Journal of Alzheimer's disease : JAD
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Cumulative evidence of gray matter abnormalities in semantic dementia (SD) has been reported using voxel-based morphometry (VBM). However, these studies have not been reviewed quantitatively. To estimate gray matter changes in SD quantitatively, we systematically searched whole-brain VBM studies comparing SD patients with healthy controls in the PubMed, ISI Web of Science, and EMABSE databases from January 1990 to August 2011. ⋯ Gray matter volume reductions were found in bilateral fusiform and inferior temporal gyri, extending to the medial portion of the temporal lobes (including amygdala and parahippocampal gyri), left temporal pole, middle temporal gyrus, and caudate. No significant increase in gray matter volume was found. Our findings provide strong evidence of atrophy in bilateral temporal lobes with predominate impairment on the left side, parahippocampal gyrus/amygdala, and left caudate, representing the pathophysiology of SD.
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Cognitive reserve is invoked to explain the protective effects of education and cognitively-stimulating activities against all-cause dementia and Alzheimer's disease (AD). For non-native English speakers (n-NES), speaking English may be a cognitive activity associated with lower dementia risk. We hypothesized that n-NES have lower risk of incident dementia/AD and that educational level might modify this relationship. ⋯ Results were similar for AD. Stratification of education into three groups revealed increased risk of dementia for n-NES with ≥ 16 years of education (HR 3.97; 95% CI 1.62-9.75; p = 0.003). We conclude that n-NES status does not appear to have an independent protective effect against incident dementia/AD, and that n-NES status may contribute to risk of dementia in an education-dependent manner.
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Medial temporal lobe and temporoparietal brain regions are among the earliest neocortical sites to undergo pathophysiologic alterations in Alzheimer's disease (AD), although the underlying white matter changes in these regions is less well known. We employed diffusion tensor imaging to evaluate early alterations in regional white matter integrity in participants diagnosed with mild cognitive impairment (MCI). The following regions of interests (ROIs) were examined: 1) anterior cingulum (AC); 2) posterior cingulum (PC); 3) genu of the corpus callosum; 4) splenium of the corpus callosum; and 5) as a control site for comparison, posterior limb of the internal capsule. ⋯ PC FA was also significantly positively correlated with hippocampal volume as well as with performance on tests of verbal memory, whereas stroke risk was significantly correlated with genu FA and was unrelated to PC FA. When investigating subtypes of our MCI population, amnestic MCI participants showed lower PC white matter integrity relative to those with non-amnestic MCI. Findings implicate involvement of posterior microstructural white matter degeneration in the development of MCI-related cognitive changes and suggest that reduced FA of the PC may be a candidate neuroimaging marker of AD risk.
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Iron abnormalities are observed in the brains of Alzheimer's disease (AD) patients, but it is unclear whether common disorders of systemic iron overload such as hemochromatosis alter risks of AD. We used microarrays and real-time reverse transcription-PCR to investigate changes in the brain transcriptome of adult Hfe-/- mice, a model of hemochromatosis, relative to age- and gender-matched wildtype controls. Classification by functional pathway analysis revealed transcript changes for various genes important in AD. ⋯ The effects appeared relatively specific for AD in that few genes pertaining to other important neurodegenerative diseases, notably Parkinson's disease and Huntington's disease, or to inflammation, oxidative stress, or apoptosis, showed altered transcript levels. The observed effects on AD-related gene transcripts do not appear to be consistent with increased AD risk in HFE hemochromatosis and might, if anything, be predicted to protect against AD to some extent. As Hfe-/- mice did not have higher brain iron levels than wildtype controls, these studies highlight the need for further research in models of more severe hemochromatosis with brain iron loading.
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Alzheimer's disease (AD) is characterized by progressive cognitive deficits, accumulation of amyloid-β (Aβ) and intracellular neurofibrillary tangles, and neuronal death. Additionally, mitochondrial dysfunction and free radical damage are hallmarks of AD brain. Here we set out to define the role of oxidative stress in AD pathogenesis and progression by chronically treating 3xTg-AD mice with the superoxide dismutase (SOD)/catalase mimetic, EUK-207. ⋯ The effects of a 3-month treatment after pathology onset at 9 months on cognitive performance, brain oxidative stress, Aβ, and tau pathology were also evaluated. EUK-207-treated 3xTg-AD mice did not display any deficit in fear conditioning and were protected against increases in brain levels of oxidized nucleic acids and lipid peroxidation; they also had reduced Aβ, tau, and hyperphosphorylated tau accumulation in amygdala and hippocampus. Our results confirm a critical role for oxidative stress in AD pathogenesis and progression and suggest the potential usefulness of EUK-207 in AD treatment.