Regulation of Placental Amino Acid Transport and Fetal Growth

Succession of rumen microbiota and metabolites across different reproductive periods in different sheep breeds and their impact on the growth and development of offspring lambs

BACKGROUND

The microbiota and metabolites in the gastrointestinal tracts of female animals at different reproductive periods are very important to the growth, development, and health of themselves and their offspring. However, the changes in the gastrointestinal microbiota and metabolites throughout reproductive period of different sheep breeds and their effects on the growth and development of offspring lambs are still unclear. Hence, this study presents an assessment of the reproductive hormone levels, immune levels, rumen microbiota, and metabolites in Hu sheep and Suffolk ewes at different reproductive periods and their effects on the growth and development of offspring lambs.

RESULTS

Hu sheep and Suffolk during non-pregnancy, pregnancy, and lactation were used as the research objects to determine reproductive and immune indexes of ewes at different periods, analyze rumen microbiome and metabolome, and track the growth performance and development of offspring lambs. The results showed that the reproductive hormone and immune levels of Hu sheep and Suffolk underwent adaptive changes across different reproductive periods. Compared with non-pregnancy, the microbial energy metabolism and lipid metabolism function decreased during Hu sheep pregnancy, and energy metabolism function decreased during lactation. In Suffolk, energy metabolism, glycan biosynthesis, and metabolism function were enhanced during pregnancy, and the metabolism of cofactors and vitamins was enhanced during lactation. Prevotella increased in Suffolk during pregnancy and lactation (P < 0.05) and was positively correlated with the birth weight and body size of the lambs (P < 0.05). Moreover, the abundances of Butyrivibrio and Rikenellaceae_RC9_gut_group during pregnancy were positively correlated with the intestinal immunity of the offspring lambs (P < 0.05), thereby regulating the intestinal immunity level of the lambs. Metabolomic analysis revealed that the protein digestion, absorption, and amino acid metabolism of Hu sheep were enhanced during pregnancy, which provided amino acids for the growth and development of pregnant ewes and fetuses and was significantly correlated with the birth weight, body size, and intestinal immunity of lambs (P < 0.05). Simultaneously, there was an increase in acetate and propionate during the pregnancy and lactation period of both Hu sheep and Suffolk, providing energy for ewes during reproductive period. Moreover, the microbiota during the lactation period was significantly correlated with the milk quality and lambs daily gain (P < 0.05).

CONCLUSIONS

This study revealed the characteristic succession changes in the rumen microbiota and its metabolites at different reproductive periods in sheep breeds and their regulation of reproductive hormone and immune levels and identified their potential effects on the growth and development of offspring lambs. The findings provide valuable insights into the health and feeding management of different sheep breeds during the reproductive stage. Video Abstract.

Unraveling the Molecular Mechanisms of the Neurodevelopmental Consequences of Fetal Protein Deficiency: Insights From Rodent Models and Public Health Implications

Fetal brain development requires increased maternal protein intake to ensure that offspring reach their optimal cognitive potential in infancy and adulthood. While protein deficiency remains a prevalent issue in developing countries, it is also reemerging in Western societies due to the growing adoption of plant-based diets, some of which are monotonous and may fail to provide sufficient amino acids crucial for the brain's critical developmental phase. Confounding variables in human nutritional research have impeded our understanding of the precise impact of protein deficiency on fetal neurodevelopment, as well as its implications for childhood neurocognitive performance. Moreover, it remains unclear whether such deficiency could predispose to mental health problems in adulthood, mirroring observations in individuals exposed to prenatal famine. In this review, we sought to evaluate mechanistic data derived from rodent models, placing special emphasis on the involvement of neuroendocrine axes, the influence of sex and timing, epigenetic modifications, and cellular metabolism. Despite notable progress, critical knowledge gaps remain, including understanding the long-term reversibility of effects due to fetal protein restriction and the interplay between genetic predisposition and environmental factors. Enhancing our understanding of the precise mechanisms that connect prenatal nutrition to brain development in future research endeavors can be significantly advanced by integrating multiomics approaches and utilizing additional alternative models such as nonhuman primates. Furthermore, it is crucial to investigate potential interventions aimed at alleviating adverse outcomes. Ultimately, this research has profound implications for guiding public health strategies aimed at raising awareness about the crucial role of optimal maternal nutrition in supporting fetal neurodevelopment.

A genetically small fetus impairs placental adaptations near term

The placenta is a gatekeeper between the mother and fetus, adapting its structure and functions to support optimal fetal growth. Studies exploring adaptations of placentae that support the development of genetically small fetuses are lacking. Here, using a mouse model of impaired fetal growth, achieved by deleting insulin-like growth factor 2 (Igf2) in the epiblast, we assessed placental nutrient transfer and umbilical artery (UA) blood flow during late gestation. At embryonic day (E) 15.5, we observed a decline in the trans-placental flux of glucose and system A amino acids (by using 3H-MeG and 14C-MeAIB), proportionate to the diminished fetal size, whereas UA blood flow was normal. However, at E18.5, the trans-placental flux of both tracers was disproportionately decreased and accompanied by blunted UA blood flow. Feto-placental growth and nutrient transfer were more impaired in female conceptuses. Thus, reducing the fetal genetic demand for growth impairs the adaptations in placental blood flow and nutrient transport that normally support the fast fetal growth during late gestation. These findings have important implications for our understanding of the pathophysiology of pregnancies afflicted by fetal growth restriction.

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.

Obesity, a Single Pathology Influencing Both Mother and Child-A Retrospective Analysis in Hospital Settings

Obesity, characterized by an excess of adipose tissue, has become a significant global health issue. The prevalence of obesity has increased markedly in recent decades worldwide, with a sharp rise also observed in developing countries, particularly in urban areas. Addressing obesity during pregnancy is crucial for several reasons and presents challenges for specialists in obstetrics and gynecology.

OBJECTIVES

The aim of the present study was to investigate the correlation between obesity and its implications for childbirth.

MATERIALS AND METHODS

We conducted a retrospective study involving 1513 patients, grouped into normal-weight, overweight, and obese categories using corrected BMI values. We performed comparative analyses to explore the association between BMI and various outcomes: the method of delivery, the Apgar score at birth, the incidence of fetal distress, fetal birth weight, the presence of pregnancy-associated pathologies, and the occurrence of postpartum hemorrhage. Descriptive statistical analysis was utilized to characterize the demographic and clinical features of the patients and newborns.

RESULTS

By examining variables such as the occurrence of fetal distress during labor, the Apgar score at delivery, and the mode of delivery, we identified an association between increasing BMI and complications during labor and delivery. The results indicate that a higher BMI is linked with increased complications and variations in the mode of delivery.

CONCLUSIONS

Obesity is the most common health issue among women of reproductive age and requires long-term care. It can contribute to numerous pregnancy-associated pathologies and affect both mother and child during labor and delivery. Obesity is associated with lower Apgar scores, the increased incidence of fetal distress, and a higher rate of cesarean section deliveries. Although the absolute risk of serious complications for mother, fetus, and newborn is low among women with obesity, adopting healthy eating and exercise behaviors prior to pregnancy, ideally, or as early in pregnancy as possible, can help minimize excessive weight gain during pregnancy.

Maternal obesity and placental function: impaired maternal-fetal axis

The prevalence of maternal obesity rapidly increases, which represents a major public health concern worldwide. Maternal obesity is characteristic by metabolic dysfunction and chronic inflammation. It is associated with health problems in both mother and offspring. Increasing evidence indicates that the placenta is an axis connecting maternal obesity with poor outcomes in the offspring. In this brief review, we have summarized the current data regarding deregulated placental function in maternal obesity. The data show that maternal obesity induces numerous placental defects, including lipid and glucose metabolism, stress response, inflammation, immune regulation and epigenetics. These placental defects affect each other and result in a stressful intrauterine environment, which transduces and mediates the adverse effects of maternal obesity to the fetus. Further investigations are required to explore the exact molecular alterations in the placenta in maternal obesity, which may pave the way to develop specific interventions for preventing epigenetic and metabolic programming in the fetus.

