Acute ethanol exposure in pregnancy alters the insulin-like growth factor axis of fetal and maternal sheep

Effect of Ethanol Consumption on the Placenta and Liver of Partially IGF-1-Deficient Mice: The Role of Metabolism via CYP2E1 and the Antioxidant Enzyme System

Simple Summary

Ethanol is the most consumed drug worldwide, even during pregnancy. One of its adverse outcomes is fetal growth restriction, an alteration in development due to decreased IGF-1 levels. Several studies have shown that ethanol can impair the IGF-1 signaling pathway, thus exacerbating IGF-1 adverse effects in both intrauterine and postnatal growth and development. In this manuscript, we used a partially IGF-1-deficient mouse model to demonstrate the key role of IGF-1 in fetal development, as well as ethanol’s adverse effects on CYP2E1 expression levels and the antioxidant enzyme system during pregnancy.

Abstract

Ethanol use during pregnancy is a risk factor for developing adverse outcomes. Its metabolism by cytochrome P450 2E1 (CYP2E1) produces radical oxygen species (ROS), promoting cellular injury and apoptosis. To date, no studies have been conducted to elucidate the teratogenic effects due to both IGF-1 deficiency and ethanol consumption in mice placentas. The aim of this study is to determine the effect of ethanol consumption on the placenta and liver of partially IGF-1-deficient mice, the role of metabolism via CYP2E1, and the antioxidant enzyme system. Heterozygous (HZ, Igf1^+/−) pregnant female mice were given water or 10% ethanol. Wild-type (WT, Igf1^+/+) female mice were used as controls. At gestational day 19, pregnant dams were euthanized, and maternal liver and placentas were collected. Pregnant HZ dams were smaller than controls, and this effect was higher due to ethanol consumption. Cyp2e1 gene was overexpressed in the liver of HZ pregnant dams exposed to ethanol; at the protein level, CYP2E1 is reduced in placentas from all genotypes. The antioxidant enzymatic system was altered by ethanol consumption in both the maternal liver and placenta. The results in this work hint that IGF-1 is involved in intrauterine development because its deficiency exacerbates ethanol’s effects on both metabolism and the placenta.

Oligodendrocyte pathology in fetal alcohol spectrum disorders

The pathology of fetal alcohol syndrome and the less severe fetal alcohol spectrum disorders includes brain dysmyelination. Recent studies have shed light on the molecular mechanisms underlying these white matter abnormalities. Rodent models of fetal alcohol syndrome and human studies have shown suppressed oligodendrocyte differentiation and apoptosis of oligodendrocyte precursor cells. Ethanol exposure led to reduced expression of myelin basic protein and delayed myelin basic protein expression in rat and mouse models of fetal alcohol syndrome and in human histopathological specimens. Several studies have reported increased expression of many chemokines in dysmyelinating disorders in central nervous system, including multiple sclerosis and fetal alcohol syndrome. Acute ethanol exposure reduced levels of the neuroprotective insulin-like growth factor-1 in fetal and maternal sheep and in human fetal brain tissues, while ethanol increased the expression of tumor necrosis factor α in mouse and human neurons. White matter lesions have been induced in the developing sheep brain by alcohol exposure in early gestation. Rat fetal alcohol syndrome models have shown reduced axon diameters, with thinner myelin sheaths, as well as reduced numbers of oligodendrocytes, which were also morphologically aberrant oligodendrocytes. Expressions of markers for mature myelination, including myelin basic protein, also were reduced. The accumulating knowledge concerning the mechanisms of ethanol-induced dysmyelination could lead to the development of strategies to prevent dysmyelination in children exposed to ethanol during fetal development. Future studies using fetal oligodendrocyte- and oligodendrocyte precursor cell-derived exosomes isolated from the mother’s blood may identify biomarkers for fetal alcohol syndrome and even implicate epigenetic changes in early development that affect oligodendrocyte precursor cell and oligodendrocyte function in adulthood. By combining various imaging modalities with molecular studies, it may be possible to determine which fetuses are at risk and to intervene therapeutically early in the pregnancy.

