Detection and cellular localization of plasma membrane-associated and cytoplasmic fatty acid-binding proteins in human placenta

Triphenyl phosphate interferes with the synthesis of steroid hormones through the PPARγ/CD36 pathway in human trophoblast JEG-3 cells

Triphenyl phosphate (TPhP), a chemical commonly found in human placenta and breast milk, has been shown to disturb the endocrine system. Our previous study confirmed that TPhP could accumulate in the placenta and interference with placental lipid metabolism and steroid hormone synthesis, as well as induce endoplasmic reticulum (ER) stress through PPARγ in human placental trophoblast JEG-3 cells. However, the molecular mechanism underlying this disruption remains unknown. Our study aimed to identify the role of the PPARγ/CD36 pathway in TPhP-induced steroid hormone disruption. We found that TPhP increased lipid accumulation, total cholesterol, low- and high-density protein cholesterol, progesterone, estradiol, glucocorticoid, and aldosterone levels, and genes related to steroid hormones synthesis, including 3βHSD1, 17βHSD1, CYP11A, CYP19, and CYP21. These effects were largely blocked by co-exposure with either a PPARγ antagonist GW9662 or knockdown of CD36 using siRNA (siCD36). Furthermore, an ER stress inhibitor 4-PBA attenuated the effect of TPhP on progesterone and glucocorticoid levels, and siCD36 reduced ER stress-related protein levels induced by TPhP, including BiP, PERK, and CHOP. These findings suggest that ER stress may also play a role in the disruption of steroid hormone synthesis by TPhP. As our study has shed light on the PPARγ/CD36 pathway's involvement in the disturbance of steroid hormone biosynthesis by TPhP in the JEG-3 cells, further investigations of the potential impacts on the placental function and following birth outcome are warranted.

The role of aryl hydrocarbon receptors in nutrient metabolism and immune regulation at the maternal-fetal interface

The maternal-fetal interface is composed of the placenta, which is affiliated with the fetus, and the maternal decidua. During pregnancy, the placenta is mainly responsible for nutrient transport and immune tolerance maintenance, which plays a key role in fetal growth and development and pregnancy maintenance. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that exists in various cell types at the maternal-fetal interface and is involved in multiple cellular processes. Recent studies have highlighted the role of AhR in regulating various physiological processes, including glucose and lipid metabolism, as well as tryptophan metabolism and immune responses, within non-pregnant tissues. This review shifts focus towards understanding how AhR modulation impacts metabolism and immune regulation at the maternal-fetal interface. This may implicate the development of pregnancy-related complications and the potential target of the AhR pathway for therapeutic strategies against poor pregnancy outcomes.

Evaluation of amniotic fluid neutrophil gelatinase-associated lipocalin and L-type fatty acid-binding protein levels during pregnancy

Objective

We aimed to examine amniotic fluid neutrophil gelatinase-associated lipocalin (NGAL) and L-type fatty acid-binding protein (L-FABP) levels during pregnancy.

Study design

This study included singleton pregnancies. Amniotic fluid samples were collected at the time of vaginal delivery, cesarean section, amniocentesis, amnioreduction, and amnioinfusion. We analyzed changes of the NGAL and L-FABP levels during pregnancy and the factors affecting these values and their association with clinical outcomes.

Results

Three hundred and one pregnancies were analyzed. Respective Pearson correlation coefficients for the NGAL and L-FABP levels and gestational age at inspection were - 0.351 and - 0.819 (p <0.001 and p < 0.001, respectively); weak and strong negative correlation were observed. The NGAL level was significantly higher in the intra-amniotic infection group than in the control group (p < 0.001). The L-FABP level was significantly higher in the fetal blood flow abnormalities group than in the control group (p < 0.001). The NGAL and L-FABP levels were significantly higher in the adverse outcomes group than in the control group (p = 0.019 and p < 0.001, respectively), and the respective areas under the concentration-time curve, with optimal cutoff values, for the NGAL and L-FABP levels were 0.693 (14,800 µg/gCr) and 0.864 (378 µg/gCr).

Conclusions

Amniotic fluid NGAL and L-FABP levels reflect fetal and neonatal immaturity. Additionally, the NGAL level is a useful predictive factor of intra-amniotic infection, and the L-FABP level is a useful predictive factor of fetal condition and short- and long-term prognoses.

DHA supplementation and pregnancy complications

Docosahexaenoic acid (DHA) supplementation is recommended for women during pregnancy because of its neurological, visual, and cognitive effects. Previous studies have suggested that DHA supplementation during pregnancy may prevent and treat certain pregnancy complications. However, there are contradictions in the current related studies, and the specific mechanism by which DHA acts remains unclear. This review summarizes the research on the relationship between DHA intake during pregnancy and preeclampsia, gestational diabetes mellitus, preterm birth, intrauterine growth restriction, and postpartum depression. Furthermore, we explore the impact of DHA intake during pregnancy on the prediction, prevention, and treatment of pregnancy complications as well as its impact on offspring neurodevelopment. Our results suggest that there is limited and controversial evidence for the protective effect of DHA intake on pregnancy complications, with the exception of preterm birth and gestational diabetes mellitus. However, additional DHA supplementation may improve long-term neurodevelopmental outcomes in the offspring of women with pregnancy complications.

Cytoplasmic fatty acid-binding proteins in metabolic diseases and cancers

Cytoplasmic fatty acid-binding proteins (FABPs) are multipurpose proteins that can modulate lipid fluxes, trafficking, signaling, and metabolism. FABPs regulate metabolic and inflammatory pathways, its inhibition can improve type 2 diabetes mellitus and atherosclerosis. In addition, FABPs are involved in obesity, metabolic disease, cardiac dysfunction, and cancers. FABPs are promising tissue biomarkers in solid tumors for diagnostic and/or prognostic targets for novel therapeutic strategies. The signaling responsive elements of FABPs and determinants of FABP-mediated functions may be exploited in preventing or treating these diseases.

The mystery of the life tree: the placenta

The placenta is the interface between the fetal and maternal environments during mammalian gestation, critically safeguarding the health of the developing fetus and the mother. Placental trophoblasts origin from embryonic trophectoderm that differentiates into various trophoblastic subtypes through villous and extravillous pathways. The trophoblasts actively interact with multiple decidual cells and immune cells at the maternal-fetal interface and thus construct fundamental functional units, which are responsible for blood perfusion, maternal-fetal material exchange, placental endocrine, immune tolerance, and adequate defense barrier against pathogen infection. Various pregnant complications are tightly associated with the defects in placental development and function maintenance. In this review, we summarize the current views and our recent progress on the mechanisms underlying the formation of placental functional units, the interactions among trophoblasts and various uterine cells, as well as the placental barrier against pathogen infections during pregnancy. The involvement of placental dysregulation in adverse pregnancy outcomes is discussed.

