Low serum adiponectin levels in subjects born small for gestational age: impact on insulin sensitivity.

OBJECTIVE: Increasing evidence point to the role of the adipose tissue on the insulin resistance associated with reduced fetal growth. Since adiponectin, exclusively produced by the adipose tissue, exerts an important insulin-sensitizing activity, it appears critical to investigate the effect of being born small for gestational age (SGA) on adiponectin production in adulthood and its relationship with insulin sensitivity. SUBJECTS AND METHODS: Serum adiponectin concentrations were measured in 486 young adults born SGA, precisely selected on birth data, who were compared to 573 age-matched subjects born appropriate for gestational age (AGA). The relationship between serum adiponectin levels and insulin-resistance indices measured under OGTT were tested and compared between the two groups. RESULTS: The SGA group demonstrated significantly reduced serum adiponectin levels than controls (12.6 +/- 6.9 vs 13.2 +/- 6.4 microg/ml, P = 0.02) and the difference remained significant when the key regulatory factors were taken into account (P = 0.008). In the AGA group, fasting I/G taken as an insulin-resistance index negatively correlated with serum adiponectin concentrations (P = 0.02), while the relationship followed a U-shape with increased fasting I/G ratio despite high concentrations of serum adiponectin in the SGA group (P = 0.12). CONCLUSION: Subjects born SGA demonstrated significantly reduced serum adiponectin levels, which were not related to insulin-resistance indices in comparison to what observed in age-matched subjects born AGA. Although this defect in adiponectin production and in its insulin-sensitizing action remains to be elucidated at the molecular level, it strengthens the critical contribution of the adipose tissue in the metabolic complications associated with reduced fetal growth.

Smallness for gestational age is associated with persistent change in insulin-like growth factor I (IGF-I) and the ratio of IGF-I/IGF-binding protein-3 in adulthood.

CONTEXT: Implication of the IGF-IGF-binding protein (IGFBP) axis in the development of metabolic and cardiovascular diseases has been well documented. It has also been shown that an adverse intrauterine environment alters the IGF-IGFBP axis during childhood. OBJECTIVE: The objective of this study was to investigate whether these alterations persist into adulthood. DESIGN AND METHODS: Fasting serum IGF-I, IGFBP-3, and insulin concentrations were measured, and their determinants were analyzed in a cohort of young adult subjects (22 yr of age) born either small (SGA; n = 461) or appropriate (AGA; n = 568) for gestational age. RESULTS: In adulthood, subjects born SGA had significantly lower mean serum IGF-I (320 +/- 137 vs. 348 +/- 143 microg/liter; P = 0.0015), IGFBP-3 (4700 +/- 700 vs. 4800 +/- 800 microg/liter; P = 0.04), and IGF-I/IGFBP-3 ratio (0.067 +/- 0.026 vs. 0.072 +/- 0.025; P = 0.01) than those born AGA. The fasting IGF-I concentration and the IGF-I/IGFBP-3 ratio were significantly inversely associated with age, body mass index, smoking, and oral contraception and were positively related to birth weight and fasting insulin levels. The IGFBP-3 concentration was significantly negatively correlated to age and smoking and was positively related to insulin concentration and oral contraception. After adjustment for age, height, body mass index, gender, smoking, and oral contraception, the mean IGF-I concentration and the mean IGF-I/IGFBP-3 ratio remained significantly lower in the SGA compared with the AGA group (P = 0.003 and P = 0.01, respectively). CONCLUSIONS: Serum IGF-I concentrations and the IGF-I/IGFBP-3 ratio are lower in adult subjects born SGA. Although the origin of this persisting alteration of the IGF-IGFBP axis in adulthood needs to be elucidated, its potential contribution to the long-term metabolic and cardiovascular complications associated with fetal growth restriction is important to consider in the future.

In situ lipolytic regulation in subjects born small for gestational age.

