Correlation between Apolipoprotein-E polymorphism and Alzheimer's disease pathology

Area of Science:

• Neuropathology
• Neurogenetics
• Dementia Research

Background:

• Alzheimer's disease (AD) and small vessel disease dementia (SVDD) are leading causes of cognitive decline.
• The apolipoprotein E (ApoE) genotype is a known risk factor for AD.
• Understanding ApoE allele frequencies in relation to neuropathology is crucial for diagnosing and potentially identifying pre-clinical dementia.

Purpose of the Study:

• To correlate ApoE allele frequencies with neuropathological changes in AD and SVDD.
• To validate previous ApoE genotyping findings in AD.
• To identify potential pre-clinical forms of AD and SVDD.

Main Methods:

• Histological examination and immunohistochemistry for tau protein and amyloid-beta on brain tissue from AD, SVDD, and control groups.
• Analysis of ApoE allele frequencies (ApoE2, ApoE3, ApoE4).
• Classification of AD cases based on cortical pathology severity.

Main Results:

• ApoE4 allele frequency was significantly increased in AD patients and also found in aged controls exhibiting AD-like neuropathology (62% of this subgroup).
• ApoE2 allele frequency was significantly increased in SVDD patients.
• Histopathological analysis identified "pre-clinical" forms of AD and SVDD in individuals without clinical dementia history.

Conclusions:

• The ApoE genotype plays a significant role in the neuropathology of both AD and SVDD.
• ApoE4 positivity in individuals with AD-like brain changes, even without clinical symptoms, suggests its role in pre-clinical AD.
• ApoE2 is associated with SVDD, highlighting distinct genetic influences on different dementia types.