Insulin-like growth factor I in fetal serum obtained by cordocentesis is correlated with intrauterine growth retardation

We examined whether insulin-like growth factor-I (IGF-I) and one of its binding proteins (IGFBP-1) in fetal serum obtained by cordocentesis is correlated with intrauterine growth retardation (IUGR) and weight estimation by ultrasound. Cordocentesis sera from 27 fetuses suspected of having IUGR were analysed for IGF-I and IGFBP-1 by radioimmunoassay. The results showed that IGF-I concentrations were correlated significantly with birth weight (P < 0.001) and placenta weight (P < 0.05). Mean fetal concentrations of IGF-I were 38 +/- 18 microg/l. In patients (n = 11) with a weight deviation at delivery <-33%, IGF-I concentrations were 24.1 +/- 13.2 microg/l. IGFBP-1 was inversely correlated with birth weight (P < 0.006) and concentrations of IGF-I. Mean plasma concentrations of IGFBP-1 were 234.2 +/- 161.4 microg/l. Furthermore, IGF-I concentrations were correlated with the weight deviation estimated by ultrasonography at the time of cordocentesis (P < 0.007), as well as with the weight deviation at delivery (P < 0.0001). The actual weight deviation at delivery was correlated more strongly with fetal IGF-I concentrations than with the estimated weight deviation at cordocentesis. The lowest concentrations of IGF-I were found in patients with a weight deviation <-33%. Very low concentrations of IGF-I are thus associated with IUGR, indicating that IGF-I measured in fetal serum may increase the predictive value of ultrasonographic weight estimation.      

Prenatal exposure to excess testosterone modifies the developmental trajectory of the insulin-like growth factor system in female sheep

Experimental elevation of maternal testosterone (T) from 30 to 90 days of gestation leads to intrauterine growth retardation (IUGR) and increased prepubertal growth rate in female lambs. This study tested the hypothesis that prenatal T treatment during mid-gestation alters the trajectory of the fetal insulin-like growth factor (IGF)–insulin-like growth factor binding protein (IGFBP) system to promote IUGR and subsequent postnatal catch-up growth in female lambs. Plasma IGF-I and IGFBPs were measured by radioimmunoassay and Western ligand blot, respectively, on 65, 90 and 140 days (d) of gestation, at birth, ∼5 months (prepubertal, the catch-up growth period), and ∼9.5 months (postpubertal). Northern blot analysis was used to measure hepatic mRNA content of IGF system components during fetal stages. At fetal 65 d, plasma protein and hepatic mRNA content of IGFBP-1, an inhibitor of IGF bioactivity, was elevated in prenatal T-treated fetuses although body weight did not differ. There was a transient increase in plasma IGF-I and IGFBP-3 concentrations at fetal 90 d in prenatal T-treated fetuses. Hepatic IGF-I mRNA and plasma IGFBP-3 content were reduced by 140 d when body weight was reduced in prenatal T-treated fetuses. Plasma IGFBP-2 content was significantly reduced in prenatal T-treated newborns, but by 4 months these females had significantly higher circulating IGF-I and IGFBP-3 concentrations and faster growth rates than control females. After puberty, plasma IGF-I remained elevated in prenatal T-treated females. These findings provide evidence that prenatal T excess programmes the developmental trajectory of the IGF/IGFBP system in female sheep to reduce IGF bioavailability during IUGR and increase IGF bioavailability during prepubertal catch-up growth.     

Hepatocyte growth factor concentration in the early second-trimester amniotic fluid does not predict fetal growth at birth.

