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

[Short stature due to intrauterine growth retardation. Clinical and hormonal-metabolic features, possibilities of growth-stimulating therapy]

The article presents data about short stature due to intrauterine development delay. This type of short stature - separate nosology, unites children born small for gestation age. The majority of them in the first years of life have accelerated growth rates, allowing the child to normalize their weight-growth indicators and catch up in the development of peers. In the absence of an accelerated growth rates, children have a high risk of lagging behind in physical development throughout childhood, achieving low final growth and becoming short adults. In addition, the fact of birth with small body sizes is associated with a number of hormonal and metabolic features, a risk of metabolic syndrome in adult years.It is assumed that the absence of postnatal growth acceleration is due to various damages to the GH-IGF1 axis (partial GH deficiency, partial resistance to GH, partial resistance to IGF1). Growth hormone therapy, initiated early in life, is able to normalize growth rates in childhood and ultimately significantly improve or normalize the final growth of short stature children born small for gestational age.

First year metabolic and hormonal behaviour define two different populations of SGA newborn for weight or height

Context

Small for gestational age (SGA) children have a particular metabolic and hormonal pattern at birth that change rapidly.

Objective

To evaluate the linear and weight growth in the first year of life in SGA children.

Design

Prospective, monocentric cohort study.

Setting

Real-world data collected from April 2012 to January 2016.

Patients

SGA newborns uniformly defined by either growth or length lower than -2 standard deviation for gestational age.

Interventions

All children were evaluated for one year after birth, at three days of life, then three, six and 12 months after birth.

Main outcome measures

Anthropometric parameters and biochemical variables, such as blood glucose, insulin, leptin, insulin-like growth factor (IGF)-1, IGF binding protein (IGFBP)3, and HOMA index.

Results

One hundred and thirty-three SGA children were enrolled. Length significantly improved one month after birth, whereas weight significantly increased only three months after birth. Biochemical variables increased during the first year of life, showing a prediction by IGFBP-3 and HOMA-index. Then, the casuistry was divided considering either weight, length or both, showing a different incidence. The biochemical variables changes recorded in the first step were maintained considering SGA children for weight or length, whereas they disappeared when weight and length were considered together.

Conclusions

Our study shows a specific catch-up growth for weight and length in SGA children. Moreover, we highlight that weight and length should be considered as independent parameters in SGA children, defining two different metabolic-hormonal populations with different conceivable predictive role in early catch-up growth and in later growth and metabolic status.

The Auxological and Metabolic Consequences for Children Born Small for Gestational Age

'Small for gestational age' (SGA) is an auxological and not an etiological definition that characterizes children born small based upon low-birth-weight and/or birth-length criteria [≥ 2 standard deviations (SD) below the mean for gestational age]. Most SGA children exhibit catch-up growth into the normal range within 6 mo of age. Overall SGA children are 4 cm shorter than expected based upon midparental height and being born SGA is a common cause of adult short stature. Recombinant human growth hormone (rhGH) has been shown to improve adult height by 0.9 SDs and is a safe treatment. Surprisingly, a higher rhGH dose (67 μgm/kg/d) did not lead to a greater adult height than a conventional dose (33 μgm/kg/d). At least 85% of SGA children treated through childhood with rhGH achieve a height within the normal adult range. Other long-term consequences for children born SGA include insulin resistance, abdominal adiposity, dyslipidemia, type 2 diabetes mellitus, and metabolic syndrome. Cross-sectional studies have found reduced insulin sensitivity in the neonatal, childhood, and young adult periods. Increased abdominal fat has been shown in preschool SGA children and is more evident in young adults. Increased adiposity markedly accentuates reduction in insulin sensitivity. Many SGA children have suffered from in utero nutritional restriction that leads to long-term growth restriction and adverse metabolic sequelae.

The Placenta as a Target for Alcohol During Pregnancy: The Close Relation with IGFs Signaling Pathway

Alcohol is one of the most consumed drugs in the world, even during pregnancy. Its use is a risk factor for developing adverse outcomes, e.g. fetal death, miscarriage, fetal growth restriction, and premature birth, also resulting in fetal alcohol spectrum disorders. Ethanol metabolism induces an oxidative environment that promotes the oxidation of lipids and proteins, triggers DNA damage, and advocates mitochondrial dysfunction, all of them leading to apoptosis and cellular injury. Several organs are altered due to this harmful behavior, the brain being one of the most affected. Throughout pregnancy, the human placenta is one of the most important organs for women's health and fetal development, as it secretes numerous hormones necessary for a suitable intrauterine environment. However, our understanding of the human placenta is very limited and even more restricted is the knowledge of the impact of toxic substances in its development and fetal growth. So, could ethanol consumption during this period have wounding effects in the placenta, compromising proper fetal organ development? Several studies have demonstrated that alcohol impairs various signaling cascades within G protein-coupled receptors and tyrosine kinase receptors, mainly through its action on insulin and insulin-like growth factor 1 (IGF-1) signaling pathway. This last cascade is involved in cell proliferation, migration, and differentiation and in placentation. This review tries to examine the current knowledge and gaps in our existing understanding of the ethanol effects in insulin/IGFs signaling pathway, which can explain the mechanism to elucidate the adverse actions of ethanol in the maternal-fetal interface of mammals.

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.

Growth Hormone Deficiency: Health and Longevity

The important role of GH in the control of mammalian longevity was first deduced from extended longevity of mice with genetic GH deficiency (GHD) or GH resistance. Mice with isolated GHD (IGHD) due to GHRH or GHRH receptor mutations, combined deficiency of GH, prolactin, and TSH, or global deletion of GH receptors live longer than do their normal siblings. They also exhibit multiple features of delayed and/or slower aging, accompanied by extension of healthspan. The unexpected, remarkable longevity benefit of severe endocrine defects in these animals presumably represents evolutionarily conserved trade-offs among aging, growth, maturation, fecundity, and the underlying anabolic processes. Importantly, the negative association of GH signaling with longevity extends to other mammalian species, apparently including humans. Data obtained in humans with IGHD type 1B, owing to a mutation of the GHRH receptor gene, in the Itabaianinha County, Brazil, provide a unique opportunity to study the impact of severe reduction in GH signaling on age-related characteristics, health, and functionality. Individuals with IGHD are characterized by proportional short stature, doll facies, high-pitched voices, and central obesity. They have delayed puberty but are fertile and generally healthy. Moreover, these IGHD individuals are partially protected from cancer and some of the common effects of aging and can attain extreme longevity, 103 years of age in one case. We think that low, but detectable, residual GH secretion combined with life-long reduction of circulating IGF-1 and with some tissue levels of IGF-1 and/or IGF-2 preserved may account for the normal longevity and apparent extension of healthspan in these individuals.

Children Born Small for Gestational Age: Differential Diagnosis, Molecular Genetic Evaluation, and Implications

Children born small for gestational age (SGA), defined as a birth weight and/or length below -2 SD score (SDS), comprise a heterogeneous group. The causes of SGA are multifactorial and include maternal lifestyle and obstetric factors, placental dysfunction, and numerous fetal (epi)genetic abnormalities. Short-term consequences of SGA include increased risks of hypothermia, polycythemia, and hypoglycemia. Although most SGA infants show catch-up growth by 2 years of age, ∼10% remain short. Short children born SGA are amenable to GH treatment, which increases their adult height by on average 1.25 SD. Add-on treatment with a gonadotropin-releasing hormone agonist may be considered in early pubertal children with an expected adult height below -2.5 SDS. A small birth size increases the risk of later neurodevelopmental problems and cardiometabolic diseases. GH treatment does not pose an additional risk.

