Untangling the evidence
Tracking down the connection between diabetes and Alzheimer's is akin to landing in the middle of an old Dragnet episode on television where Jack Webb, playing cop Joe Friday, intoned,"All we want are the facts, ma'am." Scientists understand that the two diseases are related, but they are still investigating the reason behind it.
"Many studies have linked the two diseases," says neurologist Sam Gandy, M.D., of Mount Sinai Medical School in New York. But diabetes and Alzheimer's are complex conditions, and the biological reason for the link is unclear. "The link seems to be related more to type 2 diabetes than type 1, and a key feature of type 2 diabetes is insulin resistance," he says.
Last year Gandy's laboratory studied the first gene linked to both Alzheimer's and type 2 diabetes and showed that a defect in that gene in mice is associated with the accumulation of plaques that are the hallmark of Alzheimer's.
Now Craft and her colleagues have successfully demonstrated that the nasal insulin spray "stabilizes or improves cognitive function in mild cognitive impairment or mild Alzheimer's," says Gandy. "These results must be confirmed independently, of course, before they can be accepted as fact. But if they are, although this was considered an unconventional approach, we would have a clear, plausible pathway for developing novel therapies for Alzheimer's."
William Thies, chief medical and scientific officer of the Alzheimer's Association, cautions that this is a preliminary study but notes that the results are encouraging enough to warrant a larger and longer trial. "At this point we don't have a definitive therapy for Alzheimer's, so it's good to be able to identify another direction to look for potential treatments," he says.
What to do now?
As yet, there is no cure for Alzheimer's, but preventing the development of insulin resistance through a healthy diet and exercise is an achievable goal, notes Craft. "You'll derive a benefit no matter when you start," she says. And you'll help not only your mind but your body as well.
Nissa Simon writes about health and science in New Haven, Conn.