Late-life cognitive decline is associated with hippocampal volume, above and beyond its associations with traditional neuropathologic indices

Multiple Early Biomarkers to Predict Cognitive Decline in Dementia-Free Older Adults

INTRODUCTION

Baseline olfactory impairment, poor performance on cognitive test, and medial temporal lobe atrophy are considered biomarkers for predicting future cognitive decline in dementia-free older adults. However, the combined effect of these predictors has not been fully investigated.

METHODS

A group of 110 participants without dementia were continuously recruited into this study, and underwent olfactory, cognitive tests and MRI scanning at baseline and 5-year follow-up. Olfactory function was assessed using the University of Pennsylvania Smell Identification Test (UPSIT). Participants were divided into the cognitive decliners and non-decliners.

RESULTS

Among 87 participants who completed the 5-year follow-up, cognitive decline was present in 32 cases and 55 remained stable. Compared with non-decliners, cognitive decliners presented lower scores on both the UPSIT and the Montreal Cognitive Assessment (MoCA), and smaller hippocampal volume at baseline (all P < .001). The logistic regression analysis revealed that lower scores on UPSIT and MoCA, and smaller hippocampal volume were strongly associated with subsequent cognitive decline, respectively (all P < .001). For the prediction of cognitive decline, lower score on UPSIT performed the sensitivity of 63.6% and specificity of 81.2%, lower score on MoCA with the sensitivity of 74.5% and specificity of 65.6%, smaller hippocampal volume with the sensitivity of 70.9% and specificity of 78.1%, respectively. Combining three predictors resulted in the sensitivity of 83.6% and specificity of 93.7%.

CONCLUSIONS

The combination of olfactory test, cognitive test with structural MRI may enhance the predictive ability for future cognitive decline for dementia-free older adults.

Associations of Amyloid Burden, White Matter Hyperintensities, and Hippocampal Volume With Cognitive Trajectories in the 90+ Study

BACKGROUND AND OBJECTIVES

Amyloid pathology, vascular disease pathology, and pathologies affecting the medial temporal lobe are associated with cognitive trajectories in older adults. However, only limited evidence exists on how these pathologies influence cognition in the oldest old. We evaluated whether amyloid burden, white matter hyperintensity (WMH) volume, and hippocampal volume (HV) are associated with cognitive level and decline in the oldest old.

METHODS

This was a longitudinal, observational community-based cohort study. We included participants with 18F-florbetapir PET and MRI data from the 90+ Study. Amyloid load was measured using the standardized uptake value ratio in the precuneus/posterior cingulate with eroded white matter mask as reference. WMH volume was log-transformed. All imaging measures were standardized using sample means and SDs. HV and log-WMH volume were normalized by total intracranial volume using the residual approach. Global cognitive performance was measured by the Mini-Mental State Examination (MMSE) and modified MMSE (3MS) tests, repeated every 6 months. We used linear mixed-effects models with random intercepts; random slopes; and interaction between time, time squared, and imaging variables to estimate the associations of imaging variables with cognitive level and cognitive decline. Models were adjusted for demographics, APOE genotype, and health behaviors.

RESULTS

The sample included 192 participants. The mean age was 92.9 years, 125 (65.1%) were female, 71 (37.0%) achieved a degree beyond college, and the median follow-up time was 3.0 years. A higher amyloid load was associated with a lower cognitive level (βMMSE = -0.82, 95% CI -1.17 to -0.46; β3MS = -2.77, 95% CI -3.69 to -1.84). A 1-SD decrease in HV was associated with a 0.70-point decrease in the MMSE score (95% CI -1.14 to -0.27) and a 2.27-point decrease in the 3MS score (95% CI -3.40 to -1.14). Clear nonlinear cognitive trajectories were detected. A higher amyloid burden and smaller HV were associated with faster cognitive decline. WMH volume was not significantly associated with cognitive level or decline.

DISCUSSION

Amyloid burden and hippocampal atrophy are associated with both cognitive level and cognitive decline in the oldest old. Our findings shed light on how different pathologies contributed to driving cognitive function in the oldest old.

Resistance exercise effects on hippocampus subfield volumes and biomarkers of neuroplasticity and neuroinflammation in older adults with low and high risk of mild cognitive impairment: a randomized controlled trial

Physical exercise is suggested to promote hippocampal neuroplasticity by increasing circulating neurotrophic and anti-inflammatory factors. Our aim was to explore the interplay between the effect of progressive resistance exercise on blood biomarker levels, hippocampal neurometabolite levels and hippocampal volume in older adults with a low compared to a high risk of mild cognitive impairment (MCI). Seventy apparently healthy male/female older adults (aged 60-85 years old) were randomly allocated to a 12 week lower limb progressive resistance or no intervention, stratified for low (< 26/30) or high (≥ 26/30) Montreal Cognitive Assessment (MoCA) score, indicating MCI risk. Outcome measures were blood levels of insulin-like growth factor-1 (IGF-1), interleukin-6 (IL-6) or kynurenine (KYN); hippocampal total and subfield volumes of the cornu ammonis 1 (CA1) and 4 (CA4), subiculum, presubiculum, and dentate gyrus measured with magnetic resonance imaging (MRI); and hippocampus neurometabolites including total N-acetylaspartate (NAA), myo-inositol (mIns), and total creatine (Cr) measured with proton magnetic resonance spectroscopy (1H-MRS). We evaluated the intervention effect, cognitive status effect, their interaction and the bivariate relationship between exercise-induced changes between the outcome measures. Higher kynurenine levels (p = 0.015) and lower subiculum volumes (p = 0.043) were found in older adults with high MCI risk compared to older adults with low MCI risk. Exercise-induced CA1 volume changes were negatively correlated with hippocampal tNAA/mIns level changes (r = -0.605, p = 0.006). This study provides valuable insight in the multifactorial processes related to resistance training in older adults with low or high MCI risk.

The Effects of Computerized Cognitive Training in Older Adults' Cognitive Performance and Biomarkers of Structural Brain Aging

OBJECTIVES

Cognitive training (CT) has been investigated as a means of delaying age-related cognitive decline in older adults. However, its impact on biomarkers of age-related structural brain atrophy has rarely been investigated, leading to a gap in our understanding of the linkage between improvements in cognition and brain plasticity. This study aimed to explore the impact of CT on cognitive performance and brain structure in older adults.

METHODS

One hundred twenty-four cognitively normal older adults recruited from 2 study sites were randomly assigned to either an adaptive CT (n = 60) or a casual game training (active control, AC, n = 64).

RESULTS

After 10 weeks of training, CT participants showed greater improvements in the overall cognitive composite score (Cohen's d = 0.66, p < .01) with nonsignificant benefits after 6 months from the completion of training (Cohen's d = 0.36, p = .094). The CT group showed significant maintenance of the caudate volume as well as significant maintained fractional anisotropy in the left internal capsule and in left superior longitudinal fasciculus compared to the AC group. The AC group displayed an age-related decrease in these metrics of brain structure.

DISCUSSION

Results from this multisite clinical trial demonstrate that the CT intervention improves cognitive performance and helps maintain caudate volume and integrity of white matter regions that are associated with cognitive control, adding to our understanding of the changes in brain structure contributing to changes in cognitive performance from adaptive CT.

CLINICAL TRIAL REGISTRATION

NCT03197454.

