P1‐231: Correlation of amyloid deposition with local and distal glucose metabolism in cognitively normal elderly, MCI and Alzheimer's disease

Amyloid deposition is hypothesized to be involved in the events leading to Alzheimer's disease (AD), but the mechanism is unclear. Inverse correlations between amyloid deposition and glucose metabolism in parietal regions of AD patients have been shown, suggesting local amyloid toxicity. However, the complexity of brain connectivity suggests that amyloid effects could be far removed as well. Determine associations of amyloid deposition with metabolism in amyloid-positive normal control subjects, MCI and AD patients. PiB PET and FDG PET scans were performed on 60 normal control subjects (by standard neuropsychological battery). Sixteen controls (26%; 56–80yrs) with amyloid deposition were included. Of 24 MCI patients, 14 (58%) were amyloid-positive (65–82yrs) and were included, along with 18 AD patients (100% amyloid positive; 56–94yrs). Regional PiB retention (DVR: cerebellum reference, DVR=VT/VND) and glucose metabolism (SUVR: cerebellum reference) measures were determined and atrophy-corrected using an MR-based method. PiB retention and metabolism were compared across cortical regions using Pearson's correlations. Similar to previous reports, glucose metabolism in parietal and precuneus cortices of AD patients was negatively correlated with PiB retention locally, and with PiB retention in frontal and lateral temporal cortices. Positive correlations between PiB retention and metabolism were uncommon in AD (mainly anterior cingulate). In controls, a few negative correlations were found in frontal cortex, while numerous positive correlations were found between metabolism in anterior cingulate and precuneus and PiB retention in several brain areas. In MCI, this effect was more pronounced. There were no significant negative correlations observed in MCI subjects. However, glucose metabolism in anterior cingulate showed positive correlations with PiB retention in most brain areas. Metabolism in precuneus and parietal cortex also was positively correlated with PiB retention in most posterior regions. The association of amyloid deposition and glucose metabolism appears to vary with increasing cognitive severity. In controls with amyloid deposition, we observed positive correlations of glucose metabolism in anterior cingulate and precuneus with global amyloid deposition. In MCI, this phenomenon became exaggerated and predominant. In AD, these positive correlations were rare, and negative correlations become predominant, particularly in precuneus and parietal cortex.