Li, Danni

Background Studies suggest that plasma Alzheimer's disease (AD) biomarkers may aid in the overall diagnosis of AD, but their utility among patients with atypical clinical presentations of AD are unknown. Objective The main objective of this study was to determine the relationship between amyloid-β (Aβ) and tau plasma biomarkers and PET measures of both Aβ and tau in atypical AD. The secondary objective was to determine if plasma biomarkers could differentiate patients with different atypical AD phenotypes and whether they were related to measures of disease severity. Methods We assessed whether plasma p-tau 181 and Aβ 42/40 were associated with Aβ and tau PET uptake, clinical phenotype and severity in 77 patients with PET biomarker-confirmed atypical AD. Results Plasma Aβ 42/40 ratio showed positive associations with tau PET uptake, with higher (more normal) Aβ 42/40 ratio associated with higher tau uptake; the ratio was not associated with Aβ PET. No associations were noted with plasma p-tau 181. Plasma Aβ 42/40 ratio and p-tau 181 concentrations were not associated with AD phenotype or cognitive severity. Conclusion Plasma Aβ 42/40 ratio and p-tau 181 concentrations are not associated with amyloid or tau PET or with clinical severity among individuals presenting with atypical AD.

AbstractBackgroundBlood plasma metrics provide excellent biomarkers of the presence of Alzheimer’s disease (AD) pathology in population cohorts. However, it is less clear whether plasma metrics correlate with PET measures of AD pathology in cohorts of patients with advanced AD disease, particularly in those with atypical clinical presentations of AD.MethodSeventy‐seven patients (visual variant=43, language variant=32, motor variant=1 and dysexecutive variant=1) with PET biomarker‐confirmed atypical AD were recruited by the Neurodegenerative Research group at Mayo Clinic, Rochester, MN, underwent Aβ (Pittsburgh Compound‐B) and tau (18F‐flortaucipir) PET and provided a blood sample. Blood plasma analysis was performed to assess p‐tau 181 and Aβ42/40 ratio concentrations using the Quanterix Simoa platform. Multivariate linear regression models assessed the relationship between plasma concentrations and both global Aβ, atypical AD summary and regional tau PET measures. For each PET measure, two separate models were fit to assess the influence of each plasma biomarker separately, while the third model included all plasma measures to assess the combined influence of all biomarkers on PET uptake. To investigate differences in plasma concentrations between atypical AD phenotypes, we performed Mann‐Whitney’s test across the visual and language variants of AD.ResultPlasma Aβ42/40 ratio showed positive associations with tau PET uptake, specifically within precuneus, parietal and temporal regions and was not associated with Aβ PET. There was no relationship between plasma p‐tau 181 and Aβ or tau PET uptake. However, the model that included both plasma biomarkers showed that with the addition of p‐tau 181, all significant associations between Aβ42/40 ratio and regional tau uptake were weakened to trends. The Aβ42/40 ratio continued to show no relationship with global Aβ‐PET uptake and plasma p‐tau 181 showed no relationship to PET measures (Figure 1). Lastly, no significant difference in plasma Aβ42/40 and p‐tau 181 levels was noted between the visual and language variants of AD (Figure 2).ConclusionThe lack of associations between plasma concentrations and PET measures of Aβ and tau in this relatively advanced AD cohort may suggest that plasma concentrations have greater utility as diagnostic biomarkers of early AD as compared to advanced AD.

AbstractINTRODUCTIONGlial fibrillary acidic protein (GFAP) in plasma is a proxy for astrocytic activity and is elevated in amyloid‐β (Aβ)‐positive individuals, making GFAP a potential blood‐based biomarker for Alzheimer's disease (AD).METHODSWe assessed plasma GFAP in 72 Aβ‐positive participants diagnosed with the visual or language variant of AD who underwent Aβ‐ and tau‐PET. Fifty‐nine participants had follow‐up imaging. Linear regression was applied on GFAP and imaging quantities.RESULTSGFAP did not correlate with Aβ‐ or tau‐PET cross‐sectionally. There was a limited positive correlation between GFAP and rates of tau accumulation, particularly in the language variant of AD, although associations were weaker after removing one outlier patient with the highest GFAP level.DISCUSSIONAmong Aβ‐positive AD participants with atypical presentations, plasma GFAP did not correlate with levels of AD pathology on PET, suggesting that the associations between GFAP and AD pathology might plateau during the advanced phase of the disease.

