Umbilical venous–arterial plasma composition differences suggest differential incorporation of fatty acids in NEFA and cholesteryl ester pools

Knockdown of Placental Major Facilitator Superfamily Domain Containing 2a in Pregnant Mice Reduces Fetal Brain Growth and Phospholipid Docosahexaenoic Acid Content

INTRODUCTION

Docosahexaenoic acid (DHA) is an n-3 long chain polyunsaturated fatty acid critical for fetal brain development that is transported to the fetus from the mother by the placenta. The lysophosphatidylcholine (LPC) transporter, Major Facilitator Superfamily Domain Containing 2a (MFSD2a), is localized in the basal plasma membrane of the syncytiotrophoblast of the human placenta, and MFSD2a expression correlates with umbilical cord blood LPC-DHA levels in human pregnancy. We hypothesized that placenta-specific knockdown of MFSD2a in pregnant mice reduces phospholipid DHA accumulation in the fetal brain.

METHODS

Mouse blastocysts (E3.5) were transduced with an EGFP-expressing lentivirus containing either an shRNA targeting MFSD2a or a non-coding sequence (SCR), then transferred to pseudopregnant females. At E18.5, fetuses were weighed and their placenta, brain, liver and plasma were collected. MFSD2a mRNA expression was determined by qPCR in the brain, liver and placenta and phospholipid DHA was quantified by LC-MS/MS.

RESULTS

MFSD2a-targeting shRNA reduced placental mRNA MFSD2a expression by 38% at E18.5 (n = 45, p < 0.008) compared with SCR controls. MFSD2a expression in the fetal brain and liver were unchanged. Fetal brain weight was reduced by 13% (p = 0.006). Body weight, placenta and liver weights were unaffected. Fetal brain phosphatidyl choline and phosphatidyl ethanolamine DHA content was lower in fetuses with placenta-specific MFSD2a knockdown.

CONCLUSIONS

Placenta-specific reduction in expression of the LPC-DHA transporter MFSD2a resulted in reduced fetal brain weight and lower phospholipid DHA content in the fetal brain. These data provide mechanistic evidence that placental MFSD2a mediates maternal-fetal transfer of LPC-DHA, which is critical for brain growth.

Development and validation of risk prediction models for large for gestational age infants using logistic regression and two machine learning algorithms

BACKGROUND

Large for gestational age (LGA) is one of the adverse outcomes during pregnancy that endangers the life and health of mothers and offspring. We aimed to establish prediction models for LGA at late pregnancy.

METHODS

Data were obtained from an established Chinese pregnant women cohort of 1285 pregnant women. LGA was diagnosed as >90th percentile of birth weight distribution of Chinese corresponding to gestational age of the same-sex newborns. Women with gestational diabetes mellitus (GDM) were classified into three subtypes according to the indexes of insulin sensitivity and insulin secretion. Models were established by logistic regression and decision tree/random forest algorithms, and validated by the data.

RESULTS

A total of 139 newborns were diagnosed as LGA after birth. The area under the curve (AUC) for the training set is 0.760 (95% confidence interval [CI] 0.706-0.815), and 0.748 (95% CI 0.659-0.837) for the internal validation set of the logistic regression model, which consisted of eight commonly used clinical indicators (including lipid profile) and GDM subtypes. For the prediction models established by the two machine learning algorithms, which included all the variables, the training set and the internal validation set had AUCs of 0.813 (95% CI 0.786-0.839) and 0.779 (95% CI 0.735-0.824) for the decision tree model, and 0.854 (95% CI 0.831-0.877) and 0.808 (95% CI 0.766-0.850) for the random forest model.

CONCLUSION

We established and validated three LGA risk prediction models to screen out the pregnant women with high risk of LGA at the early stage of the third trimester, which showed good prediction power and could guide early prevention strategies.

α-linolenic acid interconversion is sufficient as a source of longer chain ω-3 polyunsaturated fatty acids in humans: An opinion

α-linolenic acid (αLNA) conversion into the functionally important ω-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), has been regarded as inadequate for meeting nutritional requirements for these PUFA. This view is based on findings of small αLNA supplementation trials and stable isotope tracer studies that have been interpreted as indicating human capacity for EPA and, in particular, DHA synthesis is limited. The purpose of this review is to re-evaluate this interpretation. Markedly differing study designs, inconsistent findings and lack of trial replication preclude robust consensus regarding the nutritional adequacy of αLNA as a source of EPC and DHA. The conclusion that αLNA conversion in humans is constrained is inaccurate because it presupposes the existence of an unspecified, higher level of metabolic activity. Since capacity for EPA and DHA synthesis is the product of evolution it may be argued that the levels of EPA and DHA it maintains are nutritionally appropriate. Dietary and supra-dietary EPA plus DHA intakes confer health benefits. Paradoxically, such health benefits are also found amongst vegetarians who do not consume EPA and DHA, and for whom αLNA conversion is the primary source of ω-3 PUFA. Since there are no reported adverse effects on health or cognitive development of diets that exclude EPA and DHA, their synthesis from αLNA appears to be nutritionally adequate. This is consistent with the dietary essentiality of αLNA and has implications for developing sustainable nutritional recommendations for ω-3 PUFA.

