Objective: To identify clinical manifestations and neuropsychological effects of Alzheimer disease (AD) in apolipoprotein (ApoE) e4 carriers and to investigate the relationships between ApoE HhaI polymorphism and apolipoprotein C1 (APOC1) HpaI polymorphism in Taiwanese patients with AD.
Participants and methods: A total of 127 patients with AD and 191 elderly individuals were screened for ApoE and APOC1 polymorphism. All patients underwent neuropsychological testing, including a Mini-Mental Status Examination (MMSE), Clinical Dementia Rating (CDR), and/or the Visual Association Memory Test (VAMT) with Cognitive Abilities Screening Instrument.
Results: The frequencies of the e4 and A alleles were significantly higher in the AD group. In the patients with AD, the e4 and A allele effects on those with an age-of-onset of 60 to 79 years were stronger than those with an age-of-onset of 80 years or higher. Visual Association Memory Test performance was significantly worse in e4-allele carriers but not in A-allele carriers, in the early AD, particularly in those affected with AD for less than 2 years. Although there was no statistically significant difference in genotypic frequency between patients and controls, the 2 genes were linked. In addition, the presence of the AA genotype concomitant with the e4 allele may be better associated with AD diagnosis than either factor alone.
Conclusion: We conclude that the e4 allele affects neuropsychological performance and illness morbidity. Concomitantly, ApoE e4 and APOC1 A alleles have a better association with AD than ApoE e4 alone. In addition, APOC1 may partially contribute to the pathogenesis of AD, but the nature of its relationship with e4 requires further investigation.