The purpose of this study was to evaluate whether hepatocyte growth factor (HGF) concentrations in the early second-trimester amniotic fluid predict fetal growth at birth. HGF and insulin-like growth factor-I (IGF-I) concentrations in the early second-trimester amniotic fluid were measured in 12 pregnancies with small for gestational age (SGA) infants, 84 pregnancies with appropriate for gestational age (AGA) infants, and eight pregnancies with large for gestational age (LGA) infants. HGF concentrations were measured from the early second-trimester amniotic fluid samples using an enzyme-linked immunosorbent assay. IGF-I concentrations were measured from the early second-trimester amniotic fluid samples using an immunoradiometric assay. Maternal age in AGA group (34.2 +/- 5.5 years) was significantly lower than in SGA (37.9 +/- 3.0 years) and LGA (37.6 +/- 3.3 years) groups (P < 0.05). There were no significant differences for parity or gestational age at amniocentesis among the groups. There were significant differences for birth age, birth weight, neonatal height, and placental weight among the groups (P < 0.05). HGF concentrations in SGA, AGA and LGA groups were 16.9 +/- 6.6, 16.7 +/- 9.0 and 20.2 +/- 14.8 ng/ml respectively (not significant). There was no correlation between amniotic fluid HGF concentrations and birth weight, height or placental weight. There were also no significant differences for amniotic fluid IGF-I concentrations among the three groups. These results suggest that differences in HGF concentrations in the early second-trimester amniotic fluid do not predict fetal growth at birth. Further study is needed to clarify the role of high HGF concentrations in early second-trimester amniotic fluid during pregnancy.     

Insulin-like growth factors and their binding proteins in the venous effluents of ovary and adrenal gland in severely hyperandrogenic women

Insulin and insulin-like growth factors (IGF) are thought to play an important role in the pathogenesis of excessive androgen production. To explore this question further we measured the concentrations of IGF-I and -II and their binding proteins (IGFBP-1 and-3) in adrenal and ovarian vein samples of severely hyperandrogenic women (serum testosterone > 5 nmol/l) collected as part of their diagnostic work-up. The concentration of IGF-II was slightly but not significantly higher in the ovarian vein than in the adrenal and peripheral veins. The concentrations of IGF-I and IGFBP were identical in both the adrenal and ovarian veins and did not differ from those in the peripheral circulation. The concentration of IGFBP-1 was negatively correlated (r = -0.60, P > 0.05) with insulin and IGFBP-3 showed a strong positive correlation with IGF-1 (r = 0.90, P > 0.01). These results indicate that neither the ovary nor the adrenal gland contributes significantly to the circulating pool of IGF or their binding proteins in severely hyperandrogenic subjects. Hyperinsulinaemia is associated with low circulating IGFBP-1 concentrations and IGFBP-3 seems to be an excellent indicator of the peripheral IGF-I concentration. The concentrations of IGF-I suggested decreased somatotrophic activity in these obese, hyperinsulinaemic subjects.      

IGF-I与宫内发育迟缓及其结合蛋白的关系

目的：检测宫内发育迟缓（IUGR）儿脐血胰岛素样生长因子-I（IGF-I）、胰岛素样生长因子结合蛋白-3（IGFBP-3）水平,分析这些指标的变化程度与胎儿期生长的关系。方法：将86例脐血标本分为IUGR（即小于胎龄儿）组和适于胎龄儿（AGA）组。采用放射免疫分析（RIA）测定IGF-I水平,免疫放射分析（IR-MA）测定IGFBP-3水平。两组间比较用t检验,两变量之间的关系采用相关回归分析。结果：与AGA组相比,IUGR组脐血IGF-I和IGFBP-3水平显著降低（P均〈0.01）;IGF-I、IGFBP-3均随胎龄及出生体重增加而增加（P均〈0.01）;IGFBP-3与IGF-I呈正相关（P〈0.01）。结论：脐血IGF-I和IGFBP-3的含量可作为判断新生儿生长发育程度的一项客观指标。     

Human placental growth hormone is increased in maternal serum at 20 weeks of gestation in pregnancies with large-for-gestational-age babies

