Showing papers on "Steroid biosynthesis published in 2000"

Improvement in Mood and Fatigue after Dehydroepiandrosterone Replacement in Addison’s Disease in a Randomized, Double Blind Trial

Abstract: Dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) are adrenal precursors of steroid biosynthesis and centrally acting neurosteroids. Glucocorticoid and mineralocorticoid deficiencies in Addison’s disease require life-long hormone replacement, but the associated failure of DHEA synthesis is not corrected. We conducted a randomized, double blind study in which 39 patients with Addison’s disease received either 50 mg oral DHEA daily for 12 weeks, followed by a 4-week washout period, then 12 weeks of placebo, or vice versa. After DHEA treatment, levels of DHEAS and D 4 -androstenedione rose from subnormal to within the adult physiological range. Total testosterone increased from subnormal to low normal with a fall in serum sex hormone-binding globulin in females, but with no change in either parameter in males. In both sexes, psychological assessment showed significant enhancement of self-esteem with a tendency for improved overall well-being. Mood and fatigue also improved significantly, with benefit being evident in the evenings. No effects on cognitive or sexual function, body composition, lipids, or bone mineral density were observed. Our results indicate that DHEA replacement corrects this steroid deficiency effectively and improves some aspects of psychological function. Beneficial effects in males, independent of circulating testosterone levels, suggest that it may act directly on the central nervous system rather than by augmenting peripheral androgen biosynthesis. These positive effects, in the absence of significant adverse events, suggest a role for DHEA replacement therapy in the treatment of Addison’s disease. (J Clin Endocrinol Metab 85: 4650 ‐ 4656, 2000)

A polymorphism in the cyp17 gene is associated with prostate cancer risk

Abstract: CYP17 encodes the enzyme cytochrome P-450c17α, which mediates both 17α-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 (TC) 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. Int. J. Cancer 87:434–437, 2000. © 2000 Wiley-Liss, Inc.

The peripheral benzodiazepine receptors: a review.

Abstract: Peripheral benzodiazepine receptors (PBRs) have been identified in various peripheral tissues as well as in glial cells in the brain. This review describes the tissue and subcellular distribution of the PBR in mammalian tissues and analyzes its many putative endogenous ligands. It deals with the pharmacological, structural and molecular characterization of the PBR, the proteins associated with the receptor (VDAC, ANC, PRAX-1) and their roles in cell growth and differentiation, cancer, steroid biosynthesis, and other physiological roles.

Progesterone Synthesized by Schwann Cells during Myelin Formation Regulates Neuronal Gene Expression

Abstract: Previously, progesterone was found to regulate the initiation and biosynthetic rate of myelin synthesis in Schwann cell/neuronal cocultures. The mRNA for cytochrome P450scc (converts cholesterol to pregnenolone), 3β-hydroxysteroid dehydrogenase (3β-HSD, converts pregnenolone to progesterone), and the progesterone receptor were found to be markedly induced during active myelin synthesis. However, the cells in the cocultures responsible for these changes were not identified. In this study, in situ hybridization was used to determine the localization of the enzymes responsible for steroid biosynthesis. The mRNA for cytochrome P450scc and 3β-HSD were detected only in actively myelinating cocultures and were localized exclusively in the Schwann cells. Using immunocytochemistry, with minimal staining of the Schwann cells, we found the progesterone receptor in the dorsal root ganglia (DRG) neurons. The progesterone receptor in the neurons translocated into the nuclei of these cells when progesterone was added to neuronal cultures or during myelin synthesis in the cocultures. Additionally, a marked induction of the progesterone receptor was found in neuronal cultures after the addition of progesterone. The induction of various genes in the neurons was also investigated using mRNA differential display PCR in an attempt to elucidate the mechanism of steroid action on myelin synthesis. Two novel genes were induced in neuronal cultures by progesterone. These genes, along with the progesterone receptor, were also induced in cocultures during myelin synthesis, and their induction was blocked by RU-486 (a progesterone receptor antagonist). These genes were not induced in Schwann cells cultured alone after the addition of progesterone. These results suggest that progesterone is synthesized in Schwann cells and that it can indirectly regulate myelin formation by activating transcription via the classical steroid receptor in the DRG neurons.

