The pathophysiology of the insulin-like growth factor axis in fetal growth failure: a basis for programming by undernutrition?

Regulation of placental amino acid transport in health and disease

Abnormal fetal growth, i.e., intrauterine growth restriction (IUGR) or fetal growth restriction (FGR) and fetal overgrowth, is associated with increased perinatal morbidity and mortality and is strongly linked to the development of metabolic and cardiovascular disease in childhood and later in life. Emerging evidence suggests that changes in placental amino acid transport may contribute to abnormal fetal growth. This review is focused on amino acid transport in the human placenta, however, relevant animal models will be discussed to add mechanistic insights. At least 25 distinct amino acid transporters with different characteristics and substrate preferences have been identified in the human placenta. Of these, System A, transporting neutral nonessential amino acids, and System L, mediating the transport of essential amino acids, have been studied in some detail. Importantly, decreased placental Systems A and L transporter activity is strongly associated with IUGR and increased placental activity of these two amino acid transporters has been linked to fetal overgrowth in human pregnancy. An array of factors in the maternal circulation, including insulin, IGF-1, and adiponectin, and placental signaling pathways such as mTOR, have been identified as key regulators of placental Systems A and L. Studies using trophoblast-specific gene targeting in mice have provided compelling evidence that changes in placental Systems A and L are mechanistically linked to altered fetal growth. It is possible that targeting specific placental amino acid transporters or their upstream regulators represents a novel intervention to alleviate the short- and long-term consequences of abnormal fetal growth in the future.

Birth weight, adult body size, and risk of colorectal cancer

BACKGROUND

Evidence suggests that birth weight may be associated with colorectal cancer (CRC) risk later in life. Whether the association is mediated by adult body size remains unexamined.

METHOD

Cox proportional hazards models (Hazard Ratio (HR) and 95 % Confidence Intervals (CI)) were used to evaluate the association between self-reported birth weight (<6 lbs, 6-<8 lbs, ≥8 lbs) and CRC risk among 70,397 postmenopausal women from the Women's Health Initiative. Further, we assessed whether this association was mediated by adult body size using multiple mediation analyses.

RESULTS

Compared with birth weights of 6-< 8 lbs, birth weight ≥ 8 lbs was associated with higher CRC risk in postmenopausal women (HR = 1.31, 95 % CI 1.16-1.48). This association was significantly mediated by adult height (proportion mediated =11.4 %), weight (11.2 %), waist circumference (10.9 %), and body mass index at baseline (4.0 %). The joint effect of adult height and weight explained 21.6 % of this positive association.

CONCLUSION

Our data support the hypothesis that the intrauterine environment and fetal development may be related to the risk of developing CRC later in life. While adult body size partially explains this association, further investigation is required to identify other factors that mediate the link between birth weight and CRC.

Complex, coordinated and highly regulated changes in placental signaling and nutrient transport capacity in IUGR

The most common cause of intrauterine growth restriction (IUGR) in the developed world is placental insufficiency, a concept often used synonymously with reduced utero-placental and umbilical blood flows. However, placental insufficiency and IUGR are associated with complex, coordinated and highly regulated changes in placental signaling and nutrient transport including inhibition of insulin and mTOR signaling and down-regulation of specific amino acid transporters, Na+/K+-ATPase, the Na+/H+-exchanger, folate and lactate transporters. In contrast, placental glucose transport capacity is unaltered and Ca2+-ATPase activity and the expression of proteins involved in placental lipid transport are increased in IUGR. These findings are not entirely consistent with the traditional view that the placenta is dysfunctional in IUGR, but rather suggest that the placenta adapts to reduce fetal growth in response to an inability of the mother to allocate resources to the fetus. This new model has implications for the understanding of the mechanisms underpinning IUGR and for the development of intervention strategies.

Novel roles of mechanistic target of rapamycin signaling in regulating fetal growth†

Mechanistic target of rapamycin (mTOR) signaling functions as a central regulator of cellular metabolism, growth, and survival in response to hormones, growth factors, nutrients, energy, and stress signals. Mechanistic TOR is therefore critical for the growth of most fetal organs, and global mTOR deletion is embryonic lethal. This review discusses emerging evidence suggesting that mTOR signaling also has a role as a critical hub in the overall homeostatic control of fetal growth, adjusting the fetal growth trajectory according to the ability of the maternal supply line to support fetal growth. In the fetus, liver mTOR governs the secretion and phosphorylation of insulin-like growth factor binding protein 1 (IGFBP-1) thereby controlling the bioavailability of insulin-like growth factors (IGF-I and IGF-II), which function as important growth hormones during fetal life. In the placenta, mTOR responds to a large number of growth-related signals, including amino acids, glucose, oxygen, folate, and growth factors, to regulate trophoblast mitochondrial respiration, nutrient transport, and protein synthesis, thereby influencing fetal growth. In the maternal compartment, mTOR is an integral part of a decidual nutrient sensor which links oxygen and nutrient availability to the phosphorylation of IGFBP-1 with preferential effects on the bioavailability of IGF-I in the maternal-fetal interface and in the maternal circulation. These new roles of mTOR signaling in the regulation fetal growth will help us better understand the molecular underpinnings of abnormal fetal growth, such as intrauterine growth restriction and fetal overgrowth, and may represent novel avenues for diagnostics and intervention in important pregnancy complications.

Maternal exercise in rats upregulates the placental insulin-like growth factor system with diet- and sex-specific responses: minimal effects in mothers born growth restricted

KEY POINTS

The placental insulin-like growth factor (IGF) system is critical for normal fetoplacental growth, which is dysregulated following several pregnancy perturbations including uteroplacental insufficiency and maternal obesity. We report that the IGF system was altered in placentae of mothers born growth restricted compared to normal birth weight mothers, with maternal diet- and fetal sex-specific responses. Additionally, we report increased body weight and plasma IGF1 concentrations in fetuses from chow-fed normal birth weight mothers that exercised prior to and continued during pregnancy compared to sedentary mothers. Exercise initiated during pregnancy, on the other hand, resulted in placental morphological alterations and increased IGF1 and IGF1R protein expression, which may in part be modulated by reduced Let 7f-1 miRNA abundance. Growth restriction of mothers before birth and exercise differentially regulate the placental IGF system with diet- and sex-specific responses, probably as a means to improve fetoplacental growth and development, and hence neonatal survival. This increased neonatal survival may prevent adult disease onset.

ABSTRACT

The insulin-like growth factor (IGF) system regulates fetoplacental growth and plays a role in disease programming. Dysregulation of the IGF system is implicated in several pregnancy perturbations associated with altered fetal growth, including intrauterine growth restriction and maternal obesity. Limited human studies have demonstrated that maternal exercise enhances fetoplacental growth and decreases cord IGF ligands, which may restore the placental IGF system in complicated pregnancies. This study investigated the impact maternal exercise has on the placental IGF system in placentae from mothers born growth restricted and if these outcomes are dependent on maternal diet or fetal sex. Uteroplacental insufficiency (Restricted) or sham (Control) surgery was induced on embryonic day (E) 18 in Wistar-Kyoto rats. F1 offspring were fed a chow or high-fat diet from weaning, and at 16 weeks were randomly allocated an exercise protocol: Sedentary, Exercised prior to and during pregnancy (Exercise), or Exercised during pregnancy only (PregEx). Females were mated (20 weeks) with placentae associated with F2 fetuses collected at E20. The placental IGF system mRNA abundance and placental morphology was altered in mothers born growth restricted. Exercise increased fetal weight and Control plasma IGF1 concentrations, and decreased female placental weight. PregEx did not influence fetoplacental growth but increased placental IGF1 and IGF1R (potentially modulated by reduced Let 7f-1 miRNA) and decreased placental IGF2 protein. Importantly, these placental IGF system changes occurred with sex-specific responses. These data highlight that exercise differently influences fetoplacental growth and the placental IGF system depending on maternal exercise initiation, which may prevent the transgenerational transmission of deficits and dysfunction.

