Moderately elevated levels of insulin increase levels of inflammatory markers and beta-amyloid in plasma and cerebrospinal fluid, which may contribute to Alzheimer's disease, according to an article posted online in August by Archives of Neurology that will be in the October print issue.

According to background information in the article, "conditions of insulin resistance and hyperinsulinemia are associated with elevated levels of inflammatory markers and increase the risk for Alzheimer disease (AD). Inflammation has been proposed as a key pathogenic factor for AD."

Mark A. Fishel, MD, and his American colleagues, raised blood insulin levels (while maintaining normal blood glucose levels) in 16 healthy older adults ranging in age from 55 to 81 years, and then measured changes in levels of inflammatory markers, modulators, and beta-amyloid in plasma and cerebrospinal fluid.

"Moderate peripheral hyperinsulinemia provoked striking increases in central nervous system inflammatory markers," the authors reported. "Our findings suggest that insulin-resistant conditions such as diabetes mellitus and hypertension may increase the risk for Alzheimer’s disease, in part through insulin-induced inflammation."

"Although this model has obvious relevance for diabetes mellitus, hyperinsulinemia and insulin resistance are widespread conditions that affect many nondiabetic adults with obesity, impaired glucose tolerance, cardiovascular disease, and hypertension. Our results provide a cautionary note for the current epidemic of such conditions, which, in the context of an aging population, may provoke a dramatic increase in the prevalence of AD. More encouragingly, greater understanding of insulin's role in AD pathogenesis may lead to novel and more effective strategies for treating, delaying, or even preventing this challenging disease," concluded the authors.