N-218 MLN64, a protein with StAR-like steroidogenic activity, is folded and cleaved similarly to StAR.

Abstract: The steroidogenic acute regulatory protein (StAR) facilitates the movement of cholesterol from the outer to inner mitochondrial membrane in adrenal and gonadal cells, fostering steroid biosynthesis...

CYP17 Promoter Polymorphism and Breast Cancer in Australian Women Under Age Forty Years

Abstract: Background: The cytochrome P450c17α enzyme functions in the steroid biosynthesis pathway, and altered endogenous steroid hormone levels have been reported to be associated with a T to C polymorphism in the 5' promoter region of the CYP17 gene. Because steroid hormone exposure is known to influence breast cancer risk, we conducted a population-based, case-control-family study to assess the relationship between the CYP17 promoter polymorphism and early-onset breast cancer. Methods: Case subjects under 40 years of age at diagnosis of a first primary breast cancer, population-sampled control subjects, and the relatives of both case and control subjects were interviewed to record family history of breast cancer and other risk factors. CYP17 genotype was determined in 369 case subjects, 284 control subjects, and 91 relatives of case subjects. Genotype distributions were compared by logistic regression, and cumulative risk was estimated by a modified segregation analysis. All statistical tests were two-tailed. Results: Compared with the TT genotype (i.e., individuals homozygous for the T allele), the TC genotype was not associated with increased breast cancer risk (P = .7). Compared with the TT and TC genotypes combined, the CC genotype was associated with a relative risk of 1.81 (95% confidence interval [CI] = 1.15-2.86; P = .01) before adjustment for measured risk factors and 1.63 (95% CI = 1.00-2.64; P = .05) after adjustment. There was an excess of CC genotypes in case subjects who had at least one affected first- or second-degree relative, compared with control subjects unstratified by family history of breast cancer (23% versus 11%; P = .006), and these case subjects had a threefold to fourfold higher risk than women of other groups defined by genotype and family history of breast cancer. Analysis of breast cancer in first- and second-degree relatives of case subjects with the CC genotype, excluding two known carriers of a deleterious mutation in BRCA1 or BRCA2, gave a relative hazard in women with the CC genotype of 3.48 (95% CI = 1.13-10.74; P = .04), which is equivalent to a cumulative risk of 16% to age 70 years. Conclusions: The CC genotype may modify the effect of other familial risk factors for early-onset breast cancer.

Expression of steroid hormone receptors, their regulated proteins, and bcl-2 protein in myofibroblastoma of the breast

Abstract: Aims To investigate the possible role of steroid hormones in the pathogenesis of myofibroblastoma (MFB) of the breast, we analysed the immunohistochemical expression of oestrogen, progesterone, androgen receptors, their regulated proteins and bcl-2 protein in a series of this rare tumour. Methods and results Paraffin-embedded sections from seven cases of MFB of the breast (five male; two female) were immunohistochemically tested for the expression of oestrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), oestrogen-regulated pS2 protein, androgen-regulated prostate-specific antigen (PSA) and bcl-2 protein. Rare cases of benign spindle cell tumours or tumour-like lesions of the breast (primitive fibromatosis, inflammatory pseudotumour, muscular hamartoma) which enter into the differential diagnosis with MFB, were also investigated and compared with MFB. All cases of MFB showed a diffuse (70–90% of neoplastic cells) and strong nuclear labelling with ER and PR, whereas AR was expressed only in three cases (two men and one woman) in about 60–70% of cells. Conversely, no immunostaining was detected for the pS2 protein and PSA. bcl-2 protein immunoreactivity was found in all cases of MFB, although with a variable degree of expression. No expression for steroid hormone receptors, their regulated-proteins and bcl-2 protein was observed in the rare benign spindle cell lesions of the breast included in this study. Conclusion The in-situ detection of ER, PR and AR suggests that steroid hormones and their receptors are implicated in the pathogenesis of breast MFB. The consistent demonstration of bcl-2 protein, associated with a positive ER/PR status, provides evidence that bcl-2 may be an oestrogen-regulated protein also in MFB and that probably plays a role in the tumorigenesis. Finally, we postulate that the ER/PR and bcl-2 positive immunoprofile of MFB of the breast, in contrast to the negative profile of other rare primitive benign spindle cell lesions of the breast herein studied, might be exploited as an ancillary diagnostic aid in differential diagnosis of doubtful cases.

