Volume 85, Number 4, 2022

Pages 1399-1410

William Z. Suo (Handling Associate Editor: Bruce Citron)
GRK5 Deficiency Causes Mild Cognitive Impairment due to Alzheimer’s Disease
Abstract: Prevention of Alzheimer’s disease (AD) is a high priority mission while searching for a disease modifying therapy for AD, a devastating major public health crisis. Clinical observations have identified a prodromal stage of AD for which the patients have mild cognitive impairment (MCI) though do not yet meet AD diagnostic criteria. As an identifiable transitional stage before the onset of AD, MCI should become the high priority target for AD prevention, assuming successful prevention of MCI and/or its conversion to AD also prevents the subsequent AD. By pulling this string, one demonstrated cause of amnestic MCI appears to be the deficiency of G protein-coupled receptor-5 (GRK5). The most compelling evidence is that GRK5 knockout (GRK5KO) mice naturally develop into aMCI during aging. Moreover, GRK5 deficiency was reported to occur during prodromal stage of AD in CRND8 transgenic mice. When a GRK5KO mouse was crossbred with Tg2576 Swedish amyloid precursor protein transgenic mouse, the resulted double transgenic GAP mice displayed exaggerated behavioral and pathological changes across the spectrum of AD pathogenesis. Therefore, the GRK5 deficiency possesses unique features and advantage to serve as a prophylactic therapeutic target for MCI due to AD.

Pages 1411-1417
Short Communication

Sydney Y. Schaefer, Michael Malek-Ahmadi, Andrew Hooyman, Jace B. King, Kevin Duff (Handling Associate Editor: Madeleine Hackney)
Association Between Motor Task Performance and Hippocampal Atrophy Across Cognitively Unimpaired, Amnestic Mild Cognitive Impairment, and Alzheimer’s Disease Individuals
Abstract: Hippocampal atrophy is a widely used biomarker for Alzheimer’s disease (AD), but the cost, time, and contraindications associated with magnetic resonance imaging (MRI) limit its use. Recent work has shown that a low-cost upper extremity motor task has potential in identifying AD risk. Fifty-four older adults (15 cognitively unimpaired, 24 amnestic mild cognitive impairment, and 15 AD) completed six motor task trials and a structural MRI. Several measures of motor task performance significantly predicted bilateral hippocampal volume, controlling for age, sex, education, and memory. Thus, this motor task may be an affordable, non-invasive screen for AD risk and progression.

Pages 1419-1422

Harry S. Goldsmith
Alzheimer’s Disease: A Decreased Cerebral Blood Flow to Critical Intraneuronal Elements is the Cause
Abstract: Normally, an adequate cerebral blood flow arrives at individual cerebral neurons in which the blood flow augments activity of intraneuronal mitochondria, which is the source of intraneuronal ATP, the energy source of cerebral neurons. With a decrease in cerebral blood flow that can occur as a function of normal aging phenomena, less blood results in decreased mitochondria, decreased ATP, and a decrease in neuronal activity, which can eventually lead to Alzheimer’s disease. It has been found that placement of the omentum directly on an Alzheimer’s disease brain can lead to improved cognitive function.

Pages 1423-1439
Claudia Ramos, Camilo Villalba, Jenny García, Serggio Lanata, Hugo López, David Aguillón, Christian Cordano, Lucía Madrigal, Daniel C. Aguirre-Acevedo, Francisco Lopera
Substance Use-Related Cognitive Decline in Families with Autosomal Dominant Alzheimer’s Disease: A Cohort Study
Abstract: Background: Cigarette smoking is a known risk factor for Alzheimer's disease (AD). However, the association between neurodegeneration and other substances has not been fully determined. It is of vital importance to evaluate this relationship in populations at high risk of dementia. Since substance use possibly modifies the progression rate of cognitive decline, we studied this association in a unique and well-phenotyped cohort from the University of Antioquia: carriers of the PSEN1-E280A genetic variant. Objective: To determine the association between substance use and cognitive decline in carriers of the PSEN1-E280A genetic variant. Methods: A retrospective cohort study was conducted with 94 carriers and 69 noncarriers recruited between January 2019 and April 2020. A psychiatrist interviewed the participants using the Consumption of Alcohol, Cigarettes and other Substances questionnaire. The participants were also submitted to cognitive evaluation. The relationship between cognitive decline and substance use was explored through a mixed effects regression model. Results: There was an association between cigarettes and better performance on tasks related to perceptual organization, verbal fluency, and memory in carriers. Alcohol had a positive or negative effect on memory according to the type of alcoholic beverage. Results on marijuana use were no conclusive. Coffee was associated with progressive improvements in executive function and verbal fluency. Conclusion: Cigarette and alcohol were associated with an improvement of some cognitive assessments, possibly by a survival bias. In addition, coffee was related to improvements in executive function and language; therefore, its short-term neuroprotective potential should be studied.

Pages 1441-1452
Heng Zhang*, Diyang Lyu*, Jianping Jia, and for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
The Trajectory of Cerebrospinal Fluid Growth-Associated Protein 43 in the Alzheimer’s Disease Continuum: A Longitudinal Study
Abstract: Background: Synaptic degeneration has been suggested as an early pathological event that strongly correlates with severity of dementia in Alzheimer’s disease (AD). However, changes in longitudinal cerebrospinal fluid (CSF) growth-associated protein 43 (GAP-43) as a synaptic biomarker in the AD continuum remain unclear. Objective: To assess the trajectory of CSF GAP-43 with AD progression and its association with other AD hallmarks. Methods: CSF GAP-43 was analyzed in 788 participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), including 246 cognitively normal (CN) individuals, 415 individuals with mild cognitive impairment (MCI), and 127 with AD dementia based on cognitive assessments. The associations between a multimodal classification scheme with amyloid-β (Aβ), tau, and neurodegeneration, and changes in CSF GAP-43 over time were also analyzed. Results: CSF GAP-43 levels were increased at baseline in MCI and dementia patients, and increased significantly over time in the preclinical (Aβ-positive CN), prodromal (Aβ-positive MCI), and dementia (Aβ-positive dementia) stages of AD. Higher levels of CSF GAP-43 were also associated with higher CSF phosphorylated tau (p-tau) and total tau (t-tau), cerebral amyloid deposition and hypometabolism on positron emission tomography, the hippocampus and middle temporal atrophy, and cognitive performance deterioration at baseline and follow-up. Furthermore, CSF GAP-43 may assist in effectively predicting the probability of dementia onset at 2- or 4-year follow-up. Conclusion: CSF GAP-43 can be used as a potential biomarker associated with synaptic degeneration in subjects with AD; it may also be useful for tracking the disease progression and for monitoring the effects of clinical trials.

Pages 1453-1466
Yang Zhao*, Jian Bao*, Wei Liu, Xiaokang Gong, Zheng Liang, Wenshuang Li, Mengjuan Wu, Yifan Xiao, Binlian Sun, Xiaochuan Wang, Jian-Zhi Wang, Jun Wang, Xiji Shu (Handling Associate Editor: Cheng-Xin Gong) *These authors contributed equally to this work.
Spatial Training Attenuates Long-Term Alzheimer’s Disease-Related Pathogenic Processes in APP/PS1 Mice
Abstract: Background: Alzheimer's disease (AD), with cognitive impairment as the main clinical manifestation, is a progressive neurodegenerative disease. The assembly of amyloid-β (Aβ) as senile plaques is one of the most well-known histopathological alterations in AD. Several studies reported that cognitive training reduced Aβ deposition and delayed memory loss. However, the long-term benefits of spatial training and the underlying neurobiological mechanisms have not yet been elucidated. Objective: To explore the long-term effects of spatial training on AD-related pathogenic processes in APP/PS1 mice. Methods: We used Morris water maze (MWM), Open Field, Barnes Maze, western blotting, qPCR, and immunofluorescence. Results: One-month MWM training in APP/PS1 mice at 2.5 months of age could attenuate Aβ deposition and decrease the expression of β-secretase (BACE1) and amyloid-β protein precursor (AβPP) with long-term effects. Simultaneously, regular spatial training increased the expression of synapse-related proteins in the hippocampus. Moreover, MWM training increased adult hippocampal neurogenesis in AD model mice. Nonetheless, cognitive deficits in APP/PS1 transgenic mice at 7 months of age were not attenuated by MWM training at an early stage. Conclusion: Our study demonstrates that MWM training alleviates amyloid plaque burden and adult hippocampal neurogenesis deficits with long-term effects in AD model mice.

