Genetic Evidence Supporting a Causal Role of Depression in Alzheimer's Disease

BACKGROUND

Depression has been associated with a higher risk of Alzheimer's disease (AD) in several prospective studies; however, mechanisms underlying this association remain unclear.

METHODS

We examined genetic correlation between depression and AD using linkage disequilibrium score regression. We then tested for evidence of causality between depression and AD using Mendelian randomization and genome-wide association study results. Subsequently, cis and trans quantitative trait locus analyses for the depression genome-wide association study signals were performed to resolve the genetic signals to specific DNA methylation sites, brain transcripts, and proteins. These transcripts and proteins were then examined for associations with AD and its endophenotypes. Finally, the associations between depression polygenic risk score and AD endophenotypes were examined.

RESULTS

We detected a significant genetic correlation between depression and AD, suggesting that they have a shared genetic basis. Furthermore, we found that depression had a causal role in AD through Mendelian randomization but did not find evidence for a causal role of AD on depression. Moreover, we identified 75 brain transcripts and 28 brain proteins regulated by the depression genome-wide association study signals through quantitative trait locus analyses. Of these, 46 transcripts and seven proteins were associated with rates of cognitive decline over time, AD pathologies, and AD diagnosis in two separate cohorts, thus implicating them in AD. In addition, we found that a higher depression polygenic risk score was associated with a faster decline of episodic memory over time.

CONCLUSIONS

Depression appears to have a causal role in AD, and this causal relationship is likely driven, in part, by the 53 brain transcripts and proteins identified in this study.

Vascular pathology and pathogenesis of cognitive impairment and dementia in older adults

It is well recognized that brains of older people often harbor cerebrovascular disease pathology including vessel disease and vascular-related tissue injuries and that this is associated with vascular cognitive impairment and contributes to dementia. Here we review vascular pathologies, cognitive impairment, and dementia. We highlight the importance of mixed co-morbid AD/non-AD neurodegenerative and vascular pathology that has been collected in multiple clinical pathologic studies, especially in community-based studies. We also provide an update of vascular pathologies from the Rush Memory and Aging Project and Religious Orders Study cohorts with special emphasis on the differences across age in persons with and without dementia. Finally, we discuss neuropathological perspectives on the interpretation of clinical-pathological studies and emerging data in community-based studies.

LDL cholesterol is associated with higher AD neuropathology burden independent of APOE

OBJECTIVE

APOE is a strong risk factor for Alzheimer's disease (AD) and associated with higher low-density lipoprotein cholesterol (LDL-C) levels. Moreover, LDL-C is associated with the development of clinically ascertained AD; however, whether this association is present with the underlying neuropathological manifestations of AD or whether it is independent of the effect of APOE is unknown and is the focus of this paper.

METHODS

Individuals in the Religious Orders Study/Memory and Ageing Project cohorts with longitudinal measures of blood lipids and detailed autopsies were studied. We modelled the relationship between blood lipids and 12 age-related brain pathologies using a linear mixed model adjusted for potential confounding factors and stratified by APOE genotype with overall significance determined by meta-analysis. Blood lipids considered were LDL-C, high-density lipoprotein cholesterol and triglycerides. Brain pathologies included AD pathology measured by silver staining (Braak stage, a modified Consortium to Establish a Registry for Alzheimer's Disease [CERAD] score and global AD pathology) and immunohistochemistry (beta-amyloid and neurofibrillary tangles) as well as cerebral microinfarct, cerebral macroinfarct, cerebral amyloid angiopathy, cerebral atherosclerosis, hippocampal sclerosis, TDP-43 cytoplasmic inclusions and Lewy bodies.

RESULTS

559 participants (69.1% female) had complete data for analysis. They were followed for a median of 7 years and a median of 3 years prior to dementia onset. LDL-C was associated with all measures of AD neuropathology (neurofibrillary tangles, beta-amyloid, Braak stage, modified CERAD score and global AD pathology) and cerebral amyloid angiopathy independent of APOE after adjusting for age, sex, cholesterol-lowering medication use, body mass index, smoking and education at false discovery rate (FDR) p-value <0.05.

CONCLUSIONS

These findings implicate LDL-C in the pathophysiology of AD independent of APOE and suggest LDL-C is a modifiable risk factor for AD.

Bulk and Single-Nucleus Transcriptomics Highlight Intra-Telencephalic and Somatostatin Neurons in Alzheimer's Disease

Cortical neuron loss is a pathological hallmark of late-onset Alzheimer's disease (AD). However, it remains unclear which neuronal subtypes beyond broad excitatory and inhibitory classes are most vulnerable. Here, we analyzed cell subtype proportion differences in AD compared to non-AD controls using 1037 post-mortem brain samples from six neocortical regions. We identified the strongest associations of AD with fewer somatostatin (SST) inhibitory neurons (β = -0.48, p bonf = 8.98 × 10-9) and intra-telencephalic (IT) excitatory neurons (β = -0.45, p bonf = 4.32 × 10-7). Replication in three AD case-control single-nucleus RNAseq datasets most strongly supported the bulk tissue association of fewer SST neurons in AD. In depth analyses of cell type proportions with specific AD-related neuropathological and cognitive phenotypes revealed fewer SST neurons with greater brain-wide post-mortem tau and beta amyloid, as well as a faster rate of antemortem cognitive decline. In contrast, greater IT neuron proportions were associated with a slower rate of cognitive decline as well as greater residual cognition-a measure of cognitive resilience-but not canonical AD neuropathology. Our findings implicate somatostatin inhibitory and intra-telencephalic excitatory neuron subclasses in the pathogenesis of AD and in cognitive resilience to AD pathology, respectively.

