Daniela Germani

Low birthweight and adult insulin resistance: the “catch-up growth” hypothesis

Epidemiological studies have shown a close correlation between intrauterine growth retardation (IUGR) and the onset of insulin resistance, non-insulin-dependent diabetes mellitus (NIDDM), hypertension, hyperlipidaemia, and cardiovascular diseases in adult life.1-6 To explain this association, the concept of re-programming has been introduced: intrauterine exposure to insufficient nutrient supply during critical periods of fetal life would permanently affect the development and function of the endocrine system, leading to metabolic changes, including reduced insulin sensitivity.5 6 Although knowledge of the mechanisms involved in the re-programming process might allow new strategies for early prevention of long term metabolic disturbances to be developed, the pathophysiological link between fetal growth impairment and adult diseases is still unclear. In 1992 Hales and Barker7 proposed the model of the “thrifty phenotype,” suggesting that intrauterine malnutrition would lead to insulin resistance and decreased β cell mass, thus predisposing to NIDDM. According to this hypothesis, the endocrine alterations induced by intrauterine malnutrition are intended to divert the limited nutrient supply to maintain survival and development of vital organs, such as the brain, at the expense of growth. More recently, the “fetal salvage” hypothesis has been formulated.8 The finding that prepubertal IUGR children show a far greater insulin response than normal birthweight children, challenges the previously proposed β cell hypoplasia. …

Growth, IGF System, and Cortisol in Children with Intrauterine Growth Retardation: Is Catch-up Growth Affected by Reprogramming of the Hypothalamic-Pituitary-Adrenal Axis?

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

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

Thirty-seven children with intrauterine growth retardation (IUGR) were enrolled in a 3-mo longitudinal study. Weight, length, and knee-heel length(by knemometry) were measured at birth and at 7, 14, 30, 60, and 90 d. GH, IGF-I, IGF binding protein (BP)-3, IGFBP-1, and C-peptide were measured at birth and at 2 mo. IGFBP-3 Western immunoblotting and proteolytic activity assay were also performed. Twenty-five newborns with birth weight appropriate for gestational age were chosen as controls. At birth IUGR newborns showed levels of GH and IGFBP-1 significantly higher, and IGF-I, IGFBP-3, and C-peptide significantly lower than control subjects. At 2 mo GH and IGFBP-1 levels decreased, whereas IGF-I, IGFBP-3, and C-peptide rose, attaining the concentrations found in control subjects at birth. Baseline peptide levels as well as their 2-mo variations did not correlate with the gain in weight, supine length, and knee-heel length recorded at 3 mo. Fourteen of nineteen IUGR cord blood samples showed the presence of the intact ∼42-39-kD IGFBP-3 doublet and the major ∼29-kD fragment. At 2 mo the IGFBP-3 band pattern was characterized by the predominance of a ∼18-kD fragment in 6 of 19 tested IUGR infants. The incubation of 2-mo IUGR samples with normal adult serum induced the appearance of the ∼18-kD band, which was not modified by the addition of EDTA. These results suggest that: 1) the IGF-related growth-promoting mechanism is impaired in IUGR children at birth but is fully restored at 2 mo; 2) the cord blood levels of GH, IGF-I, IGFBP-3, IGFBP-1, and C-peptide are not predictive of the weight and length gain during the first 3 mo of life; 3) IUGR children have at least two different IGFBP-3 proteases, one cation-dependent protease that is present at birth and able to yield the major ∼29-kD IGFBP-3 fragment and a second one, with a different activation timing, which exhibits cation independence and induces the formation of a ∼18-kD IGFBP-3 form.