Developmental programming of somatic growth, behavior and endocannabinoid metabolism by variation of early postnatal nutrition in a cross-fostering mouse model

Background

Nutrient deprivation during early development has been associated with the predisposition to metabolic disorders in adulthood. Considering its interaction with metabolism, appetite and behavior, the endocannabinoid (eCB) system represents a promising target of developmental programming.

Methods

By cross-fostering and variation of litter size, early postnatal nutrition of CB6F1-hybrid mice was controlled during the lactation period (3, 6, or 10 pups/mother). After weaning and redistribution at P21, all pups received standard chow ad libitum. Gene expression analyses (liver, visceral fat, hypothalamus) were performed at P50, eCB concentrations were determined in liver and visceral fat. Locomotor activity and social behavior were analyzed by means of computer-assisted videotracking.

Results

Body growth was permanently altered, with differences for length, weight, body mass index and fat mass persisting beyond P100 (all 3>6>10,p<0.01). This was paralleled by differences in hepatic IGF-I expression (p<0.01). Distinct gene expression patterns for key enzymes of the eCB system were observed in fat (eCB-synthesis: 3>6>10 (DAGLα p<0.05; NAPE-PLD p = 0.05)) and liver (eCB-degradation: 3>6>10 (FAAH p<0.05; MGL p<0.01)). Concentrations of endocannabinoids AEA and 2-AG in liver and visceral fat were largely comparable, except for a borderline significance for higher AEA (liver, p = 0.049) in formerly overfed mice and, vice versa, tendencies (p<0.1) towards lower AEA (fat) and 2-AG (liver) in formerly underfed animals. In the arcuate nucleus, formerly underfed mice tended to express more eCB-receptor transcripts (CB1R p<0.05; CB2R p = 0.08) than their overfed fellows. Open-field social behavior testing revealed significant group differences, with formerly underfed mice turning out to be the most sociable animals (p<0.01). Locomotor activity did not differ.

Conclusion

Our data indicate a developmental plasticity of somatic growth, behavior and parameters of the eCB system, with long-lasting impact of early postnatal nutrition. Developmental programming of the eCB system in metabolically active tissues, as shown here for liver and fat, may play a role in the formation of the adult cardiometabolic risk profile following perinatal malnutrition in humans.

Low serum adiponectin levels are associated with reduced insulin sensitivity and lipid disturbances in short children born small for gestational age

BACKGROUND

Being born as small for gestational age (SGA) has an increased risk of developing metabolic/cardiovascular disturbances in later life. The role of adiponectin in the metabolic disturbance in SGA children remained undefined.

OBJECTIVE

The aim of this study was to investigate the association between serum levels of adiponectin and insulin sensitivity as well as lipid profile in short children born SGA at prepubertal ages.

PATIENTS AND METHODS

Serum levels of adiponectin, fasting glucose, insulin, IGF-I, IGFBP-1, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), apolipoprotein A-I (ApoA-I) and Apo B were measured in 30 prepubertal short children born SGA. Insulin resistance (IR) and β-cell function were assessed using the method of homeostatic model (HOMA). Data were compared to those of 30 short appropriate for gestational age (AGA) children matched for age, gender, height and body mass index, and correlation analysis was performed.

RESULTS

Short SGA children had significantly higher levels of fasting insulin, HOMA-IR and HOMA-β but lower levels of adiponectin than short AGA controls. No significant differences in the level of IGFBP-1 and IGF-I were found between the two groups. Serum levels of TC, TG, Apo B and Apo B/ApoA-I ratio were significantly higher in SGA, with 33% of hypercholesteraemia and 23% of hyperglyceridaemia. Stepwise multiple regression analysis revealed that serum adiponectin level was negatively correlated with HOMA-IR and TG and was positively correlated with birthweight SDS in SGA children.

CONCLUSIONS

These findings suggest that low serum adiponectin levels are associated with reduced insulin sensitivity and unfavourable lipid profiles in short children born SGA at prepubertal ages.

Prenatal nicotine exposure-induced intrauterine programming alteration increases the susceptibility of high-fat diet-induced non-alcoholic simple fatty liver in female adult offspring rats

“Two intrauterine programming”, involved in the intrauterine origin of high-fat diet-induced NAFL in female offspring rats, induced by prenatal nicotine exposure.

Effect of a mixture of bovine milk oligosaccharides, Lactobacillus rhamnosus NCC4007 and long-chain polyunsaturated fatty acids on catch-up growth of intra-uterine growth-restricted rats

AIM

To investigate the effect of a nutritional mixture (bovine milk oligosaccharides, Lactobacillus rhamnosus NCC4007, arachidonic and docosahexaenoic acid) on growth of intrauterine growth-restricted (IUGR) rats.

METHODS

IUGR was induced by maternal food restriction. The offspring (males and females) were assigned to: REF (non-IUGR, no mixture), IUGRc (IUGR, no mixture), or IUGRmx (IUGR, mixture). The mixture was given from day 7 to day 58, when tissues and plasma from half of the animals were collected for hormones, metabolites and microarray analysis. The rest received a high-fat diet (HFD) until day 100. Glucose tolerance was measured at 56 and 98 days, and body fat content at 21, 52 and 97 days.

RESULTS

IUGRmx had the greatest growth during lactation, but from day 22 to day 54, both IUGR groups gained less body weight than the REF (P < 0.05). In the short-term (58 days), IUGRmx tended to be longer (P = 0.06) and had less body fat (P = 0.03) than IUGRc. These differences were not seen after HFD. Microarray analysis of hepatic mRNA expression at 58 and 100 days revealed a gender-dependent treatment effect, and expression of genes related to lipid metabolism was the most affected. Twelve of these genes were selected for studying differences in DNA methylation in the promoter region, for some, we observed age- and gender-related differences but none because of treatment.

CONCLUSION

The nutritional intervention promoted catch-up growth and normalized excessive adiposity in IUGR animals at short-term. The benefits did not extend after a period of HFD. IUGR and early diet had gender-dependent effects on hepatic gene expression.

Prenatal ethanol exposure programs an increased susceptibility of non-alcoholic fatty liver disease in female adult offspring rats

Prenatal ethanol exposure (PEE) induces dyslipidemia and hyperglycemia in fetus and adult offspring. However, whether PEE increases the susceptibility to non-alcoholic fatty liver disease (NAFLD) in offspring and its underlying mechanism remain unknown. This study aimed to demonstrate an increased susceptibility to high-fat diet (HFD)-induced NAFLD and its intrauterine programming mechanisms in female rat offspring with PEE. Rat model of intrauterine growth retardation (IUGR) was established by PEE, the female fetus and adult offspring that fed normal diet (ND) or HFD were sacrificed. The results showed that, in PEE+ND group, serum corticosterone (CORT) slightly decreased and insulin-like growth factor-1 (IGF-1) and glucose increased with partial catch-up growth; In PEE+HFD group, serum CORT decreased, while serum IGF-1, glucose and triglyceride (TG) increased, with notable catch-up growth, higher metabolic status and NAFLD formation. Enhanced liver expression of the IGF-1 pathway, gluconeogenesis, and lipid synthesis as well as reduced expression of lipid output were accompanied in PEE+HFD group. In PEE fetus, serum CORT increased while IGF-1 decreased, with low body weight, hyperglycemia, and hepatocyte ultrastructural changes. Hepatic IGF-1 expression as well as lipid output was down-regulated, while lipid synthesis significantly increased. Based on these findings, we propose a "two-programming" hypothesis for an increased susceptibility to HFD-induced NAFLD in female offspring of PEE. That is, the intrauterine programming of liver glucose and lipid metabolic function is "the first programming", and postnatal adaptive catch-up growth triggered by intrauterine programming of GC-IGF1 axis acts as "the second programming".