Antibiotic therapy and association with oncological outcomes from targeted and immune-based therapy in hepatocellular carcinoma (HCC)

4089

Background: Immune checkpoint inhibitors (ICI) alone or in combination with tyrosine kinase (TKI) or VEGF pathway inhibitors (VEGFi) are therapeutic options in unresectable HCC (uHCC). Whether exposure to antibiotics (ATB), a consolidated adverse prognostic factor in ICI recipients, affects outcome in HCC remains unclear. Methods: FDA analysed patient-level data of 4098 patients receiving ICI (n = 842) either as monotherapy (n = 258) or combinations (n = 584), TKI (N = 1968), VEGFi (n = 480) or placebo (n = 808) as part of 9 international clinical trials submitted to the US Food and Drug Administration in support of marketing applications. Associations for ATB exposure within 30 days before or after initiation of anti-cancer treatment (ATB) with overall (OS) and progression-free survival (PFS) were examined across therapeutic modality. Estimates were weighted by propensity score (PSW) using clinically relevant covariates. Results: Out of 4098 patients with uHCC mostly secondary to Hepatitis B (39%) or C (21%) infection, the majority were males (83%) with a median age of 64 (range 18-88), ECOG performance status of 0 (60%) and Child-Pugh A class (98%). Most patients had metastases (68%) but did not have macrovascular invasion (71%). Overall, 620 patients (15%) were ATB+, with comparable rates across placebo (12%), TKI (16%), VEGFi (15%), and ICI (16%). In the overall population, ATB was associated with shorter PFS (2.8 vs 3.9 months [m], HR 1.29, 95%CI 1.22-1.36) and OS (6.4 vs. 8.8 m; HR 1.36, 95%CI 1.29-1.43). In PSW analyses, ATB was associated with shorter PFS in patients treated with ICI (HR 1.52, 95%CI 1.34-1.73), TKI (HR 1.29, 95%CI 1.19-1.39) and placebo (HR 1.23, 95%CI 1.11-1.37). Similar results were observed in PSW analyses of OS in patients treated with ICI (HR 1.22, 95%CI 1.08-1.38), TKI HR 1.40, 95%CI 1.30-1.52), and placebo (HR 1.40, 95%CI 1.25-1.57). Consistent outcomes were observed for ATB+ patients within ICI treatment subgroups, including patients treated with anti-PD-1 monotherapy (PFS HR 1.49, 95%CI 1.22-1.80; OS HR 1.31 1.02-1.68) and ICI combinations (PFS HR 1.50, 95%CI 1.26-1.77; OS HR 1.14 0.99-1.32). Conclusions: Unlike other oncological indications where the detrimental effect of ATB may be more prominent in ICI recipients, ATB is associated with inferior outcomes across a broad range of anti-cancer therapies for HCC and placebo. Whether ATB is causally linked to worse outcomes through disruption of the gut liver axis remains to be demonstrated in translational studies.

Caffeine Consumption and Dementia: Are Lewy Bodies the Link?

OBJECTIVE

The objective of this study was to examine the association between caffeine intake and cognitive impairment. Caffeine-neuropathology correlations and interactions with lifestyle and genetic factors impacting caffeine metabolism and response were also tested.

METHODS

We included 888 participants aged 59+ years from the Rush Memory and Aging Project (MAP) and 303,887 participants aged 55+ years from the UK Biobank (UKB). MAP participants took part in annual cognitive testing. Diagnosis of dementia was based on clinical neurological examination and standardized criteria. A subset provided postmortem tissue for neuropathologic evaluation for common age-related diseases (eg, Alzheimer's disease [AD], Lewy bodies, and vascular). For UKB, dementia was determined by linked hospital and death records. Self-reported caffeine intake was estimated using food-frequency questionnaires in both cohorts. Cox proportional hazard ratio (HR), regression, and mixed models were used to examine associations of caffeine intake with incident dementia, cognitive decline, and neuropathology.

RESULTS

In MAP, compared to ≤100 mg/day, caffeine intake >100 mg/day was associated with a significantly higher HR (95% confidence interval [CI]) of all-cause (HR = 1.35, 95% CI = 1.03-1.76) and AD (HR = 1.41, 95% CI = 1.07-1.85) dementia. Caffeine intake was not associated with cognitive decline. In UKB, compared to ≤100 mg/day, the HRs (95% CI) of all-cause dementia for consuming 100 ≤ 200, 200 ≤ 300, 300 ≤ 400, and > 400 mg/day were 0.83 (95% CI = 0.72-0.94), 0.74 (95% CI = 0.64-0.85), 0.74 (95% CI = 0.64-0.85), and 0.92 (95% CI = 0.79-1.08), respectively. Similar results were observed for Alzheimer's dementia. In MAP, caffeine intake was inversely associated with postmortem Lewy bodies but no other age-related pathologies. Caffeine intake >100 mg/day was associated with lower neocortical type Lewy bodies (odds ratio (95%CI): 0.40 (95% CI = 0.21-0.75).

