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1.  TREM2 lipid sensing sustains microglia response in an Alzheimer’s disease model 
Cell  2015;160(6):1061-1071.
Summary
Triggering receptor expressed on myeloid cells 2 (TREM2) is a microglia surface receptor that triggers intracellular protein tyrosine phosphorylation. Recent genome-wide association studies have shown that a rare R47H mutation of TREM2 correlates with a substantial increase in the risk of developing Alzheimer's disease (AD). To address the basis for this genetic association, we studied TREM2 deficiency in the 5XFAD mouse model of AD. We found that TREM2 deficiency and haploinsufficiency augment β-amyloid (Aβ) accumulation due to dysfunctional response of microglia, which become apoptotic and fail to cluster around Aβ plaques. We further demonstrate that TREM2 senses a broad array of anionic and zwitterionic lipids known to associate with fibrillar Aβ in lipid membranes and to be exposed on the surface of damaged neurons. Remarkably, the R47H mutation impairs TREM2 detection of lipid ligands. Thus, TREM2 detects damage-associated lipid patterns associated with neurodegeneration, sustaining microglia response to Aβ accumulation.
doi:10.1016/j.cell.2015.01.049
PMCID: PMC4477963  PMID: 25728668
2.  A single dose of the γ-secretase inhibitor semagacestat alters the cerebrospinal fluid peptidome in humans 
Background
In Alzheimer’s disease, beta-amyloid peptides in the brain aggregate into toxic oligomers and plaques, a process which is associated with neuronal degeneration, memory loss, and cognitive decline. One therapeutic strategy is to decrease the production of potentially toxic beta-amyloid species by the use of inhibitors or modulators of the enzymes that produce beta-amyloid from amyloid precursor protein (APP). The failures of several such drug candidates by lack of effect or undesired side-effects underscore the importance to monitor the drug effects in the brain on a molecular level. Here we evaluate if peptidomic analysis in cerebrospinal fluid (CSF) can be used for this purpose.
Methods
Fifteen human healthy volunteers, divided into three groups, received a single dose of placebo or either 140 mg or 280 mg of the γ-secretase inhibitor semagacestat (LY450139). Endogenous peptides in CSF, sampled prior to administration of the drug and at six subsequent time points, were analyzed by liquid chromatography coupled to mass spectrometry, using isobaric labeling based on the tandem mass tag approach for relative quantification.
Results
Out of 302 reproducibly detected peptides, 11 were affected by the treatment. Among these, one was derived from APP and one from amyloid precursor-like protein 1. Nine peptides were derived from proteins that may not be γ-secretase substrates per se, but that are regulated in a γ-secretase-dependent manner.
Conclusions
These results indicate that a CSF peptidomic approach may be a valuable tool both to verify target engagement and to identify other pharmacodynamic effects of the drug. Data are available via ProteomeXchange with identifier PXD003075.
Trial registration
NCT00765115, registered 30/09/2008.
Electronic supplementary material
The online version of this article (doi:10.1186/s13195-016-0178-x) contains supplementary material, which is available to authorized users.
doi:10.1186/s13195-016-0178-x
PMCID: PMC4780148  PMID: 26948580
3.  Hyperglycemia modulates extracellular amyloid-β concentrations and neuronal activity in vivo 
The Journal of Clinical Investigation  2015;125(6):2463-2467.
Epidemiological studies show that patients with type 2 diabetes (T2DM) and individuals with a diabetes-independent elevation in blood glucose have an increased risk for developing dementia, specifically dementia due to Alzheimer’s disease (AD). These observations suggest that abnormal glucose metabolism likely plays a role in some aspects of AD pathogenesis, leading us to investigate the link between aberrant glucose metabolism, T2DM, and AD in murine models. Here, we combined two techniques — glucose clamps and in vivo microdialysis — as a means to dynamically modulate blood glucose levels in awake, freely moving mice while measuring real-time changes in amyloid-β (Aβ), glucose, and lactate within the hippocampal interstitial fluid (ISF). In a murine model of AD, induction of acute hyperglycemia in young animals increased ISF Aβ production and ISF lactate, which serves as a marker of neuronal activity. These effects were exacerbated in aged AD mice with marked Aβ plaque pathology. Inward rectifying, ATP-sensitive potassium (KATP) channels mediated the response to elevated glucose levels, as pharmacological manipulation of KATP channels in the hippocampus altered both ISF Aβ levels and neuronal activity. Taken together, these results suggest that KATP channel activation mediates the response of hippocampal neurons to hyperglycemia by coupling metabolism with neuronal activity and ISF Aβ levels.
doi:10.1172/JCI79742
PMCID: PMC4497756  PMID: 25938784
Endocrinology; Metabolism; Neuroscience
4.  Cerebrospinal Fluid Markers of Neurodegeneration and Rates of Brain Atrophy in Early Alzheimer Disease 
JAMA neurology  2015;72(6):656-665.
IMPORTANCE
Measures of neuronal loss are likely good surrogates for clinical and radiological disease progression in Alzheimer disease (AD). Cerebrospinal fluid (CSF) markers of neuronal injury or neurodegeneration may offer usefulness in predicting disease progression and guiding outcome assessments and prognostic decisions in clinical trials of disease-modifying therapies. Visinin-like protein 1 (VILIP-1) has demonstrated potential usefulness as a marker of neuronal injury in AD.
