This study was undertaken to examine the regulation of leptin production from human adipocytes by tumor necrosis factor-alpha (TNFalpha). Adipocytes were isolated from adipose tissue obtained during bariatric surgical procedures (17 women and 3 men; body mass index, 52.5 +/- 2.4 kg/m2; age, 40 +/- 3 yr) and cultured in suspension. Leptin release from sc adipocytes was inhibited 17.7 +/- 5.2% (P < 0.01), 21.6 +/- 4.3% (P < 0.005), and 37.1 +/- 7.2% (P < 0.05) by 1, 10, and 100 ng/mL TNFalpha, respectively, after 48 h in culture. At 100 ng/mL, significant inhibition of leptin release (25.8 +/- 9.7%; P < 0.05) was detected by 24 h. TNFalpha (10 ng/mL) had no effect on dexamethasone (0.1 micromol/L)-stimulated leptin production in sc adipocytes. In omental adipocytes TNFalpha inhibited leptin release 21.0 +/- 9.6% and 40.8 +/- 6.3% at 10 and 100 ng/mL by 48 h (P < 0.05). Significant inhibition ofleptin release from omental adipocytes was observed at 24 h with 100 ng/mL TNFalpha (P < 0.05). Anti-TNFalpha antibody completely blocked TNFalpha inhibition of leptin release. The ob messenger ribonucleic acid was significantly reduced (23.6 +/- 5.9%) after 48 h of TNFalpha (100 ng/mL) treatment (P < 0.025). TNFalpha had no effect on glucose uptake or lactate production in sc and omental adipocytes. The data suggest that the direct paracrine effect of adipose-derived TNFalpha is inhibition of leptin production.