Pathogenesis of diabetes-induced congenital malformations

Maternal Diabetes and Risk of Hypospadias: A Systemic Review and Meta-Analysis

INTRODUCTION

This study aimed to investigate the association between maternal diabetes and the risk of hypospadias in male infants, as the relationship between them remains uncertain.

METHODS

To comprehensively evaluate the association between pregestational diabetes mellitus and gestational diabetes mellitus with hypospadias, we conducted a systematic review and meta-analysis. A thorough literature search was conducted, encompassing relevant publications published prior to January 2023. Crude odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were calculated using a random-effects model.

RESULTS

Our meta-analysis comprised a total of 13 studies, 11 of which investigated the relationship between pregestational diabetes mellitus and hypospadias, while 9 studies explored the association between gestational diabetes mellitus and hypospadias. Notably, these investigations yielded compelling evidence of significant positive associations between pregestational diabetes mellitus and hypospadias (OR = 1.51, 95% CI = 1.13-2.03), as well as between gestational diabetes mellitus and hypospadias (OR = 1.18, 95% CI = 1.04-1.35).

CONCLUSION

Our findings suggest that both pregestational diabetes mellitus and gestational diabetes mellitus are associated with an increased risk of hypospadias in offspring. Further investigations are needed to explore the optimal range of blood glucose during pregnancy that minimizes the risk of congenital malformation in the fetus, as well as to develop more effective measures for glycemic control in pregnant women.

Epigenetic implications in maternal diabetes and metabolic syndrome-associated risk of orofacial clefts

Orofacial clefts (OFCs) are one of the most common types of structural birth defects. The etiologies are complicated, involving with genetic, epigenetic, and environmental factors. Studies have found that maternal diabetes and metabolic syndrome are associated with a higher risk of OFCs in offspring. Metabolic syndrome is a clustering of several disease risk factors, including hyperglycemia, dyslipidemia, obesity, and hypertension. Metabolic disease during pregnancy can increase risk of adverse outcomes and significantly influence fetal development, including orofacial formation and fusion. An altered metabolic state may contribute to developmental disorders or congenital defects including OFCs, potentially through epigenetic modulations, such as histone modification, DNA methylation, and noncoding RNA expression to alter activities of critical morphogenetic signaling or related developmental genes. This review summarizes the currently available evidence and underlying mechanisms of how the maternal metabolic syndrome is associated with OFCs in mostly human and some animal studies. It may provide a better understanding of the interactions between intrauterine metabolic status and fetal orofacial development which might be applied toward prevention and treatments of OFCs.

Gestational diabetes is associated with the risk of offspring's congenital anomalies: a register-based cohort study

BACKGROUND

Gestational diabetes mellitus (GDM) is a common pregnancy-related disorder and a well-known risk factor for adverse pregnancy outcomes. There are conflicting findings on the association of GDM with the risk of congenital anomalies (CAs) in offspring. In this study, we aimed to determine study whether maternal GDM is associated with an increased risk of major CAs in offspring.

METHODS

This Finnish Gestational Diabetes (FinnGeDi) register-based study included 6,597 women with singleton pregnancies and a diagnosis of GDM and 51,981 singleton controls with no diabetes identified from the Finnish Medical Birth Register (MBR) in 2009. Data from MBR were combined in this study with the Register of Congenital Malformations, which includes the data of CAs. We used logistic regression to calculate odds ratios (OR) for CAs, together with their 95% confidence intervals (CIs), adjusting for maternal age, parity, pre-pregnancy body mass index (BMI), and maternal smoking status.

RESULTS

The risk of major CAs was higher in the GDM-exposed (n = 336, 5.09%) than in the non-exposed group (n = 2,255, 4.33%) (OR: 1.18, 95% CI: 1.05-1.33, p = 0.005). The adjusted OR (aOR) was 1.14 (95% CI: 1.00-1.30, p = 0.047). There was a higher overall prevalence of CAs, particularly chromosomal abnormalities (0.52% vs. 0.21%), in the GDM-exposed group (OR: 2.49, 95% Cl: 1.69-3.66, p < 0.001). The aOR was 1.93 (95% Cl: 1.25-2.99, p = 0.003).

CONCLUSIONS

Offspring exposed to GDM have a higher prevalence of major CAs. Of note, risk factors other than GDM, such as older maternal age and a higher pre-pregnancy BMI, diminished the between group differences in the prevalence of major CAs. Nevertheless, our findings suggest that offspring exposed to maternal GDM are more likely to be diagnosed with a chromosomal abnormality, independent of maternal age, parity, pre-pregnancy BMI, and smoking.

No association between major congenital malformations and exposure to Kampo medicines containing rhubarb rhizome: A Japanese database study

Traditional Japanese (Kampo) medicines containing rhubarb rhizome are prescribed for constipation during pregnancy; however, detailed safety information of their use for pregnant women is lacking. The aim of current study was to clarify the association between prescription Kampo-containing rhubarb rhizome (KRR) in the first trimester of pregnancy and congenital malformations in newborns. Using a large Japanese health insurance claims database, we included pregnant women who enrolled the same health insurance society from 3 months before pregnancy to the delivery date, who gave birth between 2010 and 2019, and those with data related to their infants. Pregnant women who were prescribed magnesium oxide (MgO), commonly used for constipation, during the first trimester of pregnancy and their infants were extracted as controls. Associations between KRR prescribed in the first pregnancy trimester and major congenital malformations (MCM) in the infants were examined using multivariate logistic regression analysis. Of 75,398 infants, 4,607 (6.1%) were diagnosed with MCMs within the first year after birth. Furthermore, 9,852 infants were born to women prescribed MgO, among whom 680 (6.9%) had MCMs; 450 infants were born to women prescribed KRR, among whom 28 (6.2%) had MCMs. Multivariate logistic regression analysis identified no difference in MCM risk between the two types of prescriptions [crude odds ratio (OR) 0.895, 95% confidence interval (CI) 0.606-1.322, adjusted OR 0.889, 95% CI 0.599-1.320]. In conclusion, the risk of MCMs did not differ between those prescribed KRR or MgO in the first trimester of pregnancy.

A systematic review of maternal diabetes and congenital skeletal malformation

The magnitude of association of skeletal anomalies with maternal diabetes is not known. The systemic review was done to detect the frequency of congenital skeletal malformations with diabetes mellitus in pregnancy in the literature evidence of the past 50 years. Literature on maternal diabetes and skeletal malformation was searched by two independent authors by following PRISMA guidelines. Strict inclusion and exclusion criteria were followed. After quality assessment, 21 original articles were included. The frequency of congenital malformation, skeletal malformation was extracted from the included studies. 11,574 congenital anomalies were detected diabetic mothers. 1182 skeletal anomalies were noted in 20,11 552 diabetic mothers. The skeletal malformation was noted in 20.4% of total anomalies. The most common skeletal malformation was the defect of the spine (39.9%). The limb deficiency was found in 32.8% of the infants of diabetic mothers. The skeletal malformations were higher, that is, 24.6% in pre-gestational diabetes. The incidence of skeletal malformation from the evidence was 1.5% (range: 0.03-4.27%) in maternal diabetes. Pre-gestation diabetes is more frequently associated with skeletal malformations, which is 1.9% (range: 0.07-5.89%). The association of congenital malformations and skeletal malformations in diabetic pregnancy is significant and hence, effective management of diabetes in childbearing age is essential to reduce this incidence and related long-term morbidity.

Stem cell fate determination through protein O-GlcNAcylation

Embryonic and adult stem cells possess the capability of self-renewal and lineage-specific differentiation. The intricate balance between self-renewal and differentiation is governed by developmental signals and cell-type-specific gene regulatory mechanisms. A perturbed intra/extracellular environment during lineage specification could affect stem cell fate decisions resulting in pathology. Growing evidence demonstrates that metabolic pathways govern epigenetic regulation of gene expression during stem cell fate commitment through the utilization of metabolic intermediates or end products of metabolic pathways as substrates for enzymatic histone/DNA modifications. UDP-GlcNAc is one such metabolite that acts as a substrate for enzymatic mono-glycosylation of various nuclear, cytosolic, and mitochondrial proteins on serine/threonine amino acid residues, a process termed protein O-GlcNAcylation. The levels of GlcNAc inside the cells depend on the nutrient availability, especially glucose. Thus, this metabolic sensor could modulate gene expression through O-GlcNAc modification of histones or other proteins in response to metabolic fluctuations. Herein, we review evidence demonstrating how stem cells couple metabolic inputs to gene regulatory pathways through O-GlcNAc-mediated epigenetic/transcriptional regulatory mechanisms to govern self-renewal and lineage-specific differentiation programs. This review will serve as a primer for researchers seeking to better understand how O-GlcNAc influences stemness and may catalyze the discovery of new stem-cell-based therapeutic approaches.