OBJECTIVE
To investigate the usefulness of CSF VILIP-1, tau, p-tau181, and Aβ42 levels in predicting rates of whole-brain and regional atrophy in early AD and cognitively normal control subjects over time.
DESIGN, SETTING, AND PARTICIPANTS
Longitudinal observational study of brain atrophy in participants with early AD and cognitively normal controls. Study participants had baseline CSF biomarker measurements and longitudinal magnetic resonance imaging assessments for a mean follow-up period of 2 to 3 years. Mixed linear models assessed the ability of standardized baseline CSF biomarker measures to predict rates of whole-brain and regional atrophy over the follow-up period. The setting was The Charles F. and Joanne Knight Alzheimer’s Disease Research Center, Washington University School of Medicine in St Louis. Participants (mean age, 72.6 years) were individuals with a clinical diagnosis of very mild AD (n = 23) and cognitively normal controls (n = 64) who were enrolled in longitudinal studies of healthy aging and dementia. The study dates were 2000 to 2010.
MAIN OUTCOMES AND MEASURES
Correlations between baseline CSF biomarker measures and rates of whole-brain or regional atrophy in the AD and control cohorts over the follow-up period.
RESULTS
Baseline CSF VILIP-1, tau, and p-tau181 levels (but not Aβ42 levels) predicted rates of whole-brain and regional atrophy in AD over the follow-up period. Baseline CSF VILIP-1 levels predicted whole-brain (P = .006), hippocampal (P = .01), and entorhinal (P = .001) atrophy rates at least as well as tau and p-tau181 in early AD. Cognitively normal controls whose CSF VILIP-1, tau, or p-tau181 levels were in the upper tercile had higher rates of whole-brain (P = .02, P = .003, and P = .02, respectively), hippocampal (P = .001, P = .01, and P = .02, respectively), and entorhinal (P = .007, P = .01, and P = .01, respectively) atrophy compared with those whose levels were in the lower 2 terciles.
CONCLUSIONS AND RELEVANCE
Cerebrospinal fluid VILIP-1 levels predict rates of whole-brain and regional atrophy similarly to tau and p-tau181 and may provide a useful CSF biomarker surrogate for neurodegeneration in early symptomatic and preclinical AD.
doi:10.1001/jamaneurol.2015.0202
PMCID: PMC4551490  PMID: 25867677
5.  Potential role of orexin and sleep modulation in the pathogenesis of Alzheimer’s disease 
The Journal of Experimental Medicine  2014;211(13):2487-2496.
Modulation of orexin and its effects on sleep/wakefulness affect amyloid-β pathology in the brain of mouse models for Alzheimer’s disease.
Age-related aggregation of amyloid-β (Aβ) is an upstream pathological event in Alzheimer’s disease (AD) pathogenesis, and it disrupts the sleep–wake cycle. The amount of sleep declines with aging and to a greater extent in AD. Poor sleep quality and insufficient amounts of sleep have been noted in humans with preclinical evidence of AD. However, how the amount and quality of sleep affects Aβ aggregation is not yet well understood. Orexins (hypocretins) initiate and maintain wakefulness, and loss of orexin-producing neurons causes narcolepsy. We tried to determine whether orexin release or secondary changes in sleep via orexin modulation affect Aβ pathology. Amyloid precursor protein (APP)/Presenilin 1 (PS1) transgenic mice, in which the orexin gene is knocked out, showed a marked decrease in the amount of Aβ pathology in the brain with an increase in sleep time. Focal overexpression of orexin in the hippocampus in APP/PS1 mice did not alter the total amount of sleep/wakefulness and the amount of Aβ pathology. In contrast, sleep deprivation or increasing wakefulness by rescue of orexinergic neurons in APP/PS1 mice lacking orexin increased the amount of Aβ pathology in the brain. Collectively, modulation of orexin and its effects on sleep appear to modulate Aβ pathology in the brain.
doi:10.1084/jem.20141788
PMCID: PMC4267230  PMID: 25422493
6.  Neurogranin as a Cerebrospinal Fluid Biomarker for Synaptic Loss in Symptomatic Alzheimer Disease 
JAMA neurology  2015;72(11):1275-1280.
IMPORTANCE
Neurogranin (NGRN) seems to be a promising novel cerebrospinal fluid (CSF) biomarker for synaptic loss; however, clinical, and especially longitudinal, data are sparse.
OBJECTIVE
To examine the utility of NGRN, with repeated CSF sampling, for diagnosis, prognosis, and monitoring of Alzheimer disease (AD).
DESIGN, SETTING, AND PARTICIPANTS
Longitudinal study of consecutive patients who underwent 2 lumbar punctures between the beginning of 1995 and the end of 2010 within the memory clinic–based Amsterdam Dementia Cohort. The study included 163 patients: 37 cognitively normal participants (mean [SE] age, 64 [2] years; 38% female; and mean [SE] Mini-Mental State Examination [MMSE] score, 28 [0.3]), 61 patients with mild cognitive impairment (MCI) (mean [SE] age, 68 [1] years; 38% female; and mean [SE] MMSE score, 27 [0.3]), and 65 patients with AD (mean [SE] age, 65 [1] years; 45% female; and mean [SE] MMSE score, 22 [0.7]). The mean (SE) interval between lumbar punctures was 2.0 (0.1) years, and the mean (SE) duration of cognitive follow-up was 3.8 (0.2) years. Measurements of CSF NGRN levels were obtained in January and February 2014.
MAIN OUTCOME AND MEASURE
Levels of NGRN in CSF samples.