The Placenta as a Target for Alcohol During Pregnancy: The Close Relation with IGFs Signaling Pathway

Alcohol is one of the most consumed drugs in the world, even during pregnancy. Its use is a risk factor for developing adverse outcomes, e.g. fetal death, miscarriage, fetal growth restriction, and premature birth, also resulting in fetal alcohol spectrum disorders. Ethanol metabolism induces an oxidative environment that promotes the oxidation of lipids and proteins, triggers DNA damage, and advocates mitochondrial dysfunction, all of them leading to apoptosis and cellular injury. Several organs are altered due to this harmful behavior, the brain being one of the most affected. Throughout pregnancy, the human placenta is one of the most important organs for women's health and fetal development, as it secretes numerous hormones necessary for a suitable intrauterine environment. However, our understanding of the human placenta is very limited and even more restricted is the knowledge of the impact of toxic substances in its development and fetal growth. So, could ethanol consumption during this period have wounding effects in the placenta, compromising proper fetal organ development? Several studies have demonstrated that alcohol impairs various signaling cascades within G protein-coupled receptors and tyrosine kinase receptors, mainly through its action on insulin and insulin-like growth factor 1 (IGF-1) signaling pathway. This last cascade is involved in cell proliferation, migration, and differentiation and in placentation. This review tries to examine the current knowledge and gaps in our existing understanding of the ethanol effects in insulin/IGFs signaling pathway, which can explain the mechanism to elucidate the adverse actions of ethanol in the maternal-fetal interface of mammals.

Ethanol-mediated alterations in oligodendrocyte differentiation in the developing brain

INTRODUCTION

Alterations of white matter integrity and subsequent white matter structural deficits are consistent findings in Fetal Alcohol Syndrome (FAS), but knowledge regarding the molecular mechanisms underlying these abnormalities is incomplete. Experimental rodent models of FAS have shown dysregulation of cytokine expression leading to apoptosis of oligodendrocyte precursor cells (OPCs) and altered oligodendrocyte (OL) differentiation, but whether this is representative of human FAS pathogenesis has not been determined.

METHODS

Fetal brain tissue (12.2-21.4 weeks gestation) from subjects undergoing elective termination of pregnancy was collected according to an IRB-approved protocol. Ethanol (EtOH) exposure status was classified based on a detailed face-to-face questionnaire adapted from the National Institute on Alcohol Abuse and Alcoholism Prenatal Alcohol and Sudden Infant Death Syndrome and Stillbirth (PASS) study. Twenty EtOH-exposed fetuses were compared with 20 gestational age matched controls. Cytokine and OPC marker mRNA expression was quantified by Real-Time Polymerase chain reaction (qRT-PCR). Patterns of protein expression of OPC markers and active Capase-3 were studied by Fluorescence Activated Cell Sorting (FACS).

RESULTS

EtOH exposure was associated with reduced markers of cell viability, OPC differentiation, and OL maturation, while early OL differentiation markers were unchanged or increased. Expression of mRNAs for proteins specific to more mature forms of OL lineage (platelet-derived growth factor α (PDGFRα) and myelin basic protein (MBP) was lower in the EtOH group than in controls. Expression of the multifunctional growth and differentiation-promoting growth factor IGF-1, which is essential for normal development, also was reduced. Reductions were not observed for markers of early stages of OL differentiation, including Nuclear transcription factor NK-2 homeobox locus 2 (Nkx2.2). Expression of mRNAs for the proinflammatory cytokine, tumor necrosis factor-α (TNFα), and several proinflammatory chemokines was higher in the EtOH group compared to controls, including: Growth regulated protein alpha/chemokine (C-X-C motif) ligand 1 (GRO-α/CXCL1), Interleukin 8/chemokine (C-X-C motif) ligand 8 (IL8/CXCL8), Chemokine (C-X-C motif) ligand 6/Granulocyte chemotactic protein 2 (CXCL16/GCP2), epithelial-derived neutrophil-activating protein 78/chemokine (C-X-C motif) ligand 5 (ENA-78/CXCL5), monocyte chemoattractant protein-1 (MCP-1). EtOH exposure also was associated with an increase in the proportion of cells expressing markers of early stage OPCs, such as A2B5 and NG2. Finally, apoptosis (measured by caspase-3 activation) was increased substantially in the EtOH group compared to controls.

