Early-life metal exposure and schizophrenia: A proof-of-concept study using novel tooth-matrix biomarkers

Causality effect of 21 metals in plasma and serum, 731 immunocytes, and schizophrenia: an intermediary Mendelian randomization study in East Asian populations

Background

Multiple clinical studies have observed a close relationship between metals in plasma and serum, immunocytes, and schizophrenia; however, it remains unclear whether there is a genetic causal effect between metals in plasma and serum,immunocytes, and schizophrenia.

Objective

This study aimed to investigate the causal effects of metals in the plasma and serum on schizophrenia and the mediating role of immunocytes using Mendelian randomization methods in an East Asian population.

Methods

Summary results for 21 metals in plasma and serum,731 immunocytes and schizophrenia were acquired from publicly available genome-wide association studies (GWASs). GWAS data for metals, immunocytes, and schizophrenia were accessed between 2024 and 11-26 and 2024-12-02,Authors had no access to identifiable individual participant data. This study utilized two-sample Mendelian randomization (MR) analysis to establish causal relationships, which was achieved by employing various statistical methods, including inverse variance-weighted, simple mode, MR-Egger, weighted median, and weighted mode. Multiple sensitivity analyses, including heterogeneity tests, horizontal pleiotropy tests, MR-PRESSO tests, and leave-one-out analyses, were performed to confirm the reliability of the MR data. Finally, mediation analysis was employed to ascertain the immunocyte pathway that leads to schizophrenia from the metals in the plasma and serum. The study used anonymized summary-level GWAS data from public databases (e.g., GWAS Catalog, iEU Open GWAS), which do not contain personally identifiable information.

Results

The data of the East Asian population were analyzed by Mendelian randomization and two serum metallic traits that may reduce the risk of schizophrenia were identified: Serum iron (odds ratio (OR):0.54, 95 % confidence interval (CI):0.30-0.96, p = 0.036) and serum molybdenum levels (odds ratio (OR):0.54, 95 % confidence interval (CI):0.34-0.87, p = 0.011) corresponds to a 46 % reduction in schizophrenia risk. A baseline lifetime risk of 1 % in the general population, this translates to an absolute risk reduction of 0.46 %, with a number needed to treat (NNT) of approximately 217 individuals to prevent one case. They exhibited a negative causal relationship with the risk of Schizophrenia. Through mediation analysis, we identified a specific immunocyte subtype, CD33dim HLA DR + CD11b- Absolute Count, that not only correlates with serum iron levels but also shows a strong association with schizophrenia risk, suggesting a potential pathway through which serum iron may influence schizophrenia development. Serum iron levels showed a negative causal relationship in schizophrenia through the mediation of immunocytes with CD33dim HLA DR + CD11b- Absolute Count (mediation proportion:21 %).

Conclusions

This study identified a causal relationship between plasma and serum metals, immunocytes, and schizophrenia in an East Asian population through Mendelian randomization analysis, providing a new theoretical basis for the early detection, diagnosis, and treatment of schizophrenia.

Zinc in psychosis (Review)

Zinc (Zn) may be associated with schizophrenia (SCH), since its altered homeostasis can contribute to abnormal glutamatergic neurotransmission, inflammation, neurodegeneration and autoimmune abnormalities. It has been proposed that a number of patients with SCH could benefit from the use of Zn, either on its own or along with vitamins C, E and B6, and prenatal supplementation of Zn during the gestation period can mitigate the lipopolysaccharide‑induced rat model of maternal immune activation. The aim of the present review was to summarize the various effects of Zn dyshomeostasis on patients with psychosis and to clarify in what ways they could benefit from Zn supplementation.

A prospective study of a whole blood metal mixture and depressive symptoms among Black women from Detroit, Michigan

Exposure to metals has been previously associated with depressive symptoms, but few studies have considered potential effects of metal mixtures. In addition, few previous studies have been conducted among Black women, who are disproportionately at risk for exposure to some metals and greater depression incidence and severity. We analyzed data from the Study of Environment, Lifestyle, and Fibroids (SELF), a prospective cohort study of reproductive-aged Black women from Detroit, to examine associations between a mixture of metals, metalloids, and trace elements ("metals") and depressive symptoms (n = 1450). SELF participants self-identified as Black or African American and were 23-34 years of age at enrollment. We collected covariate information on structured questionnaires and whole blood samples at baseline. We quantified 17 metals in whole blood using inductively coupled plasma mass spectrometer triple quadruple or Direct Mercury Analyzer-80. Participants reported depressive symptoms on the Center for Epidemiologic Studies Depression Scale (CES-D) at the 20-month follow-up visit, where higher CES-D scores reflected greater depressive symptoms. We used quantile-based g-computation to estimate the cumulative association of the metal mixture with CES-D scores, adjusting for age, household income, educational attainment, body mass index, smoking status, alcohol intake, and parity. We estimated beta coefficients (with 95 % confidence intervals [CI]) as the percent difference in CES-D scores per quartile increase in all metals. A one-quartile increase in the metal mixture was associated with 14.8 % lower (95 % CI=-26.7 %, -1.1 %) CES-D scores, reflecting lower depressive symptoms. The mixture association was driven by nickel, copper, cesium, molybdenum, and lead. Other neurotoxic metals (cadmium, arsenic, mercury, chromium) were associated with greater depressive symptoms. Findings from this study suggest that exposure to a mixture of metals may affect depressive symptoms in Black women, with individual metals acting in opposing directions.

