Microbiome-derived indole-3-lactic acid reduces amyloidopathy through aryl-hydrocarbon receptor activation.

Alzheimer's disease (AD) pathogenesis has been associated with the gut microbiome and its metabolites, though the specific mechanisms have remained unclear. In our study, we used a multi-omics approach to identify specific microbial strains and metabolites that could potentially mitigate amyloidopathy in 5xFAD mice, a widely used model for AD research. Among the microbial strains tested, three showed promising results in reducing soluble amyloid-beta (Aß) levels. Plasma metabolomics analysis revealed an enrichment of tryptophan (Trp) and indole-3-lactic acid (ILA) in mice with reduced soluble Aß levels, suggesting a potential preventative role. The administration of a combined treatment of Trp and ILA prevented both Aß accumulation and cognitive impairment in the 5xFAD mice. Our investigation into the mechanism revealed that ILA's effect on reducing Aß levels was mediated through the activation of microglia and astrocytes, facilitated by the aryl hydrocarbon receptor (AhR) signaling pathway. These mechanisms were verified through experiments in 5xFAD mice that included an additional group with the administration of ILA alone, as well as in vitro experiments using an AhR inhibitor. Clinical data analysis revealed a greater abundance of Lactobacillus reuteri in the gut of healthy individuals compared to those at early stages of Aß accumulation or with mild cognitive impairment. Additionally, human post-mortem brain analyses showed an increased expression of genes associated with the AhR signaling pathway in individuals without AD, suggesting a protective effect against AD progression. Our results indicate that ILA from gut microbes could inhibit the progression of amyloidopathy in 5xFAD mice through activation of AhR signaling in the brain.

Circadian rest-activity rhythm and longitudinal brain changes underlying late-life cognitive decline.

AIM: The neurobiological substrates underlying the relationship of circadian rest-activity rhythm (RAR) alteration with accelerated late-life cognitive decline are not clearly understood. In the present study, the longitudinal relationship of objectively measured circadian RAR with in vivo Alzheimer disease (AD) pathologies and cerebrovascular injury was investigated in older adults without dementia. METHODS: The present study included 129 participants without dementia who participated in the KBASE (Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease) cohort. All participants underwent actigraphy at baseline and two consecutive [11 C] Pittsburgh compound-B positron emission tomography (PET), [18 F] fluorodeoxyglucose-PET, magnetic resonance imaging, and Mini-Mental State Examination (MMSE) at baseline and at a 2-year follow-up assessment. The associations of circadian RAR with annualized change in neuroimaging measures including global amyloid-beta retention, AD-signature region cerebral glucose metabolism (AD-CM), and white matter hyperintensity volume were examined. RESULTS: Delayed acrophase at baseline was significantly associated with greater annualized decline of AD-CM over a 2-year period, but not with that of other neuroimaging measures. In contrast, other circadian RAR parameters at baseline had no association with annualized change of any neuroimaging measures. Annualized decline of AD-CM was also significantly positively associated with the annual change in MMSE scores. Furthermore, a mediation analysis showed that greater reduction in AD-CM mediated the effect of delayed acrophase at baseline on faster decline of MMSE score. CONCLUSION: The findings indicate that delayed acrophase in late life may cause or predict hypometabolism at AD-signature brain regions, which underlies cognitive decline in the near future.

Spouse bereavement and brain pathologies: A propensity score matching study.

