Differential regulation of genes for fetoplacental lipid pathways in pregnancy with gestational and type 1 diabetes mellitus

Sex-Specific Alterations in Placental Proteomics Induced by Intrauterine Hyperglycemia

Gestational diabetes mellitus (GDM) with intrauterine hyperglycemia induces a series of changes in the placenta, which have adverse effects on both the mother and the fetus. The aim of this study was to investigate the changes in the placenta in GDM and its gender differences. In this study, we established an intrauterine hyperglycemia model using ICR mice. We collected placental specimens from mice before birth for histological observation, along with tandem mass tag (TMT)-labeled proteomic analysis, which was stratified by sex. When the analysis was not segregated by sex, the GDM group showed 208 upregulated and 225 downregulated proteins in the placenta, primarily within the extracellular matrix and mitochondria. Altered biological processes included cholesterol metabolism and oxidative stress responses. After stratification by sex, the male subgroup showed a heightened tendency for immune-related pathway alterations, whereas the female subgroup manifested changes in branched-chain amino acid metabolism. Our study suggests that the observed sex differences in placental protein expression may explain the differential impact of GDM on offspring.

Maternal methyl donor supplementation: A potential therapy for metabolic disorder in offspring

The prevalences of diabetes mellitus and obesity are increasing yearly and has become a serious social burden. In addition to genetic factors, environmental factors in early life development are critical in influencing the prevalence of metabolic disorders in offspring. A growing body of evidence suggests the critical role of early methyl donor intervention in offspring health. Emerging studies have shown that methyl donors can influence offspring metabolism through epigenetic modifications and changing metabolism-related genes. In this review, we focus on the role of folic acid, betaine, vitamin B12, methionine, and choline in protecting against metabolic disorders in offspring. To address the current evidence on the potential role of maternal methyl donors, we summarize clinical studies as well as experimental animal models that support the impact of maternal methyl donors on offspring metabolism and discuss the mechanisms of action that may bring about these positive effects. Given the worldwide prevalence of metabolic disorders, these findings could be utilized in clinical practice, in which methyl donor supplementation in the early life years may reverse metabolic disorders in offspring and block the harmful intergenerational effect.

Signature precursor and mature microRNAs in cervical ripening during gestational diabetes mellitus lead to pre-term labor and other impediments in future

Gestational diabetes mellitus (GDM) is a pathological condition in which the placenta releases a hormone called human placental lactogen that prevents maternal insulin uptake. GDM is characterised by varying degrees of carbohydrate intolerance and is first identified during pregnancy. Around 5-17% of pregnancies are GDM pregnancies. Older or obese women have a higher risk of developing GDM during gestation. Hyperglycemia is a classic manifestation of GDM and leads to alterations in eNOS and iNOS expression and subsequently causes ROS and RNS overproduction. ROS and RNS play an important role in maintaining normal physiology, when present in low concentrations. Increased concentrations of ROS is harmful and can cause cellular and tissue damage. Oxidative stress is defined as an imbalance between pro-oxidant and antioxidant molecules that manifests due to hyperglycemia. miRNAs are short, non-coding RNAs that play a critical role in regulating gene expression. Studies have shown that the placenta expresses more than 500 miRNAs, which play a crucial role in trophoblast division, movement, and apoptosis. Latest research has revealed that hyperglycemic conditions and increased oxidative stress, characteristic of GDM, can lead to the dysregulation of miRNAs. The placenta also releases miRNAs into the maternal circulation. The secreted miRNAs are encapsulated in exosomes or vesicles. These exosomes interact with tissues and organs at distant sites, releasing their cargo intracellularly. This crosstalk between hyperglycemia, ROS and miRNA expression in GDM has detrimental effects on both foetal and maternal health. One of the complications of GDM is preterm labour. GDM induced iNOS expression has been implicated in cervical ripening, which in turn causes preterm birth. This article focuses on the speculations of oxidative and nitrative stress markers that lead to detrimental effects in GDM. We have also envisaged the role of non-coding miRNA interactions in regulating gene expression for oxidative damage.

Graphical Abstract

Holistic view of miRNA in GDM. I)(A) Placenta as a metabolic organ that provides the foetus with nutrients, oxygen and hormones to maintain pregnancy. Human placental lactogen (hPL) is one such hormone that is released into maternal circulation. hPL is known to induce insulin resistance. (B) ß-cell dysfunction leads to reduced glucose sensing and insulin production. Insulin resistance, a characteristic of GDM, exacerbates insulin ß cell dysfunction leading to maternal hyperglycemia. Hyperglycemia leads to increased ROS and RNS production through several mechanisms. Consequently, GDM is characterised by increased oxidative and nitrative stress.II)Exposure to maternal hyperglycemia causes increased ROS and RNS production in trophoblast cells. Oxidative stress caused by hyperglycemia may lead to eNOS uncoupling, causing eNOS to behave as a superoxide producing enzyme. iNOS expression in trophoblast cells leads to increased NO production. iNOS-derived NO reacts with ROS to produce RNS, thereby increasing nitrosative stress. Expression of antioxidant defences are reduced. Hyperglycemia and oxidative stress may alter the expression of some miRNAs. Some miRNAs are upregulated while others are downregulated. Some miRNAs are secreted into maternal circulation in the form of exosomes. Oxidative stress markers, nitrative stress markers and circulating miRNAs are found to be increased in maternal circulation.

Sphingolipids and acylcarnitines are altered in placentas from women with gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is the most common medical complication of pregnancy and a severe threat to pregnant people and offspring health. The molecular origins of GDM, and in particular the placental responses, are not fully known. The present study aimed to perform a comprehensive characterisation of the lipid species in placentas from pregnancies complicated with GDM using high-resolution MS lipidomics, with a particular focus on sphingolipids and acylcarnitines in a semi-targeted approach. The results indicated that despite no major disruption in lipid metabolism, placentas from GDM pregnancies showed significant alterations in sphingolipids, mostly lower abundance of total ceramides. Additionally, very long-chain ceramides and sphingomyelins with twenty-four carbons were lower, and glucosylceramides with sixteen carbons were higher in placentas from GDM pregnancies. Semi-targeted lipidomics revealed the strong impact of GDM on the placental acylcarnitine profile, particularly lower contents of medium and long-chain fatty-acyl carnitine species. The lower contents of sphingolipids may affect the secretory function of the placenta, and lower contents of long-chain fatty acylcarnitines is suggestive of mitochondrial dysfunction. These alterations in placental lipid metabolism may have consequences for fetal growth and development.

Association of Maternal Pre-Pregnancy Overweight and Obesity with Childhood Anthropometric Factors and Perinatal and Postnatal Outcomes: A Cross-Sectional Study

BACKGROUND

Pre-pregnancy overweight and obesity in reproductive-aged women becomes a growing tendency in middle- and high-income populations. This study aimed to evaluate whether maternal excess body mass index (BMI) before gestation is associated with children's anthropometric characteristics, as well as perinatal and postnatal outcomes.

METHODS

This was a cross-sectional study performed on 5198 children aged 2-5 years old and their paired mothers, assigned from 9 different areas of Greece. Maternal and childhood anthropometric data, as well as perinatal and postnatal outcomes, were collected from medical history records or validated questionnaires.

RESULTS

Prevalences of 24.4% and 30.6% of overweight/obesity were recorded for the enrolled children and their mothers 2-5 years postpartum. Maternal pre-pregnancy overweight/obesity was more frequently observed in older mothers and female children, and was also associated with high childbirth weight, preterm birth, high newborn ponderal index, caesarean section delivery, diabetes type 1, and childhood overweight/obesity at pre-school age. In multivariate analysis, maternal pre-pregnancy overweight/obesity was independently associated with a higher risk of childhood overweight/obesity at pre-school age, as well as with a higher increased incidence of childbirth weight, caesarean section delivery, and diabetes type 1.

CONCLUSIONS

Maternal overweight/obesity rates before gestation were related with increased childhood weight status at birth and 2-5 years postpartum, highlighting the necessity of encouraging healthy lifestyle promotion, including healthier nutritional habits, and focusing on obesity population policies and nutritional interventions among women of reproductive age.

