According to a new study, diabetes and Alzheimer’s disease are more closely related than previously thought. Some researchers now believe that Alzheimer’s could be a form of diabetes because findings show that insulin production in the brain declines as Alzheimer’s disease progresses.
Through a series of experiments, a group of researchers discovered that the brain produces insulin, and that insulin levels in the brains of patients with Alzheimer’s tend to fall below normal levels.
Suzanne M. de la Monte, a neuropathologist at Rhode Island Hospital and professor of pathology at Brown University Medical School, explains that insulin levels decline early and dramatically in Alzheimer’s disease. Many of the disease’s unexplained features—such as neuronal cell death and the formation of brain tangles—seem to be linked to abnormalities in insulin signaling. This suggests that Alzheimer’s is most likely a neuroendocrine disorder, or in other words, another type of diabetes.
During the early stages of Alzheimer’s, brain levels of insulin and its related cellular receptors drop sharply, according to de la Monte’s research team. They propose that Alzheimer’s might be a new form of diabetes, as insulin levels continue to decline progressively with disease severity.
The team also discovered that low levels of acetylcholine—a chemical crucial for memory and cognition, and a hallmark of Alzheimer’s—are directly linked to the loss of insulin and insulin-like growth factor function in the brain.
To reach these conclusions, the researchers autopsied brain tissue from 45 patients diagnosed with various stages of Alzheimer’s, classified by Braak Stages, and compared the samples to brain tissue from individuals without the disease.
