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PubMed1993

Changes in 17 beta,20 alpha-hydroxysteroid dehydrogenase activity supporting an increase in the estrogen/progesterone ratio of human fetal membranes at parturition.

OBJECTIVE: Our purpose was to measure the activity of the reversible enzyme 17 beta,20 alpha-hydroxysteroid dehydrogenase around parturition with estrogen and progestogen substrates. STUDY DESIGN: Classic kinetic studies and explant cultures were used to determine kinetic parameters and net enzyme activities in both oxidative and reductive directions for both sets of substrates. RESULTS: Affinity constant values for estrone, estradiol, and 20 alpha-dihydroprogesterone were 1 to 8 mumol/L. Affinity constant for progesterone was 9 to 25 mumol/L. Maximal velocities for all substrates in the chorion were 20- to 70-fold higher than in amnion and severalfold higher for estrogen substrates compared with the progestins. Around parturition there was a significant change toward net formation of the stronger estrogen (estradiol) and the weaker progestin (20 alpha-dihydroprogesterone), suggesting an increase in the local estrogen/progesterone ratio. CONCLUSION: The enzyme 17 beta,20 alpha-hydroxysteroid dehydrogenase may be an important regulator of the local estrogen/progesterone ratio in fetal membranes around the time of parturition.

20-Hydroxysteroid Dehydrogenases↗
PubMed1998

Selective inhibition of human type 1 11beta-hydroxysteroid dehydrogenase by synthetic steroids and xenobiotics.

Functional analyses were performed with microsomal human 11beta-hydroxysteroid dehydrogenase type 1 overexpressed in the yeast Pichia pastoris. Cell extracts or microsomes from transformed strains displayed dehydrogenase and reductase activities, which were up to 10 times higher than in human liver microsomes, while for whole cells cortisone reduction but no dehydrogenase activity was observed. The synthetic glucocorticoids prednisolone and prednisone were efficiently metabolized by subcellular fractions, whereas no activity was observed with dexamethasone, budesonide and deflazacort. Inhibitors found to be effective towards the recombinant 11beta-hydroxysteroid dehydrogenase include synthetic steroids and xenobiotic compounds, revealing selective inhibition of the reaction direction, useful for development of specific inhibitors.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2000

Effects of phytoestrogens on aromatase, 3beta and 17beta-hydroxysteroid dehydrogenase activities and human breast cancer cells.

Isoflavones and others phytoestrogens have been suggested to be anticarcinogenic. Anti-aromatase, antiestrogenic or antiproliferative actions of these compounds have been postulated and related to the observation that there is a reduced incidence of breast cancer associated with diet. In this study, we explored some mechanisms by which they can exert cancer-preventive effects. Phytoestrogens were tested for estimating anti-aromatase, anti-3beta-hydroxysteroid dehydrogenase delta5/delta4 isomerase (3beta-HSD) and anti-17beta-hydroxysteroid dehydrogenase (17beta-HSD) activities in human placental microsomes. We found that isoflavonoids and compounds which presented the phenolic B ring in the 3 position on the pyran ring preferentially inhibited 3beta-HSD and/or 17beta-HSD activities than aromatase activity. We also evaluated their interactions with the estrogen receptor using a stably transfected human breast cancer cell line (MVLN). On the other hand phytoestrogens were evaluated for their effects on the proliferation in estrogen-dependent (MCF-7) and independent (MDA-MB231) human breast cancer cells. We established a relationship structure-activity and determined regions or/and substituents essential for these different activities. However, at high concentrations it seems that some phytoestrogens exert their protection against breast cancer through other estrogen-independent mechanisms.

17-Hydroxysteroid Dehydrogenases↗
PubMed1997

The sheep kidney contains a novel unidirectional, high affinity NADP(+)-dependent 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD-3).

