The effect of high dose oral manganese exposure on copper, iron and zinc levels in rats

Sex-specific associations between co-exposure to multiple metals and externalizing symptoms in adolescence and young adulthood

Externalizing disorders, such as attention-deficit/hyperactivity disorder (ADHD), account for the majority of the child/adolescent referrals to mental health services and increase risk for later-life psychopathology. Although the expression of externalizing disorders is more common among males, few studies have addressed how sex modifies associations between metal exposure and adolescent externalizing symptoms. This study aimed to examine sex-specific associations between co-exposure to multiple metals and externalizing symptoms in adolescence and young adulthood. Among 150 adolescents and young adults (55% female, ages: 15-25 years) enrolled in the Public Health Impact of Metals Exposure (PHIME) study in Brescia, Italy, we measured five metals (manganese (Mn), lead (Pb), copper (Cu), chromium (Cr), nickel (Ni)) in four biological matrices (blood, urine, hair, and saliva). Externalizing symptoms were assessed using the Achenbach System of Empirically Based Assessment (ASEBA) Youth Self-Report (YSR) or Adult Self Report (ASR). Using generalized weighted quantile sum (WQS) regression, we investigated the moderating effect of sex (i.e., assigned at birth) on associations between the joint effect of exposure to the metal mixture and externalizing symptoms, adjusting for age and socioeconomic status. We observed that metal mixture exposure was differentially associated with aggressive behavior in males compared to females (β = -0.058, 95% CI [-0.126, -0.009]). In males, exposure was significantly associated with more externalizing problems, and aggressive and intrusive behaviors, driven by Pb, Cu and Cr. In females, exposure was not significantly associated with any externalizing symptoms. These findings suggest that the effect of metal exposure on externalizing symptoms differs in magnitude between the sexes, with males being more vulnerable to increased externalizing symptoms following metal exposure. Furthermore, our findings support the hypothesis that sex-specific vulnerabilities to mixed metal exposure during adolescence/young adulthood may play a role in sex disparities observed in mental health disorders, particularly those characterized by externalizing symptoms.

An explainable machine-learning approach for revealing the complex synthesis path-property relationships of nanomaterials

Machine learning (ML) models have recently shown important advantages in predicting nanomaterial properties, which avoids many trial-and-error explorations. However, complex variables that control the formation of nanomaterials exhibiting the desired properties still need to be better understood owing to the low interpretability of ML models and the lack of detailed mechanism information on nanomaterial properties. In this study, we developed a methodology for accurately predicting multiple synthesis parameter-property relationships of nanomaterials to improve the interpretability of the nanomaterial property mechanism. As a proof-of-concept, we designed glutathione-gold nanoclusters (GSH-AuNCs) exhibiting an appropriate fluorescence quantum yield (QY). First, we conducted 189 experiments and synthesized different GSH-AuNCs by varying the thiol-to-metal molar ratio and reaction temperature and time in reasonable ranges. The fluorescence QY of GSH-AuNCs could be systematically and independently programmed using different experimental parameters. We used limited GSH-AuNC synthesis parameter data to train an extreme gradient boosting regressor model. Moreover, we improved the interpretability of the ML model by combining individual conditional expectation, double-variable partial dependence, and feature interaction network analyses. The interpretability analyses established the relationship between multiple synthesis parameters and fluorescence QYs of GSH-AuNCs. The results represent an essential step towards revealing the complex fluorescence mechanism of thiolated AuNCs. Finally, we constructed a synthesis phase diagram exceeding 6.0 × 104 prediction variables for accurately predicting the fluorescence QY of GSH-AuNCs. A multidimensional synthesis phase diagram was obtained for the fluorescence QY of GSH-AuNCs by searching the synthesis parameter space in the trained ML model. Our methodology is a general and powerful complementary strategy for application in material informatics.