Diagnostic Utility of Specific Frailty Questionnaire: The Kihon Checklist for Hippocampal Atrophy in COPD

Background/Objectives: COPD patients who are frail have been reported to develop brain atrophy, but no non-invasive diagnostic tool has been developed to detect this condition. Our study aimed to explore the diagnostic utility of the Kihon Checklist (KCL), a frailty questionnaire, in assessing hippocampal volume loss in patients with COPD. Methods: We recruited 40 COPD patients and 20 healthy individuals using the KCL to assess frailty across seven structural domains. Hippocampal volumes were obtained from T1-weighted MRI images, and ROC analysis was performed to detect hippocampal atrophy. Results: Our results showed that patients with COPD had significantly greater atrophic left hippocampal volumes than healthy subjects (p < 0.05). The univariate correlation coefficient between the left hippocampal volume and KCL (1-20), which pertains to instrumental and social activities of daily living, was the largest (ρ = -0.54, p < 0.0005) among the KCL subdomains. Additionally, both KCL (1-25) and KCL (1-20) demonstrated useful diagnostic potential (93% specificity and 90% sensitivity, respectively) for identifying individuals in the lowest 25% of the left hippocampal volume (AUC = 0.82). Conclusions: Our study suggests that frailty questionnaires focusing on daily vulnerability, such as the KCL, can effectively detect hippocampal atrophy in COPD patients.

Associations between renal function, hippocampal volume, and cognitive impairment in 544 outpatients

Background

Cognitive impairment and brain atrophy are common in chronic kidney disease patients. It remains unclear whether differences in renal function, even within normal levels, influence hippocampal volume (HCV) and cognition. We aimed to investigate the association between estimated glomerular filtration rate (eGFR), HCV and cognition in outpatients.

Methods

This single-center retrospective study enrolled 544 nonrenal outpatients from our hospital. All participants underwent renal function assessment and 3.0 T magnetic resonance imaging (MRI) in the same year. HCV was also measured, and cognitive assessments were obtained. The correlations between eGFR, HCV, and cognitive function were analyzed. Logistic regression analysis was performed to identify the risk factors for hippocampal atrophy and cognitive impairment. Receiver-operator curves (ROCs) were performed to find the cut-off value of HCV that predicts cognitive impairment.

Results

The mean age of all participants was 66.5 ± 10.9 years. The mean eGFR of all participants was 88.5 ± 15.1 mL/min/1.73 m2. eGFR was positively correlated with HCV and with Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) scores. Univariate and multivariate logistic regression analysis showed Age ≥ 65 years, eGFR < 75 mL/min/1.73 m2, Glucose ≥6.1 mmol/L and combined cerebral microvascular diseases were independent risk factors for hippocampal atrophy and Age ≥ 65 years, left hippocampal volume (LHCV) <2,654 mm3 were independent risk factors for cognitive impairment in outpatients. Although initial unadjusted logistic regression analysis indicated that a lower eGFR (eGFR < 75 mL/min/1.73 m2) was associated with poorer cognitive function, this association was lost after adjusting for confounding variables. ROC curve analysis demonstrated that LHCV <2,654 mm3 had the highest AUROC [(0.842, 95% CI: 0.808-0.871)], indicating that LHCV had a credible prognostic value with a high sensitivity and specificity for predicting cognitive impairment compared with age in outpatients.

Conclusion

Higher eGFR was associated with higher HCV and better cognitive function. eGFR < 75 mL/min/1.73 m2 was an independent risk factor for hippocampal atrophy after adjusting for age. It is suggested that even eGFR < 75 mL/min/1.73 m2, lower eGFR may still be associated with hippocampal atrophy, which is further associated with cognitive impairment. LHCV was a favorable prognostic marker for predicting cognitive impairment rather than age.

Association between ABO genotypes and risk of dementia and neuroimaging markers: roles of sex and APOE status

Background

Whether the relationships between ABO blood genotypes (AA, AO, BB, BO, AB, and OO) and dementia are modified by gender and APOE status has been unclear.

Methods

We used data from the UK Biobank, a population-based cohort study of 487,425 individuals. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CI) between ABO genotypes and risk of dementia. Multivariable linear regression models were used to estimate the relationship between ABO genotypes and MRI-based brain indices.

Results

Overall, 487,425 participants were included at baseline. After 34 million person-years follow up, 7,548 patients developed all-cause dementia. Before stratifying by sex and APOE status, compared to OO genotype, BB genotype was associated with increased risk of all-cause dementia (1.36, 1.03-1.80) and other types dementia (1.65, 1.20-2.28). After stratifying by sex, only in males, BB genotype was associated with higher risk of all-cause dementia (1.44, 1.02-2.09) and other types of dementia (1.95, 1.30-2.93). AB genotype in males was also associated with increased AD (1.34, 1.04-1.72). After further stratifying by APOE e4 status, BB genotype with two APOE e4 alleles showed even stronger association with all-cause dementia 4.29 (1.57, 11.72) and other types dementia (5.49, 1.70-17.69) in males. Also in males, AA genotype with one APOE e4 was associated with increased risks of all-cause dementia (1.27, 1.04-1.55), AD (1.45, 1.09-1.94) and other types dementia (1.40, 1.08-1.81). Linear regression models showed that in both sexes with APOE e4, AA genotype was associated with reduced total grey matter volume.

Conclusion

Sex and APOE e4 carrier status modified the association between ABO genotypes and risk of dementia. In males, BB genotype was consistently associated with increased risk of dementia, especially in those with two APOE e4 alleles. Also, in males with one APOE e4, AA genotype might be linked to higher risk of dementia.

Correlating hippocampal and amygdala volumes with neuropathological burden in neurodegenerative diseases using 7T postmortem MRI

Numerous research groups worldwide have focused on postmortem imaging to bridge the resolution gap between clinical neuroimaging and neuropathology data. We developed a standardized protocol for brain embedding, imaging, and processing, facilitating alignment between antemortem MRI, postmortem MRI, and pathology to observe brain atrophy and structural damage progression over time. Using 7T postmortem ex vivo MRI, we explore the potential correlation of amygdala and hippocampal atrophy with neuropathological burden in both Down syndrome (DS) and Alzheimer's disease (AD) cohorts. Using 7T postmortem ex vivo MRI scans from 66 cases (12 DS and 54 AD) alongside a subset of antemortem scans (n=17), we correlated manually segmented hippocampal and amygdala volumes, adjusted for age, sex, and ApoE4 status, with pathological indicators such as Thal phase, Braak stage, limbic-predominant age-related TDP-43 encephalopathy (LATE) stage, hippocampal sclerosis (HS), and Lewy body (LB) stage. A significant correlation was observed between postmortem and antemortem volumes for the hippocampus, but a similar trend observed for the amygdala did not reach statistical significance. DS individuals exhibited notably smaller hippocampal and amygdala volumes compared to AD subjects. In DS, lower hippocampal and amygdala volumes correlated with more severe Braak stage, without significant associations with Thal phase. LATE and HS pathologies were uncommon in DS cases but trended toward smaller hippocampal volumes. In AD, lower hippocampal volume associated with dementia duration, advanced Thal phase, Braak stage, LATE stage, and HS presence, whereas reduced amygdala volume correlated mainly with severe LATE stage and HS, but not with Thal or Braak stages. No significant LB correlation was detected in either DS or AD cohorts. Hippocampal volume in AD appears influenced by both AD and LATE pathologies, while amygdala volume seems primarily influenced by LATE. In DS, smaller hippocampal volume, relative to AD, appears primarily influenced by tau pathology.

Long-Term Neurologic Consequences following Fetal Growth Restriction: The Impact on Brain Reserve

BACKGROUND

Fetal growth restriction (FGR) corresponds to the fetus's inability to achieve an adequate weight gain based on genetic potential and gestational age. It is an important cause of morbidity and mortality.

SUMMARY

In this review, we address the challenges of diagnosis and classification of FGR. We review how chronic fetal hypoxia impacts brain development. We describe recent advances on placental and fetal brain imaging using magnetic resonance imaging and how they offer new noninvasive means to study growth restriction in humans. We go on to review the impact of FGR on brain integrity in the neonatal period, later childhood, and adulthood and review available therapies.

KEY MESSAGES

FGR consequences are not limited to the perinatal period. We hypothesize that impaired brain reserve, as defined by structure and size, may predict some concerning epidemiological data of impaired cognitive outcomes and dementia with aging in this group of patients.

