Glycosylation defects underlying fetal alcohol spectrum disorder: a novel pathogenetic model. "When the wine goes in, strange things come out" - S.T. Coleridge, The Piccolomini

Prenatal alcohol exposure induced congenital heart diseases: From bench to bedside

Alcohol consumption is increasing worldwide. Many child-bearing-aged women consume alcohol during pregnancy, intentionally or unintentionally, thereby increasing the potential risk for severe congenital diseases. Congenital heart disease (CHD) is the most common birth defect worldwide and can result from both hereditary and acquired factors. Prenatal alcohol exposure (PAE) is considered a key factor that leads to teratogenesis in CHD and its specific phenotypes, especially defects of the cardiac septa, cardiac valves, cardiac canals, and great arteries, adjacent to the chambers, both in animal experiments and clinical retrospective studies. The mechanisms underlying CHD and its phenotypes caused by PAE are associated with changes in retinoic acid biosynthesis and its signaling pathway, apoptosis and defective function of cardiac neural crest cells, disturbance of the Wntβ-catenin signaling pathway, suppression of bone morphogenetic protein (BMP) signaling, and other epigenetic mechanisms. Drug supplements and early diagnosis can help prevent PAE from inducing CHDs.

Genetic predisposition to fetal alcohol syndrome: association with congenital disorders of N-glycosylation

BackgroundFetal alcohol syndrome (FAS) is caused by maternal alcohol consumption during pregnancy; although additional factors might be involved, as development and severity are not directly related to alcohol intake. The abnormal glycosylation caused by alcohol might play a role in FAS according to the clinical similarities shared with congenital disorders of glycosylation (CDG). Thus, mutations underlying CDG, affecting genes involved in glycosylation, could also be involved in FAS.MethodsA panel of 74 genes involved in N-glycosylation was sequenced in 25 FAS patients and 20 controls with prenatal alcohol exposure. Transferrin glycoforms were evaluated by HPLC.ResultsRare (minor allele frequency<0.009) missense/splice site variants were more frequent in FAS than controls (84% vs. 50%; P=0.034, odds ratio: 5.25, 95% confidence interval: 1.3-20.9). Remarkably, three patients, but no controls, carried variants with functional effects identified in CDG patients. Moreover, the patient with the most severe clinical phenotype was the only one carrying two variants with functional effects. Family studies support that the combination of a genetic defect and alcohol consumption during pregnancy might have a role in FAS development.ConclusionsOur study supports that the rare variants of genes involved in N-glycosylation could play a role in the development and severity of FAS under prenatal alcohol exposure.

Fetal alcohol spectrum disorders and cognitive functions of young children

Fetal alcohol spectrum disorder (FASD) is one of the main causes of mental retardation worldwide. Nearly 1% of children in North America are affected from antenatal exposure to ethanol. Its economic burden in industrialized countries is increasing. It is estimated that, in the United States, 4.0 billion dollars are annually expended in the treatment and rehabilitation of these patients. As a pathologic entity, they present with a broad symptomatology. Fetal alcohol syndrome (FAS) is the most readily recognized clinical manifestation of these disorders. Various factors seem to contribute in the pathogenesis of FASD-related cognitive disorders. During the last 20 years, several potential pretranslational and posttranslational factors have been extensively studied in various experimental animal models. Research has specifically focused on several neurotransmitters, insulin resistance, alterations of the hypothalamic-pituitary-adrenal (HPA) axis, abnormal glycosylation of several proteins, oxidative stress, nutritional antioxidants, and various epigenetic factors. The purpose of the present review is to summarize the clinical manifestations of this disorder during childhood and adolescence and to summarize the possible pathophysiologic and epigenetic pathways that have been implicated in the pathophysiology of FASD.