AIM: Spouse bereavement is one of life's greatest stresses and has been suggested to trigger or accelerate cognitive decline and dementia. However, little information is available about the potential brain pathologies underlying the association between spouse bereavement and cognitive decline. We aimed to investigate that lifetime spouse bereavement is associated with in vivo human brain pathologies underlying cognitive decline. METHODS: A total of 319 ever-married older adults between the ages of 61 and 90 years underwent comprehensive clinical assessments and multimodal brain imaging including [11 C] Pittsburgh compound B-positron emission tomography (PET), AV-1451 PET, [18 F] fluorodeoxyglucose-PET, and magnetic resonance imaging. Participants were classified as experiencing no spouse bereavement or spouse bereavement, and comparisons using propensity score matching (59 cases and 59 controls) were performed. RESULTS: Spouse bereavement was significantly associated with higher cerebral white matter hyperintensity (WMH) volume compared with no spouse bereavement. Interaction and subsequent subgroup analyses showed that spouse bereavement was significantly associated with higher WMH in the older (>75 years) subgroup and among those with no- or low-skill occupations. In addition, spouse bereavement at 60 years or older affects WMH volume compared with no spouse bereavement, whereas spouse bereavement at younger than 60 years did not. No group differences were observed in other brain pathologies between spouse bereavement categories. CONCLUSIONS: The findings suggest that the spouse bereavement may contribute to dementia or cognitive decline by increasing cerebrovascular injury, particularly in older individuals and those with no- or low-skill occupations.

Association of moderate alcohol intake with in vivo amyloid-beta deposition in human brain: A cross-sectional study.

BACKGROUND: An emerging body of literature has indicated that moderate alcohol intake may be protective against Alzheimer disease (AD) dementia. However, little information is available regarding whether moderate alcohol intake is related to reductions in amyloid-beta (Aß) deposition, or is protective via amyloid-independent mechanisms in the living human brain. Here we examined the associations of moderate alcohol intake with in vivo AD pathologies, including cerebral Aß deposition, neurodegeneration of AD-signature regions, and cerebral white matter hyperintensities (WMHs) in the living human brain. METHODS AND FINDINGS: The present study was part of the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease (KBASE), an ongoing prospective cohort study that started in 2014. As of November 2016, 414 community-dwelling individuals with neither dementia nor alcohol-related disorders (280 cognitively normal [CN] individuals and 134 individuals with mild cognitive impairment [MCI]) between 56 and 90 years of age (mean age 70.9 years ± standard deviation 7.8; male, n [%] = 180 [43.5]) were recruited from 4 sites (i.e., 2 university hospitals and 2 public centers for dementia prevention and management) around Seoul, South Korea. All the participants underwent comprehensive clinical assessments comprising lifetime and current histories of alcohol intake and multimodal brain imaging, including [11C] Pittsburgh compound B positron emission tomography (PET), [18F] fluorodeoxyglucose (FDG) PET, and magnetic resonance imaging (MRI) scans. Lifetime and current alcohol intake were categorized as follows: no drinking, <1 standard drink (SD)/week, 1-13 SDs/week, and 14+ SDs/week. A moderate lifetime alcohol intake (1-13 SDs/week) was significantly associated with a lower Aß positivity rate compared to the no drinking group, even after controlling for potential confounders (odds ratio 0.341, 95% confidence interval 0.163-0.714, p = 0.004). In contrast, current alcohol intake was not associated with amyloid deposition. Additionally, alcohol intake was not related to neurodegeneration of AD-signature regions or cerebral WMH volume. The present study had some limitations in that it had a cross-sectional design and depended on retrospective recall for alcohol drinking history. CONCLUSIONS: In this study, we observed in middle- and old-aged individuals with neither dementia nor alcohol-related disorders that moderate lifetime alcohol intake was associated with lower cerebral Aß deposition compared to a lifetime history of not drinking. Moderate lifetime alcohol intake may have a beneficial influence on AD by reducing pathological amyloid deposition rather than amyloid-independent neurodegeneration or cerebrovascular injury.

Plasma tau/amyloid-ß1-42 ratio predicts brain tau deposition and neurodegeneration in Alzheimer's disease.

