Exposure to Maternal Diabetes in Utero and DNA Methylation Patterns in the Offspring

DNA Methylation Profiles of PSMA6, PSMB5, KEAP1, and HIF1A Genes in Patients with Type 1 Diabetes and Diabetic Retinopathy

We explored differences in the DNA methylation statuses of PSMA6, PSMB5, HIF1A, and KEAP1 gene promoter regions in patients with type 1 diabetes and different diabetic retinopathy (DR) stages. Study subjects included individuals with no DR (NDR, n = 41), those with non-proliferative DR (NPDR, n = 27), and individuals with proliferative DR or those who underwent laser photocoagulation (PDR/LPC, n = 46). DNA methylation was determined by Zymo OneStep qMethyl technique. The methylation of PSMA6 (NDR 5.9 (3.9-8.7) %, NPDR 4.5 (3.8-5.7) %, PDR/LPC 6.6 (4.7-10.7) %, p = 0.003) and PSMB5 (NDR 2.2 (1.9-3.7) %, NPDR 2.2 (1.9-3.0) %, PDR/LPC 3.2 (2.5-7.1) %, p < 0.01) differed across the groups. Consistent correlations were observed between the methylation levels of HIF1A and PSMA6 in all study groups. DNA methylation levels of PSMA6, PSMB5, and HIF1A genes were positively correlated with the duration of diabetes, HbA1c, and albuminuria in certain study groups. Univariate regression models revealed a significant association between the methylation level z-scores of PSMA6, PSMB5, and HIF1A and severe DR (PSMA6: OR = 1.96 (1.15; 3.33), p = 0.013; PSMB5: OR = 1.90 (1.14; 3.16), p = 0.013; HIF1A: OR = 3.19 (1.26; 8.06), p = 0.014). PSMB5 remained significantly associated with DR in multivariate analysis. Our findings suggest significant associations between the severity of DR and the DNA methylation levels of the genes PSMA6, PSMB5, and HIF1A, but not KEAP1 gene.

Biochemical and molecular biomarkers: unraveling their role in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is the most prevalent metabolic disorder during pregnancy, causing short- and long-term complications for both mother and baby. GDM is a multifactorial disease, and it may be affected by interactions between genetic, epigenetic, and environmental factors. However, the exact etiology is poorly understood. Despite the high prevalence of GDM, there is still debate regarding the optimal time for screening, the diagnostic threshold to apply, and the best strategies for treatment. Identifying effective strategies for therapeutic purposes as well as accurate biomarkers for prognostic and diagnostic purposes will reduce the GDM incidence and improve its management. In recent years, new biochemical and molecular biomarkers such as microRNAs, single-nucleotide polymorphisms, and DNA methylation have received great interest in the diagnosis of GDM. In this review, we discuss current and future diagnostic approaches for the detection of GDM and evaluate lifestyle and pharmacological strategies for GDM prevention.

Epigenetics of type 2 diabetes and diabetes-related outcomes in the Strong Heart Study

BACKGROUND

The prevalence of type 2 diabetes has dramatically increased in the past years. Increasing evidence supports that blood DNA methylation, the best studied epigenetic mark, is related to diabetes risk. Few prospective studies, however, are available. We studied the association of blood DNA methylation with diabetes in the Strong Heart Study. We used limma, Iterative Sure Independence Screening and Cox regression to study the association of blood DNA methylation with fasting glucose, HOMA-IR and incident type 2 diabetes among 1312 American Indians from the Strong Heart Study. DNA methylation was measured using Illumina's MethylationEPIC beadchip. We also assessed the biological relevance of our findings using bioinformatics analyses.

RESULTS

Among the 358 differentially methylated positions (DMPs) that were cross-sectionally associated either with fasting glucose or HOMA-IR, 49 were prospectively associated with incident type 2 diabetes, although no DMPs remained significant after multiple comparisons correction. Multiple of the top DMPs were annotated to genes with relevant functions for diabetes including SREBF1, associated with obesity, type 2 diabetes and insulin sensitivity; ABCG1, involved in cholesterol and phospholipids transport; and HDAC1, of the HDAC family. (HDAC inhibitors have been proposed as an emerging treatment for diabetes and its complications.) CONCLUSIONS: Our results suggest that differences in peripheral blood DNA methylation are related to cross-sectional markers of glucose metabolism and insulin activity. While some of these DMPs were modestly associated with prospective incident type 2 diabetes, they did not survive multiple testing. Common DMPs with diabetes epigenome-wide association studies from other populations suggest a partially common epigenomic signature of glucose and insulin activity.

PHEVIR: an artificial intelligence algorithm that predicts the molecular role of pathogens in complex human diseases

Infectious diseases are known to cause a wide variety of post-infection complications. However, it's been challenging to identify which diseases are most associated with a given pathogen infection. Using the recently developed LeMeDISCO approach that predicts comorbid diseases associated with a given set of putative mode of action (MOA) proteins and pathogen-human protein interactomes, we developed PHEVIR, an algorithm which predicts the corresponding human disease comorbidities of 312 viruses and 57 bacteria. These predictions provide an understanding of the molecular bases of complications and means of identifying appropriate drug targets to treat them. As an illustration of its power, PHEVIR is applied to identify putative driver pathogens and corresponding human MOA proteins for Type 2 diabetes, atherosclerosis, Alzheimer's disease, and inflammatory bowel disease. Additionally, we explore the origins of the oncogenicity/oncolyticity of certain pathogens and the relationship between heart disease and influenza. The full PHEVIR database is available at https://sites.gatech.edu/cssb/phevir/ .

Epigenetic and transcriptomic alterations in offspring born to women with type 1 diabetes (the EPICOM study)

BACKGROUND

Offspring born to women with pregestational type 1 diabetes (T1DM) are exposed to an intrauterine hyperglycemic milieu and has an increased risk of metabolic disease later in life. In this present study, we hypothesize that in utero exposure to T1DM alters offspring DNA methylation and gene expression, thereby altering their risk of future disease.

METHODS

Follow-up study using data from the Epigenetic, Genetic and Environmental Effects on Growth, Metabolism and Cognitive Functions in Offspring of Women with Type 1 Diabetes (EPICOM) collected between 2012 and 2013.

SETTING

Exploratory sub-study using data from the nationwide EPICOM study.

PARTICIPANTS

Adolescent offspring born to women with T1DM (n=20) and controls (n=20) matched on age, sex, and postal code.

MAIN OUTCOME MEASURES

This study investigates DNA methylation using the 450K-Illumina Infinium assay and RNA expression (RNA sequencing) of leucocytes from peripheral blood samples.

RESULTS

We identified 9 hypomethylated and 5 hypermethylated positions (p < 0.005, |ΔM-value| > 1) and 38 up- and 1 downregulated genes (p < 0.005, log2FC ≥ 0.3) in adolescent offspring born to women with T1DM compared to controls. None of these findings remained significant after correction for multiple testing. However, we identified differences in gene co-expression networks, which could be of biological significance, using weighted gene correlation network analysis. Interestingly, one of these modules was significantly associated with offspring born to women with T1DM. Functional enrichment analysis, using the identified changes in methylation and gene expression as input, revealed enrichment in disease ontologies related to diabetes, carbohydrate and glucose metabolism, pathways including MAPK1/MAPK3 and MAPK family signaling, and genes related to T1DM, obesity, atherosclerosis, and vascular pathologies. Lastly, by integrating the DNA methylation and RNA expression data, we identified six genes where relevant methylation changes corresponded with RNA expression (CIITA, TPM1, PXN, ST8SIA1, LIPA, DAXX).

