The positive association between elevated blood lead levels and brain-specific autoantibodies in autistic children from low lead-polluted areas

Lead contamination in human milk affects infants' language trajectory: results from a prospective cohort study

Infants growing up in low- and middle-income countries are at increased risk of suffering adverse childhood experiences, including exposure to environmental pollution and lack of cognitive stimulation. In this study, we aimed to examine the levels of metals in the human milk of women living in São Paulo City, Brazil, and determine the effects on infants' neurodevelopment. For such, a total of 185 human milk samples were analyzed for arsenic (As), lead (Pb), mercury (Hg), and cadmium (Cd) using inductively coupled plasma mass spectrometry (ICP-MS). We applied the Bayley scales of infant and toddler development Third Edition (Bayley-III) to assess developmental milestones. In our analysis, we found a mean (standard deviation) concentration of As in human milk equal to 2.76 (4.09) μg L-1, followed by Pb 2.09 (5.36) and Hg 1.96 (6.68). Cd was not detected. We observed that infants exposed to Pb presented language trajectories lower than non-exposed infants (β = -0.413; 95% CI -0.653, -0.173) after adjustment for infant age, maternal education, socioeconomic status, infant sex, and sample weights. Our results report As, Pb, and Hg contamination in human milk, and that infant exposure to Pb decreased infants' language development. These results evidence maternal-child environmental exposure and its detrimental impact on infants' health.

Environmental Risk Factors in Autism Spectrum Disorder: A Narrative Review

Existing evidence indicates that environmental factors might contribute up to 50% of the variance in autism spectrum disorder (ASD) risk. This structured narrative review offers a comprehensive synthesis of current knowledge on environmental risk factors in ASD, including evaluation of conflicting evidence, exploration of underlying mechanisms, and suggestions for future research directions. Analysis of diverse epidemiological investigations indicates that certain environmental factors, including advanced parental age, preterm birth, delivery complications, and exposure to toxic metals, drugs, air pollutants, and endocrine-disrupting chemicals, are linked to an increased ASD risk through various mechanisms such as oxidative stress, inflammation, hypoxia, and its consequences, changes in neurotransmitters, disruption of signaling pathways and some others. On the other hand, pregnancy-related factors such as maternal diabetes, maternal obesity, and caesarian section show a weaker association with ASD risk. At the same time, other environmental factors, such as vaccination, maternal smoking, or alcohol consumption, are not linked to the risk of ASD. Regarding nutritional elements data are inconclusive. These findings highlight the significance of environmental factors in ASD etiology and emphasize that more focused research is needed to target the risk factors of ASD. Environmental interventions targeting modifiable risk factors might offer promising avenues for ASD prevention and treatment.

Early-Life Lead Exposure: Risks and Neurotoxic Consequences

BACKGROUND

Lead (Pb) does not have any biological function in a human, and it is likely no safe level of Pb in the human body. The Pb exposure impacts are a global concern for their potential neurotoxic consequences. Despite decreasing both the environmental Pb levels and the average blood Pb levels in the survey populations, the lifetime redistribution from the tissues-stored Pb still poses neurotoxic risks from the low-level exposure in later life. The growing fetus and children hold their innate high-susceptible to these Pb-induced neurodevelopmental and neurobehavioral effects.

OBJECTIVE

This article aims to evaluate cumulative studies and insights on the topic of Pb neurotoxicology while assessing the emerging trends in the field.

RESULTS

The Pb-induced neurochemical and neuro-immunological mechanisms are likely responsible for the high-level Pb exposure with the neurodevelopmental and neurobehavioral impacts at the initial stages. Early-life Pb exposure can still produce neurodegenerative consequences in later life due to the altered epigenetic imprints and the ongoing endogenous Pb exposure. Several mechanisms contribute to the Pb-induced neurotoxic impacts, including the direct neurochemical effects, the induction of oxidative stress and inflammation through immunologic activations, and epigenetic alterations. Furthermore, the individual nutritional status, such as macro-, micro-, or antioxidant nutrients, can significantly influence the neurotoxic impacts even at low-level exposure to Pb.

