Intrauterine growth retardation: evidence for the activation of the insulin-like growth factor (IGF)-related growth-promoting machinery and the presence of a cation-independent IGF binding protein-3 proteolytic activity by two months of life

Sheep recombinant IGF-1 promotes organ-specific growth in fetal sheep

IGF-1 is a critical fetal growth-promoting hormone. Experimental infusion of an IGF-1 analog, human recombinant LR3 IGF-1, into late gestation fetal sheep increased fetal organ growth and skeletal muscle myoblast proliferation. However, LR3 IGF-1 has a low affinity for IGF binding proteins (IGFBP), thus reducing physiologic regulation of IGF-1 bioavailability. The peptide sequences for LR3 IGF-1 and sheep IGF-1 also differ. To overcome these limitations with LR3 IGF-1, we developed an ovine (sheep) specific recombinant IGF-1 (oIGF-1) and tested its effect on growth in fetal sheep. First, we measured in vitro myoblast proliferation in response to oIGF-1. Second, we examined anabolic signaling pathways from serial skeletal muscle biopsies in fetal sheep that received oIGF-1 or saline infusion for 2 hours. Finally, we measured the effect of fetal oIGF-1 infusion versus saline infusion (SAL) for 1 week on fetal body and organ growth, in vivo myoblast proliferation, skeletal muscle fractional protein synthetic rate, IGFBP expression in skeletal muscle and liver, and IGF-1 signaling pathways in skeletal muscle. Using this approach, we showed that oIGF-1 stimulated myoblast proliferation in vitro. When infused for 1 week, oIGF-1 increased organ growth of the heart, kidney, spleen, and adrenal glands and stimulated skeletal myoblast proliferation compared to SAL without increasing muscle fractional synthetic rate or hindlimb muscle mass. Hepatic and muscular gene expression of IGFBPs one to three was similar between oIGF-1 and SAL. We conclude that oIGF-1 promotes tissue and organ-specific growth in the normal sheep fetus.

IGF-I in cord blood is predictive of final height in monozygotic twins with intra-twin birth weight differences

OBJECTIVE

Adverse prenatal conditions can exert a long-lasting impact on growth up to final height (FH). Due to different prenatal nutrient availability, monozygotic twin pairs with discordant birth weight (bw) provide an excellent model to examine the impact of genes and environment and to analyse the predictive value of bw, birth length (bl) and cord blood (cb) concentration of IGF-I on FH.

PATIENTS AND METHODS

Twenty eight monozygotic twin pairs with intra-twin bw-/bl-differences were studied at birth and longitudinally until FH. Intra-twin bw difference >1 SDS was defined "discordant" (n = 10 pairs). IGF-I was analysed in cord blood in all twins. Intra-twin differences (∆) in bw, bl and cord blood IGF-I were correlated with ∆FH.

RESULTS

Throughout growth and up until FH intra-twin length/height differences remained for all but two (26/28) twins and for all (10/10) discordant twins. In the discordant group, a highly significant intra-twin difference for FH-SDS was found with a mean intra-twin Δheight- SDS of 1.23 (range, 0.29-2.34). This corresponds to a mean Δintra-twin difference at FH of 7.9 cm (3.1 inch; range, 2-15 cm [0.79-5.9 inch]). Correlation coefficients were calculated to identify factors predicting FH: ∆bw (r = .678; P = .0005), ∆bl (r = .333; P = .0002) and ∆IGF-I in cb (r = .418; P = .0023). Interaction terms showed that IGF-I is an additional factor to the auxological data, leading to an improvement of the ∆FH modelling.

CONCLUSION

Prenatal environment leading to bw-/bl- and cbIGF-I differences in monozygotic twins had a long-lasting impact on growth until FH. Both, anthropometric data at birth and cbIGF-I are predictive of FH.

Current Insights into the Role of the Growth Hormone-Insulin-Like Growth Factor System in Short Children Born Small for Gestational Age

BACKGROUND

The reason for the insufficient catch-up growth seen in 10% of children born small for gestational age (SGA) is poorly understood. Disturbances in the growth hormone (GH) - insulin-like growth factor (IGF) axis might underlie this failure to show sufficient catch-up growth.

CONCLUSION

This review summarizes insights gained in the molecular and (epi) genetic mechanisms of the GH-IGF axis in short children born SGA. The most notable anomalies of the IGF system are the lowered IGF-I levels in both cord blood and the placenta, and the increased expression of IGF-binding proteins (IGFBP)-1 and IGFBP-2, which inhibit IGF-I, in the placenta of SGA neonates. These observations suggest a decreased bioactivity of IGF-I in utero. IGF-I levels remain reduced in SGA children with short stature, as well as IGFBP-3 and acid-labile subunit levels. Proteolysis of IGFBP-3 appears to be increased.

