Gene interactions analysis of brain spatial transcriptome for Alzheimer's disease.

Recent studies have explored the spatial transcriptomics patterns of Alzheimer's disease (AD) brain by spatial sequencing in mouse models, enabling the identification of unique genome-wide transcriptomic features associated with different spatial regions and pathological status. However, the dynamics of gene interactions that occur during amyloid-ß accumulation remain largely unknown. In this study, we performed analyses on ligand-receptor communication, transcription factor regulatory network, and spot-specific network to reveal the dependence and the dynamics of gene associations/interactions on spatial regions and pathological status with mouse and human brains. We first used a spatial transcriptomics dataset of the App NL-G-F knock-in AD and wild-type mouse model. We revealed 17 ligand-receptor pairs with opposite tendencies throughout the amyloid-ß accumulation process and showed the specific ligand-receptor interactions across the hippocampus layers at different extents of pathological changes. We then identified nerve function related transcription factors in the hippocampus and entorhinal cortex, as well as genes with different transcriptomic association degrees in AD versus wild-type mice. Finally, another independent spatial transcriptomics dataset from different AD mouse models and human single-nuclei RNA-seq data/AlzData database were used for validation. This is the first study to identify various gene associations throughout amyloid-ß accumulation based on spatial transcriptomics, establishing the foundations to reveal advanced and in-depth AD etiology from a novel perspective based on the comprehensive analyses of gene interactions that are spatio-temporal dependent.

Proactive M2 blockade prevents cognitive decline in GRK5-deficient APP transgenic mice via enhancing cholinergic neuronal resilience.

Alzheimer's disease (AD) poses an immense challenge in healthcare, lacking effective therapies. This study investigates the potential of anthranilamide derivative (AAD23), a selective M2 receptor antagonist, in proactively preventing cognitive impairments and cholinergic neuronal degeneration in G protein-coupled receptor kinase-5-deficient Swedish APP (GAP) mice. GAP mice manifest cognitive deficits by 7 months and develop senile plaques by 9 months. A 6-month AAD23 treatment was initiated at 5 months and stopped at 11 months before behavioral assessments without the treatment. AAD23-treated mice exhibited preserved cognitive abilities and improved cholinergic axonal health in the nucleus basalis of Meynert akin to wildtype mice. Conversely, vehicle-treated GAP mice displayed memory deficits and pronounced cholinergic axonal swellings in the nucleus basalis of Meynert. Notably, AAD23 treatment did not alter senile plaques and microgliosis. These findings highlight AAD23's efficacy in forestalling AD-related cognitive decline in G protein-coupled receptor kinase-5-deficient subjects, attributing its success to restoring cholinergic neuronal integrity and resilience, enhancing resistance against diverse degenerative insults.

O-GlcNAc impacts mitophagy via the PINK1-dependent pathway.

Background: The accumulation of dysfunctional mitochondria is an early feature of Alzheimer's disease (AD). The impaired turnover of damaged mitochondria increases reactive oxygen species production and lowers ATP generation, leading to cellular toxicity and neurodegeneration. Interestingly, AD exhibits a disruption in the global post-translational modification ß-N-acetylglucosamine (O-GlcNAc). O-GlcNAc is a ubiquitous single sugar modification found in the nuclear, cytoplasmic, and mitochondrial proteins. Cells maintain a homeostatic level of O-GlcNAc by cycling the addition and removal of the sugar by O-GlcNAc transferase (OGT) or O-GlcNAcase (OGA), respectively. Methods: We used patient-derived induced pluripotent stem cells, a transgenic mouse model of AD, SH-SY5Y neuroblastoma cell lines to examine the effect of sustained O-GlcNAcase inhibition by Thiamet-G (TMG) or OGT deficiency on mitophagy using biochemical analyses. Results: Here, we established an essential role for O-GlcNAc in regulating mitophagy (mitochondria-selective autophagy). Stimulating mitophagy using urolithin A (UA) decreases cellular O-GlcNAc and elevates mitochondrial O-GlcNAc. Sustained elevation in O-GlcNAcylation via pharmacologically inhibiting OGA using Thiamet-G (TMG) increases the mitochondrial level of mitophagy protein PTEN-induced kinase 1 (PINK1) and autophagy-related protein light chain 3 (LC3). Moreover, we detected O-GlcNAc on PINK1 and TMG increases its O-GlcNAcylation level. Conversely, decreasing cellular O-GlcNAcylation by knocking down OGT decreases both PINK1 protein expression and LC3 protein expression. Mitochondria isolated from CAMKII-OGT-KO mice also had decreased PINK1 and LC3. Moreover, human brain organoids treated with TMG showed significant elevation in LC3 compared to control. However, TMG-treated AD organoids showed no changes in LC3 expression. Conclusion: Collectively, these data demonstrate that O-GlcNAc plays a crucial role in the activation and progression of mitophagy, and this activation is disrupted in AD.

