Metabolism Of Dihydrotestosterone Research Articles

Genomic Markers and Personalized Medicine in Androgenetic Alopecia: A Comprehensive Review

Androgenetic alopecia (AGA) is the most common form of hair loss, significantly affecting both men and women worldwide. Characterized by progressive hair thinning and loss, AGA is primarily mediated by dihydrotestosterone (DHT). Recent research has identified numerous single-nucleotide polymorphisms (SNPs) associated with AGA, particularly in genes involved in androgen metabolism, prostaglandin pathways, and vasodilation. These genetic markers offer insights into AGA pathophysiology and potential therapeutic targets. Pharmacogenetics, the study of how genetic variations influence drug response, holds promise for personalized AGA treatment. Identifying SNPs that affect the efficacy of treatments like minoxidil and finasteride enables the development of tailored therapeutic strategies. For instance, genetic variants in the SRD5A2 gene, which affects DHT metabolism, can predict responsiveness to 5-alpha-reductase inhibitors. Beyond pharmacogenetics, RNA interference (RNAi) technologies, e.g., small interfering RNAs (siRNAs), present new therapeutic avenues. Studies have shown the efficacy of RNAi-based treatments in targeting androgen receptors, promoting hair growth in AGA models. Integrating genetic and pharmacogenetic research into clinical practice can transform AGA management, enhancing treatment efficacy and patient outcomes. In conclusion, genetic and pharmacogenetic insights are crucial for developing personalized treatments for AGA, while emerging RNAi technologies offer promising new interventions. These advancements represent significant steps toward more effective and individualized AGA therapies.

Dihydrotestosterone (DHT) rapidly increase after maximal aerobic exercise in healthy males: the lowering effect of phosphodiesterase's type 5 inhibitors on DHT response to exercise-related stress.

Few data exist on dihydrotestosterone (DHT) adaptation to exercise-related stress. The aim of the study was to investigate on serum DHT and other androgens' responses to acute aerobic exercises, and to verify if a long-acting phosphodiesterase's type 5 inhibitors could influence these responses, as previously observed for salivary testosterone. In a double-blind cross over study, 12 healthy trained male volunteers were submitted to both an acute sub-maximal and maximal exercise tests on cycle ergometer, after randomly receiving a two days placebo or tadalafil administration (20mg, Cialis®, Ely-Lilly, Indianapolis, IN, USA). Blood sample collections were performed at different time points before and after exercise. Serum DHT, total testosterone (TT), dehydroepiandrosterone sulfate (DHEAS) and luteinizing hormone (LH), were assayed. Serum DHT increase in placebo treatment immediately post maximal aerobic exercise and return to basal values at 60min of recovery whereas tadalafil administration significantly reduced the DHT increase after exercise. The values of areas under curves showed the increase of TT after acute sub-maximal and maximal exercise and of DHEAS only after acute maximal aerobic exercise independently from treatment. In addition to testosterone, also DHT plays an exercise-related adaptive role during high intensity aerobic exercise, but its rapid useful effects during exercise have to be determined. We hypothesized that the increased androgens secretion during exercise could be mainly related to steroidogenic enzymes modifications in peripheral tissues (i.e., muscles). Moreover, the blunting effect of tadalafil on DHT increase support a possible role of peripheral nitric oxide/GMPc related pathways in influencing physical-stress related DHT metabolism.

Effects of 12 Weeks Resistance Exercise on Blood Testosterone, DHT and Bone-Related Metabolism in Orchiectomized Rats

PURPOSE: Osteoporosis is a public health problem that requires constant attention in an aging society. This study examines the effects of 12 weeks of resistance training on serum sex steroid hormone and bone metabolism factors in orchiectomized rats.METHODS: A total of 30 male Sprague-Dawley (20 week-old) rats divided into three groups; (1) CON (normal-control, n=10), (2) ORX-CON (orchiectomized-control, n=10), (3) ORX-RE (orchiectomized-resistance exercise, n=10). The resistance training performed ladder climbing (8 repetitions, three days per week for 12 weeks) starting 1 week after surgery.RESULTS: The investigation revealed that compared to the CON group, the ORX-CON group showed significantly lower levels of testosterone, dihydrotestosterone (DHT), grip strength, bone mineral density (BMD) and breaking force, but much higher levels of osteocalcin and CTx-1. The ORX-RE group showed increased grip strength, hormones (testosterone and DHT), osteocalcin, and BMD compared to ORX-CON group.CONCLUSIONS: These findings suggest that resistance exercise training may be an intervention strategy for prevention osteoporosis and fracture in male aging process.

