Heavy metals and neurodegenerative diseases: an observational study.

Various metals have been associated with the pathogenesis of Alzheimer's disease (AD), principally heavy metals that are environmental pollutants (such as As, Cd, Hg, and Pb) and essential metals whose homeostasis is disturbed in AD (such as Cu, Fe, and Zn). Although there is evidence of the involvement of these metals in AD, further research is needed on their mechanisms of toxicity. To further assess the involvement of heavy and essential metals in AD pathogenesis, we compared cerebrospinal fluid (CSF) AD biomarkers to macro- and microelements measured in CSF and plasma. We tested if macro- and microelements' concentrations (heavy metals (As, Cd, Hg, Ni, Pb, and Tl), essential metals (Na, Mg, K, Ca, Fe, Co, Mn, Cu, Zn, and Mo), essential non-metals (B, P, S, and Se), and other non-essential metals (Al, Ba, Li, and Sr)) are associated with CSF AD biomarkers that reflect pathological changes in the AD brain (amyloid β1-42, total tau, phosphorylated tau isoforms, NFL, S100B, VILIP-1, YKL-40, PAPP-A, and albumin). We used inductively coupled plasma mass spectroscopy (ICP-MS) to determine macro- and microelements in CSF and plasma, and enzyme-linked immunosorbent assays (ELISA) to determine protein biomarkers of AD in CSF. This study included 193 participants (124 with AD, 50 with mild cognitive impairment, and 19 healthy controls). Simple correlation, as well as machine learning algorithms (redescription mining and principal component analysis (PCA)), demonstrated that levels of heavy metals (As, Cd, Hg, Ni, Pb, and Tl), essential metals (Ca, Co, Cu, Fe, Mg, Mn, Mo, Na, K, and Zn), and essential non-metals (P, S, and Se) are positively associated with CSF phosphorylated tau isoforms, VILIP-1, S100B, NFL, and YKL-40 in AD.

Heavy metals in the water can accumulate in the organs of fish, which was reported in various continental fish farms in Peru. The objective of the present study was to know the situational state of the water bodies and their effect on rainbow trout meat, determining the level of contamination by heavy metals. The present investigation was carried out in the Lagunillas lagoon, a high Andean zone of Santa Lucía, Puno. The physicochemical parameters of the water were determined and the quantification of heavy metals in the muscle, kidney, and liver of trout was carried out, by Atomic Absorption Spectrometry in the Testing Laboratory accredited by the Peruvian Accreditation Agency INACAL-DA (CERPER - Certifications of Peru SA). The results in the concentration of Sb (0.002 ml/Kg), As (0.0347 ml/Kg), Cd (0.001 ml/Kg), Cu (0.0024 ml/Kg), Cr (0.003 ml/Kg), Hg (0.0001 ml/Kg), and Pb (0.0004 ml/Kg) are below the maximum permissible limits established by the Ministry of the Environment and SANIPES. It is concluded that the water quality of the Lagunillas lagoon in the district of Santa Lucía, Lampa - Puno, is suitable for the cultivation of rainbow trout meat for human consumption.

The neuroendocrine and immune systems interact bidirectionally through shared ligands and receptors during inflammation, thereby regulating immune responses. Leptin, primarily known for its role in energy metabolism and appetite regulation, also modulates neuroinflammatory pathways. Its receptors are widely expressed on immune cells and contribute to immune mechanisms implicated in the pathogenesis of neuroinflammatory disorders such as multiple sclerosis (MS) and Alzheimer’s disease (AD). This review highlights recent advances in understanding leptin’s role in immune regulation, with a focus on its impact on MS and AD. A comprehensive literature review was conducted until October 2025, using PubMed, Google Scholar, and Scopus to identify studies investigating leptin in neuroinflammatory conditions, particularly MS and AD. Leptin exerts broad immunomodulatory effects by activating T cells, dendritic cells, and microglia, and promoting their proliferation and phagocytosis. Its elevation enhances Th1 and Th17 responses, drives pro-inflammatory macrophage phenotype polarization, and suppresses regulatory T cell and Th2 responses, immune pathways involved in MS. Peripheral leptin levels are increased in MS, especially during disease exacerbations. In contrast, in AD, they are typically reduced, particularly in patients with normal body mass index (BMI), where their decline contributes to amyloid-β and tau pathology. These divergent patterns position leptin as a bidirectional regulator at the intersection of immunity and neurodegeneration. Additionally, its protective or detrimental effects likely depend on whether it acts under physiological conditions or in the context of obesity-induced leptin resistance. Elevated leptin levels in obesity exacerbate inflammation and diminish its neuroprotective effects. In conclusion, leptin is elevated in MS patients but downregulated in AD, reflecting its bidirectional effects. In leptin resistance, peripheral proinflammatory signaling is maintained while central leptin signaling is restricted, thereby potentially promoting autoimmunity in MS and limiting neuroprotection in AD. Further mechanistic and longitudinal studies are needed to clarify the relationship between leptin dysregulation, leptin resistance, neuroinflammatory and neurodegenerative diseases.