Adaptive and Maladaptive DNA Breaks in Neuronal Physiology and Alzheimer's Disease.

DNA strand breaks excessively accumulate in the brains of patients with Alzheimer's disease (AD). While traditionally considered random, deleterious events, neuron activity itself induces DNA breaks, and these "adaptive" breaks help mediate synaptic plasticity and memory formation. Recent studies mapping the brain DNA break landscape reveal that despite a net increase in DNA breaks in ectopic genomic hotspots, adaptive DNA breaks around synaptic genes are lost in AD brains, and this is associated with transcriptomic dysregulation. Additionally, relationships exist between mitochondrial dysfunction, a hallmark of AD, and DNA damage, such that mitochondrial dysfunction may perturb adaptive DNA break formation, while DNA breaks may conversely impair mitochondrial function. A failure of DNA break physiology could, therefore, potentially contribute to AD pathogenesis.

Efficacy and Safety of Exogenous Ketones in People with Mild Neurocognitive Disorder and Alzheimer's Disease: A Systematic Literature Review.

CONTEXT: Mild neurocognitive disorder (NCD), formally known as mild cognitive impairment, is usually the clinical stage preceding the development of Alzheimer's disease (AD), the most prevalent major NCD, and other causes of dementia. Glucose is a major source of energy for human brain metabolism and the uptake of glucose is reduced in patients with mild NCD, AD, and other NCDs. Unlike glucose, the uptake of ketones remains normal in people with mild NCD and AD, suggesting that the use of ketone bodies may compensate for glucose energy deficiency in patients with mild NCD and AD. OBJECTIVE: The aim of this systematic review was to summarize the efficacy and safety of exogenic ketones, including medium chain triglycerides (MCTs), on cognitive function in patients with mild NCD and AD. DATA SOURCES: The Embase, MEDLINE, MEDLINE In-Process, PubMed Ahead-of-Print, Cochrane Central Register of Controlled Trials, Europe PMC databases were searched from inception to April 2022. Studies reporting cognitive function efficacy and safety outcomes from randomized controlled trials of exogenic ketones in patients with mild NCD and AD were included. DATA EXTRACTION: Data were extracted by 1 reviewer and checked by a second reviewer. Risk of bias was assessed using the Cochrane risk of bias tool, version 2. DATA ANALYSIS: This review identified 13 individual trials investigating the efficacy and safety of MCT or coconut oil for patients with mild NCD or with AD. Because of the heterogeneity of the studies, a narrative synthesis was used. CONCLUSION: Overall, improvements associated with exogenic ketones were observed in multiple aspects of cognitive abilities, although the large heterogeneity between the included studies makes it difficult to draw firm conclusions from the current literature. Although some studies investigated the impact of the apolipoprotein E ε4 allele status on treatment efficacy, the current data are insufficient to conclude whether such an effect is present. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration No. CRD42022336664.

Proteome profiling of cerebrospinal fluid using machine learning shows a unique protein signature associated with APOE4 genotype.

