Relationship Between a High-Fat Diet, Reduced Mobility, and Trace Element Overload in the Olfactory Bulbs of C57BL/6J and DBA/2J Mice.

The dysregulation of trace elements in the brain, which can be caused by genetic or environmental factors, has been associated with disease and compromised mobility. Research regarding trace elements and motor function has focused mainly on the basal ganglia, but few studies have examined the olfactory bulb in this context. Diets high in fat have been shown to have consequences of dysregulated iron and manganese in the brain and disrupted motor activity. The aim of our study was to examine the relationship between mobility and trace element disruption in the olfactory bulb in male and female C57BL/6J and DBA/2J mice fed a high-fat diet. Mobility was significantly reduced in male C57BL/6Js, but the correlation between iron and manganese in the olfactory bulb with velocity, distance travelled, and habituation was not statistically significant. However, there appears to be an overall pattern of a high-fat diet having a statistically significant impact individually on elevated iron and manganese in the olfactory bulb, reduced velocity, reduced distance travelled, and reduced habituation mainly in the male C57BL/6J strain. We found similar trends within the scientific literature to suggest that dysregulated trace element status in the olfactory bulb may be related to motor function in both humans and animals and that males may be more susceptible to the negative outcomes. Our findings contribute new information regarding the impact of diet on the brain, behavior, and potential connection between trace element dysregulation in the olfactory bulb with mobility.

Carbon Nanodots Attenuate Lipid Peroxidation in the LDL Receptor Knockout Mouse Brain.

Abnormal cholesterol metabolism can lead to oxidative stress in the brain. Low-density lipoprotein receptor (LDLr) knockout mice are models for studying altered cholesterol metabolism and oxidative stress onset in the brain. Carbon nanodots are a new class of carbon nanomaterials that possess antioxidant properties. The goal of our study was to evaluate the effectiveness of carbon nanodots in preventing brain lipid peroxidation. LDLr knockout mice and wild-type C57BL/6J mice were treated with saline or 2.5 mg/kg bw of carbon nanodots for a 16-week period. Brains were removed and dissected into the cortex, midbrain, and striatum. We measured lipid peroxidation in the mouse brain tissues using the Thiobarbituric Acid Reactive Substances Assay and iron and copper concentrations using Graphite Furnace Atomic Absorption Spectroscopy. We focused on iron and copper due to their association with oxidative stress. Iron concentrations were significantly elevated in the midbrain and striatum of the LDLr knockout mice compared to the C57BL/6J mice, whereas lipid peroxidation was greatest in the midbrain and cortex of the LDLr knockout mice. Treatment with carbon nanodots in the LDLr knockout mice attenuated both the rise in iron and lipid peroxidation, but they had no negative effect in the C57BL/6J mice, indicating the anti-oxidative stress properties of carbon nanodots. We also assessed locomotor and anxiety-like behaviors as functional indicators of lipid peroxidation and found that treatment with carbon nanodots prevented the anxiety-like behaviors displayed by the LDLr knockout mice. Overall, our results show that carbon nanodots are safe and may be an effective nanomaterial for combating the harmful effects caused by lipid peroxidation.

Influence of Sex and Strain on Hepatic and Adipose Tissue Trace Element Concentrations and Gene Expression in C57BL/6J and DBA/2J High Fat Diet Models.

The objective of this study was to determine the influence of sex and strain on the dysregulation of trace element concentration and associative gene expression due to diet induced obesity in adipose tissue and the liver. Male and female C57BL/6J (B6J) and DBA/2J (D2J) were randomly assigned to a normal-fat diet (NFD) containing 10% kcal fat/g or a mineral-matched high-fat diet (HFD) containing 60% kcal fat/g for 16 weeks. Liver and adipose tissue were assessed for copper, iron, manganese, and zinc concentrations and related changes in gene expression. Notable findings include three-way interactions of diet, sex, and strain amongst adipose tissue iron concentrations (p = 0.005), adipose hepcidin expression (p = 0.007), and hepatic iron regulatory protein (IRP) expression (p = 0.012). Cd11c to Cd163 ratio was increased in adipose tissue due to HFD amongst all biological groups except B6J females, for which tissue iron concentrations were reduced due to HFD (p = 0.002). Liver divalent metal transporter 1 (DMT-1) expression was increased due to HFD amongst B6J males (p < 0.005) and females (p < 0.004), which coincides with the reduction in hepatic iron concentrations found in these biological groups (p < 0.001). Sex, strain, and diet affected trace element concentration, the expression of genes that regulate trace element homeostasis, and the expression of macrophages that contribute to tissue iron-handling in adipose tissue. These findings suggest that sex and strain may be key factors that influence the adaptive capacity of iron mismanagement in adipose tissue and its subsequent consequences, such as insulin resistance.

