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      Lack of regulation of 11β-hydroxysteroid dehydrogenase type 1 during short-term manipulation of GH in patients with hypopituitarism

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          Abstract

          Objective

          Evidence from long-term clinical studies measuring urinary steroid ratios, and from in vitro studies, suggests that GH administered for longer than 2 months down-regulates 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), thereby reducing cortisol regeneration in liver and adipose tissue. We aimed to measure acute effects of GH on 11β-HSD1 in liver and adipose tissue in vivo, including using a stable isotope tracer.

          Design

          Observational studies of GH withdrawal and reintroduction in patients with hypopituitarism.

          Methods

          Twelve men with benign pituitary disease causing GH and ACTH deficiency on stable replacement therapy for >6 months were studied after GH withdrawal for 3 weeks, and after either placebo or GH injections were reintroduced for another 3 weeks. We measured cortisol kinetics during 9,11,12,12- 2H 4-cortisol (d4-cortisol) infusion, urinary cortisol/cortisone metabolite ratios, liver 11β-HSD1 by appearance of plasma cortisol after oral cortisone, and 11β-HSD1 mRNA levels in subcutaneous adipose biopsies.

          Results

          GH withdrawal and reintroduction had no effect on 9,12,12-[ 2H] 3-cortisol (d3-cortisol) appearance, urinary cortisol/cortisone metabolite ratios, initial appearance of cortisol after oral cortisone, or adipose 11β-HSD1 mRNA. GH withdrawal increased plasma cortisol 30–180 min after oral cortisone, increased d4-cortisol clearance, and decreased relative excretion of 5α-reduced cortisol metabolites.

          Conclusions

          In this setting, GH did not regulate 11β-HSD1 rapidly in vivo in humans. Altered cortisol metabolism with longer term changes in GH may reflect indirect effects on 11β-HSD1. These data do not suggest that glucocorticoid replacement doses need to be increased immediately after introducing GH therapy to compensate for reduced 11β-HSD1 activity, although dose adjustment may be required in the longer term.

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          Most cited references20

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          Regulation of expression of 11beta-hydroxysteroid dehydrogenase type 1 in adipose tissue: tissue-specific induction by cytokines.

          Patients with glucocorticoid excess develop central obesity, yet in simple obesity, circulating glucocorticoid levels are normal. We have suggested that the increased activity and expression of the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) generating active cortisol from cortisone within adipose tissue may be crucial in the pathogenesis of obesity. In this study primary cultures of human hepatocytes and adipose stromal cells (ASC) were used as in vitro models to investigate the tissue-specific regulation of 11betaHSD1 expression and activity. Treatment with tumor necrosis factor-alpha (TNFalpha) caused a dose-dependent increase in 11betaHSD1 activity in primary cultures of both sc [1743.1 +/- 1015.4% (TNFalpha, 10 ng/ml); P < 0.05 vs. control (100%)] and omental [375.8 +/- 57.0% (TNFalpha, 10 ng/ml); P < 0.01 vs. control (100%)] ASC, but had no effect on activity in human hepatocytes [90.2 +/- 2.8% (TNFalpha, 10 ng/ml); P = NS vs. control (100%)]. Insulin-like growth factor I (IGF-I) caused a dose-dependent inhibition of 11betaHSD1 activity in sc [49.7 +/- 15.0% (IGF-I, 100 ng/ml]; P < 0.05 vs. control (100%)] and omental [71.6 +/- 7.5 (IGF-I, 100 ng/ml); P < 0.01 vs. control (100%)] stromal cells, but not in human hepatocytes [101.8 +/- 15.7% (IGF-I, 100 ng/ml); P = NS vs. control (100%)]. Leptin treatment did not alter 11betaHSD1 activity in human hepatocytes, but increased activity in omental ASC [135.8 +/- 14.1% (leptin, 100 ng/ml); P = 0.08 vs. control (100%)]. Treatment with interleukin-1beta induced 11betaHSD1 activity and expression in sc and omental ASC in a time- and dose-dependent manner. 15-Deoxy-12,14-PGJ2, the putative endogenous ligand of the orphan nuclear receptor peroxisome proliferator-gamma, significantly increased 11betaHSD1 activity in omental cells [179.7 +/- 29.6% (1 microM); P < 0.05 vs. control (100%)] and sc [185.3 +/- 12.6% (1 microM); P < 0.01 vs. control (100%)] ASC, and it is possible that expression of this ligand may ensure continued cortisol generation to permit adipocyte differentiation. Protease inhibitors used in the treatment of human immunodeficiency virus infection are known to cause a lipodystrophic syndrome and central obesity, but saquinavir, indinavir, and neflinavir caused a dose-dependent inhibition of 11betaHSD1 activity in primary cultures of human omental ASC. 11betaHSD1 expression is increased in human adipose tissue by TNFalpha, interleukin-1beta, leptin, and orphan nuclear receptor peroxisome proliferator-gamma agonists, but is inhibited by IGF-I. This autocrine and/or paracrine regulation is tissue specific and explains recent clinical data and animal studies evaluating cortisol metabolism in obesity. Tissue-specific 11betaHSD1 regulation offers the potential for selective enzyme inhibition within adipose tissue as a novel therapy for visceral obesity.
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            Distinguishing the activities of 11beta-hydroxysteroid dehydrogenases in vivo using isotopically labeled cortisol.

