Glucose Metabolism in the Human Preterm and Term Placenta of IUGR Fetuses

Immunohistochemical localization of HCA1 receptor in placenta in presence of fetal growth restriction

INTRODUCTION

Glucose metabolism produces lactate and hydrogen ions in an anaerobic environment. Fetuses with intrauterine growth restriction are considered to become progressively lactacidemic as well as hypoxic. Roles of lactate in the placenta in the presence of fetal growth restriction (FGR) remain to be clarified.

METHODS

Immunohistochemical localization of lactate-related substances, such as a receptor for lactate (hydroxy-carboxylic acid 1 receptor (HCA1 receptor/GPR81)), monocarboxylate transporters (MCTs) for lactate, lactate dehydrogenases (LDHs), and proteins expressed in syncytiotrophoblasts or cytotrophoblasts was examined in placentas of appropriate weight for gestational age (AGA) fetus and those showing FGR.

RESULTS

Immunoreactivity for the HCA1 receptor was present in the cytoplasm of some trophoblasts, predominantly localized to their basal (fetus-facing) side, and was frequently colocalized with that for E-cadherin or serine peptidase inhibitor, Kunitz type 1 (SPINT1), a marker protein of cytotrophoblasts. Immunoreactivity for MCT1 and MCT4 was present on the basal and the microvillous (maternal-facing) membranes of trophoblasts in both groups, respectively. Clear immunoreactivity for LDHA and LDHB was also observed in the cytoplasm of trophoblasts, mainly localized to their basal side. However, there were no significant differences in immunohistochemically stained areas of lactate-related substances between AGA and late-onset FGR groups. On the other hand, there were correlations between coefficients of the presence of chorioamnionitis and the values of LDHB and E-cadherin.

DISCUSSION

Immunohistochemical localization of the HCA1 receptor was predominantly observed in the cytoplasm located on the basal side of trophoblasts, suggesting a role of lactate in human placental development, including syncytialization.

Glycolysis: A fork in the path of normal and pathological pregnancy

Glucose metabolism is vital to the survival of living organisms. Since the discovery of the Warburg effect in the 1920s, glycolysis has become a major research area in the field of metabolism. Glycolysis has been extensively studied in the field of cancer and is considered as a promising therapeutic target. However, research on the role of glycolysis in pregnancy is limited. Recent evidence suggests that blastocysts, trophoblasts, decidua, and tumors all acquire metabolic energy at specific stages in a highly similar manner. Glycolysis, carefully controlled throughout pregnancy, maintains a dynamic and coordinated state, so as to maintain the homeostasis of the maternal-fetal interface and ensure normal gestation. In the present review, we investigate metabolic remodeling and the selective propensity of the embryo and placenta for glycolysis. We then address dysregulated glycolysis that occurs in the cellular interactive network at the maternal-fetal interface in miscarriage, preeclampsia, fetal growth restriction, and gestational diabetes mellitus. We provide new insights into the field of maternal-fetal medicine from a metabolic perspective, thus revealing the mystery of human pregnancy.

Human placental development and function

The placenta is a transient fetal organ that plays a critical role in the health and wellbeing of both the fetus and its mother. Functionally, the placenta sustains the growth of the fetus as it facilitates delivery of oxygen and nutrients and removal of waste products. Not surprisingly, defective early placental development is the primary cause of common disorders of pregnancy, including recurrent miscarriage, fetal growth restriction, pre-eclampsia and stillbirth. Adverse pregnancy conditions will also affect the life-long health of the fetus via developmental programming[1]. Despite its critical importance in reproductive success and life-long health, our understanding of placental development is not extensive, largely due to ethical limitations to studying early or chronological placental development, lack of long-term in vitro models, or comparative animal models. In this review, we examine current knowledge of early human placental development, discuss the critical role of the maternal endometrium and of the fetal-maternal dialogue in pregnancy success, and we explore the latest models of trophoblast and endometrial stem cells. In addition, we discuss the role of oxygen in placental formation and function, how nutrient delivery is mediated during the periods of histotrophic nutrition (uptake of uterine secretions) and haemotrophic nutrition (exchange between the maternal and fetal circulations), and how placental endocrine function facilitates fetal growth and development.

