Meeting the fetal requirement for polyunsaturated fatty acids in pregnancy

A co-ordinated transcriptional programme in the maternal liver supplies long chain polyunsaturated fatty acids to the conceptus using phospholipids

The long and very long chain polyunsaturated fatty acids (LC-PUFAs) are preferentially transported by the mother to the fetus. Failure to supply LC-PUFAs is strongly linked with stillbirth, fetal growth restriction, and impaired neurodevelopmental outcomes. However, dietary supplementation during pregnancy is unable to simply reverse these outcomes, suggesting imperfectly understood interactions between dietary fatty acid intake and the molecular mechanisms of maternal supply. Here we employ a comprehensive approach combining untargeted and targeted lipidomics with transcriptional profiling of maternal and fetal tissues in mouse pregnancy. Comparison of wild-type mice with genetic models of impaired lipid metabolism allows us to describe maternal hepatic adaptations required to provide LC-PUFAs to the developing fetus. A late pregnancy-specific, selective activation of the Liver X Receptor signalling pathway dramatically increases maternal supply of LC-PUFAs within circulating phospholipids. Crucially, genetic ablation of this pathway in the mother reduces LC-PUFA accumulation by the fetus, specifically of docosahexaenoic acid (DHA), a critical nutrient for brain development.

Maternal serum fatty acid binding protein-4 level is upregulated in fetal growth restriction with abnormal Doppler flow patterns

PURPOSE

This study aimed to determine fatty acid binding protein-4 (FABP-4) concentrations in maternal serum of fetal growth restriction (FGR) pregnancies and controls of normal pregnancies. Furthermore, we hypothesized that the alterations in FABP-4 levels might correlate with FGR severity.

METHODS

We performed this prospective case-control study with 83 pregnant women. The study groups included 26 FGR pregnancies without abnormal fetal Doppler flow patterns and 25 pregnancies complicated with FGR accompanied by abnormal fetal Doppler flow patterns.

RESULTS

The median serum FABP-4 concentrations were significantly higher in the FGR cases with abnormal Doppler flow pattern group (2.09 ng/mL) than in the FGR cases without abnormal Doppler flow pattern group (1.62 ng/mL) and the control group (1.20 ng/mL, p < 0.001). A significant negative correlation was observed between maternal serum FABP-4 levels and time to birth from blood sample collection (r = -0.356 and p = 0.001), gestational week at birth (r = -0.386 and p < 0.001), and birth weight (r = -0.394 and p < 0.001). A 1.35 ng/mL cut-off value of serum FABP-4 level could be used to discriminate FGR cases with a 78.4% sensitivity and 60.6% specificity. The optimal cut-off value of FABP-4 levels as an indicator for the diagnosis of FGR with abnormal Doppler flow pattern was estimated to be 1.76 ng/mL, which yielded a sensitivity of 84.0% and a specificity of 75.8%.

CONCLUSION

FABP-4 is a crucial biomarker in the diagnosis and determining the severity of pregnancies with restricted fetal growth. We consider that FABP-4 is a powerful, reliable, and unique biomarker to diagnose FGR pregnancies.

Baseline red blood cell and breast milk DHA levels affect responses to standard dose of DHA in lactating women on a controlled feeding diet

BACKGROUND

The importance of providing the newborn infant with docosahexaenoic acid (DHA) from breast milk is well established. However, women in the United States, on average, have breast milk DHA levels of 0.20%, which is below the worldwide average (and proposed target) of >0.32%. Additionally, the relationship between maternal red blood cell (RBC) and breast milk DHA levels may provide insight into the sufficiency of DHA recommendations during lactation. Whether the standard recommendation of at least 200 mg/day of supplemental DHA during lactation is sufficient for most women to achieve a desirable RBC and breast milk DHA status is unknown.

