Downregulation of SOX11 in fetal heart tissue, under hyperglycemic environment, mediates cardiomyocytes apoptosis.

Gestational diabetes mellitus is one of the causes of abnormal embryonic heart development, but the mechanism is still poor. This study investigated the regulatory mechanism and role of SOX11 in congenital heart abnormality in a hyperglycemic environment. Immunohistochemistry, Western blotting, and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) showed decreased SOX11 protein and messenger RNA (mRNA) levels in the heart tissue of diabetic offspring compared with the control group. A Sequenom EpiTYPER MassArray showed that methylation sites upstream in SOX11 region 1 were increased in the diabetic group compared with the control group. Luciferase reporter assays and qRT-PCR showed that Dnmt3b overexpression decreased SOX11 promoter activity and its mRNA level, whereas Dnmt3a had little effect on regulating SOX11 expression. Furthermore, we found that Dnmt3L cooperated with Dnmt3b to regulate SOX11 gene expression. Additionally, the function of SOX11 silencing was analyzed by using small interfering RNA-mediated knockdown. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and apoptotic assays showed that SOX11 downregulation inhibited cell viability and induced apoptosis in cardiomyocytes. Overexpression of the SOX11 gene suppressed cardiomyocytes apoptosis after high glucose treatment. We identified a novel epigenetic regulatory mechanism of SOX11 during heart development in a hyperglycemic environment and revealed a distinct role of SOX11 in mediating cardiomyocytes viability and apoptosis.

Metabolic regulation and glucose sensitivity of cortical radial glial cells.

The primary stem cells of the cerebral cortex are the radial glial cells (RGCs), and disturbances in their operation lead to myriad brain disorders in all mammals from mice to humans. Here, we found in mice that maternal gestational obesity and hyperglycemia can impair the maturation of RGC fibers and delay cortical neurogenesis. To investigate potential mechanisms, we used optogenetic live-imaging approaches in embryonic cortical slices. We found that Ca2+ signaling regulates mitochondrial transport and is crucial for metabolic support in RGC fibers. Cyclic intracellular Ca2+ discharge from localized RGC fiber segments detains passing mitochondria and ensures their proper distribution and enrichment at specific sites such as endfeet. Impairment of mitochondrial function caused an acute loss of Ca2+ signaling, while hyperglycemia decreased Ca2+ activity and impaired mitochondrial transport, leading to degradation of the RGC scaffold. Our findings uncover a physiological mechanism indicating pathways by which gestational metabolic disturbances can interfere with brain development.

Hyperglycemia impedes definitive endoderm differentiation of human embryonic stem cells by modulating histone methylation patterns.

Exposure to maternal diabetes during fetal growth is a risk factor for the development of type II diabetes (T2D) in later life. Discovery of the mechanisms involved in this association should provide valuable background for therapeutic treatments. Early embryogenesis involves epigenetic changes including histone modifications. The bivalent histone methylation marks H3K4me3 and H3K27me3 are important for regulating key developmental genes during early fetal pancreas specification. We hypothesized that maternal hyperglycemia disrupted early pancreas development through changes in histone bivalency. A human embryonic stem cell line (VAL3) was used as the cell model for studying the effects of hyperglycemia upon differentiation into definitive endoderm (DE), an early stage of the pancreatic lineage. Hyperglycemic conditions significantly down-regulated the expression levels of DE markers SOX17, FOXA2, CXCR4 and EOMES during differentiation. This was associated with retention of the repressive histone methylation mark H3K27me3 on their promoters under hyperglycemic conditions. The disruption of histone methylation patterns was observed as early as the mesendoderm stage, with Wnt/ß-catenin signaling being suppressed during hyperglycemia. Treatment with Wnt/ß-catenin signaling activator CHIR-99021 restored the expression levels and chromatin methylation status of DE markers, even in a hyperglycemic environment. The disruption of DE development was also found in mouse embryos at day 7.5 post coitum from diabetic mothers. Furthermore, disruption of DE differentiation in VAL3 cells led to subsequent impairment in pancreatic progenitor formation. Thus, early exposure to hyperglycemic conditions hinders DE development with a possible relationship to the later impairment of pancreas specification.

Oxidative stress is responsible for maternal diabetes-impaired transforming growth factor beta signaling in the developing mouse heart.

