Maternal overweight induced by a diet with high content of saturated fat activates placental mTOR and eIF2alpha signaling and increases fetal growth in rats

METTL3 regulates glucose transporter expression in placenta exposed to hyperglycemia through the mTOR signaling pathway

BACKGROUND

Alterations in the placental expression of glucose transporters (GLUTs), the crucial maternal-fetal nutrient transporters, have been found in women with hyperglycemia in pregnancy (HIP). However, there is still uncertainty about the underlying effect of the high-glucose environment on placental GLUTs expression in HIP.

METHODS

We quantitatively evaluated the activity of mammalian target of rapamycin (mTOR) and expression of GLUTs (GLUT1, GLUT3, and GLUT4) in the placenta of women with normal pregnancies (CTRL, n = 12) and pregnant women complicated with poorly controlled type 2 diabetes mellitus (T2DM, n = 12) by immunohistochemistry. In addition, BeWo cells were treated with different glucose concentrations to verify the regulation of hyperglycemia. Then, changes in the expression of GLUTs following the activation or suppression of the mTOR pathway were also assessed using MHY1485/rapamycin (RAPA) treatment or small interfering RNA (siRNA)-mediated silencing approaches. Moreover, we further explored the alteration and potential upstream regulatory role of methyltransferase-like 3 (METTL3) when exposed to hyperglycemia.

RESULTS

mTOR, phosphorylated mTOR (p-mTOR), and GLUT1 protein levels were upregulated in the placenta of women with T2DM compared with those CTRL. In BeWo cells, mTOR activity increased with increasing glucose concentration, and the expression of GLUT1, GLUT3, and GLUT4 as well as GLUT1 cell membrane translocation were upregulated by hyperglycemia to varying degrees. Both the drug-mediated and genetic depletion of mTOR signaling in BeWo cells suppressed GLUTs expression, whereas MHY1485-induced mTOR activation upregulated GLUTs expression. Additionally, high glucose levels upregulated METTL3 expression and nuclear translocation, and decreasing METTL3 levels suppressed GLUTs expression and mTOR activity and vice versa . Furthermore, in METTL3 knockdown BeWo cells, the inhibitory effect on GLUTs expression was eliminated by activating the mTOR signaling pathway using MHY1485.

CONCLUSION

High-glucose environment-induced upregulation of METTL3 in trophoblasts regulates the expression of GLUTs through mTOR signaling, contributing to disordered nutrient transport in women with HIP.

Early-life exposures and long-term health: adverse gestational environments and the programming of offspring renal and vascular disease

According to the Developmental Origins of Health and Disease hypothesis, exposure to certain environmental influences during early life may be a key determinant of fetal development and short- and long-term offspring health. Indeed, adverse conditions encountered during the fetal, perinatal, and early childhood stages can alter normal development and growth, as well as put the offspring at elevated risk of developing long-term health conditions in adulthood, including chronic kidney disease and cardiovascular diseases. Of relevance in understanding the mechanistic basis of these long-term health conditions are previous findings showing low glomerular number in human intrauterine growth restriction and low birth weight-indicators of a suboptimal intrauterine environment. In different animal models, the main suboptimal intrauterine conditions studied relate to maternal dietary manipulations, poor micronutrient intake, prenatal ethanol exposure, maternal diabetes, glucocorticoid and chemical exposure, hypoxia, and placental insufficiency. These studies have demonstrated changes in kidney structure, glomerular endowment, and expression of key genes and signaling pathways controlling endocrine, excretion, and filtration function of the offspring. This review aims to summarize those studies to uncover the effects and mechanisms by which adverse gestational environments impact offspring renal and vascular health in adulthood. This is important for identifying agents and interventions that can prevent and mitigate the long-term consequences of an adverse intrauterine environment on the subsequent generation.NEW & NOTEWORTHY Human data and experimental animal data show that suboptimal environments during fetal development increase the risk of renal and vascular diseases in adult-life. This is related to permanent changes in kidney structure, function, and expression of genes and signaling pathways controlling filtration, excretion, and endocrine function. Uncovering the mechanisms by which offspring renal development and function is impacted is important for identifying ways to mitigate the development of diseases that strain health care services worldwide.

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.

Metal mixtures modeling identifies birth weight-associated gene networks in the placentas of children born extremely preterm

Prenatal exposure to toxic metals is linked to numerous adverse birth and later-in-life outcomes. These outcomes are tied to disrupted biological processes in fetal-derived tissues including the placenta and umbilical cord yet the precise pathways are understudied in these target tissues. We set out to examine the relationship between metal concentrations in umbilical cord and altered gene expression networks in placental tissue. These novel relationships were investigated in a subset of the Extremely Low Gestational Age Newborn (ELGAN) cohort (n = 226). Prenatal exposure to 11 metals/metalloids was measured using inductively coupled plasma tandem-mass spectrometry (ICP-MS/MS) in cord tissue, ensuring passage through the placental barrier. RNA-sequencing was used to quantify >37,000 mRNA transcripts. Differentially expressed genes (DEGs) were identified with respect to each metal. Weighted gene co-expression analysis identified gene networks modulated by metals. Two innovative mixtures modeling techniques, namely principal components analysis and quantile-based g-computation, were employed to identify genes/gene networks associated with multi-metal exposure. Individually, lead was associated with the strongest genomic response of 191 DEGs. Joint lead and cadmium exposure was related to 657 DEGs, including DNA Methyl Transferase 1 (DNMT1). These genes were enriched for the Eukaryotic Initiation Factor 2 (EIF2) pathway. Four gene networks, each containing genes within a Nuclear Factor kappa-light-chain-enhancer of Activated B Cells (NF-kB)-mediated network, were significantly increased in average expression level in relation to increases in all metal concentrations. All four of these metal mixture-associated gene networks were negatively correlated with important predictors of neonatal health including birth weight, placenta weight, and fetal growth. Bringing together novel methodologies from epidemiological mixtures analyses and toxicogenomics, applied to a unique cohort of extremely preterm children, the present study highlighted critical genes and pathways in the placenta dysregulated by prenatal metal mixtures. These represent potential mechanisms underlying the developmental origins of metal-induced disease.

Infant Mesenchymal Stem Cell Insulin Action Is Associated With Maternal Plasma Free Fatty Acids, Independent of Obesity Status: The Healthy Start Study

Preclinical rodent and nonhuman primate models investigating maternal obesity have highlighted the importance of the intrauterine environment in the development of insulin resistance in offspring; however, it remains unclear if these findings can be translated to humans. To investigate possible intrauterine effects in humans, we isolated mesenchymal stem cells (MSCs) from the umbilical cord tissue of infants born to mothers of normal weight or mothers with obesity. Insulin-stimulated glycogen storage was determined in MSCs undergoing myogenesis in vitro. There was no difference in insulin action based on maternal obesity. However, maternal free fatty acid (FFA) concentration, cord leptin, and intracellular triglyceride content were positively correlated with insulin action. Furthermore, MSCs from offspring born to mothers with elevated FFAs displayed elevated activation of the mTOR signaling pathway. Taken together, these data suggest that infants born to mothers with elevated lipid availability have greater insulin action in MSCs, which may indicate upregulation of growth and lipid storage pathways during periods of maternal overnutrition.

