Bridging Diabetes and Alzheimer's

Diabetes associated with pathology of Alzheimers disease

(RxWiki News) Over the years, diabetes has been linked to numerous health problems. More recent connections have been made between diabetes and cognitive decline. Now, more signs point to a link with Alzheimer's disease.

Diabetes may play a role in the processes that lead to Alzheimer's disease. Past studies have found close links between Alzheimer's and diabetes.

"Help control diabetes through diet and exercise."

Peter Frederikse, PhD, of the University of Medicine and Dentistry of New Jersey (UMDNJ), and colleagues wanted to see if untreated diabetes could explain more about the development of Alzheimer's.

"The results were striking," said Dr. Frederikse.

"Because we used diabetes as an instigator of the disease, our study shows - for the first time directly - the link between Alzheimer's and diabetes," he said.

The researchers found, when diabetes was present, a significant increase in amyloid beta peptides - a key sign of Alzheimer's disease. These peptides were found in the brain and retina (part of the eye).

When there was no diabetes, the researchers did not find signs of Alzheimer's disease.

"Second, our study examined the retina, which is considered an extension of the brain, and is more accessible for diagnostic exams," said Dr. Frederikse.

The study's results suggest that doctors and scientists may be able to follow the development and progression of Alzheimer's through retinal exams, he said.

Such eye exams could give doctors a way to see early warning signs of Alzheimer's, he said.

For their research, Dr. Frederikse and colleagues studied these disease processes in rabbits. The rabbits formed amyloid beta "oligomer" assemblies in the brain and retina.

These oligomers (a type of molecule) are now regarded as the cause of memory loss in people with Alzheimer's, said William Klein, PhD, of Northwestern University and one of the studies co-authors.

"What could cause them [oligomers] to appear and buildup in late-onset Alzheimer's disease has been a mystery, so these new findings with diabetes represent an important step," said Dr. Klein.

Past research has suggested that insulin, which plays a central role in blood sugar control and diabetes, may be important to memory formation as well.

When oligomers attach to neurons (cells that send electrical and chemical signals), they can eliminate insulin receptors, causing the brain to become unresponsive to insulin. This leads to a vicious cycle in which diabetes leads to a build-up of oligomers which, in turn, leads to more insulin resistance in the brain.

As rates of Alzheimer's and diabetes continue to grow, improving the understanding of Alzheimer's disease processes is an important goal, said co-author Chinnaswamy Kasinathan, PhD, also of UMDNJ.

Understanding these processes could allow researchers to find a biomarker (sign of disease) for Alzheimer's that could lead to better treatments, said Dr. Kasinathan.

Even though this study was done on rabbits, it has implications for future research and treatments in humans. Understanding the links between Alzheimer's and diabetes may lead to improved treatment for both conditions.

The study was supported by the National Eye Institute, the National Institute of Aging and the Neuroscience Research and Education Foundation.

The research is published in the Journal of Alzheimer's Disease.

Review Date: 
July 22, 2012