Association between the levels of toxic heavy metals and schizophrenia in the population of Guangxi, China: A case-control study

The relationship between body levels of heavy metals and the risk of schizophrenia remains unclear. This study investigates the relationship between plasma levels of toxic heavy metals and the risk of schizophrenia among adults in Guangxi, China. Plasma concentrations of lead (Pb), cadmium (Cd), arsenic (As), and chromium (Cr) were measured using inductively coupled plasma mass spectrometry (ICP-MS). To evaluate both the single and combined effects of metal exposure on the risk of schizophrenia, we employed multivariate logistic regression, Bayesian Kernel Machine Regression (BKMR), and generalized Weighted Quantile Sum (gWQS) models. Additionally, we employed the Comparative Toxicogenomics Database (CTD) to analyze the mechanistic pathways through which metal mixtures may induce schizophrenia. Relative mRNA expression levels were measured using Real-Time Quantitative Reverse Transcription Polymerase Chain Reaction (RT-qPCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted to predict potential biological functions. In logistic regression models, compared to the lowest exposure group (Q1), the odds ratios (ORs) for Pb in groups Q2, Q3, and Q4 were 2.18 (95% CI: 1.20-3.94), 4.74 (95% CI: 2.52-8.95), and 3.62 (95% CI: 1.80-7.28), respectively. Both BKMR and gWQS models indicated a positive correlation between the combined effects of toxic heavy metal mixtures and the risk of schizophrenia, with Pb demonstrating the most substantial impact, particularly in older adults and females. Elevated levels of tumor necrosis factor (TNF) and interleukin-1 beta (IL-1β) were observed in patients with schizophrenia, while the expression of tumor protein p53 (TP53) was significantly reduced. These findings underscore the critical need to avoid exposure to toxic heavy metals to prevent schizophrenia, highlighting significant public health implications.

Deciduous teeth from the New Hampshire birth cohort study: Early life environmental and dietary predictors of dentin elements

BACKGROUND

Sparse research exists on predictors of element concentrations measured in deciduous teeth.

OBJECTIVE

To estimate associations between maternal/child characteristics, elements measured in home tap water during pregnancy and element concentrations in the dentin of shed deciduous teeth.

METHODS

Our analysis included 152 pregnant person-infant dyads followed from the second trimester through the end of the first postnatal year from the New Hampshire Birth Cohort Study. During pregnancy and early infancy, we collected dietary and sociodemographic information via surveys, measured elements in home tap water, and later collected naturally exfoliated teeth from child participants. We measured longitudinal deposition of elements in dentin using LA-ICP-MS. Multivariable linear mixed models were used to estimate associations between predictors and dentin element concentrations.

RESULTS

We measured 12 elements in dentin including those previously reported (Ba, Mn, Pb, Sr, Zn) and less frequently reported (Al, As, Cd, Cu, Hg, Li, and W). A doubling of Pb or Sr concentrations in water was associated with higher dentin Pb or Sr respectively in prenatally formed [9% (95%CI: 3%, 15%); 3% (1%, 6%)] and postnatally formed [10% (2%, 19%); 6% (2%, 10%)] dentin. Formula feeding from birth to 6 weeks or 6 weeks to 4 months was associated with higher element concentrations in postnatal dentin within the given time period as compared to exclusive human milk feeding: Sr: 6 weeks: 61% (36%, 90%) and 4 months: 85% (54%, 121%); Ba: 6 weeks: 35% (3.3%, 77%) and 4 months: 42% (10%, 83%); and Li: 6 weeks: 61% (33%, 95%) and 4 months: 58% (31%, 90%).

SIGNIFICANCE

These findings offer insights into predictors of dentin elements and potential confounders in exposure-health outcome relationships during critical developmental periods.

Heavy metal concentrations and clinical symptoms in patients diagnosed with schizophrenia related to cigarette smoking

In our study, blood concentrations of lead (Pb), arsenic (As), and cadmium (Cd) and urine concentrations of thallium (Tl) were measured together with related symptoms of heavy metal poisoning in cigarette smoking volunteers diagnosed with schizophrenia, in cigarette smokers not diagnosed with schizophrenia, and in the control group of non-smokers and not diagnosed with schizophrenia volunteers. Our study was performed on 171 volunteers divided into the following subgroups: patients diagnosed with schizophrenia with at least 1 year of continuous cigarette smoking experience (56 participants), cigarette smokers not diagnosed with schizophrenia with at least one year of continuous smoking experience (58), and control group (not diagnosed with schizophrenia and non-smoking volunteers) (57). Smoking durations of cigarette smokers diagnosed with schizophrenia and cigarette smokers not diagnosed with schizophrenia are not similar (p = 0.431). Blood Pb, As, and Cd concentrations and urine Tl concentrations were the highest in the subgroup of cigarette smokers not diagnosed with schizophrenia, followed by the subgroup of cigarette smokers diagnosed with schizophrenia, and the control group. Only blood Pb concentrations were significantly higher (probability value p < 0.05) in the group of cigarette smokers not diagnosed with schizophrenia (5.16 μg/dL), comparing to the group of cigarette smokers diagnosed with schizophrenia (3.83 μg/dL) and to the control group (3.43 μg/dL). Blood Cd and As concentrations and urine Tl concentrations were significantly higher (p < 0.05) in cigarette smokers not diagnosed with schizophrenia than in the control group. The results revealed a statistically significant positive correlation (p < 0.001) in the cigarette smokers in the schizophrenia diagnosed group between blood Pb, blood As, and urine Tl concentrations and the duration of cigarette smoking.

Water, Soil, Noise, and Light Pollution: JACC Focus Seminar, Part 2

Various forms of pollution carry a substantial burden with respect to increasing the risk of causing and exacerbating noncommunicable diseases, especially cardiovascular disease. The first part of this 2-part series on pollution and cardiovascular disease provided an overview of the impact of global warming and air pollution. This second paper provides an overview of the impact of water, soil, noise, and light pollution on the cardiovascular system. This review discusses the biological mechanisms underlying these effects and potential environmental biometrics of exposure. What is clear from both these pollution papers is that significant efforts and redoubled urgency are needed to reduce the sources of pollution in our environment, to incorporate environmental risk factors into medical education, to provide resources for research, and, ultimately, to protect those who are particularly vulnerable and susceptible.

Schizophrenia as autoimmune disease: Involvement of Anti-NCAM antibodies

Understanding the etiopathogenesis of schizophrenia has always been an unsolved puzzle for modern medicine. This seems to be due to both disease complexity and lack of sufficient knowledge regarding the biological and non-biological anomalies that exhibit schizophrenia subjects. However, dysregulated immunity is a commonly identified feature in affected individuals. Thus, recently, a hallmark study showed causality relationship between anti-NCAM antibodies and schizophrenia-related behaviors in mice. NCAM plays crucial role in neurodevelopment during early life and neuroplasticity against different stressors during adulthood, and its dysfunction in schizophrenia is increasingly proven. The present review provides the main evidence that support the contribution of autoimmunity and NCAM abnormalities in the development of schizophrenia. Furthermore, it introduces five hypotheses that may explain the mechanism by which anti-NCAM antibodies are produced in the context of schizophrenia: (i) molecular mimicry, (ii) gut dysbiosis, (iii) viral infection, (iv) exposure to environmental pollutants, (v) and NCAM production anomalies.

