BP concentrations have been reported. The significance of low serum IGF-BP levels to pathophysiology of PCOD remains to be elucidated by studies on local interaction between IGF-BP and insulin in the polycystic ovary.

Human granulosa cells synthesize low molecular weight insulin-like growth factor-binding protein

Human follicular fluid contains insulin-like growth factor I (IGF-I) and its low molecular weight binding protein (IGF-BP). We studied the synthesis of IGF-BP by the granulosa cells obtained after ovarian hyperstimulation for in vitro fertilization. The granulosa cells were cultured for 72 hours in Ham's F-10 medium supplemented with 10% fetal calf serum (FCS). Samples of the culture medium were collected every 24 hours. The IGF-BP concentration in culture medium increased from 1.2 to 2.1 micrograms/l at 48 h and to 3.3 micrograms/l at 72 h. De novo synthesis of IGF-BP was shown by incorporation of labeled methionine into immunoreactive IGF-BP, as detected by SDS polyacrylamide electrophoresis (PAGE) and fluorography. Our results demonstrate synthesis of IGF-BP in the human ovary.

Dose-response characteristics for suppression of low molecular weight plasma insulin-like growth factor-binding protein by insulin

We previously demonstrated that supraphysiological insulin concentrations reduced the plasma 34K insulin-like growth factor-binding protein (IGF-BP) concentrations in humans. In this study we examined whether physiological changes in plasma insulin concentrations regulate IGF-BP and, if so, whether the regulation is influenced by race, glucose tolerance, or rate of glucose metabolism. For these purposes we 1) analyzed the relationship between fasting plasma insulin and IGF-BP concentrations in 2 racial groups (23 caucasians and 35 southwestern American Indians), 2) measured the response of plasma IGF-BP to oral glucose in 20 normal subjects, and 3) determined the dose-response characteristics of plasma IGF-BP to glucose and insulin in 23 normal subjects at 4 different insulin and glucose concentrations. The fasting plasma insulin concentration was inversely related to the plasma IGF-BP concentration in both the caucasian and Indian groups (P less than 0.0001). In the caucasian group the mean plasma IGF-BP concentration was higher [15 +/- 4 (+/- SE) micrograms/L] than in the Indian group (8 +/- 2 micrograms/L; P less than 0.05). This difference was independent of race and glucose tolerance, and it could be explained by lower plasma insulin concentrations in the caucasian (387 +/- 50 pmol/L) than in the Indian group (215 +/- 43 pmol/L; P less than 0.001). After oral glucose administration, the insulin concentration (423 +/- 72 pmol/L) was maximal 30 min after glucose treatment, and significant suppression of the IGF-BP concentration occurred at 90 min. Analysis of the dose-response curves revealed maximal suppression of IGF-BP at about 1150 pmol/L insulin, and half-maximal suppression at about 290 pmol/L. The plasma glucose concentration or the rate of glucose metabolism had no effect on the IGF-BP concentration. These data suggest that insulin is a major regulator of plasma IGF-BP concentrations under physiological conditions.

Prolonged exercise increases serum insulin-like growth factor-binding protein concentrations

We studied the response of serum 34K insulin-like growth factor-binding protein (IGF-BP) to two types of prolonged exercise. In the first study, 11 normal men performed cycle ergometer exercise, after an overnight fast, for 3 h at the intensity corresponding to 45-50% of their maximal aerobic power. After the exercise, the mean serum IGF-BP concentration was 4.9-fold higher than the baseline level (P less than 0.01), while the IGF-I concentration did not change. Resting for the same time period resulted in a 38% fall in the serum IGF-BP level (P less than 0.01). In the second study, 10 normal men and 8 type 1 diabetic men exercised, on the average, for 7.5 h in a 75-km cross-country ski race. The mean serum IGF-BP concentration increased 5.4-fold (P less than 0.01) in the normal men and 4.2-fold (P less than 0.01) in the diabetic men. The serum IGF-I concentration decreased by 19% and 21% in the normal and diabetic men, respectively (P less than 0.01). After completion of the ski race, the serum insulin and IGF-BP levels (r = -0.70; P less than 0.05), and serum IGF-I and IGF-BP levels (r = -0.72; P less than 0.05) were inversely correlated in the normal men. No such correlations were found in the diabetic men. We conclude that 1) long term exercise increases serum IGF-BP concentrations in both normal and type 1 diabetic men; and 2) the increases are inversely related to alterations in serum IGF-I and insulin concentrations in normal men. These data suggest that IGF-BP may be involved in regulation of the biological action of IGF-I during prolonged exercise.

Insulin-like growth factor (IGF-I) and its low molecular weight binding protein in human milk

Insulin-like growth factors (IGF-I and IGF-II) are mitogenic polypeptides bound in serum to specific binding proteins. This study reports the occurrence and concentrations of IGF-I and its low molecular weight IGF binding protein (IGF BP) in human milk and serum after delivery in 41 healthy women. The levels of IGF-I in milk declined between 4 and 92 hours postpartum from 49 +/- 17 micrograms/l to 29 +/- 27 micrograms/l (p less than 0.01). The level of IGF BP also declined from 165 +/- 80 micrograms/l to 97 +/- 70 micrograms/l (p less than 0.01), whereas the serum concentration of this protein remained unchanged. A positive correlation was observed between the individual levels of IGF-I and its binding protein in milk (r = 0.49, p less than 0.01), but no correlation was found between the individual levels of 34 kDa IGF BP in milk and serum. The relative abundance of IGF BP in the first milk compared to IGF-I is intriguing and its biologic significance remains to be clarified.

