Altered gene expression and spongiotrophoblast differentiation in placenta from a mouse model of diabetes in pregnancy

Small Molecule Activators of Mitochondrial Fusion Prevent Congenital Heart Defects Induced by Maternal Diabetes

Most congenital heart defect (CHD) cases are attributed to nongenetic factors; however, the mechanisms underlying nongenetic factor-induced CHDs are elusive. Maternal diabetes is one of the nongenetic factors, and this study aimed to determine whether impaired mitochondrial fusion contributes to maternal diabetes-induced CHDs and if mitochondrial fusion activators, teriflunomide and echinacoside, could reduce CHD incidence in diabetic pregnancy. We demonstrated maternal diabetes-activated FoxO3a increases miR-140 and miR-195, which in turn represses Mfn1 and Mfn2, leading to mitochondrial fusion defects and CHDs. Two mitochondrial fusion activators are effective in preventing CHDs in diabetic pregnancy.

Aberrant lipid accumulation in the mouse visceral yolk sac resulting from maternal diabetes and obesity

Maternal diabetes and obesity in pregnancy are well-known risk factors for structural birth defects, including neural tube defects and congenital heart defects. Progeny from affected pregnancies are also predisposed to developing cardiometabolic disease in later life. Based upon in vitro embryo cultures of rat embryos, it was postulated that nutrient uptake by the yolk sac is deficient in diabetic pregnancies. In contrast, using two independent mouse models of maternal diabetes, and a high-fat diet-feeding model of maternal obesity, we observed excessive lipid accumulation at 8.5 days in the yolk sac. The numbers as well as sizes of intracellular lipid droplets were increased in yolk sacs of embryos from diabetic and obese pregnancies. Maternal metabolic disease did not affect expression of lipid transporter proteins, including ApoA1, ApoB and SR-B1, consistent with our earlier report that expression of glucose and fatty acid transporter genes was also unchanged in diabetic pregnancy-derived yolk sacs. Colocalization of lipid droplets with lysosomes was significantly reduced in the yolk sacs from diabetic and obese pregnancies compared to yolk sacs from normal pregnancies. We therefore conclude that processing of lipids is defective in pregnancies affected by maternal metabolic disease, which may lead to reduced availability of lipids to the developing embryo. The possible implications of insufficient supply of lipids -and potentially of other nutrients-to the embryos experiencing adverse pregnancy conditions are discussed.

Paternal obesity induces epigenetic aberrations and gene expression changes in placenta and fetus

Paternal epigenome regulates placental and fetal growth. However, the effect of paternal obesity on placenta and its subsequent effect on the fetus via sperm remains unknown. We previously discovered abnormal methylation of imprinted genes involved in placental and fetal development in the spermatozoa of obese rats. In the present study, elaborate epigenetic characterization of sperm, placenta, and fetus was performed. For 16 weeks, male rats were fed either control or a high-fat diet. Following mating studies, sperm, placenta, and fetal tissue were collected. Significant changes were observed in placental weights, morphology, and cell populations. Methylation status of imprinted genes-Igf2, Peg3, Cdkn1c, and Gnas in spermatozoa, correlated with their expression in the placenta and fetus. Placental DNA methylating enzymes and 5-methylCytosine levels increased. Furthermore, in spermatozoa, DNA methylation of a few genes involved in pathways associated with placental endocrine function-gonadotropin-releasing hormone, prolactin, estrogen, and vascular endothelial growth factor, correlated with their expression in placenta and fetus. Changes in histone-modifying enzymes were also observed in the placenta. Histone marks H3K4me3, H3K9me3, and H4ac were downregulated, while H3K27me3 and H3ac were upregulated in placentas derived from obese male rats. This study shows that obesity-related changes in sperm methylome translate into abnormal expression in the F1-placenta fathered by the obese male, presumably affecting placental and fetal development.

β-hydroxybutyrate reduces blastocyst viability via trophectoderm-mediated metabolic aberrations in mice

STUDY QUESTION

What is the effect of the ketone β-hydroxybutyrate (βOHB) on preimplantation mouse embryo development, metabolism, epigenetics and post-transfer viability?

SUMMARY ANSWER

In vitro βOHB exposure at ketogenic diet (KD)-relevant serum concentrations significantly impaired preimplantation mouse embryo development, induced aberrant glycolytic metabolism and reduced post-transfer fetal viability in a sex-specific manner.

WHAT IS KNOWN ALREADY

A maternal KD in humans elevates gamete and offspring βOHB exposure during conception and gestation, and in rodents is associated with an increased time to pregnancy, and altered offspring organogenesis, post-natal growth and behaviour, suggesting a developmental programming effect. In vitro exposure to βOHB at supraphysiological concentrations (8–80 mM) perturbs preimplantation mouse embryo development.