METHODS

Lactating women (n = 27) at about 5 weeks postpartum were enrolled in a 10-12 week controlled feeding study that included randomization to 480 or 930 mg choline/d (diet plus supplementation). As part of the intervention, all participants were required to consume a 200 mg/d of microalgal DHA. RBC and breast milk DHA levels were measured by capillary gas chromatography in an exploratory analysis.

RESULTS

Median RBC DHA was 5.0% (95% CI: 4.3, 5.5) at baseline and 5.1% (4.6, 5.4) after 10 weeks of supplementation (P = 0.6). DHA as a percent of breast milk fatty acids increased from 0.19% (0.18, 0.33) to 0.34% (0.27, 0.38) after supplementation (P<0.05). The proportion of women meeting the target RBC DHA level of >5% was unchanged (52% at baseline and week 10). The proportion of women achieving a breast milk DHA level of >0.32% approximately doubled from 30% to 56% (p = 0.06). Baseline RBC and breast milk DHA levels affected their responses to supplementation. Those with baseline RBC and breast milk DHA levels above the median (5% and 0.19%, respectively) experienced no change or a slight decrease in levels, while those below the median had a significant increase. Choline supplementation did not significantly influence final RBC or breast milk DHA levels.

CONCLUSIONS

On average, the standard prenatal DHA dose of 200 mg/d did not increase RBC DHA but did increase breastmilk DHA over 10 weeks in a cohort of lactating women in a controlled-feeding study. Baseline DHA levels in RBC and breast milk affected the response to DHA supplementation, with lower levels being associated with a greater increase and higher levels with no change or a slight decrease. Additional larger, dose-response DHA trials accounting for usual intakes and baseline DHA status are needed to determine how to best achieve target breast milk DHA levels and to identify additional modifiers of the variable breast milk DHA response to maternal DHA supplementation.

Maternal PM2.5 exposure and abnormal placental nutrient transport

Epidemiological studies of human and animal experiments indicated that gestational exposure to atmospheric pollutants could be followed by the abnormal placental development. However, the effects of this exposure on the placental transportation for nutrients have not been systematically investigated. In this study, fine particulate matters (PM_2.5) samples were collected in Taiyuan and pregnant rodent models were administered with 3 mg/kg b.w. PM_2.5 by oropharyngeal aspiration every other day starting on embryonic day 0.5 (E0.5). Then the pregnant mice were sacrificed and their placentas were collected at different time points. The results showed that maternal PM_2.5 exposure (MPE) disrupted the expression of proliferating cell nuclear antigen (PCNA) at all time points and inhibited the cell proliferation in placenta. Following that, the capacity for placental nutrient transport was impaired. The changes at E18.5 were observed most significantly, showing the altered mRNA expression of amino acid, long-chain polyunsaturated fatty acid (LCPUFA), glucose and folate transporters. In addition, the glycogen content was elevated at E18.5, and the triglyceride content was increased at E13.5 and E15.5 and decreased at E18.5 in the placenta after MPE. In a word, the adverse effect induced by MPE revealed that MPE led tothe disruption on the nutrient supply to the developing fetus via modulating the abundance of placental nutrient transporters (PNT).

H. Smith L, Puttonen H, Fyhr IM, Sävman K, Nilsson AK, Klevebro S. Docosahexaenoic Acid and Arachidonic Acid Levels Are Associated with Early Systemic Inflammation in Extremely Preterm Infants

Fetal and early postnatal inflammation have been associated with increased morbidity in extremely preterm infants. This study aimed to demonstrate if postpartum levels of docosahexaenoic acid (DHA) and arachidonic acid (AA) were associated with early inflammation. In a cohort of 90 extremely preterm infants, DHA and AA in cord blood, on the first postnatal day and on postnatal day 7 were examined in relation to early systemic inflammation, defined as elevated C-reactive protein (CRP) and/or interleukin-6 (IL-6) within 72 h from birth, with or without positive blood culture. Median serum level of DHA was 0.5 mol% (95% CI (confidence interval) 0.2–0.9, P = 0.006) lower than the first postnatal day in infants with early systemic inflammation, compared to infants without signs of inflammation, whereas levels of AA were not statistically different between infants with and without signs of inflammation. In cord blood, lower serum levels of both DHA (correlation coefficient −0.40; P = 0.010) and AA (correlation coefficient −0.54; p < 0.001) correlated with higher levels of IL-6. Levels of DHA or AA did not differ between infants with and without histological signs of chorioamnionitis or fetal inflammation. In conclusion, serum levels of DHA at birth were associated with the inflammatory response during the early postnatal period in extremely preterm infants.

