Developmental origins of adult disease

Executive summary of the workshop "Nutritional Challenges in the High Risk Infant"

In 2009, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) invited an expert panel to a workshop to address the current knowledge gaps and lack of evidence-based guidelines that preclude optimal nutritional care for infants in neonatal intensive care units. Since much research needs to be done in this complex area of science, the group was requested to propose new research to rectify current deficiencies in this field. This paper provides a summary of the workshop presentations and discussions.

Postnatal pancreatic islet β cell function and insulin sensitivity at different stages of lifetime in rats born with intrauterine growth retardation

Epidemiological studies have linked intrauterine growth retardation (IUGR) to the metabolic diseases, consisting of insulin resistance, type 2 diabetes, obesity and coronary artery disease, during adult life. To determine the internal relationship between IUGR and islet β cell function and insulin sensitivity, we established the IUGR model by maternal nutrition restriction during mid- to late-gestation. Glucose tolerance test and insulin tolerance test(ITT) in vivo and glucose stimulated insulin secretion(GSIS) test in vitro were performed at different stages in IUGR and normal groups. Body weight, pancreas weight and pancreas/body weight of IUGR rats were much lower than those in normal group before 3 weeks of age. While the growth of IUGR rats accelerated after 3 weeks, pancreas weight and pancreas/body weight remained lower till 15 weeks of age. In the newborns, the fasting glucose and insulin levels of IUGR rats were both lower than those of controls, whereas glucose levels at 120 and 180 min after glucose load were significantly higher in IUGR group. Between 3 and 15 weeks of age, both the fasting glucose and insulin levels were elevated and the glucose tolerance was impaired with time in IUGR rats. At age 15 weeks, the area under curve of insulin(AUCi) after glucose load in IUGR rats elevated markedly. Meanwhile, the stimulating index of islets in IUGR group during GSIS test at age 15 weeks was significantly lower than that of controls. ITT showed no significant difference in two groups before 7 weeks of age. However, in 15-week-old IUGR rats, there was a markedly blunted glycemic response to insulin load compared with normal group. These findings demonstrate that IUGR rats had both impaired pancreatic development and deteriorated glucose tolerance and insulin sensitivity, which would be the internal causes why they were prone to develop type 2 diabetes.

Estrogen receptor-β and fetoplacental endothelial prostanoid biosynthesis: a link to clinically demonstrated fetal growth restriction

CONTEXT

Fetal growth restriction (FGR) due to placental dysfunction impacts short- and long-term neonatal outcomes. Abnormal umbilical artery Doppler velocimetry indicating elevated fetoplacental vascular resistance has been associated with fetal morbidity and mortality. Estrogen receptors are regulators of vasomotor tone, and fetoplacental endothelium expresses estrogen receptor-β (ESR2) as its sole estrogen receptor.

OBJECTIVE

Our objective was to elucidate the mechanism whereby ESR2 regulates placental villous endothelial cell prostanoid biosynthesis.

DESIGN AND PARTICIPANTS

We conducted immunohistochemical analysis of human placental specimens and studies of primary fetoplacental endothelial cells isolated from subjects with uncomplicated pregnancies.

MAIN OUTCOME MEASURES

We evaluated in vivo levels of ESR2 and cyclooxygenase-2 (PTGS2) in villous endothelial cells from fetuses with or without FGR and/or abnormal umbilical artery Doppler indices and in vitro effects of ESR2 on prostanoid biosynthetic gene expression.

RESULTS

ESR2 and PTGS2 expression were significantly higher within subjects with FGR with abnormal umbilical artery Doppler indices in comparison with controls (P < 0.01). ESR2 knockdown led to decreased cyclooxygenase-1 (PTGS1), PTGS2, prostaglandin F synthase (AKR1C3), and increased prostacyclin synthase (PTGIS), with opposing results found after ESR2 overexpression (P < 0.05). ESR2 mediates prostaglandin H2 substrate availability and, in the setting of differential regulation of AKR1C3 and PTGIS, altered the balance between vasodilatory and vasoconstricting prostanoid production.