STUDY DESIGN, SIZE, DURATION

A mouse model of embryo development and viability was utilized for this laboratory-based study. Embryo culture media were supplemented with βOHB at KD-relevant concentrations, and the developmental competence, physiology, epigenetic state and post-transfer viability of in vitro cultured βOHB-exposed embryos was assessed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Mouse embryos were cultured in vitro with or without βOHB at concentrations representing serum levels during pregnancy (0.1 mM), standard diet consumption (0.25 mM), KD consumption (2 mM) and diabetic ketoacidosis (4 mM). The impact of βOHB exposure on embryo development (blastocyst formation rate, morphokinetics and blastocyst total, inner cell mass and trophectoderm (TE) cell number), physiology (redox state, βOHB metabolism, glycolytic metabolism), epigenetic state (histone 3 lysine 27 β-hydroxybutyrylation, H3K27bhb) and post-transfer viability (implantation rate, fetal and placental development) was assessed.

MAIN RESULTS AND THE ROLE OF CHANCE

All βOHB concentrations tested slowed embryo development (P < 0.05), and βOHB at KD-relevant serum levels (2 mM) delayed morphokinetic development, beginning at syngamy (P < 0.05). Compared with unexposed controls, βOHB exposure reduced blastocyst total and TE cell number (≥0.25 mM; P < 0.05), reduced blastocyst glucose consumption (2 mM; P < 0.01) and increased lactate production (0.25 mM; P < 0.05) and glycolytic flux (0.25 and 2 mM; P < 0.01). Consumption of βOHB by embryos, mediated via monocarboxylate transporters, was detected throughout preimplantation development. Supraphysiological (20 mM; P < 0.001), but not physiological (0.25–4 mM) βOHB elevated H3K27bhb levels. Preimplantation βOHB exposure at serum KD levels (2 mM) reduced post-transfer viability. Implantation and fetal development rates of βOHB-treated embryos were 50% lower than controls (P < 0.05), and resultant fetuses had a shorter crown-rump length (P < 0.01) and placental diameter (P < 0.05). A strong sex-specific effect of βOHB was detected, whereby female fetuses from βOHB-treated embryos weighed less (P < 0.05), had a shorter crown-rump length (P < 0.05), and tended to have accelerated ear development (P < 0.08) compared with female control fetuses.

LIMITATIONS, REASONS FOR CAUTION

This study only assessed embryo development, physiology and viability in a mouse model utilizing in vitro βOHB exposure; the impact of in vivo exposure was not assessed. The concentrations of βOHB utilized were modelled on blood/serum levels as the true oviduct and uterine concentrations are currently unknown.

WIDER IMPLICATIONS OF THE FINDINGS

These findings indicate that the development, physiology and viability of mouse embryos is detrimentally impacted by preimplantation exposure to βOHB within a physiological range. Maternal diets which increase βOHB levels, such as a KD, may affect preimplantation embryo development and may therefore impair subsequent viability and long-term health. Consequently, our initial observations warrant follow-up studies in larger human populations. Furthermore, analysis of βOHB concentrations within human and rodent oviduct and uterine fluid under different nutritional states is also required.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the University of Melbourne and the Norma Hilda Schuster (nee Swift) Scholarship. The authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Nutrient Transporter Gene Expression in the Early Conceptus—Implications From Two Mouse Models of Diabetic Pregnancy

Maternal diabetes in early pregnancy increases the risk for birth defects in the offspring, particularly heart, and neural tube defects. While elevated glucose levels are characteristic for diabetic pregnancies, these are also accompanied by hyperlipidemia, indicating altered nutrient availability. We therefore investigated whether changes in the expression of nutrient transporters at the conception site or in the early post-implantation embryo could account for increased birth defect incidence at later developmental stages. Focusing on glucose and fatty acid transporters, we measured their expression by RT-PCR in the spontaneously diabetic non-obese mouse strain NOD, and in pregnant FVB/N mouse strain dams with Streptozotocin-induced diabetes. Sites of expression in the deciduum, extra-embryonic, and embryonic tissues were determined by RNAscope in situ hybridization. While maternal diabetes had no apparent effects on levels or cellular profiles of expression, we detected striking cell-type specificity of particular nutrient transporters. For examples, Slc2a2/Glut2 expression was restricted to the endodermal cells of the visceral yolk sac, while Slc2a1/Glut1 expression was limited to the mesodermal compartment; Slc27a4/Fatp4 and Slc27a3/Fatp3 also exhibited reciprocally exclusive expression in the endodermal and mesodermal compartments of the yolk sac, respectively. These findings not only highlight the significance of nutrient transporters in the intrauterine environment, but also raise important implications for the etiology of birth defects in diabetic pregnancies, and for strategies aimed at reducing birth defects risk by nutrient supplementation.

Effects of Maternal Diabetes and Diet on Gene Expression in the Murine Placenta

Adverse exposures during pregnancy have been shown to contribute to susceptibility for chronic diseases in offspring. Maternal diabetes during pregnancy is associated with higher risk of pregnancy complications, structural birth defects, and cardiometabolic health impairments later in life. We showed previously in a mouse model that the placenta is smaller in diabetic pregnancies, with reduced size of the junctional zone and labyrinth. In addition, cell migration is impaired, resulting in ectopic accumulation of spongiotrophoblasts within the labyrinth. The present study had the goal to identify the mechanisms underlying the growth defects and trophoblast migration abnormalities. Based upon gene expression assays of 47 candidate genes, we were able to attribute the reduced growth of diabetic placenta to alterations in the Insulin growth factor and Serotonin signaling pathways, and provide evidence for Prostaglandin signaling deficiencies as the possible cause for abnormal trophoblast migration. Furthermore, our results reinforce the notion that the exposure to maternal diabetes has particularly pronounced effects on gene expression at midgestation time points. An implication of these findings is that mechanisms underlying developmental programming act early in pregnancy, during placenta morphogenesis, and before the conceptus switches from histiotrophic to hemotrophic nutrition.

