Uptake and release of amino acids in the fetal-placental unit in human pregnancies

Maternal prediabetes as a risk factor of preeclampsia and placental dysfunction in pregnant female Sprague-Dawley rats

BACKGROUND

Prediabetes (PD) is associated with intermediate hyperglycaemia, dyslipidaemia, reduced nitric oxide (NO) bioavailability and moderate hypertension. All these factors are risk factor for preeclampsia (PE). However, the effects of the PD on placental function have not been shown. Accordingly, this study sought to investigate a possible link between maternal PD and the risk of developing PE.

METHODS

Pregnant female Sprague-Dawley rats (N = 18) were divided into normal, preeclamptic and prediabetic groups (n = 6 in each group) to study the effects of maternal PD on placenta function over the period of 19 days. Blood glucose and blood pressure were measured on gestational day (GND) 0, 9 and 18. Placental vascular endothelial growth factor (VEGF), placenta growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1) mRNA expression were measured terminally. Data were analysed using ANOVA followed by the Tukey-Kramer post hoc test. Values of p < .05 were used to indicate statistical significance.

RESULTS

Maternal PD and PE significantly increased blood glucose, decrease NO concentration and increase in MAP by comparison to the normal pregnant control group. Maternal PD significantly decreased VEGF, PlGF mRNA expression with a slight increase in sFlt-1 mRNA expression comparison to the normal pregnant control group.

CONCLUSIONS

Maternal PD is associated with placental dysfunction due to impaired glucose handling, endothelial dysfunction and an imbalance in angiogenic and antiangiogenic factors. Therefore, maternal PD is a risk factor of PE.

Regulation of placental amino acid transport in health and disease

Abnormal fetal growth, i.e., intrauterine growth restriction (IUGR) or fetal growth restriction (FGR) and fetal overgrowth, is associated with increased perinatal morbidity and mortality and is strongly linked to the development of metabolic and cardiovascular disease in childhood and later in life. Emerging evidence suggests that changes in placental amino acid transport may contribute to abnormal fetal growth. This review is focused on amino acid transport in the human placenta, however, relevant animal models will be discussed to add mechanistic insights. At least 25 distinct amino acid transporters with different characteristics and substrate preferences have been identified in the human placenta. Of these, System A, transporting neutral nonessential amino acids, and System L, mediating the transport of essential amino acids, have been studied in some detail. Importantly, decreased placental Systems A and L transporter activity is strongly associated with IUGR and increased placental activity of these two amino acid transporters has been linked to fetal overgrowth in human pregnancy. An array of factors in the maternal circulation, including insulin, IGF-1, and adiponectin, and placental signaling pathways such as mTOR, have been identified as key regulators of placental Systems A and L. Studies using trophoblast-specific gene targeting in mice have provided compelling evidence that changes in placental Systems A and L are mechanistically linked to altered fetal growth. It is possible that targeting specific placental amino acid transporters or their upstream regulators represents a novel intervention to alleviate the short- and long-term consequences of abnormal fetal growth in the future.

Angiogenic and vasoactive proteins in the maternal-fetal interface in healthy pregnancies and preeclampsia

BACKGROUND

Preeclampsia is characterized by maternal endothelial activation and placental dysfunction. Imbalance in maternal angiogenic and vasoactive factors has been linked to the pathophysiology. The contribution of the placenta as a source of these factors remains unclear. Furthermore, little is known about fetal angiogenic and vasoactive proteins and the relation between maternal and fetal levels.

OBJECTIVE

We describe placental growth factor, soluble Fms-like tyrosine kinase 1, soluble endoglin, and endothelin 1-3 in 5 vessels in healthy pregnancies, early- and late-onset preeclampsia. Specifically, we aimed to (1) compare protein abundance in vessels at the maternal-fetal interface between early- and late-onset preeclampsia, and healthy pregnancies, (2) describe placental uptake and release of proteins, and (3) describe protein abundance in the maternal vs fetal circulations.

STUDY DESIGN

Samples were collected from the maternal radial artery, uterine vein and antecubital vein, and fetal umbilical vein and artery in 75 healthy and 37 preeclamptic mother-fetus pairs (including 19 early-onset preeclampsia and 18 late-onset preeclampsia), during scheduled cesarean delivery. This method allows estimation of placental release and uptake of proteins by calculation of venoarterial differences on each side of the placenta. The microarray-based SomaScan assay quantified the proteins.

RESULTS

The abundance of soluble Fms-like tyrosine kinase 1 and endothelin 1 was higher in the maternal vessels in preeclampsia than in healthy pregnancies, with the highest abundance in early-onset preeclampsia. Placental growth factor was lower in the maternal vessels in early-onset preeclampsia than in both healthy and late-onset preeclampsia. Maternal endothelin 2 was higher in preeclampsia, with late-onset preeclampsia having the highest abundance. Our model confirmed placental release of placental growth factor and soluble Fms-like tyrosine kinase 1 to the maternal circulation in all groups. The placenta released soluble Fms-like tyrosine kinase 1 into the fetal circulation in healthy and late-onset preeclampsia pregnancies. Fetal endothelin 1 and soluble Fms-like tyrosine kinase 1 were higher in early-onset preeclampsia, whereas soluble endoglin and endothelin 3 were lower in both preeclampsia groups than healthy controls. Across groups, abundances of placental growth factor, soluble Fms-like tyrosine kinase 1, and endothelin 3 were higher in the maternal artery than the fetal umbilical vein, whereas endothelin 2 was lower.

CONCLUSION

An increasing abundance of maternal soluble Fms-like tyrosine kinase 1 and endothelin 1 across the groups healthy, late-onset preeclampsia and early-onset combined with a positive correlation may suggest that these proteins are associated with the pathophysiology and severity of the disease. Elevated endothelin 1 in the fetal circulation in early-onset preeclampsia represents a novel finding. The long-term effects of altered protein abundance in preeclampsia on fetal development and health remain unknown. Further investigation of these proteins' involvement in the pathophysiology and as treatment targets is warranted.

Predicting the onset of preeclampsia by longitudinal monitoring of metabolic changes throughout pregnancy with Raman spectroscopy

Preeclampsia is a life-threatening pregnancy disorder. Current clinical assays cannot predict the onset of preeclampsia until the late 2nd trimester, which often leads to poor maternal and neonatal outcomes. Here we show that Raman spectroscopy combined with machine learning in pregnant patient plasma enables rapid, highly sensitive maternal metabolome screening that predicts preeclampsia as early as the 1st trimester with >82% accuracy. We identified 12, 15 and 17 statistically significant metabolites in the 1st, 2nd and 3rd trimesters, respectively. Metabolic pathway analysis shows multiple pathways corresponding to amino acids, fatty acids, retinol, and sugars are enriched in the preeclamptic cohort relative to a healthy pregnancy. Leveraging Pearson's correlation analysis, we show for the first time with Raman Spectroscopy that metabolites are associated with several clinical factors, including patients' body mass index, gestational age at delivery, history of preeclampsia, and severity of preeclampsia. We also show that protein quantification alone of proinflammatory cytokines and clinically relevant angiogenic markers are inadequate in identifying at-risk patients. Our findings demonstrate that Raman spectroscopy is a powerful tool that may complement current clinical assays in early diagnosis and in the prognosis of the severity of preeclampsia to ultimately enable comprehensive prenatal care for all patients.

