Volume 100, Supplement 1, IN PROGRESS

Review
Isidro Ferrer
Amyloid-β Pathology Is the Common Nominator Proteinopathy of the Primate Brain Aging
Abstract: Senile plaques, mainly diffuse, and cerebral amyloid-β (Aβ) angiopathy are prevalent in the aging brain of non-human primates, from lemurs to non-human Hominidae. Aβ but not hyper-phosphorylated tau (HPtau) pathology is the common nominator proteinopathy of non-human primate brain aging. The abundance of Aβ in the aging primate brain is well tolerated, and the impact on cognitive functions is usually limited to particular tasks. In contrast, human brain aging is characterized by the early appearance of HPtau pathology, mainly forming neurofibrillary tangles, dystrophic neurites of neuritic plaques, and neuropil threads, preceding Aβ deposits by several decades and by its severity progressing from selected nuclei of the brain stem, entorhinal cortex, and hippocampus to the limbic system, neocortex, and other brain regions. Neurofibrillary tangles correlate with cognitive impairment and dementia in advanced cases. Aβ pathology is linked in humans to altered membrane protein and lipid composition, particularly involving lipid rafts. Although similar membrane alterations are unknown in non-human primates, membrane senescence is postulated to cause the activated β-amyloidogenic pathway, and Aβ pathology is the primary signature of non-human and human primate brain aging.

Review
D. Allan Butterfield
Activation of the Neuronal Cell Cycle in Brains in Amnestic Mild Cognitive Impairment: Early Involvement in the Progression of Alzheimer’s Disease
Abstract: Activation of cell-cycle machinery in Alzheimer’s disease (AD) brain was reported by Mark Smith and colleagues and by other researchers. Among other biochemical processes underlying this activation, the notion that AD brain, under the onslaught of oxidative and nitrosative damage leading to neuronal loss, neurons would attempt to replenish their numbers by entering the cell cycle. However, being post-mitotic, neurons entering the cell cycle would become trapped therein, ultimately leading to death of these neurons. Yang and co-workers and the Butterfield laboratory first reported that similar activation of the cell cycle was present in the brains of individuals with amnestic mild cognitive impairment (MCI), arguably the earliest clinical stage of AD, but who demonstrate normal activities of daily living and no dementia. Activation of the cell cycle in MCI brain is consonant with the concept that this process is an early aspect in the progression of AD. This brief review article discusses these findings and recognizes the contribution of Dr. Mark Smith to the investigation of cell-cycle activation in AD brain and other aspects of AD neuropathology.

Editorial
Madia Lozupone, Vittorio Dibello, Rodolfo Sardone, Mario Altamura, Antonello Bellomo, Antonio Daniele, Vincenzo Solfrizzi, Emanuela Resta, Francesco Panza
Social Dysfunction and Apathy: Transdiagnostic Domains in Late-Life Cognitive Disorders
Abstract: Social dysfunction is a maladaptive process of coping, problem solving, and achieving one’s goals. A new definition of apathy was cross-linked to social dysfunction, with a reduced goal-directed behavior and social interaction as a separate dimension. We hypothesized that these two neuropsychiatric symptoms may be included in the mild behavioral impairment diagnostic framework, operationalizing and standardizing late-life neuropsychiatric symptom assessment, to improve risk determination of dementia. Social dysfunction and apathy were transdiagnostic and prodromic for late-life cognitive disorders. A transdiagnostic approach could provide a useful mean for a better understanding of apathy and related conditions such as social behavior.

