SPP1 and Mental deterioration: Interestingly, the early elevation in metabolic markers did not persist throughout the disease course, but a second elevation occurred concurrently with the time of intense immune activation, as represented by increases in c-sTREM2, SPP1 and CHI3L1 levels that immediately preceded metabolic impairment as indicated by a reduced FDG-PET signal, rapid neurodegeneration and cognitive decline.