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1.  Diabetes and Elevated HbA1c levels are Associated with Brain Hypometabolism but not Amyloid Accumulation 
Dysfunctional insulin signaling may affect brain metabolism or amyloid deposition. We investigated the associations of type 2 diabetes with amyloid accumulation measured using 11C-Pittsburgh Compound B (PiB) and brain hypometabolism measured using 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET).
Methods
We studied a sample of non-demented participants from the population-based Mayo Clinic Study of Aging. All subjects underwent MRI, amyloid PET and FDG PET. Alzheimer’s disease (AD) signature and region of interest (ROI) measures for PiB retention ratio and FDG ratio were measured. Diabetes was assessed from the Rochester Epidemiology Project medical records-linkage system.
Results
Among 749 participants (median age 79.0 years; 56.5% male, 81.0% cognitively normal; 20.6% diabetics), FDG hypometabolism (FDG ratio < 1.31) in the AD signature meta-ROI was more common in diabetics (48.1%) than in non-diabetics (28.9%; p <0.001). The median FDG ratio was lower in diabetics vs. non-diabetics in the AD signature meta-ROI (1.32 vs. 1.40, p < 0.001), and in the angular (1.40 vs. 1.48, p < 0.001) and posterior cingulate gyri ROIs (1.63 vs. 1.72, p < 0.001). The odds ratio (OR [95% confidence interval]) for abnormal AD signature FDG hypometabolism was elevated (OR, 2.28 [1.56, 3.33]) in diabetics vs. non-diabetics after adjustment for age, sex, and education, and after additional adjustment for Apolipoprotein ε4 allele, glycemic level, and cognitive status (OR, 1.69 [1.10, 2.60]). However, AD signature PiB retention ratio was similar in diabetics vs. non-diabetics (OR, 1.03 [0.71, 1.51]; p = 0.87). In post-hoc analyses in non-diabetics, a 1% increase in HBA1c was associated with greater AD signature hypometabolism in cognitively normal subjects (OR, 1.93 [1.03, 3.62; p = 0.04]) and in the total cohort (OR 1.59 [0.92, 2.75; p = 0.10).
Conclusion
Diabetes and poor glycemic control in non-diabetics may enhance glucose hypometabolism in AD signature regions. These factors should be investigated in longitudinal studies for their role in detecting onset of symptoms in AD.
doi:10.2967/jnumed.113.132647
PMCID: PMC4011952  PMID: 24652830
Diabetes; cerebral glucose metabolism; FDG- and PiB-PET imaging; hemoglobin A1c; amyloid accumulation
2.  Comparison of 18F-FDG and PiB PET in Cognitive Impairment 
The purpose of this study was to compare the diagnostic accuracy of glucose metabolism and amyloid deposition as demonstrated by 18F-FDG and Pittsburg Compound B (PiB) PET to evaluate subjects with cognitive impairment.
Methods
Subjects were selected from existing participants in the Mayo Alzheimer’s Disease Research Center or Alzheimer’s Disease Patient Registry programs. A total of 20 healthy controls and 17 amnestic mild cognitive impairment (aMCI), 6 nonamnestic mild cognitive impairment (naMCI), and 13 Alzheimer disease (AD) subjects were imaged with both PiB and 18F-FDG PET between March 2006 and August 2007. Global measures for PiB and 18F-FDG PET uptake, normalized to cerebellum for PiB and pons for 18F-FDG, were compared. Partial-volume correction, standardized uptake value (SUV), and cortical ratio methods of image analysis were also evaluated in an attempt to optimize the analysis for each test.
Results
Significant discrimination (P < 0.05) between controls and AD, naMCI and aMCI, naMCI and AD, and aMCI and AD by PiB PET measurements was observed. The paired groupwise comparisons of the global measures demonstrated that PiB PET versus 18F-FDG PET showed similar significant group separation, with only PiB showing significant separation of naMCI and aMCI subjects.
Conclusion
PiB PET and 18F-FDG PET have similar diagnostic accuracy in early cognitive impairment. However, significantly better group discrimination in naMCI and aMCI subjects by PiB, compared with 18F-FDG, was seen and may suggest early amyloid deposition before cerebral metabolic disruption in this group.
doi:10.2967/jnumed.108.058529
PMCID: PMC2886669  PMID: 19443597
PET; dementia; 18F-FDG; PiB

Results 1-2 (2)