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

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

Placental Transcriptome Profiling in Subtypes of Diabetic Pregnancies Is Strongly Confounded by Fetal Sex

The placenta is a temporary organ with a unique structure and function to ensure healthy fetal development. Placental dysfunction is involved in pre-eclampsia (PE), fetal growth restriction, preterm birth, and gestational diabetes mellitus (GDM). A diabetic state affects maternal and fetal health and may lead to functional alterations of placental metabolism, inflammation, hypoxia, and weight, amplifying the fetal stress. The placental molecular adaptations to the diabetic environment and the adaptive spatio-temporal consequences to elevated glucose or insulin are largely unknown (2). We aimed to identify gene expression signatures related to the diabetic placental pathology of placentas from women with diabetes mellitus. Human placenta samples (n = 77) consisting of healthy controls, women with either gestational diabetes mellitus (GDM), type 1 or type 2 diabetes, and women with GDM, type 1 or type 2 diabetes and superimposed PE were collected. Interestingly, gene expression differences quantified by total RNA sequencing were mainly driven by fetal sex rather than clinical diagnosis. Association of the principal components with a full set of clinical patient data identified fetal sex as the single main explanatory variable. Accordingly, placentas complicated by type 1 and type 2 diabetes showed only few differentially expressed genes, while possible effects of GDM and diabetic pregnancy complicated by PE were not identifiable in this cohort. We conclude that fetal sex has a prominent effect on the placental transcriptome, dominating and confounding gene expression signatures resulting from diabetes mellitus in settings of well-controlled diabetic disease. Our results support the notion of placenta as a sexual dimorphic organ.

Myo-Inositol Moderates Glucose-Induced Effects on Human Placental 13C-Arachidonic Acid Metabolism

Maternal hyperglycemia is associated with disrupted transplacental arachidonic acid (AA) supply and eicosanoid synthesis, which contribute to adverse pregnancy outcomes. Since placental inositol is lowered with increasing glycemia, and since myo-inositol appears a promising intervention for gestational diabetes, we hypothesized that myo-inositol might rectify glucose-induced perturbations in placental AA metabolism. Term placental explants (n = 19) from women who underwent a mid-gestation oral glucose-tolerance-test were cultured with 13C-AA for 48 h in media containing glucose (5, 10 or 17 mM) and myo-inositol (0.3 or 60 µM). Newly synthesized 13C-AA-lipids were quantified by liquid-chromatography-mass-spectrometry. Increasing maternal fasting glycemia was associated with decreased proportions of 13C-AA-phosphatidyl-ethanolamines (PE, PE-P), but increased proportions of 13C-AA-triacylglycerides (TGs) relative to total placental 13C-AA lipids. This suggests altered placental AA compartmentalization towards storage and away from pools utilized for eicosanoid production and fetal AA supply. Compared to controls (5 mM glucose), 10 mM glucose treatment decreased the amount of four 13C-AA-phospholipids and eleven 13C-AA-TGs, whilst 17 mM glucose increased 13C-AA-PC-40:8 and 13C-AA-LPC. Glucose-induced alterations in all 13C-AA lipids (except PE-P-38:4) were attenuated by concurrent 60 µM myo-inositol treatment. Myo-inositol therefore rectifies some glucose-induced effects, but further studies are required to determine if maternal myo-inositol supplementation could reduce AA-associated pregnancy complications.

Serine Hydrolases in Lipid Homeostasis of the Placenta-Targets for Placental Function?

The metabolic state of pregnant women and their unborn children changes throughout pregnancy and adapts to the specific needs of each gestational week. These adaptions are accomplished by the actions of enzymes, which regulate the occurrence of their endogenous substrates and products in all three compartments: mother, placenta and the unborn. These enzymes determine bioactive lipid signaling, supply, and storage through the generation or degradation of lipids and fatty acids, respectively. This review focuses on the role of lipid-metabolizing serine hydrolases during normal pregnancy and in pregnancy-associated pathologies, such as preeclampsia, gestational diabetes mellitus, or preterm birth. The biochemical properties of each class of lipid hydrolases are presented, with special emphasis on their role in placental function or dysfunction. While, during a normal pregnancy, an appropriate tonus of bioactive lipids prevails, dysregulation and aberrant signaling occur in diseased states. A better understanding of the dynamics of serine hydrolases across gestation and their involvement in placental lipid homeostasis under physiological and pathophysiological conditions will help to identify new targets for placental function in the future.

Altered Lipid Metabolism in Obese Women With Gestational Diabetes and Associations With Offspring Adiposity

CONTEXT

Gestational diabetes (GDM) affects 20 million women/year worldwide and is associated with childhood obesity. Infants of affected mothers have increased adiposity from birth, which leads to obesity in later life. However, it remains unknown whether the effect of GDM upon neonatal body composition is due to hyperglycemia alone or is mediated by other pathways.

OBJECTIVE

To investigate plasma lipid profiles in obese women according to GDM diagnosis, infant birthweight percentiles, and adiposity.

DESIGN

Prospective cohort from UPBEAT trial (ISRCTN 89971375).

SETTING

Hospital and community.

PATIENTS

867 obese pregnant women recruited in early pregnancy, assessed at 28 weeks for GDM. Offspring anthropometry was assessed at birth.

OUTCOME (PRESPECIFIED)

Neonatal birth percentile and abdominal circumference.

METHODS

Lipidomic profiling in the fasting plasma oral glucose tolerance test sample using direct infusion mass spectrometry. Analysis included logistic/linear regression, unadjusted and adjusted for maternal age, body mass index, parity, ethnicity, UPBEAT trial arm, and fetal sex. The limit of significance was P = 0.05 for offspring anthropometry and P = 0.002 for lipidomic data.

RESULTS

GDM in obese women was associated with elevated plasma concentrations of specific diglycerides [DG(32:0)] and triglycerides [TG(48:0), (50:1), (50:2)] containing fatty acids (16:0), (16:1), (18:0), and (18:1), consistent with increased de novo lipogenesis. In the whole cohort, these species were associated with birthweight percentile and neonatal abdominal circumference. Effects upon infant abdominal circumference remained significant after adjustment for maternal glycemia.

CONCLUSIONS

Increased de novo lipogenesis-related species in pregnant women with obesity and GDM are associated with measures of offspring adiposity and may be a target for improving lifelong health.

The Origins of NAFLD: The Potential Implication of Intrauterine Life and Early Postnatal Period

Fetal life and the first few months after birth represent a plastic age, defined as a “window of opportunity”, as the organism is particularly susceptible to environmental pressures and has to adapt to environmental conditions. Several perturbations in pregnancy, such as excessive weight gain, obesity, gestational diabetes mellitus and an inadequate or high-fat diet, have been associated with long-term metabolic consequences in offspring, even without affecting birth weight. Moreover, great interest has also been focused on the relationship between the gut microbiome of early infants and health status in later life. Consistently, in various epidemiological studies, a condition of dysbiosis has been associated with an increased inflammatory response and metabolic alterations in the host, with important consequences on the intestinal and systemic health of the unborn child. This review aims to summarize the current knowledge on the origins of NAFLD, with particular attention to the potential implications of intrauterine life and the early postnatal period. Due to the well-known association between gut microbiota and the risk of NAFLD, a specific focus will be devoted to factors affecting early microbiota formation/composition.

Relationships Between Placental Lipid Activated/Transport-Related Factors and Macrosomia in Healthy Pregnancy

To assess associations between infants with macrosomia and placental expression levels of lipid activated/transport-related factors and umbilical cord blood lipid concentrations in healthy pregnancy. We conducted a case-control study of 38 macrosomic neonates (MS group) and 39 normal-birth-weight newborns (NC group) in a healthy pregnancy. Cord blood lipid levels were measured by automatic biochemical analyzer, mRNA and protein expression levels of placental lipid activated/transport-related factors were determined by real-time polymerase chain reaction and western blot, respectively. Compared with NC group, cord blood total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), and non-esterified fatty acid (NEFA) concentrations were decreased in the MS group. The mRNA and protein expression levels of placental peroxisome proliferator-activated receptors (PPARα, PPARγ), plasma membrane fatty acid-binding protein (FABPpm), and fatty acid translocase (FAT/CD36) were significantly higher in the MS group than the NC group. And there was a weak positive correlation between the expression of PPARγ, FABP4, and FABP3 mRNA in the placenta and the HDLC (r_s = 0.439; P = 0.005), NEFA (r_s = 0.342; P = 0.041), and TG (r_s = 0.349; P = 0.034) levels in the cord blood in the MS group, respectively. After multivariate adjustment, the logistic regression analysis showed that high placental PPARα (adjusted odds ratio [AOR] = 3.022; 95% confidence interval [CI] 1.032-8.853) and FAT/CD36 (AOR=2.989; 95%CI 1.029-8.679) and low LDLC concentration in the cord blood (AOR=0.246; 95%CI 0.080-0.759) increased the risk of macrosomia. The increased PPARα and FAT/CD36 expression levels may influence the occurrence of fetal macrosomia through regulating placental lipid transport.

