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Maternal dietary fatty acids and their roles in human placental development

Open AccessPublished:February 21, 2020DOI:https://doi.org/10.1016/j.plefa.2020.102080

      Highlights

      • Maternal fatty acids are essential for the growth and development of feto-placental unit. Maternal fatty acids modulate growth and development of trophoblast cell, and structural & functional aspects of the placenta and the fetus.
      • Long-chain fatty acids augment angiogenesis of the first-trimester placenta by stimulating vascular endothelium growth factor (VEGF), angiopoietin-like protein 4 (ANGPTL4), fatty acid-binding proteins (FABPs), or their eicosanoid metabolites.
      • Placental preferential transport of maternal plasma long-chain polyunsaturated fatty acids during the last trimester is critically essential for the development of brain and retina of the fetus.
      • Transport of maternal fatty acids to the fetus is partly mediated by plasma membrane fatty acid transport system (FAT, FATPs, p-FABPpm, & placental MFSD2a) and cytoplasmic FABPs.
      • Maternal lifestyle such as obesity, diet, metabolic states, inflammation and endocrine factors can impair placental function via altered expression of placental fatty acid transporters that lead to pregnancy complications and compromised fetal outcome.

      Abstract

      Fatty acids are essential for feto-placental growth and development. Maternal fatty acids and their metabolites are involved in every stage of pregnancy by supporting cell growth and development, cell signaling, and modulating other critical aspects of structural and functional processes. Early placentation process is critical for placental growth and function. Several fatty acids modulate angiogenesis as observed by increased tube formation and secretion of angiogenic growth factors in first-trimester human placental trophoblasts. Long-chain fatty acids stimulate angiogenesis in these cells via vascular endothelium growth factor (VEGF), angiopoietin-like protein 4 (ANGPTL4), fatty acid-binding proteins (FABPs), or eicosanoids. Inadequate placental angiogenesis and trophoblast invasion of the maternal decidua and uterine spiral arterioles leads to structural and functional deficiency of placenta, which contributes to preeclampsia, pre-term intrauterine growth restriction, and spontaneous abortion and also affects overall fetal growth and development. During the third trimester of pregnancy, placental preferential transport of maternal plasma long-chain polyunsaturated fatty acids is of critical importance for fetal growth and development. Fatty acids cross the placental microvillous and basal membranes by mainly via plasma membrane fatty acid transport system (FAT, FATP, p-FABPpm, & FFARs) and cytoplasmic FABPs. Besides, a member of the major facilitator superfamily-MFSD2a, present in the placenta is involved in the supply of DHA to the fetus. Maternal factors such as diet, obesity, endocrine, inflammation can modulate the expression and activity of the placental fatty acid transport activity and thereby impact feto-placental growth and development.
      In this review, we discuss the maternal dietary fatty acids, and placental transport and metabolism, and their roles in placental growth and development.

      Keywords

      Abbreviations:

      EFA (essential fatty acids, LCPUFA, long chain polyunsaturated fatty acids, DHA, docosahexaenoic acid), ARA (arachidonic acid, ALA, alpha-linolenic acid, LA, linoleic acid), FABPs (fatty acid-binding proteins, FAT, fatty acid translocase, FATP, fatty acid transporter protein), and p-FABPpm (placenta specific plasma membrane-associated fatty acid-binding protein), COX (cyclooxygenase, LOX, lipoxygenase), VEGF (vascular endothelial growth factor), ANGPTL4 (angiopoietin-like protein 4), MFSD2a (major facilitator super family domain containing 2a)

      1. Introduction

      Fatty acids carry out many functions throughout the life cycle. Fatty acids are crucial for regulating the architecture, dynamics, phase transitions, and permeability of the cellular membranes. Besides, they are involved in the regulation of membrane ion gates, ion channels, receptors, and cell signaling and gene expression [
      • Falomir-Lockhart L.J.
      • Cavazzutti G.F.
      • Gimenez E.
      • Toscani A.M.
      Fatty acid signaling mechanisms in neural cells: fatty acid receptors.
      ,
      • Liu J.J.
      • Green P.
      • John Mann J.
      • Rapoport S.I.
      • Sublette M.E.
      Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease.
      ,
      • Georgiadi A.
      • Kersten S.
      Mechanisms of gene regulation by fatty acids.
      ,
      • Calder P.C.
      Functional roles of fatty acids and their effects on human health.
      ]. Essential fatty acids (EFAs) belong to the n-6 (omega-6) and n-3 (omega-3) families, starting with the precursors, linoleic acid,18:2n-6 (LA) and alpha-linolenic acid, 18:3n-3 (ALA). N-3 and n-6 fatty acids play crucial biological roles that include structure and function of cell membranes, providing substrates for the production of signaling molecules such as eicosanoids, and modulating the expression of genes involved in cell homeostasis [
      • Abedi E.
      • Sahari M.A.
      Long-chain polyunsaturated fatty acid sources and evaluation of their nutritional and functional properties.
      ,
      • Chen C.T.
      • Domenichiello A.F.
      • Trepanier M.O.
      • Liu Z.
      • Masoodi M.
      • Bazinet R.P.
      The low levels of eicosapentaenoic acid in rat brain phospholipids are maintained via multiple redundant mechanisms.
      ,
      • Szefel J.
      • Kruszewski W.J.
      • Sobczak E.
      Factors influencing the eicosanoids synthesis in vivo.
      ]. The main enzymes responsible for the metabolism of both n-6 and n-3 fatty acids are the desaturases, elongases, cyclooxygenases (COXs), lipooxygenases (LOXs), and cytochrome P450 system [
      • Szefel J.
      • Kruszewski W.J.
      • Sobczak E.
      Factors influencing the eicosanoids synthesis in vivo.
      ]. Therefore, n-3 and n-6 fatty acids compete with each other for their metabolism and produce varieties of compounds with diverse physiological and pathological activities. Eicosanoids are biologically active lipids and include prostaglandins (PGs), thromboxanes (TXs), leukotrienes (LTs), and hydroxyeicosatetraenoic acids (HETEs) which have all been implicated in various physiological and pathological processes [
      • Murphy R.A.
      • Mourtzakis M.
      • Mazurak V.C.
      n-3 polyunsaturated fatty acids: the potential role for supplementation in cancer.
      ,
      • Marventano S.
      • Kolacz P.
      • Castellano S.
      • Galvano F.
      • Buscemi S.
      • Mistretta A.
      • Grosso G.
      A review of recent evidence in human studies of n-3 and n-6 PUFA intake on cardiovascular disease, cancer, and depressive disorders: does the ratio really matter?.
      ]. In general, n-6 fatty acids-derived eicosanoids are pro-inflammatory but they have important homeostatic functions. Several n-6 eicosanoids promote tumor growth and angiogenesis [
      • Pai R.
      • Szabo I.L.
      • Soreghan B.A.
      • Atay S.
      • Kawanaka H.
      • Tarnawski A.S.
      PGE(2) stimulates VEGF expression in endothelial cells via ERK2/JNK1 signaling pathways.
      ,
      • Jin Y.
      • Arita M.
      • Zhang Q.
      • Saban D.R.
      • Chauhan S.K.
      • Chiang N.
      • Serhan C.N.
      • Dana R.
      Anti-angiogenesis effect of the novel anti-inflammatory and pro-resolving lipid mediators.
      ,
      • Kamiyama M.
      • Pozzi A.
      • Yang L.
      • DeBusk L.M.
      • Breyer R.M.
      • Lin P.C.
      EP2, a receptor for PGE2, regulates tumor angiogenesis through direct effects on endothelial cell motility and survival.
      ]. In contrast, n-3 fatty acids and their eicosanoid derivatives mostly promote anti-inflammatory, anti-cancer, and anti-angiogenic activities. LCPUFAs also play essential roles in the development of the central nervous system, visual acuity, and cognitive functions [
      • Liu J.J.
      • Green P.
      • John Mann J.
      • Rapoport S.I.
      • Sublette M.E.
      Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease.
      ,
      • Mallick R.
      • Basak S.
      • Duttaroy A.K.
      Docosahexaenoic acid, 22:6n-3: its roles in the structure and function of the brain.
      ,
      • Lauritzen L.
      • Brambilla P.
      • Mazzocchi A.
      • Harslof L.B.
      • Ciappolino V.
      • Agostoni C.
      DHA effects in brain development and function.
      ]. Fatty acids and their ligands such as peroxisome proliferator-activated receptors (PPARs) can regulate expression of genes involved in fatty acids synthesis and oxidation, lipogenesis, glucose utilization, and insulin sensitivity, thermoregulation, energy partitioning, reverse cholesterol transport, cholesterol synthesis, low-density-lipoprotein-receptor expression, growth and differentiation, and inflammatory responses [
      • Sun G.Y.
      • Simonyi A.
      • Fritsche K.L.
      • Chuang D.Y.
      • Hannink M.
      • Gu Z.
      • Greenlief C.M.
      • Yao J.K.
      • Lee J.C.
      • Beversdorf D.Q.
      Docosahexaenoic acid (DHA): an essential nutrient and a nutraceutical for brain health and diseases.
      ,
      • Reimers A.
      • Ljung H.
      The emerging role of omega-3 fatty acids as a therapeutic option in neuropsychiatric disorders.
      ,
      • Hoppenbrouwers T.
      • Cvejic Hogervorst J.H.
      • Garssen J.
      • Wichers H.J.
      • Willemsen L.E.M.
      Long chain polyunsaturated fatty acids (LCPUFAs) in the prevention of food allergy.
      ,
      • Ghandour R.A.
      • Colson C.
      • Giroud M.
      • Maurer S.
      • Rekima S.
      • Ailhaud G.
      • Klingenspor M.
      • Amri E.Z.
      • Pisani D.F.
      Impact of dietary omega3 polyunsaturated fatty acid supplementation on brown and brite adipocyte function.
      ] [
      • Grygiel-Gorniak B.
      Peroxisome proliferator-activated receptors and their ligands: nutritional and clinical implications–a review.
      ,
      • Sekikawa A.
      • Mahajan H.
      • Kadowaki S.
      • Hisamatsu T.
      • Miyagawa N.
      • Fujiyoshi A.
      • Kadota A.
      • Maegawa H.
      • Murata K.
      • Miura K.
      • Edmundowicz D.
      • Ueshima H.
      • Group S.R.
      Association of blood levels of marine omega-3 fatty acids with coronary calcification and calcium density in Japanese men.
      ]. Fatty acids regulatory functions are however most probably defined by the group of specific receptors expressed in a particular cell-type and, therefore, they are dynamically modulated throughout the cell life-span, the developmental stage, and its differentiation process.
      As of today, three families of proteins (FABPs, plasma membrane FABPs, and FFARs) have been identified to be able to sense the presence and type of fatty acids whether in the extracellular medium, the cytosol or the nuclear matrix [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ,
      • Hara T.
      • Kimura I.
      • Inoue D.
      • Ichimura A.
      • Hirasawa A.
      Free fatty acid receptors and their role in regulation of energy metabolism.
      ]. At the plasma membrane, fatty acids can activate G protein-coupled receptors known as free fatty acid receptors (FFARs) [
      • Hara T.
      • Kimura I.
      • Inoue D.
      • Ichimura A.
      • Hirasawa A.
      Free fatty acid receptors and their role in regulation of energy metabolism.
      ] while in the cytosol they can be taken by FABPs and targeted to specific subcellular structures or metabolic pathways. Finally, nuclear receptors PPARs mediate fatty acids regulatory functions in the nucleus [
      • Zolezzi J.M.
      • Inestrosa N.C.
      Peroxisome proliferator-activated receptors and Alzheimer's disease: hitting the blood-brain barrier.
      ]. The specific spatio-temporal pattern of expression and the co-expression of more than one isoform from each family of proteins in a single cell suggest a platform for sensing and modulating the cellular response to the bioavailability of the different fatty acids, for example, adapting the cell to developmental or functional requirements. Therefore, the regulatory and signaling roles of free fatty acids are gaining importance in physiological and pathological processes as these receptors are better characterized.

