Programming of growth, insulin resistance and vascular dysfunction in offspring of late gestation diabetic rats

Evaluation of preadipocyte factor-1 (Pref-1) level in cord blood of newborns born by mothers with gestational diabetes mellitus (GDM)

BACKGROUND

Gestational diabetes mellitus (GDM) is the most common metabolic complication, which leads to short and long-term consequences in both mother and fetus exposed to hyperglycemia. The aetiology of this condition is proposed to be based on the dysfunction of the adipose tissue, which is characterised by the aberrant generation of adipokines. One of them is preadipocyte factor-1 (Pref-1), which could mediate controlling the adaptation of the maternal metabolism to pregnancy.

AIMS

The study aims to examine the level of Pref-1 in the cord blood of healthy pregnant women's neonates and fetuses born to mothers with GDM.

MATERIALS AND METHODS

Cord blood samples were collected from 30 newborns of mothers with GDM and 40 newborns of healthy pregnant women. Pref-1 concentrations were measured with an ELISA kit.

RESULTS

Fetal Pref-1 concentrations were significantly lower in newborns of mothers with GDM compared to the normal pregnancy group children (5.32 ± 0.29 vs. 7.38 ± 0.53; p < 0.001). Mothers with GDM had a significantly higher index of BMI before pregnancy, maternal gestational weight gain, and maternal fasting glucose. In-depth analysis through multiple variant linear regression revealed a significant association between fetal serum Pref-1 levels, exposure to GDM, and gestational age.

CONCLUSION

These findings contribute valuable insights into maternal-fetal health and pave the way for more targeted and effective clinical interventions.

STZ-induced gestational diabetes exposure alters PTEN/AKT/mTOR-mediated autophagy signaling pathway leading to increase the risk of neonatal hypoxic-ischemic encephalopathy

Exposure to gestational diabetes mellitus (GDM) during pregnancy has significant consequences for the unborn baby and newborn infant. However, whether and how GDM exposure induces the development of neonatal brain hypoxia/ischemia-sensitive phenotype and the underlying molecular mechanisms remain unclear. In this study, we used a late GDM rat model induced by administration of streptozotocin (STZ) on gestational day 12 and investigated its effects of GDM on neonatal brain development. The pregnant rats exhibited increased blood glucose levels in a dose-dependent manner after STZ administration. STZ-induced maternal hyperglycemia led to reduced blood glucose levels in neonatal offspring, resulting in growth restriction and an increased brain to body weight ratio. Importantly, GDM exposure increased susceptibility to hypoxia/ischemia (HI)-induced brain infarct sizes compared to the controls in both male and female neonatal offspring. Further molecular analysis revealed alterations in the PTEN/AKT/mTOR/autophagy signaling pathway in neonatal male offspring brains, along with increased ROS production and autophagy-related proteins (Atg5 and LC3-II). Treatment with the PTEN inhibitor bisperoxovanadate (BPV) eliminated the differences in HI-induced brain infarct sizes between the GDM-exposed and the control groups. These findings provide novel evidence of the development of a brain hypoxia/ischemia-sensitive phenotype in response to GDM exposure and highlight the role of the PTEN/AKT/mTOR/autophagy signaling pathway in this process.

Long-noncoding RNA HOXA transcript at the distal tip ameliorates the insulin resistance and hepatic gluconeogenesis in mice with gestational diabetes mellitus via the microRNA-423-5p/wingless-type MMTV integration site family member 7A axis

Long-noncoding RNA HOXA transcript at the distal tip (HOTTIP) has been probed to exert essential effects on diabetes progression, while its function in gestational diabetes mellitus (GDM) remains unclear. This study was committed to unravel the effects of HOTTIP on GDM progression via the microRNA (miR)-423-5p/wingless-type MMTV integration site family member 7A (WNT7A) axis. The GDM mouse model was established. HOTTIP, miR-423-5p and WNT7A levels in GDM mice were examined. The saline with dissolved various constructs altering HOTTIP, miR-423-5p and WNT7A expression was injected into GDM mice to detect the levels of GDM‐related biochemical indices, HOMA indices, liver gluconease: expression levels of phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G-6-Pase), glucose transporter 2 (GLUT2) and pathological changes of pancreatic tissues, and the apoptosis rate of pancreatic cells in GDM mice. The relations among HOTTIP, miR-423-5p and WNT7A were validated. HOTTIP and WNT7A levels were decreased while miR-423-5p was elevated in GDM mice. The enriched HOTTIP or silenced miR-423-5p alleviated the levels of GDM‐relatedbiochemical indices, enhanced the insulin homeostasis, elevated GLUT2 expression and decreased G-6-pase and PEPCK expression, mitigated the pathological changes of pancreatic tissues, and hindered the apoptosis of pancreatic cells. MiR-143-5p upregulation abrogated the effects of elevated HOTTIP on repressing GDM; whereas WNT7A deletion reversed the therapeutic effects of reduced miR-423-5p. HOTTIP sponged miR-423-5p that targeted WNT7A. HOTTIP ameliorates insulin resistance and hepatic gluconeogenesis in GDM mice via the modulation of the miR-423-5p/WNT7A axis. This study affords novel therapeutic modalities for GDM treatment.