The gut microbiota is a major regulator of androgen metabolism in intestinal contents.

Androgens exert important effects both in androgen-responsive tissues and in the intestinal tract. To determine the impact of the gut microbiota (GM) on intestinal androgen metabolism, we measured unconjugated (free) and glucuronidated androgen levels in intestinal contents from the small intestine, with a low bacterial density, and from cecum and colon, with a high bacterial density. Using a specific, sensitive gas chromatography-tandem mass spectrometry method, we detected high levels of glucuronidated testosterone (T) and dihydrotestosterone (DHT) in small intestinal content of mice of both sexes, whereas in the distal intestine we observed remarkably high levels of free DHT, exceeding serum levels by >20-fold. Similarly, in young adult men high levels of unconjugated DHT, >70-fold higher than in serum, were detected in feces. In contrast to mice with a normal GM composition, germ-free mice had high levels of glucuronidated T and DHT, but very low free DHT levels, in the distal intestine. These findings demonstrate that the GM is involved in intestinal metabolism and deglucuronidation of DHT and T, resulting in extremely high free levels of the most potent androgen, DHT, in the colonic content of young and healthy mice and men.

Altered polyamine profiling in the hair of patients with androgenic alopecia and alopecia areata.

Hair follicles are among the most highly proliferative tissues. Polyamines are associated with proliferation, and several polyamines including spermidine and spermine play anti-inflammatory roles. Androgenic alopecia results from increased dihydrotestosterone metabolism, and alopecia areata is an autoimmune disease. This study aimed to investigate differences in polyamine profiles in hair samples between patients with androgenic alopecia and alopecia areata. Polyamine concentrations were determined through high-performance liquid chromatography-mass spectrometry. Hair samples were derivatized with isobutyl chloroformate. Differences in polyamine levels were observed between androgenic alopecia and alopecia areata compared with normal controls. In particular, polyamine levels were higher in alopecia areata patients than in normal controls. Certain polyamines displayed different concentrations between the androgenic alopecia and alopecia areata groups, suggesting that some polyamines, particularly N-acetyl putrescine (P=0.007) and N-acetyl cadaverine (P=0.0021), are significantly different in androgenic alopecia. Furthermore, spermidine (P=0.021) was significantly different in alopecia areata. Our findings suggest that non-invasive quantification of hair polyamines may help distinguish between androgenic alopecia and alopecia areata. Our study provides novel insights into physiological alterations in patients with androgenic alopecia and those with alopecia areata and reveals some differences in polyamine levels in hair loss diseases with two different modes of action.