Association of Maternal Prepregnancy Diabetes and Gestational Diabetes Mellitus With Congenital Anomalies of the Newborn

OBJECTIVE

To examine the association of maternal prepregnancy diabetes, gestational diabetes mellitus (GDM), and 12 subtypes of congenital anomalies of the newborn.

RESEARCH DESIGN AND METHODS

We included 29,211,974 live births with maternal age ranging from 18 to 49 years old documented in the National Vital Statistics System in the U.S. from 2011 to 2018. Information on prepregnancy diabetes, GDM, and congenital anomalies was retrieved from birth certificates. Log-binomial regression was used to estimate risk ratios (RRs) and 95% CIs for congenital anomalies overall and by subtypes.

RESULTS

Of the 29,211,974 live births, there were 90,061 infants who had congenital anomalies identified at birth. The adjusted RRs of congenital anomalies at birth were 2.44 (95% CI 2.33-2.55) for prepregnancy diabetes and 1.28 (95% CI 1.24-1.31) for GDM. The associations were generally consistent across subgroups by maternal age, race/ethnicity, prepregnancy obesity status, and infant sex. For specific subtypes of congenital anomalies, maternal prepregnancy diabetes or GDM was associated with an increased risk of most subtypes. For example, the adjusted RRs of cyanotic congenital heart disease were 4.61 (95% CI 4.28-4.96) for prepregnancy diabetes and 1.50 (95% CI 1.43-1.58) for GDM; the adjusted RRs of hypospadias were 1.88 (95% CI 1.67-2.12) for prepregnancy diabetes and 1.29 (95% CI 1.21-1.36) for GDM.

CONCLUSIONS

Prepregnancy diabetes and, to a lesser extent, GDM were associated with several subtypes of congenital anomalies of the newborn. These findings suggest potential benefits of preconception counseling in women with preexisting diabetes or at risk for GDM for the prevention of congenital anomalies.

High-fat diet in pregnant rats and adverse fetal outcome

Background: Although pregestational obesity has been associated with increased risk of adverse fetal outcome, the mechanisms behind are not known. We aimed to investigate the influence of the maternal metabolic state on fetal outcome in rats exposed to either a high-fat diet (HFD) or a control diet (CD). We also investigated the impact of serum collected from HFD/CD pregnant rats on CD embryonic development in whole-embryo cultures. Material and methods: On gestational day 0, 9, 10, or 20 maternal plasma/serum samples were collected as pregnancies were terminated for the estimations of maternal metabolic state and embryo-fetal development. We measured embryonic gene expression of ROS scavenger enzymes as well as genes involved in inflammation in maternal adipose tissue. Results: In HFD maternal plasma/serum, concentrations of glucose, β-hydroxybutyrate, branched-chain amino acids, and leptin were increased, whereas those of triacylglycerol, cholesterol, and palmitic, oleic, linoleic, and α-linolenic acids were decreased. Gene expression of CuZnSOD, IL-6, IL-10, and resistin was increased in HFD maternal adipose tissue, whereas that of CuZnSOD and MnSOD was decreased in HFD-exposed embryos. HFD caused retention of most fatty acids in the maternal liver as well. Conclusion: HFD alters the maternal metabolic state, increases fetal resorptions in vivo, and increases the rate of fetal/embryonic malformations both in vivo and in vitro. These findings suggest that metabolic disturbances in HFD pregnant rats have profound adverse developmental effects in the offspring.

Pancreatic islet response to diabetes during pregnancy in rats

AIMS

The objective of this study was to assess the mechanisms underlying pancreatic islet adaptation in diabetic mothers and their pups. Additionally, the influence of pancreatic adaptations on maternal reproductive performance was also investigated.

MAIN METHODS

Wistar rats were injected with streptozotocin for diabetes induction. At adulthood (3 months), all animals underwent an oral glucose tolerance test (OGTT) for glucose assessment as an inclusion criterion. Following, the animals were mated. At day 18 of pregnancy, the mothers were killed for blood collect ion to determine fasting insulin and glucagon concentrations. The pancreas was removed and processed for the immunohistochemical analysis of insulin, glucagon, somatostatin, Ki-67 and PDX-1, superoxide dismutase 1 (SOD-1), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA). The pregnant uterus was also collected for the evaluation of embryofetal loss.

KEY FINDINGS

The diabetic rats showed increased glucose, serum glucagon and insulin concentrations, and embryofetal loss rates. They also showed a reduction in pancreatic islets area and percentage of cells stained for insulin, increased the percentage of non-β cells (alpha e delta cells) stained for Ki-67, glucagon, and somatostatin. Moreover, the cells stained for somatostatin were spread across the islets and showed stronger staining for MDA and weaker staining for GSH-Px.

SIGNIFICANCE

Diabetes leads to adaptive responses from the endocrine pancreas in pregnancy that especially involves non-β cells, modifying the mantle-core structure. Nonetheless, these adaptations are not enough for glucose homeostasis and affect the maternal environment, which in turn impairs fetal development.

Do inositol supplements enhance phosphatidylinositol supply and thus support endoplasmic reticulum function?

This review attempts to explain why consuming extra myoinositol (Ins), an essential component of membrane phospholipids, is often beneficial for patients with conditions characterised by insulin resistance, non-alcoholic fatty liver disease and endoplasmic reticulum (ER) stress. For decades we assumed that most human diets provide an adequate Ins supply, but newer evidence suggests that increasing Ins intake ameliorates several disorders, including polycystic ovary syndrome, gestational diabetes, metabolic syndrome, poor sperm development and retinopathy of prematurity. Proposed explanations often suggest functional enhancement of minor facets of Ins Biology such as insulin signalling through putative inositol-containing 'mediators', but offer no explanation for this selectivity. It is more likely that eating extra Ins corrects a deficiency of an abundant Ins-containing cell constituent, probably phosphatidylinositol (PtdIns). Much of a cell's PtdIns is in ER membranes, and an increase in ER membrane synthesis, enhancing the ER's functional capacity, is often an important part of cell responses to ER stress. This review: (a) reinterprets historical information on Ins deficiency as describing a set of events involving a failure of cells adequately to adapt to ER stress; (b) proposes that in the conditions that respond to dietary Ins there is an overstretching of Ins reserves that limits the stressed ER's ability to make the 'extra' PtdIns needed for ER membrane expansion; and (c) suggests that eating Ins supplements increases the Ins supply to Ins-deficient and ER-stressed cells, allowing them to make more PtdIns and to expand the ER membrane system and sustain ER functions.

Hyperglycemia Alters the Structure and Hemodynamics of the Developing Embryonic Heart

Congenital heart defects (CHDs) represent the most common form of human birth defects; approximately one-third of heart defects involve malformations of the outflow tract (OFT). Maternal diabetes increases the risk of CHD by 3-5 fold. During heart organogenesis, little is known about the effects of hyperglycemia on hemodynamics, which are critical to normal heart development. Heart development prior to septation in the chick embryo was studied under hyperglycemic conditions. Sustained hyperglycemic conditions were induced, raising the average plasma glucose concentration from 70 mg/dL to 180 mg/dL, akin to the fasting plasma glucose of a patient with diabetes. The OFTs were assessed for structural and hemodynamic alterations using optical coherence tomography (OCT), confocal microscopy, and microcomputed tomography. In hyperglycemic embryos, the endocardial cushions of the proximal OFT were asymmetric, and the OFTs curvature and torsion were significantly altered. The blood flow velocity through the OFT of hyperglycemic embryos was significantly decreased, including flow reversal in 30% of the cardiac cycle. Thus, hyperglycemia at the onset of gestation results in asymmetric proximal endocardial cushions, abnormal OFT curvature, and altered hemodynamics in the developing heart. If present in humans, these results may identify early developmental alterations that contribute to the increased risk for cardiac malformations in babies from diabetic mothers.