Postnatal hyperglycemia alters amino acid profile in retinas (model of Phase I ROP)

Nutritional deprivation occurring in most preterm infants postnatally can induce hyperglycemia, a significant and independent risk factor for suppressing physiological retinal vascularization (Phase I retinopathy of prematurity (ROP)), leading to compensatory but pathological neovascularization. Amino acid supplementation reduces retinal neovascularization in mice. Little is known about amino acid contribution to Phase I ROP. In mice modeling hyperglycemia-associated Phase I ROP, we found significant changes in retinal amino acids (including most decreased L-leucine, L-isoleucine, and L-valine). Parenteral L-isoleucine suppressed physiological retinal vascularization. In premature infants, severe ROP was associated with a higher mean intake of parenteral versus enteral amino acids in the first two weeks of life after adjustment for treatment group, gestational age at birth, birth weight, and sex. The number of days with parenteral amino acids support independently predicted severe ROP. Further understanding and modulating amino acids may help improve nutritional intervention and prevent Phase I ROP.

First Trimester Prediction of Preterm Birth in Patient Plasma with Machine-Learning-Guided Raman Spectroscopy and Metabolomics

Preterm birth (PTB) is the leading cause of infant deaths globally. Current clinical measures often fail to identify women who may deliver preterm. Therefore, accurate screening tools are imperative for early prediction of PTB. Here, we show that Raman spectroscopy is a promising tool for studying biological interfaces, and we examine differences in the maternal metabolome of the first trimester plasma of PTB patients and those that delivered at term (healthy). We identified fifteen statistically significant metabolites that are predictive of the onset of PTB. Mass spectrometry metabolomics validates the Raman findings identifying key metabolic pathways that are enriched in PTB. We also show that patient clinical information alone and protein quantification of standard inflammatory cytokines both fail to identify PTB patients. We show for the first time that synergistic integration of Raman and clinical data guided with machine learning results in an unprecedented 85.1% accuracy of risk stratification of PTB in the first trimester that is currently not possible clinically. Correlations between metabolites and clinical features highlight the body mass index and maternal age as contributors of metabolic rewiring. Our findings show that Raman spectral screening may complement current prenatal care for early prediction of PTB, and our approach can be translated to other patient-specific biological interfaces.

The Linear-Logistic Model: A Novel Paradigm for Estimating Dietary Amino Acid Requirements

This study aimed to determine whether current methods for estimating AA requirements for animal health and welfare are sufficient. An exploratory data analysis (EDA) was conducted, which involved a review of assumptions underlying AA requirements research, a data mining approach to identify animal responses to dietary AA levels exceeding those for maximum protein retention, and a literature review to assess the physiological relevance of the linear-logistic model developed through the data mining approach. The results showed that AA dietary levels above those for maximum growth resulted in improvements in key physiological responses, and the linear-logistic model depicted the AA level at which growth and protein retention rates were maximized, along with key metabolic functions related to milk yield, litter size, immune response, intestinal permeability, and plasma AA concentrations. The results suggest that current methods based solely on growth and protein retention measurements are insufficient for optimizing key physiological responses associated with health, survival, and reproduction. The linear-logistic model could be used to estimate AA doses that optimize these responses and, potentially, survival rates.

Causal effects of maternal circulating amino acids on offspring birthweight: a Mendelian randomisation study

BACKGROUND

Amino acids are key to protein synthesis, energy metabolism, cell signaling and gene expression; however, the contribution of specific maternal amino acids to fetal growth is unclear.

METHODS

We explored the effect of maternal circulating amino acids on fetal growth, proxied by birthweight, using two-sample Mendelian randomisation (MR) and summary data from a genome-wide association study (GWAS) of serum amino acids levels (sample 1, n = 86,507) and a maternal GWAS of offspring birthweight in UK Biobank and Early Growth Genetics Consortium, adjusting for fetal genotype effects (sample 2, n = 406,063 with maternal and/or fetal genotype effect estimates). A total of 106 independent single nucleotide polymorphisms robustly associated with 19 amino acids (p < 4.9 × 10-10) were used as genetic instrumental variables (IV). Wald ratio and inverse variance weighted methods were used in MR main analysis. A series of sensitivity analyses were performed to explore IV assumption violations.

FINDINGS

Our results provide evidence that maternal circulating glutamine (59 g offspring birthweight increase per standard deviation increase in maternal amino acid level, 95% CI: 7, 110) and serine (27 g, 95% CI: 9, 46) raise, while leucine (-59 g, 95% CI: -106, -11) and phenylalanine (-25 g, 95% CI: -47, -4) lower offspring birthweight. These findings are supported by sensitivity analyses.

INTERPRETATION

Our findings strengthen evidence for key roles of maternal circulating amino acids during pregnancy in healthy fetal growth.

FUNDING

A full list of funding bodies that contributed to this study can be found under Acknowledgments.

Timing of maternal nutrient restriction during mid- to late-gestation influences net umbilical uptake of glucose and amino acids in adolescent sheep

Previous research demonstrated that maternal nutrient restriction during mid- to late-gestation influenced net umbilical uptakes of glucose and amino acids in sheep. However, it is unclear how the timing and duration of nutrient restriction during mid- to late-gestation influences net uterine, uteroplacental, and fetal flux of glucose and amino acids. On day 50 of gestation, 41 adolescent ewe lambs carrying singletons were randomly assigned to one of six dietary treatments: 1) 100% of nutrient requirements from days 50 to 90 of gestation (CON; n = 7); 2) 60% of nutrient requirements (RES; n = 7) from days 50 to 90 of gestation; 3) 100% of nutrient requirements from days 50 to 130 of gestation (CON-CON; n = 6); 4) 100% of nutrient requirements from days 50 to 90 of gestation and 60% of nutrient requirements from days 90 to 130 of gestation (CON-RES; n = 7); 5) 60% of nutrient requirements from days 50 to 90 of gestation and 100% of nutrient requirements from days 90 to 130 of gestation (RES-CON; n = 7); or 6) 60% of nutrient requirements from days 50 to 130 of gestation (RES-RES; n = 7). On day 90 (n = 14) and day 130 (n = 27), intraoperative procedures were performed to evaluate uteroplacental blood flows, collect blood samples, and then ewes were euthanized. Net uterine, uteroplacental, and umbilical fluxes of glucose and amino acids were calculated by multiplying blood flow by the arterial-venous concentration difference. Data from days 90 and 130 were analyzed separately using ANOVA in SAS. Maternal nutrient restriction during mid-gestation increased (P = 0.04) net umbilical glucose uptake but, maternal nutrient restriction during late-gestation decreased (P = 0.02) net umbilical glucose uptake. Net umbilical essential amino acid uptake decreased (P = 0.03) with nutrient restriction during mid-gestation; however, net umbilical uptakes of Phe (P = 0.02), Thr (P = 0.05), Met (P = 0.09), and His (P = 0.08) increased or tended to increase after nutrient restriction during late-gestation. These data demonstrate that net umbilical glucose and amino acid uptakes were influenced by the timing of nutrient restriction during mid- to late-gestation. Elevated net umbilical glucose uptake after mid-gestational nutrient restriction was sustained throughout late-gestation, independent of late-gestational feeding level. Long-term adaptations in umbilical glucose uptake may have implications for prenatal and postnatal growth and development of the offspring.

Metabolic differences among newborns born to mothers with a history of leukemia or lymphoma

BACKGROUND

Leukemia and lymphoma are cancers affecting children, adolescents, and young adults and may affect reproductive outcomes and maternal metabolism. We evaluated for metabolic changes in newborns of mothers with a history of these cancers.

METHODS

A cross-sectional study was conducted on California births from 2007 to 2011 with linked maternal hospital discharge records, birth certificate, and newborn screening metabolites. History of leukemia or lymphoma was determined using ICD-9-CM codes from hospital discharge data and newborn metabolite data from the newborn screening program.

