Insulin Via Nasal Spray May Slow Alzheimer's

Insulin inhaled via a nasal spray may slow decline in cognitive function in people with Alzheimer's disease and amnestic mild cognitive impairment, a condition thought to precede Alzheimer's, according to the results of a pilot study published online first in the Archives of Neurology on Monday.

Insulin plays a number of roles in the central nervous system, and research shows insulin levels and insulin activity are lower in the central nervous system of patients with Alzheimer's.

Previous studies have shown that insulin dysregulation in the brain appears to contribute to the development of Alzheimer's disease, which in its earliest stages is marked by synaptic loss and memory impairment. Synaptic loss is where the connections between brain cells or neurons are destroyed.

More specifically, some animal studies have shown insulin may prevent synaptic loss and reduce deposits of Aβ, the main component of amyloid plaques that is found in the brains of people with Alzheimer's disease.

In the light of this, it has been suggested that restoring insulin levels to normal in patients with Alzheimer's might protect cognitive ability, hence the reason for this study.

In their randomized, controlled trial, Dr Suzanne Craft of the Veterans Affairs Puget Sound Health Care System and the University of Washington School of Medicine, Seattle, USA, and colleagues, evaluated the effects of intranasal insulin therapy on patients with amnestic mild cognitive impairment or Alzheimer's disease.

They randomly assigned 104 participants to three study groups. The average age of the participants was 72, and more than half were men. 64 of them had amnestic mild cognitive impairment, and 40 had mild to moderate Alzheimer's disease.

For four months, 36 participants received 20 International Units (IUs) of insulin a day, 38 received 40 IUs a day, and 30 received a daily placebo, all delivered via nasal spray.

The researchers looked at the effect of the treatment on cognition, daily function, and for some participants, they measured biomarkers of cerebral glucose metabolism and cerebrospinal fluid.

The primary measures were delayed story recall (how well participants recalled a story told to them immediately after and a short time after being told it), and Dementia Severity Rating Scale (DSRS) scores of the participants (a multiple choice questionnaire that is filled in by caregivers).

The researchers also took secondary measures, including one that assesses cognitive ability (the ADAS-cog scale) and one that assesses activities of daily living in people with Alzheimer's (ADCS-ADL scale).

For the biomarkers, 23 of the participants underwent lumbar puncture and 40 underwent positron emission tomography (PET) assessment with fludeoxyglucose F 18 (a measure of glucose metabolism) before and after treatment.