Cord blood leptin concentrations in relation to intrauterine growth

Influence of Pre-Pregnancy Obesity on Carbohydrate and Lipid Metabolism with Selected Adipokines in the Maternal and Fetal Compartment

A higher body mass index (BMI) before pregnancy is associated with an increased risk of maternal and perinatal complications. This study aimed to analyze selected parameters of carbohydrate and lipid metabolism, including adipokines, in obese pre-pregnant women, and their influence on the birth weight of newborns.

MATERIALS AND METHODS

The study group (O) consisted of 34 pregnant women with higher BMI (obese) before pregnancy. The control group (C) was 27 pregnant women with target BMI and physiological pregnancy. The BMI index: body weight [kg]/(height [m]² was assessed on the first obstetrical visit. The research material was the serum of pregnant women collected in the third trimester of pregnancy and umbilical cord blood collected immediately after delivery. Selected parameters of carbohydrate and lipid metabolism and adipokines were determined.

RESULTS

There were no statistically significant differences between the study group and the control group concerning the concentrations of insulin, glucose, VLDL, adiponectin, TNF-α, HOMA-IR, as well as LDH and cholesterol in maternal blood serum and umbilical cord blood serum. Total cholesterol and HDL in both maternal blood serum and umbilical cord blood were statistically significantly lower than those in the control group. The concentration of triglycerides (TG) and resistin in the blood serum of obese mothers were higher than those in the control group (p < 0.05). However, no statistically significant differences were found between the two groups regarding the concentrations of TG and resistin in the umbilical cord blood. The concentration of LDL cholesterol in the umbilical blood serum in the obese group was statistically significantly lower than that in the control group. The concentration of leptin in maternal blood serum and umbilical cord blood serum in the study group was statistically significantly higher than that in the control group.

CONCLUSIONS

Pregestational obesity does not substantially affect the basic parameters of carbohydrate metabolism in pregnant women, but it disturbs the lipid profile, which is manifested by a significant increase in triglycerides and a decrease in the level of HDL cholesterol in the serum. Preexisting obesity increases the concentration of leptin and resistin in the serum of pregnant women, which may be caused by the increased volume of adipose tissue. The concentrations of leptin and resistin in the blood of pregnant women correlate positively, and the concentrations of adiponectin and TNF-α negatively correlate with pre-pregnancy BMI values. There is a positive correlation between the concentration of leptin in the serum of umbilical cord blood and the birth weight of the newborn, which suggests that this parameter contributes to the pathomechanism of macrosomia.

Maternal obesity and ovarian failure: is leptin the culprit?

At the time of its discovery and characterization in 1994, leptin was mostly considered a metabolic hormone able to regulate body weight and energy homeostasis. However, in recent years, a great deal of literature has revealed leptin's pleiotropic nature, through its involvement in numerous physiological contexts including the regulation of the female reproductive tract and ovarian function. Obesity has been largely associated with infertility, and leptin signalling is known to be dysregulated in the ovaries of obese females. Hence, the disruption of ovarian leptin signalling was shown to contribute to the pathophysiology of ovarian failure in obese females, affecting transcriptional programmes in the gamete and somatic cells. This review attempts to uncover the underlying mechanisms contributing to female infertility associated with obesity, as well as to shed light on the role of leptin in the metabolic dysregulation within the follicle, the effects on the oocyte epigenome, and the potential long-term consequence to embryo programming.

Immune dysfunction in developmental programming of type 2 diabetes mellitus

Intrauterine growth restriction (IUGR) is a common complication of pregnancy and increases the risk of the offspring developing type 2 diabetes mellitus (T2DM) later in life. Alterations in the immune system are implicated in the pathogenesis of IUGR-induced T2DM. The development of the fetal immune system is a delicate balance as it must remain tolerant of maternal antigens whilst also preparing for the post-birth environment. In addition, the fetal immune system is susceptible to an altered intrauterine milieu caused by maternal and placental inflammatory mediators or secondary to nutrient and oxygen deprivation. Pancreatic-resident macrophages populate the pancreas during fetal development, and their phenotype is dynamic through the neonatal period. Furthermore, macrophages in the islets are instrumental in islet development as they influence β-cell proliferation and islet neogenesis. In addition, cytokines, derived from β-cells and macrophages, are important to islet homeostasis in the fetus and adult and, when perturbed, can cause islet dysfunction. Several activated immune pathways have been identified in the islets of people who experienced IUGR, with alternations in the levels of IL-1β and IL-4 as well as changes in TGFβ signalling. Leptin levels are also altered. Immunomodulation has shown therapeutic benefit in T2DM and might be particularly useful in IUGR-induced T2DM.

Birth anthropometry and cord blood leptin in Korean appropriate-for-gestational-age infants born at ≥ 28 weeks' gestation: a cross sectional study

Background

We investigated whether leptin during the third trimester was associated with fetal growth compared to IGF-1.

Methods

One hundred five appropriate-for-gestational-age (AGA) infants born at ≥28 weeks’ gestation were enrolled. Cord blood leptin and insulin like growth factor 1 (IGF-1) were collected simultaneously during delivery. Enrolled infants were stratified into three groups according to GA as follows: 28 to < 34 weeks’ gestation, very preterm (VP); 34 to < 37 weeks’ gestation, late preterm (LP); and 37 to < 41 weeks’ gestation, term. Birth weight (BW), birth length (BL), head circumference (HC), and body mass index (BMI) were measured. Leptin and IGF-1 were logarithmically transformed to normalize their distributions in multivariable regression analysis.

Results

Sixty-eight infants out of 105 infants were preterm (32.5 ± 2.5 weeks), and 37 infants were term (37.8 ± 1.2 weeks). BW, BL, HC, and BMI were higher with increasing gestational age among the three gestational age-specific groups. With regard to hormones, leptin and IGF-1 were higher with increasing gestational age. Log cord serum leptin was independently associated with BW and BL in multivariable linear regression analysis, after adjustment for confounding factors including gestational age, delivery mode, multiple pregnancy, pregnancy induced hypertension, gestational diabetes mellitus, infant’s BMI, and log cord blood IGF-1 levels.

Conclusions

During the third trimester, cord serum leptin was independently associated with fetal growth.

Preconception leptin levels and pregnancy outcomes: A prospective cohort study

OBJECTIVE

Obesity has become a major, worldwide public health issue and is associated with a greater risk of adverse pregnancy outcomes. Leptin, a hormone produced by adipocytes, is elevated in individuals with obesity and may mediate the association between obesity and pregnancy outcomes. Though leptin levels during pregnancy have been associated with pregnancy outcomes, less is understood regarding preconception levels. Therefore, the objective of this study was to evaluate associations between preconception leptin levels and adverse pregnancy outcomes.

METHODS

This was a prospective cohort study nested within a large randomized controlled trial conducted at four medical centres in the United States. A total of 1078 women completed the parent study; this analysis involved women who became pregnant during that study (n = 776). Patients were healthy women, ages 18 to 40, attempting to conceive, with 1 to 2 prior pregnancy losses. Participants were followed for less than or equal to 6 cycles while trying to conceive and throughout pregnancy if they conceived. Preconception leptin concentrations were measured in serum collected at baseline then categorized by tertiles (using the lowest as reference group). Weighted log-binomial regression estimated risk ratios (RR) and 95% confidence intervals (CIs) for pregnancy loss, preterm delivery (PTD), gestational diabetes (GDM), and hypertensive disorders in pregnancy, adjusting for age, waist-to-hip ratio (WHR), and body mass index (BMI).

RESULTS

The mean (SD) BMI in this cohort was 25.4 ± 6.0. GDM (RR 18.37; 95% CI, 2.39-141.55) and hypertensive disorders of pregnancy (RR 2.35; 95% CI, 1.20-4.61) risks were higher among women in the high tertile after adjusting for age and WHR. The associated risk persisted when adjusting for BMI for GDM but was attenuated for hypertensive disorders in pregnancy. Leptin levels were not associated with risk of pregnancy loss or PTD.