Topological network properties of resting-state functional connectivity patterns are associated with metal mixture exposure in adolescents

Introduction

Adolescent exposure to neurotoxic metals adversely impacts cognitive, motor, and behavioral development. Few studies have addressed the underlying brain mechanisms of these metal-associated developmental outcomes. Furthermore, metal exposure occurs as a mixture, yet previous studies most often consider impacts of each metal individually. In this cross-sectional study, we investigated the relationship between exposure to neurotoxic metals and topological brain metrics in adolescents.

Methods

In 193 participants (53% females, ages: 15-25 years) enrolled in the Public Health Impact of Metals Exposure (PHIME) study, we measured concentrations of four metals (manganese, lead, copper, and chromium) in multiple biological media (blood, urine, hair, and saliva) and acquired resting-state functional magnetic resonance imaging scans. Using graph theory metrics, we computed global and local efficiency (global:GE; local:LE) in 111 brain areas (Harvard Oxford Atlas). We used weighted quantile sum (WQS) regression models to examine association between metal mixtures and each graph metric (GE or LE), adjusted for sex and age.

Results

We observed significant negative associations between the metal mixture and GE and LE [βGE = -0.076, 95% CI (-0.122, -0.031); βLE= -0.051, 95% CI (-0.095, -0.006)]. Lead and chromium measured in blood contributed most to this association for GE, while chromium measured in hair contributed the most for LE.

Discussion

Our results suggest that exposure to this metal mixture during adolescence reduces the efficiency of integrating information in brain networks at both local and global levels, informing potential neural mechanisms underlying the developmental toxicity of metals. Results further suggest these associations are due to combined joint effects to different metals, rather than to a single metal.

Time course of pulmonary inflammation and trace element biodistribution during and after sub-acute inhalation exposure to copper oxide nanoparticles in a murine model

Background

It has been shown that copper oxide nanoparticles (CuO NPs) induce pulmonary toxicity after acute or sub-acute inhalation exposures. However, little is known about the biodistribution and elimination kinetics of inhaled CuO NPs from the respiratory tract. The purposes of this study were to observe the kinetics of pulmonary inflammation during and after CuO NP sub-acute inhalation exposure and to investigate copper (Cu) biodistribution and clearance rate from the exposure site and homeostasis of selected trace elements in secondary organs of BALB/c mice.

Results

Sub-acute inhalation exposure to CuO NPs led to pulmonary inflammation represented by increases in lactate dehydrogenase, total cell counts, neutrophils, macrophages, inflammatory cytokines, iron levels in bronchoalveolar lavage (BAL) fluid, and lung weight changes. Dosimetry analysis in lung tissues and BAL fluid showed Cu concentration increased steadily during exposure and gradually declined after exposure. Cu elimination from the lung showed first-order kinetics with a half-life of 6.5 days. Total Cu levels were significantly increased in whole blood and heart indicating that inhaled Cu could be translocated into the bloodstream and heart tissue, and potentially have adverse effects on the kidneys and spleen as there were significant changes in the weights of these organs; increase in the kidneys and decrease in the spleen. Furthermore, concentrations of selenium in kidneys and iron in spleen were decreased, pointing to disruption of trace element homeostasis.

Conclusions

Sub-acute inhalation exposure of CuO NPs induced pulmonary inflammation, which was correlated to Cu concentrations in the lungs and started to resolve once exposure ended. Dosimetry analysis showed that Cu in the lungs was translocated into the bloodstream and heart tissue. Secondary organs affected by CuO NPs exposure were kidneys and spleen as they showed the disruption of trace element homeostasis and organ weight changes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00480-z.