Epigenetic modifications of placenta in women with gestational diabetes mellitus and their offspring

Gestational diabetes mellitus (GDM) is a pregnancy-related complication characterized by abnormal glucose metabolism in pregnant women and has an important impact on fetal development. As a bridge between the mother and the fetus, the placenta has nutrient transport functions, endocrine functions, etc., and can regulate placental nutrient transport and fetal growth and development according to maternal metabolic status. Only by means of placental transmission can changes in maternal hyperglycemia affect the fetus. There are many reports on the placental pathophysiological changes associated with GDM, the impacts of GDM on the growth and development of offspring, and the prevalence of GDM in offspring after birth. Placental epigenetic changes in GDM are involved in the programming of fetal development and are involved in the pathogenesis of later chronic diseases. This paper summarizes the effects of changes in placental nutrient transport function and hormone secretion levels due to maternal hyperglycemia and hyperinsulinemia on the development of offspring as well as the participation of changes in placental epigenetic modifications due to maternal hyperglycemia in intrauterine fetal programming to promote a comprehensive understanding of the impacts of placental epigenetic modifications on the development of offspring from patients with GDM.

Early versus late administration of amino acids in preterm infants receiving parenteral nutrition

BACKGROUND

Observational studies in preterm newborns suggest that delay in administering amino acids (AA) could result in a protein catabolic state and impact on growth and development.

OBJECTIVES

The objective of this review was to compare the efficacy and safety of early versus late administration of intravenous AA in neonates born at < 37 weeks of gestation.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, and trial registries in March 2023. We checked the reference lists of included studies and studies/systematic reviews where subject matter related to the intervention or population examined in this review.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing early administration of AA with late administration in premature newborn infants. We defined early administration of AA solution as the administration of AA in isolation or with total parenteral nutrition within the first 24 hours of birth, and late administration as the administration of AA in isolation or with total parenteral nutrition after the first 24 hours of birth.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures. We used the GRADE approach to assess the certainty of the evidence.

MAIN RESULTS

Nine studies (383 participants) were eligible for inclusion in the review. All study participants were born at < 37 weeks of gestation and were inpatients in neonatal intensive care units. No studies reported growth during the first months of life as assessed by difference in weight. Early administration of AA may have little or no effect on growth in the first month of life as measured by length (mean difference (MD) 0.00, 95% confidence interval (CI) -0.41 to 0.41; 1 study; 21 participants; low-certainty evidence) and head circumference (MD 0.05, 95% CI -0.03 to 0.14; 2 studies; 87 participants; low-certainty evidence). No studies reported the discharge weight outcome. Early administration of AA may result in little to no difference in neurodevelopmental outcome assessed by Mental Developmental Index (MDI) of < 70 at two years of age (odds ratio 0.83, 95% CI 0.21 to 3.28; 1 study; 111 participants; low-certainty evidence). No studies reported all-cause mortality at 28 days and before discharge. Early administration of AA may result in a large increase in positive nitrogen balance in the first three days of life (MD 250.42, 95% CI 224.91 to 275.93; 4 studies; 93 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

Low-certainty evidence suggests that there may be little to no difference between early and late administration of AA in growth (measured by length and head circumference during the first month after birth) and neurodevelopmental outcome (assessed by MDI of < 70). No RCTs reported on weight in the first month of life, mortality (all-cause mortality at 28 days and before discharge), or discharge weight. Low-certainty evidence suggests a large increase in positive nitrogen balance in preterm infants who received AA within 24 hours of birth. The clinical relevance of this observation is unknown. The number of infants in the RCTs included in the review was small, and there was clinical heterogeneity amongst trials. Adequately powered trials in infants < 37 weeks' gestation are required to determine optimal timing of initiation of AA. We identified two ongoing studies. Both studies will be recruiting infants ≥ 34 weeks of gestation and may or may not add to the outcome data for this review.

Hormonal Determinants of Growth and Weight Gain in the Human Fetus and Preterm Infant

The factors controlling linear growth and weight gain in the human fetus and newborn infant are poorly understood. We review here the changes in linear growth, weight gain, lean body mass, and fat mass during mid- and late gestation and the early postnatal period in the context of changes in the secretion and action of maternal, placental, fetal, and neonatal hormones, growth factors, and adipocytokines. We assess the effects of hormonal determinants on placental nutrient delivery and the impact of preterm delivery on hormone expression and postnatal growth and metabolic function. We then discuss the effects of various maternal disorders and nutritional and pharmacologic interventions on fetal and perinatal hormone and growth factor production, growth, and fat deposition and consider important unresolved questions in the field.

Expression of nutrient transporters in placentas affected by gestational diabetes: role of leptin

Gestational diabetes mellitus (GDM) is the most frequent pathophysiological state of pregnancy, which in many cases produces fetuses with macrosomia, requiring increased nutrient transport in the placenta. Recent studies by our group have demonstrated that leptin is a key hormone in placental physiology, and its expression is increased in placentas affected by GDM. However, the effect of leptin on placental nutrient transport, such as transport of glucose, amino acids, and lipids, is not fully understood. Thus, we aimed to review literature on the leptin effect involved in placental nutrient transport as well as activated leptin signaling pathways involved in the expression of placental transporters, which may contribute to an increase in placental nutrient transport in human pregnancies complicated by GDM. Leptin appears to be a relevant key hormone that regulates placental transport, and this regulation is altered in pathophysiological conditions such as gestational diabetes. Adaptations in the placental capacity to transport glucose, amino acids, and lipids may underlie both under- or overgrowth of the fetus when maternal nutrient and hormone levels are altered due to changes in maternal nutrition or metabolic disease. Implementing new strategies to modulate placental transport may improve maternal health and prove effective in normalizing fetal growth in cases of intrauterine growth restriction and fetal overgrowth. However, further studies are needed to confirm this hypothesis.

Human Placental Adaptive Changes in Response to Maternal Obesity: Sex Specificities

Maternal obesity is increasingly prevalent and is associated with elevated morbidity and mortality rates in both mothers and children. At the interface between the mother and the fetus, the placenta mediates the impact of the maternal environment on fetal development. Most of the literature presents data on the effects of maternal obesity on placental functions and does not exclude potentially confounding factors such as metabolic diseases (e.g., gestational diabetes). In this context, the focus of this review mainly lies on the impact of maternal obesity (in the absence of gestational diabetes) on (i) endocrine function, (ii) morphological characteristics, (iii) nutrient exchanges and metabolism, (iv) inflammatory/immune status, (v) oxidative stress, and (vi) transcriptome. Moreover, some of those placental changes in response to maternal obesity could be supported by fetal sex. A better understanding of sex-specific placental responses to maternal obesity seems to be crucial for improving pregnancy outcomes and the health of mothers and children.

Pre-pregnancy body mass index and risk of maternal or infant complications with gestational diabetes mellitus as a mediator: A multicenter, longitudinal cohort study in China

AIMS

We explored the complex relationships between pre-pregnancy body mass index (pBMI) and maternal or infant complications and the mediating role of gestational diabetes mellitus (GDM) in these relationships.

METHODS

Pregnant women from 24 hospitals in 15 different provinces of China were enrolled in 2017 and followed through 2018. Propensity score-based inverse probability of treatment weighting, logistic regression, restricted cubic spline models, and causal mediation analysis were utilized. In addition, the E-value method was used to evaluate unmeasured confounding factors.

RESULTS

A total of 6174 pregnant women were finally included. Compared to women with a normal pBMI, obese women had a higher risk for gestational hypertension (odds ratio [OR] = 5.38, 95% confidence interval [CI]: 3.48-8.34), macrosomia (OR = 2.65, 95% CI: 1.83-3.84), and large for gestational age (OR = 2.05, 95% CI: 1.45-2.88); 4.73% (95% CI: 0.57%-8.88%), 4.61% (95% CI: 0.51%-9.74%), and 5.02% (95% CI: 0.13%-10.18%) of the associations, respectively, were mediated by GDM. Underweight women had a high risk for low birth weight (OR = 1.42, 95% CI: 1.15-2.08) and small for gestational age (OR = 1.62, 95% CI: 1.23-2.11). Dose-response analyses indicated that 21.0 kg/m² may be the appropriate tipping point pBMI for risk for maternal or infant complications in Chinese women.

CONCLUSION

A high or low pBMI is associated with the risk for maternal or infant complications and partly mediated by GDM. A lower pBMI cutoff of 21 kg/m² may be appropriate for risk for maternal or infant complications in pregnant Chinese women.

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.

Relationship of Glucose, C-peptide, Leptin, and BDNF in Maternal and Umbilical Vein Blood in Type-1 Diabetes

The study aimed to determine the relationship between glucose, C-peptide, brain-derived neurotrophic factor (BDNF), and leptin between mother and fetus and neonatal weight.

