Gene specific effects on brain volume and cognition of TMEM106B in frontotemporal lobar degeneration

Background and Objectives

TMEM106B has been proposed as a modifier of disease risk in FTLD-TDP, particularly in GRN mutation carriers. Furthermore, TMEM106B has been investigated as a disease modifier in the context of healthy aging and across multiple neurodegenerative diseases. The objective of this study is to evaluate and compare the effect of TMEM106B on gray matter volume and cognition in each of the common genetic FTD groups and in sporadic FTD patients.

Methods

Participants were enrolled through the ARTFL/LEFFTDS Longitudinal Frontotemporal Lobar Degeneration (ALLFTD) study, which includes symptomatic and presymptomatic individuals with a pathogenic mutation in C9orf72, GRN, MAPT, VCP, TBK1, TARDBP, symptomatic non-mutation carriers, and non-carrier family controls. All participants were genotyped for the TMEM106B rs1990622 SNP. Cross-sectionally, linear mixed-effects models were fitted to assess an association between TMEM106B and genetic group interaction with each outcome measure (gray matter volume and UDS3-EF for cognition), adjusting for education, age, sex and CDR®+NACC-FTLD sum of boxes. Subsequently, associations between TMEM106B and each outcome measure were investigated within the genetic group. For longitudinal modeling, linear mixed-effects models with time by TMEM106B predictor interactions were fitted.

Results

The minor allele of TMEM106B rs1990622, linked to a decreased risk of FTD, associated with greater gray matter volume in GRN mutation carriers under the recessive dosage model. This was most pronounced in the thalamus in the left hemisphere, with a retained association when considering presymptomatic GRN mutation carriers only. The minor allele of TMEM106B rs1990622 also associated with greater cognitive scores among all C9orf72 mutation carriers and in presymptomatic C9orf72 mutation carriers, under the recessive dosage model.

Discussion

We identified associations of TMEM106B with gray matter volume and cognition in the presence of GRN and C9orf72 mutations. This further supports TMEM106B as modifier of TDP-43 pathology. The association of TMEM106B with outcomes of interest in presymptomatic GRN and C9orf72 mutation carriers could additionally reflect TMEM106B's impact on divergent pathophysiological changes before the appearance of clinical symptoms.

Health System Change for Alzheimer's Disease-Modifying Therapies in Canada: Beginning the Discussion

Alzheimer's disease (AD) is a neurodegenerative disorder that accounts for 60%-70% of patients with dementia, and it is estimated that over one million Canadians will be living with dementia by 2030. Disease-modifying therapies (DMTs) targeting the underlying pathophysiology of AD are currently in development. Several models have demonstrated that the potential arrival of Alzheimer's DMTs will most likely overwhelm the already-constrained Canadian healthcare system. Canada does not have a strategy to address the extensive requirements of using DMTs, including providing an early diagnosis of AD, confirming DMT eligibility via amyloid biomarkers, and conducting ongoing treatment monitoring. Thus, a multidisciplinary group of experts involved in AD care in Canada gathered to review (1) the current barriers to diagnosis and management of AD; (2) how existing clinic models, including those used in multiple sclerosis (MS), could be applied to address key barriers in AD; and (3) how to design and implement optimal care pathways in the future. The actions outlined in this review will help clinicians and healthcare systems improve readiness to integrate the use of disease-modifying therapies in Alzheimer's disease, if such therapies are approved in Canada.

Economic Evaluation of Exercise or Cognitive and Social Enrichment Activities for Improved Cognition After Stroke

Importance

Cognitive impairment is prevalent in survivors of stroke, affecting approximately 30% of individuals. Physical exercise and cognitive and social enrichment activities can enhance cognitive function in patients with chronic stroke, but their cost-effectiveness compared with a balance and tone program is uncertain.

Objective

To conduct a cost-effectiveness and cost-utility analysis of multicomponent exercise or cognitive and social enrichment activities compared with a balance and tone program.

Design, Setting, and Participants

This economic evaluation used a Canadian health care systems perspective and the Vitality study, a randomized clinical trial aimed at improving cognition after stroke with a 6-month intervention and a subsequent 6-month follow-up (ie, 12 months). The economic evaluation covered the duration of the Vitality trial, between June 6, 2014, and February 26, 2019. Participants were community-dwelling adults aged 55 years and older who experienced a stroke at least 12 months prior to study enrollment in the Vancouver metropolitan area, British Columbia, Canada. Data were analyzed from June 1, 2022, to March 31, 2023.

Interventions

Participants were randomly assigned to twice-weekly classes for 1 of the 3 groups: multicomponent exercise program, cognitive and social enrichment activities program, or a balance and tone program (control).

Main Outcomes and Measures

The primary measures for the economic evaluation included cost-effectiveness (incremental costs per mean change in cognitive function, evaluated using the Alzheimer Disease Assessment Scale-Cognitive-Plus), cost-utility (incremental cost per quality-adjusted life-year gained), intervention costs, and health care costs. Since cognitive benefits 6 months after intervention cessation were not observed in the primary randomized clinical trial, an economic evaluation at 12 months was not performed.

