Engler, H. et al. Two-year follow-up of amyloid deposition in patients with Alzheimer's disease. Brain 129, 2856-2866

Department of Psychology, Stockholm University, Tukholma, Stockholm, Sweden
Brain (Impact Factor: 9.2). 11/2006; 129(Pt 11):2856-66. DOI: 10.1093/brain/awl178
Source: PubMed


Beta amyloid is one of the major histopathological hallmarks of Alzheimer's disease. We recently reported in vivo imaging of amyloid in 16 Alzheimer patients, using the PET ligand N-methyl[11C]2-(4'-methylaminophenyl)-6-hydroxy-benzothiazole (PIB). In the present study we rescanned these 16 Alzheimer patients after 2.0 +/- 0.5 years and have described the interval change in amyloid deposition and regional cerebral metabolic rate for glucose (rCMRGlc) at follow-up. Sixteen patients with Alzheimer's disease were re-examined by means of PET, using PIB and 2-[18F]fluoro-2-deoxy-d-glucose (FDG) after 2.0 +/- 0.5 years. The patients were all on cholinesterase inhibitor treatment and five also on treatment with the N-methyl-d-aspartate (NMDA) antagonist memantine. In order to estimate the accuracy of the PET PIB measurements, four additional Alzheimer patients underwent repeated examinations with PIB within 20 days (test-retest). Relative PIB retention in cortical regions differed by 3-7% in the test-retest study. No significant difference in PIB retention was observed between baseline and follow-up while a significant (P < 0.01) 20% decrease in rCMRGlc was observed in cortical brain regions. A significant negative correlation between rCMRGlc and PIB retention was observed in the parietal cortex in the Alzheimer patients at follow-up (r = 0.67, P = 0.009). A non-significant decline in Mini-Mental State Examination (MMSE) score from 24.3 +/- 3.7 (mean +/- standard deviation) to 22.7 +/- 6.1 was measured at follow-up. Five of the Alzheimer patients showed a significant decline in MMSE score of >3 (21.4 +/- 3.5 to 15.6 +/- 3.9, P < 0.01) (AD-progressive) while the rest of the patients were cognitively more stable (MMSE score = 25.6 +/- 3.1 to 25.9 +/- 3.7) (AD-stable) compared with baseline. A positive correlation (P = 0.001) was observed in the parietal cortex between Rey Auditory Verbal Learning (RAVL) test score and rCMRGlc at follow-up while a negative correlation (P = 0.018) was observed between RAVL test and PIB retention in the parietal at follow-up. Relatively stable PIB retention after 2 years of follow-up in patients with mild Alzheimer's disease suggests that amyloid deposition in the brain reaches a plateau by the early clinical stages of Alzheimer's disease and therefore may precede a decline in rCMRGlc and cognition. It appears that anti-amyloid therapies will need to induce a significant decrease in amyloid load in order for PIB PET images to detect a drug effect in Alzheimer patients. FDG imaging may be able to detect a stabilization of cerebral metabolism caused by therapy administered to patients with a clinical diagnosis of Alzheimer's disease.

