| 1. |
- Casaletto, K. B., et al.
(author)
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Neurogranin, a synaptic protein, is associated with memory independent of Alzheimer biomarkers
- 2017
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In: Neurology. - 0028-3878. ; 89:17, s. 1782-1788
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Journal article (peer-reviewed)abstract
- Objective: To determine the association between synaptic functioning as measured via neurogranin in CSF and cognition relative to established Alzheimer disease (AD) biomarkers in neurologically healthy older adults. Methods: We analyzed CSF concentrations of neurogranin, b-amyloid (Ab42), phosphorylated tau (p-tau), and total tau (t-tau) among 132 neurologically normal older adults (mean 64.5, range 55-85), along with bilateral hippocampal volumes and a measure of episodic memory (Auditory Verbal Learning Test, delayed recall). Univariable analyses examined the relationship between neurogranin and the other AD-related biomarkers. Multivariable regression models examined the relationship between neurogranin and delayed recall, adjusting for age and sex, and interaction terms (neurogranin 3 AD biomarkers). Results: Higher neurogranin concentrations were associated with older age (r 5 0.20, p 5 0.02), lower levels of p-tau and t-tau, and smaller hippocampal volumes (p>0.03), but not with CSF Ab42 (p 5 0.18). In addition, CSF neurogranin demonstrated a significant relationship with memory performance independent of the AD-related biomarkers; individuals with the lowest CSF neurogranin concentrations performed better on delayed recall than those with medium or high CSF neurogranin concentrations (p>0.01). Notably, CSF p-tau, t-tau, and Ab42 and hippocampal volumes were not significantly associated with delayed recall scores (p<0.40), and did not interact with neurogranin to predict memory (p<0.10). © 2017 The Author(s).
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| 2. |
- Darst, B. F., et al.
(author)
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Pathway-Specific Polygenic Risk Scores as Predictors of Amyloid-beta Deposition and Cognitive Function in a Sample at Increased Risk for Alzheimer's Disease
- 2017
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In: Journal of Alzheimers Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 55:2, s. 473-484
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Journal article (peer-reviewed)abstract
- Polygenic risk scores (PRSs) have been used to combine the effects of variants with small effects identified by genome-wide association studies. We explore the potential for using pathway-specific PRSs as predictors of early changes in Alzheimer's disease (AD)-related biomarkers and cognitive function. Participants were from the Wisconsin Registry for Alzheimer's Prevention, a longitudinal study of adults who were cognitively asymptomatic at enrollment and enriched for a parental history of AD. Using genes associated with AD in the International Genomics of Alzheimer's Project's meta-analysis, we identified clusters of genes that grouped into pathways involved in amyloid-beta (A beta) deposition and neurodegeneration: A beta clearance, cholesterol metabolism, and immune response. Weighted pathway-specific and overall PRSs were developed and compared to APOE alone. Mixed models were used to assess whether each PRS was associated with cognition in 1,200 individuals, cerebral A beta deposition measured using amyloid ligand (Pittsburgh compound B) positron emission imaging in 168 individuals, and cerebrospinal fluid A beta deposition, neurodegeneration, and tau pathology in 111 individuals, with replication performed in an independent sample. We found that PRSs including APOE appeared to be driven by the inclusion of APOE, suggesting that the pathway-specific PRSs used here were not more predictive than an overall PRS or APOE alone. However, pathway-specific PRSs could prove to be useful as more knowledge is gained on the genetic variants involved in specific biological pathways of AD.
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| 3. |
- Hoy, A. R., et al.
(author)
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Microstructural white matter alterations in preclinical Alzheimer's disease detected using free water elimination diffusion tensor imaging
- 2017
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In: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 12:3
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Journal article (peer-reviewed)abstract
- Brain changes associated with Alzheimer's disease (AD) begin decades before disease diagnosis. While beta-amyloid plaques and neurofibrillary tangles are defining features of AD, neuronal loss and synaptic pathology are closely related to the cognitive dysfunction. Brain imaging methods that are tuned to assess degeneration of myelinated nerve fibers in the brain (collectively called white matter) include diffusion tensor imaging (DTI) and related techniques, and are expected to shed light on disease-related loss of structural connectivity. Participants (N = 70, ages 47-76 years) from the Wisconsin Registry for Alzheimer's Prevention study underwent DTI and hybrid diffusion imaging to determine a free-water elimination (FWE-DTI) model. The study assessed the extent to which preclinical AD pathology affects brain white matter. Preclinical AD pathology was determined using cerebrospinal fluid (CSF) biomarkers. The sample was enriched for AD risk (APOE epsilon 4 and parental history of AD). AD pathology assessed by CSF analyses was significantly associated with altered microstructure on both DTI and FWE-DTI. Affected regions included frontal, parietal, and especially temporal white matter. The f-value derived from the FWE-DTI model appeared to be the most sensitive to the relationship between the CSF AD biomarkers and microstructural alterations in white matter. These findings suggest that white matter degeneration is an early pathological feature of AD that may have utility both for early disease detection and as outcome measures for clinical trials. More complex models of microstructural diffusion properties including FWE-DTI may provide increased sensitivity to early brain changes associated with AD over standard DTI.
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| 4. |
- Vogt, N. M., et al.
(author)
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Gut microbiome alterations in Alzheimer's disease
- 2017
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Journal article (peer-reviewed)abstract
- Alzheimer's disease (AD) is the most common form of dementia. However, the etiopathogenesis of this devastating disease is not fully understood. Recent studies in rodents suggest that alterations in the gut microbiome may contribute to amyloid deposition, yet the microbial communities associated with AD have not been characterized in humans. Towards this end, we characterized the bacterial taxonomic composition of fecal samples from participants with and without a diagnosis of dementia due to AD. Our analyses revealed that the gut microbiome of AD participants has decreased microbial diversity and is compositionally distinct from control age-and sex-matched individuals. We identified phylum-through genus-wide differences in bacterial abundance including decreased Firmicutes, increased Bacteroidetes, and decreased Bifidobacterium in the microbiome of AD participants. Furthermore, we observed correlations between levels of differentially abundant genera and cerebrospinal fluid (CSF) biomarkers of AD. These findings add AD to the growing list of diseases associated with gut microbial alterations, as well as suggest that gut bacterial communities may be a target for therapeutic intervention.
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