Insulinlike growth factor 1 in controls and growth-retarded fetuses

Further Evidence that an Episode of Premature Labor Is a Pathologic State: Involvement of the Insulin-Like Growth Factor System

INTRODUCTION

Approximately 47% of women with an episode of preterm labor deliver at term; however, their infants are at greater risk of being small for gestational age and for neurodevelopmental disorders. In these cases, a pathologic insult may disrupt the homeostatic responses sustaining pregnancy. We tested the hypothesis of an involvement of components of the insulin-like growth factor (IGF) system.

METHODS

This is a cross-sectional study in which maternal plasma concentrations of pregnancy-associated plasma protease (PAPP)-A, PAPP-A2, insulin-like growth factor-binding protein 1 (IGFBP-1), and IGFBP-4 were determined in the following groups of women: (1) no episodes of preterm labor, term delivery (controls, n = 100); (2) episode of preterm labor, term delivery (n = 50); (3) episode of preterm labor, preterm delivery (n = 100); (4) pregnant women at term not in labor (n = 61); and (5) pregnant women at term in labor (n = 61). Pairwise differences in maternal plasma concentrations of PAPP-A, PAPP-A2, IGFBP-1, and IGFBP-4 among study groups were assessed by fitting linear models on log-transformed data and included adjustment for relevant covariates. Significance of the group coefficient in the linear models was assessed via t-scores, with p < 0.05 deemed a significant result.

RESULTS

Compared to controls, (1) women with an episode of premature labor, regardless of a preterm or a term delivery, had higher mean plasma concentrations of PAPP-A2 and IGFBP-1 (each p < 0.05); (2) women with an episode of premature labor who delivered at term also had a higher mean concentration of PAPP-A (p < 0.05); and (3) acute histologic chorioamnionitis and spontaneous labor at term were not associated with significant changes in these analytes.

CONCLUSION

An episode of preterm labor involves the IGF system, supporting the view that the premature activation of parturition is a pathologic state, even in those women who delivered at term.

Markers of obesity and growth in preeclamptic and normotensive pregnant women

The objective of the study was to analyse leptin, IGF-1, Apo A, lipoproteins, haem oxygenase-1 (HO-1) in maternal sera and venous umbilical cord sera of newborn babies of 25 preeclamptics (group II), and 25 normotensive pregnant women (group I) as markers of obesity and growth in preeclamptic and normotensive pregnant women. Apo A I and II levels were estimated by competitive immunoassay using direct chemiluminiscence technology. Haem oxygenase-1 (HO-1), leptin and IGF-1 were analysed by ELISA. Maternal and cord blood levels of homocysteine, folic acid, lipid profile (namely, total cholesterol, triglycerides, LDL-C, VLDL-C and HDL-C), Haem oxygenase 1 were higher in preeclamptic women as compared to normotensive pregnant women. Serum and cord blood Apo A-I and Apo B, leptin levels, IGF-I were lower in preeclamptic women as compared to normotensive pregnant. The findings of high serum HO-1 levels in maternal and cord blood in preeclampsia supports the role of oxidative stress and excessive inflammatory response in the pathogenesis of preeclampsia. It seems likely that IGF-1 and leptin play a central role in controlling foetal growth. There is increasing evidence that the foundations of life-long health are, in part, laid in the uterus. Findings of present study suggest that alterations in biochemical markers of growth and obesity occur in mothers and foetuses and modifications of uterine environment can be of help to prevent future cardiovascular risk. Impact statement Preeclampsia has been reported to be associated with an increased risk of later life cardiovascular disease. However, information regarding how obesity increases the risk of preeclampsia is limited. Atherogenic milieu occurring during pregnancy persists into adulthood and foetal growth retardation is strongly associated with adult atherosclerosis. There is conflicting evidence regarding alterations of IGFs in preeclamptic pregnancies and deficit in circulating and cord blood IGF-1 levels in intrauterine growth restricted newborns and a correlation between IGF-1 levels and birth weight have been reported. Leptin is a predictor of cardiovascular risk independent of insulin resistance. Emerging evidence supports an important role for the haem oxygenase system (HO-1) in the maintenance of a healthy pregnancy, especially during pathological challenge. Conflicting data are available regarding HO-1, leptin and IGF -1 in preeclamptic mothers. The extent to which they mediate foetal growth and developmental abnormalities remains to be clarified. Serum IGF-1 levels were significantly decreased in preeclamptics and maternal IGF-1 showed a strong inverse correlation with leptin levels. High serum HO-1 levels in maternal and cord blood in preeclampsia were observed in the present study. Findings of the present study suggest that alterations in biochemical markers of growth and obesity occur in mothers and foetuses and modifications of the uterine environment can be of help to prevent future cardiovascular risk.

