Insulin attenuates the stimulatory effects of tumor necrosis factor α on 11β-hydroxysteroid dehydrogenase 1 in human adipose stromal cells

Obesity is frequently associated with insulin-resistance and abnormal glucose homeostasis. Recent evidence indicates that TNF alpha may play a role in mediating the insulin-resistance of obesity through its overexpression in adipose tissue. Previously, we have shown that human adipose stromal cells contain 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1) mRNA and activity. The present study was designed to examine the effects of insulin on 11 beta-HSD1 expression in human adipose stromal cells under basal and TNF alpha-stimulated conditions. The cells were obtained from breast adipose tissue by collagenase digestion, and grown to confluence under replicating conditions in 10% fetal bovine serum. The cells were transferred to serum-free medium for 24 h prior to treatment with either TNF alpha, insulin or both for a further 24 h. The level of 11 beta-HSD1 reductase activity was determined by measuring the conversion of [H-3]-cortisone to [H-3]-cortisol at a substrate concentration of 10 nM, Treatment with TNF alpha at concentrations of 0.1-10 ng/ml resulted in a dose dependent increase in 11 beta-HSD1 reductase activity from 1.5 to 10-fold. Insulin (0.1-100 nM) had no effect under basal conditions, but inhibited the stimulatory effects of TNF alpha (5 ng/ml) on 11 beta-HSD1 reductase activity in a dose dependent fashion (8-66%) inhibition. Northern blot analysis revealed corresponding changes in the level of 11 beta-HSD1 mRNA, suggesting that the effects of TNF alpha and insulin on 11 beta-HSD1 activity are mediated at the level of gene transcription. The interaction between insulin and TNF alpha suggests that local and systemic factors may act in a concerted fashion to modulate glucocorticoid activity in adipose and other peripheral tissues. (C) 2000 Elsevier Science Ltd. All rights reserved.