Maternal lifestyle factors in pregnancy and congenital heart defects in offspring: review of the current evidence

The prognosis of children with congenital heart defects(CHDs) continues to improve with advancing surgical techniques; however, lack of information about modifiable risk factors for malformations in cardiovascular development impeded the prevention of CHDs. We investigated an association between maternal lifestyle factors and the risk of CHDs, because epidemiological studies have reported conflicting results regarding maternal lifestyle factors and the risk of CHDs recently. A review published on 2007 provided a summary of maternal exposures associated with an increased risk of CHDs. As part of noninherited risk factors, we conducted a brief overview of studies on the evidence linking common maternal lifestyle factors, specifically smoking, alcohol, illicit drugs, caffeine, body mass index and psychological factors to the development of CHDs in offspring. Women who smoke and have an excessive body mass index(BMI) during pregnancy are suspected to be associated with CHDs in offspring. Our findings could cause public health policy makers to pay more attention to women at risk and could be used in the development of population-based prevention strategies to reduce the incidence and burden of CHDs. However, more prospective studies are needed to investigate the association between maternal lifestyle factors and CHDs.

Third trimester-equivalent ethanol exposure is characterized by an acute cellular stress response and an ontogenetic disruption of genes critical for synaptic establishment and function in mice

The developing brain is remarkably sensitive to alcohol exposure, resulting in the wide range of cognitive and neurobehavioral characteristics categorized under the term fetal alcohol spectrum disorders (FASD). The brain is particularly susceptible to alcohol during synaptogenesis, a process that occurs heavily during the third trimester and is characterized by the establishment and pruning of neural circuitry; however, the molecular response of the brain to ethanol during synaptogenesis has not been documented. To model a binge-like exposure during the third-trimester neurodevelopmental equivalent, neonate mice were given a high (5 g/kg over 2 h) dose of ethanol at postnatal day 7. Acute transcript changes within the brain were assessed using expression arrays and analyzed for associations with gene ontology functional categories, canonical pathways, and gene network interactions. The short-term effect of ethanol was characterized by an acute stress response and a downregulation of energetically costly cellular processes. Further, alterations to a number of genes with roles in synaptic transmission and hormonal signaling, particularly those associated with the neuroendocrine development and function, were evident. Ethanol exposure during synaptogenesis was also associated with altered histone deacetylase and microRNA transcript levels, suggesting that abnormal epigenetic patterning may maintain some of the persistent molecular consequences of developmental ethanol exposure. The results shed insight into the sensitivity of the brain to ethanol during the third-trimester equivalent and outline how ethanol-induced alterations to genes associated with neural connectivity may contribute to FASD phenotypes.

Chronic alcohol exposure affects the cell components involved in membrane traffic in neuronal dendrites

The specific traffic of the membrane components in neurons is a major requirement to establish and maintain neuronal domains-the axonal and the somatodendritic domains-and their polarized morphology. Unlike axons, dendrites contain membranous organelles, which are involved in the secretory pathway, including the endoplasmic reticulum, the Golgi apparatus and post-Golgi apparatus carriers, the cytoskeleton, and plasma membrane. A variety of molecules and factors are also involved in this process. Previous studies have shown that chronic alcohol exposure negatively affects several of these cell components, such as the Golgi apparatus or cytoskeleton in neurons. Yet very little information is available on the possible effects of this exposure on the remaining cell elements involved in intracellular trafficking in neurons, particularly in dendrites. By qualitative and quantitative electron microscopy, immunofluorescence and immunoblotting, we herein show that chronic exposure to moderate levels (30 mM) of ethanol in cultured neurons reduces the volume and surface density of the rough endoplasmic reticulum, and increases the levels of GRP78, a chaperone involved in endoplasmic reticulum stress. Ethanol also significantly diminishes the proportion of neurons that show an extension of Golgi into dendrites and dendritic Golgi outposts, a structure present exclusively in longer, thicker apical dendrites. Both Golgi apparatus types were also fragmented into a large number of cells. We also investigated the effect of alcohol on the levels of microtubule-based motor proteins KIF5, KIF17, KIFC2, dynein, and myosin IIb, responsible for transporting different cargoes in dendrites. Of these, alcohol differently affects several of them by lowering dynein and raising KIF5, KIFC2, and myosin IIb. These results, together with other previously published ones, suggest that practically all the protein trafficking steps in dendrites are altered to a greater or lesser extent by chronic alcohol exposure in neuronal cells, which may have negative repercussions for the development and maintenance of their polarized morphology and function.