Alterations in metal homeostasis occur prior to canonical markers in Huntington disease.

The importance of metal biology in neurodegenerative diseases such as Huntingtin Disease is well documented with evidence of direct interactions between metals such as copper, zinc, iron and manganese and mutant Huntingtin pathobiology. To date, it is unclear whether these interactions are observed in humans, how this impacts other metals, and how mutant Huntington alters homeostatic mechanisms governing levels of copper, zinc, iron and manganese in cerebrospinal fluid and blood in HD patients. Plasma and cerebrospinal fluid from control, pre-manifest, manifest and late manifest HD participants were collected as part of HD-Clarity. Levels of cerebrospinal fluid and plasma copper, zinc, iron and manganese were measured as well as levels of mutant Huntingtin and neurofilament in a sub-set of cerebrospinal fluid samples. We find that elevations in cerebrospinal fluid copper, manganese and zinc levels are altered early in disease prior to alterations in canonical biomarkers of HD although these changes are not present in plasma. We also evidence that CSF iron is elevated in manifest patients. The relationships between plasma and cerebrospinal fluid metal are altered based on disease stage. These findings demonstrate that there are alterations in metal biology selectively in the CSF which occur prior to changes in known canonical biomarkers of disease. Our work indicates that there are pathological changes related to alterations in metal biology in individuals without elevations in neurofilament and mutant Huntingtin.

Elevated whole blood manganese is associated with impaired cognition in older adults, NHANES 2013-2014 cycle.

Manganese (Mn) is found in many commonly consumed foods and therefore its deficiency is rare. However, excessive exposure to Mn from contaminated drinking water as well as occupational exposure can result in toxic accumulation in the brain, which has been associated with impaired neurological function. The objective of this study was to examine the NHANES 2013 - 2014 cycle focusing on the relationship between whole blood Mn concentrations and cognitive tests including working memory, word recall and sustained attention in elderly adults (aged 60 years and older). The different cognitive function test scores were used in principal component analysis to develop a composite score. The relationship between blood Mn concentration and cognitive function (principal component score and Digit Symbol Substitution Test (DSST)) were investigated using regression analysis. Median (95% CI) concentrations of blood Mn, serum copper, and serum iron were 8.76 (8.5, 9.1) µg/L, 114.9 µg/dL (110.3, 118.1), and 80 (78, 83) µg/dL, respectively. We found that among individuals in the highest quartile of blood Mn concentration (>11.18 µg/L), there was an inverse association between blood Mn and cognitive function as assessed using DSST (ß (95% CI) = -0.76 (-1.19 to -0.33); p = 0.003), while the inverse relationship with the composite score trended towards significance (ß (95% CI) = -0.04 (-0.08 to 0.00); p = 0.053). These findings suggest that having elevated blood Mn ay be associated with cognitive decline in aging and warrants further studies on how the different sources of Mn may contribute to this outcome.

The impact of a high-fat diet on physical activity and dopamine neurochemistry in the striatum is sex and strain dependent in C57BL/6J and DBA/2J mice.