Ex Vivo Human Placenta Perfusion, Metabolic and Functional Imaging for Obstetric Research-A Feasibility Study

Placenta metabolism is closely linked to pregnancy outcome, and few modalities are currently available for studying the human placenta. Here, we aimed to investigate a novel ex vivo human placenta perfusion system for metabolic imaging using hyperpolarized [1-¹³C]pyruvate. The metabolic effects of 3 different human placentas were investigated using functional and metabolic magnetic resonance imaging. The placenta glucose metabolism and hemodynamics were characterized with hyperpolarized [1-¹³C]pyruvate magnetic resonance imaging and by dynamic contrast-enhanced (DCE) imaging. Hyperpolarized [1-¹³C]pyruvate showed a decrease in the ¹³C-lactate/¹³C-pyruvate ratio from the highest to the lowest metabolic active placenta. The metabolic profile was complemented by a more homogenous distributed hemodynamic response, with a longer mean transit time and higher blood volume. This study shows different placenta metabolic and hemodynamic features associated with the placenta functional status using hyperpolarized magnetic resonance ex vivo. This study supports further studies using ex vivo metabolic imaging of the placenta alterations associated with pregnancy complications.

The placenta in fetal growth restriction: What is going wrong?

The placenta is essential for the efficient delivery of nutrients and oxygen from mother to fetus to maintain normal fetal growth. Dysfunctional placental development underpins many pregnancy complications, including fetal growth restriction (FGR) a condition in which the fetus does not reach its growth potential. The FGR placenta is smaller than normal placentae throughout gestation and displays maldevelopment of both the placental villi and the fetal vasculature within these villi. Specialized epithelial cells called trophoblasts exhibit abnormal function and development in FGR placentae. This includes an altered balance between proliferation and apoptotic death, premature cellular senescence, and reduced colonisation of the maternal decidual tissue. Thus, the placenta undergoes aberrant changes at the macroscopic to cellular level in FGR, which can limit exchange capacity and downstream fetal growth. This review aims to compile stereological, in vitro, and imaging data to create a holistic overview of the FGR placenta and its pathophysiology, with a focus on the contribution of trophoblasts.

Complex, coordinated and highly regulated changes in placental signaling and nutrient transport capacity in IUGR

The most common cause of intrauterine growth restriction (IUGR) in the developed world is placental insufficiency, a concept often used synonymously with reduced utero-placental and umbilical blood flows. However, placental insufficiency and IUGR are associated with complex, coordinated and highly regulated changes in placental signaling and nutrient transport including inhibition of insulin and mTOR signaling and down-regulation of specific amino acid transporters, Na+/K+-ATPase, the Na+/H+-exchanger, folate and lactate transporters. In contrast, placental glucose transport capacity is unaltered and Ca2+-ATPase activity and the expression of proteins involved in placental lipid transport are increased in IUGR. These findings are not entirely consistent with the traditional view that the placenta is dysfunctional in IUGR, but rather suggest that the placenta adapts to reduce fetal growth in response to an inability of the mother to allocate resources to the fetus. This new model has implications for the understanding of the mechanisms underpinning IUGR and for the development of intervention strategies.

Dynamic glucose enhanced MRI of the placenta in a mouse model of intrauterine inflammation

INTRODUCTION

We investigated the feasibility of dynamic glucose enhanced (DGE) MRI in accessing placental function in a mouse model of intrauterine inflammatory injury (IUI). DGE uses the glucose chemical exchange saturation transfer (glucoCEST) effect to reflect infused d-glucose.

METHODS

IUI was induced in pregnant CD1 mice by intrauterine injection of lipopolysaccharide (LPS) on embryonic day 17. In vivo MRI was performed on an 11.7 T scanner at 6 h s after injury, and glucoCEST effect was measured using an on-resonance variable delay multi-pulse (onVDMP) technique. onVDMP acquisition was repeated over a period of 25 min, and d-glucose was infused 5 min after the start. The time-resolved glucoCEST signals were characterized using the normalized signal difference (ΔS_N) between onVDMP-labeled and nonlabeled images.

RESULTS

ΔS_N in the PBS-exposed placentae (n = 6) showed an initial drop between 1 and 3 min after infusion, followed by a positive peak between 5 and 20 min, the time period expected to be associated with the process of glucose uptake and transport. In the LPS-exposed placentae (n = 10), the positive peak was reduced or even absent, and the corresponding area-under-the-curve (AUC) was significantly lower than that in the controls. Particularly, the AUC maps suggested prominent group differences in the fetal side of the placenta. We also found that glucose transporter 1 in the LPS-exposed placentae did not respond to maternal glucose challenge.