Diet Modification before or during Pregnancy on Maternal and Foetal Outcomes in Rodent Models of Maternal Obesity

The obesity epidemic has serious implications for women of reproductive age; its rising incidence is associated not just with health implications for the mother but also has transgenerational ramifications for the offspring. Increased incidence of diabetes, cardiovascular disease, obesity, and kidney disease are seen in both the mothers and the offspring. Animal models, such as rodent studies, are fundamental to studying maternal obesity and its impact on maternal and offspring health, as human studies lack rigorous controlled experimental design. Furthermore, the short and prolific reproductive potential of rodents enables examination across multiple generations and facilitates the exploration of interventional strategies to mitigate the impact of maternal obesity, both before and during pregnancy. Given that obesity is a major public health concern, it is important to obtain a greater understanding of its pathophysiology and interaction with reproductive health, placental physiology, and foetal development. This narrative review focuses on the known effects of maternal obesity on the mother and the offspring, and the benefits of interventional strategies, including dietary intervention, before or during pregnancy on maternal and foetal outcomes. It further examines the contribution of rodent models of maternal obesity to elucidating pathophysiological pathways of disease development, as well as methods to reduce the impact of obesity on the mothers and the developing foetus. The translation of these findings into the human experience will also be discussed.

Maternal Diet Quality Is Associated with Placental Proteins in the Placental Insulin/Growth Factor, Environmental Stress, Inflammation, and mTOR Signaling Pathways: The Healthy Start ECHO Cohort

BACKGROUND

Maternal nutritional status affects placental function, which may underlie the intrauterine origins of obesity and diabetes. The extent to which diet quality is associated with placental signaling and which specific pathways are impacted is unknown.

OBJECTIVES

To examine sex-specific associations of maternal diet quality according to the Healthy Eating Index (HEI)-developed to align with recommendations from the Dietary Guidelines for Americans-with placental proteins involved in metabolism and mediators of environmental stress, inflammation, and growth factors.

METHODS

Among 108 women from the Healthy Start cohort with a mean ± SD age of 29.0 ± 6.1 y and a prepregnancy BMI (in kg/m2) of 24.8 ± 5.3, we conducted multivariable linear regression analysis stratified by offspring sex. We adjusted for maternal race or ethnicity, age, education, prenatal smoking habits, and physical activity and tested for an association of maternal HEI >57 compared with ≤57 and the abundance and phosphorylation of key proteins involved in insulin/growth factor signaling; mediators of environmental stress, inflammation, and growth factors; mechanistic target of rapamycin signaling proteins; and energy sensing in placental villus samples. HEI >57 was chosen given its prior relevance among Healthy Start mother-child dyads.

RESULTS

In adjusted models, HEI >57 was associated with greater abundance of insulin receptor β (0.80; 95% CI: 0.11, 1.49) in placentas of females. In males, maternal HEI >57 was associated with greater activation and abundance of select placental nutrient-sensing proteins and environmental stress, inflammation, and growth factor proteins (S6K1Thr389/S6K1: 0.81; 95% CI: 0.21, 1.41; JNK1Thr183/Tyr185/JNK1: 0.82; 95% CI: 0.27, 1.37; JNK2Thr183/Tyr185/JNK2: 0.57; 95% CI: 0.02, 1.11).

CONCLUSIONS

Higher-quality diet had sex-specific associations with placental protein abundance/phosphorylation. Given that these proteins have been correlated with neonatal anthropometry, our findings provide insight into modifiable factors and placental pathways that should be examined in future studies as potential links between maternal diet and offspring metabolic health. This trial was registered at clinicaltrials.gov as NCT02273297.

The Placenta's Role in Sexually Dimorphic Fetal Growth Strategies

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

Paternal preconception phthalate exposure alters sperm methylome and embryonic programming

Preconception environmental conditions have been demonstrated to shape sperm epigenetics and subsequently offspring health and development. Our previous findings in humans showed that urinary anti-androgenic phthalate metabolites in males were associated with altered sperm methylation and blastocyst-stage embryo development. To corroborate this, we examined the effect of preconception exposure to di(2-ethylhexyl) phthalate (DEHP) on genome-wide DNA methylation and gene expression profiles in mice. Eight-week old C57BL/6J male mice were exposed to either a vehicle control, low, or high dose of DEHP (2.5 and 25 mg/kg/weight, respectively) for 67 days (~2 spermatogenic cycles) and were subsequently mated with unexposed females. Reduced representation bisulfite sequencing (RRBS) of epididymal sperm was performed and gastrulation stage embryos were collected for RRBS and transcriptome analyses in both embryonic and extra-embryonic lineages. Male preconception DEHP exposure resulted in 704 differentially methylated regions (DMRs; q-value < 0.05; ≥10% methylation change) in sperm, 1,716 DMRs in embryonic, and 3,181 DMRs in extra-embryonic tissue. Of these, 29 DMRs overlapped between sperm and F1 tissues, half of which showed concordant methylation changes between F0 and F1 generations. F1 transcriptomes at E7.5 were also altered by male preconception DEHP exposure including developmental gene families such as Hox, Gata, and Sox. Additionally, gene ontology analyses of DMRs and differentially expressed genes showed enrichment of multiple developmental processes including embryonic development, pattern specification and morphogenesis. These data indicate that spermatogenesis in adult may represent a sensitive window in which exposure to DEHP alters the sperm methylome as well as DNA methylation and gene expression in the developing embryo.

Maternal Metformin Treatment during Gestation and Lactation Improves Skeletal Muscle Development in Offspring of Rat Dams Fed High-Fat Diet

Maternal high-fat (HF) diet is associated with offspring metabolic disorder. This study intended to determine whether maternal metformin (MT) administration during gestation and lactation prevents the effect of maternal HF diet on offspring’s skeletal muscle (SM) development and metabolism. Pregnant Sprague-Dawley rats were divided into four groups according to maternal diet {CHOW (11.8% fat) or HF (60% fat)} and MT administration {control (CT) or MT (300 mg/kg/day)} during gestation and lactation: CH-CT, CH-MT, HF-CT, HF-MT. All offspring were weaned on CHOW diet. SM was collected at weaning and 18 weeks in offspring. Maternal metformin reduced plasma insulin, leptin, triglyceride and cholesterol levels in male and female offspring. Maternal metformin increased MyoD expression but decreased Ppargc1a, Drp1 and Mfn2 expression in SM of adult male and female offspring. Decreased MRF4 expression in SM, muscle dysfunction and mitochondrial vacuolization were observed in weaned HF-CT males, while maternal metformin normalized them. Maternal metformin increased AMPK phosphorylation and decreased 4E-BP1 phosphorylation in SM of male and female offspring. Our data demonstrate that maternal metformin during gestation and lactation can potentially overcome the negative effects of perinatal exposure to HF diet in offspring, by altering their myogenesis, mitochondrial biogenesis and dynamics through AMPK/mTOR pathways in SM.

Prenatal exercise reverses high-fat-diet-induced placental alterations and alters male fetal hypothalamus during late gestation in rats†

Maternal high-fat (HF) diet negatively affects maternal metabolism and placental function. This study aimed to determine whether gestational exercise prevents the effect of HF diet on placental amino acid transporter expression and nutrient-sensing signaling and the fetal response. Pregnant Sprague-Dawley rats were either fed with a CHOW (13.5% fat) or HF (60% fat) diet during gestation and further divided into two subgroups: voluntary exercised and sedentary. Placentae were collected on gestational day (GD) 14 and GD20, and male placentae were used in this study. We found that gestational exercise ameliorated the detrimental effects of HF diet on dams' adiposity, plasma leptin, and insulin concentrations. Maternal exercise did not influence fetoplacental growth but affected male fetal hypothalamic Leprb, Stat3, Insr, Agrp, and Pomc expressions on GD20. Maternal HF diet decreased placental labyrinth thickness and increased system A amino acid transporter SNAT2 expression, while these changes were normalized by exercise. The activation of placental mechanistic target of rapamycin complex 1/4E-BP1 and LepRb/STAT3 signaling might contribute to the increased placental SNAT2 expression in HF-fed dams, which were reversed by exercise on GD20. These data highlight that gestational exercise reverses HF-diet-induced placental alterations during late gestation without influencing fetal growth. However, maternal exercise altered fetal hypothalamic gene expression, which may affect long-term offspring health.