CONCLUSION

Prenatal EtOH exposure is associated with excessive OL apoptosis and/or delayed OL maturation in human fetal brain. This is accompanied by markedly dysregulated expression of several chemokines and cytokines, in a pattern predictive of increased OL cytotoxicity and reduced OL differentiation. These findings are consistent with findings in animal models of FAS.

Alcohol exposure during late gestation: multiple developmental outcomes in sheep

Alcohol consumption during pregnancy remains common in many countries. Exposure to even low amounts of alcohol (i.e. ethanol) in pregnancy can lead to the heterogeneous fetal alcohol spectrum disorders (FASD), while heavy alcohol consumption can result in the fetal alcohol syndrome (FAS). FAS is characterized by cerebral dysfunction, growth restriction and craniofacial malformations. However, the effects of lower doses of alcohol during pregnancy, such as those that lead to FASD, are less well understood. In this article, we discuss the findings of recent studies performed in our laboratories on the effects of fetal alcohol exposure using sheep, in which we investigated the effects of late gestational alcohol exposure on the developing brain, arteries, kidneys, heart and lungs. Our studies indicate that alcohol exposure in late gestation can (1) affect cerebral white matter development and increase the risk of hemorrhage in the fetal brain, (2) cause left ventricular hypertrophy with evidence of altered cardiomyocyte maturation, (3) lead to a decrease in nephron number in the kidney, (4) cause altered arterial wall stiffness and endothelial and smooth muscle function and (5) result in altered surfactant protein mRNA expression, surfactant phospholipid composition and pro-inflammatory cytokine mRNA expression in the lung. These findings suggest that fetal alcohol exposure in late gestation can affect multiple organs, potentially increasing the risk of disease and organ dysfunction in later life.

Low-dose maternal alcohol consumption: effects in the hearts of offspring in early life and adulthood

High alcohol consumption during pregnancy leads to deleterious effects on fetal cardiac structure and it also affects cardiomyocyte growth and maturation. This study aimed to determine whether low levels of maternal alcohol consumption are also detrimental to cardiomyocyte and cardiac growth in the early life of offspring and whether cardiac structure and function in adulthood is affected. Pregnant Sprague-Dawley rat dams were fed a control or 6% (volume/volume) liquid-based ethanol supplemented (isocaloric) diet throughout gestation. At embryonic day 20, the expression of genes involved in cardiac development was analyzed using Real-time PCR. At postnatal day 30, cardiomyocyte number, size, and nuclearity in the left ventricle (LV) were determined stereologically. In 8-month-old offspring, LV fibrosis and cardiac function (by echocardiography) were examined. Maternal ethanol consumption did not alter gene expression of the cardiac growth factors in the fetus or cardiomyocyte number in weanling offspring. However, at 8 months, there were significant increases in LV anterior and posterior wall thickness during diastole in ethanol-exposed offspring (P = 0.037 and P = 0.024, respectively), indicative of left ventricular hypertrophy; this was accompanied by a significant increase in fibrosis. Additionally, maximal aortic flow velocity was significantly decreased in ethanol-exposed offspring (P = 0.035). In conclusion, although there were no detectable early-life differences in cardiac and cardiomyocyte growth in animals exposed to a chronic low dose of ethanol during gestation, there were clearly deleterious outcomes by adulthood. This suggests that even relatively low doses of alcohol consumed during pregnancy can be detrimental to long-term cardiac health in the offspring.

