Researchers analyzed brain tissue sourced from people who had both diabetes and Alzheimer’s. The findings suggest that some anti-diabetes drugs that these people used offered protection that kept the neurodegenerative disease from progressing as rapidly as it would have otherwise.

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Many elderly people with diabetes have brain changes that are hallmarks of Alzheimer’s. Previous studies have suggested that there is a link between the risk of cognitive impairment, dementia, and type 2 diabetes, and there is evidence that an insulin receptor pathway in the brain is associated with Alzheimer’s pathologies, though the mechanism remains unknown.

A while ago, researchers at the Icahn School of Medicine at Mount Sinai in New York led by Vahram Haroutunian — a professor of psychiatry and neuroscience — found that the brains of people with Alzheimer’s who had also undergone treatment for diabetes (insulin or medicine) had reduced brain pathologies.

This time, Haroutunian and colleagues wanted to dive deeper, at the molecular level, to identify the specific pathways that may explain the association between diabetes and Alzheimer’s.

Using a technique that they designed, the team isolated brain capillaries from the brain tissues of 34 individuals who had both Alzheimer’s and type 2 diabetes, and who were treated for both. The researchers specifically focused on endothelial cells that line the inside of blood vessels and form an interface between circulating blood and the rest of the vessel wall.

The team compared the tissues to those of 30 people who had had Alzheimer’s but not diabetes, as well as 19 control subjects that had neither of the two diseases.

The findings suggest that individuals who were treated for both diseases had half as many markers for Alzheimer’s-related molecular changes in the brain’s capillary cells compared to those that only had Alzheimer’s. What’s more, the majority of molecular changes in RNA markers present in Alzheimer’s disease were not encountered in the study group that took medication for diabetes.

“The results of this study are important because they give us new insights for the treatment of Alzheimer’s disease,” said the study’s senior author, Vahram Haroutunian.

“Most modern Alzheimer’s treatments target amyloid plaques and haven’t succeeded in effectively treating the disease,” said Dr. Haroutunian. “Insulin and diabetes medications such as metformin are FDA approved and safely administered to millions of people and appear to have a beneficial effect on people with Alzheimer’s. This opens opportunities to conduct research trials on people using similar drugs or on drugs that have similar effects on the brains’ biological pathways and cell types identified in this study.”

The findings appeared in the journal PLOS One.