Correlation of Insulin-Like Growth Factor-I and -II Concentrations at Birth Measured by Mass Spectrometry and Growth from Birth to Two Months

BACKGROUND

Immunoassays used to measure insulin-like growth factor (IGF)-I and -II concentrations are susceptible to interference from IGF-binding proteins. The aim of this study was to investigate the association of IGF-I and -II concentrations at birth with neonatal anthropometry using a liquid chromatography/mass spectrometry (LCMS) assay.

METHODS

LCMS was used to measure IGF-I and -II concentrations in umbilical cord blood of term, healthy infants enrolled in the Cork BASELINE Birth Cohort Study. Weight, length, and occipitofrontal head circumference (OFC) were measured at birth and 2 months.

RESULTS

Cord blood IGF-I and -II concentrations were measured in 1,100 infants. Mean (SD) IGF-I and -II concentrations were 52.5 (23.9) ng/mL and 424.3 (98.2) ng/mL, respectively. IGF-I and -II concentrations at birth were associated (p < 0.05) with weight (R2 = 0.19, R2 = 0.01), length (R2 = 0.07, R2 = 0.004), and OFC (R2 = 0.03, R2 = 0.04) at birth. Low IGF-I concentrations at birth were associated with increases in weight (p < 0.001) and OFC (p < 0.01) Z-scores in the first 2 months.

CONCLUSION

Using an LCMS assay, we have shown that anthropometric parameters at birth are associated with IGF-I and weakly with IGF-II concentrations. This indicates that, at the time of birth, IGF-I is the more important growth factor for regulating infant growth.

Impacts of prenatal nutrition on animal production and performance: a focus on growth and metabolic and endocrine function in sheep

The concept of foetal programming (FP) originated from human epidemiological studies, where foetal life nutrition was linked to health and disease status later in life. Since the proposal of this phenomenon, it has been evaluated in various animal models to gain further insights into the mechanisms underlying the foetal origins of health and disease in humans. In FP research, the sheep has been quite extensively used as a model for humans. In this paper we will review findings mainly from our Copenhagen sheep model, on the implications of late gestation malnutrition for growth, development, and metabolic and endocrine functions later in life, and discuss how these implications may depend on the diet fed to the animal in early postnatal life. Our results have indicated that negative implications of foetal malnutrition, both as a result of overnutrition and, particularly, late gestation undernutrition, can impair a wide range of endocrine functions regulating growth and presumably also reproductive traits. These implications are not readily observable early in postnatal life, but are increasingly manifested as the animal approaches adulthood. No intervention or cure is known that can reverse this programming in postnatal life. Our findings suggest that close to normal growth and slaughter results can be obtained at least until puberty in animals which have undergone adverse programming in foetal life, but manifestation of programming effects becomes increasingly evident in adult animals. Due to the risk of transfer of the adverse programming effects to future generations, it is therefore recommended that animals that are suspected to have undergone adverse FP are not used for reproduction. Unfortunately, no reliable biomarkers have as yet been identified that allow accurate identification of adversely programmed offspring at birth, except for very low or high birth weights, and, in pigs, characteristic changes in head shape (dolphin head). Future efforts should be therefore dedicated to identify reliable biomarkers and evaluate their effectiveness for alleviation/reversal of the adverse programming in postnatal life. Our sheep studies have shown that the adverse impacts of an extreme, high-fat diet in early postnatal life, but not prenatal undernutrition, can be largely reversed by dietary correction later in life. Thus, birth (at term) appears to be a critical set point for permanent programming in animals born precocial, such as sheep. Appropriate attention to the nutrition of the late pregnant dam should therefore be a priority in animal production systems.

Hypoxia Increases IGFBP-1 Phosphorylation Mediated by mTOR Inhibition

In fetal growth restriction (FGR), fetal growth is limited by reduced nutrient and oxygen supply. Insulin-like growth factor I (IGF-I) is a key regulator of fetal growth and IGF binding protein -1(IGFBP-1) is the principal regulator of fetal IGF-I bioavailability. Phosphorylation enhances IGFBP-1's affinity for IGF-I. Hypoxia induces IGFBP-1 hyperphosphorylation, markedly decreasing IGF-I bioavailability. We recently reported that fetal liver IGFBP-1 hyperphosphorylation is associated with inhibition of the mechanistic target of rapamycin (mTOR) in a nonhuman primate model of FGR. Here, we test the hypothesis that IGFBP-1 hyperphosphorylation in response to hypoxia is mediated by mTOR inhibition. We inhibited mTOR either by rapamycin or small interfering RNA (siRNA) targeting raptor (mTOR complex [mTORC]1) and/or rictor (mTORC2) in HepG2 cells cultured under hypoxia (1% O2) or basal (20% O2) conditions. Conversely, we activated mTORC1 or mTORC1+mTORC2 by silencing endogenous mTOR inhibitors (tuberous sclerosis complex 2/DEP-domain-containing and mTOR-interacting protein). Immunoblot analysis demonstrated that both hypoxia and inhibition of mTORC1 and/or mTORC2 induced similar degrees of IGFBP-1 phosphorylation at Ser101/119/169 and reduced IGF-I receptor autophosphorylation. Activation of mTORC1+mTORC2 or mTORC1 alone prevented IGFBP-1 hyperphosphorylation in response to hypoxia. Multiple reaction monitoring-mass spectrometry showed that rapamycin and/or hypoxia increased phosphorylation also at Ser98 and at a novel site Ser174. In silico structural analysis indicated that Ser174 was in close proximity to the IGF-binding site. Together, we demonstrate that signaling through the mTORC1 or mTORC2 pathway is sufficient to induce IGFBP-1 hyperphosphorylation in response to hypoxia. This study provides novel understanding of the cellular mechanism that controls fetal IGFBP-1 phosphorylation in hypoxia, and we propose that mTOR inhibition constitutes a mechanistic link between hypoxia, reduced IGF-I bioavailability and FGR.

Insulin-like growth factor-binding protein 1 and 7 concentrations are lower in obese pregnant women, women with gestational diabetes and their fetuses

OBJECTIVE

To determine the effect of pre-existing maternal obesity and gestational diabetes mellitus (GDM) on the circulating levels of insulin growth factor-binding protein (IGFBPs) in cord and maternal plasma.

STUDY DESIGN

IGFBP-1-7 levels were measured on maternal and cord plasma from women with normal glucose tolerance (NGT) (30 non-obese and 36 obese) and GDM (44 non-obese and 26 obese) at the time of term elective cesarean section.

RESULT

Maternal plasma IGFBP-1, IGFBP-6 and IGFBP-rP1 concentrations were significantly lower in NGT obese compared with NGT non-obese women and in non-obese GDM women compared with non-obese NGT women. In cord plasma, IGFBP-1-3 and IGFBP-rP1 concentrations were significantly lower in NGT obese compared with NGT non-obese women and in non-obese GDM women compared with non-obese NGT women. Significant positive correlations were observed between maternal and cord plasma IGFBP-1 and IGFBP-rP1 levels and maternal insulin resistance. In cord plasma, significant positive correlations were observed between IGFBP-1-3 and IGFBP-rP1 levels and fetal insulin resistance. Fetal birthweight was inversely correlated with maternal plasma IGFBP-1 levels and cord plasma IGFBP-1 and IGFBP-2 levels. When corrected for maternal body mass index, the only significant relationship that still existed was between cord plasma IGFBP-1 concentrations and fetal birthweight.

CONCLUSION

At the time of term cesarean section, pre-existing maternal obesity and GDM are associated with lower IGFBP levels in maternal and cord plasma. Alterations in circulating IGF and IGFBPs may alter birthweight and/or neonatal adiposity. This may lead to alterations in optimal growth trajectory and lead to metabolic disorders later in life.

