Relationships Between the Deposition of Amyloid-beta and Tau Protein and Glymphatic System Activity in Alzheimer's Disease: Diffusion Tensor Image Study

Background: Amyloid-beta (A beta) and tau protein accumulation in the brain is thought to be one of the causes of Alzheimer's disease (AD). Recent study found that the glymphatic system was waste drainage system in the brain and promoting the elimination of A beta and tau protein. Objective: We evaluated the relationships between the glymphatic system activity and the A beta and tau protein deposition. Methods: Subjects were 21 patients with AD and 36 healthy subjects who underwent diffusion tensor imaging (DTI) scan and the positron emission tomography (PET) using with the A beta tracer: C-11-PiB and the tau/inflammatory tracer: F-18-THK5351. We computed diffusion tensor image analysis along the perivascular space (DTI-ALPS) index as the proxy of glymphatic system activity, and estimated the relationships between the DTI-ALPS index and A beta and tau protein/inflammatory deposition. Results: We found significant negative correlations between DTI-ALPS index and the standard uptake value ratio (SUVR) of C-11-PiB in the bilateral temporal and left parietal cortices and left posterior cingulate gyrus in all subjects. Further, we detected significant negative correlations between DTI-ALPS index and the SUVR of F-18-THK5351 in the bilateral temporal cortices and right parietal cortex in all participants, too. Conclusion: Our data suggested that DTI-ALPS index was a good biomarker for the evaluation of A beta and tau deposition and neuroinflammation, and this marker might be effective to estimate the glymphatic system activity.