TNF-alpha, but not IL-6, stimulates plasminogen activator inhibitor-1 expression in human subcutaneous adipose tissue

Plasminogen activator inhibitor-1 (PAI-1) is produced by adipose tissue, and elevated PAI-1 levels in plasma are a risk factor in the metabolic syndrome. We investigated the regulatory effects of TNF-alpha and IL-6 on PAI-1 gene induction in human adipose tissue. Twenty healthy men underwent a 3-h infusion of either recombinant human TNF-alpha (n = 8), recombinant human IL-6 (n = 6), or vehicle (n = 6). Biopsies were obtained from the subcutaneous abdominal adipose tissue at preinfusion, at 1, 2, and 3 h during the infusion, and at 2 h after the infusion. The mRNA expression of PAI-1 in the adipose tissue was measured using real-time PCR. The plasma levels of TNF-alpha and IL-6 reached 18 and 99 pg/ml, respectively, during the infusions. During the TNF-alpha infusion, adipose PAI-1 mRNA expression increased 2.5-fold at 1 h, 6-fold at 2 h, 9-fold at 3 h, and declined to 2-fold 2 h after the infusion stopped but did not change during IL-6 infusion and vehicle. These data demonstrate that TNF-alpha rather than IL-6 stimulates an increase in PAI-1 mRNA in the subcutaneous adipose tissue, suggesting that TNF-alpha may be involved in the pathogenesis of related metabolic disorders.