Abstract
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Objectives Brain glucose metabolism of hypertensive patients with Alzheimer’s disease (AD) is examined with 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) before and after the therapy with angiotensin receptor blocker, telmisartan.
Methods Four studied subjects underwent three FDG-PET studies with each interval of 12 weeks. Anti-hypertensive treatment except for telmisartan started after the first FDG-PET study and lasted for 24 weeks. Then additional 40 to 80 mg of telmisartan treatment started after the second FDG-PET study and lasted for 12 weeks. PET was performed using PET/CT equipment with high spatial resolution (Biograph 6 Hi-Rez; Siemens Medical Systems, Inc.). All FDG-PET images were spatially normalized using statistical parametric mapping 2 (SPM2; http://www.fil.ion.ucl.ac.uk/spm/) with an original template of FDG. Then, isotropic Gaussian smoothing was performed. To examine changes of brain glucose metabolism through a time course of 12 weeks without telmisartan, differences between the first and the second FDG-PET were statistically assessed. Then to examine differences between two conditions; with and without telmisartan, all FDG-PET were statistically assessed. In this latter analysis, to exclude the time effect in voxel intensity across three scans, the term days were included as a nuisance covariate. The analysis was performed with proportional scaling to compare regarding relative FDG distribution.
Results SPM analysis of FDG-PET showed significant decline and preservation of glucose metabolism in a localized area caudal to the rectal gyrus corresponding to olfactory tract during the first 12 weeks without telmisartan and during the following 12 weeks with telmisartan respectively.
Conclusions In AD, amyloid-β deposition is observed in the anterior olfactory nucleus (AON) of the olfactory tract. Glucose metabolism in AON may be progressively decreased and preserved by telmisartan