CONCLUSIONS

These findings suggest the possibility for intrauterine exposure to maternal T1DM to impact later in life methylation and gene expression in the offspring, a profile that may be linked to the increased risk of vascular and metabolic disease later in life.

Genomics and Epigenomics of Gestational Diabetes Mellitus: Understanding the Molecular Pathways of the Disease Pathogenesis

One of the most common complications during pregnancy is gestational diabetes mellitus (GDM), hyperglycemia that occurs for the first time during pregnancy. The condition is multifactorial, caused by an interaction between genetic, epigenetic, and environmental factors. However, the underlying mechanisms responsible for its pathogenesis remain elusive. Moreover, in contrast to several common metabolic disorders, molecular research in GDM is lagging. It is important to recognize that GDM is still commonly diagnosed during the second trimester of pregnancy using the oral glucose tolerance test (OGGT), at a time when both a fetal and maternal pathophysiology is already present, demonstrating the increased blood glucose levels associated with exacerbated insulin resistance. Therefore, early detection of metabolic changes and associated epigenetic and genetic factors that can lead to an improved prediction of adverse pregnancy outcomes and future cardio-metabolic pathologies in GDM women and their children is imperative. Several genomic and epigenetic approaches have been used to identify the genes, genetic variants, metabolic pathways, and epigenetic modifications involved in GDM to determine its etiology. In this article, we explore these factors as well as how their functional effects may contribute to immediate and future pathologies in women with GDM and their offspring from birth to adulthood. We also discuss how these approaches contribute to the changes in different molecular pathways that contribute to the GDM pathogenesis, with a special focus on the development of insulin resistance.

Developmental Effects of (Pre-)Gestational Diabetes on Offspring: Systematic Screening Using Omics Approaches

Worldwide, gestational diabetes affects 2-25% of pregnancies. Due to related disturbances of the maternal metabolism during the periconceptional period and pregnancy, children bear an increased risk for future diseases. It is well known that an aberrant intrauterine environment caused by elevated maternal glucose levels is related to elevated risks for increased birth weights and metabolic disorders in later life, such as obesity or type 2 diabetes. The complexity of disturbances induced by maternal diabetes, with multiple underlying mechanisms, makes early diagnosis or prevention a challenging task. Omics technologies allowing holistic quantification of several classes of molecules from biological fluids, cells, or tissues are powerful tools to systematically investigate the effects of maternal diabetes on the offspring in an unbiased manner. Differentially abundant molecules or distinct molecular profiles may serve as diagnostic biomarkers, which may also support the development of preventive and therapeutic strategies. In this review, we summarize key findings from state-of-the-art Omics studies addressing the impact of maternal diabetes on offspring health.

Intrauterine Programming of Cardiovascular Diseases in Maternal Diabetes

Maternal diabetes is a prevalent pathology that increases the risk of cardiovascular diseases in the offspring, the heart being one of the main target organs affected from the fetal stage until the adult life. Metabolic, pro-oxidant, and proinflammatory alterations in the fetal heart constitute the first steps in the adverse fetal programming of cardiovascular disease in the context of maternal diabetes. This review discusses both human and experimental studies addressing putative mechanisms involved in this fetal programming of heart damage in maternal diabetes. These include cardiac epigenetic changes, alterations in cardiac carbohydrate and lipid metabolism, damaging effects caused by a pro-oxidant and proinflammatory environment, alterations in the cardiac extracellular matrix remodeling, and specific signaling pathways. Putative actions to prevent cardiovascular impairments in the offspring of mothers with diabetes are also discussed.

Environmental Alterations during Embryonic Development: Studying the Impact of Stressors on Pluripotent Stem Cell-Derived Cardiomyocytes

Non-communicable diseases (NCDs) sauch as diabetes, obesity and cardiovascular diseases are rising rapidly in all countries world-wide. Environmental maternal factors (e.g., diet, oxidative stress, drugs and many others), maternal illnesses and other stressors can predispose the newborn to develop diseases during different stages of life. The connection between environmental factors and NCDs was formulated by David Barker and colleagues as the Developmental Origins of Health and Disease (DOHaD) hypothesis. In this review, we describe the DOHaD concept and the effects of several environmental stressors on the health of the progeny, providing both animal and human evidence. We focus on cardiovascular diseases which represent the leading cause of death worldwide. The purpose of this review is to discuss how in vitro studies with pluripotent stem cells (PSCs), such as embryonic and induced pluripotent stem cells (ESC, iPSC), can underpin the research on non-genetic heart conditions. The PSCs could provide a tool to recapitulate aspects of embryonic development “in a dish”, studying the effects of environmental exposure during cardiomyocyte (CM) differentiation and maturation, establishing a link to molecular mechanism and epigenetics.

DNA methylation as a mediator of associations between the environment and chronic diseases: A scoping review on application of mediation analysis

DNA methylation (DNAm) is one of the most studied epigenetic modifications. DNAm has emerged as a key biological mechanism and biomarkers to test associations between environmental exposure and outcomes in epidemiological studies. Although previous studies have focused on associations between DNAm and either exposure/outcomes, it is useful to test for mediation of the association between exposure and outcome by DNAm. The purpose of this scoping review is to introduce the methodological essence of statistical mediation analysis and to examine emerging epidemiological research applying mediation analyses. We conducted this scoping review for published peer-reviewed journals on this topic using online databases (PubMed, Scopus, Cochrane, and CINAHL) ending in December 2020. We extracted a total of 219 articles by initial screening. After reviewing titles, abstracts, and full texts, a total of 69 articles were eligible for this review. The breakdown of studies assigned to each category was 13 for smoking (18.8%), 8 for dietary intake and famine (11.6%), 6 for other lifestyle factors (8.7%), 8 for clinical endpoints (11.6%), 22 for environmental chemical exposures (31.9%), 2 for socioeconomic status (SES) (2.9%), and 10 for genetic factors and race (14.5%). In this review, we provide an exposure-wide summary for the mediation analysis using DNAm levels. However, we found heterogenous methods and interpretations in mediation analysis with typical issues such as different cell compositions and tissue-specificity. Further accumulation of evidence with diverse exposures, populations and with rigorous methodology will be expected to provide further insight in the role of DNAm in disease susceptibility.