CONCLUSION

The prevention of early-life Pb exposure is, therefore, the critical determinant for alleviating various Pb-induced neurotoxic impacts across the different age groups.

High-throughput autoantibody screening identifies differentially abundant autoantibodies in autism spectrum disorder

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by defects in two core domains, social/communication skills and restricted/repetitive behaviors or interests. There is no approved biomarker for ASD diagnosis, and the current diagnostic method is based on clinical manifestation, which tends to vary vastly between the affected individuals due to the heterogeneous nature of ASD. There is emerging evidence that supports the implication of the immune system in ASD, specifically autoimmunity; however, the role of autoantibodies in ASD children is not yet fully understood.

Materials and methods

In this study, we screened serum samples from 93 cases with ASD and 28 healthy controls utilizing high-throughput KoRectly Expressed (KREX) i-Ome protein-array technology. Our goal was to identify autoantibodies with differential expressions in ASD and to gain insights into the biological significance of these autoantibodies in the context of ASD pathogenesis.

Result

Our autoantibody expression analysis identified 29 differential autoantibodies in ASD, 4 of which were upregulated and 25 downregulated. Subsequently, gene ontology (GO) and network analysis showed that the proteins of these autoantibodies are expressed in the brain and involved in axonal guidance, chromatin binding, and multiple metabolic pathways. Correlation analysis revealed that these autoantibodies negatively correlate with the age of ASD subjects.

Conclusion

This study explored autoantibody reactivity against self-antigens in ASD individuals' serum using a high-throughput assay. The identified autoantibodies were reactive against proteins involved in axonal guidance, synaptic function, amino acid metabolism, fatty acid metabolism, and chromatin binding.

Consequences of Disturbing Manganese Homeostasis

Manganese (Mn) is an essential trace element with unique functions in the body; it acts as a cofactor for many enzymes involved in energy metabolism, the endogenous antioxidant enzyme systems, neurotransmitter production, and the regulation of reproductive hormones. However, overexposure to Mn is toxic, particularly to the central nervous system (CNS) due to it causing the progressive destruction of nerve cells. Exposure to manganese is widespread and occurs by inhalation, ingestion, or dermal contact. Associations have been observed between Mn accumulation and neurodegenerative diseases such as manganism, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. People with genetic diseases associated with a mutation in the gene associated with impaired Mn excretion, kidney disease, iron deficiency, or a vegetarian diet are at particular risk of excessive exposure to Mn. This review has collected data on the current knowledge of the source of Mn exposure, the experimental data supporting the dispersive accumulation of Mn in the brain, the controversies surrounding the reference values of biomarkers related to Mn status in different matrices, and the competitiveness of Mn with other metals, such as iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), calcium (Ca). The disturbed homeostasis of Mn in the body has been connected with susceptibility to neurodegenerative diseases, fertility, and infectious diseases. The current evidence on the involvement of Mn in metabolic diseases, such as type 2 diabetes mellitus/insulin resistance, osteoporosis, obesity, atherosclerosis, and non-alcoholic fatty liver disease, was collected and discussed.

Association Between Biological Lead Concentrations and Autism Spectrum Disorder (ASD) in Children: a Systematic Review and Meta-Analysis

Studies have been conducted in different countries of the world to illustrate a link between autism spectrum disorder (ASD) and lead (Pb) in different specimens such as hair, blood, and urine. Therefore, we carried out a systematic review and meta-analysis to determine the association between Pb concentration in biological samples (blood, urine, and hair) and ASD in children through case-control and cross-sectional studies. In this systematic review, PubMed, Web of Sciences, Scopus, and Google Scholar were searched for relevant studies from January 2000 to February 2022. A random-effects model was used to pool the results. The effect sizes were standardized mean differences (proxied by Hedges' g) followed by a 95% confidence interval. Pooling data under the random effect model from blood and hair studies showed a significant difference between the children in the ASD group and the control group in blood lead level (Hedges' g: 1.21, 95% CI: 0.33-2.09, P = 0.01) and hair level (Hedges' g: 2.20, 95% CI: 0.56-3.85, P = 0.01). For urine studies, pooling data under the random effect model from eight studies indicated no significant difference between the children in the ASD group and control group in urinary lead level (Hedges' g: - 0.34, 95% CI: - 1.14,0.45, P = 0.40). Moreover, the funnel plot and the results of the Egger test for the blood and urine samples showed no publication bias, while, for the hair samples, the funnel plot illustrated the existence of publication bias.