MP62-08 THE CATALYTIC SITE COMMON TO FOUR 3?-OXIDOREDUCTASES CONTRIBUTES TO INTRACRINE SYNTHESIS OF DHT

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology I1 Apr 2016MP62-08 THE CATALYTIC SITE COMMON TO FOUR 3?-OXIDOREDUCTASES CONTRIBUTES TO INTRACRINE SYNTHESIS OF DHT Michael Fiandalo, John Wilton, John Stocking, Krystin Mongiardo, Elena Pop, Yun Li, Kris Attwood, Elisabeth Wilson, and James Mohler Michael FiandaloMichael Fiandalo More articles by this author , John WiltonJohn Wilton More articles by this author , John StockingJohn Stocking More articles by this author , Krystin MongiardoKrystin Mongiardo More articles by this author , Elena PopElena Pop More articles by this author , Yun LiYun Li More articles by this author , Kris AttwoodKris Attwood More articles by this author , Elisabeth WilsonElisabeth Wilson More articles by this author , and James MohlerJames Mohler More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.916AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Almost all men who present with advanced prostate cancer (CaP) and some men who fail therapy are treated with androgen deprivation therapy (ADT). ADT is not curative and CaP recurs as the lethal phenotype. One mechanism that may contribute to CaP resistance to ADT is intracrine metabolism, the conversion of weak adrenal androgens to testicular androgens, testosterone (T) or dihydrotestosterone (DHT). Previous work from our laboratory has shown that the primary backdoor pathway generates DHT without using T as an intermediate substrate. The final step in the primary backdoor pathway involves the conversion of 5-androstane3α,17β-diol (androstanediol) to DHT by 4 enzymes, HSD17B6, RDH16, DHRS9 or RDH5. Inhibition of the step immediately proximate to intracrine metabolism of DHT should lower DHT more effectively than inhibitors of 5α-reductases and/or CYP17A1, which act earlier in intracrine metabolism pathways. The goal of this project is to inhibit the enzymes responsible for the conversion of androstanediol to DHT. METHODS Bioinformatics tools were used to analyze the protein sequences of these 4 enzymes to determine if these enzymes shared common catalytic amino acid residues. Site-directed mutagenesis and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to test the catalytic significance of the common catalytic amino acid residues and if mutation of these catalytic residues inhibited androstanediol conversion to DHT. RESULTS The NCBI Constraint-based Multiple Protein Alignment Tool (COBALT) showed that the 4 enzymes share catalytic amino acid residues. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) confirmed that these 4 enzymes convert androstanediol to DHT and androsterone to androstanedione. Site-directed mutagenesis was used to generate single, double or catalytic deletion enzyme mutants. LC-MS/MS showed that single, double and complete catalytic deletion of the common catalytic amino acids impaired enzyme activity. Furthermore, the impaired catalytic mutants combined with dutasteride decreased CaP cell line DHT levels more than dutasteride alone. CONCLUSIONS These results demonstrate that a new treatment directed against the terminal steps in the primary backdoor pathway may decrease DHT levels better than ADT alone. Further reduction of tissue DHT levels by inhibiting the last step in intracrine metabolism may improve response to ADT or induce re-remission of castration-recurrent CaP (CRCP) and improve survival of men with advanced CaP. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e814-e815 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Michael Fiandalo More articles by this author John Wilton More articles by this author John Stocking More articles by this author Krystin Mongiardo More articles by this author Elena Pop More articles by this author Yun Li More articles by this author Kris Attwood More articles by this author Elisabeth Wilson More articles by this author James Mohler More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Classical and Non-Classical Roles for Pre-Receptor Control of DHT Metabolism in Prostate Cancer Progression.

Androgens play an important role in prostate cancer (PCa) development and progression. Accordingly, androgen deprivation therapy remains the front-line treatment for locally recurrent or advanced PCa, but patients eventually relapse with the lethal form of the disease termed castration resistant PCa (CRPC). Importantly, castration does not eliminate androgens from the prostate tumor microenvironment which is characterized by elevated tissue androgens that are well within the range capable of activating the androgen receptor (AR). In this mini-review, we discuss emerging data that suggest a role for the enzymes mediating pre-receptor control of dihydrotestosterone (DHT) metabolism, including AKR1C2, HSD17B6, HSD17B10, and the UGT family members UGT2B15 and UGT2B17, in controlling intratumoral androgen levels, and thereby influencing PCa progression. We review the expression of steroidogenic enzymes involved in this pathway in primary PCa and CRPC, the activity and regulation of these enzymes in PCa experimental models, and the impact of genetic variation in genes mediating pre-receptor DHT metabolism on PCa risk. Finally, we discuss recent data that suggests several of these enzymes may also play an unrecognized role in CRPC progression separate from their role in androgen inactivation.

Concept and viability of androgen annihilation for advanced prostate cancer.