Role of heme oxygenase in the regulation of the renal hemodynamics in a model of sex-dependent programmed hypertension by maternal diabetes

Intrauterine programming of cardiovascular and renal function occurs in diabetes because of the adverse maternal environment. Heme oxygenase 1 (HO-1) and -2 (HO-2) exert vasodilatory and antioxidant actions, particularly in conditions of elevated HO-1 expression or deficient nitric oxide levels. We evaluated whether the activity of the heme-HO system is differentially regulated by oxidative stress in the female offspring of diabetic mothers, contributing to the improved cardiovascular function in comparison with males. Diabetes was induced in pregnant rats by a single dose of streptozotocin (STZ, 50 mg/kg ip) in late gestation. Three-month-old male offspring from diabetic mothers (MODs) exhibited higher blood pressure (BP), higher renal vascular resistance (RVR), worse endothelium-dependent response to acetylcholine (ACH), and an increased constrictor response to phenylephrine (PHE) compared with those in age-matched female offspring of diabetic mothers (FODs), which were abolished by chronic tempol (1 mM) treatment. In anesthetized animals, stannous mesoporphyrin (SnMP; 40 µmol/kg iv) administration, to inhibit HO activity, increased RVR in FODs and reduced glomerular filtration rate (GFR) in MODs, without altering these parameters in control animals. When compared with MODs, FODs showed lower nitrotirosyne levels and higher HO-1 protein expression in renal homogenates. Indeed, chronic treatment with tempol in MODs prevented elevations in nitrotyrosine levels and the acute renal hemodynamics response to SnMP. Then, maternal diabetes results in sex-specific hypertension and renal alterations associated with oxidative stress mainly in adult male offspring, which are reduced in the female offspring by elevation in HO-1 expression and lower oxidative stress levels.

Vitamin B6 deficiency disrupts serotonin signaling in pancreatic islets and induces gestational diabetes in mice

In pancreatic islets, catabolism of tryptophan into serotonin and serotonin receptor 2B (HTR2B) activation is crucial for β-cell proliferation and maternal glucose regulation during pregnancy. Factors that reduce serotonin synthesis and perturb HTR2B signaling are associated with decreased β-cell number, impaired insulin secretion, and gestational glucose intolerance in mice. Albeit the tryptophan-serotonin pathway is dependent on vitamin B6 bioavailability, how vitamin B6 deficiency impacts β-cell proliferation during pregnancy has not been investigated. In this study, we created a vitamin B6 deficient mouse model and investigated how gestational deficiency influences maternal glucose tolerance. Our studies show that gestational vitamin B6 deficiency decreases serotonin levels in maternal pancreatic islets and reduces β-cell proliferation in an HTR2B-dependent manner. These changes were associated with glucose intolerance and insulin resistance, however insulin secretion remained intact. Our findings suggest that vitamin B6 deficiency-induced gestational glucose intolerance involves additional mechanisms that are complex and insulin independent.

Fields et al. investigate the impact of vitamin B6 deficiency on islet β-cell proliferation during pregnancy, using vitamin B6-deficient mice. They find that gestational vitamin B6 deficiency decreases serotonin levels in pancreatic islets and reduces β-cell proliferation, showing that vitamin B6 deficiency regulates maternal glucose tolerance in a serotonin-dependent manner.

Exposure to maternal diabetes induces endothelial dysfunction and hypertension in adult male rat offspring

The adverse environment in early life can modulate adult phenotype, including blood pressure. Our previous study shows, in a rat streptozotocin (STZ)-induced maternal diabetes model, fetal exposure to maternal diabetes is characterized by established hypertension in the offspring. However, the exact mechanisms are not known. Our present study found, as compared with male control mother offspring (CMO), male diabetic mother offspring (DMO) had higher blood pressure with arterial dysfunction, i.e., decreased acetylcholine (Ach)-induced vasodilation. But there is no difference in blood pressure between female CMO and DMO. The decreased Ach-induced vasodilation was related to decreased nitric oxide (NO) production in the endothelium, not NO sensitivity in vascular smooth muscle because sodium nitroprusside (SNP)-mediated vasodilation was preserved; there was decreased NO production and lower eNOS phosphorylation in male DMO. The reactive oxygen species (ROS) level was increased in male DMO than CMO; normalized ROS levels with tempol increased NO production, normalized Ach-mediated vasodilation, and lowered blood pressure in male DMO rats. It indicates that diabetic programming hypertension is related to arterial dysfunction; normalizing ROS might be a potential strategy for the prevention of hypertension in the offspring.

Fetal hyperglycemia acutely induces persistent insulin resistance in skeletal muscle