Sodium Para-Aminosalicylic Acid Modulates Autophagy to Lessen Lead-Induced Neurodegeneration in Rat Cortex

Lead (Pb) is a common heavy metal contaminant in the environment, and it may perturb autophagy and cause neurodegeneration. Although sodium para-aminosalicylic (PAS-Na) has been shown to protect the brain from lead-induced toxicity, the mechanisms associated with its efficacy have yet to be fully understood. In this study, we evaluated the efficacy of PAS-Na in attenuating the neurotoxic effects of lead, as well as the specific mechanisms that mediate such protection. Lead exposure resulted in weight loss and injury to the liver and kidney, and PAS-Na had a protective effect against this damage. Both short-term and subchronic lead exposure impaired learning ability, and this effect was reversed by PAS-Na intervention. Lead exposure also perturbed autophagic processes through the modulation of autophagy-related factors. Short-term lead exposure downregulated LC3 and beclin1 and upregulated the expression of p62; subchronic lead exposure upregulated the expression of LC3, beclin1, and P62. It follows that PAS-Na had an antagonistic effect on the activation of the above autophagy-related factors. Overall, our novel findings suggest that PAS-Na can protect the rat cortex from lead-induced toxicity by regulating autophagic processes. (1) Short-term lead exposure inhibits autophagy, whereas subchronic lead exposure promotes autophagy. (2) PAS-NA ameliorated the abnormal process of lead-induced autophagy, which had a protective effect on the cerebral cortex.

A systematic literature review on the association between exposures to toxic elements and an autism spectrum disorder

BACKGROUND AND AIM

Autism spectrum disorder (ASD) is a neurodevelopmental illness characterized by difficulties in social communication and repetitive behaviors. There have been many previous studies of toxic metals in ASD. Therefore, the priority of this study is to review the relationships between exposure to toxic metals and ASD.

MATERIALS & METHODS

This study was based on a comprehensive search of international databases, such as Web of Science, Science Direct, Scopus, PubMed, and Google Scholar, for all works related to the subject under discussion from 1982 to 2022. We further summarize published data linked to this topic and discuss with clarifying evidence that agrees and conflicts with the association between exposure to toxic metals, including mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), and aluminum (Al) and ASD.

RESULTS

40 out of 63 papers met the requirements for meta-analysis. Blood Pb levels (standardized mean difference (SMD) = 0.81; 95 % confidence interval (CI): 0.36-1.25), blood Hg (SMD = 0.90; CI: 0.30-1.49), hair Pb (SMD = 1.47; CI: 0.03-2.92), urine As (SMD = 0.65; CI: 0.22-1.09), and urine Al levels (SMD = 0.85; CI: 0.40-1.29) in autistic individuals were significantly higher than those of healthy control (HC). Whereas, blood As levels (SMD = 1.33; CI: -1.32-3.97), hair As (SMD = 0.55; CI: -0.14-1.24), hair Cd (SMD = 0.60; CI: -0.31-1.51), hair Hg (SMD = 0.41; CI: -0.30-1.12), hair Al (SMD = 0.87; CI: -0.02-1.77), urine Pb (SMD = -0.68; CI: -2.55-1.20), urine Cd (SMD = -0.26; CI: -0.94-0.41), and urine Hg levels (SMD = 0.47; CI: -0.09-1.04) in autistic individuals were significantly lower than those of HC.

CONCLUSION

Toxic metal content significantly differed between individuals with ASD and HC in the current meta-analysis. The results assist in clarifying the significance of toxic metals as environmental factors in the development of ASD.