Increased Fetal Cardiovascular Disease Risk: Potential Synergy Between Gestational Diabetes Mellitus and Maternal Hypercholesterolemia

Cardiovascular diseases (CVD) remain a major cause of death worldwide. Evidence suggests that the risk for CVD can increase at the fetal stages due to maternal metabolic diseases, such as gestational diabetes mellitus (GDM) and maternal supraphysiological hypercholesterolemia (MSPH). GDM is a hyperglycemic, inflammatory, and insulin-resistant state that increases plasma levels of free fatty acids and triglycerides, impairs endothelial vascular tone regulation, and due to the increased nutrient transport, exposes the fetus to the altered metabolic conditions of the mother. MSPH involves increased levels of cholesterol (mainly as low-density lipoprotein cholesterol) which also causes endothelial dysfunction and alters nutrient transport to the fetus. Despite that an association has already been established between MSPH and increased CVD risk, however, little is known about the cellular processes underlying this relationship. Our knowledge is further obscured when the simultaneous presentation of MSPH and GDM takes place. In this context, GDM and MSPH may substantially increase fetal CVD risk due to synergistic impairment of placental nutrient transport and endothelial dysfunction. More studies on the separate and/or cumulative role of both processes are warranted to suggest specific treatment options.

Identification of maternal continuous glucose monitoring metrics related to newborn birth weight in pregnant women with gestational diabetes

PURPOSE

To identify the specific glucose metrics derived from maternal continuous glucose monitoring (CGM) data, which were associated with a higher percentile of offspring birth weight.

METHODS

In this cohort study, we recruited singleton pregnant women with GDM who underwent CGM for 5-14 days at a mean of 28.8 gestational weeks between Jan 2017 and Nov 2018. Commonly used single summary glucose metrics of glucose exposure (including mean 24-h, daytime, and nighttime glucose level) and variability (including J-index and mean amplitude of glycaemic excursions) were derived from CGM data. A novel comprehensive glucose metric-hours per-day spent in a severe variability glucose mode (HSSV)-was identified using the spectral clustering method, which reflects both glucose level and variability. Multiple linear regression models were used to estimate the associations of sex- and gestational age-adjusted birth weight percentile with CGM parameters.

RESULTS

Ninety-seven women comprising 127,279 glucose measurements were included. Each 1-SD increase in maternal nighttime mean glucose level and HSSV was associated with 6.0 (95% CI 0.4, 11.5) and 6.3 (95% CI 0.4, 12.2) percentage points increase in birth weight percentile, respectively. No associations were found between other glucose metrics and birth weight percentile.

CONCLUSION

Nighttime mean glucose level has a comparable effect size to HSSV in association with fetal growth, suggesting that endogenous hyperglycemia might drive the association between maternal hyperglycemia and birth weight. Further studies need to examine the effect of lowering nighttime glucose level and/or HSSV on preventing fetal overgrowth in GDM women.

Placental 13C-DHA metabolism and relationship with maternal BMI, glycemia and birthweight

BACKGROUND

Fetal docosahexaenoic acid (DHA) supply relies on preferential transplacental transfer, which is regulated by placental DHA lipid metabolism. Maternal hyperglycemia and obesity associate with higher birthweight and fetal DHA insufficiency but the role of placental DHA metabolism is unclear.

METHODS

Explants from 17 term placenta were incubated with 13C-labeled DHA for 48 h, at 5 or 10 mmol/L glucose treatment, and the production of 17 individual newly synthesized 13C-DHA labeled lipids quantified by liquid chromatography mass spectrometry.

RESULTS

Maternal BMI positively associated with 13C-DHA-labeled diacylglycerols, triacylglycerols, lysophospholipids, phosphatidylcholine and phosphatidylethanolamine plasmalogens, while maternal fasting glycemia positively associated with five 13C-DHA triacylglycerols. In turn, 13C-DHA-labeled phospholipids and triacylglycerols positively associated with birthweight centile. In-vitro glucose treatment increased most 13C-DHA-lipids, but decreased 13C-DHA phosphatidylethanolamine plasmalogens. However, with increasing maternal BMI, the magnitude of the glucose treatment induced increase in 13C-DHA phosphatidylcholine and 13C-DHA lysophospholipids was curtailed, with further decline in 13C-DHA phosphatidylethanolamine plasmalogens. Conversely, with increasing birthweight centile glucose treatment induced increases in 13C-DHA triacylglycerols were exaggerated, while glucose treatment induced decreases in 13C-DHA phosphatidylethanolamine plasmalogens were diminished.

CONCLUSIONS

Maternal BMI and glycemia increased the production of different placental DHA lipids implying impact on different metabolic pathways. Glucose-induced elevation in placental DHA metabolism is moderated with higher maternal BMI. In turn, findings of associations between many DHA lipids with birthweight suggest that BMI and glycemia promote fetal growth partly through changes in placental DHA metabolism.

Comprehensive analysis of DNA methylation and gene expression profiles in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) has a high prevalence during pregnancy. This research aims to identify genes and their pathways related to GDM by combining bioinformatics analysis.The DNA methylation and gene expression profiles data set was obtained from Gene Expression Omnibus. Differentially expressed genes (DEG) and differentially methylated genes (DMG) were screened by R package limma. The methylation-regulated differentially expressed genes (MeDEGs) were obtained by overlapping the DEGs and DMGs. A protein-protein interaction network was constructed using the search tool for searching interacting genes. The results are visualized in Cytoscape. Disease-related miRNAs and pathways were retrieved from Human MicroRNA Disease Database and Comparative Toxic Genome Database. Real-time quantitative PCR further verified the expression changes of these genes in GDM tissues and normal tissues.After overlapping DEGs and DMGs, 138 MeDEGs were identified. These genes were mainly enriched in the biological processes of the "immune response," "defense response," and "response to wounding." Pathway enrichment shows that these genes are involved in "Antigen processing and presentation," "Graft-versus-host disease," "Type I diabetes mellitus," and "Allograft rejection." Six mRNAs (including superoxide dismutase 2 (SOD2), mitogen-activated protein kinase kinase kinase kinase 3 (MAP4K3), dual specificity phosphatase 5 (DUSP5), p21-activated kinases 2 (PAK2), serine protease inhibitor clade E member 1 (SERPINE1), and protein phosphatase 1 regulatory subunit 15B (PPP1R15B)) were identified as being related to GDM. The results obtained by real-time quantitative PCR are consistent with the results of the microarray analysis.This study identified new types of MeDEGs and discovered their related pathways and functions in GDM, which may be used as molecular targets and diagnostic biomarkers for the precise diagnosis and treatment of GDM.

Current approaches and developments in transcript profiling of the human placenta

BACKGROUND

The placenta is the active interface between mother and foetus, bearing the molecular marks of rapid development and exposures in utero. The placenta is routinely discarded at delivery, providing a valuable resource to explore maternal-offspring health and disease in pregnancy. Genome-wide profiling of the human placental transcriptome provides an unbiased approach to study normal maternal–placental–foetal physiology and pathologies.

OBJECTIVE AND RATIONALE

To date, many studies have examined the human placental transcriptome, but often within a narrow focus. This review aims to provide a comprehensive overview of human placental transcriptome studies, encompassing those from the cellular to tissue levels and contextualize current findings from a broader perspective. We have consolidated studies into overarching themes, summarized key research findings and addressed important considerations in study design, as a means to promote wider data sharing and support larger meta-analysis of already available data and greater collaboration between researchers in order to fully capitalize on the potential of transcript profiling in future studies.

SEARCH METHODS

The PubMed database, National Center for Biotechnology Information and European Bioinformatics Institute dataset repositories were searched, to identify all relevant human studies using ‘placenta’, ‘decidua’, ‘trophoblast’, ‘transcriptome’, ‘microarray’ and ‘RNA sequencing’ as search terms until May 2019. Additional studies were found from bibliographies of identified studies.

OUTCOMES

The 179 identified studies were classifiable into four broad themes: healthy placental development, pregnancy complications, exposures during pregnancy and in vitro placental cultures. The median sample size was 13 (interquartile range 8–29). Transcriptome studies prior to 2015 were predominantly performed using microarrays, while RNA sequencing became the preferred choice in more recent studies. Development of fluidics technology, combined with RNA sequencing, has enabled transcript profiles to be generated of single cells throughout pregnancy, in contrast to previous studies relying on isolated cells. There are several key study aspects, such as sample selection criteria, sample processing and data analysis methods that may represent pitfalls and limitations, which need to be carefully considered as they influence interpretation of findings and conclusions. Furthermore, several areas of growing importance, such as maternal mental health and maternal obesity are understudied and the profiling of placentas from these conditions should be prioritized.

