Zinc Uptake by HIV-1 Viral Particles: An Isotopic Study.

Zinc, an essential trace element that serves as a cofactor for numerous cellular and viral proteins, plays a central role in the dynamics of HIV-1 infection. Among the viral proteins, the nucleocapsid NCp7, which contains two zinc finger motifs, is abundantly present viral particles and plays a crucial role in coating HIV-1 genomic RNA, thus concentrating zinc within virions. In this study, we investigated whether HIV-1 virus production impacts cellular zinc homeostasis and whether isotopic fractionation occurs between the growth medium, the producing cells, and the viral particles. We found that HIV-1 captures a significant proportion of cellular zinc in the neo-produced particles. Furthermore, as cells grow, they accumulate lighter zinc isotopes from the medium, resulting in a concentration of heavier isotopes in the media, and the viruses exhibit a similar isotopic fractionation to the producing cells. Moreover, we generated HIV-1 particles in HEK293T cells enriched with each of the five zinc isotopes to assess the potential effects on the structure and infectivity of the viruses. As no strong difference was observed between the HIV-1 particles produced in the various conditions, we have demonstrated that enriched isotopes can be accurately used in future studies to trace the fate of zinc in cells infected by HIV-1 particles. Comprehending the mechanisms underlying zinc absorption by HIV-1 viral particles offers the potential to provide insights for developing future treatments aimed at addressing this specific facet of the virus's life cycle.

Inferring odontocete life history traits in dentine using a multiproxy approach (δ15 N, δ44/42 Ca and trace elements).

RATIONALE: Understanding the interactions between marine mammals and their environment is critical for ecological and conservation purposes. Odontocetes offer a continuous record of their life history from birth as recorded in annual increments of their tooth dentine. Because dentine is not remodeled and contains collagen, nitrogen stable isotope compositions (δ15 N) reflect nursing and weaning events, life history traits that would otherwise be impossible to retrieve in such elusive marine animals. Yet, capturing the magnitude and temporal changes in these events is constrained by tooth size and sampling resolution. Moreover, historical and fossil specimens undergo collagen decay, hence the need to develop the measurements of other proxies. METHODS: Here, we present a multiproxy approach to investigate the use of Ca isotope compositions (δ44/42 Ca) in relation to δ15 N and laser ablation profiles for different trace metal (Ba, Mg, Sr, Zn) concentrations across the dentine of a single individual of the common bottlenose dolphin Tursiops truncatus. RESULTS: To help interpret the dentine data, we provide milk elemental compositions and δ44/42 Ca values for two odontocete individuals. We discuss the observed changes in δ44/42 Ca across the dentine as potential markers of birth, weaning interval, incidental ingestion of seawater, trophic level and physiology. Incidental ingestion of seawater during nursing induces a positive offset in δ44/42 Ca values recorded in the early formed dentine. CONCLUSIONS: Life history parameters of individual marine mammals are extremely difficult to retrieve due to limitations in observing specimens in the wild and the methodology presented here offers new ecological and paleoecological perspectives.

Extensive pedigrees reveal the social organization of a Neolithic community.

Social anthropology and ethnographic studies have described kinship systems and networks of contact and exchange in extant populations1-4. However, for prehistoric societies, these systems can be studied only indirectly from biological and cultural remains. Stable isotope data, sex and age at death can provide insights into the demographic structure of a burial community and identify local versus non-local childhood signatures, archaeogenetic data can reconstruct the biological relationships between individuals, which enables the reconstruction of pedigrees, and combined evidence informs on kinship practices and residence patterns in prehistoric societies. Here we report ancient DNA, strontium isotope and contextual data from more than 100 individuals from the site Gurgy 'les Noisats' (France), dated to the western European Neolithic around 4850-4500 BC. We find that this burial community was genetically connected by two main pedigrees, spanning seven generations, that were patrilocal and patrilineal, with evidence for female exogamy and exchange with genetically close neighbouring groups. The microdemographic structure of individuals linked and unlinked to the pedigrees reveals additional information about the social structure, living conditions and site occupation. The absence of half-siblings and the high number of adult full siblings suggest that there were stable health conditions and a supportive social network, facilitating high fertility and low mortality5. Age-structure differences and strontium isotope results by generation indicate that the site was used for just a few decades, providing new insights into shifting sedentary farming practices during the European Neolithic.

