Growth factors and intrauterine growth retardation. I. Serum growth hormone, insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein 3 levels in normally grown and growth-retarded human fetuses during the second half of gestation

Longitudinal growth during infancy and childhood in children from shanghai: predictors and consequences of the age at onset of the childhood phase of growth

The age at onset of the childhood phase of growth, normally occurring between 6 and 12 mo, is recognized to be an important time during postnatal human development. The aims of this present work were to identify predictors for the age at onset of the childhood phase of growth. Furthermore, this work aimed to examine the consequences that this timing would have on the subsequent heights of 1720 Shanghai children. The mean age of the infants at onset of the childhood phase of growth was 11.2 mo in boys and 10.7 mo in girls. Compared with their Swedish counterparts, these means occurred 1.3 mo later in boys and 1.4 mo later in girls. Both age at onset of the childhood phase of growth and length at 6 mo of age significantly (p < 0.05) contributed to the attained height from 12 mo of age onward; 1-mo delay in the onset of the childhood phase of growth reduced height at 5 y of age by 0.4 cm in boys and 0.5 cm in girls. The age at onset of the childhood phase of growth was negatively associated (p < 0.001) with mid-parental height, although positively related (p < 0.001) to height at 6 mo of age. There was a distinct body mass index pattern of Chinese children between birth and 6 y of age in comparison with white values. There was a sharp increase in body mass index in Shanghainese during their first 6 mo of life, followed by a gradual decline up to 24 mo. In conclusion, the age at childhood onset is equally important when studying children from Shanghai as it is with their Swedish counterparts.

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.

Onset of significant GH dependence of serum IGF-I and IGF-binding protein 3 concentrations in early life

Forty-eight normal full-term Chinese babies (25 boys and 23 girls) were followed up every 2 mo in the first year and every 3 mo during the second year of life for anthropometric measurements. Blood samples were taken at birth and at 6, 10, 12, and 18 mo after birth for serum GH-binding protein, IGF-I, and IGF-binding protein 3 analysis. Onset of the childhood phase of growth in the infants was determined from the growth data plotted on Infancy-Childhood-Puberty growth charts. The serum GH-binding protein concentrations were low in cord blood but rose significantly at 6 mo, with slower rises in late infancy and early childhood. However, a significant rise in serum IGF-I and IGF-binding protein 3 levels was only observed from 10 mo of life onward. The change in IGF-I between birth and 6 mo was significantly correlated with length gain (r(2) = 0.35, p < 0.05) and body mass index gain (r(2) = 0.41, p < 0.01) during the same period. The 34 infants with onset of childhood phase of growth between 6 and 10 mo had a higher mean serum IGF-I value at 10 mo (8.8 +/- 5.8 nM versus 4.9 +/- 3.1 nM; p < 0.05) and higher length velocity between 10 and 12 mo (16.3 +/- 4.7 cm/y versus 8.8 +/- 4.3 cm/y; p < 0.001) compared with the 14 infants with a later onset after 10 mo of age. A significant correlation between a change in serum IGF-I and IGF-binding protein 3 levels was observed during the three 6-mo periods between birth and 18 mo, but a significant correlation between a change in serum GH-binding protein and a change in serum IGF-I or IGF-binding protein 3 levels was only seen between 12 and 18 mo of age. The multiple regression analysis (r(2) = 0.43, p = 0.0002) revealed that the change in serum GH-binding protein and IGF-I concentrations between 6 and 12 mo of age and the age of onset of childhood phase of growth could explain 43% of the length gain between 6 and 12 mo of age in our babies. The results of our study support the hypothesis that the onset of the childhood phase of growth is associated with the onset of significant GH action on growth.

Maternal nutrition and fetal growth: practical issues in international health

The relationship between maternal nutrition and fetal growth is more complex than might be at first assumed. Low birthweight (LBW) increases the risk of early mortality and later morbidity, and attempts to improve fetal outcome in developing countries need to address the problem of compromised fetal growth. This paper examines the links between birthweight and women's nutritional status in both biomedical and programmatic contexts.