Ruth Iban-Arias, Shu-Han Wang, Ariana Soares Dias Portela, Eun-Jeong Yang, Elizabeth Griggs, Sibilla Masieri, Wen Hu, Lung-Chi Chen, Giulio Maria Pasinetti
Exposure to the World Trade Center Particulate Matter Alters the Gut-Brain Axis in Early Onset Alzheimer’s Disease Mice
Abstract: Background: The September 11, 2001, catastrophe unleashed widespread destruction beyond the World Trade Center (WTC), with fires and toxic gases leaving lasting impacts. First responders at Ground Zero faced prolonged exposure to hazardous particulate matter (PM), resulting in chronic health challenges. Among the multitude of health concerns, the potential association between the WTCPM and Alzheimer’s disease (AD) has emerged as an area of intense inquiry, probing the intricate interplay between environmental factors and neurodegenerative diseases. Objective: We posit that a genetic predisposition to AD in mice results in dysregulation of the gut-brain axis following chronic exposure to WTCPM. This, in turn, may heighten the risk of AD-like symptoms in these individuals. Methods: 3xTg-AD and WT mice were intranasally administered with WTCPM collected at Ground Zero within 72 hours after the attacks. Working memory and learning and recognition memory were monitored for 4 months. Moreover, brain transcriptomic analysis and gut barrier permeability along with microbiome composition were examined. Results: Our findings underscore the deleterious effects of WTCPM on cognitive function, as well as notable alterations in brain genes associated with synaptic plasticity, pro-survival, and inflammatory signaling pathways. Complementary, chronic exposure to the WTCPM led to increased gut permeability in AD mice and altered bacteria composition and expression of functional pathways in the gut. Conclusions: Our results hint at a complex interplay between gut and brain axis, suggesting potential mechanisms through which WTCPM exposure may exacerbate cognitive decline. Identifying these pathways offers opportunities for tailored interventions to alleviate neurological effects among first responders.

Viviane Amaral-Carvalho, Thais Bento Lima-Silva, Luciano Inácio Mariano, Leonardo Cruz de Souza, Henrique Cerqueira Guimarães, Valéria Santoro Bahia, Ricardo Nitrini, Maira Tonidandel Barbosa, Mônica Sanches Yassuda, Paulo Caramelli
Improved Accuracy of the Addenbrooke’s Cognitive Examination–Revised in the Diagnosis of Mild Cognitive Impairment, Mild Dementia Due to Alzheimer's Disease and Behavioral Variant Frontotemporal Dementia Using Mokken Scale Analysis
Abstract: Background: The Addenbrooke's Cognitive Examination-Revised (ACE-R) is an accessible cognitive tool that supports the early detection of mild cognitive impairment (MCI), Alzheimer’s disease (AD), and behavioral variant frontotemporal dementia (bvFTD). Objective: To investigate the diagnostic efficacy of the ACE-R in MCI, AD, and bvFTD through the identification of novel coefficients for differentiation between these diseases. Methods: We assessed 387 individuals: 102 mild AD, 37 mild bvFTD, 87 with amnestic MCI patients, and 161 cognitively unimpaired controls. The Mokken scaling technique facilitated the extraction out of the 26 ACE-R items that exhibited a common latent trait, thereby generating the Mokken scales for the AD group and the MCI group. Subsequently, we performed logistic regression, integrating each Mokken scales with sociodemographic factors, to differentiate between AD and bvFTD, as well as between AD or MCI and control groups. Ultimately, the Receiver Operating Characteristic curve analysis was employed to assess the efficacy of the coefficient’s discrimination. Results: The AD-specific Mokken scale (AD-MokACE-R) versus bvFTD exhibited an Area Under the Curve (AUC) of 0.922 (88% sensitivity and specificity). The AD-MokACE-R versus controls achieved an AUC of 0.968 (93% sensitivity, 94% specificity). The MCI-specific scale (MCI-MokACE-R) versus controls demonstrated an AUC of 0.859 (78% sensitivity, 79% specificity). Conclusions: The ACE-R's capacity is enhanced through statistical methods and demographic integration, allowing for accurate differentiation between AD and bvFTD, as well as between MCI and controls. This new method not only reinforces its clinical value in early diagnosis but also surpasses traditional approaches noted in prior studies.

