Effects of Arachidonic and Docosohexahenoic Acid Supplementation during Gestation in Rats. Implication of Placental Oxidative Stress

Identification of key metabolism-related genes and pathways in spontaneous preterm birth: combining bioinformatic analysis and machine learning

Background

Spontaneous preterm birth (sPTB) is a global disease that is a leading cause of death in neonates and children younger than 5 years of age. However, the etiology of sPTB remains poorly understood. Recent evidence has shown a strong association between metabolic disorders and sPTB. To determine the metabolic alterations in sPTB patients, we used various bioinformatics methods to analyze the abnormal changes in metabolic pathways in the preterm placenta via existing datasets.

Methods

In this study, we integrated two datasets (GSE203507 and GSE174415) from the NCBI GEO database for the following analysis. We utilized the "Deseq2" R package and WGCNA for differentially expressed genes (DEGs) analysis; the identified DEGs were subsequently compared with metabolism-related genes. To identify the altered metabolism-related pathways and hub genes in sPTB patients, we performed multiple functional enrichment analysis and applied three machine learning algorithms, LASSO, SVM-RFE, and RF, with the hub genes that were verified by immunohistochemistry. Additionally, we conducted single-sample gene set enrichment analysis to assess immune infiltration in the placenta.

Results

We identified 228 sPTB-related DEGs that were enriched in pathways such as arachidonic acid and glutathione metabolism. A total of 3 metabolism-related hub genes, namely, ANPEP, CKMT1B, and PLA2G4A, were identified and validated in external datasets and experiments. A nomogram model was developed and evaluated with 3 hub genes; the model could reliably distinguish sPTB patients and term labor patients with an area under the curve (AUC) > 0.75 for both the training and validation sets. Immune infiltration analysis revealed immune dysregulation in sPTB patients.

Conclusion

Three potential hub genes that influence the occurrence of sPTB through shadow participation in placental metabolism were identified; these results provide a new perspective for the development and targeting of treatments for sPTB.

Dietary Folic Acid Supplementation Attenuates Maternal High-Fat Diet-Induced Fetal Intrauterine Growth Retarded via Ameliorating Placental Inflammation and Oxidative Stress in Rats

The placenta is particularly susceptible to inflammation and oxidative stress, leading to placental vascular dysfunction and placental insufficiency, which is associated with fetal intrauterine growth restriction (IUGR). It is unknown whether folic acid (FA) supplementation can alleviate high-fat diet-induced IUGR in rats by improving placental function. In this study, pregnant rats were randomized into one of four diet-based groups: (1) control diet (CON), (2) control diet supplemented with FA, (3) high-fat diet (HFD), and (4) high-fat diet supplemented with FA (HFD + FA). Dams were sacrificed at gestation day 18.5 (GD18.5). The results indicated that dietary FA supplementation normalized a maternal HFD-induced decrease in fetal weight. The decrease in placental efficiency, labyrinth zone (LZ) area, blood sinusoid area, vascular density, and the levels of angiogenesis factors induced by a maternal HFD were alleviated by the addition of FA, suggesting that FA supplementation can alleviate placental vascular dysplasia. Furthermore, FA supplementation increased the protein expressions of SIRT1, inhibited NF-κB transcriptional activation, attenuated the levels of NF-κB/downstream pro-inflammatory cytokines, induced Nrf2 activation, and increased downstream target protein expression. In conclusion, we found that dietary FA supplementation during pregnancy could improve maternal HFD-induced IUGR by alleviating placental inflammation and oxidative stress, which may be associated with the regulation of SIRT1 and its mediated NF-κB and Nrf2 signaling pathways.

Altered Cord Blood Lipid Concentrations Correlate with Birth Weight and Doppler Velocimetry of Fetal Vessels in Human Fetal Growth Restriction Pregnancies