Poorly controlled diabetes mellitus alters placental structure, efficiency, and plasticity

INTRODUCTION

The hemochorial placenta provides a critical barrier at the maternal-fetal interface to modulate maternal immune tolerance and enable gas and nutrient exchange between mother and conceptus. Pregnancy outcomes are adversely affected by diabetes mellitus; however, the effects of poorly controlled diabetes on placental formation, and subsequently fetal development, are not fully understood.

RESEARCH DESIGN AND METHODS

Streptozotocin was used to induce hyperglycemia in pregnant rats for the purpose of investigating the impact of poorly controlled diabetes on placental formation and fetal development. The experimental paradigm of hypoxia exposure in the pregnant rat was also used to assess properties of placental plasticity. Euglycemic and hyperglycemic rats were exposed to ambient conditions (~21% oxygen) or hypoxia (10.5% oxygen) beginning on gestation day (gd) 6.5 and sacrificed on gd 13.5. To determine whether the interaction of hyperglycemia and hypoxia was directly altering trophoblast lineage development, rat trophoblast stem (TS) cells were cultured in high glucose (25 mM) and/or exposed to low oxygen (0.5% to 1.5%).

RESULTS

Diabetes caused placentomegaly and placental malformation, decreasing placental efficiency and fetal size. Elevated glucose disrupted rat TS cell differentiation in vitro. Evidence of altered trophoblast differentiation was also observed in vivo, as hyperglycemia affected the junctional zone transcriptome and interfered with intrauterine trophoblast invasion and uterine spiral artery remodeling. When exposed to hypoxia, hyperglycemic rats showed decreased proliferation and ectoplacental cone development on gd 9.5 and complete pregnancy loss by gd 13.5. Furthermore, elevated glucose concentrations inhibited TS cell responses to hypoxia in vitro.

CONCLUSIONS

Overall, these results indicate that alterations in placental development, efficiency, and plasticity could contribute to the suboptimal fetal outcomes in offspring from pregnancies complicated by poorly controlled diabetes.

Maternal diet modulates placental nutrient transporter gene expression in a mouse model of diabetic pregnancy

Diabetes in the mother during pregnancy is a risk factor for birth defects and perinatal complications and can affect long-term health of the offspring through developmental programming of susceptibility to metabolic disease. We previously showed that Streptozotocin-induced maternal diabetes in mice is associated with altered cell differentiation and with smaller size of the placenta. Placental size and fetal size were affected by maternal diet in this model, and maternal diet also modulated the risk for neural tube defects. In the present study, we sought to determine the extent to which these effects might be mediated through altered expression of nutrient transporters, specifically glucose and fatty acid transporters in the placenta. Our results demonstrate that expression of several transporters is modulated by both maternal diet and maternal diabetes. Diet was revealed as the more prominent determinant of nutrient transporter expression levels, even in pregnancies with uncontrolled diabetes, consistent with the role of diet in placental and fetal growth. Notably, the largest changes in nutrient transporter expression levels were detected around midgestation time points when the placenta is being formed. These findings place the critical time period for susceptibility to diet exposures earlier than previously appreciated, implying that mechanisms underlying developmental programming can act on placenta formation.

A Narrative Review of Placental Contribution to Adverse Pregnancy Outcomes in Women With Polycystic Ovary Syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy of reproductive-aged women. In pregnancy, women with PCOS experience increased risk of miscarriage, gestational diabetes, preeclampsia, and extremes of fetal birth weight, and their offspring are predisposed to reproductive and cardiometabolic dysfunction in adulthood. Pregnancy complications, adverse fetal outcomes, and developmental programming of long-term health risks are known to have placental origins. These findings highlight the plausibility of placental compromise in pregnancies of women with PCOS.

EVIDENCE SYNTHESIS

A comprehensive PubMed search was performed using terms "polycystic ovary syndrome," "placenta," "developmental programming," "hyperandrogenism," "androgen excess," "insulin resistance," "hyperinsulinemia," "pregnancy," and "pregnancy complications" in both human and animal experimental models.

CONCLUSIONS

There is limited human placental research specific to pregnancy of women with PCOS. Gestational androgen excess and insulin resistance are two clinical hallmarks of PCOS that may contribute to placental dysfunction and underlie the higher rates of maternal-fetal complications observed in pregnancies of women with PCOS. Additional research is needed to prevent adverse maternal and developmental outcomes in women with PCOS and their offspring.

