The vascular endothelium is an active, dynamic tissue that controls many important functions, including regulation of vascular tone and maintenance of blood circulation, fluidity, coagulation, and inflammatory responses. Cardiovascular risk factors affect many of the normal functions of the endothelium. In particular, oxidized low-density lipoprotein cholesterol initiates a series of events that begin with cell activation, endothelial dysfunction, local inflammation, and a procoagulant vascular surface. These conspire to result in plaque formation and ultimately plaque rupture and cardiovascular events.

Endothelial dysfunction may be evaluated by means of invasive techniques, such as coronary artery reactivity to acetylcholine, or noninvasive techniques, such as brachial artery ultrasonography. Loss of endothelium-dependent vasodilation is a characteristic feature throughout the development of atherosclerosis, and it is independently related to future adverse cardiovascular risk. Therefore, measurement of endothelial function can possibly be used to determine risk, to triage management, and to improve outcomes. At the same time, inflammation is a crucial factor in the atherosclerotic disease process. To identify and monitor the ongoing inflammatory process, markers of inflammation such as C-reactive protein (CRP) have been studied. Scientific evidence shows that elevated plasma CRP values add to the predictive ability of other established risk factors; moreover, elevated values appear to augment the Framingham Coronary Risk Score in identifying individuals who should be considered for cardioprotective treatment programs.

Interestingly, thiazolidinediones (TZDs), peroxisome proliferator-activated receptor–γ agonists that are effective in the treatment of type 2 diabetes mellitus, not only increase insulin sensitivity but can benefit endothelial function because they exhibit anti-inflammatory effects. For many individuals, including those with the metabolic syndrome and/or type 2 diabetes, endothelial dysfunction and elevated plasma CRP levels indicate increased risk of cardiovascular disease. Notably, the TZDs have been shown to reduce CRP levels and may improve endothelial function.