Analysis of Copper and Zinc Plasma Concentration and the Efficacy of Zinc Therapy in Individuals with Asperger's Syndrome, Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) and Autism

Zinc Status and Autism Spectrum Disorder in Children and Adolescents: A Systematic Review

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder, the prevalence of which has increased in children and adolescents over the years. Studies point to deficiency of trace elements as one of the factors involved in the etiology of the disorder, with zinc being one of the main trace elements investigated in individuals with ASD. The aim of this review is to summarize scientific evidence about the relationship between zinc status and ASD in children and adolescents. This review has been registered in the International Prospective Register of Systematic Reviews (registration number CRD42020157907). The methodological guidelines adopted were in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Studies were selected from an active investigation of the PubMed, Scopus, LILACS, and Google databases to search for observational studies. Fifty-two studies from twenty-two countries were included. The sample sizes ranged from 20 to 2635, and the participants ranged from 2 to 18 years old. Nine types of biological matrices were used, with hair, serum, and plasma being the most frequently used in the evaluation of zinc concentrations. Significant differences in zinc concentrations between the ASD and control groups were observed in 23 studies, of which 19 (36%) showed lower zinc concentrations in the ASD group. The classification of studies according to methodological quality resulted in high, moderate, and low quality in 10, 21, and 21 studies, respectively. In general, we did not observe a significant difference between zinc concentrations of children and adolescents with ASD compared to controls; however, studies point to an occurrence of lower concentrations of Zn in individuals with ASD. This review reveals that more prospective studies with greater methodological rigor should be conducted in order to further characterize this relation.

Plasma zinc, copper and serum ceruloplasmin levels of autism spectrum disorder children in Bangladesh

Neural and cognitive processes require zinc and copper homeostasis and a normal zinc/copper ratio. Ceruloplasmin, an intrinsic antioxidant protein, maintains copper homeostasis, which might also influence autism spectrum disorder (ASD). ASD children are frequently reported with altered levels of these elements with wide geographical variations. This study evaluated any alteration in plasma zinc, copper, zinc/copper ratio and serum ceruloplasmin levels in Bangladeshi ASD children with respect to healthy controls. A cross-sectional study was conducted on 67 children aged 2 to 9 years of both sexes. Among them, 35 had ASD, while 32 were age, sex and body mass index (BMI) matched apparently healthy children. Plasma zinc and copper levels were estimated by the flame atomic absorption spectrophotometry method. Serum ceruloplasmin levels were estimated by the immunoturbidimetric method. Zinc and zinc/copper ratio in the 2-9 years old ASD children group were significantly lower (p=0.032 and p=0.002 respectively). On the other hand, copper (p=0.020) and ceruloplasmin (p = 0.045) levels were significantly higher than those of apparently healthy children. ASD was significantly associated with zinc deficiency (p=0.000) and copper toxicity (p=0.05). All children were again divided into 2-5 and 6-9 years age groups according to laboratory reference values for zinc and copper. Copper toxicity was significantly associated with ASD in the 2-5 years old age group (p=0.011), with a significant difference in plasma copper levels (p=0.009) and zinc/copper ratio (p=0.001) but not serum ceruloplasmin levels (p=0.110) compared to healthy controls. Serum ceruloplasmin was positively associated with plasma copper in ASD children of all age groups. This study shows that ASD in Bangladesh can be associated with low plasma zinc and high plasma copper and serum ceruloplasmin levels.

Total Reflection X-ray Fluorescence Analysis of Plasma Elements in Autistic Children from India

Trace elements are essential for the human body's various physiological processes but if they are present in higher concentration, these elements turn to be toxic and cause adverse effect on physiological processes. Similarly, deficiency of these essential elements also affects physiological processes and leads to abnormal metabolic activities. There is a lot of interest in recent years to know the mystery behind the involvement of trace elements in the metabolic activities of autistic children suspecting that it may be a risk factor in the aetiology of autism. The present study aims to analyse the plasma trace elements in autistic children using the total reflection X-ray fluorescence (TXRF) technique. Plasma samples from 70 autistic children (mean age: 11.5 ± 3.1) were analysed with 70 age- and sex-matched healthy children as controls (mean age: 12 ± 2.5). TXRF analysis revealed the higher concentration of copper (1227.8 ± 17.8), chromium (7.1 ± 2.5), bromine (2695.1 ± 24) and arsenic (126.3 ± 10) and lower concentration of potassium (440.1 ± 25), iron (1039.6 ± 28), zinc (635.7 ± 21), selenium (52.3 ± 8.5), rubidium (1528.9 ± 28) and molybdenum (162,800.8 ± 14) elements in the plasma of autistic children in comparison to healthy controls. Findings of the first study from India suggest these altered concentrations in elements in autistic children over normal healthy children affect the physiological processes and metabolism. Further studies are needed to clarify the association between the altered element concentration and physiology of autism in the North Karnataka population in India.

Evaluation of elements in hair samples of children with developmental language disorder (DLD)

BACKGROUND

Recent studies have highlighted a role for trace elements and toxic metals across neurodevelopmental disorders, including developmental stuttering, Autistic Spectrum Disorders (ASD), and Attention Deficit/Hyperactivity Disorder (ADHD). However, these environmental influences have yet to be explored in relation to Developmental Language Disorder (DLD).

METHODS

Elemental hair composition of seven elements; zinc (⁶⁴Zn), magnesium (²⁶Mg), iron (⁵⁷Fe), potassium (³⁹K), aluminum (²⁷Al), lead (²⁰⁸Pb), and barium (¹³⁸Ba) were analyzed in hair samples from 35 children affected by DLD and 35 controls with typical language development (TLD) using both inductive coupled plasma optical emission spectroscopy (ICP-OES) and inductive coupled plasma mass spectroscopy (ICP-MS).

RESULTS

The concentration of ⁶⁴Zn was significantly lower in the hair of DLD group compared to the TLD control group. All other elements showed similar levels between cases and controls. This pilot study demonstrates the utility of trace elements and toxic metals screening in relation to language disorders and the use of hair samples in such investigations.

CONCLUSION

The finding that zinc levels differed between cases and controls could represent a clinically relevant result and should be replicated in larger sample size across time. A wider battery of related elements will help to better understand the role of trace elements and toxic metals in DLD.