A rodent model of low- to moderate-dose ethanol consumption during pregnancy: patterns of ethanol consumption and effects on fetal and offspring growth

It is unknown whether low to moderate maternal alcohol consumption adversely affects postnatal health. The aim of the present study was to develop a rodent model of low-moderate-dose prenatal ethanol (EtOH) exposure. Sprague-Dawley rats were fed a liquid diet with or without 6% v/v EtOH throughout gestation and the pattern of dietary consumption determined. Fetal bodyweights and hepatic alcohol-metabolising gene expression were measured on embryonic Day (E) 20 and offspring growth studied until 1 year. At E8 the plasma EtOH concentration was 0.03%. There was little difference in dietary consumption between the two treatment groups. At E20, EtOH-exposed fetuses were significantly lighter than controls and had significantly decreased ADH4 and increased CYP2E1 gene expression. Offspring killed on postnatal Day (PN) 30 did not exhibit any growth deficits. Longitudinal repeated measures of offspring growth demonstrated slower growth in males from EtOH-fed dams between 7 and 12 months of age; a cohort of male pups killed at 8 months of age had a reduced crown-rump length and kidney weight. In conclusion, a liquid diet of 6% v/v EtOH fed to pregnant dams throughout gestation caused a 3-8% reduction in fetal growth and brain sparing, with growth differences observed in male offspring later in life. This model will be useful for future studies on the effects of low-moderate EtOH on the developmental origins of health and disease.

IGF-I and IGFBP-3 before and after inpatient alcohol detoxification in alcohol-dependent subjects

Background

It is unclear whether alcohol detoxification has an effect on factors that are involved in growth, metabolic functions and cell proliferation. Alcohol abuse is associated with low IGF-I levels that tend to rise after alcohol withdrawal. There is a paucity of studies on the course of IGFBP-3 (the main binding protein for IGF-I) after alcohol detoxification.

Material/Methods

We prospectively assessed IGF-I and IGFBP-3 changes at the time of admission and after 4 to 6 weeks of detoxification in an inpatient alcohol detoxification facility in 118 alcohol-dependent subjects given a regular hospital diet. No participants dropped out of the study.

Results

Changes in IGF-I after alcohol detoxification showed a marked dimorphism in altered hepatic biochemistry upon admission, with a rise in those with normal liver enzymes upon admission (p=0.016, Kruskall-Wallis) and a drop in those with elevated liver enzymes upon admission (p=0.05); the latter was noted in subjects that had consumed alcohol close to the time of admission. Overall, however, IGF-I and IGFBP-3 were within normal limits for most subjects both upon admission and after alcohol detoxification; no significant differences were detected among the examined parameters in men vs. women, and there were no significant correlations of IGF-I, IGFBP-3 or the IGF-I/IGFBP-3 molar ratio with BMI or age.

Conclusions

Regardless of hepatic enzymes’ elevation, alcohol detoxification had overall slight effects on IGF-I and IGFBP-3.

Daily ethanol exposure during late ovine pregnancy: physiological effects in the mother and fetus in the apparent absence of overt fetal cerebral dysmorphology

High levels of ethanol (EtOH) consumption during pregnancy adversely affect fetal development; however, the effects of lower levels of exposure are less clear. Our objectives were to assess the effects of daily EtOH exposure (3.8 USA standard drinks) on fetal-maternal physiological variables and the fetal brain, particularly white matter. Pregnant ewes received daily intravenous infusions of EtOH (0.75 g/kg maternal body wt over 1 h, 8 fetuses) or saline (8 fetuses) from 95 to 133 days of gestational age (DGA; term ∼145 DGA). Maternal and fetal arterial blood was sampled at 131-133 DGA. At necropsy (134 DGA) fetal brains were collected for analysis. Maternal and fetal plasma EtOH concentrations reached similar maximal concentration (∼0.11 g/dl) and declined at the same rate. EtOH infusions produced mild reductions in fetal arterial oxygenation but there were no changes in maternal oxygenation, maternal and fetal Pa(CO(2)), or in fetal mean arterial pressure or heart rate. Following EtOH infusions, plasma lactate levels were elevated in ewes and fetuses, but arterial pH fell only in ewes. Fetal body and brain weights were similar between groups. In three of eight EtOH-exposed fetuses there were small subarachnoid hemorrhages in the cerebrum and cerebellum associated with focal cortical neuronal death and gliosis. Overall, there was no evidence of cystic lesions, inflammation, increased apoptosis, or white matter injury. We conclude that daily EtOH exposure during the third trimester-equivalent of ovine pregnancy has modest physiological effects on the fetus and no gross effects on fetal white matter development.

