Plasminogen activator inhibitor type-1 (PAI-1) is one of the most important inhibitors of endogenous fibrinolysis. Adipose tissue is a suggested source of the elevated plasma levels of
PAI-1 in
obesity. The relation between
PAI-1 and
inflammation is of particular interest, but current knowledge regarding regulation of
PAI-1 in adipose tissue is mainly based on animal studies or ex vivo experiments on human cultured adipocytes. So far, no study has described stimulated gene expression and
protein synthesis of
PAI-1 in vivo in human adipose tissue. We used open heart surgery as a model of acute systemic
inflammation. Twenty-two male patients underwent blood sampling and omental and subcutaneous adipose tissue biopsies for gene expression studies before and after surgery. Expression and localisation of
PAI-1 antigen was evaluated by immunohistochemistry. After surgery gene expression of
PAI-1 increased 27-fold in omental adipose tissue and three-fold in subcutaneous adipose tissue, but no differences were found in
tissue-type plasminogen activator (t-PA)
mRNA.
PAI-1 antigen was localised within endothelial cells and in the adipose tissue interstitium close to vessels. The upregulated gene expression and
protein synthesis in adipose tissue was followed by increased concentrations of
PAI-1 antigen in plasma. In conclusion, we present for the first time that an acute systemic
inflammation in humans increased gene expression and
protein synthesis of
PAI-1 in adipose tissue and that this increase was most prominent in omental adipose tissue.
PAI-1 synthesis in adipose tissue due to acute systemic
inflammation may be a link between
inflammation and impaired endogenous fibrinolysis.