Impact of maternal obesity on placental transcriptome and morphology associated with fetal growth restriction in mice

Effects of fermented wheat germ on the placenta of high-fat diet-induced obese maternal rats: morphology, metabolism, and nutrient transport

Maternal obesity impairs placental function, affecting fetal growth and long-term health. Although fermented wheat germ (FWG) provides health benefits, its impact on maternal obesity-related metabolic disorders and placental function remains unclear. This study investigated FWG's effects on placental morphology, metabolism, and nutrient transport in high-fat diet (HFD)-induced obese maternal rats. Wheat germ (WG) and FWG were administered from model induction, with a 45% HFD-fed for 10 weeks before conception and continued until gestational day 19.5. Results revealed that WG and FWG supplementation alleviated maternal metabolic abnormalities and mitigated placental structural damage. Additionally, this supplementation reduced placental lipid accumulation, oxidative stress, and inflammation while regulating nutrient transporter mRNA expression and inhibiting mTOR signaling activation. Compared with WG, FWG more effectively reduced maternal obesity and optimized placental nutrient transport. These findings suggest that FWG is a promising dietary intervention for disrupting the maternal obesity cycle and enhancing maternal-fetal health by alleviating obesity, mitigating metabolic dysfunction, and modulating placental morphology and function.

The whole is lesser than the sum of its parts? Dissecting layer-enriched samples of rodent placenta is worth the effort

Gene expression in the placenta, assessed by bulk RNA-seq, is a common method to explore placental function. Many rodent studies homogenize the entire placenta, and yet doing so may obscure differences within specific functional regions such as the labyrinth, junctional zone and decidua. Conversely, analysis of the whole placenta could generate apparent differences due to changes in composition (e.g., relative amounts of labyrinth vs junctional zone) rather than differential gene expression. We assess the value of dissecting and separately analysing the labyrinth and junctional zone/decidua by comparing RNA-seq results from the labyrinth, junctional zone/decidua combined, and whole placenta from an experiment examining effects of maternal food restriction and fetal sex in C57BL6/J mice at gestational day 17.5. The number of genes identified as differentially expressed in response to maternal food restriction was substantially higher in the labyrinth (910 genes), than in the junctional zone/decidua (50 genes), which in turn was slightly higher than in the whole placenta (3 genes). Only one gene was differentially expressed in all 3 tissue types, and 20 genes were differentially expressed in both the labyrinth and junctional zone/decidua. The larger number of differentially expressed genes in the labyrinth was due to both larger effect sizes and estimates of effect sizes having smaller standard errors. While dissection to obtain layer-enriched samples is slightly more time-consuming than collection of whole placenta and requires some practice, our results show that layer-enrichment is clearly worth the effort.

GEPREP: A comprehensive data atlas of RNA-seq-based gene expression profiles of exercise responses

BACKGROUND

Physical activity can regulate and affect gene expression in multiple tissues and cells. Recently, with the development of next-generation sequencing, a large number of RNA-sequencing (RNA-seq)-based gene expression profiles about physical activity have been shared in public resources; however, they are poorly curated and underutilized. To tackle this problem, we developed a data atlas of such data through comprehensive data collection, curation, and organization.

METHODS

The data atlas, termed gene expression profiles of RNA-seq-based exercise responses (GEPREP), was built on a comprehensive collection of high-quality RNA-seq data on exercise responses. The metadata of each sample were manually curated. Data were uniformly processed and batch effects corrected. All the information was well organized in an easy-to-use website for free search, visualization, and download.

RESULTS

GEPREP now includes 69 RNA-seq datasets of pre- and post-exercise, comprising 26 human datasets (1120 samples) and 43 mouse datasets (1006 samples). Specifically, there were 977 (87.2 %) human samples of skeletal muscle and 143 (12.8 %) human samples of blood. There were also samples across 9 mice tissues with skeletal muscle (359, 35.7 %) and brain (280, 27.8 %) accounting for the main fractions. Metadata-including subject, exercise interventions, sampling sites, and post-processing methods-are also included. The metadata and gene expression profiles are freely accessible at http://www.geprep.org.cn/.