Alcohol exposure during late gestation adversely affects myocardial development with implications for postnatal cardiac function

Prenatal exposure to high levels of ethanol is associated with cardiac malformations, but the effects of lower levels of exposure on the heart are unclear. Our aim was to investigate the effects of daily exposure to ethanol during late gestation, when cardiomyocytes are undergoing maturation, on the developing myocardium. Pregnant ewes were infused with either ethanol (0.75 g/kg) or saline for 1 h each day from gestational days 95 to 133 (term ∼145 days); tissues were collected at 134 days. In sheep, cardiomyocytes mature during late gestation as in humans. Within the left ventricle (LV), cardiomyocyte number was determined using unbiased stereology and cardiomyocyte size and nuclearity determined using confocal microscopy. Collagen deposition was quantified using image analysis. Genes relating to cardiomyocyte proliferation and apoptosis were examined using quantitative real-time PCR. Fetal plasma ethanol concentration reached 0.11 g/dL after EtOH infusions. Ethanol exposure induced significant increases in relative heart weight, relative LV wall volume, and cardiomyocyte cross-sectional area. Ethanol exposure advanced LV maturation in that the proportion of binucleated cardiomyocytes increased by 12%, and the number of mononucleated cardiomyocytes was decreased by a similar amount. Apoptotic gene expression increased in the ethanol-exposed hearts, although there were no significant differences between groups in total cardiomyocyte number or interstitial collagen. Daily exposure to a moderate dose of ethanol in late gestation accelerates the maturation of cardiomyocytes and increases cardiomyocyte and LV tissue volume in the fetal heart. These effects on cardiomyocyte growth may program for long-term cardiac vulnerability.

Perspectives in mammalian IGFBP-3 biology: local vs. systemic action

Insulin-like growth factor (IGF) binding protein (IGFBP)-3 has traditionally been defined by its role as a binding protein and its association with IGF delivery and availability. Development of non-IGF binding IGFBP-3 analogs and the use of cell lines devoid of type 1 IGF receptors (IGF-R) have led to critical advances in the field of IGFBP-3 biology. These studies show that IGFBP-3 has IGF-independent roles in inhibiting cell proliferation in cancer cell lines. Nuclear transcription factor, retinoid X receptor (RXR)-alpha, and IGFBP-3 functionally interact to reduce prostate tumor growth and prostate-specific antigen in vivo. Moreover, IGFBP-3 inhibits insulin-stimulated glucose uptake into adipocytes independent of IGF. The purpose of this review is to highlight IGFBP-3 as a novel effector molecule and not just another "binding protein" by discussing its IGF-independent actions on metabolism and cell growth. Although this review presents studies that assume the role of IGFBP-3 as either an endocrine or autocrine/paracrine molecule, these systems may not exist as distinct entities, justifying the examination of IGFBP-3 in an integrated model. Also, we provide an overview of factors that regulate IGFBP-3 availability, including its production, methylation, and ubiquitination. We conclude with the role of IGFBP-3 in whole body systems and possible future applications of IGFBP-3 in physiology.

Insulin-like growth factor-I mitigates motor coordination deficits associated with neonatal alcohol exposure in rats