RESULTS
Baseline CSF levels of NGRN in patients with AD (median level, 2381 pg/mL [interquartile range, 1651-3416 pg/mL]) were higher than in cognitively normal participants (median level, 1712 pg/mL [interquartile range, 1206-2724 pg/mL]) (P = .04). Baseline NGRN levels were highly correlated with total tau and tau phosphorylated at threonine 181 in all patient groups (all P < .001), but not with Aβ42. Baseline CSF levels of NGRN were also higher in patients with MCI who progressed to AD (median level, 2842 pg/mL [interquartile range, 1882-3950 pg/mL]) compared with those with stable MCI (median level, 1752 pg/mL [interquartile range, 1024-2438 pg/mL]) (P = .004), and they were predictive of progression from MCI to AD (hazard ratio, 1.8 [95% CI, 1.1-2.9]; stratified by tertiles). Linear mixed-model analyses demonstrated that within-person levels of NGRN increased over time in cognitively normal participants (mean [SE] level, 90 [45] pg/mL per year; P < .05) but not in patients with MCI or AD.
CONCLUSIONS AND RELEVANCE
Neurogranin is a promising biomarker for AD because levels were elevated in patients with AD compared with cognitively normal participants and predicted progression from MCI to AD. Within-person levels of NGRN increased in cognitively normal participants but not in patients with later stage MCI or AD, which suggests that NGRN may reflect presymptomatic synaptic dysfunction or loss.
doi:10.1001/jamaneurol.2015.1867
PMCID: PMC4694558  PMID: 26366630
7.  Murine versus human apolipoprotein E4: differential facilitation of and co-localization in cerebral amyloid angiopathy and amyloid plaques in APP transgenic mouse models 
Introduction
Amyloid β (Aβ) accumulates in the extracellular space as diffuse and neuritic plaques in Alzheimer’s disease (AD). Aβ also deposits on the walls of arterioles as cerebral amyloid angiopathy (CAA) in most cases of AD and sometimes independently of AD. Apolipoprotein E (apoE) ɛ4 is associated with increases in both Aβ plaques and CAA in humans. Studies in mouse models that develop Aβ deposition have shown that murine apoE and human apoE4 have different abilities to facilitate plaque or CAA formation when studied independently. To better understand and compare the effects of murine apoE and human apoE4, we bred 5XFAD (line 7031) transgenic mice so that they expressed one copy of murine apoE and one copy of human apoE4 under the control of the normal murine apoE regulatory elements (5XFAD/apoEm/4).
Results
The 5XFAD/apoEm/4 mice contained levels of parenchymal CAA that were intermediate between 5XFAD/apoEm/m and 5XFAD/apoE4/4 mice. In 5XFAD/apoEm/4 mice, we found that Aβ parenchymal plaques co-localized with much more apoE than did parenchymal CAA, suggesting differential co-aggregation of apoE with Aβ in plaques versus CAA. More importantly, within the brain parenchyma of the 5XFAD/apoEm/4 mice, plaques contained more murine apoE, which on its own results in more pronounced and earlier plaque formation, while CAA contained more human apoE4 which on its own results in more pronounced CAA formation. We further confirmed the co-aggregation of mouse apoE with Aβ in plaques by showing a strong correlation between insoluble mouse apoE and insoluble Aβ in PS1APP-21/apoEm/4 mice which develop plaques without CAA.
Conclusions
These studies suggest that both murine apoE and human apoE4 facilitate differential opposing effects in influencing Aβ plaques versus CAA via different co-aggregation with these two amyloid lesions and set the stage for understanding these effects at a molecular level.
Electronic supplementary material
The online version of this article (doi:10.1186/s40478-015-0250-y) contains supplementary material, which is available to authorized users.
doi:10.1186/s40478-015-0250-y
PMCID: PMC4641345  PMID: 26556230
Alzheimer’s disease; Apolipoprotein E; Amyloid plaques; Cerebral amyloid angiopathy
8.  Analysis of in vivo turnover of tau in a mouse model of tauopathy 
Background
Intracellular accumulation of tau as neurofibrillary tangles (NFTs) is the hallmark of Alzheimer’s disease (AD) as well as in other tauopathies. Tau is present not only in the cytoplasm but also in the extracellular space such as cerebrospinal fluid (CSF) and brain interstitial fluid (ISF). Although clearance is one critical parameter leading to such intracellular/extracellular tau accumulation, in vivo turnover of tau has not been well characterized. The current study has attempted to precisely determine in vivo turnover rates of tau utilizing tet-off regulatable mice. In particular, we assessed intracellular tau and extracellular tau, soluble tau, insoluble tau and phosphorylated tau at certain sites utilizing a combination of in vivo microdialysis, biochemical analysis and specific ELISAs recognizing each species. To examine the effect of a tauopathy-associated mutation on tau clearance, half-lives of various tau species were compared between the mice with a FTDP-17 mutation that induces β-sheet formation, ΔK280 mutation (pro-aggregant mice) and control mice with additional β-sheet breaking mutations (anti-aggregant mice).
Results
Here we report that tau is metabolized at much slower turnover rates in vivo than in cell culture. We found that insoluble tau in pro-aggregant mice had a significantly slower half-life (t1/2 = ~34.2 days) than soluble tau (t1/2 = ~9.7 days). In contrast, soluble tau phosphorylated in the proline rich region was cleared faster than total soluble tau. When comparing pro-aggregant mice to anti-agregant mice, turnover rates of soluble tau species were not significantly different.
