Research has proven that the pancreas is not the only place that insulin is produced. It is also produced in the brain. According to a study from Northwestern University, there is a link between Alzheimer's disease and brain insulin resistance.
Insulin receptors in the brain are sensitive to particles known as ADDL's. When someone has Alzheimer's there are accumulations of ADDL's which appear to be responsible for deteriorating synapses in the brain. ADDL's also cause disruption of the insulin receptors in the brain, which makes them insulin resistant.
Scientists feel that this is a "brain-specific" form of diabetes. Although it's not specifically called "type 3" in the abstract of the study that appeared in the Federation of American Societies for Experimental Biology Journal (FASEBJ) the research does support the current theory that Alzheimer's may someday be considered type 3 diabetes.