There remains no standard of care for patients with a rising prostate-specific antigen level after radical prostatectomy or radiotherapy but who have no radiographic metastases, even though this is the second largest group of patients with prostate cancer (CaP) in the United States. Androgen deprivation therapy (ADT) may cure some men with advanced CaP based on single-institution series and a randomized clinical trial of immediate versus delayed ADT for men found to have pelvic lymph node metastasis at the time of radical prostatectomy. ADT may be more effective when initiated for minimal disease burden, which can be detected using PSA after radical prostatectomy or radiotherapy, and if more complete disruption of the androgen axis using newer agents decreases the chance that androgen-sensitive cells survive to adapt to a low-androgen environment. Androgens may be "annihilated" simultaneously using a luteinizing hormone-releasing hormone antagonist or agonist to inhibit testicular production of testosterone, a P45017A1 (CYP17A1) inhibitor to diminish metabolism of testosterone via the adrenal pathway and dihydrotestosterone (DHT) via the backdoor pathway, a 5α-reductase (SRD5A) inhibitor to diminish testosterone reduction to DHT and backdoor metabolism of progesterone substrates to DHT, and a newer antiandrogen to compete better with DHT for the androgen receptor ligand-binding domain. Early initiation of androgen annihilation for induction as part of planned intermittent ADT should be safe, may reduce tumor burden below a threshold that allows eradication by the immune system, and may cure many men who have failed definitive local therapy.

Estrogen receptor beta dependent attenuation of cytokine-induced cyclooxygenase-2 by androgens in human brain vascular smooth muscle cells and rat mesenteric arteries

Androgens may provide protective effects in the vasculature under pathophysiological conditions. Our past studies have shown that dihydrotestosterone (DHT) decreases expression of cyclooxygenase-2 (COX-2) during cytokine, endotoxin, or hypoxic stimulation in human vascular smooth muscle cells, in an androgen receptor (AR)-independent fashion. Classically DHT is regarded as a pure AR agonist; however, it can be endogenously metabolized to 5α-androstane-3β, 17β-diol (3β-diol), which has recently been shown to be a selective estrogen receptor (ERβ) agonist. Therefore, we hypothesized that DHT’s anti-inflammatory properties following cytokine stimulation are mediated through ERβ. Using primary human brain vascular smooth muscle cells (HBVSMC), we tested whether DHT’s effect on IL-1β induced COX-2 expression was mediated via AR or ERβ. The metabolism of DHT to 3β-diol is a viable pathway in HBVSMC since mRNA for enzymes necessary for the synthesis and metabolism of 3β-diol [3alpha-hydroxysteroid dehydrogenase (HSD), 3β-HSD, 17β-HSD, CYP7B1] was detected. In addition, the expression of AR, ERα, and ERβ mRNA was detected. When applied to HBVSMC, DHT (10nM; 18h) attenuated IL-1β-induced increases in COX-2 protein expression. The AR antagonist bicalutamide did not block DHT’s ability to reduce COX-2. Both the non-selective estrogen receptor antagonist ICI 182,780 (1μM) and the selective ERβ antagonist PHTPP (1μM) inhibited the effect of DHT, suggesting that DHT actions are ERβ-mediated. In HBVSMC and in rat mesenteric arteries, 3β-diol, similar to DHT, reduced cytokine-induced COX-2 levels. In conclusion, DHT appears to be protective against the progression of vascular inflammation through metabolism to 3β-diol and activation of ERβ.

