Manganese and epilepsy: a systematic review of the literature

Consequences of Disturbing Manganese Homeostasis

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

Research progress on correlations between trace element levels and epilepsy

Research investigating the correlation between human trace element levels and disease alterations is growing. Epilepsy, a common nervous system disease, has also been found to be closely related to abnormal levels of trace elements. Studies continue to explore mechanisms of various trace elements involved in epileptic seizures through experimental animal models of epilepsy. Thus, we reviewed the research progress on the correlation between trace element levels and epilepsy in recent years and found that the trace elements most closely related to epilepsy are mainly metal ions such as selenium, iron, copper, zinc, and manganese. These results indicate that the changes in some trace elements are closely related to the increase in epilepsy susceptibility. In addition, after treatment with drugs and a ketogenic diet, the concentration of trace elements in the serum of patients with epilepsy changes. In other words, the abnormality of trace element concentrations is of great significance in the occurrence and development of epilepsy. This article is a literature update on the potential role of trace element imbalance in the development of epilepsy, providing new references for the subsequent prevention and treatment of epilepsy.

Antiepileptic effects of cobalt, manganese and magnesium on bicuculline-induced epileptiform activity in hippocampal neurons

BACKGROUND

Calcium signaling is described as a relevant factor in synchronization of neurons and increased excitability in epileptogenesis. Aim of the present investigations was to test the antiepileptic effect of the classical inorganic calcium channel blockers cobalt (Co²⁺), manganese (Mn²⁺) and magnesium (Mg²⁺).

METHODS

Experiments were carried out on hippocampal slices of guinea pigs. Epileptiform field potentials (EFP) were elicited by adding bicuculline (10 µmol/l) to the artificial cerebrospinal fluid (CSF). Kalium was elevated from normal (4 mmol/l) to 8 mmol/l. Co²⁺ (CoCl₂; 2, 1, 0.5 and 0.1 mmol/l), Mn²⁺ (MnCl₂; 2, 1, 0.5 and 0.1 mmol/l) and Mg²⁺ (MgCl₂; 8, 6, 5, 4 and 2 mmol/l) were added to the superfusate.

RESULTS

Concentrations of 2, 1 and 0.5 mmol/l Co²⁺, 2 and 1 mmol/l Mn²⁺ and 8 respectively 6 mmol/l Mg²⁺ were able to suppress EFP sufficient in a dose dependent manner. In concentrations of 0.1 mmol/l Co²⁺, 0.5 mmol/l and 0.1 mmol/l Mn²⁺ and 5 respectively 4 and 2 mmol/l Mg²⁺ suppression was incomplete. With washout of the inorganic calcium channel blockers the EFP reappeared.

DISCUSSION

All tree inorganic calcium channel blockers were able to suppress EFP in a dosage dependent and reversible manner. Weak reappearance of EFP after washout of Co²⁺ might be due to additional cytotoxic effects. The following mechanisms may contribute: i) blockade of voltage-activated calcium channels in the postsynaptic membrane, ii) changes in the activation of voltage-dependent sodium channels, iii) blockade of synaptic transmission.

Comparison of Serum Trace Nutrient Concentrations in Epileptics Compared to Healthy Dogs

Idiopathic epilepsy (IE) is a common cause of seizures in dogs. There are several investigations regarding serum concentrations of trace nutrients, including copper, selenium, zinc, manganese, and iron in human epileptics and animal models. However, research of this nature in dogs with epilepsy is lacking. The purpose of this prospective study was to compare serum concentrations of several trace nutrients in healthy dogs to dogs with idiopathic epilepsy. Healthy client-owned dogs (n = 50) and dogs with IE (n = 92) were enrolled and blood samples were collected for trace nutrient analysis. Epileptics were subdivided into three groups: controlled: n = 27, uncontrolled: n = 42, and untreated: n = 23. Serum was evaluated for concentrations of copper, selenium, zinc, cobalt, manganese, molybdenum, and iron using inductively coupled plasma mass spectroscopy. Uncontrolled epileptics had significantly higher manganese concentrations compared to normal dogs (p = 0.007). Untreated epileptics had higher iron levels than the other three groups (p = 0.04). Significantly higher levels of copper (p < 0.0001) were found in controlled and uncontrolled epileptics compared to normal or untreated dogs. Significantly higher levels of molybdenum (p = 0.01) were found in controlled epileptics compared to normal or untreated epileptics. Uncontrolled and controlled epileptics had significantly higher levels of selenium (p = 0.0003) vs. normal dogs, and uncontrolled epileptics had higher levels of zinc (p = 0.0002) than normal and untreated dogs. The significant difference in serum concentrations of several trace nutrients (manganese, selenium, and zinc) may suggest a role for these nutrients in the pathophysiology and/or treatment of epilepsy. Additionally, these results suggest that anti-convulsant therapy may affect copper and molybdenum metabolism.