The Role of Zinc and NMDA Receptors in Autism Spectrum Disorders

NMDA-type glutamate receptors are critical for synaptic plasticity in the central nervous system. Their unique properties and age-dependent arrangement of subunit types underpin their role as a coincidence detector of pre- and postsynaptic activity during brain development and maturation. NMDAR function is highly modulated by zinc, which is co-released with glutamate and concentrates in postsynaptic spines. Both NMDARs and zinc have been strongly linked to autism spectrum disorders (ASDs), suggesting that NMDARs are an important player in the beneficial effects observed with zinc in both animal models and children with ASDs. Significant evidence is emerging that these beneficial effects occur via zinc-dependent regulation of SHANK proteins, which form the backbone of the postsynaptic density. For example, dietary zinc supplementation enhances SHANK2 or SHANK3 synaptic recruitment and rescues NMDAR deficits and hypofunction in Shank3^ex13-16-/- and Tbr1^+/- ASD mice. Across multiple studies, synaptic changes occur in parallel with a reversal of ASD-associated behaviours, highlighting the zinc-dependent regulation of NMDARs and glutamatergic synapses as therapeutic targets for severe forms of ASDs, either pre- or postnatally. The data from rodent models set a strong foundation for future translational studies in human cells and people affected by ASDs.

Associations of essential element serum concentrations with autism spectrum disorder

This case-control study explored the associations between autism spectrum disorder (ASD) and the serum concentration of nine chemical elements in children. The study recruited 92 Chinese children with ASD and 103 typically developing individuals. Serum concentrations of nine chemical elements (calcium, iodine, iron, lithium, magnesium, potassium, selenium, strontium, and zinc) were determined by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES). An unconditional logistic regression model was used to analyze the associations between the serum concentrations of the elements and the risk of ASD. After adjusting for confounders, the multivariate analysis results showed that zinc ≤ 837.70 ng/mL, potassium > 170.06 μg/mL, and strontium ≤ 52.46 ng/mL were associated with an increased risk of ASD, while selenium > 159.80 ng/mL was associated with a decreased risk of ASD. Furthermore, the degree of lithium and zinc deficiency was associated with ASD severity. The results indicated that metallomic profiles of some specific elements might play important roles in the development of ASD, a finding of scientific significance for understanding the etiology, and providing dietary guidance for certain ASD types.

Metallomics analysis for early assessment and individualized intervention of neurodevelopmental disorders

The children today are in the midst of the epidemic of neurodevelopmental disorders. In this metallomics study for the scalp hair samples of total 2550 children with autistic disorders (2108 males and 442 females aged 0-15 year), it was demonstrated that near one half of the infantile individuals aged 0-3 year are suffering from zinc deficiency and toxic metal burdens. Zinc level correlated closely to the index of zinc/iron ratio more than zinc/copper ratio. Furthermore, there were significant relationships between zinc deficiency and toxic metal burdens such as lead and aluminum which were inversely associated with not only zinc level but also zinc/iron ratio with higher regression coefficients of r = -0.486 and -0.551 (p < 0.00001), respectively. High-significant inverse association was detected between zinc and molybdenum concentration (r = -0.509) and also between zinc/iron ratio and molybdenum (r = -0.548). These findings suggest that infantile zinc deficiency relates to the high burdens of not only toxic but also some essential metals such as molybdenum, iron and manganese and that these various mineral imbalances play principal roles to the etiology of neurodevelopmental disorders. We expect that the early assessment and intervention of the mineral imbalances (or dis-homeostasis) in individual child open an avenue for evidence-based individualized treatment of neurodevelopmental disorders and also of the comorbid immune disorders, in near future.

Exposure to multiple metals and the risk of dyslexia - A case control study in Shantou, China

Environmental heavy metal exposure has been considered to be the risk factor for neurodevelopmental disorders in children. However, the available data on the associations between multiple metals exposure and the risk of dyslexia in China are limited. The purpose of our study was to examine the associations between urinary metal concentrations and Chinese dyslexia risk. A total of 56 Chinese dyslexics and 60 typically developing children were recruited. The urinary concentration of 13 metals were measured by inductively coupled plasma-mass spectrometer (ICP-MS). Binary logistic regression and the Probit extension of Bayesian kernel machine regression (BKMR-P) were used to explore the associations between multiple metal exposure and the risk of Chinese dyslexia. Our results indicated that Co, Zn and Pb were significantly associated with Chinese dyslexia in the multiple-metal exposure model. After adjusting the covariates, a positive association was observed between Pb and the risk of Chinese dyslexia, with the odds ratio (OR) in the highest quartiles of 6.81 (95%CI: 1.07-43.19; p-trend = 0.024). Co and Zn were negatively associated with the risk of Chinese dyslexia. Compared to the lowest quartile, the ORs of Co and Zn in the highest quartile are 0.13 (95%CI: 0.02-0.72; p-trend = 0.026) and 0.18 (95%CI: 0.04-0.88; p-trend = 0.038), respectively. In addition, BKMR-P analysis indicated that with the cumulative level across Co, Zn and Pb increased, the risk of Chinese dyslexia gradually declined and then rebounded, albeit non-significantly, and Pb was the major contributor in this association. In general, the urinary concentrations of Co, Zn and Pb were significantly associated with Chinese dyslexia. More prospective studies are needed to confirm the health effects of multiple metals exposure in children with Chinese dyslexia.

Effects of nutritional interventions in children and adolescents with autism spectrum disorder: an overview based on a literature review

Background: Nutrition is important in autism spectrum disorder (ASD). Because nutritional problems of children with ASD can lead to nutritional deficiencies and this can also directly or indirectly affect symptoms related to autism. We investigated the effect of diet and supplementation treatments on gastrointestinal, behavioral or sleep problems based on the results of literature review. Methods: We generated four questions based on literature. We carried out title and abstract-based search using the Web of Science database. Of 4580 abstracts were identified, 192 papers were reviewed and 55 papers precisely meeting the inclusion criteria. Results: The studies examining the effects of vitamins, minerals, probiotics, and other supplements on ASD symptoms had different dosages, different treatment durations, small sample sizes and used different scales for evaluation. The results of the studies of the effectiveness of Gluten-Free and Casein-Free (GFCF) and ketogenic diet to reduce gastrointestinal, behavioral and sleeping problems in children and adolescents were contradictory. Conclusions: It is not possible to suggest the GFCF and/or ketogenic diet, vitamins, minerals and probiotics to individual with ASD based on the available evidence. By planning a sufficient and balanced diet, it should be aimed to prevent nutrient deficiency and to ensure growth in accordance with the age in children with ASD.

Assessment of Copper and Zinc Levels in Hair and Urine of Children With Attention Deficit Hyperactivity Disorder: A Case-Control Study in Eastern India

Background

Attention deficit hyperactivity disorder (ADHD) is a neuro-developmental ailment diagnosed with inattention and hyperactivity-impulsivity. It is one of the most prevalent neurodevelopmental disorders and has complex aetiology, both genetic and environmental. There is a perceived decrease in skill acquirement, leading to insufficient income and job opportunities as adults, which drives them towards poor physical and mental outcomes compared to their contemporaries without ADHD. The impact of heavy metals on ADHD is a topic of interest but is much less studied. Copper has been implicated as a pro-oxidant and in the metal accelerated production of free radicals that may affect oxidative stress. Zinc also serves as an antioxidant, and changes in its concentrations may impact the homeostasis of oxidative stress.