Insulin Resistance and Insulin-Like Growth Factors in Children with Intrauterine Growth Retardation

Aims: To investigate (a) the prevalence of insulin resistance in children with intrauterine growth retardation (IUGR); (b) whether catch-up growth is associated with a higher risk of insulin resistance; (c) the insulin-like growth factor (IGF) system status. Methods: 49 children with IUGR aged 9.1 ± 3.3 years underwent anthropometric measurements, and assessment of insulin resistance and IGF system parameters. A fasting glucose/insulin ratio (G/I) <6 was chosen as suggestive of insulin resistance. Results: 11/49 (22%) children had a G/I <6. Postnatal growth closely correlated with birth size and actual body mass index (BMI). None of the insulin resistance parameters was related to linear growth and BMI. Liver function markers were significantly related to insulin sensitivity status. The IGF system status was normal and did not correlate with insulin resistance indicators. Conclusions: (a) Children with IUGR have a high prevalence of reduced insulin sensitivity; (b) postnatal catch-up growth is related to intrauterine growth and actual nutritional status; (c) insulin sensitivity status is not related to postnatal growth but to liver function; (d) IGF system is normal and not related to the insulin resistance parameters during childhood.

In vitro effects of growth hormone (GH) and insulin-like growth factor I and II (IGF-I and -II) on chromosome fragility and p53 protein expression in human lymphocytes.

We have reported previously that growth hormone (GH) therapy increases cell radiosensitivity; in this study we tested whether GH itself or IGFs induce chromosome aberrations and investigated the expression of p53 protein in response to DNA damage.

Insulin-Like Growth Factor-I and -II Levels Are Associated with the Progression of Nonalcoholic Fatty Liver Disease in Obese Children

OBJECTIVE To correlate circulating levels of insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein (IGFBP)-3 in a population of obese children with biopsy-proven nonalcoholic fatty liver disease (NAFLD) with clinical, biochemical, and histological features. STUDY DESIGN We conducted a cross-sectional study at the Hepatometabolic Unit of the Bambino Gesù Childrens Hospital, Rome, Italy. Obese children (42 girls and 57 boys) underwent liver biopsy, anthropometry, biochemical assessment, and IGF system evaluation. Serum concentrations of IGF-I, IGF-II, and IGFBP-3 were measured. The liver biopsy features of each case were graded according to the NAFLD Activity Scoring system. The degrees of steatosis, inflammation, ballooning, and fibrosis were calculated. RESULTS Nonalcoholic steatohepatitis was diagnosed in 14/99 obese subjects. Stepwise regression analysis revealed that IGF-I was the major predictor of ballooning (β = -0.463; P < .0001) and NAFLD activity score (β = -0.457; P < .0001), IGF-I/IGFBP-3 ratio was the major predictor of liver inflammation (β = -0.285; P = .005), and IGF-II was the major predictor of liver fibrosis (β = 0.343; P < .005). CONCLUSION Circulating levels of IGF-I and IGF-II are associated with the histological stages of NAFLD and may represent novel markers of liver damage progression in obese children.

IGF2 Methylation Is Associated with Lipid Profile in Obese Children

Aim: Our aim was to investigate the relationships between the degree of IGF2 methylation and the metabolic status in obese children and adolescents. Subjects and Methods: Eighty-five obese subjects aged 11.6 ± 2.1 years were studied. Anthropometry, metabolic parameters, blood pressure and body composition were assessed. DNA methylation analysis was performed by restriction enzyme digestion assay. The study population was subdivided into two groups according to the percentage of IGF2 cytidine-guanosine (CpG) island methylation. Results: Twenty-two subjects showed intermediate methylation (a percentage of CpG site methylation comprised between 10 and 60%), 56 were hypomethylated (percentage of methylation lower than 10%), and only 1 showed a high rate of hypermethylation (percentage of methylation above 60%). Children with intermediate methylation showed significantly higher levels of triglycerides (107.6 ± 41.99 vs. 76.6 ± 30.18 mg/dl, p < 0.005) and a higher triglyceride/high-density lipoprotein-cholesterol ratio (2.23 ± 0.98 vs. 1.79 ± 0.98, p < 0.02) compared with hypomethylated children. Conclusions: These preliminary findings show for the first time a relationship between IGF2 methylation pattern and lipid profile in obese children. Although the correlation does not imply causation, if our findings are confirmed in further studies, IGF2 methylation might represent an epigenetic marker of metabolic risk.