Functional Analysis of UGT1A4 P24T and UGT1A4 L48V Variant Enzymes

Aim: To investigate the effects of two nonsynonymous SNPs, UGT1A4*2 (rs#: 6755571, 70C>A, P24T) and UGT1A4*3 (rs#: 2011425, 142T>G, L48V), on the function of UGT1A4 against dihydrotestosterone (DHT), transandrosterone (t-AND), lamotrigine (LTG) and tamoxifen (TAM). Materials & methods: Detailed kinetic experiments were conducted with recombinant UGT1A4wild-type, UGT1A4P24T and UGT1A4L48V, which were overexpressed in HEK293 cell lines. The kinetic profiles and kinetic parameters (Km, Vmax and CLint) obtained with either UGT1A4P24T or UGT1A4L48V were compared with those obtained with the wild-type enzyme. The interaction of TAM on UG1A4-catalyzed DHT glucuronidation was also investigated with the three UGT1A4 polymorphic enzymes. Results: UGT1A4L48V had higher enzyme efficiency (CLint) compared with wild-type UGT1A4 on DHT glucuronidation; UGT1A4P24T and UGT1A4L48V had lower CLint than wild-type UGT1A4 for t-AND and LTG glucuronidation. The TAM CLint with UGT1A4P24T and UGT1A4L48V glucuronidation and the UGT1A4P24T-catalyzed DHT glucuronidation were, on the other hand, similar to those of the wild-type enzyme. With all three enzymes, TAM activated UGT1A4-catalyzed DHT glucuronidation in a concentration-dependent fashion. Conclusion: Decreased CLint of UGT1A4P24T and UGT1A4L48V on LTG glucuronidation may lead to interindividual variations in LTG metabolism in vivo. However, it is less likely that these polymorphisms would have impact on DHT and t-AND metabolism in vivo because these compounds are glucuronidated by multiple enzymes. Original submitted 31 May 2011; Revision submitted 19 July 2011

The Role of Non-Aromatizable Testosterone Metabolite in Metabolic Pathways

Dihydrotestosterone (DHT) originates via irreversible reduction of testosterone by catalytic activity of 5alpha-reductase enzyme and it is demonstratively the most effective androgen. Androgens influence adipose tissue in men either directly by stimulation of the androgen receptor or indirectly, after aromatization, by acting at the estrogen receptor. DHT as a non-aromatizable androgen could be responsible for a male type fat distribution. The theory of non-aromatizable androgens as a potential cause of a male type obesity development has been studied intensively. However, physiological levels of DHT inhibit growth of mature adipocytes. In animal models, substitution of DHT in males after gonadectomy has a positive effect on body composition as a testosterone therapy. Thus, DHT within physiological range positively influences body composition. However, there are pathological conditions with an abundance of DHT, e.g. androgenic alopecia and benign prostatic hyperplasia. These diseases are considered as risk factors for development of metabolic syndrome or atherosclerosis. In obese people, DHT metabolism in adipose tissue is altered. Local abundance of non-aromatizable androgen has a negative effect on adipose tissue and it could be involved in pathogenesis of metabolic and cardiovascular diseases. Increased DHT levels, compared to physiological levels, have negative effect on development of cardiovascular diseases. Difference between the effect of physiological and increased level brings about certain paradox.

Genetic Variation of Genes Involved in Dihydrotestosterone Metabolism and the Risk of Prostate Cancer

Dihydrotestosterone (DHT) is an important factor in prostate cancer (PCA) genesis and disease progression. Given PCA's strong genetic component, we evaluated the possibility that variation in genes involved in DHT metabolism influence PCA risk. We investigated copy number variants (CNV) and single nucleotide polymorphisms (SNP). We explored associations between CNV of uridine diphospho-glucuronosyltransferase (UGT) genes from the 2B subclass, given their prostate specificity and/or involvement in steroid metabolism and PCA risk. We also investigated associations between SNPs in genes (HSD3B1, SRD5A1/2, and AKR1C2) involved in the conversion of testosterone to DHT, and in DHT metabolism and PCA risk. The population consisted of 426 men (205 controls and 221 cases) who underwent prostate-specific antigen screening as part of a PCA early detection program in Tyrol, Austria. No association between CNV in UGT2B17 and UGT2B28 and PCA risk was identified. Men carrying the AA genotype at SNP rs6428830 (HSD3B1) had an odds ratio (OR) of 2.0 [95% confidence intervals (95% CI), 1.1-4.1] compared with men with GG, and men with AG or GG versus AA in rs1691053 (SRD5A1) had an OR of 1.8 (95% CI, 1.04-3.13). Individuals carrying both risk alleles had an OR of 3.1 (95% CI, 1.4-6.7) when compared with men carrying neither (P = 0.005). Controls with the AA genotype on rs7594951 (SRD5A2) tended toward higher serum DHT levels (P = 0.03). This is the first study to implicate the 5alpha-reductase isoform 1 (SRD5A1) and PCA risk, supporting the rationale of blocking enzymatic activity of both isoforms of 5alpha-reductase for PCA chemoprevention.

