Could oxidative stress be a factor in neurodevelopmental disorders?

Exploratory study evaluating the relationships between perinatal adversity, oxidative stress, and infant neurodevelopment across the first year of life

Early childhood adversity increases risk for negative lifelong impacts on health and wellbeing. Identifying the risk factors and the associated biological adaptations early in life is critical to develop scalable early screening tools and interventions. Currently, there are limited, reliable early childhood adversity measures that can be deployed prospectively, at scale, to assess risk in pediatric settings. The goal of this two-site longitudinal study was to determine if the gold standard measure of oxidative stress, F2-Isoprostanes, is potentially a reliable measure of a physiological response to adversity of the infant and mother. The study evaluated the independent relationships between F2-Isoprostanes, perinatal adversity and infant neurocognitive development. The study included mother-infant dyads born >36 weeks' gestation. Maternal demographic information and mental health assessments were utilized to generate a perinatal cumulative risk score. Infants' development was assessed at 6 and 12 months and both mothers and infants were assayed for F2-isoprostane levels in blood and urine, respectively. Statistical analysis revealed that cumulative risk scores correlated with higher maternal (p = 0.01) and infant (p = 0.05) F2-isoprostane levels at 6 months. Infant F2-isoprostane measures at 2 months were negatively associated with Mullen Scales of Early Learning Composite scores at 12 months (p = 0.04). Lastly, higher cumulative risk scores predicted higher average maternal F2-isoprostane levels across the 1-year study time period (p = 0.04). The relationship between perinatal cumulative risk scores and higher maternal and infant F2-isoprostanes at 6 months may reflect an oxidative stress status that informs a sensitive period in which a biomarker can be utilized prospectively to reveal the physiological impact of early adversity.

Role of glucose 6-phosphate dehydrogenase (G6PD) deficiency and its association to Autism Spectrum Disorders

Autism Spectrum Disorder (ASD) is a common group of neurodevelopmental disorders which causes significant alterations in social and communication skills along with repetitive behavior and limited interests. The physiological understanding of ASD is ambiguous. Several reports suggested that environmental, genetic and epigenetic changes, neuroinflammation, mitochondrial dysfunction and metabolic alterations orchestrate the pathological outcomes of ASD. A recent report from Saudi Arabia found a mutation in X-chromosomal housekeeping glucose 6-phosphate dehydrogenase (G6PD) gene in two male ASD patients. Although, the involvement of G6PD-deficiency in the pathogenesis of ASD is poorly understood. Several reports suggested that G6PD deficiency impedes cellular detoxification of reactive oxygen species (ROS), which may result in neuronal damage and neuroinflammation. A deficiency of G6PD in newborn children may play a fundamental role in the pathogenesis of ASD. In this review, we will discuss the implications of G6PD deficiency in pathogenesis, male biasness and theranostics in ASD patients.

Neurotoxicity in pre-eclampsia involves oxidative injury, exacerbated cholinergic activity and impaired proteolytic and purinergic activities in cortex and cerebellum

Women with a history of pre-eclampsia (PE) tend to have a higher risk of developing cardiovascular and neurological diseases later in life. Imbalance in oxidative markers and purinergic enzymes have been implicated in the pathogenesis of neurological disease. This study investigated the effect of PE on oxidative imbalance, purinergic enzyme inhibitory activity, acetylcholinesterase and chymotrypsin activities in the brain of PE rat model at post-partum/post-natal day (PP/PND) 60. Pregnant rats divided into early-onset and late-onset groups were administered with Nω-nitro-l-arginine methyl through drinking water at gestational days 8-17. Rats were allowed free access to water throughout the pregnancy and allowed to deliver on their own. The mother and the pups were euthanized at PP and PND 60, respectively, the cortex and the cerebellum excised, homogenized and stored for analyses of the enzymes. Results showed an increase in nitric oxide and malondialdehyde with a concomitant decrease in reduced glutathione and superoxide dismutase, an indication of oxidative damage. Also, there was an increase in acetylcholinesterase activity with a decrease in chymotrypsin, adenylpyrophosphatase and ecto-nucleoside triphosphate diphosphohydrolase activities in both the cortex and the cerebellum of the mother and the pups at PND 60. These results indicate the involvement of oxidative stress, increased cholinergic activity and depleted proteolytic and purinergic activities in PE-induced neurotoxicity.

