Upregulation of growth signaling and nutrient transporters in cotyledons of early to mid-gestational nutrient restricted ewes

Neurodevelopment Is Dependent on Maternal Diet: Placenta and Brain Glucose Transporters GLUT1 and GLUT3

Glucose is the primary energy source for most mammalian cells and its transport is affected by a family of facilitative glucose transporters (GLUTs) encoded by the SLC2 gene. GLUT1 and GLUT3, highly expressed isoforms in the blood-brain barrier and neuronal membranes, respectively, are associated with multiple neurodevelopmental disorders including epilepsy, dyslexia, ADHD, and autism spectrum disorder (ASD). Dietary therapies, such as the ketogenic diet, are widely accepted treatments for patients with the GLUT1 deficiency syndrome, while ameliorating certain symptoms associated with GLUT3 deficiency in animal models. A ketogenic diet, high-fat diet, and calorie/energy restriction during prenatal and postnatal stages can also alter the placental and brain GLUTs expression with long-term consequences on neurobehavior. This review focuses primarily on the role of diet/energy perturbations upon GLUT isoform-mediated emergence of neurodevelopmental and neurodegenerative disorders.

Effects of maternal nutrient restriction during gestation on bovine serum microRNA abundance

The objective was to determine the effects of maternal nutrient restriction during gestation on serum microRNA (miRNA) abundance in cattle. Primiparous Angus-cross cows (n=22) were fed either control (CON; to gain 1 Kg/week) or nutrient restricted (NR; 0.55% NEm) diets based on National Research Council requirements. On day 30 of gestation, cows were blocked by body condition and randomly assigned to one of three diets: CON (n=8) days 30-190; NR (n=7) days 30-110 followed by CON days 110-190 (NR/C); or CON (n=7) days 30-110 followed by NR days 110-190 (C/NR). At 190 days of gestation, maternal serum was collected for RNA isolation and analyzed using a miRNA microarray of known Bos taurus sequences. Data were normalized using LOWESS and analyzed via ANOVA. At 190 days of gestation, 16 miRNAs exhibited differential abundance (P<0.05) between treatments. Cows that underwent NR, irrespective of when the insult occurred, had downregulated bta-miR-126-3p compared to CON cows. Bta-miR-16b was downregulated and three miRNAs upregulated in NR/C compared to C/NR and CON cows. Additionally, seven miRNAs were downregulated and four miRNAs upregulated in C/NR compared to NR/C and CON cows. Comparison of NR/C and C/NR cows revealed three differentially abundant (P<0.04) miRNAs (bta-miR-2487_L-2R-3_1ss15CT, bta-miR-215, and bta-miR-760-5p). Top KEGG pathway enrichment of target genes included: pathways in cancer, PI3K-Akt signaling, focal adhesion, Ras signaling, proteoglycans in cancer, and MAPK signaling. In summary, maternal nutrient restriction altered serum miRNA abundance profiles irrespective of the time at which the nutritional insult was induced.

Placental adaptations supporting fetal growth during normal and adverse gestational environments

NEW FINDINGS

What is the topic of this review? How the placenta, which transports nutrients and oxygen to the fetus, may alter its support of fetal growth developmentally and with adverse gestational conditions. What advances does it highlight? Placental formation and function alter with the needs of the fetus for substrates for growth during normal gestation and when there is enhanced competition for substrates in species with multiple gestations or adverse gestational environments, and this is mediated by imprinted genes, signalling pathways, mitochondria and fetal sexomes.

ABSTRACT

The placenta is vital for mammalian development and a key determinant of life-long health. It is the interface between the mother and fetus and is responsible for transporting the nutrients and oxygen a fetus needs to develop and grow. Alterations in placental formation and function, therefore, have consequences for fetal growth and birthweight, which in turn determine perinatal survival and risk of non-communicable diseases for the offspring in later postnatal life. However, the placenta is not a static organ. As this review summarizes, research from multiple species has demonstrated that placental formation and function alter developmentally to the needs of the fetus for substrates for growth during normal gestation, as well as when there is greater competition for substrates in polytocous species and monotocous species with multiple gestations. The placenta also adapts in response to the gestational environment, integrating information about the ability of the mother to provide nutrients and oxygen with the needs of the fetus in that prevailing environment. In particular, placental structure (e.g. vascularity, surface area, blood flow, diffusion distance) and transport capacity (e.g. nutrient transporter levels and activity) respond to suboptimal gestational environments, namely malnutrition, obesity, hypoxia and maternal ageing. Mechanisms mediating developmentally and environmentally induced homeostatic responses of the placenta that help support normal fetal growth include imprinted genes, signalling pathways, subcellular constituents and fetal sexomes. Identification of these placental strategies may inform the development of therapies for complicated human pregnancies and advance understanding of the pathways underlying poor fetal outcomes and their consequences for health and disease risk.

Multi-Omics Analysis Reveals the Potential Effects of Maternal Dietary Restriction on Fetal Muscle Growth and Development

In terms of fetal muscle growth, development, and health, maternal nutrition is a crucial influence, although the exact biochemical mechanism by which this occurs is still not fully understood. To examine the potential impacts of maternal dietary restriction on fetal muscle development, the sheep maternal dietary restriction model was developed for this study. In our study, 12 pregnant ewes were evenly split into two experimental groups and fed either 75% or 100% of a maternal nutrient. In addition, a multi-omics analysis was used to study the embryonic longissimus dorsis on gestational days (GD) 85 and 135. The fetal weight at GD 135 was significantly below normal due to the maternal restricted diet (p < 0.01). When fetuses were exposed to the dietary deficit, 416 mRNAs and 40 proteins were significantly changed. At GD 85, the multi-omics analysis revealed that maternal dietary restriction led to a significant up-regulation of the cell cycle regulator CDK2 gene in the cellular senescence signaling pathway, and the results of the qRT-PCR were similar to the multi-omics analysis, which showed that SIX1, PAX7, the cell cycle factors CDK4 and CDK6, and the BCL-2 apoptosis factor were up-regulated and several skeletal muscle marker genes, such as MYF5 and MyoD were down-regulated. At GD 135, maternal dietary restriction blocks the muscle fiber differentiation and maturation. The multi-omics analysis revealed that the TEAD1 gene was in the Hippo signaling pathway, the muscle marker genes MYF5 and MyoG were significantly down-regulated, and the TEAD1 binding of the down-regulated VGLL3 gene might be potential mechanisms affecting myofiber differentiation and maturation. Knocking down the CDK2 gene could inhibit the proliferation of primary embryonic myoblasts, and the expression levels of cell cycle regulatory factors CDK4 and CDK6 were significantly changed. Under low nutrient culture conditions, the number of myoblasts decreased and the expression of CDK2, CDK6, MYF5, PAX7 and BCL-2 changed, which was in perfect agreement with the multi-omics analysis. All of the findings from our study helped to clarify the potential effects of maternal dietary restriction on fetal muscle growth and development. They also provided a molecular foundation for understanding the molecular regulatory mechanisms of maternal nutrition on fetal muscle growth and development, as well as for the development of new medications and the management of related metabolic diseases.

A critical role of AMP-activated protein kinase in regulating intestinal nutrient absorption, barrier function, and intestinal diseases

As one of the most important organs in animals, the intestine is responsible for nutrient absorption and acts as a barrier between the body and the environment. Intestinal physiology and function require the participation of energy. 5'-adenosine monophosphate-activated protein kinase (AMPK), a classical and highly expressed energy regulator in intestinal cells, regulates the process of nutrient absorption and barrier function and is also involved in the therapy of intestinal diseases. Studies have yielded findings that AMPK regulates the absorption of glucose, amino acids, and fatty acids in the intestine primarily by regulating transportation systems, as we detailed here. Moreover, AMPK is involved in the regulation of the intestinal mechanical barrier and immune barrier through manipulating the expression of tight junctions, antimicrobial peptides, and secretory immunoglobulins. In addition, AMPK also participates in the regulation of intestinal diseases, which indicates that AMPK is a promising therapeutic target for intestinal diseases and cancer. In this review, we summarized the current understanding regarding how AMPK regulates intestinal nutrient absorption, barrier function, and intestinal diseases.

Chronic Hypoxia in Ovine Pregnancy Recapitulates Physiological and Molecular Markers of Preeclampsia in the Mother, Placenta, and Offspring

BACKGROUND

Preeclampsia continues to be a prevalent pregnancy complication and underlying mechanisms remain controversial. A common feature of preeclampsia is utero-placenta hypoxia. In contrast to the impact of hypoxia on the placenta and fetus, comparatively little is known about the maternal physiology.

