Showing papers on "Steroid biosynthesis published in 1998"
01 Jun 1998
TL;DR: This review examines the microchemical and molecular genetic analyses that have provided convincing evidence for an essential role of BRs in diverse developmental programs, including cell expansion, vascular differentiation, etiolation, and reproductive development.
Abstract: Brassinosteroids (BRs) are growth-promoting natural products found at low levels in pollen, seeds, and young vegetative tissues throughout the plant kingdom. Detailed studies of BR biosynthesis and metabolism, coupled with the recent identification of BR-insensitive and BR-deficient mutants, has greatly expanded our view of steroids as signals controlling plant growth and development. This review examines the microchemical and molecular genetic analyses that have provided convincing evidence for an essential role of BRs in diverse developmental programs, including cell expansion, vascular differentiation, etiolation, and reproductive development. Recent advances relevant to the molecular mechanisms of BR-regulated gene expression and BR signal transduction are also discussed.
1,352 citations
TL;DR: Exercise of PBR in Escherichia coli DE3 cells induced the ability to take up cholesterol in a time-dependent, temperature-sensitive, and energy-independent manner, and site-directed mutagenesis in the carboxy-terminal region demonstrated that bacteria expressing the mutant PBR proteins do not accumulate cholesterol, suggesting that amino acids Y153 and R156 are involved in the interaction of the receptor with cholesterol.
Abstract: In steroid-synthesizing cells, like the MA-10 mouse tumor Leydig cells, the peripheral-type benzodiazepine receptor (PBR) is an outer mitochondrial membrane protein involved in the regulation of cholesterol transport from the outer to the inner mitochondrial membrane, the rate-determining step in steroid biosynthesis. Expression of PBR in Escherichia coli DE3 cells, which have no PBR, no cholesterol, and do not make steroids, induced the ability to take up cholesterol in a time-dependent, temperature-sensitive, and energy- independent manner. These cells took up no other steroids tested. Addition of the high affinity PBR ligand PK 11195 to cholesterol-loaded membranes, obtained from cells transfected with PBR, resulted in the release of the uptaken cholesterol. Expression in DE3 cells of mutant PBRs demonstrated that deletions in the cytoplasmic carboxy-terminus dramatically reduced the cholesterol uptake function of PBR, although it retained full capacity to bind PK 11195. Site-directed mutagenesis in th...
575 citations
TL;DR: This work shows that DAX-1 blocks steroid production at multiple levels in the Y-1 mouse adrenocortical tumor cell line and results in the inhibition of the activity of the StAR, P450scc and 3β-HSD expression.
Abstract: DAX-1 is an unusual member of the nuclear hormone receptor superfamily whose expression is mainly, but not uniquely, restricted to steroidogenic tissues. We have recently shown that DAX-1 can block the first and rate-limiting step in steroid biosynthesis by repressing StAR (steroidogenic acute regulatory protein) expression. Here we show that DAX-1 blocks steroid production at multiple levels in the Y-1 mouse adrenocortical tumor cell line. Expression of DAX-1 in Y-1 cells significantly impairs both basal and cAMP-stimulated steroid production, without affecting the functionality of the cAMP-responsive PKA pathway. Experiments using an hydroxylated cholesterol derivative show that biochemical steps in steroidogenesis subsequent to cholesterol delivery to mitochondria are also impaired in Y-1 cells expressing DAX-1. This is explained by the repression of P450scc and 3β-HSD expression, in addition to StAR. DAX-1 expression in Y-1 cells results in the inhibition of the activity of the StAR, P450scc and 3β-HS...
171 citations
TL;DR: It is demonstrated that myelin-forming cells have inducible enzymes responsible for steroid biosynthesis and a critical role for endogenous steroid hormones in signaling the initiation and enhancing the rate of myelin formation is suggested.