CONCLUSION

GEPREP is a comprehensive data atlas of RNA-seq-based gene expression profiles responding to exercise. With its reliable annotations and user-friendly interfaces, it has the potential to deepen our understanding of exercise physiology.

Placental structural adaptation to maternal physical activity and sedentary behavior: findings of the DALI lifestyle study

STUDY QUESTION

Are maternal levels of moderate-to-vigorous physical activity (MVPA) and sedentary time (ST) in obese pregnant women associated with placental structural adaptations for facilitating oxygen delivery to the fetus?

SUMMARY ANSWER

Higher maternal MVPA and ST are associated with a higher density of villi, a proxy measure of placental surface area for oxygen delivery to the fetus, without further added placental vessels.

WHAT IS KNOWN ALREADY

Physical activity during pregnancy intermittently reduces uterine blood flow, potentially limiting placental and fetal oxygen supply. The placenta can mount several adaptive responses, including enlargement of the surface area of villi and/or feto-placental vessels to accommodate fetal needs. Early research on the morphology and growth of the placenta with exercise interventions has shown inconsistencies and is lacking, particularly in non-lean pregnant women.

STUDY DESIGN, SIZE, DURATION

This study is a secondary longitudinal analysis of the vitamin D and lifestyle intervention for gestational diabetes prevention (DALI) randomized controlled trial. The prospective study was conducted between 2012 and 2015 in nine European countries at 11 different sites. In this analysis, 92 pregnant women with a BMI ≥ 29 kg/m2 were combined into one cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

MVPA and percentage of time spent sedentary (% ST) were measured with accelerometers during gestation. Placental sections were immunostained for endothelial cell-specific CD34. Artificial intelligence (AI)-based stereology assessed villous density, number, and cross-sectional area of vessels on whole-slide images and in selected regions comprising peripheral villi only, where the majority of vascular adaptations occur. Expression of pro- and anti-angiogenic factors was quantified using molecular counting analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

In multivariable regression, higher levels of maternal MVPA (min/day) were associated with a higher density of villi in both whole-slide images (beta 0.12; 95% CI 0.05, 0.2) and selected regions (0.17; CI 0.07, 0.26). Unexpectedly, ST was also positively associated with density of villi (0.23; CI 0.04, 0.43). MVPA and ST were not associated with vessel count/mm2 villous area, vessel area, or pro- and anti-angiogenic factor mRNA expression. All estimates and statistical significance of the sensitivity analyses excluding smokers, women who developed gestational diabetes or pre-eclampsia and/or pregnancy-induced hypertension were similar in the main analysis.

LIMITATIONS, REASONS FOR CAUTION

The placenta is a complex organ undergoing dynamic changes. While various adjustments were made to account for different maternal contributing factors, in addition to the outcome measures, various other factors could impact oxygen delivery to the fetus.

WIDER IMPLICATIONS OF THE FINDINGS

For the first time, we evaluated the association between placental structures quantified using an AI-based approach with objectively measured physical activity and ST at multiple time points in pregnant women with obesity. The observed adaptations contribute to the advancement of our understanding of the hemodynamics and adaptations of the placental unit in response to MVPA and ST. However, our results might not be generalizable to lean pregnant women.

STUDY FUNDING/COMPETING INTEREST(S)

The DALI project has received funding from the European Community's 7th Framework Program (FP7/2007-2013) under grant agreement no. 242187. The funders had no role in study design, collection of data, analyses, writing of the article, or the decision to submit it for publication. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

ISRCTN70595832.

Obesogenic Diet in Mice Leads to Inflammation and Oxidative Stress in the Mother in Association with Sex-Specific Changes in Fetal Development, Inflammatory Markers and Placental Transcriptome

BACKGROUND

Obesity during pregnancy is related to adverse maternal and neonatal outcomes. Factors involved in these outcomes may include increased maternal insulin resistance, inflammation, oxidative stress, and nutrient mishandling. The placenta is the primary determinant of fetal outcomes, and its function can be impacted by maternal obesity. The aim of this study on mice was to determine the effect of obesity on maternal lipid handling, inflammatory and redox state, and placental oxidative stress, inflammatory signaling, and gene expression relative to female and male fetal growth.

