3β,20α-羟基甾体脱氢酶的动力学性质

3β,20α-羟基甾体脱氢酶(3β,20α-Hydroxysteroid dehydrogenase,3β,20α-HSD)是从胎羊血中分离得到的。分子量为35kD。该酶以NADPH为辅酶,有两种底物。以孕酮为底物时,Km=30.8μmol/L,Vmax=0.7nmol min~(-1)(nmol enzyme)~(-1);以5α-二氢睾酮(5α-Dihydrotestosterone,5α-DHT)为底物时,Km=74μmol/L,Vmax=1.3nmol min~(-1)(nmol enzyme)~(-1)。5α-DHT竞争性抑制20α-还原活性,Ki=102μmol/L。16α-溴代乙酰氧基(16α-Bromo acetoxyprogesterone,16α-BAP)是3β,20α-HSD不可逆竞争性抑制剂,t_(1/2)=75min。对3β和20α还原活性的抑制常数Ki分别为23μmol/L和58μmol/L。     

Use of dydrogesterone as a progestogen for oral contraception

Dydrogesterone is a potent orally active progestogen that has been used in clinical practice for over 40 years. Chemically, it belongs to the class of retrosteroids. Dydrogesterone is closely related to endogenous progesterone. It differs from most other synthetic progestogens in that it has no estrogenic, androgenic, glucocorticoid, or anabolic effects. The use of progestogens such as dydrogesterone is indicated in all cases of relative or absolute endogenous progesterone deficiency. Nowadays, dydrogesterone is mainly used in hormone replacement therapy (HRT). The present pilot study explored whether dydrogesterone could also be used as a progestogen for oral contraception. Given its highly favorable safety and tolerability profile, it would provide improvement over existing progestogens currently used in oral contraceptives (OCs). The results of this study indicate that dydrogesterone might indeed be a suitable candidate for use in oral contraception. This concept is currently being investigated further in two open-label phase II trials.     

Expression of human aldo-keto reductase 1C2 in cell lines of peritoneal endometriosis: potential implications in metabolism of progesterone and dydrogesterone and inhibition by progestins

The human aldo-keto reductase AKR1C2 converts 5α-dihydrotestosterone to the less active 3α-androstanediol and has a minor 20-ketosteroid reductase activity that metabolises progesterone to 20α-hydroxyprogesterone. AKR1C2 is expressed in different peripheral tissues, but its role in uterine diseases like endometriosis has not been studied in detail. Some progestins used for treatment of endometriosis inhibit AKR1C1 and AKR1C3, with unknown effects on AKR1C2. In this study we investigated expression of AKR1C2 in the model cell lines of peritoneal endometriosis, and examined the ability of recombinant AKR1C2 to metabolise progesterone and progestin dydrogesterone, as well as its potential inhibition by progestins. AKR1C2 is expressed in epithelial and stromal endometriotic cell lines at the mRNA level. The recombinant enzyme catalyses reduction of progesterone to 20α-hydroxyprogesterone with a 10-fold lower catalytic efficiency than the major 20-ketosteroid reductase, AKR1C1. AKR1C2 also metabolises progestin dydrogesterone to its 20α-dihydrodydrogesterone, with 8.6-fold higher catalytic efficiency than 5α-dihydrotestosterone. Among the progestins that are currently used for treatment of endometriosis, dydrogesterone, medroxyprogesterone acetate and 20α-dihydrodydrogesterone act as AKR1C2 inhibitors with low μM K(i) values in vitro. Their potential in vivo effects should be further studied.     

Progestins as inhibitors of the human 20-ketosteroid reductases, AKR1C1 and AKR1C3