Compositional structural brain signatures capture Alzheimer's genetic risk on brain structure along the disease continuum

INTRODUCTION

Traditional brain imaging genetics studies have primarily focused on how genetic factors influence the volume of specific brain regions, often neglecting the overall complexity of brain architecture and its genetic underpinnings.

METHODS

This study analyzed data from participants across the Alzheimer's disease (AD) continuum from the ALFA and ADNI studies. We exploited compositional data analysis to examine relative brain volumetric variations that (i) differentiate cognitively unimpaired (CU) individuals, defined as amyloid-negative (A-) based on CSF profiling, from those at different AD stages, and (ii) associated with increased genetic susceptibility to AD, assessed using polygenic risk scores.

RESULTS

Distinct brain signatures differentiated CU A-individuals from amyloid-positive MCI and AD. Moreover, disease stage-specific signatures were associated with higher genetic risk of AD.

DISCUSSION

The findings underscore the complex interplay between genetics and disease stages in shaping brain structure, which could inform targeted preventive strategies and interventions in preclinical AD.

Associations of brain morphology with cortical proteins of cognitive resilience

In a recent proteome-wide study, we identified several candidate proteins for drug discovery whose cortical abundance was associated with cognitive resilience to late-life brain pathologies. This study examines the extent to which these proteins are associated with the brain structures of cognitive resilience in decedents from the Religious Orders Study and Memory and Aging Project. Six proteins were associated with brain morphometric characteristics related to higher resilience (i.e., larger anterior and medial temporal lobe volumes), and five were associated with morphometric characteristics related to lower resilience (i.e., enlarged ventricles). Two synaptic proteins, RPH3A and CPLX1, remained inversely associated with the lower resilience signature, after further controlling for 10 neuropathologic indices. These findings suggest preserved brain structure in periventricular regions as a potential mechanism by which RPH3A and CPLX1 are associated with cognitive resilience. Further work is needed to elucidate other mechanisms by which targeting these proteins can circumvent the effects of pathology on individuals at risk for cognitive decline.

Septohippocampal cholinergic system at the intersection of stress and cognition: Current trends and translational implications

Deficits in hippocampus-dependent memory processes are common across psychiatric and neurodegenerative disorders such as depression, anxiety and Alzheimer's disease. Moreover, stress is a major environmental risk factor for these pathologies and it exerts detrimental effects on hippocampal functioning via the activation of hypothalamic-pituitary-adrenal (HPA) axis. The medial septum cholinergic neurons extensively innervate the hippocampus. Although, the cholinergic septohippocampal pathway (SHP) has long been implicated in learning and memory, its involvement in mediating the adaptive and maladaptive impact of stress on mnemonic processes remains less clear. Here, we discuss current research highlighting the contributions of cholinergic SHP in modulating memory encoding, consolidation and retrieval. Then, we present evidence supporting the view that neurobiological interactions between HPA axis stress response and cholinergic signalling impact hippocampal computations. Finally, we critically discuss potential challenges and opportunities to target cholinergic SHP as a therapeutic strategy to improve cognitive impairments in stress-related disorders. We argue that such efforts should consider recent conceptualisations on the dynamic nature of cholinergic signalling in modulating distinct subcomponents of memory and its interactions with cellular substrates that regulate the adaptive stress response.

Association between hippocampal microglia, AD and LATE-NC, and cognitive decline in older adults

INTRODUCTION

This study investigates the relationship between microglia inflammation in the hippocampus, brain pathologies, and cognitive decline.

METHODS

Participants underwent annual clinical evaluations and agreed to brain donation. Neuropathologic evaluations quantified microglial burden in the hippocampus, amyloid beta (Aβ), tau tangles, and limbic age-related transactive response DNA-binding protein 43 (TDP-43) encephalopathy neuropathologic changes (LATE-NC), and other common brain pathologies. Mixed-effect and linear regression models examined the association of microglia with a decline in global and domain-specific cognitive measures, and separately with brain pathologies. Path analyses estimated direct and indirect effects of microglia on global cognition.

RESULT

Hippocampal microglia were associated with a faster decline in global cognition, specifically in episodic memory, semantic memory, and perceptual speed. Tau tangles and LATE-NC were independently associated with microglia. Other pathologies, including Aβ, were not related. Regional hippocampal burden of tau tangles and TDP-43 accounted for half of the association of microglia with cognitive decline.

DISCUSSION

Microglia inflammation in the hippocampus contributes to cognitive decline. Tau tangles and LATE-NC partially mediate this association.

Effect of chemotherapy on hippocampal volume and shape in older long-term breast cancer survivors

Purpose

The objective of this study was to assess changes in hippocampal volume and shape in older long-term breast cancer survivors who were exposed to chemotherapy 5-15 years prior.

Methods

This study recruited female long-term breast cancer survivors aged 65 years or older with a history of chemotherapy (C+), age-matched breast cancer survivors who did not receive chemotherapy (C-), and healthy controls (HC). The participants were recruited 5-15 years after chemotherapy at time point 1 (TP1) and were followed up for 2 years at time point 2 (TP2). Assessments included hippocampal volume and shape from brain MRI scans and neuropsychological (NP) tests.

Results

At TP1, each of the three groups was comprised of 20 participants. The C+ group exhibited a hippocampal volume loss estimated in proportion with total intracranial volume (ICV) in both the left and right hemispheres from TP1 to TP2. Regarding the hippocampal shape at TP1, the C+ group displayed inward changes compared to the control groups. Within the C+ group, changes in right hippocampal volume adjusted with ICV were positively correlated with crystalized composite scores (R = 0.450, p = 0.044). Additionally, in C+ groups, chronological age was negatively correlated with right hippocampal volume adjusted with ICV (R = -0.585, p = 0.007).

Conclusion

The observed hippocampal volume reduction and inward shape deformation within the C+ group may serve as neural basis for cognitive changes in older long-term breast cancer survivors with history of chemotherapy treatment.

Vulnerability of the Hippocampus to Insults: Links to Blood-Brain Barrier Dysfunction

The hippocampus is a critical brain substrate for learning and memory; events that harm the hippocampus can seriously impair mental and behavioral functioning. Hippocampal pathophysiologies have been identified as potential causes and effects of a remarkably diverse array of medical diseases, psychological disorders, and environmental sources of damage. It may be that the hippocampus is more vulnerable than other brain areas to insults that are related to these conditions. One purpose of this review is to assess the vulnerability of the hippocampus to the most prevalent types of insults in multiple biomedical domains (i.e., neuroactive pathogens, neurotoxins, neurological conditions, trauma, aging, neurodegenerative disease, acquired brain injury, mental health conditions, endocrine disorders, developmental disabilities, nutrition) and to evaluate whether these insults affect the hippocampus first and more prominently compared to other brain loci. A second purpose is to consider the role of hippocampal blood-brain barrier (BBB) breakdown in either causing or worsening the harmful effects of each insult. Recent research suggests that the hippocampal BBB is more fragile compared to other brain areas and may also be more prone to the disruption of the transport mechanisms that act to maintain the internal milieu. Moreover, a compromised BBB could be a factor that is common to many different types of insults. Our analysis indicates that the hippocampus is more vulnerable to insults compared to other parts of the brain, and that developing interventions that protect the hippocampal BBB may help to prevent or ameliorate the harmful effects of many insults on memory and cognition.

Atherosclerosis and Hippocampal Volumes in Older Adults: The Role of Age and Blood Pressure

BACKGROUND

Lower hippocampal volume is associated with late-life cognitive decline and is an important, but nonspecific marker for clinical Alzheimer's dementia. Cerebrovascular disease may also be associated with hippocampal volume. Here we study the role of intracranial large vessel disease (atherosclerosis) in association with hippocampal volume and the potential role of age, average late-life blood pressure across all visits, and other factors (sex, apolipoprotein ε4 [APOE ε4], and diabetes).

