PSEN1 and diabetes mellitus: The expression levels of amyloidogenic pathway-related genes (App, Bace1, and Ps1) in both the hippocampus and PFC were significantly lower in the db_HVD group than in the db_LVD group, suggesting that high doses of dietary vitamin D level partially attenuate the diabetes-induced upregulation of these genes and may help mitigate the activation of the amyloidogenic pathway.