CONCLUSIONS

Women with higher baseline preconception leptin levels had a higher likelihood of experiencing some adverse pregnancy outcomes including GDM and hypertensive disorders of pregnancy. These findings warrant further evaluation, especially in light of the association between leptin and obesity.

Disparity in fetal growth between twin and singleton gestation: the role of adipokines

OBJECTIVE

Twin pregnancies are characterized by unique pattern of attenuated fetal weight gain during late gestation compared with singleton gestation. The mechanism(s) responsible for regulating twin growth has not yet elucidated. Leptin and adiponectin are two adipocytokines implicated in metabolism and energy balance of fetuses, newborns and adults. Moreover, these hormones have been suggested to play a role in fetal growth. The objective of the study was to determine cord blood adiponectin and leptin in twins and singletons, with and without growth impairment.

STUDY DESIGN

This was a case-control study. It included two groups of newborns, matched for gestational age and birth weight percentile: singleton (n=60 newborns) and twins (n=44 newborns). Adiponectin and leptin were determined in cord blood, and compared between the groups according to clinical and demographic characteristics. Non-parametric and parametric statistical methods were employed.

RESULTS

Median adiponectin and leptin concentrations were lower in twins vs singletons (P<0.001 for both comparisons). Among small for gestational age newborns (SGA), median concentration of adiponectin (P=0.04), but not leptin (P=0.1), was lower in twins compared to singletons. In pooled analysis (singleton plus twins), cord blood adiponectin and leptin were strongly correlated with gestational age (P<0.001 and P=0.005, respectively) and birth weight (P<0.001 and P<0.001, respectively). Regression analysis revealed that plurality (P=0.02) was significantly and independently associated with cord blood adiponectin concentrations, after adjustment for confounding variables. Similar regression in which leptin was the independent variable revealed that only birth weight (P=0.01) was significantly and independently associated with cord blood leptin concentrations.

CONCLUSIONS

Twin pregnancies are associated with lower cord blood concentrations of adiponectin and leptin compared with singleton gestations. However, only cord blood adiponectin, but not leptin, was lower in SGA neonates. Collectively, these data suggest that adiponectin may be implicated in the mechanism accounting for the growth disparity between twins and singletons.

Modeling the impact of growth and leptin deficits on the neuronal regulation of blood pressure

The risk of hypertension is increased by intrauterine growth restriction (IUGR) and preterm birth. In the search for modifiable etiologies for this life-threatening cardiovascular morbidity, a number of pathways have been investigated, including excessive glucocorticoid exposure, nutritional deficiency and aberration in sex hormone levels. As a neurotrophic hormone that is intimately involved in the cardiovascular regulation and whose levels are influenced by glucocorticoids, nutritional status and sex hormones, leptin has emerged as a putative etiologic and thus a therapeutic agent. As a product of maternal and late fetal adipocytes and the placenta, circulating leptin typically surges late in gestation and declines after delivery until the infant consumes sufficient leptin-containing breast milk or accrues sufficient leptin-secreting adipose tissue to reestablish the circulating levels. The leptin deficiency seen in IUGR infants is a multifactorial manifestation of placental insufficiency, exaggerated glucocorticoid exposure and fetal adipose deficit. The preterm infant suffers from the same cascade of events, including separation from the placenta, antenatal steroid exposure and persistently underdeveloped adipose depots. Preterm infants remain leptin deficient beyond term gestation, rendering them susceptible to neurodevelopmental impairment and subsequent cardiovascular dysregulation. This pathologic pathway is efficiently modeled by placing neonatal mice into atypically large litters, thereby recapitulating the perinatal growth restriction-adult hypertension phenotype. In this model, neonatal leptin supplementation restores the physiologic leptin surge, attenuates the leptin-triggered sympathetic activation in adulthood and prevents leptin- or stress-evoked hypertension. Further pathway interrogation and clinical translation are needed to fully test the therapeutic potential of perinatal leptin supplementation.

Neonatal adiposity increases with rising cord blood IGF-1 levels

OBJECTIVE

Infants with higher adiposity at birth may be at greater risk of developing obesity later in life. IGF-1 is important for intrauterine growth and may be a useful early life marker of adiposity, and thus later obesity risk. The aim of this study was to determine the relationship between cord blood IGF-1, neonatal anthropometrics and markers of neonatal adiposity.

DESIGN, PATIENTS AND MEASUREMENTS

A cross-sectional study design was utilized to study a multiethnic cohort of full-term neonates born to healthy mothers with normal glucose tolerance at a large university hospital. Neonatal cord blood was collected after birth and assayed for IGF-1, leptin and C-peptide. Neonatal body composition was measured between 24 and 72 h of life using the method of air displacement plethysmography.

RESULTS

Cord blood IGF-1 was positively and significantly associated with markers of neonatal adiposity in models adjusted for maternal age at delivery, race, maternal prepregnancy BMI, gestational age at delivery and neonatal sex: birthweight (r = 0·62, P < 0·001), leptin (r = 0·33, P = 0·018), fat mass (r = 0·52, P < 0·001) and percent body fat (r = 0·51, P < 0·001). Cord blood IGF-1 was not associated with cord blood C-peptide.

CONCLUSIONS

Cord blood IGF-1 is strongly associated with all measures of neonatal adiposity suggesting that IGF-1 may be an important contributor to in utero neonatal fat accumulation.

Leptin Matures Aspects of Lung Structure and Function in the Ovine Fetus

In human and ovine fetuses, glucocorticoids stimulate leptin secretion, although the extent to which leptin mediates the maturational effects of glucocorticoids on pulmonary development is unclear. This study investigated the effects of leptin administration on indices of lung structure and function before birth. Chronically catheterized singleton sheep fetuses were infused iv for 5 days with either saline or recombinant ovine leptin (0.5 mg/kg · d leptin (LEP), 0.5 LEP or 1.0 mg/kg · d, 1.0 LEP) from 125 days of gestation (term ∼145 d). Over the infusion, leptin administration increased plasma leptin, but not cortisol, concentrations. On the fifth day of infusion, 0.5 LEP reduced alveolar wall thickness and increased the volume at closing pressure of the pressure-volume deflation curve, interalveolar septal elastin content, secondary septal crest density, and the mRNA abundance of the leptin receptor (Ob-R) and surfactant protein (SP) B. Neither treatment influenced static lung compliance, maximal lung volume at 40 cmH2O, lung compartment volumes, alveolar surface area, pulmonary glycogen, protein content of the long form signaling Ob-Rb or phosphorylated signal transducers and activators of transcription-3, or mRNA levels of SP-A, C, or D, elastin, vascular endothelial growth factor-A, the vascular endothelial growth factor receptor 2, angiotensin-converting enzyme, peroxisome proliferator-activated receptor γ, or parathyroid hormone-related peptide. Leptin administration in the ovine fetus during late gestation promotes aspects of lung maturation, including up-regulation of SP-B.