Results

Among 120 participants (mean [SD] age, 71 [9] years; 74 [62%] male), 34 were randomized to the multicomponent exercise program, 34 were randomized to the social and cognitive enrichment activities program, and 52 were randomized to the balance and tone control program. At the end of the 6-month intervention, the cost per mean change in Alzheimer Disease Assessment Scale-Cognitive-Plus score demonstrated that exercise was more effective and costlier compared with the control group in terms of cognitive improvement with an incremental cost-effectiveness ratio of CAD -$8823. The cost per quality-adjusted life-year gained for both interventions was negligible, with exercise less costly (mean [SD] incremental cost, CAD -$32 [$258]) and cognitive and social enrichment more costly than the control group (mean [SD] incremental cost, CAD $1018 [$378]). The balance and tone program had the lowest delivery cost (CAD $777), and the exercise group had the lowest health care resource utilization (mean [SD] $1261 [$1188]) per person.

Conclusions and Relevance

The findings of this economic evaluation suggest that exercise demonstrated potential for cost-effectiveness to improve cognitive function in older adults with chronic stroke during a 6-month intervention.

Network Connectivity Alterations across the MAPT Mutation Clinical Spectrum

OBJECTIVE

Microtubule-associated protein tau (MAPT) mutations cause frontotemporal lobar degeneration, and novel biomarkers are urgently needed for early disease detection. We used task-free functional magnetic resonance imaging (fMRI) mapping, a promising biomarker, to analyze network connectivity in symptomatic and presymptomatic MAPT mutation carriers.

METHODS

We compared cross-sectional fMRI data between 17 symptomatic and 39 presymptomatic carriers and 81 controls with (1) seed-based analyses to examine connectivity within networks associated with the 4 most common MAPT-associated clinical syndromes (ie, salience, corticobasal syndrome, progressive supranuclear palsy syndrome, and default mode networks) and (2) whole-brain connectivity analyses. We applied K-means clustering to explore connectivity heterogeneity in presymptomatic carriers at baseline. Neuropsychological measures, plasma neurofilament light chain, and gray matter volume were compared at baseline and longitudinally between the presymptomatic subgroups defined by their baseline whole-brain connectivity profiles.

RESULTS

Symptomatic and presymptomatic carriers had connectivity disruptions within MAPT-syndromic networks. Compared to controls, presymptomatic carriers showed regions of connectivity alterations with age. Two presymptomatic subgroups were identified by clustering analysis, exhibiting predominantly either whole-brain hypoconnectivity or hyperconnectivity at baseline. At baseline, these two presymptomatic subgroups did not differ in neuropsychological measures, although the hypoconnectivity subgroup had greater plasma neurofilament light chain levels than controls. Longitudinally, both subgroups showed visual memory decline (vs controls), yet the subgroup with baseline hypoconnectivity also had worsening verbal memory and neuropsychiatric symptoms, and extensive bilateral mesial temporal gray matter decline.

INTERPRETATION

Network connectivity alterations arise as early as the presymptomatic phase. Future studies will determine whether presymptomatic carriers' baseline connectivity profiles predict symptomatic conversion. ANN NEUROL 2023;94:632-646.

Expert elicitation of risk factors for progression to dementia in individuals with mild cognitive impairment

INTRODUCTION

This study assesses experts' beliefs about important predictors of developing dementia in persons with mild cognitive impairment (MCI).

METHODS

Structured expert elicitation, a methodology to quantify expert knowledge, was used to elicit the most important risk factors for developing dementia. We recruited 11 experts (6 neurologists, 3 geriatricians, and 2 psychiatrists). Ten experts fully participated in introductory meetings, two rounds of surveys, and discussion meetings. The data from these ten experts were utilized for this study.

RESULTS

The expert elicitation identified age, CSF analysis, fluorodeoxyglucose-positron emission tomography (FDG-PET) findings, hippocampal atrophy, MoCA (or MMSE) score, parkinsonism, apathy, psychosis, informant report of cognitive symptoms, and global atrophy as the ten most important predictors of progressing to dementia in persons with MCI.

DISCUSSION

Several dementia predictors are not routinely collected in existing registries, observational studies, or usual care. This might partially explain the low uptake of existing published dementia risk scores in clinical practice.

A Systematic Review of the Genetics and Pathology of Psychosis in Frontotemporal Dementia

OBJECTIVES

Frontotemporal dementia (FTD) patients frequently present with psychosis, which complicates diagnosis and management. In this study, we aim to examine the relationship between psychosis and the most common genetic mutations predisposing to FTD, and in the different pathological subtypes of FTD.

DESIGN

We conducted a systematic review, searching the literature up to December 2022, and reviewed 50 articles that met our inclusion criteria. From the reviewed articles, we extracted and summarized data regarding the frequency of psychosis and patient characteristics in each major genetic and pathological subtype of FTD.

RESULTS

Among FTD patients with confirmed genetic mutations or pathological diagnosss, the frequency of psychosis was 24.2%. Among the genetic mutation carriers, C9orf72 mutation carriers had the highest frequency of psychosis (31.4%), whereas GRN (15.0%) and MAPT (9.2%) mutation carriers had lower frequencies of psychosis. MAPT mutation carriers notably developed psychosis at a younger age compared to other genetic groups. The most common psychotic symptoms were delusions among C9orf72 carriers and visual hallucinations among GRN mutation carriers. Among the pathological subtypes, 30% of patients with FUS pathology, 25.3% of patients with TDP-43 pathology, and 16.4% of patients with tau pathology developed psychosis. In the TDP-43 group, subtype B pathology was the most common subtype reported in association with psychosis.