The insulin-like growth factor-I (IGF-I) gene in individuals born small for gestational age (SGA)

OBJECTIVE

To investigate the association of genetic variation of the insulin-like growth factor-I (IGF-I) gene with birth size small for gestational age (SGA).

SUBJECTS

We have studied a cohort of 120 SGA patients and 147 appropriate for gestational age (AGA) controls from Haguenau, France.

METHODS

PCR-SSCP analysis was performed to detect sequence variation in the coding region of the IGF-I gene. Microsatellite markers near the IGF-I gene (intronic and D12S78) were selected and amplified to perform further analysis by association studies.

RESULTS

A novel polymorphism in intron 2 was discovered, but allele-specific PCR analysis in the 120 SGA patients and 147 AGA controls found no association between this polymorphism and birth size SGA. Chi squared (chi2) analysis found no statistically significant association between the allele distribution of the microsatellite markers in the SGA subjects and the AGA controls. Power calculations estimate that the D12S78 marker has an 80% chance of detecting a 10-15% difference.

CONCLUSIONS

These studies suggest that genetic variation of IGF-I alone does not result in birth size small for gestational age in this population. Thus, if this gene influences fetal size, it plays only a minor role in a multifactorial disorder which involves other genetic and environmental factors.

A low protein diet alters the balance of islet cell replication and apoptosis in the fetal and neonatal rat and is associated with a reduced pancreatic expression of insulin-like growth factor-II

A programmed turnover of pancreatic beta cells occurs in the neonatal rat involving a loss of beta cells by apoptosis, and their replacement by islet cell replication and neogenesis. The timing of apoptosis is associated with a loss of expression of a survival factor, insulin-like growth factor-II (IGF-II), in the pancreatic islets. Offspring from rats chronically fed a low protein isocalorific diet (LP) exhibit a reduced pancreatic beta cell mass at birth and a reduced insulin secretion in later life. This study therefore investigated the impact of LP on islet cell ontogeny in the late fetal and neonatal rat, and any associated changes in the presence of IGFs and their binding proteins (IGFBPs). Pregnant Wistar rats were fed either LP (8% protein) or normal (C) (20% protein) chow from shortly after conception until the offspring were 21 days postnatal (PN). Bromo-deoxyuridine (BrdU) was administered 1 h before rats were killed and pancreata removed from animals between 19.5 days fetal life and postnatal day 21. Offspring of rats given LP diet had reduced birthweight, pancreatic beta cell mass, and pancreas insulin content, with smaller islets compared with control fed animals, which persisted to weaning. Histological analysis showed that islets from pups given LP diet had a lower nuclear labeling index with BrdU in the beta cells, although, paradoxically, more beta cells showed immunoreactivity for proliferating cell nuclear antigen (PCNA). Because PCNA is present in G1 as well as S phase of the cell cycle, we quantified the number of beta cells immunopositive for cyclin D1, a marker of G1, and NEK2, an indicator of cells in G2 and mitosis. More beta cells in islets from LP-fed animals contained cyclin D1, but less contained NEK2 than did those in controls. This suggests that the beta cell cycle may have a prolonged G1 phase in LP-fed animals in vivo. Offspring of rats given C diet had a low rate of islet cell apoptosis detected by the TUNEL method in fetal and neonatal life (1-2%), with a transient increase to 8% at PN day 14. Offspring of rats receiving LP diet demonstrated a significantly greater level of islet cell apoptosis at every age, rising to 15% at PN 14. IGF-II mRNA was quantified in whole pancreas and was significantly reduced in LP-fed animals at ages up to PN day 10. IGF-II immunoreactivity within the islets of LP-fed rats was also less apparent, but no changes were seen in immunoreactive IGF-I or IGFBPs-2 to -5. These findings show that LP diet changes the balance of beta cell replication and apoptosis in fetal and neonatal neonatal life, which may involve an altered length of beta cell cycle, and contribute to the smaller islet size and impaired insulin release seen in later life. A reduced pancreatic expression of IGF-II may contribute to the lower beta cell proliferation rate and increased apoptosis seen in the fetus and neonate after feeding LP diet.