Abstract: Dexamethasone and progesterone have been found to accelerate the time of initiation and enhance the rate of myelin synthesis in Schwann cell/neuronal cocultures. The expression of mRNA for cytochrome P450scc (converts cholesterol to pregnenolone), 3β-hydroxysteroid dehydrogenase (converts pregnenolone to progesterone), and the progesterone receptor were detected and markedly induced during peak myelin formation in the cocultures. The mRNA for the glucocorticoid receptor was detected, but was found to be constituitively expressed. In addition, the specific activity of 3β-hydroxysteroid dehydrogenase was measured and found to increase by 10-fold. The mRNA for cytochrome P450scc and 3β-hydroxysteroid dehydrogenase also were found to be induced during the differentiation of O-2A precursor cells to oligodendrocytes. Fibroblast growth factor and platelet-derived growth factor were found to have proliferative effects on Schwann cells, but they had no effect on the initiation or the rate of myelin formation. These results demonstrate that myelin-forming cells have inducible enzymes responsible for steroid biosynthesis and suggest a critical role for endogenous steroid hormones in signaling the initiation and enhancing the rate of myelin formation.
167 citations
TL;DR: Evidence is provided that the peripheral-type benzodiazepine receptor mediates the intramitochondrial cholesterol transport and the subsequent adrenal, gonadal, placental, and brain steroid biosynthesis.
Abstract: Steroidogenesis depends on the rate of cholesterol transport from intracel- lular stores to the inner mitochondrial membrane cytochrome P-450 side-chain cleav- age enzyme. Using steroidogenic cell submitochondrial fractions, mitochondrial preparations, various cell models, and animal models and with the help of pharma- cological, biochemical, morphological, and molecular approaches, we provide evi- dence that the peripheral-type benzodiazepine receptor mediates the intramitochon- drial cholesterol transport and the subsequent adrenal, gonadal, placental, and brain steroid biosynthesis. (P.S.E.B.M. 1998, Vol 2171
90 citations
TL;DR: Results suggest that vascularization of the corpus luteum is induced by HCG-mediated effects of VEGF/VPF, which induces endothelial cell proliferation as well as angiogenesis in vivo and increases capillary permeability.
Abstract: 5 To whom correspondence should be addressed Vascularization is a prominent event during corpus luteum formation, providing low density lipoproteins for steroid biosynthesis and enabling transport of secreted steroids. The process of vascularization is controlled by specific regulators. Vascular endothelial growth factor (VEGF), otherwise named vascular permeability factor (VPF), induces endothelial cell proliferation as well as angiogenesis in vivo and increases capillary permeability. Here we report the expression of VEGF/VPF mRNA by cultured human luteinized granulosa cells (GC) for at least 10 days. Without HCG VEGF/VPF expression declined after day 4 and by day 10 was reduced to ~30% of the value at day 4. However, after culture in the presence of 1 U/ml human chorionic gonadotrophin (HCG), expression of VEGF/VPF mRNA by GC was four times greater than control experiments by day 10, and increased 100% from day 4 to day 10. Simultaneously, HCG supplementation increased VEGF/VPF secretion by GC. Medium VEGF/VPF on day 3 was 13 pM without and 11 pM with HCG. Medium VEGF/VPF on day 10 was 6 pM without HCG and 29 pM with HCG. These results suggest that vascularization of the corpus luteum is induced by HCG-mediated effects of VEGF/VPF.
74 citations
TL;DR: The 18-kDa PBR may have a more important role in steroidogenesis than in proliferation in this Leydig cell line, as compared to control and knockout MA-10 cell lines.
69 citations
TL;DR: Assessment of specific zonal localization and developmental regulation of CYP21A2 and CYP11B1/CYP11B2 in the human and rhesus monkey fetal adrenal gland suggests analogies of the three functional zones of the fetus (DZ, TZ, and FZ) to their adult counterparts (zona glomerulosa, zona fasciculata, and zona reticularis).
Abstract: Previous studies in the primate fetal adrenal gland have indicated that the gland is comprised of three functional zones: 1) the inner fetal zone (FZ), which has the enzymes necessary for dehydroepiandrosterone sulfate (DHEAS) production beginning early in gestation; 2) the transitional zone (TZ), which possesses enzymes necessary for cortisol production; and 3) the outer, definitive zone (DZ), which appears to function as a reservoir of progenitor cells that may populate the remainder of the gland and does not acquire a steroidogenic phenotype with the capacity to produce mineralocorticoids until near term. The enzymes CYP21A2 (P450 21 hydroxylase, or P450c21), CYP11B1 (11β hydroxylase or P450c11) and CYP11B2 (aldosterone synthase) are necessary for glucocorticoid and mineralocorticoid synthesis but have not been localized previously in an ontogenic manner in the primate fetal adrenal gland. Therefore, we used immunocytochemistry (ICC) to assess specific zonal localization and developmental regulation of...