INTRODUCTION: Proteome changes associated with APOE4 variant carriage that are independent of Alzheimer's disease (AD) pathology and diagnosis are unknown. This study investigated APOE4 proteome changes in people with AD, mild cognitive impairment, and no impairment. METHODS: Clinical, APOE genotype, and cerebrospinal fluid (CSF) proteome and AD biomarker data was sourced from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. Proteome profiling was done using supervised machine learning. RESULTS: We found an APOE4-specific proteome signature that was independent of cognitive diagnosis and AD pathological biomarkers, and increased risk of progression to cognitive impairment. Proteins were enriched in brain regions including the caudate and cortex and cells including endothelial cells, oligodendrocytes, and astrocytes. Enriched peripheral immune cells included T cells, macrophages, and B cells. DISCUSSION: APOE4 carriers have a unique CSF proteome signature associated with a strong brain and peripheral immune and inflammatory phenotype that likely underlies APOE4 carriers' vulnerability to cognitive decline and AD.

Spatial Dissection of the Distinct Cellular Responses to Normal Aging and Alzheimer's Disease in Human Prefrontal Cortex at Single-Nucleus Resolution.

Aging significantly elevates the risk for Alzheimer's disease (AD), contributing to the accumulation of AD pathologies, such as amyloid-ß (Aß), inflammation, and oxidative stress. The human prefrontal cortex (PFC) is highly vulnerable to the impacts of both aging and AD. Unveiling and understanding the molecular alterations in PFC associated with normal aging (NA) and AD is essential for elucidating the mechanisms of AD progression and developing novel therapeutics for this devastating disease. In this study, for the first time, we employed a cutting-edge spatial transcriptome platform, STOmics® SpaTial Enhanced Resolution Omics-sequencing (Stereo-seq), to generate the first comprehensive, subcellular resolution spatial transcriptome atlas of the human PFC from six AD cases at various neuropathological stages and six age, sex, and ethnicity matched controls. Our analyses revealed distinct transcriptional alterations across six neocortex layers, highlighted the AD-associated disruptions in laminar architecture, and identified changes in layer-to-layer interactions as AD progresses. Further, throughout the progression from NA to various stages of AD, we discovered specific genes that were significantly upregulated in neurons experiencing high stress and in nearby non-neuronal cells, compared to cells distant from the source of stress. Notably, the cell-cell interactions between the neurons under the high stress and adjacent glial cells that promote Aß clearance and neuroprotection were diminished in AD in response to stressors compared to NA. Through cell-type specific gene co-expression analysis, we identified three modules in excitatory and inhibitory neurons associated with neuronal protection, protein dephosphorylation, and negative regulation of Aß plaque formation. These modules negatively correlated with AD progression, indicating a reduced capacity for toxic substance clearance in AD subject samples. Moreover, we have discovered a novel transcription factor, ZNF460, that regulates all three modules, establishing it as a potential new therapeutic target for AD. Overall, utilizing the latest spatial transcriptome platform, our study developed the first transcriptome-wide atlas with subcellular resolution for assessing the molecular alterations in the human PFC due to AD. This atlas sheds light on the potential mechanisms underlying the progression from NA to AD.

Hippocampal transcriptome-wide association study and pathway analysis of mitochondrial solute carriers in Alzheimer's disease.

The etiopathogenesis of late-onset Alzheimer's disease (AD) is increasingly recognized as the result of the combination of the aging process, toxic proteins, brain dysmetabolism, and genetic risks. Although the role of mitochondrial dysfunction in the pathogenesis of AD has been well-appreciated, the interaction between mitochondrial function and genetic variability in promoting dementia is still poorly understood. In this study, by tissue-specific transcriptome-wide association study (TWAS) and further meta-analysis, we examined the genetic association between mitochondrial solute carrier family (SLC25) genes and AD in three independent cohorts and identified three AD-susceptibility genes, including SLC25A10, SLC25A17, and SLC25A22. Integrative analysis using neuroimaging data and hippocampal TWAS-predicted gene expression of the three susceptibility genes showed an inverse correlation of SLC25A22 with hippocampal atrophy rate in AD patients, which outweighed the impacts of sex, age, and apolipoprotein E4 (ApoE4). Furthermore, SLC25A22 downregulation demonstrated an association with AD onset, as compared with the other two transcriptome-wide significant genes. Pathway and network analysis related hippocampal SLC25A22 downregulation to defects in neuronal function and development, echoing the enrichment of SLC25A22 expression in human glutamatergic neurons. The most parsimonious interpretation of the results is that we have identified AD-susceptibility genes in the SLC25 family through the prediction of hippocampal gene expression. Moreover, our findings mechanistically yield insight into the mitochondrial cascade hypothesis of AD and pave the way for the future development of diagnostic tools for the early prevention of AD from a perspective of precision medicine by targeting the mitochondria-related genes.

