Associations between regional blood-brain barrier disruption, aging, and Alzheimers disease biomarkers in cognitively normal older adults
Background: Blood-brain barrier disruption (BBBd) has been hypothesized as a feature of aging that may lead to the development of Alzheimers disease (AD). We sought to identify the brain regions most vulnerable to BBBd during aging and examine their regional relationship with neuroimaging biomarkers of AD. Methods: We studied 31 cognitively normal older adults (OA) and 10 young adults (YA) from the Berkeley Aging Cohort Study (BACS). Both OA and YA received dynamic contrast-enhanced MRI (DCE-MRI) to quantify Ktrans values, as a measure of BBBd, in 37 brain regions across the cortex. The OA also received Pittsburgh compound B (PiB)-PET to create distribution volume ratios (DVR) images and flortaucipir (FTP)- PET to create partial volume corrected standardized uptake volume ratios (SUVR) images. Repeated measures ANOVA assessed the brain regions where OA showed greater BBBd than YA. In OA, Ktrans values were compared based on sex, A{beta} positivity status, and APOE4 carrier status within a composite region across the areas susceptible to aging. We used linear models and sparse canonical correlation analysis (SCCA) to examine the relationship between Ktrans and AD biomarkers. Results: OA showed greater BBBd than YA predominately in the temporal lobe, with some involvement of parietal, occipital and frontal lobes. Within an averaged ROI of affected regions, there was no difference in Ktrans values based on sex or A{beta} positivity, but OA who were APOE4 carriers had significantly higher Ktrans values. There was no direct relationship between averaged Ktrans and global A{beta} pathology, but there was a trend for an A{beta} status by tau interaction on Ktrans in this region. SCCA showed increased Ktrans was associated with increased PiB DVR, mainly in temporal and parietal brain regions. There was not a significant relationship between Ktrans and FTP SUVR. Discussion: Our findings indicate that the BBB shows regional vulnerability during normal aging that overlaps considerably with the pattern of AD pathology. Greater BBBd in brain regions affected in aging is related to APOE genotype and may also be related to the pathological accumulation of A{beta}.