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

Abstract

Obesity is frequently associated with insulin-resistance and abnormal glucose homeostasis. Recent evidence indicates that TNFα 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 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) mRNA and activity. The present study was designed to examine the effects of insulin on 11β-HSD1 expression in human adipose stromal cells under basal and TNFα-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 TNFα, insulin or both for a further 24 h. The level of 11β-HSD1 reductase activity was determined by measuring the conversion of [ 3H]-cortisone to [ 3H]-cortisol at a substrate concentration of 10 nM. Treatment with TNFα at concentrations of 0.1–10 ng/ml resulted in a dose dependent increase in 11β-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 TNFα (5 ng/ml) on 11β-HSD1 reductase activity in a dose dependent fashion (8–66%) inhibition). Northern blot analysis revealed corresponding changes in the level of 11β-HSD1 mRNA, suggesting that the effects of TNFα and insulin on 11β-HSD1 activity are mediated at the level of gene transcription. The interaction between insulin and TNFα suggests that local and systemic factors may act in a concerted fashion to modulate glucocorticoid activity in adipose and other peripheral tissues.