MARIE-GENICA Consortium on Genetic Susceptibility for Menopausal Hormone Therapy Related Breast Cancer Risk. Postmenopausal estrogen monotherapy-associated breast cancer risk is modified by CYP17A1_-34_T>C polymorphism

Long-term hormone therapy (HT) is a recognized risk factor for postmenopausal breast cancer. Elevated steroid hormone levels play a critical role in breast carcinogenesis and this may be contributed by the efficiency of hormone biosynthesis. Within this context, genetic polymorphisms related to steroid hormone biosynthesis may modify HT-associated postmenopausal breast cancer risk. CYP17 is a key player of this pathway and the CYP17A1_-34_T > C polymorphism has been suggested to affect breast cancer risk in women using long-term HT. We genotyped 13 polymorphisms of seven genes of the steroid hormone biosynthesis pathway in 3,149 postmenopausal breast cancer patients and 5,489 age-matched controls from Germany. We observed a significant interaction of CYP17A1_-34_T > C and HT use on breast cancer risk in a co-dominant model (P (interaction) = 0.007). Current users of estrogen monotherapy showed a significantly increased risk for duration of use per 5-year increment when they were carriers of the CYP17A1_-34_TC genotype (OR 1.13, 95% CI: 1.04-1.23 per 5 years of use). We conclude that CYP17A1_-34_T > C may be part of the genetic background to contribute to postmenopausal breast cancer risk in women using estrogen monotherapy.

Steroid 17alpha-hydroxylase deficiency: functional characterization of four mutations (A174E, V178D, R440C, L465P) in the CYP17A1 gene

CONTEXT

Steroid 17alpha-hydroxylase (CYP17A1, alias P450c17) deficiency (17OHD) is a rare form of congenital adrenal hyperplasia. The CYP17A1 enzyme catalyzes two distinct reactions, 17alpha-hydroxylase and 17,20-lyase activities.

OBJECTIVE

The aim of the study was to analyze the structural and functional consequences of three novel (A174E, V178D, and L465P) and one previously reported (R440C) CYP17A1 mutation found in three patients clinically and biochemically presenting with 17OHD.

PATIENTS AND METHODS

Two patients suffering from 46,XY disordered sex development presented at ages 5.5 and 8.8 yr, respectively, with tall stature and hypertension. Mutation analysis revealed compound heterozygous CYP17A1 mutations (A174E/K388X; V178D/R440C). The third patient (46,XX) presented with primary amenorrhea and hypertension at age 15 yr. She was homozygous for the novel L465P mutation. Functional studies employing a yeast microsomal expression system compared wild-type and mutant CYP17A1 both with regard to 17alpha-hydroxylase and 17,20-lyase activity. Mutants were examined in a computational three-dimensional model of the CYP17A1 protein.

RESULTS

The activity assays showed that all three mutants retain only 0-7% of both 17alpha-hydroxylase and 17,20-lyase activity relative to CYP17A1 wild-type activity, corresponding to the in vivo situation. Enzyme kinetic studies proved the impairment of both reactions, respectively. Computer-based three-dimensional model analysis of CYP17A1 using CYP2B4 as template showed that three of the mutations had no direct effect on the active center, whereas one affects the heme coordination.

CONCLUSION

The functional studies revealed that the described missense mutations result in severe 17OHD. Our data are important to predict the phenotypic expressions and provide important information for patient management and genetic counseling.

Polymorphism T --> C (-34 base pairs) of gene CYP17 promoter in women with polycystic ovary syndrome is associated with increased body weight and insulin resistance: a preliminary study

The aim of this study was to establish the frequency of gene CYP17 promoter polymorphism in women with polycystic ovary syndrome (PCOS) from a Chilean population and to examine the association of this polymorphism with body weight and estimate of insulin resistance in PCOS patient carriers and noncarriers of the A2 allelic variant. A total of 159 women with clinical and hormonal evidence of PCOS and 93 healthy women (HW) were evaluated. Diagnosis of PCOS was made according to the National Institutes of Health consensus criteria. In PCOS and HW, an oral glucose tolerance test was performed; and serum glucose and insulin were measured before the glucose load and 30, 60, 90, and 120 minutes after. Lipid profile and free fatty acid concentrations were determined in the basal sample. Insulin resistance was evaluated by homeostatic model assessment and insulin sensitivity index composite. A polymerase chain reaction-restriction fragment length polymorphism analysis was performed in all women to determine the A2 allele of the gene CYP17 promoter. The genotype frequency was similar between HW and PCOS women. No differences in anthropometric measurements and metabolic parameters were observed in HW carrier and noncarrier of the A2 variant. In PCOS women, an increase in body mass index, waist circumference, homeostatic model assessment of insulin resistance, and fasting insulin according to the A2 allele dosage was observed (P = .008, P = .016, P = .012, and P = .006, respectively). Polycystic ovary syndrome patient carriers of the A2 allele with a body mass index greater than 29.9 kg/m(2) showed an odds ratio of 9.1 (confidence interval, 3.0-27.4; P < .0001) for developing insulin resistance. These data suggest that the frequency of the A2 allele is similar between PCOS patients and HW; however, the presence of this gene defect in PCOS patients seems to be associated with increase in body weight, abdominal adiposity, and metabolic components.

Identification of a single nucleotide polymorphism in porcine testis cytochrome P450-c17 (CYP17) and its effect on steroidogenesis

Raising uncastrated male pigs could have significant economic benefits for pig production. Uncastrated male pigs can accumulate high levels of 16-androstene steroids, however, resulting in boar taint, which is highly objectionable to consumers. Cytochrome P450-c17 (CYP17) interacts with cytochrome b5 in the biosynthesis of the 16-androstene steroids and the sex steroids from pregnenolone. Amino acid substitutions in CYP17 could therefore affect the ability of this enzyme to catalyze the reactions leading to the production of androstenone and the sex steroids. In this study, we established a sensitive and flexible single-stranded conformational polymorphism technique capable of detecting a single nucleotide polymorphism. We then used this method to identify a substitution from T to A at nucleotide 1317 of CYP17, which caused a change in the amino acid sequence from Leu(439) to His(439). This mutation, however, did not alter the enzyme activity of CYP17 in the biosynthesis of androstenone or sex steroids. Other polymorphisms previously suggested for CYP17, which are vital for the functional interaction of CYP17 with CYB5 in human, were not observed. This study suggests that the synthesis of androstenone in pig testis is not directly affected by any polymorphisms in the coding region of the porcine CYP17 gene.

Regulation of the adrenal androgen biosynthesis

The human adrenal reticularis produces the so-called adrenal androgens, dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEA-S). As opposed to the cortisol and aldosterone little is known regarding the mechanisms that regulate the production of the adrenal androgens. Several recent studies have shown that type II 3beta-hydroxysteroid dehydrogenase (HSD3B2), cytochrome b5 (CYB5), and steroid sulfotransferase (SULT2A1) play an important role in the regulation of adrenal androgen production. Specifically, adrenal production of DHEA-S is correlated with reticularis expression of SULT2A1 and CYB5. In contrast, HSD3B2 has an inverse correlation with adrenal androgen production likely due to its unique ability to remove precursors from the pathway leading to DHEA. Therefore, its expression is limited to the adrenal glomerulosa/fasciculata but not in reticularis. The differential expression of these three proteins appears to be critical for reticularis function. In this review, we focus on studies that have begun to define the mechanisms regulating the transcription of these genes. Understanding the mechanisms controlling differential expression of these proteins should provide novel information about the human adrenal reticularis and its production of DHEA and DHEA-S.