      2. Fatty acid metabolism and their roles in feto-placental development

      LA and ALA are the two dietary EFAs that are readily available from the dietary sources such as vegetable oils, but their long-chain polyunsaturated fatty acid (LCPUFA) derivatives can be consumed in foods of animal origin. Dietary LA and ALA must be converted in the body to their long-chain metabolites LCPUFA to exert their full range of biological actions. Maternal LCPUFA status is crucial for fetal growth and development, as the fetus depends on the maternal supply of LCPUFAs such as arachidonic acid,20:4n-6 (ARA) and docosahexaenoic acid, 22:6n-3(DHA). Human fetal brain growth is at its peak velocity during the last trimester, and first few months after birth, leading to the concept that the third-trimester fetus and new-born baby are particularly vulnerable to developmental deficits if LCPUFAs status is poor. Optimal maternal transfer of DHA and ARA to the fetus during the last trimester of pregnancy, and extending into the postnatal period is remarkably coordinated. During early pregnancy, LCPUFAs derived from the diet are stored in maternal adipose tissue. During late pregnancy, enhanced lipid catabolism as a consequence of the insulin-resistant condition causes the development of maternal hyperlipidemia, which plays a key role in the availability of LCPUFAs to the fetus. Maternal body fat accumulation during early pregnancy allows the accumulation of an important store of LCPUFAs derived from both the maternal diet and maternal metabolism.
      Several studies on fatty acid composition in fetal and maternal plasma have shown that at birth, LA represents about 10% of the total fatty acids in cord plasma compared with 30% in maternal plasma, but surprisingly, ARA concentration in cord plasma is twice (about 10%) than observed in the mother (around 5%) [
      • Dutta-Roy A.K.
      Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta.
      ]. Similarly, ALA concentration in the new-born is half that in the mother (0.3% vs. 0.6%), whereas DHA concentration is double (3% vs. 1.5%) and EPA levels are equally low in fetal and maternal plasma [
      • Dutta-Roy A.K.
      Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta.
      ]. Free fatty acids (FFA) in the maternal circulation are the major source of fatty acids for transport across the placenta. An accelerated breakdown of fat depots occurs during the last trimester of pregnancy. In this stage of gestation, lipolytic activity in adipose tissue is increased. The fatty acids that are released, as well as fatty acids from dietary source and hepatic overproduction of triacylglycerol, are responsible for increasing the amount of triacylglycerol, in maternal circulation. Placental lipase activities are dramatically increased during the last trimester of pregnancy, whereas there is an overall decrease in lipoprotein lipase activity, resulting in a subsequent decrease in triacylglycerol storage. Consequently, with decreased triacylglycerol hydrolysis for maternal storage, and an increase in placental lipolytic activity, the resulting availability of triacylglycerol is utilized by placental lipase for the provision of FFA for fetal transport. The placental lipoprotein lipase (LPL), however, hydrolyses triacyglycerols from post-hepatic low-density lipoproteins (LDL) and very-low-density lipoproteins (VLDL) but not the triacylglycerols present in the chylomicrons [
      • Dutta-Roy A.K.
      Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta.
      ]. Placental LPL activity is reported to be lowered by 47% in preterm intrauterine growth retardation (IUGR) whereas in insulin-dependent diabetes mellitus IDDM pregnancies the activity is increased by 39% compared with controls.
      Placental fatty acid metabolism may play a critical role in guiding pregnancy and fetal outcome. LCPUFAs can be metabolized to important cell signaling molecules in the placenta by several major isoform families including the cyclooxygenases, lipoxygenases, and cytochrome P450 subfamily 4A (CYP4A). The increased expression of COX-2 is believed to be associated with the eicosanoids synthesis at term and parturition. However, there are other enzymes, such as cytosolic phospholipase A2 (cPLA2), which are also potential regulating steps in PGs synthesis in addition to COX. The cPLA2 catalyzes the release of free ARA, an initial and rate-limiting substrate in eicosanoids synthesis, from the sn-2 position of membrane phospholipids. Besides, oxidized lipids, including 9S- hydroxy‑octadedienoic acid (HODE), 13S-HODE, 15S‑hydroxy‑5Z,11Z,13E-eicosatetraenoic acid were shown to activate PPARγ in primary human villous trophoblasts. Placenta expresses all the enzymes necessary for mitochondrial fatty acid oxidation. Fatty acids are used as a significant metabolic fuel by human placentas at all gestational ages, and any defect within this energy-producing pathway may hamper the growth, differentiation, and function of the placenta, thereby may compromise fetal growth and development.

      3. Maternal long-chain fatty acids affect fetal brain growth and development

      As a structural component, fatty acids are involved in the function of the neuronal membrane. As expected, a change in the fatty acid composition of the synaptic membranes can affect neuronal functions in terms not only of membrane receptors, ion channels, and enzymes but also of the transmission of intra- and inter-cellular signals generated by fatty acid-derived second messengers. Comprehensive studies have shown that dietary supplementation with marine oil sources of n-3 LCPUFAs results in increased blood levels of DHA as well as an associated improvement in visual function in formula-fed infants matching that of human breastfed infants. The importance of DHA during pregnancy in fetal cognition development and its postnatal spill-over effect has been studied [
      • Innis S.M.
      Dietary omega 3 fatty acids and the developing brain.
      ]. The important role of DHA in brain development rests on its participation in maintaining membrane fluidity, impulse propagation, synaptic transmission, and its function as a cytosolic signal-transducing factor for various gene expression during the critical period of brain development [
      • Abdelwahab S.A.
      • Owada Y.
      • Kitanaka N.
      • Iwasa H.
      • Sakagami H.
      • Kondo H.
      Localization of brain-type fatty acid-binding protein in Kupffer cells of mice and its transient decrease in response to lipopolysaccharide.
      ]. Most LCPUFAs accumulate during brain development at a period of intense cell division, synaptogenesis [
      • Innis S.M.
      Dietary omega 3 fatty acids and the developing brain.
      ]. In humans, this accumulation starts at the beginning of the trimester and continues until two years of age [
      • Innis S.M.
      Dietary omega 3 fatty acids and the developing brain.
      ]. Maternal LCPUFAs are provided to the offspring via placental transfer during gestation and via lactation after birth [
      • Szajewska H.
      • Horvath A.
      • Koletzko B.
      Effect of n-3 long-chain polyunsaturated fatty acid supplementation of women with low-risk pregnancies on pregnancy outcomes and growth measures at birth: a meta-analysis of randomized controlled trials.
      ].
      Consequently, brain LCPUFA levels in the offspring much depend on maternal PUFA intake. Adequate DHA supply during the perinatal period is essential for optimal CNS development and function. In contrast, dietary n-3 LCPUFA deficiency impairs neuronal plasticity. Animal studies have demonstrated that DHA deficiency during gestation and soon after birth could not be fully corrected later in life [
      • Krabbendam L.
      • Bakker E.
      • Hornstra G.
      • van Os J.
      Relationship between DHA status at birth and child problem behaviour at 7 years of age.
      ]. At 33 weeks, the hypothalamus glycerophospholipids of young pups had significantly reduced DHA compared with controls (that had received ALA for three weeks after birth) even after dietary correction with ALA for 30 weeks. It appeared that the early deficiency of ALA had irreversibly down-regulated the converting enzyme delta-6 desaturase [
      • Li D.
      • Weisinger H.S.
      • Weisinger R.S.
      • Mathai M.
      • Armitage J.A.
      • Vingrys A.J.
      • Sinclair A.J.
      Omega 6 to omega 3 fatty acid imbalance early in life leads to persistent reductions in DHA levels in glycerophospholipids in rat hypothalamus even after long-term omega 3 fatty acid repletion.
      ]. Nervous tissue has the second-highest concentration of fatty acids after adipose tissue, and LCPUFA levels are particularly high in the retina and cerebral cortex. During the third trimester of pregnancy, DHA requirements increase to support fetal growth, particularly of the brain and eyes [
      • Innis S.M.
      Essential fatty acids in growth and development.
      ]. DHA can account for up to 50% of phospholipid fatty acids in these tissues, suggesting that it is heavily involved in neuronal and visual functions [
      • Neuringer M.
      Infant vision and retinal function in studies of dietary long-chain polyunsaturated fatty acids: methods, results, and implications.
      ]. N-3 LCPUFAs play a well-documented role in the brain development of the fetus and child. Premature infants require particular attention, as they have no reserve adipose tissue. These reserves are not generally built up until the third trimester. Premature infants are, therefore, closely dependent on maternal dietary intake of LCPUFAs . Differences in LCPUFA status were first observed by comparing breastfed infants with parenterally fed infants and infants fed formulas containing an imbalance of precursor PUFAs. DHA also showed significant effects on photoreceptor membranes and neurotransmitters involved in the signal transduction process, rhodopsin activation, rod and cone development, neuronal dendritic connectivity, and functional maturation of the central nervous system [
      • Liu J.J.
      • Green P.
      • John Mann J.
      • Rapoport S.I.
      • Sublette M.E.
      Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease.
      ,
      • Mallick R.
      • Basak S.
      • Duttaroy A.K.
      Docosahexaenoic acid, 22:6n-3: its roles in the structure and function of the brain.
      ,
      • Neuringer M.
      Infant vision and retinal function in studies of dietary long-chain polyunsaturated fatty acids: methods, results, and implications.
      ,
      • Uauy R.
      • Hoffman D.R.
      • Peirano P.
      • Birch D.G.
      • Birch E.E.
      Essential fatty acids in visual and brain development.
      ].

