Insulin and its growth factors aren't just produced in the pancreas, but in the brain as well. When levels drop in key areas of the brain, the result can be brain cell death and subsequent development of the memory problems common in people with Alzheimer's.
The research was conducted in rats, and it was identified that insulin and its growth factors IGF I and IGF II were produced in the nerve cells, neurons in several brain regions. Brain tissue from people who had died from Alzheimer's disease was also examined .It led to the of lower-than-normal levels of insulin and the growth factors in areas of the brain known to be involved in the development of the disease, such as the frontal cortex, hippocampus and hypothalamus. Conversely, levels appeared to be normal in another brain area, the cerebellum, which is generally not associated with 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 central nervous system. This raises the possibility of "type 3" diabetes which is believed to open the way for targeted treatment to the brain.