CONCLUSIONS

Higher ESR2 expression in the placental vasculature of FGR subjects with abnormal blood flow is associated with an endothelial cell phenotype that preferentially produces vasoconstrictive prostanoids. Endothelial ESR2 appears to be a master regulator of prostanoid biosynthesis and contributes to high-resistance fetoplacental blood flow, thereby increasing morbidity and mortality associated with FGR.

Type 2 diabetes across generations: from pathophysiology to prevention and management

Type 2 diabetes is now a pandemic and shows no signs of abatement. In this Seminar we review the pathophysiology of this disorder, with particular attention to epidemiology, genetics, epigenetics, and molecular cell biology. Evidence is emerging that a substantial part of diabetes susceptibility is acquired early in life, probably owing to fetal or neonatal programming via epigenetic phenomena. Maternal and early childhood health might, therefore, be crucial to the development of effective prevention strategies. Diabetes develops because of inadequate islet β-cell and adipose-tissue responses to chronic fuel excess, which results in so-called nutrient spillover, insulin resistance, and metabolic stress. The latter damages multiple organs. Insulin resistance, while forcing β cells to work harder, might also have an important defensive role against nutrient-related toxic effects in tissues such as the heart. Reversal of overnutrition, healing of the β cells, and lessening of adipose tissue defects should be treatment priorities.

mTOR phosphorylates IMP2 to promote IGF2 mRNA translation by internal ribosomal entry

Variants in the IMP2 (insulin-like growth factor 2 [IGF2] mRNA-binding protein 2) gene are implicated in susceptibility to type 2 diabetes. We describe the ability of mammalian target of rapamycin (mTOR) to regulate the cap-independent translation of IGF2 mRNA through phosphorylation of IMP2, an oncofetal RNA-binding protein. IMP2 is doubly phosphorylated in a rapamycin-inhibitable, amino acid-dependent manner in cells and by mTOR in vitro. Double phosphorylation promotes IMP2 binding to the IGF2 leader 3 mRNA 5' untranslated region, and the translational initiation of this mRNA through eIF-4E- and 5' cap-independent internal ribosomal entry. Unexpectedly, the interaction of IMP2 with mTOR complex 1 occurs through mTOR itself rather than through raptor. Whereas depletion of mTOR strongly inhibits IMP2 phosphorylation in cells, comparable depletion of raptor has no effect; moreover, the ability of mTOR to phosphorylate IMP2 in vitro is unaffected by the elimination of raptor. Dual phosphorylation of IMP2 at the mTOR sites is evident in the mouse embryo, likely coupling nutrient sufficiency to IGF2 expression and fetal growth. Doubly phosphorylated IMP2 is also widely expressed in adult tissues, including islets of Langerhans.

Maternally transmitted foetal H19 variants and associations with birth weight

This study was designed to test the hypothesis that polymorphic variation in maternally transmitted foetal H19 alleles is associated with offspring size at birth and alterations in maternal glucose concentrations in pregnancy. Inferred parent of origins of transmitted alleles from 13 haplotype tag SNPs in the H19 gene region from 845 family (mother, partner, offspring) trios from the prospective Cambridge Baby Growth Study and 315 trios from the retrospective Cambridge Wellbeing Study cohorts were tested for association with offspring size at birth measures, as well as maternal glucose concentrations 1 h after a glucose load at week 28 of pregnancy. The foetal rs2071094 allele inherited from the mother was associated with increased birth weight (p = 0.0015) adjusted for gestational age, parity and sex. In the Cambridge Baby Growth Study it was also associated with increased head circumference (p = 0.004), length (p = 0.017) and sum of skinfold thicknesses (p = 0.017) at birth. In contrast to these results there was no association between offspring birth weight and either the maternal rs2071094 genotype or the foetal allele from the father. None of the foetal alleles or maternal genotypes were associated with maternal glucose concentrations, neither were there any other associations with offspring birth weight. In conclusion, consistent with imprinting, common polymorphic variation in foetal H19 alleles transmitted only from the mother are associated with birth weight and other markers of size at birth. Polymorphic variation in H19 is not associated with significant changes in maternal glucose tolerance in the third trimester of pregnancy.

