Blood manganese levels and associated factors in a population-based study in Southern Brazil

Role of manganese in brain health and disease: Focus on oxidative stress

Manganese (Mn) is an essential trace element crucial for various physiological processes, but excessive exposure can lead to significant health concerns, particularly neurotoxicity. This review synthesizes current knowledge on Mn-induced oxidative stress and its role in cellular dysfunction and disease. We discuss how Mn promotes toxicity through multiple mechanisms, primarily through reactive oxygen species (ROS) generation, which leads to oxidative stress and disruption of cellular processes. The review examines key pathways affected by Mn toxicity, including mitochondrial dysfunction, endoplasmic reticulum stress, inflammasome activation, and epigenetic modifications. Recent studies have identified promising therapeutic compounds, including both synthetic and natural substances such as probucol, metformin, curcumin, resveratrol, and daidzein, which demonstrate protective effects through various mechanisms, including antioxidant enhancement, mitochondrial function preservation, and epigenetic pathway modulation. Understanding these mechanisms provides new insights into potential therapeutic strategies for Mn-induced disorders. This review also highlights future research directions, emphasizing the need for developing targeted therapies and investigating combination approaches to address multiple aspects of Mn toxicity simultaneously.

Associations of essential trace metals with telomere length in general population: a cross-sectional study

This study investigated the relationship between essential plasma metals (Co, Cr, Cu, Mn, Mo, Se, Zn) and telomere length in 2,194 Chinese adults aged ≥ 30 years. Metal concentrations were measured using ICP-MS, and leukocyte relative telomere length (rTL) was assessed by qPCR. In the elderly, Cr and Mn were significantly positively correlated with rTL, while Mo, Zn, and Cu showed negative correlations. In the 30-59 age group, the overall metal mixture was significantly negatively associated with rTL (estimate = -0.069, P = 0.003), with Zn as the dominant contributor. In the elderly, the metal mixture was positively associated with rTL (estimate = 0.040, P = 0.031), with Cr and Mn as main contributors. The findings highlight the importance of maintaining adequate Cr and Mn levels in older adults, and the potential adverse impact of Cu, Mo, and Zn on telomere length.

Review of non-invasive biomarkers as a tool for exposure characterization in human health risk assessments

Blood and urine are historically the most frequent matrices used for measuring chemical levels in human biomonitoring studies. As biomonitoring programs are refreshed, consideration of specific priority substances and specific population targets provide opportunities for inclusion of alternative non- or minimally invasive matrices. This review describes methods used in health risk assessment to characterize exposure and risk based upon biomarkers from noninvasive matrices other than urine or blood, including human milk, hair, fingernails, toenails, exhaled breath, deciduous teeth, sweat, semen, meconium, and feces. Illustrative examples of these methods relevant to chemical management are provided. This review suggests that, although these alternative noninvasive biomarkers are not frequently used in human health risk assessment at present, these biomarkers may prove useful in (1) characterizing exposure and health risk in vulnerable populations, (2) cumulative risk assessments, and (3) community-based risk assessments, depending upon the substance of concern. To incorporate alternative noninvasive biomarkers into human health risk assessments with confidence, more research is needed to improve our knowledge of the relationships between external dose, internal dose, and biologic consequent effects in matrices other than blood and urine.

