Influence of cerebral glucose metabolic rate on cognitive function in Alzheimer's subjects

Abstract

AbstractBackground18F‐fluorodeoxyglucose‐positron emission tomography (FDG‐PET) measures regional cerebral glucose metabolism –which is a biomarker of neuronal function in Alzheimer’s disease (AD) Neuropsychological measures such as the Alzheimer’s Disease Assessment Scale – Cognitive Subscale (ADAS‐Cog) – a measure of memory, language and praxis has been used as an outcome measure in AD clinical trials. ADAS‐Cog‐12 attempts to overcome such limitations, by including an additional delayed word recall measure. The objective of this study was to compare baseline ADAS‐Cog‐12 scores with cerebral glucose metabolic rate measured with FDG‐PET with arterial input in subjects who have undergone baseline scans for the Evaluation of Liraglutide in treatment of Alzheimer’s disease (ELAD) study.Method107 subjects diagnosed with AD underwent baseline FDG‐PET scans with continuous online blood sampling along with discrete sampling for radioactivity and plasma glucose. They also underwent detailed neurological and neuropsychological testing including ADAS‐Cog. FDG PET was analysed using spectral analysis with arterial input and following regions were sampled : hippocampus, medial temporal lobe, temporal, anterior cingulate, posterior cingulate, frontal, parietal and occipital cortices. ADAS‐Cog scores were calculated for all the subjects.ResultPearson’s product‐moment correlation showed that ADAS‐Cog scores (at 0.01 level) negatively correlated with all FDG‐PET ROIs derived from spectral analysis (‐0.36≤|r|≤‐0.54). Greatest correlations occurred between ADAS‐Cog and the temporal cortex (‐0.54), parietal cortex (‐0.51) and frontal lobe (‐0.51).ConclusionIn this study, ADAS‐Cog‐12 scores correlated well with the cerebral glucose metabolism, suggesting cerebral glucose metabolism could be used as a surrogate marker for cognitive function in Alzheimer’s disease intervention studies, and is a sensitive maker for neuronal function.