Fetal growth restriction (FGR) is associated with short- and long-term morbidity, often with fetal compromise in utero, evidenced by abnormal Doppler velocimetry of fetal vessels. Lipids are vital for growth and development, but metabolism in FGR pregnancy, where fetuses do not grow to full genetic potential, is poorly understood. We hypothesize that triglyceride concentrations are increased in placentas and that important complex lipids are reduced in cord plasma from pregnancies producing the smallest babies (birth weight < 5%) and correlate with ultrasound Dopplers. Dopplers (umbilical artery, UA; middle cerebral artery, MCA) were assessed longitudinally in pregnancies diagnosed with estimated fetal weight (EFW) < 10% at ≥29 weeks gestation. For a subset of enrolled women, placentas and cord blood were collected at delivery, fatty acids were extracted and targeted lipid class analysis (triglyceride, TG; phosphatidylcholine, PC; lysophosphatidylcholine, LPC; eicosanoid) performed by LCMS. For this sub-analysis, participants were categorized as FGR (Fenton birth weight, BW ≤ 5%) or SGA "controls" (Fenton BW > 5%). FGRs (n = 8) delivered 1 week earlier (p = 0.04), were 29% smaller (p = 0.002), and had 133% higher UA pulsatility index (PI, p = 0.02) than SGAs (n = 12). FGR plasma TG, free arachidonic acid (AA), and several eicosanoids were increased (p < 0.05); docosahexaenoic acid (DHA)-LPC was decreased (p < 0.01). Plasma TG correlated inversely with BW (p < 0.05). Plasma EET, non-esterified AA, and DHA correlated inversely with BW and directly with UA PI (p < 0.05). Placental DHA-PC and AA-PC correlated directly with MCA PI (p < 0.05). In fetuses initially referred for inadequate fetal growth (EFW < 10%), those with BW ≤ 5% demonstrated distinctly different cord plasma lipid profiles than those with BW > 5%, which correlated with Doppler PIs. This provides new insights into fetal lipidomic response to the FGR in utero environment. The impact of these changes on specific processes of growth and development (particularly fetal brain) have not been elucidated, but the relationship with Doppler PI may provide additional context for FGR surveillance, and a more targeted approach to nutritional management of these infants.

Linoleic acid and linoleate diols in neonatal cord blood influence birth weight

BACKGROUND

Low-birth-weight infants exhibit a high risk for postnatal morbidity. Cytochrome P450 (CYP) and epoxide hydrolase (EH) are involved in the metabolism of factors responsible for low-birth-weight in infants. Both CYPs and EHs have high substrate specificity and are involved in polyunsaturated fatty acid (PUFA) metabolism. The CYP pathway produces epoxy fatty acids (EpFAs), which are further degraded by soluble EH (sEH). Additionally, sEH inhibition enhances the action of EpFAs and suppresses inflammatory responses. During pregnancy, excessive activation of maternal inflammatory response is a significant factor associated with low-birth-weight. However, the association of EpFAs, which have potential anti-inflammatory properties, with the low-birth-weight of infants remains uninvestigated. This study aimed to clarify the association between the umbilical cord serum EpFA and low-birth-weight using data obtained from the Hamamatsu Birth Cohort for Mothers and Children (HBC Study) by analyzing the umbilical cord blood samples.

METHOD

We selected a subgroup of 200 infants (106 boys and 94 girls), quantified EpFA concentration in their cord blood samples collected at birth, and examined its correlation with birth weight.

RESULTS

The comparison between the low-birth-weight and normal-birth-weight groups revealed no significant correlation between PUFA and EpFA concentrations, but a significant correlation was observed in the linoleate diol concentrations of the two groups. Furthermore, birth weight did not significantly correlate with PUFA, EpFA, and diol concentrations in cord blood; however, multiple regression analysis showed a significant negative correlation of birth weight with the concentration of linoleic acid (LA) (r = -0.101, p = 0.016) as well as LA-derived dihydroxyoctadecenoic acid (diHOME) (r = -0.126, p = 0.007), 9,10-diHOME (r = -0.115, p = 0.014), and 12,13-diHOME (r = -0.126, p = 0.007) after adjusting for obstetric factors, including gestational age, infant's sex, childbirth history, delivery method, and maternal height.

CONCLUSIONS

Birth weight was significantly correlated with the concentration of LA and linoleate diol diHOME after adjusting for obstetric confounders. Our results show that CYP and sEH involved in PUFA metabolism may influence the birth weight of infants. Further validation is needed to provide insights regarding maternal intervention strategies required to avoid low-birth-weight in infants in the future.

