INSULIN AND CORTISOL PROMOTE LEPTIN PRODUCTION IN CULTURED HUMAN FAT-CELLS

The aim of this study was to investigate the regulation of leptin expr ession and production in cultured human adipocytes using the model of in vitro differentiated human adipocytes. Freshly isolated human pread ipocytes did not exhibit significant leptin mRNA and protein levels as assessed by reverse transcriptase (RT)-polymerase chain reaction (PCR ) and radioimmunoassay (RIA). However, during differentiation induced by a defined adipogenic serum-free medium, cellular leptin mRNA and le ptin protein released into the medium increased considerably in accord ance with the cellular lipid accumulation. In fully differentiated hum an fat cells, insulin provoked a dose-dependent rise in leptin protein . Cortisol at a near physiological concentration of 10(-8) mol/l was f ound to potentiate this insulin effect by almost threefold. Removal of insulin and cortisol, respectively, was followed by a rapid decrease in leptin expression, which was reversible after readdition of the hor mones. These results clearly indicate that both insulin and cortisol a re potent and possibly physiological regulators of leptin expression i n human adipose tissue.