CONCLUSION

Our systematic review suggests a high frequency of psychosis in specific subgroups of FTD patients. Further studies are required to understand the structural and biological underpinnings of psychosis in FTD.

Elicited clinician knowledge did not improve dementia risk prediction in individuals with mild cognitive impairment

OBJECTIVES

This study aims to develop and validate a Bayesian risk prediction model that combines research cohort data with elicited expert knowledge to predict dementia progression in people with mild cognitive impairment (MCI).

STUDY DESIGN AND SETTING

This is a prognostic risk prediction modeling study based on cohort data (Alzheimer's disease neuroimaging initiative [ADNI]; n = 365) of research participants with MCI and elicited expert data. Bayesian Cox models were used to combine expert knowledge and ADNI data to predict dementia progression in people with MCI. Posterior distributions were obtained based on Gibbs sampler and the predictive performance was evaluated using ten-fold cross-validation via c-index, integrated calibration index (ICI), and integrated brier score (IBS).

RESULTS

365 people with MCI were included, mean age was 73 years (SD = 7.5), and 39% developed dementia within 3 years. When expert knowledge was incorporated, the c-index, ICI, and IBS values were 0.74 (95% CI 0.70-0.79), 0.06 (95% CI 0.05-0.08), and 0.17 (95% CI 0.14-0.19), respectively. These were similar to the model without expert knowledge data.

CONCLUSION

The addition of expert knowledge did not improve model accuracy in this ADNI sample to predict dementia progression in individuals with MCI.

White-matter abnormalities in presymptomatic GRN and C9orf72 mutation carriers

A large proportion of familial frontotemporal dementia is caused by TAR DNA-binding protein 43 (transactive response DNA-binding protein 43 kDa) proteinopathies. Accordingly, carriers of autosomal dominant mutations in the genes associated with TAR DNA-binding protein 43 aggregation, such as Chromosome 9 open reading frame 72 (C9orf72) or progranulin (GRN), are at risk of later developing frontotemporal dementia. Brain imaging abnormalities that develop before dementia onset in mutation carriers may serve as proxies for the presymptomatic stages of familial frontotemporal dementia due to a genetic cause. Our study objective was to investigate brain MRI-based white-matter changes in predementia participants carrying mutations in C9orf72 or GRN genes. We analysed mutation carriers and their family member controls (noncarriers) from the University of British Columbia familial frontotemporal dementia study. First, a total of 42 participants (8 GRN carriers; 11 C9orf72 carriers; 23 noncarriers) had longitudinal T₁-weighted MRI over ∼2 years. White-matter signal hypointensities were segmented and volumes were calculated for each participant. General linear models were applied to compare the baseline burden and the annualized rate of accumulation of signal abnormalities among mutation carriers and noncarriers. Second, a total of 60 participants (9 GRN carriers; 17 C9orf72 carriers; 34 noncarriers) had cross-sectional diffusion tensor MRI available. For each participant, we calculated the average fractional anisotropy and mean, radial and axial diffusivity parameter values within the normal-appearing white-matter tissues. General linear models were applied to compare whether mutation carriers and noncarriers had different trends in diffusion tensor imaging parameter values as they neared the expected age of onset. Baseline volumes of white-matter signal abnormalities were not significantly different among mutation carriers and noncarriers. Longitudinally, GRN carriers had significantly higher annualized rates of accumulation (estimated mean: 15.87%/year) compared with C9orf72 carriers (3.69%/year) or noncarriers (2.64%/year). A significant relationship between diffusion tensor imaging parameter values and increasing expected age of onset was found in the periventricular normal-appearing white-matter region. Specifically, GRN carriers had a tendency of a faster increase of mean and radial diffusivity values and C9orf72 carriers had a tendency of a faster decline of fractional anisotropy values as they reached closer to the expected age of dementia onset. These findings suggest that white-matter changes may represent early markers of familial frontotemporal dementia due to genetic causes. However, GRN and C9orf72 mutation carriers may have different mechanisms leading to tissue abnormalities.

Müller cell degeneration and microglial dysfunction in the Alzheimer's retina

Amyloid beta (Aβ) deposits in the retina of the Alzheimer's disease (AD) eye may provide a useful diagnostic biomarker for AD. This study focused on the relationship of Aβ with macroglia and microglia, as these glial cells are hypothesized to play important roles in homeostasis and clearance of Aβ in the AD retina. Significantly higher Aβ load was found in AD compared to controls, and specifically in the mid-peripheral region. AD retina showed significantly less immunoreactivity against glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) compared to control eyes. Immunoreactivity against ionized calcium binding adapter molecule-1 (IBA-1), a microglial marker, demonstrated a higher level of microgliosis in AD compared to control retina. Within AD retina, more IBA-1 immunoreactivity was present in the mid-peripheral retina, which contained more Aβ than the central AD retina. GFAP co-localized rarely with Aβ, while IBA-1 co-localized with Aβ in more layers of control than AD donor retina. These results suggest that dysfunction of the Müller and microglial cells may be key features of the AD retina.

Effect of Exercise Training or Complex Mental and Social Activities on Cognitive Function in Adults With Chronic Stroke: A Randomized Clinical Trial

IMPORTANCE

A stroke doubles one's risk for dementia. How to promote cognitive function among persons with chronic stroke is unclear.