Conclusions
The current study provides a comprehensive description of in vivo turnover of various tau species present in mice that express human tau. The turnover rate of soluble tau was not significantly altered between pro-aggregant mice and anti-aggregant mice. This suggests that altered conformation by ΔK280 does not have a major impact on clearance pathways for soluble tau. In contrast, different tau species displayed different half-lives. Turnover was significantly delayed for insoluble tau whereas it was accelerated for soluble tau phosphorylated in the proline rich region. These differences in susceptibilities to clearance suggest that aggregation and phosphorylation influences tau clearance which may be important in tau pathogenesis.
doi:10.1186/s13024-015-0052-5
PMCID: PMC4621881  PMID: 26502977
Alzheimer’s disease; Clearance; Half-life; Extracellular tau; Tauopathy model
9.  Anti-tau antibody reduces insoluble tau and decreases brain atrophy 
Objective
We previously found a strong reduction in tau pathology and insoluble tau in P301S tau transgenic mice following intracerebroventricular infusion of the anti-tau antibody HJ8.5. We sought to determine the effects of HJ8.5 in the same model following peripheral administration.
Methods
The primary objective was to determine if HJ8.5 administered at a dose of 50 mg kg−1 week−1 by intraperitoneal (IP) injection to 6-month-old P301S mice for 3 months would influence phospho-tau (p-tau) accumulation, tau insolubility, and neurodegeneration.
Results
Treatment with HJ8.5 at 50 mg/kg showed a very strong decrease in detergent-insoluble tau. Importantly, HJ8.5 significantly reduced the loss of cortical and hippocampal tissue volumes compared to control treated mice. HJ8.5 treatment reduced hippocampal CA1 cellular layer staining with the p-tau antibody AT8 and thio-S-positive tau aggregates in piriform cortex and amygdala. Moreover, mice treated with HJ8.5 at 50 mg/kg showed a decrease in motor/sensorimotor deficits compared to vehicle-treated mice. Some effects of HJ8.5, including reduction in brain atrophy, and p-tau immunostaining were also seen with a dose of 10 mg kg−1 week−1. In BV2-microglial cells, we observed significantly higher uptake of P301S tau aggregates in the presence of HJ8.5. HJ8.5 treatment also resulted in a large dose-dependent increase of tau in the plasma.
Interpretation
Our results indicate that systemically administered anti-tau antibody HJ8.5 significantly decreases insoluble tau, decreases brain atrophy, and improves motor/sensorimotor function in a mouse model of tauopathy. These data further support the idea that anti-tau antibodies should be further assessed as a potential treatment for tauopathies.
doi:10.1002/acn3.176
PMCID: PMC4369277  PMID: 25815354
10.  In Vivo Microdialysis Reveals Age-Dependent Decrease of Brain Interstitial Fluid Tau Levels in P301S Human Tau Transgenic Mice 
Although tau is a cytoplasmic protein, it is also found in brain extracellular fluids, e.g., CSF. Recent findings suggest that aggregated tau can be transferred between cells and extracellular tau aggregates might mediate spread of tau pathology. Despite these data, details of whether tau is normally released into the brain interstitial fluid (ISF), its concentration in ISF in relation to CSF, and whether ISF tau is influenced by its aggregation are unknown. To address these issues, we developed a microdialysis technique to analyze monomeric ISF tau levels within the hippocampus of awake, freely moving mice. We detected tau in ISF of wild-type mice, suggesting that tau is released in the absence of neurodegeneration. ISF tau was significantly higher than CSF tau and their concentrations were not significantly correlated. Using P301S human tau transgenic mice (P301S tg mice), we found that ISF tau is fivefold higher than endogenous murine tau, consistent with its elevated levels of expression. However, following the onset of tau aggregation, monomeric ISF tau decreased markedly. Biochemical analysis demonstrated that soluble tau in brain homogenates decreased along with the deposition of insoluble tau. Tau fibrils injected into the hippocampus decreased ISF tau, suggesting that extracellular tau is in equilibrium with extracellular or intracellular tau aggregates. This technique should facilitate further studies of tau secretion, spread of tau pathology, the effects of different disease states on ISF tau, and the efficacy of experimental treatments.
doi:10.1523/JNEUROSCI.2569-11.2011
PMCID: PMC4299126  PMID: 21917794
11.  Cerebrospinal fluid VILIP-1 and YKL-40, candidate biomarkers to diagnose, predict and monitor Alzheimer’s disease in a memory clinic cohort 
Introduction
We examined the utility of cerebrospinal fluid (CSF) proteins, Chitinase-3-like protein 1 (CHI3L1 or YKL-40), a putative marker of inflammation, and Visinin-like protein-1 (VILIP-1), a marker for neuronal injury, for diagnostic classification and monitoring of disease progression in a memory clinic cohort.
Methods
CSF levels of YKL-40 and VILIP-1 were measured in 37 cognitively normal, 61 Mild Cognitive Impairment (MCI) and 65 Alzheimer’s disease (AD) patients from the memory clinic-based Amsterdam Dementia Cohort who underwent two lumbar punctures, with minimum interval of 6 months and a mean(SE) interval of 2.0(0.1) years. Mean(SE) cognitive follow-up was 3.8 (0.2) years. ANOVA was used to compare baseline differences of log-transformed CSF measures. Cox proportional hazard models were used to evaluate disease progression as a function of CSF tertiles. Linear mixed models were used to evaluate longitudinal change over time. All analyses were sex and age adjusted.
