Insulin resistance and Alzheimer's disease pathogenesis: potential mechanisms and implications for treatment.

Insulin modulates cognition and other aspects of normal brain function. Insulin resistance is characterized by chronic peripheral insulin elevations, and it is accompanied by reduced brain insulin levels and insulin activity. Obesity, type 2 diabetes mellitus and hypertension are strongly associated with insulin resistance. In addition, insulin resistance increases the risk of age-related memory impairment and Alzheimer's disease. Possible mechanisms through which these risks are increased include the effects of peripheral hyperinsulinemia on memory, CNS inflammation, and regulation of the beta-amyloid peptide. We have shown that raising plasma insulin in humans to levels that characterize patients with insulin resistance increases the levels of Abeta and inflammatory agents in brain. These convergent effects may impair memory and induce AD pathology. Therapeutic strategies focused on preventing or correcting insulin abnormalities may thus benefit a subset of adults with age-related memory impairment and AD.