Maternal malnutrition and placental insufficiency induce global downregulation of gene expression in fetal kidneys

Malnutrition during pregnancy causes intrauterine growth restriction and long-term changes in the offspring's physiology and metabolism. To explore molecular mechanisms by which the intrauterine environment conveys programming in fetal kidneys, an organ known to undergo substantial changes in many animal models of late gestational undernutrition, we used a microswine model of maternal protein restriction (MPR) in which sows were exposed to isocaloric low protein (LP) diet during late gestation/early lactation to encompass the bulk of nephrogenesis. To define general v. model-specific effects, we also used a sheep model of placental insufficiency. In kidneys from near-term fetal and neonatal microswine LP offspring, per cell levels of total RNA, poly(A)+ mRNA and transcripts of several randomly chosen housekeeping genes were significantly reduced compared to controls. Microarray analysis revealed only a few MPR-resistant genes that escape such downregulation. The ratio of histone modifications H3K4m3/H3K9m3 (active/silenced) was reduced at promoters of downregulated but not MPR-resistant genes suggesting that transcriptional suppression is the point of control. In juvenile offspring, on a normal diet from weaning, cellular RNA levels and histone mark patterns were recovered to near control levels, indicating that global repression of transcription is dependent on ongoing MPR. Importantly, cellular RNA content was also reduced in ovine fetal kidneys during placental insufficiency. These studies show that global repression of transcription may be a universal consequence of a poor intrauterine environment that contributes to fetal restriction.

Maternal BMI, IGF-I Levels, and Birth Weight in African American and White Infants

At birth, elevated IGF-I levels have been linked to birth weight extremes; high birth weight and low birth weight are risk factors for adult-onset chronic diseases including obesity, cardiovascular disease, and type 2 diabetes. We examined associations between plasma IGF-I levels and birth weight among infants born to African American and White obese and nonobese women. Prepregnancy weight and height were assessed among 251 pregnant women and anthropometric measurements of full term infants (≥37 weeks of gestation) were taken at birth. Circulating IGF-I was measured by ELISA in umbilical cord blood plasma. Linear regression models were utilized to examine associations between birth weight and high IGF-I, using the bottom two tertiles as referents. Compared with infants with lower IGF-I levels (≤3rd tertile), those with higher IGF-I levels (>3rd tertile) were 130 g heavier at birth, (β-coefficient = 230, se = 58.0, P = 0.0001), after adjusting for gender, race/ethnicity, gestational age, delivery route, maternal BMI and smoking. Stratified analyses suggested that these associations are more pronounced in infants born to African American women and women with BMI ≥30 kg/m²; the cross product term for IGF-I and maternal BMI was statistically significant (P ≤ 0.0004). Our findings suggest that the association between IGF-I levels and birth weight depends more on maternal obesity than African American race/ethnicity.

Placental IGF-I, IGFBP-1, zinc, and iron, and maternal and infant anthropometry at birth

AIM

To correlate placental protein levels of insulin-like growth factor (IGF)-I and insulin-like growth factor binding protein (IGFBP)-1, with previously determined levels of IGF-I and IGF-II mRNA expression, and the micronutrients zinc and iron, and maternal and newborn anthropometry.

METHODS

Placental samples were collected from rural field sites in Pakistan. Samples were divided into small and large for gestational age groups (SGA and LGA, respectively). IGFBP-1 levels were assessed using Western immunoblotting. IGF-I protein levels were assessed using ELISA techniques. IGF mRNA expression, zinc, and iron, were quantified as previously described and were used for comparative purposes only.

RESULTS

Thirty-three subjects were included (SGA, n = 12; LGA n = 21). Higher levels of IGFBP-1 were seen in the SGA group (p < 0.01). IGFBP-1 correlated positively with maternal and infant triceps skin-fold thickness in the LGA and SGA groups, respectively (p < 0.05). Significantly lower IGF-I protein levels were seen in the SGA group. IGF-I levels correlated significantly with maternal and newborn anthropometry. IGFBP-1 correlated significantly with IGF-II mRNA expression (p < 0.05).

CONCLUSION

Placental protein levels of IGF-I and IGFBP-1 appear to be associated with maternal anthropometry. Maternal anthropometry may thus influence IGFBP-1 and IGF-I levels and may possibly be used for screening of pregnancies, with the potential for timely identification of these high-risk pregnancies.

Maternal concentrations of insulin-like growth factor I and insulin-like growth factor binding protein 1 during pregnancy and birth weight of offspring

Maternal concentrations of insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein 1 (IGFBP-1) may influence fetal growth. Offspring birth weight related to maternal IGF-I and IGFBP-1 measured in pregnancy was studied in 368 randomly selected women without preeclampsia who delivered a singleton liveborn child in Norway between 1992 and 1994. Maternal IGF-I concentrations were not consistently associated with birth weight, but a 1-standard deviation stronger increase in IGF-I from the first to second trimester was associated with an 82-g (95% confidence interval (CI): 11, 153) higher birth weight. IGFBP-1 concentrations were inversely associated with birth weight: Birth weight was 71 g (95% CI: 14, 128) lower per 1-standard deviation higher IGFBP-1 in the second trimester, and an increase in IGFBP-1 from the first (below median) to second (above median) trimester was associated with a 342-g (95% CI: 124, 560) lower birth weight, compared with having low IGFBP-1 (below median) in both trimesters. Conversely, low IGFBP-1 in both trimesters was associated with a 200-350-g higher birth weight compared with other combinations of IGFBP-1. In conclusion, persistently low IGFBP-1 in pregnancy is associated with relatively higher birth weight. Maternal insulin resistance may provide a link between IGFBP-1 and offspring birth weight.

Involvement of the IGF system in fetal growth and childhood cancer: an overview of potential mechanisms

Fetal growth is determined by a complex interplay of genetic, nutritional, environmental, and hormonal factors. Greater than expected fetal growth has been positively associated with the risk of the development of some cancers in childhood, particularly acute lymphoblastic leukemia, and the biological mechanisms underlying such associations are thought to involve insulin-like growth factors (IGFs). Circulating IGF levels are highly correlated with fetal growth, and IGFs are believed to play an important role in carcinogenesis; however, these two bodies of evidence have not been well integrated and, as a result, the potential underlying biological mechanisms linking the IGF system with the development of specific childhood cancers have not been elucidated. This review aims to draw together and summarize the literature linking the IGF system, rapidity of fetal growth, and risk of some specific childhood cancers; suggest explanations for some of the inconsistencies observed in previous studies of these associations; and propose an integrated framework for the putative involvement of the IGF system in the development of at least some childhood cancers. If the challenges involved in studying the complex IGF system can be overcome, this field presents an exciting opportunity to elucidate etiological pathways to childhood malignancies.

Decreased placental expression of hPGH, IGF-I and IGFBP-1 in pregnancies complicated by fetal growth restriction

OBJECTIVE

The human Placental Growth Hormone (hPGH) and the Insulin-like Growth Factor (IGF) system are implicated in fetal development. This study aimed to evaluate the expression of hPGH, IGF-I, IGFBP-1 and IGFBP-3 genes in placentas from pregnancies complicated by fetal growth restriction (FGR).

DESIGN

The study group was comprised of term placentas from 47 FGR-complicated pregnancies of no recognizable cause. Thirty-seven placentas from normal pregnancies with appropriate for gestational age birth weight were used as controls. The expression status of the genes was evaluated by quantitative real-time PCR.

RESULTS

hPGH, IGF-I and IGFBP-1 exhibited significantly lower expression compared to the controls (p=0.003, p=0.049 and p=0.001, respectively). Numerically, lower IGFBP-3 expression was also demonstrated in the FGR-affected group, without however reaching statistical significance (p=0.129). Significant co-expression patterns were detected among the study genes in both the FGR and normal pregnancies.

CONCLUSION

Decreased placental expression levels of hPGH, IGF-I and IGFBP-1 were demonstrated in pregnancies with FGR. Whether these alterations are a causative factor of FGR or accompany other pathogenetic mechanisms requires further investigation.

