Volume 69, Number 1, IN PRESS

Mini-Forum: The IMI PharmaCog WP5-European ADNI Study: Role of Biomarkers to Diagnose and Track Short Term Disease Progression in Prodromal Alzheimer's Disease (Guest Editor: Giovanni B. Frisoni)

Editorial
Giovanni B Frisoni, Olivier Blin, Regis Bordet
One Step Forward Toward a Surrogate Endpoint for Clinical Trials of Alzheimer’s Disease Drugs: The Results of PharmaCog WP5 (European ADNI)

Moira Marizzoni, Clarissa Ferrari, Jorge Jovicich, Diego Albani, Claudio Babiloni, Libera Cavaliere, Mira Didic, Gianluigi Forloni, Samantha Galluzzi, Karl-Titus Hoffmann, José Luis Molinuevo, Flavio Nobili, Lucilla Parnetti, Pierre Payoux, Federica Ribaldi, Paolo Maria Rossini, Peter Schönknecht, Andrea Soricelli, Tilman Hensch, Magda Tsolaki, Pieter Jelle Visser, Jens Wiltfang, Jill C. Richardson, Régis Bordet, Olivier Blin, Giovanni B. Frisoni; The PharmaCog Consortium (Handling Editor: George Perry)
Predicting and Tracking Short Term Disease Progression in Amnestic Mild Cognitive Impairment Patients with Prodromal Alzheimer’s Disease: Structural Brain Biomarkers
Abstract: Background. Early Alzheimer’s disease (AD) detection using cerebrospinal fluid (CSF) biomarkers has been recommended as enrichment strategy for trials involving mild cognitive impairment (MCI) patients. Objective. To model a prodromal AD trial for identifying MRI structural biomarkers to improve subject selection and to be used as surrogate outcomes of disease progression. Methods. APOE ε4 specific CSF Aβ42/P-tau cut-offs were used to identify MCI with prodromal AD (Aβ42/P-tau positive) in the WP5-PharmaCog (E-ADNI) cohort. Linear mixed models were performed 1) with baseline structural biomarker, time, and biomarker X time interaction as factors to predict longitudinal changes in ADAS-cog13, 2) with Aβ42/P-tau status, time, and Aβ42/P-tau status X time interaction as factors to explain the longitudinal changes in MRI measures, and 3) to compute sample size estimation for a trial implemented with the selected biomarkers. Results. Only baseline lateral ventricle volume was able to identify a subgroup of prodromal AD patients who declined faster (interaction, p=0.003). Lateral ventricle volume and medial temporal lobe measures were the biomarkers most sensitive to disease progression (interaction, p≤0.042). Enrichment through ventricular volume reduced the sample size that a clinical trial would require from 13 to 76%, depending on structural outcome variable. The biomarker needing the lowest sample size was the hippocampal subfield GC-ML-DG (granule cells of molecular layer of the dentate gyrus) (n= 82 per arm to demonstrate a 20% atrophy reduction). Conclusion. MRI structural biomarkers can enrich prodromal AD with fast progressors and significantly decrease group size in clinical trials of disease modifying drugs.

Jorge Jovicich*, Claudio Babiloni*, Clarissa Ferrari, Moira Marizzoni, Davide V. Moretti, Claudio Del Percio, Roberta Lizio, Susanna Lopez, Samantha Galluzzi, Diego Albani, Libera Cavaliere, Ludovico Minati, Mira Didic, Ute Fiedler, Gianluigi Forloni, Tilman Hensch, José Luis Molinuevo, David Bartrés Faz, Flavio Nobili, Daniele Orlandi, Lucilla Parnetti, Lucia Farotti, Cinzia Costa, Pierre Payoux, Paolo Maria Rossini, Camillo Marra, Peter Schönknecht, Andrea Soricelli, Giuseppe Noce, Marco Salvatore, Magda Tsolaki, Pieter Jelle Visser, Jill C. Richardson, Jens Wiltfang, Régis Bordet, Olivier Blin, Giovanni B. Frisoni and the PharmaCog Consortium (Handling Editor: George Perry) *These authors contributed equally to this work.
Two-Year Longitudinal Monitoring of Amnestic Mild Cognitive Impairment Patients with Prodromal Alzheimer’s Disease Using Topographical Biomarkers Derived from Functional Magnetic Resonance Imaging and Electroencephalographic Activity
Abstract: Auditory “oddball” event-related potentials (aoERPs), resting state functional magnetic resonance imaging (rsfMRI) connectivity, and electroencephalographic (rsEEG) rhythms were tested as longitudinal functional biomarkers of prodromal Alzheimer’s disease (AD). Data were collected at baseline and four follow-ups at 6, 12, 18, and 24 months in amnesic mild cognitive impairment (aMCI) patients classified in two groups: “positive” (i.e., “prodromal AD”; n=81) or “negative” (n=63) based on a diagnostic marker of AD derived from cerebrospinal samples (Aβ42/P-tau ratio). A linear mixed model design was used to test functional biomarkers for Group, Time, and Group x Time effects adjusted by nuisance covariates (only data until conversion to dementia was used). Functional biomarkers that showed significant Group effects (“positive” versus “negative”, p<0.05) regardless of Time were 1) reduced rsfMRI connectivity in both the default mode network (DMN) and the posterior cingulate cortex (PCC), both also giving significant Time effects (connectivity decay regardless of Group); 2) increased rsEEG source activity at delta (< 4 Hz) and theta (4-8 Hz) rhythms and decreased source activity at low-frequency alpha (8-10.5 Hz) rhythms; and 3) reduced parietal and posterior cingulate source activities of aoERPs. Time x Group effects showed differential functional biomarker progression between groups: 1) increased rsfMRI connectivity in the left parietal cortex of the DMN nodes, consistent with compensatory effects and 2) increased limbic source activity at theta rhythms. These findings represent the first longitudinal characterization of functional biomarkers of prodromal AD relative to “negative” aMCI patients based on 5 serial recording sessions over 2 years.