Results
Baseline levels of YKL-40, but not VILIP-1, were higher in MCI and AD patients compared to cognitively normal individuals (mean (SE) pg/mL, 304 (16) and 288 (12) vs. 231 (16), p = 0.03 and p = 0.006). Baseline levels of both YKL-40 and VILIP-1 in MCI predicted progression to AD (HR 95 % CI = 3.0 (1.1–7.9) and 4.4 (1.5–13.0), respectively, for highest vs. lowest tertile). YKL-40 increased longitudinally in patients with MCI and AD (mean (SE) pg/mL per year, 8.9 (3.0) and 7.1 (3.1), respectively), but not in cognitively normal individuals, whereas levels of VILIP-1 increased only in MCI (mean (SE), 10.7 (2.6) pg/mL per year).
Conclusions
CSF levels of YKL-40 may have utility for discriminating between cognitively normal individuals and patients with MCI or AD. Increased levels of both YKL-40 and VILIP-1 may be associated with disease progression. These CSF biomarkers should be considered for future evaluation in the characterization of the natural history of AD.
doi:10.1186/s13195-015-0142-1
PMCID: PMC4574487  PMID: 26383836
12.  Longitudinal Cerebrospinal Fluid Biomarker Changes in Preclinical Alzheimer Disease During Middle Age 
JAMA neurology  2015;72(9):1029-1042.
IMPORTANCE
Individuals in the presymptomatic stage of Alzheimer disease (AD) are increasingly being targeted for AD secondary prevention trials. How early during the normal life span underlying AD pathologies begin to develop, their patterns of change over time, and their relationship with future cognitive decline remain to be determined.
OBJECTIVE
To characterize the within-person trajectories of cerebrospinal fluid (CSF) biomarkers of AD over time and their association with changes in brain amyloid deposition and cognitive decline in cognitively normal middle-aged individuals.
DESIGN, SETTING, AND PARTICIPANTS
As part of a cohort study, cognitively normal (Clinical Dementia Rating [CDR] of 0) middle-aged research volunteers (n = 169) enrolled in the Adult Children Study at Washington University, St Louis, Missouri, had undergone serial CSF collection and longitudinal clinical assessment (mean, 6 years; range, 0.91–11.3 years) at 3-year intervals at the time of analysis, between January 2003 and November 2013. A subset (n = 74) had also undergone longitudinal amyloid positron emission tomographic imaging with Pittsburgh compound B (PiB) in the same period. Serial CSF samples were analyzed for β-amyloid 40 (Aβ40), Aβ42, total tau, tau phosphorylated at threonine 181 (P-tau181), visinin-like protein 1 (VILIP-1), and chitinase-3-like protein 1 (YKL-40). Within-person measures were plotted according to age and AD risk defined by APOE genotype (ε4 carriers vs noncarriers). Linear mixed models were used to compare estimated biomarker slopes among middle-age bins at baseline (early, 45–54 years; mid, 55–64 years; late, 65–74 years) and between risk groups. Within-person changes in CSF biomarkers were also compared with changes in cortical PiB binding and progression to a CDR higher than 0 at follow-up.
MAIN OUTCOMES AND MEASURES
Changes in Aβ40, Aβ42, total tau, P-tau181, VILIP-1, and YKL-40 and, in a subset of participants, changes in cortical PiB binding.
RESULTS
While there were no consistent longitudinal patterns in Aβ40 (P = .001–.97), longitudinal reductions in Aβ42 were observed in some individuals as early as early middle age (P ≤ .05) and low Aβ42 levels were associated with the development of cortical PiB-positive amyloid plaques (area under receiver operating characteristic curve = 0.9352; 95% CI, 0.8895–0.9808), especially in mid middle age (P < .001). Markers of neuronal injury (total tau, P-tau181, and VILIP-1) dramatically increased in some individuals in mid and late middle age (P ≤ .02), whereas the neuroinflammation marker YKL-40 increased consistently throughout middle age (P ≤ .003). These patterns were more apparent in at-risk ε4 carriers (Aβ42 in an allele dose-dependent manner) and appeared to be associated with future cognitive deficits as determined by CDR.
CONCLUSIONS AND RELEVANCE
Longitudinal CSF biomarker patterns consistent with AD are first detectable during early middle age and are associated with later amyloid positivity and cognitive decline. Such measures may be useful for targeting middle-aged, asymptomatic individuals for therapeutic trials designed to prevent cognitive decline.
doi:10.1001/jamaneurol.2015.1285
PMCID: PMC4570860  PMID: 26147946
13.  The Binding of Apolipoprotein E to Oligomers and Fibrils of Amyloid-β Alters the Kinetics of Amyloid Aggregation 
Biochemistry  2014;53(40):6323-6331.