METHODS

In the prospective observational cohort study, we included 66 women with type-1 diabetes mellitus (T1DM). According to the z-score for neonatal weight, patients were divided into healthy-weight neonates (n = 42) and overweight neonates (n = 24). The maternal blood samples were taken during pregnancy and cesarean section when the umbilical vein blood sample was also withdrawn. The maternal vein sera were analyzed for fasting glucose, C-reactive protein (CRP), leptin, BDNF, TSH, FT3, and FT4. The umbilical vein sera were analyzed for glucose, C-peptide, leptin, TSH, thyroid-stimulating protein (FT3), free thyroxine (FT4), and BDNF concentration. The neonatologist measured the skinfold thickness on the third day of neonatal life.

RESULTS

A strong correlation was confirmed between maternal and umbilical vein glucose concentration and maternal glucose and C-peptide in umbilical vein blood. A negative correlation was found between the concentration of BDNF in the umbilical vein and glucose in maternal blood. A strong correlation was seen between BMI and maternal blood leptin concentration, neonatal fat body mass, and umbilical vein blood leptin concentration. Higher BMI elevated BDNF, and TSH increase the odds for overweight neonates in the first trimester of pregnancy. Maternal higher leptin concentration in the first trimester decrease the odds of overweight neonates.

CONCLUSIONS

Maternal glucose concentrations affect the fetus's glucose, C-peptide, and BDNF concentrations. Leptin levels increase in maternal blood due to increased body mass index, and in the neonate, fat body mass is responsible for increased leptin concentrations.

Inhibition of human and rat placental 3β-hydroxysteroid dehydrogenase/Δ5,4-isomerase activities by insecticides and fungicides: Mode action by docking analysis

Many insecticides and fungicides are endocrine-disrupting compounds, which possibly interfere with the placental endocrine system. In the placenta, 3β-hydroxysteroid dehydrogenase/Δ^5,4-isomerase type 1 (HSD3B1) is the major steroidogenic enzyme, which makes progesterone from pregnenolone to support the placental stability. In this study, we screened 12 classes of insecticides and fungicides to inhibit placental HSD3B1 activity and compared them to the rat homolog type 4 (HSD3B4) isoform. Human HSD3B1 activity and rat HSD3B4 activity were measured in the presence of 200 nM pregnenolone and 0.2 mM NAD⁺ and 100 μM of test chemical. Triclosan, triflumizole, dichlone, and oxine at 100 μM significantly inhibited human HSD3B1 activity with the residual activity being less than 50% of the control. Further study showed that the half-maximal inhibitory concentration (IC₅₀) values of triclosan, triflumizole, dichlone, and oxine were 85.53 ± 9.14, 73.75 ± 3.42, 2.54 ± 0.40, and 102.93 ± 6.10 μM, respectively. In the presence of pregnenolone, triclosan, triflumizole, and dichlone were mixed inhibitors of HSD3B1, while oxine was a noncompetitive inhibitor. In the presence of NAD⁺, triclosan exhibited competitive inhibition while triflumizole possessed uncompetitive inhibition. Docking analysis showed that triclosan bound NAD⁺-binding site, while triflumizole, dichlone, and oxine mostly bound steroid-binding site. When the effect of these insecticides on rat placental HSD3B4 activity was screened in the presence of 200 nM pregnenolone, atrazine, triclosan, triflumizole, oxine, cyprodinil, and diphenyltin at 100 μM significantly inhibited rat HSD3B4 activity, with IC₅₀ values of triclosan, triflumizole, oxine, and cyprodinil were 82.99 ± 6.48, 35.45 ± 2.73, 105.59 ± 12.04, and 43.37 ± 3.00 μM, respectively. The mode action analysis showed that triflumizole and cyprodinil were almost competitive inhibitors, while triclosan and oxine were almost noncompetitive inhibitors of rat HSD3B4. Docking analysis showed that triclosan and oxine bound cofactor NAD⁺ binding residues more than steroid-binding residues of rat HSD3B4 while triflumizole and cyprodinil bound most pregnenolone-interactive residues. In conclusion, some insecticides such as triclosan, triflumizole, and oxine can effectively inhibit both human and rat placental HSD3B activity and they have unique mode action due to the structure difference.

Feto-placental Unit: From Development to Function

The placenta is an intriguing organ that allows us to survive intrauterine life. This essential organ connects both mother and fetus and plays a crucial role in maternal and fetal well-being. This chapter presents an overview of the morphological and functional aspects of human placental development. First, we describe early human placental development and the characterization of the cell types found in the human placenta. Second, the human placenta from the second trimester to the term of gestation is reviewed, focusing on the morphology and specific pathologies that affect the placenta. Finally, we focus on the placenta's primary functions, such as oxygen and nutrient transport, and their importance for placental development.

Relationship between Maternal Vitamin D Levels and Adverse Outcomes

Vitamin D (VD), a fat-soluble vitamin, has a variety of functions that are important for growth and development, including regulation of cell differentiation and apoptosis, immune system development, and brain development. As such, VD status during pregnancy is critical for maternal health, fetal skeletal growth, and optimal pregnancy outcomes. Studies have confirmed that adverse pregnancy outcomes, such as preeclampsia, low birth weight, neonatal hypocalcemia, poor postnatal growth, skeletal fragility, and increased incidence of autoimmune diseases, can be associated with low VD levels during pregnancy and infancy. Thus, there is growing interest in the role of VD during pregnancy. This review summarizes the potential adverse health outcomes of maternal VD status during pregnancy for both mother and offspring (gestational diabetes mellitus, hypertensive gestational hypertension, intrauterine growth restriction, miscarriage, stillbirth, and preterm birth) and discusses the underlying mechanisms (regulation of cytokine pathways, immune system processing, internal secretion, placental function, etc.) of VD in regulating each of the outcomes. This review aims to provide a basis for public health intervention strategies to reduce the incidence of adverse pregnancies.

Maternal immune activation in rats induces dysfunction of placental leucine transport and alters fetal brain growth

Maternal infection during pregnancy increases the offspring risk of developing a variety of neurodevelopmental disorders (NDDs), including schizophrenia. While the mechanisms remain unclear, dysregulation of placental function is implicated. We hypothesised that maternal infection, leading to maternal immune activation and stimulated cytokine production, alters placental and yolk sac amino acid transport, affecting fetal brain development and thus NDD risk. Using a rat model of maternal immune activation induced by the viral mimetic polyinosinic:polycytidylic acid (poly(I:C)), we investigated placental and yolk sac expression of system L amino acid transporter subtypes which transport several essential amino acids including branched-chain amino acids (BCAA), maternal and fetal BCAA concentration, placental 14C-leucine transport activity and associated impacts on fetal growth and development. Poly(I:C) treatment increased acutely maternal IL-6 and TNFα concentration, contrasting with IL-1β. Transcriptional responses for these pro-inflammatory cytokines were found in placenta and yolk sac following poly(I:C) treatment. Placental and yolk sac weights were reduced by poly(I:C) treatment, yet fetal body weight was unaffected, while fetal brain weight was increased. Maternal plasma BCAA concentration was reduced 24 h post-poly(I:C) treatment, yet placental, but not yolk sac, BCAA concentration was increased. Placental and yolk sac gene expression of Slc7a5, Slc7a8 and Slc43a2 encoding LAT1, LAT2 and LAT4 transporter subtypes respectively, was altered by poly(I:C) treatment. Placental 14C-leucine transport was significantly reduced 24 h post-treatment, contrasting with a significant increase six days following poly(I:C) treatment. Maternal immune activation induces dysregulated placental transport of amino acids affecting fetal brain development, and NDD risk potential in offspring.

The mystery of the life tree: the placenta

The placenta is the interface between the fetal and maternal environments during mammalian gestation, critically safeguarding the health of the developing fetus and the mother. Placental trophoblasts origin from embryonic trophectoderm that differentiates into various trophoblastic subtypes through villous and extravillous pathways. The trophoblasts actively interact with multiple decidual cells and immune cells at the maternal-fetal interface and thus construct fundamental functional units, which are responsible for blood perfusion, maternal-fetal material exchange, placental endocrine, immune tolerance, and adequate defense barrier against pathogen infection. Various pregnant complications are tightly associated with the defects in placental development and function maintenance. In this review, we summarize the current views and our recent progress on the mechanisms underlying the formation of placental functional units, the interactions among trophoblasts and various uterine cells, as well as the placental barrier against pathogen infections during pregnancy. The involvement of placental dysregulation in adverse pregnancy outcomes is discussed.

