Embryopathic effects of short-term exposure to hypoglycemia in mouse embryos in vitro

Hypoglycaemia and its management in primary care setting

Hypoglycaemia is common in patients with type 1 diabetes and type 2 diabetes and constitutes a major limiting factor in achieving glycaemic control among people with diabetes. While hypoglycaemia is defined as a blood glucose level under 70 mg/dL (3.9 mmol/L), symptoms may occur at higher blood glucose levels in individuals with poor glycaemic control. Severe hypoglycaemia is defined as an episode requiring the assistance of another person to actively administer carbohydrate, glucagon, or take other corrective actions to assure neurologic recovery. Hypoglycaemia is the most important safety outcome in clinical studies of glucose lowering agents. The American Diabetes Association Standards of Medical Care recommends that a management protocol for hypoglycaemia should be designed and implemented by every hospital, along with a clear prevention and treatment plan. A tailored approach, using clinical and pathophysiologic disease stratification, can help individualize glycaemic goals and promote new therapies to improve quality of life of patients. Data from recent large clinical trials reported low risk of hypoglycaemic events with the use of newer anti-diabetic drugs. Increased hypoglycaemia risk is observed with the use of insulin and/or sulphonylureas. Vulnerable patients with T2D at dual risk of severe hypoglycaemia and cardiovascular outcomes show features of "frailty." Many of such patients may be better treated by the use of GLP-1 receptor agonists or SGLT2 inhibitors rather than insulin. Continuous glucose monitoring (CGM) should be considered for all individuals with increased risk for hypoglycaemia, impaired hypoglycaemia awareness, frequent nocturnal hypoglycaemia and with history of severe hypoglycaemia. Patients with impaired awareness of hypoglycaemia benefit from real-time CGM. The diabetes educator is an invaluable resource and can devote the time needed to thoroughly educate the individual to reduce the risk of hypoglycaemia and integrate the information within the entire construct of diabetes self-management. Conversations about hypoglycaemia facilitated by a healthcare professional may reduce the burden and fear of hypoglycaemia among patients with diabetes and their family members. Optimizing insulin doses and carbohydrate intake, in addition to a short warm up before or after the physical activity sessions may help avoiding hypoglycaemia. Several therapeutic considerations are important to reduce hypoglycaemia risk during pregnancy including administration of rapid-acting insulin analogues rather than human insulin, pre-conception initiation of insulin analogues, and immediate postpartum insulin dose reduction.

Impaired awareness of hypoglycaemia: A new risk factor for adverse pregnancy outcomes in type 1 diabetes

AIM

The aim of this study is to evaluate the impact of impaired awareness of hypoglycaemia (IAH) on metabolic control and pregnancy outcomes in women with type 1 diabetes.

MATERIAL AND METHODS

This was a single-centre prospective cohort study of singleton pregnant women with type 1 diabetes. IAH was assessed at the first antenatal visit using Clarke's test (score ≥ 3). Data on metabolic control, hypoglycaemic events, and the lipid profile were collected from prior to pregnancy and in each trimester of gestation. Pregnancy outcomes were also recorded.

RESULTS

A total of 77 patients with type 1 diabetes were included; 24 (31.2%) were classified as having IAH. Compared with the normal awareness of hypoglycaemia (NAH) group, the IAH group did not show differences in HbA_1c , weight gain, insulin doses, or severe and nonsevere hypoglycaemia events throughout pregnancy. IAH was associated with higher triglyceride concentrations in the second trimester (IAH: 154.8 ± 61.1 mg/dL, NAH: 128.6 ± 31.2 mg/dL, P = .034) and an increased risk of neonatal respiratory distress (odds ratio [OR] 11.24; 95% CI, 1.01-124.9, P = .041) in adjusted models. Increased risk of pre-eclampsia was related to higher second trimester triglyceride concentrations (OR 1.028; 95% CI, 1.004-1.053, P = .023) adjusted for confounders.

CONCLUSIONS

The IAH was associated with increased risk of neonatal respiratory distress and pre-eclampsia, despite showing no differences in metabolic control. Hypoglycaemia awareness in the first antenatal visit should be assessed to identify the subgroup of pregnant women with increased risk of complications.

The care of pregestational and gestational diabetes and drug metabolism considerations

INTRODUCTION

Normal pregnancy development involves gradual decline in insulin sensitivity, which sometimes requires pharmacotherapy. Insulin is the drug of choice for gestational and pregestational diabetes. Metabolism of traditional insulins results in inadequate onset and duration of action and marked peak activity. These properties increase risk of excessive glucose excursions, which are especially undesirable during pregnancy. Insulin analogs have been emerging as a safer and more effective treatment of diabetes during pregnancy. Areas covered: This manuscript reviews currently used antihyperglycemic agents: fast and long-acting insulins, metformin and glyburide. Trials demonstrating their efficacy and safety during pregnancy are described. Certain drug metabolism considerations (e.g. affinity to IGF-1) are emphasized. Expert opinion: The theories that insulin analogs bind to immunoglobulin and cross placenta have been disproved. Lispro, aspart, glargine and detemir do not transfer across the placenta and do not result in adverse maternal and neonatal outcomes. In addition, favorable pharmacokinetic profiles (rapid onset and 24-hour near peakless activity) substantially reduce blood glucose variability including hypoglycemia. We believe that insulin analogs should be given strong consideration for the treatment of diabetes during pregnancy. Metformin has also proven to be safe and may be considered as an initial single agent for milder gestational diabetes.