The impact of manganese on vascular endothelium

Manganese (Mn) is an essential trace element involved in various physiological processes, but excessive exposure may lead to toxicity. The vascular endothelium, a monolayer of endothelial cells within blood vessels, is a primary target of Mn toxicity. This review provides a comprehensive overview of the impact of Mn on vascular endothelium, focusing on both peripheral and brain endothelial cells. In vitro studies have demonstrated that high concentrations of Mn can induce endothelial cell cytotoxicity, increase permeability, and disrupt cell-cell junctions through mechanisms involving oxidative stress, mitochondrial damage, and activation of signaling pathways, such as Smad2/3-Snail. Conversely, low concentrations of Mn may protect endothelial cells from the deleterious effects of high glucose and advanced glycation end-products. In the central nervous system, Mn can cross the blood-brain barrier (BBB) and accumulate in the brain parenchyma, leading to neurotoxicity. Several transport mechanisms, including ZIP8, ZIP14, and SPCA1, have been identified for Mn uptake by brain endothelial cells. Mn exposure can impair BBB integrity by disrupting tight junctions and increasing permeability. In vivo studies have corroborated these findings, highlighting the importance of endothelial barriers in mediating Mn toxicity in the brain and kidneys. Maintaining optimal Mn homeostasis is crucial for preserving endothelial function, and further research is needed to develop targeted therapeutic strategies to prevent or mitigate the adverse effects of Mn overexposure.

Graphical Abstract

A Fast-Forward Dilute-and-Shoot Multielement Method for Analysis of 33 Elements in Human Whole Blood, Serum, and Urine by Inductively Coupled Plasma Mass Spectrometry: A Streamlined Approach for Clinical Diagnostic and Biomonitoring

The analysis of toxic and essential elements in human matrices is used in clinical diagnostics and for biomonitoring of different populations to study related health outcomes. This work aimed to develop fast and reliable methods for the analysis of a broad range of elements in liquid human matrices, such as whole blood, serum, and urine, with a similar setup for the three matrices and different analysis needs. An easy and fast-forward dilute-and-shoot method for 33 elements (i.e., Ag, Al, As, B, Ba, Be, Bi, Cd, Ce, Co, Cr, Cu, Hg, I, Li, Mn, Mo, Ni, Pb, Pd, Pt, Sb, Se, Sn, Sr, Te, Th, Tl, U, V, W, Zn, and Zr) was developed. 200 µL of either sample material was diluted with an alkaline reagent to a volume of 4 mL in total. Sample dilution and preparation of matrix-matched calibration standards were performed in 48-well plates by an automated liquid handler. Diluted samples were analyzed by inductively coupled plasma mass spectrometry on a Perkin Elmer NexIon 300D ICP-MS instrument equipped with an ESI-FAST SC2DX autosampler in kinetic energy discrimination mode with helium as cell gas at either 4.8 mL or 5.7 mL and 1600 W RF generator power. The method validation results showed good accuracy for fresh human samples from an external quality assessment scheme with measured concentrations within the assigned concentration ranges. Good precision and reproducibility for most elements were demonstrated with variation coefficients below or far below 8% and 15% for whole blood, 8% and 10% for serum, and 10% and 10% for urine, respectively. The developed reagent and instrumental setup were applicable to all three matrices. This minimizes the risk of human errors when switching between analyses of the different sample matrices and allows a rapid and easy analysis of whole blood, serum, and urine within one day if needed. The method demonstrated robustness over time, withstanding minor changes in the preparation of working solutions and samples, instrumental analysis, and setup. Analysis of human real samples showed the method's applicability for 33 toxic and essential elements in whole blood, serum, and urine and at concentrations relevant to clinical diagnostics as well as biomonitoring.

Increased hypertension risk for the elderly with high blood levels of strontium and lead

Hypertension has long been recognized as the global health burden. Heavy metal pollution may be one of the environmental risk factors of hypertension. However, the association remains unclear. We studied the levels of aluminum (Al), vanadium (V), manganese (Mn), arsenic (As), selenium (Se), strontium (Sr), barium (Ba), titanium (Ti), lead (Pb) and cobalt (Co) in whole blood, and the relationship between trace element exposure and hypertension in the elderly community-based Chinese population. A total of 1013 participants from the west of Anhui Province in China were consecutively enrolled in this study in 2016. The general sociodemographic characteristics, lifestyles, disease history and physical examination information were collected by face-to-face survey and physical examination. The levels of ten trace elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). Multivariable logistic regression model was used to assess the association of trace element exposure with the risk of hypertension. Results showed that the odds ratio of hypertension in the highest quartile was 1.811 (95% CI 1.175-2.790, P trend = 0.005) and 1.772 (95% CI 1.121-2.800, P trend = 0.022), respectively, after adjusting for potential confounders, as compared with the lowest quartile of blood Pb and Sr levels.

Prevalence of metal levels above the reference values in a municipality affected by the collapse of a mining tailings dam: Brumadinho Health Project

OBJECTIVE

To describe the prevalence of levels of arsenic, cadmium, mercury, lead and manganese above the reference values (RV) in the population of Brumadinho, after the rupture of the mining tailings dam and to verify the factors associated with these levels.

METHODS

Baseline study of a prospective cohort, in a representative sample of 3,080 residents (aged 12 and over) in Brumadinho, Minas Gerais. Exploratory variables (age, sex, skin color, household income, smoking and place of residence) were collected using a questionnaire and the levels of As, Cd and Hg in urine and Pb and Mn in blood were evaluated using the technique of inductively coupled plasma mass spectrometry. The distribution of prevalence of levels above the reference for metals was made, according to the exploratory variables. Multiple logistic regression analyzes were used to investigate the association between altered levels of metals and characteristics evaluated.

RESULTS

Concentrations above RV were found in 38.08% of the population for Mn, 33.37% for As, 5.04% for Pb, 0.76% for Hg and 0.17% for Cd. There was a significant association between age group and levels of Mn and Pb; and between place of residence and As level.

CONCLUSION

The results show a high prevalence of levels above the reference for Mn, As and Pb, with small differences in relation to the other variables, suggesting that it is an exposure distributed throughout the municipality.

Biomarkers of environmental manganese exposure

We conducted a critical review on biomarkers of environmental manganese (Mn) exposure to answer the following questions: 1) are there reliable biomarkers of internal Mn exposure (Mn in biological matrices) associated with external metrics of Mn exposure (Mn in environmental media)? and 2) are there accurate reference values (RVs) for Mn in biological matrices? Three bibliographic databases were searched for relevant references and identified references were screened by two independent reviewers. Of the 6342 unique references identified, 86 articles were retained for data abstraction. Our analysis of currently available evidence suggests that Mn levels in blood and urine are not useful biomarkers of Mn exposure in non-occupational settings. The strength of the association between Mn in environmental media and saliva was variable. Findings regarding the utility of hair Mn as a biomarker of environmental Mn exposure are inconsistent. Measurements of Mn in teeth are technically challenging and findings on Mn in tooth components are scarce. In non-occupationally exposed individuals, bone Mn measurements using in vivo neutron activation analysis (IVNAA) are associated with large uncertainties. Findings suggest that Mn in nails may reflect Mn in environmental media and discriminate between groups of individuals exposed to different environmental Mn levels, although more research is needed. Currently, there is no strong evidence for any biological matrix as a valid biomarker of Mn exposure in non-occupational settings. Because of methodological limitations in studies aimed at derivation of RVs for Mn in biological materials, accurate RVs are scarce.

Biomonitoring of Exposure to Metals in a Population Residing in an Industrial Area in Brazil: A Feasibility Study

Background: Industries are sources of environmental pollutants. However, there are few human biomonitoring (HBM) studies in the vicinity of industrial areas. Thus, we evaluate the feasibility of conducting an HBM study to assess exposure to metals in an industrial area in Rio de Janeiro, Brazil. Methodology: A cross-sectional survey was conducted near a steel factory. Adults (exposed = 775; controls = 775) were randomly selected and sex-matched. Subjects were interviewed using a questionnaire and a 24 h dietary recall. Blood samples were collected to analyze metal concentrations, blood count, biochemical parameters, and thyroid hormones. The feasibility of the survey was assessed following guidelines. The descriptive analysis was performed for the first 250 participants (pilot study). Results: Adjustments were made to the survey execution, including age-matching, fieldwork team, questionnaire, blood collection, and research awareness. The complete questionnaire was answered by ≥97% of participants; metals were measured in ≥98% and clinical parameters in ≥89%, except thyroid hormones (13–44%). The average age and family income were of 50 years and USD 575/month, respectively. The participants had equal distribution among sexes: 50% had a medium education level, and 59% were nonwhite. Conclusion: This preliminary HBM study demonstrates feasibility for the total population, with results indicating representativeness of the target population.

Sex-specific neurotoxic effects of heavy metal pollutants: Epidemiological, experimental evidence and candidate mechanisms

The heavy metals lead (Pb), mercury (Hg), and cadmium (Cd) are ubiquitous environmental pollutants and are known to exert severe adverse impacts on the nervous system even at low concentrations. In contrast, the heavy metal manganese (Mn) is first and foremost an essential nutrient, but it becomes neurotoxic at high levels. Neurotoxic metals also include the less prevalent metalloid arsenic (As) which is found in excessive concentrations in drinking water and food sources in many regions of the world. Males and females often differ in how they respond to environmental exposures and adverse effects on their nervous systems are no exception. Here, we review the different types of sex-specific neurotoxic effects, such as cognitive and motor impairments, that have been attributed to Pb, Hg, Mn, Cd, and As exposure throughout the life course in epidemiological as well as in experimental toxicological studies. We also discuss differential vulnerability to these metals such as distinctions in behaviors and occupations across the sexes. Finally, we explore the different mechanisms hypothesized to account for sex-based differential susceptibility including hormonal, genetic, metabolic, anatomical, neurochemical, and epigenetic perturbations. An understanding of the sex-specific effects of environmental heavy metal neurotoxicity can aid in the development of more efficient systematic approaches in risk assessment and better exposure mitigation strategies with regard to sex-linked susceptibilities and vulnerabilities.

Evaluating the risk of manganese-induced neurotoxicity of parenteral nutrition: review of the current literature

INTRODUCTION

Several diseases and clinical conditions can affect enteral nutrition and adequate gastrointestinal uptake. In this respect, parenteral nutrition (PN) is necessary for the provision of deficient trace elements. However, some essential elements, such as manganese (Mn) may be toxic to children and adults when parenterally administered in excess, leading to toxic, especially neurotoxic effects.

AREAS COVERED

Here, we briefly provide an overview on Mn, addressing its sources of exposure, the role of Mn in the etiology of neurodegenerative diseases, and focusing on potential mechanisms associated with Mn-induced neurotoxicity. In addition, we discuss the potential consequences of overexposure to Mn inherent to PN.

EXPERT OPINION

In this critical review, we suggest that additional research is required to safely set Mn levels in PN, and that eliminating Mn as an additive should be considered by physicians and nutritionists on a case by case basis in the meantime to avoid the greater risk of neurotoxicity by its presence. There is a need to better define clinical biomarkers for Mn toxicity by PN, as well as identify new effective agents to treat Mn-neurotoxicity. Moreover, we highlight the importance of the development of new guidelines and practice safeguards to protect patients from excessive Mn exposure and neurotoxicity upon PN administration.

Manganese-induced neurodegenerative diseases and possible therapeutic approaches

INTRODUCTION

Neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis and prion disease represent important public health concerns. Exposure to high levels of  heavy metals such as manganese (Mn) may contribute to their development.

AREAS COVERED

In this critical review, we address the role of Mn in the etiology of neurodegenerative diseases and discuss emerging treatments of Mn overload, such as chelation therapy. In addition, we discuss natural and synthetic compounds under development as prospective therapeutics. Moreover, bioinformatic approaches to identify new potential targets and therapeutic substances to reverse the neurodegenerative diseases are discussed.

EXPERT OPINION

Here, the authors highlight the importance of better understanding the molecular mechanisms of toxicity associated with neurodegenerative diseases, and the role of Mn in these diseases. Additional emphasis should be directed to the discovery of new agents to treat Mn-induced diseases, since present day chelator therapies have limited bioavailability. Furthermore, the authors encourage the scientific community to develop research using libraries of compounds to screen those compounds that show efficacy in regulating brain Mn levels. In addition, bioinformatics may provide novel insight for pathways and clinical treatments associated with Mn-induced neurodegeneration, leading to a new direction in Mn toxicological research.

Ambulatory Blood Pressure in Relation to Plasma and Urinary Manganese

The association of blood pressure (BP) with manganese-an essential trace element required for human health-remains poorly studied. In 734 randomly recruited Swiss participants (mean age, 47.5 years; 51.4% women), we related ambulatory BP to 2 biomarkers, plasma manganese (pMn) and the urinary manganese (uMn) excretion. To allow for diurnal variation, we assessed BP and uMn over 24 hours and during wakefulness and sleep, using split urine samples. Twenty-four-hour, daytime, and nighttime systolic/diastolic BPs averaged 119.8/78.1, 123.8/81.2, and 107.0/68.3 mm Hg; the corresponding median uMn were 199.5, 83.0, and 51.5 μmol and median pMn, 0.52 μg/L. In analyses dichotomized by the median of the biomarkers, greater pMn was associated with higher 24-hour systolic/diastolic BP (+4.1/+2.3 mm Hg; P≤0.0003), greater daytime uMn with lower daytime BP (-3.5/-1.9 mm Hg; P≤0.0067), and greater nighttime uMn with higher nighttime BP (+2.9/+1.2 mm Hg; P≤0.046). In multivariable-adjusted analyses, significance (P≤0.030) was retained for the positive association of 24-hour and daytime diastolic BP with pMn and for systolic BP in relation to uMn at night. The association sizes for a 2-fold increment in the biomarkers amounting to 0.77 mm Hg (95% CI, 0.08-1.47 mm Hg), 0.97 (CI, 0.20-1.76) and 1.33 (CI, 0.20-2.50 mm Hg), respectively. In conclusion, there were positive associations between diastolic BP and pMn over 24 hours and during daytime and between systolic BP and uMn at night.

Changes of trace element status during aging: results of the EPIC-Potsdam cohort study

Purpose

We aimed to evaluate age-dependent changes of six trace elements (TE) [manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), iodine (I), and selenium (Se)] over a 20-year period.

Methods

TE concentrations were determined using repeated serum samples taken at baseline and after 20 years of follow-up from 219 healthy participants of the EPIC-Potsdam study, using inductively coupled plasma tandem mass spectrometry. For each TE, absolute and relative differences were calculated between the two time points, as well as the proportion of individuals within normal reference ranges. Interdependence between age-related TE differences was investigated using principal component analysis (PCA). Relationships between selected factors (lifestyle, sociodemographic, anthropometric factors, and hypertension) and corresponding TE longitudinal variability were examined using multivariable linear regression models.

Results

Median age of our study sample was 58.32 years (4.42) at baseline and 40% were females. Median Mn, Zn, Se concentrations and Se to Cu ratio significantly decreased during aging while median Fe, Cu, I concentrations and Cu to Zn ratio significantly increased. A substantial percentage of the participants, at both time points, had Zn concentrations below the reference range. The first PCA-extracted factor reflected the correlated decline in both Mn and Zn over time while the second factor reflected the observed (on average) increase in both Cu and I over time. Overall, none of the investigated factors were strong determinants of TE longitudinal variability, except possibly dietary supplement use, and alcohol use for Fe.

Conclusions

In conclusion, in this population-based study of healthy elderly, decrease in Mn, Zn, and Se concentrations and increase in Fe, Cu, and I concentrations were observed over 20 years of follow-up. Further research is required to investigate dietary determinants and markers of TE status as well as the relationships between TE profiles and the risk of age-related diseases.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-02143-w) contains supplementary material, which is available to authorized users.

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.