Uteroplacental insufficiency down regulates insulin receptor and affects expression of key enzymes of long-chain fatty acid (LCFA) metabolism in skeletal muscle at birth

BackgroundEpidemiological studies have revealed a relationship between early growth restriction and the subsequent development of insulin resistance and type 2 diabetes. Ligation of the uterine arteries in rats mimics uteroplacental insufficiency and serves as a model of intrauterine growth restriction (IUGR) and subsequent developmental programming of impaired glucose tolerance, hyperinsulinemia and adiposity in the offspring. The objective of this study was to investigate the effects of uterine artery ligation on the skeletal muscle expression of insulin receptor and key enzymes of LCFA metabolism.MethodsBilateral uterine artery ligation was performed on day 19 of gestation in Sprague-Dawley pregnant rats. Muscle of the posterior limb was dissected at birth and processed by real-time RT-PCR to analyze the expression of insulin receptor, ACCα, ACCβ (acetyl-CoA carboxylase alpha and beta subunits), ACS (acyl-CoA synthase), AMPK (AMP-activated protein kinase, alpha2 catalytic subunit), CPT1B (carnitine palmitoyltransferase-1 beta subunit), MCD (malonyl-CoA decarboxylase) in 14 sham and 8 IUGR pups.Muscle tissue was treated with lysis buffer and Western immunoblotting was performed to assay the protein content of insulin receptor and ACC.ResultsA significant down regulation of insulin receptor protein (p < 0.05) and reduced expression of ACS and ACCα mRNA (p < 0.05) were observed in skeletal muscle of IUGR newborns. Immunoblotting showed no significant change in ACCα content.ConclusionOur data suggest that uteroplacental insufficiency may affect skeletal muscle metabolism down regulating insulin receptor and reducing the expression of key enzymes involved in LCFA formation and oxidation.

IGF-I and IGFBP-3 assessment in the management of childhood onset growth hormone deficiency

The diagnosis of growth hormone (GH) deficiency (GHD) in childhood is not straightforward, being still based on a comprehensive clinical, anthropometric, endocrine and neuroradiological assessment. Due to their GH dependency and relative stability in circulation, IGF-I and IGFBP-3 serum concentrations were proposed as reliable indicators of daily GH secretion. However, the sensitivity of assays for both IGF-I and IGFBP-3 is inadequate to exclude the diagnosis of GHD merely on the basis of a normal value of the two parameters, although it seems likely that IGF-I values higher than -1 SD reflect a normal GH secretion. On the other hand, as the specificity of both measurements is over 90%, subnormal concentrations strongly support the diagnosis of GHD. Finally, combining the evaluation of growth velocity with IGF-I measurement, sensitivity and specificity reach a value > or =95%, implying that two subnormal values strongly suggest and two normal values strongly oppose the diagnosis of GHD.

Changes in the Expression of Hypothalamic Lipid Sensing Genes in Rat Model of Intrauterine Growth Retardation (IUGR).

Intrauterine growth retardation (IUGR) has been linked to the development of type 2 diabetes in later life. The mechanisms underlying this phenomenon are unknown. Recent data suggest that some of the molecular defects underlying type 2 diabetes reside in the CNS. The enzyme carnitine palmitoyltransferase-1 (CPT1) regulates long-chain fatty acid (LCFA) entry into mitochondria, where LCFA undergo β-oxidation. Hypothalamic inhibition of CPT1 decreases food intake and suppresses endogenous glucose production. Our aim was to investigate the effects of uterine artery ligation, a procedure that mimics uteroplacental insufficiency, on the CNS expression of CPT1 and other key enzymes of LCFA metabolism. Bilateral uterine artery ligation was performed on d 19 of gestation in the pregnant rat; sham-operated pregnant rats served as controls. Hypothalamus, cerebellum, hippocampus, and cortex were dissected and analyzed at birth by real-time PCR. Nonesterified fatty acid (NEFA) serum levels were significantly higher in IUGR pups (p < 0.0001). In IUGR rats, the hypothalamic expression of CPT1 isoform C (p = 0.005) and acetyl-CoA carboxylase (ACC) isoforms alpha (p < 0.05) and beta (p = 0.005) were significantly decreased. The data presented here support the hypothesis that an abnormal intrauterine milieu can induce changes in hypothalamic lipid sensing.