Alzheimer's Disease Inhibiting Insulin Signaling in the Brain May Cause Diabetes

Both Alzheimer’s disease and diabetes are very common in the United States and can be potentially fatal. In the past, researchers have linked the 2 diseases.

Previous studies indicate that diabetes can cause Alzheimer’s disease (AD), but a recent study published by Alzheimer’s and Dementia suggests a new theory.

In this study, researchers found that mice with AD have insulin resistance in the hypothalamus.

This part of the brain regulates metabolism of nutrients, such as fatty acids, glucose, amino acids. The hypothalamus regulates this in different tissues in the body, including muscle, liver, and fat.

"This is the first study to suggest that Alzheimer's disease pathology increases susceptibility to diabetes due to impaired insulin signaling in the hypothalamus," said researcher Christoph Buettner, MD, PhD said in a press release. "Our research provides a rationale that therapies developed to improve insulin signaling in the brain may reduce the likelihood that a patient with Alzheimer's disease develops diabetes."

The study found that mice with AD showed higher levels of branched chain amino acids (BCAA) in their blood as well.

A previous study conducted by these researchers showed that brain insulin signaling controls BCAA levels. They concluded that BCAAs could be a biomarker of hypothalamic insulin action. This finding has yet to be confirmed in humans.

Because of their previous findings, researchers already knew the relationship between BCAA levels and insulin signaling.

"Our findings represent a turning point in the understanding of the relationship between Alzheimer's disease, type II diabetes and insulin resistance," said Sam Gandy, MD, PhD. "Compelling and unexpected results such as Dr. Buettner's are driving a complete re-evaluation of how these diseases interact. Now that we have disease genes for dementia and diabetes, those genes are our ground zero, and the challenge is to work out all the steps and missteps between the gene and the patient and then to find interventions that cure those missteps."