One of the hallmarks of Alzheimer's disease is abnormal deposition of tau proteins in the brain. Although plasma tau has been proposed as a potential biomarker for Alzheimer's disease, a direct link to brain deposition of tau is limited. Here, we estimated the amount of in vivo tau deposition in the brain by PET imaging and measured plasma levels of total tau (t-tau), phosphorylated tau (p-tau, T181) and amyloid-ß1-42. We found significant correlations of plasma p-tau, t-tau, p-tau/amyloid-ß1-42, and t-tau/amyloid-ß1-42 with brain tau deposition in cross-sectional and longitudinal manners. In particular, t-tau/amyloid-ß1-42 in plasma was highly predictive of brain tau deposition, exhibiting 80% sensitivity and 91% specificity. Interestingly, the brain regions where plasma t-tau/amyloid-ß1-42 correlated with brain tau were similar to the typical deposition sites of neurofibrillary tangles in Alzheimer's disease. Furthermore, the longitudinal changes in cerebral amyloid deposition, brain glucose metabolism, and hippocampal volume change were also highly associated with plasma t-tau/amyloid-ß1-42. These results indicate that combination of plasma tau and amyloid-ß1-42 levels might be potential biomarkers for predicting brain tau pathology and neurodegeneration.

Neuroticism, conscientiousness, and in vivo Alzheimer pathologies measured by amyloid PET and MRI.

AIM: It has been suggested that personality traits, particularly neuroticism and conscientiousness, are risk factors for Alzheimer's disease (AD) and related cognitive decline. However, the underlying pathological links between personality traits and AD-related cognitive impairments remain unclear. Thus, the present study investigated associations of neuroticism and conscientiousness with in vivo cerebral amyloid-beta (Aß) burden, AD-signature regional neurodegeneration, and white matter hyperintensities (WMH) in non-demented middle- and old-aged adults. METHODS: A total of 397 non-demented participants underwent comprehensive clinical and neuropsychological assessments, 11 C-labeled Pittsburgh Compound B positron emission tomography, and magnetic resonance imaging. Additionally, the NEO Five-Factor Inventory was administered to both the participants and their informants to measure neuroticism and conscientiousness. RESULTS: Neither neuroticism nor conscientiousness was associated with cerebral Aß deposition or WMH. In contrast, higher neuroticism and lower conscientiousness, reported by informants in particular, were significantly associated with reduced AD-signature region cortical thickness. In regards to the direct and indirect effect of each personality on AD-signature region cortical thickness, only the direct effects were found, whereas indirect effects via Aß deposition or WMH were not. CONCLUSION: The present findings suggest that amyloid-independent regional neurodegeneration might underlie relations of neuroticism and conscientiousness with AD.

Adaptive template generation for amyloid PET using a deep learning approach.

Accurate spatial normalization (SN) of amyloid positron emission tomography (PET) images for Alzheimer's disease assessment without coregistered anatomical magnetic resonance imaging (MRI) of the same individual is technically challenging. In this study, we applied deep neural networks to generate individually adaptive PET templates for robust and accurate SN of amyloid PET without using matched 3D MR images. Using 681 pairs of simultaneously acquired 11 C-PIB PET and T1-weighted 3D MRI scans of AD, MCI, and cognitively normal subjects, we trained and tested two deep neural networks [convolutional auto-encoder (CAE) and generative adversarial network (GAN)] that produce adaptive best PET templates. More specifically, the networks were trained using 685,100 pieces of augmented data generated by rotating 527 randomly selected datasets and validated using 154 datasets. The input to the supervised neural networks was the 3D PET volume in native space and the label was the spatially normalized 3D PET image using the transformation parameters obtained from MRI-based SN. The proposed deep learning approach significantly enhanced the quantitative accuracy of MRI-less amyloid PET assessment by reducing the SN error observed when an average amyloid PET template is used. Given an input image, the trained deep neural networks rapidly provide individually adaptive 3D PET templates without any discontinuity between the slices (in 0.02 s). As the proposed method does not require 3D MRI for the SN of PET images, it has great potential for use in routine analysis of amyloid PET images in clinical practice and research.

Amyloid-Independent Amnestic Mild Cognitive Impairment and Serum Apolipoprotein A1 Levels.