The 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) enzymes convert corticosterone and cortisol to 11-dehydrocorticosterone and cortisone, and are thought to convey extrinsic specificity to the mineralocorticoid receptor by limiting access of the relatively more abundant glucocorticoids to it. Two different 11 beta-hydroxysteroid dehydrogenases (11 beta-HSD) have been described and cloned. The liver-type, NADP(+)-dependent 11 beta-HSD-1, has an affinity in the micromolar range and bidirectional activity. The NAD(+)-dependent 11 beta-HSD-2 has a higher affinity, in the nanomolar range, and exhibits only oxidase activity. 11 beta-HSD-2, because of its affinity and co-localization with the mineralocorticoid receptor, is likely to serve as the "gatekeeper" for the mineralocorticoid receptor in the kidney. Although the rat kidney expresses both isoforms, only the high-affinity, NAD(+)-dependent 11 beta-HSD-2 has been reported in the sheep kidney. We found both 11 beta-HSD NAD(+)- and NADP(+)-dependent activities in sheep kidney to be present. The NAD(+)-dependent activity exhibited a Km similar to that reported in the literature, 3.85 +/- 1.28 nM for corticosterone and 21.3 +/- 5.8 for cortisol, was distributed in approximately equal amounts between microsomes and nuclei, and was unidirectional, converting corticosterone to 11-dehydrocorticosterone. The enzyme exhibited prominent substrate inhibition. The NADP(+)-dependent activity had a Km for corticosterone of 4 +/- 1.3 nM for a Km for cortisol of 35.2 +/- 2 nM, 100-fold lower than that described for the 11 beta-HSD-1 in the liver of sheep and other species, and was more prevalent in the microsomes than the nuclei. This enzyme was not inhibited by its substrate. The NAD(+)-dependent activity was approximately 3-10 times greater than the NADP(+)-dependent activity when incubated with 5 nM corticosterone substrate, but had similar activity when incubated with 100 nM substrate concentrations. CHOP cells (a modified Chinese hamster ovary cell line) transiently transfected with the sheep 11 beta-HSD-2 plasmid exhibited a marked preference for NAD+ as co-factor. Oxidation of corticosterone by transfected cells in the presence of NADP+ was present, but minimal; NADP+ did not support the metabolism of cortisol, the primary glucocorticoid of sheep. These data suggest the existence of another NADP(+)-dependent enzyme, 11 beta-HSD-3, which, because of its high affinity and unidirectional oxidase activity, may play a physiological role in the modulation of glucocorticoid binding to both the mineralocorticoid and glucocorticoid receptors.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2001

Modulation of 11 beta-hydroxysteroid dehydrogenase type 2 activity in Ishikawa cells is associated with changes in cellular proliferation.

An important determinant of the potency of steroid hormones is the presence of activating and inactivating enzymes in target cells. The 11 beta-hydroxysteroid dehydrogenase type 1 and type 2 enzymes (11 beta HSD1 and 11 beta HSD2) modulate glucocorticoid action and may be important in regulating cellular growth. In the present study we examined 11 beta-hydroxysteroid dehydrogenase in Ishikawa endometrial cancer cells to see if modulation of enzyme activity could potentiate the antiproliferative effects of glucocorticoids. Ishikawa cells contain an NAD dependent enzyme migrating at 41 kDa on Western blots, consistent with the presence of the glucocorticoid-inactivating enzyme 11 beta HSD2, while the NADP dependent 11 beta HSD1 is barely detectable. Given that glucocorticoids decrease cellular proliferation we asked whether inhibition of 11 beta HSD2 could further enhance this effect. Cultivation of cells in the presence of 1 microM cortisol resulted in an elevation of 11 beta HSD2 and this was associated with a decrease in cell number. Enzyme activity and cell proliferation showed a biphasic response to the synthetic anti-progestin and anti-glucocorticoid RU38486, with < or =10 nM exerting agonistic effects and > or =100 nM producing antagonist effects in the presence of 1 microM cortisol. Inhibition of 11 beta HSD2 activity by glycyrrhetinic acid did not enhance the anti-proliferative effects of 1 microM cortisol, but the inhibitor showed significant antiproliferative activity in the absence of added glucocorticoid, consistent with protection of the low levels of glucocorticoids present in culture medium. Interestingly, the commonly used 11 beta HSD inhibitor, Carbenoxolone, did not block 11 beta HSD2 activity in whole Ishikawa cells, and there was no effect on cell proliferation, however, complete inhibition of 11 beta HSD2 was achieved in cellular homogenates suggesting that a barrier exists to entry of the inhibitor into intact cells. This study suggests that inhibition of 11 beta HSD2 activity can enhance the antiproliferative effects of low, but not high concentrations of glucocorticoids, and that beneficial effects may be attained in vivo at the nadir of diurnal glucocorticoid levels.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗
PubMedDate not supplied

11Beta-hydroxysteroid dehydrogenase activity in progesterone biotransformation by the filamentous fungus Cochliobolus lunatus.