RESULTS

A total of 2,068,038 women without cancer history and 906 with history of leukemia or lymphoma were included. After adjusting for differences in maternal age, infant sex, age at metabolite collection, gestational age, and birthweight, among newborns born to women with history of leukemia/lymphoma, several acylcarnitines were significantly (p < .001 - based on Bonferroni correction for multiple testing) higher compared to newborns of mothers without cancer history: C3-DC (mean difference (MD) = 0.006), C5-DC (MD = 0.009), C8:1 (MD = 0.008), C14 (MD = 0.010), and C16:1 (MD = 0.011), whereas citrulline levels were significantly lower (MD = -0.581) among newborns born to mothers with history of leukemia or lymphoma compared to newborns of mothers without a history of cancer.

CONCLUSION

The varied metabolite levels suggest history of leukemia or lymphoma has metabolic impact on newborn offspring, which may have implications for future metabolic consequences such as necrotizing enterocolitis and urea cycle enzyme disorders in children born to mothers with a history of leukemia or lymphoma.

Placenta-derived proteins across gestation in healthy pregnancies-a novel approach to assess placental function?

BACKGROUND

Placenta-derived proteins in the systemic maternal circulation are suggested as potential biomarkers for placental function. However, the identity and longitudinal patterns of such proteins are largely unknown due to the inaccessibility of the human placenta and limitations in assay technologies. We aimed to identify proteins derived from and taken up by the placenta in the maternal circulation. Furthermore, we aimed to describe the longitudinal patterns across gestation of placenta-derived proteins as well as identify placenta-derived proteins that can serve as reference curves for placental function.

METHODS

We analyzed proteins in plasma samples collected in two cohorts using the Somalogic 5000-plex platform. Antecubital vein samples were collected at three time points (gestational weeks 14-16, 22-24, and 30-32) across gestation in 70 healthy pregnancies in the longitudinal STORK cohort. In the cross sectional 4-vessel cohort, blood samples were collected simultaneously from the maternal antecubital vein (AV), radial artery (RA), and uterine vein (UV) during cesarean section in 75 healthy pregnancies. Placenta-derived proteins and proteins taken up by the placenta were identified using venoarterial differences (UV-RA). Placenta-derived proteins were defined as placenta-specific by comparison to the venoarterial difference in the antecubital vein-radial artery (AV-RA). These proteins were described longitudinally based on the STORK cohort samples using a linear mixed effects model per protein. Using a machine learning algorithm, we identified placenta-derived proteins that could predict gestational age, meaning that they closely tracked gestation, and were potential read-outs of placental function.

RESULTS

Among the nearly 5000 measured proteins, we identified 256 placenta-derived proteins and 101 proteins taken up by the placenta (FDR < 0.05). Among the 256 placenta-derived proteins released to maternal circulation, 101 proteins were defined as placenta-specific. These proteins formed two clusters with distinct developmental patterns across gestation. We identified five placenta-derived proteins that closely tracked gestational age when measured in the systemic maternal circulation, termed a "placental proteomic clock."

CONCLUSIONS

Together, these data may serve as a first step towards a reference for the healthy placenta-derived proteome that can be measured in the systemic maternal circulation and potentially serve as biomarkers of placental function. The "placental proteomic clock" represents a novel concept that warrants further investigation. Deviations in the proteomic pattern across gestation of such proteomic clock proteins may serve as an indication of placental dysfunction.

The newborn metabolome: associations with gestational diabetes, sex, gestation, birth mode, and birth weight

BACKGROUND

Pathways towards many adult-onset conditions begin early in life, even in utero. Maternal health in pregnancy influences this process, but little is known how it affects neonatal metabolism. We investigated associations between pregnancy and birth factors and cord blood metabolomic profile in a large, population-derived cohort.

METHODS

Metabolites were measured using nuclear magnetic resonance in maternal (28 weeks gestation) and cord serum from 912 mother-child pairs in the Barwon Infant Study pre-birth cohort. Associations between maternal (metabolites, age, BMI, smoking), pregnancy (pre-eclampsia, gestational diabetes (GDM)), and birth characteristics (delivery mode, gestational age, weight, infant sex) with 72 cord blood metabolites were examined by linear regression.

RESULTS

Delivery mode, sex, gestational age, and birth weight were associated with specific metabolite levels in cord blood, including amino acids, fatty acids, and cholesterols. GDM was associated with higher cord blood levels of acetoacetate and 3-hydroxybutyrate.

CONCLUSIONS

Neonatal factors, particularly delivery mode, were associated with many cord blood metabolite differences, including those implicated in later risk of cardiometabolic disease. Associations between GDM and higher offspring ketone levels at birth are consistent with maternal ketosis in diabetic pregnancies. Further work is needed to determine whether these neonatal metabolome differences associate with later health outcomes.

IMPACT

Variations in blood metabolomic profile have been linked to health status in adults and children, but corresponding data in neonates are scarce. We report evidence that pregnancy complications, mode of delivery, and offspring characteristics, including sex, are independently associated with a range of circulating metabolites at birth, including ketone bodies, amino acids, cholesterols, and inflammatory markers. Independent of birth weight, exposure to gestational diabetes is associated with higher cord blood ketone bodies and citrate. These findings suggest that pregnancy complications, mode of delivery, gestational age, and measures of growth influence metabolic pathways prior to birth, potentially impacting later health and development.

Glutamine-dependent signaling controls pluripotent stem cell fate

Human pluripotent stem cells (hPSCs) can self-renew indefinitely or can be induced to differentiate. We previously showed that exogenous glutamine (Gln) withdrawal biased hPSC differentiation toward ectoderm and away from mesoderm. We revealed that, although all three germ lineages are capable of de novo Gln synthesis, only ectoderm generates sufficient Gln to sustain cell viability and differentiation, and this finding clarifies lineage fate restrictions under Gln withdrawal. Furthermore, we found that Gln acts as a signaling molecule for ectoderm that supersedes lineage-specifying cytokine induction. In contrast, Gln in mesoderm and endoderm is the preferred precursor of α-ketoglutarate without a direct signaling role. Our work raises a question about whether the nutrient environment functions directly in cell differentiation during development. Interestingly, transcriptome analysis of a gastrulation-stage human embryo shows that unique Gln enzyme-encoding gene expression patterns may also distinguish germ lineages in vivo. Together, our study suggests that intracellular Gln may help coordinate differentiation of the three germ layers.

Differences between Arterial and Venous Umbilical Cord Plasma Metabolome and Association with Parity

Umbilical cord blood is frequently used in health monitoring of the neonate. Results may be affected by the proportion of arterial and venous cord blood, the venous blood coming from the mother to supply oxygen and nutrients to the infant, and the arterial carrying waste products from the fetus. Here, we sampled arterial and venous umbilical cords separately from 48 newly delivered infants and examined plasma metabolomes using GC-MS/MS metabolomics. We investigated differences in metabolomes between arterial and venous blood and their associations with gestational length, birth weight, sex, and whether the baby was the first born or not, as well as maternal age and BMI. Using multilevel random forest analysis, a classification rate of 79% was achieved for arteriovenous differences (p = 0.004). Several monosaccharides had higher concentrations in the arterial cord plasma while amino acids were higher in venous plasma, suggesting that the main differences in the measured arterial and venous plasma metabolomes are related to amino acid and energy metabolism. Venous cord plasma metabolites related to energy metabolism were positively associated with parity (77% classification rate, p = 0.004) while arterial cord plasma metabolites were not. This underlines the importance of defining cord blood type for metabolomic studies.