Trace Element Changes in the Plasma of Autism Spectrum Disorder Children and the Positive Correlation Between Chromium and Vanadium

Existing data demonstrate a significant correlation between autism spectrum disorder (ASD) and the status of biologically essential and toxic trace elements. However, there is still a lack of data on the steady state of trace elements in ASD. We performed a case-control study to explore the association between the risk of ASD and 23 trace elements in plasma. The results showed that children with ASD had considerably decreased lithium (Li), manganese (Mn), selenium (Se), barium (Ba), mercury (Hg), and tin (Sn) levels when compared to their age- and sex-matched controls. Meanwhile, children with ASD had considerably increased plasma chromium (Cr) and vanadium (V) concentrations. We also divided each group into subgroups based on age and gender and created element-related networks for each subgroup. We detected significant element correlations within or between subgroups, as well as changes in correlations that included all elements examined. Finally, more element correlations were observed among males, which may open a new avenue for understanding the complicated process behind the sex ratio of children with ASD. Overall, our data revealed a novel relationship between elements and ASD, which may extend current understanding about ASD.

A case-control study on the relationship between urine trace element levels and autism spectrum disorder among Iranian children

Autism spectrum disorder (ASD) is a type of neurodevelopmental disorder characterized mainly by qualitative deficiencies in social communication skills, accompanied by repetitive and restricted behavior patterns. This study was conducted to investigate the associations between the risk of ASD development in children and exposure to trace elements (arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn)). Two groups of children, including 44 ASD and 35 typically developing (TD) children, were selected, and their fasting urine samples were obtained. The concentration levels of trace elements were assayed using ICP-MS. The results showed that as compared to the TD group, the concentration levels of As (p = 0.002) and Pb (p < 0.001) and also Cr (p < 0.001), Cu (p = 0.001), and Ni (p < 0.001) were significantly higher among ASD children. In terms of gender, boys with ASD showed elevated levels of Cr, Cu, Ni, and Pb, whereas the urine levels of As, Cr, Cu, Ni, and Pb were markedly higher among girls when compared to the non-ASD children. Under the logistic regression model, the risk difference for As, Co, Cr, Cu, Ni, Pb, and Zn remained significant when adjustment was applied for age and gender confounders.

Autism-like symptoms by exposure to air pollution and valproic acid-induced in male rats

Exposure to air pollution during prenatal or neonatal periods is associated with autism spectrum disorder (ASD) according to epidemiology studies. Furthermore, prenatal exposure to valproic acid (VPA) has also been found to be associated with an increased prevalence of ASD. To assess the association between simultaneous exposure to VPA and air pollutants, seven exposure groups of rats were included in current study (PM2.5 and gaseous pollutants exposed - high dose of VPA (PGE-high); PM2.5 and gaseous pollutants exposed - low dose of VPA (PGE-low); gaseous pollutants only exposed - high dose of VPA (GE-high); gaseous pollutants only exposed - low dose of VPA (GE-low); clean air exposed - high dose of VPA (CAE-high); clean air exposed - low dose of VPA (CAE-low) and clean air exposed (CAE)). The pollution-exposed rats were exposed to air pollutants from embryonic day (E0) to postnatal day 42 (PND42). In all the induced groups, decreased oxidative stress biomarkers, decreased oxytocin receptor (OXTR) levels, and increased the expression of interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor alpha (TNF-α) were found. The volumes of the cerebellum, hippocampus, striatum, and prefrontal decreased in all induced groups in comparison to CAE. Additionally, increased numerical density of glial cells and decreased of numerical density of neurons were found in all induced groups. Results show that simultaneous exposure to air pollution and VPA can cause ASD-related behavioral deficits and air pollution reinforced the mechanism of inducing ASD ̉s in VPA-induced rat model of autism.

Non-parental caregivers, low maternal education, gastrointestinal problems and high blood lead level: predictors related to the severity of autism spectrum disorder in Northeast China

Background

The prevalence of autism spectrum disorder (ASD) has increased rapidly in recent years. Environmental factors may play an important role in the pathogenesis of ASD. These factors may include socioeconomic factors, nutritional factors, heavy metal exposure, air pollution, etc. Our aim is to analyze possible environmental factors associated with the severity of ASD.