Impact of inflammation and infection on the expression of amino acid transporters in the placenta: A minireview

Amino acid transporters expressed in the placenta help to regulate the transfer of amino acids from maternal to fetal circulation. Nutritional or hormonal factors are known to potentially impact the expression of amino acid transporters in the placenta. A relatively new field of inquiry has also demonstrated that inflammation, whether associated with infection or not, also alters the expression of amino acid transporters in the placenta. Indeed, studies over the past 15 years have demonstrated that malaria, viral and bacterial models of infection, preeclampsia, and direct administration of proinflammatory cytokines can alter placental amino acid transporter expression. While such studies have largely focused on System A and System L transporters, other transporters are also affected. p38 MAPK, STAT3, mTORC1, and AMPK signaling have all been implicated in these changes, but the underlying mechanism(s) remain to be fully elucidated. Furthermore, the implications of such changes warrant further investigation. This review will summarize studies that have investigated the impact of inflammation on placental amino acid transporter expression, identify questions that remain unanswered, and propose future areas of research to advance the field. As amino acid transporters are now being considered for drug targeting and drug delivery, furthering our understanding of the regulation of these transporters during disease states will be of increasing clinical value. Significance Statement While this is a relatively new field of research, multiple studies have demonstrated that inflammation alters placental amino acid transporter expression. This review will serve to summarize, for the first time, studies in this field and identify gaps in current knowledge as research in this area moves beyond identifying changes in transporter expression to investigating the implications of such changes and the mechanisms underlying them.

Adiponectin Deficiency Alters Placenta Function but Does Not Affect Fetal Growth in Mice

Adiponectin administration to pregnant mice decreases nutrient transport and fetal growth. An adiponectin deficiency, on the other hand, as seen in obese women during pregnancy, alters fetal growth; however, the mechanism is unclear. To determine the role of adiponectin on placenta function and fetal growth, we used adiponectin knockout, adiponectin heterozygote that displays reduced adiponectin levels, and wild-type mice on a control diet or high fat/high sucrose (HF/HS) diet. Triglycerides (TGs) in the serum, liver, and placenta were measured using colorimetric assays. Gene expression was measured using quantitative RT-PCR. Adiponectin levels did not affect fetal weight, but it reduced adiponectin levels, increased fetal serum and placenta TG content. Wildtype dams on a HF/HS diet protected the fetuses from fatty acid overload as judged by increased liver TGs in dams and normal serum and liver TG levels in fetuses, while low adiponectin was associated with increased fetal liver TGs. Low maternal adiponectin increased the expression of genes involved in fatty acid transport; Lpl and Cd36 in the placenta. Adiponectin deficiency does not affect fetal growth but induces placental dysfunction and increases fetal TG load, which is enhanced with obesity. This could lead to imprinting effects on the fetus and the development of metabolic dysfunction in the offspring.

The Metabolic Signatures of Surviving Cotwins in Cases of Single Intrauterine Fetal Death During Monochorionic Diamniotic Pregnancy: A Prospective Case-Control Study

Introduction: Single intrauterine fetal death (sIUFD) in monochorionic diamniotic (MCDA) twin pregnancy may be associated with adverse clinical outcomes and possible metabolic changes in the surviving co-twin. Metabolomic profiling has not been undertaken before in these complex twin pregnancies.

Methods: In this prospectively collected case-control study, three cross-cohort comparisons were made between sIUFD MCDA (n = 16), uncomplicated MCDA (n = 16, eight pairs), and uncomplicated singleton pregnancies (n = 8). To identify major sources of variation within the sIUFD MCDA cohort, a secondary comparison was conducted between spontaneous sIUFD (n = 8) and sIUFD in MCDA twins due to selective termination of a single abnormal fetus by radiofrequency ablation (RFA) (n = 8). Metabolomics analysis of placental tissue and umbilical cord plasma was performed using LC-MS profiling. The underlying metabolic networks and pathways were analyzed by web-based platforms. Associations and statistical correlations of all identified differential metabolites with neonatal birthweight and birth length were assessed by multivariable linear regression, adjusted for maternal age and gestation.

Results: Across four comparisons, 131 and 111 differential metabolites were identified in placental tissue and cord plasma, respectively, with the highest variation seen between the spontaneous vs. single-induced IUFD in MCDA twins by RFA in the cord plasma. Conversely, the number of viable fetuses and the presence of sIUFD in MCDA twins had the highest impact on metabolite variation in placental tissue. Compounds correlated with fetal growth including placental acylcarnitines and gangliosides, along with specific amino acids (e.g., histidinyl-hydroxyproline), xenobiotics and biliverdin in cord plasma.

Conclusion: sIUFD in MCDA twin pregnancy correlates with distinctive metabolic signatures, mostly in fatty acyls and complex lipids, in placental tissue and cord plasma of the surviving cotwin. Some metabolites are also associated with fetal growth.

Inducible knockout of syncytin-a leads to poor placental glucose transport in mice

INTRODUCTION

Cell-cell fusion of cytotrophoblasts into the syncytiotrophoblast layer is a key process in placental development. Syncytin, an endogenous retroviral envelope protein, is expressed in placental trophoblasts and specifically mediates syncytiotrophoblast layer formation. Syncytin deficiency has been observed in fetal growth-restricted placentas. Abnormal fetal growth, especially fetal growth restriction, is associated with the decreased expression of glucose transporters. Here, we aimed to determine the role of syncytin in fetal growth restriction in placental glucose transport capacity.

METHODS

To better explore the function of syncytin in fetal growth-restricted placenta, we generated an inducible knockout mouse model of syncytin-a gene. The expression levels of glucose transporters in BeWo cells were measured before and after HERV-W knockdown.

RESULTS

Syncytin-A disruption was associated with significant abnormalities in placental and fetal development in mice. Syncytin-A destruction causes extensive abnormalities in the maternal-fetal exchange structures in the labyrinth, including an extremely reduced number and dramatically irregular distribution of fetal vessels. Moreover, glucose transporter 1, glucose transporters 3, and connexin 26 expression levels decreased after E14.5. Consistently, low glucose transporter 1, glucose transporter 3, and connexin 26 levels were observed in HERV-W-silenced BeWo cells.

DISCUSSION

Syncytin-A is crucial for both syncytiotrophoblast layer development and morphogenesis, suggesting that syncytin-A disruption leads to fetal growth restriction associated with abnormalities in the maternal-fetal exchange barrier and decreased glucose transport.

Placental Nutrient Transporters and Maternal Fatty Acids in SGA, AGA, and LGA Newborns From Mothers With and Without Obesity

Adverse environmental factors in early life result in fetal metabolic programming and increased risk of adult diseases. Birth weight is an indirect marker of the intrauterine environment, modulated by nutrient availability and placental transport capacity. However, studies of placental transporters in idiopathic birth weight alterations and in maternal obesity in relation to neonatal metabolic outcomes are scarce. We aimed to analyze the placental nutrient transporter protein expression in small (SGA, n = 14), adequate (AGA, n = 18), and large (LGA n = 10) gestational age term for newborns from healthy or obese mothers (LGA-OB, n = 9) and their association with maternal fatty acids, metabolic status, placental triglycerides, and neonatal outcomes. The transporter expression was determined by Western blot. The fatty acid profile was evaluated by gas chromatography, and placental triglycerides were quantified by an enzymatic colorimetric method. GLUT1 was higher in LGA and lower in SGA and positively correlated with maternal HbA1c and placental weight (PW). SNAT2 was lower in SGA, while SNAT4 was lower in LGA-OB. FATP1 was lower in SGA and higher in LGA. SNAT4 correlated negatively and FATP1 correlated positively with the PW and birth anthropometry (BA). Placental triglycerides were higher in LGA and LGA-OB and correlated with pregestational BMI, maternal insulin, and BA. Maternal docosahexaenoic acid (DHA) was higher in SGA, specifically in male placentas, correlating negatively with maternal triglycerides, PW, cord glucose, and abdominal perimeter. Palmitic acid (PA) correlated positively with FATP4 and cord insulin, linoleic acid correlated negatively with PA and maternal cholesterol, and arachidonic acid correlated inversely with maternal TG and directly with FATP4. Our study highlights the importance of placental programming in birth weight both in healthy and obese pregnancies.