Human conditions of insulin-like growth factor-I (IGF-I) deficiency

Insulin-like growth factor I (IGF-I) is a polypeptide hormone produced mainly by the liver in response to the endocrine GH stimulus, but it is also secreted by multiple tissues for autocrine/paracrine purposes. IGF-I is partly responsible for systemic GH activities although it possesses a wide number of own properties (anabolic, antioxidant, anti-inflammatory and cytoprotective actions). IGF-I is a closely regulated hormone. Consequently, its logical therapeutical applications seems to be limited to restore physiological circulating levels in order to recover the clinical consequences of IGF-I deficiency, conditions where, despite continuous discrepancies, IGF-I treatment has never been related to oncogenesis. Currently the best characterized conditions of IGF-I deficiency are Laron Syndrome, in children; liver cirrhosis, in adults; aging including age-related-cardiovascular and neurological diseases; and more recently, intrauterine growth restriction. The aim of this review is to summarize the increasing list of roles of IGF-I, both in physiological and pathological conditions, underlying that its potential therapeutical options seem to be limited to those proven states of local or systemic IGF-I deficiency as a replacement treatment, rather than increasing its level upper the normal range.

Effects of prenatal ethanol exposure on postnatal growth and the insulin-like growth factor axis

AIMS

To study the effect of in-utero alcohol exposure on the insulin-like growth factor axis (IGF) and leptin during infancy and childhood, considering that exposed children may exhibit pre- and postnatal growth retardation.

METHODS

We prospectively identified heavily drinking pregnant women who consumed on average 4 or more drinks of ethanol per day (≥ 48 g/day) and assessed growth in 69 of their offspring and an unexposed control group of 83 children, measuring serum IGF-I (radioimmunoassay), IGF-II (immunoradiometric assay, IRMA), insulin-like growth factor-binding protein 3 (IGFBP-3) (IRMA) and leptin (IRMA) at 1 month and 1, 2, 3, 4, and 5 years of age.

RESULTS

IGF-II levels increased with age in both groups, but the rate of increase was significantly higher in exposed children, and levels were significantly higher in ethanol-exposed children at 3, 4, and 5 years of age. In exposed children, IGF-I levels were higher at 3 and 4 years and leptin levels were significantly lower at 1 and 2 years. Exposed subjects showed a much lower correlation between IGF-I and growth parameters than unexposed subjects.

CONCLUSION

Exposure to ethanol during pregnancy increases IGF-I and IGF-II and decreases leptin during early childhood. The increase in serum IGF-II concentrations in ethanol-exposed children suggests that this hormone should be explored as a potential marker for prenatal alcohol exposure.

Association between height and weight catch-up growth with insulin resistance in pre-pubertal Chinese children born small for gestational age at two different ages

This study was performed to test whether children born small for gestational age (SGA) with catch-up growth (CUG) could be associated with the early development of insulin resistance and the β-cell dysfunction and to explore the impacts of height CUG and weight CUG on the insulin resistance in a Chinese population. A total of 30 children born SGA with CUG, 37 non-CUG (NCUG), and 42 born appropriate for gestational age (AGA) with normal height were recruited. Their fasting serum insulin, fasting glucose, insulin-like growth factor-1 (IGF-1) concentrations, and the homeostasis assessment model for insulin resistance (HOMA-IR) and β-cell function (HOMA%) were evaluated. The values of HOMA-IR in CUG SGA were significantly higher than that in NCUG SGA (P = 0.002) and AGA children (P = 0.036), respectively. Correlation analysis revealed that the concentrations of fasting serum insulin were positively correlated with IGF-1 (r = 0.443, P = 0.001) and Δheight standard deviation score (SDS; r = 0.500, P = 0.002) in ≤ 6-year-old SGA children, but only with Δweight SDS (r = 0.496, P = 0.030) in >6-year-old children. In conclusion, SGA children with CUG in height and a higher body mass index are prone to the development of insulin resistance. Higher levels of insulin were closely correlated with the postnatal height CUG in young SGA children and with the weight CUG in old children.

Comparative analysis of clinical, biochemical and genetic aspects associated with bone mineral density in small for gestational age children

Clinical, biochemical and genetic analysis related to bone mineral density (BMD) were carried out in children born small for gestational age (SGA) that failed to achieve postnatal catch-up growth (CUG), SGA children that completed CUG and adequate for gestational age (AGA) children. Serum IGF-I, IGF-II, IGF binding protein-3 and acid-labile subunit were lower in the SGA-CUG children as compared with the other groups. Frequencies of polymorphic variants of vitamin D receptor, estrogen receptor and collagen genes were similar among groups. The genotype 194-192 of the IGF-I gene was higher in the SGA-CUG and 196-192 was higher in the SGA+CUG group. In the SGA-CUG group, the genotype SS of the COLIA1 gene was associated with lower BMD. Therefore, IGF system and COLIA1 polymorphism distinguish prepubertal SGA-CUG children from the SGA+CUG children of the same age. Furthermore, COLIA1 polymorphism could be useful to predict osteopenia in SGA-CUG children.

Role of adiponectin and leptin on body development in infants during the first year of life

BACKGROUND

The control of growth and nutritional status in the foetus and neonate is a complex mechanism, in which also hormones produced by adipose tissue, such as adiponectin and leptin are involved. The aim of this study was to evaluate levels of adiponectin, leptin and insulin in appropriate (AGA) and small for gestational age (SGA) children during the 1st year of life and to correlate these with auxological parameters.

METHODS

In 33 AGA and 29 SGA infants, weight, length, head circumference, glucose, insulin, adiponectin and leptin levels were evaluated at the second day of life, and at one, six and twelve months, during which a portion of SGA could show catch-up growth (rapid growth in infants born small for their gestational age).

RESULTS

Both total and isoform adiponectin levels were comparable between AGA and SGA infants at birth and until age one year. These levels significantly increased from birth to the first month of life and then decreased to lower values at 1 year of age in all subjects. Circulating leptin concentrations were higher in AGA (2.1 +/- 4.1 ng/ml) than in SGA neonates (0.88 +/- 1.03 ng/ml, p < 0.05) at birth, then similar at the 1st and the 6th month of age, but they increased in SGA from six months to one year, when they showed catch-up growth. Circulating insulin levels were not statistically different in AGA and SGA neonates at any study time point. Insulin levels in both AGA and SGA infants increased over the study period, and were significantly lower at birth compared to one, six and 12 months of age.

CONCLUSIONS

During the first year of life, in both AGA and SGA infants a progressive decrease in adiponectin levels was observed, while a difference in leptin values was correlated with the nutritional status.