Methods

Twenty-four children diagnosed with ADHD were taken as cases and matched with 24 healthy controls. Hair and urine samples were collected from all the study participants. The samples were collected in sterile containers according to established protocols. Acid digestion of hair samples was done using 65% nitric acid and 30% hydrogen peroxide. Urine samples were extracted by a solution of 0.1% Triton-X-100 and 1% ultrapure nitric acid. The levels of zinc and copper were determined in both samples by inductively coupled plasma optical emission spectrometry (ICP-OES). The copper/zinc ratio (Cu/Zn) was calculated from these values. Mann Whitney U Test and receiver operating characteristic (ROC) analysis were done to estimate statistical significance.

Results

The median age of the study population was eight years. Overall, 34 male and 14 female subjects participated. There was no significant difference in height, weight and BMI between the cases and controls. Hair zinc levels in the ADHD group (198.49 µg g^-1 of hair) was significantly lower than the control group (527.05 µg g^-1 of hair). However, hair copper levels were increased significantly in the ADHD children (14.01 µg g^-1 of hair) compared to the controls (7.43 µg g^-1 of hair). Urine zinc levels were significantly lower in cases than controls (525.7 µg g^-1 of spot urine creatinine vs 1374.09 µg g^-1 of spot urine creatinine). However, copper levels in urine were higher in the ADHD children (17.01 µg g^-1 of spot urine creatinine compared to 7.26 µg g^-1 of spot urine creatinine in controls). Both hair and urine copper to zinc ratio was significantly higher in the ADHD group. On ROC analysis, the hair Cu/Zn ratio had an area under the curve (AUC) of 0.920 (p-value <0.001), and the urine Cu/Zn ratio had an AUC of 0.967 (p-value <0.001). When used as a diagnostic classifier for ADHD based on the cut-off value determined by ROC, both hair and urine Cu/Zn ratio had high sensitivity and specificity.

Conclusion

Low zinc levels in the urine and hair of children and higher levels of copper may impact the aetiology of ADHD in these children. At an early stage, the Cu/Zn ratio in both hair and urine samples may be used as a precise biomarker to identify and monitor such children.

Oxidative stress indices in ASD children in Sub-Sahara Africa

Background

The pathogenesis of autism spectrum disorder (ASD) remains a medical challenge even in the developed world. Although genetics and epigenetic factors have been variously indicted as major causes of the disorder, development of oxidative stress especially in the formative years of children has equally gained prominence as an etiological basis of the disorder. Oxidative stress is characterized by the production of excessive amounts of free radicals, decreased levels of antioxidants with the attendant imbalance in oxidant/antioxidant ratio. This study was designed to determine the levels of essential metals [magnesium (Mg), zinc (Zn), and copper (Cu)] and toxic metal, lead (Pb), and generation of oxidative stress by their abnormal interaction.

Method

Twenty-five children clinically diagnosed for ASD according to DSM-IV-TR and 25 neuro-typical (NT) children (controls), (aged 5.96 ± 1.40 years and 6.18 ± 2.59 years respectively) were recruited for this study. Essential and toxic metals were analyzed using induction-coupled plasma-mass spectrometry (ICP-MS); oxidative stress markers [malondialdehyde (MDA), total plasma peroxidase (TPP), and total antioxidant capacity (TAC)] were determined using appropriate biochemical methods. Oxidative stress index (OSI) was calculated.

Results

The levels of TPP and TAC were significantly reduced while MDA was higher in ASD compared to NT. Although OSI was higher in ASD, the difference was not significant. Pb (lead) concentration was significantly increased while Mg, Zn, and Cu levels were reduced significantly in ASD compared to NT. A significant negative correlation between Mg and OSI (r = − 0.438; p = 0.029) was observed in NT.

Conclusion

Reduction in Zn and Mg levels with a concurrent increase in Pb in children with ASD in this study may be the basis of inadequate TAC manifesting as increased MDA and reduced TPP levels. The attendant imbalance in oxidant/antioxidant ratio may result in abnormality in neuronal transduction leading to the abnormal cognitive and speech functions characteristic of ASD.

Trace elements in children with autism spectrum disorder: A meta-analysis based on case-control studies

Autism spectrum disorder (ASD) is a common childhood neurodevelopmental disorder that may be related to trace elements. However, reports on the relationship between them are still inconsistent. In this article, we conducted a meta-analysis on this issue. We searched the PubMed, EMBASE, and Cochrane databases as of November 15, 2019. A random-effects model was used, and subgroups of studies were analyzed using samples of different measurements. Twenty-two original articles were identified (18 trace elements, including a total of 1014 children with ASD and 999 healthy controls). In autistic children, the overall levels of barium (Ba), mercury (Hg), lithium (Li), and lead (Pb) were higher. There were significant differences in the levels of copper (Cu) in the hair and serum between autistic children and the control group. The levels of Hg, Li, Pb and selenium (Se) in the hair of autistic children were higher than those of healthy children, while the levels of zinc (Zn) in the blood were lower. Excessive exposure to toxic heavy metals and inadequate intake of essential metal elements may be associated with ASD. Preventing excessive exposure to toxic metals and correcting poor dietary behaviors may be beneficial for the prevention and treatment of the disease.

Perineuronal Nets and Metal Cation Concentrations in the Microenvironments of Fast-Spiking, Parvalbumin-Expressing GABAergic Interneurons: Relevance to Neurodevelopment and Neurodevelopmental Disorders

Because of their abilities to catalyze generation of toxic free radical species, free concentrations of the redox reactive metals iron and copper are highly regulated. Importantly, desired neurobiological effects of these redox reactive metal cations occur within very narrow ranges of their local concentrations. For example, synaptic release of free copper acts locally to modulate NMDA receptor-mediated neurotransmission. Moreover, within the developing brain, iron is critical to hippocampal maturation and the differentiation of parvalbumin-expressing neurons, whose soma and dendrites are surrounded by perineuronal nets (PNNs). The PNNs are a specialized component of brain extracellular matrix, whose polyanionic character supports the fast-spiking electrophysiological properties of these parvalbumin-expressing GABAergic interneurons. In addition to binding cations and creation of the Donnan equilibrium that support the fast-spiking properties of this subset of interneurons, the complex architecture of PNNs also binds metal cations, which may serve a protective function against oxidative damage, especially of these fast-spiking neurons. Data suggest that pathological disturbance of the population of fast-spiking, parvalbumin-expressing GABAergic inhibitory interneurons occur in at least some clinical presentations, which leads to disruption of the synchronous oscillatory output of assemblies of pyramidal neurons. Increased expression of the GluN2A NMDA receptor subunit on parvalbumin-expressing interneurons is linked to functional maturation of both these neurons and the perineuronal nets that surround them. Disruption of GluN2A expression shows increased susceptibility to oxidative stress, reflected in redox dysregulation and delayed maturation of PNNs. This may be especially relevant to neurodevelopmental disorders, including autism spectrum disorder. Conceivably, binding of metal redox reactive cations by the perineuronal net helps to maintain safe local concentrations, and also serves as a reservoir buffering against second-to-second fluctuations in their concentrations outside of a narrow physiological range.

