Brain Iron Research Articles

Teaching NeuroImage: Imaging in VAC14-Associated Neurodegeneration With Brain Iron Accumulation Resembles a Comet Tail.

Teaching NeuroImage: Imaging in VAC14-Associated Neurodegeneration With Brain Iron Accumulation Resembles a Comet Tail.

Hindlimb immobilization induces insulin resistance and elevates mitochondrial ROS production in the hippocampus of female rats.

Alzheimer's disease (AD) is the fifth leading cause of death in older adults, and treatment options are severely lacking. Recent findings demonstrate a strong relationship between skeletal muscle and cognitive function, with evidence supporting that muscle quality and cognitive function are positively correlated in older adults. Conversely, decreased muscle function is associated with a threefold increased risk of cognitive decline. Based on these observations, the purpose of this study was to investigate the negative effects of muscle disuse [via a model of hindlimb immobilization (HLI)] on hippocampal insulin sensitivity and mitochondrial function and identify the potential mechanisms involved. HLI for 10 days in 4-mo-old female Wistar rats resulted in the following novel findings: 1) hippocampal insulin resistance and deficits in whole body glucose homeostasis, 2) dramatically increased mitochondrial reactive oxygen species (ROS) production in the hippocampus, 3) elevated markers for amyloidogenic cleavage of amyloid precursor protein (APP) and tau protein in the hippocampus, 4) and reduced brain-derived neurotrophic factor (BDNF) expression. These findings were associated with global changes in iron homeostasis, with muscle disuse producing muscle iron accumulation in association with decreased serum and whole brain iron levels. We report the novel finding that muscle disuse alters brain iron homeostasis and reveal a strong negative correlation between muscle and brain iron content. Overall, HLI-induced muscle disuse has robust negative effects on hippocampal insulin sensitivity and ROS production in association with altered brain iron homeostasis. This work provides potential novel mechanisms that may help explain how loss of muscle function contributes to cognitive decline and AD risk.NEW & NOTEWORTHY Muscle disuse via hindlimb immobilization increased oxidative stress and insulin resistance in the hippocampus. These findings were in association with muscle iron overload in connection with iron dysregulation in the brain. Overall, our work identifies muscle disuse as a contributor to hippocampal dysfunction, potentially through an iron-based muscle-brain axis, highlighting iron dysregulation as a potential novel mechanism in the relationship between muscle health, cognitive function, and Alzheimer's disease risk.

Functional impairments in NBIA patients: Preliminary results.

Neurodegeneration with brain iron accumulation (NBIA) is a heterogeneous group (genetically and phenotypically) of genetically determined disorders. Up to date there is no cure for this disease, so the applied treatments focus on symptoms control and palliative care. The main problems are delayed motor development, gait deterioration, postural instability, cognitive dysfunctions, abnormal muscle tone and many others. As gait and balance deficits are predominant features of NBIA patients this study aimed at the use of the objective, instrumented functional tests as well as functional assessment scales to assess their functional impairments. Twenty three NBIA patients recruited for the study underwent objective, instrumented gait analysis, balance assessment, pedobarography and functional evaluation with Gross Motor Function Measure (GMFM-88). The results showed high variability and heterogeneity of NBIA functional status (GMFM from 27.5 to 100.0), but also showed some differences in gait pattern between their types (p < 0.05 at the pelvis, hip and knee). We think that these results could help design objective assessment protocols in future clinical studies.

Levodopa-induced dyskinesia: brain iron deposition as a new hypothesis.

Parkinson's disease (PD) is a common neurodegenerative disease in the older adults. The main pathological change in PD is the degenerative death of dopamine (DA) neurons in the midbrain substantia nigra, which causes a significant decrease in the DA content of the striatum. However, the exact etiology of this pathological change remains unclear. Genetic factors, environmental factors, aging, and oxidative stress may be involved in the degenerative death of dopaminergic neurons in PD. Pharmacological treatment using levodopa (L-DOPA) remains the main treatment for PD. Most patients with PD consuming L-DOPA for a long time usually develop levodopa-induced dyskinesia (LID) after 6.5years of use, and LID seriously affects the quality of life and increases the risk of disability. Recently, studies have revealed that cerebral iron deposition may be involved in LID development and that iron deposition has neurotoxic effects and accelerates disease onset. However, the relationship between cerebral iron deposition and LID remains unclear. Herein, we reviewed the mechanisms by which iron deposition may be associated with LID development, which are mainly related to oxidative stress, neuroinflammation, and mitochondrial and lysosomal dysfunction. Using iron as an important target, the search and development of safe and effective brain iron scavengers, and thus the alleviation and treatment of LID, has a very important scientific and clinical value, as well as a good application prospect.