Pre-pregnancy BMI-associated miRNA and mRNA expression signatures in the placenta highlight a sexually-dimorphic response to maternal underweight status

Pre-pregnancy body mass index (BMI) is associated with adverse pregnancy and neonatal health outcomes, with differences in risk observed between sexes. Given that the placenta is a sexually dimorphic organ and critical regulator of development, examining differences in placental mRNA and miRNA expression in relation to pre-pregnancy BMI may provide insight into responses to maternal BMI in utero. Here, genome-wide mRNA and miRNA expression levels were assessed in the placentas of infants born extremely preterm. Differences in expression were evaluated according to pre-pregnancy BMI status (1) overall and (2) in male and female placentas separately. Overall, 719 mRNAs were differentially expressed in relation to underweight status. Unexpectedly, no genes were differentially expressed in relation to overweight or obese status. In male placentas, 572 mRNAs were associated with underweight status, with 503 (70%) overlapping genes identified overall. Notably, 43/572 (8%) of the mRNAs associated with underweight status in male placentas were also gene targets of two miRNAs (miR-4057 and miR-128-1-5p) associated with underweight status in male placentas. Pathways regulating placental nutrient metabolism and angiogenesis were among those enriched in mRNAs associated with underweight status in males. This study is among the first to highlight a sexually dimorphic response to low pre-pregnancy BMI in the placenta.

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.

Lifetime Impact of Cow's Milk on Overactivation of mTORC1: From Fetal to Childhood Overgrowth, Acne, Diabetes, Cancers, and Neurodegeneration

The consumption of cow's milk is a part of the basic nutritional habits of Western industrialized countries. Recent epidemiological studies associate the intake of cow's milk with an increased risk of diseases, which are associated with overactivated mechanistic target of rapamycin complex 1 (mTORC1) signaling. This review presents current epidemiological and translational evidence linking milk consumption to the regulation of mTORC1, the master-switch for eukaryotic cell growth. Epidemiological studies confirm a correlation between cow's milk consumption and birthweight, body mass index, onset of menarche, linear growth during childhood, acne vulgaris, type 2 diabetes mellitus, prostate cancer, breast cancer, hepatocellular carcinoma, diffuse large B-cell lymphoma, neurodegenerative diseases, and all-cause mortality. Thus, long-term persistent consumption of cow's milk increases the risk of mTORC1-driven diseases of civilization. Milk is a highly conserved, lactation genome-controlled signaling system that functions as a maternal-neonatal relay for optimized species-specific activation of mTORC1, the nexus for regulation of eukaryotic cell growth, and control of autophagy. A deeper understanding of milk´s impact on mTORC1 signaling is of critical importance for the prevention of common diseases of civilization.

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.

Disruption of fertility, placenta, pregnancy outcome, and multigenerational inheritance of hepatic steatosis by organotin exposure from contaminated seafood in rats

Early life exposure to endocrine-disrupting chemicals (EDCs) is an emerging risk factor for development of complications later in life and in subsequent generations. We previously demonstrated that exposure to the EDC organotin (OT), which is present in contaminated seafood, resulted in reproductive abnormalities in female rats. However, few studies have explored the effect of OT accumulation in seafood on pregnancy outcomes. This led us to consider the potential effects of the OT present in seafood on fertility, pregnancy, the placenta, and the offspring. In this investigation, we assessed whether exposure to the OT in contaminated seafood resulted in abnormal fertility and pregnancy features and offspring complications. OT in contaminated seafood (LNI) was administered to female rats, and their fertility, pregnancy outcomes, and fetal liver morphology were assessed. LNI caused abnormal fertility, a reduction in the total number of pups, and an increase in serum testosterone levels compared to controls. Furthermore, LNI exposure caused irregular uterine morphology with inflammation and fibrosis and led to a reduction in embryonic implantation. In pregnant rats, LNI caused abnormal lipid profiles and livers with steatosis features. LNI exposure also causes placental morpho-physiology disruption, a high presence of glycogen and inflammatory cells, and irregular lipid profiles. In addition, LNI exposure caused an increase in large amounts of carbohydrate and lipid delivery to the fetus via an increase in placental nutrient sensor protein expressions (GLUT1, IRβ/mTOR and Akt). In both genders of offspring, LNI exposure led to an increase in body weights, liver megakaryocytes, lipid accumulation, and oxidative stress (OS) levels. Collectively, these data suggest that OT exposure from contaminated seafood in female rats leads to reduced fertility, uterine implantation failure, pregnancy and placental metabolic outcome irregularities, offspring adiposity, liver steatosis, and an increase in OS. Furthermore, some of the effects of OT may be the result of obesogenic and multigenerational effects of OT in adult female rats.

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.

Maternal interventions to prevent adverse fetal programming outcomes due to maternal malnutrition: Evidence in animal models

Animal studies indicate that suboptimal conditions during pregnancy adversely impact both maternal health and offspring phenotype, predisposing offspring to development of later-life diseases including obesity, diabetes, cardiovascular diseases, and behavioral and reproductive dysfunction. Effective interventions during pregnancy and/or lactation are needed to improve both maternal and offspring health. This review addresses the relationship between adverse perinatal insults and its negative impact on offspring development and presents some maternal intervention studies in animal models, such as maternal nutrition (diet modification, antioxidants, omega-3-6 (n-3-6), probiotics) or physical activity, which can prevent or alleviate negative outcomes in both mother and offspring.

Immunological observations and transcriptomic analysis of trimester-specific full-term placentas from three Zika virus-infected women

OBJECTIVES

Effects of Zika virus (ZIKV) infection on placental development during pregnancy are unclear.

METHODS

Full-term placentas from three women, each infected with ZIKV during specific pregnancy trimesters, were harvested for anatomic, immunologic and transcriptomic analysis.

RESULTS

In this study, each woman exhibited a unique immune response with raised IL-1RA, IP-10, EGF and RANTES expression and neutrophil numbers during the acute infection phase. Although ZIKV NS3 antigens co-localised to placental Hofbauer cells, the placentas showed no anatomic defects. Transcriptomic analysis of samples from the placentas revealed that infection during trimester 1 caused a disparate cellular response centred on differential eIF2 signalling, mitochondrial dysfunction and oxidative phosphorylation. Despite these, the babies were delivered without any congenital anomalies.

CONCLUSION

These findings should translate to improve clinical prenatal screening procedures for virus-infected pregnant patients.

Pre-pregnancy underweight and obesity are positively associated with small-for-gestational-age infants in a Chinese population

The association between suboptimal pre-pregnancy body mass index (BMI) and small-for-gestational-age (SGA) infants is not well defined. We investigated the association between pre-pregnancy BMI and the risk of SGA infants in a Chinese population. We performed a cohort study among 12029 mothers with a pregnancy. This cohort consisted of pregnant women that were: normal-weight (62.02%), underweight (17.09%), overweight (17.77%) and obese (3.12%). Birth sizes were reduced in the underweight and obese groups compared with the normal-weight group. Linear regression analysis indicated that birth size was positively associated with BMI in both the underweight and normal-weight groups. Further analysis showed that 12.74% of neonates were SGA infants in the underweight group, higher than 7.43% of neonates reported in the normal-weight group (adjusted RR = 1.92; 95% CI: 1.61, 2.30). Unexpectedly, 17.60% of neonates were SGA infants in the obese group, much higher than the normal-weight group (adjusted RR = 2.17; 95% CI: 1.57, 3.00). Additionally, 18.40% of neonates were large-for-gestational-age (LGA) infants in the obese group, higher than 7.26% of neonates reported in the normal-weight group (adjusted RR = 3.00; 95% CI: 2.21, 4.06). These results suggest that pre-pregnancy underweight increases the risk of SGA infants, whereas obesity increases the risks of not only LGA infants, but also SGA infants.

