Age and ApoE genotype interaction in Alzheimer's disease: an FDG-PET study

Previous positron emission tomography (PET) studies with fluorodeoxglucose (FDG) as tracer in healthy elders showed that the epsilon4 allele of the apolipoprotein E (ApoE) gene is disruptive to cerebral glucose metabolism (rCMRglu), possibly through the interaction with the aging process. The present study was aimed at assessing whether this interaction occurs in patients with Alzheimer's disease (AD). Eight-six AD patients, including 40 ApoE4 carriers and 46 non-carriers, underwent (18)F-FDG PET scanning at rest. ApoE groups were comparable for age, gender, age at onset and disease duration. SPM'99 was used to assess rCMRGlu correlations with age, differences between ApoE groups and ApoE by age interaction, correcting for disease severity. Results were reported at P<0.001, uncorrected. Correlations between age and rCMRGlu confirmed the well-known negative relationship for both groups. Lower rCMRGlu was found within the frontal and cingulate areas for ApoE4 carriers as compared with the non-carriers. Additionally, a significant ApoE by age interaction was detected in the frontal and anterior cingulate cortex, with the ApoE4 carriers having a steeper regression slope with respect to the non-carriers. These results indicate that age-related regional rCMRglu decreases within the frontal and anterior cingulate areas may be more severe in AD patients carrying the ApoE4 allele.