Pages 1467-1479
Hyemin Jang, Yu-hyun Park, Young Sim Choe, Sung Hoon Kang, Eun-Sook Kang, Seunghoon Lee, Sang Won Seo, Hee Jin Kim, Duk L. Na
Amyloid Positive Hydrocephalus: A Hydrocephalic Variant of Alzheimer’s Disease?
Abstract: Background: Alzheimer’s disease (AD) and normal pressure hydrocephalus (NPH) commonly coexist. Objective: We aimed to characterize an overlapping syndrome of AD and NPH that presents with gait disturbance, ventriculomegaly on magnetic resonance imaging, and significant amyloid deposition on positron emission tomography (PET). Methods: Of 114 patients who underwent cerebrospinal fluid (CSF) drainage for a possible diagnosis of NPH between 2015 and 2020 in Samsung Medical Center, we identified 24 patients (21.1%) with the NPH patients with amyloid deposition on PET, which we referred to as hydrocephalic AD in this study. We compared their clinical and imaging findings with those of 123 typical AD without hydrocephalic signs/symptoms. We also investigated the frequency and potential predictors of the tap test response in hydrocephalic AD. Results: Evans’ index was 0.36 ± 0.03, and a disproportionately enlarged subarachnoid space was present in 54.2% of the hydrocephalic AD patients. The mean age (75.2 ± 7.3 years) and the APOE4 frequency (68.2%) did not differ from those of AD controls. However, the hydrocephalic AD patients showed better memory and language performance, and a thinner cingulate cortex. About 42% of the hydrocephalic AD patients responded to the tap test, of whom seven underwent shunt surgery. Cognition did not improve, whereas gait improved after shunt surgery in all. Conclusion: Hydrocephalic AD has different neuropsychological and imaging characteristics from typical AD. Future studies are warranted to further investigate the effect of CSF removal on their clinical course and to elucidate the pathophysiological interaction between amyloid and NPH.

Pages 1481-1494
Naazneen Khan, Yelena Alimova, Sophie J. Clark, Hemendra Vekaria, Adeline E. Walsh, Holden C. Williams, Gregory S. Hawk, Patrick Sullivan, Lance A. Johnson, Timothy S. McClintock
Human APOE ε3 and APOE ε4 Alleles Have Differential Effects on Mouse Olfactory Epithelium
Abstract: Background: Alzheimer’s disease (AD) is a progressive age-dependent disorder whose risk is affected by genetic factors. Better models for investigating early effects of risk factors such as apolipoprotein E (APOE) genotype are needed. Objective: To determine whether APOE genotype produces neuropathologies in an AD-susceptible neural system, we compared effects of human APOE ε3 (E3) and APOE ε4 (E4) alleles on the mouse olfactory epithelium. Methods: RNA-Seq using the STAR aligner and DESeq2, immunohistochemistry for activated caspase-3 and phosphorylated histone H3, glucose uptake after oral gavage of 2-[1,2-3H (N)]-deoxy-D-glucose, and Seahorse Mito Stress tests on dissociated olfactory mucosal cells. Results: E3 and E4 olfactory mucosae show 121 differentially abundant mRNAs at age 6 months. These do not indicate differences in cell type proportions, but effects on 17 odorant receptor mRNAs suggest small differences in tissue development. Ten oxidoreductases mRNAs important for cellular metabolism and mitochondria are less abundant in E4 olfactory mucosae but this does not translate into differences in cellular respiration. E4 olfactory mucosae show lower glucose uptake, characteristic of AD susceptibility and consistent with greater expression of the glucose-sensitive gene, Asns. Olfactory sensory neuron apoptosis is unaffected at age 6 months but is greater in E4 mice at 10 months. Conclusion: Effects of human APOE alleles on mouse olfactory epithelium phenotype are apparent in early adulthood, and neuronal loss begins to increase by middle age (10 months). The olfactory epithelium is an appropriate model for the ability of human APOE alleles to modulate age-dependent effects associated with the progression of AD.

Pages 1495-1509
Zhaoyu Gao*, Rui Zhang*, Lei Jiang*, Huimin Zhou, Qian Wang, Yingxin Ma, Di Zhang, Yushi Qin, Pei Tian, Nan Zhang, Zhongli Shi, Shunjiang Xu (Handling Associate Editor: Ling-Qiang Zhu) *These authors contributed equally to this work.
Administration of miR-195 Inhibitor Enhances Memory Function Through Improving Synaptic Degradation and Mitochondrial Dysfunction of the Hippocampal Neurons in SAMP8 Mice
Abstract: Background: Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD) and miR-195 is involved in mitochondrial disorder through targeting MFN-2 protein in hippocampal neurons of AD. Objective: To clarify if administration of miR-195 inhibitor could enhance the memory deficits through improving hippocampal neuron mitochondrial dysfunction in SAMP8 mice. Methods: The expression of miR-195 was detected by RT-qPCR in primary hippocampal neurons and HT-22 cells treated with Aβ1-42. Morris water maze (MWM) was used to assess the learning and memory function in SAMP8 mice administrated with antagomir-195. Transmission electron microscopy was employed to determine the morphological changes of synapses and mitochondria of hippocampus in SAMP8 mice. Mitochondrial respiration was measured using a high-resolution oxygraph. Results: The expression of miR-195 were upregulated in the primary hippocampal neurons and HT-22 cells induced by Aβ1-42. Inhibition of miR-195 ameliorated the mitochondrial dysfunction in HT-22 cells induced by Aβ1-42, including mitochondrial morphologic damages, mitochondrial membrane potential, respiration function, and ATP production. Administration of antagomir-195 by the third ventricle injection markedly ameliorated the cognitive function, postsynaptic density thickness, length of synaptic active area, mitochondrial aspect ratio, and area in hippocampus of SAMP8 mice. Finally, antagomir-195 was able to promote an increase in the activity of respiratory chain complex CI and II in SAMP8 mice. Conclusion: This study demonstrated that miR-195 inhibitor ameliorated the cognitive impairment of AD mice by improving mitochondrial structure damages and dysfunction in the hippocampal neurons, which provide an experimental basis for further exploring the treatment strategy of AD.

Pages 1511-1518
Liling Dong*, Chenhui Mao*, Caiyan Liu, Jie Li, Xinying Huang, Jie Wang, Dan Lei, Shanshan Chu, Longze Sha, Qi Xu, Bin Peng, Liying Cui, Jing Gao *These authors contributed equally to this work.
Association Between Common Variants of APOE, ABCA7, A2M, BACE1, and Cerebrospinal Fluid Biomarkers in Alzheimer’s Disease: Data from the PUMCH Dementia Cohort
Abstract: Background: The previous studies have identified several genes in relation to Alzheimer’s disease (AD), such as ABCA7, CR1, etc. A few studies have explored the association between the common variants, mainly in the non-coding regions of these genes, and cerebrospinal fluid (CSF) biomarkers. Fewer studies target the variants in the coding regions. Objective: To illustrate the association between the common variants within or adjacent to the coding regions of AD susceptible genes and CSF biomarkers in AD patients. Methods: 75 sporadic probable AD patients were extracted from the dementia cohort of Peking Union Medical College Hospital. They all had history inquiry, physical examination, blood test, cognitive assessment, brain MRI, CSF testing of Aβ42, 181p-tau, and t-tau, and next-generation DNA sequencing. Sixty-nine common single nucleotide polymorphisms (SNPs) (minor allele frequency >0.01) within or near the coding region of 13 AD susceptible genes were included in the analysis. Results: The rs7412-CC (APOE) genotype showed lower CSF Aβ42 level and higher p-tau/Aβ42 ratio than the rs7412-CT genotype. The rs3752246-C (ABCA7) allele correlated with lower CSF Aβ42 level. The alternate alleles of six ABCA7 SNPs were related to lower CSF p-tau, including rs3745842, rs3764648, rs3764652, rs4147930, rs4147934 and rs881768. The rs11609582-TT (A2M) genotype showed higher CSF p-tau than the rs11609582-TA genotype. The p-tau/Aβ42 ratio was higher in the rs490460-TT (BACE1) genotype relative to the rs490460-GT genotype. Conclusion: Some common variants within or near the coding regions of APOE, ABCA7, A2M, and BACE1 are associated with CSF Aβ42, p-tau. or p-tau/Aβ42.

