Volume 98, Number 4, IN PRESS

Review
Punya Sachdeva*, Kannan Badri Narayanan* , Jitendra Kumar Sinha, Saurabh Gupta, Shampa Ghosh, Rakesh Bhaskar, Abdulmajeed G. Almutary, James H. Zothantluanga, Kranthi Kumar Kotta, Vinod Kumar Nelson, Ana Cláudia Paiva-Santos, Mosleh Mohammad Abomughaid, Mehnaz Kamal, Danish Iqbal, Mohammed Hamoud ALHarbi, Awadh Aedh ALMutairi, Saikat Dewanjee, Mohana Vamsi Nuli, Shanmugam Vippamakula, Saurabh Kumar Jha, Shreesh Ojha, Niraj Kumar Jha
Recent Advances in Drug Delivery Systems Targeting Insulin Signalling for the Treatment of Alzheimer's Disease
Abstract: Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by the accumulation of neurofibrillary tangles and amyloid-β plaques. Recent research has unveiled the pivotal role of insulin signaling dysfunction in the pathogenesis of AD. Insulin, once thought to be unrelated to brain function, has emerged as a crucial factor in neuronal survival, synaptic plasticity, and cognitive processes. Insulin and the downstream insulin signaling molecules are found mainly in the hippocampus and cortex. Some molecules responsible for dysfunction in insulin signaling are GSK-3β, Akt, PI3K, and IRS. Irregularities in insulin signaling or insulin resistance may arise from changes in the phosphorylation levels of key molecules, which can be influenced by both stimulation and inactivity. This, in turn, is believed to be a crucial factor contributing to the development of AD, which is characterized by oxidative stress, neuroinflammation, and other pathological hallmarks. Furthermore, this route is known to be indirectly influenced by Nrf2, NF-κB, and the caspases. This mini-review delves into the intricate relationship between insulin signaling and AD, exploring how disruptions in this pathway contribute to disease progression. Moreover, we examine recent advances in drug delivery systems designed to target insulin signaling for AD treatment. From oral insulin delivery to innovative nanoparticle approaches and intranasal administration, these strategies hold promise in mitigating the impact of insulin resistance on AD. This review consolidates current knowledge to shed light on the potential of these interventions as targeted therapeutic options for AD.

Review
Francesca Gelfo, Laura Petrosini, Laura Mandolesi, Eugenia Landolfo, Giulia Caruso, Francesca Balsamo, Sabrina Bonarota, Marco Bozzali, Carlo Caltagirone, Laura Serra
Land/Water Aerobic Activities: Two Sides of the Same Coin. A Comparative Analysis on the Effects in Cognition of Alzheimer’s Disease
Abstract: Evidence in the literature indicates that aerobic physical activity may have a protective role in aging pathologies. However, it has not been clarified whether different types of aerobic exercise produce different effects. In particular, these potential differences have not been explored in patients with Alzheimer's disease (AD). The present narrative review has the specific aim of evaluating whether land (walking/running) and water (swimming) aerobic activities exert different effects on cognitive functions and neural correlates in AD patients. In particular, the investigation is carried out by comparing the evidence provided from studies on AD animal models and on patients. On the whole, we ascertained that both human and animal studies documented beneficial effects of land and water aerobic exercise on cognition in AD. Also, the modulation of numerous biological processes is documented in association with structural modifications. Remarkably, we found that aerobic activity appears to improve cognition per se, independently from the specific kind of exercise performed. Aerobic exercise promotes brain functioning through the secretion of molecular factors from skeletal muscles and liver. These molecular factors stimulate neuroplasticity, reduce neuroinflammation, and inhibit neurodegenerative processes leading to amyloid-β accumulation. Additionally, aerobic exercise improves mitochondrial activity, reducing oxidative stress and enhancing ATP production. Aerobic activities protect against AD, but implementing exercise protocols for patients is challenging. We suggest that health policies and specialized institutions should direct increasing attention on aerobic activity as lifestyle modifiable factor for successful aging and age-related conditions.

Review
Baruh Polis, Abraham O. Samson
Addressing the Discrepancies Between Animal Models and Human Alzheimer's Disease Pathology: Implications for Translational Research
Abstract: Animal models, particularly transgenic mice, are extensively used in Alzheimer's disease (AD) research to emulate key disease hallmarks, such as amyloid plaques and neurofibrillary tangles formation. Although these models have contributed to our understanding of AD pathogenesis and can be helpful in testing potential therapeutic interventions, their reliability is dubious. While preclinical studies have shown promise, clinical trials often yield disappointing results, highlighting a notable gap and disparity between animal models and human AD pathology. Existing models frequently overlook early-stage human pathologies and other key AD characteristics, thereby limiting their application in identifying optimal therapeutic interventions. Enhancing model reliability necessitates rigorous study design, comprehensive behavioral evaluations, and biomarker utilization. Overall, a nuanced understanding of each model's neuropathology, its fidelity to human AD, and its limitations is essential for accurate interpretation and successful translation of findings. This article analyzes the discrepancies between animal models and human AD pathology that complicate the translation of findings from preclinical studies to clinical applications. We also delve into AD pathogenesis and attributes to propose a new perspective on this pathology and deliberate over the primary limitations of key experimental models. Additionally, we discuss several fundamental problems that may explain the translational failures and suggest some possible directions for more effective preclinical studies.