Roles of leptin in reproduction, pregnancy and polycystic ovary syndrome: consensus knowledge and recent developments

As an essential function for perpetuation of species, reproduction, including puberty onset, is sensitive to the size of body energy stores and the metabolic state of the organism. Accordingly, impaired energy homeostasis, ranging from extreme leanness, such as in anorexia or cachexia, to morbid obesity has an impact on the timing of puberty and is often associated to fertility problems. The neuroendocrine basis for such phenomenon is the close connection between numerous metabolic hormones and nutritional cues with the various elements of the so-called hypothalamic-pituitary-gonadal (HPG) axis. Yet, despite previous fragmentary knowledge, it was only the discovery of the adipose-hormone, leptin, in 1994 what revolutionized our understanding on how metabolic and reproductive systems closely interplay and allowed the definition of the neurohormonal causes of perturbations of puberty and fertility in conditions of impaired body energy homeostasis. In this article, we aim to provide a synoptic view of the mechanisms whereby leptin engages in the regulation of different elements of the HPG axis, with special attention to its effects and mechanisms of action on the different elements of the reproductive brain and its proven direct effects in the gonads. In addition, we will summarize the state-of-the-art regarding the putative roles of leptin during gestation, including its potential function as placental hormone. Finally, comments will be made on the eventual leptin alterations in reproductive disorders, with special attention to the polycystic ovary syndrome (PCOS), a disease in which reproductive, metabolic and neuroendocrine alterations are commonly observed. All in all, we intend to provide an updated account of our knowledge on the physiological roles of leptin in the metabolic regulation of the reproductive axis and its eventual pathophysiological implications in prevalent reproductive disorders, such as PCOS.

Adiponectin levels are reduced while markers of systemic inflammation and aortic remodelling are increased in intrauterine growth restricted mother-child couple

AIM OF THE STUDY

To investigate the relationships between the adipocytokine levels, markers of inflammation, and vascular remodelling in pregnancies complicated by intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

This was a retrospective study. One hundred and forty pregnant patients were enrolled. Adiponectin, leptin, tumor necrosis factor α (TNFα), interleukin-6 (IL-6), and C reactive protein (CRP) were assessed in IUGR, small for gestational age (SGA), and appropriate for gestational age (AGA) mother-child couples at delivery. IUGR and SGA fetuses were defined as fetuses whose estimated fetal weight (EFW) was below 10th percentile for gestational age with and without umbilical artery (UA) Doppler abnormalities, respectively. Fetal aorta intima media thickness (aIMT) was evaluated by ultrasound in the same fetal groups. Data were analyzed by R (version 2.15.2).

RESULTS

There were 37 IUGR mother-child couples, 33 SGA, and 70 AGA. Leptin, TNFα, IL-6, and CRP serum levels were higher in IUGR pregnant patients (P < 0.05). Adiponectin levels were significantly reduced in IUGR fetuses compared to SGA and AGA, while leptin, TNFα, and IL-6 levels were higher in IUGR group (P ≤ 0.05). Fetal aIMT was significantly higher in IUGR (P < 0.05) and in this group there was a negative correlation between aIMT and adiponectin/leptin ratio (A/L ratio) (P < 0.05) and between adiponectin and IL-6 levels (P < 0.05).

CONCLUSIONS

In conclusion, compared to SGA and AGA, IUGR fetuses had reduced circulating levels of adiponectin and elevated measures of aIMT and several inflammatory markers. Moreover, adiponectin levels were negatively correlated with aIMT in IUGR fetuses suggesting a possible causal link between reduced adiponectin and vessel remodelling.

Differential placental gene expression in term pregnancies affected by fetal growth restriction and macrosomia

INTRODUCTION

Extremes of fetal growth are associated with increased perinatal mortality and morbidity and a higher prevalence of cardiovascular disease, obesity and diabetes in later life. We aimed to identify changes in placental gene expression in pregnancies with evidence of growth dysfunction and candidate genes that may be used to identify abnormal patterns of growth prior to delivery.

METHODS

Growth-restricted (n = 4), macrosomic (n = 6) and normal term (n = 5) placentas were selected from a banked series (n = 200) collected immediately after caesarean section. RNA was extracted prior to microarray analysis using Affymetrix HG-U219 arrays to determine variation in gene expression. Genes of interest were confirmed using qRT-PCR.

RESULTS

338 genes in the growth-restricted and 41 genes in the macrosomic group were identified to be significantly dysregulated (>2-fold change; p < 0.05). CPXM2 and CLDN1 were upregulated and TXNDC5 and LRP2 downregulated in fetal growth restriction. In macrosomia, PHLDB2 and CLDN1 were upregulated and LEP and GCH1 were downregulated.

DISCUSSION

Dysfunctional growth is associated with differential placental gene expression and affects genes with a whole spectrum of developmental and cellular functions. Better elucidation of these pathways may allow the development of biomarkers to identify growth abnormalities and effective prenatal intervention.

Adipokines, an adipose tissue and placental product with biological functions during pregnancy

Latter half of pregnancy is characterized by a "physiological diabetogenic state" since changes in insulin-sensitivity have been well documented. These changes ensure continuous supply of nutrients to the growing fetus. In the last years the role of adipocyte-derived signaling molecules, collectively known as adipokines has been object of different in vitro and in vivo studies. Of interest, adipokines and/or their receptors are expressed in the placental tissue which, therefore, can contribute to development of maternal insulin-resistance and, as a consequence, fetal growth. Leptin, adiponectin, and resistin represent the most well studied adipokines and, with the exception of adiponectin, their serum and placental levels increase as pregnancy progresses. High levels of adipokines have also been detected in umbilical plasma hence suggesting a possible role on fetal development and metabolism; however, it remains still unclear if such adipokines can directly stimulate fetal tissues development acting as growth factors. In addition to their well known metabolic effects, we also reported studies describing the role of adipokines in promoting proliferation and invasiveness of trophoblast cells and affecting local angiogenic processes. These observations strongly suggest that adipokines, by alternatively interfering with placental development, may affect pregnancy outcome and fetal growth. However, further studies are needed to better understand the local regulation of their expression. © 2012 International Union of Biochemistry and Molecular Biology, Inc.

Effects of exercise training on maternal hormonal changes in pregnancy

CONTEXT & OBJECTIVE

A recent paper by our group reported that regular aerobic exercise during pregnancy led to lower foetal IGF-I and IGF-II concentrations and a modest reduction in offspring birth weight when compared with the offspring of nontraining control participants. Maternal hormonal alterations in response to exercise training may be associated with the regulation of nutrient availability for foetal growth through placental regulation of maternal metabolism.

OBJECTIVE

To determine whether the reduction in offspring size was associated with changes in the maternal IGF axis [including placental growth hormone (PGH)], leptin and/or free fatty acids (FFA) in response to aerobic exercise training in the second half of pregnancy.

DESIGN AND SETTING

A randomized, controlled trial of exercise in pregnancy.

PATIENTS

Eighty-four healthy nulliparous women (mean±SD age 30±4 year, BMI 25·5±4 kg/m(2) ).

MEASUREMENTS

Serum samples were drawn at 19 and 35 weeks gestation to determine serum IGF-I, IGF-II, IGF-binding protein-1, IGF-binding protein-3, PGH, leptin and FFA.

RESULTS

Exercise training in pregnancy had no impact on the pregnancy-related changes in the maternal IGF axis. Women in the exercise group experienced a 29% increase in leptin in late gestation (P=0·026 vs control) and a trend towards lower FFA (P=0·07 vs control). Late pregnancy changes in maternal leptin were inversely related to offspring birth weight (r= -0·24, P<0·05) and BMI (r= -0·25, P<0·05).

CONCLUSIONS

An increase in leptin in exercising pregnant women may reflect subtle changes within the placenta in response to regular exercise and may contribute to the reduction in offspring size previously reported in this cohort.

Leptin levels in cord blood and anthropometric measures at birth: a systematic review and meta-analysis

The role of intrauterine environment in the development of obesity is increasingly recognised. Adipokines and specifically leptin have been examined as potential biomarkers predicting early development of obesity. We conducted a systematic review and meta-analysis of the epidemiological evidence for the association between leptin levels in cord blood and anthropometric measurements at birth in healthy mother-newborn pairs. A PubMed search was performed between 1994 and 2009 and manual search of reference lists of retrieved articles. Forty-four studies met the inclusion criteria set. All studies reported a positive correlation between leptin levels and birthweight. The combined correlation coefficient (r) was 0.46 [95%CI 0.43, 0.50]. Leptin levels explained 21% of variation in birthweight. Results were similar in males (r=0.55; 0.40, 0.68) and females (r=0.60; 0.50, 0.69), and between Caucasians (r=0.45; 0.39, 0.51) and eastern Asian populations (r=0.47; 0.37, 0.55). Statistically significant positive correlations were also found for birth length (r=0.29; 0.23, 0.34) and ponderal index (r=0.36; 0.31, 0.41). There was no indication of publication bias (Egger's test P-value=0.23). This meta-analysis shows a clear but moderate correlation between leptin levels in cord blood and birthweight that is observed in different population groups.