To investigate the relationship between maternal serum concentrations of placental growth hormone (GH-V), insulin-like growth factor (IGF)-1 and 2, IGF binding proteins (IGFBP)-1 and 3 and birth weight in appropriate-for-gestational-age (AGA), large-for-gestational-age (LGA) and small-for-gestational-age (SGA) cases in a nested case-control study. Maternal serum samples were selected from the Screening for Pregnancy Endpoints (SCOPE) biobank in Auckland, New Zealand. Serum hormone concentrations were determined by ELISA. We found that maternal serum GH-V concentrations at 20 weeks of gestation in LGA pregnancies were significantly higher than in AGA and SGA pregnancies. Maternal GH-V concentrations were positively correlated to birth weights and customized birth weight centiles, while IGFBP-1 concentrations were inversely related to birth weights and customized birth weight centiles. Our findings suggest that maternal serum GH-V and IGFBP-1 concentrations at 20 weeks' gestation are associated with fetal growth.     

宫内生长迟缓胎儿脐血IGF-Ⅰ及IGFBP-3水平观察

目的：探讨新生儿脐血中胰岛素样生长因子-I（IGF-I）和胰岛素样生长因子结合蛋白-3（IGFBP-3）水平与胎儿宫内生长发育的关系。方法：采用放射免疫分析,分别对出生时体重正常新生儿与宫内生长迟缓的低体重新生儿脐血的IGF-I及IGFBP-3水平进行检测。结果：宫内发育迟缓组新生儿脐血的IGF-I及IGFBP-3的含量明显低于正常对照组（P〈0.01）,有显著差异性。结论：：IGF-I和IGFBP-3与胎儿宫内生长发育密切相关,对胎儿的宫内生长发育起着重要的调节作用。     

Iron metabolism in monochorionic twin pregnancies in relation to twin--twin transfusion syndrome

Fetal iron metabolism was investigated in monochorionic (MC) twin pregnancies in relation to twin-twin transfusion syndrome (TTTS). Matched maternal and fetal blood samples were obtained both in utero and at birth from MC twins with TTTS (n = 23) and without TTTS (n = 18). In a second group of 30 twin pairs (15 with and 15 without TTTS), liver iron content was assessed by using archived paraffin wax-embedded blocks. Serum ferritin was determined by radioimmunoassay and values are given as gestation independent Z-scores and expressed as mean with 95% confidence intervals. Ferritin concentrations in the recipients were higher than in the donors both in utero (P < 0.01) and at birth (P < 0.01). Fetal serum ferritin in non-TTTS twins were similar to the recipient twins but higher than the donor twins (P < 0.05). A significant association was found between ferritin concentrations, the total red blood cell count and haemoglobin in the TTTS twin pairs (P < 0.01) and the non-TTTS twins as a group (P < 0.01). The total stainable liver iron was comparable between twin pairs in the TTTS and non-TTTS groups. This study fails to provide evidence of iron overload in the recipient and depletion in the donor twins and, thereby, questions the validity of the conventional theory of inter-twin transfusion as the cause of TTTS.     

Erythropoietin in monochorionic twin pregnancies in relation to twin--twin transfusion syndrome

Fetal erythropoietin (Epo) concentrations were studied in monochorionic (MC) twin pregnancies in relation to twin-twin transfusion syndrome (TTTS). Matched maternal and fetal blood samples in utero were obtained from MC twins with TTTS (n = 15) and without TTTS (n = 6). In a second group of five sets of twin pairs with or without TTTS, immunolocalization of Epo was performed in archived paraffin wax sections of liver and kidney collected at autopsy. Epo was measured using a chemiluminescence assay and expressed as gestation independent Z-scores and given as mean +/- 95% confidence intervals (CI). Fetal Epo concentrations in utero were higher in MC twins with TTTS than the non-TTTS as a group (P < 0.001). There was no difference in Epo concentrations between TTTS and non-TTTS twin pairs. Fetal Epo concentrations were correlated with pO(2) in the recipient (r = 0.64; P < 0.01), donor (r = 0.64; P < 0.01) and control twins (r = 0.76; P < 0.01). Immunostaining of the fetal kidney localized Epo primarily to the cytoplasm of the proximal convoluted tubules. The intensity of staining in the kidney and liver was comparable between TTTS and non-TTTS twin pairs. Fetal Epo concentrations were higher in the TTTS than non-TTTS twin pairs and were correlated with the degree of hypoxaemia. However, Epo concentrations were comparable between donor and recipient twins, perhaps due to similar production rather than inter-twin transfusion of blood.     