Systematic Review
Michael Anekson Widjaya*, Shin-Da Lee*, Wei-Chung Cheng, Bor-Tsang Wu (Handling Associate Editor: Madeleine Hackney) *These authors contributed equally to this work.
Effects of Exercise Training on Immune-Related Genes and Pathways in the Cortex of Animal Models of Alzheimer’s Disease: A Systematic Review
Abstract: Background: Alzheimer's disease (AD) is a chronic neurodegenerative disease that affects the immune system due to the accumulation of amyloid-β (Aβ) and tau associated molecular pathology and other pathogenic processes. To address AD pathogenesis, various approaches had been conducted from drug development to lifestyle modification to reduce the prevalence of AD. Exercise is considered a prominent lifestyle modification to combat AD. Objective: This observation prompted us to review the literature on exercise related to immune genes in the cortex of animal models of AD. We focused on animal model studies due to their prevalence in this domain. Methods: The systematic review was conducted according to PRISMA standards using Web of Science (WoS) and PubMed databases. Any kind of genes, proteins, and molecular molecules were included in this systematic review. The list of these immune-related molecules was analyzed in the STRING database for functional enrichment analysis. Results: We found that 17 research studies discussed immune-related molecules and 30 immune proteins. These studies showed that exercise had the ability to ameliorate dysfunction in AD-related pathways, which led to decreasing the expression of microglia-related pathways and Th17-related immune pathways. As a result of decreasing the expression of immune-related pathways, the expression of apoptosis-related pathways was also decreasing, and neuronal survival was increased by exercise activity. Conclusions: Based on functional enrichment analysis, exercise not only could reduce apoptotic factors and immune components but also could increase cell survival and Aβ clearance in cortex samples. PROSPERO ID: CRD42022326093.

Hypothesis
Robert W.B. Love
Aniracetam: An Evidence-Based Model for Preventing the Accumulation of Amyloid-β Plaques in Alzheimer’s Disease
Abstract: Alzheimer’s disease is the leading cause of dementia in the world. It affects 6 million people in the United States and 50 million people worldwide. Alzheimer’s disease is characterized by the accumulation of amyloid-β plaques (Aβ), an increase in tau protein neurofibrillary tangles, and a loss of synapses. Since the 1990s, removing and reducing Aβ has been the focus of Alzheimer’s treatment and prevention research. The accumulation of Aβ can lead to oxidative stress, inflammation, neurotoxicity, and eventually apoptosis. These insults impair signaling systems in the brain, potentially leading to memory loss and cognitive decline. Aniracetam is a safe, effective, cognitive-enhancing drug that improves memory in both human and animal studies. Aniracetam may prevent the production and accumulation of Aβ by increasing α-secretase activity through two distinct pathways: 1) increasing brain derived neurotrophic factor expression and 2) positively modulating metabotropic glutamate receptors. This is the first paper to propose an evidence-based model for aniracetam reducing the accumulation and production of Aβ.

Hypothesis
Estela Area-Gomez*, Eric A. Schon* *These authors contributed equally to this work.
Towards a Unitary Hypothesis of Alzheimer’s Disease Pathogenesis
Abstract: The "amyloid cascade" hypothesis of Alzheimer disease (AD) pathogenesis invokes the accumulation in the brain of plaques (containing the amyloid-β protein precursor [AβPP] cleavage product amyloid-β [Aβ]) and tangles (containing hyperphosphorylated tau) as drivers of pathogenesis. However, the poor track record of clinical trials based on this hypothesis suggests that the accumulation of these peptides is not the only cause of AD. Here, an alternative hypothesis is proposed in which the AβPP cleavage product C99, not Aβ, is the main culprit, via its role as a regulator of cholesterol metabolism. C99, which is a cholesterol sensor, promotes the formation of mitochondria-associated endoplasmic reticulum (ER) membranes (MAM), a cholesterol-rich lipid raft-like subdomain of the ER that communicates, both physically and biochemically, with mitochondria. We propose that in early-onset AD (EOAD), MAM-localized C99 is elevated above normal levels, resulting in increased transport of cholesterol from the plasma membrane to membranes of intracellular organelles, such as ER/endosomes, thereby upregulating MAM function and driving pathology. By the same token, late-onset AD (LOAD) is triggered by any genetic variant that increases the accumulation of intracellular cholesterol that, in turn, boosts the levels of C99 and again upregulates MAM function. Thus, the functional cause of AD is upregulated MAM function that, in turn, causes the hallmark disease phenotypes, including the plaques and tangles. Accordingly, the MAM hypothesis invokes two key interrelated elements, C99 and cholesterol, that converge at the MAM to drive AD pathogenesis. From this perspective, AD is, at bottom, a lipid disorder.

Short Communication
Lilian Calderón-Garcidueñas, Alberto Ayala, Partha S. Mukherjee
2024 United States Elections: Air Pollution, Neurodegeneration, Neuropsychiatric, and Neurodevelopmental Disorders. Who Cares?
Abstract: Air pollution exposures ought to be of significant interest for the United States (US) public as health issues will play a role in the 2024 elections. Citizens are not aware of the harmful brain impact of exposures to ubiquitous anthropogenic combustion emissions and friction-derived nanoparticles, industrial nanoplastics, the growing risk of wildfires, and the smoke plumes of soot. Ample consideration of pediatric and early adulthood hallmarks of Alzheimer’s disease, Parkinson’s disease, frontotemporal lobar degeneration, and amyotrophic lateral sclerosis and associations with neuropsychiatric and neurodevelopmental disorders in the process of setting, reviewing, and implementing standards for particulate matter (PM)2.5, ultrafine PM, and industrial nanoparticles must be of interest to US citizens.