Resting-state functional magnetic resonance imaging (rsfMRI) is pivotal for mapping alterations in brain functional networks associated with neurodegenerative diseases, particularly Alzheimer's disease (AD). However, the causal mechanisms linking such network dysfunction to disease pathogenesis remain unresolved. This study aimed to elucidate bidirectional causal relationships between 191 resting-state fMRI phenotypes (derived from 34,691 individuals) and six neurodegenerative diseases, specifically AD, amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), multiple sclerosis (MS), dementia with Lewy bodies (DLB), and Parkinson's disease (PD), using disease-specific GWAS data from European-ancestry cohorts. Bidirectional two-sample Mendelian randomization (MR) was performed using rsfMRI phenotypes from Zhao et al. (2022) and GWAS summary statistics (AD: ieu-b-5067/ebi-a-GCST90027158, ALS: ebi-a-GCST90027164, FTD: ieu-b-43, MS: ieu-b-18, DLB: ebi-a-GCST90001390, PD: ieu-b-7). Instrumental variables were filtered for significance (p < 5 × 10^-8), with sensitivity analyses (MR-PRESSO, Cochran's Q, MR-Egger) to ensure robustness. Forward MR identified 26 rsfMRI phenotypes causally linked to neurodegenerative diseases. AD risk was associated with reduced cerebellum-subcortical connectivity (OR = 0.957, p = 0.004), while heightened cerebellar activity increased DLB risk (OR = 2.58, p = 0.0063). Reverse MR revealed 64 disease-to-network effects: AD altered default mode network connectivity (OR = 0.965, p = 0.034), and PD disrupted salience-central executive network interactions (OR = 0.950, p = 0.00011). This study establishes robust bidirectional causal pathways between brain functional networks and neurodegenerative diseases, with AD showing unique vulnerability in cerebellar-subcortical and default mode circuits. These findings highlight network-specific therapeutic targets for AD and related disorders.

Immune response plays a significant role in the progression of neurodegenerative diseases (NDs) such as Parkinson’s disease (PD), Alzheimer’s disease (AD), and multiple sclerosis (MS). It is paramount to quantify the immune and structural spatial microenvironment of ND brain using research approaches that resolve tissue at a single-cell level. Imaging Mass Cytometry™ (IMC™) is a spatial biology technique that provides quantitative phenotypic evaluation of 40-plus markers. We report the application of two new IMC imaging modes with 40-marker panels for ND research. Tissue mode (TM) was applied to perform a scan of the entire tissue followed by pixel-based analysis (PBA) to uncover spatial distribution of relevant markers. Preview mode (PM) was applied to sample the tissue at low resolution, improving informed selection of areas for high-resolution cell mode (CM) imaging on the same slide. Using TM with PBA, we quantified the spatial distribution of immune cells in tissue compartments of ND tissues. PM and CM highlighted MS lesions devoid of myelinization and a network of α-synuclein in PD tissue. Single-cell analysis identified heterogeneity of amyloid precursor protein aggregates in AD that encompassed total and phosphorylated species of tau and phosphorylated α-synuclein. Overall, whole slide imaging techniques using IMC provide quantitative immunological and structural insights into the spatial biology of ND. For Research Use Only. Not for use in diagnostic procedures.

