In adults with Alzheimer's disease, there is evidence that insulin levels are either abnormally low, or that the hormone does not function properly in the brain. As a result, it has been targeted as a possible therapeutic.
Now, for the first time, a nasally-administered treatment based on a manufactured form of the hormone, known as insulin detemir, has been tested on dementia patients, and has been shown to improve memory and certain cognitive functions.
Importantly, the nasal spray treatment had the greatest benefit for patients who possessed a gene known as APOE-e4, which has been shown to increase the risk of developing Alzheimer's.
The results of the pilot study, led by researchers at Wake Forest Baptist Medical Center in North Carolina, US, were published online by the Journal of Alzheimer's Disease.
Lead researcher Suzanne Craft told ScienceAlert that the most encouraging aspect of the study was the positive effect of the insulin detemir on "thinking abilities" for people with Alzheimer's who possess the common APOE-e4 genetic risk factor.
Apolipoprotein e is a gene that regulates cholesterol and comes in three forms: e2, e3, and e4. It was discovered in 1993, and remains the greatest genetic risk factor associated with Alzheimer's.
Patients who possess the e4 gene "are notoriously resistant to other therapies and interventions," Craft said, in a press release.
Previous studies have shown that doses of nasally-administered insulin can boost memory and cognitive functions in people with MCI and Alzheimer's.
However, this is the first study to look at insulin detemir, which is considered safer, and to have longer-lasting effects.
The study involved 60 patients diagnosed with amnestic MCI or mild Alzheimer's dementia. They were randomly assigned to receive one of two dosage levels of insulin detemir (a manufactured form of the hormone) or a placebo, for a period of 21 days.
Those patients who received 40 international unit (IU) doses of the manufactured insulin showed significant improvement in their short-term ability to retain and process verbal and visual information compared with those who received 20 IU does or a placebo.
While these doses only had short-term effects, Craft said "the nasal spray could encourage the growth of new brain connections that may provide long-lasting effects on memory."
Still, there was a hiccup in the study that surprised researchers: while people with the risky gene had improved memory, people without the gene actually had worse memory after taking the medication, said Craft.
"It suggests that this form of insulin may expose them to levels that are too high," she said.
And while there were some mild side-effects, including runny nose, nasal irritation and occasional dizziness, Craft said these will not hinder future development.
"A large, multi-site trial testing the effects of 18 months of insulin is currently underway at 30 centers in the US. If the results of that trial are positive, insulin may be proposed as a new therapy for Alzheimer's disease."
Source: EurekAlert