Dysregulation of major functional genes in frontal cortex by maternal exposure to carbon black nanoparticle is not ameliorated by ascorbic acid pretreatment

Recent cohort studies have revealed that perinatal exposure to particulate air pollution, including carbon-based nanoparticles, increases the risk of brain disorders. Although developmental neurotoxicity is currently a major issue in the toxicology of nanoparticles, critical information for understanding the mechanisms underlying the developmental neurotoxicity of airway exposure to carbon black nanoparticle (CB-NP) is still lacking. In order to investigate these mechanisms, we comprehensively analyzed fluctuations in the gene expression profile of the frontal cortex of offspring mice exposed maternally to CB-NP, using microarray analysis combined with Gene Ontology information. We also analyzed differences in the enriched function of genes dysregulated by maternal CB-NP exposure with and without ascorbic acid pretreatment to refine specific alterations in gene expression induced by CB-NP. Total of 652 and 775 genes were dysregulated by CB-NP in the frontal cortex of 6- and 12-week-old offspring mice, respectively. Among the genes dysregulated by CB-NP, those related to extracellular matrix structural constituent, cellular response to interferon-beta, muscle organ development, and cysteine-type endopeptidase inhibitor activity were ameliorated by ascorbic acid pretreatment. A large proportion of the dysregulated genes, categorized in hemostasis, growth factor, chemotaxis, cell proliferation, blood vessel, and dopaminergic neurotransmission, were, however, not ameliorated by ascorbic acid pretreatment. The lack of effects of ascorbic acid on the dysregulation of genes following maternal CB-NP exposure suggests that the contribution of oxidative stress to the effects of CB-NP on these biological functions, i.e., cell migration and proliferation, blood vessel maintenance, and dopaminergic neuron system, may be limited. At least, ascorbic acid pretreatment is hardly likely to be able to protect the brain of offspring from developmental neurotoxicity of CB-NP. The present study provides insight into the mechanisms underlying developmental neurotoxicity following maternal nanoparticle exposure.

4-hydroxynonenal protein adducts: Key mediator in Rett syndrome oxinflammation

In the last 15 years a strong correlation between oxidative stress (OxS) and Rett syndrome (RTT), a rare neurodevelopmental disorder known to be caused in 95% of the cases, by a mutation in the methyl-CpG-binding protein 2 (MECP2) gene, has been well documented. Here, we revised, summarized and discussed the current knowledge on the role of lipid peroxidation byproducts, with special emphasis on 4-hydroxynonenal (4HNE), in RTT pathophysiology. The posttranslational modifications of proteins via 4HNE, known as 4HNE protein adducts (4NHE-PAs), causing detrimental effects on protein functions, appear to contribute to the clinical severity of the syndrome, since their levels increase significantly during the subsequent 4 clinical stages, reaching the maximum degree at stage 4, represented by a late motor deterioration. In addition, 4HNE-PA are only partially removed due to the compromised functionality of the proteasome activity, contributing therefore to the cellular damage in RTT. All this will lead to a characteristic subclinical inflammation, defined "OxInflammation", derived by a positive feedback loop between OxS byproducts and inflammatory mediators that in a long run further aggravates the clinical features of RTT patients. Therefore, in a pathology completely orphan of any therapy, aiming 4HNE as a therapeutic target could represent a coadjuvant treatment with some beneficial impact in these patients.‬‬‬.