WIDER IMPLICATIONS

Integrative analysis of placental transcriptomics with other ‘omics’ (methylome, proteome and metabolome) and linkage with future outcomes from longitudinal studies is crucial in enhancing knowledge of healthy placental development and function, and in enabling the underlying causal mechanisms of pregnancy complications to be identified. Such understanding could help in predicting risk of future adversity and in designing interventions that can improve the health outcomes of both mothers and their offspring. Wider collaboration and sharing of placental transcriptome data, overcoming the challenges in obtaining sufficient numbers of quality samples with well-defined clinical characteristics, and dedication of resources to understudied areas of pregnancy will undoubtedly help drive the field forward.

Decreased serum human leukocyte antigen-G levels are associated with gestational diabetes mellitus

AIM

This study was designed to determine serum human leukocyte antigen-G (HLA-G) levels and establish whether serum HLA-G level is related with gestational diabetes mellitus (GDM).

METHODS

Twenty-five GDM patients aged between 24 and 34 years and 24 healthy pregnant women aged between 22 and 33 years were included in this study. Health status of subjects was determined by medical history, physical, and obstetric examinations. Absence of family history for Type 2 diabetes mellitus, absence of diagnosis or clinical evidence of any major disease, and absence of medication use altering glucose metabolism constituted the inclusion criteria. GDM cases who are at their 24-28 weeks of pregnancy and who have not been using any oral hypoglycemic agents were included in GDM group. Control group consisted of healthy pregnant women at their 24-28 weeks of pregnancy.

RESULTS

Women with GDM had significantly lower levels of serum HLA-G than controls. HLA-G levels were negatively correlated with all parameters of glucose metabolism including insulin (r = - 0.14; p = 0.338), fasting blood glucose (r = - 0.220; p = 0.129), 1-h oral glucose tolerance test (OGTT) blood glucose (r = - 0.18; p = 0.271), 2-h OGTT blood glucose (r = - 0.314; p = 0.172), homeostasis model assessment (r = - 0.226; p = 0.119), HbA1C (r = -0.342; p = 0.108), and WBC (r = -0.149; p = 0.307). There was a negative correlation between HLA-G and BMI (r = -0.341; p = 0.016).

CONCLUSION

Decreased circulating HLA-G level is found to be associated with insulin resistance and GDM, in this study.

Association between placenta concentrations polybrominated and polychlorinated biphenyls and gestational diabetes mellitus: a case-control study in northwestern Spain

Exposure to persistent organic pollutants begins in uterine life. The study was conducted to evaluate associations between gestational diabetes mellitus and the presence of persistent organic pollutants in placenta samples. They were derived from a birth cohort study in Ourense (NW Spain). Selective pressurized liquid extraction methodologies were used to determine targeted persistent organic pollutants in placenta samples. Cleanup of extracts was performed by solid-phase extraction using EZ-POP cartridges and detection by gas chromatography coupled to tandem mass spectrometry. Statistical calculations were performed by comparing the values obtained in the case and control groups. Statistical significance was considered as p < 0.050. Results: The concentrations of several congeners of polybrominated diphenyl ethers (PBDE) and polychlorinated biphenyls (PCB) presented lower levels in the placentas of expectant mothers with gestational diabetes mellitus when comparing them to the control cohort. This difference was statistically significant. It was revealed that this association was independent of obesity, age, parity, amenorrhoea at birth, or a family history of diabetes mellitus. To the best of our knowledge, this paper reported an inverse relationship between PBDE and PCB levels in placenta and gestational diabetes mellitus for the first time. We believe this may open a door to future studies in this field.

Higher Levels of Triglyceride, Fatty Acid Translocase, and Toll-Like Receptor 4 and Lower Level of HDL-C in Pregnant Women with GDM and Their Close Correlation with Neonatal Weight

OBJECTIVES

In this study, we aimed to compare the levels of maternal blood lipids, placental and venous blood lipid transporters, and inflammatory factor receptors in pregnant women with and without gestational diabetes mellitus (GDM). We also aimed to figure out the relationship between these values and neonatal weight.

METHODS

Fifty pregnant women with GDM under blood glucose control belong to the case group, and 50 pregnant women with normal glucose tolerance in concurrent delivery belong to the control group. Fasting venous blood of these pregnant women was taken 2 weeks before delivery, and umbilical cord blood was collected after delivery. The levels of triglyceride (TG), serum total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol (HDL-C) in maternal blood and umbilical cord blood were tested in the laboratory department of our hospital. The level of toll-like receptor 4 (TLR4) in serum of umbilical veins was detected by the double-antibody sandwich ELISA. Western blot and RT-PCR were used to detect the protein and mRNA expressions of TLR4, LPL, and FAT/CD36 in the placenta.

RESULTS

The level of TG in maternal blood in the case group was remarkably higher than that in the control group, which was opposite to the level of HDL-C. In the umbilical cord blood of women with GDM, the expression of TLR4 increased and was closely correlated with neonatal weight. In the placenta of women with GDM, the expressions of FAT/CD36 and TLR4 increased, and both of them were closely correlated with neonatal weight. Besides, TLR4 in umbilical cord blood increased and was closely correlated with neonatal weight. Although the expression of LPL in the placenta decreased, it had no obvious correlation with neonatal weight.

CONCLUSIONS

TG in maternal blood, TLR4 in the placenta and umbilical cord blood, and FAT/CD36 in the placenta were positively correlated with neonatal weight. However, HDL-C in maternal blood was negatively correlated with neonatal weight. Although the expression of LPL in the placenta reduced due to GDM, it had no correlation with neonatal weight.

Serum lipids and their association with birth weight in metformin and insulin treated patients with gestational diabetes

AIMS

To compare the effects of metformin and insulin treatment on maternal serum lipids in patients with gestational diabetes (GDM), and to analyse the associations between individual lipids and birth weight (BW).

METHODS

This is a secondary analysis of a randomized trial comparing metformin (n = 110) and insulin (n = 107) treatment of GDM. Fasting serum lipidome was measured at baseline (the time of diagnosis, mean 30 gestational weeks, gw) and at 36 gw using nuclear magnetic resonance spectroscopy.

RESULTS

Total and VLDL triglycerides, and VLDL cholesterol increased from baseline to 36 gw in both treatment groups. The rise in triglycerides was greater in the metformin treated patients (p < 0.01). Baseline total and VLDL triglycerides, VLDL cholesterol, and apolipoprotein B to A-1 ratio (apoB/apoA-1) associated positively with BW, more strongly in the metformin group. Among patients in the highest baseline VLDL cholesterol or apoB/apoA-1 quartile, those treated with insulin had lower BWs than those treated with metformin (p < 0.03).

CONCLUSION

Compared to insulin, metformin treatment of GDM led to higher maternal serum concentrations of triglyceride-rich lipoproteins. Especially triglycerides and cholesterol in VLDL were positively associated with BW. Women with high VLDL cholesterol or high apoB/apoA-1 may benefit from insulin treatment over metformin with respect to offspring BW.

Gene expression changes in arterial and venous endothelial cells exposed to gestational diabetes mellitus

We investigated the molecular changes in fetoplacental blood vessel endothelial cells in gestational diabetes mellitus (GDM). Raw gene expression profile data of arterial and venous endothelial cells from GDM complicated pregnancies and healthy controls were downloaded and used for bioinformatic analysis. There were two differentially expressed genes (DEGs) in venous endothelial cells and 178 DEGs in arterial endothelial cells induced by GDM. The altered genes were clustered to pathways associated with cell cycle, p53 signaling pathway, and cellular senescence. The disease associated gene-pathway network that was constructed comprised eight down-regulated genes (including FBXO5, CCNB1, and CDK1), one up-regulated gene (CCND2), hsa04068: FoxO signaling pathway and hsa04114: Oocyte mitosis pathway. CCND2 was a significant node in the microRNA (miRNA)-target network, which was regulated by seven miRNAs that included hsa-miR-1299, hsa-miR-1200, and hsa-miR-miR-593-5p. FBXO5 was a significant node regulated by two miRNAs. CCND2 and FBXO5 were also the significant nodes in the transcriptional factors-target network and integrated regulatory network. The cell cycle pathway was significantly altered in arterial endothelial cells during GDM, which was involved with the differential expression of CCND2 and FBXO5.

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.

Elimination of "kitome" and "splashome" contamination results in lack of detection of a unique placental microbiome

Background

A placental microbiome, which may be altered in gestational diabetes mellitus (GDM), has been described. However, publications raising doubts about the existence of a placental microbiome that is different than contaminants in DNA extraction kits and reagents (“kitomes”) have emerged. The aims of this study were to confirm the existence of a placental microbiome distinct from contaminants and determine if it is altered in GDM mothers.

