Higher CSF sTREM2 and microglia activation associate with slower rate of beta-amyloid accumulation

Microglia activation is the brain's major immune response to amyloid plaques in Alzheimer's disease (AD). Both cerebrospinal fluid (CSF) levels of soluble TREM2 (sTREM2), a biomarker of microglia activation, and microglia-PET are increased in AD; however, whether an increase in these biomarkers is associated with reduced amyloid-beta (A?) accumulation remains unclear. To address this question, we pursued a two-pronged translational approach. Firstly, in non-demented and demented individuals, we tested CSF sTREM2 at baseline to predict 1) amyloid-PET changes over 2 years and 2) tau PET cross-sectionally assessed in a subset of patients. We found higher CSF sTREM2 associated with attenuated amyloid-PET increase and lower tau-PET. Secondly, in the AppNL-G-F mouse model of amyloidosis, we studied baseline 18F-GE180 microglia-PET and longitudinal amyloid-PET to test the microglia vs. A? association, without any confounding co-pathologies often present in AD patients. Higher microglia PET at age 5-months was associated with a slower amyloid-PET increase between ages 5-to-10 months. In conclusion, higher microglia activation as determined by CSF sTREM2 or microglia-PET show protective effects on subsequent amyloid accumulation.