Different insulin-like growth factor binding species in human placenta and decidua

Previous studies demonstrated that human decidua secretes a 34K insulin-like growth factor binding protein (34K IGF-BP) earlier designated placental protein 12, whereas placenta contains IGF receptors and IGF mRNA. We studied binding of [125I]IGF-I to paired placental and decidual tissues using competitive binding, gel filtration, RIA, and cross-linking techniques, and compared the binding characteristics of these two tissues which are located in close proximity in vivo. The effect of decidual cytosols on [125I]IGF-I binding to placental membranes also was studied. Consistent with previous data the dominating binding species in placental membranes were IGF receptors. In contrast, the binding of [125I]IGF-I to decidual membranes was mainly due to binding species with mol wts of 34K and 39K. The 34K IGF-BP was more readily detected in decidual cytosols than in decidual membranes and little was detected in placental cytosols. Purified 34K IGF-BP as well as decidual cytosols inhibited [125I]IGF-I binding to placental receptors. The inhibitory effect of decidual cytosol on IGF receptor binding was linearly correlated to the decidual content of 34K IGF-BP. The results suggest that the decidual 34K IGF-BP might act as a local modulator of the IGF action at the interface between the decidua and the placenta.

Immunofluorometric demonstration and quantification of placental protein 5 in the absence of pregnancy

This time-resolved immunofluorometric assay (IFMA) developed for measurement of placental protein 5 (PP5) involves two antibodies: a monoclonal anti-PP5 antibody attached to a solid phase and an europium(III) chelate-labeled polyclonal anti-PP5 antibody as a tracer. The measuring range is 0.05-100 micrograms/L and the detection limit is 20 times lower than that of a PP5 radioimmunoassay (RIA) performed with the same polyclonal antiserum. By IFMA, PP5 could be detected and quantified in all plasma and serum samples of nonpregnant and pregnant individuals, whereas PP5 was undetectable by RIA in serum of healthy men and nonpregnant women. The mean concentration of PP5 in sera from men was 0.43 micrograms/L (SD 0.13, range 0.19-0.75, n = 47) and in sera from nonpregnant women 0.49 micrograms/L (SD 0.19, range 0.20-0.90, n = 41). PP5 concentrations in serum showed no systematic variation during the menstrual cycle. In serum samples from 60 pregnant women the results obtained by IFMA and RIA correlated well (r = 0.97).

Immunofluorometric demonstration and quantification of placental protein 5 in the absence of pregnancy

This time-resolved immunofluorometric assay (IFMA) developed for measurement of placental protein 5 (PP5) involves two antibodies: a monoclonal anti-PP5 antibody attached to a solid phase and an europium(III) chelate-labeled polyclonal anti-PP5 antibody as a tracer. The measuring range is 0.05-100 micrograms/L and the detection limit is 20 times lower than that of a PP5 radioimmunoassay (RIA) performed with the same polyclonal antiserum. By IFMA, PP5 could be detected and quantified in all plasma and serum samples of nonpregnant and pregnant individuals, whereas PP5 was undetectable by RIA in serum of healthy men and nonpregnant women. The mean concentration of PP5 in sera from men was 0.43 micrograms/L (SD 0.13, range 0.19-0.75, n = 47) and in sera from nonpregnant women 0.49 micrograms/L (SD 0.19, range 0.20-0.90, n = 41). PP5 concentrations in serum showed no systematic variation during the menstrual cycle. In serum samples from 60 pregnant women the results obtained by IFMA and RIA correlated well (r = 0.97).

Insulin-like growth factor (IGF) binding protein from human decidua inhibits the binding and biological action of IGF-I in cultured choriocarcinoma cells

The placenta expresses genes for insulin-like growth factors (IGFs) and possesses IGF-receptors, suggesting that placental growth is regulated by IGFs in an autocrine manner. We have previously shown that human decidua, but not placenta, synthesizes and secretes a 34 K IGF-binding protein (34 K IGF-BP) called placental protein 12. We now used human choriocarcinoma JEG-3 cell monolayer cultures and recombinant (Thr59)IGF-I as a model to study whether the decidual 34 K IGF-BP is able to modulate the receptor binding and biological activity of IGFs in trophoblasts. JEG-3 cells, which possess type I IGF receptors, were unable to produce IGF-BPs. Purified 34 K IGF-BP specifically bound [125I]iodo-(Thr59)IGF-I. Multiplication-stimulating activity had 2.5% the potency of (Thr59)IGF-I, and insulin had no effect on the binding of [125I] iodo-(Thr59)IGF-I. 34 K IGF-BP inhibited the binding of [125I] iodo-(Thr59)IGF-I to JEG-3 monolayers in a concentration-dependent manner by forming with the tracer a soluble complex that could not bind to the cell surface as demonstrated by competitive binding and cross-linking experiments. After incubating the cell monolayers with [125I]iodo-(Thr59)IGF-I in the presence of purified binding protein, followed by cross-linking, no affinity labeled bands were seen on autoradiography. In contrast, an intensely labeled band at 40 K was detected when the incubation medium was analyzed, suggesting that (Thr59)IGF-I and 34 K IGF-BP formed a complex in a 1:1 molar ratio. Also, 34 K IGF-BP inhibited both basal and IGF-I-stimulated uptake of alpha-[3H]aminoisobutyric acid in JEG-3 cells. RNA analysis revealed that IGF-II is expressed in JEG-3 cells. We conclude that decidual 34 K IGF-BP inhibits the cellular binding and biological action of IGFs in JEG-3 cells. Our data show that JEG-3 cells represent a cell type that can produce IGF, but not IGF-BPs. These cells may thus provide a useful model system for a better understanding of autocrine growth regulation mediated by the IGFs.