Results

We first enrolled normal weight, obese and GDM mothers (N = 17) at term elective cesarean section delivery in a pilot case control study. Bacterial DNA was extracted from placental parenchyma, maternal and cord blood, maternal vaginal-rectal swabs, and positive and negative controls with the standard Qiagen/MoBio Power Soil kit. Placentas had significantly higher copies of bacterial 16S rRNA genes than negative controls, but the placental microbiome was similar in all three groups and could not be distinguished from contaminants in blank controls. To determine the source and composition of the putative placental bacterial community identified in the pilot study, we expanded the study to 10 subjects per group (N = 30) and increased the number and variety of negative controls (N = 53). We modified our protocol to use an ultraclean DNA extraction kit (Qiagen QIAamp UCP with Pathogen Lysis Tube S), which reduced the “kitome” contamination, but we were still unable to distinguish a placental microbiome from contaminants in negative controls. We noted microbial DNA from the high biomass vaginal-rectal swabs and positive controls in placental and negative control samples and determined that this resulted from close proximity well-to-well cross contamination or “splashome”. We eliminated this source of contamination by repeating the sequencing run with a minimum of four wells separating high biomass from low biomass samples. This reduced the reads of bacterial 16S rRNA genes in placental samples to insignificant numbers.

Conclusions

We identified the problem of well-to-well contamination (“splashome”) as an additional source of error in microbiome studies of low biomass samples and found a method of eliminating it. Once “kitome” and “splashome” contaminants were eliminated, we were unable to identify a unique placental microbiome.

Role of adipose tissue in regulating fetal growth in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a global health issue with significant short and long-term complications for both mother and baby. There is a strong need to identify an effective therapeutic that can prevent the development of GDM. A better understanding of the pathophysiology of GDM and the relationship between the adipose tissue, the placenta and fetal growth is required. The placenta regulates fetal growth by modulating nutrient transfer of glucose, amino acids and fatty acids. Various factors secreted by the adipose tissue, such as adipokines, adipocytokines and more recently identified extracellular vesicles, can influence inflammation and interact with placental nutrient transport. In this review, the role of the placental nutrient transporters and the adipose-derived factors that can influence their function will be discussed. A better understanding of these factors and their relationship may make a potential target for therapeutic interventions to prevent the development of GDM and its consequences.

Bioinformatics enrichment analysis of genes and pathways related to maternal type 1 diabetes associated with adverse fetal outcomes

Maternal type 1 diabetes mellitus (T1DM) may affect fetal development by altering the gene expression profile of the umbilical cord. The present study aimed to explore the T1DM-induced gene expression changes in the fetal umbilical cord. The raw gene expression profiles (ID: GSE51546) of umbilical cord tissue obtained from six normal mothers (non-diabetic) and six type 1 diabetic mothers were used to identify the differentially expressed genes. Genes that correspond to official gene symbols were selected for protein-protein interaction (PPI) and sub-network construction (combined score > 0.4). Functional annotation for Gene Ontology (GO) and pathway enrichment analysis were performed for genes involved in networking. A total of 110 differentially expressed genes were identified of which 38 were up-regulated while 72 were down-regulated. Only 37 genes were identified to significantly interact with each other. Hub genes including HSPA4, KCTD6, UBE2G1, FBXL19, and EHMT1 were up-regulated while KBTBD7, TRIM32, and NUP were down-regulated. T1DM had a major effect on the expression of genes involved in cellular death and differentiation, cell signaling and communication, protein modification and regulation of GTPase activity. Total 27 pathways were enriched and genes related to Wnt signaling, VEGF signaling, inflammation mediated by chemokine and cytokine signaling pathways, FGF signaling pathways and GnRH receptor pathways were found significantly affected by T1DM. Our results suggest that the T1DM environment seems to alter umbilical cord gene expression involved in the regulation of pathophysiology of the diabetic mother which in turn may lead to long-term consequences in various tissues in infants. This study provides insight into the molecular mechanism underlying the adverse pregnancy outcomes of maternal T1DM.

Adipocytokines are not associated with gestational diabetes mellitus but with pregnancy status

AIMS

Adipose tissue-secreted proteins, i.e. adipocytokines, have been identified as potential mediators linking fat mass and adipose tissue dysfunction with impaired glucose homeostasis, alterations in the inflammatory status, and risk of diabetes. The aim of this study was to determine whether seven circulating adipocytokines are associated with gestational diabetes mellitus (GDM) or are altered by metabolic and weight changes during pregnancy itself.

METHODS

A panel of seven adipocytokines (i.e. adiponectin, adipocyte fatty acid-binding protein, chemerin, leptin, Pro-Enkephalin, progranulin, and Pro-Neurotensin) was quantified in serum in a cross-sectional cohort of 222 women with the following three groups matched for age and body mass index: (i) 74 pregnant women with GDM; (ii) 74 pregnant women without GDM; and (iii) 74 non-pregnant and healthy women. A stepwise statistical approach was used by performing pairwise comparisons, principal component analysis (PCA), and partial least square discriminant analysis (PLS-DA).

RESULTS

Five out of seven adipocytokines were dysregulated between pregnant and non-pregnant women, i.e. adiponectin, chemerin, leptin, Pro-Enkephalin, and progranulin. None of the adipocytokines significantly differed between GDM and non-GDM status during pregnancy. The same five adipocytokines clustered in a principal component representing pregnancy-induced effects. Fasting insulin was the most relevant parameter in the discrimination of GDM as compared to pregnant women without GDM, whereas chemerin and adiponectin were most relevant factors to discriminate pregnancy status.

CONCLUSIONS

Pregnancy status but not presence of GDM can be distinguished by the seven investigated adipocytokines in discrimination analyses.

Placental Accumulation of Triacylglycerols in Gestational Diabetes Mellitus and Its Association with Altered Fetal Growth are Related to the Differential Expressions of Proteins of Lipid Metabolism

INTRODUCTION

Gestational diabetes mellitus (GDM) exhibit altered placental lipid metabolism. The molecular basis of this altered metabolism is not clear. Altered placental expression of proteins of lipogenesis and fatty acid oxidation may be involved in the placental accumulation of triacylglycerols (TG). The present study was aimed at investigating the differential expressions of placental proteins related to lipid metabolism among GDM women in comparison with control pregnant women (CPW) and to correlate them with maternal and fetal lipid parameters as well as altered fetal growth.

MATERIALS AND METHODS

Maternal blood, cord blood, and placental samples were collected from GDM and CPW. The biochemical parameters, glucose, lipid profile and free fatty acids (FFA) were measured. The placental TG content was measured. Differential placental expressions of proteins; phosphatidylinositol-3-kinase (PI3K) p85α, PI3K p110α,liver X receptor alpha (LXRα), sterol regulatory element binding protein1(SREBP1), fatty acid synthase (FAS), stearyl CoA desaturase1 (SCD1), lipoprotein lipase (LPL),Peroxisome proliferator-activated receptor (PPAR)α and PPARγ were analysed by western blotting and immunohistochemistry.

RESULTS

Placental protein expressions of PI3K p110α, LXRα, FAS, SCD1, and LPL were found to be significantly higher, whereas PPARα and PPARγ were lower in GDM women compared with CPW. The placental TG content and cord plasma FFA were increased in GDM women compared with CPW. The placental TG content positively correlated with Ponderal index of GDM new-borns.

CONCLUSION

Differential expressions of placental proteins related to lipid metabolism in GDM might have led to placental TG accumulation. This might have contributed to the fetal overgrowth in GDM.

Diabetes Mellitus, Obesity, and the Placenta

The placenta is exposed to metabolic derangements in the maternal and fetal circulation. The effects of the early placental "exposome" determine further trajectories. Overstimulation of the fetal pancreas in early gestation results in fetal hyperinsulinemia, augmenting glucose transfer with adverse effects on the fetus. The manifold placental changes at the end of pregnancy can be regarded as adaptive responses to protect the fetus from diabetes and obesity. The causal role of the placenta, if any, in mediating long-term effects on offspring development is an important area of current and future research.

Obesity in mares promotes uterine inflammation and alters embryo lipid fingerprints and homeostasis

Maternal body composition can be an important determinant for development of obesity and metabolic syndrome in adult offspring. Obesity-related outcomes in offspring may include epigenetic alterations; however, mechanisms of fetal programming remain to be fully elucidated. This study was conducted to determine the impact of maternal obesity in the absence of a high fat diet on equine endometrium and preimplantation embryos. Embryos were collected from normal and obese mares at 8 and 16 days and a uterine biopsy at 16 days (0 day = ovulation). With the exception of 8 day embryos, each sample was divided into two pieces. One piece was analyzed for gene expression markers related to carbohydrate metabolism, lipid homeostasis, inflammation, endoplasmic reticulum stress, oxidative stress, mitochondrial stress, and components of the insulin-like growth factor (IGF) system. The second piece was analyzed for lipid content using matrix-assisted laser desorption/ionization mass spectrometry. Obese mares had elevated concentrations of insulin, leptin, and total cholesterol, and they tended to have increased triglycerides and decreased insulin sensitivity. Embryos from obese mares had altered transcript abundance in genes for inflammation and lipid homeostasis, as well as endoplasmic reticulum, oxidative and mitochondrial stress and altered lipid fingerprints. Endometrium from obese mares had increased expression of inflammatory cytokines, lipid homeostasis regulation, mitochondrial stress, and the IGF2 system. This study demonstrates that increased adiposity in mares alters the uterine environment, transcript abundance of genes for cellular functions, and lipid profiles of embryos. These alterations could affect prenatal programming, with potential long-term effects in offspring.