Novel epigenetic link between gestational diabetes mellitus and macrosomia

Background & objectives: Examine maternal gestational diabetes mellitus (GDM), macrosomia and DNA methylation in candidate genes IGF1, IGF2, H19, ARHGRF11, MEST, NR3C1, ADIPOQ and RETN. Materials & methods: A total of 1145 children (572 GDM cases and 573 controls) from the Tianjin GDM study, including 177 with macrosomia, had blood DNA collection at median age 5.9 (range: 3.1-10.0). We used logistic regression to screen for associations with GDM and model macrosomia on 37 CpGs, and performed mediation analysis. Results: One CpG was associated with macrosomia at false discovery rate (FDR) <0.05 (cg14428359 in MEST); two (cg19466922 in MEST and cg26263166 in IGF2) were associated at p < 0.05 but mediated 26 and 13%, respectively. Conclusion: MEST and IGF2 were previously identified for potential involvement in fetal growth and development (Trial Registration number: NCT01554358 [ClinicalTrials.gov]).

The role of complement in arterial hypertension and hypertensive end organ damage

Increasing evidence indicates that hypertension and hypertensive end organ damage are not only mediated by haemodynamic injury but that inflammation also plays an important role. The complement system protects the host from a hostile microbial environment and maintains tissue and cell integrity through the elimination of altered or dead cells. As an important effector arm of innate immunity, it plays also central roles in the regulation of adaptive immunity. Thus, complement activation may drive the pathology of hypertension through its effects on innate and adaptive immune responses, aside from direct effects on the vasculature. Recent experimental data strongly support a role for complement in all stages of arterial hypertension. The remarkably similar clinical and histopathological features of malignant nephrosclerosis and atypical haemolytic uraemic syndrome suggest also a role for complement in the development of malignant nephrosclerosis. Here, we review the role of complement in hypertension and hypertensive end organ damage. LINKED ARTICLES: This article is part of a themed issue on Canonical and non-canonical functions of the complement system in health and disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.14/issuetoc.

Epigenetic Modifications Associated with Exposure to Endocrine Disrupting Chemicals in Patients with Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) remains a significant clinical and public health issue due to its increasing prevalence and the possibility for numerous short- and long-term complications. The growing incidence of GDM seems to coincide with the widespread use of endocrine disrupting chemicals (EDCs). The extensive production and common use of these substances in everyday life has resulted in constant exposure to harmful substances from the environment. That may result in epigenetic changes, which may manifest themselves also after many years and be passed on to future generations. It is important to consider the possible link between environmental exposure to endocrine disrupting chemicals (EDCs) during pregnancy, epigenetic mechanisms and an increased risk for developing gestational diabetes mellitus (GDM). This manuscript attempts to summarize data on epigenetic changes in pregnant women suffering from gestational diabetes in association with EDCs. There is a chance that epigenetic marks may serve as a tool for diagnostic, prognostic, and therapeutic measures.

Gestational Diabetes Mellitus and Developmental Programming

During normal pregnancy, increased insulin resistance acts as an adaptation to enhance materno-foetal nutrient transfer and meet the nutritional needs of the developing foetus, particularly in relation to glucose requirements. However, about 1 in 6 pregnancies worldwide is affected by the inability of the mother's metabolism to maintain normoglycaemia, with the combination of insulin resistance and insufficient insulin secretion resulting in gestational diabetes mellitus (GDM). A growing body of epidemiologic work demonstrates long-term implications for adverse offspring health resulting from exposure to GDM in utero. The effect of GDM on offspring obesity and cardiometabolic health may be partly influenced by maternal obesity; this suggests that improving glucose and weight control during early pregnancy, or better still before conception, has the potential to lessen the risk to the offspring. The consequences of GDM for microbiome modification in the offspring and the impact upon offspring immune dysregulation are actively developing research areas. Some studies have suggested that GDM impacts offspring neurodevelopmental and cognitive outcomes; confirmatory studies will need to separate the effect of GDM exposure from the complex interplay of social and environmental factors. Animal and human studies have demonstrated the role of epigenetic modifications in underpinning the predisposition to adverse health in offspring exposed to suboptimal hyperglycaemic in utero environment. To date, several epigenome-wide association studies in human have extended our knowledge on linking maternal diabetes-related DNA methylation marks with childhood adiposity-related outcomes. Identification of such epigenetic marks can help guide future research to develop candidate diagnostic biomarkers and preventive or therapeutic strategies. Longer-term interventions and longitudinal studies will be needed to better understand the causality, underlying mechanisms, or impact of GDM treatments to optimize the health of future generations.

Epigenetics and gestational diabetes: a review of epigenetic epidemiology studies and their use to explore epigenetic mediation and improve prediction

Epigenetics encapsulates a group of molecular mechanisms including DNA methylation, histone modification and microRNAs (miRNAs). Gestational diabetes (GDM) increases the risk of adverse perinatal outcomes and is associated with future offspring risk of obesity and type 2 diabetes. It has been hypothesised that epigenetic mechanisms mediate an effect of GDM on offspring adiposity and type 2 diabetes and this could provide a modifiable mechanism to reduce type 2 diabetes in the next generation. Evidence for this hypothesis is lacking. Epigenetic epidemiology could also contribute to reducing type 2 diabetes by identifying biomarkers that accurately predict risk of GDM and its associated future adverse outcomes. We reviewed published human studies that explored associations between any of maternal GDM, type 2 diabetes, gestational fasting or post-load glucose and any epigenetic marker (DNA methylation, histone modification or miRNA). Of the 81 relevant studies we identified, most focused on the potential role of epigenetic mechanisms in mediating intrauterine effects of GDM on offspring outcomes. Studies were small (median total number of participants 58; median number of GDM cases 27) and most did not attempt replication. The most common epigenetic measure analysed was DNA methylation. Most studies that aimed to explore epigenetic mediation examined associations of in utero exposure to GDM with offspring cord or infant blood/placenta DNA methylation. Exploration of any causal effect, or effect on downstream offspring outcomes, was lacking. There is a need for more robust methods to explore the role of epigenetic mechanisms as possible mediators of effects of exposure to GDM on future risk of obesity and type 2 diabetes. Research to identify epigenetic biomarkers to improve identification of women at risk of GDM and its associated adverse (maternal and offspring) outcomes is currently rare but could contribute to future tools for accurate risk stratification.

Systemic endocrinopathies (thyroid conditions and diabetes): impact on postnatal life of the offspring

Fetal programming may influence childhood and adult life, determining the risk of specific diseases. During earlier stages of pregnancy, the transfer of maternal thyroid hormones to the fetus is vital for adequate neurologic development. The presence of severe maternal thyroid dysfunction, particularly severe iodine deficiency, is devastating, leading to irreversible neurologic sequelae. Moreover, mild maternal thyroid conditions, such as a mild-to-moderate iodine deficiency, may also lead to milder neurologic and behavioral conditions later during the life of the offspring. Maternal dysglycemia due to pregestational or gestational diabetes mellitus is another common situation in which fetal development encounters a hostile environment. Hyperglycemia in utero may trigger metabolic conditions in the offspring, including abnormalities of glucose tolerance and weight excess. Physicians assisting pregnant women have to be aware about these conditions, because they may go unnoticed if not properly screened. Because an early diagnosis and appropriate management may prevent most of the possible negative consequences for the progeny, the prevention, early diagnosis, and proper management of these endocrine conditions should be offered to all women undergoing pregnancy. Here, we comprehensively review the current evidence about the effects of maternal thyroid dysfunction and maternal dysglycemia on the cognitive function and carbohydrate metabolism in the offspring, two prevalent conditions of utmost importance for the child's health and development.

