Transient catabolic state with reduced IGF-I after antenatal glucocorticoids

Alterations of materno-placento-fetal glucose homeostasis after a single course of antenatal betamethasone

INTRODUCTION

Intrauterine growth impairment is associated with long-term metabolic changes (perinatal programming). We recently demonstrated that antenatal betamethasone (BET) decreased head circumference in term born females. Since glucose is the main energy source for fetal growth, BET-induced changes in maternal glucose homeostasis, a reduced transplacental glucose transfer or an altered fetal glucose utilization may be linked with the observed growth impairment.

METHODS

86 pregnant women exposed to BET (single course, <34 + 0 weeks of gestation (wks)) were compared to 92 gestational-age/sex-matched controls. Glucose, insulin, leptin, insulin-like growth factors (IGF-1, IGF-2) and their binding proteins (IGFBP-1, IGFBP-3) were measured in maternal and umbilical cord blood samples. Homeostasis Model Assessment (HOMA-IR) was calculated. Placental glucose transporter 1 and 3 (GLUT1, GLUT3) protein levels were determined. Statistics were performed for overall and subgroup analysis (gestational age, sex).

RESULTS

After BET maternal HOMA-IR was elevated, IGFBP-1 reduced. In female pregnancies, glucose levels ≥37 + 0 wks and IGF-1 levels <37 + 0 wks were tendentially increased. Placental GLUT1 and GLUT3 protein levels were not significantly altered. Fetal umbilical venous glucose levels ≥37 + 0 wks were increased. HOMA-IR tended to be elevated in females.

DISCUSSION

Growth impairment after BET appears neither caused by maternal nor fetal hypoglycemia nor changes of GLUT1 and GLUT3 total protein levels. Nonetheless, glucose homeostasis of mothers and daughters was altered even beyond the BET time frame (hyperglycemia, enhanced insulin resistance). Despite glucose supply was sufficient, an anabolic effect was apparently absent. Overall, our results highlight the relevance of adequate glucose management after BET and peripartum.

Low-dose antenatal betamethasone treatment achieves preterm lung maturation equivalent to that of the World Health Organization dexamethasone regimen but with reduced endocrine disruption in a sheep model of pregnancy

BACKGROUND

The intramuscular administration of antenatal steroids to women at risk of preterm delivery achieves high maternal and fetal plasma steroid concentrations, which are associated with adverse effects and may reduce treatment efficacy. We have demonstrated that antenatal steroid efficacy is independent of peak maternofetal steroid levels once exposure is maintained above a low threshold.

OBJECTIVE

This study aimed to test, using a sheep model of pregnancy, whether the low-dose antenatal steroid regimen proposed as part of the Antenatal Corticosteroids for Improving Outcomes in Preterm Newborns trial would achieve preterm lung maturation equivalent to that of the existing World Health Organization dexamethasone treatment regimen, but with reduced risk of adverse outcomes.

STUDY DESIGN

Following ethical review and approval, date-mated ewes with single fetuses received intramuscular injections of either (1) four 6-mg maternal intramuscular injections of dexamethasone phosphate every 12 hours (n=22), (2) 4 2-mg maternal intramuscular injections of betamethasone phosphate every 12 hours (n=21), or (3) 4 2-mL maternal intramuscular injections of saline every 12 hours (n=16). Of note, 48 hours after first injection, (124±1 day), lambs were delivered, ventilated for 30 minutes, and euthanized for sampling. Arterial blood gas, respiratory, hematological, and biochemical data were analyzed for between-group differences with analysis of variance according to distribution and variance, with P<.05 taken as significant.