BackgroundWe leveraged digital deconvolution methods to determine cellular changes from brain transcriptomics of Alzheimer’s Disease(AD), and identified a change in cellular proportion between neuropathology, and severity of the disease as determined by Clinical Dementia Rating[5]. We expanded these approaches to Cerebral Spinal Fluid(CSF), to evaluate cellular changes associated with disease progresses.MethodWe used RNAseq data from published sources to test and refine a gene panel to deconvolve ambient RNA from CSF. Candidate marker genes were selected via literature search and verified using the brainseq [1] along with the human brain single‐cell gene expression [2]. We optimized gene panels using the leave‐one‐out cross‐validation method to predict proportions of neurons, astrocytes, microglia, oligodendrocytes, macrophages and endothelial cells, using bulk and ambient RNA sequenced in single‐cell transcriptomics.ResultWe leveraged our deconvolution to ascertain whether ambient RNA captured in single‐cell gene expression from the CSF captures the cellular population structure of the brain. Preliminary results show that cellular signatures for non‐immune cells are present in CSF in AD (Gate et al. (n = 9, Control = 3, MCI = 3, AD = 3)[3] and Multiple Sclerosis(MS)(Ramesh et al. (n = 15, Control = 3, MS = 12)[4]), and the proportions of those non‐immune cells change depending on the disease state. In MS, there is an increase in the proportion of Astrocytes (p = 3.4×10e‐2) in MS samples. Similar results were found for Neurons (p = 4.4×10e‐2) and Oligodendrocyte Precursor Cells (OPC) (p = 8.2×10e‐3). In AD, we identified significant differences between AD, MCI and controls (p = 0.01) in OPC.ConclusionThese results show that ambient RNA in the CSF can capture subtle differences in cellular population structure in AD and MS. These analyses were done on a small sample size, but show the potential to analyze larger cohorts and cell‐type specific transcriptional states. We also plan to expand the process to other neurologic diseases.

PRM28 - What are indirect costs in neurodegenerative diseases? a methodological review

Imaging of amyloid β in Alzheimer's disease with 18F-BAY94-9172, a novel PET tracer: proof of mechanism

Chitinase-3-like-1 (CHI3L1) is an evolutionarily conserved protein involved in key biological processes, including tissue remodeling, angiogenesis, and neuroinflammation. It has emerged as a significant player in various neurodegenerative diseases and brain disorders. Elevated CHI3L1 levels have been observed in neurological conditions such as traumatic brain injury (TBI), Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), Creutzfeldt-Jakob disease (CJD), multiple sclerosis (MS), Neuromyelitis optica (NMO), HIV-associated dementia (HAD), Cerebral ischemic stroke (CIS), and brain tumors. This review explores the role of CHI3L1 in the pathogenesis of these disorders, with a focus on its contributions to neuroinflammation, immune cell infiltration, and neuronal degeneration. As a key regulator of neuroinflammation, CHI3L1 modulates microglia and astrocyte activity, driving the release of proinflammatory cytokines that exacerbate disease progression. In addition to its role in disease pathology, CHI3L1 has emerged as a promising biomarker for the diagnosis and monitoring of brain disorders. Elevated cerebrospinal fluid (CSF) levels of CHI3L1 have been linked to disease severity and cognitive decline, particularly in AD and MS, highlighting its potential for clinical diagnostics. Furthermore, therapeutic strategies targeting CHI3L1, such as small-molecule inhibitors and neutralizing antibodies, have shown promise in preclinical studies, demonstrating reduced neuroinflammation, amyloid plaque accumulation, and improved neuronal survival. Despite its therapeutic potential, challenges remain in developing selective and safe CHI3L1-targeted therapies, particularly in ensuring effective delivery across the blood–brain barrier and mitigating off-target effects. This review addresses the complexities of targeting CHI3L1, highlights its potential in precision medicine, and outlines future research directions aimed at unlocking its full therapeutic potential in treating neurodegenerative diseases and brain pathologies.