Diabetes in pregnancy and epigenetic mechanisms-how the first 9 months from conception might affect the child's epigenome and later risk of disease

Diabetes in pregnancy is not only associated with increased risk of pregnancy complications and subsequent maternal metabolic disease, but also increases the risk of long-term metabolic disease in the offspring. At the interface between genetic and environmental factors, epigenetic variation established in utero represents a plausible link between the in utero environment and later disease susceptibility. The identification of an epigenetic fingerprint of diabetes in pregnancy linked to the metabolic health of the offspring might provide novel biomarkers for the identification of offspring most at risk, before the onset of metabolic dysfunction, for targeted monitoring and intervention. In this Personal View, we (1) highlight the scale of the problem of diabetes in pregnancy, (2) summarise evidence for the variation in offspring epigenetic profiles following exposure to diabetes in utero, and (3) outline potential future approaches to further understand the mechanisms by which exposure to maternal metabolic dysfunction in pregnancy is transmitted through generations.

Chorionic and amniotic membrane-derived stem cells have distinct, and gestational diabetes mellitus independent, proliferative, differentiation, and immunomodulatory capacities

Placental membrane-derived mesenchymal stem cells (MSCs), with the advantages of being non-invasive and having fewer ethical issues, are a promising source for cell therapy. Gestational diabetes (GDM) alters the uterine environment and may affect the therapeutic potential of MSCs derived from placenta. Therefore, we evaluated the biological properties of amniotic (AMSCs) and chorionic membrane MSCs (CMSCs) from human GDM placenta in order to explore their therapeutic potential. In comparison of GDM-/Healthy- CMSCs and AMSCs, the immunophenotypes and typical stellate morphology of MSC were similar in CMSCs irrespective of disease state while the MSC morphology in GDM-AMSCs was less evident. GDM- and Healthy- CMSCs displayed an enhanced proliferation rate and tri-lineage differentiation capacity compared with AMSCs. Notably, GDM-CMSCs had a significantly increased adipogenic ability than Healthy-CMSCs accompanied by increased transcriptional responsiveness of PPARγ and ADIPOQ induction. The secretome effect of Healthy- and GDM- CMSCs/AMSCs by using conditioned media and coculture experiments, suggests that GDM- and Healthy- CMSCs provided an equivalent immunoregulatory effect on suppressing T-cells activation but a reduced effect of GDM-CMSCs on macrophage regulation. However, Healthy- and GDM- CMSCs displayed a superior immunomodulatory capacity in regulation of both T-cells and macrophages than AMSCs. In summary, we highlight the importance of the maternal GDM intrauterine environment during pregnancy and its impact on CMSCs/AMSCs proliferation ability, CMSCs adipogenic potential, and macrophage regulatory capacity.

Kidney cytosine methylation changes improve renal function decline estimation in patients with diabetic kidney disease

Epigenetic changes might provide the biological explanation for the long-lasting impact of metabolic alterations of diabetic kidney disease development. Here we examined cytosine methylation of human kidney tubules using Illumina Infinium 450 K arrays from 91 subjects with and without diabetes and varying degrees of kidney disease using a cross-sectional design. We identify cytosine methylation changes associated with kidney structural damage and build a model for kidney function decline. We find that the methylation levels of 65 probes are associated with the degree of kidney fibrosis at genome wide significance. In total 471 probes improve the model for kidney function decline. Methylation probes associated with kidney damage and functional decline enrich on kidney regulatory regions and associate with gene expression changes, including epidermal growth factor (EGF). Altogether, our work shows that kidney methylation differences can be detected in patients with diabetic kidney disease and improve kidney function decline models indicating that they are potentially functionally important.

Patients with diabetes commonly develop diabetic kidney disease (DKD). Here Gluck et al. identify a set of probes differentially methylated in renal samples from patients with DKD, and find that inclusion of these methylation probes improves current prediction models of renal function decline.

DNA methylation signatures in mendelian developmental disorders as a diagnostic bridge between genotype and phenotype

Epigenetic and genetic mechanisms regulate the establishment and maintenance of gene expression in its proper context. Recent genome-wide mapping approaches have identified DNA methylation (DNAm) signatures in patients clinically diagnosed with syndromes manifesting as developmental disabilities with intellectual impairments. Here, we review recent studies in which these DNA methylation signatures have enabled highly sensitive and specific screening of such individuals and have clarified ambiguous cases where subjects present with genetic sequence variants of unknown clinical significance (VUS). We propose that these episignatures be considered as echoes and/or legacies of the initiating mutational events within proteins of the so-called epigenetic machinery. As well, we discuss approaches to directly confirm the functional consequences and the implications of these episignatures to patient management and treatment.

Intrauterine exposure to hyperglycemia retards the development of brown adipose tissue

Brown adipose tissue (BAT) is an exclusive tissue of nonshivering thermogenesis. It is fueled by lipids and glucose and involved in energy and metabolic homeostasis. Intrauterine exposure to hyperglycemia during gestational diabetes mellitus may result in abnormal fetal development and metabolic phenotypes in adulthood. However, whether intrauterine hyperglycemia influences the development of BAT is unknown. In this study, mouse embryos were exposed to the intrauterine hyperglycemia environment by injecting streptozocin into pregnant mice at 1 d post coitum (dpc). The structure of BAT was examined by hematoxylin and eosin staining and immunohistochemical analysis. The glucose uptake in BAT was measured in vivo by [¹⁸F]-fluoro-2-deoxyglucose-micro-positron emission tomography. The gene expression in BAT was determined by real-time PCR, and the 5'-C-phosphate-G-3' site-specific methylation was quantitatively analyzed. Intrauterine hyperglycemia exposure resulted in the impaired structure of BAT and decreased glucose uptake function in BAT in adulthood. The expressions of the genes involved in thermogenesis and mitochondrial respiratory chain in BAT, such as Ucp1, Cox5b, and Elovl3, were down-regulated by intrauterine hyperglycemia exposure at 18.5 dpc and at 16 wk of age. Furthermore, higher methylation levels of Ucp1, Cox5b, and Elovl3 were found in offspring of mothers with streptozotocin-induced diabetes. Our results provide the evidence for enduring inhibitory effects of intrauterine hyperglycemia on BAT development in offspring. Intrauterine hyperglycemia is associated with increased DNA methylation of the BAT specific genes in offspring, which support an epigenetic involvement.-Yu, D.-Q., Lv, P.-P., Yan, Y.-S., Xu, G.-X., Sadhukhan, A., Dong, S., Shen, Y., Ren, J., Zhang, X.-Y., Feng, C., Huang, Y.-T., Tian, S., Zhou, Y., Cai, Y.-T., Ming, Z.-H., Ding, G.-L., Zhu, H., Sheng, J.-Z., Jin, M., Huang, H.-F. Intrauterine exposure to hyperglycemia retards the development of brown adipose tissue.