Offspring exposed in utero to maternal diabetes exhibit long-lasting insulin resistance, though the initiating mechanisms have received minimal experimental attention. Herein, we show that rat fetuses develop insulin resistance after only 2-day continuous exposure to isolated hyperglycemia starting on gestational day 18. Hyperglycemia-induced reductions in insulin-induced AKT phosphorylation localized primarily to fetal skeletal muscle. The skeletal muscle of hyperglycemia-exposed fetuses also exhibited impaired in vivo glucose uptake. To address longer term impacts of this short hyperglycemic exposure, neonates were cross-fostered and examined at 21 days postnatal age. Offspring formerly exposed to 2 days late gestation hyperglycemia exhibited mild glucose intolerance with insulin signaling defects localized only to skeletal muscle. Fetal hyperglycemic exposure has downstream consequences which include hyperinsulinemia and relative uteroplacental insufficiency. To determine whether these accounted for induction of insulin resistance, we examined fetuses exposed to late gestational isolated hyperinsulinemia or uterine artery ligation. Importantly, 2 days of fetal hyperinsulinemia did not impair insulin signaling in murine fetal tissues and 21-day-old offspring exposed to fetal hyperinsulinemia had normal glucose tolerance. Similarly, fetal exposure to 2-day uteroplacental insufficiency did not perturb insulin-stimulated AKT phosphorylation in fetal rats. We conclude that fetal exposure to hyperglycemia acutely produces insulin resistance. As hyperinsulinemia and placental insufficiency have no such impact, this occurs likely via direct tissue effects of hyperglycemia. Furthermore, these findings show that skeletal muscle is uniquely susceptible to immediate and persistent insulin resistance induced by hyperglycemia.

Epigenetic Down-Regulation of Sirt 1 via DNA Methylation and Oxidative Stress Signaling Contributes to the Gestational Diabetes Mellitus-Induced Fetal Programming of Heart Ischemia-Sensitive Phenotype in Late Life

Rationale: The incidence of gestational diabetes mellitus (GDM) is increasing worldwide. However, whether and how GDM exposure induces fetal programming of adult cardiac dysfunctional phenotype, especially the underlying epigenetic molecular mechanisms and theranostics remain unclear. To address this problem, we developed a late GDM rat model.

Methods: Pregnant rats were made diabetic on day 12 of gestation by streptozotocin (STZ). Experiments were conducted in 6 weeks old offspring.

Results: There were significant increases in ischemia-induced cardiac infarction and gender-dependent left ventricular (LV) dysfunction in male offspring in GDM group as compared to controls. Exposure to GDM enhanced ROS level and caused a global DNA methylation in offspring cardiomyocytes. GDM attenuated cardiac Sirt 1 protein and p-Akt/Akt levels, but enhanced autophagy-related proteins expression (Atg 5 and LC3 II/LC3 I) as compared to controls. Ex-vivo treatment of DNA methylation inhibitor, 5-Aza directly inhibited Dnmt3A and enhanced Sirt 1 protein expression in fetal hearts. Furthermore, treatment with antioxidant, N-acetyl-cysteine (NAC) in offspring reversed GDM-mediated DNA hypermethylation, Sirt1 repression and autophagy-related gene protein overexpression in the hearts, and rescued GDM-induced deterioration in heart ischemic injury and LV dysfunction.

Conclusion: Our data indicated that exposure to GDM induced offspring cardiac oxidative stress and DNA hypermethylation, resulting in an epigenetic down-regulation of Sirt1 gene and aberrant development of heart ischemia-sensitive phenotype, which suggests that Sirt 1-mediated signaling is the potential therapeutic target for the heart ischemic disease in offspring.

Programming of Vascular Dysfunction in the Intrauterine Milieu of Diabetic Pregnancies

With the rising global tide of obesity, gestational diabetes mellitus (GDM) burgeoned into one of the most common antenatal disorders worldwide. Macrosomic babies born to diabetic mothers are more likely to develop risk factors for cardiovascular disease (CVD) before they reach adulthood. Rodent studies in offspring born to hyperglycemic pregnancies show vascular dysfunction characterized by impaired nitric oxide (NO)-mediated vasodilation and increased production of contractile prostanoids by cyclooxygenase 2 (COX-2). Vascular dysfunction is a key pathogenic event in the progression of diabetes-related vascular disease, primarily attributable to glucotoxicity. Therefore, glucose-induced vascular injury may stem directly from the hyperglycemic intrauterine environment of GDM pregnancy, as evinced by studies showing endothelial activation and inflammation at birth or in childhood in offspring born to GDM mothers. This review discusses potential mechanisms by which intrauterine hyperglycemia programs dysfunction in the developing vasculature.

Increased retinol-free RBP4 contributes to insulin resistance in gestational diabetes mellitus

PURPOSE

Retinol-binding protein 4 (RBP4) is a circulating retinol transporter that is strongly associated with insulin resistance. The aim of this study was to evaluate the RBP4 and retinol level in rat model of gestational diabetes mellitus and the relationship between retinol-free RBP4 (apo-RBP4), retinol-bound RBP4 (holo-RBP4) and insulin resistance.

METHODS

Pregnant rats were administered streptozotocin to induce diabetes. The RBP4 and retinol levels were evaluated in GDM and normal pregnant rats. After then, normal pregnant rats were divided into two groups to receive either apo-RBP4 or vehicle injection. The metabolic parameters and insulin signaling in adipose tissue, skeletal muscle and liver were determined in apo-RBP4 and control groups. Primary human adipocytes were cultured in vitro with different proportions of apo-RBP4 and holo-RBP4 for 24 h. The interaction between RBP4 and STRA6 was assessed by co-immunoprecipitation, and the expression of JAK-STAT pathway and insulin signaling were detected by Western blotting and immunofluorescence.

RESULTS

We found increases in serum RBP4 levels and the RBP4:retinol ratio but not in the retinol levels in GDM rats. Exogenous apo-RBP4 injection attenuated insulin sensitivity in pregnant rats. In vitro, a prolonged interaction between RBP4 and STRA6 was observed when apo-RBP4 was present. In response to increased apo-RBP4 levels, cells showed elevated activation of the JAK2/STAT5 cascade and SOCS3 expression, decreased phosphorylation of IR and IRS1, and attenuated GLUT4 translocation and glucose uptake upon insulin stimulation.