OBJECTIVE: Subjects born small for gestational age (SGA) who are prone to develop insulin resistance in adulthood display an abnormal development pattern of the adipose tissue during fetal and postnatal life. Since the lipolytic activity of the adipose tissue is critical in the development of insulin resistance, the purpose of this study was to investigate whether SGA itself might affect lipolysis regulation. STUDY DESIGN: We studied the effect of catecholamines, by local injection of isoproterenol, and the effect of insulin, using two-step infusion at 8 and 40 mU/m2/min, on the in situ lipolysis of the subcutaneous abdominal adipose tissue of 23 subjects born SGA and 23 born appropriate for gestational age (AGA), using the microdialysis technique. RESULTS: Under isoproterenol infusion, the increase in dialysate glycerol concentration was significantly 1.5-fold higher in the SGA than in the AGA group (P=0.02) and induced a 20% increase in the plasma FFA concentration (P=0.04), whereas no significant increase was observed in the AGA group. The antilipolytic action of insulin on dialysate glycerol concentration was similar in both groups throughout the insulin infusion. CONCLUSION: Subjects born SGA demonstrated a hyperlipolytic reactivity to catecholamines, which might be regarded as an additional deleterious component of the insulin resistance associated with SGA. In contrast, being born SGA does not directly affect the antilipolytic action of insulin, showing that it does not play a major role in causing the long-term metabolic complications associated with reduced fetal growth.

Dynamic change in adiposity from fetal to postnatal life is involved in the metabolic syndrome associated with reduced fetal growth.

AIMS/HYPOTHESIS: The aims of this study were to establish the role of insulin resistance in the metabolic syndrome associated with restricted fetal growth and to characterise the fetal and postnatal determinants responsible for the long-term metabolic outcome. METHODS: The study population consisted of adults selected on birth data from a maternity registry and born either small for gestational age (SGA) (n=734, birthweight

Adult height distribution in subjects born small for gestational age.

The aim of the study was to investigate the post-natal growth of subjects born small for gestational age (SGA) by describing adult height distribution and by testing the effects of parental, neonatal and pregnancy-related parameters on the risk for adult short stature. The study population was made of adults selected on birth data from a maternity registry and born either small (SGA, n = 734, birth weight < 10th percentile) or appropriate for gestational age (AGA, n = 886, 25th < birth weight < 75th percentile) in whom anthropometric parameters were measured at 22 years of age. The SGA group demonstrated significantly reduced body size in comparison to the AGA group with a mean loss of 0.7 standard deviation (SD) in adult height. The frequency of adult short stature (< -2 SD) was 10.3% in the SGA group vs. 2.4% in the AGA group (p = 0.0001), adult height < -2.5 SD was observed in only 3.7% of the SGA group. Maternal (OR = 0.31 (0.16-0.62), p = 0.0001) and paternal (OR = 0.45 (0.31-0.67), p = 0.0001) heights and subjects birth length (OR = 0.78 (0.62-0.99), p = 0.04) significantly influenced the risk of adult short stature. In summary, post-natal growth defect remains moderate in the majority of subjects born SGA and < 4% only will end up with severe short stature requiring GH therapy according to most current recommendations. The role of parental height and birth length suggests that adult short stature in SGA subjects results at least in some cases from a familial and likely genetic growth disorder with antenatal onset.

Severe insulin resistance contrasting with mild anthropometric changes in the adipose tissue of HIV-infected children with lipohypertrophy.

BACKGROUND: The HIV-associated lipodystrophic syndrome (HIV-LDS) combines redistribution of fat mass with insulin resistance and hyperlipidemia. We have previously reported that HIV-LDS prevails in children in a comparable pattern as in adults. The metabolic activity itself of the lipodystrophic adipose tissue in HIV infection has been poorly studied. AIM AND METHODS: To assess in situ the insulin sensitivity of the lipohypertrophic subcutaneous abdominal adipose tissue using the microdialysis technique in HIV-infected children. Insulin sensitivity, assessed by the inhibition of glycerol release, was measured in the abdominal subcutaneous adipose tissue during a standard oral glucose tolerance test (OGTT) in six HIV-infected children under multi-therapy with abdominal lipohypertrophy (supra-iliac skinfold thickness >97th percentile) (HIV/LH+), in six obese children (obese group) and in eight HIV-infected children without lipodystrophy (HIV/LH-). RESULTS: Glucose tolerance was normal in all subjects. Mean insulin areas under the curve (IAUC) were significantly higher in the obese and HIV/LH+ groups than in HIV/LH- (8769+/-5429, 8161+/-4552 and 3618+/-2222 mU min l(-1), respectively; P=0.04 for the three groups comparison by the Kruskal-Wallis test), reflecting insulin resistance in the two former groups independent of a significant difference in percentage fat mass (37.2+/-4.7, 22.8+/-10.9 and 20.7+/-7.1%, respectively; P= 0.006). The crude inhibition of glycerol release, expressed as the relative change in dialysate glycerol concentration between baseline and 120 min, was not statistically different between the three groups (14% in obese, -38+/-14% in HIV/LH+ and -51+/-17% in HIV/LH- groups; P=0.3). The inhibition of glycerol release with respect to the circulating insulin level (expressed by IAUC) was similar in HIV/LH+ and obese groups (-6+/-5 x 10(-3) and -7+/-5 x 10(-3) l mU(-1) min(-1), respectively, P=0.4 for two-groups comparison by the U-Mann-Whitney test) and four-fold less than in the HIV/LH- group (-24+/-25 x 10(-3) l mU(-1) min(-1); P=0.02). CONCLUSION: These data argue in favor of insulin resistance in the adipose tissue of lipohypertrophies associated with HIV infection.