Adiponectin Deficiency Alters Placenta Function but Does Not Affect Fetal Growth in Mice

Adiponectin administration to pregnant mice decreases nutrient transport and fetal growth. An adiponectin deficiency, on the other hand, as seen in obese women during pregnancy, alters fetal growth; however, the mechanism is unclear. To determine the role of adiponectin on placenta function and fetal growth, we used adiponectin knockout, adiponectin heterozygote that displays reduced adiponectin levels, and wild-type mice on a control diet or high fat/high sucrose (HF/HS) diet. Triglycerides (TGs) in the serum, liver, and placenta were measured using colorimetric assays. Gene expression was measured using quantitative RT-PCR. Adiponectin levels did not affect fetal weight, but it reduced adiponectin levels, increased fetal serum and placenta TG content. Wildtype dams on a HF/HS diet protected the fetuses from fatty acid overload as judged by increased liver TGs in dams and normal serum and liver TG levels in fetuses, while low adiponectin was associated with increased fetal liver TGs. Low maternal adiponectin increased the expression of genes involved in fatty acid transport; Lpl and Cd36 in the placenta. Adiponectin deficiency does not affect fetal growth but induces placental dysfunction and increases fetal TG load, which is enhanced with obesity. This could lead to imprinting effects on the fetus and the development of metabolic dysfunction in the offspring.

Perinatal Dietary Polyunsaturated Fatty Acids in Brain Development, Role in Neurodevelopmental Disorders

n-3 and n-6 polyunsaturated fatty acids (PUFAs) are essential fatty acids that are provided by dietary intake. Growing evidence suggests that n-3 and n-6 PUFAs are paramount for brain functions. They constitute crucial elements of cellular membranes, especially in the brain. They are the precursors of several metabolites with different effects on inflammation and neuron outgrowth. Overall, long-chain PUFAs accumulate in the offspring brain during the embryonic and post-natal periods. In this review, we discuss how they accumulate in the developing brain, considering the maternal dietary supply, the polymorphisms of genes involved in their metabolism, and the differences linked to gender. We also report the mechanisms linking their bioavailability in the developing brain, their transfer from the mother to the embryo through the placenta, and their role in brain development. In addition, data on the potential role of altered bioavailability of long-chain n-3 PUFAs in the etiologies of neurodevelopmental diseases, such as autism, attention deficit and hyperactivity disorder, and schizophrenia, are reviewed.

Revisiting preeclampsia: a metabolic disorder of the placenta

Preeclampsia (PE) is a leading cause of maternal and neonatal mortality and morbidity worldwide, impacting the long-term health of both mother and offspring. PE has long been characterized by deficient trophoblast invasion into the uterus and consequent placental hypoperfusion, yet the upstream causative factors and effective interventional targets for PE remain unknown. Alterations in the metabolism of preeclamptic placentas are thought to result from placental ischemia, while disturbances of the metabolism and of metabolites in PE pathogenesis are largely ignored. In fact, as one of the largest fetal organs at birth, the placenta consumes a considerable amount of glucose and fatty acid. Increasing evidence suggests glucose and fatty acid exist as energy substrates and regulate placental development through bioactive derivates. Moreover, recent findings have revealed that the placental metabolism adapts readily to environmental changes, altering its response to nutrients and endocrine signals; this adaptability optimizes pregnancy outcomes by diversifying available carbon sources for energy production, hormone synthesis, angiogenesis, immune activation, and tolerance, and fetoplacental growth. These observations raise the possibility that carbohydrate and lipid metabolism abnormalities play a role in both the etiology and clinical progression of PE, sparking a renewed interest in the interrelationship between PE and metabolic dysregulation. This review will focus on key metabolic substrates and regulatory molecules in the placenta and aim to provide novel insights with respect to the metabolism's role in modulating placental development and functions. Further investigations from this perspective are poised to decipher the etiology of PE and suggest potential therapies.

Maternal Docosahexaenoic Acid Status during Pregnancy and Its Impact on Infant Neurodevelopment

Dietary components are essential for the structural and functional development of the brain. Among these, docosahexaenoic acid, 22:6n-3 (DHA), is critically necessary for the structure and development of the growing fetal brain in utero. DHA is the major n-3 long-chain polyunsaturated fatty acid in brain gray matter representing about 15% of all fatty acids in the human frontal cortex. DHA affects neurogenesis, neurotransmitter, synaptic plasticity and transmission, and signal transduction in the brain. Data from human and animal studies suggest that adequate levels of DHA in neural membranes are required for maturation of cortical astrocyte, neurovascular coupling, and glucose uptake and metabolism. Besides, some metabolites of DHA protect from oxidative tissue injury and stress in the brain. A low DHA level in the brain results in behavioral changes and is associated with learning difficulties and dementia. In humans, the third trimester-placental supply of maternal DHA to the growing fetus is critically important as the growing brain obligatory requires DHA during this window period. Besides, DHA is also involved in the early placentation process, essential for placental development. This underscores the importance of maternal intake of DHA for the structural and functional development of the brain. This review describes DHA’s multiple roles during gestation, lactation, and the consequences of its lower intake during pregnancy and postnatally on the 2019 brain development and function.

The Impact of Maternal Body Composition and Dietary Fat Consumption upon Placental Lipid Processing and Offspring Metabolic Health

The proportion of women of reproductive age who are overweight or obese is increasing globally. Gestational obesity is strongly associated in both human studies and animal models with early-onset development of adult-associated metabolic diseases including metabolic syndrome in the exposed offspring. However, animal model studies have suggested that gestational diet in obese pregnancies is an independent but underappreciated mediator of offspring risk for later life metabolic disease, and human diet consumption data have highlighted that many women do not follow nutritional guidelines prior to and during pregnancy. Thus, this review will highlight how maternal diet independent from maternal body composition impacts the risk for later-life metabolic disease in obesity-exposed offspring. A poor maternal diet, in combination with the obese metabolic state, are understood to facilitate pathological in utero programming, specifically through changes in lipid handling processes in the villous trophoblast layer of the placenta that promote an environment associated with the development of metabolic disease in the offspring. This review will additionally highlight how maternal obesity modulates villous trophoblast lipid processing functions including fatty acid transport, esterification and beta-oxidation. Further, this review will discuss how altering maternal gestational diet may ameliorate these functional changes in lipid metabolic processes in the obese placenta.