      4. Long-chain fatty acids and their roles in angiogenesis and early placentation

      Implantation and placentation depend on the invasive properties of trophoblast, which is ultimately derived from the outer trophectoderm layer of the blastocyst [
      • Moser G.
      • Huppertz B.
      Implantation and extravillous trophoblast invasion: from rare archival specimens to modern biobanking.
      ]. Because of its profound effect on caliber and vessel-wall composition, this invasion is important to ensure adequate maternal blood supply to the placenta. This is exemplified by defects in trophoblast invasion and blood flow in pregnancy complications such as preeclampsia. Invasive trophoblasts of the human placenta are critically involved in successful pregnancy outcome. These trophoblasts remodel the uterine spiral arteries to increase blood flow and oxygen delivery to the placenta and the developing fetus. This invasive behavior of trophoblasts follows a precise chronology of vascular events during the first trimester of gestation. The development of a placental vascular network is essential for the growth and maintenance of the developing embryo [
      • Basak S.
      • Duttaroy A.K.
      Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
      ,
      • Chung I.B.
      • Yelian F.D.
      • Zaher F.M.
      • Gonik B.
      • Evans M.I.
      • Diamond M.P.
      • Svinarich D.M.
      Expression and regulation of vascular endothelial growth factor in a first trimester trophoblast cell line.
      ,
      • Chaiworapongsa T.
      • Romero R.
      • Savasan Z.A.
      • Kusanovic J.P.
      • Ogge G.
      • Soto E.
      • Dong Z.
      • Tarca A.
      • Gaurav B.
      • Hassan S.S.
      Maternal plasma concentrations of angiogenic/anti-angiogenic factors are of prognostic value in patients presenting to the obstetrical triage area with the suspicion of preeclampsia.
      ]. Defective invasion of trophoblasts in the uterine spiral arteries is directly involved in preeclampsia, a major and frequent complication of human pregnancy with serious fetal and maternal consequences. The human trophoblastic invasion, unlike tumor invasion, is precisely regulated. It is temporally restricted to early pregnancy, and it is spatially confined to the endometrium, the first-third of the myometrium, and the associated spiral arterioles. Early stages of spiral artery remodeling mimic angiogenesis and therefore remain critical for the early placentation process. Several factors are involved in this angiogenic process, including vascular endothelial growth factor (VEGF), angiopoietin-like protein 4 (ANGPTL4), platelet-derived growth factor (PDGF) and platelet-activating factor (PAF) [
      • Basak S.
      • Duttaroy A.K.
      Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
      ,
      • Chung I.B.
      • Yelian F.D.
      • Zaher F.M.
      • Gonik B.
      • Evans M.I.
      • Diamond M.P.
      • Svinarich D.M.
      Expression and regulation of vascular endothelial growth factor in a first trimester trophoblast cell line.
      ,
      • Chaiworapongsa T.
      • Romero R.
      • Savasan Z.A.
      • Kusanovic J.P.
      • Ogge G.
      • Soto E.
      • Dong Z.
      • Tarca A.
      • Gaurav B.
      • Hassan S.S.
      Maternal plasma concentrations of angiogenic/anti-angiogenic factors are of prognostic value in patients presenting to the obstetrical triage area with the suspicion of preeclampsia.
      ,
      • Hill J.A.
      Maternal-embryonic cross-talk.
      ]. Both n-3 and n-6 fatty acids are involved directly or indirectly in angiogenesis [
      • Hardman W.E.
      (n-3) fatty acids and cancer therapy.
      ,
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Salvado M.D.
      • Alfranca A.
      • Haeggstrom J.Z.
      • Redondo J.M.
      Prostanoids in tumor angiogenesis: therapeutic intervention beyond COX-2.
      ]. Eicosanoids produced from ARA stimulate angiogenesis, whereas those produced from EPA and DHA inhibit angiogenesis and tumorigenesis [
      • Hardman W.E.
      (n-3) fatty acids and cancer therapy.
      ,
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Salvado M.D.
      • Alfranca A.
      • Haeggstrom J.Z.
      • Redondo J.M.
      Prostanoids in tumor angiogenesis: therapeutic intervention beyond COX-2.
      ]. Eicosanoids modulate angiogenic growth factors, cell migration, proliferation, and vascularization. N-3 fatty acids derived eicosanoids attenuate excess vascularization. Thus, high levels of tissue n-3 fatty acids can reduce angiogenesis through decreased production of pro-angiogenic ARA-derived eicosanoids, membrane receptor-ligand interactions, and through the intrinsic anti-tumor properties of n-3 fatty acids [
      • Pai R.
      • Szabo I.L.
      • Soreghan B.A.
      • Atay S.
      • Kawanaka H.
      • Tarnawski A.S.
      PGE(2) stimulates VEGF expression in endothelial cells via ERK2/JNK1 signaling pathways.
      ,
      • Kamiyama M.
      • Pozzi A.
      • Yang L.
      • DeBusk L.M.
      • Breyer R.M.
      • Lin P.C.
      EP2, a receptor for PGE2, regulates tumor angiogenesis through direct effects on endothelial cell motility and survival.
      ,
      • Bagga D.
      • Wang L.
      • Farias-Eisner R.
      • Glaspy J.A.
      • Reddy S.T.
      Differential effects of prostaglandin derived from omega-6 and omega-3 polyunsaturated fatty acids on COX-2 expression and IL-6 secretion.
      ,
      • Pola R.
      • Gaetani E.
      • Flex A.
      • Aprahamian T.R.
      • Bosch-Marce M.
      • Losordo D.W.
      • Smith R.C.
      • Pola P.
      Comparative analysis of the in vivo angiogenic properties of stable prostacyclin analogs: a possible role for peroxisome proliferator-activated receptors.
      ]. However, the angiogenic response is more complex and may involve many other factors [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Dimitriadis E.
      • White C.A.
      • Jones R.L.
      • Salamonsen L.A.
      Cytokines, chemokines and growth factors in endometrium related to implantation.
      ]. Prostaglandin E2 (PGE2) is involved in angiogenesis [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Tobin K.A.
      • Johnsen G.M.
      • Staff A.C.
      • Duttaroy A.K.
      Long-chain polyunsaturated fatty acid transport across human placental choriocarcinoma (BeWo) cells.
      ,
      • Zhang Y.
      • Daaka Y.
      PGE2 promotes angiogenesis through EP4 and PKA Cgamma pathway.
      ]. PGE2 may induce angiogenesis by acting indirectly on a variety of cell types to produce proangiogenic factors. Indeed, PGE2 increased the production of VEGF, bFGF, or CXCL1 that, in turn, act on target endothelial cells to promote the angiogenesis [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Zhang Y.
      • Daaka Y.
      PGE2 promotes angiogenesis through EP4 and PKA Cgamma pathway.
      ,
      • Weedon-Fekjaer M.S.
      • Duttaroy A.K.
      • Nebb H.I.
      Liver X receptors mediate inhibition of hCG secretion in a human placental trophoblast cell line.
      ,
      • Wang D.
      • Wang H.
      • Brown J.
      • Daikoku T.
      • Ning W.
      • Shi Q.
      • Richmond A.
      • Strieter R.
      • Dey S.K.
      • DuBois R.N.
      CXCL1 induced by prostaglandin E2 promotes angiogenesis in colorectal cancer.
      ]. Multiple signaling networks instigated by the various PGE2 receptors are thought to mediate the PGE2 induced angiogenic response. Since PGE2 is a product of COX-2, and there is ample evidence to implicate COX-2 as an angiogenesis mediator. It has been shown that overexpression of COX-2 is significantly correlated to invasiveness, prognosis, and survival in some cancers [
      • Fu S.L.
      • Wu Y.L.
      • Zhang Y.P.
      • Qiao M.M.
      • Chen Y.
      Anti-cancer effects of COX-2 inhibitors and their correlation with angiogenesis and invasion in gastric cancer.
      ]. Inhibition of COX-2 with selective COX-2 inhibitors effectively prevents inflammation, proliferation and angiogenesis, and induces apoptosis in human cells [
      • Fu S.L.
      • Wu Y.L.
      • Zhang Y.P.
      • Qiao M.M.
      • Chen Y.
      Anti-cancer effects of COX-2 inhibitors and their correlation with angiogenesis and invasion in gastric cancer.
      ]. Furthermore, n-3 fatty acids have been found to down-regulate the expression of angiogenic growth factors such as VEGF, PDGF, IL-6, and MMP-2 in cancer cells [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Kang J.X.
      • Weylandt K.H.
      Modulation of inflammatory cytokines by omega-3 fatty acids.
      ]. In marked contrast to the effects observed with the n-3 LCPUFAs, the n-6 LCPUFAs have a stimulatory or neutral effect on angiogenic processes such as tube formation, cell migration, or cell proliferation [
      • Hardman W.E.
      (n-3) fatty acids and cancer therapy.
      ,
      • Szymczak M.
      • Murray M.
      • Petrovic N.
      Modulation of angiogenesis by omega-3 polyunsaturated fatty acids is mediated by cyclooxygenases.
      ]. The expression of enzymes involved in the biosynthesis of eicosanoids, notably COX-2, 5-LOX, and 12-LOX, is upregulated during tumor initiation and progression. COX-2 contributes to neovascularization, which is essential for tumor development. Overexpression of COX-2 in colon carcinoma cells increases angiogenesis, as shown by an increased migration and tube formation of the endothelial cell by producing prostaglandins and inducing pro-angiogenic factors such as VEGF and basic fibroblast growth factor (bFGF). Besides, inflammatory cells infiltrating the tumor tissue may release pro-inflammatory cytokines such as IL-1β or TNF-α that can induce angiogenesis, an effect partially attributable to increased COX-2 expression in tumor, stromal, and vascular endothelial cells. The anti-angiogenic activity of n-3 LCPUFAs is mediated usually via inhibition of production of ARA-derived eicosanoids [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ]. LCFAs and their derivatives are reported to modulate several angiogenic factors such as VEGF, ANGPTL4, PDGF, leptin, and TNFα [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Salvado M.D.
      • Alfranca A.
      • Haeggstrom J.Z.
      • Redondo J.M.
      Prostanoids in tumor angiogenesis: therapeutic intervention beyond COX-2.
      ]. VEGF or its receptors are up-regulated in many tumors [
      • Takahashi S.
      Vascular endothelial growth factor (VEGF), vegf receptors and their inhibitors for antiangiogenic tumor therapy.
      ]. N-3 fatty acids inhibit the expression of pro-angiogenic factors [
      • Massaro M.
      • Scoditti E.
      • Carluccio M.A.
      • Campana M.C.
      • De Caterina R.
      Omega-3 fatty acids, inflammation and angiogenesis: basic mechanisms behind the cardioprotective effects of fish and fish oils.
      ,
      • Scoditti E.
      • Massaro M.
      • Carluccio M.A.
      • Distante A.
      • Storelli C.
      • De Caterina R.
      PPARgamma agonists inhibit angiogenesis by suppressing PKCalpha- and CREB-mediated COX-2 expression in the human endothelium.