Sex-Biased Associations of Circulating Ferroptosis Inhibitors with Reduced Lipid Peroxidation and Better Neurocognitive Performance in People with HIV.

Ferroptosis is implicated in viral neuropathogenesis and may underlie HIV-associated neurocognitive impairment (NCI). Emerging data also suggest differences in brain iron transport by sex. We hypothesized that circulating ferritins that inhibit ferroptosis associate with neurocognitive function and NCI in people with HIV (PWH) in a sex-biased manner. Serum ferritin heavy-chain-1 (FTH1), ferritin light-chain (FTL), and urinary F2-isoprostanes (uF2-isoPs, specific lipid peroxidation marker) were quantified in 324 PWH (including 61 women) with serial global (NPZ-4) and domain-specific neurocognitive testing. Biomarker associations with neurocognitive test scores and NCIs were evaluated by multivariable regression; correlations with uF2-isoPs were also assessed. Higher FTL and FTH1 levels were associated with less NCI in all PWH (adjusted odds ratios 0.53, 95% confidence interval (95% CI) 0.36-0.79 and 0.66, 95% CI 0.45-0.97, respectively). In women, higher FTL and FTH1 were also associated with better NPZ-4 (FTL adjusted beta (β) = 0.15, 95% CI 0.02-0.29; FTL-by-sex βinteraction = 0.32, p = 0.047) and domain-specific neurocognitive test scores. Effects on neurocognitive performance persisted for up to 5 years. Levels of both ferritins correlated inversely with uF2-isoPs in women (FTL: rho = -0.47, p < 0.001). Circulating FTL and FTH1 exert sustained, sex-biased neuroprotective effects in PWH, possibly by protecting against iron-mediated lipid peroxidation (ferroptosis). Larger studies are needed to confirm the observed sex differences and further delineate the underlying mechanisms.

Understanding the Mechanism of Ferroptosis in Neurodegenerative Diseases.

Neurodegenerative disorders are typified by the progressive degeneration and subsequent apoptosis of neuronal cells. They encompass a spectrum of conditions, including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), epilepsy, brian ischemia, brian injury, and neurodegeneration with brain iron accumulation (NBIA). Despite the considerable heterogeneity in their clinical presentation, pathophysiological underpinning and disease trajectory, a universal feature of these disorders is the functional deterioration of the nervous system concomitant with neuronal apoptosis. Ferroptosis is an iron (Fe)-dependent form of programmed cell death that has been implicated in the pathogenesis of these conditions. It is intricately associated with intracellular Fe metabolism and lipid homeostasis. The accumulation of Fe is observed in a variety of neurodegenerative diseases and has been linked to their etiology and progression, although its precise role in these pathologies has yet to be elucidated. This review aims to elucidate the characteristics and regulatory mechanisms of ferroptosis, its association with neurodegenerative diseases, and recent advances in ferroptosis-targeted therapeutic strategies. Ferroptosis may therefore be a critical area for future research into neurodegenerative diseases.

Iron Dyshomeostasis in Neurodegeneration with Brain Iron Accumulation (NBIA): Is It the Cause or the Effect?

Iron is an essential metal ion implicated in several cellular processes. However, the reactive nature of iron renders this metal ion potentially dangerous for cells, and its levels need to be tightly controlled. Alterations in the intracellular concentration of iron are associated with different neuropathological conditions, including neurodegeneration with brain iron accumulation (NBIA). As the name suggests, NBIA encompasses a class of rare and still poorly investigated neurodegenerative disorders characterized by an abnormal accumulation of iron in the brain. NBIA is mostly a genetic pathology, and to date, 10 genes have been linked to familial forms of NBIA. In the present review, after the description of the principal mechanisms implicated in iron homeostasis, we summarize the research data concerning the pathological mechanisms underlying the genetic forms of NBIA and discuss the potential involvement of iron in such processes. The picture that emerges is that, while iron overload can contribute to the pathogenesis of NBIA, it does not seem to be the causal factor in most forms of the pathology. The onset of these pathologies is rather caused by a combination of processes involving the interplay between lipid metabolism, mitochondrial functions, and autophagic activity, eventually leading to iron dyshomeostasis.