METHODS

We adopted an integrative approach to investigate the inter-relationship between chronic hypoxia during pregnancy with maternal, placental, and fetal outcomes, common in preeclampsia. We exploited a novel technique using isobaric hypoxic chambers and in vivo continuous cardiovascular recording technology for measurement of blood pressure in sheep and studied the placental stress in response to hypoxia at cellular and subcellular levels.

RESULTS

Chronic hypoxia in ovine pregnancy promoted fetal growth restriction (FGR) with evidence of fetal brain-sparing, increased placental hypoxia-mediated oxidative damage, and activated placental stress response pathways. These changes were linked with dilation of the placental endoplasmic reticulum (ER) cisternae and increased placental expression of the antiangiogenic factors sFlt-1 (soluble fms-like tyrosine kinase 1) and sEng (soluble endoglin), combined with a shift towards an angiogenic imbalance in the maternal circulation. Chronic hypoxia further led to an increase in uteroplacental vascular resistance and the fall in maternal blood pressure with advancing gestation measured in normoxic pregnancy did not occur in hypoxic pregnancy.

CONCLUSIONS

Therefore, we show in an ovine model of sea-level adverse pregnancy that chronic hypoxia recapitulates physiological and molecular features of preeclampsia in the mother, placenta, and offspring.

Effects of Mid-Gestation Nutrient Restriction, Realimentation, and Parity on the Umbilical Hemodynamics of the Pregnant Ewe

Previous studies have reported that nutritional restriction from days 50 to 130 applied in young nulliparous ewes reduces umbilical blood flow (UBF). We hypothesized that during restriction, UBF and fetal and placentome dimensional measurements would decrease compared to adequately fed ewes, but upon realimentation, ewes would have similar UBF as ewes that were not restricted. We also hypothesized that multiparous ewes would be more resilient to nutrient restriction compared to nulliparous ewes. In experiment 1, second-parity Dorset ewes carrying singletons were assigned to an adequate nutrition group (CON, n = 7) or a restricted (60% of CON) group (RES, n = 8), from days 50 to 90 of gestation. In experiment 2, on day 50 of gestation, adult (15-month) nulliparous (NUL; n = 12) and multiparous (MUL; n = 16) Dorset ewes carrying singletons were randomly assigned to receive 100% of NRC recommendations (CON) or 60% of CON (RES). On day 90, all ewes were fed 100% of nutritional recommendations according to body weight. Ewe body weight and conceptus measurements via ultrasonography were recorded every 10 days from days 50 to 130 of gestation. We measured 10 random placentomes, fetal biparietal and abdominal length, and kidney length and width. Doppler mode was used to obtain UBF, pulsatility index (PI), and resistance index (RI). Lamb weight and parturition problems were recorded. In experiment 1, on day 80, UBF decreased (P ≤ 0.05 means separation of unprotected F test), placentome size tended to decrease (P ≤ 0.10), and PI and RI tended to increase in RES vs. CON ewes (P ≤ 0.10). In experiment 2, there were no three-way interactions or main effects of treatments on UBF, PI, RI, and placentome size (P ≥ 0.57). There was a parity-by-day interaction (P &lt; 0.05) for RI, but UBF was not affected by parity or diet. After realimentation, there was no effect of treatment on ultrasound measurements in both experiments. At birth, lambs and placental measurements were not different (P ≥ 0.43). Restriction from days 50 to 90 does not seem to influence umbilical hemodynamics or conceptus growth in adult white face sheep, regardless of parity.

Effects of nutrient restriction during early or mid-gestation in bovine on placental development and miRNA expression in the cotyledon

The objective of this study was to determine effects of maternal nutrient restriction (NR) during early or mid-gestation on uterine composition and miRNA expression in cotyledons. Primiparous Angus-cross cows (n = 38) were synchronized and inseminated using male sexed semen, blocked by body condition score and body weight (BW), and assigned to treatments. Animals were fed either: control (CON; gain 1 kg/week) or NR (55% maintenance energy and crude protein requirements) based on BW. An initial set of animals were fed either NR (n = 8) or CON (n = 8) from day 30-110 of gestation. A second set of animals were fed CON (n = 8) d 30-190 (CON/CON); NR (n = 7) day 30-110 followed by CON day 110-190 (NR/CON); or CON (n = 7) day 30-110 followed by NR day 110-190 (CON/NR). Cows were harvested on day 110 or 190 of gestation to collect placental tissues. RNA was isolated from cotyledon samples (3 animals/group) prior to microarray analysis using known Bos taurus microRNA sequences. Relative microRNA abundance was analyzed via ANOVA. Maternal NR increased (P < 0.05) cotyledon weight and total placentome surface area irrespective of gestational day. At day 110 of gestation, 51 microRNAs were reduced while 91 microRNAs observed greater abundance (P < 0.05) in NR verses CON cotyledons. At day 190 of gestation, 40 microRNAs were reduced and 26 microRNAs were increased (P < 0.05) in both NR/CON and CON/NR verses CON cotyledons. Top KEGG pathway analysis included: axon guidance, endocytosis, neuroactive ligand receptor interaction, and MAPK signaling pathway. Early-gestation maternal NR altered microRNA abundance to a greater extent than mid-gestation NR.

Placental adaptations in a nonhuman primate model of gestational protein restriction

We previously demonstrated decreased placental perfusion, reduced amniotic fluid protein content, and increased pregnancy loss in a nonhuman primate model of gestational protein restriction. Here, our objective was to link these detrimental findings with a functional placental assessment. As blood flow is critical to maternal-fetal exchange, we hypothesized that a protein-restricted diet would impair placental taurine uptake. Pregnant rhesus macaques were maintained on either control chow (CON, n = 5), a 33% protein-restricted diet (PR33, n = 5), or a 50% PR diet (PR50, n = 5) prior to and throughout pregnancy. Animals were delivered on gestational day 135 (G135; term is G168). Taurine activity was determined in fresh placental villous explants. Taurine transporter (TauT) protein expression, placental growth factor (PLGF), and insulin-like growth factor (IGF)-1 and IGF-2 protein concentrations were measured, and histological assessment was performed. Fetal body weights and placental weights were comparable between all three groups at G135. Placental taurine uptake was decreased in PR33- and PR50-fed animals compared to CON, yet TauT expression was unchanged across groups. PLGF was significantly increased in PR50 vs. CON, with no change in IGF-1 or IGF-2 expression in placental homogenate from PR-fed animals. Accelerated villous maturation was observed in all PR50 cases, three of five PR33, and was absent in CON. We demonstrate conserved fetal growth, despite a decrease in placental taurine uptake. Increased expression of PLGF and expansion of the syncytiotrophoblast surface area in the severely protein-restricted animals suggest a compensatory mechanism by the placenta to maintain fetal growth.

Ruminant Placental Adaptation in Early Maternal Undernutrition: An Overview

Correct placental development during early gestation is considered the main determinant of fetal growth in late pregnancy. A reduction in maternal nourishment occurring across the early developmental window has been linked to a wide range of pregnancy disorders affecting placental transport capacity and consequently the fetal nutrient supply line, with long-term implications for offspring health and productivity. In livestock, ruminant species specifically experience maternal undernutrition in extensive systems due to seasonal changes in food availability, with significant economic losses for the farmer in some situations. In this review, we aim to discuss the effects of reduced maternal nutrition during early pregnancy on placental development with a specific focus on ruminant placenta physiology. Different types of placental adaptation strategies were examined, also considering the potential effects on the epigenetic landscape, which is known to undergo extensive reprogramming during early mammalian development. We also discussed the involvement of autophagy as a cellular degradation mechanism that may play a key role in the placental response to nutrient deficiency mediated by mammalian target of rapamycin, named the mTOR intracellular pathway.

Reduction of In Vivo Placental Amino Acid Transport Precedes the Development of Intrauterine Growth Restriction in the Non-Human Primate

Intrauterine growth restriction (IUGR) is associated with reduced placental amino acid transport (AAT). However, it remains to be established if changes in AAT contribute to restricted fetal growth. We hypothesized that reduced in vivo placental AAT precedes the development of IUGR in baboons with maternal nutrient restriction (MNR). Baboons were fed either a control (ad libitum) or MNR diet (70% of control diet) from gestational day (GD) 30. At GD 140, in vivo transplacental AA transport was measured by infusing nine ⁽¹³⁾C- or ⁽²⁾H-labeled essential amino acids (EAAs) as a bolus into the maternal circulation at cesarean section. A fetal vein-to-maternal artery mole percent excess ratio for each EAA was measured. Microvillous plasma membrane (MVM) system A and system L transport activity were determined. Fetal and placental weights were not significantly different between MNR and control. In vivo, the fetal vein-to-maternal artery mole percent excess ratio was significantly decreased for tryptophan in MNR. MVM system A and system L activity was markedly reduced in MNR. Reduction of in vivo placental amino acid transport precedes fetal growth restriction in the non-human primate, suggesting that reduced placental amino acid transfer may contribute to IUGR.