Commentary
Nicola Luigi Bragazzi, Ayoub Boulares, Sergio Garbarino
Could the Historical Transition from Segmented to Monophasic Sleep Explain the Modern Insurgence of Alzheimer’s Disease and Related Dementias?
Abstract: In their article, Finch and Burstein explore the hypothesis that Alzheimer’s disease and related dementias (ADRD) may predominantly be phenomena of the modern era. Through a review of classical Greek and Latin literature, they found minimal reference to conditions akin to ADRD, suggesting a historical rarity of severe cognitive decline. Instead, ancient texts focused on physical aspects of aging, with cognitive changes, when noted, not resembling modern-day dementia. Finch and Burstein further extend their analysis by drawing parallels with the Tsimane people of Bolivia, known for their low prevalence of dementia and cardiovascular diseases, attributed to lifestyle factors such as diet and physical activity. By comparing historical sleep patterns transitioning from segmented to monophasic sleep with those of the Tsimane community, we enriched Finch and Burstein's research, highlighting the need to take into account a range of diverse factors, including sleep, in understanding the etiopathogenesis of ADRD in today's society.

Mengxue Zhang, Yanjie Qu, Qian Li, Chao Gu, Limin Zhang, Hongxu Chen, Minrui Ding, Tong Zhang, Rongrong Zhen, Hongmei An
Correlation Between Prefrontal Functional Connectivity and the Degree of Cognitive Impairment in Alzheimer’s Disease: A fNIRS Study
Abstract: Background: The development of Alzheimer’s disease (AD) can be divided into subjective cognitive decline (SCD), mild cognitive impairment (MCI), and dementia. Early recognition of pre-AD stages may slow the progression of dementia. Objective: This study aimed to explore functional connectivity (FC) changes of the brain prefrontal cortex (PFC) in AD continuum using functional near-infrared spectroscopy (fNIRS), and to analyze its correlation with cognitive function. Methods: All participants underwent 48-channel fNIRS at resting-state. Based on Brodmann partitioning, the PFC was divided into eight subregions. The NIRSIT Analysis Tool (v3.7.5) was used to analyze mean ∆HbO2 and FC. Spearman correlation analysis was used to examine associations between FC and cognitive function. Results: Compared with HC group, the mean ∆HbO2 and FC were different between multiple subregions in the AD continuum. Both mean ∆HbO2 in the left dorsolateral PFC and average FC decreased sequentially from SCD to MCI to AD groups. Additionally, seven pairs of subregions differed in FC among the three groups: the differences between the MCI and SCD groups were in heterotopic connectivity; the differences between the AD and SCD groups were in left intrahemispheric and homotopic connectivity; whereas the MCI and AD groups differed only in homotopic connectivity. Spearman correlation results showed that FCs were positively correlated with cognitive function. Conclusions: These results suggest that the left dorsolateral PFC may be the key cortical impairment in AD. Furthermore, there are different resting-state prefrontal network patterns in AD continuum, and the degree of cognitive impairment is positively correlated with reduced FC strength.

Yiming Ruan*, Darui Zheng*, Wenxuan Guo, Xuan Cao, Wenzhang Qi, Qianqian Yuan, Xulian Zhang, Xuhong Liang, Da Zhang, Chen Xue, Chaoyong Xiao, Alzheimer’s Disease Neuroimaging Initiative *These authors contributed equally to this work.
Shared and Specific Changes of Cortico-Striatal Functional Connectivity in Stable Mild Cognitive Impairment and Progressive Mild Cognitive Impairment
Abstract: Background: Mild cognitive impairment (MCI), the prodromal stage of Alzheimer’s disease, has two distinct subtypes: stable MCI (sMCI) and progressive MCI (pMCI). Early identification of the two subtypes has important clinical significance. Objective: We aimed to compare the cortico-striatal functional connectivity (FC) differences between the two subtypes of MCI and enhance the accuracy of differential diagnosis between sMCI and pMCI. Methods: We collected resting-state fMRI data from 31 pMCI patients, 41 sMCI patients, and 81 healthy controls. We chose six pairs of seed regions, including the ventral striatum inferior, ventral striatum superior, dorsal-caudal putamen, dorsal-rostral putamen, dorsal caudate, and ventral-rostral putamen and analyzed the differences in cortico-striatal FC among the three groups, additionally, the relationship between the altered FC within the MCI subtypes and cognitive function was examined. Results: Compared to sMCI, the pMCI patients exhibited decreased FC between the left dorsal-rostral putamen and right middle temporal gyrus, the right dorsal caudate and right inferior temporal gyrus, and the left dorsal-rostral putamen and left superior frontal gyrus. Additionally, the altered FC between the right inferior temporal gyrus and right putamen was significantly associated with episodic memory and executive function. Conclusions: Our study revealed common and distinct cortico-striatal FC changes in sMCIs and pMCI across different seeds; these changes were associated with cognitive function. These findings can help us understand the underlying pathophysiological mechanisms of MCI and distinguish pMCI and sMCI in the early stage potentially.

Yaqi Li*, Xinming Xu*, Peilu Wang, Xiqun Chen,Qishan Yang, Liang Sun, Xiang Gao *These authors equally contributed to this work.
Association of Cancer History with Lifetime Risk of Dementia and Alzheimer’s Disease
Abstract: Background: The literature presents conflicting results regarding the potential protective effect of prevalent cancer on the development of dementia and Alzheimer's disease (AD). Objective: Association between cancer and subsequent risk of dementia and/or AD was reported previously, but survival bias has been of concern. Here, we aimed to calculate the lifetime risk of dementia and AD and evaluate the association of cancer history with these two conditions. Methods: In this retrospective analysis, we included 292,654 participants aged 60+ y during the follow-up and free of dementia at baseline, within the UK Biobank cohort. Lifetime risks of dementia and AD were estimated in individuals with and without cancer history, and different durations of cancer exposure and cancer types. Results: During a median of 12.5 follow-up years, 5,044 new dementia and 2,141 AD cases were reported. Lifetime risks of dementia and AD were lower in cancer survivors compared to those without cancer, and this effect was more pronounced in participants with cancer history exposure ≥ 5 years. Similar relationship was observed in individual cancer types, except for breast cancer. Conclusions: Results suggested an inverse association between cancer history and lifetime risk of dementia and AD, which may be modified by different cancer types and cancer exposure time.