脐血中胰岛素、胰岛素样生长因子-I及胰岛素样生长因子结合蛋白-2与胎儿生长受限的关系

目的探讨脐血中胰岛素、胰岛素样生长因子-I及胰岛素样生长因子结合蛋白-2的水平与胎儿生长受限的关系及意义。方法收集2011年7月～2013年5月在本院分娩的单胎足月正常妊娠（无产科并发症）孕妇及其新生儿各120例,根据出生体重将新生儿分为小于胎龄儿（SGA）组、适于胎龄儿（AGA）2组。胎儿娩出后即抽脐静脉血5ml,标本收集后用高效液相色谱法测定脐血中胰岛素、胰岛素样生长因子-I及胰岛素样生长因子结合蛋白-2的水平。结果SGA组脐带血清胰岛素、胰岛素样生长因子-I水平明显低于AGA组,差异均有统计学意义（P〈0.01）;SGA组脐血胰岛素样生长因子结合蛋白-2水平明显高于AGA、组,差异有统计学意义（P〈0.01）;脐血中胰岛素样生长因子-I与胰岛素水平呈正相关关系,而与胰岛素样生长因子结合蛋白-2呈负相关关系;脐血胰岛素、胰岛素样生长因子-I水平与新生儿出生体重呈正相关关系,而胰岛素样生长因子结合蛋白2与之呈负相关关系。结论脐血胰岛素、胰岛素样生长因子-I、胰岛素样生长因子结合蛋白2与胎儿生长受限的发生密切相关。     

Effects of insulin-like growth factors and insulin-like growth factor binding protein-2 on the in vitro proliferation of peripheral blood mononuclear cells

Increasing evidence has implicated that insulin-like growth factors (IGFs), polypeptides structurally related to proinsulin, are involved in the function and development of the immune system. To probe the relevance of IGF binding protein 2 (IGFBP-2) in T-cell activation and proliferation, we studied the role of IGFBP-2 in anti-CD3 monoclonal antibody (mAb)-activated peripheral blood mononuclear cells (PBMCs). Secretion of IGF-I, IGF-II, and IGFBP-2 by PBMCs from healthy adult donors was determined by radioimmunoassays (RIAs). The PBMC proliferative response after stimulation with anti-CD3 mAb and exposure to increasing concentrations of IGF-I, IGF-II, IGFBP-2, and anti-IGFBP-2 were determined by bromodeoxyuridine enzyme-linked immunosorbent assay. Observations were tested for significance by paired t-tests. We demonstrate an increase in IGFBP-2 secretion associated with both activation of PBMC by anti-CD3 mAb and increasing cell density. Incubation with exogenous IGFBP-2 increased the proliferation of PBMCs, whereas anti-IGFBP-2 had an antiproliferative effect on PBMCs that was reversed by simultaneous exposure to IGFBP-2. The stimulatory activity of IGFBP-2 (1-10 ng/ml) on anti-CD3 mAb-activated PBMCs was similar to that of IGF-I and IGF-II (1-100 ng/ml), with the mean increase in PBMC proliferative response ranging between 150% and 160% for IGFBP-2 (p = 0.03), 150% and 170% for IGF-I (p < 0.01), 133%-161% for IGF-II (p < 0.01), and 157% and 175% for IGF-I + IGF-II (p < 0.01). Thus, our data strongly suggest a role for IGFBP-2 as a local growth factor contributing to the proliferation and activation of mononuclear cells.     