The Role of Inflammation in the Development of GDM and the Use of Markers of Inflammation in GDM Screening

Gestational diabetes mellitus is a hyperglycaemic state first recognised in pregnancy. GDM affects both mother and child. Women with GDM and their new-borns are at risk of developing type 2 diabetes in the future. The screening and diagnostic criteria for GDM are inconsistent and thus novel biomarkers of GDM are required to strengthen the screening and diagnostic processes in GDM. Chronic low-grade inflammation is linked to the majority of the well-established risk factors of GDM such as old age, obesity and PCOS. This review provides an overview of the present knowledge on the pathology of GDM, the screening criteria applied, the role of inflammation in the development of GDM and the use of markers of inflammation namely cytokines, oxidative stress markers, lipids, amino acids and iron markers in screening and diagnosis of GDM.

Programming of Vascular Dysfunction in the Intrauterine Milieu of Diabetic Pregnancies

With the rising global tide of obesity, gestational diabetes mellitus (GDM) burgeoned into one of the most common antenatal disorders worldwide. Macrosomic babies born to diabetic mothers are more likely to develop risk factors for cardiovascular disease (CVD) before they reach adulthood. Rodent studies in offspring born to hyperglycemic pregnancies show vascular dysfunction characterized by impaired nitric oxide (NO)-mediated vasodilation and increased production of contractile prostanoids by cyclooxygenase 2 (COX-2). Vascular dysfunction is a key pathogenic event in the progression of diabetes-related vascular disease, primarily attributable to glucotoxicity. Therefore, glucose-induced vascular injury may stem directly from the hyperglycemic intrauterine environment of GDM pregnancy, as evinced by studies showing endothelial activation and inflammation at birth or in childhood in offspring born to GDM mothers. This review discusses potential mechanisms by which intrauterine hyperglycemia programs dysfunction in the developing vasculature.

DNA methylation and gene expression of TXNIP in adult offspring of women with diabetes in pregnancy

BACKGROUND

Fetal exposure to maternal diabetes increases the risk of type 2 diabetes (T2DM), possibly mediated by epigenetic mechanisms. Low blood TXNIP DNA methylation has been associated with elevated glucose levels and risk of T2DM, and increased skeletal muscle TXNIP gene expression was reported in subjects with impaired glucose metabolism or T2DM. Subcutaneous adipose tissue (SAT) and skeletal muscle play a key role in the control of whole body glucose metabolism and insulin action. The extent to which TXNIP DNA methylation levels are decreased and/or gene expression levels increased in SAT or skeletal muscle of a developmentally programmed at-risk population is unknown.

OBJECTIVE AND METHODS

The objective of this study was to investigate TXNIP DNA methylation and gene expression in SAT and skeletal muscle, and DNA methylation in blood, from adult offspring of women with gestational diabetes (O-GDM, n = 82) or type 1 diabetes (O-T1DM, n = 67) in pregnancy compared with offspring of women from the background population (O-BP, n = 57).

RESULTS

SAT TXNIP DNA methylation was increased (p = 0.032) and gene expression decreased (p = 0.001) in O-GDM, but these differences were attenuated after adjustment for confounders. Neither blood/muscle TXNIP DNA methylation nor muscle gene expression differed between groups.

CONCLUSION

We found no evidence of decreased TXNIP DNA methylation or increased gene expression in metabolic target tissues of offspring exposed to maternal diabetes. Further studies are needed to confirm and understand the paradoxical SAT TXNIP DNA methylation and gene expression changes in O-GDM subjects.

Maternal Factors that Induce Epigenetic Changes Contribute to Neurological Disorders in Offspring

It is well established that the regulation of epigenetic factors, including chromatic reorganization, histone modifications, DNA methylation, and miRNA regulation, is critical for the normal development and functioning of the human brain. There are a number of maternal factors influencing epigenetic pathways such as lifestyle, including diet, alcohol consumption, and smoking, as well as age and infections (viral or bacterial). Genetic and metabolic alterations such as obesity, gestational diabetes mellitus (GDM), and thyroidism alter epigenetic mechanisms, thereby contributing to neurodevelopmental disorders (NDs) such as embryonic neural tube defects (NTDs), autism, Down's syndrome, Rett syndrome, and later onset of neuropsychological deficits. This review comprehensively describes the recent findings in the epigenetic landscape contributing to altered molecular profiles resulting in NDs. Furthermore, we will discuss potential avenues for future research to identify diagnostic markers and therapeutic epi-drugs to reverse these abnormalities in the brain as epigenetic marks are plastic and reversible in nature.

MECHANISMS IN ENDOCRINOLOGY: Epigenetic modifications and gestational diabetes: a systematic review of published literature

OBJECTIVE

To summarize the current knowledge on epigenetic alterations in mother and offspring subjected to gestational diabetes (GDM) and indicate future topics for research.

DESIGN

Systematic review.

METHODS

We performed extensive searches in PubMed, EMBASE and Google scholar, using a combination of the search terms: GDM, gestational diabetes, epigenetic(s), methylation, histone modification, histone methylation, histone acetylation, microRNA and miRNA. Studies that compared women diagnosed with GDM and healthy controls were included. Two authors independently scanned the abstracts, and all included papers were read by at least two authors. The searches were completed on October 31st, 2016.

RESULTS

We identified 236 articles, of which 43 were considered relevant for this systematic review. Studies published showed that epigenetic alterations could be found in both mothers with GDM and their offspring. However, differences in methodology, diagnostic criteria for GDM and populations studied, together with a limited number of published studies and small sample sizes, preclude clear conclusions about the role of epigenetic modifications in transmitting risk from GDM mothers to their offspring.

CONCLUSION

The current research literature suggests that GDM may have impact on epigenetic modifications in the mother and offspring. However, larger studies that include multiple cohorts of GDM patients and their offspring are needed.

Differential methylation of genes in individuals exposed to maternal diabetes in utero

AIMS/HYPOTHESIS

Individuals exposed to maternal diabetes in utero are more likely to develop metabolic and cardiovascular diseases later in life. This may be partially attributable to epigenetic regulation of gene expression. We performed an epigenome-wide association study to examine whether differential DNA methylation, a major source of epigenetic regulation, can be observed in offspring of mothers with type 2 diabetes during the pregnancy (OMD) compared with offspring of mothers with no diabetes during the pregnancy (OMND).

METHODS

DNA methylation was measured in peripheral blood using the Illumina HumanMethylation450K BeadChip. A total of 423,311 CpG sites were analysed in 388 Pima Indian individuals, mean age at examination was 13.0 years, 187 of whom were OMD and 201 were OMND. Differences in methylation between OMD and OMND were assessed.

RESULTS

Forty-eight differentially methylated CpG sites (with an empirical false discovery rate ≤0.05), mapping to 29 genes and ten intergenic regions, were identified. The gene with the strongest evidence was LHX3, in which six CpG sites were hypermethylated in OMD compared with OMND (p ≤ 1.1 × 10^-5). Similarly, a CpG near PRDM16 was hypermethylated in OMD (1.1% higher, p = 5.6 × 10^-7), where hypermethylation also predicted future diabetes risk (HR 2.12 per SD methylation increase, p = 9.7 × 10^-5). Hypermethylation near AK3 and hypomethylation at PCDHGA4 and STC1 were associated with exposure to diabetes in utero (AK3: 2.5% higher, p = 7.8 × 10^-6; PCDHGA4: 2.8% lower, p = 3.0 × 10^-5; STC1: 2.9% lower, p = 1.6 × 10^-5) and decreased insulin secretory function among offspring with normal glucose tolerance (AK3: 0.088 SD lower per SD of methylation increase, p = 0.02; PCDHGA4: 0.08 lower SD per SD of methylation decrease, p = 0.03; STC1: 0.072 SD lower per SD of methylation decrease, p = 0.05). Seventeen CpG sites were also associated with BMI (p ≤ 0.05). Pathway analysis of the genes with at least one differentially methylated CpG (p < 0.005) showed enrichment for three relevant biological pathways.