Octreotide therapy and restricted fetal growth: pregnancy in familial hyperinsulinemic hypoglycemia

SUMMARY

Hypoglycemia during pregnancy can have serious health implications for both mother and fetus. Although not generally recommended in pregnancy, synthetic somatostatin analogues are used for the management of blood glucose levels in expectant hyperinsulinemic mothers. Recent reports suggest that octreotide treatment in pregnancy, as well as hypoglycemia in itself, may pose a risk of fetal growth restriction. During pregnancy, management of blood glucose levels in familial hyperinsulinemic hypoglycemia thus forms a medical dilemma. We report on pregnancy outcomes in a woman with symptomatic familial hyperinsulinemic hypoglycemia, type 3. During the patient's first pregnancy with a viable fetus octreotide treatment was instituted in gestational age 23 weeks to prevent severe hypoglycemic incidences. Fetal growth velocity declined, and at 37 weeks of gestation, intrauterine growth retardation was evident. During the second pregnancy with a viable fetus, blood glucose levels were managed through dietary intervention alone. Thus, the patient was advised to take small but frequent meals high in fiber and low in carbohydrates. Throughout pregnancy, no incidences of severe hypoglycemia occurred and fetal growth velocity was normal. We conclude that octreotide treatment during pregnancy may pose a risk of fetal growth restriction and warrants careful consideration. In some cases of familial hyperinsulinemic hypoglycemia, blood glucose levels can be successfully managed through diet only, also during pregnancy.

LEARNING POINTS

Gain-of-function mutations in GCK cause familial hyperinsulinemic hypoglycemia.Hypoglycemia during pregnancy may have serious health implications for mother and fetus.Pregnancy with hyperinsulinism represents a medical dilemma as hypoglycemia as well as octreotide treatment may pose a risk of fetal growth restriction.In some cases of familial hyperinsulinemic hypoglycemia, blood glucose levels can be successfully managed through diet only.

Pharmacological Management of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is one of the most common morbidities complicating pregnancy, with short- and long-term consequences to the mothers, fetuses, and newborns. Management and treatment are aimed to achieve best possible glycemic control, while avoiding hypoglycemia and ensuring maternal and fetal safety. It involves behavioral modifications, nutrition and medications, if needed; concurrent with maternal and fetal surveillance for possible adverse outcomes. This review aims to elaborate on the pharmacological options for GDM therapy. We performed an extensive literature review of different available studies, published during the last 50 years, concerning pharmacological therapy for GDM, dealing with safety and efficacy, for both fetal and maternal morbidity consequences; as well as failure and success in establishing appropriate metabolic and glucose control. Oral medication therapy is a safe and effective treatment modality for GDM and in some circumstances may serve as first-line therapy when nutritional modifications fail. When oral agents fail to establish glucose control then insulin injections should be added. Determining the best oral therapy in inconclusive, although it seems that metformin is slightly superior to glyburide, in some aspects. As for parenteral therapy, all insulins listed in this article are considered both safe and effective for treatment of hyperglycemia during pregnancy. Importantly, a better safety profile, with similar efficacy is documented for most analogues. As GDM prevalence rises, there is a need for successful monitoring and treatment for patients. Caregivers should know the possible and available therapeutic options.

Low and moderate prenatal ethanol exposures of mice during gastrulation or neurulation delays neurobehavioral development

Human and animal studies show significant delays in neurobehavioral development in offspring after prolonged prenatal exposure to moderate and high ethanol doses resulting in high blood alcohol concentration (BECs). However, none have investigated the effects of lower ethanol doses given acutely during specific developmental time periods. Here, we sought to create a mouse model for modest and circumscribed human drinking during the 3rd and 4th weeks of pregnancy. We acutely treated mice during embryo gastrulation on gestational day (GD) 7 or neurulation on GD8 with a low or moderate ethanol dose given via gavage that resulted in BECs of 107 and 177 mg/dl, respectively. We assessed neonatal physical development (pinnae unfolding, and eye opening); weight gain from postnatal day (PD) 3-65; and neurobehavioral maturation (pivoting, walking, cliff aversion, surface righting, vertical screen grasp, and rope balance) from PD3 to 17. We used a multiple linear regression model to determine the effects of dose, sex, day of treatment and birth in animals dosed during gastrulation or neurulation, relative to their vehicle controls. We found that ethanol exposure during both time points (GD7 and GD8) resulted in some delays of physical development and significant sensorimotor delays of pivoting, walking, and thick rope balance, as well as additional significant delays in cliff aversion and surface righting after GD8 treatment. We also found that treatment with the low ethanol dose more frequently affected neurobehavioral development of the surviving pups than treatment with the moderate ethanol dose, possibly due to a loss of severely affected offspring. Finally, mice born prematurely were delayed in their physical and sensorimotor development. Importantly, we showed that brief exposure to low dose ethanol, if administered during vulnerable periods of neuroanatomical development, results in significant neurobehavioral delays in neonatal mice. We thus expand concerns about alcohol consumption during the 3rd and 4th weeks of human pregnancy to include occasional light to moderate drinking.

Prenatal tolbutamide treatment alters plasma glucose and insulin concentrations and negatively affects the postnatal performance of chickens

To examine the relationship of insulin and glucose, broiler embryos were subjected to acute or prolonged hypoglycemia during the late embryonic phase by, respectively, injecting once (at embryonic day [ED] 16 or 17) or on 3 consecutive days (ED 16, 17, and 18) with tolbutamide (80 μg/g embryo weight), a substance that stimulates insulin secretion from the pancreas. After 1 tolbutamide injection, a prolonged (32 h) decrease of plasma glucose and a profound acute increase in plasma insulin were observed. The 3 consecutive tolbutamide injections induced hypoglycemia for 4 days (from ED 16 to ED 19). The postnatal performance after 3 consecutive tolbutamide injections in broiler embryos was also investigated. Body weight was lower in tolbutamide-treated chickens from hatch to 42 d compared with sham (P = 0.001) and control (P < 0.001) chickens. Feed intake was lower in the tolbutamide group from hatch to 42 d as compared with sham (P = 0.007) and control (P = 0.017) animals. In addition, at 42 d, plasma glucose concentrations, after an insulin injection challenge (50 μg/kg body weight), were higher in tolbutamide-treated chickens compared with the sham and the control group as were their basal glucose levels (P value of group effect <0.001). In conclusion, tolbutamide treatment during the late embryonic development in broilers resulted in prolonged hypoglycemia in this period and negatively influenced the posthatch performance.