New development of the yolk sac theory in diabetic embryopathy: molecular mechanism and link to structural birth defects

Maternal diabetes mellitus is a significant risk factor for structural birth defects, including congenital heart defects and neural tube defects. With the rising prevalence of type 2 diabetes mellitus and obesity in women of childbearing age, diabetes mellitus-induced birth defects have become an increasingly significant public health problem. Maternal diabetes mellitus in vivo and high glucose in vitro induce yolk sac injuries by damaging the morphologic condition of cells and altering the dynamics of organelles. The yolk sac vascular system is the first system to develop during embryogenesis; therefore, it is the most sensitive to hyperglycemia. The consequences of yolk sac injuries include impairment of nutrient transportation because of vasculopathy. Although the functional relationship between yolk sac vasculopathy and structural birth defects has not yet been established, a recent study reveals that the quality of yolk sac vasculature is related inversely to embryonic malformation rates. Studies in animal models have uncovered key molecular intermediates of diabetic yolk sac vasculopathy, which include hypoxia-inducible factor-1α, apoptosis signal-regulating kinase 1, and its inhibitor thioredoxin-1, c-Jun-N-terminal kinases, nitric oxide, and nitric oxide synthase. Yolk sac vasculopathy is also associated with abnormalities in arachidonic acid and myo-inositol. Dietary supplementation with fatty acids that restore lipid levels in the yolk sac lead to a reduction in diabetes mellitus-induced malformations. Although the role of the human yolk in embryogenesis is less extensive than in rodents, nevertheless, human embryonic vasculogenesis is affected negatively by maternal diabetes mellitus. Mechanistic studies have identified potential therapeutic targets for future intervention against yolk sac vasculopathy, birth defects, and other complications associated with diabetic pregnancies.

High glucose environment inhibits cranial neural crest survival by activating excessive autophagy in the chick embryo

High glucose levels induced by maternal diabetes could lead to defects in neural crest development during embryogenesis, but the cellular mechanism is still not understood. In this study, we observed a defect in chick cranial skeleton, especially parietal bone development in the presence of high glucose levels, which is derived from cranial neural crest cells (CNCC). In early chick embryo, we found that inducing high glucose levels could inhibit the development of CNCC, however, cell proliferation was not significantly involved. Nevertheless, apoptotic CNCC increased in the presence of high levels of glucose. In addition, the expression of apoptosis and autophagy relevant genes were elevated by high glucose treatment. Next, the application of beads soaked in either an autophagy stimulator (Tunicamycin) or inhibitor (Hydroxychloroquine) functionally proved that autophagy was involved in regulating the production of CNCC in the presence of high glucose levels. Our observations suggest that the ERK pathway, rather than the mTOR pathway, most likely participates in mediating the autophagy induced by high glucose. Taken together, our observations indicated that exposure to high levels of glucose could inhibit the survival of CNCC by affecting cell apoptosis, which might result from the dysregulation of the autophagic process.

MiR-17 Downregulation by High Glucose Stabilizes Thioredoxin-Interacting Protein and Removes Thioredoxin Inhibition on ASK1 Leading to Apoptosis

Pregestational diabetes significantly increases the risk of neural tube defects (NTDs). Maternal diabetes activates an Apoptosis Signal-regulating Kinase 1 (ASK1)-initiated pathway, which triggers neural stem cell apoptosis of the developing neuroepithelium leading to NTD formation. How high glucose of diabetes activates ASK1 is still unclear. In this study, we investigated the mechanism underlying high glucose-induced ASK1 activation. High glucose suppressed miR-17 expression, which led to an increase in its target gene Txnip (Thioredoxin-interacting protein). High glucose-increased Txnip enhanced its binding to the ASK1 inhibitor, thioredoxin (Trx), and thereby sequestered Trx from the Trx-ASK1 complex. High glucose-induced ASK1 activation and consequent apoptosis were abrogated by either the miR-17 mimic or Txnip siRNA knockdown. In contrast, the miR-17 inhibitor or Txnip ectopic overexpression mimicked the stimulative effect of high glucose on ASK1 and apoptosis. Thus, our study demonstrated that miR-17 repression mediates the pro-apoptotic effect of high glucose, and revealed a new mechanism underlying ASK1 activation, in which decreased miR-17 removes Trx inhibition on ASK1 through Txnip.

Advances in revealing the molecular targets downstream of oxidative stress-induced proapoptotic kinase signaling in diabetic embryopathy

Preexisting maternal diabetes is a high-risk factor of diabetic embryopathy, such as neural tube defects and congenital heart defects. Maternal diabetes significantly increases the production of reactive oxygen species, resulting in oxidative stress and diabetic embryopathy. Multiple cellular and metabolic factors contribute to these processes. Forkhead box O (FoxO)-3a has been demonstrated as a key transcription factor in the signaling transduction pathways responsible for maternal diabetes-induced birth defects. Apoptosis signal-regulating kinase 1 (ASK1) activated by oxidative stress stimulates nuclear translocation of FoxO3a, resulting in the overexpression of tumor necrosis factor receptor 1-associated death domain protein, which, in turn, leads to caspase-8 activation and apoptosis. Maternal diabetes-activated c-Jun N-terminal kinase (JNK)-1/2, downstream effectors of ASK1, can be blocked by superoxide dismutase-1 overexpression, suggesting that oxidative stress is responsible for JNK1/2 signaling activation. Deletion of JNK1/2 significantly suppressed the activity of FoxO3a. These observations indicate that maternal diabetes-induced oxidative stress stimulates the activation of ASK1, JNK1/2, FoxO3a, tumor necrosis factor receptor 1-associated death domain protein, caspase-8 cleavage, and finally, apoptosis and diabetic embryopathy.

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, βII 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.

Importance of maternal diabetes on the chronological deregulation of the intrauterine development: an experimental study in rat

We investigated whether maternal diabetes induced in rats using streptozotocin (STZ) on Day 5 of pregnancy affects the intrauterine developmental timeline. A total of 30 pregnant Sprague-Dawley diabetic rats (DRs) and 20 control rats (CRs) were used to obtain 21-day fetuses (F21) and newborn (NB) pups. Gestational age, weight, and body size were recorded as were the maxillofacial morphometry and morphohistological characteristics of the limbs. In DRs, pregnancy continued for ∼1.7 days, and delivery occurred 23 days postcoitus (DPC). In this group, the number of pups was lower, and 13% had maxillofacial defects. F21 in the DR group had lower weights and were smaller; moreover, the morphological characteristics of the maxillofacial structures, derived from the neural crest, were discordant with their chronological gestational age, resembling 18- to 19-day-old fetuses. These deficiencies were counterbalanced in NB pups. We conclude that hyperglycemia, which results from maternal diabetes and precedes embryo implantation, deregulates the intrauterine developmental timeline, restricts embryo-fetal growth, and primarily delays the remodeling and maturation of the structures derived from neural crest cells.

Short and long-term repercussions of the experimental diabetes in embryofetal development

BACKGROUND

Diabetic pregnancy have increased rates of congenital malformation and neonatal mortality. In vitro studies suggest hyperglycemia associated with diabetes impair embryogenesis but in vivo investigations on maternal hyperglycemic insult and early embryo development are scarce. We evaluated the embryofetal development on experimental diabetes models to assess whether hyperglycemia at preimplantation period impairs the progression of pregnancy.

METHODS

Different hyperglycemic intensities were obtained by two experimental diabetes models. Female Sprague Dawley rats received streptozotocin at birth (mild diabetes) or at day 90 of life (severe diabetes). For both diabetic groups hyperglycemia was confirmed 5 days after diabetes induction and the mating was performed around 100 day of life. For preimplantation analysis, embryos were recovered at D4 of pregnancy. Another group of animals was submitted to laparotomy at D21 to assess contents of the uterus and fetal viability.

RESULTS

Mild (i) and Severe (ii) diabetes modified the early development. Degenerating embryos percentage was higher compared to control (11%) (i) 30.7%, (ii) 37.3%. Cell number mean dropped according to hyperglycemic intensity (control 30.57, (i) 21.42, (ii) 13.42). Pre and post-implantation loss rates were higher in diabetic groups. The fetal viability also decreased from 96% in the control group to (i) 78.7% and (ii) 80.6%.

CONCLUSION

Our results show that during diabetic pregnancy, preimplantation embryos present decreased cell number due to higher apoptosis rates, which are dependent of the hyperglycemic intensity. Moreover, fetal viability was also decreased suggesting that the quality of these embryos at long-term may be questioned.