METHODS

Female mice were fed control or obesogenic high-fat/high-sugar diet (HFHS) from 9 weeks prior to, and during, pregnancy. On day 18.5 of pregnancy, maternal plasma, and liver, placenta, and fetal serum were collected to examine the immune and redox states. The placental labyrinth zone (Lz) was dissected for RNA-sequencing analysis of gene expression changes.

RESULTS

the HFHS diet induced, in the dams, hepatic steatosis, oxidative stress (reduced catalase, elevated protein oxidation) and the activation of pro-inflammatory pathways (p38-MAPK), along with imbalanced circulating cytokine concentrations (increased IL-6 and decreased IL-5 and IL-17A). HFHS fetuses were asymmetrically growth-restricted, showing sex-specific changes in circulating cytokines (GM-CSF, TNF-α, IL-6 and IFN-γ). The morphology of the placenta Lz was modified by an HFHS diet, in association with sex-specific alterations in the expression of genes and proteins implicated in oxidative stress, inflammation, and stress signaling. Placental gene expression changes were comparable to that seen in models of intrauterine inflammation and were related to a transcriptional network involving transcription factors, LYL1 and PLAG1.

CONCLUSION

This study shows that fetal growth restriction with maternal obesity is related to elevated oxidative stress, inflammatory pathways, and sex-specific placental changes. Our data are important, given the marked consequences and the rising rates of obesity worldwide.

The Long-Term Effect of Maternal Obesity on the Cardiovascular Health of the Offspring-Systematic Review

Maternal obesity may affect offspring's cardiovascular health. Our literature search using PubMed, Web of Sciences included original English research and Google Scholar articles published over the past ten years, culminating in 96 articles in this topic. A mother's obesity during pregnancy has a negative impact on the cardiovascular risk for their offspring. Dependence was observed in relation to hypertension, coronary artery disease, stroke, and heart failure. The adverse impact of an abnormal diet in pregnant mice on heart hypertrophy was observed, and was also confirmed in human research. Pregnant women with obesity were at greater risk of having a child with innate heart disease than pregnant women with normal mass. To conclude: mother's obesity has a negative impact on the long-term cardiovascular consequences for their offspring, increasing their risk of high blood pressure, coronary heart disease, stroke and heart failure. It also increases the probability of heart hypertrophy and innate heart defects.

Maternal-placental axis and its impact on fetal outcomes, metabolism, and development

Maternal obesity could impact offspring's health. During "critical period" such as pregnancy insults have a significant role in developing chronic diseases later in life. Literature has shown that diet can play a major role in essential metabolic and development processes on fetal outcomes. Moreover, the placenta, an essential organ developed in pregnancy, seems to have its functions impaired based on pre-gestational and gestational nutritional status. Specifically, a high-fat diet has been shown as a potential nutritional insult that also affects the maternal-placental axis, which is involved in offspring development and outcome. Moreover, some classes of nutrients are associated with pregnancy complications such as reduced intake of micronutrients and diabetes, preeclampsia, and preterm delivery. Thus, we will summarize the current literature on maternal environment factors that impacts the placental development and consequently the fetal an offspring health, or the maternal-placental axis, and this on fetal outcomes, metabolism, and development.

