The 1986 McCollum award lecture. Fuel-mediated teratogenesis during early organogenesis: the effects of increased concentrations of glucose, ketones, or somatomedin inhibitor during rat embryo culture

Embryonic diapause due to high glucose is related to changes in glycolysis and oxidative phosphorylation, as well as abnormalities in the TCA cycle and amino acid metabolism

Introduction

The adverse effects of high glucose on embryos can be traced to the preimplantation stage. This study aimed to observe the effect of high glucose on early-stage embryos.

Methods and results

Seven-week-old ICR female mice were superovulated and mated, and the zygotes were collected. The zygotes were randomly cultured in 5 different glucose concentrations (control, 20mM, 40mM, 60mM and 80mM glucose). The cleavage rate, blastocyst rate and total cell number of blastocyst were used to assess the embryo quality. 40 mM glucose was selected to model high glucose levels in this study. 40mM glucose arrested early embryonic development, and the blastocyst rate and total cell number of the blastocyst decreased significantly as glucose concentration was increased. The reduction in the total cell number of blastocysts in the high glucose group was attributed to decreased proliferation and increased cell apoptosis, which is associated with the diminished expression of GLUTs (GLUT1, GLUT2, GLUT3). Furthermore, the metabolic characterization of blastocyst culture was observed in the high-glucose environment.

Discussion

The balance of glycolysis and oxidative phosphorylation at the blastocyst stage was disrupted. And embryo development arrest due to high glucose is associated with changes in glycolysis and oxidative phosphorylation, as well as abnormalities in the TCA cycle and amino acid metabolism.

Maternal obesity and metabolic risk to the offspring: why lifestyle interventions may have not achieved the desired outcomes

Obesity during pregnancy is associated with an increased risk of short- and long-term metabolic dysfunction in the mother and her offspring. Both higher maternal pregravid body mass index (kg m(-2)) and excessive gestational weight gain (GWG) have been associated with adverse pregnancy outcomes such as gestational diabetes, preeclampsia and fetal adiposity. Multiple lifestyle intervention trials consisting of weight management using various diets, increased physical activity and behavioral modification techniques have been employed to avoid excessive GWG and improve perinatal outcomes. These randomized controlled trials (RCTs) have achieved modest success in decreasing excessive GWG, although the decrease in GWG was often not within the current Institute of Medicine guidelines. RCTs have generally not had any success with decreasing the risk of maternal gestational diabetes (GDM), preeclampsia or excessive fetal growth often referred to as macrosomia. Although the lack of success for these trials has been attributed to lack of statistical power and poor compliance with study protocols, our own research suggests that maternal pregravid and early pregnancy metabolic condition programs early placenta function and gene expression. These alterations in maternal/placental function occur in the first trimester of pregnancy prior to when most intervention trials are initiated. For example, maternal accrural of adipose tissue relies on prior activation of genes controlling lipogenesis and low-grade inflammation in early pregnancy. These metabolic alterations occur prior to any changes in maternal phenotype. Therefore, trials of lifestyle interventions before pregnancy are needed to demonstrate the safety and efficacy for both the mother and her offspring.

Excess nutrient supply in early life and its later metabolic consequences

Suboptimal nutrition in early life, both in utero and during infancy, is linked to increased risk of adult obesity and its associated adverse metabolic health problems. Excess nutrient supply during early life can lead to metabolic programming in the offspring. Such overnutrition can occur in the offspring of obese mothers, the offspring of mothers who gain excess weight during gestation, infants of diabetic mothers and infants who undergo rapid growth, particularly weight gain, during early infancy. Postnatal overnutrition is particularly detrimental for infants who are born small for gestational age, who are overfed to attain 'catch-up growth'. Potential mechanisms underlying metabolic programming that results from excess nutrition during early life include resetting of hypothalamic energy sensing and appetite regulation, altered adipose tissue insulin sensitivity and impaired brown adipose tissue function. More detailed understanding of the mechanisms involved in metabolic programming could enable the development of therapeutic strategies for ameliorating its ill effects. Research in this field could potentially identify optimal and appropriate preventative interventions for a burgeoning population at risk of increased mortality and morbidity from obesity and its concomitant metabolic conditions.

Hyperglycemia induces embryopathy, even in the absence of systemic maternal diabetes: an in vivo test of the fuel mediated teratogenesis hypothesis

Embryonic exposure to excess circulating fuels is proposed to underlie diabetic embryopathy. To isolate the effects of hyperglycemia from the many systemic anomalies of diabetes, we infused 4 mg/min glucose into the left uterine artery of non-diabetic pregnant rats on gestation days (GD) 7-9. Right-sided embryos and dams exhibited no glucose elevation. Embryos were assessed on GD13, comparing the left versus right uterine horns. Hyperglycemic exposure increased rates of embryopathy, resorptions, and worsened embryopathy severity. By contrast, saline infusion did not affect any of these parameters. To assess for possible embryopathy susceptibility bias between uterine horns, separate dams were given retinoic acid (25mg/kg, a mildly embryopathic dose) systemically on GD7.5. The resultant embryopathy rates were equivalent between uterine horns. We conclude that hyperglycemia, even in the absence of systemic maternal diabetes, is sufficient to produce in vivo embryopathy during organogenesis.

Understanding diabetic teratogenesis: where are we now and where are we going?

Maternal pregestational diabetes (type 1 or type 2) poses an increased risk for a broad spectrum of birth defects. To our knowledge, this problem first came to the attention of the Teratology Society at the 14th Annual Meeting in Vancouver, B.C. in 1974, with a presentation by Lewis Holmes, "Etiologic heterogeneity of neural tube defects". Although advances in the control of diabetes in the decades since the discovery of insulin in the 1920's have reduced the risk for birth defects during diabetic pregnancy, the increasing incidence of diabetes among women of childbearing years indicates that this cause of birth defects is a growing public health concern. Major advances in understanding how a disease of maternal fuel metabolism can interfere with embryogenesis of multiple organ systems have been made in recent years. In this review, we trace the history of the study of diabetic teratogenesis and discuss a model in which tissue-specific developmental control genes are regulated at specific times in embryonic development by glucose metabolism. The major function of such genes is to suppress apoptosis, perhaps to preserve proliferative capability, and inhibit premature senescence.

Protein restriction in the pregnant mouse modifies fetal growth and pulmonary development: role of fetal exposure to {beta}-hydroxybutyrate

Maternal undernutrition during sensitive periods of pregnancy results in offspring predisposed towards the development of a number of diseases of adulthood, including hypertension and diabetes. In order to determine the nature of any gross alterations in fetal growth during early organogenesis, we supplied timed-mated pregnant mice with diets containing 6% protein (6%P), 9% protein (9%P) or 18% protein (18%P; control) from day 0 of pregnancy. At embryonic days 11 (E11), 12 (E12) and 13 (E13), females were killed and fetuses removed. Gross morphological analysis revealed that fetal limb growth was impaired between E11 and E12 in 6%P animals, but this recovered by E13. Likewise, fetal liver growth and lung branching morphogenesis were seen to exhibit an initial growth impairment at E12 followed by a rapid recovery by E13. Coincident with the observed changes in fetal growth, we noted an elevation in maternal hepatic triglyceride content, expression of the ketogenic 3-hydroxy-3-methylglutaryl-CoA synthase 2 (Hmgcs2) and circulating plasma β-hydroxybutyrate (BOHB). In addition, fetal liver Hmgcs2 expression was switched on by E13 in both 6%P- and 9%P-exposed animals. Exogenous BOHB did not influence branching morphogenesis in fetal lung explant cultures; however, we cannot rule out the possibility that this may occur in vivo. In conclusion, we find that disturbance of fetal growth by maternal dietary protein restriction is associated and therefore potentially indicated by changes in maternal and fetal ketone body metabolism.

Developmental trajectories of overweight during childhood: role of early life factors

OBJECTIVE

Our goal was to identify developmental trajectories of overweight in children and to assess early life influences on these trajectories.