Diego Albani, Moira Marizzoni, Clarissa Ferrari, Federica Fusco, Lucia Boeri, Ilaria Raimondi, Jorge Jovicich, Claudio Babiloni, Andrea Soricelli, Roberta Lizio, Samantha Galluzzi, Libera Cavaliere, Mira Didic, Peter Schönknecht, José Luis Molinuevo, Flavio Nobili, Lucilla Parnetti, Pierre Payoux, Luisella Bocchio, Marco Salvatore, Paolo Maria Rossini, Magda Tsolaki, Pieter Jelle Visser, Jill C. Richardson, Jens Wiltfang, Régis Bordet, Olivier Blin, Gianluigi Forloni, Giovanni B. Frisoni and PharmaCog Consortium (Handling Editor: George Perry)
Plasma Aβ42 as a Biomarker of Prodromal Alzheimer’s Disease Progression in Patients with Amnestic Mild Cognitive Impairment: Evidence from the PharmaCog/E-ADNI Study
Abstract: It is an open issue whether blood biomarkers serve to diagnose Alzheimer’s disease (AD) or monitor its progression over time from prodromal stages. Here, we addressed this question starting from data of the European FP7 IMI-PharmaCog/E-ADNI longitudinal study in amnesic mild cognitive impairment (aMCI) patients including biological, clinical, neuropsychological (e.g., ADAS-Cog13), neuroimaging, and electroencephalographic measures. PharmaCog/E-ADNI patients were classified as “positive” (i.e., “prodromal AD”; n=76) or “negative” (n=52) based on a diagnostic cut-off of Aβ42/P-tau in cerebrospinal fluid as well as APOE ε4 genotype. Blood was sampled at baseline and at two follow-ups (12 and 18 months), when plasma amyloid peptide 42 and 40 (Aβ42, Aβ40) and apolipoprotein J (clusterin, CLU) were assessed. Linear Mixed Models found no significant differences in plasma molecules between the “positive” (i.e., prodromal AD) and “negative” groups at baseline. In contrast, plasma Aβ42 showed a greater reduction over time in the prodromal AD than the “negative” aMCI group (p=0.048), while CLU and Aβ40 increased, but similarly in the two groups. Furthermore, plasma Aβ42 correlated with the ADAS-Cog13 score both in aMCI patients as a whole and the prodromal AD group alone. Finally, CLU correlated with the ADAS-Cog13 only in the whole aMCI group, and no association with ADAS-Cog13 was found for Aβ40. In conclusion, plasma Aβ42 showed disease progression-related features in aMCI patients with prodromal AD.

Moira Marizzoni, Clarissa Ferrari, Ambra Macis, Jorge Jovicich, Diego Albani, Claudio Babiloni, Libera Cavaliere, Mira Didic, Gianluigi Forloni, Samantha Galluzzi, Karl-Titus Hoffmann, José Luis Molinuevo, Flavio Nobili, Lucilla Parnetti, Pierre Payoux, Francesca Pizzini, Paolo Maria Rossini, Marco Salvatore, Peter Schönknecht, Andrea Soricelli, Claudio Del Percio, Tilman Hensch, Ulrich Hegerl, Magda Tsolaki, Pieter Jelle Visser, Jens Wiltfang, Jill C. Richardson, Régis Bordet, Olivier Blin, Giovanni B. Frisoni; The PharmaCog Consortium (Handling Editor: George Perry)
Biomarker Matrix to Track Short Term Disease Progression in Amnestic Mild Cognitive Impairment Patients with Prodromal Alzheimer’s Disease
Abstract: Background: Assessment of human brain atrophy in temporal regions using magnetic resonance imaging (MRI), resting state functional MRI connectivity in the left parietal cortex, and limbic electroencephalographic (rsEEG) rhythms as well as plasma amyloid peptide 42 (Aβ42) has shown that each is a promising biomarker of disease progression in amnestic mild cognitive impairment (aMCI) patients with prodromal Alzheimer’s disease (AD). However, the value of their combined use is unknown. Objective: To evaluate the association with cognitive decline and the effect on sample size calculation when using a biomarker composite matrix in prodromal AD clinical trials. Methods: Multicenter longitudinal study with follow-up of 2 years or until development of incident dementia. APOE ε4-specific cerebrospinal fluid (CSF) Aβ42/P-tau cut-offs were used to identify aMCI with prodromal AD. Linear mixed models were performed 1) with repeated matrix values and time as factors to explain the longitudinal changes in ADAS-cog13, 2) with CSF Aβ42/P-tau status, time, and CSF Aβ42/P-tau status×time interaction as factors to explain the longitudinal changes in matrix measures, and 3) to compute sample size estimation for a trial implemented with the selected matrices. Results: The best composite matrix included the MRI volumes of hippocampal dentate gyrus and lateral ventricle. This matrix showed the best sensitivity to track disease progression and required a sample size 31% lower than that of the best individual biomarker (i.e., volume of hippocampal dentate gyrus). Conclusion: Optimal matrices improved the statistical power to track disease development and to measure clinical progression in the short-term period. This might contribute to optimize the design of future clinical trials in MCI.

Regular Section

Review
Jun Yuan, Bruno P. Meloni, Tianxing Shi, Anne Bonser, John M. Papadimitriou, Frank L. Mastaglia, Changqing Zhang, Minghao Zheng, Junjie Gao
The Potential Influence of Bone-Derived Modulators on the Progression of Alzheimer’s Disease
Abstract: Bone, the major structural scaffold of the human body, has recently been demonstrated to interact with several other organ systems through the actions of bone-derived cells and bone-derived cell secretory proteins. Interestingly, the brain is one organ that appears to fall into this interconnected network. Furthermore, the fact that osteoporosis and Alzheimer’s disease are two common age-related disorders raises the possibility that these two organ systems are interconnected in terms of disease pathogenesis. This review focuses on the latest evidence demonstrating the impact of bone-derived cells and bone-derived proteins on the central nervous system, and on how this may be relevant in the progression of Alzheimer’s disease and for the identification of novel therapeutic approaches to treat this neurodegenerative disorder.

