Mitochondrial genes are altered in blood early in Alzheimer's disease

Phytochemical characterization and therapeutic mechanism of Xialiqi capsule on benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a common urological condition prevalent in elderly men. Xialiqi capsule (XLQC), a traditional Chinese patent medicine, is widely used to manage BPH. However, the precise mechanisms underlying XLQC's effectiveness in treating BPH are not well-understood. We aimed to investigate the phytochemical composition and therapeutic mechanisms of XLQC in the treatment of BPH. We conducted a comprehensive investigation that integrated high-performance liquid chromatography-mass spectrometry (LC-MS/MS), network pharmacological analysis, and animal experimental validation to explore potential pharmacodynamic compounds and mechanisms of action for XLQC in BPH treatment. In this study, a total of 12 components targeting eight molecular targets were identified; the major components included Danshensu, salidroside, 6-Acetylcodeine, azelaic acid, and berberine. The targets were CASP3, MMP9, PTGS2, IL6, ESR1, ERBB2, HIF1 A, and epidermal growth factor receptor (EGFR). Enrichment analysis revealed that the molecular targets are mainly through calcium signaling pathway, endocrine resistance, steroid hormone biosynthesis, HIF- 1 signaling pathway, and estrogen signaling pathway regulates cell proliferation and apoptosis as well as oxidative stress response. In vivo animal experiments demonstrated that XLQC effectively inhibited oxidative stress (OS) and cell proliferation by reducing malondialdehyde (MDA), increasing superoxide dismutase (SOD), and inhibiting the expression of Ki- 67 in prostate tissue, thereby improving prostate tissue morphology and reducing prostate index. XLQC can inhibit oxidative stress and cell proliferation, improve the morphology of prostate tissue, reduce the prostate index, and have therapeutic effects on BPH through multi-component, multi-target, and multi-pathway effects.

Mitochondrial dynamics and bioenergetics in Alzheimer's induced pluripotent stem cell-derived neurons

Mitochondrial dysfunction is a hallmark of Alzheimer's disease, but the scope and severity of these specific deficits across forms of Alzheimer's disease are not well characterized. We designed a high-throughput longitudinal phenotypic assay to track mitochondrial dynamics and bioenergetics in glutamatergic induced pluripotent stem cell (iPSC)-derived human neurons possessing mutations in presenilin 1 (PSEN1), presenilin 2 (PSEN2) and the amyloid beta precursor protein (APP). Each gene set was composed of iPSC-derived neurons from an Alzheimer's disease patient in addition to two to three engineered mutations with appropriate isogenic and age-matched controls. These iPSC-derived neurons were imaged every other day, beginning at 10 days in vitro, to assess how mitochondrial length and content change over a 10 day time course using a mitochondrially targeted reporter. A second cytosolic reporter allowed for visualization of neurites. Bioenergetics assays, focusing on mitochondrial respiration and individual electron transport chain complexes, were also surveyed over this time course. Mutations in all three genes altered mitochondrial function measured by basal, ATP-linked and maximal oxygen consumption rates and by spare respiratory capacity, with PSEN1/PSEN2 alleles being more severe than APP mutations. Electron flow through Complexes I-IV was decreased in PSEN1/PSEN2 mutations but, in contrast, APP alleles had only modest impairments of complexes I and II. We measured aspects of mitochondrial dynamics, including fragmentation and neurite degeneration, both of which were dramatic in PSEN1/PSEN2 alleles, but essentially absent in APP alleles. The marked differences in mitochondrial pathology might occur from the distinct ways in which amyloids are processed into amyloid beta peptides and might be correlated with the disease severity.

Exploring the Mechanism of Kai-Xin-San to Improve Cognitive Deficits in AD Rats Induced by D-Gal and Aβ25-35 Based on Multi-Omics and Network Analysis

Alzheimer's disease (AD) is a common neurodegenerative disease for which there are no effective drugs. Kai-Xin-San (KXS), with definite curative effects, is widely used for the prevention and treatment of AD in China. But its mechanism is not yet fully understood. Based on our established rat model and previous pharmacodynamics study, Multi-omics (metabolomics, proteomics) and network analysis were integrated to explore the holistic mechanism of anti-AD effects of KXS. The key pathways were validated with western blot and ELISA methods. Morris water maze and Nissl staining showed that KXS could ameliorate cognitive deficits and pathological morphology of the hippocampus in AD rats. A total of nine metabolites were identified, which were related to pyrimidine metabolism, riboflavin metabolism, tyrosine metabolism, tryptophan metabolism, and glycerophospholipid metabolism. Proteomics results indicated that the improvement of cognitive deficits by KXS was closely related to the regulation of oxidative phosphorylation in mitochondria. Western blotting results showed that KXS significantly inhibited the expression of Mt-nd2 and Ndufb6 in AD rats. Integrated analysis indicated that the anti-AD targets of KXS were interrelated and KXS could exert its anti-AD effect by reducing oxidative stress, neurotoxicity, and inflammation.

Mitochondrial DNA copy number and Alzheimer's disease and Parkinson disease

INTRODUCTION

A systematic review on the association of mitochondrial DNA copy number (mtDNA-CN) with Alzheimer's disease (AD) and Parkinson disease (PD) is lacking and the causal relationship remains unclear.

OBJECTIVE

We aimed to conduct a systematic review of observational studies on the association of mtDNA-CN with AD and PD and perform a bidirectional 2-sample Mendelian randomization (MR) study to investigate their causal relationships.

METHODS

PubMed, Embase, and Web of Science were searched for eligible studies before Jan 2025. The causal links were conducted with inverse-variance weighted (IVW) method as the main analysis.

RESULTS

Fourteen case-control and 2 cohort studies investigated the association between mtDNA-CN and AD, with 13 reporting decreased mtDNA-CN associated with increased risk of AD and 3 showing no significant association. All the studies (9 case-control, 1 cross-sectional, 2 cohort studies) observed the relation between mtDNA-CN and PD except for 3 studies reporting no significant association. In MR analysis, genetically predicted mtDNA-CN was not associated with AD and PD, whereas genetically predicted AD (β -0.085, 95 % CI -0.156 to -0.013; P = 0.02) but not PD was associated with mtDNA-CN. Sensitivity and replication analyses showed a stable finding.

DISCUSSION

The systematic review found limited observational studies on mtDNA-CN and AD and PD and majority were case-control study. Findings of the bidirectional MR study did not support a causal effect of mtDNA-CN in the development of AD and PD but found that AD can lead to decreased levels of mtDNA-CN, which suggest mtDNA-CN as a potential biomarker of AD.

The role of n-3-derived specialised pro-resolving mediators (SPMs) in microglial mitochondrial respiration and inflammation resolution in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia globally and is characterised by reduced mitochondrial respiration and cortical deposition of amyloid-β plaques and neurofibrillary tangles comprised of hyper-phosphorylated tau. Despite its characterisation more than 110 years ago, the mechanisms by which AD develops are still unclear. Dysregulation of microglial phagocytosis of amyloid-β may play a key role. Microglia are the major innate immune cell of the central nervous system and are critical responders to pro-inflammatory states. Typically, microglia react with a short-lived inflammatory response. However, a dysregulation in the resolution of this microglial response results in the chronic release of inflammatory mediators. This prolongs the state of neuroinflammation, likely contributing to the pathogenesis of AD. In addition, the microglial specialised pro-resolving mediator (SPM) contribution to phagocytosis of amyloid-β is dysregulated in AD. SPMs are derivatives of dietary n-3 polyunsaturated fatty acids (PUFAs) and potentially represent a strategic target for protection against AD progression. However, there is little understanding of how mitochondrial respiration in microglia may be sustained long term by n-3-derived SPMs, and how this affects their clearance of amyloid-β. Here, we re-evaluate the current literature on SPMs in AD and propose that SPMs may improve phagocytosis of amyloid-β by microglia as a result of sustained mitochondrial respiration and allowing a pro-resolution response.

The neuroimmune nexus: unraveling the role of the mtDNA-cGAS-STING signal pathway in Alzheimer's disease

The relationship between Alzheimer's disease (AD) and neuroimmunity has gradually begun to be unveiled. Emerging evidence indicates that cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, recognizing cytosolic damage-associated molecular patterns (DAMPs), and inducing the innate immune response by activating stimulator of interferon genes (STING). Dysregulation of this pathway culminates in AD-related neuroinflammation and neurodegeneration. A substantial body of evidence indicates that mitochondria are involved in the critical pathogenic mechanisms of AD, whose damage leads to the release of mitochondrial DNA (mtDNA) into the extramitochondrial space. This leaked mtDNA serves as a DAMP, activating various pattern recognition receptors and immune defense networks in the brain, including the cGAS-STING pathway, ultimately leading to an imbalance in immune homeostasis. Therefore, modulation of the mtDNA-cGAS-STING pathway to restore neuroimmune homeostasis may offer promising prospects for improving AD treatment outcomes. In this review, we focus on the mechanisms of mtDNA release during stress and the activation of the cGAS-STING pathway. Additionally, we delve into the research progress on this pathway in AD, and further discuss the primary directions and potential hurdles in developing targeted therapeutic drugs, to gain a deeper understanding of the pathogenesis of AD and provide new approaches for its therapy.