65 citations
TL;DR: Data demonstrate that the described Tier I battery is useful for identifying endocrine-active compounds (EACs) and a distinct "fingerprint" was produced for each type of endocrine activity against which compounds with unknown activity can be compared.
64 citations
TL;DR: This study was designed to seek evidence, from endocrine and genetic studies, for impaired steroid biosynthesis in patients with acne.
Abstract: OBJECTIVE Previous endocrine studies of women with acne have produced diverse results. This study was designed to seek evidence, from endocrine and genetic studies, for impaired steroid biosynthesis in patients with acne. DESIGN Adrenal stimulation tests with synthetic adrenocorticotrophic hormone (ACTH) were performed. MEASUREMENTS Steroid hormones were measured basally and 30 minutes after ACTH. The results were correlated with analysis of the steroid 21-hydroxylase gene (CYP21). PATIENTS Fifty-one consecutive female patients (mean age 27.1 years) referred with acne. RESULTS The median plasma 17-hydroxyprogesterone (17-OHP) before and 30 minutes after ACTH were 2.5 nmol/l (range 1.1-8.2) and 7.3 (2.1-17.8) nmol/l which were significantly above normal female controls (n = 11, mean age 25.6 years) at 1.5 (0.9-4.2) and 4.6 (2.6-8.4) nmol/l. Eighteen of 51 acne patients showed an abnormal 17-OHP response. The 21-hydroxylase gene (CYP21) was examined for major deletions and for three common point mutations in 31 of the patients (14 with exaggerated 17-OHP response). One patient had a deletion of CYP21 on one allele consistent with carrier status for the classical congenital adrenal hyperplasia (CAH). Five patients, one of whom had a normal 17-OHP response to Synacthen, were heterozygous for the val 281 leu mutation in exon 7 of the CYP21 and were therefore carriers for a mutation associated with late-onset CAH. One patient with a raised 17-OHP response was homozygous for the splice site mutation in intron 2 and one patient with a normal 17-OHP response was heterozygous for the mutation. None of the patients had the ile 172 asn mutation. Eight of the 31 acne patients who had CYP21 gene analysis were carriers for mutations in the 21-hydroxylase gene but only six would have been detected by an abnormal response of 17-OHP on stimulation. CONCLUSION Although alterations of the CYP21 gene were more common in acne than in controls there is a poor correlation between these events and raised steroids and acne. Factors other than mild impairment of CYP21 contribute to the variability of the clinical phenotype in hyperandrogenic states including acne.
64 citations
TL;DR: A Tier I screening battery for detecting endocrine active compounds (EACs) has been evaluated for its ability to identify 17 beta-estradiol, a pure estrogen receptor agonist, and compared to the responses obtained from F1 generation rats from a 90-day/one-generation reproduction study to demonstrate the sensitivity of the Tier I battery against an in utero exposure for detecting EACs.
TL;DR: The results indicate that DAX-1 may be one of the factors influencing the steroid biosynthesis of adrenocortical neoplasms, and suggests that high DAx-1 expression in adrenocortsical tumors is associated with a non-functional phenotype whereas low DAX -1 expression favors mineralocorticoid secretion.
Abstract: The DAX-1 gene encodes an orphan nuclear hormone receptor essential for normal fetal development of the adrenal cortex. Recently, DAX-1 has been shown to act as a transcriptional repressor of steroidogenic acute regulatory protein gene expression (StAR), suppressing steroidogenesis. We, therefore, investigated the expression of DAX-1 in a variety of adrenocortical tumors and compared the results with StAR mRNA expression. We found low or absent DAX-1 expression in aldosterone-producing adenomas (n = 11: 35 +/- 11%; normal adrenals: 100 +/- 17%) and in aldosterone-producing adrenocortical carcinomas (n = 2: 24 and 36%). Cortisol-producing adenomas showed intermediate DAX-1 expression (n = 8; 92 +/- 16), as did 3 non-aldosterone-producing carcinomas (72, 132 and 132%). High DAX-1 expression was present in nonfunctional adenomas (n = 3; 160 +/- 17%). In contrast to DAX-1, StAR mRNA expression did not show significant variations between groups. We did not detect the expected negative correlation between DAX-1 and StAR in adrenocortical tumors. These data suggest that high DAX-1 expression in adrenocortical tumors is associated with a non-functional phenotype whereas low DAX-1 expression favors mineralocorticoid secretion. These effects on steroidogenesis are mediated by mechanisms other than repression of StAR gene expression. Our results indicate that DAX-1 may be one of the factors influencing the steroid biosynthesis of adrenocortical neoplasms.