Influence of clinical characteristics on maternal DHA and other polyunsaturated fatty acid status in pregnancy: A systematic review

INTRODUCTION

Omega-3 DHA is important for the prevention of preterm birth, however there is limited knowledge of the determinants of omega-3 status during pregnancy. The primary objective of this systematic review was to synthesise data from existing studies assessing relationships between clinical factors and maternal DHA status.

MATERIALS AND METHODS

The Medline, Embase, Amed, and CINAHL databases were searched for studies reporting measures of maternal omega-3 status and one or more clinical characteristics.

RESULTS

Eighteen studies were included in the final analyses. Factors associated with a higher BMI (overweight, higher gestational weight gain, gestational diabetes), or lower parity were each associated with higher omega-3 status in the majority of studies, with mixed findings for other comparisons.

DISCUSSION

Inconsistent findings between studies make it difficult to draw clear conclusions about the relationship between clinical factors and maternal omega-3 DHA status. However, maternal overweight and associated metabolic conditions may increase lipid metabolism.

Dietary phenylalanine requirements during early and late gestation in healthy pregnant women

BACKGROUND

Phenylalanine is an indispensable amino acid and, via tyrosine, is the precursor for the neurotransmitters dopamine, norepinephrine, and epinephrine. Currently, dietary requirements for phenylalanine during pregnancy are unknown.

OBJECTIVES

This study's aim was to determine phenylalanine requirements (in the presence of excess tyrosine) during early and late gestation using direct amino acid oxidation (DAAO; with l-[1-13C]phenylalanine) and indicator amino acid oxidation (IAAO; with l-[1-13C]leucine).

METHODS

Twenty-three healthy women (age: 30.4 ± 3.1 y, mean ± SD) were studied at a range of phenylalanine intakes (5.5-30.5 mg · kg-1 · d-1 in early and late pregnancy using DAAO, and 2.5-30.5 mg · kg-1 · d-1 in late pregnancy using IAAO) for a total of 76 study days. Test intakes were provided as 8 isocaloric and isonitrogenous meals with 1.5 g · kg-1 · d-1 protein and energy at 1.7 times the measured resting energy expenditure. Breath samples were analyzed on an isotope ratio mass spectrometer for 13C enrichment. Phenylalanine requirement was determined using a 2-phase linear regression crossover model to identify a breakpoint in 13CO2 production (representing the mean requirement) in response to phenylalanine intakes.

RESULTS

Phenylalanine requirement during early pregnancy was determined to be 15 mg · kg-1 · d-1 (95% CI: 10.4, 19.9 mg · kg-1 · d-1); during late pregnancy, it was determined to be 21 mg · kg-1 · d-1 by DAAO (95% CI: 17.4, 24.7 mg · kg-1 · d-1) and IAAO (95% CI: 10.5, 32.2 mg · kg-1 · d-1).

CONCLUSIONS

Our results suggest a higher requirement (40%) for phenylalanine during late pregnancy than during early pregnancy. Moreover, the early pregnancy requirements are higher than the previous adult male requirement (9.1 mg · kg-1 · d-1; 95% CI: 4.6, 13.6 mg · kg-1 · d-1), although the 95% CIs overlap. Both DAAO and IAAO methods provided similar breakpoints in late pregnancy, showing that the DAAO method was appropriate even though low phenylalanine intakes could not be tested. These results have potential implications for gestation stage-specific dietary phenylalanine recommendations in future.This trial was registered at clinicaltrials.gov as NCT02669381.