Are ASD and ADHD a Continuum? A Comparison of Pathophysiological Similarities Between the Disorders

OBJECTIVE

The objective of this study was to review and compare the similarities between autism spectrum disorder (ASD) and ADHD with regard to symptomatology, neurological deficits, metabolic and endocrine-related conditions, and brain pathology.

METHOD

A comprehensive review of the relevant research literature was carried out.

RESULTS

A number of important similarities between ASD and ADHD were identified, including recent increases in prevalence, male-biased incidence, shared involvement of sensory processing, motor and impulse control, abnormal patterns of neural connectivity, and sleep disturbances. Studies suggest involvement of androgen metabolism, impaired methylation, and heavy metal toxicity as possible contributing factors for both disorders.

CONCLUSION

ASD and ADHD share a number of features and pathophysiological conditions, which suggests that the two disorders may be a continuum and have a common origin.

The use of omega-3 fatty acids in mental illness

PURPOSE

This article will summarize the current evidence on the effects of omega-3 fatty acids on prevention and treatment of mental illness.

BACKGROUND

Omega-3 fatty acids are involved in many physiologic processes. Since they cannot be made de novo in the body, they are considered essential nutrients. As the Western diet evolved, dietary intake of fatty acids has shifted to increased omega-6 fatty acids and decreased omega-3 fatty acids intake. These changes have been correlated with numerous differences in prevalence and course of mental illnesses.

METHODS

A MEDLINE search from 1966 to December 2010 was completed to identify studies comparing changes in symptoms, functioning, other outcomes, and/or side effects in patients treated with omega-3 fatty acids for mental illness. The studies were reviewed and reported by specific psychiatric disorder studied.

CONCLUSIONS

Omega-3 fatty acids play a role in many biologic functions. Epidemiologic data implicate omega-3 fatty acid deficiencies in many mental illnesses. Data are most robust for omega-3 fatty acids' role in affective disorders. However, data are conflicting, negative, or absent for most mental illnesses.

Significance of long-chain polyunsaturated fatty acids (PUFAs) for the development and behaviour of children

omega-6 and omega-3 polyunsaturated fatty acids (PUFAs) play a central role in the normal development and functioning of the brain and central nervous system. Long-chain PUFAs (LC-PUFAs) such as eicosapentaenoic acid (EPA, C20:5omega-3), docosahexaenoic acid (DHA, C22:6omega-3) and arachidonic acid (AA, C20:4omega-6), in particular, are involved in numerous neuronal processes, ranging from effects on membrane fluidity to gene expression regulation. Deficiencies and imbalances of these nutrients, not only during the developmental phase but throughout the whole life span, have significant effects on brain function. Numerous observational studies have shown a link between childhood developmental disorders and omega-6:omega-3 fatty acid imbalances. For instance, neurocognitive disorders such as attention-deficit hyperactivity disorder (ADHD), dyslexia, dyspraxia and autism spectrum disorders are often associated with a relative lack of omega-3 fatty acids. In addition to a high omega-6 fatty acid intake and, in many cases, an insufficient supply of omega-3 fatty acids among the population, evidence is increasing to suggest that PUFA metabolism can be impaired in individuals with ADHD. In this context, PUFA imbalances are being discussed as potential risk factors for neurodevelopmental disorders. Another focus is whether the nutritive PUFA requirements-especially long-chain omega-3 fatty acid requirements-are higher among some individuals. Meanwhile, several controlled studies investigated the clinical benefits of LC-PUFA supplementation in affected children and adolescents, with occasionally conflicting results.