Comparison of Diagnostic Values of Maternal Arginine Concentration for Different Pregnancy Complications: A Systematic Review and Meta-Analysis

Abnormal arginine metabolism contributes to the development of intrauterine growth restriction (IUGR), preeclampsia (PE), and gestational diabetes mellitus (GDM), which increase the health burden of mothers and induce adverse birth outcomes. However, associations between maternal arginine concentration and different pregnancy complications have not been systematically compared. The PubMed, ScienceDirect, and Web of Science databases were searched for peer-reviewed publications to evaluate the diagnostic value of plasma arginine concentration in complicated pregnancies. Standardized mean difference (SMD) of the arginine concentration was pooled by a random effects model. The results show that increased maternal arginine concentrations were observed in IUGR (SMD: 0.48; 95% CI: 0.20, 0.76; I² = 47.0%) and GDM (SMD: 0.46; 95% CI: 0.11, 0.81; I² = 82.3%) cases but not in PE patients (SMD: 0.21; 95% CI: −0.04, 0.47; I² = 80.3%) compared with the normal cohorts. Subgroup analyses indicated that the non-fasting circulating arginine concentration in third trimester was increased significantly in GDM and severe IUGR pregnancies, but the change mode was dependent on ethnicity. Additionally, only severe PE persons were accompanied by higher plasma arginine concentrations. These findings suggest that maternal arginine concentration is an important reference for assessing the development of pregnancy complications.

The Function of the Kynurenine Pathway in the Placenta: A Novel Pharmacotherapeutic Target?

(L-)tryptophan is metabolized via the kynurenine pathway into several kynurenine metabolites with distinct functions. Dysfunction of the kynurenine pathway can lead to impairments in vascular regulation, immune regulation, and tolerance. The first and rate limiting enzyme of this pathway, indoleamine 2,3-dioxygenase (IDO), is highly expressed in the placenta and reduced in placentas from complicated pregnancies. IDO is essential during pregnancy, as IDO inhibition in pregnant mice resulted in fetal loss. However, the exact function of placental IDO, as well as its exact placental localization, remain controversial. This review identified that two isoforms of IDO; IDO1 and IDO2, are differently expressed between placental cells, suggesting spatial segregation. Furthermore, this review summarizes how the placental kynurenine pathway is altered in pregnancy complications, including recurrent miscarriage, preterm birth, preeclampsia, and fetal growth restriction. Importantly, we describe that these alterations do not affect maternally circulating metabolite concentrations, suggesting that the kynurenine pathway functions as a local signaling pathway. In the placenta, it is an important source of de novo placental NAD⁺ synthesis and regulates fetal tryptophan and kynurenine metabolite supply. Therefore, kynurenine pathway interventions might provide opportunities to treat pregnancy complications, and this review discusses how such treatment could affect placental function and pregnancy development.

Placenta-specific Slc38a2/SNAT2 knockdown causes fetal growth restriction in mice

Fetal growth restriction (FGR) is a complication of pregnancy that reduces birth weight, markedly increases infant mortality and morbidity and is associated with later-life cardiometabolic disease. No specific treatment is available for FGR. Placentas of human FGR infants have low abundance of sodium-coupled neutral amino acid transporter 2 (Slc38a2/SNAT2), which supplies the fetus with amino acids required for growth. We determined the mechanistic role of placental Slc38a2/SNAT2 deficiency in the development of restricted fetal growth, hypothesizing that placenta-specific Slc38a2 knockdown causes FGR in mice. Using lentiviral transduction of blastocysts with a small hairpin RNA (shRNA), we achieved 59% knockdown of placental Slc38a2, without altering fetal Slc38a2 expression. Placenta-specific Slc38a2 knockdown reduced near-term fetal and placental weight, fetal viability, trophoblast plasma membrane (TPM) SNAT2 protein abundance, and both absolute and weight-specific placental uptake of the amino acid transport System A tracer, 14C-methylaminoisobutyric acid (MeAIB). We also measured human placental SLC38A2 gene expression in a well-defined term clinical cohort and found that SLC38A2 expression was decreased in late-onset, but not early-onset FGR, compared with appropriate for gestational age (AGA) control placentas. The results demonstrate that low placental Slc38a2/SNAT2 causes FGR and could be a target for clinical therapies for late-onset FGR.

Mode of delivery was associated with transient changes in the metabolomic profile of neonates

AIMS

To estimate potential differences in neonatal metabolomic profiles at birth and at the time of newborn screening by delivery mode.

METHODS

A prospective study at Women's Clinic at Landspitali-The National University Hospital of Iceland. Women having normal vaginal birth or elective caesarean section from November 2013 to April 2014 were offered participation. Blood samples from mothers before birth and umbilical cord at birth were collected and amino acids and acylcarnitines measured by tandem mass spectrometry. Results from the Newborn screening programme in Iceland were collected. Amino acids and acylcarnitines from different samples were compared by delivery mode.

RESULTS

Eighty three normal vaginal births and 32 elective caesarean sections were included. Mean differences at birth were higher for numerous amino acids, and some acylcarnitines in neonates born vaginally compared to elective caesarean section. Maternal blood samples and newborn screening results showed small differences that lost significance after correction for multiple testing. Many amino acids and some acylcarnitines were numerically higher in cord blood compared to maternal. Many amino acids and most acylcarnitines were numerically higher in newborn screening results compared to cord blood.

CONCLUSION

We observed transient yet distinct differences in metabolomic profiles between neonates by delivery mode.

Counter-directed leucine gradient promotes amino acid transfer across the human placenta

The developing fetus is highly vulnerable to imbalances in the supply of essential amino acids (AA). Transplacental AA transfer depends on complex interactions between accumulative transporters, exchangers and facilitators, which maintain both intra-extracellular and materno-fetal substrate gradients. We determined physiological AA gradients between maternal and fetal blood and assessed their importance by studying maternal-fetal leucine transfer in human trophoblasts. Maternal-venous and corresponding fetal-arterial/fetal-venous sera were collected from 22 healthy patients at partum. The acquisition of the full AA spectra in serum was performed by ion exchange chromatography. Physiological materno-fetal AA levels were evaluated using paired two-way ANOVA with Tukey's correction. AA concentrations and gradients were tested for associations with anthropometric data by Spearman correlation analysis. Functional effects of a physiological leucine gradient versus equimolar concentrations were tested in BeWo cells using L-[³H]-leucine in conventional and Transwell-based uptake and transfer experiments. The LAT1/SLC7A5-specific inhibitor JPH203 was used to evaluate LAT1-transporter-mediated leucine transport. Maternal AA concentrations correlated with preconceptional and maternal weights at partum. Interestingly, low materno-fetal AA gradients were associated with maternal weight, BMI and gestational weight gain. Leucine uptake was promoted by increased extracellular substrate concentrations. Materno-fetal leucine transfer was significantly increased against a 137µM leucine gradient demonstrating that transplacental leucine transport is stimulated by a counter-directed gradient. Moreover, leucine transfer was inhibited by 10µM JPH203 confirming that Leu transport across the trophoblast monolayer is LAT1-dependent. This study demonstrates a currently underestimated effect of transplacental AA gradients on efficient leucine transfer which could severely affect fetal development.