Review
Juan F. Martínez, Catalina Trujillo, Analía Arévalo, Agustín Ibáñez, Juan F. Cardona (Handling Associate Editor: John Ochoa)
Assessment of Conjunctive Binding in Aging: A Promising Approach for Alzheimer’s Disease Detection
Abstract: The visual experience of objects lies in the ability to perceive and integrate their constitutive features. Conjunctive binding (CB) is the cognitive function that integrates the features of objects as wholes. This review covers the main findings (over the last 10 years) concerning the role of CB in visual working memory (VWM) and cognitive theory, its neural correlates, as well as perspectives for future work. First, we discuss the theoretical cognitive models of CB and how these relate to other cognitive functions. We then integrate neuroimaging evidence with cognitive theory to identify the neural functional network of CB for encoding and maintenance. Also, we describe the field’s transition from experimental to clinical research, which paves the way for work in the area of VWM binding and aging. Finally, we expose the challenges faced by this field of research and analyze its role in the study of dementia and the construction of neuro-cognitive models of conjunctive binding.

Short Communication
Panagiotis Alexopoulos*, Nathalie Thierjung*, Polychronis Εconomou, Lukas Werle, Felix Buhl, Simone Kagerbauer, Anastasios D. Papanastasiou, Timo Grimmer, Philippos Gourzis, Achim Berthele, Bernhard Hemmer, Hubert Kübler, Jan Martin, Antonios Politis, Robert Perneczky *These authors contributed equally to this work.
Plasma Levels of Soluble AβPPβ as a Biomarker for Alzheimer’s Disease with Dementia
Abstract: Cost- and time-effective markers of Alzheimer’s disease (AD), reliable and feasible at the population level are urgently needed. Soluble amyloid-β protein precursor β (sAβPPβ) in plasma has attracted scientific attention as a potential ΑD biomarker candidate. Here we report that plasma sAβPPβ levels in patients with AD dementia and typical for AD cerebrospinal fluid (CSF) biomarker profiles (N=33) are significantly lower (p<0.01) than those of cognitively healthy elderly individuals without AD (N=39), while CSF sAβPPβ levels did not differ between the studied groups. This provides further evidence for the potential of sAβPPβ in plasma as an AD biomarker candidate.

Ruma Raha-Chowdhury, James W. Henderson, Animesh Alexander Raha, Romina Vuono, Anastasia Bickerton, Elizabeth Jones, Robert Fincham, Kieren Allinson, Anthony Holland, Shahid H. Zaman
Choroid Plexus Acts as Gatekeeper for TREM2, Abnormal Accumulation of ApoE, and Fibrillary Tau in Alzheimer’s Disease and in Down Syndrome Dementia
Abstract: Background: Genetic factors that influence Alzheimer’s disease (AD) risk include mutations in TREM2 and allelic variants of Apolipoprotein E, influencing AD pathology in the general population and in Down syndrome (DS). Evidence shows that dysfunction of the choroid plexus may compromise the blood-cerebrospinal fluid (CSF) barrier, altering secretary, transport and immune function that can affect AD pathology. Objective: To investigate the genotype and phenotype of DS individuals in relation to choroid plexus damage and blood-CSF barrier leakage to identify markers that could facilitate early diagnosis of AD in DS. Methods: To assess allele frequency and haplotype associations ApoE, Tau, TREM2, and HLA-DR were analyzed by SNP analysis in DS participants (n=47) and controls (n=50). The corresponding plasma protein levels were measured by ELISA. Postmortem brains from DS, AD, and age-matched controls were analyzed by immunohistochemistry. Results: Haplotype analysis showed that individuals with Tau H1/H1 and ApoE ε4 genotypes were more prevalent among DS participants with an earlier diagnosis of dementia (17%) compared to H1/H2 haplotypes (6%). Plasma TREM2 levels decreased whereas phospho-tau levels increased with age in DS. In AD and DS brain, insoluble tau and ApoE were found to accumulate in the choroid plexus. Conclusion: Accumulation of tau and ApoE in the choroid plexus may increase the oligomerization rate of Aβ42 and impair tau trafficking, leading to AD pathology. We have identified a high-risk haplotype: ApoE ε4, Tau/H1, and TREM2/T, that manifests age-related changes potentially opening a window for treatment many years prior to the manifestation of the AD dementia.

Lena L. Law, Kate E. Sprecher, Ryan J. Dougherty, Dorothy F. Edwards, Rebecca L. Koscik, Catherine L. Gallagher, Cynthia M. Carlsson, Henrik Zetterberg, Kaj Blennow, Sanjay Asthana, Mark A. Sager, Bruce P. Hermann, Sterling C. Johnson, Dane B. Cook, Barbara B. Bendlin, Ozioma C. Okonkwo (Handling Associate Editor: Jeffrey Burns)
Cardiorespiratory Fitness Modifies Influence of Sleep Problems on Cerebrospinal Fluid Biomarkers in an At-Risk Cohort
Abstract: Background: Previous studies indicate that cardiorespiratory fitness (CRF) and sleep are each favorably associated with Alzheimer’s disease (AD) pathophysiology, including reduced amyloid-β (Aβ) and tau pathology. However, few studies have examined CRF and sleep in the same analysis. Objective: To examine the relationship between sleep and core AD cerebrospinal fluid (CSF) biomarkers among at-risk healthy late-middle-aged adults and determine whether CRF modifies this association. Methods: Seventy-four adults (age=64.38±5.48, 68.9% female) from the Wisconsin Registry for Alzheimer’s Prevention participated. Sleep was evaluated using the Medical Outcomes Study Sleep Scale, specifically the Sleep Problems Index I (SPI), which incorporates domains of sleep disturbance, somnolence, sleep adequacy, and shortness of breath. Higher scores indicate greater sleep problems. To assess CRF, participants underwent a graded exercise test. CSF was collected via lumbar puncture, from which Aβ42, total-tau (t-tau), and phosphorylated-tau (p-tau) were immunoassayed. Regression analyses examined the association between SPI and CSF biomarkers, and the interaction between SPI and CRF on these same biomarkers, adjusting for relevant covariates. Results: Higher SPI scores were associated with greater p-tau (p=0.027) and higher t-tau/Aβ42 (p=0.021) and p-tau/Aβ42 (p=0.009) ratios. Analyses revealed significant SPI*CRF interactions for t-tau (p=0.016), p-tau (p=0.008), and p-tau/Aβ42 (p=0.041); with a trend for t-tau/Aβ42 (p=0.061). Specifically, the relationship between poorer sleep and these biomarkers was significant among less fit individuals, but not among those who were more fit. Conclusion: In a late-middle-aged at-risk cohort, CRF attenuated the association between poor sleep and levels of select CSF biomarkers. This suggests fitness may play an important role in preventing AD by protecting against pathology, even in impaired sleep.