Abnormal Morphology of Spermatozoa in Cytochrome P450 17 -hydroxylase/17, 20-lyase (CYP17) Deficient Mice

Cytochrome P450 17alpha-hydroxylase/17, 20-lyase (CYP17) is crucial for cortisol and sex steroid biosynthesis. In a previous study we examined CYP17 function by generating mice with a targeted CYP17 deletion. We found that in addition to its role in steroid biosynthesis, CYP17 is present in germ cells. In the present study we examined the effect of CYP17 on sperm morphology. Disorganization of the sperm midpiece, small sperm mitochondria with reduced inner membranes and matrix, and irregular sperm shape were found to be associated with the CYP17 gene deletion. Treating the mice carrying the CYP17 deletion with testosterone did not alleviate the observed sperm phenotypes, suggesting that CYP17 acts in a testosterone-independent manner. These results suggest that CYP17, in addition to its role in androgen formation, is critical for proper mitochondrial architecture and sperm morphology and thus for sperm function and normal fertility.

CYP17 genotype modifies the association between lignan supply and premenopausal breast cancer risk in humans

Cytochrome P450c17alpha (CYP17) has been associated with alterations in steroid hormone levels and premenopausal breast cancer risk and could modify the association between phytoestrogen intake and breast cancer risk. We examined plasma concentrations of enterolactone and genistein, estimated dietary phytoestrogen intake, CYP17 5'-UTR MspA1 genetic polymorphism, and breast cancer risk in 267 premenopausal breast cancer patients and 573 age-matched population controls from Germany. Multivariate logistic regression was used to estimate breast cancer risk associated with quartiles of phytoestrogen intake by genotype and to investigate gene-nutrient interactions. Premenopausal breast cancer risk was not significantly associated with the CYP17 A2 genotype. We observed a significant modifying effect of CYP17 genotype on plasma enterolactone-associated breast cancer risk (P for interaction < 0.01). Plasma enterolactone was significantly inversely related to breast cancer risk only in A2A2 carriers, showing odds ratios and 95% CI of 0.02 (0.00-0.41) and 0.01 (0.00-0.21) for the third and fourth quartiles vs. the lowest quartile, respectively. This inverse association was also found for the calculated enterolignan production as well as matairesinol intake. Compared with A1A1 carriers with the lowest enterolactone supply, the risk reduction associated with a high enterolactone supply resulted in a comparably decreased breast cancer risk for all genotypes. For genistein, no clear indication for a differential effect by CYP17 genotype was obtained. Our results suggest that CYP17 genotype modifies the protective effect of lignans on premenopausal breast cancer risk. Women homozygous for A2 allele benefit most from high plasma enterolactone concentrations and a high consumption of dietary precursors.

Neurosteroids and the songbird model system

The brain is now widely recognized as having the capacity to make steroids, neurosteroidogenesis. Although many functions are known for steroids that might be made in the brain, the evolution of and natural biological functions for these neurosteroids are not fully understood. In songbirds, neurosteroids may function in the development of neural circuits controlling song and may also participate in the activation of some steroid-dependent behaviors during the non-breeding season. In addition to neuroanatomical and behavioral evidence, we have physiological, molecular, and biochemical evidence for the expression and activity of steroidogenic enzymes in the brains of developing and adult songbirds. We review the evidence published so far for songbird neurosteroidogenesis and discuss why we believe songbird species are excellent models for the study of brain steroid synthesis and action.

Haploinsufficiency of cytochrome P450 17alpha-hydroxylase/17,20 lyase (CYP17) causes infertility in male mice

Cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) is critical in determining cortisol and sex steroid biosynthesis. To investigate how CYP17 functions in vivo, we generated mice with a targeted deletion of CYP17. Although in chimeric mice Leydig cell CYP17 mRNA and intratesticular and circulating testosterone levels were dramatically reduced (80%), the remaining testosterone was sufficient to support spermatogenesis as evidenced by the generation of phenotypical black C57BL/6 mice. However, male chimeras consistently failed to generate heterozygous CYP17 mice and after five matings chimeric mice stopped mating indicating a change in sexual behavior. These results suggested that CYP17 deletion caused a primary phenotype (infertility), probably not due to the anticipated androgen imbalance and a secondary phenotype (change in sexual behavior) due to the androgen imbalance. Surprisingly, CYP17 mRNA was found in mature sperm, and serial analysis of gene expression identified CYP17 mRNA in other testicular germ cells. CYP17 mRNA levels were directly related to percent chimerism. Moreover, more than 50% of the sperm from high-percentage chimeric mice were morphologically abnormal, and half of them failed the swim test. Furthermore, 60% of swimming abnormal sperm was devoid of CYP17. These results suggest that CYP17, in addition to its role in steroidogenesis and androgen formation, is present in germ cells where it is essential for sperm function, and deletion of one allele prevents genetic transmission of mutant and wild-type alleles causing infertility followed by change in sexual behavior due to androgen imbalance.

Cytochrome P450 17alpha hydroxylase/17,20 lyase (CYP17) function in cholesterol biosynthesis: identification of squalene monooxygenase (epoxidase) activity associated with CYP17 in Leydig cells

Cytochrome P450 17alpha-hydroxylase/17,20-lyase (CYP17) is a microsomal enzyme catalyzing two distinct activities, 17alpha-hydroxylase and 17,20-lyase, essential for the biosynthesis of adrenal and gonadal steroids. CYP17 is a potent oxidant, it is present in liver and nonsteroidogenic tissues, and it has been suggested to have catalytic properties distinct to its function in steroid metabolism. To identify CYP17 functions distinct of its 17alpha-hydroxylase/17,20-lyase activity, we used MA-10 mouse tumor Leydig cells known to be defective in 17alpha-hydroxylase/17,20-lyase activity. A CYP17 knocked down MA-10 clone (MA-10(CYP17KD)) was generated by homologous recombination and its steroidogenic capacity was compared with wild-type cells (MA-10(wt)). Although no differences in cell morphology and proliferation rates were observed between these cells, the human chorionic gonadotropin-induced progesterone formation and de novo synthesis of steroids were dramatically reduced in MA-10(CYP17KD) cells; their steroidogenic ability could be rescued in part by transfecting CYP17 DNA into the cells. Knocking down CYP17 mRNA by RNA interference yielded similar results. However, no significant difference was observed in the steroidogenic ability of cells treated with 22R-hydroxycholesterol, which suggested a defect in cholesterol biosynthesis. Incubation of MA-10(CYP17KD) cells with (14)C-labeled squalene resulted in the formation of reduced amounts of radiolabeled cholesterol compared with MA-10(wt) cells. In addition, treatment of MA-10(CYP17KD) cells with various cholesterol substrates indicated that unlike squalene, addition of squalene epoxide, lanosterol, zymosterol, and desmosterol could rescue the hormone-induced progesterone formation. Further in vitro studies demonstrated that expression of mouse CYP17 in bacteria resulted in the expression of squalene monooxygenase activity. In conclusion, these studies suggest that CYP17, in addition to its 17alpha-hydroxylase/17,20-lyase activity, critical in androgen formation, also expresses a secondary activity, squalene monooxygenase (epoxidase), of a well-established enzyme involved in cholesterol biosynthesis, which may become critical under certain conditions.

