Insulin May Protect Mind, Memory
Diabetes Drugs Protect Against Alzheimer's-Related Memory Damage
Feb. 2, 2009 -- Drugs used to keep diabetes under control may also shield memory-forming nerve connections from harmful Alzheimer's-related proteins, according to a study published online today by Proceedings of the National Academy of Sciences.
Researchers at Northwestern University treated nerve cells from the hippocampus, one of the brain's critical memory centers, with insulin and the drug Avandia, which is used to treat type 2 diabetes. They discovered that insulin protected the cells from clumps of toxic proteins called amyloid beta-derived diffusible ligands (ADDLs), which target nerve connections in the brain.
The discovery that insulin may slow or prevent Alzheimer's-related memory loss fuels existing theories that the disease may be caused by a third type of diabetes.
Persons who have type 2 diabetes do not produce enough insulin, or the body does not use insulin properly. Newer research has suggested that a "type 3" diabetes may also exist. Evidence has shown that brain cells need insulin to survive and that a drop in brain insulin levels leads to brain cell damage. Memory loss can occur if the cells that die are located in the hippocampus.
"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," Sergio T. Ferreira, a member of the research team and a professor of biochemistry in Rio de Janeiro, Brazil, says in a news release.
In the current study, researchers found that insulin prevented ADDLs from attaching to connections between nerve cells, therefore protecting against damage. They also discovered that lower insulin levels were enhanced by adding Avandia, which increases the body's sensitivity to insulin. Study authors say the discovery that diabetes drugs shield nerve junctions in the brain from memory loss offers new hope for fighting the disease.
"Therapeutics designed to increase insulin sensitivity in the brain could provide new avenues for treating Alzheimer's 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, says in a news release. "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."