The levels of trace elements in sputum as biomarkers for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a rare lung disease that quickly leads to death. This paper addressed the issue of whether the levels of trace elements in sputum samples are suitable biomarkers for IPF disease. The sputum Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn concentrations were measured by sector field inductively coupled plasma mass spectrometry in populations sampled in Sardinia Island (Italy) including 31 patients with IPF, 31 patients with other lung-related diseases and 30 age- and gender-matched healthy controls. Risk factors in the disease as gender, age, severity and duration of the disease were assessed. Results showed that IPF patients had significantly increased sputum levels of Cd, Cr, Cu and Pb respect to controls. In males, but not in females, sputum levels of Cd, Cr and Cu were significantly higher in IPF cases respect to controls. In addition, Cr and Pb were increased in male patients with IPF compared to male patients with other lung diseases. Regarding Zn, it was found higher with the more serious stage of disease. Moreover, the ratios Cu/Zn, Fe/Mn and Cu/Mn were significantly increased in IPF patients and in non-IPF patients than in control subjects. These data showed clear increases in the concentration of some trace elements in sputum from patients with IPF and patients with other lung-related diseases that may contribute to the injury. The non-invasiveness of the sputum analysis is beneficial for its use as biomarker of trace element status in diseased patients for both the researcher and the clinic.

Determining the effects of manganese source and level on growth performance and carcass characteristics of growing-finishing pigs

Two experiments were conducted to determine the effects of Mn source and level on finishing pig growth performance and carcass characteristics. Dietary treatments were arranged in a 2 × 3 factorial with main effects of Mn source (MnSO₄; Eurochem, Veracruz, Mexico, or Mn hydroxychloride (IBM); Micronutrients, Indianapolis, IN) and increasing added Mn (8, 16, and 32 mg/kg of complete diet). The trace mineral premix was formulated without added Mn. Copper was added to all diets at 10 and 150 mg/kg in Exp. 1 and 2, respectively. In both experiments, 1,994 pigs (PIC; 337 × 1050; initially 34.5 ± 0.50 and 40.0 ± 0.77 kg) were used with 27 pigs per pen and 12 replicates per treatment. Diets were corn-soybean meal-distillers dried grains with solubles-based and were fed in four phases. In Exp. 1, there was a marginal Mn source × level interaction (quadratic, Ρ = 0.057) for overall feed efficiency (G:F), with a decrease then increase in pigs fed IBM, but G:F increased with increasing Mn from MnSO₄. There was no evidence for Mn source differences for average daily gain (ADG), average daily feed intake (ADFI), or body weight (BW), but pigs fed 16 mg/kg Mn, regardless of source, tended to have decreased (quadratic, Ρ < 0.05) ADG and final BW compared with other levels. For carcass yield, there was a tendency for Mn source × level interaction (quadratic, Ρ = 0.075), where carcass yield did not change by increasing MnSO₄ but was greatest for 16 mg/kg Mn from IBM. Loin depth increased (source × level, Ρ = 0.041) for pigs fed increasing Mn from MnSO₄ but decreased when Mn was increased from IBM. Pigs fed the intermediate level of Mn tended to have the lightest HCW (quadratic, Ρ = 0.071) and decreased loin depth (quadratic, Ρ = 0.044). Liver Mn concentration increased (linear, Ρ = 0.015) as added Mn increased and tended to be greater (P = 0.075) when supplied by MnSO₄ compared with IBM. In Exp. 2, there was no (P > 0.10) Mn source × level interaction observed for ADG, ADFI, and G:F. Pigs fed IBM had increased (P < 0.05) final BW, ADG, and ADFI compared with pigs fed MnSO₄. Pigs fed 16 mg/kg of Mn tended (P = 0.088) to have reduced ADFI when compared with pigs fed 8 and 32 mg/kg of Mn. In conclusion, there appears to be little benefit in growth performance by feeding more than 8 mg/kg of added Mn. When high levels of Cu were fed in Exp. 2, pigs fed IBM had improved growth performance when compared with those fed MnSO₄. Further research is needed to understand the potential benefits of Mn hydroxychloride fed in conjunction with high levels of Cu on pig growth performance.