Multi-omics analyses of early-onset familial Alzheimer's disease and Sanfilippo syndrome zebrafish models reveal commonalities in disease mechanisms

Sanfilippo syndrome (mucopolysaccharidosis type III, MPSIII) causes childhood dementia, while Alzheimer's disease is the most common type of adult-onset dementia. There is no cure for either of these diseases, and therapeutic options are extremely limited. Increasing evidence suggests commonalities in the pathogenesis of these diseases. However, a direct molecular-level comparison of these diseases has never been performed. Here, we exploited the power of zebrafish reproduction (large families of siblings from single mating events raised together in consistent environments) to conduct sensitive, internally controlled, comparative transcriptome and proteome analyses of zebrafish models of early-onset familial Alzheimer's disease (EOfAD, psen1Q96_K97del/+) and MPSIIIB (nagluA603fs/A603fs) within single families. We examined larval zebrafish (7 days post fertilisation), representing early disease stages. We also examined the brains of 6-month-old zebrafish, which are approximately equivalent to young adults in humans. We identified substantially more differentially expressed genes and pathways in MPS III zebrafish than in EOfAD-like zebrafish. This is consistent with MPS III being a rapidly progressing and earlier onset form of dementia. Similar changes in expression were detected between the two disease models in gene sets representing extracellular matrix receptor interactions in larvae, and the ribosome and lysosome pathways in 6-month-old adult brains. Cell type-specific changes were detected in MPSIIIB brains at 6 months of age, likely reflecting significant disturbances of oligodendrocyte, neural stem cell, and inflammatory cell functions and/or numbers. Our 'omics analyses have illuminated similar disease pathways between EOfAD and MPS III indicating where efforts to find mutually effective therapeutic strategies can be targeted.

Oral Asiatic Acid Improves Cognitive Function and Modulates Antioxidant and Mitochondrial Pathways in Female 5xFAD Mice

Background/Objectives: Extracts of the plant Centella asiatica can enhance mitochondrial function, promote antioxidant activity and improve cognitive deficits. Asiatic acid (AA) is one of the constituent triterpene compounds present in the plant. In this study, we explore the effects of AA on brain mitochondrial function, antioxidant response and cognition in a beta-amyloid (Aβ)-overexpressing 5xFAD mouse line. Methods: Six- to seven-month-old 5xFAD mice were treated with 1% AA for 4 weeks. In the last week of treatment, associative memory was assessed along with mitochondrial bioenergetics and the expression of mitochondrial and antioxidant response genes from isolated cortical synaptosomes. The Aβ plaque burden was also evaluated. Results: AA treatment resulted in improvements in associative memory in female 5xFAD mice without altering the Aβ plaque burden. Cortical mitochondrial function and mitochondrial gene expression were increased in the AA-treated female 5xFAD mice, as was the expression of antioxidant genes. More modest effects of AA on cortical mitochondrial function and mitochondrial and antioxidant gene expression were observed in male 5xFAD mice. Conclusions: Oral AA treatment improved cognitive and mitochondrial function and activated antioxidant in Aβ-overexpressing mice. These changes occurred independent of alterations in Aβ plaque burden, suggesting that AA could have translational therapeutic relevance in later-stage AD when plaques are well established.

Massive changes in gene expression and their cause(s) can be a unifying principle in the pathobiology of Alzheimer's disease

Understanding of the biology of Alzheimer's disease (AD) has long been fragmented, with various investigators concentrating on amyloid beta (Aβ) or tau, inflammation, cell death pathways, misfolded proteins, glia, and more. Yet data from multiple authors has repeatedly shown altered expression of myriad genes related to these seemingly disparate phenomena. In 2022, Morgan et al. organized the massive data on changes in AD in a meticulous survey of the literature and related these changes to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Their data showed that 91% of the known KEGG pathways are involved in AD and that many of these pathways are represented by the known cellular/molecular phenomena of AD. Such data then raise the fundamental question: What mechanism(s) may be responsible for such widespread changes in gene expression? We review evidence for a unifying model based on sequestrations in stress granules and alteration of nucleocytoplasmic transport in AD. HIGHLIGHTS: In Alzheimer's disease (AD), critical changes take place in neurons before the appearance of plaques or tangles. Addressing these early changes provides a path to early detection and effective intervention in AD.

Unraveling mitochondrial dysfunction: comprehensive perspectives on its impact on neurodegenerative diseases

Neurodegenerative diseases represent a significant challenge to modern medicine, with their complex etiology and progressive nature posing hurdles to effective treatment strategies. Among the various contributing factors, mitochondrial dysfunction has emerged as a pivotal player in the pathogenesis of several neurodegenerative disorders. This review paper provides a comprehensive overview of how mitochondrial impairment contributes to the development of neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, driven by bioenergetic defects, biogenesis impairment, alterations in mitochondrial dynamics (such as fusion or fission), disruptions in calcium buffering, lipid metabolism dysregulation and mitophagy dysfunction. It also covers current therapeutic interventions targeting mitochondrial dysfunction in these diseases.

Mitochondrial DNA variants and their impact on epigenetic and biological aging in young adulthood

The pace of biological aging varies between people independently of chronological age and mitochondria dysfunction is a key hallmark of biological aging. We hypothesized that higher functional impact (FI) score of mitochondrial DNA (mtDNA) variants might contribute to premature aging and tested the relationships between a novel FI score of mtDNA variants and epigenetic and biological aging in young adulthood. A total of 81 participants from the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) prenatal birth cohort had good quality genetic data as well as blood-based markers to estimate biological aging in the late 20. A subset of these participants (n = 69) also had epigenetic data to estimate epigenetic aging in the early 20s using Horvath's epigenetic clock. The novel FI score was calculated based on 7 potentially pathogenic mtDNA variants. Greater FI score of mtDNA variants was associated with older epigenetic age in the early 20s and older biological age in the late 20s. These medium to large effects were independent of sex, current BMI, cigarette smoking, cannabis, and alcohol use. These findings suggest that elevated FI score of mtDNA variants might contribute to premature aging in young adulthood.

Mitochondria and the Repurposing of Diabetes Drugs for Off-Label Health Benefits

This review describes our current understanding of the role of the mitochondria in the repurposing of the anti-diabetes drugs metformin, gliclazide, GLP-1 receptor agonists, and SGLT2 inhibitors for additional clinical benefits regarding unhealthy aging, long COVID, mental neurogenerative disorders, and obesity. Metformin, the most prominent of these diabetes drugs, has been called the "Drug of Miracles and Wonders," as clinical trials have found it to be beneficial for human patients suffering from these maladies. To promote viral replication in all infected human cells, SARS-CoV-2 stimulates the infected liver cells to produce glucose and to export it into the blood stream, which can cause diabetes in long COVID patients, and metformin, which reduces the levels of glucose in the blood, was shown to cut the incidence rate of long COVID in half for all patients recovering from SARS-CoV-2. Metformin leads to the phosphorylation of the AMP-activated protein kinase AMPK, which accelerates the import of glucose into cells via the glucose transporter GLUT4 and switches the cells to the starvation mode, counteracting the virus. Diabetes drugs also stimulate the unfolded protein response and thus mitophagy, which is beneficial for healthy aging and mental health. Diabetes drugs were also found to mimic exercise and help to reduce body weight.

Mitochondrial DNA (mtDNA) as fluid biomarker in neurodegenerative disorders: A systematic review

BACKGROUND

Several studies evaluated peripheral and cerebrospinal fluid (CSF) mtDNA as a putative biomarker in neurodegenerative diseases, often yielding inconsistent findings. We systematically reviewed the current evidence assessing blood and CSF mtDNA levels and variant burden in Parkinson's disease (PD), Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS). Multiple sclerosis (MS) was also included as a paradigm of chronic neuroinflammation-driven neurodegeneration.

METHODS

Medline, Embase, Scopus and Web of Science were searched for articles published from inception until October 2023. Studies focused on mtDNA haplogroups or hereditary pathogenic variants were excluded. Critical appraisal was performed using the Quality Assessment for Diagnostic Accuracy Studies criteria.

RESULTS

Fifty-nine original studies met our a priori-defined inclusion criteria. The majority of CSF-focused studies showed (i) decreased mtDNA levels in PD and AD; (ii) increased levels in MS compared to controls. No studies evaluated CSF mtDNA in ALS. Results focused on blood cell-free and intracellular mtDNA were contradictory, even within studies evaluating the same disease. This poor reproducibility is likely due to the lack of consideration of the many factors known to affect mtDNA levels. mtDNA damage and methylation levels were increased and reduced in patients compared to controls, respectively. A few studies investigated the correlation between mtDNA and disease severity, with conflicting results.

CONCLUSIONS

Additional well-designed studies are needed to evaluate CSF and blood mtDNA profiles as putative biomarkers in neurodegenerative diseases. The identification of "mitochondrial subtypes" of disease may enable novel precision medicine strategies to counteract neurodegeneration.

Age- and sex-associated alterations in hypothalamic mitochondrial bioenergetics and inflammatory-associated signaling in the 3xTg mouse model of Alzheimer's disease

Mitochondrial dysfunction and associated inflammatory signaling are pivotal in both aging and in Alzheimer's disease (AD). Studies have also shown that hypothalamic function is affected in AD. The hypothalamus may be a target for AD drugs given that mitochondrial alterations are observed in the hypothalamus. This study investigated how age and sex affect mitochondrial bioenergetics and inflammatory signaling in the hypothalamic mitochondria of 3xTg and control mice at 2, 6, and 13 months, aiming to enhance our understanding of these processes in aging and AD. Parameters included oxygen consumption rates, expression levels of subunits comprising mitochondrial complexes I-V, the enzymatic activity of cytochrome c oxidase (COX), transcription factors associated with inflammation such as NF-κB, pIκB-α, Nrf2, and other inflammatory biomarkers. Hypothalamic mitochondrial dysfunction was observed in 3xTg females as early as 2 months, but no changes were detected in 3xTg males until 6 months of age. In 3xTg mice, subunit expression levels for mitochondrial complexes I-II were significantly reduced in both sexes. Significant sex-based differences in COX activity were also observed at 13 months of age, with levels being lower in females compared to males. In addition, significant sex differences were indicated in NF-κB, pIκB-α, Nrf2, and other inflammatory biomarkers at different age groups during normal aging and AD progression. These findings highlight important sex differences in hypothalamic bioenergetics and inflammation, offering insights into potential new targets for preventing and/or treating AD.