Chapter 62: The human hypothalamus in development, sexual differentiation, aging and Alzheimer's disease

BackgroundPreviously, we collected age-stratified incidence data of 404 epidemiological datasets of 10 neurodegenerative diseases (NDs), namely Amyotrophic Lateral Sclerosis (ALS), Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), Fronto Temporal Dementia (FTD), Dementia with Lewy Bodies (DLB), Parkinsonism (PDM), Parkinson’s disease with Dementia (PDD), Creutzfeldt–Jakob disease (CJD), and Multiple Sclerosis (MS). We tested whether each ND follows a multistep model, found the number of steps necessary for the onset of each ND, found the number of common steps with other NDs and the number of specific steps of each ND, and built a parsimony tree of the genealogy of the NDs. The tree disclosed three groups of NDs: the stem NDs with less than 3 steps; the trunk NDs with 5–7 steps; and the crown NDs with more than 7 steps.MethodsWe made a multidimensional reduction of the previously collected age-stratified incidence epidemiological data of the 10 NDs. We studied the general range of incidence of the 10 NDs using the age- and sex-stratified incidence data. First, we calculated the log of the incidence versus the log of the age for each ND. Next, we calculated the age intervals of the spread of the incidence of each ND. We calculated the regression of the steps obtained with the multistep model versus the age of incidence of the NDs.ResultsWe found that the number of steps of the NDs is inversely correlated with the age of incidence of the NDs, and calculated the number of years required for a single step for each ND. Based on these results, we extended the genealogy tree model of the NDs to account for the time needed for a ND step to occur.ConclusionThe extended genealogy tree disclosed three groups of NDs according to the estimated time needed for a step to occur: the stem ND, HD, with 32.5 years/step, the trunk NDs ALS, FTD, PD and CJD, with 6.7–13.7 years/step; and the crown NDs PDM, PDD, AD and DLB, with 2.3–3.8 years/step. Thus, the NDs cluster into three groups according to both the number of steps and the number of years for a step to occur.

Optical coherence tomography (OCT) biomarkers are increasingly used by neurologists, psychiatrists, and ophthalmologists for the diagnosis, prognosis, and follow-up of neurodegenerative diseases. Long-term data on OCT biomarkers of selected primary and secondary neurodegenerative diseases of the central nervous system (CNS), such as multiple sclerosis (MS) or Parkinson's disease, are already available in part. In addition, there are rare neurodegenerative diseases with early disease onset that may show OCT abnormalities. Aliterature review on the association of OCT biomarkers with neurodegenerative diseases of the CNS beyond Alzheimer's disease is presented. Parkinson's disease, MS, Friedreich's ataxia, Huntington's disease, spinocerebellar ataxia, and lysosomal storage diseases are addressed. Relevant OCT biomarkers of neurodegenerative diseases are the macular ganglion cell inner plexiform layer (GCIPL) and the peripapillary retinal nerve fiber layer (pRNFL) thickness. Different sectors may be affected depending on the disease entity in addition to global pRFNL reduction. OCT‑angiography (OCT-A) is also increasingly used as abiomarker in neurodegenerative diseases. Optical coherence tomography biomarkers are used in an interdisciplinary context. Retinal pathologies should be excluded by an ophthalmologist. While OCT biomarkers are increasingly used clinically in MS, the benefit in other neurodegenerative diseases, especially the rare ones, is less well documented. Further longitudinal studies are required.