OBJECTIVES: The present study investigated the characteristics of amnestic mild cognitive impairment (aMCI) in subjects with low brain amyloid-beta (Aß) burden. Furthermore, the relationships between amyloid-independent cognitive decline and serum lipid profiles, particularly apolipoprotein A1 (APOA1), were evaluated. DESIGN: Cross-sectional and longitudinal follow-up study. SETTING: University hospital dementia clinic. PARTICIPANTS: 28 aMCI and 35 cognitive normal (CN) elderly. MEASUREMENTS: The study measures included baseline assessments of the subjects' clinical characteristics, lipid profiles, and magnetic resonance imaging and (11)C-labelled Pittsburgh Compound B (PiB) positron emission tomography scans. Based on PiB retention at baseline, the aMCI subjects were divided into low Aß (aMCI-) and high Aß (aMCI+) subgroups. All aMCI subjects were followed up over a 1-year period. RESULTS: The aMCI- group had a longer duration of illness than did the aMCI+ group. None of the aMCI- subjects were diagnosed with Alzheimer disease (AD) dementia during the 1-year follow-up period, whereas 26.7% of aMCI+ subjects developed AD dementia. The aMCI- group also exhibited lower serum APOA1 levels compared with both the aMCI+ and CN groups. Additionally, lower serum APOA1 levels were associated with cognitive decline and brain atrophy independent of Aß deposition and vascular burden. CONCLUSIONS: Patients with aMCI- likely exhibit different clinical and pathophysiological characteristics than patients with aMCI+. Additionally, APOA1 may be an important contributor underlying amyloid-independent neurodegeneration.

Association Between Serum Triglycerides and Cerebral Amyloidosis in Cognitively Normal Elderly.

OBJECTIVES: Although many preclinical studies have suggested the possible linkage between dyslipidemia and cerebral amyloid deposition, the association between serum lipid measures and cerebral amyloid-beta (Aß) deposition in human brain is still poorly known. We aimed to investigate the association in cognitively normal (CN) elderly individuals. DESIGN: Cross-sectional study. SETTING: University hospital dementia clinic. PARTICIPANTS: 59 CN elderly. MEASUREMENTS: The study measures included comprehensive clinical and neuropsychological assessment based on the CERAD protocol, magnetic resonance imaging and (11)C-labelled Pittsburgh Compound B positron emission tomography scans, and quantification for serum lipid biomarkers. RESULTS: Multiple linear regression analyses showed that a higher serum triglycerides level was associated with heavier global cerebral Aß deposition even after controlling age, sex, and apolipoprotein E ε4 genotype. Serum apolipoprotein B also showed significant positive association with global cerebral Aß deposition, but the significance disappeared after controlling serum triglycerides level. No association was found between other lipid measures and global cerebral Aß deposition. CONCLUSIONS: The findings suggest that serum triglycerides are closely associated with cerebral amyloidosis, although population-based prospective studies are needed to provide further evidence of the causative effect of triglycerides on cerebral amyloidosis.

Frequency of Depressive Syndromes in Elderly Individuals with No Cognitive Impairment, Mild Cognitive Impairment, and Alzheimer's Disease Dementia in a Memory Clinic Setting.

AIMS: The aims of this study were to investigate the frequency of various depressive syndromes in elderly individuals with no cognitive impairment (NC), mild cognitive impairment (MCI), and Alzheimer's disease dementia (AD) in a memory clinic setting, and then to test whether severe and milder forms of depressive syndromes are differentially associated with the cognitive groups. METHODS: For 216 NC, 478 MCI, and 316 AD subjects, we investigated the frequency of depressive syndromes, defined by three different categories: major and minor depressive disorder (MaDD and MiDD) according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, as well as depression according to the National Institute of Mental Health provisional diagnostic criteria for depression in Alzheimer's disease (NIMH-dAD). RESULTS: The frequency of MaDD did not show any significant difference among NC, MCI, and AD. In contrast, the frequencies of MiDD and NIMH-dAD were higher than those of MaDD and showed significant group differences with a gradual increase from NC to AD. CONCLUSION: The findings suggest that the degenerative process of Alzheimer's disease contributes to the occurrence of mild depressive conditions, but not to severe depression.

Multicenter, randomized, placebo-controlled, double-blind clinical trial of escitalopram on the progression-delaying effects in Alzheimer's disease.