Different indices of fetal growth predict bone size and volumetric density at 4 years of age

We have demonstrated previously that higher birth weight is associated with greater peak and later-life bone mineral content and that maternal body build, diet, and lifestyle influence prenatal bone mineral accrual. To examine prenatal influences on bone health further, we related ultrasound measures of fetal growth to childhood bone size and density. We derived Z-scores for fetal femur length and abdominal circumference and conditional growth velocity from 19 to 34 weeks' gestation from ultrasound measurements in participants in the Southampton Women's Survey. A total of 380 of the offspring underwent dual-energy X-ray absorptiometry (DXA) at age 4 years [whole body minus head bone area (BA), bone mineral content (BMC), areal bone mineral density (aBMD), and estimated volumetric BMD (vBMD)]. Volumetric bone mineral density was estimated using BMC adjusted for BA, height, and weight. A higher velocity of 19- to 34-week fetal femur growth was strongly associated with greater childhood skeletal size (BA: r = 0.30, p < .0001) but not with volumetric density (vBMD: r = 0.03, p = .51). Conversely, a higher velocity of 19- to 34-week fetal abdominal growth was associated with greater childhood volumetric density (vBMD: r = 0.15, p = .004) but not with skeletal size (BA: r = 0.06, p = .21). Both fetal measurements were positively associated with BMC and aBMD, indices influenced by both size and density. The velocity of fetal femur length growth from 19 to 34 weeks' gestation predicted childhood skeletal size at age 4 years, whereas the velocity of abdominal growth (a measure of liver volume and adiposity) predicted volumetric density. These results suggest a discordance between influences on skeletal size and volumetric density.

Relationship between Aortic Intima-media Thickening, Serum IGF-I and Low-density Lipoprotein Particle Diameter in Newborns with Intrauterine Growth Restriction

Much epidemiological evidence has linked low birth weight with late cardiovascular risk. In order to investigate the effect of intrauterine growth restriction (IUGR) on early atherosclerosis in the fetus, we measured aortic wall thickness (abdominal aortic intima-media thickness: aIMT) by ultrasonography in 15 neonates with IUGR and in 31 neonates considered to be appropriate for gestational age (AGA). Furthermore, we evaluated the relationship between aIMT, serum insulin-like growth factor-I (IGF-I) and low-density lipoprotein (LDL) particle size to investigate the possible effect of these atherosclerosis-related factors on the early atherosclerosis process. The results showed that the mean aIMT was significantly greater in the IUGR neonates than in the AGA neonates (least squares mean ± SE, 537 ± 24.8 vs. 471 ± 17.0 µm, p=0.037). The serum IGF-I levels were lower in the IUGR neonates than in the AGA neonates (27.9 ± 4.3 vs. 42.7 ± 2.9 ng/ml, p=0.009). A significant negative correlation was observed between aIMT and IGF-I in the IUGR neonates (r=–0.646, p=0.009); however, a positive correlation was observed between aIMT and IGF-I (r=0.416, p=0.020) in the AGA neonates. There appeared to be no relationship between aIMT and LDL particle diameter. Atherogenic small, dense LDL was not detected in the IUGR infants. In conclusion, neonates with IUGR have significant aortic thickening with decreased IGF-I, suggesting that prenatal events might predispose them to later cardiovascular risk.

Intrauterine growth restriction and adult disease: the role of adipocytokines

Intrauterine growth restriction (IUGR) is the failure of the fetus to achieve his/her intrinsic growth potential, due to anatomical and/or functional disorders and diseases in the feto-placental-maternal unit. IUGR results in significant perinatal and long-term complications, including the development of insulin resistance/metabolic syndrome in adulthood. The thrifty phenotype hypothesis holds that intrauterine malnutrition leads to an adaptive response that alters the fetal metabolic and hormonal milieu designed for intrauterine survival. This fetal programming predisposes to an increased susceptibility for chronic diseases. Although the mechanisms controlling intrauterine growth are poorly understood, adipose tissue may play an important role in linking poor fetal growth to the subsequent development of adult diseases. Adipose tissue secretes a number of hormones, called adipocytokines, important in modulating metabolism and recently involved in intrauterine growth. This review aims to summarize reported findings concerning the role of adipocytokines (leptin, adiponectin, ghrelin, tumor necrosis factor (TNF), interleukin-6 (IL6), visfatin, resistin, apelin) in early life, while attempting to speculate mechanisms through which differential regulation of adipocytokines in IUGR may influence the risk for development of chronic diseases in later life.

The hungry fetus? Role of leptin as a nutritional signal before birth

In adult animals, leptin is an adipose-derived hormone that is important primarily in the regulation of energy balance during short- and long-term changes in nutritional state. Expression of leptin and its receptors is widespread in fetal and placental tissues, although the role of leptin as a nutritional signal in utero is unclear. Before birth, leptin concentration correlates with several indices of fetal growth, and may be an endocrine marker of fetal size and energy stores in the control of metabolism and maturation of fetal tissues. In addition, leptin synthesis and plasma concentration can be modified by insulin, glucocorticoids, thyroid hormones and oxygen availability in utero, and therefore, leptin may be part of the hormonal response to changes in the intrauterine environment. Evidence is emerging to show that leptin has actions before birth that are tissue-specific and may occur in critical periods of development. Some of these actions are involved in the growth and development of the fetus and others have long-term consequences for the control of energy balance in adult life.

Role of leptin in the regulation of growth and carbohydrate metabolism in the ovine fetus during late gestation

Leptin is an important regulator of appetite and energy expenditure in adulthood, although its role as a nutritional signal in the control of growth and metabolism before birth is poorly understood. This study investigated the effects of leptin on growth, carbohydrate metabolism and insulin signalling in fetal sheep. Crown-rump length-measuring devices and vascular catheters were implanted in 12 sheep fetuses at 105-110 days of gestation (term 145 +/- 2 days). The fetuses were infused i.v. either with saline (0.9% NaCl; n = 6) or recombinant ovine leptin (0.5-1.0 mg kg(-1) day(-1); n = 6) for 5 days from 125 to 130 days when they were humanely killed and tissues collected. Leptin receptor mRNA and protein were expressed in fetal liver, skeletal muscle and perirenal adipose tissue. Throughout infusion, plasma leptin in the leptin-infused fetuses was 3- to 5-fold higher than in the saline-infused fetuses, although plasma concentrations of insulin, glucose, lactate, cortisol, catecholamines and thyroid hormones did not differ between the groups. Leptin infusion did not affect linear skeletal growth or body, placental and organ weights in utero. Hepatic glycogen content and activities of the gluconeogenic enzymes glucose-6-phosphatase and phosphoenolpyruvate carboxykinase in the leptin-infused fetuses were lower than in the saline-infused fetuses by 44, 48 and 36%, respectively; however, there were no differences in hepatic glycogen synthase activity or insulin signalling protein levels. Therefore, before birth, leptin may inhibit endogenous glucose production by the fetal liver when adipose energy stores and transplacental nutrient delivery are sufficient for the metabolic needs of the fetus. These actions of leptin in utero may contribute to the development of neonatal hypoglycaemia in macrosomic babies of diabetic mothers.