Critical role of mTOR, PPARγ and PPARδ signaling in regulating early pregnancy decidual function, embryo viability and feto-placental growth

STUDY QUESTION

What are the consequences of inhibiting mTOR, the mechanistic target of rapamycin (mTOR), and the peroxisome proliferator activated receptor gamma (PPARγ) and PPARδ pathways in the early post-implantation period on decidual function, embryo viability and feto-placental growth in the rat?

SUMMARY ANSWER

mTOR inhibition from Days 7 to 9 of pregnancy in rats caused decidual PPARγ and PPARδ upregulation on Day 9 of pregnancy and resulted in embryo resorption by Day 14 of pregnancy. PPARγ and PPARδ inhibition differentially affected decidual mTOR signaling and levels of target proteins relevant to lipid histotrophic nutrition and led to reduced feto-placental weights on Day 14 of pregnancy.

WHAT IS KNOWN ALREADY

Although mTOR, PPARγ and PPARδ are nutrient sensors important during implantation, the role of these signaling pathways in decidual function and how they interact in the early post-implantation period are unknown. Perilipin 2 (PLIN2) and fatty acid binding protein 4 (FABP4), two adipogenic proteins involved in lipid histotrophic nutrition, are targets of mTOR and PPAR signaling pathways in a variety of tissues.

STUDY DESIGN, SIZE, DURATION

Rapamycin (mTOR inhibitor, 0.75 mg/kg, sc), T0070907 (PPARγ inhibitor, 0.001 mg/kg, sc), GSK0660 (PPARδ inhibitor, 0.1 mg/kg, sc) or vehicle was injected daily to pregnant rats from Days 7 to 9 of pregnancy and the studies were performed on Day 9 of pregnancy (n = 7 per group) or Day 14 of pregnancy (n = 7 per group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

On Day 9 of pregnancy, rat decidua were collected and prepared for western blot and immunohistochemical studies. On Day 14 of pregnancy, the resorption rate, number of viable fetuses, crown-rump length and placental and decidual weights were determined.

MAIN RESULTS AND THE ROLE OF CHANCE

Inhibition of mTOR in the early post-implantation period led to a reduction in FABP4 protein levels, an increase in PLIN2 levels and an upregulation of PPARγ and PPARδ in 9-day-pregnant rat decidua. Most embryos were viable on Day 9 of pregnancy but had resorbed by Day 14 of pregnancy. This denotes a key function of mTOR in the post-implantation period and suggests that activation of PPAR signaling was insufficient to compensate for impaired nutritional/survival signaling induced by mTOR inhibition. Inhibition of PPARγ signaling resulted in decreased decidual PLIN2 and FABP4 protein expression as well as in inhibition of decidual mTOR signaling in Day 9 of pregnancy. This treatment also reduced feto-placental growth on Day 14 of pregnancy, revealing the relevance of PPARγ signaling in sustaining post-implantation growth. Moreover, following inhibition of PPARδ, PLIN2 levels were decreased and mTOR complex 1 and 2 signaling was altered in decidua on Day 9 of pregnancy. On Day 14 of pregnancy, PPARδ inhibition caused reduced feto-placental weight, increased decidual weight and increased resorption rate, suggesting a key role of PPARδ in sustaining post-implantation development.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

This is an in vivo animal study and the relevance of the results for humans remains to be established.

WIDER IMPLICATIONS OF THE FINDINGS

The early post-implantation period is a critical window of development and changes in the intrauterine environment may cause embryo resorption and lead to placental and fetal growth restriction. mTOR, PPARγ and PPARδ signaling are decidual nutrient sensors with extensive cross-talk that regulates adipogenic proteins involved in histotrophic nutrition and important for embryo viability and early placental and fetal development and growth.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided by the Agencia Nacional de Promoción Científica y Tecnológica de Argentina (PICT 2014-411 and PICT 2015-0130), and by the International Cooperation (Grants CONICET-NIH-2014 and CONICET-NIH-2017) to A.J. and T.J. The authors have no conflicts of interest.

Effects of high-fat diets on fetal growth in rodents: a systematic review

BACKGROUND

Maternal nutrition during pregnancy has life-long consequences for offspring. However, the effects of maternal overnutrition and/ or obesity on fetal growth remain poorly understood, e.g., it is not clear why birthweight is increased in some obese pregnancies but not in others. Maternal obesity is frequently studied using rodents on high-fat diets, but effects on fetal growth are inconsistent. The purpose of this review is to identify factors that contribute to reduced or increased fetal growth in rodent models of maternal overnutrition.

METHODS

We searched Web of Science and screened 2173 abstracts and 328 full texts for studies that fed mice or rats diets providing ~ 45% or ~ 60% calories from fat for 3 weeks or more prior to pregnancy. We identified 36 papers matching the search criteria that reported birthweight or fetal weight.

RESULTS

Studies that fed 45% fat diets to mice or 60% fat diets to rats generally did not show effects on fetal growth. Feeding a 45% fat diet to rats generally reduced birth and fetal weight. Feeding mice a 60% fat diet for 4-9 weeks prior to pregnancy tended to increase in fetal growth, whereas feeding this diet for a longer period tended to reduce fetal growth.

CONCLUSIONS

The high-fat diets used most often with rodents do not closely match Western diets and frequently reduce fetal growth, which is not a typical feature of obese human pregnancies. Adoption of standard protocols that more accurately mimic effects on fetal growth observed in obese human pregnancies will improve translational impact in this field.

Novel roles of mechanistic target of rapamycin signaling in regulating fetal growth†

Mechanistic target of rapamycin (mTOR) signaling functions as a central regulator of cellular metabolism, growth, and survival in response to hormones, growth factors, nutrients, energy, and stress signals. Mechanistic TOR is therefore critical for the growth of most fetal organs, and global mTOR deletion is embryonic lethal. This review discusses emerging evidence suggesting that mTOR signaling also has a role as a critical hub in the overall homeostatic control of fetal growth, adjusting the fetal growth trajectory according to the ability of the maternal supply line to support fetal growth. In the fetus, liver mTOR governs the secretion and phosphorylation of insulin-like growth factor binding protein 1 (IGFBP-1) thereby controlling the bioavailability of insulin-like growth factors (IGF-I and IGF-II), which function as important growth hormones during fetal life. In the placenta, mTOR responds to a large number of growth-related signals, including amino acids, glucose, oxygen, folate, and growth factors, to regulate trophoblast mitochondrial respiration, nutrient transport, and protein synthesis, thereby influencing fetal growth. In the maternal compartment, mTOR is an integral part of a decidual nutrient sensor which links oxygen and nutrient availability to the phosphorylation of IGFBP-1 with preferential effects on the bioavailability of IGF-I in the maternal-fetal interface and in the maternal circulation. These new roles of mTOR signaling in the regulation fetal growth will help us better understand the molecular underpinnings of abnormal fetal growth, such as intrauterine growth restriction and fetal overgrowth, and may represent novel avenues for diagnostics and intervention in important pregnancy complications.

Maternal high-fat diet sex-specifically alters placental morphology and transcriptome in rats: Assessment by next-generation sequencing

INTRODUCTION

Maternal nutrition is an extremely important health issue. We evaluated the impact of maternal high fat diet (HFD) on pregnancy outcomes, elucidated how the rat placenta and fetus respond to diet manipulation based on fetal sex, and identified candidate genes and pathways.

METHODS

Rats were fed a normal or HFD diet for 10 weeks before conception and during gestation. The placenta was collected on gestational day 21 and sexed. Placental histology was analyzed and placental candidate genes and pathways were identified using whole-genome RNA next-generation sequencing.