RESEARCH METHODS AND PROCEDURES

Participants consisted of 1739 white, black, and Hispanic children who were younger than 2 years at the first survey and were followed up to 12 years of age. Repeated measures of overweight, defined as BMI > or = 95th percentile, were used to identify overweight trajectories with a latent growth mixture modeling approach.

RESULTS

Three distinct overweight trajectories were identified: 1) early onset overweight (10.9%), 2) late onset overweight (5.2%), and 3) never overweight (83.9%). After adjustment for multiple potential risk factors, male gender [odds ratio (OR), 1.5; 95% confidence interval (CI), 1.0 to 2.2], black ethnicity (OR, 1.7; 95% CI, 1.1 to 2.6), maternal 25 < or = BMI < 30 kg/m2 (OR, 2.2; 95% CI, 1.3 to 3.7) or > or = 30 kg/m2 (OR, 5.1; 95% CI, 2.9 to 9.1), maternal weight gain during pregnancy > or = 20.43 kg (OR, 1.7; 95% CI, 1.0 to 2.9), and birth weight > or = 4000 g (OR, 2.0; 95% CI, 1.2 to 3.4) were associated with an increased risk of early onset overweight. These risk factors, except maternal weight gain, exerted similar effects on late onset overweight. In addition, maternal smoking (OR, 1.6; 95% CI, 0.8 to 3.1) and birth order > or = 3 (OR, 2.3; 95% CI, 1.0 to 5.2) were associated with an increased risk of late onset overweight only. Breastfeeding > or = 4 months was associated with a decreased risk of both early (OR, 0.7; 95% CI, 0.3 to 1.3) and late onset overweight (OR, 0.7; 95% CI, 0.3 to 1.7).

DISCUSSION

Two trajectories of overweight and one never overweight group were identified. Early life predictors may have a significant influence on the developmental trajectories of overweight in children.

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.

Diabetic embryopathy: studies using a rat embryo culture system and an animal model

The mechanism of diabetic embryopathy was investigated using in vitro experiments in a rat embryo culture system and in streptozotocin-induced diabetic pregnant rats. The energy metabolism in embryos during early organogenesis was characterized by a high rate of glucose utilization and lactic acid production (anaerobic glycolysis). Embryos uninterruptedly underwent glycolysis. When embryos were cultured with hypoglycemic serum, such embryos showed malformations in association with a significant reduction in glycolysis. In a diabetic environment, hyperglycemia caused an increased glucose flux into embryonic cells without a down-regulation of GLUT1 and an increased metabolic overload on mitochondria, leading to an increased formation of reactive oxygen species (ROS). Activation of the hexamine pathway, subsequently occurring with increased protein carbonylation and increased lipid peroxidation, also contributed to the increased generation of ROS. Hyperglycemia also caused a myo-inositol deficiency with a competitive inhibition of ambient glucose, which might have been associated with a diminished phosphoinositide signal transduction. In the presence of low activity of the mitochondrial oxidative glucose metabolism, the ROS scavenging system in the embryo was not sufficiently developed. Diabetes further weakened the antioxidant system, especially, the enzyme for GSH synthesis, gamma-GCS, thereby reducing the GSH concentration. GSH depletion also disturbed prostaglandin biosynthesis. An increased formation of ROS in a diminished GSH-dependent antioxidant system may, therefore, play an important role in the development of embryonic malformations in diabetes.

Nitric oxide modulates murine yolk sac vasculogenesis and rescues glucose induced vasculopathy

Nitric oxide (NO) has been demonstrated to mediate events during ovulation,pregnancy, blastocyst invasion and preimplantation embryogenesis. However,less is known about the role of NO during postimplantation development. Therefore, in this study, we explored the effects of NO during vascular development of the murine yolk sac, which begins shortly after implantation. Establishment of the vitelline circulation is crucial for normal embryonic growth and development. Moreover, functional inactivation of the endodermal layer of the yolk sac by environmental insults or genetic manipulations during this period leads to embryonic defects/lethality, as this structure is vital for transport, metabolism and induction of vascular development. In this study, we describe the temporally/spatially regulated distribution of nitric oxide synthase (NOS) isoforms during the three stages of yolk sac vascular development (blood island formation, primary capillary plexus formation and vessel maturation/remodeling) and found NOS expression patterns were diametrically opposed. To pharmacologically manipulate vascular development,an established in vitro system of whole murine embryo culture was employed. During blood island formation, the endoderm produced NO and inhibition of NO(L-NMMA) at this stage resulted in developmental arrest at the primary plexus stage and vasculopathy. Furthermore, administration of a NO donor did not cause abnormal vascular development; however, exogenous NO correlated with increased eNOS and decreased iNOS protein levels. Additionally, a known environmental insult (high glucose) that produces reactive oxygen species(ROS) and induces vasculopathy also altered eNOS/iNOS distribution and induced NO production during yolk sac vascular development. However, administration of a NO donor rescued the high glucose induced vasculopathy, restored the eNOS/iNOS distribution and decreased ROS production. These data suggest that NO acts as an endoderm-derived factor that modulates normal yolk sac vascular development, and decreased NO bioavailability and NO-mediated sequela may underlie high glucose induced vasculopathy.

Is There a Role for Oral Antihyperglycemics in Gestational Diabetes and Type 2 Diabetes during Pregnancy?

Diabetes mellitus is a heterogeneous disorder of glucose intolerance that is generally classified into the following categories: type 1 and type 2 diabetes and gestational diabetes (GDM). Currently, the number of pregnancies complicated by type 2 diabetes and GDM exceed those affected by type 1 diabetes. Numerous studies have established a direct relationship between maternal glycemic control and neonatal outcomes for all types of diabetes. Therefore, modern treatment protocols during pregnancy emphasize strict glycemic control by a combination of diet and medication. Traditionally, insulin therapy has been considered the gold standard for management because of its efficacy in achieving tight glucose control and the fact that it does not cross the placenta. Since GDM and type 2 diabetes are characterized by insulin resistance and relatively decreased insulin secretion, treatment with oral antihyperglycemic agents that target these defects is of potential interest. However, because of concerns regarding transplacental passage and, therefore, the possibility of fetal teratogenesis and prolonged neonatal hypoglycemia, these agents are not currently recommended in pregnancy. There are no randomized controlled trials on which to draw conclusions regarding the teratogenicity of these oral agents. However, most retrospective studies and the published clinical experience have not demonstrated an increased risk of malformed infants among women treated with oral antihyperglycemic agents. Rather, the data indicate that the increased risk for major congenital anomalies appears to be related to maternal glycemic control prior to and during conception. These studies and currently available data on the use of both metformin and sulfonylureas in pregnancy have also failed to demonstrate an increased risk of neonatal hypoglycemia and other neonatal morbidities. To date, there has only been one randomized controlled trial to test the effectiveness and safety of sulfonylurea therapy (glyburide [glibenclamide]) in the management of women with GDM. Both the insulin- and glyburide-treated women were able to achieve satisfactory glucose control and had similar perinatal outcomes. Glyburide was not detected in the cord serum of any infant in the glyburide group. In summary, based on the currently available data, it appears that glyburide could be safely and effectively utilized in the management of GDM. However, more intensive investigation regarding the safety and feasibility of oral agents in pregnancies complicated by type 2 diabetes is necessary. It is important to emphasize that it is the level of metabolic control achieved and not the mode of therapy that is crucial to improving outcomes in these pregnancies.

Reduced SOD activity and increased neural tube defects in embryos of the sensitive but not of the resistant Cohen diabetic rats cultured under diabetic conditions

BACKGROUND

The role of reactive oxygen species in the etiology of diabetes-induced anomalies was studied in a genetic model of nutritionally induced Type 2 diabetes mellitus: the Cohen diabetic sensitive (CDs) and resistant (CDr) rats. We have previously shown in this model that embryopathy may be induced by a combination of genetic and environmental factors. In our study we investigated the role of the antioxidant defense mechanism, genetic predisposition or environmental factors in embryos cultured under diabetic conditions.