Aortic intima-media thickness, serum IGF-I, IGFBP-3, and leptin levels in intrauterine growth-restricted newborns of healthy mothers

Neonates with intrauterine growth restriction (IUGR) are associated with reduced concentrations of IGF-I that might contribute to arterial wall thickening. Direct atherogenic effects of leptin have been described. We aimed to investigate the relationship among abdominal aortic intima-media thickness (aIMT), serum IGF-I, IGF binding protein-3, and leptin levels in neonates with IUGR. Abdominal aIMT was measured in 40 term neonates with IUGR and in 40 controls. Mean aIMT was significantly greater in neonates with IUGR (0.45 +/- 0.03 mm) than in controls (0.39 +/- 0.04 mm, p < 0.0001). Serum IGF-I and leptin levels were lower in neonates with IUGR than in controls. There was a significant positive correlation between aIMT and gestational age, whereas a significant negative correlation was determined between aIMT and IGF-I in the IUGR neonates. For aIMT, significant associations included serum IGF-I level (beta = -0.406, p = 0.006) and gestational age (beta = 0.331, p = 0.022) in a multiple stepwise linear regression analysis. In control neonates, serum IGF-I levels were negatively related to aIMT (beta = -0.750, p < 0.001). Neonates with IUGR have significant aIMT with decreased IGF-I. IGF-I levels determine aIMT not only in neonates with IUGR but also in healthy controls.

Correlation between birth weight, leptin, zinc and copper levels in maternal and cord blood

Leptin and zinc are involved in the regulation of appetite. Copper is a trace element regulating the functions of several cuproenzymes that are essential for life. To evaluate the relationship between zinc and copper status and the leptin system in humans, we examined whether leptin concentrations in the mother and the newborn correlate with the weight of mother, placenta and newborn. A total of 88 pregnant women at 38-42 weeks' gestation were studied. All infants were categorized as small for gestational age (SGA) (n = 16), average for gestational age (AGA) (n = 59) or large for gestational age (LGA) (n = 13). Leptin, zinc, and copper levels were measured in maternal and cord serum at birth. Maternal BMI and placental weight of the LGA groups were significantly higher than those of the SGA and AGA groups. Cord and maternal leptin levels of the SGA groups were significantly lower than those of the AGA and LGA groups. Maternal serum leptin levels were positively correlated with BMI and maternal zinc levels in all groups. Cord serum leptin levels of all groups were positively correlated with birth weight and placental weight. Birth weight was negatively correlated with maternal and cord copper level of all groups. Umbilical leptin concentrations of SGA newborns correlated with leptin concentrations of their mothers. In all pregnancies, birth weight increases in association with increase in cord leptin level. Our results suggest that maternal zinc but not copper level has an effect on maternal serum leptin levels. The increase in copper level in both maternal and cord blood may contribute to restriction in fetal growth.

Developmental control of plasma leptin and adipose leptin messenger ribonucleic acid in the ovine fetus during late gestation: role of glucocorticoids and thyroid hormones

In developed countries, the increasing incidence of obesity is a serious health problem. Leptin exposure in the perinatal period affects long-term regulation of appetite and energy expenditure, but control of leptin production in utero is unclear. This study investigated perirenal adipose tissue (PAT) and placental leptin expression in ovine fetuses during late gestation and after manipulation of plasma glucocorticoid and thyroid hormone concentrations. Between 130 and 144 d of gestation (term at 145 +/- 2 d), plasma leptin and PAT leptin mRNA levels increased in association with increments in plasma cortisol and T(3). Fetal adrenalectomy prevented these developmental changes, and exposure of intact 130 d fetuses to glucocorticoids, by cortisol infusion or maternal dexamethasone treatment, caused premature elevations in plasma leptin and PAT leptin gene expression. Fetal thyroidectomy increased plasma leptin and PAT leptin mRNA abundance, whereas intravenous T(3) infusion to intact 130 d fetuses had no effect on circulating or PAT leptin. Leptin mRNA expression was low in the ovine placenta. Therefore, in the sheep fetus, PAT appears to be a primary source of leptin in the circulation, and leptin gene expression is regulated by both glucocorticoids and thyroid hormones. Developmental changes in circulating and PAT leptin may mediate the maturational effects of cortisol in utero and have long-term consequences for appetite regulation and the development of obesity.

Course of growth during the first 6 years in children exposed in utero to tobacco smoke

OBJECTIVES

Postnatal growth in children exposed in utero to tobacco smoke is not well understood. This study investigated growth during the first 6 years in children whose mothers smoked during pregnancy.

MATERIALS AND METHODS

Weight, length, and head circumference were measured annually for 6 years in 100 children in each group of smoking (study) and nonsmoking (control) mothers.

RESULTS

Weight and head circumference were significantly smaller in the neonates whose mothers smoked >or=15 cigarettes/day, but the difference disappeared by 3 years of life. Length was significantly smaller in the study neonates at birth, followed by increasing divergence from normality up to 2 years, when the mean difference of children whose mothers smoked >or=15 cigarettes/day from control children was -3.4 cm (p <or= 0.0001). Subsequently, they manifested catch-up growth ,and the difference from the controls at 3, 4, 5, and 6 years was -2.5 cm (p <or= 0.0001), -2.2 cm (p = 0.005), -2.1 cm (p = 0.013), and -1.9 cm (p = 0.055), respectively.

DISCUSSION

The delayed growth was related to smoking per se and appeared to be independent of several confounding factors. At birth, there was a significant negative correlation between the number of cigarettes smoked per day and the growth parameters studied; it remained significant up to the 6 year only for length.

CONCLUSION

Length exhibits the most persistent growth delay of the parameters studied, but catch-up growth occurs after the second year of life, and thus, intrauterine exposure to tobacco smoke seems to have no permanent effect on children's growth.

Maternal leptin across pregnancy in women with small-for-gestational-age infants

OBJECTIVE

We hypothesized that women with small-for-gestational-age (SGA) neonates would have lower concentrations of leptin compared to women with appropriately grown infants (AGA).

STUDY DESIGN

This is a nested case-control study of normotensive nulliparous women. Cases (n = 28) delivered SGA < 10 percentile and controls (n = 77) delivered AGA. Maternal plasma leptin concentrations were compared at 18, 28, and 40 weeks' gestation via repeated measures.

RESULTS

Maternal leptin concentrations at 18 weeks were correlated with prepregnancy BMI (r = 0.69, P < .0001) and early pregnancy waist circumference (r = 0.59, P < .0001). After adjustment for maternal body composition, leptin was lower across pregnancy in women with SGA compared to AGA neonates (13.6 vs 15.2 ng/mL at 18 weeks; 13.6 vs 17.3 ng/mL at 28 weeks; 16.6 vs 20.7 ng/mL at 40 weeks; P = .04).

CONCLUSION

Maternal leptin was correlated with maternal adiposity; however, after adjustment for body composition, leptin was lower across pregnancy in women with SGA.

The relationship between birth weight leptin and bone mineral status in newborn infants

BACKGROUND

The positive relationship between fat mass, bone mass and leptin has been shown in fetal mouse cartilage/bone. It has been shown that umbilical venous leptin predicts both the size of the neonatal skeleton and its estimated volumetric mineral density.

AIMS

This study investigates how birth weight and bone mineralization correlate with leptin levels. In addition, we aimed to determine the predictive value of anthropometrics measurements and gender on variability in bone mineral status.

METHODS

Umbilical cord venous blood samples were obtained at the delivery from 100 term newborn infants. Forty of the newborn infants had birth weights appropriate for gestational age (AGA), 30 were small for gestational age (SGA) and 30 were large for gestational age (LGA). Data were acquired using the whole body dual energy X-ray obsorptiometry scanner in the first 24 h after birth.

