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Glucocorticoid Receptor Gene Variants and Neonatal Outcome in Very-Low-Birth-Weight Preterm Infants
(2016)
Background: Induction of lung maturation by prenatal steroid treatment has become the standard of care for pregnant women at risk for preterm birth. In addition to the beneficial effects on lung maturation, prenatal steroids have been shown to reduce the incidence of neonatal death, necrotizing enterocolitis, sepsis, and intraventricular hemorrhage. However, little is known about the role of interindividual differences in corticoid sensitivity arising from polymorphisms in the glucocorticoid receptor (GR) gene. Objectives: To assess the impact of GR polymorphisms N363S (rs56149945), R23K (rs6190), and BclI (rs41423247) on neonatal outcome. Methods: The GR polymorphisms N363S, R23K, and BclI were examined in 10,490 very-low-birth-weight (VLBW) preterm infants from 49 German tertiary level neonatal units (German Neonatal Network, GNN) with respect to neonatal outcome. Results: Infants carrying the BclI genotype were at higher risk to develop bronchopulmonary dysplasia (BPD) (OR 1.12 per BclI allele, 95% CI: 1.02-1.23, p = 0.013) in a logistic regression model adjusted for gestational age, mechanical ventilation, and small for gestational age status. A similar relative risk was seen in the children (89.4%) who received antenatal betamethasone treatment (OR 1.16, 95% CI: 1.05-1.27, p = 0.003), whereas no such effect was detectable in infants without antenatal steroids. N363S and R23K did not show any stable association with neonatal outcome parameters. Conclusion: Except for a slightly higher risk of BPD in carriers of the GRBclI variant, the GR gene polymorphisms BclI, N363S, and R23K did not affect neonatal outcome parameters in this large multicenter cohort of VLBW preterm infants.
Background: Levels or fluctuations in the partial pressure of CO<sub>2</sub> (PCO<sub>2</sub>) may affect outcomes for extremely low birth weight infants. Objectives: In an exploratory analysis of a randomized trial, we hypothesized that the PCO<sub>2</sub> values achieved could be related to significant outcomes. Methods: On each treatment day, infants were divided into 4 groups: relative hypocapnia, normocapnia, hypercapnia, or fluctuating PCO<sub>2</sub>. Ultimate assignment to a group for the purpose of this analysis was made according to the group in which an infant spent the most days. Statistical analyses were performed with analysis of variance (ANOVA), the Kruskal-Wallis test, the χ<sup>2</sup> test, and the Fisher exact test as well as by multiple logistic regression. Results: Of the 359 infants, 57 were classified as hypocapnic, 230 as normocapnic, 70 as hypercapnic, and 2 as fluctuating PCO<sub>2</sub>. Hypercapnic infants had a higher average product of mean airway pressure and fraction of inspired oxygen (MAP × FiO<sub>2</sub>). For this group, mortality was higher, as was the likelihood of having moderate/severe bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), and poorer neurodevelopment. Multiple logistic regression analyses showed an increased risk for BPD or death associated with birth weight (p < 0.001) and MAP × FiO<sub>2</sub> (p < 0.01). The incidence of adverse neurodevelopment was associated with birth weight (p < 0.001) and intraventricular hemorrhage (IVH; p < 0.01). Conclusions: Birth weight and respiratory morbidity, as measured by MAP × FiO<sub>2</sub>, were the most predictive of death or BPD and NEC, whereas poor neurodevelopmental outcome was associated with low birth weight and IVH. Univariate models also identified PCO<sub>2</sub>. Thus, hypercapnia seems to reflect greater disease severity, a likely contributor to differences in outcomes.
Objective
Congenital hyperinsulinism (CHI) is a rare disease characterized by persistent hypoglycemia as a result of inappropriate insulin secretion, which can lead to irreversible neurological defects in infants. Poor efficacy and strong adverse effects of the current medications impede successful treatment. The aim of the study was to investigate new approaches to silence β-cells and thus attenuate insulin secretion.
Research Design and Methods
In the scope of our research, we tested substances more selective and more potent than the gold standard diazoxide that also interact with neuroendocrine ATP-sensitive K+ (KATP) channels. Additionally, KATP channel-independent targets as Ca2+-activated K+ channels of intermediate conductance (KCa3.1) and L-type Ca2+ channels were investigated. Experiments were performed using human islet cell clusters isolated from tissue of CHI patients (histologically classified as pathological) and islet cell clusters obtained from C57BL/6N (WT) or SUR1 knockout (SUR1-/-) mice. The cytosolic Ca2+ concentration ([Ca2+]c) was used as a parameter for the pathway regulated by electrical activity and was determined by fura-2 fluorescence. The mitochondrial membrane potential (ΔΨ) was determined by rhodamine 123 fluorescence and single channel currents were measured by the patch-clamp technique.
Results
The selective KATP channel opener NN414 (5 µM) diminished [Ca2+]c in isolated human CHI islet cell clusters and WT mouse islet cell clusters stimulated with 10 mM glucose. In islet cell clusters lacking functional KATP channels (SUR1-/-) the drug was without effect. VU0071063 (30 µM), another KATP channel opener considered to be selective, lowered [Ca2+]c in human CHI islet cell clusters. The compound was also effective in islet cell clusters from SUR1-/- mice, showing that [Ca2+]c is influenced by additional effects besides KATP channels. Contrasting to NN414, the drug depolarized ΔΨ in murine islet cell clusters pointing to severe interference with mitochondrial metabolism. An opener of KCa3.1 channels, DCEBIO (100 µM), significantly decreased [Ca2+]c in SUR1-/- and human CHI islet cell clusters. To target L-type Ca2+ channels we tested two already approved drugs, dextromethorphan (DXM) and simvastatin. DXM (100 µM) efficiently diminished [Ca2+]c in stimulated human CHI islet cell clusters as well as in stimulated SUR1-/- islet cell clusters. Similar effects on [Ca2+]c were observed in experiments with simvastatin (7.2 µM).
Conclusions
NN414 seems to provide a good alternative to the currently used KATP channel opener diazoxide. Targeting KCa3.1 channels by channel openers or L-type Ca2+ channels by DXM or simvastatin might be valuable approaches for treatment of CHI caused by mutations of KATP channels not sensitive to KATP channel openers.
For surgery in congenital hyperinsulinism (CHI), a distinct surgical strategy and technique is required for focal, diffuse and atypical CHI. In focal CHI, a confined, localized and parenchyma-sparing resection which is guided by the PET-CT is always indicated in order to cure the patient. In diffuse CHI, however, the results of surgical therapy are unpredictable and cure is an exception. Therefore, a strong tendency exists nowadays that medical therapy should be preferred in diffuse CHI. In atypical CHI the situation is more complex: if the focal lesion or the segmental mosaic are not too extensive, cure by resection should be possible. But care must be taken in atypical cases not to resect too much of the gland in order not to induce diabetes.