Progesterone biotransformation was examined in relation to hydroxylating and dehydrogenating enzymes of Cochliobolus lunatus. 11beta-hydroxysteroid dehydrogenase activity (11beta-HSD) was located in cytosolic fraction and was NADP-dependent, inducible by progesterone and apparently uni-directional. Several inhibitors of 11beta-hydroxysteroid dehydrogenase were tested; furosemide, glycyrrhizic-acid and carbenoxolone did not influence the dehydrogenation of 11beta-hydroxy-4-pregnene-3,20-dione to 4-pregnene-3,11,20-trione, although grapefruit juice significantly reduced the rate of progesterone hydroxylation.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2002

Absence of type 1 11beta-hydroxysteroid dehydrogenase enzyme in koala liver.

The 11beta-hydroxysteroid dehydrogenases (11beta-HSDs) interconvert 11beta-hydroxysteroids such as cortisol into 11-oxosteroids such as cortisone. In most mammals, 11beta-HSD 1 is expressed predominantly in the liver and is active in both the oxidative (cortisol to cortisone) and dehydrogenase (cortisone to cortisol) directions, whilst 11beta-HSD 2 is expressed predominantly in the kidney and functions as a pure oxidative enzyme. We have investigated 11beta-HSD 1 activity in the Australian koala (Phascolarctos cinereus) and have found no activity (either reductive or oxidative) in hepatic microsomes. Immunoblot analysis of koala hepatic microsomes, using an 11beta-HSD 1 antibody raised against the mouse enzyme, failed to identify immunoreactive protein. Reverse transcriptase-polymerase chain reaction (RT-PCR) of koala liver mRNA and genomic PCR using primers designed against highly conserved regions of 11beta-HSD 1 nucleotide sequences were also negative. Furthermore, Southern and Northern blot analysis of koala genomic DNA and mRNA, respectively, confirmed that the koala lacks the 11beta-HSD 1 gene and gene transcript. These results support the fact that the lack of hepatic 11beta-HSD 1 activity in the koala is due to the absence of the 11beta-HSD 1 gene, and this absence is novel among mammalian species studied to date.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed1999

Type II 11beta-hydroxysteroid dehydrogenase expression in human colonic epithelial cells of inflammatory bowel disease.

Type IIbeta-hydroxysteroid dehydrogenase endows specificity on the mineralocorticoid receptor by metabolizing cortisol and regulates sodium absorption in renal and colonic epithelium. Altered expression of this enzyme may be associated with impaired sodium absorption often seen in colonic mucosa of inflammatory bowel disease. The aim of this study was to investigate possible abnormality of 11beta-hydroxysteroid dehydrogenase protein and mRNA expression in inflammatory bowel disease. In Crohn's disease, the colonic epithelium showed comparable levels of immunoreactivity and mRNA expression to those of control, except for the decreased immunoreactivity in severe inflamed lesions with deep ulcer. In contrary, a lack or decrease of immunoreactivity was relevant in ulcerative colitis regardless of the histological degree of inflammation. The mRNA expression was also significantly decreased in ulcerative colitis. This study demonstrates that abnormality of epithelial cells in ulcerative colitis includes the enzyme that regulates water and sodium absorption, which are physiologically essential.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗
PubMed1986

Active-site directed inactivation of rat ovarian 20 alpha-hydroxysteroid dehydrogenase.