OBJECTIVES: A series of preclinical studies have suggested that selective serotonin reuptake inhibitor antidepressants not only stimulate neurogenesis but also have neuroprotective effects. The present study primarily aimed to investigate whether escitalopram would decelerate the brain atrophy of patients with mild-to-moderate Alzheimer's disease (AD). We also assessed the effects of escitalopram on the cognitive function and neuropsychiatric symptoms of these participants. METHODS: Seventy-four probable AD patients without major depression were recruited from four dementia clinics of university hospitals and randomly assigned in a 1:1 ratio. Each group received 20 mg/day of escitalopram or placebo for 52 weeks. The primary outcome measures were the change rates of hippocampal and whole brain volume on magnetic resonance imaging for 52 weeks. The Alzheimer's Disease Assessment Scale-cognitive subscale, Mini-Mental State Examination, Neuropsychiatric Inventory, and Cornell Scale for Depression in Dementia (CSDD) were also applied. RESULTS: We did not find any significant differences in the changes of hippocampal or whole brain volume between the groups. Escitalopram showed significant beneficial effects on the CSDD score at 28 weeks compared with placebo (t = -2.17, df = 50.42, p = 0.035), but this finding did not persist throughout the study. CONCLUSION: The findings of the present study do not support the role of escitalopram as a progression-delaying treatment for AD. However, the negative results of the present trial should be interpreted cautiously because of the relatively small sample size. Further large-scale escitalopram trials targeting the earlier stages of AD, even prodromal AD, are still needed. Copyright © 2015 John Wiley & Sons, Ltd.

Functional Neuroanatomical Correlates of The Frontal Assessment Battery Performance in Alzheimer Disease: A FDG-PET Study.

BACKGROUND/OBJECTIVES: We aimed to elucidate the functional neuroanatomical correlates of Frontal Assessment Battery (FAB) performances by applying [(18)F]fluorodeoxyglucose positron emission tomography (FDG-PET) to a large population of patients with Alzheimer disease (AD). METHODS: The FAB was administered to 177 patients with AD, and regional cerebral glucose metabolism (rCMglc) was measured by FDG-PET scan. Correlations between FAB scores and rCMglc were explored using both region-of-interest-based (ROI-based) and voxel-based approaches. RESULTS: The ROI-based analysis showed that FAB scores correlated with the rCMglc of the dorsolateral prefrontal cortices. Voxel-based approach revealed significant positive correlations between FAB scores and rCMglc which were in various cortical regions including the temporal and parietal cortices as well as frontal regions, independent of age, gender, and education. After controlling the effect of global disease severity with Mini-Mental State Examination score, significant positive correlation was found only in the bilateral prefrontal regions. CONCLUSIONS: Although FAB scores are influenced by temporoparietal dysfunction due to the overall progression of AD, it likely reflects prefrontal dysfunction specifically regardless of global cognitive state or disease severity in patients with AD.

Comparison of regional gray matter atrophy, white matter alteration, and glucose metabolism as a predictor of the conversion to Alzheimer's disease in mild cognitive impairment.

We compared the predictive ability of the various neuroimaging tools and determined the most cost-effective, non-invasive Alzheimer's disease (AD) prediction model in mild cognitive impairment (MCI) individuals. Thirty-two MCI subjects were evaluated at baseline with [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET), MRI, diffusion tensor imaging (DTI), and neuropsychological tests, and then followed up for 2 yr. After a follow up period, 12 MCI subjects converted to AD (MCIc) and 20 did not (MCInc). Of the voxel-based statistical comparisons of baseline neuroimaging data, the MCIc showed reduced cerebral glucose metabolism (CMgl) in the temporo-parietal, posterior cingulate, precuneus, and frontal regions, and gray matter (GM) density in multiple cortical areas including the frontal, temporal and parietal regions compared to the MCInc, whereas regional fractional anisotropy derived from DTI were not significantly different between the two groups. The MCIc also had lower Mini-Mental State Examination (MMSE) score than the MCInc. Through a series of model selection steps, the MMSE combined with CMgl model was selected as a final model (classification accuracy 93.8%). In conclusion, the combination of MMSE with regional CMgl measurement based on FDG-PET is probably the most efficient, non-invasive method to predict AD in MCI individuals after a two-year follow-up period.