CYP17 promotor polymorphism and ovarian cancer risk.

Abstract: The CYP17 gene encodes the cytochrome P450c17alpha enzyme, which functions at 2 different points in the steroid biosynthesis pathway, and is considered a candidate susceptibility gene for endocrine-related tumors. A T to C substitution polymorphism exists in the 5' promoter region of this gene, and creates an additional Sp1-type motif. Several studies have examined this polymorphism as a risk factor for breast cancer, but results have been conflicting. We examined 319 cases of ovarian cancer and 298 unaffected controls for the T-C polymorphism. There was no significant difference between cases and controls for the allele frequencies (p = 0.6), or for genotype distribution (p = 0.9). The odds ratio (95% confidence interval) for ovarian cancer was 1.13 (0.70-1.82) for the putative "cancer susceptibility" CC genotype and 1.07 (0.77-1.48) for any C allele (CC or CT genotype). Results were little different after adjustment for age. Stratification of the ovarian cancer cases according to form (benign, low malignant potential or invasive), histology, grade or stage failed to reveal any heterogeneity with respect to CYP17 genotype. Our data provide no evidence for an association between ovarian cancer risk and the genotype defined by the CYP17 5' promoter region T-C polymorphism.

3β-Hydroxysteroid Dehydrogenase/Δ5→4-Isomerase Activity Associated with the Human 17β-Hydroxysteroid Dehydrogenase Type 2 Isoform1

Abstract: The type 2 isoform of human 17β-hydroxysteroid dehydrogenase (17βHSD2) efficiently catalyzes the oxidative metabolism of androgens and estrogens, and it is expressed in a large series of human peripheral tissues. To obtain a better understanding of the regulation of local steroid biosynthesis and metabolism in human tissues, we have established a dual steroidogenic activity of the 17βHSD2 enzyme after transfection of human 17βHSD2-transfected human embryonic kidney (293) cells. After transient transfection, the metabolism of testosterone, pregnenolone, and dehydroepiandrosterone (DHEA) in intact transfected 293 cells was evaluated by TLC-based radiometric assays. 17βHSD2-transfected cells converted 91% of testosterone (1 μmol/L) into androstenedione in a 2-h incubation period. In addition, pregnenolone (1 μmol/L) was converted to progesterone (18.5%), whereas DHEA (1 μmol/L) was metabolized to androstenedione (8.3% conversion) in a 15-h incubation period. The kinetics of the 3β-hydroxysteroid dehydrogenas...

The effect of stress application on vestibular compensation

Abstract: It is still unknown how stress, which is known to delay recovery from vestibular symptoms in patients with vertigo, influences recovery from vertigo. We therefore investigated the effect of stress on vestibular compensation following unilateral labyrinthectomy (UL) as a model of recovery from vertigo. In addition, we examined the effect of trilostane (4alpha, 5-epoxy-17beta-hydroxy-3-oxo-5alpha-androstane-2alpha-carbon itrile; TRIL), an inhibitor of the steroid biosynthesis enzyme delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD), on vestibular compensation under conditions of stress. After UL, Wistar rats were divided into five groups as follows and subjected to stress and/or drug application: UL only (native, n = 6); UL + stress (S, n = 6); UL + vehicle (V, n = 5); UL + stress + vehicle (S + V, n = 5); and UL + stress + TRIL (S + TRIL, n = 5). In the S group, the decrease in frequency of spontaneous nystagmus (SN) was significantly (p < 0.05) slower than, in the native group at 3, 12, 24, 30, 36 and 48 h. The decreases in frequency of SN in the V and S + V groups were similar to those in the native and S groups, respectively, suggesting that neither handling on injection nor administration of vehicle affected vestibular compensation. In the S + TRIL group, the frequency of SN was significantly (p < 0.05) less than that m the S + V group at 24 h after UL. At 30 h, the frequency of SN m the S + TRIL group was almost the same as that in the V group. These findings suggest that stress attenuates vestibular compensation and that changes in steroid concentrations account at least in part for this attenuation.