Increased placental IGF-1/mTOR activity in macrosomia born to women with gestational diabetes

AIMS

Newborns of women with gestational diabetes mellitus (GDM) are susceptible to be macrosomic, even if the blood glucose levels are in normal ranges. The underlying mechanisms are largely unknown. We tested the hypothesis that placental insulin like growth factor(IGF)-I and mammalian target of rapamycin (mTOR) signaling is activated and amino acid transporter expression is increased in women with GDM who give birth to macrosomic babies.

METHODS

50 Chinese pregnant women with GDM whose blood glucose levels were controlled within normal range were recruited and their placental tissues were collected. 23 women gave birth to macrosomia and 27 women gave birth to babies with normal birth weight. We determined the phosphorylation of key signaling molecules (including Akt, IRS-1, S6K1, 4E-BP-1, and AMPKα) in the placental IGF-I and mTOR signaling pathways. We also measured the protein expression of the amino acid transporter systems A in placenta.

RESULTS

Birth weights (range 2500-4400 g) were positively correlated to maternal IGF-1 (P < 0.05). The activity of placental IGF-I and mTOR signaling was positively correlated (P < 0.05), whereas AMPKα phosphorylation was inversely (P < 0.05) correlated to birth weight. Protein expression of the system A isoform sodium-dependent neutral amino acid transporter (SNAT) 1 were positively correlated to birth weight (P < 0.05).

CONCLUSIONS

Up-regulation of placental amino acid transporters may contribute to more macrosomic babies in women with GDM. Activation of IGF-I and mTOR signaling pathways might involve in this effect.

The Rationale for Growth Hormone Therapy in Children with Short Stature

Growth hormone (GH) was first isolated from cadaver pituitary glands, requiring laborious and expensive collection of glands, followed by extraction and purification of the hormone. This limited supply restricted its use to children with severe GH deficiency who were treated with low dosages and suboptimal schedules. The development of recombinant DNA-derived GH, allowed the production of virtually unlimited amounts of GH, leading to the approval for therapy for a large number of childhood conditions characterized by non-GH deficient short stature. The aim of this review is to provide a critical overview on the daily use of GH in two paradigmatic conditions of non-GH deficient short stature which are children born small for gestational age and with idiopathic short stature, highlighting the available strength of evidence for efficacy and safety.

Nutritional support for low birth weight infants: insights from animal studies

Infants born with low birth weights (<2500 g, LBW), accounting for about 15 % of newborns, have a high risk for postnatal growth failure and developing the metabolic syndromes such as type 2 diabetes, CVD and obesity later in life. Improper nutrition provision during critical stages, such as undernutrition during the fetal period or overnutrition during the neonatal period, has been an important mediator of these metabolic diseases. Considering the specific physiological status of LBW infants, nutritional intervention and optimisation during early life merit further attention. In this review, the physiological and metabolic defects of LBW infants were summarised from a nutritional perspective. Available strategies for nutritional interventions and optimisation of LBW infants, including patterns of nutrition supply, macronutrient proportion, supplementation of amino acids and their derivatives, fatty acids, nucleotides, vitamins, minerals as well as hormone and microbiota manipulators, were reviewed with an aim to provide new insights into the advancements of formulas and human-milk fortifiers.

Ghrelin, insulin-like growth factor I and adipocytokines concentrations in born small for gestational age prepubertal children after the catch-up growth

BACKGROUND

In children born small for gestational age (SGA) with catch-up growth, a higher risk of insulin resistance (IR) and cardiovascular diseases is noted. Ghrelin stimulates a growth hormone (GH) secretion and regulates lipid and carbohydrate metabolism. We assessed gherlin's influence on achieving normal height and the occurrence of metabolic complications in SGA children.

METHODS

Ghrelin, insulin-like growth factor type I (IGF-I), leptin, adiponectin, resistin, glucose, insulin and lipid concentrations were analysed in 134 prepubertal children in four groups: normal-height SGA, short SGA, normal-height born appropriate for gestational age (AGA) and short AGA.

RESULTS

Ghrelin and IGF-I concentrations were significantly higher while adiponectin - lower in normal-height SGA comparing to others.

CONCLUSIONS

The increased production of ghrelin and IGF-I seems to be an adaptive mechanism to achieve normal growth in SGA children. The significance of high ghrelin and low adiponectin concentrations, observed in normal-height prepubertal SGA children, requires elucidation, with reference to the development of metabolic complications.