Maternal low protein diet and fetal programming of lean type 2 diabetes

Maternal nutrition is found to be the key factor that determines fetal health in utero and metabolic health during adulthood. Metabolic diseases have been primarily attributed to impaired maternal nutrition during pregnancy, and impaired nutrition has been an immense issue across the globe. In recent years, type 2 diabetes (T2D) has reached epidemic proportion and is a severe public health problem in many countries. Although plenty of research has already been conducted to tackle T2D which is associated with obesity, little is known regarding the etiology and pathophysiology of lean T2D, a variant of T2D. Recent studies have focused on the effects of epigenetic variation on the contribution of in utero origins of lean T2D, although other mechanisms might also contribute to the pathology. Observational studies in humans and experiments in animals strongly suggest an association between maternal low protein diet and lean T2D phenotype. In addition, clear sex-specific disease prevalence was observed in different studies. Consequently, more research is essential for the understanding of the etiology and pathophysiology of lean T2D, which might help to develop better disease prevention and treatment strategies. This review examines the role of protein insufficiency in the maternal diet as the central driver of the developmental programming of lean T2D.

The effects of gestational diabetes mellitus with maternal age between 35 and 40 years on the metabolite profiles of plasma and urine

Background

Gestational diabetes mellitus (GDM) is defined as impaired glucose tolerance in pregnancy and without a history of diabetes mellitus. While there are limited metabolomic studies involving advanced maternal age in China, we aim to investigate the metabolomic profiling of plasma and urine in pregnancies complicated with GDM aged at 35–40 years at early and late gestation.

Methods

Twenty normal and 20 GDM pregnant participants (≥ 35 years old) were enlisted from the Complex Lipids in Mothers and Babies (CLIMB) study. Maternal plasma and urine collected at the first and third trimester were detected using gas chromatography-mass spectrometry (GC-MS).

Results

One hundred sixty-five metabolites and 192 metabolites were found in plasma and urine respectively. Urine metabolomic profiles were incapable to distinguish GDM from controls, in comparison, there were 14 and 39 significantly different plasma metabolites between the two groups in first and third trimester respectively. Especially, by integrating seven metabolites including cysteine, malonic acid, alanine, 11,14-eicosadienoic acid, stearic acid, arachidic acid, and 2-methyloctadecanoic acid using multivariant receiver operating characteristic models, we were capable of discriminating GDM from normal pregnancies with an area under curve of 0.928 at first trimester.

Conclusion

This study explores metabolomic profiles between GDM and normal pregnancies at the age of 35–40 years longitudinally. Several compounds have the potential to be biomarkers to predict GDM with advanced maternal age. Moreover, the discordant metabolome profiles between the two groups could be useful to understand the etiology of GDM with advanced maternal age.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04416-5.

Chemical exposures assessed via silicone wristbands and endogenous plasma metabolomics during pregnancy

BACKGROUND

Metabolomics is a promising method to investigate physiological effects of chemical exposures during pregnancy, with the potential to clarify toxicological mechanisms, suggest sensitive endpoints, and identify novel biomarkers of exposures.

OBJECTIVE

Investigate the influence of chemical exposures on the maternal plasma metabolome during pregnancy.

METHODS

Data were obtained from participants (n = 177) in the New Hampshire Birth Cohort Study, a prospective pregnancy cohort. Chemical exposures were assessed via silicone wristbands worn for one week at ~13 gestational weeks. Metabolomic features were assessed in plasma samples obtained at ~24-28 gestational weeks via the Biocrates AbsoluteIDQ® p180 kit and nuclear magnetic resonance (NMR) spectroscopy. Associations between chemical exposures and plasma metabolomics were investigated using multivariate modeling.

RESULTS

Chemical exposures predicted 11 (of 226) and 23 (of 125) metabolomic features in Biocrates and NMR, respectively. The joint chemical exposures did not significantly predict pathway enrichment, though some individual chemicals were associated with certain amino acids and related metabolic pathways. For example, N,N-diethyl-m-toluamide was associated with the amino acids glycine, L-glutamic acid, L-asparagine, and L-aspartic acid and enrichment of the ammonia recycling pathway.

SIGNIFICANCE

This study contributes evidence to the potential effects of chemical exposures during pregnancy upon the endogenous maternal plasma metabolome.

Sex differences in microRNA expression in first and third trimester human placenta†

Maternal and fetal pregnancy outcomes related to placental function vary based on fetal sex, which may be due to sexually dimorphic epigenetic regulation of RNA expression. We identified sexually dimorphic miRNA expression throughout gestation in human placentae. Next-generation sequencing identified miRNA expression profiles in first and third trimester uncomplicated pregnancies using tissue obtained at chorionic villous sampling (n = 113) and parturition (n = 47). Sequencing analysis identified 986 expressed mature miRNAs from female and male placentae at first and third trimester (baseMean>10). Of these, 11 sexually dimorphic (FDR < 0.05) miRNAs were identified in the first and 4 in the third trimester, all upregulated in females, including miR-361-5p, significant in both trimesters. Sex-specific analyses across gestation identified 677 differentially expressed (DE) miRNAs at FDR < 0.05 and baseMean>10, with 508 DE miRNAs in common between female-specific and male-specific analysis (269 upregulated in first trimester, 239 upregulated in third trimester). Of those, miR-4483 had the highest fold changes across gestation. There were 62.5% more female exclusive differences with fold change>2 across gestation than male exclusive (52 miRNAs vs 32 miRNAs), indicating miRNA expression across human gestation is sexually dimorphic. Pathway enrichment analysis identified significant pathways that were differentially regulated in first and third trimester as well as across gestation. This work provides the normative sex dimorphic miRNA atlas in first and third trimester, as well as the sex-independent and sex-specific placenta miRNA atlas across gestation, which may be used to identify biomarkers of placental function and direct functional studies investigating placental sex differences.

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.

Impact of gestational electronic cigarette vaping on amino acid signature profile in the pregnant mother and the fetus

Background

Electronic cigarettes (e-cigs) are a form of tobacco product that has become increasingly popular over the past decade. Despite the known health consequences of tobacco product exposure during pregnancy, a substantial number of daily smokers will continue to smoke during pregnancy. Our current knowledge on the effects of e-cig aerosol exposure during pregnancy is limited to a small number of animal studies, which have identified several e-cig aerosol-induced disruptions to the physiology of normal development.

Methods

To further assess the impact of prenatal e-cig aerosol exposure on maternal and fetal health, we examined the amino acid signature profiles in maternal and fetal plasma, as well as in the fetal lungs, a sensitive target organ for prenatal tobacco product exposure. Pregnant Sprague Dawley rats were randomly assigned to one of three groups and were exposed to either e-cig aerosols containing nicotine, e-cig aerosols without nicotine, or room air. Dams were exposed utilizing a state-of-the-art custom engineered e-cig vaping system that is compatible with commercially available e-cig atomizers and enables a translational inhalation delivery method comparable to human vaping.

Results

We determined that gestational exposure to e-cig aerosols results in significant alterations to the amino acid profile in the maternal and fetal compartments, including the fetal lungs. The data shows a targeted disruption to the nitric oxide pathway, branched-chain amino acid metabolism, fetal protein synthesis, and urea cycle.

Conclusion

The data presented herein provides additional support that gestational e-cig aerosol exposure can impact crucial biological processes and exemplifies the need for extensive research on exposure to e-cig aerosols.

•

First report of e-cig induced alterations to maternal/fetal amino acid profile.

•

Translational vaping paradigm utilizing custom engineered vaping system.

•

Analysis of amino acids show gestational e-cig exposure has significant effects.

•

Fetal lungs may be a sensitive target to gestational e-cig aerosol exposure.

•

Marker of dysregulation in branched-chain amino acid metabolism and urea cycle.

Effect of type 2 diabetes mellitus on placental expression and activity of nutrient transporters and their association with birth weight and neonatal adiposity

AIMS

Infants born to women with Type 2 Diabetes Mellitus (T2DM) are at risk of being born large for gestational age due to excess fetal fat accretion. Placental nutrient transport determines fetal nutrient availability, impacting fetal growth. The aims of the study were to evaluate the effect of T2DM on placental insulin signaling, placental nutrient transporters and neonatal adiposity.

METHODS

Placentas were collected from BMI-matched normoglycemic controls (NGT, n = 9) and T2DM (n = 9) women. Syncytiotrophoblast microvillous (MVM) and basal (BM) plasma membranes were isolated. Expression of glucose (GLUT1, -4), fatty acid (FATP2, -4, -6, FAT/CD36), amino acid (SNAT1, -2, -4, LAT1, -2) transporters, insulin signaling, and System A transporter activity was determined. Neonatal fat mass (%) was measured in a subset of neonates born to T2DM women.