DISCUSSION

DGE-MRI is useful for evaluating placental functions related to glucose utilization. The technique uses a non-toxic biodegradable agent (d-glucose) and thus has a potential for rapid translation to human studies of placental disorders.

Involvement of mTOR, JNK and PI3K in the negative effect of ethanol and metformin on the human first-trimester extravillous trophoblast HTR-8/SVneo cell line

Our aim was to investigate the effect of two xenobiotics to which pregnant woman may be exposed, the drug of abuse ethanol (EtOH) (and its metabolite acetaldehyde (ACA)) and the therapeutic agent metformin (METF), on placentation-related processes in an extravillous trophoblastic (EVTs) cell line (HTR-8/SVneo cells). EtOH, ACA and METF (24 h) significantly reduced cell proliferation rates, culture growth, viability and migratory capacity of HTR-8/SVneo cells. Moreover, both EtOH (100 μM) and METF (1 mM) increased the apoptosis index and inhibited ³H-deoxy-D-glucose (³H-DG) and ³H-folic acid (³H-FA) uptake. mTOR, JNK and PI3K intracellular signaling pathways were involved in the effect of EtOH upon ³H-FA uptake and in the effect of METF upon cell viability, and mTOR and JNK in the effect of EtOH upon cell viability and ³H-DG uptake. We show that EtOH and METF have a detrimental effect in placentation-related processes of HTR-8/SVneo cells. Moreover, mTOR, JNK and PI3K appear to mediate some of these negative effects.

The chinchilla as a novel animal model of pregnancy

Several parameters are important when choosing the most appropriate animal to model human obstetrics, including gestation period, number of fetuses per gestation and placental structure. The domesticated long-tailed chinchilla (Chinchilla lanigera) is a well-suited and appropriate animal model of pregnancy that often will carry only one offspring and has a long gestation period of 105-115 days. Furthermore, the chinchilla placenta is of the haemomonochorial labyrinthine type and is therefore comparable to the human villous haemomonochorial placenta. This proof-of-concept study demonstrated the feasibility in laboratory settings, and demonstrated the potential of the pregnant chinchilla as an animal model for obstetric research and its potential usefulness for non-invasive measurements in the placenta. We demonstrate measurements of the placental and fetal metabolism (demonstrated in vivo by hyperpolarized MRI and in vitro by qPCR analyses), placental vessels (demonstrated ex vivo by contrast-enhanced CT angiography) and overall anatomy (demonstrated in vivo by whole-body CT).

Proteome Differences in Placenta and Endometrium between Normal and Intrauterine Growth Restricted Pig Fetuses

Uteroplacental tissue plays a key role in substance exchanges between maternal and fetal circulation, and, therefore, in the growth and development of fetuses. In this study, proteomics and western blotting were applied to investigate the changes of proteome in the placenta and endometrium of normal and intrauterine growth restriction (IUGR) porcine fetuses during mid to late pregnancy (D60, 90, and 110 of gestation). Our results showed that proteins participating in cell structure, energy metabolism, stress response, cell turnover, as well as transport and metabolism of nutrients were differentially expressed in placenta and endometrium between normal and IUGR fetuses. Analysis of functions of these proteins suggests reductions in ATP production and nutrients transport, increases in oxidative stress and apoptosis, and impairment of cell metabolism in IUGR fetuses. Collectively, our findings aid in understanding of the mechanisms responsible for uteroplacental dysfunction in IUGR fetus, and are expected to provide new strategies to reduce fetal growth restriction in pigs and other mammals.