RESULTS

After 30 minutes of ventilation, lambs from both steroid-treated groups had significant and equivalent improvements in lung function relative to saline control (P<.05). There was no significant difference in arterial blood pH, pO₂, pCO₂, lung compliance, ventilator efficiency index, or lung volume at necropsy with a static pressure of 40 cmH₂O. The messenger RNA expression of surfactant protein (Sp)a, Spb, Spc, Spd, aquaporin (Aqp)1, Aqp5, and sodium channel epithelial 1 subunit beta (Scnn1b) was equivalent between both steroid groups. Maternal and fetal plasma neutrophil, glucose, and fetal plasma C-peptide levels were significantly elevated in the dexamethasone group, relative to the betamethasone group. Fetal plasma insulin-like growth factor 1 was significantly reduced in the dexamethasone group compared with the betamethasone group (P<0.05). Fetal adrenocorticotropic hormone (r=0.53), maternal glucose value (r=-0.52), and fetal glucose values (r=-0.42) were correlated with maternal weight in the betamethasone group (P<.05), whereas fetal pCO₂ and pO₂ were not correlated. There was no significant difference between male and female lamb outcomes in any groups for any of the items evaluated.

CONCLUSION

This study reported that in preterm lambs, a low-dose treatment regimen of 8 mg betamethasone achieves lung maturation equivalent to that of a 24-mg dexamethasone-based regimen, but with smaller perturbations to the maternofetal hypothalamic-pituitary-adrenal axis. These data suggested that given steroid pharmacokinetic differences between sheep and humans, a betamethasone dose of 2 mg may remain above the minimum dose necessary for robust maturation of the preterm lung. Maternal weight-adjusted betamethasone doses might also be a key to reducing perturbations to the maternofetal hypothalamic-pituitary-adrenal axis.

Metabolic and hormonal effects of antenatal betamethasone after 35 weeks of gestation

BACKGROUND

Antenatal corticosteroid therapy recently has been considered for term and near-term infants, in addition to preterm infants, delivered by elective cesarean section, with the aim of preventing an adverse respiratory outcome.

OBJECTIVES

The objective of this study was to investigate hormonal and metabolic effects of antenatal betamethasone when administered to term fetuses.

METHODS

Cord blood levels of cortisol, C-peptide, insulin-like growth factor I and its binding protein 3, and 5 more analytes including glucose were measured in singleton newborns of over 35 weeks of gestational age. In anticipation of a cesarean delivery, the mother was either treated or not treated with 12 mg of intramuscularly administered antenatal betamethasone approximately 24 hours prior to birth. Babies of comparable gestational age, sex, and nutritional status who were not treated antenatally served as controls.

RESULTS

Cord serum cortisol levels of the betamethasone-treated fetuses were suppressed to <10% of that of untreated controls (median levels of 11.6 nmol/L vs. 138.2 nmol/L, respectively), and their C-peptide and glucose levels were significantly higher (2.85 mcg/L vs. 1.19 mcg/L, respectively, p < 0.0001; and 62.5 mg/dL vs. 56.0 mg/dL, respectively, p = 0.01).

CONCLUSIONS

Prophylactic betamethasone therapy causes immediate hormonal alterations, which might interfere with the metabolic adaptation of the newborn. This issue deserves thorough investigation.

Antenatal glucocorticoids: where are we after forty years?

Since their introduction more than forty years ago, antenatal glucocorticoids have become a cornerstone in the management of preterm birth and have been responsible for substantial reductions in neonatal mortality and morbidity. Clinical trials conducted over the past decade have shown that these benefits may be increased further through administration of repeat doses of antenatal glucocorticoids in women at ongoing risk of preterm and in those undergoing elective cesarean at term. At the same time, a growing body of experimental animal evidence and observational data in humans has linked fetal overexposure to maternal glucocorticoids with increased risk of cardiovascular, metabolic and other disorders in later life. Despite these concerns, and somewhat surprisingly, there has been little evidence to date from randomized trials of longer-term harm from clinical doses of synthetic glucocorticoids. However, with wider clinical application of antenatal glucocorticoid therapy there has been greater need to consider the potential for later adverse effects. This paper reviews current evidence for the short- and long-term health effects of antenatal glucocorticoids and discusses the apparent discrepancy between data from randomized clinical trials and other studies.