Implications of Lead (Pb)-Induced Transcriptomic and Phenotypic Alterations in the Aged Zebrafish (Danio rerio)

Lead (Pb) is a well-known neurotoxin with established adverse effects on the neurological functions of children and younger adults, including motor, learning, and memory abilities. However, its potential impact on older adults has received less attention. Using the zebrafish model, our study aims to characterize the dose-response relationship between environmentally relevant Pb exposure levels and their effects on changes in behavior and transcriptomics during the geriatric periods. We exposed two-year-old zebrafish to waterborne lead acetate (1, 10, 100, 1000, or 10,000 µg/L) or a vehicle (DMSO) for 5 days. While lower concentrations (1-100 µg/L) reflect environmentally relevant Pb levels, higher concentrations (1000-10,000 µg/L) were included to assess acute toxicity under extreme exposure scenarios. We conducted adult behavior assessment to evaluate the locomotor activity following exposure. The same individual fish were subsequently sacrificed for brain dissection after a day of recovery in the aquatic system. RNA extraction and sequencing were then performed to evaluate the Pb-induced transcriptomic changes. Higher (1000-10,000 ug/L) Pb levels induced hyperactive locomotor patterns in aged zebrafish, while lower (10-100 ug/L) Pb levels resulted in the lowest locomotor activity compared to the control group. Exposure to 100 µg/L led to the highest number of differentially expressed genes (DEGs), while 10,000 µg/L induced larger fold changes in both directions. The neurological pathways impacted by Pb exposure include functions related to neurotransmission, such as cytoskeletal regulation and synaptogenesis, and oxidative stress response, such as mitochondrial dysfunction and downregulation of heat shock protein genes. These findings emphasize a U-shape dose-response relationship with Pb concentrations in locomotor activity and transcriptomic changes in the aging brain.

Omnibus proteome-wide association study identifies 43 risk genes for Alzheimer disease dementia

Transcriptome-wide association study (TWAS) tools have been applied to conduct proteome-wide association studies (PWASs) by integrating proteomics data with genome-wide association study (GWAS) summary data. The genetic effects of PWAS-identified significant genes are potentially mediated through genetically regulated protein abundance, thus informing the underlying disease mechanisms better than GWAS loci. However, existing TWAS/PWAS tools are limited by considering only one statistical model. We propose an omnibus PWAS pipeline to account for multiple statistical models and demonstrate improved performance by simulation and application studies of Alzheimer disease (AD) dementia. We employ the Aggregated Cauchy Association Test to derive omnibus PWAS (PWAS-O) p values from PWAS p values obtained by three existing tools assuming complementary statistical models-TIGAR, PrediXcan, and FUSION. Our simulation studies demonstrated improved power, with well-calibrated type I error, for PWAS-O over all three individual tools. We applied PWAS-O to studying AD dementia with reference proteomic data profiled from dorsolateral prefrontal cortex of postmortem brains from individuals of European ancestry. We identified 43 risk genes, including 5 not identified by previous studies, which are interconnected through a protein-protein interaction network that includes the well-known AD risk genes TOMM40, APOC1, and APOC2. We also validated causal genetic effects mediated through the proteome for 27 (63%) PWAS-O risk genes, providing insights into the underlying biological mechanisms of AD dementia and highlighting promising targets for therapeutic development. PWAS-O can be easily applied to studying other complex diseases.

Non-transgenic guinea pig strains exhibit divergent age-related changes in hippocampal mitochondrial respiration

AIM

Alzheimer's disease (AD) is the most common form of dementia. However, while 150+ animal models of AD exist, drug translation from preclinical models to humans for treatment usually fails. One factor contributing to low translation is likely the absence of neurodegenerative models that also encompass the multi-morbidities of human aging. We previously demonstrated that, in comparison to the PigmEnTed (PET) guinea pig strain which models "typical" brain aging, the Hartley strain develops hallmarks of AD like aging humans. Hartleys also exhibit age-related impairments in cartilage and skeletal muscle. Impaired mitochondrial respiration is one driver of both cellular aging and AD. In humans with cognitive decline, diminished skeletal muscle and brain respiratory control occurs in parallel. We previously reported age-related declines in skeletal muscle mitochondrial respiration in Hartleys. It is unknown if there is concomitant mitochondrial dysfunction in the brain.

METHODS

Therefore, we assessed hippocampal mitochondrial respiration in 5- and 12-month Hartley and PET guinea pigs using high-resolution respirometry.

RESULTS

At 12 months, PETs had higher complex I supported mitochondrial respiration paralleling their increase in body mass compared to 5 months PETs. Hartleys were also heavier at 12 months compared to 5 months but did not have higher complex I respiration. Compared to 5 months Hartleys, 12 months Hartleys had lower complex I mitochondrial efficiency and compensatory increases in mitochondrial proteins collectively suggesting mitochondrial dysfunction with age.

CONCLUSIONS

Therefore, Hartleys might be a relevant model to test promising therapies targeting mitochondria to slow brain aging and AD progression.

Progress in mitochondrial and omics studies in Alzheimer's disease research: from molecular mechanisms to therapeutic interventions

Alzheimer's disease (Alzheimer's disease, AD) is a progressive neurological disorder characterized by memory loss and cognitive impairment. It is characterized by the formation of tau protein neurofibrillary tangles and β-amyloid plaques. Recent studies have found that mitochondria in neuronal cells of AD patients exhibit various dysfunctions, including reduced numbers, ultrastructural changes, reduced enzyme activity, and abnormal kinetics. These abnormal mitochondria not only lead to the loss of normal neuronal cell function, but are also a major driver of AD progression. In this review, we will focus on the advances of mitochondria and their multi-omics in AD research, with particular emphasis on how mitochondrial dysfunction in AD drives disease progression. At the same time, we will focus on summarizing how mitochondrial genomics technologies have revealed specific details of these dysfunctions and how therapeutic strategies targeting mitochondria may provide new directions for future AD treatments. By delving into the key mechanisms of mitochondria in AD related to energy metabolism, altered kinetics, regulation of cell death, and dysregulation of calcium-ion homeostasis, and how mitochondrial multi-omics technologies can be utilized to provide us with a better understanding of these processes. In the future, mitochondria-centered therapeutic strategies will be a key idea in the treatment of AD.

Regulating Lars2 in mitochondria: A potential Alzheimer's therapy by inhibiting tau phosphorylation

Driven by the scarcity of effective treatment options in clinical settings, the present study aimed to identify a new potential target for Alzheimer's disease (AD) treatment. We focused on Lars2, an enzyme synthesizing mitochondrial leucyl-tRNA, and its role in maintaining mitochondrial function. Bioinformatics analysis of human brain transcriptome data revealed downregulation of Lars2 in AD patients compared to healthy controls. During in vitro experiments, the knockdown of Lars2 in mouse neuroblastoma cells (neuro-2a cells) and primary cortical neurons led to morphological changes and decreased density in mouse hippocampal neurons. To explore the underlying mechanisms, we investigated how downregulated Lars2 expression could impede the phosphatidylinositol 3-kinase/protein kinase B (PI3K-AKT) pathway, thereby mitigating AKT's inhibitory effect on glycogen synthase kinase 3 beta (GSK3β). This led to the activation of GSK3β, causing excessive phosphorylation of Tau protein and subsequent neuronal degeneration. During in vivo experiments, knockout of lars2 in hippocampal neurons confirmed cognitive impairment through the Barnes maze test, the novel object recognition test, and nest-building experiments. Additionally, immunofluorescence assays indicated an increase in p-tau, atrophy in the hippocampal region, and a decrease in neurons following Lars2 knockout. Taken together, our findings indicate that Lars2 represents a promising therapeutic target for AD.

Mitochondrial alterations in fibroblasts from sporadic Alzheimer's disease (AD) patients correlate with AD-related clinical hallmarks

Mitochondrial dysfunctions are key features of Alzheimer's disease (AD). The occurrence of these disturbances in the peripheral cells of AD patients and their potential correlation with disease progression are underinvestigated. We studied mitochondrial structure, function and mitophagy in fibroblasts from healthy volunteers and AD patients at the prodromal (AD-MCI) or demented (AD-D) stages. We carried out correlation studies with clinical cognitive scores, namely, (i) Mini-Mental State Examination (MMSE) and (ii) Dementia Rating-Scale Sum of Boxes (CDR-SOB), and with (iii) amyloid beta (Aβ) plaque burden (PiB-PET imaging) and (iv) the accumulation of peripheral amyloid precursor protein C-terminal fragments (APP-CTFs). We revealed alterations in mitochondrial structure as well as specific mitochondrial dysfunction signatures in AD-MCI and AD-D fibroblasts and revealed that defective mitophagy and autophagy are linked to impaired lysosomal activity in AD-D fibroblasts. We reported significant correlations of a subset of these dysfunctions with cognitive decline, AD-related clinical hallmarks and peripheral APP-CTFs accumulation. This study emphasizes the potential use of peripheral cells for investigating AD pathophysiology.