The role and regulation of IGFBP-1 phosphorylation in fetal growth restriction

Fetal growth restriction (FGR) increases the risk of perinatal complications and predisposes the infant to developing metabolic, cardiovascular, and neurological diseases in childhood and adulthood. The pathophysiology underlying FGR remains poorly understood and there is no specific treatment available. Biomarkers for early detection are also lacking. The insulin-like growth factor (IGF) system is an important regulator of fetal growth. IGF-I is the primary regulator of fetal growth, and fetal circulating levels of IGF-I are decreased in FGR. IGF-I activity is influenced by a family of IGF binding proteins (IGFBPs), which bind to IGF-I and decrease its bioavailability. During fetal development the predominant IGF-I binding protein in fetal circulation is IGFBP-1, which is primarily secreted by the fetal liver. IGFBP-1 binds IGF-I and thereby inhibits its bioactivity. Fetal circulating levels of IGF-I are decreased and concentrations of IGFBP-1 are increased in FGR. Phosphorylation of human IGFBP-1 at specific sites markedly increases its binding affinity for IGF-I, further limiting IGF-I bioactivity. Recent experimental evidence suggests that IGFBP-1 phosphorylation is markedly increased in the circulation of FGR fetuses suggesting an important role of IGFBP-1 phosphorylation in the regulation of fetal growth. Understanding of the significance of site-specific IGFBP-1 phosphorylation and how it is regulated to contribute to fetal growth will be an important step in designing strategies for preventing, managing, and/or treating FGR. Furthermore, IGFBP-1 hyperphosphorylation at unique sites may serve as a valuable biomarker for FGR.

Current thoughts on maternal nutrition and fetal programming of the metabolic syndrome

Chronic diseases such as type 2 diabetes and cardiovascular disease are the leading cause of death and disability worldwide. Although the metabolic syndrome has been defined in various ways, the ultimate importance of recognizing this combination of disorders is that it helps identify individuals at high risk for both type 2 diabetes and cardiovascular disease. Evidence from observational and experimental studies links adverse exposures in early life, particularly relating to nutrition, to chronic disease susceptibility in adulthood. Such studies provide the foundation and framework for the relatively new field of developmental origins of health and disease (DOHaD). Although great strides have been made in identifying the putative concepts and mechanisms relating specific exposures in early life to the risk of developing chronic diseases in adulthood, a complete picture remains obscure. To date, the main focus of the field has been on perinatal undernutrition and specific nutrient deficiencies; however, the current global health crisis of overweight and obesity demands that perinatal overnutrition and specific nutrient excesses be examined. This paper assembles current thoughts on the concepts and mechanisms behind the DOHaD as they relate to maternal nutrition, and highlights specific contributions made by macro- and micronutrients.

Catch up growth in low birth weight infants: striking a healthy balance

Catch-up growth in the first few months of life is seen almost ubiquitously in infants born small for their gestational age and conventionally considered highly desirable as it erases the growth deficit. However, recently such growth has been linked to an increased risk of later adiposity, insulin resistance and cardiovascular disease in both low income and high-income countries. In India, a third of all babies are born with a low birth weight, but the optimal growth pattern for such infants is uncertain. As a response to the high rates of infectious morbidities, undernutrition and stunting in children, the current policy is to promote rapid growth in infancy. However, with socio-economic transition and urbanization making the Indian environment more obesogenic, and the increasing prevalence of type 2 diabetes and cardiovascular disease, affecting progressively younger population, the long term adverse programming effect of fast/excessive weight gain in infancy on later body composition and metabolism may outweigh short-term benefits. This review discusses the above issues focusing on the need to strike a healthy balance between the risks and benefits of catch-up growth in Indian infants.

Mechanisms of developmental programming of the metabolic syndrome and related disorders

There is consistent epidemiological evidence linking low birth weight, preterm birth and adverse fetal growth to an elevated risk of the metabolic syndrome (obesity, raised blood pressure, raised serum triglycerides, lowered serum high-density lipoprotein cholesterol and impaired glucose tolerance or insulin resistance) and related disorders. This “fetal or developmental origins/programming of disease” concept is now well accepted but the “programming” mechanisms remain poorly understood. We reviewed the major evidence, implications and limitations of current hypotheses in interpreting developmental programming and discuss future research directions. Major current hypotheses to interpret developmental programming include: (1) thrifty phenotype; (2) postnatal accelerated or catch-up growth; (3) glucocorticoid effects; (4) epigenetic changes; (5) oxidative stress; (6) prenatal hypoxia; (7) placental dysfunction; and (8) reduced stem cell number. Some hypothetical mechanisms (2, 4 and 8) could be driven by other upstream “driver” mechanisms. There is a lack of animal studies addressing multiple mechanisms simultaneously and a lack of strong evidence linking clinical outcomes to biomarkers of the proposed programming mechanisms in humans. There are needs for (1) experimental studies addressing multiple hypothetical mechanisms simultaneously; and (2) prospective pregnancy cohort studies linking biomarkers of the proposed mechanisms to clinical outcomes or surrogate biomarker endpoints. A better understanding of the programming mechanisms is a prerequisite for developing early life interventions to arrest the increasing epidemic of the metabolic syndrome, type 2 diabetes and other related disorders.