The role of gonadal hormones and sex chromosomes in sex-dependent effects of early nutrition on metabolic health

Early-life conditions such as prenatal nutrition can have long-term effects on metabolic health, and these effects may differ between males and females. Understanding the biological mechanisms underlying sex differences in the response to early-life environment will improve interventions, but few such mechanisms have been identified, and there is no overall framework for understanding sex differences. Biological sex differences may be due to chromosomal sex, gonadal sex, or interactions between the two. This review describes approaches to distinguish between the roles of chromosomal and gonadal sex, and summarizes findings regarding sex differences in metabolism. The Four Core Genotypes (FCG) mouse model allows dissociation of the sex chromosome genotype from gonadal type, whereas the XY* mouse model can be used to distinguish effects of X chromosome dosage vs the presence of the Y chromosome. Gonadectomy can be used to distinguish between organizational (permanent) and activational (reversible) effects of sex hormones. Baseline sex differences in a variety of metabolic traits are influenced by both activational and organizational effects of gonadal hormones, as well as sex chromosome complement. Thus far, these approaches have not been widely applied to examine sex-dependent effects of prenatal conditions, although a number of studies have found activational effects of estradiol to be protective against the development of hypertension following early-life adversity. Genes that escape X chromosome inactivation (XCI), such as Kdm5c, contribute to baseline sex-differences in metabolism, while Ogt, another XCI escapee, leads to sex-dependent responses to prenatal maternal stress. Genome-wide approaches to the study of sex differences include mapping genetic loci influencing metabolic traits in a sex-dependent manner. Seeking enrichment for binding sites of hormone receptors among genes showing sexually-dimorphic expression can elucidate the relative roles of hormones. Using the approaches described herein to identify mechanisms underlying sex-dependent effects of early nutrition on metabolic health may enable the identification of fundamental mechanisms and potential interventions.

Sulforaphane induced NRF2 activation in obese pregnancy attenuates developmental redox imbalance and improves early-life cardiovascular function in offspring

In adverse pregnancy a perturbed redox environment is associated with abnormal early-life cardiovascular development and function. Previous studies have noted alterations in the expression and/or activity of Nuclear Factor E2 Related Factor 2 (NRF2) and its antioxidant targets during human gestational diabetic (GDM) pregnancy, however to our knowledge the functional role of NRF2 in fetal 'priming' of cardiovascular dysfunction in obese and GDM pregnancy has not been investigated. Using a murine model of obesity-induced glucose dysregulated pregnancy, we demonstrate that NRF2 activation by maternal sulforaphane (SFN) supplementation normalizes NRF2-linked NQO1, GCL and CuZnSOD expression in maternal and fetal liver placental and fetal heart tissue by gestational day 17.5. Activation of NRF2 in utero in wild type but not NRF2 deficient mice improved markers of placental efficiency and partially restored fetal growth. SFN supplementation was associated with reduced markers of fetal cardiac oxidative stress, including Nox2 and 3-nitrotyrosine, as well as attenuation of cardiac mass and cardiomyocyte area in male offspring by postnatal day 52 and improved vascular function in male and female offspring by postnatal day 98. Our findings are the first to highlight the functional consequences of NRF2 modulation in utero on early-life cardiovascular function in offspring, demonstrating that activation of NRF2 affords cardiovascular protection in offspring of pregnancies affected by redox dysregulation.

The Legacy of Parental Obesity: Mechanisms of Non-Genetic Transmission and Reversibility

While a dramatic increase in obesity and related comorbidities is being witnessed, the underlying mechanisms of their spread remain unresolved. Epigenetic and other non-genetic mechanisms tend to be prominent candidates involved in the establishment and transmission of obesity and associated metabolic disorders to offspring. Here, we review recent findings addressing those candidates, in the context of maternal and paternal influences, and discuss the effectiveness of preventive measures.

Sex-specific effects of maternal dietary carbohydrate quality on fetal development and offspring metabolic phenotype in mice

Objectives

In utero glycemia is an important determinant of fetal growth. Women with gestational diabetes are more likely to deliver large-for-gestational age babies that are at increased risk for obesity. The maternal nutritional state modulates the development of offspring biological systems during the critical periods of gestation and lactation. Carbohydrate typically contributes most of the dietary energy, however, there are very few mechanistic studies investigating the effects of maternal dietary carbohydrate quality on fetal and offspring outcomes. Therefore, we sought to investigate the direct effects of maternal carbohydrate quality on sex-specific offspring metabolic programming.