Biological fractionation of lithium isotopes by cellular Na+/H+ exchangers unravels fundamental transport mechanisms.

Lithium (Li) has a wide range of uses in science, medicine, and industry, but its isotopy is underexplored, except in nuclear science and in geoscience. 6Li and 7Li isotopic ratio exhibits the second largest variation on earth's surface and constitutes a widely used tool for reconstructing past oceans and climates. As large variations have been measured in mammalian organs, plants or marine species, and as 6Li elicits stronger effects than natural Li (∼95% 7Li), a central issue is the identification and quantification of biological influence of Li isotopes distribution. We show that membrane ion channels and Na+-Li+/H+ exchangers (NHEs) fractionate Li isotopes. This systematic 6Li enrichment is driven by membrane potential for channels, and by intracellular pH for NHEs, where it displays cooperativity, a hallmark of dimeric transport. Evidencing that transport proteins discriminate between isotopes differing by one neutron opens new avenues for transport mechanisms, Li physiology, and paleoenvironments.

Magnesium stable isotope composition, but not concentration, responds to obesity and early insulin-resistant conditions in minipig.

Hypomagnesemia is frequently associated with type 2 diabetes and generally correlates with unfavorable disease progression, but the magnesium status in pre-diabetic conditions remains unclear. Here, the magnesium metabolism is scrutinized in a minipig model of obesity and insulin resistance by measuring variations of the metallome-the set of inorganic elements-and the magnesium stable isotope composition in six organs of lean and obese minipigs raised on normal and Western-type diet, respectively. We found that metallomic variations are most generally insensitive to lean or obese phenotypes. The magnesium stable isotope composition of plasma, liver, kidney, and heart in lean minipigs are significantly heavier than in obese minipigs. For both lean and obese minipigs, the magnesium isotope composition of plasma and liver were negatively correlated to clinical phenotypes and plasma lipoproteins concentration as well as positively correlated to hyperinsulinemic-euglycemic clamp output. Because the magnesium isotope composition was not associated to insulin secretion, our results suggest that it is rather sensitive to whole body insulin sensitivity, opening perspectives to better comprehend the onset of insulin-resistant diabetic conditions.

The mouse metallomic landscape of aging and metabolism.

Organic elements make up 99% of an organism but without the remaining inorganic bioessential elements, termed the metallome, no life could be possible. The metallome is involved in all aspects of life, including charge balance and electrolytic activity, structure and conformation, signaling, acid-base buffering, electron and chemical group transfer, redox catalysis energy storage and biomineralization. Here, we report the evolution with age of the metallome and copper and zinc isotope compositions in five mouse organs. The aging metallome shows a conserved and reproducible fingerprint. By analyzing the metallome in tandem with the phenome, metabolome and proteome, we show networks of interactions that are organ-specific, age-dependent, isotopically-typified and that are associated with a wealth of clinical and molecular traits. We report that the copper isotope composition in liver is age-dependent, extending the existence of aging isotopic clocks beyond bulk organic elements. Furthermore, iron concentration and copper isotope composition relate to predictors of metabolic health, such as body fat percentage and maximum running capacity at the physiological level, and adipogenesis and OXPHOS at the biochemical level. Our results shed light on the metallome as an overlooked omic layer and open perspectives for potentially modulating cellular processes using careful and selective metallome manipulation.

Hfe Gene Knock-Out in a Mouse Model of Hereditary Hemochromatosis Affects Bodily Iron Isotope Compositions.

Hereditary hemochromatosis is a genetic iron overload disease related to a mutation within the HFE gene that controls the expression of hepcidin, the master regulator of systemic iron metabolism. The natural stable iron isotope composition in whole blood of control subjects is different from that of hemochromatosis patients and is sensitive to the amount of total iron removed by the phlebotomy treatment. The use of stable isotopes to unravel the pathological mechanisms of iron overload diseases is promising but hampered by the lack of data in organs involved in the iron metabolism. Here, we use Hfe -/- mice, a model of hereditary hemochromatosis, to study the impact of the knock-out on iron isotope compositions of erythrocytes, spleen and liver. Iron concentration increases in liver and red blood cells of Hfe -/- mice compared to controls. The iron stable isotope composition also increases in liver and erythrocytes, consistent with a preferential accumulation of iron heavy isotopes in Hfe -/- mice. In contrast, no difference in the iron concentration nor isotope composition is observed in spleen of Hfe -/- and control mice. Our results in mice suggest that the observed increase of whole blood isotope composition in hemochromatosis human patients does not originate from, but is aggravated by, bloodletting. The subsequent rapid increase of whole blood iron isotope composition of treated hemochromatosis patients is rather due to the release of hepatic heavy isotope-enriched iron than augmented iron dietary absorption. Further research is required to uncover the iron light isotope component that needs to balance the accumulation of hepatic iron heavy isotope, and to better understand the iron isotope fractionation associated to metabolism dysregulation during hereditary hemochromatosis.

