Effect of APOE e4 allele on age‐related brain FDG‐PET uptake in older individuals at risk of dementia

Abstract

AbstractBackgroundIn Alzheimer’s Disease (AD) patients, accumulating evidence suggests that the APOE‐e4 allele drives amyloid and tau pathology and decreases brain glucose metabolism. Similarly, in older healthy subjects, APOE‐e4 has been linked to brain hypometabolism. However, there are scarce clinical studies concerning the effect of APOE e4 and the age‐related cerebral glucose metabolism patterns of older individuals at‐risk for dementia.ObjectiveThis exploratory analysis aims to study the impact of carriage of the APOE‐e4 allele on age‐related brain glucose metabolism patterns of older individuals at‐risk for dementia.Method54 community‐dwelling older adults aged 60‐80 years with increased risk for AD due to cardiometabolic disorders (CMD, n = 32) or mild cognitive impairment (MCI, n = 22) who participated in a clinical trial. APOE genotyping was performed to identify carriers of the APOE‐e4 allele. 18F‐Fluoro‐2‐deoxy‐D‐glucose‐positron emission tomography/computed tomography (18F‐FDG PET/CT) was conducted and mean 18F‐FDG uptakes in brain regions of interest (ROI) from the atlas of anatomical labeling were obtained.Group differences by diagnosis (CMD,MCI) and APOE‐e4 status were examined using independent samples T‐tests. Linear regression models were conducted to evaluate the effect of age over mean 18F‐FDG uptake in each ROI. Age*APOE‐e4 interactions were examined, and the models were adjusted for diagnosis subgroup and gender effects. Adjusted models were corrected for multiple testing using the False Discovery Ratio (FDR).ResultMean 18F‐FDG uptake at each ROI was comparable between diagnosis and APOE‐e4 allele status groups. After correcting adjusted models for multiple testing, significant Age*APOE‐e4 interactions were found at the right inferior occipital gyrus (β ‐0.13, 95% CI ‐0.25 – 0.02, p = 0.035, FDR = 0.039), right paracentral lobule (β ‐0.14, 95% CI ‐0.25 – ‐0.03, p = 0.016, FDR = 0.024), and left superior parietal gyrus (β ‐0.11, 95% CI ‐0.20 – ‐0.02, p = 0.014, FDR = 0.021).ConclusionIn older individuals at risk of dementia, carriage of the APOE‐e4 allele was associated with an increased age‐related reduction in mean 18F‐FDG uptake in the right inferior occipital gyrus, right paracentral lobule, and left superior parietal gyrus. Knowledge of age‐ and APOE‐e4 allele‐related cerebral metabolic changes is critical to correctly interpreting brain 18F‐FDG PET/CT findings.