Impaired regulation of glucose transporter 4 gene expression in insulin resistance associated with in utero undernutrition.

The aim of this study was to investigate whether insulin resistance-associated in utero undernutrition was related to changes in insulin action on gene expression of molecules involved in the insulin signaling pathway and peripheral glucose metabolism in muscle and adipose tissue. Thirteen insulin-resistant subjects born with intrauterine growth retardation (IUGR) were matched for age, gender, and body mass index to 13 controls. Gene expression of insulin receptor, insulin receptor substrate-1, p85alpha phosphatidylinositol 3-kinase, glucose transporter-4 (GLUT4), hexokinase II, and glycogen synthase was studied in skeletal muscle at baseline and after a 3-h euglycemic insulin stimulation. Target messenger ribonucleic acid (mRNA) levels were quantified using the RT-competitive PCR method. Insulin-stimulated glucose uptake was significantly lower in IUGR-born subjects than in controls (36.9 +/- 12, 7 vs. 53.9 +/- 12.7 micromol/kg.min; P = 0.007), affecting both the glucose oxidation rate and the nonoxidative glucose disposal rate. At baseline, the expression of the six genes in muscle did not significantly differ between the two groups. The insulin-induced changes over baseline were comparable in both groups for all mRNAs, except GLUT4. In contrast to what observed in the control group (mean increment, 49 +/- 23%; P = 0.0009), GLUT4 expression was not stimulated by insulin in the IUGR group (8 +/- 8%; P = 0.42). Moreover, the magnitude of the defect in GLUT4 mRNA regulation by insulin was correlated to the degree of insulin resistance (r = 0.73; P = 0.01). A similar lack of significant GLUT4 mRNA stimulation by insulin was observed in the adipose tissue of IUGR-born subjects. In conclusion, insulin resistance in IUGR-born subjects is associated with an impaired regulation of GLUT4 expression by insulin in muscle and adipose tissue. Our data provide additional information about the mechanism of insulin resistance associated with in utero undernutrition and strengthen the role of glucose transport in the control of insulin sensitivity.

Relatively low serum leptin levels in adults born with intra-uterine growth retardation.

BACKGROUND: In-utero under-nutrition dramatically alters the development of adipose tissue, during the fetal and the neonatal period. THE AIM OF THE STUDY: To investigate whether adults born with intra-uterine growth retardation (IUGR) show evidence of impaired adipose tissue development and leptin regulation. DESIGN: Serum leptin concentrations were measured in 26 healthy adults born with IUGR and 25 controls aged 24 y who have been studied previously, 3 y ago. RESULTS: The IUGR group demonstrated a significant increase of body mass index (BMI) in comparison to controls between 21 and 24 y of age (4.8+/-7.7%, P=0.004 vs 0.8+/-6.7%, P=0.70). Percentage of total body fat mass was significantly higher in IUGR-born subjects than in controls (27.2+/-7.6 vs 22.0+/-7.3%, P=0.02). Fasting insulin was significantly higher in the IUGR group (7.5+/-3.8 vs 5.3+/-2.3 miccroU/ml, P=0.03). Surprisingly, crude serum leptin concentrations did not significantly differ between the two groups. Moreover, adjusted means of serum leptin levels were significantly lower in IUGR-born subjects than in controls when corrected for body fat mass, gender and fasting insulin (11.3 vs 13.8 ng/ml, P=0.02). SUMMARY: Adults born with IUGR developed an excess of adipose tissue associated with relatively low serum leptin levels suggestive of an altered adipocyte function. Considering the close relationship between adipose tissue and insulin-sensitivity, these observations point to the potential implication of abnormal adipose tissue development in the long-term metabolic consequences associated with in-utero undernutrition.

Syndrome X: a consequence of intra-uterine malnutrition?