TL;DR: Data indicate that TTN stimulates the biosynthesis of 3-keto-17 alpha-hydroxysteroids in frog hypothalamic neurons through activation of peripheral-type benzodiazepine receptors likely located at the plasma membrane level.
TL;DR: Low-density cholesterol rather than LDL is thought to be the preferred lipoprotein as a source of steroidogenic substrate cholesterol in bovine adrenal fasciculo-reticularis cells.
TL;DR: Abnormal metabolism of adrenocortical steroids may perpetuate depression, and alterations of synthesis or metabolism of these steroids may lead to a remission.
Abstract: Objectif : Les patients qui souffrent de depression majeure presentent souvent des taux eleves de cortisol ainsi qu 'une resistance a la dexamethasone. Nous avons cherche a connaitre l'effet des inhibiteurs de la biosynthese des steroides sur la depression majeure, et etudie les changements endocriniens produits. Methode : Apres une periode de sevrage, 20 patients resistant au traitement et souffrant de depression grave ont recu de l'aminoglutethimide, de la meryrapone et/ou de la ketoconazole, de meme qu'une faible dose de cortisol pendant 8 semaines. Chaque semaine ou plus souvent, on a suivi, a l'aide de l'echelle de depression de Hamilton (HAMD), les niveaux de cortisone, de sulfate de dehydroepiandrosterone (DHAS), de corticotrophine (ACTH) et de testosterone, preleves a huit heures du matin. Un test de freinage de la dexamethasone (DST) a ete administre avant et apres le traitement. Resultats : Dix-sept patients (85 %) ont acheve la serie de traitement, et on a enregistre une baisse moyenne significative (P < 0,0001 de 50 %) des resultats a l'echelle HAMD, a la 7 ieme semaine de traitement. Les niveaux de cortisol ont considerablement fluctue et demeuraient souvent eleves, meme apres une amelioration de l'etat clinique du patient. Les niveaux de sulfate de dehydroepiandrosterone ont baisse plus uniformement et se sont reveles un bon indicateur de conformite et, jusqu'a un certain point, d'efficacite avec le traitement a l'aminoglutethimide et a la ketoconazole. La correlation entre le DHAS et l'HAMD ( r = 0,94) etait significative (P = 0,02). Chez les hommes, les niveaux de testosterone ont baisse a cause de la ketoconazole, mais sont rapidement revenus a la normale au terme du traitement. Les niveaux de corticotrophine etaient normaux ou eleves, selon le dosage, et ont augmente (P = 0,07; n = 13) chez la plupart des sujets durant le traitement. Des 6 repondeurs a qui l'on avait administre des DST non- suppresseurs avant le debut du traitement, 5 sont revenus a des niveaux normaux 1 ou 2 semaines apres la fin du traitement (P = 0,0006). Conclusion: Il se peut que le metabolisme anormal des steroides corticoides perpetue la depression. La modification de leur synthese ou de leur metabolisme peut occasionner la remission.
TL;DR: The squalene-hopene cyclase (SHC) is the only enzyme involved in the biosynthesis of hopanoid lipids that has been characterized on the genetic level as mentioned in this paper.
TL;DR: The prl1 mutation results in cell elongation defects, de-repression of numerous stress-induced genes, and augments the sensitivity of plants to glucose, cold stress and several hormones, including cytokinin, ethylene, auxin, and abscisic acid.
Abstract: Molecular analysis of Arabidopsis mutants displaying hypocotyl elongation defects in both the dark and light revealed recently that steroids play an essential role as hormones in plants. Deficiencies in brassinosteroid biosynthesis and signalling permit photomorphogenic development and light––regulated gene expression in the dark, and result in severe dwarfism, male sterility and de–repression of stress–induced genes in the light. A cytochrome P450 steroid hydroxylase (CYP90) controls a rate limiting step in brassinosteroid biosynthesis and appears to function as a signalling factor in stress responses. Another key step in steroid biosynthesis is controlled by the Arabidopsis SNF1 kinases that phosphorylate the 3–hydroxy–3methylglutaryl–CoA reductase. The activity of SNF1 kinases is regulated by PRL1, an evolutionarily conserved α–importin–binding nuclear WD–protein. The prl1 mutation results in cell elongation defects, de–repression of numerous stress–induced genes, and augments the sensitivity of plants to glucose, cold stress and several hormones, including cytokinin, ethylene, auxin, and abscisic acid.