METHODS

CDs, CDr and Sabra rat 11.5-day old embryos were studied after 28 hr of culture in control (low glucose), high glucose, diabetic sub-teratogenic, and diabetic teratogenic media. Embryos were monitored for growth retardation and congenital anomalies. Activity of superoxide dismutase (SOD) and catalase-like (CAT) enzymes was measured in embryonic homogenates.

RESULTS

In control medium, CDs embryos were significantly underdeveloped but exhibited no anomalies and SOD activity was not significantly different from that of CDr embryos. In high glucose medium, CDs embryos were smaller than CDr and Sabra embryos and smaller than CDs embryos cultured in control medium. Neural tube defects (NTD) were found predominantly in the CDs embryos starting from 14% in the high glucose medium and increasing to 29% in the sub-teratogenic medium. In the teratogenic medium, < 50% of the CDs and Sabra embryos were alive whereas all (100%) of the CDr embryos were alive. SOD activity significantly increased in CDs embryos when cultured in the high glucose medium but was significantly reduced in the sub-teratogenic medium. SOD activity was increased significantly in the Sabra embryos cultured in the sub-teratogenic medium but did not change in CDr embryos cultured in either one of the different culture media. CAT activity did not show any significant trend in either one of the rat strains or in any of the different culture conditions.

CONCLUSIONS

Our results suggest that genetic susceptibility plays an important role in inducing underdevelopment and NTD in cultured CDs embryos in sub-teratogenic medium and in protecting the CDr embryos under the same conditions. The combination of a sub-teratogenic environment with genetic susceptibility is sufficient to reduce the activity of SOD, hence decreasing the ability of the CDs embryos to cope with diabetic sub-teratogenic environment and prevent NTD.

Apoptosis in normal rat embryo tissues during early organogenesis: the possible involvement of Bax and Bcl-2

Apoptosis commonly occurs in a variety of developmental processes in mammals. In this study, we investigated the relationship between apoptosis and the expression of both Bax and Bcl-2 during the early organogenesis period (9.5-11.5 days of gestation) of rat embryos. Apoptotic cells detected by the terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) method were extremely abundant in the foregut diverticulum at 9.5 days of gestation, while they largely disappeared at 10.5 and 11.5 days of gestation, although they were detected in newly formed mid- and hindgut diverticulum at these times. Real-time RT-PCR analysis of whole embryos revealed that the expression of bax mRNA was constant at days 9.5 to 11.5, while the expression of bcl-2 mRNA gradually increased. Immunohistochemical studies of Bax and Bcl-2 expression revealed that these apoptotic cells were exactly positive to Bax in mirror sections, while their expression of Bcl-2 was generally too low to be detected. A disappearance of apoptotic cells was associated with strong Bcl-2 expression in the foregut diverticulum at 10.5 and 11.5 days of gestation. It was similarly observed that apoptotic cells detected in the cardiogenic area at 9.5 days of gestation disappeared with the formation of the primitive heart tube--accompanied by a strong expression of both Bcl-2 and Bax--in the developmental process of the primitive heart. Apoptotic cells were also observed in the primitive brain vesicle, optic vesicle, otic vesicle, and thyroid primordium at 10.5 and 11.5 days of gestation during the developmental process, with a strong expression of Bax. These results indicate that the Bax and Bcl-2 may be important in regulating the induction of embryonic cell apoptosis during early organogenesis.

Patterns of congenital anomalies and relationship to initial maternal fasting glucose levels in pregnancies complicated by type 2 and gestational diabetes

OBJECTIVES

We sought to determine the types of congenital anomalies affecting infants of women with gestational diabetes mellitus or type 2 diabetes and to examine the relationship between those malformation types and measures of initial glycemia of women at entry into prenatal care with type 2 diabetes or at time of diagnosis in women with gestational diabetes mellitus.

STUDY DESIGN

A total of 4,180 pregnancies complicated by gestational diabetes mellitus (n = 3764) or type 2 diabetes (n = 416) that were delivered after 20 weeks of gestation were reviewed for the presence of congenital malformations diagnosed before hospital discharge. Anomalies were categorized as being absent, minor, major, genetic syndromes, or aneuploidies. Major anomalies were further categorized by the number and type of affected organ systems. In addition to maternal clinical and historical parameters, the initial fasting serum glucose either from the diagnostic glucose tolerance test (gestational diabetes mellitus) or at entry to prenatal care (type 2 diabetes) and the initial glycosylated hemoglobin before insulin therapy were examined for a relationship to anomalies.

RESULTS

The initial fasting serum glucose and glycosylated hemoglobin levels were significantly higher in pregnancies with major (n = 143) and minor (n = 112) anomalies and genetic syndromes (n = 9) compared with pregnancies with no anomalies (n = 3895). Of those pregnancies with major anomalies, the most commonly affected organ systems were the cardiac (37.6%), musculoskeletal (14.7%), and central nervous systems (9.8%) and anomalies involving multiple organ systems (16%). There was no increased predominance of any specific organ system involvement seen with increasing fasting serum glucose levels in pregnancies with major congenital anomalies. Pregnancies with major anomalies affecting multiple organ systems had significantly higher initial fasting serum glucose levels (166 +/- 64 mg/dL) compared with pregnancies in which one organ system was affected (141 +/- 55 mg/dL, P <.04) or no organ systems were affected (115 +/- 38 mg/dL, P <.0001).

CONCLUSION

Congenital anomalies in offspring of women with gestational and type 2 diabetes affect the same organ systems that have been previously described in pregnancies complicated by type 1 diabetes. Increasing hyperglycemia at diagnosis or presentation for care was associated with an increasing risk of anomalies in general and with anomalies involving multiple organ systems without a preferential increase in involvement of specific organ system.

Maternal hyperglycemia alters glucose transport and utilization in mouse preimplantation embryos

Glucose utilization was studied in preimplantation embryos from normal and diabetic mice. With use of ultramicrofluorometric enzyme assays, intraembryonic free glucose in single embryos recovered from control and streptozotocin-induced hyperglycemic mice was measured at 24, 48, 72, and 96 h after mating. Free glucose concentrations dropped significantly in diabetics at 48 and 96 h, corresponding to the two-cell and blastocyst stages (48 h: diabetic 0.23 +/- 0.09 vs. control 2.30 +/- 0.43 mmol/kg wet wt; P < 0.001; 96 h: diabetic 0.31 +/- 0.29 vs. control 5.12 +/- 0.17 mmol/kg wet wt; P < 0.001). Hexokinase activity was not significantly different in the same groups. Transport was then compared using nonradioactive 2-deoxyglucose uptake and microfluorometric enzyme assays. The 2-deoxyglucose uptake was significantly lower at both 48 and 96 h in embryos from diabetic vs. control mice (48 h diabetic, 0.037 +/- 0. 003; control, 0.091 +/- 0.021 mmol . kg wet wt-1 . 10 min-1, P < 0. 05; 96 h diabetic, 0.249 +/- 0.008; control, 0.389 +/- 0.007 mmol . kg wet wt-1 . 10 min-1, P < 0.02). When competitive quantitative reverse transcription-polymerase chain reaction was used, there was 44 and 68% reduction in the GLUT-1 mRNA at 48 h (P < 0.001) and 96 h (P < 0.05), respectively, in diabetic vs. control mice. GLUT-2 and GLUT-3 mRNA values were decreased 63 and 77%, respectively (P < 0.01, P < 0.01) at 96 h. Quantitative immunofluorescence microscopy demonstrated 49 +/- 6 and 66 +/- 4% less GLUT-1 protein at 48 and 96 h and 90 +/- 5 and 84 +/- 6% less GLUT-2 and -3 protein, respectively, at 96 h in diabetic embryos. These findings suggest that, in response to a maternal diabetic state, preimplantation mouse embryos experience a decrease in glucose utilization directly related to a decrease in glucose transport at both the mRNA and protein levels.

Diabetes mellitus in pregnancy. What are the best treatment options?