Murali Vijayan, P. Hemachandra Reddy
Unveiling the Role of Novel miRNA PC-5P-12969 in Alleviating Alzheimer’s Disease
Abstract: Background: The intricate and complex molecular mechanisms that underlie the progression of Alzheimer’s disease (AD) have prompted a concerted and vigorous research endeavor aimed at uncovering potential avenues for therapeutic intervention. Objective: This study aims to elucidate the role of miRNA PC-5P-12969 in the pathogenesis of AD. Methods: We assessed the differential expression of miRNA PC-5P-12969 in postmortem AD brains, AD animal and cell models using real-time reverse-transcriptase RT-PCR, we also checked the gene and protein expression of GSK3α and APP. Results: Our investigation revealed a notable upregulation of miRNA PC-5P-12969 in postmortem brains of AD patients, in transgenic mouse models of AD, and in mutant APP overexpressing-HT22 cells. Additionally, our findings indicate that overexpression of miRNA PC-5P-12969 exerts a protective effect on cell survival, while concurrently mitigating apoptotic cell death. Further-more, we established a robust and specific interaction between miRNA PC-5P-12969 and GSK3α. Our luciferase reporter assays provided confirmation of the binding between miRNA PC-5P-12969 and the 3’-UTR of the GSK3α gene. Manipulation of miRNA PC-5P-12969 levels in cellular models of AD yielded noteworthy alterations in the gene and protein expression levels of both GSK3α and APP. Remarkably, the manipulation of miRNA PC-5P-12969 levels yielded significant enhancements in mitochondrial respiration and ATP production, concurrently with a reduction in mitochondrial fragmentation, thus unveiling a potential regulatory role of miRNA PC-5P-12969 in these vital cellular processes. Conclusions: In summary, this study sheds light on the crucial role of miRNA PC-5P-12969 and its direct interaction with GSK3α in the context of AD.

Erica Acquarone, Elentina K. Argyrousi, Ottavio Arancio, D. Martin Watterson, Saktimayee M. Roy (Handling Associate Editor: Daniela Puzzo)
The 5HT2b Receptor in Alzheimer’s Disease: Increased Levels in Patient Brains and Antagonist Attenuation of Amyloid and Tau Induced Dysfunction
Abstract: Background: Neurodegenerative diseases manifest behavioral dysfunction with disease progression. Intervention with neuropsychiatric drugs is part of most multi-drug treatment paradigms. However, only a fraction of patients responds to the treatments and those responding must deal with drug-drug interactions and tolerance issues generally attributed to off-target activities. Recent efforts have focused on the identification of underexplored targets and exploration of improved outcomes by treatment with selective molecular probes. Objective: As part of ongoing efforts to identify and validate additional targets amenable to therapeutic intervention, we examined levels of the serotonin 5-HT2b receptor (5-HT2bR) in Alzheimer’s disease (AD) brains and the potential of a selective 5-HT2bR antagonist to counteract synaptic plasticity and memory damage induced by AD-related proteins, amyloid-β, and tau. Methods: This work used a combination of biochemical, chemical biology, electrophysiological, and behavioral techniques. Biochemical methods included analysis of protein levels. Chemical biology methods included the use of an in vivo molecular probe MW071, a selective antagonist for the 5HT2bR. Electrophysiological methods included assessment of long-term potentiation (LTP), a type of synaptic plasticity thought to underlie memory formation. Behavioral studies investigated spatial memory and associative memory. Results: 5HT2bR levels are increased in brain specimens of AD patients compared to controls. 5HT2bR antagonist treatment rescued amyloid-β and tau oligomer-induced impairment of synaptic plasticity and memory. Conclusions: The increased levels of 5HT-2bR in AD patient brains and the attenuation of disease-related synaptic and behavioral dysfunctions by MW071 treatment suggest that the 5HT-2bR is a molecular target worth pursuing as a potential therapeutic target.

Marina Tedeschi Dauar, Cynthia Picard, Anne Labonté, John Breitner, Pedro Rosa-Neto, Sylvia Villeneuve, Judes Poirier for the PREVENT-AD Research Group (Handling Associate Editor: Kenneth Witwer)
Contactin 5 and Apolipoproteins Interplay in Alzheimer’s Disease
Abstract: Background: Apolipoproteins and contactin 5 are proteins associated with Alzheimer’s disease (AD) pathophysiology. Apolipoproteins act on transport and clearance of cholesterol and phospholipids during synaptic turnover and terminal proliferation. Contactin 5 is a neuronal membrane protein involved in key processes of neurodevelopment. Objective: To investigate the interactions between contactin 5 and apolipoproteins in AD, and the role of these proteins in response to neuronal damage. Methods: Apolipoproteins (measured by Luminex), contactin 5 (measured by Olink’s proximity extension assay), and cholesterol (measured by liquid chromatography mass spectrometry) were assessed in the cerebrospinal fluid (CSF) and plasma of cognitively unimpaired participants (n=93). Gene expression was measured using polymerase chain reaction in the frontal cortex of autopsied-confirmed AD (n=57) and control subjects (n=31) and in the hippocampi of mice following entorhinal cortex lesions. Results: Contactin 5 positively correlated with apolipoproteins B (p=5.4x10-8), D (p=1.86x10-4), E (p=2.92x10-9), J (p=2.65x10-9), and with cholesterol (p=0.0096) in the CSF, and with cholesterol (p=0.02), HDL (p=0.0143), and LDL (p=0.0121) in the plasma. Negative correlations were seen between CNTN5, APOB (p=0.034) and APOE (p=0.015) mRNA levels in the brains of control subjects. In the mouse model, apoe and apoj gene expression increased during the reinnervation phase (p<0.05), while apob (p=0.023) and apod (p=0.006) increased in the deafferentation stage. Conclusions: Extensive interactions were observed between contactin 5 and apolipoproteins and cholesterol, possibly due to neuronal damage. The alterations in gene expression of apolipoproteins suggest a role in axonal, terminal, and synaptic remodeling in response to entorhinal cortex damage.