Placental function in maternal obesity

Maternal obesity is associated with pregnancy complications and increases the risk for the infant to develop obesity, diabetes and cardiovascular disease later in life. However, the mechanisms linking the maternal obesogenic environment to adverse short- and long-term outcomes remain poorly understood. As compared with pregnant women with normal BMI, women entering pregnancy obese have more pronounced insulin resistance, higher circulating plasma insulin, leptin, IGF-1, lipids and possibly proinflammatory cytokines and lower plasma adiponectin. Importantly, the changes in maternal levels of nutrients, growth factors and hormones in maternal obesity modulate placental function. For example, high insulin, leptin, IGF-1 and low adiponectin in obese pregnant women activate mTOR signaling in the placenta, promoting protein synthesis, mitochondrial function and nutrient transport. These changes are believed to increase fetal nutrient supply and contribute to fetal overgrowth and/or adiposity in offspring, which increases the risk to develop disease later in life. However, the majority of obese women give birth to normal weight infants and these pregnancies are also associated with activation of inflammatory signaling pathways, oxidative stress, decreased oxidative phosphorylation and lipid accumulation in the placenta. Recent bioinformatics approaches have expanded our understanding of how maternal obesity affects the placenta; however, the link between changes in placental function and adverse outcomes in obese women giving birth to normal sized infants is unclear. Interventions that specifically target placental function, such as activation of placental adiponectin receptors, may prevent the transmission of metabolic disease from obese women to the next generation.

Role of adipose tissue in regulating fetal growth in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a global health issue with significant short and long-term complications for both mother and baby. There is a strong need to identify an effective therapeutic that can prevent the development of GDM. A better understanding of the pathophysiology of GDM and the relationship between the adipose tissue, the placenta and fetal growth is required. The placenta regulates fetal growth by modulating nutrient transfer of glucose, amino acids and fatty acids. Various factors secreted by the adipose tissue, such as adipokines, adipocytokines and more recently identified extracellular vesicles, can influence inflammation and interact with placental nutrient transport. In this review, the role of the placental nutrient transporters and the adipose-derived factors that can influence their function will be discussed. A better understanding of these factors and their relationship may make a potential target for therapeutic interventions to prevent the development of GDM and its consequences.

Peroxisome proliferator-activated receptor β/δ and γ agonists differentially affect prostaglandin E2 and cytokine synthesis and nutrient transporter expression in porcine trophoblast cells during implantation

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor family of ligand-dependent transcription factors. PPARs have been shown to be important regulators of female reproductive functions, including conceptus development and placenta formation. This study examines the effect of PPARβ/δ and PPARγ agonists and antagonists on (1) the synthesis of prostaglandin (PG) E2, interleukin (IL) 6, interferon (IFN) γ, and tumor necrosis factor (TNF) α and (2) the mRNA expression of genes encoding nutrient transporters and/or binding proteins in Day 15 conceptus trophoblast cells. The study also examines whether PPAR agonist-modulated IL6, IFNγ, and TNFα secretion is mediated via mitogen-activated protein kinase (MAPK) pathways. Trophoblast cells were exposed to L-165,041 (a PPARβ/δ agonist) or rosiglitazone (a PPARγ agonist) in the presence or absence of GSK3787 (a PPARβ/δ antagonist) or GW9662 (a PPARγ antagonist) or in the presence or absence of U0126 (a MAPK inhibitor). Rosiglitazone stimulated PGE synthase and IFNG mRNA expression in trophoblast cells and enhanced PGE2 concentrations in the incubation medium. Moreover, cells treated with rosiglitazone exhibited increased abundance of the solute carrier organic anion transporter family member 2A1 (SLCO2A1, a PG transporter) and of fatty acid binding protein (FABP) 5 transcripts. All these effects were abolished by the addition of GW9662, which indicates that the action of rosiglitazone is PPARγ-dependent in the studied cells. L-165,041 inhibited TNFα synthesis and decreased the mRNA expression of FABP3 and IL6 in trophoblast cells. However, this effect was not abolished by the addition of GSK3787 into the incubation medium, suggesting that L-165,041 action is independent of PPARβ/δ. The inhibitory effect of L-165,041 on TNFα concentration and the stimulatory effect of rosiglitazone on IFNγ accumulation in the medium were not observed in the presence of the MAPK inhibitor, suggesting that the action of both agonists may be mediated by MAPKs. In conclusion, PPARβ/δ and PPARγ agonists are differentially involved in the trophoblast expression of genes related to conceptus development and implantation in pigs. Furthermore, L-165,041 and rosiglitazone may have PPAR-dependent and -independent effects in conceptus trophoblast cells.

Changes in Placental Nutrient Transporter Protein Expression and Activity Across Gestation in Normal and Obese Women

Fetal growth and development are dependent on placental nutrient transport. The syncytiotrophoblast (ST) and its two polarized plasma membranes, the maternal-facing microvillous membrane (MVM) and fetal-facing basal membrane (BM), represent the primary barrier in the human placenta, controlling transplacental transfer of small solutes. MVM and BM nutrient transporter expression and activity are increased in obese mothers delivering large babies. However, placental nutrient transporter expression and activity in early gestation in normal and obese women are largely unknown. Placentas from normal BMI and obese women at 6-24 weeks of gestation, and term placentas from normal BMI women, were collected and ST plasma membranes isolated. The activity and protein expression of amino acid, glucose, and fatty acid transporters was assessed. No significant differences were observed in placental nutrient transporter protein expression between normal BMI and obese women in early pregnancy. In the MVM, system A amino acid activity (p = 0.02), SNAT2 (p < 0.0001), SNAT4 (p < 0.001), and GLUT1 (p = 0.01) protein expression were higher at term compared with early gestation. In contrast, MVM system L activity (p = 0.001), FATP4 (p = 0.03), and FATP6 (p = 0.009) protein expression were lower at term compared with early pregnancy. In the BM, there was no change in system L activity across gestation; however, BM FATP6 (p = 0.002) protein expression was lower at term compared with early pregnancy. These results suggest that placental transport of amino acids, glucose, and fatty acids are subjected to coordinated regulation across gestation to meet a fetal nutrient demand that changes with advancing pregnancy.

Expression and role of peroxisome proliferator-activated receptors in the porcine early placenta trophoblast