The human aldo-keto reductases 1C1 and 1C3 (AKR1C1 and AKR1C3) are important 20-ketosteroid reductases in pre-receptor regulation of progesterone action. Both AKR1C1 and AKR1C3 convert progesterone to the less potent metabolite 20α-hydroxyprogesterone, although AKR1C1 has a higher catalytic efficiency than AKR1C3. Recently, we reported significant up-regulation of AKR1C1 and AKR1C3 in ovarian endometriosis, a complex estrogen-dependent disease. The typical characteristics of endometriosis are increased formation of estradiol, which stimulates proliferation of endometriotic tissue, and disturbed action of the protective progesterone. Although progestins have been used for treatment of endometriosis since the 1960s, their detailed mechanisms of action are still not completely understood. In the present study, we evaluated the potential inhibitory effects of progestins on the pre-receptor regulatory enzymes AKR1C1 and AKR1C3. We examined the following progestins as inhibitors of progesterone reduction catalyzed by recombinant AKR1C1 and AKR1C3: progesterone derivatives (dydrogesterone, its metabolite, 20α-hydroxydydrogesterone; and medroxyprogesterone acetate), 19-nortestosterone derivatives (desogestrel, norethinodrone and levonorgestrel), and the androgen danazol. Dydrogesterone, medroxyprogesterone acetate, 20α-hydroxydydrogesterone and norethinodrone inhibited AKR1C1 and AKR1C3 with K(i) values of 1.9 μM, 7.9 μM, 20.8 μM and 48.0 μM, and of 0.5 μM, 1.4 μM, 18.2 μM and 6.6 μM, respectively. Levonorgestrel and desogestrel preferentially inhibited AKR1C3 with K(i) values of 5.6μM and 39.1μM, respectively. Our data thus show that dydrogesterone, medroxyprogesterone acetate, 20α-hydroxydydrogesterone and norethinodrone inhibit AKR1C1 and AKR1C3 in vitro, although their physiological inhibitory effects still need to be evaluated further. Additionally, we investigated whether progestin dydrogesterone can be metabolized to its active 20α-hydroxymetabolite by AKR1C1 and AKR1C3. AKR1C1 converted dydrogesterone with a high catalytic efficiency while AKR1C3 was less active, which suggests that in vivo dydrogesterone is metabolized mainly by AKR1C1. Docking simulations of dydrogesterone into AKR1C1 and AKR1C3 also support these experimental data.     

Characterization of rat and mouse NAD+-dependent 3alpha/17beta/20alpha-hydroxysteroid dehydrogenases and identification of substrate specificity determinants by site-directed mutagenesis

In this study, we characterized rat and mouse aldo-keto reductases (AKR1C16 and AKR1C13, respectively) with 92% sequence identity. The recombinant enzymes oxidized non-steroidal alcohols using NAD⁺ as the preferred coenzyme, and showed low 3α/17β/20α-hydroxysteroid dehydrogenase (HSD) activities. The substrate specificity differs from that of rat NAD⁺-dependent 3α-HSD (AKR1C17) that shares 95% sequence identity with AKR1C16. To elucidate the residues determining the substrate specificity of the enzymes, we performed site-directed mutagenesis of Tyr24, Asp128 and Phe129 of AKR1C16 with the corresponding residues (Ser, Tyr and Leu, respectively) of AKR1C17. The double mutation (Asp128/Tyr-Phe129/Leu) had few effects on the substrate specificity, while the Tyr24/Ser mutant showed only 3α-HSD activity, and the triple mutation of the three residues produced an enzyme that had almost the same properties as AKR1C17. The importance of the residue 24 for substrate recognition was verified by the mutagenesis of Ser24/Tyr of AKR1C17 which resulted in a decrease in 3α-HSD activity and appearance of 17β- and 20α-HSD activities. AKR1C16 is also 92% identical with rat NAD⁺-dependent 17β-HSD (AKR1C24), which possesses Tyr24. The replacement of Asp128, Phe129 and Ser137 of AKR1C16 with the corresponding residues (Glu, Ser and Phe, respectively) of AKR1C24 increased the catalytic efficiency for 17β- and 20α-hydroxysteroids.     