Accumulation of advanced glycation end products in the rabbit blastocyst under maternal diabetes

Diabetes mellitus (DM) during pregnancy is one of the leading causes of perinatal morbidity and birth defects. The mechanism by which maternal hyperglycemia, the major teratogenic factor, induces embryonic malformations remains unclear. Advanced glycation end products (AGEs) are known to accumulate during the course of DM and contribute to the development of diabetic complications. Employing a diabetic rabbit model, we investigated the influence of maternal hyperglycemia during the preimplantation period on AGE formation (pentosidine, argpyrimidine, and Nε-carboxymethyllysine (CML)) in the reproductive tract and the embryo itself. As a consequence of type 1 DM, the AGE levels in blood plasma increased up to 50%, correlating closely with an AGE accumulation in the endometrium of diabetic females. Embryos from diabetic mothers had increased protein-bound CML levels and showed enhanced fluorescent signals for AGE-specific fluorescence in the blastocyst cavity fluid (BCF). The quantification of CML by HPLC–mass spectrometry (MS/MS) showed a higher amount of soluble CML in the BCF of blastocysts from diabetic rabbits (0.26±0.05 μmol/l) compared with controls (0.18±0.02 μmol/l). The high amount of AGEs in blastocysts from diabetic mothers correlates positively with an increased AGER (receptor for AGE (RAGE)) mRNA expression. Our study gives alarming insights into the consequences of poorly controlled maternal diabetes for AGE formation in the embryo. Maternal hyperglycemia during the preimplantation period is correlated with an increase in AGE formation in the uterine environment and the embryo itself. This may influence the development of the embryo through increased AGE-mediated cellular stress by RAGEs.

Streptozotocin-induced diabetes models: pathophysiological mechanisms and fetal outcomes

Glucose homeostasis is controlled by endocrine pancreatic cells, and any pancreatic disturbance can result in diabetes. Because 8% to 12% of diabetic pregnant women present with malformed fetuses, there is great interest in understanding the etiology, pathophysiological mechanisms, and treatment of gestational diabetes. Hyperglycemia enhances the production of reactive oxygen species, leading to oxidative stress, which is involved in diabetic teratogenesis. It has also been suggested that maternal diabetes alters embryonic gene expression, which might cause malformations. Due to ethical issues involving human studies that sometimes have invasive aspects and the multiplicity of uncontrolled variables that can alter the uterine environment during clinical studies, it is necessary to use animal models to better understand diabetic pathophysiology. This review aimed to gather information about pathophysiological mechanisms and fetal outcomes in streptozotocin-induced diabetic rats. To understand the pathophysiological mechanisms and factors involved in diabetes, the use of pancreatic regeneration studies is increasing in an attempt to understand the behavior of pancreatic beta cells. In addition, these studies suggest a new preventive concept as a treatment basis for diabetes, introducing therapeutic efforts to minimize or prevent diabetes-induced oxidative stress, DNA damage, and teratogenesis.

Protective effect of Cissus quadrangularis Linn. on diabetes induced delayed fetal skeletal ossification

BACKGROUND

Delayed fetal skeletal ossification is one of the known complications of maternal diabetes.

OBJECTIVE

The present study was designed to evaluate the protective role of petroleum ether extract of Cissus quadrangularis (PECQ) on diabetes-induced delayed fetal skeletal ossification.

MATERIALS AND METHODS

Female Wistar rats were rendered diabetic with streptozotocin (STZ, 40 mg/kg, intraperitonial) before mating. After confirmation of pregnancy, the pregnant rats were divided into three groups: normal control group, diabetic control group, and diabetic + CQ group. The diabetic + CQ group pregnant rats were treated with PECQ (500 mg/kg body weight) throughout their gestation period. Immediately after delivery, pups were collected from all three groups and processed for alizarin red S-alcian blue staining in order to examine the pattern of skeletal ossification.

RESULTS

Fewer ossification centers and decreased extent of ossification of forelimb and hindlimb bones were observed in the neonatal pups of diabetic control group as compared to those in the normal control group. PECQ pretreatment significantly restored the ossification centers and improved the extent of ossification of forelimb and hindlimb bones in the neonatal pups of diabetic + CQ group as compared to those in the diabetic control group.

CONCLUSIONS

The results suggested that PECQ treatment is effective against diabetes-induced delayed fetal skeletal ossification. However, further studies on the isolation and characterization of active constituents of PECQ, which can cross the placental barrier and are responsible for the bone anabolic activity are warranted.

Mild diabetes models and their maternal-fetal repercussions

The presence of diabetes in pregnancy leads to hormonal and metabolic changes making inappropriate intrauterine environment, favoring the onset of maternal and fetal complications. Human studies that explore mechanisms responsible for changes caused by diabetes are limited not only for ethical reasons but also by the many uncontrollable variables. Thus, there is a need to develop appropriate experimental models. The diabetes induced in laboratory animals can be performed by different methods depending on dose, route of administration, and the strain and age of animal used. Many of these studies are carried out in neonatal period or during pregnancy, but the results presented are controversial. So this paper, addresses the review about the different models of mild diabetes induction using streptozotocin in pregnant rats and their repercussions on the maternal and fetal organisms to propose an adequate model for each approached issue.

New concepts in diabetic embryopathy

Diabetes mellitus is responsible for nearly 10% of fetal anomalies in diabetic pregnancies. Although aggressive perinatal care and glycemic control are available in developed countries, the birth defect rate in diabetic pregnancies remains higher than that in the general population. Major cellular activities (ie, proliferation and apoptosis) and intracellular metabolic conditions (ie, nitrosative, oxidative, and endoplasmic reticulum stress) have been shown to be associated with diabetic embryopathy using animal models. Translating advances made in animal studies into clinical applications in humans requires collaborative efforts across the basic research, preclinical, and clinical communities.

Dietary supplementation with Ipomoea aquatica (whole leaf powder) attenuates maternal and fetal oxidative stress in streptozotocin-diabetic rats

BACKGROUND

The rate of congenital anomalies, as well as morbidity and mortality of both the mother and fetus, is increased in diabetic pregnancy. Oxidative stress (OS) has been implicated in these effects because of the beneficial effects of several antioxidants in diabetic embryopathy. In the present study, we assessed attenuation of maternal and fetal OS and diabetic embryopathy by Ipomoea aquatica Forsk. (Convolvulaceae).

METHODS

Pregnant rats were divided into four groups: Group I, untreated non-diabetic control; Group II, rats fed a 2%I. aquatica (IA)-supplemented diet; Group III, streptozotocin (STZ)-diabetic rats fed a normal diet; Group IV, STZ-diabetic rats fed an IA-supplemented diet. Rats were rendered diabetic with a single injection of STZ (40 mg/kg) on gestational day (GD) 4. Dams were killed on GD20 and markers of OS were determined in the maternal liver and fetal brain and liver.

RESULTS

Embryopathy increased significantly in STZ-diabetic rats (by 40% versus control), but IA supplementation provided significant protection (36% reduction in embryopathy in the IA group versus the STZ-diabetic group). Interestingly, IA supplementation significantly offset diabetes-associated OS in the maternal liver, as evidenced by reductions in malondialdehyde (MDA; 25% reduction versus STZ-diabetes) and reactive oxygen species (ROS; 72% reduction) and increases in glutathione (53% reduction) and total thiols (45% reduction). In addition, IA supplementation offered significant protection against diabetes-induced OS in the fetal brain and liver, as evidenced by increased levels of antioxidant molecules and enzymes and reductions in ROS and MDA compared with fetuses from STZ-diabetic rats.

CONCLUSIONS

The data suggest that IA supplementation during pregnancy provides considerable protection against diabetes-induced OS in the mother and fetus. Thus, I. aquatica may be an effective therapeutic supplement.

Hyperglycemia slows embryonic growth and suppresses cell cycle via cyclin D1 and p21

In pregnant women, the diabetic condition results in a three- to fivefold increased risk for fetal cardiac malformations as a result of elevated glucose concentrations and the resultant osmotic stress in the developing embryo and fetus. Heart development before septation in the chick embryo was studied under two hyperglycemic conditions. Pulsed hyperglycemia induced by daily administration of glucose during 3 days of development caused daily spikes in plasma glucose concentration. In a second model, sustained hyperglycemia was induced with a single injection of glucose into the yolk on day 0. The sustained model raised the average plasma glucose concentration from 70 mg/dL to 180 mg/dL and led to decreased gene expression of glucose transporter GLUT1. Both models of hyperglycemia reduced embryo size, increased mortality, and delayed development. Within the heart outflow tract, reduced proliferation of myocardial and endocardial cells resulted from the sustained hyperglycemia and hyperosmolarity. The cell cycle inhibitor p21 was significantly increased, whereas cyclin D1, a cell cycle promoter, decreased in sustained hyperglycemia compared with controls. The evidence suggests that hyperglycemia-induced developmental delays are associated with slowed cell cycle progression, leading to reduced cellular proliferation. The suppression of critical developmental steps may underlie the cardiac defects observed during late gestation under hyperglycemic conditions.

