U. S. researchers said on Monday that drugs used to control diabetes may help protect memory forming nerve connections from harmful Alzheimer's related proteins. The discovery that insulin could slow or prevent memory loss associated with Alzheimer's supported the theory that Alzheimer's may be a third form of diabetes.

William Klein of Northwestern University, whose study appears in the Proceedings of the National Academy of Sciences, said, "Our results demonstrate that bolstering insulin signaling can protect neurons from harm." Klein added that the findings support the theory that Alzheimer's is like diabetes of the brain.

"In Type 1 diabetes, your pancreas isn't making insulin. In Type 2 diabetes, your tissues are insensitive to insulin because of problems in the insulin receptor. Type 3 is where that insulin receptor problem is localized in the brain," Klein said.

In some people this is noticed as they age. "As you get older, some individuals start to have less effective insulin signaling, including in the brain," he said.

In the study researchers treated nerve cells from one of the brain's critical memory centers, the hippocampus, with insulin and Avandia, a drug used to treat type 2 diabetes. They found that the insulin protected the cells from clumps of toxic proteins called amyloid beta-derived diffusible ligands (ADDLs), which target nerve connections in the brain. "It blocked all of the effects of ADDLs," Klein said.

The effect was enhanced when the drug rosiglitazone, which increases insulin sensitivity, was added.

Studies conducted earlier have shown that diabetics have a greater risk of getting Alzheimer's than the general population.

Recent research has indicated that a type 3 diabetes may also exist. It has been seen that brain cells need insulin to survive and a drop in the brain's insulin level leads to brain damage. If cells that are located in the hippocampus die memory loss can occur.

Sergio T. Ferreira, a member of the research team and a professor of biochemistry in Rio de Janeiro, Brazil said, "Recognizing that Alzheimer's disease is a type of brain diabetes points the way to novel discoveries that may finally result in disease-modifying treatments for this devastating disease."

Senior author William L. Klein, a professor of neurobiology and physiology in the Weinberg College of Arts and Sciences and a researcher in Northwestern's Cognitive Neurology and Alzheimer's Disease Center said, "Therapeutics designed to increase insulin sensitivity in the brain could provide new avenues for treating Alzheimer's disease. Sensitivity to insulin can decline with aging, which presents a novel risk factor for Alzheimer's disease. Our results demonstrate that bolstering insulin signaling can protect neurons from harm."

Klein said the findings indicate that remedies to protect people from diabetes, including a healthy diet and exercise, are as important to avoid Alzheimer's disease.