Diabetic embryopathy: a developmental perspective from fertilization to adulthood

Maternal diabetes mellitus is one of the strongest human teratogens. Despite recent advances in the fields of clinical embryology, experimental teratology and preventive medicine, diabetes-related perturbations of the maternofetal unit maintain a considerable impact on the Healthcare System. Classic consequences of prenatal exposure to hyperglycemia encompass (early) spontaneous abortions, perinatal death and malformations. The spectrum of related malformations comprises some recurrent blastogenic monotopic patterns, i.e. holoprosencephaly, caudal dysgenesis and oculoauriculovertebral spectrum, as well as pleiotropic syndromes, i.e. femoral hypoplasia-unusual face syndrome. Despite this, most malformed fetuses display multiple blastogenic defects of the VACTERL type, whose (apparently) casual combination preclude recognizing recurrent patterns, but accurately testifies to their developmental stage at onset. With the application of developmental biology in modern medicine, the effects of diabetes on the unborn patient are expanded to include the predisposition to develop insulin resistance in adulthood. The mechanisms underlying the transgenerational correlation between maternal diabetes and proneness to adult disorders in the offspring remain unclear, and the epigenetic plasticity may represent the missing link. In this scenario, a development-driven summary of the multifaced consequences of maternal diabetes on fertility and child health may add a practical resource to the repertoire of available information on early stages of embryogenesis.

Impaired hormonal counterregulation to biochemical hypoglycaemia does not explain the high incidence of severe hypoglycaemia during pregnancy in women with type 1 diabetes

AIMS

To explore hormonal counterregulation to biochemical hypoglycaemia during pregnancy.

METHODS

Observational study of 107 consecutive pregnant women with type 1 diabetes (median duration 16 years (range 1-36), HbA1c 6.6% (4.9-10.5) in early pregnancy) and 22 healthy pregnant women. At 8, 14, 21, 27 and 33 weeks (women with diabetes) and 15, 28 and 34 weeks (healthy women) blood was sampled for measurements of glucose, adrenaline, noradrenaline, cortisol and glucagon. Each woman's measurement of serum glucose was matched with her corresponding hormone concentrations. Severe hypoglycaemia (requiring help from another person) was recorded prospectively.

RESULTS

During normoglycaemia (serum glucose > 3.9 mmol/L), adrenaline concentrations were higher in early pregnancy compared with late pregnancy in women with diabetes (21 (7-111) pg/ml vs. 17 (2-131), p = 0.02) and healthy women (21 (10-37) pg/ml vs. 13 (5-49), p = 0.046). Biochemical hypoglycaemia (serum glucose ≤ 3.9 mmol/L) occurred in 70 women with diabetes (65%) in at least one of the five samplings. At 8 and 33 weeks, adrenaline concentrations at biochemical hypoglycaemia were similar (30 (5-164) pg/ml and 29 (9-152), p = 0.79). Adrenaline concentrations at biochemical hypoglycaemia increased from normoglycaemia at diabetes duration < 16 years (p = 0.03). In first trimester, adrenaline concentrations were comparable in women with or without severe hypoglycaemia (24 (14-164) pg/ml vs. 33 (5-86), p = 0.35). Noradrenaline, glucagon and cortisol concentrations did not increase during biochemical hypoglycaemia.

CONCLUSION

Adrenaline response to biochemical hypoglycaemia was present at similar levels in early and late pregnancy, particularly in shorter diabetes duration, and was not associated with severe hypoglycaemia in early pregnancy.

Managing type 1 diabetes mellitus in pregnancy--from planning to breastfeeding

Type 1 diabetes mellitus in pregnant women increases the risk of adverse outcomes for mother and offspring. Careful preconception counselling and screening is important, with particular focus on glycaemic control, indications for antihypertensive therapy, screening for diabetic nephropathy, diabetic retinopathy and thyroid dysfunction, as well as review of other medications. Supplementation with folic acid should be initiated before conception in order to minimize the risk of fetal malformations. Obtaining and maintaining tight control of blood glucose and blood pressure before and during pregnancy is crucial for optimizing outcomes; however, the risk of severe hypoglycaemia during pregnancy is a major obstacle. Although pregnancy does not result in deterioration of kidney function in women with diabetic nephropathy and normal serum creatinine levels, pregnancy complications such as pre-eclampsia and preterm delivery are more frequent in these women than in women with T1DM and normal kidney function. Rapid-acting insulin analogues are considered safe to use in pregnancy and studies on long-acting insulin analogues have provided reassuring results. Immediately after delivery the insulin requirement declines to approximately 60% of the prepregnancy dose, and remains 10% lower than before pregnancy during breastfeeding.

Fertility and pregnancy-associated ß-cell proliferation in mice deficient in proglucagon-derived peptides

Proglucagon, which is encoded by the glucagon gene (Gcg), is the precursor of several peptide hormones, including glucagon and glucagon-like peptide 1 (GLP-1). Whereas glucagon stimulates hepatic glycogenolysis and gluconeogenesis, GLP-1 stimulates insulin secretion to lower blood glucose and also supports ß-cell proliferation and protection from apoptotic stimuli. Pregnancy is a strong inducer of change in islet function, however the roles of proglucagon-derived peptides in pregnancy are only partially understood. In the present study, we analyzed fertility and pregnancy-associated changes in homozygous glucagon-green fluorescent protein (gfp) knock-in mice (Gcg^gfp/gfp), which lack all the peptides derived from proglucagon. Female Gcg^gfp/gfp mice could deliver and raise Gcg^gfp/gfp pups to weaning and Gcg^gfp/gfp pups from Gcg^gfp/gfp dams were viable and fertile. Pregnancy induced ß-cell proliferation in Gcg^gfp/gfp mice as well as in control mice. However, serum insulin levels in pregnant Gcg^gfp/gfp females were lower than those in control pregnant females under ad libitum feeding, and blood glucose levels in pregnant Gcg^gfp/gfp females were higher after gestational day 12. Gcg^gfp/gfp females showed a decreased pregnancy rate and smaller litter size. The rate of successful breeding was significantly lower in Gcg^gfp/gfp females and was not improved by experience of breeding. Taken together, proglucagon-derived peptides are not required for pregnancy-associated ß-cell proliferation, however, are required for regulation of blood glucose levels and normal reproductive capacity. Gcg^gfp/gfp mice may serve as a novel model to analyze the effect of mild hyperglycemia during late gestational periods.