RESULTS

GLUT1 protein expression was increased (p = 0.001) and GLUT4 decreased (p = 0.006) in BM from T2DM. MVM FATP6 expression was increased (p = 0.02) and correlated with birth weight in both T2DM and NGT groups (r = 0.65, p = 0.02). BM FATP6 expression was increased (p = 0.01) in T2DM. In MVM of T2DM placentas, SNAT1 expression was increased (p = 0.05) and correlated with birth weight (r = 0.84, p = 0.004); SNAT2 was increased (p = 0.01), however System A transporter activity was not different between groups. MVM LAT1 expression was increased (p = 0.01) in T2DM and correlated with birth weight (r = 0.59, p = 0.04) and neonatal fat mass (r = 0.76, p = 0.06).

CONCLUSION

In pregnancies complicated by T2DM placental protein expression of transporters for glucose, amino acids and fatty acids is increased, which may contribute to increased fetal growth and neonatal adiposity.

Developmental origins of metabolic diseases

Almost 2 billion adults in the world are overweight, and more than half of them are classified as obese, while nearly one-third of children globally experience poor growth and development. Given the vast amount of knowledge that has been gleaned from decades of research on growth and development, a number of questions remain as to why the world is now in the midst of a global epidemic of obesity accompanied by the "double burden of malnutrition," where overweight coexists with underweight and micronutrient deficiencies. This challenge to the human condition can be attributed to nutritional and environmental exposures during pregnancy that may program a fetus to have a higher risk of chronic diseases in adulthood. To explore this concept, frequently called the developmental origins of health and disease (DOHaD), this review considers a host of factors and physiological mechanisms that drive a fetus or child toward a higher risk of obesity, fatty liver disease, hypertension, and/or type 2 diabetes (T2D). To that end, this review explores the epidemiology of DOHaD with discussions focused on adaptations to human energetics, placental development, dysmetabolism, and key environmental exposures that act to promote chronic diseases in adulthood. These areas are complementary and additive in understanding how providing the best conditions for optimal growth can create the best possible conditions for lifelong health. Moreover, understanding both physiological as well as epigenetic and molecular mechanisms for DOHaD is vital to most fully address the global issues of obesity and other chronic diseases.

Amino Acid Composition of Amniotic Fluid during the Perinatal Period Reflects Mother's Fat and Carbohydrate Intake

Dietary content during pregnancy is important because it is necessary for the growth of the fetus. With the assumption that the nutritional status of the fetus can be monitored by measuring amino acid concentrations in the amniotic fluid, we investigated whether the habitual dietary intake of pregnant women affected the composition of the amniotic fluid and the significance of performing amniotic fluid analysis. The subjects were 34 mothers who delivered full-term babies by cesarean section. Three biological samples were collected from the mothers: blood, cord blood, and amniotic fluid. At the same time, the mothers' prenatal nutritional intake information was also recorded. When the amino acid contents of the samples were compared with the mothers' nutrient intake, many amino acids in the amniotic fluid were positively correlated with lipid intake, but not with protein intake. There was a negative correlation between lipid intake and carbohydrate intake, and the amino acid contents of the amniotic fluid were also negatively correlated with carbohydrate intake. The results of this study were consistent with those found in animal models, suggesting that the analysis of amniotic fluid may be a useful method to investigate the effects of habitual diet during human pregnancy on the fetus.

Effects of Maternal Obesity On Placental Phenotype

The incidence of obesity is rising rapidly worldwide with the consequence that more women are entering pregnancy overweight or obese. This leads to an increased incidence of clinical complications during pregnancy and of poor obstetric outcomes. The offspring of obese pregnancies are often macrosomic at birth although there is also a subset of the progeny that are growth-restricted at term. Maternal obesity during pregnancy is also associated with cardiovascular, metabolic and endocrine dysfunction in the offspring later in life. As the interface between the mother and fetus, the placenta has a central role in programming intrauterine development and is known to adapt its phenotype in response to environmental conditions such as maternal undernutrition and hypoxia. However, less is known about placental function in the abnormal metabolic and endocrine environment associated with maternal obesity during pregnancy. This review discusses the placental consequences of maternal obesity induced either naturally or experimentally by increasing maternal nutritional intake and/or changing the dietary composition. It takes a comparative, multi-species approach and focusses on placental size, morphology, nutrient transport, metabolism and endocrine function during the later stages of obese pregnancy. It also examines the interventions that have been made during pregnancy in an attempt to alleviate the more adverse impacts of maternal obesity on placental phenotype. The review highlights the potential role of adaptations in placental phenotype as a contributory factor to the pregnancy complications and changes in fetal growth and development that are associated with maternal obesity.

Late gestation fetal hyperglucagonaemia impairs placental function and results in diminished fetal protein accretion and decreased fetal growth

KEY POINTS

Fetal glucagon concentrations are elevated in the setting of placental insufficiency, hypoxia and elevated stress hormones. Chronically elevated glucagon concentrations in the adult result in profound decreases in amino acid concentrations and lean body mass. Experimental elevation of fetal glucagon concentrations in a late-gestation pregnant sheep results in lower fetal amino acid concentrations, lower protein accretion and lower fetal weight, in addition to decreased placental function. This study demonstrates a negative effect of glucagon on fetal protein accretion and growth, and also provides the first example of a fetal hormone that negatively regulates placental nutrient transport and blood flow.

ABSTRACT

Fetal glucagon concentrations are elevated in the setting of placental insufficiency and fetal stress. Postnatal studies have demonstrated the importance of glucagon in amino acid metabolism, and limited fetal studies have suggested that glucagon inhibits umbilical uptake of certain amino acids. We hypothesized that chronic fetal hyperglucagonaemia would decrease amino acid transfer and increase amino acid oxidation by the fetus. Late gestation singleton fetal sheep received a direct intravenous infusion of glucagon (GCG; 5 or 50 ng/kg/min; n = 7 and 5, respectively) or a vehicle control (n = 10) for 8-10 days. Fetal and maternal nutrient concentrations, uterine and umbilical blood flows, fetal leucine flux, nutrient uptake rates, placental secretion of chorionic somatomammotropin (CSH), and targeted placental gene expression were measured. GCG fetuses had 13% lower fetal weight compared to controls (P = 0.0239) and >28% lower concentrations of 16 out of 21 amino acids (P < 0.02). Additionally, protein synthesis was 49% lower (P = 0.0005), and protein accretion was 92% lower in GCG fetuses (P = 0.0006). Uterine blood flow was 33% lower in ewes with GCG fetuses (P = 0.0154), while umbilical blood flow was similar. Fetal hyperglucagonaemia lowered uterine uptake of 10 amino acids by >48% (P < 0.05) and umbilical uptake of seven amino acids by >29% (P < 0.04). Placental secretion of CSH into maternal circulation was reduced by 80% compared to controls (P = 0.0080). This study demonstrates a negative effect of glucagon on fetal protein accretion and growth. It also demonstrates that glucagon, a hormone of fetal origin, negatively regulates maternal placental nutrient transport function, placental CSH production and uterine blood flow.

Maternal Obesity and Risk of Low Birth Weight, Fetal Growth Restriction, and Macrosomia: Multiple Analyses

The associations between maternal pre-pregnancy obesity and low birth weight (LBW, <2500 g) remain inconclusive. Therefore, birth weight in a Polish prospective cohort of 912 mothers was investigated depending on the pre-pregnancy body mass index (BMI). The whole cohort and the subgroup of gestational weight gain (GWG) in the range of the Institute of Medicine (IOM) recommendations, as well as 'healthy' women (who did not develop diabetes or hypertension in this pregnancy) were investigated. Adjusted odds ratios (AOR) of the newborn outcomes (with 95% confidence intervals, CI) for obesity (BMI ≥ 30 kg/m²) vs. normal BMI (18.5-24.9 kg/m²) were calculated using multiple logistic regression. Risk profiles (in the Lowess method) were presented for BMI values (kg/m²) and threshold BMI values were calculated. (1) In the cohort, LBW affected 6.6% of pregnancies, fetal growth restriction (FGR) 2.3%, and macrosomia 10.6%. (2) The adjusted risk of macrosomia was more than three-fold higher for obesity compared to normal BMI in the whole cohort (AOR = 3.21 (1.69-6.1), p < 0.001) and the result was maintained in the subgroups. A 17-fold higher adjusted LBW risk for obesity was found (AOR = 17.42 (1.5-202.6), p = 0.022), but only in the normal GWG subgroup. The FGR risk profile was U-shaped: in the entire cohort, the risk was more than three times higher for obesity (AOR = 3.12 (1.02-9.54), p = 0.045) and underweight (AOR = 3.84 (1.13-13.0), p = 0.031). (3) The risk profiles showed that the highest BMI values were found to be associated with a higher risk of these three newborn outcomes and the threshold BMI was 23.7 kg/m² for macrosomia, 26.2 kg/m² for LBW, and 31.8 kg/m² for FGR. These results confirm the multidirectional effects of obesity on fetal growth (low birth weight, fetal growth restriction, and macrosomia). The results for LBW were heavily masked by the effects of abnormal gestational weight gain.

