Relation of cord serum levels of growth hormone, insulin-like growth factors, insulin-like growth factor binding proteins, leptin, and interleukin-6 with birth weight, birth length, and head circumference in term and preterm neonates

Inflammation at birth and the insulin-like growth factor system in very preterm infants

BACKGROUND

Foetal inflammation is associated with an increased risk of brain damage in preterm infants whereas IGF-I is essential for cerebral development and exhibits anti-apoptotic properties.

AIM

To assess levels of IGF-I and IGF binding proteins at very preterm birth and to evaluate their relationship with foetal pro-inflammation and cerebral damage.

METHODS

Levels of IGF-I, IGF binding protein 3 (IGFBP-3), high- (hp) and low-phosphorylated (lp) IGFBP-1 in cord blood and neonatal blood at 72 h after delivery were analysed in relation to levels of cytokines and cerebral damage as detected by ultrasound in 74 inborn infants [mean gestational age (GA) 27.1 weeks]. Evaluation was performed separately according to birth weight for GA.

RESULTS

In cord blood of infants appropriate for gestational age (AGA) higher levels of IL-6 and IL-8 were associated with lower IGF-I (r =-0.38, p = 0.008 and r =-0.36, p = 0.014). Higher levels of IL-6, IL-8 and TNF-alpha were associated with both higher levels of lpIGFBP-1 (r = 0.54, p < 0.001, r = 0.50, p < 0.001 and r = 0.13, p = 0.012, respectively) and hpIGFBP-1 (r = 0.55, p < 0.001, r = 0.45, p = 0.002 and r = 0.32, p = 0.026, respectively). Infants with intraventricular haemorrhage grade III (n = 5) had higher levels of lp/hpIGFBP-1 in cord blood (p = 0.001 and 0.002, respectively).

CONCLUSION

Pro-inflammation at birth is associated with changes in the IGF-system. This may be of importance for development of brain damage in preterm infants.

Postnatal nutrition and adult health programming

The early postnatal interplay between nutrition, growth patterns, and metabolic and epigenetic phenomena is crucial in determining subsequent health; health that extends through the lifetime of the individual and very likely even into subsequent generations. Recent research in the area of postnatal nutrition and its relationship to adult health, with an emphasis on the appropriate-for-gestational-age infant who is born prematurely and who undergoes growth delays, is presented. Select studies in animals, pertinent to understanding the mechanisms of how early postnatal under- and overnutrition might affect adult health and propagate to subsequent generations, are reviewed. Scientifically based approaches to administering postnatal nutrition designed to improve outcomes and areas where future investigations are needed are presented.

Elevated placental expression of the imprinted PHLDA2 gene is associated with low birth weight

The identification of genes that regulate fetal growth will help establish the reasons for intrauterine growth restriction. Most autosomal genes are expressed biallelically, but some are imprinted, expressed only from one parental allele. Imprinted genes are associated with fetal growth and development. The growth of the fetus in utero relies on effective nutrient transfer from the mother to the fetus via the placenta. Some current research on the genetic control of fetal growth has focused on genes that display imprinted expression in utero. The expression levels of four imprinted genes, the paternally expressed insulin growth factor 2 (IGF2), the mesoderm-specific transcript isoform 1 (MEST); the maternally expressed pleckstrin homology-like domain, family A, member 2 (PHLDA2); and the polymorphically imprinted insulin-like growth factor 2 (IGF2R) gene are all known to have roles in fetal growth and were studied in the placentae of 200 white European, normal term babies. The quantitative expression analysis with real-time PCR showed the maternally expressing PHLDA2 but not the paternally expressing IGF2 and MEST, nor the polymorphic maternally expressing IGF2R placental levels to have a statistically significant effect on birth weight. PHLDA2 expression levels are negatively correlated with size at birth. These data implicate PHLDA2 as an imprinted gene important in fetal growth and also as a potential marker of fetal growth.

Interleukin-6 and insulin-like growth factor system relationships and differences in the human placenta and fetus from the 35th week of gestation

