Diabetes and Alzheimer's: Another Possible Link

Type 2 diabetes patients may have more tangles, thinner cortex in brains

Type 2 diabetes patients are more likely to live with dementia in old age than other patients. New evidence may shed some light on why that is.

A new study from Australia found that patients with type 2 diabetes may have more tangles and thinner cortexes in their brains than patients without the disorder — even when not currently affected by Alzheimer's disease.

Brain tangles are created when proteins (called tau) collapse. In a healthy brain, the tau help stabilize the brain pathways that transport essential nutrients between cells and neurons. When the tau collapse, they can form twisted threads that block these pathways. This can eventually lead to brain cell death.

According to the Alzheimer's Association, tangles are thought to be one of the main causes of cell death and tissue loss in the brains of Alzheimer's patients.

"This interesting development further defines how the diseases may be connected," said lead study author Velandai Srikanth, MD, PhD, an associate professor of Neuroscience at Monash University in Melbourne, in a press release.

Type 2 diabetes is a chronic condition that affects the way the body processes blood sugar. Dementia is an umbrella term for cognitive decline that interferes with daily life. Alzheimer's disease is the most common form of dementia.

Dr. Srikanth and team looked at 816 patients with an average age of 74.

Of these patients, 397 had mild cognitive impairment (which may lead to dementia in the future), 191 had Alzheimer's disease and 228 had no cognitive issues. A total of 124 patients also had type 2 diabetes.

The patients with diabetes tended to have more buildup of tau in their brains, whether or not they had cognitive decline.

These patients also tended to have thinner cortexes (the layer of the brain with most nerve cells), whether or not they had cognitive decline.

The buildup of tangles may contribute to this loss of brain tissue.

"Due to the fact that nerve cells in the brain do not replace themselves, it is extremely important to find ways to reduce the death of current brain cells," Dr. Srikanth said. "Studies such as ours seek to understand how diseases like diabetes may directly or indirectly affect brain cell death."

This study was published Sept. 2 in the journal Neurology.

The National Institutes of Health funded this research. No conflicts of interest were disclosed.