Multi-Omics after O-GlcNAc Alteration Identifies Cellular Processes Working Synergistically to Promote Aneuploidy.

Pharmacologic or genetic manipulation of O-GlcNAcylation, an intracellular, single sugar post-translational modification, are difficult to interpret due to the pleotropic nature of O-GlcNAc and the vast signaling pathways it regulates. To address this issue, we employed either OGT (O-GlcNAc transferase), OGA (O-GlcNAcase) liver knockouts, or pharmacological inhibition of OGA coupled with multi-Omics analysis and bioinformatics. We identified numerous genes, proteins, phospho-proteins, or metabolites that were either inversely or equivalently changed between conditions. Moreover, we identified pathways in OGT knockout samples associated with increased aneuploidy. To test and validate these pathways, we induced liver growth in OGT knockouts by partial hepatectomy. OGT knockout livers showed a robust aneuploidy phenotype with disruptions in mitosis, nutrient sensing, protein metabolism/amino acid metabolism, stress response, and HIPPO signaling demonstrating how OGT is essential in controlling aneuploidy pathways. Moreover, these data show how a multi-Omics platform can discern how OGT can synergistically fine-tune multiple cellular pathways.

Late-Life Alcohol Exposure Does Not Exacerbate Age-Dependent Reductions in Mouse Spatial Memory and Brain TFEB Activity.

Alcohol consumption is believed to affect Alzheimer's disease (AD) risk, but the contributing mechanisms are not well understood. A potential mediator of the proposed alcohol-AD connection is autophagy, a degradation pathway that maintains organelle and protein homeostasis. Autophagy is in turn regulated through the activity of Transcription factor EB (TFEB), which promotes lysosome and autophagy-related gene expression. To explore the effect of alcohol on brain TFEB and autophagy, we exposed young (3-month old) and aged (23-month old) mice to two alcohol-feeding paradigms and assessed biochemical, transcriptome, histology, and behavioral endpoints. In young mice, alcohol decreased hippocampal nuclear TFEB staining but increased SQSTM1/p62, LC3-II, ubiquitinated proteins, and phosphorylated Tau. Hippocampal TFEB activity was lower in aged mice than it was in young mice, and Gao-binge alcohol feeding did not worsen the age-related reduction in TFEB activity. To better assess the impact of chronic alcohol exposure, we fed young and aged mice alcohol for four weeks before completing Morris Water and Barnes Maze spatial memory testing. The aged mice showed worse spatial memory on both tests. While alcohol feeding slightly impaired spatial memory in the young mice, it had little effect or even slightly improved spatial memory in the aged mice. These findings suggest that aging is a far more important driver of spatial memory impairment and reduced autophagy flux than alcohol consumption.

Protocol for a single-arm, pilot trial of creatine monohydrate supplementation in patients with Alzheimer's disease.