Equine odontoclastic tooth resorption and hypercementosis (EOTRH): microspatial distribution of trace elements in hypercementosis-affected and unaffected hard dental tissues

Equine Odontoclastic Tooth Resorption and Hypercementosis (EOTRH) is a common, painful and poorly understood disease. Enamel, dentin and cementum accumulate both essential and toxic trace elements during mineralization. Characterization of the spatial accumulation pattern of trace elements may provide insight into the role that toxic elements play and inform biological processes affecting these hard dental tissues for future research. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to map the distribution of multiple trace elements and heavy metals across equine healthy and diseased (hypercementosis-affected) hard dental tissues among four teeth extracted from horses with EOTRH. Results showed banding patterns of some trace elements (lead, strontium, barium), reflecting the temporal component of accumulation of trace elements during dentin mineralization. Essential elements zinc and magnesium did not show banding patterns. Comparison to the unaffected cementum and dentin adjacent to the hypercementosis region showed that there is an underlying incremental pattern in the uptake of some metals with spatial irregularities. This supports a possible metabolic change involved in hypercementosis lesion development. This represents the first use of LA-ICP-MS to study the microspatial distribution of trace elements in equine teeth, establishing a baseline for elemental distribution in normal and EOTRH impacted dental hard tissue.

Reprint of: Elemental dysregulation in psychotic spectrum disorders: A review and research synthesis

Accumulating evidence from observational studies, genetic research, and animal models suggests a relationship between toxic and nutritive elements and psychotic spectrum disorders (PSD). This review systematically evaluates the current research evidence for two hypotheses: 1) that exposures to abnormal levels of toxic and nutritive elements early in life contributes to the subsequent development of PSD, and 2) that an imbalance of element levels is linked to psychotic illness and clinical severity. We focused on the extant literature on five elements, lead (Pb), copper (Cu), magnesium (Mg), manganese (Mn), and zinc (Zn), because of their previously documented associations with psychiatric problems and the availability of pertinent literature. The review identified 38 studies of which 11 measured Pb, 27 measured Cu, 16 measured Mg, 15 measured Mn, and 25 measured Zn concentrations in PSD patients and controls. A majority of research has been conducted on nutritive element imbalance, and findings are largely mixed. While it is biologically plausible that element dysregulation is an important modifiable risk factor for PSD, more research into exposure in early life is needed to better characterize this relationship.

Modification by genetic polymorphism of lead-induced IQ alteration: a systematic review

As well as a lead-related environmental factor, genetic factors could also corroborate important changes in intelligence quotient (IQ) through single-nucleotide polymorphisms. Thus, a systematic review was carried out to evaluate the possible influence of polymorphism on blood Pb levels and IQ points in pediatric patients (0-19 years old). Following the PRISMA guideline, the studies were systematically collected on PubMed, Scopus, and Embase databases. Six genes (transferrin (TF); glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A); glutamate ionotropic receptor NMDA type subunit 2B (GRIN2B); dopamine receptor D2/ankyrin repeat and kinase domain containing 1 ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1); aminolevulinate dehydratase (ALAD); vitamin D receptor (VDR)) were found in six selected articles. In these genes, 11 single-nucleotide polymorphisms were searched and six different types of variations (missense variant, intron variant, synonymous variant, stop, stop gained) were observed. Due to the few studies in the literature, there is no conclusive data to point out that there is a direct relationship between polymorphisms, Pb levels, and reduction of IQ points.

Association Between Measures Derived From Children's Primary Exfoliated Teeth and Psychopathology Symptoms: Results From a Community-Based Study

Mental disorders are among the most disabling health conditions globally. However, there remains a lack of valid, reliable, noninvasive, and inexpensive biomarkers to identify (at an early age) people who are at the greatest risk of experiencing a future mental health condition. Exfoliated primary teeth, when used in combination with established and emerging tools (e.g., family history, imaging, genetics, epigenetics), may provide important additional insights about vulnerability to mental illness. Teeth are especially promising because they develop in parallel with the brain and maintain a permanent record of environmental insults occurring during prenatal and perinatal development. Despite their potential, few empirical studies have investigated features of exfoliated teeth in relation to mental health. Here, we used micro-CT imaging to test the hypothesis that measures derived from exfoliated primary incisors associated with psychopathology symptoms in a community-based sample of children (n = 37). We found that enamel volume (β = −0.77, 95% CI, −1.35 to −0.18, P = 0.01) had large negative associations with internalizing symptoms, and enamel mineral density (β = 0.77, 95% CI, 0.18–1.35, P = 0.01) had large positive associations with internalizing behavioral symptoms, even after stringent control for multiple testing. Pulp volume (β = −0.50, 95% CI, −0.90 to −0.09, P = 0.02) had a moderately-large negative association with externalizing behavioral symptoms, though these associations did not survive multiple testing correction. These results support the ongoing investigation of teeth as potential novel biomarkers of mental health risk.