Methods

Female C57BL/6 mice were fed one of five isocaloric diets: four high-sugar diets based on glucose, sucrose, isomaltulose or fructose (all containing 60% energy as carbohydrate), or a standard, minimally processed, chow diet, and were mated with chow-fed males. Half of the dams were sacrificed for fetus dissection and placental collection, with the remaining giving live birth. All dams were metabolically profiled before and during pregnancy, and pups were similarly profiled at 12 weeks of age.

Results

Overall, glucose-fed dams were heavier and fatter than chow or isomaltulose-fed dams. Female fetuses from glucose and isomaltulose-fed mothers weighed less and had smaller livers, than those from chow-fed mothers, with isomaltulose-fed female fetuses also having decreased placental mass. In contrast, male fetuses responded differently to the maternal diets, with heart mass being significantly increased when their mothers were fed fructose-containing diets, that is, sucrose, isomaltulose and fructose. High-sugar fed female offspring weighed the same, but were significantly fatter, than chow-fed offspring at 12 weeks of age, while glucose and isomaltulose-fed male pups displayed a similar phenotype to their mothers’.

Conclusion

While both glucose and isomaltulose diets constrained fetal growth in females, only placentas from isomaltulose-fed dams were significantly smaller than those from chow-fed mothers, suggesting the mechanisms through which fetal growth is reduced may be different. Female fetuses of isomaltulose-fed mothers were also lighter than sucrose-fed fetuses suggesting the glycemic index, or rate of glucose digestion and absorption, may be an important factor in determining nutrient availability to the growing fetus.

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 body mass index is associated with an altered immunological profile at 28 weeks of gestation

Healthy pregnancy is accompanied by various immunological and metabolic adaptations. Maternal obesity has been implicated in adverse pregnancy outcomes such as miscarriage, preeclampsia, and gestational diabetes mellitus (GDM), while posing a risk to the neonate. There is a lack of knowledge surrounding obesity and the maternal immune system. The objective of this study was to consider if immunological changes in pregnancy are influenced by maternal obesity. Peripheral blood was collected from fasted GDM-negative pregnant women at 26-28 weeks of gestation. Analysis was done using immunoassay, flow cytometry, bioenergetics analysis, and cell culture. The plasma profile was significantly altered with increasing BMI, specifically leptin (r = 0.7635), MCP-1 (r = 0.3024), and IL-6 (r = 0.4985). Circulating leukocyte populations were also affected with changes in the relative abundance of intermediate monocytes (r = -0.2394), CD4:CD8 T-cell ratios (r = 0.2789), and NKT cells (r = -0.2842). Monocytes analysed in more detail revealed elevated CCR2 expression and decreased mitochondrial content with increased BMI. However, LPS-stimulated cytokine production and bioenergetic profile of PBMCs were not affected by maternal BMI. The Th profile skews towards Th17 with increasing BMI; Th2 (r = -0.3202) and Th9 (r = -0.3205) cells were diminished in maternal obesity, and CytoStim™-stimulation exacerbates IL-6 (r = 0.4166), IL-17A (r = 0.2753), IL-17F (r = 0.2973), and IL-22 (r = 0.2257) production with BMI, while decreasing IL-4 (r = -0.2806). Maternal obesity during pregnancy creates an inflammatory microenvironment. Successful pregnancy requires Th2-biased responses yet increasing maternal BMI favours a Th17 response that could be detrimental to pregnancy. Further research should investigate key populations of cells identified here to further understand the immunological challenges that beset pregnant women with obesity.