Maternal undernutrition and endocrine development

Maternal undernutrition, whether it occurs before conception, throughout gestation or during lactation, may lead to physiological adaptations in the fetus that will affect the health of the offspring in adult life. The timing, severity, duration and nature of the maternal nutritional insult may affect the offspring differently. Other factors determining outcome following maternal undernutrition are fetal number and gender. Importantly, effects of maternal undernutrition may be carried over into subsequent generations. This review examines the endocrine pathways disrupted by maternal undernutrition that affect the long-term postnatal health of the offspring. Maternal and childhood undernutrition are highly prevalent in low- and middle-income countries, and, in developed countries, unintentional undernutrition may arise from maternal dieting. It is, therefore, important that we better understand the mechanisms driving the long-term effects of maternal undernutrition, as well as identifying treatments to ameliorate the associated mortality and morbidity.

Intrauterine growth restriction as a potential risk factor for disease onset in adulthood

Intrauterine growth restriction (IUGR) is a risk factor for cardiovascular disease, type 2 diabetes mellitus, and obesity in adulthood. Several studies on diverse geographic and ethnic cohorts have provided evidence that being born small for gestational age (SGA) increases adult disease risk through various pathways of metabolic dysregulation. Unfavorable influences in the fetal environment may program metabolic homeostasis in later life affecting blood pressure, glucose tolerance and lipid regulation. Fetal restricted protein supply may impair the development of the kidney and reduce the nephron number, which is involved in blood pressure regulation. Moreover, children exposed to IUGR may exhibit postnatal rapid catch-up growth, altered body composition, increased visceral adiposity and low adiponectin levels which predispose to cardiovascular disease and type 2 diabetes mellitus in adulthood. Impairment in fetal pancreatic development and subsequent insulin signalling deficits due to IUGR may also be involved in the pathogenesis of these conditions. This review summarizes some of the hypotheses that have been put forward to explain the association between fetal growth restriction and subsequent metabolic dysregulation that may increase adult disease risk.

Reduction of IGF-binding protein-3 as a potential marker of intra-uterine growth restriction

BACKGROUND

Growth factor-binding proteins influence the growth of infants starting in utero. Adaptation of the fetus to an adverse uterine environment is associated with changes in the growth hormone-growth factor-insulin axis.

AIMS

To evaluate serum levels of IGF-I and IGFBP-3 in small and appropriate for gestational age newborn infants.

METHODS

Fifty-four newborn infants, small (SGA, n=28) or appropriate (AGA, n=26) for gestational age were matched by gestational age and sex. Blood was collected on the first day of life, and anthropometric measurements were taken at birth. The serum levels of IGF-I and IGFBP-3 were compared, and correlated with the anthropometric measurements.

RESULTS

On the first day of life, mean serum IGFBP-3 levels were significantly lower in SGA babies and correlated with weight, length, head circumference, and ponderal index (weight/length 3) (P<0.0001). In contrast, no associations were found between IGF-I serum levels and these anthropometric measurements.

CONCLUSION

Our data show that SGA babies have significantly reduced IGFBP-3 concentrations at birth.

Insulin-like growth factor-binding protein-1: serum levels, promoter polymorphism, and associations with components of the metabolic syndrome in short subjects born small for gestational age

CONTEXT

IGF binding protein (IGFBP)-1 is the only acute regulator of IGF-I bioavailability. Its production is suppressed by insulin, and low levels are associated with hyperinsulinemia and cardiovascular disease risk in adults. Data on IGFBP-1 levels in short, small for gestational age (SGA) subjects are scarce, and associations with IGFBP1 promoter single nucleotide polymorphisms have not been established.

OBJECTIVE

The aim of the study was to determine IGFBP-1 levels in short SGA subjects compared with those in controls, to assess genotype frequency of the -575 G/A single nucleotide polymorphism, and to determine its impact on IGFBP-1 levels.

SUBJECTS

A total of 272 short subjects born SGA and 330 subjects with normal stature (245 children, 85 young adults) participated in the study.

OUTCOME MEASURES

We measured fasting levels of IGFBP-1, IGF-I, insulin and lipid parameters, and body composition.

RESULTS

IGFBP-1 sd score (SDS) was comparable to controls in lean, short, SGA children but significantly lower in short SGA adults with normal fat mass (P < 0.001). IGFBP-1 SDS correlated significantly with insulin levels, systolic blood pressure SDS, and various lipid parameters. Baseline IGFBP-1 SDS was lowest in SGA children with -575 GG genotype and significantly higher in SGA children with one or two copies of the A allele. In response to a given insulin level, children with the AA genotype had a significantly higher IGFBP-1 SDS compared to children with the GG genotype.

CONCLUSION

Normal IGFBP-1 levels in lean, short, SGA children may reflect a normal metabolic state, despite reported hyperinsulinemia. IGFBP-1 is modulated by polymorphic variability and seems to be an additional player in the complex interaction between the IGF-IGFBP axis, glucose homeostasis, and lipid metabolism.

Intrauterine growth restriction due to uteroplacental insufficiency decreased white matter and altered NMDAR subunit composition in juvenile rat hippocampi

Uteroplacental insufficiency (UPI), the major cause of intrauterine growth restriction (IUGR) in developed nations, predisposes to learning impairment. The underlying mechanism is unknown. Neuronal N-methyl-d-aspartate receptors (NMDARs) are critical for synaptogenesis and learning throughout life. We hypothesized that UPI-induced IUGR alters rat hippocampal NMDAR NR2A/NR2B subunit ratio and/or NR1 mRNA isoform expression and synaptic density at day 21 (P21). To test this hypothesis, IUGR was induced by bilateral uterine artery ligation of the late-gestation Sprague-Dawley dam. At P21, hippocampal NMDAR subunit mRNA and protein were measured, as were levels of synaptophysin. Neuronal, synaptic, and glial density in CA1, CA3, and dentate gyrus (DG) was assessed by immunofluorescence. IUGR increased NR1 mRNA isoform NR1-3a and 1-3b expression in both sexes. In P21 males, IUGR increased protein levels of NR1 C2′ and decreased NR1 C2, NR2A, and the NR2A-to-NR2B ratio, whereas in females, IUGR increased NR2B protein. In males, IUGR was associated with decreased myelin basic protein-to-neuronal nuclei ratio in CA1, CA3, and DG. We conclude that IUGR has sex-specific effects and that neither neuronal loss nor decreased synaptic density appears to account for the changes in NMDAR subunits. Rather, it is possible that synaptic NMDAR subunit composition is altered. Our results suggest that apparent recovery in the IUGR hippocampus may be associated with synaptic hyperexcitability. We speculate that the NMDAR plays an important role in IUGR-associated cognitive impairment.

Insulin, adiponectin, IGFBP-1 levels and body composition in small for gestational age born non-obese children during prepubertal ages

BACKGROUND

Being small for gestational age (SGA) at birth and postnatal growth pattern may have an impact on insulin resistance and body composition in later life. Adiponectin is a strong determinant of insulin sensitivity.

OBJECTIVE

The aim of this study was to evaluate insulin resistance and adiponectin levels in SGA born children with catch-up growth (CUG) in the absence of obesity in prepubertal ages and relations with body composition and insulin-like growth factor binding protein (IGFBP)-1.

METHODS

Twenty-four (15F, 9M) SGA born children with CUG but without obesity were evaluated at age 6.3 +/- 0.5 years with respect to glucose, insulin, IGFBP-1, leptin and adiponectin levels, and body composition by dual-energy X-ray absorptiometry (DEXA). Their data were compared to that of 62 (27F, 35M) appropriate for gestational age (AGA) children.