Peroxisome proliferator-activated receptors (PPARs) are members of a nuclear receptor family of ligand-dependent transcription factors. Three isoforms of PPAR named PPARα, PPARβ/δ, and PPARγ have been described, each encoded by a separate gene: PPARA, PPARD, and PPARG, respectively. In the present study, we examined the profiles of PPAR and retinoid X receptor (RXR; PPAR heterodimer partner) mRNA expression and PPAR DNA binding activity in porcine trophoblast tissue collected on days 15, 20, 25, and 30 of pregnancy and in day-20 embryos. Placenta trophoblast cells isolated on day 25 of pregnancy were used to determine effects of (1) cytokines on PPAR and RXR mRNA expression and (2) PPAR agonists on prostaglandin (PG) E2 synthesis and the expression of genes involved in steroidogenesis, fatty acid binding, and PG transport, as well as on cell proliferation. The mRNA expression of PPARA and RXRB was greater in trophoblast tissue collected on days 25 and 30 of pregnancy compared with day 15 (P < 0.05), while DNA binding activity of PPARα decreased between day 15 and 25 (P < 0.05). Increased concentrations of PPARD and RXRA transcripts were observed in trophoblasts collected on day 20 compared to trophoblasts from days 15 and 30 (P < 0.05). Moreover, concentrations of DNA-bound PPARβ/δ and PPARγ proteins increased in day-30 trophoblasts compared to day 15 (P < 0.01) and day 20 (P < 0.05), respectively. On day 20 of gestation, the mRNA expression of PPARD, PPARG, and RXRA and protein levels of PPARα and PPARγ isoforms were greater in trophoblast than embryonic tissue (P < 0.01). Interleukin 1β and/or interferon γ, but not IL6 and leukemia inhibitory factor, upregulated PPAR and RXR mRNA expression in placenta trophoblast cells in vitro (P < 0.05). Rosiglitazone (a PPARγ agonist) stimulated prostaglandin E synthase mRNA expression in trophoblast cells and PGE2 accumulation in incubation medium (P < 0.05). Moreover, activation of PPAR isoforms differentially affected the expression of genes involved in steroidogenesis, fatty acid binding, and PG transport in studied cells. Finally, PPARα and PPARγ agonists stimulated trophoblast cell proliferation (P < 0.05), and this effect was abolished by the addition of a respective PPAR antagonist (P < 0.05). Overall, these results point to a role of PPAR isoforms in porcine placenta development and function.

Loss of Aquaporin-3 in Placenta and Fetal Membranes Induces Growth Restriction in Mice

Aquaporin (AQP) 3, a facilitated transporter of water and glycerol, expresses in placenta and fetal membranes, but the detailed localization and function of AQP3 in placenta remain unclear. To elucidate a role of AQP3 in placenta, we defined the expression and cellular localization of AQP3 in placenta and fetal membranes, and investigated the structural and functional differences between wild-type and AQP3 null mice. Gestational sacs were removed during mid-gestational period and amniotic fluid was aspirated for measurements of volume and composition. Fetuses with attached placenta and fetal membranes were weighed and processed for histological assessment. AQP3 strongly expressed in basolateral membrane of visceral yolk sac cells of fetal membrane, the syncytiotrophoblasts of the labyrinthine placenta and fetal nucleated red blood cell membrane. Mice lacking AQP3 did not exhibit a significant defect in differentiation of trophoblast stem cells and normal placentation. However, AQP3 null fetuses were smaller than their control litter mates in spite of a decrease in litter size. The total amniotic fluid volume per gestational sac was reduced, but the amniotic fluid-to-fetal weight ratio was increased in AQP3 null mice compared with wild-type mice. Glycerol, free fatty acid and triglyceride levels in amniotic fluid of AQP3 null mice were significantly reduced, whereas lactate level increased when compared to those of wild-type mice. These results suggest a role for AQP3 in supplying nutrients from yolk sac and maternal blood to developing fetus by facilitating transport of glycerol in addition to water, and its implication for the fetal growth in utero.

Fatty acid transporting proteins: Roles in brain development, aging, and stroke

Polyunsaturated fatty acids are required for the brain development and significantly impact aging and stroke. Due to the hydrophobicity of fatty acids, fatty acids transportation related proteins that include fatty acid binding proteins (FABPs), long chain acyl-coA synthase (ACS), fatty acid transportation proteins (FATPs), fatty acid translocase (FAT/CD36) and newly reported major facilitator superfamily domain-containing protein (Mfsd2a) play critical roles in the uptake of various fatty acids, especially polyunsaturated fatty acids. They are not only involved in neurodevelopment, but also have great impact on neurological disease, such as aging related dementia and stroke.

Differential Long-Chain Polyunsaturated Fatty Acids Status and Placental Transport in Adolescent Pregnancies

Adolescent pregnancy increases risk of adverse perinatal outcomes. Placental delivery of long-chain polyunsaturated fatty acids (LCPUFA) is essential for fetal growth and development. In this pilot study, we aimed to assess maternal and fetal status of fatty acids (FA) measured at birth and the expression of key genes involved in FA uptake, transport and metabolism in the placenta of fifteen adolescents and fifteen adults. FA were quantified by gas-liquid chromatography. Placental expression of FA transporters was assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and peroxisome proliferator-activated receptor gamma (PPARγ) was quantified by Western Blot. Adolescents had lower docosahexaenoic acid (DHA, 22:6 n-3) and total n-3 FA levels in maternal erythrocytes and placenta, but these were not different in fetal erythrocytes. Arachidonic acid (AA, 20:4 n-6) concentration was increased in placenta but lower in fetal circulation. Plasma membrane fatty acid binding protein (FABPpm) and fatty acid transport protein (FATP) 4 mRNA expressions were not different, however FATP1, fatty acid translocase (FAT/CD36) and fatty acid binding protein 3 (FABP3) mRNA and PPARγ protein levels were decreased in placenta of adolescents. Despite significant downregulation of FATP1, CD36 and FABP3, there was only a modest decrease in LCPUFA (10%) and AA (12%) and no difference in DHA content in cord blood, suggesting that FA transfer to the fetus was partially protected by other factors in adolescents from this cohort.

Distribution of Fatty Acids and Lipids During Pregnancy

Maternal fatty acid and lipid metabolism undergoes changes during pregnancy to facilitate fetal growth and development. Different types of fatty acids have different roles in maintaining a successful pregnancy and they are incorporated into different forms of lipids for the purpose of storage and transport. This chapter aims to provide an understanding of the distribution and metabolism of fatty acids and lipids in the maternal, placental, and fetal compartments. We further describe how this distribution is altered in maternal obesity, preterm birth, and pregnancy complications such as gestational diabetes mellitus, preeclampsia, and intrauterine growth restriction.

Effects of Prenatal Nutrition and the Role of the Placenta in Health and Disease

Epidemiologic studies identified the linkage between exposures to stresses, including the type and plane of nutrition in utero with development of disease in later life. Given the critical roles of the placenta in mediating transport of nutrients between the mother and fetus and regulation of maternal metabolism, recent attention has focused on the role of the placenta in mediating the effect of altered nutritional exposures on the development of disease in later life. In this chapter we describe the mechanisms of nutrient transport in the placenta, the influence of placental metabolism on this, and how placental energetics influence placental function in response to a variety of stressors. Further the recent "recognition" that the placenta itself has a sex which affects its function may begin to help elucidate the mechanisms underlying the well-known dimorphism in development of disease in adult life.

Isolation and Purification of Villous Cytotrophoblast Cells from Term Human Placenta

The placenta is a key element during pregnancy for the health of the fetus and the mother, which justifies why placental studies are so important. One of the best models for placental studies is the primary cell culture of cytotrophoblast cells from human term placentas. In this chapter, we will detail firstly the isolation of cytotrophoblast cells, with tissue preparation, digestion, Percoll gradient, and cell freezing, and secondly the cell immunopurification and seeding.