RESULTS

Leptin concentrations were higher in LGA (36.6 +/-12.0 ng/ml; p < 0.0001), but lower in SGA (11.7 +/- 5.6 ng/ml; p < 0.001) than in AGA infants (20.3 +/- 7.6 ng/ml). Whole body bone mineral density and whole body bone mineral content were higher in LGA babies (0.442 +/- 0.025 g/cm(2), 71.6 +/- 9.0 g, p < 0.01, p < 0.001, respectively) but lower in SGA (0.381 +/- 0.027 g/cm(2), 29.1 +/- 9.1 g, p < 0.001, p < 0.001, respectively) than in AGA babies (0.426 +/- 0.022 g/cm(2), 53.7 +/- 9.6 g, respectively). The percentage of whole body bone mineral content was lower in SGA (1.3 +/- 0.3) than in AGA (1.6 +/- 0.2, p < 0.001) and LGA (1.7 +/- 0.2, p < 0.001). In stepwise linear regression analyses models; leptin is not found related to the bone indices.

CONCLUSION

Our study does not provide support for the hypothesis that leptin may play a major role in the regulation of bone metabolism in the developing skeleton.

Determinants of early life leptin levels and later life degenerative outcomes

The early (intrauterine and neonatal) life environment plays an important role in programming the susceptibility in later life to chronic degenerative diseases, such as obesity, cardiovascular diseases, diabetes mellitus, cancer and osteoporosis. Among other hormones, leptin plays a major role in the regulation of the overall metabolism and has multiple neuroendocrine (adeno- and neuro-hypophysis axes and the hypothalamus-pituitary-adrenal axis) and immune functions. The hormone exerts its actions beginning in the early life time period, regulating the intrauterine and early extrauterine life growth and development, as well as the adaptation to extrauterine life, neonatal thermogenesis and response to stress. Recent findings also support a role of leptin in the process of fetal bone remodeling and brain development. Therefore, it is of interest to explore the physiology of leptin in early life, as well as those factors that may perturb the balance of the hormone with pathological consequences in terms of confining an increased risk for disease in later life. This review aims to summarize reported findings concerning the role of leptin in early life, as well as the association of fetal, maternal and placental factors with leptin levels, while attempting to speculate mechanisms through which these factors may influence the risk for developing chronic diseases in later life.

Reproductive Tract Infections in Horses

Diagnosis, treatment, and, ultimately, prevention of reproductive disease are vital components of equine veterinary medicine. A thorough understanding of anatomy and physiology is necessary to reconcile the pathologic findings of disease. Only then can a rational treatment plan be formulated. Many recent advances in knowledge about the reproductive system of multiple species have application to the mare and stallion.

Cord blood leptin and IGF-I in relation to birth weight differences and head circumference in monozygotic twins

OBJECTIVES

To investigate a potential role of leptin and insulin-like growth factor (IGF)-I on fetal growth and metabolic function we determined plasma leptin and IGF-I concentrations in twins in relation to discordant fetal growth.

STUDY DESIGN

In studying monochorionic twins with inter-twin birth weight difference, we investigated the relative contribution of genetic (fetus) versus environmental (maternal/placental) factors on growth. Thirty-six sets of twins (14 with discordant growth, birth weight difference >15%) who had been treated for severe twin-to-twin transfusion syndrome (TTTS) by laser coagulation were studied. Cord blood samples were collected at birth and analyzed for IGF-I and leptin. Inter-twin differences (delta) of birth weight and head circumference were correlated to delta hormone levels.

RESULTS

An inter-twin correlation for leptin (r = 0.69; p <0.0001) and delta IGF-I (r = 0.49; p <0.0001) was found. delta birth weight correlated significantly with delta IGF-I (r = 0.67; p <0.0001) but not with delta leptin (r = 0.23; p = 0.19). delta IGF-I concentrations did not correlate with delta leptin (r = 0.18). delta head circumference correlated significantly with delta leptin (r = 0.47; p <0.01) and with delta IGF-I (r = 0.46; p <0.01). Using a multiple regression model with head circumference as dependent variable, adjusted for gestational age, head circumference remained significantly associated with higher leptin concentrations in all patients (p = 0.03).

CONCLUSION

IGF-I is a good indicator for fetal growth and brain development. Leptin seems to be mainly genetically determined but may play a role in fetal brain development and is not only an index for fetal fat mass.

Resistin in preterm and term newborns: relation to anthropometry, leptin, and insulin

This study aimed to investigate 1) the plasma resistin concentration at birth, 2) the relationship of resistin with leptin and insulin, and 3) the association of resistin with anthropometric indexes in newborn infants. Blood samples for hormonal assay were obtained from preterm and term newborns within the first 2 h of life and before milk feeding or energy intake. Although these infants required blood sampling for clinical reasons, all were proved to be noninfected. Plasma resistin was significantly higher in term than in preterm infants. It was also significantly correlated with serum leptin, and both hormones were significantly associated with gestational age and anthropometric indexes. Infants who were born vaginally were found to have significantly higher plasma resistin levels compared with those who were born by cesarean section. In the multivariate forward stepwise regression models, resistin was found to be significantly associated with the mode of delivery and gestational age or birth weight. The association among resistin, leptin, and anthropometric indexes suggested that both hormones might be gestation related. A high circulating resistin level at term gestation could be advantageous to the infant by promoting hepatic glucose production and preventing hypoglycemia after birth. Infants who were born vaginally had significantly higher plasma resistin levels, suggesting that this hormone might also be associated with stress or inflammation induced by the birth process.

Umbilical cord leptin predicts neonatal bone mass

Evidence is accumulating that the risk of osteoporosis in later life may be determined in part by environmental influences on bone development during intrauterine and early postnatal life. A potential role for fetal leptin in mediating these effects is suggested by animal studies showing that leptin influences prenatal osteoblast growth and development, and that fetal leptin concentrations are altered by changes in maternal nutrition. In a group of term human infants we reported previously that maternal birthweight, smoking, fat mass, and exercise during late pregnancy independently predict neonatal bone mass. To investigate the potential role of leptin in mediating these effects, we now relate leptin concentrations in umbilical venous serum to neonatal bone mass and body composition in 117 infants. There were strong positive associations between umbilical venous leptin concentration and each of whole body bone mineral contents (BMC) (r = 0.42, P < or = 0.001) and estimated volumetric bone density (r = 0.21, P = 0.02); whole body lean mass (r = 0.21, P < or = 0.024); and whole body fat mass (r = 0.60, P < 0.001). The associations with neonatal BMC and fat mass, but not with lean mass, were independent of associations that we have reported previously between cord serum insulin-like growth factor 1 (IGF-1) concentrations and neonatal body composition. Among the maternal determinants of neonatal bone mass, cord leptin explained the relationship with maternal fat stores, but not those with the mother's own birthweight, smoking, or physical activity. We conclude that umbilical venous leptin predicts both the size of the neonatal skeleton and its estimated volumetric mineral density. In addition, among previously documented maternal determinants of neonatal bone mass in healthy pregnancies, maternal fat stores may mediate their effect on fetal bone accrual through variation in fetal leptin concentrations.

The evaluation of serum leptin level and other hormonal parameters in children with severe malnutrition

OBJECTIVES

Protein-energy malnutrition (PEM) is a clinical problem caused by inadequate intake of one or more nutritional elements, and remains as one of the most important health problems in developing countries. The aim of this study is to determine the relationship among leptin concentrations, body weight and concentrations of some serum hormones, e.g., basal GH, IGF-1, basal cortisol and IGF-BP3, in severe malnourished children, and to determine the effects of leptin in malnourished children.

DESIGN AND METHODS

The study group consisted of 36 children diagnosed with PEM. Thirty healthy children were enrolled as the control group. After an overnight fast and before initiation of feedings, fasting venous blood samples were obtained from a forearm vein with needle technique for routine tests, and leptin, IGF-1, IGF-BP3, basal GH and cortisol levels were measured. Tests were carried out in the laboratories of the Department of Biochemistry by commercial kits.