Wenzhang Wang, Fanpeng Zhao, Sandy Torres, Peggy L.R. Harris, Xinglong Wang, Lihua Peng, Sandra L. Siedlak, Xiongwei Zhu (Handling Editor: Paula Moreira)
Space-Like Irradiation Exacerbated Cognitive Deficits and Amyloid Pathology in CRND8 Mouse Model of Alzheimer’s Disease
Abstract: Background: Space radiation was linked to neurological damage and behavioral deficits which raised concerns of increased degenerative risk on the brain and development of Alzheimer’s disease following space travel. Objective: In this study, we investigated the effects of irradiation by 56Fe and 28Si in CRND8 mice, an Alzheimer’s disease mouse model. Methods: Six-month-old CRND8 mice were exposed to whole body irradiation by 56Fe and 28Si at 0.5 Gy and 2 Gy doses. Behavior tests were administered 1-month to 3-months post-irradiation. Amyloid deposition and synapse changes were analyzed 3-months and 6-months post-irradiation. Results: The Novel Object Recognition test showed some decline in 8-month-old mice compared to non-irradiated CRND8 mice. Male mice also showed a loss of freezing behavior in the fear conditioning contextual test following irradiation. Golgi staining revealed a loss of spines in hippocampal neurons after irradiation. Total amyloid immunohistochemistry showed a robust increase in 3-months post-irradiation 56Fe groups which became normalized to non-irradiated group by 6-months post-irradiation. However, 2 Gy 28Si caused a trend towards increased plaque load at 3-months post-irradiation which became significant at 6-months post irradiation only in male CRND8 mice. While 0.5 Gy Fe did not induce obvious changes in the total number of iba-1 positive microglia, more hippocampal microglia were found to express PCNA after 0.5 Gy Fe treatment, suggesting potential involvement of microglial dysfunction. Conclusions: Overall, our study provides new evidence of gender-specific and ion-dependent effects of space radiation on cognition and amyloid pathology in AD models.

Hypothesis
Pravat K. Mandal, Joseph C. Maroon, Avantika Samkaria, Yashika Arora, Shallu Sharma, Ashutosh Pandey
Iron Chelators and Alzheimer’s Disease Clinical Trials
Abstract: Alzheimer’s disease (AD) is a major neurodegenerative disorder impacting millions of people with cognitive impairment and affecting activities of daily living. The deposition of neurofibrillary tangles of hyperphosphorylated tau proteins and accumulation of amyloid-β (Aβ) are the main pathological characteristics of AD. However, the actual causal process of AD is not yet identified. Oxidative stress occurs prior to amyloid Aβ plaque formation and tau phosphorylation in AD. The role of master antioxidant, glutathione, and metal ions (e.g., iron) in AD are the frontline area of AD research. Iron overload in specific brain regions in AD is associated with the rate of cognitive decline. We have presented the outcome from various interventional trials involving iron chelators intended to minimize the iron overload in AD. To date, however, no significant positive outcomes have been reported using iron chelators in AD and promoting more research in the quest of iron chelator for AD.

Short Communication
Jesús Avila
Delaying Brain Aging or Decreasing Tau Levels as Strategies to Prevent Alzheimer's Disease: In Memoriam of Mark A. Smith
Abstract: Aging is the main risk for neurodegenerative disorders like Alzheimer's disease. In this short review, I will comment on how delaying brain aging through the addition of Yamanaka Factors Yamanaka Factors or small compounds that bind to the folate receptor alpha, which promote the expression of the Yamanaka Factors or decrease tau levels in brain cells from older subjects could serve as strategies to prevent Alzheimer's disease.

Editorial
Virginia Boccardi, Roberta Cecchetti, Carmelinda Ruggiero, Patrizia Mecocci
Geroscience and the Fight Against Alzheimer’s Disease: Between Myth and Reality
Abstract: Aging is associated with a gradual decline in cellular stability, leading to a decrease in overall health. In the brain, this process is closely linked with an increased risk of neurodegenerative diseases, including Alzheimer's disease. Understanding the mechanisms of brain aging is crucial for developing strategies aimed at enhancing both lifespan and health span. Recent advancements in geroscience, the study of the relationship between aging and age-related diseases, have begun to redefine our understanding of Alzheimer’s disease, guiding the development of preventive medical strategies that target the aging process itself rather than merely addressing the symptomatic manifestations of the disease.