CONCLUSION

Apo-RBP4 is a ligand that activates the STRA6 signaling cascade, inducing insulin resistance in GDM.

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

Impact of maternal nutritional status before and during pregnancy on neonatal body composition: A cross-sectional study

BACKGROUND

The existence of early factors which, acting during critical periods of intrauterine or immediate postnatal development, determine long-term health has become increasingly recognized. Both high and low birth weight have been associated with cardiovascular risk factors in adulthood. Therefore, body composition at birth rather than birth weight may be a marker to predict future diseases. Maternal weight previous to and gained during pregnancy is associated with intrauterine fetal growth.

OBJECTIVE

To evaluate the correlation between maternal nutritional status before and during pregnancy and neonatal body composition.

MATERIAL AND METHODS

We studied consecutive mother-child pairs at delivery at an Argentinean public hospital during 5 months period, evaluating maternal and neonatal anthropometry before 24h of life as well as the history of the mother before and during pregnancy. Neonatal body composition was calculated according to a mathematical formula based on skinfold thickness measurement validated in newborns.

RESULTS

Mothers of newborns with high body fat mass were more frequently obese (72.7% versus 35.1%, p 0.005), and more frequently showed weight gain above 18kg during pregnancy (76.4% versus 31%, p 0.03).

CONCLUSIONS

Our findings confirm the hypothesis that maternal obesity before pregnancy is highly correlated with neonatal fat mass in the first hours of life.

Alterations in perivascular innervation function in mesenteric arteries from offspring of diabetic rats

BACKGROUND AND PURPOSE

We have reported that exposure to a diabetic intrauterine environment during pregnancy increases blood pressure in adult offspring, but the mechanisms involved are not completely understood. This study was designed to analyse a possible role of perivascular sympathetic and nitrergic innervation in the superior mesenteric artery (SMA) in this effect.

EXPERIMENTAL APPROACH

Diabetes was induced in pregnant Wistar rats by a single injection of streptozotocin. Endothelium-denuded vascular rings from the offspring of control (O-CR) and diabetic rats (O-DR) were used. Vasomotor responses to electrical field stimulation (EFS), NA and the NO donor DEA-NO were studied. The expressions of neuronal NOS (nNOS) and phospho-nNOS (P-nNOS) and release of NA, ATP and NO were determined. Sympathetic and nitrergic nerve densities were analysed by immunofluorescence.

KEY RESULTS

Blood pressure was higher in O-DR animals. EFS-induced vasoconstriction was greater in O-DR animals. This response was decreased by phentolamine more in O-DR animals than their controls. L-NAME increased EFS-induced vasoconstriction more strongly in O-DR than in O-CR segments. Vasomotor responses to NA or DEA-NO were not modified. NA, ATP and NO release was increased in segments from O-DR. nNOS expression was not modified, whereas P-nNOS expression was increased in O-DR. Sympathetic and nitrergic nerve densities were similar in both experimental groups.

CONCLUSIONS AND IMPLICATIONS

The activity of sympathetic and nitrergic innervation is increased in SMA from O-DR animals. The net effect is an increase in EFS-induced contractions in these animals. These effects may contribute to the increased blood pressure observed in the offspring of diabetic rats.

Placental DNA methylation of peroxisome-proliferator-activated receptor-γ co-activator-1α promoter is associated with maternal gestational glucose level

Among all the participants, the maternal gestational glucose level was positively correlated with placental DNA methylation. The correlation between gestational 2-h post-OGTT glycaemia and CpG site-specific methylation in placenta was stronger in the gestational diabetes group.

Growth and endothelial function in the first 2 years of life

OBJECTIVE

To test the hypothesis that the inverse association between infant growth and endothelial function at 6 months would persist to 24 months and that accelerated growth would lead to an increased percent body fat, which would, in turn, impact negatively on endothelial function.

STUDY DESIGN

In a prospective observational study, 104 healthy term newborns underwent anthropometry and measurements of vascular vasodilation at 0, 6, 12, and 24 months. We recorded maximum vasodilation in response to acetylcholine (endothelium-dependent) and nitroprusside (endothelium-independent) by use of laser-Doppler vascular perfusion monitoring of the forearm skin vasculature. Additional anthropometry at 1 and 3 months was collected from child welfare centers. The data were analyzed by multilevel linear regression.

RESULTS

Weight gain from 0-1 month was associated inversely with maximum perfusion in response to acetylcholine at the age of 2 years (b = -8.28 perfusion units [PU] per Δ z-score, P = .03). Weight gain from 0-1 month was related positively to maximum perfusion in response to nitroprusside (b = 10.12 PU per Δ z-score, P = .04), as was birth weight (b = 8.02 PU per z-score, P = .02). Body fat percentage did not have a significant effect in any of the perfusion models and was not related to maximum perfusion at 2 years.

CONCLUSION

Infant weight gain from 0-1 month is inversely related to endothelial function in healthy term infants, at least to the age of 2 years. This relationship was not explained by an increased percentage body fat.