Peripheral insulin resistance and impaired insulin signaling contribute to abnormal glucose metabolism in preterm baboons

Premature infants develop hyperglycemia shortly after birth, increasing their morbidity and death. Surviving infants have increased incidence of diabetes as young adults. Our understanding of the biological basis for the insulin resistance of prematurity and developmental regulation of glucose production remains fragmentary. The objective of this study was to examine maturational differences in insulin sensitivity and the insulin-signaling pathway in skeletal muscle and adipose tissue of 30 neonatal baboons using the euglycemic hyperinsulinemic clamp. Preterm baboons (67% gestation) had reduced peripheral insulin sensitivity shortly after birth (M value 12.5 ± 1.5 vs 21.8 ± 4.4 mg/kg · min in term baboons) and at 2 weeks of age (M value 12.8 ± 2.6 vs 16.3 ± 4.2, respectively). Insulin increased Akt phosphorylation, but these responses were significantly lower in preterm baboons during the first week of life (3.2-fold vs 9.8-fold). Preterm baboons had lower glucose transporter-1 protein content throughout the first 2 weeks of life (8%-12% of term). In preterm baboons, serum free fatty acids (FFAs) did not decrease in response to insulin, whereas FFAs decreased by greater than 80% in term baboons; the impaired suppression of FFAs in the preterm animals was paired with a decreased glucose transporter-4 protein content in adipose tissue. In conclusion, peripheral insulin resistance and impaired non-insulin-dependent glucose uptake play an important role in hyperglycemia of prematurity. Impaired insulin signaling (reduced Akt) contributes to the defect in insulin-stimulated glucose disposal. Counterregulatory hormones are not major contributors.

Placental adaptations in growth restriction

The placenta is the primary interface between the fetus and mother and plays an important role in maintaining fetal development and growth by facilitating the transfer of substrates and participating in modulating the maternal immune response to prevent immunological rejection of the conceptus. The major substrates required for fetal growth include oxygen, glucose, amino acids and fatty acids, and their transport processes depend on morphological characteristics of the placenta, such as placental size, morphology, blood flow and vascularity. Other factors including insulin-like growth factors, apoptosis, autophagy and glucocorticoid exposure also affect placental growth and substrate transport capacity. Intrauterine growth restriction (IUGR) is often a consequence of insufficiency, and is associated with a high incidence of perinatal morbidity and mortality, as well as increased risk of cardiovascular and metabolic diseases in later life. Several different experimental methods have been used to induce placental insufficiency and IUGR in animal models and a range of factors that regulate placental growth and substrate transport capacity have been demonstrated. While no model system completely recapitulates human IUGR, these animal models allow us to carefully dissect cellular and molecular mechanisms to improve our understanding and facilitate development of therapeutic interventions.

Developmental regulation of key gluconeogenic molecules in nonhuman primates

Aberrant glucose regulation is common in preterm and full‐term neonates leading to short and long‐term morbidity/mortality; however, glucose metabolism in this population is understudied. The aim of this study was to investigate developmental differences in hepatic gluconeogenic pathways in fetal/newborn baboons. Fifteen fetal baboons were delivered at 125 day (d) gestational age (GA), 140d GA, and 175d GA (term = 185d GA) via cesarean section and sacrificed at birth. Term and healthy adult baboons were used as controls. Protein content and gene expression of key hepatic gluconeogenic molecules were measured: cytosolic and mitochondrial phosphoenolpyruvate carboxykinase (PEPCK‐C and PEPCK‐M), glucose‐6‐phosphatase‐alpha (G6Pase‐α), G6Pase‐β, fructose‐1,6‐bisphosphatase (FBPase), and forkhead box‐O1 (FOXO1). Protein content of PEPCK‐M increased with advancing gestation in fetal baboons (9.6 fold increase from 125d GA to 175d GA, P < 0.001). PEPCK‐C gene expression was consistent with these developmental differences. Phosphorylation of FOXO1 was significantly lower in preterm fetal baboons compared to adults, and gene expression of FOXO1 was lower in all neonates when compared to adults (10% and 62% of adults respectively, P < 0.05). The FOXO1 target gene G6Pase expression was higher in preterm animals compared to term animals. No significant differences were found in G6Pase‐α, G6Pase‐β, FOXO1, and FBPase during fetal development. In conclusion, significant developmental differences are found in hepatic gluconeogenic molecules in fetal and neonatal baboons, which may impact the responses to insulin during the neonatal period. Further studies under insulin‐stimulated conditions are required to understand the physiologic impact of these maturational differences.

Significant developmental differences were found in several hepatic gluconeogenic molecules. In particular, phosphorylated FOXO1 was significantly reduced in the liver of premature fetal baboons compared to adults and may contribute the increased incidence of hyperglycemia seen in prematurity. In addition, PEPCK increased with advancing gestational age and may play a key role in glucose regulation during the newborn period.