Hypoglycaemia during pregnancy in women with Type 1 diabetes

AIMS

To explore incidence, risk factors, possible pathophysiological factors and clinical management of hypoglycaemia during pregnancy in women with Type 1 diabetes.

METHODS

Literature review.

RESULTS

In women with Type 1 diabetes, severe hypoglycaemia occurs three to five times more frequently in early pregnancy than in the period prior to pregnancy, whereas in the third trimester the incidence of severe hypoglycaemia is lower than in the year preceding pregnancy. The frequency distribution of severe hypoglycaemia is much skewed, as 10% of the pregnant women account for 60% of all recorded events. Risk factors for severe hypoglycaemia during pregnancy include a history with severe hypoglycaemia in the year preceding pregnancy, impaired hypoglycaemia awareness, long duration of diabetes, low HbA(1c) in early pregnancy, fluctuating plasma glucose values (≤ 3.9 mmol/l or ≥ 10.0 mmol/l) and excessive use of supplementary insulin injections between meals. Pregnancy-induced nausea and vomiting seem not to be contributing factors.

CONCLUSIONS

Striving for near-normoglycaemia with focus on reduction of plasma glucose fluctuations during pregnancy should have high priority among clinicians with the persistent aim of improving pregnancy outcome among women with Type 1 diabetes. Pre-conception counselling, carbohydrate counting, use of insulin analogues, continuous subcutaneous insulin infusion (insulin pump) therapy and real-time continuous glucose monitoring with alarms for low glucose values might be relevant tools to obtain near-normoglycaemia without episodes of severe hypoglycaemia.

Acute effects of thymoquinone on the pregnant rat and embryo-fetal development

The effect of a single intraperitoneal (i.p.) injection of thymoquinone (TQ) on the pregnant rat and embryo-fetal development was investigated. Pregnant female Wistar rats received 15, 35, and 50 mg/kg body weight of TQ i.p. on day 11 or 14 of gestation, and on day 18 of gestation they were sacrificed and laparotomized. Results showed that TQ induces maternal and embryonic toxicities in a dose- and time-dependent manner. With a dose of 50 mg/kg, treated rats experienced a significant decrease in maternal body weight and complete fetal resorption when the dose was given on day 11 of gestation. On the other hand, 46.2% of implants were resorbed and the viable fetuses showed no TQ-related malformations when the dose was given on day 14 of gestation. At a lower TQ dose of 35 mg/kg, maternal and embryonic toxicities were observed only when it was given on day 11 of gestation. The dose of 15 mg/kg was considered to be a dose with no observed adverse effect level for maternal and embryo-fetal toxicities when it was given day 11 or 14 of gestation. Based on the results of this study, TQ, at doses of 50 and 35 mg/kg, has a potentially disruptive effect on embryonic development during the second trimester of rat pregnancy.

Pregnancy management of women with pregestational diabetes

Optimal glycemic control is pivotal to the successful outcome of diabetic pregnancy. The goals for glycemic control include levels for preprandial and postprandial glucose and HbA1c as well as avoidance of severe hypoglycemia. These goals are best obtained with diet, exercise, and insulin treatment, often a multiple-dose insulin regimen or insulin pump. A focus on blood pressure, microalbuminuria, diabetic nephropathy, and diabetic retinopathy is needed.

Treatment of gestational diabetes mellitus: glyburide compared to subcutaneous insulin therapy and associated perinatal outcomes

OBJECTIVE

To examine perinatal outcomes in women with gestational diabetes mellitus treated with glyburide compared to insulin injections.

STUDY DESIGN

This is a retrospective cohort study of women diagnosed with gestational diabetes mellitus (GDM) who required pharmaceutical therapy and were enrolled in the Sweet Success California Diabetes and Pregnancy Program between 2001 and 2004, a California state-wide program. Women managed with glyburide were compared to women treated with insulin injections. Perinatal outcomes were compared using chi-square test and multivariable logistic regression models; statistical significance was indicated by p < 0.05 and 95% confidence intervals (CI).

RESULTS

Among the 10,682 women with GDM who required medical therapy and met study criteria, 2073 (19.4%) received glyburide and 8609 (80.6%) received subcutaneous insulin injections. Compared to insulin therapy and controlling for confounders, oral hypoglycemic treatment was associated with increased risk of birthweight >4000 g (aOR = 1.29; 95% CI [1.03-1.64]), and admission to the intensive care nursery (aOR = 1.46 [1.07-2.00]).

CONCLUSION

Neonates born to women with gestational diabetes managed on glyburide, and were more likely to be macrosomic and to be admitted to the intensive care unit compared to those treated with insulin injections. These findings should be examined in a large, prospective trial.

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.

Can Pregnant Diabetics be Treated with Glyburide?