Xenopus laevis CYP17 regulates androgen biosynthesis independent of the cofactor cytochrome b5

The enzyme CYP17 primarily regulates androgen production by mediating four reactions: conversion of pregnenolone and progesterone to 17-hydroxypregnenolone and 17-hydroxyprogesterone, respectively (17alpha-hydroxylase activity), followed by conversion of the 17-hydroxylated steroids to dehydroepiandrosterone and androstenedione, respectively (17,20-lyase activity). Most mammalian CYP17 isoforms have high 17alpha-hydroxylase relative to 17,20-lyase activities and preferentially mediate one of the two 17,20-lyase reactions. In contrast, Xenopus laevis CYP17 potently regulates all four reactions in the frog ovary. CYP17 isoforms generally rely on the cofactor cytochrome b(5) for the 17,20-lyase reaction, suggesting that the high lyase activity of Xenopus CYP17 might be due to a lesser dependence on b(5). The kinetics of Xenopus CYP17 expressed in yeast microsomes were therefore examined in the absence and presence of Xenopus on human b(5). Xenopus CYP17 mediated both 17,20-lyase reactions in the absence of b(5), confirming that the activity did not require b(5). However, both Xenopus and human b(5) slightly enhanced Xenopus CYP17-mediated lyase activity, indicating that the enzyme was still at least partially responsive to b(5). Surprisingly, only the human b(5) cofactor enhanced human CYP17-mediated lyase activity, implying that the human enzyme had more specific cofactor requirements than Xenopus CYP17. Studies using human/Xenopus chimeric b(5) proteins revealed that human b(5) residues 16-41 were important for the specific regulation of the lyase activity of HuCYP17, possibly serving as an interacting domain with the enzyme. CYP17 may therefore have evolved from a general producer of sex steroids in lower vertebrates to a more tightly regulated producer of both sex steroids and glucocorticoids in mammals.

Functional characterization of mutant CYP17 genes isolated from a 17 alpha-hydroxylase/17,20-lyase-deficient patient

CYP17 has a dual enzymatic activity that is necessary for steroid hormone biosynthesis. It catalyzes the 17 alpha-hydroxylation of progesterone or pregnenolone and also removes an acetyl moiety of hydroxy-progesterone or hydroxypregnenolone by its 17,20-lyase activity to produce androstenedione or dehydroepiandrosterone (DHEA), respectively. We previously isolated a compound heterozygous mutant of CYP17 from a Korean female patient: 1-base deletion and 1-base transversion mutation at 1 allele and 3-base deletion mutation at the other allele. Here we tested the functional activities of these 2 mutant CYP17 alleles using a transfection analysis in COS-1 cells with radiolabeled substrates and thin layer chromatography. Both mutant CYP17 genes lost not only 17 alpha-hydroxylation activity, but also 17,20-lyase activity in this assay system. This nonfunctional nature of 2 mutant CYP17 genes explains the clinical manifestation of a patient who had 17 alpha-hydroxylase deficiency.

Deletion of the mouse P450c17 gene causes early embryonic lethality

Dehydroepiandrosterone (DHEA), a 19-carbon precursor of sex steroids, is abundantly produced in the human but not the mouse adrenal. However, mice produce DHEA and DHEA-sulfate (DHEAS) in the fetal brain. DHEA stimulates axonal growth from specific populations of mouse neocortical neurons in vitro, while DHEAS stimulates dendritic growth from those cells. The synthesis of DHEA and sex steroids, but not mouse glucocorticoids and mineralocorticoids, requires P450c17, which catalyzes both 17 alpha-hydroxylase and 17,20-lyase activities. We hypothesized that P450c17-knockout mice would have disordered sex steroid synthesis and disordered brain DHEA production and thus provide phenotypic clues about the functions of DHEA in mouse brain development. We deleted the mouse P450c17 gene in 127/SvJ mice and obtained several lines of mice from two lines of targeted embryonic stem cells. Heterozygotes were phenotypically and reproductively normal, but in all mouse lines, P450c17(-/-) zygotes died by embryonic day 7, prior to gastrulation. The cause of this early lethality is unknown, as there is no known function of fetal steroids at embryonic day 7. Immunocytochemistry identified P450c17 in embryonic endoderm in E7 wild-type and heterozygous embryos, but its function in these cells is unknown. Enzyme assays of wild-type embryos showed a rapid rise in 17-hydroxylase activity between E6 and E7 and the presence of C(17,20)-lyase activity at E7. Treatment of pregnant females with subcutaneous pellets releasing DHEA or 17-OH pregnenolone at a constant rate failed to rescue P450c17(-/-) fetuses. Treatment of normal pregnant females with pellets releasing pregnenolone or progesterone did not cause fetal demise. These data suggest that steroid products of P450c17 have heretofore-unknown essential functions in early embryonic mouse development.

[Disorder of androgen biosynthesis]

Disorders of androgen biosynthesis are a relatively rare cause of sexual ambiguity in 46XY genetic males. The biosynthesis of androgen requires the steroidogenic acute regulatory protein (StAR) and the steroidogenic enzymes P450scc, 3 beta HSDII, P450c17, 17 beta HSDIII, and 5 alpha-reductase. Deficiencies have been reported in these enzymes, leading to male pseudohermaphroditism. Here we describe three enzymes 3 beta HSDII, P450c17, and 17 beta HSDIII, their roles and mechanisms of action special reference to diagnosis and treatment for the patients with deficiencies of these enzymes.

Association of CYP17, CYP19, CYP1B1, and COMT Polymorphisms with Serum and Urinary Sex Hormone Concentrations in Postmenopausal Women

Women with high circulating estrogen concentrations have an increased risk of breast cancer; thus, it is important to understand factors, including genetic variability, that influence estrogen concentrations. Several genetic polymorphisms that may influence sex hormone concentrations have been identified, including CYP17 (5'-untranslated region T-->C), CYP19 [intron 4 (TTTA)(n = 7-13) and a 3-bp deletion (-3)], CYP1B1 (Val(432)Leu), and COMT (Val(108/158)Met). We examined associations between these polymorphisms and serum concentrations of estrogens, androgens, and sex hormone-binding globulin and urinary concentrations of 2- and 16alpha-hydroxyestrone in 171 postmenopausal women, using data from the prerandomization visit of an exercise clinical trial. Participants were sedentary, not taking hormone therapy, and had a body mass index >24.0. Compared with noncarriers, women carrying two CYP19 7r(-3) alleles had 26% lower estrone (P < 0.001), 19% lower estradiol (P = 0.01), 23% lower free estradiol (P = 0.01), and 22% higher sex hormone-binding globulin concentrations (P = 0.06). Compared with noncarriers, women carrying at least one CYP19 8r allele had 20% higher estrone (P = 0.003), 18% higher estradiol (P = 0.02), and 21% higher free estradiol concentrations (P = 0.01). Women with the COMT Met/Met genotype had 28% higher 2-hydroxyestrone (P = 0.08) and 31% higher 16alpha-hydroxyestrone concentrations (P = 0.02), compared with Val/Val women. Few associations were found for CYP17 and CYP1B1 or with serum androgen concentrations. This study provides further evidence that genetic variation may appreciably alter sex hormone concentrations in postmenopausal women not taking hormone therapy.

Hypertension and adrenal disorders

Adrenal disorders causing hypertension can be related to the dysfunction of either the adrenal cortex or the adrenal medulla. These disorders, including congenital adrenal hyperplasia (CAH), owing to 11B-hydroxylase deficiency and to 17alpha-hydroxylase deficiency; apparent mineralocorticoid excess; familial hyperaldosteronism type I; primary aldosteronism; Cushing's syndrome; and familial glucocorticoid resistance, primarily affect the adrenal cortex and cause low-renin hypertension. The classic disorder of the adrenal medulla resulting in hypertension is pheochromocytoma, although hypertension in obesity might also be associated with catecholamine secretion. In this review, we discuss these etiologies and the most recent advances in our knowledge of their pathophysiology, diagnosis, and treatment.