Maternal Obesity Influences Placental Nutrient Transport, Inflammatory Status, and Morphology in Human Term Placenta

CONTEXT

Maternal obesity has a significant impact on placental development. However, this impact on the placenta's structure and function (ie, nutrient transport and hormone and cytokine production) is a controversial subject.

OBJECTIVE

We hypothesized that maternal obesity is associated with morphologic, secretory, and nutrient-related changes and elevated levels of inflammation in the placenta.

DESIGN

We collected samples of placental tissue from 2 well-defined groups of pregnant women from 2017 to 2019. We compared the 2 groups regarding placental cytokine and hormone secretion, immune cell content, morphology, and placental nutrient transporter expressions.

SETTING

Placenta were collected after caesarean section performed by experienced clinicians at Centre Hospitalier Intercommunal (CHI) of Poissy-Saint-Germain-en-Laye.

PATIENTS

The main inclusion criteria were an age between 27 and 37 years old, no complications of pregnancy, and a first-trimester body mass index of 18-25 kg/m2 for the nonobese (control) group and 30-40 kg/m2 for the obese group.

RESULTS

In contrast to our starting hypothesis, we observed that maternal obesity was associated with (1) lower placental IL-6 expression and macrophage/leukocyte infiltration, (2) lower placental expression of GLUT1 and SNAT1-2, (3) a lower placental vessel density, and (4) lower levels of placental leptin and human chorionic gonadotropin production.

CONCLUSION

These results suggest that the placenta is a plastic organ and could optimize fetal growth. A better understanding of placental adaptation is required because these changes may partly determine the fetal outcome in cases of maternal obesity.

Preconceptional Lipid-Based Nutrient Supplementation in 2 Low-Resource Countries Results in Distinctly Different IGF-1/mTOR Placental Responses

BACKGROUND

Preconceptional maternal small-quantity lipid-based nutrient supplementation (SQLNS) improved intrauterine linear growth in low-resource countries as demonstrated by the Women First Preconception Maternal Nutrition Trial (WF). Fetal growth is dependent on nutrient availability and regulated by insulin-like growth factor 1 (IGF-1) through changes in placental transfer capacity, mediated by the mechanistic target of rapamycin (mTOR) pathway.

OBJECTIVES

Our objective was to evaluate the role of placental mTOR and IGF-1 signaling on fetal growth in women from 2 low-resource countries with high rates of stunting after they received preconceptional SQLNS.

METHODS

We studied 48 women from preconception through delivery who were from Guatemala and Pakistan and received SQLNS or not, as part of the WF study. Placental samples were obtained at delivery (control, n = 24; SQLNS, n = 24). Placental protein or mRNA expression of eukaryotic translation initiation factor binding protein-1 (4E-BP1), ribosomal protein S6 (rpS6), AMP-activated protein kinase α (AMPKA), IGF-1, insulin-like growth factor receptor (IGF-1R), and pregnancy associated plasma protein (PAPP)-A, and DNA methylation of the IGF1 promoter were determined. Maternal serum IGF-1, insulin-like growth factor binding protein (IGFBP)-3, IGFBP-4, IGFBP-5, PAPP-A, PAPP-A2, and zinc were measured.

RESULTS

Mean ± SEM maternal prepregnancy BMI differed between participants in Guatemala (26.5 ± 1.3) and Pakistan (19.8 ± 0.7) (P < 0.001). In Pakistani participants, SQLNS increased the placental rpS6(T37/46):rpS6 ratio (1.5-fold) and decreased the AMPKA(T172):AMPKA ratio. Placental IGF1 mRNA expression was positively correlated with birth length and birth weight z-scores. Placental PAPP-A (30-fold) and maternal serum zinc (1.2-fold) increased with SQLNS. In Guatemalan participants SQLNS did not influence placental mTOR signaling. Placental IGF-1R protein expression was positively associated with birth length and birth weight z-scores. SQLNS increased placental PAPP-A (40-fold) and maternal serum IGFBP-4 (1.6-fold).

CONCLUSIONS

In Pakistani pregnant women with poor nutritional status, preconceptional SQLNS activated placental mTOR and IGF-1 signaling and was associated with improved fetal growth. In contrast, in Guatemalan women SQLNS did not activate placental nutrient-sensing pathways. In populations experiencing childhood stunting, preconceptional SQLNS improves placental function and fetal growth only in the context of poor maternal nutrition. This trial was registered at clinicaltrials.gov as NCT01883193.

Effects of maternal nutrient restriction during the periconceptional period on placental development in the mouse

Maternal undernutrition has detrimental effects on fetal development and adult health. Total caloric restriction during early pregnancy followed by adequate nutrition for the remainder of gestation, is particularly linked to cardiovascular and metabolic disease risks during adulthood. The placenta is responsible for transport of nutrients from the maternal to fetal circulation, and the efficiency with which it does so can be adjusted to the maternal nutrient supply. There is evidence that placental adaptations to nutrient restriction in early pregnancy may be retained even when adequate nutrition is restored later in pregnancy, leading to a potential mismatch between placental efficiency and maternal nutrient supplies. However, in the mouse, 50% caloric restriction from days 1.5-11.5 of gestation, while temporarily altering placental structure and gene expression, had no significant effect on day 18.5. The periconceptional period, during which oocyte maturation, fertilization, and preimplantation development occur may be especially critical in creating lasting impact on the placenta. Here, mice were subjected to 50% caloric restriction from 3 weeks prior to pregnancy through d11.5, and then placental structure, the expression of key nutrient transporters, and global DNA methylation levels were examined at gestation d18.5. Prior exposure to caloric restriction increased maternal blood space area, but decreased expression of the key System A amino acid transporter Slc38a4 at d18.5. Neither placental and fetal weights, nor placental DNA methylation levels were affected. Thus, total caloric restriction beginning in the periconceptional period does have a lasting impact on placental development in the mouse, but without changing placental efficiency.

Role of Dietary Amino Acids and Nutrient Sensing System in Pregnancy Associated Disorders

Defective implantation is related to pregnancy-associated disorders such as spontaneous miscarriage, intrauterine fetal growth restriction and others. Several factors proclaimed to be involved such as physiological, nutritional, environmental and managemental that leads to cause oxidative stress. Overloading of free radicals promotes oxidative stress, and the internal body system could not combat its ability to encounter the damaging effects and subsequently leading to pregnancy-related disorders. During pregnancy, essential amino acids display important role for optimum fetal growth and other necessary functions for continuing fruitful pregnancy. In this context, dietary amino acids have received much attention regarding the nutritional concerns during pregnancy. Arginine, glutamine, tryptophan and taurine play a crucial role in fetal growth, development and survival while ornithine and proline are important players for the regulation of gene expression, protein synthesis and angiogenesis. Moreover, amino acids also stimulate the mammalian target of rapamycin (mTOR) signaling pathway which plays a central role in the synthesis of proteins in placenta, uterus and fetus. This review article explores the significances of dietary amino acids in pregnancy development, regulation of nutrient-sensing pathways such as mTOR, peroxisome proliferator-activated receptors (PPARs), insulin/insulin-like growth factor signaling pathway (IIS) and 5' adenosine monophosphate-activated protein kinase (AMPK) which exhibit important role in reproduction and its related problems. In addition, the antioxidant function of dietary amino acids against oxidative stress triggering pregnancy disorders and their possible outcomes will also be enlightened. Dietary supplementation of amino acids during pregnancy could help mitigate reproductive disorders and thereby improving fertility in animals as well as humans.

