A team of Department of Veteran Affairs (VA) researchers were intrigued by studies that suggested that low levels of insulin in the brain could contribute to Alzheimer’s disease. The researchers, led by Dr. Suzanne Craft, decided to test the benefits of restoring normal insulin levels in the brains of Alzheimer’s patients.
Insulin is an important hormone which plays a major role in turning blood sugar into energy for cells. A lack of insulin, or an inability to properly use it, results in diabetes. Diabetes is a known risk factor for Alzheimer’s, although the connection is not yet clear.
Alzheimer’s is a disease in which cognitive functioning declines over time, causing progressive memory loss, loss of motor and language skills, impaired reasoning, emotional instability, and eventually full-blown dementia. The disease is associated with abnormal protein deposits in the brain called plaques.
The VA team used an insulin nasal spray that could deliver insulin rapidly and directly to the brain without increasing insulin levels elsewhere in the body. They recruited 104 adults with mild amnestic cognitive impairment or mild to moderate Alzheimer’s disease. They divided the participants into three groups, with one group receiving 20 international units (IU) of insulin, one receiving 40 IU, and the third receiving an inactive saline placebo. The insulin dose or placebo was delivered daily through a nasal spray for four months.
Memory, cognition and functioning ability tests were conducted on the participants both before and after the four month period. The patients in the treated groups showed an increase in brain glucose metabolism following insulin therapy. Both insulin doses improved the patients’ general cognition and functioning about 20%, and the 20 IU insulin dose also improved memory. The group receiving the placebo showed a slight decline in cognitive abilities. The treatment did not result in any major side effects, although some participants did report a mild headache or a runny nose.
Insulin appears to protect the brain against the toxic effects of beta-amyloid, the protein behind the brain plaques present in Alzheimer’s. It also prevents the formation of a toxic form of the protein tau, a biomarker for Alzheimer’s found in the cerebrospinal fluid. Insulin also promotes cell repair and growth, which may also help combat degenerative brain disease.
VA Chief Research and Development Officer Dr. Joel Kupersmith says, “VA researchers are exploring a number of possible approaches to help prevent of effectively treat this devastating disease, and these are among the most promising results to date.” The research is even more important and encouraging because there is currently no effective treatment to delay or treat Alzheimer’s disease.
There are a great many unanswered questions about the connection between insulin and Alzheimer’s, and it’s still premature to consider insulin a new treatment. Researchers still don’t know much of the daily insulin injections required by many diabetics gets into the brain, and what effects it may have in the brain of the average diabetic.
Researchers are calling for further studies to explore the use of insulin to treat Alzheimer’s, and to hopefully establish an optimal insulin dosage and dosing schedule. Any treatment which could improve the lives of the estimated 5.4 million Americans that suffer from Alzheimer’s and their caregivers can not come soon enough.