Receptor binding of allylestrenol, a progestagen of the 19-nortestosterone series without androgenic properties

Allylestrenol (17 alpha-allyl-17 beta-hydroxy-4-estren) is an orally active progestagen of the 19-nortestosterone series resembling progesterone since it has no detectable androgenic activity in animal studies and in the human. In the present study, the affinity of its 3-keto metabolite for the transformed progesterone receptor in intact MCF-7 cells was about twice that of progesterone and cyproterone acetate and about 2-3 times less than that of medroxyprogesterone acetate and norethisterone, reflecting the known progestational activity of allylestrenol. The affinity of 3-ketoallylestrenol for the transformed androgen receptor in intact MCF-7 cells was weak (like other progestagens lacking androgenic activity or possessing anti-androgenic activity) and lower than that of weakly androgenic progestagens. On the other hand, the relatively high affinity of 3-keto-allylestrenol for the non-transformed androgen receptor at 4 degrees C in the cytosol fraction did not reflect the known lack of androgenic activity of allylestrenol. Thus competitive studies carried out with transformed receptor complexes in intact cells at 37 degrees C and non-transformed complexes in cytosol distinguish progestagen with weak androgenic activity (e.g. norethisterone) from those displaying no androgenic activity or possessing anti-androgenic activity (e.g. 3-keto-allylestrenol, progesterone, cyproterone acetate and spironolactone).     

Subcellular Distribution of 3α-Hydroxysteroid Dehydrogenase and Antiestrogen Action on Androgen-Metabolizing Enzymes in Rat Pituitary Gland

Abstract: Gonadectomy of male rats led to a threefold increase of 3α-hydroxysteroid dehydrogenase (3α-HSDH) activity in pituitary homogenates that could be completely reversed by chronic administration of estradiol or 5α-dihydrotestosterone (DHT). 3α-HSDH was found to be distributed mainly between the 10,000 g and 100,000 g sediments from whole homogenates. The microsomal enzyme activity showed a substantial specificity for NADH whereas the cytosolic enzyme (100,000 g supernatant) demonstrated a slight preference for NADPH. The changes in V _max found in homogenates following gonadectomy and gonadal steroid administration reflected changes in NADH- linked activity of the microsomal, but not the cytosolic enzyme. Estradiol-induced suppression of NADH-linked 3α-HSDH activity in pituitary homogenates from gonadectomized rats of either sex was accompanied by a similar suppression of NADPH-linked 5α-reductase activity and a marked decrease of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release. In the ovariectomized rat chronic administration of nonsteroidal antiestrogens had strong estrogenic effects on 3α-HSDH activity and LH release, but not on 5α-reductase activity and FSH release. In the gonadectomized male rat, which was much less sensitive to intrinsic estrogenicity of the antiestrogens tested, nafoxidine completely blocked estradiol-induced suppression of 5α-reductase activity and FSH release and partially antagonized suppression of LH release. The trans -isomeric, substituted triphenylethylenes, tamoxifen, and enclomiphene, as well as nitromifene (mixture of trans and cis isomers) were able partially to counteract estradiol-induced suppression of 5α-reductase, but not 3α-HSDH activity. It is concluded that estradiol action on pituitary 5α-reductase, but not 3α-HSDH activity, involves an estrogen receptor mechanism.     

The preclinical biology of a new potent and selective progestin: trimegestone

Trimegestone (TMG) is a 19-norpregnane progestin being developed, in combination with an estrogen, for the treatment of postmenopausal symptoms. TMG binds to the human progesterone receptor with an affinity greater than medroxyprogesterone acetate (MPA), norethindrone (NET), and levonorgestrel (LNG). In contrast, TMG binds with low affinity to the androgen, glucocorticoid and mineralocorticoid receptor and has no measurable affinity for the estrogen receptor. Compared to other progestins, TMG demonstrates an improved separation of its PR affinity from its affinity to other classical steroid hormone receptors. In vivo, TMG has potent progestin activity. For example, TMG produces glandular differentiation of the uterine endometrium in rabbits and is about 30 and 60 times more potent than MPA and NET, respectively. In the rat, TMG maintains pregnancy, induces deciduoma formation, inhibits ovulation and has uterine anti-estrogenic activity. With respect to these endpoints, TMG appears to be more potent and selective on uterine epithelial responses than other classical progestin responses. In vivo, TMG does not have significant androgenic, glucocorticoid, anti-glucocorticoid or mineralocorticoid activity but does have anti-mineralocorticoid activity and modest anti-androgenic effects. This overall profile is qualitatively similar to progesterone. When TMG is administered chronically, it antagonizes the effect of estradiol on the uterus but does not antagonize the beneficial bone sparing activity of estradiol. In rat studies evaluating CNS GABAA receptor modulatory activity, TMG is less active on this likely undesirable endpoint than progesterone and norethindrone acetate, which may translate into fewer mood-related side effects. The results indicate that TMG is a potent and selective progestin with a preclinical profile well suited for hormone replacement therapy.     