RESULTS

Pup weights in both sexes from HFD dams were reduced. The weight of the placenta from the HFD group was also decreased in both sexes, but changes in placental layer distributions were only significant for female fetuses. Maternal HFD altered the placental transcriptome in a sex-specific manner. Activation of the placental renin-angiotensin system (RAS) by maternal HFD was associated with fetal growth restriction in both fetal sexes.

CONCLUSIONS

The placenta reacts to maternal HFD by altering the placental layer distribution and gene expression in a sex-specific manner. The male placenta in late gestation is thought to exhibit greater plasticity relative to the female placenta; however, fetuses of both sexes exhibited similar growth restriction. Our data reveal an association between the placental RAS and HFD-induced fetal growth restriction.

Exercise initiated during pregnancy in rats born growth restricted alters placental mTOR and nutrient transporter expression

KEY POINTS

Fetal growth is dependent on effective placental nutrient transportation, which is regulated by mammalian target of rapamycin (mTOR) complex 1 modulation of nutrient transporter expression. These transporters are dysregulated in pregnancies affected by uteroplacental insufficiency and maternal obesity. Nutrient transporters and mTOR were altered in placentae of mothers born growth restricted compared to normal birth weight dams, with maternal diet- and fetal sex-specific responses. Exercise initiated during pregnancy downregulated mTOR protein expression, despite an increase in mTOR activation in male associated placentae, and reduced nutrient transporter gene abundance, which was also dependent on maternal diet and fetal sex. Limited changes were characterized with exercise initiated before and continued throughout pregnancy in nutrient transporter and mTOR expression. Maternal exercise during pregnancy differentially regulated mTOR and nutrient transporters in a diet- and sex-specific manner, which likely aimed to improve late gestational placental growth and neonatal survival.

ABSTRACT

Adequate transplacental nutrient delivery is essential for fetoplacental development. Intrauterine growth restriction and maternal obesity independently alter placental nutrient transporter expression. Although exercise is beneficial for maternal health, limited studies have characterized how the timing of exercise initiation influences placental nutrient transport. Therefore, this study investigated the impact of maternal exercise on placental mechanistic target of rapamycin (mTOR) and nutrient transporter expression in growth restricted mothers and whether these outcomes were dependent on maternal diet or fetal sex. Uteroplacental insufficiency or sham surgery was induced on embryonic day (E) 18 in Wistar-Kyoto rats. F1 offspring were fed a chow or high-fat diet from weaning and at 16 weeks were randomly allocated to an exercise protocol: sedentary, exercised prior to and during pregnancy, or exercised during pregnancy only. Females were mated with normal males (20 weeks) and F2 placentae collected at E20. Exercise during pregnancy only, reduced mTOR protein expression in all groups and increased mTOR activation in male associated placentae. Exercise during pregnancy only, decreased the expression of amino acid transporters in a diet- and sex-specific manner. Maternal growth restriction altered mTOR and system A amino acid transporter expression in a sex- and diet-specific manner. These data highlight that maternal exercise initiated during pregnancy alters placental mTOR expression, which may directly regulate amino acid transporter expression, to a greater extent than exercise initiated prior to and continued during pregnancy, in a diet- and fetal sex-dependent manner. These findings highlight that the timing of exercise initiation is important for optimal placental function.

Feeding a slowly digestible carbohydrate diet during pregnancy of insulin-resistant rats prevents the excess of adipogenesis in their offspring

An obesogenic environment during pregnancy has been shown to increase the risk of dysregulation on adipogenesis and insulin resistance in the offspring. Being essential for the growing fetus, glucose supply is guaranteed by a number of modifications in the mother's metabolism, and thus, glucose control during pregnancy especially among obese or diabetic women is paramount to prevent adverse consequences in their children. Besides the election of low-glycemic-index carbohydrates, the rate of carbohydrate digestion could be relevant to keep a good glucose control. In the present study, we compared the effects of two high-fat diets with similar glycemic load but different rates of carbohydrate digestion given to pregnant insulin-resistant rats. After birth, all animals were fed a standard diet until age 14 weeks. We analyzed offspring body composition, plasma and adipocyte lipidomics, lipid metabolism in adipose tissue and insulin sensitivity. Those animals whose mothers were fed the rapid-digesting carbohydrate diet exhibited an excessive adipogenesis. Thus, these animals showed a marked lipidemia, increased lipid synthesis in the adipose tissue and reduced glucose transporter amount in the adipose. On the contrary, those animals whose mothers were fed the slow-digesting carbohydrate diet showed a profile in the measured parameters closer to that of the offspring of healthy mothers. These results support the hypothesis that not only glycemic index but the rate of carbohydrate digestion during gestation may be critical to regulate the programming of adipogenesis in the offspring.

Altered maternal and placental lipid metabolism and fetal fat development in obesity: Current knowledge and advances in non-invasive assessment

Abnormal maternal lipid profiles, a hallmark of increased maternal adiposity, are associated with pregnancy complications such as preeclampsia and gestational diabetes, and offspring long-term metabolic health is impacted as the consequence of altered fetal growth, physiology and often iatrogenic prematurity. The metabolic changes associated with maternal obesity and/or the consumption of a high-fat diet effecting maternal lipid profiles and metabolism have also been documented to specifically affect placental function and may underlie changes in fetal development and life course disease risk. The placenta plays a critical role in mediating nutritional signals between the fetus and the mother. As obesity rates in women of reproductive age continue to increase, it is becoming evident that inclusion of new technologies that allow for a better understanding of early changes in placental lipid transport and metabolism, non-invasively in maternal circulation, maternal tissues, placenta, fetal circulation and fetal tissues are needed to aid timely clinical diagnosis and treatment for obesity-associated diseases. This review describes pregnancy lipid homeostasis, with specific reference to changes arising from altered maternal body composition on placental and fetal lipid transport and metabolism. Current technologies for lipid assessments, such as metabolomics and lipidomics may be impacted by labour or mode of delivery and are only reflective of a single time point. This review further addresses how established and novel technologies for assessing lipids and their metabolism non-invasively and during the course of pregnancy may guide future research into the effect of maternal metabolic health on pregnancy outcome, placenta and fetus.

Association between Maternal and Foetal Erythrocyte Fatty Acid Profiles and Birth Weight

Regular foetal development is crucial for assuring good health status in the offspring. The quality and quantity of maternal dietary fatty acids (FAs) can affect growth. The study aimed to: (1) investigate the association of maternal/foetal lipid profiles with birth weight (BW); and (2) compare these profiles in small, appropriate, and large for gestational age (SGA, AGA, and LGA) infants. FAs were measured in erythrocyte membranes using gas chromatography analysis in 607 mother–infant pairs (316 males, 52.1%). In the quantile regression, a significant association between BW and levels of maternal linoleic acid (LA; C18:2, n-6; coefficient: 18.66; p = 0.010), arachidonic acid (AA; C20:4, n-6; coefficient: 11.35; p = 0.007), docosahexaenoic acid (DHA; C22:6, n-3; coefficient: 29.73; p = 0.007), polyunsaturated FAs (coefficient: 8.55; p = 0.001), foetal DHA (coefficient: −22.82; p = 0.037), and saturated FAs (coefficient: −65.41; p = 0.002) was found. Myristic (C14:0) and pentadecanoic acids (C15:0), both maternal (p = 0.000; p = 0.017) and foetal (p = 0.009; p = 0.002), and maternal erucic acid (C22:1, n-9; p = 0.026) were found at higher levels in SGA infants as compared to AGA ones. Conversely, maternal LA, AA, and omega 6 FAs levels were higher in AGA infants (p = 0.037; p = 0.003; p = 0.026, respectively). Maternal and foetal polyunsaturated and omega 6 FAs levels are positively related to BW, while a lipid profile rich in saturated FAs and erucic acid may influence the risk of SGA.