Xenopus laevis ovarian CYP17 is a highly potent enzyme expressed exclusively in oocytes. Evidence that oocytes play a critical role in Xenopus ovarian androgen production

Progesterone has long been considered the primary mediator of Xenopus oocyte maturation. We have recently shown, however, that androgens, which are equal or more potent promoters of maturation and are present at higher levels in ovulating frogs, may also be playing an important physiologic role in mediating maturation. Here, we examined the role of CYP17, a key enzyme mediating sex steroid synthesis, in Xenopus ovarian androgen production. We found that the 17,20-lyase activities of Xenopus CYP17 exceeded the 17alpha-hydroxylase activities in both the Delta4 and Delta5 pathways; thus, Xenopus CYP17 rapidly converted pregnenolone and progesterone to dehydroepiandrosterone (DHEA) and androstenedione, respectively. This remarkably robust activity exceeds that of CYP17 from most higher vertebrates, and likely explains why virtually no progesterone is detected in ovulating frogs. Additionally, ovarian CYP17 activity was present exclusively in oocytes, although all other enzymes involved in sex steroid production were expressed almost entirely in surrounding follicular cells. This compartmentalization suggests a "two-cell" model whereby Xenopus ovarian androgen production requires both follicular cells and oocytes themselves. The requirement of oocytes for ovarian androgen production further introduces the unusual paradigm whereby germ cells may be responsible for producing important steroids used to mediate their own maturation.

Premature adrenarche

Adrenarche is the puberty of the adrenal gland. The descriptive term "pubarche" indicates the appearance of pubic hair, which may be accompanied by axillary hair. This process is considered premature if it occurs before age 8 yr in girls and 9 yr in boys. The chief hormonal products of adrenarche are DHEA and DHEAS. The well-documented evolution of adrenarche in primates and men is incompatible with either a neutral or harmful role for DHEA and implies most likely a positive role for some aspects of young adult pubertal maturation and developmental maturation. Premature adrenarche has no adverse effects on the onset and progression of gonadarche and/or final height. Mechanisms for initiation of adrenal androgen secretion at adrenarche are still not well understood. Maturational increases in 17-hydroxylase and 17,20-lyase are seen together with a lower activity of 3beta-hydroxysteroid dehydrogenase (3beta-HSD). There is good evidence that the zona reticularis is the source of adrenal androgens. Adrenarche and gonadarche are regulated differently. Although premature adrenarche has been thought to be a benign, normal variant of puberty, our findings indicate that, for certain girls, premature adrenarche represents an early clinical feature of syndrome X (obesity, hypertension, dyslipidemia, insulin resistance). Perhaps the early identification of these patients will permit early therapy, such as lifestyle changes, including dietary and activity level intervention. As insulin resistance is an underlying feature of premature adrenarche, it seems rational to assess the efficacy and safety of using insulin-sensitizing agents to treat these individuals. In the absence of controlled longitudinal studies, the cross-sectional data available from our studies suggest that premature pubarche driven by premature adrenarche and hyperinsulinemia may precede the development of ovarian hyperandrogenism, and this sequence may have an early origin with low birth weight serving as a marker. Premature adrenarche may thus be a forerunner of syndrome X in some girls.

Intra-adrenal regulation of androgen synthesis

The adrenal cortex encloses the neuroendocrine medulla and is itself subdivided into three distinct zones, each having a specific function and regulation. While the glomerulosa and the fasciculata control vital systems of mineral and energy supply, which are stringently regulated by higher control factors, the function of the reticularis is less clear, beyond supplying a pool of weak androgens, and consequently we do not understand its redundant regulation. The following questions need to be answered: 1. How is the formation of dehydroepiandrosterone (DHEA) and androstenedione differently regulated from glucocorticoid synthesis in normally functioning adrenals? 2. How might growth factors, which increase prepubertally, prime the adrenarche? 3. The regulation of the 17/20-lyase enzyme activity is one of the key factors of adrenal androgen secretion (review [2]). How can the two activities of the P450c17 enzyme be differently regulated in the same cell in a developmentally dependent fashion? This review focuses on the intra-adrenal growth factor system and on the role of 17/20-lyase regulation, as well as on their possible interactions. The increase of activity of the 17/20-lyase enzymatic activity is necessary for the rise of C19 steroids, while the relative increase of formation of DHEA is only possible in the presence of a low 3beta-hydroxysteroid-dehydrogenase (3betaHSD) activity.

A polymorphism in the CYP17 gene is associated with prostate cancer risk

CYP17 encodes the enzyme cytochrome P-450c17 alpha, which mediates both 17 alpha-hydroxylase and 17,20-lyase in the steroid biosynthesis pathway. A polymorphism in the 5; promoter region of the CYP17 gene has been described. Steroid hormones, especially androgens, are believed to play a key role in the etiology of prostate cancer. Therefore, polymorphisms in genes involved in the androgen metabolism may affect the risk of prostate cancer. We conducted a case-control study of 63 patients with untreated histologically proven prostate cancer and 126 age-matched control men with benign prostatic hyperplasia (BPH) to determine whether a polymorphism in the CYP17 gene is associated with prostate cancer risk. This polymorphism was investigated by PCR/RFLP using DNA from lymphocytes. The transition (T-->C) in the risk allele (A2) creates a new recognition site for the restriction enzyme MspAI, which permits designation of the wildtype (A1) and the risk allele (A2). The prevalence of the A2/A2 genotype was significantly higher (P = 0.03) in the cancer group (23.8%) than in the BPH control group (9.5%). We found an increased risk in men carrying 2 A2 alleles (OR = 2.80, 95%CI = 1.02-77.76). For carrier with at least 1 A2 allele, the OR was 0.90 (95%CI = 0.43-1.89). After stratification by median age (66 years) at time of diagnosis, a marked increased risk was found in carriers of the A2/A2 genotype older than 66 years (OR = 8.93, 95%CI = 1.78-49.19, P = 0.01). Although the sample size is rather small and the controls are BPH patients, our results suggest that the CYP17A2/A2 genotype may be a biomarker for prostate cancer risk, especially for older men.

The use of computational chemistry in the study of sex steroid biosynthesis

Many of the steroidogenic enzymes and cofactor proteins are bound to intracellular membranes, frustrating standard methods of structure determination. Structural models of steroidogenic P450 enzymes, however, may be predicted from the x-ray crystal structures of prokaryotic P450s. Using P450-BMP as primary structural template, models of hepatic and steroidogenic P450s have been generated using computational chemistry and graphics techniques. We have developed an analogous model of human P450c17 using an approach that relies heavily on energy minimization and molecular dynamics to yield the final structure. The final model predicts the known activities of the enzyme and explains why all reported mutations disrupt one or more activities. Although the term "computational chemistry" suggests that modeling is an operator-independent, fully automated process, modeling exercises are fraught with pitfalls, choices, and practical dilemmas which make each attempt a unique endeavor. This paper describes the procedure in detail, using P450c17 as an example, and highlights the opportunities that computational chemistry offers for the study of sex steroid biosynthesis.

Biochemical and functional analysis of nuclear receptors as targets in cAMP-dependent control of bovine CYP17

Several lines of evidence have suggested that the nuclear receptor Steroidogenic Factor-1 (SF-1 or Ad4BP) may be directly involved in the cAMP-dependent regulation of steroid hydroxylase genes in adrenocortical cells. In the bovine CYP17 gene, which encodes the cytochrome P450 17alpha-hydroxylase, an SF-1 site is present within cAMP-responsive sequence 2 (CRS2) and mutations which interfere with SF-1 binding correlate with decreases in cAMP-stimulated transcription of a linked reporter gene. In order to determine whether the cAMP response relies on structures within SF-1 itself, mutations and deletions were introduced. We demonstrate that even a single point mutation (E454A) in the transactivating AF-2 domain drastically reduces the ability of SF-1 to mediate cAMP-dependent transcription. Furthermore, the mutation results in a protein which acts in a dominant negative fashion with respect to cAMP-dependent regulation of the bovine CYP17 gene. Finally, we demonstrate that the coactivators CBP and SRC-1 are limiting with respect to cAMP-induced CRS2-dependent transcription in Y1 adrenocortical tumor cells, suggesting that part of the action of cAMP may be to influence the interaction of SF-1 with other cofactors via the AF-2 domain.