Until the last decade, oral hypoglycemic agents have not been recommended in pregnancy owing to fear of their potential adverse fetal effects, including teratogenicity and neonatal hypoglycemia. However, the evidence in support of these recommendations is weak and is principally based on case series involving the use of first-generation sulfonylureas. Studies using a single-cotyledon placental model have found glyburide to only minimally cross the placenta, an observation that paved the way for a landmark randomized clinical trial that found glyburide to be as safe and effective as insulin in the management of gestational diabetes mellitus. Still, contradicting results regarding its trans-placental transfer, lack of adequate data regarding its safety during the first trimester and reports of increased neonatal morbidity raise concerns regarding the universal application of glyburide as an alternative to insulin therapy in diabetic pregnant women. Thus, there is a need for large, randomized, controlled trials with adequate power to evaluate the possibility of increased neonatal metabolic complications as well as the long-term outcome of infants born to mothers treated with glyburide and insulin. Unless future studies refute current data regarding the efficacy and safety of glyburide, we believe that, owing to its ease of administration, convenience and low cost, glyburide will become the first line of medical treatment in patients with gestational diabetes mellitus within the next few years.

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.

Hypoglycemia induced changes in cell death and cell proliferation in the organogenesis stage embryonic mouse heart

BACKGROUND

Hypoglycemia is a side effect of diabetes therapy and causes abnormal heart development. Embryonic heart cells are largely resistant to teratogen-induced apoptosis.

METHODS

Hypoglycemia was tested for effects on cell death and cell proliferation in embryonic heart cells by exposing mouse embryos on embryonic day (E) 9.5 (plug = E0.5) to hypoglycemia (30-50 mg/dl glucose) in vivo or in vitro for 24 hr. Long-term effects of in vivo exposure on conceptus viability were evaluated at E18.5. Cell death was evaluated on E10.5 by: 1) two TUNEL assays in sectioned embryos to demonstrate DNA fragmentation; 2) confocal microscopy in whole embryos stained with Lysotracker; 3) flow cytometry in dispersed heart cells stained for TUNEL and myosin heavy chain (MHC) to quantify and characterize cell type susceptibility; and 4) immunohistochemistry (IHC) and Western analysis in sectioned embryos to evaluate potential involvement of caspase-3 active subunit and p53. Effects on cell proliferation were evaluated by IHC and Western analysis of proliferating cell nuclear antigen (PCNA).

RESULTS

In vivo hypoglycemic exposure on E9.5 reduced viability in conceptuses examined on E18.5. Hearts examined on E10.5 demonstrated increased TUNEL and Lysotracker staining. In hearts of embryos exposed to hypoglycemia, flow cytometry demonstrated increased TUNEL-positive cells and cells dual-labeled for TUNEL and MHC. Protein expression of caspase-3 active subunit and p53 was increased and PCNA was markedly reduced in hearts of embryos exposed to hypoglycemia.

CONCLUSIONS

Hypoglycemia reduces embryonic viability, induces significant cell death, and reduces cell proliferation in the E9.5 mouse heart, and these processes may involve active caspase-3 and p53.

Oral hypoglycemic agents in pregnancy: their time has come

Oral agents are the mainstay of pharmacological treatment for non-pregnant women with type 2 diabetes. It has been proposed that, owing to the similarity between gestational and type 2 diabetes, some of these drugs could be used effectively and safely as alternatives to insulin therapy. This efficacious alternative provides the physician with more choices that, in turn, translate into more complex decision-making for the management of gestational diabetes. This article illustrates the pharmacological characteristics of oral hypoglycemic agents and placental transfer, provides evidence for the lack of association between congenital anomalies and the drugs, and reviews current studies and the clinical outcomes when these drugs are used.

Maternal hypoglycemia during pregnancy in type 1 diabetes: maternal and fetal consequences

There is strong evidence that the avoidance of hyperglycemia is essential inoptimizing pregnancy outcome in type 1 diabetes. The price to pay is a striking increase in severe hypoglycemia (SH), defined as episodes requiring help from another person. During type 1 diabetic pregnancy, occurrence rates of SH up to 15 times higher as in the intensively treated group of the Diabetes Control and Complications Trial (DCCT) are reported. Blood glucose (BG) treatment targets differ considerably between clinics; some authors advocate lower limits as low as 3.3 mmol/l. Improved glycemic control and/or recurrent hypoglycemia (i.e. BG <3.9 mmol/l) may result in impairment of glucose counterregulatory responses. Also, glucose counterregulation may be altered by pregnancy itself. Short-acting insulin analogs may help reduce hypoglycemia with preservation of good glycemic control, but their use during pregnancy has yet to be proven safe.Several clinical studies did not establish an association between maternal hypoglycemia and diabetic embryopathy. However, animal studies clearly indicate that hypoglycemia is potentially teratogenic during organogenesis. Increased rates of macrosomia continue to be observed despite near normal HbA(1c) levels. This may, at least in part, be the result of rebound hyperglycemia elicited by hypoglycemia. Exposure to hypoglycemia in utero may have long-term effects on offspring including neuropsychological defects. It is yet unclear to what extent the benefits of tight glycemic control balance with the increased risk of (severe) hypoglycemia during type 1 diabetic pregnancy. Efforts must be made to avoid low BG, i.e. <3.9 mmol/l, when tightening glycemic control.

Risk indicators predictive for severe hypoglycemia during the first trimester of type 1 diabetic pregnancy

OBJECTIVES

To investigate the frequency of severe hypoglycemia (SH) and hypoglycemic coma during the first trimester of type 1 diabetic pregnancy and in the 4 months before gestation and to identify risk indicators predicting first trimester SH in a nonselected nationwide cohort of pregnant women with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We conducted a longitudinal cohort survey in 278 pregnant type 1 diabetic women using questionnaires at inclusion and at 17 weeks of gestation, addressing the frequencies of SH (i.e., external help required) and hypoglycemic coma, general characteristics, hypoglycemia awareness, blood glucose symptom threshold, and the Hypoglycemia Fear Survey.