Fetal hyperglycemia and a high-fat diet contribute to aberrant glucose tolerance and hematopoiesis in adult rats

BACKGROUND

Children exposed to gestational diabetes mellitus (GDM) during pregnancy are at increased risk of obesity, diabetes, and hypertension. Our goal was to identify metabolic and hematopoietic alterations after intrauterine exposure to maternal hyperglycemia that may contribute to the pathogenesis of chronic morbidities.

METHODS

Streptozotocin treatment induced maternal hyperglycemia during the last third of gestation in rat dams. Offspring of control mothers (OCM) and diabetic mothers (ODM) were evaluated for weight, glucose tolerance, insulin tolerance, and hematopoiesis defects. The effects of aging were examined in normal and high-fat diet (HFD)-fed young (8-wk-old) and aged (11-mo-old) OCM and ODM rats.

RESULTS

Young adult ODM males on a normal diet, but not females, displayed improved glucose tolerance due to increased insulin levels. Aged ODM males and females gained more weight than OCM on a HFD and had worse glucose tolerance. Aged ODM males fed a HFD were also neutrophilic. Increases in bone marrow cellularity and myeloid progenitors preceded neutrophilia in ODM males fed a HFD.

CONCLUSION

When combined with other risk factors like HFD and aging, changes in glucose metabolism and hematopoiesis may contribute to the increased risk of obesity, type 2 diabetes, and hypertension observed in children of GDM mothers.

Gene-environment interactions controlling energy and glucose homeostasis and the developmental origins of obesity

Obesity and type 2 diabetes mellitus (T2DM) often occur together and affect a growing number of individuals in both the developed and developing worlds. Both are associated with a number of other serious illnesses that lead to increased rates of mortality. There is likely a polygenic mode of inheritance underlying both disorders, but it has become increasingly clear that the pre- and postnatal environments play critical roles in pushing predisposed individuals over the edge into a disease state. This review focuses on the many genetic and environmental variables that interact to cause predisposed individuals to become obese and diabetic. The brain and its interactions with the external and internal environment are a major focus given the prominent role these interactions play in the regulation of energy and glucose homeostasis in health and disease.

Advancements and challenges in generating accurate animal models of gestational diabetes mellitus

The maintenance of glucose homeostasis during pregnancy is critical to the health and well-being of both the mother and the developing fetus. Strikingly, approximately 7% of human pregnancies are characterized by insufficient insulin production or signaling, resulting in gestational diabetes mellitus (GDM). In addition to the acute health concerns of hyperglycemia, women diagnosed with GDM during pregnancy have an increased incidence of complications during pregnancy as well as an increased risk of developing type 2 diabetes (T2D) later in life. Furthermore, children born to mothers diagnosed with GDM have increased incidence of perinatal complications, including hypoglycemia, respiratory distress syndrome, and macrosomia, as well as an increased risk of being obese or developing T2D as adults. No single environmental or genetic factor is solely responsible for the disease; instead, a variety of risk factors, including weight, ethnicity, genetics, and family history, contribute to the likelihood of developing GDM, making the generation of animal models that fully recapitulate the disease difficult. Here, we discuss and critique the various animal models that have been generated to better understand the etiology of diabetes during pregnancy and its physiological impacts on both the mother and the fetus. Strategies utilized are diverse in nature and include the use of surgical manipulation, pharmacological treatment, nutritional manipulation, and genetic approaches in a variety of animal models. Continued development of animal models of GDM is essential for understanding the consequences of this disease as well as providing insights into potential treatments and preventative measures.

Effect of age and COX-2-derived prostanoids on the progression of adult vascular dysfunction in the offspring of diabetic rats

BACKGROUND AND PURPOSE

The present study was designed to determine how diabetes in pregnancy affects vascular function in their offspring, the influence of age and whether COX activation is involved in this effect.

EXPERIMENTAL APPROACH

Relaxation responses to ACh were analysed in mesenteric resistance arteries from the offspring of control rats (O-CR) and those of diabetic rats (O-DR) at 3, 6 and 12 months of age. TxB₂, PGE₂ and PGF(2α) release were determined by enzyme immunoassay. COX-1 and COX-2 expression were measured by Western blot analysis.

KEY RESULTS

O-DR developed hypertension from 6 months of age compared with O-CR. In O-DR, relaxation responses to ACh were impaired in all ages studied and were restored by COX-2 inhibition. TP receptor blockade (SQ29548) restored ACh relaxation in arteries from 3-month-old O-DR while TP and EP receptor blockade (SQ29548 + AH6809) was required to restore it in 6-month-old O-DR. In 12-month-old O-DR, ACh relaxation was restored when TP, EP and FP receptors were blocked (SQ29548 + AH6809 + AL8810). ACh-stimulated TxB₂ was higher in all O-DR. ACh-stimulated PGE₂ release was increased in arteries from 6- and 12-month-old O-DR, whereas PGF(2α) was increased only in 12-month-old O-DR. COX-2, but not COX-1, expression was higher in O-DR than O-CR.

CONCLUSIONS AND IMPLICATIONS

The results indicate an age-dependent up-regulation of COX-2 coupled to an enhanced formation of vasoconstrictor prostanoids in resistance arteries from O-DR. This effect plays a key role in the pathogenesis of endothelial dysfunction, which in turn could contribute to the progression of vascular dysfunction in these rats.