Jiesheng Mao, Haoxiang Hu, Yunhan Zhao, Mi Zhou, Xiaokai Yang
Association Between Composite Dietary Antioxidant Index and Cognitive Function Among Aging Americans from NHANES 2011-2014
Abstract: Background: Antioxidant diets are considered to be protective factors for cognitive function. However, comprehensive measures of antioxidant diets are lacking. Objective: To examine the association between the Composite Dietary Antioxidant Index (CDAI) and cognitive function in the elderly. Methods: This cross-sectional study included a total of 2,456 participants (≥60 years old) from NHANES 2011-2014. Calculation of CDAI based on 6 minerals and vitamins (manganese, selenium, zinc, vitamins A, C, and E). Cognitive function was measured by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word Learning sub-test, Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). We also created a composite cognitive z-score to represent global cognition. The statistical analyses we used included multiple linear regression analyses, subgroup analyses, curve-fitting analyses, and threshold effects analyses. Results: After controlling for demographic characteristics, lifestyle factors, and disease history, multivariate linear regression analyses showed that increased CDAI was positively associated with scores on global cognitive function and each cognitive domain (p < 0.05), with subgroup analyses suggesting that this association was more pronounced in stroke patients (p for interaction < 0.05). Curve-fitting analyses and threshold effect analyses showed saturation effects between CDAI and CREAD Test, AFT, and composite Z-score, and an inverted U-shaped relationship with DSST, with inflection points of -1.89, 0.79, 1.13, and 1.77, respectively. Conclusions: Our findings support that higher levels of CDAI are correlated with significantly elevated cognitive function. Maintaining CDAI in an appropriate range may contribute to cognitive health in elderly.

Patrik Mattsson, Zsolt Cselényi, Anton Forsberg Morén, Yvonne Freund-Levi, Lars-Olof Wahlund, Christer Halldin, Lars Farde
High Contrast PET Imaging of Subcortical and Allocortical Amyloid-β in Early Alzheimer’s Disease Using [11C]AZD2184
Abstract: Background: Deposits of amyloid-β (Aβ) appear early in Alzheimer’s disease (AD). Objective: The aim of the present study was to compare the presence of cortical and subcortical Aβ in early AD using positron emission tomography (PET). Methods: Eight cognitively unimpaired (CU) subjects, 8 with mild cognitive impairment (MCI) and 8 with mild AD were examined with PET and [11C]AZD2184. A data driven cut-point for Aβ positivity was defined by Gaussian mixture model of isocortex binding potential (BPND) values. Results: Sixteen subjects (3 CU, 5 MCI and 8 AD) were Aβ-positive. BPND was lower in subcortical and allocortical regions compared to isocortex. Fifteen of the 16 Aβ-positive subjects displayed Aβ binding in striatum, 14 in thalamus and 10 in allocortical regions. Conclusions: Aβ deposits appear to be widespread in early AD. It cannot be excluded that deposits appear simultaneously throughout the whole brain which has implications for improved diagnostics and disease monitoring.

Soeren Mattke, Hankyung Jun, Samantha Chu, Mark Hanson
Disparities in Access to Diagnostic Evaluation for Alzheimer’s Disease in Individuals Dually Eligible for Medicare and Medicaid: A Modeling Study
Abstract: Background: Individuals dually eligible for Medicare and Medicaid (duals) may face greater obstacles to access to disease-modifying Alzheimer’s treatments in spite of their higher disease burden, because of clinicians’ reluctance to accept Medicaid and the so-called “lesser of” policy, under which Medicaid may pay providers lower rates. Objective: To project differential wait times for duals compared to Medicare-only beneficiaries by state Methods: We used State Medicaid payment policy and Medicare enrollment data and a Markov model to predict differential wait times for duals and non-duals from 2023 to 2050. We estimated available diagnostic appointments by state for both groups based on reluctance of clinicians to accept Medicaid and the “lesser of” policy for each year. Results: We estimate overall average wait times of almost two years (22.9 months) but almost three times as long for duals (59.8 months) than non-duals (20.7 months) because of higher disease burden. The effects of Medicaid payment policy would increase average wait times for duals to 89 months with 20 states having wait times of 99 months or more, which would effectively deprive duals of access. Conclusions: The added average wait times in many states would effectively deprive duals from access to treatment and translate into avoidable disease progression and mortality. Policy interventions to reduce financial and nonfinancial obstacles are dearly needed to avoid deepening disparities. Examples are coverage arrangements that integrate Medicare and Medicaid coverage, covering the co-payment for physician services in full, and stricter network adequacy requirements for Medicaid Managed Care plans.