Review: The placenta is a programming agent for cardiovascular disease

Cardiovascular disease remains the number one killer in western nations in spite of declines in death rates following improvements in clinical care. It has been 20 years since David Barker and colleagues showed that slow rates of prenatal growth predict mortality from ischemic heart disease. Thus, fetal undergrowth and its associated cardiovascular diseases must be due, in part, to placental inadequacies. This conclusion is supported by a number of studies linking placental characteristics with various adult diseases. A "U" shaped relationship between placental-to-fetal weight ratio and heart disease provides powerful evidence that placental growth-regulating processes initiate vulnerabilities for later heart disease in offspring. Recent evidence from Finland indicates that placental morphological characteristics predict risks for coronary artery disease, heart failure, hypertension and several cancers. The level of risk imparted by placental shape is sex dependent. Further, maternal diet and body composition strongly influence placental growth, levels of inflammation, nutrient transport capacity and oxidative stress, with subsequent effects on offspring health. Several animal models have demonstrated the placental roots of vulnerability for heart disease. These include findings that abnormal endothelial development in the placenta is associated with undergrown myocardial walls in the embryo, and that placental insufficiency leads to depressed maturation and proliferation of working cardiomyocytes in the fetal heart. Together these models suggest that the ultimate fitness of the heart is determined by hemodynamic, growth factor, and oxygen/nutrient cues before birth, all of which are influenced, if not regulated by the placenta.

Hypoxia and leucine deprivation induce human insulin-like growth factor binding protein-1 hyperphosphorylation and increase its biological activity

Fetal growth restriction is often caused by uteroplacental insufficiency that leads to fetal hypoxia and nutrient deprivation. Elevated IGF binding protein (IGFBP)-1 expression associated with fetal growth restriction has been documented. In this study we tested the hypothesis that hypoxia and nutrient deprivation induce IGFBP-1 phosphorylation and increase its biological potency in inhibiting IGF actions. HepG2 cells were subjected to hypoxia and leucine deprivation to mimic the deprivation of metabolic substrates. The total IGFBP-1 levels measured by ELISA were approximately 2- to 2.5-fold higher in hypoxia and leucine deprivation-treated cells compared with the controls. Two-dimensional immunoblotting showed that whereas the nonphosphorylated isoform is the predominant IGFBP-1 in the controls, the highly phosphorylated isoforms were dominant in hypoxia and leucine deprivation-treated cells. Liquid chromatography-tandem mass spectrometry analysis revealed four serine phosphorylation sites: three known sites (pSer 101, pSer 119, and pSer 169); and a novel site (pSer 98). Liquid chromatography-mass spectrometry was used to estimate the changes of phosphorylation upon treatment. Biacore analysis indicated that the highly phosphorylated IGFBP-1 isoforms found in hypoxia and leucine deprivation-treated cells had greater affinity for IGF-I [dissociation constant 5.83E (times 10 to the power)--0 m and 6.40E-09 m] relative to the IGFBP-1 from the controls (dissociation constant approximately 1.54E-07 m). Furthermore, the highly phosphorylated IGFBP-1 had a stronger effect in inhibiting IGF-I-stimulated cell proliferation. These findings suggest that IGFBP-1 phosphorylation may be a novel mechanism of fetal adaptive response to hypoxia and nutrient restriction.

The herbal medicine Tokishakuyakusan increases fetal blood glucose concentrations and growth hormone levels and improves intrauterine growth retardation induced by N(omega)-nitro-L-arginine methyl ester

N(omega)-Nitro-L-arginine methyl ester (L-NAME) induces a pre-eclampsia-like syndrome in pregnant rats. We have previously reported the anti-hypertensive effects of several Japanese traditional (Kampo) medicines in this model, and one of these, Tokishakuyakusan (TS), also improved intrauterine growth retardation (IUGR). In the present study, we characterized the effect of TS on IUGR. TS administration reversed the decrease in fetal body weight and fetal blood glucose concentration induced by the infusion of L-NAME. Growth hormone (GH) levels in the fetal blood, which were decreased by L-NAME infusion, were also significantly elevated by TS; however, levels of GH releasing hormone (GHRH) and insulin-like growth factor I (IGF-I) were unchanged and only slightly changed, respectively. Treatment with L-NAME with or without TS had no apparent effect on GH, GHRH, and IGF-I levels of dams. In an immunocytochemical study, the number of GH-positive cells in the fetal pituitary gland was significantly increased in TS-treated rats. These data suggest that enhanced proliferation of somatotrope cells of the pituitary gland and the resultant increase in GH secretion in the fetus may be involved in the improvement of IUGR by TS.

The insulin-like growth factor system and the fetal brain: effects of poor maternal nutrition

The insulin-like growth factor (IGF) signaling system plays indispensable roles in pre- and post-natal brain growth and development. A large body of studies using both in vivo null mutant and transgenic mice and in vitro neuronal culture techniques indicate that IGF-I acts directly on the brain while IGF-II effects are mediated to a large extent by IGF-II control of placental growth. It appears that all of the mechanisms, except migration, that are involved in normal brain development, e.g., proliferation, apoptosis, maturation and differentiation, are influenced by IGF-I. While IGF system members are produced in the brain, recent reports in post-natal animals indicate that normal brain health and function are dependent upon transfer of circulating IGF-I from the liver and its transfer across the blood brain barrier. Data showing that this phenomenon applies to pre-natal brain growth and development would make an important contribution to fetal physiology. A number of kinase pathways are able to participate in IGF signaling in brain with respect to nutrient restriction; among the most important are the PI3K/AKT, Ras-Raf-MEK-ERK and mTOR-nutrient sensing pathways. Both maternal and fetal IGF-I peripheral plasma concentrations are greatly reduced in nutrient restriction while IGF-II does not appear to be affected. Nutrient restriction also affects IGF binding protein concentrations while effects on the IGF-I receptor appear to vary with the paradigm. Studies on the effects of nutrient restriction on the fetal primate brain in relation to activity of the IGF system are needed to determine the applicability of rodent studies to humans.

Consequences of food energy excess and positive energy balance

This paper discusses possible consequences of energy excess throughout the life cycle. Firstly we consider the effects of foods on hunger, satiety and satiation. Also, the changes in food availability and consumption in relation to changes in social and economic determinants of energy excess. The relationship between physical activity and energy intake (EI) is also considered. Secondly we explore the definition of energy excess and the metabolic effects of macronutrients (mainly in relation to fuel partitioning oxidation/storage) on energy balance. The cellular and molecular regulation determined by specific genes involved in lipogenesis, fuel partitioning and/or in energy dissipation are explored. Thirdly, we examine the main consequences induced by energy excess and positive energy balance, starting with the alterations in glucose utilisation (insulin resistance) leading to type 2 diabetes and the linkage of energy excess with other non-communicable diseases (NCDs). Biological, social and psychological consequences during perinatal, childhood and adolescence periods are specifically analysed. Fourthly, the transition from energy deficit to excess, under the optic of a developing country is analysed with country examples drawn from Latin America. The possible role of supplementary food programmes in determining positive energy balance is discussed especially in relation to pre-school and school feeding programmes. Fifthly, we deal with the economic costs of energy excess and obesity related diseases. Finally, some areas where further research is needed are described; biological and genetic determinants of individual and population energy requirements, foods and food preparations as actually consumed, consumer education and research needs on social determinants of energy imbalances.

Proteomic analysis of amniotic fluid in pregnancies with Down syndrome

Proteomic analysis is widely used for the detection of diagnostic markers. In the present study amniotic fluid supernatants (AFS) from pregnancies with Down syndrome (DS) fetuses and from chromosomally normal fetuses in the 17th week of gestation were analyzed by 2-DE. Gel comparison revealed significant differences in the two groups. Spots with different expression levels were excised and proteins were identified by MALDI-MS and nano-ESI-MS/MS. Splicing factor arginine/serine-rich 4 (SFRS4; Q08170) was present only in AFS from DS fetuses and completely absent in the control group. Quantitative differences were detected for alpha-1-microglobulin (AMBP; P02760), collagen alpha 1 (I) chain (CO1A1; P02452), collagen alpha 1 (III) chain (CO3A1; P02461), collagen alpha 1 (V) chain d (CO5A1; P20908), and basement membrane-specific heparin sulfate proteoglycan core protein (PGBM; P98160). These proteins were increased in cases with DS, whereas protein IBP-1 (P08833) was decreased by 40% compared with chromosomally normal fetuses. Four proteins, CO1A1, CO3A1, CO5A1, and PGBM, appeared as fragments. As differentially expressed proteins were present in all pregnancies with DS tested, they may represent useful potential markers for prenatal diagnosis. However, for protein biomarkers to be of any clinical utility, systematic analysis of the maternal serum should be conducted.