BACKGROUND: Obesity has been linked to behavioral and biochemical changes, such as reduced physical activity, dysregulated dopamine metabolism, and gene expression alterations in the brain. The impact of a continuous high-fat diet and resulting state of obesity may vary depending on sex and genetics. OBJECTIVE: The aim of this study was to investigate the impact of a high-fat diet on physical activity, gene expression in the striatum, and dopamine neurochemistry using male and female mice from different strains as a model to examine sex and strain influences on dopamine-mediated behavior and neurobiology. METHODS: Male and female mice from the C57BL/6J (B6J) and DBA/2J (D2J) strains were randomly assigned a control low-fat diet with 10% kcal fat or a high-fat diet with 60% kcal fat for 16 weeks. We assessed ambulation and habituation using the open field test; dopamine release and reuptake using ex-vivo fast scan cyclic voltammetry; and striatal mRNA expression of dopamine receptor D2, alpha synuclein, and tyrosine hydroxylase. RESULTS: Mice fed a high-fat diet exhibited reduced motor activity, but only obese B6J male mice displayed reduced habituation. Dopamine clearance in the dorsal striatum was reduced only in obese D2J mice, while dopamine clearance in the nucleus accumbens core was reduced only in male obese D2J mice. Striatal dopamine receptor D2 gene expression was upregulated exclusively in obese male B6J mice. CONCLUSION: Our study provides evidence for important sex and strain influences on the impact of a high-fat diet and obesity-induced behavior alterations and neurobiology dysregulation in the striatum.

YAC128 mouse model of Huntington disease is protected against subtle chronic manganese (Mn)-induced behavioral and neuropathological changes.

Manganese (Mn) is an essential micronutrient but excessive levels induce neurotoxic effects. Increasing evidence suggests a deficit of bioavailable Mn in Huntington disease (HD), an inherited neurodegenerative disease characterized by motor and cognitive disturbances. Previous studies have shown rescue of some molecular HD phenotypes by acute Mn exposure. This study simultaneously examined the potential for chronic Mn exposure to attenuate HD behavioral phenotypes, and for the HD genotype to offer protection against detrimental effects of chronic Mn exposure. In two independent studies a chronic Mn exposure paradigm was implemented in the YAC128 mouse model of HD and behavior was assessed at several timepoints. Study 1 exposed WT and YAC128 mice to twice weekly subcutaneous injections of 0, 5, 15, or 50 mg/kg MnCl[2] tetrahydrate from 12 to 32 weeks of age. A promising protective effect against motor coordination decline in 5 mg/kg MnCl[2] tetrahydrate-treated YAC128 mice was detected. Study 2 thus exposed WT and YAC128 mice to either 0 or 5 mg/kg MnCl[2] tetrahydrate from 12 to 52 weeks of age (with a partial randomized treatment crossover at 31 weeks). The same protective effect was not observed under these conditions at higher statistical power. We report subtle toxicological changes in exploratory behavior and total activity induced by chronic Mn exposure in WT mice only, despite similar total increases in brain Mn in WT and YAC128 mice. Further, chronic Mn treatment resulted in a 10-12 % decrease in striatal NeuN positive cell density in WT mice but not YAC128 mice, despite vehicle cell counts already being reduced compared to WT mice as expected for the HD genotype. The subtle changes observed in specific outcome measures, but not others, following long-term low-level Mn exposure in WT mice delineate the neurobehavioral and neuropathological effects at the threshold of chronic Mn toxicity. We conclude that these chronic low-dose Mn exposures do not significantly rescue behavioral HD phenotypes, but YAC2128 mice are protected against the subtle Mn-induced behavioral changes and decreased striatal neuron density observed in Mn-exposed WT mice.

Genetic differences in ethanol consumption: effects on iron, copper, and zinc regulation in mouse hippocampus.

One common characteristic of neurodegenerative diseases is dysregulation of iron, usually with observed increases in its concentration in various regions. Heavy alcohol consumption is believed to contribute to such iron dysregulation in the brain with accompanying dementia. To examine this effect and related genetic-based individual differences in an animal model, we subjected female mice from 12 BXD recombinant inbred strains to 16 weeks of alcohol consumption using the drinking in the dark (DID) method. Daily consumption was recorded and at the end of 16 weeks hippocampus tissues harvested. Concentrations of iron, copper and zinc were measured using X-ray fluorescence technology. The results showed that, DID increased iron overall across all strains, ranging from 3 to 68%. Copper and Zinc both decreased, ranging from 0.4-42 and 5-35% respectively. Analysis of variance revealed significant strain by treatment interactions for all three metals. Additionally, in the DID group, we observed strain differences in reduction of hippocampus mass. These findings are particularly interesting to us because high alcohol consumption in humans has been associated with neurodegeneration and dementia related to disruption of iron regulation. The findings of alcohol consumption associated decreases in copper and zinc are novel. The role of copper regulation and neurological function related to alcohol consumption is as yet largely unexplored. The role of zinc is better known as a neuromodulator in the hippocampus and appears to be protective against neurological damage. It would seem then, that the alcohol-related decrease in zinc in the hippocampus would be of concern and warrants further study.