The Placenta's Role in Sexually Dimorphic Fetal Growth Strategies

Fetal sex affects the risk of pregnancy complications and the long-term effects of prenatal environment on health. Some have hypothesized that growth strategies differ between the sexes, whereby males prioritize growth whereas females are more responsive to their environment. This review evaluates the role of the placenta in such strategies, focusing on (1) mechanisms underlying sexual dimorphism in gene expression, (2) the nature and extent of sexual dimorphism in placental gene expression, (3) sexually dimorphic responses to nutrient supply, and (4) sexual dimorphism in morphology and histopathology. The sex chromosomes contribute to sex differences in placental gene expression, and fetal hormones may play a role later in development. Sexually dimorphic placental gene expression may contribute to differences in the prevalence of complications such as preeclampsia, although this link is not clear. Placental responses to nutrient supply frequently show sexual dimorphism, but there is no consistent pattern where one sex is more responsive. There are sex differences in the prevalence of placental histopathologies, and placental changes in pregnancy complications, but also many similarities. Overall, no clear patterns support the hypothesis that females are more responsive to the maternal environment, or that males prioritize growth. While male fetuses are at greater risk of a variety of complications, total prenatal mortality is higher in females, such that males exposed to early insults may be more likely to survive and be observed in studies of adverse outcomes. Going forward, robust statistical approaches to test for sex-dependent effects must be more widely adopted to reduce the incidence of spurious results.

Maternal omega-3 fatty acids maintained positive maternal lipids and cytokines profile, and improved pregnancy outcomes of C57BL/6 mice

Omega (n)-3 polyunsaturated fatty acids (PUFA) are known to regulate lipid metabolism and inflammation; however, the regulation of maternal lipid metabolism and cytokines profile by n-3 PUFA during different gestation stages, and its impact on fetal sustainability is not known. We investigated the effects of maternal diet varying in n-3 PUFA prior to, and during gestation, on maternal metabolic profile, placental inflammatory cytokines, and fetal outcomes. Female C57BL/6 mice were fed either a high, low or very low (9, 3 or 1% w/w n-3 PUFA) diet, containing n-6:n-3 PUFA of 5:1, 20:1 and 40:1, respectively for two weeks before mating, and throughout pregnancy. Animals were sacrificed prior to mating (NP), and during pregnancy at gestation days 6.5, 12.5 and 18.5. Maternal metabolic profile, placental cytokines and fetal outcomes were determined. Our results show for the first time that a maternal diet high in n-3 PUFA prevented dyslipidemia in NP mice, and maintained the expected lipid profile during pregnancy. However, females fed the very low n-3 PUFA diet became hyperlipidemic prior to pregnancy, and carried this profile into pregnancy. Maternal diet high in n-3 PUFA maintained maternal plasma progesterone and placental pro-inflammatory cytokines profile, and sustained fetal numbers throughout pregnancy, while females fed the low and very-low n-3 PUFA diet had fewer fetuses. Our findings demonstrate the importance of maternal diet before, and during pregnancy, to maintain maternal metabolic profile and fetus sustainability. These findings are important when designing dietary strategies to optimize maternal metabolism during pregnancy for successful pregnancy outcome.

Impact of Maternal Obesity on the Metabolism and Bioavailability of Polyunsaturated Fatty Acids during Pregnancy and Breastfeeding

Prenatal and postnatal development are closely related to healthy maternal conditions that allow for the provision of all nutritional requirements to the offspring. In this regard, an appropriate supply of fatty acids (FA), mainly n-3 and n-6 long-chain polyunsaturated fatty acids (LCPUFA), is crucial to ensure a normal development, because they are an integral part of cell membranes and participate in the synthesis of bioactive molecules that regulate multiple signaling pathways. On the other hand, maternal obesity and excessive gestational weight gain affect FA supply to the fetus and neonate, altering placental nutrient transfer, as well as the production and composition of breast milk during lactation. In this regard, maternal obesity modifies FA profile, resulting in low n-3 and elevated n-6 PUFA levels in maternal and fetal circulation during pregnancy, as well as in breast milk during lactation. These modifications are associated with a pro-inflammatory state and oxidative stress with short and long-term consequences in different organs of the fetus and neonate, including in the liver, brain, skeletal muscle, and adipose tissue. Altogether, these changes confer to the offspring a higher risk of developing obesity and its complications, as well as neuropsychiatric disorders, asthma, and cancer. Considering the consequences of an abnormal FA supply to offspring induced by maternal obesity, we aimed to review the effects of obesity on the metabolism and bioavailability of FA during pregnancy and breastfeeding, with an emphasis on LCPUFA homeostasis.

