Aluminium and calcium in soil and food from Guam, Palau and Jamaica: Implications for amyotrophic lateral sclerosis and parkinsonism-dementia syndromes of Guam

Metals and Metalloids Increase in Cycas micronesica Seed Gametophyte Tissue in Shaded Growth Conditions

Exposure to environmental toxins may be partly responsible for mammal neurodegenerative disorders. Consumption of seeds from Guam's cycad tree has been linked to the disorder known as amyotrophic lateral sclerosis-parkinsonism dementia complex (ALS-PDC). The unambiguous identification of causal agents of ALS-PDC has been elusive. We have examined the levels of eight metals and metalloids in cycad seeds as a function of the ambient shade in which the plants were grown. Of these metals, the data strongly suggest that aluminum (Al) and selenium (Se) are present in washed flour prepared from southern Guam's cycad seed tissues at elevated levels, especially when the trees are grown in shade. Previous authors have speculated that Al and Se are involved in various ALS outcomes, and our results support this interpretation.

Cellular and pathological heterogeneity of primary tauopathies

Microtubule-associated protein tau is abnormally aggregated in neuronal and glial cells in a range of neurodegenerative diseases that are collectively referred to as tauopathies. Multiple studies have suggested that pathological tau species may act as a seed that promotes aggregation of endogenous tau in naïve cells and contributes to propagation of tau pathology. While they share pathological tau aggregation as a common feature, tauopathies are distinct from one another with respect to predominant tau isoforms that accumulate and the selective vulnerability of brain regions and cell types that have tau inclusions. For instance, primary tauopathies present with glial tau pathology, while it is mostly neuronal in Alzheimer's disease (AD). Also, morphologies of tau inclusions can greatly vary even within the same cell type, suggesting distinct mechanisms or distinct tau conformers in each tauopathy. Neuropathological heterogeneity across tauopathies challenges our understanding of pathophysiology behind tau seeding and aggregation, as well as our efforts to develop effective therapeutic strategies for AD and other tauopathies. In this review, we describe diverse neuropathological features of tau inclusions in neurodegenerative tauopathies and discuss what has been learned from experimental studies with mouse models, advanced transcriptomics, and cryo-electron microscopy (cryo-EM) on the biology underlying cell type-specific tau pathology.

Western Pacific ALS-PDC: Evidence implicating cycad genotoxins

Amyotrophic Lateral Sclerosis and Parkinsonism-Dementia Complex (ALS-PDC) is a disappearing neurodegenerative disorder of apparent environmental origin formerly hyperendemic among Chamorros of Guam-USA, Japanese residents of the Kii Peninsula, Honshu Island, Japan and Auyu-Jakai linguistic groups of Papua-Indonesia on the island of New Guinea. The most plausible etiology is exposure to genotoxins in seed of neurotoxic cycad plants formerly used for food and/or medicine. Primary suspicion falls on methylazoxymethanol (MAM), the aglycone of cycasin and on the non-protein amino acid β-N-methylamino-L-alanine, both of which are metabolized to formaldehyde. Human and animal studies suggest: (a) exposures occurred early in life and sometimes during late fetal brain development, (b) clinical expression of neurodegenerative disease appeared years or decades later, and (c) pathological changes in various tissues indicate the disease was not confined to the CNS. Experimental evidence points to toxic molecular mechanisms involving DNA damage, epigenetic changes, transcriptional mutagenesis, neuronal cell-cycle reactivation and perturbation of the ubiquitin-proteasome system that led to polyproteinopathy and culminated in neuronal degeneration. Lessons learned from research on ALS-PDC include: (a) familial disease may reflect common toxic exposures across generations, (b) primary disease prevention follows cessation of exposure to culpable environmental triggers; and (c) disease latency provides a prolonged period during which to intervene therapeutically. Exposure to genotoxic chemicals ("slow toxins") in the early stages of life should be considered in the search for the etiology of ALS-PDC-related neurodegenerative disorders, including sporadic forms of ALS, progressive supranuclear palsy and Alzheimer's disease.

No association between soil constituents and amyotrophic lateral sclerosis relative risk in Ireland

INTRODUCTION

We have recently mapped ALS spatial risk in Ireland using Bayesian and cluster analysis methods at electoral division (ED) and small area (SA) levels. As a number of metal elements (both minerals and toxins) have been proposed as risk factors for ALS, here we extend this analysis to include soil constituents from the Irish National Soils Database as Bayesian conditional auto-regression covariates to determine associations with small area ALS risk.

METHODS

Data on 45 different soil parameters were obtained under license from National Soils Database (via Irish EPA). We interpolated average values of each soil constituent for each small area using ordinary kriging. All cases of ALS in Ireland from January 1995 to December 2013 were identified from the Irish ALS register and observed and age and gender standardised expected cases were calculated for each SA. Besag-York-Mollié (BYM) models were then built including each parameter from the national soils database in turn as a Bayesian covariate in the BYM model. Models were compared using the deviance information criterion (DIC) and separate models were built for ALS subtypes.

RESULTS

1701 ALS patients were included - 959 (56%) were male, 938 (55%) had limb onset ALS. 315 Bayesian models were built in total. Of the 315 models built, only one resulted in a coefficient that did not overlap zero. For limb onset cases, total magnesium had a mean coefficient of 0.319 (credible interval 0.033-0.607).

DISCUSSION

We report the first spatial analysis of potential association between ALS and soil minerals using a population-based dataset collected over 18 years. Our sole non-zero finding is likely a random finding due to the high number of models built. We did not find any evidence to support soil mineral and toxin levels as risk factors for ALS. However as soil parameters are an ecological assessment of exposure in a given area, individual level measures of exposure are required.

Progressive supranuclear palsy and its relation to pacific foci of the parkinsonism-dementia complex and Guadeloupean parkinsonism

Steele, Richardson and Olszweski in 1964 described a distinctive clinical and pathological entity they called progressive supranuclear palsy (PSP). Now on Guadeloupe in the Carribbean French West Indies, Caparros-Lefebvre is identifying many patients with similar clinical and histological features. Others have a clinical syndrome of atypical parkinsonism that resembles the parkinsonism-dementia complex (PDC) of Guam and the Kii peninsula of Japan (PDC). But in those Pacific foci the histology is different and the abnormal tau is of Alzheimer's type rather than the PSP type of Guadeloupe. In both locales, neurotoxins of local foods are implicated in etiology. Future studies will confirm if Guadeloupean parkinsonism is truly a geographic focus of PSP, and if dietary factors account for both.

Motor neuron disease on the Kii Peninsula of Japan: excess manganese intake from food coupled with low magnesium in drinking water as a risk factor

To identify important risk factors of motor neuron disease (MND) in a focus (Hohara) on the Kii peninsula of Japan, 24-h dietary duplicates, rice, drinking water, and soils were analysed for metals in Hohara and control areas. The manganese content in 24-h food in Hohara was significantly (P < 0.01) higher than that in the remote control areas. The incidence of MND in Hohara was well explained by the two parameters, manganese content in food and the magnesium concentration in drinking water (r2 = 0.99), suggesting that MND in this focus can be understood as a result of excess intake of manganese from food coupled with low intake of magnesium from drinking water. The reference to epidemiology and occupational medicine supports this conclusion. The crude annual MND incidence per 10(5) population in other foci may be predicted as MND = e alpha ln[beta(Mn in food)gamma/(Mg in water)], where alpha is 5.389-5.748, beta is 0.170-0.166, and gamma is 1.239-1.226.