Lactation and gestation controls on calcium isotopic compositions in a mammalian model.

Lactation and gestation are among the physiological events that trigger the most intense changes in body calcium (Ca) fluxes. Along with the composition of the animal 2021 diet, these events are suspected to impact the Ca isotopic composition of Ca body reservoirs but their dynamics are poorly understood. In this study, we monitored a group of domestic sows across a full reproduction cycle. We collected tissues and fluids (blood, urine, milk, colostrum, umbilical blood, adult and piglet bones) at different steps of gestation and lactation, and analyzed their Ca isotopic compositions (i.e. δ44/42Ca) by means of multi-collector inductively coupled plasma mass spectrometry. Among other results, we report the first observations of Ca isotopic fractionation between maternal and umbilical blood (Δ44/42Caumbilical blood-sow blood = -0.18 ± 0.11‰, n = 3). Our data also highlight that gestation and lactation periods are characterized by small diet-bone Ca isotopic offsets (Δ44/42Cabone-diet = -0.28 ± 0.11‰, n = 3), with 44Ca-enriched blood compositions during nursing (Δ44/42Canursing blood-gestation blood = $+ 0.42{\rm{\,\,}}_{ - 0.12}^{ + 0.11}$‰, n = 3). Under the light of an up-to-date mammalian box model, we explored different scenarios of gestation and lactation Ca fluxes experienced by a sow-like animal. These simulations suggest that gestation changes on body δ44/42Ca values may result from the intensification of Ca absorption by the animal, whereas the production of 44Ca-depleted milk is the main driver for the 44Ca enrichment in blood during lactation. In addition, our results also support that bone mineralization could be associated with a more restricted Ca isotopic fractionation than previously envisioned. Together, these results refine the framework of Ca isotope applications, notably regarding the monitoring of human bone balance and the study of species and ecosystems from the present and the past.

Determination of magnesium isotopic ratios of biological reference materials via multi-collector inductively coupled plasma mass spectrometry.

RATIONALE: Despite a wide range of potential applications, magnesium (Mg) isotope composition has been so far sparsely measured in reference materials with a biological matrix, which is important for the quality control of the results. We describe a method enabling the chemical separation of Mg in geological and biological materials and the determination of its stable isotope composition. METHODS: Different geological (BHVO-1, BHVO-2, BCR-1, and IAPSO) and biological (SRM-1577c, BCR-383, BCR380R, ERM-CE464, DORM-2, DORM-4, TORT-3, and FBS) reference materials were used to test the performance of a new sample preparation procedure for Mg isotopic analysis. The procedure consisted of a simple three-stage elution method to separate Mg from the matrix. Mg isotopic analyses were performed in two different laboratories and with three different multi-collector inductively coupled plasma mass spectrometry instruments. RESULTS: The biological reference materials show a wide range of δ26 Mg values (relative to DSM3 standard), spanning over 2‰, from 0.52 ± 0.29‰ (2SD, n = 7) in bovine liver (SRM-1577c) to -1.45 ± 0.20‰ (2SD, n = 5) in tuna fish (ERM-CE464), with an external precision of 0.03‰ (2SD, n = 85). CONCLUSIONS: This study indicates that isotopic measurements of Mg in biological reference materials show good performance, with the results being within the accepted range. We confirmed that δ26 Mg values in liver are the most positive of all biological materials reported so far.

Isotopic calcium biogeochemistry of MIS 5 fossil vertebrate bones: application to the study of the dietary reconstruction of Regourdou 1 Neandertal fossil.