Iron chelation by oral deferoxamine treatment decreased brain iron and iron signaling proteins.

Deferoxamine (DFO) and other iron chelators are clinically used for cancer and stroke. They may also be useful for Alzheimers disease (AD) to diminish iron from microbleeds. DFO may also stimulate antioxidant membrane repair which is impaired during AD. DFO, and other chelators do enter the brain despite some contrary reports. Low dose, oral DFO was given in lab chow to wildtype (WT) C57BL/6 mice to evaluate potential impact on iron levels, iron-signaling and storage proteins, and amyloid precursor protein (APP) and processing enzymes. Young WT mice do not have microbleeds or disrupted blood-brain barrier of AD mice. Iron was measured by MRI and chemically after two weeks of dietary DFO. Cerebral cortex was examined for changes in iron metabolism, antioxidant signaling, and APP processing by Western blot. DFO decreased brain iron by 18% (MRI) and decreased seven major proteins that mediate iron metabolism by at least 25%. The iron storage proteins ferritin light and heavy chain decreased by at least 30%. APP and secretase enzymes also decreased by 30%. WT mice respond to DFO with decreased APP, amyloid processing enzymes, and antioxidant repair. Potential DFO treatment for early-stage AD by DFO should consider the benefits of lowered APP and secretase enzymes.

Associations between sex, systemic iron and inflammatory status and subcortical brain iron.

Brain iron increases in several neurodegenerative diseases are associated with disease progression. However, the causes of increased brain iron remain unclear. This study investigates relationships between subcortical iron, systemic iron and inflammatory status. Brain magnetic resonance imaging (MRI) scans and blood plasma samples were collected from cognitively healthy females (n = 176, mean age = 61.4 ± 4.5 years, age range = 28-72 years) and males (n = 152, mean age = 62.0 ± 5.1 years, age range = 32-74 years). Regional brain iron was quantified using quantitative susceptibility mapping. To assess systemic iron, haematocrit, ferritin and soluble transferrin receptor were measured, and total body iron index was calculated. To assess systemic inflammation, C-reactive protein (CRP), neutrophil:lymphocyte ratio (NLR), macrophage colony-stimulating factor 1 (MCSF), interleukin 6 (IL6) and interleukin 1β (IL1β) were measured. We demonstrated that iron levels in the right hippocampus were higher in males compared with females, while iron in the right caudate was higher in females compared with males. There were no significant associations observed between subcortical iron levels and blood markers of iron and inflammatory status indicating that such blood measures are not markers of brain iron. These results suggest that brain iron may be regulated independently of blood iron and so directly targeting global iron change in the treatment of neurodegenerative disease may have differential impacts on blood and brain iron.

Iron Accumulation and Metabolic Alterations in Aneurysmal Subarachnoid Hemorrhage

Background Aneurysmal subarachnoid hemorrhage (aSAH) is a severe type of stroke that is associated with poor outcome. A subset of patients with aSAH will develop secondary complications, most notably delayed cerebral ischemia (DCI), which potentiates neurological injury. In this study, we investigate the relationship between cerebrospinal fluid (CSF) iron accumulation, brain metabolism, and neuronal injury in patients with aSAH with or without DCI. Methods We collected longitudinal CSF samples of patients immediately after hospitalization and 5 to 8 days after onset of ictus. CSF was analyzed with electron paramagnetic resonance spectroscopy and metabolomics to determine the presence of redox‐active iron species and metabolic alterations associated with aSAH and DCI. Neuronal pathology induced by iron overload was characterized in neuronal and meningeal cell models. Results Electron paramagnetic resonance spectroscopy identified higher levels of an Fe(III) protoporphyrin IX (hemin)‐like molecule in the CSF of patients who developed DCI compared with patients who did not show secondary ischemic injury after aSAH or controls without neurological disease. Treatment of a human neuronal cell line with Fe(III)‐containing hemin resulted in the disruption of the axonal mitochondrial network and loss of viability. This was cell‐type dependent as a meningeal cell line was resistant to hemin treatment, despite both cell types upregulating the iron ferroxidase ceruloplasmin. Metabolomic profiling of the same CSF samples uncovered significant dysregulation of metabolic pathways associated with energy generation and amino acid utilization, consistent with mitochondrial dysfunction. Using machine learning, we identified a set of metabolites that predicted intensive care unit length of stay. Conclusion aSAH leads to the accumulation of an Fe(III)‐containing heme species in the CSF of a subset of patients who subsequently develop DCI. The accumulation of an Fe(III) protoporphyrin induces axonal mitochondrial dysfunction, leading to cell death. aSAH alters the CSF metabolome involved in mitochondrial function and a subset of these metabolites are predictive of intensive care unit stay. These results identify potential biomarkers for mitochondrial pathology and provide insight into alterations in brain iron metabolism triggered by aSAH.