METHODS AND RESULTS

Data came from 765 community-based older people (91 years old on average at death; 72% women), from 2 ongoing clinical-pathologic cohort studies. Participants completed baseline assessment, annual standardized blood pressure measurements, vascular risk assessment for diabetes, and blood draws to determine APOE genotype, and at death, brains were removed and underwent ex vivo magnetic resonance imaging and neuropathologic evaluation for atherosclerosis pathology and other cerebrovascular and neurodegenerative pathologies. Linear regression models examined the association of atherosclerosis and hippocampal to hemisphere volume ratio and whether age at death, blood pressure, and other factors modified associations. In linear regression models adjusted for demographics and neurodegenerative and other cerebrovascular pathologies, atherosclerosis severity was associated with a lower hippocampal to hemisphere volume ratio. In separate models, we found the effect of atherosclerosis on the ratio of hippocampal to hemisphere volume was attenuated among advanced age at death or having higher systolic blood pressure (interaction terms P≤0.03). We did not find confounding or interactions with sex, diabetes, or APOE ε4.

CONCLUSIONS

Atherosclerosis severity is associated with lower hippocampal volume, independent of neurodegenerative and other cerebrovascular pathologies. Higher systolic blood pressures and advanced age attenuate associations.

Gray matter structural covariance networks patterns associated with autopsy-confirmed LATE-NC compared to Alzheimer's disease pathology

BACKGROUND

Cases with the limbic-predominant age-related TAR DNA-binding protein 43 (TDP-43) encephalopathy neuropathologic change (LATE-NC), Alzheimer's disease (AD), and mixed AD+TDP-43 pathology (AD+LATE-NC) share similar symptoms, which makes it a challenge for accurate diagnosis. Exploring the patterns of gray matter structural covariance networks (SCNs) in these three types may help to clarify the underlying mechanism and provide a basis for clinical interventions.

METHODS

We included ante-mortem MRI data of 10 LATE-NC, 39  AD, and 25  AD+LATE-NC from the ADNI autopsy sample. We used four regions of interest (left posterior cingulate cortex, right entorhinal cortex, frontoinsular and dorsolateral prefrontal cortex) to anchor the default mode network (DMN), salience network (SN), and executive control network (ECN). Finally, we assessed the SCN alternations using a multi-regression model-based linear-interaction analysis.

RESULTS

Cases with autopsy-confirmed LATE-NC and AD showed increased structural associations involving DMN, ECN, and SN. Cases with AD+LATE-NC showed increased structural association within DMN while decreased structural association between DMN and ECN. The volume of peak clusters showed significant associations with cognition and AD pathology.

CONCLUSIONS

This study showed different SCN patterns in the cases with LATE-NC, AD, and AD+LATE-NC, and indicated the network disconnection mechanism underlying these three neuropathological progressions. Further, SCN may serve as an effective biomarker to distinguish between different types of dementia.

14-3-3 [Formula: see text]-reported early synaptic injury in Alzheimer's disease is independently mediated by sTREM2

INTRODUCTION

Synaptic loss is closely associated with tau aggregation and microglia activation in later stages of Alzheimer's disease (AD). However, synaptic damage happens early in AD at the very early stages of tau accumulation. It remains unclear whether microglia activation independently causes synaptic cleavage before tau aggregation appears.

METHODS

We investigated 104 participants across the AD continuum by measuring 14-3-3 zeta/delta ([Formula: see text]) as a cerebrospinal fluid biomarker for synaptic degradation, and fluid and imaging biomarkers of tau, amyloidosis, astrogliosis, neurodegeneration, and inflammation. We performed correlation analyses in cognitively unimpaired and impaired participants and used structural equation models to estimate the impact of microglia activation on synaptic injury in different disease stages.

RESULTS

14-3-3 [Formula: see text] was increased in participants with amyloid pathology at the early stages of tau aggregation before hippocampal volume loss was detectable. 14-3-3 [Formula: see text] correlated with amyloidosis and tau load in all participants but only with biomarkers of neurodegeneration and memory deficits in cognitively unimpaired participants. This early synaptic damage was independently mediated by sTREM2. At later disease stages, tau and astrogliosis additionally mediated synaptic loss.

CONCLUSIONS

Our results advertise that sTREM2 is mediating synaptic injury at the early stages of tau accumulation, underlining the importance of microglia activation for AD disease propagation.

Retinal ganglion cell-inner plexiform layer, white matter hyperintensities, and their interaction with cognition in older adults

Purpose

We explored the interaction of optical coherence tomography (OCT) parameters and white matter hyperintensities with cognitive measures in our older adult cohort.

Methods

This observational study enrolled participants who underwent a comprehensive neuropsychological battery, structural 3-T brain magnetic resonance imaging (MRI), visual acuity examination, and OCT imaging. Cerebral small vessel disease (CSVD) markers were read on MR images; lacune, cerebral microbleeds (CMB), white matter hyperintensities (WMH), and enlarged perivascular spaces (EPVS), were defined according to the STRIVE standards. Retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) thicknesses (μm) were measured on the OCT tool.

Results

Older adults with cognitive impairment (CI) showed lower RNFL (p = 0.001), GCIPL (p = 0.009) thicknesses, and lower hippocampal volume (p = 0.004) when compared to non-cognitively impaired (NCI). RNFL (p = 0.006) and GCIPL thicknesses (p = 0.032) correlated with MoCA scores. GCIPL thickness (p = 0.037), total WMH (p = 0.003), PWMH (p = 0.041), and DWMH (p = 0.001) correlated with hippocampal volume in our older adults after adjusting for covariates. With hippocampal volume as the outcome, a significant interaction (p < 0.05) between GCIPL and PWMH and total WMH was observed in our older adults.

Conclusion

Both GCIPL thinning and higher WMH burden (especially PWMH) are associated with hippocampal volume and older adults with both pathologies are more susceptible to subclinical cognitive decline.

Genetically instrumented LDL-cholesterol lowering and multiple disease outcomes: A Mendelian randomization phenome-wide association study in the UK Biobank

AIMS

Lipid-lowering medications are widely used to control blood cholesterol levels and manage a range of cardiovascular and lipid disorders. We aimed to explore the possible associations between LDL lowering and multiple disease outcomes or biomarkers.

METHODS

We performed a Mendelian randomization phenome-wide association study (MR-PheWAS) in 337 475 UK Biobank participants to test for associations between four proposed LDL-C-lowering genetic risk scores (PCSK9, HMGCR, NPC1L1 and LDLR) and 1135 disease outcomes, with follow-up MR analyses in 52 serum, urine, imaging and clinical biomarkers. We used inverse-variance weighted MR in the main analyses and complementary MR methods (weighted median, weighted mode, MR-Egger and MR-PRESSO) as sensitivity analyses. We accounted for multiple testing with false discovery rate correction (P < 2.0 × 10-4 for phecodes, P < 1.3 × 10-2 for biomarkers).

RESULTS

We found evidence for an association between genetically instrumented LDL lowering and 10 distinct disease outcomes, suggesting potential causality. All genetic instruments were associated with hyperlipidaemias and cardiovascular diseases in the expected directions. Biomarker analyses supported an effect of LDL-C lowering through PCSK9 on lung function (FEV [beta per 1 mg/dL lower LDL-C -1.49, 95% CI -2.21, -0.78]; FVC [-1.42, 95% CI -2.29, -0.54]) and through HMGCR on hippocampal volume (beta per 1 mg/dL lower LDL-C 6.09, 95% CI 1.74, 10.44).

CONCLUSIONS

We found genetic evidence to support both positive and negative effects of LDL-C lowering through all four LDL-C-lowering pathways. Future studies should further explore the effects of LDL-C lowering on lung function and changes in brain volume.