Cholecystokinin, gastrin, cholecystokinin/gastrin receptors, and bitter taste receptor TAS2R14: trophoblast expression and signaling

We investigated expression of cholecystokinin (CCK) in humans and mice, and the bitter taste receptor TAS2R14 in the human placenta. Because CCK and gastrin activate the CCKBR receptor, we also explored placental gastrin expression. Finally, we investigated calcium signaling by CCK and TAS2R14. By RT-PCR, we found CCK/Cck and GAST/Gast mRNA expression in both normal human and mouse placentas, as well as in human trophoblast cell lines (TCL). Although both Cckar and -br mRNA were expressed in the mouse placenta, only CCKBR mRNA was detected in the human placenta and TCL. mRNA expression for TAS2R14 was also observed in the human placenta and TCL. Using immunohistochemistry, CCK protein was localized to the syncytiotrophoblast (ST) and extravillous trophoblast (EVT) in the human term placenta, and to trophoblast glycogen cells in mouse and human placentas. Gastrin and TAS2R14 proteins were also observed in ST and EVT of the human placenta. Both sulfated and nonsulfated CCK elicited a comparable rise in intracellular calcium in TCL, consistent with CCKBR expression. Three TAS2R14 agonists, flufenamic acid, chlorhexidine, and diphenhydramine, also evoked rises in intracellular calcium in TCL. These results establish CCK, gastrin, and their receptor(s) in both human and mouse placentas, and TAS2R14 in the human placenta. Both CCK and TAS2R14 agonists increased intracellular calcium in human TCL. Although the roles of these ligands and receptors, and their potential cross talk in normal and pathological placentas, are currently unknown, this study opens new avenues for placental research.

Adverse effects of Hif1a mutation and maternal diabetes on the offspring heart

Background

Epidemiological studies show that maternal diabetes predisposes offspring to cardiovascular and metabolic disorders. However, the precise mechanisms for the underlying penetrance and disease predisposition remain poorly understood. We examined whether hypoxia-inducible factor 1 alpha, in combination with exposure to a diabetic intrauterine environment, influences the function and molecular structure of the adult offspring heart.

Methods and results

In a mouse model, we demonstrated that haploinsufficient (Hif1a^+/−) offspring from a diabetic pregnancy developed left ventricle dysfunction at 12 weeks of age, as manifested by decreased fractional shortening and structural remodeling of the myocardium. Transcriptional profiling by RNA-seq revealed significant transcriptome changes in the left ventricle of diabetes-exposed Hif1a^+/− offspring associated with development, metabolism, apoptosis, and blood vessel physiology. In contrast, both wild type and Hif1a^+/− offspring from diabetic pregnancies showed changes in immune system processes and inflammatory responses. Immunohistochemical analyses demonstrated that the combination of haploinsufficiency of Hif1a and exposure to maternal diabetes resulted in impaired macrophage infiltration, increased levels of advanced glycation end products, and changes in vascular homeostasis in the adult offspring heart.

Conclusions

Together our findings provide evidence that a global reduction in Hif1a gene dosage increases predisposition of the offspring exposed to maternal diabetes to cardiac dysfunction, and also underscore Hif1a as a critical factor in the fetal programming of adult cardiovascular disease.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0713-0) contains supplementary material, which is available to authorized users.

Identification of the functional pathways altered by placental cell exposure to high glucose: lessons from the transcript and metabolite interactome

The specific consequences of hyperglycaemia on placental metabolism and function are incompletely understood but likely contribute to poor pregnancy outcomes associated with diabetes mellitus (DM). This study aimed to identify the functional biochemical pathways perturbed by placental exposure to high glucose levels through integrative analysis of the trophoblast transcriptome and metabolome. The human trophoblast cell line, BeWo, was cultured in 5 or 25 mM glucose, as a model of the placenta in DM. Transcriptomic analysis using microarrays, demonstrated 5632 differentially expressed gene transcripts (≥± 1.3 fold change (FC)) following exposure to high glucose. These genes were used to generate interactome models of transcript response using BioGRID (non-inferred network: 2500 nodes (genes) and 10541 protein-protein interactions). Ultra performance-liquid chromatography-mass spectrometry (MS) and gas chromatography-MS analysis of intracellular extracts and culture medium were used to assess the response of metabolite profiles to high glucose concentration. The interactions of altered genes and metabolites were assessed using the MetScape interactome database, resulting in an integrated model of systemic transcriptome (2969 genes) and metabolome (41 metabolites) response within placental cells exposed to high glucose. The functional pathways which demonstrated significant change in response to high glucose included fatty acid β-oxidation, phospholipid metabolism and phosphatidylinositol phosphate signalling.