Placental DNA Methylation Abnormalities in Prenatal Conotruncal Heart Defects

Objective: This study aims to characterize the abnormal changes in placental DNA methylation associated with conotruncal heart defects (CTDs) and the level of methylation as epigenetic biomarkers for CTDs detection. Methods: This was a prospective study involving 28 fetuses diagnosed with CTDs in the second trimester at Beijing Anzhen Hospital between September 2020 and June 2021. These cases were classified into four groups based on their subtypes. 12 normal fetuses were used as controls. Placental tissue was obtained after inducing labor in fetuses. To identify differential methylation sites (DMSs) and regions (DMRs) in cases vs. controls, an Infinium Human Methylation 850 k bead chip was used. Differential methylation was assessed by comparing the β-values for individual CpG loci. Based on the p-value (<0.05), the most discriminating CpG sites were identified. The area under the receiver-operating-characteristics curve (AUC) was used to determine the predictive accuracy of CpG loci with significant methylation changes for CTDs. The function of genes was assessed through KEGG enrichment analysis, Gene Ontology (GO) analysis, and KEGG pathway analysis. Results: In comparison to the control group, the DNA methylation of the placental tissue is significantly different in fetuses with CTDs. We identified the most significantly different methylated loci and they demonstrated excellent individual predictive accuracy for CTDs detection with AUC >0.9 in cases compared with controls. HOXD9, CNN1, NOTCH1, and ECE1 were identified as CTDs-detection candidate genes. Conclusion Our study established the abnormal changes in placental methylation associated with CTDs and potential epigenetic biomarkers for CTDs detection.

Obesity phenotype induced by high-fat diet leads to maternal-fetal constraint, placental inefficiency, and fetal growth restriction in mice

The aim of this study was to investigate certain parameters regarding the maternal-fetal outcomes in a diet-induced obesity model. Obese, glucose-intolerant females who were exposed to a high-fat diet prior to pregnancy had lower placental efficiency and lower birth weight pups compared to the controls. Simple linear regression analyses showed that maternal obesity disrupts the proportionality between maternal and fetal outcomes during pregnancy. Maternal obesity is correlated with fetal outcomes, perhaps because of problems with hormonal signaling and exacerbation of inflammation in the maternal metabolic environment. The maternal obese phenotype altered the thickness of the placental layer, the transport of fatty acids, and the expression of growth factors. For example, lower expression of epidermal growth factor receptor (EGFR) mRNA in the obesity-prone group may have contributed to the rupture of the placental layers, leading to adverse fetal outcomes. Furthermore, maintenance of maternal glucose homeostasis and overexpression of placental growth factor (PGF) in the obesity-resistant group likely protected the placenta and fetuses from morphological and functional damage.

Maternal but not fetoplacental health can be improved by metformin in a murine diet-induced model of maternal obesity and glucose intolerance

Maternal obesity is a global problem that increases the risk of short- and long-term adverse outcomes for mother and child, many of which are linked to gestational diabetes mellitus. Effective treatments are essential to prevent the transmission of poor metabolic health from mother to child. Metformin is an effective glucose lowering drug commonly used to treat gestational diabetes mellitus; however, its wider effects on maternal and fetal health are poorly explored. In this study we used a mouse (C57Bl6/J) model of diet-induced (high sugar/high fat) maternal obesity to explore the impact of metformin on maternal and feto-placental health. Metformin (300 mg kg-1  day-1 ) was given to obese females via the diet and was shown to achieve clinically relevant concentrations in maternal serum (1669 ± 568 nM in late pregnancy). Obese dams developed glucose intolerance during pregnancy and had reduced uterine artery compliance. Metformin treatment of obese dams improved maternal glucose tolerance, reduced maternal fat mass and restored uterine artery function. Placental efficiency was reduced in obese dams, with increased calcification and reduced labyrinthine area. Consequently, fetuses from obese dams weighed less (P < 0.001) at the end of gestation. Despite normalisation of maternal parameters, metformin did not correct placental structure or fetal growth restriction. Metformin levels were substantial in the placenta and fetal circulation (109.7 ± 125.4 nmol g-1 in the placenta and 2063 ± 2327 nM in fetal plasma). These findings reveal the distinct effects of metformin administration during pregnancy on mother and fetus and highlight the complex balance of risk vs. benefits that are weighed in obstetric medical treatments. KEY POINTS: Maternal obesity and gestational diabetes mellitus have detrimental short- and long-term effects for mother and child. Metformin is commonly used to treat gestational diabetes mellitus in many populations worldwide but the effects on fetus and placenta are unknown. In a mouse model of diet-induced obesity and glucose intolerance in pregnancy we show reduced uterine artery compliance, placental structural changes and reduced fetal growth. Metformin treatment improved maternal metabolic health and uterine artery compliance but did not rescue obesity-induced changes in the fetus or placenta. Metformin crossed the placenta into the fetal circulation and entered fetal tissue. Metformin has beneficial effects on maternal health beyond glycaemic control. However, despite improvements in maternal physiology, metformin did not prevent fetal growth restriction or placental ageing. The high uptake of metformin into the placental and fetal circulation highlights the potential for direct immediate effects of metformin on the fetus with possible long-term consequences postnatally.