Role of 11β-OH-C(19) and C(21) steroids in the coupling of 11β-HSD1 and 17β-HSD3 in regulation of testosterone biosynthesis in rat Leydig cells

Here we describe further experiments to support our hypothesis that bidirectional 11β-HSD1-dehydrogenase in Leydig cells is a NADP(H) regenerating system. In the absence of androstenedione (AD), substrate for 17β-HSD3, incubation of Leydig cells with corticosterone (B) or several C₁₉- and C₂₁-11β-OH-steroids, in the presence of [³H]-11-dehydro-corticosterone (A), stimulated 11β-HSD1-reductase activity. However, in presence of 30 μM AD, testosterone (Teso) synthesis is stimulated from 4 to 197 picomole/25,000 cells/30 min and concomitantly inhibited 11β-HSD1-reductase activity, due to competition for the common cofactor NADPH needed for both reactions. Testo production was further significantly increased (p < 0.05) to 224-267 picomole/25,000 cells/30 min when 10 μM 11β-OH-steroids (in addition to 30 μM AD) were also included. Similar results were obtained in experiments conducted with lower concentrations of AD (5 μM), and B or A (500 nM).Incubations of 0.3-6.0 μM of corticosterone (plus or minus 30 μM AD) were then performed to test the effectiveness of 17β-HSD3 as a possible NADP⁺ regenerating system. In the absence of AD, increasing amounts (3-44 pmol/25,000 cells/30 min) of 11-dehydro-corticosterone were produced with increasing concentrations of corticosterone in the medium. When 30 μM AD was included, the rate of 11-dehydro-corticosterone formation dramatically increased 1.3-5-fold producing 4-210 pmol/25,000 cells/30 min of 11-dehydro-corticosterone. We conclude that 11β-HSD1 is enzymatically coupled to 17β-HSD3, utilizing NADPH and NADP in intermeshed regeneration systems.     

Metabolism of cortisone-4- 14 C by rat lung tissue

The metabolism of cortisone-4-¹⁴C has been studied in male rat lung tissue preparations. Data indicate the presence of 11β-hydroxysteroid dehydrogenase, Δ⁴-5α-reductase, 3α-hydroxysteroid dehydrogenase and 20α-hydroxysteroid dehydrogenase activity in this tissue. Metabolites identified were hydrocortisone, 17α, 20α, 21-trihydroxy-4-pregnene-3, 11-dione and 3α, 17α, 21-trihydroxy-5α-pregnan-11,20-dione.     

Discovery of 2-methyl-1-{1-[(5-methyl-1H-indol-2-yl)carbonyl]piperidin-4-yl}propan-2-ol: A novel,potent and selective type 5 17β-hydroxysteroid dehydrogenase inhibitor

Type 5 17β-hydroxysteroid dehydrogenase (17β-HSD5), also known as aldo-keto reductase 1C3 (AKR1C3), is a member of the aldo-keto reductase superfamily of enzymes and is expressed in the human prostate. One of the main functions of 17β-HSD5 is to catalyze the conversion of the weak androgen, androstenedione, to the potent androgen, testosterone. The concentration of intraprostatic 5α-dihydrotestosterone (DHT) in patients following chemical or surgical castration has been reported to remain as high as 39% of that of healthy men, with 17β-HSD5 shown to be involved in this androgen synthesis. Inhibition of 17β-HSD5 therefore represents a promising target for the treatment of castration-resistant prostate cancer (CRPC). To investigate this, we conducted high-throughput screening (HTS) and identified compound 2, which displayed a structure distinct from known 17β-HSD5 inhibitors. To optimize the inhibitory activity of compound 2, we first introduced a primary alcohol group. We then converted the primary alcohol group to a tertiary alcohol, which further enhanced the inhibitory activity, improved metabolic stability, and led to the identification of compound 17. Oral administration of compound 17 to castrated nude mice bearing the CWR22R xenograft resulted in the suppression of androstenedione (AD)-induced intratumoral testosterone production. Compound 17 also demonstrated good isoform selectivity, minimal inhibitory activity against either CYP or hERG, and enhanced pharmacokinetic and physicochemical properties.     