Shoshana H. Bardach, Gregory A. Jicha, Shama Karanth, Xuan Zhang, Erin L. Abner (Handling Associate Editor: Jeff Burns)
Genetic Sample Provision Among National Alzheimer’s Coordinating Center Participants
Abstract: Background: Genetic data help detect preclinical Alzheimer’s disease and target individuals for clinical trials, making genetic research engagement critical for continued advancement in dementia prevention and treatment. Objective: To understand what individual and institutional factors may relate to provision of genetic samples within the Alzheimer’s Disease Centers. Methods: Data from the National Alzheimer’s Coordinating Center Uniform Data Set (2009-2016) were obtained along with genetic sample availability. Logistic regression was used to assess independent contributions of demographic and clinical characteristics to the probability of sample provision. Sites contributing data completed a brief survey exploring regulatory and scientific issues related to genetic research engagement. Results: Just over half (52.1%) of the 27,519 unique participants had genetic data available. Female sex, white race, non-Hispanic ethnicity, normal cognition, and greater than 5 years of follow-up were associated with greater probability of availability. Sites identified refusals as the most frequent barrier to sample provision, followed by staff availability. Conclusion: These results highlight the importance of strategies to promote minority engagement and encourage earlier genetic research participation.

Rong Huang, Sai Tian, Jing Han, Hongyan Lin, Dan Guo, Jiaqi Wang, Ke An, Shaohua Wang
U-Shaped Association between Serum Uric Acid Levels and Cognitive Functions in Patients with Type 2 Diabetes: A Cross-Sectional Study
Abstract: Background: Serum uric acid (SUA) is a natural antioxidant that may exert neuroprotective effects against neurodegenerative diseases. The relationship between uric acid and cognitive functions has been extensively studied, but results remain conflicting. Objective: To investigate potential associations between SUA level and mild cognitive impairment (MCI), and different domains of cognitive performances in patients with type 2 diabetes mellitus (T2DM). Methods: A total of 352 T2DM subjects (208 males and 144 females) were enrolled. SUA level was determined by using the uricase method. Cognitive performances were assessed using a validated neuropsychological test battery. Generalized additive models and binary logistic regression analysis were fitted to determine the association between SUA and cognitive functions. Results: A total of 157 T2DM patients had MCI, and 195 normal cognition. Compared with the controls, MCI patients exhibited lower SUA level (p=0.009). Generalized additive models revealed a U-shaped curve relationship among SUA with Montreal Cognitive Assessment, Auditory Verbal Learning Test-immediate recall and Trail Making Test-B scores (all p<0.05). Further logistic regression analysis showed a significant trend toward decreased MCI risk with increased SUA level among the subjects whose SUA level was below the cut-point (388.63 μmol/L); each unit increment in SUA level reduced the MCI risk by 0.7% (p=0.003). Conclusion: A U-shaped association between SUA level and global cognitive function, especially executive and memory function, existed in T2DM patients. Our findings will provide additional suggestions that an increase of SUA to a certain level may be a novel method to reduce the burden of T2DM-associated cognitive impairment.

Chunfei Li, Ranjan Duara, David A. Loewenstein, Walter Izquierdo, Mercedes Cabrerizo, Warren Barker, Malek Adjouadi; for the Alzheimer’s Disease Neuroimaging Initiative (Handling Associate Editor: Saeid Taheri)
Greater Regional Cortical Thickness Is Associated with Selective Vulnerability to Atrophy in Alzheimer’s Disease, Independent of Amyloid Load and APOE Genotype
Abstract: Background: Regional cortical thickness (rCTh) among cognitively normal (CN) adults (rCThCN) varies greatly between brain regions, as does the vulnerability to neurodegeneration. Objective: The goal of this study was to: 1) rank order rCThCN for various brain regions, and 2) explore their vulnerability to neurodegeneration in Alzheimer’s disease (AD) within these brain regions. Methods: The relationship between rCTh among the CN group (rCThCN) and the percent difference in CTh (%CThDiff) in each region between the CN group and AD patients was examined. Pearson correlation analysis was performed accounting for amyloid-β (Aβ) protein and APOE genotype using 210 age, gender, and APOE matched CN (n = 105, age range: 56-90) and AD (n = 105, age range: 56-90) ADNI participants. Results: Strong positive correlations were observed between rCThCN and %CThDiff accounting for Aβ deposition and APOE status. Regions, such as the entorhinal cortex, which had the greatest CTh in the CN state, were also the regions which had the greatest %CThDiff. Conclusions: Regions with the greatest CTh at the CN stage are found to aggregate in disease prone regions of AD, namely in the medial temporal lobe, including the temporal pole, ERC, parahippocampal gyrus, fusiform and the middle and inferior temporal gyrus. Although rCTh has been found to vary considerably across the different regions of the brain, our results indicate that regions with the greatest CTh at the CN stage are actually regions which have been found to be most vulnerable to neurodegeneration in AD.