Yanxi Chen, Yi Su, Jianfeng Wu, Kewei Chen, Alireza Atri, Richard J. Caselli, Eric M. Reiman, Yalin Wang, for the Alzheimer’s Disease Neuroimaging Initiative
Combining Blood-Based Biomarkers and Structural MRI Measurements to Distinguish Persons with and without Significant Amyloid Plaques
Abstract: Background: Amyloid-β (Aβ) plaques play a pivotal role in Alzheimer's disease. The current positron emission tomography (PET) is expensive and limited in availability. In contrast, blood-based biomarkers (BBBMs) show potential for characterizing Aβ plaques more affordably. We have previously proposed an MRI-based hippocampal morphometry measure to be an indicator of Aβ plaques. Objective: To develop and validate an integrated model to predict brain amyloid PET positivity combining MRI feature and plasma Aβ42/40 ratio. Methods: We extracted hippocampal multivariate morphometry statistics from MR images and together with plasma Aβ42/40 trained a random forest classifier to perform a binary classification of participant brain amyloid PET positivity. We evaluated the model performance using two distinct cohorts, one from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) and the other from the Banner Alzheimer’s Institute (BAI), including prediction accuracy, precision, recall rate, F1 score, and AUC score. Results: Results from ADNI (mean age 72.6, Aβ+ rate 49.5%) and BAI (mean age 66.2, Aβ+ rate 36.9%) datasets revealed the integrated multimodal (IMM) model’s superior performance over unimodal models. The IMM model achieved prediction accuracies of 0.86 in ADNI and 0.92 in BAI, surpassing unimodal models based solely on structural MRI (0.81 and 0.87) or plasma Aβ42/40 (0.73 and 0.81) predictors. Conclusions: Our IMM model, combining MRI and BBBM data, offers a highly accurate approach to predict brain amyloid PET positivity. This innovative multiplex biomarker strategy presents an accessible and cost-effective avenue for advancing Alzheimer's disease diagnostics, leveraging diverse pathologic features related to Aβ plaques and structural MRI.

Susanne G. Mueller (Handling Associate Editor: Lori Beason-Held)
Traumatic Brain Injury and Post-Traumatic Stress Disorder and Their Influence on Development and Pattern of Alzheimer’s Disease Pathology in Later Life
Abstract: Background: Traumatic brain injury (TBI) and posttraumatic stress disorder (PTSD) are potential risk factors for the development of dementia including Alzheimer’s disease (AD) in later life. The findings of studies investigating this question are inconsistent though. Objective: To investigate if these inconsistencies are caused by the existence of subgroups with different vulnerability for AD pathology and if these subgroups are characterized by atypical tau load/atrophy pattern. Methods: The MRI and PET data of 89 subjects with or without previous TBI and/or PTSD from the DoD ADNI database were used to calculate an age-corrected gray matter tau mismatch metric (ageN-T mismatch-score and matrix) for each subject. This metric provides a measure to what degree regional tau accumulation drives regional gray matter atrophy (matrix) and can be used to calculate a summary score (score) reflecting the severity of AD pathology in an individual. Results: The ageN-T mismatch summary score was positively correlated with whole brain beta-amyloid load and general cognitive function but not with PTSD or TBI severity. Hierarchical cluster analysis identified five different spatial patterns of tau-gray matter interactions. These clusters reflected the different stages of the typical AD tau progression pattern. None was exclusively associated with PTSD and/or TBI. Conclusions: These findings suggest that a) although subsets of patients with PTSD and/or TBI develop AD-pathology, a history of TBI or PTSD alone or both is not associated with a significantly higher risk to develop AD pathology in later life. b) remote TBI or PTSD do not modify the typical AD pathology distribution pattern.

Maresa Buchholz*, Isabel Zöllinger*, Jochen René Thyrian, Melanie Luppa, Andrea Zülke, Juliane Döhring, Laura Lunden, Linda Sanftenberg, Christian Brettschneider, David Czock, Thomas Frese, Jochen Gensichen, Wolfgang Hoffmann, Hanna Kaduszkiewicz, Hans-Helmut König, Birgitt Wiese, Steffi G. Riedel-Heller, Iris Blotenberg *These authors contributed equally to this work.
Factors Associated with Lower Social Activity in German Older Adults at Increased Risk of Dementia: A Cross-Sectional Analysis
Abstract: Background: Studies demonstrate associations between low social activity in older adults and cognitive decline. Little has been investigated regarding which factors are associated with low social activity in older adults at increased risk of dementia. Objective: We investigate which sociodemographic, psychological, health-related, and environmental factors are associated with low social activity in older adults at increased risk of dementia. Additionally, we describe the stages of health behavior change, the types of social activities, and the duration of the current level of social activity. Methods: We used baseline data of 1,015 participants from the AgeWell.de trial. We conducted logistic and Poisson regression analyses to investigate factors associated with low social activity. We report descriptive statistics on the stages of change in the sample, the types of social activities most frequently pursued, and the duration of the current level of social activity. Results: Lower income, non-usage of public transport, depressive symptoms, cognitive, mobility, and hearing impairment were negatively associated with social activity. The majority of the sample was in the maintenance stage, followed by the precontemplation stage. The most common social activities were traveling and hobbies with others. Participants have maintained their current level of social activity for several years. Conclusions: We identified a lack of resources (income, transport), depressive symptoms and poorer health (cognitive, mobility and hearing impairment) as barriers to social activity. Interventions promoting social activity in older adults at risk of dementia may specifically target individuals with these risk factors. Low-threshold opportunities for social activity may be particularly beneficial.

Andrew C. Robinson, Tawfique Bin Rizwan, Yvonne S. Davidson, James Minshull, Phillip Tinkler, Antony Payton, David M.A. Mann, Federico Roncaroli
Self-Reported Late-Life Hypertension Is Associated with a Healthy Cognitive Status and Reduced Alzheimer’s Disease Pathology Burden
Abstract: Background: While mid-life hypertension represents a risk factor for the development of Alzheimer's disease (AD), the risk after the age of 65 is less certain. Establishing relationships between late life hypertension and the pathological changes of AD could be crucial in understanding the relevance of blood pressure as a risk factor for this disorder. Objective: We investigated associations between self-reported late-life hypertension, cognitive status and AD pathology at death. The impact of antihypertensive medication was also examined. Methods: Using the Cornell Medical Index questionnaire, we ascertained whether participants had ever reported hypertension. We also noted use of antihypertensive medication. The donated brains of 108 individuals were assessed for AD pathology using consensus guidelines. Statistical analysis aimed to elucidate relationships between hypertension and AD pathology. Results: We found no associations between self-reported hypertension and cognitive impairment at death. However, those with hypertension were significantly more likely to exhibit lower levels of AD pathology as measured by Thal phase, Braak stage, CERAD score, and NIA-AA criteria—even after controlling for sex, level of education and presence of APOE ε4 allele(s). No significant associations could be found when examining use of antihypertensive medications. Conclusions: Our findings suggest that late-life hypertension is associated with less severe AD pathology. We postulate that AD pathology may be promoted by reduced cerebral blood flow.