Prenatal alcohol exposure can affect brain development, leading to behavioral problems, including overactivity, motor dysfunction and learning deficits. Despite warnings about the effects of drinking during pregnancy, rates of fetal alcohol syndrome remain unchanged and thus, there is an urgent need to identify interventions that reduce the severity of alcohol's teratogenic effects. Insulin-like growth factor-I (IGF-I) is neuroprotective against ethanol-related toxicity and promotes white matter production following a number of insults. Given that prenatal alcohol leads to cell death and white matter deficits, the present study examined whether IGF-I could reduce the severity of behavioral deficits associated with developmental alcohol exposure. Sprague-Dawley rat pups received ethanol intubations (5.25 g/kg/day) or sham intubations on postnatal days (PD) 4-9, a period of brain development equivalent to the third trimester. On PD 10-13, subjects from each treatment received 0 or 10 microg IGF-I intranasally each day. Subjects were then tested on a series of behavioral tasks including open field activity (PD 18-21), parallel bar motor coordination (PD 30-32) and Morris maze spatial learning (PD 45-52). Ethanol exposure produced overactivity, motor coordination impairments, and spatial learning deficits. IGF-I treatment significantly mitigated ethanol's effects on motor coordination, but not on the other two behavioral tasks. These data indicate that IGF-I may be a potential treatment for some of ethanol's damaging effects, a finding that has important implications for children of women who drink alcohol during pregnancy.

Repeated betamethasone treatment of pregnant sheep programs persistent reductions in circulating IGF-I and IGF-binding proteins in progeny

Exposure to synthetic glucocorticoids in utero markedly improves survival after preterm birth, but repeated exposures impair fetal and postnatal growth and are associated with evidence of insulin resistance in later life. The insulin-like growth factor (IGF) axis is an important regulator of growth and metabolism before and after birth. We have therefore investigated the effects of repeated maternal betamethasone injections on plasma IGF-I, IGF-II, and IGF-binding proteins (IGFBP) in fetal and postnatal progeny in the sheep. Pregnant sheep carrying male fetuses were injected with saline or betamethasone at 104, 111, and 118 days of gestation (dG, term approximately 150 dG). Plasma samples were collected postmortem from fetuses before (75, 84, 101 dG) or after one (109 dG), two (116 dG), or three (121-122, 132-133, 145-147 dG) doses of saline or betamethasone and from progeny at 42 and 84 days of age. Fetal weight was reduced after two or more maternal betamethasone injections, and this effect persisted to term. Repeated betamethasone exposures reduced plasma IGF-I and total IGFBP in fetuses at 133 dG and progeny at 84 days, and reduced plasma IGFBP-3 at 84 days. Fetal plasma IGF-II tended to increase transiently at 109 dG following the first betamethasone injection. Fetal, placental, and/or postnatal weights correlated positively with concomitant plasma IGF-I, IGF-II, and total IGFBP. We conclude that repeated exposure to synthetic glucocorticoids in utero programs the IGF axis before and after birth, which may contribute to the adverse effects of betamethasone exposure on growth and metabolism.

Repeated ethanol exposure during late gestation decreases nephron endowment in fetal sheep

Maternal alcohol consumption during pregnancy can affect fetal development, but little is known about the effects on the developing kidney. Our objectives were to determine the effects of repeated ethanol exposure during the latter half of gestation on glomerular (nephron) number and expression of key genes involved in renal development or function in the ovine fetal kidney. Pregnant ewes received daily intravenous infusion of ethanol (0.75 g/kg, n=5) or saline (control, n=5) over 1 h from 95 to 133 days of gestational age (DGA; term is approximately 147 DGA). Maternal and fetal arterial blood samples were taken before and after the start of the daily ethanol infusions for determination of blood ethanol concentration (BEC). Necropsy was performed at 134 DGA, and fetal kidneys were collected for determination of total glomerular number using the physical disector/fractionator technique; at this gestational age nephrogenesis is completed in sheep. Maximal maternal and fetal BECs of 0.12+/-0.01 g/dl (mean+/-SE) and 0.11+/-0.01 g/dl, respectively, were reached 1 h after starting maternal ethanol infusions. Ethanol exposure had no effect on fetal body weight, kidney weight, or the gene expression of members of the renin-angiotensin system, insulin-like growth factors, and sodium channels. However, fetal glomerular number was lower after ethanol exposure (377,585+/-8,325) than in controls (423,177+/-17,178, P<0.001). The data demonstrate that our regimen of fetal ethanol exposure during the latter half of gestation results in an 11% reduction in nephron endowment without affecting the overall growth of the kidney or fetus or the expression of key genes involved in renal development or function. A reduced nephron endowment of this magnitude could have important implications for the cardiovascular health of offspring during postnatal life.