TL;DR: The Q258X mutation was identified in 9 out of 10 alleles, indicating that the genetic defect in the StAR gene of Korean patients with CLAH is highly homogeneous probably due to a founder effect.
Abstract: Congenital lipoid adrenal hyperplasia (CLAH) is a rare autosomal recessive disorder of steroid biosynthesis, caused by a molecular defect in the steroidogenic acute regulatory protein (StAR). Patients with CLAH usually manifest severe salt wasting, hypovolemia, enlargement of the adrenal glands and complete female external genitalia irrespective of the gonadal sex. CLAH seems to be more common in Koreans and Japanese than in other ethnic populations, with a preponderance of the mutation of a glutamine to a stop codon at the 258th amino acid residue (Q258X) in the StAR gene. Clinical findings of five unrelated Korean patients with CLAH and their molecular defects in the StAR gene are described, and the gene frequency of the Q258X mutation in the Korean population is investigated. All patients developed hypovolemic shock due to severe salt wasting in the first three months after birth. All were hyperpigmented, and three of five phenotypic females were genetic males. The basal ACTH level was extremely high in all patients with the minimal concentrations of all adrenal and gonadal steroids. The Q258X mutation was identified in 9 out of 10 alleles, indicating that the genetic defect in the StAR gene of Korean patients with CLAH is highly homogeneous probably due to a founder effect. The carrier frequency of the Q258X mutation in the normal Korean population has been estimated as approximately 1 in 250 with the allele frequency of 1 in 500. However, the confidence limits of the gene frequency for the mutant allele are wide (0.5 to 8.0 among 1,000 alleles). This implies that the carrier frequency could be lower, down to 1/1,000, or higher, up to 16/1,000.
TL;DR: It is concluded that AG induces profound ACTH-R down-regulation in the NCI-h295 cell line either by affecting the gene expression or by decreasing transcript accumulation via an effect on RNA stability.
Abstract: The adrenostatic compound aminoglutethimide (AG), a potent inhibitor of the P450 side chain cleavage enzyme, is used in the treatment of ACTH-dependent or adrenal Cushing's syndrome. Recently, AG has been shown to inhibit ACTH receptor (ACTH-R) mRNA expression in ovine adrenocortical cells in a time-dependent fashion. To investigate whether ACTH-R down-regulation will also be induced in tumor cells, we studied the effect of AG on ACTH-R expression in the human NCI-h295 adrenocortical carcinoma cell line, which expresses functional ACTH receptors and produces steroids of the glucocorticoid, mineralocorticoid and androgen pathway. The cells were incubated in triplicate with increasing doses of AG (3, 30, 300 microM) which suppressed steroid secretion dose-dependently. After 48 h, cells were harvested, and total RNA was extracted, electrophoresed, blotted and hybridized with a human ACTH-R cDNA probe. In parallel experiments, after preincubation with AG the cells were stimulated with ACTH (10 nM) for 10 min and the intracellular cAMP accumulation was determined by RIA. AG significantly suppressed the baseline ACTH-R mRNA expression in a dose-dependent fashion (300 microM AG, 5+/-1%; 30 microM AG, 64+/-1%; 3 microM AG, 108+/-19% compared with control cells, 100+/-11%). The reduced ACTH-R mRNA expression was paralleled by low ACTH-induced cAMP accumulation indicating reduced expression of the ACTH-R protein. The adrenostatic compound metyrapone, an inhibitor of 11beta-hydroxylase activity, also suppressed ACTH-R mRNA expression in a similar fashion. Stimulation of the protein kinase A pathway by simultaneous incubation of ACTH (10 nM) or forskolin (10 microM) together with AG was not able to overcome the steroid biosynthesis blockade, but reversed the inhibitory effects of AG on the ACTH-R mRNA expression. Also, cortisol (12 microM) reversed the AG-induced ACTH-R mRNA expression. We conclude that AG induces profound ACTH-R down-regulation in the NCI-h295 cell line either by affecting the gene expression or by decreasing transcript accumulation via an effect on RNA stability. This novel action of AG can be reversed by stimulation of the cAMP pathway and of the glucocorticoid-mediated signal transduction cascade. As the down-regulation occurs in vitro at concentrations which are reached during treatment with AG in humans it may contribute to its therapeutic activity in adrenal disease.