Diabetes mellitus complicates somewhere between 1 and 20% of all pregnancies worldwide. Women with all types of diabetes, including type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus, and gestational diabetes mellitus, as well as their infants, are at increased risk for a number of different complications. However, achieving and maintaining euglycemia throughout gestation has been demonstrated to reduce the risk of adverse outcome for both the mother and her offspring. Traditional management approaches use a combination of diet, exercise, intensive insulin regimens and multiple self monitored blood glucose determinations. There are a number of newer agents available to treat diabetes mellitus; however, their safety in pregnancy has not been thoroughly tested. Although the oral hypoglycaemic drugs are not customarily used during gestation in most of the US and Europe they have had considerable use in South Africa. Animal and human studies of the teratogenic effects of these drugs have yielded conflicting data and it is difficult to distinguish between the teratogenic effects of poor maternal metabolic control and the agents themselves. This article also addresses the current state of the knowledge regarding the drug safety of a variety of medications for conditions, including hypertension and preterm labour, commonly encountered in the management of the pregnant women with diabetes mellitus.

Metabolic alteration in neural tissue of rat embryos exposed to beta-hydroxybutyrate during organogenesis

Hyperketonemia has been identified as an important factor in diabetic pregnancy affecting growth and development of the offspring. In order to assess the immediate metabolic alterations in embryos caused by excess ketone bodies, we studied rat embryonic neural tissue exposed to a high concentration of beta-hydroxybutyrate in vitro. Beta-hydroxybutyrate inhibited oxygen uptake of the neural tissue of day 9 and day 10 embryos by 12.8% and 1 1.2%, but did not affect that of day 11 and day 12 tissue. In contrast, glucose utilization of the neural tissue of day 9 and day 10 embryos was not altered. However, a 30% decrease in glucose utilization was observed in the neural tissue of day 11 and day 12 embryos exposed to beta-hydroxybutyrate. Thus, beta-hydroxybutyrate induced different metabolic alterations in the embryonic neural tissue during early and late organogenesis, which suggests different modes of teratogenic action of ketone bodies in different parts of gestation.

Dietary myo-inositol therapy in hyperglycemia-induced embryopathy

Dysmorphogenesis in diabetic mothers occurs more frequently than in the general population. This phenomenon is believed to be caused by the teratogenic effects of metabolic fuel mixtures with associated membrane injury and aberrations in the biochemical constituents. The present experiment was designed to determine: 1) if hyperglycemia-induced membrane injury is associated with intracellular and/or extracellular lipid disturbances; 2) if supplemental myo-inositol therapy prevents hyperglycemia-induced embryopathy; 3) if a correlation exists between dietary myo-inositol, serum and tissue levels of myo-inositol, and conceptus development; and 4) the cellular content of arachidonic acid following myo-inositol supplementation. Sixty-five female Sprague-Dawley rats were mated, and divided into three groups. One group was nondiabetic normal controls, and two groups had diabetes experimentally induced with streptozotocin. Of the diabetic groups, one received a normal diet, while the other received a myo-inositol-supplemented diet during the period of organogenesis. Blood samples were collected on days 0 and 12 of pregnancy. Embryos and yolk sacs were analyzed for myo-inositol and arachidonic acid levels, using mass spectrochromatography. Dietary myo-inositol supplementation of diabetic mothers resulted in a significant decrease in the incidence of neural tube defects when compared with diabetics not receiving supplements (9.5 vs. 20.4%; P < 0.05). This protective effect was incomplete, based on the incidence observed in the nondiabetic controls (9.5 vs. 3.8%; P < 0.05). The myo-inositol embryonic tissue levels in the diabetic group which had been fed a regular diet without supplementation were significantly lower than in the nondiabetic group. Dietary therapy successfully restored myo-inositol levels in the yolk sacs, as suggested by similar tissue levels in diabetics receiving myo-inositol supplementation and normal controls (18.7 +/- 1.3 vs. 19.1 +/- 2.0 ng/mg; P = ns). Dietary therapy, however, failed to restore myo-inositol levels in the embryos, suggesting hyperglycemia-induced faulty transport of nutrients from the yolk sac to the embryo. No correlation was noted between maternal blood levels of myo-inositol, with or without supplementation, and the clinical outcome. Tissue arachidonic acid levels were markedly reduced in the conceptuses of diabetic mothers with (0.4 +/- 0.1 micrograms/mg) or without (0.25 +/- 0.08 micrograms/mg) myo-inositol supplementation when compared to the nondiabetic controls (3.33 +/- 0.24 micrograms/mg). These data demonstrate that diabetes-induced embryopathy is associated with a deficiency state in both myo-inositol and arachidonic acid. The myo-inositol deficiency is not demonstrated at the serum level, but rather at the tissue level, suggesting a paracrine action. Dietary supplementation of myo-inositol is associated with an increase in tissue myo-inositol levels and a decrease in malformations. This therapy holds promise for use as a dietary prophylaxis against diabetic embryopathy.

Decreased catalase activity in malformation-prone embryos of diabetic rats

The risk for congenital malformation is increased in diabetic pregnancy. An excess of radical oxygen species (ROS) in the embryo has been suggested as a major teratogenic mechanism. We have used 2 rat strains, denoted H and U, with different catalase isoenzymes to study if the type of ROS scavenging enzyme may be of importance for the embryonic dysmorphogenesis in diabetic pregnancy. Rats were mated H x H and U x U, and about half of the females had streptozotocin-induced diabetes. Embryos were harvested from female rats on day 11 and day 20 of pregnancy. On day 11, the H embryos showed larger crown-rump length (3.9 mm) than the U embryos (2.9 mm), a difference that remained in the embryos of diabetic rats (3.1 mm and 2.5 mm in the H and U strains, respectively). H embryos displayed higher activity of catalase (1.8 +/- 0.1 U/micrograms DNA) than U embryos (1.1 +/- 0.1 U/micrograms DNA), and the difference increased further when the H and U mothers were diabetic (H: 2.1 +/- 0.2 U/micrograms DNA, U: 0.6 +/- 0.1 U/micrograms DNA). In the day-20 fetuses, diabetes in the mother caused increased resorption rate in both strains (from 3.2% to 10.6% in H rats, from 6.8% to 39.5% in U rats), and high rate of congenital malformations in the U strain (H: 0% malformations, U: 20% malformations). We found a strain-related difference in embryo catalase activity with higher activity in the teratogenically resistant H embryos compared to the malformation-prone U embryos. Provided that this difference between the strains signifies a genetic difference of functional antioxidative importance, the results may suggest that catalase enzyme activity has a protective role in opposing embryonic dysmorphogenesis in diabetic rat pregnancy.

Congenital malformations in offspring of women with hyperglycemia first detected during pregnancy

OBJECTIVES

Our aim was to determine risk factors for congenital malformations in offspring of women with hyperglycemia first detected during pregnancy (i.e., women with gestational diabetes).

STUDY DESIGN

A total of 3743 pregnancies complicated by gestational diabetes mellitus delivered at > 20 weeks of gestation were reviewed for the presence of congenital malformations diagnosed before hospital discharge. Anomalies were categorized as major, minor, or absent. Pregnancies with genetic syndromes and aneuploidies were excluded. In addition to maternal clinical and historic parameters, diagnostic glycemic parameters (fasting and post-glucose-challenge levels from the diagnostic glucose tolerance test, highest fasting serum glucose level, and hemoglobin A1c level before insulin therapy) were examined by logistic regression for predictive risk of major anomalies.

