The results of the pathway enrichment analysis showed that in twenty-one cellular pathways, LTP, MAPK signaling pathway, GnRH signaling pathway, ErbB signaling pathway, adherens junction, focal adhesion, cell cycle, pathways in cancer and AD appeared in the PPI and MetaCore or PPI and co-expression sub-network in the brains of SAMP8 mice at the same time (Figure 5) (Supplement Table 5). Here, GNRH1 is linked to Alzheimer disease.