Normal lactational environment restores cardiomyocyte number after uteroplacental insufficiency: implications for the preterm neonate

A reduced complement of cardiomyocytes in early life can adversely affect life-long cardiac functional reserve. In the present study, using a cross-fostering approach in rats, we examined the contributions of the prenatal and postnatal environments in the programming of cardiomyocyte growth. Rat dams underwent either bilateral uterine vessel ligation (Restricted) or sham surgery (Control) on day 18 of gestation. One day after birth, Control and Restricted pups were cross-fostered onto Control (normal lactation) or Restricted (impaired lactation due to impaired mammary gland formation) mothers. In male offspring, genes involved in cardiomyocyte differentiation, proliferation, hypertrophy and apoptosis were examined at gestational day 20 and postnatal days 1 and 7 to assess effects on cardiomyocyte growth. At postnatal day 7 cardiomyocyte number was determined stereologically. Offspring were examined at age 6 mo for evidence of hypertension and pathological cardiac gene expression. There was an increase in Igf1 and Igf2 mRNA expression in hearts of Restricted pups at gestational day 20. At postnatal day 7, Agtr1a and Agtr1b mRNA expression as well as Bcl2 and Cmyc were elevated in all hearts from offspring that were prenatally or postnatally growth restricted. There was a significant reduction (-29%) in cardiomyocyte number in the Restricted-on-Restricted group. Importantly, this deficit was prevented by optimization of postnatal nutrition (in the Restricted-on-Control group). At 6 mo, blood pressure was significantly elevated in the Restricted-on-Restricted group, but there was no difference in expression of the cardiac hypertrophy, remodeling or angiogenic genes across groups. In conclusion, the findings reveal a critical developmental window, when cardiomyocytes are still proliferating, whereby improved neonatal nutrition has the capacity to restore cardiomyocyte number to normal levels. These findings are of particular relevance to the preterm infant who is born at a time when cardiomyocytes are immature and still dividing.

Risk factors and growth factors in ROP

Retinopathy of prematurity (ROP) is a multifactorial disease which incidence is increasing with increasing survival of very preterm infants. Pathogenic pathway is characterised by abnormal retinal vascular development modulated by vascular growth factors: low IGF-1 in the first phase and high VEGF in the second phase. Many causal factors are able to influence retinal vascularization: gestational age, birth weight, oxygen administration, perinatal bacterial or fungal infections, and blood transfusions. All risk factors, both oxygen and not-oxygen-regulated, have been studied considering the whole period from hospital birth to the hospital discharge, but it is possible that postnatal risk factors may be determinant in a time-dependent way. Analysis of factors involved in the pathogenesis of ROP suggests that their action begins long before anatomical clinical features become appreciable and this is strengthened by the essential role of risk factors from the first two to four weeks of life, thus preventive strategies in very preterm infants should be carried out since birth.

The presence of the d3-growth hormone receptor polymorphism is negatively associated with fetal growth but positively associated with postnatal growth in healthy subjects

CONTEXT

A common polymorphism in the GH receptor (GHR) gene has been linked to increased growth response in GH-treated patients. No former study has focused on the association to prenatal growth.

OBJECTIVE

The aim of the study was to evaluate the association between the d3-GHR isoforms and spontaneous pre- and postnatal growth.

DESIGN

A prospective study was conducted on third-trimester fetal growth velocity (FGV), birth weight, birth length, and postnatal growth.