Increased cyclooxygenase-2-derived prostanoids contributes to the hyperreactivity to noradrenaline in mesenteric resistance arteries from offspring of diabetic rats

This study analyzed the effect of in utero exposure to maternal diabetes on contraction to noradrenaline in mesenteric resistance arteries (MRA) from adult offspring, focusing on the role of cyclooxygenase (COX)-derived prostanoids. Diabetes in the maternal rat was induced by a single injection of streptozotocin (50 mg/kg body weight) on day 7 of pregnancy. Contraction to noradrenaline was analyzed in isolated MRA from offspring of diabetic (O-DR) and non-diabetic (O-CR) rats at 3, 6 and 12 months of age. Release of thromboxane A₂ (TxA₂) and prostaglandins E₂ (PGE₂) and F_2α (PGF_2α), was measured by specific enzyme immunoassay kits. O-DR developed hypertension from 6 months of age compared with O-CR. Arteries from O-DR were hyperactive to noradrenaline only at 6 and 12 months of age. Endothelial removal abolished this hyperreactivity to noradrenaline between O-CR and O-DR. Preincubation with either the COX-1/2 (indomethacin) or COX-2 inhibitor (NS-398) decreased noradrenaline contraction only in 6- and 12-month-old O-DR, while it remained unmodified by COX-1 inhibitor SC-560. In vessels from 6-month-old O-DR, a similar reduction in the contraction to noradrenaline produced by NS-398 was observed when TP and EP receptors were blocked (SQ29548+AH6809). In 12-month-old O-DR, this effect was only achieved when TP, EP and FP were blocked (SQ29548+AH6809+AL8810). Noradrenaline-stimulated TxB₂ and PGE₂ release was higher in 6- and 12-month-old O-DR, whereas PGF_2α was increased only in 12-month-old O-DR. Our results demonstrated that in utero exposure to maternal hyperglycaemia in rats increases the participation of COX-2-derived prostanoids on contraction to noradrenaline, which might help to explain the greater response to this agonist in MRA from 6- and 12-month-old offspring. As increased contractile response in resistance vessels may contribute to hypertension, our results suggest a role for these COX-2-derived prostanoids in elevating vascular resistance and blood pressure in offspring of diabetic rats.

Sex-specific programming of hypertension in offspring of late-gestation diabetic rats

BACKGROUND

The intrauterine environment strongly influences adult disease susceptibility. We used a rat model of third-trimester maternal diabetes to test the hypothesis that adult offspring exposed to hyperglycemia in utero display increased blood pressure and alterations in vascular responsiveness.

METHODS

Diabetes was induced by streptozotocin injection to pregnant rats on gestation day 13 (term 21 d) and partially controlled with insulin injections. Hemodynamic function was evaluated in 6-12-mo-old offspring.

RESULTS

Male but not female offspring of diabetic mothers (ODM) had significantly increased blood pressure as compared with controls; heart rate (HR) was similar. For both sexes, HR baroreflex responses were similar as were in vivo hemodynamic responses to angiotensin II, nitric oxide synthase inhibition, and ganglionic blockade. Aortic contractility to angiotensin II was similar in the two groups. Nitric oxide synthase inhibition and the Cu/Zn superoxide dismutase inhibitor diethyldithiocarbamate, but not the superoxide dismutase-mimetic Tempol, significantly increased contractile responses to angiotensin II in controls but not ODM. Reduced nicotinamide adenine dinucleotide phosphate-stimulated superoxide production was greater in male ODM than in controls (P < 0.05).

CONCLUSION

Exposure to hyperglycemia in utero results in sex-specific cardiovascular changes in adult offspring. Impaired nitric oxide-reactive oxygen species signaling may play a significant role in the hemodynamic phenotype of ODM.

Sex dimorphism in the relation between early adiposity and cardiometabolic risk in adolescents

CONTEXT

Birth weight and childhood adiposity are associated with subsequent cardiovascular risk.

OBJECTIVE

We investigated the associations between metabolic clusters in young adults with body fat distribution from early childhood, focusing on sex differences.

DESIGN, SETTING, AND PATIENTS

A total of 1053 17 yr olds from an Australian birth cohort had measures of anthropometry, blood pressure, and fasting insulin, glucose, and lipids.

MAIN OUTCOME MEASURES

Two-step cluster analysis identified 17 yr olds at high metabolic risk. The two risk groups were compared by sex with regard to birth weight and serial anthropometry, including skinfold thickness from nine time-points.

RESULTS

The "high-risk" metabolic cluster at age 17 yr included 16% of males and 19% of females. Compared to the "low-risk" group, the high-risk cluster participants had greater waist circumference, triglycerides, insulin, and systolic blood pressure and lower high-density lipoprotein-cholesterol (all P <0.0001). There was a significant birth weight by sex interaction upon the metabolic cluster outcome (P = 0.011). Compared to their low-risk counterparts, females in the high-risk cluster at 17 yr were heavier from birth (odds ratio, 1.8; 95% confidence interval, 1.0, 3.2) (P = 0.034), with consistently higher body mass index and skinfold thickness thereafter. In contrast, there was no statistical difference in birth weight between high- and low-risk males (odds ratio, 0.62; 95% confidence interval, 0.38, 1.02).

CONCLUSIONS

These data show sexual dimorphism in effects of early life body mass index and fat distribution upon cardiometabolic risk factors. Females in a contemporary population are particularly prone to increased risk when born heavier. This has implications for targeted prevention of obesity and metabolic diseases with increasing maternal obesity and gestational diabetes.