RESULTS

One or more major congenital anomalies were present in 108 (2.9%) of the newborns; an additional 91 (2.4%) had only minor anomalies. None of the maternal variables were associated with the risk of minor anomalies. By contrast, parity, a history of gestational diabetes mellitus, and several glycemic parameters were associated with the risk of major anomalies. The highest fasting serum glucose level was the best independent predictor (odds ratio 1.13/10 mg/dl, 95% confidence interval 1.09 to 1.34). The fasting serum glucose level at diagnosis, a parameter that is almost uniformly available to clinicians, gave similar predictive information about the risk of major anomalies (odds ratio 1.13, 95% confidence interval 1.08 to 1.14). Stratification of women into subgroups of fasting serum glucose level at diagnosis revealed the incidence of major anomalies to be as follows: 2.1% with a fasting serum glucose level < 120 mg/dl (2973 pregnancies), 5.2% with a fasting serum glucose level of 121 to 260 mg/dl (747 pregnancies), and 30.4% with a fasting serum glucose level > 260 mg/dl (23 pregnancies).

CONCLUSION

In a large population of women without a diagnosis of diabetes before pregnancy, the maternal fasting serum glucose concentration at diagnosis was a useful predictor of the risk of major but not minor anomalies. The rate of major anomalies doubled with a fasting glucose level > 120 mg/dl. Thus a fasting glucose level below that of overt diabetes outside of pregnancy carries an important risk of major anomalies that must be considered in the counseling and management of these patients.

Levels of amniotic fluid insulin and profiles of maternal blood glucose in pregnant women with diabetes type-I

The aim of this study was to investigate the relationship between amniotic fluid insulin (AF-insulin) measurements and maternal blood glucose levels in pregnancies complicated by insulin-dependent maternal diabetes mellitus (IDDM). Twenty-five patients with IDDM underwent amniocentesis (AC) in the third trimester. Twelve patients had a second amniocentesis after 2-3 weeks. The maternal blood glucose values (MBG) 2 weeks before amniocentesis were correlated with AF-insulin. Mean (+/-S.D.) MBG in the group with AF-insulin > 97th centile (n = 7) was 6.1 +/- 1 mmol/l. MBG in the group with AF-insulin < 97th centile (n = 18) was 5.3 +/- 1.2 mmol/l (r = 0.2948; P-value 0.162). In the group with repeated AC and AF-insulin > 97th centile (n = 6) the correlation coefficient was 0.722 (P = 0.043), whereas in the group with normal AF-insulin (n = 6) no correlation was found (r = -0.213; P = 0.686). These results indicate that no significant correlation exists between MBG values and concentration of AF-insulin. MBG is not appropriate for the diagnosis of fetal hyperinsulinism in well-controlled women with IDDM. In individual cases with AF-insulin > 97th centile a decrease of MBG causes lower AF-insulin levels. These results indicate that there seems to be an individual threshold for maternal MBG which causes hyperinsulinism. Fetal hyperinsulinism not only depends on blood glucose levels. Different fetal sensitivity to maternal glucose stimuli or a different glucose transport across the placenta in the individual fetus could be responsible for these results.

Ultrasound growth parameters in relation to levels of amniotic fluid insulin in women with diabetes type-I

The aim of the study was to investigate the correlation between ultrasound parameters and levels of amniotic fluid insulin (AF-insulin) in pregnancies complicated by insulin-dependent diabetes mellitus (IDDM). In 129 women with IDDM amniocentesis was performed between 28 and 35 weeks of gestation. The levels of AF-insulin were measured by radioimmunoassay (Pharmacia RIA 100) and were correlated with biparietal diameter (BPD), abdominal diameter (AD), abdominal circumference (AC), and femur length (FL). The women were maintained at good glycemic control (fructosamine level: mean +/- S.D.: 236.3 +/- 40 micromol/l) and delivered infants with a mean (+/- S.D.) birth weight of 3477 +/- 640 g. The sensitivity of BPD, AD, AC and FL to detect fetuses with pathological levels of AF-insulin was 50%, 62%, 67% and 49%, respectively. The sensitivities of AD and AC in a selected group (n = 14) with highly pathological levels of AF-insulin (> 20 microU/ml) were both 80%, whereas the specificity was 56% and 46%, respectively. In women with IDDM, fetal biparietal diameter, abdominal diameter, abdominal circumference, and femur length are not reliable markers for the identification of fetal hyperinsulinism. Only cases with highly pathological levels of AF-insulin can be detected by abdominal measurements.

Dietary intake of myo-inositol and neural tube defects in offspring of diabetic rats

OBJECTIVE

Embryopathy in diabetic mothers occurs at a rate four to five times higher than that observed in the general population. The current investigation was undertaken to assess the use of dietary myo-inositol supplementation as a pharmacologic prophylaxis to obviate the teratogenic effects of hyperglycemia in an in vivo study.

STUDY DESIGN

Seventy Sprague-Dawley rats were mated and after conception were randomly divided into five groups: one group was nondiabetic normal controls and four groups had diabetes experimentally induced with streptozotocin. Of the diabetic groups, one received the usual diet, whereas the others received, respectively, 0.08, 0.16, and 0.5 mg/day supplemental myo-inositol orally.

RESULTS

With the myo-inositol supplementation (0.08 mg/day), the incidence of neural tube defects was significantly reduced from 20.4% to 9.5% (p < 0.01). The most effective dosage of myo-inositol was 0.08 mg/day. Increasing the dose of myo-inositol beyond that level did not significantly reduce the rate of neural tube defects. However, the resorption rate was increased to 29.8%.

CONCLUSION

These data demonstrate that myo-inositol supplementation reduces the incidence of diabetic embryopathy and may serve as a pharmacologic prophylaxis against diabetes-induced congenital malformations.

High glucose concentration inhibits migration of rat cranial neural crest cells in vitro

Cranial neural crest cells give rise to a large part of the facial structures, and disturbed development of these cells may therefore cause congenital malformations affecting the head and face. We studied the effects of increased glucose concentration on the migration and development of cranial neural crest cells, maintained in vitro for 48 h. Pre-migratory cranial neural crest cells were removed from embryos of normal and diabetic rats on gestational day 9. After 24 h in 10 mmol/l glucose the cells were exposed to glucose concentrations of 10, 30, or 50 mmol/l for another 24 h. The cultures were photographed at 24 h and 48 h in a phase-contrast microscope to evaluate cell morphology, cell number, and cell migration. Exposure to 50 mmol/l glucose reduced the total number of neural crest cells, their mean migratory distance and migratory area expansion compared to cells cultured in 10 mmol/l glucose. To investigate the effect of antioxidant agents, high glucose cultures were studied after addition of N-acetylcysteine (NAC), or superoxide dismutase (SOD). Addition of NAC diminished the inhibitory effect of high glucose, whereas SOD did not offer any improvement in cell development. Neural crest cell culture from embryos of diabetic rats showed reduced cell migration in vitro at all glucose concentrations compared to normal cells. In addition, the cells from embryos of diabetic rats showed reduced migratory area expansion after culture in the basal 10 mmol/l glucose concentration, indicating that maternal diabetes permanently influences the future development of premigratory cranial neural crest cells. These findings indicate that high glucose concentration inhibits cranial neural crest development in vitro, and that antioxidant therapy may diminish this inhibition. Free radical oxygen species may be involved in the induction of malformations and antioxidants may therefore have a role in future attempts to block the teratogenic effects of diabetic pregnancy.

Synchronization of the factors critical for diabetic teratogenesis: an in vitro model

OBJECTIVE

Our goal was to determine the relationship between critical factors and conditions such as gestational age and exposure time to elevated glucose levels in diabetic embryopathy.

STUDY DESIGN

A postimplantation rat embryo culture was used as a model for investigation. The effect of various factors on embryonic development was studied. Experiments were conducted with increasing glucose concentrations (150 to 905 mg/dl, n = 186), at various gestational ages (10 to 12 days, n = 169), and for varying durations of exposure (30 to 180 minutes, n = 169). Gross morphologic characteristics of the yolk sac and embryo were assessed.

RESULTS

Embryopathy was induced by hyperglycemia in a dose-related fashion: a 20% rate at two times control glucose concentration, almost a 50% rate at four times control, and approximately a 100% abnormality rate at more than six times control. A critical window in gestational age, days 10 to 11, and a minimum exposure time to hyperglycemia of 2 hours were necessary to induce teratogenesis.