Pages 1519-1528
Michelle M. Dunk, Ira Driscoll for the Alzheimer’s Disease Neuroimaging Initiative
Total Cholesterol and APOE-Related Risk for Alzheimer’s Disease in the Alzheimer’s Disease Neuroimaging Initiative
Abstract: Background: APOE ε4 allele confers greatest genetic risk for Alzheimer’s disease (AD), yet mechanisms underlying this risk remain elusive. APOE is involved in lipid metabolism, and literature suggest relationships between high total cholesterol, APOE, and AD. Further investigation is needed to elucidate the potential role of total cholesterol in AD risk. Objective: To investigate the relationship between total cholesterol and APOE-related AD risk in the Alzheimer’s Disease Neuroimaging Initiative. Methods: Participants (N=1,534) were classified as controls (cognitively normal; N=404), early mild cognitive impairment (MCI; N=294), late MCI (N=539), or AD (N=297). Total cholesterol levels were compared across APOE genotype and diagnosis. Mendelian randomization was performed to examine causality between total cholesterol and AD risk using APOE as a genetic instrument. Results: Total cholesterol was higher in APOE4+ compared to APOE3 and APOE2+ (ps<0.04) carriers. Those with AD and late MCI (ps<0.001) had higher total cholesterol than the control group. Comparing APOE4+ to APOE3 carriers, the predicted odds ratios per mg/dL greater total cholesterol were 1.11 for MCI (95% confidence interval, 1.04-7.32), 1.05 for early MCI (1.01-3.22), 1.13 for late MCI (1.05-11.70), 1.21 for AD (1.09-54.05), and 1.13 for composite dementia (MCI or AD; 1.06-11.59) (ps<0.05, F-statistics>10). Conclusion: Higher total cholesterol may be a significant contributor to AD risk, particularly in APOE4 carriers who, based on existing literature, tend to have impaired cholesterol metabolism. Our findings highlight a possible mechanism by which APOE confers AD risk and indicate potential for AD risk modification through maintenance of healthy total cholesterol levels.

Pages 1529-1544
Makoto Kurano, Kazuhisa Tsukamoto, Eri Sakai, Masumi Hara, Yutaka Yatomi
Isoform-Dependent Effects of Apolipoprotein E on Sphingolipid Metabolism in Neural Cells
Abstract: Background: Sphingosine 1-phosphate (S1P) and ceramides have been implicated in the development of Alzheimer’s disease. Apolipoprotein E (ApoE) isoforms are also involved in the development of Alzheimer’s disease. Objective: We aimed at elucidating the potential association of the ApoE isoforms with sphingolipid metabolism in the central nervous system. Methods: We investigated the modulations of apolipoprotein M (apoM), a carrier of S1P, S1P, and ceramides in Apoeshl mice, which spontaneously lack apoE, and U251 cells and SH-SY5Y cells infected with adenovirus vectors encoding for apoE2, apoE3, and apoE4. Results: In the brains of Apoeshl mice, the levels of apoM were lower, while those of ceramides were higher. In U251 cells, cellular apoM and S1P levels were the highest in the cells overexpressing apoE2 among the apoE isoforms. The cellular and medium contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 and increased in the cells overexpressing apoE4. In SH-SY5Y cells, apoM mRNA and medium S1P levels were also the highest in the cells overexpressing apoE2. The cellular contents of ceramides decreased in the order of the cells overexpressing apoE3 > apoE2 = apoE4 and those in medium decreased in the order of the cells overexpressing apoE3 > apoE2, while increased in the cells overexpressing apoE4. Conclusion: The modulation of apoM and S1P might partly explain the protective effects of apoE2 against Alzheimer’s disease, and the modulation of ceramides might be one of the mechanisms explaining the association of apoE4 with the development of Alzheimer’s disease.

Pages 1545-1554
Xiao Luo#, Hui Hong#, Shuyue Wang#, Kaicheng Li, Qingze Zeng, Luwei Hong, Xiaocao Liu, Zheyu Li, Yanv Fu, Yeerfan Jiaerken, XiaoPei Xu, Xinfeng Yu, Peiyu Huang*, Minming Zhang* #These authors contributed equally to this work. *These authors should be considered joint senior authors.
Exploration of the Mechanism Underlying the Association of Incident Microinfarct and Motor Deficit: A Preliminary Functional MRI Study
Abstract: Background: Cerebral microinfarcts (CMIs) might cause measurable disruption to brain connections and are associated with cognitive decline, but the association between CMIs and motor impairment is still unclear. Objective: To assess the CMIs effect on motor function in vivo and explore the potential neuropathological mechanism based on graph-based network method. Methods: We identified 133 non-demented middle-aged and elderly participants who underwent MRI scanning, cognitive, and motor assessment. The short physical performance battery (SPPB) assessed motor function, including balance, walking speed, and chair stand. We grouped participants into 34 incident CMIs carriers and 99 non-CMIs carriers as controls, depending on diffusion-weighted imaging. Then we assessed the independent CMIs effects on motor function and explored neural mechanisms of CMIs on motor impairment via mapping of degree centrality (DC) and eigenvector centrality (EC). Results: CMIs carriers had worse motor function than non-carriers. Linear regression analyses showed that CMIs independently contributed to motor function. CMIs carriers had decreased EC in the precuneus, while increased DC and EC in the middle temporal gyrus and increased DC in the inferior frontal gyrus compared to controls (p<0.05, corrected). Correlation analyses showed that EC of precuneus was related to SPPB (r=0.25) and balance (r=0.27); however, DC (r=-0.25) and EC (r=-0.25) of middle temporal gyrus was related with SPPB in all participants (p<0.05, corrected). Conclusion: CMIs represent an independent risk factor for motor dysfunction. The relationship between CMIs and motor function may be attributed to suppression of functional hub region and compensatory activation of motor-related regions.

Pages 1555-1571
Mona Abdelhamid, Chunyu Zhou, Kazuya Ohno, Tetsuya Kuhara, Ferdous Taslima, Mohammad Abdullah, Cha-Gyun Jung, Makoto Michikawa
Probiotic Bifidobacterium breve Prevents Memory Impairment Through the Reduction of Both Amyloid-β Production and Microglia Activation in APP Knock-In Mouse
Abstract: Background: Probiotic supplementation reestablishes microbiome diversity and improves brain function in Alzheimer’s disease (AD); their molecular mechanisms, however, have not yet been fully illustrated. Objective: We investigated the effects of orally supplemented Bifidobacterium breve MCC1274 on cognitive function and AD-like pathologies in AppNL-G- F mice. Methods: Three-month-old AppNL-G-F mice were orally supplemented with B. breve MCC1274 for four months. The short-term memory function was evaluated using a novel object recognition test. Amyloid plaques, amyloid-β (Aβ) levels, Aβ fibril, amyloid-β protein precursor and its processing enzymes, its metabolic products, glial activity, and cell proliferation in the subgranular zone of the dentate gyrus were evaluated by immunohistochemistry, Aβ ELISA, western blotting, and immunofluorescence staining. The mRNA expression levels of pro- and anti-inflammatory cytokines were determined by qRT-PCR analysis. Results: We found that the oral B. breve MCC1 274 supplementation prevented memory impairment in AppNL-G-F mice and decreased hippocampal Aβ levels through the enhancement of the a-disintegrin and metalloproteinase 10 (ADAM10) level. Moreover, administration of the probiotic activated the ERK/HIF-1α signaling pathway responsible for increasing the ADAM10 level and also attenuated microglial activation, which in turn led to reduction in the mRNA expression levels of pro-inflammatory cytokines in the brain. In addition, B. breve MCC1274 supplementation increased the level of synaptic proteins in the hippocampus. Conclusion: Our findings support the possibility that oral B. breve MCC1274 supplementation might be used as a potential preventive therapy for AD progression.