The influence of sex and strain on trace element dysregulation in the brain due to diet-induced obesity.

BACKGROUND: The objective of this study was to identify interaction effects between diet, sex, and strain on trace element dysregulation and gene expression alterations due to diet-induced obesity (DIO) in the hippocampus, striatum, and midbrain. METHODS: Male and female C57BL/6 J (B6 J) and DBA/2 J (D2 J) mice were fed either a low fat (10 % kcal) diet (LFD) or high fat (60 % kcal) diet (HFD) for 16 weeks, then assessed for trace element concentrations and gene expression patterns in the brain. RESULTS: In the hippocampus, zinc was significantly increased by 48 % in D2 J males but decreased by 44 % in D2 J females, and divalent metal transporter 1 was substantially upregulated in B6 J males due to DIO. In the striatum, iron was significantly elevated in B6 J female mice, and ceruloplasmin was significantly upregulated in D2 J female mice due to DIO. In the midbrain, D2 J males fed a HFD had a 48 % reduction in Cu compared to the LFD group, and D2 J females had a 37 % reduction in Cu compared to the control group. CONCLUSIONS: The alteration of trace element homeostasis and gene expression due to DIO was brain-region dependent and was highly influenced by sex and strain. A significant three-way interaction between diet, sex, and strain was discovered for zinc in the hippocampus (for mice fed a HFD, zinc increased in male D2 Js, decreased in female D2 Js, and had no effect in B6 J mice). A significant diet by sex interaction was observed for iron in the striatum (iron increased only in female mice fed a HFD). A main effect of decreased copper in the midbrain was found for the D2 J strain fed a HFD. These results emphasize the importance of considering sex and genetics as biological factors when investigating potential associations between DIO and neurodegenerative disease.

Diet-Induced Obesity Disrupts Trace Element Homeostasis and Gene Expression in the Olfactory Bulb.

The aim of this study was to determine the impact of diet-induced obesity (DIO) on trace element homeostasis and gene expression in the olfactory bulb and to identify potential interaction effects between diet, sex, and strain. Our study is based on evidence that obesity and olfactory bulb impairments are linked to neurodegenerative processes. Briefly, C57BL/6J (B6J) and DBA/2J (D2J) male and female mice were fed either a low-fat diet or a high-fat diet for 16 weeks. Brain tissue was then evaluated for iron, manganese, copper, and zinc concentrations and mRNA gene expression. There was a statistically significant diet-by-sex interaction for iron and a three-way interaction between diet, sex, and strain for zinc in the olfactory bulb. Obese male B6J mice had a striking 75% increase in iron and a 50% increase in manganese compared with the control. There was an increase in zinc due to DIO in B6J males and D2J females, but a decrease in zinc in B6J females and D2J males. Obese male D2J mice had significantly upregulated mRNA gene expression for divalent metal transporter 1, alpha-synuclein, amyloid precursor protein, dopamine receptor D2, and tyrosine hydroxylase. B6J females with DIO had significantly upregulated brain-derived neurotrophic factor expression. Our results demonstrate that DIO has the potential to disrupt trace element homeostasis and mRNA gene expression in the olfactory bulb, with effects that depend on sex and genetics. We found that DIO led to alterations in iron and manganese predominantly in male B6J mice, and gene expression dysregulation mainly in male D2J mice. These results have important implications for health outcomes related to obesity with possible connections to neurodegenerative disease.

Huntington's disease genotype suppresses global manganese-responsive processes in pre-manifest and manifest YAC128 mice.