Aetiology of idiopathic scoliosis: current concepts

The aetiology of the three-dimensional spinal deformity of idiopathic scoliosis (IS) is unknown. Progressive adolescent idiopathic scoliosis (AIS) that mainly affects girls is generally attributed to relative anterior spinal overgrowth from a mechanical mechanism (torsion) during the adolescent growth spurt. Established biological risk factors to AIS are growth velocity and potential residual spinal growth assessed by maturity indicators. Spine slenderness and ectomorphy in girls are thought to be risk factors for AIS. Claimed biomechanical susceptibilities are (1) a fixed lordotic area and hypokyphosis and (2) concave periapical rib overgrowth. MRI has revealed neuroanatomical abnormalities in approximately 20% of younger children with IS. A neuromuscular cause for AIS is probable but not established. Possible susceptibilities to AIS in tissues relate to muscles, ligaments, discs, skeletal proportions and asymmetries, the latter also affecting soft tissues (e.g. dermatoglyphics). AIS is generally considered to be multi-factorial in origin. The many anomalies detected, particularly left-right asymmetries, have led to spatiotemporal aetiologic concepts involving chronomics and the genome altered by nurture without the necessity for a disease process. Genetic susceptibilities defined in twins are being evaluated in family studies; polymorphisms in the oestrogen receptor gene are associated with curve severity. A neurodevelopmental concept is outlined for the aetiology of progressive AIS. This concept involves lipid peroxidation and, if substantiated, has initial therapeutic potential by dietary anti-oxidants. Growth saltations have not been evaluated in IS.

[The treatment of Attention-Deficit/Hyperactivity Disorders with polyunsaturated fatty acids - an effective treatment alternative?]

OBJECTIVES

Both omega-3 and omega-6 long-chain polyunsaturated fatty acids (PUFA) have a substantial impact on human brain development and function. However, in western industrial countries omega-3 LC-PUFA in particular are often lacking in diets. Increasing evidence indicates that LC-PUFA imbalance or deficiencies may be associated with Attention Deficit/Hyperactivity Disorder (ADHD) through involvement in the dopaminergic corico-striatal metabolism. Preliminary study result suggest that dietary supplementation with LC-PUFA might be effective in the treatment of ADHD.

METHODS

This review summarizes the knowledge in terms of a hypothesized pathogenetic relationship between fatty acid metabolism and ADHD and discusses the possible clinical benefit of a primary or combined treatment with LC-PUFA.

RESULTS

Actually it is unclear whether a deficit in intake or metabolism of LC-PUFA may play a major role in the pathogenesis of ADHD. Moreover treatment studies yielded conflicting results. A combination of Omega-3 and Omega-6 - fatty acids might attenuate the symptoms of ADHD significantly, thus making this dietary intake useful.

CONCLUSIONS

Considerable research has to be done in the future to identify ideal therapeutic combinations and dosages of various fatty acids, and to develop reliable ways of defining those individuals to benefit from this treatment access.

Endophenotype properties of niacin sensitivity as marker of impaired prostaglandin signalling in schizophrenia

BACKGROUND

Disruption of arachidonic acid pathways and prostaglandin signalling has been implicated in the pathophysiology of schizophrenia.

AIMS

We intended to study prostaglandin signalling in groups of young schizophrenia patients, first-degree relatives, and healthy controls in order to assess effects of heritability on this biological marker-one important endophenotype criterion.

METHOD

Namely, we assessed intensity of methylnicotinate skin flushing using optical reflection spectroscopy. Tests were applied to 19 adolescent first-episode schizophrenia patients, 21 first-degree relatives, and groups of age and gender matched healthy controls.

RESULTS

Compared to healthy controls, attenuation of skin flushing at low niacin concentrations was found only in schizophrenia patients, but not in first-degree relatives.

CONCLUSION

While our results indicate niacin hyposensitivity as reliable biological marker in schizophrenia, they do not provide clear evidence for its heritability. Particularly, the results in adolescent schizophrenia patients are suggestive for the perception of attenuated niacin flushing as secondary to the pathophysiology at the onset of schizophrenic illness, namely increased oxidative stress, alterations of unspecific immune-response or inflammation-like processes.