Melissa J. Alldred, Harshitha Pidikiti, Kryillos W. Ibrahim, Sang Han Lee, Adriana Heguy, Gabriel E. Hoffman, Elliott J. Mufson, Grace E. Stutzmann, Stephen D. Ginsberg
Hippocampal CA1 Pyramidal Neurons Display Sublayer and Circuitry Dependent Degenerative Expression Profiles in Aged Female Down Syndrome Mice
Abstract: Background: Individuals with Down syndrome (DS) have intellectual disability and develop Alzheimer’s disease (AD) pathology during midlife, particularly in the hippocampal component of the medial temporal lobe memory circuit. However, molecular and cellular mechanisms underlying selective vulnerability of hippocampal CA1 neurons remains a major knowledge gap during DS/AD onset. This is compounded by evidence showing spatial (e.g., deep versus superficial) localization of pyramidal neurons (PNs) has profound effects on activity and innervation within the CA1 region. Objective: We investigated whether there is a spatial profiling difference in CA1 PNs in an aged female DS/AD mouse model. We posit dysfunction may be dependent on spatial localization and innervation patterns within discrete CA1 subfields. Methods: Laser capture microdissection was performed on trisomic CA1 PNs in an established mouse model of DS/AD compared to disomic controls, isolating the entire CA1 pyramidal neuron layer and sublayer microisolations of deep and superficial PNs from the distal CA1 (CA1a) region. Results: RNA sequencing and bioinformatic inquiry revealed dysregulation of CA1 PNs based on spatial location and innervation patterns. The entire CA1 region displayed the most differentially expressed genes (DEGs) in trisomic mice reflecting innate DS vulnerability, while trisomic CA1a deep PNs exhibited fewer but more physiologically relevant DEGs, as evidenced by bioinformatic inquiry. Conclusions: CA1a deep neurons displayed numerous DEGs linked to cognitive functions whereas CA1a superficial neurons, with approximately equal numbers of DEGs, were not linked to pathways of dysregulation, suggesting the spatial location of vulnerable CA1 PNs plays an important role in circuit dissolution.

Review
Gerhard Leinenga, Pranesh Padmanabhan, Jürgen Götz
Improving Cognition Without Clearing Amyloid: Effects of Tau and Ultrasound Neuromodulation
Abstract: Alzheimer’s disease is characterized by progressive impairment of neuronal functions culminating in neuronal loss and dementia. A universal feature of dementia is protein aggregation, a process by which a monomer forms intermediate oligomeric assembly states and filaments that develop into end-stage hallmark lesions. In Alzheimer’s disease, this is exemplified by extracellular amyloid- (Aβ) plaques which have been placed upstream of tau, found in intracellular neurofibrillary tangles and dystrophic neurites. This implies causality that can be modelled as a linear activation cascade. When Aβ load is reduced, for example, in response to an anti-Aβ immunotherapy, cognitive functions improve in plaque-forming mice. They also deteriorate less in clinical trial cohorts although real-world clinical benefits remain to be demonstrated. Given the existence of aged humans with unimpaired cognition despite a high plaque load, the central role of Aβ has been challenged. A counter argument has been that clinical symptoms would eventually develop if these aged individuals were to live long enough. Alternatively, intrinsic mechanisms that protect the brain in the presence of pathology may exist. In fact, Aβ toxicity can be abolished by either reducing or manipulating tau (through which Aβ signals), at least in preclinical models. In addition to manipulating steps in this linear pathocascade model, mechanisms of restoring brain reserve can also counteract Aβ toxicity. Low-intensity ultrasound is a neuromodulatory modality that can improve cognitive functions in Aβ-depositing mice without the need for removing Aβ. Together, this highlights a dissociation of Aβ and cognition, with important implications for therapeutic interventions.