Nutrition and Metabolic Adaptations in Physiological and Complicated Pregnancy: Focus on Obesity and Gestational Diabetes

Pregnancy offers a window of opportunity to program the future health of both mothers and offspring. During gestation, women experience a series of physical and metabolic modifications and adaptations, which aim to protect the fetus development and are closely related to both pre-gestational nutritional status and gestational weight gain. Moreover, pre-gestational obesity represents a challenge of treatment, and nowadays there are new evidence as regard its management, especially the adequate weight gain. Recent evidence has highlighted the determinant role of nutritional status and maternal diet on both pregnancy outcomes and long-term risk of chronic diseases, through a transgenerational flow, conceptualized by the Development Origin of Health and Diseases (Dohad) theory. In this review we will analyse the physiological and endocrine adaptation in pregnancy, and the metabolic complications, thus the focal points for nutritional and therapeutic strategies that we must early implement, virtually before conception, to safeguard the health of both mother and progeny. We will summarize the current nutritional recommendations and the use of nutraceuticals in pregnancy, with a focus on the management of pregnancy complicated by obesity and hyperglycemia, assessing the most recent evidence about the effects of ante-natal nutrition on the long-term, on either maternal health or metabolic risk of the offspring.

Differential expression of system L amino acid transporter subtypes in rat placenta and yolk sac

INTRODUCTION

Amino acid transport across the placenta is crucial for fetal growth. In rodent models, the visceral yolk sac (referred to as yolk sac hereafter) is also likely to contribute to fetal amino acid provision. System L amino acid transporters mediate the transport of essential amino acids. System L activity is mediated by light chains LAT1 (Slc7a5) and LAT2 (Slc7a8) which form functional complexes by heterodimeric linkage to CD98 (Slc3a2). LAT4 (Slc43a2) is monomeric, possessing overlapping amino acid substrate specificity with LAT1 and LAT2.

METHODS

This study investigates the expression of these LAT subtypes in fetus-matched rat placenta and yolk sac.

RESULTS

Slc7a5, Slc7a8 and Slc43a2 transcripts were expressed in placenta and yolk sac with similar expression patterns between sexes. LAT1 expression was significantly higher in placenta than yolk sac. Conversely, LAT2 and LAT4 expression was significantly higher in yolk sac than placenta; CD98 expression was comparable. LAT1, LAT2, LAT4 and CD98 were distributed to rat placental labyrinth zone (LZ) and junctional zone (JZ). LAT1 and LAT4 demonstrated higher expression in LZ, whilst LAT2 was more intensely distributed to JZ. LAT1, LAT2, LAT4 and CD98 were expressed in yolk sac, with punctate LAT1 staining to endodermal cell cytoplasm, contrasting with the intense LAT2, LAT4 and CD98 endodermal cell basolateral distribution, accounting for greater LAT2 and LAT4 expression in yolk sac compared to placenta.

CONCLUSION

LAT1, LAT2 and LAT4 are expressed in rat placenta and yolk sac implicating a combined role for these LAT subtypes in supporting fetal growth and development.

Regulation of maternal-fetal metabolic communication

Pregnancy may be the most nutritionally sensitive stage in the life cycle, and improved metabolic health during gestation and early postnatal life can reduce the risk of chronic disease in adulthood. Successful pregnancy requires coordinated metabolic, hormonal, and immunological communication. In this review, maternal-fetal metabolic communication is defined as the bidirectional communication of nutritional status and metabolic demand by various modes including circulating metabolites, endocrine molecules, and other secreted factors. Emphasis is placed on metabolites as a means of maternal-fetal communication by synthesizing findings from studies in humans, non-human primates, domestic animals, rabbits, and rodents. In this review, fetal, placental, and maternal metabolic adaptations are discussed in turn. (1) Fetal macronutrient needs are summarized in terms of the physiological adaptations in place to ensure their proper allocation. (2) Placental metabolite transport and maternal physiological adaptations during gestation, including changes in energy budget, are also discussed. (3) Maternal nutrient limitation and metabolic disorders of pregnancy serve as case studies of the dynamic nature of maternal-fetal metabolic communication. The review concludes with a summary of recent research efforts to identify metabolites, endocrine molecules, and other secreted factors that mediate this communication, with particular emphasis on serum/plasma metabolomics in humans, non-human primates, and rodents. A better understanding of maternal-fetal metabolic communication in health and disease may reveal novel biomarkers and therapeutic targets for metabolic disorders of pregnancy.

Differentially expressed genes in cotyledon of ewes fed mycotoxins

BACKGROUND

Ergot alkaloids (E+) are mycotoxins produced by the endophytic fungus, Epichloë coenophiala, in tall fescue that are associated with ergotism in animals. Exposure to ergot alkaloids during gestation reduces fetal weight and placental mass in sheep. These reductions are related to vasoconstrictive effects of ergot alkaloids and potential alterations in nutrient transport to the fetus. Cotyledon samples were obtained from eight ewes that were fed E+ (n = 4; E+/E+) or E- (endophyte-free without ergot alkaloids; n = 4; E-/E-) seed during both mid (d 35 to 85) and late (d 85-133) gestation to assess differentially expressed genes associated with ergot alkaloid induced reductions in placental mass and fetal weight, and discover potential adaptive mechanisms to alter nutrient supply to fetus.

RESULTS

Ewes fed E+/E+ fescue seed during both mid and late gestation had 20% reduction in fetal body weight and 33% reduction in cotyledon mass compared to controls (E-/E-). Over 13,000 genes were identified with 110 upregulated and 33 downregulated. Four genes had a |log2FC| > 5 for ewes consuming E+/E+ treatment compared to controls: LECT2, SLC22A9, APOC3, and MBL2. REViGO revealed clusters of upregulated genes associated glucose, carbohydrates, lipid, protein, macromolecular and cellular metabolism, regulation of wound healing and response to starvation. For downregulated genes, no clusters were present, but all enriched GO terms were associated with anion and monocarboxylic acid transport. The complement and coagulation cascade and the peroxisome proliferator-activated receptor signaling pathway were found to be enriched for ewes consuming E+/E+ treatment.

CONCLUSIONS

Consumption of ergot alkaloids during gestation altered the cotyledonary transcriptome specifically related to macronutrient metabolism, wound healing and starvation. These results show that ergot alkaloid exposure upregulates genes involved in nutrient metabolism to supply the fetus with additional substrates in attempts to rescue fetal growth.

[Analysis of metabolic pathways in intrauterine growth restriction]

Objective was to analyze metabolic pathways based on a study of the metabolomic profile of pregnant women with intrauterine growth restriction. The metabolic profile of pregnant women with fetal growth restriction has been analyzed using liquid chromatography-mass spectrometry. At the second stage pathways were identified using SMPDB and MetaboAnalyst databases to clarify the relationship between metabolites. Biological networks allow to determine the effect of proteins on the metabolic pathways involved in pathogenesis of IUGR and determine the epigenetic mechanisms of its formation.

Abnormalities of placental development and function are associated with the different fetal growth patterns of hypoplastic left heart syndrome and transposition of the great arteries

BACKGROUND

Birthweight is a critical predictor of congenital heart disease (CHD) surgical outcomes. Hypoplastic left heart syndrome (HLHS) is cyanotic CHD with known fetal growth restriction and placental abnormalities. Transposition of the great arteries (TGA) is cyanotic CHD with normal fetal growth. Comparison of the placenta in these diagnoses may provide insights on the fetal growth abnormality of CHD.

METHODS

Clinical data and placental histology from placentas associated with Transposition of the Great Arteries (TGA) were analyzed for gross pathology, morphology, maturity and vascularity and compared to both control and previously analyzed HLHS placentas [1]. RNA was isolated from HLHS, TGA and control placentas and sequenced by Illumina HiSeq.Transcriptome analysis was performed using AltAnalyze. Immunohistochemistry was utilized to assess placental nutrient transporter expression in all three groups.

RESULTS

Placental weight was reduced in TGA cases, and demonstrated reduced villous vasculature, immature terminal villi in the parenchyma compared to controls and reflected our previous data from HLHS placentas. However, birth weight was not reduced in TGA cases compared to controls in contrast to the HLHS cohort and birthweight:placental weight ratio was significantly increased in TGA cases but not HLHS compared to control. Transcriptomic and histologic analysis demonstrates reduced cell activity and nutrient transport capability in HLHS but not TGA placentas which appear to increase/maintain these mechanisms.

CONCLUSIONS

Despite common vascular disturbances in placentas from HLHAs and TGA, these do not account for the disparities in birthweights frequently seen between these CHD subtypes, in contrast our transcriptomic and histologic analyses reveal differentially regulated mechanisms between the subtypes that may explain these disparities.