Growth and body composition in very young SGA children

Infants with a very low birth weight are at risk of a reduced number of nephrons predisposing to kidney disorder, hypertension, and metabolic syndrome. Approximately 3% of infants are born small for gestational age (SGA), defined as birth weight and/or length at least 2 SD below the mean for gestational age (GA), independently of whether these children are born prematurely or at term. About 10% of these children do not show postnatal catch-up growth and remain of short stature during childhood. Most of these infants are not growth hormone (GH)-deficient, but may have GH resistance. Although GH-resistant, the majority of patients benefit from GH therapy, normalize height during childhood, maintain a normal growth velocity during puberty, and attain a normal adult height. To date, GH has been shown to be safe and no significant adverse effects have been demonstrated. Children with congenital chronic kidney disease (CKD) are born with subnormal birth weight and length and about 25% are born SGA. Shortness and need for GH treatment is highly correlated with weight at birth and gestational age. Primary renal disorders modify the response to GH treatment. Analysis of whether SGA is an additional risk factor for CKD regarding the development of hypertension, metabolic syndrome and cardiovascular complications is required.

Effect of maternal asthma, inhaled glucocorticoids and cigarette use during pregnancy on the newborn insulin-like growth factor axis

BACKGROUND

Fetal growth varies in a sex-specific manner in response to maternal asthma during pregnancy, but the mechanisms are unclear.

OBJECTIVE

We examined the influence of maternal asthma severity and associated exposures, inhaled glucocorticoid treatment, maternal cigarette use, and fetal sex on fetal growth and placental function during pregnancy and on the newborn insulin-like growth factor (IGF) axis. STUDY SUBJECTS AND DESIGN: Fetal growth was assessed in a prospective cohort of asthmatic and non-asthmatic women (n=145). At delivery, umbilical vein plasma was collected from male (n=61, controls n=16 and asthmatic n=45) or female (n=84, controls n=22 and asthmatic n=62) fetuses. Cord plasma insulin-like growth factor (IGF) binding protein (BP)-1, IGFBP-3, IGF-1 and IGF-2 were measured by radioimmunoassay and ELISA.

RESULTS

Cord plasma IGF-1 was the main component of the neonatal IGF axis altered by asthma and cigarette use. IGF-1 was increased in the presence of mild asthma and a male fetus and decreased in the presence of a female fetus and maternal asthma with cigarette use. IGFBP-3 was also decreased in the female fetuses of pregnancies complicated by asthma and cigarette use. Inhaled glucocorticoid use for the treatment of asthma did not affect the IGF axis. The strongest overall predictor of female birth weight after accounting for asthma severity, inhaled glucocorticoid treatment and cigarette use was IGF-1. For males, the strongest predictor of birth weight was IGFBP-3.

CONCLUSION

The data suggest male and female fetuses institute different strategies in response to adverse pregnancy conditions such as asthma and cigarette use.

Small for gestational age: short stature and beyond

Depending on the definitions used, up to 10% of all live-born neonates are small for gestational age (SGA). Although the vast majority of these children show catch-up growth by 2 yr of age, one in 10 does not. It is increasingly recognized that those who are born SGA are at risk of developing metabolic disease later in life. Reduced fetal growth has been shown to be associated with an increased risk of insulin resistance, obesity, cardiovascular disease, and type 2 diabetes mellitus. The majority of pathology is seen in adults who show spontaneous catch-up growth as children. There is evidence to suggest that some of the metabolic consequences of intrauterine growth retardation in children born SGA can be mitigated by ensuring early appropriate catch-up growth, while avoiding excessive weight gain. Implicitly, this argument questions current infant formula feeding practices. The risk is less clear for individuals who do not show catch-up growth and who are treated with GH for short stature. Recent data, however, suggest that long-term treatment with GH does not increase the risk of type 2 diabetes mellitus and the metabolic syndrome in young adults born SGA.