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.

The Metallome as a Link Between the "Omes" in Autism Spectrum Disorders

Metal dyshomeostasis plays a significant role in various neurological diseases such as Alzheimer's disease, Parkinson's disease, Autism Spectrum Disorders (ASD), and many more. Like studies investigating the proteome, transcriptome, epigenome, microbiome, etc., for years, metallomics studies have focused on data from their domain, i.e., trace metal composition, only. Still, few have considered the links between other "omes," which may together result in an individual's specific pathologies. In particular, ASD have been reported to have multitudes of possible causal effects. Metallomics data focusing on metal deficiencies and dyshomeostasis can be linked to functions of metalloenzymes, metal transporters, and transcription factors, thus affecting the proteome and transcriptome. Furthermore, recent studies in ASD have emphasized the gut-brain axis, with alterations in the microbiome being linked to changes in the metabolome and inflammatory processes. However, the microbiome and other "omes" are heavily influenced by the metallome. Thus, here, we will summarize the known implications of a changed metallome for other "omes" in the body in the context of "omics" studies in ASD. We will highlight possible connections and propose a model that may explain the so far independently reported pathologies in ASD.

Zinc and Copper Brain Levels and Expression of Neurotransmitter Receptors in Two Rat ASD Models

Zinc and copper are important trace elements necessary for the proper functioning of neurons. Impaired zinc and/or copper metabolism and signaling are implicated in many brain diseases, including autism (ASD). In our studies, autistic-like behavior in rat offsprings was induced by application to pregnant mothers valproic acid or thalidomide. Zinc and copper contents were measured in serum and brain structures: hippocampus, cerebral cortex, and cerebellum. Our research shows no interconnections in the particular metal concentrations measured in autistic animal brains and their sera. Based on patient researches, we studied 26 genes belonging to disturbed neurotransmitter pathways. In the same brain regions, we examined the expression of genes encoding proteins of cholinergic, adrenergic, serotonin, and dopamine receptors. In both rats’ ASD models, 17 out of the tested gene expression were decreased. In the cerebellum and cerebral cortex, expression of genes encoding cholinergic, adrenergic, and dopaminergic receptors decreased, whereas in the hippocampus only expression of serotoninergic receptors genes was downregulated. The changes in metals content observed in the rat brain can be secondary phenomena, perhaps elements of mechanisms that compensate for neurotransmission dysfunctions.

Evaluation of Zn, Cu, and Se Levels in the North American Autism Spectrum Disorder Population

Metal ion dyshomeostasis and disparate levels of biometals like zinc (Zn), copper (Cu), and selenium (Se) have been implicated as a potential causative factor for Autism Spectrum Disorder (ASD). In this study, we have enrolled 129 children (aged 2–4 years) in North America, of which 64 children had a diagnosis of ASD and 65 were controls. Hair, nail, and blood samples were collected and quantitatively analyzed for Zn, Cu and Se using inductively coupled plasma mass spectrometry (ICP-MS). Of the analyzed biometals, serum Se (116.83 ± 14.84 ng/mL) was found to be significantly lower in male ASD cases compared to male healthy controls (128.21 ± 9.11 ng/mL; p < 0.005). A similar trend was found for nail Se levels in ASD (1.01 ± 0.15 mcg/g) versus that of controls (1.11 ± 0.17 mcg/g) with a p-value of 0.0132 using a stratified Wilcoxon rank sum testing. The level of Se in ASD cohort was co-analyzed for psychometric correlation and found a negative correlation between total ADOS score and serum Se levels. However, we did not observe any significant difference in Zn, Cu, and Zn/Cu ratio in ASD cases versus controls in this cohort of North American children. Further studies are recommended to better understand the biology of the relationship between Se and ASD status.

Abnormal Levels of Metal Micronutrients and Autism Spectrum Disorder: A Perspective Review

The aim of the present review is to summarize the prevalence of abnormal levels of various metal micronutrients including copper (Cu), iron (Fe), magnesium (Mg), zinc (Zn), and selenium (Se) in Autism Spectrum Disorder (ASD) using hair, nail and serum samples. A correlation of selected abnormal metal ions with known neurodevelopmental processes using Gene Ontology (GO) term was also conducted. Data included in this review are derived from ASD clinical studies performed globally. Metal ion disparity data is also analyzed and discussed based on gender (Male/Female) to establish any gender dependent correlation. Finally, a rational perspective and possible path to better understand the role of metal micronutrients in ASD is suggested.

The status of chemical elements in the blood plasma of children with autism spectrum disorder in Tunisia: a case-control study

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders defined by a deficit in social interactions and the presence of restricted and stereotypical behaviors or interests. The etiologies of autism remain mostly unknown. Many genetic and environmental factors have been suspected. Among these environmental factors, exposure to several chemical elements has been previously studied. The purpose of this study was to compare the levels of trace elements in the blood plasma of children with ASD with typically developed children (TDC). The participants in this study consisted of 89 children with ASD (14 girls and 74 boys) and 70 TD children (29 girls and 41 boys). The levels of 33 chemical elements have been analyzed by inductively coupled plasma spectrometry (ICP-MS). We detected significant differences in the levels of eight elements between the two groups, among which there were three rare earth elements (REEs): Eu, Pr, and Sc (p = 0.000, p = 0.023, and p < 0.001 respectively); four heavy metals: Bi, Tl, Ti, and V (p = 0.004, p < 0.001, p = 0.001, and p = 0.001 respectively); and one essential element: Cu (p = 0.043). Children with ASD had higher levels of Er, Pr, Sc, Bi, Tl, Ti, and V, and lower levels of Cu in comparison with the TD group. The children exposed to passive smoking had lower levels of lead (Pb) compared with children without exposure (p = 0.018). Four elements (Cr, Er, Dy, and Pr) were negatively correlated to the severity of ASD. The level of Cu was significantly associated with autistic children's behavior (p = 0.014). These results suggest that children with ASD might have abnormal plasma levels of certain chemical elements (including Er, Pr, Sc, Bi, Tl, Ti, and V, and Cu), and some of these elements might be associated with certain clinical features.