BACKGROUND: Impaired brain bioenergetics is a pathological hallmark of Alzheimer's disease (AD) and is a compelling target for AD treatment. Patients with AD exhibit dysfunction in the brain creatine (Cr) system, which is integral in maintaining bioenergetic flux. Recent studies in AD mouse models suggest Cr supplementation improves brain mitochondrial function and may be protective of AD peptide pathology and cognition. AIMS: The Creatine to Augment Bioenergetics in Alzheimer's disease (CABA) study is designed to primarily assess the feasibility of supplementation with 20 g/day of creatine monohydrate (CrM) in patients with cognitive impairment due to AD. Secondary aims are designed to generate preliminary data investigating changes in brain Cr levels, cognition, peripheral and brain mitochondrial function, and muscle strength and size. METHODS: CABA is an 8-week, single-arm pilot study that will recruit 20 patients with cognitive impairment due to AD. Participants attend five in-person study visits: two visits at baseline to conduct screening and baseline assessments, a 4-week visit, and two 8-week visits. Outcomes assessment includes recruitment, retention, and compliance, cognitive testing, magnetic resonance spectroscopy of brain metabolites, platelet and lymphocyte mitochondrial function, and muscle strength and morphology at baseline and 8 weeks. DISCUSSION: CABA is the first study to investigate CrM as a potential treatment in patients with AD. The pilot data generated by this study are pertinent to inform the design of future large-scale efficacy trials. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05383833 , registered on 20 May 2022.

Loss of Adaptive DNA Breaks in Alzheimer's Disease Brains.

Background: DNA breaks accumulate in Alzheimer's disease (AD) brains. While their role as true genomic lesions is recognized, DNA breaks also support cognitive function by facilitating the expression of activity-dependent immediate early genes. This process involves TOP2B, a DNA topoisomerase that catalyzes the formation of DNA double-strand breaks. Objective: To characterize how AD impacts adaptive DNA breaks at nervous system genes. Methods: We leveraged the ability of DNA single- and double-strand breaks to activate poly(ADP-ribose) polymerases (PARPs) that conjugate poly(ADP-ribose) (PAR) to adjacent proteins. To characterize the genomic sites harboring DNA breaks in AD brains, nuclei extracted from 3 AD and 3 non-demented autopsy brains (frontal cortex, all male donors, age 78 to 91 years of age) were analyzed through CUT&RUN in which we targeted PAR with subsequent DNA sequencing. Results: Although the AD brains contained 19.9 times more PAR peaks than the non-demented brains, PAR peaks at nervous system genes were profoundly lost in AD brains, and the expression of these genes was downregulated. This result is consistent with our previous CUT&RUN targeting γH2AX, which marks DNA double-strand breaks. In addition, TOP2B expression was significantly decreased in the AD brains. Conclusions: Although AD brains contain a net increase in DNA breaks, adaptive DNA breaks at nervous system genes are lost in AD brains. This could potentially reflect diminished TOP2B expression and contribute to impaired neuron function and cognition in AD patients.

Traumatic Brain Injury Alters the Trajectory of Age-Related Mitochondrial Change.

Background: Some epidemiologic studies associate traumatic brain injury (TBI) with Alzheimer's disease (AD). Objective: To test whether a TBI-induced acceleration of age-related mitochondrial change could potentially mediate the reported TBI-AD association. Methods: We administered unilateral controlled cortical impact (CCI) or sham injuries to 5-month-old C57BL/6J and tau transgenic rTg4510 mice. In the non-transgenics, we assessed behavior (1-5 days, 1 month, and 15 months), lesion size (1 and 15 months), respiratory chain enzymes (1 and 15 months), and mitochondrial DNA copy number (mtDNAcn) (1 and 15 months) after CCI/sham. In the transgenics we quantified post-injury mtDNAcn and tangle burden. Results: In the non-transgenics CCI caused acute behavioral deficits that improved or resolved by 1-month post-injury. Protein-normalized complex I and cytochrome oxidase activities were not significantly altered at 1 or 15 months, although complex I activity in the CCI ipsilesional cortex declined during that period. Hippocampal mtDNAcn was not altered by injury at 1 month, increased with age, and rose to the greatest extent in the CCI contralesional hippocampus. In the injured then aged transgenics, the ipsilesional hippocampus contained less mtDNA and fewer tangles than the contralesional hippocampus; mtDNAcn and tangle counts did not correlate. Conclusions: As mice age their brains increase mtDNAcn as part of a compensatory response that preserves mitochondrial function, and TBI enhances this response. TBI may, therefore, increase the amount of compensation required to preserve late-life mitochondrial function. If TBI does modify AD risk, altering the trajectory or biology of aging-related mitochondrial changes could mediate the effect.