Manganese (Mn) is an essential micronutrient required for the proper function of several enzymes. Accumulating evidence demonstrates a selective decrease of bioavailable Mn in vulnerable cell types of Huntington's Disease (HD), an inherited progressive neurodegenerative disorder with no cure. Amelioration of underlying pathophysiology, such as alterations in Mn-dependent biology, may be therapeutic. We therefore sought to investigate global Mn-dependent and Mn-responsive biology following various Mn exposures in a mouse model of HD. YAC128 and wildtype (WT) littermate control mice received one of three different Mn exposure paradigms by subcutaneous injection of 50 mg kg-1 MnCl2·4(H2O) across two distinct HD disease stages. "Pre-manifest" (12-week old mice) mice received either a single (1 injection) or week-long (3 injections) exposure of Mn or vehicle (H2O) and were sacrificed at the pre-manifest stage. "Manifest" (32-week old) mice were sacrificed following either a week-long Mn or vehicle exposure during the manifest stage, or a 20-week-long chronic (2× weekly injections) exposure that began in the pre-manifest stage. Tissue Mn, mRNA, protein, and metabolites were measured in the striatum, the brain region most sensitive to neurodegeneration in HD. Across all Mn exposure paradigms, pre-manifest YAC128 mice exhibited a suppressed response to transcriptional and protein changes and manifest YAC128 mice showed a suppressed metabolic response, despite equivalent elevations in whole striatal Mn. We conclude that YAC128 mice respond differentially to Mn compared to WT as measured by global transcriptional, translational, and metabolomic changes, suggesting an impairment in Mn homeostasis across two different disease stages in YAC128 mice.

Manganese: Its Role in Disease and Health.

Manganese is an essential dietary element that functions primarily as a coenzyme in several biological processes. These processes include, but are not limited to, macronutrient metabolism, bone formation, free radical defense systems, and in the brain, ammonia clearance and neurotransmitter synthesis. It is a critical component in dozens of proteins and enzymes, and is found in all tissues. Concentrated levels of Mn are found in tissues rich in mitochondria and melanin, with both, liver, and pancreas having the highest concentrations under normal conditions. However, overexposure to environmental Mn via industrial occupation or contaminated drinking water can lead to toxic brain Mn accumulation that has been associated with neurological impairment. The objective of this chapter is to address the biological importance of Mn (essentiality), routes of exposure, factors dictating Mn status, a brief discussion of Mn neurotoxicity, and proposed methods for neurotoxicity remediation.

Iron and manganese-related CNS toxicity: mechanisms, diagnosis and treatment.

INTRODUCTION: Iron (Fe) and manganese (Mn) are essential nutrients for humans. They act as cofactors for a variety of enzymes. In the central nervous system (CNS), these two metals are involved in diverse neurological activities. Dyshomeostasis may interfere with the critical enzymatic activities, hence altering the neurophysiological status and resulting in neurological diseases. Areas covered: In this review, the authors cover the molecular mechanisms of Fe/Mn-induced toxicity and neurological diseases, as well as the diagnosis and potential treatment. Given that both Fe and Mn are abundant in the earth crust, nutritional deficiency is rare. In this review the authors focus on the neurological disorders associated with Mn and Fe overload. Expert commentary: Oxidative stress and mitochondrial dysfunction are the primary molecular mechanism that mediates Fe/Mn-induced neurotoxicity. Although increased Fe or Mn concentrations have been found in brain of patients, it remains controversial whether the elevated metal amounts are the primary cause or secondary consequence of neurological diseases. Currently, treatments are far from satisfactory, although chelation therapy can significantly decrease brain Fe and Mn levels. Studies to determine the primary cause and establish the molecular mechanism of toxicity may help to adapt more comprehensive and satisfactory treatments in the future.

The impact of obesity on brain iron levels and α-synuclein expression is regionally dependent.