Nutritive Manganese and Zinc Overdosing in Aging C. elegans Result in a Metallothionein-Mediated Alteration in Metal Homeostasis

SCOPE

Manganese (Mn) and zinc (Zn) are not only essential trace elements, but also potential exogenous risk factors for various diseases. Since the disturbed homeostasis of single metals can result in detrimental health effects, concerns have emerged regarding the consequences of excessive exposures to multiple metals, either via nutritional supplementation or parenteral nutrition. This study focuses on Mn-Zn-interactions in the nematode Caenorhabditis elegans (C. elegans) model, taking into account aspects related to aging and age-dependent neurodegeneration.

METHODS AND RESULTS

Chronic co-exposure of C. elegans to Mn and Zn increases metal uptake, exceeding levels of single metal exposures. Supplementation with Mn and/or Zn also leads to an age-dependent increase in metal content, a decline in overall mRNA expression, and metal co-supplementation induced expression of target genes involved in Mn and Zn homeostasis, in particular metallothionein 1 (mtl-1). Studies in transgenic worms reveal that mtl-1 played a prominent role in mediating age- and diet-dependent alterations in metal homeostasis. Metal dyshomeostasis is further induced in parkin-deficient nematodes (Parkinson's disease (PD) model), but this did not accelerate the age-dependent dopaminergic neurodegeneration.

CONCLUSIONS

A nutritive overdose of Mn and Zn can alter interactions between essential metals in an aging organism, and metallothionein 1 acts as a potential protective modulator in regulating homeostasis.

Effect of Zn Supplementation on Trace Element Status in Rats with Diet-Induced Non-alcoholic Fatty Liver Disease

The present study aimed to assess the effect of Zn supplementation on trace element levels in the liver, serum, and hair of rats with dietary-induced non-alcoholic fatty liver disease (NAFLD). A total of 26 3-month-old female Wistar rats were divided into four groups: control, NAFLD, Zn-supplemented (227 mg/L zinc as Zn sulfate Zn(SO)₄ dissolved in a drinking water), and NAFLD-Zn-supplemented. NAFLD was verified by histological assessment of liver samples. The serum was examined for routine biochemical parameters. Trace elements content was assessed using inductively coupled plasma mass spectrometry (ICP-MS). Zn treatment resulted in an improvement in liver weight and morphology. Dietary supplementation with Zn prevented NAFLD-induced decrease liver Co. The tendency to increase liver Fe in the Zn-treated group was observed. Zn treatment decreased hepatic Al and serum V levels. However, Zn administration did not affect NAFLD-induced I, Mn, and Se depletion in the liver. Hair Zn levels raised in Zn-supplemented groups. Conclusively, the results of the study indicate that Zn supplementation could have a beneficial effect in modulation of the altered trace element status and liver morphology. HIGHLIGHTS: •Zn treatment improved liver weight and morphology in rats with NAFLD. •Zn supplementation decreased liver Al in NAFLD. •Treatment by Zn prevented depletion of liver Co. •Zn decreased serum V and increased hair Zn levels. •No effect of Zn on NAFLD-induced hepatic I, Mn and Se depletion was observed.

Principal Components and Hierarchical Cluster Analyses of Trace Metals and Total Hydrocarbons in Gills, Intestines and Muscles of Clarias gariepinus (Burchell, 1822)