The long-term consequences of intra-uterine growth retardation (IUGR) on postnatal growth and development are well known. More recently, several epidemiological and clinical studies in adults have provided evidence that low birth weight is an independent risk factor for the syndrome of insulin resistance in mid to late adulthood. In the present study, we demonstrated that individuals born small for gestational age showed isolated insulin resistance in early adulthood with no impairment of serum lipid concentrations and blood pressure at this age. Angiotensin-I converting enzyme gene polymorphism has also been shown to modulate the effect on insulin resistance of being small for gestational age. Fetal malnutrition may be the critical factor to explain the relationship between IUGR and insulin resistance which might be modulated by genetic factors.

Clinical and metabolic presentation of the lipodystrophic syndrome in HIV-infected children.

OBJECTIVE: To investigate body fat distribution and glucose and lipid metabolism in HIV-infected children with the aim of describing the lipodystrophic syndrome in children. DESIGN: Cross-sectional study including 39 HIV-infected children aged 3-18 years. MAIN OUTCOME MEASURES: Clinical lipodystrophy was defined as peripheral fat wasting (facial and/or buttock and/or limb atrophy with arm skinfold thickness lower than the third percentile of the reference values for sex and age) and/or truncal adiposity (breast enlargement and/or buffalo neck and/or relative abdominal obesity with trunk : arm skinfold ratio > 2 standard deviations). Fasting serum lipid concentrations were measured and an oral glucose tolerance test was performed. RESULTS: Of 39 HIV-infected children, lipodystrophy was observed in 13 children (33.3%): eight with truncal lipohypertrophy, three with peripheral lipoatrophy and two with combined lipodystrophy. Combined lipodystrophies were observed only in adolescents with a more severe presentation than in prepubertal children. Lipodystrophic children had higher fasting insulinaemia (7.0+/-8.5 versus 3.0+/-2.3 microU/ml; P = 0.07), suggesting a certain degree of insulin-resistance. Hypercholesterolaemia (23% versus 15%; P = 0.59 ) and hypertriglyceridaemia (15% versus 11%; P = 0.76) were observed with the same proportion in the lipodystrophic as in the non-lipodystrophic groups; 23% of the non-lipodystrophic children had dyslipidaemia. CONCLUSION: The lipodystrophic syndrome prevails in HIV-infected children in the three clinical forms initially described in adults but appears less severe before the initiation of puberty. Insulin-resistance occurs in lipodystrophic children only, whereas dyslipidaemia exists in non-lipodystrophic children as well, suggesting that dyslipidaemia could reflect subclinical alteration of the adipose tissue.

Insulin resistance early in adulthood in subjects born with intrauterine growth retardation.

In a case-control study that investigated the effect of intrauterine growth retardation (IUGR) on glucose homeostasis, 20-yr-old adults born with IUGR were shown to be hyperinsulinemic in an oral glucose tolerance test, suggestive of insulin resistance. The aim of this study was to ascertain the decreased insulin sensitivity in young IUGR-born adults compared to that in controls. We studied 26 IUGR-born subjects and 25 controls, aged 25 yr. Insulin sensitivity was assessed by peripheral glucose uptake and monitoring free fatty acid (FFA) concentrations under euglycemic hyperinsulinemic clamp. The percent body fat was significantly higher in the IUGR group (27.2 +/- 7.6% vs. 22.0 +/- 7.3%; P = 0.02), contrasting with comparable body mass index in both groups. Insulin-stimulated glucose uptake was significantly lower in IUGR-born subjects than in controls (6.7 +/- 2.9 vs. 8.0 +/- 1.9 mg/kg fat-free mass x min; P = 0.05), and the difference remained significant after adjustment for body mass index, total body fat, or waist to hip ratio. In IUGR-born subjects, insulin-stimulated FFA suppression correlated significantly with peripheral glucose uptake (r2 = 0.23; P = 0.02). First phase insulin release in the iv glucose tolerance test, adjusted for insulin sensitivity, did not significantly differ between IUGR and control groups (442 +/- 284 vs. 391 +/- 209 pmol/L; P = 0.86). In conclusion, IUGR subjects have decreased insulin-stimulated glucose uptake as early as 25 yr of age without major impairment of insulin secretion. Low glucose uptake is associated with a lesser degree of FFA suppression in adipose tissue, which suggests a role of adipose tissue at an early stage of insulin resistance in these subjects.

No evidence for a major beta-cell dysfunction in young adults born with intra-uterine growth retardation.

