Endocrine Abstracts

Glucocorticoids regulate transcription of many genes through the binding to the glucocorticoid receptor (GR) however, their intracellular levels are tightly regulated by the microsomal enzyme 11beta-hydroxysteroid dehydrogenase. Two isozymes of this enzyme have been cloned and characterised; 11beta- hydroxysteroid dehydrogenase type 1 (11beta-HSD1) which is mainly expressed in the liver and adipose tissue and 11beta-HSD type 2 expressed in the kidney and placenta. Within 2.5kb of human 11beta-HSD1 promoter region there are five putative glucocorticoid responsive elements potentially involved in glucocorticoid gene regulation. To decipher the mechanisms that regulate 11beta-HSD1 gene induction at the transcriptional level, we carried out transfection studies using four fragments encoding -2506 to +83 (2506pr), -1382 to +83 (1382pr), -804 to +83 (804pr) and -301 to +83 (301pr) of human 11beta-HSD type 1 promoter (11beta-HSD1pr), cloned into the pGL3-enhancer vector. Luciferase activities were measured following transient transfection of the human embryonic liver cell line, WRL68. Basal luciferase activities (fold-increase above control levels, n=3) were significantly higher for the 301pr (1.89±0.30), 804pr (1.79±0.15) and 1382pr (2.33±0.12; mean±se, p<0.05) promoter constructs. Luciferase activity reverted to control levels (0.71±0.13) for 2506pr, suggesting that potent suppressor elements may exist in the 5' promoter region between -1382 and -2506bp. Since our previous studies showed up-regulation of 11beta-HSD1 expression in human preadipocytes by cortisol, the effect of glucocorticoids on our human 11beta-HSD1pr constructs was investigated. We observed an induction of luciferase activity, above control levels, of 2.57±0.18-fold for 301pr, 2.25±0.18-fold for 802pr and 2.09±0.03-fold (mean±se, p<0.05) for 1382pr by 100nM cortisol. This effect of cortisol was diminished when cells were transfected with the 2506pr construct (1.22±0.03). These data demonstrate the glucocorticoid induction of human 11beta-HSD1 gene expression. 11beta-HSD1 has emerged as a novel therapeutic target to improve insulin sensitivity and obesity by inhibiting cortisol generation locally within liver and adipose tissue.