Obesity Impairs Embryonic Myogenesis by Enhancing BMP Signaling within the Dermomyotome

Obesity during pregnancy leads to adverse health outcomes in offspring. However, the initial effects of maternal obesity (MO) on embryonic organogenesis have yet to be thoroughly examined. Using unbiased single-cell transcriptomic analyses (scRNA-seq), the effects of MO on the myogenic process is investigated in embryonic day 9.5 (E9.5) mouse embryos. The results suggest that MO induces systematic hypoxia, which is correlated with enhanced BMP signaling and impairs skeletal muscle differentiation within the dermomyotome (DM). The Notch-signaling effectors, HES1 and HEY1, which also act down-stream of BMP signaling, suppress myogenic differentiation through transcriptionally repressing the important myogenic regulator MEF2C. Moreover, the major hypoxia effector, HIF1A, enhances expression of HES1 and HEY1 and blocks myogenic differentiation in vitro. In summary, this data demonstrate that MO induces hypoxia and impairs myogenic differentiation by up-regulating BMP signaling within the DM, which may account for the disruptions of skeletal muscle development and function in progeny.

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 Intervention during Obese Glucose-Intolerant Pregnancy Affects Adiposity in Young Adult Mouse Offspring in a Sex-Specific Manner

Background: Metformin is commonly used to treat gestational diabetes mellitus. This study investigated the effect of maternal metformin intervention during obese glucose-intolerant pregnancy on the gonadal white adipose tissue (WAT) of 8-week-old male and female mouse offspring. Methods: C57BL/6J female mice were provided with a control (Con) or obesogenic diet (Ob) to induce pre-conception obesity. Half the obese dams were treated orally with 300 mg/kg/d of metformin (Ob-Met) during pregnancy. Gonadal WAT depots from 8-week-old offspring were investigated for adipocyte size, macrophage infiltration and mRNA expression of pro-inflammatory genes using RT-PCR. Results: Gestational metformin attenuated the adiposity in obese dams and increased the gestation length without correcting the offspring in utero growth restriction and catch-up growth caused by maternal obesity. Despite similar body weight, the Ob and Ob-Met offspring of both sexes showed adipocyte hypertrophy in young adulthood. Male Ob-Met offspring had increased WAT depot weight (p < 0.05), exaggerated adipocyte hyperplasia (p < 0.05 vs. Con and Ob offspring), increased macrophage infiltration measured via histology (p < 0.05) and the mRNA expression of F4/80 (p < 0.05). These changes were not observed in female Ob-Met offspring. Conclusions: Maternal metformin intervention during obese pregnancy causes excessive adiposity, adipocyte hyperplasia and WAT inflammation in male offspring, highlighting sex-specific effects of prenatal metformin exposure on offspring WAT.

