Study of Nasal Insulin to Fight Forgetfulness - Long-acting Insulin Detemir - 120 Days (SL120)

It is well-known that insulin, a hormone that is naturally secreted by the pancreas, plays an important physiological role by regulating blood sugar levels in the body. Researchers now know that insulin plays many important roles in the brain as well. Insulin seems to be especially active in the part of the brain that corresponds to learning and memory. Studies have shown that when people have insufficient insulin in the brain (which, for example, is the case with Type-II diabetes), they are increasingly at risk to develop memory problems and Alzheimer's disease. In a past study, the investigators administered intravenous insulin to participants and found that it improves memory. However, that particular method would not be a practical intervention for people with Alzheimer's disease due to the risks of hypoglycemia or exacerbation of insulin resistance. Instead, the investigators use an "intranasal" method of administration, in which the insulin is inserted into a device, and administered intranasally. In this method, the insulin travels directly to the brain, and bypasses the body. Past studies have also demonstrated that this can be a reliable way to improve memory, and it does not change the body's blood glucose levels.

In our past studies, investigators have used regular insulin, which lasts about 3-4 hours and creates a similar "spike" in insulin that one would have after eating a meal. However, in normal physiology, the pancreas also releases small and more constant "pulses" of insulin throughout the day and night, establishing a base level of insulin. Accordingly, several longer-lasting types of insulin are now available that last closer to 10-12 hours, mimicking that basal level of insulin. The current study uses a long-lasting type of insulin called "insulin detemir," to determine if learning and memory will benefit from a more consistent supplement of insulin. The investigators want to determine whether this treatment can benefit people who already have a memory impairment-either they have a diagnosis of Alzheimer's disease (AD) or have a mild cognitive impairment (MCI), a condition that precedes Alzheimer's disease. The investigators will examine cognition, daily function, cerebral blood flow, and different markers of Alzheimer's disease that are in the blood and cerebral spinal fluid (CSF) as outcome measures.

The investigators have these specific aims:

1. We will test the hypothesis that compared to placebo, four months of treatment with intranasal insulin or insulin detemir will improve cognition and function in adults with AD or MCI, but that greater effects will be observed for insulin detemir.
2. We will examine the effects of intranasal insulin and insulin detemir on cerebral blood flow in adults with AD or MCI.
3. We will examine the effects of intranasal insulin and insulin detemir on CSF Aβ, tau and inflammatory markers in adults with AD or MCI.

To examine these hypotheses, the investigators are recruiting approximately 90 participants who have been diagnosed with AD or mild cognitive impairment. They will be randomly selected to take a placebo (saline), insulin detemir, or insulin. Cognition, the level of daily functioning, glucose tolerance, and cerebral blood flow will be tested before they begin the study drug, and after 16 weeks of the study drug. Some participants will also undergo a lumbar puncture both before beginning study drug and after 16 weeks of taking the study drug.