Morphological and physiological effects of beta-hydroxybutyrate on rat embryos grown in vitro at different stages

Offspring of women with hyperemesis gravidarum are more likely to have cardiovascular abnormalities

BACKGROUND

Hyperemesis gravidarum (HG) is a severe form of pregnancy-related nausea and vomiting affecting 0.3-2.3% of pregnancies, which can lead to fluid, electrolyte, and acid-base imbalances, nutritional deficiencies, and weight loss, and is usually severe enough to require hospitalization. Abnormally elevated urinary ketones are commonly seen in patients with HG, and ketone bodies are free to pass through the placenta, and maternal hyperketonemia, with or without acidosis, is associated with an increased rate of stillbirth, an increased incidence of congenital anomalies, and impaired neurophysiologic development of the infant. This study investigates the obstetric outcomes of patients with HG and whether HG increases the incidence of cardiovascular disease in the offspring.

METHODS

This study included 1020 pregnant women who were hospitalized in our hospital for HG and ultimately delivered in our hospital as well as pregnant women without HG in early gestation and delivered in our hospital from January 2019-January 2020, and we collected and followed up the clinical information of the pregnant women and their offspring.

RESULTS

Pregnant women with HG were more likely to have severe urinary ketones, the rate of early miscarriage and mid-term miscarriage was significantly higher in women with HG compared to pregnant women without HG. Fetal and neonatal head and abdominal circumferences were smaller in HG group than in control group. Neonatal birth weight and length were also lower in the HG group and cardiovascular anomalies were more likely to occur in the offspring of women with HG when all births were followed up for 3 years.

CONCLUSIONS

HG may cause poor obstetric outcomes and was associated with the development of cardiovascular disease in the offspring of women with HG.

Ketone Bodies in Diabetes Mellitus: Friend or Foe?

In glucose-deprived conditions, ketone bodies are produced by the liver mitochondria, through the catabolism of fatty acids, and are used peripherally, as an alternative energy source. Ketones are produced in the body under normal conditions, including during pregnancy and the neonatal period, when following a ketogenic diet (KD), fasting, or exercising. Additionally, ketone synthesis is also augmented under pathological conditions, including cases of diabetic ketoacidosis (DKA), alcoholism, and several metabolic disorders. Nonetheless, diet is the main regulator of total body ketone concentrations. The KDs are mimicking the fasting state, altering the default metabolism towards the use of ketones as the primary fuel source. Recently, KD has gained recognition as a medical nutrition therapy for a plethora of metabolic conditions, including obesity and diabetes mellitus (DM). The present review aims to discuss the role of ketones, KDs, ketonemia, and ketonuria in DM, presenting all the available new evidence in a comprehensive manner.

Maternal Obesity and Diabetes Mellitus as Risk Factors for Congenital Heart Disease in the Offspring

Congenital heart disease (CHD) is the most common anatomical malformation occurring live‐born infants and an increasing cause of morbidity and mortality across the lifespan and throughout the world. Population‐based observations have long described associations between maternal cardiometabolic disorders and the risk of CHD in the offspring. Here we review the epidemiological evidence and clinical observations relating maternal obesity and diabetes mellitus to the risk of CHD offspring with particular attention to mechanistic models of maternal‐fetal risk transmission and first trimester disturbances of fetal cardiac development. A deeper understanding of maternal risk factors holds the potential to improve both prenatal detection of CHD by identifying at‐risk pregnancies, along with primary prevention of disease by improving preconception and prenatal treatment of at‐risk mothers.

The status of diabetic embryopathy

Diabetic embryopathy is a theoretical enigma and a clinical challenge. Both type 1 and type 2 diabetic pregnancy carry a significant risk for fetal maldevelopment, and the precise reasons for the diabetes-induced teratogenicity are not clearly identified. The experimental work in this field has revealed a partial, however complex, answer to the teratological question, and we will review some of the latest suggestions.

New concepts in diabetic embryopathy

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

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.

Localized fetomaternal hyperglycemia: spatial and kinetic definition by positron emission tomography

BACKGROUND

Complex but common maternal diseases such as diabetes and obesity contribute to adverse fetal outcomes. Understanding of the mechanisms involved is hampered by difficulty in isolating individual elements of complex maternal states in vivo. We approached this problem in the context of maternal diabetes and sought an approach to expose the developing fetus in vivo to isolated hyperglycemia in the pregnant rat.

METHODOLOGY AND PRINCIPAL FINDINGS

We hypothesized that glucose infused into the arterial supply of one uterine horn would more highly expose fetuses in the ipsilateral versus contralateral uterine horn. To test this, the glucose tracer [18F]fluorodeoxyglucose (FDG) was infused via the left uterine artery. Regional glucose uptake into maternal tissues and fetuses was quantified using positron emission tomography (PET). Upon infusion, FDG accumulation began in the left-sided placentae, subsequently spreading to the fetuses. Over two hours after completion of the infusion, FDG accumulation was significantly greater in left compared to right uterine horn fetuses, favoring the left by 1.9+/-0.1 and 2.8+/-0.3 fold under fasted and hyperinsulinemic conditions (p<10(-11) n=32-35 and p<10(-12) n=27-45) respectively. By contrast, centrally administered [3H]-2-deoxyglucose accumulated equally between the fetuses of the two uterine horns. Induction of significant hyperglycemia (10(3) mg/dL) localized to the left uterine artery was sustained for at least 48 hours while maternal euglycemia was maintained.

CONCLUSIONS AND SIGNIFICANCE

This approach exposes selected fetuses to localized hyperglycemia in vivo, minimizing exposure of the mother and thus secondary effects. Additionally, a set of less exposed internal control fetuses are maintained for comparison, allowing direct study of the in vivo fetal effects of isolated hyperglycemia. Broadly, this approach can be extended to study a variety of maternal-sided perturbations suspected to directly affect fetal health.