Heat shock protein production and immunity and altered fetal development in diabetic pregnant rats

We evaluated associations between the concentrations of heat shock proteins (hsp60 and hsp70) and their respective antibodies, alterations in maternal reproductive performance, and fetal malformations in pregnant rats with hyperglycemia. Mild diabetes (MD) or severe diabetes (SD) was induced in Sprague-Dawley rats prior to mating; non-treated non-diabetic rats (ND) served as controls. On day 21 of pregnancy, maternal blood was analyzed for hsp60 and hsp70 and their antibodies; and fetuses were weighed and analyzed for congenital malformations. Hsp and anti-hsp levels were correlated with blood glucose levels during gestation. There was a positive correlation between hsp60 and hsp70 levels and the total number of malformations (R = 0.5908, P = 0.0024; R = 0.4877, P = 0.0134, respectively) and the number of malformations per fetus (R = 0.6103, P = 0.0015; R = 0.4875, P = 0.0134, respectively). The anti-hsp60 IgG concentration was correlated with the number of malformations per fetus (R = 0.3887, P = 0.0451) and the anti-hsp70 IgG level correlated with the total number of malformations (R = 0.3999, P = 0.0387). Moreover, both hsp and anti-hsp antibodies showed negative correlations with fetal weight. The results suggest that there is a relationship between hsp60 and hsp70 levels and their respective antibodies and alterations in maternal reproductive performance and impaired fetal development and growth in pregnancies associated with diabetes.

Zinc supplementation prevents cardiomyocyte apoptosis and congenital heart defects in embryos of diabetic mice

Oxidative stress induced by maternal diabetes plays an important role in the development of cardiac malformations. Zinc (Zn) supplementation of animals and humans has been shown to ameliorate oxidative stress induced by diabetic cardiomyopathy. However, the role of Zn in the prevention of oxidative stress induced by diabetic cardiac embryopathy remains unknown. We analyzed the preventive role of Zn in diabetic cardiac embryopathy by both in vivo and in vitro studies. In vivo study revealed a significant decrease in lipid peroxidation, superoxide ions, and oxidized glutathione and an increase in reduced glutathione, nitric oxide, and superoxide dismutase in the developing heart at embryonic days (E) 13.5 and 15.5 in the Zn-supplemented diabetic group when compared to the diabetic group. In addition, significantly down-regulated protein and mRNA expression of metallothionein (MT) in the developing heart of embryos from diabetic group was rescued by Zn supplement. Further, the nuclear microscopy results showed that trace elements such as phosphorus, calcium, and Zn levels were significantly increased (P<0.001), whereas the iron level was significantly decreased (P<0.05) in the developing heart of embryos from the Zn-supplemented diabetic group. In vitro study showed a significant increase in cellular apoptosis and the generation of reactive oxygen species (ROS) in H9c2 (rat embryonic cardiomyoblast) cells exposed to high glucose concentrations. Supplementation with Zn significantly decreased apoptosis and reduced the levels of ROS. In summary, oxidative stress induced by maternal diabetes could play a role in the development and progression of cardiac embryopathy, and Zn supplementation could be a potential therapy for diabetic cardiac embryopathy.

Neonatally induced mild diabetes in rats and its effect on maternal, placental, and fetal parameters

The aim of this study was to assess placental changes and reproductive outcomes in neonatally induced mild diabetic dams and fetal development in their offspring. At birth, female rats were assigned either to control or diabetic group (100 mg of streptozotocin/Kg, subcutaneously). At adulthood, the female rats were mated. During pregnancy, the blood glucose levels and glucose and insulin tolerance tests were performed. At term, maternal reproductive outcomes, fetal and placental weight, and placental morphology were analyzed. Diabetic rats had smaller number of living fetuses, implantations and corpora lutea, and increased rate of embryonic loss. Placenta showed morphometric alterations in decidua area. Our results showed that mild diabetes was sufficient to trigger alterations in maternal organism leading to impaired decidua development contributing to failure in embryonic implantation and early embryonic losses. Regardless placental decidua alteration, the labyrinth, which is responsible for the maternal-fetal exchanges, showed no morphometric changes contributing to an appropriate fetal development, which was able to maintain normal fetal weight at term in mild diabetic rats. Thus, this experimental model of diabetes induction at the day of birth was more effective to reproduce the reproductive alterations of diabetic women.

Does maternal body mass index during pregnancy influence risk of schizophrenia in the adult offspring?

Maternal obesity in pregnancy has been linked with several adverse outcomes in offspring including schizophrenia. The rising prevalence of obesity may contribute to an increase in the number of schizophrenia cases in the near future; therefore, it warrants further exploration. We reviewed current evidence regarding maternal body mass index (BMI) in pregnancy and risk of schizophrenia in adult offspring. We searched PubMed and Embase databases and included studies that were based on large and representative population-based datasets. A qualitative review was undertaken due to heterogeneity between studies. Four studies with 305 cases of schizophrenia and 24,442 controls were included. Maternal obesity (pre-pregnant BMI over 29 or 30 compared with mothers with low or average BMI) was associated with two- to threefold increased risk of schizophrenia in the adult offspring in two birth cohorts. High maternal BMI at both early and late pregnancy also increased risk of schizophrenia in the offspring. Discrepant findings from one study could be attributable to sample characteristics and other factors. The area needs more research. Future studies should take into account obstetric complications, diabetes, maternal infections and immune responses that might potentially mediate this association.

Reduction in embryonic malformations and alleviation of endoplasmic reticulum stress by nitric oxide synthase inhibition in diabetic embryopathy

Maternal diabetes-induced neural tube defects (NTDs) are associated with increased programmed cell death (apoptosis) in the neuroepithelium, which is related to intracellular nitrosative stress. To alleviate nitrosative stress, diabetic pregnant mice were fed via gavage an inhibitor of nitric oxide (NO) synthase (NOS) 2, L-N6-(1-iminoethyl)-lysine (L-NIL; 80 mg/kg), once a day from embryonic (E) day 7.5 to 9.5 during early stages of neurulation. The treatment significantly reduced NTD rate in the embryos, compared with that in vehicle (normal saline)-treated diabetic group. In addition to alleviation of nitrosative stress, endoplasmic reticulum (ER) stress was also ameliorated, assessed by quantification of associated factors. Apoptosis was reduced, indicated by caspase 8 activation. These results show that nitrosative stress is important in diabetes-induced NTDs via exacerbating ER stress, leading to increased apoptosis. Oral treatment with NOS-2 inhibitor alleviates nitrosative and ER stress, decreases apoptosis, and reduces NTDs in the embryos, providing information for further interventional studies to reduce diabetes-associated birth defects.

Genetic basis of susceptibility to teratogen induced birth defects

Birth defects remain the leading cause of infant death in US. The field of teratology has been focused on the causes and underlying mechanisms of birth defects for decades, yet our understanding of these critical issues remain unacceptably vague. Conclusions from years of animal and human studies made it clear that the vast majority of birth defects have multifactorial origins, with contributions from environmental and genetic factors. The environment comprises not only of the physical, biological, and chemical external environment surrounding the pregnant woman, but it also includes the internal environment of the woman's body that interact with the developing embryo in a complex fashion. The importance of maternal and embryonic genetic factors consisting of countless genetic variants/mutations that exist within every individual contribute to birth defect susceptibility is only now being more fully appreciated. This great complexity of the genome and its diversity within individuals and populations seems to be the principal reason why the same teratogenic exposure can induce severe malformation in one embryo, while fail to do so to other exposed embryos. As the interaction between genetic and environmental factors has long been recognized as the first "Principle of Teratology" by Wilson and Warkany [1965. Teratology: Principles and techniques. Chicago: University of Chicago Press], it is only recently that the appropriate investigative tools have been developed with which to fully investigate this fundamental principle. The introduction of high throughput technologies like whole genome sequencing or genome-wide association studies are promising to deliver an enormous amount of new data that will shed light on the genomic factors that contribute susceptibility to environmental teratogens. In this review, we attempt to summarize the epidemiological and experimental literature concerning birth defects whose phenotypic expression can be clearly related to the interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. © 2011 Wiley-Liss, Inc.

Role of HIF-1α in maternal hyperglycemia-induced embryonic vasculopathy

OBJECTIVE

Maternal diabetes adversely impacts embryonic vasculogenesis, which results in embryonic vasculopathy. The purpose of our study is to determine whether hypoxia inducible factor (HIF)-1α plays a role in diabetic embryonic vasculopathy.

STUDY DESIGN

Levels of HIF-1α were determined in mouse conceptuses. Conceptuses on day 7 of pregnancy were cultured under euglycemic (150 mg/dL glucose) and hyperglycemic (300 mg/dL) conditions with or without AdCA5, or in the presence or absence of 2.0 μg/mL human recombinant thioredoxin, an endogenous antioxidant protein. AdCA5 is an adenovirus encoding a constitutively active form of HIF-1α.