OBJECTIVE

To evaluate the effect of exercise (EX) or cognitive and social enrichment activities (ENRICH) on cognitive function in adults with chronic stroke.

DESIGN, SETTING, AND PARTICIPANTS

This was a 3-group parallel, single-blinded, single-site, proof-of-concept randomized clinical trial at a research center in Vancouver, British Columbia, Canada. Participants included community-dwelling adults with chronic stroke, aged 55 years and older, able to walk 6 meters, and without dementia. The trial included a 6-month intervention and a 6-month follow-up. Randomization occurred from June 6, 2014, to February 26, 2019. Measurement occurred at baseline, 6 months, and 12 months. Data were analyzed from January to November 2021.

INTERVENTIONS

Participants were randomly allocated to twice-weekly supervised classes of: (1) EX, a multicomponent exercise program; (2) ENRICH, a program of cognitive and social enrichment activities; or (3) balance and tone (BAT), a control group that included stretches and light-intensity exercises.

MAIN OUTCOMES AND MEASURES

The primary outcome was the Alzheimer Disease Assessment Scale-Cognitive-Plus (ADAS-Cog-Plus), which included the 13-item ADAS-Cog, Trail Making Test Parts A and B, Digit Span Forward and Backward, Animal Fluency, and Vegetable Fluency.

RESULTS

One-hundred and twenty participants, with a mean (range) of 1.2 (1-4) strokes, a mean (SD) of 66.5 (53.8) months since the most recent stroke, mean (SD) baseline age of 70 (8) years, mean (SD) baseline ADAS-Cog-Plus of 0.22 (0.81), and 74 (62%) male participants, were randomized to EX (34 participants), ENRICH (34 participants), or BAT (52 participants). Seventeen withdrew during the 6-month intervention and another 7 during the 6-month follow-up. Including all 120 participants, at the end of the 6-month intervention, EX significantly improved ADAS-Cog-Plus performance compared with BAT (estimated mean difference: -0.24; 95% CI, -0.43 to -0.04; P = .02). This difference did not persist at the 6-month follow-up (estimated mean difference: -0.08; 95% CI, -0.29 to 0.12; P = .43). For the 13-item ADAS-Cog, the EX group improved by 5.65 points over the 6-month intervention (95% CI, 2.74 to 8.57 points; P < .001), exceeding the minimally clinical difference of 3.0 points.

CONCLUSIONS AND RELEVANCE

These findings suggest that exercise can induce clinically important improvements in cognitive function in adults with chronic stroke. Future studies need to replicate current findings and to understand training parameters, moderators, and mediators to maximize benefits.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01916486.

Reshaping the path of mild cognitive impairment by refining exercise prescription: a study protocol of a randomized controlled trial to understand the "what," "for whom," and "how" of exercise to promote cognitive function

Background

Targeted exercise training is a promising strategy for promoting cognitive function and preventing dementia in older age. Despite the utility of exercise as an intervention, variation still exists in exercise-induced cognitive gains and questions remain regarding the type of training (i.e., what), as well as moderators (i.e., for whom) and mechanisms (i.e., how) of benefit. Both aerobic training (AT) and resistance training (RT) enhance cognitive function in older adults without cognitive impairment; however, the vast majority of trials have focused exclusively on AT. Thus, more research is needed on RT, as well as on the combination of AT and RT, in older adults with mild cognitive impairment (MCI), a prodromal stage of dementia. Therefore, we aim to conduct a 6-month, 2 × 2 factorial randomized controlled trial in older adults with MCI to assess the individual effects of AT and RT, and the combined effect of AT and RT on cognitive function and to determine the possible underlying biological mechanisms.

Methods

Two hundred and sixteen community-dwelling adults, aged 65 to 85 years, with MCI from metropolitan Vancouver will be recruited to participate in this study. Randomization will be stratified by biological sex and participants will be randomly allocated to one of the four experimental groups: (1) 4×/week balance and tone (BAT; i.e., active control); (2) combined 2×/week AT + 2×/week RT; (3) 2×/week AT + 2×/week BAT; or (4) 2×/week RT + 2×/week BAT. The primary outcome is cognitive function as measured by the Alzheimer’s Disease Assessment Scale-Cognitive-Plus. Secondary outcomes include cognitive function, health-related quality of life, physical function, actigraphy measures, questionnaires, and falls. Outcomes will be measured at baseline, 6 months (i.e., trial completion), and 18 months (i.e., 12-month follow-up).

Discussion

Establishing the efficacy of different types and combinations of exercise training to minimize cognitive decline will advance our ability to prescribe exercise as “medicine” to treat MCI and delay the onset and progression of dementia. This trial is extremely timely as cognitive impairment and dementia pose a growing threat to global public health.

Trial registration

ClinicalTrials.gov NCT02737878. Registered on April 14, 2016.

Informant-based tools for assessment and monitoring of cognition, behavior, and function in neurocognitive disorders: Systematic review and report from a CCCDTD5 Working Group

OBJECTIVE

As part of the fifth Canadian Consensus Conference on the Diagnosis and Treatment of Dementia, we assessed the literature on informant-based tools for assessment and monitoring of cognition, behavior, and function in neurocognitive disorders (NCDs) to provide evidence-based recommendations for clinicians and researchers.