Asoprisnil (J867): a selective progesterone receptor modulator for gynecological therapy

Asoprisnil is a novel selective steroid receptor modulator that shows unique pharmacodynamic effects in animal models and humans. Asoprisnil, its major metabolite J912, and structurally related compounds represent a new class of progesterone receptor (PR) ligands that exhibit partial agonist and antagonist activities in vivo. Asoprisnil demonstrates a high degree of receptor and tissue selectivity, with high-binding affinity for PR, moderate affinity for glucocorticoid receptor (GR), low affinity for androgen receptor (AR), and no binding affinity for estrogen or mineralocorticoid receptors. In the rabbit endometrium, both asoprisnil and J912 induce partial agonist and antagonist effects. Asoprisnil induces mucification of the guinea pig vagina and has pronounced anti-uterotrophic effects in normal and ovariectomized guinea pigs. Unlike antiprogestins, asoprisnil shows only marginal labor-inducing activity during mid-pregnancy and is completely ineffective in inducing preterm parturition in the guinea pig. Asoprisnil exhibits only marginal antiglucocorticoid activity in transactivation in vitro assays and animal models. In male rats, asoprisnil showed weak androgenic and anti-androgenic properties. In toxicological studies in female cynomolgus monkeys, asoprisnil treatment abolished menstrual cyclicity and endometrial atrophy. Early clinical studies of asoprisnil in normal volunteers demonstrated a dose-dependent suppression of menstruation irrespective of the effects on ovulation, with no change in basal estrogen concentrations and no antiglucocorticoid effects. Unlike progestins, asoprisnil does not induce breakthrough bleeding. With favorable safety and tolerability profiles thus far, asoprisnil appears promising as a novel treatment of gynecological disorders, such as uterine fibroids and endometriosis.     

In vitro effects of estrogens on rat prostatic 5 alpha-reduction of testosterone

The inhibitory effects of a variety of estrogens on rat prostate testosterone Δ4–5α-reductase activity were measured by a specific $\text{in vitro}$ assay. The conversion of ³H-testosterone (initial concentration 2.8 × 10^?9 M) to labelled 5α-dihydrotestosterone and 5α-androstane-3α, 17β-diol was used as a measure of Δ4?5a-reductase activity. At a concentration of 1.8 × 10^?6 M, estradiol was the most potent inhibitor (83.4%) of the estrogens tested. Various ester derivatives, e.g. 3-acetate, 3-phosphate, were effective inhibitors. The 17-glucuronide and 3-sulfate conjugates were less effective inhibitors. The estriol isomers exerted similar degrees of inhibition (40–60%). The 3-methoxy derivatives of estradiol and estriol were poor inhibitors. The introduction of certain groups into the steroid structure, e.g. 15α-hydroxy and 6-ketone, greatly decreased the inhibitory effect of estradiol. The nature of the oxygen function at carbon 17 did not greatly influence the inhibitory effects.     

Bifunctional enzyme activity at the same active site: Competitive inhibition kinetics with 3α/20β-hydroxysteroid dehydrogenase

20β-Hydroxy-5α-pregnan-3-one (HPO) is a competitive inhibitor of reduction by 3a/20β-hydroxysteroid dehydrogenase (3α/20β-HSD; E.C.1.1.1.53) of 17β-hydroxy-5α-androstan-3-one (DHT; 3α-activity; K_i = 4.6 × 10^?5M) and of 6β-acetoxyprogesterone (6β-AP; 20β-activity; K_i = 4.34 × 10^?5M). HPO and DHT inhibit affinity alkylation of 3α/20β-HSD by 6β-bromoacetoxyprogesterone (6β-BAP). The facts that 1) enzyme 3α-activity and 20β-activity are both competitively inhibited by HPO with practically identical K_i-values, 2) 6β-BAP is solely a 20β-activity substrate for 3α/20β-HSD, 3) one mole of 6β-BAP reacts with one mole of 30/20β-HSD to simultaneously inactivate 3α- and 20β-activity and 4) inactivation of 3α/20β-HSD by 6β-BAP is inhibited by DHT (a Cig-steroid) or HPO (a C₂₁-steroid), support the view that the same active site of 3α/20β-HSD possesses both 3α- and 20β-activity. Bifunctional activity at the same active site is considered for other steroid-specific enzymes in female mammalian reproductive systems.     