Yanchao Liu*, Benrong He*, Kai Du, Jie Zheng, Dan Ke, Wen Mo, Yanni Li, Tao Jiang, Rui Xiong, Fei Sun, Shi Zhao, Wei Wei, Zhipeng Xu, Shujuan Zhang, Shihong Li, Xin Wang, Qiuzhi Zhou, Jinwang Ye, Yi Liang, Hao Lin, Yong Liu, Liangkai Chen, Huaqiu Zhang, Yao Zhang, Yang Gao, Jian-Zhi Wang *These authors contributed equally to this work.
Periphery Biomarkers Predicting Conversion of Type 2 Diabetes to Pre-Alzheimer-Like Cognitive Decline: A Multicenter Follow-Up Study
Abstract: Background: The prevalence of Alzheimer’s disease (AD) is increasing, therefore, identifying biomarkers to predict those vulnerable to AD is imperative. Type 2 diabetes (T2D) serves as an independent risk factor for AD. Early prediction of T2D patients who may be more susceptible to AD, so as to achieve early intervention, is of great significance to reduce the prevalence of AD. Objective: To establish periphery biomarkers that could predict conversion of T2D into pre-AD-like cognitive decline. Methods: A follow-up study was carried out from 159 T2D patients at baseline. The correlations of cognitive states (by MMSE score) with multi-periphery biomarkers, including APOE genotype, plasma amyloid-β level, platelet GSK-3β activity, and olfactory score were analyzed by logistic regression. ROC curve was used for establishing the prediction model. Additionally, MRI acquired from 38 T2D patients for analyzing the correlation among cognitive function, biomarkers and brain structure. Results: Compared with the patients who maintained normal cognitive functions during the follow-up period, the patients who developed MCI showed worse olfactory function, higher platelet GSK-3β activity, and higher plasma Aβ42/Aβ40 ratio. We conducted a predictive model which T2D patients had more chance of suffering from pre-AD-like cognitive decline. The MRI data revealed MMSE scores were positively correlated with brain structures. However, platelet GSK-3β activity was negatively correlated with brain structures. Conclusions: Elevated platelet GSK-3β activity and plasma Aβ42/Aβ40 ratio with reduced olfactory function are correlated with pre-AD-like cognitive decline in T2D patients, which used for predicting which T2D patients will convert into pre-AD-like cognitive decline in very early stage.

Lena Pickert*, Irundika H.K. Dias*, Alexander Thimm, Johann Weber, Sewa Abdullah, Joris Deelen, M. Cristina Polidori *The authors contributed equally to this work.
Micronutrients, Frailty, and Cognitive Impairment: Design and Preliminary Results from the CogLife 2.0 Study
Abstract: Background: Among preventive strategies against dementia, nutrition is considered a powerful one and the recently established “nutritional cognitive neuroscience of aging” is a highly active research field. Objective: The present study was designed to deeply characterize older adults across the continuum from cognitive integrity to mild cognitive impairment (MCI) and better elucidate the prognostic role of lipophilic micronutrients within their lipidomic signature. Methods: 123 participants older than 65 years across the continuum from cognitive integrity to MCI were included [49 with subjective cognitive impairment, 29 women, 72.5±5.4 years, 26 MCI, 9 women, 74.5±5.8 years and 50 without cognitive impairment, 21 women, 70.8±4.3 years]. All participants underwent neuropsychological and nutritional examination as well as comprehensive geriatric assessment with calculation of the Multidimensional Prognostic Index (MPI) as a proxy of frailty and biological age and blood withdrawal for the analyses of lipophilic micronutrients, metabolomics and oxylipidomics. One year after the evaluation, same tests are ongoing. Results: After adjustment for age, sex, daily fruit and vegetable intake and cholesterol, we found a significant positive correlation between lutein and the number of correct words in category fluency (p=0.016). Conclusions: This result supports the importance of carotenoids as robust biomarkers of cognitive performance independent of the nutritional status and frailty of the participants, as the entire present study collective was robust (MPI 0-0.33). The complete analyses of the metabolome and the oxylipidome will hopefully shed light on the metabolic and prognostic signature of cognitive decline in the rapidly growing population at risk of frailty.