Methods

All participating children were divided into two groups (mild and moderate/severe) according to the severity of their symptoms, as determined by their Childhood Autism Rating Scale (CARS) scores. The socioeconomic, demographic factors and the nutritional factors that may affect the severity of ASD were included in the logistic regression to analyze whether they were predictors that affected the severity of ASD.

Results

Logistic regression showed that caregivers(P = 0.042), maternal education (P = 0.030), gastrointestinal problems (P = 0.041) and a high serum concentration of lead (P = 0.003) were statistically significantly associated with ASD severity.

Conclusion

Many environmental factors affect the severity of ASD. We concluded that non-parental caregivers, low maternal education, gastrointestinal problems and high blood lead level maybe predictors that affected the severity of ASD in northeast China.

Autism spectrum disorder: Trace elements imbalances and the pathogenesis and severity of autistic symptoms

The identification of biomarkers as diagnostic tools and predictors of response to treatment of neurological developmental disorders (NDD) such as schizophrenia (SZ), attention deficit hyperactivity disorder (ADHD), or autism spectrum disorder (ASD), still remains an important challenge for clinical medicine. Metallomic profiles of ASD patients cover, besides essential elements such as cobalt, chromium, copper, iron, manganese, molybdenum, zinc, selenium, also toxic metals burden of: aluminum, arsenic, mercury, lead, beryllium, nickel, cadmium. Performed studies indicate that children with ASD present a reduced ability of eliminating toxic metals, which leads to these metals' accumulation and aggravation of autistic symptoms. Extensive metallomic studies allow a better understanding of the importance of trace elements as environmental factors in the pathogenesis of ASD. Even though a mineral imbalance is a fact in ASD, we are still expecting relevant tests and the elaboration of reference levels of trace elements as potential biomarkers useful in diagnosis, prevention, and treatment of ASD.

Role of metallic pollutants in neurodegeneration: effects of aluminum, lead, mercury, and arsenic in mediating brain impairment events and autism spectrum disorder

Autism spectrum disorder (ASD) is a developmental disorder of the brain characterized by shortfall in the social portfolio of an individual and abbreviated interactive and communication aspects rendering stereotypical behavior and pitfalls in a child's memory, thinking, and learning capabilities. The incidence of ASD has accelerated since the past decade, portraying environment as one of the primary assets, comprising of metallic components aiming to curb the neurodevelopmental pathways in an individual. Many regulations like Clean Air Act and critical steps taken by countries all over the globe, like Sweden and the USA, have rendered the necessity to study the effects of environmental metallic components on ASD progression. The review focuses on the primary metallic components present in the environment (aluminum, lead, mercury, and arsenic), responsible for accelerating ASD symptoms by a set of general mechanisms like oxidative stress reduction, glycolysis suppression, microglial activation, and metalloprotein disruption, resulting in apoptotic signaling, neurotoxic effects, and neuroinflammatory responses. The effect of these metals can be retarded by certain protective strategies like chelation, dietary correction, certain agents (curcumin, mangiferin, selenium), and detoxification enhancement, which can necessarily halt the neurodegenerative effects.

Oxidative Stress in Autism Spectrum Disorder

According to the United States Centers for Disease Control and Prevention (CDC), as of July 11, 2016, the reported average incidence of children diagnosed with an autism spectrum disorder (ASD) was 1 in 68 (1.46%) among 8-year-old children born in 2004 and living within the 11 monitoring sites' surveillance areas in the United States of America (USA) in 2012. ASD is a multifaceted neurodevelopmental disorder that is also considered a hidden disability, as, for the most part; there are no apparent morphological differences between children with ASD and typically developing children. ASD is diagnosed based upon a triad of features including impairment in socialization, impairment in language, and repetitive and stereotypic behaviors. The increasing incidence of ASD in the pediatric population and the lack of successful curative therapies make ASD one of the most challenging disorders for medicine. ASD neurobiology is thought to be associated with oxidative stress, as shown by increased levels of reactive oxygen species and increased lipid peroxidation, as well as an increase in other indicators of oxidative stress. Children with ASD diagnosis are considered more vulnerable to oxidative stress because of their imbalance in intracellular and extracellular glutathione levels and decreased glutathione reserve capacity. Several studies have suggested that the redox imbalance and oxidative stress are integral parts of ASD pathophysiology. As such, early assessment and treatment of antioxidant status may result in a better prognosis as it could decrease the oxidative stress in the brain before it can induce more irreversible brain damage. In this review, many aspects of the role of oxidative stress in ASD are discussed, taking into account that the process of oxidative stress may be a target for therapeutic interventions.