Bayesian genome-wide TWAS with reference transcriptomic data of brain and blood tissues identified 141 risk genes for Alzheimer's disease dementia

BACKGROUND

Transcriptome-wide association study (TWAS) is an influential tool for identifying genes associated with complex diseases whose genetic effects are likely mediated through transcriptome. TWAS utilizes reference genetic and transcriptomic data to estimate effect sizes of genetic variants on gene expression (i.e., effect sizes of a broad sense of expression quantitative trait loci, eQTL). These estimated effect sizes are employed as variant weights in gene-based association tests, facilitating the mapping of risk genes with genome-wide association study (GWAS) data. However, most existing TWAS of Alzheimer's disease (AD) dementia are limited to studying only cis-eQTL proximal to the test gene. To overcome this limitation, we applied the Bayesian Genome-wide TWAS (BGW-TWAS) method to leveraging both cis- and trans- eQTL of brain and blood tissues, in order to enhance mapping risk genes for AD dementia.

METHODS

We first applied BGW-TWAS to the Genotype-Tissue Expression (GTEx) V8 dataset to estimate cis- and trans- eQTL effect sizes of the prefrontal cortex, cortex, and whole blood tissues. Estimated eQTL effect sizes were integrated with the summary data of the most recent GWAS of AD dementia to obtain BGW-TWAS (i.e., gene-based association test) p-values of AD dementia per gene per tissue type. Then we used the aggregated Cauchy association test to combine TWAS p-values across three tissues to obtain omnibus TWAS p-values per gene.

RESULTS

We identified 85 significant genes in prefrontal cortex, 82 in cortex, and 76 in whole blood that were significantly associated with AD dementia. By combining BGW-TWAS p-values across these three tissues, we obtained 141 significant risk genes including 34 genes primarily due to trans-eQTL and 35 mapped risk genes in GWAS Catalog. With these 141 significant risk genes, we detected functional clusters comprised of both known mapped GWAS risk genes of AD in GWAS Catalog and our identified TWAS risk genes by protein-protein interaction network analysis, as well as several enriched phenotypes related to AD.

CONCLUSION

We applied BGW-TWAS and aggregated Cauchy test methods to integrate both cis- and trans- eQTL data of brain and blood tissues with GWAS summary data, identifying 141 TWAS risk genes of AD dementia. These identified risk genes provide novel insights into the underlying biological mechanisms of AD dementia and potential gene targets for therapeutics development.

The Role of Mitochondrial Copy Number in Neurodegenerative Diseases: Present Insights and Future Directions

Neurodegenerative diseases are progressive disorders that affect the central nervous system (CNS) and represent the major cause of premature death in the elderly. One of the possible determinants of neurodegeneration is the change in mitochondrial function and content. Altered levels of mitochondrial DNA copy number (mtDNA-CN) in biological fluids have been reported during both the early stages and progression of the diseases. In patients affected by neurodegenerative diseases, changes in mtDNA-CN levels appear to correlate with mitochondrial dysfunction, cognitive decline, disease progression, and ultimately therapeutic interventions. In this review, we report the main results published up to April 2024, regarding the evaluation of mtDNA-CN levels in blood samples from patients affected by Alzheimer's (AD), Parkinson's (PD), and Huntington's diseases (HD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). The aim is to show a probable link between mtDNA-CN changes and neurodegenerative disorders. Understanding the causes underlying this association could provide useful information on the molecular mechanisms involved in neurodegeneration and offer the development of new diagnostic approaches and therapeutic interventions.

Deciphering Staphylococcus aureus-host dynamics using dual activity-based protein profiling of ATP-interacting proteins

The utilization of ATP within cells plays a fundamental role in cellular processes that are essential for the regulation of host-pathogen dynamics and the subsequent immune response. This study focuses on ATP-binding proteins to dissect the complex interplay between Staphylococcus aureus and human cells, particularly macrophages (THP-1) and keratinocytes (HaCaT), during an intracellular infection. A snapshot of the various protein activity and function is provided using a desthiobiotin-ATP probe, which targets ATP-interacting proteins. In S. aureus, we observe enrichment in pathways required for nutrient acquisition, biosynthesis and metabolism of amino acids, and energy metabolism when located inside human cells. Additionally, the direct profiling of the protein activity revealed specific adaptations of S. aureus to the keratinocytes and macrophages. Mapping the differentially activated proteins to biochemical pathways in the human cells with intracellular bacteria revealed cell-type-specific adaptations to bacterial challenges where THP-1 cells prioritized immune defenses, autophagic cell death, and inflammation. In contrast, HaCaT cells emphasized barrier integrity and immune activation. We also observe bacterial modulation of host processes and metabolic shifts. These findings offer valuable insights into the dynamics of S. aureus-host cell interactions, shedding light on modulating host immune responses to S. aureus, which could involve developing immunomodulatory therapies.

IMPORTANCE

This study uses a chemoproteomic approach to target active ATP-interacting proteins and examines the dynamic proteomic interactions between Staphylococcus aureus and human cell lines THP-1 and HaCaT. It uncovers the distinct responses of macrophages and keratinocytes during bacterial infection. S. aureus demonstrated a tailored response to the intracellular environment of each cell type and adaptation during exposure to professional and non-professional phagocytes. It also highlights strategies employed by S. aureus to persist within host cells. This study offers significant insights into the human cell response to S. aureus infection, illuminating the complex proteomic shifts that underlie the defense mechanisms of macrophages and keratinocytes. Notably, the study underscores the nuanced interplay between the host's metabolic reprogramming and immune strategy, suggesting potential therapeutic targets for enhancing host defense and inhibiting bacterial survival. The findings enhance our understanding of host-pathogen interactions and can inform the development of targeted therapies against S. aureus infections.

Ribonucleotide reductase inhibition improves the symptoms of a Caenorhabditis elegans model of Alzheimer's disease

Alzheimer's disease is the main cause of aging-associated dementia, for which there is no effective treatment. In this work, we reanalyze the information of a previous genome wide association study, using a new pipeline design to identify novel potential drugs. With this approach, ribonucleoside-diphosphate reductase gene (RRM2B) emerged as a candidate target and its inhibitor, 2', 2'-difluoro 2'deoxycytidine (gemcitabine), as a potential pharmaceutical drug against Alzheimer's disease. We functionally verified the effect of inhibiting the RRM2B homolog, rnr-2, in an Alzheimer's model of Caenorhabditis elegans, which accumulates human Aβ1-42 peptide to an irreversible paralysis. RNA interference against rnr-2 and also treatment with 200 ng/ml of gemcitabine, showed an improvement of the phenotype. Gemcitabine treatment increased the intracellular ATP level 3.03 times, which may point to its mechanism of action. Gemcitabine has been extensively used in humans for cancer treatment but at higher concentrations. The 200 ng/ml concentration did not exert a significant effect over cell cycle, or affected cell viability when assayed in the microglia N13 cell line. Thus, the inhibitory drug of the RRM2B activity could be of potential use to treat Alzheimer's disease and particularly gemcitabine might be considered as a promising candidate to be repurposed for its treatment.

Tissue-specific atlas of trans-models for gene regulation elucidates complex regulation patterns

BACKGROUND

Deciphering gene regulation is essential for understanding the underlying mechanisms of healthy and disease states. While the regulatory networks formed by transcription factors (TFs) and their target genes has been mostly studied with relation to cis effects such as in TF binding sites, we focused on trans effects of TFs on the expression of their transcribed genes and their potential mechanisms.

RESULTS

We provide a comprehensive tissue-specific atlas, spanning 49 tissues of TF variations affecting gene expression through computational models considering two potential mechanisms, including combinatorial regulation by the expression of the TFs, and by genetic variants within the TF. We demonstrate that similarity between tissues based on our discovered genes corresponds to other types of tissue similarity. The genes affected by complex TF regulation, and their modelled TFs, were highly enriched for pharmacogenomic functions, while the TFs themselves were also enriched in several cancer and metabolic pathways. Additionally, genes that appear in multiple clusters are enriched for regulation of immune system while tissue clusters include cluster-specific genes that are enriched for biological functions and diseases previously associated with the tissues forming the cluster. Finally, our atlas exposes multilevel regulation across multiple tissues, where TFs regulate other TFs through the two tested mechanisms.

CONCLUSIONS

Our tissue-specific atlas provides hierarchical tissue-specific trans genetic regulations that can be further studied for association with human phenotypes.

Mitochondria in the Central Nervous System in Health and Disease: The Puzzle of the Therapeutic Potential of Mitochondrial Transplantation

Mitochondria, the energy suppliers of the cells, play a central role in a variety of cellular processes essential for survival or leading to cell death. Consequently, mitochondrial dysfunction is implicated in numerous general and CNS disorders. The clinical manifestations of mitochondrial dysfunction include metabolic disorders, dysfunction of the immune system, tumorigenesis, and neuronal and behavioral abnormalities. In this review, we focus on the mitochondrial role in the CNS, which has unique characteristics and is therefore highly dependent on the mitochondria. First, we review the role of mitochondria in neuronal development, synaptogenesis, plasticity, and behavior as well as their adaptation to the intricate connections between the different cell types in the brain. Then, we review the sparse knowledge of the mechanisms of exogenous mitochondrial uptake and describe attempts to determine their half-life and transplantation long-term effects on neuronal sprouting, cellular proteome, and behavior. We further discuss the potential of mitochondrial transplantation to serve as a tool to study the causal link between mitochondria and neuronal activity and behavior. Next, we describe mitochondrial transplantation's therapeutic potential in various CNS disorders. Finally, we discuss the basic and reverse-translation challenges of this approach that currently hinder the clinical use of mitochondrial transplantation.