CONCLUSIONS/INTERPRETATION

Intrauterine exposure to diabetes can affect methylation at multiple genomic sites. Methylation status at some of these sites can impair insulin secretion, increase body weight and increase risk of type 2 diabetes.

Gene Expression and DNA Methylation of PPARGC1A in Muscle and Adipose Tissue From Adult Offspring of Women With Diabetes in Pregnancy

Prenatal exposure to maternal hyperglycemia is associated with an increased risk of later adverse metabolic health. Changes in the regulation of peroxisome proliferator-activated receptor-γ coactivator-1α (PPARGC1A) in skeletal muscle and subcutaneous adipose tissue (SAT) is suggested to play a role in the developmental programming of dysmetabolism based on studies of human subjects exposed to an abnormal intrauterine environment (e.g., individuals with a low birth weight). We studied 206 adult offspring of women with gestational diabetes mellitus (O-GDM) or type 1 diabetes (O-T1D) and of women from the background population (O-BP) using a clinical examination, oral glucose tolerance test, and gene expression and DNA methylation of PPARGC1A in skeletal muscle and SAT. Plasma glucose was significantly higher for both O-GDM and O-T1D compared with O-BP (P < 0.05). PPARGC1A gene expression in muscle was lower in O-GDM compared with O-BP (P = 0.0003), whereas no differences were found between O-T1D and O-BP in either tissue. PPARGC1A DNA methylation percentages in muscle and SAT were similar among all groups. Decreased PPARGC1A gene expression in muscle has previously been associated with abnormal insulin function and may thus contribute to the increased risk of metabolic disease in O-GDM. The unaltered PPARGC1A gene expression in muscle of O-T1D suggests that factors other than intrauterine hyperglycemia may contribute to the decreased PPARGC1A expression in O-GDM.

The role of syncytins in human reproduction and reproductive organ cancers

Human life begins with sperm and oocyte fusion. After fertilization, various fusion events occur during human embryogenesis and morphogenesis. For example, the fusion of trophoblastic cells constitutes a key process for normal placental development. Fusion in the placenta is facilitated by syncytin 1 and syncytin 2. These syncytins arose from retroviral sequences that entered the primate genome 25 million and more than 40 million years ago respectively. About 8% of the human genome consists of similar human endogenous retroviral (HERVs) sequences. Many are inactive because of mutations or deletions. However, the role of the few that remain transcriptionally active has not been fully elucidated. Syncytin proteins maintain cell-cell fusogenic activity based on ENV: gene-mediated viral cell entry. In this review, we summarize how syncytins and their receptors are involved in fusion events during human reproduction. The significance of syncytins in tumorigenesis is also discussed.

DNA Methylation Profiling at Single-Base Resolution Reveals Gestational Folic Acid Supplementation Influences the Epigenome of Mouse Offspring Cerebellum

It is becoming increasingly more evident that lifestyle, environmental factors, and maternal nutrition during gestation can influence the epigenome of the developing fetus and thus modulate the physiological outcome. Variations in the intake of maternal nutrients affecting one-carbon metabolism may influence brain development and exert long-term effects on the health of the progeny. In this study, we investigated whether supplementation with high maternal folic acid during gestation alters DNA methylation and gene expression in the cerebellum of mouse offspring. We used reduced representation bisulfite sequencing to analyze the DNA methylation profile at the single-base resolution level. The genome-wide DNA methylation analysis revealed that supplementation with higher maternal folic acid resulted in distinct methylation patterns (P < 0.05) of CpG and non-CpG sites in the cerebellum of offspring. Such variations of methylation and gene expression in the cerebellum of offspring were highly sex-specific, including several genes of the neuronal pathways. These findings demonstrate that alterations in the level of maternal folic acid during gestation can influence methylation and gene expression in the cerebellum of offspring. Such changes in the offspring epigenome may alter neurodevelopment and influence the functional outcome of neurologic and psychiatric diseases.

Gestational diabetic transcriptomic profiling of microdissected human trophoblast

Gestational diabetes mellitus (GDM), the most common metabolic complication of pregnancy, is influenced by the placenta, and its prevalence directly increases with obesity. Therefore, to define the aetiology of GDM requires that the confounding influence of obesity and the heterogeneous nature of the placenta impairing accurate quantitative studies be accounted for. Using laser capture microdissection (LCM), we optimized RNA extraction from human placental trophoblast, the metabolic cellular interface between mother and foetus. This allowed specific transcriptomic profiling of trophoblast isolated from GDM, and obese and normal human placentae. Genome-wide gene expression analysis was performed on the RNA extracted from the trophoblast of GDM and obese and normal placentae. Forty-five differentially expressed genes (DEGs) specifically discriminated GDM from matched obese subjects. Two genes previously linked with GDM, pregnancy specific beta-1 glycoprotein 6 (PSG6) and placental system A sodium-dependent transporter system (SLC38A1), were significantly increased in GDM. A number of these DEGs (8 ubiquitin-conjugating enzymes (UBE) splice variants (UBE2D3 variants 1, 3, 4, 5, 6, 7, and 9) and UBE2V1 variant 4)) were involved in RNA processing and splicing, and a significant number of the DEGs, including the UBE variants, were associated with increased maternal fasting plasma glucose.It is concluded that DEGs discriminating GDM from obese subjects were pinpointed. Our data indicate a biological link between genes involved in RNA processing and splicing, ubiquitination, and fasting plasma glucose in GDM taking into account obesity as the confounder.

Epigenetic and genetic variations at the TNNT1 gene locus are associated with HDL-C levels and coronary artery disease

AIM

To assess whether epigenetic and genetic variations at the TNNT1 gene locus are associated with high-density lipoprotein cholesterol (HDL-C) and coronary artery disease (CAD). Patients, materials & methods: TNNT1 DNA methylation and c.-20G>A polymorphism were genotyped in subjects with and without familial hypercholesterolemia (FH).

RESULTS

Lower TNNT1 DNA methylation levels were independently associated with lower HDL-C levels and with the TNNT1 c.-20G>A polymorphism. In FH men, carriers of the TNNT1 c.-20G>A polymorphism had lower HDL-C levels and an increased risk of CAD compared with noncarriers. In non-FH men, a higher TNNT1 DNA methylation level was associated with CAD.

CONCLUSION

These results suggest that TNNT1 genetic and epigenetic variations are associated with HDL-C levels and CAD.