Protection against Aß-induced neuronal damage by KU-32: PDHK1 inhibition as important target.

A feature of most neurodegenerative diseases is the presence of "mis-folded proteins" that form aggregates, suggesting suboptimal activity of neuronal molecular chaperones. Heat shock protein 90 (Hsp90) is the master regulator of cell responses to "proteotoxic" stresses. Some Hsp90 modulators activate cascades leading to upregulation of additional chaperones. Novobiocin is a modulator at the C-terminal ATP-binding site of Hsp90. Of several novobiocin analogs synthesized and tested for protection against amyloid beta (Aß)-induced neuronal death, "KU-32" was the most potent in protecting primary neurons, but did not increase expression of other chaperones believed to help clear misfolded proteins. However, KU-32 reversed Aß-induced superoxide formation, activated Complex I of the electron transfer chain in mitochondria, and blocked the Aß-induced inhibition of Complex I in neuroblastoma cells. A mechanism for these effects of KU-32 on mitochondrial metabolism appeared to be the inhibition of pyruvate dehydrogenase kinase (PDHK), both in isolated brain mitochondria and in SH-SY5Y cells. PDHK inhibition by the classic enzyme inhibitor, dichloroacetate, led to neuroprotection from Aß25-35-induced cell injury similarly to KU-32. Inhibition of PDHK in neurons would lead to activation of the PDH complex, increased acetyl-CoA generation, stimulation of the tricarboxylic acid cycle and Complex I in the electron transfer chain, and enhanced oxidative phosphorylation. A focus of future studies may be on the potential value of PDHK as a target in AD therapy.

Mitochondria-sequestered Aß renders synaptic mitochondria vulnerable in the elderly with a risk of Alzheimer disease.

Mitochondria are critical for neurophysiology, and mitochondrial dysfunction constitutes a characteristic pathology in both brain aging and Alzheimer disease (AD). Whether mitochondrial deficiency in brain aging and AD is mechanistically linked, however, remains controversial. We report a correlation between intrasynaptosomal amyloid ß 42 (Aß42) and synaptic mitochondrial bioenergetics inefficiency in both aging and amnestic mild cognitive impairment, a transitional stage between normal aging and AD. Experiments using a mouse model expressing nonmutant humanized Aß (humanized Aß-knockin [hAß-KI] mice) confirmed the association of increased intramitochondrial sequestration of Aß42 with exacerbated synaptic mitochondrial dysfunction in an aging factor- and AD risk-bearing context. Also, in comparison with global cerebral Aß, intramitochondrial Aß was relatively preserved from activated microglial phagocytosis in aged hAß-KI mice. The most parsimonious interpretation of our results is that aging-related mitochondrial Aß sequestration renders synaptic mitochondrial dysfunction in the transitional stage between normal aging and AD. Mitochondrial dysfunction in both brain aging and the prodromal stage of AD may follow a continuous transition in response to escalated intraneuronal, especially intramitochondrial Aß, accumulation. Moreover, our findings further implicate a pivotal role of mitochondria in harboring early amyloidosis during the conversion from normal to pathological aging.

FUS G559A Mutation in a Patient with a Frontotemporal Dementia-Motor Neuron Disease Compatible Syndrome: A Case Report.

Fused in sarcoma (FUS) mutations cause frontotemporal dementia (FTD) and motor neuron disease (MND). Here, we describe a 43-year-old man with progressive behavioral and cognitive change, myelopathy, clinical and electrophysiologic evidence of MND, and a FUS variant of unknown significance (VUS). This VUS, a heterozygous G559A transition (Gly187Ser), was previously reported in a patient with sporadic MND and affects important FUS biophysical properties. While this rare variant's presence in a second patient with a related neurodegenerative syndrome does not establish pathogenicity, it raises the question of whether its association with our patient is coincidental and increases the possibility that FUS G559A is pathogenic.