Metabolic Culprits in Obese Pregnancies and Gestational Diabetes Mellitus: Big Babies, Big Twists, Big Picture : The 2018 Norbert Freinkel Award Lecture

Pregnancy has been equated to a "stress test" in which placental hormones and growth factors expose a mother's predisposition toward metabolic disease, unleashing her previously occult insulin resistance (IR), mild β-cell dysfunction, and glucose and lipid surplus due to the formidable forces of pregnancy-induced IR. Although pregnancy-induced IR is intended to assure adequate nutrition to the fetus and placenta, in mothers with obesity, metabolic syndrome, or those who develop gestational diabetes mellitus, this overnutrition to the fetus carries a lifetime risk for increased metabolic disease. Norbert Freinkel, nearly 40 years ago, coined this excess intrauterine nutrient exposure and subsequent offspring developmental risk "fuel-mediated teratogenesis," not limited to only excess maternal glucose. Our attempts to better elucidate the causes and mechanisms behind this double-edged IR of pregnancy, to metabolically characterize the intrauterine environment that results in changes in newborn body composition and later childhood obesity risk, and to examine potential therapeutic approaches that might target maternal metabolism are the focus of this article. Rapidly advancing technologies in genomics, proteomics, and metabolomics offer us innovative approaches to interrogate these metabolic processes in the mother, her microbiome, the placenta, and her offspring that contribute to a phenotype at risk for future metabolic disease. If we are successful in our efforts, the researcher, endocrinologist, obstetrician, and health care provider fortunate enough to care for pregnant women have the unique opportunity to positively impact health outcomes not only in the short term but in the long run, not just in one life but in two-and possibly, for the next generation.

A short periconceptional exposure to maternal type-1 diabetes is sufficient to disrupt the feto-placental phenotype in a rabbit model

Tight metabolic control of type-1 diabetes is essential during gestation, but it could be crucial during the periconception period. Feto-placental consequences of maternal type-1 diabetes around the time of conception need to be explored. Using a rabbit model, type-1 diabetes was induced by alloxan 7 days before mating. Glycemia was maintained at 15-20 mmol/L with exogenous insulin injections to prevent ketoacidosis. At 4 days post-conception (dpc), embryos were collected from diabetic (D) or normoglycemic control (C) dams, respectively, and transferred into non-diabetic recipients. At 28dpc, D- and C-feto-placental units were collected for biometry, placental analyses and lipid profiles. D-fetuses were growth-retarded, hyperglycemic and dyslipidemic compared to C-fetuses. The efficiency of D-placentas was associated with an increased gene expression related to nutrient supply and lipid metabolism whereas volume density of fetal vessels decreased. Fetal plasma, placental and fetal liver membranes had specific fatty acid signatures depending on embryonic origin. Tissues from D-fetuses contained more omega-6 polyunsaturated fatty acids. The concentrations of docosahexaenoic acid decreased while linoleic acid increased in the heart of D-fetuses. This study demonstrates that a short exposure to maternal type-1 diabetes in the periconception window, until the blastocyst stage, is able to irreversibly malprogram the feto-placental phenotype, through precocious and persistent structural and molecular adaptations of placenta.

The Impact of Maternal Pre-Pregnancy Body Weight and Gestational Diabetes on Markers of Folate Metabolism in the Placenta

Dietary methyl donors, including folate, may modify the placenta and size at birth but the influence of maternal body weight has not been widely investigated. We therefore examined whether maternal or fetal folate status, together with indices of placental folate transport, were modulated by either maternal pre-pregnancy body mass index (BMI i.e., overweight: 25 ≤ BMI < 30 or obesity: BMI ≥ 30 kg/m²) and/or gestational diabetes mellitus (GD). We utilised a sub-sample of 135 pregnant women participating in the Spanish PREOBE survey for our analysis (i.e., 59 healthy normal weight, 29 overweight, 22 obese and 25 GD). They were blood sampled at 34 weeks gestation, and, at delivery, when a placental sample was taken together with maternal and cord blood. Placental gene expression of folate transporters and DNA methyltransferases (DNMT) were all measured. Folate plasma concentrations were determined with an electro-chemiluminescence immunoassay. Food diaries indicated that folate intake was unaffected by BMI or GD and, although all women maintained normal folate concentrations (i.e., 5–16 ng/mL), higher BMIs were associated with reduced maternal folate concentrations at delivery. Umbilical cord folate was not different, reflecting an increased concentration gradient between the mother and her fetus. Placental mRNA abundance for the folate receptor alpha (FOLR1) was reduced with obesity, whilst DNMT1 was increased with raised BMI, responses that were unaffected by GD. Multi-regression analysis to determine the best predictors for placental FOLR1 indicated that pre-gestational BMI had the greatest influence. In conclusion, the placenta’s capacity to maintain fetal folate supply was not compromised by either obesity or GD.

Diabetes in Pregnancy and MicroRNAs: Promises and Limitations in Their Clinical Application

Maternal diabetes is associated with an increased risk of complications for the mother and her offspring. The latter have an increased risk of foetal macrosomia, hypoglycaemia, respiratory distress syndrome, preterm delivery, malformations and mortality but also of life-long development of obesity and diabetes. Epigenetics have been proposed as an explanation for this long-term risk, and microRNAs (miRNAs) may play a role, both in short- and long-term outcomes. Gestation is associated with increasing maternal insulin resistance, as well as β-cell expansion, to account for the increased insulin needs and studies performed in pregnant rats support a role of miRNAs in this expansion. Furthermore, several miRNAs are involved in pancreatic embryonic development. On the other hand, maternal diabetes is associated with changes in miRNA both in maternal and in foetal tissues. This review aims to summarise the existing knowledge on miRNAs in gestational and pre-gestational diabetes, both as diagnostic biomarkers and as mechanistic players, in the development of gestational diabetes itself and also of short- and long-term complications for the mother and her offspring.

The Pathophysiology of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a serious pregnancy complication, in which women without previously diagnosed diabetes develop chronic hyperglycemia during gestation. In most cases, this hyperglycemia is the result of impaired glucose tolerance due to pancreatic β-cell dysfunction on a background of chronic insulin resistance. Risk factors for GDM include overweight and obesity, advanced maternal age, and a family history or any form of diabetes. Consequences of GDM include increased risk of maternal cardiovascular disease and type 2 diabetes and macrosomia and birth complications in the infant. There is also a longer-term risk of obesity, type 2 diabetes, and cardiovascular disease in the child. GDM affects approximately 16.5% of pregnancies worldwide, and this number is set to increase with the escalating obesity epidemic. While several management strategies exist-including insulin and lifestyle interventions-there is not yet a cure or an efficacious prevention strategy. One reason for this is that the molecular mechanisms underlying GDM are poorly defined. This review discusses what is known about the pathophysiology of GDM, and where there are gaps in the literature that warrant further exploration.

Maternal Lipids and Fetal Overgrowth: Making Fat from Fat

There is increasing recognition that maternal glucose concentrations lower than those previously used for diagnosis of gestational diabetes mellitus (GDM) and targeted for treatment can result in excess fetal growth. Yet, mothers with GDM who appear to have optimal glycemic control and mothers with obesity and normal glucose tolerance still have a significantly increased risk for delivering infants who are large for gestational age, or even more importantly, who have increased adiposity at birth. What is less appreciated is that in addition to glucose, maternal lipids are also substrates for fetal fat accretion and that placental lipases can hydrolyze maternal triglycerides (TGs) to free fatty acids for fetal-placental availability. Maternal TG levels are 40% to 50% higher on average in mothers with obesity and GDM compared to those in normal-weight mothers early in pregnancy and are sustained at higher levels throughout gestation. Increasing evidence supports that maternal TG, both fasting and postprandial, are also predictors of newborn adiposity (newborn %fat), a risk factor for childhood obesity, and that early exposure is at least as strong of a risk factor as later exposure in mothers with obesity. In the setting of maternal nutrient excess and maternal insulin resistance, which lead to fetal hyperinsulinemia, excess free fatty acid exposure in the fetus may result in lipid storage and fetal fat development in subcutaneous and possibly other depots. In this commentary, we provide further evidence to make a case for targeting maternal fasting and postprandial TG in mothers with obesity who have elevated TG in early pregnancy to determine whether a TG-lowering interventional approach might limit fetal overgrowth and potentially mitigate the intrauterine contribution to childhood obesity and metabolic disease.

