The development of an appropriate animal model, targeting the murine APOE gene for replacement with the human APOE-ε4 (apoE-ε4/apoE4 mouse) [33], opened a window for new possibilities of characterizing the apoE-ε4 phenotype and of studying the effects of very early AD-like pathology development in relation with lipid-based treatment. The gene discussed is APOE; the disease is Alzheimer disease.