Cerebral Glucose Metabolism is Associated with Verbal but not Visual Memory Performance in Community-Dwelling Older Adults.

Increasing evidence suggests that Alzheimer's disease (AD) sufferers show region-specific reductions in cerebral glucose metabolism, as measured by [18F]-fluoro-2-deoxyglucose positron emission tomography (18F-FDG PET). We investigated preclinical disease stage by cross-sectionally examining the association between global cognition, verbal and visual memory, and 18F-FDG PET standardized uptake value ratio (SUVR) in 43 healthy control individuals, subsequently focusing on differences between subjective memory complainers and non-memory complainers. The 18F-FDG PET regions of interest investigated include the hippocampus, amygdala, posterior cingulate, superior parietal, entorhinal cortices, frontal cortex, temporal cortex, and inferior parietal region. In the cohort as a whole, verbal logical memory immediate recall was positively associated with 18F-FDG PET SUVR in both the left hippocampus and right amygdala. There were no associations observed between global cognition, delayed recall in logical memory, or visual reproduction and 18F-FDG PET SUVR. Following stratification of the cohort into subjective memory complainers and non-complainers, verbal logical memory immediate recall was positively associated with 18F-FDG PET SUVR in the right amygdala in those with subjective memory complaints. There were no significant associations observed in non-memory complainers between 18F-FDG PET SUVR in regions of interest and cognitive performance. We observed subjective memory complaint-specific associations between 18F-FDG PET SUVR and immediate verbal memory performance in our cohort, however found no associations between delayed recall of verbal memory performance or visual memory performance. It is here argued that the neural mechanisms underlying verbal and visual memory performance may in fact differ in their pathways, and the characteristic reduction of 18F-FDG PET SUVR observed in this and previous studies likely reflects the pathophysiological changes in specific brain regions that occur in preclinical AD.

Effect of long-term homocysteine reduction with B vitamins on arterial wall inflammation assessed by fluorodeoxyglucose positron emission tomography: a randomised double-blind, placebo-controlled trial.

BACKGROUND: Homocysteine may promote atherosclerosis by exacerbating inflammatory processes within the arterial wall. B-vitamin supplements reduce total plasma homocysteine concentrations (tHcy), but it is not known whether the treatment also reduces arterial wall inflammation. We used (18)F-fluorodeoxygluose positron emission tomography ((18)F-FDG PET) to investigate whether long-term homocysteine-lowering treatment alters arterial wall inflammation in patients with a history of ischemic stroke. METHODS: 30 stroke patients were randomly assigned to B-vitamin therapy (folic acid 2 mg, vitamin B(6) 25 mg and vitamin B(12) 0.5 mg) or placebo in a double-blind clinical trial. After a mean treatment period of 4.0 +/- 0.7 years, all subjects had tHcy, carotid intima-medial thickness (CIMT) and flow-mediated dilation (FMD) of the brachial artery measured and underwent an (18)F-FDG PET scan. Standardised uptake values (SUV) were measured at six sites in the carotid, femoral and aortic arteries. Areas of locally increased tracer uptake in the arterial wall ('hot spots') were also identified and counted. RESULTS: Long-term B-vitamin treatment significantly reduced tHcy compared with placebo (8.4 micromol/l, 95% confidence interval, CI, 7.2-9.6 vs. 11.6 micromol/l, 95% CI 10.0-13.4, p = 0.002). The treatment did not affect mean arterial SUV (2.0 +/- 0.3 vitamins vs. 2.1 +/- 0.3 placebo, p = 0.65) or the number of hot spots (n = 1.1 +/- 1.0 vitamins vs. n = 1.2 +/- 1.0 placebo, p = 0.65). There was no significant correlation between mean arterial SUV and CIMT or FMD. CONCLUSIONS: These results suggest that a long-term Hcy reduction with B vitamins does not affect arterial wall inflammation assessed by (18)F-FDG PET.