Infant of diabetic mother: what one needs to know?

The global incidence of diabetes mellitus, including diabetes in pregnant women, is on the rise. Diabetes mellitus in a pregnant woman jeopardizes not only maternal health but can also have significant implications on the child to be born. Therefore, timely diagnosis and strict glycemic control are of utmost importance in achieving a safe outcome for both the mother and fetus. The treating physician should be aware of the complications that can arise due to poor glycemic control during pregnancy. The objective of this article is to discuss the key concerns in a neonate born to diabetic mother, the underlying pathogenesis, and the screening schedule during pregnancy.

BMI-Independent Effects of Gestational Diabetes on Human Placenta

PURPOSE

Recently, alterations in maternal lipid metabolism were associated with gestational diabetes mellitus (GDM). However, detailed plasma lipid profiles and their relevance for placental and fetal metabolism are currently not understood.

METHODS

Maternal and placental lipid profiles were characterized in women with GDM and women with normal glucose tolerance (NGT). Inflammatory gene expression was compared in placentas and primary term trophoblasts between the groups. In addition, trophoblasts were stimulated with nonesterified fatty acids (NEFAs), and effects on gene expression were quantified. Finally, placental macrophage content and cord blood concentrations of inflammatory parameters and NEFAs were compared between women with GDM and women with NGT with similar body mass index (BMI).

RESULTS

Palmitate and stearate levels were elevated in both maternal plasma and placental tissue of women with GDM. Placental GDM-associated elevations of IL6, IL8, and TLR2 expression were reflected in trophoblasts derived from women with GDM. Stimulation of primary trophoblasts with palmitate led to increased mRNA expression and protein release of the cytokine IL6 and the chemokine IL8. In line with this, elevated amounts of CD68-positive cells were quantified in the placental tissue of women with GDM. No GDM-associated elevations in a range of inflammatory parameters and NEFAs in cord blood of NGT vs GDM neonates was found.

CONCLUSIONS

GDM, independently of BMI, altered maternal plasma NEFAs and the placental lipid profile. GDM was associated with trophoblast and whole-placenta lipoinflammation; however, this was not accompanied by elevated concentrations of inflammatory cytokines or NEFAs in neonatal cord blood.

Placental lipid processing in response to a maternal high-fat diet and diabetes in rats

BackgroundDiabetes and obesity during pregnancy have an impact on the health of both mothers and developing babies. Prevention focuses on glycemic control, but increasing evidence implicates a role for lipids. Using a rat model, we showed that a maternal high-fat (HF) diet increased perinatal morbidity and mortality, but lipid processing across the maternal-placental-fetal triad remained unstudied. We hypothesized that HF diet would disrupt placental lipid processing to exaggerate fuel-mediated consequences of diabetic pregnancy.MethodsWe compared circulating lipid profiles, hormones, and inflammatory markers in dams and rat offspring from normal, diabetes-exposed, HF-diet-exposed, and combination-exposed pregnancies. Placentae were examined for lipid accumulation and expression of fuel transporters.ResultsMaternal HF diet exaggerated hyperlipidemia of pregnancy, with diabetes marked dyslipidemia developed in dams but not in offspring. Placentae demonstrated lipid accumulation and lower expression of fatty acid (FA) transporters. Diet-exposed offspring had a lower fraction of circulating essential FAs. Pregnancy loss was significantly higher in diet-exposed but not in diabetes-exposed pregnancies, which could not be explained by differences in hormone production. Although not confirmed, inflammation may play a role.ConclusionMaternal hyperlipidemia contributes to placental lipid droplet accumulation, perinatal mortality, and aberrant FA profiles that may influence the health of the developing offspring.

Implications of Lipids in Neonatal Body Weight and Fat Mass in Gestational Diabetic Mothers and Non-Diabetic Controls

PURPOSE OF REVIEW

Maternal lipid metabolism greatly changes during pregnancy and we review in this article how they influence fetal adiposity and growth under non-diabetic and gestational diabetic conditions.

RECENT FINDINGS

In pregnant women without diabetes (control), maternal glycemia correlates with neonatal glycemia, neonatal body weight and fat mass. In pregnant women with gestational diabetes mellitus (GDM), maternal glucose correlates with neither neonatal glycemia, neonatal birth weight nor fat mass, but maternal triacylglycerols (TAG), non-esterified fatty acids (NEFA) and glycerol do correlate with birth weight and neonatal adiposity. The proportions of maternal plasma arachidonic (AA) and docosahexaenoic (DHA) acids decrease from the first to the third trimester of pregnancy, and at term these long-chain polyunsaturated fatty acids are higher in cord blood plasma than in mothers, indicating efficient placental transfer. In control or pregnant women with GDM at term, the maternal concentration of individual fatty acids does not correlate with neonatal body weight or fat mass, but cord blood fatty acid levels correlate with birth weight and neonatal adiposity-positively in controls, but negatively in GDM. The proportion of AA and DHA in umbilical artery plasma in GDM is lower than in controls but not in umbilical vein plasma. Therefore, an increased utilization of those two fatty acids by fetal tissues, rather than impaired placental transfer, is responsible for their smaller proportion in plasma of GDM newborns. In control pregnant women, maternal glycemia controls neonatal body weight and fat mass, whereas in mothers with GDM-even with good glycemic control-maternal lipids and their greater utilization by the fetus play a critical role in neonatal body weight and fat mass. We propose that altered lipid metabolism rather than hyperglycemia constitutes a risk for macrosomia in GDM.

Effects of Prenatal Nutrition and the Role of the Placenta in Health and Disease

Epidemiologic studies identified the linkage between exposures to stresses, including the type and plane of nutrition in utero with development of disease in later life. Given the critical roles of the placenta in mediating transport of nutrients between the mother and fetus and regulation of maternal metabolism, recent attention has focused on the role of the placenta in mediating the effect of altered nutritional exposures on the development of disease in later life. In this chapter we describe the mechanisms of nutrient transport in the placenta, the influence of placental metabolism on this, and how placental energetics influence placental function in response to a variety of stressors. Further the recent "recognition" that the placenta itself has a sex which affects its function may begin to help elucidate the mechanisms underlying the well-known dimorphism in development of disease in adult life.

Changes in LXR signaling influence early-pregnancy lipogenesis and protect against dysregulated fetoplacental lipid homeostasis

Human pregnancy is associated with enhanced de novo lipogenesis in the early stages followed by hyperlipidemia during advanced gestation. Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that stimulate de novo lipogenesis and also promote the efflux of cholesterol from extrahepatic tissues followed by its transport back to the liver for biliary excretion. Although LXR is recognized as a master regulator of triglyceride and cholesterol homeostasis, it is unknown whether it facilitates the gestational adaptations in lipid metabolism. To address this question, biochemical profiling, protein quantification, and gene expression studies were used, and gestational metabolic changes in T0901317-treated wild-type mice and Lxrab^-/- mutants were investigated. Here, we show that altered LXR signaling contributes to the enhanced lipogenesis in early pregnancy by increasing the expression of hepatic Fas and stearoyl-CoA desaturase 1 (Scd1). Both the pharmacological activation of LXR with T0901317 and the genetic ablation of its two isoforms disrupted the increase in hepatic fatty acid biosynthesis and the development of hypertriglyceridemia during early gestation. We also demonstrate that absence of LXR enhances maternal white adipose tissue lipolysis, causing abnormal accumulation of triglycerides, cholesterol, and free fatty acids in the fetal liver. Together, these data identify LXR as an important factor in early-pregnancy lipogenesis that is also necessary to protect against abnormalities in fetoplacental lipid homeostasis.

Maternal rates of lipolysis and glucose production in late pregnancy are independently related to foetal weight

OBJECTIVE

Associations between maternal glucose levels and increased foetal growth are well established, and independent relationships with maternal weight, weight gain and insulin resistance are also observed. The relative roles of lipolysis and glucose production in the determination of these observations remain unclear.

DESIGN

We examined, through detailed physiological studies, the relationship between maternal late gestational energy substrate production (glucose and glycerol), maternal weight and weight gain, and estimated foetal size in the third trimester.

PATIENTS

Twenty-one nulliparous pregnant women, without gestational diabetes (GDM) assessed at 28 weeks with oral glucose tolerance test, were recruited.