Supplementation with polyunsaturated fatty acids in pregnant rats with mild diabetes normalizes placental PPARγ and mTOR signaling in female offspring developing gestational diabetes

Maternal diabetes impairs fetoplacental development and programs metabolic diseases in the offspring. We have previously reported that female offspring of pregnant rats with mild diabetes develop gestational diabetes mellitus (GDM) when they become pregnant. Here, we studied the effects of supplementation with polyunsaturated fatty acids (PUFAs) in pregnant mild diabetic rats (F0) by feeding a 6% safflower-oil-enriched diet from day 1 to 14 followed by a 6% chia-oil-enriched diet from day 14 of pregnancy to term. We analyzed maternal metabolic parameters and placental signaling at term in pregnant offspring (F1). The offspring of both PUFAs-treated and untreated mild diabetic rats developed GDM. Although gestational hyperglycemia was not prevented by dietary PUFAs treatment in F0, triglyceridemia and cholesterolemia in F1 mothers were normalized by F0 PUFAs dietary treatment. In the placenta of F1 GDM rats, PPARγ levels were reduced and lipoperoxidation was increased, changes that were prevented by the maternal diets enriched in PUFAs in the F0 generation. Moreover, fetal overgrowth and placental activation of mTOR signaling pathways were reduced in F1 GDM rats whose mothers were treated with PUFAs diets. These results suggest that F0 PUFAs dietary treatment in pregnancies with mild diabetes improves maternal dyslipidemia, fetal overgrowth and placental signaling in female offspring when they become pregnant. We speculate that an increased PUFAs intake in pregnancies complicated by diabetes may prove effective to ameliorate metabolic programming in the offspring, thereby improving the health of future generations.

The Impact of Traditional Food and Lifestyle Behavior on Epigenetic Burden of Chronic Disease

Noncommunicable chronic diseases (NCCDs) are the leading causes of morbidity and mortality globally. The mismatch between present day diets and ancestral genome is suggested to contribute to the NCCDs burden, which is promoted by traditional risk factors like unhealthy diets, physical inactivity, alcohol and tobacco. However, epigenetic evidence now suggests that cumulatively inherited epigenetic modifications may have made humans more prone to the effects of present day lifestyle factors. Perinatal starvation was widespread in the 19th century. This together with more recent events like increasing consumption of western and low fiber diets, smoking, harmful use of alcohol, physical inactivity, and environmental pollutants may have programed the human epigenome for higher NCCDs risk. In this review, on the basis of available epigenetic data it is hypothesized that transgenerational effects of lifestyle factors may be contributing to the current global burden of NCCDs. Thus, there is a need to reconsider prevention strategies so that the subsequent generations will not have to pay for our sins and those of our ancestors.

Maternal body mass index impacts fetal-placental size at birth and umbilical cord oxygen values with implications for regulatory mechanisms

BACKGROUND

Maternal under- and over-nutrition are known to effect fetal growth with altered placental development and nutrient transport, but whether fetal oxygenation is also altered remains unknown.

AIMS

To examine linkages between maternal BMI and birth weights, placental weights, and umbilical vein and artery PO_2, with implications for signaling mechanisms.

STUDY DESIGN

Population-based cohort study.

SUBJECTS

Analysis of hospital database information on all patients with pre-pregnant BMI values delivering viable, singleton infants between Jan 1, 1999 and Dec 31, 2010 (N=29,212). BMI was categorized into underweight, normal weight, overweight, and obese, with birth weights categorized into small (SGA), appropriate (AGA), and large for gestational age (LGA).

OUTCOME MEASURES

Maternal BMI, birth and placental weights, umbilical vein and artery PO₂.

RESULTS

Underweight mothers with smaller infants and overweight/obese mothers with larger infants had disproportionately large placentas, suggesting compensatory and/or enhanced placental growth in these pregnancies. All SGA infants had lower umbilical vein and artery PO₂, consistent with aberrant placental development leading to diffusional impairment of oxygen. Both maternal overweight/obese BMI and LGA resulted in lower artery PO₂, likely due to increased growth rates with the larger size in these infants.

CONCLUSIONS

These findings support fetal hypoxemia as a common determinant of growth restriction, whether in underweight mothers and due to under-nutrition or in overweight/obese mothers and due to placental insufficiency. However, oxygen is unlikely to be the primary promotor for fetal growth in overweight/obese mothers and LGA infants, with other substrates of more importance as nutritional cues in these pregnancies.

Maternal obesity alters fatty acid oxidation, AMPK activity, and associated DNA methylation in mesenchymal stem cells from human infants

Objective

Infants born to mothers with obesity have greater adiposity, ectopic fat storage, and are at increased risk for childhood obesity and metabolic disease compared with infants of normal weight mothers, though the cellular mechanisms mediating these effects are unclear.

Methods

We tested the hypothesis that human, umbilical cord-derived mesenchymal stem cells (MSCs) from infants born to obese (Ob-MSC) versus normal weight (NW-MSC) mothers demonstrate altered fatty acid metabolism consistent with adult obesity. In infant MSCs undergoing myogenesis in vitro, we measured cellular lipid metabolism and AMPK activity, AMPK activation in response to cellular nutrient stress, and MSC DNA methylation and mRNA content of genes related to oxidative metabolism.

Results

We found that Ob-MSCs exhibit greater lipid accumulation, lower fatty acid oxidation (FAO), and dysregulation of AMPK activity when undergoing myogenesis in vitro. Further experiments revealed a clear phenotype distinction within the Ob-MSC group where more severe MSC metabolic perturbation corresponded to greater neonatal adiposity and umbilical cord blood insulin levels. Targeted analysis of DNA methylation array revealed Ob-MSC hypermethylation in genes regulating FAO (PRKAG2, ACC2, CPT1A, SDHC) and corresponding lower mRNA content of these genes. Moreover, MSC methylation was positively correlated with infant adiposity.

Conclusions

These data suggest that greater infant adiposity is associated with suppressed AMPK activity and reduced lipid oxidation in MSCs from infants born to mothers with obesity and may be an important, early marker of underlying obesity risk.

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Mesenchymal stem cells from infants of obese mothers have greater lipid content in vitro.

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This is attributable to lower fatty acid oxidation, not greater fatty acid uptake.

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AMPK is dysregulated in these cells and corresponds to higher infant adiposity.

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Epigenetic differences in genes regulating these pathways are observed in the cells.

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.

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.

Prenatal high-fat diet alters placental morphology, nutrient transporter expression, and mtorc1 signaling in rat

OBJECTIVE

This study aimed to determine how the rat placenta and fetus respond to maternal high-fat (HF) diet during gestation and to identify the possible mechanisms.

METHODS

Pregnant Sprague-Dawley rats were fed with standard chow (13.5% fat) or HF (60% fat) diet during gestation. Placentas were collected on gestation day 21.

RESULTS

HF dams had greater fat mass, higher plasma leptin, lower plasma adiponectin, and impaired glucose tolerance during pregnancy. The placental labyrinth thickness was reduced in both male and female fetuses of HF dams. In HF male placentas, glucose transporter 3 gene expression, system A amino acid transporter (SNAT) 2 gene expression, and SNAT2 protein expression were increased through the activation of the mTORC1 4EBP1 branch. In HF female placentas, gene expression of insulin-like growth factor 2 (IGF2) and IGF2 receptor was elevated compared to placentas of females fed standard chow. Although male and female placentas responded differently to prenatal HF diet exposure, both male and female fetal weight was not altered by maternal HF diet.

CONCLUSIONS

Placenta responds and adapts to maternal metabolic changes by altering placental layer thickness, mTORC1 signaling, expression of nutrient transporters, and growth factors in a sex-specific manner.