Separation of Interstitial and Tubular Cells of Human Testis by Means of an Anti-Substance P-Antiserum. Androstane-3β, 17β-Diol is Exclusively Formed by Seminiferous Tubules: Die Trennung von interstitiellen und tubulären Zellen des menschlichen Hodens mi

Leydig cells and seminiferous tubules of human testicular tissue were successfully separated by means of an anti-substance P-antiserum. On incubation with (14C)-testosterone or (14C)-dihydrotestosterone (DHT) it could be shown that besides DHT and 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) also 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol) originated in the tubular compartment. The ratio 3 alpha/3 beta-diol was found to be higher (0.7) here compared to incubation with whole testicular tissue (0.2), indicating that the testicular interstitium influences the metabolism of DHT by the seminiferous tubules.

The Effect of Allelic Variation in Aldo-Keto Reductase 1C2 on the in Vitro Metabolism of Dihydrotestosterone

Aldo-keto reductase (AKR) 1C2 is a human, cytosolic enzyme that has an important role in the deactivation of the potent androgen dihydrotestosterone (DHT). AKR1C2 can regulate the extent and duration of activation of the androgen receptor by catalyzing the reduction of DHT to the less potent receptor ligand 3alpha-diol. In this study, we functionally characterize in vitro the effect of 11 naturally occurring nonsynonymous single nucleotide polymorphisms on the ability of AKR1C2 to reduce DHT to 3alpha-diol. The wild-type and variant enzymes were expressed using a transfected insect cell system, and their kinetic activities were measured using both a specific fluorogenic probe and DHT as substrates. This functional characterization demonstrates that several variant AKR1C2 proteins have significantly reduced or altered reductase activities as shown by their measured kinetic parameters. Data from our two separate in vitro studies revealed significant reductions in V(max) for two variants (F46Y and L172Q) and significantly lower apparent K(m) values for three variants (L172Q, K185E, and R258C) compared with the wild type. These results provide evidence that several naturally occurring nonsynonymous single nucleotide polymorphisms in AKR1C2 result in reduced enzyme activities. These variant AKR1C2 alleles may represent one factor involved in the variable degradation of DHT in vivo.

Androgen biosynthetic pathways in the human prostate

It is well recognized that there are two androgens, namely testosterone (T) and dihydrotestosterone (DHT); T plays an important role in the testis and muscle, and DHT is crucial for the development, function and pathology of the prostate. It is generally thought that DHT is produced from the 5alpha-reduction of circulating T before being inactivated by 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) that converts DHT into 5alpha-androstane-3alpha,17beta-diol (3alpha-diol). However, the presence of various steroidogenic enzymes in the prostate as well as the availability at high levels of various steroid precursors such as dehydroepiandrosterone sulphate (DHEAS), dehydroepiandrosterone (DHEA) and 4-androstenedione (4-dione) strongly suggest the existence of additional pathways involved in the biosynthesis and metabolism of DHT. Because steroidogenesis could be different in different species, data from the literature obtained from various human, dog, rat and mouse prostate tissues, as well as primary cells and prostatic cancer cell lines, provide a somewhat confusing picture. In the present chapter, we review the data in order to provide a clearer picture of the pathways involved in DHT biosynthesis and metabolism in the human prostate.