BACKGROUND: The importance of iron homeostasis is particularly apparent in the brain, where iron deficiency results in impaired cognition and iron accumulation is associated with neurodegenerative diseases. Obesity is linked to iron deficiency systemically, but the effects of obesity on brain iron and its associated consequences, including neurodegenerative processes remain unexplored. This preliminary study examined the effect of dietary-induced obesity on brain regional iron, α-synuclein expression, and F2-isoprostane (oxidative stress marker) concentrations in selected brain regions. OBJECTIVE: The objective of the study was to elucidate the vulnerability of selected brain regions (e.g. midbrain, hippocampus) to the possible process of neurodegeneration due to the altered iron content associated with obesity. METHODS: Twenty-one-day-old male C57BL/6J mice were fed with a high-fat diet (60% kcal from fat) or a control-fat diet (10% kcal from fat) for 20 weeks. Brain samples were collected and dissected into hippocampus, midbrain, striatum, and thalamus regions. Iron content, ferritin H (FtH) and α-synuclein protein and mRNA expressions, and F2-isoprostane were measured in selected regions. RESULTS: The results indicated that obesity caused significant differences in iron levels in the midbrain and thalamus, but not in the hippocampus or striatum, compared to control mice. Furthermore, markers of neurodegeneration (α-synuclein mRNA expression and F2-isoprostanes) were increased in the midbrain. DISCUSSION: These results support previous findings that brain iron metabolism responds to environmental stress in a regionally distinct manner and suggests that alterations in brain iron metabolism due to obesity may be relevant in neurodegeneration.

MFehi adipose tissue macrophages compensate for tissue iron perturbations in mice.

Resident adipose tissue macrophages (ATMs) play multiple roles to maintain tissue homeostasis, such as removing excess free fatty acids and regulation of the extracellular matrix. The phagocytic nature and oxidative resiliency of macrophages not only allows them to function as innate immune cells but also to respond to specific tissue needs, such as iron homeostasis. MFehi ATMs are a subtype of resident ATMs that we recently identified to have twice the intracellular iron content as other ATMs and elevated expression of iron-handling genes. Although studies have demonstrated that iron homeostasis is important for adipocyte health, little is known about how MFehi ATMs may respond to and influence adipose tissue iron availability. Two methodologies were used to address this question: dietary iron supplementation and intraperitoneal iron injection. Upon exposure to high dietary iron, MFehi ATMs accumulated excess iron, whereas the iron content of MFelo ATMs and adipocytes remained unchanged. In this model of chronic iron excess, MFehi ATMs exhibited increased expression of genes involved in iron storage. In the injection model, MFehi ATMs incorporated high levels of iron, and adipocytes were spared iron overload. This acute model of iron overload was associated with increased numbers of MFehi ATMs; 17% could be attributed to monocyte recruitment and 83% to MFelo ATM incorporation into the MFehi pool. The MFehi ATM population maintained its low inflammatory profile and iron-cycling expression profile. These studies expand the field's understanding of ATMs and confirm that they can respond as a tissue iron sink in models of iron overload.

The Effects of Dietary Fat and Iron Interaction on Brain Regional Iron Contents and Stereotypical Behaviors in Male C57BL/6J Mice.

Adequate brain iron levels are essential for enzyme activities, myelination, and neurotransmitter synthesis in the brain. Although systemic iron deficiency has been found in genetically or dietary-induced obese subjects, the effects of obesity-associated iron dysregulation in brain regions have not been examined. The objective of this study was to examine the effect of dietary fat and iron interaction on brain regional iron contents and regional-associated behavior patterns in a mouse model. Thirty C57BL/6J male weanling mice were randomly assigned to six dietary treatment groups (n = 5) with varying fat (control/high) and iron (control/high/low) contents. The stereotypical behaviors were measured during the 24th week. Blood, liver, and brain tissues were collected at the end of the 24th week. Brains were dissected into the hippocampus, midbrain, striatum, and thalamus regions. Iron contents and ferritin heavy chain (FtH) protein and mRNA expressions in these regions were measured. Correlations between stereotypical behaviors and brain regional iron contents were analyzed at the 5% significance level. Results showed that high-fat diet altered the stereotypical behaviors such as inactivity and total distance traveled (P < 0.05). The high-fat diet altered brain iron contents and FtH protein and mRNA expressions in a regional-specific manner: (1) high-fat diet significantly decreased the brain iron content in the striatum (P < 0.05), but not other regions, and (2) thalamus has a more distinct change in FtH mRNA expression compared with other regions. Furthermore, high-fat diet resulted in a significant decreased total distance traveled and a significant correlation between iron content and sleeping in midbrain (P < 0.05). Dietary iron also decreased brain iron content and FtH protein expression in a regionally specific manner. The effect of interaction between dietary fat and iron was observed in brain iron content and behaviors. All these findings will lay foundations to further explore the links among obesity, behaviors, and brain iron alteration.

PARK2 patient neuroprogenitors show increased mitochondrial sensitivity to copper.