Antigenic Targets of Patient and Maternal Autoantibodies in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder whose behavioral symptoms become apparent in early childhood. The underlying pathophysiological mechanisms are only partially understood and the clinical manifestations are heterogeneous in nature, which poses a major challenge for diagnosis, prognosis and intervention. In the last years, an important role of a dysregulated immune system in ASD has emerged, but the mechanisms connecting this to a disruption of brain development are still largely unknown. Although ASD is not considered as a typical autoimmune disease, self-reactive antibodies or autoantibodies against a wide variety of targets have been found in a subset of ASD patients. In addition, autoantibodies reactive to fetal brain proteins have also been described in the prenatal stage of neurodevelopment, where they can be transferred from the mother to the fetus by transplacental transport. In this review, we give an extensive overview of the antibodies described in ASD according to their target antigens, their different origins, and timing of exposure during neurodevelopment.

Toxic metal(loid)-based pollutants and their possible role in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social interaction, verbal and non-verbal communication, and stereotypic behaviors. Many studies support a significant relationship between many different environmental factors in ASD etiology. These factors include increased daily exposure to various toxic metal-based environmental pollutants, which represent a cause for concern in public health. This article reviews the most relevant toxic metals, commonly found, environmental pollutants, i.e., lead (Pb), mercury (Hg), aluminum (Al), and the metalloid arsenic (As). Additionally, it discusses how pollutants can be a possible pathogenetic cause of ASD through various mechanisms including neuroinflammation in different regions of the brain, fundamentally occurring through elevation of the proinflammatory profile of cytokines and aberrant expression of nuclear factor kappa B (NF-κB). Due to the worldwide increase in toxic environmental pollution, studies on the role of pollutants in neurodevelopmental disorders, including direct effects on the developing brain and the subjects' genetic susceptibility and polymorphism, are of utmost importance to achieve the best therapeutic approach and preventive strategies.

Blood Mercury, Arsenic, Cadmium, and Lead in Children with Autism Spectrum Disorder

Environmental factors have been implicated in the etiology of autism spectrum disorder (ASD); however, the role of heavy metals has not been fully defined. This study investigated whether blood levels of mercury, arsenic, cadmium, and lead of children with ASD significantly differ from those of age- and sex-matched controls. One hundred eighty unrelated children with ASD and 184 healthy controls were recruited. Data showed that the children with ASD had significantly (p < 0.001) higher levels of mercury and arsenic and a lower level of cadmium. The levels of lead did not differ significantly between the groups. The results of this study are consistent with numerous previous studies, supporting an important role for heavy metal exposure, particularly mercury, in the etiology of ASD. It is desirable to continue future research into the relationship between ASD and heavy metal exposure.

Systematic review and meta-analysis links autism and toxic metals and highlights the impact of country development status: Higher blood and erythrocyte levels for mercury and lead, and higher hair antimony, cadmium, lead, and mercury

BACKGROUND

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder that affects cognitive and higher cognitive functions. Increasing prevalence of ASD and high rates of related comorbidities has caused serious health loss and placed an onerous burden on the supporting families, caregivers, and health care services. Heavy metals are among environmental factors that may contribute to ASD. However, due to inconsistencies across studies, it is still hard to explain the association between ASD and toxic metals. Therefore the objective of this study was to investigate the difference in heavy metal measures between patients with ASD and control subjects.

METHODS

We included observational studies that measured levels of toxic metals (antimony, arsenic, cadmium, lead, manganese, mercury, nickel, silver, and thallium) in different specimens (whole blood, plasma, serum, red cells, hair and urine) for patients with ASD and for controls. The main electronic medical database (PubMed and Scopus) were searched from inception through October 2016.