IQ alteration induced by lead in developed and underdeveloped/developing countries: A systematic review and a meta-analysis

The aim of this study was to evaluate the effects of Pb exposure on full-scale IQ score in pediatric subjects. Following PRISMA guidelines, the data from January 2010 to April 2020 were systematically searched and collected on electronic databases (PubMed, Scopus, and Embase). The eligibility criteria included cross-sectional, cohort, and case-control studies that were published in English, from 2010 to 2020, that analyzed the blood Pb levels of pediatric subjects (0-19 years) and possible changes in the full-scale IQ score. In this study, 2174 scientific papers were collected from three electronic databases. From those, 726 were duplicates and 1421 were excluded because they did not meet the eligibility criteria, resulting in a total of 27 papers, from which, seven were used to perform the meta-analysis. The 27 scientific papers systematically selected for this study were separated by the country where the study was realized in developed and underdeveloped/developing countries. In the underdeveloped/developing countries the blood Pb levels are higher and showed a greater variation (1.30-11.66 μgPb/dL of blood) than in countries with higher development index (0.57-4.80 μgPb/dL of blood). The full-scale IQ score are inversely proportional to the blood Pb values, and it is possible to see that in the underdeveloped/developing countries the full-scale IQ score showed lower values and greater variation (59.2-111) compared to the individuals from developed countries (91.9-114.5). In conclusion, it was observed that blood Pb levels alter the full-scale IQ score. Thus, policies for the prevention of environmental contamination and the reduction of Pb exposure must be taken, mainly, in underdeveloped/developing countries.

Critical windows of susceptibility in the association between manganese and neurocognition in Italian adolescents living near ferro-manganese industry

INTRODUCTION

Understanding the neurodevelopmental effects of manganese (Mn) is complicated due to its essentiality for growth and development. While evidence exists for the harmful effects of excess Mn, pediatric epidemiologic studies have observed inconsistent associations between Mn and child cognition.

OBJECTIVE

We sought to estimate prospective associations between Mn measured in three different early-life time windows with adolescent cognition using deciduous teeth biomarkers.

METHODS

Deciduous teeth were collected from 195 participants (ages 10-14 years) of the Public Health Impact of Manganese Exposure (PHIME) study in Brescia, Italy. Measurements of tooth Mn represented prenatal (∼14 weeks gestation - birth), early postnatal (birth - 1.5 years) and childhood (∼1.5 - 6 years) time windows. Neuropsychologists administered the Wechsler Intelligence Scale for Children, 3rd edition (WISC-III), to obtain composite IQ and subtest scores. Associations between tooth Mn at each time window and adolescent WISC-III scores were estimated using multivariable linear regression. We tested differences in associations between Mn and outcomes across time windows using multiple informant models. Sex-specific associations were explored in stratified models.

RESULTS

Adjusted associations between tooth Mn and composite IQ scores were positive in the prenatal period and negative in the childhood period. Associations were strongest for subtest scores that reflect working memory, problem solving, visuospatial ability and attention: prenatal Mn was positively associated with Digits backward [SD change in score per interquartile range increase in Mn: β = 0.20 (95 % CI: 0.02, 0.38)] and Block design [β = 0.21 (0.01, 0.41)] and early postnatal Mn was positively associated with Digits forward [β = 0.24 (0.09, 0.40)], while childhood Mn was negatively associated with Coding [β = -0.14 (-0.28, -0.001)]. Sex-stratified analyses suggested different Mn-cognition associations for boys and girls and was also dependent on the time window of exposure.

CONCLUSION

Our results suggest that exposure timing is critical when evaluating Mn associations between Mn and cognition. Higher prenatal Mn was beneficial for adolescent cognition; however, these beneficial associations shifted towards harmful effects in later time windows. Cognitive domains most sensitive to Mn across time windows included visuospatial ability, working memory, attention and problem-solving.

Tooth biomarkers to characterize the temporal dynamics of the fetal and early-life exposome

BACKGROUND

Teeth have unique histology that make this biomatrix a time-capsule for retrospective exposure analysis of fetal and early life. However, most analytic methods require pulverizing the whole tooth, which eliminates exposure timing information. Further, the range of chemicals and endogenous exposures that can be measured in teeth has yet to be fully characterized.

METHODS

We performed untargeted metabolomics on micro-dissected layers from naturally shed deciduous teeth. Using four liquid-chromatography high-resolution mass spectrometry analytical modes, we profiled small molecules (<1000 Da) from prenatal and postnatal tooth fractions. In addition, we employed linear regression on the tooth fraction pairs from 31 children to identify metabolites that discriminate between prenatal and postnatal exposures.

RESULTS

Of over 10,000 features measured in teeth dentin, 390 unique compounds were annotated from 62 chemical classes. The class with the largest number of compounds was carboxylic acids and their derivatives (36%). Of the annotated exogenous metabolites (phthalates, parabens, perfluoroalkyl compounds, and cotinine) and endogenous metabolites (fatty acids, steroids, carnitines, amino acids, and others), 91 are linked to 256 health conditions through published literature. Differential analysis revealed 267 metabolites significantly different between the prenatal and the postnatal tooth fractions (adj. p-value < 0.05, Bonferroni correction), and 21 metabolites exclusive to the prenatal fraction.

CONCLUSIONS

The prenatal and early postnatal exposome revealed from dental biomarkers represents a broad range of endogenous and exogenous metabolites for a comprehensive characterization in environmental health research. Most importantly, this technology provides a direct window into fetal exposures that is not possible by maternal biomarkers. Indeed, we identified several metabolites exclusively in the prenatal fraction, suggesting unique fetal exposures that are markedly different to postnatal exposures. Expansion of databases that include tooth matrix metabolites will strengthen biological interpretation and shed light on exposures during gestation and early life that may be causally linked with later health conditions.

Lead (Pb) induced Oxidative Stress as a Mechanism to Cause Neurotoxicity in Drosophila melanogaster

The widespread use of lead (Pb) has caused global contamination, inevitable human exposure, and public health problems. Pb neurotoxicity has been linked to various human diseases, but its associated mechanism causing neurotoxicity is unknown. Drosophila melanogaster as a model organism has been used to study the mechanism involved in Pb-caused neurotoxicity and the potential role of antioxidants in ameliorating its harmful effects. The larval feeding technique was adopted to administer different concentrations of Pb (0.2-0.8 mM) to Oregon-R (ORR), superoxide dismutase (Sod), or catalase (Cat) overexpressing, and Sod or Cat knockdown flies to analyse Pb load, oxidative stress components, DNA damage, apoptosis and vacuolation in the brain. The results revealed that Pb accumulation in the Drosophila brain induces oxidative stress by generating reactive oxygen species (ROS) and lipid peroxidation (LPO), depleting antioxidant enzymes. Molecular docking studies have evidenced it. Pb directly binds to antioxidants and major grooves of DNA, leading to DNA damage. Increased DNA damage, apoptosis, vacuolation in brains of Pb-treated ORR, Sod, or Cat knockdown flies; and on the contrary, reduced oxidative DNA damage, apoptosis, and vacuolation in brains of Pb treated Sod or Cat overexpressed flies put forward that oxidative stress is the mechanism in Pb caused neurotoxicity.