A normative study of total scores of the CERAD neuropsychological assessment battery in an educationally diverse elderly population.

BACKGROUND: This study aimed to investigate the influences of age, education, and gender on the two total scores (TS-I and TS-II) of the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological assessment battery (CERAD-NP) and to provide normative information based on an analysis for a large number of elderly persons with a wide range of educational levels. METHODS: In the study, 1,987 community-dwelling healthy volunteers (620 males and 1,367 females; 50-90 years of age; and zero to 25 years of education) were included. People with serious neurological, medical, and psychiatric disorders (including dementia) were excluded. All participants underwent the CERAD-NP assessment. TS-I was generated by summing raw scores from the CERAD-NP subtests, excluding Mini-Mental State Examination and Constructional Praxis (CP) recall subtests. TS-II was calculated by adding CP recall score to TS-I. RESULTS: Both TS-I and TS-II were significantly influenced by demographic variables. Education accounted for the greatest proportion of score variance. Interaction effect between age and gender was found. Based on the results obtained, normative data of the CERAD-NP total scores were stratified by age (six overlapping tables), education (four strata), and gender. CONCLUSIONS: The normative information will be very useful for better interpretation of the CERAD-NP total scores in various clinical and research settings and for comparing individuals' performance of the battery across countries.

Association between brain amyloid deposition and longitudinal changes of white matter hyperintensities.

BACKGROUND: Growing evidence suggests that not only cerebrovascular disease but also Alzheimer's disease (AD) pathological process itself cause cerebral white matter degeneration, resulting in white matter hyperintensities (WMHs). Some preclinical evidence also indicates that white matter degeneration may precede or affect the development of AD pathology. This study aimed to clarify the direction of influence between in vivo AD pathologies, particularly beta-amyloid (Aß) and tau deposition, and WMHs through longitudinal approach. METHODS: Total 282 older adults including cognitively normal and cognitively impaired individuals were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease (KBASE) cohort. The participants underwent comprehensive clinical and neuropsychological assessment, [11C] Pittsburgh Compound B PET for measuring Aß deposition, [18F] AV-1451 PET for measuring tau deposition, and MRI scans with fluid-attenuated inversion recovery image for measuring WMH volume. The relationships between Aß or tau deposition and WMH volume were examined using multiple linear regression analysis. In this analysis, baseline Aß or tau were used as independent variables, and change of WMH volume over 2 years was used as dependent variable to examine the effect of AD pathology on increase of WMH volume. Additionally, we set baseline WMH volume as independent variable and longitudinal change of Aß or tau deposition for 2 years as dependent variables to investigate whether WMH volume could precede AD pathologies. RESULTS: Baseline Aß deposition, but not tau deposition, had significant positive association with longitudinal change of WMH volume over 2 years. Baseline WMH volume was not related with any of longitudinal change of Aß or tau deposition for 2 years. We also found a significant interaction effect between baseline Aß deposition and sex on longitudinal change of WMH volume. Subsequent subgroup analyses showed that high baseline Aß deposition was associated with increase of WMH volume over 2 years in female, but not in male. CONCLUSIONS: Our findings suggest that Aß deposition accelerates cerebral WMHs, particularly in female, whereas white matter degeneration appears not influence on longitudinal Aß increase. The results also did not support any direction of influence between tau deposition and WMHs.

Moderation of thyroid hormones for the relationship between amyloid and tau pathology.

