What started as a speculative notion is now gaining ground: Alzheimer’s disease is synonymous with type 3 diabetes. Multiple experiments have shown a connection between insulin, a major player in diabetes, and Alzheimer’s, but the connection is made through a different route than the connections between insulin and type 1 and 2 diabetes.
Similar to other studies, the study that made the first proposed connection started with beta amyloid plaques. Dr. Suzanne de la Monte, a neuropathologist at Brown University, was interested in how plaques develop in the brain. In 2005, her laboratory at Brown Medical School published the novel paper “Impaired Insulin and Insulin-Like Growth Factor Expression and Signalizing in Alzheimer’s Disease–Is This Type 3 Diabetes?” in the journal Journal of Alzheimer’s Disease. When her research team blocked the insulin pathway in the brains of rats, the rats exhibited signs of Alzheimer’s.
Ultimately, it appears plaques are allowed to develop in the absence — or at least shortage — of insulin, lending Alzheimer’s the new name. Creating a new designation for diabetes was nothing new. Previously, juvenile diabetes, in which autoimmunity destroys pancreatic insulin-producing beta cells, was the only form of diabetes. Then, as more doctors began seeing patients with a diminished yet still present ability to produce insulin, two categories were developed. Juvenile became known as type 1 and adult-onset became known as type 2. It is possible for some individuals to experience type 1.5 diabetes, where symptoms match neither type 1 nor type 2 exactly.
The type 3 phenomenon is similar to the case of type 2 diabetes in terms of lack of insulin. Accordingly, it has been recommended that individuals with a higher genetic risk for developing Alzheimer’s disease eat a diet low in carbohydrates, minimizing the intake of foods typically associated with type 2 diabetes onset.
Adding to the similarities of Alzheimer’s and diabetes, diabetic patients can experience diabetic neuropathy. Diabetic neuropathy is triggered by glucose-induced inflammation and can lad to destruction of nerve tissue. In Alzheimer’s, patients’ nerves are damaged.
Overall, designating Alzheimer’s disease as type 3 diabetes sheds light on the mechanisms behind disease onset and progression. The controversy is now waning, and more scientists are accepting the idea, studying further, and continuing to develop treatments for patients.
Information from this article references “Alzheimer’s New Name: Type 3 Diabetes,” published in Diabetes Health.