RESULTS

Maternal diabetes significantly reduced HIF-1α protein expression. The administration of 1 μL (1 × 10(7) infectious units/mL) per 1 mL culture medium AdCA5 completely reversed hyperglycemia-reduced vasculature morphological scores and vascular endothelial growth factor expression. Thioredoxin treatment reversed hyperglycemia-reduced HIF-1α levels.

CONCLUSION

We conclude that reduced HIF-1α plays a critical role in the induction of diabetic embryonic vasculopathy, and that oxidative stress is implicated in hyperglycemia-induced HIF-1α reduction.

Cardiac malformations and alteration of TGFbeta signaling system in diabetic embryopathy

BACKGROUND

Cardiovascular defects are the most common anomalies in diabetic embryopathy. The mechanisms underlying the manifestation of the defects remain to be addressed.

METHODS

Female mice were administered streptozotocin to induce diabetes. Embryos from euglycemic (control) and hyperglycemic groups were examined for morphological and histological evaluation of malformations. Cell proliferation and programmed cell death (apoptosis) were assessed using mitotic markers (BrdU and Ki67) and TUNEL assay, respectively. Expression of eight four genes in the TGFbeta signaling system was analyzed using real-time RT-PCR.

RESULTS

Structural abnormalities were observed in the heart and neural tube in diabetic groups, with significantly higher malformation rates than in control groups. Moreover, malformation rates in the heart were higher than those in the neural tube. Cardiac abnormalities including dilated heart tube, smaller ventricles, conotruncal stenosis, and abnormal heart looping were seen during early morphogenesis prior to cardiac septation [embryonic day (E) 9.5-11.5]. Histological examinations showed hypoplastic myocardium and endocardial cushions. After cardiac septation (E15.5), ventricular septal defects were observed, which were manifested in the non-muscular portion of the septum. Significant decreases in cell proliferation with no differences in apoptosis were observed in the myocardium and endocardial cushions in diabetic compared to control groups. Factors in the TGFbeta signaling that regulate heart development were downregulated by maternal diabetes.

CONCLUSIONS

Maternal diabetes causes malformations in the heart of the embryo. The heart is more susceptible to maternal diabetic insults than the neural tube. Malformations in the heart prior to septation are associated with decreased cell proliferation, but not increased apoptosis. The TGFbeta signaling is involved in cardiac malformations in diabetic embryopathy.

Importance of gene-environment interactions in the etiology of selected birth defects

It is generally understood that both genetic and environmental factors contribute to the highly complex etiology of structural birth defects, including neural tube defects, oral clefts and congenital heart defects, by disrupting highly regulated embryonic developmental processes. The intrauterine environment of the developing embryo/fetus is determined by maternal factors such as health/disease status, lifestyle, medication, exposure to environmental teratogens, as well as the maternal genotype. Certain genetic characteristics of the embryo/fetus also predispose it to developmental abnormalities. Epidemiologic and animal studies conducted over the last few decades have suggested that the interplay between genes and environmental factors underlies the etiological heterogeneity of these defects. It is now widely believed that the study of gene-environment interactions will lead to better understanding of the biological mechanisms and pathological processes that contribute to the development of complex birth defects. It is only through such an understanding that more efficient measures will be developed to prevent these severe, costly and often deadly defects. In this review, we attempt to summarize the complex clinical and experimental literature on current hypotheses of interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. These include maternal folate nutritional status, maternal diabetes/obesity-related conditions, and maternal exposure to selected medications and environmental contaminants. Our goal is to highlight the potential gene-environment interactions affecting early embryogenesis that deserve comprehensive study.

Caspase-8: a key role in the pathogenesis of diabetic embryopathy

Maternal diabetes causes neural tube defects in embryos, which are associated with increased apoptosis in the neuroepithelium. Many factors, including effector caspases, have been shown to be involved in the events. However, the key regulators have not been identified and the underlying mechanisms remain to be addressed. Caspase-8, an initiator caspase, has been shown to be altered in diabetic embryopathy, suggesting a role as an upstream apoptotic regulator. Using mouse embryos as a model system, this study demonstrates that caspase-8 is required for the production of hyperglycemia-associated embryonic malformations. Caspase-8 was shown to be expressed in the developing neural tube. Its activity, as evidenced by enhanced cleavage, was increased by hyperglycemia. These changes were associated with increased formation of the active cleavage of Bid. Inhibition of caspase-8 activity in high glucose-challenged embryos reduced the rate of embryonic malformation and this was associated with decreased apoptosis in the neuroepithelium of the neural tube. Inhibition of caspase-8 activity also reduced hyperglycemia-induced Bid activation and caspase-9 cleavage. These data suggest that caspase-8 may control diabetic embryopathy-associated apoptosis via regulation of the Bid-stimulated mitochondrion/caspase-9 pathway.

Congenital anomalies in diabetic pregnancy

Congenital malformations are more common in infants of diabetic women than in children of non-diabetic women. The etiology, pathogenesis and prevention of the diabetes-induced malformations have spurred considerable clinical and basic research efforts. The ultimate aim of these studies has been to obtain an understanding of the teratogenic process, which may enable precise preventive therapeutic measures in diabetic pregnancies. The results of the clinical and basic studies support the view of an early gestational induction of the malformations in diabetic pregnancy by a teratogenic process of multifactorial etiology. There may be possible targets for new therapeutic efforts revealed by the research work. Thus, future additions to the therapeutic efforts may include supplementation with antioxidants and/or folic acid, although more research is needed to delineate the dosages and compounds to be used. As the research into genetic predisposition for the teratogenic induction of malformations by maternal diabetes starts to reveal new genes and gene products involved in the etiology of the malformations, a set of new targets for intervention may arise.

Demonstration of the essential role of protein kinase C isoforms in hyperglycemia-induced embryonic malformations

To address the role of PKC isoforms in hyperglycemia-induced apoptosis and malformations in the embryos of diabetic pregnancies, expression of PKCalpha, beta1, beta 2, gamma, delta, epsilon, and zeta was examined in the neural tube of rat embryos and showed to overlap with the regions of increased apoptosis. Levels of activated (phosphorylated) PKCalpha , beta2, and delta were increased in the embryos of diabetic dams whereas those of PKCepsilon and zeta were decreased when compared with those in control groups. Cytosolic phospholipase A(2) (cPLA(2)) was also activated. Blocking the activity of PKCalpha , beta2, and delta using isoform-specific inhibitors in embryos cultured in hyperglycemia (40 mM) reduced malformation rates when compared with those in untreated hyperglycemic and euglycemic (8.3 mM) groups. These observations demonstrate that PKCalpha, beta2, and delta play an essential role in diabetic embryopathy. Activation of cPLA(2) was also decreased, suggesting that PKCs mediate the hyperglycemic effects through the cPLA(2)-phospholipid peroxidation pathway.

Blockade of c-Jun N-terminal kinase activation abrogates hyperglycemia-induced yolk sac vasculopathy in vitro

OBJECTIVE

Maternal hyperglycemia has an impact on both the function and morphology of the rodent visceral yolk sac; the objective of the present study was to determine whether hyperglycemia in vitro affects yolk sac vasculogenesis. Because maternal hyperglycemia triggers c-Jun N-terminal kinase (JNK) 1 and 2 activation in the yolk sac, we tested whether the inhibition of JNK activation would ameliorate hyperglycemia-induced yolk sac vasculopathy. In rodents, the yolk sac serves as the primitive placenta after implantation and before the formation of the chorioallantoic placenta. Furthermore, during this early stage, the nutrition from mother to embryo is considered to be facilitated by a tissue-to-tissue form of nutrition, referred to as histiotropic nutrition, and subsequently via yolk sac facilitation (hemotropic nutrition). In addition, during embryopathy, teratogen such as hyperglycemia is associated with concomitant injury to the yolk sac and embryo.

STUDY DESIGN

Rat embryos at embryonic day 9 were cultured under euglycemic (150 mg/dL glucose) and hyperglycemic (500 mg /dL glucose) conditions. JNK activation was inhibited using a JNK1/2-specific inhibitor SP60025 at concentrations of 40, 400, and 800 nM. After 48 hours, the development of yolk sac vasculatures was evaluated by assigning to arbitrative scores on the basis of yolk sac vasculature morphology. The correlation between yolk sac vasculature and embryonic malformation rates was assessed. Levels of phosphorylated JNK1/2 and Bcl-2-associated X protein (Bax) in the yolk sacs from conceptuses of the euglycemic and hyperglycemic groups were determined by Western blotting with densitometric quantification.