The association between low birth weight and the later development of type 2 diabetes is well established. It has been hypothesized that in utero undernutrition may affect pancreatic beta-cell development, leading to an impaired beta-cell function in adulthood. We have previously demonstrated that intrauterine growth retardation (IUGR) is associated with insulin-resistance early in adulthood. The aim of this study was to test whether IUGR would affect beta-cell function in young adults. Twelve 25-yr-old insulin-resistant subjects with IUGR were matched for age gender and body mass index (BMI) to 13 controls. All of them had normal glucose tolerance. Mean fasting plasma glucose did not significantly differ between the group with IUGR and the control group (97 +/- 7 vs. 98 +/- 4 mg/dL; p = 0.83). Blood glucose was maintained at 124.8 +/- 6.5 vs. 126.2 +/- 7.5 mg/dL above the basal glycemia in the IUGR and control groups (p = 0.64) throughout the hyperglycemic clamp. Serum insulin concentrations did not significantly differ between the group with IUGR and the control group either during the first (0-10 min) phase (311 +/- 252 vs. 248 +/- 184 pmol/L, p = 0.85) or during the second (80-100 min) phase (575 +/- 284 vs. 559 +/- 413 pmol/L, p = 0.72). C-peptide concentrations were similar in both groups during the two phases (2.35 +/- 1.44 vs. 2.59 +/- 1.10 nmol/L, p = 0.39 and 4.86 +/- 1.36 vs. 4.96 +/- 1.41 nmol/L, p = 0.91). In conclusion, our data do not argue in favor of an impairment of beta-cell function at 25 yr of age as a consequence of in utero undernutrition, but rather suggest that insulin resistance might be the primary defect responsible for the development of metabolic disorders associated with IUGR in adulthood.

Intrauterine growth retardation predisposes to insulin resistance but not to hyperandrogenism in young women.

It was recently suggested that precocious pubarche associated with subsequent functional ovarian hyperandrogenism and hyperinsulinemia could have a common origin in reduced fetal growth. We previously reported that young women born with intrauterine growth retardation (IUGR: birth weight less than the third percentile) were hyperinsulinemic and less insulin sensitive than women born with normal birth weight. The aim of the present study was to investigate whether these IUGR-born women demonstrated hyperandrogenism compared with controls. Our study population was composed of 130 IUGR-born women and 150 controls, of similar age (20.6 +/- 3.2 vs. 20.4 +/- 2.0 yr). Hormonal contraception in terms of frequency and medication, including antiandrogenic therapy, was identical in the 2 groups. After adjustment for hormonal contraception, being born with IUGR had no independent effect on serum androgen concentrations. In women who were not receiving hormonal contraception, no statistical differences were found between IUGR-born women (n = 67) and controls (n = 64) for delta4-androstenedione (2.26 +/- 0.68 vs. 2.24 +/- 0.55 ng/mL; P = 0.76), dehydroepiandrosterone sulfate (2294 +/- 1117 vs. 2489 +/- 1235 ng/mL; P = 0.24), testosterone (0.82 +/- 0.85 vs. 0.70 +/- 0.26 ng/mL; P = 0.80), or serum sex hormone-binding protein concentrations (45.5 +/- 28.2 vs. 53.1 +/- 30.3 nmol/L; P = 0.27). In both IUGR and control groups, sex hormone-binding protein correlated negatively with fasting insulin (r = -0.23; P = 0.03 and r = -0.26; P = 0.05), but serum androgen levels did not correlate with insulin. In summary, hyperinsulinemia observed in young women born with IUGR is not associated with hyperandrogenism. Consequently, our results do not support the hypothesis of a common in utero programming of hyperandrogenism and hyperinsulinemia.

High serum leptin concentrations during catch-up growth of children born with intrauterine growth retardation.

The aim of the study was to investigate how leptin could be involved in catch-up growth of children born with intrauterine growth retardation (IUGR). The study population was made up of 70 newborns with IUGR longitudinally studied during the first 2 yr of life and 35 newborns and 32, 66, and 61 children with normal birth weight aged 3 days, 12 months, and 24 months, respectively. Postnatal patterns of body mass index (BMI) were similar in the 2 groups, but BMI remained significantly lower in IUGR over the study period. In contrast, children born with IUGR aged 1 yr had significantly higher serum leptin levels than normal children (P < 0.0001) independently of BMI. The correlation observed between BMI and serum leptin at birth in both groups and in the control group thereafter disappeared in children born with IUGR. Similarly, sexual dimorphism observed in normal children over the study period was not observed in the IUGR group during the first 2 yr of life. In summary, serum leptin is effective and regulated during the first years of life as it is in older children. Children born with IUGR demonstrate high serum leptin values during the first year of life, with a loss of the regulatory effect of BMI and gender. We suggest that these children develop an adaptative leptin resistance beneficial for their catch-up growth. An alternative hypothesis is that these observations could reflect an adipocyte dysfunction, a consequence of the special time course of adipose tissue development in children born with IUGR.