Gestation Food Restriction and Refeeding Compensate Maternal Energy Status and Alleviate Metabolic Consequences in Juvenile Offspring in a Rabbit Model

Nutritional status during gestation can influence mother and offspring metabolism. Undernutrition in pregnancy affects women in both western and developing countries, and it is associated with a high prevalence of chronic diseases in later life. The present work was conducted in the rabbit model, as a longitudinal study, to examine the effect of food restriction during early and mid-gestation, and re-feeding ad libitum until the end of pregnancy on metabolic status and body reserves of mother and, its association with development and metabolism of fetuses and female offspring to the juvenile stage. Little changes in live body weight (LBW), compensatory feed intake, similar body reserves, and metabolism were observed in dams. Placenta biometry and efficiency were slightly affected, but fetal BW and phenotype were not modified. However, hyperinsulinemia, insulin resistance, and hypertriglyceridemia were demonstrated in pre-term fetuses. In the juvenile period, these changes were not evidenced, and a similar pattern of growth and serum metabolic parameters in offspring of food-restricted mothers were found, except in serum aminotransferases levels, which increased. These were associated with higher liver fibrosis. Maternal food restriction in the early and mid-pregnancy followed by re-feeding in our rabbit model established a compensatory energy status in dams and alleviated potential long-term consequences in growth and metabolism in the offspring, even if fetal metabolism was altered.

Stimulation of soluble guanylate cyclase diminishes intrauterine growth restriction in a rat model of placental ischemia

Placental ischemia in preeclampsia (PE) results in hypertension and intrauterine growth restriction (IUGR). Stimulation of soluble guanylate cyclase (sGC) reduces blood pressure in the clinically relevant reduced uterine perfusion pressure (RUPP) rat model of PE, implicating involvement in RUPP-induced hypertension. However, the contribution of sGC in the development of IUGR in PE is not known. Thus, this study demonstrated the efficacy of Riociguat, an sGC stimulator, in IUGR reversion in the RUPP rat model of PE, and tested the hypothesis that improvement in fetal weight occurs in association with improvement in placental perfusion, placental morphology, and placental nutrient transport protein expression. Sham or RUPP surgery was performed at gestational day 14 (G14) with administration of vehicle (Sham or RUPP) or the sGC stimulator (Riociguat, 10 mg/kg/day sc; sGC-treated) until G20. Fetal weight was reduced (P = 0.004) at G20 in RUPP but not in sGC-treated RUPP compared with Sham, the control group. At G20, uterine artery resistance index (UARI) was increased (P = 0.010) in RUPP, indicating poor placental perfusion; proportional junctional zone surface area was elevated (P = 0.035), indicating impaired placental development. These effects were ameliorated in sGC-treated RUPP. Placental protein expression of nutrient transporter heart fatty acid-binding protein (hFABP) was increased (P = 0.008) in RUPP but not in sGC-treated RUPP, suggesting a compensatory mechanism to maintain normal neurodevelopment. Yet, UARI (P < 0.001), proportional junctional zone surface area (P = 0.013), and placental hFABP protein expression (P = 0.008) were increased in sGC-treated Sham, suggesting a potential adverse effect of Riociguat. Collectively, these results suggest sGC contributes to IUGR in PE.

Associations between the activity of placental nutrient-sensing pathways and neonatal and postnatal metabolic health: the ECHO Healthy Start cohort

OBJECTIVE

Our hypothesis was that the activity of placental nutrient-sensing pathways is associated with adiposity and metabolic health in childhood.

RESEARCH DESIGN AND METHODS

Using placental villus samples from healthy mothers from the Healthy Start Study, we measured the abundance and phosphorylation of key intermediates in the mTOR, insulin, AMPK, and ER stress signaling pathways. Using multivariate multiple regression models, we tested the association between placental proteins and offspring adiposity (%fat mass) at birth (n = 109), 4-6 months (n = 104), and 4-6 years old (n = 64), adjusted for offspring sex and age.

RESULTS

Placental mTORC1 phosphorylation was positively associated with adiposity at birth (R2 = 0.13, P = 0.009) and 4-6 years (R2 = 0.15, P = 0.046). The mTORC2 target PKCα was positively associated with systolic blood pressure at 4-6 years (β = 2.90, P = 0.005). AMPK phosphorylation was positively associated with adiposity at birth (β = 2.32, P = 0.023), but the ratio of phosphorylated to total AMPK was negatively associated with skinfold thickness (β = -2.37, P = 0.022) and body weight (β = -2.92, P = 0.005) at 4-6 years.

CONCLUSIONS

This is the first report of associations between key placental protein activity measures and longitudinal child outcomes at various life stages. Our data indicate that AMPK and mTOR signaling are linked to cardiometabolic measures at birth and 4-6 years, providing novel insight into potential mechanisms underpinning how metabolic signaling in the placenta is associated with future risk of cardiovascular disease.

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.

Lipid metabolism is altered in maternal, placental, and fetal tissues of ewes with small for gestational age fetuses†

Nutrient restriction (NR) has the potential to negatively impact birthweight, an indicator of neonatal survival and lifelong health. Those fetuses are termed as small for gestational age (SGA). Interestingly, there is a spectral phenotype of fetal growth rates in response to NR associated with changes in placental development, nutrient and waste transport, and lipid metabolism. A sheep model with a maternal diet, starting at Day 35, of 100% National Research Council (NRC) nutrient requirements (n = 8) or 50% NRC (n = 28) was used to assess alterations in fetuses designated NR SGA (n = 7) or NR NonSGA (n = 7) based on fetal weight at Day 135 of pregnancy. Allantoic fluid concentrations of triglycerides were greater in NR SGA fetuses than 100% NRC and NR NonSGA fetuses at Day 70 (P < 0.05). There was a negative correlation between allantoic fluid concentrations of triglycerides (R2 = 0.207) and bile acids (R2 = 0.179) on Day 70 and fetal weight at Day 135 for NR ewes (P < 0.05). Bile acids were more abundant in maternal and fetal blood for NR SGA compared to 100% NRC and NR NonSGA ewes (P < 0.05). Maternal blood concentrations of NEFAs increased in late pregnancy in NR NonSGA compared to NR SGA ewes (P < 0.05). Protein expression of fatty acid transporter SLC27A6 localized to placentomal maternal and fetal epithelia and decreased in Day 70 NR SGA compared to 100% NRC and NR NonSGA placentomes (P < 0.05). These results identify novel factors associated with an ability of placentae and fetuses in NR NonSGA ewes to adapt to, and overcome, nutritional hardship during pregnancy.

A Review of Maternal Nutrition during Pregnancy and Impact on the Offspring through Development: Evidence from Animal Models of Over- and Undernutrition

Similarities in offspring phenotype due to maternal under- or over-nutrition during gestation have been observed in studies conducted at University of Wyoming. In these studies, ewes were either nutrient-restricted (NR) from early to mid-gestation, or fed an obesogenic diet (MO) from preconception through term. Offspring necropsies occurred at mid-gestation, late-gestation, and after parturition. At mid gestation, body weights of NR fetuses were ~30% lighter than controls, whereas MO fetuses were ~30% heavier than those of controls. At birth, lambs born to NR, MO, and control ewes exhibited similar weights. This was a consequence of accelerated fetal growth rates in NR ewes, and reduced fetal growth rates in MO ewes in late gestation, when compared to their respective controls. These fetal growth patterns resulted in remarkably similar effects of increased susceptibility to obesity, cardiovascular disease, and glucose intolerance in offspring programmed mostly during fetal stages of development. These data provide evidence that maternal under- and over-nutrition similarly induce the development of the same cadre of physical and metabolic problems in postnatal life.

Identification of Pathways Associated with Placental Adaptation to Maternal Nutrient Restriction in Sheep

Maternal nutrient restriction impairs placental growth and development, but available evidence suggests that adaptive mechanisms exist, in a subset of nutrient restricted (NR) ewes, that support normal fetal growth and do not result in intrauterine growth restriction (IUGR). This study utilized Affymetrix GeneChip Bovine and Ovine Genome 1.0 ST Arrays to identify novel placental genes associated with differential fetal growth rates within NR ewes. Singleton pregnancies were generated by embryo transfer and, beginning on Day 35 of pregnancy, ewes received either a 100% National Research Council (NRC) (control-fed group; n = 7) or 50% NRC (NR group; n = 24) diet until necropsy on Day 125. Fetuses from NR ewes were separated into NR non-IUGR (n = 6) and NR IUGR (n = 6) groups based on Day 125 fetal weight for microarray analysis. Of the 103 differentially expressed genes identified, 15 were upregulated and 88 were downregulated in NR non-IUGR compared to IUGR placentomes. Bioinformatics analysis revealed that upregulated gene clusters in NR non-IUGR placentomes associated with cell membranes, receptors, and signaling. Downregulated gene clusters associated with immune response, nutrient transport, and metabolism. Results illustrate that placentomal gene expression in late gestation is indicative of an altered placental immune response, which is associated with enhanced fetal growth, in a subpopulation of NR ewes.