Poorly-defined interactions between environmental and genetic risk factors underlie Parkinson's disease (PD) etiology. Here we tested the hypothesis that human stem cell derived forebrain neuroprogenitors from patients with known familial risk for early onset PD will exhibit enhanced sensitivity to PD environmental risk factors compared to healthy control subjects without a family history of PD. Two male siblings (SM and PM) with biallelic loss-of-function mutations in PARK2 were identified. Human induced pluripotent stem cells (hiPSCs) from SM, PM, and four control subjects with no known family histories of PD or related neurodegenerative diseases were utilized. We tested the hypothesis that hiPSC-derived neuroprogenitors from patients with PARK2 mutations would show heightened cell death, mitochondrial dysfunction, and reactive oxygen species generation compared to control cells as a result of exposure to heavy metals (PD environmental risk factors). We report that PARK2 mutant neuroprogenitors showed increased cytotoxicity with copper (Cu) and cadmium (Cd) exposure but not manganese (Mn) or methyl mercury (MeHg) relative to control neuroprogenitors. PARK2 mutant neuroprogenitors also showed a substantial increase in mitochondrial fragmentation, initial ROS generation, and loss of mitochondrial membrane potential following Cu exposure. Our data substantiate Cu exposure as an environmental risk factor for PD. Furthermore, we report a shift in the lowest observable effect level (LOEL) for greater sensitivity to Cu-dependent mitochondrial dysfunction in patients SM and PM relative to controls, correlating with their increased genetic risk for PD.

Manganese accumulation in membrane fractions of primary astrocytes is associated with decreased γ-aminobutyric acid (GABA) uptake, and is exacerbated by oleic acid and palmitate.

Manganese (Mn) exposure interferes with GABA uptake; however, the effects of Mn on GABA transport proteins (GATs) have not been identified. We sought to characterize how Mn impairs GAT function in primary rat astrocytes. Astrocytes exposed to Mn (500 µM) had significantly reduced (3)H-GABA uptake despite no change in membrane or cytosolic GAT3 protein levels. Co-treatment with 100 µM oleic or palmitic acids (both known to be elevated in Mn neurotoxicity), exacerbated the Mn-induced decline in (3)H-GABA uptake. Mn accumulation in the membrane fraction of astrocytes was enhanced with fatty acid administration, and was negatively correlated with (3)H-GABA uptake. Furthermore, control cells exposed to Mn only during the experimental uptake had significantly reduced (3)H-GABA uptake, and the addition of GABA (50 µM) blunted cytosolic Mn accumulation. These data indicate that reduced GAT function in astrocytes is influenced by Mn and fatty acids accumulating at or interacting with the plasma membrane.

Obesity alters adipose tissue macrophage iron content and tissue iron distribution.

Adipose tissue (AT) expansion is accompanied by the infiltration and accumulation of AT macrophages (ATMs), as well as a shift in ATM polarization. Several studies have implicated recruited M1 ATMs in the metabolic consequences of obesity; however, little is known regarding the role of alternatively activated resident M2 ATMs in AT homeostasis or how their function is altered in obesity. Herein, we report the discovery of a population of alternatively activated ATMs with elevated cellular iron content and an iron-recycling gene expression profile. These iron-rich ATMs are referred to as MFe(hi), and the remaining ATMs are referred to as MFe(lo). In lean mice, ~25% of the ATMs are MFe(hi); this percentage decreases in obesity owing to the recruitment of MFe(lo) macrophages. Similar to MFe(lo) cells, MFe(hi) ATMs undergo an inflammatory shift in obesity. In vivo, obesity reduces the iron content of MFe(hi) ATMs and the gene expression of iron importers as well as the iron exporter, ferroportin, suggesting an impaired ability to handle iron. In vitro, exposure of primary peritoneal macrophages to saturated fatty acids also alters iron metabolism gene expression. Finally, the impaired MFe(hi) iron handling coincides with adipocyte iron overload in obese mice. In conclusion, in obesity, iron distribution is altered both at the cellular and tissue levels, with AT playing a predominant role in this change. An increased availability of fatty acids during obesity may contribute to the observed changes in MFe(hi) ATM phenotype and their reduced capacity to handle iron.