Comparative interactome mapping of Tau-protein in classical and rapidly progressive Alzheimer's disease identifies subtype-specific pathways

AIMS

Tau is a key player in Alzheimer's disease (AD) and other Tauopathies. Tau pathology in the brain directly correlates with neurodegeneration in AD. The recent identification of a rapid variant of AD demands an urgent need to uncover underlying mechanisms leading to differential progression in AD. Accordingly, we aimed to dissect the underlying differential mechanisms of toxicity associated with the Tau protein in AD subtypes and to find out subtype-dependent biomarkers and therapeutic targets.

METHODS

To identify and characterise subtype-specific Tau-associated mechanisms of pathology, we performed comparative interactome mapping of Tau protein in classical AD (cAD) and rapidly progressive AD (rpAD) cases using co-immunoprecipitation coupled with quantitative mass spectrometry. The mass spectrometry data were extensively analysed using several bioinformatics approaches.

RESULTS

The comparative interactome mapping of Tau protein revealed distinct and unique interactors (DPYSL4, ARHGEF2, TUBA4A and UQCRC2) in subtypes of AD. Interestingly, an analysis of the Tau-interacting proteins indicated enrichment of mitochondrial organisation processes, including negative regulation of mitochondrion organisation, mitochondrial outer membrane permeabilisation involved in programmed cell death, regulation of autophagy of mitochondrion and necroptotic processes, specifically in the rpAD interactome. While, in cAD, the top enriched processes were related to oxidation-reduction process, transport and monocarboxylic acid metabolism.

CONCLUSIONS

Overall, our results provide a comprehensive map of Tau-interacting protein networks in a subtype-dependent manner and shed light on differential functions/pathways in AD subtypes. This comprehensive map of the Tau-interactome has provided subsets of disease-related proteins that can serve as novel biomarkers/biomarker panels and new drug targets.

Microglia sense astrocyte dysfunction and prevent disease progression in an Alexander disease model

Alexander disease (AxD) is an intractable neurodegenerative disorder caused by GFAP mutations. It is a primary astrocyte disease with a pathological hallmark of Rosenthal fibres within astrocytes. AxD astrocytes show several abnormal phenotypes. Our previous study showed that AxD astrocytes in model mice exhibit aberrant Ca2+ signals that induce AxD aetiology. Here, we show that microglia have unique phenotypes with morphological and functional alterations, which are related to the pathogenesis of AxD. Immunohistochemical studies of 60TM mice (AxD model) showed that AxD microglia exhibited highly ramified morphology. Functional changes in microglia were assessed by Ca2+ imaging using hippocampal brain slices from Iba1-GCaMP6-60TM mice and two-photon microscopy. We found that AxD microglia showed aberrant Ca2+ signals, with high frequency Ca2+ signals in both the processes and cell bodies. These microglial Ca2+ signals were inhibited by pharmacological blockade or genetic knockdown of P2Y12 receptors but not by tetrodotoxin, indicating that these signals are independent of neuronal activity but dependent on extracellular ATP from non-neuronal cells. Our single-cell RNA sequencing data showed that the expression level of Entpd2, an astrocyte-specific gene encoding the ATP-degrading enzyme NTPDase2, was lower in AxD astrocytes than in wild-type astrocytes. In situ ATP imaging using the adeno-associated virus vector GfaABC1D ATP1.0 showed that exogenously applied ATP was present longer in 60TM mice than in wild-type mice. Thus, the increased ATP level caused by the decrease in its metabolizing enzyme in astrocytes could be responsible for the enhancement of microglial Ca2+ signals. To determine whether these P2Y12 receptor-mediated Ca2+ signals in AxD microglia play a significant role in the pathological mechanism, a P2Y12 receptor antagonist, clopidogrel, was administered. Clopidogrel significantly exacerbated pathological markers in AxD model mice and attenuated the morphological features of microglia, suggesting that microglia play a protective role against AxD pathology via P2Y12 receptors. Taken together, we demonstrated that microglia sense AxD astrocyte dysfunction via P2Y12 receptors as an increase in extracellular ATP and alter their morphology and Ca2+ signalling, thereby protecting against AxD pathology. Although AxD is a primary astrocyte disease, our study may facilitate understanding of the role of microglia as a disease modifier, which may contribute to the clinical diversity of AxD.

Associations between mitochondrial biomarkers, urban residential exposures and childhood asthma outcomes over 6 months

Determining biomarkers of responses to environmental exposures and evaluating whether they predict respiratory outcomes may help optimize environmental and medical approaches to childhood asthma. Relative mitochondrial (mt) DNA abundance and other potential mitochondrial indicators of oxidative stress may provide a sensitive metric of the child's shifting molecular responses to its changing environment. We leveraged two urban childhood cohorts (Environmental Control as Add-on Therapy in Childhood Asthma (ECATCh); Columbia Center for Children's Environmental Health (CCCEH)) to ascertain whether biomarkers in buccal mtDNA associate with airway inflammation and altered lung function over 6 months of time and capture biologic responses to multiple external stressors such as indoor allergens and fine particulate matter (PM2.5). Relative mtDNA content was amplified by qPCR and methylation of transfer RNA phenylalanine/rRNA 12S (TF/RNR1), cytochrome c oxidase (CO1), and carboxypeptidase O (CPO) was measured by pyrosequencing. Data on residential exposures and respiratory outcomes were harmonized between the two cohorts. Repeated measures and multiple regression models were utilized to assess relationships between mitochondrial biomarkers, respiratory outcomes, and residential exposures (PM2.5, allergens), adjusted for potential confounders and time-varying asthma. We found across the 6 month visits, a 0.64 fold higher level of TF/RNR1 methylation was detected among those with asthma in comparison to those without asthma ((parameter estimate (PE) 0.64, standard error 0.28, p = 0.03). In prospective analyses, CPO methylation was associated with subsequent reduced forced vital capacity (FVC; PE -0.03, standard error 0.01, p = 0.02). Bedroom dust mouse allergen, but not indoor PM2.5, was associated with higher methylation of TF/RNR1 (PE 0.015, standard error 0.006, p = 0.01). Select mtDNA measures in buccal cells may indicate children's responses to toxic environmental exposures and associate selectively with asthma and lung function.

Neuroproteomic Analysis after SARS-CoV-2 Infection Reveals Overrepresented Neurodegeneration Pathways and Disrupted Metabolic Pathways

Besides respiratory illness, SARS-CoV-2, the causative agent of COVID-19, leads to neurological symptoms. The molecular mechanisms leading to neuropathology after SARS-CoV-2 infection are sparsely explored. SARS-CoV-2 enters human cells via different receptors, including ACE-2, TMPRSS2, and TMEM106B. In this study, we used a human-induced pluripotent stem cell-derived neuronal model, which expresses ACE-2, TMPRSS2, TMEM106B, and other possible SARS-CoV-2 receptors, to evaluate its susceptibility to SARS-CoV-2 infection. The neurons were exposed to SARS-CoV-2, followed by RT-qPCR, immunocytochemistry, and proteomic analyses of the infected neurons. Our findings showed that SARS-CoV-2 infects neurons at a lower rate than other human cells; however, the virus could not replicate or produce infectious virions in this neuronal model. Despite the aborted SARS-CoV-2 replication, the infected neuronal nuclei showed irregular morphology compared to other human cells. Since cytokine storm is a significant effect of SARS-CoV-2 infection in COVID-19 patients, in addition to the direct neuronal infection, the neurons were treated with pre-conditioned media from SARS-CoV-2-infected lung cells, and the neuroproteomic changes were investigated. The limited SARS-CoV-2 infection in the neurons and the neurons treated with the pre-conditioned media showed changes in the neuroproteomic profile, particularly affecting mitochondrial proteins and apoptotic and metabolic pathways, which may lead to the development of neurological complications. The findings from our study uncover a possible mechanism behind SARS-CoV-2-mediated neuropathology that might contribute to the lingering effects of the virus on the human brain.

Mitochondria and Oxidative Stress as a Link between Alzheimer's Disease and Diabetes Mellitus

This review is devoted to the problems of the common features linking metabolic disorders and type 2 diabetes with the development of Alzheimer's disease. The pathogenesis of Alzheimer's disease closely intersects with the mechanisms of type 2 diabetes development, and an important risk factor for both pathologies is aging. Common pathological mechanisms include both factors in the development of oxidative stress, neuroinflammation, insulin resistance, and amyloidosis, as well as impaired mitochondrial dysfunctions and increasing cell death. The currently available drugs for the treatment of type 2 diabetes and Alzheimer's disease have limited therapeutic efficacy. It is important to note that drugs used to treat Alzheimer's disease, in particular acetylcholinesterase inhibitors, show a positive therapeutic potential in the treatment of type 2 diabetes, while drugs used in the treatment of type 2 diabetes can also prevent a number of pathologies characteristic for Alzheimer's disease. A promising direction in the search for a strategy for the treatment of type 2 diabetes and Alzheimer's disease may be the creation of complex multi-target drugs that have neuroprotective potential and affect specific common targets for type 2 diabetes and Alzheimer's disease.

