Effect of Tumor Necrosis Factor Alpha and Transforming Growth Factor Beta 1 on Plasminogen Activator Inhibitor-1 Secretion from Subcutaneous and Omental Human Fat Cells in Suspension Culture

Elevated levels of plasminogen activator inhibitor-1 (PAI-1) are characteristic of the obese state and may contribute to the association between obesity and cardiovascular disease. In this study, we measured the rate of secretion of PAI-1 antigen in isolated subcutaneous and omental abdominal adipocytes from severely obese and non-obese individuals and studied the effect of selected cytokines on PAI-1 release using a suspension culture technique. PAI-1 secretion was approximately 2-fold greater in isolated fat cells from the obese versus non-obese subjects. In addition, PAI-1 mRNA levels were higher in adipose tissue samples from obese versus non-obese individuals (P < .05). PAI-1 release was also approximately 2-fold greater in omental versus subcutaneous adipocytes from both obese and non-obese subjects (each P < .05). A 24-hour exposure to 1 nmol/L tumor necrosis factor alpha (TNF-alpha) slightly increased PAI-1 release from both subcutaneous and omental adipocytes (30% +/- 21% and 17% +/- 18%, respectively, nonsignificant [NS]). Transforming growth factor beta 1 (TGF-beta1) induced a significant dose-dependent increase of PAI-1 release into the medium. Exposure to 400 pmol/L TGF-beta1 of subcutaneous and omental fat cells from both obese and non-obese individuals elevated PAI-1 secretion by 2-fold. These data provide evidence that human fat cells release a substantial amount of PAI-1 in a depot-specific manner and that TGF-beta1 particularly contributes to the regulation of PAI-1 secretion.