RESULTS

SGA and AGA children had similar height standard deviation score (SDS) corrected for parental height and body mass index (BMI) SDS. Homeostasis model for insulin resistance (HOMA-IR) was significantly high in SGA (0.7 +/- 0.6) than in AGA children (0.4 +/- 0.2) (P = 0.029). There were no significant differences in leptin, IGFBP-1, adiponectin, and total and truncal fat between SGA and AGA children. However, being born SGA and having higher BMI in the upper half for the distribution in the sample, although within normal ranges, was associated with lower adiponectin levels (estimated means of log adiponectin levels 3.8 +/- 0.3 vs. 4.4 +/- 0.1 microg/ml, P = 0.040).

CONCLUSIONS

SGA children with CUG and with no obesity have higher insulin levels compared to AGA children. Both SGA birth and recent size seem to have an effect on serum adiponectin levels in childhood.

Insulin resistance and body composition in preterm born children during prepubertal ages

BACKGROUND

Premature born children may show insulin resistance in childhood which may be due to intrauterine or postnatal adverse environmental factors.

OBJECTIVE

Aim of this study was to evaluate insulin resistance and body composition in preterm born children born appropriate for gestational age (AGA) or small for gestational age (SGA) and relations with IGF-I, IGFBP-3 axis.

METHODS

Ninety-three preterm born children grouped as premature SGA (n = 30) and premature AGA (n = 63) were evaluated at age 4.6 +/- 0.2 years and 4.7 +/- 0.1 years with respect to their glucose, insulin, IGF-I, IGFBP-3, IGFBP-1, leptin levels and body composition by dual-energy X-ray absorptiometry. Their data were compared to that of body mass index (BMI) matched term SGA (n = 42) and term AGA (n = 44) children of age 4.5 +/- 0.2 and 3.8 +/- 0.1 years. All children had height appropriate for their target height. Insulin resistance was evaluated by basal insulin and homeostasis model assessment for insulin resistance (HOMA-IR).

RESULTS

Basal insulin level was similar in preterm AGA (4.3 +/- 1.4 pmol/l) and term AGA (7.9 +/- 6.4 pmol/l) children at similar and normal BMI levels. Preterm SGA children had insulin levels (5.0 +/- 3.6 pmol/l) similar to preterm AGA children but significantly lower than that in term SGA children (23.7 +/- 20.8 pmol/l) (P = 0.001). Similar results were obtained for HOMA-IR. Term SGA children had also significantly lower IGFBP-1 levels. Body composition, leptin and IGFBP-3 did not differ between the respective groups. IGF-I was lower in preterm AGA (5.0 +/- 0.6 nmol/l) than in term AGA (8.3 +/- 1.2 nmol/l) (P < 0.001) children.

CONCLUSIONS

Premature born AGA and SGA children do not have insulin resistance when compared to term children if they have made a catch-up growth appropriate for their target height and have normal BMI. The similar insulin levels in preterm SGA and preterm AGA children together with increased insulin levels in term SGA children points to the fact that it is the intrauterine restriction in the third trimester that has an adverse effect on future adverse metabolic outcome.

Changes in insulin sensitivity and glucose metabolism during therapy with recombinant human growth hormone in short children born small for gestational age show a negative correlation with baseline measurements

Recombinant human growth hormone (rhGH) is an effective therapy for children with short stature born small for gestational age (SGA); however, insulin resistance can develop during treatment. This retrospective analysis assessed the effect of rhGH treatment (0.067 mg/kg/day) on glucose metabolism and insulin secretion in children with short stature born SGA, and measured whether baseline characteristics correlated with changes in insulin resistance or glucose sensitivity during treatment. Baseline glucose area under the concentration-time curve (AUC) was negatively correlated with the change in glucose AUC (p<0.001). Similar negative correlations were seen between baseline insulin AUC and the change in insulin AUC during treatment (p<0.001); and between baseline HOMA-IR (homeostatic model of insulin resistance) and the change in HOMA-IR during treatment (p<0.001). Small but significant changes, not thought to be clinically significant, were seen in indicators of insulin sensitivity during rhGH treatment. Glucose levels remained within the normal range during oral glucose tolerance testing.

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.

Serum levels of adiponectin and IGFBP-1 in short children born small for gestational age

OBJECTIVE

The aim of this study was to quantify serum adiponectin concentrations in short children born small for gestational age (SGA) compared with those in children born appropriate for gestational age (AGA), and to assess the relationship between the serum levels of adiponectin and insulin-like growth factor binding protein-1 (IGFBP-1) known as a predictor of the development of type 2 diabetes mellitus and cardiovascular disease.

SUBJECTS AND METHODS

Sixteen prepubertal short children born SGA and 20 short children born AGA, matched for age, body mass index, height, pubertal status, gestational age, bone age and midparental height, were included in the study. The serum levels of adiponectin, IGFBP-1, insulin and insulin-like growth factor-I (IGF-I) were measured in the fasting state.

RESULTS

The levels of serum adiponectin were significantly lower in the SGA than in AGA children (10.5 +/- 4.2 vs. 13.9 +/- 5.1 micro g/ml, P < 0.05). The levels of serum IGFBP-1, insulin and IGF-I were all similar in both groups. Overall, there was a significant positive correlation between adiponectin and IGFBP-1 (r = 0.40, P < 0.05).

CONCLUSIONS

Our results suggest that hypoadiponectinaemia in short SGA children without catch-up growth may reflect insulin resistance and imply a higher risk of developing type 2 diabetes mellitus. Additionally, adiponectin may be a more sensitive indicator for latent insulin resistance than IGFBP-1 in short SGA children.

Longitudinal changes in insulin-like growth factor-I, insulin sensitivity, and secretion from birth to age three years in small-for-gestational-age children

INTRODUCTION

Insulin resistance (IR) develops as early as age 1 to 3 yr in small for gestational age (SGA) infants who show rapid catch-up postnatal weight gain. In contrast, greater insulin secretion is related to infancy height gains. We hypothesized that IGF-I levels could be differentially related to gains in length and weight and also differentially related to IR and insulin secretion.

METHODS

In a prospective study of 50 SGA (birth weight < 5th percentile) and 14 normal birth weight [appropriate for gestational age (AGA)] newborns, we measured serum IGF-I levels at birth, 1 yr, and 3 yr. IR (by homeostasis model assessment) and insulin secretion (by short iv glucose tolerance test) were also measured at 1 yr and 3 yr.

RESULTS

SGA infants had similar mean length and weight at 3 yr compared with AGA infants. SGA infants had lower IGF-I levels at birth (P < 0.0001), but conversely they had higher IGF-I levels at 3 yr (P = 0.003) than AGA infants. Within the SGA group, at 1 yr IGF-I was associated with length gain from birth and insulin secretion (P < 0.0001); in contrast at 3 yr IGF-I was positively related to weight, body mass index, and IR.

CONCLUSIONS

IGF-I levels increased rapidly from birth in SGA, but not AGA children. During the key first-year growth period, IGF-I levels were related to beta-cell function and longitudinal growth. In contrast, by 3 yr, when catch-up growth was completed, IGF-I levels were related to body mass index and IR, and these higher IGF-I levels in SGA infants might indicate the presence of relative IGF-I resistance.

Insulin sensitivity and insulin secretion at birth in intrauterine growth retarded infants

AIM

To study insulin sensitivity, secretion and relation of insulin levels with birth weight and ponderal index in intrauterine growth retarded (IUGR) infants at birth.