Placental lipid transport and content in response to maternal overweight and gestational diabetes mellitus in human term placenta

BACKGROUND AND AIMS

Placental lipid transport is altered in women with high prepregnancy body mass index (pre-BMI) or gestational diabetes (GDM), which consequently affects foetal growth. However, the interaction of maternal overweight (OW) and GDM on placental lipid metabolism and possible adaptations are less studied. We aimed to examine whether maternal OW or GDM is the main factor disrupting placental lipid processing in human term placenta.

METHODS AND RESULTS

A total of 152 lean (18.5 ≤ pre-BMI ≤ 23.9 kg/m²) and OW (24 ≤ pre-BMI ≤ 27.9 kg/m²) pregnant women with or without GDM with a scheduled delivery by caesarean section were recruited. Maternal venous blood samples were used to measure metabolic parameters during pregnancy. Term placentas and cord blood were collected at delivery to determine placental lipid metabolism and foetal circulating lipid levels. Maternal OW significantly increased the placental mRNA expression of genes involved in lipid metabolism (FAT/CD36, FATP1, FATP4, FATP6, and PPAR-α), elevated placental lipid content (triglyceride, cholesterol), enhanced placental mTORC1-rpS6 and ERK1/2 signalling, increased cord blood insulin levels and birth weight. Neonatal birth weight was positively correlated with maternal pre-BMI, placental ERK1/2 signalling and cord blood insulin. There was an interaction between OW and GDM in regulating key placental fuel transport and storage gene expression (LPL, FATP6, FABP7, PPAR-α, PPAR-β, PPAR-γ, IR-β, GLUT1, SNAT2, SNAT4, and LAT1).

CONCLUSION

Maternal OW mainly affects placental lipid metabolism, which may contribute to foetal overgrowth and may impact long-term offspring health. GDM plays a less significant role in affecting placental lipid transfer and other mechanisms may be involved.

Mice exposed to maternal androgen excess and diet-induced obesity have altered phosphorylation of catechol-O-methyltransferase in the placenta and fetal liver

BACKGROUND/OBJECTIVES

Maternal obesity together with androgen excess in mice negatively affects placental function and maternal and fetal liver function as demonstrated by increased triglyceride content with dysfunctional expression of enzymes and transcription factors involved in de novo lipogenesis and fat storage. To identify changes in molecular pathways that might promote diseases in adulthood, we performed a global proteomic analysis using a liquid-chromatography/mass-spectrometry system to investigate total and phosphorylated proteins in the placenta and fetal liver in a mouse model that combines maternal obesity with maternal androgen excess.

METHODS

After ten weeks on a control diet (CD) or high fat/high sugar-diet, dams were mated with males fed the CD. Between gestational day (GD) 16.5 and GD 18.5, mice were injected with vehicle or dihydrotestosterone (DHT) and sacrificed at GD 18.5 prior to dissection of the placentas and fetal livers. Four pools of female placentas and fetal livers were subjected to a global proteomic analysis. Total and phosphorylated proteins were filtered by ANOVA q < 0.05, and this was followed by two-way ANOVA to determine the effect of maternal obesity and/or androgen exposure.

RESULTS

In placenta, phosphorylated ATP-citrate synthase was decreased due to maternal obesity, and phosphorylated catechol-O-methyltransferase (COMT) was differentially expressed due to the interaction between maternal diet and DHT exposure. In fetal liver, five total proteins and 48 proteins phosphorylated in one or more sites, were differentially expressed due to maternal obesity or androgen excess. In fetal liver, phosphorylated COMT expression was higher in fetus exposed to maternal obesity.

CONCLUSION

These results suggest a common regulatory mechanism of catecholamine metabolism in the placenta and the fetal liver as demonstrated by higher phosphorylated COMT expression in the placenta and fetal liver from animals exposed to diet-induced maternal obesity and lower expression of phosphorylated COMT in animals exposed to maternal androgen excess.