Role of zinc in neonatal growth and brain growth: review and scoping review

This manuscript includes (1) a narrative review of Zinc as an essential nutrient for fetal and neonatal growth and brain growth and development and (2) a scoping review of studies assessing the effects of Zinc supplementation on survival, growth, brain growth, and neurodevelopment in neonates. Very preterm infants and small for gestational age infants are at risk for Zinc deficiency. Zinc deficiency can cause several complications including periorificial lesions, delayed wound healing, hair loss, diarrhea, immune deficiency, growth failure with stunting, and brain atrophy and dysfunction. Zinc is considered essential for oligodendrogenesis, neurogenesis, neuronal differentiation, white matter growth, and multiple biological and physiological roles in neurobiology. Data support the possibility that the critical period of Zinc delivery for brain growth in the mouse starts at 18 days of a 20-21-day pregnancy and extends during lactation and in human may start at 26 weeks of gestation and extend until at least 44 weeks of postmenstrual age. Studies are needed to better elucidate Zinc requirement in extremely low gestational age neonates to minimize morbidity, optimize growth, and brain growth, prevent periventricular leukomalacia and optimize neurodevelopment. IMPACT: Zinc is essential for growth and brain growth and development. In the USA, very preterm small for gestational age infants are at risk for Zinc deficiency. Data support the possibility that the critical period of Zinc delivery for brain growth in the mouse starts at 18 days of a 20-21-day pregnancy and extends during lactation and in human may start at 26 weeks' gestation and extend until at least 44 weeks of postmenstrual age. Several randomized trials of Zinc supplementation in neonates have shown improvement in growth when using high enough dose, for long duration in patients likely to or proven to have a Zinc deficiency. Studies are needed to better elucidate Zinc requirement in extremely low gestational age neonates to minimize morbidity, optimize growth and brain growth, prevent periventricular leukomalacia and optimize neurodevelopment.

Cord serum metabolome and birth weight in patients with gestational diabetes treated with metformin, insulin, or diet alone

INTRODUCTION

Recent research has demonstrated the benefits of metformin treatment in gestational diabetes (GDM) on short-term pregnancy outcomes (including excessive fetal growth and pre-eclampsia), but its effects on fetal metabolism remain mostly unknown. Our aim was to study the effects of metformin treatment compared with insulin or diet on the cord serum metabolome and also to assess how these metabolites are related to birth weight (BW) in pregnancies complicated by GDM.

RESEARCH DESIGN AND METHODS

Cord serum samples were available from 113, 97, and 98 patients with GDM treated with diet, insulin, and metformin, respectively. A targeted metabolome was measured using nuclear magnetic resonance spectroscopy. The patients in the metformin and insulin groups had participated in a previous randomized trial (NCT01240785).

RESULTS

Cord serum alanine was elevated in the metformin group (0.53 mmol/L) compared with the insulin (0.45 mmol/L, p<0.001) and the diet groups (0.46 mmol/L, p<0.0001). All other measured metabolites were similar between the groups. The triglyceride (TG)-to-phosphoglyceride ratio, average very low-density lipoprotein particle diameter, docosahexaenoic acid, omega-3 fatty acids (FAs), and ratios of omega-3 and monounsaturated FA to total FA were inversely related to BW. The omega-6-to-total-FA and omega-6-to-omega-3-FA ratios were positively related to BW. Cholesterol in very large and large high-density lipoprotein (HDL) was positively (p<0.01) associated with BW when adjusted for maternal prepregnancy body mass index, gestational weight gain, glycated hemoglobin, and mode of delivery.

CONCLUSIONS

Metformin treatment in GDM leads to an increase in cord serum alanine. The possible long-term implications of elevated neonatal alanine in this context need to be evaluated in future studies. Although previous studies have shown that metformin increased maternal TG levels, the cord serum TG levels were not affected. Cord serum HDL cholesterol and several FA variables are related to the regulation of fetal growth in GDM. Moreover, these associations seem to be independent of maternal confounding factors.

TRIAL REGISTRATION NUMBER

NCT01240785.

Seeing the fetus from a DOHaD perspective: discussion paper from the advanced imaging techniques of DOHaD applications workshop held at the 2019 DOHaD World Congress

Advanced imaging techniques are enhancing research capacity focussed on the developmental origins of adult health and disease (DOHaD) hypothesis, and consequently increasing awareness of future health risks across various subareas of DOHaD research themes. Understanding how these advanced imaging techniques in animal models and human population studies can be both additively and synergistically used alongside traditional techniques in DOHaD-focussed laboratories is therefore of great interest. Global experts in advanced imaging techniques congregated at the advanced imaging workshop at the 2019 DOHaD World Congress in Melbourne, Australia. This review summarizes the presentations of new imaging modalities and novel applications to DOHaD research and discussions had by DOHaD researchers that are currently utilizing advanced imaging techniques including MRI, hyperpolarized MRI, ultrasound, and synchrotron-based techniques to aid their DOHaD research focus.

Does metabolomic profile differ with regard to birth weight?

BACKGROUND

Macrosomia and child obesity are growing health-care issues worldwide. The purpose of the study was to evaluate how extremely high or low birth weight affects metabolic markers evaluated in newborn screening.

METHODS

The study was register-based and included full-term singletons born in Iceland from 2009 to 2012 with newborn screening samples taken 72-96 h after birth. Three groups based on birth weight were compared: low birth weight (<2500 g), appropriate-for-gestational age, and extreme macrosomia (≥5000 g). The comparison was adjusted for possible confounding factors.

RESULTS

Compared to appropriate-for-gestational age neonates, both low birth weight and extreme macrosomia were associated with higher levels of glutamic acid. The amino acids alanine and threonine were increased in low birth weight neonates. Free carnitine and some medium- and long-chain acylcarnitines were higher in low birth weight infants. Hydroxybutyrylcarnitine was lower in low birth weight infants, but higher in extremely macrosomic neonates. Acetylcarnitine was higher in low birth weight and extremely macrosomic neonates. Succinylcarnitine was lower and hexadecenoylcarnitine higher in macrosomic newborns.

CONCLUSION

Low birth weight and extremely macrosomic neonates show distinctive differences in their metabolomic profile compared to appropriate-for-gestational age newborns. The differences are not explained by gestational age.

IMPACT

The key message of this article is that both low birth weight and extremely macrosomic newborns show dissimilar metabolomic profiles compared to appropriate-for-gestational age neonates. The article contributes to knowledge on what affects evaluation of results in newborn screening. The impact of this article is to provide information on metabolism at both ends of the birth weight range after accounting for confounding factors including gestational age.

Effect of amino acid infusion during cesarean delivery on newborn temperature: a randomized controlled trial

BACKGROUND

The effect of maternal amino acid (AA) infusion before and during cesarean delivery on neonatal temperature remains unknown. We hypothesized that thermogenic effects of AA metabolism would help maintain body temperature of newborn babies and their mothers.

METHODS

Seventy-six parturients scheduled for elective singleton term cesarean delivery were equally randomized to receive intravenous 200 ml of AA or placebo approximately 1 h before subarachnoid block (infusion rate:100 ml/h). The primary outcome was the newborn rectal temperature at 0, 5 and 10 min after birth. The secondary outcomes included the maternal rectal temperature at six time-points: T0 = before starting study solution infusion, T1 = 30 min after starting infusion, T2 = one hour after starting infusion, T3 = during spinal block, T4 = half an hour after spinal block, T5 = at the time of birth and T6 = at the end of infusion, as well as maternal thermal discomfort and shivering episodes.

RESULTS

There were no differences in newborn temperature between the two groups at any of the time-points (intervention-time-interaction effect, P = 0.206). The newborn temperature (mean [95%CI] °C) at birth was 37.5 [37.43-37.66] in the AA and 37.4 [37.34-37.55] in the placebo group. It showed a significant (P < 0.001) downward trend at 5 and 10 min after birth (time effect) in both groups. One neonate in the AA and five in the placebo group were hypothermic (temperature < 36.5 °C) (P = 0.20). There was a significant difference in the maternal temperature at all time points between the two groups (Intervention-time interaction effect, P < 0.001). However, after adjustment for multiplicity, the difference was significant only at T6 (P = 0.001). The mean difference [95%CI] in temperature decline from baseline (T0) till the end of infusion (T6) between the two groups was - 0.39 [- 0.55;- 0.22] °C (P < 0.0001). Six mothers receiving placebo and none receiving AA developed hypothermia (temperature < 36 °C) (P = 0.025). Maternal thermal discomfort and shivering episodes were unaffected by AA therapy.

