Alzheimer's plaques reduced by diabetes therapy

NEW YORK (Reuters Health) - In a postmortem study of patients who had Alzheimer's disease, those who also had diabetes and were treated with insulin and oral hypoglycemic drugs had lower densities of neural plaques in the brain, a hallmark of this dementia, than did other diabetics or those without diabetes, new research shows.

In several studies, type 2 diabetes has been identified as a risk factor for Alzheimer's disease. The link between diabetes and Alzheimer's neuropathology, by contrast, is less clear, according to the report in the medical journal Neurology.

The current study, conducted by Dr. M. S. Beeri, from Mount Sinai School of Medicine in New York, and colleagues, involved an analysis of the neural plaques and neurofibrillary tangles in brain specimens from Alzheimer's disease patients, which included 124 subjects with diabetes and 124 without diabetes.

The diabetic group consisted of 29 patients who had never taken drugs for their diabetes, 49 who had received insulin only, 28 treated with agents other than insulin, and 18 treated with both insulin and oral antidiabetic mediations.

The overall neural plaque rating, the rating in various regions of the brain, and the total neural plaque count differed significantly among the groups. In all of the analyses, the combined medication group had fewer neural plaques than did the other groups.

By contrast, the authors found no significant difference in the neurofibrillary tangles among the groups.

These findings provide evidence that patients with Alzheimer's disease and diabetes taking the combination of insulin and hypoglycemic medications have "substantially lower" neural plaque densities in the brain, the researchers conclude. They suggest that insulin pathways should be considered potentially important in the development of Alzheimer's disease and the deposition of neural plaques that characterize this dementia.

SOURCE: Neurology, September 2, 2008.