New Insights on the Role of Manganese in Alzheimer's Disease and Parkinson's Disease

Manganese (Mn) is an essential trace element that is naturally found in the environment and is necessary as a cofactor for many enzymes and is important in several physiological processes that support development, growth, and neuronal function. However, overexposure to Mn may induce neurotoxicity and may contribute to the development of Alzheimer's disease (AD) and Parkinson's disease (PD). The present review aims to provide new insights into the involvement of Mn in the etiology of AD and PD. Here, we discuss the critical role of Mn in the etiology of these disorders and provide a summary of the proposed mechanisms underlying Mn-induced neurodegeneration. In addition, we review some new therapy options for AD and PD related to Mn overload.

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.

Elevated Serum Lipid Peroxidation and Reduced Vitamin C and Trace Element Concentrations Are Correlated With Epilepsy

BACKGROUND

Epilepsy is one of the chronic and heterogeneous epidemic neurological disorders leading to substantial mortality. The aim of the present study was to investigate the serum levels of malondialdehyde (MDA), vitamin C, and trace elements namely zinc (Zn), copper (Cu), and manganese (Mn) in epileptic patients of Bangladesh and to establish if there are any pathophysiological correlations.

METHODS

This was a case-control study with 40 generalized epileptic patients and 40 healthy subjects as controls. Epilepsy was determined by the presence of seizure events with an abnormal electroencephalography and magnetic resonance imaging report of brain.

RESULTS

Anthropometric parameters highlighted that age is a major risk factor of epilepsy and men are more prone to epilepsy than women. Blood serum analysis demonstrated significantly ( P < .001) higher values of MDA and lower level of vitamin C in the patient group (4.41 ± 0.76 μmol/mL and 18.31 ± 0.84 μmol/L, respectively) compared with control (1.81 ± 0.70 μmol/mL and 29.72 ± 1.06 μmol/L, respectively). Pearson's correlation analysis revealed a negative correlation between the serum level of MDA and vitamin C for both patient ( r = -0.023, P = .887) and control group ( r = -0.142, P = .383). This study also revealed that the trace elements (Zn, Cu) were significantly ( P < .05) lower in epileptics (68.32 ± 4.59 and 50.81 ± 2.54 μg/dL, respectively) where the level of Mn in patients (187.71 ± 9.04 μg/dL) was almost similar to that of the control group ( P > .05). The univariate analysis demonstrated that zinc <70 μg/dL (odds ratio = 3.56, P < .05) and copper <50 μg/dL were associated (odds ratio = 14.73, P < .001) with an increased risk of epilepsy. Establishment of interelement relationship strongly supported that there was a disturbance in the element homeostasis of epileptic patients.

CONCLUSIONS

The study results strengthen the role of lipid peroxidation, antioxidants and trace elements in the pathogenesis and warrant larger studies to investigate the association of these biochemical parameters with epilepsy.

A review of the implications and challenges of manganese removal from mine drainage

Manganese (Mn) is the third most abundant transition metal in the Earth's crust. Decades of increasing worldwide mining activities have inevitably led to the release of large amounts of this metal into the environment. Mine drainage, either acidic or neutral, often contains high levels of Mn, which have potentially detrimental effects on ecosystems and receiving water bodies. This review provides a comprehensive assessment of the main implications and challenges of Mn treatment in mine drainage. With this aim, the beneficial and adverse effects of Mn on ecosystems and human health are presented first. A comparison of background and mine effluents Mn contents is also provided, further stressing the need for Mn removal from mine drainage. Several technical options to address Mn contamination in acid and neutral mine drainage, and the challenges associated with Mn removal, are subsequently discussed. Thus, this paper presents up-to-date knowledge on the available physicochemical and biological processes deemed operative in Mn removal during mine drainage treatment and their limitations considering the distinctive behavior of Mn. The discussion is further extended to passive treatment systems, which are the most commonly implemented systems for mine drainage treatment on abandoned or closed mine sites, and highlights both their design criteria and operation requirements, as well as the factors that influence Mn removal efficiency. Finally, new perspectives on future research and development needs are identified to address the challenges in Mn removal during mine drainage treatment.

Mechanisms of divalent metal toxicity in affective disorders

Metals are required for proper brain development and play an important role in a number of neurobiological functions. The divalent metal transporter 1 (DMT1) is a major metal transporter involved in the absorption and metabolism of several essential metals like iron and manganese. However, non-essential divalent metals are also transported through this transporter. Therefore, altered expression of DMT1 can modify the absorption of toxic metals and metal-induced toxicity. An accumulating body of evidence has suggested that increased metal stores in the brain are associated with elevated oxidative stress promoted by the ability of metals to catalyze redox reactions, resulting in abnormal neurobehavioral function and the progression of neurodegenerative diseases. Metal overload has also been implicated in impaired emotional behavior, although the underlying mechanisms are not well understood with limited information. The current review focuses on psychiatric dysfunction associated with imbalanced metabolism of metals that are transported by DMT1. The investigations with respect to the toxic effects of metal overload on behavior and their underlying mechanisms of toxicity could provide several new therapeutic targets to treat metal-associated affective disorders.

