Inhalation of insulin through the nose twice a day appears to slow down and, in some cases, reverse symptoms of memory loss in people with early signs of Alzheimer's disease, a new study finds.

The results were published in the journal Archives of Neurology.

The study, led by Suzanne Craft, a professor of psychiatry and behavioral sciences at the University of Washington, was supported by the U.S. National Institutes of Health. She led the research team at the Veterans Affairs Puget Sound Health Care System and the university's medical school in Seattle.

The study involved 104 patients with mild cognitive decline or mild to moderate case of Alzheimer's.

Study participants were randomly assigned to one of three groups. In first group, 36 participants got a moderate dose of insulin sprayed daily into their nose. In second group, 36 patients got a higher dose daily. In third group, 30 participants got a placebo daily for four months.

Treatments were given through a nasal drug delivery device made by Kurve Technology of Bothell, Wash.

After four months, the group that got the moderate insulin dose showed improvements in delayed story recall compared with the placebo group. There was no improvement in the group that got the high dose compared with the placebo group.

Alzheimer's disease, the most common form of dementia in the elderly, initially causes difficulty with thought, memory and language, and insulin dysfunction is thought to play a role in the symptoms.

The researchers assessed insulin's effects on thought processes, everyday functioning and glucose metabolism in the brain, among other factors. Insulin is a metabolic hormone best known for its role in treating diabetes, a condition in which the hormone is either insufficiently produced or poorly used by the body's organs. Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body.

Insulin causes cells in the liver, muscle and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle. Insulin stops the use of fat as an energy source by inhibiting the release of glucagon.

Insulin also influences other body functions, such as vascular compliance and cognition. Once insulin enters the human brain, it enhances learning and memory and benefits verbal memory, in particular. Enhancing brain insulin signaling by means of intranasal insulin administration also enhances the acute thermo-regulatory and gluco-regulatory response to food intake, suggesting that central nervous insulin contributes to the control of whole-body energy homeostasis in humans.

The study authors also found that participants with Alzheimer's who got either dose of insulin, better preserved functions as compared to people taking the placebo.

The placebo group showed slight declines overall.

More research is needed to see if insulin therapy can be recommended for staving off the symptoms of Alzheimer's, but researchers are optimistic about the findings.

Medicine