Pages 1573-1582
Xiaoqi Wang, Qiuhui Bi, Jie Lu, Piu Chan, Xiaochen Hu, Li Su, Frank Jessen, Hua Lin, Chunlei Han, Ni Shu, Hesheng Liu, Ying Han (Handling Associate Editor: Ling-Qiang Zhu)
Difference in Amyloid Load Between Single Memory Domain and Multidomain Subjective Cognitive Decline: A Study from the SILCODE
Abstract: Background: Subjective cognitive decline (SCD), an at-risk condition of Alzheimer’s disease (AD), can involve various cognitive domains, such as memory, language, planning, and attention. Objective: We aims to explore the differences in amyloid load between the single memory domain SCD (sd-SCD) and the multidomain SCD (md-SCD) and assess the relationship of amyloid pathology with quantitative SCD scores and objective cognition. Methods: A total of 63 SCD participants from the SILCODE study underwent the clinical evaluation, neuropsychological assessment, and 18F-florbetapir PET scan. Global amyloid standard uptake value ratio (SUVr) was calculated. Additionally, regional amyloid SUVr was quantified in 12 brain regions of interests. A nonparametric rank ANCOVA was used to compare the global and regional amyloid SUVr between the md-SCD (n=34) and sd-SCD (n=29) groups. A multiple linear regression analysis was conducted to test the relationship of amyloid SUVr with quantitative SCD scores and objective cognition. Results: Compared with individuals with sd-SCD, individuals with md-SCD had increased global amyloid SUVr (F=5.033, p=0.029) and regional amyloid SUVr in the left middle temporal gyrus (F=12.309, p=0.001; Bonferroni corrected), after controlling for the effects of age, sex, and education. When pooling all SCD participants together, the increased global amyloid SUVr was related with higher SCD-plus sum scores and lower Auditory Verbal Learning Test-delayed recall scores. Conclusion: According to our findings, individuals with md-SCD showed higher amyloid accumulation than individuals with sd-SCD, suggesting that md-SCD may experience a more advanced stage of SCD. Additionally, increased global amyloid load was predictive of a poorer episodic memory function in SCD individuals.

Pages 1583-1592
Yifei Ren, Yi Dong, Tingting Hou, Xiaolei Han, Rui Liu, Yongxiang Wang, Shan Xu, Xiang Wang, Roberto Monastero, Lin Cong, Yifeng Du, Chengxuan Qiu (Handling Associate Editor: Patrizia Mecocci)
Prevalence, Incidence, and Progression of Cognitive Impairment, No Dementia Among Rural-Dwelling Chinese Older Adults
Abstract: Background: Few studies have examined occurrence and progression of cognitive impairment, no dementia (CIND) in rural China. Objective: To determine the prevalence and incidence of CIND in rural-dwelling Chinese older adults, and to examine risk and protective factors associated with progression to CIND and dementia. Methods: This population-based study included 2,781 dementia-free participants (age ≥65 years) who were examined at baseline (2014) and followed in 2018. Demographic, epidemiological, clinical, and neuropsychological data were collected following a structured questionnaire. We defined CIND according to subjective cognitive complaints and the age- and education-specific Mini-Mental State Examination (MMSE) score. Data were analyzed with the multinomial logistic regression models. Results: The overall prevalence of CIND was 10.54% and the incidence was 28.26 per 1,000 person-years. CIND at baseline was associated with the multi-adjusted odds ratio (OR) of 2.06 (95% confidence interval=1.23-3.47) for incident dementia. Multinomial logistic regression analysis suggested that compared with no CIND, the multi-adjusted OR of incident CIND was 2.21 (1.51-3.23) for women and 0.62 (0.38-0.99) for high social support, whereas the multi-adjusted OR of incident dementia was 1.14 (1.09-1.18) for older age, 0.29 (0.16-0.53) for high education, and 2.91 (1.47-5.74) for having a stroke history. Conclusion: CIND affects over one-tenth of older adults living in rural communities of western Shandong province. People with CIND are twice as likely to progress to dementia as people without CIND. Female sex, low education, stroke history, and low social support are associated with an increased risk of progression from normal cognition to CIND or dementia.

Pages 1593-1600
Jauhtai Cheng, J. Kaci Fairchild, M. Windy McNerney, Art Noda, J. Wesson Ashford, Trisha Suppes, Steven Z. Chao, Joy Taylor, Allyson C. Rosen, Timothy C. Durazzo, Laura C. Lazzeroni, Jerome Yesavage
Repetitive Transcranial Magnetic Stimulation as a Treatment for Veterans with Cognitive Impairment and Multiple Comorbidities
Abstract: Background: Despite decades of research efforts, current treatments for Alzheimer’s disease (AD) are of limited effectiveness and do not halt the progression of the disease and associated cognitive decline. Studies have shown that repetitive transcranial magnetic stimulation (rTMS) may improve cognition. Objective: We conducted a pilot study to investigate the effect of rTMS on cognitive function in Veterans with numerous medical comorbidities. Methods: Participants underwent 20 sessions, over the course of approximately 4 weeks, of 10 Hz rTMS at the left dorsolateral prefrontal cortex with intensity of 120% resting motor threshold. Outcome measures including memory, language, verbal fluency, and executive functions were acquired at baseline, end of treatment, and 4 months after the last rTMS session. Twenty-six Veterans completed the study (13 in the active rTMS group, 13 in the sham rTMS group). Results: The study protocol was well-tolerated. Active, compared to sham, rTMS showed improved auditory-verbal memory at the end of treatment and at 4-month follow-up. However, the active rTMS group demonstrated a trend in decreased semantic verbal fluency at the end of treatment and at 4-month follow up. Conclusion: These preliminary results show rTMS is safe in general in this elderly Veteran population with multiple co-morbidities. Patients in the sham group showed an expected, slight decline in the California Verbal Learning Test scores over the course of the study, whereas the active treatment group showed a slight improvement at the 4-month post-treatment follow up. These effects need to be confirmed by studies of larger sample sizes.

Pages 1601-1619
Mona Khorani*, Gerd Bobe*, Donald G. Matthews*, Armando Alcazar Magana, Maya Caruso, Nora E. Gray, Joseph F. Quinn, Jan F. Stevens, Amala Soumyanath, Claudia S. Maier *These authors contributed equally to this work.
The Impact of the hAPP695SW Transgene and Associated Amyloid-β Accumulation on Murine Hippocampal Biochemical Pathways
Abstract: Background: Alzheimer’s disease (AD) is a neurodegenerative disease characterized by the accumulation of amyloid-β (Aβ) peptide in the brain. Objective: Gain a better insight into alterations in major biochemical pathways underlying AD. Methods: We compared metabolomic profiles of hippocampal tissue of 20-month-old female Tg2576 mice expressing the familial AD-associated hAPP695SW transgene with their 20-month-old wild type female littermates. Results: The hAPP695SW transgene causes overproduction and accumulation of Aβ in the brain. Out of 180 annotated metabolites, 54 metabolites differed (30 higher and 24 lower in Tg2576 versus wild-type hippocampal tissue) and were linked to the amino acid, nucleic acid, glycerophospholipid, ceramide, and fatty acid metabolism. Our results point to 1) heightened metabolic activity as indicated by higher levels of urea, enhanced fatty acid β-oxidation, and lower fatty acid levels; 2) enhanced redox regulation; and 3) an imbalance of neuro-excitatory and neuro-inhibitory metabolites in hippocampal tissue of aged hAPP695SW transgenic mice. Conclusion: Taken together, our results suggest that dysregulation of multiple metabolic pathways associated with a concomitant shift to an excitatory-inhibitory imbalance are contributing mechanisms of AD-related pathology in the Tg2576 mouse.