INTERPRETATION

Caffeine intake was inconsistently associated with clinical dementia; potentially explained by cohort differences in underlying dementia etiology. Lewy bodies may link caffeine to lower risk in some persons. ANN NEUROL 2022;91:834-846.

Neuropathology of Dementia Disorders

PURPOSE OF REVIEW

This article provides an overview of the neuropathology of common age-related dementing disorders, focusing on the pathologies that underlie Alzheimer disease (AD) and related dementias, including Lewy body dementias, frontotemporal dementia, vascular dementia, limbic-predominant age-related transactive response DNA-binding protein 43 (TDP-43) encephalopathy (LATE), and mixed-etiology dementias. This article also discusses the underlying proteinopathies of neurodegenerative diseases (eg, amyloid-β, paired helical filament tau, α-synuclein, and TDP-43 pathology) and vascular pathologies, including tissue injury (eg, infarcts, hemorrhages) with or without vessel disease.

RECENT FINDINGS

New criteria for AD pathologic diagnosis highlight amyloid-β as the sine qua non of AD; they require molecular markers of amyloid and establish a minimum threshold of Braak neurofibrillary tangle stage 3. Pathologic diagnosis is separated from clinical disease (ie, pathologic diagnosis no longer requires dementia). TDP-43 pathology, a major pathology in a frontotemporal dementia subtype, was found as a central pathology in LATE, a newly named amnestic disorder. Multiple pathologies (often co-occurring with AD) contribute to dementia and add complexity to the clinical picture. Conversely, Lewy body, LATE, and vascular dementias often have accompanying AD pathology. Pathology and biomarker studies highlight subclinical pathologies in older people without cognitive impairment. This resilience to brain pathology is common and is known as cognitive reserve.

SUMMARY

The pathologies of dementia in aging are most commonly amyloid, tangles, Lewy bodies, TDP-43, hippocampal sclerosis, and vascular pathologies. These pathologies often co-occur (mixed pathologies), which may make specific clinical diagnoses difficult. In addition, dementia-related pathologies are often subclinical, suggesting varying levels of resilience in older people.

Association of Traumatic Brain Injury With and Without Loss of Consciousness With Neuropathologic Outcomes in Community-Dwelling Older Persons

Importance

A history of traumatic brain injury (TBI) has been considered a risk factor for Alzheimer dementia. However, the specific association of TBI, even without loss of consciousness (LOC), with pathologic findings that underlie Alzheimer dementia, including Alzheimer disease (AD), non-AD neurodegenerative, and vascular pathologic findings, remains unclear.

Objective

To examine the association between TBI with and without LOC and neuropathologic findings in community-based cohorts.

Design, Setting, and Participants

This cross-sectional analysis used neuropathologic data from 1689 participants from the Religious Orders Study, the Rush Memory and Aging Project, and the Minority Aging Research Study. These studies began enrollment in 1994, 1997, and 2004, respectively. The current study's data set was frozen on April 3, 2021, when the mean (SD) length of follow-up for the participants was 8.7 (5.5) years.

Exposure

Traumatic brain injury exposure was assessed using a standardized, self-reported questionnaire at baseline and annual follow-up visits. Participants were categorized into those (1) without TBI exposure (n = 1024), (2) with TBI with LOC (n = 161), or (3) with TBI without LOC (n = 504).

Main Outcomes and Measures

Neuropathologic measures of amyloid-β, paired helical filament tangles, neocortical Lewy bodies, transactive response DNA-binding protein 43, hippocampal sclerosis, gross infarcts, and microinfarcts were assessed. Multiple linear regression and logistic regression models were used to determine whether TBI with or without LOC (compared with no TBI exposure as the reference group) was associated with neuropathologic outcomes after adjusting for age at death, sex, and educational level. Whether the apolipoprotein E (APOE) ε4 allele and sex differences modified associations was also examined.

Results

A total of 1689 participants (1138 [67%] women and 551 [33%] men; mean [SD] age at death, 89.2 [6.7] years; 80 [5%] Black, 46 [3%] Latino, 1639 [97%] non-Latino, and 1601 [95%] White) participated in the study. Compared with participants without TBI, participants with TBI with LOC had a greater amyloid-β load (estimate, 0.25; 95% CI, 0.06-0.43; P = .008) and higher odds of having 1 or more gross infarcts (odds ratio [OR], 1.45; 95% CI, 1.04-2.02; P = .02) and 1 or more microinfarcts (OR, 1.70; 95% CI, 1.21-2.38; P = .002), particularly subcortical microinfarcts (OR, 1.85; 95% CI, 1.23-2.79; P = .002). Those with TBI without LOC had higher odds of neocortical Lewy bodies (OR, 1.37; 95% CI, 1.01-1.87; P = .04) and 1 or more cortical microinfarcts (OR, 1.43; 95% CI, 1.09-1.87; P = .008). The association of TBI with and without LOC with vascular pathologic outcomes persisted after controlling for vascular risk factors and vascular disease burden. Traumatic brain injury with or without LOC was not associated with paired helical filament tangles, transactive response DNA-binding protein 43, or hippocampal sclerosis. No interactions occurred with APOE ε4 or sex.

