The overall in vivo experimental procedure is illustrated in Figure 1A. Given the pathophysiological role of ApoE on both atherosclerosis and AD, we first focused our view particularly on the brain’s ChP region, the blood-cerebrospinal fluid (CSF) barrier, of ApoE−/− mice to elucidate the neuroprotective effect of β-OHB. Here, APOE is linked to atherosclerosis.