            The isozymes of 11beta-hydroxysteroid dehydrogenase (11betaHSDs) catalyze the interconversion of cortisol and cortisone. The type 2 dehydrogenase inactivates cortisol to cortisone, whereas the type 1 catalyzes predominantly the reverse reductive reaction. These reactions take place in different tissues, where they are subject to distinct regulation, and may be important in common pathologies. Current methods to determine the activities of these enzymes in vivo rely only on the balance between cortisol and cortisone, do not measure turnover, and cannot distinguish between the two reactions. We have investigated the use of [9,11,12,12-2H4]cortisol (d4F) to distinguish the dehydrogenase and reductase activities. On metabolism by dehydrogenation, d4F loses 11alpha- deuterium, forming trideuterated cortisone (d3E) and is regenerated by reduction to trideuterated cortisol (d3F). Healthy men (n = 6) participated in a randomized, double blind, cross-over study comparing oral placebo and the 11betaHSD inhibitor, carbenoxolone (100 mg every 8 h for 7 d). d4F and its metabolites were measured in plasma and urine during a steady state infusion. Inhibition of 11betaHSDs by carbenoxolone was measured by increased steady state concentrations of d4F (41 +/- 5.1 vs. 48 +/- 7.7 nM; P < 0.05) and a fall in the rate of appearance of d3F (P < 0.05). 11betaHSD1 reductase activity could be measured specifically as conversion of d3E to d3F (28 +/- 4.2 vs. 17 +/- 3.1 nM; P < 0.05), whereas 11betaHSD2 could be measured by initial rates of appearance of d3E or from urinary ratios of d4F/(d3E + d3F) (0.73 +/- 0.06 vs. 1.02 +/- 0.03; P < 0.05). This technique offers a significant advance in the methods available to measure turnover in 11betaHSDs and isozymes of 11betaHSDs in vivo in human studies, and this study confirms that carbenoxolone inhibits both isozymes of 11betaHSD.
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              Modulation of glucocorticoid metabolism by the growth hormone - IGF-1 axis.

              The growth hormone-insulin-like growth factor 1 (GH-IGF-1) axis plays an important role in modulating the peripheral metabolism of glucocorticoids mainly through its effect on the isoenzyme 11 beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1) which, in vivo, functions as a reductase catalysing the conversion of cortisone to cortisol. Several in vivo and ex vivo studies have shown that the GH-IGF-I system inhibits the expression and activity of 11beta-HSD1 in adipose tissues and the liver resulting in reduced local regeneration of cortisol. This interaction has clinically significant implications as it may at least partly explain the phenotypes of acromegaly and adult GH deficiency and the effects that treatment of these conditions has on body composition. In addition, by accelerating the peripheral metabolism of cortisol, GH therapy may precipitate adrenal insufficiency in susceptible hypopituitary patients, and endocrinologists should be mindful of this phenomenon when starting hypopituitary patients on GH replacement therapy.

                Author and article information

                Journal
                Eur J Endocrinol
                EJE
                European Journal of Endocrinology
                BioScientifica (Bristol )
                0804-4643
                1479-683X
                September 2009
                : 161
                : 3
                : 375-380
                Affiliations
                [1 ]simpleDepartment of Endocrinology and Metabolism simpleResearch Centre for Endocrinology and Metabolism, Sahlgrenska University Hospital Gröna stråket 8, Göteborg, 413 45Sweden
                [2 ]simpleEndocrinology Unit simpleQueen's Medical Research Institute, Centre for Cardiovascular Science, University of Edinburgh Edinburgh, ScotlandUK
                Author notes
                (Correspondence should be addressed to H A Sigurjonsdottir; Email: helga.sigurjonsdottir@ 123456gu.se )
                Article
                EJE090315
                10.1530/EJE-09-0315
                2754375
                19549748
                0981e1f0-7d8e-4f19-9359-e757a93a0cb5
                © 2009 European Society of Endocrinology

                This is an Open Access article distributed under the terms of the European Journal of Endocrinology's Re-use Licence which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 5 June 2009
                : 17 June 2009
                Funding
                Funded by: British Heart Foundation
                Categories
                Clinical Study

                Endocrinology & Diabetes
                Endocrinology & Diabetes

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