Conclusions and Relevance

This cross-sectional analysis suggests that a history of TBI, even without LOC, is associated with age-related neuropathologic outcomes, both neurodegenerative and vascular. The variation in the neuropathologic outcomes in individuals with and without LOC may provide clues to potential mechanisms, diagnoses, and management in persons with TBI.

Cortical Proteins and Individual Differences in Cognitive Resilience in Older Adults

BACKGROUND AND OBJECTIVES

Cognitive resilience is a well-recognized concept, but knowledge gaps about its underlying mechanisms have made it difficult to develop instruments that identify older adults with high or low resilience. We tested whether aggregating cortical peptides associated with cognitive resilience into an index can identify adults with higher or lower cognitive resilience.

METHODS

We used data from 1,192 older decedents, including annual clinical testing, indices of 10 Alzheimer disease (AD) and related dementia (ADRD) pathologies, and 226 proteotypic peptides measured in the dorsal lateral prefrontal cortex. We used linear mixed-effects models to identify peptides that were related to cognitive resilience (i.e., cognitive decline not explained by ADRD pathologies [false discovery rate <0.05]). We aggregated the expression levels of these resilience peptides into a person-specific cognitive resilience index and examined its association with AD clinical and pathologic phenotypes.

RESULTS

We constructed a resilience index from 52 of 226 peptides related to cognitive resilience. A higher index was associated with slower cognitive decline (estimate 0.05, SE 0.003, p < 0.001) and slower motor decline (estimate 0.005, SE 0.001, p < 0.001). Most resilience peptides (70%) were specific to cognitive decline, but 30% also provided resilience for motor decline. A higher index was also related to a lower burden of AD pathologies (odds ratio [OR] 0.41, SE 0.01, p < 0.001) and modified the association of AD pathology with cognition in that a higher index modified the negative effects of AD pathology on AD dementia proximate to death (OR 0.70, SE 0.14, p = 0.010). Up to 90% of cognitive resilience peptides were related to AD pathologic phenotypes.

DISCUSSION

Cortical proteins may provide some degree of cognitive resilience. These multifunctional proteins also seem to provide resilience to other AD clinical phenotypes and have independent associations with ADRD pathologies. Resilience proteins may be high-value therapeutic targets for drug discovery of interventions that maintain brain health in aging adults via multiple pathways.

Association of Statins With Cerebral Atherosclerosis and Incident Parkinsonism in Older Adults

BACKGROUND

The burden of cerebrovascular disease pathologies is associated with progressive parkinsonism in older adults. We tested the hypothesis that older adults using statins have a lower risk of developing parkinsonism.

METHODS

We studied older adults with annual clinical testing of four parkinsonian signs and assessment of statin use based on inspection of all medications. Parkinsonism was present if there was clinical evidence of 2 or more parkinsonian signs. Postmortem brain exam collected indices of pathologies including atherosclerosis of the large vessels of the Circle of Willis. We examined if baseline statin use was related to incident parkinsonism. Then in decedents, we examined whether statin use prior to death was related to pathologies and whether pathologies linked the association of statin use with parkinsonism.

RESULTS

Mean age of the participants (n=2841) at study baseline was 76.3 (SD=7.4) years, and 75% were women. During an average follow-up of 6 years (mean=5.6, SD=4.9), 50% (n=1432) of participants developed parkinsonism. Statin use at baseline (n=936) was associated with a lower risk of parkinsonism (HR=0.84, 95%CI: 0.74-0.96, p=0.008) controlling for demographics, vascular risk factors and diseases. Among the decedents [n=1044, age at death (mean=89.2, SD=6.7)], statin-use prior to death was associated with a lower odds of atherosclerosis (OR=0.63, 95%CI: 0.50-0.79, p<0.001). In a mediation analysis, both a direct (OR=0.73, 95%CI: 0.54-0.93, p=0.008) and an indirect (OR=0.92, 95%CI: 0.88-0.97, p=0.002) pathway via less severe atherosclerosis linked statins to parkinsonism indicating that atherosclerosis mediated 17% of the association between statins and parkinsonism.

CONCLUSION

Adults using statins have a lower risk of parkinsonism that may be partially mediated by a lower odds of brain atherosclerosis. These findings highlight the role of cerebrovascular pathologies in late-life parkinsonism and suggest a potential role for statins in decreasing its magnitude.

Neuropathologic Correlates of Human Cortical Proteins in Alzheimer Disease and Related Dementias

BACKGROUND AND OBJECTIVES

Alzheimer dementia is a complex clinical syndrome that can be defined broadly as an amnestic multidomain dementia. We previously reported human cortical proteins that are implicated in Alzheimer dementia. To understand the pathologic correlates of these proteins for underlying disease mechanisms, we investigated cortical protein associations with common age-related neuropathologies.