Extremely low values of serum leptin in children with congenital generalized lipoatrophy.

Congenital generalized lipoatrophy (CGL) is a syndrome with multiple clinical manifestations and complete atrophy of adipose tissue. The exact mechanism of this disease remains unknown. One hypothesis presupposes an abnormal development of adipocytes. Leptin, the adipocyte-specific product of the ob gene, acts as a regulatory factor of body weight. In children, as in adults, leptin levels are correlated with body mass index (BMI) and body fat mass. Some authors have demonstrated that adults with congenital or acquired generalized lipoatrophy have decreased leptin concentrations. In order to study serum leptin profile during childhood in this disease, we measured serum leptin concentrations in six children aged 5.5-11 years suffering from CGL, and investigated the relationship between metabolic parameters and the variations in leptin levels. Serum leptin concentrations (1.19+/-0.32 ng/ml (+/- S.D.)) were extremely low compared with those observed in normal children. No significant correlation was found with BMI, which is known to be one of the major determinants of serum leptin. Serum leptin values were significantly correlated with fasting insulin levels (r=0.83, P=0.024). In conclusion, extremely low leptin values measured in children with CGL could be regarded as one among other diagnostic parameters. However, the detectable levels observed in all of these children support the evidence that a small amount of body fat is likely to be present in these patients, despite complete subcutaneous lipoatrophy. Our data suggest that this small amount of adipose tissue could be metabolically active and, at least in part, sensitive to insulin. Further investigations are required to uncover the pathophysiological mechanisms of this syndrome, known to be commonly associated with insulin resistance.

Exploration of glucose homeostasis during fasting in growth hormone-deficient children.

In order to define more precisely the risk of hypoglycaemia in GH-deficient children and to clarify the role of growth hormone (GH) in glucose homeostasis, a 24-h fast was monitored in 10 GH-deficient children aged 1.1-6.5 y. Asymptomatic hypoglycaemia (blood glucose < or = 2.6 mmol/l) occurred in 9/10 children, 2 of whom prematurely interrupted the test. Blood glucose profile was not reproducible between children and had no correlation with age (p = 0.48). Gluconeogenesis was considered as non-altered as read from the normal plasma lactate and pyruvate concentrations throughout the test. Plasma ketone body concentrations increased during the test, but were lower than expected with respect to the decrease of blood glucose. This suggests insufficient ketogenesis which could exacerbate hypoglycaemia in GH-deficient children if brain glucose utilization were not alleviated by ketone body oxidization, as is normally the case. The positive glucose response after glucagon stimulation in 6/10 patients indicated normal hepatic glycogen content. However, these responses were unexpected following the prolonged fast and its concomitant hypoglycaemia, and would therefore tend to suggest a defect in glycogenolysis. These results confirm the tendency to hypoglycaemia, even after infancy, in GH-deficient children. These hypoglycaemias may occur by different types of malfunctioning, such as insufficient ketogenesis or a defect in glycogenolysis. These hypotheses require confirmation by a more systematic study of the metabolic and hormonal changes that occur during fasting in both GH-deficient and normal children.

Ontogeny of leptin in human fetuses and newborns: effect of intrauterine growth retardation on serum leptin concentrations.

The aim of this study was to investigate the ontogeny of serum leptin concentrations during the second half of gestation and at birth in small for gestational age and normal fetuses and newborns. Serum leptin concentrations were measured in arterial cord blood of fetuses (n = 79) and newborns (n = 132), with or without intrauterine growth retardation, at 18-42 weeks gestation. Serum leptin was detectable in fetal cord blood in all subjects as early as 18 weeks gestation. Leptin levels dramatically increased after 34 weeks gestation. In newborns, serum leptin concentrations were positively correlated with body weight (P < 0.001) and body mass index (P < 0.001). Newborns with intrauterine growth retardation had significantly lower serum leptin values (P < 0.001) than those with normal growth, and leptin levels were only positively correlated with body mass index (P < 0.001). These results suggest that the development of adipose tissue and the accumulation of fat mass are the major determinants of fetal and neonatal serum leptin levels. In addition, a gender difference, with higher leptin concentrations in female fetuses, was observed during the last weeks of gestation and was confirmed at birth regardless of growth status, suggesting that a sexual dimorphism already exists in utero.