Nutrition and its role in human evolution

Our understanding of human evolution has improved rapidly over recent decades, facilitated by large-scale cataloguing of genomic variability amongst both modern and archaic humans. It seems clear that the evolution of the ancestors of chimpanzees and hominins separated 7-9 million years ago with some migration out of Africa by the earlier hominins; Homo sapiens slowly emerged as climate change resulted in drier, less forested African conditions. The African populations expanded and evolved in many different conditions with slow mutation and selection rates in the human genome, but with much more rapid mutation occurring in mitochondrial DNA. We now have evidence stretching back 300 000 years of humans in their current form, but there are clearly four very different large African language groups that correlate with population DNA differences. Then, about 50 000-100 000 years ago a small subset of modern humans also migrated out of Africa resulting in a persistent signature of more limited genetic diversity amongst non-African populations. Hybridization with archaic hominins occurred around this time such that all non-African modern humans possess some Neanderthal ancestry and Melanesian populations additionally possess some Denisovan ancestry. Human populations both within and outside Africa also adapted to diverse aspects of their local environment including altitude, climate, UV exposure, diet and pathogens, in some cases leaving clear signatures of patterns of genetic variation. Notable examples include haemoglobin changes conferring resistance to malaria, other immune changes and the skin adaptations favouring the synthesis of vitamin D. As humans migrated across Eurasia, further major mitochondrial changes occurred with some interbreeding with ancient hominins and the development of alcohol intolerance. More recently, an ability to retain lactase persistence into adulthood has evolved rapidly under the environmental stimulus of pastoralism with the ability to husband lactating ruminants. Increased amylase copy numbers seem to relate to the availability of starchy foods, whereas the capacity to desaturase and elongate monounsaturated fatty acids in different societies seems to be influenced by whether there is a lack of supply of readily available dietary sources of long-chain polyunsaturated fatty acids. The process of human evolution includes genetic drift and adaptation to local environments, in part through changes in mitochondrial and nuclear DNA. These genetic changes may underlie susceptibilities to some modern human pathologies including folate-responsive neural tube defects, diabetes, other age-related pathologies and mental health disorders.

Implications of Lipids in Neonatal Body Weight and Fat Mass in Gestational Diabetic Mothers and Non-Diabetic Controls

PURPOSE OF REVIEW

Maternal lipid metabolism greatly changes during pregnancy and we review in this article how they influence fetal adiposity and growth under non-diabetic and gestational diabetic conditions.

RECENT FINDINGS

In pregnant women without diabetes (control), maternal glycemia correlates with neonatal glycemia, neonatal body weight and fat mass. In pregnant women with gestational diabetes mellitus (GDM), maternal glucose correlates with neither neonatal glycemia, neonatal birth weight nor fat mass, but maternal triacylglycerols (TAG), non-esterified fatty acids (NEFA) and glycerol do correlate with birth weight and neonatal adiposity. The proportions of maternal plasma arachidonic (AA) and docosahexaenoic (DHA) acids decrease from the first to the third trimester of pregnancy, and at term these long-chain polyunsaturated fatty acids are higher in cord blood plasma than in mothers, indicating efficient placental transfer. In control or pregnant women with GDM at term, the maternal concentration of individual fatty acids does not correlate with neonatal body weight or fat mass, but cord blood fatty acid levels correlate with birth weight and neonatal adiposity-positively in controls, but negatively in GDM. The proportion of AA and DHA in umbilical artery plasma in GDM is lower than in controls but not in umbilical vein plasma. Therefore, an increased utilization of those two fatty acids by fetal tissues, rather than impaired placental transfer, is responsible for their smaller proportion in plasma of GDM newborns. In control pregnant women, maternal glycemia controls neonatal body weight and fat mass, whereas in mothers with GDM-even with good glycemic control-maternal lipids and their greater utilization by the fetus play a critical role in neonatal body weight and fat mass. We propose that altered lipid metabolism rather than hyperglycemia constitutes a risk for macrosomia in GDM.