OBJECTIVE: Oxidative stress plays a causal role in diabetic embryopathy. Maternal diabetes induces heart defects and impaired transforming growth factor beta (TGFß) signaling, which is essential for cardiogenesis. We hypothesize that mitigating oxidative stress through superoxide dismutase 1 (SOD1) overexpression in transgenic (Tg) mice reverses maternal hyperglycemia-impaired TGFß signaling and its downstream effectors. STUDY DESIGN: Day 12.5 embryonic hearts from wild-type (WT) and SOD1 overexpressing embryos of nondiabetic (ND) and diabetic mellitus (DM) dams were used for the detection of oxidative stress markers: 4-hydroxynonenal (4-HNE) and malondlaldehyde (MDA), and TGFß1, 2, and 3, phosphor (p)-TGFß receptor II (TßRII), p-phosphorylated mothers against decapentaplegic (Smad)2, and p-Smad3. The expression of 3 TGFß-responsive genes was also assessed. Day 11.5 embryonic hearts were explanted and cultured ex vivo, with or without treatments of a SOD1 mimetic (Tempol; Enzo Life Science, Farmingdale, NY) or a TGFß recombinant protein for the detection of TGFß signaling intermediates. RESULTS: Levels of 4-HNE and MDA were significantly increased by maternal diabetes, and SOD1 overexpression blocked the increase of these 2 oxidative stress markers. Maternal diabetes suppresses the TGFß signaling pathway by down-regulating TGFß1 and TGFß3 expression. Consequently, phosphorylation of TßRII, Smad2, and Smad3, downstream effectors of TGFß, and expression of 3 TGFß-responsive genes were reduced by maternal diabetes, and these reductions were prevented by SOD1 overexpression. Treatment with Tempol or TGFß recombinant protein restored high-glucose-suppressed TGFß signaling intermediates and responsive gene expression. CONCLUSION: Oxidative stress mediates the inhibitory effect of hyperglycemia in the developing heart. Antioxidants, TGFß recombinant proteins, or TGFß agonists may have potential therapeutic values in the prevention of heart defects in diabetic pregnancies.

Decoding the oxidative stress hypothesis in diabetic embryopathy through proapoptotic kinase signaling.

Maternal diabetes-induced birth defects occur in 6-10% of babies born to mothers with pregestational diabetes, representing a significant maternal-fetal health problem. Currently, these congenital malformations represent a significant maternal-fetal medicine issue, but are likely to create an even greater public health threat as 3 million women of reproductive age (19-44 years) have diabetes in the United States alone, and this number is expected to double by 2030. Neural tube defects (NTDs) and congenital heart defects are the most common types of birth defects associated with maternal diabetes. Animal studies have revealed that embryos under hyperglycemic conditions exhibit high levels of oxidative stress resulting from enhanced production of reactive oxygen species and impaired antioxidant capability. Oxidative stress activates a set of proapoptotic kinase signaling intermediates leading to abnormal cell death in the embryonic neural tube, which causes NTD formation. Work in animal models also has revealed that maternal diabetes triggers a series of signaling intermediates: protein kinase C (PKC) isoforms, PKCα, ßII and δ; apoptosis signal-regulating kinase 1; c-Jun-N-terminal kinase (JNK)1/2; caspase; and apoptosis. Specifically, maternal diabetes in rodent models activates the proapoptotic unfolded protein response and endoplasmic reticulum (ER) stress. A reciprocal causation between JNK1/2 activation and ER stress exists in diabetic embryopathy. Molecular studies further demonstrate that deletion of the genes for Prkc, Ask1, Jnk1, or Jnk2 abolishes maternal diabetes-induced neural progenitor apoptosis and ameliorates NTD formation. Similar preventive effects are also observed when apoptosis signal-regulating kinase 1, JNK1/2, or ER stress is inhibited. Cell membrane stabilizers and antioxidant supplements are also effective in prevention of diabetes-induced birth defects. Mechanistic studies have revealed important insights into our understanding the cause of diabetic embryopathy and have provided a basis for future interventions against birth defects or other pregnancy complications associated with maternal diabetes. The knowledge of a molecular pathway map identified in animal studies has created unique opportunities to identify molecular targets for therapeutic intervention.

Critical periods of increased fetal vulnerability to a maternal high fat diet.

BACKGROUND: Fetal adaptations to high fat (HF) diet in utero (IU) that may predispose to Metabolic Syndrome (MetS) in adulthood include changes in fetal hepatic gene expression. Studies were performed to determine whether maternal exposure to HF diet at different stages during pregnancy had different effects on the fetus, including hepatic gene expression. METHODS: Female wild type mice were fed either a HF or breeding chow (C) for 2 wks prior to mating. The experimental groups were composed of embryonic day (e) 18.5 fetuses obtained from WT female mice that were fed HF (HF, 35.5% fat) or breeding chow (C, 9.5% fat) for 2 wk before mating until e9.5 of pregnancy (periconception-midpregnancy). At e9.5 dams were switched to the opposite diet (C-HF or HF-C). RESULTS: Exposure to HF diet throughout pregnancy reduced maternal weight gain compared to C diet (p < 0.02 HF vs. C). HF-C dams had significantly decreased adiponectin levels and litter size when compared to C-HF (p < 0.02 HF-C vs C-HF). Independent of the timing of exposure to HF, fetal weight and length were significantly decreased when compared to C diet (HF, C-HF and HF-C vs. C p < 0.02). HF diet during the second half of pregnancy increased expression of genes in the fetal liver associated with fetal growth (C-HF vs C p < 0.001), glucose production (C-HF vs C p < 0.04), oxidative stress and inflammation (C-HF vs C p < 0.01) compared to C diet. CONCLUSIONS: This model defines that there are critical periods during gestation in which the fetus is actively shaped by the environment. Early exposure to a HF diet determines litter size while exposure to HF during the second half of pregnancy leads to dysregulation of expression of key genes responsible for fetal growth, hepatic glucose production and oxidative stress. These findings underscore the importance of future studies designed to clarify how these critical periods may influence future risk of developing MetS later in life.

