Scientists believe a type of protein, which is produced by regular exercise, may hold the key to treating Alzheimer's disease.
Brain molecule PGC-1 alpha, which has also been shown to help protect against type 2 diabetes, was found in greater supply in the brains of healthy individuals who had died than in the brains of dead Alzheimer's patients.
The study, published in the Journal of Alzheimer's Disease, found that cells containing more PGC-1 alpha produced less of the toxic amyloid protein that gathers in the brains of people with Alzheimer's.
The findings could help to explain the results of previous studies that have shown people who exercise more regularly have less of a chance of developing Alzheimer's than those who do not.
Magdalena Sastre, from Imperial College London, who led the study, said: "These early results tell us much more about how diabetes and Alzheimer's are linked, but more importantly, they have given us a potential treatment target.
"Research is the only way to defeat dementia, and it is essential that we follow up this work to see whether drugs that raise the levels of the PGC-1alpha protein could help protect against Alzheimer's."