Different expression of placental pyruvate kinase in normal, preeclamptic and intrauterine growth restriction pregnancies

INTRODUCTION

Preeclampsia (PE) and intrauterine growth restriction (IUGR) are two diseases that affect pregnant women and their unborn children. These diseases cause low birth weight, pre-term delivery, and neurological and cardiovascular disorders in babies. Combined they account for 20% of preterm deliveries. Pyruvate kinase M2 (PKM2) is a metabolism enzyme found in developing embryonic and cancer tissues. Our objective is to determine the expression of PKM2 in human PE and IUGR compared to normal pregnancies. Understanding expression of PKM2 in PE and IUGR could help us to better understand the mechanisms and find treatments for PE and IUGR.

METHODS

Human placental tissues were obtained for PKM2 determination and analyzed by immunohistochemistry, Western blot, and a pyruvate assay. Placental samples were homogenized and cytoplasmic and nuclear proteins were extracted for Western blot analysis.

RESULTS

Preeclampsia samples had elevated levels of p-PKM2, p-ERK, and ERK in the cytoplasm. Beta-catenin and lactose dehydrogenase (LDH) were also elevated in preeclampsia placenta samples.

DISCUSSION AND CONCLUSION

We conclude that PKM2 is expressed in normal, PE and IUGR pregnancies. Also, that this expression is increased in the PE placenta at delivery. These results suggest placental metabolism through PKM2 could play a role in human preeclampsia.

Dynamic proteomic profiles of in vivo- and in vitro-produced mouse postimplantation extraembryonic tissues and placentas

As the interface between the mother and the developing fetus, the placenta is believed to play an important role in assisted reproductive technology (ART)-induced aberrant intrauterine and postnatal development. However, the mechanisms underlying aberrant placentation remain unclear, especially during extraembryonic tissue development and early stages of placental formation. Using a mouse model, this investigation provides the first comparative proteomic analysis of in vivo (IVO) and in vitro-produced (IVP) extraembryonic tissues and placentas after IVO fertilization and development, or in vitro fertilization and culture, respectively. We identified 165 and 178 differentially expressed proteins (DEPs) between IVO and IVP extraembryonic tissues and placentas on Embryonic Day 7.5 (E7.5) and E10.5, respectively. Many DEPs were functionally associated with genetic information processing, such as impaired de novo DNA methylation, as well as posttranscriptional, translational and posttranslational dysregulation. These novel findings were further confirmed by global hypomethylation, and a lower level of correlation was found between the transcriptome and proteome in the IVP groups. In addition, numerous DEPs were involved in energy and amino acid metabolism, cytoskeleton organization and transport, and vasculogenesis and angiogenesis. These disturbed processes and pathways are likely to be associated with embryonic intrauterine growth restriction, an enlarged placenta, and impaired labyrinth morphogenesis. This study provides a direct and comprehensive reference for the further exploration of the placental mechanisms that underlie ART-induced developmental aberrations.

Placental gene expression patterns of endoglin (CD105) in intrauterine growth restriction

OBJECTIVE

In this study, we describe placental gene expression patterns of endoglin in pregnancies with intrauterine growth restriction (IUGR) compared to normal pregnancies.

METHODS

Placental samples were obtained from 101 pregnancies with IUGR using 140 normal pregnancy cases as control. Gene expression patterns and protein levels of the endoglin were compared between the two groups. For the gene expression analysis real-time PCR was applied, while for the estimation of placental protein level we performed Western analysis.

RESULTS

The placental endoglin gene was significantly overexpressed in the IUGR group versus the control group (Ln2(α): 1.69). The placental endoglin protein level proved to be significantly higher in case of IUGR (endoglin/β-actin ratio: 13.8 ± 2.3) versus the control cases (5.3 ± 1.1). The placental gene expression as well as the protein levels of endoglin showed no significant difference between female and male newborns. Concerning the placental gene expression and protein level, no significant difference was justified between the more (0-5 percentile) and less (5-10 percentile) severe cases of IUGR.

CONCLUSION

Increased placental gene expression of endoglin may result in vascular dysfunction leading to chronic fetal hypoxia, which may induce VEGF-A to stimulate angiogenesis. This can be explained as feed back response to restore fetal placental circulation.