Fetal Head Growth during Early to Mid-Gestation Associated with Weight Gain in Mothers with Hyperemesis Gravidarum: A Retrospective Cohort Study

The epigenetic impact of malnutrition in mothers with hyperemesis gravidarum (HG) on their offspring has not been fully elucidated. Recently, several reports have demonstrated that children born to mothers with HG were small for gestational age and had low birth weight, reduced insulin sensitivity, and neurodevelopmental delays during childhood. Therefore, we examined the relationship between fetal growth and changes in the maternal body weight in HG cases. A total of 34 patients with HG were hospitalized and delivered at term between 2009 and 2012. The records of 69 cases of pregnant women without a history of HG were extracted after matching their maternal age, parity, pregestational body mass index (BMI), gestational age, and fetal sex ratio with those of the HG group for comparison. The maternal weight gain at term was less in the HG than in the control group. There was no statistical difference in birth weight, placental weight, and ultrasonic fetometric parameters expressed in standard deviation (SD) scores, including biparietal diameter, abdominal circumference, and femur length, between the HG and the control group. Whereas fetal head growth in the HG group was positively associated with maternal weight gain at 20 weeks of gestation only, this association was not observed in the control group. We herein demonstrate that maternal weight gain from the nadir is associated with fetal head growth at mid-gestation. Thus, maternal undernutrition in the first trimester of pregnancy could affect fetal brain growth and development, leading to an increased risk of neurodevelopmental delays in later life.

Is there a definite relationship between placental mTOR signaling and fetal growth?

Fetal growth restriction and overgrowth are common obstetrical complications that result in adverse perinatal outcomes and long-term health risks later in life, including neurodevelopmental dysfunction and adult metabolic syndrome. The placenta plays a critical role in the nutrition transfer from mother to fetus and even exerts adaptive mechanism when the fetus is under poor developmental conditions. The mammalian/mechanistic target of rapamycin (mTOR) signaling serves as a critical hub of cell growth, survival, and metabolism in response to nutrients, growth factors, energy, and stress signals. Placental mTOR signaling regulates placental function, including oxygen and nutrient transport. Therefore, placental mTOR signaling is hypothesized to have a positive relationship with fetal growth. In this review, we summarize that most studies support the current evidence that there is connection between placental mTOR signaling and abnormal fetal growth; however, but more studies should be performed following a vigorous and unanimous method for assessment to determine placental mTOR activity.

Region-specific changes in the mRNA and protein expression of LCPUFA biosynthesis enzymes and transporters in the placentae of women with preeclampsia

The biosynthesis and transport of long chain polyunsaturated fatty acids (LCPUFA) require the activity of fatty acid desaturase (FADS) enzymes, fatty acid transport proteins (FATP) and fatty acid binding proteins (FABP). In a previous study we have demonstrated region-specific changes in the LCPUFA levels in preeclampsia (PE) as compared to the normotensive control (NC) placentae.

AIM

To understand the region-specific changes in the mRNA levels and protein expression of biosynthesis enzymes and transporters of LCPUFA in PE and NC placentae.

METHODS

In this cross-sectional study, 20 NC women and 44 women with PE (23 term (TPE) and 21 preterm PE (PTPE)) were recruited. The samples were collected from four regions of the placentae considering cord insertion as the center (CM, central maternal/basal; CF, central fetal/chorionic; PM, peripheral maternal/basal and PF, peripheral fetal/chorionic). The mRNA levels were estimated using qRT-PCR. Statistical analysis was done using both post hoc least significant difference (LSD) test and Benjamini Hochberg correction in the analysis of covariance. Preliminarily, localization and expression of proteins were studied by immunohistochemistry (n = 3/group).

RESULTS

The mRNA levels of FADS1, FADS2 and FATP1 were lower in the central regions (CM and CF) of the PE placentae (both TPE and PTPE) as compared to NC. These differences in the mRNA levels were observed by the LSD test and were not significant after the Benjamini Hochberg correction. Preliminary findings of IHC indicate that the protein expression of FADS1 and FATP4 was higher in the basal regions (CM and PM) of the PE placentae as compared to NC. FADS1, FADS2 and FATP4 proteins were localized in the syncytiotrophoblasts, cytotrophoblasts, mesenchymal cells, endothelial cells of the fetal capillaries and extravillous trophoblasts of the placenta.

CONCLUSION

FADS enzymes are detected in the placentae of Indian women. In PE placentae, there are region-specific alterations in the mRNA and protein levels of LCPUFA biosynthesis enzymes (FADS1 and FADS2) and transporters (FATP1, FATP4 and FABP3) as compared to term NC. These changes were more pronounced toward the basal side and region around the cord insertion.

Maternal diet modulates placental nutrient transporter gene expression in a mouse model of diabetic pregnancy

Diabetes in the mother during pregnancy is a risk factor for birth defects and perinatal complications and can affect long-term health of the offspring through developmental programming of susceptibility to metabolic disease. We previously showed that Streptozotocin-induced maternal diabetes in mice is associated with altered cell differentiation and with smaller size of the placenta. Placental size and fetal size were affected by maternal diet in this model, and maternal diet also modulated the risk for neural tube defects. In the present study, we sought to determine the extent to which these effects might be mediated through altered expression of nutrient transporters, specifically glucose and fatty acid transporters in the placenta. Our results demonstrate that expression of several transporters is modulated by both maternal diet and maternal diabetes. Diet was revealed as the more prominent determinant of nutrient transporter expression levels, even in pregnancies with uncontrolled diabetes, consistent with the role of diet in placental and fetal growth. Notably, the largest changes in nutrient transporter expression levels were detected around midgestation time points when the placenta is being formed. These findings place the critical time period for susceptibility to diet exposures earlier than previously appreciated, implying that mechanisms underlying developmental programming can act on placenta formation.

Maternal High-Fat Diet Consumption and Chronic Hyperandrogenemia Are Associated With Placental Dysfunction in Female Rhesus Macaques

The risk of adverse perinatal outcomes with maternal polycystic ovary syndrome may differ among hyperandrogenic and nonhyperandrogenic phenotypes and is likely modulated by maternal obesity and diet. The relative contribution of maternal hyperandrogenism and nutritional status to placental dysfunction is unknown. Female rhesus macaques (N = 39) were assigned at puberty to one of four treatment groups: subcutaneous cholesterol implants and a standard chow diet (controls); testosterone (T) implants and a normal diet; cholesterol implants and a high-fat, Western-style diet (WSD); and testosterone implants in combination with a high-fat diet. After 3.5 years of treatment, contrast-enhanced and Doppler ultrasound analyses of placental blood flow were performed for a representative subset of animals from each treatment group during pregnancy, and placental architecture assessed with stereological analysis. Placental growth factors, cellular nutrient sensors, and angiogenic markers were measured with ELISA and Western blotting. WSD consumption was associated with a 30% increase in placental flux rate relative to that in animals receiving a normal diet. T and WSD treatments were each independently associated with increased villous volume, and T also was associated with an ∼ 40% decrease fetal capillary volume on stereological analysis. T treatment was associated with significantly increased mTOR and SOCS3 expression. WSD consumption was associated with decreased GLUT1 expression and microvillous membrane localization. Hyperandrogenemic and nonhyperandrogenemic phenotypes are associated with altered placental angiogenesis, nutrient sensing, and glucose transport. WSD and T appear to have distinct effects on vascular impedance and capillary angiogenesis.

Developmental Resiliency: In Utero Adaption to Environmental Stimuli

Stimuli experienced in utero can have a lasting impact on livestock growth, reproduction, and performance. Variations in environment, production system, and management strategies lead to discrepancies in the literature regarding how specific treatments influence animal performance. Studies comparing the influence of maternal undernutrition to well-fed counterparts typically result in decreased productivity of offspring. Via adaptation to nutritional or environmental stressors, dams may develop mechanisms to ensure proper nutrient supply to the fetus. It appears nutrient deprivation must be severe for consistent results. Potential mechanisms for altered performance in grazing systems and overnutrition settings are discussed.