The effect of malnutrition on protein glycosylation in children

OBJECTIVE

The goal of this study was to evaluate the effect of protein energy malnutrition on protein glycosylation by investigating transferrin isoform pattern and its relationship to the degree of malnutrition and the biochemical markers of nutritional status in children.

METHODS

Forty one children with mild (n=23) and severely/moderately (n=18) acute malnutrition and 29 controls were enrolled in the study. Serum transferrin isoforms were determined by isoelectric focusing electrophoresis. Transferrin, prealbumin, zinc, iron and insulin-like growth factor-1 (IGF-1) were measured using automated analyzers. Findings : Asialotransferrin and disialotransferrin were significantly higher in severely/moderately malnourished patients compared to controls (P=0.04 and P=0.04, respectively). Other transferrin isoform patterns were not different among three groups. Serum IGF-1, transferrin and iron levels of severely/ moderately malnourished group were significantly lower than tose of controls (P=0.001, 0.02 and 0.03, respectively). Serum prealbumin and zinc levels were similar in all three groups. Serum IGF-1, transferrin and iron levels, and all transferrin isoform patterns were not significantly different in mildly malnutrition group from other two groups.

CONCLUSION

The changes in transferrin isoform pattern observed in malnourished patients may indicate that malnutrition is a catabolic state which has effects on glycosylation.

Ethanol exposure alters early cardiac function in the looping heart: a mechanism for congenital heart defects?

Alcohol-induced congenital heart defects are frequently among the most life threatening and require surgical correction in newborns. The etiology of these defects, collectively known as fetal alcohol syndrome, has been the focus of much study, particularly involving cellular and molecular mechanisms. Few studies have addressed the influential role of altered cardiac function in early embryogenesis because of a lack of tools with the capability to assay tiny beating hearts. To overcome this gap in our understanding, we used optical coherence tomography (OCT), a nondestructive imaging modality capable of micrometer-scale resolution imaging, to rapidly and accurately map cardiovascular structure and hemodynamics in real time under physiological conditions. In this study, we exposed avian embryos to a single dose of alcohol/ethanol at gastrulation when the embryo is sensitive to the induction of birth defects. Late-stage hearts were analyzed using standard histological analysis with a focus on the atrio-ventricular valves. Early cardiac function was assayed using Doppler OCT, and structural analysis of the cardiac cushions was performed using OCT imaging. Our results indicated that ethanol-exposed embryos developed late-stage valvuloseptal defects. At early stages, they exhibited increased regurgitant flow and developed smaller atrio-ventricular cardiac cushions, compared with controls (uninjected and saline-injected embryos). The embryos also exhibited abnormal flexion/torsion of the body. Our evidence suggests that ethanol-induced alterations in early cardiac function have the potential to contribute to late-stage valve and septal defects, thus demonstrating that functional parameters may serve as early and sensitive gauges of cardiac normalcy and abnormalities.

Screening for congenital disorders of glycosylation in the first weeks of life

Inherited monogenetic human disorders due to deficiencies in the complex metabolic pathways for N- and O-glycosylation of glycoconjugates are termed 'congenital disorders of glycosylation' (CDG). Since the number of these defects with mostly severe multisystemic phenotypes has been rapidly expanding in recent years, the interest of paediatricians has also increased resulting in a rising amount of patient samples with the suspicion of CDG. In general, primary diagnostics for CDG start with investigations on the glycosylation state of serum transferrin, the 'gold standard' in the field for many years. However, the use of transferrin shows an analytical problem in the time span from birth up to the 3rd month of life. In this developmental period oligosaccharide moieties N-linked to proteins are often incomplete, resembling a CDG pattern and leading to false-positive results. It is therefore necessary to establish a reliable and fast diagnostic procedure for this span of life. Here we show that the glycosylation state of serum α-1-antitrypsin is already fully existent shortly after birth allowing an alternative diagnostic approach for the investigation of CDG in the first weeks of life. The method can easily be established in every laboratory especially with previous experience in transferrin analysis.