Review
Allyson C. Rosen, James A. Lavacot, Victoria Klee, Yuvall Luria, Malia Rumbaugh
A Decade of Protecting Progress: Ethics Review
Abstract: Ethics Review began a decade ago with a mission to identify ethical concerns that hold back innovation and to promote solutions that would move the field forward. Over this time, blood biomarkers for brain pathology and medications that treat that pathology promise to transform research and care. A central problem is that the evidence needed to guide test interpretation and practice is accumulating and there are unanswered questions. At the same time, people living with and at risk for dementia want access to their test results and involvement in their care. We promote dialog among diverse people across many institutions through collaboration with the Advisory Group on Risk Evidence Education for Dementia (AGREEDementia.org). Over the years Ethics Review continues to publish these dialogs and solutions to overcome the paralysis of indecision and ethical concerns.

Review
Reinaldo B. Oriá, Carr J. Smith, J. Wesson Ashford, Michael P. Vitek, Richard L. Guerrant
Pros and Cons of APOE4 Homozygosity and Effects on Neuroplasticity, Malnutrition, and Infections in Early Life Adversity, Alzheimer’s Disease, and Alzheimer’s Prevention
Abstract: Fortea et al.’s. (2024) recent data analysis elegantly calls attention to familial late-onset Alzheimer’s disease (AD) with APOE4 homozygosity. The article by Grant (2024) reviews the factors associated with AD, particularly the APOE genotype and lifestyle, and the broad implications for prevention, both for individuals with the lifestyles associated with living in resource-rich countries and for those enduring environmental adversity in poverty settings, including high exposure to enteric pathogens and precarious access to healthcare. Grant discusses the issue of APOE genotype and its implications for the benefits of lifestyle modifications. This review highlights that bearing APOE4 could constitute an evolutionary benefit in coping with heavy enteric infections and malnutrition early in life in the critical formative first two years of brain development. However, the critical issue may be that this genotype could be a health concern under shifts in lifestyle and unhealthy diets during aging, leading to severe cognitive impairments and increased risk of AD. This commentary supports the discussions of Grant and the benefits of improving lifestyle for decreasing the risks for AD while providing further understanding and modelling of the early life benefits of APOE4 amidst adversity. This attention to the pathophysiology of AD should help further elucidate these critical, newly appreciated pathogenic pathways for developing approaches to the prevention and management in the context of the APOE genetic variations associated with AD.

Richard Merrick, Carol Brayne
Sex Differences in Dementia, Cognition, and Health in the Cognitive Function and Ageing Studies (CFAS)
Abstract: Background: There is renewed interest in whether sex differences in dementia risk exist, and what influence social and biological factors have. Objective: To review evidence from the Cognitive Function and Ageing Studies (CFAS), a multi-center population-representative cohort study in the UK; focusing on dementia and cognition, incorporating findings on participants’ health and social circumstances. Methods: After identifying all CFAS publications, the results of all sex-stratified primary analyses of CFAS data were narratively reviewed. Results: Of 337 publications, 94 report results by sex (including null findings), which are summarized by theme: dementia epidemiology, cognition, mental health, health expectancy, social context and biological resource (including neuropathology). Conclusions: Where differences are found they most commonly favor men; however, greater mortality in men may confound associations with age-related outcomes. This ‘survival bias’ may explain findings of greater risk of dementia and faster cognitive decline in women. Age-specific dementia incidence was similar between sexes, although reduced incidence across study generations was more pronounced in men. Mood disorders were more prevalent in women, but adjusting for disability and deprivation attenuated the association. Prominent findings from other cohorts that women have more Alzheimer’s disease pathology and greater risk of dementia from the Apolipoprotein E ε4 allele were not observed, warranting further investigation. The ‘male-female health-survival paradox’ is demonstrated whereby women live longer but with more comorbidity and disability. Examining why health expectancies changed differently over two decades for each sex (interacting with deprivation) may inform population interventions to improve cognitive, mental and physical health in later life.