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    • "For instance, Lowe et al. (2014) studied only healthy controls, whereas Furst et al. (2012) focused on subjects with Alzheimer's disease. A second source for the discrepancies may be the limited sample sizes of most studies: with the exception of Lowe et al. (2014), previous studies comprised fewer than 100 subjects and the specific regional analysis within a single disease group did typically not exceed two dozen subjects (Engler et al., 2006; Edison et al. 2007; Li et al., 2008; Cohen et al., 2009; La Joie et al., 2012). Moreover, many studies relied on a plain correlation analysis between the regional tracer intensities without correcting for cofounders such as age, sex, education and extent of amyloid pathology. "
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    ABSTRACT: In its original form, the amyloid cascade hypothesis of Alzheimer's disease holds that fibrillar deposits of amyloid are an early, driving force in pathological events leading ultimately to neuronal death. Early clinicopathological investigations highlighted a number of inconsistencies leading to an updated hypothesis in which amyloid plaques give way to amyloid oligomers as the driving force in pathogenesis. Rather than focusing on the inconsistencies, amyloid imaging studies have tended to highlight the overlap between regions that show early amyloid plaque signal on positron emission tomography and that also happen to be affected early in Alzheimer's disease. Recent imaging studies investigating the regional dependency between metabolism and amyloid plaque deposition have arrived at conflicting results, with some showing regional associations and other not. We extracted multimodal neuroimaging data from the Alzheimer's disease neuroimaging database for 227 healthy controls and 434 subjects with mild cognitive impairment. We analysed regional patterns of amyloid deposition, regional glucose metabolism and regional atrophy using florbetapir ((18)F) positron emission tomography, (18)F-fluordeoxyglucose positron emission tomography and T1-weighted magnetic resonance imaging, respectively. Specifically, we derived grey matter density and standardized uptake value ratios for both positron emission tomography tracers in 404 functionally defined regions of interest. We examined the relation between regional glucose metabolism and amyloid plaques using linear models. For each region of interest, correcting for regional grey matter density, age, education and disease status, we tested the association of regional glucose metabolism with (i) cortex-wide florbetapir uptake; (ii) regional (i.e. in the same region of interest) florbetapir uptake; and (iii) regional florbetapir uptake while correcting in addition for cortex-wide florbetapir uptake. P-values for each setting were Bonferroni corrected for 404 tests. Regions showing significant hypometabolism with increasing cortex-wide amyloid burden were classic Alzheimer's disease-related regions: the medial and lateral parietal cortices. The associations between regional amyloid burden and regional metabolism were more heterogeneous: there were significant hypometabolic effects in posterior cingulate, precuneus, and parietal regions but also significant positive associations in bilateral hippocampus and entorhinal cortex. However, after correcting for global amyloid burden, few of the negative associations remained and the number of positive associations increased. Given the wide-spread distribution of amyloid plaques, if the canonical cascade hypothesis were true, we would expect wide-spread, cortical hypometabolism. Instead, cortical hypometabolism appears to be linked to global amyloid burden. Thus we conclude that regional fibrillar amyloid deposition has little to no association with regional hypometabolism.
    Brain 09/2015; DOI:10.1093/brain/awv278 · 9.20 Impact Factor
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    • "© 2015 – IOS Press and the authors. All rights reserved mild AD than in healthy controls [19, 23–24] and appears to reach a plateau in the early stages of AD with no further significant progression over time [21] [22] [25] [26]. CSF biomarkers such as A and tau reflect the brain pathology in patients with AD [27]. "
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    ABSTRACT: New therapeutic strategies in Alzheimer's disease (AD) are focused on targeting amyloid-β (Aβ) to modify the underlying cause of the disease rather than just the symptoms. The aim of this study was to investigate the long-term effects of treatment with the anti-Aβ compound phenserine on (i) cerebrospinal fluid (CSF) biomarkers for Aβ and tau pathology and (ii) brain metabolism as assessed by the regional cerebral metabolic rate for glucose (rCMRglc), using positron emission tomography. Twenty patients with mild AD were included in the study and after 12 months treatment with phenserine, CSF Aβ 40 and α- and β-secretase-cleaved soluble amyloid-β protein precursor (sAβPP) levels had significantly increased and rCMRglc had stabilized. Levels of CSF Aβ 40 and sAβPP correlated positively with rCMRglc and cognition while CSF Aβ 42 levels, the Aβ 42/40 ratio, P-tau, and T-tau correlated negatively with rCMRglc and cognition. In summary, long-term phenserine treatment resulted in increased levels of CSF Aβ 40, sAβPPα, and sAβPPβ, which positively correlated with improvements in rCMRglc and cognition. The study illustrates the value of using biomarkers in the CSF and brain for evaluation of drug effects.
    Journal of Alzheimer's disease: JAD 09/2015; 47(3):691-704. DOI:10.3233/JAD-132474 · 4.15 Impact Factor
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    • "Pittsburgh compound B ( 11 C-PiB) is one of the most widely used, and allows for longitudinal and quantitative assessments of Ab accumulation in AD patients. 11 C-PiB has also been demonstrated to facilitate prediction of the conversion from mild cognitive impairment to AD, and serving for evaluation of anti-amyloid therapies (Klunk et al. 2004; Engler et al. 2006; Ikonomovic et al. 2008; Leinonen et al. 2008; Okello et al. 2009b). There are two main subtypes of senile plaques; non-classic plaques including diffuse and primitive plaques are not clearly associated with neurodegerative changes, while neuritic (classic/typical) plaques are often concurrent with dystrophic neurites and activation of inflammatory microglia (Bobinski et al. 1996; Rapp et al. 2010). "
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