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, 6, 264-271

Isotopic Evidence for Disrupted Copper Metabolism in Amyotrophic Lateral Sclerosis

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Isotopic Evidence for Disrupted Copper Metabolism in Amyotrophic Lateral Sclerosis

Lucie Sauzéat et al. iScience.

Abstract

Redox-active metals are thought to be implicated in neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). To address this point, we measured the concentrations of 12 elements and, for the first time, the stable isotope compositions of copper (redox-active) and zinc (redox-inactive) in human cerebrospinal fluids of 31 patients with ALS, 11 age-matched controls (CTRL), and 14 patients with Alzheimer disease. We first show that metal concentrations weakly discriminate patients with ALS from the two other groups. We then report that zinc isotopic compositions are similar in the three groups, but that patients with ALS have significantly 65copper-enriched isotopic compositions relative to CTRL and patients with AD. This result unambiguously demonstrates that copper is implicated in ALS. We suggest that this copper isotopic signature may result from abnormal protein aggregation in the brain parenchyma, and propose that isotopic analysis is a potential tool that may help unraveling the molecular mechanisms at work in ALS.

Keywords: Clinical Neuroscience; Isotope Chemistry; Neuroscience; Nuclear Medicine.

Figures

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Figure 1
Figure 1
Principal Component Analysis of the Results The PCA allows the distinction of patients with ALS (green points) from CTRL subjects (yellow points) and subjects with AD (pink points). Concentrations and isotopic compositions are normalized to their SD. The two principal components (PC1 and PC2) are represented and explain ∼50% of the total variance in chemical composition. For each component, black straight lines show the loading factors (i.e., the weight of each variable on the principal components). Circles and squares points stand for male and female subjects, respectively. No significant variation is observed between the male and the female subjects within the ALS group.
Figure 2
Figure 2
Copper (δ65Cu) and Zinc (δ66Zn) Isotopic Variability in Cerebrospinal Fluids (A and B) (A) Copper (δ65Cu) and (B) zinc (δ66Zn) isotopic compositions measured in CSFs of CTRL (yellow dots), patients with AD (red dots), and patients with ALS (green dots). Circle and square points are for male and female subjects, respectively. For each boxplot, the central mark is the median; the edges of the box are the first (i.e., 25th percentiles) and the third quartiles (i.e., 75th percentiles), respectively; and the points outside the boxes extend to the most extreme data points (i.e., not considered outliers). Significance level (i.e., p value) was determined using non-parametric “two-sided,” Wilcoxon-Mann-Whitney U tests. **p < 0.005, *p < 0.05.
Figure 3
Figure 3
Cu Isotope Mass Balance between CSF and Brain Calculation of the Cu isotopic offset in the CSF (Δδ65CuCSF) that results from the incorporation of Cu in the brain (% of exchanged Cu) associated with an isotopic fractionation Δδ65CuB. The calculations are made with two values of Δδ65CuB (0.5‰ in red and 0.05‰ in blue) and two extreme values of the MB/MCSF ratio. The results thus define two areas in red and blue that overlap giving the dark blue area. The results discussed in the text corresponding to some proportions of exchanged Cu for a Δδ65CuCSF value of 0.2‰, which represents the difference between CTRL and ALS δ65Cu mean values, are illustrated.

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