3α-Hydroxysteroid Dehydrogenase Type III Deficiency: A Novel Mechanism for Hirsutism

Dihydrotestosterone (DHT), the primary active androgen in peripheral target tissues, is metabolized by 3alpha-hydroxysteroid dehydrogenase type III (3alpha-HSD), encoded by the AKR1C2 gene, forming 5alpha-androstane-3alpha,17beta-diol (3alpha-diol). 3alpha-HSD may play a role in the pathogenesis of hirsutism. Our objective was to evaluate the role of 3alpha-HSD in hirsutism by comparing 1) tissue levels of active androgens, 2) relative gene expression of AKR1C2, and 3) activity of 3alpha-HSD in genital skin from normal and hirsute women. Genital skin was obtained from normal and hirsute women. After homogenization, testosterone (T) and DHT levels were quantified by conventional RIA. From isolated RNA, relative expression of AKR1C2 was determined by real-time PCR. In addition, minced genital skin was incubated with [(3)H]DHT, and the product, [(3)H]3alpha-diol, was quantified by radio-HPLC. The study took place at an inner-city hospital. PATIENTS included women undergoing posterior colporrhaphy. We assessed 1) tissue levels of T, DHT, and 3alpha-diol; 2) relative expression of AKR1C2; and 3) conversion ratio of [(3)H]3alpha-diol to [(3)H]DHT. In genital skin, tissue DHT and T concentrations in hirsute women were 1.90-fold and 1.84-fold higher than in normal women (P =0 .002 and 0.03), and relative expression of AKR1C2 mRNA was reduced approximately 7-fold (P = 0.04). Genital skin from hirsute women showed less metabolism of [(3)H]DHT to [(3)H]3alpha-diol (conversion ratio, 0.24 +/- 0.19 vs. 0.85 +/- 0.55, P = 0.01). In genital skin of hirsute women, reduced AKR1C2 gene expression and 3alpha-HSD activity results in decreased DHT metabolism and elevated tissue levels of DHT. Diminished DHT metabolism may play an important role in the pathogenesis of hirsutism.

Impaired Dihydrotestosterone Catabolism in Human Prostate Cancer: Critical Role of AKR1C2 as a Pre-Receptor Regulator of Androgen Receptor Signaling

We previously reported the selective loss of AKR1C2 and AKR1C1 in prostate cancers compared with their expression in paired benign tissues. We now report that dihydrotestosterone (DHT) levels are significantly greater in prostate cancer tumors compared with their paired benign tissues. Decreased catabolism seems to account for the increased DHT levels as expression of AKR1C2 and SRD5A2 was reduced in these tumors compared with their paired benign tissues. After 4 h of incubation with benign tissue samples, (3)H-DHT was predominantly catabolized to the 5alpha-androstane-3alpha,17beta-diol metabolite. Reduced capacity to metabolize DHT was observed in tumor samples from four of five freshly isolated pairs of tissue samples, which paralleled loss of AKR1C2 and AKR1C1 expression. LAPC-4 cells transiently transfected with AKR1C1 and AKR1C2, but not AKR1C3, were able to significantly inhibit a dose-dependent, DHT-stimulated proliferation, which was associated with a significant reduction in the concentration of DHT remaining in the media. R1881-stimulated proliferation was equivalent in all transfected cells, showing that metabolism of DHT was responsible for the inhibition of proliferation. PC-3 cells overexpressing AKR1C2 and, to a lesser extent, AKR1C1 were able to significantly inhibit DHT-dependent androgen receptor reporter activity, which was abrogated by increasing DHT levels. We speculate that selective loss of AKR1C2 in prostate cancer promotes clonal expansion of tumor cells by enhancement of androgen-dependent cellular proliferation by reducing DHT metabolism.