CONCLUSIONS

Diabetic teratogenesis occurs in a dose-related fashion and requires a minimum exposure time and critical gestational age. Only synchronization of these critical conditions induces embryonic maldevelopment. Furthermore, nonsynchronized aberrant conditions may result in apparently normal embryonic development.

Inhibitors of glycolytic metabolism affect neurulation-staged mouse conceptuses in vitro

In order to evaluate the apparent discordance between altered glucose metabolism and embryonic energy production, the effects of inhibitors of glucose utilization on morphological development and biochemical changes in mouse embryos in culture were evaluated. Day 9 ICR mouse conceptuses having 3-6 pairs of somites were prepared for culture as previously described. 2-Deoxyglucose (2DG) produced a concentration-dependent effect on development. A 25 microM 2DG concentration did not induce neural tube closure defects (NTDs) but 100 microM, 100% of embryos exhibited this defect. A 17% reduction in the rate of lactate production by the conceptus was produced by a 24-hr exposure period to 100 microM 2DG. Iodoacetate, which inhibits glyceraldehyde-3-phosphate dehydrogenase in adult tissues, produced high rates of NTDs at concentrations > or = 2.5 microM. Following a 24 hour exposure to iodoacetate, lactate production was inhibited at 10 and 25 microM. The effects of 2DG on embryonic ATP content were assessed to test the hypothesis that effects on glucose utilization would effect embryonic ATP content. Despite using 2DG concentrations that alter development and inhibit glycolysis, there were no effects on whole embryo or visceral yolk sac (VYS) ATP content. However, when the embryo was divided into regions, there was a specific reduction in ATP content in the head following a 24-hr exposure period. No effect of 2DG on head ATP content was produced after 12 hr of exposure. To determine if there were region specific differences in 2DG uptake and distribution that could account for the differential effects of 2DG on ATP content, 14C-2DG accumulation in different regions of the embryo and VYS was determined over the 24-hr culture period. The uptake of 2DG was dependent on the medium 2DG concentration and suggested a higher accumulation in regions with decreased ATP. However, when the uptake was monitored for a 1-hr period after a 24-hr exposure, there was no region specific differences in 2DG uptake. These studies further document the adverse developmental effects of inhibitors of glucose utilization during the early stage of neurulation. The biochemical mechanism for induction of these defects is unclear, but an effect on ATP content does not appear to be solely responsible for the dysmorphogenesis.

Interactive effects of alcohol and diabetes during pregnancy on the rat fetus

To determine the effect of maternal diabetes and alcohol intake, separately and in combination, on fetal growth and development, pregnant rats were divided into four groups: diabetic (D), diabetic plus alcohol (DA), control (C), and control plus alcohol (CA). Diabetes was induced by administration of streptozotocin before mating and alcohol was administered by gavage (2 g/kg body weight/day) on days 6-11 of gestation. Both diabetic groups (D and DA) had significantly lower weight gain during pregnancy compared to the controls (C and CA), despite the fact that the former consumed more food and water. Alcohol treatment resulted in reduced water and food intake and lower weight gain in the diabetic rats (DA), but not in the non-diabetic rats (CA), compared to their respective controls (D and C). On day 21 of gestation fetal body weights were significantly less and placental weights were significantly greater in the diabetic groups (D and DA) compared with the non-diabetic groups (C and CA). Differences in fetal and placental weights between rats exposed and not exposed to alcohol (C vs. CA and D vs. DA) were not significant. The number of fetuses with external malformations was significantly greater in the litters of alcohol exposed diabetic (DA) than non-alcohol exposed (D) animals. No external or skeletal malformations were observed in fetuses of non-diabetic rats regardless of whether or not they received alcohol (C or CA). The skeletal development of fetuses of diabetic rats, judged by the number and size of ossification centers on day 21 of gestation, was retarded when compared with fetuses of non-diabetic rats. Alcohol further retarded skeletal development of fetuses of diabetic animals (DA vs. D), but not of fetuses of non-diabetic rats (CA vs. C). It is concluded that maternal alcohol administration potentiates the effects of maternal diabetes on the incidence of fetal malformations and the retardation of skeletal development.

Embryonic growth impaired by maternal hypoglycemia during early organogenesis in normal and diabetic rats

The effect of maternal hypoglycemia on early organogenesis was studied in normal and diabetic rats. Female Wistar rats were made diabetic by an intravenous injection of streptozotocin (45 mg/kg) 2-3 weeks before conception. On day 9.5 or 10.5 of embryo development, both control and diabetic dams received saline or Actrapid human insulin (400 mU/rat) intraperitoneally after 19-h starvation. The fasting plasma glucose levels in diabetic dams decreased from approximately 23 to 8 mM. Hypoglycemia as low as 3.5 mM was maintained for 60 min in insulin-treated mother rats. Pregnancy was terminated on day 11.6 of embryo development. A significant growth retardation was found in diabetic embryos as compared with normal embryos. Maternal hypoglycemia lowered the DNA content in normal but not diabetic embryos, while the teratogenic effect of maternal hypoglycemia was not pronounced in either normal or diabetic embryos. These data may suggest that maternal hypoglycemia in vivo in early pregnancy influences the embryogenesis but not teratogenesis of rat embryos.

Blood levels of insulin-like growth factors I and II in neonates of non-insulin-dependent diabetic rats

Circulating levels of insulin like growth factor I (IGF-I) and insulin like growth factor II (IGF-II) were evaluated in plasma samples during the first 72 h of life in neonates of diabetic and control mother rats. Diabetes had been induced in the diabetic dams by streptozotocin at 2 days of age. The rats developed non-insulin dependent diabetes (at 6 weeks of age) and became pregnant at 11 weeks of age. Maternal blood glucose levels were higher in the diabetic mothers (P < 0.05) during the last two-thirds of gestation. Complications occurred at the end of 7.1% of the diabetic pregnancies but none of the controls. Analysis of neonates plasma glucose, IGF-I, and IGF-II concentrations in the first 12, 24, 48, and 72 h after birth revealed higher glucose levels in neonates of diabetic mothers at 72 h compared with controls (118 +/- 7 vs 85 +/- 5 mg/dl, P < 0.05) but there was no difference in IGF-I or IGF-II levels between the groups at any time point. Thus, acquired impaired glucose homeostasis may be seen in neonates of mildly diabetic mothers at early stages of their life but their circulating insulin-like growth factors levels are normal. These data do not support the proposition that fetal IGF-I and -II affect the outcome of pregnancies complicated by mild diabetes in the rodent.

Effects of the biguanide class of oral hypoglycemic agents on mouse embryogenesis

The incidence of birth defects among offspring of mothers with non-insulin dependent diabetes mellitus (NIDDM) is 2-3-fold higher than among infants of non diabetics. Since mothers with NIDDM are frequently given oral hypoglycemic agents, including sulphonylureas and biguanides, to control their disease and since these agents have been associated with the occurrence of congenital malformations in humans and animals, the embryotoxic effects of the most commonly employed biguanides, metformin and phenformin, were evaluated in whole embryo culture. Neurulating mouse embryos were exposed to therapeutic concentrations (metformin 500-2,550 mg per day; phenformin 50-400 mg per day, respectively) of the compounds for 24-48 h. Concentrations of metformin in culture ranged from 0.15 to 1.8 mg/ml and phenformin from 2.5 x 10(-5) to 0.4 mg/ml. Cultures were terminated and scored for gross morphological alterations and total protein content. Metformin produced no alterations in embryonic growth and no major malformations. Approximately 10% of all embryos exposed to metformin regardless of dose, exhibited open cranial neuropores after 24 h of culture. However, this anomaly appeared to represent a delay in closure as opposed to an overt defect, since no embryos exposed to the highest concentration of the drug and cultured for 48 h showed open neural tubes. In contrast, phenformin produced dose dependent changes in incidence of malformations, protein content, and embryolethality. Malformations included neural tube closure defects, craniofacial hypoplasia, and reduction in size of the first and second visceral arches. Doses above 0.1 mg/ml produced embryolethality and all embryos were killed at the 0.4 mg/ml concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic interactions of diabetes and pregnancy

Many of the embryonic and fetal abnormalities that occur in pregnancies complicated by maternal diabetes are the result of development in a metabolically abnormal environment. Diabetic embryopathy (birth defects and spontaneous abortions) results from maternal metabolic abnormalities during the first 6-7 weeks of gestation. The embryopathy appears to be multifactorial in origin, and the resulting defects remain important causes of morbidity and mortality in diabetic pregnancies. Diabetic fetopathy (predominantly macrosomia and neonatal hypoglycemia) results from fetal overnutrition and hyperinsulinemia during the second and third trimesters. Fetopathy may cause significant morbidity not only in the perinatal period, but also in later life as overweight infants grow up to be overweight children and young adults. Careful regulation of maternal metabolism from the preconceptional period onward can reduce greatly or even eliminate the excess risks that have been incurred by infants of diabetic mothers in the past. Successful management of maternal diabetes requires knowledge of the alterations in intermediary metabolism that normally occur during pregnancy, as discussed in this chapter.