Transcriptomic Analysis in the Hippocampus and Retina of Tg2576 AD Mice Reveals Defective Mitochondrial Oxidative Phosphorylation and Recovery by Tau 12A12mAb Treatment

Increasing evidence implicates decreased energy metabolism and mitochondrial dysfunctions among the earliest pathogenic events of Alzheimer's disease (AD). However, the molecular mechanisms underlying bioenergetic dysfunctions in AD remain, to date, largely unknown. In this work, we analyzed transcriptomic changes occurring in the hippocampus and retina of a Tg2576 AD mouse model and wild-type controls, evaluating their functional implications by gene set enrichment analysis. The results revealed that oxidative phosphorylation and mitochondrial-related pathways are significantly down-regulated in both tissues of Tg2576 mice, supporting the role of these processes in the pathogenesis of AD. In addition, we also analyzed transcriptomic changes occurring in Tg2576 mice treated with the 12A12 monoclonal antibody that neutralizes an AD-relevant tau-derived neurotoxic peptide in vivo. Our analysis showed that the mitochondrial alterations observed in AD mice were significantly reverted by treatment with 12A12mAb, supporting bioenergetic pathways as key mediators of its in vivo neuroprotective and anti-amyloidogenic effects. This study provides, for the first time, a comprehensive characterization of molecular events underlying the disrupted mitochondrial bioenergetics in AD pathology, laying the foundation for the future development of diagnostic and therapeutic tools.

Navigating Early Alzheimer's Diagnosis: A Comprehensive Review of Diagnostic Innovations

The hunt for early Alzheimer's disease detection has created cutting-edge diagnostic instruments with enormous promise. This article examines the many facets of these developments, focusing on how they have revolutionised diagnosis and patient outcomes. These tools make it possible to detect tiny brain changes even before they give birth to clinical symptoms by combining cutting-edge biomarkers, neuroimaging methods, and machine-learning algorithms. A significant opportunity for therapies that can slow the course of the disease exists during this early detection stage. Additionally, these cutting-edge techniques improve diagnostic precision, objectivity, and accessibility. Liquid biopsies and blood-based biomarkers provide non-invasive alternatives, filling accessibility gaps in diagnosis. While issues with standardisation, ethics, and data integration continue, collaboration within research, clinical practice, and policy realms fuels positive developments. As technology advances, the way towards better Alzheimer's diagnosis becomes more evident, giving patients and families dealing with this difficult illness fresh hope. The synergy between scientific advancement and compassionate treatment is crucial for improving Alzheimer's disease diagnosis, as this paper emphasises.

Endotype Characterization Reveals Mechanistic Differences Across Brain Regions in Sporadic Alzheimer's Disease

Background

While Alzheimer's disease (AD) pathology is associated with altered brain structure, it is not clear whether gene expression changes mirror the onset and evolution of pathology in distinct brain regions. Deciphering the mechanisms which cause the differential manifestation of the disease across different regions has the potential to help early diagnosis.

Objective

We aimed to identify common and unique endotypes and their regulation in tangle-free neurons in sporadic AD (SAD) across six brain regions: entorhinal cortex (EC), hippocampus (HC), medial temporal gyrus (MTG), posterior cingulate (PC), superior frontal gyrus (SFG), and visual cortex (VCX).

Methods

To decipher the states of tangle-free neurons across different brain regions in human subjects afflicted with AD, we performed analysis of the neural transcriptome. We explored changes in differential gene expression, functional and transcription factor target enrichment, and co-expression gene module detection analysis to discern disease-state transcriptomic variances and characterize endotypes. Additionally, we compared our results to tangled AD neuron microarray-based study and the Allen Brain Atlas.

Results

We identified impaired neuron function in EC, MTG, PC, and VCX resulting from REST activation and reversal of mature neurons to a precursor-like state in EC, MTG, and SFG linked to SOX2 activation. Additionally, decreased neuron function and increased dedifferentiation were linked to the activation of SUZ12. Energetic deficit connected to NRF1 inactivation was found in HC, PC, and VCX.

Conclusions

Our findings suggest that SAD manifestation varies in scale and severity in different brain regions. We identify endotypes, such as energetic shortfalls, impaired neuronal function, and dedifferentiation.

Repurposing of Tibolone in Alzheimer's Disease

Alzheimer's disease (AD) is a debilitating neurodegenerative disease characterised by the accumulation of amyloid-beta and tau in the brain, leading to the progressive loss of memory and cognition. The causes of its pathogenesis are still not fully understood, but some risk factors, such as age, genetics, and hormones, may play a crucial role. Studies show that postmenopausal women have a higher risk of developing AD, possibly due to the decrease in hormone levels, especially oestrogen, which may be directly related to a reduction in the activity of oestrogen receptors, especially beta (ERβ), which favours a more hostile cellular environment, leading to mitochondrial dysfunction, mainly affecting key processes related to transport, metabolism, and oxidative phosphorylation. Given the influence of hormones on biological processes at the mitochondrial level, hormone therapies are of clinical interest to reduce the risk or delay the onset of symptoms associated with AD. One drug with such potential is tibolone, which is used in clinics to treat menopause-related symptoms. It can reduce amyloid burden and have benefits on mitochondrial integrity and dynamics. Many of its protective effects are mediated through steroid receptors and may also be related to neuroglobin, whose elevated levels have been shown to protect against neurological diseases. Its importance has increased exponentially due to its implication in the pathogenesis of AD. In this review, we discuss recent advances in tibolone, focusing on its mitochondrial-protective effects, and highlight how valuable this compound could be as a therapeutic alternative to mitigate the molecular pathways characteristic of AD.

Longitudinal APOE4- and amyloid-dependent changes in the blood transcriptome in cognitively intact older adults

BACKGROUND

Gene expression is dysregulated in Alzheimer's disease (AD) patients, both in peripheral blood and post mortem brain. We investigated peripheral whole-blood gene (co)expression to determine molecular changes prior to symptom onset.

METHODS

RNA was extracted and sequenced for 65 cognitively healthy F-PACK participants (65 (56-80) years, 34 APOE4 non-carriers, 31 APOE4 carriers), at baseline and follow-up (interval: 5.0 (3.4-8.6) years). Participants received amyloid PET at both time points and amyloid rate of change derived. Accumulators were defined with rate of change ≥ 2.19 Centiloids. We performed differential gene expression and weighted gene co-expression network analysis to identify differentially expressed genes and networks of co-expressed genes, respectively, with respect to traits of interest (APOE4 status, amyloid accumulation (binary/continuous)), and amyloid positivity status, followed by Gene Ontology annotation.

RESULTS

There were 166 significant differentially expressed genes at follow-up compared to baseline in APOE4 carriers only, whereas 12 significant differentially expressed genes were found only in APOE4 non-carriers, over time. Among the significant genes in APOE4 carriers, several had strong evidence for a pathogenic role in AD based on direct association scores generated from the DISQOVER platform: NGRN, IGF2, GMPR, CLDN5, SMIM24. Top enrichment terms showed upregulated mitochondrial and metabolic pathways, and an exacerbated upregulation of ribosomal pathways in APOE4 carriers compared to non-carriers. Similarly, there were 33 unique significant differentially expressed genes at follow-up compared to baseline in individuals classified as amyloid negative at baseline and positive at follow-up or amyloid positive at both time points and 32 unique significant differentially expressed genes over time in individuals amyloid negative at both time points. Among the significant genes in the first group, the top five with the highest direct association scores were as follows: RPL17-C18orf32, HSP90AA1, MBP, SIRPB1, and GRINA. Top enrichment terms included upregulated metabolism and focal adhesion pathways. Baseline and follow-up gene co-expression networks were separately built. Seventeen baseline co-expression modules were derived, with one significantly negatively associated with amyloid accumulator status (r² =  - 0.25, p = 0.046). This was enriched for proteasomal protein catabolic process and myeloid cell development. Thirty-two follow-up modules were derived, with two significantly associated with APOE4 status: one downregulated (r² =  - 0.27, p = 0.035) and one upregulated (r² = 0.26, p = 0.039) module. Top enrichment processes for the downregulated module included proteasomal protein catabolic process and myeloid cell homeostasis. Top enrichment processes for the upregulated module included cytoplasmic translation and rRNA processing.

CONCLUSIONS

We show that there are longitudinal gene expression changes that implicate a disrupted immune system, protein removal, and metabolism in cognitively intact individuals who carry APOE4 or who accumulate in cortical amyloid. This provides insight into the pathophysiology of AD, whilst providing novel targets for drug and therapeutic development.

Bayesian genome-wide TWAS with reference transcriptomic data of brain and blood tissues identified 93 risk genes for Alzheimer's disease dementia

Background

Transcriptome-wide association study (TWAS) is an influential tool for identifying novel genes associated with complex diseases, where their genetic effects may be mediated through transcriptome. TWAS utilizes reference genetic and transcriptomic data to estimate genetic effect sizes on expression quantitative traits of target genes (i.e., effect sizes of a broad sense of expression quantitative trait loci, eQTL). These estimated effect sizes are then employed as variant weights in burden gene-based association test statistics, facilitating the mapping of risk genes for complex diseases with genome-wide association study (GWAS) data. However, most existing TWAS of Alzheimer's disease (AD) dementia have primarily focused on cis -eQTL, disregarding potential trans -eQTL. To overcome this limitation, we applied the Bayesian Genome-wide TWAS (BGW-TWAS) method which incorporated both cis - and trans -eQTL of brain and blood tissues to enhance mapping risk genes for AD dementia.

Methods

We first applied BGW-TWAS to the Genotype-Tissue Expression (GTEx) V8 dataset to estimate cis - and trans -eQTL effect sizes of the prefrontal cortex, cortex, and whole blood tissues. Subsequently, estimated eQTL effect sizes were integrated with the summary data of the most recent GWAS of AD dementia to obtain BGW-TWAS (i.e., gene-based association test) p-values of AD dementia per tissue type. Finally, we used the aggregated Cauchy association test to combine TWAS p-values across three tissues to obtain omnibus TWAS p-values per gene.