Maternal preeclampsia and neonatal outcomes

Preeclampsia is a multiorgan, heterogeneous disorder of pregnancy associated with significant maternal and neonatal morbidity and mortality. Optimal strategies in the care of the women with preeclampsia have not been fully elucidated, leaving physicians with incomplete data to guide their clinical decision making. Because preeclampsia is a progressive disorder, in some circumstances, delivery is needed to halt the progression to the benefit of the mother and fetus. However, the need for premature delivery has adverse effects on important neonatal outcomes not limited to the most premature infants. Late-preterm infants account for approximately two thirds of all preterm deliveries and are at significant risk for morbidity and mortality. Reviewed is the current literature in the diagnosis and obstetrical management of preeclampsia, the outcomes of late-preterm infants, and potential strategies to optimize fetal outcomes in pregnancies complicated by preeclampsia.

Oxidative stress in twin neonates is influenced by birth weight and weight discordance

OBJECTIVES

To evaluate the extent of oxidative stress in neonates born from multiple gestation pregnancies who are at high risk of prematurity and growth abnormalities.

DESIGN AND METHODS

Blood samples were collected from umbilical cord of 72 twins, born at gestational age of 28-38 weeks, and 20 consecutive control singletons. Oxidative stress parameters (15-F(2t)-isoprostane, a marker of lipid peroxidation, and total antioxidant capacity, tAOC), were measured in cord plasma.

RESULTS

Levels of 15-F(2t)-isoprostane showed a moderate negative correlation with birth weight and were higher in small co-twins of discordant pairs; tAOC was positively correlated with birth weight but no significant difference was found between co-twins.

CONCLUSIONS

Oxidative stress levels in twins are mainly influenced by birth weight and weight discordance. We suggest that evaluation of cord blood 15-F(2t)-isoprostane might be of clinical value as maker of pre- and perinatal distress in twinning.

Epigenetics meets endocrinology

Although genetics determines endocrine phenotypes, it cannot fully explain the great variability and reversibility of the system in response to environmental changes. Evidence now suggests that epigenetics, i.e. heritable but reversible changes in gene function without changes in nucleotide sequence, links genetics and environment in shaping endocrine function. Epigenetic mechanisms, including DNA methylation, histone modification, and microRNA, partition the genome into active and inactive domains based on endogenous and exogenous environmental changes and developmental stages, creating phenotype plasticity that can explain interindividual and population endocrine variability. We will review the current understanding of epigenetics in endocrinology, specifically, the regulation by epigenetics of the three levels of hormone action (synthesis and release, circulating and target tissue levels, and target-organ responsiveness) and the epigenetic action of endocrine disruptors. We will also discuss the impacts of hormones on epigenetics. We propose a three-dimensional model (genetics, environment, and developmental stage) to explain the phenomena related to progressive changes in endocrine functions with age, the early origin of endocrine disorders, phenotype discordance between monozygotic twins, rapid shifts in disease patterns among populations experiencing major lifestyle changes such as immigration, and the many endocrine disruptions in contemporary life. We emphasize that the key for understanding epigenetics in endocrinology is the identification, through advanced high-throughput screening technologies, of plasticity genes or loci that respond directly to a specific environmental stimulus. Investigations to determine whether epigenetic changes induced by today's lifestyles or environmental 'exposures' can be inherited and are reversible should open doors for applying epigenetics to the prevention and treatment of endocrine disorders.

Challenges and prospects for pharmacotherapy in functional gastrointestinal disorders

Functional gastrointestinal disorders, such as irritable bowel syndrome and functional dyspepsia, are complex conditions with multiple factors contributing to their pathophysiology. As a consequence they are difficult to treat and have posed significant challenges to the pharmaceutical industry when trying to develop new and effective treatments. This review provides an overview of these difficulties and how the industry is reshaping its drug developmental strategies. It describes some of the more significant and encouraging advances that have occurred, and discusses how future research might embrace the opportunities provided by advances in genetic and in particular, epigenetic research.