Consequences of Intrauterine Growth Restriction for the Kidney

Low birth weight due to intrauterine growth restriction is associated with various diseases in adulthood, such as hypertension, cardiovascular disease, insulin resistance and end-stage renal disease. The purpose of this review is to describe the effects of intrauterine growth restriction on the kidney. Nephrogenesis requires a fine balance of many factors that can be disturbed by intrauterine growth restriction, leading to a low nephron endowment. The compensatory hyperfiltration in the remaining nephrons results in glomerular and systemic hypertension. Hyperfiltration is attributed to several factors, including the renin-angiotensin system (RAS), insulin-like growth factor (IGF-I) and nitric oxide. Data from human and animal studies are presented, and suggest a faltering IGF-I and an inhibited RAS in intrauterine growth restriction. Hyperfiltration makes the kidney more vulnerable during additional kidney disease, and is associated with glomerular damage and kidney failure in the long run. Animal studies have provided a possible therapy with blockage of the RAS at an early stage in order to prevent the compensatory glomerular hyperfiltration, but this is far from being applicable to humans. Research is needed to further unravel the effect of intrauterine growth restriction on the kidney.

Associations of the IGF/IGFBP axis and respiratory diseases in neonatal patients during the first 6 months of life

OBJECTIVES

To analyse IGFs in respect to somatic growth and neonatal diseases during the first 6 months of life.

METHODS

IGF-I, IGF-II and IGF binding proteins (IGFBP-1, -2, -3) were determined by immunoassays in neonatal patients after birth (n = 67) and at 3 (3 mo; n = 75) and 6 months (6 mo; n = 47) of corrected postnatal age. Data on growth were tested for associations to the gestational age, birth weight (bw) SDS (/-2 SDS), neonatal morbidity and therapeutic strategies.

RESULTS

All IGFs and IGFBPs changed significantly between birth and 3 mo of corrected age (p < 0.05). Perinatal respiratory diseases influenced IGF-II at 3 mo, and bronchopulmonary dysplasia IGF-II at 3 and 6 mo (all p < 0.05). IGF-I differed between the subgroups bw /-2 SDS (p < 0.05). At 3 mo, IGFBP-1 was significantly increased in infants with glucocorticoid administration during the first four weeks of life.

CONCLUSION

The first months of life are characterised by a pole reversal of the somatotropic axis: IGFBP-1 and -2 decrease and IGFBP-3 increases. Respiratory diseases with an origin in the neonatal period, glucocorticoid therapy and low birth weight have an impact on the IGF pattern up to 6 mo. Prospective studies are necessary to investigate, whether the described link between the IGF/IGFBP axis and respiratory morbidity in neonatal patients has an impact on development in later infancy.

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, approximately 5 months (prepubertal, the catch-up growth period), and approximately 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.

IGF-1 and Retinopathy of Prematurity in the Preterm Infant

BACKGROUND

Retinopathy of prematurity (ROP) continues to be a major cause of blindness in children. Although ablation of the retina reduces the incidence of blindness by suppressing the neovascular phase of ROP, the visual outcomes after treatment are often poor. Preventive therapy is required and will likely come from a better understanding of the pathophysiology of the disease.

OBJECTIVES

To study the role of insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGF) in both the proliferative phase of ROP (phase II) and in the early phase when blood vessels are lost.

METHODS

Using both a mouse model of ROP and clinical studies the relationship between IGF-1, VEGF and both vessel loss and vessels proliferation in the retina was studied.

RESULTS

IGF-1 is required for maximum VEGF activation of vascular endothelial cell proliferation and survival pathways. IGF-1 levels are deficient after premature birth, setting the stage for retinal vascular loss and ROP.

CONCLUSIONS

Restoration of IGF-1 to levels found in utero may help prevent ROP.

Mothers in Stress: Consequences for the Offspring

No memories exist on one's time before birth. However, this does not imply that the developing fetus is not susceptible to external impulses. On the contrary, the fetus is extremely vulnerable e.g. to environmental challenges, and a wealth of data reveals that conditions in utero affect the health of the fetus before and after birth. Threats for the growing fetus include psychological challenges perceived by the mother, e.g. high levels of stress during pregnancy. However, stress experienced during pregnancy not only leads to pregnancy complications like miscarriage, pre-eclampsia, preterm parturition, low birth weight or major congenital malformations, stress also increases the risk of the child to develop diseases in the subsequent periods of life. This condition is termed fetal programming of adult disease. Programming agents seem to include growth factors, cytokines and hormones, all of which can be altered by stress. As a consequence, such 'stress-modified' systems of the offspring are more susceptible to environmental influences during later life, e.g. the development of atopic diseases upon exposure to antigens. The present review illuminates the complexity of stress perception on fetal programming focusing predominately on the onset of atopic diseases on the background of published evidence from immunology, endocrinology, neurobiology and neonatology.

Maternal plasma concentrations of insulinlike growth factor-1 and insulinlike growth factor-binding protein-1 in early pregnancy and subsequent risk of preeclampsia

OBJECTIVES

We investigated the relationship between maternal plasma free insulinlike growth factor-1 (IGF-1) and insulinlike growth factor-binding protein-1 (IGFBP-1) concentrations and risk of preeclampsia.

DESIGN AND METHODS

Maternal blood samples were collected at 13 weeks' gestation on average. From the cohort, we selected 53 women who developed preeclampsia and 477 who remained normotensive. Free IGF-1 and IGFBP-1 concentrations were measured using immunoassays. Logistic regression procedures were used to calculate odds ratios (OR) and 95% confidence intervals (95% CI).

RESULTS

Women who developed preeclampsia had 18% and 27% lower concentrations of free IGF-1 and IGFBP-1, respectively, than controls (P < 0.05). There was a 57% reduced risk of preeclampsia among women with free IGF-1 concentrations of >or= 0.81 ng/mL (OR = 0.43, 95% CI 0.23-0.83) and a 43% reduced risk among women with IGFBP-1 concentrations of >or= 72.36 ng/mL (OR = 0.53, 95% CI 0.23-1.21).

CONCLUSIONS

Alterations of free IGF-1 and IGFBP-1 concentrations in maternal plasma during early pregnancy are associated with risk of preeclampsia. These associations may help to further elucidate the pathologic processes of preeclampsia.

Longitudinal analysis of serum insulin-like growth factor-I and insulin-like growth factor binding protein-1 in antiphospholipid syndrome and in healthy pregnancy

OBJECTIVE

The purpose of this study was to determine the concentrations of serum insulin-like growth factor-I and insulin-like growth factor binding protein-1 in pregnancies that are complicated with primary antiphospholipid syndrome.

STUDY DESIGN

Longitudinal blood samples were collected from 8 weeks of gestation in 28 women with treated primary antiphospholipid syndrome and 19 control women. Serum insulin-like growth factor-I and insulin-like growth factor binding protein-1 were measured by immunoradiometric assay.

RESULTS

Three antiphospholipid syndrome pregnancies miscarried, four pregnancies had intrauterine growth restriction and preeclampsia, six pregnancies had a thrombotic event, and one pregnancy had abruptio placentae. Mean (+/-SD) birth weight in antiphospholipid syndrome group was 2867 +/- 914 g (control, 3492 +/- 527 g; P =.02), and the mean gestation at delivery was 36.5 +/- 5.2 weeks (control, 40.3 +/- 0.7 weeks; P =.002). Insulin-like growth factor binding protein-1 and insulin-like growth factor-I concentrations increased with gestational age in both groups (2.8% and 2.4% per week), but insulin-like growth factor binding protein-1 was 61% higher in the antiphospholipid syndrome group (95% CI, 16%-122%; P =.004). Insulin-like growth factor-I was not significantly different (8% higher in antiphospholipid syndrome; 95% CI, -10% to 30%; P =.41).