METHODS

We studied 30 IUGR and 30 healthy newborns born at term by vaginal delivery in Jipmer, Pondicherry, India. Cord blood was collected at the time of delivery for measurement of plasma glucose and insulin.

RESULTS

When compared with healthy newborns, IUGR newborns had lower plasma glucose levels (mean 2.3+/-0.98 versus 4.1+/-0.51 mmol/L, p<0.001); lower plasma insulin levels (mean 4.5+/-2.64 versus 11.03+/-1.68 microU/L, p<0.001); higher insulin sensitivity calculated using G/I ratio (mean 11.6+/-5.1 versus 6.7+/-0.31, p<0.001), HOMA IS (mean 5.5+/-6.0 versus 0.53+/-0.15, p<0.001), and QUICKI (mean 0.47+/-0.12 versus 0.34+/-0.02, p<0.001); and decreased pancreatic beta-cell function test measured as I/G (mean 0.10+/-0.037 versus 0.15+/-0.006, p<0.001). A positive correlation was identified between insulin levels and birth weight in both the healthy control group (r2 = 0.17, p = 0.024) and IUGR group (r2 = 0.13, p = 0.048). However correlation of insulin levels with ponderal index was much more confident in both healthy control (r2 = 0.90, p<0.001) and IUGR groups (r2 = 0.28, p = 0.003). Insulin status correlated both with birth weight and ponderal index more confidently in control group than in IUGR group.

CONCLUSION

At birth, IUGR infants are hypoglycaemic, hypoinsulinaemic and display increased insulin sensitivity and decreased pancreatic beta-cell function. Insulin levels correlate with ponderal index much more confidently than with birth weight.

Clinical utility of measurements of insulin-like growth factor 1

Plasma insulin-like growth factor 1 (IGF-I) concentrations are regulated by genetic factors, nutrient intake, growth hormone (GH) and other hormones such as T4, cortisol and sex steroids. The accuracy of IGF-I measurement in diagnosing GH deficiency or excess depends, in part, on the relative contributions of each of these variables. Since their respective influence may vary widely between individuals, the establishment of well-defined normal ranges is necessary, which requires adequate numbers of normal individuals, in order for IGF-I measurements to have maximum utility. In states of GH deficiency, the influence of these non-GH-related factors predominates. Although IGF-I levels have utility as a screening test in children and young adults, they cannot be used as a stand-alone test for the diagnosis of GH deficiency. By contrast, in acromegaly, GH is the predominant determinant of IGF-I levels and, therefore, measurement of IGF-I is a very useful diagnostic test. In acromegaly, IGF-I levels are useful for assessing the relative degree of GH excess, because changes in IGF-I correlate with changes in symptoms and soft-tissue growth. IGF-I is also very useful in monitoring the symptomatic response to therapy.

Postnatal growth, neurodevelopment and altered adiposity after preterm birth--from a clinical nutrition perspective

Evidence reveals a dilemma that under-nutrition and growth retardation during brain growth are associated with neurodevelopmental deficits, and nutritional supplement resulting in catch-up growth and relative visceral adiposity leads to metabolic/cardiovascular morbidities. Hyperinsulinaemia secondary to insulin resistance appears to play a central role in the development of visceral adiposity through its action on adipocyte beta3-adrenoceptor.

CONCLUSION

Optimal nutritional management to minimize hyperinsulinaemia and insulin resistance may potentially improve neurodevelopment and facilitate catch-up growth with normal body composition.

Growth Hormone Therapy in Short Children Born Small for Gestational Age

There is still a lack of data from randomized, controlled, long-term studies of growth hormone (GH) treatment in children born small for gestational age (SGA), but the available evidence indicates consistently that GH therapy is a valid growth-promoting treatment in these children, particularly if started early. Whilst side effects appear uncommon, ongoing surveillance is required and treated children should be monitored for changes in glucose homeostasis, lipid profiles and blood pressure, especially during puberty. We provide an update on the safety and efficacy of GH treatment in short children born SGA.

High serum levels of growth hormone (GH) and insulin-like growth factor-I (IGF-I) during high-dose GH treatment in short children born small for gestational age

CONTEXT

Epidemiological studies have indicated that high serum levels of GH and IGF-I are associated with long-term risks.

OBJECTIVE

The objective of the study was to evaluate the changes in serum levels of GH during overnight profiles, IGF-I, and IGF binding protein 3 (IGFBP-3) in short small for gestational age (SGA) children during GH treatment with two doses.

PATIENTS

Thirty-six prepubertal short SGA children were the subjects of this study.

INTERVENTION

Subjects received 1 (group A) or 2 (group B) mg GH/m(2).d.

MAIN OUTCOME MEASURES

At baseline and after 6 months of GH treatment, overnight GH profiles were performed, and serum IGF-I and IGFBP-3 levels were measured.

RESULTS

After 6 months, group B had significantly higher GH levels during the profile (mean, maximum, and area under the curve above zero line) than group A (P < 0.009). In group B, maximum GH levels increased from 43.9-161 mU/liter (P < 0.0002), and in group A, from 57.2-104 mU/liter (P = 0.002). During the profile (i.e. 12 h per day), children of group B had mean GH levels of 64.4 vs. 34.8 mU/liter in group A (P = 0.001). The IGF-I and IGF-I to IGFBP-3 ratio sd scores increased significantly in both groups, but were higher in group B than A [1.5 vs. 0.2 (P = 0.002) and 1.4 vs. 0.3 (P = 0.007), respectively]. In group B, 74% of the children had IGF-I levels in the highest quintile during GH treatment compared with 19% in group A.

CONCLUSION

Our study shows that high-dose GH treatment in short SGA children results in high serum GH and IGF-I levels in most children. We recommend monitoring IGF-I levels during GH therapy to ensure that these remain within the normal range.

Effect of nutrient restriction on the somatotropes and substance P-immunoreactive cells in the pituitary of the female ovine fetus

The maternal environment affects fetal development and may influence the physiology of the adult. Fetal growth hormone (GH) is increased by maternal undernutrition but the mechanisms responsible are unknown. This study determined the effect of maternal undernutrition on the development of fetal pituitary somatotropes in the female. Ewes were grouped randomly into control (fed 100% of requirements) or nutrient restricted (fed 50%) from Days 28 to 78 of gestation. At Day 78, the ewes were killed and fetuses collected (Day 78 NR (nutrient restricted): n=6; Day 78C (control): n=6). Remaining ewes were realimented to 100% of nutritional requirements and were killed at Day 135 (Day 135 NR (nutrient restricted): n=6; Day 135 C (control): n=6). Somatotropes were visualized immunocytochemically and the size, mean density, total percentage and proportion colocalized with substance P were determined for each group. Nutrient restriction increased (p<0.01) the density of pituitary cells in Day 78 fetuses but this difference was no longer apparent by Day 135 after realimentation. The density and proportion of somatotropes were not different between treatment groups at Day 78 but were significantly (p<0.05) lower in the nutrient restricted Day 135 fetuses as compared to the Day 135 control animals. Somatotropes from restricted fetuses were significantly (p<0.001) larger at Day 78. Nutrient restriction increased the density (p<0.001) and percentage (p<0.05) of substance P-immunoreactive cells Day 135 fetuses. Similarly, the proportion of somatotropes that expressed substance P was significantly (p<0.05) increased by nutrient restriction in the Day 135 fetuses. Although nearly two thirds of substance P-immunoreactive cells co-expressed GH, there was no significant effect of treatment on this co-expression. Additional studies are required to determine if other components of the neuroendocrine GH axis are affected by this nutritional insult, if the alterations that we have observed, particularly in the tachykinin system, persist into adulthood and, importantly, what are the long-term consequences of an altered GH axis.

