Here is a decent reference. Difficult to read but the conclusion at the bottom of the page is - "Altogether, the results from these studies provide strong evidence in support of the hypothesis that AD represents a form of diabetes mellitus that selectively afflicts the brain. " - wherein they showed that oxidative stress (as caused by insulin resistance) causes Alzheimer's symptoms in mice.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769828/