METHODS

Participants were community-dwelling older adults from 2 cohort studies of aging and dementia. All underwent detailed annual clinical evaluations, and brain autopsies were performed after death. We use Alzheimer disease (AD) to refer to pathologically defined disease and Alzheimer dementia to refer to the clinical syndrome. Indices for AD, cortical Lewy bodies, limbic predominant age-related TAR DNA binding protein 43 encephalopathy neuropathologic changes (LATE-NC), hippocampal sclerosis, macroscopic infarcts, microinfarcts, cerebral amyloid angiopathy, atherosclerosis, and arteriolosclerosis were quantified during uniform structured neuropathologic evaluations. High-throughput protein abundances from frozen dorsolateral prefrontal cortex were quantified with mass spectrometry-based tandem mass tag proteomics analysis. Eleven human cortical proteins implicated in Alzheimer dementia, including angiotensin-converting enzyme, calcium-regulated heat-stable protein 1 (CHSP1), procathepsin H (CATH), double C2-like domain-containing protein α, islet cell autoantigen 1-like protein, serine β-lactamase-like protein LACTB, mitochondrial, pleckstrin homology domain-containing family A member 1, replication termination factor 2, sorting nexin-32, syntaxin-4, and syntaxin-6 (STX6), were previously identified with an integrative approach. Logistic regression analysis examined the association of protein expression with each of the neuropathologic indices.

RESULTS

A total of 391 older adults were included. We did not observe associations of these protein targets with pathologic diagnosis of AD. In contrast, multiple proteins were associated with non-AD neurodegenerative and cerebrovascular conditions. In particular, higher CHSP1 expression was associated with cortical Lewy bodies and macroscopic infarcts, and higher CATH expression was associated with LATE-NC and arteriolosclerosis. Furthermore, while higher STX6 expression increased the risk of Alzheimer dementia, the protein was not associated with any of the neuropathologic indices investigated.

DISCUSSION

Cortical proteins implicated in Alzheimer dementia do not necessarily work through AD pathogenesis; rather, non-AD neurodegenerative and vascular diseases and other pathways are at play. Furthermore, some proteins are pleiotrophic and associated with both neurodegenerative and cerebrovascular pathologies.

Association between WWOX/MAF variants and dementia-related neuropathologic endophenotypes

The genetic locus containing the WWOX and MAF genes was implicated as a clinical Alzheimer's disease (AD) risk locus in two recent large meta-analytic genome wide association studies (GWAS). In a prior GWAS, we identified a variant in WWOX as a suggestive risk allele for hippocampal sclerosis. We hypothesized that the WWOX/MAF locus may be preferentially associated with non-plaque- and non-tau-related neuropathological changes (NC). Data from research participants with GWAS and autopsy measures from the National Alzheimer's Coordinating Center and the Religious Orders Study and the Rush Memory and Aging Project were meta-analyzed. Notably, no variants in the locus were significantly associated with ADNC. However, several WWOX/MAF variants had significant adjusted associations with limbic-predominant age-related TDP-43 encephalopathy NC (LATE-NC), HS, and brain arteriolosclerosis. These associations remained largely unchanged after adjustment for ADNC (operationalized with standard semiquantitative staging), suggesting that these associations are independent of ADNC. Thus, WWOX genetic variants were associated pathologically with LATE-NC, not ADNC.

Association of small vessel disease with tau pathology

Emerging evidence suggests that small vessel disease (SVD) is a risk factor for clinical dementia and may contribute to AD neuropathological changes. Watershed brain regions are located at the most distal areas between arterial territories, making them vulnerable to SVD-related changes. We examined the association of pathologic markers of SVD, specifically arteriolosclerosis in watershed brain regions, with AD pathologic changes. Participants (N = 982; mean age-at-death = 90; 69% women) were enrolled as part of one of two cohort studies of aging and dementia. At autopsy, neuropathological evaluation included semi-quantitative grading of arteriolosclerosis pathology from 2 cortical watershed regions: the anterior watershed (AWS) and posterior watershed (PWS), densities for cortical β-amyloid and tau-tangle pathology, and other common age-related pathologies. Linear regression models examined the association of watershed arteriolosclerosis pathology with β-amyloid and tau-tangle burden. In follow-up analyses, available ex-vivo MRI and proteomics data in a subset of decedents were leveraged to examine the association of whole brain measure of WMH, as a presumed MRI marker of SVD, with β-amyloid and tau-tangle burden, as well as to examine the association of watershed arteriolosclerosis with proteomic tau. Watershed arteriolosclerosis was common, with 45% of older persons having moderate-to-severe arteriolosclerosis pathology in the AWS region, and 35% in the PWS. In fully adjusted models that controlled for demographics and common age-related pathologies, an increase in severity of PWS arteriolosclerosis was associated with a higher burden of tau-tangle burden, specifically neocortical tau burden, but not with β-amyloid. AWS arteriolosclerosis was not associated with β-amyloid or tau pathology. Ex-vivo WMH was associated with greater tau-tangle pathology burden but not β-amyloid. Furthermore, PWS arteriolosclerosis was associated with higher abundance of tau phosphopeptides, that promote formation of tau aggregates. These data provide compelling evidence that SVD, specifically posterior watershed arteriolosclerosis pathology, is linked with tau pathological changes in the aging brain.