Rat ovarian 20 alpha-hydroxysteroid dehydrogenase plays a pivotal role in leuteolysis and parturition by catalysing the reduction of progesterone to give the progestationally inactive steroid 20 alpha-hydroxyprogesterone. Putative mechanism based inhibitors of this enzyme were synthesized as potential progestational maintaining agents, including the epimeric allylic alcohol pair 3 beta-hydroxy-alpha-vinyl-5 alpha-androstane-17 beta-methanol and the related vinyl ketone 1-(3 beta-hydroxy-5 alpha-androstan-17 beta-yl)-2-propen-1-one. The vinyl ketone inactivates rat ovarian 20 alpha-hydroxysteroid dehydrogenase, semi-purified by poly(L-lysine)-agarose column chromatography, in a rapid time-dependent manner. Analysis of the pseudo-first-order inactivation plots gave a Ki of 2.0 microM for the inhibitor and a t1/2 for the enzyme of 20 s at saturation. These data indicate that the vinyl ketone is a potent and efficient inactivator of the ovarian dehydrogenase. Neither dialysis in the presence or absence of a competing nucleophile nor gel filtration reserves the inactivation, suggesting that a stable covalent bond is formed between the enzyme and steroid ligand. Both substrates (20 alpha-hydroxyprogesterone and NADP+) protect the enzyme from inactivation; moreover, initial velocity measurements in the presence of saturating concentrations of both substrates indicate that the vinyl ketone can behave as a competitive inhibitor, yielding a Ki value identical with that obtained in the inactivation experiments. Our results imply that the vinyl ketone is an active-site directed alkylating agent. By contrast the allylic alcohol pair 3 beta-hydroxy-alpha-vinyl-5 alpha-androstane-17 beta-methanol are neither substrates nor inhibitors of the ovarian enzyme and appear to be excluded from the catalytic site. The rapid inactivation observed with the vinyl ketone suggests that this compound may be useful as a progestational maintaining agent.

20-Hydroxysteroid Dehydrogenases↗
PubMed1990

Evidence that enzyme-generated aromatic Michael acceptors covalently modify the nucleotide-binding site of 3 alpha-hydroxysteroid dehydrogenase.

The non-steroidal allylic and acetylenic alcohols 1-(4'-nitrophenyl)prop-2-en-1-ol (I) and 1-(4'-nitrophenyl)prop-2-yn-1-ol (II) are oxidized by homogeneous 3 alpha-hydroxysteroid dehydrogenase to the corresponding alpha beta-unsaturated ketones 1-(4'-nitrophenyl)prop-2-en-1-one (III) and 1-(4'-nitrophenyl)prop-2-yn-1-one (IV), which then inactivate the enzyme selectively with high affinity; low effective partition ratios are observed for the parent alcohols [Ricigliano & Penning (1989) Biochem. J. 262, 139-149]. Inactivation of 3 alpha-hydroxysteroid dehydrogenase by compound (I) displays an NAD+ concentration optimum. Scavenging experiments indicate that the enzyme-generated inactivators (III) and (IV) alkylate the enzyme via a release-and-return mechanism. Several lines of evidence suggest that compounds (III) and (IV) covalently modify the NAD(P)(+)-binding site. First, micromolar concentrations of NAD(P)H offer substantial protection against enzyme inactivation mediated by Michael acceptors (III) and (IV). In these protection studies Kd measurements for NAD(P)H approached those measured by fluorescence titration of free enzyme. Secondly, under initial-velocity conditions compounds (III) and (IV) act essentially as competitive inhibitors of NAD+ binding, and as mixed competitive or non-competitive inhibitors against androsterone binding. Thirdly, enzyme inactivated with either compound (III) or compound (IV) fails to bind to NAD+ affinity columns (e.g. Affi-gel Blue). Under the same conditions of chromatography native enzyme and enzyme affinity-labelled at the steroid-binding site with 17 beta-bromoacetoxy-5 alpha-dihydrotestosterone is retained on the affinity column. A kinetic scheme that represents the inactivation of the homogeneous dehydrogenase by the enzyme-generated alkylators (III) and (IV) is presented.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Structural and functional comparison of two human liver dihydrodiol dehydrogenases associated with 3 alpha-hydroxysteroid dehydrogenase activity.

