Conditions: Mild Cognitive Impairment
Keywords: Metformin Mild Cognitive Impairment (MCI) Alzheimer's Disease (AD) Overweight Insulin
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 80
Healthy volunteers: no

Brief summary:
Hyperinsulinemia and type 2 diabetes (T2D) are important potential risk factors for cognitive decline and Alzheimer's disease (AD). Two thirds of the US adult population are at risk for hyperinsulinemia and T2D, and half of the population 85 years and older have AD. Peripheral hyperinsulinemia can impair the clearance of amyloid beta in the brain, the main culprit in AD. Thus, the investigators hypothesize that lowering peripheral insulin in overweight persons with amnestic mild cognitive impairment (AMCI), a transition state between normal cognition and AD, can decrease the risk of cognitive decline and progression to AD. The investigators propose to conduct a phase II double blinded placebo controlled randomized clinical trial of metformin, a safe and effective medication that prevents hyperinsulinemia and diabetes, to test this hypothesis among 80 overweight persons aged 55 to 90 years with AMCI. The main outcome of the study will be changes in performance in a memory test (total recall of the Selective Reminding Test) and the Score a test of general cognitive function used in clinical trials (the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog)). Another aim is to compare brain function in an area affected by Alzheimer's disease between the metformin and placebo group mean changes from beginning to end among 40 participants using a PET scan.

Detailed description:
The prevalence of Alzheimer's disease (AD) is expected to quadruple by the year 2047. There are no known curative or preventive measures for AD. Current treatment options for AD only address symptoms, and no treatments are available that focus on delaying the actual disease process. One of the currently accepted hypothesis of the pathogenesis of AD is that the main culprit is the accumulation of Aβ in the brain, and this process has become a target for treatments and preventive measures. Amnestic mild cognitive impairment (MCI) has been used to describe a transitional state between normal cognitive function and AD, and has thus been targeted for interventions. Persons with MCI progress to AD at the rate of nearly 10% to 15% per year. The criteria most commonly used for the definition of AD dementia from MCI. The investigators propose to use these criteria with slight modification to recruit persons for a pilot trail of AD prevention in persons with amnestic MCI.

Peripheral hyperinsulinemia (high insulin levels) potentially impair Aβ clearance, and in this study we are proposing to use metformin, an insulin lowering agent, to prevent AD by improving Aβ clearance in the brain. The insulin resistance syndrome and hyperinsulinemia are common in individuals with and without diabetes, and are related to increased risk of cardiovascular and cerebrovascular outcomes. Hyperinsulinemia predicts the development of diabetes; therefore, diabetes can be considered a consequence and a marker of past hyperinsulinemia. According to NHANES III data, more than 40% of the population over the age of 60 years has problems of glucose intolerance or diabetes, all related to insulin resistance and hyperinsulinemia. The investigators have found that the risk of AD in individuals without diabetes increases with increasing levels of fasting insulin, and that high insulin levels are related to a faster decline in memory scores. The high prevalence of hyperinsulinemia and diabetes (49% of the elderly in Northern Manhattan) and its biological plausibility as a risk factor for cognitive decline and AD has attracted increasing attention. In this application we are targeting hyperinsulinemia, the most important risk factor for AD identified in the elderly population of Northern Manhattan. The risk of AD attributable to hyperinsulinemia or diabetes in Northern Manhattan was 39%, and is higher in Hispanics and African-Americans, who have a higher prevalence of diabetes and insulin resistance, and will comprise the majority of our sample.

Arms:
arm 1: Placebo identical to metformin arm 2: Metformin 1000 mg twice a day

Interventions: intervention 1: Metformin intervention 2: Placebo
Intervention descriptions: intervention 1: Metformin 1000 mg twice a day titrated from 500 mg once a day intervention 2: Placebo identical to metformin 2 tablets twice a day titrated from one table once a day

Protocol document: