Association of soil selenium, strontium, and magnesium concentrations with Parkinson's disease mortality rates in the USA

The Role of Magnesium in Parkinson's Disease: Status Quo and Implications for Future Research

Neurodegenerative diseases represent an increasing economic, social, and, above all, medical burden worldwide. The second most prevalent disease in this category is Parkinson's disease, surpassed only by Alzheimer's. It is a treatable but still incurable systemic disease with a pathogenesis that has not yet been elucidated. Several theories are currently being developed to explain the causes and progression of Parkinson's disease. Magnesium is one of the essential macronutrients and is absolutely necessary for life as we know it. The magnesium cation performs several important functions in the cell in the context of energetic metabolism, substrate metabolism, cell signalling, and the regulation of the homeostasis of other ions. Several of these cellular processes have been simultaneously described as being disrupted in the development and progression of Parkinson's disease. The relationship between magnesium homeostasis and the pathogenesis of Parkinson's disease has received little scientific attention to date. The aim of this review is to summarise and critically evaluate the current state of knowledge on the possible role of magnesium in the pathogenesis of Parkinson's disease and to outline possible future directions for research in this area.

Association of dietary selenium intake and all-cause mortality of Parkinson's disease and its interaction with blood cadmium level: a retrospective cohort study

BACKGROUND

Parkinson's disease (PD) is a slowly progressive neurodegenerating disease that may eventually lead to disabling condition and pose a threat to the health of aging populations. This study aimed to explore the association of two potential risk factors, selenium and cadmium, with the prognosis of Parkinson's disease as well as their interaction effect.

METHODS

Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 2005-2006 to 2015-2016 and National Death Index (NDI). Participants were classified as Parkinson's patients by self-reported anti-Parkinson medications usage. Cox regression models and restricted cubic spline models were applied to evaluate the association between PD mortality and selenium intake level as well as blood cadmium level. Subgroup analysis was also conducted to explore the interaction between them.

RESULTS

A total of 184 individuals were included. In full adjusted cox regression model (adjusted for age, gender, race, hypertension, pesticide exposure, smoking status and caffeine intake), compared with participants with low selenium intake, those with normal selenium intake level were significantly associated with less risk of death (95%CI: 0.18-0.76, P = 0.005) while no significant association was found between low selenium intake group and high selenium group (95%CI: 0.16-1.20, P = 0.112). Restricted cubic spline model indicated a nonlinear relationship between selenium intake and PD mortality (P for nonlinearity = 0.050). The association between PD mortality and blood cadmium level was not significant (95%CI: 0.19-5.57, P = 0.112). However, the interaction term of selenium intake and blood cadmium showed significance in the cox model (P for interaction = 0.048). Subgroup analysis showed that the significant protective effect of selenium intake existed in populations with high blood cadmium but not in populations with low blood cadmium.

CONCLUSION

Moderate increase of selenium intake had a protective effect on PD mortality especially in high blood cadmium populations.

Association Between the Ratios of Selenium to Several Elements and Mild Cognitive Impairment in the Elderly

To investigate the relationship between the correlation ratios of selenium (Se) and other elements and mild cognitive impairment (MCI) among older adults. A total of 1000 individuals participated in our research analysis. The concentrations of elements in whole blood were determined using inductively coupled plasma mass spectrometry to reflect their exposure levels. Participants' cognitive function was assessed using the Mini-Mental State Examination. Logistic regression analysis was used to evaluate the relationship between elemental ratios and MCI. Se concentration was positively correlated with red blood cell count (r = 0.219, p < 0.001), haemoglobin level (r = 0.355, p < 0.001), haematocrit (r = 0.215, p < 0.001), mean corpuscular haemoglobin (r = 0.294, p < 0.001) and mean corpuscular haemoglobin concentration (r = 0.428, p < 0.001) and negatively correlated with red cell volume distribution width-standard deviation (r = -0.232, p < 0.001) and platelet distribution width (r = -0.382, p < 0.001). Compared with the normal group, the ratios of Se/vanadium (V), Se/lead (Pb) and Se/cadmium (Cd) in the whole blood of the MCI group were significantly lower (all p < 0.001), while the ratios of manganese (Mn)/Se and iron (Fe)/Se were higher (all p < 0.001). The increase in the ratios of Se/V, Se/Pb and Se/Cd is related to a decreased risk of MCI among older adults; contrarily, an increase in the ratios of Mn/Se and Fe/Se may be a risk factor for MCI.

The position of geochemical variables as causal co-factors of diseases of unknown aetiology

Abstract

The term diseases of unknown aetiology (DUA) or idiopathic diseases is used to describe diseases that are of uncertain or unknown cause or origin. Among plausible geoenvironmental co-factors in causation of DUA, this article focusses on the entry of trace elements, including metals and metalloids into humans, and their involvement in humoral and cellular immune responses, representing potentially toxic agents with implications as co-factors for certain DUA. Several trace elements/metals/metalloids (micronutrients) play vital roles as co-factors for essential enzymes and antioxidant molecules, thus, conferring protection against disease. However, inborn errors of trace element/metal/metalloid metabolisms can occur to produce toxicity, such as when there are basic defects in the element transport mechanism. Ultimately, it is the amount of trace element, metal or metalloid that is taken up, its mode of accumulation in human tissues, and related geomedical attributes such as the chemical form and bioavailability that decisively determine whether the exerted effects are toxic or beneficial. Several case descriptions of DUA that are common worldwide are given to illustrate our knowledge so far of how trace element/metal/metalloid interactions in the immune system may engender its dysregulation and be implicated as causal co-factors of DUA.

Article highlights

The importance of a proper understanding of geochemical perturbations in human metabolisms is emphasisedIt is proferred that such an understanding would aid greatly in the decipherment of diseases of unknown aetiology (DUA)The thesis presented may pave the way towards better diagnosis and therapy of DUA.

Cerebrospinal Fluid Iron-Ferritin Ratio as a Potential Progression Marker for Parkinson's Disease

Longitudinal PD CSF samples were subjected to ICP-MS and the total amount of iron and other bioelements was quantified. Additionally, ferritin and protein biomarkers of neurodegeneration were measured. Over time, mean iron levels significantly increased while levels of ferritin decreased.

Mechanisms of Metal-Induced Mitochondrial Dysfunction in Neurological Disorders

Metals are actively involved in multiple catalytic physiological activities. However, metal overload may result in neurotoxicity as it increases formation of reactive oxygen species (ROS) and elevates oxidative stress in the nervous system. Mitochondria are a key target of metal-induced toxicity, given their role in energy production. As the brain consumes a large amount of energy, mitochondrial dysfunction and the subsequent decrease in levels of ATP may significantly disrupt brain function, resulting in neuronal cell death and ensuing neurological disorders. Here, we address contemporary studies on metal-induced mitochondrial dysfunction and its impact on the nervous system.

"Metal elements and pesticides as risk factors for Parkinson's disease - A review"

Essential metals including iron (Fe) and manganese (Mn) with known physiological functions in human body play an important role in cell homeostasis. Excessive exposure to these essential as well as non-essential metals including mercury (Hg) and Aluminum (Al) may contribute to pathological conditions, including PD. Each metal could be toxic through specific pathways. Epidemiological evidences from occupational and ecological studies besides various in vivo and in vitro studies have revealed the possible pathogenic role and neurotoxicity of different metals. Pesticides are substances that aim to mitigate the harm done by pests to plants and crops, and are extensively used to boost agricultural production. This review provides an outline of our current knowledge on the possible association between metals and PD. We have discussed the potential association between these two, furthermore the chemical properties, biological and toxicological aspects as well as possible mechanisms of Fe, Mn, Cu, Zn, Al, Ca, Pb, Hg and Zn in PD pathogenesis. In addition, we review recent evidence on deregulated microRNAs upon pesticide exposure and possible role of deregulated miRNA and pesticides to PD pathogenesis.

Elemental quantification and analysis of structural abnormalities in neurons from Parkinson's-diseased brains by X-ray fluorescence microscopy and diffraction

In this work we use scanning X-ray microscopy to study the structure and elemental composition of neuromelanin-positive neurons in substantia nigra tissue of Parkinson patients (PD) and controls. A total of 53 neurons were analyzed with X-ray fluorescence (XRF) and diffraction using sub-µm-focused synchrotron radiation. A statistical evaluation identified copper as the most group-discriminating element and indicated that interindividual and intraindividual variations are of great relevance in tissue measurements of diseased patients and prevent from automated group clustering. XRF analyses of two Lewy bodies (LBs) highlight a heterogeneity in elemental distributions in these LBs, whereas an innovative X-ray diffraction-based method approach was used to reveal β-sheet-rich crystalline structures in LBs. Overall, sub-µm-focus X-ray microscopy highlighted the elemental heterogeneity in PD pathology.

Dietary Antioxidants and Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder caused by the depletion of dopaminergic neurons in the basal ganglia, the movement center of the brain. Approximately 60,000 people are diagnosed with PD in the United States each year. Although the direct cause of PD can vary, accumulation of oxidative stress-induced neuronal damage due to increased production of reactive oxygen species (ROS) or impaired intracellular antioxidant defenses invariably occurs at the cellular levels. Pharmaceuticals such as dopaminergic prodrugs and agonists can alleviate some of the symptoms of PD. Currently, however, there is no treatment to halt the progression of PD pathology. Due to the nature of PD, a long and progressive neurodegenerative process, strategies to prevent or delay PD pathology may be well suited to lifestyle changes like dietary modification with antioxidant-rich foods to improve intracellular redox homeostasis. In this review, we discuss cellular and genetic factors that increase oxidative stress in PD. We also discuss neuroprotective roles of dietary antioxidants including vitamin C, vitamin E, carotenoids, selenium, and polyphenols along with their potential mechanisms to alleviate PD pathology.

Urine metals concentrations and dyslexia among children in China

BACKGROUND

Exposures to heavy metals has been linked to many developmental disorders. However, few studies have investigated the effects of exposure and co-exposure to metals on dyslexia, especially with regard to dyslexics in China.

OBJECTIVES

To investigate the association between urine metal concentrations and dyslexia in a case-control study among children in China.

METHODS

A case-control study was conducted in the Tongji Reading Environment and Dyslexia (READ) research program. A total of 228 dyslexics and 228 controls were matched on gender, age (within one year), and grade. The concentrations of 21 urine metals were measured by an inductively coupled plasma-mass spectrometer (ICP-MS). Multivariable conditional logistic regression models were applied to estimate the adjusted odds ratios (ORs) of Chinese dyslexia.

RESULTS

After adjusting for potential confounders, two metals (selenium and argentum) were significantly associated with dyslexia in single-metal multivariable models. Argentum was positively associated with the risk of dyslexia, while selenium was negatively associated. In the multiple-metal model, compared with extreme quartiles, the ORs (95% CIs) for selenium was 0.36 (95% CI: 0.14-0.93; P_trend = 0.029). In the joint association analysis, children with higher levels of urine argentum and lower level of urine selenium had a significantly higher risk of dyslexia than those with low levels of argentum and selenium (OR = 5.06, 95% CI: 1.67-18.84).

CONCLUSIONS

The findings suggest that exposure to selenium and argentum may relate to dyslexia in China. Longitudinal studies are needed to further evaluate these relationships and investigate potential mechanisms.

Selenium Status in Elderly People: Longevity and Age-Related Diseases

BACKGROUND

Selenium (Se) is a trace element active in selenoproteins, which can regulate oxidative stress. It is generally perceived as an import factor for maintaining health in the elderly.

METHODS

The goal of this review is to discuss selenium concentration in biological samples, primarily serum or plasma, as a function of age and its relation with longevity. The elemental level in various age-related diseases is reviewed.

CONCLUSION

Highest selenium values were observed in healthy adults, while in an elderly population significantly lower concentrations were reported. Variables responsible for contradictory findings are mentioned. Risk and benefits of Se-supplementation still remain under debate.

Selenium speciation analysis in the cerebrospinal fluid of patients with Parkinson's disease

BACKGROUND

The aim of the study was to investigate if speciation analysis by liquid chromatography coupled to mass spectrometry could be used to detect organic and inorganic binding forms of selenium in the cerebrospinal fluid (CSF) of patients with Parkinson's disease (PD) and age-matched control subjects (AMC).

METHODS

PD patients and control subjects were enrolled from three different neurological departments. CSF samples were collected according to standardized biomarker protocols and subjected to inductively coupled plasma mass spectrometry (ICP-MS) for total selenium determination and ion exchange chromatography (IEC) hyphenated to ICP-MS for selenium speciation analysis.

RESULTS

75 PD patients and 68 age-matched controls were enrolled for speciation analysis. 8 different species could be detected, but only selenoprotein P (SELENOP), human serum albumin-bound Se (Se-HSA), selenomethionine (Se-Met) and an unidentified Se-compound (U2) presented with more than 50% values above the limit of quantification, without showing significant differences between both groups (p > 0.05). The Se-HSA / Se-Met ratio yielded a significant difference between PD and AMC (p = 0.045). The inorganic species Se-IV and Se-VI were only detectable in a minor part of PD and AMC samples. A highly significant correlation between total selenium levels and SELENOP (PD p < 0.0001; AMC p < 0.0001) and Se-HSA (PD p < 0.0001; AMC p < 0.0001) could be demonstrated, respectively.

