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Inhibition of amyloid-β (Aβ) aggregation is an attractive therapeutic strategy for treatment of Alzheimer's disease (AD). We previously reported that vitamin A and β-carotene inhibit fibrillation of Aβ40 and Aβ42 (Ono et al, 2004, Exp Neurol). In this study, we firstly examined the effects of vitamin A (retinoic acid, retinol, and retinal), β-carotene, vitamin B2, vitamin B6, vitamin C, vitamin E, coenzyme Q10, and α-lipoic acid on oligomerization of Aβ40 and Aβ42 in vitro; vitamin A and β-carotene dose-dependently inhibited oligomerization of Aβ40 and Aβ42. Furthermore, retinoic acid decreased cellular toxicity by inhibition of Aβ42 oligomerization. Second, we analyzed how vitamin A inhibits Aβ aggregation by using fluorescence spectroscopy and thioflavin T assay with two Aβ fragments, Aβ1-16 and Aβ25-35. A fluorescence peak of retinoic acid was greatly restrained in the presence of Aβ25-35, and retinoic acid inhibited aggregation of Aβ25-35, but not of Aβ1-16, which suggest the specific binding of retinoic acid to the C-terminal portion of Aβ. Thus, vitamin A and β-carotene might be key molecules for prevention of AD.

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Background/Aim: Magnetic resonance imaging (MRI), cerebral blood flow single photon emission computed tomography (CBF-SPECT), fluorodeoxyglucose-positron emission tomography (FDG-PET) and cerebrospinal fluid (CSF) biomarkers are used for the diagnosis of Alzheimer’s disease (AD). We aimed to reveal the relative sensitivity of these tools in a memory clinic setting. Methods: In 207 patients with probable AD in our memory clinic, medial temporal lobe atrophy on MRI, hypoperfusion/hypometabolism of the parietotemporal lobe and posterior cingulate gyrus in ethylcysteinate dimer-CBF-SPECT/FDG-PET, and abnormalities of CSF amyloid β-protein 1–42, total tau and phosphorylated tau were evaluated as findings characteristic of AD. Results: The AD findings were observed in 77.4% of all AD patients with MRI, 81.6% with CBF-SPECT, 93.1% with FDG-PET and 94.0% with CSF biomarkers. At the stage of Clinical Dementia Rating (CDR) 0.5, CSF biomarkers were the most sensitive (90.0%); at the stage of CDR 1, FDG-PET (96.7%) and CSF biomarkers (95.5%) were highly sensitive. At the stage of CDR 2, all tools showed high positive percentages. Conclusion: The diagnosis of AD was most often supported by CSF biomarkers and FDG-PET at the early stage of dementia (CDR 1) and by CSF biomarkers at the earlier stage (CDR 0.5).