TL;DR: Steroidogenic factor-1 plays a key role in the development and differentiation of the reproductive system and its role in hormone-dependent regulation of reproductive function in vivo is uncertain, but its function may be subject to modulation by coactivators or corespressors and hormones, as well as by post-translational modifications.
Abstract: To characterize the unique features of steroidogenic factor-1 (SF-1) among members of the steroid receptor superfamily of proteins and review its role in reproductive development and function. We reviewed all pertinent articles that describe structural or functional aspects of SF-1. We also introduced results obtained recently by our group. Unlike other steroid receptors, SF-1 binds as a monomer to a DNA response element, which is composed of an estrogen receptor “half site.” Furthermore, SF-1 lacks a specific ligand that is required for either interaction with DNA or modulation of its transactivation function. Steroidogenic factor-1 is highly expressed in steroid-producing tissues and in gonadotrophs and plays a pivotal role in regulating the expression of enzymes and hormones essential for steroid biosynthesis pathways. A dramatic phenotype was revealed using SF-1 deficient mice: these mice lack gonads and adrenal glands, establishing SF-1 as an essential embryonic regulator of steroidogenic organ development. While SF-1 is required for basal expression of steroidogenic enzymes, its role in hormone-dependent regulation of reproductive function in vivo is uncertain, but its function may be subject to modulation by coactivators or corespressors and hormones, as well as by post-translational modifications. Steroidogenic factor-1 plays a key role in the development and differentiation of the reproductive system. Understanding the mechanism of action of SF-1 is expected to provide new clues to the etiology of maldevelopment of the gonads and adrenal glands, and to dysfunctional associated with steroid biosynthesis during early embryonic development and throughout differentiation.
TL;DR: Seven SNPs of the CYP17A1 gene in a large population of subjects had no significant association with PCOS, however, one haplotype had a p-value of p=0.001, suggesting that it may be associated with the pathogenesis of PCOS in a Korean population.
Abstract: Women with polycystic ovary syndrome (PCOS) are characterized by excess androgen secretion and anovulatory infertility as a cause of follicular maturation arrest, and they are also associated with insulin resistance and obesity. Recently, it was suggested that one of the etiologies for PCOS is an abnormality of steroid hormones, and excessive secretion of androgen. The endoplasmic reticular cytochrome P450, 17alpha-hydroxylase (CYP17A), plays a key role in the mechanism of steroid hormones such as adrenal and gonadal steroid biosynthesis. Therefore, we studied the association between single nucleotide polymorphisms (SNPs) of the A1 allelic variant of the CYP17 gene and PCOS in a Korean population. The study recruited 134 Korean women with PCOS and 100 healthy women as controls. Using the HapAnalyzer, the genotype of the CYP17A1 polymorphism in PCOS and control patients were analyzed. We considered a p-value lower than 0.05 to be statistically significant. After genotypic analysis, we found seven SNPs of the CYP17A1 gene in a large population of subjects. The frequency of seven SNPs had no significant association with PCOS. However, one haplotype (ht3) had a p-value of p=0.001, suggesting that it may be associated with the pathogenesis of PCOS in a Korean population.
TL;DR: Both the testis and ovary explant assays appear to have limited utility for detecting aromatase inhibitors; however, they may have utility in confirming in vivo findings.
TL;DR: Results provide strong support that the gonadotrophic hormones are the primary regulator of neonatal Leydig cell development in primates, and also suggest cell regression, rather than apoptosis, being the mechanism of this inhibition.