METHODS

A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses standards guidelines. Publications that validated the informant-based tools or described their key properties were reviewed. Quality of the studies was assessed using the modified Quality Assessment tool for Diagnostic Accuracy Studies.

RESULTS

Out of 386 publications identified through systematic search, 34 that described 19 informant-based tools were included in the final review. Most of these tools are backed by good-quality studies and are appropriate to use in clinical care or research. The tools vary in their psychometric properties, domains covered, comprehensiveness, completion time, and ability to detect longitudinal change. Based on these properties, we identify different tools that may be appropriate for primary care, specialized memory clinic, or research settings. We also identify barriers to use of these tools in routine clinical practice.

CONCLUSION

There are several good-quality tools available to collect informant-report for assessment and monitoring of cognition, behavior, or function in patients with NCDs. Clinicians and researchers may choose a particular tool based on their specific needs such as domains of interest, desired psychometric properties, and feasibility. Further work is needed to make the tools more user-friendly and to adopt them into routine clinical care.

Cardiovascular risk moderates the effect of aerobic exercise on executive functions in older adults with subcortical ischemic vascular cognitive impairment

Aerobic training (AT) can promote cognitive function in adults with Subcortical Ischemic Vascular Cognitive Impairment (SIVCI) by modifying cardiovascular risk factors. However, pre-existing cardiovascular health may attenuate the benefits of AT on cognitive outcomes in SIVCI. We examined whether baseline cardiovascular risk moderates the effect of a 6-month progressive AT program on executive functions with a secondary analysis of a randomized controlled trial in 71 adults, who were randomized to either: (1) 3×/week progressive AT; or (2) education program (CON). Three executive processes were measured: (1) response inhibition by Stroop Test; (2) working memory by digits backward test; and (3) set shifting by the Trail Making Test. Baseline cardiovascular risk was calculated using the Framingham cardiovascular disease (CVD) Risk Score (FCRS), and participants were classified as either low risk (< 20% FCRS score; LCVR) or high risk (≥ 20% FCRS score; HCVR). A complete case analysis (n = 58) was conducted using an analysis of covariance (ANCOVA) to evaluate between-group differences in the three executive processes. A significant interaction was found between cardiovascular risk group and intervention group (AT or CON) for the digit span backward and the Trail Making Test. AT improved performance compared with CON in those with LCVR, while in those with HCVR, AT did not improve performance compared with CON. Baseline cardiovascular risk significantly moderates the efficacy of AT on cognition. Our findings highlight the importance of intervening early in the disease course of SIVCI, when cardiovascular risk may be lower, to reap maximum benefits of aerobic exercise.

Cerebral Amyloid-β Deposition Is Associated with Impaired Gait Speed and Lower Extremity Function

BACKGROUND

Impaired physical function (i.e., slowing of gait, muscle weakness, and poor mobility) is common in older adults with cognitive impairment and dementia. Evidence suggests that cerebral small vessel disease, specifically white matter lesions (WMLs), is associated with impaired physical function, but little research has been conducted to understand the specific role of Alzheimer's disease pathology in physical outcomes.

OBJECTIVE

The objective of this study was to examine the association between cerebral amyloid-β (Aβ) deposition and physical function in people with cognitive impairment.

METHODS

Thirty participants completed an 11C Pittsburgh compound B (PIB) position emission tomography (PET) scan to quantify global Aβ deposition using standardized uptake value ratio (SUVR). We assessed usual gait speed, muscle strength of the lower extremities, balance, and functional mobility using the Short Physical Performance Battery (SPPB) and the Timed Up and Go Test (TUGT). Multiple linear regression analyses examined the association between Aβ and each measure of physical function, adjusting for age, body mass index, and WML load.

RESULTS

Global PIB SUVR was significantly associated with usual gait speed (β= -0.52, p = 0.01) and SPPB performance (β= -0.47, p = 0.02), such that increased Aβ deposition was associated with reduced performance on both measures. Global PIB SUVR was not significantly associated with TUGT performance (β= 0.32, p = 0.08).

CONCLUSIONS

Cerebral Aβ deposition is associated with reduced gait speed, muscle strength, and balance in older adults with cognitive impairment independent of WML load. However, Aβ deposition was not associated with functional mobility.

Trehalose Inhibits Aβ Generation and Plaque Formation in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, and there has been no disease-modifying treatment for AD. Recent studies suggest that trehalose may have beneficial effect on neurodegenerative diseases through regulating autophagy and facilitating aggregated protein clearance. However, the effects of trehalose on AD-related neuropathologies are still unknown. Western blot was performed to examine the effects of trehalose on APP processing in vitro and in vivo. ELISA and immunohistochemical staining were conducted to measure Aβ production in vitro and neuritic plaque formation in APP23 transgenic mice, respectively. Trehalose treatment significantly decreased Aβ generation in HAW and 20E2 cells. Furthermore, trehalose treatment increased the levels of APP and its CTFs, and significantly reduced Aβ generation and neuritic plaque formation in APP23 mice. Our study showed that trehalose affected the APP processing both in vitro and in vivo and suggests that trehalose treatment may offer as a therapeutic strategy to ameliorate AD pathology by inhibiting Aβ generation and neuritic plaque formation.