Severe maternal hyperglycemia exacerbates the development of insulin resistance and fatty liver in the offspring on high fat diet

BACKGROUND

Adverse maternal environments may predispose the offspring to metabolic syndrome in adulthoods, but the underlying mechanism has not been fully understood.

METHODS

Maternal hyperglycemia was induced by streptozotocin (STZ) injection while control (CON) rats received citrate buffer. Litters were adjusted to eight pups per dam and then weaned to standard diet. Since 13 weeks old, a subset of offspring from STZ and CON dams were switched to high fat diet (HFD) for another 13 weeks. Glucose and insulin tolerance tests (GTT and ITT) and insulin secretion assay were performed; serum levels of lipids and leptin were measured. Hepatic fat accumulation and islet area were evaluated through haematoxylin and eosin staining.

RESULTS

STZ offspring exhibited lower survival rate, lower birth weights, and growth inhibition which persisted throughout the study. STZ offspring on HFD showed more severe impairment in GTT and ITT, and more profound hepatic steatosis and more severe hyperlipidemia compared with CON-HFD rats.

CONCLUSIONS

Offspring from diabetic dams would be prone to exhibit low birth weight and postnatal growth inhibition, but could maintain normal glucose tolerance and insulin sensitivity. HFD accelerates development of insulin resistance in the offspring of diabetic dams mainly via a compensatory response of islets.

Maternal Hyperglycemia Disrupts Histone 3 Lysine 36 Trimethylation of the IGF-1 Gene

In utero environmental adaptation may predispose to lifelong morbidity. Organisms fine-tune gene expression to achieve environmental adaptation by epigenetic alterations of histone markers of gene accessibility. One example of epigenetics is how uteroplacental insufficiency-induced intrauterine growth restriction (IUGR), which predisposes to adult onset insulin resistance, decreases postnatal IGF-1 mRNA variants and the gene elongation mark histone 3 trimethylation of lysine 36 of the IGF-1 gene (H3Me3K36). Limitations in the study of epigenetics exist due to lack of a primary transgenic epigenetic model. Therefore we examined the epigenetic profile of insulin-like growth factor 1 (IGF-1) in a well-characterized rat model of maternal hyperglycemia to determine if the epigenetic profile of IGF-1 is conserved in disparate models of in utero adaptation. We hypothesized that maternal hyperglycemia would increase IGF-1 mRNA variants and H3Me3K36. However maternal hyperglycemia decreased hepatic IGF-1 mRNA variants and H3Me3K36. This finding is intriguing given that despite different prenatal insults and growth, both maternal hyperglycemia and IUGR predispose to adult onset insulin resistance. We speculate that H3Me3K36 of the IGF-1 gene is sensitive to the glucose level of the prenatal environment, with resultant alteration of IGF-1 mRNA expression and ultimately vulnerability to adult onset insulin resistance.

Chronic pulsatile hyperglycemia reduces insulin secretion and increases accumulation of reactive oxygen species in fetal sheep islets

Children from diabetic pregnancies have a greater incidence of type 2 diabetes. Our objective was to determine if exposure to mild-moderate hyperglycemia, by modeling managed diabetic pregnancies, affects fetal β-cell function. In sheep fetuses, β-cell responsiveness was examined after 2 weeks of sustained hyperglycemia with 3 pulses/day, mimicking postprandial excursions, and compared to saline-infused controls (n = 10). Two pulsatile hyperglycemia (PHG) treatments were studied: mild (mPHG, n = 5) with +15% sustained and +55% pulse; and moderate (PHG, n = 10) with +20% sustained and +100% pulse. Fetal glucose-stimulated insulin secretion and glucose-potentiated arginine insulin secretion were lower (P < 0.05) in PHG (0.86 ± 0.13 and 2.91 ± 0.39  ng/ml plasma insulin) but not in mPHG fetuses (1.21 ± 0.08 and 4.25 ± 0.56  ng/ml) compared to controls (1.58 ± 0.25 and 4.51 ± 0.56  ng/ml). Islet insulin content was 35% lower in PHG and 35% higher in mPHG vs controls (P < 0.01). Insulin secretion and maximally stimulated insulin release were also reduced (P < 0.05) in PHG islets due to lower islet insulin content. Isolated PHG islets also had 63% greater (P < 0.01) reactive oxygen species (ROS) accumulation at 11.1  mmol/l glucose than controls (P < 0.01), but oxidative damage was not detected in islet proteins. PHG fetuses showed evidence of oxidative damage to skeletal muscle proteins (P < 0.05) but not insulin resistance. Our findings show that PHG induced dysregulation of islet ROS handling and decreased islet insulin content, but these outcomes are independent. The β-cell outcomes were dependent on the severity of hyperglycemia because mPHG fetuses had no distinguishable impairments in ROS handling or insulin secretion but greater insulin content.

Programming of adult cardiovascular disease following exposure to late-gestation hyperglycemia

BACKGROUND

In utero exposure to hyperglycemia is becoming increasingly prevalent as the number of women entering pregnancy with type II diabetes, or developing gestational diabetes, increases. Both animal studies and epidemiologic investigations have found cardiovascular abnormalities in adult offspring of hyperglycemic mothers (OHM).

OBJECTIVE

We hypothesized that adult OHM would have abnormal cardiac function in vivo and increased susceptibility to ischemia.