Keap1-Nrf2 regulated redox signaling in utero: Priming of disease susceptibility in offspring

Intrauterine exposure to gestational diabetes, pre-eclampsia or intrauterine growth restriction alters the redox status of the developing fetus. Such pregnancy-related diseases in most cases do not have a readily identifiable genetic cause, and epigenetic 'priming' mechanisms in utero may predispose both mother and child to later-life onset of cardiovascular and metabolic diseases. The concept of 'fetal programing' or 'developmental priming' and its association with an increased risk of disease in childhood or adulthood has been reviewed extensively. This review focuses on adaptive changes in the in utero redox environment during normal pregnancy and the consequences of alterations in redox control associated with pregnancies characterized by oxidative stress. We evaluate the evidence that the Keap1-Nrf2 pathway is important for protecting the fetus against adverse conditions in utero and may itself be subject to epigenetic priming, potentially contributing to an increased risk of vascular disease and insulin resistance in later life.

Lifestyle, pregnancy and epigenetic effects

Rapidly growing evidences link maternal lifestyle and prenatal factors with serious health consequences and diseases later in life. Extensive epidemiological studies have identified a number of factors such as diet, stress, gestational diabetes, exposure to tobacco and alcohol during gestation as influencing normal fetal development. In light of recent discoveries, epigenetic mechanisms such as alteration of DNA methylation, chromatin modifications and modulation of gene expression during gestation are believed to possibly account for various types of plasticity such as neural tube defects, autism spectrum disorder, congenital heart defects, oral clefts, allergies and cancer. The purpose of this article is to review a number of published studies to fill the gap in our understanding of how maternal lifestyle and intrauterine environment influence molecular modifications in the offspring, with an emphasis on epigenetic alterations. To support these associations, we highlighted laboratory studies of rodents and epidemiological studies of human based on sampling population cohorts.

Epigenetic Regulation of Placenta-Specific 8 Contributes to Altered Function of Endothelial Colony-Forming Cells Exposed to Intrauterine Gestational Diabetes Mellitus

Intrauterine exposure to gestational diabetes mellitus (GDM) is linked to development of hypertension, obesity, and type 2 diabetes in children. Our previous studies determined that endothelial colony-forming cells (ECFCs) from neonates exposed to GDM exhibit impaired function. The current goals were to identify aberrantly expressed genes that contribute to impaired function of GDM-exposed ECFCs and to evaluate for evidence of altered epigenetic regulation of gene expression. Genome-wide mRNA expression analysis was conducted on ECFCs from control and GDM pregnancies. Candidate genes were validated by quantitative RT-PCR and Western blotting. Bisulfite sequencing evaluated DNA methylation of placenta-specific 8 (PLAC8). Proliferation and senescence assays of ECFCs transfected with siRNA to knockdown PLAC8 were performed to determine functional impact. Thirty-eight genes were differentially expressed between control and GDM-exposed ECFCs. PLAC8 was highly expressed in GDM-exposed ECFCs, and PLAC8 expression correlated with maternal hyperglycemia. Methylation status of 17 CpG sites in PLAC8 negatively correlated with mRNA expression. Knockdown of PLAC8 in GDM-exposed ECFCs improved proliferation and senescence defects. This study provides strong evidence in neonatal endothelial progenitor cells that GDM exposure in utero leads to altered gene expression and DNA methylation, suggesting the possibility of altered epigenetic regulation.

Gestational Diabetes Alters Offspring DNA Methylation Profiles in Human and Rat: Identification of Key Pathways Involved in Endocrine System Disorders, Insulin Signaling, Diabetes Signaling, and ILK Signaling

Gestational diabetes is associated with risk for metabolic disease later in life. Using a cross-species approach in rat and humans, we examined the hypothesis that gestational diabetes during pregnancy triggers changes in the methylome of the offspring that might be mediating these risks. We show in a gestation diabetes rat model, the Cohen diabetic rat, that gestational diabetes triggers wide alterations in DNA methylation in the placenta in both candidate diabetes genes and genome-wide promoters, thus providing evidence for a causal relationship between diabetes during pregnancy and DNA methylation alterations. There is a significant overlap between differentially methylated genes in the placenta and the liver of the rat offspring. Several genes differentially methylated in rat placenta exposed to maternal diabetes are also differentially methylated in the human placenta of offspring exposed to gestational diabetes in utero. DNA methylation changes inversely correlate with changes in expression. The changes in DNA methylation affect known functional gene pathways involved in endocrine function, metabolism, and insulin responses. These data provide support to the hypothesis that early-life exposures and their effects on metabolic disease are mediated by DNA methylation changes. This has important diagnostic and therapeutic implications.

Long-term parental methamphetamine exposure of mice influences behavior and hippocampal DNA methylation of the offspring

The high rate of methamphetamine (METH) abuse among young adults and women of childbearing age makes it imperative to determine the long-term effects of METH exposure on the offspring. We hypothesized that parental METH exposure modulates offspring behavior by disrupting epigenetic programming of gene expression in the brain. To simulate the human pattern of drug use, male and female C57Bl/6J mice were exposed to escalating doses of METH or saline from adolescence through adulthood; following mating, females continue to receive drug or saline through gestational day 17. F1 METH male offspring showed enhanced response to cocaine-conditioned reward and hyperlocomotion. Both F1 METH male and female offspring had reduced response to conditioned fear. Cross-fostering experiments have shown that certain behavioral phenotypes were modulated by maternal care of either METH or saline dams. Analysis of offspring hippocampal DNA methylation showed differentially methylated regions as a result of both METH in utero exposure and maternal care. Our results suggest that behavioral phenotypes and epigenotypes of offspring that were exposed to METH in utero are vulnerable to (a) METH exposure during embryonic development, a period when wide epigenetic reprogramming occurs, and (b) postnatal maternal care.

Nongenetic inheritance and transgenerational epigenetics

The idea that inherited genotypes define phenotypes has been paramount in modern biology. The question remains, however, whether stable phenotypes could be also inherited from parents independently of the genetic sequence per se. Recent data suggest that parental experiences can be transmitted behaviorally, through in utero exposure of the developing fetus to the maternal environment, or through either the male or female germline. The challenge is to delineate a plausible mechanism. In the past decade it has been proposed that epigenetic mechanisms are involved in multigenerational transmission of phenotypes and transgenerational inheritance. The prospect that ancestral experiences are written in our epigenome has immense implications for our understanding of human behavior, health, and disease.

Screening and management of gestational diabetes

Gestational diabetes (GDM) is a frequent medical condition during pregnancy. It is associated with an increased risk of complications for both the mother and the baby during pregnancy and post partum. The International Association of Diabetes and Pregnancy Study Groups (IADPSG) has proposed a new screening strategy for overt diabetes in pregnancy and screening for GDM. However, there is still a lack of international uniformity in the approach to the screening and diagnosis of GDM. Controversies include universal versus selective screening, the optimal time for screening, appropriate tests and cutoff values, and whether testing should be conducted in one or two steps. This review gives an update on screening for GDM and overt diabetes during pregnancy. We also give an overview on the medical and obstetrical management of GDM.