Regulation of Placental Development and Its Impact on Fetal Growth-New Insights From Mouse Models

The placenta is the chief regulator of nutrient supply to the growing embryo during gestation. As such, adequate placental function is instrumental for developmental progression throughout intrauterine development. One of the most common complications during pregnancy is insufficient growth of the fetus, a problem termed intrauterine growth restriction (IUGR) that is most frequently rooted in a malfunctional placenta. Together with conventional gene targeting approaches, recent advances in screening mouse mutants for placental defects, combined with the ability to rapidly induce mutations in vitro and in vivo by CRISPR-Cas9 technology, has provided new insights into the contribution of the genome to normal placental development. Most importantly, these data have demonstrated that far more genes are required for normal placentation than previously appreciated. Here, we provide a summary of common types of placental defects in established mouse mutants, which will help us gain a better understanding of the genes impacting on human placentation. Based on a recent mouse mutant screen, we then provide examples on how these data can be mined to identify novel molecular hubs that may be critical for placental development. Given the close association between placental defects and abnormal cardiovascular and brain development, these functional nodes may also shed light onto the etiology of birth defects that co-occur with placental malformations. Taken together, recent insights into the regulation of mouse placental development have opened up new avenues for research that will promote the study of human pregnancy conditions, notably those based on defects in placentation that underlie the most common pregnancy pathologies such as IUGR and pre-eclampsia.

Matrix metalloproteinase 14 modulates diabetes and Alzheimer's disease cross-talk: a meta-analysis

Diabetes mellitus is associated with dementia, but whether diabetes is associated with Alzheimer's disease remains controversial. Alzheimer's disease is characterized by amyloid beta aggregation. We hypothesized that genes, involved in amyloid beta degradation, may be altered due to diabetes and thus participate in progression of Alzheimer's disease. Expression profiling of amyloid beta-degrading enzymes in streptozotocin-induced diabetic mice and their correlation with expression of amyloid precursor protein in hippocampus of Alzheimer's disease patients were accessed. We found that matrix metalloproteinase 14 decreased in brain but not in other tissues of streptozotocin-induced diabetic mice, and was negatively correlated with expression of amyloid precursor protein in hippocampus of Alzheimer's disease patients. These findings suggested matrix metalloproteinase 14 may link insulin-deficient diabetes to Alzheimer's disease.

Renal injury is accelerated by global hypoxia-inducible factor 1 alpha deficiency in a mouse model of STZ-induced diabetes

BACKGROUND

Hypoxia inducible factor 1 (HIF-1) activates protective pathways to counteract hypoxia and prevent tissue damage in conjunction with renal injury. The aim of this study was to evaluate a role of HIF-1 in diabetes-induced kidney damage.

METHODS

We used a streptozotocin-induced diabetes mouse model and compared biochemical, histological and molecular parameters associated with kidney damage in Hif1α deficient (Hif1α ^+/- ) and wild-type mice.

RESULTS

We showed that Hif1α deficiency accelerated pathological changes in the early stage of DN. Six weeks after diabetes-induction, Hif1α deficient mice showed more prominent changes in biochemical serum parameters associated with glomerular injury, increased expression of podocyte damage markers, and loss of podocytes compared to wild-type mice. These results indicate that Hif1α deficiency specifically affects podocyte survival in the early phase of DN, resulting in diabetic glomerular injury. In contrast, renal fibrosis was not affected by the global reduction of Hif1α, at least not in the early phase of diabetic exposure.

CONCLUSIONS

Together our data reveal that HIF-1 has an essential role in the early response to prevent diabetes-induced tissue damage and that impaired HIF-1 signaling results in a faster progression of DN. Although the modulation of HIF-1 activity is a high-priority target for clinical treatments, further study is required to investigate HIF-1 as a potential therapeutic target for the treatment of DN.

Transgenerational inheritance of susceptibility to diabetes-induced male subfertility

Male infertility is a worldwide problem associated with genetic background, environmental factors, and diseases. One of the suspected contributing factors to male infertility is diabetes mellitus. We investigated the molecular and morphological changes in sperms and testicular tissue of diabetic males. The study was performed in streptozotocin-induced type 1 diabetes mouse model. Diabetes decreased sperm concentration and viability and increased sperm apoptosis. Changes in protamine 1/protamine 2 ratio indicated reduced sperm quality. The testicular tissue of diabetic males showed significant tissue damage, disruption of meiotic progression, and changes in the expression of genes encoding proteins important for spermiogenesis. Paternal diabetes altered sperm quality and expression pattern in the testes in offspring of two subsequent generations. Our study revealed that paternal diabetes increased susceptibility to infertility in offspring through gametic alternations. Our data also provide a mechanistic basis for transgenerational inheritance of diabetes-associated pathologies since protamines may be involved in epigenetic regulations.

Cellular Stress, Excessive Apoptosis, and the Effect of Metformin in a Mouse Model of Type 2 Diabetic Embryopathy

Increasing prevalence of type 2 diabetes in women of childbearing age has led to a higher incidence of diabetes-associated birth defects. We established a model of type 2 diabetic embryopathy by feeding 4-week-old female mice a high-fat diet (HFD) (60% fat). After 15 weeks on HFD, the mice showed characteristics of type 2 diabetes mellitus (DM) and were mated with lean male mice. During pregnancy, control dams fed a normal diet (10% fat) were maintained on either normal diet or HFD, serving as a control group with elevated circulating free fatty acids. DM dams produced offspring at a rate of 11.3% for neural tube defect (NTD) formation, whereas no embryos in the control groups developed NTDs. Elevated markers of oxidative stress, endoplasmic reticulum stress, caspase activation, and neuroepithelial cell apoptosis (causal events in type 1 diabetic embryopathy) were observed in embryos of DM dams. DM dams treated with 200 mg/kg metformin in drinking water ameliorated fasting hyperglycemia, glucose intolerance, and insulin resistance with consequent reduction of cellular stress, apoptosis, and NTDs in their embryos. We conclude that cellular stress and apoptosis occur and that metformin effectively reduces type 2 diabetic embryopathy in a useful rodent model.