N-Acetylcysteine Amide against Aβ-Induced Alzheimer's-like Pathology in Rats

Oxidative stress with a depletion of glutathione is a key factor in the initiation and progression of Alzheimer's disease (AD). N-Acetylcysteine (NAC), a glutathione precursor, provides neuroprotective effects in AD animal models. Its amide form, N-Acetylcysteine amide (NACA), has an extended bioavailability compared to NAC. This study evaluates the neuroprotective effects of NACA against Aβ1-42 peptide-induced AD-like pathology in rats. Male Wistar rats (2.5 months old) were divided into five groups: Normal Control (NC), Sham (SH), Aβ, Aβ + NACA and NACA + Aβ + NACA (n = 8 in all groups). AD-like pathology was induced by the intracerebroventricular infusion of Aβ1-42 peptide into the lateral ventricle. NACA (75 mg/kg) was administered either as a restorative (i.e., injection of NACA for 7 consecutive days after inducing AD-like pathology (Aβ + N group)), or as prophylactic (for 7 days before and 7 days after inducing the pathology (N + Aβ + N group)). Learning and memory, neurogenesis, expression of AD pathology markers, antioxidant parameters, neuroprotection, astrogliosis and microgliosis were studied in the hippocampus and the prefrontal cortex. All data were analyzed with a one-way ANOVA test followed by Bonferroni's multiple comparison test. NACA treatment reversed the cognitive deficits and reduced oxidative stress in the hippocampus and prefrontal cortex. Western blot analysis for Tau, Synaptophysin and Aβ, as well as a histopathological evaluation through immunostaining for neurogenesis, the expression of neurofibrillary tangles, β-amyloid peptide, synaptophysin, neuronal morphology and gliosis, showed a neuroprotective effect of NACA. In conclusion, this study demonstrates the neuroprotective effects of NACA against β-amyloid induced AD-like pathology.

Contribution of Alzheimer's disease pathology to biological and clinical progression: A longitudinal study across two cohorts

INTRODUCTION

Amyloid beta (Aβ) deposition, tau accumulation, and brain atrophy occurr in sequence, but the contribution of Alzheimer's disease (AD) pathology to biological and clinical progression remains unclear.

METHODS

We included 290 and 70 participants with longitudinal assessment on Aβ-positron emission tomography (PET), tau-PET, magnetic resonance imaging, and cognitive function from the Harvard Aging Brain Study (HABS) and Alzheimer's Disease Neuroimaging Initiative (ADNI) datasets, respectively. Partial least squares structural equation modeling (PLS-SEM) was used to determine the contribution of AD pathology to the biological and clinical longitudinal changes.

RESULTS

Imaging biomarkers and cognitive function were significantly associated in cross-sectional and longitudinal analyses. At the final time point, the percentage of variance explained by PLS-SEM was 27% for Aβ, 30% for tau (Aβ accounted for 61%), 29% for brain atrophy (tau accounted for 37%), and 37% for cognitive decline (brain atrophy accounted for 35%).

DISCUSSION

This study highlights distinctive contributing proportions of AD pathology to biological and clinical progression. Treatments targeting Aβ and tau may partially block AD progression.

The psychological basis of hunger and its dysfunctions

This article describes a new and emerging psychological perspective on hunger, together with the implications of that perspective, which is based upon learning and memory. Hunger is a psychological state characterized by a desire to eat. Historically, conceptions of hunger have largely been expressed in terms of physiology (eg, biological process X causes hunger). However, physiology neither offers a psychological account of hunger nor explains why memory impairment can eliminate hunger. Two forms of hunger are identified - specific and general. Specific hunger is for particular palatable foods. It involves recollecting episodic memories of eating that food, when an associated cue is encountered (eg, an advert). General hunger is a desire to eat triggered by temporal (eg, it is lunchtime) or interoceptive (eg, tummy rumble) cues. It involves semantic memory retrieval, which then augments the expected - remembered - pleasure for any food. Both hungers are supported by the medial temporal lobe memory system. Damage to this system can occur from eating a Western-style diet and, longer-term, from obesity and its consequences. Medial temporal lobe memory damage may cause deficits in specific hunger, but most especially in general hunger, resulting in little motivation to eat foods that the individual considers to be of low-to-moderate palatability, such as fruit and vegetables. The implications of this account for teaching people hunger, for how hunger is affected by diet, for public education, and pharmaceutical intervention, are discussed. Psychological concepts of hunger are widely used in nutritional practice. This article provides a new and emerging perspective on the psychological basis of hunger and its implications.

Astrocytic aerobic glycolysis provides lactate to support neuronal oxidative metabolism in the hippocampus

Under physiological conditions, the energetic demand of the brain is met by glucose oxidation. However, ample evidence suggests that lactate produced by astrocytes through aerobic glycolysis may also be an oxidative fuel, highlighting the metabolic compartmentalization between neural cells. Herein, we investigate the roles of glucose and lactate in oxidative metabolism in hippocampal slices, a model that preserves neuron-glia interactions. To this purpose, we used high-resolution respirometry to measure oxygen consumption (O2 flux) at the whole tissue level and amperometric lactate microbiosensors to evaluate the concentration dynamics of extracellular lactate. We found that lactate is produced from glucose and transported to the extracellular space by neural cells in hippocampal tissue. Under resting conditions, endogenous lactate was used by neurons to support oxidative metabolism, which was boosted by exogenously added lactate even in the presence of excess glucose. Depolarization of hippocampal tissue with high K+ significantly increased the rate of oxidative phosphorylation, which was accompanied by a transient decrease in extracellular lactate concentration. Both effects were reverted by inhibition of the neuronal lactate transporter, monocarboxylate transporters 2 (MCT2), supporting the concept of an inward flux of lactate to neurons to fuel oxidative metabolism. We conclude that astrocytes are the main source of extracellular lactate which is used by neurons to fuel oxidative metabolism, both under resting and stimulated conditions.

PRO: Do We Still Need Whole-Brain Irradiation for Brain Metastases?

(1) Background: In recent decades, the use of whole-brain radiation therapy (WBRT) in the treatment of brain metastases has significantly decreased, with clinicians fearing adverse neurocognitive events and data showing limited efficacy regarding local tumor control and overall survival. The present study thus aimed to reassess the role that WBRT holds in the treatment of brain metastases. (2) Methods: This review summarizes the available evidence from 1990 until today supporting the use of WBRT, as well as new developments in WBRT and their clinical implications. (3) Results: While one to four brain metastases should be exclusively treated with radiosurgery, WBRT does remain an option for patients with multiple metastases. In particular, hippocampus-avoidance WBRT, WBRT with dose escalation to the metastases, and their combination have shown promising results and offer valid alternatives to local stereotactic radiotherapy. Ongoing and published prospective trials on the efficacy and toxicity of these new methods are presented. (4) Conclusions: Unlike conventional WBRT, which has limited indications, modern WBRT techniques continue to have a significant role to play in the treatment of multiple brain metastases. In which situations radiosurgery or WBRT should be the first option should be investigated in further studies. Until then, the therapeutic decision must be made individually depending on the oncological context.

The use of hippocampal grading as a biomarker for preclinical and prodromal Alzheimer's disease

Hippocampal changes are associated with increased age and cognitive decline due to mild cognitive impairment (MCI) and Alzheimer's disease (AD). These associations are often observed only in the later stages of decline. This study examined if hippocampal grading, a method measuring local morphological similarity of the hippocampus to cognitively normal controls (NCs) and AD participants, is associated with cognition in NCs, subjective cognitive decline (SCD), early (eMCI), late (lMCI), and AD. A total of 1620 Alzheimer's Disease Neuroimaging Initiative participants were examined (495 NC, 262 eMCI, 545 lMCI, and 318 AD) because they had baseline MRIs and Alzheimer's disease Assessment Scale (ADAS-13) and Clinical Dementia Rating-Sum of Boxes (CDR-SB) scores. In a sub-analysis, NCs with episodic memory scores (as measured by Rey Auditory Verbal Learning Test, RAVLT) were divided into those with subjective cognitive decline (SCD+; 103) and those without (SCD-; 390). Linear regressions evaluated the influence of hippocampal grading on cognition in preclinical and prodromal AD. Lower global cognition, as measured by increased ADAS-13, was associated with hippocampal grading: NC (p < .001), eMCI (p < .05), lMCI (p < .05), and AD (p = .01). Lower global cognition as measured increased CDR-SB was associated with hippocampal grading in lMCI (p < .05) and AD (p < .001). Lower RAVLT performance was associated with hippocampal grading in SCD- (p < .05) and SCD+ (p < .05). These findings suggest that hippocampal grading is associated with global cognition in NC, eMCI, lMCI, and AD. Early changes in episodic memory during pre-clinical AD are associated with changes in hippocampal grading. Hippocampal grading may be sensitive to progressive changes early in the disease course.