Congenital anomalies in diabetic pregnancy

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

Pathogenesis of diabetes-induced congenital malformations

The increased rate of fetal malformation in diabetic pregnancy represents both a clinical problem and a research challenge. In recent years, experimental and clinical studies have given insight into the teratological mechanisms and generated suggestions for improved future treatment regimens. The teratological role of disturbances in the metabolism of inositol, prostaglandins, and reactive oxygen species has been particularly highlighted, and the beneficial effect of dietary addition of inositol, arachidonic acid and antioxidants has been elucidated in experimental work. Changes in gene expression and induction of apoptosis in embryos exposed to a diabetic environment have been investigated and assigned roles in the teratogenic processes. The diabetic environment appears to simultaneously induce alterations in several interrelated teratological pathways. The complex pathogenesis of diabetic embryopathy has started to unravel, and future research efforts will utilize both clinical intervention studies and experimental work that aim to characterize the human applicability and the cell biological components of the discovered teratological mechanisms.

Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes

Ketone bodies are produced by the liver and used peripherally as an energy source when glucose is not readily available. The two main ketone bodies are acetoacetate (AcAc) and 3-beta-hydroxybutyrate (3HB), while acetone is the third, and least abundant, ketone body. Ketones are always present in the blood and their levels increase during fasting and prolonged exercise. They are also found in the blood of neonates and pregnant women. Diabetes is the most common pathological cause of elevated blood ketones. In diabetic ketoacidosis (DKA), high levels of ketones are produced in response to low insulin levels and high levels of counterregulatory hormones. In acute DKA, the ketone body ratio (3HB:AcAc) rises from normal (1:1) to as high as 10:1. In response to insulin therapy, 3HB levels commonly decrease long before AcAc levels. The frequently employed nitroprusside test only detects AcAc in blood and urine. This test is inconvenient, does not assess the best indicator of ketone body levels (3HB), provides only a semiquantitative assessment of ketone levels and is associated with false-positive results. Recently, inexpensive quantitative tests of 3HB levels have become available for use with small blood samples (5-25 microl). These tests offer new options for monitoring and treating diabetes and other states characterized by the abnormal metabolism of ketone bodies.

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.

The pathogenesis of diabetes-associated congenital malformations

Congenital malformations convey a major financial and social burden to society. Epidemiologic, clinical, and animal studies indicate that these malformations occur in early pregnancy, are influenced by an aberrant metabolic fuel milieu, and seem to result from a combination of more than one factor acting synchronously. Unfortunately, during the critical period of organogenesis, the pregnancy is hardly recognizable, making evaluation and study of relevant maternal embryonic parameters extremely difficult. Additionally, there are obvious limitations to human study for technical and ethical reasons. Animal experimentation, however, has demonstrated that these malformations can be produced in many vertebrates and are similar to those seen in humans. The mechanism for induction of dysmorphogenesis in experimental diabetic pregnancy has been shown to include generation of free oxygen radicals and are associated with alterations in the embryonic levels of arachidonic acid, prostaglandins, and myo-inositol. Most of the earlier experimental studies focused on defects at the level of the embryo excluding the extraembryonic membranes. Current investigations provide evidence that the yolk sac has an integral role in diabetic embryopathy. The experimental use of several different compounds, such as arachidonic acid, myo-inositol, and antioxidants, offers significant promise for the future in possibly serving as a pharmacologic prophylaxis against diabetic embryopathy.

Computer modelling of neural tube defects

Neurulation, the curling of the neuroepithelium to form the neural tube, is an essential component of the development of animal embryos. Defects of neural tube formation, which occur with an overall frequency of one in 500 human births, are the cause of severe and distressing congenital abnormalities. However, despite the fact that there is increasing information from animal experiments about the mechanisms which effect neural tube formation, much less is known about the fundamental causes of neural tube defects (NTD). The use of computer models provides one way of gaining clues about the ways in which neurulation may be compromised. Here we employ one computer model to examine the robustness of different cellular mechanisms which are thought to contribute to neurulation. The model, modified from that of Odell et al (Odell, G.M., Oster, G., Alberch, P. and Burnside, B., (1981)) mimics neurulation by laterally propagating a wave of apical contraction along an active zone within a ring of cells. We link the results to experimental evidence gained from studies of embryos in which neurulation has been perturbed. The results indicate that alteration of one of the properties of non-neural tissue can delay or inhibit neurulation, supporting the idea, gained from observation of embryos bearing genes which predispose to NTD, that the tissue underlying the neuroepithelium may contribute to the elevation of the neural folds. The results also show that reduction of the contractile properties of a small proportion of the neuroepithelial cell population may have a profound effect on overall tissue profiling. The results suggest that the elevation of the neural folds, and hence successful neurulation, may be vulnerable to relatively minor deficiencies in cell properties.

Interlaboratory evaluation of three culture media for postimplantation rodent embryos

The first aim of the study was to compare the ability of rat serum, human serum, and a mixture of human and rat serum (4:1) to support in vitro development of rodent postimplantation embryos. The comparison was made in three laboratories using rat embryos and in one laboratory using mouse embryos. Batches of sera, initial developmental stage, duration of culture, and endpoints were identical in the laboratories. The second aim of the study was to evaluate if other variables that could not be standardized would significantly influence the results of the laboratories. No reproducible difference was observed among the culture media or among the laboratories except that growth and differentiation were slower in the laboratory using mouse embryos. Further experiments are needed to exclude small differences in performance of the media.