One of the newer and more unorthodox theories posits that Alzheimer's may actually be a form of diabetes. Some experts have even taken to calling the brain disease type 3 diabetes, as distinct from the insulin-dependent (type 1) and adult-onset (type 2) varieties of the condition.
The diabetes hypothesis stems from growing evidence that cells in the brains of Alzheimer's victims are resistant to insulin; just as in diabetes, the cells don't respond appropriately to this hormone. As a result, neurons are deprived of glucose, which they need for energy. As the evidence mounts, the type 3 label is gaining currency in Alzheimer's research circles and is drawing attention from the pharmaceutical industry.
The link between the two diseases was made about a decade ago when scientists found accumulations of insulin in the brains of Alzheimer's patients. Doctors have long known that patients with diabetes were two to five times more likely to develop the brain-killing illness, but most Alzheimer's patients are not diabetic. Insulin creation in the brain is a separate process from insulin production elsewhere in the body, says Brown University's Dr. Suzanne de la Monte. Thus insulin resistance is separate, too. De la Monte believes that insulin resistance happens early on in Alzheimer's disease and may be the cause of dementia.
A research team led by neurobiologist William L. Klein at Northwestern University came up with more supporting evidence for the type 3 diabetes theory in September, 2007. Klein, a founder of Acumen Pharmaceuticals (a startup company in partnership with Merck), discovered that a toxic protein called ADDL damages insulin receptors on the surface of brain cells, rendering them less responsive to the hormone. "I think it's likely that if you block ADDL, you will be able to reverse or prevent Alzheimer's," he says--a bold statement given that no drug has yet been able to do either.
Source: BusinessWeek, December 17, 2007