Expectations and clinical meaningfulness of randomized controlled trials

Alzheimer's disease (AD) clinical trials are designed and powered to detect the impact of a therapeutic intervention, and there has been considerable discussion on what constitutes a clinically meaningful change in those receiving treatment versus placebo. The pathology of AD is complex, beginning many years before clinical symptoms are detectable, with multiple potential opportunities for therapeutic engagement. Introducing treatment strategies early in the disease and assessing meaningful change over the course of an 18-month clinical trial are critical to understanding the value to an effective intervention. With new clinical trial data expected soon on emerging therapeutics from several AD studies, the Alzheimer's Association convened a work group of experts to discuss key considerations for interpreting data from cognitive and functional measures and what is considered a clinically meaningful benefit or meaningful slowing of this fatal disease. Our expectations of outcomes from therapeutic interventions in AD may need to be modified.

Association of Traumatic Brain Injury with Late Life Neuropathological Outcomes in a Community-Based Cohort

BACKGROUND

Prior studies into the association of head trauma with neuropathology have been limited by incomplete lifetime neurotrauma exposure characterization.

OBJECTIVE

To investigate the neuropathological sequelae of traumatic brain injury (TBI) in an autopsy sample using three sources of TBI ascertainment, weighting findings to reflect associations in the larger, community-based cohort.

METHODS

Self-reported head trauma with loss of consciousness (LOC) exposure was collected in biennial clinic visits from 780 older adults from the Adult Changes in Thought study who later died and donated their brain for research. Self-report data were supplemented with medical record abstraction, and, for 244 people, structured interviews on lifetime head trauma. Neuropathology outcomes included Braak stage, CERAD neuritic plaque density, Lewy body distribution, vascular pathology, hippocampal sclerosis, and cerebral/cortical atrophy. Exposures were TBI with or without LOC. Modified Poisson regressions adjusting for age, sex, education, and APOE ɛ4 genotype were weighted back to the full cohort of 5,546 participants.

RESULTS

TBI with LOC was associated with the presence of cerebral cortical atrophy (Relative Risk 1.22, 95% CI 1.02, 1.42). None of the other outcomes was associated with TBI with or without LOC.

CONCLUSION

TBI with LOC was associated with increased risk of cerebral cortical atrophy. Despite our enhanced TBI ascertainment, we found no association with the Alzheimer's disease-related neuropathologic outcomes among people who survived to at least age 65 without dementia. This suggests the pathophysiological processes underlying post-traumatic neurodegeneration are distinct from the hallmark pathologies of Alzheimer's disease.

Stage-dependent differential influence of metabolic and structural networks on memory across Alzheimer's disease continuum

Background

Large-scale neuronal network breakdown underlies memory impairment in Alzheimer's disease (AD). However, the differential trajectories of the relationships between network organisation and memory across pathology and cognitive stages in AD remain elusive. We determined whether and how the influences of individual-level structural and metabolic covariance network integrity on memory varied with amyloid pathology across clinical stages without assuming a constant relationship.

Methods

Seven hundred and eight participants from the Alzheimer's Disease Neuroimaging Initiative were studied. Individual-level structural and metabolic covariance scores in higher-level cognitive and hippocampal networks were derived from magnetic resonance imaging and [18F] fluorodeoxyglucose positron emission tomography using seed-based partial least square analyses. The non-linear associations between network scores and memory across cognitive stages in each pathology group were examined using sparse varying coefficient modelling.

Results

We showed that the associations of memory with structural and metabolic networks in the hippocampal and default mode regions exhibited pathology-dependent differential trajectories across cognitive stages using sparse varying coefficient modelling. In amyloid pathology group, there was an early influence of hippocampal structural network deterioration on memory impairment in the preclinical stage, and a biphasic influence of the angular gyrus-seeded default mode metabolic network on memory in both preclinical and dementia stages. In non-amyloid pathology groups, in contrast, the trajectory of the hippocampus-memory association was opposite and weaker overall, while no metabolism covariance networks were related to memory. Key findings were replicated in a larger cohort of 1280 participants.

Conclusions

Our findings highlight potential windows of early intervention targeting network breakdown at the preclinical AD stage.

Funding

Data collection and sharing for this project was funded by the Alzheimer's Disease Neuroimaging Initiative (ADNI) (National Institutes of Health Grant U01 AG024904) and DOD ADNI (Department of Defense award number W81XWH-12-2-0012). We also acknowledge the funding support from the Duke NUS/Khoo Bridge Funding Award (KBrFA/2019-0020) and NMRC Open Fund Large Collaborative Grant (OFLCG09May0035).

Cognitive Sequelae and Hippocampal Dysfunction in Chronic Kidney Disease following 5/6 Nephrectomy

Neurological disorders are prevalent in patients with chronic kidney disease (CKD). Vascular factors and uremic toxins are involved with cognitive impairment in CKD. In addition, vascular dementia-induced alterations in the structure and function of the hippocampus can lead to deficits in hippocampal synaptic plasticity and cognitive function. However, regardless of this clinical evidence, the pathophysiology of cognitive impairment in patients with CKD is not fully understood. We used male Sprague Dawley rats and performed 5/6 nephrectomy to observe the changes in behavior, field excitatory postsynaptic potential, and immunostaining of the hippocampus following CKD progression. We measured the hippocampus volume on magnetic resonance imaging scans in the controls (n = 34) and end-stage renal disease (ESRD) hemodialysis patients (n = 42). In four cognition-related behavior assays, including novel object recognition, Y-maze, Barnes maze, and classical contextual fear conditioning, we identified deficits in spatial working memory, learning and memory, and contextual memory, as well as the ability to distinguish familiar and new objects, in the rats with CKD. Immunohistochemical staining of Na⁺/H⁺ exchanger1 was increased in the hippocampus of the CKD rat models. We performed double immunofluorescent staining for aquaporin-4 and glial fibrillary acidic protein and then verified the high coexpression in the hippocampus of the CKD rat model. Furthermore, results from recoding of the field excitatory postsynaptic potential (fEPSP) in the hippocampus showed the reduced amplitude and slope of fEPSP in the CKD rats. ESRD patients with cognitive impairment showed a significant decrease in the hippocampus volume compared with ESRD patients without cognitive impairment or the controls. Our findings suggest that uremia resulting from decreased kidney function may cause the destruction of the blood–brain barrier and hippocampus-related cognitive impairment in CKD.

Contribution of Alzheimer's biomarkers and risk factors to cognitive impairment and decline across the Alzheimer's disease continuum

INTRODUCTION

Amyloid beta (Aβ), tau, and neurodegeneration jointly with the Alzheimer's disease (AD) risk factors affect the severity of clinical symptoms and disease progression.

METHODS

Within 248 Aβ-positive elderly with and without cognitive impairment and dementia, partial least squares structural equation pathway modeling was used to assess the direct and indirect effects of imaging biomarkers (global Aβ-positron emission tomography [PET] uptake, regional tau-PET uptake, and regional magnetic resonance imaging-based atrophy) and risk-factors (age, sex, education, apolipoprotein E [APOE], and white-matter lesions) on cross-sectional cognitive impairment and longitudinal cognitive decline.