RESULTS

Under hyperglycemic conditions, yolk sac development was morphologically impaired. The yolk sac vasculature score of the hyperglycemic group was significantly lower than that of the euglycemic group. Yolk sac vasculature morphologic scores were inversely correlated with embryonic malformation rates. Levels of phosphorylated JNK1/2 and Bax in yolk sacs of the hyperglycemic group were significantly higher than those in yolk sacs of the euglycemic group. JNK1/2-specific inhibitor, SP600125, ameliorated the adverse effect of hyperglycemia on yolk sac vasculature development. Whereas the vasculature morphologic score of yolk sacs in the hyperglycemic group was 54% lower than that of euglycemic group, the vasculature morphologic score of yolk sacs in hyperglycemic plus 800 nM SP600125 group was as same as that in the euglycemic group. Thus, SP600125 at 800 nM completely reversed hyperglycemia-induced vasculopathy as well as embryopathy.

CONCLUSION

Hyperglycemia in vitro induces yolk sac vasculopathy. Embryonic malformation is inversely correlated with the yolk sac vasculature development, suggesting that hyperglycemia-induced yolk sac vasculopathy may be one of the causative factors in hyperglycemia-induced embryonic malformation. Blockade of JNK1/2 activation restores hyperglycemia-induced vasculopathy and reduces the malformation rates. These findings indicate that JNK1/2 activation mediates the deleterious effect of hyperglycemia on yolk sac vasculature and embryonic development.

Activation of oxidative stress signaling that is implicated in apoptosis with a mouse model of diabetic embryopathy

OBJECTIVE

A mouse model of diabetic embryopathy in C57BL/6J background was established to use the resources of genetically engineered mice in which a specific gene is deleted or overexpressed. To test whether our previous fundamental findings in the rat model of diabetic embryopathy are transferable to this mouse model of diabetic embryopathy, levels of phosphorylated-JNK1/2 (c-Jun N-terminal kinase 1 and 2) and apoptotic markers (cleaved caspase 3) were determined. To establish a link between oxidative stress signaling and diabetic embryopathy, levels of phosphorylated-p66Shc (which is a key signaling molecule that mediates oxidative stress-induced apoptosis) were evaluated.

STUDY DESIGN

Diabetes mellitus was induced in female C57BL/6J mice by an intravenous injection of streptozotocin (75 mg/kg). Glucose levels were controlled by the subcutaneous implantation of insulin pellets. The female mice were mated with normal male mice. At gestation day 5 or embryonic day 5 (E5), the insulin pellets were removed from a group of animals, which made them hyperglycemic (> 250 mg/dL glucose). The animals with retained insulin pellets served as controls. On embryonic day 11, mice were killed, and embryos were dissected from the uteri for examination. Embryos and yolk sacs from individual conceptus were collected. Levels of phosphorylated-JNK1/2, phosphorylated-p66Shc, and cleaved caspase 3 were determined in the embryos and yolk sacs.

RESULTS

Malformation rates in embryos from diabetic mice were 3-fold higher than those in embryos from nondiabetic or diabetic/euglycemic control groups. JNK1/2, especially p54 JNK isoform, which is predominantly expressed by jnk2 gene, was activated in malformed embryos and their respective yolk sacs from diabetic mice and was significantly higher than those in normally developed embryos and their respective yolk sacs from nondiabetic and diabetic mice. Correlating to JNK1/2 activation, phosphorylated-p66Shc was also significantly increased in malformed embryos and their respective yolk sacs from diabetic mice than in normally developed embryos and their respective yolk sacs from nondiabetic and diabetic mice. Cleaved caspase 3 was observed in malformed embryos from diabetic mice.

CONCLUSION

The present study shows that maternal hyperglycemia is able to induce embryonic dysmorphogenesis in C57BL/6J mice that is comparable with that seen in the rat model of diabetic embryopathy. Like the well-studied rat model of diabetic embryopathy, activation of JNK1/2 and p66Shc and the increase of apoptotic markers are manifested in this mouse model of diabetic embryopathy. These findings suggest that the activation of oxidative stress signaling in diabetic embryopathy leads to excessive embryonic cell apoptosis and ultimately embryonic dysmorphogenesis. To apply the powerful genetic approach to the research of diabetic embryopathy, a mouse is a better animal model than a rat because all gene knockout (deletion) and gene transgenic (gene overexpression) animals are made in the mouse. The mouse model of diabetic embryopathy that was established in the present study may serve as a suitable substitute for the rat model of diabetic embryopathy, thus enabling us and other investigators to use genetically engineered technologies in the study of diabetic embryopathy.

Nitroxide radicals protect cultured rat embryos and yolk sacs from diabetic-induced damage

BACKGROUND

Diabetic teratogenicity relates, partly, to embryonic oxidative stress and the extent of the embryonic damage can apparently be reduced by antioxidants. We investigated the effects of superoxide dismutase-mimics nitroxides, 2,2,6,6-tetramethyl piperidine-N-oxyl (TPL) as an effective antioxidant, on diabetes-induced embryopathy.

METHODS

Embryos (10.5 day old) and their yolk sacs from Sabra female rats were cultured for 28 h in the absence or in the presence of nitroxides at 0.05-0.4 mM in control, diabetic subteratogenic, or diabetic teratogenic media, and monitored for growth retardation and congenital anomalies. The oxidant/antioxidant status was examined by oxygen radical absorbance capacity and lipid peroxidation assays, whereas the yolk sac function was evaluated by endocytosis assay.

RESULTS

Diabetic culture medium inhibited embryonic and yolk sac growth, induced a high rate of NTDs, reduced yolk sac endocytosis and embryonic antioxidant capacity, and increased lipid peroxidation. These effects were more prominent in the embryos with NTD compared to those without NTD. TPL added to diabetic teratogenic medium improved embryonic and yolk sac growth, reduced the rate of NTDs, and improved yolk sac function. The oxidant/antioxidant status of embryos was also improved. TPL at 1 mM did not damage the embryos cultured in control medium.

CONCLUSIONS

In diabetic culture medium, oxidative damage is higher in the malformed rat embryos compared to those without anomalies; the nitroxide provides protection against diabetes-induced teratogenicity in a dose-dependent manner. The yolk sac damage, apparently caused by the same mechanism, might be an additional contributor to the embryonic damage observed in diabetes.

Analysis of polyploid cells in mouse embryonic cells cultured under diabetic conditions

To clarify the cytogenetic effects of glucose and ketone bodies on the pathogenesis of diabetes-associated congenital anomalies, we cultured cells from gestation-day-8 ICR mouse embryos under the diabetic condition. Cells were cultured in the medium with glucose (300 mg/dL) plus DL-2-hydroxybutyric acid (32 mM) (G + B group), glucose alone (G group), or neither of them (C group) for 5 days. At the end of the culture, cells were analyzed for the chromosomes. After 3-4 days culture, when the living cells grew into a mono-layered sheet, cells floating in the medium were observed and showed morphological features of apoptosis. Ratio of the floating cells was significantly higher in the G + B group than in the G or C group (P < 0.05), suggesting the deleterious effect of glucose and ketone body. Polyploidy was observed in the cultured cells more frequently in the G + B group (64.1%) than in the G group (49.0%), which was higher than the C group (20.5%) (G + B vs G: P < 0.05, G vs C: P < 0.001). The higher ratio of the polyploidy, but not of the aneuploidy, in the G + B and G groups suggested the specific effect of glucose and ketone body for inducing polyploidy. These results suggest that diabetic condition causes polyploidy in cultured embryonic cells.

Experimental mechanisms of diabetic embryopathy and strategies for developing therapeutic interventions

A high frequency of birth defects is seen in infants born to diabetic mothers. The mechanisms by which maternal hyperglycemia, the major teratogenic factor, induces embryonic malformations remain to be addressed. It has been shown that increases in programmed cell death are one of the factors causing embryonic malformations. Hyperglycemia-induced apoptosis is associated with oxidative stress, lipid peroxidation, and decreased antioxidant defense capacity in the embryos. Recent studies have revealed that mitogen-activated protein kinases as intracellular signaling factors are involved in hyperglycemia-induced embryopathy. Based on the findings, interventions to prevent embryonic malformations have been explored. Strategies include supplementation of molecules that are deficient in the embryos under hyperglycemic conditions and antioxidants to alleviate the adverse effects of oxidative stress. The ultimate goal is to develop multi-nutrient dietary supplements to eliminate embryonic abnormalities induced by maternal diabetes.