Two monomeric dihydrodiol dehydrogenases with pI values of 5.4 and 7.6 were co-purified with androsterone dehydrogenase activity to homogeneity from human liver. The two enzymes differed from each other on peptide mapping and in their heat-stabilities; with respect to the latter the dihydrodiol dehydrogenase and 3 alpha-hydroxysteroid dehydrogenase activities of the respective enzymes were similarly inactivated. The pI 5.4 enzyme was equally active towards trans- and cis-benzene dihydrodiols, and towards (S)- and (R)-forms of indan-1-ol and 1,2,3,4-tetrahydronaphth-1-ol and oxidized the 3 alpha-hydroxy group of C19-, C21- and C24-steroids, whereas the pI 7.6 enzyme showed high specificity for trans-benzene dihydrodiol, (S)-forms of the alicyclic alcohols and C19- and C21-steroids. Although the two enzymes reduced various xenobiotic carbonyl compounds and the 3-oxo group of C19- and C21-steroids, and were A-specific in the hydrogen transfer from NADPH, only the pI 5.4 enzyme showed reductase activity towards 7 alpha-hydroxy-5 beta-cholestan-3-one and dehydrolithocholic acid. The affinity of the two enzymes for the steroidal substrates was higher than that for the xenobiotic substrates. The two enzymes also showed different susceptibilities to the inhibition by anti-inflammatory drugs and bile acids. Whereas the pI-5.4 enzyme was highly sensitive to anti-inflammatory steroids, showing mixed-type inhibitions with respect to indan-1-ol and androsterone, the pI 7.6 enzyme was inhibited more potently by non-steroidal anti-inflammatory drugs and bile acids than by the steroidal drugs, and the inhibitions were all competitive. These structural and functional differences suggest that the two enzymes are 3 alpha-hydroxysteroid dehydrogenase isoenzymes.

3-Hydroxysteroid Dehydrogenases↗
PubMed1994

Molecular cloning of cDNA for rat ovarian 20 alpha-hydroxysteroid dehydrogenase (HSD1).

20 alpha-Hydroxysteroid dehydrogenase (20 alpha-HSD, EC 1.1.1.149) catalyses the conversion of progesterone into 20 alpha-dihydroprogesterone (20 alpha-OHP). Previously, we purified the enzyme (37 kDa) from rat ovary and determined its N-terminal amino acid sequence. In the present study we succeeded in cloning a full-length 20 alpha-HSD cDNA. mRNA was extracted from immature rat ovaries after successive treatment with equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). A cDNA library was constructed in lambda ZAP. For screening, a 576 bp probe was amplified by the PCR using mixed primers based on the N-terminal sequence of 20 alpha-HSD, and labelled with [32P]dCTP. Eight positive clones were isolated from 1.2 x 10(4) recombinants. Analysis of the nucleotide sequence revealed that one clone of 1.2 kbp cDNA (pHSD12-07) contained a polyadenylation site and an open reading frame encoding 323 amino acids with the N-terminal sequence of 20 alpha-HSD. The fusion protein of pHSD12-07 produced by Escherichia coli reacted with a specific polyclonal antibody generated against rat ovarian 20 alpha-HSD. In addition, the in vitro transcription-translation product produced by Xenopus oocytes showed 20 alpha-HSD activity and Northern-blotting analysis revealed that the ovaries from normal adult rats contained a 1.2 kb mRNA. Thus we succeeded in isolating a clone encoding the full length of rat ovarian 20 alpha-HSD. The sequence showed high similarity with those of rat liver 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD), bovine lung prostaglandin F synthase (PGFS), human liver chlordecone reductase (CDR), frog lens rho-crystallin and aldose reductases, indicating that 20 alpha-HSD belongs to the aldo-keto reductase family.

20-Hydroxysteroid Dehydrogenases↗
PubMed1994

Purification of NADPH-dependent dehydroascorbate reductase from rat liver and its identification with 3 alpha-hydroxysteroid dehydrogenase.

Rat liver cytosol has been found to reduce dehydroascorbic acid (DHAA) to ascorbic acid in the presence of NADPH. The enzyme responsible for such activity has been purified by ammonium sulphate fractionation, DEAE-Sepharose, Sephadex G-100 SF and Reactive Red column chromatography, with an overall recovery of 27%. SDS/PAGE of the purified enzyme showed one single protein band with an M(r) of 37,500. A similar value (36,800) was found by gel filtration on a Sephadex G-100 SF column. The results indicate that the enzyme is a homogeneous monomer. The Km for DHAA was 4.6 mM and the Vmax. was 1.55 units/mg of protein; for NADPH Km and Vmax. were 4.3 microM and 1.10 units/mg of protein respectively. The optimum pH was around 6.2. Several typical substrates and inhibitors of the aldo-keto reductase superfamily have been tested. The strong inhibition of DHAA reductase effected by steroidal and non-steroidal anti-inflammatory drugs, together with the ability to reduce 5 alpha-androstane-3,17-dione strongly, suggest the possibility that DHAA reductase corresponds to 3 alpha-hydroxysteroid dehydrogenase. Microsequence analysis performed on the electro-transferred enzyme band shows that the N-terminus is blocked. Internal primary structure data were obtained from CNBr-derived fragments and definitely proved the identity of NADPH-dependent DHAA reductase with 3 alpha-hydroxysteroid dehydrogenase.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Activation of human liver 3 alpha-hydroxysteroid dehydrogenase by sulphobromophthalein.