Assisted reproduction causes placental maldevelopment and dysfunction linked to reduced fetal weight in mice

Compelling evidence indicates that stress in utero, as manifested by low birth weight (LBW), increases the risk of metabolic syndrome in adulthood. Singletons conceived by assisted reproductive technology (ART) display a significant increase in LBW risk and ART offspring have a different metabolic profile starting at birth. Here, used mouse as a model, we found that ART resulted in reduced fetal weight and placental overgrowth at embryonic day 18.5 (E18.5). The ART placentae exhibited histomorphological alterations with defects in placental layer segregation and glycogen cells migration at E18.5. Further, ART treatments resulted in downregulation of a majority of placental nutrient transporters and reduction in placental efficiency. Moreover, the ART placentae were associated with increased methylation levels at imprinting control regions of H19, KvDMR1 and disrupted expression of a majority of imprinted genes important for placental development and function at E18.5. Our results from the mouse model show the first piece of evidence that ART treatment could affect fetal growth by disrupting placental development and function, suggests that perturbation of genomic imprinting resulted from embryo manipulation may contribute to these problems.

Effect of maternal diabetes on the embryo, fetus, and children: congenital anomalies, genetic and epigenetic changes and developmental outcomes

INTRODUCTION

Pregestational and gestational diabetes mellitus (PGDM; GDM) are significant health concerns because they are associated with an increased rate of malformations and maternal health complications.

METHODS

We reviewed the data that help us to understand the effects of diabetes in pregnancy.

RESULTS

Diabetic embryopathy can affect any developing organ system, but cardiovascular and neural tube defects are among the most frequent anomalies. Other complications include preeclampsia, preterm delivery, fetal growth abnormalities, and perinatal mortality. Neurodevelopmental studies on offspring of mothers with diabetes demonstrated increased rate of Gross and Fine motor abnormalities, of Attention Deficit Hyperactivity Disorder, learning difficulties, and possibly also Autism Spectrum Disorder. The mechanisms underlying the effects of maternal hyperglycemia on the developing fetus may involve increased oxidative stress, hypoxia, apoptosis, and epigenetic changes. Evidence for epigenetic changes are the following: not all progeny are affected and not to the same extent; maternal diet may influence pregnancy outcomes; and maternal diabetes alters embryonic transcriptional profiles and increases the variation between transcriptomic profiles as a result of altered gene regulation. Research in animal models has revealed that maternal hyperglycemia is a teratogen, and has helped uncover potential therapeutic targets which, when blocked, can mitigate or ameliorate the negative effects of diabetes on the developing fetus.

CONCLUSIONS

Tight metabolic control, surveillance, and labor management remain the cornerstone of care for pregnant women with diabetes, but advances in the field indicate that new treatments to protect the mother and baby are not far from becoming clinical realities.

Maternal hyperglycemia activates an ASK1-FoxO3a-caspase 8 pathway that leads to embryonic neural tube defects

Neural tube defects result from failure to completely close neural tubes during development. Maternal diabetes is a substantial risk factor for neural tube defects, and available evidence suggests that the mechanism that links hyperglycemia to neural tube defects involves oxidative stress and apoptosis. We demonstrated that maternal hyperglycemia correlated with activation of the apoptosis signal-regulating kinase 1 (ASK1) in the developing neural tube, and Ask1 gene deletion was associated with reduced neuroepithelial cell apoptosis and development of neural tube defects. ASK1 activation stimulated the activity of the transcription factor FoxO3a, which increased the abundance of the apoptosis-promoting adaptor protein TRADD, leading to activation of caspase 8. Hyperglycemia-induced apoptosis and the development of neural tube defects were reduced with genetic ablation of either FoxO3a or Casp8 or inhibition of ASK1 by thioredoxin. Examination of human neural tissues affected by neural tube defects revealed increased activation or abundance of ASK1, FoxO3a, TRADD, and caspase 8. Thus, activation of an ASK1-FoxO3a-TRADD-caspase 8 pathway participates in the development of neural tube defects, which could be prevented by inhibiting intermediates in this cascade.