Insulin-like growth factor binding protein concentration and post- translational modification in embryological fluid

Levels of proteolytic activity directed against insulin-like growth factor binding protein 3 (IGFBP-3) and the distribution of phosphorylated isoforms of IGFBP-1 were assessed in matched sample sets of maternal serum, coelomic fluid and amniotic fluid from 21 pregnancies at 6-12 weeks gestation. In addition, concentrations of immunoreactive IGFBP-1 to -3, insulin-like growth factor (IGF)-I and - II were determined in all three compartments in 21 pregnancies, and in coelomic fluid and maternal serum in 58 pregnancies. IGF-I concentrations were highest in maternal serum and similarly low in coelomic and amniotic fluid. IGF-II concentrations were also highest in maternal serum but easily detectable in coelomic fluid where concentrations showed a significant correlation with gestational age. IGFBP-1 concentrations were higher in coelomic fluid than in either maternal serum or amniotic fluid and showed a significant correlation with gestational age in this compartment. Analysis of IGFBP-1 phosphoforms showed clear differences in phosphorylation of IGFBP-1 between groups with maternal serum containing predominantly the phosphorylated forms and coelomic fluid almost exclusively the non- phosphorylated form. First trimester amniotic fluid IGFBP-1 was barely detectable and appeared non-phosphorylated. These findings suggest that the high IGF-II concentrations and lack of inhibitory phosphoforms of IGFBP-1 in coelomic fluid could potentially enhance mitogenic activity in the early human gestational sac. IGFBP-2 concentrations were high in coelomic fluid compared with maternal serum whereas coelomic fluid IGFBP-3 concentrations were intermediate, easily detectable and correlated strongly with gestational age. Protease activity was far less in coelomic fluid than in matched maternal serum samples. Marked differences in both concentrations and post-translational modification of IGFBPs in maternal serum compared with embryonic fluid suggest different regulatory pathways.      

The role of insulin-like growth factor binding protein-1 phosphoisoforms in pregnancies with impaired placental function identified by doppler ultrasound.

This study was performed to investigate the hypothesis that insulin-like growth factor binding protein-1 (IGFBP-1) is involved in the pathogenesis of trophoblast invasion and impaired placentation in human pregnancy. The role of total and non-phosphorylated IGFBP-1 in women with fetal growth restriction and in high risk pregnancies identified by uterine artery Doppler ultrasound screening was examined. This was a prospective study of women booked for antenatal care having second trimester anomaly scans and Doppler screening between 22-26 weeks gestation. Women were divided into three groups and compared: normal uterine artery Doppler and normal fetal growth (control group, n = 10); abnormal Doppler and normal fetal growth [bilateral uterine artery notches (BN; n = 16); abnormal Doppler and intrauterine growth restriction (IUGR; n = 8)]. Maternal serum was collected, stored and assayed simultaneously for total and non-phosphorylated IGFBP-1. There was elevated total and non-phosphorylated IGFBP-1 (mean 44.99 +/- 12.19 and 29.61 +/- 10.38 microg/l respectively) in the IUGR group compared with controls (mean 17.96 +/- 3.24 and 12.18 +/- 1.55 microg/l, P < 0.05). This finding suggests that the various IGFBP-1 isoforms, the degree of phosphorylation and the ratios of these different forms locally may be important during trophoblast invasion and may be implicated in clinical manifestations of impaired placentation later in the second trimester.     

Expression of insulin-like growth factor in the placenta of intrauterine growth-retarded human fetuses

Many cases of intrauterine growth retardation (IUGR) are the result of placental and fetal tissue insufficiency. Insulin-like growth factor-I (IGF-I) is known to play a role in placental and fetal growth. An immunocytochemical study was performed to localize IGF-I peptides in human placenta and umbilical cords of normal (n = 3) and IUGR (n = 3) fetuses. The peripartum fetal conditions were evaluated as well. Immunoreactive IGF-I was detected in the cytotrophoblast, syncytiotrophoblast, amnion, endothelial cells of fetal capillaries and in the decidua in both normal and IUGR placental tissue. A more robust immunostaining and increased numbers of positively stained cells were found in the decidua of IUGR placenta (p < 0.001). Intense immunostaining was also found in endothelial cells, smooth muscle cells and fibroblasts of the umbilical vein. IGF-I immunoreactivity was also present in stroma (Hofbauer cells and/or fibroblasts) of IUGR villi. Our results indicate that expression of IGF-I is high in specific sites in placenta and umbilical cords, which indicates a paracrine and/or endocrine function. The increased expression of IGF-I in placenta of IUGR fetuses indicates its involvement in restoring normal growth by means of a positive feed-back mechanism.     