Improving pregnancy outcomes in humans through studies in sheep

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

Effects of maternal nutrient restriction during early or mid-gestation without realimentation on maternal physiology and foetal growth and development in beef cattle

The aim of this study is to determine the effects of early and mid-gestation nutrient restriction on maternal metabolites and foetal growth. Primiparous Angus cows were synchronized and inseminated with semen from one sire. Dietary treatments were: control to gain 1 kg/week (CON) or 0.55% maintenance energy and CP requirements (nutrient restricted; NR). A subset of dams was fed NR (n=8) or CON (n=8) from days 30 to 110 of gestation. Another group was fed CON (n=8), days 30 to 190; NR (n=7), days 30 to 110 followed by CON days 110 to 190; or CON, (n=7) days 30 to 110 followed by NR days 110 to 190. Cows were harvested at days 110 or 190 of gestation, when foetal measurements and samples were collected. Cows that were NR during days 30 to 110 or 110 to 190 of gestation lost significant BW and body condition score (P<0.001), this was associated with reduced plasma glucose during NR (P<0.002). Foetal weights, empty foetal weights, abdominal and thoracic circumferences were all reduced (P<0.03) in day 110 NR animals. Foetal perirenal adipose as a percentage of empty foetal weight was increased (P=0.01) in NR day 110 female foetuses compared with CON foetus. Maternal serum triglycerides at day 110 of gestation were decreased (P<0.05) in NR dams, whereas foetal serum triglycerides were increased (P<0.05) in response to maternal NR. Foetal weights tended to be reduced (P=0.08) in NR/CON and CON/NR v. CON/CON cattle at day 190 of gestation. Empty foetal weights, abdominal and thoracic circumferences were reduced (P⩽0.03) in NR/CON and CON/NR v. CON/CON cattle. Brain weight as a percentage of empty foetal weight was increased (P<0.001) in NR/CON and CON/NR v. CON/CON cattle. Foetal perirenal adipose as a percentage of empty foetal weight was increased (P=0.003) in NR/CON and CON/NR v. CON/CON cattle. Maternal serum triglycerides at day 190 of gestation were decreased (P<0.05) in association with maternal NR. Foetal serum triglycerides at day 190 of gestation were increased (P<0.05) in response to maternal NR during early gestation but decreased by NR in mid gestation compared with CON foetuses. The data show that maternal nutrient restriction during early or mid-gestation cause's asymmetrical foetal growth restriction, regardless if the restriction is preceded or followed by a period of non-restriction.

Placental phenotype and the insulin-like growth factors: resource allocation to fetal growth

The placenta is the main determinant of fetal growth and development in utero. It supplies all the nutrients and oxygen required for fetal growth and secretes hormones that facilitate maternal allocation of nutrients to the fetus. Furthermore, the placenta responds to nutritional and metabolic signals in the mother by altering its structural and functional phenotype, which can lead to changes in maternal resource allocation to the fetus. The molecular mechanisms by which the placenta senses and responds to environmental cues are poorly understood. This review discusses the role of the insulin-like growth factors (IGFs) in controlling placental resource allocation to fetal growth, particularly in response to adverse gestational environments. In particular, it assesses the impact of the IGFs and their signalling machinery on placental morphogenesis, substrate transport and hormone secretion, primarily in the laboratory species, although it draws on data from human and other species where relevant. It also considers the role of the IGFs as environmental signals in linking resource availability to fetal growth through changes in the morphological and functional phenotype of the placenta. As altered fetal growth is associated with increased perinatal morbidity and mortality and a greater risk of developing adult-onset diseases in later life, understanding the role of IGFs during pregnancy in regulating placental resource allocation to fetal growth is important for identifying the mechanisms underlying the developmental programming of offspring phenotype by suboptimal intrauterine growth.

Dietary -carbamylglutamate and rumen-protected -arginine supplementation ameliorate fetal growth restriction in undernourished ewes

This study was conducted with an ovine intrauterine growth restriction (IUGR) model to test the hypothesis that dietary -carbamylglutamate (NCG) and rumen-protected -Arg (RP-Arg) supplementation are effective in ameliorating fetal growth restriction in undernourished ewes. Beginning on d 35 of gestation, ewes were fed a diet providing 100% of NRC-recommended nutrient requirements, 50% of NRC recommendations (50% NRC), 50% of NRC recommendations supplemented with 20 g/d RP-Arg (providing 10 g/d of Arg), and 50% of NRC recommendations supplemented with 5 g/d NCG product (providing 2.5 g/d of NCG). On d 110, maternal, fetal, and placental tissues and fluids were collected and weighed. Ewe weights were lower ( < 0.05) in nutrient-restricted ewes compared with adequately fed ewes. Maternal RP-Arg or NCG supplementation did not alter ( = 0.26) maternal BW in nutrient-restricted ewes. Weights of most fetal organs were increased ( < 0.05) in RP-Arg-treated and NCG-treated underfed ewes compared with 50% NRC-fed ewes. Supplementation of RP-Arg or NCG reduced ( < 0.05) concentrations of β-hydroxybutyrate, triglycerides, and ammonia in serum of underfed ewes but had no effect on concentrations of lactate and GH. Maternal RP-Arg or NCG supplementation markedly improved ( < 0.05) concentrations of AA (particularly arginine-family AA and branched-chain AA) and polyamines in maternal and fetal plasma and in fetal allantoic and amniotic fluids within nutrient-restricted ewes. These novel results indicate that dietary NCG and RP-Arg supplementation to underfed ewes ameliorated fetal growth restriction, at least in part, by increasing the availability of AA in the conceptus and provide support for its clinical use to ameliorate IUGR in humans and sheep industry production.

Placental Origins of Chronic Disease

Epidemiological evidence links an individual's susceptibility to chronic disease in adult life to events during their intrauterine phase of development. Biologically this should not be unexpected, for organ systems are at their most plastic when progenitor cells are proliferating and differentiating. Influences operating at this time can permanently affect their structure and functional capacity, and the activity of enzyme systems and endocrine axes. It is now appreciated that such effects lay the foundations for a diverse array of diseases that become manifest many years later, often in response to secondary environmental stressors. Fetal development is underpinned by the placenta, the organ that forms the interface between the fetus and its mother. All nutrients and oxygen reaching the fetus must pass through this organ. The placenta also has major endocrine functions, orchestrating maternal adaptations to pregnancy and mobilizing resources for fetal use. In addition, it acts as a selective barrier, creating a protective milieu by minimizing exposure of the fetus to maternal hormones, such as glucocorticoids, xenobiotics, pathogens, and parasites. The placenta shows a remarkable capacity to adapt to adverse environmental cues and lessen their impact on the fetus. However, if placental function is impaired, or its capacity to adapt is exceeded, then fetal development may be compromised. Here, we explore the complex relationships between the placental phenotype and developmental programming of chronic disease in the offspring. Ensuring optimal placentation offers a new approach to the prevention of disorders such as cardiovascular disease, diabetes, and obesity, which are reaching epidemic proportions.

Intrauterine Growth Restriction: Hungry for an Answer

Intrauterine growth restriction (IUGR) has been defined in several ways, but in general describes a condition in which the fetus exhibits poor growth in utero. This complication of pregnancy poses a significant public health burden as well as increased morbidity and mortality for the offspring. In human IUGR, alteration in fetal glucose and insulin homeostasis occurs in an effort to conserve energy and survive at the expense of fetal growth in an environment of inadequate nutrient provision. Several animal models of IUGR have been utilized to study the effects of IUGR on fetal glucose handling, as well as the postnatal reprogramming of energy metabolite handling, which may be unmasked in adulthood as a maladaptive propensity for cardiometabolic disease. This developmental programming may be mediated in part by epigenetic modification of essential regulators of glucose homeostasis. Several pharmacological therapies and nonpharmacological lifestyle modifications have shown early promise in mitigating the risk for or severity of adult metabolic phenotypes but still require further study of unanticipated and/or untoward side effects.

The Effect of Zinc Supplementation on Expressed Levels of Peroxisome Proliferator-Activated Receptor Gamma and Glucose Transporter Type 1 Genes in Newborns of Women with Gestational Diabetes Mellitus

The current study was designed to determine the beneficial effects of zinc supplementation on expressed levels of peroxisome proliferator-activated receptor gamma (PPAR-γ) and glucose transporter type 1 (GLUT1) genes in newborns of women with gestational diabetes mellitus (GDM). This randomized, double-blind, placebo-controlled clinical trial was performed among 40 women with GDM. Patients were randomly allocated to intake either 233 mg zinc gluconate (containing 30 mg zinc) (n = 20) or a placebo (n = 20) for 6 weeks. PPAR-γ and GLUT1 mRNA levels were quantified in umbilical cord blood of newborns of women with GDM. After 6 weeks of intervention, the change in serum zinc levels was greater in women consuming zinc than in the placebo group (+11.1 ± 13.4 vs. -4.8 ± 17.3 mg/dL, P = 0.002). Quantitative results of RT-PCR demonstrated that compared with the placebo, zinc supplementation resulted in a significant increase of expressed levels of PPAR-γ mRNA (P < 0.001) and GLUT1 mRNA (P < 0.001) in umbilical cord blood of newborns of women with GDM. Taken together, the current study demonstrated that zinc supplementation for 6 weeks among GDM women increased the mRNA levels of PPAR-γ and GLUT1 in their newborns compared with the placebo group.

