Amino acid patterns predict white matter integrity measures in the brain in patients across the Alzheimer's disease continuum.

White matter (WM) degeneration is suggested to predict the early signs of Alzheimer's disease (AD). The exact structural regions of brain circuitry involved are not known. This study aims to examine the associations between WM tract integrity, represented by the diffusion tensor imaging (DTI) measures, and AD diagnosis and to denote the key substrates in predicting AD. It included DTI measures of mean diffusivity (MD), fractional anisotropy, radial diffusivity and axial diffusivity of 18 main WM tracts in 84 non-Hispanic white participants from the Alzheimer's Disease Neuroimaging Initiative dataset. The multivariable general linear model was used to examine the association of AD diagnosis with each DTI measure adjusting for age, gender and education. The corpus callosum, fornix, cingulum hippocampus, uncinate fasciculus, sagittal striatum, left posterior thalamic radiation and fornix-stria terminalis showed significant increases in MD, radial and axial diffusivity, whereas the splenium of corpus callosum and the fornix showed significant decreases in fractional anisotropy among AD patients. Variable cluster analysis identified that hippocampus volume, mini-mental state examination (MMSE), cingulate gyrus/hippocampus, inferior fronto-occipital fasciculus and uncinate fasciculus are highly correlated in one cluster with MD measures. In conclusion, there were significant differences in DTI measures between the brain WM of AD patients and controls. Age is the risk factor associated with AD, not gender or education. Right cingulum gyrus and right uncinate fasciculus are particularly affected, correlating well with a cognitive test MMSE and MD measures for dementia in AD patients and could be a region of focus for AD staging.

CSF sTREM2 has opposite association with brain structural damage rate at early and late stage of Alzheimer’s disease

The blood biomarker neurofilament light (NFL) is one of the most widely used for monitoring Alzheimer's disease (AD). According to recent research, a higher NFL plasma level has a substantial predictive value for cognitive deterioration in AD patients. Diffusion tensor imaging (DTI) is an MRI-based approach for detecting neurodegeneration, white matter (WM)disruption, and synaptic damage. There have been few studies on the relationship between plasma NFL and WM microstructure integrity. The goal of the current study is to assessthe associations between plasma levels of NFL, CSF total tau, phosphorylated tau181 (P-tau181), and amyloid-β (Aβ) with WM microstructural alterations. We herein have investigated the cross-sectional association between plasma levels of NFL and WM microstructural alterations as evaluated by DTI in 92 patients with mild cognitive impairment (MCI) provided by Alzheimer's Disease Neuroimaging Initiative (ADNI) participants. We analyzed the potential association between plasma NFL levels and radial diffusivity (RD), axial diffusivity (AxD), mean diffusivity (MD), and fractional anisotropy (FA) in each region of the Montreal Neurological Institute and Hospital(MNI) atlas, using simple linear regression models stratified by age, sex, and APOE ε4 genotype. Our findings demonstrated a significant association between plasma NFL levels and disrupted WM microstructureacross the brain. In distinct areas, plasma NFL has a negative association with FA in the fornix, fronto-occipital fasciculus, corpus callosum, uncinate fasciculus, internal capsule, and corona radiata and a positive association with RD, AxD, and MD values in sagittal stratum, corpus callosum, fronto-occipital fasciculus, corona radiata, internal capsule, thalamic radiation, hippocampal cingulum, fornix, and cingulum. Lower FA and higher RD, AxD, and MD values are related to demyelination and degeneration in WM. Our findings revealed that the level of NFL in the blood is linked to WM alterations in MCI patients. Plasma NFL has the potential to be a biomarker for microstructural alterations. However, further longitudinal studies are necessary to validate the predictive role of plasma NFL in cognitive decline.

Decision letter: Stage-dependent differential influence of metabolic and structural networks on memory across Alzheimer’s disease continuum

Cerebral amyloid-β accumulation and changes in white matter (WM) microstructure are imaging characteristics in clinical Alzheimer's disease and have also been reported in cognitively healthy older adults. However, the relationship between amyloid deposition and WM microstructure is not well understood. Here, we investigated the impact of quantitative cerebral amyloid load on WM microstructure in a group of cognitively healthy older adults. AV45-positron emission tomography and diffusion tensor imaging (DTI) scans of forty-four participants (age-range: 60 to 89 years) from the Alzheimer's Disease Neuroimaging Initiative were analyzed. Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (DR), and axial diffusivity (DA) were calculated to characterize WM microstructure. Regression analyses demonstrated non-linear (quadratic) relationships between amyloid deposition and FA, MD, as well as RD in widespread WM regions. At low amyloid burden, higher deposition was associated with increased FA as well as decreased MD and DR. At higher amyloid burden, higher deposition was associated with decreased FA as well as increased MD and DR. Additional regression analyses demonstrated an interaction effect between amyloid load and global WM FA, MD, DR, and DA on cognition, suggesting that cognition is only affected when amyloid is increasing and WM integrity is decreasing. Thus, increases in FA and decreases in MD and RD with increasing amyloid load at low levels of amyloid burden may indicate compensatory processes that preserve cognitive functioning. Potential mechanisms underlying the observed non-linear association between amyloid deposition and DTI metrics of WM microstructure are discussed.