Results

We identified 37 genes in prefrontal cortex, 55 in cortex, and 51 in whole blood that were significantly associated with AD dementia. By combining BGW-TWAS p-values across these three tissues, we obtained 93 significant risk genes including 29 genes primarily due to trans -eQTL and 50 novel genes. Utilizing protein-protein interaction network and phenotype enrichment analyses with these 93 significant risk genes, we detected 5 functional clusters comprised of both known and novel AD risk genes and 7 enriched phenotypes.

Conclusion

We applied BGW-TWAS and aggregated Cauchy test methods to integrate both cis - and trans -eQTL data of brain and blood tissues with GWAS summary data to identify risk genes of AD dementia. The risk genes we identified provide novel insights into the underlying biological pathways implicated in AD dementia.

Mitochondria-wide association study observed significant interactions of mitochondrial respiratory and the inflammatory in the development of anxiety and depression

The aim of this study was to investigate the possible interaction of mitochondrial dysfunction and inflammatory cytokines in the risk of anxiety and depression. We utilized the UK Biobank for the sample of this study. A mitochondria-wide association(MiWAS) and interaction analysis was performed to investigate the interaction effects of mitochondrial DNA (mtDNA)×C-reactive protein (CRP) on the risks of self-reported anxiety (N = 72,476), general anxiety disorder (GAD-7) scores (N = 80,853), self-reported depression (N = 80,778), Patient Health Questionnaire (PHQ-9) scores (N = 80,520) in total samples, females and males, respectively, adjusting for sex, age, Townsend deprivation index (TDI), education score, alcohol intake, smoking and 10 principal components. In all, 25 mtSNPs and 10 mtSNPs showed significant level of association with self-reported anxiety and GAD-7 score respectively. A total of seven significant mtDNA × CRP interactions were found for anxiety, such as m.3915G>A(MT-ND1) for self-reported anxiety in total subjects (P = 6.59 × 10^-3), m.4561T>C(MT-ND2) (P = 3.04 × 10^-3) for GAD-7 score in total subjects. For depression, MiWAS identified 17 significant mtSNPs for self-reported depression and 14 significant mtSNPs for PHQ-9 scores. 17 significant mtDNA associations (2 for self-reported depression and 15 for PHQ-9 score) was identified, such as m.14869G>A(MT-CYB; P = 2.22 × 10^-3) associated with self-reported depression and m.4561T>C (MT-ND2; P value = 3.02 × 10^-8) associated with PHQ-9 score in all subjects. In addition, 5 common mtDNA shared with anxiety and depression were found in MiWAS, and 4 common mtDNA variants were detected to interact with CRP for anxiety and depression, such as m.9899T>C(MT-CO3). Our study suggests the important interaction effects of mitochondrial function and CRP on the risks of anxiety and depression.

Selected Biomarkers of Oxidative Stress and Energy Metabolism Disorders in Neurological Diseases

Neurological diseases can be broadly divided according to causal factors into circulatory system disorders leading to ischemic stroke; degeneration of the nerve cells leading to neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's (PD) diseases, and immune system disorders; bioelectric activity (epileptic) problems; and genetically determined conditions as well as viral and bacterial infections developing inflammation. Regardless of the cause of neurological diseases, they are usually accompanied by disturbances of the central energy in a completely unexplained mechanism. The brain makes up only 2% of the human body's weight; however, while working, it uses as much as 20% of the energy obtained by the body. The energy requirements of the brain are very high, and regulatory mechanisms in the brain operate to ensure adequate neuronal activity. Therefore, an understanding of neuroenergetics is rapidly evolving from a "neurocentric" view to a more integrated picture involving cooperativity between structural and molecular factors in the central nervous system. This article reviewed selected molecular biomarkers of oxidative stress and energy metabolism disorders such as homocysteine, DNA damage such as 8-oxo2dG, genetic variants, and antioxidants such as glutathione in selected neurological diseases including ischemic stroke, AD, PD, and epilepsy. This review summarizes our and others' recent research on oxidative stress in neurological disorders. In the future, the diagnosis and treatment of neurological diseases may be substantially improved by identifying specific early markers of metabolic and energy disorders.

ApoE Modifier Alleles for Alzheimer's Disease Discovered by Information Theory Dependency Measures: MIST Software Package

Information theory-based measures of variable dependency (previously published) have been implemented into a software package, MIST. The design of the software and its potential uses are described, and a demonstration is presented in the discovery of modifier alleles of the ApoE gene in affecting Alzheimer's disease (AD) by analyzing the UK Biobank dataset. The modifier genes uncovered overlap strongly with genes found to be associated with AD. Others include many known to influence AD. We discuss a range of uses of the dependency calculations using MIST that can uncover additional genetic effects in similar complex datasets, like higher degrees of interaction and phenotypic pleiotropy.

Modifications of the endosomal compartment in fibroblasts from sporadic Alzheimer's disease patients are associated with cognitive impairment

Morphological alterations of the endosomal compartment have been widely described in post-mortem brains from Alzheimer's disease (AD) patients and subjects with Down syndrome (DS) who are at high risk for AD. Immunostaining with antibodies against endosomal markers such as Early Endosome Antigen 1 (EEA1) revealed increased size of EEA1-positive puncta. In DS, peripheral cells such as peripheral blood mononuclear cells (PBMCs) and fibroblasts, share similar phenotype even in the absence of AD. We previously found that PBMCs from AD patients have larger EEA1-positive puncta, correlating with brain amyloid load. Here we analysed the endosomal compartment of fibroblasts from a very well characterised cohort of AD patients (IMABio3) who underwent thorough clinical, imaging and biomarkers assessments. Twenty-one subjects were included (7 AD with mild cognitive impairment (AD-MCI), 7 AD with dementia (AD-D) and 7 controls) who had amyloid-PET at baseline (PiB) and neuropsychological tests at baseline and close to skin biopsy. Fibroblasts isolated from skin biopsies were immunostained with anti-EEA1 antibody and imaged using a spinning disk microscope. Endosomal compartment ultrastructure was also analysed by electron microscopy. All fibroblast lines were genotyped and their AD risk factors identified. Our results show a trend to an increased EEA1-positive puncta volume in fibroblasts from AD-D as compared to controls (p.adj = 0.12) and reveal enhanced endosome area in fibroblasts from AD-MCI and AD-AD versus controls. Larger puncta size correlated with PiB retention in different brain areas and with worse cognitive scores at the time of biopsy as well as faster decline from baseline to the time of biopsy. Finally, we identified three genetic risk factors for AD (ABCA1, COX7C and MYO15A) that were associated with larger EEA1 puncta volume. In conclusion, the endosomal compartment in fibroblasts could be used as cellular peripheral biomarker for both amyloid deposition and cognitive decline in AD patients.

Vitamin D, a Secosteroid Hormone and Its Multifunctional Receptor, Vitamin D Receptor, in Alzheimer's Type Neurodegeneration

Vitamin D is a secosteroid hormone exerting neurosteroid-like properties. Its well-known nuclear hormone receptor, and recently proposed as a mitochondrial transcription factor, vitamin D receptor, acts for its primary functions. The second receptor is an endoplasmic reticulum protein, protein disulfide isomerase A3 (PDIA3), suggested to act as a rapid response. Vitamin D has effects on various systems, particularly through calcium metabolism. Among them, the nervous system has an important place in the context of our subject. Recent studies have shown that vitamin D and its receptors have numerous effects on the nervous system. Neurodegeneration is a long-term process. Throughout a human life span, so is vitamin D deficiency. Our previous studies and others have suggested that the out-come of long-term vitamin D deficiency (hypovitaminosis D or inefficient utilization of vitamin D), may lead neurons to be vulnerable to aging and neurodegeneration. We suggest that keeping vitamin D levels at adequate levels at all stages of life, considering new approaches such as agonists that can activate vitamin D receptors, and utilizing other derivatives produced in the synthesis process with UVB are crucial when considering vitamin D-based intervention studies. Given most aspects of vitamin D, this review outlines how vitamin D and its receptors work and are involved in neurodegeneration, emphasizing Alzheimer's disease.

The Neuropharmacological Effects of Magnolol and Honokiol: A Review of Signal Pathways and Molecular Mechanisms

Magnolol and honokiol are natural lignans with good physiological effects. As the main active substances derived from Magnolia officinalis, their pharmacological activities have attracted extensive attention. It is reported that both of them can cross the blood-brain barrier (BBB) and exert neuroprotective effects through a variety of mechanisms. This suggests that these two ingredients can be used as effective therapeutic compounds to treat a wide range of neurological diseases. This article provides a review of the mechanisms involved in the therapeutic effects of magnolol and honokiol in combating diseases, such as cerebral ischemia, neuroinflammation, Alzheimer's disease, and brain tumors, as well as psychiatric disorders, such as anxiety and depression. Although magnolol and honokiol have the pharmacological effects described above, their clinical potential remains untapped. More research is needed to improve the bioavailability of magnolol and honokiol and perform experiments to examine the therapeutic potential of magnolol and honokiol.