Elemental dysregulation in psychotic spectrum disorders: A review and research synthesis

Accumulating evidence from observational studies, genetic research, and animal models suggests a relationship between toxic and nutritive elements and psychotic spectrum disorders (PSD). This review systematically evaluates the current research evidence for two hypotheses: 1) that exposures to abnormal levels of toxic and nutritive elements early in life contributes to the subsequent development of PSD, and 2) that an imbalance of element levels is linked to psychotic illness and clinical severity. We focused on the extant literature on five elements, lead (Pb), copper (Cu), magnesium (Mg), manganese (Mn), and zinc (Zn), because of their previously documented associations with psychiatric problems and the availability of pertinent literature. The review identified 38 studies of which 11 measured Pb, 27 measured Cu, 16 measured Mg, 15 measured Mn, and 25 measured Zn concentrations in PSD patients and controls. A majority of research has been conducted on nutritive element imbalance, and findings are largely mixed. While it is biologically plausible that element dysregulation is an important modifiable risk factor for PSD, more research into exposure in early life is needed to better characterize this relationship.

Using primary teeth and archived dried spots for exposomic studies in children: Exploring new paths in the environmental epidemiology of pediatric cancer

It is estimated that 300,000 children 0-14 years of age are diagnosed with cancer worldwide each year. While the absolute risk of cancer in children is low, it is the leading cause of death due to disease in children in high-income countries. In spite of this, the etiologies of pediatric cancer are largely unknown. Environmental exposures have long been thought to play an etiologic role. However, to date, there are few well-established environmental risk factors for pediatric malignancies, likely due to technical barriers in collecting biological samples prospectively in pediatric populations for direct measurements. In this review, we propose the use of novel or underutilized biospecimens (dried blood spots and teeth) and molecular approaches for exposure assessment (epigenetics, metabolomics, and somatic mutational profiles). Future epidemiologic studies of pediatric cancer should incorporate novel exposure assessment methodologies, data on molecular features of tumors, and a more complete assessment of gene-environment interactions.

Early-life lead exposure and neurodevelopmental disorders

Lead (Pb²⁺) exposure is a global public health problem of major proportion with an alarming number of children with blood Pb²⁺ levels > 10 >g/dL, twice the current CDC reference level for Pb²⁺ exposure. Mounting evidence from population-based studies suggests an association between chronic early life Pb²⁺ exposure (CELLE) and psychiatric disorders, specifically schizophrenia (SZ). Preclinical studies suggest a common mechanism in the pathophysiology of CELLE and SZ, NMDA receptor hypofunction. Here we describe human and experimental animal studies providing the evidence for such an association. Further, recent preclinical studies indicate that Pb²⁺-induced changes in neurotransmitter receptors that mediate the action(s) of drugs of abuse are increased in brain regions associated with addiction circuits in adolescence, a period of increased susceptibility to drug use and abuse and expression of psychiatric disease in humans. In summary, the relationship between the global burden of childhood Pb²⁺ exposure and the latent onset of psychiatric disorders and predisposition to drug use requires further investigations in human populations.

Beyond the Mind-Serum Trace Element Levels in Schizophrenic Patients: A Systematic Review

The alterations in serum trace element levels are common phenomena observed in patients with different psychiatric conditions such as schizophrenia, autism spectrum disorder, or major depressive disorder. The fluctuations in the trace element concentrations might act as potential diagnostic and prognostic biomarkers of many psychiatric and neurological disorders. This paper aimed to assess the alterations in serum trace element concentrations in patients with a diagnosed schizophrenia. The authors made a systematic review, extracting papers from the PubMed, Web of Science, and Scopus databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Among 5009 articles identified through database searching, 59 of them were assessed for eligibility. Ultimately, 33 articles were included in the qualitative synthesis. This review includes the analysis of serum levels of the following trace elements: iron, nickel, molybdenum, phosphorus, lead, chromium, antimony, uranium, magnesium, aluminum, zinc, copper, selenium, calcium, and manganese. Currently, there is no consistency regarding serum trace element levels in schizophrenic patients. Thus, it cannot be considered as a reliable prognostic or diagnostic marker of schizophrenia. However, it can be assumed that altered concentrations of those elements are crucial regarding the onset and exaggeration of either psychotic or negative symptoms or cognitive dysfunctions.

Air Pollution-Related Brain Metal Dyshomeostasis as a Potential Risk Factor for Neurodevelopmental Disorders and Neurodegenerative Diseases

Increasing evidence links air pollution (AP) exposure to effects on the central nervous system structure and function. Particulate matter AP, especially the ultrafine (nanoparticle) components, can carry numerous metal and trace element contaminants that can reach the brain in utero and after birth. Excess brain exposure to either essential or non-essential elements can result in brain dyshomeostasis, which has been implicated in both neurodevelopmental disorders (NDDs; autism spectrum disorder, schizophrenia, and attention deficit hyperactivity disorder) and neurodegenerative diseases (NDGDs; Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis). This review summarizes the current understanding of the extent to which the inhalational or intranasal instillation of metals reproduces in vivo the shared features of NDDs and NDGDs, including enlarged lateral ventricles, alterations in myelination, glutamatergic dysfunction, neuronal cell death, inflammation, microglial activation, oxidative stress, mitochondrial dysfunction, altered social behaviors, cognitive dysfunction, and impulsivity. Although evidence is limited to date, neuronal cell death, oxidative stress, and mitochondrial dysfunction are reproduced by numerous metals. Understanding the specific contribution of metals/trace elements to this neurotoxicity can guide the development of more realistic animal exposure models of human AP exposure and consequently lead to a more meaningful approach to mechanistic studies, potential intervention strategies, and regulatory requirements.