Blood-Based Transcriptomic Biomarkers Are Predictive of Neurodegeneration Rather Than Alzheimer's Disease.

Alzheimer's disease (AD) is a growing global health crisis affecting millions and incurring substantial economic costs. However, clinical diagnosis remains challenging, with misdiagnoses and underdiagnoses being prevalent. There is an increased focus on putative, blood-based biomarkers that may be useful for the diagnosis as well as early detection of AD. In the present study, we used an unbiased combination of machine learning and functional network analyses to identify blood gene biomarker candidates in AD. Using supervised machine learning, we also determined whether these candidates were indeed unique to AD or whether they were indicative of other neurodegenerative diseases, such as Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Our analyses showed that genes involved in spliceosome assembly, RNA binding, transcription, protein synthesis, mitoribosomes, and NADH dehydrogenase were the best-performing genes for identifying AD patients relative to cognitively healthy controls. This transcriptomic signature, however, was not unique to AD, and subsequent machine learning showed that this signature could also predict PD and ALS relative to controls without neurodegenerative disease. Combined, our results suggest that mRNA from whole blood can indeed be used to screen for patients with neurodegeneration but may be less effective in diagnosing the specific neurodegenerative disease.

Alzheimer's disease cortical morphological phenotypes are associated with TOMM40'523-APOE haplotypes.

Both the APOE ε4 and TOMM40 rs10524523 ("523") genes have been associated with risk for Alzheimer's disease (AD) and neuroimaging biomarkers of AD. No studies have investigated the relationship of TOMM40'523-APOE ε4 on the structural complexity of the brain in AD individuals. We quantified brain morphology and multiple cortical attributes in individuals with mild cognitive impairment (MCI) and AD, then tested whether APOE ε4 or TOMM40 poly-T genotypes were related to AD morphological biomarkers in cognitively unimpaired (CU) and MCI/AD individuals. We identified several AD-specific phenotypes in brain morphology and found that TOMM40 poly-T short alleles are associated with early, AD-specific brain morphological differences in healthy aging. We observed decreased cortical thickness, sulcal depth, and fractal dimension in CU individuals with the poly-T short alleles. Moreover, in MCI/AD participants, the APOE ε4 (TOMM40 L) individuals had a higher rate of gene-related morphological markers indicative of AD. Our data suggest that TOMM40'523 is associated with early brain structure variations in the precuneus, temporal, and limbic cortices.

TOMM40 '523 Genotype Distinguishes Patterns of Cognitive Improvement for Executive Function in APOEɛ3 Homozygotes.

BACKGROUND: TOMM40 '523 has been associated with cognitive performance and risk for developing Alzheimer's disease independent of the effect of APOE genotype. Few studies have considered the longitudinal effect of this genotype on change in cognition over time. OBJECTIVE: Our objective was to evaluate the relationship between TOMM40 genotype status and change in cognitive performance in the TOMMORROW study, which was designed to prospectively evaluate an algorithm that includes TOMM40 '523 for genetic risk for conversion to mild cognitive impairment. METHODS: We used latent growth curve models to estimate the effect of TOMM40 allele carrier (short, very long) status on the intercept and slope of change in cognitive performance in four broad cognitive domains (attention, memory, executive function, and language) and a combined overall cognitive score over 30 months. RESULTS: TOMM40 very long allele carriers had significantly lower baseline performance for the combined overall cognitive function score (B = -0.088, p = 0.034) and for the executive function domain score (B = -0.143, p = 0.013). Slopes for TOMM40 very long carriers had significantly greater increases over time for the executive function domain score only. In sensitivity analyses, the results for executive function were observed in participants who remained clinically stable, but not in those who progressed clinically over the study duration. CONCLUSIONS: Our results add to the growing body of evidence that TOMM40, in the absence of APOEɛ4, may contribute to cognitive changes with aging and dementia and support the view that mitochondrial function is an important contributor to Alzheimer's disease risk.