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.

Babies Born Small for Gestational Age: Insulin Sensitivity and Growth Hormone Treatment

Epidemiological studies have identified an association between size at birth and adult risk for type 2 diabetes mellitus and cardiovascular disease. In contemporary populations, children who are relatively small at birth and show rapid infancy weight gain are at greatest risk for the development of childhood obesity, increased visceral fat and insulin resistance: possible early markers of adult disease risk. Individuals presenting to growth clinics with short stature and a history of low birthweight will not have shown post-natal catch-up growth and may be a very heterogeneous group. Nevertheless, there are some data to suggest that as a group they are insulin resistant with decreased lean mass. Growth hormone treatment leads to reversible worsening of the insulin resistance, and short-term data do not indicate an increased risk for type 2 diabetes. However, further long-term follow-up is required, and particular care should be taken in monitoring children with a strong family history of type 2 diabetes and those from ethnic groups in which there is a high background prevalence of the disease.

Longitudinal changes in insulin sensitivity and secretion from birth to age three years in small- and appropriate-for-gestational-age children

AIMS/HYPOTHESIS

Insulin resistance and type 2 diabetes risk in human subjects who were small-for-gestational-age (SGA) at birth may be a consequence of rapid early postnatal weight gain.

MATERIALS AND METHODS

We prospectively studied early changes in fasting insulin sensitivity and insulin secretion, assessed by a short intravenous glucose tolerance test that was conducted several times from birth to 3 years of age in 55 SGA (birthweight below fifth percentile) newborns and in 13 newborns with a birthweight appropriate for gestational age (AGA).

RESULTS

Most SGA infants showed postnatal upward weight centile crossing and by 3 years were similar in size to AGA infants. SGA infants had lower pre-feed insulin levels at postnatal age 48 h than AGA infants (median 34.4 vs 59.7 pmol/l, p<0.05), but by the age of 3 years they had higher fasting insulin levels (median 38.9 vs 23.8 pmol/l, p<0.005), which were related to rate of weight gain between 0 and 3 years (r=0.47, p=0.0003). First-phase insulin secretion did not differ between SGA and AGA infants, but SGA infants had a lower glucose disposition index (beta cell compensation) (median 235 vs 501 min mmol(-1) l(-1), p=0.02), which persisted after allowing for postnatal weight gain (p=0.009).

CONCLUSIONS/INTERPRETATION

SGA infants showed a marked transition from lower pre-feed insulin and increased insulin sensitivity at birth to insulin resistance over the first 3 years of life. This transition was related to rapid postnatal weight gain, which could indicate a propensity to central fat deposition. The additional observation of reduced compensatory beta cell secretion underlines the need for long-term surveillance of glucose homeostasis in all SGA subjects, whether or not they show postnatal catch-up growth.

Growth hormone therapy in short children born small for gestational age

Being born small for gestational age (SGA) is one of the most common causes of childhood short stature, and recombinant GH therapy has been recently licensed to promote growth in short SGA children from the age of 4 years old. Studies are now reporting very encouraging effects on adult height gains, especially in those children who started GH therapy early, at least 2 years prior to the onset of puberty. Compared to the age at starting treatment, the GH dose has a less significant impact on final height, and more attention needs to be paid now to identify earlier those SGA children who fail to catch-up spontaneously. The benefits are not just in terms of height, but also in body composition and possibly blood pressure and lipid levels. However the risk of side effects and long-term complications, particularly related to the expected metabolic effects of GH in inducing insulin resistance and hyperinsulinaemia, need to be carefully monitored especially in SGA children with a family history of type 2 diabetes. Recently, GH therapy was found to amplify the adrenarche of short SGA children and to induce a pro-inflammatory shift, as judged by a rise of neutrophil count and circulating interleukin-6 (IL-6), and a fall in adiponectin levels. Further progress is anticipated to assess the addition of insulin-sensitizing therapy to attenuate the GH-induced hyperinsulinemia, in order to alter the pro-inflammatory course, to avoid excessive release of adrenal androgens, and to slow down the potential rapid tempo of pubertal progression in SGA children. In the meantime, post-SGA short stature is rapidly becoming one of the prime indications for GH therapy in childhood.

Fetal origins of adult disease: a paediatric perspective

Prepubertal children born SGA or VLBW premature exhibit marked insulin resistance. There are similarities between SGA and VLBW children in that both are exposed to sub-optimal environments that encompass undernutrition and/or malnutrition during the equivalent of the last trimester of pregnancy. Although both SGA and VLBW groups fail to reach genetic height potential and are recognized causes of short stature in childhood, there are differences between the groups with respect to the growth hormone and IGF-I axis.SGA children have elevated IGFI levels, possibly due to either hyperinsulinism or partial IGF-I resistance, whereas VLBW children have low IGF-I and IGFBP-3 levels suggestive of GH resistance. Thus the nature and timing of the early insult may lead to discordant changes to the metabolic and endocrine axes.IVF children are taller with increased IGF I, IGF II and IGFBP3 expression. These changes could be due to alterations in the environment of the periconceptual embryo resulting in changes in imprinting of genes involved in growth and development. The phenotypic, endocrine and metabolic consequences of alterations in the periconceptual, fetal and early neonatal periods is an area of intense investigation. Future research in this field is likely to focus on the mechanisms through which environmental changes lead to these programmed effects.

Endocrine and metabolic consequences of intrauterine growth retardation

Size at birth and early infancy growth rates have been linked to long-term risks for diseases, such as type 2 diabetes and cardiovascular disease. These associations could be explained by permanent programming of metabolic responses and selective survival of those genetically predisposed to such adaptations. These epidemiologic associations may also affect long-term disease risk in short small-for-gestational age children, who are often treated with growth hormone. Study of the mechanisms and genetic factors involved in the association between small size at birth, rapid postnatal weight gain, and adult disease may promote the early identification of subjects with the highest disease risk and new opportunities to develop targeted early interventions.

Regional Brazilian diet-induced pre-natal malnutrition in rats is correlated with the proliferation of cultured vascular smooth muscle cells

OBJECTIVES

Pre-natal malnutrition induces hypertension and insulin resistance, pathologies commonly linked to atherosclerotic disease. The proliferation of vascular smooth muscle cells (SMCs) is important during development of the atherosclerotic plaque. In this work, we investigated whether the serum of pre-natal malnourished Wistar rats could alter the proliferation of aortic and renal artery SMCs in culture. Malnutrition was induced by feeding a basic regional diet available in a rural area of Pernambuco State, Brazil. This diet was rich in carbohydrates and deficient in proteins, lipids, vitamins and minerals, including sodium chloride.

