Depot-specific release of leptin from subcutaneous and omental adipocytes in suspension culture: effect of tumor necrosis factor-alpha and transforming growth factor-beta1

Abstract

Leptin secretion from subcutaneous fat cells was 2- to 3-fold higher than that from omental fat cells after incubation for 2 and 24h respectively. A 2-h exposure of adipocytes to 1nmol/l TNF-alpha and 400pmol/l TGF-beta1 respectively did not significantly affect leptin secretion. Whereas a 24-h incubation with 1nmol/l TNF-alpha also did not influence leptin secretion from fat cells from both depots, exposure of omental fat cells to 400pmol/l TGF-beta1 for 24h resulted in a significant inhibitory effect (by 33%) on leptin secretion (P<0.05). A 24- and 48-h exposure of in vitro differentiated human adipocytes to TNF-alpha led to a significant decrease in leptin mRNA levels to 70 +/- 8% and 49 +/- 13% of controls respectively. Similarly, TGF-beta1 decreased leptin mRNA expression in newly differentiated human adipocytes to 77 +/- 12% after 24h and to 54 +/- 8% after 48h compared with control cultures. These data provide evidence that long-term exposure of human fat cells to TNF-alpha or TGF-beta1 may suppress leptin expression in human adipose tissue. The inhibitory effect of TGF-beta1 appears to be more pronounced in omental as compared with subcutaneous adipocytes.