Fatty acid transporter expression and regulation is impaired in placental macrovascular endothelial cells in obese women

OBJECTIVE

Fetal fatty acid (FA) delivery is ultimately controlled by placental transport. Focus has been the maternal-placental interface, but regulation at the feto-placental interface is unknown.

METHODS

Placental macrovascular endothelial cells (EC) (n = 4/group) and trophoblasts (TB) (n = 5/group) were isolated from lean (pregravid BMI <25 kg/m²) and obese (body mass index (BMI) > 30) women. Fatty acid transporters FAT/CD36, FABPpm, FATP4, FABP 3, 4 and 5, PLIN2 and PPARα, δ, γ expression, was measured in EC and TB. Transporter response to 24 h palmitate (PA) was assessed.

RESULTS

mRNA expression of FABP3, 4, 5 and PPARγ was 2- to 3-fold reduced in EC of obese versus lean women (p < .03), but not in TB. Protein level of FABPpm was 20% lower in obese (p < .05). Palmitate (PA) up-regulated CD36, FABP3, FABP4, and PLIN2 gene expression by 3- to 4-fold in lean but not obese EC (p < .05), while PA increased FABP4 and PLIN2 in lean and obese TB, and FABP5 in lean (p < .05) EC. PA exposure up-regulated peroxisome proliferator activated receptors (PPARs) 2-fold in lean and obese EC (p < .05), but not in TB.

CONCLUSIONS

In obese women, FA transporter expression is lower in placental EC, but not TB, and less sensitive to saturated FA, compared to lean women. FA transport may be regulated at the feto-placental interface.

Fatty acid-binding protein3 expression in BeWo cells, a human placental choriocarcinoma cell line

Cellular uptake of long chain fatty acids in human placental trophoblasts is thought to be mediated by several membrane- and cytoplasmic fatty acid-binding proteins (FABP). FABP3 was shown to be involved in long chain polyunsaturated fatty acids (LCPUFA) uptake in human trophoblastic choriocarcinoma cells, BeWo as the uptake of arachidonic acid,20:4n-6 (ARA) was decreased in FABP3-knockdown BeWo cells. However, the regulation of expression of FABP3 in these cells is not yet well known. The aim of the present study was to examine the FABP3 expression by LCPUFAs, insulin and LXR agonists in BeWo cells. Among all these fatty acids tested, only ARA dose-dependently stimulated the expression of FABP3 protein in these cells after 24h incubation while other fatty acids had no such effect. In addition, LXR agonist and insulin dose-dependently increased FABP3 protein expression in these cells after 24h incubation. Insulin-stimulated FABP3 protein expression was accompanied with an increased arachidonic acid uptake. Differentiated BeWo cells had lesser expression of FABP3 protein than in the undifferentiated cells as the cellular differentiation state was measured by hCG production. In preeclamptic placental tissue, lowered expression of FABP3 protein was observed compared with those in normal pregnancy. All these data indicate that FABP3 may in be part involved in ARA uptake in these cells and its expression may be regulated by ARA, insulin, LXR and the state of cellular differentiation.

Prepartum maternal diets supplemented with oilseeds alter the fatty acid profile in bovine neonatal plasma possibly through reduced placental expression of fatty acid transporter protein 4 and fatty acid translocase

In the present study, we determined the effects of maternal dietary fat and the type of fat on plasma fatty acids and the expression of placental fatty acid transporter genes. In Experiment 1, Holstein cows in the last 35 days of gestation received diets containing sunflower seed (n = 8; high in linoleic acid (LA)), canola seed (n = 7; high in oleic acid (OLA)) or no oilseed (n = 7; control). Fatty acids were quantified in dam and neonate plasma at calving. In Experiment 2, placental cotyledons were collected (LA: n = 4; OLA: n = 4; control: n = 5) to quantify gene expression. Maternal long-chain polyunsaturated fatty acids, neonatal total n-3 fatty acids and eicosapentaenoic acid (EPA) declined, whereas docosahexaenoic acid (DHA) and total fat tended to decline following fat supplementation prepartum. Feeding of LA versus OLA prepartum tended to increase peroxisome proliferator-activated receptor α (PPARA) expression, whereas peroxisome proliferator-activated receptor δ (PPARD) and peroxisome proliferator-activated receptor γ (PPARG) expression tended to be higher in OLA- than LA-fed cows. Expression of fatty acid transporter protein 4 (FATP4) and fatty acid translocase (FAT/CD36) expression was lower in placental tissue of cows fed fat compared with control cows. Reduced total n-3 fatty acids, EPA and DHA in neonates born of dams fed fat prepartum is likely due to changes in PPARs and reduced expression of placental FATP4 and FAT/CD36.

Maternal obesity modulates intracellular lipid turnover in the human term placenta

BACKGROUND

Obesity before pregnancy is associated with impaired metabolic status of the mother and the offspring later in life. These adverse effects have been attributed to epigenetic changes in utero, but little is known about the role of placental metabolism and its contribution to fetal development.

OBJECTIVES

We examined the impact of maternal pre-pregnancy obesity on the expression of genes involved in placental lipid metabolism in lean and obese women.

SUBJECTS/METHODS

Seventy-three lean and obese women with healthy pregnancy were recruited at term elective cesarean delivery. Metabolic parameters were measured on maternal venous blood samples. Expression of 88 genes involved in lipid metabolism was measured in whole placenta tissue. Proteins of genes differently expressed in response to maternal obesity were quantified, correlated with maternal parameters and immunolocalized in placenta sections. Isolated primary trophoblasts were used for in vitro assays.

RESULTS

Triglyceride (TG) content was increased in placental tissue of obese (1.10, CI 1.04-1.24 mg g^-1, P<0.05) vs lean (0.84, CI 0.72-1.02 mg g^-1) women. Among target genes examined, six showed positive correlation (P<0.05) with maternal pre-pregnancy BMI, namely ATGL (PNPLA2), FATP1 (SLC27A1), FATP3 (SLC27A3), PLIN2, PPARG and CGI-58 (ABHD5). CGI-58 protein abundance was twofold higher (P<0.001) in placentas of obese vs lean women. CGI-58 protein levels correlated positively with maternal insulin levels and pre-pregnancy body mass index (R=0.63, P<0.001 and R=0.64, P<0.001, respectively). CGI-58 and PLIN2 were primarily located in the syncytiotrophoblast and, were upregulated (1.38- and 500-fold, respectively) upon oleic acid and insulin treatment of cultured trophoblast cells.

CONCLUSION

Pre-gravid obesity significantly modifies the expression of placental genes related to transport and storage of neutral lipids. We propose that the upregulation of CGI-58, a master regulator of TG hydrolysis, contributes to the turnover of intracellular lipids in placenta of obese women, and is tightly regulated by metabolic factors of the mother.