A physiological increase in maternal cortisol alters uteroplacental metabolism in the pregnant ewe

Key points

Fetal nutrient supply is dependent, in part, upon the transport capacity and metabolism of the placenta.

The stress hormone, cortisol, alters metabolism in the adult and fetus but it is not known whether cortisol in the pregnant mother affects metabolism of the placenta.

In this study, when cortisol concentrations were raised in pregnant sheep by infusion, proportionately more of the glucose taken up by the uterus was consumed by the uteroplacental tissues while less was transferred to the fetus, despite an increased placental glucose transport capacity. Concomitantly, the uteroplacental tissues produced lactate at a greater rate.

The results show that maternal cortisol concentrations regulate uteroplacental glycolytic metabolism, producing lactate for use in utero.

Prolonged increases in placental lactate production induced by cortisol overexposure may contribute to the adverse effects of maternal stress on fetal wellbeing.

Abstract

Fetal nutrition is determined by maternal availability, placental transport and uteroplacental metabolism of carbohydrates. Cortisol affects maternal and fetal metabolism, but whether maternal cortisol concentrations within the physiological range regulate uteroplacental carbohydrate metabolism remains unknown. This study determined the effect of maternal cortisol infusion (1.2 mg kg⁻¹ day⁻¹i.v. for 5 days, n = 20) on fetal glucose, lactate and oxygen supplies in pregnant ewes on day ∼130 of pregnancy (term = 145 days). Compared to saline infusion (n = 21), cortisol infusion increased maternal, but not fetal, plasma cortisol (P < 0.05). Cortisol infusion also raised maternal insulin, glucose and lactate concentrations, and blood pH, PCO2 and HCO₃⁻ concentration. Although total uterine glucose uptake determined by Fick's principle was unaffected, a greater proportion was consumed by the uteroplacental tissues, so net fetal glucose uptake was 29% lower in cortisol‐infused than control ewes (P < 0.05). Concomitantly, uteroplacental lactate production was > 2‐fold greater in cortisol‐ than saline‐treated ewes (P < 0.05), although uteroplacental O₂ consumption was unaffected by maternal treatment. Materno‐fetal clearance of non‐metabolizable [³H]methyl‐d‐glucose and placental SLC2A8 (glucose transporter 8) gene expression were also greater with cortisol treatment. Fetal plasma glucose, lactate or α‐amino nitrogen concentrations were unaffected by treatment although fetal plasma fructose and hepatic lactate dehydrogenase activity were greater in cortisol‐ than saline‐treated ewes (P < 0.05). Fetal plasma insulin levels and body weight were also unaffected by maternal treatment. During stress, cortisol‐dependent regulation of uteroplacental glycolysis may allow increased maternal control over fetal nutrition and metabolism. However, when maternal cortisol concentrations are raised chronically, prolonged elevation of uteroplacental lactate production may compromise fetal wellbeing.

Fetal nutrient supply is dependent, in part, upon the transport capacity and metabolism of the placenta.

The stress hormone, cortisol, alters metabolism in the adult and fetus but it is not known whether cortisol in the pregnant mother affects metabolism of the placenta.

In this study, when cortisol concentrations were raised in pregnant sheep by infusion, proportionately more of the glucose taken up by the uterus was consumed by the uteroplacental tissues while less was transferred to the fetus, despite an increased placental glucose transport capacity. Concomitantly, the uteroplacental tissues produced lactate at a greater rate.

The results show that maternal cortisol concentrations regulate uteroplacental glycolytic metabolism, producing lactate for use in utero.

Prolonged increases in placental lactate production induced by cortisol overexposure may contribute to the adverse effects of maternal stress on fetal wellbeing.

Placental phenotype and resource allocation to fetal growth are modified by the timing and degree of hypoxia during mouse pregnancy

Key points

Hypoxia is a major cause of fetal growth restriction, particularly at high altitude, although little is known about its effects on placental phenotype and resource allocation to fetal growth.

In the present study, maternal hypoxia induced morphological and functional changes in the mouse placenta, which depended on the timing and severity of hypoxia, as well as the degree of maternal hypophagia.

Hypoxia at 13% inspired oxygen induced beneficial changes in placental morphology, nutrient transport and metabolic signalling pathways associated with little or no change in fetal growth, irrespective of gestational age.

Hypoxia at 10% inspired oxygen adversely affected placental phenotype and resulted in severe fetal growth restriction, which was due partly to maternal hypophagia.

There is a threshold between 13% and 10% inspired oxygen, corresponding to altitudes of ∼3700 m and 5800 m, respectively, at which the mouse placenta no longer adapts to support fetal resource allocation. This has implications for high altitude human pregnancies.

Abstract

The placenta adapts its transport capacity to nutritional cues developmentally, although relatively little is known about placental transport phenotype in response to hypoxia, a major cause of fetal growth restriction. The present study determined the effects of both moderate hypoxia (13% inspired O₂) between days (D)11 and D16 or D14 and D19 of pregnancy and severe hypoxia (10% inspired O₂) from D14 to D19 on placental morphology, transport capacity and fetal growth on D16 and D19 (term∼D20.5), relative to normoxic mice in 21% O₂. Placental morphology adapted beneficially to 13% O₂; fetal capillary volume increased at both ages, exchange area increased at D16 and exchange barrier thickness reduced at D19. Exposure to 13% O₂ had no effect on placental nutrient transport on D16 but increased placental uptake and clearance of ³H‐methyl‐d‐glucose at D19. By contrast, 10% O₂ impaired fetal vascularity, increased barrier thickness and reduced placental ¹⁴C‐methylaminoisobutyric acid clearance at D19. Consequently, fetal growth was only marginally affected in 13% O₂ (unchanged at D16 and −5% at D19) but was severely restricted in 10% O₂ (−21% at D19). The hypoxia‐induced changes in placental phenotype were accompanied by altered placental insulin‐like growth factor (IGF)‐2 expression and insulin/IGF signalling, as well as by maternal hypophagia depending on the timing and severity of the hypoxia. Overall, the present study shows that the mouse placenta can integrate signals of oxygen and nutrient availability, possibly through the insulin‐IGF pathway, to adapt its phenotype and optimize maternal resource allocation to fetal growth during late pregnancy. It also suggests that there is a threshold between 13% and 10% inspired O₂ at which these adaptations no longer occur.

Hypoxia is a major cause of fetal growth restriction, particularly at high altitude, although little is known about its effects on placental phenotype and resource allocation to fetal growth.

In the present study, maternal hypoxia induced morphological and functional changes in the mouse placenta, which depended on the timing and severity of hypoxia, as well as the degree of maternal hypophagia.

Hypoxia at 13% inspired oxygen induced beneficial changes in placental morphology, nutrient transport and metabolic signalling pathways associated with little or no change in fetal growth, irrespective of gestational age.

Hypoxia at 10% inspired oxygen adversely affected placental phenotype and resulted in severe fetal growth restriction, which was due partly to maternal hypophagia.

There is a threshold between 13% and 10% inspired oxygen, corresponding to altitudes of ∼3700 m and 5800 m, respectively, at which the mouse placenta no longer adapts to support fetal resource allocation. This has implications for high altitude human pregnancies.

The placental mTOR-pathway: correlation with early growth trajectories following intrauterine growth restriction?

Idiopathic intrauterine growth restriction (IUGR) is a result of impaired placental nutrient supply. Newborns with IUGR exhibiting postnatal catch-up growth are of higher risk for cardiovascular and metabolic co-morbidities in adult life. Mammalian target of rapamycin (mTOR) was recently shown to function as a placental nutrient sensor. Thus, we determined possible correlations of members of the placental mTOR signaling cascade with auxologic parameters of postnatal growth. The protein expression and activity of mTOR-pathway signaling components, Akt, AMP-activated protein kinase α, mTOR, p70S6kinase1 and insulin receptor substrate-1 were analysed via western blotting in IUGR v. matched appropriate-for-gestational age (AGA) placentas. Moreover, mTOR was immunohistochemically stained in placental sections. Data from western blot analyses were correlated with retrospective auxological follow-up data at 1 year of age. We found significant catch-up growth in the 1st year of life in the IUGR group. MTOR and its activated form are immunohistochemically detected in multiple placental compartments. We identified correlations of placental mTOR-pathway signaling components to auxological data at birth and at 1 year of life in IUGR. Analysis of the protein expression and phosphorylation level of mTOR-pathway components in IUGR and AGA placentas postpartum, however, did not reveal pathognomonic changes. Our findings suggest that the level of activated mTOR correlates with early catch-up growth following IUGR. However, the complexity of signals converging at the mTOR nexus and its cellular distribution pattern seem to limit its potential as biomarker in this setting.