Biotransformation of progesterone by suspension cultures of Digitalis purpurea cultured cells

It has been shown that the cultured cells of Digitalis purpruea are capable of transforming progesterone (I) to 5α-pregnane-3,20-dione (II), 5α-pregnan-3β-ol-20-one (III), its glucoside (IV), 5α-pregnane-3β,20α-diol (V), its glucoside (VI), 5α-pregnane-3β,20β-diol (VII), its glucoside (VIII), Δ⁴-pregnen-20α-ol-3-one (IX), its glucoside (X), Δ-pregnen-20β-ol-3-one (XI) and its glucoside (XII). 5α-Pregnan-3β-ol-20-one glucoside (IV), 5α-pregnane-3β,20α-diol glucoside (VI), 5α-pregnane-3β,20β-diol glucoside (VIII), Δ⁴-pregnen-20α-ol-3-one glucoside (X) and Δ⁴-pregnen-20β-ol-3-one glucoside (XII) have been found for the first time as new metabolises by plant tissue cultures. A scheme for the biotransformation of progesterone (I) has been proposed, and the reduction and glucosidation activities distinctly have been observed in these cultured cells.     

Molecular interactions of progesterone derivatives with 5α-reductase types 1 and 2 and androgen receptors

The aim of this study was to ascertain the inhibitory effect of several progesterone derivatives for 5α-reductase types 1 and 2 isozymes and to determine the binding to the androgen receptor.The 3,20-dioxopregna-4-ene-17α-yl acetate 4 containing an acetoxy group in C-17 and steroid 17α-hydroxypregn-4-ene-3,20-dione 5 having a hydroxyl group in the same position inhibited both isozymes. On the other hand, 17α-hydroxy-4,5-epoxypregnan-3,20-dione 6 with an epoxy function at C-4, inhibited only the type 1 enzyme. Steroid 4-chloro-17α-hydroxypregn-4-ene-3,20-dione 7a and 4-bromo-17α-hydroxypregn-4-ene-3,20-dione 7b having the C-4 conjugated system and a chlorine or a bromine atom at C-4 respectively, inhibited both types of 5α-reductase. These results indicate that an increase in the electronegativity of ring A produces a major inhibitory activity for 5α-reductase type 1; however this increase was not observed for type 2 enzyme. When the free hydroxyl group of 7a or 7b was esterified, compounds 3,20-dioxo-4-chloropregn-4-ene-17α yl-4-ethylbenzoate 8a and 3,20-dioxo-4-bromopregn-4-ene-17α yl-4-ethylbenzoate 8b were obtained; these steroids inhibited only the 5α-reductase type 2 enzyme.Finasteride and steroids 4, 5, 7b, 8a showed a comparable in vivo pharmacological activity, however the IC₅₀ values of these compounds were higher as compared to that of finasteride.These results indicated also that steroids 4, 5, 7a, and 7b bind to the androgen receptor whereas compounds 6, 8a and 8b failed to do so.The overall data from this study showed that steroids 5 and 7b bind to the AR and decreased of the growth of prostate and seminal vesicles. Moreover, 4 decreased also the growth of seminal vesicles.     