CONCLUSION

Serum concentrations of insulin-like growth factor binding protein-1 are abnormal in the antiphospholipid syndrome group and may reflect abnormalities in trophoblast invasion.

Regulation of insulin-like growth factor-I and insulin-like growth factor binding protein-1 concentrations in preterm fetuses

OBJECTIVE

Our purpose was to evaluate which factors regulate insulin-like growth factor-I and insulin-like growth factor binding protein-1 concentrations in preterm fetuses.

STUDY DESIGN

We studied 76 singleton births between 25 and 36 weeks of gestation. Forty-nine pregnancies were complicated by hypertensive disease; 24 pregnancies were complicated by preterm labor or preterm rupture of membranes; and antenatal glucocorticoids were given in 49 pregnancies. Pathology reports showed infarct(s) or hematoma(s) in 31 of 69 placentas. We recorded blood gas values in umbilical artery and vein and measured glucose, C-peptide, and insulin-like growth factor-I and insulin-like growth factor binding protein-1 concentrations in umbilical vein.

RESULTS

Birth weight correlated with umbilical vein insulin-like growth factor-I (r = 0.68, P <.0001) and inversely with insulin-like growth factor binding protein-1 (r = -0.26, P =.02). Babies with birth weight of </=25th percentile had lower insulin-like growth factor-I but higher insulin-like growth factor binding protein-1 levels than babies at >25th percentile. Two-factor analysis of variance showed that umbilical vein insulin-like growth factor-I was determined by gestational age (P =.0004) and birth weight percentile (P <.0001), whereas insulin-like growth factor binding protein-1 was not affected by gestational age. Umbilical vein C-peptide was highly correlated with insulin-like growth factor binding protein-1 (r = -0.55, P <.0001), but not insulin-like growth factor-I, levels. Blood gas values in umbilical artery and vein, particularly umbilical artery PO (2), were correlated with umbilical vein insulin-like growth factor-I and insulin-like growth factor binding protein-1 (r = 0.51 and -0.48, respectively; P <.0001); changes in insulin-like growth factor-I and insulin-like growth factor binding protein-1 occurred at umbilical artery PO (2) <14.8 mm Hg. Multiple regression analysis showed that umbilical vein insulin-like growth factor-I was predicted by umbilical artery PO (2), gestational age, and the presence of placental infarcts/hematomas (R (2) of model = 0.58, P <.0001), and umbilical vein insulin-like growth factor binding protein-1 by umbilical vein C-peptide, umbilical artery PO (2), and placental infarcts/hematomas (R (2) = 0.49, P <.0001).

CONCLUSION

In the preterm fetus, circulating insulin-like growth factor-I is related to gestational age and the in utero growth potential, whereas insulin-like growth factor binding protein-1 is related only to the in utero growth potential. The PO (2) is a robust determinant of both insulin-like growth factor-I and insulin-like growth factor binding protein-1 levels; hypoxia may restrain fetal growth through its effects on the insulin-like growth factor/insulin-like growth factor binding protein axis. Insulin is a powerful determinant of insulin-like growth factor binding protein-1, but not insulin-like growth factor-I, concentrations in the preterm fetus.

Altered placental development and intrauterine growth restriction in IGF binding protein-1 transgenic mice

IGF binding protein-1 (IGFBP-1) is a secretory product of decidualized endometrium and a major constituent of amniotic fluid. It is thought to modulate the actions of the IGFs on trophoblast cells and is therefore potentially important in regulating placental development and fetal growth. To investigate this hypothesis, we have studied the effects of decidual IGFBP-1 excess on fetoplacental growth in transgenic mice overexpressing human IGFBP-1. Endogenous fetal IGFBP-1 overexpression is associated with a transient impairment of fetal growth in midgestation. Maternal decidual IGFBP-1 excess is also associated with impaired fetal growth in midgestation independent of fetal genotype, indicating placental insufficiency. Our data also demonstrate that amniotic fluid IGFBP-1 is derived almost exclusively from maternal sources. Decidual IGFBP-1 overexpression has a marked effect on placental development. Placental morphology is abnormal in transgenic females due to altered trophoblast invasion and differentiation. These changes result in an increase in placental mass throughout pregnancy. This study provides the first compelling in vivo evidence that IGFBP-1 plays a role in placentation and suggests that IGFBP-1 has a pathological role in preeclampsia, a disorder characterized by shallow uterine invasion and altered placental development.

Insulin-like growth factor I and leptin in umbilical cord plasma and infant birth size at term

OBJECTIVE

To determine the independent contributions to infant birth size of insulin-like growth factor I (IGF-I) and leptin measured in umbilical cord plasma.

METHODS

Umbilical cord blood was collected in 12 804 consecutive deliveries, and cord plasma from 585 singleton infants born at term after uncomplicated pregnancies was analyzed for leptin, IGF-I, and 2 IGF-binding proteins (IGFBP-1 and IGFBP-3). In multivariable analyses, we assessed maternal and infant covariates of leptin and IGF-I, and we evaluated the independent contribution of cord levels of leptin and IGF-I on infant birth size.

RESULTS

Cord plasma levels of IGF-I were lower in women who reported smoking at the beginning of pregnancy compared with nonsmokers. In female infants, levels of IGF-I and leptin were higher than in male infants after adjustment for ponderal index and maternal factors. We found a strong parallel increase in umbilical IGF-I and leptin with increasing birth weight and birth length. For IGFBP-1, there was an opposite pattern: IGFBP-1 increased with decreasing birth size. The multivariable analysis, adjusted for length of gestation and maternal age, parity, prepregnancy weight, smoking during pregnancy, and offspring sex, showed that IGF-I and leptin, independent of each other, were associated with birth weight and birth length.

CONCLUSIONS

Levels of IGF-I and leptin in umbilical cord plasma were higher in girls than in boys, but in both sexes, these 2 factors contributed independently and positively to birth weight and length. For IGFBP-1, high levels were associated with low birth weight and reduced length. If intrauterine growth is related to the risk of developing adult diseases, IGF-I, IGFBP-1, and leptin may be involved in the underlying processes.1131-1135 insulin like growth factors, leptin, umbilical cord plasma, birth weight.

The somatotropic axis in short children born small for gestational age: relation to insulin resistance

To determine whether hyperinsulinemia and reduced insulin sensitivity in individuals born small for gestational age (SGA) could be related to persisting abnormalities of the GH/IGF-I axis, we assessed overnight GH secretory profiles and measured fasting glucose, insulin, intact and 32,33 split proinsulin, and IGF-I levels in 16 short SGA children (age range 2.3-8.0 y) and in controls. Insulin sensitivity was calculated using the homeostasis model. Compared with short normal-birthweight controls (n = 7, age range 2.3-5.0 y), short SGA children had higher fasting insulin levels (means: 26.8 vs 20.6 pmol/L, p = 0.02), lower insulin sensitivity [means: 204 vs 284 %homeostasis model assessment (HOMA), p = 0.01], and higher beta cell function (112 vs 89 %HOMA, p = 0.04). SGA children also had lower levels of IGFBP-1 (87.0 vs 133.8, p = 0.04), but similar IGF-I levels (IGF-I SDS: -1.1 vs -1.7, p = 0.4). Compared with normal-height controls (n = 15, age range 5.6-12.1 y), SGA children had higher overnight GH secretion (GH maximum: 55.9 vs 39.6 mU/L, p = 0.01; mean: 13.1 vs 8.9, p = 0.004; minimum: 1.2 vs 0.6, p = 0.02). Interestingly, among SGA children, fasting insulin levels and insulin sensitivity were significantly related to overnight GH secretion (insulin sensitivity vs maximum GH: r = -0.68, p = 0.01; vs GH pulse amplitude r = -0.71, p = 0.007). The only hormone level significantly related to current height velocity was C-peptide (r = 0.75, p = 0.008). In conclusion, elevated fasting insulin levels and reduced insulin sensitivity in short SGA children was related to elevated levels of overnight GH secretion. We hypothesize that resistance to the somatotropic actions of GH and IGF-I in short SGA children may contribute directly to reduced insulin sensitivity.