Sarah Patrick, Rachel Corrigan, John Grizzani, Megan Mey, Jeff Blair, Merce Pallas, Antonio Camins, Hyoung-gon Lee, Gemma Casadesus
Neuroprotective Effects of the Amylin Analog, Pramlintide, on Alzheimer’s Disease Are Associated with Oxidative Stress Regulation Mechanisms
Abstract: Administration of the recombinant analog of the pancreatic amyloid amylin, Pramlintide, has shown therapeutic benefits in aging and Alzheimer’s disease (AD) models, both on cognition and amyloid-β (Aβ) pathology. However, the neuroprotective mechanisms underlying the benefits of Pramlintide remain unclear. Given the early and critical role of oxidative stress in AD pathogenesis and the known reactive oxygen species (ROS) modulating function of amyloids, we sought to determine whether Pramlintide’s neuroprotective effects involve regulation of oxidative stress mechanisms. To address this, we treated APP/PS1 transgenic mice with Pramlintide for 3 months, starting at 5.5 months prior to widespread AD pathology onset, and measured cognition (Morris Water Maze), AD pathology, and oxidative stress-related markers and enzymes in vivo. In vitro, we determined the ability of Pramlintide to modulate H2O2-induced oxidative stress levels. Our data show that Pramlintide improved cognitive function, altered amyloid-processing enzymes, reduced plaque burden in the hippocampus, and regulated endogenous antioxidant enzymes (MnSOD and GPx1) and the stress marker HO-1 in a location specific manner. In vitro, Pramlintide treatment in neuronal models reduced H2O2-induced endogenous ROS production and lipid peroxidation in a dose-dependent manner. Together, these results indicate that Pramlintide’s benefits on cognitive function and pathology may involve antioxidant-like properties of this compound.

Wei-Wei Li, Ying-Ying Shen, Ding-Yuan Tian, Xian-Le Bu, Fan Zeng, Yu-Hui Liu, Yang Chen, Xiu-Qing Yao, Hui-Yun Li, Dong-Wan Chen, Fa-Ying Zhou, Heng Yang, Qi-Ming Li, Wei-Qi Bao, Yi-Hui Guan, Hua-Dong Zhou, Rong-Bing Jin, Yan-Jiang Wang (Handling Associate Editor: Jin-Tai Yu)
Brain Amyloid-β Deposition and Blood Biomarkers in Patients with Clinically Diagnosed Alzheimer’s Disease
Abstract: Brain amyloid-β (Aβ) deposition is a hallmark to define Alzheimer’s disease (AD). We investigated the positive rate of brain Aβ deposition assessed with amyloid PET and blood Aβ levels in a cohort of probable AD patients who were diagnosed according to the 1984 NINCDS-ADRDA criteria. Eighty-four subjects with a clinical diagnosis of probable AD dementia, amnestic mild cognitive impairment (MCI), and cognitively normal (CN) status were subjected to 11C-Pittsburgh compound (PiB)-PET and 18F-fluorodeoxyglucose (FDG)-PET scans. Plasma biomarkers of Aβ42, Aβ40, and T-tau were measured using single molecule array technology. The positive rate of PiB-PET, the associations between PiB-PET status and FDG-PET, plasma biomarkers, and clinical manifestations were analyzed. PiB-PET was positive in 77.36% of probable AD patients, 31.80% of MCI patients, and 0 of NC. Plasma Aβ42/Aβ40 ratio was associated with PiB-PET, the ROC curve analysis revealing an AUC of 0.77 (95%CI: 0.66-0.87), with a sensitivity of 82% and specificity of 64%. Some clinical manifestations were associated with amyloid PET imaging. Our findings indicate that only three-fourths of patients diagnosed with probable AD fit the pathological criteria, suggesting that we should be cautious regarding the accuracy of AD diagnosis when no biomarker evidence is available in our clinical practice.

Andrea Saul Costa, Franca Rosa Guerini, Beatrice Arosio, Daniela Galimberti, Milena Zanzottera, Anna Bianchi, Raffaello Nemni, Mario Clerici
SNARE Complex Polymorphisms Associate with Alterations of Visual Selective Attention in Alzheimer’s Disease
Abstract: The SNARE complex plays a crucial role in the synaptic exocytosis of neurotransmitters, a process involved in the Alzheimer's disease (AD), the most common form of dementia. SNAP-25, STX1a, and VAMP2 are the core proteins of the SNARE complex, and changes in protein level are suggested to contribute to cognitive impairment and neuropsychiatric disorders. Single nucleotide polymorphisms (SNPs) in SNARE complex genes were shown to be associated with different diseases and different cognitive impairments. Chi-square analysis was used to compare case-control difference of ApoE4, SNAP-25 rs363039, rs363043, rs363950, STX1a rs4717806, rs2293489, and VAMP2 26bp Ins/Del genotype distribution in 192 AD, 187 mild cognitive impairment (MCI), and 200 healthy controls (HC). Results of genotype and allelic distribution of SNAP-25 rs363050 showed that AA genotype (AD versus HC: p=1.5x10-4; MCI versus HC: p=8.7x10-3) as well as A allele (AD versus HC: p=6.0x10-4; MCI versus HC: p=5.7x10-3) are significantly more frequent in AD and MCI compared to HC. Genotype distribution of STX1a rs4717806 and rs2293489 resulted significantly different in AD compared to HC (p=0.032 and p=0.047, respectively). Moreover, distribution of the STX1a rs4717806 allele in SNAP-25 rs363050 AA carriers was significantly different between MCI and HC (p=0.018). Notably, in MCI, visual selective attention impairment was associated with the STX1a rs4717806 AA (pc=0.027) genotype as well as the SNAP-25/STX1a rs363050/rs4717806 AA/A (pc=0.022) combination. These data suggest that SNPs in SNARE complex genes may interfere and/or modulate the activity of the SNARE complex resulting in impairments of neurotransmission that involve attention brain areas.