Artificial intelligence-driven meta-analysis of brain gene expression identifies novel gene candidates and a role for mitochondria in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia. There is no treatment and AD models have focused on a small subset of genes identified in familial AD. Microarray studies have identified thousands of dysregulated genes in the brains of patients with AD yet identifying the best gene candidates to both model and treat AD remains a challenge. We performed a meta-analysis of microarray data from the frontal cortex (n = 697) and cerebellum (n = 230) of AD patients and healthy controls. A two-stage artificial intelligence approach, with both unsupervised and supervised machine learning, combined with a functional network analysis was used to identify functionally connected and biologically relevant novel gene candidates in AD. We found that in the frontal cortex, genes involved in mitochondrial energy, ATP, and oxidative phosphorylation, were the most significant dysregulated genes. In the cerebellum, dysregulated genes were involved in mitochondrial cellular biosynthesis (mitochondrial ribosomes). Although there was little overlap between dysregulated genes between the frontal cortex and cerebellum, machine learning models comprised of this overlap. A further functional network analysis of these genes identified that two downregulated genes, ATP5L and ATP5H, which both encode subunits of ATP synthase (mitochondrial complex V) may play a role in AD. Combined, our results suggest that mitochondrial dysfunction, particularly a deficit in energy homeostasis, may play an important role in AD.

Structural and functional diversity of mitochondria in vestibular/cochlear hair cells and vestibular calyx afferents

Mitochondria supply energy in the form of ATP to drive a plethora of cellular processes. In heart and liver cells, mitochondria occupy over 20% of the cellular volume and the major need for ATP is easily identifiable - i.e., to drive cross-bridge recycling in cardiac cells or biosynthetic machinery in liver cells. In vestibular and cochlear hair cells the overall cellular mitochondrial volume is much less, and mitochondria structure varies dramatically in different regions of the cell. The regional demands for ATP and cellular forces that govern mitochondrial structure and localization are not well understood. Below we review our current understanding of the heterogeneity of form and function in hair cell mitochondria. A particular focus of this review will be on regional specialization in vestibular hair cells, where large mitochondria are found beneath the cuticular plate in close association with the striated organelle. Recent findings on the role of mitochondria in hair cell death and aging are covered along with potential therapeutic approaches. Potential avenues for future research are discussed, including the need for integrated computational modeling of mitochondrial function in hair cells and the vestibular afferent calyx.

Metabolic Regulation of Glia and Their Neuroinflammatory Role in Alzheimer's Disease

Alzheimer's disease (AD) is an aging-related neurodegenerative disorder. It is characterized clinically by progressive memory loss and impaired cognitive function. Its progression occurs from neuronal synapse loss to amyloid pathology and Tau deposit which eventually leads to the compromised neuronal function. Neurons in central nervous tissue work in a composite and intricate network with the glia and vascular cells. Microglia and astrocytes are becoming the prime focus due to their involvement in various aspects of neurophysiology, such as trophic support to neurons, synaptic modulation, and brain surveillance. AD is also often considered as the sequela of prolonged metabolic dyshomeostasis. The neuron and glia have different metabolic profiles as cytosolic glycolysis and mitochondrial-dependent oxidative phosphorylation (OXPHOS), especially under dyshomeostasis or with aging pertaining to their unique genetic built-up. Various efforts are being put in to decipher the role of mitochondrial dynamics regarding their trafficking, fission/fusion imbalance, and mitophagy spanning over both neurons and glia to improve aging-related brain health. The mitochondrial dysfunction may lead to activation in various signaling mechanisms causing metabolic reprogramming in glia cells, further accelerating AD-related pathogenic events. The glycolytic-dominant astrocytes switch to the neurotoxic phenotype, i.e., disease-associated astrocyte under metabolic stress. The microglia also transform from resting to reactive phenotype, i.e., disease-associated microglia. It may also exist in otherwise a misconception an M1, glycolytic, or M2, an OXPHOS-dependent phenotype. Further, glial transformation plays a vital role in regulating hallmarks of AD pathologies like synapse maintenance, amyloid, and Tau clearance. In this updated review, we have tried to emphasize the metabolic regulation of glial reactivity, mitochondrial quality control mechanisms, and their neuroinflammatory response in Alzheimer's progression.

Transcriptomic and epigenomic landscapes of Alzheimer's disease evidence mitochondrial-related pathways

Alzheimers disease (AD) is the main cause of dementia and it is defined by cognitive decline coupled to extracellular deposit of amyloid-beta protein and intracellular hyperphosphorylation of tau protein. Historically, efforts to target such hallmarks have failed in numerous clinical trials. In addition to these hallmark-targeted approaches, several clinical trials focus on other AD pathological processes, such as inflammation, mitochondrial dysfunction, and oxidative stress. Mitochondria and mitochondrial-related mechanisms have become an attractive target for disease-modifying strategies, as mitochondrial dysfunction prior to clinical onset has been widely described in AD patients and AD animal models. Mitochondrial function relies on both the nuclear and mitochondrial genome. Findings from omics technologies have shed light on AD pathophysiology at different levels (e.g., epigenome, transcriptome and proteome). Most of these studies have focused on the nuclear-encoded components. The first part of this review provides an updated overview of the mechanisms that regulate mitochondrial gene expression and function. The second part of this review focuses on evidence of mitochondrial dysfunction in AD. We have focused on published findings and datasets that study AD. We analyzed published data and provide examples for mitochondrial-related pathways. These pathways are strikingly dysregulated in AD neurons and glia in sex-, cell- and disease stage-specific manners. Analysis of mitochondrial omics data highlights the involvement of mitochondria in AD, providing a rationale for further disease modeling and drug targeting.

Could Amyloid-β 1-42 or α-Synuclein Interact Directly with Mitochondrial DNA? A Hypothesis

The amyloid β (Aβ) and the α-synuclein (α-syn) are shown to be translocated into mitochondria. Even though their roles are widely investigated in pathological conditions, information on the presence and functions of Aβ and α-syn in mitochondria in endogenous levels is somewhat limited. We hypothesized that endogenous Aβ fragments or α-syn could interact with mitochondrial DNA (mtDNA) directly or influence RNAs or transcription factors in mitochondria and change the mtDNA transcription profile. In this review, we summarized clues of these possible interactions.

Investigation of Mitochondrial Related Variants in a Cerebral Small Vessel Disease Cohort

Monogenic forms of cerebral small vessel disease (CSVD) can be caused by both variants in nuclear DNA and mitochondrial DNA (mtDNA). Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is known to have a phenotype similar to Cerebral Autosomal Dominant Arteriopathy with Sub-cortical Infarcts and Leukoencephalopathy (CADASIL), and can be caused by variants in the mitochondrial genome and in several nuclear-encoded mitochondrial protein (NEMP) genes. The aim of this study was to screen for variants in the mitochondrial genome and NEMP genes in a NOTCH3-negative CADASIL cohort, to identify a potential link between mitochondrial dysfunction and CSVD pathology. Whole exome sequencing was performed for 50 patients with CADASIL-like symptomology on the Ion Torrent system. Mitochondrial sequencing was performed using an in-house designed protocol with sequencing run on the Ion GeneStudio S5 Plus (S5 +). NEMP genes and mitochondrial sequencing data were examined for rare (MAF < 0.001), non-synonymous variants that were predicted to have a deleterious effect on the protein. We identified 29 candidate NEMP variants that had links to either MELAS-, encephalopathy-, or Alzheimer's disease-related phenotypes. Based on these changes, variants affecting POLG, MTO1, LONP1, NDUFAF6, NDUFB3, and TCIRG1 were thought to play a potential role in CSVD pathology in this cohort. Overall, the exploration of the mitochondrial genome identified a potential role for mitochondrial related proteins and mtDNA variants contributing to CSVD pathologies.

Mitochondrial and redox modifications in early stages of Huntington's disease

Deficits in mitochondrial function and redox deregulation have been attributed to Huntington's disease (HD), a genetic neurodegenerative disorder largely affecting the striatum. However, whether these changes occur in early stages of the disease and can be detected in vivo is still unclear. In the present study, we analysed changes in mitochondrial function and production of reactive oxygen species (ROS) at early stages and with disease progression. Studies were performed in vivo in human brain by PET using [⁶⁴Cu]-ATSM and ex vivo in human skin fibroblasts of premanifest and prodromal (Pre-M) and manifest HD carriers. In vivo brain [⁶⁴Cu]-ATSM PET in YAC128 transgenic mouse and striatal and cortical isolated mitochondria were assessed at presymptomatic (3 month-old, mo) and symptomatic (6–12 mo) stages. Pre-M HD carriers exhibited enhanced whole-brain (with exception of caudate) [⁶⁴Cu]-ATSM labelling, correlating with CAG repeat number. Fibroblasts from Pre-M showed enhanced basal and maximal respiration, proton leak and increased hydrogen peroxide (H₂O₂) levels, later progressing in manifest HD. Mitochondria from fibroblasts of Pre-M HD carriers also showed reduced circularity, while higher number of mitochondrial DNA copies correlated with maximal respiratory capacity. In vivo animal PET analysis showed increased accumulation of [⁶⁴Cu]-ATSM in YAC128 mouse striatum. YAC128 mouse (at 3 months) striatal isolated mitochondria exhibited a rise in basal and maximal mitochondrial respiration and in ATP production, and increased complex II and III activities. YAC128 mouse striatal mitochondria also showed enhanced mitochondrial H₂O₂ levels and circularity, revealed by brain ultrastructure analysis, and defects in Ca²⁺ handling, supporting increased striatal susceptibility. Data demonstrate both human and mouse mitochondrial overactivity and altered morphology at early HD stages, facilitating redox unbalance, the latter progressing with manifest disease.

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Pre-manifest HD carriers and presymptomatic YAC128 mice show increased brain [⁶⁴Cu]-ATSM labelling.

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Increased [⁶⁴Cu]-ATSM brain retention correlates with raised ROS levels in human and mouse samples.

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Increased [⁶⁴Cu]-ATSM correlates with enhanced mitochondrial activity and mtDNA copy number.

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Presymptomatic YAC128 mouse striatal mitochondria show altered morphology and Ca²⁺ handling.