[Expression of FABP7 in mouse placenta tissue and human trophoblast HTR-8/Svneo cells]

OBJECTIVE

To detect the expression of FABP7 in the placenta of pregnant mice and in HTR-8/Svneo cells.

METHODS

Real-time PCR and immunofluorescence were used to detect FABP7 mRNA and protein expressions in the uterine and placental tissue of pregnant mice at different days of gestation. FABP7 expression was also detected in cultured HTR-8/Svneo cells using immunofluorescence assay. The mice were treated with E₂, P₄ or their combination for 6 and 24 h and Fabp7 mRNA level in the uterus was detected with real-time PCR.

RESULTS

At 7.5-10.5 days of gestation, the pregnant mice showed positive expressions of Fabp7 mRNA in the uterus and placenta, and FABP7 protein was detected in the decidualized cells and trophoblast giant cells. The expressions of FABP7 were detected at both the mRNA and protein levels in cultured HTR-8/Svneo cells. In mice treated with P4 alone or with E₂+P₄ for 6 and 24 h, the expression level of Fabp7 mRNA was upregulated in the uterus. Fabp7 upregulation was observed in mice at 24 h following E₂ treatment but not at 6 h.

CONCLUSION

FABP7 is expressed in trophoblast giant cells and decidual cells in the placental tissue of mice and in cultured HTR-8/Svneo cells, suggesting the involvement of FABP7 in placental development and in maintenance of pregnancy. E₂ and P₄ can regulate the expression of FABP7 in mouse uterus.

Maternal Fatty Acids and Their Association with Birth Outcome: A Prospective Study

Maternal nutrition, especially LCPUFA, is an important factor in determining fetal growth and development. Our earlier cross sectional study reports lower docosahexanoic acid (DHA) levels at the time of delivery in mothers delivering low birth weight (LBW) babies. This study was undertaken to examine the role of the maternal omega-3 and omega-6 fatty acid profile across the gestation in fetal growth. This is a hospital based study where women were recruited in early gestation. Maternal blood was collected at 3 time points, i.e., T1 = 16^th–20^th week, T2 = 26^th–30^th week and T3 = at delivery. Cord blood was collected at delivery. At delivery, these women were divided into 2 groups: those delivering at term a baby weighing >2.5kg [Normal birth weight (NBW) group] and those delivering at term a baby weighing <2.5kg [LBW group]. The study reports data on 111 women recruited at T1, out of which 60 women delivered an NBW baby at term and 51 women delivered an LBW baby at term. Fatty acids were analysed using gas chromatography. At T1 of gestation, maternal erythrocyte DHA levels were positively (p<0.05) associated with baby weight. Maternal plasma and erythrocyte arachidonic acid and total erythrocyte omega-6 fatty acid levels at T2 were higher (p<0.05 for both) in the LBW group. Total erythrocyte omega-3 fatty acid levels were lower (p<0.05) while total erythrocyte omega-6 fatty acid levels were higher (p<0.05) in the LBW group at delivery. Our data demonstrates the possible role of LCPUFA in the etiology of LBW babies right from early pregnancy.