RESULTS

The occurrence of SH (including hypoglycemic coma) rose from 0.9 +/- 2.4 episodes per 4 months before gestation to 2.6 +/- 6.3 episodes during the first trimester (P < 0.001), including an increase in episodes of coma from 0.3 +/- 1.3 to 0.7 +/- 3.7 (P=0.03). The proportion of women affected by SH rose from 25 to 41% (P < 0.001). First-trimester SH was independently related to a history of SH before gestation (odds ratio [95%CI]: 9.2 [3.9-21.7]), a 10 years' longer diabetes duration (1.6 [1.0-2.4]), an HbA1c level < or = 6.5% (2.5 [1.3-5.0]), and a 0.1 unit/kg higher daily insulin dose (5.4 [1.5-18.9]), adjusted for a decreased symptom threshold.

CONCLUSIONS

In type 1 diabetic pregnancy, the risk of SH is increased already before pregnancy and rises further during the first trimester. A history of SH before gestation, longer duration of diabetes, an HbA1c level < or = 6.5%, and a higher total daily insulin dose were risk indicators predictive for SH during the first trimester. Further research should aim to elucidate how the benefits of strict glycemic control balance with the markedly increased risk of SH early in pregnancy.

A comparison of glyburide and insulin in women with gestational diabetes mellitus

BACKGROUND

Women with gestational diabetes mellitus are rarely treated with a sulfonylurea drug, because of concern about teratogenicity and neonatal hypoglycemia. There is little information about the efficacy of these drugs in this group of women.

METHODS

We studied 404 women with singleton pregnancies and gestational diabetes that required treatment. The women were randomly assigned between 11 and 33 weeks of gestation to receive glyburide or insulin according to an intensified treatment protocol. The primary end point was achievement of the desired level of glycemic control. Secondary end points included maternal and neonatal complications.

RESULTS

The mean (+/-SD) pretreatment blood glucose concentration as measured at home for one week was 114+/-19 mg per deciliter (6.4+/-1.1 mmol per liter) in the glyburide group and 116+/-22 mg per deciliter (6.5+/-1.2 mmol per liter) in the insulin group (P=0.33). The mean concentrations during treatment were 105+/-16 mg per deciliter (5.9+/-0.9 mmol per liter) in the glyburide group and 105+/-18 mg per deciliter (5.9+/-1.0 mmol per liter) in the insulin group (P=0.99). Eight women in the glyburide group (4 percent) required insulin therapy. There were no significant differences between the glyburide and insulin groups in the percentage of infants who were large for gestational age (12 percent and 13 percent, respectively); who had macrosomia, defined as a birth weight of 4000 g or more (7 percent and 4 percent); who had lung complications (8 percent and 6 percent); who had hypoglycemia (9 percent and 6 percent); who were admitted to a neonatal intensive care unit (6 percent and 7 percent); or who had fetal anomalies (2 percent and 2 percent). The cord-serum insulin concentrations were similar in the two groups, and glyburide was not detected in the cord serum of any infant in the glyburide group.

CONCLUSIONS

In women with gestational diabetes, glyburide is a clinically effective alternative to insulin therapy.

Glycemic control in the diabetic pregnancy: is tighter always better?

Glucose is the principal nutrient that the mother supplies to the fetus through the placenta by way of concentration-dependent mechanisms. In the presence of maternal hypoglycemia, with limited glucose supply, fetal hypoglycemia and hypoinsulinism ensue. This may be viewed as an adaptive mechanism to increase the chances of fetal survival in the face of limited maternal supply, albeit of a growth-restricted fetus. Fetal nutrient deprivation and the resulting hypoinsulinism may have both short- and long-term consequences. Intrauterine growth failure is associated with higher rates of gestational age-specific neonatal mortality and with long-term cognitive deficits. Furthermore, epidemiologic data suggest that diabetes, coronary artery disease, and hypertension are more common among adults who were small for gestational age at birth. Thus, pancreatic failure in adulthood may be either a response to excessive exposure to glucose as a result of maternal hyperglycemia, or as a result of hypoglycemia where nutrient deprivation leads to fetal growth restriction and reduced islet cell proliferation. Because low mean concentrations of maternal glucose in gestational diabetes are associated with an increased risk of fetal growth restriction, overzealous glycemic control during pregnancy may raise concerns regarding the possible effects on the infant. In the mother with Type 1 diabetes, strict glycemic control is often associated with an increased incidence of severe hypoglycemia. Up to 40% of women report at least one episode of severe hypoglycemia during pregnancy, requiring assistance by another person or professional intervention. It is quite possible that in some patients striving to optimize pregnancy outcome by maintaining the best possible glycemic control jeopardizes the well-being of the mother and the fetus. Thus, with respect to tight glycemic control of pregnant women with diabetes, the question arises: How tight is too tight? Is there a threshold below which the trade-off in terms of maternal morbidity as well as fetal growth restriction and its consequences outweighs the benefits of preventing the effects of maternal hyperglycemia?

An avian model for comparative studies of insulin teratogenicity

This study was designed to explore the effects of purified insulin during early stages of chick embryo development, and to search for variations between different molecular structures of the hormone. Chicken embryos were treated in ovo with a single dose of insulin (porcine or bovine), in only one stage of development between day 0 and day 9. Two susceptible periods were found. The earliest period (day 0 to day 3), characterized by abnormalities in the caudal vertebrae and a high mortality rate, was followed by a period with a different set of malformations, a syndrome classified as achondroplasia. The rate of achondroplastic embryos was significantly higher with porcine rather than with bovine insulin. Paradoxically, insulin at physiological doses has stimulatory effects in growth and development but, in contrast, has inhibitory effects at higher doses. The precise signalling cascade of events in the target cells is still unclear. The possible interpretations of our results are discussed. The similarity between the insulin-induced abnormalities in the chicken embryos and the caudal regression syndrome, the most common malformation found in infants of diabetic women, suggests a common mechanism. This circumstance offers the chicken embryos as an excellent in vivo model for research on the mechanism of action of insulin during normal and abnormal development.

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.