[The regulation of steroidogenesis by 17 alpha-hydroxylase/17,20-lyase (P450c17)]

Cytochrome P450c17 (P450c17) catalyzes 17 alpha-hydroxylation and 17, 20-lyase reactions. This enzyme plays a key role in determination of the balance between glucocorticoids and steroid sex hormones. In this review we discuss recent progress in the studies of both transcriptional regulation of CYP17 encoding P450c17 and enzymatic regulation of P450c17. Several transcription factors involved in cAMP-dependent transcription of the gene have been isolated and identified to be members of the atypical homeodomain "TALE" superfamily containing Pbx, Meis, Pknox and TGIF families. The studies of enzymatic regulation of P450c17 suggest that cytochrome b5 (b5), a heme protein, may switch the reaction of P450c17 by enhancing the 17, 20-lyase activity to increase the level of plasma C19 steroids. The importance of b5 in the synthesis of C19 steroids has also been shown in a clinical study reporting that the external genitalia was abnormal in a patient having a defect in b5. Therefore, this enhancement by b5 on the lyase activity of P450c17 may be essential to normal sexual differentiation in humans and also important in control of an optimal balance between sex steroid hormones and glucocorticoids. In addition, the age-dependent expression of P450c17 in immature rat livers is also discussed.

Sterol uptake in Saccharomyces cerevisiae heme auxotrophic mutants is affected by ergosterol and oleate but not by palmitoleate or by sterol esterification

The relationship between sterol uptake and heme competence in two yeast strains impaired in heme synthesis, namely, G204 and H12-6A, was analyzed. To evaluate heme availability, a heterologous 17alpha-hydroxylase cytochrome P-450 cDNA (P-450c17) was expressed in these strains, and its activity was measured in vivo. Heme deficiency in G204 led to accumulation of squalene and lethality. The heterologous cytochrome P-450 was inactive in this strain. The leaky H12-6A strain presented a slightly modified sterol content compared to that for the wild type, and the P-450c17 recovered partial activity. By analyzing sterol transfer on nongrowing cells, it was shown that the cells were permeable toward exogenous cholesterol when they were depleted of endogenous sterols, which was the case for G204 but not for H12-6A. It was concluded that the fully blocked heme mutant (G204) replenishes its diminishing endogenous sterol levels during growth by replacement with sterol from the outside medium. Endogenous sterol biosynthesis appears to be the primary factor capable of excluding exogenous sterol. Oleate but not palmitoleate was identified as a component that reduced but did not prevent sterol transfer. Sterol transfer was only slightly affected by a lack of esterification. It is described herein how avoidance of the potential cytotoxicity of the early intermediates of the mevalonate pathway could be achieved by a secondary heme mutation in erg auxotrophs.

Developmentally regulated expression and activity of 17alpha-hydroxylase/C-17,20-lyase cytochrome P450 in rat liver

We have investigated the developmental pattern of expression and activity of 17alpha-hydroxylase/C-17,20-lyase cytochrome P450 (cytochrome P450c17) in the liver, stomach, duodenum, and testis of rats from day 18 of pregnancy to adulthood. In the male liver, the enzyme became detectable at birth (135 pmol/mg protein x min) at a level comparable to that in the testis (188 pmol/mg protein x min). The activity then increased dramatically, reaching a peak at 8 days (691 pmol/mg protein x min), which was more than 4-fold the testicular levels in rats of the same age or in adults. Thereafter it declined steadily, becoming undetectable from puberty onward. The hepatic peak followed a depression in testicular activity (58 pmol/mg protein x min) on day 6. Northern and immunoblot analyses showed a good temporal correlation between enzyme activity and the occurrence of P450c17 messenger RNA (mRNA) and protein. The same patterns of mRNA and protein occurrence were observed in female rat liver, indicating that the hepatic CYP17 expression is not sexually dimorphic. Sequencing confirmed a complete identity in the coding region between hepatic and gonadal mRNAs. Hepatic P450c17 mRNA, however, was 150-200 bases longer than the gonadal counterparts. No significant expression of mRNAs encoding P450scc and P450arom was observed in liver of either sex at any age. In stomach and duodenum, enzyme activity was much lower (maxima at 25 and 14 pmol/mg protein x min, respectively) than that in liver, but persisted from the time of weaning onward. It is suggested that the hepatic peak in P450c17 activity may serve to convert circulating progestogens into androgens for gonadal aromatization during Sertoli and granulosa cell proliferation.

Immunolocalisation of P450(C17) in the fetal sheep adrenal gland during gestation and in response to ACTH and glucocorticoid administration

In sheep, increased output of cortisol from the fetal adrenal gland is critical to organ maturation and parturition. Cortisol synthesis is determined in part by the activity of P450(C17) enzyme. We have used immunohistochemistry and Western immunoblotting to examine the distribution of P450(C17) in the ovine fetal adrenal during gestation, and after ACTH or dexamethasone administration to fetuses between Days 125 and 130. The patterns were compared with changes in 3beta-hydroxysteroid dehydrogenase (3beta-HSD) localisation and levels. Adrenal tissue was obtained from four fetuses at each of Days 63-65, 100, 125-130 and term (>140 days). Further animals were chronically catheterised and infused with ACTH, dexamethasone or saline for 96 h beginning on Day 125. Immunohistochemistry for P450(C17), 3beta-HSD, and phenylethanolamine-N-methyl transferase (PNMT) was conducted using standard techniques. At Day 63-65 of pregnancy immunoreactive (ir-)P450(C17) was present in cords of cells throughout the adrenal gland. Ir-P450(C17) was reduced or was undetectable at Day 100, but had increased by Day 125-130, and was present throughout the zona fasciculata of the adrenal cortex of term animals. An increase in P450(C17) protein was also seen between Day 100 and 125 by Western blotting, and after ACTH treatment. Dexamethasone administration led to a marked reduction in ir-P450(C17) levels. In contrast, ir-3beta-HSD was present in the fetal adrenal cortex between Day 100 and term, and was less affected by ACTH or dexamethasone treatment. We conclude that P450(C17) in the fetal sheep adrenal is responsive to regulation by ACTH, and that changes in its levels correlate with previously reported alterations in patterns of cortisol output by the fetal adrenal gland.

Lack of relationship between 17-hydroxyprogesterone response to buserelin testing and hyperinsulinemia in polycystic ovary syndrome

OBJECTIVE

To determine whether hyperinsulinism affects cytochrome P450c17 alpha activity by investigating the correlation between 17-hydroxyprogesterone (17-OHP) hyper-responsiveness to the gonadotropin-releasing hormone (GnRH) agonist, buserelin, and the insulin response to oral glucose in polycystic ovary syndrome (PCOS).

DESIGN

Ultrasound, clinical and hormonal parameters were used to define PCOS in this prospective clinical study. We investigated the correlation between the 17-OHP response to buserelin testing and the insulin response to oral glucose in PCOS.

METHODS

Twenty-eight women with PCOS and eighteen normal women were included in the study. 17-OHP response to buserelin, and insulin and C-peptide responses to oral glucose were measured.