RESULTS

Sixteen percent of variance in cross-sectional cognitive impairment was accounted for by Aβ, 46% to 47% by tau, and 25% to 29% by atrophy, although 53% to 58% of total variance in cognitive impairment was explained by incorporating mediated and direct effects of AD risk factors. The Aβ-tau-atrophy pathway accounted for 50% to 56% of variance in longitudinal cognitive decline while Aβ, tau, and atrophy independently explained 16%, 46% to 47%, and 25% to 29% of the variance, respectively.

DISCUSSION

These findings emphasize that treatments that remove Aβ and completely stop downstream effects on tau and neurodegeneration would only be partially effective in slowing of cognitive decline or reversing cognitive impairment.

Brain Imaging Features Associated with 20-Year Cognitive Decline in a Community-Based Multiethnic Cohort without Dementia

INTRODUCTION

This study aimed to characterize the association of cognitive decline starting in midlife with brain pathology in late life in the absence of dementia.

METHODS

Nondemented Atherosclerosis Risk in Communities participants with brain imaging, all cognitive factor scores (CFSs), and nonmissing covariates were included. CFSs were collected at three visits across 21 years (1990-2013) (short-term cognitive change [1990-1996], long-term cognitive change [1990-2013]), and brain magnetic resonance imaging and florbetapir positron emission tomography (PET) imaging were collected in 2011-13 (PET subset n = 327). Outcomes of interest were total and regional brain volumes (cm3), log2 (white matter hyperintensity volume), white matter integrity (fractional anisotropy, mean diffusivity), ≥1 lacunar infarct (3-20 mm), and elevated brain β-amyloid (SUVR >1.2). Multivariable linear/logistic regression related outcomes to CFS slopes after adjusting for demographics and total intracranial volume.

RESULTS

At baseline, the 1,734 participants had a mean (SD) age of 55 (5.2) years, and were 60% female and 26% Black. After adjustment, a 1-SD larger long-term decline in CFS was associated with a smaller relative total brain volume by 1.2% (95% CI: 1.0, 1.5), a smaller relative temporal lobe meta region volume by 1.9% (1.5, 2.3), a 13% (9, 17) larger volume of white matter hyperintensities, a 1.3-fold (1.2, 1.4) higher odds of having ≥1 lacune, and 1.7-fold (1.3, 2.2) higher odds of elevated brain β-amyloid deposition and worse white matter integrity. Some long-term associations were also found for midlife short-term declines in CFS.

CONCLUSIONS

This study provides evidence that starting in midlife, short-term and long-term declines in cognition are associated with multiple deleterious late-life differences in nondemented brains.

Sulfiredoxin-1 blood mRNA expression levels negatively correlate with hippocampal atrophy and cognitive decline

Introduction: Cognitive decline, correlating with hippocampal atrophy, characterizes several neurodegenerative disorders having a background of low-level chronic inflammation and oxidative stress.

Methods: In this cross-sectional study, we examined how cognitive decline and hippocampal subfields volume are associated with the expression of redox and inflammatory genes in peripheral blood. We analyzed 34 individuals with different cognitive scores according to Mini-Mental State Examination, corrected by age and education (adjMMSE). We identified a group presenting cognitive decline (CD) with adjMMSE<27 (n=14) and a normal cognition (NC) group with adjMMSE≥27 (n=20). A multiparametric approach, comprising structural magnetic resonance imaging measurement of different hippocampal segments and blood mRNA expression of redox and inflammatory genes was applied.

Results: Our findings indicate that hippocampal segment volumes correlate positively with adjMMSE and negatively with the blood transcript levels of 19 genes, mostly redox genes correlating especially with the left subiculum and presubiculum. A strong negative correlation between hippocampal subfields atrophy and Sulfiredoxin-1 ( SRXN1) redox gene was emphasized.

Conclusions: Concluding, these results suggest that SRXN1 might be a valuable candidate blood biomarker for non-invasively monitoring the evolution of hippocampal atrophy in CD patients.

Dementia is associated with medial temporal atrophy even after accounting for neuropathologies

Brain atrophy is associated with degenerative neuropathologies and the clinical status of dementia. Whether dementia is associated with atrophy independent of neuropathologies is not known. In this study, we examined the pattern of atrophy associated with dementia while accounting for the most common dementia-related neuropathologies. We used data from National Alzheimer's Coordinating Center (n = 129) and Alzheimer's Disease Neuroimaging Initiative (n = 47) participants with suitable in vivo 3D-T1w MRI and autopsy data. We determined dementia status at the visit closest to MRI. We examined the following dichotomized neuropathological variables: Alzheimer's disease neuropathology, hippocampal sclerosis, Lewy bodies, cerebral amyloid angiopathy and atherosclerosis. Voxel-based morphometry identified areas associated with dementia after accounting for neuropathologies. Identified regions of interest were further analysed. We used multiple linear regression models adjusted for neuropathologies and demographic variables. We also examined models with dementia and Clinical Dementia Rating sum of the boxes as the outcome and explored the potential mediating effect of medial temporal lobe structure volumes on the relationship between pathology and cognition. We found strong associations for dementia with volumes of the hippocampus, amygdala and parahippocampus (semi-partial correlations ≥ 0.28, P < 0.0001 for all regions in National Alzheimer's Coordinating Center; semi-partial correlations ≥ 0.35, P ≤ 0.01 for hippocampus and parahippocampus in Alzheimer's Disease Neuroimaging Initiative). Dementia status accounted for more unique variance in atrophy in these structures (∼8%) compared with neuropathological variables; the only exception was hippocampal sclerosis which accounted for more variance in hippocampal atrophy (10%). We also found that the volumes of the medial temporal lobe structures contributed towards explaining the variance in Clinical Dementia Rating sum of the boxes (ranging from 5% to 9%) independent of neuropathologies and partially mediated the association between Alzheimer's disease neuropathology and cognition. Even after accounting for the most common neuropathologies, dementia still had among the strongest associations with atrophy of medial temporal lobe structures. This suggests that atrophy of the medial temporal lobe is most related to the clinical status of dementia rather than Alzheimer's disease or other neuropathologies, with the potential exception of hippocampal sclerosis.

Can exercise training teach us how to treat Alzheimer's disease?

Alzheimer's disease (AD) is the most common cause of dementia and there is currently no cure. Novel approaches to treat AD and curb the rapidly increasing worldwide prevalence and costs of dementia are needed. Physical inactivity is a significant modifiable risk factor for AD, estimated to contribute to 12.7% of AD cases worldwide. Exercise interventions in humans and animals have shown beneficial effects of exercise on brain plasticity and cognitive functions. In animal studies, exercise also improved AD pathology. The mechanisms underlying these effects of exercise seem to be associated mainly with exercise performance or cardiorespiratory fitness. In addition, exercise-induced molecules of peripheral origin seem to play an important role. Since exercise affects the whole body, there likely is no single therapeutic target that could mimic all the benefits of exercise. However, systemic strategies may be a viable means to convey broad therapeutic effects in AD patients. Here, we review the potential of physical activity and exercise training in AD prevention and treatment, shining light on recently discovered underlying mechanisms and concluding with a view on future development of exercise-free treatment strategies for AD.