Deposition of amyloid-β (Aβ) in Alzheimer’s disease (AD) is strongly correlated with the APOE genotype. However, the role of apolipoprotein E (apoE) in Aβ aggregation has remained unclear. Here we have used different apoE preparations, such as recombinant protein or protein isolated from cultured astrocytes, to examine the effect of apoE on the aggregation of both Aβ1–40 and Aβ1–42. The kinetics of aggregation, measured by the loss of fluorescence of tetramethylrhodamine-labeled Aβ, is shown to be dramatically slowed by the presence of substoichiometric concentrations of apoE. Using these concentrations, we conclude that apoE binds primarily to and affects the growth of oligomers that lead to the nuclei required for fibril growth. At higher apoE concentrations, the protein also binds to Aβ fibrils, resulting in fibril stabilization and a slower rate of fibril growth. The aggregation of Aβ1–40 is dependent on the apoE isoform, being the most dramatic for apoE4 and less so for apoE3 and apoE2. Our results indicate that the detrimental role of apoE4 in AD could be related to apoE-induced stabilization of the soluble but cytotoxic oligomeric forms and intermediates of Aβ, as well as fibril stabilization.
doi:10.1021/bi5008172
PMCID: PMC4196732  PMID: 25207746
14.  Anti-ApoE Antibody Given after Plaque Onset Decreases Aβ Accumulation and Improves Brain Function in a Mouse Model of Aβ Amyloidosis 
The Journal of Neuroscience  2014;34(21):7281-7292.
Apolipoprotein E (apoE) is the strongest known genetic risk factor for late onset Alzheimer's disease (AD). It influences amyloid-β (Aβ) clearance and aggregation, which likely contributes in large part to its role in AD pathogenesis. We recently found that HJ6.3, a monoclonal antibody against apoE, significantly reduced Aβ plaque load when given to APPswe/PS1ΔE9 (APP/PS1) mice starting before the onset of plaque deposition. To determine whether the anti-apoE antibody HJ6.3 affects Aβ plaques, neuronal network function, and behavior in APP/PS1 mice after plaque onset, we administered HJ6.3 (10 mg/kg/week) or PBS intraperitoneally to 7-month-old APP/PS1 mice for 21 weeks. HJ6.3 mildly improved spatial learning performance in the water maze, restored resting-state functional connectivity, and modestly reduced brain Aβ plaque load. There was no effect of HJ6.3 on total plasma cholesterol or cerebral amyloid angiopathy. To investigate the underlying mechanisms of anti-apoE immunotherapy, HJ6.3 was applied to the brain cortical surface and amyloid deposition was followed over 2 weeks using in vivo imaging. Acute exposure to HJ6.3 affected the course of amyloid deposition in that it prevented the formation of new amyloid deposits, limited their growth, and was associated with occasional clearance of plaques, a process likely associated with direct binding to amyloid aggregates. Topical application of HJ6.3 for only 14 d also decreased the density of amyloid plaques assessed postmortem. Collectively, these studies suggest that anti-apoE antibodies have therapeutic potential when given before or after the onset of Aβ pathology.
doi:10.1523/JNEUROSCI.0646-14.2014
PMCID: PMC4028501  PMID: 24849360
Alzheimer's; amyloid; antibody; apolipoprotein E
15.  Neuroprotective role of SIRT1 in mammalian models of Huntington’s disease through activation of multiple SIRT1 targets 
Nature medicine  2011;18(1):153-158.
Huntington’s disease (HD) is a fatal neurodegenerative disorder caused by an expanded polyglutamine repeat in huntingtin (Htt) protein. Current management strategies temporarily relieve disease symptoms, but fail to affect the underlying disease progression. We previously demonstrated that calorie restriction ameliorated HD pathogenesis and slowed disease progression in HD mice1. We now report that overexpression of SIRT1, a mediator of beneficial metabolic effects of calorie restriction, protects neurons against mutant Htt toxicity, whereas reduction of SIRT1 exacerbates mutant Htt toxicity. Overexpression of SIRT1 significantly improves motor function, reduces brain atrophy, and attenuates mutant Htt-mediated metabolic abnormalities in both fragment and full-length HD mouse models. Further mechanistic studies suggest that SIRT1 prevents mutant Htt-induced decline in BDNF levels and its receptor Trk-B signaling, and restores medium spiny neuronal DARPP32 levels in the striatum. SIRT1 deacetylase activity is required for SIRT1-mediated neuroprotection in HD models. Notably, we demonstrate that mutant Htt interacts with SIRT1 and inhibits SIRT1 deacetylase activity. Inhibition of SIRT1 deacetylase activity results in hyperacetylation of SIRT1 substrates such as FOXO3a thereby inhibiting its prosurvival function. Overexpression of SIRT1 counteracts mutant Htt-induced deacetylase deficit, enhances deacetylation of FOXO3a, and facilitates cell survival. These findings demonstrate a neuroprotective role of SIRT1 in mammalian HD models, indicate key mediators of this protection, and open new avenues for the development of neuroprotective strategies in HD.
doi:10.1038/nm.2558
PMCID: PMC4551453  PMID: 22179319
16.  Anti-tau antibodies that block tau aggregate seeding in vitro markedly decrease pathology and improve cognition in vivo 
Neuron  2013;80(2):402-414.