Critical Review of Exposure and Effects: Implications for Setting Regulatory Health Criteria for Ingested Copper

Decades of study indicate that copper oral exposures are typically not a human health concern. Ingesting high levels of soluble copper salts can cause acute gastrointestinal symptoms and, in uncommon cases, liver toxicity in susceptible individuals with repeated exposure. This focused toxicological review evaluated the current literature since the last comprehensive reviews (2007-2010). Our review identified limitations in the existing United States and international guidance for determining an oral reference dose (RfD) for essential metals like copper. Instead, an alternative method using categorical regression analysis to develop an optimal dose that considers deficiency, toxicity, and integrates information from human and animal studies was reviewed for interpreting an oral RfD for copper. We also considered subchronic or chronic toxicity from genetic susceptibility to copper dysregulation leading to rare occurrences of liver and other organ toxicity with elevated copper exposure. Based on this approach, an oral RfD of 0.04 mg Cu/kg/day would be protective of acute or chronic toxicity in adults and children. This RfD is also protective for possible genetic susceptibility to elevated copper exposure and allows for background dietary exposures. This dose is not intended to be protective of patients with rare genetic disorders for copper sensitivity within typical nutritional intake ranges, nor is it protective for those with excessive supplement intake. Less soluble mineral forms of copper in soil have reduced bioavailability as compared with more soluble copper in water and diet, which should be considered in using this RfD for risk assessments of copper.

The role of zinc supplementation on the metallothionein system in children with autism spectrum disorder

The present research was carried out to elucidate the role of zinc (Zn) supplementation on the plasma concentration and gene expression, as well as the effects on cognitive-motor performance, in a cohort of children with autism spectrum disorder (ASD). The study was performed on a cohort of 30 pediatric subjects with ASD, encompassing an age range of 3-8 years. The impact of Zn supplementation was investigated in 3 months (or 12 weeks) on the ASD children. Each daily dosage of Zn was calculated as being equal to the body weight in kg plus 15-20 mg. The effect of Zn was also evaluated on the serum level of metallothionein 1 (MT-1A), and the severity of autism via scores on the Childhood Autism Rating Scale. The effect of Zn was investigated on the gene expression of MT1-A before and after Zn supplementation. The data of the present study showed an increase in cognitive-motor performance and an increased serum metallothionein concentration, as well as a significant lowering in the circulating serum levels of copper (Cu) following Zn supplementation. In the cohort of ASD patients, the genetic expression of MT-1 was higher after Zn therapy than before the treatment. In conclusion, Zn supplementation might be an important factor in the treatment of children with ASD.

Evaluation of Whole Blood Trace Element Levels in Chinese Children with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, which has increased markedly during the last decades. Essential trace elements play an important role in neurological function and their imbalances are common in children with ASD. The objective of the present study was to investigate whole blood levels of trace elements including zinc (Zn), copper (Cu), iron (Fe), and magnesium (Mg) in Chinese children with ASD. In total, 113 children diagnosed with ASD and 141 age-matched and gender-matched neurotypical children, divided into two gender and age groups of preschool age (2-5 years old) and school (6-10 years old) age, were examined. The quantitative analyses of whole blood trace element contents were performed by using flame atomic absorption spectroscopy. In the present study, the children with ASD generally had lower whole blood levels of Zn than the neurotypical controls. No significant differences in the whole blood Cu, Zn/Cu ratio, Fe, or Mg was detected between the ASD group and the control group. It is notable that whole blood Fe level in boys with ASD was significantly higher than in girls with ASD, and was nearly significant when compared with the control level of boys. After stratification for age, a significant 6% decrease in whole blood Zn levels was detected in preschool-aged children with ASD as compared to the control values. However, this significant ASD-related change was not detected in school-aged children. The whole blood Zn level and Zn/Cu ratio were significantly increased in school-aged children than in preschool-aged children in both ASD and control group. In addition, school-aged children with ASD had a significantly higher level of whole blood Fe than preschool-aged children with ASD. The results of the present study suggest an association between whole blood levels of Zn in Chinese children with ASD.

Zinc and vitamin A deficiency in a cohort of children with autism spectrum disorder

BACKGROUND AND OBJECTIVES

Studies suggest that trace element and vitamin deficiencies are common in children with autism spectrum disorder (ASD). Data describing the rates of vitamin and trace element deficiencies in the ASD population of the northwest of Ireland is lacking. We wished to determine the prevalence of zinc and vitamin A deficiency in the ASD population compared with controls within this geographical area.

METHODS

Parents of children aged 2-18 years with ASD were invited to participate in the study. The control group consisted of well children attending the paediatric department for routine blood sampling. Children on vitamin supplements were excluded from both ASD and control groups. Informed written consent was obtained prior to recruitment. Samples were analysed for zinc and vitamin A levels according to standardized laboratory procedures.

RESULTS

Seventy-four of the 150 children with ASD who were invited and 72 controls underwent blood sampling. Mean zinc and vitamin A levels were normal in both groups. There were significantly more males in the ASD group (88% versus 56%, p value < 0.001). The mean (SD) zinc level was not different between the groups (ASD 11.7 [1.7] versus control 11.6 [2.1] μmol/L, p value = 0.86). The mean (standard deviation) vitamin A level was higher in the ASD group (ASD 350.6 [82.6] versus 319.2 [82.8] μg/L, p value = 0.03), but this was likely confounded by age.

CONCLUSION

Children with ASD in the northwest of Ireland have mean zinc and vitamin A levels within the normal range. It is important that these findings are relayed to health professionals and to parents of children with ASD so that informed decisions on vitamin supplementation can be made.

The contribution of environmental exposure to the etiology of autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition of heterogeneous etiology. While it is widely recognized that genetic and environmental factors and their interactions contribute to autism phenotypes, their precise causal mechanisms remain poorly understood. This article reviews our current understanding of environmental risk factors of ASD and their presumed adverse physiological mechanisms. It comprehensively maps the significance of parental age, teratogenic compounds, perinatal risks, medication, smoking and alcohol use, nutrition, vaccination, toxic exposures, as well as the role of extreme psychosocial factors. Further, we consider the role of potential protective factors such as folate and fatty acid intake. Evidence indicates an increased offspring vulnerability to ASD through advanced maternal and paternal age, valproate intake, toxic chemical exposure, maternal diabetes, enhanced steroidogenic activity, immune activation, and possibly altered zinc-copper cycles and treatment with selective serotonin reuptake inhibitors. Epidemiological studies demonstrate no evidence for vaccination posing an autism risk. It is concluded that future research needs to consider categorical autism, broader autism phenotypes, as well as autistic traits, and examine more homogenous autism variants by subgroup stratification. Our understanding of autism etiology could be advanced by research aimed at disentangling the causal and non-causal environmental effects, both founding and moderating, and gene-environment interplay using twin studies, longitudinal and experimental designs. The specificity of many environmental risks for ASD remains unknown and control of multiple confounders has been limited. Further understanding of the critical windows of neurodevelopmental vulnerability and investigating the fit of multiple hit and cumulative risk models are likely promising approaches in enhancing the understanding of role of environmental factors in the etiology of ASD.