SETTING

The study was conducted at Copenhagen University Hospital.

PARTICIPANTS

A total of 115 healthy adolescents were divided into those born small for gestational age (SGA) and appropriate for gestational age with or without intrauterine growth restriction.

MAIN OUTCOME MEASURES

FGV was measured by serial ultrasonography, birth weight, birth length, and adolescent height. Isoforms of the d3-GHR gene (fl/fl, d3/fl, and d3/d3) were determined.

RESULTS

The prevalence of the d3-GHR isoforms was 50% but differed among the groups (P = 0.006), with a high prevalence (88%) in the group born SGA with verified intrauterine growth restriction. The d3-GRH allele were associated with decreased third-trimester FGV (P = 0.05) in SGA subjects. In the entire cohort, carriers of the d3-GHR allele had a significantly increased height (-0.10 vs. 0.34 SD score; P = 0.017) and change in height from birth to adolescence compared with carriers of the full-length GHR allele (0.57 vs. -0.02 SD score; P = 0.005).

CONCLUSIONS

This study showed an increased spontaneous postnatal growth velocity in the carriers of the d3-GHR allele. Interestingly, we found the opposite effect on prenatal growth in the SGA group, with a decreased FGV in carriers of the d3-GHR allele.

Insulin-like growth factor (IGF)-I and insulin in normal and growth-restricted mother/infant pairs

Insulin-like growth factor (IGF)-I and insulin are essential for fetal growth. We investigated perinatal changes of both factors in 40 mothers and their 20 appropriate-for-gestational-age (AGA) and 20 intrauterine-growth-restricted (IUGR) fetuses and neonates on day 1 (N1) and day 4 (N4) postpartum. Fetal and N1, but not N4, IGF-I levels were increased in AGA (P < .001 and P = .037, resp.). N1 insulin levels were lower in IUGR (P = .048). Maternal, fetal, and N1 IGF-I, and fetal insulin levels positively correlated with customized centiles (r = .374, P = .035, r = .608, P < .001, r = .485, P = .006, and r = .654, P = .021, resp.). Female infants presented elevated fetal and N4 IGF-I levels (P = .023 and P = .016, resp.). Positive correlations of maternal, fetal, and neonatal IGF-I levels, and fetal insulin levels with customized centiles underline implication of both hormones in fetal growth. IUGR infants present gradually increasing IGF-I levels. Higher IGF-I levels are documented in females.

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.

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.

Uteroplacental insufficiency lowers the threshold towards hypoxia-induced cerebral apoptosis in growth-retarded fetal rats

Infants suffering uteroplacental insufficiency and hypoxic ischemic injury often demonstrate cerebral apoptosis. Our objective was to determine the global effects of uteroplacental insufficiency upon cerebral gene expression of the apoptosis related proteins Bcl-2 and Bax and their role in increasing vulnerability to hypoxia-induced cerebral apoptosis. We therefore caused uteroplacental insufficiency and growth retardation by performing bilateral uterine artery ligation upon pregnant rats 2 days prior to term delivery and elicited further perinatal fetal hypoxia by placing maternal rats in 14% FiO(2) 3 h prior to delivery. We quantified cerebral levels of Bcl-2 and Bax mRNA, lipid peroxidation, caspase-3 activity, and cAMP in control and growth retarded term rat pups that experienced either normoxia or hypoxia. Uteroplacental insufficiency alone caused a significant decrease in cerebral Bcl-2 mRNA levels without altering cerebral Bax mRNA levels, malondialdehyde levels, or caspase-3 activity. In contrast, uteroplacental insufficiency and subsequent fetal hypoxia significantly increased cerebral Bax mRNA levels, lipid peroxidation and caspase-3 activity; Bcl-2 mRNA levels continued to be decreased. Hypoxia alone increased cerebral cAMP levels, whereas uteroplacental insufficiency and subsequent hypoxia decreased cerebral cAMP levels. We speculate that the decrease in Bcl-2 gene expression increases the vulnerability towards cerebral apoptosis in fetal rats exposed initially to uteroplacental insufficiency and subsequent hypoxic stress.