RESULTS

Twenty-five women with PCOS had an increased 17-OHP response. The PCOS patients showed significantly higher mean post-glucose load insulin and C-peptide levels than controls (P < 0.05). No significant correlations were found between basal 17-OHP and fasting insulin or fasting C-peptide, between peak 17-OHP and fasting insulin, peak insulin or peak C-peptide, between 17-OHP area under the curve (AUC) and insulin AUC or C-peptide AUC, and between percent increment in 17-OHP and insulin AUC or C-peptide AUC (P > 0.05).

CONCLUSIONS

Lack of a relationship between the 17-OHP response to the GnRH agonist buserelin and hyperinsulinism suggests that hyperinsulinism may not play a role in the dysregulation of the cytochrome P450c17 alpha enzyme seen in PCOS.

A polymorphism in the CYP17 gene increases the risk of breast cancer

We conducted a case-control study to determine whether a polymorphism in the CYP17 gene was associated with risk of breast cancer. We found an increased risk of advanced breast cancer in women carrying an A2 allele. The odds ratio was 2.5 [95% confidence interval (CI), 1.07-5.94] for regional or metastatic disease. Among controls, the A1/A1 genotype was associated with a later age at menarche. The reduced risk of breast cancer associated with a later age of menarche was largely limited to A1/A1 women: odds ratio, 0.47 (CI, 0.22-0.98) for breast cancer and later age at menarche among A1 homozygotes compared with 0.80 (CI, 0.51-1.27) for A1/A2 and A2/A2 genotypes. These findings suggest that the CYP17 genotype may be a biomarker for the onset of ovulation and advanced breast cancer risk.

[Human folliculogenesis and local regulation]

It is well known that gonadotropin controls a major part of follicular development. However, the mechanism of local regulation under the control of gonadotropins in still unclear. In this study, we focused on the local regulation of steroidogenesis, growth factors and cell proliferation to evaluate the human follicular development. To assess steroidogenesis, it is important to detect the expression of steroidogenic enzymes in the granulosa and theca cells during folliculogenesis. We initially tried to find out the transcription factor Ad4BP that binds the Ad4 site and regulates the function of steroidogenic enzyme. By immunohistochemistry, the expression of Ad4BP was confirmed sporaf1p4lly in preantral granulosa cells. In the antral follicles, the expression of Ad4BP was observed both in the granulosa and theca cell. According steroidogenic enzyme, we evaluated temporal and spatial localization of cholesterol side chain cleavage (scc), 3 beta hydroxysteroid dehydrogenase (3 beta HSD), 17 alpha hydroxylase (17 alpha) and aromatase, and steroid receptors. In briefly, the localizations of scc, 3 beta HSD and 17 alpha were observed in preantral follicles and the mRNA expressions of these enzymes were confirmed in the theca cell by in situ hybridization method. Expression of aromatase was generally observed in only one follicle (antral or mature follicle) per case in mid proliferative to premenstrual phase. The localization of androgen and estrogen receptor was observed in the antral follicle granulosa cells, and estrogen receptor was detected only in aromatase positive follicles. These results suggested that Ad4BP initially controls the function of steroidogenic enzymes and steroidogenic enzymes gradually express from primary follicles to mature follicles. At antral follicle stage, steroid metabolism completes to produce testosterone. When aromatase and estrogen receptor express in antral follicle, this antral follicle develops as the dominant follicle and produces estradiol to promote follicle maturation. We therefore speculate that the expression of aromatase and estrogen receptor have an important role for the selection of dominant follicle in human. According growth factors for follicular development, it has been demonstrated to be important in the biological activity in the ovary. In this study, we examined the localization of EGF, TGF alpha and their receptor (EGFR). The localization of EGF was not confirmed both mRNA and protein level through follicular development. On the other hand, the localization and expression of TGF alpha was confirmed in theca cells and EGFR in granulosa cells at antral stage.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal androgen excess in women: lack of a role for 17-hydroxylase and 17,20-lyase dysregulation

Some investigators have suggested that "dysregulation" of cytochrome P450c17 alpha may result in the exaggerated secretion of ovarian androgens in hyperandrogenism. Although the majority of hyperandrogenic (HA) patients demonstrate an ovarian source for their androgens, approximately 50% also display adrenocortical hyperactivity and adrenal androgen excess. To determine whether 17-hydroxylase (17-OH) and/or 17,20-lyase dysregulation is responsible for the adrenocortical abnormalities noted in many HA patients, we studied 92 consecutive women with hirsutism and/or HA oligomenorrhea; 26 healthy eumenorrheic nonhirsute women served as controls. The basal levels of total and free testosterone (T), sex hormone-binding globulin, and dehydroepiandrosterone sulfate were measured, and pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone, dehydroepiandrosterone, and androstenedione were measured 0 and 60 min after the acute iv administration of ACTH-(1-24). Controls and HA patients did not differ in mean age or body mass, but HA women had higher basal T, free T, dehydroepiandrosterone sulfate, androstenedione, and LH/FSH and lower sex hormone-binding globulin levels. The mean estimated basal 17-OH activity was higher among HA patients than in controls. Although 52 HA patients demonstrated solely an exaggerated basal delta 5-17-OH activity estimate, few HA patients had an exaggerated estimate for either basal delta 4-17-OH or ACTH-stimulated 17-OH activity. No HA patient demonstrated an exaggerated 17,20-lyase basal activity, whereas 14 demonstrated an exaggerated delta 4-17,20-lyase ACTH-stimulated activity only. There was no association between these estimates of 17-OH and 17,20-lyase activities and the circulating adrenal androgen levels in HA women. Importantly, none of the patients demonstrated an increase in the basal activities of both 17-OH and 17,20-lyase, and only 4 patients demonstrated an exaggerated ACTH-stimulated activity of both 17-OH and 17,20-lyase. In conclusion, the steroidogenic profile observed in this population of HA women before and after ACTH-(1-24) stimulation is not consistent with dysregulation of cytochrome P450c17 alpha and probably represents a generalized alteration of adrenocortical control or biosynthesis.

Ovarian suppression with triptorelin and adrenal stimulation with adrenocorticotropin in functional hyperadrogenism: role of adrenal and ovarian cytochrome P450c17 alpha

OBJECTIVES

To validate combined ovarian suppression with triptorelin and adrenal stimulation with ACTH in the diagnosis of female hyperandrogenism and to provide new insights into the adrenal-ovarian relationship present in this disorder.

DESIGN

Comparison of sexual steroids and basal and ACTH-stimulated steroid levels before and after ovarian suppression induced by triptorelin.

SETTING

Department of Endocrinology, Hospital Ramón y Cajal, Madrid, Spain.

PARTICIPANTS

Thirty-nine nonselected women with hyperandrogenism.

MAIN OUTCOME MEASURES

Serum levels of T, 17-hydroxyprogesterone (17-OHP), 17-hydroxy-pregnenolone, DHEA and DHEAS, androstenedione (delta 4-A), 11-deoxycortisol, and cortisol.

RESULTS

Elevated T independent of ovarian suppression pointed to an adrenal disorder in six patients (one with an androgen-producing adenoma, two with late-onset 21-hydroxylase deficiency, three with functional adrenal hyperandrogenism). Nineteen patients had functional ovarian hyperandrogenism as elevated T normalized after ovarian suppression and were subdivided into ovDHEAS+ (n = 7) and ovDHEAS = (n = 12) subgroups depending on the presence of DHEAS hypersecretion. Finally, 14 patients had idiopathic hirsutism according to normal T before and after ovarian suppression. Comparisons of initial hormonal values between groups and with reference values obtained from normal women (n = 11) disclosed in functional adrenal hyperandrogenism an elevation of T and basal and stimulated DHEAS, delta 4-A, and 17-OHP with respect to normal women. These abnormalities were also present in ovDHEAS+ except for basal delta 4-A, which was normal, whereas only T and stimulated 17-OHP were elevated in ovDHEAS =. In the idiopathic group all steroids were normal with the exception of a mild elevation in stimulated DHEAS.