Vasculocentric Axonal NfH in Small Vessel Disease

Cerebral small vessel disease (SVD) causes lacunar stroke and vascular cognitive impairment in older people. The pathogenic pathways from vessel pathology to parenchymal damage in SVD are unknown. Neurofilaments are axonal structural proteins. Neurofilament-light (NfL) is an emerging biomarker for neurological disease. Here, we examined the high molecular weight form neurofilament-heavy (NfH) and quantified a characteristic pattern of peri-arterial (vasculocentric) NfH labeling. Subcortical frontal and parietal white matter from young adult controls, aged controls, and older people with SVD or severe Alzheimer disease (n = 52) was immunohistochemically labeled for hyperphosphorylated NfH (pNfH). The extent of pNfH immunolabeling and the degree of vasculocentric axonal pNfH were quantified. Axonal pNfH immunolabeling was sparse in young adults but a common finding in older persons (controls, SVD, or AD). Axonal pNfH was often markedly concentrated around small penetrating arteries. This vasculocentric feature was more common in older people with SVD than in those with severe AD (p = 0.004). We conclude that axonal pNfH is a feature of subcortical white matter in aged brains. Vasculocentric axonal pNfH is a novel parenchymal lesion that is co-located with SVD arteriopathy and could be a consequence of vessel pathology.

Brain microRNAs are associated with variation in cognitive trajectory in advanced age

In advancing age, some individuals maintain a stable cognitive performance over time, while others experience a rapid decline. Such variation in cognitive trajectory is only partially explained by common neurodegenerative pathologies. Hence, we aimed to identify new molecular processes underlying variation in cognitive trajectory using brain microRNA profile followed by an integrative analysis with brain transcriptome and proteome. Individual cognitive trajectories were derived from longitudinally assessed cognitive-test scores of older-adult brain donors from four longitudinal cohorts. Postmortem brain microRNA profiles, transcriptomes, and proteomes were derived from the dorsolateral prefrontal cortex. The global microRNA association study of cognitive trajectory was performed in a discovery (n = 454) and replication cohort (n = 134), followed by a meta-analysis that identified 6 microRNAs. Among these, miR-132-3p and miR-29a-3p were most significantly associated with cognitive trajectory. They explain 18.2% and 2.0% of the variance of cognitive trajectory, respectively, and act independently of the eight measured neurodegenerative pathologies. Furthermore, integrative transcriptomic and proteomic analyses revealed that miR-132-3p was significantly associated with 24 of the 47 modules of co-expressed genes of the transcriptome, miR-29a-3p with 3 modules, and identified 84 and 214 downstream targets of miR-132-3p and miR-29a-3p, respectively, in cognitive trajectory. This is the first global microRNA study of cognitive trajectory to our knowledge. We identified miR-29a-3p and miR-132-3p as novel and robust contributors to cognitive trajectory independently of the eight known cerebral pathologies. Our findings lay a foundation for future studies investigating mechanisms and developing interventions to enhance cognitive stability in advanced age.

Neuropathology of Vascular Brain Health: Insights From Ex Vivo Magnetic Resonance Imaging-Histopathology Studies in Cerebral Small Vessel Disease

Sporadic cerebral small vessel disease (SVD) is a major contributor to vascular cognitive impairment and dementia in the aging human brain. On neuropathology, sporadic SVD is characterized by abnormalities to the small vessels of the brain predominantly in the form of cerebral amyloid angiopathy and arteriolosclerosis. These pathologies frequently coexist with Alzheimer disease changes, such as plaques and tangles, in a single brain. Conversely, during life, magnetic resonance imaging (MRI) only captures the larger manifestations of SVD in the form of parenchymal brain abnormalities. There appears to be a major knowledge gap regarding the underlying neuropathology of individual MRI-detectable SVD abnormalities. Ex vivo MRI in postmortem human brain tissue is a powerful tool to bridge this gap. This review summarizes current insights into the histopathologic correlations of MRI manifestations of SVD, their underlying cause, presumed pathophysiology, and associated secondary tissue injury. Moreover, we discuss the advantages and limitations of ex vivo MRI-guided histopathologic investigations and make recommendations for future studies.

Blood-brain barrier link to human cognitive impairment and Alzheimer's Disease

Vascular dysfunction is frequently seen in disorders associated with cognitive impairment, dementia and Alzheimer's disease (AD). Recent advances in neuroimaging and fluid biomarkers suggest that vascular dysfunction is not an innocent bystander only accompanying neuronal dysfunction. Loss of cerebrovascular integrity, often referred to as breakdown in the blood-brain barrier (BBB), has recently shown to be an early biomarker of human cognitive dysfunction and possibly underlying mechanism of age-related cognitive decline. Damage to the BBB may initiate or further invoke a range of tissue injuries causing synaptic and neuronal dysfunction and cognitive impairment that may contribute to AD. Therefore, better understanding of how vascular dysfunction caused by BBB breakdown interacts with amyloid-β and tau AD biomarkers to confer cognitive impairment may lead to new ways of thinking about pathogenesis, and possibly treatment and prevention of early cognitive impairment, dementia and AD, for which we still do not have effective therapies.

