Glucose metabolism and gray-matter concentration in apolipoprotein E ε4 positive normal subjects.
Level 4 - case-series / case-control
Cross-sectional case-control study comparing imaging biomarkers between genetic risk groups
PubMed 22188720 · doi:10.1016/j.neurobiolaging.2011.11.020
What was done
A cross-sectional neuroimaging study evaluated 45 cognitively normal apolipoprotein E (ApoE) ε4 allele carriers and 45 noncarriers. All participants underwent 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to measure cerebral glucose metabolism and magnetic resonance imaging (MRI) analyzed by voxel-based morphometry (VBM) to assess gray-matter concentration. Mean z-scores in predefined Alzheimer's disease-specific regions of interest were generated from individual normal database sets to determine the prevalence of AD-like imaging abnormalities.
What was found
The prevalence of AD-like hypometabolism on FDG-PET was identical in both groups at 8.9% (4/45). The prevalence of AD-like gray matter atrophy on VBM was 17.7% (8/45) in ε4 carriers compared with 8.8% (4/45) in noncarriers, which did not differ significantly. The majority of cognitively normal ApoE ε4 carriers exhibited preserved FDG uptake and gray matter concentration.
Why it matters
The findings indicate that possessing the ApoE ε4 risk allele does not inevitably lead to early AD-typical structural or metabolic brain alterations prior to cognitive symptom onset.
Limits
The sample size was modest (n = 45 per group), which may have underpowered the study to detect small differences in atrophy rates. The cross-sectional design cannot evaluate longitudinal progression or future risk of clinical conversion. The abstract does not specify participant age, sex distributions, or exact p-values and confidence intervals.
Cited by
- context Metabolic issues in cerebral glucose utilization can be detected on fluorodeoxyglucose PET scans 20 years before clinical memory loss appears.