The aim of the study was to comparatively analyze the interrelationships among iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr) and total hydrocarbons (THCs) in the gills, intestines and muscles of Clarias gariepinus collected from Osse River, Nigeria, between the periods of April, 2013 to September, 2014. The trace metals in the fish tissues were analyzed using Atomic Absorption Spectrophotometer (AAS, Philips model PU 9100), while total hydrocarbons were analyzed using High Performance Liquid Chromatograph (HPLC,Prominence Dual brand from HGE) equipped with a detector Shimadzu UV-Visible (UV-Vis Prominence SPD 20 A). The concentrations of trace metals and THCs in the tissues were subjected to principal component analysis (PCA), in conjunction with hierarchical cluster analysis (HCA), backed up by correlation analysis (CA). In the most prioritized component among the hierarchies of contaminants, characterized as principal component 1, results of communality extractions and rotated component matrices revealed the order of contaminants was Mn > Cu > Zn > Fe > Cr in the intestines, Cr > Cu > THCs > Mn > Fe in the muscle, while Pb > Cr > Fe > Mn was the order in the gills of the fish. Iron inhibited accumulation of the other trace metals in the gills, where its threshold of essentiality was maximal. Noteworthy is the fact that Mn and Cu were the most active components in the muscle and concurrently of excess concentrations in the tissue, which is the major edible part of fish, and constitutes its main body weight, hence holds its nutritional and economic values. High level of variability which occurred in the toxicant profile across the tissues of C. gariepinus is a function of uptake route, varied organ functions and specificity of tissue permeability of the compared organs. The study demonstrated variability in organ accumulation capacity and toxicant's competitiveness irrespective of bioavailability. The study provides data useful for future ecotoxicological studies and safety of consumers of the fish.

Manganese transporter Slc30a10 controls physiological manganese excretion and toxicity

Manganese (Mn), an essential metal and nutrient, is toxic in excess. Toxicity classically results from inhalational exposures in individuals who work in industrial settings. The first known disease of inherited Mn excess, identified in 2012, is caused by mutations in the metal exporter SLC30A10 and is characterized by Mn excess, dystonia, cirrhosis, and polycythemia. To investigate the role of SLC30A10 in Mn homeostasis, we first generated whole-body Slc30a10-deficient mice, which developed severe Mn excess and impaired systemic and biliary Mn excretion. Slc30a10 localized to canalicular membranes of hepatocytes, but mice with liver Slc30a10 deficiency developed minimal Mn excess despite impaired biliary Mn excretion. Slc30a10 also localized to the apical membrane of enterocytes, but mice with Slc30a10 deficiency in small intestines developed minimal Mn excess despite impaired Mn export into the lumen of the small intestines. Finally, mice with Slc30a10 deficiency in liver and small intestines developed Mn excess that was less severe than that observed in mice with whole-body Slc30a10 deficiency, suggesting that additional sites of Slc30a10 expression contribute to Mn homeostasis. Overall, these results indicated that Slc30a10 is essential for Mn excretion by hepatocytes and enterocytes and could be an effective target for pharmacological intervention to treat Mn toxicity.

Transcriptome Analysis Reveals Distinct Responses to Physiologic versus Toxic Manganese Exposure in Human Neuroblastoma Cells

Manganese (Mn) is an essential trace element, which also causes neurotoxicity in exposed occupational workers. Mn causes mitochondrial toxicity; however, little is known about transcriptional responses discriminated by physiological and toxicological levels of Mn. Identification of such mechanisms could provide means to evaluate risk of Mn toxicity and also potential avenues to protect against adverse effects. To study the Mn dose-response effects on transcription, analyzed by RNA-Seq, we used human SH-SY5Y neuroblastoma cells exposed for 5 h to Mn (0 to 100 μM), a time point where no immediate cell death occurred at any of the doses. Results showed widespread effects on abundance of protein-coding genes for metabolism of reactive oxygen species, energy sensing, glycolysis, and protein homeostasis including the unfolded protein response and transcriptional regulation. Exposure to a concentration (10 μM Mn for 5 h) that did not result in cell death after 24-h increased abundance of differentially expressed genes (DEGs) in the protein secretion pathway that function in protein trafficking and cellular homeostasis. These include BET1 (Golgi vesicular membrane-trafficking protein), ADAM10 (ADAM metallopeptidase domain 10), and ARFGAP3 (ADP-ribosylation factor GTPase-activating protein 3). In contrast, 5-h exposure to 100 μM Mn, a concentration that caused cell death after 24 h, increased abundance of DEGs for components of the mitochondrial oxidative phosphorylation pathway. Integrated pathway analysis results showed that protein secretion gene set was associated with amino acid metabolites in response to 10 μM Mn, while oxidative phosphorylation gene set was associated with energy, lipid, and neurotransmitter metabolites at 100 μM Mn. These results show that differential effects of Mn occur at a concentration which does not cause subsequent cell death compared to a concentration that causes subsequent cell death. If these responses translate to effects on the secretory pathway and mitochondrial functions in vivo, differential activities of these systems could provide a sensitive basis to discriminate sub-toxic and toxic environmental and occupational Mn exposures.