Summary
Tau aggregation occurs in neurodegenerative diseases including Alzheimer's disease and many other disorders collectively termed tauopathies. Trans-cellular propagation of tau pathology, mediated by extracellular tau aggregates, may underlie pathogenesis of these conditions. P301S tau transgenic mice express mutant human tau protein, and develop progressive tau pathology. Using a cell-based biosensor assay, we screened anti-tau monoclonal antibodies for their ability to block seeding activity present in P301S brain lysates. We infused 3 effective antibodies or controls into the lateral ventricle of P301S mice for 3 months. The antibodies markedly reduced hyperphosphorylated, aggregated, and insoluble tau. They also blocked development of tau seeding activity detected in brain lysates using the biosensor assay, reduced microglial activation, and improved cognitive deficits. These data imply a central role for extracellular tau aggregates in the development of pathology. They also suggest immunotherapy specifically designed to block trans-cellular aggregate propagation will be a productive treatment strategy.
doi:10.1016/j.neuron.2013.07.046
PMCID: PMC3924573  PMID: 24075978
17.  The sleep–wake cycle and Alzheimer’s disease: what do we know? 
SUMMARY
Sleep–wake disturbances are a highly prevalent and often disabling feature of Alzheimer’s disease (AD). A cardinal feature of AD includes the formation of amyloid plaques, associated with the extracellular accumulation of the amyloid-β (Aβ) peptide. Evidence from animal and human studies suggests that Aβ pathology may disrupt the sleep–wake cycle, in that as Aβ accumulates, more sleep–wake fragmentation develops. Furthermore, recent research in animal and human studies suggests that the sleep–wake cycle itself may influence Alzheimer’s disease onset and progression. Chronic sleep deprivation increases amyloid plaque deposition, and sleep extension results in fewer plaques in experimental models. In this review geared towards the practicing clinician, we discuss possible mechanisms underlying the reciprocal relationship between the sleep–wake cycle and AD pathology and behavior, and present current approaches to therapy for sleep disorders in AD.
doi:10.2217/nmt.14.33
PMCID: PMC4257134  PMID: 25405649
Alzheimer’s; amyloid; amyloid-β; circadian; EEG; glia; hypocretin; orexin; sleep; wake
18.  Neuronal activity regulates extracellular tau in vivo 
Neuronal activity promotes the release of extracellular tau in vivo.
Tau is primarily a cytoplasmic protein that stabilizes microtubules. However, it is also found in the extracellular space of the brain at appreciable concentrations. Although its presence there may be relevant to the intercellular spread of tau pathology, the cellular mechanisms regulating tau release into the extracellular space are not well understood. To test this in the context of neuronal networks in vivo, we used in vivo microdialysis. Increasing neuronal activity rapidly increased the steady-state levels of extracellular tau in vivo. Importantly, presynaptic glutamate release is sufficient to drive tau release. Although tau release occurred within hours in response to neuronal activity, the elimination rate of tau from the extracellular compartment and the brain is slow (half-life of ∼11 d). The in vivo results provide one mechanism underlying neuronal tau release and may link trans-synaptic spread of tau pathology with synaptic activity itself.
doi:10.1084/jem.20131685
PMCID: PMC3949564  PMID: 24534188
19.  Apolipoprotein E Mediation of Neuro-inflammation in a Murine Model of Multiple Sclerosis 
Journal of neuroimmunology  2014;271(0):8-17.
Apolipoprotein E (ApoE) functions as a ligand in receptor-mediated endocytosis of lipoprotein particles and has been demonstrated to play a role in antigen presentation. To explore the contribution of ApoE during autoimmune central nervous system (CNS) demyelination, we examined the clinical, cellular immune function, and pathologic consequences of experimental autoimmune encephalomyelitis (EAE) induction in ApoE knockout (ApoE−/−) mice. We observed reduced clinical severity of EAE in ApoE −/− mice in comparison to WT mice that was concomitant with an early reduction of dendritic cells (DCs) followed by a reduction of additional innate cells in the spinal cord at the peak of disease without any differences in axonal damage. While T cell priming was enhanced in ApoE −/− mice, reduced severity of EAE was also observed in ApoE −/− recipients of encephalitogenic wild type T cells. Expression of ApoE during EAE was elevated within the CNS of wild type mice, particularly by innate cells such as DCs. Overall, ApoE promotes clinical EAE, likely by mediation of inflammation localized within the CNS.
doi:10.1016/j.jneuroim.2014.03.010
PMCID: PMC4042395  PMID: 24794230
EAE; Antigen Presentation; Apolipoprotein E; Dendritic Cells
20.  Missense variant in TREML2 protects against Alzheimer’s Disease 
Neurobiology of aging  2013;35(6):1510.e19-1510.e26.
TREM and TREM-like receptors are a structurally similar protein family encoded by genes clustered on chromosome 6p21.11. Recent studies have identified a rare coding variant (p.R47H) in TREM2 that confers a high risk for Alzheimer’s disease (AD). In addition, common SNPs in this genomic region are associated with cerebrospinal fluid (CSF) biomarkers for AD and a common intergenic variant found near the TREML2 gene has been identified to be protective for AD. However, little is known about the functional variant underlying the latter association or its relationship with the p.R47H. Here, we report comprehensive analyses using whole-exome sequencing data, CSF biomarker analyses, meta-analyses (16,254 cases and 20,052 controls) and cell-based functional studies to support the role of the TREML2 coding missense variant p.S144G (rs3747742) as a potential driver of the meta-analysis AD-associated GWAS signal. Additionally, we demonstrate that the protective role of TREML2 in AD is independent of the role of TREM2 gene as a risk factor for AD.
doi:10.1016/j.neurobiolaging.2013.12.010
PMCID: PMC3961557  PMID: 24439484
21.  Sleep quality and preclinical Alzheimer Disease 
JAMA neurology  2013;70(5):587-593.
Objective
Sleep and circadian problems are very common in Alzheimer Disease (AD). Recent animal studies suggest a bidirectional relationship between sleep and amyloid-β (Aβ), a key molecule involved in AD pathogenesis. This study tested whether Aβ deposition in preclinical AD, prior to the appearance of cognitive impairment, is associated with changes in quality or quantity of sleep.