Brief hypoglycemia alters morphology, function, and metabolism of the embryonic mouse heart

This study examined effects of brief embryonic exposure to hypoglycemia on the developing mouse heart during organogenesis. Mouse embryos were exposed in whole-embryo culture to brief periods (2, 4, or 6 h) of hypoglycemia (20, 40, or 80 mg/dL glucose) at three developmental stages (10, 20, or 30 somites), and hearts were examined for morphologic, functional, and metabolic effects. Hypoglycemia produced abnormal cardiac structure and expansion and pericardial edema, and it disrupted histologic integrity and growth of the heart, particularly at 20 somites. Embryonic heart rate was decreased by hypoglycemia at all three stages. Cardiac glucose uptake and glycolysis were increased by hypoglycemia, suggesting a compensatory response to glucose deficiency, with little effect on ATP levels. In summary, brief embryonic exposure to hypoglycemia affects the morphology, function, and metabolism of the developing heart. Mechanisms by which metabolic responses are related to morphologic and functional effects are currently unclear.

Multifactorial basis of the syndrome of diabetic embryopathy

OBJECTIVE

The aim of the current paper is to explore the multifactorial basis of diabetes-induced embryopathy.

METHOD

A review of the literature regarding congenital malformations was undertaken to elucidate new advances in our understanding of diabetic embryopathy. Data from both clinical and experimental studies were collected and analyzed.

RESULTS

Numerous investigators have demonstrated that hyperglycemia and other metabolic fuels produce teratogenic effects during organogenesis. However, the exact mechanism(s) involved have not been completely elucidated. We and others have shown that aberrant metabolic fuels including hyperglycemia and hyperketonemia are teratogenic and that these effects occur via the yolk sac which appears to be the target site of injury. Other proposed etiologic factors include nutrient deficient states in membrane lipids such as arachidonic acid and myo-inositol as well as the generation of excess free oxygen radicals. This review highlights the multiple theories that have been proposed and summarizes the experimental and clinical data which support a multifactorial basis.

CONCLUSIONS

Evidence suggests that although the teratogenic process in the diabetic pregnancy is multifactorial, it may operate via a common pathway. Prevention of malformations in offspring of diabetic rats is achieved by glycemic control during organogenesis. Similar results may be obtained in a hyperglycemic state, provided there is restoration of essential fatty acid/phospholipid deficiency state and normalization of excess free radicals which may be achieved through dietary supplementation of polyunsaturated fatty acids, myoinositol, or antioxidants. The latter approach offers great promise as an adjunct to periconceptional glycemic control and as a dietary prophylaxis against the syndrome of diabetic embryopathy.

Mouse embryonic cardiac metabolism under euglycemic and hypoglycemic conditions

Children of mothers with insulin-dependent diabetic mothers (IDDM) have a 2-4 times higher incidence of congenital birth defects as compared to the general population, including cardiac abnormalities, of unknown etiology. Using rodent embryos to explore potential teratogenic factors of the altered IDDM metabolism, it has been shown that exposure to hypoglycemia in vitro results in a variety of defects, including cardiac malformations. Since pregnant diabetics experience frequent episodes of low blood glucose, it was hypothesized that hypoglycemia may play a role in the generation of heart abnormalities seen in children born to IDDM mothers. Several studies have indicated that during embryogenesis the heart is dependent on glucose for energy production such that under hypoglycemic conditions, insufficient amounts of ATP may be produced resulting in abnormalities. To test this hypothesis, cardiac ATP content was monitored in D10-D12 (plug day = D1) hearts. In addition, the contribution of glycolysis and the Krebs cycle to ATP production was monitored. D10 hearts exposed to euglycemic control conditions were found to be primarily dependent on glycolysis for ATP production from glucose before switching to the Krebs cycle and oxidative phosphorylation for energy production from this substrate on D11. Exposure to hypoglycemia did not alter the timing of this maturation process or deplete cardiac ATP content. However, cardiac lactate levels increased approximately twofold in the presence of hypoglycemia on d10. Since increased concentrations of lactate are harmful to many tissues and have been shown to be detrimental to the adult rat heart, lactic acidosis may explain the origin of cardiac defects produced by hypoglycemia, and not a deficiency of ATP.

Management of hypoglycemia and diabetic ketoacidosis in pregnancy

The article discusses the incidence and management of hypoglycemia and diabetic ketoacidosis (DKA) in pregnancy. Additional topics addressed are the incidence of hypoglycemia, pathophysiology, diagnosis and management of hypoglycemia in pregnancy, fetal monitoring with short- and long-term fetal sequelae, and prevention of hypoglycemic recurrences. Subsequently, attention is focused on the diagnosis and management of hyperglycemia and DKA in pregnancy.

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.

Diabetic embryopathy: possible pathogenesis

Despite recent emphasis upon improved metabolic control during early diabetic pregnancy, the offspring of insulin-dependent diabetic women continue to have a 2- to 4-fold increased risk of congenital malformations. We recently evaluated the affected offspring of 4 insulin-dependent diabetic women. All had abnormal ears in association with vertebral defects. Our analysis of the structural defects of these infants and a review of the literature suggest that the pathogenesis of some cases of the diabetic embryopathy may involve a primary insult to developing somite mesoderm and associated cephalic neural crest cells.

Normalization of blood glucose in insulin-dependent diabetic pregnancies and the risks of hypoglycemia: a therapeutic dilemma

Intensive insulin therapy delays the onset and progression of microvascular complications in insulin-dependent diabetes mellitus (IDDM). Such therapy, however, is associated with an increased risk of potentially life-threatening hypoglycemia due to the loss of normal counterregulatory hormonal responses to hypoglycemia and to the syndrome of hypoglycemia unawareness. Current standards for glycemic control during pregnancy in IDDM women require intensive insulin therapy to optimize pregnancy outcome. Therefore, obstetricians and gynecologists providing prenatal care for women with IDDM should be aware that intensive insulin therapy predisposes these patients to the significant risks of severe hypoglycemia. It often becomes necessary to individualize the optimal balance between glycemic control during pregnancy and the risks of hypoglycemia.