Nicotine-induced prenatal overexposure to maternal glucocorticoid and intrauterine growth retardation in rat

Overexposure to glucocorticoid during fetal development can result in intrauterine growth retardation (IUGR) as well as other diseases after birth. The purpose of this study is to investigate the possibility of glucocorticoid disturbance-mediated nicotine-induced IUGR after chronic prenatal exposure. Nicotine at 1.0mg/kg twice a day was administered subcutaneously to pregnant rats from gestational day (GD) 8 to GD 15 (mid-gestation) or GD 21 (late-gestation). Placental weights and fetal developmental parameters were recorded. Corticosterone levels were determined by radioimmunoassay. The mRNA expressions of adrenal steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side chain cleavage (P450scc) and placental 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD-2) were determined using real-time quantitative RT-PCR. The results showed that prenatal chronic nicotine exposure causes IUGR in rats (P<0.01); in response to nicotine exposure, maternal serum corticosterone levels were elevated at mid- and late-gestations (P<0.05); mRNA expressions of StAR and P450scc increased in maternal adrenals (P<0.05 or 0.01) but decreased in fetal adrenals (P=0.16 or 0.11). Furthermore, the mRNA levels of placental 11 beta-HSD-2 were reduced at mid- and late-gestations (P<0.05). These results suggest that nicotine-induced IUGR is associated with the disturbances of glucocorticoid homeostasis in maternal and fetal rats. A possible underlying mechanism is that long term nicotine administration leads to fetal overexposure to maternal glucocorticoid by the combined effect of increased maternal glucocorticoid level and impaired placental barrier to it, all of which eventually leads to the fetal adrenocortical dysfunction and IUGR.     

Antenatal dexamethasone therapy does not affect circulating concentrations of insulin-like growth factor binding protein-1

In animals, dexamethasone administration during pregnancy leads to fetal growth restriction due to enhanced expression of insulin-like growth factor binding protein-1 (IGFBP-1). In humans, there is also a significant inverse correlation between maternal and fetal concentrations of IGFBP-1 and birth weight. During pregnancy, maternal IGFBP-1 is derived from the decidualized endometrium. We have studied the effect of dexamethasone on circulating concentrations of IGFBP-1 in 12 pregnant women who received dexamethasone therapy for fetal lung maturation in anticipation of premature delivery before 34 completed weeks of gestation. Blood samples were collected before dexamethasone administration, at 24 h and 48 h after the course of dexamethasone, and within 24 h of delivery, for the measurement of IGFBP-1. There was no significant change in plasma IGFBP-1 concentrations at 24 and 48 h following dexamethasone therapy, and at delivery (P = 0.666, 0.307 and 0.398, respectively). Therefore, antenatal dexamethasone therapy does not influence decidual synthesis of IGFBP-1.      

母血及脐血中抵抗素水平与胎儿出生体重关系的研究

目的探讨母血及脐血抵抗素水平与胎儿出生体重的关系。方法采用酶联免疫吸附法检测14例分娩正常出生体重儿组（AGA组）、14例高出生体重儿组（LGA组）及14例低出生体重儿组（SGA组）母血及脐血血清抵抗素水平。结果（1）AGA组、LGA组、SGA组母血抵抗素水平分别为10.51±1.64、9.26±1.28、12.77±2.90μg/L,脐血抵抗素水平分别为20.43±1.78、18.63±1.70、24.41±4.80μg/L;（2）LGA组与AGA组比较,母血与脐血抵抗素水平的差异均有显著性（均P〈0.05）,SGA组与AGA组比较,母血与脐血抵抗素水平的差异也均有显著性（均P〈0.05）;（3）脐血与母血抵抗素水平成正相关（r=0.869,P〈0.05）;（4）母血与脐血抵抗素水平与胎儿出生体重均成负相关（r=-0.662,P〈0.05：r=-0.678,P〈0.05）。结论抵抗素水平的变化可能在胎儿出生体重的调节中起重要作用。     