The calcium isotopic composition (δ44/42Ca) of bone and tooth enamel can be used for dietary reconstructions of extant and extinct mammals. In natural conditions, the δ44/42Ca value of bone and teeth varies according to dietary intake with a constant isotopic offset of about -0.6‰. Owing to the poor conservation of collagen, carbon (C), and nitrogen (N) isotopic compositions of the Regourdou Mousterian site (MIS 5, Dordogne, France) previously failed to provide any paleodietary information. Therefore, to reconstruct the trophic chain, we have measured calcium (Ca) isotopes from fossil bone samples of the fauna from the Regourdou site, as well as from three bone samples of the Regourdou 1 Neandertal specimen. The results show a taxon-dependent patterning of the Ca isotopic compositions: herbivores generally have higher δ44/42Ca values than carnivores. All the δ44/42Ca values of Regourdou 1 are low (<-1.6‰), placing this specimen amid carnivores. Using a bone-muscle Ca isotopic offset determined on extant animals, we further show that the δ44/42Ca value of the Regourdou 1 diet, and that of most carnivores, cannot be accounted for by the consumption of meat only, as plants and meat have indistinguishable δ44/42Ca values. Mass balance calculations indicate that the low δ44/42Ca values of the Neandertal's carnivorous diet are explained by the ingestion of bone marrow containing as little as 1% trabecular bone. Our results show that the Regourdou 1 Neanderthal consumed a mixture of various herbivorous prey, as well as trabecular bone, which probably occurred when marrow was ingested, by accident or intentionally.

Inter-comparison of stable iron, copper and zinc isotopic compositions in six reference materials of biological origin.

There is a lack of certified reference materials with an organic matrix for which metal isotope ratios have been certified. Here, we have determined the iron, copper and zinc stable isotopic compositions for six reference materials of biological origin with diverse matrices, i.e. BCR-380R (whole milk), BCR-383 (beans), ERM-CE464 (tuna fish), SRM-1577c (bovine liver), DORM-4 (fish protein) and TORT-3 (lobster hepatopancreas) in three different labs. The concentrations for six major and sixteen trace elements, spanning almost four orders of magnitude, were also measured and the results obtained show an excellent agreement with certified values, demonstrating that the dissolution step was quantitative for all the standards. By taking literature data into account, 39 possible pair-wise comparisons of mean iron, copper and zinc isotopic values (δ values) could be made. Results of Tukey multiple comparisons of means yielded 11 significantly different pairs. Most of these differences are of the same order of magnitude as the estimated mean expanded uncertainties (U, k = 2) (±0.10‰, ±0.05‰, and ±0.05‰ for the δ56Fe, δ65Cu and δ66Zn values, respectively). The present inter-comparison study finally proposes nineteen new preferred values for the Cu, Zn and Fe isotopic compositions of six reference materials of biological origin.

The blood copper isotopic composition is a prognostic indicator of the hepatic injury in Wilson disease.

Wilson disease (WD) is an autosomal recessive disorder of copper (Cu) metabolism. The gene responsible for WD, ATP7B, is involved in the cellular transport of Cu, and mutations in the ATP7B gene induce accumulation of Cu in the liver and ultimately in the brain. In a pilot study, the natural variations of copper stable isotope ratios (65Cu/63Cu) in the serum of WD patients have been shown to differ from that of healthy controls. In the present study, we challenged these first results by measuring the 65Cu/63Cu ratios in the blood of treated (n = 25), naïve patients (n = 11) and age matched healthy controls (n = 75). The results show that naïve patients and healthy controls exhibit undistinguishable 65Cu/63Cu ratios, implying that the Cu isotopic ratio cannot serve as a reliable diagnostic biomarker. The type of treatment (d-penicillamine vs. triethylenetetramine) does not affect the 65Cu/63Cu ratios in WD patients, which remain constant regardless of the type and duration of the treatment. In addition, the 65Cu/63Cu ratios do not vary in naïve patients after the onset of the treatment. However, the 65Cu/63Cu ratios decrease with the degree of liver fibrosis and the gradient of the phenotypic presentation, i.e. presymptomatic, hepatic and neurologic. To get insights into the mechanisms at work, we study the effects of the progress of the WD on the organism by measuring the Cu concentrations and the 65Cu/63Cu ratios in the liver, feces and plasma of 12 and 45 week old Atp7b-/- mice. The evolution of the 65Cu/63Cu ratios is marked by a decrease in all tissues. The results show that 63Cu accumulates in the liver preferentially to 65Cu due to the preferential cellular entry of 63Cu and the impairment of the 63Cu exit by ceruloplasmin. The hepatic accumulation of monovalent 63Cu+ is likely to fuel the production of free radicals, which is potentially an explanation of the pathogenicity of WD. Altogether, the results suggest that the blood 65Cu/63Cu ratio recapitulates WD progression and is a potential prognostic biomarker of WD.

