FOXO3 and Alzheimer disease: For investigating the relations between TREM2 and/or FoxO3a in AD pathology, first, the TREM2 level was examined by qPCR and western blot in whole hippocampus, in which the mRNA and protein level of TREM2 were significantly increased in the hippocampus in 5xFAD than WT (Figure 2A–2C).