Pages 1621-1637
Benson Wu, Mohammad Usama Toseef, Ariana M. Stickel, Hector M. González, Wassim Tarraf
Associations Between Midlife Functional Limitations and Self-Reported Health and Cognitive Status: Results from the 1998-2016 Health and Retirement Study
Abstract: Background: Life-course approaches to identify and help improve modifiable risk factors, particularly in midlife, may mitigate cognitive aging. Objective: We examined how midlife self-rated physical functioning and health may predict cognitive health in older age. Methods: We used data from the Health and Retirement Study (1998-2016; unweighted-N=4,685). We used survey multinomial logistic regression and latent growth curve models to examine how midlife (age 50-64 years) activities of daily living (ADL), physical function, and self-reported health affect cognitive trajectories and cognitive impairment not dementia (CIND) and dementia status 18 years later. Then, we tested for sex and racial/ethnic modifications. Results: After covariates-adjustment, worse instrumental ADL (IADL) functioning, mobility, and self-reported health were associated with both CIND and dementia. Hispanics were more likely to meet criteria for dementia than non-Hispanic Whites given increasing IADL impairment. Conclusion: Midlife health, activities limitations, and difficulties with mobility are predictive of dementia in later life. Hispanics may be more susceptible to dementia in the presence of midlife IADLs. Assessing midlife physical function and general health with brief questionnaires may be useful for predicting cognitive impairment and dementia in later life.

Pages 1639-1655
Noemi Massetti*, Mirella Russo*, Raffaella Franciotti*, Davide Nardini, Giorgio Mandolini, Alberto Granzotto, Manuela Bomba, Stefano Delli Pizzi, Alessandra Mosca, Reinhold Scherer, Marco Onofrj, and Stefano L. Sensi for the Alzheimer’s Disease Neuroimaging Initiative (ADNI)§ and the Alzheimer's Disease Metabolomics Consortium (ADMC) *These authors contributed equally to this work.
A Machine Learning-Based Holistic Approach to Predict the Clinical Course of Patients within the Alzheimer’s Disease Spectrum
Abstract: Background: Alzheimer's disease (AD) is a neurodegenerative condition driven by multifactorial etiology. Mild cognitive impairment (MCI) is a transitional condition between healthy aging and dementia. No reliable biomarkers are available to predict the conversion from MCI to AD. Objective: To evaluate the use of machine learning (ML) on a wealth of data offered by the Alzheimer's Disease Neuroimaging Initiative (ADNI) and Alzheimer's Disease Metabolomics Consortium (ADMC) database in the prediction of the MCI to AD conversion. Methods: We implemented an ML-based Random Forest (RF) algorithm to predict conversion from MCI to AD. Data related to the study population (587 MCI subjects) were analyzed by RF as separate or combined features and assessed for classification power. Four classes of variables were considered: neuropsychological test scores, AD-related cerebrospinal fluid (CSF) biomarkers, peripheral biomarkers, and structural magnetic resonance imaging (MRI) variables. Results: The ML-based algorithm exhibited 86% accuracy in predicting the AD conversion of MCI subjects. When assessing the features that helped the most, neuropsychological test scores, MRI data, and CSF biomarkers were the most relevant in the MCI to AD prediction. Peripheral parameters were effective when employed in association with neuropsychological test scores. Age and sex differences modulated the prediction accuracy. AD conversion was more effectively predicted in females and younger subjects. Conclusion: Our findings support the notion that AD-related neurodegenerative processes result from the concerted activity of multiple pathological mechanisms and factors that act inside and outside the brain and are dynamically affected by age and sex.

Pages 1657-1666
Emer R. McGrath, Jayandra J. Himali, Daniel Levy, Qiong Yang, Charles S. DeCarli, Paul Courchesne, Claudia L. Satizabal, Rebecca Finney, Ramachandran S. Vasan, Alexa S. Beiser, Sudha Seshadri (Handling Association Editor: Inga Zerr) *These authors contributed equally to this work.
Plasma EFEMP1 Is Associated with Brain Aging and Dementia: The Framingham Heart Study
Abstract: Background: Epidermal growth factor containing fibulin extracellular matrix protein-1 (EFEMP1) has been associated with increased white matter hyperintensities (WMH) burden and disorders of premature aging and may have a shared pathophysiological role in the development of WMH and dementia. Objective: To determine the association between plasma EFEMP1 levels and MRI markers of vascular brain injury and incident all-cause and Alzheimer’s disease (AD) dementia. Methods: We measured plasma EFEMP1 levels in 1597 [53% women, mean age 68.7 (SD 5.7) years] dementia-free Framingham Offspring cohort participants between 1998-2001 and subsequently followed them for incident dementia. Secondary outcomes included stroke, structural MRI brain measures and neurocognitive test performance. Results: During a median 11.8 [Q1, Q3: 7.1, 13.3] year follow-up, 131 participants developed dementia. The highest quintile of plasma EFEMP1, compared to the bottom four quintiles, was associated with an increased risk of time to incident all-cause dementia (HR 1.77, 95% CI 1.18-2.64) and AD dementia (HR 1.76, 95% CI 1.11-2.81) but not with markers of vascular brain injury (WMH, covert brain infarcts or stroke). Higher circulating EFEMP1 concentrations were also cross-sectionally associated with lower total brain (β±SE, -0.280.11, p=0.01) and hippocampal volumes (-0.0060.003, p=0.04) and impaired abstract reasoning (Similarities test, -0.18±0.08, p=0.018 per standard deviation increment in EFEMP1). Conclusion: Elevated circulating EFEMP1 is associated with an increased risk of all-cause and AD dementia, smaller hippocampal and total brain volumes, and poorer cognitive performance. EFEMP1 may play an important biological role in the development of AD dementia. Further studies to validate these findings are warranted.

Pages 1667-1676
Maeva Dhaynaut*, Giulia Sprugnoli*, Davide Cappon, Joanna Macone, Justin S. Sanchez, Marc Normandin, Nicolas Guehl, Giacomo Koch, Rachel Paciorek, Ann Connor, Daniel Press, Keith Johnson, Alvaro Pascual-Leone, Georges El-Fakhri**, Emiliano Santarnecchi** *,**These authors contributed equally to this work.
Impact of 40 Hz Transcranial Alternating Current Stimulation on Cerebral Tau Burden in Patients with Alzheimer’s Disease: A Case Series
Abstract: Background: Alzheimer’s disease (AD) is characterized by diffuse amyloid-β (Aβ) and phosphorylated Tau (p-Tau) aggregates as well as neuroinflammation. Exogenously-induced 40 Hz gamma oscillations have been showing to reduce Aβ and p-Tau deposition presumably via microglia activation in AD mouse models. Objective: We aimed to translate preclinical data on gamma-induction in AD patients by means of transcranial alternating current stimulation (tACS). Methods: Four participants with mild-to-moderate AD received 1 h of daily 40 Hz (gamma) tACS for 4 weeks (Monday to Friday) targeting the bitemporal lobes (20 h treatment duration). Participant underwent Aβ, p-Tau, and microglia PET imaging with [11C]-PiB, [18F]-FTP, and [11C]-PBR28 respectively, before and after the intervention along with electrophysiological assessment. Results: No adverse events were reported, and an increase in gamma spectral power on EEG was observed after the treatment. [18F]-FTP PET revealed a significant decrease over 2% of p-Tau burden in 3/4 patients following the tACS treatment, primarily involving the temporal lobe regions targeted by tACS and especially mesial regions (e.g., entorhinal cortex). The amount of intracerebral Aβ as measured by [11C]-PiB was not significantly influenced by tACS, whereas 1/4 reported a significant decrease of microglia activation as measured by [11C]-PBR28. Conclusion: tACS seems to represent a safe and feasible option for gamma induction in AD patients, with preliminary evidence of a possible effect on protein clearance partially mimicking what is observed in animal models. Longer interventions and placebo control conditions are needed to fully evaluate the potential for tACS to slow disease progression.