CONCLUSIONS

Speciation analysis yielded new insight into selenium homeostasis in PD but cannot be used to establish a diagnostic biomarker. The small number of detectable values for Se-IV and Se-VI suggests an inferior role of these potentially neurotoxic binding forms in PD pathology in contrast to other neurodegenerative disorders.

Elemental fingerprint: Reassessment of a cerebrospinal fluid biomarker for Parkinson's disease

The aim of the study was to validate a predictive biomarker machine learning model for the classification of Parkinson's disease (PD) and age-matched controls (AMC), based on bioelement abundance in the cerebrospinal fluid (CSF). For this multicentric trial, participants were enrolled from four different centers. CSF was collected according to standardized protocols. For bioelement determination, CSF samples were subjected to inductively coupled plasma mass spectrometry. A predefined Support Vector Machine (SVM) model, trained on a previous discovery cohort was applied for differentiation, based on the levels of six different bioelements. 82 PD patients, 68 age-matched controls and 7 additional Normal Pressure Hydrocephalus (NPH) patients were included to validate a predefined SVM model. Six differentiating elements (As, Fe, Mg, Ni, Se, Sr) were quantified. Based on their levels, SVM was successfully applied to a new local cohort (AUROC 0.76, Sensitivity 0.80, Specificity 0.83), without taking any additional features into account. The same model did not discriminate PD and AMCs / NPH from three external cohorts, likely due to center effects. However, discrimination was possible in cohorts with a full elemental data set, now using center-specific discovery cohorts and a cross validated approach (AUROC 0.78 and 0.88, respectively). Pooled PD CSF iron levels showed a clear correlation with disease duration (p = .0001). In summary, bioelemental CSF patterns, obtained by mass spectrometry and integrated into a predictive model yield the potential to facilitate the differentiation of PD and AMC. Center-specific biases interfere with application in external cohorts. This must be carefully addressed using center-defined, local reference values and models.

Mobility, distribution, and potential risk assessment of selected trace elements in soils of the Nile Delta, Egypt

Environmental pollution has received considerable attention over the last 50 years. Recently, there has been an increasing interest in pollution of the Nile Delta, Egypt, which is one of the longest settled deltaic systems in the world. Pollution in the delta is increasingly recognized as a serious health concern that requires proper management of ecosystems. Therefore, this project aimed to study the distribution and assess the risk associated with selected trace elements (TEs) in different soils (i.e., marine, fluvial, and lacustrine parent materials) in the northern Nile Delta. Mehlich-3 extraction was used to determine the availability of antimony, vanadium, strontium, and molybdenum in agro-ecosystems in this area and their spatial distributions were investigated. Five indices were used to assess ecological risk. Results showed that TEs were higher in the southern part of the study area because it is affected by multiple pollution sources. The available concentrations of TEs were Sr < V < Sb < Mo. The bioavailability of Sr was highest among the studied TEs. The studied indices suggested the study area was moderately polluted by Sr and Sb. Furthermore, the results showed that marine soils had higher TE levels then lacustrine and fluvial soils. The ecological risk assessment indicated that V and Mo were of natural origin, while Sr and Sb were anthropogenically linked. Therefore, the situation calls for planning to reduce pollution sources, especially in the protected north Nile Delta, so these productive soils do not threaten human and ecological health.

Comparison of methods for addressing the point-to-area data transformation to make data suitable for environmental, health and socio-economic studies

Soil lead (Pb) provides an important exposure pathway to the human body through soil ingestion and dust inhalation and is closely associated with human health as well as social behaviour. The challenge of transforming different spatial supports arises when linking point data (Pb concentration) to areal data (health status or social behaviour). A detailed review of methodologies for integrating point and areal data has been carried out. Among a number of methodologies, eight methods: (1) average, (2) median, (3) centroids inverse distance weighted (IDW), (4) average block IDW, (5) median block IDW, (6) centroids ordinary kriging (OK), (7) average block OK and (8) median block OK, have been compared using Pb data set in the Greater London Authority (GLA) area. The results indicated that the method of median block IDW was recommended for further investigation of the relationship between Pb concentration and socio-economic factors in the ward-level of the GLA area. The reasons were (i) spatial interpolations were useful for predicting unobserved values when simple average and median could not work in the locations where there were no samples collected in some areal units; (ii) the median value was more suitable than the average value for a skewed data set; (iii) the block method reduced estimation error and provided more representative values of areal units than the centroid method; (iv) IDW reserved more spatial variation than OK, containing more local maxima (hotspot) and local minima. Despite that it is still hard to decide the optimal method, this study has highlighted the point-to-area transformation issue and provided valuable examples to compare the different methods.