Neural plate microvillus lengthening in rat embryos grown in various concentrations of glucose and further studies of the mechanism

Glucose is an important cellular nutrient, and in the early embryo, which is dependent mostly on anaerobic glycolysis, it is even more essential. Based on tissue culture cells in which glucose utilization has become membrane-limited, a concept has been developed that the tip of the microvilli is the entrance compartment for glucose and that the shaft sets up a diffusion barrier. An increase in length of the microvillus is associated with decreased entry of phosphorylated hexose into the cells. Our previous findings of lengthening of the microvilli of the neural plate cells after 40 min exposure to glucose at room temperature have been extended to a 17 hr whole embryo culture system. In cultures where the final concentration of glucose was 20 and 24 mg/dl there was embryonic death. In those cultures ending with 29-137 mg/dl of glucose the embryos developed normally. Those grown in dialyzed serum supplemented with B vitamins and glucose grew equally as well as those in whole rat serum. Somite numbers attained did not change with increasing glucose concentration but a modest increase in micromoles of glucose used per embryo was found, suggesting the presence of another source of energy at lower glucose concentrations. The average glucose utilization per gram of protein per hour was 844 mumol in these day 9.5-10 embryos and this compares to 733 mumol previously found using uniformly labeled 14C glucose on day 10.3. Lactate production averaged 85% of the glucose utilized. Pyruvate did not support growth in the absence of glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

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)

Embryopathic effects of the oral hypoglycemic agent chlorpropamide in cultured mouse embryos

OBJECTIVES

The oral hypoglycemic agent chlorpropamide was evaluated for embryopathic effects in the mouse embryo model.

STUDY DESIGN

Mouse embryos (n = 10 to 31 per group) were exposed in whole embryo culture to serum from chlorpropamide-treated rats or chlorpropamide-supplemented control rat serum. Hypoglycemic serum from chlorpropamide-treated rats was supplemented with glucose to control for effects of hypoglycemia. Differences in malformation rates were evaluated by Fisher's exact test and numerical differences by analysis of variance.

RESULTS

Mouse embryos were malformed by > or = 24 micrograms/ml of chlorpropamide, embryonic protein content and somites were decreased by > or = 130 micrograms/ml of chlorpropamide, and visceral yolk sac protein was reduced by > 500 micrograms/ml of chlorpropamide. Similar development occurred in serum from chlorpropamide-treated rats and chlorpropamide-supplemented control serum, and growth was not improved by adding glucose.

CONCLUSIONS

Chlorpropamide produces malformations and growth retardation in mouse embryos in vitro at concentrations overlapping therapeutic levels in humans. Chlorpropamide-induced defects are not mediated by hypoglycemia or by products of chlorpropamide metabolism.

The effect of tolbutamide on rat embryonic development in vitro

Tolbutamide (TOLB) is a sulfonylurea used to treat non-insulin-dependent diabetes mellitus and is a suspected teratogen. However, it is not possible to discriminate between potential teratogenic effects of TOLB and malformations produced by either drug-induced hypoglycemia or the diabetic state itself. We examined the direct effect of TOLB on rat embryos cultured in a rodent whole embryo culture system. CD strain rat embryos were cultured for 48 h beginning on day 9 of gestation (plug day = day 0). Tolbutamide was added at various concentrations (90-3,600 microM). At the end of culture, viable embryos were examined for morphological score, number of somite pairs, crown-rump and head lengths, and DNA and protein content. Tolbutamide produced dose-related decreases in all endpoints at concentrations (2,250-3,600 microM) which are two to four times the human therapeutic concentration. Sera from TOLB-treated rats were adjusted to contain equal concentrations of glucose and insulin and then used for embryo culture. Serum from TOLB-treated rats had no observable effect on embryonic development. The mechanism for the embryotoxic effect of TOLB is unknown; however, the drug was previously demonstrated to alter activity of purified yeast glutathione reductase (GR). Because GR may be important for normal embryonic development, the effect of TOLB on this enzyme activity in cultured rat embryos was evaluated. Tolbutamide (2,700 microM) reduced embryonic GR activity by 35-57%. These results indicate that TOLB has a direct embryotoxic effect at levels 2 to 4 times the usual therapeutic serum concentrations on developing rodent embryos which may be mediated by GR inhibition.

Hypoglycaemia in pregnancy

Normally there is a very close relationship between maternal and fetal glucose concentrations during both early and late gestation. Maternal hypoglycaemia during pregnancy will therefore not only affect the mother herself but also the conceptus. As can be judged from the literature, acute hypoglycaemic episodes are only rarely seen in non-diabetic pregnancies. In recent years it has become increasingly evident that insulin-dependent diabetic patients, whether pregnant or not, run a much increased risk of having severe hypoglycaemia (SH) attacks (i.e. the patient needs the assistance of another person to relieve the attack) whenever attempts are made to introduce tight blood glucose control. Very high incidence rates of SH between 19% and 44% have been reported in diabetic pregnancy. Episodes of SH could have serious consequences; neuroglycopenia seems especially hazardous for the mother particularly during the performance of a critical task like driving a car. While hypoglycaemia has embryopathic effects in rodents, there are no data in the human to support a teratogenic effect. Insulin-induced hypoglycaemia in the last trimester of diabetic pregnancy may increase fetal body movement and decrease the fetal heart rate variability. A number of very rare conditions such as insulinoma, severe malaria, HELLP syndrome (haemolysis, elevated liver enzymes, low platelet count), severe fulminating liver disease, and ACTH and/or growth hormone deficiency have been reported to be associated with SH. Relative hypoglycaemia--i.e. low fasting blood glucose and 'flat' glucose tolerance test--is frequently seen in normotensive pregnant women with intrauterine fetal growth retardation. This pattern of maternal carbohydrate metabolism could lead to fetal hypoglycaemia and hypoinsulinaemia and contribute to poor fetal growth.