Plant polyisoprenoids and control of cholesterol level

The ability of plant polyisoprenoids (polyprenols and polyprenyl phosphates) to diminish the levels of serum cholesterol affecting its biosynthetic pathway are highlighted here. Possible mechanism of such process is discussed. It is also noted that polyisoprenoids can prevent toxic injuries of the liver and restore disturbed hepatic functions. The possibility of polyprenyl phosphates to reveal at the same time anti-inflammatory action suppressing lipoxygenase activity and lowering the levels of proinflammatory cytokines will be illustrated. Attention will be focused on the potential usefulness of plant polyisoprenoids in the course of prevention and treatment of hypercholesterolemia. High efficiency for combined use of polyprenyl phosphate and β-sitosterol, which leads to substantial enhancement of the ability to overcome hypercholesterolemia versus the individual constituents will be demonstrated.

Chronic alcohol alters dendritic spine development in neurons in primary culture

Dendritic spines are specialised membrane protrusions of neuronal dendrites that receive the majority of excitatory synaptic inputs. Abnormal changes in their density, size and morphology have been associated with various neurological and psychiatric disorders, including those deriving from drug addiction. Dendritic spine formation, morphology and synaptic functions are governed by the actin cytoskeleton. Previous in vivo studies have shown that ethanol alters the number and morphology of spines, although the mechanisms underlying these alterations remain unknown. It has also been described how chronic ethanol exposure affects the levels, assembly and cellular organisation of the actin cytoskeleton in hippocampal neurons in primary culture. Therefore, we hypothesised that the ethanol-induced alterations in the number and shape of dendritic spines are due to alterations in the mechanisms regulating actin cytoskeleton integrity. The results presented herein show that chronic exposure to moderate levels of alcohol (30 mM) during the first 2 weeks of culture reduces dendritic spine density and alters the proportion of the different morphologies of these structures in hippocampal neurons, which affects the formation of mature spines. Apparently, these effects are associated with an increase in the G-actin/F-actin ratio due to a reduction of the F-actin fraction, leading to changes in the levels of the different factors regulating the organisation of this cytoskeletal component. The data presented herein indicate that these effects occur between weeks 1 and 2 of culture, an important period in dendritic spines development. These changes may be related to the dysfunction in the memory and learning processes present in children prenatally exposed to ethanol.

Perinatal and early infantile symptoms in congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) are a rapidly growing family of inborn errors. Screening for CDG in suspected cases is usually performed in the first year of life by serum transferrin isoelectric focusing or mass spectrometry. Based on the transferrin analysis patients can be biochemically diagnosed with a type 1 or type 2 transferrin pattern, and labeled as CDG-I, or CDG-II. The diagnosis of CDG is frequently delayed due to the highly variable phenotype, some cases showing single organ involvement and others mimicking syndromes, like skeletal dysplasia, cutis laxa syndrome, or congenital muscle dystrophy. The aim of our study was to evaluate perinatal abnormalities and early discriminative symptoms in 58 patients consecutively diagnosed with diverse CDG-subtypes. Neonatal findings and clinical features in the first months of life were studied in 36 children with CDG-I and 22 with CDG-II. Maternal complications were found in five, small for gestational age in nine patients. Five children had abnormal neonatal screening results for hypothyroidism. Congenital microcephaly and neonatal seizures were common in CDG-II. Inverted nipples were uncommon with 5 out of 58 children. Dysmorphic features were mostly nonspecific, except for cutis laxa. Early complications included feeding problems, cardiomyopathy, thrombosis, and bleeding. Cases presenting in the neonatal period had the highest mortality rate. Survival in CDG patients is highly dependent on early intervention therapy. We recommend low threshold screening for glycosylation disorders in infants with neurologic symptoms, even in the absence of abnormal fat distribution. Growth retardation and neonatal bleeding increase suspicion for CDG.