New perspectives on placental fatty acid transfer

The human foetus depends on placental transfer for the fatty acids required for its growth and development. Long chain polyunsaturated fatty acids (LC-PUFAs) may specifically influence neurodevelopment. Therefore, it is important to understand the mechanisms of placental transfer of LC-PUFAs. The simple view of placental fatty acid transfer is that it occurs by diffusion down the maternal to foetal gradient, facilitated by membrane transporters. This view has been complicated by studies highlighting the role of placental metabolism in fatty acid transfer. Most fatty acids taken up by the placenta will be esterified and incorporated into lipid rather than diffusing directly across to the foetus. Furthermore, this esterification is likely to mean that placental intracellular "free" fatty acid concentrations are lower than in foetal plasma which would not be conducive to simple diffusion of fatty acids to the foetus. Placental structure poses additional questions, in particular how fatty acids cross the hydrophilic villous stroma separating the trophoblast from the endothelium and how they cross the endothelium itself. The understanding of placental fatty acid transfer needs to evolve to address these questions. The role of the placenta is not simply to mediate solute transfer; it is also a central endocrine organ of pregnancy. Placental-derived lipid mediators, such as prostaglandins, have well-established roles in parturition and, almost certainly, throughout gestation. Metabolic targeting of specific fatty acids to different lipid pools in the placenta may determine their availability as both nutrients and signalling molecules. Placental transfer will determine fatty acid availability within the foetus as well as influencing maternal levels. Fatty acids and their derivatives may also act as signals to the placenta indicating metabolic states in both mother and foetus. Placental uptake and metabolism of LC-PUFAs are important to meet both foetal and placental demands. This paper will review placental fatty acid transfer and metabolism and highlight issues which need to be addressed.

Effect of maternal metabolism on fetal supply: Glucose, non-esterified fatty acids and beta-hydroxybutyrate concentrations in canine maternal serum and fetal fluids at term pregnancy

The progressive adaptations in carbohydrate and lipid metabolism during canine pregnancy are reflected in the concentrations of glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). The levels of these metabolites in the bitch likely affect fetal concentrations and the composition of amniotic and allantoic fluids (AMF and ALF, respectively). We studied 31 canine parturitions (Cesarean sections) and found that glucose, NEFA and BHB concentrations were significantly higher in maternal serum than in AMF or ALF. Glucose levels in maternal serum, AMF and ALF were closely related (R² ≥ 0.821, P < 0.0001) as well as serum and AMF BHB levels (R² = 0.661, P < 0.0001). In maternal serum, increases in NEFA were associated with increased BHB, and both were negatively related to glucose (P ≤ 0.010). To estimate the effect of the metabolic burden of pregnancy, we evaluated these variables in relation to the dam's body weight and to the ratio of litter weight to the dam's body weight (LW/BW). Maternal serum glucose was not influenced by LW/BW, but it was lower in small than in large/giant bitches. Small breed dogs and those with >10% LW/BW had significantly higher serum NEFA and BHB concentrations. Glucose in AMF and ALF was independent of LW/BW (P ≥ 0.399). AMF NEFA was lower and BHB higher, if LW/BW was >10% (P ≤ 0.048). In conclusion, the extent of the metabolic load of pregnancy in bitches depends on breed size and on the ratio of litter weight to dam's body weight. Maternal concentrations of glucose, BHB and NEFA determine the concentrations of these metabolites in fetal fluids.

Maternal and fetal lipid metabolism under normal and gestational diabetic conditions

Maternal lipids are strong determinants of fetal fat mass. Here we review the overall lipid metabolism in normal and gestational diabetes mellitus (GDM) pregnancies. During early pregnancy, the increase in maternal fat depots is facilitated by insulin, followed by increased adipose tissue breakdown and subsequent hypertriglyceridemia, mainly as a result of insulin resistance (IR) and estrogen effects. The response to diabetes is variable as a result of greater IR but decreased estrogen levels. The vast majority of fatty acids (FAs) in the maternal circulation are esterified and associated with lipoproteins. These are taken up by the placenta and hydrolyzed by lipases. The released FAs enter various metabolic routes and are released into fetal circulation. Although these determinants are modified in maternal GDM, the fetus does not seem to receive more FAs than in non-GDM pregnancies. Long-chain polyunsaturated FAs are essential for fetal development and are obtained from the mother. Mitochondrial FA oxidation occurs in fetal tissue and in placenta and contributes to energy production. Fetal fat accretion during the last weeks of gestation occurs very rapidly and is sustained not only by FAs crossing the placenta, but also by fetal lipogenesis. Fetal hyperinsulinemia in GDM mothers promotes excess accretion of adipose tissue, which gives rise to altered adipocytokine profiles. Fetal lipoproteins are low at birth, but the GDM effects are unclear. The increase in body fat in neonates of GDM women is a risk factor for obesity in early childhood and later life.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Cord blood n-3 LC-PUFA is associated with adiponectin concentrations at 10 years of age

