Why Some Researchers are Calling Alzheimer’s “Type 3 Diabetes”

Could insulin treat Alzheimer’s the same way it treats diabetes? Evidence shows Alzheimer’s might be more similar to a metabolic disorder, like diabetes, than previously thought.

While the brain only amounts to two percent of our body weight, it uses up more than 20 percent of our total energy. Studies show junk food like candy and soda, which contain large amounts of sugar, could disrupt the brain’s energy balance, increasing the risk of a metabolic disorder. That metabolic dysregulation, in turn, could make it harder for nutrients to reach the brain, causing cells to starve and die, leading to Alzheimer’s.

TLDR: Sugary foods are an Alzheimer’s risk factor. That has led some scientists to begin referring to Alzheimer’s as “Type 3 diabetes.”

This “Type 3 diabetes” perspective is a new way of looking at Alzheimer’s disease — and it might explain the link between Alzheimer’s risk, type 2 diabetes, and the role of insulin in the brain. Research has already prodded some of these complex and little understood relationships, finding that, for example, some diabetes medications are known to reduce the risk of developing Alzheimer’s.

If this idea turns out to be true, it could mean repurposing diabetes treatments like insulin into Alzheimer’s drugs.

The link between diabetes and Alzheimer’s

The greatest genetic risk factor for developing Alzheimer’s in certain populations — ApoE4 — also happens to be a major risk factor for diabetes. High blood sugar is also linked as a risk factor for developing Alzheimer’s and dementia, as well as a contributor to the onset of type 2 diabetes. Interestingly, getting blood sugar under control helps reduce the risk of both diabetes and Alzheimer’s. These similarities lead researchers to conclude that Alzheimer’s might be a form of diabetes that affects the brain.

Scientists have also discovered that insulin plays an important role in the brain’s metabolism. Elsewhere in the body, insulin helps sugar in the blood enter the cells so that it may be used for energy. In the brain, insulin and other signaling molecules that activate insulin receptors are important for regulating neuronal metabolism, survival, and even cognition.

Insulin resistance in the brain

In type 2 diabetes, insulin receptors throughout the body became resistant. They become less sensitive to insulin as a signal for mobilizing sugar and energy, leading to impaired metabolism throughout the body. The same may occur in Alzheimer’s disease making it harder for neurons to access all the energy they need to function properly.

Since insulin receptors also activate protective pathways within the brain, insulin resistance makes the cells more likely to get damaged and die. There is evidence that the buildup of toxic beta-amyloid plaques leads to the development of insulin resistance. However, the cause-and effect isn’t exactly clear. It could be problems with insulin in the first place that lead to the production of beta-amyloid plaques.

Treating Alzheimer’s and diabetes together

Could insulin treat Alzheimer’s the same way it treats diabetes? There is already evidence that administering insulin intranasally improved working memory in healthy men and women. There are also a few studies conducted in people with Alzheimer’s disease or mild cognitive impairment that found chronic administration of intranasal insulin improved attention and retention of new memories.

More studies are underway to determine whether insulin or other next-generation diabetes drugs could be effective treatments for Alzheimer’s.

To learn about clinical trials of new medications that aim to modify the pathology of Alzheimer's disease, call Charter Research at 407-337-1000 (Orlando) or 352-775-1000 (The Villages).