Long-chain polyunsaturated fatty acids in childhood developmental and psychiatric disorders

Both omega-3 and omega-6 long-chain PUFA (LC-PUFA) are crucial to brain development and function, but omega-3 LC-PUFA in particular are often lacking in modern diets in developed countries. Increasing evidence, reviewed here, indicates that LC-PUFA deficiencies or imbalances are associated with childhood developmental and psychiatric disorders including ADHD, dyslexia, dyspraxia, and autistic spectrum disorders. These conditions show a high clinical overlap and run in the same families, as well as showing associations with various adult psychiatric disorders in which FA abnormalities are already implicated, such as depression, other mood disorders, and schizophrenia. Preliminary evidence from controlled trials also suggests that dietary supplementation with LC-PUFA might help in the management of these kinds of childhood behavioral and learning difficulties. Treatment with omega-3 FA appears most promising, but the few small studies published to date have involved different populations, study designs, treatments, and outcome measures. Large-scale studies are now needed to confirm the benefits reported. Further research is also required to assess the durability of such treatment effects, to determine optimal treatment compositions and dosages, and to develop reliable ways of identifying those individuals most likely to benefit from this kind of treatment. Childhood developmental and psychiatric disorders clearly reflect multifactorial influences, but the study of LC-PUFA and their metabolism could offer important new approaches to their early identification and management. Heterogeneity and comorbidity are such, however, that a focus on specific traits or symptoms may prove more fruitful than an exclusive reliance on current diagnostic categories.

Essential fatty acids and phospholipase A2 in autistic spectrum disorders

A health questionnaire based on parental observations of clinical signs of fatty acid deficiency (FAD) showed that patients with autism and Asperger's syndrome (ASP) had significantly higher FAD scores (6.34+/-4.37 and 7.64+/-6.20, respectively) compared to controls (1.78+/-1.68). Patients with regressive autism had significantly higher percentages of 18:0,18:2n-6 and total saturates in their RBC membranes compared to controls, while 24:0, 22:5n-6, 24:1 and the 20:4n-6/20:5n-3 ratio were significantly higher in both regressive autism and ASP groups compared to controls. By comparison, the 18:1n-9 and 20:4n-6 values were significantly lower in patients with regressive autism compared to controls while 22:5n-3, total n-3 and total dimethyl acetals were significantly lower in both regressive autism and ASP groups compared to controls. Storage of RBC at -20 degrees C for 6 weeks resulted in significant reductions in highly unsaturated fatty acid levels in polar lipids of patients with regressive autism, compared to patients with classical autism or ASP, or controls. Patients diagnosed with both autism and ASP showed significantly increased levels of EPA ( approximately 200%) and DHA ( approximately 40%), and significantly reduced levels of ARA ( approximately 20%), 20:3n-6 and ARA/EPA ratio in their RBC polar lipids, when supplemented with EPA-rich fish oils, compared to controls and non-supplemented patients with autism. Patients with both regressive autism and classical autism/Asperger's syndrome had significantly higher concentrations of RBC type IV phospholipase A2 compared to controls. However, patients with autism/ASP, who had taken EPA supplements, had significantly reduced PLA2 concentrations compared to unsupplemented patients with classical autism or ASP.

Increased levels of ethane, a non-invasive marker of n-3 fatty acid oxidation, in breath of children with attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) comprises a range of behavioural problems including inattention, hyperactivity and impulsivity. Diagnosis and treatment of the disorder is made difficult due to its unknown biological basis. Several studies have identified abnormalities in membrane fatty acids in some subjects with ADHD, and some success has been reported using lipid therapies. We have measured exhalant ethane levels, a non-invasive measure of oxidative damage to n-3 fatty acids, to probe biochemical alterations in ADHD. Patients with ADHD (N = 10) had higher levels of ethane in exhalant than in healthy volunteers (N = 12) with approximately 50% of ADHD cases being above the control range. In contrast, levels of butane, a marker of protein oxidation, were unaltered. Our data, although preliminary, suggests that some patients with ADHD have higher rates of oxidative breakdown of n-3 polyunsaturated fatty acids (PUFAs). Such a biochemical abnormality may underlie the previously observed fatty acid deficiencies, as well as providing further rationale for the use of anti-oxidant and/or lipid supplementation therapy in the treatment of ADHD. Larger studies of ADHD using this non-invasive assessment of oxidative stress appear warranted.

