Plasma Glucose Levels Affect Cerebral 18F-FDG Distribution in Cognitively Normal Subjects With Diabetes

Purpose Increased plasma glucose levels can relatively reduce 18F-FDG uptake in Alzheimer disease (AD)–related regions and alter the cerebral distribution pattern of 18F-FDG, resulting in the appearance of an AD-like pattern. However, the relationship between the reversibility of the AD-like pattern and plasma glucose levels is uncertain. Methods Four cognitively normal elderly subjects with diabetes underwent longitudinal 18F-FDG PET more than 5 times at various levels of plasma glucose. 18F-FDG data were proportionally scaled with a global normalization method and used in volume of interest–based and voxelwise analyses. Volumes of interest were placed on representative AD-related regions: precuneus/posterior cingulate (PP), lateral parietal cortex, and frontal cortex. Results Volume of interest–based analyses showed negative correlations of plasma glucose levels with 18F-FDG uptake in the PP (r = −0.79, P < 0.001), lateral parietal cortex (r = −0.62, P = 0.002), and frontal cortex (r = −0.73, P < 0.001), controlling for the effects of interindividual differences and age. Voxelwise analyses also showed negative correlations between the 2 factors in the PP and medial frontal areas (P < 0.05, familywise error rate corrected). Conclusions This study indicates that the distribution pattern of 18F-FDG changes depending on plasma glucose levels in an individual and that the AD-like pattern can appear or disappear with increasing or decreasing plasma glucose levels, respectively.