Recent studies have shown that amyloid-β (Aβ) burden influenced white matter (WM) integrity before the onset of dementia. To assess whether the effects of Aβ burden on WM integrity in cognitively normal (CN) individuals were regionally specific. Our cohort consisted of 71 CNs from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database who underwent both AV45 amyloid-PET and diffusion tensor imaging. Standardized uptake value ratio (SUVR) was computed across four bilateral regions of interest (ROIs) corresponding to four stages of in vivo amyloid staging model (Amyloid stages I-IV). Linear regression models were conducted in entire CN group and between APOEɛ4 carriers and non-carriers. Our results indicated that higher global Aβ-SUVR was associated with higher mean diffusivity (MD) in the entire CN group (p = 0.023), and with both higher MD (p = 0.015) and lower fractional anisotropy (FA) (p = 0.026) in APOEɛ4 carriers. Subregion analysis showed that higher Amyloid stage I-II Aβ-SUVRs were associated with higher MD (Stage-1: p = 0.030; Stage-2: p = 0.016) in the entire CN group, and with both higher MD (Stage-1: p = 0.004; Stage-2: p = 0.010) and lower FA (Stage-1: p = 0.022; Stage-2: p = 0.014) in APOEɛ4 carriers. No associations were found in APOEɛ4 non-carriers and in Amyloid stage III-IV ROIs. Our results indicated that the effects of Aβ burden on WM integrity in CNs might be regionally specific, particularly in Amyloid stage I-II ROIs, and modulated by APOEɛ4 status.

Associations between neuropsychiatric symptoms, white matter microstructural integrity, and diagnostic status in the spectrum of Alzheimer’s disease

Multimer detection system-oligomeric amyloid-β (MDS-OAβ) measure plasma OAβ level, which is associated with earlier Alzheimer's disease (AD) pathology. However, no study has investigated MDS-OAβ differences in cognitive normal older adults (CN) with or without cerebral Aβ burden and its correlation with Aβ deposition and white matter (WM) integrity. To investigate associations among cerebral Aβ burden, MDS-OAβ, and WM integrity in CN. This is a single center, cross-sectional study which used data from Catholic Aging Brain Imaging (CABI) database. CABI database contains brain scans of patients who visited the outpatient clinic at Catholic Brain Health Center, Yeouido St. Mary's Hospital, The Catholic University of Korea, between 2017 and 2022. A total 34 amyloid-PET negative CN and 23 amyloid-PET positive CN were included. Plasma Aβ level using MDS-OAβ, cerebral Aβ deposition level using global standardized uptake value ratio (SUVR) values, WM integrity using fractional anisotropy (FA) and mean diffusivity (MD), and cortical thickness from structural MRI were utilized. The amyloid-PET positive group showed higher MDS-OAβ level than the amyloid-PET negative group (0.997 ± 0.19 vs. 0.79 ± 0.28, P <0.005), but they did not differ in WM integrity or cortical thickness. The MDS-OAβ positive group showed higher global cerebral Aβ deposition or mean global SUVR values (0.609 ± 0.135 vs. 0.533 ± 0.121 vs. P <0.05), lower regional FA of left forceps minor and the right superior longitudinal fasciculus (family-wise error rate, p <0.05), and lower cortical thickness of left fusiform (p <0.05, Monte Carlo simulation) than the MDS-OAβ negative group. MDS-OAβ was positively associated with global cerebral Aβ deposition (r=0.278, P <0.05) and negatively associated (r = - 0.324, P < 0.05) with regional WM integrity. In this study, MDS-OAβ value demonstrated earlier and different AD pathology than cerebral Aβ retention according to amyloid-PET. Longitudinal studies are needed to elucidate the causal relationships of plasma OAβ and cerebral Aβ with WM integrity disturbance and cortical atrophy during the AD trajectory.