RESULTS

52 studies were eligible to be included in the present systematic review, of which 48 studies were included in the meta-analyses. The hair concentrations of antimony (standardized mean difference (SMD)=0.24; 95% confidence interval (CI): 0.03 to 0.45) and lead (SMD=0.60; 95% confidence interval (CI): 0.17 to 1.03) in ASD patients were significantly higher than those of control subjects. ASD patients had higher erythrocyte levels of lead (SMD=1.55, CI: 0.2 to 2.89) and mercury (SMD=1.56, CI: 0.42 to 2.70). There were significantly higher blood lead levels in ASD patients (SMD=0.43, CI: 0.02 to 0.85). Sensitivity analyses showed that ASD patients in developed but not in developing countries have lower hair concentrations of cadmium (SMD=-0.29, CI: -0.46 to -0.12). Also, such analyses indicated that ASD patients in developing but not in developed lands have higher hair concentrations of lead (SMD=1.58, CI: 0.80 to 2.36) and mercury (SMD=0.77, CI: 0.31 to 1.23). These findings were confirmed by meta-regression analyses indicating that development status of countries significantly influences the overall effect size of mean difference for hair arsenic, cadmium, lead, and mercury between patients with ASD and controls.

CONCLUSION

The findings help highlighting the role of toxic metals as environmental factors in the etiology of ASD, especially in developing lands. While there are environmental factors other than toxic metals that greatly contribute to the etiology of ASD in developed lands. It would be, thus, expected that classification of ASD includes etiological entities of ASD on the basis of implication of industrial pollutants (developed vs. developing ASD).

Assessment of gender and age effects on serum and hair trace element levels in children with autism spectrum disorder

The primary objective of the present study was to investigate the levels of essential trace elements in hair and serum in children with autism spectrum disorder (ASD) and investigate the age and gender effects. Children with ASD were characterized by significantly higher levels of copper (Cu) (+8%), iron (Fe) (+5%), and selenium (Se) (+13%) levels in hair and only 8% higher serum Cu levels. After stratification for gender, ASD boys were characterized by significantly increased hair Cu (+ 25%), Fe (+ 25%), and Se (+ 9%) levels, whereas in girls only Se content was elevated (+ 15%). Boys and girls suffering from ASD were characterized by significantly higher serum manganese (Mn) (+20%) and Cu (+18%) as compared to the control values, respectively. In the group of younger children (2-5 years), no significant group difference in hair trace element levels was detected, whereas serum Cu levels were significantly higher (+7%). In turn, the serum concentration of Se in ASD children was 11% lower than that in neurotypical children. In the group of older children with ASD (6-10 years), hair Fe and Se levels were 21% and 16% higher, whereas in serum only Cu levels were increased (+12%) as compared to the controls. Correlation analysis also revealed a different relationship between serum and hair trace element levels with respect to gender and age. Therefore, it is highly recommended to assess several bioindicative matrices for critical evaluation of trace element status in patients with ASD in order to develop adequate personalized nutritional correction.

Relationship between selenium, lead, and mercury in red blood cells of Saudi autistic children

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that can cause significant social, communication and behavioral challenges. Environmental contribution to ASD is due in large part to the sensitivity of the developing brain to external exposures such as lead (Pb), and mercury (Hg) as toxic heavy metals or due to a poor detoxification ability as the phenotype of this disorder. Selenium (Se) as an antioxidant element that counteracts the neurotoxicity of Hg, and Pb, presumably through the formation of nontoxic complexes. In the present study, Pb, Hg, and Se were measured in red blood cells (RBCs) of 35 children with ASD and 30 age- and gender-matched healthy control children using atomic absorption spectrometry. Receiver Operating Characteristics (ROC) analysis of the obtained data was performed to measure the predictive value of their absolute and relative concentrations. The obtained data demonstrates a significant elevation of Hg and Pb together with a significant decrease in the Se levels in RBCs of patients with ASD when compared to the healthy controls. The ratios of Se to both Pb and Hg were remarkably altered, being indicative of heavy metal neurotoxicity in patients with ASD. In conclusion, the present study indicates the importance of Se for prevention and/or therapy of heavy metal neurotoxicity.