Real-Time Tracking of BODIPY-C12 Long-Chain Fatty Acid in Human Term Placenta Reveals Unique Lipid Dynamics in Cytotrophoblast Cells

While the human placenta must provide selected long-chain fatty acids to support the developing fetal brain, little is known about the mechanisms underlying the transport process. We tracked the movement of the fluorescently labeled long-chain fatty acid analogue, BODIPY-C₁₂, across the cell layers of living explants of human term placenta. Although all layers took up the fatty acid, rapid esterification of long-chain fatty acids and incorporation into lipid droplets was exclusive to the inner layer cytotrophoblast cells rather than the expected outer syncytiotrophoblast layer. Cytotrophoblast is a progenitor cell layer previously relegated to a repair role. As isolated cytotrophoblasts differentiated into syncytialized cells in culture, they weakened their lipid processing capacity. Syncytializing cells suppress previously active genes that regulate fatty-acid uptake (SLC27A2/FATP2, FABP4, ACSL5) and lipid metabolism (GPAT3, LPCAT3). We speculate that cytotrophoblast performs a previously unrecognized role in regulating placental fatty acid uptake and metabolism.

Protein expression of fatty acid transporter 2 is polarized to the trophoblast basal plasma membrane and increased in placentas from overweight/obese women

BACKGROUND

Obese and overweight women are more likely to deliver a large infant or an infant with increased adiposity, however the underlying mechanisms are not well established. We tested the hypothesis that placental capacity to transport fatty acid is increased in overweight/obese women.

METHODS

Pregnant women with body mass index (BMI) ranging from 18.4 to 54.3 kg/m(2) and with uncomplicated term pregnancies were recruited for collection of blood samples and placental tissue. Maternal and fetal levels of non-esterified fatty acids (NEFAs) were measured in plasma. The expression and localization of CD36/fatty acid translocase (FAT), fatty acid transport protein (FATP)2, and FATP4 was determined in fixed placental tissue and in isolated syncytiotrophoblast plasma membranes from normal and high BMI mothers.

RESULTS

Maternal and fetal plasma NEFA levels did not correlate (n = 42). FATP2 and FATP4 expressions were higher in the basal plasma membrane (BPM) compared to the microvillous membrane (P < 0.001; n = 7) per unit membrane protein. BPM expression of FATP2 correlated with maternal BMI (P < 0.01; n = 30); there was no association between CD36/FAT or FATP4 expression and maternal BMI.

CONCLUSION

The polarization of FATPs to the BPM will facilitate fatty acid transfer across the placenta. In overweight/obese pregnancies, the increased FATP2 expression could contribute to increased fatty acid delivery to the fetus and while we have no direct data we speculate that this could lead accelerated fetal growth or increased fat deposition.

Placental Nutrient Transport and Intrauterine Growth Restriction

Intrauterine growth restriction refers to the inability of the fetus to reach its genetically determined potential size. Fetal growth restriction affects approximately 5–15% of all pregnancies in the United States and Europe. In developing countries the occurrence varies widely between 10 and 55%, impacting about 30 million newborns per year. Besides having high perinatal mortality rates these infants are at greater risk for severe adverse outcomes, such as hypoxic ischemic encephalopathy and cerebral palsy. Moreover, reduced fetal growth has lifelong health consequences, including higher risks of developing metabolic and cardiovascular diseases in adulthood. Numerous reports indicate placental insufficiency as one of the underlying causes leading to altered fetal growth and impaired placental capacity of delivering nutrients to the fetus has been shown to contribute to the etiology of intrauterine growth restriction. Indeed, reduced expression and/or activity of placental nutrient transporters have been demonstrated in several conditions associated with an increased risk of delivering a small or growth restricted infant. This review focuses on human pregnancies and summarizes the changes in placental amino acid, fatty acid, and glucose transport reported in conditions associated with intrauterine growth restriction, such as maternal undernutrition, pre-eclampsia, young maternal age, high altitude and infection.

Increased placental fatty acid transporter 6 and binding protein 3 expression and fetal liver lipid accumulation in a mouse model of obesity in pregnancy

Obesity in pregnancy is associated with increased fetal growth and adiposity, which, in part, is determined by transplacental nutrient supply. Trophoblast uptake and intracellular trafficking of lipids are dependent on placental fatty acid transport proteins (FATP), translocase (FAT/CD36), and fatty acid binding proteins (FABP). We hypothesized that maternal obesity in mice leads to increased placental expression of FAT/CD36, FATPs, and FABPs, and lipid accumulation in the fetal liver. C57/BL6J female mice were fed either a control (C; n = 10) or an obesogenic (OB; n = 10) high-fat, high-sugar diet before mating and throughout pregnancy. At E18.5, placentas and fetal livers were collected. Trophoblast plasma membranes (TPM) were isolated from placental homogenates. Expression of FAT/CD36 and FATP (TPM) and FABP (homogenates) was determined by immunoblotting. Gene expression was assessed by RT-quantitative PCR. Sections of fetal livers were stained for Oil Red O, and lipid droplets were quantified. TPM protein expression of FAT/CD36, FATP 2, and FATP 4 was comparable between C and OB groups. Conversely, TPM FATP 6 expression was increased by 35% in OB compared with C placentas without changes in mRNA expression. FABPs 1, 3-5 and PPARγ were expressed in homogenates, and FABP 3 expression increased 27% in OB compared with C placentas; however, no changes were observed in mRNA expression. Lipid droplet accumulation was 10-fold higher in the livers of fetuses from OB compared with C group. We propose that increased lipid transport capacity in obese mice promotes transplacental fatty acid transport and contributes to excess lipid accumulation in the fetal liver.

Placental fatty acid transport in maternal obesity

Pregestational obesity is a significant risk factor for adverse pregnancy outcomes. Maternal obesity is associated with a specific proinflammatory, endocrine and metabolic phenotype that may lead to higher supply of nutrients to the feto-placental unit and to excessive fetal fat accumulation. In particular, obesity may influence placental fatty acid (FA) transport in several ways, leading to increased diffusion driving force across the placenta, and to altered placental development, size and exchange surface area. Animal models show that maternal obesity is associated with increased expression of specific FA carriers and inflammatory signaling molecules in placental cotyledonary tissue, resulting in enhanced lipid transfer across the placenta, dislipidemia, fat accumulation and possibly altered development in fetuses. Cell culture experiments confirmed that inflammatory molecules, adipokines and FA, all significantly altered in obesity, are important regulators of placental lipid exchange. Expression studies in placentas of obese-diabetic women found a significant increase in FA binding protein-4 expression and in cellular triglyceride content, resulting in increased triglyceride cord blood concentrations. The expression and activity of carriers involved in placental lipid transport are influenced by the endocrine, inflammatory and metabolic milieu of obesity, and further studies are needed to elucidate the strong association between maternal obesity and fetal overgrowth.

