Insulin was discovered in 1922 by Banting and Best. Since that time, extensive research on
the mechanisms of insulin activity and action has continued. Currently, it is known that the role of insulin
is much greater than simply regulating carbohydrate metabolism. Insulin in physiological concentration
is also necessary to maintain normal vascular function.
Insulin resistance is defined as a pathological condition characterized by reduced sensitivity of skeletal
muscles, liver, and adipose tissue, to insulin and its downstream metabolic effects under normal serum
glucose concentrations. There are also selective forms of insulin resistance with unique features, including
vascular insulin resistance. Insulin resistance, both classical and vascular, contributes to vascular
impairment resulting in increased risk of cardiovascular disease. Furthermore, in the elderly population,
additional factors including redistribution of fat concentrations, low-grade inflammation, and decreased
self-repair capacity [or cell senescence] amplify the vascular abnormalities related to insulin resistance.