Oxidative stress in Rett syndrome

The investigation of parameters that might influence the neurological evolution of Rett syndrome might also yield new information about its pathogenic mechanisms. Oxidative stress caused by oxygen free radicals is involved in the neuropathology of several neurodegenerative disorders, as well as in stroke and seizures. To evaluate the free radical metabolism in Rett syndrome, we measured red blood cell antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase) and plasma malondialdehyde, as lipid peroxidation marker in a group of patients with Rett syndrome. No significant differences were observed in erythrocyte glutathione peroxidase, glutathione reductase and catalase activities, between the Rett syndrome patients and the control group. Erythrocyte superoxide dismutase activities were significantly decreased in Rett syndrome patients (P<0.001) compared with the control group. Plasma malondialdehyde concentrations were significantly increased in Rett syndrome patients (P<0.001). An unbalanced nutritional status in Rett syndrome might explain the reduced enzyme activity found in these patients. Our results suggest that free radicals generated from oxidation reactions might contribute to the pathogenesis of Rett syndrome. The high levels of malondialdehyde reflect peroxidative damage of biomembranes that may contribute to progressive dementia, impaired motor function, behavioural changes, and seizures, in Rett syndrome. We found a probable relationship between the degree of oxidative stress and the severity of symptoms, which should be further investigated with a larger number of patients in different disease stages.

Fatty acid metabolism in neurodevelopmental disorder: a new perspective on associations between attention-deficit/hyperactivity disorder, dyslexia, dyspraxia and the autistic spectrum

There is increasing evidence that abnormalities of fatty acid and membrane phospholipid metabolism play a part in a wide range of neurodevelopmental and psychiatric disorders. This proposal is discussed here in relation to attention-deficit/hyperactivity disorder (ADHD), dyslexia, developmental coordination disorder (dyspraxia) and the autistic spectrum. These are among the most common neurodevelopmental disorders of childhood, with significant implications for society as well as for those directly affected. However, controversy still surrounds both the identification and management of these conditions, and while their aetiology is recognized as being complex and multifactorial, little progress has yet been made in elucidating predisposing factors at the biological level. An overview is provided here of the contents of this Special Issue, which contains a selection of reports from a unique multidisciplinary workshop involving both researchers and clinicians. Its purpose was to explore the possibility that ADHD, dyslexia, dyspraxia and autism fall within a phospholipid spectrum of disorders. This proposal could explain the high degree of co-morbidity between these conditions, their aggregation within families and relation to other psychiatric disorders, and a range of associated features that are already well known at a clinical level. The existing evidence for fatty acid abnormalities in these disorders is summarized, and new approaches are outlined that have the potential to improve both the identification and the management of these and related neurodevelopmental and psychiatric conditions.

Potential diagnostic aids for abnormal fatty acid metabolism in a range of neurodevelopmental disorders

Disorders of neurodevelopment include attention deficit hyperactivity disorder, dyspraxia, dyslexia and autism. There is considerable co-morbidity of these disorders and their identification often presents difficulties to those making a diagnosis. This is especially difficult when a multidisciplinary approach is not adopted. All of these disorders have been reported as associated with fatty acid abnormalities ranging from genetic abnormalities in the enzymes involved in phospholipid metabolism to symptoms reportedly improved following dietary supplementation with long chain fatty acids. If definitive disorders of lipid metabolism could be defined then the diagnosis and subsequent management of neurodevelopmental disorders might be transformed. In the identification of those disorders of development which involve lipid metabolism, there are now several tests, measures of lipid metabolism, which could be useful.