Reduced Maternal Erythrocyte Long Chain Polyunsaturated Fatty Acids Exist in Early Pregnancy in Preeclampsia

The present prospective study examines proportions of maternal erythrocyte fatty acids across gestation and their association with cord erythrocyte fatty acids in normotensive control (NC) and preeclamptic pregnancies. We hypothesize that maternal fatty acid status in early pregnancy influences fetal fatty acid stores in preeclampsia. 137 NC women and 58 women with preeclampsia were included in this study. Maternal blood was collected at 3 time points during pregnancy (16-20th weeks, 26-30th weeks and at delivery). Cord blood was collected at delivery. Fatty acids were analyzed using gas chromatography. The proportions of maternal erythrocyte α-linolenic acid, docosahexaenoic acid, nervonic acid, and monounsaturated fatty acids (MUFA) (p < 0.05 for all) were lower while total n-6 fatty acids were higher (p < 0.05) at 16-20th weeks of gestation in preeclampsia as compared with NC. Cord 18:3n-3, 22:6n-3, 24:1n-9, MUFA, and total n-3 fatty acids (p < 0.05 for all) were also lower in preeclampsia as compared with NC. A positive association was observed between maternal erythrocyte 22:6n-3 and 24:1n-9 at 16-20th weeks with the same fatty acids in cord erythrocytes (p < 0.05 for both) in preeclampsia. Our study for the first time indicates alteration in maternal erythrocyte fatty acids at 16th weeks of gestation which is further reflected in cord erythrocytes at delivery in preeclampsia.

Nutrient availability, the microbiome, and intestinal transport during pregnancy

Adequate adaptation of the gastrointestinal tract is important during pregnancy to ensure that the increased metabolic demands by the developing fetus are met. These include changes in surface area mediated by villus hypertrophy and enhanced functional capacity of individual nutrient receptors, including those transporting glucose, fructose, leucine, and calcium. These processes are regulated either by the enhanced nutrient demand or are facilitated by changes in the secretion of pregnancy hormones. Our review also covers recent research into the microbiome, and how pregnancy could lead to microbial adaptations, which are beneficial to the mother, yet are also similar to those seen in the metabolic syndrome. The potential role of diet in modulating the microbiome during pregnancy, as well as the potential for the intestinal microbiota to induce pregnancy complications, are examined. Gaps in the current literature are highlighted, including those where only historical evidence is available, and we suggest areas that should be a priority for further research. In summary, although a significant degree of adaptation has been described, there are both well-established processes and more recent discoveries, such as changes within the maternal microbiome, that pose new questions as to how the gastrointestinal tract effectively adapts to pregnancy, especially in conjunction with maternal obesity.

Fatty acid binding protein-4 is expressed in the mouse placental labyrinth, yet is dispensable for placental triglyceride accumulation and fetal growth

INTRODUCTION

Fatty Acid Binding Protein-4 (FABP4) is a member of a family of FABP proteins that regulate intracellular lipid trafficking in diverse tissues. We recently showed that FABP4 regulates triglyceride accumulation in primary human trophoblasts. To assess the function of placental FABP4 in vivo, we tested the hypothesis that FABP4 is expressed in the murine placenta, and regulates placenta triglyceride accumulation.

METHODS

C57Bl/6 wild type or Fabp4-null mice were time-bred, and fetuses and placentas harvested at different time points during pregnancy. Placental FABP4 expression was assessed at different gestational ages, using quantitative PCR, immunohistochemistry, immunofluorescence and western immunoblotting. FABPs expression was examined by RT-qPCR. Placental lipids were extracted using the Folch method and triglyceride levels determined using a colorimetric quantification kit.

RESULTS

Using immunohistochemistry, we found that FABP4 was expressed in the placental labyrinthine layer, predominantly in endothelial cells in association with CD31 positive fetal capillaries. The level of placental FABP4 mRNA and protein increased from E12.5 to E16.5 and slightly decreased at E18.5. Breeding of Fabp4 heterozygous mice resulted in embryonic genotypes that followed a Mendelian distribution and exhibited normal weight and morphology, triglyceride content, and expression of other FABP family members. Exposure to hypoxia (O2 = 12%) between E12.5-E18.5 did not uncover a difference between wild type and Fabp4-null mice.

CONCLUSIONS

FABP4 is expressed in the mouse placental labyrinth, with highest expression at E16.5. FABP4 is dispensable for feto-placental growth and placental lipid accumulation.