PAI-1 is a serine protease inhibitor, which can exist, either in an active inhibitory conformation or in an inactive or latent conformation. PAI-1 is produced mainly by the endothelium but is also secreted by other tissue types including adipose tissue. PAI-1 is the principal inhibitor of tissue plasminogen activator and urokinase, therefore inhibiting fibrinolysis. Increased levels of PAI-1 have been linked with various conditions including cardiovascular disease, thrombosis, insulin resistance and obesity.