Abstract: Little is known of the cell biology of Leydig cells during the neonatal activation of the hypothalamic-pituitary-testicular (HPT) axis The current study examined the effect of blockade of the HPT axis with a GnRH antagonist (antide) on the neonatal population of Leydig cells in the new world primate, the common marmoset Three sets of twins, age 7 weeks, were studied: in each pair one twin was used as a control, while the other received treatment with GnRH antagonist from the day of birth to suppress pituitary gonadotrophin secretion Leydig cells of treated animals were dramatically different from those of controls The cells were atrophic and exhibited very irregular nuclei The organelles involved in steroid synthesis were reduced to the extent to being barely evident The smooth endoplasmic reticulum (SER) was greatly diminished in quantity and distribution The usual form of the SER (anastomosing tubules) was not evident, but, instead, the SER was relatively unbranched Peroxisomes, organelles involved in transfer of cholesterol to the mitochondria, were greatly reduced in number Mitochondria were relatively sparse and exhibited a non-typical morphology, as tubular elements of the cristae were rarely evident Thus, the central apparatus in steroid production, the SER, mitochondria and peroxisomes, was essentially shut down in the GnRH-antagonist-treated animals Storage of cholesterol, the precursor of steroid biosynthesis, was also not in evidence, as lipid droplets were extremely rare Two prominent features of control in neonatal marmoset Leydig cells, the membranofibrillar inclusion (MFI) and basal laminae, remain prominent in the Leydig cells of treated animals Evidence of apoptosis was not observed These results provide strong support that the gonadotrophic hormones are the primary regulator of neonatal Leydig cell development in primates, and also suggest cell regression, rather than apoptosis, being the mechanism of this inhibition
TL;DR: From a fetal and neonatal standpoint, accurate prenatal diagnosis of 21-hydroxylase deficiency and 11-hydrogenase deficiency is now possible, which allows for prenatal treatment in an attempt to minimize clinical problems in the neonates.
TL;DR: Both TC and DBI levels were higher in HCC patients when compared with age, sex and Child-Pugh class matched cirrhotic controls, and the data may be the result of the metabolic influence of tumors that enhances steroid biosynthesis during tumor proliferation.
TL;DR: The data suggest that COUP-TFI, N-CoR, and SMRT may play a differential role in steroid biosynthesis of non-hyperfunctioning adenomas.
Abstract: Recently, it has been shown that CYP17 gene transcription is activated by SF-1 (Steroidogenic Factor-1) binding to a cyclic AMP-responsive sequence within the promoter region of the gene, whereas it is inhibited by COUP-TF (Chicken Ovalbumin Upstream Promoter-Transcription Factor) binding to the sequence. We have shown that transcriptional repression by COUP-TFI is mediated by corepressors, N-CoR (nuclear receptor corepressor) and SMRT (silencing mediator for retinoid and thyroid hormone-receptor). Therefore, we compared the expression of COUP-TFI, N-CoR and SMRT in non-hyperfunctioning adrenocortical adenomas and normal adrenal glands. We found significantly higher expression of COUP-TFI mRNA in non-hyperfunctioning adenomas (n=5, 227±18%) than in normal adrenals (n=5, 96±4%). Interestingly, the pattern of N-CoR and SMRT expression was different compared with COUP-TFI expression. These data suggest that COUP-TFI, N-CoR, and SMRT may play a differential role in steroid biosynthesis of non-hyperfunctioning...
TL;DR: It is concluded that steroidogenesis and accumulation of mature StAR protein are inhibited as a consequence of the induction of apoptosis and reduced levels of StAR may be partially attributed to inhibition of import because of the loss of delta psi.
Abstract: Apoptosis inhibits steroid biosynthesis, but it is not clear how the Steroidogenic Acute Regulatory (StAR) protein, is affected. To characterize StAR expression during apoptosis, mouse MA-10 Leydig tumor cells were treated with ethane dimethane sulfonate (EDS), an inducer of apoptosis, and the metal ion chelator NNN'N'-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN), an inducer of cell death. Both chemicals induced cell death and similarly inhibited dbcAMP-stimulated steroidogenesis and accumulation of the 30 kDa form of StAR. Utilizing the dye JC-1, it was found that TPEN and EDS also impaired the mitochondrial electrochemical potential (delta psi). In Sertoli cells, which also express StAR, EDS induced cell death and attenuated StAR expression. We conclude 1) steroidogenesis and accumulation of mature StAR protein are inhibited as a consequence of the induction of apoptosis; 2) reduced levels of StAR may be partially attributed to inhibition of import because of the loss of delta psi; 3) loss of steroidogenesis is probably due to loss of StAR synthesis and disruption of delta psi.
