Alzheimer's: Diabetes of the Brain?

By Dr. Suzanne DeLaMonte Alpert Medical School, Brown University Neuropathologist, Rhode Island Hospital

Posted on | By Dr. Suzanne DeLaMonte | Comments ()

Although we’ve always known that Alzheimer’s disease is typically associated with numerous tangles and plaque in the brain, the exact cause of these abnormalities has been hard to pin down. Now, we may be closer to an answer.

In many respects, Alzheimer’s is a brain form of diabetes. Even in the earliest stages of disease, the brain’s ability to metabolize sugar is reduced. Normally, insulin plays a big role in helping the brain take up sugar from the blood. But, in Alzheimer’s, insulin is not very effective in the brain. Consequently, the brain cells practically starve to death.

How is that like diabetes?

These days, most people with diabetes have Type 2 diabetes mellitus. Basically, cells throughout the body become resistant to insulin signals. In an effort to encourage cells to take up more sugar from the blood, the pancreas increases the output of insulin. Imagine having to knock louder on a door to make the person inside open up and answer. The high levels of insulin could damage small blood vessels in the brain, and eventually lead to poor brain circulation. This problem could partly explain why Type 2 diabetes harms the brain. In Alzheimer’s, the brain, especially parts that deal with memory and personality, become resistant to insulin.

Why does the brain need insulin?

As in most organs, insulin stimulates brain cells to take up glucose or sugar, and metabolize it to make energy. Insulin also is very important for making chemicals known as neurotransmitters, which are needed for neurons to communicate with each other. Insulin also stimulates many functions that are needed to form new memories and conquer tasks that require learning and memory.

Where does the insulin come from in the brain?

Very sensitive tests showed that insulin is made in the brain. It’s made in neurons, and the hormone made in the brain is the same as that produced in the pancreas. This point may seem surprising, but if you consider the fact that every other gut hormone is also made in the brain, it only makes sense that insulin would be among them. Insulin that’s made by the pancreas and present in blood does gets into the brain as well.

 Dr. Suzanne DeLaMonte

Article written by Dr. Suzanne DeLaMonte
Alpert Medical School, Brown University Neuropathologist, Rhode Island Hospital