Rare variants and biological pathways identified in treatment-refractory depression

Individuals diagnosed with major depressive disorder not responding to at least two adequate treatments are defined as treatment-refractory major depressive disorder (TR-MDD). Some TR-MDD patients have altered metabolic phenotypes that may be pharmacologically reversed. The characterization of these phenotypes and their underlying etiologies is paramount, particularly their genetic components. In this study, TR-MDD patients (n = 124) were recruited and metabolites were quantified in their cerebrospinal fluid (CSF) and peripheral blood. Three sub-categories of deficiencies were examined, namely 5-methyltetrahydrofolte (in CSF; n = 13), tetrahydrobiopterin (in CSF; n = 11), and abnormal acylcarnitine profiles (in peripheral blood; n = 8). Whole exome sequencing was performed on genomic DNA from the entire TR-MDD cohort and exonic variant allele frequencies for cases were compared to a control cohort (1:5 matching on ancestry). Low frequency, damaging alleles were identified and used for in silico pathway analyses. Three association signals for TR-MDD approached genome-wide significance on chromosomes 22, 7, and 3. Three risk-associated variants from a prior depression study were replicated. Relevant biological pathways were identified that contained an enrichment of rare, damaging variants in central nervous system (CNS)-specific pathways, including neurotransmitter receptors, potassium channels, and synapse transmission. Some TR-MDD patients had rare variants in genes that were previously associated with other psychiatric disorders, psychiatric endophenotypes, CNS structural defects, and CNS-related cellular and molecular functions. Exome analysis of metabolically phenotyped TR-MDD patients has identified potentially functional gene pathways and low frequency, deleterious gene variants for further investigation. Further studies in larger cohorts of biochemically phenotyped TR-MDD patients are desirable to extend and confirm these findings.

Lagged WQS regression for mixtures with many components

The developmental timing of exposures to toxic chemicals or combinations of chemicals may be as important as the dosage itself. This concept is called "critical windows of exposure." The time boundaries of such windows can be detected if exposure data are collected repeatedly in short time intervals. The development of tooth-matrix biomarkers which provide prenatal and postnatal exposure measures in repeated intervals can provide such data. Using teeth, we use reverse distributed lagged models (DLMs) to incorporate weekly prenatal and postnatal measures of exposures to estimate time-varying associations with developmental effects. The analysis of such data using lagged weighted quantile sum (WQS) regression as an extension to reverse DLMs for complex mixtures was first proposed by Bello et al. This prior algorithm was not operationally generalizable to large numbers of components (say, more than five or six). We propose a revised algorithm that may be useful for larger mixtures by combining time-specific WQS(t) indices in a reverse DLM. We demonstrate the new algorithm using tooth data in association with a neurodevelopmental score and in simulated data from 3 cases wherein different components of a mixture have time varying associations and in the case where none have associations. The new algorithm correctly detects the simulated associations when the number of samples within the time-specific analyses is moderate to large.

Beyond the looking glass: recent advances in understanding the impact of environmental exposures on neuropsychiatric disease

The etiologic pathways leading to neuropsychiatric diseases remain poorly defined. As genomic technologies have advanced over the past several decades, considerable progress has been made linking neuropsychiatric disorders to genetic underpinnings. Interest and consideration of nongenetic risk factors (e.g., lead exposure and schizophrenia) have, in contrast, lagged behind heritable frameworks of explanation. Thus, the association of neuropsychiatric illness to environmental chemical exposure, and their potential interactions with genetic susceptibility, are largely unexplored. In this review, we describe emerging approaches for considering the impact of chemical risk factors acting alone and in concert with genetic risk, and point to the potential role of epigenetics in mediating exposure effects on transcription of genes implicated in mental disorders. We highlight recent examples of research in nongenetic risk factors in psychiatric disorders that point to potential shared biological mechanisms-synaptic dysfunction, immune alterations, and gut-brain interactions. We outline new tools and resources that can be harnessed for the study of environmental factors in psychiatric disorders. These tools, combined with emerging experimental evidence, suggest that there is a need to broadly incorporate environmental exposures in psychiatric research, with the ultimate goal of identifying modifiable risk factors and informing new treatment strategies for neuropsychiatric disease.

Early life metal dysregulation in amyotrophic lateral sclerosis

OBJECTIVE

Deficiencies and excess of essential elements and toxic metals are implicated in amyotrophic lateral sclerosis (ALS), but the age when metal dysregulation appears remains unknown. This study aims to determine whether metal uptake is dysregulated during childhood in individuals eventually diagnosed with ALS.

METHODS

Laser ablation-inductively coupled plasma-mass spectrometry was used to obtain time series data of metal uptake using biomarkers in teeth from autopsies or dental extractions of ALS (n = 36) and control (n = 31) participants. Covariate data included sex, smoking, occupational exposures, and ALS family history. Case-control differences were identified in temporal profiles of metal uptake for individual metals using distributed lag models. Weighted quantile sum (WQS) regression was used for metals mixture analyses. Similar analyses were performed on an ALS mouse model to further verify the relevance of dysregulation of metals in ALS.

RESULTS

Metal levels were higher in cases than in controls: 1.49 times for chromium (1.11-1.82; at 15 years), 1.82 times for manganese (1.34-2.46; at birth), 1.65 times for nickel (1.22-2.01; at 8 years), 2.46 times for tin (1.65-3.30; at 2 years), and 2.46 times for zinc (1.49-3.67; at 6 years). Co-exposure to 11 elements indicated that childhood metal dysregulation was associated with ALS. The mixture contribution of metals to disease outcome was likewise apparent in tooth biomarkers of an ALS mouse model, and differences in metal distribution were evident in ALS mouse brains compared to brains from littermate controls.

INTERPRETATION

Overall, our study reveals direct evidence that altered metal uptake during specific early life time windows is associated with adult-onset ALS.

