Public release date: 26-Sep-2007

EVANSTON, Ill. — Insulin, it turns out, may be as important for the mind as it is for the body. Research in the last few years has raised the possibility that Alzheimer’s memory loss could be due to a novel third form of diabetes.

With other research showing that levels of brain insulin and its related receptors are lower in individuals with Alzheimer’s disease, the Northwestern study sheds light on the emerging idea of Alzheimer’s being a “type 3” diabetes.

Now scientists at Northwestern University have discovered why brain insulin signaling — crucial for memory formation — would stop working in Alzheimer’s disease. They have shown that a toxic protein found in the brains of individuals with Alzheimer’s removes insulin receptors from nerve cells, rendering those neurons insulin resistant. (The protein, known to attack memory-forming synapses, is called an ADDL for “amyloid ß-derived diffusible ligand.”)

In the brain, insulin and insulin receptors are vital to learning and memory. When insulin binds to a receptor at a synapse, it turns on a mechanism necessary for nerve cells to survive and memories to form. That Alzheimer’s disease may in part be caused by insulin resistance in the brain has scientists asking how that process gets initiated.