Early prenatal food supplementation ameliorates the negative association of maternal stress with birth size in a randomised trial

Low birthweight increases the risk of infant mortality, morbidity and poor development. Maternal nutrition and stress influence birth size, but their combined effect is not known. We hypothesised that an early-invitation time to start a prenatal food supplementation programme could reduce the negative influence of prenatal maternal stress on birth size, and that effect would differ by infant sex. A cohort of 1041 pregnant women, who had delivered an infant, June 2003-March 2004, was sampled from among 3267 in the randomised controlled trial, Maternal Infant Nutritional Interventions Matlab, conducted in Matlab, Bangladesh. At 8 weeks gestation, women were randomly assigned an invitation to start food supplements (2.5 MJ d(-1) ; 6 days a week) either early (∼9 weeks gestation; early-invitation group) or at usual start time for the governmental programme (∼20 weeks gestation; usual-invitation group). Morning concentration of cortisol was measured from one saliva sample/woman at 28-32 weeks gestation to assess stress. Birth-size measurements for 90% of infants were collected within 4 days of birth. In a general linear model, there was an interaction between invitation time to start the food supplementation programme and cortisol with birthweight, length and head circumference of male infants, but not female infants. Among the usual-invitation group only, male infants whose mothers had higher prenatal cortisol weighed less than those whose mothers had lower prenatal cortisol. Prenatal food supplementation programmes that begin first trimester may support greater birth size of male infants despite high maternal stress where low birthweight is a public health concern.

The effects of intrauterine growth restriction and antenatal glucocorticoids on ovine fetal lung development

INTRODUCTION

Intrauterine growth restriction (IUGR) is associated with high rates of neonatal morbidity. IUGR babies are often born preterm and are, therefore, exposed to antenatal glucocorticoids. Antenatal glucocorticoids significantly improve overall survival rates of preterm infants, but there is a paucity of information about their effects on IUGR Infants.

METHODS

We induced IUGR in sheep by single umbilical artery ligation (SUAL), or sham in control fetuses. To half the ewes, we administered betamethasone (BM) on d 5 (BM1) and 6 (BM2) following surgery, and collected fetal lung tissue on d 7.

RESULTS

SUAL alone was associated with higher circulating fetal cortisol levels (2.8 ± 0.4 vs. 1.0 ± 0.4, P = 0.001) as compared with controls but not with changes in lung morphology or surfactant protein (SP) gene expression. BM was associated with a significant reduction in lung tissue density (P = 0.048). There were no significant differences between groups in lung DNA concentration or septal crest density. SP-A, SP-B, and SP-C gene expressions were significantly increased in control and SUAL fetuses that were administered BM.

DISCUSSION

These results show that in SUAL fetuses, maternal BM is associated with acceleration of fetal lung structure, as occurs in normally grown fetuses, and that BM induces SP production, an effect not observed in SUAL-induced IUGR fetuses alone.

Gene expression patterns of insulin-like growth factor 1, insulin-like growth factor 2 and insulin-like growth factor binding protein 3 in human placenta from pregnancies with intrauterine growth restriction

INTRODUCTION

In this study, we compared insulin-like growth factor (IGF)-gene expression patterns and characteristics of glucose and insulin metabolism in human placenta from pregnancies with or without intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

We compared 101 human placentas from intrauterine growth restriction pregnancies to those of 140 normal pregnancies treated at our department in a one-year period. We have also assessed the serum glucose and insulin levels of the IUGR and control groups. Several possible predicting factors of IUGR were also investigated.

RESULTS

Risk for IUGR was suggested by gestational weight gain and gestational increase in maternal body mass index (BMI) as well as maternal birthweight. In pregnancies without IUGR, umbilical cord glucose and insulin levels were significantly higher than in pregnancies with IUGR. In placentas from pregnancies with IUGR an overexpression of the IGF-2 and the insulin-like growth factor binding protein (IGFBP)-3 genes was found. In placentas from pregnancies with male fetal gender we found a significant overexpression of the IGF-2 gene.

DISCUSSION

Gestational weight gain and BMI increase seem to predict the development of IUGR. Insulin and carbohydrate metabolism are also impaired in IUGR fetuses. In the placentas from pregnancies with IUGR, IGF-2 is overexpressed reflecting its physiological role in optimizing energy distribution in a low-energy environment.

