Insulin is not just produced in the pancreas, but also in the brain. This raises the possibility of a Type 3 diabetes.
It has previously been known that insulin resistance, a characteristic of diabetes, is tied to neurodegeneration. Scientists have now demonstrated a link between diabetes and Alzheimer's disease by studying a gene abnormality in rats that blocks insulin signalling in the brain. A drop in insulin production in the brain contributes to the degeneration of brain cells, an early symptom of Alzheimer's. These abnormalities do not correspond to Type 1 or Type 2 diabetes, but reflect a different and more complex disease process that originates in the CNS (central nervous system).
Researchers at Rhode Island Hospital and Brown Medical School have discovered that insulin and its related proteins are produced in the brain, and that reduced levels of both are linked to Alzheimer's disease. The findings are reported in the March 2005 issue of the Journal of Alzheimer's Disease.