RESULTS

Serum leptin levels of infants with marasmus and kwashiorkor were significantly lower than that of the controls (2.09 +/- 0.93 and 2.27 +/- 1.01, 6.82 +/- 2.28 ng/ml, respectively, P < 0.001). However, there was no significant difference between serum leptin levels in children with marasmus and those with kwashiorkor (P > 0.05). Serum IGF-1 and IGF-BP3 levels were significantly lower in malnourished children (P < 0.001, both). Also, basal GH and cortisol levels were significantly higher in malnourished children (P < 0.001, both). There was a positive correlation among serum leptin levels and IGF-1 and IGF-BP3 levels and also a negative correlation among serum leptin levels and basal GH and cortisol levels in children diagnosed with marasmus or kwashiorkor and the control group.

CONCLUSIONS

The decrease of energy intake and adipose tissue and serum IGF-1 levels in children with PEM may result in decrease of leptin secretion. Decrease in serum leptin levels may initiate food intake by increasing appetite and stimulating the secretion of cortisol and GH that might increase energy expenditure through an autocrine mechanism. Moreover, serum leptin level may be an important signal to reflect the metabolism of children with PEM.

The maternal endocrine environment in the low-protein model of intra-uterine growth restriction

Many adult diseases, including type 2 diabetes, hypertension and cardiovascular disease, are related to low birth weight. The mechanistic basis of this relationship is not known. To investigate the role of fetal undernutrition, we used a rat model of maternal protein restriction in which dams were fed a diet containing 80 g protein/kg (v. 200 g/kg in the control group) throughout gestation and lactation. Offspring were born smaller than controls and in adulthood developed diabetes, hyperinsulinaemia and tissue insulin resistance. To determine possible mechanisms of fetal programming, circulating levels of several hormones were measured in maternal plasma at gestational days 14, 17 and 21 and fetal plasma at gestational day 21. Several differences were noted at day 14, when glucose concentrations in maternal and feto-placental blood were raised significantly (P=0.04 and P=0.0001 respectively); insulin levels in the low-protein (LP) dams were raised (P=0.04), prolactin levels were raised (P=0.047) and progesterone levels were reduced (P=0.02). Circulating 17beta-oestradiol in the LP dams was raised by 35 % over those of the controls from day 17 to day 21 (P=0.008). A significant decrease in maternal leptin levels (P=0.004) was observed at gestation on day 21. Neither oestradiol nor leptin levels were altered in the fetal circulation at day 21. Maternal and fetal corticosterone levels were comparable with control levels, suggesting that they do not initiate the programming effects in this model. Our present results suggest that maternal protein restriction imposes changes in maternal levels of glucose, insulin, prolactin, progesterone, oestradiol and leptin; these changes could influence the programming of eventual adult disease in the developing fetus.

Umbilical cord and maternal blood leptin concentrations in intrauterine growth retardation

Leptin, the ob gene product, plays an important role in the regulation of body fat mass and weight. In previous studies, it was demonstrated that leptin is detectable in human fetal cord blood as early as at 18 weeks of gestation and that serum leptin concentrations are significantly reduced in small gestational age newborns. In the present study, we investigated whether umbilical and maternal serum leptin concentrations correlate with intrauterine growth retardation (IUGR). In addition, we aimed to determine the relationships between leptin concentration in the maternal and cord blood. We studied 40 newborn infants (21 female and 19 male; gestational age, 38-42 weeks) and their mothers. Of the infants studied, 10 had IUGR. Serum leptin concentrations were measured by radioimmunoassay. All newborns had detectable leptin concentrations. Leptin concentrations were significantly lower in newborns with IUGR and in their mothers (n = 10; 3.53 +/- 1.42 ng/ml, 6.75 +/- 1.47 ng/ml, respectively) than in infants experiencing normal growth and their mothers (n = 30; 5.58 +/- 2.98 ng/ml, 9.85 +/- 6.50 ng/ml, respectively) (p < 0.01 for newborns, p < 0.05 for mothers). There was no significant correlation between umbilical leptin concentration and maternal leptin concentration (r = 0.229; p = 0.155) in all study groups but, significantly, a correlation was observed in the group with IUGR (r = 0.736; p = 0.015). There were no significant correlations between both umbilical and maternal leptin concentrations and parity, delivery type and gestational age. There was a correlation between umbilical leptin concentration and birth weight of newborns (r = 0.383; p = 0.015) but no correlation with body mass index (BMI) of the newborns (r = 0.034; p = 0.834). Maternal leptin concentrations correlated with maternal weight and BMI (r=0.606; p=0.000, r=0.535; p=0.000, respectively). There was no correlation between maternal leptin concentrations and birth weight of the newborns (r=0.179; p=0.269) and with BMI of the newborns (r = 0.146; p = 0.367). There was no gender difference in leptin concentrations in the newborns (n=21; 5.50 +/- 3.37 ng/ml, for females; n = 19; 4.58 +/- 1.98 ng/ml for males) (p = 0.296). In summary, we have shown that IUGR is associated with a decreased leptin concentration in newborns and their mothers. The association between umbilical serum leptin and birth weight in this and other studies suggests a pivotal role of fetal leptin in regulating fetal growth and development.

Is leptin the link between fat and bone mass?

Recently, leptin has emerged as a potential candidate responsible for protective effects of fat on bone tissue. However, it remains difficult to draw a clear picture of leptin effects on bone metabolism because published data are sometimes conflicting or apparently contradictory. Beyond differences in models or experimental procedures, it is tempting to hypothesize that leptin exerts dual effects depending on bone tissue, skeletal maturity, and/or signaling pathway. Early in life, leptin could stimulate bone growth and bone size through direct angiogenic and osteogenic effects on stromal precursor cells. Later, it may decrease bone remodeling in the mature skeleton, when trabecular bone turnover is high, by stimulating osteoprotegerin (OPG) expression. Leptin negative effects on bone formation effected through central nervous system pathway could counterbalance these peripheral and positive effects, the latter being predominant when the blood-brain barrier permeability decreases or the serum leptin level rises above a certain threshold. Thus, the sex-dependent specificity of the relationship between leptin and bone mineral density (BMD) in human studies could be, at least in part, caused by serum leptin levels that are two- to threefold higher in women than in men, independent of adiposity. Although these hypotheses remain highly speculative and require further investigations, existing studies consistently support the role of leptin as a link between fat and bone.

Prospective function of placental leptin at maternal-fetal interface

Leptin is an endocrine and a growth factor which is important for regulation of body fat, feeding, and energy homeostasis. The anti-obesity function of leptin has been recently extended to reproduction, puberty and pregnancy as an endocrine signal to the hypothalamus. Leptin controls the functional integrity of the feto-placental unit thereby maintaining pregnancy by virtue of its immunomodulatory property via T lymphocytes or other proto-oncogenes. Dysregulation of autocrine/paracrine function of leptin at feto-placento-maternal interface may be implicated in the pathogenesis of recurrent miscarriage gestational diabetes, pre-eclampsia and intra-uterine fetal growth retardation including disturbance of fetal bone turnover. This review will focus on the role of leptin in normal and abnormal pregnancy and fetal growth.

Leptin secretion to both the maternal and fetal circulation in the ex vivo perfused human term placenta

The contribution of placental leptin, if any, to both the fetal and maternal circulation and its role in pregnancy remains to be determined. In an experiment to investigate this, 27 placentae from term pregnancies were perfused ex vivo (gestational age=39.5 s.d. 1.2; range=38-42 weeks: fetal weight=3285 s.d. 482; range=2480-4420; birthweight centile range=4th to the 98th) at both the maternal and fetal interface. Placental leptin was exported into both the maternal and fetal circulations. The log leptin production by the maternal side of the placenta was significantly greater (P=0.001) than that for the fetal side (5.193 s.d.1.049 versus 4.387 s.d. 0.768 ng/placenta/min). There was no significant relationship between maternal and fetal log leptin production and maternal body mass index, birthweight, birthweight centile, ponderal index or gestational age or with cord blood pO(2), pCO(2) and pH. There was however, a significant increase in the maternal log leptin production with increasing fetal to placental weight ratio (P=0.017; r(2)=20.7 per cent) but no corresponding relationship for fetal leptin production. It is proposed that such a mechanism would allow the placenta to modulate fat supply to the fetus in response to the fetal demand relative to placental supply.