Prospects of Zinc Supplementation in Autism Spectrum Disorders and Shankopathies Such as Phelan McDermid Syndrome

The loss of one copy of SHANK3 (SH3 and multiple ankyrin repeat domains 3) in humans highly contributes to Phelan McDermid syndrome (PMDS). In addition, SHANK3 was identified as a major autism candidate gene. Interestingly, the protein encoded by the SHANK3 gene is regulated by zinc. While zinc deficiency depletes synaptic pools of Shank3, increased zinc levels were shown to promote synaptic scaffold formation. Therefore, the hypothesis arises that patients with PMDS and Autism caused by Shankopathies, having one intact copy of SHANK3 left, may benefit from zinc supplementation, as elevated zinc may drive remaining Shank3 into the post-synaptic density (PSD) and may additional recruit Shank2, a second zinc-dependent member of the SHANK gene family. Further, elevated synaptic zinc levels may modulate E/I ratios affecting other synaptic components such as NMDARs. However, several factors need to be considered in relation to zinc supplementation such as the role of Shank3 in the gastrointestinal (GI) system-the location of zinc absorption in humans. Therefore, here, we briefly discuss the prospect and impediments of zinc supplementation in disorders affecting Shank3 such as PMDS and propose a model for most efficacious supplementation.

The toxicology of mercury: Current research and emerging trends

Mercury (Hg) is a persistent bio-accumulative toxic metal with unique physicochemical properties of public health concern since their natural and anthropogenic diffusions still induce high risk to human and environmental health. The goal of this review was to analyze scientific literature evaluating the role of global concerns over Hg exposure due to human exposure to ingestion of contaminated seafood (methyl-Hg) as well as elemental Hg levels of dental amalgam fillings (metallic Hg), vaccines (ethyl-Hg) and contaminated water and air (Hg chloride). Mercury has been recognized as a neurotoxicant as well as immunotoxic and designated by the World Health Organization as one of the ten most dangerous chemicals to public health. It has been shown that the half-life of inorganic Hg in human brains is several years to several decades. Mercury occurs in the environment under different chemical forms as elemental Hg (metallic), inorganic and organic Hg. Despite the raising understanding of the Hg toxicokinetics, there is still fully justified to further explore the emerging theories about its bioavailability and adverse effects in humans. In this review, we describe current research and emerging trends in Hg toxicity with the purpose of providing up-to-date information for a better understanding of the kinetics of this metal, presenting comprehensive knowledge on published data analyzing its metabolism, interaction with other metals, distribution, internal doses and targets, and reservoir organs.

Assessment of serum trace elements and electrolytes in children with childhood and atypical autism

The existing data demonstrate a significant interrelation between ASD and essential and toxic trace elements status of the organism. However, data on trace element homeostasis in particular ASD forms are insufficient. Therefore, the objective of the present study was to assess the level of trace elements and electrolytes in serum of children with childhood and atypical autism. A total of 48 children with ASD (24 with childhood and 24 with atypical autism) and age- and sex-adjusted controls were examined. Serum trace elements and electrolytes were assessed using inductively-coupled plasma mass spectrometry. The obtained data demonstrate that children with ASD unspecified are characterized by significantly lower Ni, Cr, and Se levels as compared to the age- and sex-matched controls. At the same time, significantly decreased serum Ni and Se concentrations were detected in patients with childhood autism. In turn, children with atypical autism were characterized by more variable serum trace element spectrum. In particular, atypical autism is associated with lower serum Al, As, Ni, Cr, Mn, and Se levels in comparison to the control values. Moreover, Al and Mn concentration in this group was also lower than that in childhood autism patients. Generally, the obtained data demonstrate lower levels of both essential and toxic trace elements in atypical autism group, being indicative of profound alteration of trace elements metabolism. However, further detailed metabolic studies are required to reveal critical differences in metabolic pathways being responsible for difference in trace element status and clinical course of the disease.

Shank3 Is Part of a Zinc-Sensitive Signaling System That Regulates Excitatory Synaptic Strength

Shank3 is a multidomain scaffold protein localized to the postsynaptic density of excitatory synapses. Functional studies in vivo and in vitro support the concept that Shank3 is critical for synaptic plasticity and the trans-synaptic coupling between the reliability of presynaptic neurotransmitter release and postsynaptic responsiveness. However, how Shank3 regulates synaptic strength remains unclear. The C terminus of Shank3 contains a sterile alpha motif (SAM) domain that is essential for its postsynaptic localization and also binds zinc, thus raising the possibility that changing zinc levels modulate Shank3 function in dendritic spines. In support of this hypothesis, we find that zinc is a potent regulator of Shank3 activation and dynamics in rat hippocampal neurons. Moreover, we show that zinc modulation of synaptic transmission is Shank3 dependent. Interestingly, an autism spectrum disorder (ASD)-associated variant of Shank3 (Shank3(R87C)) retains its zinc sensitivity and supports zinc-dependent activation of AMPAR-mediated synaptic transmission. However, elevated zinc was unable to rescue defects in trans-synaptic signaling caused by the R87C mutation, implying that trans-synaptic increases in neurotransmitter release are not necessary for the postsynaptic effects of zinc. Together, these data suggest that Shank3 is a key component of a zinc-sensitive signaling system, regulating synaptic strength that may be impaired in ASD.

SIGNIFICANCE STATEMENT

Shank3 is a postsynaptic protein associated with neurodevelopmental disorders such as autism and schizophrenia. In this study, we show that Shank3 is a key component of a zinc-sensitive signaling system that regulates excitatory synaptic transmission. Intriguingly, an autism-associated mutation in Shank3 partially impairs this signaling system. Therefore, perturbation of zinc homeostasis may impair, not only synaptic functionality and plasticity, but also may lead to cognitive and behavioral abnormalities seen in patients with psychiatric disorders.

