APOE and Alzheimer disease: Research has focused on animal models replicating sporadic AD, including: i) age-related models, using aged wildtype mice/rats or SAMP8 mice to mimic AD-like dementia; ii) models based on genetic risk factors like ApoE ε4, linked to both early- and late-onset AD in genome-wide association studies (GWAS); and iii) models involving environmental factors, heavy metal exposure, chemicals like streptozotocin (STZ) administered intracerebroventricularly, scopolamine, aluminum chloride (AlCl3), and hyperhomocysteinemia.