BACKGROUND: Altered thyroid hormone levels have been associated with increased risk of Alzheimer's disease (AD) dementia and related cognitive decline. However, the neuropathological substrates underlying the link between thyroid hormones and AD dementia are not yet fully understood. We first investigated the association between serum thyroid hormone levels and in vivo AD pathologies including both beta-amyloid (Aß) and tau deposition measured by positron emission tomography (PET). Given the well-known relationship between Aß and tau pathology in AD, we additionally examined the moderating effects of thyroid hormone levels on the association between Aß and tau deposition. METHODS: This cross-sectional study was conducted as part of the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's Disease (KBASE) cohort. This study included a total of 291 cognitively normal adults aged 55 to 90. All participants received comprehensive clinical assessments, measurements for serum total triiodothyronine (T3), free triiodothyronine (fT3), free thyroxine (fT4), and thyroid-stimulating hormone (TSH), and brain imaging evaluations including [11C]-Pittsburgh compound B (PiB)- PET and [18F] AV-1451 PET. RESULTS: No associations were found between either thyroid hormones or TSH and Aß and tau deposition on PET. However, fT4 (p = 0.002) and fT3 (p = 0.001) exhibited significant interactions with Aß on tau deposition: The sensitivity analyses conducted after the removal of an outlier showed that the interaction effect between fT4 and Aß deposition was not significant, whereas the interaction between fT3 and Aß deposition remained significant. However, further subgroup analyses demonstrated a more pronounced positive relationship between Aß and tau in both the higher fT4 and fT3 groups compared to the lower group, irrespective of outlier removal. Meanwhile, neither T3 nor TSH had any interaction with Aß on tau deposition. CONCLUSION: Our findings suggest that serum thyroid hormones may moderate the relationship between cerebral Aß and tau pathology. Higher levels of serum thyroid hormones could potentially accelerate the Aß-dependent tau deposition in the brain. Further replication studies in independent samples are needed to verify the current results.

Moderation of Amyloid-ß Deposition on the Effect of Cholinesterase Inhibitors on Cognition in Mild Cognitive Impairment.

Background: Clinical trial findings on cholinesterase inhibitors (ChEIs) for mild cognitive impairment (MCI) are inconclusive, offering limited support for their MCI treatment. Given that nearly half of amnestic MCI cases lack cerebral amyloid-ß (Aß) deposition, a hallmark of Alzheimer's disease; this Aß heterogeneity may explain inconsistent results. Objective: This study aimed to assess whether Aß deposition moderates ChEI effects on amnestic MCI cognition. Methods: We examined 118 individuals with amnestic MCI (ages 55-90) in a longitudinal cohort study. Baseline and 2-year follow-up assessments included clinical evaluations, neuropsychological testing, and multimodal neuroimaging. Generalized linear models were primarily analyzed to test amyloid positivity's moderation of ChEI effects on cognitive change over 2 years. Cognitive outcomes included Mini-Mental Status Examination score, the total score of the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological battery, and Clinical Dementia Rating-sum of boxes. Results: The analysis found no significant ChEI use x amyloid positivity interaction for all cognitive outcomes. ChEI use, irrespective of Aß status, was associated with more cognitive decline over the 2-year period. Conclusions: Aß pathology does not appear to moderate ChEI effects on cognitive decline in MCI.

Plasma Leptin and Alzheimer Protein Pathologies Among Older Adults.