      ]. EPA and DHA significantly suppress endothelial cell proliferation, migration, and tubule formation [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Kanayasu T.
      • Morita I.
      • Nakao-Hayashi J.
      • Asuwa N.
      • Fujisawa C.
      • Ishii T.
      • Ito H.
      • Murota S.
      Eicosapentaenoic acid inhibits tube formation of vascular endothelial cells in vitro.
      ,
      • Yang S.P.
      • Morita I.
      • Murota S.I.
      Eicosapentaenoic acid attenuates vascular endothelial growth factor-induced proliferation via inhibiting FLK-1 receptor expression in bovine carotid artery endothelial cells.
      ,
      • Murota S.I.
      • Onodera M.
      • Morita I.
      Regulation of angiogenesis by controlling VEGF receptor.
      ,
      • Kim H.J.
      • Vosseler C.A.
      • Weber P.C.
      • Erl W.
      Docosahexaenoic acid induces apoptosis in proliferating human endothelial cells.
      ]. Down-regulation of VEGF receptors by EPA is mediated via suppression of NFκB activation [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Ghosh-Choudhury T.
      • Mandal C.C.
      • Woodruff K.
      • St Clair P.
      • Fernandes G.
      • Choudhury G.G.
      • Ghosh-Choudhury N.
      Fish oil targets PTEN to regulate NFKAPPAB for downregulation of anti-apoptotic genes in breast tumor growth.
      ]. In addition, EPA down-regulates expression of Flk-1 receptors in a dose-dependent manner, whereas it up-regulates the expression of Flt-1 receptors [
      • Yang S.P.
      • Morita I.
      • Murota S.I.
      Eicosapentaenoic acid attenuates vascular endothelial growth factor-induced proliferation via inhibiting FLK-1 receptor expression in bovine carotid artery endothelial cells.
      ]. The tube formation induced by VEGF was suppressed by n-3 LCPUFAs via down-regulation of VEGFR-2 in the endothelial cells [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Szymczak M.
      • Murray M.
      • Petrovic N.
      Modulation of angiogenesis by omega-3 polyunsaturated fatty acids is mediated by cyclooxygenases.
      ,
      • Tsuji M.
      • Murota S.I.
      • Morita I.
      Docosapentaenoic acid (22:5, n-3) suppressed tube-forming activity in endothelial cells induced by vascular endothelial growth factor.
      ,
      • Calviello G.
      • Di Nicuolo F.
      • Gragnoli S.
      • Piccioni E.
      • Serini S.
      • Maggiano N.
      • Tringali G.
      • Navarra P.
      • Ranelletti F.O.
      • Palozza P.
      n-3 PUFAs reduce VEGF expression in human colon cancer cells modulating the COX-2/PGE2 induced ERK-1 and -2 and HIF-1alpha induction pathway.
      ]. EPA and DHA have shown to have potent anti-angiogenic effects in cancer cells by inhibiting the production of many important angiogenic mediators such as VEGF, PDGF, COX-2, PGE2, nitric oxide (NO) [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ]. 4‑hydroxy‑DHA, a 5-Lipoxygenase product of DHA, was reported to inhibit endothelial cell proliferation and sprouting angiogenesis via PPARγ [
      • Sapieha P.
      • Stahl A.
      • Chen J.
      • Seaward M.R.
      • Willett K.L.
      • Krah N.M.
      • Dennison R.J.
      • Connor K.M.
      • Aderman C.M.
      • Liclican E.
      • Carughi A.
      • Perelman D.
      • Kanaoka Y.
      • Sangiovanni J.P.
      • Gronert K.
      • Smith L.E.
      5-Lipoxygenase metabolite 4-HDHA is a mediator of the antiangiogenic effect of omega-3 polyunsaturated fatty acids.
      ]. N-3 LCPUFAs can increase NO production by displacing eNOS from the caveolar fraction [
      • Li Q.
      • Zhang Q.
      • Wang M.
      • Zhao S.
      • Ma J.
      • Luo N.
      • Li N.
      • Li Y.
      • Xu G.
      • Li J.
      Eicosapentaenoic acid modifies lipid composition in caveolae and induces translocation of endothelial nitric oxide synthase.
      ]. Increased NO levels by these fatty acids may decrease VEGFR2 signal mediated angiogenesis [
      • Matesanz N.
      • Park G.
      • McAllister H.
      • Leahey W.
      • Devine A.
      • McVeigh G.E.
      • Gardiner T.A.
      • McDonald D.M.
      Docosahexaenoic acid improves the nitroso-redox balance and reduces VEGF-mediated angiogenic signaling in microvascular endothelial cells.
      ]. Indeed, a high ratio of O2/NO is implicated as a contributory factor in impaired angiogenesis in diabetes [
      • Matesanz N.
      • Park G.
      • McAllister H.
      • Leahey W.
      • Devine A.
      • McVeigh G.E.
      • Gardiner T.A.
      • McDonald D.M.
      Docosahexaenoic acid improves the nitroso-redox balance and reduces VEGF-mediated angiogenic signaling in microvascular endothelial cells.
      ,
      • Hamed E.A.
      • Zakary M.M.
      • Abdelal R.M.
      • Abdel Moneim E.M.
      Vasculopathy in type 2 diabetes mellitus: role of specific angiogenic modulators.
      ]. Since tumor progression and metastasis depend on angiogenesis, reducing the tissue n-6 /n-3 fatty acids may be beneficial in cancers. EPA and DHA inhibit, whereas n-6 LCPUFA such ARA promotes angiogenesis [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ,
      • Sapieha P.
      • Stahl A.
      • Chen J.
      • Seaward M.R.
      • Willett K.L.
      • Krah N.M.
      • Dennison R.J.
      • Connor K.M.
      • Aderman C.M.
      • Liclican E.
      • Carughi A.
      • Perelman D.
      • Kanaoka Y.
      • Sangiovanni J.P.
      • Gronert K.
      • Smith L.E.
      5-Lipoxygenase metabolite 4-HDHA is a mediator of the antiangiogenic effect of omega-3 polyunsaturated fatty acids.
      ,
      • Sterescu A.E.
      • Rousseau-Harsany E.
      • Farrell C.
      • Powell J.
      • David M.
      • Dubois J.
      The potential efficacy of omega-3 fatty acids as anti-angiogenic agents in benign vascular tumors of infancy.
      ,
      • Chen J.
      Src may be involved in the anti-cancer effect of conjugated linoleic acid. Comment on: CLA reduces breast cancer cell growth and invasion through ER and PI3K/Akt pathways.
      ]. N-3 LCPUFAs influence angiogenesis via several mechanisms including modulation in the expression of angiogenic factors, VEGF, ANGPTL4 and other mediators such as eicosanoids, cyclooxygenase (COX), fatty acid-binding proteins (FABPs), and nitric oxide (NO) [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ]. In contrast to its effects in cancer cells, DHA increased tube formation to the greatest extent as compared to other long-chain fatty acids such as EPA and ARA in EVT, HTR8/SVneocells. Table 1 shows the effect of long-chain fatty acids on the mRNA expression of angiogenic growth factors in human placental first-trimester trophoblast cells. DHA stimulated tube formation by increased expression and secretion of the most potent angiogenic factor, VEGFA, in extravillous trophoblast cells [
      • Johnsen G.M.
      • Basak S.
      • Weedon-Fekjaer M.S.
      • Staff A.C.
      • Duttaroy A.K.
      Docosahexaenoic acid stimulates tube formation in first trimester trophoblast cells, HTR8/SVneo.
      ]. Thus, DHA may also help early placentation process by increasing angiogenesis [
      • Johnsen G.M.
      • Basak S.
      • Weedon-Fekjaer M.S.
      • Staff A.C.
      • Duttaroy A.K.
      Docosahexaenoic acid stimulates tube formation in first trimester trophoblast cells, HTR8/SVneo.
      ]. This is in contrast with the generally observed inhibitory effects of DHA on angiogenesis in many cell types, including tumor [
      • Spencer L.
      • Mann C.
      • Metcalfe M.
      • Webb M.
      • Pollard C.
      • Spencer D.
      • Berry D.
      • Steward W.
      • Dennison A.
      The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
      ]. The mechanism responsible for the increased expression of VEGFA in placental trophoblast cells by DHA is not known at present. Expression of VEGFA by DHA, however, is unique as its mRNA is induced by a variety of growth factors and cytokines, including PDGF, EGF, TNFα, TGF-β1, and IL-1β, but not by any fatty acids. DHA-induced VEGFA expression was not accompanied by the expression of COX-2, and HIF1α genes in these cells [
      • Johnsen G.M.
      • Basak S.
      • Weedon-Fekjaer M.S.
      • Staff A.C.
      • Duttaroy A.K.
      Docosahexaenoic acid stimulates tube formation in first trimester trophoblast cells, HTR8/SVneo.
      ], indicating that DHA metabolites per se may not be involved in the VEGFA expression. Since the PPARγ ligand did not stimulate VEGFA expression in these cells, it is unlikely that DHA stimulation of VEGFA expression involves PPARγ [
      • Gottlicher M.
      • Demoz A.
      • Svensson D.
      • Tollet P.
      • Berge R.K.
      • Gustafsson J.A.
      Structural and metabolic requirements for activators of the peroxisome proliferator-activated receptor.
      ]. DHA may also alter phosphorylation events in native mRNA processing, mRNA transport, and stabilization and mRNA degradation rates [
      • Uauy R.
      • Hoffman D.R.
      • Peirano P.
      • Birch D.G.
      • Birch E.E.
      Essential fatty acids in visual and brain development.
      ]. DHA stimulates VEGFA expression and secretion, whereas fatty acids such as EPA, ARA, OA, and CLA promote ANGPTL4 secretion without affecting VEGF synthesis in the placental trophoblast cells. These data indicate the different mechanisms of action of DHA compared with other fatty acids in the angiogenic process [
      • Johnsen G.M.
      • Basak S.
      • Weedon-Fekjaer M.S.
      • Staff A.C.
      • Duttaroy A.K.
      Docosahexaenoic acid stimulates tube formation in first trimester trophoblast cells, HTR8/SVneo.
      ]. The mechanism responsible for increased secretion of ANGPTL4 in placental trophoblast cells by fatty acids other than DHA is yet to be resolved. Long-chain fatty acids induce VEGFA and ANGPTL4 expression in placental first-trimester trophoblast cells; the effects of these fatty acids were quite the opposite to what was observed in case tumors [
      • Basak S.
      • Duttaroy A.K.
      Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
      ,
      • Johnsen G.M.
      • Basak S.
      • Weedon-Fekjaer M.S.
      • Staff A.C.
      • Duttaroy A.K.
      Docosahexaenoic acid stimulates tube formation in first trimester trophoblast cells, HTR8/SVneo.
      ,
      • Kang J.X.
      • Liu A.
      The role of the tissue omega-6/omega-3 fatty acid ratio in regulating tumor angiogenesis.
      ,
      • Basak S.
      • Duttaroy A.K.
      cis-9,trans-11 conjugated linoleic acid stimulates expression of angiopoietin like-4 in the placental extravillous trophoblast cells.
      ]. Early placental angiogenesis is critical for the establishment of the placental vascularization and thus for normal fetal growth and development. Inadequate placental vascular development may compromise the feto-placental growth and development. With the recent spate of studies on regulators of angiogenesis, these observations lead us to believe that regulation of placental angiogenesis could become a novel and powerful way for ensuring positive outcomes for most pregnancies.
      Table 1Effect of long-chain fatty acids on the mRNA expression of angiogenic growth factors in human placental first-trimester trophoblasts.
      Long-chain fatty acids (100μM)Angiogenic factors