Review
William B. Grant
A Brief History of the Progress in Our Understanding of Genetics and Lifestyle, Especially Diet, in the Risk of Alzheimer’s Disease
Abstract: The two major determining factors for Alzheimer’s disease (AD) are genetics and lifestyle. Alleles of the apolipoprotein E (APOE) gene play important roles in the development of late-onset AD, with APOE ε4 increasing risk, APOE ε3 being neutral, and APOE ε2 reducing risk. Several modifiable lifestyle factors have been studied in terms of how they can modify the risk of AD. Among these factors are dietary pattern, nutritional supplements such as omega-3 fatty acids, and B vitamins, physical exercise, and obesity, and vitamin D. The Western diet increases risk of AD, while dietary patterns such as the Mediterranean and vegetarian/vegan diets reduce risk. Foods associated with reduced risk include coffee, fruits and vegetables, whole grains and legumes, and fish, while meat and ultraprocessed foods are associated with increased risk, especially when they lead to obesity. In multi-country ecological studies, the amount of meat in the national diet has the highest correlation with risk of AD. The history of research regarding dietary patterns on risk of AD is emphasized in this review. The risk of AD can be modified starting at least by mid-life. People with greater genetic risk for AD would benefit more by choosing lifestyle factors to reduce and/or delay incidence of AD.

Sofia Egebäck Arulf, Robin Ziyue Zhou, Bjørn-Eivind Kirsebom, Alenka Jejcic, Tormod Fladby, Bengt Winblad, Lars Tjernberg, Sophia Schedin-Weiss
Bisecting N-Acetylglucosamine Correlates with Phospho-Tau181 in Subjective Cognitive Decline but not in Control Cases
Abstract: Background: The N-glycan structure bisecting N-acetylglucosamine (bisecting GlcNAc) is present on several N-glycans that are elevated in Alzheimer’s disease (AD), and previous studies have shown that bisecting GlcNAc levels correlate with total tau and phospho-tau181 in cerebrospinal fluid at early stages of AD. A recent population-based study showed that bisecting GlcNAc correlates with total tau also in blood and that this correlation could predict conversion to dementia. Objective: In this study, we have further investigated how bisecting GlcNAc relates to total tau and phospho-tau 181 in CSF samples from controls and cases with early cognitive deficits, stratified by amyloid/tau status and gender. Methods: Relative levels of bisecting GlcNAc in cerebrospinal fluid were measured by an enzyme-linked lectin assay in individuals with subjective cognitive decline, mild cognitive impairment and controls from the Norwegian Dementia Disease Initiation cohort. Results: As in our previous study, the correlation between bisecting GlcNAc and total tau or phospho-tau181 was particularly strong in the subjective cognitive decline group. The correlation was observed in amyloid negative and tau negative as well as amyloid positive and tau positive individuals, both in females and in males. Interestingly, among the amyloid negative and tau negative individuals, the correlation was observed in individuals with subjective cognitive decline but not in the controls. Conclusions: Thus, bisecting GlcNAc could be a biomarker for early cognitive decline.

Purna Poudel, Shaun Frost, Shaun Eslick, Hamid Sohrabi, Kevin Taddei, Ralph N. Martins, Eugene Hone
Hyperspectral Retinal Imaging as a Non-Invasive Marker to Determine Brain Amyloid Status
Abstract: Background: As an extension of the central nervous system (CNS), the retina shares many similarities with the brain and can manifest signs of various neurological diseases, including Alzheimer’s disease (AD). Objective: To investigate the retinal spectral features and develop a classification model to differentiate individuals with different brain amyloid levels. Methods: Sixty-six participants with varying brain amyloid-β protein levels were non-invasively imaged using a hyperspectral retinal camera in the wavelength range of 450–900 nm in 5 nm steps. Multiple retina features from the central and superior views were selected and analyzed to identify their variability among individuals with different brain amyloid loads. Results: The retinal reflectance spectra in the 450–585 nm wavelengths exhibited a significant difference in individuals with increasing brain amyloid. The retinal features in the superior view showed higher inter-subject variability. A classification model was trained to differentiate individuals with varying amyloid levels using the spectra of extracted retinal features. The performance of the spectral classification model was dependent upon retinal features and showed 0.758–0.879 accuracy, 0.718–0.909 sensitivity, 0.764–0.912 specificity, and 0.745–0.891 area under curve for the right eye. Conclusions: This study highlights the spectral variation of retinal features associated with brain amyloid loads. It also demonstrates the feasibility of the retinal hyperspectral imaging technique as a potential method to identify individuals in the preclinical phase of AD as an inexpensive alternative to brain imaging.

