APOE and Alzheimer disease: In fact, many studies on neurodegenerative diseases, including Alzheimer's disease, have shown that in both clinical and related animal models the gene Apoe can affect the phenotype related to lipid metabolism of microglia and then participate in the process of neuropathological phenotype [43, 44]. The main apolipoprotein synthesized in the CNS, ApoE plays a neuroprotective role in the conditions of experimental subarachnoid hemorrhage by participating in reducing early brain injury via microglial quiescence [45].