Assessing Brain Iron and Its Relationship to Cognition and Comorbidity in Children With Attention-Deficit/Hyperactivity Disorder With Quantitative Susceptibility Mapping

BackgroundQuantitative susceptibility mapping is a neuroimaging technique that detects local changes in magnetic susceptibility induced by brain iron. Brain iron and the dopaminergic system are linked because iron is an important cofactor for dopamine synthesis. Attention-deficit/hyperactivity disorder (ADHD) is associated with dysregulation of dopaminergic transmission. Therefore, we applied quantitative susceptibility mapping on subcortical structures to study potential alterations in brain iron and its impact on cognition and mental health in children with ADHD. MethodsQuantitative susceptibility mapping data (3T) of 111 participants (nADHD = 58, mean [SD] age = 13.2 [0.63] years; nControl = 53, mean [SD] age = 13.2 [0.51] years) were analyzed. Subcortical regional brain iron values were extracted. Analysis of variance was used to examine group differences for each region of interest. For dimensional approaches, Pearson correlation analysis was performed across the cohort to examine the association of brain iron with symptoms, mental health, and cognition. ResultsNo significant differences were found in iron susceptibility between participants with ADHD and control participants, between participants with persistent ADHD and those with remitted ADHD, or between participants treated with medication and medication-naïve participants. An unexpected finding was that children with an internalizing disorder had significantly higher iron susceptibility, but the result did not survive multiple comparison correction. Higher brain iron was associated with sustained attention, but not inhibition, IQ, or working memory. ConclusionsThis is the first study to address brain iron susceptibility and its association with comorbidities and cognition in ADHD. Alterations in brain iron may not fully account for a diagnosis of ADHD but may be an indicator of internalizing problems in children. Alterations in brain iron content in children were linked to detrimental sustained attention and may represent developmental variation in cognition.

Frontal pole iron deposition is associated with cognitive decline in patients with carotid atherosclerosis stenosis: a quantitative susceptibility mapping study

