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The Alzheimer's disease biomarkers are neurochemical indicators used to assess the risk or presence of the disease. The biomarkers can be used to diagnose Alzheimer's disease (AD) in a very early stage, but they also provide objective and reliable measures of disease progress. It is imperative to diagnose AD disease as soon as possible, because neuropathologic changes of AD precede the symptoms by years. It is well known that beta amyloid (Aβ) is a good indicator of AD disease, which has facilitated doctors to accurately pre-diagnose cases of AD disease. When Aβ peptide is released by proteolytic cleavage of amyloid precursor protein,〔 〕 some Aβ peptides that are solubilized are detected in CSF and blood plasma which makes AB peptides a promising candidate for biological markers. It has been shown that the beta-amyloid biomarker shows 80% or above sensitivity and specificity, in distinguishing AD from dementia. It is believed that beta-amyloid as a biomarker will provide a future for diagnosis of AD and eventually treatment of AD, which is the hope of many elderly people. ==Amyloid beta== Aβ is composed of a family of peptides produced by proteolytic cleavage of the type I transmembrane spanning glycoprotein amyloid precursor protein (APP). Senile plaque Aβ protein species ends in residue 40 or 42,〔 〕 but it is suspected that Aβ42 form is crucial in the pathogenesis of AD. Although Aβ42 makes up less than 10% of total AB, it aggregates at much faster rates than Aβ40.〔 〕 Aβ42 is the initial and major component of senile plaque deposits. While the most prevalent hypothesis for mechanisms of Aβ-mediated "neurotoxicity" is structural damage to the synapse, various mechanisms such as oxidative stress,〔 〕 altered calcium homeostasis, induction of apoptosis, structural damage, chronic inflammation and neuronal formation of amyloid has been proposed. Observation of AB42/AB40 ratio has been a promising biomarker for AD. However, as AB42 fails to be a reliable biomarker in plasma, attention was drawn for alternative biomarkers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alzheimer's disease biomarkers」の詳細全文を読む スポンサード リンク
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