An elevated ratio of n-6 to n-3 long-chain (LC-) polyunsaturated fatty acids (PUFA) may be a potential risk factor for obesity development. N-3 LC-PUFA are thought to alter adiponectin concentrations, and thus may have a beneficial effect on weight development. We analysed the association between n-3 LC-PUFA concentrations in cord blood and adiponectin concentrations at 10 years. Fatty acid composition was measured in cord blood and at 10 years of age by gas chromatography, and adiponectin concentrations were measured only at 10 years of age in 237 children from the Munich LISAplus birth cohort study. Linear regression models assessed associations between n-3 LC-PUFA, n-6 LC-PUFA and the n-6/n-3 ratio in cord blood with adiponectin concentrations at 10 years of age. LC-PUFA were presented as percentages and categorized into tertiles. Regression models were adjusted for LC-PUFA percentages at 10 years of age and other potential confounding factors. Cord blood n-3 LC-PUFA tertiles were significantly associated with adiponectin concentrations in an inverse J-shaped relationship [2nd tertile versus 1st tertile: Beta=1.84 (SE=0.65), and 3rd tertile versus 1st tertile: 1.02 (0.68), p-value<0.01 (ANOVA)]. Further, cord blood n-6/n-3 ratios were significantly associated with adiponectin concentrations [2nd tertile versus 1st tertile: 0.14 (0.67), and 3rd tertile versus 1st tertile: -1.37 (0.68), p-value=0.03 (ANOVA)]. The cord blood n-6 LC-PUFA tertiles were not associated with adiponectin concentrations. Our results suggest that a higher n-3 LC-PUFA concentrations and a lower n-6/n-3 ratio in cord blood are associated with higher adiponectin concentrations at 10 years of age.

Early developmental conditioning of later health and disease: physiology or pathophysiology?

Extensive experimental animal studies and epidemiological observations have shown that environmental influences during early development affect the risk of later pathophysiological processes associated with chronic, especially noncommunicable, disease (NCD). This field is recognized as the developmental origins of health and disease (DOHaD). We discuss the extent to which DOHaD represents the result of the physiological processes of developmental plasticity, which may have potential adverse consequences in terms of NCD risk later, or whether it is the manifestation of pathophysiological processes acting in early life but only becoming apparent as disease later. We argue that the evidence suggests the former, through the operation of conditioning processes induced across the normal range of developmental environments, and we summarize current knowledge of the physiological processes involved. The adaptive pathway to later risk accords with current concepts in evolutionary developmental biology, especially those concerning parental effects. Outside the normal range, effects on development can result in nonadaptive processes, and we review their underlying mechanisms and consequences. New concepts concerning the underlying epigenetic and other mechanisms involved in both disruptive and nondisruptive pathways to disease are reviewed, including the evidence for transgenerational passage of risk from both maternal and paternal lines. These concepts have wider implications for understanding the causes and possible prevention of NCDs such as type 2 diabetes and cardiovascular disease, for broader social policy and for the increasing attention paid in public health to the lifecourse approach to NCD prevention.

Automated high-throughput fatty acid analysis of umbilical cord serum and application to an epidemiological study

Large population studies show that polyunsaturated fatty acids are important for human health, but determining relationships between the health benefits and the fatty acid content has been hampered by the unavailability of labor-effective high-throughput technologies. An automated high throughput fatty acid analysis was developed from a previous procedure based on direct transesterification including the automation of chemical procedures, data acquisition and automatic data processing. The method was validated and applied to umbilical cord serum samples in an epidemiological study. The method was linear in the range of 1-600 μg/mL serum with r² ≥ 0.99. The within-run CV was <5.4% for 23 fatty acids and a range of recoveries over three concentrations were 76-119% in a low-lipid matrix with the exception of 14:0. The fatty acid concentration as measured by the robotic method for human plasma was in good agreement with the Lepage & Roy method. The fatty acid profile in umbilical cord serum from American subjects (n = 287) showed an average of 38.0, 24.9, 32.0 and 4.6% of total fatty acids for saturates, monounsaturates, n-6 and n-3 polyunsaturates, respectively. This is the first report of a complete, validated, cost-effective, automated, high throughput fatty acid measurement method along with application to a population-based study. Automated fatty acid analysis coupled with automated data processing greatly facilitates the high throughput, 72 samples transesterified in 6 h, required for large population-based studies.