Dysregulated biodynamics in metabolic attractor systems precede the emergence of amyotrophic lateral sclerosis

Evolutionarily conserved mechanisms maintain homeostasis of essential elements, and are believed to be highly time-variant. However, current approaches measure elemental biomarkers at a few discrete time-points, ignoring complex higher-order dynamical features. To study dynamical properties of elemental homeostasis, we apply laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) to tooth samples to generate 500 temporally sequential measurements of elemental concentrations from birth to 10 years. We applied dynamical system and Information Theory-based analyses to reveal the longest-known attractor system in mammalian biology underlying the metabolism of nutrient elements, and identify distinct and consistent transitions between stable and unstable states throughout development. Extending these dynamical features to disease prediction, we find that attractor topography of nutrient metabolism is altered in amyotrophic lateral sclerosis (ALS), as early as childhood, suggesting these pathways are involved in disease risk. Mechanistic analysis was undertaken in a transgenic mouse model of ALS, where we find similar marked disruptions in elemental attractor systems as in humans. Our results demonstrate the application of a phenomological analysis of dynamical systems underlying elemental metabolism, and emphasize the utility of these measures in characterizing risk of disease.

The metabolism of essential elements in early life is essential to healthy growth and development. Elemental homeostasis is typically studied by characterizing distributions of elemental concentrations at the level of the population. Here, we introduce a new method of characterizing elemental metabolism at the level of the individual. Using tooth-based biomarkers, we tracked the longitudinal trajectory of essential elements throughout childhood at weekly temporal resolution from birth through approximately 10 years of life. We analyzed these trajectories to identify the formation of stable dynamic states (attractors) and transitions between these states throughout development. We found that metabolic dynamics were specific to discrete elemental pathways; copper metabolism typically involved the formation of multiple discrete states throughout childhood, whereas other elements, such as zinc, tended to persist in a single stable dynamic throughout development. Next, we compared elemental biodynamics in neurologically healthy cases and subjects that were later diagnosed with amyotrophic lateral sclerosis (ALS). We found these patterns were dysregulated in ALS, and also found similar results in a mouse model of ALS. Overall, our results provide a novel approach to characterize elemental biodynamics throughout development, and emphasize that the dysregulation of these processes may be predictive of later onset of disease.

Teeth as Potential New Tools to Measure Early-Life Adversity and Subsequent Mental Health Risk: An Interdisciplinary Review and Conceptual Model

Early-life adversity affects nearly half of all youths in the United States and is a known risk factor for psychiatric disorders across the life course. One strategy to prevent mental illness may be to target interventions toward children who are exposed to adversity, particularly during sensitive periods when these adversities may have even more enduring effects. However, a major obstacle impeding progress in this area is the lack of tools to reliably and validly measure the existence and timing of early-life adversity. In this review, we summarize empirical work across dentistry, anthropology, and archaeology on human tooth development and discuss how teeth preserve a time-resolved record of our life experiences. Specifically, we articulate how teeth have been examined in these fields as biological fossils in which the history of an individual's early-life experiences is permanently imprinted; this area of research is related to, but distinct from, studies of oral health. We then integrate these insights with knowledge about the role of psychosocial adversity in shaping psychopathology risk to present a working conceptual model, which proposes that teeth may be an understudied yet suggestive new tool to identify individuals at risk for mental health problems following early-life psychosocial stress exposure. We end by presenting a research agenda and discussion of future directions for rigorously testing this possibility and with a call to action for interdisciplinary research to meet the urgent need for new biomarkers of adversity and psychiatric outcomes.

Trace elements in schizophrenia: a systematic review and meta-analysis of 39 studies (N = 5151 participants)

Context

The pathogenesis of schizophrenia appears to be multifaceted.

Objective

The aim of this meta-analysis of studies that investigated blood and hair concentrations of trace elements in people diagnosed with schizophrenia was to determine whether levels of trace elements in patients with schizophrenia differ from those in healthy individuals.

Data Sources

The PubMed, Scopus, and Web of Science databases were searched to January 2018.

Study Selection

Studies that compared concentrations of trace elements in patients with schizophrenia with those in healthy controls, in patients with schizophrenia under different treatment regimens, or in patients with schizophrenia at different stages of disease were included.

Data Extraction

Data on study and sample characteristics and measures of trace elements were extracted.

Results

Thirty-nine studies with a total of 5151 participants were included. Meta-analysis of combined plasma and serum data showed higher levels of copper, lower levels of iron, and lower levels of zinc among patients with schizophrenia vs controls without schizophrenia. Subgroup analyses confirmed the following: higher levels of copper in plasma, in users of typical antipsychotic drugs, and in males; lower levels of zinc in serum, in patients in Asia, in drug-naive/drug-free patients, and in inpatients; lower levels of iron in serum, in patients in Asia, in drug-naive/drug-free patients, in patients on antipsychotic drugs, in inpatients, in patients with acute or newly diagnosed schizophrenia, in patients with chronic or previously diagnosed schizophrenia, and in males; and lower levels of manganese in plasma and in patients with chronic or previously diagnosed schizophrenia.

Conclusions

This meta-analysis provides evidence of an excess of copper, along with deficiencies of zinc, iron, and manganese, in patients with schizophrenia.

Effects of combined arsenic and lead exposure on the brain monoaminergic system and behavioral functions in rats: Reversal effect of MiADMSA

In this study, we evaluated the therapeutic efficacy of monoisoamyldimercaptosuccinic acid (MiADMSA) against individual and combined effects of arsenic (As) and lead (Pb) on the monoaminergic system and behavioral functions in rats. Pregnant rats were exposed to sodium metaarsenite (50 ppm) and lead acetate (0.2%) individually and in combination (As = 25 ppm + Pb = 0.1%) via drinking water from gestation day (GD) 6 to postnatal day (PND) 21. MiADMSA (50 mg/kg body weight) was given orally through gavage for 3 consecutive days to pups from PND 18 to PND 20. The results showed increases in synaptosomal epinephrine, dopamine, and norepinephrine levels with individual metal exposures and decreases with combined exposure to As and Pb in the cortex, cerebellum, and hippocampus in PND 21, PND 28, and 3 months age-group rats. We found decreased activity of mitochondrial monoamine oxidase in the selected brain regions following individual and combined exposures to Pb and As. In addition, rats treated with Pb and As alone or in combination showed significant deficits in open-field behavior, grip strength, locomotor activity, and exploratory behavior at PND 28 and 3 months of age. However, MiADMSA administration showed reversal effects against the As- and/or Pb-induced impairments in the monoaminergic system as well as in behavioral functions of rats. Our data demonstrated that the mixture of Pb and As induced synergistic toxicity to developing brain leading to impairments in neurobehavioral functions and also suggest therapeutic efficacy of MiADMSA against Pb- and/or As-induced developmental neurotoxicity.