Lipid Metabolism Is Dysregulated before, during and after Pregnancy in a Mouse Model of Gestational Diabetes

The aim of the current study was to test the hypothesis that maternal lipid metabolism was modulated during normal pregnancy and that these modulations are altered in gestational diabetes mellitus (GDM). We tested this hypothesis using an established mouse model of diet-induced obesity with pregnancy-associated loss of glucose tolerance and a novel lipid analysis tool, Lipid Traffic Analysis, that uses the temporal distribution of lipids to identify differences in the control of lipid metabolism through a time course. Our results suggest that the start of pregnancy is associated with several changes in lipid metabolism, including fewer variables associated with de novo lipogenesis and fewer PUFA-containing lipids in the circulation. Several of the changes in lipid metabolism in healthy pregnancies were less apparent or occurred later in dams who developed GDM. Some changes in maternal lipid metabolism in the obese-GDM group were so late as to only occur as the control dams' systems began to switch back towards the non-pregnant state. These results demonstrate that lipid metabolism is modulated in healthy pregnancy and the timing of these changes is altered in GDM pregnancies. These findings raise important questions about how lipid metabolism contributes to changes in metabolism during healthy pregnancies. Furthermore, as alterations in the lipidome are present before the loss of glucose tolerance, they could contribute to the development of GDM mechanistically.

Sex-Biased lncRNA Signature in Fetal Growth Restriction (FGR)

Impaired fetal growth is one of the most important causes of prematurity, stillbirth and infant mortality. The pathogenesis of idiopathic fetal growth restriction (FGR) is poorly understood but is thought to be multifactorial and comprise a range of genetic causes. This research aimed to investigate non-coding RNAs (lncRNAs) in the placentas of male and female fetuses affected by FGR. RNA-Seq data were analyzed to detect lncRNAs, their potential target genes and circular RNAs (circRNAs); a differential analysis was also performed. The multilevel bioinformatic analysis enabled the detection of 23,137 placental lncRNAs and 4263 of them were classified as novel. In FGR-affected female fetuses’ placentas (ff-FGR), among 19 transcriptionally active regions (TARs), five differentially expressed lncRNAs (DELs) and 12 differentially expressed protein-coding genes (DEGs) were identified. Within 232 differentially expressed TARs identified in male fetuses (mf-FGR), 33 encompassed novel and 176 known lncRNAs, and 52 DEGs were upregulated, while 180 revealed decreased expression. In ff-FGR ACTA2-AS1, lncRNA expression was significantly correlated with five DEGs, and in mf-FGR, 25 TARs were associated with DELs correlated with 157 unique DEGs. Backsplicing circRNA processes were detected in the range of H19 lncRNA, in both ff- and mf-FGR placentas. The performed global lncRNAs characteristics in terms of fetal sex showed dysregulation of DELs, DEGs and circRNAs that may affect fetus growth and pregnancy outcomes. In female placentas, DELs and DEGs were associated mainly with the vasculature, while in male placentas, disturbed expression predominantly affected immune processes.

Examining Sex Differences in the Human Placental Transcriptome During the First Fetal Androgen Peak

Sex differences in human placenta exist from early pregnancy to term, however, it is unclear whether these differences are driven solely by sex chromosome complement or are subject to differential sex hormonal regulation. Here, we survey the human chorionic villus (CV) transcriptome for sex-linked signatures from 11 to 16 gestational weeks, corresponding to the first window of increasing testis-derived androgen production in male fetuses. Illumina HiSeq RNA sequencing was performed on Lexogen Quantseq 3' libraries derived from CV biopsies (n = 11 females, n = 12 males). Differential expression (DE) was performed to identify sex-linked transcriptional signatures, followed by chromosome mapping, pathway analysis, predicted protein interaction, and post-hoc linear regressions to identify transcripts that trend over time. We observe 322 transcripts DE between male and female CV from 11 to 16 weeks, with 22 transcripts logFC > 1. Contrary to our predictions, the difference between male and female expression of DE autosomal genes was more pronounced at the earlier gestational ages. In females, we found selective upregulation of extracellular matrix components, along with a number of X-linked genes. In males, DE transcripts centered on chromosome 19, with mitochondrial, immune, and pregnancy maintenance-related transcripts upregulated. Among the highest differentially expressed autosomal genes were CCRL2, LGALS13, and LGALS14, which are known to regulate immune cell interactions. Our results provide insight into sex-linked gene expression in late first and early second trimester developing human placenta and lay the groundwork to understand the mechanistic origins of sex differences in prenatal development.