Glucose and amino acid kinetic response to graded infusion of rhIGF-I in the late gestation ovine fetus

Insulin-like growth factor I (IGF-I) has anabolic effects and is thought to be important in fetal development. The present study was designed to determine the dose response of recombinant human (rh) IGF-I on ovine fetal glucose and amino acid kinetics. Chronically catheterized fetal lambs were studied at 122-127 days gestation. The kinetics of leucine, phenylalanine, and glucose were measured before and during the infusion of rhIGF-I. rhIGF-I was infused into the fetal inferior vena cava at low, medium, or high rates (9.9, 20.1, or 40.2 nmol/h, respectively). A stepwise increase in serum IGF-I was achieved (164 +/- 3, 222 +/- 7, and 275 +/- 5 ng/ml). Insulin concentrations were decreased at the medium and high rhIGF doses. The rate of appearance (Ra) of leucine and phenylalanine and leucine oxidation decreased. Phenylalanine appearance from protein breakdown was decreased, with a maximal suppression of 30% observed at the highest rate of infusion. Glucose Ra was increased at the medium and high doses; other aspects of glucose metabolism were unchanged. The change in both glucose Ra and suppression of proteolysis was significantly correlated to the rhIGF-I infusion rate. It is concluded that rhIGF-I exerts dose-related effects in the ovine fetus, increasing fetoplacental glucose turnover and causing significant suppression of both proteolysis and amino acid oxidation.

Effect of rhIGF-I infusion on whole fetal and fetal skeletal muscle protein metabolism in sheep

Insulin-like growth factor I (IGF-I) has been shown to have significant anabolic effects in the regulation of fetal protein metabolism. To investigate the tissue-specific effects of IGF-I on fetal skeletal muscle metabolism, we infused recombinant human (rh) IGF-I directly into the hindlimb of nine chronically catheterized, late-gestation fetal sheep. Substrate balance and amino acid kinetics were measured across the hindlimb and were compared with the effects at the whole body level before and during a 3-h infusion of rhIGF-I into the external iliac artery at 150 microgram/h. Infusion of rhIGF-I resulted in increases in IGF-I concentrations by 2- to 5. 75-fold in the ipsilateral iliac vein and by nearly 3-fold in the abdominal aorta. In the study limb, IGF-I had no effect on protein synthesis (phenylalanine rate of disposal 0.88 +/- 0.13 before vs. 0. 73 +/- 0.19 micromol/min during IGF-I) or breakdown (phenylalanine rate of appearance 0.67 +/- 0.13 before vs. 0.60 +/- 0.17 micromol/min during IGF-I) and did not alter net phenylalanine balance. IGF-I also did not affect hindlimb oxygen or glucose uptake. In contrast, at the whole body level, the rate of appearance of leucine, indicative of fetal protein breakdown, decreased during IGF-I infusion (rate of appearance of leucine 41.1 +/- 3.3 to 37.6 +/- 2.7 micromol/min) as did fetal leucine oxidation (8.4 +/- 0.8 to 6.8 +/- 0.6 micromol/min). There was no change in the umbilical uptake of leucine, and although not statistically significant, fetal leucine accretion increased 2.4-fold. These results provide further evidence that IGF-I promotes fetal protein accretion; however, its site of action is in tissues other than skeletal muscle.