StARTing to understand cholesterol transfer.

Abstract: The crystal structure of a lipid transfer START domain has been solved and shown to contain a hydrophobic tunnel that likely binds cholesterol These results have implications for understanding the mechanism of action of the steroidogenic acute regulatory protein (StAR), which is indispensable in steroid biosynthesis

Substitution of M398T in the second transmembrane helix of the LH receptor in a patient with familial male-limited precocious puberty.

Abstract: Familial male-limited precocious puberty (MPP) is described in a 10 year old patient with typical symptoms of the disease. Sequence analysis of genomic DNA clearly demonstrated a heterozygous T1193C transition in exon 11 of the LH receptor (LHR) gene, which results in M398T substitution in the second transmembrane helix of the protein product of this gene. The same mutation was found in the patient's mother and in her brother. The grandmother and the relatives of the patient's father were free of the mutation. The boy was successfully treated with inhibitors of steroid biosynthesis and androgen antagonists. It is suggested that this mutation caused constitutive activation of the LHR, which results in excessive formation of androgens in Leydig cells and is responsible for the symptoms of precocious puberty in this patient. This is the second case of the familial form of MPP that was maternally inherited.

Steroids and reproductive biology in the Blotched Blue-tongued Lizard, Tiliqua nigrolutea

Abstract: This thesis documents the annual profiles of the primary reproductive steroids testosterone (T), 17beta-oestradiol (E2) and progesterone (P4), in the reproductive cycles of male and female blue-tongued lizards, Tiliqua nigrolutea. Data collected from a large captive population over three consecutive reproductive seasons are included. Reproductive cycles are discussed in the context of other viviparous squamate reptiles, while a broader comparative approach is used to consider patterns of steroid biosynthesis and peripheral metabolism. The annual patterns of circulating concentrations of T, E2 and P4 have been characterised for both sexes. In males, peak plasma T (10.9 +/- 3.00 ng ml-1) and E2 (778.0 +/- 120.00 pg ml-1) concentrations occur coincident with late spermatogenesis and observations of mating, respectively. Plasma P4 concentrations remain basal (< 1.2 ng ml-1) throughout the annual reproductive cycle. In females, increasing plasma E2 concentrations (275.2 +/- 33.87 pg ml-1 - 715.1 +/- 106.68 pg ml-1) are associated with vitellogenesis and plasma T peaks (6.3 +/- 0.63 ng ml-1) in the mating and peri-ovulatory period. In pregnant females, plasma P4 concentrations are elevated for the first two thirds of gestation, peaking in the second trimester at 12.7 +/- 1.27 ng ml-1 and falling rapidly prior to parturition. Concurrently, plasma P4 concentrations in non-reproductively active adult females remain basal (1 - 2 ng ml-1) throughout the year. There is good circumstantial evidence for a multiennial reproductive cycle in females. Parturition occurs late in the active season, presumably leaving little time for females to store sufficient fat reserves to become vitellogenic in the following spring: reproductive opportunities are effectively missed in at least one year following a reproductive effort. Observed reproductive behaviours, including agonistic male - male interactions, mating, and parturition, are documented. An investigation of gonadal steroid biosynthetic pathways in this viviparous squamate is presented. This compares variation in the relative contributions of the delta-4 and delta-5 steroidogenic pathways according to sex and reproductive condition. The delta-4 pathway predominates in both sexes, aligning this species phylogenetically with other reptiles. However, there are clear differences between sexes and with changing reproductive condition in the patterns of production of pathway intermediates and end-products. Additionally, detection of a possibly novel polar steroid as a major end-product of steroid biosynthesis in both sexes is reported. Peripheral (extragonadal) metabolism of T and E2 in a number of reproductively relevant steroid target tissues is compared at times of year chosen to represent three clearly distinctive reproductive conditions in each sex. There are differences both between sexes, between tissue types and with changing reproductive condition in the relative proportions of steroid conjugates and non-conjugated derivatives produced. Biosynthetic pathway activity and peripheral steroid metabolism both appear to be plastic in response to changing reproductive condition in Tiliqua nigrolutea. With a comprehensive database of information about the reproductive endocrinology and physiology of Tiliqua nigrolutea, this species is now available as a model to further examine selected aspects of the steroid hormone control of reproductive physiology and behaviour in a cool temperate, viviparous reptile.