CONCLUSIONS

These results show a continuum of abnormalities in hyperandrogenic women, suggesting an enhanced cytochrome P450c17 alpha activity in the adrenal and the ovary as the shared mechanism between functional adrenal hyperandrogenism and functional ovarian hyperandrogenism.

Interleukin-1 inhibits Leydig cell steroidogenesis primarily by decreasing 17 alpha-hydroxylase/C17-20 lyase cytochrome P450 expression

Macrophage-secreted cytokines, such as interleukin-1 (IL-1), have been shown to modulate Leydig cell function. The present study examined the effect of recombinant murine IL-1 alpha on Leydig cell steroidogenesis and its mechanism of action. Addition of IL-1 to macrophage-depleted primary cultures of mouse Leydig cells caused a dose-dependent decrease in cAMP-dependent testosterone production and 17 alpha-hydroxylase/C17-20 lyase (P450c17) mRNA levels. Chronic treatment (48 h) of Leydig cells in culture with 50 microM 8-bromo-cAMP (8-Br-cAMP) resulted in a 60-fold increase in testosterone production. Treatment with 8-Br-cAMP plus 0.2 and 2 U/ml IL-1 decreased testosterone production to 63 +/- 14% and 41 +/- 19%, respectively, while 5, 10, and 20 U/ml IL-1 decreased testosterone production to less than 5% that of cells treated with 8-Br-cAMP alone. Chronic treatment with IL-1 plus 8-Br-cAMP caused a shift in steroid production from testosterone to progesterone, but total steroid production (the sum of testosterone plus progesterone) was unaffected by IL-1 treatment. Treatment with 8-Br-cAMP alone caused a marked increase in P450c17 mRNA levels compared to that in control cultures, where P450c17 mRNA was undetectable. IL-1 caused a dose-dependent decrease in 8-Br-cAMP-stimulated P450c17 levels (0.2 U/ml by 31 +/- 9%, 2 U/ml by 82 +/- 12%, and 10 or 20 U/ml by 100% compared to that in cells treated with 8-Br-cAMP alone). In contrast to the effect on P450c17 mRNA, only the highest concentrations of IL-1 (10 and 20 U/ml) had any effect on cholesterol side-chain cleavage enzyme (P450scc) mRNA levels (53 +/- 16% and 38 +/- 20% decreases, respectively). The inhibitory effect of IL-1 on 8-Br-cAMP-stimulated P450c17 expression was reversible. Within 12 h after the removal of IL-1, P450c17 mRNA was restored to 24%; after 24 h, to 36%; after 36 h, to 65%; and after 48 h, to 84% of that with 8-Br-cAMP alone. P450c17 expression was more sensitive to IL-1-mediated inhibition than P450scc; therefore, inhibition of P450c17 is most likely primarily responsible for the observed inhibitory effects of IL-1 on Leydig cell testosterone production.

Stimulation by voluntary exercise of adrenal glucocorticoid secretion in mature female hamsters

The possibility that habitual voluntary running induces a chronic change in adrenal glucocorticoid synthesis and secretion was examined in freely running mature female hamsters, in whom this behavior accelerates growth, reduces body fat levels, and elevates core temperature. Hamsters were free to run on horizontal discs or in vertical wheels between 32 and 80 days, in 14L:10D or in 10L:14D photoperiods, and at the end of this period, corticosterone and cortisol steroidogenesis and serial plasma corticosterone concentrations during day and night were used as measures of the chronic stimulation of adrenal cortical activity. Habitual voluntary running significantly increased steroidogenesis of both glucocorticoids and plasma corticosterone concentrations and alone accounted for all the variance in enhanced synthesis and secretion of corticosterone. Acute exercise and/or the nocturnal phase of circadian period enhanced the chronic stimulatory effects of exercise on cortisol. Despite its voluntary and apparently stress-free nature, running induces chronic increases in basal glucocorticoid secretion in mature female hamsters. Putative oversecretion of corticotropin releasing factor in freely running hamsters could account for increased steroidogenesis, acceleration of growth, reduced body fat levels, and core temperature elevation.

Primary pigmented nodular adrenocortical disease (PPNAD): immunohistochemical and in situ hybridization analysis of steroidogenic enzymes in eight cases

Primary pigmented nodular adrenocortical disease (PPNAD) is a rare but an interesting adrenocortical disorder associated with ACTH-independent hypercortisolism. We have studied eight cases of the adrenals with PPNAD by immunohistochemistry of all steroidogenic enzymes involved in cortisol biosynthesis (P-45scc, 3 beta-HSD, P-450c21, P-45017 alpha, and P-45011 beta) and also by performing in situ hybridization of P-45017 alpha in seven cases in order to localize the sites of specific steroidogenesis in this unique disorder. Immunoreactivity of all the enzymes examined was intense in almost all of the cells in adrenocortical nodules, especially the cells with abundant eosinophilic cytoplasm in all the cases examined. The internodular cortex, which demonstrated atrophy in five cases, normal appearance in two cases and hyperplasia in one case, was negative for the enzymes with an exception of 3 beta-HSD. Hybridization signals of P-45017 alpha were condensed over the nodules in in situ hybridization study, suggestive of an increased production of the enzyme itself in cortical cells of the nodules. These results may be consistent with autonomous cortisol production by the nodular cells and indicate that almost all of the cells in the nodules produce cortisol, which can also explain the presence of hypercortisolism despite small sizes of adrenals in PPNAD. Immunoreactivity of steroidogenic enzymes is observed in a small cluster of cortical cells with abundant eosinophilic cytoplasm located at the zona reticularis but not in adjacent non-nodular cortex, which may support an abnormal development of the zona reticularis as a possible pathogenesis of this disorder.

Role of the steroid 17 alpha-hydroxylase in spironolactone-mediated destruction of adrenal cytochrome P-450

Previous investigations have established that spironolactone (SL) is converted to a reactive metabolite by adrenal microsomal enzymes, resulting in the degradation of cytochrome P-450 (P-450). Deacetylation of SL to 7 alpha-thiospironolactone (7 alpha-thio-SL) is the first step in the activation pathway, but further NADPH-dependent metabolism of 7 alpha-thio-SL is required for P-450 destruction. Studies were done to evaluate the role of the steroid 17 alpha-hydroxylase in the activation of 7 alpha-thio-SL by adrenal microsomes. Incubation of guinea pig adrenal microsomes with 7 alpha-thio-SL in the presence of NADPH effected greater than 50% declines in P-450 content and in 17 alpha-hydroxylase activity but no change in the rate of 21-hydroxylation. Preincubation of the microsomes with antisera to the 17 alpha-hydroxylase P-450 isozyme (P-450(17 alpha,lyase)) decreased 17 alpha-hydroxylase but not 21-hydroxylase activity and prevented the degradation of P-450 by 7 alpha-thio-SL. Control IgG had no effect on 17 alpha-hydroxylase activity or on the 7 alpha-thio-SL-mediated destruction of P-450. When added to a purified P-450(17 alpha,lyase) preparation, 7 alpha-thio-SL and the endogenous substrate progesterone caused typical type I spectral changes, but SL did not. Incubation of a purified and reconstituted 17 alpha-hydroxylase system, consisting of P-450(17 alpha,lyase), NADPH-P-450 reductase, cytochrome b5, and dilauroylphosphatidylcholine, with 7 alpha-thio-SL plus NADPH effected the complete degradation of the P-450(17 alpha,lyase). Neither progesterone nor SL caused P-450 destruction with the reconstituted enzyme preparation. The results provide direct evidence for the activation of 7 alpha-thio-SL by the 17 alpha-hydroxylase and support the hypothesis that a mechanism-based inhibition of the enzyme occurs. The data also provide additional evidence that 7 alpha-thio-SL is an obligatory intermediate in the degradation of P-450 by SL.