An overview of the current progress, challenges, and prospects of human biomonitoring and exposome studies

Human Biomonitoring (HB), the process for determining whether and to what extent chemical substances penetrated our bodies, serves as a useful tool to quantify human exposure to pollutants. In cases of nutrition and physiologic status, HB plays a critical role in the identification of excess or deficiency of essential nutrients. In pollutant HB studies, levels of substances measured in body fluids (blood, urine, and breast milk) or tissues (hair, nails or teeth) aid in the identification of potential health risks or associated adverse effects. However, even as a widespread practice in several countries, most HB studies reflect exposure to a single compound or mixtures which are measured at a single time point in lifecycle. On the other hand, throughout an individual's lifespan, the contact with different physical, chemical, and social stressors occurs at varying intensities, differing times and durations. Further, the interaction between stressors and body receptors leads to dynamic responses of the entire biological system including proteome, metabolome, transcriptome, and adductome. Bearing this in mind, a relatively new vision in exposure science, defined as the exposome, is postulated to expand the traditional practice of measuring a single exposure to one or few chemicals at one-time point to an approach that addresses measures of exposure to multiple stressors throughout the lifespan. With the exposome concept, the science of exposure advances to an Environment-Wide Association Perspective, which might exhibit a stronger relationship with good health or disease conditions for an individual (phenotype). Thus, this critical review focused on the current progress of HB and exposome investigations, anticipating some challenges, strategies, and future needs to be taken into account for designing future surveys.

Metal bashing: iron deficiency and manganese overexposure impact on peripheral nerves

Iron (Fe) deficiency (FeD) and manganese (Mn) overexposure (MnOE) may result in several neurological alterations in the nervous system. Iron deficiency produces unique neurological deficits due to its elemental role in central nervous system (CNS) development and myelination, which might persist after normalization of Fe in the diet. Conversely, MnOE is associated with diverse neurocognitive deficits. Despite these well-known neurotoxic effects on the CNS, the influence of FeD and MnOE on the peripheral nervous system (PNS) remains poorly understood. The aim of the present investigation was to examine the effects of developmental FeD and MnOE or their combination on the sciatic nerve of young and adult rats. The parameters measured included divalent metal transporter 1 (DMT1), transferrin receptor (TfR), myelin basic protein (MBP) and peripheral myelin protein 22 (PMP22) expression, as well as Fe levels in the nerve. Our results showed that FeD produced a significant reduction in MBP and PMP22 content at P29, which persisted at P60 after Fe-sufficient diet replenishment regardless of Mn exposure levels. At P60 MnOE significantly increased sciatic nerve Fe content and DMT1 expression. However, the combination of FeD and MnOE produced no marked motor skill impairment. Evidence indicates that FeD appears to hinder developmental peripheral myelination, while MnOE may directly alter Fe homeostasis. Further studies are required to elucidate the interplay between these pathological conditions.

Biomarkers of exposure and effect in a working population exposed to lead, manganese and arsenic

Lead (Pb), manganese (Mn) and arsenic (As) are among the major toxicants in mining environments. Miners are commonly and repeatedly exposed to this toxic mixture. Some adverse effects may appear at concentrations below environmental quality guidelines for individual mixture components. Further, Pb, Mn, and As induce common adverse outcomes, such as interferences in the cholinergic system and heme synthesis. It is thus vital to monitor miners through biomarkers (BM), such that subclinical effects may be identified at an early stage. The main objectives of this study were to evaluate the exposure of a mining population to these three metals and determine alterations in cholinergic and heme synthesis parameters. Blood and urine samples of workers (n = 60) were obtained from a Portuguese mining industry and compared with a control population (n = 80). The levels of the metals were determined in biological samples, as well as urinary heme precursor levels, delta aminolevulinic acid (ALA) and porphyrins, and blood acetylcholinesterase (AChE) activity. The miners exhibited significantly higher values of Pb and As in blood and urine compared to control. In the case of Mn near or slightly higher than limit values were found. Our data show that heme precursors may be used simultaneously with metal levels as BMs for multiple metal exposures on an individual basis, resulting in 94.3% and 95.7% accuracy, respectively, in blood and urine, for subjects correctly identified with respect to occupation. This study also revealed that biological monitoring of this working population regarding metal body burden and heme precursor accumulation is advisable.