METHODS AND RESULTS

Serum was obtained from the blood of 90-day-old control and pre-natal undernourished rats. SMCs from control Wistar rats at the 6th passage were allowed to adhere to plates in Dulbecco's modified Eagle's medium (DMEM) supplemented with fetal calf serum (10%). Subsequently, the SMCs were maintained in DMEM supplemented with rat serum (10%). The number of cells was counted on the 3rd, 6th and 8th days of culture into rat serum. [3H]-thymidine incorporation into SMCs was evaluated after 20 h or 6 days of incubation. The birth weight of male and female undernourished offspring was 25% (p<0.05) and 46% (p<0.05) lower, respectively, than their corresponding control groups. On the 8th day of culture, the number of aortic SMCs in the serum of undernourished male and female rats, as well as renal artery SMCs in the serum of undernourished female rats, was higher than in the serum of control rats. The [3H]-thymidine incorporation was higher in aortic SMCs incubated for 6 days in the serum of undernourished male and female rats. At confluence, the density of aortic SMCs was higher than that of renal artery SMCs.

CONCLUSIONS

Pre-natal malnutrition produces serum with altered properties that can affect the proliferation of SMCs and may contribute to atherosclerotic disease.

Growth hormone therapy for children born small for gestational age: height gain is less dose dependent over the long term than over the short term

BACKGROUND

Approximately 3% of children are born small for gestational age (SGA), and approximately 10% of SGA children maintain a small body size throughout childhood and often into adult life. Among short SGA children, growth hormone (GH) therapy increases short-term growth in a dose-dependent manner; experience with long-term therapy is limited.

OBJECTIVE

To delineate the dose dependency of long-term height gain among short SGA children receiving GH therapy.

METHODS

We performed an epianalysis of the first adult height data for SGA children (n = 28) enrolled in 3 randomized trials comparing the growth-promoting efficacy of 2 continuous GH regimens (33 or 67 microg/kg per day for approximately 10 years, starting at approximately 5 years of age); in addition, we performed a meta-analysis of the adult height results published previously and those presented here.

RESULTS

Epianalysis outcomes (n = 28) suggested that adult height increased more with a higher-dose regimen than with a lower-dose regimen. In the meta-analysis (n = 82), the higher-dose regimen was found to elicit a long-term height gain superior to that achieved with the lower-dose regimen by a mean of 0.4 SD (approximately 1 inch). Children who were shorter at the start of therapy experienced more long-term height gain.

CONCLUSIONS

These findings confirm GH therapy as an effective and safe approach to reduce the adult height deficit that short SGA children otherwise face. In addition, the first meta-analysis indicated that height gain is less dose dependent over the long term than over the short term, at least within the dose range explored to date. For SGA children whose stature is not extremely short, current data support the use of a GH dose of approximately 33 microg/kg per day from start to adult height, particularly if treatment starts at a young age; shorter children (for example, height below -3 SD) might benefit from an approach in which short-term catch-up growth is achieved with a higher dose (> or =50 microg/kg per day) and long-term growth to adult height is ensured with a GH dose of approximately 33 mug/kg per day. Because GH-induced accelerations of height and weight gain evolve in parallel, the dose tapering from > or =50 microg/kg to approximately 33 microg/kg can be accomplished by simply maintaining the absolute GH dose (in micrograms) while the child gains weight (in kilograms). With this algorithm, more growth-responsive children taper their GH dose down to approximately 33 microg/kg per day more quickly.

Serum markers of GH and insulin action in 12-year-old children born small for gestational age

OBJECTIVES

Our aim was to determine whether markers of growth hormone and insulin action differ between children born small for gestational age (SGA) and those born of an appropriate size for gestational age (AGA).

DESIGN

Fifty-five SGA children and their 55 age- and sex-matched AGA control subjects were studied in a case-control setting at 12 years of age.

METHODS

We examined serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, IGF-binding protein (IGFBP)-1 and IGFBP-3, sex hormone binding globulin (SHBG), leptin, fasting insulin, and blood glucose. Insulin sensitivity was evaluated by the homeostasis model assessment for insulin resistance (HOMA-IR).

RESULTS

The body mass index (BMI), sex, and puberty-adjusted mean serum IGF-I concentration was higher in the SGA than in the AGA children (303.4 vs 282.3 microg/l, P = 0.006). The mean serum concentrations of IGF-II, IGFBP-I, IGFBP-3, SHBG, fasting insulin, blood glucose and HOMA-IR did not differ between the SGA and the AGA group. The BMI, sex, and puberty-adjusted mean serum leptin concentration was lower in the SGA than in the AGA children (7.9 vs 10.1 microg/l, P = 0.037). In multiple logistic regression analysis, high HOMA-IR predicted high serum IGF-I levels in the SGA children (odds ratio 8.3; 95% confidence interval 1.7-41; P = 0.010), whereas in the AGA group HOMA-IR did not associate with the serum IGF-I level.

CONCLUSIONS

The BMI, sex, and puberty-adjusted mean serum IGF-I concentration was significantly higher and the leptin concentration was lower in the SGA than in the AGA children. No differences were found in the indices of insulin action or sensitivity between the SGA and AGA children at 12 years of age. However, HOMA-IR strongly associated with serum IGF-I levels in the SGA children.

Spontaneous growth hormone secretion and IGF1:IGFBP3 molar ratios in children born small for gestational age (SGA)

OBJECTIVE

To analyze spontaneous nocturnal GH profiles, IGF1 and IGFBP3 serum levels, as well as IGF1:IGFBP3 molar ratios in SGA children without postnatal catch-up growth.

METHODS

Short statured prepubertal SGA children (n = 24) were matched retrospectively for sex, age and BMI to short statured children born appropriate for gestational age (AGA), who underwent the same diagnostic program. GH deficiency was excluded in all children by a normal increase of GH in 2 stimulation tests (>8 microg/L). For assessment of spontaneous nocturnal GH secretion, GH serum levels were measured every 20 min for 10 h. Pulsatility was analyzed with Pulsar.

RESULTS

None of the Pulsar derived descriptive parameters showed a significant difference between SGA and AGA children. Overall, median IGF1 levels were approximately one SDS below zero SDS (p < 0.001), whereas IGFBP3 levels were normal in both groups. Thus, the IGF1:IGFBP3 molar ratios were significantly lower from zero (p < 0.01) in SGA as well as in AGA children. However, IGF1- and IGFBP3-SDS levels related either to chronological or to bone age did not differ significantly between SGA and AGA children.

CONCLUSIONS

Building matched pairs of short statured children born either SGA or AGA for sex, age and BMI we did not find any significant differences in spontaneous nocturnal GH secretion, IGF1, IGFBP3, and IGF1:IGFBP3 molar ratios.

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.

Metabolism of oral glucose in children born small for gestational age: evidence for an impaired whole body glucose oxidation

Epidemiological studies indicate that intrauterine growth restriction confers an increased risk of developing type 2 diabetes mellitus in subsequent life. Several studies have further documented the presence of insulin resistance in young adults or adolescent children born small for gestational age. Since most studies addressed postpubertal individuals, and since puberty markedly affects energy metabolism, we evaluated the disposal of oral glucose in a group including mainly prepubertal and early pubertal children with intrauterine growth restriction and in healthy age- and weight-matched control children. All children had an evaluation of their body composition by skinfold thickness measurements. They were then studied in standardized conditions and received 4 consecutive hourly loads of 180 mg glucose/kg body weight to reach a near steady state. Energy expenditure and substrate oxidation were evaluated during the fourth hour by indirect calorimetry. Compared to both age- and weight-matched children, children born small for gestational age had lower stature. Their energy expenditure was not significantly decreased, but they had lower glucose oxidation rates. These results indicate that metabolic alterations are present early in children born small for gestational age, and are possibly related to alterations of body composition.