Seyed Hani Hojjati, Gloria C. Chiang, Tracy A. Butler, Mony de Leon, Ajay Gupta, Yi Li, Mert R. Sabuncu, Farnia Feiz, Siddharth Nayak, Jacob Shteingart, Sindy Ozoria, Saman Gholipour Picha, Yaakov Stern, José A. Luchsinger, Davangere P. Devanand, Qolamreza R. Razlighi (Handling Associate Editor: Babak Ardekani)
Remote Associations Between Tau and Cortical Amyloid-β Are Stage-Dependent
Abstract: Background: Histopathologic studies of Alzheimer's disease (AD) suggest that extracellular amyloid-β (Aβ) plaques promote the spread of neurofibrillary tau tangles. However, these two proteinopathies initiate in spatially distinct brain regions, so how they interact during AD progression is unclear. Objective: In this study, we utilized Aβ and tau positron emission tomography (PET) scans from 572 older subjects (476 healthy controls (HC), 14 with mild cognitive impairment (MCI), 82 with mild AD), at varying stages of the disease, to investigate to what degree tau is associated with cortical Aβ deposition. Methods: Using multiple linear regression models and a pseudo-longitudinal ordering technique, we investigated remote tau-Aβ associations in four pathologic phases of AD progression based on tau spread: 1) no-tau, 2) pre-acceleration, 3) acceleration, and 4) post-acceleration. Results: No significant tau-Aβ association was detected in the no-tau phase. In the pre-acceleration phase, the earliest stage of tau deposition, associations emerged between regional tau in medial temporal lobe (MTL) (i.e., entorhinal cortex, parahippocampal gyrus) and cortical Aβ in lateral temporal lobe regions. The strongest tau-Aβ associations were found in the acceleration phase, in which tau in MTL regions was strongly associated with cortical Aβ (i.e., temporal and frontal lobes regions). Strikingly, in the post-acceleration phase, including 96% of symptomatic subjects, tau-Aβ associations were no longer significant. Conclusions: The results indicate that associations between tau and Aβ are stage-dependent, which could have important implications for understanding the interplay between these two proteinopathies during the progressive stages of AD.

Timofey L. Galankin, Anton Y. Bespalov, Hans J. Moebius
Clusterization of Behavioral and Psychological Symptoms of Dementia as Assessed by Neuropsychiatric Inventory: A Case Against the Use of Principal Component Analysis
Abstract: Background: The term Behavioral and Psychological Symptoms of Dementia (BPSD) covers a group of phenomenologically and medically distinct symptoms that rarely occur in isolation. Their therapy represents a major unmet medical need across dementias of different types, including Alzheimer's disease. Understanding of the symptom occurrence and their clusterization can inform clinical drug development and use of existing and future BPSD treatments. Objective: The primary aim of the present study was to investigate the ability of a commonly used principal component analysis to identify BPSD patterns as assessed by Neuropsychiatric Inventory (NPI). Methods: NPI scores from the Aging, Demographics, and Memory Study (ADAMS) were used to characterize reported occurrence of individual symptoms and their combinations. Based on this information, we have designed and conducted a simulation experiment to compare Principal Component analysis (PCA) and zero-inflated PCA (ZI PCA) by their ability to reveal true symptom associations. Results: Exploratory analysis of the ADAMS database revealed overlapping multivariate distributions of NPI symptom scores. Simulation experiments have indicated that PCA and ZI PCA cannot handle data with multiple overlapping patterns. Although the principal component analysis approach is commonly applied to NPI scores, it is at risk to reveal BPSD clusters that are a statistical phenomenon rather than symptom associations occurring in clinical practice. Conclusions: We recommend the thorough characterization of multivariate distributions before subjecting any dataset to Principal Component Analysis.

Jiaqi Wen, Xiwa Hao, Yanhong Jia, Baojun Wang, Jiangxia Pang, Furu Liang
Sex Differences in the Association Between LDL/HDL with Cognitive Decline in Older Adults: National Health and Nutrition Examination Survey
Abstract: Background: Lipids have a significant impact on the development and functioning of the nervous system, but the sex differences between the association of LDL/HDL, which reflects lipid metabolic status, and cognitive impairment remains unclear. Objective: We aimed to determine if there were sex differences between the association of LDL/HDL and cognitive function in US older adults. Methods: This population-based cross-sectional study used data from the National Health and Nutrition Examination Survey (NHANES) 2011-2012 and 2013-2014 cycles. The main outcome was poor cognitive performance defined by the Digit Symbol Substitution Test (DSST) < 34 based on published literature. Results: A total of 1,225 participants were included in the study, with a cognitive impairment incidence of 25.6% (314/1,225). Multivariate regression models demonstrated a significant association between cognitive decline and each 1-unit increase in LDL/HDL, after adjusting for all covariates (adjusted odds ratio [OR] = 1.36, 95% confidence interval [CI]: 1.11-1.67). Furthermore, subgroup analysis revealed an interaction between LDL/HDL and cognitive impairment in sex subgroups. Conclusions: LDL/HDL was associated with cognitive impairment in the US older adult population in adjusted models, although the significance of this association was not observed in females.