<h3>Objective:</h3> Use biomarkers such as PET and CSF proteins to distinguishing multiple sclerosis-related cognitive impairment from co-existent progressive neurodegenerative diseases such as Alzheimer disease. <h3>Background:</h3> Among people with multiple sclerosis, cognitive impairment occurs commonly and is a potent predictor of disability. Some multiple sclerosis patients present with severe cognitive impairment, and distinguishing multiple sclerosis-related cognitive impairment from co-existent progressive neurodegenerative diseases such as Alzheimer disease poses a diagnostic challenge. <h3>Design/Methods:</h3> The study was a retrospective, descriptive study on convenience samples of separate cohorts, one of cognitively impaired multiple sclerosis patients evaluated on autopsy to demonstrate coincidence of both multiple sclerosis and neurodegenerative cognitive diseases. The second cohort were cognitively impaired multiple sclerosis patients evaluated by biomarker to investigate possible additional neurodegenerative cognitive disorders contributing to the cognitive impairment. <h3>Results:</h3> We investigated selected biomarkers among 31 severely impaired patients (biomarker cohort) and 12 severely impaired patients assessed at autopsy and selected 24 (23 biomarker cohort, 1 autopsy cohort) had comprehensive neurocognitive testing. Biomarker cohort investigations included 18F-Fluorodeoxyglucose PET and/or CSF amyloid Aβ1–42, phospho-tau and total tau levels. The autopsy cohort was evaluated with comprehensive neuropathological assessment for aetiology of cognitive impairment. The cohorts shared similar sex, age at multiple sclerosis onset and multiple sclerosis clinical course. The autopsy-cohort patients were older at diagnosis (69.5 versus 57 years, P=0.006), had longer disease duration [median (range) 20 years (3–59) versus 9 (1–32), P=0.001] and had more impaired bedside mental status scores at last follow-up [Kokmen median (range) 23 (1–38) versus 31 (9–34) P=0.01]. Autopsy-cohort patients confirmed, or excluded, coexistent neurogenerative disease by neuropathology gold standard. Most bio marker-cohort patients had informative results evaluating coexistent neurogenerative disease. <h3>Conclusions:</h3> Biomarkers may be useful in indicating a coexistent neurodegenerative disease earlier, and in life, in patients with multiple sclerosis and significant cognitive impairment. <b>Disclosure:</b> Dr. Londono has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Genentech. Dr. Arumaithurai has nothing to disclose. Eleni Constantopoulos has nothing to disclose. Dr. Basso has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Taylor and Francis. The institution of Ross Reichard has received research support from NIH. An immediate family member of Ross Reichard has received publishing royalties from a publication relating to health care. The institution of Dr. Flanagan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Alexion. Dr. Flanagan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Genentech. Dr. Flanagan has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Horizon Therapeutics. Dr. Flanagan has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Pharmacy times. The institution of Dr. Flanagan has received research support from Viela Bio. Dr. Flanagan has received research support from UCB. Dr. Flanagan has received publishing royalties from a publication relating to health care. Dr. Flanagan has a non-compensated relationship as a Member of medical Advisory Board with The MOG Project that is relevant to AAN interests or activities. Dr. Flanagan has a non-compensated relationship as a Editorial board member with Journal of The Neurologic Sciences that is relevant to AAN interests or activities. Dr. Flanagan has a non-compensated relationship as a Editorial board member with Neuroimmunology Reports that is relevant to AAN interests or activities. Dr. Keegan has received publishing royalties from a publication relating to health care.

Taming of macrophage and microglial cell activation by microRNA-124

Neurodegenerative diseases involve progressive neuronal dysfunction and cognitive decline, posing substantial global challenges. Although the precise causes remain unclear, several studies highlight the role of protein metabolism abnormalities in disease development. This study investigates the causal links between variations in mitochondrial protein genes and neurodegenerative diseases, aiming to elucidate their potential contributions to disease progression and identify novel therapeutic strategies. Herein, we utilized data from genome-wide association studies (GWAS) on mitochondrial proteins and neurodegenerative diseases. Bidirectional Mendelian randomization (MR), employing instrumental variables (IVs), was used to assess causal relationships. The primary method for estimating causal effects was the inverse variance-weighted (IVW) method, supplemented by additional MR approaches. Bidirectional MR revealed significant associations between mitochondrial protein gene variants and neurodegenerative diseases. Specifically, associations were found with Alzheimer's disease (AD) (three proteins), Parkinson's disease (PD) (four proteins), amyotrophic lateral sclerosis (ALS) (six proteins), multiple sclerosis (two proteins), and dementia with Lewy bodies (four proteins). Conversely, analyses indicated significant associations of neurodegenerative diseases with mitochondrial protein gene variants, notably with AD, dementia with Lewy bodies, and multiple sclerosis, affecting multiple mitochondrial protein levels. Bidirectional causality was observed between dementia with Lewy bodies and C21orf33. Using MR, we identified significant links between mitochondrial protein gene mutations and the risk of neurodegenerative diseases. These results highlight reciprocal relationships where certain neurodegenerative diseases influence mitochondrial protein expression levels. These findings underscore the pivotal role of mitochondrial proteins in neurodegenerative diseases, offering critical insights into disease mechanisms and potential therapeutic avenues.