Pages 1677-1687
Lotte Gerritsen, Emma L. Twait, Palmi V. Jonsson, Vilmundur Gudnason, Lenore J. Launer, Mirjam I. Geerlings
Depression and Dementia: The Role of Cortisol and Vascular Brain Lesions. AGES-Reykjavik Study
Abstract: Background: Late-life depression (LLD) is related to an increased risk of developing dementia; however, the biological mechanisms explaining this relationship remain unclear. Objective: To determine whether the relationship between LLD and dementia can be best explained by the glucocorticoid cascade or vascular hypothesis. Methods: Data are from 4,354 persons (mean age 76±5 years) without dementia at baseline from the AGES-Reykjavik Study. LLD was assessed with the MINI diagnostic interview (current and remitted major depressive disorder [MDD]) and the Geriatric Depression Scale-15. Morning and evening salivary cortisol were collected (glucocorticoid cascade hypothesis). White matter hyperintensities (WMH; vascular hypothesis) volume was assessed using 1.5T brain MRI. Using Cox proportional hazard models, we estimated the associations of LLD, cortisol levels, and WMH volume with incident all-cause dementia, AD, and non-AD dementia. Results: During 8.8±3.2 years of follow-up, 843 persons developed dementia, including 397 with AD. Current MDD was associated with an increased risk of developing all-cause dementia (HR=2.17; 95% CI 1.66-2.67), with risks similar for AD and non-AD, while remitted MDD was not (HR=1.02; 95% CI 0.55-1.49). Depressive symptoms were also associated with increased risk of dementia, in particular non-AD dementias. Higher levels of evening cortisol increased risk of dementia, but this was independent of MDD. WMH partially explained the relation between current MDD and dementia risk but remained increased (HR=1.71; 95% CI 1.34-2.08). Conclusion: The current study highlights the importance of LLD in developing dementia. However, neither the glucocorticoid cascade nor the vascular hypotheses fully explained the relation between depression and dementia.

Pages 1689-1700
Hyejin Ahn, Dahyun Yi*, Kyungjin Chu, Haejung Joung, Younghwa Lee, Gi Jung Juna, Kiyoung Sung, Dongkyun Han, Jun Ho Lee, Min Soo Byun, Dong Young Lee* (Handling Associate Editor: Jong Min Lee) *These authors contributed equally to this work.
Functional Neural Correlates of Semantic Fluency Task Performance in Mild Cognitive Impairment and Alzheimer’s Disease: An FDG-PET Study
Abstract: Background: Total score (TS) of semantic verbal fluency test (SVFT) is generally used to interpret results, but it is ambiguous as to specific neural functions it reflects. Different SVFT strategy scores reflecting qualitative aspects are proposed to identify specific cognitive functions to overcome limitations of using the TS. Objective: Functional neural correlates of the TS as well as the other strategy scores in subjects with mild cognitive impairment (MCI) and Alzheimer’s disease (AD) dementia using Fluorine-18-Fluorodeoxyglucose positron emission tomography (FDG-PET). Methods: Correlations between various SVFT scores (i.e., TS, mean cluster size, switching (SW), hard switching, cluster switching (CSW)) and cerebral glucose metabolism were explored using voxelwise whole-brain approach. Subgroup analyses were also performed based on the diagnosis and investigated the effects of disease severity on the associations. Results: Significant positive correlation between TS and cerebral glucose metabolism was found in prefrontal, parietal, cingulate, temporal cortex, and subcortical regions. Significantly increased glucose metabolism associated with the SW were found in similar but smaller regions, mainly in the fronto-parieto-temporal regions. CSW was only correlated with the caudate. In the subgroup analysis conducted to assess different contribution of clinical severity, differential associations between the strategy scores and regional glucose metabolism were found. Conclusion: SW and CSW may reflect specific language and executive functions better than the TS. The SVFT is influenced by brain dysfunction due to the progression of AD, as demonstrated by the SW with larger involvement of temporal lobe for the AD, and CSW with significant association only for the MCI.

Pages 1701-1720
Wolfgang J. Streit, Jonas Rotter, Karsten Winter, Wolf Müller, Habibeh Khoshbouei, Ingo Bechmann
Droplet Degeneration of Hippocampal and Cortical Neurons Signifies the Beginning of Neuritic Plaque Formation
Abstract: Background: Neuritic plaques contain neural and microglial elements, and amyloid-β protein (Aβ), but their pathogenesis remains unknown. Objective: Elucidate neuritic plaque pathogenesis. Methods: Histochemical visualization of hyperphosphorylated-tau positive (p-tau+) structures, microglia, Aβ, and iron. Results: Disintegration of large projection neurons in human hippocampus and neocortex presents as droplet degeneration: pretangle neurons break up into spheres of numerous p-tau+ droplets of various sizes, which marks the beginning of neuritic plaques. These droplet spheres develop in the absence of colocalized Aβ deposits but once formed become encased in diffuse Aβ with great specificity. In contrast, neurofibrillary tangles often do not colocalize with Aβ. Double-labelling for p-tau and microglia showed a lack of microglial activation or phagocytosis of p-tau+ degeneration droplets but revealed massive upregulation of ferritin in microglia suggesting presence of high levels of free iron. Perl’s Prussian blue produced positive staining of microglia, droplet spheres, and Aβ plaque cores supporting the suggestion that droplet degeneration of pretangle neurons in the hippocampus and cortex represents ferroptosis, which is accompanied by the release of neuronal iron extracellularly. Conclusion: Age-related iron accumulation and ferroptosis in the CNS likely trigger at least two endogenous mechanisms of neuroprotective iron sequestration and chelation, microglial ferritin expression and Aβ deposition, respectively, both contributing to the formation of neuritic plaques. Since neurofibrillary tangles and Aβ deposits colocalize infrequently, tangle formation likely does not involve release of neuronal iron extracellularly. In human brain, targeted deposition of Aβ occurs specifically in response to ongoing ferroptotic droplet degeneration thereby producing neuritic plaques.

Pages 1721-1734
Stefanie A.G. Black, Anastasiia A. Stepanchuk, George W. Templeton, Yda Hernandez, Tomoko Ota, Shyamosree Roychoudhury, Eric E. Smith, Philip A. Barber, Zahinoor Ismail, Karyn Fischer, Angela Zwiers, Marc J. Poulin, Kaj Blennow, Henrik Zetterberg, Peter K. Stys, Shigeki Tsutsui
Diagnosing Alzheimer’s Disease from Circulating Blood Leukocytes Using a Fluorescent Amyloid Probe
Abstract: Background: Toxic amyloid-β (Aβ) peptides aggregate into higher molecular weight assemblies and accumulate not only in the extracellular space, but also in the walls of blood vessels in the brain, increasing their permeability, and promoting immune cell migration and activation. Given the prominent role of the immune system, phagocytic blood cells may contact pathological brain materials. Objective: To develop a novel method for early Alzheimer’s disease (AD) detection, we used blood leukocytes, that could act as "sentinels" after trafficking through the brain microvasculature, to detect pathological amyloid by labelling with a conformationally-sensitive fluorescent amyloid probe and imaging with confocal spectral microscopy. Methods: Formalin-fixed peripheral blood mononuclear cells (PBMCs) from cognitively healthy control (HC) subjects, mild cognitive impairment (MCI) and AD patients were stained with the fluorescent amyloid probe K114, and imaged. Results were validated against cerebrospinal fluid (CSF) biomarkers and clinical diagnosis. Results: K114-labeled leukocytes exhibited distinctive fluorescent spectral signatures in MCI/AD subjects. Comparing subjects with single CSF biomarker-positive AD/MCI to negative controls, our technique yielded modest AUCs, which improved to the 0.90 range when only MCI subjects were included in order to measure performance in an early disease state. Combining CSF Aβ42 and t-Tau metrics further improved the AUC to 0.93. Conclusion: Our method holds promise for sensitive detection of AD-related protein misfolding in circulating leukocytes, particularly in the early stages of disease.