Mild gestational hyperglycemia in rat induces fetal overgrowth and modulates placental growth factors and nutrient transporters expression

Mild gestational hyperglycemia is often associated with fetal overgrowth that can predispose the offspring to metabolic diseases later in life. We hypothesized that unfavorable intrauterine environment may compromise the development of placenta and contribute to fetal overgrowth. Therefore, we developed a rat model and investigated the effects of maternal dysglycemia on fetal growth and placental gene expression. Female rats were treated with single injection of nicotinamide plus streptozotocin (N-STZ) 1-week before mating and were studied at gestational day 21. N-STZ pregnant females displayed impaired glucose tolerance that is associated with a lower insulin secretion. Moderate hyperglycemia induced fetal overgrowth in 40% of newborns, from pregnancies with 10 to 14 pups. The incidence of macrosomia was less than 5% in the N-STZ pregnancies when the litter size exceeds 15 newborns. We found that placental mass and the labyrinthine layer were increased in macrosomic placentas. The expression of genes involved in placental development and nutrient transfer was down regulated in the N-STZ placentas of macrosomic and normosomic pups from pregnancies with 10 to 14 ones. However, we observed that lipoprotein lipase 1 (LPL1) gene expression was significantly increased in the N-STZ placentas of macrosomic pups. In pregnancies with 15 pups or more, the expression of IGFs and glucose transporter genes was also modulated in the control placentas with no additional effect in the N-STZ ones. These data suggest that placental gene expression is modulated by gestational conditions that might disrupt the fetal growth. We described here a new model of maternal glucose intolerance that results in fetal overgrowth. We proposed that over-expression of LPL1 in the placenta may contribute to the increased fetal growth in the N-STZ pregnancies. N-STZ model offers the opportunity to determinate whether these neonatal outcomes may contribute to developmental programming of metabolic diseases in adulthood.

Mutation at the folate receptor 4 locus modulates gene expression profiles in the mouse uterus in response to periconceptional folate supplementation

Periconceptional supplementation of folic acid to the diet of women is considered a great success for a public health intervention. Higher folate status, either by supplementation, or via the mandatory fortification of grain products in the United States, has led to significant reduction in the incidence of neural tube defects. Besides birth defects, folate deficiency has been linked to a variety of morbidities, most notably to increased risk for cancer. However, recent evidence suggests that excess folate may be detrimental - for birth defect incidence or in the progression of cancer. How folate mediates beneficial or detrimental effects is not well understood. It is also unknown what molecular responses are elicited in women taking folate supplements, and thus experience a bolus of folate on top of the status achieved by fortification. To characterize the response to a periconceptional regimen of supplementation with folinic acid, we performed gene expression profiling experiments on uterus tissue of pregnant mice with either wildtype alleles or targeted disruption at the folate receptor 4 locus. We observed that, depending on the genetic background, folinic acid supplementation affects expression of genes that contribute to lipid metabolism, protein synthesis, mitochondrial function, cell cycle, and cell activation. The extent of the response is strongly modulated by the genetic background. Finally, we provide evidence that folinic acid supplementation in the mutant paradigm affects histone methylation status, a potential mechanism of gene regulation in this model.

Increased susceptibility of HIF-1α heterozygous-null mice to cardiovascular malformations associated with maternal diabetes

Cardiovascular malformations are the most common manifestation of diabetic embryopathy. The molecular mechanisms underlying the teratogenic effect of maternal diabetes have not been fully elucidated. Using genome-wide expression profiling, we previously demonstrated that exposure to maternal diabetes resulted in dysregulation of the hypoxia-inducible factor 1 (HIF-1) pathway in the developing embryo. We thus considered a possible link between HIF-1-regulated pathways and the development of congenital malformations. HIF-1α heterozygous-null (Hif1a(+/-)) and wild type (Wt) littermate embryos were exposed to the intrauterine environment of a diabetic mother to analyze the frequency and morphology of congenital defects, and assess gene expression changes in Wt and Hif1a(+/-) embryos. We observed a decreased number of embryos per litter and an increased incidence of heart malformations, including atrioventricular septal defects and reduced myocardial mass, in diabetes-exposed Hif1a(+/-) embryos as compared to Wt embryos. We also detected significant differences in the expression of key cardiac transcription factors, including Nkx2.5, Tbx5, and Mef2C, in diabetes-exposed Hif1a(+/-) embryonic hearts compared to Wt littermates. Thus, partial global HIF-1α deficiency alters gene expression in the developing heart and increases susceptibility to congenital defects in a mouse model of diabetic pregnancy.

Morphometric analysis of the placenta in the New World mouse Necromys lasiurus (Rodentia, Cricetidae): a comparison of placental development in cricetids and murids

BACKGROUND

Stereology is an established method to extrapolate three-dimensional quantities from two-dimensional images. It was applied to placentation in the mouse, but not yet for other rodents. Herein, we provide the first study on quantitative placental development in a sigmodontine rodent species with relatively similar gestational time. Placental structure was also compared to the mouse, in order to evaluate similarities and differences in developmental patterns at the end of gestation.

METHODS

Fetal and placental tissues of Necromys lasiurus were collected and weighed at 3 different stages of gestation (early, mid and late gestation) for placental stereology. The total and relative volumes of placenta and of its main layers were investigated. Volume fractions of labyrinth components were quantified by the One Stop method in 31 placentae collected from different individuals, using the Mercator software. Data generated at the end of gestation from N. lasiurus placentae were compared to those of Mus musculus domesticus obtained at the same stage.