CONCLUSIONS

Under the conditions of this study, maternal AA infusion before and during spinal anesthesia for cesarean delivery did not influence the neonatal temperature within 10 min after birth. In addition, the maternal temperature was only maintained at two hours of AA infusion.

TRIAL REGISTRATION

ClinicalTrials.government, Identifier NCT02575170 . Registered on 10th April, 2015 - Retrospectively registered.

Glycine, a Dispensable Amino Acid, Is Conditionally Indispensable in Late Stages of Human Pregnancy

BACKGROUND

Recently, we showed that there are higher protein, lysine, and phenylalanine requirements in late stages of pregnancy compared with early stages. Animal studies have suggested an increased dietary need for specific dispensable amino acids in pregnancy; whether such a need exists in human pregnancies is unknown.

OBJECTIVE

The objective of the current study was to examine whether healthy pregnant women at midgestation (20-29 wk) and late gestation (30-40 wk) have a dietary demand for glycine, a dispensable amino acid, using the indicator amino acid oxidation method and measurement of plasma 5-oxoproline concentrations.

METHODS

Seventeen healthy women (aged 26-36 y) randomly received different test glycine intakes (range: 5-100 mg·kg-1·d-1) during each study day in midgestation (∼26 wk, n = 17 observations in 9 women) and late gestation (∼35 wk, n = 19 observations in 8 women). Diets were isocaloric with energy at 1.7 × resting energy expenditure. Protein was given as a crystalline amino acid mixture based on egg protein composition at current estimated average requirement (EAR; 0.88 g·kg-1·d-1). Breath samples were collected at baseline and isotopic steady state to measure oxidation of L-[1-13C]phenylalanine to 13CO2 (F13CO2). Plasma was collected at the sixth hour of the study day. Linear regression crossover analysis and simple linear regression were used to assess responses in F13CO2 and plasma 5-oxoproline concentrations to different glycine intakes.

RESULTS

No statistically significant responses were observed in midgestation. However, in late gestation, lower glycine intakes resulted in higher rates of F13CO2 (suggesting low protein synthesis) with a breakpoint for phenylalanine oxidation at >37 mg glycine·kg-1·d-1 and higher plasma 5-oxoproline (suggesting low glycine availability) with a breakpoint >27 mg glycine·kg-1·d-1.

CONCLUSIONS

The findings suggest that glycine should be considered a "conditionally" indispensable amino acid during late gestation, especially when protein intakes are at 0.88 g·kg-1·d-1, the current EAR. This trial was registered at clinicaltrials.gov as NCT02149953.

Distinct maternal amino acids and oxylipins predict infant fat mass and fat-free mass indices

Interested in maternal determinants of infant fat mass index (FMI) and fat-free mass index (FFMI), considered as predictors for later development of obesity, we analysed amino acids (AA) and oxylipins in maternal serum and breast milk (BM). FMI and FFMI were calculated in 47 term infants aged 4 months (T4). Serum AA were analysed in pregnancy (T1, T2) and 6-8 weeks postpartum (T3). At T3, AA and oxylipins were analysed in BM. Biomarker-index-associations were identified by regression analysis. Infant FMI (4.1 ± 1.31 kg/m²; MW ± SD) was predicted by T2 proline (R² adj.: 7.6%, p = .036) and T3 BM 11-hydroxy-eicosatetraenoic-acid (11-HETE) and 13-hydroxy-docosahexaenoic-acid (13-HDHA; together:35.5% R² adj., p < .001). Maternal peripartum antibiotics (AB) emerged as confounders (+AB: 23.5% higher FMI; p = .025). Infant FFMI (12.1 ± 1.19 kg/m²; MW ± SD) was predicted by histidine (R² adj.: 14.5%, p < .001) and 17-HDHA (BM, R² adj.:19.3%, p < .001), determined at T3. Confirmed in a larger cohort, the parameters could elucidate connections between maternal metabolic status, nutrition, and infant body development.

Diabetes Leads to Alterations in Normal Metabolic Transitions of Pregnancy as Revealed by Time-Course Metabolomics

Women with diabetes during pregnancy are at increased risk of poor maternal and neonatal outcomes. Despite this, the effects of pre-gestational (PGDM) or gestational diabetes (GDM) on metabolism during pregnancy are not well understood. In this study, we utilized metabolomics to identify serum metabolic changes in women with and without diabetes during pregnancy and the cord blood at birth. We observed elevations in tricarboxylic acid (TCA) cycle intermediates, carbohydrates, ketones, and lipids, and a decrease in amino acids across gestation in all individuals. In early gestation, PGDM had elevations in branched-chain amino acids and sugars compared to controls, whereas GDM had increased lipids and decreased amino acids during pregnancy. In both GDM and PGDM, carbohydrate and amino acid pathways were altered, but in PGDM, hemoglobin A1c and isoleucine were significantly increased compared to GDM. Cord blood from GDM and PGDM newborns had similar increases in carbohydrates and choline metabolism compared to controls, and these alterations were not maternal in origin. Our results revealed that PGDM and GDM have distinct metabolic changes during pregnancy. A better understanding of diabetic metabolism during pregnancy can assist in improved management and development of therapeutics and help mitigate poor outcomes in both the mother and newborn.

Concentrations of fatty acids among macrosomic neonates delivered by healthy women and women with type 1 diabetes mellitus

OBJECTIVE

To evaluate the concentration and profile of fatty acids (FAs) among macrosomic neonates delivered by healthy pregnant women and pregnant women with type 1 diabetes mellitus (T1DM).

METHODS

A prospective study of women who delivered macrosomic neonates at a University Hospital Center, Zagreb, Croatia, 2016-2018. Maternal, umbilical vein, and arterial blood samples were collected immediately on delivery. After lipid extraction, total FAs in maternal, umbilical vein, and arterial serum samples were assessed by gas chromatography. Data were compared between women with T1DM and healthy control women.

RESULTS

In total, 50 women were enrolled: 22 with T1DM and 28 control women. Neonates in the T1DM group had a higher ponderal index as compared with the control group (P=0.006). Umbilical vein insulin, insulin resistance, and leptin concentration were higher in the T1DM group than in the control group (all P<0.001). Umbilical vein serum concentrations of total saturated, monounsaturated, n-3 polyunsaturated, and n-6 polyunsaturated FAs were higher in the T1DM group (P=0.004, P<0.001, P=0.015, and P=0.014, respectively).

CONCLUSION

Macrosomic neonates delivered by women with T1DM had a higher Ponderal index, and higher concentrations of insulin, leptin, and FAs in the umbilical vein and artery as compared with control group newborns.

Multi-proxy stable isotope analyses of dentine microsections reveal diachronic changes in life history adaptations, mobility, and tuberculosis-induced wasting in prehistoric Liguria (Finale Ligure, Italy, northwestern Mediterranean)

OBJECTIVE

To reconstruct breastfeeding and weaning practices, metabolic stress including tuberculosis-induced wasting, and residential mobility of children in Neolithic and Metal Ages to infer their local ecologies.

MATERIALS

Seven permanent teeth from individuals dated to the Neolithic, Copper, Bronze, and Iron Ages buried in nearby caves in western Liguria, Italy.