Calcium isotopic ecology of Turkana Basin hominins.

Diet is a major driver of hominin evolution, but most of the geochemical evidence relies on carbon isotopes (δ13C). Here, we report enamel stable calcium isotope (δ44/42Ca) values against δ13C values for several hominins and co-existing primates in the Turkana Basin area, circa 4 to 2 Ma. Australopithecus anamensis clusters with mammal browsers, Kenyanthropus platyops is distinct from A. anamensis in foraging into more open environments and the coexisting Theropithecus brumpti encompasses both the grazer and omnivore/carnivore domains. Early Homo is remarkable for its wide distribution in δ44/42Ca values, possibly reflecting omnivorous and opportunistic preferences. Paranthropus boisei is uniquely distributed in the δ13C versus δ44/42Ca iso-space being distinct from all other hominins from the Turkana Basin area as well as from the co-existing Theropithecus oswaldi. Several hypotheses are explored to discuss the unique δ44/42Ca values of Paranthropus boisei including significant differences observed with δ44/42Ca values recently reported for P. robustus from South Africa, questioning the monophyly of this genus.

A liver-targeting Cu(i) chelator relocates Cu in hepatocytes and promotes Cu excretion in a murine model of Wilson's disease.

Copper chelation is the most commonly used therapeutic strategy nowadays to treat Wilson's disease, a genetic disorder primarily inducing a pathological accumulation of Cu in the liver. The mechanism of action of Chel2, a liver-targeting Cu(i) chelator known to promote intracellular Cu chelation, was studied in hepatic cells that reconstitute polarized epithelia with functional bile canaliculi, reminiscent of the excretion pathway in the liver. The interplay between Chel2 and Cu localization in these cells was demonstrated through confocal microscopy using a fluorescent derivative and nano X-ray fluorescence. The Cu(i) bound chelator was found in vesicles potentially excreted in the canaliculi. Moreover, injection of Chel2 either intravenously or subcutaneously to a murine model of Wilson's disease increased excretion of Cu in the faeces, confirming in vivo biliary excretion. Therefore, Chel2 turns out to be a possible means to collect and excrete hepatic Cu in the faeces, hence restoring the physiological pathway.

Identification of inorganic particles resulting from degradation of ESSURE® implants: Study of 10 cases.

OBJECTIVE: Approximately 750,000 women worldwide have undergone ESSURE hysteroscopic sterilization since 2002. In 2015, an increase in adverse effects was noted, with gynaecological and systemic symptoms reported. Scanning electron microscopy (SEM) analysis of fallopian tube and uterine horn tissues and implants, after hysterectomy or salpingectomy, revealed the presence of inorganic particles resulting from implant degradation. STUDY DESIGN: Ten patients (age 42-53 years) were included in this study. Of these, eight patients had undergone hysterectomy and two patients had undergone salpingectomy. Mean exposure time was 85.5 months (standard deviation 26.8 months, range 34-105 months). Mineralogical analyses were performed on 13 tissue biopsies and four implants by SEM coupled with energy dispersive x-ray spectrometry. RESULTS: In five of the 10 patients, tin particles were observed in fallopian tube or uterine horn tissues with inflammatory cell reactions. In the other five cases, iron, chromium, nickel or platinum particles were observed. For implants, major deterioration of the weld zone was observed with either destroyed appearance or the presence of an organic coating containing numerous particles. DISCUSSION AND CONCLUSION: Analysis of the preclinical studies performed by the manufacturer suggests that degradation of the tin weld plays a major role in these adverse events, with increasing leaching and corrosion between 3 and 6 months for an intratubal insert that si designed to remain in an woman's body for her entire life. For patients with gynaecological symptoms (e.g. pain, metrorragies) needing explantation, these findings raise the question of a causal relationship between tin particles from implant degradation and the inflammatory tissue response. For patients with systemic symptoms (e.g. blurred vision, headache, asthenia, myalgia), the hypothesis that these symptoms may be related to the formation of organotin (chemical compounds based on tin with hydrocarbon substituents) in the body has yet to be proven. Tin levels in blood have to be measured before and after explantation. To the authors' knowledge, this is the first study to report significant degradation of the ESSURE implant weld, evidenced by the detection of tin particles in the uterine tissue of patients and comparison of the welding zone between unused and used implants.