The longitudinal evaluation of familial frontotemporal dementia subjects protocol: Framework and methodology

INTRODUCTION

It is important to establish the natural history of familial frontotemporal lobar degeneration (f-FTLD) and provide clinical and biomarker data for planning these studies, particularly in the asymptomatic phase.

METHODS

The Longitudinal Evaluation of Familial Frontotemporal Dementia Subjects protocol was designed to enroll and follow at least 300 subjects for more than at least three annual visits who are members of kindreds with a mutation in one of the three most common f-FTLD genes-microtubule-associated protein tau, progranulin, or chromosome 9 open reading frame 72.

RESULTS

We present the theoretical considerations of f-FTLD and the aims/objectives of this protocol. We also describe the design and methodology for evaluating and rating subjects, in which detailed clinical and neuropsychological assessments are performed, biofluid samples are collected, and magnetic resonance imaging scans are performed using a standard protocol.

DISCUSSION

These data and samples, which are available to interested investigators worldwide, will facilitate planning for upcoming disease-modifying therapeutic trials in f-FTLD.

THE ROLE OF S100B IN AEROBIC TRAINING EFFICACY IN OLDER ADULTS WITH MILD VASCULAR COGNITIVE IMPAIRMENT

Aerobic training improves cognitive and brain outcomes across different populations and neurocognitive disorders of aging, including mild subcortical ischemic vascular cognitive impairment (SIVCI). However, little is known of the underlying mechanisms through which aerobic training exerts its beneficial effects on the brain. Recently, S100 calcium-binding protein B (S100B) has been proposed as a possible mediator of aerobic training. At low levels, S100B is neurotrophic but at higher levels it is neurotoxic. Elevated levels of S100B have been associated with decreased performance on measures of global cognitive function. Thus, we conducted a secondary analysis of data collected from the proof-of-concept single-blind randomized controlled trial (NCT01027858) in older adults with mild SIVCI to determine whether the beneficial effects of 6-months, thrice weekly, moderate intensity aerobic training on cognitive performance is related to changes in S100B levels. In a subsample of 45 participants, blood samples were collected both before and after trial completion. Global cognitive function was assessed using Mini Mental State Examination (MMSE). At trial completion, aerobic training decreased circulating levels of S100B compared with usual care plus education (F(1,41) = 6.673, p = 0.013, ηp2 = 0.140; Figure 1). Furthermore, reduced S100B levels were associated with improved global cognitive function in those who received the aerobic exercise intervention (partial r = -0.519, p = 0.023). Together these findings suggest that S100B is a promising target mediating the beneficial effects of moderate-intensity aerobic training on brain health in older adults with mild SIVCI.

AEROBIC TRAINING, THE DEFAULT MODE NETWORK, AND COGNITION IN OLDER ADULTS WITH MILD VASCULAR COGNITIVE IMPAIRMENT

Aerobic training has been shown to be effective at improving cognitive and brain outcomes in older adults with mild subcortical ischemic vascular cognitive impairment (SIVCI). However, uncertainty remains regarding the underlying neurobiological mechanisms by which exercise elicits these improvements in cognition. Increased aberrant functional connectivity of the default mode network has been highlighted as a factor contributing to cognitive decline in older adults with cognitive impairment. Greater connectivity of the DMN at rest is associated with poorer performance on attention-demanding tasks, indicative of a lack of ability to deactivate the network on task. Our previous work on a randomized controlled trial of participants with mild SIVCI, demonstrated that 6-months of thrice weekly aerobic training led to improved global cognitive function, as measured by Alzheimer’s disease Assessment Scale-Cognitive subscale (ADAS-Cog), compared with a health education program. Thus, we conducted secondary analyses to investigate whether these changes in global cognitive function were associated with changes in resting state DMN connectivity. A subsample of 21 participants underwent a resting state functional magnetic resonance imaging (fMRI) scan before and after trial completion. Change in resting state DMN connectivity was found to significantly predict change in ADAS-Cog score (β = -.442, p=.038) after controlling for age, intervention group, and baseline functional capacity (R2=.467, F(4,16)= 3.507, p=.031). These findings suggest that functional connectivity of the DMN may underlie changes in global cognitive function. Furthermore, aerobic exercise is a promising intervention by which to elicit these changes in older adults with mild SIVCI.

Genome-wide analyses as part of the international FTLD-TDP whole-genome sequencing consortium reveals novel disease risk factors and increases support for immune dysfunction in FTLD