METHODS

Carbon, nitrogen, and sulfur stable isotope analyses on dentine microsections. Tooth maturation was used to calculate age at death.

RESULTS

Two Neolithic children present longer pattern of weaning and appear to have been weaned using animal protein in contrast to the earlier weaning of Metal Ages children, which were probably weaned with vegetable resources. Sulfur isotopes suggest local origin of Neolithic and Cooper Age children, and non-local origins for Bronze and Iron Age children. Intense catabolism in the last two years is apparent in the adolescent with tuberculosis.

CONCLUSIONS

Shortening in weaning patterns during the Metal Ages are likely driven by the intensification of agricultural practices and cultivation of new crops during Bronze and Iron Ages. Neolithic food choices and delayed weaning patterns may represent one of the strategies to maximize growth and immune potential in a local economy/ecology with high-infectious load. Tuberculosis was a chronic and long-lasting disease.

SIGNIFICANCE

The first combined carbon, nitrogen, and sulfur analysis on prehistoric dentine microsections revealing changing human life history adaptations within the same region.

LIMITATIONS

Small sample size.

SUGGESTIONS FOR FURTHER RESEARCH

Increase the sulfur isotope dataset, use new EA-IRMS equipment, and provide data on amino acid to better define weaning food composition.

Protein intakes to optimize outcomes for preterm infants

Proteins are key structural components of all human cells and are also involved in key physiologic processes through their roles as enzymes, hormones and transport proteins. Protein requirements are substantially higher in preterm infants than those born at term, yet inadequate protein intakes are a common problem on many neonatal units. Very preterm infants (VPT, <32 weeks) commonly receive parenteral amino acid solutions which are typically commenced on admission, and increased over the next few days. Several recent studies have explored differing parenteral amino acid intakes in the first few days, and recommendations have recently been updated. Parenteral nutrition intakes are decreased as enteral feeds are tolerated, but human milk alone will not meet protein needs in most VPT and supplementation or fortification will be required. This review paper considers basic protein and amino acid physiology in the newborn period, and the evidence base for current recommendations.

Maternal-fetal cholesterol transfer in human term pregnancies

OBJECTIVES

The extent to which the human term fetus utilizes cholesterol released from the placenta has remained elusive. Our aims were to estimate the net mass of cholesterol taken up by the uteroplacental unit, released by the placenta and taken up by the fetus. Thereby we aimed to explore the maternal-fetal cholesterol transfer and hypothesized that maternal levels and uteroplacental uptake were correlated to the fetal uptake of cholesterol.

METHODS

A cross-sectional in vivo study of 179 fasting, healthy women with uncomplicated singleton pregnancies. Blood flow in the uterine artery (n = 70) and umbilical vein (n = 125) was measured by Doppler ultrasound. Blood samples from the maternal radial artery, antecubital vein and uterine vein, and the umbilical artery and vein were obtained during cesarean section. Cholesterol was determined enzymatically.

RESULTS

We found a significant uteroplacental uptake (median [Q1,Q3]) of total (3.50 [-36.8,61.1]) and HDL cholesterol (6.69 [-3.78,17.9]) μmol/min, and a fetal uptake of HDL (8.07 [4.48,12.59]), LDL (5.97 [2.77,8.92]) and total cholesterol (13.2 [8.06,21.58]) μmol/min. Maternal cholesterol levels were not correlated to fetal uptake of cholesterol. There was a correlation between uteroplacental uptake of total (rho 0.35, p 0.003) and LDL cholesterol (rho 0.25, p 0.03) and the fetal uptake of LDL cholesterol from the umbilical circulation. The fetal uptake of cholesterol from HDL was higher than from LDL (p < 0.001).

CONCLUSION

Fetal cholesterol uptake is independent of maternal cholesterol levels, but related to the uteroplacental uptake of cholesterol from LDL. This suggests that the placenta influences maternal-fetal cholesterol transfer at term.

Evidence of adaptation of maternofetal transport of glutamine relative to placental size in normal mice, and in those with fetal growth restriction

Key points

Fetal growth restriction (FGR) is a major risk factor for stillbirth and has significant impact upon lifelong health.

A small, poorly functioning placenta, as evidenced by reduced transport of nutrients to the baby, underpins FGR. It remains unclear how a small but normal placenta differs from the small FGR placenta in terms of ability to transfer nutrients to the fetus.

Placental transport of glutamine and glutamate, key amino acids for fetal growth, was assessed in normal mice and those with FGR.

Glutamine and glutamate transport was greater in the lightest versus heaviest placenta in a litter of normally grown mice. Placentas of mice with FGR had increased transport capacity in mid‐pregnancy, but this adaptation was insufficient in late pregnancy.

Placental adaptations, in terms of increased nutrient transport (per gram) to compensate for small size, appear to achieve appropriate fetal growth in normal pregnancy. Failure of this adaptation might contribute to FGR.

Abstract

Fetal growth restriction (FGR), a major risk factor for stillbirth, and neonatal and adulthood morbidity, is associated with reduced placental size and decreased placental nutrient transport. In mice, a small, normal placenta increases its nutrient transport, thus compensating for its reduced size and maintaining normal fetal growth. Whether this adaptation occurs for glutamine and glutamate, two key amino acids for placental metabolism and fetal growth, is unknown. Additionally, an assessment of placental transport of glutamine and glutamate between FGR and normal pregnancy is currently lacking. We thus tested the hypothesis that the transport of glutamine and glutamate would be increased (per gram of tissue) in a small normal placenta [C57BL6/J (wild‐type, WT) mice], but that this adaptation fails in the small dysfunctional placenta in FGR [insulin‐like growth factor 2 knockout (P0) mouse model of FGR]. In WT mice, comparing the lightest versus heaviest placenta in a litter, unidirectional maternofetal clearance (K_mf) of ¹⁴C‐glutamine and ¹⁴C‐glutamate (^glutamineK_mf and ^glutamateK_mf) was significantly higher at embryonic day (E) 18.5, in line with increased expression of LAT1, a glutamine transporter protein. In P0 mice, ^glutamineK_mf and ^glutamateK_mf were higher (P0 versus wild‐type littermates, WTL) at E15.5. At E18.5, ^glutamineK_mf remained elevated whereas ^glutamateK_mf was similar between groups. In summary, we provide evidence that ^glutamineK_mf and ^glutamateK_mf adapt according to placental size in WT mice. The placenta of the growth‐restricted P0 fetus also elevates transport capacity to compensate for size at E15.5, but this adaptation is insufficient at E18.5; this may contribute to decreased fetal growth.

Fetal growth restriction (FGR) is a major risk factor for stillbirth and has significant impact upon lifelong health.

A small, poorly functioning placenta, as evidenced by reduced transport of nutrients to the baby, underpins FGR. It remains unclear how a small but normal placenta differs from the small FGR placenta in terms of ability to transfer nutrients to the fetus.

Placental transport of glutamine and glutamate, key amino acids for fetal growth, was assessed in normal mice and those with FGR.

Glutamine and glutamate transport was greater in the lightest versus heaviest placenta in a litter of normally grown mice. Placentas of mice with FGR had increased transport capacity in mid‐pregnancy, but this adaptation was insufficient in late pregnancy.

Placental adaptations, in terms of increased nutrient transport (per gram) to compensate for small size, appear to achieve appropriate fetal growth in normal pregnancy. Failure of this adaptation might contribute to FGR.