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.

Peroxisome proliferator activator receptor gamma (PPARG) regulates conceptus elongation in sheep

The ovine blastocyst hatches from the zona pellucida by Day 8 and develops into an ovoid or tubular conceptus (embryo and associated extraembryonic membranes) that grows and elongates into a filamentous form between Days 12 and 16. The trophectoderm of the elongating conceptus synthesizes and secretes interferon tau (IFNT) as well as prostaglandins (PGs) via prostaglandin synthase two (PTGS2). Intrauterine infusion of a PTGS2 inhibitor prevents conceptus elongation in sheep. Although many PGs are secreted, PGI2 and PGJ2 can activate nuclear peroxisome proliferator activator receptors (PPARs) that heterodimerize with retinoic X receptors (RXRs) to regulate gene expression and cellular function. Expression of PPARD, PPARG, RXRA, RXRB, and RXRG is detected in the elongating ovine conceptus, and nuclear PPARD and PPARG are present in the trophectoderm. Consequently, PPARD and PPARG are hypothesized to have essential roles in conceptus elongation in ruminants. In utero loss-of-function studies of PPARD and PPARG in the ovine conceptus trophectoderm were conducted using morpholino antisense oligonucleotides (MAOs) that inhibit mRNA translation. Elongating, filamentous-type conceptuses were recovered from ewes infused with a control morpholino or PPARD MAO. In contrast, PPARG MAO resulted in severely growth-retarded conceptuses or conceptus fragments with apoptotic trophectoderm. In order to identify PPARG-regulated genes, PPARG chromatin immunoprecipitation sequencing and RNA sequencing were conducted using Day 14 ovine conceptuses. These analyses revealed candidate PPARG-regulated genes involved in biological pathways, including lipid and glucose uptake, transport, and metabolism. Collectively, results support the hypothesis that PTGS2-derived PGs and PPARG are essential regulators of conceptus elongation, with specific roles in trophectoderm survival and proliferation.

Fatty Acid Binding Protein 3 Is Involved in n-3 and n-6 PUFA transport in mouse trophoblasts

BACKGROUND

Low placental fatty acid (FA) transport during the embryonic period has been suggested to result in fetal developmental disorders and various adult metabolic diseases, but the molecular mechanism by which FAs are transported through the placental unit remains largely unknown.

OBJECTIVE

The aim of this study was to examine the distribution and functional relevance of FA binding protein (FABP), a cellular chaperone of FAs, in the mouse placenta.

METHODS

We clarified the localization of FABPs and sought to examine their function in placental FA transport through the phenotypic analysis of Fabp3-knockout mice.

RESULTS

Four FABPs (FABP3, FABP4, FABP5, and FABP7) were expressed with spatial heterogeneity in the placenta, and FABP3 was dominantly localized to the trophoblast cells. In placentas from the Fabp3-knockout mice (both sexes), the transport coefficients for linoleic acid (LA) were significantly reduced compared with those from wild-type mice by 25% and 44% at embryonic day (E) 15.5 and E18.5, respectively, whereas those for α-linolenic acid (ALA) were reduced by 19% and 17%, respectively. The accumulation of LA (18% and 27% at E15.5 and E18.5) and ALA (16% at E15.5) was also significantly less in the Fabp3-knockout fetuses than in wild-type fetuses. In contrast, transport and accumulation of palmitic acid (PA) were unaffected and glucose uptake significantly increased by 23% in the gene-ablated mice compared with wild-type mice at E18.5. Incorporation of LA (51% and 52% at 1 and 60 min, respectively) and ALA (23% at 60 min), but not PA, was significantly less in FABP3-knockdown BeWo cells than in controls, whereas glucose uptake was significantly upregulated by 51%, 50%, 31%, and 33% at 1, 20, 40, and 60 min, respectively.

CONCLUSIONS

Collectively FABP3 regulates n-3 (ω-3) and n-6 (ω-6) polyunsaturated FA transport in trophoblasts and plays a pivotal role in fetal development.

Maternal-fetal nutrient transport in pregnancy pathologies: the role of the placenta

Appropriate in utero growth is essential for offspring development and is a critical contributor to long-term health. Fetal growth is largely dictated by the availability of nutrients in maternal circulation and the ability of these nutrients to be transported into fetal circulation via the placenta. Substrate flux across placental gradients is dependent on the accessibility and activity of nutrient-specific transporters. Changes in the expression and activity of these transporters is implicated in cases of restricted and excessive fetal growth, and may represent a control mechanism by which fetal growth rate attempts to match availability of nutrients in maternal circulation. This review provides an overview of placenta nutrient transport with an emphasis on macro-nutrient transporters. It highlights the changes in expression and activity of these transporters associated with common pregnancy pathologies, including intrauterine growth restriction, macrosomia, diabetes and obesity, as well as the potential impact of maternal diet. Molecular signaling pathways linking maternal nutrient availability and placenta nutrient transport are discussed. How sexual dimorphism affects fetal growth strategies and the placenta’s response to an altered intrauterine environment is considered. Further knowledge in this area may be the first step in the development of targeted interventions to help optimize fetal growth.

Maternal dietary omega-3 fatty acids and placental function

The developing fetus requires substantial amounts of fatty acids to support rapid cellular growth and activity. Although the fatty acid composition delivered to the fetus is largely determined by maternal circulating levels, the placenta preferentially transfers physiologically important long-chain polyunsaturated fatty acids (LC-PUFAs), particularly omega-3 (n-3) PUFAs. Maternal dietary supplementation with n-3 PUFAs during pregnancy has been shown to increase gestation length, enhance fetal growth, and reduce the risk of pregnancy complications, although the precise mechanisms governing these effects remain uncertain. Omega-3 PUFAs are involved in several physiological pathways which could account for these effects, including anti-inflammatory, pro-resolving, and anti-oxidative pathways. Recent studies have shown that maternal dietary n-3 PUFA supplementation during rat pregnancy can reduce placental oxidative damage and increase placental levels of pro-resolving mediators, effects associated with enhanced fetal and placental growth. Because several placental disorders, such as intrauterine growth restriction, preeclampsia, and gestational diabetes mellitus, are associated with heightened placental inflammation and oxidative stress, there is considerable interest in the potential for dietary n-3 PUFAs as a therapeutic intervention for these disorders. In this study, we review the impact of dietary n-3 PUFAs on placental function, with particular focus on placental inflammation, inflammatory resolution, and oxidative stress.