Microglial Correlates of Late Life Physical Activity: Relationship with Synaptic and Cognitive Aging in Older Adults

Physical activity relates to reduced dementia risk, but the cellular and molecular mechanisms are unknown. We translated animal and in vitro studies demonstrating a causal link between physical activity and microglial homeostasis into humans. Decedents from Rush Memory and Aging Project completed actigraphy monitoring (average daily activity) and cognitive evaluation in life, and neuropathological examination at autopsy. Brain tissue was analyzed for microglial activation via immunohistochemistry (anti-human HLA-DP-DQ-DR) and morphology (% Stage I, II, or III), and synaptic protein levels (SNAP-25, synaptophysin, complexin-I, VAMP, syntaxin, synaptotagmin-1). Proportion of morphologically activated microglia (PAM) was estimated in ventromedial caudate, posterior putamen, inferior temporal (IT), and middle frontal gyrus. The 167 decedents averaged 90 years at death, two-thirds were nondemented, and 60% evidenced pathologic Alzheimer's disease (AD). Adjusting for age, sex, education, and motor performances, greater physical activity associated with lower PAM in the ventromedial caudate and IT. Relationships between physical activity and PAM in the ventromedial caudate or IT were particularly prominent in adults evidencing microinfarcts or AD pathology, respectively. Mediational analyses indicated that PAM IT mediated ∼30% of the relationships between (1) physical activity and synaptic protein in IT, and (2) physical activity and global cognition, in separate models. However, the size of the mediation depended on AD pathology ranging from >40% in adults with high AD burden, but <10% in adults with low AD burden. Lower microglial activation may be a pathway linking physical activity to age-related brain health in humans. Physical activity may promote AD-related synaptic and cognitive resilience through reduction of pro-inflammatory microglial states.SIGNIFICANCE STATEMENT Physical activity relates to better cognitive aging and reduced risk of neurodegenerative disease, yet the cellular and molecular pathways linking behavior-to-brain in humans are unknown. Animal studies indicate that increasing physical activity leads to decreased microglial activation and corresponding increases in synaptogenesis and neurogenesis. We objectively monitored physical activity (accelerometer-based actigraphy) and cognitive performances in life, and quantified microglial activation and synaptic markers in brain tissue at death in older adults. These are the first data supporting microglial activation as a physiological pathway by which physical activity relates to brain heath in humans. Although more interventional work is needed, we suggest that physical activity may be a modifiable behavior leveraged to reduce pro-inflammatory microglial states in humans.

Pelargonidin and Berry Intake Association with Alzheimer's Disease Neuropathology: A Community-Based Study

BACKGROUND

An anthocyanidin, pelargonidin, primarily found in berries, has antioxidant and anti-inflammatory properties, and is associated with better cognition and reduced Alzheimer's dementia risk.

OBJECTIVE

This study investigated if pelargonidin or berry intake is associated with Alzheimer's disease (AD) neuropathology in human brains.

METHODS

The study was conducted among 575 deceased participants (age at death = 91.3±6.1 years; 70% females) of the Rush Memory and Aging Project, with dietary data (assessed using a food frequency questionnaire) and neuropathological evaluations. Calorie-adjusted pelargonidin intake was modeled in quartiles and berry intake as continuous (servings/week). Mean amyloid-beta load and phosphorylated tau neuronal neurofibrillary tangle density across multiple cortical regions were assessed using immunohistochemistry. Global AD pathology burden, a quantitative summary score of neurofibrillary tangles, and diffuse and neuritic plaques using Bielschowsky silver stains in multiple brain regions, was also assessed.

RESULTS

In a linear regression model adjusted for age at death, sex, education, APOE ɛ4 status, vitamin E, and vitamin C, participants in the highest quartile of pelargonidin intake when compared to those in the lowest quartile, had less amyloid-β load (β (SE) = -0.293 (0.14), p = 0.038), and fewer phosphorylated tau tangles (β (SE) = -0.310, p = 0.051). Among APOE ɛ4 non-carriers, higher strawberry (β (SE) = -0.227 (0.11), p = 0.037) and pelargonidin (Q4 versus Q1: β (SE) = -0.401 (0.16), p = 0.011; p trend = 0.010) intake was associated with less phosphorylated tau tangles, no association was observed in APOE ɛ4 carriers. Berry intake was not associated with AD pathology. However, excluding participants with dementia or mild cognitive impairment at baseline, strawberry (p = 0.004) and pelargonidin (ptrend = 0.007) intake were associated with fewer phosphorylated tau tangles.

CONCLUSION

Higher intake of pelargonidin, a bioactive present in strawberries, is associated with less AD neuropathology, primarily phosphorylated tau tangles.

Association of vitamin K with cognitive decline and neuropathology in community‐dwelling older persons

Higher vitamin K intakes have been associated with better cognitive function, suggestive of a vitamin K mechanistic effect or simply reflective of a healthy diet. To test the hypothesis that brain vitamin K is linked to cognitive decline and dementia, vitamin K concentrations were measured in four brain regions, and their associations with cognitive and neuropathological outcomes were estimated in 325 decedents of the Rush Memory and Aging Project. Menaquinone‐4 (MK4) was the main vitamin K form in the brain regions evaluated. Higher brain MK4 concentrations were associated with a 17% to 20% lower odds of dementia or mild cognitive impairment (MCI) (P‐value < .014), with a 14% to 16% lower odds of Braak stage ≥IV (P‐value < 0.045), with lower Alzheimer's disease global pathology scores and fewer neuronal neurofibrillary tangles (P‐value < 0.012). These findings provide new and compelling evidence implicating vitamin K in neuropathology underlying cognitive decline and dementia.