RESULTS

A significant increase in the total absolute volumes of the placenta and its main layers occurred from early to mid-gestation, followed by a reduction near term, with the labyrinth layer becoming the most prominent area. Moreover, at the end of gestation, the total volume of the mouse placenta was significantly increased compared to that of N. lasiurus although the proportions of the labyrinth layer and junctional zones were similar. Analysis of the volume fractions of the components in the labyrinth indicated a significant increase in fetal vessels and sinusoidal giant cells, a decrease in labyrinthine trophoblast whereas the proportion of maternal blood space remained stable in the course of gestation. On the other hand, in the mouse, volume fractions of fetal vessels and sinusoidal giant cells decreased whereas the volume fraction of labyrinthine trophoblast increased compared to N. lasiurus placenta.

CONCLUSIONS

Placental development differed between N. lasiurus and M. musculus domesticus. In particular, the low placental efficiency in N. lasiurus seemed to induce morphological optimization of fetomaternal exchanges. In conclusion, despite similar structural aspects of placentation in these species, the quantitative dynamics showed important differences.

Oxidative stress-induced JNK1/2 activation triggers proapoptotic signaling and apoptosis that leads to diabetic embryopathy

Oxidative stress and apoptosis are implicated in the pathogenesis of diabetic embryopathy. The proapoptotic c-Jun NH(2)-terminal kinases (JNK)1/2 activation is associated with diabetic embryopathy. We sought to determine whether 1) hyperglycemia-induced oxidative stress is responsible for the activation of JNK1/2 signaling, 2) JNK1 contributes to the teratogenicity of hyperglycemia, and 3) both JNK1 and JNK2 activation cause activation of downstream transcription factors, caspase activation, and apoptosis, resulting in neural tube defects (NTDs). Wild-type (WT) embryos from nondiabetic WT dams and WT, superoxide dismutase (SOD)1-overexpressing, jnk1(+/-), jnk1(-/-), and jnk2(-/-) embryos exposed to maternal hyperglycemia were used to assess JNK1/2 activation, NTDs, activation of transcription factors downstream of JNK1/2, caspase cascade, and apoptosis. SOD1 overexpression abolished diabetes-induced activation of JNK1/2 and their downstream effectors: phosphorylation of c-Jun, activating transcription factor 2, and E twenty-six-like transcription factor 1 and dephosphorylation of forkhead box class O3a. jnk1(-/-) embryos had significantly lower incidences of NTDs than those of WT or jnk1(+/-) embryos. Either jnk1 or jnk2 gene deletion blocked diabetes-induced activation of JNK1/2 signaling, caspases 3 and 8, and apoptosis in Sox1(+) neural progenitors of the developing neural tube. Our results show that JNK1 and JNK2 are equally involved in diabetic embryopathy and that the oxidative stress-JNK1/2-caspase pathway mediates the proapoptotic signals and the teratogenicity of maternal diabetes.

Maternal diet modulates placenta growth and gene expression in a mouse model of diabetic pregnancy

Unfavorable maternal diet during pregnancy can predispose the offspring to diseases later in life, such as hypertension, metabolic syndrome, and obesity. However, the molecular basis for this phenomenon of "developmental programming" is poorly understood. We have recently shown that a diet nutritionally optimized for pregnancy can nevertheless be harmful in the context of diabetic pregnancy in the mouse, associated with a high incidence of neural tube defects and intrauterine growth restriction. We hypothesized that placental abnormalities may contribute to impaired fetal growth in these pregnancies, and therefore investigated the role of maternal diet in the placenta. LabDiet 5015 diet was associated with reduced placental growth, commencing at midgestation, when compared to pregnancies in which the diabetic dam was fed LabDiet 5001 maintenance chow. Furthermore, by quantitative RT-PCR we identify 34 genes whose expression in placenta at midgestation is modulated by diet, diabetes, or both, establishing biomarkers for gene-environment interactions in the placenta. These results implicate maternal diet as an important factor in pregnancy complications and suggest that the early phases of placenta development could be a critical time window for developmental origins of adult disease.

[Analysis of gene expression profile of peripheral ganglia in early stage type Ⅱ diabetic rats]

Diabetic neuropathy (DN) is defined as the presence of symptoms and/or signs of peripheral nerve dysfunction in people with diabetes. The aim of this study is to screen differentially expressed genes in peripheral ganglia in early stage type Ⅱ experimental diabetic rats. We compared gene expression profiles of peripheral ganglia in type Ⅱ diabetic and nondiabetic rats based on Illumina® Sentrix® BeadChip arrays. The results showed that 158 out of a total of 12 604 known genes were significantly differentially expressed, including 87 up-regulated and 71 down-regulated genes, in diabetic rats compared with those in the nondiabetic rats. It is noted that some up-regulated genes are involved in the biological processes of neuronal cytoskeleton and motor proteins. In contrast, the down-regulated genes are associated with the response to virus\biotic stimulus\ other organism in diabetic rats. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the most significant pathway enriched in the changed gene set is metabolism (P < 0.001). These results indicated that metabolic changes in peripheral ganglia of diabetic rats could be induced by hyperglycemia. Hyperglycemia could change the expression of genes involved in neuronal cytoskeleton and motor proteins through immune inflammatory response, and then impair the structure and function of the peripheral ganglia.