GDM-Induced Macrosomia Is Reversed by Cav-1 via AMPK-Mediated Fatty Acid Transport and GLUT1-Mediated Glucose Transport in Placenta

Objective

To investigate if the role of Cav-1 in GDM-induced macrosomia is through regulating AMPK signaling pathway in placenta.

Methods

We used diagnostic criteria of gestational diabetes mellitus (GDM) and macrosomia to separate and compare placental protein and mRNA levels from GDM with macrosomia group (GDMM), GDM with normal birth weight group (GDMN) and normal glucose tolerance (NGT) with normal birth weight group (CON). Western blotting was performed to examine differentially expressed proteins of caveolin-1 (Cav-1) and Adenosine monophosphate-activated protein kinase (AMPK) signaling pathway related proteins, including phosphorylated-AMPKα(Thr172), AMPKα, phosphorylated-Acetyl-CoA carboxylase(Ser79) (p-ACC(Ser79)), ACC and glucose transporter 1 (GLUT1) in placenta between the three groups. The mRNA levels of Cav-1, AMPKα, ACC and GLUT1 in placenta were measured by real time-PCR.

Results

In the GDMM placenta group, both protein and mRNA levels of Cav-1 were down-regulated, while GLUT1 was up-regulated; the phosphorylation and mRNA levels of ACC and AMPKα were decreased, but total ACC protein levels were increased compared to both the GDMN (p<0.05) and CON groups (p<0.05). In GDMM placenta group, there was a significant negative correlation observed between neonatal birth weight (NBW) and protein expression levels of Cav-1, p-ACC(Ser79) and p-AMPKα(Thr172) (p<0.05), while positive relationship with ACC and GLUT1 protein levels. Besides, in GDMM group placental mRNA levels, NBW had a positive correlation with GLUT1 (p<0.05), while negative with Cav-1, AMPKα and ACC expression (p<0.05). Cav-1 protein expression was positively associated with p-AMPK and p-ACC (p<0.05), and negatively associated with GLUT1 (p<0.05). Interestingly, p-AMPK protein expression was closely related to p-ACC (p<0.05), but not with GLUT1.

Conclusion

GDM-induced macrosomias have more severe inhibition of Cav-1 expression in placenta. Cav-1 is associated with placental glucose and fatty acid transport via the induction of AMPK signaling pathway and the reduction of GLUT1 signaling pathway to reverse GDM-induced macrosomia.

Transcriptome sequencing reveals genetic mechanisms underlying the transition between the laying and brooding phases and gene expression changes associated with divergent reproductive phenotypes in chickens

Transition from laying to incubation behavior in chicken is an interesting topic in reproductive biology. The decline of incubation behavior in chicken population has led to considerable phenotypic differences in reproductive traits between breeds. However, the exact genetic mechanism of the reproductive phase transition still largely unknown and little is known about the gene expression changes that contribute to the phenotypic differences. We performed mRNA sequencing to investigate the molecular mechanism underlying the transition from laying to brooding and to detect difference in gene regulation underlying the phenotypic diversification using two chicken breeds. The majority of gene expression changes during phase transition were steroidogenesis and hormone-releasing genes. Brooding chickens shared a conservative pattern of greatly inhibited steroidogenic enzyme genes in the pituitary gland, therefore, low levels of steroidogenic enzymes might result in reproductive defects such as ovary regression and brooding onset. The conserved network responsible for brooding behavior was maintained by steroid biosynthesis and hormonal interactions. Interestingly, three transcription factors, SREBF2, NR5A1 and PGR, act as central signal modulators of steroid biosynthesis and hormonal interactions during the transition from laying to brooding modes at the molecular level. Furthermore, Genes correlated with protein synthesis and accumulation showed expression variation between breeds, which might result in different concentrations of and sensitivities to reproduction-related hormones. This study provided a new insight in neuroendocrine system at the molecular level, and helps to understand the genetic and hormonal responses that ultimately translate into behavior in chicken.

The Programming Power of the Placenta

Size at birth is a critical determinant of life expectancy, and is dependent primarily on the placental supply of nutrients. However, the placenta is not just a passive organ for the materno-fetal transfer of nutrients and oxygen. Studies show that the placenta can adapt morphologically and functionally to optimize substrate supply, and thus fetal growth, under adverse intrauterine conditions. These adaptations help meet the fetal drive for growth, and their effectiveness will determine the amount and relative proportions of specific metabolic substrates supplied to the fetus at different stages of development. This flow of nutrients will ultimately program physiological systems at the gene, cell, tissue, organ, and system levels, and inadequacies can cause permanent structural and functional changes that lead to overt disease, particularly with increasing age. This review examines the environmental regulation of the placental phenotype with particular emphasis on the impact of maternal nutritional challenges and oxygen scarcity in mice, rats and guinea pigs. It also focuses on the effects of such conditions on fetal growth and the developmental programming of disease postnatally. A challenge for future research is to link placental structure and function with clinical phenotypes in the offspring.

A novel rat model of gestational diabetes induced by intrauterine programming is associated with alterations in placental signaling and fetal overgrowth

A family history of diabetes predisposes to gestational diabetes mellitus (GDM). We hypothesized that female offspring of rats with pre-gestational diabetes will develop GDM, a pathology associated with fetal overgrowth and altered placental signaling. We found normal glycemia and insulinemia in the offspring from pre-gestational diabetic rats at three months of age. However, consistent with GDM, maternal hyperglycemia and hyperinsulinemia and increased fetal weight were evident when compared to controls. In this intrauterine programmed GDM model, the placentas showed alterations in mTOR pathway: unchanged phosphorylation of 4EBP-1 and PKCα despite reduced total expression of 4EBP-1 and PKCα, and increased phosphorylation of SGK1. GDM placentas also showed reduced expression of PPARα and PPARγ, and increased lipoperoxidation, nitric oxide production and peroxynitrite-induced damage. We conclude that exposure of maternal diabetes in utero programs GDM in the female offspring, leading to a GDM model associated with impaired placental signaling pathways, increased pro-oxidant/pro-inflammatory environment and fetal overgrowth.

Dietary leucine supplementation minimises tumour-induced damage in placental tissues of pregnant, tumour-bearing rats

Background

The occurrence of cancer during pregnancy merges two complex, poorly understood metabolic and hormonal conditions. This association can exacerbate the conditions of both the mother and the foetus. The branched-chain amino acid leucine enhances cellular activity, particularly by increasing protein synthesis. This study aimed to analyse the modulatory effect of a leucine-rich diet on direct and indirect tumour-induced placental damage. This was accomplished by evaluating the expression of genes involved in protein synthesis and degradation and assessing anti-oxidant enzyme activity in placental tissues collected from pregnant, tumour-bearing rats.

Results

Pregnant rats were either implanted with Walker 256 tumour cells or injected with ascitic fluid (to study the indirect effects of tumour growth) and then fed a leucine-rich diet. Animals in a control group underwent the same procedures but were fed a normal diet. On the 20^th day of pregnancy, tumour growth was observed. Dams fed a normoprotein diet showed the greatest tumour growth. Injection with ascitic fluid mimicked the effects of tumour growth. Decreased placental protein synthesis and increased protein degradation were observed in both the tumour-bearing and the ascitic fluid-injected groups that were fed a normoprotein diet. These effects resulted in low placental DNA and protein content and high lipid peroxidation (measured by malondialdehyde content). Decreased placental protein synthesis-related gene expression was observed in the tumour group concomitant with increased expression of genes encoding protein degradation-associated proteins and proteolytic subunits.