Early-Life Exposure to Lead Induces Cognitive Impairment in Elder Mice Targeting SIRT1 Phosphorylation and Oxidative Alterations

Pb is a potential risk factor for cognition, mainly mediated by enhanced oxidative stress. Resveratrol, a natural polyphenol with crucial anti-oxidative property, is recently implicated in preventing cognitive deficits in normal aging and neurodegenerative disorders. Its beneficial effects have been linked to sirtuin 1(SIRT1) activation. The aim of this work is to investigate the possible linkage between alterations in Pb-induced oxidative damage and cognitive impairment by prolonged treatment of resveratrol. Male C57BL/6 mice were given Pb(Ac)₂ treatment or deionized H₂O for 12 weeks, and subjected to resveratrol gavage at the dose of 50 mg/kgBw•d or vehicle after Pb exposure. Results from biochemical analysis and immunohistofluorescence showed that Pb induced oxidative DNA damage and decreased cortical antioxidant biomarker. As expected, these abnormalities were improved by resveratrol treatment. Morris water maze test, Western blotting, immunohistofluorescence staining and RT-qPCR indicated that resveratrol ameliorated spatial learning and memory deficits with alterations in hippocampal BDNF-TrkB signaling, promoted nuclear localization and phosphorylation of hippocampal SIRT1, partly increased protein levels of AMPK and PGC-1α involving in modulation of antioxidant response in Pb-exposed mice. Our results support the hypothesis that resveratrol could attenuate Pb-induced cognitive impairment which was associated with activating SIRT1 via modulation of oxidative stress. Additionally, resveratrol also repressed the Pb-induce amyloidogenic processing with resultant decline in cortical Aβ₁₋₋₄₀. Noteworthy, such effects were not mediated by resveratrol treatment alone. These findings emphasize the potential of SIRT1 activator as an efficacious dietary intervention to downgrade the Pb-induced neurotoxic lesion.

Altered urinary porphyrins and mercury exposure as biomarkers for autism severity in Egyptian children with autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that affects social, communication, and behavioral development. Recent evidence supported but also questioned the hypothetical role of compounds containing mercury (Hg) as contributors to the development of ASD. Specific alterations in the urinary excretion of porphyrin-containing ring catabolites have been associated with exposure to Hg in ASD patients. In the present study, the level of urinary porphyrins, as biomarkers of Hg toxicity in children with ASD, was evaluated, and its correlation with severity of the autistic behavior further explored. A total of 100 children was enrolled in the present study. They were classified into three groups: children with ASD (40), healthy controls (40), and healthy siblings of the ASD children (20). Children with ASD were diagnosed using DSM-IV-TR, ADI-R, and CARS tests. Urinary porphyrins were evaluated within the three groups using high-performance liquid chromatography (HPLC), after plasma evaluation of mercury (Hg) and lead (Pb) in the same groups. Results showed that children with ASD had significantly higher levels of Hg, Pb, and the porphyrins pentacarboxyporphyrin, coproporphyrin, precoproporphyrin, uroporphyrins, and hexacarboxyporphyrin compared to healthy controls and healthy siblings of the ASD children. However, there was no significant statistical difference in the level of heptacarboxyporphyrin among the three groups, while a significant positive correlation between the levels of coproporphyrin and precoproporphyrin and autism severity was observed. Mothers of ASD children showed a higher percentage of dental amalgam restorations compared to the mothers of healthy controls suggesting that high Hg levels in children with ASD may relate to the increased exposure to Hg from maternal dental amalgam during pregnancy and lactation. The results showed that the ASD children in the present study had increased blood Hg and Pb levels compared with healthy control children indicating that disordered porphyrin metabolism might interfere with the pathology associated with the autistic neurologic phenotype. The present study indicates that coproporphyrin and precoproporhyrin may be utilized as possible biomarkers for heavy metal exposure and autism severity in children with ASD.