Cognitive development prior to onset of psychosis

Schizophrenia patients commonly exhibit substantial and diffuse cognitive impairment. Evidence suggests that subtle cognitive deficits are already apparent in childhood and adolescence, many years prior to onset of psychosis. While there is almost unequivocal evidence of some degree of cognitive impairment in individuals who later develop schizophrenia, the literature remains inconclusive regarding the exact nature of this impairment and warrants careful review and interpretation. Meta-analytic findings suggest that individuals who later develop schizophrenia, but not related disorders, such as bipolar disorder, exhibit a premorbid IQ deficit of around 8 points. Several studies have also found evidence for premorbid deficits across most cognitive domains, such as language, processing speed and executive functions. Longitudinal studies, although rare, suggest that individuals who go on to develop schizophrenia may show a course of increasing cognitive impairment prior to onset of psychosis. While evidence regarding the etiology of premorbid deficits is scarce, common and rare genetic variants, as well as environmental factors such as obstetric complications and cannabis use may play an important role and warrant further examination. In this selected review, we give an overview of population-based studies on premorbid cognitive deficits in schizophrenia, with a special focus on evidence regarding the specificity, profile and course of these deficits.

Manganese in teeth and neurobehavior: Sex-specific windows of susceptibility

BACKGROUND

Manganese (Mn) is an essential element required for growth and development, but higher body burdens have been associated with neurobehavioral decrements in children.

OBJECTIVES

We examined whether prenatal or postnatal Mn measured in deciduous teeth was associated with scores on a test of visuospatial learning and memory.

METHODS

Deciduous teeth were collected from 142 participants (ages 10-14years) residing near varied ferro‑manganese industry in Italy. Mn concentrations were measured in prenatal and postnatal tooth regions by laser ablation inductively coupled plasma mass spectrometry (ICP-MS). The Virtual Radial Arm Maze (VRAM), an animal-human analogue task, was used to assess visuospatial learning and memory. We used generalized additive, linear and zero-inflated Poisson mixed regression models to estimate associations between prenatal or postnatal Mn concentrations and repeated measures of all four VRAM outcomes: time, distance, working and reference memory errors. Effect measure modification by sex was examined in stratified models.

RESULTS

U-shaped associations between prenatal Mn and VRAM outcomes were observed among girls only (pGAMM=0.001 to 0.02 in stratified models). Compared to the mid-tertile of prenatal Mn, girls in the highest tertile took 7.7s [95% CI: -6.1, 21.5] longer to complete the task, traveled 2.3 maze units [0.1, 4.4] farther, and committed more working and reference memory errors (β for count ratio=1.33 [1.01, 1.83]; 1.10 [0.98, 1.24], respectively). This association was not observed among boys. In contrast, for postnatal Mn, no significant associations were found, and patterns were similar for boys and girls.

CONCLUSIONS

The prenatal period may be a critical window for the impact of environmental Mn on visuospatial ability and executive function, especially for females.

New Research Strategy for Measuring Pre- and Postnatal Metal Dysregulation in Psychotic Disorders

While previous studies have found evidence for detrimental effects of metals on neurodevelopment, the long-term effects on mental health remain unclear. The objective was to explore the effect of early metal exposure on risk of psychotic disorder and on symptom severity following illness onset. Through the use of validated tooth-biomarkers, we estimated pre- and postnatal exposure levels of essential elements (copper, magnesium, manganese, and zinc) and elements associated with neurotoxicity (lead, arsenic, lithium, and tin). We found consistently higher levels of lithium in patients compared to controls. Higher levels of magnesium and lower levels of zinc were associated with more severe psychopathology over 20 years after metal exposure. The results show promise for the use of teeth biomarkers in examining early environmental risk for psychosis and underscore the relevance of studying metal exposure during critical neurodevelopmental periods.

Magnesium in schizophrenia

Many psychopathological symptoms, including schizophrenia, can be associated with magnesium metabolism disturbances. In the literature, contradictory data exist regarding magnesium levels in patients with this disorder. However, this situation might be caused by determination of extracellular concentration of magnesium; although, this is mainly an intracellular ion. There are no data concerning determination of the ionized fraction of magnesium in patients with schizophrenia, while the ionized fraction represents 67% of the total pool of magnesium in healthy people. Also, the mechanism of magnesium action-the effect of magnesium ions on NMDA and GABA receptors-has not yet been fully investigated. There are preliminary studies aimed at increasing the effectiveness of schizophrenia pharmacotherapy via magnesium supplementation. Multidirectional activity of magnesium can significantly increase its therapeutic effect in psychiatry. This observation is confirmed by recent studies conducted by various research teams. However, further studies on the role of magnesium supplementation in patients with schizophrenia are needed.

The effect of lead exposure on fatty acid composition in mouse brain analyzed using pseudo-catalytic derivatization

We performed toxicological study of mice exposed to lead by quantifying fatty acids in brain of the mice. This study suggests that the introduced analytical method had an extremely high tolerance against impurities such as water and extractives; thus, it led to the enhanced resolution in visualizing the spectrum of fatty acid profiles in animal brain. Furthermore, one of the biggest technical advantages achieved in this study was the quantitation of fatty acid methyl ester profiles of mouse brain using a trace amount of sample (e.g., 100 μL mixture). Methanol was screened as the most effective extraction solvent for mouse brain. The behavioral test of the mice before and after lead exposure was conducted to see the effect of lead exposure on fatty acid composition of the mice' brain. The lead exposure led to changes in disease-related behavior of the mice. Also, the lead exposure induced significant alterations of fatty acid profile (C16:0, C 18:0, and C 18:1) in brain of the mice, implicated in pathology of psychiatric diseases. The alteration of fatty acid profile of brain of the mice suggests that the derivatizing technique can be applicable to most research fields associated with the environmental neurotoxins with better resolution in a short time, as compared to the current protocols for lipid analysis.