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Modulation of 11 beta-hydroxysteroid dehydrogenase type 1 in mature human subcutaneous adipocytes by hypothalamic
Mark Friedberg1, Emmanouil Zoumakis, Naoki Hiroi
1Pediatric and Reproductive Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
Glucocorticoids are regulated at the prereceptor level by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), which interconverts inactive cortisone and active cortisol. In a previous study, we noted that patients with hypothalamic obesity had an increased ratio of cortisol/cortisone metabolites, suggesting enhanced 11 beta-HSD-1 activity. In this in vitro study, we tested the hypothesis that adipose 11 beta-HSD-1 is regulated by the hypothalamus via circulating hormones, sympathetic nervous system innervation, and/or cytokines. Preadipocytes were retrieved from sc fat from healthy nonobese individuals and differentiated in vitro to mature adipocytes. Cells were incubated with several potential effectors, and the activity of 11 beta-HSD-1 was assayed by measuring conversion of added 500 nM cortisone to cortisol. Expression of 11 beta-HSD-1 mRNA was determined by real-time PCR, whereas lipolytic effects were determined by measuring glycerol concentration in the culture medium. CRH down-regulated 11 beta-HSD-1 activity with maximal effect at 10(-9)M (65 +/- 10% of control; P < 0.001) and caused a reduction in lipolysis. Likewise, ACTH down-regulated 11 beta-HSD-1 activity with maximal effect at 10(-9) M (65 +/- 20%; P < 0.05) and reduced medium glycerol. Neither CRH nor ACTH affected 11 beta-HSD-1 mRNA expression. TNF alpha up-regulated 11 beta-HSD-1 activity maximally at 0.6 x 10(-9) M (140 +/- 20%; P < 0.001); the same cytokine increased 11 beta-HSD-1 mRNA levels to 3-fold of control (P < 0.05) and increased medium glycerol levels to 165 +/- 14% of control (P < 0.01). IL-1 beta also up-regulated 11 beta-HSD-1 activity maximally at 0.6 x 10(-9) M (160 +/- 33%; P < 0.001) and caused an increase in glycerol levels (159 +/- 11% of control; P < 0.001). Of the adrenergic agonists, salbutamol up-regulated 11 beta-HSD-1 activity maximally at 10(-7) M (162 +/- 46%; P < 0.02), and clonidine down-regulated it at 10(-7) M (82 +/- 15%; P < 0.005). We conclude that possible distinct hypothalamic mediators regulating adipose tissue 11 beta-HSD-1 might include down-regulation of 11 beta-HSD-1 activity by CRH, ACTH, and alpha 2 sympathetic stimulation, and up-regulation of the enzyme by beta 2 sympathetic stimulation and by the cytokines TNFalpha and IL-1 beta.