Polymorphisms within exon 9 but not intron 8 of the vitamin D receptor are associated with the nephropathic complication of type-2 diabetes

The impact of several environmental and genetic factors on diabetes and its complications is well documented but there is an urgent need to understand more about genetic risk factors associated with this disease. The present study was aimed at examining the two single nucleotide polymorphisms (SNP) in intron 8 and exon 9 of the vitamin D receptor (VDR) gene in nephropathic and non-nephropathic type-2 diabetic patients. In this clinical study, peripheral blood samples were obtained from 100 type-2 diabetic patients, 100 nephropathic type-2 diabetic patients and 100 healthy controls. DNA was extracted and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to examine two SNP polymorphisms within the VDR gene. Our results showed a significant difference in the Taq-1 evaluated genotypes of exon 9 in the VDR gene of diabetic individuals with (P=0.012) and without (P ≤ 0.001) nephropathy. Analysis of the Taq-1 evaluated alleles of nephropathic (P=0.917) and non-nephropathic (P=1.000) did not show a significant difference. We also evaluated the intron 8 Apa-1 alleles in patients with (P=0.480) and without nephropathy (P=0.543) and determined there were no differences between these groups. Our results also showed that the frequency of Apa-1 genotypes did not differ in nephropathic (P=0.224) and non-nephropathic (P=0.236) diabetic patients. Based on our results, it can be concluded that VDR and its functional polymorphism in exon 9 may play an important role in pathogenesis of type-2 diabetes and more investigations are required to clarify their role in nephropathy.

Epigenetic regulation of the expression of genes involved in steroid hormone biosynthesis and action

Steroid hormones participate in organ development, reproduction, body homeostasis, and stress responses. The steroid machinery is expressed in a development- and tissue-specific manner, with the expression of these factors being tightly regulated by an array of transcription factors (TFs). Epigenetics provides an additional layer of gene regulation through DNA methylation and histone tail modifications. Evidence of epigenetic regulation of key steroidogenic enzymes is increasing, though this does not seem to be a predominant regulatory pathway. Steroid hormones exert their action in target tissues through steroid nuclear receptors belonging to the NR3A and NR3C families. Nuclear receptor expression levels and post-translational modifications regulate their function and dictate their sensitivity to steroid ligands. Nuclear receptors and TFs are more likely to be epigenetically regulated than proteins involved in steroidogenesis and have secondary impact on the expression of these steroidogenic enzymes. Here we review evidence for epigenetic regulation of enzymes, transcription factors, and nuclear receptors related to steroid biogenesis and action.

Environmental exposures and development

PURPOSE OF REVIEW

Summarize recent studies exploring the relationship between paternal and maternal environmental exposures to chemicals before, at the time of and after conception to adverse developmental outcomes including preterm birth, death, structural and functional abnormalities and growth restriction.

RECENT FINDINGS

Recent studies have demonstrated that human pregnancy and development are vulnerable to environmental exposures of the father and mother to chemical, biological and physical agents. Exposures associated with adverse developmental outcomes include air and water pollution, chemicals in foods, occupational exposures, agricultural chemicals, metals, persistent and volatile organics. Developmental endpoints which are linked with these exposures include growth restriction, functional abnormalities, structural abnormalities, preterm delivery and death. Despite this general understanding we still have incomplete knowledge concerning most exposures and the biological interactions responsible for impaired development and preterm delivery.

SUMMARY

Whereas single genes and individual chemical exposures are responsible for some instances of adverse pregnancy outcome or developmental disease, gene-environment interactions are responsible for the majority. These gene-environment interactions may occur in the father, mother, placenta or fetus, suggesting that critical attention be given to maternal and paternal exposures and gene expression as they relate to the mode of action of the putative developmental toxicant both prior to and during pregnancy.

Pathogenesis of Interstitial Lung Disease in Children and Adults

Interstitial lung diseases (ILDs) occur across the lifespan, from birth to advanced age. However, the causes, clinical manifestations, histopathology, and management of ILD differ greatly among infants, older children, and adults. The historical approach of classifying childhood ILD (chILD) using adult classification schemes may therefore have done more harm than good. Nevertheless, identification of novel forms of chILD in the past decade, such as surfactant metabolism dysfunction disorders and neuroendocrine cell hyperplasia of infancy (NEHI), as well as genomic analysis of adult ILDs, has taught us that identical genotypes may result in distinct phenotypes at different ages and developmental stages, and that lung developmental pathways and cellular phenotypes are often recapitulated in adult ILDs. Thus comparison of the pathophysiology of ILD in children and adults in the context of lung development is useful in understanding the pathogenesis of these disorders, and may lead to novel therapeutic interventions for ILDs at all ages.