The integrity of the insulin-like growth factor (IGF) system is essential for normal fetal growth. Cytokine and IGF-IGFBP relationships have been shown in specific tissues, but it is unknown whether these occur in the placenta. We aimed to assess possible differences in the IGF system depending on gestational age (GA) from week 35 to 40, and to study relationships of IL-6 with components of the IGF system in the placenta and newborn infant. We followed 32 normal births and collected whole villous tissue and cord serum. Total RNA was extracted from the placenta samples, reverse transcribed and then real-time quantitative (TaqMan) RT-PCR was performed to quantify cDNA for IGF-I, IGF-II, IGFBP-1, IGFBP-2 and IL-6. The corresponding proteins were assayed in placenta lysates and cord serum using specific commercial kits. Two groups of subjects (Group 1, 35-37 weeks GA, N=12 and Group 2, 38-40 weeks GA, N=20) were studied. In placenta, IGF-I mRNA was more abundant than IGF-II mRNA at all times and together with IGFBP-1mRNA were less expressed at term. IGFBP-2 and IL-6 mRNAs were higher after week 37 GA. IL-6 and IGFBP-2 gene expression were closely related. The corresponding proteins showed similar differences to the genes but IGF-I was undetectable in the lysates, whereas IGF-II was abundant. IGFBP-2 concentrations were very high and greater than those of IGFBP-1. In the newborn, no difference was seen in any cord serum protein after week 35 GA. IGFBP-1 was negatively correlated with parameters of neonatal size. In conclusion, this study reports new insights into IL-6, IGF-IGFBP relationships within the human placenta and shows the importance of comparing subjects with the same GA.

Estrogen and -Fetoprotein Levels in Maternal and Umbilical Cord Blood Samples in Relation to Birth Weight

Birth weight has been associated with a subsequent risk of breast cancer. The present study examined associations between birth weight and pregnancy estrogens and alpha-fetoprotein (AFP). The concentrations of estradiol, estriol, and AFP were measured in maternal and umbilical cord blood samples from 194 women during pregnancy and at birth. Birth weight was significantly positively correlated with maternal serum estradiol and estriol levels in the 29th week (estradiol: r = 0.16, P = 0.03; estriol: r = 0.29, P = 0.001) and at delivery (estradiol: r = 0.20, P = 0.01; estriol: r = 0.41, P < 0.0001) after controlling for covariates. The umbilical cord estriol level was moderately but significantly correlated with birth weight (r = 0.15, P = 0.049). There was no significant association between umbilical cord serum estradiol and birth weight. There was no significant association between birth weight and maternal serum AFP in any gestational week. Umbilical cord AFP was significantly inversely correlated with birth weight (r = -0.16, P = 0.04). Umbilical cord AFP was unrelated to cord levels of estradiol and estriol. The data suggested a greater exposure to estriol and a lower exposure to AFP among high birth weight babies.

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.

Elevated circulating insulin-like growth factor binding protein-1 is sufficient to cause fetal growth restriction

IGF binding protein-1 (IGFBP-1) inhibits the mitogenic actions of the IGFs. Circulating IGFBP-1 is elevated in newborns and experimental animals with fetal growth restriction (FGR). To establish a causal relationship between high circulating IGFBP-1 and FGR, we have generated transgenic mice using the mouse alpha-fetoprotein gene promoter to target overexpression of human IGFBP-1 (hIGFBP-1) in the fetal liver. These transgenic mice (AFP-BP1) expressed hIGFBP-1 mainly in the fetal hepatocytes, starting at embryonic d 14.5 (E14.5), with lower levels in the gut. The expression peaked at 1 wk postnatally (plasma concentration, 474 +/- 34 ng/ml). At birth, AFP-BP1 pups were 18% smaller [weighed 1.34 +/- 0.02 g compared with 1.62 +/- 0.04 g for wild type (WT); P < 0.05], and they did not demonstrate any postnatal catch-up growth. The placentas of the AFP-BP1 mice were larger than WT from E16.5 onwards (150 +/- 12 for AFP-BP1 vs. 100 +/- 5 mg for WT at E16.5; P < 0.05). Thus, this model of FGR is associated with a larger placenta, but without postnatal catch-up growth. Overall, these data clearly demonstrate that high concentrations of circulating IGFBP-1 are sufficient to cause FGR.

Leptin in pregnancy: an update

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

An IGF-I promoter polymorphism modifies the relationships between birth weight and risk factors for cardiovascular disease and diabetes at age 36

OBJECTIVE

To investigate whether IGF-I promoter polymorphism was associated with birth weight and risk factors for cardiovascular disease (CVD) and type 2 diabetes (T2DM), and whether the birth weight--risk factor relationship was the same for each genotype.

DESIGN AND PARTICIPANTS

264 subjects (mean age 36 years) had data available on birth weight, IGF-I promoter polymorphism genotype, CVD and T2DM risk factors. Student's t-test and regression analyses were applied to analyse differences in birth weight and differences in the birth weight--risk factors relationship between the genotypes.