A low-protein diet during gestation in rats activates the placental mammalian amino acid response pathway and programs the growth capacity of offspring

Placental efficiency is a predictor of fetal growth and development, which is also controlled by maternal gestational health and diet. The present study investigated the effects of a gestational low-protein diet on offspring growth capacity as well as the diet's contribution to altered expression of placental genes associated with the mammalian amino acid response (AAR) pathway. To assess these outcomes, timed-pregnant Sprague Dawley rats were fed a control (C) diet with 18% protein or a low-protein (LP) diet with 9% protein throughout gestation (Expt. 1) or throughout gestation and lactation (Expt. 2). Placentas were collected during natural delivery and quantitative RT-PCR and Western-blot analyses were performed to determine placental mRNA and protein levels. By the end of the lactation period, offspring of dams fed the LP diet had stunted growth in both experiments. mRNA expression of target genes in the AAR pathway, such as activating transcription factor-3 (Atf3), asparagine synthetase (Asns), and Sodium-dependent neutral amino acid transporter-2 (Snat2), was greater in placentas of rats fed the LP diet compared with controls, as were placental ATF4 and p-eIF2α protein levels. The increase in mRNA expression of AAR pathway-associated genes was correlated with the stunting of offspring growth (Atf3: R(2) = 0.32, P = 0.086; Asns: R(2) = 0.44, P < 0.05; Snat2: R(2) = 0.33, P = 0.084). Our study showed that the mammalian AAR pathway in placenta is upregulated by a maternal low-protein diet and this activation may act as a cue for the fetus to develop an adaptive response suited to their predicted postnatal environment, i.e. a more favorable phenotype for their survival.

Impaired cell fusion and differentiation in placentae from patients with intrauterine growth restriction correlate with reduced levels of HERV envelope genes

One leading cause of perinatal morbidity and mortality is intrauterine growth restriction (IUGR). Several causes for IUGR have been proposed involving cytotrophoblast dysfunction. Envelope genes of the human endogenous retrovirus (HERV)-W (Syncytin-1), -FRD (Syncytin-2), and -P(b) have fusogenic properties, whereas envelope genes of HERV-R, -V1, and -V2 have putative placental functions. All six HERV envelope genes and three known cellular receptors were analyzed for expression in human control and IUGR placentae (n = 38) and in cultured cytotrophoblasts from control and IUGR (n = 8) placentae. All envelope genes demonstrated downregulation in IUGR compared to control placentae tissues, which were confirmed with cultured cytotrophoblasts. Examination of the Syncytin-1 and Syncytin-2 receptors ASCT-1/-2 and MFSD2 showed that MFSD2 was significantly expressed lower in IUGR than in control placentae and cytotrophoblasts. A reduction of Syncytin-1 protein expression was confirmed for IUGR placentae with immunoblotting and paraffin tissue sections. Embedded placental IUGR tissues showed an overall disorganized syncytiotrophoblast layer with fewer nuclei. Cytotrophoblasts from IUGR placentae demonstrated a lower cell fusion index and nuclei per syncytiotrophoblast in vitro. Fusogenic and non-fusogenic envelope genes are dysregulated in IUGR placentae and may contribute to the etiology of growth restriction in utero.

Placental gene expression is related to glucose metabolism and fetal cord blood levels of insulin and insulin-like growth factors in intrauterine growth restriction

Despite the importance of glucose for fetal growth, placental gene expression related to the glycolytic pathway has not been studied. Insulin-like growth factors (IGFs) and insulin are known to play a critical role in fetal growth. In our study, we identified differentially expressed genes related to the glycolytic pathway using oligonucleotide microarray analysis and confirmed these genes with quantitative real-time PCR between uncomplicated pregnancies and pregnancies with intrauterine growth restriction (IUGR). We also compared the concentrations of insulin and IGFs in cord blood between the two groups. Microarray experiments identified increased expression of glycolytic enzyme-related genes, including lactate dehydrogenase C (LDHC), dihydrolipoamide S-acetyltransferase (DLAT), 6 phosphofructo-2-kinase/fructose-2, 6-biphosphatase 2 (PFKFB2), oxoglutarate dehydrogenase, phosphorylase, and insulin-like growth factor (IGF)-II and decreased expression of IGF-I in placentas from pregnancies with IUGR (p<0.05). There were significantly lower concentrations of glucose, insulin, IGF-1, and IGF-II in the fetal cord blood of pregnancies with IUGR (p<0.05). Microarray analysis revealed increased expression of enzyme genes related to the tricarboxylic acid cycle pathway in placentas from pregnancies with IUGR; the cause of hypoglycaemia in IUGR is attributed to increased glycolytic pathway activity in placentas from pregnancies with IUGR.