Metabolic Heat Stress Adaption in Transition Cows: Differences in Macronutrient Oxidation between Late-Gestating and Early-Lactating German Holstein Dairy Cows

High ambient temperatures have severe adverse effects on biological functions of high-yielding dairy cows. The metabolic adaption to heat stress was examined in 14 German Holsteins transition cows assigned to two groups, one heat-stressed (HS) and one pair-fed (PF) at the level of HS. After 6 days of thermoneutrality and ad libitum feeding (P1), cows were challenged for 6 days (P2) by heat stress (temperature humidity index (THI) = 76) or thermoneutral pair-feeding in climatic chambers 3 weeks ante partum and again 3 weeks post-partum. On the sixth day of each period P1 or P2, oxidative metabolism was analyzed for 24 hours in open circuit respiration chambers. Water and feed intake, vital parameters and milk yield were recorded. Daily blood samples were analyzed for glucose, β-hydroxybutyric acid, non-esterified fatty acids, urea, creatinine, methyl histidine, adrenaline and noradrenaline. In general, heat stress caused marked effects on water homeorhesis with impairments of renal function and a strong adrenergic response accompanied with a prevalence of carbohydrate oxidation over fat catabolism. Heat-stressed cows extensively degraded tissue protein as reflected by the increase of plasma urea, creatinine and methyl histidine concentrations. However, the acute metabolic heat stress response in dry cows differed from early-lactating cows as the prepartal adipose tissue was not refractory to lipolytic, adrenergic stimuli, and the rate of amino acid oxidation was lower than in the postpartal stage. Together with the lower endogenous metabolic heat load, metabolic adaption in dry cows is indicative for a higher heat tolerance and the prioritization of the nutritional requirements of the fast-growing near-term fetus. These findings indicate that the development of future nutritional strategies for attenuating impairments of health and performance due to ambient heat requires the consideration of the physiological stage of dairy cows.

Maternal nutrition modifies trophoblast giant cell phenotype and fetal growth in mice

Mammalian placentation is dependent upon the action of trophoblast cells at the time of implantation. Appropriate fetal growth, regulated by maternal nutrition and nutrient transport across the placenta, is a critical factor for adult offspring long-term health. We have demonstrated that a mouse maternal low-protein diet (LPD) fed exclusively during preimplantation development (Emb-LPD) increases offspring growth but programmes adult cardiovascular and metabolic disease. In this study, we investigate the impact of maternal nutrition on post-implantation trophoblast phenotype and fetal growth. Ectoplacental cone explants were isolated at day 8 of gestation from female mice fed either normal protein diet (NPD: 18% casein), LPD (9% casein) or Emb-LPD and cultured in vitro. We observed enhanced spreading and cell division within proliferative and secondary trophoblast giant cells (TGCs) emerging from explants isolated from LPD-fed females when compared with NPD and Emb-LPD explants after 24 and 48 h. Moreover, both LPD and Emb-LPD explants showed substantial expansion of TGC area during 24–48 h, not observed in NPD. No difference in invasive capacity was observed between treatments using Matrigel transwell migration assays. At day 17 of gestation, LPD- and Emb-LPD-fed conceptuses displayed smaller placentas and larger fetuses respectively, resulting in increased fetal:placental ratios in both groups compared with NPD conceptuses. Analysis of placental and yolk sac nutrient signalling within the mammalian target of rapamycin complex 1 pathway revealed similar levels of total and phosphorylated downstream targets across groups. These data demonstrate that early post-implantation embryos modify trophoblast phenotype to regulate fetal growth under conditions of poor maternal nutrition.

The dilution effect and the importance of selecting the right internal control genes for RT-qPCR: a paradigmatic approach in fetal sheep

BACKGROUND

The key to understanding changes in gene expression levels using reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) relies on the ability to rationalize the technique using internal control genes (ICGs). However, the use of ICGs has become increasingly problematic given that any genes, including housekeeping genes, thought to be stable across different tissue types, ages and treatment protocols, can be regulated at transcriptomic level. Our interest in prenatal glucocorticoid (GC) effects on fetal growth has resulted in our investigation of suitable ICGs relevant in this model. The usefulness of RNA18S, ACTB, HPRT1, RPLP0, PPIA and TUBB as ICGs was analyzed according to effects of early dexamethasone (DEX) treatment, gender, and gestational age by two approaches: (1) the classical approach where raw (i.e., not normalized) RT-qPCR data of tested ICGs were statistically analyzed and the best ICG selected based on absence of any significant effect; (2) used of published algorithms. For the latter the geNorm Visual Basic application was mainly used, but data were also analyzed by Normfinder and Bestkeeper. In order to account for confounding effects on the geNorm analysis due to co-regulation among ICGs tested, network analysis was performed using Ingenuity Pathway Analysis software. The expression of RNA18S, the most abundant transcript, and correlation of ICGs with RNA18S, total RNA, and liver-specific genes were also performed to assess potential dilution effect of raw RT-qPCR data. The effect of the two approaches used to select the best ICG(s) was compared by normalization of NR3C1 (glucocorticoid receptor) mRNA expression, as an example for a target gene.

RESULTS

Raw RT-qPCR data of all the tested ICGs was significantly reduced across gestation. TUBB was the only ICG that was affected by DEX treatment. Using approach (1) all tested ICGs would have been rejected because they would initially appear as not reliable for normalization. However, geNorm analysis (approach 2) of the ICGs indicated that the geometrical mean of PPIA, HPRT1, RNA18S and RPLPO can be considered a reliable approach for normalization of target genes in both control and DEX treated groups. Different subset of ICGs were tested for normalization of NR3C1 expression and, despite the overall pattern of the mean was not extremely different, the statistical analysis uncovered a significant influence of the use of different normalization approaches on the expression of the target gene. We observed a decrease of total RNA through gestation, a lower decrease in raw RT-qPCR data of the two rRNA measured compared to ICGs, and a positive correlation between raw RT-qPCR data of ICGs and total RNA. Based on the same amount of total RNA to performed RT-qPCR analysis, those data indicated that other mRNA might have had a large increase in expression and, as consequence, had artificially diluted the stably expressed genes, such as ICGs. This point was demonstrated by a significant negative correlation of raw RT-qPCR data between ICGs and liver-specific genes.

CONCLUSION

The study confirmed the necessity of assessing multiple ICGs using algorithms in order to obtain a reliable normalization of RT-qPCR data. Our data indicated that the use of the geometrical mean of PPIA, HPRT1, RNA18S and RPLPO can provide a reliable normalization for the proposed study. Furthermore, the dilution effect observed support the unreliability of the classical approach to test ICGs. Finally, the observed change in the composition of RNA species through time reveals the limitation of the use of ICGs to normalize RT-qPCR data, especially if absolute quantification is required.

Maternal-fetal nutrient transport in pregnancy pathologies: the role of the placenta

Appropriate in utero growth is essential for offspring development and is a critical contributor to long-term health. Fetal growth is largely dictated by the availability of nutrients in maternal circulation and the ability of these nutrients to be transported into fetal circulation via the placenta. Substrate flux across placental gradients is dependent on the accessibility and activity of nutrient-specific transporters. Changes in the expression and activity of these transporters is implicated in cases of restricted and excessive fetal growth, and may represent a control mechanism by which fetal growth rate attempts to match availability of nutrients in maternal circulation. This review provides an overview of placenta nutrient transport with an emphasis on macro-nutrient transporters. It highlights the changes in expression and activity of these transporters associated with common pregnancy pathologies, including intrauterine growth restriction, macrosomia, diabetes and obesity, as well as the potential impact of maternal diet. Molecular signaling pathways linking maternal nutrient availability and placenta nutrient transport are discussed. How sexual dimorphism affects fetal growth strategies and the placenta’s response to an altered intrauterine environment is considered. Further knowledge in this area may be the first step in the development of targeted interventions to help optimize fetal growth.

The role of placental nutrient sensing in maternal-fetal resource allocation

The placenta mediates maternal-fetal exchange and has historically been regarded as a passive conduit for nutrients. However, emerging evidence suggests that the placenta actively responds to nutritional and metabolic signals from the mother and the fetus. We propose that the placenta integrates a multitude of maternal and fetal nutritional cues with information from intrinsic nutrient-sensing signaling pathways to match fetal demand with maternal supply by regulating maternal physiology, placental growth, and nutrient transport. This process, which we have called placental nutrient sensing, ensures optimal allocation of resources between the mother and the fetus to maximize the chances for propagation of parental genes without jeopardizing maternal health. We suggest that these mechanisms have evolved because of the evolutionary pressures of maternal undernutrition, which result in decreased placental growth and down-regulation of nutrient transporters, thereby limiting fetal growth to ensure maternal survival. These regulatory loops may also function in response to maternal overnutrition, leading to increased placental growth and nutrient transport in cases of maternal obesity or gestational diabetes. Thus, placental nutrient sensing modulates maternal-fetal resource allocation to increase the likelihood of reproductive success. This model implies that the placenta plays a critical role in mediating fetal programming and determining lifelong health.