      mRNA level (gene/TBP)
      VEGFANGPTL4
      Control1.01.0
      OA0.968.5
      t-9 ELA0.761.95
      ARA1.218
      p <0.05 vs control (Adapted from [34]).
      c9,t11-CLA1.1312.43
      p <0.05 vs control (Adapted from [34]).
      EPA1.920.0
      p <0.05 vs control (Adapted from [34]).
      DHA2.1
      p <0.05 vs control (Adapted from [34]).
      23.7
      p <0.05 vs control (Adapted from [34]).
      low asterisk p <0.05 vs control (Adapted from
      • Basak S.
      • Duttaroy A.K.
      Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
      ).

      5. The human placental fatty acid transport system

      The maternal, fetal, and neonatal EFA/LCPUFAs status is an important determinant of feto-placental growth and development [
      • Innis S.M.
      Essential fatty acids in growth and development.
      ,
      • Uauy R.
      • Hoffman D.R.
      • Peirano P.
      • Birch D.G.
      • Birch E.E.
      Essential fatty acids in visual and brain development.
      ]. The critical requirement of these fatty acids in feto-placental unit demands an efficient transport of these LCPUFAs to the fetus by the placenta. The human placenta plays a crucial role in mobilizing the fat stores of maternal adipose tissue and actively concentrating and channeling important LCPUFAs to the fetus via multiple mechanisms including selective uptake by the trophoblast, intracellular metabolic channeling and selective supply to the fetal circulation. There are several membrane proteins thought to be responsible for the tissue fatty acid uptake of the placenta [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ,
      • Dutta-Roy A.K.
      Cellular uptake of long-chain fatty acids: role of membrane-associated fatty-acid-binding/transport proteins.
      ]. These include the 40-kDa plasma membrane-associated fatty acid-binding protein (FABPpm), the heavily glycosylated 88-kDa fatty acid translocase (FAT), also known as CD36 and a family of 63–70-kDa fatty acid transport proteins (FATP 1–6) [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ]. FABPpm, that specifically binds to long-chain fatty acids was isolated and purified from human placental membranes [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ]. The human placental p-FABPpm, located exclusively on the maternal-facing membranes of the placenta, may be involved in the sequestration of maternal LCPUFAs [
      • Dutta-Roy A.K.
      Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta.
      ]. Radiolabelled fatty acid-binding revealed that p-FABPpm had higher affinities (Kd) and binding capacities (Bmax) for LCPUFAs compared with other fatty acids. The presence of p-FABPpm in the placental membrane facing maternal circulation may enforce the uni-directional flow of the LCPUFA from the mother to the fetus. In contrast, FAT and FATPs are present on both microvillous and basal membranes of the human placenta [
      • Dutta-Roy A.K.
      Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta.
      ]. Location of FAT and FATP on both sides of the bipolar placental trophoblast cells may favor the transport of general FFA pool in both directions, i.e., from the mother to the fetus and vice versa.
      FAT/CD36 is heavily glycosylated fatty acid translocase (FAT/CD36), the sequence of which is 85% homologous with that of glycoprotein IV (CD36), is an integral membrane protein (23). This 472-amino-acid (53 kDa) protein is substantially glycosylated (10 predicted N-linked glycosylated sites). Unlike FABPpm, FATP, FAT is a multifunctional protein and has a number of putative ligands including FFAs, collagen, thrombospondin and oxidized LDL. The presence of FAT/CD36 was demonstrated in human placenta using both pure trophoblast cells and placental membrane preparations. FAT is present in both the placental membranes, microvillous, and basal membranes [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ]. Little is known about the regulation of FAT/CD36 function in placental cells, but several lines point towards a translocational mechanism for increasing LCFA uptake by different cells. Caveolin-1 may control FAT/CD36 mediated fatty acid uptake by increasing its surface availability.
      FATP is the family of integral transmembrane proteins consists of six (FATP 1–6) isoforms which show different tissue expression patterns. FATP-1 was first identified in human placental membranes. Later other isoforms of FATPs have been detected in human placenta. Consistent with the role of FATP-1 in fatty acid internalization, a significant portion of FATP-1 is localized at the plasma membrane. FATPs are classified as fatty acid transport proteins because, when overexpressed, they increase the rate of fatty acid internalization, most notably at low concentrations when diffusion may not be sufficient. FATP is suggested to act in concert with fatty acylCoA synthetase, an enzyme that prevents efflux of the incorporated fatty acids by their conversion into acyl-CoA derivatives and hence rendering fatty acid uptake unidirectional. These long-chain fatty acyl-CoA esters act both as substrates and intermediates in various intracellular functions. FATP-mediated uptake of long-chain fatty acids was diminished in the face of cellular depletion of ATP. Thus, FATP is likely to be responsible for the increased uptake of long-chain fatty acids necessary to sustain increased β-oxidation. Therefore, the tissue-selective effects of various PPARs and their ligands produced by FATP and ACS may provide insight into the relationship between FFA uptake and triglyceride synthesis and β-oxidation of fatty acids. Additionally, FATP-1 possesses ACS activity toward long-chain fatty acids (16–22 carbons), although ACS activity of FATP-1 is very low as compared to ACSL1. FATP-1 has one membrane-spanning region and several membrane-associated regions. Since this arrangement does not typically support for a channel or transporter, FATP may, therefore, increases the fatty acid internalization by increasing the rate of “flip-flop,” trapping the fatty acids in the inner leaflet of the plasma membrane, or activating the fatty acid to its CoA formation. Disruption of the FATP-4 gene in mice demonstrated its essential function in normal mouse development. However, little is known on the specificity of FATPs for different fatty acids. PPAR-γ and RXR regulate fatty acid transport in primary human trophoblasts [
      • Schaiff W.T.
      • Bildirici I.
      • Cheong M.
      • Chern P.L.
      • Nelson D.M.
      • Sadovsky Y.
      Peroxisome proliferator-activated receptor-gamma and retinoid X receptor signaling regulate fatty acid uptake by primary human placental trophoblasts.
      ] . The incubation of human trophoblast cells with both PPAR-γ and RXR agonists resulted in elevated mRNA expression of FATP-1 and FATP-4 but not FATP-2, −3 and −6 in these cells [
      • Schaiff W.T.
      • Bildirici I.
      • Cheong M.
      • Chern P.L.
      • Nelson D.M.
      • Sadovsky Y.
      Peroxisome proliferator-activated receptor-gamma and retinoid X receptor signaling regulate fatty acid uptake by primary human placental trophoblasts.
      ]. Similar results were reported in vivo by using PPAR-γ agonist that resulted in an increase in the placental expression of FABPpm and FAT/CD36 [
      • Schaiff W.T.
      • Bildirici I.
      • Cheong M.
      • Chern P.L.
      • Nelson D.M.
      • Sadovsky Y.
      Peroxisome proliferator-activated receptor-gamma and retinoid X receptor signaling regulate fatty acid uptake by primary human placental trophoblasts.
      ]. Human placental MFSD2a (the major facilitator superfamily domain-containing 2a) also contributes to fetal DHA by transporting DHA containing lysophospholipids [
      • Prieto-Sanchez M.T.
      • Ruiz-Palacios M.
      • Blanco-Carnero J.E.
      • Pagan A.
      • Hellmuth C.
      • Uhl O.
      • Peissner W.
      • Ruiz-Alcaraz A.J.
      • Parrilla J.J.
      • Koletzko B.
      • Larque E.
      Placental MFSD2a transporter is related to decreased DHA in cord blood of women with treated gestational diabetes.
      ].
      The presence of several FABPs was demonstrated in human placental trophoblasts [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ]. The significance of the presence of several cytoplasmic FABPs in trophoblasts is not known but indicates that complex interactions of these proteins may be essential for active fatty acid transport and metabolism in the placenta. Also, the involvement of several nuclear transcription factors (PPARs, LXR, RXR, and SREBP-1) in the expression of genes responsible for fatty acids uptake, placental trophoblast differentiation and human chorionic gonadotropin (hCG) production indicating regulatory roles of fatty acid-activated transcriptions factors in placenta biology [
      • Weedon-Fekjaer M.S.
      • Duttaroy A.K.
      • Nebb H.I.
      Liver X receptors mediate inhibition of hCG secretion in a human placental trophoblast cell line.
      ]. The uptake of individual fatty acids was almost equally inhibited by triacsin C (an inhibitor of CoA formation) indicating that CoA formation step may be involved in the uptake of these fatty acids in the first-trimester human trophoblast cells, HTR8/SVneo. This is again in contrast to what was observed in triacsin C induced inhibition of the DHA uptake by the last trimester placental trophoblasts where DHA uptake was inhibited least by triacsin C compared with other fatty acids [
      • Tobin K.A.
      • Johnsen G.M.
      • Staff A.C.
      • Duttaroy A.K.
      Long-chain polyunsaturated fatty acid transport across human placental choriocarcinoma (BeWo) cells.
      ]. DHA by avoiding CoA formation in the last trimester trophoblasts may allow preferential transport across these cells. The first-trimester trophoblast cells are not fatty acid transporting cells like last trimester placental trophoblast cells. Fig. 1 summarizes the roles of fatty acid uptake and metabolism in human placental first and third-trimester trophoblasts.
      Fig 1
      Fig. 1Effects of long-chain fatty acids in human placental trophoblasts Uptake, metabolism and their effects on early placentation and fetal development
      The left panel is showing the effects of long-chain fatty acids on cellular growth and angiogenesis the first-trimester placental trophoblasts. Pro-angiogenic growth factors such as ANGPTL4, VEGF, and FABP-4 are involved in the placental angiogenesis. A possible contribution of these fatty acids in modulating angiogenic growth factors such as VEGF and ANGPTL4 is depicted. The right panel reflects the schematic overview of proteins involved in fatty acid uptake and transport in last trimester trophoblast cells. The location of FAT and FATP on both sides of the bipolar placental cells and the lack of specificity for particular types of FFAs allow transport by all FFAs (non-essential, essential and long-hain polyunsaturated) bi-directionally, i.e., from the mother to the fetus and vice versa. However, by virtue of its exclusive location on both sides and preference for LCPUFAs, p-FABPpm is thought to be involved in sequestering maternal plasma LCPUFAs to the placenta. Cytoplasmic FABPs may be responsible for the trans cytoplasmic movement of FFAs to their sites of esterification, ß-oxidation, or the fetal circulation via placental basal membranes.
      FFA-Free fatty acids; FATP: Fatty acid transporter protein; pFABPpm: Plasma membrane fatty acid-binding protein; ACSL: Acyl-CoA synthetase; ADRP: Adipose differentiation-related protein; ACBP: Acyl-CoA binding protein; TAG: Triacylglycerol; DHA: Docosahexaenoic acid; FAs: Fatty acids; FABP4: Fatty acid-binding protein 4.
      Adapted from Refs. [
      • Duttaroy A.K.
      Transport of fatty acids across the human placenta: a review.
      ,
      • Basak S.
      • Duttaroy A.K.
      Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
      ].

      6. Effects of maternal diet, metabolic and disease states on human placental fatty acid transport system

      Maternal diet, obesity, metabolic and endocrine status during pregnancy are known to modulate placental structure and function. The metabolic changes associated with maternal obesity and diabetes affect the placental transfer of nutrients and metabolic status in the fetus. Therefore, these maternal factors can affect placental lipid metabolism and their delivery to the fetus. Impaired placental nutrients delivery can lead to many complications during pregnancy, including fetal outcome. Placental LCPUFA transport and metabolism are altered in diabetes, obesity and other pathological conditions [
      • Desoye G.
      • Gauster M.
      • Wadsack C.
      Placental transport in pregnancy pathologies.
      ]. LCPUFA are preferentially stored in triglyceride fraction of the IUGR placenta led to impaired efflux of fatty acids across the placenta towards the fetal side [
      • Chassen S.S.
      • Ferchaud-Roucher V.
      • Gupta M.B.
      • Jansson T.
      • Powell T.L.
      Alterations in placental long chain polyunsaturated fatty acid metabolism in human intrauterine growth restriction.
      ]. Placental expression of fatty acid transport proteins is differed in intrauterine growth restriction due to lower concentrations of ARA and DHA and lower DHA/ALA ratio as compared to normal pregnancies. In IUGR placenta, mRNA expression of FATPs (−1, −2 and −4) and FABPs (−1 and −3) was increased as a compensatory mechanism but failed to sustain normal LC-PUFA supply to the fetus in IUGR [
      • Assumpcao R.P.
      • Mucci D.B.
      • Fonseca F.C.P.
      • Marcondes H.
      • Sardinha F.L.C.
      • Citelli M.
      • Tavares do carmo M.G.
      Fatty acid profile of maternal and fetal erythrocytes and placental expression of fatty acid transport proteins in normal and intrauterine growth restriction pregnancies.
      ]. Recent data suggest brain DHA uptake is facilitated by a transporter major facilitator superfamily domain-containing 2A (MFSD2a) located in the blood-brain barrier vessel that is specifically involved in transporting lysophosphatidylcholine form of DHA from the circulation into the brain. Role of this transporter in the placenta is not reported in details. Data shows that placental MFSD2a transporter expression is decreased and correlates to decreased DHA in cord blood of women with gestational diabetes indicates its role in contributing materno-fetal DHA transport [
      • Prieto-Sanchez M.T.
      • Ruiz-Palacios M.
      • Blanco-Carnero J.E.
      • Pagan A.
      • Hellmuth C.
      • Uhl O.
      • Peissner W.
      • Ruiz-Alcaraz A.J.
      • Parrilla J.J.
      • Koletzko B.
      • Larque E.
      Placental MFSD2a transporter is related to decreased DHA in cord blood of women with treated gestational diabetes.
      ]. High pre-pregnancy BMI and GDM alter mRNA expression of genes involved in fatty acid uptake and metabolism with decreased placental FATP1, FATP4 and increased FAT/CD36 and FATP6 expressions [
      • Segura M.T.
      • Demmelmair H.
      • Krauss-Etschmann S.
      • Nathan P.
      • Dehmel S.
      • Padilla M.C.
      • Rueda R.
      • Koletzko B.
      • Campoy C.
      Maternal BMI and gestational diabetes alter placental lipid transporters and fatty acid composition.
      ]. In overweight/obese pregnancies, the increased FATP2 expression was suspected to increase fatty acid delivery to the fetus, however, accelerated fetal growth or increased fat deposition could not be explained due to these changes [
      • Lager S.
      • Ramirez V.I.
      • Gaccioli F.
      • Jang B.
      • Jansson T.
      • Powell T.L.
      Protein expression of fatty acid transporter 2 is polarized to the trophoblast basal plasma membrane and increased in placentas from overweight/obese women.
      ]. Placental fatty acid transporter activities are increased by DHA (800 mg) supplementation during pregnancy in obese women. It further led to a decrease in placental inflammation and upregulated the expression of fatty acid transporting protein 4 proteins in the placenta [
      • Lager S.
      • Ramirez V.I.
      • Acosta O.
      • Meireles C.
      • Miller E.
      • Gaccioli F.
      • Rosario F.J.
      • Gelfond J.A.L.
      • Hakala K.
      • Weintraub S.T.
      • Krummel D.A.
      • Powell T.L.
      Docosahexaenoic acid supplementation in pregnancy modulates placental cellular signaling and nutrient transport capacity in obese women.
      ]. In adolescent pregnancies, placental FATP1, CD36 and FABP3 expression were significantly downregulated with a modest decrease in overall LCPUFA (10%) levels without affecting cord blood DHA levels [
      • Fonseca F.
      • Mucci D.B.
      • Assumpcao R.P.
      • Marcondes H.
      • Sardinha F.L.C.
      • Silva S.V.
      • Citelli M.
      • Tavares do Carmo M.D.G.
      Differential long-chain polyunsaturated fatty acids status and placental transport in adolescent pregnancies.
      ].