AbstractBackgroundPhysical activity is associated with reduced risk for Alzheimer’s disease (AD). Aerobic exercise produced modest‐to‐moderate cognitive gains in older adults with mild cognitive impairment or AD dementia. In animal models, aerobic exercise modifies AD’s AT(N) biomarkers of Amyloid‐beta (Aβ), hyperphosphorylated Tau, and Neurodegeneration. However, most observational studies didn’t find significant associations between physical activity and AT(N) biomarkers. Few exercise trials included biomarkers, partially attributable to the prohibitive cost and invasiveness of cerebrospinal fluid or PET biomarkers and reported mixed effects on central AT(N) biomarkers. Plasma Aβ42/40 ratio, phosphorylated tau 181 (p‐tau181), and total tau (t‐tau) demonstrate robust correlations with central amyloid and tau levels and offer an opportunity for inclusion in exercise trials.MethodThis pilot study examined the preliminary effects of 6‐month aerobic exercise on plasma Aβ42/40 ratio, p‐tau181, and t‐tau in older adults with mild‐to‐moderate AD dementia. Twenty‐six participants were eligible, and all consented to enroll (8 in stretching, 18 in cycling). Plasma Aβ42/40 ratio, p‐tau181, and t‐tau were measured using Simoa™ assays at baseline, 3, and 6 months. Data were analyzed using Cohen’s d, multilevel model, and intention‐to‐treat.ResultThe sample averaged 77.58±6.99 years old, 15.44±3.00 years of education, 65% male, and 96.2% carrying an APOE e4 allele. The 6‐month within‐group trajectories of changes in outcomes trended differently but were not statistically significant. Aβ42/40 ratio (mean ± standard deviation) increased by 0.001±0.012, p‐tau181 increased by 0.609±1.417 pg/ml, and t‐tau decreased by 0.020±0.279 ng/ml in the stretching group, while Aβ42/40 ratio decreased by 0.001±0.010, p‐tau181 increased by 0.101±1.579 pg/ml, and t‐tau decreased by 0.075±0.215 pg/ml in the cycling group. Between‐group differences were not significant. Effect sizes for 6‐month within‐group changes were small except for p‐tau181 in stretching (d = 0.43 [‐.65, 1.45]) and t‐tau in cycling (‐0.35 [‐0.87, 0.17]). Most 6‐month between‐group effect sizes were also small except for p‐tau181 (d = .40 [‐.70, 1.51]) and t‐tau (d = .53 [‐.40, 1.46]), a trend favoring cycling.ConclusionBlood biomarkers are highly feasible and tolerable. Exercise modalities may affect AD plasma biomarkers differently. Aerobic exercise may reduce p‐tau181 levels and stretching exercise may improve Aβ42/40 ratio, which need to be validated in future trials.

Background: Utilities of blood-based biomarkers in Alzheimer’s disease (AD) clinical trials remain unknown. Objective: To evaluate the ability of plasma neurofilament light chain (NfL) to predict future declines in cognition and activities of daily living (ADL) outcomes in 26 older adults with mild-to-moderate AD dementia from the FIT-AD Trial. Methods: Plasma NfL was measured at baseline and 3 and 6 months. Cognition and ADL were assessed using the AD Assessment Scale-Cognition (ADAS-Cog) and AD Uniform Dataset Instruments and Disability Assessment for Dementia (DAD), respectively, at baseline, 3, 6, 9, and 12 months. Linear mixed effects models were used to examine the associations between baseline or change in plasma NfL and changes in outcomes. Results: Higher baseline plasma NfL was associated with greater rate of decline in ADAS-Cog from baseline to 6 months (standardized estimate of 0.00462, p = 0.02853) and in ADL from baseline to 12 months (standardized estimate of –0.00284, p = 0.03338). Greater increase in plasma NfL in short term from baseline to 3 months was associated with greater rate of decline in memory and ADL from 3 to 6 months (standardized estimate of –0.04638 [0.003], p = 0.01635; standardized estimate of –0.03818, p = 0.0435) and greater rate of decline in ADL from 3 to 12 month (standardized estimate of –0.01492, p = 0.01082). Conclusion: This study demonstrated that plasma NfL might have the potential to predict cognitive and function decline up to 12 months. However, future studies with bigger sample sizes need to confirm the findings.