Pages 1735-1744
Felipe Botero-Rodríguez, Ana Melisa Córdoba Sastoque, José Manuel Santacruz Escudero, Hernando Santamaría-García
Neuropsychiatric Symptoms in Patients with Neurocognitive Disorder and Their Performance Between Mild and Major Stages
Abstract: Background: The neuropsychiatric symptoms (NPS) in patients with neurocognitive disorders (NCD) increases the risk of exhibiting significant cognitive and functional decline. However, to the best of our knowledge, few studies have evaluated to what extent the presence of chronic and early NPS impacts cognition and functionality in patients with minor or major stages of NCD. Objective: We aimed to assess the interplay between early and chronic NPS and cognitive and functional presentation of patients with mild and major forms of NCD. Methods: We used two NPS tools tracking early and late NPS and assessed to what extent they determine cognitive and functional outcomes in patients with mild and major forms of NCD. Results: We found an inverse relationship between the presence of NPS, as measured by the Neuropsychiatric Inventory and Mild Behavioral Impairment Checklist (MBI-C), and cognitive and functional variables in major forms of NCD. In contrast, the minor stage of NCD was associated with increased MBI-C scores. Conclusion: Our results revealed that NPS are associated with cognitive and functional outcomes in mild and chronic forms of NCD. Crucially our results suggest that NPS could be considered as a pathological marker of the clinical course of dementia. Additionally, our study calls to study early and late forms of NPS as both impact cognition and functionality of NCD.

Pages 1745-1754
Yuqing Sun, Meng Wang, Yuxin Zhao, Ke Hu, Yong Liu, Bing Liu, Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Jin-Tai Yu)
A Pathway-Specific Polygenic Risk Score Is Associated with Tau Pathology and Cognitive Decline
Abstract: Background: Tauopathy is a primary neuropathological hallmark of Alzheimer’s disease with a strong relationship to cognitive impairment. In the brain, tau aggregation is associated with the regulation of tau kinases and the binding ability of tau to microtubules. Objective: To explore the potential for using specific polygenic risk scores (PRSs), combining the genetic influences involved in tau-protein kinases and the tau-protein binding pathway, as predictors of tau pathology and cognitive decline in non-demented individuals. Methods: We computed a pathway-specific PRS using summary statistics from previous large-scale genome-wide association studies of dementia. We examined whether PRS is related to tau uptake in positron emission tomography (PET), tau levels, and the rate of tau level changes in cerebrospinal fluid (CSF). We further assessed whether PRS is associated with memory impairment mediated by CSF tau levels. Results: A higher PRS was related to elevated CSF tau levels and tau-PET uptake at baseline, as well as greater rates of change in CSF tau levels. Moreover, PRS was associated with memory impairment, mediated by increased CSF tau levels. The association between PRS and tau pathology was significant when APOE was excluded, even among females. However, the effect of PRS on cognitive decline appeared to be driven by the inclusion of APOE. Conclusion: The influence of genetic risk in a specific tau-related biological pathway may make an individual more susceptible to tau pathology, resulting in cognitive dysfunction in an early preclinical phase of the disease.

Pages 1755-1766
Dana Broberg*, Dickson Wong*, Miranda Bellyou, Manuel Montero-Odasso, Olivier Beauchet, Cedric Annweiler, Robert Bartha *These authors contributed equally to this work.
Effects of Memantine and High Dose Vitamin D on Gait in Male APP/PS1 Alzheimer’s Disease Mice Following Vitamin D Deprivation
Abstract: Background: Altered gait is a frequent feature of Alzheimer’s disease (AD), as is vitamin D deficiency. Treatment with memantine and vitamin D can protect cortical axons from exposure to amyloid-β and glutamate toxicity, suggesting this combination may mitigate altered gait in AD. Objective: Investigate the effects of vitamin D deprivation and subsequent treatment with memantine and vitamin D enrichment on gait performance in APPswe/PS1dE9 mice. Methods: Male APPswe/PS1dE9 mice were split into four groups (n=14 each) at 2.5 months of age. A control group was fed a standard diet throughout while the other three groups started a vitamin D-deficient diet at month 6. One group remained on this deficient diet for the rest of the study. At month 9, the other two groups began treatment with either memantine alone or memantine combined with 10 IU/g of vitamin D. Gait was assessed using CatWalk at months 6, 9, 12, and 15. Results: Vitamin D deprivation led to a 13% increase in hind stride width by month 15 (p<0.001). Examination of the treatment groups at month 15 revealed that mice treated with memantine alone still showed an increase in hind stride width compared to controls (p<0.01), while mice treated with memantine and vitamin D did not (p=0.21). Conclusion: Vitamin D deprivation led to impaired postural control in the APPswe/PS1dE9 model. Treatment with memantine and vitamin D, but not memantine alone, prevented this impairment. Future work should explore the potential for treatments incorporating vitamin D supplementation to improve gait in people with AD.

Pages 1767-1781
Graciela C. Alatorre-Cruz, Thalía Fernández, Susana A. Castro-Chavira, Mauricio González-López, Sergio M. Sánchez-Moguel, Juan Silva-Pereyra
One-Year Follow-Up of Healthy Older Adults with Electroencephalographic Risk for Neurocognitive Disorder After Neurofeedback Training
Abstract: Background: In healthy older adults, excess theta activity is an electroencephalographic (EEG) predictor of cognitive impairment. In a previous study, neurofeedback (NFB) treatment reinforcing reductions theta activity resulted in EEG reorganization and cognitive improvement. Objective: To explore the clinical applicability of this NFB treatment, the present study performed a 1-year follow-up to determine its lasting effects. Methods: Twenty seniors with excessive theta activity in their EEG were randomly assigned to the experimental or control group. The experimental group received an auditory reward when the theta absolute power (AP) was reduced. The control group received the reward randomly. Results: Both groups showed a significant decrease in theta activity at the training electrode. However, the EEG results showed that only the experimental group underwent global changes after treatment. These changes consisted of delta and theta decreases and beta increases. Although no changes were found in any group during the period between the posttreatment evaluation and follow-up, more pronounced theta decreases and beta increases were observed in the experimental group when the follow-up and pretreatment measures were compared. Executive functions showed a tendency to improve two months after treatment which became significant one year later. Conclusion: These results suggest that the EEG and behavioral benefits of this NFB treatment persist for at least one year, which adds up to the available evidence contributing to identifying factors that increase its efficacy level. The relevance of this study lies in its prophylactic features of addressing a clinically healthy population with EEG risk of cognitive decline.

Pages 1783-1794
Qingqing Liu, Zaisheng Ling, Jinpeng Zhang, Hongli Yu, Ye Wang, Yang Xue, Chunyan Wang, Jiwei Zhao, Jingwei Cao, Shurong Duan, Jingkun Zhao
lncRNA MIR600HG Knockdown Alleviates Cognitive Impairment in Alzheimer's Disease Through NEDD4L Mediated PINK1 Degradation
Abstract: Background: Growing evidence has demonstrated that long non-coding RNAs (lncRNAs) play a critical role in Alzheimer's disease (AD), which is characterized by sustained mitochondrial dysfunction, inevitable memory loss, and cognitive decline. However, the potential function of lncRNAs MIR600 Host Gene (MIR600HG) in AD remains unanswered. Objective: Our study aimed to investigate the role of MIR600HG and its related molecular mechanism in AD. Methods: The expression of MIR600HG was examined by qRT-PCR. The MIR600HG interacting proteins were identified by RNA pull-down assay and mass spectrometry and verified by RNA immunoprecipitation. Immunofluorescence staining was applied to examine the colocalization of PINK1 and NEDD4L. The PINK1 level and the activation of autophagy were detected by immunoblotting. Morris water maze test was performed to evaluate cognitive decline in AD mice model. Results: MIR600HG expression was elevated during aging in two different types of AD transgenic mouse models. Next, we found that increased MIR600HG directly interact with NEDD4L, which promoted PINK1 ubiquitination and degradation, and as well as autophagy activation. Additionally, MIR600HG promoted Aβ production and suppressed Cytochrome C Oxidase activity. Administration of AAV-shMIR600HG restored the Cytochrome C Oxidase activity and inhibited Aβ production. Furthermore, PINK1 overexpression or MIR600HG knockdown significantly ameliorated the cognitive impairment in APP/PS1 mice. PINK1 depletion recovered the spatial memory defect in the AAV-shMIR600HG injected APP/PS1 mice. Conclusion: MIR600HG was increased in AD and promoted AD pathogenesis. Targeting MIR600HG significantly improved cognitive function in AD mice, which could pave the way for exciting new avenues in AD therapeutic strategy research.