Fredrik Jernerén, Tommy Cederholm, Helga Refsum, A. David Smith, Cheryl Turner, Jan Palmblad, Maria Eriksdotter, Erik Hjorth, Gerd Faxen-Irving, Lars-Olof Wahlund, Marianne Schultzberg, Hans Basun, Yvonne Freund-Levi (Handling Associate Editor: Amos Korczyn)
Homocysteine Status Modifies the Treatment Effect of Omega-3 Fatty Acids on Cognition in a Randomized Clinical Trial in Mild to Moderate Alzheimer’s Disease: The OmegAD Study
Abstract: Background: Trials of supplementation with omega-3 fatty acids (ω3-FAs) in patients with mild cognitive impairment or Alzheimer’s disease (AD) have given inconsistent effects on cognitive decline. There is evidence of an interaction between B vitamin status and ω3-FAs in relation to brain atrophy and cognitive decline. Objective: We investigated whether baseline levels of plasma total homocysteine (tHcy), a marker of B vitamin status, modify the effects of ω3-FAs supplementation on cognitive performance in moderate AD. Methods: This post hoc analysis of the OmegAD trial included 171 community-based patients with AD (MMSE ≥ 15): 88 patients received daily doses of 1.7 g docosahexaenoic acid and 0.6 g eicosapentaenoic acid for 6 months. Treatment outcome on cognition was analyzed according to baseline levels of tHcy using a general linear model and ANCOVA. Results: We found significant interactions between ω3-FA supplementation and tHcy on cognition and clinical stage assessed by MMSE (p = 0.040), global CDR (p = 0.059), and CDRsob (p = 0.023), but not on ADAS-cog (p = 0.649). In patients with tHcy levels < 11.7 μmol/L, ω3-FA supplementation improved cognitive performance as measured by MMSE (+7.1%, 95% CI: 0.59 to 13.7%, p = 0.033) and clinical status as measured by CDRsob (-22.3%, 95% CI: -5.8 to -38.7%, p = 0.009) compared to placebo. Conclusion: The effect of ω3-FA supplementation on MMSE and CDR appears to be influenced by baseline tHcy, suggesting that adequate B vitamin status is required to obtain beneficial effects of ω3-FA on cognition.

Qiongqiong Qiu, Luxi Shen, Longfei Jia, Qi Wang, Fangyu Li, Ying Li, Jianping Jia
A Novel PSEN1 M139L Mutation Found in a Chinese Pedigree with Early-Onset Alzheimer’s Disease Increases Aβ42/Aβ40 ratio
Abstract: Background: Presenilin1 (PSEN1) is the most common gene related to familial Alzheimer’s disease (AD). Only several mutation types from Chinese have been reported, with less biological function research conducted. Objectives: We explore the pathological function of PSEN1 M139L, a mutation located at α-helix of PSEN1 transmembrane 2, using predictive programs and in vitro study and compare its effects on Aβ production to those of an artificial PSEN1 S141G located at non α-helix. Methods: APP, PSEN1, and PSEN2 genes were screened for mutations using Sanger sequencing in the DNA samples of the proband and additional available family members. Disease-mutation cosegregation analysis and three software programs were performed to predict the mutation’s pathogenicity. In vitro, we investigated the impact of these mutations on Aβ production in HEK293-APPswe cells using lentiviral vectors harboring PSEN1 WT, PSEN1 M139L, the positive control (PSEN1 M139V) and the non α-helical mutation (PSEN1 S141G). In addition, we co-transfected PSEN1 and tau into cells to determine the mutations’ impact on tau phosphorylation. Results: PSEN1 M139L mutation was discovered in the index patient and four affected siblings. Cosegregation analysis and silicon prediction suggested the mutation was probably disease causing. In vitro studies demonstrated that both PSEN1 M139L and PSEN1 S141G caused elevated ratios of Aβ42/Aβ40, but changes of tau phosphorylation were not detected. Conclusion: The novel PSEN1 M139L mutation found in familial AD increases the Aβ42/Aβ40 ratio significantly. Mutations at non α-helical face of PSEN1 TM2 can affect Aβ production and the region may play a key role in PSEN1 function.

Seung Joo Kim, Na-Yeon Jung, Young Ju Kim, Seong Beom Park, KoWoon Kim, Yeshin Kim, Hyemin Jang, Si Eun Kim, Soo Hyun Cho, Jun Pyo Kim, Young Hee Jung, Sook-Young Woo, Seon Woo Kim, Samuel N. Lockhart, Eun-Joo Kim, Hee Jin Kim, Jong-Min Lee, Juhee Chin, Duk L. Na, Sang Won Seo
Clinical Effects of Frontal Behavioral Impairment: Cortical Thickness and Cognitive Decline in Individuals with Subjective Cognitive Decline and Amnestic Mild Cognitive Impairment
Abstract: Background: Frontal behavioral impairment (FrBI) is commonly observed in various degenerative diseases and refers to various behavioral symptoms. Objective: We investigated the effects of the presence of FrBI on cortical thickness, and the longitudinal neuropsychological changes in people in the predementia stage. Methods: A total of 794 individuals completed neuropsychological tests and the Frontal Behavioral Inventory (FBI) Questionnaire, and underwent magnetic resonance (MR) scanning. Participants were analyzed and grouped into non-FrBI (FBI = 0) or FrBI (FBI≥1). Cortical thickness was measured on MR images using a surface-based method. Results: In total, 281 people with subjective cognitive decline (SCD) and 513 with amnestic mild cognitive impairment (aMCI) were assessed for FrBI. Relative to people without FrBI, those with FrBI presented reduced cortical thickness in the frontal, anterior temporal and lateral parietal regions (p < 0.05, FDR corrected). People with FrBI developed Alzheimer’s disease, rather than behavioral variant frontotemporal dementia, as observed over seven years. Mixed effects models reported that people with FrBI have greater cognitive decline than those with non-FrBI in multiple domains, including language, memory, and executive functions (p < 0.05, FDR corrected). Furthermore, while negative FrBI symptoms (e.g., deficit behaviors) were associated with greater declines in multiple domains, positive FrBI symptoms (e.g., disinhibition symptoms) were related to declines in visuospatial function and verbal memory. Finally, the occurrence of both types of symptoms correlated with multi-domain cognitive decline. Conclusions: FrBI predicted worse clinical outcomes, including reduced cortical thickness and cognitive decline, which are not necessarily specific to frontal dysfunction.