Frontotemporal lobar degeneration with neuronal inclusions of the TAR DNA-binding protein 43 (FTLD-TDP) represents the most common pathological subtype of FTLD. We established the international FTLD-TDP whole-genome sequencing consortium to thoroughly characterize the known genetic causes of FTLD-TDP and identify novel genetic risk factors. Through the study of 1131 unrelated Caucasian patients, we estimated that C9orf72 repeat expansions and GRN loss-of-function mutations account for 25.5% and 13.9% of FTLD-TDP patients, respectively. Mutations in TBK1 (1.5%) and other known FTLD genes (1.4%) were rare, and the disease in 57.7% of FTLD-TDP patients was unexplained by the known FTLD genes. To unravel the contribution of common genetic factors to the FTLD-TDP etiology in these patients, we conducted a two-stage association study comprising the analysis of whole-genome sequencing data from 517 FTLD-TDP patients and 838 controls, followed by targeted genotyping of the most associated genomic loci in 119 additional FTLD-TDP patients and 1653 controls. We identified three genome-wide significant FTLD-TDP risk loci: one new locus at chromosome 7q36 within the DPP6 gene led by rs118113626 (p value = 4.82e - 08, OR = 2.12), and two known loci: UNC13A, led by rs1297319 (p value = 1.27e - 08, OR = 1.50) and HLA-DQA2 led by rs17219281 (p value = 3.22e - 08, OR = 1.98). While HLA represents a locus previously implicated in clinical FTLD and related neurodegenerative disorders, the association signal in our study is independent from previously reported associations. Through inspection of our whole-genome sequence data for genes with an excess of rare loss-of-function variants in FTLD-TDP patients (n ≥ 3) as compared to controls (n = 0), we further discovered a possible role for genes functioning within the TBK1-related immune pathway (e.g., DHX58, TRIM21, IRF7) in the genetic etiology of FTLD-TDP. Together, our study based on the largest cohort of unrelated FTLD-TDP patients assembled to date provides a comprehensive view of the genetic landscape of FTLD-TDP, nominates novel FTLD-TDP risk loci, and strongly implicates the immune pathway in FTLD-TDP pathogenesis.

Detection of cognitive impairment using a machine-learning algorithm

PURPOSE

The Mini-Mental State Examination (MMSE) is one of the most frequently used bedside screening measures of cognition. However, the Korean Dementia Screening Questionnaire (KDSQ) is an easier and more reliable screening method. Instead, other clinical variables and raw data were used for this study without the consideration of a cutoff value. The objective of this study was to develop a machine-learning algorithm for the detection of cognitive impairment (CI) based on the KDSQ and the MMSE.

PATIENTS AND METHODS

The original dataset from the Clinical Research Center for Dementia of South Korea study was obtained. In total, 9,885 and 300 patients were randomly allocated to the training and test datasets, respectively. We selected up to 24 variables including sex, age, education duration, diabetes mellitus, and hypertension. We trained a machine-learning algorithm using TensorFlow based on the training dataset and then calculated its accuracy using the test dataset. The cost was calculated by conducting a logistic regression.

RESULTS

The accuracy of the model in predicting CI based on the KDSQ only, the MMSE only, and the combination of the KDSQ and MMSE was 84.3%, 88.3%, and 86.3%, respectively. For the KDSQ, the sensitivity for detecting CI was 91.50% and the specificity for detecting normal cognition (NL) was 59.60%. The sensitivity of the MMSE was 94.35%, and the specificity was 59.62%. When combining the KDSQ and the MMSE, the sensitivity for detecting CI was 91.5% and the specificity for detecting NL was 61.5%.

CONCLUSION

The algorithm predicting CI based on the MMSE is superior. However, the KDSQ can be administered more easily in clinical practice and the algorithm using KDSQ is a comparable screening tool.

The role of exercise in mitigating subcortical ischemic vascular cognitive impairment

Subcortical ischemic vascular cognitive impairment (SIVCI) is the most preventable form of cognitive dysfunction. There is converging evidence from animal and human studies that indicate vascular injury as the primary cause of SIVCI. Currently, there are no curative pharmaceutical treatments for vascular dementia; however, exercise may be a promising strategy to combat SIVCI. This review will focus on the role of exercise as a strategy to prevent or slow the progression of SIVCI, with particular emphasis on the mechanisms by which exercise may improve cerebrovascular function. We propose that exercise may be an effective strategy to combat SIVCI by improving cognitive function, increasing the bioavailability of neurotrophins, stimulating endothelial function, and controlling vascular risk factors. This article is part of the Special Issue "Vascular Dementia".

Sex differences in the prevalence of genetic mutations in FTD and ALS: A meta-analysis

OBJECTIVE

To conduct a meta-analysis that investigates sex differences in the prevalence of mutations in the 3 most common genes that cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD)-chromosome 9 open reading frame 72 (C9orf72), progranulin (GRN), or microtubule-associated protein tau (MAPT)-in patients clinically diagnosed with these conditions.

METHODS

MEDLINE, EMBASE, and PsycINFO databases were searched (inception to June 30, 2016). Studies of patients with FTD or ALS that reported the number of men and women with and without mutations of interest were selected. Female to male pooled risk ratios (RR) and 95% confidence intervals (CI) for each mutation were calculated using random-effects models.

RESULTS

Thirty-two articles reporting 12,784 patients with ALS (including 1,244 C9orf72 mutation carriers) revealed a higher prevalence of female patients with C9orf72-related ALS (RR 1.16, 95% CI 1.04-1.29). Twenty-three articles reporting 5,320 patients with FTD (including 488 C9orf72 mutation carriers) revealed no sex differences in C9orf72-related FTD (RR 0.95, 95% CI 0.81-1.12). Thirty-six articles reporting 3,857 patients with FTD (including 369 GRN mutation carriers) revealed a higher prevalence of female patients with GRN-related FTD (RR 1.33, 95% CI 1.09-1.62). Finally, 21 articles reporting 2,377 patients with FTD (including 215 MAPT mutation carriers) revealed no sex difference in MAPT-related FTD (RR 1.21, 95% CI 0.95-1.55).

CONCLUSIONS

Higher female prevalence of C9orf72 hexanucleotide repeat expansions in ALS and GRN mutations in FTD suggest that sex-related risk factors might moderate C9orf72 and GRN-mediated phenotypic expression.