Neonatal glucocorticoid treatment increased depression-like behaviour in adult rats

Synthetic glucocorticoid dexamethasone (DEX) is frequently used as a therapeutic agent to lessen the morbidity of chronic lung disease in premature infants. Previous studies suggested that neonatal DEX treatment altered brain development and cognitive function. It has been recognized that the amygdala is involved in emotional processes and also a critical site of neuronal plasticity for fear conditioning. Little is known about the possible long-term adverse effect of neonatal DEX treatment on amygdala function. The present study was aimed to evaluate the possible effect of neonatal DEX treatment on the synaptic function of amygdala in adult rats. Newborn Wistar rats were subjected to subcutaneous tapering-dose injections of DEX (0.5, 0.3 and 0.1 mg/kg) from post-natal day one to three, PN1-PN3. Animals were then subjected to a forced swimming test (FST) and electrophysiological recording aged eight weeks. The results of the FST showed neonatal DEX treatment increased depression-like behaviour in adulthood. After acute stress evoking, the percentage of time spent free floating is significantly increased in the DEX treated group compared with the control animals. Furthermore, neonatal DEX treatment elevated long-term potentiation (LTP) response and the phosphorylation level of MAPK in the lateral nucleus of amygdala (LA). Intracerebroventricular infusion of the MAPK inhibitor, PD98059, showed significant rescue effects including reduced depression-like behaviour and restoration of LTP to within normal range. In conclusion, our results suggested that MAPK signalling cascade in the LA plays an important role in the adverse effect of neonatal DEX treatment on amygdala function, which may result in adverse consequences in adult age, such as the enhancement of susceptibility for a depressive disorder in later life.

Prenatal betamethasone does not affect glutamatergic or GABAergic neurogenesis in preterm newborns

Prenatal glucocorticoids (GCs) are routinely used for pregnant women in preterm labor to prevent respiratory distress syndrome and intraventricular hemorrhage in premature infants. However, the effect of antenatal GCs on neurogenesis in preterm neonates remains elusive. Herein, we hypothesized that prenatal GCs might suppress both glutamatergic and GABAergic neurogenesis in preterm rabbits and that this treatment would induce distinct changes in the expression of transcription factors regulating these developmental events. To test our hypotheses, we treated pregnant rabbits with betamethasone at E27 and E28, delivered the pups at E29 (term=32d), and assessed neurogenesis at birth and postnatal day 3. We quantified radial glia (Sox2(+)) and intermediate progenitor cells (Tbr2(+)) in the dorsal cortical subventricular zone to assess glutamatergic neuronal progenitors, and counted Nkx2.1(+) and Dlx2(+) cells in the ganglionic eminence to evaluate GABAergic neurogenesis. In addition, we assayed transcription factors regulating neurogenesis. We found that prenatal GCs did not affect the densities of radial glia and intermediate progenitors of glutamatergic or GABAergic neurons. The number of GABA(+) interneurons in the ganglionic eminence was similar between the prenatal GC-treated pups compared to untreated controls. Moreover, the mRNA expression of transcription factors, including Pax6, Ngn1/2, Emx1/2, Insm1, Dlx1, Nkx2.1, and Gsh2, were comparable between the two groups. However, there was a transient elevation in Mash1 protein in betamethasone-treated pups relative to controls at birth. These data suggest that prenatal GC treatment does not significantly impact the balance of glutamatergic and GABAergic neurogenesis in premature infants.

Antenatal glucocorticoids reduce growth in appropriately grown and growth-restricted ovine fetuses in a sex-specific manner

Antenatal glucocorticoids are administered to mature the fetal lungs before preterm birth. Glucocorticoids also have non-pulmonary effects, including reducing fetal body and brain growth. The present study examined whether glucocorticoid administration has a sex-specific effect on growth in appropriately grown (control) and intrauterine growth-restricted (IUGR) fetal sheep. IUGR was induced at 0.7 gestation in fetal sheep by single umbilical artery ligation. On Days 5 and 6 after surgery, IUGR or control fetuses were exposed to the synthetic glucocorticoid betamethasone (BM; 11.4mg) or saline via intramuscular maternal administration. On Day 7, a postmortem was conducted to determine fetal sex and weight. Compared with control fetuses, the birthweight of male and female IUGR fetuses was significantly reduced (by 18.5±4.4% (P=0.002) and 21.7±6.0% (P=0.001), respectively). Maternal administration of BM significantly reduced bodyweight in both control and IUGR fetuses (by 11.3±2.8% and 20.5±3.6% in control male and female fetuses, respectively; and by 22.9±3.1% and 38.3±3.4% in IUGR male and female fetuses, respectively; P<0.001 for all, versus control+saline) fetuses. In control and IUGR animals the degree of growth restriction was greater in females than males (P<0.05) following administration of BM. These data suggest that antenatal glucocorticoids reduce fetal growth in a sex-specific manner, with females more growth restricted than males.