01 Jan 1998
TL;DR: A protein with homology to a region in the C-terminal portion of the StAR protein has been cloned and shown to display some cholesterol transferring capacity, suggesting that StAR is the acute regulator of steroid biosynthesis.
Abstract: The acute biosynthesis of steroid hormones in response to trophic hormone stimulation is controlled by transferring substrate cholesterol from the outer mitochondrial membrane to the inner mitochondrial membrane where it is converted into pregnenolone, the first steroid synthesized, by the cytochorme P450 side chain cleavage enzyme system. This regulation is cycloheximide sensitive and thus requires a protein factor whose role it is to mediate this transfer of cholesterol. One candidate for the regulatory protein is the mitochondrial phosphoprotein, the steroidogenic acute regulatory (StAR) protein. Cloning and sequencing of the StAR cDNA indicated that it was a novel protein. Transient transfections with the cDNA for the StAR protein resulted in increased steroid production in both MA-10 and COS-1 cells in the absence of stimulation. Mutations in the StAR gene have been shown to cause the potentially lethal disease, congenital lipoid adrenal hyperplasia, a condition in which cholesterol transfer to the P450scc is blocked. Recently, a protein with homology to a region in the C-terminal portion of the StAR protein has been cloned and shown to display some cholesterol transferring capacity. While it appears that StAR is the acute regulator of steroid biosynthesis, the mechanism which results in cholesterol transfer to the inner mitochondrial membrane is still unknown.
TL;DR: The results of recent studies support the concept of an oligogenic disorder in which genes affecting metabolic pathways in glucose homeostasis and steroid biosynthesis are both involved and support the proposed interaction of a small number of key genes with environmental, particularly nutritional, factors.
Abstract: Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age. Familial clustering of cases suggests that genetic factors play an important part in its aetiology. A number of studies of families with several cases of PCOS have produced results suggesting an autosomal dominant trait. Detailed analysis of a large number of affected families has, however, cast some doubt about the mode of inheritance. An autosomal dominant trait remains possible but a more complex aetiology seems more likely. The results of our recent studies support the concept of an oligogenic disorder in which genes affecting metabolic pathways in glucose homeostasis and steroid biosynthesis are both involved. We review evidence for an important role for the insulin gene minisatellite in the aetiology of anovulatory PCOS and for the gene coding for P450 cholesterol side chain cleavage (CYP11a) in the mechanism of excessive androgen secretion in women with polycystic ovaries. We propose that the heterogeneity of clinical and biochemical features in PCOS can be explained by the interaction of a small number of key genes with environmental, particularly nutritional, factors.
Dissertation•
01 Jan 1998
TL;DR: In this paper, the synthesis of ring junction azasteroid ring systems using acyl radical cascade reactions was discussed. But the synthesis was not successful and the problems that they encountered were discussed.
Abstract: Our work has been concerned with the synthesis of azasteroid ring systems, utilising acyl radical cascade reactions. Chapter 1 comprises an overview of published work relevant to our studies: an analysis of steroid biosynthesis and synthesis; a review of the use of azasteroids, their biological activity and current synthetic techniques in azasteroid formation. This initial chapter also includes an introduction to published work in the area of nitrogen heterocycle synthesis using radical reactions and finally the use of acyl radicals in synthesis, particularly cascade reactions.
Chapter 2 starts by describing the requirements of a reaction system for use in acyl radical cascades and then discusses the relevance of this to the synthesis of ring junction azasteroids. Our attempts to synthesise ring junction azasteroids and the problems that we encountered are then discussed.
Subsequent sections describe the disconnection of azasteroids where nitrogen is part of the body of the ring and the synthetic work that we performed in this area. Using cyclohexenyl enamides as the terminal electrophore in cascade reactions we were able to synthesise a 12-aza-D-homosteroid in nine steps. The final step was a cascade reaction involving three consecutive 6-endo-trig cyclisations starting from an acyl radical and terminating on an cyclohexenyl enamide electrophore. An extensive, though unsuccessful, study attempting to use linear enamides in cascade reactions is described showing routes towards the synthesis of steroid models.
Finally we reveal the work that was performed in the use of highly stabilised enamides as radical acceptors. This work resulted in the formation of a bicyclo[8.3.0]tridecene after a 10-endo-trig, 5-exo-trig cascade from a linear precursor designed to form a 7-azaandrostane skeleton.