Researchers are investigating insulin as a possible treatment for Alzheimer's disease, and in a preliminary study, the results look promising. A study in the journal Archives of Neurology suggests that intranasal insulin - that is, delivered through the nose - may help with cognition and functioning in patients who have both mild and more severe dementia.
It's premature to think of this as a treatment; the study only looked at 104 people, and needs to be repeated in much larger groups before it can be deemed effective. But it sets the stage for broader clinical trials.
Recent research has suggested that insulin plays an important role in a number of brain functions, in addition to regulating blood sugar. Insulin promotes cell repair and cell genesis, so the thinking is that it could actually modify the course of Alzheimer's disease, says lead study author Suzanne Craft, professor of psychiatry at VA Pugent Sound and University of Washington.
It also appears to protect against the toxic effects of beta-amyloid, the protein involved in the brain plaques associated with dementia. Insulin also prevents the formation of the toxic form of tau, a biomarker found in the cerebrospinal fluid of Alzheimers' patients, Craft said.
"What we saw was that for the insulin-treated patients, the ones who had improvement in memory and function had improvement in spinal fluid biomarkers," she said.
The goal of this study was to supplement and normalize the insulin levels in the brain without affecting levels in the rest of the body. This was done with a device that was designed to deliver insulin through the nose to the brain without getting too much into the blood.
Researchers tested patients who had either early Alzheimer's or mild cognitive impairment, a team for the early stages of dementia.
Patients treated with insulin were able to remember information over a period of time better than those who got placebo; in fact, performance improved 20%. They also showed an enhancement in brain glucose metabolism in some areas; those who received placebo tended to show a decline.
Alzheimer's patients in the insulin group benefited more in terms of daily function than those with mild cognitive impairment, but by definition mild cognitive impairment does not greatly impair daily functioning.
The treatment had the mild side effects of occasional mild headache and runny nose, but had a good safety profile generally, Craft said.
In patients with mild cognitive impairment, researchers observed improvement in daily function and general cognitive abilities.
But researchers don't know what would be the optimal dosing and schedule of intranasal insulin for treating dementia; that is still an open question.
So what does this mean for diabetics who already give themselves daily injections of insulin to manage their condition?
Researchers don't yet understand how much of that insulin is actually getting into the brain, Craft said; and if you're not diabetic, having high levels of insulin in the blood is probably not good in the long run, so no one should experiment with this at home. Diabetes is a known risk factor for Alzheimer's, but there are a lot of unanswered questions about that connection.
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