The contributions of plasma IGF-I, IGFBP-3 and leptin to growth in extremely premature infants during the first two years

We determined the contributions of IGF-I, IGFBP-3 and leptin to growth in extremely premature infants over the first two years. Weight (Wt), crown-to heel length (CHL), plasma IGF-I, IGFBP-3 and leptin were measured in infants (gestation 24-33 wk) at birth (n = 54), expected date of delivery (EDD) and 6, 12 and 24 mo post-EDD (n = 29). Area under the curve (AUC) for hormone levels was calculated over 4 periods: birth-EDD, EDD-200 d, EDD-350 d and EDD-700 d. IGFBP-3, but not IGF-I or leptin, on day 1 correlated with birth Wt SD scores (SDS) (r = 0.46, p = 0.002) and CHL SDS (r = 0.41, p = 0.01). Wt SDS at EDD correlated with AUC IGF-I, IGFBP-3 and leptin (birth-EDD), but leptin was the best predictor in multiple regression (r = 0.65, p < 0.0001). Wt at EDD + 700 d correlated with AUC leptin (EDD-700 d) (r = 0.62, p = 0.002). CHL SDS at EDD correlated with AUC IGFBP-3 and leptin (birth-EDD), but IGFBP-3 was the best predictor (r = 0.55, p < 0.0001). CHL at EDD + 700 d correlated with AUC IGF-I and IGFBP-3 (EDD-700 d), but IGFBP-3 was the best predictor (r = 0.47, p = 0.01). Wt and CHL at birth were associated with IGFBP-3 levels in these infants. Wt at EDD and EDD + 700 d was predicted by concurrent leptin output while linear growth at EDD and EDD + 700 d was predicted by IGFBP-3 output.

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.

Pituitary mRNA expression of the growth hormone axis in the 1-year-old intrauterine growth restricted rat

Intrauterine growth restriction (IUGR) is one of the major causes of short stature in childhood. Abnormalities in the growth hormone (GH) axis have frequently been observed in children who are born intrauterine growth restricted and GH treatment is effective to improve final height. However, the way that the GH axis is involved is not fully understood. Previously, when investigating the effect of IUGR on the central somatotrophic axis, a hypothalamic effect was discovered with elevated somatostatin and decreased neuropeptide Y mRNA expression levels, whereas serum GH and insulin-like growth factor I (IGFI) were unaltered. These findings were thought to indicate a hypothalamic alteration of the GH axis due to IUGR, probably to compensate pituitary output, thereby normalising peripheral values of GH and IGFI. Therefore, the present study aimed to evaluate the effect of IUGR on the pituitary GH axis in this rat model. Pups from rats that underwent bilateral uterine artery ligation at day 17 of pregnancy were studied. Pituitary glands were collected from 1-year-old offspring for quantitative measurements of GH, GH-receptor (GH-R), GH-releasing hormone receptor (GHRH-R), somatostatin receptor subtype 2 and 5, IGFI and IGFI receptor mRNA levels using a real-time reverse transcriptase-polymerase chain reaction. In addition, liver GH-R and IGFI mRNA expression levels were measured and a radioimmunoassay was performed to determine serum IGFI levels. In the IUGR rat, levels of pituitary GH, GH-R and GHRH-R relative gene expression (RGE) were increased. No differences were found in the RGE level of all other pituitary growth factors, liver GH-R and IGFI, and serum IGFI concentration between IUGR and control rats. The present data show that intrauterine growth failure leads to changes in the pituitary that might counterbalance the effects found previously in the hypothalamus.

Hormonal regulation of postnatal growth in children born small for gestational age

Children born small for gestational age (SGA) are at high risk of permanent short stature, with approximately 10% continuing to have stature below the third centile throughout childhood and adolescence and into adulthood. The mechanisms involved in catch-up growth, and those that prevent catch-up growth, are still unknown. To date, no reliable anthropometric or endocrine parameter predictive of postnatal catch-up growth has been identified. However, subtle abnormalities in the growth hormone-insulin-like growth factor axis, the hypothalamic-pituitary-adrenal axis and thyroid function have been described, and a mechanism involving intrauterine programming of hypothalamic-pituitary function has been proposed.

Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus

The environment in which the fetus develops is critical for its survival and long-term health. The regulation of normal human fetal growth involves many multidirectional interactions between the mother, placenta, and fetus. The mother supplies nutrients and oxygen to the fetus via the placenta. The fetus influences the provision of maternal nutrients via the placental production of hormones that regulate maternal metabolism. The placenta is the site of exchange between mother and fetus and regulates fetal growth via the production and metabolism of growth-regulating hormones such as IGFs and glucocorticoids. Adequate trophoblast invasion in early pregnancy and increased uteroplacental blood flow ensure sufficient growth of the uterus, placenta, and fetus. The placenta may respond to fetal endocrine signals to increase transport of maternal nutrients by growth of the placenta, by activation of transport systems, and by production of placental hormones to influence maternal physiology and even behavior. There are consequences of poor fetal growth both in the short term and long term, in the form of increased mortality and morbidity. Endocrine regulation of fetal growth involves interactions between the mother, placenta, and fetus, and these effects may program long-term physiology.

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.

Laboratory tests and measurements in children born small for gestational age (SGA)

Children born small for gestational age are at high risk of developing insulin resistance, type 2 diabetes, hyperlipidemia, hypertension and cardiovascular disease in adulthood. In addition, approximately 10% of SGA children do not achieve a normal adult height. Studies performed in SGA children to evaluate markers of metabolic disease in prepubertal, pubertal and adolescent subjects, indicate a higher prevalence of subtle endocrine and metabolic abnormalities that may precede the onset of overt disease in adulthood. At present, however, there are no conclusive data supporting the need of systematic close monitoring of GH-IGF, hypothalamus-pituitary-adrenal and hypothalamus-pituitary-gonadal axes, as well as insulin sensitivity, glucose homeostasis, and lipid metabolism. Monitoring of metabolic parameters should probably be reserved to SGA children with genetic predisposition to type 2 diabetes and hyperlipidemia, as early identification of metabolic alterations might prompt effective preventive interventions and, ultimately, reduce cardiovascular risk.

Insulin sensitivity in children born small for gestational age (SGA)

In the past decade, several epidemiological studies have shown a relationship between intrauterine growth retardation and insulin resistance, type 2 diabetes and cardiovascular disease in adulthood. Although the biological mechanisms underlying this association are still largely unknown, different explanatory hypotheses have been proposed. It seems likely that the various pathways may interact with each other, all contributing at different degrees to the development of the metabolic disturbances.

Growth, IGF system, and cortisol in children with intrauterine growth retardation: is catch-up growth affected by reprogramming of the hypothalamic-pituitary-adrenal axis?

Intrauterine growth retardation (IUGR) is one of the major causes of short stature in childhood. Although postnatal catch-up growth occurs in the majority of IUGR children, approximately 20% of them remain permanently short. The mechanisms that allow catch-up growth or, on the contrary, prevent IUGR children from achieving a normal height are still unknown. Our aim was to investigate whether intrauterine reprogramming of hypothalamic-pituitary-adrenal axis may be involved in postnatal growth retardation of IUGR children through a modulation of the function of the IGF system. Anthropometry, IGF system assessment, cortisol measurement, and lipid profile evaluation were performed in 49 IUGR children. Children were subdivided into two groups according to their actual height corrected for midparental height: CG (catch-up growth) group, 19 children with corrected height >or=0 z-score; and NCG (noncatch-up growth) group, 30 subjects with corrected height <0 z-score. CG children showed significantly higher birth weight (p < 0.005) and body mass index (p < 0.05). No significant differences in IGF-I, IGF-II, IGF binding protein (IGFBP)-1, IGFBP-3, soluble IGF-II receptor levels (IGF2R), IGF-II/IGF2R ratio, and relative amounts of IGFBP-3 circulating forms were found between CG and NCG children. None of the IGF system-related variables correlated with anthropometric indices. NCG children showed significantly higher concentrations of cortisol (p < 0.005) and cortisol levels resulted inversely to birth weigh (r = -0.34, p < 0.05), birth length (r = -0.36, p < 0.05), and corrected height (r = -0.44, p < 0.01). Whereas total and HDL cholesterol concentrations were not significantly different in the two groups, LDL cholesterol levels were significantly higher in NCG children (p < 0.05), and five of 49 showed LDL cholesterol concentrations >3.4 mM (130 mg/dL). LDL cholesterol was inversely related to birth weight (r = -0.31, p < 0.05), corrected stature (r = -0.32, p < 0.05), and actual height (r = -0.31, p < 0.05) and directly related to the levels of IGF2R (r = 0.44, p < 0.01). Reanalysis of 15 of 30 IUGR newborns in whom we previously reported an inverse relationship between cord blood cortisol levels and first trimester length gain (r = -0.54, p < 0.005) showed that the relative amount of the IGFBP-3 18-kD fragment was related inversely to cortisol (r = -0.67, p < 0.01) and directly to early postnatal growth (r = 0.65, p < 0.05). Our results suggest that catch-up growth in IUGR children might be affected by intrauterine reprogramming of hypothalamic-pituitary-adrenal axis, which may result in a permanent modification of the neuroendocrine response to stress: children with increased cortisol secretion may be at higher risk of growth failure. During the neonatal period cortisol might act by limiting IGFBP-3 proteolysis and, therefore, reducing IGF bioavailability.