Innate Immune Cells and Toll-like Receptor-Dependent Responses at the Maternal-Fetal Interface

During pregnancy, the placenta, the mother and the fetus exploit several mechanisms in order to avoid fetal rejection and to maintain an immunotolerant environment throughout nine months. During this time, immune cells from the fetal and maternal compartments interact to provide an adequate defense in case of an infection and to promote a tolerogenic milieu for the fetus to develop peacefully. Trophoblasts and decidual cells, together with resident natural killer cells, dendritic cells, Hofbauer cells and other macrophages, among other cell types, contribute to the modulation of the uterine environment to sustain a successful pregnancy. In this review, the authors outlined some of the various roles that the innate immune system plays at the maternal-fetal interface. First, the cell populations that are recruited into gestational tissues and their immune mechanisms were examined. In the second part, the Toll-like receptor (TLR)-dependent immune responses at the maternal-fetal interface was summarized, in terms of their specific cytokine/chemokine/antimicrobial peptide expression profiles throughout pregnancy.

Use of Glucose, Glutamine and Fatty Acids for Trophoblast Respiration in Lean, Obese and Gestational Diabetic Women

PURPOSE

Maternal obesity and gestational diabetes (GDM) are associated with adverse outcomes particularly with a male fetus. The composition and amount of substrate supplied to the placenta is altered in these conditions. We hypothesized that there are sexually dimorphic differences in utilization of glucose, fatty acids and glutamine between trophoblast of lean, obese and GDM women.

METHODS

Trophoblast were isolated from term male or female placentas from lean, obese or GDM women (n = 4-6/group) and syncytiotrophoblast formed over 72 hr before measuring mitochondrial respiration by fuel flex assay (Seahorse XF96 analyzer). Dependency, capacity and flexibility for use of glucose, glutamine and fatty acids was measured with western blot of glucose transporter GLUT1, glutaminase and carnitine palmitoyl-transferase 1A, (CPT1A).

RESULTS

Sexual dimorphism in syncytiotrophoblast fuel utilization was seen in GDM vs lean with a significant increase in glucose dependency in male and glucose capacity in female, whereas for glutamine capacity significantly decreased in male and female but dependency only in female. Fatty acid dependency and capacity significantly increased in male and capacity in female trophoblast of GDM vs either lean or obese. In male but not female trophoblast flexibility to use all three fuels significantly decreased from lean to obese and GDM. In male trophoblast there were significant associations between GLUT1 and glucose dependency (positive) and flexibility (negative).

MAIN CONCLUSIONS

Human syncytiotrophoblast utilizes glutamine for mitochondrial respiration. Utilization of glucose, fatty acids and glutamine changes in a sexually dimorphic manner with obesity and GDM predominantly with a male placenta.

Phenylalanine and tyrosine measurements across gestation by tandem mass spectrometer on dried blood spot cards from normal pregnant women

Purpose:

Maternal phenylketonuria (MPKU) requires strict control of phenylalanine (Phe) and supplemental tyrosine (Tyr). Monitoring during pregnancy using dried blood spot (DBS) cards by tandem mass spectrometry (MS/MS) is now standard practice, however there are no Phe and Tyr reference ranges for DBS MS/MS method in healthy pregnant women.

Methods:

DBS cards (63 −1364 days in storage) from healthy women with singleton pregnancies were analyzed by MS/MS. 390 DBS cards from 170 pregnancies (5/1–39/6 weeks’ gestation), were tested.

Results:

Both Phe and Tyr levels declined from the first trimester (Phe: 36.2 +/− 10.6; Tyr 25.7 +/−9.7 micromol/L) to the second trimester (Phe 33.4 +/− 9.3; Tyr 21.7 +/− 6.7 micromol/L) and remained stable in the third trimester (Phe 32.3 +/− 8.7; Tyr 21.0 +/− 6.6 micromol/L). Phe and Tyr levels declined over time since collection (Phe: 0.004 micromol/L per day; Tyr 0.002 micromol/L). Nomograms by gestational age were created using raw data and data adjusted for time from sample collection. Reference ranges by trimester are provided.

Conclusion:

Both Phe and Tyr decline quickly during the first trimester and remain relatively constant over the second and third trimesters. These nomograms will provide a valuable resource for care of MPKU.

Improving pregnancy outcomes in humans through studies in sheep

Experimental studies that are relevant to human pregnancy rely on the selection of appropriate animal models as an important element in experimental design. Consideration of the strengths and weaknesses of any animal model of human disease is fundamental to effective and meaningful translation of preclinical research. Studies in sheep have made significant contributions to our understanding of the normal and abnormal development of the fetus. As a model of human pregnancy, studies in sheep have enabled scientists and clinicians to answer questions about the etiology and treatment of poor maternal, placental, and fetal health and to provide an evidence base for translation of interventions to the clinic. The aim of this review is to highlight the advances in perinatal human medicine that have been achieved following translation of research using the pregnant sheep and fetus.

The human placental proteome secreted into the maternal and fetal circulations in normal pregnancy based on 4-vessel sampling

We sought to identify proteins secreted by the human placenta into the maternal and fetal circulations. Blood samples from the maternal radial artery and uterine vein and umbilical artery and vein were obtained during cesarean section in 35 healthy women with term pregnancy. Slow off-rate modified aptamer (SOMA) protein-binding technology was used to quantify 1310 known proteins. The uteroplacental and umbilical venoarterial concentration differences were calculated. Thirty-four proteins were significantly secreted by the placenta into the maternal circulation, including placental growth factor, growth/differentiation factor 15, and matrix metalloproteinase 12. There were 341 proteins significantly secreted by the placenta into the fetal circulation. Only 7 proteins were secreted into both the fetal and maternal circulations, suggesting a distinct directionality in placental protein release. We examined changes across gestation in the proteins found to be significantly secreted by the placenta into the maternal circulation using serial blood samples from healthy women. Among the 34 proteins secreted into the maternal circulation, 8 changed significantly across gestation. The identified profiles of secreted placental proteins will allow us to identify novel minimally invasive biomarkers for human placental function across gestation and discover previously unknown proteins secreted by the human placenta that regulate maternal physiology and fetal development.-Michelsen, T. M., Henriksen, T., Reinhold, D., Powell, T. L., Jansson, T. The human placental proteome secreted into the maternal and fetal circulations in normal pregnancy based on 4-vessel sampling.

Placental release of taurine to both the maternal and fetal circulations in human term pregnancies

Taurine is regarded as an essential amino acid in utero, and fetal taurine supply is believed to rely solely on placental transfer from maternal plasma. Despite its potential role in intrauterine growth restriction and other developmental disturbances, human in vivo studies of taurine transfer between the maternal, placental, and fetal compartments are scarce. We studied placental transfer of taurine in uncomplicated human term pregnancies in vivo in a cross-sectional study of 179 mother-fetus pairs. During cesarean section, we obtained placental tissue and plasma from incoming and outgoing vessels on the maternal and fetal sides of the placenta. Taurine was measured by liquid chromatography-tandem mass spectrometry. We calculated paired arteriovenous differences, and measured placental expression of the taurine biosynthetic enzyme cysteine sulfinic acid decarboxylase (CSAD) with quantitative real-time polymerase chain reaction and western blot. We observed a fetal uptake (p < 0.001), an uteroplacental release (p < 0.001), and a negative placental consumption of taurine (p = 0.001), demonstrating a bilateral placental release to the maternal and fetal compartments. Increasing umbilical vein concentrations and fetal uptake was associated with the uteroplacental release to the maternal circulation (r_s = - 0.19, p = 0.01/r_s = - 0.24, p = 0.003), but not with taurine concentrations in placental tissue. CSAD-mRNA was expressed in placental tissue, suggesting a potential for placental taurine synthesis. Our observations show that the placenta has the capacity to a bilateral taurine release, indicating a fundamental role of taurine in the human placental homeostasis beyond the supply to the fetus.