Objective: To investigate the correlation between brain iron deposition and cognitive function in patients with carotid atherosclerosis stenosis (CAS) based on quantitative susceptibility mapping (QSM). Methods: This single-center prospective study was performed at the Department of Vascular Surgery, Nanjing Drum Tower Hospital from January 2022 to June 2022. Patients who met the ataxation criteria were divided into the CAS group (n=16) and the CAS with mild cognitive impairment (CAS-MCI) group (n=17) according to the Montreal Cognitive Assessment (MoCA) scores. All patients completed QSM imaging and whole-brain analyses were performed for absolute susceptibility values in cortical regions. Age, sex, education years, hypertension, and diabetes mellitus were included as covariates in all analyses. Partial correlation analyses were used to determine the correlation between bilateral CAS degrees and cortical susceptibility values. Further, mediation analyses were performed to determine whether and how cortical susceptibility values affect cognition in CAS patients. Receiver operating characteristic (ROC) curve analysis was also performed to evaluate the predictive worth of differential brain region susceptibility values for cognitive decline. Independent sample t test and Mann-Whitney U test was used to compare quantitative variables. The comparison of categorical variables was conducted using χ2 test, Fisher's exact test or Wilcoxon rank sum test. Results: A total of 33 patients were included in the study, including 16 in the CAS group and 17 in the CAS-MCI group. There were 23 males and 10 females, aged (62.8±9.0) years (range: 48 to 88 years). CAS-MCI group showed higher right CAS grades (Z=-2.037, P=0.042). Whole-brain cortical QSM analyses showed higher susceptibility values in the frontal pole ((-0.210±0.080)×10-8 vs.(-0.130±0.120)×10-8;t=-2.187, P=0.037), superior frontal gyrus ((-0.604±0.243)×10-8 vs. (-0.428±0.203)×10-8;t=-2.223,P=0.034), and temporal pole ((-0.081±0.115)×10-8 vs. (0.054±0.190)×10-8;t=-2.417, P=0.022) in CAS-MCI group compared to CAS group. The susceptibility value of the frontal pole showed a positive correlation with the right CAS grade (r=0.424, P=0.009),while a quasi-significant positive correlation with the left CAS (r=0.313, P=0.070). The susceptibility values of the frontal and temporal poles were negatively correlated with the MoCA score (frontal pole: r=-0.391, P=0.027; temporal pole: r=-0.410, P=0.020). Mediation analysis showed the effect of right CAS on cognition was fully mediated by the susceptibility value of the frontal pole. The ROC curve revealed that the area under the curve of using hypertension combined with the susceptibility value of the frontal pole to predict cognitive decline was 0.882 (95% CI:0.763 to 0.989) with 82% of sensitivity and 83% of specificity. Conclusions: Multiple cortical regions show iron deposition in CAS-MCI patients. Right CAS plays an important role in cognitive decline, frontal pole iron deposition mediates the effect of right CAS on cognitive function. Quantified frontal pole susceptibility is useful for the diagnosis of cognitive decline in patients with CAS.

A common variant in the iron regulatory gene (Hfe) alters the metabolic and transcriptional landscape in brain regions vulnerable to neurodegeneration.

The role of iron dyshomeostasis in neurodegenerative disease has implicated the involvement of genes that regulate brain iron. The homeostatic iron regulatory gene (HFE) has been at the forefront of these studies given the role of the H63D variant (H67D in mice) in increasing brain iron load. Despite iron's role in oxidative stress production, H67D mice have shown robust protection against neurotoxins and improved recovery from intracerebral hemorrhage. Previous data support the notion that H67D mice adapt to the increased brain iron concentrations and hence develop a neuroprotective environment. This adaptation is particularly evident in the lumbar spinal cord (LSC) and ventral midbrain (VM), both relevant to neurodegeneration. We studied C57BL6/129 mice with homozygous H67D compared to WT HFE. Immunohistochemistry was used to analyze dopaminergic (in the VM) and motor (in the LSC) neuron population maturation in the first 3 months. Immunoblotting was used to measure protein carbonyl content and the expression of oxidative phosphorylation complexes. Seahorse assay was used to analyze metabolism of mitochondria isolated from the LSC and VM. Finally, a Nanostring transcriptomic analysis of genes relevant to neurodegeneration within these regions was performed. Compared to WT mice, we found no difference in the viability of motor neurons in the LSC, but the dopaminergic neurons in H67D mice experienced significant decline before 3 months of age. Both regions in H67D mice had alterations in oxidative phosphorylation complex expression indicative of stress adaptation. Mitochondria from both regions of H67D mice demonstrated metabolic differences compared to WT. Transcriptional differences in these regions of H67D mice were related to cell structure and adhesion as well as cell signaling. Overall, we found that the LSC and VM undergo significant and distinct metabolic and transcriptional changes in adaptation to iron-related stress induced by the H67D HFE gene variant.

Assessment of the degree of disability of the Polish NBIA-MPAN population based on a patient survey

Neurodegeneration with brain iron accumulation (NBIA) describes a group of extremely rare hereditary disorders with an estimated prevalence of 1–3/1,000,000. Mitochondrial membrane protein associated neurodegeneration (MPAN) is the third most common form of NBIA, accounting for 10% of NBIA cases globally and up to 50% of cases in Poland. This survey was conducted by the Association NBIA Poland to collect data on the functioning of patients with NBIA/MPAN based on self-reported EQ-5D-5L (EuroQoL 5-Dimension 5-Level) scores. A total of 50 patients living in Poland, including 26 patients with NBIA/MPAN, participated in the study. The mean age of NBIA/MPAN patients was 22 years; the mean age at symptom onset is 10 years. At the time of the survey, most patients were disabled and required assistance with daily activities. More than 50% of participants needed help with hygiene or dressing, and 40% were unable to walk on their own. Nearly 50% of patients declared symptoms indicating lowered mood. The survey showed that NBIA/MPAN leads to significant disability within a short period of time after symptom onset. Intensive work is underway to discover the role of the C19orf12 protein and develop therapeutic strategies. Actions are necessary to improve the comfort of everyday life of patients with NBIA/MPAN and to improve access to rehabilitation, including home-based programmes.