Longitudinal white matter change in frontotemporal dementia subtypes and sporadic late onset Alzheimer's disease

BackgroundCarrying the Apolipoprotein (APOE) ε4 allele lowers age of onset and increases Alzheimer's disease (AD) risk. Neuropathological findings suggest a mixed etiology in many AD patients, and vascular pathology is common.ObjectiveThis study tested the interactive effect of APOE status and multiple vascular comorbidities on white matter (WM) microstructure in aging and early AD.Methods195 participants from the VPH-DARE@IT dataset were stratified in low/high vascular burden based on the Framingham Risk Score (BMI version). Tract-based spatial statistics was used for WM analyses.ResultsThere was a main effect of APOE, with APOE ɛ4 carriers having higher fractional anisotropy (FA) and lower axial diffusivity (AxD), mean diffusivity (MD), and radial diffusivity (RD) than non-carriers. There was a main effect of vascular burden with lower FA and higher AxD, MD, and RD in the high-burden than the low-burden group. A significant interaction between APOE genotype and vascular burden was also found for all diffusion indices. Post-hoc comparisons revealed lower left hemisphere WM integrity when comparing the low risk group (i.e., non-carriers low burden) to intermediate risk groups (i.e., non-carriers high burden or ɛ4 carriers low burden). The contrasts between the two intermediate risk groups showed altered WM integrity bilaterally. Only the non-carriers high burden showed greater alterations in WM integrity when compared with the high risk group (i.e., ɛ4 carriers high burden) mainly in right hemisphere tracts.ConclusionsThese findings indicate an interactive effect of a risk gene and vascular comorbidities on WM integrity in aging and early AD.

Early degeneration of the cholinergic nucleus basalis of Meynert contributes to cognitive decline in Alzheimer's disease (AD). Microstructural damage in downstream cholinergic tracts-the cingulum bundle (CGC), entorhinal cortex (EC), and uncinate fasciculus (UNC)-often precedes volumetric atrophy. While cholinesterase inhibitors (ChEIs) can preserve cortical and hippocampal volume, their influence on white-matter integrity is unclear. To determine whether ChEIs slow microstructural decline in four cholinergic tracts (CGC, EC, UNC, posterior thalamic radiation [PTR]) in mild cognitive impairment (MCI), and whether baseline cognitive status modulates this effect. Diffusion-tensor imaging from the Alzheimer's Disease Neuroimaging Initiative was analyzed in 46 MCI participants receiving donepezil or rivastigmine and 62 untreated MCI controls, each scanned serially over two years. Fractional anisotropy (FA) and mean diffusivity (MD) indexed tract integrity. Linear mixed-effects models tested time × medication × baseline cognition (ADAS-Cog13) interactions, adjusting for age, sex, APOE ε4, and white-matter hyperintensity burden. Across groups, CGC showed progressive degeneration (FA↓, MD↑; p < 0.001). Significant three-way interactions emerged for MD in bilateral CGC, FA in right EC, and MD in left PTR (all p < 0.01). ChEI users with milder baseline impairment (lower ADAS-Cog13) exhibited attenuated FA loss and MD increase, indicating slower microstructural decline; those with greater initial impairment derived minimal benefit. No medication effect was detected in UNC. ChEIs confer tract-specific, stage-dependent protection of cholinergic white matter, particularly in early MCI. The findings underscore the value of initiating ChEI therapy before substantial cognitive deterioration and highlight the need for stage-tailored interventions aimed at preserving white-matter integrity in prodromal AD.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by early metabolic and structural brain changes. These alterations are often detectable during mild cognitive impairment due to AD (AD-MCI), a prodromal stage of the disease. The posterior cingulate cortex (PCC), a critical brain region involved in memory and self-referential processing, is particularly vulnerable to these changes. We recruited 21 healthy controls (HC) and 20 AD-MCI patients to participate in this study. Point-Resolved Echo Spin Spectroscopy (PRESS) combined with MEGA-PRESS was employed to accurately measure levels of Gamma-Aminobutyric Acid (GABA) and Glx (Combination of Glutamate and Glutamine) in the PCC. Additionally, diffusion tensor imaging (DTI) was utilized to assess white matter (WM) microstructure integrity. Key metabolites, including N-acetylaspartate (NAA), choline (Cho), and myo-inositol (mI), were quantified to provide insights into neuronal health and metabolic status, while WM integrity was evaluated using fractional anisotropy (FA) and mean diffusivity (MD) metrics. In the PCC, AD-MCI patients exhibited a significant reduction in tNAA/tCr (1.22 ± 0.09 vs. HC 1.32 ± 0.07, p < 0.001) and NAA/mI (1.22 ± 0.12 vs. HC 1.44 ± 0.12, p < 0.001), along with an increase in mI/Cr (1.84 ± 0.28 vs. HC 1.60 ± 0.29, p = 0.012) and decreased GABA+/water (2.23 ± 0.78 vs. HC 2.98 ± 0.73, p = 0.003). Diffusion metrics revealed higher mean diffusivity in PCC-connected gray matter (GM_MD: 10.40 ± 0.79 vs. 9.53 ± 0.80 × 10⁻⁴ mm²/s, p < 0.01) and white matter (WM_MD: 0.09 ± 0.01 vs. 0.08 ± 0.01 × 10⁻² mm²/s, p < 0.01). Notably, in AD-MCI, NAA/mI was negatively correlated with WM_MD (r = - 0.462, p = 0.047), and tNAA/tCr was positively correlated with WM_FA (r = 0.580, p = 0.009). PCC neurochemical-microstructural decoupling (NAA/mI-MD dissociation with preserved tNAA/tCr-FA coupling) marks early AD progression. This dissociation pattern, reflecting concurrent neuronal dysfunction and compensatory glial responses, proposes a novel multimodal biomarker for tracking axonal degeneration prior to overt cognitive decline.