The Role of Arachidonic and Linoleic Acid Derivatives in Pathological Pregnancies and the Human Reproduction Process

The aim of the available literature review was to focus on the role of the proinflammatory mediators of AA and LA derivatives in pathological conditions related to reproduction and pregnancy. Arachidonic (AA) and linoleic acid (LA) derivatives play important roles in human fertility and the course of pathological pregnancies. Recent studies have demonstrated that uncontrolled inflammation has a significant impact on reproduction, spermatogenesis, endometriosis, polycystic ovary syndrome (PCOS) genesis, implantation, pregnancy and labor. In addition, cyclooxygenase-mediated prostaglandins and AA metabolite levels are higher in women’s ovarian tissue when suffering from PCOS. It has been demonstrated that abnormal cyclooxygenase-2 (COX-2) levels are associated with ovulation failure, infertility, and implantation disorders and the increase in 9-HODE/13-HODE was a feature recognized in PCOS patients. Maintaining inflammation without neutrophil participation allows pregnant women to tolerate the fetus, while excessive inflammatory activation may lead to miscarriages and other pathological complications in pregnancies. Additionally AA and LA derivatives play an important role in pregnancy pathologies, e.g., gestational diabetes mellitus, preeclampsia (PE), and fetal growth, among others. The pathogenesis of PE and other pathological states in pregnancy involving eicosanoids have not been fully identified. A significant expression of 15-LOX-1,2 was found in women with PE, leading to an increase in the synthesis of AA and LA derivatives, such as hydroxyeicozatetraenoic acids (HETE) and hydroxyoctadecadiene acids (HODE). Synthesis of the metabolites 5-, 8-, 12-, and 15-HETE increased in the placenta, while 20-HETE increased only in umbilical cord blood in women with preeclampsia compared to normal pregnancies. In obese women with gestational diabetes mellitus (GDM) an increase in epoxygenase products in the cytochrome P450 (CYP) and the level of 20-HETE associated with the occurrence of insulin resistance (IR) were found. In addition, 12- and 20-HETE levels were associated with arterial vasoconstriction and epoxyeicosatrienoic acids (EETs) with arterial vasodilatation and uterine relaxation. Furthermore, higher levels of 5- and 15-HETE were associated with premature labor. By analyzing the influence of free fatty acids (FFA) and their derivatives on male reproduction, it was found that an increase in the AA in semen reduces its amount and the ratio of omega-6 to omega-3 fatty acids showed higher values in infertile men compared to the fertile control group. There are several studies on the role of HETE/HODE in relation to male fertility. 15-Hydroperoxyeicosatetraenoic acid may affect the integrity of the membrane and sperm function. Moreover, the incubation of sperm with physiologically low levels of prostaglandins (PGE2/PGF2α) improves the functionality of human sperm. Undoubtedly, these problems are still insufficiently understood and require further research. However, HETE and HODE could serve as predictive and diagnostic biomarkers for pregnancy pathologies (especially in women with risk factors for overweight and obesity). Such knowledge may be helpful in finding new treatment strategies for infertility and the course of high-risk pregnancies.

Maternal dietary deficiency of n-3 fatty acids affects metabolic and epigenetic phenotypes of the developing fetus

Polyunsaturated fatty acids (PUFAs) play multiple physiological roles. They regulate the structure and function of cell membranes and cell growth and proliferation, and apoptosis. In addition, PUFAs are involved in cellular signaling, gene expression and serve as precursors to second messengers such as eicosanoids, docosanoids etc. and regulate several physiological processes including placentation, inflammation, immunity, angiogenesis, platelet function, synaptic plasticity, neurogenesis, bone formation, energy homeostasis, pain sensitivity, stress, and cognitive functions. Linoleic acid, 18:2n-6 (LA) and alpha-linolenic acid, 18:3n-3 (ALA) are the two essential fatty acids obtained from the diets and subsequently their long-chain polyunsaturated fatty acids (LCPUFAs) are accumulated in the body. The maternal plasma LCPUFAs especially accumulated in larger amounts in the brain during the third trimester of pregnancy via the placenta and postnatally from mother's breast milk. Various studies, including ours, suggest PUFA's important role in placentation, as well as in growth and development of the offspring. However, intakes of maternal n-3 PUFAs during pregnancy and lactation are much lower in India compared with the Western population. In India, n-3 fatty acid status is further reduced by higher intake of n-6 PUFA rich oils and trans fats. More data on the impacts of long term maternal n-3 PUFA deficiency on placental structure and function, gene expression, epigenetic changes and resultant cognitive function of fetus & infants are emerging. This review summarizes the impacts of n-3 PUFA deficiency in utero on fetal growth and development, adiposity, energy metabolism, musculoskeletal development, and epigenetic changes in feto-placental axis from the recently available pre-clinical and clinical data.