Size at birth, adult intestinal calcium absorption and 1,25(OH)(2) vitamin D

BACKGROUND

Adult bone mineral status is modified by early environmental influences, but the mechanism of this phenomenon is unknown. Intestinal calcium absorption and vitamin D metabolism are integrally involved in bone metabolism and may be programmed during early life.

AIM

To examine the early-life influences on calcium absorption and its control in 322 post-menopausal female twins.

METHODS

Intestinal calcium absorption was assessed by the stable strontium (Sr) method. Serum PTH, 25(OH) and 1,25(OH)(2) vitamin D were measured and recalled birth weight recorded.

RESULTS

Fractional intestinal Sr absorption (alpha Sr) was correlated with serum 1,25(OH)(2) vitamin D (p<0.001), but not with 25(OH) vitamin D. Birth weight was inversely associated with serum 1,25(OH)(2) vitamin D (p=0.04), the association being independent of serum calcium, phosphate, creatinine and PTH. Birth weight was inversely correlated with alpha Sr (p=0.03), this association being independent of age, season, customary calcium intake and serum 25(OH) vitamin D; however, when serum 1,25(OH)(2) vitamin D was added into the model, the association became non-significant, suggesting that the association was partially mediated via serum 1,25(OH)(2) vitamin D.

DISCUSSION

We found a significant inverse association between birth weight and intestinal calcium absorption that is partially explained by an association between serum 1,25(OH)(2) vitamin D and birth weight. This suggests a mechanism whereby the intra-uterine environment might affect adult skeletal status.

Relation between serum insulinlike growth factor-1, insulinlike growth factor binding protein-2, and insulinlike growth factor binding protein-3 and nutritional intake in premature infants with bronchopulmonary dysplasia

BACKGROUND

The usefulness of serum insulinlike growth factor (IGF)-system-peptide measurement to assess the adequacy of nutritional intake in premature infants with chronic lung disease bronchopulmonary dysplasia (BPD) was assessed.

METHODS

Twenty-nine premature infants had serial measurements taken of their serum IGF-1, insulinlike growth factor binding protein (IGFBP)-2, and IGFBP-3 concentrations between 2 and 6 weeks of age. Regression analyses were used to examine the relation between nutritional parameters and IGF-1, IGFBP-2, and IGFBP-3 concentrations in premature infants with and without BPD.

RESULTS

The group of infants with BPD (n = 12) did not differ from infants without BPD (n = 17) in gestational age or weight at entry, but gained less weight during the study period. In infants without BPD, IGF-1 correlated positively with protein intake (r = 0.50) and caloric intake (r = 0.41) over the 3 days before sample collection and with weight change over the previous week (r = 0.46). In contrast, infants with BPD showed a significant correlation between IGF-1 and weight change (r = 0.54) only. There was a significant negative correlation between IGFBP-2 and protein intake in infants without BPD (r = -0.50) and in infants with BPD (r = -0.41). Negative correlations between IGFBP-2 and both weight change (r = -0.64) and caloric intake (r = -0.43) over the previous week were found only in the group of infants without BPD. IGFBP-3 correlated positively with weight changes and protein intake in both groups but correlated with caloric intake only in the group without BPD. Multiple regression analyses were used to determine significant independent variables associated with IGF-1, IGFBP-2, and IGFBP-3. In infants without BPD, significant independent predictors of IGFBP-2 were 7-day weight change and 2-day protein intake; 3-day caloric intake was the only significant independent predictor for IGFBP-3. For infants with BPD, 3-day weight gain was the only independent variable associated with serum IGF-1. Protein intake in the week before sample collection was an independent predictor of IGFBP-2 and 3-day weight change and 2-day protein intake were independent predictors of IGFBP-3.

CONCLUSIONS

These results confirm that changes in serum IGF-1, IGFBP-2, and IGFBP-3 reflect the nutritional status of premature infants and demonstrate that the relation between these proteins and nutritional intake differs in premature infants with and without BPD. Refinement of these observations by future studies may permit a more accurate determination of the protein and caloric intake sufficient for growth and repair after injury in premature infants with lung disease.

Programming other hormones that affect insulin

The metabolic syndrome is associated with a marked increase in risk of type 2 diabetes and atherosclerotic vascular disease (AVD). The mechanism responsible for the metabolic syndrome is uncertain, but recent evidence suggests that a combination of low birth weight and adult obesity is associated with a markedly increased prevalence. Insulin resistance is the cardinal feature of the metabolic syndrome. Several hormones, have modes of action that either potentiate or reduce the biological actions of insulin and, therefore, attenuate or induce insulin resistance. Since insulin action may be modified, these hormones potentially contribute to the pathogenesis of the metabolic syndrome. The purpose of this review is to discuss programming of hormones that modulate insulin action. The review focuses on two major endocrine pathways: (i) glucocorticoid hormone action; and (ii) the growth hormone (GH)-insulin-like growth factor (IGF-1) axis, and discusses mechanisms linking abnormal activity of these pathways with reduced early growth, adult obesity and the metabolic syndrome.

Insulin-like growth factor serum concentrations reflect insufficient growth in a hypoplastic infant with partial trisomy 9q in the 12th week of life

This report presents changes of IGFs and IGFBPs in a female infant with partial trisomy 9q in the 12th week of life. Studying deficient growth in this hypoplastic infant (birth weight 1405 g, birth length 36 cm) with dysmorphic features, the following changes in IGFs and IGFBPs were detected (microg/l): IGF-I: 26.5 vs 48.1 in healthy infants; IGF-II: 420 vs 728; IGFBP-2: 931 vs 524; IGFBP-3: 800 vs 1070. This demonstrates that IGFs and IGFBPs may reflect individual insufficient growth even at this early age.

Maternal insulin-like growth factor binding protein-1, body mass index, and fetal growth

AIM

To examine the hypothesis that the maternal insulin-like growth factor system may constrain fetal growth.

METHODS

A prospective observational study of maternal serum insulin-like growth factor binding protein-1 (IGFBP-1) and fetal growth was undertaken in neonates with birthweights below the 5th centile. They had been classified either as having fetal growth restriction (FGR) due to placental dysfunction (increased umbilical artery Doppler pulsatility index (PI); n = 25) or as being small for gestational age (SGA; normal umbilical artery PI, growth velocity and amniotic fluid; n = 27). Eighty nine controls had normal birthweights (5th-95th centile), umbilical artery PI, growth velocity, and amniotic fluid. IGFBP-1 was measured by radioimmunoassay.

RESULTS

Among the controls, there was no significant correlation between IGFBP-1 and birthweight after allowing for body mass index (BMI). Maternal BMI was high in FGR and after adjusting for this, IGFBP-1 was increased (109 ng/ml) compared with SGA babies (69 ng/ml) and controls (57 ng/ml) and correlated with the umbilical artery PI.

CONCLUSIONS

Maternal IGFBP-1 is probably not part of normal placental function. Its increase in FGR could be the cause or consequence of impaired placental perfusion, but high IGFBP-1 concentrations might further reduce the availability of maternal IGF-I to the placenta. This could worsen placental function and so adversely affect fetal growth.

Precocious pubarche, dyslipidemia, and low IGF binding protein-1 in girls: relation to reduced prenatal growth

An increasing series of pediatric endocrinopathies and metabolic anomalies has been recognized as related to reduced prenatal growth. We have tested whether the association of precocious pubarche (PP), dyslipidemia, and low serum IGF binding protein-1 in girls is also related to reduced prenatal growth. Fasting serum lipids, lipoproteins, and IGFBP-1 concentrations were measured in 187 girls (83 without PP and 104 with PP; mean age, 11.8 y; range, 5-18 y) with known birthweight and gestational age, the latter being transformed into birthweight SD scores. Birthweight SD scores of girls with PP were lower than those of girls without PP. Within the group of PP girls, those with dyslipidemia and low IGFBP-1 had lower (p < 0.0001) birth-weight SD scores (-2.02+/-0.23; mean +/- SEM) than those with normal lipids, lipoproteins, and IGFBP-1 (-0.37+/-0.15), whereas girls with an intermediate number of abnormalities had intermediate birthweight SD scores (-0.80+/-0.18). In conclusion, dyslipidemia and low serum IGFBP-1 in girls with PP were found to be related to reduced prenatal growth, an observation pointing to the prenatal origin of these metabolic abnormalities.

