Insulin and Alzheimer’s Disease

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Nearly 21 million Americans have diabetes, a disease that makes the body less able to convert sugar to energy. According to the American Diabetes Association, 27 percent of people aged 65 and older in the United States have diabetes and about half have prediabetes. When diabetes is not controlled, too much sugar remains in the blood. Over time, this can damage organs, including the brain. In fact, numerous studies have found that individuals with diabetes, especially type 2 diabetes, have a lower level of cognitive function and are at higher risk for dementia than individuals without diabetes.

Most people don’t know that diabetes may contribute to Alzheimer’s.

Insulin resistance in the brain is another common feature of Alzheimer’s disease. For reasons researchers do not completely understand, the brain becomes resistant to the normal effects of insulin, including the conversion of glucose to energy that brain cells can use to fuel cell functioning. Some research suggests that beta-amyloid decreases the body’s ability to use insulin. Other research has found reduced levels of insulin in the brain.

What researchers do know is that diabetes raises the risk of heart disease and stroke, which hurt the heart and blood vessels. Damaged blood vessels in the brain may contribute to Alzheimer’s disease. High blood sugar also causes inflammation. This may damage brain cells and help Alzheimer’s to develop. Lastly, the brain depends on many different chemicals, which may be unbalanced by too much insulin. Some of these changes may help trigger Alzheimer’s disease.

Current drug in research that targets insulin resistance: Intranasal insulin

Intranasal insulin is a therapy being tested in multiple studies for its effects on memory, thinking and daily functioning in people with mild cognitive impairment and mild-to-moderate Alzheimer’s disease. There is growing evidence that insulin plays an important role in keeping the brain healthy. Intranasal administration of insulin may help by increasing insulin signaling in the brain. (Drug is still in research; not available to the public.)

In the video below, Suzanne Craft, Ph.D., discusses the role insulin plays in the brain, and the benefits of diet and exercise in improving insulin metabolism.