Expression of steroidogenic acute regulatory protein and its regulation by interferon-gamma in rat corpus luteum

Abstract: The steroidogenic acute regulatory protein (StAR) is the key regulatory protein of steroidogenesis.De novo synthesis of StAR protein is required for intramitochondrial translocation of cholesterol to the cytochrome P450 side chain cleavage enzyme which is located on the matrix side of the inner mitochondrial membrane. This is the rate-limiting step of steroid biosynthesis. Usingin situ hybridization and immunohistochemistry we studied StAR expression in various stages of the corpora luteal and its regulation by interferon-gamma (IFNγ) in the adult pseudopregnant rat. The results indicated that expression of StAR in the corpora luteal was correlated with progesteron production and IFNγ was capable of inhibiting its expression.

A polymorphism study of the CYP19 gene in endometrial cancer patients

Abstract: A strong connection is known to exist between initiation/promotion of endometrial cancer and excess of estrogens. Therefore, participation of certain alleles of genetic polymorphisms in steroid biosynthesis or metabolism may be responsible for predisposition to the disease. The present study, comparing CYP19 (aromatase) gene polymorphism in 85 patients and 110 healthy females, pointed to a more frequent occurrence of relatively longer alleles (A6 and A7) of the CYP19 gene in the former group. Furthermore, precisely those genotypes co-occurred more frequently with elevated blood levels of estradiol and testosterone in postmenopausal patients. Hence, CYP19 gene polymorphism may be regarded as a factor of genetic risk for endometrial carcinoma.

Gonadotropin-Releasing Hormone: Agonists and Antagonists

Abstract: In adult women the cyclic function of the ovaries is embedded in the hypothalamic, pituitary, and ovarian feedback mechanisms [1]. The hypothalamus is the superordinate organ releasing gonadotropin-releasing hormone (GnRH) in a pulsatile manner. GnRH is secreted by the neural cells of the nucleus arcuatus in the mediobasal portion of the hypothalamus. The axons in these neurons are in close contact with the vessels of the hypothalamic-pituitary portal vein system. The pulsatile release of GnRH by the hypothalamic neurons causes the gonadotropic cells of the adenopituitary, which make up about 10% of its cell mass, to release the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH), also in pulses. FSH and LH in turn control follicular maturation and gonadal sexual steroid biosynthesis. The spontaneous activity of the hypothalamic pulse generator is modulated by a number of neurotransmitters (norepinephrine, γ-aminobutyric acid, dopamine, serotonin), neuropeptides (neuropeptide Y, proenkephalin, prodynorphin, proopiomelanocortin, corticotropin-releasing hormone), endogenous opioids (β-endorphin), and steroids (estradiol, progesterone, and testosterone). For example, an oversupply of endogenous opioids as seen in anorexia nervosa can slow the pulse generator and cause hypothalamically induced hypogonadotropic amenorrhea. This has been successfully treated and an ovulatory cycle established by using an opiate antagonist [2].

Mercuric Triflate and Olefin Cyclization

Abstract: During a trip to Indonesia, I came across a tropical fruit, duku. By extraction of the fruit skin, a hair growth active triterpene lansic acid (1) was isolated. In our planned total synthesis of 1, an effective olefin cyclization agent was required, and mercuric triflate (2) was bone. Then we carried out syntheses of a variety of polycyclic terpenoids and investigated the mechanism of biomimetic olefin cyclization. Upon cyclization of geranylgeranyl acetate, we detected chair/boat/chair cyclization products along with chair/chair/chair cyclization in 1 : 5 ratio. On the basis of the observation that the mercuric triflate is stable but still reactive enough in the presence of water, we trapped each cationic intermediate with water by cyclization in aqueous media. This is the first experimental evidence of the stepwise mechanism of olefin cyclization that takes place via conformationally flexible cationic intermediates. In this review we also deal with an approach into the mystery of the steroid biosynthesis, and a synthetic study toward the taxane skeleton by means of mercuric triflate-induced olefin cyclization.