MEASUREMENTS

Rates of hepatic glucose production (GPR) and rates of glycerol production (reflecting lipolysis) using [¹³ C₆ ]-glucose and [² H₅ ]-glycerol were measured at 34-36 weeks of gestation. Respiratory quotient was assessed by indirect calorimetry and body composition by measurements of total body water (TBW; H₂¹⁸ O) and body density (BODPOD). Foetal weight was estimated from ultrasound measures of biparietal diameter, femoral length and abdominal circumference.

RESULTS

At 34-36 weeks, bivariate analyses showed that GPR and lipolysis correlated with estimated foetal weight (r=.71 and .72, respectively) as well as with maternal weight, fat mass and fat-free mass, but not maternal weight gain. In multivariate analyses, rates of both glucose production (r=.42) and lipolysis (r=.47) were independently associated with foetal size explaining 63% of the variance.

CONCLUSIONS

Both maternal rates of lipolysis and hepatic glucose production in late gestation are strongly related to estimated foetal weight.

Choline prevents fetal overgrowth and normalizes placental fatty acid and glucose metabolism in a mouse model of maternal obesity

Maternal obesity increases placental transport of macronutrients, resulting in fetal overgrowth and obesity later in life. Choline participates in fatty acid metabolism, serves as a methyl donor and influences growth signaling, which may modify placental macronutrient homeostasis and affect fetal growth. Using a mouse model of maternal obesity, we assessed the effect of maternal choline supplementation on preventing fetal overgrowth and restoring placental macronutrient homeostasis. C57BL/6J mice were fed either a high-fat (HF, 60% kcal from fat) diet or a normal (NF, 10% kcal from fat) diet with a drinking supply of either 25 mM choline chloride or control purified water, respectively, beginning 4 weeks prior to mating until gestational day 12.5. Fetal and placental weight, metabolites and gene expression were measured. HF feeding significantly (P<.05) increased placental and fetal weight in the HF-control (HFCO) versus NF-control (NFCO) animals, whereas the HF choline-supplemented (HFCS) group effectively normalized placental and fetal weight to the levels of the NFCO group. Compared to HFCO, the HFCS group had lower (P<.05) glucose transporter 1 and fatty acid transport protein 1 expression as well as lower accumulation of glycogen in the placenta. The HFCS group also had lower (P<.05) placental 4E-binding protein 1 and ribosomal protein s6 phosphorylation, which are indicators of mechanistic target of rapamycin complex 1 activation favoring macronutrient anabolism. In summary, our results suggest that maternal choline supplementation prevented fetal overgrowth in obese mice at midgestation and improved biomarkers of placental macronutrient homeostasis.

Maternal BMI and gestational diabetes alter placental lipid transporters and fatty acid composition

INTRODUCTION

Placental fatty acid (FA) uptake and metabolism depend on maternal supply which may be altered when women have a high pre-pregnancy body mass index (BMI) or develop gestational diabetes (GDM). Consequently, an impaired FA transport to the fetus may negatively affect fetal development. While placental adaptation of maternal-fetal glucose transfer in mild GDM has been described, knowledge on placental FA acid metabolism and possible adaptations in response to maternal obesity or GDM is lacking. We aimed to analyze the FA composition and the expression of key genes involved in FA uptake and metabolism in placentas from women with pre-pregnancy normal weight (18.5 ≤ BMI<25 kg/m2), overweight (25 ≤ BMI<30 kg/m²), obesity (BMI ≥ 30 kg/m²), and lean pregnant women with GDM.

METHODS

Placental FA content was determined by gas liquid chromatography. Placental mRNA expression of FA transport proteins (FATP1, FATP4, FATP6), FA binding proteins (FABP3, FABP4, FABP7), FA translocase (FAT/CD36) and enzymes (Endothelial lipase (EL) and lipoprotein lipase (LPL)) were quantified by qRT-PCR.

RESULTS

High pre-pregnancy BMI and GDM were associated with decreased placental FATP1, FATP4, EL and increased FAT/CD36 and FATP6 expressions. LPL mRNA levels and placental total FA content were similar among groups. Specific FA, including some long-chain polyunsaturated FA, were altered.

DISCUSSION

Our results demonstrate that high pre-pregnancy BMI or GDM independently alter mRNA expression levels of genes involved in FA uptake and metabolism and the placental FA profile, which could affect fetal development and long-term health.

Insulin Treatment May Alter Fatty Acid Carriers in Placentas from Gestational Diabetes Subjects

There is little information available on the effect of Gestational diabetes mellitus (GDM) treatment (diet or insulin) on placental lipid carriers, which may influence fetal fat accretion. Insulin may activate placental insulin receptors protein kinase (AKT) and extracellular signal regulated kinase ERK mediators, which might affect lipid metabolism. Placenta was collected from 25 control women, 23 GDM-Diet and 20 GDM-Insulin. Western blotting of insulin signaling mediators and lipid carriers was performed. The human choricarcinoma-derived cell line BeWo was preincubated with insulin inhibitors protein kinase (AKT) and extracellular signal regulated kinase (ERK) and ERK inhibitors to evaluate insulin regulation of lipid carriers. Maternal serum insulin at recruitment correlated to ultrasound fetal abdominal circumference in offspring of GDM and placental endothelial lipase (EL). Lipoprotein lipase in placenta was significantly reduced in both GDM, while most of the other lipid carriers tended to higher values, although not significantly. There was a significant increase in both phosphorylated-Akt and ERK in placentas from GDM-Insulin patients; both were associated to placental fatty acid translocase (FAT), fatty acid binding protein (A-FABP), and EL. BeWo cells treated with insulin pathway inhibitors significantly reduced A-FABP, fatty acid transport protein (FATP-1), and EL levels, confirming the role of insulin on these carriers. We conclude that insulin promotes the phosphorylation of placental insulin mediators contributing to higher levels of some specific fatty acid carriers in the placenta and fetal adiposity in GDM.

Placental lipoprotein lipase DNA methylation alterations are associated with gestational diabetes and body composition at 5 years of age

Gestational diabetes mellitus (GDM) is associated with obesity in childhood. This suggests that consequences of in utero exposure to maternal hyperglycemia extend beyond the fetal development, possibly through epigenetic programming. The aims of this study were to assess whether placental DNA methylation (DNAm) marks were associated with maternal GDM status and to offspring body composition at 5 years old in a prospective birth cohort. DNAm levels were measured in the fetal side of the placenta in 66 samples (24 from GDM mothers) using bisDNA-pyrosequencing. Anthropometric and body composition (bioimpedance) were measured in children at 5 years of age. Mann-Whitney and Spearman tests were used to assess associations between GDM, placental DNAm levels at the lipoprotein lipase (LPL) locus and children's weight, height, body mass index (BMI), body fat, and lean masses at 5 years of age. Weight, height, and BMI z-scores were computed according to the World Health Organization growth chart. Analyses were adjusted for gestational age at birth, child sex, maternal age, and pre-pregnancy BMI. LPL DNAm levels were positively correlated with birth weight z-scores (r = 0.252, P = 0.04), and with mid-childhood weight z-scores (r = 0.314, P = 0.01) and fat mass (r = 0.275, P = 0.04), and negatively correlated with lean mass (r = -0.306, P = 0.02). We found a negative correlation between LPL DNAm and mRNA levels in placenta (r = -0.459; P < 0.001), which highlights the regulation of transcriptional activity by these epivariations. We demonstrated that alterations in fetal placental DNAm levels at the LPL gene locus are associated with the anthropometric profile in children at 5 years of age. These findings support the concept of fetal metabolic programming through epigenetic changes.

Diabetic pregnancy, maternal and fetal docosahexaenoic acid: a review of existing evidence

OBJECTIVE

Docosahexaenoic acid (DHA) is vital for fetal development especially during the third trimester of gestation when the speed of fetal brain growth is at its peak. Diabetes modifies the maternal fatty acid profile, which may in turn change the quantity and/or quality of lipids transferred to the fetus. Neonates born to diabetic mothers might be more vulnerable to DHA deficiency leading to lower cognitive scores together with lower overall intellectual quotients when compared to control. We reviewed the influence of type 1 or type 2 pre-gestational (PGD) and gestational diabetes mellitus (GDM) on maternal and fetal DHA levels.

METHOD

We searched MEDLINE articles about PGD and/or GDM and DHA published before October 2016.

RESULTS

Maternal blood DHA level seems higher in those with diabetes than those without diabetes. However, DHA in cord plasma of neonates born to PGD and/or GDM mothers seem lower compared to neonates born to nondiabetic mothers.

CONCLUSIONS

Altogether, these results suggest that the transfer of DHA from the mother to the fetus may be deficient or dysregulated in diabetic pregnancies. What remains to be understood is how placental lipid transport is regulated and whether there is a link with clinical neurodevelopmental phenotypes in the newborns.