Conclusions

Consumption of a leucine-rich diet counteracted the effects produced by tumour growth and injection with ascitic fluid. The diet enhanced cell signalling, ameliorated deficiencies in DNA and protein content, and balanced protein synthesis and degradation processes in the placenta. The improvements in cell signalling included changes in the mTOR/eIF pathway. In conclusion, consumption of a leucine-rich diet improved placental metabolism and cell signalling in tumour-bearing rats, and these changes reduced the deleterious effects caused by tumour growth.

Increased placental fatty acid transporter 6 and binding protein 3 expression and fetal liver lipid accumulation in a mouse model of obesity in pregnancy

Obesity in pregnancy is associated with increased fetal growth and adiposity, which, in part, is determined by transplacental nutrient supply. Trophoblast uptake and intracellular trafficking of lipids are dependent on placental fatty acid transport proteins (FATP), translocase (FAT/CD36), and fatty acid binding proteins (FABP). We hypothesized that maternal obesity in mice leads to increased placental expression of FAT/CD36, FATPs, and FABPs, and lipid accumulation in the fetal liver. C57/BL6J female mice were fed either a control (C; n = 10) or an obesogenic (OB; n = 10) high-fat, high-sugar diet before mating and throughout pregnancy. At E18.5, placentas and fetal livers were collected. Trophoblast plasma membranes (TPM) were isolated from placental homogenates. Expression of FAT/CD36 and FATP (TPM) and FABP (homogenates) was determined by immunoblotting. Gene expression was assessed by RT-quantitative PCR. Sections of fetal livers were stained for Oil Red O, and lipid droplets were quantified. TPM protein expression of FAT/CD36, FATP 2, and FATP 4 was comparable between C and OB groups. Conversely, TPM FATP 6 expression was increased by 35% in OB compared with C placentas without changes in mRNA expression. FABPs 1, 3-5 and PPARγ were expressed in homogenates, and FABP 3 expression increased 27% in OB compared with C placentas; however, no changes were observed in mRNA expression. Lipid droplet accumulation was 10-fold higher in the livers of fetuses from OB compared with C group. We propose that increased lipid transport capacity in obese mice promotes transplacental fatty acid transport and contributes to excess lipid accumulation in the fetal liver.

Activation of placental insulin and mTOR signaling in a mouse model of maternal obesity associated with fetal overgrowth

Fetal overgrowth is common in obese women and is associated with perinatal complications and increased risk for the child to develop metabolic syndrome later in life. Placental nutrient transport capacity has been reported to be increased in obese women giving birth to large infants; however, the underlying mechanisms are not well established. Obesity in pregnancy is characterized by elevated maternal serum insulin and leptin, hormones that stimulate placental amino acid transporters in vitro. We hypothesized that maternal obesity activates placental insulin/IGF-I/mTOR and leptin signaling pathways. We tested this hypothesis in a mouse model of obesity in pregnancy that is associated with fetal overgrowth. C57BL/6J female mice were fed a control (C) or a high-fat/high-sugar (HF/HS) pelleted diet supplemented by ad libitum access to sucrose (20%) solution. Placentas were collected at embryonic day 18.5. Using Western blot analysis, placental mTOR activity was determined along with energy, inflammatory, leptin, and insulin signaling pathways (upstream modulators of mTOR). Phosphorylation of S6 ribosomal protein (S-235/236), 4E-BP1 (T-37/46), Insulin receptor substrate 1 (Y-608), Akt (T-308), and STAT-3 (Y-705) was increased in obese dams. In contrast, expression of placental caspase-1, IкBα, IL-1β, and phosphorylated-JNK(p46/54-T183/Y185) was unaltered. Fetal amino acid availability is a key determinant of fetal growth. We propose that activation of placental insulin/IGF-I/mTOR and leptin signaling pathways in obese mice stimulates placental amino acid transport and contributes to increased fetal growth.

Maternal health and eating habits: metabolic consequences and impact on child health

Apart from direct inheritance and the effects of a shared environment, maternal health, eating habits and diet can affect offspring health by developmental programming. Suboptimal maternal nutrition (i.e., either a reduction or an increase above requirement) or other insults experienced by the developing fetus can induce significant changes in adipose tissue and brain development, energy homeostasis, and the structure of vital organs. These can produce long-lasting adaptations that influence later energy balance, and increase the susceptibility of that individual to obesity and the components of the metabolic syndrome. Studies that elucidate the mechanisms behind these associations will have a positive impact on the health of the future adult population and may help to contain the obesity epidemic.

Adiponectin supplementation in pregnant mice prevents the adverse effects of maternal obesity on placental function and fetal growth

Mothers with obesity or gestational diabetes mellitus have low circulating levels of adiponectin (ADN) and frequently deliver large babies with increased fat mass, who are susceptible to perinatal complications and to development of metabolic syndrome later in life. It is currently unknown if the inverse correlation between maternal ADN and fetal growth reflects a cause-and-effect relationship. We tested the hypothesis that ADN supplementation in obese pregnant dams improves maternal insulin sensitivity, restores normal placental insulin/mechanistic target of rapamycin complex 1 (mTORC1) signaling and nutrient transport, and prevents fetal overgrowth. Compared with dams on a control diet, female C57BL/6J mice fed an obesogenic diet before mating and throughout gestation had increased fasting serum leptin, insulin, and C-peptide, and reduced high-molecular-weight ADN at embryonic day (E) 18.5. Placental insulin and mTORC1 signaling was activated, peroxisome proliferator-activated receptor-α (PPARα) phosphorylation was reduced, placental transport of glucose and amino acids in vivo was increased, and fetal weights were 29% higher in obese dams. Maternal ADN infusion in obese dams from E14.5 to E18.5 normalized maternal insulin sensitivity, placental insulin/mTORC1 and PPARα signaling, nutrient transport, and fetal growth without affecting maternal fat mass. Using a mouse model with striking similarities to obese pregnant women, we demonstrate that ADN functions as an endocrine link between maternal adipose tissue and fetal growth by regulating placental function. Importantly, maternal ADN supplementation reversed the adverse effects of maternal obesity on placental function and fetal growth. Improving maternal ADN levels may serve as an effective intervention strategy to prevent fetal overgrowth caused by maternal obesity.

Maternal High-fat Diet Accelerates Development of Crohn's Disease-like Ileitis in TNFΔARE/WT Offspring

BACKGROUND

Maternal high-fat diet (HFD) and obesity increases the risk of the offspring to develop inflammatory processes in various organs including the gut. We hypothesized that maternal diet-induced obesity programs the fetal gut towards inflammation in a mouse model of genetically-driven Crohn's disease (CD)-like ileitis.

METHODS

TNF(WT/WT) and TNF(ΔARE/WT) dams were fed an experimental control diet (CTRLD; 13 kJ% fat) or HFD (48 kJ%). Offspring mice were fed CTRLD or HFD at 4 weeks of age. Metabolic characteristics and severity of CD-like ileitis was assessed in 8- and 12-week old WT and ARE offspring measuring tissue histopathology and markers of inflammation in the distal ileum as well as plasma cytokine and LPS levels. To study prenatal effects, we laser microdissected fetal intestinal epithelial cells at 17.5 days postconception and performed microarray-based global gene expression analysis.

RESULTS

Maternal HFD significantly accelerated the severity of CD-like ileitis in HFD-fed ARE mice at early life stages associated with increased mucosal neutrophil infiltration, Il12p40 expression, and portal vein LPS levels. In contrast to WT mice, metabolic characteristics of ARE offspring were not affected by maternal HFD. Gene expression patterns in fetal intestinal epithelial cells of ARE mice remained largely unchanged under conditions of maternal diet-induced obesity suggesting that the positive association of intestinal inflammation, portal vein endotoxemia, and plasma TNF levels is independent of prenatal conditioning of the gut epithelium.

CONCLUSIONS

Maternal HFD promotes the early onset of severe CD-like ileitis in genetically susceptible offspring independent of metabolic alterations.