Abstracts: Alzheimer's Disease

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Causative genes in Alzheimer's disease.

Recently, some Alzheimer-associated genes have been found: amyloid precursor protein (APP), apolipoprotein E (apoE), presenilin 1 (PS-1) and presenilin 2 (PS-2). First, we examined mutations of APR PS-1, and PS-2 genes in familiar Alzheimer's disease (FAD) (7 cases) found in San-in district by single-strand conformation polymorphism and sequence analysis. These seven cases with FAD did not show any mutations of APR PS-1, and PS-2 genes. Other susceptibility genes of FAD still remain to be not identified. Many reports have established that apoE genotype distribution for the epsilon 4 allele is a susceptibility factor for the earlier onset and more rapid progression of Alzheimer's disease (AD). However, the cause of sporadic AD (SAD) has not been elucidated fully. Other genetic factors may be associated with development of SAD. Second, we investigated the association between polymorphisms of the estrogen receptor (ER) alpha gene and SAD. The frequencies of P and X alleles in SAD were significantly higher than those in the control group (p < 0.05). Polymorphisms of the ER alpha gene may be a genetic risk factor for SAD. The apoE genotype is a genetic factor closely related SAD, but it is not full by appreciated how apoE has an effect on developing AD. There are few reports on the quantitative change of apoE, namely the expression of apoE mRNA. Third, ApoE mRNA level in the brains of patients with Alzheimer's disease (27 cases) and Down's syndrome (11 cases)was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). ApoE mRNA level in the DS as well as AD was significantly higher than that in control group (p < 0.05, p < 0.05, respectively). High levels of apoE mRNA in AD and DS may play an important role in the development of Alzheimer pathology.

Nippon Ronen Igakkai Zasshi 2001 Mar;38(2):117-20

Cerebral metabolic and cognitive decline in persons at genetic risk for Alzheimer's disease.

The major known genetic risk for Alzheimer's disease (AD), apolipoprotein E-4 (APOE-4), is associated with lowered parietal, temporal, and posterior cingulate cerebral glucose metabolism in patients with a clinical diagnosis of AD. To determine cognitive and metabolic decline patterns according to genetic risk, we investigated cerebral metabolic rates by using positron emission tomography in middle-aged and older nondemented persons with normal memory performance. A single copy of the APOE-4 allele was associated with lowered inferior parietal, lateral temporal, and posterior cingulate metabolism, which predicted cognitive decline after 2 years of longitudinal follow-up. For the 20 nondemented subjects followed longitudinally, memory performance scores did not decline significantly, but cortical metabolic rates did. In APOE-4 carriers, a 4% left posterior cingulate metabolic decline was observed, and inferior parietal and lateral temporal regions demonstrated the greatest magnitude (5%) of metabolic decline after 2 years. These results indicate that the combination of cerebral metabolic rates and genetic risk factors provides a means for preclinical AD detection that will assist in response monitoring during experimental treatments.

Proc Natl Acad Sci U S A. 2000 May 23;97(11):5696-8

Beta-amyloid therapies in Alzheimer's disease.

Neurones in the brain produce beta-amyloid fragments from a larger precursor molecule termed the amyloid precursor protein (APP). When released from the cell, these protein fragments may accumulate in extracellular amyloid plaques and consequently hasten the onset and progression of Alzheimer's disease (AD). Amyloid-beta fragments are generated through the action of specific proteases within the cell. Two of these enzymes, beta- and gamma-secretase, are particularly important in the formation of beta-amyloid as they cleave within the APP protein to give rise to the N-terminal and C-terminal ends of the beta-amyloid fragment, respectively. Consequently, many researchers are investigating therapeutic approaches that inhibit either beta- or gamma-secretase activity, with the ultimate goal of limiting amyloid-beta; production. An alternative AD therapeutic approach that is being investigated is to employ anti- beta-amyloid antibodies to dissolve plaques that have already formed. Both of these approaches focus on the possibility that accrual of amyloid-beta leads to neuronal degeneration and cognitive impairment characterized by AD and test the hypothesis that limiting amyloid-beta deposition in neuritic plaques may be an effective treatment for AD.

Expert Opin Investig Drugs 2001 Apr;10(4):593-605

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