Effect of antenatal betamethasone on maternal and fetal amino acid concentration

OBJECTIVE

To determine the concentration of amino acids in women receiving the first course of antenatal betamethasone and to evaluate the umbilical venous and arterial amino acid concentrations at the time of elective cesarean section after betamethasone administration.

STUDY DESIGN

Blood samples were collected from 34 pregnant women at risk of premature delivery before and 24 and 48 hours after the first course of betamethasone. In addition, maternal and cord blood samples were collected in 13 women undergoing an elective cesarean section between 24 and 192 hours after betamethasone.

RESULTS

Maternal amino acid concentrations were significantly increased after the first dose of betamethasone. Overall total amino nitrogen increased 17.5% 24 hours after betamethasone administration and 20.5% after 48 hours. The concentration of most amino acids was increased both in the umbilical vein and artery after maternal betamethasone administration.

CONCLUSION

The concentration of maternal and fetal amino acids increases significantly after betamethasone administration.

Oxidative stress after antenatal betamethasone: acute downregulation of glutathione peroxidase-3

BACKGROUND

Human and experimental data show that antenatal exposure to glucocorticoids (GC) temporarily reduces fetal well-being and impairs the fetal response to hypoxemia.

AIMS

We tested the hypothesis that antenatal betamethasone provokes transient oxidative stress, which may be triggered directly by the GC or indirectly by metabolic signals such as increased glucose and free fatty acid (FFA) concentrations.

STUDY DESIGN

Prospective (single center, 18 months) cohort study in newborns <34 weeks gestational age at birth.

METHODS

We studied 105 newborns and measured oxidative damage to lipids [malondialdehyde (MDA)] and proteins (protein carbonyls), as well as glutathione peroxidase-3 (GPx3), an important antioxidant enzyme, in umbilical vein (UV) plasma. In addition, we measured umbilical artery and UV blood gases, and metabolic indices (plasma glucose, FFA and insulin) in UV.

RESULTS

MDA but not protein carbonyl concentrations was inversely related to time elapsed since the first or last betamethasone administration (p=0.006); MDA remained elevated by 69-96% for at least 72 h after the last betamethasone. By contrast, GPx3 concentrations were repressed in newborns who received betamethasone < or =24h before birth. GPx3 and MDA concentrations were correlated (r=-0.38, p<0.001). Labor, GA, sex, size at birth, blood gases or metabolic indices did not explain the effects of betamethasone on MDA and GPx3.

CONCLUSIONS

Antenatal GC elicit a rapid suppression of the GPx3 antioxidant defense system which may contribute to a longer-lasting but also transient rise in lipid oxidative damage.

Should we be prescribing repeated courses of antenatal corticosteroids?

Single-course treatment with antenatal corticosteroids has been shown to enhance fetal maturation before preterm birth and to improve outcomes for the preterm infant. Based on this success, practitioners expanded use of the treatment to repeated courses of antenatal corticosteroids ahead of evidence demonstrating benefit and excluding harm. Experiments with animals and cohort studies have provided a body of evidence suggesting that repeated doses may further improve lung maturation but may be accompanied by deleterious effects on the developing brain and other organs. Randomised controlled trials of repeated treatments to date have provided mixed evidence but in general may indicate a small benefit in terms of postnatal lung function, but this is accompanied by restricted growth which may include the brain. In view of the well-established role that corticosteroids are known to play in brain development, and the marginal difference that repeated courses may make to outcome in the context of modern neonatal care, antenatal corticosteroid treatments should be restricted to single-course treatment.