      7. FABPs and their roles in angiogenesis

      Recent data suggested that certain FABPs have a role in angiogenesis. FABP expression is widely regulated by various pro-angiogenic mediators [
      • Mousiolis A.V.
      • Kollia P.
      • Skentou C.
      • Messinis I.E.
      Effects of leptin on the expression of fatty acid-binding proteins in human placental cell cultures.
      ]. Among FABPs, FABP4 originally identified as an adipocyte-specific protein promotes the proliferation of endothelial cells. FABP4 mRNA and protein levels were significantly induced in cultured endothelial cells by VEGF and bFGF treatment. First-trimester trophoblast cells, HTR8/SVneoexpress and secrete VEGF significantly in the presence of fatty acids and FABP-4 was thought to be a mediator of these associations of VEGF, ANGPTL4 and FABP4. The effect of VEGF-A on FABP-4 expression was inhibited by siRNA-mediated knockdown of VEGFR2, whereas the VEGFR1 agonists, PIGF1 and 2, had no such effect. Thus, FABP-4 emerged as a novel target of the VEGF/VEGFR2 pathway and a positive regulator of cell proliferation and angiogenesis in endothelial cells [
      • Elmasri H.
      • Karaaslan C.
      • Teper Y.
      • Ghelfi E.
      • Weng M.
      • Ince T.A.
      • Kozakewich H.
      • Bischoff J.
      • Cataltepe S.
      Fatty acid binding protein 4 is a target of VEGF and a regulator of cell proliferation in endothelial cells.
      ,
      • Cataltepe O.
      • Arikan M.C.
      • Ghelfi E.
      • Karaaslan C.
      • Ozsurekci Y.
      • Dresser K.
      • Li Y.
      • Smith T.W.
      • Cataltepe S.
      Fatty acid binding protein 4 is expressed in distinct endothelial and non-endothelial cell populations in glioblastoma.
      ,
      • Elmasri H.
      • Ghelfi E.
      • Yu C.W.
      • Traphagen S.
      • Cernadas M.
      • Cao H.
      • Shi G.P.
      • Plutzky J.
      • Sahin M.
      • Hotamisligil G.
      • Cataltepe S.
      Endothelial cell-fatty acid binding protein 4 promotes angiogenesis: role of stem cell factor/c-kit pathway.
      ,
      • Ghelfi E.
      • Yu C.W.
      • Elmasri H.
      • Terwelp M.
      • Lee C.G.
      • Bhandari V.
      • Comhair S.A.
      • Erzurum S.C.
      • Hotamisligil G.S.
      • Elias J.A.
      • Cataltepe S.
      Fatty acid binding protein 4 regulates VEGF-induced airway angiogenesis and inflammation in a transgenic mouse model: implications for asthma.
      ]. FABP-4 was expressed in an angiogenesis-dependent pathology, infantile hemangioma, being the most common tumor of infancy and endothelial cells [
      • Fishman S.J.
      • Mulliken J.B.
      Hemangiomas and vascular malformations of infancy and childhood.
      ]. FABP-4 has a role in the activation of mitogenic pathways and the expression of several key mediators of angiogenesis. The expression of FABPs was regulated by fatty acids and leptin in the first trimester trophoblastic cells, HTR8/SVneo. c9t11-CLA, EPA, DHA, and leptin stimulated expression of FABP4 that was demonstrated as a target protein for VEGF. Leptin, a potent angiogenic growth factor stimulates mRNA expression of FABP4 along with several proangiogenic factors in first-trimester placental cells [
      • Basak S.
      • Duttaroy A.K.
      Leptin induces tube formation in first-trimester extravillous trophoblast cells.
      ]. Further, expression of FABP-5 has been shown to modulate MMP-9 production and regulates invasive property of oral cancer cells [
      • Fang L.Y.
      • Wong T.Y.
      • Chiang W.F.
      • Chen Y.L.
      Fatty-acid-binding protein 5 promotes cell proliferation and invasion in oral squamous cell carcinoma.
      ]. Despite similar ligand binding characteristics and highly homologous tertiary structures, each FABP appears to have unique functions in specific tissues [
      • Storch J.
      • Thumser A.E.
      Tissue-specific functions in the fatty acid-binding protein family.
      ]. Recent data demonstrated that maternal serum FABP-4 is independently associated with the subsequent development of preeclampsia [
      • Yan Y.
      • Peng H.
      • Wang P.
      • Wang H.
      • Dong M.
      Increased expression of fatty acid binding protein 4 in preeclamptic placenta and its relevance to preeclampsia.
      ]. Elevated maternal serum FABP4 levels may also play a role in the pathogenesis of preeclampsia through pathways related to insulin resistance, inflammation, and abnormal lipid metabolism. Increasing evidence suggests the angiogenic role of fatty acid transport/binding proteins in different cell systems, including first-trimester placental trophoblast [
      • Basak S.
      • Duttaroy A.K.
      Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
      ,
      • Basak S.
      • Duttaroy A.K.
      cis-9,trans-11 conjugated linoleic acid stimulates expression of angiopoietin like-4 in the placental extravillous trophoblast cells.
      ,
      • Ghelfi E.
      • Yu C.W.
      • Elmasri H.
      • Terwelp M.
      • Lee C.G.
      • Bhandari V.
      • Comhair S.A.
      • Erzurum S.C.
      • Hotamisligil G.S.
      • Elias J.A.
      • Cataltepe S.
      Fatty acid binding protein 4 regulates VEGF-induced airway angiogenesis and inflammation in a transgenic mouse model: implications for asthma.
      ]. A basal level of tube formation was maximally decreased in the presence of FABP4 inhibitor compared with other VEGF signaling pathway inhibitors such as P38/MAPK, l-NAME, Whereas DHA- and VEGF- induced tube formation was maximally inhibited by p38 MAP kinase inhibitor (63.7% and 34.5%, respectively). ANGPTL4 and oleic acid (OA)-induced tube formation was not inhibited by any of these inhibitors. The FABP4 inhibitor also attenuated cell growth but did not affect 14C fatty acid uptake. FABP4, therefore, may be involved in part in the basal level, and stimulated tube formation by VEGF, DHA, and leptin whereas it has little or no effect in ANGPTL4- and OA-induced tube formation in these cells [
      • Pandya A.D.
      • Das M.K.
      • Sarkar A.
      • Vilasagaram S.
      • Basak S.
      • Duttaroy A.K.
      Tube formation in the first trimester placental trophoblast cells: differential effects of angiogenic growth factors and fatty acids.
      ]. Thus, FABP4 may play a differential role in fatty acids, and angiogenic growth factors mediated tube formation in the first-trimester trophoblast cells in vitro.

      8. Conclusions

      Most research on the developmental origins of health and disease has implicated poor nutrition in the fetus, most often conferred by deficiencies in maternal nutrition, as an important causality that programs offspring's physiology for the adult disease that includes preeclampsia, pre-term birth, and gestational diabetes, as well as IUGR. The fetal origins, and now developmental origins, of health and disease hypothesis, asserts that prenatal and early postnatal life exposures are critical in determining adult health because these are likely to program organ function for life. In fact, placental growth during early and mid-pregnancy has a powerful influence on fetal growth during late pregnancy. Early placental angiogenesis is critical for the establishment of the placental size, vascularization and thus for normal fetal growth and development. LCPUFAs favors placental growth by increasing angiogenesis in placental first-trimester trophoblast cells. The dietary fatty acids not only stimulated the expression of major angiogenic factors such as VEGF and ANGPTL4 but also FABP-4 and FABP-3, which are known to modulate angiogenesis directly. The human placental trophoblasts play a crucial role in mobilizing the maternal fatty acids and channeling important LCPUFAs to the fetus via multiple mechanisms including selective uptake by the trophoblast, intracellular metabolic channeling and selective export to the fetal circulation. Among the fatty acid-binding/transport proteins, p-FABPpm, located exclusively on the maternal-facing membranes of the placenta, may be involved in the sequestration of maternal LCPUFAs by the placenta. In addition, placental MFSD2a is reported to be involved in the maternal transfer of DHA to the fetus. The impacts of maternal factors such as diet, obesity, endocrine, inflammatory factors on the placental fatty acid transport system are yet to be deciphered fully. A better understanding of fatty acid transport physiology in the fetoplacental unit is needed in order to address the feto-placental growth and development.

      Acknowledgments

      This study was supported by the grant from the Thune Holst Foundation and HRD fellowship, Department of Health Research (Dr Sanjay Basak), Government of India.