Down-regulation of placental transport of amino acids precedes the development of intrauterine growth restriction in rats fed a low protein diet

Intrauterine growth restriction (IUGR) represents an important risk factor for perinatal complications and for adult disease. IUGR is associated with a down-regulation of placental amino acid transporters; however, whether these changes are primary events directly contributing to IUGR or a secondary consequence is unknown. We investigated the time course of changes in placental and fetal growth, placental nutrient transport in vivo and the expression of placental nutrient transporters in pregnant rats subjected to protein malnutrition, a model for IUGR. Pregnant rats were given either a low protein (LP) diet ( n = 64) or an isocaloric control diet ( n = 66) throughout pregnancy. Maternal insulin, leptin and IGF-I levels decreased, whereas maternal amino acid concentrations increased moderately in response to the LP diet. Fetal and placental weights in the LP group were unaltered compared to control diet at gestational day (GD) 15, 18 and 19 but significantly reduced at GD 21. Placental system A transport activity was reduced at GD 19 and 21 in response to a low protein diet. Placental protein expression of SNAT2 was decreased at GD 21. In conclusion, placental amino acid transport is down-regulated prior to the development of IUGR, suggesting that these placental transport changes are a cause, rather than a consequence, of IUGR. Reduced maternal levels of insulin, leptin and IGF-1 may link maternal protein malnutrition to reduced fetal growth by down-regulation of key placental amino acid transporters.     

Secretion of insulin-like growth factor (IGF)-I and -II and IGF binding proteins (IGFBPs) in fetal stromal-vascular (S-V) cell cultures obtained before and after the onset of adipogenesis in vivo

The present study examined the influence of dexamethasone (DEX) treatment on preadipocyte differentiation and insulin-like growth factor binding protein (IGFBP) secretion in stromal-vascular (S-V) cell cultures established from subcutaneous adipose tissue obtained from nine 75 day and four 50 day pig fetuses. Cultures of S-V cells from four young pigs (5-7 days old) were also studied. Each fetal S-V cell culture represented 1 pool of S-V cells/dam. Cultures were seeded and plated in 10% FBS from day 0-3 and treated with insulin (ITS) + 10 nM DEX from day 3-6 (late DEX treatment). Alternatively, cultures were seeded and plated in 10% FBS + 80 nM DEX from day 0-3 and treated with insulin alone from day 3-6 (early DEX treatment). Conditioned media was collected on day 6 of culture after 3 days of conditioning, and prepared for subsequent 125I-IGF-I ligand blot analysis for IGFBPs and RIA for IGF-I and IGF-II. Early and late DEX increased (P<0.05) preadipocyte (AD-3+) recruitment but only early DEX increased preadipocyte differentiation (lipid + and C/EBP alpha+) by day 6 in S-V cultures from 75 day fetuses. Levels of IGFBP-2, IGFBP-4, IGF-I and IGF-II in media conditioned by 75 day fetal S-V cultures were not influenced by late DEX. However, late DEX reduced levels of 29 kDa IGFBPs and markedly increased (P<0.05) IGFBP-3 levels in 75 day S-V media. Late DEX also markedly increased (P<0.05) IGFBP-3 levels in 50 day S-V media but had little influence on other IGFBPs. Early DEX treatment increased (P<0.05) IGFBP-4 levels in 75 day S-V media but had little to no influence on levels of IGF-I, IGF-II and other IGFBPs. These studies indicate that IGFBP-4 may regulate local metabolism during preadipocyte differentiation, whereas IGFBP-3 may antagonize preadipocyte differentiation by targeting IGF-I away from differentiating cells and towards growing cells.