Modulation of hepatic inflammatory risk markers of cardiovascular diseases by PPAR-alpha activators: clinical and experimental evidence.

Atherosclerosis is a long-term chronic inflammatory disease associated with increased concentrations of inflammatory hepatic markers, such as CRP and fibrinogen, and of peripheral origin, such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-6. Peroxisome proliferator-activated receptor (PPAR-)-alpha is a ligand-activated transcription factor that regulates expression of key genes involved in lipid homeostasis and modulates the inflammatory response both in the vascular wall and the liver. PPAR-alpha is activated by natural ligands, such as fatty acids, as well as the lipid-lowering fibrates. PPAR-alpha agonists impact on different steps of atherogenesis: (1) early markers of atherosclerosis, such as vascular wall reactivity, are improved, (2) however, reduced expression of adhesion molecules on the surface of endothelial cells, accompanied by decreased levels of inflammatory cytokines, such as TNF-alpha, IL-1, and IL-6, leads to a decreased leukocyte recruitment into the arterial wall; (3) in later stages of the atherosclerotic process, PPAR-alpha agonists may promote plaque stabilization and reduce cardiovascular events, via effects on metalloproteinases, such as MMP9. Moreover, PPAR-alpha activation by fibrates also impairs proinflammatory cytokine-signaling pathways in the liver resulting in the modulation of the acute phase response reaction via mechanisms independent of changes in lipoprotein levels. Effective coronary artery disease (CAD) prevention requires the use of agents that act beyond low-density lipoprotein cholesterol-lowering. PPAR-alpha agonists appear to comprehensively address some of the abnormalities of the most common clinical phenotypes of the high CAD risk patient of the 21st century such as in the metabolic syndrome and type 2 diabetes: low high-density lipoprotein cholesterol, high triglycerides, small, dense low-density lipoprotein, and a proinflammatory, procoagulant state.