      References

        • Falomir-Lockhart L.J.
        • Cavazzutti G.F.
        • Gimenez E.
        • Toscani A.M.
        Fatty acid signaling mechanisms in neural cells: fatty acid receptors.
        Front Cell Neurosci. 2019; 13: 162
        • Liu J.J.
        • Green P.
        • John Mann J.
        • Rapoport S.I.
        • Sublette M.E.
        Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease.
        Brain Res. 2015; 1597: 220-246
        • Georgiadi A.
        • Kersten S.
        Mechanisms of gene regulation by fatty acids.
        Adv. Nutr. 2012; 3: 127-134
        • Calder P.C.
        Functional roles of fatty acids and their effects on human health.
        JPEN J. Parenter. Enteral Nutr. 2015; 39: 18S-32S
        • Abedi E.
        • Sahari M.A.
        Long-chain polyunsaturated fatty acid sources and evaluation of their nutritional and functional properties.
        Food Sci. Nutr. 2014; 2: 443-463
        • Chen C.T.
        • Domenichiello A.F.
        • Trepanier M.O.
        • Liu Z.
        • Masoodi M.
        • Bazinet R.P.
        The low levels of eicosapentaenoic acid in rat brain phospholipids are maintained via multiple redundant mechanisms.
        J. Lipid Res. 2013; 54: 2410-2422
        • Szefel J.
        • Kruszewski W.J.
        • Sobczak E.
        Factors influencing the eicosanoids synthesis in vivo.
        Biomed. Res. Int. 2015; 2015690692
        • Murphy R.A.
        • Mourtzakis M.
        • Mazurak V.C.
        n-3 polyunsaturated fatty acids: the potential role for supplementation in cancer.
        Curr. Opin. Clin. Nutr. Metab. Care. 2012; 15: 246-251
        • Marventano S.
        • Kolacz P.
        • Castellano S.
        • Galvano F.
        • Buscemi S.
        • Mistretta A.
        • Grosso G.
        A review of recent evidence in human studies of n-3 and n-6 PUFA intake on cardiovascular disease, cancer, and depressive disorders: does the ratio really matter?.
        Int. J. Food Sci. Nutr. 2015; 66: 611-622
        • Pai R.
        • Szabo I.L.
        • Soreghan B.A.
        • Atay S.
        • Kawanaka H.
        • Tarnawski A.S.
        PGE(2) stimulates VEGF expression in endothelial cells via ERK2/JNK1 signaling pathways.
        Biochem. Biophys. Res. Commun. 2001; 286: 923-928
        • Jin Y.
        • Arita M.
        • Zhang Q.
        • Saban D.R.
        • Chauhan S.K.
        • Chiang N.
        • Serhan C.N.
        • Dana R.
        Anti-angiogenesis effect of the novel anti-inflammatory and pro-resolving lipid mediators.
        Invest. Ophthalmol. Vis. Sci. 2009; 50: 4743-4752
        • Kamiyama M.
        • Pozzi A.
        • Yang L.
        • DeBusk L.M.
        • Breyer R.M.
        • Lin P.C.
        EP2, a receptor for PGE2, regulates tumor angiogenesis through direct effects on endothelial cell motility and survival.
        Oncogene. 2006; 25: 7019-7028
        • Mallick R.
        • Basak S.
        • Duttaroy A.K.
        Docosahexaenoic acid, 22:6n-3: its roles in the structure and function of the brain.
        Int. J. Dev. Neurosci. 2019; 79: 21-31
        • Lauritzen L.
        • Brambilla P.
        • Mazzocchi A.
        • Harslof L.B.
        • Ciappolino V.
        • Agostoni C.
        DHA effects in brain development and function.
        Nutrients. 2016; 8
        • Sun G.Y.
        • Simonyi A.
        • Fritsche K.L.
        • Chuang D.Y.
        • Hannink M.
        • Gu Z.
        • Greenlief C.M.
        • Yao J.K.
        • Lee J.C.
        • Beversdorf D.Q.
        Docosahexaenoic acid (DHA): an essential nutrient and a nutraceutical for brain health and diseases.
        Prostaglandins Leukot. Essent. Fatty Acids. 2018; 136: 3-13
        • Reimers A.
        • Ljung H.
        The emerging role of omega-3 fatty acids as a therapeutic option in neuropsychiatric disorders.
        Ther. Adv. Psychopharmacol. 2019; 92045125319858901
        • Hoppenbrouwers T.
        • Cvejic Hogervorst J.H.
        • Garssen J.
        • Wichers H.J.
        • Willemsen L.E.M.
        Long chain polyunsaturated fatty acids (LCPUFAs) in the prevention of food allergy.
        Front. Immunol. 2019; 10: 1118
        • Ghandour R.A.
        • Colson C.
        • Giroud M.
        • Maurer S.
        • Rekima S.
        • Ailhaud G.
        • Klingenspor M.
        • Amri E.Z.
        • Pisani D.F.
        Impact of dietary omega3 polyunsaturated fatty acid supplementation on brown and brite adipocyte function.
        J. Lipid Res. 2018; 59: 452-461
        • Grygiel-Gorniak B.
        Peroxisome proliferator-activated receptors and their ligands: nutritional and clinical implications–a review.
        Nutr. J. 2014; 13: 17
        • Sekikawa A.
        • Mahajan H.
        • Kadowaki S.
        • Hisamatsu T.
        • Miyagawa N.
        • Fujiyoshi A.
        • Kadota A.
        • Maegawa H.
        • Murata K.
        • Miura K.
        • Edmundowicz D.
        • Ueshima H.
        • Group S.R.
        Association of blood levels of marine omega-3 fatty acids with coronary calcification and calcium density in Japanese men.
        Eur. J. Clin. Nutr. 2019; 73: 783-792
        • Duttaroy A.K.
        Transport of fatty acids across the human placenta: a review.
        Prog. Lipid Res. 2009; 48: 52-61
        • Hara T.
        • Kimura I.
        • Inoue D.
        • Ichimura A.
        • Hirasawa A.
        Free fatty acid receptors and their role in regulation of energy metabolism.
        Rev. Physiol. Biochem. Pharmacol. 2013; 164: 77-116
        • Zolezzi J.M.
        • Inestrosa N.C.
        Peroxisome proliferator-activated receptors and Alzheimer's disease: hitting the blood-brain barrier.
        Mol. Neurobiol. 2013; 48: 438-451
        • Dutta-Roy A.K.
        Transport mechanisms for long-chain polyunsaturated fatty acids in the human placenta.
        Am. J. Clin. Nutr. 2000; 71: 315S-322S
        • Innis S.M.
        Dietary omega 3 fatty acids and the developing brain.
        Brain Res. 2008; 1237: 35-43
        • Abdelwahab S.A.
        • Owada Y.
        • Kitanaka N.
        • Iwasa H.
        • Sakagami H.
        • Kondo H.
        Localization of brain-type fatty acid-binding protein in Kupffer cells of mice and its transient decrease in response to lipopolysaccharide.
        Histochem. Cell Biol. 2003; 119: 469-475
        • Szajewska H.
        • Horvath A.
        • Koletzko B.
        Effect of n-3 long-chain polyunsaturated fatty acid supplementation of women with low-risk pregnancies on pregnancy outcomes and growth measures at birth: a meta-analysis of randomized controlled trials.
        Am. J. Clin. Nutr. 2006; 83: 1337-1344
        • Krabbendam L.
        • Bakker E.
        • Hornstra G.
        • van Os J.
        Relationship between DHA status at birth and child problem behaviour at 7 years of age.
        Prostaglandins Leukot. Essent. Fatty Acids. 2007; 76: 29-34
        • Li D.
        • Weisinger H.S.
        • Weisinger R.S.
        • Mathai M.
        • Armitage J.A.
        • Vingrys A.J.
        • Sinclair A.J.
        Omega 6 to omega 3 fatty acid imbalance early in life leads to persistent reductions in DHA levels in glycerophospholipids in rat hypothalamus even after long-term omega 3 fatty acid repletion.
        Prostaglandins Leukot. Essent. Fatty Acids. 2006; 74: 391-399
        • Innis S.M.
        Essential fatty acids in growth and development.
        Prog. Lipid Res. 1991; 30: 39-103
        • Neuringer M.
        Infant vision and retinal function in studies of dietary long-chain polyunsaturated fatty acids: methods, results, and implications.
        Am. J. Clin. Nutr. 2000; 71: 256S-267S
        • Uauy R.
        • Hoffman D.R.
        • Peirano P.
        • Birch D.G.
        • Birch E.E.
        Essential fatty acids in visual and brain development.
        Lipids. 2001; 36: 885-895
        • Moser G.
        • Huppertz B.
        Implantation and extravillous trophoblast invasion: from rare archival specimens to modern biobanking.
        Placenta. 2017; 56: 19-26
        • Basak S.
        • Duttaroy A.K.
        Effects of fatty acids on angiogenic activity in the placental extravillious trophoblast cells.
        Prostaglandins Leukot. Essent. Fatty Acids. 2013; 88: 155-162
        • Chung I.B.
        • Yelian F.D.
        • Zaher F.M.
        • Gonik B.
        • Evans M.I.
        • Diamond M.P.
        • Svinarich D.M.
        Expression and regulation of vascular endothelial growth factor in a first trimester trophoblast cell line.
        Placenta. 2000; 21: 320-324
        • Chaiworapongsa T.
        • Romero R.
        • Savasan Z.A.
        • Kusanovic J.P.
        • Ogge G.
        • Soto E.
        • Dong Z.
        • Tarca A.
        • Gaurav B.
        • Hassan S.S.
        Maternal plasma concentrations of angiogenic/anti-angiogenic factors are of prognostic value in patients presenting to the obstetrical triage area with the suspicion of preeclampsia.
        J. Matern. Fetal Neonatal Med. 2011; 24: 1187-1207
        • Hill J.A.
        Maternal-embryonic cross-talk.
        Ann. N. Y. Acad. Sci. 2001; 943: 17-25
        • Hardman W.E.
        (n-3) fatty acids and cancer therapy.
        J. Nutr. 2004; 134: 3427S-3430S
        • Spencer L.
        • Mann C.
        • Metcalfe M.
        • Webb M.
        • Pollard C.
        • Spencer D.
        • Berry D.
        • Steward W.
        • Dennison A.
        The effect of omega-3 FAs on tumour angiogenesis and their therapeutic potential.
        Eur. J. Cancer. 2009; 45: 2077-2086
        • Salvado M.D.
        • Alfranca A.
        • Haeggstrom J.Z.
        • Redondo J.M.
        Prostanoids in tumor angiogenesis: therapeutic intervention beyond COX-2.
        Trends Mol. Med. 2012; 18: 233-243
        • Bagga D.
        • Wang L.
        • Farias-Eisner R.
        • Glaspy J.A.
        • Reddy S.T.
        Differential effects of prostaglandin derived from omega-6 and omega-3 polyunsaturated fatty acids on COX-2 expression and IL-6 secretion.
        Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 1751-1756
        • Pola R.
        • Gaetani E.
        • Flex A.
        • Aprahamian T.R.
        • Bosch-Marce M.
        • Losordo D.W.
        • Smith R.C.
        • Pola P.
        Comparative analysis of the in vivo angiogenic properties of stable prostacyclin analogs: a possible role for peroxisome proliferator-activated receptors.
        J. Mol. Cell Cardiol. 2004; 36: 363-370
        • Dimitriadis E.
        • White C.A.
        • Jones R.L.
        • Salamonsen L.A.
        Cytokines, chemokines and growth factors in endometrium related to implantation.
        Hum. Reprod. Update. 2005; 11: 613-630
        • Tobin K.A.
        • Johnsen G.M.
        • Staff A.C.
        • Duttaroy A.K.
        Long-chain polyunsaturated fatty acid transport across human placental choriocarcinoma (BeWo) cells.
        Placenta. 2009; 30: 41-47
        • Zhang Y.
        • Daaka Y.
        PGE2 promotes angiogenesis through EP4 and PKA Cgamma pathway.
        Blood. 2011; 118: 5355-5364
        • Weedon-Fekjaer M.S.
        • Duttaroy A.K.
        • Nebb H.I.
        Liver X receptors mediate inhibition of hCG secretion in a human placental trophoblast cell line.
        Placenta. 2005; 26: 721-728
        • Wang D.
        • Wang H.
        • Brown J.
        • Daikoku T.
        • Ning W.
        • Shi Q.
        • Richmond A.
        • Strieter R.
        • Dey S.K.
        • DuBois R.N.
        CXCL1 induced by prostaglandin E2 promotes angiogenesis in colorectal cancer.
        J. Exp. Med. 2006; 203: 941-951
        • Fu S.L.
        • Wu Y.L.
        • Zhang Y.P.
        • Qiao M.M.
        • Chen Y.
        Anti-cancer effects of COX-2 inhibitors and their correlation with angiogenesis and invasion in gastric cancer.
        World J. Gastroenterol. 2004; 10: 1971-1974
        • Kang J.X.
        • Weylandt K.H.
        Modulation of inflammatory cytokines by omega-3 fatty acids.
        Subcell. Biochem. 2008; 49: 133-143
        • Szymczak M.
        • Murray M.
        • Petrovic N.
        Modulation of angiogenesis by omega-3 polyunsaturated fatty acids is mediated by cyclooxygenases.