Brain iron deficiency and periodic limb movement disorder with parasomnias

Brain iron deficiency and periodic limb movement disorder with parasomnias

Iron Reduces the Trafficking of Fatty Acids from Human Immortalised Brain Microvascular Endothelial Cells Through Modulation of Fatty Acid Transport Protein 1 (FATP1/SLC27A1)

PurposeAlzheimer’s disease (AD) is associated with brain accumulation of amyloid-beta (Aβ) and neurofibrillary tangle formation, in addition to reduced brain docosahexaenoic acid (DHA) and increased brain iron levels. DHA requires access across the blood–brain barrier (BBB) to enter the brain, and iron has been shown to affect the expression and function of a number of BBB transporters. Therefore, this study aimed to assess the effect of iron on the expression and function of fatty acid binding protein 5 (FABP5) and fatty acid transport protein 1 (FATP1), both which mediate brain endothelial cell trafficking of DHA.MethodsThe mRNA and protein levels of FABP5 and FATP1 in human cerebral microvascular endothelial (hCMEC/D3) cells was assessed by RT-qPCR and Western blot, respectively following ferric ammonium citrate (FAC) treatment (up to 750 µM, 72 h). The function of FABP5 and FATP1 was assessed via uptake and efflux of radiolabelled 3H-oleic acid and 14C-DHA.ResultsFAC (500 µM, 72 h) had no impact on the expression of FABP5 at the protein and mRNA level in hCMEC/D3 cells, which was associated with a lack of effect on the uptake of 14C-DHA. FAC led to a 19.7% reduction in FATP1 protein abundance in hCMEC/D3 cells with no impact on mRNA levels, and this was associated with up to a 32.6% reduction in efflux of 14C-DHA.ConclusionsThese studies demonstrate a role of iron in down-regulating FATP1 protein abundance and function at the BBB, which may have implications on fatty acid access to the brain.Graphical

Differently Distributed Iron Deposition in Mild and Moderate Stroke with Small Artery Occlusion: A Pilot Voxel-Based Susceptibility Mapping Study.

Small artery occlusion (SAO) is a common ischemic stroke subtype. However, its clinical outcome can be more severe than commonly understood. The severity of SAO can vary, ranging from mild to moderate. Iron deposition has been associated with the development and progression of stroke. However, its specific distribution and relationship with stroke severity in SAO remain unclear. The study's purpose is to investigate the differences in iron deposition between mild stroke with SAO (SAO-MiS) and moderate stroke with SAO (SAO-MoS) through quantitative susceptibility mapping (QSM) and its association with neurological deficits. Sixty-eight SAO participants within 24 hours of first onset were enrolled and separated into SAO-MiS and SAO-MoS according to the National Institutes of Health Stroke Scale (NIHSS) scores. QSM helped calculate the susceptibility maps, reflecting the iron content within the brain. The susceptibility maps were analyzed using voxel-wise statistical analysis to compare the iron deposition between SAO-MiS and SAO-MoS. Then, differentially distributed iron deposition helped differentiate between mild and moderate stroke using support vector machine (SVM) methods. Compared with SAO-MiS, SAO-MoS depicted elevated iron deposition in the left pallidum, parahippocampal gyrus, and superior frontal gyrus medial region, and is lower in the right superior/middle frontal gyrus and bilateral supplementary motor area. Based on iron deposition, the SVM classifier's analysis revealed a high power to discriminate SAO-MoS from SAO-MiS. In addition, fibrinogen, triglyceride (TG), and total cholesterol (TC) were linked with QSM values in specific brain regions. Our study first revealed the brain iron distribution after SAO and differently distributed iron deposition in SAO-MiS and SAO-MoS. The results indicate that iron deposition could play a role in the pathophysiology of SAO and its correlation with stroke severity.