Genetic, nongenetic and epigenetic risk determinants in developmental programming of type 2 diabetes

Low birthweight (LBW) individuals and offspring of women with gestational diabetes mellitus (GDM) exhibit increased risk of developing type 2 diabetes (T2D) and associated cardiometabolic traits in adulthood, which for both groups may be mediated by adverse events and developmental changes in fetal life. T2D is a multifactorial disease occurring as a result of complicated interplay between genetic and both prenatal and postnatal nongenetic factors, and it remains unknown to what extent the increased risk of T2D associated with LBW or GDM in the mother may be due to, or confounded by, genetic factors. Indeed, it has been shown that genetic changes influencing risk of diabetes may also be associated with reduced fetal growth as a result of reduced insulin secretion and/or action. Similarly, increased risk of T2D among offspring could be explained by T2D susceptibility genes shared between the mother and her offspring. Epigenetic mechanisms may explain the link between factors operating in fetal life and later risk of developing T2D, but so far convincing evidence is lacking for epigenetic changes as a prime and direct cause of T2D. This review addresses recent literature on the early origins of adult disease hypothesis, with a special emphasis on the role of genetic compared with nongenetic and epigenetic risk determinants and disease mechanisms.

Gestational diabetes as one of the "great obstetrical syndromes"--the maternal, placental, and fetal dialog

Gestational diabetes mellitus (GDM)-associated fetal and neonatal adverse outcome results from the metabolic milieu projected on the fetus via the placental interface. Therefore, it can be considered to be one of the great obstetrical syndromes. Placentas from GDM pregnancies differ from nondiabetic pregnancies by an increased placental to fetal ratio and by histological findings such as villous fibrinoid necrosis, villous immaturity, chorangiosis, and ischemic changes. While early onset diabetes is more associated with marked structural changes of the placenta, GDM that rises at late gestation is associated more with placental functional changes. These placental changes, causing increased intervillous diffusion distance of immature villi and placental size to perfusion mismatch, may predispose the fetus to chronic and acute changes in gas and nutrient exchange thus turning the placenta from being a "fetus protector" to a potential source of adverse outcome. Understanding placental changes and how they affect outcome is necessary in order to develop effective screening, prevention, and management approaches.

DNA damage and its cellular response in mother and fetus exposed to hyperglycemic environment

The increased production of reactive oxygen species (ROS) plays a key role in pathogenesis of diabetic complications. ROS are generated by exogenous and endogenous factors such as during hyperglycemia. When ROS production exceeds the detoxification and scavenging capacity of the cell, oxidative stress ensues. Oxidative stress induces DNA damage and when DNA damage exceeds the cellular capacity to repair it, the accumulation of errors can overwhelm the cell resulting in cell death or fixation of genome mutations that can be transmitted to future cell generations. These mutations can lead to and/or play a role in cancer development. This review aims at (i) understanding the types and consequences of DNA damage during hyperglycemic pregnancy; (ii) identifying the biological role of DNA repair during pregnancy, and (iii) proposing clinical interventions to maintain genome integrity. While hyperglycemia can damage the maternal genetic material, the impact of hyperglycemia on fetal cells is still unclear. DNA repair mechanisms may be important to prevent the deleterious effects of hyperglycemia both in mother and in fetus DNA and, as such, prevent the development of diseases in adulthood. Hence, in clinical practice, maternal glycemic control may represent an important point of intervention to prevent the deleterious effects of maternal hyperglycemia to DNA.

Impact of gestational hyperglycemia on maternal and child health

PURPOSE OF REVIEW

To address the recent evidence regarding the association between hyperglycemia during pregnancy and adverse short-term and long-term outcome for both mothers and offspring.

RECENT FINDINGS

Recent data suggest a relationship between hyperglycemia during pregnancy and adverse short-term fetal outcomes, mainly those associated with excessive fetal growth. The degree of hyperglycemia plays an important role in risk stratification. Moreover, the long-term effect of hyperglycemia during pregnancy is expressed mainly as cardiometabolic morbidity and increased risk for the development of metabolic syndrome both maternal and in early adolescence. Alternation in DNA methylation and gene expression of metabolic pathways were found in association with hyperglycemia in utero, supporting the 'developmental origins of disease' hypothesis.

SUMMARY

The effect of hyperglycemia on the early life metabolic environment may contribute to the subsequent risk of cardiovascular or metabolic morbidity later in life. It is also a sign of future maternal metabolic alternation. Several future randomized trials, hopefully will help to determine if early intervention could decrease the risk for gestational diabetes and whether long term adverse outcome are preventable and importantly the association with degree of maternal hyperglycemia in pregnancy and future morbidity.

Maternal obesity and the developmental programming of hypertension: a role for leptin

Mother-child cohort studies have established that both pre-pregnancy body mass index (BMI) and gestational weight gain are independently associated with cardio-metabolic risk factors in young adult offspring, including systolic and diastolic blood pressure. Animal models in sheep and non-human primates provide further evidence for the influence of maternal obesity on offspring cardiovascular function, whilst recent studies in rodents suggest that perinatal exposure to the metabolic milieu of maternal obesity may permanently change the central regulatory pathways involved in blood pressure regulation. Leptin plays an important role in the central control of appetite, is also involved in activation of efferent sympathetic pathways to both thermogenic and non-thermogenic tissues, such as the kidney, and is therefore implicated in obesity-related hypertension. Leptin is also thought to have a neurotrophic role in the development of the hypothalamus, and altered neonatal leptin profiles secondary to maternal obesity are associated with permanently altered hypothalamic structure and function. In rodent studies, maternal obesity confers persistent sympathoexcitatory hyper-responsiveness and hypertension acquired in the early stages of development. Experimental neonatal hyperleptinaemia in naive rat pups provides further evidence of heightened sympathetic tone and proof of principle that hyperleptinaemia during a critical window of hypothalamic development may directly lead to adulthood hypertension. Insight from these animal models raises the possibility that early-life exposure to leptin in humans may lead to early onset essential hypertension. Ongoing mother-child cohort and intervention studies in obese pregnant women provide a unique opportunity to address associations between maternal obesity and offspring cardiovascular function. The goal of the review is to highlight the potential importance of leptin in the developmental programming of hypertension in obese pregnancy.

Early Life Origins of Metabolic Syndrome: The Role of Environmental Toxicants

Metabolic syndrome (MetS) affects more than 47 million people in the U.S. Even more alarming, MetS, once regarded as an "adult problem", has become increasingly common in children. To date, most related research and intervention efforts have occurred in the adult medicine arena, with limited understanding of the root causes and lengthy latency of MetS. This review highlights new science on the early life origins of MetS, with a particular focus on exposure to two groups of environmental toxicants: endocrine disrupting chemicals (EDCs) and metals during the prenatal and early postnatal periods, and their specific effects and important differences in the development of MetS. It also summarizes available data on epigenetic effects, including the role of EDCs in the androgen/estrogen pathways. Emerging evidence supports the link between exposures to environmental toxicants during early life and the development of MetS later in life. Additional research is needed to address important research gaps in this area, including prospective birth cohort studies to delineate temporal and dose-response relationships, important differences in the effects of various environmental toxicants and their joint effects on MetS, as well as epigenetic mechanisms underlying the effects of specific toxicants such as EDCs and metals.