        Blood. 2008; 111: 3514-3521
        • Takahashi S.
        Vascular endothelial growth factor (VEGF), vegf receptors and their inhibitors for antiangiogenic tumor therapy.
        Biol. Pharm. Bull. 2011; 34: 1785-1788
        • Massaro M.
        • Scoditti E.
        • Carluccio M.A.
        • Campana M.C.
        • De Caterina R.
        Omega-3 fatty acids, inflammation and angiogenesis: basic mechanisms behind the cardioprotective effects of fish and fish oils.
        Cell. Mol. Biol. (Noisy-le-grand). 2010; 56: 59-82
        • Scoditti E.
        • Massaro M.
        • Carluccio M.A.
        • Distante A.
        • Storelli C.
        • De Caterina R.
        PPARgamma agonists inhibit angiogenesis by suppressing PKCalpha- and CREB-mediated COX-2 expression in the human endothelium.
        Cardiovasc. Res. 2010; 86: 302-310
        • Kanayasu T.
        • Morita I.
        • Nakao-Hayashi J.
        • Asuwa N.
        • Fujisawa C.
        • Ishii T.
        • Ito H.
        • Murota S.
        Eicosapentaenoic acid inhibits tube formation of vascular endothelial cells in vitro.
        Lipids. 1991; 26: 271-276
        • Yang S.P.
        • Morita I.
        • Murota S.I.
        Eicosapentaenoic acid attenuates vascular endothelial growth factor-induced proliferation via inhibiting FLK-1 receptor expression in bovine carotid artery endothelial cells.
        J. Cell. Physiol. 1998; 176: 342-349
        • Murota S.I.
        • Onodera M.
        • Morita I.
        Regulation of angiogenesis by controlling VEGF receptor.
        Ann. N. Y. Acad. Sci. 2000; 902 (discussion 212-203): 208-212
        • Kim H.J.
        • Vosseler C.A.
        • Weber P.C.
        • Erl W.
        Docosahexaenoic acid induces apoptosis in proliferating human endothelial cells.
        J. Cell. Physiol. 2005; 204: 881-888
        • Ghosh-Choudhury T.
        • Mandal C.C.
        • Woodruff K.
        • St Clair P.
        • Fernandes G.
        • Choudhury G.G.
        • Ghosh-Choudhury N.
        Fish oil targets PTEN to regulate NFKAPPAB for downregulation of anti-apoptotic genes in breast tumor growth.
        Breast Cancer Res. Treat. 2009; 118: 213-228
        • Tsuji M.
        • Murota S.I.
        • Morita I.
        Docosapentaenoic acid (22:5, n-3) suppressed tube-forming activity in endothelial cells induced by vascular endothelial growth factor.
        Prostaglandins Leukot. Essent. Fatty Acids. 2003; 68: 337-342
        • Calviello G.
        • Di Nicuolo F.
        • Gragnoli S.
        • Piccioni E.
        • Serini S.
        • Maggiano N.
        • Tringali G.
        • Navarra P.
        • Ranelletti F.O.
        • Palozza P.
        n-3 PUFAs reduce VEGF expression in human colon cancer cells modulating the COX-2/PGE2 induced ERK-1 and -2 and HIF-1alpha induction pathway.
        Carcinogenesis. 2004; 25: 2303-2310
        • Sapieha P.
        • Stahl A.
        • Chen J.
        • Seaward M.R.
        • Willett K.L.
        • Krah N.M.
        • Dennison R.J.
        • Connor K.M.
        • Aderman C.M.
        • Liclican E.
        • Carughi A.
        • Perelman D.
        • Kanaoka Y.
        • Sangiovanni J.P.
        • Gronert K.
        • Smith L.E.
        5-Lipoxygenase metabolite 4-HDHA is a mediator of the antiangiogenic effect of omega-3 polyunsaturated fatty acids.
        Sci. Transl. Med. 2011; 3: 69ra12
        • Li Q.
        • Zhang Q.
        • Wang M.
        • Zhao S.
        • Ma J.
        • Luo N.
        • Li N.
        • Li Y.
        • Xu G.
        • Li J.
        Eicosapentaenoic acid modifies lipid composition in caveolae and induces translocation of endothelial nitric oxide synthase.
        Biochimie. 2007; 89: 169-177
        • Matesanz N.
        • Park G.
        • McAllister H.
        • Leahey W.
        • Devine A.
        • McVeigh G.E.
        • Gardiner T.A.
        • McDonald D.M.
        Docosahexaenoic acid improves the nitroso-redox balance and reduces VEGF-mediated angiogenic signaling in microvascular endothelial cells.
        Invest. Ophthalmol. Vis. Sci. 2010; 51: 6815-6825
        • Hamed E.A.
        • Zakary M.M.
        • Abdelal R.M.
        • Abdel Moneim E.M.
        Vasculopathy in type 2 diabetes mellitus: role of specific angiogenic modulators.
        J. Physiol. Biochem. 2011; 67: 339-349
        • Sterescu A.E.
        • Rousseau-Harsany E.
        • Farrell C.
        • Powell J.
        • David M.
        • Dubois J.
        The potential efficacy of omega-3 fatty acids as anti-angiogenic agents in benign vascular tumors of infancy.
        Med. Hypotheses. 2006; 66: 1121-1124
        • Chen J.
        Src may be involved in the anti-cancer effect of conjugated linoleic acid. Comment on: CLA reduces breast cancer cell growth and invasion through ER and PI3K/Akt pathways.
        Chem. Biol. Interact. 2010; 186 (author reply 252-253): 250-251
        • Johnsen G.M.
        • Basak S.
        • Weedon-Fekjaer M.S.
        • Staff A.C.
        • Duttaroy A.K.
        Docosahexaenoic acid stimulates tube formation in first trimester trophoblast cells, HTR8/SVneo.
        Placenta. 2011; 32: 626-632
        • Gottlicher M.
        • Demoz A.
        • Svensson D.
        • Tollet P.
        • Berge R.K.
        • Gustafsson J.A.
        Structural and metabolic requirements for activators of the peroxisome proliferator-activated receptor.
        Biochem. Pharmacol. 1993; 46: 2177-2184
        • Kang J.X.
        • Liu A.
        The role of the tissue omega-6/omega-3 fatty acid ratio in regulating tumor angiogenesis.
        Cancer Metastasis Rev. 2013; 32: 201-210
        • Basak S.
        • Duttaroy A.K.
        cis-9,trans-11 conjugated linoleic acid stimulates expression of angiopoietin like-4 in the placental extravillous trophoblast cells.
        Biochim. Biophys. Acta. 2013; 1831: 834-843
        • Dutta-Roy A.K.
        Cellular uptake of long-chain fatty acids: role of membrane-associated fatty-acid-binding/transport proteins.
        Cell. Mol. Life Sci. 2000; 57: 1360-1372
        • Schaiff W.T.
        • Bildirici I.
        • Cheong M.
        • Chern P.L.
        • Nelson D.M.
        • Sadovsky Y.
        Peroxisome proliferator-activated receptor-gamma and retinoid X receptor signaling regulate fatty acid uptake by primary human placental trophoblasts.
        J. Clin. Endocrinol. Metab. 2005; 90: 4267-4275
        • Prieto-Sanchez M.T.
        • Ruiz-Palacios M.
        • Blanco-Carnero J.E.
        • Pagan A.
        • Hellmuth C.
        • Uhl O.
        • Peissner W.
        • Ruiz-Alcaraz A.J.
        • Parrilla J.J.
        • Koletzko B.
        • Larque E.
        Placental MFSD2a transporter is related to decreased DHA in cord blood of women with treated gestational diabetes.
        Clin. Nutr. 2017; 36: 513-521
        • Desoye G.
        • Gauster M.
        • Wadsack C.
        Placental transport in pregnancy pathologies.
        Am. J. Clin. Nutr. 2011; 94: 1896S-1902S
        • Chassen S.S.
        • Ferchaud-Roucher V.
        • Gupta M.B.
        • Jansson T.
        • Powell T.L.
        Alterations in placental long chain polyunsaturated fatty acid metabolism in human intrauterine growth restriction.
        Clin. Sci. 2018; 132: 595-607
        • Assumpcao R.P.
        • Mucci D.B.
        • Fonseca F.C.P.
        • Marcondes H.
        • Sardinha F.L.C.
        • Citelli M.
        • Tavares do carmo M.G.
        Fatty acid profile of maternal and fetal erythrocytes and placental expression of fatty acid transport proteins in normal and intrauterine growth restriction pregnancies.
        Prostaglandins Leukot. Essent. Fatty Acids. 2017; 125: 24-31
        • Segura M.T.
        • Demmelmair H.
        • Krauss-Etschmann S.
        • Nathan P.
        • Dehmel S.
        • Padilla M.C.
        • Rueda R.
        • Koletzko B.
        • Campoy C.
        Maternal BMI and gestational diabetes alter placental lipid transporters and fatty acid composition.
        Placenta. 2017; 57: 144-151
        • Lager S.
        • Ramirez V.I.
        • Gaccioli F.
        • Jang B.
        • Jansson T.
        • Powell T.L.
        Protein expression of fatty acid transporter 2 is polarized to the trophoblast basal plasma membrane and increased in placentas from overweight/obese women.
        Placenta. 2016; 40: 60-66
        • Lager S.
        • Ramirez V.I.
        • Acosta O.
        • Meireles C.
        • Miller E.
        • Gaccioli F.
        • Rosario F.J.
        • Gelfond J.A.L.
        • Hakala K.
        • Weintraub S.T.
        • Krummel D.A.
        • Powell T.L.
        Docosahexaenoic acid supplementation in pregnancy modulates placental cellular signaling and nutrient transport capacity in obese women.
        J. Clin. Endocrinol. Metab. 2017; 102: 4557-4567
        • Fonseca F.
        • Mucci D.B.
        • Assumpcao R.P.
        • Marcondes H.
        • Sardinha F.L.C.
        • Silva S.V.
        • Citelli M.
        • Tavares do Carmo M.D.G.
        Differential long-chain polyunsaturated fatty acids status and placental transport in adolescent pregnancies.
        Nutrients. 2018; : 10
        • Mousiolis A.V.
        • Kollia P.
        • Skentou C.
        • Messinis I.E.
        Effects of leptin on the expression of fatty acid-binding proteins in human placental cell cultures.
        Mol. Med. Rep. 2012; 5: 497-502
        • Elmasri H.
        • Karaaslan C.
        • Teper Y.
        • Ghelfi E.
        • Weng M.
        • Ince T.A.
        • Kozakewich H.
        • Bischoff J.
        • Cataltepe S.
        Fatty acid binding protein 4 is a target of VEGF and a regulator of cell proliferation in endothelial cells.
        FASEB J. 2009; 23: 3865-3873
        • Cataltepe O.
        • Arikan M.C.
        • Ghelfi E.
        • Karaaslan C.
        • Ozsurekci Y.
        • Dresser K.
        • Li Y.
        • Smith T.W.
        • Cataltepe S.
        Fatty acid binding protein 4 is expressed in distinct endothelial and non-endothelial cell populations in glioblastoma.
        Neuropathol. Appl. Neurobiol. 2012; 38: 400-410
        • Elmasri H.
        • Ghelfi E.
        • Yu C.W.
        • Traphagen S.
        • Cernadas M.
        • Cao H.
        • Shi G.P.
        • Plutzky J.
        • Sahin M.
        • Hotamisligil G.
        • Cataltepe S.
        Endothelial cell-fatty acid binding protein 4 promotes angiogenesis: role of stem cell factor/c-kit pathway.
        Angiogenesis. 2012; 15: 457-468
        • Ghelfi E.
        • Yu C.W.
        • Elmasri H.
        • Terwelp M.
        • Lee C.G.
        • Bhandari V.
        • Comhair S.A.
        • Erzurum S.C.
        • Hotamisligil G.S.
        • Elias J.A.
        • Cataltepe S.
        Fatty acid binding protein 4 regulates VEGF-induced airway angiogenesis and inflammation in a transgenic mouse model: implications for asthma.
        Am. J. Pathol. 2013; 182: 1425-1433
        • Fishman S.J.
        • Mulliken J.B.
        Hemangiomas and vascular malformations of infancy and childhood.
        Pediatr. Clin. North Am. 1993; 40: 1177-1200
        • Basak S.
        • Duttaroy A.K.
        Leptin induces tube formation in first-trimester extravillous trophoblast cells.
        Eur. J. Obstet. Gynecol. Reprod. Biol. 2012; 164: 24-29
        • Fang L.Y.
        • Wong T.Y.
        • Chiang W.F.
        • Chen Y.L.
        Fatty-acid-binding protein 5 promotes cell proliferation and invasion in oral squamous cell carcinoma.
        J. Oral Pathol. Med. 2010; 39: 342-348
        • Storch J.
        • Thumser A.E.
        Tissue-specific functions in the fatty acid-binding protein family.
        J. Biol. Chem. 2010; 285: 32679-32683
        • Yan Y.
        • Peng H.
        • Wang P.
        • Wang H.
        • Dong M.
        Increased expression of fatty acid binding protein 4 in preeclamptic placenta and its relevance to preeclampsia.
        Placenta. 2016; 39: 94-100
        • Pandya A.D.
        • Das M.K.
        • Sarkar A.
        • Vilasagaram S.
        • Basak S.
        • Duttaroy A.K.
        Tube formation in the first trimester placental trophoblast cells: differential effects of angiogenic growth factors and fatty acids.
        Cell Biol. Int. 2016; 40: 652-661