Newborn birth weight correlates with placental zinc, umbilical insulin-like growth factor I, and leptin levels in preeclampsia

BACKGROUND

The aim of the present study was to determine whether newborn birth weights were associated with insulin-like growth factor I (IGF-I), zinc, and leptin in preeclamptic and normotensive pregnancies.

METHODS

This study was done cross-sectionally and included 15 women with moderate preeclampsia (PE group) and 11 normotensive pregnant women (NT group) of similar gestational age. Maternal and umbilical cord serum levels of zinc, IGF-I, IGF binding proteins (IGFBPs), leptin, and placental zinc were assessed in each group.

RESULTS

As compared with the NT group, the PE group had significantly (p <0.05) lower newborn birth weight [3.33 (3.11-3.55) vs. 2.80 (2.40-3.17) kg], maternal IGF-I [303 (276-364) vs. 198 (153-244) ng/mL], and umbilical IGF-I [87 (71-126) vs. 44 (26-98) ng/mL]. In addition, low IGFBP-3 and high IGFBP-1 were observed in the PE group. In the PE group, birth weight correlated positively with placental zinc (rho = 0.56, p = 0.04), maternal IGF-I (rho = 0.76, p = 0.004), umbilical cord IGF-I (rho = 0.75, p = 0.005), and umbilical cord leptin (rho = 0.61, p = 0.02) levels. Stepwise multiple regression analysis showed that among these variables, umbilical IGF-I was the major predictor of birth weight. In the NT group, birth weight did not correlate with any of these variables.

CONCLUSIONS

The present study indicates that moderate preeclampsia is associated with low newborn birth weight, IGF-I, IGFBP-3, and high IGFBP-1 without significant changes in zinc and leptin levels. In addition, umbilical IGF-I was the major predictor of newborn birth weight.

Zinc and perinatal growth

AIM

To study the relationship between zinc, insulin-like growth factor (IGF-I), osteocalcin and perinatal growth.

MATERIALS AND METHODS

Anthropometric variables, serum levels of IGF-I, osteocalcin and zinc were measured in preterm (PT) appropriate for gestational age (AGA), full term (FT) small for gestational age (SGA) and FT AGA newborns at birth (n=52), at first week (n=38) and at third week (n=38) of postnatal age.

RESULTS

At birth, the FT SGA had lower levels of IGF-I. At the first week after birth, both FT SGA and PT AGA infants had less deposits of subcutaneous fat; FT SGA infants also showed significantly lower osteocalcin and zinc levels. At 3 weeks of postnatal life, FT SGA infants continued to show significantly lower zinc levels. They had increased their fat deposits so that differences between groups in skinfold measurements failed to be significant. The highest levels of osteocalcin were found in PT AGA infants at the third week after birth.

CONCLUSIONS

Perinatal nutrition influences the IGF-I levels. The low concentration of osteocalcin found in SGA infants at first week of life probably reflects decreased bone turnover. During the first weeks of life, there is a progressive decrease in the serum levels of zinc, accentuated in the FT SGA group.

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.

Collagen cross-links and early postnatal growth in newborns with intrauterine growth retardation

This study assessed growth and skeletal metabolism in full-term newborns with intrauterine growth retardation (IUGR) and determined the value of the urinary excretion of collagen cross-links in predicting postnatal catch-up growth. We studied 38 newborns (16 females) born at term with a birth weight less than the 10th centile of the reference and a ponderal index ([PI] 100 x weight in g/length in cm3) of 2.27 +/- 0.19. The sample was divided into 23 children with proportionate ([P] PI > or = 10th centile of the reference) and 15 with nonproportionate ([NP] PI < 10th centile of the reference) IUGR. The weight, head circumference, length, and knee-heel length of the newborns at days 7, 14, 30, 60, and 90 were measured. The height of 23 of the 38 children was also assessed at 27 +/- 6 months of life. Urinary collagen cross-links were analyzed by high-performance liquid chromatography at day 14 and day 60. Most of the infants (68%) underwent catch-up growth, and the growth performance at 3 months was independent of the proportions at birth. Children who did not show catch-up growth in the first trimester of life failed to normalize in height in the following 2 years. The urinary excretion of pyridinoline (Pyd) was not related to the anthropometric measurements. In P children, urinary excretion of deoxypiridinoline (Dpd) at day 14 significantly correlated with the gain in length during the first 3 months, accounting for 25% of the variance. In NP children, these correlations between urinary Dpd and the gain in length were not significant. The evaluation of urinary Dpd excretion at 2 weeks of age might help to determine the therapeutic regimen in IUGR children.