Importance: Many epidemiologic studies have suggested that low levels of plasma leptin, a major adipokine, are associated with increased risk of Alzheimer disease (AD) dementia and cognitive decline. Nevertheless, the mechanistic pathway linking plasma leptin and AD-related cognitive decline is not yet fully understood. Objective: To examine the association of plasma leptin levels with in vivo AD pathologies, including amyloid-beta (Aß) and tau deposition, through both cross-sectional and longitudinal approaches among cognitively unimpaired older adults. Design, Setting, and Participants: This was a longitudinal cohort study from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer Disease. Data were collected from January 1, 2014, to December 31, 2020, and data were analyzed from July 11 to September 6, 2022. The study included a total of 208 cognitively unimpaired participants who underwent baseline positron emission tomography (PET) scans for brain Aß deposition. For longitudinal analyses, 192 participants who completed both baseline and 2-year follow-up PET scans for brain Aß deposition were included. Exposure: Plasma leptin levels as assessed by enzyme-linked immunosorbent assay. Main Outcomes and Measures: Baseline levels and longitudinal changes of global Aß and AD-signature region tau deposition measured by PET scans. Results: Among the 208 participants, the mean (SD) age was 66.0 (11.3) years, 114 were women (54.8%), and 37 were apolipoprotein E ε4 carriers (17.8%). Lower plasma leptin levels had a significant cross-sectional association with greater brain Aß deposition (ß = -0.04; 95% CI, -0.09 to 0.00; P = .046), while there was no significant association between plasma leptin levels and tau deposition (ß = -0.02; 95% CI, -0.05 to 0.02; P = .41). In contrast, longitudinal analyses revealed that there was a significant association between lower baseline leptin levels and greater increase of tau deposition over 2 years (ß = -0.06; 95% CI, -0.11 to -0.01; P = .03), whereas plasma leptin levels did not have a significant association with longitudinal change of Aß deposition (ß = 0.006; 95% CI, 0.00-0.02; P = .27). Conclusions and Relevance: The present findings suggest that plasma leptin may be protective for the development or progression of AD pathology, including both Aß and tau deposition.

Association of Central Auditory Processing Dysfunction With Preclinical Alzheimer's Disease.

OBJECTIVE: To investigate whether central auditory processing dysfunction measured by the dichotic digit test-1 digit (DDT1) is present in preclinical Alzheimer's disease (AD) individuals who are cognitively normal (CN) older adults with the cerebral beta-amyloid (Aß) deposition and to explore the potential of the DDT1 as a screening test for preclinical AD. STUDY DESIGN: Cross-sectional design. SETTING: A prospective observational cohort study. METHODS: CN older adults with a global clinical dementia rating score of 0 were included. The hearing test battery including pure-tone audiometry, speech audiometry, distortion product otoacoustic emission, and DDT1 was administered to participants. RESULTS: Fifty CN older adults were included. Among them, 38 individuals were included in the Aß deposition negative (AN) group and 12 were included in the Aß deposition positive (AP) group. The DDT1 scores of both the better and worse ears were significantly lower in the AP group than in the AN group (p = .008 and p = .015, respectively). No significant differences were observed between the groups in tests of the peripheral auditory pathways. In multivariable logistic regression analysis adjusted for apolipoprotein E4 positivity, the DDT1 better ear score predicted the AP group (p = .036, odds ratio = 0.892, 95% confidence interval: 0.780-0.985) with relatively high diagnostic accuracy. CONCLUSION: Our findings suggest that Aß deposition may affect the central auditory pathway even before cognitive decline appears. DDT1, which can easily be applied to the old-age population, may have the potential as a screening tool for preclinical AD.

Enlarged perivascular spaces are associated with decreased brain tau deposition.

AIMS: The aim of this study was to investigate the associations of enlarged perivascular spaces (EPVS) in the basal ganglia (BG) and centrum semiovale (CSO) with beta-amyloid (Aß) and tau deposition in older adults with a diverse cognitive spectrum. METHODS: A total of 163 (68 cognitively normal and 95 cognitively impaired) older participants underwent [11 C] Pittsburgh compound B and [18 F] AV-1451 PET, and MRI. EPVS in the BG and CSO and other small vessel disease markers, such as white matter hyperintensities, lacunes, and deep and lobar microbleeds, were assessed. RESULTS: Increased EPVS in the BG showed a significant association with lower cerebral tau deposition, even after controlling for other small vessel disease markers. Further exploratory analyses showed that this association was significant in cognitively impaired, Aß-positive, or APOE4-positive individuals, but not significant in the cognitively normal, Aß-negative, or APOE4-negative participants. In contrast to EPVS in the BG, EPVS in the CSO did not have any relationship with cerebral tau deposition. In addition, none of the two types of EPVS were associated with cerebral Aß deposition. CONCLUSION: Brain tau deposition appears to be reduced with increased EPVS in the BG, especially in individuals with cognitive impairment, pathological amyloid burden, or genetic Alzheimer's disease risk.