Targeting the Erk1/2 and autophagy signaling easily improved the neurobalst differentiation and cognitive function after young transient forebrain ischemia compared to old gerbils

The hippocampal neurogenesis occurs constitutively throughout adulthood in mammalian species, but declines with age. In this study, we overtly found that the neuroblast proliferation and differentiation in the subgranular zone and the maturation into fully functional and integrated neurons in the granule-cell layer in young gerbils following cerebral ischemia/reperfusion was much more than those in old gerbils. The neurological function and cognitive and memory-function rehabilitation in the young gerbils improved faster than those in the old one. These results demonstrated that, during long term after cerebral ischemia/reperfusion, the ability of neurogenesis and recovery of nerve function in young animals were significantly higher than that in the old animals. We found that, after 14- and 28-day cerebral ischemia/reperfusion, the phosphorylation of MEK1/2, ERK1/2, p90RSK, and MSK1/2 protein levels in the hippocampus of young gerbils was significantly much higher than that of old gerbils. The levels of autophagy-related proteins, including Beclin-1, Atg3, Atg5, and LC3 in the hippocampus were effectively maintained and elevated at 28 days after cerebral ischemia/reperfusion in the young gerbils compared with those in the old gerbils. These results indicated that an increase or maintenance of the phosphorylation of ERK1/2 signal pathway and autophagy-related proteins was closely associated with the neuroblast proliferation and differentiation and the process of maturation into neurons. Further, we proved that neuroblast proliferation and differentiation in the dentate gyrus and cognitive function were significantly reversed in young cerebral ischemic gerbils by administering the ERK inhibitor (U0126) and autophagy inhibitor (3MA). In brief, following experimental young ischemic stroke, the long-term promotion of the neurogenesis in the young gerbil’s hippocampal dentate gyrus by upregulating the phosphorylation of ERK signaling pathway and maintaining autophagy-related protein levels, it overtly improved the neurological function and cognitive and memory function.

Inferring protein expression changes from mRNA in Alzheimer's dementia using deep neural networks

Identifying the molecular systems and proteins that modify the progression of Alzheimer's disease and related dementias (ADRD) is central to drug target selection. However, discordance between mRNA and protein abundance, and the scarcity of proteomic data, has limited our ability to advance candidate targets that are mainly based on gene expression. Therefore, by using a deep neural network that predicts protein abundance from mRNA expression, here we attempt to track the early protein drivers of ADRD. Specifically, by applying the clei2block deep learning model to 1192 brain RNA-seq samples, we identify protein modules and disease-associated expression changes that were not directly observed at the mRNA level. Moreover, pseudo-temporal trajectory inference based on the predicted proteome became more closely correlated with cognitive decline and hippocampal atrophy compared to RNA-based trajectories. This suggests that the predicted changes in protein expression could provide a better molecular representation of ADRD progression. Furthermore, overlaying clinical traits on protein pseudotime trajectory identifies protein modules altered before cognitive impairment. These results demonstrate how our method can be used to identify potential early protein drivers and possible drug targets for treating and/or preventing ADRD.

Emotion Processing Dysfunction in Alzheimer's Disease: An Overview of Behavioral Findings, Systems Neural Correlates, and Underlying Neural Biology

We described behavioral studies to highlight emotional processing deficits in Alzheimer's disease (AD). The findings suggest prominent deficit in recognizing negative emotions, pronounced effect of positive emotion on enhancing memory, and a critical role of cognitive deficits in manifesting emotional processing dysfunction in AD. We reviewed imaging studies to highlight morphometric and functional markers of hippocampal circuit dysfunction in emotional processing deficits. Despite amygdala reactivity to emotional stimuli, hippocampal dysfunction conduces to deficits in emotional memory. Finally, the reviewed studies implicating major neurotransmitter systems in anxiety and depression in AD supported altered cholinergic and noradrenergic signaling in AD emotional disorders. Overall, the studies showed altered emotions early in the course of illness and suggest the need of multimodal imaging for further investigations. Particularly, longitudinal studies with multiple behavioral paradigms translatable between preclinical and clinical models would provide data to elucidate the time course and underlying neurobiology of emotion processing dysfunction in AD.

Reducing Your Risk of Alzheimer's Dementia: Building a Better Brain as We Age

Alzheimer' dementia is a large and growing public health problem. Of utmost importance for limiting the impact of the disease on society is the prevention of dementia, that is, delay onset either by years whereby death ensues prior to dementia onset. The Religious Orders Study and the Rush Memory and Aging Project are two harmonized cohort studies of aging and dementia that include organ donation at death. Ongoing since 1994 and 1997, respectively, we published on the association of numerous experiential, psychological, and medical risk factors for dementia, many of which are potentially modifiable. Here, selected findings are reviewed based on a presentation at the 2020 National Academy of Neuropsychology given virtually in Chicago in October of 2020.

Hippocampus-Avoidance Whole-Brain Radiation Therapy Is Efficient in the Long-Term Preservation of Hippocampal Volume

Background and Purpose

With improved life expectancy, preventing neurocognitive decline after cerebral radiotherapy is gaining more importance. Hippocampal damage has been considered the main culprit for cognitive deficits following conventional whole-brain radiation therapy (WBRT). Here, we aimed to determine to which extent hippocampus-avoidance WBRT (HA-WBRT) can prevent hippocampal atrophy compared to conventional WBRT.

Methods and Materials

Thirty-five HA-WBRT and 48 WBRT patients were retrospectively selected, comprising a total of 544 contrast-enhanced T1-weighted magnetic resonance imaging studies, longitudinally acquired within 24 months before and 48 months after radiotherapy. HA-WBRT patients were treated analogously to the ongoing HIPPORAD-trial (DRKS00004598) protocol with 30 Gy in 12 fractions and dose to 98% of the hippocampus ≤ 9 Gy and to 2% ≤ 17 Gy. WBRT was mainly performed with 35 Gy in 14 fractions or 30 Gy in 10 fractions. Anatomical images were segmented and the hippocampal volume was quantified using the Computational Anatomy Toolbox (CAT), including neuroradiological expert review of the segmentations.

Results

After statistically controlling for confounding variables such as age, gender, and total intracranial volume, hippocampal atrophy was found after both WBRT and HA-WBRT (p < 10^-6). However, hippocampal decline across time following HA-WBRT was approximately three times lower than following conventional WBRT (p < 10^-6), with an average atrophy of 3.1% versus 8.5% in the first 2 years after radiation therapy, respectively.

Conclusion

HA-WBRT is a therapeutic option for patients with multiple brain metastases, which can effectively and durably minimize hippocampal atrophy compared to conventional WBRT.

The impact of physical exercise on hippocampus, in physiological condition and ageing-related decline: current evidence from animal and human studies

Physical exercise (PE), notoriously, promotes a state of general well-being, throughout the entire human lifespan. Moreover, maintaining an adequate and regular PE habit results to be a powerful preventive factor towards many diseases and may also help in managing existing pathological conditions. PE induces structural and functional changes in various districts of the body, determining biological and psychological benefits. Additionally, in elderly, PE might represent a remarkable tool reducing cognitive impairments related to the normal aging processes and it has also been found to have an impact in neurodegenerative diseases such as Alzheimer's disease. The present review aims to provide an overview about PE effects on hippocampus, since it is one of the brain regions most susceptible to aging and, therefore, involved in diseases characterized by cognitive impairment.

Relationship Between Alzheimer's Disease and Retinal Choroidal Thickness: A Cross-Sectional Study

BACKGROUND

The choroid is involved directly or indirectly in many pathological conditions such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS).

OBJECTIVE

The objective of this study was to investigate the association between retinal choroidal properties and the pathology of AD by determining choroidal thickness, hippocampus volume, cognitive functions, and plasma BACE1 activity.

METHODS

In this cross-sectional study, 37 patients with AD and 34 age-matched controls were included. Retinal choroidal thickness was measured via enhanced depth imaging optical coherence tomography. Hippocampal volume was measured via 3.0T MRI. Cognitive functions were evaluated using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog). Plasma BACE1 activity was analyzed using a fluorescence substrate-based plasma assay, and regression model were to analyze the data.

RESULTS

Retinal choroidal thickness was significantly thinner in the AD group than in the control group [(114.81±81.30) μm versus (233.79±38.29) μm, p < 0.05]. Multivariable regression analysis indicated that the ADAS-cog scores (β=-0.772, p = 0.000) and age (β=-0.176, p = 0.015) were independently associated with choroidal thickness. The logistic regression model revealed that the subfoveal choroidal thickness was a significant predictor for AD (OR = 0.984, 95% CI: 0.972-0.997).

CONCLUSION

There was a general tendency of choroid thinning as the cognitive function declined. Although choroidal thickness was not a potential indicator for early stage AD, it was valuable in monitoring AD progression.