Denise Wilfling, Martin N. Dichter, Diana Trutschel, Sascha Köpke
Prevalence of Sleep Disturbances in German Nursing Home Residents with Dementia: A Multicenter Cross-Sectional Study
Abstract: Background: Sleep disturbances and insomnia occur frequently in people with dementia and are associated with a number of problems for affected persons, relatives, and carers. Objective: Considering the lack of high-quality data especially from Germany, this study aimed to determine the prevalence of sleep disturbances and possible associated factors with in German nursing home residents. Methods: Multicenter cross-sectional study. Nursing homes in Northern Germany were randomly selected from nursing home registers and contacted consecutively. All residents with cognitive impairment living in the nursing homes were included. Data collection took place between June and December 2017. In addition to the characteristics of nursing homes, nurses, and residents, sleep disturbances of residents with dementia were assessed using the Sleep Disorder Inventory (SDI). Descriptive statistics were applied for prevalence assessment. A generalized linear mixed model was used to investigate associated factors. Results: 38 nursing homes and 1,187 residents with cognitive impairment were included in the study. Sleep disturbances were reported for 23% of residents with pronounced differences between centers, ranging from 0-85%. The prescription of psychotropic drugs (OR 4.47; 95% CI 3.06-6.43; p<0.01), residence at a specialized dementia care unit (OR 2.43; 95% CI 1.30-4.53; p<0.01), and male sex (OR 1.56, 95% CI 1.08-2.25, p<0.02) were significantly associated with sleep problems. Conclusions: In Germany, prevalence of sleep disturbances in people with dementia is comparable to reports from other countries. Therefore, the development and rigorous evaluation of preferably non-pharmacological interventions is strongly warranted.

Chenxi Li, Youjun Li, Liang Zheng, Xiaoqi Zhu, Bixin Shao, Geng Fan, Tian Liu,Jue Wang, Alzheimer’s Disease Neuroimaging Initiative
Abnormal Brain Network Connectivity in a Triple-Network Model of Alzheimer’s Disease
Abstract: Resting-state fMRI studies have demonstrated that Alzheimer’s disease (AD) is associated with aberrant organization and function of large-scale brain networks. However, the nature of the disruption of cross-network interactions in the key neurocognitive networks in the brain remains unclear. In this paper, we examined the ‘triple-network model’, including the default mode network (DMN), salience network (SN), and central executive network (CEN), to identify the cross-network interactions in late mild cognitive impairment (LMCI) and AD. With resting-state fMRI, we tested cross-network functional connectivity among the DMN, SN, and CEN in 33 AD patients, 24 LMCI, and 25 well-matched normal control subjects. Then, we identified the most influential brain regions affected by AD and LMCI. Finally, we investigated the relationship between aberrant functional connectivity and clinical cognitive dysfunction. We found the cross-network functional connectivity of the SN-centered ‘triple-network model’ was significantly impaired in the AD group and the alterations were negatively correlated with the Mini-Mental State Examination (MMSE) scores. For the LMCI group, the functional connectivity of the SN-centered ‘triple-network model’ also changed compared to AD; however, we found no correlation with MMSE score. As predicted, the abnormal connections among the three networks mainly overlap with the key nodes of the three networks. Overall, our findings suggested that the interactions of the SN-centered ‘triple-network model’ are impaired in AD patients and that these alterations contribute to the decline in cognitive function. This ‘triple-network model’ provides new insights into AD and provides more information about the dysregulation of brain networks in AD.

Yanfeng Jiang*, Yingzhe Wang*, Ziyu Yuan, Kelin Xu, Kexun Zhang, Zhen Zhu, Peixi Li, Chen Suo, Weizhong Tian, Min Fan, Li Jin**, Weimin Ye**, Qiang Dong, Mei Cui, Xingdong Chen (Handling Associate Editor: Jin-Tai Yu) *These authors contributed equally to this work. **Joint senior authors.
Total Cerebral Small Vessel Disease Burden Is Related to Worse Performance on the Mini-Mental State Examination and Incident Dementia: A Prospective 5-Year Follow-Up
Abstract: Individual cerebral small vessel disease (CSVD) may cause cognitive decline. However, the association between total burden of CSVD and cognitive deterioration in the general population remains unclear. We aimed to determine whether total CSVD score is associated with cognitive performance change and incident dementia in the general population. In the longitudinal population-based Taizhou Imaging Study, 556 participants free of neurological disorders underwent brain MRI and neuropsychological testing at baseline. A total of 456 participants were followed up for cognitive performance for a mean (standard deviation) of 4.6 (0.6) years. Total CSVD score (range 0–4) was calculated by assigning 1 point for the presence of each of the following markers: lacune, white matter hyperintensity, cerebral microbleed, and perivascular space. Beta regression was used to evaluate the association between total CSVD burden and MMSE score change. The association of prevalent CSVD with incident dementia was studied using Fisher’s exact test. CSVDs were present in 262 individuals (47.1%). The total CSVD score was significantly associated with MMSE score decline (p = 0.001). Compared to those with no CSVD, participants with 4 CSVD markers had a steeper decline in MMSE score (β: -0.53, 95% CI: -0.86 to -0.21; p = 0.001). A total of 15 participants developed dementia during follow-up. The presence of more than three CSVD markers at baseline was associated with a significantly higher risk of dementia (p = 0.020). Total CSVD burden appears to be associated with MMSE score decline and incident dementia in a general population in China.

