An intriguing early report found that a squirt of insulin deep into the nose helped ease the symptoms of early Alzheimer's disease. But the results, though promising, are preliminary, and more studies are needed to determine if the novel treatment might be an effective new dementia treatment.
The nasal drug, which people with diabetes commonly use as an injection to help keep blood sugar levels under control, also helped people with mild cognitive impairment, a form of memory loss that may lead to full-blown Alzheimer's.
In the study, the insulin was given in an aerosol form through a special device that delivered a spray deep into the nasal passages. The nose was chosen as a route of delivery of the insulin because it is known that many substances can be transported directly to the brain by passing along the olfactory nerve. This is the nerve that transmits information about odors to the brain, and is responsible for our sense of smell. Giving insulin nasally allowed relatively high concentrations of the drug to penetrate into the brain without causing dangerously high levels elsewhere in the body. The nasal form of the drug, and the device used to deliver it nasally, are only available in study settings.
For the study, researchers at the University of Washington studied 104 adults with mild Alzheimer's or mild cognitive impairment. They were divided into three groups. Some got a placebo nasal spray, and others got nasal insulin at a dose of 20 or 40 International Units. Doctors, patients or caregivers did not know who was getting what.
Participants were treated daily for a period of four months. Those getting the nasal insulin did better on tests of memory and thinking; the lower dose appeared to be more effective than the higher dose for some memory tests. Insulin appeared to produce either modest benefits or to preserve cognitive function, compared to those getting the dummy drug, who tended to continue to deteriorate.
Caregivers also rated those who had gotten insulin higher on how well they carried out everyday tasks. Markers for Alzheimer's in the spinal fluid showed signs of improvement as well in those getting the insulin sprays.
Nasal irritation was the most common side effect. Otherwise, the treatment appeared to be fairly safe.
Insulin has effects throughout the body, including the brain. The hippocampus and other regions of the brain critical for memory are rich in receptors for insulin. Insulin binds to these receptors, and might promote growth of the connections between brain cells. Insulin also might help stem the buildup of beta-amyloid, a toxic protein that builds up in the brains of those with Alzheimer's.
Other studies have shown that people with Alzheimer's have less insulin in their brains, and fewer connections between brain cells. This new finding may help to protect the brain against loss of brain cells.
Injections of insulin, the method used by people with diabetes, do not have the same brain benefits. But it's important that people with diabetes control their blood sugar, with insulin if necessary, to help protect the brain and other organs.
The researchers note that the benefits were modest, but promising. They are planning testing in many more people over longer periods to assess the safety and effectiveness of the new approach to treatment.
Current Alzheimer's treatments do nothing to delay Alzheimer's onset. Effective treatments to stem, or reverse, the brain changes are desperately needed.
By alzinfo.org, The Alzheimer's Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer's Research Foundation at The Rockefeller University.
Source: Suzanne Craft, Laura D. Baker, Thomas J. Montine, et al: "Intranasal Insulin Therapy for Alzheimer's Disease and Amnestic Mild Cognitive Impairment: A Pilot Clinical Trial." Archives of Neurology, Sept. 15, 2011, online first.