ASP85TYR POLYMORPHISM IN THE UDP-GLUCURONOSYLTRANSFERASE (UGT) 2B15 GENE AND THE RISK OF PROSTATE CANCER

An amino acid changing polymorphism in the UDP-glucuronosyltransferase (UGT) 2B15 gene has been described at codon 85 (aspartate>tyrosine). The UGT2B15 allele exhibits 2-fold decreased activity for dihydrotestosterone, which was suggested to be associated with the risk of prostate cancer based on in vitro functional analysis. We determined whether this polymorphism can be used to predict individual susceptibility to prostate cancer. UGT2B15 expression was determined by reverse transcription-polymerase chain reaction of normal prostate tissues. Prevalence of the UGT2B15 Asp85Tyr polymorphism was compared between cases and controls by allele specific polymerase chain reaction analysis using genomic DNA isolated from 155 incident white patients with primary prostate cancer and 155 individually age matched (+/-5 years) white controls. UGT2B15 mRNA was detected in all prostate tissues tested. A significant association was found between UGT2B15 genotypes and prostate cancer risk. A significantly increased risk of prostate cancer was observed in subjects with the homozygous UGT2B15 genotype (OR 2.7, 95% CI 1.1 to 6.6). These results suggest that the UGT2B15 enzyme may have a role in the metabolism of dihydrotestosterone in prostate tissue and UGT2B15 Asp85Tyr polymorphism is associated with prostate cancer risk.

Intrinsic regional differences in androgen receptors and dihydrotestosterone metabolism in human preadipocytes.

Androgens play an important role in regulating the central obesity that is a strong risk factor for cardiovascular disease and insulin resistance. This study confirms that androgen receptors are present in subcultured human preadipocytes, with androgen receptor gene expression and saturable specific dihydrotestosterone binding, dissociation constant 1.02 - 2.56 nM and maximal binding capacity 30.8 - 55.7 fmol/mg protein. There was an intrinsic regional difference in androgen receptor complement, with more androgen receptors in visceral than in subcutaneous preadipocytes. Dihydrotestosterone was metabolised by human preadipocytes, with more androstanediol produced by subcutaneous than visceral preadipocytes. While dihydrotestosterone metabolism was insufficient to explain the regional variation in androgen binding, both of these differences would reduce the androgen responsiveness of the subcutaneous preadipocytes compared with visceral preadipocytes. There were no gender differences in androgen binding or metabolism. While the direct effects of androgens on human PAs remain uncertain, these regional differences suggest that AR-mediated regulation of certain PA functions influences adipose tissue distribution.

Function of human brain short chain L-3-hydroxyacyl coenzyme A dehydrogenase in androgen metabolism

Human brain short chain L-3-hydroxyacyl-CoA dehydrogenase (SCHAD) has been demonstrated to be a unique 3α-hydroxysteroid dehydrogenase (HSD) that can convert 5α-androstane-3α,17β-diol (3α-adiol) to dihydrotestosterone (DHT), whose affinity to the androgen receptor is 10 5-fold higher than that of 3α-adiol. The catalytic efficiency of human SCHAD for this oxidative 3α-HSD reaction was estimated to be 164 min −1 mM −1, about 10-fold higher than that measured for the backward reaction. Thus, human brain SCHAD may function in androgen metabolism as a new kind of 3α-HSD by counteracting all other known 3α-HSDs, which would unidirectionally catalyze the reduction of DHT to the almost inactive 3α-adiol. Human SCHAD is identical to an amyloid-β binding protein (ERAB) involved in Alzheimer’s disease, which was previously reported to be associated with the endoplasmic reticulum. This protein is, in fact, localized in mitochondria, not endoplasmic reticulum, as evidenced by immunocytochemical studies and its noncleavable mitochondrial targeting sequence and lack of endoplasmic reticulum targeting signals or transmembrane segments. These results prompt the suggestion that the mitochondrion plays not only an essential role in the initial step of steroidogenesis, but also important roles in the intracellular homeostasis of sex steroid hormones. Northern blot analysis revealed that the human SCHAD gene is expressed in both gonadal and peripheral tissues including the prostate whose growth notably requires DHT, the most potent androgen. This study represents the first report of a 3α-HSD that could act to generate DHT from 3α-adiol and thereby maintain intracellular DHT levels. We propose that inhibitors of the 3α-HSD activity of human brain SCHAD could be useful for the treatment of benign prostatic hyperplasia and other disorders involving DHT metabolism, in combination with known inhibitors of steroid 5α-reductases.