Researchers at Rhode Island Hospital and Brown Medical School have discovered that insulin and its receptors drop significantly in the brain during the early stages of Alzheimer’s disease, and that levels decline progressively as the disease becomes more severe, leading to further evidence that Alzheimer’s is a new type of diabetes. They also found that acetylcholine deficiency, a hallmark of the disease, is linked directly to the loss of insulin and insulin-like growth factor function in the brain. The study, published in the November issue of the Journal of Alzheimer’s Disease (http://www.j-alz.com), is the first to look at insulin levels early in the course of the disease. The authors’ previous work published earlier this year primarily focused on the late stages of Alzheimer’s. “Insulin disappears early and dramatically in Alzheimer’s disease. And many of the unexplained features of Alzheimer’s, such as cell death and tangles in the brain, appear to be linked to abnormalities in insulin signaling. This demonstrates that the disease is most likely a neuroendocrine disorder, or another type of diabetes,” says senior author Suzanne M. de la Monte, a neuropathologist at Rhode Island Hospital and a professor of pathology at Brown Medical School in Providence, RI. The study analyzed postmortem brain tissue of 45 patients with a diagnosis of either normal aging or different degrees of Alzheimer’s neurodegeneration, termed “Braak Stages.” Researchers analyzed insulin and insulin receptor function in the frontal cortex, a major area affected by Alzheimer’s. They found that with increasing severity of the disease, levels of insulin receptors and the brain’s ability to respond to insulin decreased markedly.