IGF-IR signal transduction protein content and its activation by IGF-I in human placentas: relationship with gestational age and birth weight

Introduction

The human placenta expresses the IGF-I and IGF-IR proteins and their intracellular signal components (IRS-1, AKT and mTOR). The aim of this study was to assess the IGF-IR content and activation of downstream signaling molecules in placentas from newborns who were classified by gestational age and birth weight. We studied placentas from 25 term appropriate (T-AGA), 26 term small (T-SGA), 22 preterm AGA (PT-AGA), and 20 preterm SGA (PT-SGA) newborns. The total and phosphorylated IGF-IR, IRS-1, AKT, and mTOR contents were determined by Western Blot and normalized by actin or with their respective total content. The effect of IGF-I was determined by stimulating placental explants with recombinant IGF-I 10^-8 mol/L for 15, 30, and 60 minutes.

Results

The IGF-IR content was higher in T-SGA compared to T-AGA placentas, and the IRS-1 content was higher in PT-placentas compared with their respective T-placentas. The effect of IGF-I on the phosphorylated forms of IGF-IR was increased in T-SGA (150%) and PT-SGA (300%) compared with their respective AGA placentas. In addition, AKT serine phosphorylation was higher in PT-SGA compared to PT-AGA and T-SGA placentas (90% and 390% respectively).

Conclusion

The higher protein content and response to IGF-I of IGF-IR, IRS-1, and AKT observed in SGA placentas may represent a compensatory mechanism in response to fetal growth restriction.

Early-life glucocorticoid exposure: the hypothalamic-pituitary-adrenal axis, placental function, and long-term disease risk

An adverse early-life environment is associated with long-term disease consequences. Adversity early in life is hypothesized to elicit developmental adaptations that serve to improve fetal and postnatal survival and prepare the organism for a particular range of postnatal environments. These processes, although adaptive in their nature, may later prove to be maladaptive or disadvantageous if the prenatal and postnatal environments are widely discrepant. The exposure of the fetus to elevated levels of either endogenous or synthetic glucocorticoids is one model of early-life adversity that contributes substantially to the propensity of developing disease. Moreover, early-life glucocorticoid exposure has direct clinical relevance because synthetic glucocorticoids are routinely used in the management of women at risk of early preterm birth. In this regard, reports of adverse events in human newborns have raised concerns about the safety of glucocorticoid treatment; synthetic glucocorticoids have detrimental effects on fetal growth and development, childhood cognition, and long-term behavioral outcomes. Experimental evidence supports a link between prenatal exposure to synthetic glucocorticoids and alterations in fetal development and changes in placental function, and many of these alterations appear to be permanent. Because the placenta is the conduit between the maternal and fetal environments, it is likely that placental function plays a key role in mediating effects of fetal glucocorticoid exposure on hypothalamic-pituitary-adrenal axis development and long-term disease risk. Here we review recent insights into how the placenta responds to changes in the intrauterine glucocorticoid environment and discuss possible mechanisms by which the placenta mediates fetal hypothalamic-pituitary-adrenal development, metabolism, cardiovascular function, and reproduction.

An obesogenic diet during mouse pregnancy modifies maternal nutrient partitioning and the fetal growth trajectory

In developed societies, high-sugar and high-fat (HSHF) diets are now the norm and are increasing the rates of maternal obesity during pregnancy. In pregnant rodents, these diets lead to cardiovascular and metabolic dysfunction in their adult offspring, but the intrauterine mechanisms involved remain unknown. This study shows that, relative to standard chow, HSHF feeding throughout mouse pregnancy increases maternal adiposity (+30%, P<0.05) and reduces fetoplacental growth at d 16 (-10%, P<0.001). At d 19, however, HSHF diet group pup weight had normalized, despite the HSHF diet group placenta remaining small and morphologically compromised. This altered fetal growth trajectory was associated with enhanced placental glucose and amino acid transfer (+35%, P<0.001) and expression of their transporters (+40%, P<0.024). HSHF feeding also up-regulated placental expression of fatty acid transporter protein, metabolic signaling pathways (phosphoinositol 3-kinase and mitogen-activated protein kinase), and several growth regulatory imprinted genes (Igf2, Dlk1, Snrpn, Grb10, and H19) independently of changes in DNA methylation. Obesogenic diets during pregnancy, therefore, alter maternal nutrient partitioning, partly through changes in the placental phenotype, which helps to meet fetal nutrient demands for growth near term. However, by altering provision of specific nutrients, dietary-induced placental adaptations have important roles in programming development with health implications for the offspring in later life.

Stress responses at the endometrial-placental interface regulate labyrinthine placental differentiation from trophoblast stem cells

Development can happen in one of two ways. Cells performing a necessary function can differentiate from stem cells before the need for it arises and stress does not develop. Or need arises before function, stress develops and stress signals are part of the normal stimuli that regulate developmental mechanisms. These mechanisms adjust stem cell differentiation to produce function in a timely and proportional manner. In this review, we will interpret data from studies of null lethal mutants for placental stress genes that suggest the latter possibility. Acknowledged stress pathways participate in stress-induced and -regulated differentiation in two ways. These pathways manage the homeostatic response to maintain stem cells during the stress. Stress pathways also direct stem cell differentiation to increase the first essential lineage and suppress later lineages when stem cell accumulation is diminished. This stress-induced differentiation maintains the conceptus during stress. Pathogenic outcomes arise because population sizes of normal stem cells are first depleted by decreased accumulation. The fraction of stem cells is further decreased by differentiation that is induced to compensate for smaller stem cell populations. Analysis of placental lethal null mutant genes known to mediate stress responses suggests that the labyrinthine placenta develops during, and is regulated by, hypoxic stress.

The emerging role of mTORC1 signaling in placental nutrient-sensing

Nutrient-sensing signaling pathways regulate cell metabolism and growth in response to altered nutrient levels and growth factor signaling. Because trophoblast cell metabolism and associated signaling influence fetal nutrient availability, trophoblast nutrient sensors may have a unique role in regulating fetal growth. We review data in support of a role for mammalian target of rapamycin complex 1 (mTORC1) in placental nutrient-sensing. Placental insulin/IGF-I signaling and fetal levels of oxygen, glucose and amino acids (AAs) are altered in pregnancy complications such as intrauterine growth restriction, and all these factors are well-established upstream regulators of mTORC1. Furthermore, mTORC1 is a positive regulator of placental AA transporters, suggesting that trophoblast mTORC1 modulates AA transfer across the placenta. In addition, placental mTORC1 signaling is also known to be modulated in pregnancy complications associated with altered fetal growth and in animal models in which maternal nutrient availability has been altered experimentally. Recently, significant progress has been made in identifying the molecular mechanisms by which mTORC1 senses AAs, a process requiring shuttling of mTOR to late endosomal and lysosomal compartments (LELs). We recently identified members of the proton-assisted amino acid transporter (PAT/SLC36) family as critical components of the AA-sensing system or 'nutrisome' that regulates mTORC1 on LEL membranes, placing AA transporters and their subcellular regulation both upstream and downstream of mTORC1-driven processes. We propose a model in which placental mTORC1 signaling constitutes a critical link between maternal nutrient availability and fetal growth, thereby influencing the long-term health of the fetus.

Evidence for similar changes in offspring phenotype following either maternal undernutrition or overnutrition: potential impact on fetal epigenetic mechanisms

The goal of this review is to shed light on the role of maternal malnutrition in inducing epigenetic changes in gene expression, leading to alterations in fetal growth and development, and to altered postnatal phenotype and the development of metabolic disease. We present evidence supporting the concept that both maternal undernutrition and overnutrition can induce the same cadre of fetal organ and tissue abnormalities and lead to the same postnatal metabolic changes in the resulting offspring. Furthermore, we present evidence that in both overnourished and undernourished ovine pregnancies, fetuses experience a period of nutrient restriction as a result of alterations in placental delivery of maternal nutrients into the fetal compartment. We argue that this bout of reduced fetal nutrition in undernourished and overnourished pregnancies leads to the development of a thrifty phenotype in which the fetus attempts to alter the function of its tissues and organs to maximise its chances of survival in a postnatal environment that is deficient in nutrients. Importantly, we present evidence to support the concept that these phenotypic changes in offspring quality resulting from maternal malnutrition are transmitted to subsequent generations, independent of their maternal nutritional inputs.