Absence of temperature effect on elution profiles on anionic and cationic ion-exchange resins from 4°C to 28°C.

RATIONALE: In labs devoted to the geochemistry of non-traditional isotopes, chemical elution is necessary to purify the element of interest. Elution is always performed in over-pressured and air-conditioned clean rooms. We took advantage of an air-conditioning failure in our lab during summer 2018 to study the effect of temperature on the characteristics of the elution profiles of ion-exchange resins. METHODS: We performed the ion-exchange separation of copper, iron and zinc on macroporous anionic AG MP-1 resin and that of calcium on cationic AG 50W-X12 resin, at 28°C, prior to the measurement of their isotopic ratios by mass spectrometry. We further performed these experiments in a clean hood in a cold room at 4°C. The elution curves were processed on biological standards, i.e. bovine liver (SRM-1577c), fetal bovine serum (FBS), bone meal (SRM-1486) and the seawater IAPSO standard. RESULTS: The elution profiles of major elements for each matrix, and those of copper, iron, zinc and calcium, were compared with those classically achieved at 20°C in air-conditioned conditions. The results show that the elution profiles preserve their characteristics whatever the temperature, suggesting that partitioning coefficients between resin and solution are thermo-independent in the range of temperature from 4°C to 28°C. CONCLUSIONS: If generalized to other matrices, notably inorganic, and to other elements, notably the extreme case of the separation of Rare Earth Elements, the present results suggest that clean labs may not have to be air-conditioned. This would reduce installation and operating costs and have a positive effect on the environment, paving the way for the development of a "green geochemistry".

Calcium isotopic patterns in enamel reflect different nursing behaviors among South African early hominins.

Nursing is pivotal in the social and biological evolution of hominins, but to date, early-life behavior among hominin lineages is a matter of debate. The calcium isotopic compositions (δ44/42Ca) of tooth enamel can provide dietary information on this period. Here, we measure the δ44/42Ca values in spatially located microsized regions in tooth enamel of 37 South African hominins to reconstruct early-life dietary-specific variability in Australopithecus africanus, Paranthropus robustus, and early Homo. Very low δ44/42Ca values (<-1.4‰), indicative of milk consumption, are measured in early Homo but not in A. africanus and P. robustus. In these latter taxa, transitional or adult nonmilk foods must have been provided in substantial quantities relative to breast milk rapidly after birth. The results suggest that early Homo have continued a predominantly breast milk-based nursing period for longer than A. africanus and P. robustus and have consequently more prolonged interbirth interval.

Dynamic homeostasis modeling of Zn isotope ratios in the human body.

Recent research performed on volunteers and patients suggested that diet, health, and basal metabolic rates (BMR) are factors controlling the bodily Zn isotope compositions (isotopic homeostasis). However, our poor understanding of the variability of Zn distribution among the different organs and fluids of the human body, and the ensuing isotope fractionation, limits the use of this isotopic system as a typical diagnostic tool for cancers and for past hominin diet reconstructions. Using box model calculations, we investigated the dynamics of Zn isotope variability in blood and other body tissues as well as the consistency of the hypothesis of heavy Zn isotope accumulation through time in the human body. We compare the results of the model with data obtained from control feeding experiments and from archeological samples. Model simulations indicate that the absence of an aging drift in non-circumpolar populations cannot be explained by their lower BMR. We argue that the drift observed in the blood of a circumpolar population results from a differential diet between young and older individuals in this population. When applied to the δ66Zn measured in blood, bones, or teeth, the present box model also offers insight into the isotope composition of the human diet, and therefore into its nature. Applying the model to isotopic observations on the remains of past hominins is a promising tool for diet reconstruction.

Isotopic Evidence for Disrupted Copper Metabolism in Amyotrophic Lateral Sclerosis.

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.