Manganese-Enhanced MRI: Biological Applications in Neuroscience

Magnetic resonance imaging (MRI) is an excellent non-invasive tool to investigate biological systems. The administration of the paramagnetic divalent ion manganese (Mn²⁺) enhances MRI contrast in vivo. Due to similarities between Mn²⁺ and calcium (Ca²⁺), the premise of manganese-enhanced MRI (MEMRI) is that the former may enter neurons and other excitable cells through voltage-gated Ca²⁺ channels. As such, MEMRI has been used to trace neuronal pathways, define morphological boundaries, and study connectivity in morphological and functional imaging studies. In this article, we provide a brief overview of MEMRI and discuss recently published data to illustrate the usefulness of this method, particularly in animal models.

Genetic determinants of common epilepsies: a meta-analysis of genome-wide association studies

Background

The epilepsies are a clinically heterogeneous group of neurological disorders. Despite strong evidence for heritability, genome-wide association studies have had little success in identification of risk loci associated with epilepsy, probably because of relatively small sample sizes and insufficient power. We aimed to identify risk loci through meta-analyses of genome-wide association studies for all epilepsy and the two largest clinical subtypes (genetic generalised epilepsy and focal epilepsy).

Methods

We combined genome-wide association data from 12 cohorts of individuals with epilepsy and controls from population-based datasets. Controls were ethnically matched with cases. We phenotyped individuals with epilepsy into categories of genetic generalised epilepsy, focal epilepsy, or unclassified epilepsy. After standardised filtering for quality control and imputation to account for different genotyping platforms across sites, investigators at each site conducted a linear mixed-model association analysis for each dataset. Combining summary statistics, we conducted fixed-effects meta-analyses of all epilepsy, focal epilepsy, and genetic generalised epilepsy. We set the genome-wide significance threshold at p<1·66 × 10⁻⁸.

Findings

We included 8696 cases and 26 157 controls in our analysis. Meta-analysis of the all-epilepsy cohort identified loci at 2q24.3 (p=8·71 × 10⁻¹⁰), implicating SCN1A, and at 4p15.1 (p=5·44 × 10⁻⁹), harbouring PCDH7, which encodes a protocadherin molecule not previously implicated in epilepsy. For the cohort of genetic generalised epilepsy, we noted a single signal at 2p16.1 (p=9·99 × 10⁻⁹), implicating VRK2 or FANCL. No single nucleotide polymorphism achieved genome-wide significance for focal epilepsy.

Interpretation

This meta-analysis describes a new locus not previously implicated in epilepsy and provides further evidence about the genetic architecture of these disorders, with the ultimate aim of assisting in disease classification and prognosis. The data suggest that specific loci can act pleiotropically raising risk for epilepsy broadly, or can have effects limited to a specific epilepsy subtype. Future genetic analyses might benefit from both lumping (ie, grouping of epilepsy types together) or splitting (ie, analysis of specific clinical subtypes).

Funding

International League Against Epilepsy and multiple governmental and philanthropic agencies.

Hepatoprotective effect of manganese chloride against CCl4-induced liver injury in rats

The aim of the present study is to evaluate the protective effect of manganese chloride against carbon tetrachloride (CCl4)-induced liver injury in rats. Manganese chloride (0.001, 0.01, 0.05 and 0.1 g/kg bw) was administered intragastrically for 28 consecutive days to male CCl4-treated rats. The hepatoprotective activity was assessed using various biochemical parameters such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), γ-glutamyltransferase (GGT) and superoxide dismutase (SOD). Histopathological changes in the liver of different groups were also studied. Administration of CCl4 increased the serum ALT, AST, ALP and GGT but decreased SOD levels in rats. Treatment with manganese chloride significantly attenuated these changes to nearly normal levels. The animals treated with manganese chloride have shown decreased necrotic zones and hepatocellular degeneration when compared to the liver exposed to CCl4 intoxication alone. Thus, the histopathological studies also supported the protective effect of manganese chloride. Therefore, the results of this study suggest that manganese chloride exerts hepatoprotection via promoting antioxidative properties against CCl4-induced oxidative liver damage.

A review of the effects of vitamins and other dietary supplements on seizure activity

The role of pharmacological and surgical management of epilepsy continues to expand, but these treatments are often associated with significant side effects and morbidity. As a result, many patients with epilepsy and their physicians alike have gained interest in the role of vitamins and other dietary supplements for seizure management. In this review, we examine the potential anticonvulsant and proconvulsant effects of commonly used dietary supplements, as well as their potential effects on cognition or behavior. Our review was conducted through a literature search focusing on clinical trials involving patients with epilepsy and their seizure response to dietary supplementation. We summarize findings from previous clinical studies and comment on practical considerations regarding dietary supplementation for patients with epilepsy.