Methods
Cognitively normal, middle-aged individuals (n=142) had sleep objectively measured using actigraphy for 2 weeks. Concurrent sleep diaries provided nap information. Cerebrospinal fluid Aβ42 levels were used to determine whether amyloid deposition was present or absent. Sleep parameters were assessed with regard to amyloid deposition.
Results
Amyloid deposition was associated with worse sleep quality, specifically worse sleep efficiency (% time in bed that was spent asleep), compared to those without amyloid deposition. In contrast, quantity of sleep was not different between groups, as measured by total sleep time. Frequent napping was associated with amyloid deposition.
Interpretation
Amyloid deposition in the preclinical stage of AD appears to be associated with worse sleep quality, but not with changes in sleep quantity.
doi:10.1001/jamaneurol.2013.2334
PMCID: PMC3676720  PMID: 23479184
22.  Ptau-Aβ42 ratio as a continuous trait for biomarker discovery for early stage Alzheimer’s disease in multiplex immunoassay panels of Cerebrospinal fluid 
Biological psychiatry  2014;75(9):723-731.
Background
Identification of the physiological changes that occur during the early stages of Alzheimer’s disease (AD) may provide critical insights for the diagnosis, prognosis and treatment of disease. Cerebrospinal fluid (CSF) biomarkers are a rich source of information that reflect the brain proteome.
Methods
We applied a novel approach to screen a panel of ~190 CSF analytes quantified by multiplex immunoassay and detected common associations in the Knight- Alzheimer’s Disease Research Center (ADRC;N=311) and the Alzheimer’s Disease Neuroimaging Initiative (ADNI;N=293) cohorts. CSF ptau181-Aβ42 ratio was used as a continuous trait, rather than case control status in these analyses.
Results
We demonstrate the ptau181-Aβ42 ratio has more statistical power than traditional modeling approaches and that the levels of CSF Fatty Acid Binding Protein (H-FABP) and 12 other correlated analytes increase as the disease progresses. These results were validated using the traditional case control status model. Stratification of our dataset demonstrated that increases in these analytes occur very early in the disease course and were apparent even in non-demented individuals with AD pathology (low ptau181, low Aβ42) compared to pathology-negative elderly control subjects (low ptau181, high Aβ42). FABP-Aβ42 ratio demonstrates a similar hazard ratio for disease conversion to ptau181-Aβ42 even though the overlap in classification is incomplete suggesting that FABP contributes independent information as a predictor
Conclusions
Our results clearly indicate that the approach presented here can be employed to correctly identify novel biomarkers for AD, and that CSF H-FABP levels start to increase at very early stages of the disease.
doi:10.1016/j.biopsych.2013.11.032
PMCID: PMC4007142  PMID: 24548642
Alzheimer’s disease; Biomarkers; cerebrospinal fluid (CSF); Ptau-Aβ42 ratio; Heart Fatty Acid binding protein; Brain Proteome - Rules Based Medicine Discovery Multi-Analyte Profile 1.0
24.  Functional connectivity and graph theory in preclinical Alzheimer’s disease 
Neurobiology of aging  2013;35(4):10.1016/j.neurobiolaging.2013.10.081.
Alzheimer’s disease (AD) has a long preclinical phase in which amyloid and tau cerebral pathology accumulate without producing cognitive symptoms. Resting state functional connectivity MRI (rs-fcMRI) has demonstrated that brain networks degrade during symptomatic AD. It is unclear to what extent these degradations exist prior to symptomatic onset. In this study, we investigated graph theory metrics of functional integration (path length), functional segregation (clustering coefficient), and functional distinctness (modularity) as a function of disease severity. Further, we assessed whether these graph metrics were affected in cognitively normal participants with cerebrospinal fluid evidence of preclinical AD. Clustering coefficient and modularity, but not path length, were reduced in AD. Cognitively normal participants who harbored AD biomarker pathology also showed reduced values in these graph measures, demonstrating brain changes similar to, but smaller than, symptomatic AD. Only modularity was significantly affected by age. We also demonstrate that AD has a particular effect on hub-like regions in the brain. We conclude that AD causes large-scale disconnection that is present before onset of symptoms.
doi:10.1016/j.neurobiolaging.2013.10.081
PMCID: PMC3880636  PMID: 24216223
Alzheimer’s disease; biomarker; functional connectivity; graph theory; resting-state
25.  Progress Update: Fluid and Imaging Biomarkers in Alzheimer’s Disease 
Biological psychiatry  2013;75(7):520-526.
Alzheimer’s disease (AD) is a growing health crisis around the world. While significant progress has been made in our understanding of AD pathogenesis, there is currently no effective treatment to delay the onset of or prevent the disease. The focus has now shifted to the identification and treatment of AD in the early clinical stages as well as before cognitive symptoms emerge – during the long preclinical stage. With this shift in focus, diagnosis of individuals with AD can be more accurate when clinical symptoms and signs are combined with biomarkers. Biomarkers can improve both the diagnostic and prognostic accuracy of AD and its differentiation from other neurodegenerative diseases. This review will discuss fluid and imaging biomarkers that have shown promise in such areas, as well as some of the current challenges that face the field.
doi:10.1016/j.biopsych.2013.07.031
PMCID: PMC3947397  PMID: 24012326
Alzheimer disease; biomarker; cerebrospinal fluid; neuroimaging; diagnosis; prognosis

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