Regulation of nutrient transport across the placenta

Abnormal fetal growth, both growth restriction and overgrowth, is associated with perinatal complications and an increased risk of metabolic and cardiovascular disease later in life. Fetal growth is dependent on nutrient availability, which in turn is related to the capacity of the placenta to transport these nutrients. The activity of a range of nutrient transporters has been reported to be decreased in placentas of growth restricted fetuses, whereas at least some studies indicate that placental nutrient transport is upregulated in fetal overgrowth. These findings suggest that changes in placental nutrient transport may directly contribute to the development of abnormal fetal growth. Detailed information on the mechanisms by which placental nutrient transporters are regulated will therefore help us to better understand how important pregnancy complications develop and may provide a foundation for designing novel intervention strategies. In this paper we will focus on recent studies of regulatory mechanisms that modulate placental transport of amino acids, fatty acids, and glucose.

Modulation of fatty acid transport and metabolism by maternal obesity in the human full-term placenta

Knowledge of the consequences of maternal obesity in human placental fatty acids (FA) transport and metabolism is limited. Animal studies suggest that placental uptake of maternal FA is altered by maternal overnutrition. We hypothesized that high maternal body mass index (BMI) affects human placental FA transport by modifying expression of key transporters. Full-term placentas were obtained by vaginal delivery from normal weight (BMI, 18.5-24.9 kg/m(2)) and obese (BMI > 30 kg/m(2)) women. Blood samples were collected from the mother at each trimester and from cord blood at delivery. mRNA and protein expression levels were evaluated with real-time RT-PCR and Western blotting. Lipoprotein lipase (LPL) activity was evaluated using enzyme fluorescence. In vitro linoleic acid transport was studied with isolated trophoblasts. Our results demonstrated that maternal obesity is associated with increased placental weight, decreased gestational age, decreased maternal high-density lipoprotein (HDL) levels during the first and third trimesters, increased maternal triglyceride levels during the second and third trimesters, and increased maternal T3 levels during all trimesters, and decreased maternal cholesterol (CHOL) and low-density lipoprotein (LDL) levels during the third trimester; and increased newborn CHOL, LDL, apolipoprotein B100, and T3 levels. Increases in placental CD36 mRNA and protein expression levels, decreased SLC27A4 and FABP1 mRNA and protein and FABP3 protein expression, and increased LPL activity and decreased villus cytotrophoblast linoleic acid transport were also observed. No changes were seen in expression of PPARA, PPARD, or PPARG mRNA and protein. Overall this study demonstrated that maternal obesity impacts placental FA uptake without affecting fetal growth. These changes, however, could modify the fetus metabolism and its predisposition to develop diseases later in life.

Mechanisms involved in the selective transfer of long chain polyunsaturated Fatty acids to the fetus

The concentration of long chain polyunsaturated fatty acid (LCPUFA) in the fetal brain increases dramatically from the third trimester until 18 months of life. Several studies have shown an association between the percentage of maternal plasma docosahexaenoic acid (DHA) during gestation and development of cognitive functions in the neonate. Since only very low levels of LCPUFA are synthesized in the fetus and placenta, their primary source for the fetus is the maternal circulation. Both in vitro and human in vivo studies using labeled fatty acids have shown preferential transfer of LCPUFA from the placenta to the fetus compared with other fatty acids, although the mechanisms involved are still uncertain. The placenta takes up circulating maternal non-esterified fatty acids (NEFA) and fatty acids released mainly by maternal lipoprotein lipase and endothelial lipase. These NEFA may enter the cell by passive diffusion or by means of membrane carrier proteins. Once in the cytosol, NEFA bind to cytosolic fatty acid-binding proteins for transfer to the fetal circulation or can be oxidized within the trophoblasts, and even re-esterified and stored in lipid droplets. Although trophoblast cells are not specialized for lipid storage, LCPUFA may up-regulate peroxisome proliferator activated receptor-γ (PPARγ) and hence the gene expression of fatty acid transport carriers, fatty acid acyl-CoA-synthetases and adipophilin or other enzymes involved in lipolysis, modifying the rate of placental transfer, and metabolism. The placental transfer of LCPUFA during pregnancy seems to be a key factor in the neurological development of the fetus. Increased knowledge of the factors that modify placental transfer of fatty acids would contribute to our understanding of this complex process.

Uptake of dietary retinoids at the maternal-fetal barrier: in vivo evidence for the role of lipoprotein lipase and alternative pathways

Dietary retinoids (vitamin A and its derivatives) contribute to normal embryonic development. However, the mechanism(s) involved in the transfer of recently ingested vitamin A from mother to embryo is not fully understood. We investigated in vivo whether lipoprotein lipase (LPL) facilitates the placental uptake of dietary retinyl ester incorporated in chylomicrons and their remnants and its transfer to the embryo. We examined the effects of both genetic ablation (MCK-L0 mice) and pharmacological inhibition (P-407) of LPL by maintaining wild type and MCK-L0 mice on diets with different vitamin A content or administering them an oral gavage dose of [(3)H]retinol with or without P-407 treatment. We showed that LPL expressed in placenta facilitates uptake of retinoids by this organ and their transfer to the embryo, mainly through its catalytic activity. In addition, through its "bridging function," LPL can mediate the acquisition of nascent chylomicrons by the placenta, although less efficiently. Quantitative real-time PCR and Western blot analysis showed that placental LPL acts in concert with LDL receptor and LRP1. Finally, by knocking out the retinol-binding protein (RBP) gene in the MCK-L0 background (MCK-L0-RBP(-/-) mice) we demonstrated that the placenta acquires dietary retinoids also via the maternal circulating RBP-retinol complex. RBP expressed in the placenta facilitate the transfer of postprandial retinoids across the placental layers toward the embryo.

Differential regulation of genes for fetoplacental lipid pathways in pregnancy with gestational and type 1 diabetes mellitus

OBJECTIVE

Changes in metabolic homeostasis in pregnant diabetic women are potential determinants of increased adiposity of the fetus. The aim of this study was to characterize diabetes mellitus-induced changes in genes for fetoplacental energy metabolism in relation to fetal adiposity.

STUDY DESIGN

Placentas of women with type 1 diabetes mellitus, gestational diabetes mellitus (GDM), or no complications were analyzed by microarray profiling. The pattern of gene expression was assessed in primary placental cell cultures.

RESULTS

Diabetes mellitus was associated with 49 alterations in gene expression at key steps in placental energy metabolism, with 67% of the alterations related to lipid pathways and 9% of the alterations related to glucose pathways. Preferential activation of lipid genes was observed in pregnancy with GDM. Type 1 diabetes mellitus induced fewer lipid modifications but an enhancement of glycosylation and acylation pathways. Oleate enhanced expression of genes for fatty acid esterification and the formation of lipid droplets 3 times as much as glucose in cultured placental cells.

CONCLUSION

These results point to fatty acids as preferential lipogenic substrates for placental cells and suggest that genes for fetoplacental lipid metabolism are enhanced selectively in GDM. The recruited genes may be instrumental in increasing transplacental lipid fluxes and the delivery of lipid substrates for fetal use.