Programming effects of glucocorticoids.

Fetal glucocorticoid overexposure is a key potential mechanism underlying the link between low birthweight and later life diseases. The fetus is protected from high maternal glucocorticoid levels by the placental enzyme 11ß-hydroxysteroid dehydrogenase type 2. Antenatal glucocorticoid administration to women at threat of preterm labor, and high endogenous maternal glucocorticoid levels during pregnancy associate with lower birthweight. Long-term consequences for offspring include hypothalamic-pituitary-adrenal axis activation, increased metabolic and cardiovascular disorders, and neurodevelopmental sequelae. Strategies are needed to limit antenatal glucocorticoid use to those most at risk of preterm labor and to identify those most at risk of future disease.

Cardiovascular disease risk in the offspring of diabetic women: the impact of the intrauterine environment.

The incidence of gestational diabetes is increasing worldwide, exposing large numbers of infants to hyperglycaemia whilst in utero. This exposure may have a long-term negative impact on the cardiovascular health of the offspring. Novel methods to assess cardiovascular status in the neonatal period are now available-including measuring arterial intima-media thickness and retinal photography. These measures will allow researchers to assess the relative impact of intrauterine exposures, distinguishing these from genetic or postnatal environmental factors. Understanding the long-term impact of the intrauterine environment should allow the development of more effective health policy and interventions to decrease the future burden of cardiovascular disease. Initiating disease prevention aimed at the developing fetus during the antenatal period may optimise community health outcomes.

Oxygen modulates the response of first-trimester trophoblasts to hyperglycemia.

Pregestational diabetes retards early embryonic growth. Placental and fetal growth are closely associated, suggesting that placental growth is also impaired. During the first trimester of gestation, oxygen tension rises steeply, leading to excessive production of reactive oxygen species (ROS), which is exacerbated in diabetes and may affect placental development. We hypothesized that oxygen modifies hyperglycemic effects on ROS formation, resulting in decreased first-trimester trophoblast growth. This was tested using a first trimester trophoblast-derived cell line (ACH-3P). Normoglycemia did not alter ACH-3P proliferation at 2.5%, 8%, and 21% oxygen. Hyperglycemic conditions for up to 3 days reduced cell number by 65% and resulted in cell cycle (G(1)- and S-phase) changes but only at 21% oxygen. Proliferation reduction could be partially restored by an inhibitor of mitogen-activated protein kinase (MAPK) ERK1/2 but not of Akt/PkB. Intracellular ROS elevation under hyperglycemia was oxygen independent, whereas mitochondrial superoxide levels were enhanced under hyperglycemia only at 21% oxygen. Intervention to modulate cytosolic and mitochondrial ROS, using ROS formation inducers and inhibitors, did not alter cell growth under hyperglycemia at 21% oxygen. The combination of hyperglycemia and high oxygen levels (21%) reduces proliferation of human first-trimester trophoblasts in a ROS-independent manner involving MAPK. This may account for reduced placental growth and, therefore, also for embryonic growth during the first-trimester pregestational diabetic pregnancies when the oxygen tension increases.

Expression of glucocorticoid receptor and glucose transporter-1 during placental development in the diabetic rat.

In various tissues, glucocorticoids (GCs) are known to downregulate glucose transport systems; however, their effects on glucose transporters (GLUTs) in the placenta of a diabetic rat are unknown. Glucocorticoid hormone action within the cell is regulated by the glucocorticoid receptor (GR). Thus, this study was designed to investigate the relationship between GR and glucose transporter expression in the placenta of the diabetic rat. Our immunohistochemical results indicated that GR and glucose transporter protein 1 (GLUT 1) are expressed ubiquitously in the trophoblast and endothelial cells of the labyrinthine zone, where maternal fetal transport takes place in the rat placenta. Expression of GR in the junctional zone of the rat placenta was detected in giant cells, and in some spongiotrophoblast cells, but not in the glycogen cells. GLUT 1 was present, especially in glycogen cells during early pregnancy, and in the spongiotrophoblast cells of the junctional zone during late pregnancy. Amounts of GR and GLUT 1 protein were increased towards the end of gestation both in the control and the diabetic placenta. However, at days 17 and 19 of gestation, only the placental GR protein was significantly increased in the streptozotocin-induced diabetic rats compared to control rats. Diabetes led to a significant decrease in placental weight at gestation day 15. In contrast, at gestational days 17 and 21, the weights of the diabetic placenta were significantly increased as compared with the controls. Moreover, diabetes induced fetus intrauterine growth retardation at gestational days 13, 17 and 21. In conclusion, the localization pattern of GR and GLUT 1 proteins in the same cell types led us to believe that there might be a relationship between GR and GLUT 1 expressions at the cellular level. GLUT 1 does not play a pivotal role in diabetic pregnancies. However, placental growth abnormalities during diabetic pregnancy may be related to the amount of GR.