Differential Expression of Glucose Transporters in Rabbit Placenta: Effect of Hypercholesterolemia in Dams1

Low birth weight is observed in rabbit offspring when maternal hypercholesterolemia is induced during gestation, but the related etiology is still unknown. Glucose is one of the most important substances during fetal development, and defect in glucose supply to fetus was related to pathophysiological mechanisms in intrauterine growth restriction. Thus, the aim of this work was to evaluate the impact of maternal hypercholesterolemia during rabbit gestation on the glucose metabolism and the routing of glucose transporters (SLC2 and SLC5 [previously known as GLUT and SGLT]) in placenta. In this study, maternal and offspring serum levels of glucose and insulin were evaluated for control and hypercholesterolemic groups, and the mRNA and protein expressions of placental SLCs were quantified by real-time RT-PCR and Western immunoblot, respectively. Our data demonstrate that maternal hypercholesterolemia during gestation: 1) induces offspring hypoglycemia; 2) does not modify the genetic and protein expressions of SLC2A1 and SLC2A4 (previously GLUT1 and GLUT4) in total placental extract; 3) downregulates the placental SLC5A1 (previously SGLT1) protein expression without affecting its mRNA levels; 4) impairs the translocation of SLC2A1 but not SLC2A4 from cytoplasmatic pool to the cell membrane surface. Then we assume that reduction of offspring birth weight in presence of maternal hypercholesterolemia may be related to the offspring's hypoglycemia and the reduction of the cell surface expression of placental SLC2A1.

[Biochemical profile of fetal blood sampled by cordocentesis in 35 pregnancies complicated by growth retardation]

AIM OF THE STUDY

Intra-uterine growth retardation (IUGR) is a frequent pathology in obstetrics characterized by high heterogeneity. Fetal smallness is sometimes constitutional, but can also be accompanied by fetal distress and vital risks for the infant. In 35 pregnancies complicated by IUGR of different etiologies, we measured on fetal blood obtained by cordocentesis, biochemical variables characteristic of the fetuses' respiratory and metabolic status. The aim of the study was to identify the discriminative biological alterations, related to growth retardation and fetal distress.

PATIENTS AND METHODS

The studied population includes 27 cases of severe IUGR, of gestational age 30,2+/-4,6 weeks of gestation (WG) (divided into 20 cases of isolated IUGR and 7 cases of IUGR associated with malformative syndrome), as well as 8 cases of moderate IUGR, of gestational age 26+/-4,5 WG; all fetuses had normal karyotypes. A group of 73 normal fetuses, of gestational age 26,3+/-5,7 WG, constituted a reference population. PH, pCO(2), bicarbonate concentration, pO(2) and SaO(2), as well as glucose, pyruvate, lactate, free fatty acids, aceto-acetate, beta-hydroxybutyrate and cholesterol concentrations were measured on umbilical venous blood (UVB).

RESULTS

In case of severe but isolated growth retardation, UVB analysis showed the frequency of acid-base and gasometric disturbances: acidemia and hypoxemia (65% of cases), hypercapnia (60% of cases). Metabolic abnormalities were shown: decrease in glycemia (35% of cases), increase in pyruvatemia and lactatemia (40% of cases), increased free fatty acids serum concentration; a diminution of umbilical venous cholesterol level, the most frequent abnormality, can be seen in 70% of fetuses. In case of severe IUGR associated with malformative syndrome, UVB acid-base and metabolic changes were rarely seen; however, UVB cholesterol level is low in some cases. In case of growth retardation classified as moderate, modifications are relatively not frequent and essentially gasometric.

CONCLUSION

In about 60% of cases of severe and isolated IUGR, there is a risk of fetal distress, related to an alteration of the transplacental transfer of respiratory gases and nutritional substrates; chronic fetal malnutrition can be involved, with an impact on the growth of the fetus. In case of IUGR associated with malformative syndrome, fetal smallness is probably a result of intrinsic fetal damage, without nutritional origin.