Purification and characterization of NADP-dependent 7β-hydroxysteroid dehydrogenase from Peptostreptococcus productus strain b-52

An NADP-dependent 7β-hydroxysteroid dehydrogenase was purified 11.5-fold over the activity in crude cell extracts prepared from Peptostreptococcus productus strain b-52, by using Sephadex G-200 and DEAE-cellulose column chromatography. 7β-Dehydrogenation was the sole transformation of bile acids catalyzed by the partially purified enzyme. The enzyme preparation (spec. act. 2.781 IU per mg protein) had an optimum pH of 9.8. Lineweaver-Burk plots showed a Michaelis constant (K_m) value of 0.05 mM for 3α,7β-dihydroxy-5β-cholanic acid whereas higher values were obtained with 3α,7β-dihydroxy-5β-cholanoyl glycine (0.20 mM), and 3α,7β-dihydroxy-5β-cholanoyl taurine (0.26 mM). NADP but not NAD could function as an electron acceptor, and has a K_m value of 0.30 mM. A molecular weight of 64 000 was determined by SDS-polyacrylamide gel electrophoresis. The addition of 0.4 mM of either bile acid to the growth medium suppressed not only cell growth, but also the enzyme yield.     

Tissue selectivity and potential clinical applications of trenbolone (17β-hydroxyestra-4,9,11-trien-3-one): A potent anabolic steroid with reduced androgenic and estrogenic activity

Recently, the development of selective androgen receptor modulators (SARMs) has been suggested as a means of combating the deleterious catabolic effects of hypogonadism, especially in skeletal muscle and bone, without inducing the undesirable androgenic effects (e.g., prostate enlargement and polycythemia) associated with testosterone administration. 17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone; 17β-TBOH), a synthetic analog of testosterone, may be capable of inducing SARM-like effects as it binds to androgen receptors (ARs) with approximately three times the affinity of testosterone and has been shown to augment skeletal muscle mass and bone growth and reduce adiposity in a variety of mammalian species. In addition to its direct actions through ARs, 17β-TBOH may also exert anabolic effects by altering the action of endogenous growth factors or inhibiting the action of glucocorticoids. Compared to testosterone, 17β-TBOH appears to induce less growth in androgen-sensitive organs which highly express the 5α reductase enzyme (e.g., prostate tissue and accessory sex organs). The reduced androgenic effects result from the fact that 17β-TBOH is metabolized to less potent androgens in vivo; while testosterone undergoes tissue-specific biotransformation to more potent steroids, dihydrotestosterone and 17β-estradiol, via the 5α-reductase and aromatase enzymes, respectively. Thus the metabolism of 17β-TBOH provides a basis for future research evaluating its safety and efficacy as a means of combating muscle and bone wasting conditions, obesity, and/or androgen insensitivity syndromes in humans, similar to that of other SARMs which are currently in development.     

Local metabolism of glucocorticoids in Prague hereditary hypertriglyceridemic rats--effect of hypertriglyceridemia and gender

11β-Hydroxysteroid dehydrogenase type 1 (11HSD1) is a microsomal NADPH-dependent oxidoreductase which elevates intracellular concentrations of active glucocorticoids. Data obtained from mouse strains with genetically manipulated 11HSD1 showed that local metabolism of glucocorticoids plays an important role in the development of metabolic syndrome. Tissue specific dysregulation of 11HSD1 was also found in other models of metabolic syndrome as well as in a number of clinical studies. Here, we studied local glucocorticoid action in the liver, subcutaneous adipose tissue (SAT) and skeletal muscles of male and female Prague hereditary hypertriglyceridemic rats (HHTg) and their normotriglyceridemic counterpart, the Wistar rats. 11HSD1 bioactivity was measured as a conversion of [³H]11-dehydrocorticosterone to [³H]corticosterone or vice versa. Additionally to express level of active 11HSD1 protein, enzyme activity was measured in tissue homogenates. mRNA abundance of 11HSD1, hexoso-6-phosphate dehydrogenase (H6PDH) and the glucocorticoid receptor (GR) was measured by real-time PCR. In comparison with normotriglyceridemic animals, female HHTg rats showed enhanced regeneration of glucocorticoids in the liver and the absence of any changes in SAT and skeletal muscle. In contrast to females, the glucocorticoid regeneration in males of HHTg rats was unchanged in liver, but stimulated in SAT and downregulated in muscle. Furthermore, SAT and skeletal muscle exhibited not only 11-reductase but also 11-oxidase catalyzed by 11HSD1. In females of both strains, 11-oxidase activity largely exceeded 11-reductase activity. No dramatic changes were found in the mRNA expression of H6PDH and GR. Our data provide evidence that the relationship between hypertriglyceridemia and glucocorticoid action is complex and gender specific.