Complex Profiles of Cerebrovascular Disease Pathologies in the Aging Brain and Their Relationship With Cognitive Decline

BACKGROUND AND PURPOSE

Cerebrovascular disease (CVD) pathologies including vessel disease (atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy) and tissue injury (macroinfarcts and microinfarcts) each contribute to Alzheimer and other forms of dementia. CVD is often a complex mix of neuropathologies, with little known about the frequencies of differing combinations or their associations with cognition.

METHODS

We investigated 32 possible CVD combinations (3 types of vessel disease and 2 types of tissue injury) using autopsy data from 1474 decedents (≈88 years at death; 65% female) of Rush Alzheimer's Disease Center studies. We determined frequencies of all 32 CVD combinations and their relationships with global and domain-specific cognitive decline using mixed-effect models adjusted for demographics, neuropathologies, time before death, and interactions of these variables with time.

RESULTS

Of the 1184 decedents with CVD neuropathology (80% of the total sample), 37% had a single CVD (67-148 decedents/group) while 63% had mixed CVD profiles (11-54 decedents/group). When considered as 2 distinct groups, the mixed CVD profile group (but not the single CVD profile group) showed a faster cognitive decline across all domains assessed compared with decedents without CVD neuropathology. Most mixed CVD profiles, especially those involving both atherosclerosis and arteriolosclerosis, showed faster cognitive decline than any single CVD profile considered alone; specific mixed CVD profiles differentially associated with individual cognitive domains.

CONCLUSIONS

Mixed CVD, more common than single CVD, is associated with cognitive decline, and distinct mixed CVD profiles show domain-specific associations with cognitive decline. CVD is not monolithic but consists of heterogenous person-specific combinations with distinct contributions to cognitive decline.

Genome-wide association study and functional validation implicates JADE1 in tauopathy

Primary age-related tauopathy (PART) is a neurodegenerative pathology with features distinct from but also overlapping with Alzheimer disease (AD). While both exhibit Alzheimer-type temporal lobe neurofibrillary degeneration alongside amnestic cognitive impairment, PART develops independently of amyloid-β (Aβ) plaques. The pathogenesis of PART is not known, but evidence suggests an association with genes that promote tau pathology and others that protect from Aβ toxicity. Here, we performed a genetic association study in an autopsy cohort of individuals with PART (n = 647) using Braak neurofibrillary tangle stage as a quantitative trait. We found some significant associations with candidate loci associated with AD (SLC24A4, MS4A6A, HS3ST1) and progressive supranuclear palsy (MAPT and EIF2AK3). Genome-wide association analysis revealed a novel significant association with a single nucleotide polymorphism on chromosome 4 (rs56405341) in a locus containing three genes, including JADE1 which was significantly upregulated in tangle-bearing neurons by single-soma RNA-seq. Immunohistochemical studies using antisera targeting JADE1 protein revealed localization within tau aggregates in autopsy brains with four microtubule-binding domain repeats (4R) isoforms and mixed 3R/4R, but not with 3R exclusively. Co-immunoprecipitation in post-mortem human PART brain tissue revealed a specific binding of JADE1 protein to four repeat tau lacking N-terminal inserts (0N4R). Finally, knockdown of the Drosophila JADE1 homolog rhinoceros (rno) enhanced tau-induced toxicity and apoptosis in vivo in a humanized 0N4R mutant tau knock-in model, as quantified by rough eye phenotype and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) in the fly brain. Together, these findings indicate that PART has a genetic architecture that partially overlaps with AD and other tauopathies and suggests a novel role for JADE1 as a modifier of neurofibrillary degeneration.

Dementia and autopsy-verified causes of death in racially-diverse older Brazilians

BACKGROUND

While dementia has been associated with specific causes of death, previous studies were relatively small autopsy series or population-based studies lacking autopsy confirmation and were restricted to Non-Latinx Whites. Here, we examine the association of dementia with autopsy-verified causes of death in racially-diverse older Brazilians.

METHODS

As part of the Pathology, Alzheimer´s and Related Dementias Study (PARDoS), a community-based study in Brazil, we included 1941 racially-diverse deceased, 65 years or older at death. We conducted a structured interview with legal informants including the Clinical Dementia Rating (CDR) Scale for dementia proximate to death. Causes of death were assessed after full-body autopsy and macroscopic examination of the brain, thoracic and abdominal/pelvic organs. Up to four causes of death were reported for each decedent. Causes of death were classified as circulatory, infectious, cancer and other. Logistic regression was used to determine associations of dementia with cause of death, controlling for age, sex, race, and education.

RESULTS

Dementia was associated with a higher odds of an infectious cause of death (OR = 1.81, 95%CI:1.45-2.25), and with a lower odds of a circulatory disease as cause of death (OR = 0.69, 95%CI:0.54-0.86) and cancer as cause of death (OR = 0.41, 95%CI:0.24-0.71). Dementia was associated with a higher odds of pneumonia (OR = 1.92, 95%CI:1.53-2.40) and pulmonary embolism (OR = 2.31, 95%CI:1.75-3.05) as causes of death and with a lower odds of acute myocardial infarction (OR = 0.42, 95%CI:0.31-0.56) and arterial disease (OR = 0.76, 95%CI:0.61-0.94) as causes of death.

CONCLUSION

Racially-diverse older Brazilians with dementia had a higher odds of an infectious cause of death and a lower odds of cancer and circulatory disease as causes of death than those without dementia.