Pages 1795-1806
Jianlin Wang*, Pan Wang*, Yuan Jiang, Zedong Wang, Hong Zhang, Hongyi Li, Bharat B. Biswal *These authors contributed equally to this work.
Hippocampus-Based Dynamic Functional Connectivity Mapping in the Early Stages of Alzheimer’s Disease
Abstract: Background: The hippocampus with varying degrees of atrophy was a crucial neuroimaging feature resulting in the declining memory and cognitive function in Alzheimer’s disease (AD). However, the abnormal dynamic functional connectivity (DFC) in both white matter (WM) and gray matter (GM) from the left and right hippocampus remains unclear. Objective: To explore the abnormal DFC within WM and GM from the left and right hippocampus across the different stages of AD. Methods: Current study employed the OASIS-3 dataset including 43 mild cognitive impairment (MCI), 71 pre-mild cognitive impairment (pre-MCI), and matched 87 normal cognitive (NC). Adopting the FMRIB’s Integrated Registration and Segmentation Tool, we obtained the left and right hippocampus mask. Based on above hippocampus mask as seed point, we calculated the DFC between left/right hippocampus and all voxel time series within whole brain. One-way ANOVA analysis was performed to estimate the abnormal DFC among MCI, pre-MCI, and NC groups. Results: We found that MCI and pre-MCI groups showed the common abnormalities of DFC in the Temporal_Mid_L, Cingulum_Mid_L, and Thalamus_L. Specific abnormalities were found in the Cerebelum_9_L and Precuneus of MCI group and Vermis_8 and Caudate_L of pre-MCI group. In addition, we found that DFC within WM regions also showed the common low DFC for the Cerebellum anterior lobe-WM, Corpus callosum, and Frontal lobe-WM in MCI and pre-MCI group. Conclusion: Our findings provided a novel information for discover the pathophysiological mechanisms of AD and indicate WM lesions were also an important cause of cognitive decline in AD.

Pages 1807-1817
Panteleimon Giannakopoulos, Cristelle Rodriguez, Marie-Louise Montandon, Valentina Garibotto, Sven Haller, François R. Herrmann
Personality Impact on Alzheimer’s Disease-Signature and Vascular Imaging Markers: A PET-MRI Study
Abstract: Background: Several studies postulated that personality is an independent determinant of cognitive trajectories in old age. Objective: This study explores the impact of personality on widely used Alzheimer’s disease (AD) and vascular imaging markers. Methods: We examined the association between personality and three classical AD imaging markers (centiloid-based-amyloid load, MRI volumetry in hippocampus, and media temporal lobe atrophy), and two vascular MRI parameters (Fazekas score and number of cortical microbleeds) assessed at baseline and upon a 54-month-follow-up. Personality was assessed with the Neuroticism Extraversion Openness Personality Inventory-Revised. Regression models were used to identify predictors of imaging markers including sex, personality factors, presence of APOE ε4 allele and cognitive evolution over time. Results: Cortical GM volumes were negatively associated with higher levels of Conscientiousness both at baseline and follow-up. In contrast, higher scores of Openness were related to better preservation of left hippocampal volumes in these two time points and negatively associated with medial temporal atrophy at baseline. Amyloid load was not affected by personality factors. Cases with higher Extraversion scores displayed higher numbers of cortical microbleeds at baseline. Conclusion: Personality impact on brain morphometry is detected only in some among the routinely used imaging markers. The most robust associations concern the positive role of high levels of Conscientiousness and Openness on AD-signature MRI markers. Higher extraversion levels are associated with increased vulnerability to cortical microbleeds pointing to the fact that the socially favorable traits may have a detrimental effect on brain integrity in old age.

Pages 1819-1833
Sally Day, Stefanie Roberts, Nathalie H. Launder, Anita M.Y. Goh, Brian Draper, Alex Bahar-Fuchs, Samantha M. Loi, Kate Laver, Adrienne Withall, Monica Cations
Age of Symptom Onset and Longitudinal Course of Sporadic Alzheimer’s Disease, Frontotemporal Dementia, and Vascular Dementia: A Systematic Review and Meta-Analysis
Abstract: Background: Understanding how the age of dementia symptom onset affects the longitudinal course of dementia can assist with prognosis and care planning. Objective: To synthesize evidence regarding the relationship of age of symptom onset with the longitudinal course of sporadic Alzheimer’s disease (AD), vascular dementia (VaD), and frontotemporal dementia (FTD). Methods: We searched Medline, CINAHL, Embase, PsycINFO, PubMed, and Scopus for longitudinal studies that examined the impact of sporadic AD, VaD, or FTD symptom onset age on measures of cognition, function, or behavioral symptoms. Studies that examined age at diagnosis only were excluded. Quantitative meta-analysis was conducted where studies reported sufficient data for pooling. Results: Thirty studies met all inclusion criteria (people with AD (n=26), FTD (n=4)) though no studies examined VaD. Earlier onset of AD was associated with more rapid annual cognitive decline (estimate=-0.07; 95% CI -0.14 to 0.00; p=0.045). Most studies that stratified their sample reported that younger AD onset (usually < 65 years) was associated with more rapid cognitive decline. Other evidence was inconclusive. Conclusion: Younger people with AD appear to have a poorer prognosis in terms of faster cognitive decline than older people with AD. More research is required to determine the impact of symptom onset age in VaD and FTD, and on functional decline in all dementias.

Pages 1835-1844
Keun-Hwa Jung, Kyung-Il Park, Woo-Jin Lee, Hyo-Shin Son, Kon Chu, Sang Kun Lee
Association of Plasma Oligomerized Amyloid-β and Cerebral White Matter Lesions in a Health Screening Population
Abstract: Background: Cerebral white matter lesions (WML) are related to a higher risk of vascular and Alzheimer’s dementia. Moreover, oligomerized amyloid-β (OAβ) can be measured from blood for dementia screening. Objective: We aimed to investigate the relationship of plasma OAβ levels with clinical and radiological variables in a health screening population. Methods: WML, other volumetric parameters of magnetic resonance images, cognitive assessment, and plasma OAβ level were evaluated. Results: Ninety-two participants were analyzed. The majority of participants’ clinical dementia rating was 0 or 0.5 (96.7%). White matter hyperintensities (WMH) increased with age, but OAβ levels did not (r2=0.19, p<0.001, r2=0.03, p=0.10, respectively). No volumetric data, including cortical thickness/hippocampal volume, showed any significant correlation with OAβ. Log-WMH volume was positively correlated with OAβ (r=0.24, p=0.02), and this association was significant in the periventricular area. White matter signal abnormalities from 3D-T1 images were also correlated with the OAβ in the periventricular area (p=0.039). Multivariate linear regression showed that log-WMH values were independently associated with OAβ (B=0.879 (95% confidence interval 0.098 –1.660, p=0.028)). Higher tertiles of WMH showed higher OAβ levels than lower tertiles showed (p=0.044). Using a cutoff of 0.78 ng/mL, the high OAβ group had a larger WMH volume, especially in the periventricular area, than the low OAβ group (p=0.036). Conclusion: Both WML and plasma OAβ levels can be early markers for neurodegeneration in the healthcare population. The lesions, especially in the periventricular area, might be related to amyloid pathogenesis, which strengthens the importance of WML in the predementia stage.