METHODS

Pregnant rats were made diabetic on day 12 of gestation. Serum glucose was monitored twice daily and insulin provided to maintain serum glucose at 200-400 mg/dl. Offspring were fostered to normal mothers after birth. Adult OHM were studied at 8-10 months of age with echocardiography to assess in vivo cardiac function and isolated hearts to determine the response to ischemia.

RESULTS

Echocardiography found significant diastolic dysfunction in male OHM compared to male controls. In isolated hearts, baseline cardiac function and left ventricular compliance was significantly diminished in male OHM compared to controls. Ischemia caused a significant decline in heart function in controls and female OHM, while function in male OHM remained unchanged.

CONCLUSIONS

Adult male OHM demonstrate programmed cardiac dysfunction. Given the growing number of pregnancies complicated by hyperglycemia, additional assessment of cardiac function of adults born to diabetic mothers may be warranted.

Maternal malnutrition programs pancreatic islet mitochondrial dysfunction in the adult offspring

Accumulating evidence has shown that maternal malnutrition increases the risk of metabolic disease in the progeny. We previously reported that prenatal exposure to a low-protein diet (LP) leads to mitochondrial dysfunction in pancreatic islets from adult rodent offspring that could relate physiological and cellular alterations due to early diet. We aim to determine whether mitochondrial dysfunction could be a common consequence of prenatal nutritional unbalances. Pregnant Wistar rats received either a global food restriction (GFR), consisting in the reduction by 50% of the normal daily food intake, or a high-fat diet (HF) throughout gestation. GFR or HF diet during pregnancy leads to a lack of increase in insulin release and ATP content in response to glucose stimulation in islets from 3-month-old male and female offspring. These similar consequences originated from impairment in either glucose sensing or glucose metabolism, depending on the type of early malnutrition and on the sex of the progeny. Indeed, the glucose transport across β-cell membrane seemed compromised in female HF offspring, since GLUT-2 gene was markedly underexpressed. Additionally, for each progeny, consequences downstream the entry of glucose were also apparent. Expression of genes involved in glycolysis, TCA cycle and oxidative phosphorylations was altered in GFR and HF rats in a sex- and diet-dependent manner. Moreover, prenatal malnutrition affected the regulators of mitochondrial biogenesis, namely, PPAR coactivator 1 alpha (PGC-1α), since its expression was higher in islets from GFR rats. In conclusion, programming of mitochondrial dysfunction is a consequence of maternal malnutrition, which may predispose to glucose intolerance in the adult offspring.

Animal models in diabetes and pregnancy

The worldwide increase in the incidence of diabetes, the increase in type 2 diabetes in women at reproductive ages, and the cross-generation of the intrauterine programming of type 2 diabetes are the bases for the growing interest in the use of experimental diabetic models in order to gain insight into the mechanisms of induction of developmental alterations in maternal diabetes. In this scenario, experimental models that present the most common features of diabetes in pregnancy are highly required. Several important aspects of human diabetic pregnancies such as the increased rates of spontaneous abortions, malformations, fetoplacental impairments, and offspring diseases in later life can be approached by using the appropriate animal models. The purpose of this review is to give a practical and critical guide into the most frequently used experimental models in diabetes and pregnancy, discuss their advantages and limitations, and describe the aspects of diabetes and pregnancy for which these models are thought to be adequate. This review provides a comprehensive view and an extensive analysis of the different models and phenotypes addressed in diabetic animals throughout pregnancy. The review includes an analysis of the surgical, chemical-induced, and genetic experimental models of diabetes and an evaluation of their use to analyze early pregnancy defects, induction of congenital malformations, placental and fetal alterations, and the intrauterine programming of metabolic diseases in the offspring's later life.

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.

Maternal low-protein diet alters pancreatic islet mitochondrial function in a sex-specific manner in the adult rat

Mitochondrial dysfunction may be a long-term consequence of a poor nutritional environment during early life. Our aim was to investigate whether a maternal low-protein (LP) diet may program mitochondrial dysfunction in islets of adult progeny before glucose intolerance ensues. To address this, pregnant Wistar rats were fed isocaloric diets containing either 20% protein (control) or 8% protein (LP diet) throughout gestation. From birth, offspring received the control diet. The mitochondrial function was analyzed in islets of 3-mo-old offspring. Related to their basal insulin release, cultured islets from both male and female LP offspring presented a lower response to glucose challenge and a blunted ATP production compared with control offspring. The expression of malate dehydrogenase as well as the subunit 6 of the ATP synthase encoded by mitochondrial genome (mtDNA) was lower in these islets, reducing the capacity of ATP production through the Krebs cycle and oxidative phosphorylation. However, mtDNA content was unchanged in LP islets compared with control. Several consequences of protein restriction during fetal life were more marked in male offspring. Only LP males showed an increased reactive oxygen species production associated with a higher expression of mitochondrial subunits of the electron transport chain NADH-ubiquinone oxireductase subunit 4L, an overexpression of peroxisome proliferator-activated receptor-gamma and uncoupling protein-2, and a strongly reduced beta-cell mass. In conclusion, mitochondrial function is clearly altered in islets from LP adult offspring in a sex-specific manner. That may provide a cellular explanation for the earlier development of glucose intolerance in male than in female offspring of dams fed an LP diet.