APOE and early-onset autosomal dominant Alzheimer disease: ApoE fragmentation has been extensively studied in relation to Alzheimer's disease; therefore, it could be worth mentioning that P. gingivalis has been shown to be able to invade the brain,35 and possibly the gingipain‐induced proteolysis of lipoproteins may be a mechanism involved in the local atherogenic process and in the degenerating brain as well.