Glucose and scyllo-inositol impair phosphoinositide hydrolysis in the 10.5-day cultured rat conceptus: a role in dysmorphogenesis?

Culture of the postimplantation rat conceptus from gestational day 9.5-10.5 in media supplemented with d-glucose or scyllo-inositol decreases tissue myo-inositol and phosphoinositides with a concomitant increase in dysmorphogenesis. A number of mitogenic agents initiate cellular proliferation and differentiation through receptors coupled to phosphoinositide hydrolysis. To test whether the decrease in conceptus phosphoinositides is associated with a reduced phosphoinositide hydrolytic response, we developed a protocol to stimulate phosphoinositide hydrolysis. Phosphoinositide hydrolysis was monitored by measurement of [3H]inositol phosphates after preincubation in serum free media. We examined the ability of serum, platelet-derived growth factor (PDGF), epidermal-derived growth factor (EGF), insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2), endothelin-1 (ET-1), and endothelin-2 (ET-2), to stimulate phosphoinositide hydrolysis. As measured by [3H]inositol monophosphate ([3H]InsP1) accumulation, normal rat seru, ET-1, and ET-2 stimulated phosphoinositide hydrolysis 47%, 420%, and 154% above the basal rate observed in serum free controls. EGF stimulated a statistically insignificant 15% increase while PDGF, IGF-1, or IGF-2 were without effect. We further characterized ET-1 stimulated phosphoinositide hydrolysis. Dose-response studies disclosed that incremental increases in [3H]InsP1 (129-420%) are observed over a concentration range of 10-1,000 nM. Maximal stimulation was not reached even at 1,000 nM. Temporally [3H]InsP1 and [3H]InsP3 levels increased linearly during incubation periods of 15-60 min. We further analyzed ET-1 stimulated phosphoinositide hydrolysis in 10.5-day conceptuses cultured for 24 hr in media containing high concentrations of glucose (23.3-56.6 mM) or scyllo-inositol (0.55, 5.5 mM). Under these dysmorphogenic conditions that concomitantly decrease the phosphoinositide precursor pool the response to ET-1 was blunted 28-76% for glucose and 29-65% for scyllo-inositol. This suggests that the effect of glucose and scyllo-inositol on lowering phosphoinositide precursor pools also results in a decrease in the response to agonists using the inositol/lipid intracellular pathway. This impaired signaling response may contribute to initiating dysmorphogenic events in diabetic embryopathy.

Glucose transporter gene expression in rat conceptus during high glucose culture

We investigated the expression of glucose transporter genes and protein in embryo and yolk sac during organogenesis and the regulation of glucose transporters during culture in hyperglycaemic media. Erythrocyte-type glucose transporter (GLUT 1) and brain-type glucose transporter (GLUT 3) mRNA were expressed in embryo and yolk sac. The expression of GLUT-1 and GLUT-3 mRNA was abundant on day 9-11 and day 9-10 in the embryo, respectively, and day 9-14 and day 10-11 in the yolk sac, respectively. The levels of GLUT-1 protein in the embryo increased in parallel with the expression of GLUT-1 mRNA during the corresponding period. Immunohistochemical staining of GLUT-1 protein was found principally in the neuroepithelial cells surrounding the neural tube in the embryo on day 10 and appeared in the microvessels surrounding the neural tube after day 12. To test whether the expression of glucose transporter genes and protein was suppressed during hyperglycaemia, conceptuses were cultured in high glucose medium. The abundant expression of GLUT-1 protein was not decreased during culture in high glucose media for 24 h (day 9-10) and was only down-regulated by prolonged exposure to this media for 48 h (day 9-11). We have demonstrated the predominant expression of the high affinity glucose transporter (GLUT 1 and GLUT 3) genes and (GLUT 1) protein in embryo during the early period of organogenesis. The persistently abundant expression of glucose transporter during the critical period of neural tube formation (day 9-10) even in the presence of hyperglycaemia may explain one of the mechanism of increased glucose flux into the neuroepithelium, which may lead to neural tube defects.

Effects of altered maternal metabolism during gastrulation and neurulation stages of embryogenesis

In summary, many congenital malformations are produced during gastrulation and neurulation stages of embryogenesis at a time when no definitive chorioallantoic placenta has been established. In rodents, altered maternal metabolism may have a direct impact on the embryo or an indirect impact via disruption of the nutritive function of the visceral yolk sac. If similar mechanisms operate in human embryos, these factors probably alter functions of the trophoblastic shell. In any case, it is crucial to remember that the metabolic status of the embryo is rapidly changing and during early stages of organogenesis may respond to alterations in nutrients quite differently during the first four weeks of gestation than at later stages of organogenesis and the fetal period.

Effects of ethanol on glucose utilization by cultured mammalian embryos

We have previously observed correlations between placental glucose transfer and growth of fetuses of ethanol (EtOH)-fed and control rats. In the present study, whole mammalian embryos were used to define the interaction of glucose supply and the effects of EtOH on growth and differentiation. Rat embryos were cultured in 75% normal rat serum from day 9.5 to day 11.5 of gestation. EtOH produced dose-dependent reductions of embryo protein content (mean +/- SEM = 212 +/- 5, 171 +/- 11, 141 +/- 16, and 113 +/- 9 micrograms/embryo in the presence of 0, 25, 50, and 100 mM EtoH, respectively). Somite number was 25.7 +/- 0.3, 23.4 +/- 0.7, 21.8 +/- 0.7, and 21.1 +/- 0.4 under the same conditions. Exposure to ethanol during the first 24 hr in culture decreased embryo protein content to the same extent as exposure for the entire 48-hr culture period. After 46 hr in culture, control and ethanol-exposed embryos were incubated with 14C-glucose for 2 hr. Ethanol produced dose-dependent reductions of CO2 production, anabolic utilization, lactate release, and total glucose utilization. Glucose supplementation (300 mg/dl) significantly increased embryo protein content and each of these glucose utilization parameters. When glucose utilization was expressed relative to embryo protein content, incorporation of the label into embryonic tissues was significantly reduced by ethanol and increased by glucose supplementation. Embryo protein content correlated closely (r = 0.871, p less than 0.0001) with anabolic glucose utilization. Thus, ethanol directly affects embryo glucose utilization, both as an energy source and as a synthetic substrate, in addition to its effects on placental glucose transfer.