Janet Janbek, Thomas Munk Laursen, Niels Frimodt-Møller, Melinda Magyari, Jürgen G. Haas, Richard Lathe, Gunhild Waldemar
Risk of Major Types of Dementias Following Hospital-Diagnosed Infections and Autoimmune Diseases
Abstract: Background: Population-based studies have shown an increased risk of dementia after infections, but weaker links were reported for autoimmune diseases. Evidence is scarce for whether the links may be modified by the dementia or exposure subtype. Objective: We aimed to investigate the association between infections and/or autoimmune diseases and rates of major types of dementias in the short- and long terms. Methods: Nationwide nested case-control study of dementia cases (65+ years) diagnosed in Denmark 2016–2020 and dementia-free controls. Exposures were hospital-diagnosed infections and autoimmune diseases in the preceding 35 years. Two groups of dementia cases were those diagnosed in memory clinics (MC) and those diagnosed outside memory clinics (non-memory clinic cases, NMC). Results: In total, 26,738 individuals were MC and 12,534 were NMC cases. Following any infection, the incidence rate ratio (IRR) for MC cases was 1.23 (95% CI 1.20–1.27) and 1.70 for NMC cases (1.62–1.76). Long-term increased rates were seen for vascular dementia and NMC cases. IRRs for autoimmune diseases were overall statistically insignificant. Conclusions: Cases with vascular dementia and not Alzheimer’s disease, and a subgroup of cases identified with poorer health have increased long-term risk following infections. Autoimmune diseases were not associated with any type of dementia. Notably increased risks (attributed to the short term) and for NMC cases may indicate that immunosenescence rather than de novo infection explains the links. Future focus on such groups and on the role of vascular pathology will explain the infection-dementia links, especially in the long term.

Marta Moreno-Rodriguez, Sylvia E. Perez, Jonatan Martinez-Gardeazabal, Ivan Manuel, Michael Malek-Ahmadi, Rafael Rodriguez-Puertas, Elliott J. Mufson
Frontal Cortex Lipid Alterations During the Onset of Alzheimer’s Disease
Abstract: Background: Although sporadic Alzheimer’s disease (AD) is a neurodegenerative disorder of unknown etiology, familial AD is associated with specific gene mutations. A commonality between these forms of AD is that both display multiple pathogenic events including cholinergic and lipid dysregulation. Objective: We aimed to identify the relevant lipids and the activity of their related receptors in the frontal cortex, correlating them with cognitive function throughout the progression of AD. Methods: MALDI-mass spectrometry imaging (MSI) and functional autoradiography was used to evaluate the distribution of phospholipids/sphingolipids and the activity of cannabinoid 1 (CB1), sphingosine 1-phosphate 1 (S1P1), and muscarinic M2/M4 receptors in the frontal cortex (FC) of people that come to autopsy with premortem clinical diagnosis of AD, mild cognitive impairment (MCI), and no cognitive impairment (NCI). Results: MALDI-MSI revealed an increase in myelin-related lipids, such as diacylglycerol (DG) 36:1, DG 38:5, and phosphatidic acid (PA) 40:6 in the white matter (WM) in MCI compared to NCI, and a downregulation of WM phosphatidylinositol (PI) 38:4 and PI 38:5 levels in AD compared to NCI. Interestingly, elevated levels of phosphatidylcholine (PC) 32:1, PC 34:0, and sphingomyelin 38:1 were observed in discrete lipid accumulations in the FC supragranular layers during disease progression. Muscarinic M2/M4 receptor activation in layers V-VI decreased in AD compared to MCI. CB1 receptor activity was upregulated in layers V-VI, while S1P1 was downregulated within WM in AD relative to NCI. Conclusions: FC WM lipidomic alterations are associated with myelin dyshomeostasis in prodromal AD, suggesting WM lipid maintenance as a potential therapeutic target for dementia.

Cinzia Costa*, Elena Nardi Cesarini*, Paolo Eusebi, David Franchini, Paola Casucci, Marcello F. De Giorgi, Carmen Calvello, Federico Paolini Paoletti, Michele Romoli*, Lucilla Parnetti *These authors contributed equally to this work.
Incidence and Risk Factors of Epilepsy in Patients with Dementia: A Population-Based Study Using Regional Healthcare Databases in Umbria
Abstract: Background: Dementia is prevalent among the elderly, also representing a risk for seizures/epilepsy. Estimations of epilepsy risk in dementia patients are not widely available. Objective: Our research aims to ascertain the incidence of epilepsy and its associated risk factors in subjects with dementia in the Umbria region, based on data from healthcare databases. Methods: In this retrospective study based on the healthcare administrative database of Umbria, we identified all patients diagnosed with dementia from 2013 to 2017, based on ICD-9-CM codes. For epilepsy ascertainment, we used a validated algorithm that required an EEG and the prescription of one or more anti-seizure medications post-dementia diagnosis. A case-control analysis was conducted, matching five non-dementia subjects by gender and age to each dementia patient. Cox proportional hazards models were then utilized in the analysis. Results: We identified 7,314 dementia cases, also including 35,280 age- and sex-matched control subjects. Out of patients with dementia, 148 individuals (2.02%) were diagnosed with epilepsy. We observed a progressive increase in the cumulative incidence of seizures over time, registering 1.45% in the first year following the diagnosis, and rising to 1.96% after three years. Analysis using Cox regression revealed a significant association between the development of epilepsy and dementia (HR=4.58, 95%CI=3.67-5.72). Additional risk factors were male gender (HR=1.35, 95%CI=1.07-1.69) and a younger age at dementia onset (HR=1.03, 95%CI=0.96-0.98). Conclusions: Dementia increases epilepsy risk, especially with early onset and male gender. Clinicians should have a low threshold to suspect seizures in dementia cases.