Determination of toxic and essential elements in children's blood with inductively coupled plasma-mass spectrometry

Recent studies have suggested that low blood lead level, less than 50 microg L(-1), can influence the neurobehavioral performance of children. In addition, nutritional deficiencies in some essential elements may increase the toxicity of lead, and some essential elements may influence the blood concentrations of lead and other toxic metals. These findings, coupled with the scarcity of available data on some elements in children's blood and the introduction of methylcyclopentadienyl manganese tricarbonyl (MMT) to gasoline, accentuate the need to monitor the concentrations of lead, manganese, and other heavy metals and essential elements in children's blood. This study reports on the multi-element analysis of blood of South African school children using inductively coupled plasma-mass spectrometry (ICP-MS). The sample preparation consisted of a nitric acid/hydrogen peroxide open digestion and subsequent dilution with MilliQ water. The accuracy and precision were evaluated from quintuplet analyses of Seronorm trace elements whole blood reference material and human blood samples. Concentrations of lead, arsenic, manganese, copper, zinc, selenium, cobalt, and chromium in the blood of South African school children were determined. The average values were: lead 56.4 microg L(-1), arsenic 1.53 microg L(-1), manganese 8.48 microg L(-1), copper 1195 microg L(-1), zinc 3431 microg L(-1), selenium 176 microg L(-1), cobalt 0.80 microg L(-1), and chromium 1.25 microg L(-1). The level of lead was in line with some reported lower concentrations. The concentrations of arsenic and manganese were generally lower than those found in the literature. The concentrations of cobalt, copper, selenium, and chromium were higher than those found in other studies, whereas that of zinc was lower.

Reporting of systematic reviews of micronutrients and health: a critical appraisal

BACKGROUND

The quality of nutrition-related systematic reviews (SRs) is an unstudied but important factor affecting their usefulness.

OBJECTIVES

The objectives were to evaluate the reporting quality of published SRs and to identify areas of improvement.

DESIGN

Descriptive and exploratory analyses of the reporting quality (7 nutrition items and 28 SR reporting items) of all English-language SRs published through July 2007 linking micronutrients and health outcomes in humans were conducted. Factors that may be associated with reporting quality were also evaluated.

RESULTS

We identified 141 eligible SRs of 21 micronutrients. Ninety SRs that included only interventional studies met a higher proportion of our reporting criteria (median: 62%; interquartile range: 51%, 72%) than did 31 SRs with only observational studies (median: 53%; interquartile range: 47%, 60%) or 20 SRs with both study designs (median: 47%; interquartile range: 39%, 52%) (P < 0.001). SRs published after consensus reporting standards (since 2003) met a higher proportion of the reporting criteria than did earlier SRs (median: 59% compared with 50%; P = 0.01); however, the reporting of nutrition variables remained unchanged (median: 38% compared with 33%; P = 0.7). The least-reported nutrition criteria were baseline nutrient exposures (28%) and effects of measurement errors from nutrition exposures (24%). Only 58 SRs (41%) used quality scales or checklists to assess the methodologic quality of the primary studies included.

CONCLUSIONS

The reporting quality of SRs has improved 3 y after publication of SR reporting standards, but the reporting of nutrition variables has not. Improved adherence to consensus methods and reporting standards should improve the utility of nutrition SRs.

Basal ganglia neurotransmitter concentrations in rhesus monkeys following subchronic manganese sulfate inhalation

BACKGROUND

Manganese neurotoxicity in humans is recognized as a form of parkinsonism with lesions occurring predominantly within the globus pallidus, subthalamic nucleus, putamen, and caudate nucleus.

METHODS

This study evaluated dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, serotonin, norepinephrine, 5-hydroxyindoleacetic acid, gamma-aminobutyric acid (GABA), and glutamate concentrations in the globus pallidus, caudate, and putamen of male rhesus monkeys exposed subchronically to either air or manganese sulfate (MnSO4) at 0.06, 0.3, or 1.5 mg Mn/m3.

RESULTS

An approximate 1.5-6-fold increase (vs. air-exposed controls) in mean brain manganese concentration was observed following subchronic MnSO4 exposure. A marginally significant (P < 0.1) decrease in pallidal GABA and 5-hydroxyindoleacetic acid concentration and caudate norepinephrine concentration occurred in monkeys exposed to MnSO4 at 1.5 mg Mn/m3.

CONCLUSIONS

Despite the presence of increased tissue manganese concentrations, high-dose exposure to MnSO4 was associated with relatively few changes in basal ganglial neurotransmitter concentrations.