Abstract Background: Alzheimer’s disease (AD) is an epidemic with tremendous public health impacts because there are currently no disease-modifying therapeutics. Randomized controlled trials (RCTs) for prevention of AD dementia often use clinical endpoints that take years to manifest (e.g., cognition) or surrogate endpoints that are costly or invasive (e.g., magnetic resonance imaging [MRI]). Blood biomarkers represent a clinically applicable alternative surrogate endpoint for RCTs that would be both cost-effective and minimally invasive, but little is known about their value as surrogate endpoints for treatment responses in the prevention of AD dementia. Methods: The objective of this study is to investigate blood neuropathological, neurodegenerative, and neurotrophic biomarkers as surrogate endpoints for treatment responses to 3 interventions in older adults with amnestic mild cognitive impairment (aMCI, a prodromal stage of AD): aerobic exercise; cognitive training; and combined aerobic exercise and cognitive training (ACT). We chose these three sets of biomarkers for their unique mechanistic associations with AD pathology, neurodegeneration and neurogenesis. This study is built on the ACT Trial (1R01AG055469), a single-blinded, multi-site, 2×2 factorial Phase II RCT that examines the synergistic effects of a 6-month ACT intervention on cognition and MRI biomarkers (AD-signature cortical thickness and hippocampal volume) (n=128). In this ACT Trial Blood Biomarkers Study, we will enroll 120 ACT Trial aMCI participants and measure blood biomarkers at baseline, 3, 6, 12 and 18 months. The goals are to: (1) Determine the effect of interventions on blood biomarkers over 6 months; (2) Evaluate blood biomarkers as surrogate endpoints for predicting cognitive responses to interventions over 18 months; and (3; exploratory) Examine blood biomarkers as surrogate endpoints for predicting brain MRI biomarker responses to interventions over 18 months. Discussion: This study aims to identify new blood biomarkers that can track cognitive decline or AD-related brain atrophy among aMCI patients subjected to a regimen of aerobic exercise and cognitive training. Findings from this study will drive the further use of blood biomarkers in developing effective prevention and treatment strategies for AD dementia. Trial registration number: This study is an ancillary study of the ACT Trial which was registered with ClinicalTrials.gov, NCT03313895.

Abstract Background: Alzheimer’s disease (AD) is an epidemic with tremendous public health impacts because there are currently no disease-modifying therapeutics. Randomized controlled trials (RCTs) for prevention of AD dementia often use clinical endpoints that take years to manifest (e.g., cognition) or surrogate endpoints that are costly or invasive (e.g., magnetic resonance imaging [MRI]). Blood biomarkers represent a clinically applicable alternative surrogate endpoint for RCTs that would be both cost-effective and minimally invasive, but little is known about their value as surrogate endpoints for treatment responses in the prevention of AD dementia. Methods: The objective of this study is to investigate blood neuropathological, neurodegenerative, and neurotrophic biomarkers as surrogate endpoints for treatment responses to 3 interventions in older adults with amnestic mild cognitive impairment (aMCI, a prodromal stage of AD): aerobic exercise; cognitive training; and combined aerobic exercise and cognitive training (ACT). We chose these three sets of biomarkers for their unique mechanistic associations with AD pathology, neurodegeneration and neurogenesis. This study is built on the ACT Trial (1R01AG055469), a single-blinded, multi-site, 2×2 factorial Phase II RCT that examines the synergistic effects of a 6-month ACT intervention on cognition and MRI biomarkers (AD-signature cortical thickness and hippocampal volume) (n=128). In this ACT Trial Blood Biomarkers Study, we will enroll 120 ACT Trial aMCI participants and measure blood biomarkers at baseline, 3, 6, 12 and 18 months. The goals are to: (1) Determine the effect of interventions on blood biomarkers over 6 months; (2) Evaluate blood biomarkers as surrogate endpoints for predicting cognitive responses to interventions over 18 months; and (3; exploratory) Examine blood biomarkers as surrogate endpoints for predicting brain MRI biomarker responses to interventions over 18 months. Discussion: This study aims to identify new blood biomarkers that can track cognitive decline or AD-related brain atrophy among aMCI patients subjected to a regimen of aerobic exercise and cognitive training. Findings from this study will drive the further use of blood biomarkers in developing effective prevention and treatment strategies for AD dementia. Trial registration number: This study is an ancillary study of the ACT Trial which was registered with ClinicalTrials.gov, NCT03313895.