Battle against Alzheimer's Disease: The Scope and Potential Value of Magnetic Resonance Imaging Biomarkers

Amnestic mild cognitive impairment (MCI) is a transitional stage between normal aging and Alzheimer's disease (AD). However, the clinical conversion from MCI to AD is unpredictable. Hence, identification of noninvasive biomarkers able to detect early changes induced by dementia is a pressing need. To explore the added value of histogram analysis applied to measures derived from diffusion tensor imaging (DTI) for detecting brain tissue differences between AD, MCI, and healthy subjects (HS). Prospective. A local cohort (57 AD, 28 MCI, 23 HS), and an Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort (41 AD, 58 MCI, 41 HS). 3T. Dual-echo turbo spin echo (TSE); fluid-attenuated inversion recovery (FLAIR); modified-driven-equilibrium-Fourier-transform (MDEFT); inversion-recovery spoiled gradient recalled (IR-SPGR); diffusion tensor imaging (DTI). Normal-appearing white matter (NAWM) masks were obtained using the T1 -weighted volumes for tissue segmentation and T2 -weighted images for removal of hyperintensities/lesions. From DTI images, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AXD), and radial diffusivity (RD) were obtained. NAWM histograms of FA, MD, AXD, and RD were derived and characterized estimating: peak height, peak location, mean value (MV), and quartiles (C25, C50, C75), which were compared between groups. Receiver operating characteristic (ROC) and area under ROC curves (AUC) were calculated. To confirm our results, the same analysis was repeated on the ADNI dataset. One-way analysis of variance (ANOVA), post-hoc Student's t-test, multiclass ROC analysis. For the local cohort, C25 of AXD had the maximum capability of group discrimination with AUC of 0.80 for "HS vs. patients" comparison and 0.74 for "AD vs. others" comparison. For the ADNI cohort, MV of AXD revealed the maximum group discrimination capability with AUC of 0.75 for "HS vs. patients" comparison and 0.75 for "AD vs. others" comparison. AXD of NAWM might be an early marker of microstructural brain tissue changes occurring during the AD course and might be useful for assessing disease progression. 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017.

Alzheimer's Disease (AD) is characterized by cognitive impairments that hinder daily activities and lead to personal and behavioral problems. Plasma hyperphosphorylated tau protein at threonine 181 (p-tau181) has recently emerged as a new sensitive tool for the diagnosis of AD patients. We herein investigated the association of plasma P-tau181 and white matter (WM) microstructural changes in AD. We obtained data from a large prospective cohort of elderly individuals participating in the Alzheimer's Disease Neuroimaging Initiative (ADNI), which included baseline measurements of plasma P-tau181 and imaging findings. A subset of 41 patients with AD, 119 patients with mild cognitive impairments (MCI), and 43 healthy controls (HC) was included in the study, all of whom had baseline blood P-tau181 levels and had also undergone Diffusion Tensor Imaging. The analysis revealed that the plasma level of P-tau181 has a positive correlation with changes in Mean Diffusivity (MD), Radial Diffusivity (RD), and Axial Diffusivity (AxD), but a negative with Fractional Anisotropy (FA) parameters in WM regions of all participants. There is also a significant association between WM microstructural changes in different regions and P-tau181 plasma measurements within each MCI, HC, and AD group. In conclusion, our findings clarified that plasma P-tau181 levels are associated with changes in WM integrity in AD. P-tau181 could improve the accuracy of diagnostic procedures and support the application of blood-based biomarkers to diagnose WM neurodegeneration. Longitudinal clinical studies are also needed to demonstrate the efficacy of the P-tau181 biomarker and predict its role in structural changes.