Aron S. Buchman, Lei Yu , Shahram Oveisgharan , Andrea R. Zammit, Tianhao Wang, Joshua M. Shulman, Veronique VanderHorst, Sukrit Nag, David A. Bennett
Parkinson’s Disease and Other Alzheimer’s Disease and Related Dementia Pathologies and the Progression of Parkinsonism in Older Adults
Abstract: Background: The interrelationship of parkinsonism, Parkinson’s disease (PD) and other Alzheimer’s disease (AD) and Alzheimer's disease and related dementias (ADRD) pathologies is unclear. Objective: We examined the progression of parkinsonian signs in adults with and without parkinsonism, and their underlying brain pathologies. Methods: Annual parkinsonian signs were based on a modified Unified Parkinson’s Disease Rating Scale. We used linear mixed effects models to compare the progression of parkinsonian signs in 3 groups categorized based on all available clinical evaluations: Group1 (never parkinsonism or clinical PD), Group2 (ever parkinsonism, but never clinical PD), Group3 (ever clinical PD). In decedents, we examined the progression of parkinsonian signs with PD and eight other AD/ADRD pathologies. Results: During average follow-up of 8 years, parkinsonian signs on average increased by 7.3% SD/year (N=3,807). The progression of parkinsonian signs was slowest in Group1 (never parkinsonism or clinical PD), intermediate in Group2, and fastest in Group3. In decedents (n=1,717) pathologic PD and cerebrovascular (CVD) pathologies were associated with a faster rate of progressive parkinsonian signs (all p values <0.05). However, pathologic PD was rare in adults without clinical PD (Group1, 5%; Group2, 7% versus Group3, 55%). Yet, 70% of adults in Group2 without pathologic PD showed one or more CVD pathologies. In Group2, adults with pathologic PD showed faster progression of parkinsonian signs compared with those without evidence of pathologic PD and their rate of progression was indistinguishable from adults with clinical PD. Conclusions: Parkinsonism in old age is more commonly related to cerebrovascular pathologies relative to pathologic PD and only a minority manifest prodromal PD.

Review
Sónia C. Correia, George Perry, Paula I. Moreira (Handling Editor: Jesus Ávila)
Fueling Alzheimer’s Disease: Where Does Immunometabolism Stand?
Abstract: More than a century after the first description of Alzheimer’s disease (AD), the road to a cure for this complex and heterogeneous neurodegenerative disorder has been paved by countless descriptive hypotheses and successive clinical trial failures. Auspiciously, the era of genome-wide association studies revolutionized the classical “neurocentric” view of AD by providing clues that brain-resident immune cells (i.e., microglia and astrocytes) are also key players in the pathological and clinical trajectory of this neurodegenerative disorder. Considering that the intercommunication among neurons, astrocytes, and microglia is fundamental for the functional organization of the brain, it is evident that the disruption of the proper functioning of this “triad” could contribute to the neuroinflammatory and neurodegenerative events that occur in the AD brain. Importantly, recent scientific progress in the burgeoning field of immunometabolism, a crossroad between metabolism and immune response, shed light on the importance of metabolic reprogramming of brain-resident immune cells in AD pathology. In this sense, the present review is aimed to summarize and discuss the current knowledge on the metabolic patterns of brain-resident immune cells during the AD continuum, putting a special focus on glucose, amino acids, and lipid metabolism. Changing the “old” picture of AD pathological basis by integrating the role of brain-resident immune cells it is imperative to establish new and feasible therapeutic interventions able to curb neuroinflammatory and neurodegenerative processes, and consequently cognitive deterioration.