Human liver contains at least two isoenzymes (DD2 and DD4) of 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase. The NADP(H)-linked oxidoreductase activities of DD4 were activated more than 4-fold by sulphobromophthalein at concentrations above 20 microM and under physiological pH conditions. Sulphobromophthalein did not stimulate the activities of DD2 and human liver aldehyde reductase, which are functionally and/or structurally related to DD4. No stimulatory effect on the activity of DD4 was observed with other organic anions such as Indocyanine Green, haematin and Rose Bengal. The binding of sulphobromophthalein to DD4 was instantaneous and reversible, and was detected by fluorescence and ultrafiltration assays. The activation by sulphobromophthalein decreased the activation energy in the dehydrogenation reaction for the enzyme, and increased both kcat, and Km values for the coenzymes and substrates. Kinetic analyses with respect to concentrations of NADP+ and (S)-(+)-indan-1-ol indicated that sulphobromophthalein was a non-essential activator of mixed type showing a dissociation constant of 2.6 microM. Thus, the human 3 alpha-hydroxysteroid dehydrogenase isoenzyme has a binding site specific to sulphobromophthalein, and the hepatic metabolism mediated by this isoenzyme may be influenced when this drug is administered.

3-Hydroxysteroid Dehydrogenases↗
PubMed1998

The effect of growth hormone replacement therapy on cortisol-cortisone interconversion in hypopituitary adults: evidence for growth hormone modulation of extrarenal 11 beta-hydroxysteroid dehydrogenase activity.

OBJECTIVE: Growth hormone (GH) replacement therapy in hypopituitary adults has been associated with a decreased urinary ratio of 11-hydroxy/11-oxo-cortisol metabolites (CoM). This could result from GH regulation of the activity of hepatic or renal 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD1 and 2), the enzymes responsible for cortisol-cortisone interconversion, or alternatively it might reflect decreased cortisol availability. To elucidate this, we examined the effect of GH on urinary cortisol, cortisone and cortisol metabolites in hypopituitary adults at increasing doses of hydrocortisone replacement. DESIGN: Patients received increasing twice daily doses of hydrocortisone (HC) (10/10, 20/10, 40/20 mg) each week, before and during 2 months of GH replacement (0.25 U/kg/week). PATIENTS: Seven hypopituitary adults (three men and four women, age range 47-64 years) with combined GH and ACTH deficiency. Three additional patients with GH deficiency, but intact ACTH reserve, were also studied. MEASUREMENTS: Urine steroid metabolite profiles were measured in 24-hour urine collections by gas chromatography after each week of treatment. Urinary free cortisol and free cortisone were measured by radioimmunoassay as a measure of renal 11 beta-HSD-2 activity. RESULTS: Total urinary CoM increased with rising doses of HC, but at each particular HC dose, were unchanged after GH (before versus after GH, median (range): 9.67 (7.86-12.59) versus 9.93 (8.31-14.08); 15.87 (12.37-31.39) versus 17.07 (12.64-23.81); 26.68 (19.07-42.14) versus 26.77 (8.01-37.62) mg/24 hours). The urine ratio 11-hydroxy/11-oxo-CoM decreased significantly with GH treatment, at each HC dose schedule (1.22 (1.02-1.96) versus 0.92 (0.83-1.63) P = 0.018; 1.53 (1.30-2.23) versus 1.23 (0.93-1.46) P = 0.018; 1.87 (1.45-2.70) versus 1.56 (1.22-1.79) P = 0.018). The urinary ratio tetrahydrocortisols/tetrahydrocortisone, an alternative index of 11 beta-HSD activity, also fell with GH therapy at each HC dose (P = 0.049; P = 0.018; P = 0.043). In contrast, the urinary 20-hydroxy/20-oxo-CoM ratio exhibited a small increase with GH, suggesting that the changes observed above were not simply due to changes in redox status. The patients with GH deficiency, but intact ACTH reserve, demonstrated changes in urine steroid profiles similar to the group receiving hydrocortisone replacement. Urinary free cortisone and urinary free cortisol/free cortisone ratios did not change with GH therapy, but the serum cortisol/ cortisone ratio fell significantly with GH therapy at each hydrocortisone dose. CONCLUSIONS: GH therapy decreases the urinary ratios 11-hydroxy/11-oxo-cortisol metabolites and tetrahydrocortisols/tetrahydrocortisone, but not urinary free cortisone or the urinary free cortisol/free cortisone ratio. This effect is not secondary to reduced cortisol availability. These findings provide further evidence for direct or indirect modulation of cortisol metabolism by growth hormone and suggest that this occurs at hepatic or an alternative site of 11 beta-hydroxysteroid dehydrogenase-1 activity.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed2004