Associations between cerebral amyloid and changes in cognitive function and falls risk in subcortical ischemic vascular cognitive impairment

Background

To determine the association between amyloid-beta (Aβ) plaque deposition and changes in global cognition, executive functions, information processing speed, and falls risk over a 12-month period in older adults with a primary clinical diagnosis of subcortical ischemic vascular cognitive impairment (SIVCI).

Methods

This is a secondary analysis of data acquired from a subset of participants (N = 22) who were enrolled in a randomized controlled trial of aerobic exercise (NCT01027858). The subset of individuals completed an ¹¹C Pittsburgh compound B (PIB) scan. Cognitive function and falls risk were assessed at baseline, 6-months, and 12-months. Global cognition, executive functions, and information processing speed were measured using: 1) ADAS-Cog; 2) Trail Making Test; 3) Digit Span Test; 4) Stroop Test, and 5) Digit Symbol Substitution Test. Falls risk was measured using the Physiological Profile Assessment. Hierarchical multiple linear regression analyses determined the unique contribution of Aβ on changes in cognitive function and falls risk at 12-months after controlling for experimental group (i.e. aerobic exercise training or usual care control) and baseline performance. To correct for multiple comparisons, we applied the Benjamini-Hochberg procedure to obtain a false discovery rate corrected threshold using alpha = 0.05.

Results

Higher PIB retention was significantly associated with greater decrements in set shifting (Trail Making Test, adjusted R² = 35.3%, p = 0.002), attention and conflict resolution (Stroop Test, adjusted R² = 33.4%, p = 0.01), and information processing speed (Digit Symbol Substitution Test, adjusted R² = 24.4%, p = 0.001) over a 12-month period. Additionally, higher PIB retention was significantly associated with increased falls risk (Physiological Profile Assessment, adjusted R² = 49.1%, p = 0.04). PIB retention was not significantly associated with change in ADAS-Cog and Verbal Digit Span Test (p > 0.05).

Conclusions

Symptoms associated with SIVCI may be amplified by secondary Aβ pathology.

Trial registration

ClinicalTrials.gov, NCT01027858, December 7, 2009.

Economic evaluation of aerobic exercise training in older adults with vascular cognitive impairment: PROMoTE trial

BACKGROUND/OBJECTIVES

Evidence suggests that aerobic exercise may slow the progression of subcortical ischaemic vascular cognitive impairment (SIVCI) by modifying cardiovascular risk factors. Yet the economic consequences relating to aerobic training (AT) remain unknown. Therefore, our primary objective was to estimate the incremental cost per quality-adjusted life years (QALYs) gained of a thrice weekly AT intervention compared with usual care.

DESIGN

Cost-utility analysis alongside a randomised trial.

SETTING

Vancouver, British Columbia, Canada.

PARTICIPANTS

70 adults (mean age of 74 years, 51% women) who meet the diagnostic criteria for mild SIVCI.

INTERVENTION

A 6-month, thrice weekly, progressive aerobic exercise training programme compared with usual care (CON; comparator) with a follow-up assessment 6 months after formal cessation of aerobic exercise training.

MEASUREMENTS

Healthcare resource usage was estimated over the 6-month intervention and 6-month follow-up period. Health status (using the EQ-5D-3L) at baseline and trial completion and 6-month follow-up was used to calculate QALYs. The incremental cost-utility ratio (cost per QALY gained) was calculated.

RESULTS

QALYs were both modestly greater, indicating a health gain. Total healthcare costs (ie, 1791±1369 {2015 $CAD} at 6 months) were greater, indicating a greater cost for the thrice weekly AT group compared with CON. From the Canadian healthcare system perspective, the incremental cost-utility ratios for thrice weekly AT were cost-effective compared with CON, when using a willingness to pay threshold of $CAD 20 000 per QALY gained or higher.

CONCLUSIONS

AT represents an attractive and potentially cost-effective strategy for older adults with mild SIVCI.

TRIAL REGISTRATION NUMBER

NCT01027858.

The prevalence of depressive symptoms in frontotemporal dementia: a meta-analysis

BACKGROUND

Depression is common in Alzheimer's and vascular dementia and is associated with poorer outcomes; however, less is known about the impact of depression on frontotemporal dementia (FTD). Here, we conducted a meta-analysis of diagnostic methods and the prevalence of depressive symptoms in FTD.

METHODS

PubMed, EMBASE and PsychINFO were queried for 'depression' and/or 'depressive mood' in behavioral- and language-variant FTD. The prevalence and diagnosis of depressive symptoms were extracted from relevant studies and the results pooled using a random-effects model.

RESULTS

We included 29 studies in this meta-analysis, with sample sizes ranging from 3 to 73 (n = 870). The omnibus estimated event rate of depressed mood was 0.334 (33%; 95% CI: 0.268-0.407). Symptoms were most commonly assessed via standardized neuropsychiatric rating scales, with other methods including subjective caregiver reports and chart reviews. The study results were heterogeneous due to the variability in diagnostic methods.

CONCLUSIONS

Depressive symptoms similar to those in other dementias are commonly detected in FTD. However, the diagnostic methods are heterogeneous, and symptoms of depression often overlap with manifestations of FTD. Having a standardized diagnostic approach to depression in FTD will greatly facilitate future research in this area.