RESULTS

Male variant carriers (VCs) of the IGF-I promoter polymorphism had a 0.2 kg lower birth weight than men with the wild type allele (p = 0.009). Of the risk factors for CVD and T2DM, solely LDL concentration was associated with the genotype for the polymorphism. Most birth weight--risk factor relationships were stronger in the VC subjects; among others the birth weight--systolic blood pressure relationship: 1 kg lower birth weight was related to an 8.0 mmHg higher systolic blood pressure

CONCLUSION

The polymorphism in the promoter region of the IGF-I gene is related to birth weight in men only, and to LDL concentration only. Furthermore, the genotype for this polymorphism modified the relationships between birth weight and the risk factors, especially for systolic and diastolic blood pressure.

The role of maternal factors, postnatal nutrition, weight gain, and gender in regulation of serum IGF-I among preterm infants

IGF-I is important for somatic growth and development of the human fetus and neonate. IGF-I also plays an important role in normal vascularization of human retina, as it has been suggested that insufficient IGF-I may be a factor in the development of retinopathy of prematurity. The principal regulator of the bioavailability of IGF-I in the circulation is IGF binding protein 3 (IGFBP-3). The aim of this study was to study factors associated with postnatal serum concentrations of IGF-I and of IGFBP-3 in preterm infants from birth to an age corresponding to 40 wk postmenstruation. We conducted a prospective, longitudinal study in which we measured serum IGF-I and IGFBP-3 concentrations in 76 preterm infants from birth (postmenstrual ages 23-32 wk) until discharge from hospital around 40 wk. Information regarding nutrition, weight gain, maternal factors, and treatment with corticosteroids were collected weekly. Variables found to be associated with postnatal change over time of serum IGF-I and IGFBP-3 were postmenstrual age (p<0.001), weight gain (standard deviation score) (p<0.001), and enteral intake of protein (p<0.001). Male gender was associated with lower IGF-I levels (p<0.001). The relationship between protein intake and IGF-I (and also between protein intake and IGFBP-3) was positive, as was the relationship between weight gain and IGF-I (and between weight gain and IGFBP-3). These results indicate that the degree of prematurity, low enteral protein intake, male gender, and slow weight gain are associated with a slower postnatal increase of IGF-I in preterm infants.

Early postnatal growth in preterm infants and cord blood leptin

Although circulating leptin and insulin concentration is linked to intrauterine growth, fetal development and birth weight in full-term infants, there has been no enquiry into the influence of cord blood insulin and leptin for catch-up growth in preterm infants. The study evaluated the association of cord blood leptin with growth and weight gain of 96 premature babies during 6 months (corrected age). The temporal changes of anthropometric indexes over this period were calculated by repeated random regression (PROC MIXED) using SAS. Cord blood leptin was negatively associated with the rate of change in BMI (p=0.01) and length (p<0.001), from birth until 64 postnatal weeks. Insulin was positively associated with the change rate in BMI (p=0.03); however, this disappeared when adjusted for birth weight. For the first time, the association between lower leptin levels with greater catch up growth is shown for both BMI and length among preterm children. In conclusion, leptin levels at birth, but not insulin levels, predict growth rates.

Intrauterine growth retardation and consequences for endocrine and cardiovascular diseases in adult life: does insulin-like growth factor-I play a role?

Low birth weight has been associated with an increased incidence of ischaemic heart disease (IHD) and type 2 diabetes. Endocrine regulation of fetal growth by growth hormone (GH) and insulin-like growth factor (IGF)-I is complex. Placental GH is detectable in maternal serum from the 8th to the 12th gestational week, and rises gradually during pregnancy where it replaces pituitary GH in the maternal circulation. The rise in placental GH may explain the pregnancy-induced rise in maternal serum IGF-I levels. In the fetal compartment, IGF-I levels increase significantly in normally growing fetuses from 18 to 40 weeks of gestation, but IGF-I levels are four to five times lower than those in the maternal circulation. Thus IGF-I levels in fetal as well as in maternal circulation are thought to regulate fetal growth. Circulating levels of IGF-I are thought to be genetically controlled and several IGF-I gene polymorphisms have been described. IGF-I gene polymorphisms are associated with birth weight in some studies but not in all. Likewise, IGF-I gene polymorphisms are associated with serum IGF-I in healthy adults in some studies, although some controversy exists. Serum IGF-I decreases with increasing age in healthy adults, and this decline could hypothetically be responsible for the increased risk of IHD with ageing. A recent nested case-control study found that adults without IHD, but with low circulating IGF-I levels and high IGF binding protein-3 levels, had a significantly increased risk of developing IHD during a 15-year follow-up period. In summary, the GH/IGF-I axis is involved in the regulation of fetal growth. Furthermore, it has been suggested that low IGF-I may increase the risk of IHD in otherwise healthy subjects. Hypothetically, intrauterine programming of the GH/IGF axis may influence postnatal growth, insulin resistance and consequently the risk of cardiovascular disease. Thus IGF-I may serve as a link between fetal growth and adult-onset disease.