Dietary vitamin and lipid therapy rescues aberrant signaling and apoptosis and prevents hyperglycemia-induced diabetic embryopathy in rats

OBJECTIVE

Maternal diabetes causes developmental malformations in the embryo. Dietary supplementation with antioxidants can reduce the malformation rates in animal models. To investigate the molecular mechanisms underlying diabetes-induced embryonic abnormalities and dietary interventions, activity of mitogen-activated protein kinases and factors associated with apoptotic pathways were examined in the maternal diabetic rat model.

STUDY DESIGN

Diabetes was induced in pregnant rats using streptozotocin. In the yolk sacs of the embryos, activity of the extracellular signal-regulated kinases, Raf-1, and Akt was dramatically reduced in diabetic rats, whereas that of c-jun N-terminal kinases/stress-activated protein kinases was increased.

RESULTS

When the diabetic dams were fed with arachidonic acid, vitamin E, or a combination of arachidonic acid, vitamin E, and myoinositol, the changes in the expression of these kinases were reversed and correlated with the decreases in the rates of apoptosis and embryonic malformations.

CONCLUSION

These results suggest that mitogen-activated protein kinases are involved in diabetic embryopathy, and dietary supplementations can rescue the aberrant signaling pathways and reduce embryonic malformation rate.

Antioxidative treatment of pregnant diabetic rats diminishes embryonic dysmorphogenesis

BACKGROUND

Diabetic pregnancy is still associated with an increased rate of congenital malformations despite extensive clinical efforts to normalize the risk for the offspring. The etiology of diabetic embryopathy is not clear; however, experimental studies have suggested a role for oxidative stress in the teratogenicity of diabetic pregnancy. The antioxidants alpha-tocopherol and ascorbate have improved fetal outcome in diabetic rodent pregnancy when supplemented in moderate to high doses. In the present work we investigated if extremely high doses of either alpha-tocopherol or ascorbate might further improve fetal outcome in offspring of diabetic rats and, in addition, if such treatment may exert any adverse effects of fetal development.

METHODS

Nondiabetic and streptozotocin diabetic female rats were fed 2, 5, 10, or 15% alpha-tocopherol or 4, 10, or 15% ascorbate in their diet.

RESULTS

Both alpha-tocopherol and ascorbate treatment improved fetal morphology in offspring of diabetic rats. There was a dose-dependent improvement for the alpha-tocopherol supplementation, in which the higher doses diminished fetal dysmorphogenesis more than the 2% diet. The ascorbate supplementation was less dose-dependent; however, the higher doses tended to improve fetal outcome more than the lower doses. No adverse effects of the antioxidants were noted in the offspring with the exception of 1 case of agnathia in a fetus of a nondiabetic rat supplemented with 15% alpha-tocopherol.

CONCLUSIONS

These results indicate that very high doses of dietary antioxidants may be needed to normalize the development of the offspring in experimental diabetic pregnancy, but that treatment with such high doses may also have adverse effects in nondiabetic pregnancy.

Periconceptional dietary intake of myo-inositol and neural tube defects in offspring

BACKGROUND

Periconceptional intake of nutrients in addition to folic acid may contribute to neural tube defect (NTD) etiologies; a likely candidate is myo-inositol. We investigated whether maternal periconceptional dietary intake of myo-inositol influenced NTD risk.

METHODS

Data were derived from a case-control study of fetuses and infants with NTDs among 1989-1991 California births. Interviews were conducted with mothers of 454 NTD cases and with mothers of 462 nonmalformed controls. A standard 100-item food frequency questionnaire was used to assess nutrient intake.

RESULTS

We observed small increases in risk, with increases slightly more evident for anencephaly, associated with intakes of myo-inositol less than the highest intake quartile, e.g., risk of anencephaly was 1.3 (0.7-2.4) among fetuses whose mothers consumed lowest versus highest intakes of myo-inositol. These small increases, however, were imprecise, and also did not indicate increasing risk with decreasing level of myo-inositol intake. Adjusted risk estimates did not differ considerably from their unadjusted counterparts.

CONCLUSIONS

Our results do not indicate that myo-inositol intake, as measured in this study, is strongly associated with risk of human NTDs.

Effects of alpha-lipoic acid supplementation on maternal diabetes-induced growth retardation and congenital anomalies in rat fetuses

The mechanism of diabetic embryopathy is not known. Excessive reactive oxygen species (ROS) produced in diabetes may be causally related to foetal anomalies. The objective of this study was to determine whether supplementation with the antioxidant lipoic acid (LA) could prevent maternal diabetes-related foetal malformations and intrauterine growth retardation (IUGR) in rats. Pregnant rats were non-treated (Group I) or made diabetic on gestation day (GD) 2 by injecting streptozotocin (Group II). Group III was injected with 20 mg kg(-1) of LA daily starting on GD 6 and continued through GD 19. Group IV was administered only Tris buffer on the corresponding days. Group V was a set of STZ-treated animals, which were supplemented with a daily dose of 20 mg kg(-1) of LA from GD 6 through GD 19. All fetuses were collected on GD 20. Lipoic acid did not affect the blood sugar levels of diabetic animals significantly but improved their body weight gain and reduced food and water consumption. Diabetic group had a high incidence of embryonic resorption, IUGR, craniofacial malformations, supernumerary ribs and skeletal hypoplasia. Lipoic acid significantly reduced these abnormalities. These data support the hypothesis that ROS are causally related to fetal maldevelopment and IUGR associated with maternal diabetes in the rat. They also highlight the possible role of antioxidants in the normal processes of embryo survival, growth and development.

Plasma AA and DHA levels are not compromised in newly diagnosed gestational diabetic women

OBJECTIVE

The polyunsaturated fatty acids, arachidonic (AA) and docosahexaenoic (DHA), are vital structural and functional components of the neural, vascular and visual systems. There is increased demand for these fatty acids during pregnancy. Diabetes impairs the synthesis of both AA and DHA. We have investigated the possibility that pregnancy-induced diabetes compromises the levels of plasma AA and DHA in newly diagnosed expectant mothers.

DESIGN

Cross-sectional study.

SETTING

London, UK.

SUBJECTS AND METHODS

Venous blood was obtained from 44 women with gestational diabetes mellitus (GDM) and from the same number of nondiabetics, during the third trimester. Fatty acid composition of plasma choline phosphoglycerides (CPG), triglycerides (TG) and cholesterol esters (CE) was analysed.

RESULTS

The GDM women had higher levels of AA (20:4n-6; P<0.0001) and AA/linoleic acid ratio (20:4n-6/18:2n-6; P<0.01) in the CPG, and linoleic acid (LA; P<0.0001), total n-6 (P<0.01), DHA (P<0.05) and n-3 metabolites (P<0.05) in TG compared to their nondiabetic counterparts. Similarly, AA (P<0.0001), osbond acid (22:5n-6; P<0.05), total n-6 metabolites (P<0.0001), AA/LA (P<0.0001) and n-6 metabolites/LA (P<0.01) were higher in the CE of the GDM women. There was no difference in the levels of DHA in CPG and CE between the two groups (P>0.05).

CONCLUSIONS

The results of this study do not provide evidence that the activity of delta-6 or delta-5 desaturases, which are vital for the synthesis of AA and DHA, is compromised by pregnancy-induced diabetes. However, since the samples were taken at diagnosis, it is conceivable that the duration of the diabetes was too short to have a discernable adverse effect on the levels of AA and DHA in plasma lipids.

Maternal diabetes in the rat impairs the formation of neural-crest derived cranial nerve ganglia in the offspring

AIMS/HYPOTHESIS

Maternal diabetes mellitus increases the risk for fetal malformations. Several of these malformations are found in organs and tissues derived from the neural crest. Previous studies have shown changes in fetal organs of neural crest origin in experimental diabetes and changes in migration of neural crest cells exposed to high glucose in vitro.

METHODS

We used whole-mount neurofilament staining of embryos from normal and diabetic mothers to investigate the development of cranial nerve ganglia. Neural tube explants were cultured in 10 and 40 mmol/l glucose and cell death and caspase activity was measured with flow cytometry.

RESULTS

The development of cranial ganglia V, VII, VIII, IX and X was impaired in day 10-11 embryos of diabetic rats. There was also a higher rate of cell death of neural crest derived cells cultured in 40 mmol/l glucose for 20 h (35% compared to 12% in 10 mmol/l). However, exposure of cells to 40 mmol/l glucose in culture did not increase the activation of the cell death effector proteins-caspases-measured as cellular binding of the activated caspase marker VAD-FMK. This suggests that the cell death is not caused by caspase-dependent apoptosis or that the caspases are activated at an earlier stage.

CONCLUSION/INTERPRETATION

The development of neural crest-derived structures is disturbed already at the organogenic period in embryos of diabetic rats and this deteriorated development could be due to high-glucose induced increase in cell death of neural crest derived cells.