Regulation of testicular P-450 cholesterol side-chain cleavage and P-450 C17-20 lyase/C17 hydroxylase enzymes in the neonatal and adult rat

Adult Leydig cells respond to LH or hCG with an initial stimulation of testosterone secretion followed by LH receptor down-regulation and blockade of androgen biosynthesis. In contrast, fetal Leydig cells respond with increased LH receptor number and enhanced steroidogenesis. In this study, the molecular mechanisms of high-dose hCG treatment on steroidogenesis in adult and neonatal testes (containing predominantly the fetal generation of Leydig cells) were examined using two recombinant DNA clones specific for enzymes of the rat steroidogenic pathway (P-450 cholesterol side-chain cleavage enzyme, P-450scc and P-450 17 alpha-hydroxylase/C17-20 lyase, P-450c17). We treated adult (60 days of age) and neonatal (2 days of age) rats with a single high dose of hCG (600 IU/kg), sc. The high dose of hCG caused neonatal testicular P450scc and P450c17 mRNA levels to increase, and stimulated adult testicular P450scc mRNA levels, but caused a decrease in adult P450c17 mRNA levels. These studies suggest that high doses of hCG regulate testosterone production differently in adult and fetal Leydig cells at a pretranslational level of the P450c17 enzyme, while mRNA for P450scc is stimulated in both the adult and fetal Leydig cell.

Regulation of 3 beta-hydroxysteroid dehydrogenase in adrenocortical cells: effects of angiotensin-II and transforming growth factor beta

The maintenance of optimal steroidogenesis in adrenocortical cells primarily depends on the chronic action of ACTH to promote the synthesis of the various steroid metabolizing enzymes. In the steroidogenic pathway, the ratio of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) to 17 alpha-hydroxylase cytochrome P450 (P-450(17 alpha)) plays a key role in determining the final steroid products released by adrenal cells. The differences in these enzymes are particularly important when one considers the adrenal zones and the secretion of the zone-specific steroids. In the present study we have investigated the regulation of 3 beta HSD with regard to its enzyme activity, levels of protein and changes in specific mRNA encoding for this enzyme. Following eight days in primary culture, bovine adrenocortical (BAC) cells were found to respond to both ACTH and Bu2 cAMP by increased cortisol production. In addition, 3 beta HSD activity, enzyme protein and mRNA levels were increased in response to both factors. The increases varied from 2-fold for activity to 5-7 fold for mRNA. ACTH and Bu2cAMP also greatly increased P-450(17 alpha) from the near undetectable levels in control cells. In order to examine the possibility of differential regulation of these adrenal steroidogenic enzymes we determined the effects of angiotensin II (A-II) and transforming growth factor beta (TGF beta) on the levels of these enzymes. Both of these factors decreased the ACTH-stimulated levels of P-450(17 alpha) enzyme and mRNA to near nondetectable levels observed within control cells. In addition, these compounds inhibited the ACTH induction of 3 beta HSD. While the mechanism of TGF beta action is not clear, A-II probably is acting through protein kinase C. Indeed the protein kinase C activating phorbol ester, TPA, mimicked the inhibitory effects of A-II on 3 beta HSD and P450(17 alpha). It is important to point out, however, that the effects of A-II and TGF beta on P450(17 alpha) activity appeared more pronounced than their action of 3 beta HSD. This observation may relate to the relative stability of 3 beta HSD as compared to P450(17 alpha). Taken together these data indicate that, while A-II and TGF beta each decrease the levels of steroid-metabolizing enzymes, a differential regulation is observed in that P-450(17 alpha) protein and activity levels are much more sensitive to treatment with these factors.

Effects of restraint stress on plasma LH and testosterone concentrations, Leydig cell LH/hCG receptors, and in vitro testicular steroidogenesis in adult rats

We examined the effect of restraint stress (3 hr) on plasma LH and testosterone levels, on the Leydig cell LH/hCG receptor, and on the activity of enzymes in the testicular steroidogenic pathway of the adult rat. Restraint stress caused a 47% reduction in plasma testosterone concentrations, but had no effect on plasma LH levels. The binding capacity and affinity of Leydig cell LH/hCG receptors were not affected by restraint. Stress did not affect the testicular activity of 20,22 desmolase or 3 beta-hydroxysteroid dehydrogenase, but testicular interstitial cells of stressed rats incubated in vitro with progesterone as a substrate produced more 17 alpha-hydroxyprogesterone but less testosterone than control cells, and when incubated with 17 alpha-hydroxypregnenolone, produced 39% less androstenedione and 40% less testosterone than control cells. These results suggest that restraint stress inhibited 17,20 desmolase but not 17 alpha-hydroxylase activity. When the delta 4 pathway was blocked with cyanoketone (3 beta-HSD inhibitor), stress did not alter the production of pregnenolone or 17 alpha-hydroxypregnenolone, but the production of dehydroepiandrosterone by cells from stressed rats was subnormal, suggesting again a reduction of 17,20 desmolase activity. The data suggest that a major site of the inhibitory action of restraint stress on testicular steroidogenesis is the 17,20 desmolase step. The disruption of androgen production by restraint appears to be LH independent since stress did not affect plasma LH levels, the binding capacity or affinity of LH/hCG receptors, or the activity of 20,22 desmolase.

Dysregulation of cytochrome P450c 17 alpha as the cause of polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) appears to be due to a previously unrecognized type of steroidogenic abnormality, one in which hyperandrogenism arises from a regulatory abnormality (dysregulation) rather than from enzyme deficiency. It appears that PCOS typically arises from masculinized regulation of the androgen-forming enzyme (cytochrome P450c17 alpha) within ovarian thecal cells. This may arise by either excessive stimulation by luteinizing hormone (LH) or by escape from desensitization to LH. We review evidence which is compatible with the concept that the latter situation may result from an intrinsic intraovarian flaw in the paracrine feedback mechanism by which thecal androgen biosynthesis is inhibited and that coexistent adrenal 17-ketosteroid hyper-responsiveness to corticotropin (ACTH) may be due to a similar type of dysregulation of adrenocortical P450c17 alpha.

Lactogen and LH receptors. Rat P-450 17 alpha, structural analysis and hormonal regulation of mRNA levels in the Leydig cell

A complete amino acid sequence for rat testis P-450 17 alpha was deduced from nucleotide analysis of a cDNA clone isolated from a rat Leydig cell library. This cDNA expressed in COS-1 cells both 17 alpha-hydroxylase and 17,20 lyase activities. Rat P-450 17 alpha exhibited significant similarity to the nucleotide and deduced amino acid sequences of the bovine and human P-450 17 alpha, particularly with the highly conserved regions and secondary structure. The rat P-450 17 alpha is anchored to the ER by two transmembrane regions: the N-terminal insertion peptide and the stop-transfer sequence. The C-terminal is associated with the ER by four hydrophobic clefts including the steroid-binding site. We have demonstrated a dual effect of hCG, causing early increases of Leydig cell P-450 17 alpha mRNA levels at low doses, while higher desensitizing doses caused marked subsequent reduction of mRNA levels. Our studies demonstrate that gonadotropin stimulation and desensitization of P-450 17 alpha dependent enzymes (17 alpha-hydroxylase/17,20 desmolase) in the adult rat testis and E2 induced desensitization in fetal Leydig cells are related to levels of P-450 17 alpha mRNA.