Neurotoxicity of Copper

Copper is an essential trace metal that is required for several important biological processes, however, an excess of copper can be toxic to cells. Therefore, systemic and cellular copper homeostasis is tightly regulated, but dysregulation of copper homeostasis may occur in disease states, resulting either in copper deficiency or copper overload and toxicity. This chapter will give an overview on the biological roles of copper and of the mechanisms involved in copper uptake, storage, and distribution. In addition, we will describe potential mechanisms of the cellular toxicity of copper and copper oxide nanoparticles. Finally, we will summarize the current knowledge on the connection of copper toxicity with neurodegenerative diseases.

Premutation in the Fragile X Mental Retardation 1 (FMR1) Gene Affects Maternal Zn-milk and Perinatal Brain Bioenergetics and Scaffolding

Fragile X premutation alleles have 55–200 CGG repeats in the 5′ UTR of the FMR1 gene. Altered zinc (Zn) homeostasis has been reported in fibroblasts from >60 years old premutation carriers, in which Zn supplementation significantly restored Zn-dependent mitochondrial protein import/processing and function. Given that mitochondria play a critical role in synaptic transmission, brain function, and cognition, we tested FMRP protein expression, brain bioenergetics, and expression of the Zn-dependent synaptic scaffolding protein SH3 and multiple ankyrin repeat domains 3 (Shank3) in a knock-in (KI) premutation mouse model with 180 CGG repeats. Mitochondrial outcomes correlated with FMRP protein expression (but not FMR1 gene expression) in KI mice and human fibroblasts from carriers of the pre- and full-mutation. Significant deficits in brain bioenergetics, Zn levels, and Shank3 protein expression were observed in the Zn-rich regions KI hippocampus and cerebellum at PND21, with some of these effects lasting into adulthood (PND210). A strong genotype × age interaction was observed for most of the outcomes tested in hippocampus and cerebellum, whereas in cortex, age played a major role. Given that the most significant effects were observed at the end of the lactation period, we hypothesized that KI milk might have a role at compounding the deleterious effects on the FMR1 genetic background. A higher gene expression of ZnT4 and ZnT6, Zn transporters abundant in brain and lactating mammary glands, was observed in the latter tissue of KI dams. A cross-fostering experiment allowed improving cortex bioenergetics in KI pups nursing on WT milk. Conversely, WT pups nursing on KI milk showed deficits in hippocampus and cerebellum bioenergetics. A highly significant milk type × genotype interaction was observed for all three-brain regions, being cortex the most influenced. Finally, lower milk-Zn levels were recorded in milk from lactating women carrying the premutation as well as other Zn-related outcomes (Zn-dependent alkaline phosphatase activity and lactose biosynthesis—whose limiting step is the Zn-dependent β-1,4-galactosyltransferase). In premutation carriers, altered Zn homeostasis, brain bioenergetics and Shank3 levels could be compounded by Zn-deficient milk, increasing the risk of developing emotional and neurological/cognitive problems and/or FXTAS later in life.

The Relationship between Zinc Levels and Autism: A Systematic Review and Meta-analysis

OBJECTIVE

Autism is a complex behaviorally defined disorder.There is a relationship between zinc (Zn) levels in autistic patients and development of pathogenesis, but the conclusion is not permanent.

MATERIALS & METHODS

The present study conducted to estimate this probability using meta-analysis method. In this study, Fixed Effect Model, twelve articles published from 1978 to 2012 were selected by searching Google scholar, PubMed, ISI Web of Science, and Scopus and information were analyzed. I² statistics were calculated to examine heterogeneity. The information was analyzed using R and STATA Ver. 12.2.

RESULTS

There was no significant statistical difference between hair, nail, and teeth Zn levels between controls and autistic patients: -0.471 [95% confidence interval (95% CI): -1.172 to 0.231]. There was significant statistical difference between plasma Zn concentration and autistic patients besides healthy controls: -0.253 (95% CI: 0.498 to -0.007). Using a Random Effect Model, the overall Integration of data from the two groups was -0.414 (95% CI: -0.878 to -0.051).

CONCLUSION

Based on sensitivity analysis, zinc supplements can be used for the nutritional therapy for autistic patients.

Trans-synaptic zinc mobilization improves social interaction in two mouse models of autism through NMDAR activation

Genetic aspects of autism spectrum disorders (ASDs) have recently been extensively explored, but environmental influences that affect ASDs have received considerably less attention. Zinc (Zn) is a nutritional factor implicated in ASDs, but evidence for a strong association and linking mechanism is largely lacking. Here we report that trans-synaptic Zn mobilization rapidly rescues social interaction in two independent mouse models of ASD. In mice lacking Shank2, an excitatory postsynaptic scaffolding protein, postsynaptic Zn elevation induced by clioquinol (a Zn chelator and ionophore) improves social interaction. Postsynaptic Zn is mainly derived from presynaptic pools and activates NMDA receptors (NMDARs) through postsynaptic activation of the tyrosine kinase Src. Clioquinol also improves social interaction in mice haploinsufficient for the transcription factor Tbr1, which accompanies NMDAR activation in the amygdala. These results suggest that trans-synaptic Zn mobilization induced by clioquinol rescues social deficits in mouse models of ASD through postsynaptic Src and NMDAR activation.

Zinc is a nutritional factor implicated in autism spectrum disorders (ASDs), but evidence for a strong association and linking mechanism is largely lacking. Here, the authors report that trans-synaptic zinc mobilization rapidly rescues social interaction in two independent mouse models of ASD.

Levels of metals in the blood and specific porphyrins in the urine in children with autism spectrum disorders

The aim of the present study was to determine the levels of metals in blood (zinc (Zn), copper (Cu), aluminium (Al), lead (Pb) and mercury (Hg)), as well as the specific porphyrin levels in the urine of patients with autism spectrum disorder (ASD) compared with patients with other neurological disorders. The study was performed in a group of children with ASD (N = 52, average age = 6.2 years) and a control group of children with other neurological disorders (N = 22, average age = 6.6 years), matched in terms of intellectual abilities (Mann-Whitney U = 565.0, p = 0.595). Measurement of metals in blood was performed by atomic absorption spectrometry, while the HPLC method via a fluorescence detector was used to test urinary porphyrin levels. Results were compared across groups using a multivariate analysis of covariance (MANCOVA). In addition, a generalized linear model was used to establish the impact of group membership on the blood Cu/Zn ratio. In terms of blood levels of metals, no significant difference between the groups was found. However, compared to the control group, ASD group had significantly elevated blood Cu/Zn ratio (Wald χ (2) = 6.6, df = 1, p = 0.010). Additionally, no significant difference between the groups was found in terms of uroporphyrin I, heptacarboxyporphyrin I, hexacarboxyporphyrin and pentacarboxyporphyrin I. However, the levels of coproporphyrin I and coproporphyrin III were lower in the ASD group compared to the controls. Due to observed higher Cu/Zn ratio, it is suggested to test blood levels of Zn and Cu in all autistic children and give them a Zn supplement if needed.