Effects of in vivo exposure of pregnant hamsters to glucose. 1. Abnormalities in LVG strain fetuses following intermittent multiple treatments with two isomers

The increased frequency of congenital malformations including caudal regression syndrome, in infants of women with insulin-dependent diabetes mellitus is well documented. Most of the related animal research has involved the in vitro embryo culturing methodology. This study involved the alternative in vivo approach in order to determine the effects of treatment of pregnant hamsters with the D- and L-isomers of glucose at five times just before and during the period of embryonic organogenesis on maternal blood glucose levels and the rates and types of fetal abnormalities. One group of animals was injected with 5 doses (4 g/kg each) of D-glucose, i.e., on gestation day (D) 6, 3 PM; D7, 8 AM and 3 PM; D8, 8 AM and 3 PM. Two other groups were treated the same way but with L-glucose (4 g/kg per dose) and water (10 ml/kg per dose), respectively. The D-glucose treatment produced alternating periods of hyperglycemia and normoglycemia in the pregnant hamsters, enlarged placentae and fetuses with small urinary bladders, microphthalmia and skeletal abnormalities of the sternum, caudal vertebrae, pelvic bones, and femora. The L-glucose treatment did not produce changes in maternal blood D-glucose levels but did produce fetuses with small urinary bladders, microphthalmia and abnormal ossification limited to the manubrium. Several interpretations of the D-glucose-induced fetal abnormalities involving the vertebrae, proximal hindlimb bones and urinary bladders are discussed, including the consideration that this cluster has interesting similarities to the spectrum of skeletal and soft tissue abnormalities of human diabetes-related caudal regression syndrome.

Preconceptional nutrition

Preconceptional nutrition assessment and intervention is essential for optimal pregnancy outcome. Attainment of an appropriate prepregnancy weight is crucial to the success of a subsequent pregnancy. Metabolic stabilization of disease states or surgery induced imbalances are vital in any woman in which these problems occur. The effect of medications on nutrient status and use of nutrient supplements should be evaluated. Prior to conception women should be counseled to increase the nutrient density of their diet with special emphasis on iron, calcium, magnesium, zinc, folate, and vitamin B-6.

Myo-inositol and prostaglandins reverse the glucose inhibition of neural tube fusion in cultured mouse embryos

Neural tube defects in infants of diabetic mothers constitute an important and frequent cause of neonatal mortality/morbidity and long-term chronic handicaps. The mechanism by which normal neural tube fusion occurs is not known. The failure of rostral neural tube fusion seen in mouse embryos incubated in the presence of excess-D-glucose can be significantly prevented by the supplementation of myo-inositol to the culture medium. This protective effect of myo-inositol is reversed by indomethacin, an inhibitor of arachidonic acid metabolism leading to prostaglandin synthesis. Prostaglandin E2 added to the culture medium completely protects against the glucose-induced neural tube defect. These data suggest that the failure of neural tube fusion seen in diabetic embryopathy is mediated through a mechanism involving abnormalities in both the myo-inositol and arachidonic acid pathways, resulting in a functional deficiency of prostaglandins at a critical time of neural tube fusion.

Effects of hyperglycaemia on sorbitol and myo-inositol contents of cultured embryos: treatment with aldose reductase inhibitor and myo-inositol supplementation

To demonstrate the myo-inositol depletion hypothesis in hyperglycaemia-induced embryopathy, rat conceptuses of 9.5 days of gestation in the early head-fold stage were grown in vitro during neural tube formation for 48 h with increasing amounts of glucose. The effects of an aldose reductase inhibitor and the myo-inositol supplementation were also investigated. Sorbitol and myo-inositol contents were measured in separated embryos and extra-embryonic membranes including yolk sac and amnion at the end of culture. After addition of 33.3 mmol/l and 66.7 mmol/l glucose to the culture media, the myo-inositol content of the embryos was significantly decreased by 43.1% (p less than 0.05) and 64.6% (p less than 0.01) of the control group, while a marked accumulation of sorbitol was observed (25 and 41 times that of the control). Although the addition of an aldose reductase inhibitor (0.7 mmol/l) to the hyperglycaemic culture media containing an additional 66.7 mmol/l glucose significantly reduced the sorbitol content of embryos to approximately one-eighth, the myo-inositol content of embryos remained decreased and the frequency of neural lesions was unchanged (23.1% vs 23.9%, NS). Supplementation of the myo-inositol (0.28 mmol/l) completely restored the myo-inositol content of the embryos and resulted in a significant decrease in the frequency of neural lesions (7.1% vs 23.9%, p less than 0.01) and a significant increase in crown-rump length and somite numbers. Much less significantly, sorbitol accumulation was also observed in the extra-embryonic membrane in response to hyperglycaemia, neither hyperglycaemia nor the myo-inositol supplementation modified the myo-inositol contents of the extra-embryonic membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes and diet in pregnancy

The mean additional energy requirement for pregnancy has been calculated at 285 kcal daily and it reflects the energy needs for production of the fetoplacental unit and for the maternal physiological adaptations to pregnancy. In practice there is considerable variation in energy requirement due to alterations in maternal energy expenditure. Optimal energy intakes are dictated also by the pre-pregnancy maternal weight. The outcome of pregnancy is improved in the underweight mother by an intake which produces a weight gain in pregnancy of approximately 14 kg, whereas a rise of only 7 kg may be optimal for the obese mother. Obesity with or without diabetes is associated with macrosomia and other problems and it is sensible to attempt to limit weight gain in pregnancy at a time when maternal motivation is high. Diabetes in pregnancy may arise in patients with pre-existing NIDDM or IDDM, but more commonly it is diagnosed for the first time during pregnancy and it usually disappears after delivery (gestational diabetes). Recent evidence suggests that gestational diabetes has a strong genetic component and is usually NIDDM precipitated early in life by the pregnancy. Both gestational diabetes and NIDDM are characterized by insulin deficiency and by insulin resistance. Long-term follow-up studies have demonstrated that NIDDM or impaired glucose tolerance develop in later life in 50-70% of women with previous gestational diabetes. The adverse effects of pregnancy on the mother with pre-existing diabetes may be minimized by good diabetic control as may be adverse effects on the fetus and neonate of diabetes in the mother. An increased incidence of fetal malformations persists in pregnancies with pre-existing maternal diabetes. Diabetes of any form may be associated with neonatal hypoglycaemia. The aim of therapy is to produce maternal normoglycaemia throughout pregnancy by dietary measures and insulin treatment if required. Women with pre-existing diabetes should tighten their blood glucose control from before conception. Optimization of insulin therapy and diet are required for IDDM and most NIDDM women will require insulin treatment in pregnancy. Gestational diabetics require diet and possibly insulin. Most pregnancies now proceed to term.

Development of the conducting airway epithelium in fetal Syrian golden hamsters during normal and diabetic pregnancies

The conducting airway epithelium of fetal Syrian golden hamsters was studied from gestational day 12 to day 15, during normal and uncontrolled diabetic pregnancies. Diabetes was induced in the pregnant hamsters by injecting streptozotocin at 60 mg/kg body weight, subcutaneously, early on gestational day 10. Cells in S-phase were labelled immunochemically with bromodeoxyuridine (BrdU), and the day on which endocrine cells and ciliated cells first appeared was determined. In control fetuses, the BrdU-labelling indices (LI's) of different anatomical airway levels were significantly different from one gestational day to the next. For example, the LI of the lobar bronchus was significantly different on each gestational day (P less than .0001), and the same was true of the bronchioles. Moreover, the difference between LI's of the lobar bronchus and bronchioles-terminal buds was highly significant on day 12 (P less than .0001), and on day 13 the differences between lobar bronchus and bronchioles, lobar bronchus and terminal buds, and bronchioles and terminal buds were also highly significant (P less than .0001). However, on gestational days 14 and 15, the LI's were reduced and were comparable at different airway levels. The BrdU-labelling indices were very consistent among fetuses of the same age, and the differences between the average LI's for pups of different litters was numerically very small. Hyperglycemia (mild, moderate, severe) did not alter LI's in the fetal airway epithelial cells. Furthermore, although glycogen was not depleted from the airway epithelium of the hyperglycemic fetuses as it was in the controls, the endocrine cells first appeared on gestational days 12, 13, and 14, respectively, in the trachea, lobar bronchus and bronchioles, followed 1 day later by the ciliated cells, in the fetuses of control and diabetic mothers. In our experimental model, induction of diabetes in the pregnant hamsters on gestational day 10 did not appear to alter development or differentiation of the fetal conducting airway epithelium.