Dietary Manganese Exposure in the Adult Population in Germany-What Does it Mean in Relation to Health Risks?

Manganese is both an essential nutrient and a potential neurotoxicant. Therefore, the question arises whether the dietary manganese intake in the German population is on the low or high side. Results from a pilot total diet study in Germany presented here reveal that the average dietary manganese intake in the general population in Germany aged 14-80 years is about 2.8 mg day^-1 for a person of 70 kg body weight. This exposure level is within the intake range of 2-5 mg per person and day as recommended by the societies for nutrition in Germany, Austria, and Switzerland. No information on the dietary exposure of children in Germany can be provided so far. Although reliable information on health effects related to oral manganese exposure is limited, there is no indication from the literature that these dietary intake levels are associated with adverse health effects either by manganese deficiency or excess. However, there is limited evidence that manganese taken up as a highly bioavailable bolus, for example, uptake via drinking water or food supplements, could pose a potential risk to human health-particularly in certain subpopulations-when certain intake amounts, which are currently not well defined, are exceeded.

In vitro gastrointestinal digestion to evaluate the total, bioaccessible and bioavailable concentrations of iron and manganese in açaí (Euterpe oleracea Mart.) pulps

Açaí pulp consumption has increased in Brazil and worldwide. Recently, a high average content of manganese (450 mg/kg) was observed in açaí pulp, raising the hypothesis of toxicological effects associated to its ingestion. However, the total concentration of an element does not reflect the real benefits and risks of consuming a food. In this context, the total, bioaccessible and bioavailable concentrations of Fe and Mn were assessed in 9 açaí pulps. Fe and Mn contents ranged from 27.6 to 73 and from 145 to 1197 mg kg^-1, respectively. Fe and Mn bioaccessibilities represented from 29 to 40 and from 39 to 55% of total amounts. Fe bioavailabilities were lower than LOQ and those of Mn varied from 8 to 17% of total. A daily consumption of 100 g of açaí pulp exceeds by at least 1.5-fold the recommended Mn daily intakes for adults whereas poorly contributes to Fe intakes. Since the lowest Mn bioaccessible and bioavailable fraction corresponded to a Mn intake value higher than the tolerable upper intakes for children and that high amounts of Mn intake may impair Fe absorption, higher açaí consumption may be worrisome. Future nutritional, toxicological and speciation studies must be undertaken.

How tapeworm infection and consumption of a Cd and Zn hyperaccumulating plant may affect Cu, Fe, and Mn concentrations in an animal-a plant consumer and tapeworm host

This study evaluated the effects of a hyperaccumulator plant (Arabidopsis halleri), containing surplus of cadmium (Cd) and zinc (Zn) and being an admixture to the rat feed, on concentrations of copper (Cu), iron (Fe), and manganese (Mn) in the tissues of experimental rats infected/uninfected with the tapeworm (Hymenolepis diminuta). Male Wistar rats were divided into three groups (00, P0, and PT); the P0 and PT animals were fed a standard mixture for rats (ST-1) supplemented with the plant A. halleri at a weekly Zn and Cd dosage of 123 and 1 mg, respectively. Moreover, rats from the group PT were infected with the tapeworm. The group 00 served as control animals fed only ST-1 having no tapeworm infection. Rats were euthanized after 6 weeks, and Cu, Fe, and Mn levels were determined in rat and tapeworm tissues. The results indicated that both the consumption of hyperaccumulator plant and/or presence of tapeworms did have significant effect on Cu, Fe, and Mn concentrations in the host tissues. Concentrations of all the elements were higher in the rat liver and partially kidneys than in the tapeworms, and the concentrations of Cu, Fe, and Mn were affected by the consumption of Cd/Zn hyperaccumulator plants. Particularly, Fe concentrations in all rat tissues were significantly increased by consumption of A. halleri while decreased by the presence of tapeworms. Overall, the consumption of a Cd/Zn hyperaccumulator plant and tapeworm infection cause an imbalance in Cu, Fe, and Mn concentrations in the tissues of a consumer (experimental rats).