Leptin--much more than a satiety signal

Much attention has focused on the effects of leptin as a central satiety agent. There is now a significant amount of evidence that leptin is active in the periphery. This review focuses on the ability of leptin to modify insulin sensitivity, tissue metabolism, stress responses, and reproductive function. Leptin's effect on several of these systems is mediated via the hypothalamic-pituitary axis. Therefore, although in vitro studies provide evidence for direct effects on specific tissues and metabolic pathways, it is essential to consider the interactions between leptin and other regulatory factors in vivo. Little is known about the regulation of peripheral receptor expression or the production of binding proteins. Both of these factors determine the bioactivity of circulating leptin and have the potential to induce a peripheral resistance to leptin, similar to the central "leptin resistance" observed in obese subjects. Future research will clarify which of the endocrine and metabolic actions of peripheral leptin are of physiological relevance and which should be considered a pharmacological manipulation.

Leptin and pregnancy outcome

Leptin, a recently discovered hormone that is involved in the regulation of body weight, appears to be one of the hormonal factors that signal the body's readiness for sexual maturation and reproduction to the brain. The present review focuses on clinical and experimental studies that describe the roles of maternal and foetal leptin as predictive factors for the physiological and pathophysiological development of the foetus during pregnancy, assisted reproduction and neonatal life. Through evaluating alterations of maternal serum leptin levels, a physiological hyperleptinaemia has been observed to occur, particularly during the second and third trimesters of pregnancy, which is not associated with a decreased food intake or reduced metabolic activity in the pregnant women. This state of leptin resistance is comparable to the condition in obesity. In contrast, hypoleptinaemia is suggested to be an indicator for the cessation of pregnancy, either naturally at term or as a result of pathology at any time during gestation. Thus, an appropriate maternal leptin level seems to be a prerequisite for a normal pregnancy. The main source of foetal leptin is the still immature foetal adipose tissue. As intrauterine growth has been found to be independently associated with cord blood leptin level, it has been suggested that leptin plays a role as a regulator of foetal growth. During assisted reproduction cycles leptin levels in the follicular fluid of patients may be also of predictive value, with low levels predicting therapeutic failure. Finally, the relevance of leptin to postnatal development is reviewed; leptin may be important for regulation of satiety and peripheral metabolism. In summary, leptin appears to be an important permissive factor that is involved in female reproduction.

Leptin in pregnancy

Leptin is a polypeptide hormone that aids in the regulation of body weight and energy homeostasis and is linked to a variety of reproductive processes in both animals and humans. Thus, leptin may help regulate ovarian development and steroidogenesis and serve as either a primary signal initiating puberty or as a permissive regulator of sexual maturation. Perhaps significantly, peripheral leptin concentrations, adjusted for adiposity, are dramatically higher in females than in males throughout life. During primate pregnancy, maternal levels that arise from adipose stores and perhaps the placenta increase with advancing gestational age. Proposed physiological roles for leptin in pregnancy include the regulation of conceptus growth and development, fetal/placental angiogenesis, embryonic hematopoiesis, and hormone biosynthesis within the maternal-fetoplacental unit. The specific localization of both leptin and its receptor in the syncytiotrophoblast implies autocrine and/or paracrine relationships in this endocrinologically active tissue. Interactions of leptin with mechanisms regulating pre-eclampsia and maternal diabetes have also been suggested. Collectively, therefore, reports suggest that a better understanding of the regulation of leptin and its role(s) throughout gestation may eventually impact those causes of human perinatal morbidity and mortality that are exacerbated by intrauterine growth retardation, macrosomia, placental insufficiency, or prematurity.

Fetal plasma leptin concentrations: relationship with different intrauterine growth patterns from 19 weeks to term

The relationship between in utero fetal growth and fetal leptin concentrations was investigated between 19 and 41 wk in 40 normal (appropriate for gestational age, AGA) fetuses, in 25 intrauterine growth-restricted (IUGR) fetuses, and in 18 fetuses from gestational diabetic mothers (GDM), representing different intrauterine growth patterns. Umbilical venous plasma leptin concentrations were determined at the time of either in utero fetal blood sampling or delivery. Plasma leptin was measurable as early as 19 wk of gestation. A significant difference was observed between umbilical venous and arterial plasma leptin concentrations (0.6+/-0.6 ng/mL; p<0.01). In AGA and in IUGR fetuses, significant positive relationships were found between fetal leptin concentrations and both gestational age (p<0.001) and fetal weight (p<0.001). Leptin concentrations were significantly higher in AGA than IUGR only after 34 wk (p<0.05), but leptin per kilogram fetal weight (leptin/kg) was not significantly different. In IUGR with abnormal umbilical arterial Doppler velocimetry and fetal heart rate, leptin/kg significantly higher than in IUGR with normal biophysical and biochemical parameters was found (p<0.05). Both circulating plasma leptin and leptin/kg were significantly higher in GDM than in normal fetuses (p<0.001) and correlated with abdominal fat mass measured by ultrasound. No gender differences were observed in any group of fetuses. These findings indicate a clear relationship between fetal leptin concentrations and fetal fat mass. Data in severe IUGR suggest the presence of increased leptin concentrations associated with in utero signs of fetal distress.

Fetal growth

Recent epidemiological and experimental studies show that abnormal fetal growth can lead to serious complications, including stillbirth, perinatal morbidity and disorders extending well beyond the neonatal period. It is now clear that the intrauterine milieu is as important as genetic endowment in shaping the future health of the conceptus. Maternal characteristics such as weight, height, parity and ethnic group need to be adjusted for, and pathological factors such as smoking excluded, to establish appropriate standards and improve the distinction between what is normal and abnormal. Currently, the aetiology of growth restriction is not well understood and preventative measures are ineffective. Elective delivery remains the principal management option, which emphasizes the need for better screening techniques for the timely detection of intrauterine growth failure.

Physiological roles of the leptin endocrine system: differences between mice and humans

Leptin is a 16-kDa cytokine secreted in humans primarily but not exclusively by adipose tissues. Its concentration in blood is usually proportional to body fat mass, but is higher in women than in men not only because of a different distribution of and greater fat mass in women, but also because testosterone reduces its level in men. Leptin features in different ways during the life span. It is synthesized in the ovary, transported in the oocyte, and made by both fetus and placenta, particularly during the last month of gestation. It is made by the lactating mammary gland and ingested by the newborn infant in its milk. The prime importance of leptin is realized at puberty when it is necessary for progression to a normal adult reproductive status in females. Fasting and chronic undernutrition result in a lower level of leptin in the blood. Lack of leptin results in hunger, ensuring that the individual eat to survive, and also inhibition of reproduction, until such time as food and fat stores are adequate to supply energy for pregnancy and lactation. Thus, leptin is important for survival of the individual and survival of the species. Although an extremely rare genetic absence of leptin induces hyperphagia and obesity in humans, as it does in mice, there appears to be little role for leptin in humans in ensuring that fat stores are not in excess of adequate, that is, in preventing obesity. The mouse differs from humans in many respects, in particular in the far more drastic ways it conserves energy when it very rapidly adapts to lack of food. These include not only suppression of reproduction but also lowering of its body temperature (torpor), suppressing its thyroid function, suppressing its growth, and increasing secretion of stress hormones (from the adrenal). This review concentrates on roles of leptin in human physiology and pathophysiology but also discusses why some observations on actions of leptin in mice are not applicable to humans.