DSM-5 ASD moves forward into the past

The fifth edition of the diagnostic and statistical manual of mental disorders (DSM-5) (APA in diagnostic and statistical manual of mental disorders, Author, Washington, 2013) has decided to merge the subtypes of pervasive developmental disorders into a single category of autism spectrum disorder (ASD) on the assumption that they cannot be reliably differentiated from one another. The purpose of this review is to analyze the basis of this assumption by examining the comparative studies between Asperger's disorder (AsD) and autistic disorder (AD), and between pervasive developmental disorder not otherwise specified (PDDNOS) and AD. In all, 125 studies compared AsD with AD. Of these, 30 studies concluded that AsD and AD were similar conditions while 95 studies found quantitative and qualitative differences between them. Likewise, 37 studies compared PDDNOS with AD. Nine of these concluded that PDDNOS did not differ significantly from AD while 28 reported quantitative and qualitative differences between them. Taken together, these findings do not support the conceptualization of AD, AsD and PDDNOS as a single category of ASD. Irrespective of the changes proposed by the DSM-5, future research and clinical practice will continue to find ways to meaningfully subtype the ASD.

Essential elements in depression and anxiety. Part II

In this paper we continue to discuss the involvement of essential elements in depression and anxiety, and the possible mechanisms that link elements to the neurobiology underlying depression/anxiety. The present paper is focused on copper, selenium, manganese, iodine and vanadium. Different aspects of relationship between elements and depression or anxiety are reviewed, e.g. the association of the amount of an element in a diet or the serum level of an element and depressive or anxiety-like symptoms. Moreover, the relation of selected elements to the pathophysiology of depression or anxiety is discussed in the context of enzymes which require these elements as co-factors and are involved in the underlying pathophysiology of these disorders.

Mass spectrometry for the study of autism and neurodevelopmental disorders

Mass spectrometry (MS) has been increasingly used to study central nervous system disorders, including autism spectrum disorders (ASDs). The first studies of ASD using MS focused on the identification of external toxins, but current research is more directed at understanding endogenous protein changes that occur in ASD (ASD proteomics). This chapter focuses on how MS has been used to study ASDs, with particular focus on proteomic analysis. Other neurodevelopmental disorders have been investigated using this technique, including genetic syndromes associated with autism such as fragile X syndrome and Smith-Lemli-Opitz syndrome.

Mass spectrometry as a tool for studying autism spectrum disorder

Autism spectrum disorders (ASDs) are increasing in incidence but have an incompletely understood etiology. Tools for uncovering clues to the cause of ASDs and means for diagnoses are valuable to the field. Mass Spectrometry (MS) has been a useful method for evaluating differences between individuals with ASDs versus matched controls. Different biological substances can be evaluated using MS, including urine, blood, saliva, and hair. This technique has been used to evaluate relatively unsupported hypotheses based on introduction of exogenous factors, such as opiate and heavy metal excretion theories of ASDs. MS has also been used to support disturbances in serotonin-related molecules, which have been more consistently observed in ASDs. Serotonergic system markers, markers for oxidative stress, cholesterol system disturbances, peptide hypo-phosphorylation and methylation have been measured using MS in ASDs, although further analyses with larger numbers of subjects are needed (as well as consideration of behavioral data). Refinements in MS and data analysis are ongoing, allowing for the possibility that future studies examining body fluids and specimens from ASD subjects could continue to yield novel insights. This review summarizes MS investigations that have been conducted to study ASD to date and provides insight into future promising applications for this technique, with focus on proteomic studies.

Unique acyl-carnitine profiles are potential biomarkers for acquired mitochondrial disease in autism spectrum disorder

Autism spectrum disorder (ASD) has been associated with mitochondrial disease (MD). Interestingly, most individuals with ASD and MD do not have a specific genetic mutation to explain the MD, raising the possibility of that MD may be acquired, at least in a subgroup of children with ASD. Acquired MD has been demonstrated in a rodent ASD model in which propionic acid (PPA), an enteric bacterial fermentation product of ASD-associated gut bacteria, is infused intracerebroventricularly. This animal model shows validity as it demonstrates many behavioral, metabolic, neuropathologic and neurophysiologic abnormalities associated with ASD. This animal model also demonstrates a unique pattern of elevations in short-chain and long-chain acyl-carnitines suggesting abnormalities in fatty-acid metabolism. To determine if the same pattern of biomarkers of abnormal fatty-acid metabolism are present in children with ASD, the laboratory results from a large cohort of children with ASD (n=213) who underwent screening for metabolic disorders, including mitochondrial and fatty-acid oxidation disorders, in a medically based autism clinic were reviewed. Acyl-carnitine panels were determined to be abnormal if three or more individual acyl-carnitine species were abnormal in the panel and these abnormalities were verified by repeated testing. Overall, 17% of individuals with ASD demonstrated consistently abnormal acyl-carnitine panels. Next, it was determined if specific acyl-carnitine species were consistently elevated across the individuals with consistently abnormal acyl-carnitine panels. Significant elevations in short-chain and long-chain, but not medium-chain, acyl-carnitines were found in the ASD individuals with consistently abnormal acyl-carnitine panels-a pattern consistent with the PPA rodent ASD model. Examination of electron transport chain function in muscle and fibroblast culture, histological and electron microscopy examination of muscle and other biomarkers of mitochondrial metabolism revealed a pattern consistent with the notion that PPA could be interfering with mitochondrial metabolism at the level of the tricarboxylic-acid cycle (TCAC). The function of the fatty-acid oxidation pathway in fibroblast cultures and biomarkers for abnormalities in non-mitochondrial fatty-acid metabolism were not consistently abnormal across the subgroup of ASD children, consistent with the notion that the abnormalities in fatty-acid metabolism found in this subgroup of children with ASD were secondary to TCAC abnormalities. Glutathione metabolism was abnormal in the subset of ASD individuals with consistent acyl-carnitine panel abnormalities in a pattern similar to glutathione abnormalities found in the PPA rodent model of ASD. These data suggest that there are similar pathological processes between a subset of ASD children and an animal model of ASD with acquired mitochondrial dysfunction. Future studies need to identify additional parallels between the PPA rodent model of ASD and this subset of ASD individuals with this unique pattern of acyl-carnitine abnormalities. A better understanding of this animal model and subset of children with ASD should lead to better insight in mechanisms behind environmentally induced ASD pathophysiology and should provide guidance for developing preventive and symptomatic treatments.