Growth and insulin-like growth factors (IGFs) in children with insulin-dependent diabetes mellitus at the onset of disease: evidence for normal growth, age dependency of the IGF system alterations, and presence of a small (approximately 18-kilodalton) IGF-binding protein-3 fragment in serum

Data on growth of children with insulin-dependent diabetes mellitus (IDDM) before the onset of disease are conflicting, and although the insulin-like growth factor (IGF) system has almost invariably been found altered at diagnosis, most of previous studies are affected by the small number of patients investigated. We studied 60 IDDM children at the onset of disease, comparing their stature with target height, normal growth standards, and height of 102 sex- and age-matched controls. Furthermore, we assessed serum IGF-I, IGF-II, and IGF-binding protein-3 (IGFBP-3) levels and IGFBP-3 circulating forms. IDDM children were subdivided into 2 groups according to an age above (n = 26) or below (n = 34) 6 yr. The values of endocrine variables of diabetics older than 6 yr were compared with those of 34 age-matched controls. Although the height of diabetics was higher than growth reference values (mean height +/- SD, 0.64+/-1.4 z-score) and their target height (mean target height +/- SD, 0.1+/-0.84 z-score; P < 0.005), no significant difference in height was found between IDDM children and controls (mean height +/- SD, 0.64+/-0.95 z-score) even analyzing the 2 age groups separately. Overall, IDDM children showed reduced levels of IGF-I (mean +/- SD, -0.65+/-1.9 z-score) and normal levels of IGF-II (mean +/- SD, -0.05+/-1.2 z-score) and IGFBP-3 (mean +/- SD, -0.06+/-1.2 z-score). However, whereas patients younger than 6 yr showed normal values of IGF-I, IGF-II, and IGFBP-3, these peptides were significantly reduced in older subjects compared with either younger IDDM children or controls (P < 0.01). IGFBP-3 immunoblot analysis revealed the presence of an approximately 18-kDa fragment of IGFBP-3 in addition to the major approximately 29-kDa fragment and the intact form (approximately 42-39 kDa) in 46 of 60 IDDM patients, whereas the approximately 18-kDa band was absent in all 34 control sera. No relationship was found between the endocrine variables and stature at diagnosis. In conclusion, our results indicate that IDDM children at the onset of disease are not taller than healthy peers and have increased IGFBP-3 proteolytic activity. Finally, although the IGF system is normal in younger IDDM children, older patients have reduced IGF levels.

Insulin-like growth factors in obstetrics

Data from a number of studies reported during the past two decades indicate that the insulin-like growth factor (IGF) system, including IGF-I and IGF-II, their receptors and six high-affinity binding proteins, is involved in the control of foetal and placental growth and development. Recent studies that addressed the role of the IGF system in pregnancy and the clinical usefulness of IGF and IGF-binding protein measurements in obstetrics are reviewed and discussed.

Preeclampsia is associated with low circulating levels of insulin-like growth factor I and 1,25-dihydroxyvitamin D in maternal and umbilical cord compartments

Insulin-like growth factor I (IGF-I) stimulates renal and placental 1,25-dihydroxyvitamin D [1,25-(OH)2D] and is considered an important regulator of fetal growth. As 1,25-(OH)2D and birth weight are low in preeclampsia, this study was undertaken to determine whether circulating levels of IGF-I were associated with serum 1,25-(OH)2D concentrations in preeclamptic (PE group) and normotensive (NT group) pregnancies. Maternal and umbilical cord serum levels of IGF-I and 1,25-(OH)2D were significantly (P < 0.01) lower in the PE group than in the NT group. The concentrations of these two hormones correlated significantly in the umbilical cord (P < 0.05) and in the maternal (P < 0.001) compartments of the PE and NT groups, respectively. The amount of IGFBP-3 was 64% lower whereas that of IGFBP-1 was 2.9-fold higher in umbilical cord serum of the PE group compared with the NT group. In addition, maternal and umbilical cord serum IGF-I correlated significantly (P < 0.05) with weight and length at birth only in the PE group. In conclusion, the results of this study indicate that circulating IGF-I and 1,25-(OH)2D levels in both maternal and umbilical cord compartments are low in preeclampsia. Furthermore, this study suggests a differential regulatory effect of IGF-I on 1,25-(OH)2D synthesis and fetal growth depending on the presence or absence of preeclampsia.