[Periventricular leukomalacia and brain protection. II. Diagnosis, sequelae and neuroprotection]

The term 'periventricular leukomalacia' (PVL) usually covers necrotic and/or gliotic lesions from perinatal origin occurring in the periventricular ring of telencephalic white matter. Carrying motor and neuropsychological consequences, PVLs could be the most severe danger for very premature brains. Positive rolandic sharp waves recorded on EEG and precocious abnormally echogenous periventricular images on ultrasound suggest prospective periventricular cysts. Cystic periventricular cavitations certify the diagnosis of PVL. More subtle lesions of PVL do not reach the cystic grade and their diagnosis is confirmed by MRI. Treatment of infections is already available and potentially a tool for prevention. When the overwhelming glutamatergic signal has been triggered, neuroprotective agents turning off the excitotoxic cascade, including calcium blockers, growth factors and others, are promising therapeutic tools.

[Periventricular leukomalacia. I. Histological and pathophysiological aspects]

The term 'periventricular leukomalacia' (PVL) usually covers necrotic and/or gliotic lesions from perinatal origin occurring in the periventricular ring of telencephalic white matter. PVLs are found post-mortem in one third of brains from autopsies of premature infants; PVLs are diagnosed in 4 to 10% of infants born before 33 weeks of gestation and remaining alive more than 3 days after birth. PVL is very rare in at term infants. The proportion of PVLs from prenatal origin is estimated between one third and one half of cases. Recent progresses in neuroepidemiology, developmental neurobiology and imaging methods permit to revisit the pathophysiology of PVLs on a multifactorial basis. The final result of these multiple factors seem to be calcium influx due to glutamatergic overactivation triggered by cytokines, infection and inflammation, and deficit in neurotrophic factors. Periventricular topography can be explained by properties of intracerebral vascular wall at this stage of angiogenesis and by perfusion failure/hypoxia.

Developmental pattern of fetal growth hormone, insulin-like growth factor I, growth hormone binding protein and insulin-like growth factor binding protein-3

AIMS

To evaluate the developmental pattern of fetal growth hormone (GH), insulin-like growth factor I (IGF-I), GH binding protein (GHBP) and IGF binding protein-3 (IGF-3); to determine the implications for fetal growth.

METHODS

Serum GH, IGF-I, GHBP and IGFBP-3 were measured in 53 fetuses, 41 aged 20-26 weeks (group A) and 12 aged 31-38 weeks (group B). Fetal blood samples were obtained by direct puncture of the umbilical vein in utero. Fetal blood samples were taken to rule out beta thalassaemia, chromosome alterations, mother to fetus transmissible infections, and for maternal rhesus factor. GHBP was determined by gel filtration chromatography of serum incubated overnight with 125I-GH. GH, IGF-I and IGFBP-3 were determined by radioimmunoassay.

RESULTS

Fetal serum GH concentrations in group A (median 29 micrograms/l, range 11-92) were significantly higher (P < 0.01) than those of group B (median 16.7 micrograms/l, range 4.5-29). IGF-I in group A (median 20 micrograms/l, range 4.1-53.3) was significantly lower (P < 0.01) than in group B (median 75.2 micrograms/l, range 27.8-122.3). Similarly, IGFBP-3 concentrations in group A (median 950 micrograms/l, range 580-1260) were significantly lower than those of group B (median 1920 micrograms/l, range 1070-1770). There was no significant difference between GHBP values in group A (median 8.6%, range 6.6-12.6) and group B (median 8.3%, range 6-14.3). Gestational age correlated positively with IGF-I concentrations (P < 0.0001) and IGFBP-3 (P < 0.0001) and negatively with GH (P < 0.0001). GHBP values did not correlate with gestational age. Multiple regression analysis showed a negative correlation between GH:IGF-I ratio and fetal growth indices

CONCLUSIONS

The simultaneous evaluation of fetal GH, IGF-I, IGFBP-3 and GHBP suggests that the GH-IGF-I axis might already be functional in utero. The progressive improvement in the efficiency of this axis in the last part of gestation does not seem to be due to an increase in GH receptors.