Pharmacodynamics and pharmacokinetics of synthetic mineralocorticoids and glucocorticoids: receptor transactivation and prereceptor metabolism by 11beta-hydroxysteroid-dehydrogenases.

Glucocorticoid (GC) and mineralocorticoid (MC) action in target tissues is determined by prereceptor metabolism by 11beta-hydroxysteroid-dehydrogenases (HSDs) and receptor transactivation. We characterized these parameters for steroids often used in clinical practice. HSD activity was examined in human liver (HSD1) and kidney microsomes (HSD2) and in CHO cells stably transfected with both enzymes. GC and MC transcriptional activity was tested by luciferase assay in CV-1 cells transfected with human GC or MC receptor expression vectors. The 11-hydroxy-group is necessary for GC and MC receptor transactivation. As HSD2 oxidizes 11-hydroxysteroids to inactive 11-dehydrosteroids, GC and MC activity in HSD2-expressing tissues (kidney, colon) is regulated by this enzyme. As 9alpha-fluorination (such as in 9alpha-fluorocortisol) decreases oxidation by HSD2 and increases both GC and MC receptor transactivation, this modification leads to optimal, but non-selective transactivation of both receptors. Increased GC receptor and decreased MC receptor transactivation leading to more selective GC activity is reached using the following substituents: 16beta-methyl (in betamethasone), 16alpha-methyl (in dexamethasone) and triangle up 1-dehydro-configuration (in prednisolone). Whereas the modifications in position 16 decrease oxidation by HSD2, the triangle up 1-dehydro-configuration increases HSD2-activity leading to an enhanced inactivation of prednisolone compared to all other steroids. 9alpha-fluorocortisol, the most frequently used substance for MC-substitution, seems to be the best choice of available steroids for this purpose. Whereas GC selectivity can be improved by hydrophobic substituents in position 16 and the triangle up 1-dehydro-configuration, maximal GC activity needs additional fluorination in position 9alpha (such as in dexamethasone). For GC therapy directed to HSD2-expressing organs, widely used prednisolone does not seem to be the optimal recommendation.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed2000

Type 1 11beta -hydroxysteroid dehydrogenase mediates glucocorticoid activation and insulin release in pancreatic islets.

Metabolic transformation of glucocorticoid hormones constitutes a determinant of their cell-specific effects. The most important reaction for this class of steroids is the reversible C11 keto/beta-hydroxyl conversion between receptor-binding 11beta-OH steroids and the nonbinding 11-oxo compounds, carried out by 11beta-hydroxysteroid dehydrogenases (11beta-HSDs). In this study, we determined the role of glucocorticoid conversion by 11beta-HSD in pancreatic islets and its function in the regulation of insulin release. Pancreatic islets isolated from ob/ob mice display type 1 11beta-hydroxysteroid dehydrogenase activity, i.e. in intact cells the reductive reaction prevails, leading from dehydrocorticosterone to corticosterone. Expression of type 1 11beta-HSD mRNA was detected by reverse transcriptase-polymerase chain reaction in islets isolated from ob/ob mice and also from human tissue. Incubation of beta-cells in the presence of 11-dehydrocorticosterone leads to a dose-dependent inhibition of insulin release, indicating cellular activation of 11-dehydrocorticosterone to the receptor ligand, further confirmed by reporter gene assays. Inhibition of 11beta-HSD activity by carbenoxolone reverses inhibition of insulin release. The presence of 11beta-HSD in islets supports the concept that reactivation of inert circulating hormone precursors in a cell-specific manner plays a major role in glucocorticoid physiology in rodents and man.

11-beta-Hydroxysteroid Dehydrogenases↗