Interactions of manganese with iron, zinc, and copper in neonatal C57BL/6J and parkin mice following developmental oral manganese exposure

High dose manganese (Mn) exposure can result in changes in tissue concentrations of other essential metals due to Mn-induced alterations in metal absorption and competition for metal transporters and regulatory proteins. We evaluated responses in mice with a Parkin gene defect (parkin mice) and a wildtype strain (C57BL/6J) following neonatal Mn exposure. Neonatal parkin and C57BL/6J littermates were randomly assigned to 0, 11, or 25 mg Mn/kg-day dose groups with oral exposures occurring from postnatal day (PND) 1 through PND 28. We report liver, femur, olfactory bulb, striatum, and frontal cortex iron, copper, and zinc concentrations and changes in hepatic gene expression of different metal transporters in PND 29 parkin and C57BL/6J mice. A companion manuscript (Foster et al., 2017) [1] describes the primary study findings. This data provides insights into strain differences in the way Mn interacts with other trace metals in mice.

Loss of divalent metal transporter 1 function promotes brain copper accumulation and increases impulsivity

The divalent metal transporter 1 (DMT1) is a major iron transporter required for iron absorption and erythropoiesis. Loss of DMT1 function results in microcytic anemia. While iron plays an important role in neural function, the behavioral consequences of DMT1 deficiency are largely unexplored. The goal of this study was to define the neurobehavioral and neurochemical phenotypes of homozygous Belgrade (b/b) rats that carry DMT1 mutation and explore potential mechanisms of these phenotypes. The b/b rats (11-12 weeks old) and their healthy littermate heterozygous (+/b) Belgrade rats were subject to elevated plus maze tasks. The b/b rats spent more time in open arms, entered open arms more frequently and traveled more distance in the maze than +/b controls, suggesting increased impulsivity. Impaired emotional behavior was associated with down-regulation of GABA in the hippocampus in b/b rats. Also, b/b rats showed increased GABAA receptor α1 and GABA transporter, indicating altered GABAergic function. Furthermore, metal analysis revealed that b/b rats have decreased total iron, but normal non-heme iron, in the brain. Interestingly, b/b rats exhibited unusually high copper levels in most brain regions, including striatum and hippocampus. Quantitative PCR analysis showed that both copper importer copper transporter 1 and exporter copper-transporting ATPase 1 were up-regulated in the hippocampus from b/b rats. Finally, b/b rats exhibited increased 8-isoprostane levels and decreased glutathione/glutathione disulfide ratio in the hippocampus, reflecting elevated oxidative stress. Combined, our results suggest that copper loading in DMT1 deficiency could induce oxidative stress and impair GABA metabolism, which promote impulsivity-like behavior. Iron-copper model: Mutations in the divalent metal transporter 1 (DMT1) decrease body iron status and up-regulate copper absorption, which leads to copper loading in the brain and consequently increases metal-induced oxidative stress. This event disrupts GABAergic neurotransmission and promotes impulsivity-like behavior. Our model provides better understanding of physiological risks associated with imbalanced metal metabolism in mental function and, more specifically, the interactions with GABA and redox control in the treatment of emotional disorders.