Tessandra Stewart, Min Shi, Aanchal Mehrotra, Patrick Aro, David Soltys, Kathleen F. Kerr, Cyrus P. Zabetian, Elaine R. Peskind, Peggy Taylor, Leslie M. Shaw, John Q. Trojanowski, Jing Zhang, from the Alzheimer’s Disease Neuroimaging Initiative
Impact of Pre-Analytical Differences on Biomarkers in the ADNI and PPMI Studies: Implications in the Era of Classifying Disease Based on Biomarkers
Abstract: Background: Neurodegenerative diseases require characterization based on underlying biology using biochemical biomarkers. Mixed pathology complicates discovery of biomarkers and characterization of cohorts, but inclusion of greater numbers of patients with different, related diseases with frequently co-occurring pathology could allow better accuracy. Combining cohorts collected from different studies would be a more efficient use of resources than recruiting subjects from each population of interest for each study. Objective: To explore the possibility of combining existing datasets by controlling pre-analytic variables in the Alzheimer’s Disease Neuroimaging Initiative (ADNI) and Parkinson’s Progression Markers Initiative (PPMI) studies. Methods: Cerebrospinal fluid (CSF) was collected and processed from 30 subjects according to both the ADNI and PPMI protocols. Relationships between reported levels of Alzheimer’s disease (AD) and Parkinson’s disease (PD) biomarkers in the same subject under each protocol were examined. Results: Protocol-related differences were observed for Aβ, but not t-tau or α-syn, and trended different for p-tau and pS129. Values of α-syn differed by platform. Conversion of α-syn values between ADNI and PPMI platforms did not completely eliminate differences in distribution. Discussion: Factors not captured in the pre-analytical sample handling influence reported biomarker values. Assay standardization and better harmonized characterization of cohorts should be included in future studies of CSF biomarkers.

Mamen Regalado-Reyes, Diana Furcila, Félix Hernández, Jesús Ávila, Javier DeFelipe, Gonzalo León-Espinosa
Phospho-Tau Changes in the Human CA1 During Alzheimer’s Disease Progression
Abstract: Despite extensive studies regarding tau phosphorylation progression in both human Alzheimer’s disease cases and animal models, the molecular and structural changes responsible for neurofibrillary tangle development are still not well understood. Here, by using the antibodies AT100 (recognizes tau protein phosphorylated at Thr212 and Ser214 in the proline-rich region) and pS396 (recognizes tau protein phosphorylated at serine residue 396 in the C-terminal region), we examined phospho-tau immunostaining in neurons from the hippocampal CA1 region of 21 human cases with tau pathology ranging from Braak stage I to VI. Our results indicate that the AT100/pS396 ratio decreases in CA1 in accordance with the severity of the disease, along with its colocalization. We therefore propose the AT100/pS396 ratio as a new tool to analyze the tau pathology progression. Our findings also suggest a conformational modification in tau protein that may cause the disappearance of the AT100 epitope in the late stages of tau pathology, which may play a role in the toxic tangle aggregation. Thus, this study provides new insights underlying the stages for the formation of neurofibrillary tangles in Alzheimer’s disease.

Ya Miao*, Donghao Guo*, Wei Li, Yuan Zhong (Handling Associate Editor: Yong Guo) *These authors contributed equally to this work.
Diabetes Promotes Development of Alzheimer’s Disease Through Suppression of Autophagy
Abstract: Recent studies suggest that diabetes predisposes patients to develop neurodegenerative Alzheimer’s disease (AD), although the underlying mechanisms have yet to be determined. Compromised autophagy of neuronal cells, which occurs in the early stages of AD, has been shown to enhance disease progression. However, autophagic regulation as a mechanism connecting diabetes and AD has not been shown before. Here, we found that streptozotocin (STZ)-induced diabetic rats exhibited poorer performance on the social recognition test, Morris water maze, and plus-maze discriminative avoidance task, compared to PBS-treated normoglycemic control rats, likely resulting from increased brain deposition of amyloid-β peptide aggregates (Aβ) and increased phosphorylation of tau protein, two pathological features of AD. Moreover, diabetes-induced AD-like behavioral and pathological changes were associated with a decrease in neuronal cell autophagy. Furthermore, compromised cell autophagy was recapitulated in vitro in neuronal cells cultured in high glucose conditions. Thus, our data suggest that hyperglycemia in diabetes may directly inhibit neuronal cell autophagy, which subsequently enhances AD-associated pathological progression.

Cheng Cao, Yu Hasegawa, Kenyu Hayashi, Yushin Takemoto, Shokei Kim-Mitsuyama
Chronic Angiotensin 1-7 Infusion Prevents Angiotensin-II-Induced Cognitive Dysfunction and Skeletal Muscle Injury in a Mouse Model of Alzheimer’s Disease
Abstract: Alzheimer’s disease (AD) is increasingly viewed as a neurological disease accompanied by a systemic disorder. Accumulating evidence supports that angiotensin II and angiotensin 1-7 exert opposite effects on various organs including the brain. However, the interaction between angiotensin II and angiotensin 1-7 in AD remains to be defined. The present study was undertaken to examine the interaction between these peptides in AD. 5XFAD mice, a useful model of AD, were separated into three groups: 1) saline-infused, 2) angiotensin II-infused, and 3) angiotensin II-infused and angiotensin 1-7-co-infused. These peptides were systemically given to 5XFAD mice via osmotic minipump for 4 weeks. Systemic angiotensin II infusion for 4 weeks induced significant hypertension in both wild-type and 5XFAD mice. Angiotensin II induced cognitive abnormality in 5XFAD mice as estimated by the Morris water maze test and the nest building test, and this effect was associated with cerebral blood flow reduction, cortical arterial amyloid-β deposition, hippocampal inflammation, and neuron loss in 5XFAD mice. In addition, angiotensin II infusion led to gastrocnemius muscle atrophy in 5XFAD mice. Co-infusion of angiotensin 1-7 prevented the above-mentioned detrimental effects of angiotensin II in the brain and gastrocnemius muscle in 5XFAD mice, without significant influence on blood pressure. The left ventricular hypertrophic response to angiotensin II was attenuated in 5XFAD mice compared with wild-type mice, which was not significantly altered by co-administration of angiotensin 1-7. Our results show that angiotensin 1-7 counteracts angiotensin II-induced cognitive impairment, brain injury, and skeletal muscle injury in AD mice.