Impaired Response of Serum IGF-I Levels to Puberty in Previously Malnourished Adolescents

Serum levels of IGF-I were measured in Barbadian children, aged 9-15 years, half of whom had experienced protein-energy malnutrition limited to the first year of life. Despite current nutritional adequacy, menarche was delayed more than one year in the girls with a history of early malnutrition and their IGF-I levels failed to show the 60% postmenarchic increase seen in the controls. In addition, the IGF-I levels of boys and girls with prior malnutrition in infancy were not significantly correlated with current anthropometric measurements, whereas IGF-I values of control boys and girls were significantly correlated for almost every growth parameter. Infantile malnutrition may cause an alteration in hypothalamic function resulting both in delayed onset of hypothalamic pituitary functions needed for puberty, and in an impaired growth hormone-IGF-I response.

A prospective study of maternal serum insulin-like growth factor-I in pregnancies with appropriately grown or growth restricted fetuses

OBJECTIVE

To determine whether there is a relationship between maternal serum insulin-like growth factor-I and fetal growth, consistent with the hypothesis that insulin-like growth factor-I influences maternal constraint upon fetal growth by controlling placental transfer.

DESIGN

A prospective, observational study.

SETTING

Fetal medicine unit and antenatal clinic of a large teaching hospital.

POPULATION

One hundred and forty-one pregnant women identified as having small or normally grown fetuses.

METHODS

Fetuses were scanned every two weeks with maternal venesection at each visit. Cases (birthweight < 5th centile) were assigned to two groups: fetal growth restriction due to placental dysfunction (umbilical artery Doppler, growth velocity pulsatility index > +2 SD; n = 25) and normal small-for-gestational-age (normal Doppler, growth velocity and amniotic fluid; n = 27). Eighty-nine controls had birthweights between the 5th and the 95th centiles, normal Doppler, growth velocity and amniotic fluid. Insulin-like growth factor-I was measured by radioimmunoassay, and its relationship to gestational age and birthweight was assessed by regression analysis. Comparisons between case groups were made by Student's t test or analysis of covariance to allow for the effect of birthweight.

OUTCOME MEASURE

The last insulin-like growth factor-I level before delivery within the different subgroups.

RESULTS

In controls, maternal insulin-like growth factor-I increased with gestational age (r = 0.40; P = 0.0001) but did not correlate with birthweight. Insulin-like growth factor-I was low in the mothers of growth restricted fetuses (-1.56 SD; P = 0.0001), but not in those with small-for-gestational age fetuses.

CONCLUSIONS

The control and small-for-gestational-age data suggest that maternal insulin-like growth factor-I is not associated with endocrine control of normal placental function. Low insulin-like growth factor-I relates to poor placental transfer, as indicated by Doppler, rather than to low birthweight. Whether this is a regulatory mechanism, a cause or a consequence of placental dysfunction needs further study.

Hypoxia stimulates insulin-like growth factor binding protein 1 (IGFBP-1) gene expression in HepG2 cells: a possible model for IGFBP-1 expression in fetal hypoxia

IGFBP-1 is elevated in fetuses with long-term, chronic hypoxia and intrauterine growth restriction. We investigated the hypothesis that hypoxia regulates IGFBP-1 in the human fetus in vivo and IGFBP-1 gene expression and protein in vitro. Umbilical artery IGFBP-1 levels (mean +/- SEM) from term babies with respiratory acidosis (acute hypoxia), normal babies, and those with mixed respiratory/metabolic acidosis (more profound and prolonged hypoxia) were measured using an immunoradiometric assay. IGFBP-1 levels were similar in normal (n = 12) and acutely hypoxic (n = 6) babies (189.1 +/- 71.8 vs. 175.8 +/- 45.9 ng /ml, respectively, P = 0.789). However, with more profound and prolonged hypoxia (n = 19), IGFBP-1 levels were markedly elevated (470.6 +/- 80.0 ng /ml, P = 0.044). To investigate IGFBP-1 regulation by hypoxia in vitro, HepG2 cells were incubated under hypoxia (pO2 = 2%) and normoxia (pO2 = 20%). IGFBP-1 protein and mRNA increased 8- and 12-fold, respectively, under hypoxic conditions. Hypoxia did not affect protein or mRNA levels of IGFBP-2 or -4. IGFBP-5 and -6 mRNAs, undetectable in control cells, were not induced by hypoxia, whereas minimally expressed IGFBP-3 mRNA increased twofold. Investigation into IGFBP-1 gene structure revealed three potential consensus sequences for the hypoxia response element (HRE) in the first intron. To investigate functionality, a 372-bp fragment of IGFBP-1 intron 1, containing putative HREs, was placed 5' to a heterologous hsp70 promoter in a plasmid using luciferase as a reporter gene. Under hypoxia, reporter gene activity increased up to 30-fold. Mutations in the middle HRE abolished reporter activity in response to hypoxia, suggesting that this HRE is functional in the IGFBP-1 hypoxia response. Cotransfection of HRE reporter genes with a constitutively expressing hypoxia-inducible factor 1 plasmid in HepG2 cells resulted in a fourfold induction of reporter activity, suggesting a role for hypoxia-inducible factor 1 in hypoxia induction of IGFBP-1 gene expression. These data support the hypothesis that hypoxia regulation of IGFBP-1 may be a mechanism operating in the human fetus to restrict insulin-like growth factor-mediated growth in utero under conditions of chronic hypoxia and limited substrate availability.

Insulin-like growth factor-1 in relation to adult weight and birth weight in healthy nulliparous women

OBJECTIVE

To study the relationships between plasma insulin-like growth factor-1 (IGF-1) concentrations and birth weight, current weight and other constitutional factors among healthy, nulliparous women aged 19-25 years.

DESIGN AND METHODS

Forty healthy female university students aged 19-25 years volunteered for this study. They had never been pregnant and were not using oral contraceptives (OCs). Blood samples were drawn both in the follicular and luteal cycle phases (08:00-10:00 h) and weight, height, and waist-hip ratio were measured at the same time by one person (H.J). Information regarding age, birth weight, OC use, etc. was obtained from a questionnaire filled out by the women. Plasma IGF-1 concentrations were analyzed by radio immunoassay.

RESULTS

In a multivariate model including birth weight, current weight and age, IGF-1 was significantly inversely associated with birth weight in both cycle phases, while current weight was positively associated with IGF-1 in both cycle phases although only significantly so in the follicular phase. IGF-1 concentrations in both cycle phases showed a non-significant decrease with age.

CONCLUSION

In this group of 19-25-year-old healthy nulliparous women IGF-1 displayed a significant inverse association with birth weight in both cycle phases given that the current weight was adjusted for, while current weight was positively related to IGF-1 concentrations.

Food restriction alters pregnancy-associated changes in IGF and IGFBP in the guinea pig

The effect of moderate food restriction on pregnancy-associated changes in weight gain, body composition, and circulating insulin-like growth factors (IGF) I and II and IGF-binding proteins (IGFBP)-1 through-4 and their relationship was determined in the guinea pig. Pregnancy did not stimulate weight gain but reduced fat deposition in ad libitum-fed animals and increased weight gain and fat deposition in food-restricted animals relative to their respective virginal group. Pregnancy increased the abundance of circulating IGF-I regardless of food intake and increased that of IGF-II in food-restricted animals only. Pregnancy also increased circulating IGFBP-1 and -2 in ad libitum-fed and food-restricted animals and IGFBP-4 in ad libitum-fed animals. Multiple regression analysis showed that maternal weight gain was negatively associated with circulating IGF-II and IGFBP-2. Fetal weight was positively associated with maternal circulating IGF-II and negatively associated with maternal circulating IGFBP-1 and -2. Significant interactions indicate, however, that the role of IGF-II and IGFBP-1 on fetal growth is dependent on the nutritional status of the mother.