Insulin Triggers Amyloid Buildup High insulin levels are known to cause blood vessels to become inflamed. Inflamed tissues send off chemical warning signals. These warning signals set off an avalanche of tissue-damaging effects. But insulin doesn't just cause inflammation in the lower body. It also causes inflammation in the brain, find University of Washington researcher Suzanne Craft, PhD, and colleagues. One dangerous effect of this insulin-caused brain inflammation is increased brain levels of beta-amyloid. Beta-amyloid is the twisted protein that's the main ingredient in the sticky plaques that clog the brains of people with Alzheimer's disease. "What was striking was the magnitude of the effect," Craft tells WebMD. "Inflammation can be a result of amyloid elevations but can also create an environment in which amyloid is made more readily. Inflammation can be both the result and cause of amyloid production."

Brave Volunteers Craft's research team signed up 16 very brave volunteers. These men and women, ranging in age from 55 to 81, let research doctors give them two-hour infusions of both insulin and sugar. This kept their blood sugar at normal levels while creating the same kind of high insulin levels seen in people with insulin resistance. The volunteers then let the researchers give them a spinal tap so they could analyze their spinal fluid. Just this brief rise in insulin levels had what Craft calls "striking" effects: It set off inflammation in the brain.

The spinal fluid had increased levels of a compound called F2-isoprostane. Alzheimer's patients have unusually high brain levels of F2-isoprostane.

Brain levels of beta-amyloid increased.