Brain Magnetic Resonance Imaging in Wilson's Disease-Significance and Practical Aspects-A Narrative Review.

Wilson's disease (WD) is a genetic disorder of copper metabolism with pathological copper accumulation in many organs, resulting in clinical symptoms, mostly hepatic and neuropsychiatric. As copper accumulates in the brain during WD, and almost 50% of WD patients at diagnosis present with neurological symptoms, neuroimaging studies (especially brain magnetic resonance imaging (MRI)) are part of WD diagnosis. The classical sequences (T1, T2, and fluid-attenuated inversion recovery) were used to describe brain MRI; however, with the development of neuroradiology, several papers proposed the use of new MRI sequences and techniques like susceptibility-weighted images, T2*, diffusion MRI, tractography, volumetric assessment and post-processing brain MRI analysis of paramagnetic accumulation-quantitative susceptibility mapping. Based on these neuroradiological data in WD, currently, brain MRI semiquantitative scale and the pathognomonic neuroradiological brain MRI signs in WD were proposed. Further, the volumetric studies and brain iron accumulation MRI analysis suggested brain atrophy and iron accumulation as biomarkers of neurological WD disease severity. All these results highlight the significance of brain MRI examinations in WD. Due to the extreme progress of these studies, based on the available literature, the authors present the current state of knowledge about the significance, practical aspects, and future directions of brain MRI in WD.

How to accurately quantify brain magnetic susceptibility in the context of Parkinson's disease: Validation on phantoms and healthy volunteers at 1.5 and 3 T.

Currently, brain iron content represents a new neuromarker for understanding the physiopathological mechanisms leading to Parkinson's disease (PD). In vivo quantification of biological iron is possible by reconstructing magnetic susceptibility maps obtained using quantitative susceptibility mapping (QSM). Applying QSM is challenging, as up to now, no standardization of acquisition protocols and phase image processing has emerged from referenced studies. Our objectives were to compare the accuracy and the sensitivity of 10 QSM pipelines built from algorithms from the literature, applied on phantoms data and on brain data. Two phantoms, with known magnetic susceptibility ranges, were created from several solutions of gadolinium chelate. Twenty healthy volunteers from two age groups were included. Phantoms and brain data were acquired at 1.5 and 3 T, respectively. Susceptibility-weighted images were obtained using a 3D multigradient-recalled-echo sequence. For brain data, 3D anatomical T1- and T2-weighted images were also acquired to segment the deep gray nuclei of interest. Concerning in vitro data, the linear dependence of magnetic susceptibility versus gadolinium concentration and deviations from the theoretically expected values were calculated. For brain data, the accuracy and sensitivity of the QSM pipelines were evaluated in comparison with results from the literature and regarding the expected magnetic susceptibility increase with age, respectively. A nonparametric Mann-Whitney U-test was used to compare the magnetic susceptibility quantification in deep gray nuclei between the two age groups. Our methodology enabled quantifying magnetic susceptibility in human brain and the results were consistent with those from the literature. Statistically significant differences were obtained between the two age groups in all cerebral regions of interest. Our results show the importance of optimizing QSM pipelines according to the application and the targeted magnetic susceptibility range, to achieve accurate quantification. We were able to define the optimal QSM pipeline for future applications on patients with PD.

Whole-exome sequencing identifies protein-coding variants associated with brain iron in 29,828 individuals

Iron plays a fundamental role in multiple brain disorders. However, the genetic underpinnings of brain iron and its implications for these disorders are still lacking. Here, we conduct an exome-wide association analysis of brain iron, measured by quantitative susceptibility mapping technique, across 26 brain regions among 26,789 UK Biobank participants. We find 36 genes linked to brain iron, with 29 not being previously reported, and 16 of them can be replicated in an independent dataset with 3,039 subjects. Many of these genes are involved in iron transport and homeostasis, such as FTH1 and MLX. Several genes, while not previously connected to brain iron, are associated with iron-related brain disorders like Parkinson’s (STAB1, KCNA10), Alzheimer’s (SHANK1), and depression (GFAP). Mendelian randomization analysis reveals six causal relationships from regional brain iron to brain disorders, such as from the hippocampus to depression and from the substantia nigra to Parkinson’s. These insights advance our understanding of the genetic architecture of brain iron and offer potential therapeutic targets for brain disorders.