Serum levels of leptin, insulin-like growth factor-I and insulin-like growth factor binding protein-3 in women with pre-eclampsia, and their relationship to insulin resistance

The present study was carried out to compare serum levels of leptin, insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-3 (IGFBP-3), homeostasis model assessment--(pancreatic beta-cell function) (HOMA-(%B)) and homeostasis model assessment--(tissue insulin sensitivity) (HOMA-(%S)) in women with mild and severe pre-eclampsia and normotensive pregnant women; and to evaluate the possible relationships between these parameters in the pathogenesis of pre-eclampsia. Seventy-three women were divided into three groups: group A consisted of 20 normotensive pregnant women (NPW); group B consisted of 25 women with mild pre-eclampsia (MPE); and group C consisted of 28 women with severe pre-eclampsia (SPE). Serum level of leptin was measured by enzyme immunoassay using a commercial kit. Serum levels of IGF-I and IGFBP-3 were measured with a two-site immunoradiometric assay. Serum level of insulin was measured by the electrochemiluminescence immunoassay method. HOMA used indices of pancreatic beta-cell function and tissue insulin sensitivity. Differences between groups were compared by one-way analyses of variance and the post hoc Tukey-HSD test for multiple comparisons; however, when a variable was not normally distributed, the Mann-Whitney U test was used. Associations between variables were tested using Pearson's coefficient of correlation. Birth weight was significantly lower (p < 0.001) in the MPE and SPE groups than in the NPW group. Serum levels of leptin and insulin in women with SPE and MPE were significantly higher (p < 0.001) than in NPW. Serum levels of IGF-I and IGFBP-3 were significantly lower in women with SPE and MPE compared with NPW (p < 0.001). The mean HOMA-(%B) level in women with SPE and MPE was significantly higher than in NPW (p < 0.001), whereas the mean HOMA-(%S) level in women with SPE and MPE was significantly lower than in NPW (p < 0.001). In the SPE group, systolic blood pressure correlated significantly with serum levels of IGF-I and leptin (r = 0.375, p < 0.05 and r = 0.495, p < 0.01, respectively). A negative correlation between mean HOMA-(%S) level and serum IGFBP-3 level was noted (r = -0.357, p < 0.05). There was a positive correlation between serum level of IGF-I and mean HOMA-(%B) level in mildly pre-eclamptic women (r = 0.541, p < 0.01). We conclude that pre-eclampsia is associated with insulin resistance; and that existing hyperinsulinemia and insulin resistance in women with pre-eclampsia seem not to correlate with leptin and birth weight, but may correlate positively with IGF-1 and IGFBP-3. Therefore we think that hyperleptinemia, low IGF-I or IGFBP-3, and insulin resistance may contribute to the pathogenesis of pre-eclampsia.

IGFBP-1 levels in adult women born small for gestational age suggest insulin resistance in spite of normal BMI

OBJECTIVE

Impaired fetal development may contribute to decreased insulin sensitivity. This study was designed to characterize serum markers of insulin resistance in adults born small for date or born prematurely.

STUDY DESIGN

Fifty subjects, all women, were evaluated at a mean age +/- SD of 26 +/- 2 years (range: 23-30 years). They were allocated to three groups: (i) born fullterm with birth weight <2600 g (n = 18) (small for gestational age, SGA), (ii) born before gestational week 32 (n = 15) (ex-preterm), and (iii) controls, born fullterm with appropriate birth weight (n = 17). Anthropometric data as well as fasting serum samples of plasma B-glucose, serum lipids, insulin, insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-1 (IGFBP-1) levels were determined.

RESULTS

In the SGA group final height was lower and they weighed less compared with the controls. Fasting insulin and glucose levels did not differ amongst the groups. Triglycerides were lower in the SGA group and in the ex-preterm group compared with the controls (P < 0.05). The SGA group showed lower IGFBP-1 levels compared with the controls median 17 (range 3-121) vs. 26 (7-67) microg L-1; P < 0.05]. The IGF-I levels in the SGA, ex-preterm and control groups were 212 +/- 58, 259 +/- 37 and 216 +/- 32 microg L-1, respectively, corresponding to a mean SD score of -0.8 +/- 1.0, 0.1 +/- 0.6 and -0.6 +/- 0.6.

CONCLUSION

As IGFBP-1 is a marker of insulin sensitivity, the low levels observed in adult women with normal BMI, born small for date, suggest relative insulin resistance in spite of normal BMI.